钛无缝异径管试制成功

与管路系统相配套的管件主要有四种:管头、异径管(大小头)、三通和管帽.采用无缝管件可以减少管路传输阻力、提高抗腐蚀性和延长设备使用寿命.西北有色金属研究院在1991年首创无缝钛弯头之后,又试制成功钛无缝异径管管件.用旋压方法生产异径管虽然可行,但由于模具昂贵、生产周期长、效率低,难以适应市场需要.以往的异径管管件大多采用卷焊,卷焊工艺过程繁杂、成品率低、质量差,不能满足化工部标准.该院用特种热挤压法生产异径管,质量与无缝钛弯头一样达到了化工部要求,内外表面精度达到国标要求,金相组织为等轴状细晶粒,     

某新型窗口式排水井的设计及应用

针对传统窗口式排水井使用过程中存在的缺陷,提出了一种新型窗口式排水井。该新型窗口式排水井在窗口位置预埋异径管作为进水窗口,使用盲法兰进行封堵,不仅封堵方便、密封性较好,且泄流能力增大,使排水井更为稳定。     

一种八辊冷轧机的轧辊偏心补偿控制

轧辊偏心是影响高精度板带材质量的重要因素,通过对八辊冷轧机轧辊偏心信号的分析计算,得出了一种偏心补偿控制方法。通过对轧辊圆周定点轧制力数据采样间接得出偏心信号,然后将偏心信号处理转换为液压偏心调整机构的电压信号,以补偿轧辊偏心的影响。补偿后,轧制出口厚度精度得到了明显改善。     

无缝钢管三辊轧制荒管壁厚偏心分析

 三辊轧制荒管壁厚偏心控制是无缝钢管壁厚精度控制的重要环节。基于生产试验分析了荒管壁厚偏心的特征,运用解析方法建立了三辊轧制荒管壁厚偏心的理论计算模型,针对实际生产条件进行了预报计算与比较,分析了三辊轧管工艺因素对荒管壁厚偏心的影响特点,并进一步讨论了改善荒管壁厚偏心的方法。研究结果表明,荒管壁厚偏心的基本特征表现为“偏心螺旋型”,在荒管壁厚不均中的占比达80%以上;毛管壁厚偏心和温度偏心是影响三辊轧制荒管壁厚偏心的最重要因素;增大三辊轧制减壁量、降低毛管温度、提高轧辊台肩高度、增大轧辊转速有利于减小荒管壁厚偏心。     

冷轧机轧辊偏心的自抗扰重复补偿控制

针对冷轧机由于轧辊偏心扰动引起出口厚度波动问题,提出一种轧辊偏心自抗扰重复补偿控制策略。首先设计改进型重复控制器对由轧制力反映出的偏心扰动信号进行高精度跟踪,从而在无需偏心扰动信号数学模型的条件下获得偏心补偿信号;然后设计自抗扰控制器改善重复控制器的稳定性和鲁棒性,同时对轧辊偏心扰动进行快速补偿。仿真结果表明,所提出的控制方法在系统参数发生摄动及偏心信号发生变化的情况下,仍能够对轧辊偏心进行有效补偿。     

基于自适应稀疏表示的冷轧轧辊偏心诊断

轧辊偏心是冷连轧过程中导致带钢厚度偏差和质量缺陷的重要因素之一,针对轧辊偏心特征由于机架间的耦合作用和累计效应难以提取的问题,提出基于稀疏自适应匹配追踪(sparsity adaptive matching pursuit, SAMP)的偏心诊断方法。首先根据轧辊偏心模型构建偏心特征冗余字典,采用正交匹配追踪(orthogonal matching pursuit, OMP)算法将厚度数据进行稀疏分解,提取轧辊偏心特征。其次,采用匹配测试方法预测初始稀疏度,并通过迭代估计偏心和噪声的能量自适应地确定最优稀疏度,对偏心信号进行去噪。最后重构偏心信号并进行频谱分析,辨识各机架的轧辊偏心状态。经过仿真和实验验证,本方法比小波分析方法对早期偏心故障有更好的诊断效果,诊断结果为监控轧辊工作状态、优化换辊周期提供了可靠的依据。     

基于神经网络的可逆冷带轧机偏心的检测与补偿

详细讨论了可逆冷带轧机轧辊的偏心问题,分析了偏心产生的原因,并在前人偏心补偿方法的基础之上提出了一种基于神经网络的用于轧辊偏心检测和补偿的方法,进行了仿真研究,提出了轧辊偏心补偿在实际当中的实现方法以及可行性.     

