A technique for characterizing microsegregation in multicomponent alloys and its application to single-crystal superalloy castings

Instrumental errors in microsegregation measurements in multicomponent alloys complicate the treatment of randomly sampled data. In this article, two new alloy-independent data treatment algorithms are presented that are capable of separating the effects of scatter in the data from the underlying segregation trends, assigning each measurement location a unique fraction solid. These new methods are physically reasonable and result in improved estimates of segregation parameters, particularly the solute partitioning at the dendrite tip. This is demonstrated by determining the microsegregation in four successive generations of single-crystal (SX) nickel-based superalloys. Artificial, noise-induced, tails commonly seen in the microsegregation profiles are also minimized. A methodology for evaluating sorting schemes is introduced that does not depend upon a priori knowledge of the partitioning direction. Comparison is made to both other sorting methods and CALPHAD predicted partition coefficients. Implications for alloy design are reported, illustrating the interaction between solute species such as Ru, Re, Co, and W.     

Analytical,numerical, and experimental analysis of inverse macrosegregation during upward unidirectional solidification of Al-Cu alloys

The present work focuses on the influence of alloy solute content, melt superheat, and metal/mold heat transfer on inverse segregation during upward solidification of Al-Cu alloys. The experimental segregation profiles of Al 4.5 wt pct Cu, 6.2 wt pct Cu, and 8.1 wt pct Cu alloys are compared with theoretical predictions furnished by analytical and numerical models, with transient h _i profiles being determined in each experiment. The analytical model is based on an analytical heat-transfer model coupled with the classical local solute redistribution equation proposed by Flemings and Nereo. The numerical model is that proposed by Voller, with some changes introduced to take into account different thermophysical properties for the liquid and solid phases, time variable metal/mold interface heat-transfer coefficient, and a variable space grid to assure the accuracy of results without raising the number of nodes. It was observed that the numerical predictions generally conform with the experimental segregation measurements and that the predicted analytical segregation, despite its simplicity, also compares favorably with the experimental scatter except for high melt superheat.     

板坯连铸机二冷水控制模型与应用

介绍一种采用目标温度控制的二冷水控制模型及其应用。该模型以冶金准则和传热学为基础,根据现场的实际工艺和设备参数,得出最佳的配水参数。各控制回路根据模型给出的配水参数,控制各回路的实际水量,以达到最佳的冷却效果。     

大气扩散模式及其应用

在进行环境质量评价时,一般都用大气扩散模式进行预测,本文分析了影响大气扩散的气象因子,讨论了高斯模式在其基本条件发生变化时的修正方法并在实际工作中进行应用。     

隧道健康动态评价模型与应用

在隧道健康安全评价的指标体系及其等级标准的基础上,通过规范化处理样本资料库中的元素,消除了指标类型和量纲的影响后,提出用集对分析方法构造可变模糊集的相对差异度函数,合理的确定了各层相关隧道健康评价指标处于级别标准区间的相对隶属函数,采用乘积标度法确定相关指标权重后,得出了隧道健康模糊综合评价动态模型.确定健康级别指标特征值后,结合实例计算证明了文中所提方法的科学性与合理性,有利于推动可变模糊集理论在土木工程领域的进一步发展.     

A stochastic model of preference change and its application to 1992 presidential election panel data.

The authors present and test a model for the evolution of preferences. Personal preferences are represented by rankings with possible ties and are posited to change under the influence of "tokens" of information in the environment. These tokens may not be directly controlled or observed by the researcher. The authors apply the model to 1992 National Election Study panel data (W. E. Miller, D. R. Kinder, S. J. Rosenstone, & NES, 1993). The parameter estimates suggest that negative campaigning played a major role in the information flow. Democrats and Republicans experienced a barrage of contradicting information about Perot; Democrats, Republicans, and Independents each received or perceived different information. A shift in the perception of the candidates led the Republicans to evaluate Bush and Perot less favorably after the election. These results demonstrate the model's potential to analyze persuasion as a real-time stochastic process and without a media content analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Physiologically based pharmacokinetic model for digoxin disposition in dogs and its preliminary application to humans

