Showing 1–45 of 45 results for author: Dai, C

Multipulse Soliton Attractors Facilitated by High-Birefringence Fibers

Authors: Xuepeng Wang, Haoyu Feng, Zhentao Ju, Boris A. Malomed, Chaoqing Dai

Abstract: The stability of optical solitons is a crucial factor in various applications. This work reveals a novel stable multipulse soliton attractor in fiber lasers. The attractor represents a bound state of multiple solitons, pulling other dynamical states toward itself. By introducing a polarization-maintaining fiber (PMF), the enhanced birefringence in the cavity induces the differential group delay (D… ▽ More The stability of optical solitons is a crucial factor in various applications. This work reveals a novel stable multipulse soliton attractor in fiber lasers. The attractor represents a bound state of multiple solitons, pulling other dynamical states toward itself. By introducing a polarization-maintaining fiber (PMF), the enhanced birefringence in the cavity induces the differential group delay (DGD) between the polarization components of the pulse, leading to soliton splitting and, ultimately, the formation of multi-soliton states. These multi-solitons, affected by intracavity nonlinear and dissipative effects, form attractors consisting of one to seven soliton pulses. Through a combination of experiments and numerical simulations, we systematically investigate the robustness and dynamical behavior of the multipulse soliton attractors. In this context, we analyze disturbances introduced by "rogue" solitons with different frequencies and conduct a comprehensive study of their interaction with the multipulse soliton attractors. The results show that the multipulse soliton attractors are structurally stable and highly resistant to external disturbances, highlighting their potential for high-precision fiber lasers and advanced multipulse systems. △ Less

Submitted 13 August, 2025; originally announced August 2025.

Comments: to be published in Optics Letters

Terahertz-field activation of polar skyrons

Authors: Huaiyu Wang, Vladimir Stoica, Cheng Dai, Marek Paściak, Sujit Das, Tiannan Yang, Mauro A. P. Gonçalves, Jiri Kulda, Margaret R. McCarter, Anudeep Mangu, Yue Cao, Hari Padma, Utkarsh Saha, Diling Zhu, Takahiro Sato, Sanghoon Song, Mathias Hoffmann, Patrick Kramer, Silke Nelson, Yanwen Sun, Quynh Nguyen, Zhan Zhang, Ramamoorthy Ramesh, Lane Martin, Aaron M. Lindenberg , et al. (5 additional authors not shown)

Abstract: Unraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuit… ▽ More Unraveling collective modes arising from coupled degrees of freedom is crucial for understanding complex interactions in solids and developing new functionalities. Unique collective behaviors emerge when two degrees of freedom, ordered on distinct length scales, interact. Polar skyrmions, three-dimensional electric polarization textures in ferroelectric superlattices, disrupt the lattice continuity at the nanometer scale with nontrivial topology, leading to previously unexplored collective modes. Here, using terahertz-field excitation and femtosecond x-ray diffraction, we discovered subterahertz collective modes, dubbed 'skyrons', which appear as swirling patterns of atomic displacements functioning as atomic-scale gearsets. Momentum-resolved time-domain measurements of diffuse scattering revealed an avoided crossing in the dispersion relation of skyrons. We further demonstrated that the amplitude and dispersion of skyrons can be controlled by sample temperature and electric-field bias. Atomistic simulations and dynamical phase-field modeling provided microscopic insights into the three-dimensional crystallographic and polarization dynamics. The discovery of skyrons and their coupling with terahertz fields opens avenues for ultrafast control of topological polar structures. △ Less

Submitted 1 September, 2025; v1 submitted 15 May, 2025; originally announced May 2025.

Report number: ISSN 2041-1723

Journal ref: Nat Commun 16, 8994 (2025)

Performance Study of a Position-sensitive Plastic Scintillator Detector

Authors: S. K. Lv, C. S. Dai, D. D. Hu, T. C. Zhong, W. F. Wu, X. J. Wang

Abstract: For a long time, scintillator detectors have suffered from relatively weak spatial resolution due to various influencing factors. Additionally, the high cost of photomultiplier tubes (PMTs) has limited the widespread adoption of scintillator detectors as position-sensitive detectors in particle and nuclear physics experiments. In recent years, thanks to the rapid development of silicon photomultip… ▽ More For a long time, scintillator detectors have suffered from relatively weak spatial resolution due to various influencing factors. Additionally, the high cost of photomultiplier tubes (PMTs) has limited the widespread adoption of scintillator detectors as position-sensitive detectors in particle and nuclear physics experiments. In recent years, thanks to the rapid development of silicon photomultipliers (SiPMs), their excellent cost-performance ratio has led to a renewed interest in scintillator detectors in particle and nuclear physics. This project provides a detailed discussion of a detector based on scintillators coupled with SiPMs, focusing on how to improve the detector's position accuracy. By developing algorithms based on traditional optical propagation, a position resolution of mm level has been achieved. Furthermore, the introduction of a machine learning CNN algorithm has further enhanced the detector's position resolution. △ Less

Submitted 26 April, 2025; originally announced April 2025.

Proceedings to the 27th Workshop "What Comes Beyond the Standard Models" Bled, July 8-17, 2024

Authors: R. Bernabei, P. Belli, A. Bussolotti, V. Caracciolo, R. Cerulli, A. Leoncini, V. Merlo, F. Montecchia, F. Cappella, A. d'Angelo, A. Incicchitti, A. Mattei, C. J. Dai, X. H. Ma, X. D. Sheng, Z. P. Ye, V. A. Beylin, M. Yu. Khlopov, D. O. Sopin, T. E. Bikbaev, M. Yu. Khlopov, A. G. Mayorov, Stanley Brodsky, Daniele Fargion, A. M. Kharakashyan , et al. (10 additional authors not shown)

Abstract: The series of meetings ``What comes beyond the Standard Models'' started in 1998 with the idea of organizing a workshop where participants would spend most of the time in discussions, confronting different approaches and ideas. The idea was successful and has developed into an annual workshop, which is taking place every year since 1998. Very open-minded and fruitful discussions have become the… ▽ More The series of meetings ``What comes beyond the Standard Models'' started in 1998 with the idea of organizing a workshop where participants would spend most of the time in discussions, confronting different approaches and ideas. The idea was successful and has developed into an annual workshop, which is taking place every year since 1998. Very open-minded and fruitful discussions have become the trademark of our workshops, producing several published works. We discussed a lot of concepts which could help to understand our universe from the level of the second quantized elementary fermion and boson fields up to the level of the born of our universe. △ Less

Submitted 20 April, 2025; originally announced April 2025.

Comments: Proceedings for our meeting "What comes beyond the Standard Models'', which covered a broad series of subjects

Journal ref: Proceedings to the 27th workshop 'What Comes Beyond the Standard Models', Bled, July 8.-17., 2024. Založba Univerze v Ljubljani

Chirality transfer from chiral perovskite to molecular dopants via charge transfer states

Authors: Guan-Lin Chen, Hsinhan Tsai, Aaron Forde, Kai-Wei Tseng, Zhe-Yu Liu, Chi-An Dai, Tong Xiao, Mircea Coltlet, Leeyih Wang, Sergei Tretiak, Wanyi Nie

Abstract: Chiral perovskites are emerging semiconducting materials with broken symmetry that can selectively absorb and emit circularly polarized light. However, most of the chiral perovskites are typically low-dimensional structures with limited electrical conductivity and their light absorption occurs in the UV region. In this work, we find doping 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TC… ▽ More Chiral perovskites are emerging semiconducting materials with broken symmetry that can selectively absorb and emit circularly polarized light. However, most of the chiral perovskites are typically low-dimensional structures with limited electrical conductivity and their light absorption occurs in the UV region. In this work, we find doping 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the chiral perovskite matrix can improve the electrical conductivity with an addition of visible light absorption through the emerging charge-transfer electronic states. The new absorption feature exhibits strong circular dichroism adapted from the chiral matrix, which is indicative of a chirality transfer from the host to the guest via an electronic coupling. The charge transfer state is validated by transient absorption spectroscopy and theory modeling. Quantum-chemical modeling identifies a strong wave function overlap between an electron and a hole of the guest-host in a closely packed crystal configuration forming the charge-transfer absorption state. We then integrate the doped chiral perovskite film in photodetectors and demonstrate a selective detection of circularly polarized light both in the UV and visible range. Our results suggest a universal approach of introducing visible photo absorption states to the chiral matrix to broaden the optical active range and enhance the conductivity. △ Less

Submitted 15 January, 2025; originally announced January 2025.

