Quantification of Tafel coefficients according to passive/active state of steel carbonation‐induced corrosion in concrete

Statistical quantification of Tafel coefficients is investigated in this study for isolated steel rebar embedded in concrete. The survey is supported by a wide experimental campaign carried out earlier to characterize the passive and active states of carbonation‐induced corrosion of steel. Electrochemical measurements (polarization resistance, corrosion potential, Tafel coefficients) and gravimetric estimations of iron loss were regularly conducted over 417 days on 108 concrete specimens. The statistical analysis reveals that the mean value of Tafel coefficients, both cathodic and anodic, is higher under active corrosion, which seems to contradict the general tendency found for chloride‐induced corrosion, while their coefficient of variation is smaller. The statistical inference was based on the first step of distributions fitting the experimental data and then on the second step of goodness‐of‐fit tests. The most suitable of the distributions proposed were the Burr, Rayleigh, and Gamma distributions. A similar analysis was made for the corrosion potential and polarization resistance. The findings of the study will be valuable for probabilistic approaches to corrosion where probabilistic distributions are required.     

Modelling of induced aeration in turbine aerators by use of radial basis function neural networks

Gas induction in agitated vessels with turbine impellers can be modelled accurately by means of radial basis function neural nets. The results obtained with the radial basis neural net were significantly better than those obtained by multivariate regression models or standard back propagation neural nets. Moreover, by using the radial basis function neural net model, it was possible to conduct a sensitivity analysis of the variables affecting aeration. Increased medium density showed a strong adverse effect, while variation of the viscosity can cause an increase or a decrease in the rate of aeration, depending on the prevailing process conditions.     

枝晶凝固过程中的溶质浓度分布模拟

采用元胞自动机方法(cellular automation)对单个枝晶凝固过程中的显微偏析和枝晶形貌进行了模拟，在模拟的过程中，对固相和液相中的溶质传输分别进行了计算，同时考虑到凝固过程中同相分数的变化对溶质传输的影响与文献中通常采用的浓度势方法的计算结果进行对比，模拟结果显示本文使用的计算方法模拟显微偏析过程中波动小、结果更为稳定。     

Design of experiments for Quick U-building method for building energy performance measurement

Quick U-building (QUB) is a method for short time measurement of energy performance of buildings, typically one night. It uses the indoor air temperature response to the power delivered to the indoor air by electric heaters. This paper introduces a method for estimating the expected measurement error as a function of the amplitude and the time duration of the input signal based on the decomposition of the time response of a state-space model into a sum of exponentials by using the eigenvalues of the state matrix. It is shown that the buildings have a group of dominant time constants, which gives an exponential response, and many very short and very large time constants, which have a small influence on the response. The analysis of the eigenvalues demonstrates that the QUB experiment may be done in a rather short time as compared with the largest time constant of the building.     

套管螺纹全参数化几何模型及旋合仿真

根据圆锥螺旋面形成理论,推导出了构成ＡＰＩ圆套管螺纹四段圆锥螺旋面的方程,建立了套管螺纹全参数化的几何模型,以此模型研制了接箍和套管内外螺纹旋合过程的计算机仿真系统,可用于研究套管螺纹设计参数的变化对接箍和套管内外螺纹旋合几何接触性能的影响。     

Configuration-oriented product modelling and knowledge management for made-to-order manufacturing enterprises

In made-to-order (MTO) manufacturing enterprises (ME), product architectures are usually modularised and components standardised. Product configuration is a key technology for order realisation in MTO–ME and is a typical knowledge-based application. Through a configuration process, product modules or components are selected and assembled according to customer requirements. Product configuration relates to a great deal of knowledge that represents complexity relations among components or modules, such as configuration rules and assembly constraints. Traditional product modelling techniques are focused mainly on physical product modelling and geometric representation, which makes them insufficient to help in the product configuration process. This paper discusses configuration-oriented product modelling and knowledge management for MTO–ME. A general process of product configuration modelling is proposed. The configuration model represents a product family from which a specific configuration solution or product variant can be derived. Actually, configuration modelling is a process which captures and represents product knowledge. In this paper, product knowledge is organised and managed through a knowledge component (KCOM) that includes configuration rules and constraints. A KCOM-based product knowledge representation model is presented. Finally, a PDM system is extended to support product modelling and knowledge management for MTO configurable products .     

MODELLING OF P/M FORMING PROCESSES BY FEM

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考虑围压效应和强度脆性跌落的岩石全应力–应变曲线统计损伤模拟方法

为了建立能够较准确地描述岩石全应力–应变曲线的统计损伤模拟方法,针对目前统计损伤本构模型在模拟围压效应和强度脆性跌落方面存在的严重缺陷,首先,基于三轴压缩条件下脆性岩石基本变形特征,将岩石视为由软物质和硬物质两种细观化材料串联组成,建立宏细观物质变形分析模型;然后,基于瞬时应变分析方法和统计损伤理论,分别提出软物质和硬物质的变形分析方法,从而建立能够考虑围压效应和强度脆性跌落的岩石全应力–应变曲线统计损伤本构模型,给出参数的确定方法;最后,通过模型验证与分析,模型不但能够描述岩石初始宏观变形特征与围压之间的关系,也能够消除岩石轴向峰后理论变形曲线存在的随机性,从而能够较准确地模拟出岩石全应力–应变曲线,表明方法具有一定的合理性和可行性。     

湖北省优秀博士学位论文的统计分析

统计分析了湖北省近4年的378篇优秀博士学位论文的相关数据,运用定量分析的方法重点剖析优秀博士学位论文的学位授予单位和学科领域的分布特点,总结出湖北省优秀博士学位论文产生的一些必要条件和规律,并提出了一点建设性的意见。     

Optimized centre-feed clarifier design for the Tai Po Sewage Treatment Works,Hong Kong

Stability of sludge blanket is a critical factor controlling the performance of clarifiers. A three-dimensional computational fluid dynamics (CFD) model was applied to optimize the clarifier design at the Tai Po Sewage Treatment Works, Hong Kong. Validated by field data, the CFD model evaluated the key clarifier design elements including side-water depth, centre-feed inlet, flocculation well and returned activated sludge (RAS) flow. Based on field observations and modelling results, the new design aims at eliminating the strong turbulence typical of centre-feed inlets in the clarifier, thus creating a better flocculation environment, and reducing disturbance to the sludge blanket. The modelling results also demonstrated a marked improvement in clarifier performance after the increase in clarifier depth and hence sludge storage capacity. The increased storage capacity reduces the risk of high sludge blanket levels upsetting the clarified effluent quality under high flow or solids loading conditions.