Wernhuar Tarng

Scheduling periodic and aperiodic tasks in hard real-time computing systems

Scheduling periodic and aperiodic tasks to meet their time constraints has been an important issue in the design of real-time computing systems. Usually, the task scheduling algorithms in such systems must satisfy the deadlines of periodic tasks and provide fast response times for aperiodic tasks. A simple and efficient approach to scheduling real-time tasks is the use of a periodic server in a static preemptive scheduling algorithm. Periodic tasks, including the server, are scheduled at priori to meet their deadlines according to the knowledge of their periods and computation times. The scheduling of aperiodic tasks is then managed by the periodic server during its service time. In this paper, a new scheduling algorithm is proposed. The new algorithm creates a periodic server which will have the highest priority but not necessarily the shortest period. The server is suspended to reduce the overhead if there are no aperiodic tasks waiting, and is activated immediately upon the arrival of the next aperiodic task. After activated, the server performs its duty periodically until all waiting aperiodic tasks are completed. For a set of tasks scheduled by this algorithm, the deadlines of periodic tasks are guaranteed by a deterministic feasibility check, and the mean response time of aperiodic tasks are estimated using a queueing model. Based on the analytical results, we can determine the period and service time of the server producing the minimum mean response time for aperiodic tasks. The analytical results are compared with simulation results to demonstrate the correctness of our model.

A Cluster Allocation and Routing Algorithm Based on Node Density for Extending the Lifetime of Wireless Sensor Networks

The electricity of sensor nodes in wireless sensor networks is very limited, so it is an important research topic to deploy the sensor nodes and cooperate with an efficient routing algorithm for extending the network lifetime. In the related research, LEACH routing algorithm randomly selects cluster heads in each round to form a cluster network, which may cause additional power consumption and inability to maintain the optimal routes for data transmission. The cluster allocation and routing algorithm proposed in this study is based on the cluster architecture of LEACH, and the objective is to produce clusters with more sensor nodes to balance energy consumption of cluster head. For indirect-transmission routing algorithms, the sensor nodes near the base station may consume more energy due to a larger amount of data transmission. Therefore, this study proposed to increase the node density near the base station during deployment to compensate for the requirement of high energy consumption. The experimental results show that the proposed algorithm based on node density distribution can efficiently increase the lifetime of wireless sensor networks.

X-Ray Shadow Projection Microscopy and Microtomography

A laboratory X-ray projection microscope is under development in AMIL at the State University of New York at Buffalo. The design of the X-ray source and of the image recording system is optimized to obtain high resolution. The source spot size is minimized by using a focussed electron beam incident on a thin film target. Two-dimensional images are recorded using a high resolution phosphor and slow scan CCD camera. Three-dimensional images are prepared from the two-dimensional images and presented either as stereo pairs or as full tomographic reconstructions.

The Influence of a Motion-sensing and Game-based Mobile Learning System on Learning Achievement and Learning Retention

This study combined context-aware mechanisms with the main functions of smart phones to develop a motion-sensing and game-based mobile learning system that can provide related information about many plants in the Taipei Botanical Garden. This study developed six types of motions on smart phones involving common botanical misconceptions and integrated these motions into botany-themed learning activities. The purpose was to correct such misconceptions through motion-based learning. This study investigated the influence of whether or not using motion-sensing educational mobile games on learning achievement and learning retention. Experimental results showed that learning achievement in the experimental group (which used motion-sensing mobile learning) and the control group (which did use non-motion-sensing mobile learning) both were improved, moreover, the learning retention of the experimental group significantly exceeded those of the control group.

The Effectiveness of Scaffolding in a Web-Based, Adaptive Learning System

This study combined ideas from learning hierarchy and scaffolding theory to design a web-based, adaptive learning system to investigate the effectiveness of scaffolding for elementary school students having different levels of learning achievement. The topic chosen for learning was the Three States of Water. A quasi-experiment was conducted. In this experiment, students were divided into three groups: control group (without scaffolds), experimental group A (scaffolds providing by on-line conversation) and experimental group B (scaffolds providing by face-to-face conversation). The experimental results showed significant improvement for students after they had studied using the web-based, adaptive learning system. Specifically, scaffolds in the form of face-to-face conversations greatly enhanced the learning of high-achievement students. However, there were no significant differences between the low-achievement students with or without the provision of scaffolds. It was also discovered that the web-based, adaptive learning system could help students develop their learning responsibility.

