检索结果-南通市图书馆

Flow and Heat Transfer Characteristics in Rotating Two-pass Channels Cooled by Superheated Steam

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2012年第4期25卷 524-532页

作者： WANG Wei GAO Jianmin XU Liang shi xiaojun State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong UniversityXi'an 710049China

In a modern gas turbine,using superheated steam to cool the vane and blade for internal convection cooling is a promising alternative to traditional compressor ***,further investigations of steam cooling need to be *** this paper,the three-dimensional flow and heat transfer characteristics of steam are numerically investigated in two-pass square channels with 45° ribbed walls under stationary and rotating *** investigated rotation numbers are 0 and *** simulation is carried out by solving the Reynolds averaged Navier-Stokes equations employing the Reynolds stress turbulence model,especially considering two additional terms for Coriolis and rotational buoyancy forces caused by the rotating *** comparison,calculations for the air-cooled channels are done first at a Reynolds number of 25 000 and inlet coolant-to-wall density ratio of *** results are compared with the experiment *** the flow and heat transfer in steam-cooled channels are analyzed under the same operating *** results indicate that the superheated steam has better heat transfer performance than *** to the combined effect of rotation,skewed ribs and 180° sharp turn,the secondary flow pattern in steam-cooled rotating two-pass channels is quite *** complex secondary flow pattern leads to strong anisotropic turbulence and high level of anisotropy of Reynolds stresses,which have a significant impact on the local heat transfer coefficient distributions.

关键词： turbine steam cooling rotation numerical analysis heat transfer secondary flow Reynolds stress

Determining threshold default risk criterion for trade credit granting

在线全文

学校读者我要写书评

暂无评论

Journal of Southeast University(English Edition) 2008年第S1期24卷 49-53页

作者： shi, xiaojun Zheng, Haitao School of Economics and Management Beijing University of Aeronautics and Astronautics Beijing 100083 China

To solve the problem of setting threshold default risk criterion to select retailer eligible for trade credit granting, a novel method of solving simultaneous equations is proposed. This method is based on the bilevel programming modeling of trade credit decisions as an interaction between supplier and retailer. First, the bilevel programming is set up where the supplier decides on credit terms at the top level considering a retailer's default risk, and the retailer determines the order quantity at the lower level in response to the credit terms offered. By solving this bilevel programming, the relationship between the optimal terms and the corresponding default risk can be derived. Second, set the extreme scenario where the threshold default risk is approached as the point causing a zero marginal profit to the supplier. Another equation describing this particular scenario can also be derived. Thus, a system of two equations with two unknown variables can be obtained where the exact threshold default risk criterion can be found by solving them. A numerical example is presented as an illustration of the method proposed. It shows that the threshold criterion can be uniquely determined when the financial costs, inventory costs, and the marketing parameters of supplier and buyer are specified.

关键词： trade credit credit term threshold default risk

Optimal pressure-sensitive cuts for surface acoustic waves on langasite

在线全文

学校读者我要写书评

暂无评论

Science in China(Series F) 2006年第2期49卷 254-261页

作者： HAN Tao JI xiaojun shi Wenkang School of Electronic Information and Electrical Engineering Shanghai Jiaotong University Shanghai200240 China

The crystal langasite manifests its unique advantages and potentials for high temperature applications due to a high electromechanical coupling coefficient, temperature compensated orientations for surface acoustic wave （SAW）, and temperature stability. In order to analyze the pressure-induced frequency shift in SAW resonator type sensors at high temperature, this paper presents the electroelastic wave equations employing the effective material constants for small vibrations superimposed on biases originated from homogeneous temperature and external pressure fields in the Lagrangian description. Incorporated with the first-order perturbation integration, a model including both the mechanical and electrical perturbation items originating from thermal biases and small pressure fields is proposed. This universal model is suitable for substrate with high piezoelectricity and can be applied at either room temperature or high temperature circumstance. The criteria of optimal cuts for SAW pressure sensitivity, i.e., high electromechanical coupling coefficient and low temperature coefficient of delay, are proposed. A thorough investigation in trebly rotated cuts has shown that optimal pressure sensitive crystallographic areas can be obtained. The areas suitable for pressure sensors at room temperature are defined with Euler angles Ω1： φ=0°-0.6°, θ=144.4°-145.8°, ψ =23.2°-24.1°,Ω2： φ=59.4°-61.°, θ=34.2°-36.2°, ψ =24.1°-22.3°,Ω3： φ=119°-120°, θ=143.8°-145.5°, ψ =22.3°-23.5° The areas suitable for pressure sensors at high temperature are defined with Euler angles Ⅰ： φ=8°-30°, θ=24°-36°, ψ =4°-25°Ⅱ： φ=30°-55°, θ=144.4°-158°, ψ =4°-28° A set of experiments employing LGS （0, 150°, 22°） and （0, 90°, 0） has been performed to check the validity of the proposed calculation. The experimental relative sensitivity is in excellent agreement with the theoretical results.

