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This study developed an assessment system for evaluating junior high students' collaborative problem-solving skills (CPS) in the context of science, technology, engineering, and mathematics (STEM) education. The main theoretical basis for designing the CPS learning goals of this assessment system is the matrix of collaborative problem solving proposed by the Organisation for Economic Cooperation Development (OECD). In this assessment system, there are eight assessment modules in STEM education developed by four groups of researchers who participated in this study. The modules were delivered as a web-based learning platform, where the computer was programmed to act as the agent of collaboration (rather than human-to-human collaboration), thus making this exploratory study more unique. The eight modules included problem tasks such as designing shelves, using a microwave oven, construct a house, etc. In order to ensure the validity of the assessment system, including the eight assessment modules in STEM education, three specialists were invited to examine the eight modules' content validity. Additionally, in order to ensure criterion-related validity of the effectiveness of the modules, they were tested among 222 Taiwanese junior high students. Discrimination and difficulty indices were obtained for student CPS performance on each of the eight modules. Furthermore, intercorrelations were obtained for the students' performance on each of the eight assessment modules in relation to overall and each of three collaborative problem-solving skills, i.e., (1) Establishing and maintaining shared understandings, (2) Taking appropriate action to solve the problem, and (3) Establishing and maintaining team organization. The following conclusions are drawn: (1) there was an evidence that the assessment system items had acceptable difficulty and satisfactory discrimination; (2) the intercorrelations of the students'

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For products sold with a warranty, preventive maintenance (PM) by either the manufacturer and/or the buyer has an effect on the total cost for both parties. In this investigation, we use a model to study the effect of PM carried out by the buyer on items sold under a free-replacement renewing warranty. For the manufacturer, if the product fails during the warranty period, it shall either be repaired (minor failure) or replaced completely (catastrophic failure) by a new one with a new warranty and at no cost to the buyer. When the product is out-of-warranty and if the product fails due to a catastrophic failure before its useful life limit, the buyer will incur a penalty cost, the amount of which depends on the failure time. Under such a framework, the cost model is derived and the effects of three PM options on the cost are examined both from the manufacturer's and buyer's perspectives. The results show that a significant cost saving can be obtained by taking the optimal PM action route.

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This paper considers a general repairable product sold under a failure-free renewing warranty agreement. In the case of a general repairable model, there can be two types of failure: type I failure (a minor failure), which can be rectified by minimal repairs; and type II failure (a catastrophic failure), which can be removed only by replacement. After a minimal repair, the product is operational but the failure rate of the product remains unchanged. The aim of this paper is to determine the optimal warranty period and the optimal out-of-warranty replacement age, from the perspective of the seller (manufacturer) and the buyer (consumer), respectively, while minimizing the corresponding cost functions. Finally, a numerical example is presented.