Development of a Lunar-Phase Observation System Based on Augmented Reality and Mobile Learning Technologies

Observing the lunar phase requires long-term involvement, and it is often obstructed by bad weather or tall buildings. In this study, a lunar-phase observation system is developed using the augmented reality (AR) technology and the sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices to help students observe and record lunar phases easily. By holding the mobile device towards the moon in the sky, the screen will show the virtual moon at the position of the real moon. The system allows the user to record the lunar phase, including its azimuth/elevation angles and the observation date and time. In addition, the system can shorten the learning process by setting different dates and times for observation, so it can solve the problem of being unable to observe and record lunar phases due to a bad weather or the moon appearing late in the night. Therefore, it is an effective tool for astronomy education in elementary and high schools. A teaching experiment has been conducted to analyze the learning effectiveness of the system and the results show that it is effective in learning the lunar concepts. The questionnaire results reveal that students considered the system easy to operate and it is useful in locating the moon and recording the lunar data.

Development of a virtual butterfly ecological system based on augmented reality and mobile learning technologies

A campus butterfly garden is a useful resource for teaching natural science. Students can learn about butterfly ecology by breeding and observation activities to understand the continuation of life and develop the sentiments of respecting life. However, a butterfly garden requires professional planning, construction and maintenance for sustainable development. In this study, augmented reality and mobile learning technologies were used to develop a virtual butterfly ecological system by integrating with the host plants and nectar plants in campus. Students can use smart phones or tablet PCs to breed virtual butterflies on host plants and observe their life cycles at different growing stages. With the available space in campus, a virtual butterfly garden was designed as a greenhouse where the users could observe different species of butterflies using the tracking telescope. The virtual butterfly ecological system can increase the learning motivation and interest of students through virtual breeding and observation activities. It has both educational and entertaining functions, and is therefore a suitable assistant tool for science education in elementary and high schools.

ENHANCING THE ACCURACY OF LICENSE PLATE RECOGNITION SYSTEMS WITH THE ANGLE RECOVERY METHOD

The motor vehicle is an important way of transportation for modern people, and its license plate is just like our identification cards which can be used for effective management of motor vehicles. Hence, the development of a recognition system for license plates can reduce the workload of managing motor vehicles. A license plate recognition system based on computer vision often causes recognition errors due to the plates angle problem and thus needs to be assisted by manual recognition. In this study, a recovery method for license plate images with large angles is proposed based on perspective projection to increase the recognition accuracy. The experimental results show that applying the angle recovery method to a license plate recognition system can reduce its errors, especially for license plate images with large angles. For the case of small angles, a recognition rate of 89% can be achieved by the angle recovery method, slightly higher than that of the plane rotation method (86%). For the case of a wide range of different angles, the average recognition rate achieved by the angle recovery method is 87.5%, much higher than that of the plane rotation method (57.5%). Thus, the angle recovery method is effective for enhancing the accuracy of license plate recognition systems.

Development of a Motion Sensing and Automatic Positioning Universal Planisphere Using Augmented Reality Technology

This study combines the augmented reality technology and the sensor functions of GPS, electronic compass, and 3-axis accelerometer on mobile devices to develop a motion sensing and automatic positioning universal planisphere. It can create local star charts according to the current date, time, and position and help users locate constellations on the planisphere easily through motion sensing operation. By holding the mobile device towards the target constellation in the sky, the azimuth and elevation angles are obtained automatically for mapping to its correct position on the star chart. The proposed system combines observational activities with physical operation and spatial cognition for developing correct astronomical concepts, thus making learning more effective. It contains a built-in 3D virtual starry sky to enable observation in classroom for supporting teaching applications. The learning process can be shortened by setting varying observation date, time, and latitude. Therefore, it is a useful tool for astronomy education.

A Machine Learning Approach for Analyzing Musical Expressions of Piano Performance

This paper proposed a machine learning approach for analyzing teachers’ expert knowledge of classifying students’ piano performance into approximate expression categories. Students are usually confused when learning the expressive performance because of teachers’ subjective intention difference on the same performance. In this paper, teacher models will be built by analyzing teachers’ classification rules. By replaying their performances and read teachers’ suggestions in graphical and textual modes which are generated automatically by teacher model, students could understand the nuance of performance features on each expression. Three teachers and ten students joined this experiment. Sixty piano performances were recorded for constructing the teacher models. The average accuracy of teacher models for classifying performance expression is 70.8%. Questionnaires reflect both teachers and students are satisfied with the user interface, generated suggestions, and classification rules.