• Steel and Composite Structures
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• 제33권1호
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• pp.123-131
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• 2019

The present investigation is concerned with two dimensional deformation in a homogeneous nonlocal thermoelastic solid with two temperature. The nonlocal thermoelastic solid is subjected to inclined load. Laplace and Fourier transforms are used to solve the problem. The bounding surface is subjected to concentrated and distributed sources. The analytical expressions of displacement, stress components, temperature change are obtained in the transformed domain. Numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of angle of inclination and nonlocal parameter on the components of displacements, stresses and conductive temperature. Some special cases are also deduced from the present investigation.

• 대한인간공학회지
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• 제36권5호
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• pp.485-498
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• 2017

Objective: This study aims to survey and compare three systemic accident investigation techniques of Accimap, STAMP and FRAM, based on the application studies of the Sewol ferry accident. Background: Traditional accident investigation methods such as domino models, FTA, etc. work well for losses caused by physical component failures or actions of human in relatively simple systems, but are unable to depict mechanisms generating errors and violations in the current complex socio-technical systems. For better understanding the structure and behavior of the socio-technical systems, systemic techniques have been developed and used. Method: This study was mainly based on survey of literatures through surfing webpages of ScienceDirect and Google, and ergonomics relevant journals. The key words of Sewol, Sewol ferry, Sewol ferry accident, etc. were used in the survey. Results: Three systemic accident investigation methods included similar actors in the Sewol ferry accident including government, Ministry of Ocean and Fisheries, Korean Coast Guard, Korean Register of Shipping, Korea Shipping Association, Chonghaejin Marine Company, crew members. The methods graphically represented each level's failures or performance variabilities of relevant functions and relationships between them. It was shown that the systemic methods consider the entire system, ranging from the environment in which the accident occurred, to the role of government in shaping the system of work. Each method has its own comparative pros and cons, but the Accimap has advantages in terms of time of analysis, data required, model complexity and degree of comprehensiveness. Conclusion: This study reviewed and compared three systemic accident investigation methods, which showed that there are systemic characteristics and pros and cons in the methods. Application: The results would be used as a guideline when selecting accident investigation methods.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.822-826
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• 2015

이 연구에서는 터널 시공 시 터널 배수관으로 유입되는 미세입자의 흐름과 이에 의한 물리/화학적 폐색현상에 따른 터널배수재의 성능저하를 PVDF film의 진동을 이용하여 성능을 향상시키는 방법의 적용 가능성에 대해 실내실험을 통하여 고찰하였다. 연구에서 터널로 유입되는 미세입자 슬러리 유입의 터널 환경을 모사하여 진행하였고 PVDF film을 이용한 기초 실험과 배수재를 모사한 모형실험으로 나누어 수행하였다. 기초 실험에서는 PVDF film에 50% 함수비(민물과 바닷물)의 점토를 흘려 주파수별 점토 슬러리의 흐름특성에 대한 효율성을 고찰하였으며 배수재 모사 실험에서는 배수관에 부직포를 부착시켜 슬러리의 흐름과 막힘 현상 해소에 대한 진동 효과를 고찰하였다. 실험결과는 진동에 의한 배수재의 배수성능, 즉 슬러리의 흐름과 막힘 해소현상이 아주 높게 나타났다. 이상의 실험결과를 종합하여 배수관을 기존 배수재와 융합, 응용, 활용할 수 있는 하이브리드 배수시스템을 개발할 수 있는 기초 자료를 확립하였다.

• Geomechanics and Engineering
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• 제38권2호
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• pp.157-164
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• 2024

This paper describes the general trends of the stress-strain behavior of Korean weathered soil prior to failure and behavior at failure under triaxial loading. The isotropically consolidated samples were tested in a testing device under monotonic undrained loading. Relative density, effective mean pressure and fine content were the factors varied in the experimental investigation. The test results were analyzed and their behaviors were interpreted within the framework of plasticity constitutive model for a weathered Korean silty sand. Possible physical bases for the proposed forms are discussed. Validation of the applied model using the laboratory results is also given.

• 한국정밀공학회지
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• 제16권12호
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• pp.40-45
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• 1999

Electrical damages to critical parts in rotation machinery have caused may machinery failures and hours of costly downtime. The problem of shaft currents generated in non-electrical machines have puzzled both users and manufacturers of these machines. The main solution for preventing electro- magnetic type damage is to demagnetize all of the machinery parts, however this is costly and time consuming. Therefore a thorough investigation into the causes and physical characteristics of electro- magnetic shaft currents is needed. In this paper, the self excitation theory was developed for a simple model, and axial flux Faraday disk machine surrounded by a long solenoid. Experimental tests were conducted to investigate the physical characteristics on an electromagnetic self excitation rig. The theory showed that the directions of both the shaft rotation and the coil turns should e identical if self excitation is to occur. From the tests, the electromagnetic type shaft current had both AC and DC components occurred at all vibration frequencies. This could point to the way to detect small instabilities or natural frequency locations by monitoring shaft currents.

