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Effects of Geometric Parameters on Performance of Rectangular Submerged Inlet for Aircraft

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Transactions of Nanjing University of Aeronautics and Astronautics 2021年第6期38卷 984-992页

作者： LIU Chao pei houju CHEN Changdong XU Wenbing YANG Kaijie Environment Control and Oxygen System Department Shanghai Aircraft Design and Research InstituteShanghai 201210P.R.China AVIC Nanjing Servo Control System Corporation Nanjing 210016P.R.China College of Energy&Power Engineering Jiangsu University of Science and TechnologyZhenjiang 212003P.R.China Key Laboratory of Aircraft Environment Control and Life Support MIITNanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China

To improve the comfortability and safety of aircraft,the demand of rectangular submerged inlets(RSIs)with low resistance is proposed to increase the inlet flow rate of ram air. A theoretical model is built to numerically analyze the effects of geometric parameters on the inlet mass flow rate of RSIs. The geometric parameters in question here encompass the aspect ratio of 2—4,the ramp angle of 6°—7°,the characteristic parameter of the throat of 0.20 —0.30,the ramp length of 939—1 337 mm,and the cone angle of 0° —3°. Simulation results demonstrate that the mass flow rate(MFR)is positively correlated with the aspect ratio,ramp angle,ramp length,and cone angle,and negatively correlated with characteristic parameter of the throat. Within the range of the geometric parameters considered,the RSI with the aspect ratio of 3,the ramp angle of 6°,the characteristic parameter of the throat of 0.20,the ramp length of 1 337 mm,and the cone angle of 3° obtains the largest MFR value of about 2.251 kg/s.

关键词： ram air system rectangular submerged inlet geometric parameter mass flow rate(MFR)

Design of efficient thermoelectric generators

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Science China Materials 2024年第1期67卷 377-378页

作者： Min Liu Yanzhong pei Interdisciplinary Materials Research Center School of Materials Science and EngineeringTongji UniversityShanghai 201804China

Thermoelectricity,which enables direct conversion between heat and electricity,undergoes impressive developments in recent decades,and is particularly promising for recovering low-grade heat of<600 K[1,2].Currently,only Bi2Te3-based thermoelectric devices are commercialized[3].However,the scarcity of tellurium(Te)(Fig.1a)is the main *** leads to numerous recent efforts on the development of efficient nonBi2Te3 thermoelectrics as potential alternatives,and successful examples(Fig.1b)include Mg3Sb2-alloys[2,3]and MgAgSb[1,2].

关键词： enable efficient electricity

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基于M-L湍流模型的浮空器强迫对流换热

化工学报 2020年第S1期71卷 136-141页

作者：裴后举蒋彦龙施红崔永龙陈常栋钱晓辉南京航空航天大学飞行器环境控制与生命保障工业和信息化部重点实验室江苏南京210016 江苏科技大学能源动力工程学院江苏镇江212003

外表面强迫对流换热是影响临近空间浮空器热控的重要因素,而流体的流动状态对强迫对流换热具有十分重要的影响。目前对浮空器外表面强迫对流换热的仿真研究多采用雷诺时均方程,将流动作为全湍流进行计算,且并未考虑转捩现象的影响。为... 详细信息

外表面强迫对流换热是影响临近空间浮空器热控的重要因素,而流体的流动状态对强迫对流换热具有十分重要的影响。目前对浮空器外表面强迫对流换热的仿真研究多采用雷诺时均方程,将流动作为全湍流进行计算,且并未考虑转捩现象的影响。为了研究转捩现象对强迫对流换热的影响,首先通过在Reynolds数为1.14×10^6情况下采用M-L转捩模型球体浮空器绕流得到的结果与实验结果以及采用Shear Stress Transfer(SST)k-ω、k-ε模型模拟结果进行对比分析,验证了M-L转捩模型在模拟球体浮空器强迫对流换热时的优越性。在验证数值模拟方法的基础上,分析了Reynolds数对球体浮空器强迫对流换热的影响。基于数值模拟得到的结果,在Reynolds数为10^6~10^8的范围内,拟合得到了球体浮空器强迫对流换热关系式。

关键词：强迫对流换热热力学 M-L模型转捩过程湍流热力学过程

Relationship between seismic structures and the diverse rupture processes of the 2023 Türkiye earthquake doublet

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Science China Earth Sciences 2024年第9期67卷 2810-2823页

