• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.223-227
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• 2003

In this study, ultrasonic rotary motors using a bolted langevin type ultrasonic vibrator were designed and fabricated. The stator vibrator has a longitudinal transducer section composed of two metal blocks and two piezoelectric ceramic elements (thickness-polarized) and a mode conversion metal block section called a torsion coupler. And, three kinds of motors were studied by finite element analysis and experiments. So, as material of torsion coupler which generate mode conversion of vibration copper, brass, and phosphor bronze were used. As a result, speed and torque were changed in proportion to the electrical input Voltage, but it was saturated in high voltage. And bad efficiency which was different from a expectation was measured in this motors. So, various problems should be improved for practical use. Finally, The motor which has 1 [cm] diameter was fabricated to present a possibility of miniaturization of this type motors.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.465-475
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• 1999

The objective of the present work is to assess the analysis capability of two wall film condensation models, the default and the alternative models, of RELAP5/MOD3.2 on condensation experiments in the presence of noncondensable gas in a vertical tube of PCCS of CP-1300. In the calculation of a base case the default model of RELAP5/MOD3.2 under-predicts the heat transfer coefficients, and Its alternative model over-predicts them throughout the condensing tube, Also, both models over-predict the void fractions. The nodalization study shows that the variation of the node number does not change both modeling results of RELAP5/MOD3.2 Sensitivity study for varying input parameters shows that the inlet steam-air mixture flow rate, the inlet air mass fraction, and the inlet saturated steam temperature give significant changes of their heat transfer coefficients Run statistics show that the grind time of the default model is always higher than that of the alternative model by about 23%.

• Journal of Magnetics
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• v.16 no.1
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• pp.74-76
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• 2011

Interior permanent-magnet synchronous motors (IPMSMs) produce both magnetic and reluctance torques. The reluctance torque is due to the difference between the d- and q-axis inductances based on the geometric rotor structure. The steady-state performance analysis and precise control of the IPMSMs greatly depend on the accurate determination of the parameters. The three essential parameters of the IPMSMs are the armature flux linkage of the permanent magnet, the d-axis inductance, and the q-axis inductance. In the basic design step of an IPMSM, the inductance parameters are very important for determining the motor characteristics, such as the input voltage, torque, and efficiency. Thus, it is very important to accurately estimate the values of the motor inductances. The inductance parameters of IPMSMs have nonlinear characteristics along the magnet size because the iron core is saturated by the magnet and armature reaction fluxes. In this study, the inductance parameters were calculated using both the magnetic-equivalent-circuit method and the finite-element method (FEM). Then the calculated parameters were compensated by the saturation coefficient function, which was also calculated via the magnetic-equivalent-circuit method and FEM.

• 대한공업교육학회지
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• v.34 no.2
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• pp.179-204
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• 2009

As the concern with the educational training for human resources development in organizations grows, various programs are being offered in many places. Accordingly, the issue of securing the validity of the education and the importance of its assessment at the level of continuous quality management of the programs draw our attention. The purpose of this study is to offer the basic data of evaluation criteria for human resources development which knowledge-and-information saturated society requires, and also to draw out the greater area of human resources development educational program based on CIPP(Context, Input, Process, Product) model by Stufflebeam, an evaluation model concentrated on process, through literature and case study in and out of Korea. The result of the study is as follows. First, the evaluation areas drawn out by the greater sphere of context evaluation of human resources education program are needs analysis, goal setting, and organizational environment. Second, the evaluation areas drawn out by the greater sphere of input evaluation of human resources education program are educational program strategies, human resources, and physical resources. Third, the evaluation areas drawn out by the greater sphere of process evaluation of human resources education program are educational program management, teaching-learning strategies, and educational support environment. Fourth, the evaluation areas drawn out by the greater sphere of product evaluation of human resources education program are influence, effect, durability, and transference. The author supposes that these results will be able to become the basic materials for the systematic approach to educational programs through the analysis of evaluation criteria for and the greater sphere of educational program of human resources development.

