bluuebunny/crossref_metadata_2025 huggingface dataset:
An array of microresonators as a photonic extreme learning machine
Authors: Biasi Stefano , Franchi Riccardo , Cerini Lorenzo , Pavesi Lorenzo
Published: September 2023

Machine learning technologies have found fertile ground in optics due to their promising features based on speed and parallelism. Feed-forward neural networks are one of the most widely used machine learning algorithms due to their simplicity and universal approximation capability. However, the typical training procedure, where all weights are optimized, can be time and energy consuming. An alternative approach is the Extreme Learning Machine, a feed-forward neural network in which only the output weights are trained, while the internal connections are random. Here we present an experimental implementation of a photonic extreme learning machine (PELM) in an integrated silicon chip. The PELM is based on the processing of the image of the scattered light by an array of 18 gratings coupled to microresonators. Light propagation in the microresonator array is a linear process while light detection by the video camera is a nonlinear process. Training is done offline by analyzing the recorded scattered light image with a linear classifier. We provide a proof-of-concept demonstration of the PELM by solving both binary and analog tasks, and show how the performance depends on the number of microresonators used in the readout procedure.
Revealing the ultrafast spontaneous emission in plasmon-enhanced monolayer semiconductor nano-light sources
Authors: Sun Jiawei , Hu Huatian , Chen Wen , Xu Yuhao , Tang Jibo , Li Yang , Xu Hongxing
Published: September 2023

Nanoscale spontaneous light sources are promising alternatives to lasers for high-speed optical communications and interconnections through energy-efficient integrated circuits. Yet, developing the spontaneous light sources faster than lasers is hampered by the detection means (e.g., time-resolved fluorescence spectroscopy). Here, by coupling monolayer WSe2 to individual plasmonic nanocavities, we achieved an efficient spontaneous light source with potential ultrafast modulation bandwidth and superior brightness. The ultrafast radiative decay rates can be determined and derived solely from the experimental parameters by combining the coupling strength and the photoluminescence enhancement in a single nanocavity-WSe2 hybrid. As a result, the hybrid light source has a radiative lifetime down to 350 fs, indicating a potential modulation bandwidth up to 440 GHz, which is 10 times of the traditional semiconductor lasers. Furthermore, the quantum yield is enhanced by a factor of over 300-folds up to 20.8% through making full use of the highly confined nanocavity mode. The nanocavity-WSe2 hybrid we built provides a promising approach for constructing high-speed light-emitting devices.
In search of universalities in the dissociative photoionization of PANHs via isomerizations
Authors: S Arun , Ramanathan Karthick , Selvaraj Muthuamirthambal , Cautero Marco , Richter Robert , Pal Nitish , Chiarinelli Jacopo , Bolognesi Paola , Avaldi Lorenzo , Vinitha M. V. , Jureddy Chinmai Sai , Kadhane Umesh R.
Published: September 2023

In search of the cause behind the similarities often seen in the fragmentation of PANHs, vacuum ultraviolet (VUV) photodissociation of two pairs of isomers quinoline–isoquinoline and 2-naphthylamine-3-methyl-quinoline are studied using the velocity map imaging technique. The internal energy dependence of all primary fragmentation channels is obtained for all four target molecules. The decay dynamics of the four molecules is studied by comparing their various experimental signatures. The dominant channel for the first pair of isomers is found to be hydrogen cyanide (HCN) neutral loss, while the second pair of isomers lose HCNH neutral as its dominant channel. Despite this difference in their primary decay products and the differences in the structures of the four targets, various similarities in their experimental signatures are found, which could be explained by isomerization mechanisms to common structures. The fundamental role of these isomerization in controlling different dissociative channels is explored via a detailed analysis of the experimental photoelectron–photoion coincidences and the investigation of the theoretical potential energy surface. These results add to the notion of a universal PANH fragmentation mechanism and suggests the seven member isomerization as a key candidate for this universal mechanism. The balance between isomerization, dissociation, and other key mechanistic processes in the reaction pathways, such as hydrogen migrations, is also highlighted for the four molecules.
Simulation of neutral beam current drive on EAST tokamak
Authors: Hu Youjun , Xu Xingyuan , Hu Yunchan , He Kaiyang , Wang Jinfang
Published: September 2023

A neutral beam current drive on the EAST tokamak is studied by using Monte Carlo test particle code TGCO. The phase-space structure of the steady-state fast ion distribution is examined and visualized. We find that trapped ions carry co-current current near the edge and countercurrent current near the core. However, the magnitude of the trapped ion current is one order smaller than that of the passing ions. Therefore, their contribution to the fast ion current is negligible (1% of the fast ion current). We examine the dependence of the fast ion current on two basic plasma parameters: the plasma current Ip and plasma density ne. The results indicate that the dependence of fast ion current on Ip is not monotonic: with Ip increasing, the fast ion current first increases and then decreases. This dependence can be explained by the change of trapped fraction and drift-orbit width with Ip. The fast ion current decreases with the increase in plasma density ne. This dependence is related to the variation of the slowing-down time with ne, which is already well known and is confirmed in our specific situation. The electron shielding effect to the fast ion current is taken into account by using a fitting formula applicable to general tokamak equilibria and arbitrary collisionality regime. The dependence of the net current on the plasma current and density follows the same trend as that of the fast ion current.
Hybrid integration of ensemble nitrogen-vacancy centers in single-crystal diamond based on pick-flip-and-place transfer printing
Authors: Katsumi Ryota , Takada Kosuke , Naruse Shun , Kawai Kenta , Sato Daichi , Hizawa Takeshi , Yatsui Takashi
Published: September 2023