作者： Zhi WANG Yi FU Shunping pei CAS Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China Key Laboratory of Tibetan Plateau Earth System Environment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Recent geodetic and seismological observations of two major earthquakes in southeastern Türkiye in February 2023 have revealed complex rupture initiation,propagation,and segmentation along the East Anatolian Fault Zone(EAFZ)and surrounding ***,the role of upper crust structures along the EAFZ in determining the diverse rupture processes of this earthquake doublet remains *** further investigate this,we employed double-difference location and seismic tomography techniques to determine high-resolution seismic velocities(V_(P),V_(S))and Poisson’s ratio(σ)structures using a multiparameter joint tomographic *** dataset includes 100,833 high-quality source-receiver travel-time pairs of P-and *** find that the unique rupture processes of this earthquake doublet were primarily influenced by contrasting crustal seismic structures and localized geological *** M_(w)7.8 mainshock was initiated within a transitional edge zone characterized by a rigid part(asperity)of the seismogenic zone with sharp contrast variations in rock strength ranging from low to high along the *** comparison,the M_(w)7.6 rupture originated in a ductile belt featuring fluid saturation with low-VP,low-VS,and high-σvalues that extended parallel to the Cardak *** pronounced contrast structures observed along the former rupture can be attributed to the oblique collision system between the weakened section of the east Anatolian plateau and the brittle Arabian platform,while the latter rupture was initiated within the ductile structure associated with fluid intrusion caused by the northward subduction of the Cyprus slab and subsequent ***,the occurrence of the first earthquake(E1)serves to alleviate shear stress on the second earthquake(E2)fault,potentially impeding the initiation of an E2 *** the contrary,this event also significantly reduces the normal stress acting on the E2 fault due to a double left-lateral strike-slip system

关键词： 2023 Turkiye earthquake doublet Joint seismic tomography Tomographic transition edge Seismic rupture process Strong fault coupling

Study on 6-DOF active vibration-isolation system of the ultra-precision turning lathe based on GA-BP-PID control for dynamic loads

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Advances in Manufacturing 2024年第1期12卷 33-60页

作者： Bo Wang Zhong Jiang pei-Da Hu Department of Precision Instrument Tsinghua UniversityBeijing100084People’s Republic of China Institute of Machinery Manufacturing Technology China Academy of Engineering PhysicsMianyang621900SichuanPeople’s Republic of China

The vibration disturbance from an external environment affects the machining accuracy of ultra-precision machining *** active vibration-isolation systems(AVIS)have been developed based on static *** a vibration-isolation load changes dynamically during ultra-precision turning lathe machining,the system parameters change,and the efficiency of the active vibration-isolation system based on the traditional control strategy *** solve this problem,this paper proposes a vibration-isolation control strategy based on a genetic algorithm-back propagation neural network-PID control(GA-BP-PID),which can automatically adjust the control parameters according to the machining ***-isolation simulations and experiments based on passive vibration isolation,a PID algorithm,and the GA-BP-PID algorithm under dynamic load machining conditions were *** experimental results demonstrated that the active vibration-isolation control strategy designed in this study could effectively attenuate vibration disturbances in the external environment under dynamic load *** design is reasonable and feasible.

关键词： Ultra-precision diamond turning lathe Active vibration isolation Six degrees of freedom Dynamic load Genetic algorithm-back propagation neural network-PID(GA-BP-PID)control

Influence of cutterhead opening ratio on soil arching effect and face stability during tunnelling through non-uniform soils

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Underground Space 2024年第4期17卷 45-59页

作者： Xue-Jian Chen pei-pei Fang Qiu-Nan Chen Jun Hu Kai Yao Yong Liu State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan 430072China Hubei Technology Innovation Center for Smart Hydropower Wuhan 430000China College of Civil Engineering Anhui Jianzhu UniversityHefei 230601China School of Civil Engineering Hunan University of Science and TechnologyXiangtan 411201China School of Civil and Architectural Engineering Hainan UniversityHaikou 570228China School of Qilu Transportation Shandong UniversityJinan 250002China

Tunnelling has increasingly become an essential tool in the exploration of underground space.A typical construction problem is the face instability during tunnelling,posing a great threat to associated *** face instability often occurs with the soil arching *** study investigates the combined effect of cutterhead opening ratio and soil non-uniformity on soil arching effect and face stability,via conducting random finite-element analysis coupled with Monte–Carlo *** results underscore that the face stability is strongly associated with the evolution of stress *** obtained stability factors in the uniform soils can serve as a reference for the design of support pressure in practical tunnelling *** addition,non-uniform soils exhibit a lower stability factor than uniform soils,which implies that the latter likely yields an underestimated probability of face *** tunnel face is found to have a probability of failure more than 50%if the spatial non-uniformity of soil is *** the end,a practical framework is established to determine factor of safety(FOS)corresponding to different levels of probability of face failure considering various opening ratios in non-uniform *** required FOS is 1.70 to limit the probability of face instability no more than 0.1%.Our findings can facilitate the prediction of probability of instability in the conventionally deterministic design of face pressure.

