检索结果-南通市图书馆

Numerical Investigation of the Fluid Flow Characteristics in the Hub Plate Crown of a Centrifugal Pump

Chinese Journal of Mechanical Engineering 2018年第4期31卷 182-191页

作者： Wei Dong Wu-li chu School of Power and Energy Northwestern Polytechnical University Collaborative Innovation Center of Advanced AeroEngine

Due to the lack of understanding in the flow mechanism of the hub plate crown, the current calculation of the disc friction loss and the axial thrust in the centrifugal pump often uses empirical formulas. Research on the flow characteristics of the hub plate crown is of practical significance. The shroud and hub cavities are respectively studied with regard to tangential and radial velocities at the four different angular positions(0°, 90°, 180°, and 270°) at the four different operational points(0.6 Qsp, 0.8 Qsp, 1.0 Qsp, and 1.2 Qsp). Results indicate that at the same operational point, the smaller the volute chamber sectional area is, the higher the tangential velocity of the fluid core zone of the shroud cavity is. Radial leakage flow from the volute to the seal ring at the same operational point appears in 0° and 90° direction;when the flow is large, the tangential and radial velocities of the shroud and hub cavities with the same radius tend to be equal with axial symmetry. The axial leakage flow through the balance holes significantly affects the radial distribution of both tangential and radial velocities of fluid flow in the hub cavity. The numerical calculation results of fluid leakage through the clearance of back sealing ring are in good agreement with the test results. Accordingly, the magnitude of leakage is closely related to the fluid pressure and velocity distribution in the hub plate crown of the centrifugal pump. The analysis of the flow characteristics in the hub plate crown of the centrifugal pump could reveal the cause of the disc friction loss from the mechanism, providing a significant guidance for improving the accuracy of calculation and balancing the axial thrust in the centrifugal pump.

关键词： Centrifugal pump Shroud cavity Hub cavity Leakage of clearance Numerical simulation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

引用

Journal of Hydrodynamics 2012年第3期24卷 332-338页

作者： li Wei li Xiao-ping li Shun-chu li Quan-yong State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu 610500 China Institute of Applied Mathematics Xihua University Chengdu 610039 China

When the classical nonlinear partial differential equations are used to model the fractal reservoir, based on the assumption of low compressibility fluids, the effects of the quadratic gradient term are ignored, which would be questionable for mixed gas reservoirs and low permeability reservoirs. To consider the influence of the wellbore storage, the nonlinear mathematical flow model of the fractal multilayer reservoir is built in this paper, with three kinds of outer boundaries （infinite boundaries, constant pressure boundaries and closed boundaries）. Using the Laplace transform method, the solutions for the dimensionless reservoir pressure and the bottom hole pressure in the Laplace space are obtained. An analysis shows that the solutions involve similar structures even for three different kinds of outer boundaries, and can be unified as a continuous fraction. The unified expression would make it more convenient to analyze the formation parameters, which greatly facilitates the development of the well test analysis software.

关键词： fractal multilayer reservoir quadratic gradient wellbore storage similar structure

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

A Modified Tikhonov Regularization Method for an Axisymmetric Backward Heat Equation

引用

Acta Mathematica Sinica,English Series 2010年第11期26卷 2157-2164页

作者： Wei CHENG chu li FU College of Science He'nan University of Technology Zhengzhou 450001 P. R. China School of Mathematics and Statistics Lanzhou University Lanzhou 730000 P. R. China

This paper deals with the inverse time problem for an axisymmetric heat equation. The problem is ill-posed. A modified Tikhonov regularization method is applied to formulate regularized solution which is stably convergent to the exact one. estimate between the approximate solution and exact technical inequality and improving a priori smoothness Meanwhile, a logarithmic-HSlder type error solution is obtained by introducing a rather assumption.

关键词： Ill-posed problem axisymmetric backward heat equation regularization error estimate

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fractal photonic anomalous Floquet topologicalinsulators to generate multiple quantum chiraledge states

引用

light(Science & Applications) 2023年第11期12卷 2498-2507页

作者： Meng li chu li linyu Yan Qiang li Qihuang Gong Yan li State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of PhysicsPeking UniversityBeijing 100871China Frontiers Science Center for Nano-Optoelectronics Peking UniversityBeijing 100871China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuanShanxi 030006China Hefei National Laboratory Hefei 230088China Peking University Yangtze Delta Institute of Optoelectronics Nantong 226010China

