• Journal of Energy Engineering
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• v.6 no.1
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• pp.104-113
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• 1997

This study aims to develop an analysis model using a commercial process simulator-ASPEN PLUS for an IGCC (Integrated Gasification Combined Cycle) system consisting a dry coal feeding, oxygen-blown entrained gasification process by Shell, a low temperature gas clean up process, a General Electric MS7001FA gas turbine, a three pressure, natural recirculation heat recovery steam generator, a regenerative, condensing steam turbine and a cryogenic air separation unit. The comparison between those results of this study and reference one done by other engineer at design conditions shows consistency which means the soundness of this model. The greater moisture contents in Illinois#6 coal causes decreasing gasifier temperature and the greater ash and sulfur content hurt system efficiency due to increased heat loss. As the results of sensitivity analysis using developed model for the parameters of gasifier operating pressure, steam/coal ratio and oxygen/coal ratio, the gasifier temperature increases while combustible gases (CO＋H2) decreases throughout the pressure going up. In the steam/coal ratio analysis, when the feeding steam increases the maximum combustible gas generation point moves to lower oxygen/coal ratio feeding condition. Finally, for the oxygen/coal ratio analysis, it shows oxygen/coal ratio 0.77 as a optimum operating condition at steam/coal feeding ratio 0.2.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.167-173
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• 2015

This paper attempts to estimate the electricity demand function in Korea with quarterly data of average temperature, GDP and electricity price over the period 2005-2013. We apply lagged dependent variable model and ordinary least square method as a robust approach to estimating the parameters of the electricity demand function. The results show that short-run price and income elasticities of the electricity demand are estimated to be -0.569 and 0.631, respectively. They are statistically significant at the 1% level. Moreover, long-run income and price elasticities are estimated to be 1.589 and -1.433, respectively Both of results reveal that the demand for electricity is price- and income-elastic in the long-run. The relationship between electricity consumption and temperature is supported by many of references as a U-shaped relationship, and the base temperature of electricity demand is about $15.2^{\circ}C$. It is shown that power of explanation and goodness-of-fit statistics are improved in the use of the lagged dependent variable model rather than conventional model.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.80-89
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• 1998

To understand the temporal variation of phytoplankton community in the Antarctic coastal ecosystem, physicochemical parameters, chlorophyll a, and primary productivity were measured as a component of the 7th KARP (Korea Antarctic Research Program) in 1994. Data were collected every month between February and December except four months (June-September) when the study area was frozen. Chlorophyll a concentrations ranged from negligible to 3.03 ${\mu}g/l$, averaging 0.63 ${\mu}g/l$. The primary productivity ranged 0.53-18.95 mg C/$m^3{\cdot}day$, and the depth-integrated primary productivity ranged 41.28-560.20 mg C/$m^3{\cdot}day$. A positive relationship was observed between the phytoplankton biomass and irradiance ($r^2$=0.29, p < 0.01). The degree of correlation between the primary productivity and irradiance ($r^2$=0.85, p < 0.001) was significantly higher than that between the phytoplankton biomass and irradiance. However, neither temperature nor inorganic nutrients seem to affect the temporal variation of primary productivity.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.27-27
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• 2009

