• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제31권5호
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• pp.55-62
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• 2003

Subdomain-interface variational formulation is presented to solve a class of dynamic contact problems of composite structures. The penalty method is used for imposing inequality constraints on contact surfaces and for connecting finite element subdomains that satisfy interface compatibility conditions. As a result, any complex-shaped domain can be easily divided into independently modeled subdomains without considering the conformity of meshes on interfaces. Some advantageous features of the present method are shown through a set a numerical studies with a developed computer code.

• Asia-Pacific Journal of Business
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• 제3권2호
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• pp.34-41
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• 2012

The aim of this paper is to depict the social problems common to South Korea and Japan by comparing their consumption behaviors. For that purpose, we utilize the Survey of Household Economy of both countries and attempt to determine the similarities and differences between the two countries. Our empirical analysis revealed the following. First, although both countries are aging, the first quartile (the poorest in under the definition in this paper) in South Korea has aged more rapidly than in to Japan. As the wages in these two countries formerly increased with age, this substantial divergence in the age composition in the poorest quartile is a remarkable change and suggests that income inequality has been more widely spreading out in South Korea than in Japan. Furthermore, the education expenditure ratio in South Korea is statistically significant for higher income level, while this is not the case in Japan. If the opportunity for better education is dominated by wealthier households, the prompt implementation of a policy to break this vicious circle is necessary in South Korea.

• Journal of the Institute of Electronics Engineers of Korea CI
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• 제41권3호
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• pp.79-90
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• 2004

Systematical robust stability analysis and design scheme for the feedback linearization control systems via fuzzy modeling are proposed. It is considered that uncertainty and disturbances are included in the Takagi-Sugeno fuzzy models representing the nonlinear plants. Robust stability of the closed system is analyzed by casting the systems into the diagonal norm bounded linear differential inclusions and by converting the analysis and design problems into the linear matrix inequality optimization, a numerical method for finding the maximum stable ranges of the fuzzy feedback linearization control gains is also proposed. To verify the effectiveness of the proposed scheme, the robust stability analysis and control design examples are given.

• Journal of the Korean Institute of Intelligent Systems
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• 제17권4호
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• pp.483-487
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• 2007

This paper is concerned with the observer design problem for linear neutral systems with time-varying delays. The problem addressed is that of designing a full-order observer that guarantees the exponential stability of the error system. An effective algebraic matrix equation approach is developed to solve this problem. In particular, both observer analysis and design problems are investigated. Sufficient conditions for a linear neutral system to be stable are first established. Furthermore, an illustrative example is used to demonstrate the validity of the proposed design procedure.

• Smart Structures and Systems
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• 제24권1호
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• pp.67-81
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• 2019

Rows of closely adjacent buildings with similar dynamic characteristics are common building arrangements in residential areas. In this paper, we present a vibration control strategy for the seismic protection of this kind of multibuilding systems. The proposed approach uses an advanced Linear Matrix Inequality (LMI) computational procedure to carry out the integrated design of distributed multiactuation schemes that combine interbuilding linking devices with interstory actuators implemented at different levels of the buildings. The controller designs are formulated as static output-feedback H-infinity control problems that include the interstory drifts, interbuilding approachings and control efforts as controlled-output variables. The advantages of the LMI computational procedure are also exploited to design a fully-decentralized velocity-feedback controller, which can define a passive control system with high-performance characteristics. The main ideas are presented by means of a system of three adjacent five-story identical buildings, and a proper set of numerical simulations are conducted to demonstrate the behavior of the different control configurations. The obtained results indicate that interstory-interbuilding multiactuation schemes can be used to design effective vibration control systems for adjacent buildings with similar dynamic characteristics. Specifically, this kind of control systems is able to mitigate the vibrational response of the individual buildings while maintaining reduced levels of pounding risk.

• Journal of the Korean Society of Food Culture
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• 제38권2호
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• pp.119-127
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• 2023

The labor environment in Korea has changed and problems related to employment types are treated as important issues. Especially, the ratio of irregular workers has not only increased relatively, but the labor conditions in Korea also have worsened in the current years. Studies have reported an association between temporary workers and the prevalence of diseases. However, there is insufficient research on chronic disease and employment types. Methods: The current study examines the prevalence rate of diseases and health behavior by categorizing employment types among Korean adults. Data were obtained from the 2016-2018 Korea National Health and Nutrition Examination Survey. Totally, the data of 2,366 workers (1,239 regular and 1,127 irregular) were analyzed in the study. The types of employment were classified by a questionnaire querying about working conditions. The results showed that irregular workers earned less than regular workers and had a significantly higher prevalence of diabetes mellitus and hypertension. We propose that if discrimination related to working conditions were relieved, irregular workers would be able to invest more time to exercise and doing check-ups regularly. In addition, individual nutrition consultations considering the knowledge and personal environmental factors of each individual are necessary for the improved health of all workers.