• International Journal of Precision Engineering and Manufacturing
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• 제3권1호
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• pp.20-25
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• 2002

Electrical damages to critical parts in rotating machinery have caused many machinery failures and hours of costly downtime. The problem of shaft currents generated in non-electrical machines has puzzled both users and manufacturers of these machines. The main solution for preventing electromagnetic type damage is to demagnetize all of the machinery parts, however this is costly and time consuming. Therefore a thorough investigation into the causes and physical characteristics of electromagnetic shaft currents is needed. In this paper, the self excitation theory was developed far a simple model, an axial flux Faraday disk machine surrounded by a long solenoid. Experimental tests were conducted to investigate the physical characteristics on an electromagnetic self excitation rig. The theory showed that the directions of both the shaft rotation and the coil turns should be identical if self excitation is to occur. From the tests, the electromagnetic type shaft current had both AC and DC components occurred at all vibration frequencies. This could point to a way to detect small instabilities or natural frequency locations by monitoring shaft currents.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.316-322
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• 2002

This paper presents the temperature-dependent hysteresis identification of an electro-rheological (ER) fluid under various operating temperatures using the Preisach model. As a first step, polymethylaniline (PMA) particles are prepared and mixed with silicone oil to make an ER fluid. A couette type electroviscometer is then employed to obtain the field-dependent shear stress. In order to show the suitability of the Preisach model to predict a physical hysteresis phenomenon of the ER fluid, two significant properties; the minor loop property and the wiping-out property are experimentally examined under three dominant temperature conditions. Subsequently, the Preisach model fur the PMA-based ER fluid is identified using experimental first order descending (FOD) curves. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one under the both specified and unspecified temperatures. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• 한국소음진동공학회논문집
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• 제12권8호
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• pp.648-656
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• 2002

This paper presents the identification of temperature-dependent hysteresis of an electro-rheological (ER) fluid under various operating temperatures using the Preisach model. As a first step, polymethylaniline (PMA) particles are prepared and mixed with silicone oil to make an ER fluid. A couette type electroviscometer is then employed to obtain the field-dependent shear stress. In order to show the suitability of the Preisach model to predict a physical hysteresis phenomenon of the ER fluid, two significant properties; the minor loop property and the wiping-out property are experimentally examined under three dominant temperature conditions. Subsequently, the Preisach model for the PMA-based ER fluid is identified using experimental multiple first order descending (FOD) curves. The effectiveness of the identified hysteresis model is verified in the time domain by comparing the predicted field-dependent shear stress with the measured one under the both specified and unspecified temperatures. In addition, the hysteresis model proposed in this work is compared to Bingham model.

• 한국보육지원학회지
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• 제16권5호
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• pp.69-86
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• 2020

Objective: The purpose of this research was to examine the prediction models of conflict and intimacy in teacher-child relationships based on decision tree analysis. Methods: The participants were 297 preschool children from ages three to five including 166 boys and 131 girls. Teacher-child relationships were measured by the Student-Teacher Relationship Scale(STRS). Physical aggression, relational aggression, social withdrawal, and prosocial behaviors were measured by teacher ratings. Moreover, ADHD-RS(Attentive Deficit Hyperactivity Disorder Rating Scale) was used to measure ADHD. The data was analyzed with decision tree analysis. Results: According to the prediction model for teacher-child conflict, the significant predictors were physical aggression and social withdrawal. According to the prediction model for teacher-child intimacy, the significant predictors were prosocial behaviors and relational aggression. However, children's age, gender and ADHD were not significant predictors. Conclusion/Implications: The findings suggest that social behaviors may be closely related with teacher-child relationships for preschool children. Based on the results of this study, intervention suggestions were made.

• 한국노년학
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• 제37권3호
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• pp.567-582
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• 2017

본 연구의 목적은 지역사회 노인의 행동계획, 신체활동, 우울로 구성된 경로모형을 분석하여 그 관계에 대한 이해를 증진시키고, 지역사회 노인의 우울관리를 위한 행동계획과 신체활동의 활용에 대해 제안하는 것이다. 이를 위해 선행연구를 고찰하고 신체활동 프로그램을 실시하여 참여노인의 행동계획, 신체활동, 우울 간 관계를 경로모형으로 설정하였다. 수도권 지역의 5개 복지관을 이용하면서 우울증상을 호소하는 노인 116명을 대상으로 행동계획이 포함된 신체활동 프로그램을 실시하고 설정된 경로모형을 검증하였다. 연구결과, 첫째, 설정된 경로모형은 실제 자료에 부합한 것으로 나타났다. 둘째, 행동계획이 증가할수록 신체활동도 증가하였다. 셋째, 행동계획이 사후우울에 부적 영향을 미쳤다. 넷째, 신체활동이 사후우울에 부적인 영향을 미쳤다. 다섯째, 행동계획이 사후우울에 대해 신체활동보다 상대적으로 더 큰 영향을 미쳤고, 우울과 행동계획과의 관계에서 신체활동이 매개효과를 나타냄을 확인하였다. 이러한 결과를 바탕으로 국가적 차원의 신체활동증진전략에 행동계획 지침의 포함, 지역사회 정신보건 관련 기관에 행동계획을 포함한 신체활동 프로그램의 보급과 전달체계 구축, 행동계획 수행의 질적 향상을 위한 내러티브 접근의 활용 등을 제언하였다.