Showing 1–50 of 81 results for author: Dai, X

Homojunction-induced thermopower enhancement in polymer films

Authors: Zhen Xu, Hui Li, Guangzheng Zuo, Xiaojuan Dai, Jincheng Liao, Guofeng Cheng, Jian Song, Wenqing Zhang, Martijn Kemerink, Lidong Chen

Abstract: It has been more than twenty years since conductive polymers began to receive attention as an emerging thermoelectric material. However, the trade-off between electrical conductivity (σ) and thermopower (S) has proven to be a major challenge that has obstructed their use in actual devices. Here we report the discovery that the thermopower of the p- and n-type legs of organic thermogenerators can b… ▽ More It has been more than twenty years since conductive polymers began to receive attention as an emerging thermoelectric material. However, the trade-off between electrical conductivity (σ) and thermopower (S) has proven to be a major challenge that has obstructed their use in actual devices. Here we report the discovery that the thermopower of the p- and n-type legs of organic thermogenerators can be substantially enhanced, without significant deterioration of σ, by constructing an in-plane segmented structure consisting of a homojunction with different doping levels on either side. In such segmented layers, the S is abnormally higher than the average value of the constituent parts when applying a forward temperature gradient (heating the heavily doped counterpart), while it is lower upon a reverse temperature gradient. Typically, for a two-stage segmented film of p-type PDPP-Se, an abnormally large S of 210 uV K-1 and σ of 2.5*10^4 S m-1 are obtained, resulting in a large power factor (PF) of 1100 uW m-1 K-2 and a record ZT of 1.36 at room temperature. The enhanced thermopower is attributed to an additional voltage developed at the homojunction under heating as explained by kinetic Monte Carlo simulations. This finding provides a breakthrough approach to the modulation of thermoelectric transport properties of conductive polymers. △ Less

Submitted 7 August, 2026; originally announced August 2026.

Comments: 75 pages, 45 figures

Antichiral hinge states in a higher-order photonic nodal ring semimetal

Authors: Yuchen Peng, Deep Mondal, Yuting Yang, Wanting Wu, Bo Zhao, Shuaiyang Wei, Zhenzhi Liu, Wenrong Qi, Xiaokang Dai, Minqi Cheng, Weili Li, Xinyi Zhang, Fei-Fei Li, Rimi Banerjee, Minggui Wei, Jingyi Tian, Peiheng Zhou, Subhaskar Mandal, Baile Zhang, Gui-Geng Liu

Abstract: Antichiral states propagate in the same direction on opposite boundaries, defying the conventional constraint that boundary modes must cancel net chirality. Previously found antichiral states have been limited to first-order topological semimetals. However, antichiral hinge states, the antichiral counterpart of recently discovered higher-order chiral hinge states, remain elusive. Here, we report t… ▽ More Antichiral states propagate in the same direction on opposite boundaries, defying the conventional constraint that boundary modes must cancel net chirality. Previously found antichiral states have been limited to first-order topological semimetals. However, antichiral hinge states, the antichiral counterpart of recently discovered higher-order chiral hinge states, remain elusive. Here, we report the observation of antichiral hinge states in a higher-order nodal-ring semimetal made of a three-dimensional gyromagnetic photonic crystal. Near-field scanning measurements reveal a pair of hinge states at two parallel one-dimensional boundaries propagating unidirectionally along the same direction, with robust transport against metallic scatterers. Their spatial positions can be reconfigured by adding or removing photonic layers. The additionally observed antichiral and drumhead surface states manifest a hierarchy of first- and second-order topological boundary states within a single photonic system. Our work extends antichiral states to higher-order topological semimetals and has potential applications in robust and reconfigurable photonic routing. △ Less

Submitted 28 July, 2026; originally announced July 2026.

Plenoptic imaging of particle interactions in scintillation detectors

Authors: Xiang Dai, Chi-Jui Ho, Kevin Tandi, Chang Lee, Alex Bocchieri, David Parra, Forrest Peterson, Talha Sultan, Felicia Sutanto, Andreas Velten, Jingke Xu, Nicholas Antipa

Abstract: Accurate 3D localization of radiation interactions in scintillation detectors is essential for nuclear and particle physics, safeguards, and medical imaging, but remains difficult in light-starved regimes with limited photon statistics. We present PRISM, a multifocal plenoptic imaging system designed for millimeter-scale 3D position reconstruction in a single-volume scintillator. PRISM uses a mult… ▽ More Accurate 3D localization of radiation interactions in scintillation detectors is essential for nuclear and particle physics, safeguards, and medical imaging, but remains difficult in light-starved regimes with limited photon statistics. We present PRISM, a multifocal plenoptic imaging system designed for millimeter-scale 3D position reconstruction in a single-volume scintillator. PRISM uses a multifocal microlens array with diverse focal lengths and high effective numerical aperture to balance photon collection with spatial and depth encoding. A Cram'er--Rao lower bound analysis shows that the multifocal design improves axial sensitivity over conventional unifocal plenoptic systems under photon-limited conditions. We build a prototype system, calibrate its optical response with a tunable light source, and form photon-limited measurements with $\mathcal{O}(100)$ detected photons. For sparse single-vertex events, we reconstruct interaction locations using an Alternating Descent Conditional Gradient-inspired algorithm and demonstrate an average 3D localization error of approximately 1 mm. We also provide an initial evaluation of double-vertex events, showing that localization improves as the axial separation between interactions increases. These results demonstrate that multifocal plenoptic imaging can mitigate the traditional trade-off between light collection and spatial resolution, providing a photon-efficient approach to 3D reconstruction in scintillation detectors and a foundation for future multi-scattering event reconstruction. △ Less

Submitted 1 July, 2026; originally announced July 2026.

Report number: LLNL-JRNL-2020946

Predicting the single-site and multi-site event discrimination power of dual-phase time projection chambers

Authors: A. B. M. Rafi Sazzad, Clarke A. Hardy, Xiang Dai, Jingke Xu, Brian G. Lenardo, Felicia Sutanto, Nicholas A. Antipa, Jeremy D. Koertzen, Prince John, Abraham Akinin, Teal J. Pershing

Abstract: Dual-phase xenon time projection chambers (TPCs) are widely used in searches for rare dark matter and neutrino interactions, in part because of their excellent position reconstruction capability in 3D. Despite their millimeter-scale resolution along the charge drift axis, xenon TPCs face challenges in resolving single-site (SS) and multi-site (MS) interactions in the transverse plane. In this pape… ▽ More Dual-phase xenon time projection chambers (TPCs) are widely used in searches for rare dark matter and neutrino interactions, in part because of their excellent position reconstruction capability in 3D. Despite their millimeter-scale resolution along the charge drift axis, xenon TPCs face challenges in resolving single-site (SS) and multi-site (MS) interactions in the transverse plane. In this paper, we build a generic TPC model with an idealized signal readout, and use Fisher Information (FI) to predict its theoretical capability of differentiating SS and MS events using the electroluminescence signal. We also demonstrate via simulation that, when only statistical photon noise is present, the theoretical limits can be approached with conventional reconstruction algorithms like maximum likelihood estimation, and with a convolutional neural network classifier. The implications of this study on future TPC experiments will be discussed. △ Less

Submitted 2 February, 2026; v1 submitted 2 October, 2025; originally announced October 2025.

Comments: 29 pages, 17 figures

Report number: LLNL-JRNL-2011380

Extreme Solar Storm Reveals Causal Interactions in Space Weather

Authors: Xinan Dai, Haiyang Fu, Zichong Yan, Zitong Wang, Feng Xu, Chi Wang, Yuhong Liu, YaQiu Jin

Abstract: Solar storms perturb Earth's magnetosphere, triggering geomagnetic storms that threaten space-based systems and infrastructure. Despite advances in spaceborne and ground-based observations, the causal chain driving solar-magnetosphere-ionosphere dynamics remains elusive due to multiphysics coupling, nonlinearity, and cross-scale complexity. This study presents an information-theoretic framework to… ▽ More Solar storms perturb Earth's magnetosphere, triggering geomagnetic storms that threaten space-based systems and infrastructure. Despite advances in spaceborne and ground-based observations, the causal chain driving solar-magnetosphere-ionosphere dynamics remains elusive due to multiphysics coupling, nonlinearity, and cross-scale complexity. This study presents an information-theoretic framework to decipher interaction mechanisms in extreme solar geomagnetic storms across intensity levels within space weather causal chains, using 1980-2024 datasets. Unexpectedly, we uncover auroral spatial causality patterns associated with space weather threats in the Arctic during May 2024 extreme storms. By integrating causal consistency constraints into spatiotemporal modeling, SolarAurora outperforms existing frameworks, achieving superior accuracy in forecasting May/October 2024 events. These results advance understanding of space weather dynamics and establish a promising framework for scientific discovery and forecasting extreme space weather events. △ Less

Submitted 27 July, 2025; originally announced August 2025.

Single-shot HDR using conventional image sensor shutter functions and optical randomization

Authors: Xiang Dai, Kyrollos Yanny, Kristina Monakhova, Nicholas Antipa

Abstract: High-dynamic-range (HDR) imaging is an essential technique for overcoming the dynamic range limits of image sensors. The classic method relies on multiple exposures, which slows capture time, resulting in motion artifacts when imaging dynamic scenes. Single-shot HDR imaging alleviates this issue by encoding HDR data into a single exposure, then computationally recovering it. Many established metho… ▽ More High-dynamic-range (HDR) imaging is an essential technique for overcoming the dynamic range limits of image sensors. The classic method relies on multiple exposures, which slows capture time, resulting in motion artifacts when imaging dynamic scenes. Single-shot HDR imaging alleviates this issue by encoding HDR data into a single exposure, then computationally recovering it. Many established methods use strong image priors to recover improperly exposed image detail. These approaches struggle with extended highlight regions. We utilize the global reset release (GRR) shutter mode of an off-the-shelf sensor. GRR shutter mode applies a longer exposure time to rows closer to the bottom of the sensor. We use optics that relay a randomly permuted (shuffled) image onto the sensor, effectively creating spatially randomized exposures across the scene. The exposure diversity allows us to recover HDR data by solving an optimization problem with a simple total variation image prior. In simulation, we demonstrate that our method outperforms other single-shot methods when many sensor pixels are saturated (10% or more), and is competitive at a modest saturation (1%). Finally, we demonstrate a physical lab prototype that uses an off-the-shelf random fiber bundle for the optical shuffling. The fiber bundle is coupled to a low-cost commercial sensor operating in GRR shutter mode. Our prototype achieves a dynamic range of up to 73dB using an 8-bit sensor with 48dB dynamic range. △ Less

Submitted 12 September, 2025; v1 submitted 27 June, 2025; originally announced June 2025.

