检索结果-南通市图书馆

Temporal variation of soil water and its influencing factors in hilly area of Chongqing,China

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

International Journal of Agricultural and Biological Engineering 2014年第4期7卷 47-59页

作者： Zhong Shouqin zhang weihua Lv Jiake Wei Chaofu College of Resources and Environment Southwest UniversityChongqing 400700China School of Computer and Information Science Southwest UniversityChongqing 400700China

The paper studied the temporal variation of soil water content and its influencing factors in hilly area of Chongqing by the yearly data of 2006 and *** to precipitation anomaly percentage,the year 2006 was a dry year and 2007 a normal *** the dry year 2006,the variations of soil moisture in all three layers(0-10 cm,10-20 cm,20-40 cm)were medium(10%30%),and those of the two deeper layers were weak(CV<10%).Hence,the seasonal variation of soil moisture in the humid area was large in the dry year and small in the wet *** probability distributions of soil moisture in all three layers in both dry and normal years showed single-peak ***,peak locations and values varied with different layers and *** factors affecting the temporal variation of soil moisture in the 0-10 cm layer,during March to May,the meteorological factors including temperature,sunshine and precipitation were all inversely correlated with soil water content *** correlations with average temperature and accumulated temperature were both highly significant P<0.01(P=0.00).The inverse correlations with sunshine and precipitation were significant P<0.05(P=0.01).Among soil physical properties,except for bulk density which was inversely correlated with soil moisture,all other properties were positively *** material was positively correlated with soil moisture,which suggested that organics had the sponge effect and contributed to soil water storage and *** the period of June to September,there was no significant correlation between soil water content and total *** meteorological factors of temperature,accumulated temperature and sunshine were all inversely and highly significantly correlated with soil water content P<0.01(P=0.00).

关键词： soil water temporal variation influencing factors hilly area

考虑闸瓦制动的重载列车动力学建模与车辆曲线制动安全分析

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

重庆理工大学学报（自然科学） 2024年第6期38卷 155-163页

作者：贾彬王志伟张铭涛刘鹏飞刘国云张卫华西南交通大学轨道交通运载系统全国重点实验室成都610031 西南交通大学机械工程学院摩擦学研究所成都610031 石家庄铁道大学省部共建交通工程结构力学行为与系统安全国家重点实验室石家庄050043 重载快捷大功率电力机车全国重点实验室湖南株洲412001

为探究制动系统对重载列车动力学的影响,以我国万吨重载列车为研究对象,建立了考虑基础制动装置的一维-三维混合万吨重载列车动力学模型。该模型可以反映三维车辆运动姿态变化以及闸瓦-踏面摩擦等因素对列车制动性能的影响,并通过试验... 详细信息

为探究制动系统对重载列车动力学的影响,以我国万吨重载列车为研究对象,建立了考虑基础制动装置的一维-三维混合万吨重载列车动力学模型。该模型可以反映三维车辆运动姿态变化以及闸瓦-踏面摩擦等因素对列车制动性能的影响,并通过试验数据以及其他模型对比等方式验证了所提出模型的有效性。基于此,分析了紧急制动时曲线路段下万吨重载列车最危险位置处车辆的轮轨动态相互作用和运行安全性。结果表明:紧急制动时,考虑闸瓦-踏面摩擦的基础制动装置对车钩力变化趋势及最大值的位置影响较小。闸瓦制动模型的轴重转移现象更显著,符合实际制动过程中闸瓦-车轮摩擦特性。随着曲线半径的降低,脱轨系数和倾覆系数显著增加,相比于曲线半径1400 m,曲线半径600 m紧急制动时,脱轨系数和倾覆系数分别增加了340.35%和31.72%。

关键词：重载列车紧急制动闸瓦制动曲线通过

在线全文

学校读者我要写书评

暂无评论

基于钻冲压协调作业的煤层卸压增透技术

煤矿安全 2024年第2期55卷 62-70页

作者：杨程涛武腾飞张卫华熊俊杰河南能源集团研究总院有限公司河南郑州450046 河南省低渗突出煤层煤与瓦斯共采工程技术研究中心河南郑州450046 鹤壁煤电股份有限公司第六煤矿河南鹤壁458006