关键词： surface acoustic wave langasite pressure sensitivity high temperature.

Dynamics,stability,and control of a four-cable mount system for wind tunnel test

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第2期36卷 58-75页

作者： Zhenjun ZHAO Zhanwei ZHAO Yu YAN Kaichun ZENG xiaojun shi Han WU School of Mechanical and Materials Engineering North China University of TechnologyBeijing 100144China High Speed Aerodynamics Institute China Aerodynamics Research and Development CenterMianyang 621000China

A four-cable mount system is proposed for full-model wind tunnel flutter tests,which may adjust the pitch and roll attitude of the aircraft scaled model and ensure that the model is not subjected to cable *** system provides sufficient support to simulate the free flight of the aircraft by applying appropriate spring stiffness and cable *** proposed fourcable mount system is modeled based on Lagrange mechanics,and its dynamics equations consider aerodynamic *** singularity of the system and its bifurcation characteristics under flow conditions are analysed to determine the supercritical bifurcation phenomenon for different tension levels and distances from the front suspension point to the mass centre of the *** mathematical expressions of the longitudinal flight stability of the cable mount system are derived by linearising the system dynamics equations using small *** influence of the cable tension,spring stiffness,suspension point position,and other factors on the flight stability of the aircraft are analysed.A feedforward control algorithm is proposed to minimize the total elastic potential energy of the *** results show that the model is in the level flight state when the elastic potential energy of the four-cable mount system is minimized.A feedback control design method is proposed based on the Lyapunov stability theory to derive the closed-loop stability *** system dynamics model that includes the aircraft rigid body model,flexible cables,pulleys,springs,aerodynamic model,and servo motor control is established using the flexible multibody dynamics method.A multibody dynamics solver and Simulink are used to simulate the attitude adjustment of the model in the wind tunnel and verify the supercritical bifurcation characteristics of the system and the effectiveness of the feedback and feedforward control.

关键词： Bifurcation Cable Flight dynamics Flutter Nonlinear control systems Wind tunnels

Lamb wave sensors array for nonviscous liquid sensing

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2006年第4期49卷 461-472页

作者： CHEN Zhijun HAN Tao JI xiaojun GUO Huawei shi Wenkang Department of Instrumentation Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Instrumentation Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Instrumentation Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Instrumentation Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Instrumentation Engineering Shanghai Jiao Tong University Shanghai 200240 China

The interdigital transducer (IDT) can excite Lamb wave in a piezoelectric plate loading with a liquid layer, and the phase velocity of Lamb wave is associated with the properties of the liquid layer. In this paper, the concept of effective permittivity is introduced to study the Lamb wave's potential application in liquid sensing. Considering the measuring of ideal nonviscous liquid, the sensors array is designed to sense the density and the dielectric constant of the liquid layer simultaneously. Using LiNbO3 as piezoelectric material, in order to improve the sensors array sensitivity and the electro-mechanical coupling coefficient, the optimized results including plate thicknesses and cut orientations are presented by numerical simulation. These studies show that the Lamb wave sensors array can be potential in liquid sensing.

关键词： Lamb wave sensors array, density, dielectric constant, plate thickness, cut orientation.

Relationship of species diversity between overstory trees and understory herbs along the environmental gradients in the Tianshan Wild Fruit Forests, Northwest China

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2020年第4期12卷 618-629页

作者： CHENG Junhui shi xiaojun FAN Pengrui ZHOU Xiaobing SHENG Jiandong ZHANG Yuanming Xinjiang Key Laboratory of Soil and Plant Ecological Processes College of Grassland and Environmental SciencesXinjiang Agricultural UniversityUrumqi 830052China State Key Laboratory of Desert and Oasis Ecology Xinjiang Institute of Ecology and GeographyChinese Academy of SciencesUrumqi 830011China

In forest ecosystems, interactions between overstory trees and understory herbs play an important role in driving plant species diversity. However, reported links between overstory tree and understory herb species diversity have been inconsistent, due to variations in forest types and environmental conditions. Here, we measured species richness(SR) and diversity(Shannon-Wiener(H') and Simpson's(D) indices) of overstory trees and understory herbs in the protected Tianshan Wild Fruit Forest(TWFF), Northwest China, to explore their relationships along the latitudinal, longitudinal, elevational, and climatic(current climate and paleoclimate) gradients in 2018. We found that SR, and H' and D diversity indices of overstory trees and understory herbs exhibited a unimodal pattern with increasing latitude and elevation(P<0.05) and negative associations with longitude(P<0.01). Along the climatic gradients, there were U-shaped patterns in SR, and H' and D diversity indices between trees and herbs(P<0.05). SR, and H' and D diversity indices for overstory tree species were positively associated with those for understory herbs(P<0.01). These findings indicate that overstory trees and understory herbs should be protected concurrently in the TWFF to increase effectiveness of species diversity conservation programs.

