• Journal of KSNVE
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• v.5 no.2
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• pp.163-168
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• 1995

A criterion for the selection of spindle motor speeds in a hard disk drive (HDD) is investigated to guarantee stability and reduce nonrepeatable runout of a spining disk. Since the natural frequencies of the spining disk and the forced frequencies generated from the spindle motor depend on the rotating speed, careful consideration should be taken to avoid the resonance between the disk and motor. To do this, the natural frequencies of the spining disk are calculated and they are compared with the forced frequencies from the spindle motor.

• Journal of Power System Engineering
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• v.11 no.2
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• pp.51-57
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• 2007

As a shot sleeve in die casting plays a critical role in delivering molten metal to a die cavity, any disruption to its function in the injection stage results in deterioration of the quality of final castings. To guarantee a smooth operation of a shot sleeve, its structural stability should be maintained. Despite the simple geometry, design of shot sleeve is based on individual engineer's experience and no agreement on the design is present. In this study, we newly propose a systematic methodology to determine a minimum wall thickness of a shot sleeve to prevent yielding or plastic deformation. Analytical calculations incorporating numerical analysis produce a rational design rule for minimum thickness of a shot sleeve subject to metal intensification pressure and geometric die constraint. To validate the proposed design guideline, authors present real data on a collection of actual shot sleeves. Upon checking their conformity to the new design rule, we discovered a strong correlation between the design of wall thickness and premature failures.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.491-499
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• 1999

This paper is on the high perfonnance propulsion IGBT VVVF inverter adopted new technique for railways. To prove the high performance and stabilit~r of traction, running tests are carried out under the simulated condition alike real field. The tests are perfonned on not only a steady states but also a transient states such a as input voltage variation using inertia load equivalent to 160tons train. The vector control technique is a adopted to improve traction for 4 motors. The low switching synchronous PW1\l method based on a space v voltage vector modulation is pro\XlSed as the optimal method for propulsion system railway. The output voltage l is controlled continuously to six step by prolxlsed ovennodu]ation technique without sudden torque variation.

• Convergence Security Journal
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• v.17 no.3
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• pp.83-93
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• 2017

The U.S.-China Relations could be analyzed two perspectives and their basis under major international p olitics theory-power transition with conditions: (1) North Korean's nuclear puzzle, (2) THAAD in the Kor ean Peninsula and (3) the U.S.-ROK Alliance. One perspective is the global order dominates the regional order, and then stable regional order comes out. The other is the regional order dominates the global ord er, and China wages a regional hegemonic conflict against the United States. Consequently, America's o verwhelming leadership in North Korean's nuclear, THAAD and U.S.-ROK Alliance as national power is expected to endure. But China also has expected empowerment and cooperation for the peace and stabilit y on the Korean Peninsula military problems. In this perspective, South Korea needs to pay attention to the changing power distribution and competition between the U.S. and China and needs to strengthen a balancing and harmonious diplomatic strategy, so called 'see-saw diplomacy'.

• Journal of Digital Convergence
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• v.19 no.8
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• pp.141-149
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• 2021

This study investigated the effect of accounting information on dividend policy as a measure of corporate conservatism from the perspective of the internal accounting management system. The verification is based on a sample of 543 companies listed on securities (excluding KOSDAQ and financial industry) among the Bank of Korea (2019) 「2018 Corporate Management Analysis」 and company analysis of the Korea Productivity Center (financial data disclosed as listed companies as a December settlement company) was composed. Using SPSS 22, empirical analysis was conducted using exploratory factor analysis and regression analysis. The first is the verification related to corporate conservatism and the role of dividend policy, and it is verification of whether internal accounting management influences financial decision-making. Second, if internal accounting management exists, it is a verification of how conservatism and investment policies (in-house reserve, debt borrowing, capital increase, dividends, etc.) affect the corporate value according to accounting information. As a result, from the perspective of the internal accounting management system, it was found that among the variables of accounting information, profitability can have a positive effect on corporate conservatism and dividend policy as a corporate valuation method of reinvestment. In addition, it has been proven that corporate conservatism has an effect on profitability-to-value through capital accumulation and reinvestment such as surplus and internal reserves. In the future, we will study and discuss the complementarity of corporate conservatism and dividend policy in relation to governance structure and improvement of the internal accounting management system.