太阳能系统的蓄热技术综述

蓄热、蓄能是发展太阳能系统的关键技术问题。针对太阳能具有的稀薄性、间歇性和不可靠性,介绍了短期蓄热、季节性蓄热、显热蓄热、化学反应蓄热、相变蓄热等几种太阳能蓄热技术,分析了国内外对蓄热技术的研究现状。分析认为,相变材料的导热率和相变蓄热技术的应用成本是未来相关研究的主要方向。     

固体电蓄热装置结构优化及蓄放热特性的模拟

固体电蓄热技术被广泛应用于实现弃风消纳、调节电网负荷平衡中,选择合适的蓄热材料和明确蓄热体的蓄放热特性对实现高效调峰具有重要意义.本文运用软件Fluent对固体电蓄热装置的蓄放热过程进行数值模拟,研究了氧化镁、堇青石、刚玉砖、黏土砖4种材料以及孔隙率对蓄热性能的影响;分析了在不同风速下蓄热体的放热特性.结果表明:蓄热过程中,氧化镁砖和刚玉砖相比堇青石和黏土砖蓄热温度低,但蓄热量大;随着蓄热体孔隙率的增大,蓄热温度增大,蓄热量降低;放热过程中,当蓄热体的初始温度为800 K时,放热风速控制在16 m/s最为合适.     

低应力蜂窝陶瓷蓄热体的研制与应用

针对常用蜂窝陶瓷蓄热体正方形格孔直折角应力集中、成形困难、使用寿命短的不足,通过对蓄热体的结构、成形模具和蓄热体挤压成形材料的研究,研制出一种新型结构低应力蜂窝陶瓷蓄热体。结果表明,新型蓄热体改善了蓄热体的综合力学指标,提高了成品率,取得了良好的应用效果。     

蜂窝状蓄热体热态实验平台设计研究

结合理论研究,设计开发了蜂窝状蓄热体热态实验研究的平台,详细制定了工作平台的工艺参数、工作原理和工艺流程,为研究蜂窝陶瓷蓄热体的各项参教对蓄热室传热特性和阻力特性的影响、研究蓄热室的断面形状和蜂窝陶瓷蓄热体的流道长度等结构参数对蓄热室传热特性和阻力特性的影响、研究换向时间、蓄热体内气流速度、燃烧热负荷等操作参数对蓄热室传热特性和阻力特性的影响等工作奠定了基础。     

蓄热体热过程模拟研究

在考虑蓄热体沿气体流动方向热传导,并将空气、烟气流动中对蓄热体的传热,看做气柱微元及蓄热体微元的体积内热源情况下,建立了蓄热体数学模型.采用有限差分方法对控制方程进行离散化,对蓄热体热过程进行了数值模拟.分析了材料物性及热工操作等参数对蓄热体工作的影响,对蓄热式加热炉蓄热体的选择提供了理论参考.     

蓄热式烧嘴热工特性分析

根据蓄热烧嘴热工特性,对轧钢加热炉采用蜂窝蓄热烧嘴中出现的一些问题进行了分析,总结出合理的蓄热烧嘴的结构、蓄热体尺寸、预热气体流量、烧嘴换向时间等热工参数,提出蜂窝蓄热烧嘴在实际设计中应注意的几个方面,使其发挥更好的换热效果。     

蜂窝蓄热体使用效果分析及改进

针对蜂窝蓄热体使用过程中出现的变形、堵塞及烧塌的问题,提出了蜂窝蓄热体的改进措施.通过对蜂窝蓄热体的结构进行改进,提高蓄热体的耐压强度和耐火度,调整换向时间等,提高了蜂窝蓄热体的综合性能.     

新型蓄热体结构参数对换热比表面积的影响

针对常用的陶瓷蓄热小球流动阻力大、蜂窝陶瓷蓄热体平行独立直通道间气流分布不均匀的缺点,提出一种前后、上下、左右通孔垂直相交贯通的新型蓄热体结构,并分析通孔结构、通孔尺寸对蓄热体换热比表面的影响规律。分析结果表明,通过调整新型蓄热体的通孔结构与尺寸能够达到常规蓄热体换热比表面积的要求。     

