Research of SAR Image Reconstruction Algorithm Based on Compressive Sensing

传统的Nyquist采样定理要求信号的采样频率不能低于模拟信号频谱中最高频率的2倍，这给采样的成本以及后续的处理与传输带来了很多困难。近年诞生的压缩感知理论，针对稀疏信号或可压缩信号，它的采样速率不取决于信号的带宽，而决取于信息在信号中的结构和内容，因此可以突破Nyquist采样定理的瓶颈。同时该理论在采样的同时直接获取压缩数据，这样可以减少采样数据，节省存储空间。 重建算法是压缩感知理论中的核心步骤，也是目前的研究热点。因此本文在对压缩感知理论整体框架进行研究的基础下，主要对重建算法中的贪婪迭代算法进行研究。本文首先对贪婪迭代算法中的经典算法——正交匹配追踪算法以及它的改进算法——基于小波...The sampling rate must be two times higher than the highest frequency of the analog signal based on Nyquist sampling theorem. This will increase the cost of sampling and lead to difficulty to process and transmit. Recently, a new sampling theorem called compressive sensing has been proposed. Based on this theoretical frame, the sampling rate for the sparse and compressive signal is not depend on t...学位：工学硕士院系专业：信息科学与技术学院通信工程系_信号与信息处理学号：2332009115282

The Empirical Analysis of RMB Appreciation Expectation and Chinese Housing Prices

从短期来看,热钱流入对房价的影响可以分解为“资本流动效应“和“流动性效应“。从长期来看,人民币升值预期还会通过巴拉萨-萨缪尔森效应、财富效应等“结构性效应“影响房地产价格。本文通过HP滤波、基于VAr模型的格兰杰因果检验和协整检验讨论了以上人民币升值预期影响房地产价格的效应,结果发现:(1)人民币升值预期引起了热钱流入,但是热钱流入的“资本流动效应“并不明显,即热钱流入房地产部门并不能在短期内显著影响房价;(2)热钱流入引发的“流动性效应“,在短期内能够影响房地产价格波动;(3)人民币升值预期会通过“结构性效应“中的财富效用渠道对房地产价格产生长期性影响,但是“结构性“效应中的巴拉萨-萨缪尔森效应并不明显。Traditional literature on the impact of RMB appreciation on housing prices has mainly focused on the impact of hot money on housing prices.However,RMB appreciation can affect housing prices in many ways.In the short term,hot money may drive up housing prices through the channel of"capital inflow"effect and"liquidity"effect.In the long term,"structural"effects such as Balassa-Samuelson effect and wealth effect are likely to connect the RMB appreciation and housing prices.This paper employs empirical methods to investigate the three effects and the results indicate that hot money cannot affect housing prices prominently,but liquidity caused by hot money lead to higher volatility of housing prices.In addition,empirical results support the long-term"structural"effects between RMB appreciation and housing prices.国家自然科学基金应急项目“欧洲主权债务危机的影响及对策研究”(71241017); 国家社会科学基金一般项目(12BGJ042); 2012年教育部新世纪优秀人才支持计划; 中央财经大学青年科研创新团队“系统性金融风险的识别、度量与管理”资助项

微乳薄层色谱法鉴别甘草的研究

国家自然科学基金重点项目(20235020

产前滴滴涕或多氯联苯暴露与出生缺陷风险相关性的Meta分析

目的系统评价孕妇产前暴露于滴滴涕(DDT)或多氯联苯(PCBs)与新生儿出生缺陷风险之间的关系。方法计算机检索PubMed、EMbase、WanFang Data、VIP和CNKI数据库,搜集有关产前DDT或PCBs暴露与出生缺陷关系的病例-对照研究,检索时限均从建库至2017年2月。由2名研究者独立筛选文献、提取资料并评价纳入研究的偏倚风险后,采用Stata 13.0软件进行Meta分析。结果共纳入14个研究,包括2 238例出生缺陷新生儿和2 355例对照新生儿。Meta分析结果显示:产前暴露于高水平的DDT会导致新生儿隐睾发生率增加[OR=1.12,95%CI(1.09,1.15),P<0.001]。而DDT暴露与尿道下裂和神经管畸形发生没有相关性。产前暴露于高水平的PCBs与隐睾、尿道下裂、神经管畸形发生也没有相关性。结论孕妇产前暴露于高水平的DDT可能是隐睾发生的危险因素。受纳入研究数量和质量的限制,上述结论尚待更多高质量研究予以验证。厦门市科技计划项目(编号:3502Z20163006);;厦门市集美区科技计划项目(编号:20142C01

