检索结果-南通市图书馆

维普期刊数据库博看期刊

四种组合方法规划髋臼前柱置钉通道的比较研究

在线全文

学校读者我要写书评

暂无评论

中国骨伤 2024年第8期37卷 801-807页

作者：易礼杨李必文唐鹏唐虎谭文甫南华大学机械工程学院湖南衡阳421001 南华大学附属第二医院创伤骨科湖南衡阳421001

目的:探讨基于大密度点云数据实现对髋臼前柱置钉通道的全局优化。方法:2022年1月至2023年1月行完整CT扫描成年人正常骨盆CT数据40例,其中男22例,女18例;年龄20~54岁。选取其中3个样本的医学影像数据进行试验研究。规划髋臼前柱置钉通道... 详细信息

目的:探讨基于大密度点云数据实现对髋臼前柱置钉通道的全局优化。方法:2022年1月至2023年1月行完整CT扫描成年人正常骨盆CT数据40例,其中男22例,女18例;年龄20~54岁。选取其中3个样本的医学影像数据进行试验研究。规划髋臼前柱置钉通道,针对现行CAD规划方法是否具有先进性的问题,提出了点云获取渠道相同、方向线创建软件各异、三维设计与虚拟试验软件相同的4种组合方法:Mimics+Imageware+UG、Mimics+3DReshaper+UG、Mimics+ZEISS Quality Suite+UG与Mimics+Design X+UG,并依据二次修剪模型的中心点点集和实体点云分别创建方向线,应用于3个髋臼样本左侧前柱置钉通道的规划。以未出现髋臼窝和耻骨穿破现象的最大内接圆柱体作为髋臼前柱的置钉安全通道来评价各方法的先进性。结果:在选取相关特征明显的中心点点集作为样本点时,方向线的拟合效果均优于未去噪的实体点云拟合效果;Mimics+Imageware+UG和Mimics+3DReshaper+UG的组合方法在利用中心点点集进行规划时能够高效、稳定地获得理想的规划结果,分别在髋臼样本1、2、3中得到的最大内接圆直径为10.35、9.62、9.24 mm;方向线依据实体点云时,Mimics+ZEISS Quality Suite+UG和Mimics+Design X+UG的组合方法均不适用;而Mimics+3DReshaper+UG的实体点云去噪规划法可以稳定地获得数值最大的置钉安全通道,分别在髋臼样本1、2、3中得到的最大内接圆直径为10.66、10.96、9.48 mm。结论:在进行髋臼内固定术时推荐置钉通道规划人员采用鲁棒性好的Mimics+Imageware+UG或Mimics+3DReshaper+UG中心点点集规划法,如果时间充裕,建议采用Mimics+3DReshaper+UG的实体点云去噪规划法以获得数值最大的置钉安全通道。

关键词：髋臼前柱置钉通道全局优化方向线创建方法规划差异机制

Influence of adding carbon nanotubes and graphite to Ag-MoS_2 composites on the electrical sliding wear properties

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2010年第1期23卷 27-34页

作者： Shu li yi FENG Xiting yang ~ v Department of Material Science and Engineering Hefei University of Technology Hefei 230009 China

Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.

关键词： Ag-MoS2 composite Carbon nanotube Graphite Contact voltage drop Friction coefficient Wear loss

Biometric-based personal identity-authentication system and security analysis

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2006年第4期13卷 43-47页

作者： li Chao yang yi-xian NIU Xin-xin Information Security Centre Key Laboratory of Networking and Switching Technologies Beijing University of Posts and Telecommunications Beijing 100876 China

The traditional authentication system is based on the secret key, and is mainly based on public key infrastructure （PKI）. Unfortunately, a key has many disadvantages, for example, the key can be forgotten or stolen, and can be easily cracked. Nowadays, authentication systems using biometric technology have become more prevalent because of the advantages over password-based authentication systems. In this article, several biometfic authentication models are presented, upon which most biometric authentication systems are based. Biometric authentication systems based-on these models provide high security for access control in non-face-to-face environment such as e-commerce, over open network.

