防止汽轮机组转子弯曲的技术措施

汽轮机组转子弯曲事故将严重影响汽轮机转子的使用寿命,对于防止汽轮机组转子弯曲应做好三个方面的工作:掌握必要的基础技术资料,做好基础技术工作;保持设备的运转良好,系统结构合理;保证运行过程中操作准确无误。     

The sidestep cutting manoeuvre requires exertion of lumbosacral lateral flexion torque to avoid excessive pelvic obliquity

During sidestep cutting, the pelvis is supported only on one side; this affects the athlete’s posture. This study investigated the mechanism to avoid excessive pelvic obliquity during sidestep cutting. Ten physically active men performed sidestep cutting with maximal effort, and we captured the kinematics and kinetics with force platforms and an eight-camera motion capture system. Our results indicated that the stance hip exerted little abduction torque; however, lumbosacral lateral flexion torque was exerted towards the free-leg side (peak value: 3.39 ± 0.91 N m/kg). Although bilateral hip joint forces acted to drop the free-leg side of the pelvis, the net torque around pelvic elevation/drop axis was nearly zero during the entire stance phase and the change in the angular momentum around the pelvic elevation/drop axis from touchdown to toe-off was negligible (?0.004 ± 0.003 N m s/kg). The integrated components of lateral flexor for elevating the free-leg side of the pelvis (0.220 ± 0.072 N m s/kg) were significantly larger than any other integrated components, which were all negligible (<0.010 N m s/kg). Thus, sidestep cutting requires the lumbosacral lateral flexion torque exertion to neutralise the passive action that drops the free-leg side of the pelvis.     

“期刊承认”与“共同体承认”:我国学术知识生产动力机制的“悖论”

本文在整合布迪厄与默顿关于知识生产动力机制相关理论的基础上,运用深度访谈和文献研究的方法,考察了量化考评制度对两所地方性大学44名学术人知识生产实践和观念的影响.文章认为,由于我国的"期刊承认"并未得到大部分学术人的真正认同,已非"共同体承认"的有机组成部分,"期刊承认"与"共同体承认"之间的冲突导致了我国学术知识生产动机机制的失灵.     

动态法测杨氏模量共振频率的拟合研究

分析讨论了动力学法测杨氏模量基频固有频率的最小二乘法拟合,指出在笔者采用数据的试验条件下,拟合多项式的幂次以3~4次为宜.     

EEG dynamics reflects the partial and holistic effects in mental imagery generation

Mental imagery generation is essential in the retrieval and storage of knowledge. Previous studies have indicated that the holistic properties of mental imagery generation can be evaluated more easily than the partial properties. However, the relationship between partial and holistic mental imagery generations has not been clearly demonstrated. To address this issue, we designed a task to investigate the changes in the spectrum of the electroencephalogram (EEG) during partial or holistic imagery generation. EEG signals were obtained from 18 healthy subjects, and a statistical measure of spectral dynamics between two EEG signals in per frequency band was performed. Additionally, a bicoherence spectrum analysis was used to detect the phase coupling within these two imagery conditions. Our results indicated that EEG of the partial imagery appeared earlier and stronger than that of the holistic imagery in the theta (5–8 Hz) range in a time window around 220 to 300 ms after cue onset, and a slight decrease in the alpha (8–12 Hz) band was observed at around 270 ms. The scalp topography of these changes in the theta and alpha bands distributed overall significantly in the frontal and central-temporal areas. The significant phase coupling within two conditions was remarkable at high frequency. From these results, we infer that there are complex relations between partial and holistic imageries. The generation of partial mental imagery is not a subprocess of holistic imagery, but it is relevant to holistic imagery and requires correct modification from the holistic information.     

商业计划与新企业生成:环境不确定性与产品创新性的角色

以两轮中国创业动态跟踪调查(CPSED)收集的321个创业者数据为样本,采用层级式的逻辑回归方法,实证考察不同程度外部环境不确定性和产品创新性约束条件下商业计划正式程度对新企业生成的内在影响机制。研究发现:创业者制定的商业计划正式程度越高,新企业成功生成的可能性越大,而外部环境不确定性和内部产品创新性调节着上述影响机制。因此,在创业初期资源匮乏的条件下,关键并不在于是否制定商业计划,而是应该根据外部环境不确定性以及创业者打算供给产品的创新性来权变地选择不同正式程度的商业计划,以促使新企业的成功生成。     

权变视角下企业网络位置与产品创新绩效关系研究

当前对企业选择网络中心位置还是网络中介位置进行产品创新仍存有争论,而同时引入技术战略导向和市场动态性两个调节变量分析两种网络位置对产品创新绩效的权变效应有可能破解这个难题。通过对浙江省208家制造企业的实证研究发现,两种网络位置对产品创新绩效都有正向影响,且企业技术战略导向越高,这种正向效应越显著;市场动态性越高,网络中介位置对产品绩效的正向效应越显著,但市场动态性对网络中心位置与产品创新绩效关系负向调节作用并不显著。研究结论不仅明确了不同网络位置发挥效用的具体情境,也为企业选择合适的网络位置进行产品创新提供了启示。     

基于转运协调机制的救灾物资库存控制策略与仿真

通过地方储备库之间的灾后救灾物资转运,可以解决本地救灾物资储备不足和被破坏等问题,并且规避应急采购响应时间长和物流配送成本高等的缺点。本文建立的具有转运机制的救灾物资储备因果回路图显示,转运本身不会使得系统库存趋于合理化,而只能通过应急采购这一系统的负反馈回路将各地方储备库的目标库存调整至合理水平。同时,一系列仿真对比试验也表明,相同的库存策略的实施效果因需求概率、单位转运成本和灾前采购成本而异;同时,各储备地既希望充分利用转运的优势,降低本地成本,又希望规避对方的转运需求带来的本地采购成本的上升,矛盾的双方必须放到统一的灾前物资储备规划系统中,才能以最少的总库存成本满足最高的总体救灾需求。     

企业内知识转移的系统动力学建模与仿真

知识转移在企业发展中起着越来越重要的作用。本文通过对企业内员工之间的知识转移过程及影响因素的分析,在Vensim PLE软件环境下对企业内知识转移进行因果关系分析,构建企业内知识转移的系统动力学模型,并进行仿真和灵敏度分析。此仿真可为企业制定有效的知识转移策略提供理论依据。