检索结果-南通市图书馆

Numerical simulations of sloshing and suppressing sloshing using the optimization technology method

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2018年第6期39卷 845-854页

作者： Hui GUAN Yifei XUE Zhiiun wei Chuijie WU College of Meteorology and Oceanography National University of Defense Technology Nanjing 211101 China School of Aerospace Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Structural Analysis for Industrial Equipment School of Aeronautics and Astronautics Dalian University of Technology Dalian 116024 Liaoning Province China School of Aeronautics and Astronautics Dalian University of Technology Dalian 116024 Liaoning Province China

Sloshing is a common phenomenon in nature and industry, and it is important in many fields, such as marine engineering and aerospace engineering. To reduce the sloshing load on the side walls, the topology optimization and optimal control methods are used to design the shape of the board, which is fixed in the middle of the tank. The results show that the new board shape, which is designed via topology optimization, can significantly reduce the sloshing load on the side wall.

关键词： sloshing volume of fluid (VOF) method suppressing sloshing topologyoptimization

Unified Coordinate System Model for Performance Calculation of Fix-pad Journal Bearing with Different Pad Preload

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2014年第3期27卷 537-542页

作者： ZHU Aibin YANG Yulei CHEN wei YUAN Xiaoyang Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System Xi'an Jiaotong University

Traditional model for calculating performance parameters of a fix-pad journal bearing leads to heavy workload, complicated and changeable formulae as it requires deriving various geometric formulae with different bearing types such as circular journal bearing, dislocated bearing and elliptic bearing. Considering different pad preload ratios for non-standard bearing, traditional model not only becomes more complicated but also reduces scalability and promotion of the calculation programs. For the complexly case of traditional model while dealing with various fix-pad journal bearings, unified coordinate system model for performance calculation of fix-pad journal bearing is presented in the paper. A unified coordinate system with the bearing center at the origin is established, and the eccentricity ratio and attitude angle of axis relative to each pad are calculated through the coordinates of journal center and each pad center. Geometric description of fix-pad journal bearing is unified in this model, which can be used for both various standard bearing and non-standard bearing with different pad preload ratios. Validity of this model is verified with an elliptical bearing. Performance of a non-standard four-leaf bearing with different pad preload ratios is calculated based on this model. The calculation result shows that increasing preload ratio of the pad 1 and keeping that of the left three pads constant improves bearing capacity, stiffness and damping coefficients. This research presents a unified coordinate system model unifies performance calculation of fix-pad journal bearings and studied a non-standard four-leaf bearing with different pad preload ratios, the research conclusions provides new methods for performance calculation of fix-pad journal bearings.

关键词： fix-pad journal bearing performance calculation unified coordinate system model

The Influence of Different Solar System Planetary Ephemerides on Pulsar Timing

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第8期24卷 85-99页

作者： Jian-Peng Dai wei Han Na Wang School of Physical Science and Technology Xinjiang UniversityUrumqi 830046China Xinjiang Astronomical Observatory Chinese Academy of SciencesUrumqi 830011China University of Chinese Academy of Sciences Beijing 100049China Xinjiang Key Laboratory of Radio Astrophysics Urumqi 830011China

Pulsar timing offers a comprehensive avenue for exploring diverse topics in physics and *** solar system planetary ephemeris is crucial for pulsar timing as it provides the positions and velocities of solar system planets including the ***,it is inevitable that inherent inconsistencies exist in these *** between various ephemerides can significantly impact pulsar timing and parameter ***,pulsar timing highly depends on the JPL DE ephemeris,for instance,the Pulsar Timing Array data analysis predominantly utilizes *** this study,we examine inconsistencies across various ephemeris series,including JPL DE,EPM,and ***,discrepancies emerge particularly between the current ephemeris DE436 and the earliest released ephemeris DE200,as well as the most recent ephemerides,e.g.,DE440,INPOP21A,and *** detailed analysis of the effects of ephemeris on geometric correction procedures for the conversion of measured topocentric times of arrival is presented in this *** researches reveal that variations in the Roemer delays across different ephemerides lead to distinct *** timing residuals and the fact that these discrepancies can be readily incorporated into the subsequent pulsar parameters,leading to inconsistent fitting estimates,suggest that the influence of errors in the ephemeris on the timing process might currently be underappreciated.

