大长径比自旋弹箭横向自振特性的有限元计算方法与结果分析

本文研究大长径比自旋弹箭在飞行时横向振动的自振特性。本文将转子动力学应用于弹道学 ,采用有限元法 ,建立自旋弹箭横向振动自振特性方程。同时给出了计算方法。利用该方程和该方法 ,开发了相应的计算程序。通过数值计算 ,可给出细长旋转弹箭飞行时的进动转速和临界转速 ,以及相应的位移和角度振型。利用该程序 ,进行了实例计算和分析。     

Poly(butylene terephthalate)–clay nanocomposites prepared by melt intercalation: morphology and thermomechanical properties

Nanocomposites based on poly(butylene terephthalate) (PBT) and an organoclay (Cloisite 30B) were prepared by melt blending using a twin‐screw extruder. Two kinds of PBTs, ie PBT‐A and PBT‐B, with different inherent viscosities (η_inh), were used for this study (η_inh of PBT‐A and PBT‐B were 0.74 and 1.48, respectively). Dispersion of the clay layers in the PBT nanocomposites was characterized by using X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Tensile and dynamic mechanical properties and non‐isothermal crystallization temperatures of the nanocomposites were also examined. Nanocomposites based on the higher‐viscosity PBT (PBT‐B) showed a higher degree of exfoliation of the clay and a higher reinforcing effect when compared to the composites based on the lower‐viscosity PBT (PBT‐A). The clay nanolayers dispersed in PBT matrices lead to increases in the non‐isothermal crystallization temperatures of the PBTs, with such increases being more significant for the PBT‐B nanocomposites than for the PBT‐A nanoocomposites. Copyright © 2004 Society of Chemical Industry     

Influence of ethyl methacrylate content on the volume‐phase transition of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] microgels

A novel series of temperature‐sensitive poly[(N‐isopropylacrylamide)‐co‐(ethyl methacrylate)] (p(NIPAM‐co‐EMA)) microgels was prepared by the surfactant‐free radical polymerization of N‐isopropylacrylamide (NIPAM) with ethyl methacrylate (EMA). The shape, size dispersity and volume‐phase transition behavior of the microgels were investigated by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS) and differential scanning calorimetry (DSC). The transmission electron micrographs and DLS results showed that microgels with narrow distributions were prepared. It was shown from UV–Vis, DLS and DSC measurements that the volume‐phase transition temperature (VPTT) of the p(NIPAM‐co‐EMA) microgels decreased with increasing incorporation of EMA, but the temperature‐sensitivity was impaired when more EMA was incorporated, causing the volume‐phase transition of the microgels to become more continuous. It is noteworthy that incorporation of moderate amounts of EMA could not only lower the VPTT but also enhance the temperature‐sensitivity of the microgels. The reason for this phenomenon could be attributed to changes in the complicated interactions between the various molecules. Copyright © 2004 Society of Chemical Industry     

Facile modifications of polyimide via chloromethylation: II. Synthesis and characterization of thermocurable transparent polyimide having methylene acrylate side groups

From chloromethylated polyimide, a useful starting material for modification of aromatic polyimides, a thermocurable transparent polyimide having acrylate side groups was prepared. In the presence of 1,8‐diazabicyclo[5,4,0]undec‐7‐ene, chloromethylated polyimide was esterified with acrylic acid to synthesize poly(imide methylene acrylate). The polymer was soluble in organic solvent, which makes it possible to prepare a planar film by spin coating. The polymer film became insoluble after thermal treatment at 230 °C for 30 min. Optical transparency of the film at 400 nm (for 1 µm thickness) was higher than 98 % and not affected by further heating at 230 °C for 250 min. Adhesion properties measured by the ASTM D3359‐B method ranged from 4B to 5B. Preliminary results of planarization testing showed a high degree of planarization (DOP) value (>0.53). These properties demonstrate that poly(imide methylene acrylate) could be utilized as a thermocurable transparent material in fabricating display devices such as TFT‐LCD. Copyright © 2004 Society of Chemical Industry     

Precision equipment for symmetrical bending— Part 1. The loading system

The design and performance of precision bending equipment for testing straight beams with constant rectangular section under a pure bending moment is described. Part 1 deals with the loading arrangements and Part 2 with the rig for measuring beam deflection. The methods for recording deflection of strain gauges applied on the beam have been described elsewhere.^1–4
The reactions to the deadweight gravity loads are taken via ball bearings. The total bending moment inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2Ga confidence interval about the mean (2G_cim), is about ± 25 x. 10^-4%, for 23 tests with a steel beam with 15 mm × 75 mm cross sectional dimensions, loaded to 1-1.5 mm/m strain.
The measuring rig stands on the beam via hardened and polished spherical segment feet and uses a capacitive transducer system with less than 5nm resolution. Various application tasks are described. The total inaccuracy of the measured deflection, i.e. apart from bending moment inaccuracy, is about ± 35 times 10^4% for about 10 reproduced, not repeated, tests with the same steel beam. The deflection for such a beam is of the order of 2 to 4 mm.     

液化天然气供气站的工艺设计

〗LNG供气站的设计核心是工艺设计，设计中应注意以下几点：正确处理技术先进性与经济合理性的关系，综合权衡设置费与运营费的比例，力求项目全寿命费用最低；大多数城市LNG供气站均利用空气气化LNG，单罐容积为100 m³的真空压力式储罐广泛用于储存量为1200 m³以下的LNG供气站；为正确设置储罐安全阀的开启压力和排放压力，必须根据储罐的最高工作压力按照规范正确确定储罐的设计压力；储罐上2套独立的液位计和高、低限报警自动切断装置可确保储罐安全运行；空温式气化器的气化能力按用气城市高峰小时计算流量的1.3~1.5倍确定，为便于自然化霜应设置2套空温式气化器切换使用；空温式气化器出口串接水浴式加热器可提高冬季或雨天出口天然气温度，保护碳钢管道并降低供销差；LNG储罐区应设置围堰，消防用水量为喷淋与水枪用水量之和。最后建议，必须尽快颁布国家LNG设计规范，以提高我国的LNG设计水平。     

Generalized difference control of parallel streams temperatures

A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes.     

改性生物质作为型煤黏结剂的研究

探讨了用NaOH改性生物质秸秆作为型煤黏结剂的可行性,考察了NaOH溶液浓度对生物质改性的影响以及生物质添加量、无机物(MgO和MgCl2)添加量对型煤机械强度、防水性能和着火温度的影响。研究结果表明,NaOH改性液的质量分数为1.0%~2.0%时,制得的生物质型煤有较高的机械强度;生物质添加量在2%~20%时,随生物质添加量的增加,机械强度增加,着火温度降低,但防水性较差;而在生物质型煤中加入适量无机黏结剂后,型煤有很高的浸水强度,表现出优越的防水性能。     

微型生化分析仪样品室温度控制系统研究

结合微型生化分析仪样品室的要求,设计了一种基于单片机的微型生化分析仪样品室温度控制系统.它以AT89S51为核心,采用单总线高精度数字温度传感器DS18B20对样品室温度采样,同时利用汇编语言编写温度设定与控制程序,采用半导体制冷的方式,实现了温度在25℃、30℃、32℃和37℃四个温度值的稳定,控制精度达±0.5℃.     

Operation of superconducting fault current limiter using vacuum interrupter driven by electromagnetic repulsion force for commutating switch

Using conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20315