Prospective Elementary Teachers' Knowledge of Teaching Science as Argument: A Case Study

The National Research Council emphasizes the centrality of discourse and practices associated with constructing, evaluating, and using scientific explanations. These expectations increase already daunting challenges for those who teach science at the elementary school level. This study followed a multiparticipant case study approach examining prospective elementary teachers' self‐reports of teaching science as argument. Findings yield that the presence of opportunities for physical experimentation with firsthand data during science instruction helped participants increase their emphasis on evidence‐based explanations. Participants also viewed science talks as essential and fundamental for engaging students in evidence‐based explanations. Finally, participants demonstrated attention to scientific subject matter. These findings are discussed in terms of their implications for teacher education.     

惯例复制与知识转移:作用机制的权变条件研究

针对惯例复制过程中与外部情景难以匹配的复制困境,分析了常规惯例复制和柔性惯例复制对知识转移的单独以及联合作用的关系悖论,对比分析作用机制在网络闭合性和环境不确定性约束下的权变性影响。以研发密集型企业为对象,运用多元回归分析进行实证检验。结果表明:网络闭合性和环境不确定性是惯例复制对知识转移的单独以及联合作用的权变条件;网络闭合性强化了常规惯例复制机制的促进作用,但限制了柔性惯例复制机制的效能发挥;环境不确定性削弱了常规惯例复制机制的促进作用,对柔性惯例复制机制的作用效果不显著;网络闭合性低或环境不确定性低时,两种惯例复制机制的联合作用相互补充,而网络闭合性高或环境不确定性高时,两种惯例复制机制相互替代。研究结论有助于揭示惯例复制的权变作用,对提升技术创新网络的知识转移效率具有重要意义。     

Toward Best Approximation of Nonlinear Systems: A Case of Models with Memory

The problem of nonlinear dynamical system modeling, considered in this paper, is motivated by restrictions arising in real-world tasks. The restrictions are that first, a system input cannot be entirely observed for one trial. Second, the system model must be subjected to the causality principle. Third, the input is corrupted by noise so that no relationship between the reference input and noise is known. Fourth, the model should have some degrees of freedom so that the associated accuracy can be regulated by a variation of these freedom degrees. We propose and justify new procedures for the nonlinear system modeling that are initialized by these motivations. The models are nonlinear and given by so called r-degree operators that can be reduced to a matrix form presentation. To satisfy the restrictions above, the matrices have special structures that we call the lower p-band matrices. The degree r of the models is the required degree of freedom. The rigorous analysis of errors associated with the presented techniques is given. Numerical experiments with real data demonstrate the efficiency of the proposed approach.     

Hannah's Prior Knowledge About Chemicals: A Case Study of One Fourth‐Grade Child

Chemical principles are taught in elementary education across much of the United States because the National Science Education Standards include concepts about the nature of matter, states of matter, and changes in matter among other science concepts within the first to fifth grade levels. “Chemicals” is a word related to the nature of matter that is used not only in formal instruction, but also in everyday conversations. Children's prior knowledge about chemicals gained from everyday experiences will influence how they learn about chemical principles. The research described herein reveals insights into one child's conceptual structure related to the word “chemical,” which includes how she uses the word both inside and outside of school. Hannah was purposefully chosen for this case study because she exemplified “children's science.” Her understanding of chemicals as cleaners, in foods, and used for a purpose were primarily gained from everyday experiences. The implications of these findings are discussed with respect to both future research and elementary science education.     

Biased Random Walks, Lyapunov Functions, and Stochastic Analysis of Best Fit Bin Packing

We study the average case performance of the Best Fit algorithm for on-line bin packing under the distributionU{j, k}, in which the item sizes are uniformly distributed in the discrete range {1/k, 2/k,…,j/k}. Our main result is that, in the casej = k − 2, the expected waste for an infinite stream of items remains bounded. This settles an open problem posed by Coffmanet al.[[4]]. It is also the first result which involves a detailed analysis of the infinite multidimensional Markov chain underlying the algorithm.     

A Decomposition Method for Transfer Line Life Cycle Cost Optimisation

A new method to search best parameters of a transfer line so that the cost of each manufactured part will be minimised. The synchronised transfer lines with parallel machining are considered. Such lines are widely used in mass and large-scale mechanical production. The objective is to minimise the line life cycle cost per part under the given productivity and technological constraints. The design decisions to be optimised are: number of spindles and workstations. This will be accomplished by defining subsets of tasks which are performed by one spindle head and cutting conditions for each spindle. The paper focuses on a mathematical model of the problem and methods used to solve it. This model is formulated in terms of mixed (discrete and non-linear) programming and graph theory. A special decomposition scheme based on the parametric decomposition technique is proposed. For solving the sub-problems obtained after decomposition, a Branch-and-Bound algorithm as well as a shortest path technique are used.     