关键词： (stars)pulsars general-Planetary Systems-time-ephemerides

Reducing DRAM refreshing in an error correction manner

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2015年第12期58卷 190-203页

作者： ZHU DanFeng WANG Rui wei YanJiang QIAN DePei School of Computer Science and Engineering Beihang University

Dynamic random access memory(DRAM) is facing the challenge of technology scaling. The decreasing feature size makes it harder to make DRAM cells which can keep the current data-holding time. When DRAM cells cannot hold data for a long time, DRAM chips need a more frequent refreshing operation. Therefore, in the near future, time and energy cost on DRAM refreshing will be no longer trivial. In this paper, we propose DRAM Error Correction Pointer(ECP), an error-correction-manner framework, to reduce DRAM refreshes without data loss. We exploit the non-uniform feature of DRAM cells with respect to the data retention time. Compared with the conventional refreshing mechanisms, which refresh DRAM chips by the retention time of the leakiest cells, we refresh the chips much fewer times, and treat the not-in-time refreshed cells as fault elements. We use the structure of ECP as a fault tolerant element. By recording the data which are supposed to be written into the leaky cells in our DRAM-ECP structures, DRAM-ECP can significantly decrease refreshing frequency. When these data are to be read out, DRAM-ECP retrieves the data stored in ECPs and covers them to the corresponding position in the data row. Our experiments show that DRAM-ECP can reduce over 70%refreshing operations than the current refreshing mechanism and also get significant energy saving.

关键词： DRAM refreshing error correction DRAM-ECP counting bloom filter retention time

Synthesis of Cu3.8Ni/CoO and Cu3.8Ni/MnO nanoparticles for advanced lithium-ion battery anode materials

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2017年第3期10卷 1033-1043页

作者： Jaewon Lee Huazhang Zhu wei Deng Yue Wu School of Chemical and Environmental Engineering Shanghai Institute of Technology Shanghai 200235 China Department of Chemical and Biological Engineering Iowa State University 2114 Sweeney Hall Ames IA 50010 USA School of Chemical Engineering Purdue University 480 Stadium Mall Drive West Lafayette IN 47907 USA

We synthesized Cu3.8Ni/CoO and Cu3.8Ni/MnO nanoparticles via an easy and scalable solution synthesis. The synthesized Cu3.8Ni/CoO and Cu3.8Ni/MnO nano- particles were annealed to remove the organic surfactants without phase transitions or side reactions. Electrons can be transferred via metallic Cu3.8Ni, which will not react with lithium ions. The heterogeneous structures of Cu3.8Ni/CoO and Cu3.8Ni/MnO nanopartides could enhance the lithium ion mobility and improve the life cycle, and these materials are therefore promising candidates as high- power-density and high-energy-density anode materials for lithium-ion batteries in diverse applications, such as electrical vehicles.

关键词： metal oxide nanoparticles lithium ion battery metallic

Prediction of stable high-pressure structures of tantalum nitride TaN2

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

Journal of Materials Science & Technology 2019年第10期35卷 2297-2304页

作者： Wandong Xing Zijie wei Rong Yu Fanyan Meng Department of Physics University of Science and Technology BeijingBeijing Engineering Research Center of Detection and Application for Weak Magnetic FieldBeijing100083China School of Automation University of Science and Technology BeijingBeijing100083China National Center for Electron Microscopy in Beijing School of Materials Science and EngineeringKey Laboratory of Advanced Materials of Ministry of Education of ChinaState Key Laboratory of New Ceramics and Fine ProcessingTsinghua UniversityBeijing100084China

Structure searches based on a combination of first-principles calculations and a particle swarm optimization technique unravel two new stable high-pressure structures(C2/m and Cmce) for Ta N2. The structural features, mechanical properties, formation enthalpies, electronic structure, and phase diagram of Ta N2 are fully investigated. Being mechanically and dynamically stable, the two phases could be made metastable experimentally at ambient conditions.

