Porous Iron–Cobalt Alloy/Nitrogen‐Doped Carbon Cages Synthesized via Pyrolysis of Complex Metal–Organic Framework Hybrids for Oxygen Reduction

Efficient and stable nonprecious metal electrocatalysts for oxygen reduction are of great significance in some important electrochemical energy storage and conversion systems. As a unique class of porous hybrid materials, metal–organic frameworks (MOFs) and their composites are recently considered as promising precursors to derive advanced functional materials with controlled structures and compositions. Here, an “MOF‐in‐MOF hybrid” confined pyrolysis strategy is developed for the synthesis of porous Fe–Co alloy/N‐doped carbon cages. A unique “MOF‐in‐MOF hybrid” architecture constructed from a Zn‐based MOF core and a Co‐based MOF hybrid shell encapsulated with FeOOH nanorods is first prepared, followed by a pyrolysis process to obtain a cage‐shaped hybrid material consisting of Fe–Co alloy nanocrystallites evenly distributed inside a porous N‐doped carbon microshell. Of note, this strategy can be extended to synthesize many other multifunctional “nanosubstrate‐in‐MOF hybrid” core–shelled structures. Benefiting from the structural and compositional advantages, the as‐derived hybrid cages exhibit superior electrocatalytic performance for the oxygen reduction reaction in alkaline solution. The present approach may provide some insight in design and synthesis of complex MOF hybrid structures and their derived functional materials for energy storage and conversion applications.     

Li掺杂量对Li-N共掺ZnO薄膜光学性能的影响

本文利用溶胶-凝胶旋涂法在玻璃衬底上制备了 本征、N单掺和Li-N共掺的ZnO薄膜。 研究Li掺杂量的改变对薄膜的晶体结构、表面形貌、透过性能和发光性能的影响。采用了紫 外-可见分光光度计(UV-VIS)、光致发光谱(PL)、扫描电子显微镜(SEM)和X射线衍 射 仪(XRD)等表征手段对样品进行了测试。结果表明:Li掺杂量的改变对薄膜的结构和性能 都有一定的影响,随着Li掺杂量的增加,(002)衍射峰强度增大,晶 粒尺寸先增加后减小, 紫外发射峰的强度和薄膜的透过性能同样是先增强后减弱。当Li元素的原子比为6at%时, 薄膜的c轴择优取向明显,结晶性能最好,薄膜紫外发光最强,透过率最大。     

有线数字电视机顶盒高清交互终端软件统一平台的构建与实现

“有线数字电视机顶盒高清交互终端软件统一平台”是一种建立在不同类型机顶盒硬件基础上的系统软件,向下提供跨硬件平台的接口,实现对硬件平台的操作;向上提供应用程序开发接口,实现与上层应用程序的对接。该平台实现了机顶盒软硬件的分离,解决了机顶盒软件升级难度大、成本高、周期长和部署新业务困难的难题,同时支持高清交互业务的实现,提高了广电网络技术应用水平和服务质量。该平台通过在山西晋中、长治等地有线电视网络近三年的规模应用,取得了良好的经济效益和社会效益。     

The measurement of carbon dioxide transmission of edible films by a static method

A static method is proposed for the measurement of CO₂ transmission of edible films. It is based on the absorption of CO₂ transmitted through the film on an absorbent ascarite II. Water is evolved during absorption of CO₂ by ascarite II and that is absorbed by a desiccant, anhydrous CaCl₂. Total CO₂ transmission is determined from the increase in weight of the absorbents. The transmission parameters, CO₂ transmission rate (CO₂TR), CO₂ permeance and CO₂ permeability (CO₂P), are also calculated. The edible film used was composed of methyl cellulose and polyethylene glycol. An attempt was made to determine the optimum amounts of ascarite II and CaCl₂ to be used. Finally, the effect of CO₂ pressure on the transmission parameters was also examined. CO₂TR was found to increase with increasing pressure while CO₂ permeance and CO₂P values were found to decrease with increasing pressure. © 1999 Society of Chemical Industry     

The choice of strains of Lactobacillus species for the lactic acid fermentation of vegetable juices

 The reasons for using lactic acid bacteria are to make food durable, to improve its taste and to maintain the nutritive, physiological and hygienic value of the fermentation products. Sixteen strains of the genus Lactobacillus were tested on samples of white fresh cabbage and of a sterilized cabbage and carrot juice mixture. After 7 days of lactic acid fermentation at 27  °C or 30  °C, reducing sugars, total acidity, pH value, lactic, citric and acetic acids, ammonia, nitrates and nitrites were measured in the samples. On the basis of the criteria mentioned above three strains were acceptable. These strains reduced the content of nitrates in the original samples. Received: 14 December 1998 / Revised version: 18 March 1999     

New neural method for bias dependent noise modelling of microwave transistors

A new method for accurate determination of noise parameters of microwave transistors for various bias conditions is proposed in this paper. The proposed model consists of a transistor empirical noise model (modification of Pospieszalski’s noise model) and two artificial neural networks. With the aim to avoid extraction of the empirical model parameters for each bias point, an artificial neural network is used to introduce bias-dependence of the equivalent circuit parameters. Accuracy of such bias-dependent model is further improved by using an additional neural network aimed to correct the noise parameters’ values. The proposed modeling approach is exemplified by modelling of a MESFET device in packaged form. The noise parameters obtained by the simulation agree well with the measured data.     

Coupling GIS with Hydrologic and Hydraulic Flood Modelling

Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management.     

迭代学习控制在GTAW焊接过程中的应用研究

针对相同工件的批量焊接,并且焊接轨迹相同的情况下,焊接过程具有极高的重复性。提出了基于迭代学习控制(ILC)的脉冲气体钨极氩弧焊(GTAW)焊接过程跟踪控制方法。根据GTAW焊接的动态过程模型,设计了GTAW焊接过程控制的ILC算法,并对算法的收敛性进行了证明。研究结果表明,ILC可以有效地利用焊接过程中的重复信息,经过60次迭代学习后,焊接系统输出可以较好的达到期望轨迹,并获得较高的控制精度,验证了方法的有效性。与PID控制相比ILC控制器不但可以获得较好的跟踪效果,而且还能有效抑制外部扰动的作用,具有较强的鲁棒性。     

3G网络传输需求和解决方案研究

3G代表了未来移动通信的发展走向,是移动用户发展、移动业务发展的必然趋势,在3G网络建设中应立足现有网络情况,充分考虑3G网络特点,建设满足3G业务需求的传输网络.本文首先对3G网络传输需求进行分析,并结合现有3G设备分析了可能采用的传输技术方案,最后从实际的运营商现状出发,提出较为合理的解决方案.     

一种新型毫米波矩形波导-微带过渡结构

介绍了一种新颖的、适用于毫米波频段的矩形波导-微带过渡电路结构。该过渡电路具有插入损耗低、频带宽、重复性好的特性。其矩形波导E面相对于微带电路面,以及电磁信号传输方向的位置与脊波导-微带过渡相同。该过渡电路的微带线与波导的转换部分采用非接触式结构,并设计了可调节元件,从而在有一定加工误差的条件下改善其产品传输特性。利用高频仿真软件CST,在Ka频段进行了优化仿真,并对利用其优化值所设计的一对背靠背的电路实物进行了测试,在32～40 GHz的频率范围内,插入损耗小于2.36 dB,回波损耗大于7.22 dB;在整个Ka频段内,插入损耗小于3.49 dB。