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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(More)
In recent years, the applications of wireless sensor networks have increased steadily. Sensor nodes are often scattered outdoors and their energy consumption depends heavily on the area of coverage and network topology. Many studies were focused on saving the energy of sensor nodes to maintain their functionality. This work aims at extending the lifetime of(More)
ABSTRAcT This study combined ideas from learning hierarchy and scaffolding theory to design a web-based, adap-tive 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(More)
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(More)
As the advance of information and communication technologies, the Internet has become an integral part of human life. Although it can provide us with many convenient services, there also exist some potential risks for its users. For example, hackers may try to steal confidential data for illegal benefits, and they use a variety of methods to achieve the(More)
Due to the needs of many demanding users in wireless networks, the transmission distance and bandwidth of IEEE 802.11 has become inadequate to satisfy their requirements. Therefore, the next generation of wireless network IEEE 802.16 standard has been developed. The latter has a higher bandwidth to cover a wider area of communication with lower costs in(More)