Qtech-413 粘弹阻尼材料在盾构隧道中减振性能研究

根据盾构隧道的结构特点,用Qtech-413 粘弹阻尼材料对盾构管片标准块进行约束阻尼处理,通过单点锤击振动实验,得到处理前后结构的时域波形、固有频率、复合损耗因子等振动特性。实验结果显示:经过约束阻尼处理后,盾构管片振动加速度幅值降低了26.7%,振动时长降低了50%;各阶固有频率均有所降低,且随着频率的增加,降幅逐渐增加;各阶复合损耗因子均有所升高,高频增幅比低频增幅更大;振动总级值降低了10 dB 左右。因此,Qtech-413 粘弹阻尼材料应用于盾构隧道能降低振动加速度幅值、振动时间、固有频率和振动总级值,增加复合损耗因子,对高阶固有频率和复合损耗因子影响较大,低阶影响较小

Amide Activation by Tf2O: Reduction of Amides to Amines by NaBH4 under Mild Conditions

An expeditious and practical method for the reduction of amides to amines is reported. The method is consisted of activation of amides with Tf2O followed by reduction with sodium borohydride in THF at room temperature. Various amides/lactams gave the corresponding amines in good to excellent yields, even with hindered amides and secondary amides. This method also presents other advantages such as TBDPS-group tolerance, short reaction time, simple workup and purification procedure.NSF of China [20832005]; National Basic Research Program (973 Program) of China [2010CB833200

First asymmetric synthesis of piperidine alkaloid (-)-morusimic acid D

The first asymmetric synthesis of (-)-morusimic acid D, a 2,3-trans-2,6-cis-2-methyl-6-substituted piperidin-3-ol containing alkaloid is reported. The key steps are the reductive alkylation of N,O-diprotected 3-hydroxyglutarimide, a stepwise reductive alkylation, and an asymmetric aldol-type reaction using a modified Evans chiral auxiliary

酰胺直接转化:策略与近期进展

以酰胺直接转化的C—C键形成方法为主线,简要回顾近年取得的主要突破.内容涵盖基于三氟甲磺酸酐活化、化学选择性试剂的还原官能化策略,以及两类催化转化.这些重要进展表明温和条件下的酰胺转化可达到优异的化学选择性、官能团容忍性和较好的底物普适性,转化产物还包括多种官能化的胺、酮和烯胺酯(酮)化合物等,并已在天然产物和生理活性化合物的合成中得到应用与检验.国家重点研发计划(No.2017YFA0207302);;国家自然科学基金(Nos.21332007,21472153,21672176);;教育部长江学者和创新团队发展计划;;中央高校基本科研业务费专项资金(No.20720170092)的资助~

Studies towards the Total Asymmetric Synthesis of the Pentacyclic Indole Alkaloid Arboflorine: Asymmetric Synthesis of a Key Intermediate

The synthesis of a plausible key intermediate for a biomimetic asymmetric synthesis of indole alkaloid arboflorine is described. The method featured the use of Ellman's sulfinamide chemistry for the establishment of the first chiral center, and the Polonovski-Potier reaction for the formation of the alpha-aminonitrile moiety.NSF of China[20832005]; NFFTBS[J1030415]; National Basic Research Program (973 Program) of China[2010CB833200

二碘化钐参与及二茂钛催化的氮α-位碳自由基偶联反应及其在含氮杂环合成中的应用

氮α-位碳-碳键的构造是含氮有机化合物合成中的基本方法。通过氮α-位的碳正离子(亚胺鎓)、碳负离子和碳自由基中间体是实现这一目标的主要途径。相对而言,通过氮α-位碳自由基中间体构造碳-碳键可在较温和的中性条件下进行,且可实现对亚胺鎓离子的极性反转,因而是对正、负离子极性反应的重要补充。作为温和的单电子还原剂,Kagan试剂(二碘化钐)可还原多种含氮有机物产生氮α-位自由基,进而发生自由基偶联反应,在形成氮α-位碳-碳键的方法学发展中扮演了重要的角色。本文综述了二碘化钐参与的氮α-位自由基偶联反应在有机合成中的研究进展,重点归纳评述了二碘化钐参与的亚胺、硝酮、氮杂半缩醛、酰亚胺和酰胺等底物与醛/酮及与缺电子烯烃的自由基偶联反应,为了探讨、克服二碘化钐在相关反应中的局限性,也介绍了二茂钛催化的氮α-位碳自由基偶联反应的最新进展。此外,还重点评述了这些合成方法在含氮活性化合物、生物碱和中间体的简捷合成中的应用。国家重点研发计划(No.2017YFA0207302);;国家自然科学基金项目(No.21472153,21672176,21332007,21172183,21472157,21672175);;教育部长江学者和创新团队发展计划资助~

Accounting Fraud and Audit Strategy of Real Estate Enterprise in China

在我国房地产市场蓬勃发展的今天，房地产行业正逐步成为国民经济支柱产业之一。房地产开发企业作为这个行业的重要经济主体，所具有经营收入、成本和存货会计确认计量主观性强的特征，构成了其会计舞弊的客观条件，在主观经济利益驱动下，部分房地产开发企业发生会计舞弊和偷漏税款的情况已经非常严重。在这种现实环境下，房地产开发企业无疑已经成为我国注册会计师所面对的高审计风险对象之一。2006年2月15日，财政部发布了新的注册会计师审计准则，实现了与国际审计准则趋同，标志着我国注册会计师审计向现代风险导向审计模式全面转型。本文选择运用现代风险导向审计理论来降低房地产开发企业的审计风险的课题，是具有一定的理论和现实意...Estate industry is in the progress of being a mainstay of national economy with the rapid expanding estate market in current China. As the main economy body in the field, real estate development enterprise has the accounting character of subjective opinion in recognition and measurement of sales、cost and inventory, which result in much accounting fraud and tax dodging and evasion for the purpose o...学位：会计硕士院系专业：管理学院会计系_会计学学号：X20041106

A flexible carbanionic approach to protected trans-(2R,3S)-2-substituted 3-aminopyrrolidines: application to the asymmetric synthesis of (+)-absouline

Based on the use of phenyl thioether (3S)-7 as a synthetic equivalent to the N- and alpha-dianions (3S)-2a, a new carbanionic approach to trans-(2R,3S)-2-substituted 3-aminopyrrolidines (10) is described. Application of the method to the asymmetric synthesis of 1-aminopyrrolizidine alkaloid (+)-absouline is also reported