低压断路器的选择性探讨DiscussiononSelectivityofLowVoltageCircuitBreakers

本文介绍了在配电线路中对不同低压断路器进行选择的原则。着重阐述了几种断路器之间的配合,过载情况、短路情况下的选择性。并阐述了国内外现阶段最新的低压断路器的选择性技术。     

Et-Ph-BCTABipy的合成及其对Pd2+的萃取性能

合成了N，N′-二乙基-N，N′-二苯基-［2，2′-联吡啶］-6，6′-二硫代酰胺(Et-Ph-BCTABipy)萃取剂，并利用¹³C NMR和¹H NMR对其进行了表征；研究了相接触时间、萃取剂浓度、水相初始酸度和Pd²⁺浓度等因素对Et-Ph-BCTABipy萃取Pd²⁺性能的影响，利用摩尔比法确定了Et-Ph-BCTABipy与Pd²⁺所形成的配合物组成；同时，在Ln(Ⅲ)与Pd²⁺共存体系中研究了Et-Ph-BCTABipy对Pd²⁺的萃取选择性。结果表明：Et-Ph-BCTABipy在HNO₃体系中对Pd²⁺具有较强的萃取性能和较高的萃取选择性；萃取过程中Et-Ph-BCTABipy与Pd²⁺以1∶2的比例结合，其萃取平衡常数K_ex=3.42×10⁶。     

Ca-Mg-Al复合氧化物催化尿素与1,2-丙二醇制碳酸丙烯酯

采用共沉淀法制备了系列Ca-Mg-Al复合氧化物催化剂，通过对沉淀剂配比、沉淀液pH值及焙烧温度等制备条件的考察，得到以Na₂CO₃为沉淀剂、pH=9.5、850℃下焙烧4h制备的Ca-Mg-Al催化活性最高。在 n(PG)∶n(urea)=1.5∶1、反应温度为145℃、绝压20kPa、反应时间4h、催化剂用量为尿素质量的5%时，碳酸丙烯酯收率达到84.6%。采用XRF、XRD、NH₃-TPD、SEM及BET对催化剂的组成、晶型及酸性进行了表征，发现随着沉淀剂中Na₂CO₃的含量增加，催化剂中CaO∶MgO的比例增大，碳酸丙烯酯的收率亦升高；经850℃焙烧后，催化剂中存在CaO和MgO两种活性中心，起协同催化作用；随着焙烧温度由700℃升高到850℃，NH₃-TPD脱附曲线向低温方向偏移，且强酸中心NH₃脱附峰面积比由81.14%明显下降为0，中强酸中心NH₃脱附峰面积比由0增加到78.07%，而碳酸丙烯酯收率由68%增加到84.6%，这表明催化剂强酸性位的减少是催化活性增加的主要原因。     

C10+重芳烃加氢机理及热力学研究进展

随着国内{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃产量逐年提升，炼厂对提质增效需求日益高涨，对{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃高效转化利用技术的需求也日益迫切。由于{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃富含稠环芳烃，而加氢是稠环芳烃转化为单环芳烃的重要手段，因此，{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃中代表性芳烃的加氢机理和热力学研究日趋受到重视。本文从{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃原料性质分析入手，详细阐述了{\mathrm{C}}_{\mathrm{10}}^{\text{+}}重芳烃中代表性芳烃的加氢反应路径及机理、加氢反应热力学的研究进展，以期为实际应用和催化剂开发提供参考。稠环芳烃组成对适宜的加氢反应条件、单环芳烃产品收率、氢耗、反应放热等都有较大影响，为了最大化生产低碳芳烃、降低氢耗，需要根据重芳烃的组成，从原料预切割/预处理、催化剂结构及活性中心、工艺条件这3个方面同时着手进行优化，进而实现对加氢过程的定向调控。     

Integrated design of filtering antenna with high selectivity and improved performance for L-band applications

