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Boulder-induced form roughness and skin shear stresses in a gravel-bed stream

Journal of Mountain Science 2024年第1期21卷 346-360页

作者： DAS Ratul DATTA Akash Civil Engineering Department National Institute of Technology AgartalaAgartala-799046India

Boulder spacing in mountain rivers and near-wake flow zones within the boulder array is very useful for fish habitat and growth of aquatic *** present study aims to investigate how the boulder array and spacing influence the near-bed flow structures in a gravel-bed *** are staggered over a gravel-bed stream with three different inter-boulder spacing namely(a)large(b)medium and(c)small *** acoustic Doppler velocimeter was used for flow measurements in a rectangular channel and the results were compared with those acquired from numerical *** time-averaged velocity profiles at the near-wake flow zones of boulders experience maximum flow retardation which is an outcome of the boulder-induced form *** ratio of velocity differences associated to form and skin roughness and its positive magnitude reveals the dominance of form roughness closest to the *** roughness computed is 1.75 to 2 times higher than the skin roughness at the near-wake flow *** particular,the collective immobile boulders placed at different inter-boulder spacings developed high and low bed shear stresses closest to the *** low bed shear stresses characterised by a secondary peak developed at the trough location of the boulders is attributed to the skin shear ***,the spatial averaging of time-averaged flow quantities gives additional impetus to present an improved illustration of fluid shear *** formation of form-induced shear stress is estimated to be 17%to 23%of doubleaveraged Reynolds shear stress and partially compensates for the damping of time-averaged Reynolds shear stress in the interfacial *** quadrant analysis of spatial velocity fluctuations depicts that the form-induced shear stresses are dominant in the interfacial sub-layer and have no significance above the gravel-bed surface.

关键词： Array of boulders Near wake flow zones Velocity distributions Skin roughness Form induced shear stresses

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Model dependent analysis of ■→■ decays in beyond standard model

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Chinese Physics C 2024年第9期48卷 86-99页

作者： S.Mahata M.Mandal H.Mahapatra S.Biswas S.Sahoo Department of Physics National Institute of Technology Durgapur

Motivated by the recent experimental results of branching fractions for ■→■ decays,which deviate from their SM predictions,we hve investigated these decays in W' model and scalar leptoquark model to determine potential signatures of new physics(NP) in semileptonic charm decays induced by c→■ *** recent experimental results of branching fractions for semileptonic D meson decays,new coupling parameters are predicted for the aforementioned NP *** fraction,forward-backward asymmetry,and lepton polarization asymmetry are examined by considering the predicted NP coupling *** results of branching fractions in scalar leptoquark model are found very close to the experimental results and exist around the range of 1σ *** presented a comparative study of the NP models to check their sensitivity on these *** anticipate that further research on these decays will significantly support our findings.

关键词： $ W' $ boson charm decay flavour changing charged current new physics scalar leptoquark

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Impact of dark current on pinned photo-diode capacitance of CMOS image sensor in low illumination regime

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Optoelectronics Letters 2024年第11期20卷 654-657页

作者： Mohsin Suharwerdi Gausia Qazi Department of Electronics & Communication Engineering National Institute of Technology

Applications for quanta and space sensing both depend on efficient low-light imaging. To precisely optimize and design image sensor pixels for these applications, it is crucial to analyze the mechanisms behind dark cu... 详细信息

关键词： A

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High-order Autler–Townes splitting in electrically tunable photonic molecules

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Photonics Research 2024年第8期12卷 1794-1801页

作者： YIHAO CHEN JUNTAO DUAN JIN LI YAN CHEN JIEWEN LI JIANAN DUAN XIAOCHUAN XU JIAWEI WANG School of Integrated Circuit Harbin Institute of Technology(Shenzhen)Shenzhen 518055China College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China national Key Laboratory of Laser Spatial Information Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

Whispering gallery mode optical microresonators represent a promising avenue for realizing optical analogs of coherent light–atom interactions,circumventing experimental ***-optical analogs of Autler–Townes splitting have been widely demonstrated,harnessing coupled optical microresonators,also known as photonic molecules,wherein the strong coupling between resonant fields enables energy level ***,we report the characterizations of Autler–Townes splitting in waveguide-coupled microring dimers featuring mismatched *** exploiting backscattering-induced coupling via Rayleigh and Mie scatterers in individual rings,high-order Autler–Townes splitting has been realized,yielding supermode hybridization in a multi-level *** resonance detuning using an integrated phase shifter,intra-cavity coupling-induced splitting becomes almost indistinguishable at the zero-detuning point where the strong inter-cavity coupling counteracts the imbalance of backscattering strengths in individual *** demonstrations on the maturing silicon photonics platform,our findings establish a framework of electrically tunable photonic molecules for coupling-mediated Autler–Townes splitting,offering promising prospects for on-chip signal generation and processing across classical and quantum regimes.

