大功率GTO损耗特性的实验研究

为适应大功率门极关断晶闸管 ( GTO)不断增长的实验要求 ,建立了较大容量 ( 4 0 MVA/ 5 k V/ 8k A)的实验电路和快响应的测试设备 ,给出了选取电压和电流传感器的一般原则 ,并详细分析了影响 GTO开关波形的各种因素。基于所建实验系统 ,通过改变主电路和吸收电路的参数配置 ,系统研究了不同工况下 GTO的动态损耗特性。通过分析提出了开通和关断损耗的改进计算方法 ,在获得较高准确度( 95 % )的同时可降低对示波器测量分辨率的要求。实验方法和结果为 GTO的动态开关特性研究和应用系统设计提供了参考依据。     

±20Mvar STATCOM装置的GTO关断吸收电路

分析了大功率门极可关断晶闸管 ( GTO)关断过程中过电压 V1,V2 和 V3的形成原因及抑制过电压的措施。通过对几种低损耗吸收电路的分析 ,设计了± 2 0 Mvar静止同步补偿器 ( STATCOM)装置中 4.5k V/ 4 k A GTO吸收电路。设计的吸收电路为低损耗的带钳位的三角形吸收电路。给出的关断试验结果证明了抑制过电压措施的必要性及正确性 ,并证明了所设计的吸收电路完全满足大功率两电平GTO逆变器装置的使用要求。     

采用Kriging模型的开关磁阻电机开通角与关断角寻优方法

针对传统密集采样方法获得采用角度位置控制的开关磁阻电机最优开通角与关断角所需实验次数多、耗时长,效率低的问题,提出一种采用Kriging模型的最优开通角和关断角实验求取方法来减少实验采样次数,提高寻优效率。首先,通过少量的初始样本点建立开通角和关断角与电机振动加速度之间的预测模型;之后,根据得到的预测模型有针对性地在最优开通角和关断角可能出现的区域进行采样计算;最后,当区域缩小到满足精度要求的大小后,对该区域进行密集采样,从而快速准确发现最优开通角和关断角。实验结果表明,基于Kriging预测模型获取相同开关磁阻电机最优开通角和关断角(误差小于1%以内)所需样本数仅为传统的密集采样方法的12.4%,计算时间缩短了62.8%。因此,所提方法能显著提高开关磁阻电机的开通角和关断角寻优实验效率。     

GTO开关元件氢泡线流场显示仪

实验表明,采用可关断可控硅(GTO)开关元件在明渠水流中产生氢泡线,这一技术可以用在水质较差的大型水槽中进行流场显示.     

ASVG的建模及其特征谐波分析

设计了一种由可关断晶闸管GTO(GateTurn_off)构成的三极 48脉冲电压源强迫换流器ASVG(AdvancedStaticVarGeneraror)模型 ,从理论上详细推导、分析了由这种三极 48脉冲电压源强迫换流器构成的ASVG输出电压的特征谐波 ;并使用Matlab电力系统仿真工具箱仿真验证了本文提出的ASVG模型及其谐波方法分析的正确性。     

GTO功率步进电机驱动电源的研究

功率步进电机的GTO驱动电源,采用了新型开关元件“可关断可控硅”(简称GTO)。该线路为自行设计并有别于国内外的其它驱动电源。对于1 kg-m～5 kg-m,静态电流8A～25A的4～6相功率步进电机都能被驱动,井能发挥较高的性能指标,对于较大电感和互感的电机也具有良好的适应性。本文说明了GTO功率步进电机驱动电源的工作原理、性能指标以及为提高工作可靠性而采取的措施,并对主电路的工作进行了分析。     

带转差控制的GTO PWM变频调速系统

简化交流电机变频调速系统,提高它的性能,是中外科枝工作者都在努力研究的课题。在变频调速系统中采用可关断晶闸管(GTO)作逆变器的开关元件,为简化系统结构,提高性能提供了一个有利的条件。在用 GTO 作逆变器开关元件时的工作条件与出厂时元件测试条件有许多不同,本文从这一角度出发对元件的参数与特性作了介绍,还介绍了适用于逆变器的门极电路.本文简要介绍了作者在 GTO 变频调速系统方面的一些设想与实验研究结果:适用于高频高速的 GTO 变频电源(1974),适用于中小容量的 GTO PWM 变频调速系统(1980),对通常转差频率控制方法的改进及带新型转差频率控制的 GTO-PWM 变频调速系统(1983),后者可以获得与直流电机双环调连系统相似的性能,装量的结构却此较简单,成本比直流可逆系统低,作者认为这是一种有前途的交流调速系统。本文还简要介绍了近年来日本在这方面的一些研究情况。     

微进给工作台伺服控制技术

为实现母盘刻录机中光学头的精密进给,研制了精密微进给工作台及其伺服控制系统.利用线光栅作为工作台位移检测工具,采用数字比例积分微分(PID)伺服滤波器实现位移控制.经实验方法测定,系统摩擦可以近似为Coulomb摩擦加Stribeck效应的模型.采用了基于该模型的摩擦补偿方法以消除电机死区影响.为实现精确轨迹控制,控制系统采用了零相位误差跟踪控制(ZPETC)技术.针对高增益PID、摩擦补偿和ZPETC加摩擦补偿这3种控制方法,分别进行了轨迹跟踪实验,其轨迹误差分别为±0.8、±0.6 和±0.3 μm.     

可关断晶闸管门极电路初探

可关断晶闸管(GTO)是具有自关断能力的新一代电力电子元件。由于GTO对门极电路有着特殊要求,使得门极电路成为GTO应用技术的关键本文仅就门极电路作一初步探讨。     

环形狭缝通道内干涸点及其位置的实验研究

以蒸馏水为工质 ,对压力范围为 2 .0～ 4 .0MPa ,质量流量 5～ 1 8kg/h ,间隙为 1mm的环形狭缝通道中的流动沸腾进行了实验研究 ,分析了影响干涸点 (DO点 )的界限含气量及其位置 (Lcr)的有关因素 ,采用多元线性回归分析技术整理试验数据 ,得到了有关干涸区传热特性的经验公式 ,试验结果与计算结果误差为± 1 0 % ,此关系式可以用来预测实验范围内的界限含气量及其位置     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.