• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.856-859
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• 2010

WSN is composed of a lot of small sensors with the limited hardware resources. In WSN, at the initial stage, sensor nodes are randomly deployed over the region of interest, and self-configure the clustered networks by grouping a bunch of sensor nodes and selecting a cluster header among them. Specially, in Mobile-WSN environment, in which the administrator's intervention is restricted, the self-configuration capability is essential to establish a power-conservative Mobile-WSN which provides broad sensing coverage and communication coverage. In this paper, we propose a self-configuration routing protocol for Mobile-WSN, which consists of step-wise novel protocols for initial deployment, effective joining and removal of sensor nodes, which result in reducing overall power consumption, and extending the lifetime of network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.890-893
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• 2010

In wireless sensor networks, each node generally uses a battery because it is hard to replace or charge. For this reason, study for life time prolongation of each node within the limited energy source has become an important issue. So many ways are suggested to minimize the energy consumption for each node, especially energy efficient MAC protocols have been studied actively. T-MAC of contention based MAC protocol is that added the adaptability on fixed duty cycle of S-MAC. T-MAC allocates the fixed timeout before each node goes to sleep mode from active mode. If no data exchanged in a timeout, each node goes to sleep mode. Because of the timeout is always fixed, the absence of data exchange in a timeout will cause unnecessary energy consumption. In this paper, in order to improve the energy efficiency, we propose a MAC protocol based on adaptive timeout that analyze the probability of the timeout, and provides the modified timeout.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.477-479
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• 2017

With the recent advances in medical technology and health care, the prevention and treatment of diseases has developed. Accordingly aging has rapidly progressed. In this life span and aging society, demand for diagnostic centered medical care is increasing rapidly. In this paper, we propose a wearable patient check system based on FPGA that can be controlled by sensors. In the existing hospital, a doctor or nurse visited the patient every hour to check the condition. However, in this paper, patients, doctors and nurses can check the patient's condition at the desired time using patient check system. In addition, the tilt sensor is used for the patient who is uncomfortable to easily control. The proposed FPGA-based hardware architecture consists of an algorithm for enlarged image processing, a TFT-LCD Controller, a CIS Controller, and a Memory Controller to output the patient's status image. Implemented and validated using the DE2-115 test board with Cyclone IV EP4CE115F29C7 FPGA device and its operating frequency is 50MHz.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.222-230
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• 2009

A sensor network is an important element of the ubiquitous and it consists of sensor fields that contain sensor nodes and sink nodes that collect data from sensor nodes. Since each sensor node has limited resources, one of the important issues covered in the past sensor network studies has been maximizing the usage of limited energy to extend network lifetime. However, most studies have only considered fixed sink nodes, which created various problems for cases with multiple mobile sink nodes. Accordingly, while maintaining routes to mobile sink nodes, this study aims to deploy the hybrid communication mode that combines single and multi-hop modes for intra-cluster and inter-cluster transmission to resolve the problem of failed data transmission to mobile sink nodes caused by disconnected routes. Furthermore, a 2-level hierarchical routing protocol was used to reduce the number of sensor nodes participating in data transmission, and cross-shape trajectory forwarding was employed in packet transmission to provide an efficient data dissemination method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.77-83
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• 2016

Recently, interests for maintenance of transmission tower are increasing to extend life of structures and reduce maintenance cost. However, existing classical diagnosis method of corrosion deteriorated degree on the transmission tower steel members, visual inspection, has a problem that error often due to difference of inspector's individual knowledge and experience. In order to solve the problem, this study carried out to develop the corrosion deterioration inspection tool for transmission tower steel members. This tool is composed of camera equipment and computer-aided diagnosis system. We standardized the photographing method by camera equipment to obtain suitable pictures for image processing. Diagnosis system was designed to evaluate automatically degree of corrosion deterioration for member of transmission tower on the basis of the RGB color image processing techniques. It is anticipated that developed the corrosion deterioration inspection tool will be very helpful in decision of optimal maintenance time for transmission tower corrosion.

• The KIPS Transactions:PartD
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• v.15D no.5
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• pp.589-598
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• 2008

Recently, Mobile Computing Devices are used generally. And Information which is processed by Mobile computing devices is increasing. Because information is digitalizing. So Mobile computing Devices demand an Embedded DBMS for efficient management of information. Moreover Mobile computing Devices demand an efficient storage management in NAND-type flash memory because the NAND-type flash memory is using generally in Mobile computing devices and the NAND-type flash memory is more expensive than the magnetic disks. So that in this paper, we present an efficient Compressed Data Management System for the embedded DBMS that is used in flash memory. This proposed system improve the space utilization and extend a lifetime of a flash memory because it decreases the size of data.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.7-11
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• 2008

This paper presents the experimental results on the oil leakage characteristics of stem seals depending on the driving distance in LPG vehicle. The increased speeds of the camshaft and oil temperatures do not affect to the oil leakage of the seals because of the low level of driving distances less than 40,000 km. But the increased driving distance over 50,000 km to 100,000 km shows a rapid deteriorating the sealing performance, which may increase the oil leakage through the rubbing surfaces between the poppet valves and stem seals. In this result, the stem seal may be exchanged about the driving distance of 50,000 km to 60,000 km with a currently used stem seal in LPG car. Thus, the stem seal for a poppet valve should be resigned for the increased durability and long life.

• Nuclear Engineering and Technology
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• v.19 no.3
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• pp.169-179
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• 1987

The change of material J-R (J-T) curve with crack extension and J-calculation method was investigated to give experimental and analytical method for reliable J-R (J-T) curve, which was adapted recently as a tool for instability analysis of Nuclear Pressure Vessel. Experiments were carried out by Single Specimen Unloading Compliance Method using 1/2"T, Compact-Tension Type fracture mechanic specimens which were the same size and material as domestic nuclear pressure vessel material surveillance specimens. The results revealed that crack extension up to 25~30% of initial uncracked ligament and JD (Deformation theory J) calculation method, currently being used in NUREG-0744, could give rather reliable material J-R (J-T) curve than the small crack extension and JM (Modified J) calculation method. But as JM results more or less higher J at instability, the application of JM should be considered regarding to the problem of power plant availability.lity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.592-598
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• 2017

The purpose of this study is to suggest a new inspection period of ${\triangle}{\triangle}$ guided missiles by analyzing their reliability using field data. The ${\triangle}{\triangle}$ guided missile has an inspection period of five years which was determined using prediction data during its development process. However, from the analysis of its field data, it was shown that the inspection period could be extended to more than 18 years. Based on this result, a policy is proposed to reevaluate the inspection period by means of practical reliability tests.

• Journal of Korea Multimedia Society
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• v.10 no.2
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• pp.236-245
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• 2007

Wireless sensor networks consist of numerous nodes equipped with small-sized and limited calculation capacities and storage space as well as low-capacity batteries. Therefore, the key issue is to reduce energy consumption of sensor nodes in sensor network environment. To reduce energy consumption of sensor nodes, consideration must be given to decreasing frequency of messages transmitted by nodes. Also, considering network application, security of sensor networks is also considered important. Therefore, this study proposes a key distribution scheme in dynamic clustering model. The dynamic clustering model used for this scheme is very effective in extending life span of wireless sensor networks. The proposed scheme provides improved security compared to the existing key distribution scheme by applying grid-based key distribution scheme and allocating polynomial s hare to the nodes forming a cluster. Also, comparison was made with the previously proposed grid-based, location-based and cluster-based key distribution schemes to illustrate the advantages of the proposed scheme.