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951.
军民一体化是当今世界各国国家创新系统演进的共同趋势,本文特别分析了美国和日本国家创新系统演进中的军民一体化模式,从而得出其中蕴含的两用政策寓意,并对两用政策内涵进行具体剖析。  相似文献   
952.
This paper presents the analysis and control of active magnetic bearing (AMB) systems with a flexible rotor. A sliding mode controller design scheme is proposed to compensate for the nonlinear effects of the AMB system. A nonlinear model of the AMB system with an electromagnetic actuator and a flexible rotor is proposed to facilitate the present system analysis and controller design. This nonlinear model takes into account the dynamics of the flexible rotor, the characteristics of the nonlinear electromagnetic suspended system, and the contact force between the auxiliary bearing and the shaft. This study also considers the auto-centering control of the AMB system when subjected to disturbances and variations in the system parameters. The numerical results show that the system exhibits a periodic motion and demonstrates high accuracy and robustness when operating under sliding mode control.  相似文献   
953.
动态全参数自调整BP神经网络预测模型的建立   总被引:8,自引:0,他引:8  
李晓峰 《预测》2001,20(3):69-71
本文从减少干预的思想出发,提出了BP神经网络动态全参数自调整学习算法,使得隐层节点和学习速率的选取全部动态实现,实现了学习速率和网络的适应能力,最后又将改善后的BP神经网络应用到经济领域中,得到了比常规经济学模型更优的效果。  相似文献   
954.
万寿竹六个居群的核型研究   总被引:1,自引:0,他引:1  
本文研究了在云南境内的万寿竹Disporum cantoniense (Lour.)Merr.从滇东南经滇中到滇西 北不同居群间的核型变异。该种的染色体数目较为稳定,2n=14,没有观察到不同数目的变异。六个 居群的不对称性均属于3B型,但各个居群的核型结构表现出一定的差异,核型间随体位置和数目的不 同以及同源染色体的杂合性是居群间变异的主要特征,这种种内不同居群间核型的变异或许与该种的地理分布及生境有一定的相关性。  相似文献   
955.
This study is designed to isolate and purify a novel anti-clotting protein component from the venom of Enhydrina schistosa, and explore its biochemical and biological activities. The active protein was purified from the venom of E. schistosa by ion-exchange chromatography using DEAE-cellulose. The venom protein was tested by various parameters such as, proteolytic, haemolytic, phospholipase and anti-coagulant activities. 80 % purity was obtained in the final stage of purification and the purity level of venom was revealed as a single protein band of about 44 kDa in SDS-polyacrylamide electrophoresis under reducing conditions. The results showed that the Potent hemolytic activity was observed against cow, goat, chicken and human (A, B and O positive) erythrocytes. Furthermore, the clotting assays showed that the venom of E. schistosa significantly prolonged in activated partial thromboplastin time, thrombin time, and prothrombin time. Venomous enzymes which hydrolyzed casein and gelatin substrate were found in this venom protein. Gelatinolytic activity was optimal at pH 5–9 and 1H NMR analysis of purified venom was the base line information for the structural determination. These results suggested that the E. schistosa venom holds good promise for the development of novel lead compounds for pharmacological applications in near future.  相似文献   
956.
寄存器传输级(RTL)测试产生及时延测试是当今集成电路(IC)测试技术中亟待解决的问题和研究的热点.首先从IC逻辑测试的测试产生和IC时延测试方法这两个方面系统地综述了测试产生和时延测试领域迄今为止的主要研究成果.在RTL行为描述的测试产生方面,提出了新的RTL行为模型的描述方法:行为阶段聚类描述,并提出了基于聚类的测试产生技术.将这些技术集成到RTL级ATPG系统ATCLUB中,在提高测试产生效率及缩短测试长度方面效果显著.在IC时延测试方面,提出了一种新的可变双观测点的时延测试方法。基于该方法提出了新的时延故障诊断方法,实现和完善了可变双观测点的时延测试系统DTwDO.DTwDO提供了从时延测试到故障诊断等一系列测试工具,有效减少了测试通路数,提高了故障覆盖率,并有很高的故障定位成功率.  相似文献   
957.
"参"在传世文献中用作度量衡单位时多为重量单位,而秦汉简帛文献中则非如此,亦非指酒器"觯",而是用作容量单位,为"小斗"的"三分之一"。  相似文献   
958.
敦煌石窟中书写藏汉文字的T形榜子颇具时代特征,榆林窟第25窟八大菩萨曼荼罗造像中的T形榜子更具研究价值,有三个方面的问题需作研究:1.为什么榆林第25窟T形榜子仅出现在八大菩萨曼荼罗造像中?2.为什么该T形榜子中未写藏文?3.为什么主尊T形榜子中汉文题名清净法身卢舍那佛,而与主尊本身的大日如来形象不合?  相似文献   
959.
This observational study examined kindergarteners’ (n = 170) exposure to literacy instruction in their classrooms (n = 36), child-by-instruction interactions, and behavioral engagement in relation to literacy skills. Time spent in four instructional contexts was coded according to who managed children's attention (teacher-managed, TM or child-managed, CM), and the content focus (basic skills such as teaching letters and their sounds, or meaning-focused such as discussing a book); children's behavioral engagement and off-task behavior were also coded live five times over the year. Word-reading and phonological awareness skills were assessed in fall and spring. Hierarchical Linear Modeling results indicated that kindergarteners with lower initial skills gained more in word-reading, but not phonological awareness, when they were exposed to relatively more time in TM basic skills instruction. In contrast, more time in CM meaning-focused instruction did not interact with initial skills to predict either outcome. Engagement analyses indicated that students were more likely to be off-task in CM than in TM contexts. Children who spent more time off-task during TM contexts had lower spring scores on both outcomes. Discussion explores the implications of this work for both literacy learning and behavioral engagement in the transition year of kindergarten.  相似文献   
960.
Contributions to this special section represent advances in understanding help seeking as a self-regulated learning strategy that occurs in classrooms, during computer-mediated communications, and when using intelligent systems that provide help to improve learners’ help-seeking skills and knowledge acquisition. Collectively, the research and development contributes information relevant for all phases of the help-seeking process. My comments focus on: (a) features of technology-supported help seeking that have implications for motivation, (b) the need for increased attention to the instructional context in which technology-supported help seeking occurs, (c) a necessary convergence of classroom and technology-supported help-seeking research paradigms, and (d) reconsideration of help seeking as a social-interactive strategy.  相似文献   
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