微型机控制规则采样交—交变频器

本文介绍一种用微型机控制交交变频器的新方法。微型机取代了三相可调频正弦基波波发生器,V/f变换器、模拟比较器,产生相位控制的触发脉冲并保证触发脉冲与交流电源的同步又可控硅的触发导通顺序。相位控制中用规则采样代替传统的余弦波交截法,降低了变频器输出波形的次谐波分量幅值。文中介绍了触发原理和系统硬件软件结构。根据本文原理制成的实验室装置工作稳定可靠,输出电压波形整齐,从而为变频器在改善特性,提高可靠性、简化系统和降低投资方面提供了新的途径。     

基于TL494的逆变电源的设计与制作

介绍以电压驱动脉冲宽度控制芯片TL494为核心的逆变电路,该电路可以将12 V的直流电压转变为220 V、50 Hz的交流电压,可广泛应用于各种不间断供电场合.     

新型弧焊电源的研制——集成控制可控硅逆变弧焊电源

本文介绍了以半桥串联逆变谐振电路（Ｐ．Ｆ．Ｍ）为基础，利用快速可控硅作开关原件，制造的新型可控硅集成逆变弧焊电源的方法。在控制系统上采用集成控制，通过理论分析与试验结果论述了触发脉冲产生过程及空载电压的建立方式，使该电源具有高效、节能、节材、恒流静特性和动特性好等优点     

一种新的电流型可控硅交流电机调速电源

该电流型可控硅交流电机调速电源,采用150°导通角,具有低百分比的高次谐波,优于120°导通角的调速电源。主电路采用可控硅整流和辅助可控硅关断的三相桥式逆变器。逆变主触发信号由单板机控制,并与同步脉冲列相“与”而成,较好地解决了脉冲变压器的饱和问题。实验所得的电流波形经谐波分析证明了预期的效果。本电源用于交流电机的调速,可以降低电机的损耗。     

一种新型晶闸管逆变定角触发控制电路的设计与实现

提出了一种采用波形变换及锁相的方法,产生晶闸管并联谐振逆变触发脉冲的电路,给出了具体电路框图及原理分析.并设计实现了此触发控制电路.实际应用和测试结果表明,由该电路产生的逆变触发脉冲的超前触发角度不随输出电压、负载及工作频率的变化而改变,并在一定范围内具有可调性.     

正弦型高功率因数GTO串级调速装置

在提高常规串级凋速装置的功率因数的基础上,研究了能降低逆变电流中谐波成分的逆变控制方案。使用GTO代替常规逆变器中的可控硅,借助次谐波PWM技术选择最佳开关点,并使逆变器触发角a基180°-270°内变化,则能抑制逆变器的谐波电流,还能提高逆变器的功率因数。这套装置用于串级调速的实验表明:电流超前型的功率因数比滞后型的有明显提高,逆变电流中低次谐波大大减少。     

高精度高压脉冲电源原理与实验研究

在脉冲电场非热效应应用中，高精度高压脉冲电源是关键技术之一。利用大功率开关器件(IGBT)配合脉冲升压变压器可以得到高精度高压脉冲电源。该电源通过复杂可编程逻辑器件(CPLD)来产生脉冲触发信号，经大功率IGBT专用驱动模块驱动，可以实现脉冲电压在0～10kV，脉冲频率在10Hz～5kHz，脉冲宽度在2～30μs以及脉冲个数在1～100内的精确控制，并可实现脉冲宽度以1μs为步长增减，可以满足脉冲电场非热效应应用的参数要求。     

微机控制的脉冲MIG/MAG焊接电源的研制

主电路采用IGBT为主控开关功率转换器件 ,利用 16位高性能单片机 80C196KC ,对微机控制脉冲MIG逆变弧焊电源的组成和控制原理进行实时精确控制的研制 ,并做了可靠性与抗干扰设计 .研制结果表明 :该焊机脉冲频率带宽大 ,为 0 .5～ 2 5 0Hz ,响应速度快 ,抗干扰能力强 ,能够满足全位置焊接的需要 .     

采用8031单片机触发可控硅变流器

本系统采用MCS—51系列8031单片机为基础结合外围器来实现对可控硅变流器的触发控制。为实现触发脉冲与电源信号的同步，采用锁相环技术及过零触发的方法。由软件控制可产生不同变流器(单相桥、三相半波、三相全控桥等)所要求的不同触发脉冲。     

可实时调整刺激参数的功能性电刺激仪的研制

基于STM32微处理器设计并实现了可实时调整刺激强度的功能性电刺激仪.通过上位机设定刺激参数值;通过数字电位器或DAC转换器控制恒压源的电压实现设定的恒流输出;通过改变H桥开关管的导通时间控制脉冲的频率和脉宽实现设定的频率和脉宽,分别进行电阻和人体实验测试.结果表明,功能性电刺激器的电流幅度、频率和脉冲宽度分别在0～50 mA, 0～100 Hz和0～1 000μs范围内连续可调.该电刺激仪可以实时调整刺激参数,为闭环FES的应用提供基础.     

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.     

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.     

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.     

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.     

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.     

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.