• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.241-250
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• 2000

Chua's circuit is a simple electronic network which exhibits a variety of bifurcation and attractors. The circuit consists of two capacitors, an inductor, a linear resistor, and a nonlinear resistor. In this paper, a transmitter and a receiver using two identical Chua's circuits are proposed and synchronizations and secure communication of a lossy equivalent transmission are investigated. Since the synchronization of the lossy equivalent transmission system is impossible by coupled synchronization, theory having both the drive-response and the coupled synchronization is proposed. The proposed method is synthesizing the desired information with the chaos circuit by adding the information signal to the chaos signal in the lossy equivalent transmission system.

• Korean Journal of Culture and Social Issue
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• v.28 no.4
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• pp.661-690
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• 2022

Adolescent delinquency is a substantial social problem that occurs in both offline and online domains. The current study utilized random forest algorithms to identify predictors of adolescents' online and offline delinquency. Further, we explored the applicability of classic delinquency theories (social learning, strain, social control, routine activities, and labeling theory). We used the first-grade and fourth-grade elementary school panels as well as the first-grade middle school panel (N=4,137) among the sixth wave of the nationally-representative Korean Children and Youth Panel Survey 2010 for analysis. Random forest algorithms were used instead of the conventional regression analysis to improve the predictive performance of the model and possibly consider many predictors in the model. Random forest algorithm results showed that classic delinquency theories designed to explain offline delinquency were also applicable to online delinquency. Specifically, salient predictors of online delinquency were closely related to individual factors(routine activities and labeling theory). Social factors(social control and social learning theory) were particularly important for understanding offline delinquency. General strain theory was the commonly important theoretical framework that predicted both offline and online delinquency. Findings may provide evidence for more tailored prevention and intervention strategies against offline and online adolescent delinquency.

• Journal of the Korean Chemical Society
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• v.44 no.6
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• pp.587-591
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• 2000

Many theories have been suggested to obtain an equation of state for polymeric liquids. Most of them are based on the concepts of cell, hole, free volume or lattice etc. One of the most succesful theories is an equation of state theory of Flory and his coworkers based on the concept of free volume. In this work, van der Waals potential used in Flory's theory was modified, giving a new equation of state for polymeric liquids. The calculated results showed that the new equation of state gave better agreement with experimental PVT data than Flory's theory.

• Korean Journal of Logic
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• v.14 no.3
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• pp.1-26
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• 2011

This essay attempts to evaluate the pessimistic induction within the case of the historical development of space-time theories, which are claimed to undergo a radical ontological change providing evidence for the pessimistic induction. In my view, this claim misleads us to see the discontinuity of the structure of classical and relativistic space-time by means of a doubtful interpretation of space-time theories, which holds that space-time causally explains the phenomena of motions.

• The Korean Journal of Financial Management
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• v.25 no.2
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• pp.33-68
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• 2008

The purpose of this paper is to test the market timing hypothesis and impact of macro economic variables on capital structure choice as well as the traditional static trade-off and pecking order theories of capital structure in a integrated framework. Through a two stage test of target capital structure and capital structure choice, none of theories was consistently supported, but most of them were partly supported. In the first stage analysis of target ratio, coefficients of firm-specific variables generally supported the predictions of pecking order theory rather than those of the static trade-off theory. However, the result of the second stage test on capital structure choice supported the hypothesis of the static trade-off theory, which claims that firms usually set and pursue the target leverage ratio. Further, the result of the seconde stage shows that a simple pecking oder theory does not hold because firms with deficit of internal fund tend to issue bonds rather than stocks to raise outside fund. Also, the result indicates that the market timing hypothesis holds because firms with over-valued stocks tend to issue stocks rather than bonds. However, contrary to Korajczyk and Levy(2003), the impact of macro economic variables such as term or credit spreads on capital structure choice was negligible, and the impact of macro economic and market timing hypothesis variables were not greater in financially unconstrained firms as Korajczyk and Levy(2003) suggested.