Comments: Published in ACM Transactions on Graphics (TOG), Volume 44, Issue 5, October 2025. DOI: 10.1145/3748718

Journal ref: ACM Trans. Graph. 44, 5, Article 172 (October 2025), 20 pages

Reinforcement-learning-assisted control of four-roll mills: geometric symmetry and inertial effect

Authors: Xuan Dai, Da Xu, Mengqi Zhang, Yantao Yang

Abstract: Embedding the intrinsic symmetry of a flow system in training its machine learning algorithms has become a significant trend in the recent surge of their application in fluid mechanics. This paper leverages the geometric symmetry of a four-roll mill (FRM) to enhance its training efficiency. Stabilizing and precisely controlling droplet trajectories in a FRM is challenging due to the unstable natur… ▽ More Embedding the intrinsic symmetry of a flow system in training its machine learning algorithms has become a significant trend in the recent surge of their application in fluid mechanics. This paper leverages the geometric symmetry of a four-roll mill (FRM) to enhance its training efficiency. Stabilizing and precisely controlling droplet trajectories in a FRM is challenging due to the unstable nature of the extensional flow with a saddle point. Extending the work of Vona & Lauga, this study applies Deep Reinforcement Learning (DRL) to effectively guide a displaced droplet to the center of the FRM. Through direct numerical simulations, we explore the applicability of DRL in controlling FRM flow with moderate inertial effects, i.e., Reynolds number $\sim\mathcal{O}(1)$, a nonlinear regime previously unexplored. The FRM's geometric symmetry allows control policies trained in one of the eight sub-quadrants to be extended to the entire domain, reducing training costs. Our results indicate that the DRL-based control method can successfully guide a displaced droplet to the target center with robust performance across various starting positions, even from substantially far distances. The work also highlights potential directions for future research, particularly focusing on efficiently addressing the delay effects in flow response caused by inertia. This study presents new advances in controlling droplet trajectories in more nonlinear and complex situations, with potential applications to other nonlinear flows. The geometric symmetry used in this cutting-edge reinforcement learning approach can also be applied to other control methods. △ Less

Submitted 2 May, 2025; v1 submitted 28 April, 2025; originally announced April 2025.

Journal ref: J. Fluid Mech. 1012 (2025) A8

Crystal structure prediction with host-guided inpainting generation and foundation potentials

Authors: Peichen Zhong, Xinzhe Dai, Bowen Deng, Gerbrand Ceder, Kristin A. Persson

Abstract: Unconditional crystal structure generation with diffusion models faces challenges in identifying symmetric crystals as the unit cell size increases. We present the Crystal Host-Guided Generation (CHGGen) framework to address this challenge through conditional generation using an inpainting method, which optimizes a fraction of atomic positions within a predefined and symmetrized host structure to… ▽ More Unconditional crystal structure generation with diffusion models faces challenges in identifying symmetric crystals as the unit cell size increases. We present the Crystal Host-Guided Generation (CHGGen) framework to address this challenge through conditional generation using an inpainting method, which optimizes a fraction of atomic positions within a predefined and symmetrized host structure to improve the success rate for symmetric structure generation. By integrating inpainting structure generation with a foundation potential for structure optimization, we demonstrate the method on the ZnS-P$_2$S$_5$ and Li-Si chemical systems, where the inpainting method generates a higher fraction of symmetric structures than unconditional generation. The practical significance of CHGGen extends to enabling the structural modification of crystal structures, particularly for systems with partial occupancy or intercalation chemistry. The inpainting method also allows for seamless integration with other generative models, providing a versatile framework for accelerating materials discovery. △ Less

Submitted 6 September, 2025; v1 submitted 23 April, 2025; originally announced April 2025.

Catalight -- an open source automated photocatalytic reactor package illustrated through plasmonic acetylene hydrogenation

Authors: B. B. Bourgeois, A. X. Dai, C. C. Carlin, L. Yuan, A. Al-Zubeidi, W-H. Cheng, D. F. Swearer, J. A. Dionne

Abstract: An open-source and modular Python package, Catalight, is developed and demonstrated to automate (photo)catalysis measurements. (Photo)catalysis experiments require studying several parameters to evaluate performance, including temperature, gas flow rate and composition, illumination power, and spectral profile. Catalight orchestrates measurements over this complicated parameter space and systemati… ▽ More An open-source and modular Python package, Catalight, is developed and demonstrated to automate (photo)catalysis measurements. (Photo)catalysis experiments require studying several parameters to evaluate performance, including temperature, gas flow rate and composition, illumination power, and spectral profile. Catalight orchestrates measurements over this complicated parameter space and systematically stores, analyzes, and visualizes the resulting data. To showcase the capabilities of Catalight, we perform an automated apparent activation barrier measurement of acetylene hydrogenation over a plasmonic AuPd catalyst on Al2O3 support, simultaneously varying laser power, wavelength, and temperature in a multi-day experiment controlled by a simple Python script. Our chemical results unexpectedly show an increased activation barrier upon light excitation, contrary to previous findings for other plasmonic reactions and catalysts. We show that the reaction rate order with respect to both acetylene and hydrogen is unchanged upon illumination, suggesting that molecular surface coverage is not changing under light excitation. By analyzing the inhomogeneity of the laser induced heating, we attribute these results to a partial photothermal effect combined with a photochemical/hot electron driven mechanism. Our findings highlight the capabilities of a new experiment automation tool; explore the photocatalytic mechanism for an industrially relevant reaction; and identify systematic sources of error in canon photocatalysis experimental procedures. △ Less

Submitted 9 April, 2025; originally announced April 2025.

A stable phase-locking-free single beam optical lattice with multiple configurations

Authors: Yirong Wang, Xiaoyu Dai, Xue Zhao, Guangren Sun, Kuiyi Gao, Wei Zhang

Abstract: Optical lattices formed by interfering laser beams are widely used to trap and manipulate atoms for quantum simulation, metrology, and computation. To stabilize optical lattices in experiments, it is usually challenging to implement delicate phase-locking systems with complicated optics and electronics to reduce the relative phase fluctuation of multiple laser beams. Here we report a phase-locking… ▽ More Optical lattices formed by interfering laser beams are widely used to trap and manipulate atoms for quantum simulation, metrology, and computation. To stabilize optical lattices in experiments, it is usually challenging to implement delicate phase-locking systems with complicated optics and electronics to reduce the relative phase fluctuation of multiple laser beams. Here we report a phase-locking-free scheme to implement optical lattices by passing a single laser beam through a prism with n-fold symmetric facets and large apex angles. The scheme ensures a stable optical lattice since the interference occurs among different deflected parts of a single laser beam without any moving component. Various lattice configurations, including a triangular lattice and a quasi-crystal lattice with ten-fold symmetry are demonstrated. In both cases, stability measurements show a change of lattice constant in less than 1.14%, and a drift of lattice position in less than 1.61%. △ Less

Submitted 3 January, 2025; originally announced January 2025.

Journal ref: Rev. Sci. Instrum. 96, 123202 (2025)

Two-dimensional moiré phonon polaritons

Authors: Hao Shi, Chu Li, Ding Pan, Xi Dai

Abstract: Phonon polaritons (PhPs) are hybrid light-matter modes. We investigate them in two-dimensional (2D) materials with twisted moiré structures, revealing that the moiré potential creates a new class of `moiré PhPs'. These exhibit a fundamental spectral reconstruction into multiple branches and, crucially, electromagnetic wavefunctions that are nano-patterned by the superlattice. Through numerical sim… ▽ More Phonon polaritons (PhPs) are hybrid light-matter modes. We investigate them in two-dimensional (2D) materials with twisted moiré structures, revealing that the moiré potential creates a new class of `moiré PhPs'. These exhibit a fundamental spectral reconstruction into multiple branches and, crucially, electromagnetic wavefunctions that are nano-patterned by the superlattice. Through numerical simulations based on realistic lattice models, we confirm the existence of these intriguing modes. The inherent nanoscale structuring produces a robust, spatially varying near-field response, establishing moiré superlattices as a platform for engineering light-matter interactions. △ Less

Submitted 8 September, 2025; v1 submitted 31 December, 2024; originally announced January 2025.

Journal ref: Nano Lett. 25, 15460 (2025)

Decoupling of carbonate-organic carbon isotope during the Carnian Pluvial Episode

Authors: Enhao Jia, Kui Wu, Yong Du, Yuyang Wu, Fengyu Wang, Xu Dai, Huyue Song, Daoliang Chu, Lei Zhong, Zhiwei Yuan, Xiangmin Chen, Zhe Li, Haijun Song

Abstract: The Carnian Pluvial Episode (CPE) was a major global climate change event in the early Late Triassic that significantly affected marine ecosystems and carbon cycles. One of the most prominent features of the CPE is the coupled multiple negative carbonate-organic carbon isotope excursions. However, at Erguan and Xiashulao from eastern Tethys, a decoupling between carbonate-organic carbon isotope du… ▽ More The Carnian Pluvial Episode (CPE) was a major global climate change event in the early Late Triassic that significantly affected marine ecosystems and carbon cycles. One of the most prominent features of the CPE is the coupled multiple negative carbonate-organic carbon isotope excursions. However, at Erguan and Xiashulao from eastern Tethys, a decoupling between carbonate-organic carbon isotope during CPE was observed. At the end of early Carnian (Julian), the carbonate carbon isotope showed a negative excursion of 2-3 per-mille, while the organic carbon isotope exhibited a positive excursion of about 3-4 per-mille. In addition, increased terrestrial inputs is indicated by the rising C/N (3 to 10) and decreasing Y/Ho (42 to 27) that coexist with this decoupling. The coupling of carbon isotope negative excursions is from the shallow shelves and the deep slopes, whereas the decoupling occurs from the deep shelf to the shallow slope. In the deep shelf to the shallow slope, sedimentary organic matter is mainly sourced from pelagic before the CPE as evidenced by low C/N (3) and high Y/Ho (36-42). During the CPE, the increased fresh water flux (Sr/Ba <1) enhanced terrestrial input in organic matter, which may cause positive excursions in the carbon isotope record with elevated TOC content. As a result, the carbonate-organic carbon isotope decoupled. In contrast, organic matter in sediments from the shallow shelf and deep slope are mainly from terrestrial and pelagic sources, respectively. This study reveals the significant impact of terrestrial inputs on marine carbon cycling during the Carnian Pluvial Episode, highlighting the crucial role of climate events in modifying the carbon isotope record. △ Less

Submitted 25 December, 2024; v1 submitted 18 December, 2024; originally announced December 2024.

