An Analysis of Dual Margin of China’s Export Growth and its Determinants

进入21世纪以来，中国对外贸易高速发展。就出口规模而言，目前中国已经成为排名世界第一的出口大国。可以说，中国出口的高速增长给中国经济发展注入了强劲的动力。金融危机爆发以来，中国出口发展受到较大的影响。目前，外部经济形势的发展前景并不明朗，这要求我们透过中国出口繁荣的表象，深入探究中国现存的粗放型发展模式究竟能否持续，出口大国是否代表中国已经成为出口强国。此外，20世纪90年代以来，为了降低出口风险，中国政府推行“市场多元化”战略，究竟其战略成效如何，市场多元化和产品专业化对中国出口增长的贡献如何，这都是本文所希望解决的问题。 本文首先回顾了出口增长的二元边际理论，然后在细分的HS6位级数水平...China’s export had been enjoying a prosperous development in the 21th century. In terms of total export volume, China had obtained world No.1 ranking. The quick development of China’s foreign trade strongly supported the economic development of China. However, the world financial crisis had a strong influence on China’s foreign trade development. Now the direction of the world economy is not clear...学位：经济学硕士院系专业：经济学院_国际贸易学学号：1572010115183

Jointing sparse recovery estimation algorithm of underwater acoustic channels with long time delay spread

对具有长时延扩展的水声信道,传统的信道估计算法如最小二乘法将在大量零值抽头产生严重的估计噪声,导致估计性能下降,同时信道估计时所需的较高估计器阶数大大提高了运算复杂度。压缩感知信道估计方法可有效利用多径稀疏特性改善性能,但需采用较大的训练序列长度以保证稀疏恢复精度,由此导致额外的系统开销。利用水声信道多径稀疏结构在数据块间存在的相关性,建立基于分布式压缩感知的长时延水声信道联合稀疏模型,从而可利用同步正交匹配追踪算法进行联合重构,以进一步减小系统的训练序列开销,提高估计性能。最后通过仿真和海上实验验证了所提方法的有效性。Efficient estimation of underwater acoustic channels with a large time delay spread was addressed. For the conventional channel estimation methods such as LS, this type of channel estimation would produce serious estimation noise in zero-value taps which lead to poor performance of channel estimation. At the same time, a large time delay spread posed significant difficulties such as large channel order and the corresponding huge computation complexity. Compressed sensing(CS) channel estimation algorithm offered a solution to this problem by exploiting the sparsity of channel to improve the estimation performance. However, to ensure acceptable estimation performance, a long training sequence was needed, which unfortunately would cause additional overhead. A method was proposed which exploiting the joint correlation of sparse multipath structure between adjacent data blocks to deal with the estimation of long time delay channels under the framework of distributed compressed sensing(DCS).Thus the large time delay underwater acoustic channels can be jointly reconstructed by the simultaneous orthogonal matching pursuit(SOMP) algorithm to facilitate the system overhead reduction and estimation performance improvement. Simulation as well as the sea trial results indicate the effectiveness of the proposed method.国家自然科学基金资助项目(No.11274259,No.11574258)~

跨介质水声网络试验平台设计与试验

由于进行真实的水下网络系统试验较为困难,近年来提出的众多专门针对水声网络的媒体接入控制(MAC)协议和路由协议大多只有仿真结果。为了便于在真实的水下环境中对通信性能、网络协议等研究进行评估分析,以海洋环境立体监测中网络化环境参数获取作为应用背景,设计并构建了一个跨介质水声网络试验平台,实现了水下网络和岸上控制中心的连接,介绍了水声网络平台技术方案及软硬件实现,并进行了试验平台的湖试试验,试验结果表明了该平台进行跨介质水声网络性能评估、测试的有效性。国家自然科学基金项目资助(11574258