• Journal of Energy Engineering
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• v.22 no.1
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• pp.17-27
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• 2013

Korean domestic electricity market is saturated through trying to find ways to overcome the limitations of the domestic electricity industry with overseas electricity markets. Korean electricity industry in the overseas market in order to pursue continuous growth, competitive and aggressive investment in overseas market is promoting. This paper attempts to apply input-output analysis to estimate the role of coal thermal power plant sector exports national economy. More specifically, this study shows what national economy effect of production-inducing effect, value-added inducing effect, and employment-inducing effect are explored with demand-driven model. After define coal thermal power plant sector what small sized of Input-Output table 168 sectors among 17 sectors, this study pays particular and close attention to coal thermal power plant sector by taking the sector as exogenous specification and then investigating economic impacts of it. This study uses coal thermal power plant exportation case of Vietnam project, production-inducing effect, value-added inducing effect, and employment-inducing effect are 2,853 billion won, 973 billion won and 14,761 persons, respectively.

• Journal of Energy Engineering
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• v.21 no.2
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• pp.158-167
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• 2012

The purpose of this paper is to examine the factors that encouraged the industrial growth of Koran city gas industry during 1995-2009, by carrying out input-output structural decomposition analysis(IO-SDA) using Syrquin's model. The results show that the main factors which contributed to the growth of the Korean city gas industry are final domestic demand(48.4%) and technological change(38.6%). By examining the results for the three periods of 1995-2000, 2000-2005, and 2005-2009, the tendency of changes between the two main factors is drawn. In contrast to the drastic decreasing tendency of the final domestic demand's contribution to the growth, 84.5%, 18.9%, and 15.4%, respectively for each period, there is an increasing tendency for technological change as seen by the results of 7.4%, 70.0%, and 42.2%, respectively. These findings may be a result from the fact that the rate of gas supply in the residential sector has been saturated recently. They are also reflective of the energy consumption trend of industrial activities as there has been a shift in the approach for supplying energy, from the traditional approach which use fossil fuels to the newer approach which uses environmentally friendly energy sources. For the continued growth of the city gas industry, policymakers sould consider greater investment in the expansion of city gas supply infrastructure for industrial activities rather than for the residential sector.

• Journal of the Korean GEO-environmental Society
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• v.9 no.1
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• pp.47-54
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• 2008

In this study, the effect of water content condition was investigated on the Mohr-Coulomb shear strength parameters which are commonly used as the input data in the soil slope analysis. For the purpose, a series of direct shear test was conducted in different water content conditions on the two types of weathered soils and a dam core material, obtained from the domestic slope construction sites and the dam construction site, respectively. The comparisons between the values of the Mohr-Coulomb ${\phi}_{peak}$ and $c_{peak}$, estimated from the relationships between the normal stress and the peak shear stress for the samples in the four different water content conditions (i.e., dry side, optimum, wet side, and saturated), showed that overall, the values of $c_{peak}$ decreased gradually while those of ${\phi}_{peak}$ did not vary much with increasing the water content. A rough estimate for the varying ratio of the values of ${\phi}_{peak}$ and $c_{peak}$ indicated that the values of $c_{peak}$ decreased by every 25% of the $c_{peak}$ values in dry side, while those of ${\phi}_{peak}$ were constant, as the water content condition changed from dry, optimum, and wet to saturated, respectively.

• Geotechnical Engineering
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• v.8 no.2
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• pp.5-20
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• 1992

