曳引式电梯自提升安装法

曳引电梯自提升安装法,是一种较为合理的安装方法。本文介绍了该方法的特点、工艺流程、施工准备、安装过程、调整程序,供电梯安装单位参考。     

论解放战争时期中间路线的兴衰及成因

抗日战争胜利初期,国共内战迫在眉睫。为挽救危局,强国富民,中间人士提出所谓中间路线,企图走“第三条道路”实现和平建国。在反动政府的强力弹压和中共的教育帮助下,中间路线退出历史舞台。民主党派的转型历程充分昭示了中国人民在中共领导下走上新民主主义道路的必然性。     

汽轮机回热系统给水焓升的最优分配

从汽轮机回热系统的实际情况出发，运用非线性规划理论和计算机技术，解决了给水焓升设计中的最优分配问题。结合具体实例，针对国产200MW汽轮机回热系统给水焓升的分配进行了说明。     

Assessment of Capillary Rise from Shallow Groundwater by the Simulation Model SIMWASER Using Either Estimated Pedotransfer Functions or Measured Hydraulic Parameters

The performance of the water balance and crop growth model SIMWASER to estimate the water supply of a lawn by capillary rise from shallow ground water was investigated by using lysimeter measurements with a sandy and a clayey soil. Moreover the robustness of the model was evaluated by running it either with measured hydraulic soil parameters or with estimated pedotransfer functions (PTFs) derived from texture and bulk density. Simulations were performed for the years 1996–1998 with input data from the lysimeter station Berlin-Dahlem (Germany) for lysimeters containing undisturbed sandy or clayey soil monoliths, with groundwater at 135 cm depth. Simulated evapotranspiration and percolation/capillary rise were in good agreement with the measured data for all variants, while simulated soil water storage was acceptable only for the variants using hydraulic soil data based on laboratory measurements or using PTFs derived from known soil class and bulk density. PTFs based on mean total pore volume of the respective soil classes yielded soil water storages which were evidently too high; therefore they should be used with care and must be avoided at all in simulating the soil water balance of arid sites with shallow groundwater.     

On using peak amplitude and rise time for AE source characterization

Acoustic Emission (AE) signals, which are electrical version of acoustic emissions, are usually analysed using a set of signal parameters. The major objective of signal analysis is to study the characteristics of the sources of emissions. Peak amplitude(P _a ) and rise time(R _t ) are two such parameters used for source characterization. In this paper, we theoretically investigate the efficiency ofP _a andR _t to classify and characterize AE sources by modelling the input stress pulse and transducer. Analytical expressions obtained forP _a andR _t clearly indicate their use and efficiency for source characterization. It is believed that these results may be of use to investigators in areas like control systems and signal processing also     

关于离子注入中温升的探讨

本文在理论和试验两个方面探讨了离子注入中的热效应和温升现象。注入样品的温升对离子注入层的性能有直接影响。分析了理论计算注入样品温升的一些情况。给出了实际测量注入样品温升的几种试验方法。阐明了控制注入样品温升的若干可能途径。     

浅谈变频器供电条件下电动机的温升与对策

随着变频调速技术的蓬勃发展，变频器供电电机的温升问题已引起人们的广泛关注。本文首先讨论了电动机的温升限度；然后结合感应电机温升实验的相关数据分析了变频器供电对电动机温升的影响及其原因；最后从降低发热量和提高散热能力两方面提出缓解电机温升的措施，并指出了实际应用中应注意的问题。     

钢水化学热法升温技术的研究

依据热力学原理，用计算机计算了某些元素与合金的氧化热效应。综述了各种上化学热法升温技术的应用效果。分析讨论了发热剂的类型，升温速度和热效率问题等。     

高层钢结构的安装测控技术

介绍了高层钢结构安装测控的基本方法和工艺流程 ,并对高层钢结构安装中的控制要点和控制方法进行了详细论述。     

Finite-size effects in surface tension: Thermodynamics and the Gaussian interface model

It has been suggested by Kayser that finite-size effects associated with capillary waves might play a significant role in some surface tension measurements; for capillary rise between plates a distance D apart, an effect varying as 1/D and apparently observable in measurements, was proposed. In reconsidering this problem, one must analyze the thermodynamics of finite-size corrections to surface tension. In particular, one sees that capillary rise between plates does not measure the interfacial free energy density but, rather, a derivative of the interfacial free energy with respect to a system dimension. The quantity needed to draw definite conclusions, the finite-size residual free energy, can be calculated within the harmonic or Gaussian capillary wave model in d spatial dimensions with the aid of Poisson summation techniques and should yield the correct leading asymptotic behavior. For d=3 and experimentally relevant parameter values, the results are independent of the short-wavelength cutoff needed in the model and can be checked against the theory of conformai covariance at two-dimensional critical points. It is found that the finite-size effects in capillary-rise measurements of surface tension vary as 1/D ² (with a universal coefficient) but are too small to be seen in current experiments.Invited paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.