无缝钢管斜轧穿孔毛管壁厚偏心分析

斜轧穿孔毛管壁厚偏心是导致无缝钢管壁厚不均的重要原因,深入认识毛管壁厚偏心的特征和影响因素,是控制无缝钢管壁厚精度的必要前提。基于生产试验对无缝钢管斜轧穿孔毛管壁厚偏心进行了表征,运用解析方法建立了无缝钢管斜轧穿孔毛管壁厚偏心的计算模型,针对实际生产条件进行了预报计算和比较,研究了斜轧穿孔工艺因素对毛管壁厚偏心的影响,并分析了改善毛管壁厚偏心的方法。研究结果表明,无缝钢管斜轧穿孔毛管壁厚偏心的基本特征表现为"偏心螺旋型",在毛管壁厚不均中占比70%以上;管坯温度偏心是影响毛管壁厚偏心非常重要的因素,建议控制在10℃以内;增大斜轧穿孔变形量和毛管旋转次数有利于改善毛管壁厚偏心,相应的措施是减小送进角、增大顶头直径、减小管坯直径、增大轧辊过渡带长度;增大斜轧穿孔速度有利于改善毛管壁厚偏心。     

可逆冷带轧机偏心的影响与检测

讨论了冷带轧机中轧辊偏心的起因 ,深入分析了偏心对带材厚度的影响 ,提出了一种将轧辊等效 ,然后作N次等分的轧辊偏心检测方法 ,并应用最小二乘方法计算轧辊偏心量的大小。     

一种单机架可逆式冷轧机轧辊偏心补偿方法

在深入分析轧辊偏心对板带材厚度影响的基础上,从偏心控制原理和偏心信号模型入手,研究了一种单机架可逆冷轧机轧辊偏心补偿方案。该方案的检测及运算过程简单,运算量小,采用等间距抽样采集数据,避免了传统偏心补偿的缺陷。其偏心补偿投入唐钢1〖KG-*9〗650 mm可逆式冷轧机厚度控制系统后,控制效果良好,产品厚度偏差提高到±5 μm以内。     

Investigation of Flow Upstream of Orifices

A physical model study is conducted to investigate the flow field upstream of orifices. In particular, new experimental data for the upstream flow pattern resulting from multiple orifices, an orifice near a free surface, and a large orifice (where the pressure gradient across the orifice cannot be ignored) are collected and presented. A new potential flow solution for flow behind orifices is developed to include pressure gradient effects as well as to accurately superpose the solution due to multiple orifices and determine a solution close to orifices. The proposed solution compares well with the measured data for multiple orifices and for an orifice near a free surface. For a large orifice, the skew in the velocity profile in the vertical direction due to the pressure gradient is accurately predicted.     

Importance of Lower-Bound Capacities in the Design of Deep Foundations

There is generally a physical limit to the smallest possible capacity for a deep foundation. However, a lower bound on the capacity has rarely been accounted for in performing reliability analyses and developing reliability-based design codes. The objectives of this paper are to investigate the effect of having a lower-bound capacity on the reliability of a geotechnical engineering system and to propose a load and resistance factor design (LRFD) checking format that includes information on the lower-bound capacity in design. It is concluded that a lower-bound capacity can cause a significant increase in the calculated reliability for a geotechnical design even if it is an uncertain estimate. Two alternative LRFD formats that incorporate lower-bound capacities and that would not require substantive changes to existing codes are proposed. Real-world examples dealing with the design of onshore and offshore foundations indicate that the incorporation of a lower-bound capacity into design is expected to provide a more realistic quantification of reliability for decision-making purposes and therefore a more rational and efficient basis for design.     

Approximation of Well Function and Identification of Leaky Aquifer Parameters

The existing equation for leaky aquifers is transformed into a nondimensional form using new parameters and a scaled well function for leaky aquifers is proposed. A computationally simple function is developed for accurately approximating the scaled well function for the practical range of the parameters. Utilizing this function (approximation), an optimization method is proposed for identifying the leaky-aquifer parameters from observed drawdowns. The new function has an enhanced utility when a repetitive numerical evaluation of the well function for leaky aquifers is needed, e.g., while estimating the aquifer parameters using optimization or Kalman filter or artificial neural network methods. The application of the proposed method is illustrated using a few sets of published data. The proposed method outperforms the extended Kalman filter method, based on the reported results in the literature.     

