• Journal of Korean Society of Steel Construction
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• 제18권1호
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• pp.11-22
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• 2006

Message Signs (VMS) structures offer an increase in traffic safety through their ability to relay massages to motorists for warnings of hazards ahead, traffic congestion, accidents, and lane closings. The geometry of these signs sometimes results in the significant cyclic loading of the supports structure due to wind gusts, which can result from passing trucks or from natural wind. This study presents the results of analytical and experimental investigations of VMS structures. The commercially available softwareGTSTRUDL (2003) was used to perform space-frame structural analyses of these welded tubular structures. Fatigue evaluations were performed using stress ranges from field measurements and from structural analyses. Based on the results of the structural analyses that were conducted, where fatigue design loadings that had been derived from AASHTO Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals (2001) were used, the structures that had been studied were found not to have infinite fatigue life. According to the limited measurements that were made in this study, the fatigue design loadings derived from AASHTO Specifications (2001) appear to be conservative, but they are not overly conservative. The results of this study should be used to make a reasonable design of VMS structures, and to maintain their standards.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제13권5호
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• pp.2156-2169
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• 2012

This study was performed to find out the relationship between farmer's syndrome and self-conscious fatigue symptoms in farmers of suburban area. The questionnaire was prepared to survey the socio-demographic characteristics, health-related behaviors, farming activities, farmer's syndrome, and self-conscious fatigue symptoms of the farmers, and the survey was carried out from April 1 to June 30, 2011 by interviewing 296 farmers residing suburban area of Daejeon city. As a results, the ratio of farmers who had positive farmer's syndrome, doubtful syndrome, and no syndrome were 34.1%, 47.6%, and 18.2%, respectively. The farmer's syndrome was positively correlated with the self-conscious fatigue symptoms, and farmers with self-conscious fatigue symptoms in high risk group were at higher risk of having farmer's syndrome. The results of hierarchic multiple regression analysis indicated that sex, education, health, and self-conscious fatigue symptom were correlated with the farmer's syndrome. Among the affective factors variables, independently self-conscious fatigue symptom was the most influential. As a conclusion, the occurrence of farmer's syndrome was influenced by the socio-demographic characteristics, health-related behaviors, and self-conscious fatigue symptoms of the farmers. Especially, self-conscious fatigue symptom was independently influenced the occurrence of farmer's syndrome.

• Journal of the Korean Data and Information Science Society
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• 제22권1호
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• pp.37-47
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• 2011

Stock price index option market has various investment strategies that have been developed. Specially, arbitrage strategies are very important to be efficient in option market. The purpose of this study is to improve profit using rough set and Box spread by using past option trading data. Option trading data was based on an actual stock exchange market tick data ranging from 2001 to 2006. Validation process was carried out by transferring the tick data into one-minute intervals. Box spread arbitrage strategies is low risk but low profit. It can be accomplished by back-testing of the existing strategy of the past data and by using rough set, which limit the time line of dealing. This study can make more stable profits with lower risk if control the strategy that can produces a higher profit module compared to that of the same level of risk.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권4호
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• pp.433-438
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• 2018

This study examined the effects of ambiguity aversion on the self-protection and self-insurance efforts using a two-period model to consider the time difference between making an effort and occurring loss, which is in contrast with the existing one-period model. The loss follows a binary distribution while the distribution is ambiguous. The distribution depends on the state variable. First, the effort of ambiguity averse individuals is not always greater than that of ambiguity neutral ones. Second, the effects of absolute ambiguity aversion (AAA), which does not appear in one-period model, were observed. Not-increasing AAA is a sufficient condition to increase the efforts of ambiguity averse individuals compared to those of ambiguity neutral ones. In addition, the change in effort also depends on the probability function of the state. Lastly, the results hold even when the individual is risk neutral or risk loving. As a result, ambiguity aversion needs to be considered independently with risk aversion.

• Korean Journal of Social Welfare
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• 제59권2호
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• pp.251-275
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• 2007

The purpose of this study was to investigate the relationship between child maltreatment, protective factors, and resilience in elementary school students. It was especially focused on what direct effect of the risk factor(child maltreatment) and protective factors to child resilience, and how protective factors affect the resilience of maltreated child. In the concrete, this study intended to find out whether protective factors mediate between child maltreatment and resilience. This study based on data from the first wave of 'Korean Youth Panel Survey(KYPS)' and subjects consisted of 2,844 4th grade elementary school students. In addition, to test the proposed models, the Mplus-structural equation modeling-was used. The major findings are as follows: First, when child maltreatment increased, resilience decreased. Second, when protective factors increased, resilience increased. Third, protective factors act as buffers against the negative effects of child maltreatment on resilience by mediation. Results indicated that child maltreatment related negatively to resilience and protective factors related positively to resilience. In addition, a mediational model in which protective factors mediates child maltreatment and resilience was supported. In conclusion, various theoretical and practical implications for social work practice focusing on the maltreated children were discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제6권3호
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• pp.75-86
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• 1986

