北京市耕地多功能空间分异及其社会经济协调模式解释   总被引：15，自引：0，他引：15  

施园园  赵华甫  郧文聚  汤怀志  徐阳 《资源科学》2015,37(2):247-257

以北京市为例,在解析识别耕地功能表征因子的基础上,分别对北京13个区县(不包括中心城区)耕地的生产、生态、社会功能进行评价,利用GIS反映多功能的空间分布形态,并通过信息熵模型对耕地多功能与社会经济的空间相关性进行测算,讨论各区县耕地多功能与其经济社会发展的互动关系以及发展阶段的协调模式。本文旨在揭示北京市耕地多功能在社会经济影响下的空间分异特征,为制定科学的耕地多功能利用布局方案提供理论依据。研究结果表明:北京市各区县经济社会发展水平与耕地多功能的空间相关性较强,具有明显的空间分异特征;此外在经济与政策的共同驱动下,多功能与经济的组合模式随着经济发展经历高生产-中社会-低生态的正三角形态向低生产-中社会-高生态的倒三角形态演变的一般过程。  相似文献   

Perform kicking with or without jumping: joint coordination and kinetic differences between Taekwondo back kicks and jumping back kicks     

Kuangyou B. Cheng  Ying-Hsun Wang  Shih-Yu Kuo  Kuan-Mao Wang  Yi-Chang Huang 《Journal of sports sciences》2015,33(15):1614-1621

We investigated joint coordination differences between Taekwondo back kicks and jumping back kicks, and how jumping (in performing the latter) would alter engaging ground reaction forces (GRF) in executing kicking. Ten skilful athletes volunteered to perform both kinds of kicking within the shortest time for three successful trials. Three high-speed cameras and two force platforms were used for data collection, and the trial with the shortest execution time was selected for analysis. Movements were divided into the rotation and attack phases. With comparable execution time and maximum joint linear/angular speeds, back kicks and jumping back kicks differ mainly in larger GRF in the latter, and in greater target acceleration in the former probably because the support leg prevented athletes’ rebounding after impact. In addition, more prominent antiphase and in-phase coordination between the shoulder segment and knee joint, and elongated rotation phase were found in jumping back kicks. Larger GRF values in jumping back kicks were generated for jump take-off rather than for a more powerful attack. In back kicks although the support leg remained ground contact, greatly decreased GRF in the attack phase suggested that the support leg mainly served as a rotation axis.  相似文献   

基于和式太极三直五顺拳理对预防太极拳运动膝关节损伤的研究     

牛炎涛  刘巧芳 《搏击·武术科学》2015,(6)

文章通过太极拳运动对膝关节损伤的相关文献查询,得出常见的太极拳运动膝关节损伤病例,对文献结论分析得出造成损伤的因素有两个方面,一是动作技术不正确不规范造成,二是膝关节受力过重造成。通过对和式太极拳三直五顺拳理要求分析,得出五顺是太极拳动作技术要求,三直是减轻膝关节受力要求,与造成膝关节损伤的两个方面具有对应关系,提出三直五顺拳理对练习者的要求在保护膝关节损伤的重要性。  相似文献   

Effects of changing speed on knee and ankle joint load during walking and running     

Ana Cristina de David  Felipe Pivetta Carpes  Darren Stefanyshyn 《Journal of sports sciences》2015,33(4):391-397

Joint moments can be used as an indicator of joint loading and have potential application for sports performance and injury prevention. The effects of changing walking and running speeds on joint moments for the different planes of motion still are debatable. Here, we compared knee and ankle moments during walking and running at different speeds. Data were collected from 11 recreational male runners to determine knee and ankle joint moments during different conditions. Conditions include walking at a comfortable speed (self-selected pacing), fast walking (fastest speed possible), slow running (speed corresponding to 30% slower than running) and running (at 4 m · s^?1 ± 10%). A different joint moment pattern was observed between walking and running. We observed a general increase in joint load for sagittal and frontal planes as speed increased, while the effects of speed were not clear in the transverse plane moments. Although differences tend to be more pronounced when gait changed from walking to running, the peak moments, in general, increased when speed increased from comfortable walking to fast walking and from slow running to running mainly in the sagittal and frontal planes. Knee flexion moment was higher in walking than in running due to larger knee extension. Results suggest caution when recommending walking over running in an attempt to reduce knee joint loading. The different effects of speed increments during walking and running should be considered with regard to the prevention of injuries and for rehabilitation purposes.  相似文献   