Anomalous Floquet topological insulators with vanishing Chern numbers but supporting chiral edge modes are attracting more and more *** the existing anomalous Floquet topological insulators usually support only one kind of chiral edge mode even at a large lattice size,they are unscalable and unapplicable for multistate topological quantum ***,fractal topological insulators with self-similarity have been explored to support more nontrivial ***,we demonstrate the first experimental realization of fractal photonic anomalous Floquet topological insulators based on dual Sierpinski carpet consisting of directional couplers using the femtosecond laser direct *** fabricated lattices support much more kinds of chiral edge states with fewer waveguides and enable perfect hopping of quantum states with near unit transfer *** of zero-dimensional bound modes for quantum state transport in previous laser direct-written topological insulators,we generate multiple propagating single-photon chiral edge states in the fractal lattice and observe high-visibility quantum *** suggest the successful realization of highly indistinguishable single-photon chiral edge states,which can be applied in various quantum *** work provides the potential for enhancing the multi-fold manipulation of quantum states,enlarging the encodable quantum information capacity in a single lattice via high-dimensional encoding and many other fractal applications.

关键词： topological quantum chiral

来源：

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

Phase field simulation of the 180°domain-switching process in PbTiO_3 single crystal under an antiparallel electric field

引用

International Journal of Minerals,Metallurgy and Materials 2010年第4期17卷 494-499页

作者： Ping-li liu Wu-Yang chu li-Jie Qiao Corrosion and Protection Center Key Laboratory of Environmental Fracture University of Science and Technology Beijing Beijing 100083 China

The process of 180°domain switching in PbTiO_3 single crystal under an antiparallel electric field was investigated by the three-dimensional phase field simulation,especially the effect of electric field on the type and duration of domain *** is found that the polarization reversal of domains takes place under an antiparallel electric field in PbTiO_3 single *** results of the phase field simulation indicate that there is only 90°domain switching under a weak electric *** the rise of the electric field,180°domain switching *** the electric field is strengthened further,90°domain switching disappears and the duration of domain switching is shortened.

关键词： phase field simulation ferroelectric materials electric field domain switching

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于FPGA的MobileNetV1目标检测加速器设计

引用

现代电子技术 2025年第1期48卷 151-156页

作者：严飞郑绪文孟川李楚刘银萍南京信息工程大学自动化学院江苏南京210044 江苏省大气环境与装备技术协同创新中心江苏南京210044 南京信息工程大学应急管理学院江苏南京210044

卷积神经网络是目标检测中的常用算法,但由于卷积神经网络参数量和计算量巨大导致检测速度慢、功耗高,且难以部署到硬件平台,故文中提出一种采用CPU与FPGA融合结构实现MobileNetV1目标检测加速的应用方法。首先,通过设置宽度超参数和分... 详细信息

卷积神经网络是目标检测中的常用算法,但由于卷积神经网络参数量和计算量巨大导致检测速度慢、功耗高,且难以部署到硬件平台,故文中提出一种采用CPU与FPGA融合结构实现MobileNetV1目标检测加速的应用方法。首先,通过设置宽度超参数和分辨率超参数以及网络参数定点化来减少网络模型的参数量和计算量;其次,对卷积层和批量归一化层进行融合,减少网络复杂性,提升网络计算速度;然后,设计一种八通道核间并行卷积计算引擎,每个通道利用行缓存乘法和加法树结构实现卷积运算;最后,利用FPGA并行计算和流水线结构,通过对此八通道卷积计算引擎合理的复用完成三种不同类型的卷积计算,减少硬件资源使用量、降低功耗。实验结果表明,该设计可以对MobileNetV1目标检测进行硬件加速,帧率可达56.7 f/s,功耗仅为0.603 W。

关键词：卷积神经网络目标检测 FPGA MobileNetV1 并行计算硬件加速

来源：

维普期刊数据库

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

A high-performance and endurable SSD cache for parity-based RAID

引用

Frontiers of Computer Science 2019年第1期13卷 16-34页

作者： chu li Dan FENG Yu HUA Fang WANG Wuhan National Lab for Optoelectronics Key Laboratory of Information Storage System(School of Computer Science and TechnologyHuazhong University of Science and Technology) Ministry of Education of ChinaWuhan 430074China

Solid-state drives (SSDs)have been widely used as caching tier for disk-based RAID systems to speed up dataintensive ***,traditional cache schemes fail to effectively boost the parity-based RAID storage sys- tems (e.g.,RAID-5/6),which have poor random write performance due to the small-write ***'s worse,intensive cache writes can wear out the SSD quickly,which causes performance degradation and cost *** this article,we present the design and implementation of KDD, an efficient SSD-based caching system which Keeps Data and Deltas in *** write requests hit in the cache, KDD dispatches the data to the RAID storage without updating the parity blocks to mitigate the small write penalty, and compactly stores the compressed deltas in SSD to reduce the cache write traffic while guaranteeing reliability in case of disk *** addition,KDD organizes the metadata partition on SSD as a circular log to make the cache persistent with low *** evaluate the performance of KDD via both simulations and prototype *** results show that KDD effectively reduces the small write penalty while extending the lifetime of the SSD-based cache by up to 6.85 times.

