基于综合等效灵敏度的短路电流抑制措施确定方法

随着电网规模的不断增大,短路电流超标已成为电力系统安全运行所面临的重大问题。文中提出了一种限制电网短路电流的综合等效灵敏度法,将限制短路电流问题分为限制短路电流和电气安全校核2个子问题。在限制短路电流子问题中,统一了线路开断、发电机停运、线路出串、线路装设串联阻抗、更换高阻抗变压器、母线分裂等限流措施的模拟,进而利用支路阻抗追加法计算上述措施实施后的节点阻抗参数和元件开断的短路电流综合等效灵敏度。在电气安全校核子问题中,对电网进行潮流和稳定校核,实现短路电流限制。青海电网的实际算例验证了文中方法的有效性,研究成果可为青海电网限制短路电流提供借鉴。     

A thyristor- and thermistor-based inrush current limiter for DC-link start-up

Large inrush currents can be harmful to equipment subjected to it and can also disturb other devices through voltage dips. Traditional ways of dealing with large inrush currents include the usage of parasitic elements in the supply, negative temperature coefficient (NTC) resistances and start-up relays. These solutions have several disadvantages among which are a non-negligible standby consumption, using a relay or a compromise between inrush current and load losses using an NTC. This paper proposes a solution which solves these disadvantages. The proposed circuit uses a semi-controlled bridge rectifier requiring a very low standby power consumption and is capable of withstanding grid interruptions. Moreover, it is designed to power on only when the load is not too heavy. This is accomplished by the use of positive temperature coefficient thermistors. The presented solution can be used for DC-link start-up circuits in applications with a power range from several watts up to a few kilowatts and it is particularly suitable for on-board battery chargers designed for electrical vehicles.     

浅述赫佐格与德默隆作品中混凝土的设计手法

以混凝土材料的建造和表现为题,通过对瑞士建筑师雅克.赫佐格与皮埃尔.德默隆有关作品的介绍,阐述与分析了他们对于混凝土材料特点的独特理解和运用,以期有针对性的对于我国当前建筑领域中混凝土材料设计方法上的局限起到一定的学习和借鉴作用。     

Phosphorous limitation in an arctic river biofilm—A whole ecosystem experiment

A fourth-order arctic river was experimentally enriched with phosphate (7.7 ± 7.0 μ g 1⁻¹) to determine the effect of such a loading (equivalent to a community of 10,000 people) upon the trophically important biofilm. The effect upon a light-grown biofilm (an autotrophic/heterotrophic assemblage) and a dark-grown biofilm (predominantly heterotrophic assemblage) was determined after 28 days of colonization. Seven attributes of the biofilms were monitored, 2 autotrophic indices, chlorophyll , [¹⁴C]HCO₃ incorporation into lipids and 5 heterotrophic indices; [¹⁴C]acetate incorporation into lipids, metabolic heat output, turn-over times of microbially labile glucose and glutamate and mineralization of microbially recalcitrant ring-labelled [¹⁴C]hydroxybenzoic acid. The findings showed that the addition of phosphorus resulted in a substantial stimulation of both autotrophic and heterotrophic processes suggesting that arctic rivers of this type would be liable to cultural eutrophication.     

建筑的符号意义

研究了建筑符号表达的多种含义,介绍了文丘里提出的“鸭子”和装饰性庇护所两种不同类型建筑的符号意义,探讨了符号意义的局限性,指出人们应当理性地看待符号在建筑中的地位,并在符号运用上提倡创新,对丰富建筑风格具有积极作用。     

浅谈中国古典园林与现代西方园林的融合

针对中国古典园林与西方现代园林以风格时代服务对象的不同,分析研究了两种园林的优势性和局限性,探讨了人性化现代园林的融合,指出应取两种园林的优势性,去其局限性,以达到中国古典园林和西方现代园林适应现代园林的融合.     

钢筋混凝土连续梁弯矩调幅法的研究

通过对Ⅱ、Ⅲ级钢筋混凝土连续梁的对比试验,研究了Ⅲ级钢筋混凝土连续梁的弯矩调幅问题,探讨了不同钢筋型号、不同混凝土受压区高度对调幅限值的影响.试验证明;所有Ⅲ级钢筋混凝土连续梁均达到了充分内力重分布且都满足正常使用要求.本文提出了Ⅲ级钢筋混凝土连续梁的调幅限值及其适用条件.     

快速真空断路器在电力系统中的应用

介绍了涡流驱动型快速真空断路器的原理,分析了目前配网消弧消谐、故障选线及触电防护、电网短路电流限制、串联补偿及变压器直流偏磁抑制等技术的现状和存在的问题。根据快速真空断路器特点,提出了解决相关技术问题的方法,阐述了相关装置的结构、试验及应用情况,并对快速真空断路器在电力系统中的应用进行了展望。     

论缔约中信赖利益损害赔偿的范围和限度

缔约过失责任损害赔偿适用于当事人违反附随义务、合同被确认无效或可撤销时一方信赖对方缔约行为时所产生的信赖利益受损情形。这种信赖利益的损害赔偿除须具备一般民事责任的4个构成要件外,还应满足以下两个条件：损害赔偿时间上始于当事人双方以缔约为目的而进行接触磋商之时,信赖合同的一方须善意无过失。应当指出,目前我国《民法通则》61条,《合同法》42、43、58条对此做了规定,但立法对缔约过失责任中的信赖利益损害赔偿的范围和赔偿限度都不明确,文章建议缔约过失责任中的信赖利益损害赔偿应包含间接损失、赔偿不得超过履行利益、不适用过失相抵规则。     

Impact of applied cell voltage on the performance of a microbial electrolysis cell fully catalysed by microorganisms

The effect of the operating voltage on the performance of a microbial electrolysis cell (MEC) equipped with both a bioanode and a biocathode for hydrogen production is reported. Chronoamperometry tests ranged between 0.3 and 2.0 V were carried out after both bioelectrodes were developed. A maximum current density up to 1.6 A m⁻² was recorded at 1.0 V with hydrogen production rate of nearly 6.0 ± 1.5 L m⁻² cathode day⁻¹. Trace amounts of methane, acetone and formate were detected in cathode's headspace and catholyte which followed the same trend as hydrogen production rate. Meanwhile substrate consumption in anolyte also followed the trend of hydrogen production and current density changes. The bioanode could utilise up to 95% of acetate in the tested voltage ranges, however, at a cell voltage of 2.0 V the bioanode's activity stopped due to oxygen evolution from water hydrolysis. Cyclic voltammograms revealed that the bioanode activity was vital to maintain the functionality of the whole system. The biocathode relied on the bioanode to maintain its potential during the hydrogen evolution. The overall energy efficiency recovered from both bioanode and external power in terms of hydrogen production at the cathode was determined as 29.4 ± 9.0%, within which substrate oxidation contributed up to nearly 1/3 of the total energy marking the importance of bioanode recovering energy from wastewater to reduce the external power supply.