• International journal of advanced smart convergence
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• 제12권1호
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• pp.82-91
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• 2023

In 2020 when the COVID-19 pandemic began in full-scale, the WHO Director-General warned of the dangers of an infodemic. The infodemic is a phenomenon in which false information spreads rapidly like an epidemic and causes chaos, and it was noted that the COVID-19 pandemic is not just limited to health problems, but also linked to a variety of issues such as human rights, economic inequality, various discrimination, hate speech, fake news, global governance etc. In the field of education, it is necessary to think about how to connect this global situation with school classes. Accordingly, this study suggested the direction for global citizenship education by analyzing how the infodemic spreads on Korean social media with the case of the recent global COVID-19 pandemic. According to the research results, the rate of negative emotions was higher than positive ones in the emotions that generate infodemic, while anxiety and anger were focused among negative emotions. In addition, the infodemic tended to spread widely with the feelings of anger rather than anxiety, and the feelings of anger led to advocating aggressive policies against certain country and regions. Therefore, global citizenship education is required to focus on a sense of duty and responsibility as a citizen, not on the level of national identity based on an exclusive sense of belonging. Furthermore, global citizenship education needs to lead to presenting a blueprint for education in a way that can enhance the awareness of the global community for joint response to global challenges and realize common prosperity based on sustainability and justice.

• Smart Structures and Systems
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• 제31권1호
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• pp.69-78
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• 2023

The purpose of this paper is to develop a scalable grey predictive controller with unavoidable random delays. Grey prediction is proposed to solve problems caused by incorrect parameter selection and to eliminate the effects of dynamic coupling between degrees of freedom (DOFs) in nonlinear systems. To address the stability problem, this study develops an improved gray-predictive adaptive fuzzy controller, which can not only solve the implementation problem by determining the stability of the system, but also apply the Linear Matrix Inequality (LMI) law to calculate Fuzzy change parameters. Fuzzy logic controllers manipulate robotic systems to improve their control performance. The stability is proved using Lyapunov stability theorem. In this article, the authors compare different controllers and the proposed predictive controller can significantly reduce the vibration of offshore platforms while keeping the required control force within an ideal small range. This paper presents a robust fuzzy control design that uses a model-based approach to overcome the effects of modeling errors. To guarantee the asymptotic stability of large nonlinear systems with multiple lags, the stability criterion is derived from the direct Lyapunov method. Based on this criterion and a distributed control system, a set of model-based fuzzy controllers is synthesized to stabilize large-scale nonlinear systems with multiple delays.

• Journal of Korea Game Society
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• 제15권6호
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• pp.107-120
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• 2015

Free-to-Play of Digital Game became to be one of the largest profit business models because of its stable profit and ability to attract new players. However as the services that are provided gets diversified, some problem come up with mass imbalance in the gameplay experience. Therefore in this process to organize the concepts and features of the Free-to-Play and typing research depending on the acquisition method, durability, and function of revelation target. It was able to derive the three problems, which are inequality in the gameplay experience, economic imbalance in the game world, and player's breakaway. The goal of study is to explain by giving specific examples with these three problems and offer rational solutions. These kinds of study will give a lead on how the Free-to-Play model should be applied to the Korean game market.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제35권3호
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• pp.259-266
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• 2011

We present a new dual sequential approximate optimization (SAO) algorithm called SD-TDQAO (sequential dual two-point diagonal quadratic approximate optimization). This algorithm solves engineering optimization problems with a nonlinear objective and nonlinear inequality constraints. The two-point diagonal quadratic approximation (TDQA) was originally non-convex and inseparable quadratic approximation in the primal design variable space. To use the dual method, SD-TDQAO uses diagonal quadratic explicit separable approximation; this can easily ensure convexity and separability. An important feature is that the second-derivative terms of the quadratic approximation are approximated by TDQA, which uses only information on the function and the derivative values at two consecutive iteration points. The algorithm will be illustrated using mathematical and topological test problems, and its performance will be compared with that of the MMA algorithm.