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LAMINAR DEVELOPING FLOW IN THE ENTRANCE REGION OF ROTATING CURVED PIPES

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Journal of Hydrodynamics 2006年第4期18卷 418-423页

作者： ma jian-feng shen xin-rong zhang ming-kan zhang ben-zhao Department of Mechanics Zhejiang University Hangzhou 310027 China

Three-dimensional laminar flow in the entrance region of rotating curved pipes was investigated. The governing equations were written in an orthogonal curvilinear coordinate system and solved with a fully three-dimensional numerical method. The development of secondary flow, axial velocity, local and average friction factors for different cases of rotation were given and discussed in detail. The results show that rotation influences the flow structure and friction factor greatly and that the secondary flow is sink-type in the early stage of development and then turns to vortex structure. The average friction factor and the intensity of secondary flow have drastic decrease near the entrance. At some proper rotation, the average friction factor can be noticeably reduced.

关键词： developing flow secondary flow rotating curved pipe

A STUDY ON THE FLOW IN HELICAL ELLIPTICAL PIPES WITH GALERKIN METHOD

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Journal of Hydrodynamics 2006年第1期18卷 70-76页

作者： ma jian-feng shen xin-rong zhang ben-zhao zhang ming-kan Department of Mechanics Zhejiang University Hangzhou 310027 China

The fully developed laminar flow in helical elliptical pipes is influenced by curvature, torsion and aspect ratio of cross-section. With the aid of the symbolic manipulation technique, the governing equations were solved by the Galerkin method, The procedures of implementing the Galerkin method for flows in curvilinear pipes were discussed. The effects of the aspect ratio and torsion on the flow structure, wall shear stress and flow ratio were examined in detail. The results show that the flow characteristic for aspect ratio larger than unit is quite different from those for the aspect ratio smaller than unit.

关键词： Galerkin method helical elliptical pipe secondary flow

FLOW OF OLDROYD-B FLUID IN ROTATING CURVED SQUARE DUCTS

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Journal of Hydrodynamics 2007年第1期19卷 36-41页

作者： zhang ming-kan shen xin-rong ma jian-feng zhang ben-zhao Institute of Fluid Engineering Zhejiang University Hangzhou 310027 China

The fully developed Oldroyd-B fluid flow through rotating square ducts was numerically studied. The effects of the rotation on secondary flow, axial velocity, and axial normal stress were examined in detail. The results indicated that all of the secondary flow, the axial flow, and the axial normal stress were evidently affected by the rotation. The Taylor-Proudman phenomenon could be observed in the flow. For the secondary flow, the four vortices structure and the six vortices structure were described. Recent studies also showed the effects of rotation on the axial normal stress.

关键词： curved ducts Oldroyd-B fluid rotating axialnormal stress

Effect of heat treatment on microstructural evolution,mechanical properties and tribological properties of H13 steel prepared using selective laser melting

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Journal of Iron and Steel Research International 2024年第5期31卷 1246-1259页

作者： Li-xiong Han Yan Wang Shi-feng Liu zhao-hui zhang Wei Liu xin Yang Dang-shen ma jian Zhou Ying-kang Wei College of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina Zhejiang University City College Hangzhou310015ZhejiangChina China Iron and Steel Research Institute Group Co. Ltd.Beijing100081China

H13 tool steel was successfully prepared by selective laser melting(SLM)*** effects of heat treatment on the microstructure,mechanical properties,and tribological properties of SLMed H13 steel were *** heat treatment process involved a solution treatment and a double aging treatment of the deposited H13 tool steel prepared by *** aim is to optimize the microstructure and mechanical properties of SLMed H13 *** to the rapid heating and cooling effects of SLM,carbide precipitation in the deposited H13 steel was not uniform and residual stresses were *** purpose of the solution treatment is to dissolve the solution at a high temperature to eliminate the residual stresses and defects introduced by the SLM-forming *** solution treatment and first aging treatment produced the precipitation of small carbides at the grain boundaries and inside the crystals,which increased the hardness of SLMed H13 *** hardness increased from 538±4.0 HV of the as-deposited sample to 548±5.8 HV of samples after the first aging ***,the ultimate tensile strength and the elongation at break decreased from 1882 MPa and 11.5%in the as-deposited sample to 1697 MPa and 7.9%in those after the first aging treatment,***,the friction coefficient and wear rate in the as-deposited sample decreased from 0.5160 and 2.36×10^(–6)mm^(−3)N^(−1)m^(−1)to 0.4244 and 1.04×10^(–6)mm^(−3)N^(−1)m^(−1),***,the distribution of carbides inside the crystals was not *** second aging treatment adjusted the morphology of carbide precipitation and made it more uniform,but the precipitation of carbides grew and settled at the bottom of the grain *** hardness decreased to 533±6.7 HV compared with that with the first aging treatment,but the ultimate tensile strength and plasticity reached a balance(1807 MPa,14.05%).Accordingly,the friction coefficient and wear rate also showed a stable and decreasin