Incorporating color centers in diamond with mature integrated photonics using hybrid integration techniques such as transfer printing provides a promising route toward scalable quantum applications. However, single-crystal diamond nanostructures fabricated using current etching technologies have triangular bottoms that are unsuitable for conventional pick-and-place integration. Herein, we present an alternative approach for deterministically integrating diamond nanostructures on chip. We demonstrate the hybrid integration of a diamond triangular nanobeam containing a nitrogen-vacancy ensemble on an SiO2 chip by picking it up using a weak adhesive film, flipping it, and transferring it to a stronger one. This “pick-flip-and-place” approach provides a flat diamond-chip interface, enabling the high-yield hybrid integration regardless of the shape of diamond nanostructures. Additionally, diamond nanofabrication is facilitated by transfer-printing hard masks for diamond etching. We also show that the integrated diamond nanobeam functions as a nanoscale quantum sensor. Our proposed approach paves the way toward scalable hybrid-diamond quantum photonics.
Growth of magnetooptical cerium-substituted yttrium iron garnet on yttrium aluminum garnet using ion beam sputtering
Authors: Yoshihara Yuki , Ishiyama Kazushi , Watanabe Toshiaki , Lim Pang Boey , Inoue Mitsuteru , Ross Caroline A. , Goto Taichi
Published: September 2023

Cerium-substituted yttrium iron garnet (Ce:YIG, Ce0.9Y2.1Fe5O12) was epitaxially grown on a (111)-oriented yttrium aluminum garnet (YAG) substrate using radio frequency ion beam sputtering. Magnetic hysteresis loops, transmissivity spectra, and magnetooptical (MO) responses, including Faraday rotation and Faraday ellipticity, were measured. The structural properties of the grown Ce:YIG were characterized using the x-ray rocking curve, reciprocal space map, pole figure, and x-ray reflectivity. X-ray photoelectron spectrometry revealed a dominant Ce3+ state in the grown Ce:YIG, but the transmission electron microscopy images showed columnar growth of Ce:YIG. This study demonstrates integration of epitaxial Ce:YIG on YAG, marking a significant step toward the fusion of MO garnets and laser crystals.
Crystallization and refluidization in very-narrow fluidized beds
Authors: Oliveira Vinícius P. S. , Borges Danilo S. , Franklin Erick M.
Published: September 2023

Fluidization of solid particles by an ascending fluid is frequent in industry because of the high rates of mass and heat transfers achieved. However, in some cases, blockages occur and hinder the correct functioning of the fluidized bed. In this paper, we investigate the crystallization (defluidization) and refluidization that take place in very-narrow solid–liquid fluidized beds under steady flow conditions. For that, we carried out experiments where either monodisperse or bidisperse beds were immersed in water flows whose velocities were above those necessary for fluidization, and the ratio between the tube and grain diameters was smaller than 6. For monodisperse beds consisting of regular spheres, we observed that crystallization and refluidization alternate successively along time, which we quantify in terms of macroscopic structures and agitation of individual grains. We found the characteristic times for crystallization and propose a new macroscopic parameter quantifying the degree of bed agitation. The bidisperse beds consisted of less regular spheres placed on the bottom of a layer of regular spheres (the latter was identical to the monodisperse beds tested). We measured the changes that macroscopic structures and agitation of grains undergo and show that the higher agitation in the bottom-layer hinders crystallization of the top layer. Our results bring new insights into the dynamics of very-narrow beds, in addition to proposing a way of mitigating defluidization.
Compressible Rayleigh–Taylor instability subject to isochoric initial background state
Authors: Majumder Swapnil , Sharma Bajrang , Livescu Daniel , Girimaji Sharath S.
Published: September 2023

The effect of compressibility on the single-mode Rayleigh–Taylor instability is examined using two (2D) and three-dimensional (3D) direct numerical simulations. To isolate compressibility from background stratification effects, this work employs a constant density profile on each side of the interface. The numerical simulations are performed at various Reynolds numbers using the gas kinetic method for static Mach numbers up to M = 0.4. The most important finding is that compressibility acting in isolation enhances the instability and perturbations grows faster with increasing Mach number, unlike previous results with background isothermal state, which show suppression of the instability at higher static Mach numbers. In addition, compressibility is also shown to increase the bubble-spike asymmetry. While the instability grows faster for the 3D case, the findings are qualitatively similar in 2D and 3D. The dynamical reasons underlying the effect of compressibility are elucidated by examining the evolution of vorticity and turbulent kinetic energy transport equations.
Electrically modulated photoresponse and optically modulated electroresistance in a ferroelectric heterostructure with PbZr0.2Ti0.8O3 barriers
Authors: Han Zhuokun , Zhang Boyong , Wang Fenglin , Luo Bingcheng , Wang Shuanhu , Zhai Wei , Wang Jianyuan
Published: September 2023

