快速凝固过程分析

从快速凝固的基本原理着手,详细总结了快速凝固技术的冷却方式判定方法,从物质的导热原理出发讨论了单辊熔体急冷法、双辊熔体急冷法的冷却方式,分别概括了它们的界面导热系数的计算,分析了冷却速度的计算方法。对快速凝固的过程分析具有参考价值。     

连铸凝固过程中的流动特征

 为了控制连铸坯内部质量,通过建立有机透明丁二腈-水溶液凝固模型试验和多场耦合凝固传输数学模型的方法研究连铸凝固过程中的流动。在模型试验类连铸冷却条件下,正在凝固的透明合金展现出凝固前沿下降流和中心上升流组成的蝶形对流。流场的速度变化存在着阶段性,凝固早期流动较快,流速按自然指数规律快速衰减;凝固中期流场较为稳定;末期逐渐衰减至固相速度。基于连续介质模型建立的2D传输凝固模型可以计算流动、温度和溶质场多场耦合的结果,数值计算结果同样显示出相应蝶形对流及流速变化规律。研究中还发现流场对溶质分布的综合影响,凝固前沿下降流加重最终凝固区域的溶质浓度,上升流则促进溶质在纵向的再分布,溶质的最终分布由整个凝固过程决定。     

板坯连铸结晶器中三维凝固壳厚度分布的数值模拟及实验验证

建立了连铸结晶器中三维凝固壳厚度分布的计算模型和计算方法，提出了非耦合计算时流动计算域与凝固传热计算域的衔接问题，以及铸坯表面换热系数确定的方法。针对２５０ｍｍ×１３００ｍｍ板坯连铸实际工况，用所建立的模型放处理方法数值模拟了其结晶器中的三维温度场和三维凝固壳厚度分布。同时用实测的凝固壳厚度分布数据验证了本计算听模型、边界条件和计算方法。本采用的方法可满足工程精度、并较简便实用。     

反向凝固复合不锈钢带厚度数值计算

通过建立一维变物性参数凝固传热模型计算了用反向凝固工艺生产复合不锈钢带时钢带的厚度变化，计算结果与实验结果吻合较好，且很好地说明了钢带厚度的变化规律。     

Al-Si合金快速等轴凝固界面响应函数及组织选择

在快速枝晶及共晶生长理论模型基础上,使用最高界面生长温度判据,建立了共晶合金快速等轴凝固界面响应函数(IRF)模型,分析了Al-Si合金系各种相及组织的竞争生长,绘制了非平衡组织选择图.计算结果与实验结果基本吻合,说明所建立的界面响应函数模型可以较好地预测Al-Si合金等轴凝固过程中的非平衡组织选择及形态演化.     

用差分法求解金属凝固传热问题的一个注记

本文引入固相率指数的概念,并假定该指数是固相率的线性函数,通过适当选取该函数,找到了一种求解金属凝固传热问题时使差分解的凝固速度接近分析解的方法。并发现,对于合金凝固,在固相线温度一定的情况下,液相线温度的高低对凝固速度几乎没有影响。同时,探讨了该法对连铸传热差分计算的影响。     

连铸板坯凝固末端位置的研究

 连铸坯凝固末端位置的确定方法有实验测定法和数学模型法。针对鞍钢厚板坯连铸机,采用有效比热容法建立板坯连铸二冷凝固传热数学模型来预报凝固末端的位置,用实验测定值验证了模型的可靠性。应用数学模型分析拉速对厚板坯凝固末端位置的影响,将计算结果回归得到了X65管线钢和船板钢在不同拉速范围内凝固末段位置和拉速的数学关系式,可为现场控制连铸凝固终点提供参考。     

连铸板坯凝固过程应变及内裂纹研究

通过建立连铸板坯凝固过程的传热模型,获得板坯冷却传热过程的主要凝固参数,在此基础上建立了凝固前沿坯壳所承受的应变模型,定量计算了凝固过程的主要应变,讨论了其主要影响因素,并针对实际铸机的设备和工艺状况,计算了其生产过程的应变,讨论了具体钢种产生裂纹的可能性。     

