• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.389-396
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• 2005

In this paper, we propose a pre-distortion method using the NLMS(Normalized Least Mean Square) algorithm to cope with hish PAPR(Peak to Average Power Ratio) problem in OFDM communication system. This proposed scheme estimates the distortion characteristics of HPA, and changes the characteristic against the distortion. Therefore, it can be shown that the adaptive characteristic of the NLMS pre-distorter is good to track the various nonlinear characteristic of HPA, even though HPA characteristic is changed by temperature variation or aging. From the performance analysis, SNR efficiency of NLMS pre-distorter is about $0.5\;\cal{dB}$ less than that of common numerical non-adaptive pre-distorter, when IBO(Input Back Off) is $0\;\cal{dB}$. However, the NLMS pre-distorter is better than the common numerical pre-distorter, because these two pre-distorters have similar performance in higher than $3\;\cal{dB}$ IBO, and the NLMS pre-distorter maintains the constant performance even though characteristic of HPA is changed.

• Journal of the Korean Data and Information Science Society
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• v.25 no.6
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• pp.1407-1418
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• 2014

Korean youth spend tremendous time in school for preparing for college admissions. Their academic achievement and overall satisfaction with their lives are affected by how well they adapt to life in school. Successful adaptation to school is important enough to affect a student's future social life. One of the factors that affect adaptation to school is the psychological condition of adolescent anxiety. Anxiety is one of the common mental disorders that appear in people who are not familiar with new environments. Anxiety is known to be related to behavioral problems, and problems with psychological and emotional adaptation. This condition is dramatically increased in adolescents.Parental conflict in particular is known to be a major factor in affecting youth anxiety. As parental conflict became more severe, children felt more negative emotions such as anger, sadness and worry. Moreover, when a child's issue caused the parental conflict, there were more side effects in the emotional condition of the child. This study shows how parental conflict affects a child's anxiety and a child's school life.This problem is analyzed through structural equation modeling.

• Journal of the Korean Data and Information Science Society
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• v.25 no.6
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• pp.1361-1369
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• 2014

This research is for analyzing the change rate of housing rent price index produced by KAB (Korea Appraisal Board) in the monthly periodical, Survey on Housing Monthly Rent. The index is a very important and useful indicator to understand and diagnose the house rental market. However, the index is criticized in that it tends to decline when the price level of Jeonse (i.e., a typical type of dwellings in Korea, generally leased on a deposit basis for 1 or 2 years) is highly going up, which is inconsistent with the actual economic sentiment of tenants. We verify the reason why such phenomenon occurs and suggest a simple but novel method to analyze properly the change rate of the index. The main findings are as follows. The key factor to trigger the problem is the use of the conversion rate for Jeonse-to-monthly rent for constructing the rent price indexes. We separate the effect of the conversion rate out of the change rate of the index and quantify the adjusted real change rate showing an increase of the rent price level which is masked by the conversion rate before.

• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.185-191
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• 2008

To fundamentally solve the problem of deterioration of concrete structures, it has been researched that the high durable concrete structure reinforced with the FRP rebar can be one of major solution to the newly-developed concrete structure. FRP rebar has lots of advantages such as non-corrosive, high performance and light weight against the conventional steel rebar. Among these kinds of FRP rebars, GFRP rebar has usually been considered as the best reinforcement because of its economic point of view. Even though the material capacity of the GFRP rebar was already investigated, there are some problems such as low modulus of elastic that will be cause for degrade of the serviceability of flexural concrete member reinforced with the GFRP rebar. Thus, the deflection characteristics of the GFRP rebar reinforced concrete structure should be considered then investigated. In this study, ACI 440 guideline (2003), ISIS Canada Design Manual (2001) and Toutanji et al. (2000) was considered for predicting the moment of inertia of the concrete beam reinforced with the GFRP rebar. And it was also evaluated that load-deflection relationship had a good accordance with the test and analysis result. In the result of this study, it could be estimated that the load-deflection relationship using the suggested equation of moment of inertia in this study indicated better accordance with the test result than that of the others until failure.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.8-15
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• 2016

The purpose of this study is to design a model with the structural stability so as not to lose the operational function due to structural plastic or fail of a sliding blast door by blast pressure to this aim, a numerical simulation was performed using full-size experiments and M&S (Modeling & Simulation) of the sliding blast door. The sliding blast door ($W3,000{\times}H2,500mm$) under the blast load is in the form of a sliding type 2-way metal grill, which was applied by a design blast pressure (reflected pressure $P_r$) of 17 bar. According to the experimental results of a real sliding blast door under blast load, the blast pressure reached the sliding blast door approximately 4.3 ms after the explosion and lasted about 4.0 ms thereafter. The maximum blast pressure($P_r$) was 347.7 psi (2,397.3 kPa), it is similar to the UFC 3-340-02 of Parameter(91 %). In addition, operation inspection that was conducted for the sliding blast door after real test showed a problem of losing the door opening function, which was because of the fail of the Reversal Bolt that was installed to prevent the shock due to rebound of the blast door from the blast pressure. According to the reproduction of the experiment through M&S by applying the blast pressure measurement value of the full-size experiments, the sliding blast door showed a similar result to the full-size experiment in that the reversal bolt part failed to lose the function. In addition, as the pressure is concentrated on the failed reversal bolt, the Principal Tensile Failure Stress was exceeded in only 1.25 ms after the explosion, and the reversal bolt completely failed after 5.4 ms. Based on the result of the failed reversal bolt through the full-size experiment and M&S, the shape and size of the bolts were changed to re-design the M&S and re-analyze the sliding blast door. According to the M&S re-analysis result when the reversal bolt was designed in a square of 25 mm ($625mm^2$), the maximum pressure that the reversal bolt receives showed 81% of the principal tensile failure stress of the material, in plastic stage before fail.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.6
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• pp.1351-1364
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• 2019