A Method for Fabricating CMOS Back-End-of-Line-Compatible Solid-State Nanopore Devices

Authors: Mohamed Yassine Bouhamidi, Chunhui Dai, Michel Stephan, Joyeeta Nag, Justin Kinney, Lei Wan, Matthew Waugh, Kyle Briggs, Jordan Katine, Vincent Tabard-Cossa, Daniel Bedau

Abstract: Solid-state nanopores, nm-sized holes in thin, freestanding membranes, are powerful single-molecule sensors capable of interrogating a wide range of target analytes, from small molecules to large polymers. Interestingly, due to their high spatial resolution, nanopores can also identify tags on long polymers, making them an attractive option as the reading element for molecular information storage… ▽ More Solid-state nanopores, nm-sized holes in thin, freestanding membranes, are powerful single-molecule sensors capable of interrogating a wide range of target analytes, from small molecules to large polymers. Interestingly, due to their high spatial resolution, nanopores can also identify tags on long polymers, making them an attractive option as the reading element for molecular information storage strategies. To fully leverage the compact and robust nature of solid-state nanopores, however, they will need to be packaged in a highly parallelized manner with on-chip electronic signal processing capabilities to rapidly and accurately handle the data generated. Additionally, the membrane itself must have specific physical, chemical, and electrical properties to ensure sufficient signal-to-noise ratios are achieved, with the traditional membrane material being SiNX . Unfortunately, the typical method of deposition, low-pressure vapour deposition, requires temperatures beyond the thermal budget of CMOS back-end-of-line integration processes, limiting the potential to generate an on-chip solution. To this end, we explore various lower-temperature deposition techniques that are BEOL-compatible to generate SiNx membranes for solid-state nanopore use, and successfully demonstrate the ability for these alternative methods to generate low-noise nanopores that are capable of performing single-molecule experiments. △ Less

Submitted 26 November, 2024; originally announced November 2024.

Polarization induced buildup and switching mechanisms for soliton molecules composed of noise like pulse transition states

Authors: Zhi-Zeng Si, Zhen-Tao Ju, Long-Fei Ren, Xue-Peng Wang, Boris A. Malomed, Chao-Qing Dai

Abstract: Buildup and switching mechanisms of solitons in complex nonlinear systems are fundamentally important dynamical regimes. Using a novel strongly nonlinear optical system,the work reveals a new buildup scenario for soliton molecules , which includes a long-duration stage dominated by the emergence of transient NLPs modes to withstand strong disturbances arising from turbulence and extreme nonlineari… ▽ More Buildup and switching mechanisms of solitons in complex nonlinear systems are fundamentally important dynamical regimes. Using a novel strongly nonlinear optical system,the work reveals a new buildup scenario for soliton molecules , which includes a long-duration stage dominated by the emergence of transient NLPs modes to withstand strong disturbances arising from turbulence and extreme nonlinearity in the optical cavity. Systematic simulations reveal effects of the PC rotation angle and intra-cavity nonlinearity on the periodic phase transitions between the different soliton states, and accurately reproduce the experimentally observed buildup and switching mechanisms. These findings could enhance our fundamental study and points to potential uses in designing information encoding systems. △ Less

Submitted 20 August, 2024; originally announced August 2024.

Comments: To be published in LASER & PHOTONICS REVIEWS

Deep learning for dynamic modeling and coded information storage of vector-soliton pulsations in mode-locked fiber lasers

Authors: Zhi-Zeng Si, Da-Lei Wang, Bo-Wei Zhu, Zhen-Tao Ju, Xue-Peng Wang, Wei Liu, Boris A. Malomed, Yue-Yue Wang, Chao-Qing Dai

Abstract: Soliton pulsations are ubiquitous feature of non-stationary soliton dynamics in mode-locked lasers and many other physical systems. To overcome difficulties related to huge amount of necessary computations and low efficiency of traditional numerical methods in modeling the evolution of non-stationary solitons, we propose a two-parallel bidirectional long short-term memory recurrent neural network,… ▽ More Soliton pulsations are ubiquitous feature of non-stationary soliton dynamics in mode-locked lasers and many other physical systems. To overcome difficulties related to huge amount of necessary computations and low efficiency of traditional numerical methods in modeling the evolution of non-stationary solitons, we propose a two-parallel bidirectional long short-term memory recurrent neural network, with the main objective to predict dynamics of vector-soliton pulsations in various complex states, whose real-time dynamics is verified by experiments. Besides, the scheme of coded information storage based on the TP-Bi_LSTM RNN, instead of actual pulse signals, is realized too. The findings offer new applications of deep learning to ultrafast optics and information storage. △ Less

Submitted 5 August, 2024; v1 submitted 26 July, 2024; originally announced July 2024.

Comments: To be published in Laser & Photonics Reviews;https://doi.org/10.1002/lpor.202400097

High-efficiency generation of vectorial holograms with metasurfaces

Authors: Tong Liu, Changhong Dai, Dongyi Wang, Lei Zhou

Abstract: Holography plays a crucial role in optics applications, but it traditionally requires complex setup and bulky devices, being unfavourable for optics integration. While metasurface-based holograms are ultra-compact and easy to realize, holographic images generated are mostly restricted to scalar ones, with a few recent attempts on vectorial holograms suffering from complex meta-structures and low e… ▽ More Holography plays a crucial role in optics applications, but it traditionally requires complex setup and bulky devices, being unfavourable for optics integration. While metasurface-based holograms are ultra-compact and easy to realize, holographic images generated are mostly restricted to scalar ones, with a few recent attempts on vectorial holograms suffering from complex meta-structures and low efficiencies. Here, we propose and experimentally demonstrate an efficient meta-platform to generate vectorial holograms with arbitrarily designed wave fronts and polarization distributions based on ultra-compact metaatoms. Combining GS algorithm and the wave-decomposition technique, we establish a generic strategy to retrieve the optical property, i.e., the distributions of reflection phase and polarization-conversion capability of the metasurface to generate a target vectorial holographic image. We next design a series of high-efficiency and deep-subwavelength metaatoms exhibiting arbitrarily designed reflection phases and polarization-conversion capabilities, and experimentally characterize their optical properties. Based on these metaatoms, we finally realize a series of meta-holograms that can generate pre-designed vectorial holographic images upon external illuminations, and experimentally characterize their working performances. Our work provides a high-efficiency and ultra-thin platform to generate vectorial holographic images, which can find many applications in onchip photonics. △ Less

Submitted 14 June, 2024; originally announced June 2024.

Miniaturized time-correlated single-photon counting module for time-of-flight non-line-of-sight imaging applications

Authors: Jie Wu, Chao Yu, Jian-Wei Zeng, Chen Dai, Feihu Xu, Jun Zhang

Abstract: Single-photon time-of-flight (TOF) non-line-of-sight (NLOS) imaging enables the high-resolution reconstruction of objects outside the field of view. The compactness of TOF NLOS imaging systems, entailing the miniaturization of key components within such systems is crucial for practical applications. Here, we present a miniaturized four-channel time-correlated single-photon counting module dedicate… ▽ More Single-photon time-of-flight (TOF) non-line-of-sight (NLOS) imaging enables the high-resolution reconstruction of objects outside the field of view. The compactness of TOF NLOS imaging systems, entailing the miniaturization of key components within such systems is crucial for practical applications. Here, we present a miniaturized four-channel time-correlated single-photon counting module dedicated to TOF NLOS imaging applications. The module achieves excellent performance with a 10 ps bin size and 27.4 ps minimum root-mean-square time resolution. We present the results of TOF NLOS imaging experiment using an InGaAs/InP single-photon detector and the time-correlated single-photon counting module, and show that a 6.3 cm lateral resolution and 2.3 cm depth resolution can be achieved under the conditions of 5 m imaging distance and 1 ms pixel dwell time. △ Less

Submitted 9 March, 2024; originally announced April 2024.

Comments: Published by Review of Scientific Instrument

Journal ref: Rev. Sci. Instrum. 95, 035107 (2024)

A hybrid neural-network and MAC scheme for Stokes interface problems

Authors: Che-Chia Chang, Chen-Yang Dai, Wei-Fan Hu, Te-Sheng Lin, Ming-Chih Lai

Abstract: In this paper, we present a hybrid neural-network and MAC (Marker-And-Cell) scheme for solving Stokes equations with singular forces on an embedded interface in regular domains. As known, the solution variables (the pressure and velocity) exhibit non-smooth behaviors across the interface so extra discretization efforts must be paid near the interface in order to have small order of local truncatio… ▽ More In this paper, we present a hybrid neural-network and MAC (Marker-And-Cell) scheme for solving Stokes equations with singular forces on an embedded interface in regular domains. As known, the solution variables (the pressure and velocity) exhibit non-smooth behaviors across the interface so extra discretization efforts must be paid near the interface in order to have small order of local truncation errors in finite difference schemes. The present hybrid approach avoids such additional difficulty. It combines the expressive power of neural networks with the convergence of finite difference schemes to ease the code implementation and to achieve good accuracy at the same time. The key idea is to decompose the solution into singular and regular parts. The neural network learning machinery incorporating the given jump conditions finds the singular part solution, while the standard MAC scheme is used to obtain the regular part solution with associated boundary conditions. The two- and three-dimensional numerical results show that the present hybrid method converges with second-order accuracy for the velocity and first-order accuracy for the pressure, and it is comparable with the traditional immersed interface method in literature. △ Less

Submitted 3 April, 2024; v1 submitted 9 June, 2023; originally announced June 2023.

