• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.758-771
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• 2021

This paper presents a novel control scheme for the three-dimensional (3D) path following of underactuated Autonomous Underwater Vehicle (AUVs) subject to unknown internal and external disturbances, in term of the time scale decomposition method. As illustration, two-time scale motions are first artificially forced into the closed-loop control system, by appropriately selecting the control gain of the integrator. Using the singular perturbation theory, the integrator is considered as a fast dynamical control law that designed to shape the space configuration of fast variable. And then the stabilizing controller is designed in the reduced model independently, based on the time scale decomposition method, leading to a relatively simple control law. The stability of the resultant closed-loop system is demonstrated by constructing a composite Lyapunov function. Finally, simulation results are provided to prove the efficacy of the proposed controller for path following of underactuated AUVs under internal and external disturbances.

• Journal of The Korean Association of Information Education
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• v.20 no.1
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• pp.93-100
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• 2016

Computer Science Unplugged is a collection of free learning activities that teach Computer Science through engaging games and puzzles that use cards, string, crayons and lots of running around. In spite of the success of unplugged activities, the unplugged resources for experiencing the concepts of data structures is lacked. In this study, we design, implement and survey the 3 hour lessons of the core concepts of graph theory and the shortest path algorithm for the primary students using computer science unplugged activities. Our survey results showed that our lesson plan is adequate for primary school students and will have a positive effects for primary school students.

• Journal of Information Technology Applications and Management
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• v.22 no.4
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• pp.1-37
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• 2015

Micro small business start-ups are receiving financial and marketing support from government or public authority, but business closure rate is very high and it causes a hugh burden to households and national economy. This study aims to verify the causal relationship between the self-determination characteristic of small business start-ups and entrepreneurial intention through learning orientation and innovation ability. The man's intrinsic motivation of self-determination theory is expected to have an impact on the entrepreneurial intention of small business start-ups. The self-determination theory includes perceived autonomy, perceived competence, perceived relationship as independent variables. This study presented a research model for explaining the entrepreneurial intention of small business start-ups, and collected 260 survey responses from the small business start-ups In order to validate the proposed research model, PLS analysis is performed with valid 246 questionnaires. By PLS technique, the measurement reliability and validity of research variables are tested and the path analysis is conducted to do the hypothesis test. Path analysis shows that perceived autonomy does not significantly affect the learning orientation and innovation ability. On the other hand, perceived competence significantly influences learning orientation and innovation ability. Perceived relationships had significant influence on learning orientation. It is found that the parameters of learning orientation and innovation ability significantly influence the dependent variable of entrepreneurial intention. Based on the results, a policy and strategy for supporting small business start-up are presented.

• Journal of Distribution Science
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• v.14 no.2
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• pp.41-45
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• 2016

Purpose - Finding an optimal path is an essential component for the design and operation of smart transportation or logistics network. Many applications in navigation system assume that travel time of each link is fixed and same. However, in practice, the travel time of each link changes over time. In this paper, we introduce a new transportation problem to find a latest departing time and delivery path between the two nodes, while not violating the appointed time at the destination node. Research design, data, and methodology - To solve the problem, we suggest a mathematical model based on network optimization theory and a backward search method to find an optimal solution. Results - First, we introduce a dynamic transportation problem which is different with traditional shortest path or minimum cost path. Second, we propose an algorithm solution based on backward search to solve the problem in a large-sized network. Conclusions - We proposed a new transportation problem which is different with traditional shortest path or minimum cost path. We analyzed the problem under the conditions that travel time is changing, and proposed an algorithm to solve them. Extending our models for visiting two or more destinations is one of the further research topics.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.10
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• pp.539-554
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• 2007

In this Paper, we investigate conditions for proper interval graphs to have k-disjoint path covers of three types each: one-to-one, one-to-many, and many-to-many. It was proved that for $k{\geq}2$, a proper interval graph is one-to-one k-disjoint path coverable if and only if the graph is k-connected, and is one-to-many k-disjoint path coverable if and only if the graph is k+1-connected. For $k{\geq}3$, a Proper interval graph is (paired) many-to-many k-disjoint path coverable if and only if the graph is 2k-1-connected.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.602-603
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• 2008