• Journal of the Korean Society for Library and Information Science
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• v.56 no.1
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• pp.425-447
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• 2022

The purpose of this study is to introduce the Theory of Information Worlds which analyzes information behaviors in the social perspective. This study analyzed dissertations using the theory to provide the understanding of the theory and suggest theoretical implications. The theory was developed by Burnett and Jeager in 2008, and since then it was applied in 14 dissertations. Key concepts of the theory include social norms, social types, information value, information behavior, and boundaries. These concepts are intervened in the process of creation and control of behavior through interaction each other. Qualitative research was adopted in more research rather than quantitative research; especially interview and content analysis were applied. It is expected that the spectrum of information behavior research in Korea is broaden and deeper through this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.469-481
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• 2016

In this paper, a mathematical methodology was theoretically studied to obtain the impact force caused by the collision between rigid bodies. This theoretical methodology was applied to compute the impact force applied on the spent nuclear fuel disposal canister that accidentally drops and collides onto the ground. From this study, the impact force required to ensure a structurally safe canister design was theoretically formulated. The main content of the theoretical study concerns the rigid body kinematics and equation of motion during collision between two rigid bodies. On the basis of this study, a general impact theory to compute the impact force caused by the collision between two bodies was developed. This general impact theory was applied to theoretically formulate the approximate mathematical solution of the impact force that affects the spent nuclear fuel disposal canister that accidentally falls to the ground. Simultaneously, a numerical analysis was performed using the computer code to compute the numerical solution of the impact force, and the numerical result was compared with the approximate mathematical solution.

• Korean Journal of Cognitive Science
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• v.27 no.4
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• pp.541-572
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• 2016

Causal reasoning is actively studied not only by psychologists but, in recent years, also by cognitive scientists taking the Bayesian approach. This paper seeks to provide an overview of the recent trends in causal reasoning research with a focus on the power probabilistic contrast theory of causality, a major psychological theory on causal inference. The power probabilistic contrast theory (PPCT) assumes that a cause is a power that initiates or inhibits the result. This power is purported be understood through statistical correlation under certain conditions. The paper examines the supporting empirical evidence in the development of PPCT. Also, introduced are the theoretical dispute between the PPCT and the model based on Bayesian approach, and the current developments and implications of research on causal invariance hypothesis, which states that cause operates identically regardless of the context. Recent studies have produced experimental results that cannot be readily explained by existing empirical approach. Therefore, these results call for serious examination of the power theory of causality by researchers in neighboring fields such as philosophy, statistics, and artificial intelligence.

• Korean Journal of Social Welfare
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• v.56 no.4
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• pp.195-214
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• 2004

As one of the essential elements of social work practice, knowledge articulates what the social work profession is doing and ought to do. With an emphasis on building a body of knowledge for the profession, this study analyses the nature of social work knowledge. First, the study examines concepts of social work theories and models, which are built around separate clusters of concepts from a broad base of theoretical orientation. The study reviews epistemological and ideological debates over how to perceive and approach social issues and the role of the social work profession. In organizing a clear conceptual framework for social work practice, different frames of reference and selective and fragmentary knowledge from other disciplines are considered barriers. For the development of a clear identity as a unified profession and the prospects of a value-based profession, more attention needs to be given to specify practical knowledge that is contextual and appropriate to practice settings and more sensitive to social issues.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.600-606
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• 2007

3D finite element analyses of a corrugated steel web girder and a steel truss web girder are conducted to investigate the static and dynamic behaviour of the hybrid girders. And the analyses results are compared with those by the equivalent beam theory. The equivalent theory is a theory that all section properties of a truss structure are replaced by section properties of a beam including a shear coefficient. When applying the equivalent beam theory, the shear coefficient of the corrugated steel web girder is estimated as the area ratio of flange section to web section and that of the steel truss web girder is calculated by the equation proposed by Abdel. Static deflections and natural frequencies by 3D finite element analyses and those by the equivalent beam theory are in good agreement.