When SCADA is exposed to cyber threats and attacks, serious disasters can occur throughout society. This is because various security threats have not been considered when building SCADA. The bigger problem is that it is difficult to patch vulnerabilities quickly because of its availability. Digital forensics procedures and techniques need to be used to analyze and investigate vulnerabilities in SCADA systems in order to respond quickly against cyber threats and to prevent incidents. This paper addresses SCADA forensics taxonomy and research trends for effective digital forensics investigation on SCADA system. As a result, we have not been able to find any research that goes far beyond traditional digital forensics on procedures and methodologies. But it is meaningful to develop an approach methodology using the characteristics of the SCADA system, or an exclusive tool for SCADA. Analysis techniques mainly focused on PLC and SCADA network protocol. It is because the cyber threats and attacks targeting SCADA are mostly related to PLC or network protocol. Such research seems to continue in the future. Unfortunately, there is lack of discussion about the 'Evidence Capability' such as the preservation or integrity of the evidence extracting from SCADA system in the past researches.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.214-215
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• 2013

Current competition among companies than regional, the time constraints, it is globalization, Tilt the efforts of many to be operated by building the efficient distribution system to reduce logistics costs and improve customer service it is reality's there. Therefore, the need for industrial complexes environmentally friendly can be cost competitive companies perform cavitation region's increased. To build the distribution center these logistics system through a joint of freight and appropriate policy is required. In particular, efficient operation through the system construction of industrial complexes in the logistics system is very important in terms of friendly low-cost urban logistics, the environment. Since the traffic volume which is Jipufa and utilization of network is transported by a more appropriate technicians and means suitable operating model can efficiency is improved. However, despite these advantages, research network design has not been actively conducted due to the complexity of the problem. Therefore, in this study, by analyzing the logistics system, and presents the operating model through a simulation and basic settings for the model of the logistics complex based on the analysis result, the construction of infrastructure of logistics industry complex it is intended to present the article.

• Journal of Navigation and Port Research
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• v.37 no.4
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• pp.391-400
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• 2013

Each country has recently established and operated so called Aids to Navigation(AtoN) AIS system collecting and transferring information on the sea state and AtoN's position. Korea has also decided to introduce the system and been establishing it. And it has already installed and operated this system in Incheon and Daesan. For the purpose of giving the national standards of AtoN AIS, this paper is to investigate the present states of AtoN AIS systems in the above two area and to suggest the improvement to the operation of AtoN AIS system. To make it, the paper deals with the international regulations of related AtoN AIS and the cases of foreign's AtoN AIS system installed and also investigates the operation states of the system, in five modules such as system management, system composition, information, function and cooperation. The followings are concluded; improving the inconsistency of system management, reducing operator's confusion caused by excessive display of AtoN AIS system, improving the problem of receiving unnecessary information, improving the functional problems caused by AIS communication inability and improving AtoN AIS information which is presently not used on board.

• Journal of KIISE:Information Networking
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• v.30 no.6
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• pp.729-742
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• 2003

Mobile Communication has a possibility of eavesdropping by nature of wireless channel. It is known that eavesdropping of CDMA system is impossible because the voice data spreads with the PN. First of all, we show that it is possible to eavesdrop the CDMA channel by analysis of the forward channel in case that we know the ESN and the MIN. We can monitor the forward traffic channel with easy since ESN and MIN are exposed during the call processing in CDMA service in Korea. In this paper, we will show security weakness and propose an enhanced mechanism for CDMA service. We consider the problem of security in the CDMA service. CDMA system has wireless channels to transmit voice or data. By this reason, CDMA communication has a possibility of being eavesdropped by someone. It is known that eavesdropping in CDMA system is impossible because the voice data spreads with the PN. However, we can eavesdrop the CDMA data in FCM protocol in case that we know the ESN and the MIN. In CDMA system, ESN and MIN are exposed to the wireless channel. In this paper, we analyze the flow of the voice and signal in the CDMA system and monitor the forward traffic channel by the FCM protocol. The FCM protocol is proposed to monitor the forward channel in CDMA system. We can show the possibility of monitoring in one-way channel of CDMA system by the FCM protocol. The test instrument based on the FCM protocol is proposed to monitor the CDMA forward channel. We will show the system architecture of the test instrument to monitor the forward channel in CDMA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.858-864
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• 2011

There is no standard model for a Stated Period Check and a Precise Safety Diagnosis to remove electric fire and shock in the university Lab and institute. Especially, the research for the Stated Period Check and the Precise Safety Diagnosis of the Lab related to electrical field is very weak currently, and it is very necessary to build a detail safety plan. This paper informs the specific standard guideline of the safety check list, method and equipment and it shows the way to evaluate safety grade too. This paper also provides the information of R&D process through the analysis of electrical safety check list of ordinary R&D Lab. It shows a new detail guideline to R&D Lab, and the new guideline removes existing problem and deliver the effective standard model to each R&D Lab. The standard model developed in this research adopts the clear guideline of each check list for the electrical environment of current R&D Lab. This standard model can be applied for every R&D Lab to detect routine safety check and detail safety check immediately. This Research will generally improve not only the effective safety check, but also the safety level for R&D Lab to prevent the electrical accidents.