A physiologically based pharmacokinetic model for digoxin disposition developed in the rat was modified to account for the interspecies differences in tissue-to-plasma digoxin concentration ratios and applied to the dog. The model provided a quantitative assessment of the time course of digoxin concentrations in dog plasma, various tissues, and urine. It also predicted the effect of renal failure on digoxin pharmacokinetics in the dog. An attempt to scale the dog model to humans by simply considering differences in organ volumes, organ flow rates, and digoxin clearances was partially successful. Good predictions of plasma digoxin concentration and urinary digoxin excretion after a single dose and of steady-state plasma, heart, and skeletal muscle digoxin concentrations were obtained. However, the model predicted considerably higher kidney digoxin concentrations than are actually found. Although the model adequately characterized the time course of digoxin concentrations in patients with moderate renal impairment, it provided a relatively poor fit to that observed in anuric patients.     

Analyzing numerical responses: A model and its application to examples from personnel and organizational management.

We analyze the structure of the numerical responses of persons connected with money and present a mental model together with its connection to fuzzy theory. The numerical response is one single number containing information about the value and the exactness of a variable. We test the rules describing the process, generating these responses experimentally as well as using examples from a questionnaire, and provide further empirical evidence. The simultaneous determination of the value and exactness of a response resulting in one number causes severe problems in using these responses as input to decision models. We propose a pre-analysis of the data with the rules provided in this paper. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A thermodynamic model of solid solutions and its application in solid alloys

Based on the free volume theory,lattice model,the Scatchard-Hildebrand theory,novel expressions of configuration partition function and excessive Gibbs free ene...     

A thermodynamic prediction for microporosity formation in aluminum-rich Al-Cu alloys

A computer model is used to predict the formation and the amount of microporosity in directionally solidified Al-4.5 wt pct Cu alloy. The model considers the interplay between so-called “solidification shrinkage” and “gas porosity” that are often thought to be two contributing and different causes of interdendritic porosity. There is an accounting of the alloy element, Cu, and of dissolved hydrogen in the solid- and liquid-phase during solidification. Consistent with thermodynamics, therefore, a prediction of forming the gas-phase in the interdendritic liquid is made. The local pressure within the interdendritic liquid is calculated by macrosegregation theory that considers the convection of the interdendritic liquid, which is driven by density variations within the mushy zone. Process variables that have been investigated include the effects of thermal gradients and solidification rate, and the effect of the concentration of hydrogen on the formation and the amount of interdendritic porosity. These calculations show that for an initial hydrogen content less than approximately 0.03 ppm, no interdendritic porosity results. For initial hydrogen contents in the range of 0.03 to 1 ppm, there is interdendritic porosity. The amount is sensitive to the thermal gradient and solidification rate; an increase in either or both of these variables decreases the amount of interdendritic porosity.     

神经网络内模控制及其在电加热炉上的应用

构造了一种ＢＰ网络，作为力学持久机电加热炉的神经网络模型，建立了引入前馈补偿的神经网络内模控制器，实现了无偏跟踪控制。     

Estimation model of the hearth refractory thickness and its application to the operation

A numerical model considering heat flow path and heat flux area was developed to estimate residual refractory thickness of blast furnace hearth. The predictions indicated that the wear profile of Kwangyang No. 1 BF was elephant foot type, deeply eroded around the tap‐hole and the corner of the hearth. The high heat load at the hearth sidewall was caused mainly by the carbon brick with low thermal conductivity, and it resulted in a severe erosion of hearth refractory. In the early stage of the furnace campaign, the wear rate of hearth refractory turned out to be higher than that of the following 7 years. Additionally, a thermal analysis of the hearth shell was carried out by means of an infrared camera, which is effective for simultaneous observation of a large area. A locally hot spotted region was not detected and the measured results showed a good agreement with the temperature trends measured by thermocouple.