Ferroelectric heterostructures hold great promise for developing multifunctional memristors and optoelectronic devices. In this study, we report a ferroelectrically modulated photoresponse and optically modulated electroresistance behaviors in the Pt/PbZr0.2Ti0.8O3(PZT)/Nb-doped SrTiO3 (NSTO) heterostructure. The short-circuit photocurrent rises from 28 nA (after poling at +5 V) to 345 nA (after poling at −5 V) when illuminated with 360 nm of 10 mW·cm−2, exhibiting a massive photocurrent variation ratio of 1230%. This result can be attributed to the modulation of the ferroelectric polarization on the built-in field at the PZT/NSTO interface, which impacts the separation of photogenerated carriers. Furthermore, the heterostructure has a large high/low resistance ratio of 6 × 105%, which decreases to 2 × 104% when illuminated with 360 nm light. This finding is attributed to ferroelectric polarization and light illumination modulating the barrier height and width. Overall, this research suggests a promising strategy for developing self-powered heterojunction photodetectors and multifunctional memory devices.
Boosting of stable synchronization in coupled non-identical counter-rotating chaotic systems
Authors: Sivaganesh G. , Srinivasan K. , Fonzin Fozin T. , Gladwin Pradeep R.
Published: September 2023

Achieving synchronization in coupled non-identical chaotic systems has been a difficult endeavor, and improving the stability of synchronization in such systems poses additional challenges. This research work addresses these challenges by identifying stable synchronization in coupled non-identical chaotic systems and enhancing its stability. The study explores chaotic attractors that arise from various system parameters to provide generalized results. Furthermore, the impact of the transient uncoupling factor on improving synchronization stability in coupled non-identical counter-rotating chaotic oscillators is discussed. By investigating these aspects, the research aims to contribute to the understanding and advancement of synchronization in coupled non-identical chaotic systems.
Theoretical modeling of the terahertz spectrum of l-tyrosine leads to experimental verification of previously unobserved vibrational mode
Authors: Sanders T. J. , Allen J. L. , Horvat J. , Lewis R. A.
Published: September 2023

We have calculated the theoretical terahertz spectrum of the amino acid l-tyrosine using density functional theory (DFT). We tried two electron density functionals, Perdew–Burke–Ernzerhof (PBE) and PBE-d3. PBE-d3 includes dispersion corrections to build in van der Waals interactions, which play a role in intermolecular bonding. Both DFT models predicted a low-frequency mode that has not been previously reported. We designed an experiment to search for this mode. Using a deliberately thick sample, intense synchrotron radiation, low temperatures, and temperature variation has enabled us to observe a new resonance at 1.79 ±0.01 THz. While the PBE and PBE-d3 spectra are similar and both match the low-energy experimental data, overall the PBE-d3 appears to be slightly superior. Further refinement still of the functional may lead to even better agreement with experiment above 2.4 THz.
Perspectives on ultraintense laser-driven terahertz radiation from plasmas
Authors: Liao Guoqian , Li Yutong
Published: September 2023

High-power terahertz (THz) radiation is fundamental to numerous applications in many fields. Ultraintense laser-produced plasmas have attracted ever-increasing interest as a damage-free medium for generating high-peak-power THz pulses. This article gives the authors' perspectives on how the field of ultraintense laser-driven THz radiation from plasmas developed and where the field is headed. In particular, recent advances and some new ideas are outlined in terms of THz genesis, metrology, and applications. In addition to pushing the limits of achievable THz pulse energies and peak powers, much attention will be paid on the tunability of THz properties. Single-shot THz metrology will develop toward multi-dimensional resolution. The resulting extreme THz radiation offers immense opportunities in the THz control over matter and THz-driven strong-field physics. A selection of illustrative application cases in the field of materials, chemistry, and biology are briefly discussed. In the authors' opinion, the concerted advances in these aspects will propel this field into the bright future.
Computational analysis of cilia-mediated flow dynamics of Jeffrey nanofluid in physiologically realistic geometries
Authors: Ijaz Khan M. , Abbasi Aamar , Danish Sherjeel , Farooq Waseh
Published: September 2023

Cilia play important roles in fluid transport and development by propagating metachronal waves along cell surfaces. This study numerically investigates the biomechanics of cilia-driven flow of Jeffrey nanofluid in a wavy curved channel. The orthogonal curvilinear coordinates are used for the mathematical formulation of the problem in a set of partial differential equations. The governing equations are simplified using the dimensionless numbers and stream functions and then reduced using the long wavelength and low Reynolds number assumptions. Shooting method is applied to determine velocity, temperature, and nanoparticle concentration profiles. The resultant velocity, temperature profiles, nanoparticle concentration profiles, and streamlines are interpreted and elucidated graphically. The parametric analyses systematically examine the impacts of channel curvature, thermal buoyancy forces, nanoparticle concentrations, Jeffrey fluid rheology, and cilia motion kinematics on transport phenomena. Key findings show temperature and concentration gradients strongly influenced by cilia beating. The study provides deeper insight into the influence of these parameters on the cilia-driven flow in a complex wavy curved channel, bearing potential applications in heat transfer systems, nanotechnology, and biotechnology, among other fields.
Counterpoise correction from a practical perspective: is the result worth the cost?
Authors: Chan Bun , Ho Junming
Published: September 2023