关键词： diversity indices overstory trees understory herbs paleoclimate current climate elevation

Survey of Pedestrian Action Recognition Techniques for Autonomous Driving

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2020年第4期25卷 458-470页

作者： Li Chen Nan Ma Patrick Wang Jiahong Li Pengfei Wang Guilin Pang xiaojun shi Beijing Key Laboratory of Information Service Engineering College of RoboticsBeijing Union UniversityBeijing 100101China Northeastern University BostonMA 02115USA the Communication and Information Center of Ministry of Emergency Management of the People’s Republic of China Beijing 100013China the College of Robotics Beijing Union UniversityBeijing 100101China

The development of autonomous driving has brought with it requirements for intelligence,safety,and *** example of this is the need to construct effective forms of interactive cognition between pedestrians and vehicles in dynamic,complex,and uncertain *** action detection is a form of interactive cognition that is fundamental to the success of autonomous driving ***,vehicles need to detect pedestrians,recognize their limb movements,and understand the meaning of their actions before making appropriate decisions in *** this survey,we present a detailed description of the architecture for pedestrian action recognition in autonomous driving,and compare the existing mainstream pedestrian action recognition *** also introduce several commonly used datasets used in pedestrian motion ***,we present several suggestions for future research directions.

关键词： autonomous driving pedestrian action recognition action datasets two-stream network

Integrating biochar and bacteria for sustainable remediation of metal-contaminated soils

在线全文

学校读者我要写书评

暂无评论

Biochar 2023年第1期5卷 1098-1116页

作者： Peng Ouyang Mathiyazhagan Narayanan xiaojun shi Xinping Chen Zhenlun Li Yongming Luo Ying Ma College of Resources and Environment Southwest UniversityChongqing 400716China Division of Research and Innovation Department of BiotechnologySaveetha School of EngineeringSaveetha Institute of Medical and Technical ScienceChennai 602105Tamil NaduIndia Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China

Due to anthropogenic activities,heavy metal(HM)pollution in soils has increased,resulting in severe ecological problems and posing a constant threat to human *** various remediation methods,bacterial remediation is a relatively clean,efficient,and minimally negative ***,bacterial agents face multiple environmental stresses,making them challenging to achieve long-lasting and stable restoration *** address this issue,supportive organic substances such as biochar can be added to the soil with *** to bibliometric studies,integrating biochar and bacteria is extensively researched and widely used for HM-contaminated soil *** integrating biochar and bacteria,heavy metals in the soil can be remediated,and soil conditions can be improved over *** can also better promote plant growth or contribute effectively to phytoremediation processes when assisted by ***,the remediation agents integrating biochar and bacteria are still some distance away from large-scale use because of their high cost and possible environmental ***,further discussion on the interaction between biochar and bacteria and the integration approach,along with their remediation efficiency and environmental friendliness,is needed to achieve sustainable remediation of HM-contaminated soils by integrating biochar and *** paper discusses the potential mechanisms of biochar-bacteria-metal interactions,current advancements in biochar-bacteria combinations for HM-contaminated soil treatment,and their application in sustainable remediation,analyzes the interaction between biochar and bacteria and compares the remediation effect of different ways and feedstocks to integrate biochar and ***,future directions of biochar-bacteria combinations are presented,along with evidence and strategies for improving their commercialization and implementation.

关键词： Biochar Heavy metals Bioremediation Plant-beneficial bacteria Soil pollution

MoTransFrame:Model Transfer Framework for CNNs on Low-Resource Edge Computing Node

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2020年第12期65卷 2321-2334页

作者： Panyu Liu Huilin Ren xiaojun shi Yangyang Li Zhiping Cai Fang Liu Huacheng Zeng National University of Defense Technology Changsha410073China Training and Administration Department the Central Military CommissionBeijing100851China Department of Science and Technology China Electronics Technology Group CorporationBeijing100846China National Engineering Laboratory for Public Safety Risk Perception and Control by Big Data Beijing100041China School of Design Hunan UniversityChangsha410082China Department of Electrical and Computer Engineering University of LouisvilleLouisvilleKY 40292USA

Deep learning technology has been widely used in computer vision,speech recognition,natural language processing,and other related *** deep learning algorithm has high precision and high ***,the lack of resources in the edge terminal equipment makes it difficult to run deep learning algorithms that require more memory and computing *** this paper,we propose MoTransFrame,a general model processing framework for deep learning *** of designing a model compression algorithm with a high compression ratio,MoTransFrame can transplant popular convolutional neural networks models to resources-starved edge devices promptly and *** the integration method,Deep learning models can be converted into portable projects for Arduino,a typical edge device with limited *** experiments show that MoTransFrame has good adaptability in edge devices with limited *** is more flexible than other model transplantation *** can keep a small loss of model accuracy when the number of parameters is compressed by tens of *** the same time,the computational resources needed in the reasoning process are less than what the edge node could handle.

关键词： Edge computing convolutional neural network model transformation model compression