Proceedings to the 25th International Workshop "What Comes Beyond the Standard Models", July 4 -- July 10, 2022, Bled, Slovenia

Authors: R. Bernabei, P. Belli, A. Bussolotti, V. Caracciolo, R. Cerulli, N. Ferrari, A. Leoncini, V. Merlo, F. Montecchia, F. Cappella, A. dAngelo, A. Incicchitti, A. Mattei, C. J. Dai, X. H. Ma, X. D. Sheng, Z. P. Ye, V. Beylin, L. Bonora, S. J. Brodsky, Paul H. Frampton, A. Ghoshal, G. Lambiase, S. Pal, A. Paul , et al. (29 additional authors not shown)

Abstract: Proceedings for our meeting ``What comes beyond the Standard Models'', which covered a broad series of subjects. Proceedings for our meeting ``What comes beyond the Standard Models'', which covered a broad series of subjects. △ Less

Submitted 29 March, 2023; originally announced March 2023.

Comments: This is the proceedings for the 25th Workshop in Bled for "What comes beyond the Standard Models'' including also a webinar "meeting'' using Cosmovia on the same subject

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)

Atmospheric turbulence does not change the degree of polarization of vector beams

Authors: Zhiwei Tao, Azezigul Abdukirim, Congming Dai, Pengfei Wu, Haiping Mei, Yichong Ren, Chuankai Luo, Ruizhong Rao, Heli Wei

Abstract: We propose a novel theoretical framework to demonstrate vector beams whose degree of polarization does not change on atmospheric propagation. Inspired by the Fresnel equations, we derive the reflective and refractive field of vector beams propagating through a phase screen by employing the continuity of electromagnetic field. We generalize the conventional split-step beam propagation method by con… ▽ More We propose a novel theoretical framework to demonstrate vector beams whose degree of polarization does not change on atmospheric propagation. Inspired by the Fresnel equations, we derive the reflective and refractive field of vector beams propagating through a phase screen by employing the continuity of electromagnetic field. We generalize the conventional split-step beam propagation method by considering the vectorial properties in the vacuum diffraction and the refractive properties of a single phase screen. Based on this vectorial propagation model, we extensively calculate the change of degree of polarization (DOP) of vector beams under different beam parameters and turbulence parameters both in free-space and satellite-mediated links. Our result is that whatever in the free-space or satellite-mediated regime, the change of DOP mainly fluctuates around the order of $10^{-13}$ to $10^{-6}$, which is almost negligible. △ Less

Submitted 23 February, 2023; originally announced February 2023.

Comments: 7 pages, 4 figures

Deep Learning Models for River Classification at Sub-Meter Resolutions from Multispectral and Panchromatic Commercial Satellite Imagery

Authors: Joachim Moortgat, Ziwei Li, Michael Durand, Ian Howat, Bidhyananda Yadav, Chunli Dai

Abstract: Remote sensing of the Earth's surface water is critical in a wide range of environmental studies, from evaluating the societal impacts of seasonal droughts and floods to the large-scale implications of climate change. Consequently, a large literature exists on the classification of water from satellite imagery. Yet, previous methods have been limited by 1) the spatial resolution of public satellit… ▽ More Remote sensing of the Earth's surface water is critical in a wide range of environmental studies, from evaluating the societal impacts of seasonal droughts and floods to the large-scale implications of climate change. Consequently, a large literature exists on the classification of water from satellite imagery. Yet, previous methods have been limited by 1) the spatial resolution of public satellite imagery, 2) classification schemes that operate at the pixel level, and 3) the need for multiple spectral bands. We advance the state-of-the-art by 1) using commercial imagery with panchromatic and multispectral resolutions of 30 cm and 1.2 m, respectively, 2) developing multiple fully convolutional neural networks (FCN) that can learn the morphological features of water bodies in addition to their spectral properties, and 3) FCN that can classify water even from panchromatic imagery. This study focuses on rivers in the Arctic, using images from the Quickbird, WorldView, and GeoEye satellites. Because no training data are available at such high resolutions, we construct those manually. First, we use the RGB, and NIR bands of the 8-band multispectral sensors. Those trained models all achieve excellent precision and recall over 90% on validation data, aided by on-the-fly preprocessing of the training data specific to satellite imagery. In a novel approach, we then use results from the multispectral model to generate training data for FCN that only require panchromatic imagery, of which considerably more is available. Despite the smaller feature space, these models still achieve a precision and recall of over 85%. We provide our open-source codes and trained model parameters to the remote sensing community, which paves the way to a wide range of environmental hydrology applications at vastly superior accuracies and 2 orders of magnitude higher spatial resolution than previously possible. △ Less

Submitted 27 December, 2022; originally announced December 2022.

Comments: 21 pages, 10 figures, 3 tables

Journal ref: Remote Sensing of Environment, Volume 282, 1 December 2022, page 113279

Predicting nonlinear dynamics of optical solitons in optical fiber via the SCPINN

Authors: Yin Fang, Wen-Bo Bo, Ru-Ru Wang, Yue-Yue Wang, Chao-Qing Dai

Abstract: The strongly-constrained physics-informed neural network (SCPINN) is proposed by adding the information of compound derivative embedded into the soft-constraint of physics-informed neural network(PINN). It is used to predict nonlinear dynamics and the formation process of bright and dark picosecond optical solitons, and femtosecond soliton molecule in the single-mode fiber, and reveal the variatio… ▽ More The strongly-constrained physics-informed neural network (SCPINN) is proposed by adding the information of compound derivative embedded into the soft-constraint of physics-informed neural network(PINN). It is used to predict nonlinear dynamics and the formation process of bright and dark picosecond optical solitons, and femtosecond soliton molecule in the single-mode fiber, and reveal the variation of physical quantities including the energy, amplitude, spectrum and phase of pulses during the soliton transmission. The adaptive weight is introduced to accelerate the convergence of loss function in this new neural network. Compared with the PINN, the accuracy of SCPINN in predicting soliton dynamics is improved by 5-11 times. Therefore, the SCPINN is a forward-looking method to study the modeling and analysis of soliton dynamics in the fiber. △ Less

Submitted 15 November, 2022; originally announced November 2022.

The Extreme Cardiac MRI Analysis Challenge under Respiratory Motion (CMRxMotion)

Authors: Shuo Wang, Chen Qin, Chengyan Wang, Kang Wang, Haoran Wang, Chen Chen, Cheng Ouyang, Xutong Kuang, Chengliang Dai, Yuanhan Mo, Zhang Shi, Chenchen Dai, Xinrong Chen, He Wang, Wenjia Bai

Abstract: The quality of cardiac magnetic resonance (CMR) imaging is susceptible to respiratory motion artifacts. The model robustness of automated segmentation techniques in face of real-world respiratory motion artifacts is unclear. This manuscript describes the design of extreme cardiac MRI analysis challenge under respiratory motion (CMRxMotion Challenge). The challenge aims to establish a public benchm… ▽ More The quality of cardiac magnetic resonance (CMR) imaging is susceptible to respiratory motion artifacts. The model robustness of automated segmentation techniques in face of real-world respiratory motion artifacts is unclear. This manuscript describes the design of extreme cardiac MRI analysis challenge under respiratory motion (CMRxMotion Challenge). The challenge aims to establish a public benchmark dataset to assess the effects of respiratory motion on image quality and examine the robustness of segmentation models. The challenge recruited 40 healthy volunteers to perform different breath-hold behaviors during one imaging visit, obtaining paired cine imaging with artifacts. Radiologists assessed the image quality and annotated the level of respiratory motion artifacts. For those images with diagnostic quality, radiologists further segmented the left ventricle, left ventricle myocardium and right ventricle. The images of training set (20 volunteers) along with the annotations are released to the challenge participants, to develop an automated image quality assessment model (Task 1) and an automated segmentation model (Task 2). The images of validation set (5 volunteers) are released to the challenge participants but the annotations are withheld for online evaluation of submitted predictions. Both the images and annotations of the test set (15 volunteers) were withheld and only used for offline evaluation of submitted containerized dockers. The image quality assessment task is quantitatively evaluated by the Cohen's kappa statistics and the segmentation task is evaluated by the Dice scores and Hausdorff distances. △ Less

Submitted 12 October, 2022; originally announced October 2022.