The welded joint of the rail of railroad had shown the complicated behaviour of fatigue crack growth due to the effect of low toughness, residual stress, welding stress and strain etc. resulting from welding. Also, the welding connection has been necessary as making longer the rail, thus fatique fracture has often occurred at welded joints. From above, in this paper, faigue test was done at base metal, gas pressure and thermit welded joints to give the basic data to construct S-N diagrams. From this, it was known that the base metal was better than welded joint and gas pressure better than thermit welded joints in the resistance against the behaviour of fatigue crack growth. And it was also found that it is very dangerous to control fracture only by the method of material mechanics.

• The Journal of the Convergence on Culture Technology
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• 제6권4호
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• pp.703-708
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• 2020

As the risk of earthquakes increases recently, earthquake-resistant designs were getting interest. For this reason, this study applies that Friction pendulum-type seismic isolator is a device that attenuates seismic energy by friction and pendulum motion. The friction pendulum-type seismic isolator of this study is very easy to transport, install and maintain with light weight of metal by applying the slider using high strength engineering plastic. In addition, there is an advantage that the corrosion resistance is very excellent compared to the existing metal parts. However, there is concern about long-term durability by replacing metal materials. In this study, the frictional pendulum-type seismic isolator with EP was applied to compressive-shear test, repeated fatigue test, and ultimate load test after fatigue test, and analyzed the deformation and shear or properties after the test. As the results, the adequacy of long term fatigue durability was experimentally proven.

• Journal of the Korean Institute of Gas
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• 제21권3호
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• pp.39-45
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• 2017

The LNG storage tank as core facility of LNG industry is mainly composed of the inner tank of nikel 9% steel and the outer tank of prestressed concrete. To respond proactively increased risk of structure performance deterioration due to fatigue of the inner tank and durability reduction of the outer tank, life evaluation program for LNG storage tank is needed. In this study, life evaluation program for LNG storage tank was developed to assess fatigue of the inner tank and durability(carbonation and chloride attack) of the outer tank. By defining the main three scenarios in the inner tank, the fatigue life analysis is conducted from structural analysis and Miner's damage rule. Carbonation progress of the outer tank is predicted according to thickness of cover concrete by using carbon dioxide contents and data of penetration depth. To consider a variety of input conditions and a reliability in results of chloride attack, the evaluation of choride attack for the outer tank is constructed through Life-365 program of open source.

• Korean Journal of Psychosomatic Medicine
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• 제28권2호
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• pp.135-142
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• 2020

Objectives : To identify the relationship between somatization, stress, depression, anxiety, and psychological symptoms risk for nurses working in the intensive care unit. Create clinical evidence of psychosomatic medicine research and complement the meaning of somatization. Methods : Seventy of the mental health checkups conducted by the National Mental Health Center among the nurses using tools including Perceived Stress scale, Fatigue Severity Scale, Patient Health questionnaire-15, Korean Beck Depression Inventory, Korean Beck Anxiety Inventory, and Symptom Checklist-90-Revision. Results : 12.9% of the patients experienced more than moderate somatization. There was no statistical relationship between somatization and psychological stress perception, but feeling of anxiety and decreased self-confidence were related to the level of somatization. The group with severe somatization experienced more depression and anxiety. The group with high physical fatigue also had no statistical relationship with psychological stress perception, but had an effect on the feeling of tension, stress, or decreased control. Physical fatigue level was increased by experience of depression, not by anxiety. For psychological symptoms the higher the level of somatization, the higher the obsession and hostility was explored. In the linear regression model, stress, depression, and anxiety accounted for 39.3% of somatization and 16.1% of physical fatigue symptoms. Conclusions : We can estimate the decrease in stress cognitive symptoms, accompanying depression and anxiety, compulsion and hostility as characteristics of somatization. The causal relationship between somatization and psychological symptoms cannot be confirmed in this study, but the interrelationships are observed, can be referred to mediation strategies.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제5권2호
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• pp.121-131
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• 1985

The characteristic of fatigue crack growth in the homogeneous or the soft welded connections used SWS-53 steel and HT-80 steel as base metals is examined by fractographic analysis. As a result of this analysis, the fact that the characteristic of fatigue crack growth which is observed and measured at the surface has wide application to engineering practice is verified. Also, the fact that the welded parts of HT-80 steel have much danger of brittle fracture is prooved. Considering that the striations are observed at the welded parts of SWS-58 steel and the spacing of striations has higher numerical value than da/dN, we can prove that inner fatigue crack growth may develop in zig-zag directions.