美国蓄热式烧嘴的研究与发展

一、双蓄热床烧嘴系统蓄热式烧嘴是一种组合式烧嘴系统,每个系统有两个蓄热床,因此又可叫做双蓄热床烧嘴系统。这种系统采用了具有较高的蓄热和放热能力的新材料。这种新材料还可以设计出几何结构紧凑和小巧玲珑的蓄热床。这种蓄热式烧嘴系统,具有较短的换向周期,因此换热效率较高。这一系统能够广泛地应用于间歇式炉、再加热炉、辐射管炉和连续加热炉等各种炉型。     

换向时间对加热炉蓄热室内温度分布的影响

采用高温空气燃烧技术的蓄热式加热炉在钢铁企业应用广泛。蓄热室是蓄热式加热炉的重要组成部件，换向时间是加热炉蓄热室的重要操作参数。为了探讨换向时间对蓄热室内温度分布的影响，以鞍钢连轧作业区1号加热炉为原型，搭建了加热炉蓄热室的试验装置。填充了10层蜂窝陶瓷蓄热体，开展了换向时间对蓄热室温度变化规律、沿蓄热室长度方向温度梯度变化规律影响的试验研究，分析了换向时间对蓄热室传热性能的影响。研究表明，蓄热室的温度随换向时间的延长呈现周期性变化。随换向时间延长，蓄热室平均温度呈现出先降低后升高的趋势，沿蓄热室长度方向的平均温度梯度先增大后减小。试验用加热炉的最佳换向时间为70 s，对应的热回收率、温度效率和综合传热系数分别为81.6%、91.4%和18.3 W/(m2·℃)。     

Compound Problem Solving: Insights from the Workplace for Engineering Education

For engineering educators who incorporate real-world problems into their teaching, it is essential to understand real-world problem solving and the nature of problems for better design of the instruction. Prior research provided evidence that real-world problems involve many stakeholders, are complex, and have multiple solutions and solution paths. The purpose of this paper is to provide additional insights particularly into the structure/class of workplace problems and associated models of expertise. This paper describes the findings of a study that employed a two-step process: (1)?a single-case study of a steel engineer generating a model of compound problem solving and (2)?a multi-case comparison of 90 problem-solving narratives of other engineers to the single case. The study is located in a U.S. context. Results indicate that real-world problems are intertwined problems (compound problems) and that transitions from one problem type to another within a compound problem are a unique class of problems themselves. These transition problems have properties that are not represented in other problem types and provide insights into expertise and expertise development in problem solving.     

Equivalence in symbolic and nonsymbolic contexts: Benefits of solving problems with manipulatives.

Children's failure on equivalence problems (e.g., 5 + 4 = 7 + __) is believed to be the result of misunderstanding the equal sign and has been tested using symbolic problems (including "="). For Study 1 (N = 48), we designed a nonsymbolic method for presenting equivalence problems to determine whether Grade 2 children's difficulty is due to the presence of symbols or to a more fundamental misunderstanding of equivalence. Children's superior performance on nonsymbolic versus symbolic problems suggests that children fail to map their understanding of equivalence onto problems presented with the symbols of arithmetic. For Study 2 (N = 32), we implemented a within-subject design to assess whether experience with nonsymbolic problems would facilitate performance on symbolic problems. This hypothesis was confirmed. Exposure to nonsymbolic problems may have enabled children to map their successful concepts and strategies to symbolic equivalence problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

热传导两点边值问题的通用数值解法

根据一维稳态导热的肋片问题为一个两点边值问题的数值解法通用性不强、不易理解情况,通过引入“边界函数”给出了一种通用性强也易于理解的通用数值解法．这种解法逻辑简单,使用方便,且无需修改算法程序主体．     

Infancy parenting and externalizing psychopathology from childhood through adulthood: Developmental trends.

Developmental models and previous findings suggest that early parenting is more strongly associated with externalizing problems in early childhood than it is in adolescence. In this article, the authors address whether the association of poor-quality infancy parenting and externalizing problems “rebounds” in adulthood. Poor-quality infancy parenting was associated with externalizing problems at kindergarten and first grade (mother report) as well as at 23 and 26 years (self report). Infancy parenting was not significantly associated with either mothers’ or youths’ reports of externalizing problems at 16 years. These findings are consistent with the notion that poor-quality infancy parenting is a risk factor for externalizing problems in developmental periods for which externalizing behavior is most deviant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Can memory requirements account for species' differences in invisible displacement tasks?