为了解决鹤壁矿区瓦斯抽采钻孔影响范围小、衰减速度快,瓦斯灾害治理难度大,治理周期长等问题,提出了冲压协调作业的工艺流程,形成了以自动钻机群打钻-临时封孔预抽-预抽后冲压联合作业的钻冲压协调作业技术模式,并在鹤煤六矿进行工业... 详细信息

为了解决鹤壁矿区瓦斯抽采钻孔影响范围小、衰减速度快,瓦斯灾害治理难度大,治理周期长等问题,提出了冲压协调作业的工艺流程,形成了以自动钻机群打钻-临时封孔预抽-预抽后冲压联合作业的钻冲压协调作业技术模式,并在鹤煤六矿进行工业性试验。现场应用结果表明:该技术模式充分发挥了自动钻机连续打钻、快速作业、减员提效的优势,实现了瓦斯抽采钻孔施工作业、水力化冲压协调增透作业的专业化、连续化、规模化,使底板岩巷内施工穿层钻孔治理瓦斯的施工工效在同等地质条件下提高48%;同时,利用自动钻机施工抽采钻孔完成后,对其进行临时封孔抽采,使钻孔内的游离态瓦斯经过抽采后大幅减少,大大降低了水力化措施施工期间巷道瓦斯超限事故发生的频率,有效保障了施工的安全;试验钻孔平均瓦斯体积分数是常规水力冲压措施的1.31倍,试验单元钻孔平均日抽采纯量是常规水力冲压措施的1.79倍。

关键词：水力冲孔水力压裂智能化减人提效瓦斯抽采卸压增透

Microstructure and mechanical properties of ZrO_2(Y_2O_3)-Al_2O_3 nanocomposites prepared by spark plasma sintering

在线全文

学校读者我要写书评

暂无评论

Particuology 2012年第3期10卷 345-351页

作者： Shufeng Li Hiroshi Izui Michiharu Okano weihua zhang Taku Watanabe College of Science and Technology Nihon University7-24-1NarashinodaiFunabashiChiba 274-8501Japan College of Science and Technology Nihon University1-8-14KandasurugadaiChiyoda.Tokyo 101-8308Japan College of Materials Science and Technology Xi'an University of Technology5 SouthJinhua RoadXi'anShaanxi 710048China

Zirconia （yttria）-alumina ceramic nanocomposites were fabricated from different powders by spark plasma sintering （SPS）. One powder was a commercially available nanocomposite powder TZP-3Y2OA, consisting of 3 mol% yttria-stabilized zirconia （3-YSZ） reinforced with 20wt% alumina, and the other, used as a comparison, was a conventional mechanically mixed powder 3YSZ-2OA, a blend made of 3 mol% yttria-stabilized zirconia powder ZrO2 （3Y） and 20 wt% ,x-alumina powder. The effect of the sintering temperature on the densification, the sintering behavior, the mechanical properties and the microstructure of the composites was investigated. The results showed that the density increased with increasing sintering temperature, and thus, the mechanical properties were strengthened because of the increased densification. The nanocomposite powder TZP-3Y20A was easily sintered, and good mechanical properties were achieved as compared with the powder from the conventional mechanically mixed method, the maximum flexural strength and fracture toughness of which were 967 MPa and 5.27 MPa m 1/2, respectively.

关键词： Zirconia-aluminaNanocompositeSpark plasma sintering (SPS)Mechanical propertiesMicrohardnessFracture toughnessDensification

Collaborative Simulation Method with Spatiotemporal Synchronization Process Control

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2016年第6期29卷 1074-1082页

作者： ZOU Yisheng DING Guofu zhang weihua zhang Jian QIN Shengfeng TAN John Kian School of Mechanical Engineering Southwest Jiaotong University Chengdu 610031 China State Key Laboratory of Traction Power Southwest Jiaotong University Chengdu 610031 China Northumbria School of Design Northumbria University Newcastle upon Tyne NE1 8ST UK School of Mechanical and Construction Engineering Northumbria University Newcastle upon Tyne NE1 8ST UK