Comments: 49 pages, 10 figures

Atmospheric Pressure Ammonia Synthesis on AuRu Catalysts Enabled by Plasmon-Controlled Hydrogenation and Nitrogen-species Desorption

Authors: Lin Yuan, Briley B. Bourgeois, Elijah Begin, Yirui Zhang, Alan X. Dai, Zhihua Cheng, Amy S. McKeown-Green, Zhichen Xue, Yi Cui, Kun Xu, Yu Wang, Matthew R. Jones, Yi Cui, Arun Majumdar, Junwei Lucas Bao, Jennifer A. Dionne

Abstract: Ammonia is a key component of fertilizer and a potential clean fuel and hydrogen carrier. The Haber-Bosch process for ammonia synthesis consumes more than half of industrial hydrogen and contributes up to ~3% of global greenhouse gas emissions. Light-driven reactions via surface plasmon resonances offer a less energy-intensive pathway for ammonia production by altering reaction intermediates. Here… ▽ More Ammonia is a key component of fertilizer and a potential clean fuel and hydrogen carrier. The Haber-Bosch process for ammonia synthesis consumes more than half of industrial hydrogen and contributes up to ~3% of global greenhouse gas emissions. Light-driven reactions via surface plasmon resonances offer a less energy-intensive pathway for ammonia production by altering reaction intermediates. Here, we report gold-ruthenium plasmonic bimetallic alloys for ammonia synthesis at room temperature and pressure, driven by visible light. We use colloidal synthesis to create AuRu$_x$ alloys (x=0.1, 0.2, 0.3) and disperse these nanoparticles on MgO supports for gas-phase ammonia synthesis. We observe a ~60 $μ$mol/g/h reactivity and ~0.12% external quantum efficiency on a AuRu$_0$$_.$$_2$ sample under 100 mW/cm$^2$ visible light. In-situ diffuse reflective infrared Fourier transform spectroscopic measurements show that hydrogenation of nitrogen adsorbates is accelerated under light compared to thermocatalysis. Combining wavelength-dependent reactivity and spectroscopic findings with semi-classical electromagnetic modeling, we show plasmonic bimetallic alloys expedite ammonia synthesis by aiding hydrogenation of adsorbed nitrogen species via plasmon-mediated hot electrons. Quantum mechanical calculations reveal hydrogen-assisted N$_2$ splitting in the excited state is key to activating the reaction under ambient conditions. Therefore, light or H$_2$ alone cannot dissociate N$_2$ -- the key bottleneck to breaking N$_2$'s triple bond. Our findings are consistent with recent hypotheses on how nitrogenase enzymes catalyze ammonia production at mild conditions and provide insights for sustainable photochemical transformations. △ Less

Submitted 2 October, 2024; originally announced October 2024.

Comments: 21 pages, 4 figures, journal article submission soon

Drone based superconducting single photon detection system with detection efficiency more than 90%

Authors: Ruoyan Ma, Zhimin Guo, Dai Chen, Xiaojun Dai, You Xiao, ChengJun Zhang, Jiamin Xiong, Jia Huang, Xingyu Zhang, Xiaoyu Liu, Liangliang Rong, Hao Li, Xiaofu Zhang, Lixing You

Abstract: Bounded by the size, weight, and power consumption (SWaP) of conventional superconducting single photon detectors (SSPD), applications of SSPDs were commonly confined in the laboratory. However, booming demands for high efficiency single photon detector incorporated with avionic platforms arise with the development of remote imaging and sensing or long-haul quantum communication without topographi… ▽ More Bounded by the size, weight, and power consumption (SWaP) of conventional superconducting single photon detectors (SSPD), applications of SSPDs were commonly confined in the laboratory. However, booming demands for high efficiency single photon detector incorporated with avionic platforms arise with the development of remote imaging and sensing or long-haul quantum communication without topographical constraints. We herein designed and manufactured the first drone based SSPD system with a SDE as high as 91.8%. This drone based SSPD system is established with high performance NbTiN SSPDs, self-developed miniature liquid helium dewar, and homemade integrated electric setups, which is able to be launched in complex topographical conditions. Such a drone based SSPD system may open the use of SSPDs for applications that demand high-SDE in complex environments. △ Less

Submitted 11 August, 2024; originally announced August 2024.

Asymmetric interaction preference induces cooperation in human-agent hybrid game

Authors: Danyang Jia, Xiangfeng Dai, Junliang Xing, Pin Tao, Yuanchun Shi, Zhen Wang

Abstract: With the development of artificial intelligence, human beings are increasingly interested in human-agent collaboration, which generates a series of problems about the relationship between agents and humans, such as trust and cooperation. This inevitably induces the inherent human characteristic that there are subjective interaction preferences for different groups, especially in human-agent hybrid… ▽ More With the development of artificial intelligence, human beings are increasingly interested in human-agent collaboration, which generates a series of problems about the relationship between agents and humans, such as trust and cooperation. This inevitably induces the inherent human characteristic that there are subjective interaction preferences for different groups, especially in human-agent hybrid systems where human-human interaction, agent-agent interaction, and human-agent interaction coexist. However, understanding how individual interaction preferences affect the cooperation of the system remains a major challenge. Therefore, this paper proposes a human-agent hybrid prisoner's dilemma game system under the framework of evolutionary game. In spatial networks, the most significant difference between agents and humans is the flexibility of decision, where humans have higher adaptive capabilities, follow link dynamics, and adopt free decision rules, which enable them to choose different strategies for different neighbors. However, agents follow node dynamics and adopt consistent decision rules, applying the same strategy to different neighbors. We give the subjective preferences of any individual to different groups, involving the interaction preferences between homogeneous groups and heterogeneous groups respectively. The simulation results show that both human and agent have asymmetric interaction preferences for groups with different identities, which can significantly improve the cooperative behavior of the system. In the hybrid system, human groups show more stable prosocial behavior. Agent groups can form highly cooperative clusters under the condition of strong interaction preference for human groups. In addition, giving agents the ability to identify opponents can effectively alleviate the interaction dilemma of agents. △ Less

Submitted 19 July, 2024; originally announced July 2024.

Journal ref: Sci China Inf Sci, 68(11) (2025): 212201

Large Language Model-Augmented Auto-Delineation of Treatment Target Volume in Radiation Therapy

Authors: Praveenbalaji Rajendran, Yong Yang, Thomas R. Niedermayr, Michael Gensheimer, Beth Beadle, Quynh-Thu Le, Lei Xing, Xianjin Dai

Abstract: Radiation therapy (RT) is one of the most effective treatments for cancer, and its success relies on the accurate delineation of targets. However, target delineation is a comprehensive medical decision that currently relies purely on manual processes by human experts. Manual delineation is time-consuming, laborious, and subject to interobserver variations. Although the advancements in artificial i… ▽ More Radiation therapy (RT) is one of the most effective treatments for cancer, and its success relies on the accurate delineation of targets. However, target delineation is a comprehensive medical decision that currently relies purely on manual processes by human experts. Manual delineation is time-consuming, laborious, and subject to interobserver variations. Although the advancements in artificial intelligence (AI) techniques have significantly enhanced the auto-contouring of normal tissues, accurate delineation of RT target volumes remains a challenge. In this study, we propose a visual language model-based RT target volume auto-delineation network termed Radformer. The Radformer utilizes a hierarichal vision transformer as the backbone and incorporates large language models to extract text-rich features from clinical data. We introduce a visual language attention module (VLAM) for integrating visual and linguistic features for language-aware visual encoding (LAVE). The Radformer has been evaluated on a dataset comprising 2985 patients with head-and-neck cancer who underwent RT. Metrics, including the Dice similarity coefficient (DSC), intersection over union (IOU), and 95th percentile Hausdorff distance (HD95), were used to evaluate the performance of the model quantitatively. Our results demonstrate that the Radformer has superior segmentation performance compared to other state-of-the-art models, validating its potential for adoption in RT practice. △ Less

Submitted 9 July, 2024; originally announced July 2024.

Preliminary Design of a General Electronics Platform for Accelerator Facilities

Authors: Jinfu Zhu, Hongli Ding, Haokui Li, Qiaoye Ran, Xiwen Dai, Wei Li, Jiawei Han, Yue Li, Zhiyuan Zhang, Weixin Qiu, Weiqing Zhang

Abstract: Many accelerators require considerable electronic systems for tests, verification, and operation. In Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), to meet the early tests and verification of various systems, save development expenses, and improve the reusability of hardware, firmware, and software systems, we have considered the needs of each system and preliminarily designed a… ▽ More Many accelerators require considerable electronic systems for tests, verification, and operation. In Shenzhen Superconducting Soft X-ray Free Electron Laser (S3FEL), to meet the early tests and verification of various systems, save development expenses, and improve the reusability of hardware, firmware, and software systems, we have considered the needs of each system and preliminarily designed a general electronics platform based on MicroTCA.4. The Advanced Mezzanine Card (AMC) will place an FPGA Mezzanine Card (FMC) that supports 500 MSPS to 2 GSPS ADC/DAC. We will design two FMC cards on the Rear Transition Module (RTM), which can be used for analog signal conditioning and waveform digitization by 10 MSPS to 250 MSPS ADC/DAC or motor control. The commercial MCH, CPU, power module, and MTCA crate are deployed. This platform can also be applied to other accelerator facilities. △ Less

Submitted 11 May, 2024; originally announced June 2024.

Comments: 3 pages, 4 figures, 2024 IEEE Real-Time Conference

An efficient method to generate near-ideal hollow beams of different shapes for box potential of quantum gases

Authors: Tongtong Ren, Yirong Wang, Xiaoyu Dai, Xiaoxu Gao, Guangren Sun, Xue Zhao, Kuiyi Gao, Zhiyue Zheng, Wei Zhang

Abstract: Ultracold quantum gases are usually prepared in conservative traps for quantum simulation experiments. The atomic density inhomogeneity, together with the consequent position-dependent energy and time scales of cold atoms in traditional harmonic traps, makes it difficult to manipulate and detect the sample at a better level. These problems are partially solved by optical box traps of blue-detuned… ▽ More Ultracold quantum gases are usually prepared in conservative traps for quantum simulation experiments. The atomic density inhomogeneity, together with the consequent position-dependent energy and time scales of cold atoms in traditional harmonic traps, makes it difficult to manipulate and detect the sample at a better level. These problems are partially solved by optical box traps of blue-detuned hollow beams. However, generating a high-quality hollow beam with high light efficiency for the box trap is challenging. Here, we present a scheme that combines the fixed optics, including axicons and prisms, to pre-shape a Gaussian beam into a hollow beam, with a digital micromirror device (DMD) to improve the quality of the hollow beam further, providing a nearly ideal optical potential of various shapes for preparing highly homogeneous cold atoms. The highest power-law exponent of potential walls can reach a value over 100, and the light efficiency from a Gaussian to a hollow beam is also improved compared to direct optical shaping by a mask or a DMD. Combined with a one-dimensional optical lattice, a nearly ideal two-dimensional uniform quantum gas with different geometrical boundaries can be prepared for exploring quantum many-body physics to an unprecedented level. △ Less

Submitted 25 April, 2024; originally announced April 2024.