We tested the hypothesis that poor performance on the Piagetian invisible displacement task is related to increased memory requirements. Rhesus monkeys and orangutans received 3 types of problems (invisible, visible, and no transfer problems) each containing a number of steps equivalent to that of standard invisible displacements. If failure to solve invisible displacements was due to increased memory requirements, then the primates should perform at chance level on all 3 problems. However, rhesus monkeys solved visible and no transfer problems, but not invisible transfer problems. Half of the orangutans solved all 3 transfer problems, although their performance on invisible transfer problems was lower than that on the other problems. A subsequent cuing phase led to improved performance, and a few monkeys solved invisible transfer problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal depression and early positive parenting predict future conduct problems in young children with attention-deficit/hyperactivity disorder.

Children with attention-deficit/hyperactivity disorder (ADHD) are at risk for adverse outcomes such as substance abuse and criminality, particularly if they develop conduct problems. Little is known about early predictors of the developmental course of conduct problems among children with ADHD, however. Parental psychopathology and parenting were assessed in 108 children who first met Diagnostic and Statistical Manual of Mental Disorders (4th ed.) criteria for ADHD at 4-7 years old. When demographic variables and baseline ADHD and conduct problems were controlled, maternal depression predicted conduct problems 2-8 years following the initial assessment, whereas positive parenting during the structured parent- child interaction task predicted fewer future conduct problems. These findings suggest that maternal depression is a risk factor, whereas early positive parenting is a protective factor, for the developmental course of conduct problems among children with ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

软硬件协同设计复杂问题的计算模型和算法

软硬件划分是设计复杂嵌入式系统的关键环节.论文综述了近年来提出的解决软硬件划分问题的计算模型和相应算法.软硬件划分问题可以建模成各种限定不同约束条件的背包问题模型,同时需要考虑任务块间的通信消耗.背包问题中的子项相当于软硬件划分问题中的任务块.论文针对不同的计算模型,介绍了相应的精确算法和启发式算法.论文最后探讨了若干待研究的潜在问题.     

Adults' Understanding of Inversion Concepts: How Does Performance on Addition and Subtraction Inversion Problems Compare to Performance on Multiplication and Division Inversion Problems?

Problems of the form a + b - b have been used to assess conceptual understanding of the relationship between addition and subtraction. No study has investigated the same relationship between multiplication and division on problems of the form d × e ÷ e. In both types of inversion problems, no calculation is required if the inverse relationship between the operations is understood. Adult participants solved addition/subtraction and multiplication/division inversion (e.g., 9 × 22 ÷ 22) and standard (e.g., 2 + 27 - 28) problems. Participants started to use the inversion strategy earlier and more frequently on addition/subtraction problems. Participants took longer to solve both types of multiplication/division problems. Overall, conceptual understanding of the relationship between multiplication and division was not as strong as that between addition and subtraction. One explanation for this difference in performance is that the operation of division is more weakly represented and understood than the other operations and that this weakness affects performance on problems of the form d × e ÷ e. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

1＋1铝热轧机组电源动态补偿及滤波方案探讨

分析1＋1热轧机组供电系统存在的功率因数低、高次谐波、越级跳闸等问题,对高压SVC（TCR型）动态补偿、高压SVC（TSC型）动态补偿、低压TSC型就地补偿等几种解决问题的方案进行探讨,得出采用低压TSC型就地补偿是解决问题的最佳方案之结论,可为国内同行的动态补偿改造选型提供借鉴。     

Non-similarity combinatorial problems

Similarity problems intensively investigated in computational molecular biology have the following two stringology models: find the longest string included in any string of a given finite language, and find the shortest string including every string of a given finite language. These two problems are exemplified by the two well-known pairs of problems, the longest common subsequence (or substring) problem and the shortest common supersequence (or superstring) problem, interpretations. In this paper we consider opposite problems connected with string non-inclusion relations: find the shortest string included in no string of a given finite language and find the longest string including no string of a given finite language. The predicate "string alpha is not included in string beta" is interpreted either as "alpha is not a subsequence of beta" or as "alpha is not a substring of beta". The main purpose is to determine the complexity status of the non-similarity problems. Using graph approaches, we present NP-hardness proofs for the first interpretation and polynomial-time algorithms for the second one. Special cases of the problems, and related issues are discussed.