A fast and versatile cross-linking strategy via o-phthalaldehyde condensation for mechanically strengthened and functional hydrogels

Fast and catalyst-free cross-linking strategy is of great significance for construction of covalently cross-linked hydrogels. Here, we report the condensation reaction between o-phthalaldehyde (OPA) and N-nucleophiles (primary amine, hydrazide and aminooxy) for hydrogel formation for the first time. When four-arm poly(ethylene glycol) (4aPEG) capped with OPA was mixed with various N-nucleophile-terminated 4aPEG as building blocks, hydrogels were formed with superfast gelation rate, higher mechanical strength and markedly lower critical gelation concentrations, compared to benzaldehyde-based counterparts. Small molecule model reactions indicate the key to these cross-links is the fast formation of heterocycle phthalimidine product or isoindole (bis)hemiaminal intermediates, depending on the N-nucleophiles. The second-order rate constant for the formation of phthalimidine linkage (4.3 M⁻¹ s⁻¹) is over 3000 times and 200 times higher than those for acylhydrazone and oxime formation from benzaldehyde, respectively, and comparable to many cycloaddition click reactions. Based on the versatile OPA chemistry, various hydrogels can be readily prepared from naturally derived polysaccharides, proteins or synthetic polymers without complicated chemical modification. Moreover, biofunctionality is facilely imparted to the hydrogels by introducing amine-bearing peptides via the reaction between OPA and amino group.     

图书馆大数据服务背景下用户隐私权危机的治理策略

大数据在图书馆创新服务模式的同时也导致用户的隐私权危机。如何化解用户隐私权危机,保障用户隐私安全问题成为图书馆开展大数据服务的一个重要课题。本文通过梳理国内外用户隐私泄露案例和图书馆用户隐私权侵权状况,从大数据基础设施、管理方式和应用误区3个方面分析图书馆用户隐私泄露的原因。以此为基础,从构建国家立法监督、行业规范管理、技术研发保障和个人维权意识4个角度阐述图书馆用户隐私权危机的治理策略。     

实名SNS社交网络与微博的特征分析——以人人网与新浪微博为例

以人人网和新浪微博为例,通过SPSS统计软件分析比较实名SNS社交网络与微博的功能特征与用户行为特点。研究认为人人网用户活跃度与用户本身隐私保护意识有一定联系;新浪微博用户活跃度与用户的学历存在一定联系。人人网与新浪微博同时存在用户被动接收推送广告信息问题,影响了用户的体验度。探讨了人人网与新浪微博的商业化运营趋势,为实名社交网站和微博的完善与差别化发展提供了理论依据。     

浅析乳品安全与质量控制教学改革策略

乳品安全与质量控制是乳品工程专业的一门专业必修课程,为了提高教学质量,培养学生的学习兴趣和能力,本文主要从教学方式的改革、实践教学体系的建立及和谐师生关系的构建等三个方面提出教学改革策略,来实现本课程的教学目标。     

Fractional order sliding mode control of a pneumatic position servo system

Gas flow has fractional order dynamics; therefore, it is reasonable to assume that the pneumatic systems with a proportional valve to regulate gas flow have fractional order dynamics as well. There is a hypothesis that the fractional order control has better control performance for this inherent fractional order system, although the model used for fractional controller design is integer order. To test this hypothesis, a fractional order sliding mode controller is proposed to control the pneumatic position servo system, which is based on the exponential reaching law. In this method, the fractional order derivative is introduced into the sliding mode surface. The stability of the controller is proven using Lyapunov theorem. Since the pressure sensor is not required, the control system configuration is simple and inexpensive. The experimental results presented indicate the proposed method has better control performance than the fractional order proportional integral derivative (FPID) controller and some conventional integral order control methods. Points to be noticed here are that the fractional order sliding mode control is superior to the integral order sliding mode counterpart, and the FPID is superior to the corresponding integral order PID, both with optimal parameters. Among all the methods compared, the proposed method achieves the highest tracking accuracy. Moreover, the proposed controller has less chattering in the manipulated variable, the energy consumption of the controller is therefore substantially reduced.     

抽油机减速箱缺油保护系统的研制

抽油机减速箱损坏的主要原因是减速箱润滑油不足造成的,而目前抽油机减速箱内的油量情况难于实时发现并采取措施,减速箱缺油后,抽油机不能立即停机,而减速箱继续在缺油状态下长期运转,在大多数情况下将造成齿轮、轴承的损坏,甚至报废。为解决这一问题,我们研制了一种实时报警装置,当油量少于设定最小值时,它可以在现场发出报警信号,并对抽油机按要求采取强制停机等措施。     

基于ASP.Net应用系统的网络安全研究与设计

介绍了基于ASP.Net平台B/S架构的应用系统网络安全的设计,分析了B/S三层网络架构的安全机制,给出了通过身份验证、权限控制、数据加密、存储过程访问数据库等手段实现系统的安全性的技术要点。     

专利联盟成员的专利许可投入决策研究

专利许可是企业专利战略中的最核心部分之一,专利联盟正不断涌现,专利联盟成员企业的独自专利许可投入决策是本文的研究问题。研究表明,联盟成员独自许可投入对联盟许可收益的影响、对自身其他专利收入的影响、对其他联盟成员收益的影响、联盟成员的联盟收益分配比例等,都会对最优独自许可投入产生影响。而联盟成员之间独自许可的替代影响不会对最优许可投入产生影响。     

高校学报《稿约》的现状调查与撰写建议

调查了我国100种高校学报的<稿约>.认为目前我国高校学报<稿约>缺乏必要的规范性,在学科要求、征稿范围、稿件格式、投稿方式、作者文德和稿件收费等方面存在着一些问题.针对这些问题提出了改进建议.     

平面图的星色数

由Ｖｉｎｃｅ引进的星色数的概念是图的色数的一个自然推广，它们之间有着许多类似的性质．本文给出了一类星色数为３．５的平面图，回答了Ｖｉｎｃｅ提出的部分问题．