Journal ref: Rev. Sci. Instrum. 95, 083202 (2024)

Excitonic Instability in Ta2Pd3Te5 Monolayer

Authors: Jingyu Yao, Haohao Sheng, Ruihan Zhang, Rongtian Pang, Jin-Jian Zhou, Quansheng Wu, Hongming Weng, Xi Dai, Zhong Fang, Zhijun Wang

Abstract: By systematic theoretical calculations, we have revealed an excitonic insulator (EI) in the Ta2Pd3Te5 monolayer. The bulk Ta2Pd3Te5 is a van der Waals (vdW) layered compound, whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy. First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke-Johnson functional. Due to… ▽ More By systematic theoretical calculations, we have revealed an excitonic insulator (EI) in the Ta2Pd3Te5 monolayer. The bulk Ta2Pd3Te5 is a van der Waals (vdW) layered compound, whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy. First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke-Johnson functional. Due to the same symmetry of the band-edge states, the two-dimensional polarization $α_{2D}$ would be finite as the band gap goes to zero, allowing for an EI state in the compound. Using the first-principles many-body perturbation theory, the GW plus Bethe-Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap, indicating the excitonic instability. The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion. Our findings suggest that the Ta2Pd3Te5 monolayer is an excitonic insulator without structural distortion. △ Less

Submitted 23 August, 2024; v1 submitted 2 January, 2024; originally announced January 2024.

Comments: 6 pages, 4 figures

Journal ref: Chinese Physics Letters 41, 097101 (2024)

High Q and high gradient performance of the first medium-temperature baking 1.3 GHz cryomodule

Authors: Jiyuan Zhai, Weimin Pan, Feisi He, Rui Ge, Zhenghui Mi, Peng Sha, Song Jin, Ruixiong Han, Qunyao Wang, Haiying Lin, Guangwei Wang, Mei Li, Minjing Sang, Liangrui Sun, Rui Ye, Tongxian Zhao, Shaopeng Li, Keyu Zhu, Baiqi Liu, Xiaolong Wang, Xiangchen Yang, Xiaojuan Bian, Xiangzhen Zhang, Huizhou Ma, Xuwen Dai , et al. (14 additional authors not shown)

Abstract: World's first 1.3 GHz cryomodule containing eight 9-cell superconducting radio-frequency (RF) cavities treated by medium-temperature furnace baking (mid-T bake) was developed, assembled and tested at IHEP for the Dalian Advanced Light Source (DALS) and CEPC R&D. The 9-cell cavities in the cryomodule achieved an unprecedented highest average Q0 of 3.8E10 at 16 MV/m and 3.6E10 at 21 MV/m in the hori… ▽ More World's first 1.3 GHz cryomodule containing eight 9-cell superconducting radio-frequency (RF) cavities treated by medium-temperature furnace baking (mid-T bake) was developed, assembled and tested at IHEP for the Dalian Advanced Light Source (DALS) and CEPC R&D. The 9-cell cavities in the cryomodule achieved an unprecedented highest average Q0 of 3.8E10 at 16 MV/m and 3.6E10 at 21 MV/m in the horizontal test. The cryomodule can operate stably up to a total CW RF voltage greater than 191 MV, with an average cavity CW accelerating gradient of more than 23 MV/m. The results significantly exceed the specifications of CEPC, DALS and the other high repetition rate free electron laser facilities (LCLS-II, LCLS-II-HE, SHINE, S3FEL). There is evidence that the mid-T bake cavity may not require fast cool-down or long processing time in the cryomodule. This paper reviews the cryomodule performance and discusses some important issues in cryomodule assembly and testing. △ Less

Submitted 2 December, 2023; originally announced December 2023.

Comments: 5 pages, 6 figures

Low-level radiofrequency system upgrade for the Dalian Coherent Light Source

Authors: H. L. Ding, J. F. Zhu, H. K. Li, J. W. Han, X. W. Dai, J. Y. Yang, W. Q. Zhang

Abstract: DCLS (Dalian Coherent Light Source) is an FEL (Free-Electron Laser) user facility at EUV (Extreme Ultraviolet). The primary accelerator of DCLS operates at a repetition rate of 20 Hz, and the beam is divided at the end of the linear accelerator through Kicker to make two 10 Hz beamlines work simultaneously. In the past year, we have completed the upgrade of the DCLS LLRF (Low-Level Radiofrequency)… ▽ More DCLS (Dalian Coherent Light Source) is an FEL (Free-Electron Laser) user facility at EUV (Extreme Ultraviolet). The primary accelerator of DCLS operates at a repetition rate of 20 Hz, and the beam is divided at the end of the linear accelerator through Kicker to make two 10 Hz beamlines work simultaneously. In the past year, we have completed the upgrade of the DCLS LLRF (Low-Level Radiofrequency) system, including setting the microwave amplitude and phase for two beamlines based on event timing, optimizing the microwave stability, and generating microwave excitation with the arbitrary shape of amplitude and phase. We added two special event codes and a repetition rate division of 10 Hz in the event timing system and set the microwave amplitude and phase by judging the event code in LLRF. The amplitude and phase stability of the microwave was improved with an intra-pulse feedforward algorithm. In addition, we have also generated microwave excitation with arbitrary amplitude and phase shapes to meet the dual beam operation in the future. Detailed information on functions or algorithms will be presented in this paper. △ Less

Submitted 24 October, 2023; originally announced November 2023.

Comments: Poster presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199)

Report number: LLRF2023/14

A low-delay reference tracking algorithm for microwave measurement and control

Authors: J. F. Zhu, H. L. Ding, H. K. Li, J. W. Han, X. W. Dai, Z. C. Chen, J. Y. Yang, W. Q. Zhang

Abstract: In FEL (Free-Electron Laser) accelerators, LLRF (Low-Level Radiofrequency) systems usually deploy feedback or feedforward algorithms requiring precise microwave measurement. The slow drift of the clock allocation network of LLRF significantly impacts the measured microwave phase, thereby affecting the stability of the closed-loop operation. The reference tracking algorithm is used to eliminate the… ▽ More In FEL (Free-Electron Laser) accelerators, LLRF (Low-Level Radiofrequency) systems usually deploy feedback or feedforward algorithms requiring precise microwave measurement. The slow drift of the clock allocation network of LLRF significantly impacts the measured microwave phase, thereby affecting the stability of the closed-loop operation. The reference tracking algorithm is used to eliminate the measurement drift. The conventional algorithm is to perform phase and amplitude demodulation on the synchronous reference signal from the main oscillator and subtract the reference phase in other measurement channels. The demodulation is usually based on the CORDIC, which requires approximately 16 clock cycles in FPGA (Field Programmable Gate Arrays). This paper uses the multiplication of complex numbers, which only requires four clock cycles of computational delay and achieves phase subtraction point by point. However, experiments show that it causes irrelevant amplitude noise to overlap and increase the amplitude measurement noise. Nevertheless, this reference tracking algorithm is suitable for control algorithms with low-delay requirements of microwave measurement. △ Less

Submitted 24 October, 2023; originally announced November 2023.

Comments: Poster presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199)

Report number: LLRF2023/18

The microwave amplitude and phase setting based on event timing for the DCLS

Authors: J. F. Zhu, H. L. Ding, H. K. Li, J. W. Han, X. W. Dai, B. Xu, L. Shi, J. Y. Yang, W. Q. Zhang

Abstract: The primary accelerator of DCLS (Dalian Coherent Light Source) operates at a repetition rate of 20 Hz now, and the beam is divided at the end of the linear accelera-tor through Kicker to make two 10 Hz beamlines work simultaneously. For the simultaneous emission FEL of two beamlines, the beam energy of the two beamlines is required to be controlled independently, so we need to set the amplitude an… ▽ More The primary accelerator of DCLS (Dalian Coherent Light Source) operates at a repetition rate of 20 Hz now, and the beam is divided at the end of the linear accelera-tor through Kicker to make two 10 Hz beamlines work simultaneously. For the simultaneous emission FEL of two beamlines, the beam energy of the two beamlines is required to be controlled independently, so we need to set the amplitude and phase of each beamline. This paper implements a microwave amplitude and phase setting function based on event timing. We upgraded the EVG/EVR event timing system and LLRF (Low-Level Radiofrequency) system. Two special event codes and a repetition rate division of 10 Hz are added to the event timing system, and we can set the microwave amplitude and phase by judging the event code in LLRF. We ulti-mately perform the microwave triggering at a repetition rate of 10 Hz for each beamline and validate this function through beam experiments. △ Less

Submitted 24 October, 2023; originally announced November 2023.

Comments: Poster presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199)

Report number: LLRF2023/19

Implementation of microwave with arbitrary amplitude and phase for the DCLS

Authors: H. K. Li, H. L. Ding, Y. Li, J. F. Zhu, J. W. Han, X. W. Dai, J. Y. Yang, W. Q. Zhang

Abstract: In many experiments, the simultaneous emission of multiple wavelengths of FEL (Free-Electron Laser) is significant. For the pulsed-mode FEL facility, we must accelerate multiple electron beams in one microwave pulse, and they may be in different amplitudes and phases in the acceleration field. Therefore, we implement a microwave excitation, whose amplitude and phase have arbitrary shapes in the LL… ▽ More In many experiments, the simultaneous emission of multiple wavelengths of FEL (Free-Electron Laser) is significant. For the pulsed-mode FEL facility, we must accelerate multiple electron beams in one microwave pulse, and they may be in different amplitudes and phases in the acceleration field. Therefore, we implement a microwave excitation, whose amplitude and phase have arbitrary shapes in the LLRF (Low-Level Radiofrequency) system. We generate a microwave pulse with step-shaped amplitude and phase for dual beam operation in DCLS (Dalian Coherent Light Source). The microwave system of the primary accelerator has four pulsed LLRF devices, which output excitation to drive four solid-state amplifiers and then excite two 50 MW and two 80 MW klystrons, respectively. Preliminary experiments have shown that this step-shaped microwave can be used for the DCLS twin-bunch operation. △ Less

Submitted 24 October, 2023; originally announced October 2023.