In the present study, we have examined the utility of counterpoise (CP) corrections, the zero-cost geometric counterpoise (gCP) correction, and the double-ζ vDZP basis set, in representative examples of computational chemistry investigations. The tests include reaction energies and barriers in mechanisms of catalysis, and binding of substrates with enzyme active sites. Drawbacks of the CP approach include: it is more costly than calculations with the same basis set without applying CP corrections, multiple computations may be required where a single species is used in multiple instances, and it is only applicable to intermolecular interactions. In comparison, using gCP or vDZP is less costly. Their overall accuracy is comparable to CP, although the three approaches show variable performances for different systems. Thus, the use of a large basis set remains more consistent in obtaining results that are closer to the basis-set limit. Where the computational cost poses a challenge, the use of gCP or vDZP would be more advantageous than CP in terms of cost and simplicity.
Quantum Squeezing of Matter-Wave Solitons in Bose-Einstein Condensates
Authors: Zhu 朱 Jinzhong 锦忠 , Huang 黄 Guoxiang 国翔
Published: September 2023

We investigate the quantum squeezing of matter-wave solitons in atomic Bose–Einstein condensates. By calculating quantum fluctuations of the solitons via solving the Bogoliubov–de Gennes equations, we show that significant quantum squeezing can be realized for both bright and dark solitons. We also show that the squeezing efficiency of the solitons can be enhanced and manipulated by atom–atom interaction and soliton blackness. The results reported here are beneficial not only for understanding quantum property of matter-wave solitons, but also for promising applications of Bose-condensed quantum gases.
Superconductivity above 30K Achieved in Dense Scandium
Authors: He 何 Xin 鑫 , Zhang 张 Changling 昌玲 , Li 李 Zhiwen 芷文 , Zhang 张 Sijia 思佳 , Feng 冯 Shaomin 少敏 , Zhao 赵 Jianfa 建发 , Lu 卢 Ke 可 , Min 闵 Baosen 保森 , Peng 彭 Yi 毅 , Wang 望 Xiancheng 贤成 , Song 宋 Jin 静 , Wang 王 Luhong 鲁红 , I. Kawaguchi Saori , Ji 吉 Cheng 诚 , Li 李 Bing 冰 , Liu 刘 Haozhe 浩哲 , Tse J. S. , Jin 靳 Changqing 常青
Published: September 2023

Superconductivity is one of most intriguing quantum phenomena, and the quest for elemental superconductors with high critical temperature (T
c) is of great scientific significance due to their relatively simple material composition and the underlying mechanism. Here we report the experimental discovery of densely compressed scandium (Sc) becoming the first elemental superconductor with T
c breaking into 30 K range, which is comparable to the T
c values of the classic La–Ba–Cu–O or LaFeAsO superconductors. Our results show that

T
c

onset

of Sc increases from ∼ 3 K at around 43 GPa to ∼ 32 K at about 283 GPa (

T
c

zero

∼
31

K), which is well above liquid neon temperature. Interestingly, measured T
c shows no sign of saturation up to the maximum pressure achieved in our experiments, indicating that T
c may be even higher upon further compression.
Webs, Nijenhuis operators, and heavenly PDEs
Authors: Panasyuk Andriy , Szereszewski Adam
Published: September 2023

In 1989 Mason and Newman (Commun. Math. Phys.
121 659–68) proved that there is a 1-1-correspondence between self-dual metrics satisfying Einstein vacuum equation (in complex case or in neutral signature) and pairs of commuting parameter depending vector fields

X
1

(
λ
)
,

X
2

(
λ
)

which are divergence free with respect to some volume form. Earlier Plebański (1975 J. Math. Phys.
16 2395–402) showed instances of such vector fields depending of one function of four variables satisfying the so-called I or II Plebański heavenly PDEs. Other PDEs leading to Mason–Newman vector fields are also known in the literature: Park (1992 Int. J. Mod. Phys. A 7 1415), Husain (1994 Phys. Rev. Lett.
72 800), Grant (1993 Phys. Rev. D 48 2606–12), Schief (Phys. Lett. A 223 55–62). In this paper we discuss these matters in the context of the web theory, i.e. theory of collections of foliations on a manifold, understood from the point of view of Nijenhuis operators. In particular we show how to apply this theory for constructing new ‘heavenly’ PDEs based on different normal forms of Nijenhuis operators in 4D, which are integrable similarly to their predecessors. Relation with the Hirota dispersionless systems of PDEs and the corresponding Veronese webs, which was recently observed by Konopelchenko–Schief–Szereszewski, is established in all the cases. We also discuss some higher dimensional generalizations of the ‘heavenly’ PDEs and the existence of related vacuum Einstein metrics in 4D-case.
First-principles studies on the structural, electronic, and optical properties of 2D transition metal dichalcogenide (TMDC) and Janus TMDCs heterobilayers
Authors: Habib Haris , Zhao Wenjing , Mir Sibgha , Ma Liang , Tian Guangjun
Published: September 2023

