• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2201-2210
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• 2000

Vibration of a rotating disk-spindle system is analyzed by using Hamilton's principle, FEM and substructure synthesis. A rotating disk undergoes the rigid body motion and the elastic deformation. It s equation of motion is derived by Kirchhoff plate theory and von Karman nonlinear strain. A rotating shaft is described by Rayleigh beam theory considering the axial rigid body motion. The stationay shaft supporting the rotating disk-spindle-bearing system is modeled by Euler beam theory, and the stiffness of ball bearing is determined by A.B.Jones' theory. FEM is used to solve the derived governing equations, and substructure synthesis is introduced to assemble each structure of the rotating disk-spindle system. The developed theory is applied to the spindle system of a 35' computer hard disk drive with 3 disks to verify the simulation results. The simulation results agree very well with the experimental ones. The proposed theory may be effectively expanded to the complex structure of a disk-spindle system.

• Journal of Distribution Science
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• v.18 no.11
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• pp.47-59
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• 2020

Purpose: The purpose of this study is to investigate the distribution of ancient Korean books around the world, and to study the process and impact of Myongsimbogam's distribution to East Asia and Europe. Research design, data and methodology: This study conducted literature research as its research method. The scope of research covers Korea, China, Japan, Vietnam, Spain, Germany and Russia. Results: Ancient Korean books were distributed through the Kwanpan and Banggakbon, and leaked overseas in historical circumstances. Myongsimbogam was distributed to Korea, China, Japan, Vietnam, Spain, France, Germany, and Russia. Myongsimbogam was the first ancient book to be translated into Western languages. Conclusions: The distribution of Myongsimbogam promoted the exchange of spiritual civilizations in the East and West, and became the basis for maintaining an individual philosophy, as well as social order. Therefore, the distribution of Myongsimbogam needs to be further expanded. For this, it is necessary to translate Myongsimbogam into English and popularize it through e-books, audio books and various lectures. While previous studies on Myongsimbogam have mainly focused on personality and moral education, this study is significant in that it examines the distribution and dissemination process of Myongsimbogam, its influence and significance.

• Journal of Advanced Navigation Technology
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• v.9 no.2
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• pp.109-120
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• 2005

In this paper, bit error rate (BER) characteristics, sensitivity and minimum allowable launching power are numerically investigated as a function of amplifier spacing that consisted of 1,200 km WDM systems with MSSI method. It is conformed that the sensitivity and minimum allowable launching power are gradually degraded as amplifier spacings are gradually expanded, but those are not largely affected by modulation format. The sensitivity of RZ transmission system is smaller than that of NRZ transmission system, but minimum allowable launching power of NRZ transmission system is smaller than that of RZ transmission system. And, it is confirmed that the best amplifier spacing in NRZ and RZ transmission system is less than 50 km, because the sensitivity and minimum allowable launching power are less affected by fiber dispersion, channel wavelength and pump light power.

• Journal of the Korean Society of Costume
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• v.59 no.7
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• pp.114-126
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• 2009

The purpose of this study is to analyze the art characteristics of Japonism expressed in Art Nouveau jewelry. This study also provided an opportunity to seek for the development direction of contemporary jewelry design for the future. The influence of Japanese arts in Art Nouveau jewelry, was mostly from Ukiyo-e, an art form from the Edo Dynasty in Japan. Japanese arts soon inspired the origination of Art Nouveau across Europe in the late 19th century. And the scope of its infuluence is shown in jewelry which created by contemporary painters and designers. Ukiyo-e, a folk painting was created from multi-color wooden printmaking emerged many Japanese art collectors, including Samuel Bing and Arthur Lasenby Liberty. This became a source of new inspirations for Degas, Monet, Gogh and the origin of Japonism. The layout techniques that used perspectives higher than eye level and that extremely cut or expanded major objects for emphasis were typical Ukiyo-e characteristics. The result of this study is found out by showing the evidence that influence of this Ukiyo-e's method came up with specificity as planity, naturality, decoration and express on the Art Nouveau jewelry.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.568-573
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• 2003

When a safety valve equipped in a nuclear power plant opens in an instant by an accident, a moving shock wave propagates downstream the valve, inducing a complicated unsteady flow field. The moving shock wave may exert severe load to the structure. So, to reduce the load acting on the wall of POSRV, a gradual opening of POSRV is adopted in general. In theses connections, a numerical work is performed to investigate the effect of valve opening time on the unsteady flow fields downstream of the valve. Compressible, two-dimensional Navier-Stokes equations are used with the finite volume method. The obtained results show that sharp pressure rise through moving shock tor the case of instant opening is attenuated by employing the gradual opening of valve. It is turned that the flows for the two cases of gradual valve opening time show the similar to that of highly under-expanded one in jet structure having expansion and compression waves and Mach stem. Also, comparing with the results for the two cases of opening time, the shorter the valve opening is, the pressure gradient at the downstream of the valve becomes softly.

