• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.2 no.4
• /
• pp.23-32
• /
• 1982

In order to obtain the necessary data for the safety maintenance, repair, and reinforcement of steel structures, experiment was carried out to examine the mechanical capacity and toughness variation for steel with service history and without. In this paper, hardening and embrittlement by fatigue accumulation, and the decrease of toughness was examined and weld that was commonly used as the connection method of steel structure was also examined. It was found that hardening and embrittlement have more effect on the decrease of toughness than the increase of strength. Such a tendency was also similary state in case of weld. And it was found that, in the weld of steel with service history and without, embrittlement was observed at normal temperature.

• Journal of the Korea Society for Simulation
• /
• v.17 no.3
• /
• pp.95-105
• /
• 2008

In this paper, we propose the DAMMC(Distributed Authentication Model using Multi-level Cluster) for wireless sensor networks. The proposed model is that one cluster header in m-layer has a role of CA(Certificate Authority) but it just authenticates sensor nodes in lower layer for providing an efficient authentication without authenticating overhead among clusters. In here, the m-layer for authentication can be properly predefined by user in consideration of various network environments. And also, the DAMMC uses certificates based on the threshold cryptography scheme for more reliable configuration of WSN. Experimental results show that the cost of generation and reconfiguration certification are decreased but the security performance are increased compared to the existing method.

• Convergence Security Journal
• /
• v.13 no.3
• /
• pp.33-38
• /
• 2013

Security between mobile nodes and efficient communication is one of the most important parts of the MANET. In particular, the wireless network is significantly higher for the attack threats because of collaborative structure for open communication media and communication. However, application of existing security mechanisms and intrusion detection system is not easy due to the characteristics of MANET. It is because collection and integration of adult data by the dynamic topology due to the mobility of nodes and many network sensors is difficult. In this study, we propose cooperative security system technique that can improve the reliability based on authentication assessing confidence about the whole nodes which joins to network and detect effectively this when intrusion occurs. Cluster head which manages the cluster performs CA role for the certificate issue and the gateway node performs role of intrusion detection system. Intrusion detection is performed by cooperating with neighboring nodes when attack is not detected in one intrusion detection node. The performance of the proposed method was confirmed through experiments comparing with the SRP technique.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.9
• /
• pp.47-52
• /
• 2016

Unusual extreme weather events, which exceed a safe design capacity of the infrastructure, increase the frequency of natural disasters and has also been enlarged damage scale. Aging buildings and rapid urban progress act as weighting factors for the new composite disasters. Technological advances support detecting pre-disaster risk, real-time data analysis, and rapid response to the disaster site, but it is insufficient that emergency relief for buried alive must take advantage of the proven technologies through field tests. This study aims to evaluate directional drilling performance through underground soils and the reinforced concrete structure for primary lifeline installation in order to quickly provide relief supplies for buried alive when urban structures collapse.

• Progress in Medical Physics
• /
• v.13 no.2
• /
• pp.90-97
• /
• 2002

The simulator which has a identical geometry with radiotherapy equipments, is a essential equipment to accomplish optimized radiotherapy plan through simulation by using diagnostic low energy X-ray. A Radiotherapy simulator has a combined technology from the therapeutic and diagnostic radiology and needs a periodical test for mechanical and optical properties, X-ray generator, image intensifier of simulator to keep the proper maintenance and radiation safety. Hence, tests were done and classified as i) mechanical and optical parameter for the gantry, collimator, and couch ii) key performance of the X-ray generator such as a kVp, mAs, and timer iii) performance of the image intensifier such as a resolution and contrast for three kinds of simulator, common use in clinic. The above result of tests will be applied to the acceptance test and periodical quality assurance procedure.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.5 s.72
• /
• pp.641-652
• /
• 2004

The strong beam-to-column axis connections in steel structures have been studied for a long time to develop the strength and resistance of the connections. There have been very few studies, however, related to weak axis connections. Domestically, the bracket-type connection is commonly used in weak axis connections to elevate the efficiency of the constructions when the steel structures are constructed. The bracket-type connection detail has been applied moderately to weak axis connections. Therefore, the bracket-type connection in weak axis connections might be brittle and over-designed. The results of this study showed that the welding on the web of the column and the beam was unnecessary. In addition, this study confirmed that the new weak axis connection proposed in this study was superior to the previous connection in terms of strength and ductility.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.11
• /
• pp.1397-1405
• /
• 2013

The optimal rib pattern design of B-pillar trim considering occupant head protection can be determined by two methods. One is the conventional approximate optimization method that uses the statistical design of experiments (DOE) and response surface method (RSM). Generally, approximated optimum results are obtained through the iterative process by trial-and-error. The quality of results strongly depends on the factors and levels assigned by a designer. The other is a methodology derived from previous work by the authors, called the sequential design of experiments (SDOE), to reduce the trial-and-error procedure and to find an appropriate condition for using artificial neural network (ANN) systematically. An appropriate condition is determined from the iterative process based on the analysis of means. With this new technique and ANN, it is possible to find an optimum design accurately and efficiently.

• The Journal of the Korea Contents Association
• /
• v.7 no.11
• /
• pp.43-51
• /
• 2007

Access control techniques should be flexible enough to support all protection granularity levels. Since access control policies are very likely to be specified in relation to document types, it is necessary to properly manage a situation in which documents fail to be dealt with by the existing access control policies. The existing access control has not taken information structures and semantics into full account due to the fundamental limitations of HTML. In addition, access control for XML documents allows only read operations, and there exists the problem of slowing down system performance due to the complex authorization evaluation process. In order to resolve this problem, this paper designs a XML Access Control Management System which is capable of making fined-grained access control. And then, in developing an access control system, it describes the subject and object policies of authorization for XML document on which authorization levels should be specified and which access control should be performed.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• autumn
• /
• pp.439-443
• /
• 2001

A lot of buildings, especially apartment housing, have been dismantled so as to enhance the value of the building without exact assesment for the service life and deterioration degree of the building. Remodeling for an aged building is becoming a hot issue to owners in the public sector and the private sector. Peoples including owner, tenants, constructors recognize the fact that the efficient maintenance of the building during the service life and lengthening the practical service life are very important in point of minimizing LCC. This study suggest a decision making system to judge whether to remodel(renovate) or to reconstruct an aged building. The system is composed of structural performance assesment elapsed(or practical service) life evaluation against whole service life, deterioration assesment of the building equipment, dweller's satisfaction, etc.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.12B
• /
• pp.1574-1585
• /
• 2011

This paper proposes a real-time algorithm for speed limit sign recognition for advanced safety vehicle system. The proposed algorithm uses Block-DCT in extracting features from a given ROI(Region Of Interest) instead of using entire pixel values as in previous works. The proposed algorithm chooses parts of the DCT coefficients according to the proposed discriminant factor, uses correlation coefficients and variances among ROIs from training samples to reduce amount of arithmetic operations without performance degradation in classification process. The algorithm recognizes the speed limit signs using the information obtained during training process by calculating LDA and Mahalanobis Distance. To increase the hit rate of recognition, it uses accumulated classification results computed for a sequence of frames. Experimental results show that the hit rate of recognition for sequential frames reaches up to 100 %. When compared with previous works, numbers of multiply and add operations are reduced by 69.3 % and 67.9 %, respectively. Start after striking space key 2 times.