The design modification of problematic component in a given vibration path is disallowed in order to sacrifice other performances such as ride comport or handling of a vehicle. For this, the paper presents a new contribution analysis based on transmissibility ratio (TR) of acceleration in a definite vibration path to find a proper candidate for design modification. The new contribution analysis is based on the fact that the sensitivity of TR over a small design change is inversely proportional to the magnitude of TR. The new methodology can significantly relieve efforts of time-consumming modal analysis for detail modal information. The theory of proposed contribution analysis is simulated with five-degree-of-freedom open vibration path and confirms that the contribution result is well matched with the variance of TR over a dynamic change on a vibration path.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.12
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• pp.691-698
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• 2003

In this paper, we propose a problem, called one-to-one disjoint path cover problem, whether or not there exist k disjoint paths joining a pair of vertices which pass through all the vertices other than the two exactly once. A graph which for an arbitrary k, has a one-to-one disjoint path cover between an arbitrary pair of vertices has a hamiltonian property stronger than hamiltonian-connectedness. We investigate this problem on recursive circulants and prove that for an arbitrary k $k(1{\leq}k{\leq}m)$$ G(2^m,4)$,$m{\geq}3$, has a one-to-one disjoint path cover consisting of k paths between an arbitrary pair of vortices.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.4
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• pp.132-137
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• 2007

A point-wise car-like robot moving in the plane changes its direction with a constraint on turning curvature. In this paper, we consider the problem of computing a shortest path of bounded curvature between a prescribed initial configuration (position and orientation) and a polygonal goal, and propose a new geometric proof showing that the shortest path is either of type CC or CS (or their substring), where C specifies a non-degenerate circular arc and S specifies a non-degenerate straight line segment. Based on the geometric property of the shortest path, the shortest path from a configuration to a polygonal goal can be computed in linear time.

• Journal of the Economic Geographical Society of Korea
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• v.18 no.1
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• pp.60-75
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• 2015

The Ruhr area in the Northwestern Germany grew rapidly from the 1850s based on coal mining and iron and steel industries, playing a key role as an engine of industrial growth. Since the 1950s, however, the area has been experiencing a serious economic crisis as the traditional industries declined. The crisis was comprised of increasing unemployment and abandoned industrial lands and facilities. Oberhausen and Gelsenkirhen are typical cities of the Ruhr, characterized by such economic crisis. Oberhausen attempted to solve the problems by developing a large leisure town, composed of a sopping mall, restaurants, and other arts and cultural activities, on a former steel mill site. Gelsenkirhen, on the other hand, went on to promote renewable energy industries, business incubators, and energy-saving housing complexes. This paper analyses the processes and outcomes of urban revitalization policies of the two cities, based on the path dependence theory, and draws theoretical and policy implications.

• Korean Journal of Social Welfare
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• v.65 no.2
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• pp.231-254
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• 2013

The growth of legal and illegal gambling industry in Korea has increased the gambling accessibility. Actually, the prevalence of gambling addiction in Korea is significantly higher than those in western countries. The problems related to gambling make negative consequences in the individual, familial and socio-economical aspect. Previous studies showed that the prevalence of problem gambling by college students was much higher than that by adolescence and adult due to the nature of psychosocial developmental stage. The purpose of this study is to explore the path of problem gambling among college students based on the Jacob's general theory of addiction. Participants are 366 male college students who have experienced on gambling behavior. The main results are as follows. First, the problem gambling prevalence of participants is 14%. Second, statistical analysis using structural equation modeling shows the significant pathway among psychological vulnerability, needs to escape and problem gambling. Instead, the physiological vulnerability is not significant on the path to problem gambling. On the basis of these findings, the implications for social welfare prevention and intervention to college students are discussed.