“系统动力学基础”教学准备与课程设计

“系统动力学基础”是培养学员系统思维、因果思维,以及利用建模仿真方法解决复杂系统实际问题的理论性与实践性兼备的一门课程。本文从课程教学准备与课程设计角度出发,探讨了在教学准备阶段需要了解授课对象的基本情况,精心选取教材,积极参加教学交流;在课程整体设计阶段需要系统做好顶层设计,科学选取教学内容,准确把握课程特色。     

基于系统动力学的企业R&D活动过程的演化机理研究

以企业RD活动过程为研究对象,从政府与企业RD投入的研究视角,基于企业技术中心的创新体系,建立RD投入与创新产出中间过程的系统动力学模型。实证分析混合RD投入下企业RD筹资子系统、支出子系统和产出子系统间的结构关系和动态演化过程。研究发现,企业RD筹资过程相比RD支出过程,对创新活动的促进效果更为显著;企业充分发挥了其在创新过程中的主体地位,无论是企业自身的RD筹资额增加,还是对企业内部的研发支出增加,都会促进创新效应。     

中国绿色经济发展展望--基于系统动力学模型的情景分析

绿色经济已经在世界范围内引起各国政府的重视。本研究构建的中国可持续发展模型,选择农业、森林、绿色建筑、可再生能源和核能、城市生活垃圾、城市交通、水泥产业7个行业从绿色经济的角度进行界定和模拟,通过情景仿真分析,分析发展绿色经济对中国经济、社会、环境系统的潜在影响。模拟结果显示,走绿色发展道路,中国可以实现更有质量的经济增长。同时,需要加强部门间的统筹协调,从整体层面制定绿色经济相关规划。     

协同动力视角下新能源产业成长机制研究

将新能源产业看作一个复杂的系统,运用系统动力学的方法理论对其进行建模分析。新能源产业成长受内在要素和外在要素共同影响,把市场需求、技术进步、政府推动看作是新能源产业发展的外部要素,企业竞争与协作看作是内部要素。通过绘制系统因果回路图及流图建立新能源产业成长动力模型。最后,运用协同学理论分析该动力机制模型,并为我国新能源产业发展提出针对性政策建议。     

考虑土地资源占用的港口与城市经济互动发展系统仿真——以深圳市为例

在分析港口与城市经济互动发展系统结构和特征的基础上,构建了基于系统动力学(SD)的因果关系图,选取城市GDP、港口通过能力、港区占地面积、港口深水岸线长度作为状态变量,构建系统流图和系统动力学方程。以深圳市为例进行实证分析,通过对仿真模型结构和行为的检验,验证了模型的有效性。选取港口投资政策因子、岸线消耗系数、港区土地占用系数、港外土地占用系数以及表示港口业对航运服务业和港口物流业促进程度的乘数作为控制变量进行仿真,分析这些因素对港口与城市经济互动发展系统的影响。仿真结果表明,为实现深圳港口和城市2020年发展目标,需要适当的增加港口建设投资,但要避免码头重复建设带来的土地资源大量占用问题;集约利用港口土地资源,提高土地资源的利用效率;同时提升港口的物流和航运服务功能,以实现港口的转型升级。     

我国数字化专业科技期刊集群的形成与发展

探讨我国数字化专业科技期刊集群这一新兴出版模式的形成与发展.基于集群理论界定我国数字化专业科技期刊集群的概念,梳理我国数字化专业科技期刊集群的现实格局.从基本因素和扩展因素2个层面阐释其集聚动因,从组织结构、形成动力和群内关系上归纳其集聚模式.对其未来发展方向做了展望.     

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

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.     

Intentional thought dynamics during exercise performed until volitional exhaustion

Using a non-linear approach, intentional dynamics of thoughts were examined during constant cycling performed until volitional exhaustion. Participants (n = 12) completed two sessions at 80% W_max. Their (1) intrinsic thought dynamics (i.e., no-imposed thoughts condition) and (2) intentional thought dynamics (i.e., imposed task-unrelated thoughts condition; TUT) were recorded and then classified into four categories: internal and external TUT (TUT-I, TUT-E) and external and internal task-related thoughts (TRT-E, TRT-I). The probability estimates for maintaining each thought category stable, the rate of switching from one category to another, and the entropy dynamics along the testing procedure were assessed and compared through time phase. Friedman ANOVA tests revealed a significant effect of effort increase on thought contents only in the imposed TUT test. While TUT-I probabilities decreased significantly (P < .001) as effort increased, TRT-I probabilities increased (P < .05). Moreover, the entropy to the entire thought dynamics increased at the outset of task performance and decreased upon approaching volitional exhaustion (P < .001). As time spent in constant effort increased, and volitional exhaustion approached, task relatedness (TUT, TRT), direction (internal, external), and entropy of thought contents changed unintentionally providing further evidence for a nonlinear dynamics of attention focus.     

分子动力学方法研究环氧树脂力学性能参数

采用分子动力学方法,计算交联度92%的环氧树脂的力学性能参数,并比较不同温度下,环氧树脂力学性能参数的改变。研究结果表明,分子动力学模拟结果与试验结果相吻合。模拟结果显示,随着温度升高,交联环氧树脂的弹性模量、剪切模量和体积模量等性能下降,温度高于玻璃温度之后,环氧树脂力学性能下降显著。     

建筑设备专业流体力学的教学

流体力学是工科院校一门重要的专业基础课。针对建筑设备工程专业的相关专业课程和专科技术人才培养目标,调整流体力学的教学思路和方法。