关键词： tunable tuning waveguide

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The quantum Ising model for perfect matching and solving it with variational quantum eigensolver

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Science China(Information Sciences) 2024年第9期67卷 306-320页

作者： Qilin ZHENG Pingyu ZHU Chao WU Miaomiao YU Weihong LUO Ping XU institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Hefei national Laboratory

Obtaining all perfect matchings of a graph is a tough problem in graph theory, and its complexity belongs to the #P-Complete class. The problem is closely related to combinatorics, marriage matching problems, dense subgraphs, the Gaussian boson sampling, chemical molecular structures, and dimer *** this paper, we propose a quadratic unconstrained binary optimization formula of the perfect matching problem and translate it into the quantum Ising model. We can obtain all perfect matchings by mapping them to the ground state of the quantum Ising Hamiltonian and solving it with the variational quantum eigensolver. Adjusting the model's parameters can also achieve the maximum or minimum weighted perfect matching. The experimental results on a superconducting quantum computer of the Origin Quantum Computing technology Company show that our model can encode 2~n dimensional optimization space with only O（n） qubits consumption and achieve a high success probability of the ground state corresponding to all perfect matchings. In addition, the further simulation results show that the model can support a scale of more than 14 qubits, effectively resist the adverse effects of noise, and obtain a high success probability at a shallow variational depth. This method can be extended to other combinatorial optimization problems.

关键词： perfect matching Ising model quantum Hamiltonian variational quantum eigensolver quadratic unconstrained binary optimization

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A highly sensitive LITES sensor based on a multi-pass cell with dense spot pattern and a novel quartz tuning fork with low frequency

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Opto-Electronic Advances 2024年第3期7卷 26-34页

作者： Yahui Liu Shunda Qiao Chao Fang Ying He Haiyue Sun Jian Liu Yufei Ma national Key Laboratory of Science and technology on Tunable Laser Harbin Institute of TechnologyHarbin 150000China Zhengzhou Research institute Harbin Institute of TechnologyZhengzhou 450000China Advanced Microscopy and Instrumentation Research Center School of Instrumentation Science and EngineeringHarbin Institute of TechnologyHarbin 150080China.

A highly sensitive light-induced thermoelectric spectroscopy(LITES)sensor based on a multi-pass cell(MPC)with dense spot pattern and a novel quartz tuning fork(QTF)with low resonance frequency is reported in this *** erbi-um-doped fiber amplifier(EDFA)was employed to amplify the output optical power so that the signal level was further *** optical path length(OPL)and the ratio of optical path length to volume(RLV)of the MPC is 37.7 m and 13.8 cm^(-2),respectively.A commercial QTF and a self-designed trapezoidal-tip QTF with low frequency of 9461.83 Hz were used as the detectors of the sensor,*** target gas selected to test the performance of the system was acetylene(C2H2).When the optical power was constant at 1000 mW,the minimum detection limit(MDL)of the C2H2-LITES sensor can be achieved 48.3 ppb when using the commercial QTF and 24.6 ppb when using the trapezoid-al-tip *** improvement of the detection performance by a factor of 1.96 was achieved after replacing the commer-cial QTF with the trapezoidal-tip QTF.

关键词： light-induced thermoelectric spectroscopy quartz tuning fork multi-pass cell gas sensing

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(Lu_(1/7)Yb_(1/7)Sc_(1/7)Er_(1/7)Y_(1/7)Ho_(1/7)Dy_(1/7))_(2)Si_(2)O_(7)high entropy rare-earth disilicate with low thermal conductivity and excellent resistance to CMAS corrosion

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Journal of Advanced Ceramics 2024年第5期13卷 549-560页

作者： Xu Wang Mingyu Meng Feihan Xu Ling Liu Lihong Gao Shizhen Zhu Zhuang Ma School of Materials Science and Engineering Beijing Institute of TechnologyBeijing 100081China national Key Laboratory of Science and technology on Materials under Shock and Impact Beijing 100081China Tangshan Research institute Beijing Institute of TechnologyTangshan 063000China