Requisite Decision Modelling: A Case Study

This case study in decision analysis concerns a company that had to decide between continuing to manufacture an old product that might in the near future by banned by the government or introducing an improved but conventional product that would beat the ban but might lose market share to competing products using microchip technology. A decision tree with three attributes describing the consequences over a ten-year horizon modelled the problem. Implementation on a micro computer facilitated extensive sensitivity analyses, the final round of which were conducted by the Board of Directors. More and more pessimistic assumptions were made until the decision switched from the new to the old product; at that point no Director believed all the assumptions. Thus, agreement was reached about the decision even though the Directors disagreed about the uncertainties. The case illustrates ‘requisite’ rather than optimal decision modelling and shows the essential roles of problem structure and sensitivity analysis.     

Solid Waste Collection: A Case Study

Planning for urban solid waste management requires an assessment of many complex interactions among transportation systems, land use patterns, urban growth and development, and public health considerations. The authors discuss the application of a data acquisition and analysis system and a simulation model to the complex problems of the solid waste management system in Cleveland, Ohio. As the result of applying these techniques, Cleveland's solid waste managers reduced their annual budget of $14.8 million in 1970 to a low of $8.8 million in 1972. The total savings in a 3-yr period were $14.6 million based on the 1970 budget. In addition, the city reduced its solid waste work force from 1640 to 850 and the number of collection routes from 224 to 102, and it redesigned its collection routing system. The management structure of the Division of Solid Waste Collection and Disposal was completely reorganized to take advantage of and to supplement these major organizational changes. The City Council has, moreover, passed an ordinance which will allow the construction of transfer stations, as recommended in the study; one such facility has been built, and land has been purchased for the other.     

Optimization in Pottery Manufacturing: A Case Study

The paper reports what is believed to be the first application of mathematical programming to the manufacture of pottery. The problem has a number of distinctive features requiring special treatment in its specification. Short term (product mix) and medium term (acquisition of new plant) decisions within the firm are examined and a framework for the evaluation of improvements in methods to reduce production losses is given.     

The Design of Storage Calorifiers: A Case Study

To date, no scientific method for the sizing of storage calorifiers has existed. This short paper outlines the analytical methods which were established to provide design criteria for the storage calorifiers serving hospital ward units. A full report of the survey which was carried out is contained in a paper entitled “A study of water consumption in ward units”.     

Inquiry Teaching and Learning: The Best Math Class Study

This research reports on prospective middle school teachers' perceptions of a “best mathematics class” during their involvement in an inquiry‐designed mathematics content course. Grounded in the prestigious Glenn Commission report ( U.S. Department of Education, 2000 ), the study examined the prospective teachers' perceptions of effective mathematics instruction both prior to and after completing the inquiry course. Pre‐essay analysis revealed that students could be grouped into one of two categories: the Watch‐Learn‐Practice view and the Self as Initiator view. Post‐essay analysis indicated that over two thirds of all students involved in the study changed their views of a best math class after the inquiry courses. The Watch‐Learn‐Practice group's changes focused on developing reasoning skills and learning how one “knows” in mathematics. The Self as Initiator group noted expanded roles for the students, particularly emphasizing the importance of going beyond basic requirements to think deeply about the why and how of mathematics and expanded views of the benefits of group learning.     

Assessment of Manufacturing System Reliability: A Case Study

Reduction of unproductive work-in-process (WIP) inventory has been a subject of global concern lately. Detailed examination often reveals that such unproductive WIP is the result of a low manufacturing system reliability (MSR). The impact of poor MSR is felt all the more in industries where material cost constitutes a significant portion of the total manufacturing cost. Guided by these considerations, in this paper a case study is reported wherein an analysis has been made to assess MSR in a multinational switchgear industry located in Western India. The paper provides a few practical guidelines towards maintaining a certain level of MSR by suitably adjusting factors like utilization level of machines, utilization level of tools, tool down-time, mean production rate per tool, etc. Detailed sensitivity analysis on the simulation results has also been presented, which is believed to help substantially in decisions related to the finer adjustments of these factors.     

Best polynomial approximations: A corrected proof

A proof is given of a theorem concerning the best (in the sense of thep-norm) piecewise polynomial approximation of degreen for a function belonging toC ⁿ⁺¹[a,b]. This corrects an earlier, erroneous proof of the same theorem.