When designing a complex mechatronics system, such as high speed trains, it is relatively difficult to effectively simulate the entire system＇s dynamic behaviors because it involves multi-disciplinary subsystems. Currently, a most practical approach for multi-disciplinary simulation is interface based coupling simulation method, but it faces a twofold challenge： spatial and time unsynchronizations among multi-directional coupling simulation of subsystems. A new collaborative simulation method with spatiotemporal synchronization process control is proposed for coupling simulating a given complex mechatronics system across multiple subsystems on different platforms. The method consists of 1） a coupler-based coupling mechanisms to define the interfacing and interaction mechanisms among subsystems, and 2） a simulation process control algorithm to realize the coupling simulation in a spatiotemporal synchronized manner. The test results from a case study show that the proposed method 1） can certainly be used to simulate the sub-systems interactions under different simulation conditions in an engineering system, and 2） effectively supports multi-directional coupling simulation among multi-disciplinary subsystems. This method has been successfully applied in China high speed train design and development processes, demonstrating that it can be applied in a wide range of engineering systems design and simulation with improved efficiency and effectiveness.

关键词： design automation collaborative simulation space and time synchronization process control coupling algorithms mechatronic system design

RESEARCH AND DEVELOPMENT OF VIRTUAL PROTOTYPE OF RUNNING GEARS FOR RAILWAY VEHICLE

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2008年第1期21卷 36-41页

作者： ZOU Yisheng DING Guofu zhang weihua XU Mingheng HE Yong College of Mechanical Engineering Southwest Jiaotong University Chengdu 610031 China Traction Power State Key Laboratory Southwest Jiaotong University Chengdu 610031 China

Virtual prototype is an important idea to resolve design problems of railway vehicle. A different development method, which is based on national product and autonomous development, and would like to reflect the specialty of railway vehicle development in China, is presented. According to the developing process of railway vehicle, the research contents and developing method are pointed out. The integration between CAD and performance analysis software on dynamics and strength is mainly considered. In CAD environment, the properties for dynamics computing are extracted directly from the model and exported with model. This method can avoid data losing caused by model rebuilding in CAE software, and increase the direct dependence of product CAD. Then the vehicle model with properties will be used for real-time dynamics and kinematics analysis and simulation. Therefore, the strength of the parts can be analyzed. The results of dynamics and strength analysis will be fed back to optimize the design model. All operations are dispatched by a control platform, and all data are managed according to the principle of PDM. Testing results show this method is correct.

关键词： Virtual prototype Railway vehicle Property extraction Dynamics analysis Strength analysis

家长近视防控认知和技能与小学生健康用眼行为的关联

在线全文

学校读者我要写书评

暂无评论

中国学校卫生 2024年第7期45卷 923-927页

作者：章小花童敏张卫华徐加伟曹斌沈洁田倩倩史慧静上海市浦东新区眼病牙病防治所预防科 201399 复旦大学公共卫生学院上海交通大学医学院上海交通大学中国医院发展研究院

目的探讨家长近视防控的认知和技能水平与小学生健康用眼行为之间的关联,为开展家庭精准宣教提供依据。方法2022年10—12月,采取分层整群随机抽样方法抽取上海市浦东新区8所小学一至五年级共4979名学生,采用自制问卷调查小学生健康用眼... 详细信息

