• 산업기술연구
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• 제35권
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• pp.95-102
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• 2015

Two extreme wind speed prediction models, the EWM(Extreme wind speed model) in IEC61400-1 and the Gumbel method were compared in this study. The two models were used to predict extreme wind speeds of six different sites in Korea and the results were compared with long term wind data. The NCAR reanalysis data were used for inputs to two models. Various periods of input wind data were tried from 1 year to 50 years and the results were compared with the 50 year maximum wind speed of NCAR wind data. It was found that the EWM model underpredicted the extreme wind speed more than 5 % for two sites. Predictions from Gumbel method overpredicted the extreme wind speed or underpredicted it less than 5 % for all cases when the period of the input data is longer than 10 years. The period of the input wind data less than 3 years resulted in large prediction errors for Gumbel method. Predictions from the EWM model were not, however, much affected by the period of the input wind data.

• 통상정보연구
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• 제9권2호
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• pp.423-439
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• 2007

The purpose of this study was to analyze market competitiveness of Korean and Chinese computer parts industry in the between two countries' market by using Index of Export Bias and Market Comparative Advantage Index. For attaining the purpose of study, we classified the computer parts which exported to the two countries' market and the imported products as the memory devices and input/output peripheral devices. Analyzing period was 2001-2006. The analysis of Korean results of Index of Export Bias indicated that memory devices represented low overall numerical value and the Chinese results of Index of Export Bias indicated that memory devices represented high gradual numerical value. On the other hand, Korean input/output peripheral devices have been increasing steadily for analysis period and China input/output peripheral devices have been decreasing steadily for analysis period. Additional results indicated that the Korean and China computer parts which gained market competitiveness between two countries market were as follows. Korean memory devices have been losing competitiveness in the China market steadily and Chinese memory devices have been acquire competitiveness in the Korean market gradually. In input/output peripheral devices case, Korean products represented powerful competitiveness in the China market and Chinese products have been gaining competitiveness in the Korea market.

• 한국전기전자재료학회논문지
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• 제31권4호
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• pp.193-197
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• 2018

The ratio of the period of a diffractive element to the input beam size is a critical parameter in a diffractive beam shaper. We measured and calculated the Fraunhofer diffraction patterns of a periodic hologram with an input beam size similar to the period of the hologram. The measured intensities show very complicated patterns and are strongly dependent upon the center position of the laser beam relative to the hologram. Using a diffraction formula for a periodic hologram, we calculated the diffracted light intensities and fit them to the measured ones. The measured and calculated intensities are in good agreement even when the beam diameter of the incident laser is similar to the period of the hologram. We can therefore use this formula to estimate the output of a periodic beam shaper even under such an extreme condition.

• 전자공학회논문지B
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• 제31B권3호
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• pp.53-59
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• 1994

A new fully differential sample-and-hold circuit which can effectively compensate the offset voltage of an operational amplifier and the charge injection of a MOS switch is presented. The proposed circuit shows a true sample-and-hold function without a reset period or an input-track period. The prototype fabricated using a 1.2$\mu$m double-polysilicon CMOS process occupies an area of 550$\mu$m$\times$288$\mu$m and the error of the sampled ouput is 0.056% on average for 3V input at DC.

• 한국경영과학회지
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• 제37권4호
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• pp.37-50
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• 2012

The existing DEA models have been devoted to evaluate relative efficiency of DMUs based on multiple input and output factors of a same period. However, a certain kind of lead time can be required to produce outputs using inputs in an organization. R&D evaluation is a typical area with this kinds of time lag. Thus, the purpose of this paper is to develop a new DEA model to deal with time lag effect in performance evaluation. The proposed model is to find relative efficiency of each DMU for each period considering the time lag effect. A case example using a real data set is also given to show the usage or implication of the suggested model. The results are compared with the ones of the CCR model and the multi-periods input model.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.58-65
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• 1998

A purpose of this research is to develope the calculation methods of design input seismic loads, Where, calculation methods are ; (1) Considering different recurrence period of earthquakes which was proposed by ATC 14. (2) Using earthquake records which was modified Korean codes. Responce spectra that was adopted by codes has an estimated recurrence interval of 500 years, with approximately a 90 percent probability of not being exceeded in 50 years. But If we considered the life-time of existing buildings in some cases, response spectra be modified with return period of earthquakes. If we be design highrise and irregular buildings, dynamic analysis method that use time history records should be used. But in Korea, time history records of earthquakes was very few. Therefore to use foreign countries's earthquake record, it is need to select of records considered Korean coeds. As a results, this study propose a calculation method of seismic design input loads that considered return period of earthquakes and also propose using method of earthquakes.

