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Nusselt number correlation for turbulent heat transfer of helium-xenon gas mixtures

Nuclear Science and Techniques 2021年第11期32卷 119-133页

作者： Biao Zhou yu Ji Jun sun yu-Liang sun Institute of Nuclear and New Energy Technology Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China

A gas-cooled nuclear reactor combined with a Brayton cycle shows promise as a technology for highpower space nuclear power ***,a helium-xenon gas mixture with a molecular weight of14.5-40.0 g/mol is adopted as the working fluid to reduce the mass and volume of the *** Prandtl number for helium-xenon mixtures with this recommended mixing ratio may be as low as *** the convective heat transfer is closely related to the Prandtl number,different heat transfer correlations are often needed for fluids with various Prandtl *** studies have established heat transfer correlations for fluids with medium-high Prandtl numbers(such as air and water)and extremely lowPrandtl fluids(such as liquid metals);however,these correlations cannot be directly recommended for such helium-xenon mixtures without *** study initially assessed the applicability of existing Nusselt number correlations,finding that the selected correlations are unsuitable for helium-xenon *** establish a more general heat transfer correlation,a theoretical derivation was conducted using the turbulent boundary layer *** simulations of turbulent heat transfer for helium-xenon mixtures were carried out using Ansys *** on simulated results,the parameters in the derived heat transfer correlation are *** is found that calculations using the new correlation were in good agreement with the experimental data,verifying its applicability to the turbulent heat transfer for helium-xenon *** effect of variable gas properties on turbulent heat transfer was also analyzed,and a modified heat transfer correlation with the temperature ratio was *** on the working conditions adopted in this study,the numerical error of the property-variable heat transfer correlation was almost within 10%.

关键词： Gas-cooled nuclear reactor Space nuclear power Helium–xenon mixtures Convective heat transfer Nusselt number

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Model-data-driven P-wave impedance inversion using ResNets and the normalized zero-lag cross-correlation objective function

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Petroleum Science 2022年第6期19卷 2711-2719页

作者： yu-Hang sun Yang Liu CNPC Key Laboratory of Geophysical Prospecting and State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing102249China China University of Petroleum(Beijing) Karamay CampusKaramayXinjiang834000China

Model-driven and data-driven inversions are two prominent methods for obtaining P-wave impedance,which is significant in reservoir description and *** on proper initial models,most model-driven methods primarily use the limited frequency bandwidth information of seismic data and can invert P-wave impedance with high accuracy,but not high *** data-driven methods mainly employ the information from well-log data and can provide high-accuracy and highresolution P-wave impedance owing to the superior nonlinear curve fitting capacity of neural ***,these methods require a significant number of training samples,which are frequently *** obtain P-wave impedance with both high accuracy and high resolution,we propose a model-data-driven inversion method using Res Nets and the normalized zero-lag cross-correlation objective function which is effective for avoiding local minima and suppressing random *** using initial models and training samples,the proposed model-data-driven method can invert P-wave impedance with satisfactory accuracy and *** on synthetic and field data demonstrate the proposed method’s efficacy and practicability.

关键词： Model-data-driven P-wave impedance inversion Res Nets Zero-lag cross-correlation

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Compactly Supported Distributional Solutions of Nonstationary Nonhomogeneous Refinement Equations

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Acta Mathematica Sinica,English Series 2001年第1期17卷 1-14页

作者： Qi yu sun Department of Mathematics National University of Singapore

Let A be a matrix with the absolute values of all eigenvalues strictly larger than one, and let Z0 be a subset of Z such that n∈Z0 implies n+1∈Z0. Denote the space of all compactly supported distributions by D’, and the usual convolution between two compactly supported distributions f and g by f*g. For any bounded sequence Gn and Hn, n∈Z0, in D’, define the corresponding nonstationary nonhomogeneous refinement equation Φn=Hn*Φn+1（A.）+Gn for all n∈Z0, （*） where Φn, n∈Z0, is in a bounded set of D’. The nonstationary nonhomogeneous refinement equation （*） arises in the construction of wavelets on bounded domain, multiwavelets, and of biorthogonal wavelets on nonuniform meshes. In this paper, we study the existence problem of compactly supported distributional solutions Φn, n∈Z0, of the equation （*）. In fact, we reduce the existence problem to finding a bounded solution Fn of the linear equations n-Sn n+1= n for all n∈Z0, where the matrices Sn and the vectors n, n∈Z0, can be constructed explicitly from Hn and Gn respectively. The results above are still new even for stationary nonhomogeneous refinement equations.