An integrated design of compact filtering antenna having high selectivity and suppressed unwanted harmonics is proposed in this paper. The proposed filtering antenna is obtained by integrating a modified elliptic-shaped monopole antenna with a modified interdigital bandpass filter (IBPF). At first, a modified elliptic-shaped monopole antenna is designed and investigated through numerical simulation and experimentally. Further, the modified IBPF reported in the literature is integrated with the proposed monopole antenna to achieve good passband selectivity and suppressed unwanted harmonics for the proposed filtering antenna. The proposed filtering antenna is analysed through numerical simulation software. The simulated −10 dB reflection coefficient bandwidth of the proposed filtering antenna covers the frequency range 1.01–1.96 GHz with improved band-edge selectivity and unwanted harmonic suppression up to 8 GHz (= 5.4 f₀, where f₀ is the centre frequency of passband). It has nearly stable omnidirectional radiation patterns over the whole frequency band. The proposed filtering antenna was fabricated and experimentally tested. The experimental results are nearly in agreement with corresponding numerical simulation results. The proposed filtering antenna can be a suitable candidate for various L-band wireless communication applications.     

Synthesis of a novel inorganic cation exchanger based on molybdate: Applications for removal of Pb2+, Fe3+ and Mn2+ ions from polluted water

A novel manganese phosphomolybdate exchanger was synthesized, dried at different temperatures, and evaluated for the elimination of lead, iron, and manganese ions from aqueous solutions. The chemical structure of the cation exchanger was established using Fourier-transform infrared, scanning electron microscopy, Thermo gravimetric analysis/ Differential thermal analysis, and X-ray diffraction. The adsorption performance of the heavy metals Pb²⁺, Fe³⁺, and Mn²⁺ toward the synthesized material has been studied. The obtained outcomes show that the selectivity of the cationic exchanger was descending in this order, Pb²⁺ > Fe³⁺ > Mn²⁺. The highest adsorption capacity was shown to be decreased as drying temperature of the exchanger increases from 50°C to 800°C.     

The Avenue of Sphinxes： Restoration of a Legend

The redevelopment of historic cities is often challenged by intricate--and in many cases contradictory--missions. From one side, there is the urge to comprehensively preserve cultural resources. At the same time, opportunities of economic growth should be made available and needs of contemporary living maintained and nourished. The main aim of this paper is to reconcile probable incompatibilities between such missions through promoting ＂sensitive＂ redevelopment approaches in historic cities. The paper focuses on the city of Luxor, Egypt with its immensely capturing yet quite undermined legend： the Avenue of Sphinxes. In Luxor, the injection of nonintrusive interventions presents itself as a highly potential candidate in protecting and enhancing the experience of the avenue while meeting contemporary needs of living. Adopting less sensitive development approaches can lead the quality of experiencing the whole city to be worsened for the increasing numbers of tourists and locals.     

A novel route to synthesis of glycerol dimethyl ether from epichlorohydrin with high selectivity

The effective utilization of glycerol, a by-product in the production of biodiesel, into useful chemicals is desirable from the viewpoint of green chemistry. With this in mind, a novel and highly selective route to synthesizing glycerol dimethyl ether (2,3-dimethoxy-1-propanol), a potential fuel additive, from glycerol was proposed. This route uses both glycerol and methanol as starting materials, takes epichlorohydrin as an intermediate product, and utilizes HCl as a recycling agent. Hereinto, the key step of this route is the reaction between epichlorohydrin and methanol to produce 2,3-dimethoxy-1-propanol which is identified by GC–MS, ESI-MS, IR and NMR. The thermodynamics of this reaction was analyzed and the result showed that the thermodynamics of a reaction was favorable and a high product yield was expected. The effect of various parameters such as kind of acid catalyst, molar ratio of epichlorohydrin to methanol, reaction temperature and reaction time was studied. Among various acid catalysts investigated, the acidic ionic liquid [HSO₃-b-N(CH₃)₃]HSO₄ exhibited the highest activity and selectivity: conversion of epichlorohydrin of 100% and selectivity of 2,3-dimethoxy-1-propanol of 99% at 393 K, 10 h, an initial pressure of 0.1 MPa and a molar ratio of catalyst:ECH:CH₃OH of 0.01:1:5. After the reaction, [HSO₃-b-N(CH₃)₃]HSO₄ was separated by vacuum distillation and then reused for the next cycle directly. The results showed that the product selectivity remained at about 94% but the conversion of epichlorohydrin dropped to 75% after being used five times. Subsequently, a reaction mechanism for the synthesis of 2,3-dimethoxy-1-propanol from epichlorohydrin and methanol was proposed.