Low thermal conductivity,compatible thermal expansion coefficient,and good calcium–magnesium–aluminosilicate(CMAS)corrosion resistance are critical requirements for environmental barrier coatings used on silicon-based ***2Si2O7(RE=rare earth)has been widely recognized as one of the most promising candidates for environmental barrier coatings due to its good water vapor corrosion ***,the relatively high thermal conductivity and poor resistance to CMAS corrosion have limited its practical *** by the high entropy effect,in this work,a novel rare earth disilicate(Lu_(_(1/7))Yb_(_(1/7))Sc_(_(1/7))Er_(_(1/7))Y_(_(1/7))Ho_(_(1/7))Dy_(_(1/7)))2Si2O7((7RE_(_(1/7)))2Si2O7)has been designed and synthesized by a solid reaction process.(7RE_(_(1/7)))2Si2O7 showed a low thermal conductivity of 1.81 W·m^(−1)·K^(−1)at 1273 ***,the thermal expansion coefficient of(7RE_(_(1/7)))_(2)Si_(2)O_(7)(4.07×10^(−6)℃^(−1)from room temperature(RT)to 1400℃)is close to that of the SiC-based ceramic matrix composites(SiC-CMCs)((4.5–5.5)×10^(−6)℃^(−1)).Additionally,(7RE_(_(1/7)))2Si2O7 exhibited excellent resistance to CMAS *** exposed to CMAS at 1300℃for 48 h,the reaction layer thickness was 22μ*** improved performance of(7RE_(_(1/7)))2Si2O7 highlights its potential as a promising candidate for thermal/environmental barrier coatings.

关键词： high entropy disilicate (Lu_(1/7)Yb_(1/7)Sc_(1/7)Er_(1/7)Y_(1/7)Ho_(1/7)Dy_(1/7))_(2)Si_(2)O_(7)((7RE_(1/7))_(2)Si_(2)O_(7)) high-temperature thermal properties calcium-magnesium-aluminosilicate(CMAS)corrosion

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Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB

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Journal of Magnesium and Alloys 2024年第4期12卷 1638-1662页

作者： Shambhu Kumar Manjhi Srikanth Bontha A.S.S.Balan Department of Mechanical Engineering National Institute of Technology KarnatakaSurathkalSrinivasanagarMangaloreKarnataka 575025India

Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace ***,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing *** this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 *** findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED *** Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the *** treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress ***,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature *** contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue *** findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy *** study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface d

关键词： Wire arc additive manufacturing AZ31 Mg alloy Low plasticity burnishing Low cycle fatigue test Strain amplitude

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Limits of Depth: Over-Smoothing and Over-Squashing in GNNs

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Big Data Mining and Analytics 2024年第1期7卷 205-216页

作者： Aafaq Mohi ud din Shaima Qureshi Department of Computer Science and Engineering National Institute of Technology SrinagarSrinagar 190006India

Graph Neural Networks(GNNs)have become a widely used tool for learning and analyzing data on graph structures,largely due to their ability to preserve graph structure and properties via graph representation ***,the effect of depth on the performance of GNNs,particularly isotropic and anisotropic models,remains an active area of *** study presents a comprehensive exploration of the impact of depth on GNNs,with a focus on the phenomena of over-smoothing and the bottleneck effect in deep graph neural *** research investigates the tradeoff between depth and performance,revealing that increasing depth can lead to over-smoothing and a decrease in performance due to the bottleneck *** also examine the impact of node degrees on classification accuracy,finding that nodes with low degrees can pose challenges for accurate *** experiments use several benchmark datasets and a range of evaluation metrics to compare isotropic and anisotropic GNNs of varying depths,also explore the scalability of these *** findings provide valuable insights into the design of deep GNNs and offer potential avenues for future research to improve their performance.

关键词： Graph Neural Networks(GNNs) learning on graphs over-smoothing over-squashing isotropic-GNNs anisotropic-GNNs

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Mathematical modelling of ball and plate system with experimental and correlation function-based model validation

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Control Theory and technology 2024年第2期22卷 326-341页

作者： T.R.Dil Kumar S.J.Mija Department of Electrical Engineering National Institute of Technology CalicutKozhikode673601KeralaIndia

The ball and plate system is an inherently nonlinear under actuated benchmark system used for validating the performance of various control schemes. A mathematical model depicting the dynamics close to that of the system is very much required for such a test bed. In this correspondence, the complete nonlinear model, a simplified nonlinear model, and a linearized model of the ball and plate system are developed. The system comprises a ball and plate mechanism and a rotary servo unit. The ball and plate mechanism is modelled using the Euler–Lagrange method, whereas the rotary servo subsystem is modelled from the first principles. The nonlinear model of the combined system is developed by including the dynamics of the servo motor with gear and rolling resistance between the ball and the plate. The simplified nonlinear model of the system is obtained with suitable assumptions. The model is linearized around the operating point using the Jacobian. The validity of the developed models is investigated through correlation function analysis. The open-loop response of the three models, viz., nonlinear, simplified nonlinear, and linearized models, is analyzed in the MATLAB/Simulink platform. Since the open-loop system is unstable, the experimental validation of the model is performed with a double-loop PSO (particle swarm optimization) PID control scheme.

关键词： Ball and plate system Correlation function Model validation Particle swarm optimization(PSO) PSO PID controller

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