利用灵山洞钟乳石中流体包裹体研究更新世古环境     

周念清 刘斌李彩霞  唐益群 《中国科技期刊研究》2007,23(9):2045-2051

流体包裹体在喀斯特溶洞化学沉积物中广泛分布，这些在化学沉积过程中所形成的流体包裹体蕴藏着大量的古环境演化和气候变迁的重要信息。通过采集杭州灵山洞中更新世形成的钟乳石样品，对不同纹圈中流体包裹体进行测定，研究流体包裹体的特征，利用不混溶气-水包裹体中最大密度判别和计算方法确定六个纹圈中精确的形成温度和压力；根据气-水-岩化学反应平衡热力学方法，计算出CO2成分浓度和古地水中pH值及钟乳石样品形成过程中的CaCO3饱和度等。揭示了杭州地区更新纪古环境演化规律。  相似文献   

基于学生学习感受为主导、数据分析 为方法的学生评教思考          下载免费PDF全文

张婷  李静  潘玉芳 《上海教育评估研究》2016,5(2):72-76

本文分析了目前高校学生评教工作中存在的问题,提出从学生学习感受出发科学设计 评价指标,并应用数据分析的方法检测指标设计的合理性,引入有效参评率提高数据采集过程的 工作效率,在数据分析的基础上对评价结果进行客观分析。一系列尝试取得了一些成效,具有一定 借鉴意义。  相似文献   

经济危机对企业研发回报率的影响——基于Perez巨浪模型的实证分析     

苏依依  王敏 《科研管理》2021,42(5):39-46

现有文献主要关注经济危机对企业研发创新的负面影响,同时也指出了危机可带来社会技术范式的变革,从而迎来“黄金时代”。基于Perez巨浪模型,探究在全球范围内危机前后不同企业、行业和国家企业研发回报率的变化趋势。以1986～2014年间全球63个国家的52638个企业年度数据为调查对象,结果表明,经济危机后,不论对企业增长还是利润率而言,企业都获得更高的研发回报率;低市场份额企业的研发回报率提高程度大于高市场份额企业;低杠杆率企业的研发回报率提高程度大于高杠杆企业;服务型企业的研发回报率提高程度大于制造型企业;发展中国家与发达国家企业研发回报率差异不显著。研究结果为Perez的巨浪模型提供了实证支持,并为危机后企业研发提供了管理启示。  相似文献   

Hybrid adaptive bionic fuzzy control method for MIMO systems with dead-zone input     

《Journal of The Franklin Institute》2023,360(10):6804-6826

In this research, a hybrid adaptive bionic fuzzy control strategy is developed for a class of complicated nonlinear multiple-input-multiple-output (MIMO) systems with dead-zone input. The first component of the bionic adaptive controller is a general phrase for tunning system parameters depending on the present state, and the second component is a trend-based compensation for adjusting the system parameters. This technique makes the system more intelligent and boosts its anti-interference capabilities. The stability and convergence are analyzed using the Lyapunov synthetic method, and thus the parameter restrictions of the MIMO system are provided. Finally, the strong anti-interference of the system is verified by the simulations.  相似文献   

Finite-time formation control of nonaffine nonlinear systems under directed communication interactions     

《Journal of The Franklin Institute》2023,360(11):7180-7205

This paper studies the problem of finite-time formation tracking control for networked nonaffine nonlinear systems with unmeasured dynamics and unknown uncertainties/disturbances under directed topology. A unified distributed control framework is proposed by integrating adaptive backstepping control, dynamic gain control and dynamic surface control based on finite-time theory and consensus theory. Auxiliary dynamics are designed to construct control gains with non-Lipschitz dynamics so as to guarantee finite-time convergence of formation errors. Adaptive control is used to compensate for uncertain control efforts of the transformed systems derived from original nonaffine systems. It is shown that formation tracking is achieved during a finite-time period via the proposed controller, where fractional power terms are only associated with auxiliary dynamics instead of interacted information among the networked nonlinear systems in comparison with most existing finite-time cooperative controllers. Moreover, the continuity of the proposed controller is guaranteed by setting the exponents of fractional powers to an appropriate interval. It is also shown that the improved dynamic surface control method could guarantee finite-time convergence of formation errors, which could not be accomplished by conventional dynamic surface control. Finally, simulation results show the effectiveness of the proposed control scheme.  相似文献   

九运会男子百米途中跑技术分析     

虞玉华  郭俊人  卢伟华  韩甲 《天津体育学院学报》2003,18(2):35-37

通过对九运会中国男子百米跑优秀运动员途中跑的技术录像解析，分析所获得的速度、角速度、步频、步长、单步各时相等运动学参数的具体指标，并与国内外优秀百米跑选手作比较，结果认为，九运会男子百米途中跑速度较以往有了明显的提高，原因主要是步长的提高，但与国外优秀选手还有差距，主要原因是步长不足；中国百米跑运动员应减少腾空时间以增大身体重心位移的支撑与腾空时间比；九运会男子百米跑运动员的摆腿及摆臂技术差异较大，且摆臂时前摆不足后摆过大，使身体产生向前的动力不足。  相似文献   

Stability and dissipative analysis for a class of stochastic system with time-delay     

Hao Zhang  Huaicheng Yan 《Journal of The Franklin Institute》2010,347(5):882-3355

This paper deals with the stability and dissipative problem of a class of stochastic hybrid system. The system under study involves Markovian jump, impulsive effects and time delay, which are often encountered in practice and are the sources of instability. Our attention is focused on analysis of whether the stochastic hybrid system with time-delay is stochastically asymptotically stable and strictly (Q, S, R) dissipative. By introducing an extra artificial time instance, the equivalent system is obtained and the sufficient conditions are derived by using linear matrix inequality (LMI) techniques. The main results of this paper unify the existing results on H_∞ control.  相似文献   

Polymorphisms in the vitamin D receptor and the androgen receptor gene associated with the risk of urolithiasis     

Rama Devi Mittal  D. K. Mishra  P. Srivastava  P. Manchanda  H. K. Bid  R. Kapoor 《Indian journal of clinical biochemistry : IJCB》2010,25(2):119-126

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满足顾客需求的产品平台稳健性研究     

王成龙  叶明海 《科研管理》2010,31(5):141-147

摘要：针对汽车产品平台稳健性问题,依据产品开发流程,应用质量功能展开理论,建立了空间变量指数模型,提出了减少顾客需求不确定性的方法。运用案例研究方法,以上海某汽车企业参与全球产品平台开发为例,采用空间变量指数模型进行分析,对模型进行了检验并提出了对策,验证了空间变量指数模型在降低不确定性方面是可行的,最终能够降低成本并实现提升企业竞争力的目标。  相似文献   

基于效率、回应性、公平的公共服务绩效评价——以上海市公共汽车交通的服务绩效为例     

王欢明  诸大建 《软科学》2010,24(7):1-5

在理论研究层面,从效率、回应性、公平三维度构建公共服务绩效公式,追求单位成本服务满意最大化。在案例分析层面,以上海市公共汽车交通服务为例,通过灰色评价衡量其服务绩效为"一般"水平,并逐步迈入"较满意"行列。据此,提出的政策建议是提高技术效率和公众满意度。  相似文献