挠性枢轴支承扭转刚度的计算探讨

挠性枢轴支承是一些用于航空，航天领域内的高精密装置的关键部件之一，它的扭转刚度及对应的变形状态是支承在工作时必须控制的重要性能指标，这些指标如不符合要求，整个装置将会失效。该数产品目前仍依赖进口。本文应用计算功能与ＡＤＩＮＡ相同的ＭＦＥＰ软件中的ＭＦＧＳ方法对有着支承样品的上述性能进行了非线性有限元计算和相应的线性有限元计算，计算结果表明，支承弹簧片插入弧形体中那部分的实际焊接深度对上述的性能有很     

Power Evaluation of the Los Angeles Oxygen–Fed Ozone System

The Los Angeles Department of Water and Power (LADWP) operates a 600 mgd (2,270 ML/day) direct filtration water treatment plant which includes a 7,900 lb/day (149 kg/hr) ozonation system. Ozone is applied as a preoxidant for the purposes of disinfection and microflocculation. The ozonation system is unique in that high purity oxygen is generated on–site and is used as the feed–gas in a once–through system. The process was selected through competitive bids and evaluated for total present worth from 20–year life cycle costs which included capital plus energy expenses. Power consumption (and penalty) was valued at $6,500/kW. System power demand was measured at nine ozone production rates. A minimum specific energy of 6.5 kWh/lb (14.3 kWh/kg) of ozone was observed when generating ozone at a concentration between 5 and 6 % (wt) [65 and 80 g/m³; where the standard temperature and pressure are 70F (21.11 C) and 1 atm, respectively]. The test methodology and data assessment considerations were developed jointly by the owner and manufacturer, and produced results with practical significance beyond the performance testing objective.     

中厚板轧机刚度模型的工程应用

分析了韶钢2500mm中厚板轧机弹跳方程的测试和建模方法，通过计算厚度和实测厚度的比较，说明压靠状态对厚度计算值的影响，指出为该轧机建立的弹跳方程，其厚度计算精度已接近一般激光测厚仪的水平，在规程计算、AGC调节和成品厚度控制中相当有效。     

基于ANSYS的非线性弹簧振子动力学仿真

本文在理论分析的基础上,利用MAPLE软件研究了一类弹簧振子周期运动的特点,分析了系统参数对运动周期的影响,并借助ANSYS/LS-DYNA软件用有限元方法验证了弹簧质量系统的周期。     

Way forward in meeting energy challenges in Pakistan

In this review the energy potential of Pakistan from hydro, coal, wind, solar and nuclear sources has been discussed. The new projects that are being commissioned on coal, wind, solar, hydel and nuclear-based technologies have also been mentioned. The review has also explored the future prospects of the country’s energy requirements. Pakistan has potential to produce 100,000?MW of electricity from Thar coal for 20 years, 56,000?MW of hydroelectricity, 150,000?MW of wind energy and ～50,000?MW from solar sources. The coal-fired power generation is expected to 11,500?MW in period 2017–2019. The country is moving in the right direction to cater its energy needs. However, there is a need to find local and foreign investment in the country to meet high energy demands in the country in future.     

Rural Migrants’ Residential Mobility: Housing and Locational Outcomes of Forced Moves in China

This paper analyses the residential mobility of China’s rural–urban migrants in light of evidence from Yangzhou, a medium-sized city in Jiangsu province. To evaluate the effects of forced moves induced by demolition-led redevelopment, these outcomes are compared to those of voluntary moves. The evaluation is specifically concerned with dwelling attributes and location characteristics. Dwelling attributes consist of tenure and housing facilities, while commuting distance, distance to the city centre and the length of a child’s trip to school comprise the location characteristics. Logistic regression of data from a 2012–2013 survey shows that a voluntary relocation and the intention to move prior to notification of intended demolition are likely to result in positive outcomes. The migrants’ relocation strategy involves making a trade-off between better dwelling attributes and a better location. When housing improvement is their major concern, they tend to move to peripheral areas. However, it seems that children’s educational opportunities are being factored into the trade-off. In that case, migrants purchase an apartment in a specific school district or at least move closer to it. For the sake of their children, they relegate other motives to second place.     

