西气东输管道在线气体质量检测系统

西气东输管道公司与下游近50家用户签订了照付不议天然气销售合同,作为计量交接必不可少的一部分,天然气气质的检测尤为重要。介绍了西气东输管道使用的气相色谱分析仪、水露点分析仪、硫化氢分析仪等在线检测仪器的设备性能、日常维护保养,并对使用中遇到的问题进行了分析,提出了解决办法。

Dynamic Performance of a Semi-Submersible Platform Subject to Wind and Waves

By applying experimental and numerical simulations, the motion performance of a semi-submersible platform with mooring positoning system under combined actions of wind and waves is studied. The numerical simulation is conducted by the method of nonlinear time domain coupled analysis, and the mooring forces are calculated by the piecewise extrapolating method. The scale in the model experiment is 1:100, and the mooring system of the model is designed with the method of equivalent water-depth truncation by comparing the numerical and the experimental results, the platform motion and mooring forces subject to wind and waves are investigated. The results indicate that the numerically simulated mooring forces agree well with the experimental results in static equivalent field, but show some difference in dynamic equivalent field; the numerically simulated platform motions coincide well with the experimental results. The maximum motion of the platform under operating conditions is 20.5 m. It means that the horizontal displacement is 2% less than the water depth, which satisfies the operating requirements.

Prediction of Cracking Gas Compressor Performance and Its Application in Process Optimization

Cracking gas compressor is usually a centrifugal compressor. The information on the performance of a centrifugal compressor under all conditions is not available, which restricts the operation optimization for compressor. To solve this problem, two back propagation (BP) neural networks were introduced to model the performance of a compressor by using the data provided by manufacturer. The input data of the model under other conditions should be corrected according to the similarity theory. The method was used to optimize the system of a cracking gas compressor by embedding the compressor performance model into the ASPEN PLUS model of compressor. The result shows that it is an effective method to optimize the compressor system.

Composite iterative learning controller design for gradually varying references with applications in an AFM system

Learning control for gradually varying references in iteration domain was considered in this research, and a composite iterative learning control strategy was proposed to enable a plant to track unknown iteration-dependent trajectories. Specifically, by decoupling the current reference into the desired trajectory of the last trial and a disturbance signal with small magnitude, the learning and feedback parts were designed respectively to ensure fine tracking performance. After some theoretical analysis, the judging condition on whether the composite iterative learning control approach achieves better control results than pure feedback contro! was obtained for varying references. The convergence property of the closed-loop system was rigorously studied and the saturation problem was also addressed in the controller. The designed composite iterative learning control strategy is successfully employed in an atomic force microscope system, with both simulation and experimental results clearly demonstrating its superior performance.

The synthesis of micro-sized silicon carbide whiskers and the application for heat transfer enhancement

This paper presents a simple and cost-effective method for the production of micro-sized silicon carbide whiskers at high yield and the effect on heat transfer enhancement for the whisker laden fluids. For SiC whisker synthesis, the starting powder mix- ture is obtained by milling short carbon fibers with the white ashes of rice hulls. Calcina：ion in argon, together with the subse- quent purification process, results in a high yield of SiC whiskers, which possess a diameter of 200-400 nm and a length of several tens of microns. The formation of the whiskers is discussed according to VS growth mechanism. Convective heat transfer performance in small channel tubes is then studied for fluid systems mixed with those micro-sized SiC whiskers at different concentrations. The heat transfer coefficient of SiC containing fluid can be significantly improved in comparison to the base fluid.

PROPERTIES OF STORAGE FUNCTIONS AND APPLICATIONS TO NONLINEAR STOCHASTIC H∞ CONTROL

This paper discusses the properties of the storage functions for a class of nonlinear stochastic systems. Some necessary and sufficient conditions for a function to be a storage function are derived. As applications, the finite and infinite horizon nonlinear stochastic H∞ controls for systems with state, control, and external disturbance dependent noise are investigated, which generalize the previous results.