Van der Waals heterobilayers formed by vertically stacked two-dimensional materials could be a viable candidate for optoelectronics. This study carried out first-principles calculations to study the geometrical, electronic and optical properties of heterobilayers consisting transition metal dichalcogenide (TMDC) SnSe2 and Janus TMDCs ZrSSe and SnSSe. Eight possible configurations SeSnSe–SSnSe (I), SeSnSe–SeSnS (II), SeSnSe–SZrSe (III), SeSnSe–SeZrS (IV), SSnSe–SZrSe (V), SSnSe–SeZrS (VI), SeSnS–SZrSe (VII) and SeSnS–SeZrS (VIII) are dynamically, thermally, energetically and mechanical stable. Six configurations, (I, II, III, IV, V and VI) have indirect band gaps with type-II band alignments, enhancing carrier lifetime an essential feature for potential applications in photovoltaic and nanoelectronics devices. In contrast, VII and VIII have indirect band gap with a type-I band alignment, facilitating efficient recombination of electron–hole pairs under high irradiation. All heterobilayers demonstrated significant optical absorption in the visible region. These findings highlight the potential utilization of heterobilayers in electronic and optoelectronic devices.
A robust intelligent fault diagnosis method for rotating machinery under noisy labels
Authors: Chen Chengyuan , Wang Yi , Ruan Hulin , Qin Yi , Tang Baoping
Published: September 2023

Despite achieving considerable success, the fault diagnosis methods will still be disturbed by noisy labels, this causes the model’s degradation and reduced diagnostic precision. Focused on solving the above issues, a robust intelligent fault diagnosis approach for rotating machinery under noisy labels is proposed. Firstly, we maintain two deep neural networks (DNNs) and alternatively execute parameters updating and models optimization by referring to the Co-teaching strategy, which can maximize filtering different error types and implement pre-training of DNNs. Secondly, adopting a two-component Gaussian mixture model (GMM) to fit training dataset’s cross-entropy (CE) loss and realize the clean and noisy labels division according to the threshold. Then, a data augmentation method called Mixup operation is employed in semi-supervised learning (SSL) to increase noise robustness and avoid error accumulation, subsequently, performing fine-tuning and correction for clean and noisy samples. Challenging experiments on a transmission gearbox dataset under different noisy labels levels show that the proposed method has robustness to noise and significantly surpasses other approaches, which provides an important reference value for accurate fault diagnosis for rotating equipment parts with noisy labels.
The real-time vision measurement of multi geometric information of the rolled ring in the hot ring rolling process based on deep learning
Authors: Huang Kangwen , Wang Xiaokai , Dong Jie , Han Xinghui , Hua Lin
Published: September 2023

Hot ring rolling (HRR) is an advanced incremental metal-forming technology to manufacture high-performance rings. Nowadays, the mechanical or laser-sensors measurement methods can only obtain one value of the dimensions on the ring circumference per time unit, the measurement data is single and the information is limited. This paper presents a real-time vision measurement method for multi geometric information of the rolled ring such as ring’s diameter, center position, circularity and growth speed in HRR process. Firstly, the deep learning model is constructed to intelligently and quickly identify rolled ring targets from complex image backgrounds, then the adaptive linear gray scale transformation algorithm is proposed to adjust the gray scale contrast of the image according to changes in ring temperature, the interference of oxide scales and flying chips are eliminated by morphology operation. Finally, the least square method is used to fit the contour points, and further the rolled ring’s geometric information and corresponding variation trend are calculated. Several experiments are conducted on a vertical HRR mill, the geometric information of the rolled ring during the HRR is measured in real-time under the interference of harsh working conditions. For the ring with outer diameter of 350 mm, the measurement error of ring’s outer and inner diameter is less than 0.8 mm, the average processing time per image takes about 80 ms. The research provides a basis for accurate measurement of HRR process.
Advanced techniques in automated high-resolution scanning transmission electron microscopy
Authors: Pattison Alexander J , Pedroso Cassio C S , Cohen Bruce E , Ondry Justin C , Alivisatos A Paul , Theis Wolfgang , Ercius Peter
Published: September 2023

Scanning transmission electron microscopy is a common tool used to study the atomic structure of materials. It is an inherently multimodal tool allowing for the simultaneous acquisition of multiple information channels. Despite its versatility, however, experimental workflows currently rely heavily on experienced human operators and can only acquire data from small regions of a sample at a time. Here, we demonstrate a flexible pipeline-based system for high-throughput acquisition of atomic-resolution structural data using an all-piezo sample stage applied to large-scale imaging of nanoparticles and multimodal data acquisition. The system is available as part of the user program of the Molecular Foundry at Lawrence Berkeley National Laboratory.
Enhancing the mechanical properties of hydrogels with vinyl-functionalized nanocrystalline cellulose as a green crosslinker
Authors: Islam Hasanul Banna Muhammad Zukaul , Krishna Suresh Babu Naidu , Imran Abu Bin
Published: September 2023

Hydrogels have gained significant attention in scientific communities for their versatile applications, but several challenges need to be addressed to exploit their potential fully. Conventional hydrogels suffer from poor mechanical strength, limiting their use in many applications. Moreover, the crosslinking agents used to produce them are often toxic, carcinogenic, and not bio-friendly. This study presents a novel approach to overcome these limitations by using bio-friendly modified nanocrystalline cellulose as a crosslinker to prepare highly stretchable and tough thermosensitive hydrogels. The surface of nanocrystalline cellulose was modified with 3-methacryloxypropyltrimethoxysilane (MPTS) to obtain modified nanocrystalline cellulose (M-NCC) crosslinker and used during free radical polymerization of thermosensitive N-isopropyl acrylamide (NIPA) monomer to synthesize NIPA/M-NCC hydrogel. The resulting nanocomposite hydrogels exhibit superior mechanical, thermal, and temperature-responsive swelling properties compared to conventional hydrogels prepared with traditional bi-functional N, N′-methylene bis (acrylamide) (MBA) as a crosslinker. The elongation at break, tensile strength, and toughness of the NIPA/M-NCC hydrogels significantly increase and Young’s modulus decrease than conventional hydrogel. The designed M-NCC crosslinker could be utilized to improve the mechanical strength of any polymeric elastomer or hydrogel systems produced through chain polymerization.
Comparison of ultrasound elastography, magnetic resonance elastography and finite element model to quantify nonlinear shear modulus
Authors: Pagé Gwenaël , Bied Marion , Garteiser Philippe , Van Beers Bernard , Etaix Nicolas , Fraschini Christophe , Bel-Brunon Aline , Gennisson Jean-Luc
Published: September 2023

