建筑工程测量中高差闭合差的计算与调整

在高程控制测量中,可以通过计算高差闭合差来检验观测成果的质量。而高差闭合差这一概念,在建筑工程测量的实际应用中容易混淆。文章从高差闭合差计算、调整和高程计算三个方面入手,给出了对高差闭合差理解的思路,以及在控制测量中高差闭合差平差的新方法。经实践验证,有益于工作效率的提高。     

河北省关闭煤矿地质环境影响评价

在对河北省主要的关闭煤矿实地调查和遥感影像解译基础上,将关闭煤矿的地质环境影响评价指标体系划分为3个要素和11个指标,利用模糊综合评价方法建立了关闭煤矿的地质环境影响评价模型,采用改良指数标度的层次分析法确定各指标权重。评价结果显示,在118处较大规模的关闭煤矿中,36处煤矿地质环境影响程度为严重和较严重状态,82处为轻微和较轻状态。严重、较严重的煤矿主要分布在蔚县矿区、宣下矿区、邯郸矿区。地质环境问题主要影响因子为土地资源压占、含水层破坏、地面塌陷和地裂缝等。     

衬套内外封闭8字形油槽加工装置

通过对衬套油槽的分析,提出了车衬套内外封闭8字形油槽的加工装置,并详细分析了该加工装置的结构。经生产实践证明:该加工装置调试简单,工作时稳定性强,加工出的零件达到了使用要求。     

闭路磨磷矿石制浆的设计及应用

某磷肥项目磷酸装置的原料制备采用棒磨机十分级机＋球磨机的湿法闭路磨矿工艺。介绍了该工艺的原料粒度分布、工艺流程和系统控制；论述了棒磨机、斜窄流分级机等主要设备的工作原理和结构特征；通过磨矿系统产品分析数据，总结了湿法闭路磨矿工艺的应用效果和相关注意事项。     

可控硅整流机组的调试经验

阐述了甘肃金川集团有限公司动力厂可控硅整流机组的调试经过,总结了调试准备工作、轻载试验、重载试验及重载设备制作经验,并进行了水电阻的计算.     

Approximation analysis of multi-class closed queueing maintenance networks with a parts inventory system and two-phase Coxian time distributions

We consider a maintenance network where a set of bases is supported by a replacement parts inventory system and a centrally located repair depot. The ordering policy for the parts is the (S, Q) inventory policy. We extended the previous results to the network, where processing times at each node follow a two-phase Coxian distribution. The proposed network was modeled as a multi-class closed queueing network with a synchronization station. To make the analysis of the network computationally tractable, we developed a two-phase approximation method. In the first phase of the method, the proposed network was analyzed with the previous algorithm based on a product-form approximation. In the second phase, a sub-network was again analyzed with the procedure of a product-form approximation method such that the state space of the sub-network was reduced. In the analysis of a sub-network, a recursive method was also used to solve balance equations by exploiting the special structure of the Markov chain. The new algorithm provided a good estimation of the performance measures of interest. In addition to being accurate, the new algorithm is simple and converges rapidly.     

Numerical Simulation of Currents Distribution Along Grounding Grid Buried in Horizontal Multi-layered Earth in Frequency Domain Based Dynamic State Complex Image Method

A new mathematical model for accurately computing currents along a grounding grid buried in a horizontal multi-layered earth model has been developed in this article, which is a hybrid of Galerkin’s method of moment and the conventional nodal analysis method; the propagation effect of an electromagnetic wave has been considered. The dynamic state complex image method and closed form of Green’s function of a dipole or monopole in the multi-layered earth model are introduced to enhance efficiency of the method calculation; meanwhile, an analytical formula for mutual induction and impedance coefficients calculation have been adopted to accelerate the calculation. Finally, some numerical results about the distribution of an electromagnetic field and currents along a grounding grid have been discussed, and some conclusions have been obtained.     

变频技术在350MW机组闭式水系统中的应用

本文介绍了大唐长春第三热电厂350MW机组单元制闭合大回路系统闭式冷却水泵变频改造的方案和实施情况,并对产生的经济效益和运行效果进行了评估。其结论为:变频技术在闭式冷却水泵的应用即实现了全厂冷却水量的安全稳定调节,又达到了节能降耗目的。     

Constructing hyperchaotic systems at will

Over the last two decades, chaotification has received increasing attention from various communities of science and engineering. This paper aims at developing a unified chaotification framework for generating desired higher‐dimensional dissipative hyperchaotic systems by using a single‐parameter controller. The main idea is to use a block diagonal matrix in the design of the nominal system, so as to construct a desired hyperchaotic system. Specifically, the proposed scheme is to assign desired closed‐loop poles to the controlled system, allocating the corresponding numbers of eigenvalues with positive real parts at two types of saddle‐focus equilibria. For the non‐degenerate case, the number of positive Lyapunov exponents of the controlled system is given by the largest number of positive Lyapunov exponents of the desired hyperchaotic system. Two representative examples are given to illustrate and verify the proposed design method. Finally, the digital signal processor is employed to implement the above 10‐dimensional hyperchaotic systems, and the experimental observation is also given. Copyright © 2015 John Wiley & Sons, Ltd.     

双闭环模糊PI控制的双馈式风机并网研究

将模糊控制与PI控制相结合,应用于双馈式风机网侧变换器控制中。采用外环电压模糊PI控制、内环电流控制的双闭环控制系统来克服运行时发电机参数发生变化带来的干扰。在Matlab/Simulink中搭建仿真模型进行仿真,结果表明:该方法在运行过程中可以很好地克服风速和电机参数变化的影响,定子端电压的波形、幅值、频率均达到并网要求,谐波含量少。