• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.7
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• pp.455-462
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• 2017

The magnetic interaction between elliptic Janus magnetic particles are investigated using a direct simulation method. Each particle is a one-to-one mixture of paramagnetic and nonmagnetic materials. The fluid is assumed to be incompressible Newtonian and nonmagnetic. A uniform magnetic field is applied externally in a horizontal direction. A finite-element-based fictitious domain method is employed to solve the magnetic particulate flow in the creeping flow regime. In the magnetic problem, the magnetic field in the entire domain, including the particles and the fluid, is obtained by solving the governing equation for the magnetic potential. Then, the magnetic forces acting on the particles are calculated via a Maxwell stress tensor formulation. In a single particle problem, it is found that the orientation angle at equilibrium is affected by the aspect ratio of the particle. As for the two-particle interaction, the dynamics and the final conformation of the particles are significantly influenced by the aspect ratio, the orientation, and the spatial positions of the particles. For the given positions of the particles, the fluid flow is also influenced by the orientation of each particle. The self-assembly structure of the particles is not a fixed one, but it varies with the above-mentioned factors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.3076-3082
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• 2010

The techniques and the products which use various video compression codec are come out from army or civil field. In existing high-end PC environment, process of the video compression codec does not become a problem, but in embedded system environments which limited system resources, because the system load due to the high-resolution images compressed by high-density, issues of performance and utilization are highlighted. This paper proposes the DirectShow Filter interfaces which are a hardware method in order to solve the problem existing software algorithms for image compression performance and peripheral interfaces.

• Journal of the Korea Convergence Society
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• v.8 no.10
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• pp.323-332
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• 2017

This study is convergence study of path model for the relationship among self esteem(SE), critical thinking disposition(CTD), problem solving skills(PSS) and motivation toward learning(MTL). The survey was performed on 207 nursing students in one college. Data was collected using a structured questionnaires and analysed with PASW 18.0 and AMOS 18.0. Model fit indices were in good agreement with recommended level(${\chi}^2/df=2.128$, GFI=.995, AGFI=.949, RMSEA=.074, CFI=.993, NFI=.988). Based on the path model, SE(${\beta}=.205$), PSS(${\beta}=.420$) showed a direct effect on MTL while CTD(${\beta}=.182$) showed a indirect effect on MTL. The SE showed a direct effect on CTD(${\beta}=.398$) and CTD(${\beta}=.433$) showed a direct effect on PSS. The findings indicate the necessity of developing educational programs to enhance nursing student's SE for increasing of MTL.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.1
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• pp.10-18
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• 2010

The purpose of this paper deals with direct multiple-shooting method (DMS) to resolve helicopter maneuver problems of helicopters. The maneuver problem is transformed into nonlinear problems and solved DMS technique. The DMS method is easy in handling constraints and it has large convergence radius compared to other strategies. When parameterized with piecewise constant controls, the problems become most effectively tractable because the search direction is easily estimated by solving the structured Karush-Kuhn-Tucker (KKT) system. However, generally the computation of function, gradients and Hessian matrices has considerably time-consuming for complex system such as helicopter. This study focused on the approximation of the KKT system using the matrix exponential and its integrals. The propose method is validated by solving optimal control problems for the linear system where the KKT system is exactly expressed with the matrix exponential and its integrals. The trajectory tracking problem of various maneuvers like bob up, sidestep near hovering flight speed and hurdle hop, slalom, transient turn, acceleration and deceleration are analyzed to investigate the effects of algorithmic details. The results show the matrix exponential approach to compute gradients and the Hessian matrix is most efficient among the implemented methods when combined with the mixed time integration method for the system dynamics. The analyses with the proposed method show good convergence and capability of tracking the prescribed trajectory. Therefore, it can be used to solve critical areas of helicopter flight dynamic problems.