Objective. The aim of this study is to validate the estimation of the nonlinear shear modulus (

A

) from the acoustoelasticity theory with two experimental methods, ultrasound (US) elastography and magnetic resonance elastography (MRE), and a finite element method. Approach. Experiments were performed on agar (2%)—gelatin (8%) phantom considered as homogeneous, elastic and isotropic. Two specific setups were built to ensure a uniaxial stress step by step on the phantom, one for US and a nonmagnetic version for MRE. The stress was controlled identically in both imaging techniques, with a water tank placed on the top of the phantom and filled with increasing masses of water during the experiment. In US, the supersonic shear wave elastography was implemented on an ultrafast US device, driving a 6 MHz linear array to measure shear wave speed. In MRE, a gradient-echo sequence was used in which the three spatial directions of a 40 Hz continuous wave displacement generated with an external driver were encoded successively. Numerically, a finite element method was developed to simulate the propagation of the shear wave in a uniaxially stressed soft medium. Main results. Similar shear moduli were estimated at zero stress using experimental methods,

μ

0

U
S

= 12.3 ± 0.3 kPa and

μ

0

M
R
E

= 11.5 ± 0.7 kPa. Numerical simulations were set with a shear modulus of 12 kPa and the resulting nonlinear shear modulus was found to be −58.1 ± 0.7 kPa. A very good agreement between the finite element model and the experimental models (

A

U
S

= −58.9 ± 9.9 kPa and

A

M
R
E

= −52.8 ± 6.5 kPa) was obtained. Significance. These results show the validity of such nonlinear shear modulus measurement quantification in shear wave elastography. This work paves the way to develop nonlinear elastography technique to get a new biomarker for medical diagnosis.
Extracting the gradient component of the gamma index using the Lie derivative method
Authors: Anetai Yusuke , Doi Kentaro , Takegawa Hideki , Koike Yuhei , Nishio Teiji , Nakamura Mitsuhiro
Published: September 2023

Objective. The gamma index (γ) has been extensively investigated in the medical physics and applied in clinical practice. However, γ has a significant limitation when used to evaluate the dose-gradient region, leading to inconveniences, particularly in stereotactic radiotherapy (SRT). This study proposes a novel evaluation method combined with γ to extract clinically problematic dose-gradient regions caused by irradiation including certain errors. Approach. A flow-vector field in the dose distribution is obtained when the dose is considered a scalar potential. Using the Lie derivative from differential geometry, we defined L, S, and U to evaluate the intensity, vorticity, and flow amount of deviation between two dose distributions, respectively. These metrics multiplied by γ (γL, γS, γU), along with the threshold value σ, were verified in the ideal SRT case and in a clinical case of irradiation near the brainstem region using radiochromic films. Moreover, Moran’s gradient index (MGI), Bakai’s χ factor, and the structural similarity index (SSIM) were investigated for comparisons. Main results. A high L-metric value mainly extracted high-dose-gradient induced deviations, which was supported by high S and U metrics observed as a robust deviation and an influence of the dose-gradient, respectively. The S-metric also denotes the measured similarity between the compared dose distributions. In the γ distribution, γL sensitively detected the dose-gradient region in the film measurement, despite the presence of noise. The threshold σ successfully extracted the gradient-error region where γ > 1 analysis underestimated, and σ = 0.1 (plan) and σ = 0.001 (film measurement) were obtained according to the compared resolutions. However, the MGI, χ, and SSIM failed to detect the clinically interested region. Significance. Although further studies are required to clarify the error details, this study demonstrated that the Lie derivative method provided a novel perspective for the identifying gradient-induced error regions and enabled enhanced and clinically significant evaluations of γ.
Characterization of cardiovascular and cerebrovascular controls via spectral causality analysis in patients undergoing surgical aortic valve replacement during a three-month follow-up
Authors: Bari Vlasta , Gelpi Francesca , Cairo Beatrice , Anguissola Martina , Pugliese Sara , De Maria Beatrice , Bertoldo Enrico Giuseppe , Fiolo Valentina , Callus Edward , De Vincentiis Carlo , Volpe Marianna , Molfetta Raffaella , Ranucci Marco , Porta Alberto
Published: September 2023