关键词： Selective laser melting H13 steel Solution aging Double aging Friction and wear Retained austenite

UNSTEADY INTERMITTENT FLOW IN A ROTATING CURVED PIPE

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Journal of Hydrodynamics 2004年第2期16卷 158-165页

作者： YINjian-an shenxin-rong CHENHua-jun zhangben-zhao DepartmentofMechanics ZhejiangUniversityHangzhou310027Chinae-mail：mec-zbzq@emb***

The effects of rotation and intermittent frequency on the flow transition ofsecondary flow and, main flow were examined in detail. Certain hitherto unknown flow patterns werefound. A numerical study was performed to study the characteristics of unsteady intermittent flow ina rotating curved pipe. Due to the rotation, both the Coriolis force and the centrifugal forcecould contribute to the unsteady intermittent flow and some complicated phenomena can be found. Theresults indicate that the unsteady intermittent flow are mainly characterized by five parameters:the Dean number Dn, the curvature κ, the maximal force ratio F (of the Coriolis force to thecentrifugal force in a cycle), the intermittent frequency parameter η (the ratio of a pulslatingtime to the cycle period), and the Womersley number α. Present works shows the natures of theunsteady intermittent flow in a rotating curved pipe.

关键词： unsteady flow secondary flow rotating pipes

Application of an artificial intelligence system for endoscopic diagnosis of superficial esophageal squamous cell carcinoma

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World Journal of Gastroenterology 2022年第37期28卷 5483-5493页

作者： Qian-Qian Meng Ye Gao Han Lin Tian-Jiao Wang Yan-rong zhang jian feng zhao-shen Li Lei xin Luo-Wei Wang Department of Gastroenterology Changhai HospitalShanghai 200433China Qingdao Medcare Digital Engineering Co.Ltd. Qingdao Medcare Digital Engineering Co.Ltd.Qingdao 26600Shandong ProvinceChina

BACKGROUND Upper gastrointestinal endoscopy is critical for esophageal squamous cell carcinoma(ESCC)detection;however,endoscopists require long-term training to avoid missing superficial *** To develop a deep learning computer-assisted diagnosis(CAD)system for endoscopic detection of superficial ESCC and investigate its application *** We configured the CAD system for white-light and narrow-band imaging modes based on the YOLO v5 algorithm.A total of 4447 images from 837 patients and 1695 images from 323 patients were included in the training and testing datasets,*** experts and two non-expert endoscopists reviewed the testing dataset independently and with computer *** diagnostic performance was evaluated in terms of the area under the receiver operating characteristic curve,accuracy,sensitivity,and *** The area under the receiver operating characteristics curve,accuracy,sensitivity,and specificity of the CAD system were 0.982[95%confidence interval(CI):0.969-0.994],92.9%(95%CI:89.5%-95.2%),91.9%(95%CI:87.4%-94.9%),and 94.7%(95%CI:89.0%-97.6%),*** accuracy of CAD was significantly higher than that of non-expert endoscopists(78.3%,Pmance of the CAD system is promising and may assist in improving detectability,particularly for inexperienced endoscopists.