Comments: Poster presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199)

Report number: LLRF2023/20

An Intra-pulse feedforward algorithm for improving pulsed microwave stability

Authors: J. W. Han, H. L. Ding, J. F. Zhu, H. K. Li, X. W. Dai, J. Y. Yang, W. Q. Zhang

Abstract: During the pulsed operation of the linear accelerator in DCLS (Dalian Coherent Light Source), we found a strong correlation between the klystron modulator's high voltage and the klystron output microwave, with noticeable jitter among adjacent microwaves. Therefore, we propose an intra-pulse feedforward algorithm and implement it in LLRF (Low-Level Radiofrequency) systems. This algorithm assumes th… ▽ More During the pulsed operation of the linear accelerator in DCLS (Dalian Coherent Light Source), we found a strong correlation between the klystron modulator's high voltage and the klystron output microwave, with noticeable jitter among adjacent microwaves. Therefore, we propose an intra-pulse feedforward algorithm and implement it in LLRF (Low-Level Radiofrequency) systems. This algorithm assumes that the transfer model of the microwave system is linear within a small range of work points and measures the transfer coefficient of the microwave between the LLRF and klystron. For each pulsed microwave of the klystron output, the LLRF system first calculates the vector deviation between the initial measurement within its pulse and the target. The deviation will be compensated in the LLRF excitation so that the jitter in the later part of the pulsed microwave is suppressed. Experiments have shown that this algorithm can effectively suppress the jitter among adjacent microwaves, e.g., improving the amplitude and phase stability (RMS) from 0.11%/0.2° to 0.1%/0.05°. This algorithm can also be applied to other accelerators operating in pulsed modes. △ Less

Submitted 24 October, 2023; originally announced October 2023.

Comments: Talk presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199)

Report number: LLRF2023/17

Interactive diversity disrupts cyclic dominance but maintains cooperation in spatial social dilemma games

Authors: Danyang Jia, Chen Shen, Xiangfeng Dai, Junliang Xing, Pin Tao, Yuanchun Shi, Zhen Wang

Abstract: Cyclic dominance has become a pivotal factor in sustaining cooperation within structured populations. However, this comprehension has predominantly revolved around node dynamics, where players are confined to employing the same strategy with all their neighbors. What has been largely overlooked is the profound influence of interactive diversity, where players can adapt distinct responses to differ… ▽ More Cyclic dominance has become a pivotal factor in sustaining cooperation within structured populations. However, this comprehension has predominantly revolved around node dynamics, where players are confined to employing the same strategy with all their neighbors. What has been largely overlooked is the profound influence of interactive diversity, where players can adapt distinct responses to different neighbors, on the dynamics of cyclic dominance and the broader patterns of cooperation. This investigation delves into the often-neglected role of interactive diversity in cyclic dominance and cooperation, utilizing a volunteer prisoner's dilemma model deployed on various network structures. Within this framework, we differentiate between `node players,' who adhere to a consistent strategy with all their neighbors, and `link players,' who adjust their strategies based on specific interactions, influenced by both direct and indirect emotional factors. Direct emotion governs the strategy between two interacting players, while indirect emotion encompasses the impact of third-party influences on strategic decisions. Through Monte Carlo simulations, we unveil a multifaceted relationship: interactive diversity generally disrupts cyclic dominance, yet its impact on cooperation varies, contingent on the prevalence of indirect strategy formulation. These findings suggest that the significance of cyclic dominance in fostering cooperation may have been overemphasized, as cooperation can persist even in the absence of strong cyclic dominance, owing to the presence of interactive diversity. △ Less

Submitted 26 September, 2023; originally announced September 2023.

Journal ref: Knowledge-Based Systems 299 (2024): 111962

Solvable BCS-Hubbard Liouvillians in arbitrary dimensions

Authors: Xu-Dong Dai, Fei Song, Zhong Wang

Abstract: We present the construction of a solvable Lindblad model in arbitrary dimensions, wherein the Liouvillian can be mapped to a BCS-Hubbard model featuring an imaginary interaction. The Hilbert space of the system can be divided into multiple sectors, each characterized by an onsite invariant configuration. The model exhibits bistable steady states in all spatial dimensions, which is guaranteed by th… ▽ More We present the construction of a solvable Lindblad model in arbitrary dimensions, wherein the Liouvillian can be mapped to a BCS-Hubbard model featuring an imaginary interaction. The Hilbert space of the system can be divided into multiple sectors, each characterized by an onsite invariant configuration. The model exhibits bistable steady states in all spatial dimensions, which is guaranteed by the fermion-number parity. Notably, the Liouvillian gap exhibits a Zeno transition, below which the Liouvillian gap is linear with respect to the dissipation. We also uncover a generic dimension-dependent gap behavior: In one dimension, the gap originates from multiple sectors with spectral crossing; in higher dimensions, a single sector determines the gap. △ Less

Submitted 14 September, 2023; v1 submitted 22 June, 2023; originally announced June 2023.

Comments: 7 pages, 2 figures

Journal ref: Phys. Rev. B 108, 115127 (2023)

The LHCb upgrade I

Authors: LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, C. Achard, T. Ackernley, B. Adeva, M. Adinolfi, P. Adlarson, H. Afsharnia, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, Z. Aliouche, P. Alvarez Cartelle, R. Amalric, S. Amato , et al. (1298 additional authors not shown)

Abstract: The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their select… ▽ More The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software. △ Less

Submitted 10 September, 2024; v1 submitted 17 May, 2023; originally announced May 2023.

Comments: All figures and tables, along with any supplementary material and additional information, are available at http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-DP-2022-002.html (LHCb public pages)

Report number: LHCb-DP-2022-002

Journal ref: JINST 19 (2024) P05065

Super-Resolution Imaging via Angular Magnification

Authors: Yi Zhou, Dingpeng Liao, Kun Zhang, Zijie Ma, Shikai Wu, Jun Ma, Xuemei Dai, Zhengguo Shang, Zhongquan Wen, Gang Chen

Abstract: The far-field resolution of optical imaging systems is restricted by the Abbe diffraction limit, a direct result of the wave nature of light. One successful technological approach to circumventing this limit is to reduce the effective size of a point-spread-function. In the past decades, great endeavors have been made to engineer an effective point-spread-function by exploiting different mechanism… ▽ More The far-field resolution of optical imaging systems is restricted by the Abbe diffraction limit, a direct result of the wave nature of light. One successful technological approach to circumventing this limit is to reduce the effective size of a point-spread-function. In the past decades, great endeavors have been made to engineer an effective point-spread-function by exploiting different mechanisms, including optical nonlinearities and structured light illumination. However, these methods are hard to be applied to objects in a far distance. Here, we propose a new way to achieve super-resolution in a far field by utilizing angular magnification. We present the first proof-of-concept demonstration of such an idea and demonstrate a new class of lenses with angular magnification for far-field super-resolution imaging. Both theoretical and experimental results demonstrate a more than two-fold enhancement beyond the angular-resolution limit in the far-field imaging. The proposed approach can be applied to super-resolution imaging of objects in far distance. It has promising potential applications in super-resolution telescopes and remote sensing. △ Less

Submitted 17 May, 2023; originally announced May 2023.

Tensorial tomographic Fourier Ptychography with applications to muscle tissue imaging

Authors: Shiqi Xu, Xiang Dai, Paul Ritter, Kyung Chul Lee, Xi Yang, Lucas Kreiss, Kevin C. Zhou, Kanghyun Kim, Amey Chaware, Jadee Neff, Carolyn Glass, Seung Ah Lee, Oliver Friedrich, Roarke Horstmeyer

Abstract: We report Tensorial tomographic Fourier Ptychography (ToFu), a new non-scanning label-free tomographic microscopy method for simultaneous imaging of quantitative phase and anisotropic specimen information in 3D. Built upon Fourier Ptychography, a quantitative phase imaging technique, ToFu additionally highlights the vectorial nature of light. The imaging setup consists of a standard microscope equ… ▽ More We report Tensorial tomographic Fourier Ptychography (ToFu), a new non-scanning label-free tomographic microscopy method for simultaneous imaging of quantitative phase and anisotropic specimen information in 3D. Built upon Fourier Ptychography, a quantitative phase imaging technique, ToFu additionally highlights the vectorial nature of light. The imaging setup consists of a standard microscope equipped with an LED matrix, a polarization generator, and a polarization-sensitive camera. Permittivity tensors of anisotropic samples are computationally recovered from polarized intensity measurements across three dimensions. We demonstrate ToFu's efficiency through volumetric reconstructions of refractive index, birefringence, and orientation for various validation samples, as well as tissue samples from muscle fibers and diseased heart tissue. Our reconstructions of muscle fibers resolve their 3D fine-filament structure and yield consistent morphological measurements compared to gold-standard second harmonic generation scanning confocal microscope images found in the literature. Additionally, we demonstrate reconstructions of a heart tissue sample that carries important polarization information for detecting cardiac amyloidosis. △ Less

Submitted 13 May, 2023; v1 submitted 8 May, 2023; originally announced May 2023.

Journal ref: Tensorial tomographic Fourier Ptychography with applications to muscle tissue imaging, Adv. Photon. 6(2), 026004 (2024)

Stiefel-Whitney topological charges in a three-dimensional acoustic nodal-line crystal

Authors: Haoran Xue, Z. Y. Chen, Zheyu Cheng, J. X. Dai, Yang Long, Y. X. Zhao, Baile Zhang

Abstract: Band topology of materials describes the extent Bloch wavefunctions are twisted in momentum space. Such descriptions rely on a set of topological invariants, generally referred to as topological charges, which form a characteristic class in the mathematical structure of fiber bundles associated with the Bloch wavefunctions. For example, the celebrated Chern number and its variants belong to the Ch… ▽ More Band topology of materials describes the extent Bloch wavefunctions are twisted in momentum space. Such descriptions rely on a set of topological invariants, generally referred to as topological charges, which form a characteristic class in the mathematical structure of fiber bundles associated with the Bloch wavefunctions. For example, the celebrated Chern number and its variants belong to the Chern class, characterizing topological charges for complex Bloch wavefunctions. Nevertheless, under the space-time inversion symmetry, Bloch wavefunctions can be purely real in the entire momentum space; consequently, their topological classification does not fall into the Chern class, but requires another characteristic class known as the Stiefel-Whitney class. Here, in a three-dimensional acoustic crystal, we demonstrate a topological nodal-line semimetal that is characterized by a doublet of topological charges, the first and second Stiefel-Whitney numbers, simultaneously. Such a doubly charged nodal line gives rise to a doubled bulk-boundary correspondence: while the first Stiefel-Whitney number induces ordinary drumhead states of the nodal line, the second Stiefel-Whitney number supports hinge Fermi arc states at odd inversion-related pairs of hinges. These results establish the Stiefel-Whitney topological charges as intrinsic topological invariants for topological materials, with their unique bulk-boundary correspondence beyond the conventional framework of topological band theory. △ Less

Submitted 13 April, 2023; originally announced April 2023.

