• 한국항해항만학회지
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• 제36권5호
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• pp.379-385
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• 2012

본 논문에서는 수상 및 수중운동체의 안정성 및 안정화기법에 관해 고찰한다. 선박이 운동을 하게 되면 부가질량이 변하게 되고 대칭인 시스템행렬이 비대칭이 된다. 비대칭성에 따라 시스템의 안정성해석방법도 달라지는데 예를 들어 가속도 피드백을 통해 비대칭요소를 제거하여 대칭으로 변환시키는 것이 가장 대표적인 해석 및 안정화 기법이다. 시스템 모델자체는 어디까지나 모델이기 때문에 대상시스템을 명확하게 수식으로 표현할 수 없으므로 피드백에 의한 비대칭요소를 소거시키는 방법은 타당하지 못하다. 따라서 본 논문에서는 대칭행렬이 비대칭행렬로 변하는 제약에 구애받지 않는, 보다 일반성을 갖는 안정성해석법을 제안하였다. 그리고 시스템 안정성 조건을 행렬부등식으로 변환하여 나타내었다. 이것은 안정성 해석 및 안정화를 위한 제어이득을 효율적으로 계산할 수 있는 방법으로 다양한 제약조건에도 유연하게 대응할 수 있다. 시뮬레이션을 통해 제안한 기법의 유효성을 검증하였다.

• 한국지능시스템학회논문지
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• 제14권1호
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• pp.46-51
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• 2004

본 논문에서는 선형행렬 부등식을 이용한 TS 퍼지 분류기 설계 방법을 제안한다. TS 퍼지 분류기를 설계하기 위해 퍼지규칙의 후반부 파라메터가 분류기의 성능을 최대로 하도록 동정되어야 한다. 이러한 동정 문제를 해결하기 위해 볼록 최적화 기법이 사용되었다. 후반부 파라메터 동정 문제는 볼록 최적화 문제로 변환되며, 선형행렬 부등식으로 표현된다. 선형행렬 부등식으로 표현된 볼록 최적화 문제는 일반 고유값 문제로 근사화 되며, 일반 고유값 문제를 최적화함으로써 최소의 분류 에러를 가지는 최적의 후반부 파라메터가 결정된다. 제안된 분류기의 성능을 평가하기 위해 IRIS 데이터와 Wisconsin Breast Cancer Database 데이터에 대한 분류기의 성능을 모의 실험을 통해 확인하였다. 마지막으로, 모의 실험 결과 제안된 TS 퍼지 분류기의 성능의 우수성을 확인할 수 있었다.

• 보건행정학회지
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• 제29권3호
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• pp.288-302
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• 2019

Background: The one-person households (OPH) are rapidly increasing and vulnerable to socioeconomic and health problems. Because it is predicted to be inequitable to health care utilization, we would like to find out about the equity of health care utilization of the OPH by comparison with the multi-person households (MPH). Methods: This study followed the theoretical framework of Wagstaff and van Doorslaer (2000), O'Donnell and his colleagues (2008), where the horizontal inequity index is the difference between the concentration indices of actual health care utilization and health care needs. This study employed the 9th Korea Health Panel survey, and a total of 10,807 cases were analyzed. Health care needs were measured by age, sex, subjective health status, chronic disease count, Charlson's Comorbidity Index, limitation of activities, and disability. Results: Compared with the MPH, there were pro-poor inequities in hospitalization, emergency utilization, hospitalization out-of-pocket payments, and pro-rich inequities in outpatient out-of-pocket payments for the OPH. The decomposition of the concentration index revealed that chronic disease count made the largest contribution to socioeconomic inequality in outpatient utilization. Age, health insurance, economic activities, and subjective health status also proved more important contributors to inequality. The variables contributing to the hospitalization and emergency utilization inequity were age, education, Charlson's Comorbidity Index, marital status, and income. Conclusion: Because the OPH was more vulnerable to health problems than the MPH and there were pro-poor inequities in medical utilization, hospitalization, and emergency costs, it is necessary to develop a policy that can correct and improve the portion of high contribution to medical utilization of the OPH.

• International Journal of Computer Science & Network Security
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• 제21권12spc호
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• pp.629-635
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• 2021

In the spring, 2020, the pandemic caused quarantine and all educational institutions switched to distance learning, which led to significant changes in the field of education around the world. It has become necessary to build its capacity to provide distance learning to protect education and create opportunities for more individualized approaches to teaching and learning not only during future pandemics but also during other possible issues, such as natural disasters, when a developed flexible curricula could be taught face-to-face or online. The article presents an analysis of distance education in the world during a pandemic, analyzes significant changes, and implements measures in the field of education in Ukraine and around the world. The role of public and international organizations in the implementation of quarantine in the conditions of COVID-19, which partially took over the functions of state and local authorities, is emphasized. The closure of schools under COVID-19 has led to a de facto deterioration in learning outcomes, so we have analyzed the effects of distance learning and digital inequality in the world. It is shown how the COVID-19 pandemic affected access to public services in Ukraine.