关键词： Nonhomogeneous refinement equation Nonstationary refinement equation Colltinuous refinement equation Refinement equation Wavelets

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Fracture Toughness Properties of Three Different Biomaterials Measured by Nanoindentation

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Journal of Bionic Engineering 2007年第1期4卷 11-17页

作者： Ji-yu sun Jin Tong Key Laboratory of Terrain-Machine Bionics Engineering （Ministry of Education China） Jilin University （Nanling Campus） Changchun 130022 P. R. China

The fracture toughness of hard biomaterials, such as nacre, bovine hoof wall and beetle cuticle, is associated with fibrous or lamellar structures that deflect or stop growing cracks. Their hardness and reduced modulus were measured by using a nanoindenter in this paper. Micro/nanoscale cracks were generated by nanoindentation using a Berkovich tip. Nanoindentation of nacre and bovine hoof wall resulted in pile-up around the indent. It was found that the fracture toughness （Kc） of bovine hoof wall is the maximum, the second is nacre, and the elytra cuticle of dung beetle is the least one.

关键词： biomimetics bionics biomaterials nanoindentation laminated structure fracture toughness

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Botanical drug clinical trial: Common issues and future options

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Acta Pharmaceutica Sinica B 2021年第1期11卷 300-303页

作者： yu sun Jiahua Qian Department of Traditional Chinese Medicine and Ethnopharmaceuticals Center for Drug EvaluationNational Medical Products AdministrationBeijing 100022China Center for Drug Evaluation National Medical Products AdministrationBeijing 100022China

In order to understand this disparity between human use and drugs approved by regulatory agencies,we analyzed botanical drug clinical trials registered at *** to detect trends in current trials and guide future trials.A total of 195 botanical drug clinical trials were registered from 2016 to2019,of which 81 are phaseⅡor phaseⅡ/Ⅲ.95%of all phaseⅡandⅡ/Ⅲstudies were designed with100 or less participants per arm,indicating a more observational nature due to the limited power to detect differences in outcomes between treatment and control *** to the limited number of participants,efficacy outcome from results may be highly subjective.14%of the total trials were phaseⅠ*** botanical drugs with well-documented or extensive history of human use,phaseⅠmay not provide significant additional information,and may,therefore,not be *** the trial design,we suggest added-on studies when botanical drugs are used as part of a combination ***,we believe standardized data collection methods and criteria are critical to utilizing the vast collection of human experience as quality evidence to support regulatory approval.

关键词： Traditional Chinese medicine(TCM) Botanical drug Clinical trial Real-world evidence(RWE) Randomized-controlled trial(RCT)

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AN ADAPTIVE NONMONOTONIC TRUST REGION METHOD WITH CURVILINEAR SEARCHES

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Journal of Computational Mathematics 2006年第6期24卷 761-770页

作者： Qun-yan Zhou Wen-yu sun School of Mathematics and Computer Science Nanjing Normal University Nanjing 210097 China Department of Mathematics Jiangsu Teacher University of Technology Changzhou 213001 China

In this paper, an algorithm for unconstrained optimization that employs both trust region techniques and curvilinear searches is proposed. At every iteration, we solve the trust region subproblem whose radius is generated adaptively only once. Nonmonotonic backtracking curvilinear searches are performed when the solution of the subproblem is unacceptable. The global convergence and fast local convergence rate of the proposed algorithms are established under some reasonable conditions. The results of numerical ＇experiments are reported to show the effectiveness of the proposed algorithms.

关键词： Unconstrained optimization Preconditioned gradient path Trust region method,Curvilinear search.