关键词： biometric identity authentication PKI security

Prokaryotic Expression and Purification of HIV-1 Vif and hAPOBEC3G, Preparation of Polyclonal Antibodies

在线全文

学校读者我要写书评

暂无评论

Virologica Sinica 2008年第3期23卷 173-182页

作者： Lan li yi-shu yang Ze-lin li yi ZENG College of life Science ＆ Bio-engineering Beijing University of Technology Beijing 100124 China

To prepare HIV-1 Vif and hAPOBEC3G and to produce their antibodies, the full length gene fragment of HIV-1 vif was amplified by PCR from a plasmid of HIV-1 NL4.3 cDNA, and the APOBEC3G gene was obtained by RT-PCR from the total RNA of H9 cells. The resulting DNA construct was cloned into a prokaryotic expression vector (pET-32a). Recombinant pET-vif and pET-APOBEC3G were expressed respectively in Eserichia coli BL21 (DE3) as an insoluble protein. The vector also contained a six-histidine tag at the C-terminus for convenient purification and detection. To express and purify the HIV-1 Vif and hAPOBEC3G in *** cells, the accuracy of inserted gene and specificity of proteins were detected by the two enzyme digestion method, SDS-PAGE, and Western blotting. Rabbits were then immunized by Vif or APOBEC3G protein and serum samples were tested by indirect EliSA to determine the level of antibodies. Immunoenzyme and immunofluorescence assays were performed to identify the specificity of polyclonal antibodies. The titer of the anti-Vif antibodies was 1:204800, and that of the anti-APOBEC3G antibodies was 1:102400. Thus the antibodies could detect the antigen expression in the cells, demonstrating that fusion proteins with high purity and their corresponding polyclonal antibodies with high titer and specificity were achieved.

关键词： Human immunodeficiency virus type 1 (HIV-1) Viral infectivity factor hAPOBEC3G Protein purification Polyclonal antibody

基于DPSIR-对称交互熵的泰安市水—城地人产系统协调性评价

在线全文

学校读者我要写书评

暂无评论

水电能源科学 2024年第5期42卷 80-83,18页

作者：潘慧民门宝辉王红瑞李一阳李永坤王丽晶华北电力大学水利与水电工程学院北京102206 北京师范大学水科学研究院北京100875 北京市水科学技术研究院北京100048

为将四水四定落到实处,构建了基于DPSIR-对称交互熵的水—城地人产系统评价模型,通过构建山东省泰安市评价指标体系,开展协调性发展综合评价,进而建立耦合协调度模型评价各子系统间发展协调性。研究表明,各子系统综合评价值呈现波动上... 详细信息

为将四水四定落到实处,构建了基于DPSIR-对称交互熵的水—城地人产系统评价模型,通过构建山东省泰安市评价指标体系,开展协调性发展综合评价,进而建立耦合协调度模型评价各子系统间发展协调性。研究表明,各子系统综合评价值呈现波动上升趋势,其中状态(S)和响应(R)子系统波动上升趋势最为稳定,最不稳定的为压力(P)子系统;按照历年系统耦合协调度将2006年以来泰安市水—城地人产系统发展划分为过渡阶段(2006~2010年)、协调发展阶段(2011~2019年)、高质量发展阶段(2020年以后);宁阳县、东平县协调度仍有待提高,未来应当着重推进泰安市水网建设、供、用水结构优化和产业结构升级等工作。研究结果可为泰安市国土空间规划及水利高质量发展提供支持。

关键词：四水四定 DPSIR模型对称交互熵耦合协调度模型协调性评价

Novel scheduling strategy for downlink multiuser MIMO system: Particle swarm optimization

在线全文

学校读者我要写书评

暂无评论

Science in China(Series F) 2009年第12期52卷 2279-2289页

作者： HEI YongQiang li XiaoHui yi KeChu yang Hong State Key Laboratory of Integrated Services Networks Xidian University Xi'an 710071 China

In this paper the scheduling problem in downlink multiuser MIMO system is described as an optimization problem and particle swarm optimization （PSO） algorithm is introduced to address such problem. Two PSO scheduling methods with different objective functions applicable to different requirements on capacity and complexity are investigated. One is the capacity based PSO（C-PSO） scheduling method aiming at achieving the near optimal capacity; and the other is the lower bound of eigenvalue based PSO （LBE-PSO） scheduling method with the purpose of reducing computational complexity and at the same time achieving as large as possible capacity gain. Furthermore, convergence analysis of PSO from both the particle and the velocity aspects is also presented to derive the convergent condition, which is validated by several examples of different parameter values. Simulation results reveal that the C-PSO can obtain nearly the same capacity as the exhaustive search method with lower complexity, while the LBE-PSO provides a viable approach by striking a better tradeoff between capacity and computational complexity.