Objective. Aortic valve stenosis (AVS) induces left ventricular function adaptations and surgical aortic valve replacement (SAVR) restores blood flow profile across aortic valve. Modifications of cardiac hemodynamics induced by AVS and SAVR might alter cardiovascular (CV) and cerebrovascular (CBV) controls. The study aims at characterizing CV and CBV regulations one day before SAVR (PRE), within one week after SAVR (POST), and after a three-month follow-up (POST3) in 73 AVS patients (age: 63.9 ± 12.9 yrs; 48 males, 25 females) from spontaneous fluctuations of heart period (HP), systolic arterial pressure, mean arterial pressure and mean cerebral blood velocity. Approach. CV and CBV regulations were typified via a bivariate autoregressive approach computing traditional frequency domain markers and causal squared coherence (CK
2) from CV and CBV variabilities. Univariate time and frequency domain indexes were calculated as well. Analyses were carried out in frequency bands typical of CV and CBV controls at supine rest and during active standing. A surrogate method was exploited to check uncoupling condition. Main results. We found that: (i) CV regulation is impaired in AVS patients; (ii) CV regulation worsens in POST; (iii) CV regulation recovers in POST3 and CV response to active standing is even better than in PRE; (iv) CBV regulation is preserved in AVS patients; (v) SAVR does not affect CBV control; (vi) parameters of the CBV control in POST3 and PRE are similar. Significance.
CK
2 is particularly useful to characterize CV and CBV controls in AVS patients and to monitor of patient’s evolution after SAVR.
High-speed imaging reveals the dynamics of the initiation and subsequent evolution of a nanosecond discharge propagating along the air–water interface
Authors: Hoffer Petr , Prukner Václav , Arora Garima , Šimek Milan
Published: September 2023

A nanosecond DBD-like discharge in a coplanar electrode configuration propagating along the water–air interface is an efficient source of reactive species to produce plasma-activated water. In this letter, we report on the mechanism of the discharge onset as well as on further developments over hundreds of nanoseconds. We combined ultrafast optical imaging with electrical characteristics to capture basic morphological imprints of individual discharge phases occurring during a single discharge event with high temporal resolution. We show that during the first nanoseconds, a diffuse bi-directional ionizing avalanche expands over the liquid surface at high speed (>5

×

105 m s−1). Later, discrete plasma filaments form from the diffuse plasma due to an ionization instability. The filaments, during their subsequent elongation (∼2

×

105 m s−1), retain the diffuse plasma at both ends. The filaments re-ignite in the same positions on the liquid surface over several successive (mainly capacitive) current pulses (∼1 μs apart), which result from discontinuities in the driving voltage.
Cylindrical helical cell metamaterial with large strain zero Poisson’s ratio for shape morphing analysis
Authors: Qin Qing , Dayyani Iman
Published: September 2023

In this paper, a novel cylindrical metamaterial with helical cell exhibiting zero Poisson’s ratio (ZPR) in two different directions is introduced. Detailed Computer-aided design modelling of a curved optimised spring element is demonstrated for numerical and experimental analysis. High fidelity finite element models are developed to assess the homogenisation study of Poisson’s ratios, normalised Young’s modulus and torsion behaviour, demonstrating the curvature effect and independency of mechanical behaviour of cylindrical optimised spring element metamaterial from tessellation numbers. Buckling and frequency analysis of the cylindrical metamaterial with spring element are compared with equivalent shell cylinders. Moreover, experimental analysis is performed to validate the large strain ZPR and deformation mechanism demonstrated in numerical simulations. Finally, radical shape morphing analysis under different bending conditions for cylindrical metamaterial with helical cell is investigated, including deformation and actuation energy and compared with positive and negative Poisson’s ratio cylinders formed by honeycomb and auxetic cells.
Modelling of the deformation behaviour of a magnetic hydrogel in a magnetic field gradient
Authors: Czichy C , Odenbach S
Published: September 2023

An ink made of alginate and methylcellulose with embedded magnetite microparticles was developed for extrusion printing. Constructs, so-called scaffolds, are colonised with cells which can be activated by mechanical stimulation. In this work, a defined magnetic field gradient is applied to achieve non-contact deformation. However, the deformation behaviour or relevant material parameters of the hybrid material are unknown. While the properties were determined with experiments adapted to hydrogels, a separate experimental set-up for micro-computed tomography, adapting the Maxwell configuration, was developed to investigate the deformation behaviour. These analyses were performed depending on ageing and particle concentration. For these tests, strands were used as bending beams, since these are simple and well known systems. Firstly, a model for the bending curve was erected, which defines a range in which the real bending curve would be expected. It was compared with the measured bending curves. There was very good agreement for the first days. On day 14, the measured bending curves were still within the calculated range, but at the lower limit due to the shortcomings of the model as the violation of the small deformations condition at this point. Secondly, the bending as a function of incubation duration was observed by a series of radiograms when a magnetic field gradient was applied. From this, a functional approach was formulated to describe the system response. Some parameters have already been identified, for others a proposal is given. Thirdly, microscopic analyses were carried out to observe the effects of the field gradient on particle distribution and structure. It was revealed that a homogeneous particle distribution was found even after 2.5 h. Also, in the direction of the field gradient, no chains were formed and no damage of the network could be detected. The obtained results show, that the material is suitable for mechanical stimulation.
Identification and reconstruction of anomalous data in dam monitoring considering temporal correlation
Authors: Chen Yongjiang , Wang Kui , Zhao Mingjie , Xiong Yong , Li Chuanzhou , Liu JianFeng
Published: September 2023

