• International Journal of Contents
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• v.4 no.2
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• pp.19-23
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• 2008

This paper presents a novel method to construct a personalized e-Learning system based on dynamic estimations of item parameters and learners' abilities, where the learning content objects are of the same intrinsic quality or homogeneously distributed and the estimations are carried out using IRT(Item Response Theory). The system dynamically connects the test and the corresponding learning procedures. Test results are directly applied to estimate examinee's ability and are used to modify the item parameters and the difficulties of learning content objects during the learning procedure is being operated. We define the learning unit 'Node' as an amount of learning objects operated so that new parameters can be re-estimated. There are various content objects in a Node and the parameters estimated at the end of current Node are directly applied to the next Node. We offer the most appropriate learning Node for a person's ability throughout the estimation processes of IRT. As a result, this scheme improves learning efficiency in web-base e-Learning environments offering the most appropriate learning objects and items to the individual students according to their estimated abilities. This scheme can be applied to any e-Learning subject having homogeneous learning objects and unidimensional test items. In order to construct the system, we present an operation scenario using the proposed system architecture with the essential databases and agents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12B
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• pp.1435-1443
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• 2009

In this paper, an energy harvesting sensor network system is modeled and simulated by using the DEVS (Discrete Event System Specification) formalism. The system is composed of a sink (master) node, which is battery or mains powered, and a set of sensor (slave) nodes, each of which harvests ambient energy and converts it into electrical energy. For simulation, (i) the behavior of energy harvesting and storing circuits of the slave node is partitioned into a set of piecewise continuous segments and then each segment is represented as a discrete state; (ii) the interaction among the master node and components of the slave node is investigated preciously; and (iii) the investigated result is modeled and simulated by using the DEVS formalism.

• Journal of Sensor Science and Technology
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• v.14 no.3
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• pp.198-205
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• 2005

Recently, the systems using multiple sensors such as magnetic, acoustic and pressure sensor are used for detection of underwater objects or vehicles. Those systems have difficulty of maintenance and repair because they operate underwater. Thus, this paper describes a hybrid detection system with long term operating reliability. This has a multi-signal transmission structure to have a high reliability. First, a signal transmission & receiving part, which transfers data from underwater sensors to land and receive control message from land through optical cable, has 4 multi-path. Second, the nodes for signal transmission are connected dually each other with single-hop construction and sensors are connected to a couple of neighboring nodes. This enables the output signal to transmit from a node to the next node and the next but one node together. Also, the signal from a sensor can be transmitted to two nodes at the same time. Therefore, the system with this construction has high reliability in long term operation because it makes possible to transmit sensor data to another node which works normally although a transmission node or cable in system have some faults.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1786-1804
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• 2013

We consider a specific interference-limited wireless relay system that comprises several cooperation units (CUs) which are defined as a source and destination node pair with an associated relay node. In the wireless relay system, all source nodes simultaneously transmit their own signals and the relay node in each CU then forwards the received signal to the destination node, causing co-channel interference at both the relay node and the destination node in each CU. The co-channel interference at the relay node is closely related to that at the destination node in each CU. We first derive the end-to-end outage probability in a CU over Rayleigh slow-fading channels with interference for the decode-and-forward (DF) relaying strategy. Then, on the assumption that each CU is allocated with equal power we design an optimal power allocation between the source node and the relay node in each CU to minimize the outage probability of the investigated CU. At last, in the case that each CU is not allocated with equal power and the sum of their power is constrained, we present an optimal power allocation between CUs to minimize the sum of the outage probability of all CUs. The analytical results are verified by simulations.