关键词： multiuser MIMO scheduling downlink transmission particle swarm optimization

职校学生24小时活动与抑郁症状关系的横断面研究

在线全文

学校读者我要写书评

暂无评论

复旦学报（医学版） 2024年第2期51卷 159-165页

作者：汤表倩陈勃昊李艺扬刘汗青许曙青王书梅复旦大学公共卫生学院妇幼与儿少卫生教研室上海200032 江苏联合职业技术学院南京工程分院南京211135

目的使用等时替代模型,探索有、无抑郁症状的职校学生10 min/天身体活动(physical activity,PA)、久坐行为(sedentary behavior,SB)和睡眠(sleep,SLP)之间等时替代与抑郁症状量表得分的关联。方法采用方便整群抽样方法,选取上海市和江... 详细信息

目的使用等时替代模型,探索有、无抑郁症状的职校学生10 min/天身体活动(physical activity,PA)、久坐行为(sedentary behavior,SB)和睡眠(sleep,SLP)之间等时替代与抑郁症状量表得分的关联。方法采用方便整群抽样方法,选取上海市和江苏省的14所职校,调查对象为1~3年级学生,于2021年12月—2022年1月开展问卷调查。根据流调中心抑郁量表(Centre for Epidemiologic Studies Depression Scale,CES-D)得分将学生分为有抑郁症状组和无抑郁症状组。结果共收回问卷40339份,其中能够清楚记得过去1周身体活动时间的问卷10086份,数据清洗后获得有效问卷8149份,包括无抑郁症状组5496人(67.44%),有抑郁症状组2653人(32.56%)。调查对象平均年龄(16.70±1.19)岁。无抑郁症状组的中强度身体活动(moderate physical activity,MPA)替代其他所有研究的行为均与CES-D得分呈负相关,高强度身体活动(vigorous physical activity,VPA)替代MPA和SB均与CES-D得分呈正相关;有抑郁症状组的MPA替代步行、SB和SLP均与CES-D得分呈负相关。MPA替代步行、SB和SLP与CES-D得分的负关联,在有抑郁症状组中的强度大于无抑郁症状组。结论职校学生抑郁症状检出率较高,学生MPA替代步行、SB和SLP与CES-D得分呈负相关,有抑郁症状组中的关联大于无抑郁症状组。

关键词：抑郁症状身体活动(PA) 久坐行为(SB) 睡眠(SLP) 等时替代模型(ISM) 青少年

Nonlinear dynamic analysis of a rotor/bearing/seal system

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第1期12卷 46-55页

作者： Wei li yi yang De-ren SHENG Jian-hong CHEN Yong-qiang CHE Department of Energy Engineering Zhejiang University Hangzhou 310027 China

In this study a new dynamic model of a rotor system is established based on the Hamilton principle and the finite element method (FEM). We analyze the dynamic behavior of the rotor system with the coupled effects of the nonlinear oil film force, the nonlinear seal force, and the mass eccentricity of the disk. The equations of the motion are solved effectively using the fourth order Runge-Kutta method in MATLAB. The dynamic behavior of the system is illustrated by bifurcation diagrams, largest Lyapunov exponents, phase trajectory diagrams, and Poincaré maps. The numerical results show that the rotational speed of the rotor, the pressure drop in the seal, the seal length, the seal clearance, and the mass eccentricity of the disk are the key parameters that significantly affect the dynamic characteristics of the rotor system. The motion of the rotor system exhibits complex types of periodic, quasi-periodic, double-periodic, multi-periodic, and chaotic vibrations. This analysis can be used to guide the design of seal parameters and to diagnose the vibration of rotor/bearing/seal systems.

关键词： Nonlinear Rotor system Hamilton principle Dynamic Finite element method (FEM)

Superior Latent Heat Eutectic Salt Na_(2)CO_(3)-li_(2)CO_(3)-liF for Thermal Energy Storage:Preparation and Performance Investigation

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2024年第2期33卷 501-508页

作者： li Weiwei MIAO Qi ZHANG Yelong DING Hongliang yang Sa LAI Yuan FENG Daili DING Yulong JIN yi TAN linghua School of Chemistry and Chemical Engineering Nanjing University of Science&TechnologyNanjing210094China National Special Superfine Powder Engineering Research Center Nanjing University of Science and TechnologyNanjing210094China Nanjing Jinhe Energy Material Co. LtdNanjing210047China School of Chemical Engineering University of BirminghamBirminghamB152TTUK School of Energy&Environmental Engineering University of Science and Technology BeijingBeijing100083China

In this paper,a novel ternary eutectic salt Na_(2)CO_(3)-li_(2)CO_(3)-liF was designed and investigated for concentrated solar power(CSP).The FactSage software was used to predict the composition and eutectic point of Na_(2)CO_(3)-li_(2)CO_(3)-*** microstructure,thermophysical properties,and thermal stability of eutectic salts were experimentally measured using various analytical *** a mass ratio of 57%:32%:11%,the eutectic salt exhibited excellent thermal storage properties with a fusion enthalpy of 413 J/g and a melting point of 426.8℃.The excellent thermal stability of the eutectic salt was reflected by a weight loss of only 0.8% at 600℃.

关键词： phase change materials ternary eutectic salt latent heat thermal stability