数字式变压器差动保护误动分析及防范措施

通过对一起主变差动保护误动原因的分析,介绍了HN-2042型数字式变压器差动保护电流相位校正和幅值平衡补偿的基本原理,对误动原因进行了定性分析和定量计算,从技术和管理方面提出了防范措施。     

陶瓷企业电能平衡测试图算法

一、前言企业电能平衡测试是一门新兴学科,也是一项系统工程,它技术性强,面广复杂,计算工作量很大。八十年代初始创于日本等国家,我国于1981年开始起步,在辽宁、青岛等省市试点。江西省南昌市于1986年将江西化纤厂、江西橡胶厂和南昌齿轮厂列为试点企业。1988年先后对三十一家企业开展了电能平衡测试工作。景德镇市于1989年开始对重点耗电企业(含陶瓷企业)也开展了这项测试。根据国家颁布的《企业电能平衡导则》的规定,要对变配电变压器、供电网络、长期运     

大庆油田抽油机节能降耗技术实践探究

针对大庆油田矿区抽油机的平衡率非常低,传统式铁芯变压器存在空载时损失降耗较高,轻烃生产过程中产生的废气量较大,生产运行中线损明显且能源消耗很大等问题,大庆采油厂主要采取了改变相位角,提高平衡率;引进新型机,改装老式机;利用富余气,节能降耗;调配电装备,更新变压器;提高功因数,增加载荷量等抽油机节能降耗技术。但还应调整改进老旧耗能设备;加大抽油机智能节电控制系统的研究应用;加大内控管理力度,加快科技降耗节奏,加强节能综合治理。     

三相平衡的必要性及降损方法

配电网三相负荷不平衡对供电电网以及变压器,电动机等电器都会造成不利的影响,致使低压电网的可靠性和稳定性差,线损率较高。本文结合工程实例,通过对变压器损耗及线路损耗的分析,提出变压器和配电干线三相不平衡的最低要求,通过对第九采油厂办公、生活三相平衡调查,探讨了提高公用变压器的功率因数、加强就地平衡补偿、减少配网损耗的措施。     

切割塔的操作浅析

原料油切割系统是加氢装置工艺流程的第一个处理工序,切割系统操作是否平稳直接关系到后路反应系统操作的稳定性及装置产品的质量。本文以切割塔的三个平衡:物料平衡、气液平衡和热量平衡进行分析,阐述以物料平衡为主,相应调节热量平衡,最终达到气液相平衡的方法。     

平衡式布置浇注系统中非平衡充模流动影响因素研究

针对平衡式布置的浇注系统在充填过程中会出现非平衡充模现象,从而导致制品品质出现差异情况,以常规的H型流道为基准样本,流道抬高一定高度的优化H型流道为对比样本,非平衡系数作为重要的考察指标,研究在平衡式布置浇注系统中注射充填速率、材料以及流道结构对非平衡充模流动的影响。研究表明:剪切热是产生非平衡流动的根源,而充填速率与流道结构同剪切热的产生具有直接而重要的关系;调整合适的工艺参数找到较好的平衡充填点,对制品品质的优劣具有重要作用。     

平衡施肥应重视中、微量元素的有效施用

叙述平衡施肥对农作物生长的重要意义,分析平衡施肥与农作物平衡吸收的矛盾,提出跨越农作物平衡吸收的措施。并提出平衡施肥也应重视中微量元素的施用,才能有效提高农作物的产量和质量,提高肥料的利用率,减少化肥对环境的污染,提高农民的产出与投入比。     

平衡施肥理论与肥料高效利用

结合施肥实践阐述了平衡施肥原理中静态的横向平衡和动态的纵向平衡概念,并提出具有纵向平衡特点的速度复合型控释肥,其养分释放速度能与作物的养分需求基本一致,可显著提高肥料利用率和作物产量。     

节能型游梁式抽油机自平衡系统设计

目前,常规游梁式抽油机平衡调节方式存在劳动强度大、工作效率和调整精度低、安全性差等问题。因此,研究抽油机的自平衡系统有重要意义。该装置由机械系统和电气系统组成,机械系统是指加在游梁上的一个可移动的平衡块,由丝杆的转动来移动平衡块,从而达到调节平衡的目的;电气系统的设计主要目的是检测平衡度、判断抽油机是否平衡和控制电动机运转等。由于抽油机每年耗电量巨大,研究此系统是为了达到节能的目的     

华北油田欠平衡钻井液的选择和应用

华北油田的大部分油藏已进入开发中后期,但剩余储量规模仍然相当可观,实施欠平衡钻井技术是提高勘探综合效益的一条行之有效的途径。近两年,华北油田的欠平衡钻井技术发展迅速,欠平衡钻井液的合理设计是欠平衡钻井成功的关键之一,而钻井液的开发和应用必须和现场紧密结合,因此,如何开发适宜的适应本地区地质特征的欠平衡钻井液是今后发展的重点,本文阐明了华北油田地区对欠平衡钻井液的要求,介绍了欠平衡钻井液尤其是无荧光水包白油的现场应用,以及今后面临的挑战。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料,介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比,介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序,对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。