The physical-based and lumped-parameter hydrologic groundwater flow model for predicting the rainfall-triggered rise of groundwater levels in hillside slopes is developed in this paper to assess the risk of landslides. The developed model consists of a vertical infiltration model for unsaturated zone linked to a linear storage reservoir model(LSRM) for saturated zone. The groundwater flow model has uncertain constants like soil depttL slope angle, saturated permeability, and potential evapotranspiration and four free model parameters like a, b, c, and K. The free model parameters could be estimated from known input-output records. The BARD algorithm is uses as the parameter estimation technique which is based on a linearization of the proposed model by Gauss -Newton method and Taylor series expansion. The application to examine the capacity of prediction shows that the developed model has a potential of use in forecast systems of predicting landslides and that the optimal estimate of potential 'a' in infiltration model is the most important in the global optimum analysis because small variation of it results in the large change of the objective function, the sum of squares of deviations of the observed and computed groundwater levels. 본 논문에서는 가파른 산사면에서 산사태의 발생을 예측하기 위한 수문학적 인 지하수 흐름 모델을 개발하였다. 이 모델은 물리적인 개념에 기본하였으며, Lumped-parameter를 이용하였다. 개발된 지하수 흐름 모델은 두 모델을 조합하여 구성되어 있으며, 비포화대 흐름을 위해서는 수정된 abcd 모델을, 포화대 흐름에 대해서는 시간 지체 효과를 고려할 수 있는 선형 저수지 모델을 이용하였다. 지하수 흐름 모델은 토층의 두께, 산사면의 경사각, 포화투수계수, 잠재 증발산 량과 같은 불확실한 상수들과 a, b, c, 그리고 K와 같은 자유모델변수들을 가진다. 자유모델변수들은 유입-유출 자료들로부터 평가할 수 있으며, 이를 위해서 본 논문에서는 Gauss-Newton 방법을 이용한 Bard 알고리즘을 사용하였다. 서울 구로구 시흥동 산사태 발생 지역의 산사면에 대하여 개발된 모델을 적용하여 예제 해석을 수행함으로써, 지하수 흐름 모델이 산사태 발생 예측을 위하여 이용할 수 있음을 입증하였다. 또한, 매개변수분석 연구를 통하여, 변수 a값은 작은 변화에 대하여 목적함수값에 큰 변화를 일으키므로 a의 값에 대한 최적값을 구하는 것이 가장 중요한 요소라는 결론을 얻었다.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.221-242
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• 2021

A numerical study of the performance assesment of coupled thermo-hydro-mechanical (THM) processes in improved Korean reference disposal system (KRS⁺) for high-level radioactive waste is conducted using TOUGH2-MP/FLAC3D simulator. Decay heat from high-level radioactive waste increases the temperature of the repository, and it decreases as decay heat is reduced. The maximum temperature of the repository is below a maximum temperature criterion of 100℃. Saturation of bentonite buffer adjacent to the canister is initially reduced due to pore water evaporation induced by temperature increase. Bentonite buffer is saturated 250 years after the disposal of high-level radioactive waste by inflow of groundwater from the surrounding rock mass. Initial saturation of rock mass decreases as groundwater in rock mass is moved to bentnonite buffer by suction, but rock mass is saturated after inflow of groundwater from the far-field area. Stress changes at rock mass are compared to the Mohr-Coulomb failure criterion and the spalling strength in order to investigate the potential rock failure by thermal stress and swelling pressure. Additional simulations are conducted with the reduced spacing of deposition holes. The maximum temperature of bentonite buffer exceeds 100℃ as deposition hole spacing is smaller than 5.5 m. However, temperature of about 56.1% volume of bentonite buffer is below 90℃. The methodology of numerical modeling used in this study can be applied to the performance assessment of coupled THM processes for high-level radioactive waste repositories with various input parameters and geological conditions such as site-specific stress models and geothermal gradients.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.8
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• pp.587-590
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• 1999

In this study, it is the purpose to develope a cheap and compact $CO_2$ laser and to apply 60 Hz AC discharges as a new exciting source. An axial and water cooledtype was adopted as the laser mode. The laser performance characteristics as various parameters, such as gas pressure and discharge current, have been investigated. And the laser output and the efficiency of DC and 60 Hz AC discharge-exciting type have been measured and compared for the different input powers at the static operational pressure. As a result, the case of 60 Hz AC discharge-exciting type, the laser oscillation began at the condition of operational pressure 6 Torr and discharge current 5 mA. A maximum laser output of about 32 W was obtained at an operational pressure of 18 Toorr and a discharge current of 30 mA. In addition, the laser output was saturated from an operational pressure of about 14 Torr and a discharge current of about 20 mA. In this $CO_2$ laser, the laser output of 60 Hz AC discharge-exciting type was slightly higher than that of DC discharge-exciting type. And the laser efficiency was about 10 to 13% for the various operational pressures and the discharge currents.