In dam monitoring, anomalous data is often removed directly by researchers. However, some anomalous data may be due to sudden changes in the state of the dam itself and should not be removed. In this study, anomalous data in dam monitoring is divided into two categories: anomalous error data caused by anomalies in the monitoring equipment, and anomalous warning data caused by sudden changes in the state of the dam itself. Then we propose a method for identifying and reconstructing anomalous data in dam monitoring that takes into account temporal correlation. This method is able to identify and retain anomalous warning data, while removing and reconstructing anomalous error data. To determine the temporal correlation between dam monitoring parameters (e.g. water level, horizontal displacement, etc), we use association rules, and to reconstruct the removed dam monitoring data in the case of an incomplete dataset, we propose a dam monitoring data reconstruction network (DMDRN) based on generative adversarial network. On this basis and in combination with the density-based spatial clustering of applications with noise algorithm, the types of anomalous data in dam monitoring are identified, and the anomalous error data is reconstructed based on DMDRN. Our approach has been successfully validated in two experiments to identify and reconstruct anomalous data at a particular dam in China.
Quantum resonant optical bistability with a narrow atomic transition: bistability phase diagram in the bad cavity regime
Authors: Rivero D , Pessoa Jr C A , de França G H , Teixeira R C , Slama S , Courteille Ph W
Published: September 2023

We report on the observation of a novel manifestation of saturation-induced optical bistability in a resonantly pumped optical ring cavity interacting strongly with a cloud of atoms via a narrow atomic transition. The bistability emerges, above a critical pump rate, as an additional peak in the cavity’s normal mode spectrum close to atomic resonance. This third transmission peak is usually suppressed due to strong resonant absorption, but in our experiment it is visible because of the linewidth of the atomic transition being much smaller than that of the cavity, which sets the experiment into the bad-cavity regime. Relying on complete saturation of the transition, this bistability has a quantum origin and cannot be mimicked by a classical material presenting a nonlinear refraction index. The appearance of the central peak in addition to the normal modes is predicted by a semi-classical model derived from the Tavis–Cummings Hamiltonian from which we derive a bistability phase diagram that connects our observations with former work on optical bistability in the good cavity regime. The phase diagram reveals several so far unexplored bistable phases.
Variable mechanism of electrical impedance for MCT high voltage switch under synergetic action of the mechanical and electric loads
Authors: Chen Chuang , Guo Zihan , Guo Yuyang , Wang Ruizhi , Tang Enling
Published: September 2023

To study the electromechanical coupling effect of Metal Oxide Semiconductor Controlled Thyristor (MCT) high voltage switch under the synergistic action of mechanical load and strong voltage in the actual use of penetrating hard targets and launching, the universal testing machine was used to simulate the overload environment. The rising edge time, falling time and impedance changes in the conduction path of MCT under different stress–strain were tested, respectively. Experimental results showed that the rise time of MCT decreased from 0.08 ms to 0.03 ms when the uniaxial compressive stress increased from 1.20 MPa to 7.3 MPa, and the rising edge time after unloading was 0.04 ms. The falling time had no obvious change with the increase of stress. The total resistance in the path decreased from 833.30 Ω to 564.22 Ω with the increase of strain. The stress–strain of each part of MCT under different uniaxial compressive stress was collected by COMSOL Multiphysics finite element software. Based on the Schrödinger equation, the potential energy operator was established. By introducing the strain Hamiltonian H

ε,ν
, the E(k)-k model near the minimum value of the conduction band of Si was established by using the k·p perturbation method. Combined with the physical field interface of Schrödinger equation in COMSOL Multiphysics, the valence band structure of Si material under uniaxial strain was studied on the basis of strain Hamiltonian perturbation. The results showed that the 6-degree degenerate valley (Δ6) in the conduction band was split into a 2-degree degenerate valley (Δ2) and a 4-degree degenerate valley (Δ4) due to the stress effect. The strain caused more electrons to occupy the lower Δ4 energy valley, resulting in a decrease in the effective mass of the total conductivity. Therefore, the electron mobility of Si was increased under uniaxial strain. The uniaxial compressive stress could more effectively reduce the curvature radius of valence band top, the effective mass of carriers and the interband scattering between light and heavy hole bands, which was beneficial to improve the hole mobility.
Evaluation of Renewable Energy Accommodation Capacity Considering Multiple Flexibility Resources of Source-Load-Storage
Authors: Liu Juan , Wang Zhimin , Zhao Shuang , Chen Yu , Wang Lingyi , Zhang Xiuzhao , Chen Wen
Published: September 2023

The utilization of multiple flexibility resources (MFR), such as source-load-storage (SLS-sides), plays a vital role in promoting the integration of large-scale grid-connected renewable energy (RE). Analyzing the renewable energy accommodation capacity (REAC) and assessing the impact of flexibility resources on enhancing REAC is vital for the coordinated development of SLS sides. This study focuses on the technical mechanisms of thermal power (TP) deep peak regulation, load demand response (DR), and energy storage (ES). Considering the operational constraints of these MFR, an evaluation model for REAC is established. The model is a multi-objective optimization framework that encompasses the maximized installed capacity of RE while minimizing the comprehensive expenses of the power system. A hierarchical decoupling solution method is used to solve the evaluation model, obtaining the Pareto optimal solution set for RE installed capacity and power system operating cost. Subsequently, a fuzzy membership function is applied to select a compromise solution, quantitatively characterizing the REAC. The case study results demonstrate that by effectively coordinating the “SLS-sides” MFR, the REAC of the IEEE-RTS96 system can be improved from 1, 758 MW to 2, 731 MW, indicating a remarkable enhancement of 55.35%.