圆形平面活塞式换能器的近场辐射特性的改善

平面活塞型超声换能器是长期来在超声检测以及其他超声应用技术中广泛采用的一种换能器类型。由于制作工艺简单，结构坚固，且又利用压电陶瓷的纵向机电耦合系数，因此具有良好的电声性能。然而，这种类型的换能器在媒质中产生的辐射声场，有其“先天性”的不足之处，在近场中无论平面活塞的频率和半径如何变化，轴上和沿径向上都呈现出极大和极小交替分布的干涉现象，因此我们有必要继续寻求更为理想的辐射形式。 本文分别设计和讨论了二种辐射形式的超声换能器:束控换能器和高斯换能器。在理论上讨论了这二种换能器的辐射声场分布、结构特点，并在实验中测量出了声场径向和轴向声压的相对值，从而验证了这两种换能器能有效的消除近场的零点，...学位：理学硕士院系专业：海洋与环境学院海洋学系_物理海洋学学号：19982700

Effects of Different Concentrations of Alcohol On Spatial Learning and Memory Ability and Hippocampal GFAP/NEUN in Mice

目的 探究长期饮酒对小鼠行为学能力以及空间学习记忆能力的影响。方法 雄性KM小鼠45只,随机分成对照组（Con）,低剂量组（Low）和高剂量组（High）。分别每天对照组0.10 ml/10 g自来水,低剂量组0.05 ml/10 g的56度红星二锅头,高剂量组0.10 ml/10 g的56度红星二锅头进行灌胃。连续灌胃13 d后进行衣架实验测行为学能力,最后取海马做免疫荧光染色观察海马神经元和星形胶质细胞。结果衣架实验得分,自主活动数值总体显示Low组高于其他两组,而且与Con组差异显著;免疫荧光结果显示无论是CA3区,还是DG区,海马的星形胶质细胞含量与神经元细胞含量比值上Con,Low,High三组依次升高,而且Con,High之间对比,P〈0.05,差异有统计学意义。结论 长期大量饮酒会损伤学习记忆能力,但适量饮酒可以促进机体兴奋性和活动度。Objective To investigated the effects of long-term alcohol drinking on the ability of learning and memory in mice. Methods 45 male KM mice were randomly divided into control group （Con）, low dose group （Low） and high dose group （High）. The control group were daily 0.10 ml/10 g tap water, low dose group 0.05 ml/10 g, 56 degree star erguotou, high dose group 0.10 ml/10 g, 56 degree star Erguotou by intragastric administration. After 13 days of continuous feeding, the experiment was conducted to test the behavior of the horse＇s tail, and the hippocampus was observed by immunofluorescence staining. Results The hanger score, numerical display Low overall locomotor activity was higher than the other two groups, and group Con; immunofluorescence results showed that both the CA3 region or DG region, astrocytes and neurons of hippocampus content ratio on Con, Low, High three group were significantly increased, and Con, High had significant difference, Conclusion A large number of long-term drinking will damage the ability of learning and memory, but moderate alcohol consumption can promote the body excitability and activity

Regional Characteristics of Vertical and Sectional Distributions of Sound Velocity in Southern Taiwan Strait

根据台湾海峡南部 1997年 8月的 CTD资料 ,分析存在的几种主要类型的声速垂直、断面分布状况以及它们的一些重要特征 ,并简略讨论了声速分布与温度、盐度的关系以及声速的时间变化特征Several main types and their important characteristics of vertical and sectional distributions of sound velocity are analyzed based on CTD data in the southern sea area of the Taiwan Strait in August 1997 The relation between sound velocity and temperature,salinity, and the time series variation of sound velocity are also discussed briefly国家基金重点项目资助 !(项目号 :4963 62 2 0

Distributive features of sound velocity in middle and northern Taiwan Strait in February and March,1998

根据台湾海峡中、北部海区 1998年 2～ 3月实测的温、盐资料计算得出的声速 ,分析了该海区存在的几种主要类型的声速垂直分布状况以及声速垂直分布和平面分布的一些重要特征。By using sound velocity calculated by the temperature and salinity data obtained in the middle and northern Taiwan Strait in February and March of 1998, several main types of vertical distributions of sound velocity and some of the important characteristics of vertical and horizontal distributions of sound velocity in the studied area have been analysed in detail.国家自然科学基金!资助项目(49636220号

Effect of ultrasonic waves on the hatching rate of Anemia eggs

研究了固定频率和强度的超声波对饵料生物丰年虫卵（CHIrOCEPHAluS）孵化的影响。实验结果表明，在适宜的超声波辐照下，丰年虫卵的孵化率比对照组提高 8%，孵化时间提前2H.This paper deals with the effect of ultrasonic wave of certain frequency and intensity on the hatching rates of the food organism Anemia eggs.The results show that the hatching rate and the hatching time of Anemia eggs is 8% higher and 2 hours shorter in the experimental group than those in control group, respectively, when the eggs are treated with suitable ultrasonic wave

空间激光干涉引力波探测与早期宇宙结构形成

空间引力波探测是研究宇宙早期恒星演化和星系形成、黑洞和星系的共同成长等天文学和宇宙学重大问题的一条重要可能途径。经过两期科学院先导科技专项空间科学预研究课题的开展,通过权衡技术的可行性与科学的前瞻性,选择以高红移开始的中至大质量双黑洞并合系统、星团等稠密动力学环境中涉及中等质量黑洞的双黑洞引力波波源为主要科学目标,给出了我国毫赫兹至赫兹频段空间引力波探测任务计划的初步设计。以该任务设计建议为依据,简要介绍空间引力波探测及其作为一种新的天文观测手段的科学内涵,以及我国空间引力波探测任务设计的科学目标和探测潜力

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel