地下难采矿体回采工艺系统可靠性研究

基于地下难采矿体的回采工艺系统,采用系统工程分析方法,分析影响地下回采系统可靠性的各个环节,并结合实际情况,确定采矿系统是由多个环节串联而成。在此基础上运用马尔可夫过程建立回采工艺系统的可靠性数学模型,并确定其可靠性指标,通过计算分析研究系统的可靠性。运用Monte-Carlo数值模拟法代替传统方法计算故障率、修复率,一定程度上提高了计算结果的精度。结果表明：马尔科夫过程与Monte-Carlo模拟方法在一定程度上提高了地下难采矿体回采工艺系统可靠性的评价水平,这对矿体在回采方案设计、加强安全管理、提高回采效率、有效预防事故等方面有理论指导作用。     

基于GE Fanuc PLC的Accu Roll轧管机组基础自动化系统的设计与实现

介绍了GE Fanuc PLC作为Accu Roll轧管机组的基础控制单元的整套自动化系统的设计及实现情况。简述了该机组主要设备的工作流程、自动化系统的控制范围与功能要求;详细描述了采用GE Fanuc方案的系统硬件、软件配置,程序架构和相应控制功能与特点。     

A novel frequency method for quantitative analysis of fluorescence dye concentration by using series photodetector frequency circuit system

This study reported the frequency characteristics of series photodetector frequency circuit system for detection of fluorescence dye concentration. In the condition of the same fluorescence intensity, the series photodetector frequency circuit system with higher responsivity of photodetector had higher frequency shift. The 100 MHz series photodetector frequency circuit system was applied to determine the fluorescence dye concentration of HEX by frequency shift. The correlation curve showed that the frequency shift was linearly related to the logarithm of fluorescence dye concentration from 100 pmol 3 μl⁻¹ to 10 amol 3 μl⁻¹. The proposed method can be applied simply and the detection limit of fluorescence dye concentration was lower than the conventional fluorescence technique by 2–3 orders.     

Electrical characteristics of an organic thin copolymer/p-Si Schottky barrier diode

We have fabricated a poly(aniline-3-methyl thiophene) organic thin material on p-Si substrate by placing a solution of copolymer in acetonitrile on top of a p-Si substrate and then evaporating the solvent. The electrical and interface state density properties of the poly(aniline-3-methyl thiophene) copolymer/p-Si/Al diode have been investigated through methods using current-voltage (I-V), Cheung's, and a modified Norde's function. Good agreement was observed with the values of barrier height as obtained from all of these methods. The diode shows a non-ideal I-V behavior with an ideality factor greater than unity, which could be ascribed to the interfacial layer, interface states and series resistance. The interface state density of diode was determined using the forward-bias I-V characteristic technique at room temperature, and it decreases exponentially with bias from 1.39 × 10¹⁶ cm⁻² eV⁻¹ in (0.06 − E_v) eV to 4.86 × 10¹⁵ cm⁻² eV⁻¹ in (0.51 − E_v) eV.     

Estimating life cycle plant maintenance costs

The financial success or otherwise of a maintenance strategy can be determined realistically only when actual costs are compared with target ‘predicted’ values. This is because, in the absence of accurate cost control mechanisms, maintenance expenditure can exceed capital cost. In order to address this problem, a methodology is presented for predicting life cycle maintenance expenditure over the useful life of tracked hydraulic excavators. First, time series analysis (using a moving centred average) illustrates that the trend in maintenance cost expenditure is difficult to isolate due to large perturbations in periodic unscheduled maintenance. Such expenditure accounts for 92% of total maintenance cost. Second, cumulative costs of maintenance are modelled using a cubic equation, with time (in hours) as the predictor (x_n) variable. Model performance is robust with a coefficient of determination (R²) of 0.99 and a mean percentage error (MPE) of minus 3.94. The paper concludes with direction for future research in this field, particularly with respect to expanding the model's application to machines of various weights, manufacturers and machines operating in other industries, and determination of criteria with which to predict when a plant item will reach the end of its useful life.     

I/A Series DCS在柴油加氢装置优化中的应用

运用I/A Series DCS对柴油加氢装置的系统配置和功能进行优化,重点介绍过程控制的优化方法和尚未解决的部分问题.     

一种高功率因数的串联变频方案

本文介绍了一种高功率因数的串联变频方案,其新颖之处在于主电路采用晶体管和晶闸管混合逆变器,控制电路全由集成电路组成,文中详细介绍了该串联变频方案的组成和工作原理,并给出了满意的实验结果。     

对称型双公比传动系统Xm值计算公式及其应用

本文简述了采用混合公比的要点,并利用传动特性式及下平上斜型结构网的对应式(本文称下平上斜结构式),依此分析导出了最末扩大组级比指数X_m值的计算公式.此公式可在机床设计中实际应用.本文的探讨方法可用于非对称型混合公比之研究.此外,还略述了P_0=2的理由.     

500kV伊敏─冯屯串联补偿站设计原则的研究──特高压线路用串联补偿站的典型单元

本文结合东北地区伊敏－齐齐哈尔冯屯变电站５００ｋＶ输电工程提出了５００ｋＶ等级串联电容补偿站的通用设计。设计中的主要技术为“积木式”构思，即用典型单元装配成不同参数的串补站，便于通用、制造与维护。本设计中采用的扩大的典型单元使辅助设备减少了几乎一半。新一代的ＺｎＯ保护装置，提高了串补站的性能。双回线中串补站的新型主结线方式，可以使串补站的电容器容量减少一半，就伊敏－冯屯串补站而言，可节省基建投资近５０００万元。本文所述的典型单元除对地绝缘外也可用于任何电压等级（７５０～１２００ｋＶ）。     

串补线路故障点位置的模型识别方法

文中提出了一种判断串补线路单相接地故障时故障点相对于串联补偿电容位置的模型识别方法，该方法通过比较不同模型计算出线路电感值的离散度来识别故障位置。将该方法和传统的距离保护相配合，可以解决传统距离保护在串补线路中超越的问题，使得距离Ⅰ段可以按全线阻抗整定，而不必考虑电容的容抗，很大程度地提高了距离Ⅰ段的灵敏度。判别过程仅利用MOV导通前一段时间的暂态量数据，不受MOV非线性特性的影响，避开了MOV导通后串补电容上电压准确值难以获得的问题。该方法仅利用单端电气量，无需通讯通道；数字仿真结果表明：该方法具有很好的适应性，适合于各种电压等级、各种频率的系统，线路各处故障。