• 한국지반공학회지:지반
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• 제14권4호
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• pp.129-140
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• 1998

탄소성 유한 요소 해석은 기지의 변형률 증분에 대한 응력 적분을 필요로 하며, 탄소성 구성 모델의 경우 특별한 경우를 제외하고는 해석적인 응력 적분이 불가능하고 수치적인 방법을 필요로 한다. 이때 응력 수치 적분의 정확도가 비선형 유한요소해의 전체적인 정확도에 상당히 큰 영향을 미치게 된다. 본 연구에서는 탄소성 구성 관계의 응력 적분을 위하여 외연적 방법중의 하나로서 Sloan이 제안한 단계분할 절차를 보완하여 안정적이고 정착한 응력 수치 적분법을 제시하고자 한다. 수정 오일러 절차에 따른 오차 조절의 기본 개념은 그대로 사용하고 오차를 평가하는 기준에 응력 수준이 영향을 미치는 단점을 보완하여 응력 수준에 관계없는 안정적이고 정확한 수치 적분법을 제시하였으며, 그 결과의 신뢰성을 삼축시험모사를 이용하여 검증하였다.

• International Journal of Railway
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• 제3권4호
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• pp.117-122
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• 2010

In transportation geotechnical engineering, stress-strain behavior of earth structures has been analyzed by numerical simulations with the implemented plasticity constitutive model. It is a fact that many advanced plasticity constitutive models on predicting the mechanical behavior of soils have been developed as well as experimental research works for geotechnical applications in the past decades. In this study, recently developed, a unified constitutive model for both clay and sand, which is referred to as CASM (clay and sand model), was compared with a classical constitutive model, Cam-Clay model. Moreover, integration methods of stress-strain rate equations using CASM were presented for simulation of undrained and drained triaxial compression tests. As a conclusion, it was observed that semi-implicit integration method has more improved accuracy of capturing strain rate response to applied stress than explicit integration by the multiple correction and iteration.

• East Asian Economic Review
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• 제19권4호
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• pp.325-355
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• 2015

This paper looks at the integration of regions and nations through the prism of the merger of populations (societies). The paper employs a particular index of social stress. Stylized examples of the merging of two populations suggest that with integration, the social stress index will increase. The examples form the basis for the development of new formulas for calculating the social stress of an integrated population as a function of the levels of social stress of the constituent populations when apart. The formulas reveal that the social stress of an integrated population is higher than the sum of the levels of social stress of the constituent populations when apart. This raises the distinct possibility that the merging of populations may be a social liability: integration may fail to give the populace a sense of improved wellbeing.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.885-900
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• 2015

This paper introduces Romberg-Richardson's method as one of the numerical integration tools for computation of stress intensity factor in a pre-cracked specimen subjected to a complex stress field across the crack faces. Also, the computation of stress intensity factor for various stress fields using existing three methods: average stress over interval method, piecewise linear stress method, piecewise quadratic method are modified by using Richardson extrapolation method. The direct integration method is used as reference for constant and linear stress distribution across the crack faces while Gauss-Chebyshev method is used as reference for nonlinear distribution of stress across the crack faces in order to obtain the stress intensity factor. It is found that modified methods (average stress over intervals-Richardson method, piecewise linear stress-Richardson method, piecewise quadratic-Richardson method) yield more accurate results after a few numbers of iterations than those obtained using these methods in their original form. Romberg-Richardson's method is proven to be more efficient and accurate than Gauss-Chebyshev method for complex stress field.

• 한국재료학회지
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• 제22권6호
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• pp.292-297
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• 2012

In order to improve osseointegration of dental implants with bone we studied an implant with holes inside its body to deliver bioactive materials based on a proposed patent. Bioactive materials can be selectively applied through holes to a patient according to diagnosis and the integration progress. After the bioactive material is applied, bone can grow into the holes to increase implant bonding and also enhance surface integration. In order to improve the concept and study the effect of bioactive material injection on implant integration, design optimization and integration research were undertaken utilizing the finite element method. A 2-dimensional simulation study showed that when bone grew into the holes after the bioactive material was injected, stress vertically distributed in the upper part of the implant was relieved and mild stress appeared at the opening of the injection holes. This confirmed the effect of the bioactive material and the contribution of the injection holes, but the maximum stress increased ten-fold at the opening. In order to reduce the maximum stress, the size, location, and the number of holes were varied and the effects were studied. When bioactive materials formed an interface layer between the implant and the mandible and four holes were filled with cortical and cancellous bones all the stress concentrated opposite to the loading side without holes disappeared. The stresses at the four outlets of the holes was mildly elevated but the maximum stress value was ten-fold greater compared to the case without the bioactive material.