Comments: 12 pages, 10 figures

Journal ref: Nat. Commun. 14, 4563 (2023)

Sensitivity-Tunable Terahertz Liquid/Gas Biosensor Based on Surface Plasmon Resonance with Dirac Semimetal

Authors: Mengjiao Ren, Chengpeng Ji, Xueyan Tang, Haishan Tian, Leyong Jiang, Xiaoyu Dai, Xinghua Wu

Abstract: In this paper, we study the sensitivity-tunable Terahertz (THz) liquid/gas biosensor in a coupling prism-three-dimensional Dirac semimetal (3D DSM) multilayer structure. The high sensitivity of the biosensor originates from the sharp reflected peak caused by surface plasmon resonance (SPR) mode. This structure achieves the tunability of sensitivity due to that the reflectance could be modulated by… ▽ More In this paper, we study the sensitivity-tunable Terahertz (THz) liquid/gas biosensor in a coupling prism-three-dimensional Dirac semimetal (3D DSM) multilayer structure. The high sensitivity of the biosensor originates from the sharp reflected peak caused by surface plasmon resonance (SPR) mode. This structure achieves the tunability of sensitivity due to that the reflectance could be modulated by the Fermi energy of 3D DSM. Besides, it is found that the sensitivity curve depends heavily on the structural parameters of 3D DSM. After parameter optimization, we obtained sensitivity over 100°/RIU for liquid biosensor. We believe this simple structure provides a reference idea for realizing high sensitivity and tunable biosensor device. △ Less

Submitted 12 April, 2023; originally announced April 2023.

Comments: 17 pages, 3798 figures

STCF Conceptual Design Report: Volume 1 -- Physics & Detector

Authors: M. Achasov, X. C. Ai, R. Aliberti, L. P. An, Q. An, X. Z. Bai, Y. Bai, O. Bakina, A. Barnyakov, V. Blinov, V. Bobrovnikov, D. Bodrov, A. Bogomyagkov, A. Bondar, I. Boyko, Z. H. Bu, F. M. Cai, H. Cai, J. J. Cao, Q. H. Cao, Z. Cao, Q. Chang, K. T. Chao, D. Y. Chen, H. Chen , et al. (413 additional authors not shown)

Abstract: The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII,… ▽ More The Super $τ$-Charm facility (STCF) is an electron-positron collider proposed by the Chinese particle physics community. It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of $0.5\times 10^{35}{\rm cm}^{-2}{\rm s}^{-1}$ or higher. The STCF will produce a data sample about a factor of 100 larger than that by the present $τ$-Charm factory -- the BEPCII, providing a unique platform for exploring the asymmetry of matter-antimatter (charge-parity violation), in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions, as well as searching for exotic hadrons and physics beyond the Standard Model. The STCF project in China is under development with an extensive R\&D program. This document presents the physics opportunities at the STCF, describes conceptual designs of the STCF detector system, and discusses future plans for detector R\&D and physics case studies. △ Less

Submitted 5 October, 2023; v1 submitted 28 March, 2023; originally announced March 2023.

Journal ref: Front. Phys. 19(1), 14701 (2024)

An extended plane wave framework for the electronic structure calculations of twisted bilayer material systems

Authors: Xiaoying Dai, Aihui Zhou, Yuzhi Zhou

Abstract: In this paper, we propose an extended plane wave framework to make the electronic structure calculations of the twisted bilayer 2D material systems practically feasible. Based on the foundation in [Y. Zhou, H. Chen, A. Zhou, J. Comput. Phys. 384, 99 (2019)], following extensions take place: (1) an tensor-producted basis set, which adopts PWs in the incommensurate dimensions, and localized basis in… ▽ More In this paper, we propose an extended plane wave framework to make the electronic structure calculations of the twisted bilayer 2D material systems practically feasible. Based on the foundation in [Y. Zhou, H. Chen, A. Zhou, J. Comput. Phys. 384, 99 (2019)], following extensions take place: (1) an tensor-producted basis set, which adopts PWs in the incommensurate dimensions, and localized basis in the interlayer dimension, (2) a practical application of a novel cutoff techniques we have recently developed, and (3) a quasi-band structure picture under the small twisted angles and weak interlayer coupling limits. With (1) and (2) now the dimensions of Hamiltonian matrix are reduced by about 2 orders of magnitude compared with the original framework. And (3) enables us to better organize the calculations and understand the results. For numerical examples, we study the electronic structures of the linear bilayer graphene lattice system with the magic twisted angle ($\sim 1.05^{\circ}$). The famous flat bands have been reproduced with their features in quantitative agreement with those from experiments and other theoretical calculations. Moreover, the extended framework has much less computational cost compared to the commensurate cell approximations, and is more extendable compared to the traditional model hamiltonians and tight binding models. Finally this framework can readily accommodate nonlinear models thus will laid the foundations for more effective yet accurate Density Functional Theory (DFT) calculations. △ Less

Submitted 3 January, 2023; originally announced January 2023.

A Method to Load Tellurium in Liquid Scintillator for the Study of Neutrinoless Double Beta Decay

Authors: D. J. Auty, D. Bartlett, S. D. Biller, D. Chauhan, M. Chen, O. Chkvorets, S. Connolly, X. Dai, E. Fletcher, K. Frankiewicz, D. Gooding, C. Grant, S. Hall, D. Horne, S. Hans, B. Hreljac, T. Kaptanoglu, B. Krar, C. Kraus, T. Kroupova', I. Lam, Y. Liu, S. Maguire, C. Miller, S. Manecki , et al. (12 additional authors not shown)

Abstract: A method has been developed to load tellurium into liquid scintillator so as to permit searches for neutrinoless double beta decay with high sensitivity. The approach involves the synthesis of an oil-soluble tellurium compound from telluric acid and an organic diol. The process utilises distillable chemicals that can be safely handled underground and affords low radioactive backgrounds, low optica… ▽ More A method has been developed to load tellurium into liquid scintillator so as to permit searches for neutrinoless double beta decay with high sensitivity. The approach involves the synthesis of an oil-soluble tellurium compound from telluric acid and an organic diol. The process utilises distillable chemicals that can be safely handled underground and affords low radioactive backgrounds, low optical absorption and high light yields at loading levels of at least several percent Te by weight. △ Less

Submitted 4 April, 2023; v1 submitted 23 December, 2022; originally announced December 2022.

Comments: 15 pages, 12 figures

Journal ref: Nuclear Inst. and Methods in Physics Research, A 1051 (2023) 168204

Truncated atomic plane wave method for the subband structure calculations of Moiré systems

Authors: Wangqian Miao, Chu Li, Xu Han, Ding Pan, Xi Dai

Abstract: We propose a highly efficient and accurate numerical scheme named Truncated Atomic Plane Wave (TAPW) method to determine the subband structure of Twisted Bilayer Graphene (TBG) inspired by BM model. Our method utilizes real space information of carbon atoms in the moiré unit cell and projects the full tight binding Hamiltonian into a much smaller subspace using atomic plane waves. We present accur… ▽ More We propose a highly efficient and accurate numerical scheme named Truncated Atomic Plane Wave (TAPW) method to determine the subband structure of Twisted Bilayer Graphene (TBG) inspired by BM model. Our method utilizes real space information of carbon atoms in the moiré unit cell and projects the full tight binding Hamiltonian into a much smaller subspace using atomic plane waves. We present accurate electronic band structures of TBG in a wide range of twist angles together with detailed moiré potential and screened Coulomb interaction at the first magic angle using our new method. Furthermore, we generalize our formalism to solve the problem of low frequency moiré phonons in TBG. △ Less

Submitted 15 February, 2023; v1 submitted 5 October, 2022; originally announced October 2022.

Landmark Tracking in Liver US images Using Cascade Convolutional Neural Networks with Long Short-Term Memory

Authors: Yupei Zhang, Xianjin Dai, Zhen Tian, Yang Lei, Jacob F. Wynne, Pretesh Patel, Yue Chen, Tian Liu, Xiaofeng Yang

Abstract: This study proposed a deep learning-based tracking method for ultrasound (US) image-guided radiation therapy. The proposed cascade deep learning model is composed of an attention network, a mask region-based convolutional neural network (mask R-CNN), and a long short-term memory (LSTM) network. The attention network learns a mapping from a US image to a suspected area of landmark motion in order t… ▽ More This study proposed a deep learning-based tracking method for ultrasound (US) image-guided radiation therapy. The proposed cascade deep learning model is composed of an attention network, a mask region-based convolutional neural network (mask R-CNN), and a long short-term memory (LSTM) network. The attention network learns a mapping from a US image to a suspected area of landmark motion in order to reduce the search region. The mask R-CNN then produces multiple region-of-interest (ROI) proposals in the reduced region and identifies the proposed landmark via three network heads: bounding box regression, proposal classification, and landmark segmentation. The LSTM network models the temporal relationship among the successive image frames for bounding box regression and proposal classification. To consolidate the final proposal, a selection method is designed according to the similarities between sequential frames. The proposed method was tested on the liver US tracking datasets used in the Medical Image Computing and Computer Assisted Interventions (MICCAI) 2015 challenges, where the landmarks were annotated by three experienced observers to obtain their mean positions. Five-fold cross-validation on the 24 given US sequences with ground truths shows that the mean tracking error for all landmarks is 0.65+/-0.56 mm, and the errors of all landmarks are within 2 mm. We further tested the proposed model on 69 landmarks from the testing dataset that has a similar image pattern to the training pattern, resulting in a mean tracking error of 0.94+/-0.83 mm. Our experimental results have demonstrated the feasibility and accuracy of our proposed method in tracking liver anatomic landmarks using US images, providing a potential solution for real-time liver tracking for active motion management during radiation therapy. △ Less

Submitted 14 September, 2022; originally announced September 2022.

