悬浮型速溶PHPAM堵水剂及其堵水技术

本文介绍了以悬浮型速溶PHPAM为基础研制的低温油井堵水剂,讨论了影响堵水剂交联时间和成胶粘度的因素,制定了移动式弹性隔板堵水工艺并成功地应用于二连油田蒙古林砾岩油藏的油井堵水。该堵剂适用于30—60℃油井,交联时间可控、配制简便、快速、施工周期短。     

Oxidation behaviour of some modern heat-resistant cast steels

The kinetics and morphological development of the oxidation of a selection of modern heat-resistant cast steels have been examined and compared with those of the traditional material, HK40. The materials examined had Cr contents of 24 to 29 weight percent (wt %), Ni contents of 30 to 46 wt %and in several cases minority additions of Nb, W, or both. One steel contained 3.3 wt % Al. Kinetics were measured gravimetrically over periods of 6 to 100 h and found to be parabolic in all cases except for the Al-containing steel, which oxidized in an irregular and irreproducible fashion. All steels formed an external scale of Cr₂O₃ with a Mn-rich spinel layer at the outer surface. Beneath this scale was a layer of alloy depleted in both Cr and Mn. Within the depleted layer inter-dendritic carbides had been destroyed, leaving either oxide near the external alloy surface or voids deeper within the alloy.     

Thermal analysis of high efficiency deep grinding

Regimes of deep grinding range from creep grinding conducted at low workspeeds to High Efficiency Deep Grinding (HEDG) at fast workspeeds. At intermediate depths of cut, grinding is likely to be impossible due to high temperatures and damage to the workpiece and wheel. Analytical techniques for the determination of temperatures in deep grinding processes are discussed. An explanation is proposed for why it is possible to work efficiently at these two extremes of removal rate without experiencing the severe problems experienced in the intermediate range. Methods are required for determining the transition conditions so that process engineers can select process conditions for efficient material removal and high quality of manufactured products using high efficiency deep grinding. This paper provides a method for order of magnitude estimation of temperatures. It is proposed that the angle of inclination of the contact plane is an important parameter for the achievement of high workspeeds. It is argued that workpiece melting provides an ultimate boundary for energy dissipation within the workpiece.     

Parameters and micromechanisms of fatigue crack growth in sheet magnesium alloy samples

Growth rates of part-through and through fatigue cracks have been measured for two magnesium alloys — MA12 and IMV6 — and the micromechanisms of fatigue fracture were studied at all stages of growth. Conclusions about the peculiarities of the kinetics and micromechanisms of part-through and through crack growth, depending on the applied stress amplitudes and alloy structure, are made from a comparison of the results obtained.     

Temperature measurements in a laminar plasma jet generated at reduced pressure

Double electrostatic probe method and Boltzmann-plot method are applied to measure the electron temperature and the excitation temperature of a DC laminar argon plasma jet generated at reduced pressure. Attempts are also made to measure the gas temperature by using a pair of WRe-5/26 thermocouple. Experimental results show that the measured excitation temperature at the jet center increases with the vacuum chamber pressure and the arc current, but is appreciably lower than the measured electron temperature, indicating that the plasma jet under study is evidently deviated from the LTE state. The temperature indicated by the thermocouple probe is much lower than the measured excitation temperature and electron temperature. Theoretical analysis shows that the thermocouple method intended for gas temperature measurement contains very large errors due to rarefied-gas heat transfer effects, and thus is unsuitable for this purpose.     

The role of ricochet impacts on impact vaporization

Vaporization of carbonate targets by hypervelocity impact increases with decreasing impact angle (from the horizontal), in contrast with expectations based only on peak shock pressures. Experiments at the NASA Ames Vertical Gun Range were designed to allow isolating the underlying controlling processes and probing the vapor composition using high-speed spectroscopy. Vaporization associated with the maximum peak pressures (first contact) was separated from vaporization generated only by downrange ricochet impacts through the use of split targets. Four telescopes isolated the vapor with different velocities and revealed that grazing ricochet debris downrange contributed a significant fraction to the overall vaporization process. These results can be understood by the high temperatures and low pressures created by high strain-rate shear.     

A review on spindle thermal error compensation in machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.     

一线总线型温度传感器在多点测温中的编码优化

运用数字型传感器DS18X20按一线总线方式进行多点测温的关键技术是传感器的地址编码问题。使用少数几位十进制编码取代48位二进制序列号作地址编码容易在工程中实施。根据地址码与序列号的关系介绍了3种处理方式：手工编制关系表、逐次比较式建立关系表和内嵌式智能建表，并对3种处理方式的可行性和实用性进行了比较。根据器件结构特征重点分析了效率最高的了第3种方法，并阐述了编码器的设计和使用方法。     

Environmental performance of a naturally ventilated city centre library

To tackle climate change it is essential to reduce carbon dioxide emissions. To this end, it is important to reduce the energy demands of non-domestic buildings. Naturally ventilated buildings can have low energy demands but the strategy is difficult to implement in deep plan, urban locations. The Frederick Lanchester Library at Coventry University, UK, incorporates natural ventilation, daylighting and passive cooling strategies. By using lightwells and perimeter stacks to supply and exhaust air, it can be ventilated by natural means despite its deep plan form and sealed façade. This paper describes the building and presents the energy consumption and the internal temperatures and CO₂ levels recorded in 2004/2005. The building's performance is compared to the original design criteria and good practice guidelines. Recommendations for the design of such buildings are made and the likely performance in other UK cities is assessed. It is concluded that the building uses under half the energy of a standard air-conditioned building and yet, in summer, can keep the interior comfortable and up to 5 °C below ambient. The design would perform equally well in the typical weather conditions experienced at 13 other UK cities, but not in London. It is concluded that deep-plan, naturally ventilated buildings with sealed facades, if well designed, could maintain thermal comfort in all but a very few UK locations, whilst consuming much less energy than even good practice standards.     

Temperatures and ages of boxed beef packed and distributed in Canada

Boxes of beef were examined when product was packed and when boxes were loaded out of five packing plants, when boxes were loaded into and loaded out of seven refrigerated warehouses, and when boxes were received and opened at 21 retail stores. At each stage of handling at each facility, the boxes to be examined were selected at random. For each selected box, the temperature of product at the centre of the box was measured, and the date of packing and the plant of origin were noted. When cuts were packed, the minimum, median and maximum temperatures were about 2, 6 and 18 °C, respectively. Temperatures were successively lower when boxes were loaded out of packing plants, into warehouses and out of warehouses. When loaded out of warehouses, the minimum, median and maximum temperatures were about −2, 1 and 8 °C, respectively. The ranges of temperatures were similar, but the median temperatures were about 2 or 1.5 °C, respectively, when boxes were received at or were opened at retail stores. At packing plants and warehouses, the temperatures of manufacturing and ground beef were lower than those of cuts, but at the retail store the temperatures of all types of product were similar. When boxes were opened at retail stores, the minimum, median and maximum ages of cuts were about 2, 20 and 130 days, respectively; and the corresponding ages for manufacturing and ground beef were 2, 7 and 56 days, respectively. The data indicate that boxed beef is generally cooled to and maintained at temperatures within the range sought by the meat industry. However, cooling to chiller temperatures of product that is packed while warm can take several days; and some product is held for times that are excessive in view of the temperatures of boxed beef.