射钉法在铸坯凝固终点预报模型中的应用

为了精确掌握连铸机的综合冷却特性,验证铸机模型计算的准确性,进而为优化二次冷却制度提供依据,采用射钉法分别对新钢3号特厚板连铸机中碳钢和高碳钢进行了射钉试验,测量出典型工况条件下矫直区前后位置处铸坯凝固坯壳厚度,并以测得的凝壳厚度为边界模拟预报出凝固终点的位置。从模型计算预报的结果来看,中碳钢在典型工况条件下凝固终点的位置距离弯月面的距离为33.7m,而高碳钢在典型工况条件下凝固终点的位置距离弯月面的距离为27.6m。射钉试验与凝固模拟相结合预报的凝固末端为末端大压下位置设定提供了理论依据。     

不同拉速对薄板坯凝固过程及组织的影响

针对薄板坯在凝固过程中容易出现铸坯裂纹、疏松、缩孔等质量问题,以某厂生产的高拉速薄板坯为研究对象,通过建立传热凝固有限元和元胞自动机相结合的CAFE模型,基于ProCAST平台开展凝固传热全过程数值计算,探究不同拉速下的结晶器末端坯壳生长情况、不同拉速对凝固传热过程的温度场和三维凝固组织的影响.结果表明,在不同的拉速下...     

Practice effects on two memory retrievals from a single cue.

The effects of practice on 2 retrievals from a single cue were investigated. In Experiment 1, participants were given extended single-task practice and were then tested on a dual memory retrieval task. Performance was consistent with a sequential retrieval model proposed by T. C. Rickard and H. Pashler (2003). In Experiment 2, participants practiced both single- and dual-retrieval tasks extensively. Initially, data from all participants indicated sequential retrieval. However, participants who grouped the 2 response outputs were eventually able to perform the dual task with a latency that approached the prediction of a parallel race model. Models that assume a transition from sequential to parallel retrieval with practice, along with other models that assume an immutable retrieval bottleneck at all practice levels, are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Economic Value of Combined Best Practice Use

This paper measures the value of best practices based on data taken from the Construction Industry Institute Benchmarking and Metrics database. A three-step process provides the basis for measuring the potential benefits of increased best practice use. First, a practice use index is derived to model the way in which best practices are utilized on actual projects. The index combines data from eight best practices to create a single measure of practice utilization. Second, a project performance index, combining cost and schedule metrics, is derived as an indicator of overall project performance. Third, the practice use index is correlated with cost, schedule, and overall project performance metrics. Both owners and contractors benefit from increased practice use. Potential cost savings for owners range from $1.7 to $3.4 million, depending on industry group and project size. Potential cost savings for contractors are higher, averaging $7.2 million for the typical $88 million heavy industrial project. Benefits from schedule reductions are most apparent for owners. On large building projects, schedule reductions for owners average 27 weeks. Finally, improvements in overall project performance on the order of 30% are observed for both owners and contractors.     

Positive practice in family therapy

Positive practice, a brief integrative approach to consultation with families, is described in this paper. A clear distinction is made between the stages of planning, assessment, therapy, and disengagement. Guidelines for progression from one stage to the next are provided. Frameworks for deciding who to invite to preliminary sessions and methods for planning and organizing lines of inquiry are incorporated into this approach to practice. A three-column model is used to construct formulations. The model allows therapists and clients to map information about the pattern of interaction around the presenting problem, beliefs that constrain family members from altering their roles in these problem-maintaining patterns, and factors that have predisposed family members to hold these beliefs. Positive practice offers methods for evolving new behavioral patterns and belief systems within sessions and for arranging homework tasks for clients between sessions. It also incorporates methods for dealing with resistance, for managing therapeutic crises, for convening individual sessions and broader network meetings, for disengaging from the consultation process, and for recontracting for further episodes of therapy. This evolving approach to practice draws on ideas from many traditions within the family therapy field and takes account of recent research relevant to the practice of family therapy.     