The influence of simulated mutilation upon the perception of the human figure.

"Employing 14 sets of anisekonic lenses of ascending power in the psychophysical method of limits, the "distortion thresholds" for an apparently mutilated figure and for a normal figure were established for a sample of 12 S's. The results show the threshold for the mutilated figure to be significantly higher than for the normal figure. This indicates that a greater amount of optical change is required to bring about a concomitant perceptual change for the mutilated as compared with the normal figure." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Orientation of selective effects of body tilt on visually induced perception of self-motion

In this study, to test an inference from the 1991 Previc hypothesis that right-handers have a right-ear advantage, the durations of hearing for the right and left ears were compared for 81 right- and 45 left-handed high school students. In the present study, right-handedness was associated with a right-ear advantage and left-handedness was associated with a left-ear advantage. In addition, there was a significant positive correlation between the durations of hearing for the right and left ears and the scores for right-handedness for right-handed subjects. The durations of hearing for the right and left ears were negatively correlated with the left-handedness for left-handed subjects. These results suggest hand preference may be related to asymmetry of aural sensitivity.     

Theoretical Interpretation of Impulse Response Tests of Embedded Concrete Structures

For a concrete beam resting on a bed of sand, an analytical solution technique is derived by which the mobility can be identified. To achieve realistic predictions, significant damping in the bed needs to be introduced. The modest damping of the concrete has little effect on the mobility for small frequencies whereas it has a significant effect for higher frequencies. An imperfection in the bed in terms of a void increases the mobility dramatically for low frequencies whereas the mobility for higher frequencies is almost unchanged. An imperfection in the beam in terms of honeycombing of the concrete, on the other hand, manifests itself by increasing the mobility for high frequencies while leaving the mobility for small frequencies less influenced. These latter conclusions are in good agreement with field experience for concrete slabs resting on soil.     

钢管外表面磨光机组主要技术参数的技术

钢管外表面磨光机组可清除钢管外表面的缺陷,还可对钢管进行整体磨光加工,并能清除钢管表面的氧化铁皮。为此设计了一套钢管外表面磨光机组,经合理选用技术参数,实现了钢管外表面的整体修磨,提高了钢管外表面质量。     

夹送辊的力能参数计算

本文介绍夹送辊力能参数的计算方法，可供设计计算参考     

Closed-Form Expression of the Response Time of an Open Channel

Computing accurately the response time of an open channel is of extreme importance for management operations on canal networks, such as feed-forward control problems. The methods proposed in the literature to approximate the response time do not always account for the influence of a cross structure at the downstream end of a canal pool, which may have a significant impact on the response time. This paper proposes a new approach to compute the response time, accounting explicitly for the backwater and the feedback effects due to the downstream cross structure. The method provides a distributed analytical expression of the response time as a function of the characteristics of the canal (geometry, roughness) and of the downstream cross structure. A test canal with a weir or a gate at the downstream end is used to compare the new method with some of the others. Results show that the proposed expression accurately reproduces the response time for various backwater and downstream boundary conditions.     

Probabilistic Approach for Budgeting in Portfolio of Projects

This paper presents a mathematical model for calculating the budgetary impact of increasing the required confidence level in a probabilistic risk assessment for a portfolio of projects. The model provides a rational approach for establishing a probabilistic budget for an individual project in such a way that the budget for a portfolio of projects will meet a required confidence level. The use of probabilistic risk assessment in major infrastructure projects is increasing to cope with major cost overruns and schedule delays. The outcome of the probabilistic risk assessment is often a distribution for project costs. The question is at what level of confidence (i.e., the probability that budget would be sufficient given the cost distribution) should be used for establishing the budget. The proposed method looks at a portfolio of such projects being funded by the same owner. The owner can establish a target probability with respect to its annual budget. The model can help the owner establish confidence level for individual projects and also examine the effect of changing the confidence level of the portfolio budget on the budget and the confidence level of individual projects. The paper is relevant to practitioners because it provides a methodology for establishing confidence levels by the owner agencies in the emerging field of cost risk assessment for infrastructure projects. A numerical example is provided using actual transit project data to demonstrate the model application.