• The Journal of the Korea Contents Association
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• v.22 no.9
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• pp.283-297
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• 2022

This study analyzed to strategy and structure of outward foreign direct investment(OFDI) by Chinese Enterprises in 'one belt, one load' countries along the line from the perspective of Dunning's OLI paradigm. Chinese enterprises' investment in 'one belt, one road' countries was largely promoted for two strategic purposes. One is an investment to secure energy resources due to the nature of resource holdings in 'one belt, one road' countries, and the other is a transfer investment to solve the problem of surplus facilities, a problem in China's domestic economy. Chinese enterprises' investments in these 'one belt, one road' countries is evaluated to have been made with Dunning's investment decision conditions in the OLI paradigm, namely, Ownership specific advantages, Location specific advantages, and Internalization specific advantages. only if there is a difference, investment country, investment method, and investment industry are different due to the structure of international relations, religious conflict and cultural heterogeneity, institutional investment environment of the region, and awareness of Chinese enterprises.

• Journal of Korean Academy of Nursing
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• v.36 no.1
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• pp.25-36
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• 2006

Purpose: The purpose of the study was to identify the adaptation process to problem based learning(PBL) among nursing students who have experienced PBL classes for two years. Method: Data was collected from 11 nursing students with in-depth interviews and direct observation of their PBL experiences by a researcher who has been a facilitator for PBL class for 3years. Immediately after the interviews all of them were transcribed. It was analyzed by the Ground theory of Corbin and Strauss. Results: A derived core category was 'Acquiring PBL'. 4 stages of the acquiring process were derived and written in time sequence: chaos, confusion, beginning insight, and achievement stage. Conclusion: The results will not only expand understanding of the students for the facilitator and school which has adopted PBL but also provide information to develop an orientation program for PBL. Further research on the facilitator's role experiences is recommended.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.364-373
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• 1999

A combination of conjugate gradient and Levenberg-Marquardt method is used to estimate the spatially varying scattering coefficient, ${\sigma}(r)$, in the solid and hollow spheres by utilizing the measured transmitted beams from the solution of an inverse analysis. The direct radiation problem associated with the inverse problem is solved by using the $S_{12}-approximation$ of the discrete ordinates method. The accuracy of the computations increased when the results from the conjugate gradient method are used as an initial guess for the Levenberg-Marquardt method of minimization. Optical thickness up to ${\tau}_0=3$ is used for the computations. Three different values of standard deviation are considered to examine the accuracy of the solution from the inverse analysis.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.5
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• pp.34-40
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• 2003

This paper presents the inertial force problem of ultrahigh-speed injection molding machine using linear motors, and presents its solutions. To make very thin products by injection molding, very high injection speed is required, and linear motors are used for this purpose. However, direct drive by linear motors may cause brief nozzle separation from the sprue bushing because of the inertia force which is as large as the total output thrust of the linear motors, and this momentary separation can cause molten plastic to leak. In this paper, two solutions are proposed for this inertia force problem. One is the mechanical cancellation of the inertia force, and the other is to increase the nozzle contact force. With the latter solution, the stationary platen bending worsens, so a new nozzle contact mechanism is also proposed, which can prevent the stationary platen bending.

• Research in Mathematical Education
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• v.8 no.3
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• pp.123-144
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• 2004

There is a tradition of advocating the 'two basics' (basic knowledge and basic skills) in Chinese mathematics education. The direct consequence is that Chinese students are able to produce excellent performance in the international mathematics examinations and outstanding results in the international mathematics competitions. In this article, we will present why and how Chinese teachers teach the 'two basics,' and how combine the pupil's creativity with their 'two basics.' Open ended problem solving is a way to meet the goal. The following topics will be concerned: Culture background; the speed of computation; 'make perfect' ; Efficiency in classroom; Balance between 'two basics' and personal development. In Particular, Chinese mathematics educators pay more attentions to the link between open ended problem solving and the 'two basics' principal.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1320-1326
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• 2002

In a one-dimensional heat conduction domain with heated and insulated walls, an integral approach is proposed to estimate time-dependent boundary heat flux without internal measurements. It is assumed that the expression of the heat flux is not known a priori. Hence, the present inverse heat conduction problem is classified as a function estimation problem. The spatial temperature distribution is approximated as a third-order polynomial of position, whose four coefficients are determined from the heat fluxes and the temperatures at both ends at each measurement. After integrating the heat conduction equation over spatial and time domain, respectively, a simple and non-iterative recursive equation to estimate the time-dependent boundary heat flux is derived. Several examples are introduced to show the effectiveness of the present approach.