高压共轨喷油系统中的电磁阀

研究了电磁材料和线圈结构等因素对高速电磁阀的影响，并采用有限单元法对电磁阀的特性进行了分析计算．结果表明：影响电磁阀性能的主要参数有驱动电压、初始气隙、预紧力、运动部件的质量等．通过降低驱动电压，减小初始气隙，降低弹簧预肾力，减轻电磁阀运动部件的质量，均可以提高电磁阀的性能．     

自动变速器脉宽调制开关电磁阀工作频率研究

脉宽调制开关式电磁阀是汽车自动变速器中常用的一种换档执行元件,其控制信号分为低频信号和高频信号,低频信号用于离合器调压控制,高频信号则用于离合器油压保持控制.针对电磁阀工作频率的选择方法进行了理论分析和试验研究.对于低频信号频率需要考虑电磁阀本身的固有频率、开启和关断的响应时间及控制系统采样频率等因素影响,并尽可能采用较高的值,以获得较高的调压精度.对于高频信号频率,则要考虑到保持电流的波动、电磁干扰、磁损及驱动元件的驱动特性等因素,再选择尽可能低的占空比,以获得理想的保持电流及关断的响应速度.     

基于PWM控制模式的高速开关阀开关特性分析及优化

高速开关电磁阀作为自动变速器电液控制系统的核心控制元件,其开关响应特性直接影响自动变速换挡执行机构的响应速度和作动品质。文章在分析高速开关电磁阀结构及工作原理的基础上,建立了基于Matlab/Simulink平台上PWM维持占空比方式控制下的仿真模型,并通过仿真分析研究开关特性及关键参数对维持占空比及关闭时延的影响。结果表明,与定压信号控制方式相比,采用PWM维持占空比的控制方式以及结构参数优化调节,有效提高了阀开关动作的整体响应速度。     

共轨喷油器电磁阀双电压式驱动模块设计

设计了电磁阀双电压式驱动方法的硬件电路和驱动程序．硬件电路由驱动电压产生电路和控制电路组成,驱动电压产生电路用它激式极性反转型开关电源产生可调的高压和中压,控制电路控制高压和中压的开启和关闭时刻．驱动程序通过设置定时器匹配中断的方式实现高压和中压持续时间的控制．试验结果表明,电磁阀开启电流大。保持电流较低且保持平稳,电流特性符合电磁阀的驱动要求,可通过微调电压来调制保持电流．     

一种用于PWM变换器的斜坡补偿电路设计

针对传统斜坡补偿的PWM变换器的电流输出能力会随着补偿电流的增加而下降的缺点,设计了一种用于峰值电流模式PWM变换器的斜坡补偿电路.通过改进系统箝位电路,使箝位电压能够随着补偿电流动态变化,从而保持系统的输出电流能力恒定,减小输出电压纹波.仿真采用CSMC 0.6 μm工艺,结果表明:在输入电压大于1 V、占空比大于50 %时,输出电压纹波在10 mV左右,大大提高了负载能力和系统稳定性.     

电压型PWM整流器电流控制策略的研究

电压型PWM整流器通过对整流器直流侧电压PWM调制，不但能使直流电压在一定范围内可调，而且使整流器的交流侧电流正弦化，并能够实现单位功率因数运行，实现高功率因数的整流装置．而控制PWM整流器交流侧的方法有多种，从电压型PWM整流器的静态模型入手，详细分析了电压型PWM整流器交流侧电流电流的控制规律，得出了一种间接电流控制模型，并阐述了间接电流控制的PWM整流器系统的设计，最后对该方法进行仿真，结果表明，采用这种电流控制，能够实现PWM整流器高功率因数运行．     

磁性源电磁法发射电流分段控制方法

针对磁性源发射系统中脉冲宽度调制(PWM)控制方法电磁干扰强及上升沿、下降沿拖尾严重的问题,提出一种磁性源电磁法发射电流分段控制的方法。将发射电流分为4段精确控制,即通过引进高压辅助电源的方法控制发射电流的上升沿、平顶段与下降沿,并利用软硬件相结合的方法消除下降沿过冲。讨论供电电压与波形线性度、延迟时间的关系,给出具体设计方案及电路参数计算,采用仿真和实验的方法与PWM控制方法所得电流波形进行对比分析。研究结果表明:通过输出电流分段控制方法得到的输出电流波形的上升沿时间小于1.5 ms;下降沿时间小于0.5 ms,过冲电流小于3 A,线性度大于0.875,与PWM控制方法所得波形相比,其上升沿提升速度快,下降沿延迟时间短,线性度高,反向过冲电流小。     

三相PWM整流器不平衡电网下的功率波动抑制控制

在电网电压不平衡下三相电压型整流器会产生负序电流致使有功功率和无功功率波动,而功率的波动又会导致网侧电流的畸变和直流侧电压的波动,从而影响整流器的工作性能。为了解决这些问题,本文利用不平衡电网下无功功率的新定义在α-β两相静止坐标系下建立了三相PWM整流器的数学模型,推导出有功和无功的功率表达式,得到了更为简单的参考电流计算表达式,并提出了相应的控制方案。通过功率平衡控制,可以使电网电流总谐波畸变率降低并且有效抑制直流侧电压的二倍频波动。对所建议的方法通过实验进行了验证,实验结果表明该策略的有效性。     

高速电磁开关阀开关特性的机理研究

为改善高速电磁阀的开关特性,从电磁阀的数学模型着手,用实验仿真的方法,分析了高速电磁阀的开关特性机理,提出了高速开关阀的设计准则,探讨了阀芯质量、阀芯行程、线圈匝数、线圈电阻、驱动电压与电流等各参数对开关特性的影响．提供了寻找电磁阀快速开关的有效方法．     

一种基于半自动弧焊发电机外部电流/电压的控制方法

半自动弧焊发电机通常工作在平特性或降特性状态,工作于平特性时要求电压基本恒定,工作于降特性时要求电流基本恒定。数据采集模块采集焊接电流/电压,并送单片机分析处理,利用模糊控制理论,通过计算隶属度把电流/电压信号分成过强、强、中、弱和微弱5类,不同类型采用不同的控制策略来控制PWM信号的占空比,PWM信号调节发电机励磁回路电流,以达到对发电机输出电流和电压的控制,从而实现对半自动弧焊发电机的焊接电流/电压进行控制。     

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.