• 한국치위생학회지
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• 제19권4호
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• pp.565-575
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• 2019

Objectives: In this study, both subjective and objective levels of oral health were used to identify the relationship between oral health inequalities. Methods: Korean National Health and Nutritional Examination Survey data from 2013 to 2015 were combined to create an analysis plan. Oral health questions categorized as subjective oral health conditions and oral health-related diseases used dental tissue disease status as data measured by the Community Periodical Index(CPI) and decayed, missing, filled teeth(DMFT) experience. Other data on oral health behaviors such as toothache experience, the frequency of toothbrush use, chewing problems, oral examination status, and unmet dental care needs were classified and analyzed according to the socioeconomic level. Data were analyzed using frequency and cross analyses, and the statistical significance level was set at 0.05. Results: It was found that higher the economic and educational level, better was the subjective oral health, lower the CPI, lower the experience of toothache, higher the frequency of toothbrush use, lower the number of people having chewing problems, and higher the frequency of oral checkups. Conclusions: Oral health inequality exists among social classes. It is suggested that continuous research and efforts be carried out to promote oral health while considering socioeconomic and educational levels. Further, active government efforts will be needed to address polarization by social class.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.848-849
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• 2007

This paper presents an efficient approach for solving the economic dispatch (ED) problems with valve-point effects using differential evolution (DE). A DE, one of the evolutionary algorithms (EAs), is a novel optimization method capable of handling nonlinear, non-differentiable, and nonconvex functions. And an efficient constraints treatment method (CTM) is applied to handle the equality and inequality constraints. The resultant DE-CTM algorithm is very effective in solving the ED problems with nonconvex cost functions. To verify the superiority of the proposed method, a sample ED problem with valve-point effects is tested and its results are compared with those of previous works. The simulation results clearly show that the proposed DE-CTM algorithm outperforms other state-of-the-art algorithms in solving ED problems with valve-point effects

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제23권2호
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• pp.65-92
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• 2019

We survey a recently developed immersed finite element method (IFEM) for the interface problems. The IFEM uses structured grids such as uniform grids, even if the interface is a smooth curve. Instead of fitting the curved interface, the bases are modified so that they satisfy the jump conditions along the interface. The early versions of IFEM [1, 2] were suboptimal in convergence order [3]. Later, the consistency terms were added to the bilinear forms [4, 5], thus the scheme became optimal and the error estimates were proven. For elasticity problems with interfaces, we modify the Crouzeix-Raviart based element to satisfy the traction conditions along the interface [6], but the consistency terms are not needed. To satisfy the Korn's inequality, we add the stabilizing terms to the bilinear form. The optimal error estimate was shown for a triangular grid. Lastly, we describe the multigrid algorithms for the discretized system arising from IFEM. The prolongation operators are designed so that the prolongated function satisfy the flux continuity condition along the interface. The W-cycle convergence was proved, and the number of V-cycle is independent of the mesh size.

• Journal of applied mathematics & informatics
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• 제25권1_2호
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• pp.255-267
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• 2007

In this work, by using Xu's inequality, Nalder's results, the notion of $(A,\;{\eta})-accretive$ mappings and the new resolvent operator technique associated with $(A,\;{\eta})-accretive$ mappings due to Lan et al., we study the existence of solutions for a new class of $(A,\;{\eta})-accretive$ variational inclusion problems with non-accretive set-valued mappings and the convergence of the iterative sequences generated by the algorithms in Banach spaces. Our results are new and extend, improve and unify the corresponding results in this field.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.95-96
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• 2016

This paper presents a voltage and frequency droop control for accurate power sharing of parallel distributed generation (DG) inverters in low voltage microgrid. In practice, line impedances between inverters and the point of common coupling of a microgrid are not always equal. This inequality in line impedances often results in reactive power sharing mismatch among inverters. To address this problem, intensive researches have been conducting. Although these methods can solve the unbalanced reactive power sharing, there are still problems remain unresolved, such as complicated structure or circulating current. To overcome such problems, a new droop control scheme is proposed, which not only guarantees accurate reactive power sharing but also has simple structure so that it can be easily implemented in existing systems without any hardware modification. The simulation is performed using Matlab/Simulinks to validate the proposed scheme.

• Journal of applied mathematics & informatics
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• 제29권5_6호
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• pp.1395-1407
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• 2011

When a Sequential Quadratic Programming (SQP) method is used to solve the nonlinear programming problems, one of the main difficulties is that the Quadratic Programming (QP) subproblem may be incompatible. In this paper, an SQP algorithm is given by modifying the traditional QP subproblem and applying a class of $l_{\infty}$ penalty function whose penalty parameters can be adjusted automatically. The new QP subproblem is compatible. Under the extended Mangasarian-Fromovitz constraint qualification condition and the boundedness of the iterates, the algorithm is showed to be globally convergent to a KKT point of the non-linear programming problem.