基于WEB的电子邮件取证研究

伴随着网络与信息化的快速发展,电子邮件逐渐成为犯罪活动的可能证据载体,这使得电子邮件取证成为世界范围内需要引起重视的课题.本文主要研究电子邮件取证的现状,电子邮件的证据效力问题和进行电子邮件取证时需要了解的一些基本技术.     

酒类检测用基体标准样品/标准物质研制与应用现状

检测用基体标准样品/标准物质被广泛应用于过程控制和结果评价,是食品安全监管和行业健康发展的技术支撑。整理我国酒类检测用基体标准样品/标准物质的研制现状,分析基体标准样品/标准物质的应用方式和应用领域,剖析当前面临主要问题,并提出针对性建议,旨在为后续酒类标准样品/标准物质研究提供一定的借鉴。     

Research progress on chemical modification of silk fibroin and its applications北大核心CSCD

Mulberry silk is composed of the two major parts of two triangle-like silk fibroin fibers and sericin covering the fibers and a few lipids. After removing the sericin on the raw silk what is left is the silk fibroin fiber. Silk fibroin is the main part of silk accounting for about 75% of the total weight. Silk fibroin contains 18 natural amino acids such as glycine Gly alanine Ala serine Ser serine aspartic acid Asp and tyrosine Tyr . The secondary structure of silk fibroin has three main conformations α-helix β-fold and random coil. Under certain conditions the three conformations can transform into each other and change the mechanical properties of the silk fibroin material. Silk fibroin extracted from silk fiber is a natural polymer with biocompatibility and biodegradability. It can be further processed into different forms of materials nanoparticles films hydrogels sponges etc. It has been applied in many fields such as biomedicine and cosmetics. In order to meet the needs of different fields researchers have conducted further chemical modification treatment based on the original excellent properties of silk fibroin. Meanwhile the active groups on various amino acid residues in silk fibroin also provide chemical reaction sites for the chemical modification of silk fibroin. The chemical modification methods of silk fibroin mainly include amino acid residue modification macromolecular grafting modification and crosslinking reaction modification. Among them amino acid residue modification can modify protein amino acid residues by chemical reagents and some groups can be introduced into the side chains of silk fibroin macromolecules. Grafting modification of silk fibroin macromolecules is one of the main means to bind functional compounds to silk fibroin macromolecular chains. The properties of grafted silk fibroin are affected by the type and grafting rate of the grafts. The chemical crosslinking reaction modification of silk fibroin macromolecules is to make the macromolecular chains connected by covalent bonds and form a network structure by means of crosslinking agents enzymes or ultraviolet irradiation. The cross-linking reaction can not only form covalent bonds within and between the molecular chains of silk fibroin thus changing its structural properties and improving its stability but be used to form covalent bonds with other polymers. At present the chemical modification of silk fibroin is mainly applied in the fields of silk textiles biomedicine and environmental science. In the field of silk textiles graft copolymerization modification of vinyl and other monomers crosslinking agent modification and other methods are used to overcome the shortcomings of silk like being easy to wrinkle. The graft modified monomers mainly include ethylene methacrylate and methylacrylamide. The active groups on crosslinking agents such as polycarboxylic acid / anhydride and epoxide are covalently combined with carboxyl hydroxyl and amino groups on macromolecules of silk fibroin to improve the wrinkle resistance of silk fabrics. In the field of biomedicine silk fibroin materials with appropriate chemical modification have better biological activity drug delivery ability antimicrobial properties and mechanical properties. The optimization of these properties enables silk fibroin materials to show great potential in drug control delivery tissue regeneration and wound repair. The applied research in the field of environmental science mainly focuses on the adsorption separation and catalysis of impurities in water. Therefore the modification of amino acid residues grafting and cross-linking of protein macromolecules can change some important properties of silk fibroin and meet the requirements of various applications and functionalization of silk fibroin. In many fields of chemical modification and application of silk fibroin protein fruitful results have been achieved which has laid a good foundation for the further development of related fields and also shows that the chemical modification of silk fibroin material has great potential and application prospects. However there are still some problems that need to be overcome and further improved in the current chemical modification methods such as mild modification conditions and accurate adjustment of the degree of modification which will be the research direction of related fields in the future. © 2022 Authors. All rights reserved.     

对大型建筑设计院转型经营的探讨(下)——转型后总承包模式选择的建议

最近几十年,随着我国加入世贸组织和经济全球化进程的加快,我国建筑行业呈现出快速发展的态势,同时也为了加入WTO以后,国际工程市场的变化,满足我国建筑企业走向国际市场的需要,建筑设计企业向总承包转型的推进势在必行。本文结合自己工作实践和对相关政策法规的学习,提出设计企业向工程总承包转型模式的选择建议,供同行参考。     

CAT挖掘机液压系统发热的故障分析

液压系统发热是指液压系统的油温超出系统规定的温度较多。如CAT挖掘机正常工况下,液压系统油温应在50°C以下,(油泵的温度较之高5-10°C),如果温度超出80°C,,则为液压系统发热?液压系统发热会造成操作不灵活、作业不连续、工作无力以及工作压力降低等故障。现就液压系统发热原因及造成的危害和预防措施进行如下简单的分析和探讨。     

某长江港口码头初期雨水收集处理工程设计实例

某港口现有散货堆场初期雨水,未经处理直接外排至市政管网,为响应环保要求,提高环保设施管理水平,本文对某港口初期雨水收集处理进行设计,主要含初期雨水的计算、收集及达标处理,计算采用参考港口工程环境保护设计规范和室外排水规范比较采用最大值,初期雨水处置采用混凝沉淀工艺,出水达到地方《污水排入城镇下水道水质标准》。     

蓄电池组的自动测试系统

蓄电池组性能好坏的监测及判定是当前急需解决却尚未很好解决的难题.文章介绍了一种专利技术:"浮地式电压温度监测探头"实现的蓄电池组自动监测系统.系统采用了串行总线结构,由电压温度探头、嵌入式控制器和主控制器组成,实现了全数字化测试.该设计可实现对蓄电池组中单体蓄电池的电压、电流、温度及内阻的在线监测,能及时发现失效电池,改善了蓄电池的维护效果,提高了电池的可靠性,并且主控制器可以与远端的控制中心相连,实现了对蓄电池组的远程实时在线监测.     

海洋生物副产品中胆固醇提取工艺的研究

为解决胆固醇提取原料的来源限制,开发新工艺,采用钙盐络合胆固醇,先皂化预处理,成钙盐、渗滤、浓缩、溶解结晶和重结晶,得到高含量胆固醇。以胆固醇的收得率为参考指标,优化了氢氧化钠的最佳添加量为20%、氯化钙的最佳添加量为25%、丙酮的最佳添加量为钙盐质量的10倍,胆固醇的收得率为15%,所得产品指标达到147℃胆固醇的质量要求。     

振动采油法处理油层技术综述

本文介绍了振动波的作用机理和目前已经用于油层的各种振动采油技术的作用机理、处理工艺、所需设备及现场应用效果。最后介绍了目前应用较广泛的低频水力振荡器的研制工作。     

基于GSM短消息的振动数据采集系统设计

振动数据的采集是桥梁健康监测工作的重要环节,利用传统的有线传输方式会给测试工作带来人力、物力的极大浪费,如果采用无线传输方式,就会大大减轻工作量.作者通过深入分析无线数据传输技术原理,在总结和借鉴现代传感技术及数据采集技术的基础上,设计完成了基于GSM短消息的振动数据采集系统.该系统具有方便可靠、成本低廉的优势,并介绍了该系统的软、硬件设计方案,并对其可行性进行了详细分析.