Effect of absorption layer on interior sound field of sonar dome

Using the finite element method (FEM) and boundary element method (BEM) and considering the sound absorption layer which is covered on the backing of the sonar dome, the interior field in the dome which is excited by the incident plane wave has been studied. This method is validated by comparing numerical results with that of classic elastic theory. Then the effect of parameters of the sound absorption layer on interior sound field has been analyzed. The numerical calculation results show that uniformity of interior sound pressure is improved when the backing is covered with a sound absorption layer. The thicker the layer is, or the higher the loss factor of layer is, the more uniform the sound field is.     

跟随模式BiSAR动目标成像

机载双站合成孔径雷达(BiSAR)对地面运动目标的检测与成像是雷达成像技术中一个重要研究内容.当地面目标运动时,目标回波信号方位向多普勒频率发生变化,带来图像位置偏移和散焦等问题.文中给出了跟随模式的BiSAR几何结构,在此基础上建立了地面成像区域目标的运动模型,进而研究了目标的不同运动分量对BiSAR成像的影响和BiSAR对动目标的检测和成像技术,并给出了计算机仿真结果.     

我国道路运输市场的发展及政策变革研究

我国道路运输市场发展到目前大致经历的五个阶段,印证了道路运输业政策经历了放松管制、鼓励进入,加强管制、整顿调整市场结构,再放松管制,再加强管制这样的循环。总结过去发展道路运输市场的经验和教训,认清道路运输市场的现状,目的是针对当前问题采取进一步的措施．推动道路运输市场更好更快地发展。     

加固后双曲拱桥有限元分析与试验研究

对一采用异型截面拱加固法加固的双曲拱桥进行有限元分析和试验研究,从理论上验证该加固方法的有效性和合理性.在总结已有研究成果的基础上,利用ANSYS分析软件中实体单位对加固后的双曲拱桥进行有限元模拟,假设新老混凝土结合面不产生滑移,且能够共同参与受力.通过计算结果与试验测量值进行对比,证明ANSYS软件中实体单元分析加固后双曲拱桥的可行性.     

公共交通定价与最优政府补偿模型

为了完善公共交通定价与政府补偿机制,分析了规模报酬递增、正外部性和次优理论3个潜在经济机理,建立了3个定价与补偿优化模型,并以西安公交为例进行了公共交通定价与补偿模型的应用。分析结果表明:基于规模报酬递增的边际成本定价与补偿模型,社会福利最佳且最为实用;基于正外部性的供求平衡定价与补偿模型,企业福利最佳;基于次优理论的Ramsey定价与补偿模型,在原理诠释方面最佳;补偿模型测算2009年西安公交的政府补偿金额为9.78亿元,符合现实需求,模型有效。     

Comparative study on ghrelin level change and its related factors in hypertensive elders with psychological distress

Objective To investigate the change of plasma ghrelin level and explore the related factors of ghrelin alteration in elderly hypertensive patients with psychological distress. Methods A total of 300 elders, who were screened with Hamilton Anxiety Scale (HAMA), Hamilton Rating Scale for Depression (HAMD), and the Symptom Checklist-90 (SCL-90) for psychological stress and somato-psychological manifestations respectively, were divided into hypertension group (n=148) and non-hypertension group (n=152). Their blood samples were collected to measure the plasma level of ghrelin and total cortisol on the same day. Results The incidences of anxiety and depression were 27.7% and 11.7%, respectively, in all the enrolled elders. However, the rates of psychological distress, particularly anxiety, were significantly higher in the hypertensive elders than in the non-hypertensive ones (43.2% vs. 12.5%). Anxiety was positively related to the cortisol level but negatively related to the plasma ghrelin level, and the latter two were negatively correlated with each other. Conclusion Chronic increase of plasma cortisol induced by long-term anxiety can lead to the reduction of ghrelin level, which then adversely affects blood pressure in elders with psychological distress. Therefore, ghrelin might be a selective antihypertensive medicine for hypertensive elders with anxiety.     

Inhibitory action of docetaxel on the proliferation of HeLa and SiHa cells

Objective To study the inhibitory action of docetaxel (DOC) on the proliferation of HeLa and SiHa cells. Methods Cell morphological changes were observed with inverted phase contrast microscope. MTT was adopted to test and calculate the cell inhibition ratio. Flow cytometry was used to detect cell cycle. Results DOC had an obvious concentration-dependent inhibitory effect on the proliferation of both HeLa and SiHa cells. The inhibition ratio of DOC on SiHa was significantly higher than that on HeLa (P<0.05). DOC blocked HeLa at G2/M phase. Under the effect of DOC, the cell cycle of SiHa was not changed much. Conclusion DOC has an obvious inhibitory action on both HeLa and SiHa cells, which shows a promising prospect of DOC in clinical treatment of cervical cancer.     

F3000车型总装配线工艺改造

通过对总装配线现状和F3000车型的主要结构特征进行分析,从工艺流程、设备、工装等方面对总装配线进行改造,实现F3000车型批量装配的目标。     

重庆滨江路加筋护岸工程加固方案研究

在对重庆滨江路加筋护岸整治工程安全性分析基础上。运用二维有限元数值计算法和强度折减理论对两种加固方案进行了安全性分析。经综合比较,推荐采用格宾块石箱体结构方案进行加固。     

汽车动力总成隔振难点与被动悬置改进技术

简述了发动机导致车内噪声的两种方式,即振动传递方式和辐射方式.基于发动机的激励特点和传递方式论述了发动机对整车振动噪声的影响规律及控制措施.基于动力总成隔振悬置需要满足的诸多冲突因素和约束条件,论述了汽车动力总成隔振设计难点,并阐述了被动式悬置改进技术.