A novel SiO2 supported Pd metal catalyst for the Heck reaction

A ligand-free heterogeneous metal catalyst system (represented as Pd/SiO₂ (O)) derived by calcination of Pd(acac)₂/SiO₂ in air and its catalytic properties toward the Heck coupling of bromobenzene (PhBr) and styrene have been studied. X-ray photoelectron spectroscopy (XPS) and catalytic results demonstrate that most of Pd²⁺ is reduced to Pd⁰ on SiO₂ by N,N-dimethylacetamide (DMA) during the Heck reaction and that the resulting Pd⁰/SiO₂ is highly active for the Heck reaction, the remaining Pd²⁺/SiO₂ is not responsible for the high activity. Pd/SiO₂ (O) possesses incomparable advantages over a heterogeneous homolog (represented as Pd/SiO₂ (H)) prepared by reduction of Pd(acac)₂/SiO₂ in H₂ as a pre-catalyst in both activity and catalyst recycling. The activity over Pd/SiO₂ (O) is comparable to that over a homogeneous Pd system. Transmission electron microscopy (TEM) analysis illustrates that the high activity over Pd/SiO₂ (O) consists in the small size of supported Pd particles generated in-situ with gentle reducing agents at a mild temperature.     

Enactment of IDEF0 models

This paper presents an integrated approach to the enactment of IDEF0 models to facilitate the development and maintenance of responsive and coherent manufacturing systems. The approach basically involves the enhancement of an IDEF0 model to include additional information about system behaviour and IT infrastructural aspects; and the use of a computer simulator to read and interpret the enhanced IDEF0 model, simulate the model, and control the actual activities. The approach allows a seamless transition from system modelling, through simulation, to maintenance. It is expected that such an approach will greatly expedite the development and maintenance of manufacturing systems. A prototype software tool has been developed at the Gintic Institute of Manufacturing Technology to support the integrated approach.     

基于频域介电谱的一起220 kV主变压器套管故障诊断分析

围绕实际运维过程中的主变压器套管绝缘状态评估,介绍了频域介电谱的测试原理,结合一起某220 kV变电站主变压器套管故障诊断案例,对套管介损值异常进行分析,为主变压器套管故障诊断提供了相关建议.     

The performance enhancements of upflow anaerobic sludge blanket (UASB) reactors for domestic sludge treatment--a state-of-the-art review

Nowadays, carbon emission and therefore carbon footprint of water utilities is an important issue. In this respect, we should consider the opportunities to reduce carbon footprint for small and large wastewater treatment plants. The use of anaerobic rather than aerobic treatment processes would achieve this aim because no aeration is required and the generation of methane can be used within the plant. High-rate anaerobic digesters receive great interests due to their high loading capacity and low sludge production. Among them, the upflow anaerobic sludge blanket (UASB) reactors have been most widely used. However, there are still unresolved issues inhibiting the widespread of this technology in developing countries or countries with climate temperature fluctuations (such as subtropical regions). A large number of studies have been carried out in order to enhance the performance of UASB reactors but there is a lack of updated documentation. In face of the existing limitations and the increasing importance of this technology, the authors present an up-to-date review on the performance enhancements of UASB reactors over the last decade. The important aspects of this article are: (i) enhancing the start-up and granulation in UASB reactors, (ii) coupling with post-treatment unit to overcome the temperature constraint, and (iii) improving the removal efficiencies of the organic matter, nutrients and pathogens in the final effluent. Finally the authors have highlighted future research direction based on their critical analysis.     

Vapor Pressure of Explosives: A Critical Review

A critical review of vapor pressure data for military, civilian, and homemade explosives, explosive precursors, and explosive taggants is presented. It gives reference to a large number of papers and reports presenting original vapor pressure measurements and additionally an overview of measurements techniques for vapor pressure measurements and data analysis of vapor pressure measurements. Vapor pressure data, including Clausius–Clapeyron parameters (A and B in: log10(p)=A−B/T), calculated vapor pressure at room temperature, and heat of sublimation or heat of vaporization are included. The following classes of compounds are treated; military explosives (TNT, RDX, HMX, PETN, HNS, TATB, AP), civilian explosives (NG, EGDN, AN), explosive taggants (EGDN, DNMB, 2‐NT, 4‐NT), home‐made explosives (TATP, DADP, HMTD). and explosive precursors [HP(aq), NM, IPN, DNT].     

页岩微观孔隙成因类型研究

运用场发射扫描电镜对黔北及黔西北地区黑色页岩微观孔隙的大小、形态、分布以及渗流特征进行 了观察与描述,并以孔隙成因与孔隙发育位置为主次分类依据,将页岩孔隙分为原生沉积型、成岩后生改 造型及混合成因型 3 个大类和粒间孔、晶内孔、古生物化石孔及有机质孔等 10 个亚类。 探讨了影响页岩 孔隙发育的主要因素及孔隙演化特征,对页岩储层的含气性研究具有一定的理论意义和实践价值。     

如何用无桥图腾柱功率因数校正控制器实现出色的AC-DC功率转换效率

电网提供的电能是交流电,但我们使用的大多数设备都需要直流电,这意味着进行这种转换的交流/直流电源是能源网上最常见的负载之一.随着世界关注能效以保护环境并管理运营成本,这些电源的高效运行变得越来越重要.     

Study of TATP: Spontaneous Transformation of TATP to DADP – Full Paper

The TATP prepared in the presence of catalysts such as methanesulfonic, perchloric, or sulfuric acid, has been found to undergo spontaneous transformation to DADP. This transformation, however, does not occur if TATP is purified or prepared using hydrochloric acid. Using nitric acid or tin(IV) chloride for catalysis results in TATP that transforms to DADP only to a small extent (max. 1%). The rate of transformation depends on the storage temperature and on the molar ratio of catalyst to acetone (n_c/n_a) used during the preparation of TATP. The faster rate of the transformation was observed at high temperatures and higher molar ratio n_c/n_a.