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Coarse-Grained Configurational Polymer Fingerprints for Property Prediction using Machine Learning
Authors:
Ishan Kumar,
Prateek K Jha
Abstract:
In this work, we present a method to generate a configurational level fingerprint for polymers using the Bead-Spring-Model. Unlike some of the previous fingerprinting approaches that employ monomer-level information where atomistic descriptors are computed using quantum chemistry calculations, this approach incorporates configurational information from a coarse-grained model of a long polymer chai…
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In this work, we present a method to generate a configurational level fingerprint for polymers using the Bead-Spring-Model. Unlike some of the previous fingerprinting approaches that employ monomer-level information where atomistic descriptors are computed using quantum chemistry calculations, this approach incorporates configurational information from a coarse-grained model of a long polymer chain. The proposed approach may be advantageous for the study of behavior resulting from large molecular weights. To create this fingerprint, we make use of two kinds of descriptors. First, we calculate certain geometric descriptors like Re2, Rg2 etc. and label them as Calculated Descriptors. Second, we generate a set of data-driven descriptors using an unsupervised autoencoder model and call them Learnt Descriptors. Using a combination of both of them, we are able to learn mappings from the structure to various properties of the polymer chain by training ML models. We test our fingerprint to predict the probability of occurrence of a configuration at equilibrium, which is approximated by a simple linear relationship between the instantaneous internal energy and equilibrium average internal energy.
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Submitted 20 November, 2023;
originally announced November 2023.
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Simultaneous measurements of unstable and stable Alfvén Eigenmodes in JET
Authors:
R. A. Tinguely,
J. Gonzalez-Martin,
P. G. Puglia,
N. Fil,
S. Dowson,
M. Porkolab,
I. Kumar,
M. Podestà,
M. Baruzzo,
A. Fasoli,
Ye. O. Kazakov,
M. F. F. Nave,
M. Nocente,
J. Ongena,
Ž. Štancar,
JET Contributors
Abstract:
In this paper, we report the novel experimental observation of both unstable and stable Toroidicity-induced Alfvén Eigenmodes (TAEs) measured simultaneously in a JET tokamak plasma. The three-ion-heating scheme (D-DNBI-3He) is employed to accelerate deuterons to MeV energies, thereby destabilizing TAEs with toroidal mode numbers n = 3-5, each decreasing in mode amplitude. At the same time, the Alf…
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In this paper, we report the novel experimental observation of both unstable and stable Toroidicity-induced Alfvén Eigenmodes (TAEs) measured simultaneously in a JET tokamak plasma. The three-ion-heating scheme (D-DNBI-3He) is employed to accelerate deuterons to MeV energies, thereby destabilizing TAEs with toroidal mode numbers n = 3-5, each decreasing in mode amplitude. At the same time, the Alfvén Eigenmode Active Diagnostic resonantly excites a stable n = 6 TAE with total normalized damping rate $-γ/ω_0 \approx$ 1%-4%. Hybrid kinetic-MHD modeling with codes NOVA-K and MEGA both find eigenmodes with similar frequencies, mode structures, and radial locations as in experiment. NOVA-K demonstrates good agreement with the n = 3, 4, and 6 TAEs, matching the damping rate of the n = 6 mode within uncertainties and identifying radiative damping as the dominant contribution. Improved agreement is found with MEGA for all modes: the unstable n = 3-5 and stable n = 2, 6 modes, with the latter two stabilized by higher intrinsic damping and lower fast ion drive, respectively. While some discrepancies remain to be resolved, this unique validation effort gives us confidence in TAE stability predictions for future fusion devices.
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Submitted 9 August, 2022;
originally announced August 2022.
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Simultaneous existence of ultra-high and ultra-low spectral sensitivity for Directional Couplers
Authors:
Garima Bawa,
Indrajeet Kumar,
Saurabh Mani Tripathi
Abstract:
We present the experimental evidence for the existence of two exciting wavelengths, termed critical and cross-over wavelength in the transmission spectrum of fiber-optic directional coupler, whose properties are conjugate to each other. The spectral shift associated with the transmission maxima/minima suddenly flip around these wavelengths and the spectrum shows largest (nil) spectral shift for th…
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We present the experimental evidence for the existence of two exciting wavelengths, termed critical and cross-over wavelength in the transmission spectrum of fiber-optic directional coupler, whose properties are conjugate to each other. The spectral shift associated with the transmission maxima/minima suddenly flip around these wavelengths and the spectrum shows largest (nil) spectral shift for the transmission maxima/minima closest to the critical ( at the cross-over) wavelength, corresponding to the same perturbation parameter. A theoretical explanation of the observed experimental behavior has also been presented, highlighting that the underlying mechanisms for the existence of these wavelengths are entirely different. The knowledge of the precise spectral location of these wavelengths is necessary to avoid false alarms.