房产税试点改革对城市扩张的影响

以重庆和上海房产税试点改革为自然实验,在比较两地改革方案异同的基础上,采用合成控制法对房产税试点改革对城市扩张的影响进行了研究。研究结果显示:房产税试点改革使重庆的城市扩张与没有试点改革时相比出现了一定程度的下降。这是因为重庆对本市居民新购独栋商品住宅和高档住房给予100平方米的免税优惠政策抑制了大户型住房的供给和需求,进而降低住房的占地面积,起到了抑制城市扩张的作用。西藏自治区哲学社会科学专项资金项目《西藏提高政府公共服务产品供给能力研究》(17CJY002

Study on the Mate-selection Intention of the“Floating”Girls

利用抽样问卷调查资料,描述和发现外来打工妹的择偶意愿及其主要特点,并通过多元回归估计,检验所提出理论假设。实证结果基本上支持外来打工妹择偶意愿的再社会化理论和边缘化理论。Using the data from a questionnaire sampling survey, the present paper describes the mateselection intention and its major characteristics of the “floating” girls, and conducts a statistical test of the theoretical hypothesis through a regression analysis. The results support the resocialization and marginalization theories of the “floating” girls’ mateselection intention

Effect of double abutment absorption of alveolar bone in rigid fixed bridge on the stress distribution of abutments

目的:探讨固定桥双基牙侧牙槽骨有不同程度水平吸收时,基牙牙周膜的等效应力值和分布的变化,以指导临床固定桥的合理设计。方法:采用螺旋CT扫描技术与MIMICS、AnSyS软件相结合建立双基牙侧牙槽骨有不同程度水平吸收后的三基牙双端固定桥的三维有限元模型,施加垂直和斜向45°载荷,分析双基牙侧牙周膜的应力分布状况。结果:1斜向载荷下各模型应力值均大于垂直向载荷时的应力,应力集中现象也较垂直向载荷时明显;2在垂直或倾斜载荷下,有牙槽骨吸收的第二前磨牙侧增加牙周组织健康的第一前磨牙时,应力均变大以分担牙合力;若增加的第一前磨牙有不同程度的牙槽骨吸收,垂直载荷时应力值变化不大,斜向载荷时应力值减小,但应力集中现象较无吸收时明显。结论:增加牙槽骨有不同程度吸收的基牙不能有效地发挥分散牙合力的作用,不适合做固定桥基牙。加载方向是影响应力分布的重要因素,应注意防止产生过大的侧向力。AIM: To investigate the stress distribution of abutment tooth periodontal ligament when there are different levels of alveolar bone resorption at the abutment teeth with rigid fixed bridge design.METHODS: A three dimensional finite element model with different levels of alveolar horizontal absorption at the abutment teeth was established by CT scanning using Mimics 8.1 and Ansys 11.0.Vertical and oblique loading was added to test stress the distribution at the abutment teeth.RESULTS: When the periodontally healthy first premolar was added as additional abutment tooth,vertical loading and oblique loading could result in more evenly distributed stress.However,when alveolar bone resorption existed in first premolar,little stress distribution change was observed at vertical loading.But oblique loading led to more concentrated stress.CONCLUSION: Adding an abutment tooth with alveolar bone resorption can not improve stress distribution,hence it is not suitable for rigid fixed bridge.The direction of loading seems to play a significant role in determining stress distribution.The oblique force on the bridge should be avoided or reduced as possible.厦门市科技局资助课题(3502Z20094013

圣·约翰草提取物片治疗抑郁障碍专家共识

结合循证医学证据,本文归纳圣·约翰草提取物片治疗抑郁障碍的专家共识

微流体驱动与控制技术

在微流控系统所需的功能单元中，微流体驱动与控制操作单元尤为重要。微系统条件下，表面张力的影响变得十分明显，在工程意义上，常规的流体体积流动的驱动方法在微管道中往往效果不好甚至是不可行的。本文简要评述了用于微流体驱动的机械微型泵技术，基于电、光、磁等的非机械微型泵技术，以及微流体的高效混合控制等技术的研究现状，对微流体驱动与控制的未来作了展望