Attenuation predictions at extremely low frequencies formeasurement-while-drilling electromagnetic telemetry system

Extremely low frequencies (ELFs) are employed to transmit data from underground to the ground surface in the measurement-while-drilling electromagnetic (MWD-EM) telemetry system. Based on electromagnetic field theory, the present work is aimed at predicting the receivability of the signals at the surface. A unified analytic method that is suitable for vertical, directional, or horizontal wells is presented. Attenuation properties are examined for various parameters, including the Earth's conductivity, operating frequency and the length of the drill string. The frequency dependence of the receivability in reference to a noise level is illustrated for different depths of well and different cases. It is also demonstrated that the electric field distributions at the surface have the same features for the three types of well, and that the measurements should be carried out near the well heads for any type of well. A scale model experiment is made to test the authors' theoretical results. The measured data and the computed results are comparable     

近代新疆石油工业的三次盛衰

光绪三十二年（１９０６），新疆布政使王树木丹组织了油苗普查，引进了钻采设备，在独山子开展了新疆石油工业的草创工作，但这项新兴的事业很快随清朝的灭亡而衰落了。民国７～１２年（１９１８～１９２３），新疆省长杨增新再次组织石油采炼，但因经费不足，没有很大起色，而地方人士潘祖焕在汪家沟设厂，却首创了略有盈利的采炼实业，为新疆石油工业的二次兴盛作了贡献。本世纪４０年代初，中苏合作，在独山子油矿建成了相当大的生产经营规模，新疆石油工业出现了第三个鼎盛时期。后来由于盛世才投靠国民党，反共反苏，与苏联关系恶化，独山子的石油采炼如昙花一现，迅速走向衰落。     

铸造合金凝固过程瞬时应力的测试

以计算机采集处理系统为手段,测试了应力框铸件凝固过程的瞬时应力.结果表明,该方法简便、速度快,精度高,可获得铸件凝固过程瞬时应力及温度的动态变化过程。     

高频热处理技术的新进展

就高频感应加热设备、高频热处理的发展等若干问题进行较为详尽的评介,并提出几点看法.     

Amplified distributed reflective optical star couplers

A practical configuration for an amplified distributed reflective N-star coupler using 2×2 3-dB fiber couplers and minimum numbers of erbium-doped fibers, pump lasers, and standard fibers is presented. The constitution and characteristics of this coupler are investigated. Besides a tremendous amount of saving of the required standard fibers, this distributed coupler is more efficient, more reliable, more flexible for future expansion, and more cost-effective for application in optical networks     

Pultruded fibre reinforced polyurethane composites II. Effect of processing parameters on mechanical and thermal properties

This paper presents a novel process for the fabrication of pultruded polyurethane (PU) composites. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) and thermal properties (HDT) of the fibre reinforced PU composites by pultrusion have been studied. The processing parameters investigated include pulling rate (in-line speed), die temperature, filler type and content, and post-cure time and temperature. Results show that the composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio, the mechanical properties and the thermal properties of composites, the optimum die temperature can be determined. It is found that the mechanical and thermal properties increase with filler content for various types of filler. The mechanical and thermal properties increase at a suitable post-cure temperature and time. Furthermore, the properties which decreased due to the degradation of composite materials for a long post-cure time will be discussed.     

Mechanism of iodine vapor sorption in polyacetylene

Simultaneous measurements of weight uptake and conductivity variation during iodine vapor sorption of polyacetylenes (PA) at 20–25°C show that the sorption is a two-stages process. For the first stage, iodine diffusion to the fibrilar surface of the cis-rich and trans-rich PA is of Knudsen type pore diffusion as supported by the sorption measurements of hexane for the cis-rich PA, and has a diffusion coefficient in the order of 10⁷ cm²/sec. Conductivity of the PA rises rapidly and reaches a maximum at end of the stage. For the second stage, the diffusion is more restrictive and has a diffusion coefficient lower than the first stage by a factor of about 10 due to multilayer sorption of iodine, which leads to a decrease in the pore diameter and therefor the diffusion rate. In addition to the restricted diffusion in the second stage, diffusion of the iodine molecules adsorped on the fibrilar surface into the interior of the fibrils is appreciable for cis-rich PA (leading to a conductivity drop) and is negliglible for tran-rich PA (leading to insignificant variation in conductivity).     

PLC在电厂输煤系统中的应用

介绍了可编程序控制器在电厂皮带机输煤控制系统中的应用，详细说明了远程I／O控制系统的特点和功能。     

碳钢与不锈钢表面高浓度渗铬法

在氩气气氛下，应用固体渗铬填料法对碳钢、不锈钢作了表面高铬浓度的渗铬处理，探讨了渗铬温度、时间和渗铬组分对渗层表面铬含量、厚度，试样增重和物相组分影响，碳钢、不锈钢的表面渗铬浓度分别达８０－９４ｗｔ％和７０－８２ｗｔ％。