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Submitted 8 July, 2020;
originally announced July 2020.
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Ultra-high Sensitive Surface Plasmon Resonance Based Sensor with Dual Resonance
Authors:
Indrajeet Kumar,
Ranjeet Dwivedi,
Saurabh Mani Tripathi
Abstract:
We show that for the optimized angle of incidence, the SPR based optical sensors exhibit dual resonance in the near-infrared region around which the sensor becomes exceptionally high sensitive. Both the resonances show opposite spectral shift with an ambient refractive index, increasing the differential shift by many folds. The physical reason behind the dual resonance and opposite spectral shifts…
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We show that for the optimized angle of incidence, the SPR based optical sensors exhibit dual resonance in the near-infrared region around which the sensor becomes exceptionally high sensitive. Both the resonances show opposite spectral shift with an ambient refractive index, increasing the differential shift by many folds. The physical reason behind the dual resonance and opposite spectral shifts are also explained using the modal analysis and the phase-matching condition. The presence of dual resonance is highly susceptible to the angle of incidence, which facilitates the sensors to work in a wide range from gaseous specimen to biological ones with extremely high sensitivity of 460 um/RIU and 290 um/RIU, respectively. The considered sensor has broader prospects for the detection of bio-chemicals and gases without changing its geometrical parameters.
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Submitted 4 July, 2020;
originally announced July 2020.
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Single-Multi-Single Fibre Optic Structure Based Water Depth Sensor
Authors:
Garima Bawa,
Krishnendu Dandapat,
Gyanendra Kumar,
Indrajeet Kumar,
Saurabh Mani Tripathi
Abstract:
We propose and demonstrate a technique easy to fabricate and measure water depth based on selective mode excitation using single-multi-single (SMS) mode structure. The high extinction ratio has been achieved by equally exciting preselected modes of the multi-mode fibre (MMF) by optimizing the core offset at both the input/output splices of the SMS structure, and a wavelength shifting has been achi…
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We propose and demonstrate a technique easy to fabricate and measure water depth based on selective mode excitation using single-multi-single (SMS) mode structure. The high extinction ratio has been achieved by equally exciting preselected modes of the multi-mode fibre (MMF) by optimizing the core offset at both the input/output splices of the SMS structure, and a wavelength shifting has been achieved by varying the ratio of major to minor axis of the MMF loop. A theoretical analysis of the observed behaviour is also presented showing an excellent agreement between the theoretical and experimental results.
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Submitted 14 October, 2018;
originally announced December 2018.
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Ultra high sensitive long period fiber grating based sensor for detection of adulterator in ethanol
Authors:
Krishnendu Dandapat,
Indrajeet Kumar,
Saurabh Mani Tripathi
Abstract:
An ultra-sensitive sensor based on long-period fiber graings (LPFGs) has been fabricated for the detection of methanol and water content in ethanol. Our sensor is very compact in size, highly accurate and easy to fabricate making it very useful than the conventional surface plasmon resonance (SPR) sensor, which is bulky and expensive. We show that our sensor is capable to achieve an ultra sensitiv…
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An ultra-sensitive sensor based on long-period fiber graings (LPFGs) has been fabricated for the detection of methanol and water content in ethanol. Our sensor is very compact in size, highly accurate and easy to fabricate making it very useful than the conventional surface plasmon resonance (SPR) sensor, which is bulky and expensive. We show that our sensor is capable to achieve an ultra sensitivity of 696.34 pm/ Volume-percent methanol and 655.3 pm/ Volume-percent water in presence of methanol and water in ethanol respectively. Our sensor is capable of detecting minimum 1.5 x 10^-3 Volume-percent methanol and water in ethanol, which is far better than all the methods reported till now.
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Submitted 29 August, 2018;
originally announced October 2018.