检索结果-南通市图书馆

A study on the stability of laminar open-channel flow over a sandy rippled bed

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2005年第1期48卷 83-103页

作者： bai Yuchuan xu Haijue Institute for Sedimentation River and Coastal Engineering Tianjin University Tianjin 300072 China Institute for Sedimentation River and Coastal Engineering Tianjin University Tianjin 300072 China

The bed of a river often features some kinds of bedform, such as sand ripples, dunes, and so on. Even if the bed is smooth initially, disturbances arising from the bed or other external sources will cause the laminar flow in an open channel to become unstable as soon as the flow develops, thereby leading to the formation of sand ripples on the bed. In return, the formation of the sand ripples will modfy the instability path of the laminar flow passing over them. The wavy character of the bed will induce further instability of the flow, which is essentially different from that on a smooth bed: the neutral curve will move forward and the critical Reynolds number will decrease. The flow is unstable in response to a wider range of the disturbance wave number, or the laminar flow instability can happen more easily. The propagation speed of the sand ripples also affects the flow instability, since the stability of open channel flow over a movable bed is fundamentally different from that on a rigid bed. These instability effects are discussed in detail in this paper.

关键词： bed with sand ripples, open channel, flow instability.

Three-component one-pot synthesis of 1,2,3,4-tetrahydroquinoline derivatives in hexafluoroisopropanol

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2008年第8期19卷 921-924页

作者： Jie Zhou bai Ling xu Institute of Materia Medica Chinese Academy of Medical Sciences ＆ Peking Union Medical College Beijing 100050 China

The one-pot aza-Diels-Alder reaction of substituted aromatic amines, ethyl glyoxylate and benzyl vinylcarbamate or N- benzyloxycarbonyl 2-pyrroline was conducted in hexafluoroisopropanol, providing the desired 1,2,3,4... 详细信息

关键词： Aza-Diels-Alder reaction Tetrahydroquinoline Hexafluoroisopropanol (HFIP) Fluorinated solvent

Grignard Addition to Quinoxalinium Salt: Synthesis of 1, 2-Dihydro-quinoxaline and 1, 2, 3, 4-Tetrahydroquinoxaline Derivatives

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2006年第2期17卷 165-168页

作者： Lian You ZHENG xu bai The Center for Combinatorial Chemistry and Drug Discovery Jilin University Changchun 130012

Grignard additions to a quinoxalinium salt were studied. Depending on the ratio of the reagents and reaction temperature, 1, 2, 3, 4-tetrahydroquinoxaline and 1, 2-dihydroquinoxaline derivatives could be resulted sele... 详细信息

关键词： Grignard addition quinoxalinium salt dihydroquinoxaline tetrahydroquinoxaline.

Quantitative Analysis of Frosting Characteristics on the Drip Tray of A Cryogenic Valve for LNG Ships

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2024年第4期38卷 572-585页

作者： bai xu CHEN Guan-yu DU Yue xu Cao CHEN Jia-jing School of Naval Architecture&Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

Cryogenic valves play a crucial role in the production and transportation of liquefied natural gas(LNG),and are primarily responsible for efficiently controlling the inflow and outflow of LNG and regulating ***,due to their operation in low-temperature and high-humidity environments,crucial components such as drip trays are susceptible to frosting,which may lead to LNG leakage,thereby causing severe safety *** this study,the user-defined function(UDF)is employed to redevelop Fluent,which integrates the frost growth model with the Eulerian multiphase flow model,to conduct a quantitative analysis of frosting on drip trays of cryogenic *** effects of environmental parameters,such as wind speed,ambient temperature,air humidity,and cold surface temperature on the growth of the frost layer were *** study reveals a limiting wind speed between 1 m/s and 2 m/*** reaching this limit speed,the growth of the frost layer reaches its maximum,and further increases in the wind speed have no significant effect on the growth of the frost ***,the influence of the change in the flow field on droplet impingement and freezing during the growth of the frost layer is considered through the coupling method of the kinematic characteristics of water droplets and the collection coefficient of water *** study identifies the influence of different parameters on the droplet impact efficiency,leading to the modification of the frost layer on the drip tray.

关键词： LNG carrier drip tray frost effective impact coefficient

A self-adaptive correction method for perspective distortions of image

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2019年第3期13卷 588-598页

作者： Lihua WU Qinghua SHANG Yupeng SUN xu bai School of Measurement and Communication Harbin University of Science and Technology Harbin 150080 China

Frequently, the shooting angles available to photograph an object are limited, and the resultant images contain perspective distortions. These distortions make more difficult to perform subsequent tasks like feature extraction and information identification. This paper suggested a perspective correction method that extracts automatically distortion features through edge detection. Results showed that this method is powerful in correcting images with perspective distortions. The corrected image has virtually little information missing, clear features and high recovery rate.