The Quadruplon in a Monolayer Semiconductor

Authors: Jiacheng Tang, Hao Sun, Qiyao Zhang, Xingcan Dai, Zhen Wang, Cun-Zheng Ning

Abstract: Understanding the structure of matter or materials and interaction or correlations among the constituent elementary particles are the central tasks of all branches of science, from physics, chemistry, to biology. In physics, this ultimate goal has spurred a constant search for high-order correlated entities or composite particles for nearly all states and forms of matter, from elementary particles… ▽ More Understanding the structure of matter or materials and interaction or correlations among the constituent elementary particles are the central tasks of all branches of science, from physics, chemistry, to biology. In physics, this ultimate goal has spurred a constant search for high-order correlated entities or composite particles for nearly all states and forms of matter, from elementary particles, nuclei, cold atoms, to condensed matter. So far, such composite particles involving two or three constituent particles have been experimentally identified, such as the Cooper pairs, excitons, and trions in condensed matter physics, or diquarks and mesons in quantum chromodynamics. Although the four-body irreducible entities have long been predicted theoretically in a variety of materials systems alternatively as quadruplons, quadrons, or quartets, the closely related experimental observation so far seems to be restricted to the field of elementary particles (e.g. the recent tetraquark at CERN) only. In this article, we present the first experimental evidence for the existence of a four-body irreducible entity, the quadruplon, involving two electrons and two holes in a monolayer of Molybdenum Ditelluride. Using the optical pump-probe technique, we discovered a series of new spectral features that are distinct from those of trions and bi-excitons. By solving the four-body Bethe-Salpeter equation in conjunction with the cluster expansion approach, we are able to explain these spectral features in terms of the four-body irreducible cluster or the quadruplons. In contrast to a bi-exciton which consists of two weakly bound excitons, a quadruplon consists of two electrons and two holes without the presence of an exciton. △ Less

Submitted 4 May, 2024; v1 submitted 26 July, 2022; originally announced July 2022.

Highly fabrication tolerant InP based polarization beam splitter based on p-i-n structure

Authors: Nicolás Abadía, Xiangyang Dai, Qiaoyin Lu, Wei-Hua Guo, David Patel, David V. Plant, John F. Donegan

Abstract: In this work, a novel highly fabrication tolerant polarization beam splitter (PBS) is presented on an InP platform. To achieve the splitting, we combine the Pockels effect and the plasma dispersion effect in a symmetric 1x2 Mach-Zehnder interferometer (MZI). One p-i-n phase shifter of the MZI is driven in forward bias to exploit the plasma dispersion effect and modify the phase of both the TE and… ▽ More In this work, a novel highly fabrication tolerant polarization beam splitter (PBS) is presented on an InP platform. To achieve the splitting, we combine the Pockels effect and the plasma dispersion effect in a symmetric 1x2 Mach-Zehnder interferometer (MZI). One p-i-n phase shifter of the MZI is driven in forward bias to exploit the plasma dispersion effect and modify the phase of both the TE and TM mode. The other arm of the MZI is driven in reverse bias to exploit the Pockels effect which affects only the TE mode. By adjusting the voltages of the two phase shifters, a different interference condition can be set for the TE and the TM modes thereby splitting them at the output of the MZI. By adjusting the voltages, the very tight fabrication tolerances known for fully passive PBS are eased. The experimental results show that an extinction ratio better than 15 dB and an on-chip loss of 3.5 dB over the full C-band (1530-1565nm) are achieved. △ Less

Submitted 19 July, 2022; v1 submitted 27 April, 2022; originally announced April 2022.

Comments: 8 pages, 7 figures, and 2 tables. Published version: see https://doi.org/10.1364/OE.25.010070. Related works: see https://doi.org/10.1364/OE.22.011236, https://doi.org/10.1364/oe.26.030292, and https://doi.org/10.1063/5.0044490. Keywords: Photonic Integrated Circuits; Integrated Optics Devices; Beam Splitters; Polarization-Selective Devices

Journal ref: Opt. Express 25, 10070-10077 (2017)

Tensorial tomographic differential phase-contrast microscopy

Authors: Shiqi Xu, Xiang Dai, Xi Yang, Kevin C. Zhou, Kanghyun Kim, Vinayak Pathak, Carolyn Glass, Roarke Horstmeyer

Abstract: We report Tensorial Tomographic Differential Phase-Contrast microscopy (T2DPC), a quantitative label-free tomographic imaging method for simultaneous measurement of phase and anisotropy. T2DPC extends differential phase-contrast microscopy, a quantitative phase imaging technique, to highlight the vectorial nature of light. The method solves for permittivity tensor of anisotropic samples from inten… ▽ More We report Tensorial Tomographic Differential Phase-Contrast microscopy (T2DPC), a quantitative label-free tomographic imaging method for simultaneous measurement of phase and anisotropy. T2DPC extends differential phase-contrast microscopy, a quantitative phase imaging technique, to highlight the vectorial nature of light. The method solves for permittivity tensor of anisotropic samples from intensity measurements acquired with a standard microscope equipped with an LED matrix, a circular polarizer, and a polarization-sensitive camera. We demonstrate accurate volumetric reconstructions of refractive index, birefringence, and orientation for various validation samples, and show that the reconstructed polarization structures of a biological specimen are predictive of pathology. △ Less

Submitted 6 September, 2022; v1 submitted 24 April, 2022; originally announced April 2022.

A three-dimensional dynamic mode decomposition analysis of wind farm flow aerodynamics

Authors: Xuan Dai, Da Xu, Mengqi Zhang, Richard J. A. M. Stevens

Abstract: High-fidelity large-eddy simulations are suitable to obtain insight into the complex flow dynamics in extended wind farms. In order to better understand these flow dynamics, we use dynamic mode decomposition (DMD) to analyze and reconstruct the flow field in large-scale numerically simulated wind farms by large-eddy simulations (LES). Different wind farm layouts are considered, and we find that a… ▽ More High-fidelity large-eddy simulations are suitable to obtain insight into the complex flow dynamics in extended wind farms. In order to better understand these flow dynamics, we use dynamic mode decomposition (DMD) to analyze and reconstruct the flow field in large-scale numerically simulated wind farms by large-eddy simulations (LES). Different wind farm layouts are considered, and we find that a combination of horizontal and vertical staggering leads to improved wind farm performance compared to traditional horizontal staggering. We analyze the wind farm flows using the amplitude selection (AP) and sparsity-promoting (SP method) DMD approach. We find that the AP method tends to select modes with a small length scale and a high frequency, while the SP method selects large coherent structures with low frequency. The latter are somewhat reminiscent of modes obtained using proper orthogonal decomposition (POD). We find that a relatively limited number of SP-DMD modes is sufficient to accurately reconstruct the flow field in the entire wind farm, whereas the AP-DMD method requires more modes to achieve an accurate reconstruction. Thus, the SP-DMD method has a smaller performance loss compared to the AP-DMD method in terms of the reconstruction of the flow field. △ Less

Submitted 24 April, 2022; originally announced April 2022.

On The Low Speed Limits of Lorentz's Transformation

Authors: Hao Chen, Wei E. I. Sha, Xi Dai, Yue Yu

Abstract: This article contains a digest of the theory of electromagnetism and a review of the transformation between inertial frames, especially under low speed limits. The covariant nature of the Maxwell's equations is explained using the conventional language. We show that even under low speed limits, the relativistic effects should not be neglected to get a self-consistent theory of the electromagnetic… ▽ More This article contains a digest of the theory of electromagnetism and a review of the transformation between inertial frames, especially under low speed limits. The covariant nature of the Maxwell's equations is explained using the conventional language. We show that even under low speed limits, the relativistic effects should not be neglected to get a self-consistent theory of the electromagnetic fields, unless the intrinsic dynamics of these fields has been omitted completely. The quasi-static limits, where the relativistic effects can be partly neglected are also reviewed, to clarify some common misunderstandings and imprecise use of the theory in presence of moving media and other related situations. The discussion presented in this paper provide a clear view of why classical electromagnetic theory is relativistic in its essence. △ Less

Submitted 30 April, 2022; v1 submitted 17 February, 2022; originally announced February 2022.

Comments: 8+10 pages

Journal ref: Progress In Electromagnetics Research, Vol. 174, 1-22, 2022

Convergent and orthogonality preserving schemes for approximating the Kohn-Sham orbitals

Authors: Xiaoying Dai, Liwei Zhang, Aihui Zhou

Abstract: To obtain convergent numerical approximations without using any orthogonalization operations is of great importance in electronic structure calculations. In this paper, we propose and analyze a class of iteration schemes for the discretized Kohn- Sham Density Functional Theory model, with which the iterative approximations are guaranteed to converge to the Kohn-Sham orbitals exponentially without… ▽ More To obtain convergent numerical approximations without using any orthogonalization operations is of great importance in electronic structure calculations. In this paper, we propose and analyze a class of iteration schemes for the discretized Kohn- Sham Density Functional Theory model, with which the iterative approximations are guaranteed to converge to the Kohn-Sham orbitals exponentially without any orthogonalization as long as the initial orbitals are orthogonal and the time step sizes are given properly. In addition, we present a feasible and efficient approach to get suitable time step sizes and report some numerical experiments to validate our theory. △ Less

Submitted 27 September, 2022; v1 submitted 2 November, 2021; originally announced November 2021.

Comments: 25 pages, 3 Figures and 1 table

MSC Class: 37M05; 81Q05; 81Q35

Quantitative Jones matrix imaging using vectorial Fourier ptychography

Authors: Xiang Dai, Shiqi Xu, Xi Yang, Kevin C. Zhou, Carolyn Glass, Pavan Chandra Konda, Roarke Horstmeyer

Abstract: This paper presents a microscopic imaging technique that uses variable-angle illumination to recover the complex polarimetric properties of a specimen at high resolution and over a large field-of-view. The approach extends Fourier ptychography, which is a synthetic aperture-based imaging approach to improve resolution with phaseless measurements, to additionally account for the vectorial nature of… ▽ More This paper presents a microscopic imaging technique that uses variable-angle illumination to recover the complex polarimetric properties of a specimen at high resolution and over a large field-of-view. The approach extends Fourier ptychography, which is a synthetic aperture-based imaging approach to improve resolution with phaseless measurements, to additionally account for the vectorial nature of light. After images are acquired using a standard microscope outfitted with an LED illumination array and two polarizers, our vectorial Fourier Ptychography (vFP) algorithm solves for the complex 2x2 Jones matrix of the anisotropic specimen of interest at each resolved spatial location. We introduce a new sequential Gauss-Newton-based solver that additionally jointly estimates and removes polarization-dependent imaging system aberrations. We demonstrate effective vFP performance by generating large-area (29 mm$^2$), high-resolution (1.24 $μ$m full-pitch) reconstructions of sample absorption, phase, orientation, diattenuation, and retardance for a variety of calibration samples and biological specimens. △ Less

Submitted 15 October, 2021; v1 submitted 30 September, 2021; originally announced October 2021.