Comments: Summary of CMRxMotion Challenge Design

Dark Matter: DAMA/LIBRA and its perspectives

Authors: R. Bernabei, P. Belli, F. Cappella, V. Caracciolo, R. Cerulli, C. J. Dai, A. d'Angelo, A. Incicchitti, A. Leoncini, X. H. Ma, V. Merlo, F. Montecchia, X. D. Sheng, Z. P. Ye

Abstract: The long-standing model-independent annual modulation effect measured by DAMA deep underground at Gran Sasso Laboratory with different experimental configurations is summarized and perspectives will be highlighted. DAMA/LIBRA-phase2 set-up, $\simeq$ 250 kg highly radio-pure NaI(Tl) confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulat… ▽ More The long-standing model-independent annual modulation effect measured by DAMA deep underground at Gran Sasso Laboratory with different experimental configurations is summarized and perspectives will be highlighted. DAMA/LIBRA-phase2 set-up, $\simeq$ 250 kg highly radio-pure NaI(Tl) confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature at high C.L.; the full exposure is 2.86 ton $\times$ yr over 22 annual cycles. The experiment is currently collecting data in the DAMA/LIBRA-phase2 empowered configuration with an even lower software energy threshold. Other recent claims are shortly commented. △ Less

Submitted 2 September, 2022; originally announced September 2022.

Comments: Proceedings of IDM 2022, July 18-22, 2022. A Section is dedicated to rebut the arguments of arXiv:2208.05158

The reconstructed thermal lattice Boltzmann flux solver and its applications for simulations of thermal flows

Authors: Jinhua Lu, Chuanshan Dai, Peng Yu

Abstract: The thermal lattice Boltzmann flux solver (TLBFS) has been proposed to overcome the drawbacks of the thermal lattice Boltzmann models. However, as a weakly compressible model, its mechanism of good numerical stability for high Rayleigh number thermal flows is still unclear. To reveal the mechanism, the present paper firstly derives the macroscopic equations of TLBFS (MEs-TLBFS) with actual numeric… ▽ More The thermal lattice Boltzmann flux solver (TLBFS) has been proposed to overcome the drawbacks of the thermal lattice Boltzmann models. However, as a weakly compressible model, its mechanism of good numerical stability for high Rayleigh number thermal flows is still unclear. To reveal the mechanism, the present paper firstly derives the macroscopic equations of TLBFS (MEs-TLBFS) with actual numerical dissipation terms by approximating its computational process. By solving MEs-TLBFS with the finite volume method, the reconstructed TLBFS (RTLBFS) is proposed. Detailed analyses prove that these actual numerical dissipation terms are the mechanism of the good numerical stability of TLBFS for high Rayleigh number thermal flows. More detailed numerical tests indicate RTLBFS has similar performances as TLBFS for stability, accuracy, and efficiency. Moreover, the present RTLBFS shows a clear mechanism to achieve good numerical stability for high Rayleigh number flows. △ Less

Submitted 27 February, 2022; originally announced February 2022.

Evidence for mechanical softening-hardening dual anomaly in transition metals from shock compressed vanadium

Authors: Hao Wang, J. Li, X. M. Zhou, Y. Tan, L. Hao, Y. Y. Yu, C. D. Dai, K. Jin, Q. Wu, Q. M. Jing, X. R. Chen, X. Z. Yan, Y. X. Wang, Hua Y. Geng

Abstract: Solid usually becomes harder and tougher under compression, and turns softer at elevated temperature. Recently, compression-induced softening and heating-induced hardening (CISHIH) dual anomaly was predicted in group VB elements such as vanadium. Here, the evidence for this counterintuitive phenomenon is reported. By using accurate high-temperature high-pressure sound velocities measured at Hugoni… ▽ More Solid usually becomes harder and tougher under compression, and turns softer at elevated temperature. Recently, compression-induced softening and heating-induced hardening (CISHIH) dual anomaly was predicted in group VB elements such as vanadium. Here, the evidence for this counterintuitive phenomenon is reported. By using accurate high-temperature high-pressure sound velocities measured at Hugoniot states generated by shock-waves, together with first-principles calculations, we observe not only the prominent compression-induced sound velocity reduction, but also strong heating-induced sound velocity enhancement, in shocked vanadium. The former corresponds to the softening in shear modulus by compression, whereas the latter reflects the reverse hardening by heat. These experiments also unveil another anomaly in Young's modulus that wasn't reported before. Based on the experimental and theoretical data, we infer that vanadium might transition from BCC into two different rhombohedral (RH1 and RH2) phases at about 79GPa and 116GPa along the Hugoniot, respectively, which implies a dramatic difference in static and dynamic loading, as well as the significance of deviatoric stress and rate-relevant effects in high-pressure phase transition dynamics. △ Less

Submitted 31 January, 2022; originally announced January 2022.

Comments: 43 pages, 16 figures, with Supplementary Material

Journal ref: Physical Review B 104, 134102 (2021)

Generation and dynamics of soliton and soliton molecules from a VSe2/GO-based fiber laser

Authors: Benhai Wang, Haobin Han, Lijun Yu, Yueyue Wang, Chaoqing Dai

Abstract: Recently, in addition to exploring the application of new saturable absorber devices in fiber lasers, soliton dynamics has also become a focus of current research. In this article, we report an ultrashort pulse fiber laser based on VSe2/GO nanocomposite and verify the formation process of soliton and soliton molecules by the numerical simulation. The prepared VSe2/GO-based device shows excellent s… ▽ More Recently, in addition to exploring the application of new saturable absorber devices in fiber lasers, soliton dynamics has also become a focus of current research. In this article, we report an ultrashort pulse fiber laser based on VSe2/GO nanocomposite and verify the formation process of soliton and soliton molecules by the numerical simulation. The prepared VSe2/GO-based device shows excellent saturable absorption characteristics with a modulation depth of 14.3% and a saturation absorption intensity of 0.93MW/cm2. The conventional soliton is obtained with pulse width of 573fs, which is currently the narrowest pulse width based on VSe2-related material, and has a signal-to-noise ratio of 60.4 dB. In addition, the soliton molecules are realized based on the VSe2/GO for the first time and have a pulse interval of ~2.2ps. We study the soliton dynamics through numerical simulation and reveal that before the formation of the soliton, it undergoes multiple nonlinear stages, such as soliton mode-locking, soliton splitting, and soliton oscillation. Furthermore, the results of numerical simulation are agreed well with the experimental data. These results indicate that the VSe2/GO might be another promising saturable absorber material for ultrafast photonics, and deepen the understanding of soliton dynamics in ultrafast fiber lasers. △ Less

Submitted 9 November, 2021; originally announced November 2021.

The dark matter: DAMA/LIBRA and its perspectives

Authors: R. Bernabei, P. Belli, V. Caracciolo, R. Cerulli, V. Merlo, F. Cappella, A. d'Angelo, A. Incicchitti, C. J. Dai, X. H. Ma, X. D. Sheng, F. Montecchia, Z. P. Ye

Abstract: Experimental observations and theoretical arguments point out that Dark Matter (DM) particles are one of the most prominent component of the Universe. This motivated the pioneer DAMA experiment to investigate the presence of these particles in the galactic halo, by exploiting the model independent signature of the DM annual modulation of the rate and very highly radio-pure apparatus in underground… ▽ More Experimental observations and theoretical arguments point out that Dark Matter (DM) particles are one of the most prominent component of the Universe. This motivated the pioneer DAMA experiment to investigate the presence of these particles in the galactic halo, by exploiting the model independent signature of the DM annual modulation of the rate and very highly radio-pure apparatus in underground site. In this paper the results obtained by other two annual cycles of DAMA/LIBRA-phase2 are presented and the long-standing model-independent annual modulation effect measured by DAMA deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. with different experimental configurations is summarized. The improved experimental configuration of DAMA/LIBRA-phase2, $\simeq$ 250 kg highly radio-pure NaI(Tl), allowed to lower the software energy threshold. The total exposure of DAMA/LIBRA-phase2 over 8 annual cycles is 1.53 ton $\times$ yr. DAMA/LIBRA-phase2 confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 11.8 $σ$ C.L. in the energy region (1-6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1 (2.86 ton $\times$ yr), the achieved C.L. is 13.7 $σ$; the modulation amplitude of the single-hit scintillation events is: $(0.01014 \pm 0.00074)$ cpd/kg/keV, the measured phase is $(142.4 \pm 4.2)$ days and the measured period is $(0.99834 \pm 0.00067)$ yr, all these values are well in agreement with those expected for DM particles. No systematics or side reaction able to mimic the exploited DM signature (i.e. to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature), has been found or suggested by anyone throughout some decades thus far. △ Less

Submitted 10 October, 2021; originally announced October 2021.