Physical modeling of behaviors of cast-in-place concrete piled raft compared to free-standing pile group in sand

Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method is too conservative. Only when the pile cap is elevated from the ground level, the raft bearing contribution can be neglected. In a piled raft foundation, pile–soil–raft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. The available laboratory studies mainly focused on steel piles. The present study aims to compare the behaviors of piled raft foundations with free-standing pile groups in sand, using laboratory physical models. Cast-in-place concrete piles and concrete raft are used for the tests. The tests are conducted on single pile, single pile in pile group, unpiled raft, free-standing pile group and piled raft foundation. We examine the effects of the number of piles, the pile installation method and the interaction between different components of foundation. The results indicate that the ultimate bearing capacity of the piled raft foundation is considerably higher than that of the free-standing pile group with the same number of piles. With installation of the single pile in the group, the pile bearing capacity and stiffness increase. Installation of the piles beneath the raft decreases the bearing capacity of the raft. When the raft bearing capacity is not included in the design process, the allowable bearing capacity of the piled raft is underestimated by more than 200%. This deviation intensifies with increasing spacing of the piles.     

Calibration of viscoelastic parameters by means of transients in a branched water pipeline system

In this paper, different arrangements of Kelvin–Voigt elements are implemented in an admittance matrix model to investigate the transient modeling of water distribution systems. The viscoelastic parameters are calibrated by experimental data acquired during a transient in a branched system of three HDPE pipes at the Water Engineering Laboratory of the University of Perugia, Italy. The dependence of the viscoelastic parameters on the branch characteristic time is investigated. Models with a single set of elements for all branches are compared with models with different sets of elements for each branch. When the same number of parameters is used, the former perform better than the latter. No evident correlation is found between the retardation times of the viscoelastic parameters and the branch characteristic times. The use of two measurement sections instead of one does not modify the calibration results significantly.     

Quality index and hot tearing susceptibility of Al–7Si–0.35Mg–xCu alloys

The effects of Cu addition (0.5%, 1%, 1.5%, 2%, and 3%, mass fraction) on the quality index (Q_i) and hot tearing susceptibility (HTS) of A356 alloy were investigated. According to the results, Cu addition up to 1.5% increases the Q_i by almost 10%, which seems to be due to its solid solution strengthening and dispersion hardening effect of Cu-rich Al₂Cu and AlMgCuSi compounds. However, further addition of Cu (up to 3%) decreases the Q_i by almost 12%, which is likely due to the reduction of tensile strength and elongation caused by increased volume fraction of brittle Cu-rich intermetallics and microporosities in the microstructure. It is also found that Cu increases the HTS of A356 alloy measured by constrained rod casting method. According to the thermal analysis results, Cu widens the solidification range of the alloy, which in turn, decreases its fluidity and increases the time period during which the mushy-state alloy is exposed to the hot tearing susceptible zone. SEM examination of the hot tear surfaces in high-Cu alloys also demonstrates their rough nature and the occurrence of interdendritic/intergranular microcracks as convincing evidences for the initiation of hot tears in the late stages of solidification in which there is not enough time for crack healing.     

High temperature stress–strain curves of MnS and their applications in finite element simulation

A novel method for testing stress–strain curves of non-metallic materials was presented. The high temperature stress–strain curves of MnS were preliminarily obtained and corrected to account for the influence of friction. Using the finite element method, the influence of deformation parameters on the deformation evolution of MnS inclusions was investigated based on the experimental reference data. The corresponding physical experiment was designed for comparative analysis. The results indicate that the experimental high-temperature deformation data of MnS are highly reliable. In the process of matrix deformation, the shapes of MnS inclusions change from spherical to ellipsoidal and even to lamellar. There are some differences in the morphological deformation of MnS inclusions located at different positions. With the increase in the initial size of MnS inclusions, the risk of failing the inclusion-flaw inspection increases and the forging quality further deteriorates.