水分对木质工字梁翼缘/腹板接口性能的影响     

李军伟  陈竹 《深圳职业技术学院学报》2015,(1)

木质工字梁（Wood I-Beam,简称：IB）在使用过程中将不可避免地遇到潮湿环境的影响,研究水分对翼缘/腹板接口性能的影响,对确保IB接口最佳胶合状态以及最终产品尺寸稳定性至关重要．研究结果表明：IB的综合性纤维饱和点只有25%左右;含水率从8.9%提高到25%的接口的承压能力下降了47.2%,含水率从25%提高到53%的接口的承压能力仅下降了0.6%;水分对IB翼缘和腹板尺寸变化的影响是水分影响接口承载能力的间接因素;吸湿后接口的承载能力并不能恢复到吸湿前的初始水平;解吸至8.9%含水率的IB接口的承载能力比吸湿前同等含水率的IB接口低了17.8%．  相似文献   

Students’ use of the interactive whiteboard during physics group work     

Magnus Strøm Mellingsæter  Berit Bungum 《European Journal of Engineering Education》2015,40(2):115-127

This paper presents a case study of how the interactive whiteboard (IWB) may facilitate collective meaning-making processes in group work in engineering education. In the case, first-year students attended group-work sessions as an organised part of a basic physics course at a Norwegian university college. Each student group was equipped with an IWB, which the groups used to write down and hand in their solutions to the physics problems. Based on a Vygotskian, dialectical stance, this study investigates how the students used the IWB in the group-work situation. From qualitative analysis of video data, we identified four group-work processes where the IWB played a key role: exploratory, explanatory, clarifying and insertion. The results show that the IWB may facilitate a ‘joint workspace’, a social realm in which the students’ dialogues are situated.  相似文献   

飞机蒙皮对接处结构疲劳性能研究     

蔡玲 《中国科技信息》2014,(9):46-47

本文旨在通过研究飞机中常见的蒙皮对接处结构连接形式,对比常见的两种对接形式蒙皮端部的钉载,得出更优的结构设计。分别对第一种连接方式进行工程分析和有限元分析,对第二种连接进行有限元分析,得出对于第一种连接方式,有限元分析和工程分析结果一致;相对于第一种连接方式端部载荷降低了40%。从传载比的计算结果可以看出第二种连接方式明显降低了蒙皮端部连接处的传载比,明显改善了该危险部位的疲劳细节,而且采用了指形板,达到减重效果,符合运营商的经济性要求。  相似文献   

某型号飞机前机身普通框接头R区疲劳分析     

丁丹烨 《中国科技信息》2014,(7):189-190

在民用飞机设计中,疲劳性能是飞机设计中要考虑的一个重要因素。而接头破坏可能是引起飞机结构失效的最常见的根源,且接头的疲劳强度分析在飞机结构分析中占有非常重要的地位。本文通过算例介绍了某型号飞机前机身普通框接头R区的疲劳分析方法,为接头的疲劳特性评估提供依据,以帮助结构工程师设计能够满足疲劳强度要求的接头尺寸,亦可为飞机的疲劳强度验证试验提供支持。  相似文献   

高压设备电气接头发热缺陷的检测与处理方案分析     

边宏超  王庆水  袁兆军  孙鹏 《中国科技纵横》2014,(14):185-186

目前在110kV电压等级及以上变电站中,输变电设备电气接头不同程度发热的现象时常存在,这对设备本身造成伤害,也对电网安全可靠运行构成很大影响,必须采用有效手段加强检测,尽早发现热点并进行处理和防范。本文以实际运行中一个接头发热案例,分析了故障原因,提出了检测和防范措施。  相似文献   

通信作者不当署名行为界定及规则改进          下载免费PDF全文

熊皓男 《中国科学院院刊》2022,37(10):1491-1499

通信作者是特殊的署名类型,存在特殊的学术不端行为。通信作者的职责是完成论文通信事宜,其不当署名具体表现为标注不适格、侵犯其他作者署名权、未履行通信作者义务。良善的通信作者制度设计可以有效预防不当署名等学术不端行为,而现有的通信作者制度难以胜任。其改革应从制定通信作者署名规则、完善通信作者奖励机制、推行合作作者贡献声明 3 个方面进行。通过精细的角色分工、公正的奖励机制、科学的责任分配等方式,减少纠纷、促进协作。  相似文献