Comments: Proceedings of the Sixteenth Marcel Grossmann Meeting - MG16, July 5-10, 2021. arXiv admin note: substantial text overlap with arXiv:1805.10486, arXiv:1308.5109, arXiv:1002.1028, arXiv:1306.1411

Modified physics-informed neural network method based on the conservation law constraint and its prediction of optical solitons

Authors: Gang-Zhou Wu, Yin Fang, Yue-Yue Wang, Chao-Qing Dai

Abstract: Based on conservation laws as one of the important integrable properties of nonlinear physical models, we design a modified physics-informed neural network method based on the conservation law constraint. From a global perspective, this method imposes physical constraints on the solution of nonlinear physical models by introducing the conservation law into the mean square error of the loss functio… ▽ More Based on conservation laws as one of the important integrable properties of nonlinear physical models, we design a modified physics-informed neural network method based on the conservation law constraint. From a global perspective, this method imposes physical constraints on the solution of nonlinear physical models by introducing the conservation law into the mean square error of the loss function to train the neural network. Using this method, we mainly study the standard nonlinear Schrödinger equation and predict various data-driven optical soliton solutions, including one-soliton, soliton molecules, two-soliton interaction, and rogue wave. In addition, based on various exact solutions, we use the modified physics-informed neural network method based on the conservation law constraint to predict the dispersion and nonlinear coefficients of the standard nonlinear Schrödinger equation. Compared with the traditional physics-informed neural network method, the modified method can significantly improve the calculation accuracy. △ Less

Submitted 23 August, 2021; originally announced August 2021.

Predicting the dynamic process and model parameters of the vector optical solitons in birefringent fibers via the modified PINN

Authors: Gang-Zhou Wu, Yin Fang, Yue-Yue Wang, Guo-Cheng Wu, Chao-Qing Dai

Abstract: A modified physics-informed neural network is used to predict the dynamics of optical pulses including one-soliton, two-soliton, and rogue wave based on the coupled nonlinear Schrödinger equation in birefringent fibers. At the same time, the elastic collision process of the mixed bright-dark soliton is predicted. Compared the predicted results with the exact solution, the modified physics-informed… ▽ More A modified physics-informed neural network is used to predict the dynamics of optical pulses including one-soliton, two-soliton, and rogue wave based on the coupled nonlinear Schrödinger equation in birefringent fibers. At the same time, the elastic collision process of the mixed bright-dark soliton is predicted. Compared the predicted results with the exact solution, the modified physics-informed neural network method is proven to be effective to solve the coupled nonlinear Schrödinger equation. Moreover, the dispersion coefficients and nonlinearity coefficients of the coupled nonlinear Schrodinger equation can be learned by modified physics-informed neural network. This provides a reference for us to use deep learning methods to study the dynamic characteristics of solitons in optical fibers. △ Less

Submitted 26 August, 2021; originally announced August 2021.

Self-cleaning effect in an all-fiber spatiotemporal mode-locked laser based on graded-index multimode fiber

Authors: Chuansheng Dai, Zhipeng Dong, Jiaqiang Lin, Yimin Zhang, Peijun Yao, Lixin Xu, Chun Gu

Abstract: We demonstrate an all-fiber spatiotemporal mode-locked laser based on graded-index multimode fiber. Due to the high damage threshold of graded-index multimode fiber devices, the output single-pulse energy reach up to 11.67 nJ. The beam quality at mode-locked state is significantly improved compared with continuous wave state as a result of the self-cleaning effect. By amplifying the pulse in the m… ▽ More We demonstrate an all-fiber spatiotemporal mode-locked laser based on graded-index multimode fiber. Due to the high damage threshold of graded-index multimode fiber devices, the output single-pulse energy reach up to 11.67 nJ. The beam quality at mode-locked state is significantly improved compared with continuous wave state as a result of the self-cleaning effect. By amplifying the pulse in the multimode fiber amplifier, high power pulses with high beam quality can be obtained in the all-fiber system based on graded-index MMFs. △ Less

Submitted 22 October, 2020; originally announced October 2020.

Comments: 8 pages, 5 figures

Late 19th-Century Navigational Uncertainties and Their Influence on Sea Surface Temperature Estimates

Authors: Chenguang Dai, Duo Chan, Peter Huybers, Natesh Pillai

Abstract: Accurate estimates of historical changes in sea surface temperatures (SSTs) and their uncertainties are important for documenting and understanding historical changes in climate. A source of uncertainty that has not previously been quantified in historical SST estimates stems from position errors. A Bayesian inference framework is proposed for quantifying errors in reported positions and their imp… ▽ More Accurate estimates of historical changes in sea surface temperatures (SSTs) and their uncertainties are important for documenting and understanding historical changes in climate. A source of uncertainty that has not previously been quantified in historical SST estimates stems from position errors. A Bayesian inference framework is proposed for quantifying errors in reported positions and their implications on SST estimates. The analysis framework is applied to data from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS3.0) in 1885, a time when astronomical and chronometer estimation of position was common, but predating the use of radio signals. Focus is upon a subset of 943 ship tracks from ICOADS3.0 that report their position every two hours to a precision of 0.01° longitude and latitude. These data are interpreted as positions determined by dead reckoning that are periodically updated by celestial correction techniques. The posterior medians of uncertainties in celestial correction are 33.1 km (0.30° on the equator) in longitude and 24.4 km (0.22°) in latitude, respectively. The posterior medians of two-hourly dead reckoning uncertainties are 19.2% for ship speed and 13.2° for ship heading, leading to random position uncertainties with median 0.18° (20 km on the equator) in longitude and 0.15° (17 km) in latitude. Reported ship tracks also contain systematic position uncertainties relating to precursor dead-reckoning positions not being updated after obtaining celestial position estimates, indicating that more accurate positions can be provided for SST observations. Finally, we translate position errors into SST uncertainties by sampling an ensemble of SSTs from the Multi-scale Ultra-high resolution Sea Surface Temperature (MURSST) data set. △ Less

Submitted 13 December, 2020; v1 submitted 10 October, 2019; originally announced October 2019.

Experimental demonstration of a dusty plasma ratchet rectification and its reversal

Authors: Ya-feng He, Bao-quan Ai, Chao-xing Dai, Chao Song, Rui-qi Wang, Wen-tao Sun, Fu-cheng Liu, Yan Feng

Abstract: The naturally persistent flow of hundreds of dust particles is experimentally achieved in a dusty plasma system with the asymmetric sawteeth of gears on the electrode. It is also demonstrated that the direction of the dust particle flowcan be controlled by changing the plasma conditions of the gas pressure or the plasma power. Numerical simulations of dust particles with the ion drag inside the as… ▽ More The naturally persistent flow of hundreds of dust particles is experimentally achieved in a dusty plasma system with the asymmetric sawteeth of gears on the electrode. It is also demonstrated that the direction of the dust particle flowcan be controlled by changing the plasma conditions of the gas pressure or the plasma power. Numerical simulations of dust particles with the ion drag inside the asymmetric sawteeth verify the experimental observations of the flow rectification of dust particles. Both experiments and simulations suggest that the asymmetric potential and the collective effect are the twokeys in this dusty plasma ratchet.With the nonequilibrium ion drag, the dust flow along the asymmetric orientation of this electric potential of the ratchet can be reversed by changing the balance height of dust particles using different plasma conditions. △ Less

Submitted 22 February, 2020; v1 submitted 20 August, 2019; originally announced August 2019.

Comments: 5 pages,5 figures

Journal ref: Phys. Rev. Lett. 124, 075001 (2020)

Improved model-dependent corollary analyses after the first six annual cycles of DAMA/LIBRA-phase2

Authors: R. Bernabei, P. Belli, F. Cappella, V. Caracciolo, R. Cerulli, C. J. Dai, A. d'Angelo, A. Di Marco, H. L. He, A. Incicchitti, X. H. Ma, V. Merlo, F. Montecchia, X. D. Sheng, Z. P. Ye

Abstract: Several of the many proposed Dark Matter candidate particles, already investigated with lower exposure and a higher software energy threshold, are further analyzed including the first DAMA/LIBRA--phase2 data release, with an exposure of 1.13 ton $\times$ yr and a lower software energy threshold (1 keV). The cumulative exposure above 2 keV considering also DAMA/NaI and DAMA/LIBRA--phase1 results is… ▽ More Several of the many proposed Dark Matter candidate particles, already investigated with lower exposure and a higher software energy threshold, are further analyzed including the first DAMA/LIBRA--phase2 data release, with an exposure of 1.13 ton $\times$ yr and a lower software energy threshold (1 keV). The cumulative exposure above 2 keV considering also DAMA/NaI and DAMA/LIBRA--phase1 results is now 2.46 ton $\times$ yr. The analysis permits to constraint the parameters' space of the considered candidates restricting their values -- with respect to previous analyses -- thanks to the increase of the exposure and to the lower energy threshold. △ Less

Submitted 23 December, 2019; v1 submitted 15 July, 2019; originally announced July 2019.