Self-empowerment in health promotion: a realistic target?

There have been many calls for nurses to adopt a self-empowerment model for health promotion practice rather than continuing to work from the medical model. Continuing with our series on health promotion, this article examines features of the self-empowerment approach and questions whether its goals are achievable.     

The increase in angiotensin type-2 receptor mRNA level by glutamate stimulation in cultured rat cortical cells

Advanced practice nurses are challenged to assess comprehensively the value of their role and the impact of their practice. Value is defined as quality divided by cost. The correlations among the structure, strategies of care (process), and their objectives (outcome) are key to the assessment of the quality of care and the impact of the advanced practice nurse's role. Advanced practice nurses are challenged to provide high quality care for a competitive or decreased cost. For the profession of nursing, outcomes are the result of interventions based on the nurse's clinical judgment and theoretical, practical, or scientific knowledge. An evaluation model is presented that comprehensively measures the impact of advanced practice nurses on patients and families, and an example is presented. Using the model will give credibility and validity to the APNs' positive impact on the quality and financial outcomes of care for each patient and for entire patient populations.     

Signal recency effects can be distinguished from signal repetition effects in serial CRT tasks.

Reaction time (RT) is reduced in serial choice tasks when a particular signal, as distinct from the response made to it, is repeated on successive trials, N–1 and N. This experiment with 30 undergraduates showed a separate signal recency effect. RT is also reduced when a signal presented on trial N–2 recurs on trial N. In 3 many-to-one signal-to-response mapping tasks (2 responses 4 signals, 2 responses 8 signals, and 2 responses 16 signals), the effects of recent occurrence of signals were shown to be distinct from the effects of recent occurrence of responses made to them. The magnitude of signal recency effects varies directly with set size, but decreases, and may eventually disappear, with practice. The effect decreases with practice faster when signal sets are small than when they are large. A simple model accounts for these results and for earlier data from many-to-one mapping tasks that show that variations in signal entropy cease to affect choice reaction time if practice is sufficiently prolonged. Predictions from this model for changes in component RT distributions with signal set size, signal repetition, signal recency, and practice suggest further experiments. (French summary) (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

应变速率的影响与带钢热轧模型预报精度改进

轧制力预报模型是带钢热轧模型的核心，而变形阻力模型作为轧制力预报模型的核心，直接决定轧制力预报精度。从解决调试生产中存在的实际问题出发，对变形阻力模型的结构以及自适应方法进行分析。指出应变速率的影响、存在的问题以及相应的改进措施，并进一步阐明在实践中应用所取得的良好效果。     

Effects of practice and some methodological considerations in training counseling interviewing skills.

Studied 3 areas of counseling interview training (the role of practice, the use of modeling, and evaluation procedures) in 51 university students from a counseling class. Ss were randomly assigned to 5 training conditions: (a) audiovisual model followed by practice, (b) audiovisual model followed by no practice, (c) written model followed by practice, (d) written model followed by no practice, and (e) a comparison training group. Ss' responses to an audiotape of structured interview segments were evaluated, and outcome measures were the frequencies of total and preferred use of open-ended questions, tacting response, and silence. The frequencies for both the total use and total preferred use of interviewing skills were significantly higher for Ss in the practice training condition than in the no-practice training condition regardless of the model. The effects of the research methodologies currently in use are dicussed in light of the results of this study. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working with alcoholics and drug abusers in private practice: A psychoanalytic-chemical dependency model.

Describes a combined model of chemical dependency and psychoanalytic approaches in the psychotherapeutic treatment of alcoholics and drug abusers. The ambiguity of treatment goals and impediments and enhancements inherent in private practice with this population are discussed. Modifications in treatment are recommended on the basis of contributions from the addictions field, the self-help movement, and etiologic research. The broadening scope of psychoanalytic theory and practice with greater applicability to the treatment of addiction is reviewed. Clinical material illustrates psychoanalytic principles and the combined model of psychotherapy with alcoholics and drug abusers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)