An optical biomimetic eyes with interested object imaging

Authors: Jun Li, Shimei Chen, Shangyuan Wang, Miao Lei, Xiaofang Dai, Chuangxue Liang, Kunyuan Xu, Shuxin Lin, Yuhui Li, Yuer Fan, Ting Zhong

Abstract: We presented an optical system to perform imaging interested objects in complex scenes, like the creature easy see the interested prey in the hunt for complex environments. It utilized Deep-learning network to learn the interested objects's vision features and designed the corresponding "imaging matrices", furthermore the learned matrixes act as the measurement matrix to complete compressive imagi… ▽ More We presented an optical system to perform imaging interested objects in complex scenes, like the creature easy see the interested prey in the hunt for complex environments. It utilized Deep-learning network to learn the interested objects's vision features and designed the corresponding "imaging matrices", furthermore the learned matrixes act as the measurement matrix to complete compressive imaging with a single-pixel camera, finally we can using the compressed image data to only image the interested objects without the rest objects and backgrounds of the scenes with the previous Deep-learning network. Our results demonstrate that no matter interested object is single feature or rich details, the interference can be successfully filtered out and this idea can be applied in some common applications that effectively improve the performance. This bio-inspired optical system can act as the creature eye to achieve success on interested-based object imaging, object detection, object recognition and object tracking, etc. △ Less

Submitted 8 August, 2021; originally announced August 2021.

Comments: 19pages,7 figures,3 tables

Contrarians synchronize beyond the limit of pairwise interactions

Authors: K. Kovalenko, X. Dai, K. Alfaro-Bittner, A. M. Raigorodskii, M. Perc, S. Boccaletti

Abstract: We give evidence that a population of pure contrarians globally coupled D-dimensional Kuramoto oscillators reaches a collective synchronous state when the interplay between the units goes beyond the limit of pairwise interactions. Namely, we will show that the presence of higher order interactions may induce the appearance of a coherent state even when the oscillators are coupled negatively to the… ▽ More We give evidence that a population of pure contrarians globally coupled D-dimensional Kuramoto oscillators reaches a collective synchronous state when the interplay between the units goes beyond the limit of pairwise interactions. Namely, we will show that the presence of higher order interactions may induce the appearance of a coherent state even when the oscillators are coupled negatively to the mean field. An exact solution for the description of the microscopic dynamics for forward and backward transitions is provided, which entails imperfect symmetry breaking of the population into a frequency-locked state featuring two clusters of different instantaneous phases. Our results contribute to a better understanding of the powerful potential of group interactions entailing multi-dimensional choices and novel dynamical states in many circumstances, such as in social systems. △ Less

Submitted 7 November, 2021; v1 submitted 8 July, 2021; originally announced July 2021.

Comments: 12 pages, 5 figures; accepted for publication in Physical Review Letters

Journal ref: Phys. Rev. Lett. 127, 258301 (2021)

The SNO+ Experiment

Authors: SNO+ Collaboration, :, V. Albanese, R. Alves, M. R. Anderson, S. Andringa, L. Anselmo, E. Arushanova, S. Asahi, M. Askins, D. J. Auty, A. R. Back, S. Back, F. Barão, Z. Barnard, A. Barr, N. Barros, D. Bartlett, R. Bayes, C. Beaudoin, E. W. Beier, G. Berardi, A. Bialek, S. D. Biller, E. Blucher , et al. (229 additional authors not shown)

Abstract: The SNO+ experiment is located 2 km underground at SNOLAB in Sudbury, Canada. A low background search for neutrinoless double beta ($0νββ$) decay will be conducted using 780 tonnes of liquid scintillator loaded with 3.9 tonnes of natural tellurium, corresponding to 1.3 tonnes of $^{130}$Te. This paper provides a general overview of the SNO+ experiment, including detector design, construction of pr… ▽ More The SNO+ experiment is located 2 km underground at SNOLAB in Sudbury, Canada. A low background search for neutrinoless double beta ($0νββ$) decay will be conducted using 780 tonnes of liquid scintillator loaded with 3.9 tonnes of natural tellurium, corresponding to 1.3 tonnes of $^{130}$Te. This paper provides a general overview of the SNO+ experiment, including detector design, construction of process plants, commissioning efforts, electronics upgrades, data acquisition systems, and calibration techniques. The SNO+ collaboration is reusing the acrylic vessel, PMT array, and electronics of the SNO detector, having made a number of experimental upgrades and essential adaptations for use with the liquid scintillator. With low backgrounds and a low energy threshold, the SNO+ collaboration will also pursue a rich physics program beyond the search for $0νββ$ decay, including studies of geo- and reactor antineutrinos, supernova and solar neutrinos, and exotic physics such as the search for invisible nucleon decay. The SNO+ approach to the search for $0νββ$ decay is scalable: a future phase with high $^{130}$Te-loading is envisioned to probe an effective Majorana mass in the inverted mass ordering region. △ Less

Submitted 25 August, 2021; v1 submitted 23 April, 2021; originally announced April 2021.

Comments: 61 pages, 23 figures, 4 tables

Journal ref: The SNO+ collaboration, 2021 JINST 16 P08059

Multiple-Fold Fermions and Topological Fermi Arcs Induced Catalytic Enhancement in Nanoporous Electride C12A7

Authors: Weizhen Meng, Xiaoming Zhang, Ying Liu, Xuefang Dai, Guodong Liu, Liangzhi Kou

Abstract: Topological materials are recently regarded as the idea catalysts due to the protected surface metallic states and high carrier mobility, however the fundamental mechanism and the underlying relationship between the catalytic performance and topological states are in debate. Here, by means of symmetry analysis and first-principles calculations, we discover that the electride material of C12A7 host… ▽ More Topological materials are recently regarded as the idea catalysts due to the protected surface metallic states and high carrier mobility, however the fundamental mechanism and the underlying relationship between the catalytic performance and topological states are in debate. Here, by means of symmetry analysis and first-principles calculations, we discover that the electride material of C12A7 hosts the multiple-fold fermions due to the interstitial-electrons, with the sixfold- and fourfold- degenerate points locating at high symmetric points near the Fermi energy, which are identified as the underlying reason of the enhanced catalytic ability in C12A7-based catalysts. The multiple-fold fermions exhibit much longer Fermi arcs on the (001) surface than traditional Weyl/Dirac fermions, the surface is thus highly chemical active and possesses a low Gibbs free energy for the hydrogen evolution reaction. The underlying relationship between catalytic performance and the topological surface state is explicitly verified by artificially hole doping, external strain and similar electride without the Fermi arcs, where the Gibbs free energies are significantly increased when the Fermi arcs is shifted to higher energy level. This work offers a guiding principle for understanding catalytic nature of electrides and the topological quantum catalysts. △ Less

Submitted 19 August, 2021; v1 submitted 7 April, 2021; originally announced April 2021.

Journal ref: Adv. Sci. 2022, 2205940

Parasitic modes suppression in CW cold tests of 1.3 GHz 9-cell high Q cavities at IHEP

Authors: Zhenghui Mi, Feisi He, Weimin Pan, Peng Sha, Jiyuan Zhai, Xuwen Dai, Song Jina, Zhanjun Zhang, Chao Dong, Baiqi Liu, Hui Zhao, Rui Gea, Jianbing Zhao, Zhihui Mu, Lei Du, Liangrui Sun, Liang Zhang, Conglai Yang, Xiaobing Zheng, Haiying Lin, Guangwei Wang, Xiangcong He

Abstract: The CW RF test of 1.3 GHz 9-cell cavity in liquid helium bath at 2 K is a very important key point in the cavity procurement. Some problems can be found through the test, according which to optimized and improve the process of cavity. Recently, Medium temperature (mid-T) furnace bake of 1.3 GHz 9-cell cavities have been carried out at IHEP. Through the proceed of mid-T bake, the quality factor of… ▽ More The CW RF test of 1.3 GHz 9-cell cavity in liquid helium bath at 2 K is a very important key point in the cavity procurement. Some problems can be found through the test, according which to optimized and improve the process of cavity. Recently, Medium temperature (mid-T) furnace bake of 1.3 GHz 9-cell cavities have been carried out at IHEP. Through the proceed of mid-T bake, the quality factor of cavity has been greatly improved. While the excitation of the parasitic modes in the high Q cavities CW cold test has been encountered, which implies an error source for the cavity gradient and quality factor determination. In order to ensure the testing accuracy of superconducting cavity, we have improved the testing system. Finally, the parasitic mode is completely suppressed and the CW RF cold test of high Q cavity is guaranteed. △ Less

Submitted 26 March, 2021; originally announced March 2021.

Medium-temperature furnace bake of Superconducting Radio-Frequency cavities at IHEP

Authors: Feisi He, Weimin Pan, Peng Sha, Jiyuan Zhai, Zhenghui Mi, Xuwen Dai, Song Jin, Zhanjun Zhang, Chao Dong, Baiqi Liu, Hui Zhao, Rui Ge, Jianbing Zhao, Zhihui Mu, Lei Du, Liangrui Sun, Liang Zhang, Conglai Yang, Xiaobing Zheng

Abstract: Recently, heat treatment between 250 C and 500 C has been attempted to improve quality factor of superconducting radio-frequency cavities at FNAL and KEK. Experiments of such medium temperature (mid-T) bake with furnaces have also been carried out at IHEP. Firstly, eleven 1.3 GHz 1-cell cavities were treated with different temperatures at a small furnace. The average quality factor has reached 3.6… ▽ More Recently, heat treatment between 250 C and 500 C has been attempted to improve quality factor of superconducting radio-frequency cavities at FNAL and KEK. Experiments of such medium temperature (mid-T) bake with furnaces have also been carried out at IHEP. Firstly, eleven 1.3 GHz 1-cell cavities were treated with different temperatures at a small furnace. The average quality factor has reached 3.6E10 when the gradient is 16 MV/m. Then, the recipe of mid-T furnace bake at 300 C for 3 hours has been applied to six 1.3 GHz 9-cell cavities at a new big furnace. The average quality factor has reached 3.8E10 when the gradient is 16 MV/m. △ Less

Submitted 8 December, 2020; originally announced December 2020.

Comments: 10 pages, 12 figures