Impactfactors and optimization method on the separation of active components in licorice by micellar thin layer chromatography

第一作者Tel: 15012701322; E－mail: [email protected][中文文摘]目的:为甘草的胶束薄层色谱指纹图谱寻找最优胶束流动相。方法:首先采用单因子法,寻找影响甘草胶束薄层色谱的影响因素,在此基础上,采用控制加权可变步长单纯形优化法进行甘草胶束薄层色谱指纹图谱的流动相优化。结果:对甘草的胶束薄层色谱分离条件(表面活性剂的种类和含量、醇和酸改性剂的影响等)进行了实验,表明纯胶束薄层色谱的柱效较低,加入醇和酸类改性剂后柱效有明显提高。通过对改性胶束的进一步优化(控制加权可变步长单纯形优化法),得到优化的甘草改性胶束展开剂组成为:0.23 mol.L-1的SDS+16%(v/v)正丁醇+11%(v/v)甲酸。本研究对胶束薄层色谱的一些分离机理亦进行了探讨。结论:胶束薄层色谱的表面活性剂和各添加剂间存在交互作用,需采用合适的优化方法,才能达到分离中药材复杂活性成分群的目的。[英文文摘]Objective: To seek the best mobile phase of micellar thin-layer chromatography(MTLC)of licorice fingerprint.Method: Single impact factor of mobile phase in licorice MTLC fingerprint was tested individually and controlled weighted centroid simplex method was used finally to optimize the mobile phase of licorice MTLC fingerprint.Results: The selectivity of micellar TLC was studied for the separation of active components in licorice under various operation variables including concentrations of surfactant and co-surfactant,surfactant type,addition of acid modifier,et al.The results show that the low chromatography efficiency of micellar TLC could be improved by the addition of alcohol and acid modifier.Using controlled weighted centroid simplex ethod,optimization micellar TLC developing system of licorice was achieved which consists of 0. 23 mol·L－1 SDS,16%( v /v) n －butanol and 11% ( v /v) methyl acid.In addition,the separation mechanism of micellar TLC was also discussed.Conclusion:he appropriate optimization method should be tried to get the reliable mobile phase for the alternate impact of several parameters in MTLC国家自然科学基金资助项目(No.20235020

Impactfactors and optimization method on the separation of active components in licorice by micellar thin layer chromatography

第一作者Tel: 15012701322; E－mail: [email protected][中文文摘]目的:为甘草的胶束薄层色谱指纹图谱寻找最优胶束流动相。方法:首先采用单因子法,寻找影响甘草胶束薄层色谱的影响因素,在此基础上,采用控制加权可变步长单纯形优化法进行甘草胶束薄层色谱指纹图谱的流动相优化。结果:对甘草的胶束薄层色谱分离条件(表面活性剂的种类和含量、醇和酸改性剂的影响等)进行了实验,表明纯胶束薄层色谱的柱效较低,加入醇和酸类改性剂后柱效有明显提高。通过对改性胶束的进一步优化(控制加权可变步长单纯形优化法),得到优化的甘草改性胶束展开剂组成为:0.23 mol.L-1的SDS+16%(v/v)正丁醇+11%(v/v)甲酸。本研究对胶束薄层色谱的一些分离机理亦进行了探讨。结论:胶束薄层色谱的表面活性剂和各添加剂间存在交互作用,需采用合适的优化方法,才能达到分离中药材复杂活性成分群的目的。[英文文摘]Objective: To seek the best mobile phase of micellar thin-layer chromatography(MTLC)of licorice fingerprint.Method: Single impact factor of mobile phase in licorice MTLC fingerprint was tested individually and controlled weighted centroid simplex method was used finally to optimize the mobile phase of licorice MTLC fingerprint.Results: The selectivity of micellar TLC was studied for the separation of active components in licorice under various operation variables including concentrations of surfactant and co-surfactant,surfactant type,addition of acid modifier,et al.The results show that the low chromatography efficiency of micellar TLC could be improved by the addition of alcohol and acid modifier.Using controlled weighted centroid simplex ethod,optimization micellar TLC developing system of licorice was achieved which consists of 0. 23 mol·L－1 SDS,16%( v /v) n －butanol and 11% ( v /v) methyl acid.In addition,the separation mechanism of micellar TLC was also discussed.Conclusion:he appropriate optimization method should be tried to get the reliable mobile phase for the alternate impact of several parameters in MTLC国家自然科学基金资助项目(No.20235020

