排序方式: 共有17条查询结果,搜索用时 15 毫秒
1.
刘相秋 《高技术通讯(英文版)》2009,15(2):135-140
A simplified dynamic model of a dish antenna in satellite is established in this article.The modelcan be easily used to analyze the dynamic behaviour of the antenna structure.In terms of the simplifiedmodel,effects on dynamic characters due to the disorder of parameters are investigated in details.Thefrequencies calculated by the simplified model accord with those computed by ANSYS.Based on the modeshapes of disordered and perfect structure,the influence law and varying trend of dynamic characters ofant... 相似文献
2.
次子空间与不变次子空间的一些性质 总被引:1,自引:0,他引:1
Li Zhenzhu 《渤海大学学报(自然科学版)》1998,(1)
本文给出了次子空间与不变次子空间的概念,并探讨了它们的一些性质。 相似文献
3.
基于安徽省巢湖市狮子口剖面上泥盆统(法门阶)五通组的标本,对龙潭楔叶Sphenophyllum lungtanense Gothan et Sze的叶形和脉式等重要特征取得了新认识。华南晚泥盆世楔叶目的起源和演化分异模式不同于劳俄大陆的同类植物,它们兼有原始和进化的营养器官(枝状、线状或片状叶)和生殖器官(缺少或具有孢子叶),显示出较高的形态多样性和镶嵌演化。 相似文献
4.
为了研究锦鸡儿种子的休眠机制和解除休眠的最佳条件与方法,采用物理与化学方法对不同种源地的刺叶锦鸡儿与荒漠锦鸡儿进行破除休眠研究。结果表明:种皮厚度是影响刺叶锦鸡儿与荒漠锦鸡儿种子萌发的重要因素。在物理与化学方法中,热水处理、机械处理和浓硫酸处理能有效破除2种锦鸡儿种子种皮的阻碍性功能,显著提高锦鸡儿种子的萌发率与萌发指数。浓硫酸处理萌发率可达100%,热水处理萌发率最高值为96%。热水处理、浓硫酸处理具有操作简单、成本低等优点,是锦鸡儿属植物应用于生产实践中的良好方法。 相似文献
5.
Jing Lu Jimin Zhao Kangdong Liu Jun Zhao Hongyan Yang Youtian Huang Zhenzhu Qin Ruihua Bai Pei Li Junfen Ma Wenhai Yan Mingyao Zhao Ziming Dong 《Cellular and molecular life sciences : CMLS》2010,67(12):2091-2106
Endothelial-like differentiation of dendritic cells (DCs) is a new phenomenon, and the mechanism is still elusive. Here, we show that the tumor microenvironment derived from the human esophageal squamous cell carcinoma (ESCC) cell line EC9706 can induce immature DCs (iDCs) differentiate toward endothelial cells, and become endothelial-like cells, but it has no obvious influence on mature DCs. During the course of endothelial-like differentiation of iDCs, a sustained activation of mitogen-activated protein kinase/extracelluar signal-regulated kinase1/2 (MAPK/ERK1/2) and cAMP response element-binding protein (CREB) was detected. Incubation of iDCs with MEK phosphorylation inhibitor PD98059 blocked the MAPK/ERK1/2 and CREB phosphorylation as well as the endothelial-like differentiation of iDCs. Inhibition of vascular endothelial growth factor-A (VEGF-A) in the microenvironment with its antibody blocked the endothelial-like differentiation and the phosphorylation of MAPK/ERK1/2 and CREB. These data suggest that MAPK/ERK1/2 signaling pathway activated by VEGF-A could mediate endothelial-like differentiation of iDCs in the ESCC microenvironment. 相似文献
6.
李珍珠 《西华师范大学学报(哲学社会科学版)》1999,20(1):86-88
对复数域上次正定阵证明了1个Minkwski不等式,从而推广改进了姚存峰的《复数域上的次正定矩》一文的结果。 相似文献
7.
基于安徽省巢湖市狮子口剖面上泥盆统(法门阶)五通组的标本,对龙潭楔叶Sphenophyllum lungtanense Gothan et Sze的叶形和脉式等重要特征取得了新认识。华南晚泥盆世楔叶目的起源和演化分异模式不同于劳俄大陆的同类植物,它们兼有原始和进化的营养器官(枝状、线状或片状叶)和生殖器官(缺少或具有孢子叶),显示出较高的形态多样性和镶嵌演化。 相似文献
8.
In this paper numerical simulations of active vibration control for conical shell structure with distributed piezoelectric actuators is presented. The dynamic equations of conical shell structure are derived using the finite element model (FEM) based on Mindlin's plate theory. The results of modal calculations with FEM model are accurate enough for engineering applications in comparison with experiment results. The Electromechanical influence of distributed piezoelectric actuators is treated as a boundary condition for estimating the control force. The independent modal space control (IMSC) method is adopted and the optimal linear quadratic state feedback control is implemented so that the best control performance with the least control cost can be achieved. Optimal control effects are compared with controlled responses with other non-optimal control parameters. Numerical simulation results are given to demonstrate the effectiveness of the control scheme. 相似文献
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10.
镉(Ⅱ)、汞(Ⅱ)离子催化四苯基卟啉钴(Ⅱ)的生成反应 总被引:1,自引:1,他引:1
胡珍珠 《湖北师范学院学报(自然科学版)》1999,(4)
用分光光度法研究了钴(Ⅱ)与四苯基卟啉H2TPP在DMF溶剂中生成CoTPP的动力学以及镉(Ⅱ).汞(Ⅱ)离子对该反应的催化作用,提出了反应机理,并研究了温度对反应动力学参数的影响,求得基元反应的活化参数△Hm≠、△Sm≠及平衡步的△Hmφ△Smφ。 相似文献