• 설비공학논문집
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• 제5권3호
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• pp.179-186
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• 1993

The characteristics of pressure-drop oscillations(PDO) in boiling channel are studied experimentally. The effects of initial and boundary conditions on PDO are investigated in terms of oscillation period and amplitude. The period and amplitude of PDO are increased with the increase in the compressible volume in surge tank and heat input. However the amplitude of PDO is decreased with fluid temperature under low subcooling condition. Higher initial insurge flowrate resulted in almost invariant oscillation period but lower amplitude. At higher heat input the oscillation of heater wall temperature is significant, whose period is the same as that of pressure-drop instability.

• Journal of Power Electronics
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• 제12권6호
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• pp.912-924
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• 2012

In hybrid renewable power systems, the use of a multiple-input dc/dc converter (MIC) leads to simpler circuit and lower cost, when compared to the conventional use of several single-input converters. This paper proposed a novel three-input buck/boost/buck-boost converter, which can be used in applications with various values of input voltage. The energy sources in this converter can deliver power to the load either simultaneously or individually in one switching period. The steady relationship, the power management strategy and the small-signal circuit model of this converter have been derived. With decoupling technology, modeling and regulator design can be obtained under multi-loop control modes. Finally, three generating methods of a multiple-input buck/boost/buck-boost converter is given, and this method can be extended to the other multiple-input dc/dc converters.

• 한국영어학회지:영어학
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• 제1권4호
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• pp.587-608
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• 2001

When teaching English in elementary schools was introduced in Korea in 1997, the theoretical basis was the critical period hypothesis (CPH). The object of this study was to test whether the Korean situation satisfies the conditions for the CPH such as the amount of English input and needs. As a test for this, English input and needs were compared in Korea, the U.S.A. and Singapore. The items for English input were on a continuum of primary to secondary sources and the items for English needs were on a continuum of immediate to future needs. The 0-5 scale was used. The result showed that the total means of English input were 4.87, 4.62, and 1.05 for children in the U.S.A., Singapore and Korea respectively. The total means of English needs were 4.32, 3.81, and 1.52 for children in the U.S.A., Singapore and Korea respectively. These figures show that Korean children's levels of both input and needs were from “almost none” to “little,” while those of children in the U.S.A. and Singapore were from “much” to “very much.” This shows that teaching English in Korea presently is far from meeting the conditions that are expected by the CPH. As an alternative to explain what happens cognitively to Korean children, this paper suggests the automatization and proceduralization processes.

• Earthquakes and Structures
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• 제6권2호
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• pp.201-216
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• 2014

Many building codes use the empirical equation to determine fundamental period of vibration where in effect of length, width and the stiffness of the building is not explicitly accounted for. Also the equation, estimates the fundamental period of vibration with large safety margin beyond certain height of the building. An attempt is made to arrive at the simple empirical equations for fundamental period of vibration with adequate safety margin, using soft computing technique of Genetic Programming (GP). In the present study, GP models are developed in four categories, varying the number of input parameters in each category. Input parameters are chosen to represent mass, stiffness and geometry of the buildings directly or indirectly. Total numbers of 206 buildings are analyzed out of which, data set of 142 buildings is used to develop these models. It is observed that GP models developed under B and C category yield the same equation for fundamental period of vibration along X direction as well as along Y direction whereas the equation of fundamental period of vibration along X direction and along Y direction is of the same form for category D. The equations obtained as an output of GP models clearly indicate the influence of mass, geometry and stiffness of the building over fundamental period of vibration. These equations are then compared with the equation recommended by other researcher.