目的探讨家长近视防控的认知和技能水平与小学生健康用眼行为之间的关联,为开展家庭精准宣教提供依据。方法2022年10—12月,采取分层整群随机抽样方法抽取上海市浦东新区8所小学一至五年级共4979名学生,采用自制问卷调查小学生健康用眼行为及其家长对近视防控的认知与技能水平。采用χ~2检验、独立样本t检验及Logistic回归分析家长近视防控认知和技能与小学生健康用眼行为的关联。结果小学生家长对近视防控的认知和技能水平较高者分别占50.97%和56.36%。认知条目中,中低年级小学生家长在“知道孩子近视的主要原因”“知道正确的近视防控知识”“知道在控制和治疗孩子近视过程中,家庭成员间要相互支持”“懂得引导孩子科学正确用眼是家长的职责”条目得分上均高于高年级小学生家长(3.05±1.21,2.97±1.20;5.92±0.86,5.83±0.86;4.46±0.88,4.40±0.93;3.88±1.04,3.72±1.07),差异均有统计学意义(t值分别为2.04,3.39,2.00,4.87,P值均<0.05);技能条目中,不同年级小学生家长在所有条目得分上差异均有统计学意义(t=2.93~7.31,P值均<0.05)。认知水平中,家长在“知道孩子近视的主要原因”“知道正确的近视防控知识”“知道《综合防控儿童青少年近视实施方案》”“担心孩子未来的求学和就业因近视会受到影响”“懂得引导孩子科学正确用眼是家长的职责”等方面得分为满分者占比较低,分别为12.71%,22.90%,19.30%,21.83%,22.47%。技能水平中,家长在“孩子做作业、读书、写字的时候提醒孩子休息眼睛”“与孩子共处时会刻意回避使用手机”“过去一年带孩子去医院屈光筛查的次数”“会给孩子布置额外的学习任务”等方面满分者占比较低,分别为33.26%,15.12%,9.00%,5.36%。相对于认知而言,家长近视防控的技能对不同学段学生健康用眼行为4个维度(读写、视屏、户外活动和睡眠时长)的作用更加凸显(OR=1.41~3.37,P值均<0.05)。结论家长近视防控的认知和技能还存在薄弱环节,与小学生健康用眼行为存在关联。应强化对家长近视防控的精准健康宣教,培养小学生健康用眼行为,减少其近视的发生。

关键词：近视认知眼行为回归分析学生

Improvement of Low OCV in MH/Ni Battery

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2004年第Z1期22卷 344-346页

作者： zhang Zhong Liang Wanlong zhang weihua Xing Zhiqiang Ma Yijun Inner Mongolia Rare Earth Ovonic High-Power MH/Ni Battery CO. Ltd. Baotou 014030 China Inner Mongolia Rare Earth Ovonic High-Power MH/Ni Battery CO. Ltd.Baotou 014030 China Inner Mongolia Rare Earth Ovonic High-Power MH/Ni Battery CO. Ltd.Baotou 014030 China Inner Mongolia Rare Earth Ovonic High-Power MH/Ni Battery CO. Ltd.Baotou 014030 China Inner Mongolia Rare Earth Ovonic High-Power MH/Ni Battery CO. Ltd.Baotou 014030 China

In MH/Ni high power battery production, a large percent of batteries were found with an open circuit voltage lower than 1.18 V after formation, open circuit voltage of another large percent of batteries could be even as low as1.00 ～ 1.10 V after one month *** this situation, we analysed the causes of the problem, and provided some efficient solution based on many *** was proved that these solutions are working very well to prevent the low open circuit voltage and being used in real production.

关键词： MH/Ni battery open circuit voltage stand life

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

虚拟现实环境下的协同式三维建模方法

图学学报 2024年第1期45卷 169-182页

作者：王浩淼桑胜举段晓东张伟华陶体伟马婷泰山学院信息科学技术学院山东泰安271000 大连民族大学大数据应用技术国家民委重点实验室辽宁大连116000 大连民族大学设计学院辽宁大连116000 中国电信泰安分公司山东泰安271000

三维建模技术在各个领域发挥着重要作用,但以桌面交互为主的三维建模方式仍复杂、抽象且不支持在线协作。为此,借助虚拟现实(VR)技术的沉浸性、交互性、想象性等优点,提出一种VR环境下的网络协同三维建模方法,使得用户以沉浸式的交互方... 详细信息

三维建模技术在各个领域发挥着重要作用,但以桌面交互为主的三维建模方式仍复杂、抽象且不支持在线协作。为此,借助虚拟现实(VR)技术的沉浸性、交互性、想象性等优点,提出一种VR环境下的网络协同三维建模方法,使得用户以沉浸式的交互方式建立三维模型,并支持多人实时在线可视化协作。首先,提出了一种VR环境下的三维模型绘制交互方式;其次,将三维模型进行分类,提出一种分层构建式的三维模型网格生成算法,用于建立平面模型和立体模型;最后,设计了一种VR环境下的三维建模网络协同模块,并基于Socket通信实现了网络同步。通过与传统三维建模软件的三维建模方法进行对比实验表明,该方法更加简捷、直观和高效,且易于普通用户掌握。

关键词：虚拟现实三维建模网格生成网络协同沉浸式交互