关键词： Particle swarm optimization First-principles Tantalum nitride Crystal structure High pressure

A New System to Evaluate Comprehensive Performance of Hard-Rock Tunnel Boring Machine Cutterheads

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2019年第6期32卷 72-84页

作者： Ye Zhu wei Sun Junzhou Huo Zhichao Meng School of Mechanical and Engineering Dalian Jiaotong UniversityDalin 116000China School of Mechanical and Engineering Dalian University of TechnologyDalian 116000China

The accurate performance evaluation of a cutterhead is essential to improving cutterhead structure design and predicting project cost. Through extensive research, this paper evaluates the performance of a tunnel boring machine(TBM) cutterhead for cutting ability and slagging ability. This paper propose cutting efficiency, stability, and continuity of slagging as the evaluation indexes of comprehensive cutterhead performance. On the basis of research of true TBM engineering applications, this paper proposes a calculation method for each index. A slagging efficiency index with a ratio of the maximum di erence between the slagging amount and average slagging is established. And a slagging stability index with a ratio of the maximum slagging fluctuation and average slagging is presented. Meanwhile, a cutting efficiency index by the weighed average value of multistage rock fragmentation of a cutter’s specific energy is established. The Robbins and China Railway Construction Corporation(CRCC) cutterheads are evaluated. The results show that under the same thrust and torque, the slagging stability of the CRCC scheme is worse, but the slagging continuity of the CRCC scheme is better. The cutting ability index shows that the CRCC cutterhead is more efficient.

关键词： Evaluation of cutterhead Cutting ability Slagging ability Rock fragmentation load

Statistical analysis on strain-rate effects during serrations in a Zr-based bulk metallic glass

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2017年第4期24卷 455-461页

作者： Bo Yuan Jiao-jiao Li Jun-wei Qiao College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024ShanxiChina Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024ShanxiChina

By means of statistical analysis,the deformation mechanisms taking place in elastic loading and plastic shearing stages during serrated flows on the stress-strain curves for bulk metallic glasses were studied *** serration number presented a linear increasing tendency with the decrease of applied strain rates due to the reduction of free *** excellent plastic deformation was illustrated from the influences of structure arrangement with activation *** using mean-field theory（MFT）,maximum elastic-energy density at different strain rates could be predicted by MFT besides maximum stress drops during *** results were helpful for understanding the serrated flow behavior or designing decent schemes to improve the plasticity of bulk metallic glasses at room temperature.

关键词： Bulk metallic glass Shear band Mean-field theory Serration

Performance comparison between waverider and wide-speed-range gliding vehicle based on CFD approaches

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2019年第10期62卷 1861-1870页

作者： ZHANG TianTian WANG ZhenGuo HUANG wei YAN XiaoTing Science and Technology on Scramjet Laboratory National University of Defense Technology

Wide-speed-range gliding vehicle(WSRGV) is designed to adapt to the variable cruising environment that hypersonic vehicles will encounter during the mission implementation. Based on the cone-derived theory, a novel design technique of WSRGV has been developed. Theoretically, the functional relationship between cone-derived waverider’s volumetric efficiency and its design Mach number can be built through sampling approach as long as the geometries of design conical shock wave and the upper base curve are fixed. Based on the functional relationship, a cone-derived waverider that owns the same volumetric efficiency with a giving WSRGV can be acquired. This paper compared the aerodynamic performance between WSRGV and the cone-derived waverider sharing the same volumetric efficiency in a wide Mach number range. Their aerodynamic properties versus angle of attack have also been compared under the waverider’s design Mach number. The obtained result shows that WSRGV shares similar aerodynamic performance with the cone-derived waverider with the same volumetric efficiency. The aero-surfaces in the margin area of this kind of configuration have a larger contribution to the lift-to-drag ratio in comparison with the aero-surfaces in the central area. The configuration with a thick central body and thin margin place owns not only better aerodynamic performance but also better loading property.

关键词： wide-speed range cone-derived waverider volumetric efficiency lift-to-drag ratio loading property