• KIEAE Journal
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• v.16 no.5
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• pp.93-101
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• 2016

Purpose : This research aims to present policy plans for community vitality in the field of the urban regeneration project by analyzing aspects for vitality via domestic and abroad city policies and cases. Methods: The research method works as follows: The first step is 1) to introduce the concept of evaluation matrix to analyze cases of urban generation, 2) to apply to the proposed evaluation matrix, and then 3) to analyze communities' decline diagnosis, counterstrategies, and promotion process. And the second step is to draw features and evaluation of cases and to present the policy plan for communities' vitality with the urban regeneration project in South Korea via a comprehensive analysis. Result : This research confirmed the fact that when different sectors is expanded toward a mutual cooperation, communities are vitalized, having a mutual effect on other related sectors by taking a part in the community positively. Especially in the base of each characteristic and estimation, when various activities and socio-economic programs with residents are promoted in the integrated system, communities are successful. Through this results we present four policy plans for community vitality of the urban regeneration project in South Korea.

• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.545-551
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• 2010

A new family of DC to AC converters, referred to as multilevel inverter, has received much attention from industries and researchers for its high power and voltage applications. One of the conventional techniques for implementing the switching algorithm in these inverters is optimized harmonic stepped waveform (OHSW). However, the major problem in using this technique is eliminating low order harmonics by solving the nonlinear and complex equations. In this paper, a new approach called the "bacterial foraging algorithm" (BFA) is employed. This algorithm eliminates and optimizes the harmonics in a multilevel inverter. This method has higher speed, precision, and convergence power compared with the genetic algorithm (GA), a famous evolutionary algorithm. The proposed technique can be expanded in any number of levels. The purpose of optimization is to remove some low order harmonics, as well as to ensure the fundamental harmonic retained at the desired value. As a case study, a 13-level inverter is chosen. The comparison results by MATLAB software between the two optimization methods (BFA and GA) have shown the effectiveness and superiority of BFA over GA where convergence is desired to achieve global optimum.

• The KSFM Journal of Fluid Machinery
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• v.17 no.4
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• pp.5-10
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• 2014

It is possible for the nation's largest flowmeter calibration system in K-water to calibrate flow rate up to $2,700m^3/h$ and diameter 800mm. However, the calibration and measurement capability of K-water's system is not satisfied in comparison with other developed countries. In this study, we find the dominant factors related to the uncertainty of weight and time measurement for gravimetric flowmeter calibration system. As a results of improving the system, the combined standard uncertainty has been improved $1.099{\times}10^{-3}$ to $2.332{\times}10^{-4}$. So calibration and measurement capability got 0.08 percent of the relative expanded uncertainty for maximum flow rate using the coverage factor(k=2).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.571-576
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• 1994

In recent years, ultrasonic has been widely applied in measurement and industrial fields and its application range has been expanded as a result of continuous research and development. Wire Bonding Machine, an instrument fabricating semi-conductor, makes use of ultrasonic bonding method. In order to improve the currently used wire bonding machine using ultrasonic energy, technical accumulation is needed steadily through development of exciting device of ultrasonic composed of piezoelectic vibrator and horn. This study investigates the design conditions affecting the dynamic characteristics through the theoretical and experimental analysis of piezoelectric vibrator and horn, The study conducts separately the system identification of piezoelectric vibrator in time domain and the modal analysis of horn in frequency domain. In theoretical model, the integrated modeling is conducted via a combination of dynamic identification of piezoelectric vibrator and theoretical analysis of horn. Hence comparison is made for theoretical and experimental results of the dynamic characteristics of the ultrasonic transducer composed of piezoelectric vibrator and horn. Form the results of this study we develop the design technique of ultrasonic transducer using dynamic characteristic analysis and propose the possibility of ultrasonic welding considering the optimal condition of the natural frequency and vibration mode of horn.

• Water Engineering Research
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• v.6 no.2
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• pp.91-99
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• 2005

One of the most important factors for estimating a flood runoff from streams is the lag time. It is well known that the lag time is affected by the morphometric properties of basin which can be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) was applied for calculating the lag time of geomorphologic instantaneous unit hydrograph(GIUH) at a basin outlet. The lag time was obtained from the observed data of rainfall and runoff by using the method of moments and the procedure based on geomorphology was used for GIUH. The relationships between the basin morphometric properties and the hydrological response were discussed based on application to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse were examined how they are transformed from upstream area to downstream one. As a result, the relationship between the lag time and descriptors was shown to be close, and the shape of ellipse was presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.