关键词： solid-state drive (SSD) parity-based RAID small write problem write endurance

来源：

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

Influences of the diameter of the balance hole on the flow characteristics in the hub cavity of the centrifugal pump

引用

Journal of Hydrodynamics 2019年第5期31卷 1060-1068页

作者： Wei Dong Wu-li chu Zai-lun liu College of Water Resources and Architectural Engineering Northwest A&F UniversityYangling 712100China School of Power and Energy Northwestern Polytechnical UniversityXi'an 710129China College of Energy and Power Engineering Lanzhou University of TechnologyLanzhou 730050China

The diameter of the impeller balance hole in a centrifugal pump is closely related to axial ***,to select the appropriate diameter of a balance hole is crucial for balancing the axial force of the centrifugal *** the validation of the CFD method and the grids independence study,the characteristics of flow in the hub cavity have been analyzed in 4 cases with different diameters of balance *** leakage rate of the liquid in the hub cavity of the centrifugal pump is calculated and compared with the test *** to the research,when no balance hole exists,the distribution of liquid velocity in the core area of the hub cavity exhibits axial symmetry,and the circumferential velocity component is approximately 0.4 times of the impeller's rotational *** the balance hole exists,the distribution of liquid velocity in the hub cavity does not exhibit axial symmetry,and the circumferential velocity component is larger than 0.4 times of the impeller's rotational *** radial leakage velocity on the turbulent boundary layer of the pump cover will increase with the increasing diameter of the balance hole.

关键词： Centrifugal pump balance hole hub cavity circumferential velocity component radial velocity component

来源：

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

Degree Conditions on Copies of Forests in Graphs

引用

Journal of the Operations Research Society of China 2023年第3期11卷 667-672页

作者： Xiao-Dong Chen Shuai-Jun Chen Ming-chu li School of Mathematics Liaoning Normal UniversityDalian116029LiaoningChina College of Science Liaoning University of TechnologyJinzhou121001LiaoningChina School of Softsware Dalian University of TechnologyDalian116024LiaoningChina

For a graph G,letμ(G)=min{max{d(x),d(y)}:x≠y,xy∉E(G),x,y∈V(G)}if G is non-complete,otherwise,μ(G)=+∞.For a given positive number s,we call that a graph G satisfies Fan-type conditions ifμ(G)≥***μ(G)≥s,then a vertex v is called a small vertex if the degree of v in G is less than *** this paper,we prove that for a forest F with m edges,if G is a graph of order n≥|F|andμ(G)≥m with at most max{n−2m,0}small vertices,then G contains a copy of *** also give examples to illustrate both the bounds in our result are best possible.

关键词： Fan-type conditions Forest Copy Small vertex

来源：

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

Self-supporting trimetallic PtAuBi aerogels as electrocatalyst for ethanol oxidation reaction

引用

Chinese Journal of Structural Chemistry 2023年第8期42卷 21-30页

作者： chu li Xiaoguo Tie Yulin Min Qunjie Xu Qiaoxia li Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power College of Environmental and Chemical EngineeringShanghai University of Electric PowerYangpu District2588 Changyang RoadShanghai200090China Shanghai Institute of Pollution Control and Ecological Security Shanghai200090China

The creation of anodic ethanol oxidation reaction catalysts with superior all-around performance for direct ethanol fuel cells(DEFCs)has continued to attract the attention of *** ultrathin trimetallic PtAuBi aerogel with branching,rough-surfaced 1D nanowires that self-assemble into a 3D porous network structure has been created in this *** has a mass activity(MA)of 8045 mA mgPt^(-1)in an alkaline medium,which is 7.56 times greater than that of commercial Pt/C(1064 mA mgPt^(-1)).Notably,the catalytic activity and resistance to CO poisoning of PtAuBi aerogels are improved by the addition of an efficient"active additive"*** results analysis reveals that the increased performance of PtAuBi aerogel is mostly attributable to the integrated function of the 3D porous network structure,the downward shift of the Pt d-band center,and the synergistic effect of the"Pt-Bi"and/or"Pt-Au"dual active sites.

关键词： PtAuBi aerogels Ethanol oxidation reaction Carbon monoxide tolerance Direct ethanol fuel cells

来源：

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

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：