关键词： Computer-aided diagnosis Artificial intelligence Deep learning Esophageal squamous cell carcinoma Early detection of cancer Upper gastrointestinal endoscopy

Wide-range tracking technique for process-variation-robust clock and data recovery applications

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Frontiers of Information Technology & Electronic Engineering 2017年第5期18卷 729-737页

作者： Jun-sheng LV You LI Yu-mei ZHOU jian-zhong zhao Hai-hua shen feng zhang Institute of Microelectronics Chinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100029China

A wide-range tracking technique for clock and data recovery(CDR) circuit is presented. Compared to the traditional technique, a digital CDR controller with calibration is adopted to extend the tracking range. Because of the use of digital circuits in the design, CDR is not sensitive to process and power supply variations. To verify the technique, the whole CDR circuit is implemented using 65-nm CMOS technology. Measurements show that the tracking range of CDR is greater than ±6×10-3 at 5 Gb/s. The receiver has good jitter tolerance performance and achieves a bit error rate of <10–12. The re-timed and re-multiplexed serial data has a root-mean-square jitter of 6.7 ps.

关键词： Clock and data recovery Digital loop filter Phase interpolator

Rapid lithium-ion insertion/extraction and migration behavior of Na_(2)WO_(4)-encapsulated lithium-rich layered oxide cathode

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Rare Metals 2024年第8期43卷 3647-3660页

作者： Yu-shen zhao Fan-Fan Wang jian-Cang Wang Peng-Fei Wang Ting-feng Yi Jun-Hong zhang School of materials Science and Engineering Northeastern UniversityShenyangShenyang 110819China Key Laboratory of Dielectric and Electrolyte Functional material Hebei Province School of Resources and MaterialsNortheastern University at QinhuangdaoQinhuangdao 066004China Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology College of Chemistry and Chemical EngineeringLiaocheng UniversityLiaocheng 252059China

Due to the low cost,high working voltage and high storage capacity,Li-rich Mn-based layered compounds show promise as the cathode materials for lithiumion batteries(LIBs).However,the side reactions at the solid-liquid interface of the cathode will lead to rapid capacity decay and inferior rate ***,this article proposes a liquid-phase dispersion strategy to introduce a Na_(2)WO_(4)layer on the Li_(1.2)Ni_(0.13)-Co_(0.13)Mn_(0.54)O_(2) cathode,which can reduce the side effects between raw materials and electrolyte and promote the insertion/extraction rate of Li^(+),thus enhancing the material stability and rate *** a result,the capacity retention rate is 96.9%after 200 cycles under ***,the capacities are 177.5,149.5,111.1 and58.3 mah·g^(-1)at 1C,2C,5C and 10C,implying a superior fast charging *** exceptional performance can be ascribed to both the increased conductivity and enhanced structural stability of the cathode ***'s more,based on the investigation of ion insertion/extraction behavior in electrode materials and the ion migration kinetics in the electrolyte,this study suggests that coating Li-rich Mn-based materials with Na_(2)WO_(4)can be a promising strategy to improve their performance in LIBs.

关键词： Li-ion battery Coating Rate performance Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2) Reaction kinetics

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S形复合管道周期流动的数值研究

浙江大学学报（工学版） 2006年第8期40卷 1408-1412页

作者：麻剑锋沈新荣章本照浙江大学工程力学系浙江杭州310027

采用贴体坐标系下的SIMPLE方法研究了S形复合管道中三维周期性充分发展的层流流动.对流项采用一阶迎风格式和QUICK格式相结合的方法,保证了解的收敛性和高精度特性.数值实验表明,在一个流动周期内,S形复合管道中前后两个半圆弧段中的流... 详细信息

采用贴体坐标系下的SIMPLE方法研究了S形复合管道中三维周期性充分发展的层流流动.对流项采用一阶迎风格式和QUICK格式相结合的方法,保证了解的收敛性和高精度特性.数值实验表明,在一个流动周期内,S形复合管道中前后两个半圆弧段中的流动结构一致,但二次流旋转方向和轴向速度的偏移方向相反.曲率对流动有很大的影响,曲率越大轴向速度的最大值越小,二次流的最大值越大.在前后半个周期开始阶段,二次流都有一个突然变小和改变旋转方向的过程.流动阻力随着曲率的增大而增大.

关键词： S形复合管道周期流动二次流动