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In order to develop successful teaching approaches to transformations of matter, we need to know more about how young students develop an understanding of these processes. In this longitudinal study, we followed 25 students from 7 to 13 years of age in their reasoning about transformations of matter. The questions addressed included how the students’ understanding of transformations of matter changed and how we can make sense of individual learning pathways. In interviews performed once or twice every year the students described and explained three situations: fading leaves left on the ground, a burning candle, and a glass of water covered with a glass plate on which some mist had formed. When analysing the interviews, we found a common pathway of how the students’ ideas changed over the years in each one of the situations. When analysing individual student’s interviews with Ausubel’s assimilation theory we could discern subordinate, superordinate and combinatorial learning. How these findings can contribute to an improvement of teaching about transformations of matter is discussed.  相似文献   
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This study was designed to analyze the effects of the support programs provided in education welfare action zones. Education welfare action zone policy came into effect by government from 2003 to guarantee actual educational opportunity to disadvantaged children in urban areas by providing educational, cultural, and welfare service. Education welfare action zones were selected in low-income group area in the metropolis. In this regard, both quantitative and qualitative analytical methods were used to ascertain the effects of the program. The qualitative analysis included a preliminary examination of conditions prior to the actual commencement of the program, which was then followed by an investigation of specific schools used, as case studies in order to identify the changes that had taken place during the program’s implementation process, and the program’s effect. Meanwhile, a quantitative analysis was employed to verify the actual changes that took place in several different aspects, changes that were revealed by the case studies.  相似文献   
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This paper examines differences in mathematics achievement among eighth-grade students using a secondary analysis of the data. The students, who are from Malaysia, had participated in the Trend International Mathematics and Science Study (TIMSS) 1999. A series of school, home, demographic and socio-economic variables were used to investigate the differences in the mean student mathematics scores. Evidence from the data shows that gender, the language spoken at home, expected educational level, family background, and home educational resources and aids have a significant influence on the students’ level of mathematics achievement.  相似文献   
998.
Research in non-equalization machining method for spatial cam   总被引:1,自引:0,他引:1  
Many kinds of devices with cam have been widely used in various mechanical equipments. However, non-equalization machining for spatial cam trough remains to be a difficult problem. This paper focuses on the analysis of running conditions and machining processes of spatial cam with oscillating follower. We point out the common errors in the biased distance cutting. By analyzing the motion of oscillating follower of spatial cam, we present a new 3D curve expansion model of spatial cam trough-outline. Based on this model, we have proposed a machining method for trochoidal milling with non-equalization diameter cutter. This new method has led to a creative and effective way for non-equalization diameter machining for spatial cam with oscillating follower.  相似文献   
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Based on input-output approach, the robust stability and stabilization problems for uncertain singular systemswith time-varying delays are investigated. The parameter uncertainties are assumed to be norm-bounded and the time-varying delays include both discrete delay and distributed delay. By introducing a new input-output model, the time-delay system is embedded in a family of systems with a forward system without time delay and a dynamical feedback uncertainty. A sufficient and necessary condition, which guarantees the system regular, impulse-free and stable for all admissible uncertainties, is obtained. Based on the strict linear matrix inequality, the desired robust state feedback controller is also obtained. Finally, a numerical example is provided to demonstrate the application of the proposed method.  相似文献   
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We propose the spectrum allocation and resource scheduling algorithms in cognitive point to multipoint (PMP) networks with rapid changes of spectrum opportunities and present a media access control (MAC) protocol based on these algorithms. The objective of spectrum allocation is to make efficient use of the spectrum while maintaining the transceiver synchronization on frequency and time in the network. The objective of resource scheduling is to guarantee the quality of service (QoS) requirements of different kinds of connections and to minimize the total energy consumption in the network as well. By sensing only a small set of possible channels in each slot based on the state transition probability of each channel, our spectrum allocation algorithm achieves high spectrum efficiency in the network. The resource scheduling problem is divided into three sub problems and we derive optimal solutions to these problems by greedy algorithm and convex optimization. The simulation results show that our algorithm can make efficient use of the spectrum and the network resources at a cost of low computational complexity.  相似文献   
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