• 전자공학회논문지 IE
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• v.46 no.3
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• pp.55-61
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• 2009

This paper describes an assistant system for elders who live alone. The developed system is composed of a wearable RFID system, a gateway system, and server system. The wearable RFID system is installed in glove. The wearable RFID system can be considered as a wireless sensor network which has a sink node and sensor node with a RFID reader. The sensor node can read RFID tags on the various objects used in daily living such as furniture, medicines, sugar and salt bottles, and ok. The sensor node transmits wireless packets to the sink node. The sink node sends the received packet immediately to a server system via a gateway system. The gateway provides users with audio-visual information of objects. The server system is composed of a database server and a web server. The data from each wearable RFID system is collected into a database, and then the data are processed to visualize the measurement of daily living activities of users. The processed data can be provided for someone who wants to know about user's daily living patterns in house such as family, caregivers, and medical crew.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.13-19
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• 2004

A system for detecting underwater target demands a high operational reliability because of the difficulty of maintenance and repair when the system has a few troubles during long operating period. Therefore, in this paper, we have proposed a signal transport system with a high reliability in an underwater sensor array system composed of magnetic and acoustic sensors. In this system, the nodes for signal transport are connected dually each other with single-hop construction and a magnetic sensor is connected to a couple of neighboring nodes. This enables the output signal to transport from a node to the next node and the next but one node. Also, the signal from a magnetic sensor can be transported to two nodes at the same time. Thus, the system with this construction makes possible to transport sensor data to another node which works normally when a transport node or cable have some faults and will operate normally although it happens some problems in a few signal transport nodes and connection cables.

• International Journal of High-Rise Buildings
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• v.1 no.1
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• pp.29-36
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• 2012

The diagrid structural system is considered to be not only the best structural system for constructing free form structures, but also a very effective system in resisting lateral load. As a newly investigated structural system, its complicated node has not yet been completely investigated and minimal experimentation of manufacturing and constructing the system have been conducted. Therefore, the constructing cost of the diagrid structural system is still comparatively high. In this paper, the cyclic performance of a diagrid node with an H-section brace will be discussed. Design details that consider productivity were proposed and their structural performances were assessed through experimental and analytical investigation.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2140-2142
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• 2003

Recently, TCP/IP on Ethernet protocol is in use environment of LAN have developed a single chip by hardware. Therefore, the study about the single chip applies to the system control application like information electronic appliances, manufacturing automation machine has been made progress. This paper is the development of experimental Client node and Serve node that can transfer input-output data needed on Network Control System Client node is a sensor part of control system, that is, an analog signal is applicable to output data convert AD through LAN. Server node data sended in client convert DA, and then it is applicable to driver of Control System, so it achieves its part. In this study, is prove that using TCP/IP construct Network Control System.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.30-35
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• 2022

Rendering is widely used for visual effects in animations and movies. Although rendering is computing-intensive, we observe that it accompanies heavy I/O because of large input data. This becomes technical hurdles for multi-node rendering performed on public cloud nodes. To reduce the overhead of data transmission in multi-node rendering, this paper analyzes the characteristics of rendering workloads, and presents the cooperative caching scheme for multi-node rendering. Our caching scheme has the function of synchronization between original data in local storage and cached data in rendering nodes, and the cached data are shared between multiple rendering nodes. We perform measurement experiments in real system environments and show that the proposed cooperative caching scheme improves the conventional caching scheme used in the network file system by 27% on average.

• International Journal of High-Rise Buildings
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• v.1 no.1
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• pp.21-28
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• 2012

Diagrid system has been in the spotlight for its superiority in terms of the resistance to lateral force when applied to skyscrapers. In diagrid system, most of columns can be eliminated because vertical loads (gravity loads) and horizontal loads (lateral loads) are delivered simultaneously thanks to the triangular shape of diagrid. However, lack of studies on connection shape and node connection details makes it hard to employ the system to the buildings. In this study, the structural safety of the node connections in circular steel tube diagrid system which has been considered in the Cyclone Tower in Korea (Seven stories below and fifty-one above the ground) was evaluated using the 4 full-scale specimens. The parameters are the extended length (20 mm, 40 mm & 60 mm), thickness (40 mm & 50 mm).