Comments: 48 pages, 33 figures; in press on Nucl. Phys. At. Energy (2019)

Journal ref: Nucl. Phys. At. Energy 20 (2019) 317-348

Graphene Induced Large Shift of Surface Plasmon Resonances of Gold Films: Effective Medium Theory for Atomically Thin Materials

Authors: Md Kamrul Alam, Chao Niu, Yanan Wang, Wei Wang, Yang Li, Chong Dai, Tian Tong, Xiaonan Shan, Earl Charlson, Steven Pei, Xiang-Tian Kong, Yandi Hu, Alexey Belyanin, Gila Stein, Zhaoping Liu, Jonathan Hu, Zhiming Wang, Jiming Bao

Abstract: Despite successful modeling of graphene as a 0.34-nm thick optical film synthesized by exfoliation or chemical vapor deposition (CVD), graphene induced shift of surface plasmon resonance (SPR) of gold films has remained controversial. Here we report the resolution of this controversy by developing a clean CVD graphene transfer method and extending Maxwell-Garnet effective medium theory (EMT) to 2D… ▽ More Despite successful modeling of graphene as a 0.34-nm thick optical film synthesized by exfoliation or chemical vapor deposition (CVD), graphene induced shift of surface plasmon resonance (SPR) of gold films has remained controversial. Here we report the resolution of this controversy by developing a clean CVD graphene transfer method and extending Maxwell-Garnet effective medium theory (EMT) to 2D materials. A SPR shift of 0.24 is obtained and it agrees well with 2D EMT in which wrinkled graphene is treated as a 3-nm graphene/air layered composite, in agreement with the average roughness measured by atomic force microscope. Because the anisotropic built-in boundary condition of 2D EMT is compatible with graphene's optical anisotropy, graphene can be modelled as a film thicker than 0.34-nm without changing its optical property; however, its actual roughness, i.e., effective thickness will significantly alter its response to strong out-of-plane fields, leading to a larger SPR shift. △ Less

Submitted 17 April, 2019; originally announced April 2019.

Comments: 18 pages, 5 figures

Journal ref: Phys. Rev. Research 2, 013008 (2020)

An all-fiber laser oscillating directly at single TE01 mode through ring-core fibers

Authors: Yimin Zhang, Hongxun Li, Chuansheng Dai, Runxia Tao, Lixin Xu, Chun Gu, Wei Chen, Yonggang Zhu, Peijun Yao, Qiwen Zhan

Abstract: Cylindrical vector beams (CVBs) have a wide range of applications owing to their particular polarization characteristics and optical field distributions. For the first time, an azimuthally polarized fiber laser without any polarization controller is proposed and demonstrated experimentally. The scheme is based on a self-designed ring-core fiber and transverse mode filter (TMF). The ring-core fiber… ▽ More Cylindrical vector beams (CVBs) have a wide range of applications owing to their particular polarization characteristics and optical field distributions. For the first time, an azimuthally polarized fiber laser without any polarization controller is proposed and demonstrated experimentally. The scheme is based on a self-designed ring-core fiber and transverse mode filter (TMF). The ring-core fiber can break the degeneracy of LP11 modes and make the TE01 mode propagate stably in the fiber laser. The TMF, which made from the ring-core fiber by depositing a layer of Aluminum on the cladding surface, can effectively suppress the modes other than TE01 mode. The fiber laser can stably operate at TE01 mode with a narrow 30dB linewidth of 0.18nm, which indicates the laser is polarization-maintained. This study opens a new avenue toward the true application of CVBs fiber lasers. △ Less

Submitted 10 November, 2018; originally announced November 2018.

Comments: 10 pages, 10 figures

First model independent results from DAMA/LIBRA-phase2

Authors: R. Bernabei, P. Belli, A. Bussolotti, F. Cappella, V. Caracciolo, R. Cerulli, C. J. Dai, A. d'Angelo, A. Di Marco, H. L. He, A. Incicchitti, X. H. Ma, A. Mattei, V. Merlo, F. Montecchia, X. D. Sheng, Z. P. Ye

Abstract: The first model independent results obtained by the DAMA/LIBRA-phase2 experiment are presented. The data have been collected over 6 annual cycles corresponding to a total exposure of 1.13 ton $\times$ yr, deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. The DAMA/LIBRA-phase2 apparatus, $\simeq$ 250 kg highly radio-pure NaI(Tl), profits from a second generation high qua… ▽ More The first model independent results obtained by the DAMA/LIBRA-phase2 experiment are presented. The data have been collected over 6 annual cycles corresponding to a total exposure of 1.13 ton $\times$ yr, deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. The DAMA/LIBRA-phase2 apparatus, $\simeq$ 250 kg highly radio-pure NaI(Tl), profits from a second generation high quantum efficiency photomultipliers and of new electronics with respect to DAMA/LIBRA-phase1. The improved experimental configuration has also allowed to lower the software energy threshold. New data analysis strategies are presented. The DAMA/LIBRA-phase2 data confirm the evidence of a signal that meets all the requirements of the model independent Dark Matter (DM) annual modulation signature, at 9.5 $σ$ C.L. in the energy region (1-6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA-phase1 (exposure $1.33$ ton $\times$ yr, collected over 14 annual cycles), the achieved C.L. for the full exposure (2.46 ton $\times$ yr) is 12.9 $σ$; the modulation amplitude of the single-hit scintillation events is: $(0.0103 \pm 0.0008)$ cpd/kg/keV, the measured phase is $(145 \pm 5)$ days and the measured period is $(0.999 \pm 0.001)$ yr, all these values are well in agreement with those expected for DM particles. No systematics or side reaction able to mimic the exploited DM signature (i.e. to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature), has been found or suggested by anyone throughout some decades thus far. △ Less

Submitted 11 January, 2019; v1 submitted 26 May, 2018; originally announced May 2018.

Comments: 28 pages, 17 figures, 5 tables. In press on Journal Nucl. Phys. and Atomic Energy. arXiv admin note: substantial text overlap with arXiv:1308.5109, arXiv:1002.1028, arXiv:1306.1411

Journal ref: Nucl. Phys. At. Energy 19 (2018) 307-325

Efficient Phase Diagram Sampling by Active Learning

Authors: Chengyu Dai, Isaac R. Bruss, Sharon C. Glotzer

Abstract: We address the problem of efficient phase diagram sampling by adopting active learning techniques from machine learning, and achieve an 80% reduction in the sample size (number of sampled statepoints) needed to establish the phase boundary up to a given precision in example application. Traditionally, data is collected on a uniform grid of predetermined statepoints. This approach, also known as gr… ▽ More We address the problem of efficient phase diagram sampling by adopting active learning techniques from machine learning, and achieve an 80% reduction in the sample size (number of sampled statepoints) needed to establish the phase boundary up to a given precision in example application. Traditionally, data is collected on a uniform grid of predetermined statepoints. This approach, also known as grid search in the machine learning community, suffers from low efficiency by sampling statepoints that provide no information about the phase boundaries. We propose an active learning approach to overcome this deficiency by adaptively choosing the next most informative statepoint(s) every round. This is done by interpolating the sampled statepoints' phases by Gaussian Process regression. An acquisition function quantifies the informativeness of possible next statepoints, maximizing the information content in each subsequently sampled statepoint. We also generalize our approach with state-of-the-art batch sampling techniques to better utilize parallel computing resources. We demonstrate the usefulness of our approach in a few example simulations relevant to soft matter physics, although our algorithms are general. Our active learning enhanced phase diagram sampling method greatly accelerates research and opens up opportunities for extra-large scale exploration of a wide range of phase diagrams by simulations or experiments. △ Less

Submitted 8 March, 2018; originally announced March 2018.

OpenFermion: The Electronic Structure Package for Quantum Computers

Authors: Jarrod R. McClean, Kevin J. Sung, Ian D. Kivlichan, Yudong Cao, Chengyu Dai, E. Schuyler Fried, Craig Gidney, Brendan Gimby, Pranav Gokhale, Thomas Häner, Tarini Hardikar, Vojtěch Havlíček, Oscar Higgott, Cupjin Huang, Josh Izaac, Zhang Jiang, Xinle Liu, Sam McArdle, Matthew Neeley, Thomas O'Brien, Bryan O'Gorman, Isil Ozfidan, Maxwell D. Radin, Jhonathan Romero, Nicholas Rubin , et al. (10 additional authors not shown)

Abstract: Quantum simulation of chemistry and materials is predicted to be an important application for both near-term and fault-tolerant quantum devices. However, at present, developing and studying algorithms for these problems can be difficult due to the prohibitive amount of domain knowledge required in both the area of chemistry and quantum algorithms. To help bridge this gap and open the field to more… ▽ More Quantum simulation of chemistry and materials is predicted to be an important application for both near-term and fault-tolerant quantum devices. However, at present, developing and studying algorithms for these problems can be difficult due to the prohibitive amount of domain knowledge required in both the area of chemistry and quantum algorithms. To help bridge this gap and open the field to more researchers, we have developed the OpenFermion software package (www.openfermion.org). OpenFermion is an open-source software library written largely in Python under an Apache 2.0 license, aimed at enabling the simulation of fermionic models and quantum chemistry problems on quantum hardware. Beginning with an interface to common electronic structure packages, it simplifies the translation between a molecular specification and a quantum circuit for solving or studying the electronic structure problem on a quantum computer, minimizing the amount of domain expertise required to enter the field. The package is designed to be extensible and robust, maintaining high software standards in documentation and testing. This release paper outlines the key motivations behind design choices in OpenFermion and discusses some basic OpenFermion functionality which we believe will aid the community in the development of better quantum algorithms and tools for this exciting area of research. △ Less

Submitted 27 February, 2019; v1 submitted 20 October, 2017; originally announced October 2017.