Stabilization of anti-aromatic and strained five-membered rings with a transition metal

1981年诺贝尔化学奖获得者、美国康奈尔大学RoaldHoffmann教授评价该项工作说：'The　paper is an excellent one--it's　quite a mazing that the parent Os　system,molecule 1,chooses to give the osmapentalyne'。德国化学家Uwe Rosenthal教授等在同期《自然—化学》杂志的《News and Views》栏目以《Breaking the rules》为题撰文评述了这一研究成果。全文地址：http://www.nature.com/nchem/journal/vaop/ncurrent/pdf/nchem.1702.pdfAnti-aromatic compounds, as well as small cyclic alkynes or carbynes, are particularly challenging synthetic goals. The combination of their destabilizing features hinders attempts to prepare molecules such as pentalyne, an 8π-electron anti-aromatic bicycle with extremely high ring strain. Here we describe the facile synthesis of osmapentalyne derivatives that are thermally viable, despite containing the smallest angles observed so far at a carbyne carbon. The compounds are characterized using X-ray crystallography, and their computed energies and magnetic properties reveal aromatic character. Hence, the incorporation of the osmium centre not only reduces the ring strain of the parent pentalyne, but also converts its Hückel anti-aromaticity into Craig-type Möbius aromaticity in the metallapentalynes. The concept of aromaticity is thus extended to five-membered rings containing a metal–carbon triple bond. Moreover, these metal–aromatic compounds exhibit unusual optical effects such as near-infrared photoluminescence with particularly large Stokes shifts, long lifetimes and aggregation enhancement

Synthesis of Poly(Lactic Acid-co-Glycolic Acid) by Direct Melt Polycondensation Without Catalysts

以乳酸(lA)、乙醇酸(gA)为原料,在无催化剂、高真空条件下直接熔融缩聚合成聚乳酸-乙醇酸(PlgA)无规共聚物,对产物进行了gPC、fTIr1、H-nMr表征,并研究了反应时间、聚合温度、lA/gA投料比对PlgA分子质量的影响.结果表明:在所研究的聚合温度范围内,PlgA分子质量随聚合时间的延长先增大后减小;聚合温度越高,PlgA所能达到的最高分子质量越小,最佳聚合温度范围为160--170℃,最佳反应时间范围为57--69 H;在相同反应条件下,lA/gA投料比越小,PlgA分子质量越大.该研究为PlgA的合成提供一种安全、经济、有效的新途径.Poly(lactic acid-co-glycolic acid)(PLGA) was synthesized with lactic acid and glycolic acid by direct melt polycondensation without catalysts.The products were characterized by GPC,FTIR,1H-NMR.In this work,the effects of reaction time,polymerization temperature(Tp) and LA/GA feed ratio on molecular weight were investigated.Results indicated that in the range of Tp we discussed,molecular weight gradually increased and then decreased as the reaction time increased;the maximal molecular weight of PLGA decreased while Tp increased;the optimal ranges of Tp and reaction time were 160--170 ℃ and 57--69 h respectively;under the same reaction conditions,the molecular weight of PLGA increased while the LA/GA feed ratio decreased.The objective of this study is to develop an economical,safe and effective method for the synthesis of PLGA