• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.23-29
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• 2005

In order to improve the efficiency of hydraulic gear pumps or motors especially for high operating pressure, power losses due to viscous friction and leak flow through gear teeth end-gaps are considered in this paper. Optimal gaps minimizing the power loss for pumps and motors with uniform heights of gaps are analysed first. And the effect of the shapes of gaps with unequal heights on the power loss are studied and discussed by simulation. Considering that the outer shell lacing gear teeth may expand due to high internal pressure or thermal stress, the results drawn in this paper can be used for the design of high efficiency pumps and motors.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.40-44
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• 2005

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe but residual gas, is called "Blowby gas", enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the crankcase isn't vented, this causes many bad effects such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So, most automobiles are constituted with a PCV (Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new engines, engineers are designing it depending on their experiments than theoretical knowledge. Mush efforts and times are needed for new development. This study will show quantitative results to increase the possibilities of reduction of developing time.

• IE interfaces
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• v.20 no.3
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• pp.267-276
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• 2007

When a company makes a decision on an investment for a new product as a source for a new program, it is not easy for them to take a proper decision-making process in this highly volatile market. There could be several ways to make an investment decision on a new program. A company needs to choose the most suitable way of investment which is reflected current corporate circumstances and potential risks. We check up the process of the engineering economic decision in a automotive part manufacturing company. We define the gap between the theory and practice on engineering economic decisions. We present advices to make a decision desirably.

• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.718-730
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• 2004

The solution for the natural convection in internally finned horizontal annuli is obtained by using a numerical simulation of time-dependent and two-dimensional governing equations. The fins existing in annuli influence the flow pattern, temperature distribution and heat transfer rate. The variations of the On configuration suppress or accelerate the free convective effects compared to those of the smooth tubes. The effects of fin configuration, number of fins and ratio of annulus gap width to the inner cylinder radius on the fluid flow and heat transfer in annuli are demonstrated by the distribution of the velocity vector, isotherms and streamlines. The governing equations are solved efficiently by using a parallel implementation. The technique is adopted for reduction of the computation cost. The parallelization is performed with the domain decomposition technique and message passing between sub-domains on the basis of the MPI library. The results from parallel computation reveal in consistency with those of the sequential program. Moreover, the speed-up ratio shows linearity with the number of processor.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1225-1231
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• 2000

This paper proposes a V-shaped Lyapunov function approach for the model-based control of flexible-joint robots, in which a new model-based nonlinear control scheme is designed based on a V-shaped Lyapunov function. The proposed control guarantees global asymptotic stability for link trajectory control while keeping all internal signals bounded. Since joint flexibility is used as a control parameter, the proposed control is not restricted by the degree of joint flexibility and be applied to flexibility-joint, partly-flexibility, or rigid-joint robots without modification. the effectiveness of the proposed control has been by computer simulation.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.44
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• pp.181-210
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• 2009

This paper discusses global expansion and global strategies of shipping firms. Acknowledging the lack of research on global expansion by freight transport companies, this paper employs the resource-focused model, and explores "why shipping companies emerge" and "why the strategic behaviour of shipping companies is different in the global market". Despite there being a plethora of theoretical and empirical studies on the international operations of business organisations, it is acknowledged that researchers have largely neglected the issues regarding the international expansion within the freight transport industry. Identifying the general lack of contemporary studies concerning the international behaviour of shipping firms, this study addresses the important gap in our knowledge in the theoretical manner. The theoretical analysis suggests that the shipping company's internal resources can be a real reason for the international market participation.

• Korean Journal of Human Ecology
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• v.17 no.1
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• pp.35-43
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• 2008

The purpose of this study is to develop evaluation tools for young children's mathematical ability based on the content standards of NCTM and to verify the suitability of the tools. The tools consist of 5 sub-tests with 90 items, including number and operation, algebra, geometry, measurement, data analysis and probability. The tool analysis was examined with 300 three-to five-years-old children and 31 math education professionals. The results of this research are as follows : First, in order of age the passing rate increased. The gap between high and low score group reveals a statistically meaningful difference. Second, the internal consistency reliability coefficient, Cronbach ${\alpha}$, is .96. Test-retest reliability is around .90. The concurrent validity correlation between this tools and Choi Hye-Jin's test(2003) is .85. The analysis of the content validity was proved appropriately by math education professionals.

• Knowledge Management Research
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• v.17 no.4
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• pp.163-189
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• 2016

The importance of Information technology (IT) has been growing. Thus, it is critical for firms to choose the optimal information technology development mode in order to ensure that maximum benefit is derived from IT. Despite its importance, however, there is little comprehensive research on choosing the IT development mode that firms undertake. To fill this gap, this study attempts to propose a parsimonious as well as comprehensive IT development framework based on strategic value and the uniqueness of IT resources. In addition, this study analyzes the impact of the fit between the theoretically proposed IT development mode and the actually used mode on the performance of Korean firms. This study contributes to and expands the literature on IT development modes by considering various development modes in real time. Moreover, the results serve as a stepping stone for managers who want to develop or adopt IT effectively.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.269-272
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• 2006

The hydroforming processing is a relatively new technology in comparison with conventional stamping process. The hydroforming processing makes torsion beam in rear suspension of automobile. The durability of torsion beam is very important characteristic that operate in an automobile. In order to optimize the hydroforming process and satisfy the durability, the hydroforming simulation which could control an axial compression and high internal pressure with computer simulation has to be operated. This paper is about an optimum design to improve the kinematic and compliance characteristics of a torsion-beam of suspension system. The result from finite element analysis shows that the forming and the durability are optimized. If there is effect of First pressure in hydroforming processing that gap is in the die tool, the prototype of tube is not satisfied on the durability test.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.55.1-55
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• 2002

In the era of home automation, we need more context-aware and intelligent service applications than before. For these applications, a service gateway as a platform is required to bridge the gap between external data networks to internal home networks. Also, the sonics gateway enables customers to receive new classes of home services. The OSGi service platform is a good solution for the service gateway since it can deliver new applications dynamically from a broader network. In the near future, every home will be equipped with a residential gateway powered by the OSGi, and will demand value-added service applications, such as home security monitoring and safety alerts. In this pa...