Comments: 22 pages

Using Mineral Oil to Improve the Performance of Multi-Crystal Detector for Dark Matter Searching

Authors: J. C. Liu, C. Guo, Z. Y. Yu, M. Y. Guan, Z. M. Wang, X. H. Ma, C. G. Yang, P. Zhang, C. J. Dai, W. L. Zhong, Z. H. Li, Y. P. Zhang, C. C. Zhang, Y. T. Wei, W. X. Xiong, H. Q. Zhang

Abstract: The inorganic crystals have been widely used for dark matter direct searching for many decades. However, limited by the crystal growth technique, a lot of small crystals have to be used together for large target mass, which results in a degradation of light collection efficiency. An experiment was built up to study the degradation, and the method of soaking crystals into mineral oil to improve the… ▽ More The inorganic crystals have been widely used for dark matter direct searching for many decades. However, limited by the crystal growth technique, a lot of small crystals have to be used together for large target mass, which results in a degradation of light collection efficiency. An experiment was built up to study the degradation, and the method of soaking crystals into mineral oil to improve the efficiency as well as reduce the interface effect were proposed and validated. Good data and MC agreements were achieved in the experiment. △ Less

Submitted 4 September, 2017; v1 submitted 3 July, 2017; originally announced July 2017.

Journal ref: 2017 JINST 12 P09022

DAMA/LIBRA results and perspectives

Authors: R. Bernabei, P. Belli, S. d'Angelo, A. Di Marco, F. Montecchia, A. d'Angelo, A. Incicchitti, F. Cappella, V. Caracciolo, R. Cerulli, C. J. Dai, H. L. He, H. H. Kuang, X. H. Ma, X. D. Sheng, R. G. Wang, Z. P. Ye

Abstract: The DAMA/LIBRA experiment ($\sim$ 250 kg of highly radio-pure NaI(Tl)) is running deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. Here we briefly recall the results obtained in its first phase of measurements (DAMA/LIBRA--phase1, total exposure: 1.04 ton $\times$ yr). DAMA/LIBRA--phase1 and the former DAMA/NaI (cumulative exposure: $1.33$ ton $\times$ yr) give evidenc… ▽ More The DAMA/LIBRA experiment ($\sim$ 250 kg of highly radio-pure NaI(Tl)) is running deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. Here we briefly recall the results obtained in its first phase of measurements (DAMA/LIBRA--phase1, total exposure: 1.04 ton $\times$ yr). DAMA/LIBRA--phase1 and the former DAMA/NaI (cumulative exposure: $1.33$ ton $\times$ yr) give evidence at 9.3 $σ$ C.L. for the presence of DM particles in the galactic halo by exploiting the model-independent DM annual modulation signature. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. At present DAMA/LIBRA--phase2 is running with increased sensitivity. △ Less

Submitted 5 December, 2016; originally announced December 2016.

Comments: Proceedings to the 19th Workshop "What Comes Beyond the Standard Models", Bled, July 11. -- 19., 2016

Journal ref: EPJ Web of Conferences 136, 05001 (2017)

Neutron Beam Tests of Barium Fluoride Crystal for Dark Matter Direct Detection

Authors: Cong Guo, Xinhua Ma, Zhimin Wang, Jie Bao, Changjiang Dai, Mengyun Guan, Jinchang Liu, Zuhao Li, Jie Ren, Xichao Ruan, Changgen Yang, Zeyuan Yu, Weili Zhong

Abstract: In order to test the capabilities of Barium Fluoride (BaF2) Crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and γ events are obtained for various recoil energies of the F content in… ▽ More In order to test the capabilities of Barium Fluoride (BaF2) Crystal for dark matter direct detection, nuclear recoils are studied with mono-energetic neutron beam. The energy spectra of nuclear recoils, quenching factors for elastic scattering neutrons and discrimination capability between neutron inelastic scattering events and γ events are obtained for various recoil energies of the F content in BaF2. △ Less

Submitted 10 July, 2016; originally announced July 2016.

Comments: 15 pages,8 figures

Neutron Beam Tests of $CsI(Na)$ and $CaF_{2}(Eu)$ Crystals for Dark Matter Direct Search

Authors: Cong Guo, Xinhua Ma, Zhimin Wang, Jie Bao, Changjiang Dai, Mengyun Guan, Jinchang Liu, Zuhao Li, Jie Ren, Xichao Ruan, Changgen Yang, Zeyuan Yu, Weili Zhong, Conett Huerta

Abstract: In recent decades, inorganic crystals have been widely used in dark matter direct search experiments. To contribute to the understanding of the capabilities of $CsI(Na)$ and $CaF_{2}(Eu)$ crystals, a mono-energetic neutron beam is utilized to study the properties of nuclear recoils, which are expected to be similar to signals of dark matter direct detection. The quenching factor of nuclear recoils… ▽ More In recent decades, inorganic crystals have been widely used in dark matter direct search experiments. To contribute to the understanding of the capabilities of $CsI(Na)$ and $CaF_{2}(Eu)$ crystals, a mono-energetic neutron beam is utilized to study the properties of nuclear recoils, which are expected to be similar to signals of dark matter direct detection. The quenching factor of nuclear recoils in $CsI(Na)$ and $CaF_{2}(Eu)$, as well as an improved discrimination factor between nuclear recoils and $γ$ backgrounds in $CsI(Na)$, are reported. △ Less

Submitted 16 February, 2016; originally announced February 2016.

Comments: 13 pages, 12 figures

Journal ref: Nuclear Inst. and Methods in Physics Research, A (2016), pp. 38-44

No role for neutrons, muons and solar neutrinos in the DAMA annual modulation results

Authors: R. Bernabei, P. Belli, F. Cappella, V. Caracciolo, R. Cerulli, C. J. Dai, A. d'Angelo, S. d'Angelo, A. Di Marco, H. L. He, A. Incicchitti, H. H. Kuang, X. H. Ma, F. Montecchia, X. D. Sheng, R. G. Wang, Z. P. Ye

Abstract: This paper summarizes in a simple and intuitive way why the neutrons, the muons and the solar neutrinos cannot give any significant contribution to the DAMA annual modulation results. A number of these elements have already been presented in individual papers; they are recalled here. Afterwards, few simple considerations are summarized which already demonstrate the incorrectness of the claim repor… ▽ More This paper summarizes in a simple and intuitive way why the neutrons, the muons and the solar neutrinos cannot give any significant contribution to the DAMA annual modulation results. A number of these elements have already been presented in individual papers; they are recalled here. Afterwards, few simple considerations are summarized which already demonstrate the incorrectness of the claim reported in PRL 113 (2014) 081302. △ Less

Submitted 11 September, 2014; originally announced September 2014.

Comments: 11 pages, 1 table

Journal ref: Eur. Phys. J. C 74 (2014) 3196

DAMA/LIBRA results and perspectives, Bled 2013

Authors: R. Bernabei, P. Belli, S. d'Angelo, A. Di Marco, F. Montecchia, F. Cappella, A. d'Angelo, A. Incicchitti, V. Caracciolo, S. Castellano, R. Cerulli, C. J. Dai, H. L. He, X. H. Ma, X. D. Sheng, R. G. Wang, Z. P. Ye

Abstract: The DAMA/LIBRA experiment is composed by about 250 kg of highly radiopure NaI(Tl). It is in operation at the underground Gran Sasso National Laboratory of the INFN. The main aim of the experiment is to investigate the Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The DAMA/LIBRA experiment and the former DAMA/NaI (the first gener… ▽ More The DAMA/LIBRA experiment is composed by about 250 kg of highly radiopure NaI(Tl). It is in operation at the underground Gran Sasso National Laboratory of the INFN. The main aim of the experiment is to investigate the Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The DAMA/LIBRA experiment and the former DAMA/NaI (the first generation experiment having an exposed mass of about 100 kg) have released results corresponding to a total exposure of 1.17 ton $\times$ yr over 13 annual cycles; they have provided a model independent evidence of the presence of DM particles in the galactic halo at 8.9 $σ$ C.L.. The results of a further annual cycle, concluding the DAMA/LIBRA--phase1, have been released after this Workshop and are not included here. In the fall 2010 an important upgrade of the experiment have been performed. All the PMTs of the NaI(Tl) detectors have been replaced with new ones having higher quantum efficiency with the aim to decrease the software energy threshold considered in the data analysis. The perspectives of the running DAMA/LIBRA--phase2 will be shortly summarized. △ Less

Submitted 6 March, 2014; originally announced March 2014.

