contact stress and steady thermal analysis of herringbone gears in a gas turbine

To obtain the distribution characteristic of contact stress and the bulk temperature on the surface of herringbone gears, parameter modeling of gears was carried out by parametric design language. A numerical simulation was given to calculate the contact stress field and the steady thermal field by combining heat transfer theory, tribology theory, and mesh theory. The distribution of contact stress, the bulk temperature and heat flux also were analyzed. The analysis results show that the distribution of the load along the contact line possesses regularity. The heat flux along the tooth depth direction decreases first and then increases. The effect of thermal conduction of the tooth is stronger than that of convective heat transfer. The conclusion indicates that the finite element emulation method can be used to estimate the transmission performance of herringbone gears.     

基于GF集理论的五自由度混联机器人构型综合

基于GF集理论提出了一种简单而有效的混联机器人构型综合方法。首先阐述了GF集的基本概念、运算法则及转动特征存在条件。其次通过分析混联机构结构组成特点,提出了基于GF集元素组合和转动轴线迁移定理安排混联机构拓扑结构的方法,建立了混联机构数综合方程并给出了混联机构构型综合的具体步骤。基于该构型综合理论,综合出了具有确定运动特征的3T2R混联机构。针对综合出的混联机构,提出了一种混联机构末端运动特征的分析方法,运用该方法分析了一种综合得到的3PRPaRRR混联机构,证明了该构型理论的正确性。设计出的3PRPaRRR混联机构具有结构紧凑、定位精确、高速等优点,同时给出了实例应用。     

Study on Intelligent Displaying Mechanism of Control Fissure of Perilous Rock

Perilous rock is a kind of typical disaster and characterized by multitudinous structural planes; when the disaster happens, only one of the planes is the control fissue and the others are secondary. In this paper, the authors have done some attempts for     

Landfill Leachate Treatment by Cavitating Water Jets

Cavitating water jets were used to degrade complicated organic compounds sampled from landfill leachate from a sanitary landfill in Chongqing, P. R. China. The law of chemical oxygen demand (COD) and the impact of factors such as pumping pressure, confining pressure, cavitating time and pH were evaluated in the experiment. We concluded that a cavitating water jet can degrade complicated organic compounds. Cavitating water jets therefore can improve biological oxygen demand (BOD)5/COD. The optimal cavitating condition was also obtained: at a pH 9.0, confining pressure 0.6MPa, cavitating time 90mins and pumping pressure 10MPa,the COD, BOD5 and BOD5/COD increase to 124.8%, 293.3% and 52.44% respectively. Chromaticity decreases while SS increase to 191.5%. These changes create good conditions for subsequent treatment.     

A cusp catastrophe model study of destabilization of soft sandwich rock slope

A slope geomechanical model was proposed based on the destabilization characteristics of soft sandwich rock slopes. Based on an analysis of the effects of internal external factors on slope stability, the cusp catastrophe model of slopes can be employed to analyze and predict the necessary conditions leading to slope catastrophes. During the processing of the mass and energy exchange with the external, this may lead to the change of controlling variables. Slides or quick or slow creeping thus may take place due to environmental complexity. This work helps deepen understanding of the formation of landslides and makes feasible the applcation of the catastrophe model to slope destabilization investigations.     

Corrosion behavior and mechanism of AZ40magnesium alloy in simulated sea water

Tafel polarization curve and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the corrosion behavior of AZ40 magnesium alloy in simulated sea water. The surface morphology of the alloy during exposure was observed with an optical microscope and a scanning electron microscope. The pH variation of bulk solution during corrosion was recorded. The results show that the major corrosin forms of AZ40 magnesium alloy in simulated sea water were characterized by pitting and filliform corrosion. The corrosion occurs spontanesously. The insovable corrosion products, which precip it ate on the alloy surface were characterized by porsity and hetorogeneity, indicating that these products can not prerent further alloy corrosion. Therefore, the corrosion of AZ40 magnesium alloy spreads rapidly and the alloy surface is destroyed severely during short exposure period.      

Site selection for a measuring and controlling device of initial phase based on maximum elevation angle

We introduced a site selection method based on the modified maximum elevation angle intended for mountains possibly affecting the measurement and control of the initial phase in a launching port located in mountainous areas. To use the former analysis results, the method, along the helices whose center is the launcher's project point, analyze each point's visibility on the helices. The visible area can be obtained by comparing the visibility at each moment in the initial phase. Finally, there can be three points in the above visible area with distances longer than required.     

An edge detection method based on a good point set genetic algorithm

In order to improve the convergence rate of genetic algorithms based on edge detection, a novel edge detection method based on a good point set genetic algorithm (GGA) was proposed. The proposed method designed the crossover operation with the theory of good point set in which the progeny inherits the common genes of the parents which represent its family so as to improve the convergence rate of the genetic algorithm. Furthermore, before the algorithm was used for edge detection, the feature space of the image grey level was transformed into the feature space of the fuzzy entropy. Dissimilarity enhancement processing next was applied to the image by using a fuzzy entropy theory to filter the non edge pixels so as to reduce the scale of the solution domain. This approach offered another efficient way to improve the convergence rate. Experimental results show the proposed algorithm performs very well in terms of convergence rate. The detected edge image is well localized, thin, and robustly resistant to noise.     

Simulation and experimental study of the fire performance of underground shopping streets

Underground streets have been developed in cities with land shortages. We simulated the dynamic distribution characteristics of smoke flow and temperature from fires under natural conditions in underground streets. The experiment was carried out at the Sichuan Fire Research Institute of Public Security Ministry, P.R. China. A 500 kg fire source was used in a real underground street. Temperature distribution at different heights and personnel escape routes are shown in two typical sections. The comparison between the computer simulation data and experimental data validates the simulation. This study provides a valuable reference for fire assessment of underground shopping streets.     

Influence analysis of fuel quality on engine emission performance

Quality, composition, and characteristics of fuel from 7 areas of P. R. China were analyzed. Fuel quality factors influencing engine emission performance were studied. Using fuel from the HuaZhong and XiNan areas, engine COx, HC, and NOx emissions were tested by adjusting the excess air coefficient and the advanced ignition angle. In light of the characteristics of aromatic hydrocarbon and alkenes of fuel from different areas in P. R. China, we have shown engines can operate smoothly and engine emissions can be decreased when the excess air coefficient and the advanced ignition angle are properly adjusted.