• 한국지반공학회지:지반
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• 제12권4호
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• pp.145-156
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• 1996

연약한 지반의 거동을 적절하게 표현할 수 있는 일반 등방경화 규칙에 근거한 비등방경화 구성모델을 비선형 유한요소해석에 적용하기 위하여 내재적인 응력적분기법을 정식화하였다. 정식화된 응력적분기법은 비선형 해석시에 필요한 응력을 일반 사다리꼴규칙에 의하여 내재적으로 적분하고 응력변형률 접선계수를 비선형 해법에 일관되게 도출할 수 있다. 이러한 알고리즘을 통하여 해의 정확도 및 수렴도를 확보할 수 있으므로, 비등방경화 구성 관계를 적용한 비선형 해석을 정확하고 효율적으로 수행할 수 있는 토대를 구축할 수 있었다.

• Structural Engineering and Mechanics
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• 제59권5호
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• pp.901-920
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• 2016

MeshFree methods have become popular owing to the ease with which high stress gradients can be identified and node density distribution can be reformulated to accomplish faster convergence. This paper presents a strategy for nodal density refinement with strain energy as basis in Element-Free Galerkin MeshFree technique. Two popular flat plate problems are considered for the demonstration of the proposed strategies. Issue of integration errors introduced during nodal density refinement have been addressed by suggesting integration cell refinement. High stress effects around two symmetrical semi-circular notches under in-plane axial load have been addressed in the first problem. The second considers crack propagation under mode I and mode II fracture loading by the way of introducing high stress intensity through line crack. The computational efficacy of the adaptive refinement strategies proposed has been highlighted.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.94-102
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• 2007

Applications of bonded dissimilar materials such as large scale integration (LSI) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in LSI. In order to investigate stress singularities on the bonded interface edges and delamination of die pad and resin in the IC package. In this paper, stress singularity factors(${\Gamma}_i$) and stress intensity factors($K_i$) considering thermal stress in the IC package were analyzed by using the 2-dimensional elastic boundary element method(BEM).

• Child Health Nursing Research
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• 제13권1호
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• pp.73-80
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• 2007

Purpose: As a result of dramatic advances in the medical and surgical management of congenital heart disease (CHD), many babies born with cardiac anomalies today can expect to reach adulthood. The main purpose of this study was to examine the relationship between parenting stress and personal resources of mothers of children with CHD. Method: Fifty-one mothers of children with CHD were recruited at the pediatric cardiac outpatient clinic from July 14th to September 25th 2006. Abidin's parenting stress index/short form (PSI/SF) and Brandt and Weinert's personal resource questionnaire (PRQ) were used. PSI has 3 sub-concepts; parental role distress, dysfunctional parent-child interaction, and difficult child. PRQ has 4 sub-concepts; intimacy, social integration, worth, and assistance. Data were analyzed using SPSS 13.0 version. Results: Correlation analysis showed that parenting stress was significantly related to 'intimacy', 'social integration', and 'worth' of mothers. Multiple regression analysis showed that parenting stress was significantly related to personal resource of mother and information by internet. Conclusion: Mothers who felt they had supportive friends and family, high self esteem, and social integration reported lower parenting stress. Also, internet may be an effective method to provide information and share experience for mothers of children with CHD.

• 디지털융복합연구
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• 제20권2호
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• pp.543-551
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• 2022

본 연구의 목적은 간호대학생의 통합성과 임상실습 스트레스 정도를 파악하여 학과만족도와의 관계를 파악하는 것에 있다. 자료 수집은 2021년 6월부터 7월까지 진행하였다. 임상실습 경험이 1회 이상인 간호대학생 3, 4학년을 대상으로 통합성, 임상실습 스트레스, 학과만족도 척도로 이루어진 설문지로 자료를 수집하였고, 총 394부의 자료를 SPSS 프로그램으로 분석하였다. 연구결과 통합성은 학과만족도에 정적 상관관계를(r=.412, p<.01), 임상실습 스트레스와는 부적 상관관계를 보이는 것으로 나타났다(r=-.193, p<.01). 간호대학생의 학과만족도에 영향을 미치는 예측요인은 통합성(β=.406, p<.001)과 입학 동기(β=.166, p=.006)로 전체 변량을 20% 설명하였다. 결과적으로 통합성과 입학 동기는 학과만족도에 영향을 미치는 것으로 확인되었으며, 간호대학생들의 학과만족도를 높이기 위해서는 입학초기부터 통합성 증진프로그램과 학과적응 프로그램 운영이 필요할 것으로 사료된다.