Comments: Appeared in Proceedings to the 16th Workshop "What Comes Beyond the Standard Models?", Bled 14-21 of July 2013, Vol. 14, No. 2, DMFA Zaloznistvo, Ljubljana, Dec. 2013

Optical rogue waves in the generalized inhomogeneous higher-order nonlinear Schrodinger equation with modulating coefficients

Authors: Zhenya Yan, Chaoqing Dai

Abstract: The higher-order dispersive and nonlinear effects (alias {\it the perturbation terms}) like the third-order dispersion, the self-steepening, and the self-frequency shift play important roles in the study of the ultra-short optical pulse propagation. We consider optical rogue wave solutions and interactions for the generalized higher-order nonlinear Schrödinger (NLS) equation with space- and time-m… ▽ More The higher-order dispersive and nonlinear effects (alias {\it the perturbation terms}) like the third-order dispersion, the self-steepening, and the self-frequency shift play important roles in the study of the ultra-short optical pulse propagation. We consider optical rogue wave solutions and interactions for the generalized higher-order nonlinear Schrödinger (NLS) equation with space- and time-modulated parameters. A proper transformation is presented to reduce the generalized higher-order NLS equation to the integrable Hirota equation with constant coefficients. This transformation allows us to relate certain class of exact solutions of the generalized higher-order NLS equation to the variety of solutions of the integrable Hirota equation. In particular, we illustrate the approach in terms of two lowest-order rational solutions of the Hirota equation as seeding functions to generate rogue wave solutions localized in time that have complicated evolution in space with or without the differential gain or loss term. We simply analyze the physical mechanisms of the obtained optical rogue waves on the basis of these constraints. Finally, The stability of the obtained rogue-wave solutions is addressed numerically. The obtained rogue wave solutions may raise the possibility of relative experiments and potential applications in nonlinear optics and other fields of nonlinear science as Bose-Einstein condensates and ocean △ Less

Submitted 13 October, 2013; originally announced October 2013.

Comments: 12 pages, 10 figures

Journal ref: JOURNAL OF OPTICS 15 (2013) 064012

Femtosecond Hot-Exciton Emission in a Ladder-Type pi-Conjugated Rigid-Polymer Nanowire

Authors: D. C. Dai, A. P. Monkman

Abstract: A hot-exciton is usually the initial elementary excitation product of the solid phase, particularly in low dimensional photonic materials, which is a bottle-neck to all subsequent processes. Measurement of hot-exciton emission (HExEm) is a great challenge due to fast EK relaxation and thus very weak transient emission. Here we report the first unambiguous observation of femtosecond HExEm from thin… ▽ More A hot-exciton is usually the initial elementary excitation product of the solid phase, particularly in low dimensional photonic materials, which is a bottle-neck to all subsequent processes. Measurement of hot-exciton emission (HExEm) is a great challenge due to fast EK relaxation and thus very weak transient emission. Here we report the first unambiguous observation of femtosecond HExEm from thin films of a model quasi-one-dimensional π-conjugated organic rigid-rod quantum nanowire, MeLPPP (methyl-substituted ladder-type poly(para-phenylenes), by using femtosecond time-resolved fluorescence spectroscopy. The results show the clear HExEm from the cooling hot-excitons has a lifetime of ~500 to ~800 fs, and concomitant very weak density-dependent singlet-singlet annihilation (SSA) due to this ultrashort dwelling time. △ Less

Submitted 23 April, 2012; originally announced April 2012.

Comments: 18 pages, 3+4 figures

Journal ref: http://link.aps.org/doi/10.1103/PhysRevB.87.045308 (2013)

Brief comment: Dicke Superradiance and Superfluorescence Find Application for Remote Sensing in Air

Authors: D. C. Dai

Abstract: This letter briefly introduces the concepts of Dicke superradiance (SR) and superfluorescence (SF), their difference to amplified spontaneous emission (ASE), and the hints for identifying them in experiment. As a typical example it analyzes the latest observations by Dogariu et al. (Science 331, 442, 2011), and clarifies that it is SR. It also highlights the revealed potential significant applicat… ▽ More This letter briefly introduces the concepts of Dicke superradiance (SR) and superfluorescence (SF), their difference to amplified spontaneous emission (ASE), and the hints for identifying them in experiment. As a typical example it analyzes the latest observations by Dogariu et al. (Science 331, 442, 2011), and clarifies that it is SR. It also highlights the revealed potential significant application of SR and SF for remote sensing in air. △ Less

Submitted 26 August, 2011; originally announced August 2011.

Comments: 1.5 pages, 1 illustration figure, manuscript finished in March 2011, declined by two journals

Observation of Superfluorescence from a Spontaneous Coherence of Excitons in ZnTe Crystal: Evidence for Bose-Einstein Condensation of Excitons?

Authors: D. C. Dai, A. P. Monkman

Abstract: Superfluorescence (SF) is the emission from a dense coherent system in population inversion, formed from an initially incoherent ensemble. This is characterised by an induction time (t_D) for the spontaneous development of the macroscopic quantum coherence. Here we report detailed observation of SF on ultrafast timescale from a quantum ensemble of coherent excitons in highly excited intrinsic bulk… ▽ More Superfluorescence (SF) is the emission from a dense coherent system in population inversion, formed from an initially incoherent ensemble. This is characterised by an induction time (t_D) for the spontaneous development of the macroscopic quantum coherence. Here we report detailed observation of SF on ultrafast timescale from a quantum ensemble of coherent excitons in highly excited intrinsic bulk ZnTe single crystal at 5 K, showing a characteristic t_D from 40 ps to 10 ps, quantum noise and fluctuations, and quantum beating and ringing. From this clear observation of SF from a spontaneous coherence of excitons we infer that this is indicative of the formation of BEC of excitons on an ultrafast timescale. △ Less

Submitted 26 July, 2011; originally announced July 2011.

Comments: 8 pages, 3 figures, submitted to PRB

Journal ref: Phys. Rev. B 84, 115206 (2011)

Technical aspects and dark matter searches

Authors: R. Bernabei, P. Belli, F. Cappella, R. Cerulli, C. J. Dai, A. d'Angelo, H. L. He, A. Incicchitti, H. H. Kuang, X. H. Ma, F. Montecchia, F. Nozzoli, D. Prosperi, X. D. Sheng, Z. P. Ye

Abstract: A variety of detectors has been proposed for dark matter direct detection, but most of them -- by the fact -- are still at R&D stage. In many cases, it is claimed that the lack of an adequate detectors' radio-purity might be compensated through heavy uses of MonteCarlo simulations, subtractions and handlings of the measured counting rates, in order to claim higher sensitivity (just for a particu… ▽ More A variety of detectors has been proposed for dark matter direct detection, but most of them -- by the fact -- are still at R&D stage. In many cases, it is claimed that the lack of an adequate detectors' radio-purity might be compensated through heavy uses of MonteCarlo simulations, subtractions and handlings of the measured counting rates, in order to claim higher sensitivity (just for a particular scenario). The relevance of a correct evaluation of systematic effects in the use of MonteCarlo simulations at very low energy (which has always been safely discouraged in the field so far) and of multiple subtractions and handling procedures applied to the measured counting rate is shortly addressed here at some extent. Many other aspects would also deserve suitably deep investigations. △ Less

Submitted 21 December, 2009; originally announced December 2009.

Comments: Proceedings of TAUP2009, talk presented by F.Nozzoli

Journal ref: J.Phys.Conf.Ser.203:012040,2010

Science with the new generation high energy gamma- ray experiments

Authors: M. Alvarez, D. D'Armiento, G. Agnetta, A. Alberdi, A. Antonelli, A. Argan, P. Assis, E. A. Baltz, C. Bambi, G. Barbiellini, H. Bartko, M. Basset, D. Bastieri, P. Belli, G. Benford, L. Bergstrom, R. Bernabei, G. Bertone, A. Biland, B. Biondo, F. Bocchino, E. Branchini, M. Brigida, T. Bringmann, P. Brogueira , et al. (175 additional authors not shown)

Abstract: This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invaria… ▽ More This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invariance. △ Less

Submitted 4 December, 2007; originally announced December 2007.

Comments: 328 pages, 7.8Mb, Proceedings of the 5th SCINEGHE Workshop, June 18-20, 2007 http://www.roma2.infn.it/SciNeGHE07/

Journal ref: Frascati Physics Series vol.45 (2007) A.Lionetto, A.Morselli editors ISBN 978-88-86409-54-0