关键词： perspective correction perspective transformation Hough transform edge detection

Prediction Model of Kinetic Energy Conversion of Tandem Dual-Oscillator Based on Flow-Induced Vibration Experiment

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China Ocean Engineering 2022年第5期36卷 707-719页

作者： bai xu SUN Meng HAN Chuan-yu SUN Hai School of Naval Architecture&Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Marine Renewable Energy Laboratory Department of Naval Architecture&Marine EngineeringUniversity of MichiganAnn Arbor MI 48109-2145USA College of Aerospace and Civil Engineering Harbin Engineering UniversityHarbin 150001China

Flow-induced vibration energy harvesting devices typically use an elastically supported body immersed in an oncoming flow to convert the sea and river current's hydrokinetic energy into electrical *** proportion of energy the device collects is greatly influenced by parameters such as the water flow velocity,spacing between device components,structure size,and damping *** parameter optimization and performance predictions of flow-induced vibration energy harvesting devices,we train a model of the power harvesting efficiency under different damping ratios,stiffnesses,spacing ratios,and reduced velocities based on experimental *** improve the prediction accuracy,a feedforward network structure is optimized by using the topological evolutionary algorithm and a radial basis function *** analysis reveals that the radial basis function network model provides the best agreement with the experimental results and realizes accurate predictions of the power harvested by a dual-oscillator system in the vortex-induced vibration,transition region,and *** prediction results show that the model's maximum power harvesting efficiency occurs in the vortex-induced *** efficiency increases and then decreases with increasing stiffness and reduced velocity in this phase;an increase in the spacing ratio causes the effi-ciency to decrease and then increase;finally,increasing the damping ratio enhances the *** device achieves maximum power harvesting efficiency at a reduced velocity of U_(r)=*** proposed model effectively predicts the maximum efficiency and the corresponding damping ratio and stiffness of the vortex-induced vibration and galloping,providing a new method for predicting tandem dual-oscillator hydrodynamic power conversion in flow-induced vibration.

关键词： flow-induced vibration tandem double-oscillator radial basis function prediction

3D non-isothermal phase-field simulation of microstructure evolution during selective laser sintering

在线全文

学校读者我要写书评

暂无评论

npj Computational Materials 2019年第1期5卷 442-453页

作者： Yangyiwei Yang Olav Ragnvaldsen Yang bai Min Yi bai-Xiang xu Mechanics of Functional Materials Division Institute of Materials ScienceTechnische Universität Darmstadt64287 DarmstadtGermany Department of Materials Science and Engineering Norwegian University of Science and Technology7491 TrondheimNorway State Key Laboratory of Mechanics and Control of Mechanical Structures&Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education&College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics(NUAA)210016 NanjingChina

During selective laser sintering(SLS),the microstructure evolution and local temperature variation interact *** of conventional isothermal sintering model is thereby insufficient to describe *** this work,we construct our model from entropy level,and derive the non-isothermal kinetics for order parameters along with the heat transfer equation coupled with microstructure *** from partial melting and laser-powder interaction are also *** then perform 3D finite element non-isothermal phase-field simulations of the SLS single *** confront the high computation cost,we propose a novel algorithm analogy to minimum coloring problem and manage to simulate a system of 200 grains with grain tracking algorithm using as low as 8 non-conserved order ***,applying the model to SLS of the stainless steel 316L powder,we identify the influences of laser power and scan speed on microstructural features,including the porosity,surface morphology,temperature profile,grain geometry,and *** further validate the first-order kinetics of the transient porosity during densification,and demonstrate the applicability of the developed model in predicting the linkage of densification factor to the specific energy input during SLS.

关键词： microstructure isothermal kinetics

Voltage-driven charge-mediated fast 180 degree magnetization switching in nanoheterostructure at room temperature

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

npj Computational Materials 2017年第1期3卷 137-145页

作者： Min Yi Hongbin Zhang bai-Xiang xu Department of Materials and Earth Sciences Technische Universitat Darmstadt64287 DarmstadtGermany

Voltage-driven 180°magnetization switching without electric current provides the possibility for revolutionizing the *** demonstrated the voltage-driven charge-mediated 180°magnetization switching at room temperature by combining firstprinciples calculations and temperature-dependent magnetization dynamics *** electric field(E)-induced interface charge is found to allow a giant modulation of the magnetic anisotropy(K)of the *** K is revealed to vary linearly with respect to E and the epitaxial *** dynamics simulations using the so-obtained K show that both inplane and perpendicular 180°switching can be achieved by E *** temperature effect renders the 180°switching as probability *** analysis indicates a fast(around 4 ns)and low-error-probability 180°switching achievable at room temperature by controlling the magnitude of E and the pulse *** study inspires the rational design of miniaturized nanoscale spintronic devices where thermal fluctuation has a great impact.

关键词： magnetization charge render

Electric field induced magnetization reversal in magnet/insulator nanoheterostructure

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Smart and Nano Materials 2020年第3期11卷 298-309页

作者： Qihua Gong Min Yi bai-Xiang xu Institute of Materials Science Technische Universität DarmstadtDarmstadtGermany State Key Lab of Mechanics and Control of Mechanical Structures&Key Lab for Intelligent Nano Materials and Devices of Ministry of Education&College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics(NUAA)NanjingChina

Electric-field control of magnetization reversal is promising for lowpower *** in a magnet/insulator nanoheterostructure which is the fundamental unit of magnetic tunneling junction in spintronics,we demonstrate the electric field induced 180°magne-tization switching through a multiscale study combining firstprinciples calculations and finite-temperature magnetization *** the model nanoheterostructure MgO/Fe/Cu with insu-lator MgO,soft nanomagnet Fe and capping layer Cu,through firstprinciples calculations we find its magnetocrystalline anisotropy linearly varying with the electric *** finite-temperature magnetization dynamics which is informed by the first-principles results,we disclose that a room-temperature 180°magnetization switching with switching probability higher than 90%is achievable by controlling the electric-field pulse and the nanoheterostructure *** 180°switching could be fast realized within 5 *** study is useful for the design of low-power,fast,and miniaturized nanoscale electric-field-controlled spintronics.

关键词： Magnetization reversal nanoheterostructure electric field spintronics multiscale simulations switching probability