As the use of wireless sensor networks (WSNs)

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Monitoring a user's mobility during daily life is an essential requirement in providing advanced mobile services. While extensive attempts have been made to monitor user mobility, previous work has rarely addressed issues with battery lifetime in real deployment. In this paper, we introduce SmartDC, a mobility prediction-based adaptive duty cycling scheme to provide contextual information about a user's mobility: time-resolved places and paths. Unlike previous approaches that focused on minimizing energy consumption for tracking raw coordinates, we propose efficient techniques to maximize the accuracy of monitoring meaningful places with a given energy constraint. SmartDC comprises unsupervised mobility learner, mobility predictor, and Markov decision process-based adaptive duty cycling. SmartDC estimates the regularity of individual mobility and predicts residence time at places to determine efficient sensing schedules. Our experiment results show that SmartDC consumes 81% less energy than the periodic sensing schemes, and 87% less energy than a scheme employing context-aware sensing, yet it still correctly monitors 80% of a user's location changes within a 160-second delay.

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accelerated by the readily-available hardware platforms, as well as This paper presents the design principles, implementation, and core system software such as sensor node operating systems in evaluation of the RETOS operating system which is specifically particular. From the early days, much effort has been given to developed for micro sensor nodes. RETOS has four distinct develop efficient and yet complete operating systems for micro objectives, which are to provide (1) a multithreaded programming sensor nodes. For instance, TinyOS [1] has historically been used by interface, (2) system resiliency, (3) kerel extensibility with many practitioners in the field and even advocated as "the" dynamic reconfiguration, and (4) WSN-oriented network operating system for WSN. Other operating systems such as abstraction. RETOS is a multithreaded operating system, hence it SOS[2], Contiki[3], MANTIS[4], and t-kernel[5] have challenged provides the commonly used thread model of programming the success of TinyOS and provide incremental, or even alternative interface to developers. We have used various implementation solutions for many practical issues still being debated in the related techniques to optimize the performance and resource usage of communities.multithreading. RETOS also provides software solutions to separate Writing an operating system for micro sensor platforms poses kernel from user applications, and supports their robust execution on several unprecedented problems. First, the OS implementation MMU-less hardware. The RETOS kernel can be dynamically should consider microcontrollers which typically provide very reconfigured, via loadable kernel framework, so a applicationlimited processing power, memory and battery life-time. The eventoptimized and resource-efficient kernel is constructed. Finally, the driven paradigm for sensor OS is especially favored for the networking architecture in RETOS is designed with a layering resource-constrained environment, and we have seen the concept to provide WSN-specific network abstraction. RETOS proliferation of TinyOS or SOS in this context. Second, the currently supports Atmel ATmegal28, TI MSP430, and Chipcon application programming model should be seriously considered to CC2430 family of microcontrollers. Several real-world WSN provide an easy and convenient programming interface to applications are developed for RETOS and the overall evaluation of application developers, without needing to be aware of underlying the systems is described in the paper.operating system principles. The event-driven operating systems, for example, enforce programmers to structure and program an Categories and Subject Descriptors application as a state machine in terms of tasks and event handlers. D.4.7 [Operating systems]: Organization and DesignUnderstanding this concept is an easy task for experts, but conventional programmers who are accustomed to a process model General Terms of programming may find the concept hard to grasp. Third, a micro Design,eralerimentation, Measurement, Perfonnan...

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This study developed learning progression-based measures of science teachers' content knowledge (CK) and pedagogical content knowledge (PCK). The measures focus on an important topic in secondary science curriculum using scientific reasoning (i.e., tracing matter, tracing energy, and connecting scales) to explain plants gaining weight and exchanging gases. Using a design-based research approach, we conducted the research in four cycles. The findings reported in this article were based on the data collected in the last two cycles (year 2011-2012 and year 2012-2013). This study contains two parts. First, 194 teachers participated in professional development workshops and completed a teacher assessment measuring CK and PCK. A learning progression-based scoring system was developed for these measures. Second, a subgroup of 25 teachers participated in a teaching experiment. These teachers taught a learning progression-based unit on plant growth and functioning. Their students took written assessments both before and after the teaching intervention. In this process, validity evidence from multiple sources was obtained and analyzed to evaluate the claim that the assessment scores tell how well teachers understand the knowledge essential for teaching the science topic. This validity argument supports our interpretations that led to three results. First, teachers' overall performance on CK was a bit higher than PCK, but not significantly different. Second, two challenges confronting teachers are adaptively applying scientific principles and understanding students' intuitive ideas. Third, there was a statistically significant relationship between teachers' measured CK and PCK and students' learning from the plant unit. #

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