关键词： Tunnel Face stability Soil arching effect Cutterhead opening ratio Non-uniform soil Random field

Performance analysis of a photovoltaic/thermal system with lunar regolith-based thermal storage for the lunar base

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Science China(Technological Sciences) 2024年第4期67卷 1113-1123页

作者： SUN WenGan ZHAO Bin pei Yu SHI LingFeng HU MaoBin LI MuJun REN Xiao pei Gang Deep Space Exploration Laboratory Hefei 230026China Department of Thermal Science and Energy Engineering University of Science and Technology of ChinaHefei 230026China Department of Mechanical and Aerospace Engineering University of California San DiegoLa JollaCA 92093USA Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China College of New Energy China University of Petroleum(East China)Qingdao 266000China

Powering a moon base,especially keeping it warm during the long lunar night,is a big *** paper introduces a photovoltaic/thermal(PV/T)system incorporating regolith thermal storage to solve the challenge of power and heat provision for the lunar base *** vacuum of space around the moon helps this system by reducing heat *** the moon's daytime,the system not only generates electricity but also captures *** stored heat in the regolith is then used at night,reducing the amount of equipment we need to send from *** spectrally selective PV/T panels are designed to absorb a wide range of sunlight(0.3–2.5μm)while minimizing heat loss in the infrared range(3–30μm).Simulation results of the hybrid solar energy system indicate the average value of the overall efficiency is 45.9%,which relatively elevates 56.1%compared to the PV *** launch mass of the proposed PV/T system is only 8.4%of a traditional photovoltaic-lithium battery system with the same amount of energy *** the total specific energy of the proposed system is 7.3 kWh kg^(-1),while that of the photovoltaic-lithium battery system is about 0.3 kWh kg^(-1).In summary,this study proposes an alternative combined heat and electricity supply system for the lunar base,which can greatly reduce the launch mass and free up load for other scientific research equipment.

关键词： in-situ resource utilization(IRSU) regolith thermal storage photovoltaic/thermal(PV/T) spectral selectivity

Numerical study of submerged bending vegetation under unidirectional flow

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Water Science and Engineering 2024年第1期17卷 92-100页

作者： pei-pei Zhang Yi-qing Gong Ken Vui Chua Jie Dai Jing-qiao Mao College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China Institute of Water Science and Technology Hohai UniversityNanjing 210098China School of Engineering Cardiff UniversityCardiff CF243AAUK

Submerged vegetation commonly grows and plays a vital role in aquatic ecosystems,but it is also regarded as a barrier to the passing *** simulations of flow through and over submerged vegetation were carried out to investigate the effect of vegetation density on flow *** simulations were computationally set up to replicate flume experiments,in which vegetation was mimicked with flexible plastic *** fluid-structure interaction between flow and flexible vegetation was solved by coupling the two modules of the COMSOL *** cases with different vegetation densities were simulated,and the results were successfully validated against the experimental *** contours of the simulated time-averaged streamwise velocity and Reynolds stress were extracted to highlight the differences in mean and turbulent flow *** turbulence intensity was found to be more sensitive to vegetation density than the time-averaged *** developing length increased with the spacing between *** snapshots of the bending vegetation under instantaneous velocity and vorticity revealed that flexible vegetation responded to the effects of eddies in the shear layer by swaying *** first two rows of vegetation suffered stronger approaching flow and were prone to more streamlined *** addition,the origin of tip vortices was investigated via the distribution of *** results reveal the variation of flow properties with bending submerged vegetation and provide useful reference for optimizationofrestorationprojects.

关键词： Computational fluid dynamics Fluid-structure interaction Turbulence Flexible and submerged vegetation

Uniqueness Problem for the Backward Differential Equation of a Continuous-State Branching Process

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Acta Mathematica Sinica,English Series 2024年第8期40卷 1825-1836页

作者： pei Sen LI Zeng Hu LI School of Mathematics and Statistics Beijing Institute of TechnologyBeijing 100872P.R.China School of Mathematical Sciences Beijing Normal UniversityBeijing 100875P.R.China

The distributional properties of a multi-dimensional continuous-state branching process are determined by its cumulant semigroup,which is defined by the backward differential *** provide a proof of the assertion of Rhyzhov and Skorokhod(Theory ***.,1970)on the uniqueness of the solutions to the equation,which is based on a characterization of the process as the pathwise unique solution to a system of stochastic equations.

关键词： Continuous-state branching process multi-dimensional backward differential equation stochastic equation generator