Synthesis of nanocrystalline MgAl2O4 spinel powders by a novel chemical method

A novel chemical method for the preparation of nanocrystalline MgAl₂O₄ spinel powders has been developed in this paper. The mixed magnesium-aluminum hydroxide precipitates were initially formed in a three-dimensional space network microarea. After being calcined at above 700 °C, the nanocrystalline MgAl₂O₄ spinel powders were obtained. The precursor and as-calcined powders were characterized using TGA-DTA, XRD and TEM. The MgAl₂O₄ spinel powders calcined at 850 °C for 2 h are of narrow distribution, little agglomeration and small particle size of ∼ 24 nm. The reason for the synthesis of high-quality powders was explained.     

食品安全事件中传统媒体和网络媒体应用Meta分析

以内容分析和文献探讨作为主要方法对2008年爱尔兰二嗯英危机（一场导致了全球爱尔兰猪肉制品召回的食品安全事件）中媒体报道情况进行了研究。通过信息筛选工具挑选出了141篇新闻报道和175篇博文、论坛帖子和微博分别作为传统媒体和网络媒体报道的代表。制定了编码程序对媒体报道内容的信息资源、主题和语气态度进行分析。结果表明在爱尔兰二嗯英危急中媒体报道主要集中在官方通知后的第一周内。传统媒体报道资源多种多样包括政治机构、科学人员和食品供应商。而网络媒体则聚焦速度更快，聚焦时间更短，首选信息资源为源自于其它媒体平台信息且报道主题有限。传统媒体和网络媒体负面消极的报道不尽相同，但超半数的报道都不约而同的使用了中立或者混合的语气态度。除了这些不同点外，从某种程度上来说，网络媒体，尤其是微博，是对传统媒体的附和重复。     

Integration of biohydrogen,biomethane and bioelectrochemical systems

Anaerobic bioprocesses such as Anaerobic digestion (AD), fermentative biohydrogen (BioH₂), and Bioelectrochemical system (BES), converting municipal, agro-industrial wastes and crops to energy have attracted accelerating interest. Anaerobic digestion (AD) however, still requires optimisation of conversion efficiency from biomass to methane. Augmenting methane energy production with simultaneous BioH₂ and bioelectrochemical stage(s) would increase process efficiencies while meeting post treatment effluent quality. Pre-treatment of feedstock increase bacterial accessibility to biomass, thus increasing the conversion yield to target product, but an alternative is separating the acidogenic/hydrolytic processes of AD from methanogenesis. Acidogenesis can be combined with BioH₂ production, prior to methanogenesis. Depending on operating conditions and without further treatment after digestion, the methanogenic stage may discharge a digestate with significant organic strength including volatile fatty acids (VFAs). To meet wastewater discharge consents; adequate use of digestates on land; to minimise environmental impact and; enhance recovery of energy, VFAs should be low. Concatenating bioelectrochemical systems (BES) producing hydrogen and/or electricity can facilitate effluent polishing and improved energy efficiency. Various configurations of the BioH₂, methanogenesis and BES are plausible, and should improve the conversion of wet biomass to energy.     

某公路大桥加固设计

通过对某高速公路大桥病害原因调查及分析,根据具体病害和结构特点,提出了该大桥T梁、横隔版及盖梁的加固设计方案,并借助于桥梁博士建立全桥结构分析模型,对加固前后内力进行了对比。结果表明,针对不同病害特点选取合理的加固方案,能有效增强桥梁的承载能力或降低截面弯矩,使部分病害严重的桥梁经加固后仍处于安全工作状态,既节约了资金又保证了安全,也为类似工程设计提供了参考。     

土力学课程教学方法研究与应用

土力学教学改革要根据学科特点,以学生为主,复杂问题简单化,注重能力培养,应用多种教学方法相结合的教学手段,制定思路框架清晰、重点突出、实用性强的教学内容。     

基于AT89S52单片机的8路抢答器的设计

目前市场上的智力竞赛抢答器已经相当成熟,但由很多电路组成,线路复杂,可靠性不高,功能也比较简单,特别是抢答器路数很多时,实现起来比较困难。因此设计以单片机为核心的新型智能抢答器,利用AT89S52单片机及外围接口实现抢答系统,结合单片机的定时器/计数器的功能,将软、硬件有机地结合起来,使得系统能够正确地进行计时,使数码管能够正确地显示时间。所设计的系统具有反应快、操作简单、实用性强的特点。     

Porosity changes during packed bed solid-state fermentation

Porosity is one of the key parameters in a typical solid-state fermentation model that represents the intra and inter-particle void spaces in bioreactor bed. In this research, the particle density and moisture content of the bed were used to determine the porosity changes of the solid substrate bed during the fermentation of Aspergillus niger in a laboratory scale packed-bed bioreactor. Biomass growth was also monitored by means of measuring CO₂ and O₂ in the bioreactors outlet gas online. As such, an experimental relationship between humidity and porosity has been developed and can be used in solid-state fermentation modeling.     

Influence of coupling agent on microcosmic morphology and dielectric properties of energy-storage nanocomposite

A series of PVDF-based composite materials with 20 % volume concentrations of nano-sized BaTiO₃ fillers were prepared and studied by solutions-casting. The samples were added with different contents of KH550 as coupling agent. The four main dielectric parameters: dielectric constant, dielectric loss tangent, dielectric breakdown strength and resistivity under high electrical field, were tested. And the energy-storage densities of the samples were also calculated. The results showed that the nanocomposites with 1.0 wt% of KH550 exhibited the appropriate dielectric constant, loss tangent, high dielectric breakdown strengths, high resistivity and high energy-storage density, which was 27.74, 0.039, 245 MV/m, 1,625 MΩ m and 7.4 J/cm³, respectively. This implied that such kind of composites could be used as the dielectric layers of pulsed-power capacitors. In order to explain the relationships between the dielectric properties and the microcosmic physical and chemical properties, the samples were also studied by XRD, SEM and FTIR. The results demonstrated that the coupling agent could improve the filler-matrix interfaces and had significant influence on the dielectric properties of the nanocomposites.     

移动给煤机程控改造

针对某电力公司的移动给煤机在生产中控制系统存在的突出问题进行分析研究,并针对存在的问题进行相应的程控改造,改造后的控制系统不仅增加了运行的可靠性,同时还节约了成本,降低了劳动强度,在使用时达到了预期的效果。     

语音放大电路的设计与实现

设计了一款低成本、大功率的语音放大器。该设计采用带通滤波电路对输入的音频信号进行处理,专业音频放大芯片NE5532对语音信号进行初级功率放大、三极管和大功率晶体管2N7300组成后级功率放大后推动扬声器。通过测试,该语音放大电路可以提供40 W的功率,远大于普通家用语音功率放大器,而且成本又远低于专业语音功率放大器,完全满足需要。