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Steered coherence and entanglement in the Heisenberg XX chain under twisted boundary conditions

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Chinese Physics B 2021年第7期30卷 139-144页

作者： yu-Hang sun yu-Xia Xie School of Science Xi'an University of Posts and TelecommunicationsXi'an 710121China

We study steered coherence(SC)and entanglement in a three-spin Heisenberg XX model under twisted boundary conditions and show that their strengths can be significantly enhanced by tuning the twist *** optimal twist angleθ_(opt)for achieving the maximum l_(1) norm of SC isπin the region of weak field B and decreases gradually fromπto 0 when B increases after a critical value,while for the relative entropy of SC,θ_(opt)equalsπin the weak field region and 0 *** entanglement and the critical temperature above which the entanglement vanishes can also be significantly enhanced by tuning the twist angle from 0 toπ.

关键词： quantum coherence entanglement twisted boundary conditions

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A NONMONOTONE SECOND-ORDER STEPLENGTH METHOD FOR UNCONSTRAINED MINIMIZATION

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Journal of Computational Mathematics 2007年第1期25卷 104-112页

作者： Qun-yan Zhou Wen-yu sun Department of Basic Science Jiangsu Teachers University of Technology Changzhou 213001 China School of Mathematics and Computer Science Nanjing Normal University Nanjin9 210097 China School of Mathematics and Computer Science Nanjing Normal University Nanjing 210097 China

In this paper, a nonmonotone method based on McCormick＇s second-order Armijo＇s step-size rule [7] for unconstrained optimization problems is proposed. Every limit point of the sequence generated by using this procedure is proved to be a stationary point with the second-order optimality conditions. Numerical tests on a set of standard test problems are presented and show that the new algorithm is efficient and robust.

关键词： Nonmonotone method Armijo's line search Direction of negative curvature,Unconstrained optimization.

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Integrated lifting line/surface panel method for optimal propeller design with consideration of hub effect

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Journal of Hydrodynamics 2019年第6期31卷 1218-1230页

作者： Wen-yu sun Guo-fu Huang China Ship Scientific Research Center Wuxi 214082China

An optimal marine propeller design method is proposed,which integrates the lifting line and surface panel method and is characterized by the use of the surface panel method to take the hub effect into *** developing an integrated approach instead of an iterative method for the calculation of the interaction between the hub and the designed blades,the hub effects on the optimal circulation can be accounted for throughout the theoretical design *** new integrated method provides a fast and accurate enough method to model the straight forward hub surface,in the optimal propeller design.A systematic design procedure from the basic design inputs to the blade geometry determination is performed and the designed propellers are validated by the surface panel method and the RANS *** design and analysis cases are considered by different approaches with comparison and *** a comparative study including different hub geometries is also performed to reveal the mechanism of the hub effect on the distributions of the propeller optimal loads.

关键词： Optimal circulation design lifting line method surface panel method hub effect

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Optimization for Deep Learning:An Overview

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Journal of the Operations Research Society of China 2020年第2期8卷 249-294页

作者： Ruo-yu sun Department of Industrial and Enterprise Systems Engineering and affiliated to Coordinated Science LaboratoryUniversity of Illinois at Urbana-ChampaignUrbanaIL 61801USA Department of Electrical and Computer Engineering University of Illinois at Urbana-ChampaignUrbanaIL 61801USA

Optimization is a critical component in deep *** think optimization for neural networks is an interesting topic for theoretical research due to various ***,its tractability despite non-convexity is an intriguing question and may greatly expand our understanding of tractable ***,classical optimization theory is far from enough to explain many ***,we would like to understand the challenges and opportunities from a theoretical perspective and review the existing research in this ***,we discuss the issue of gradient explosion/vanishing and the more general issue of undesirable spectrum and then discuss practical solutions including careful initialization,normalization methods and skip ***,we review generic optimization methods used in training neural networks,such as stochastic gradient descent and adaptive gradient methods,and existing theoretical ***,we review existing research on the global issues of neural network training,including results on global landscape,mode connectivity,lottery ticket hypothesis and neural tangent kernel.

关键词： Deep learning Non-convex optimization Neural networks Convergence Landscape

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