드라이브 샤프트는 일반적으로 엔진에서 발생된 회전력을 바퀴에 직접 전달하는 동시에 조향기능을 수행하는 자동차 부품이다. 최근에 경량화를 통한 에너지 절감을 위하여 기존 스틸소재를 알루미늄으로 대체하는 방안에 대한 연구가 집중되고 있다. 그러나 알루미늄 단일소재로 드라이브 샤프트를 제조하는 것은 비경제적이며 또한 기 개발된 자동차 부품들과의 연결을 고려하여 알루미늄 튜브와 스틸 요크의 이종금속 접합기술이 요구된다. 전자기 펄스용접은 전자기력을 이용하여 용접대상물을 고속으로 충돌시켜 용접하는 기술로서 열 발생이 적어 재료의 특성차로 인한 결함 및 변형이 발생하지 않아, 이종금속간 고품질 용접이 가능하며, 전자기 펄스 용접부의 품질과 밀접한 관계를 갖는 공정변수 경우 모재와 접합재의 재질 따라 적정 공정변수 범위가 변화되므로 공정에 따른 데이터의 축적은 대단히 중요하다. 전자기 펄스 용접을 이용한 이종금속 접합시 접합부 품질에 영향을 미치는 공정변수는 충전전압, 모재와 접합재 사이의 간격 및 접합재의 직경과 두께의 비(D/T비)로서 보고되었으며, Al/Steel 이종 금속 접합시 이들 공정변수가 접합부에 미치는 영향 및 최적의 공정변수 도출을 위한 연구는 시도되지 않았다. 따라서 본 연구는 전자기 펄스 용접기술을 이용한 Al/Steel 이종금속 접합 실험을 통하여 전자기 펄스용접의 적정성과 최적의 충전전압, 모재와 접합재 사이의 간격, D/T비를 도출하고자 한다. 전자기 펄스 용접 장치는 한국생산기술연구원과 웰메이트(주)에서 공동으로 개발한 $120{\mu}F$의 캐패시터 6개로 구성된 'W-MPW36'을 사용하였으며 이 장치의 최대충전전압과 최대접합용량은 각각 10kV, 36kJ이다. 접합재는 전기 전도율의 높은 Al 1070 파이프를 사용하였으며 모재는 기존 스틸 요크재인 SM45C 환봉을 사용하였다. 기보고된 연구를 통하여 코일과 접합재 사이의 간격이 좁을수록 높은 전자기력이 접합재에 작용하는 것을 확인하였으나 코일내 접합재와 모재 삽입 편의를 위하여 1mm로 설정하였다. 접합부의 품질 평가를 위하여 수압시험을 실시하였으며, 시험 후 접합부 단면을 주사전자현미경(SEM)을 이용하여 관찰하였다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.13 no.4
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• pp.283-293
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• 2015

The buffer is a key component of the engineered barrier system in a high-level radioactive waste (HLW) repository. The present study reviewed the requirements and functional criteria of the buffer reported in literature, and also based on the results, proposed an approach to establish a buffer concept which is applicable to an HLW repository in Korea. The hydraulic conductivity, radionuclide-retarding capacity (equilibrium distribution coefficient and diffusion coefficient), swelling pressure, thermal conductivity, mechanical properties, organic carbon content, and illitization rate were considered as major technical parameters for the functional criteria of the buffer. Domestic bentonite (Ca-bentonite) and, as an alternative, MX-80 (Na-bentonite) were proposed for the buffer of an HLW repository in Korea. The technical specifications for those proposed bentonites were set to parameter values that conservatively satisfy Korea's functional criteria for the Ca-bentonite and Swedish criteria for the Na-bentonite. The thickness of the buffer was determined by evaluating the means of shear behavior, radionuclide release, and heat conduction, which resulted in the proper buffer thickness of 0.25 to 0.5 m. However, the final thickness of the buffer should be determined by considering coupled thermal-hydraulic-mechanical evaluation and economics and engineering aspects as well.

• Research in Plant Disease
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• v.23 no.2
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• pp.193-201
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• 2017

Major tomato viruses in Korea are Tomato chlorosis virus (ToCV), Tomato spotted wilt virus (TSWV), Cucumber mosaic virus (CMV), Pepper mottle virus (PepMoV), and Tomato mosaic virus (ToMV). RT-PCR conditions for the viruses were examined, especially in primer set and RT-PCR mixture. Total 46 primer sets from the unique sequence of the viruses were tested for nonspecific background products in a RT-PCR mixture without template. Among them 16 primer sets were applied to healthy tomato RNA, resulting the compatibility between RT-PCR mixture and primer set influenced RT-PCR to reduce nonspecific background products. Based on the combinations among cDNA synthesis parameters and RT-PCR mixtures, two reaction mixtures were finally selected for ToCV detection. The condition allowed to determine more specific primer sets; C029 (ToCV), C072 (TSWV), C070 (CMV), C048 (PepMoV), and C065 (ToMV). These primer sets are expected to be of use to specific detection of the major viruses in tomato plants.

• International Journal of Highway Engineering
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• v.8 no.3 s.29
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• pp.143-153
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• 2006

The differences in the stress distribution and the critical stresses in concrete pavement systems were analyzed when the dual-wheel single-, tandem-, and tridem-axle loads were applied at the interior and the edge of the pavement. The effects of the concrete elastic modulus, slab thickness, foundation stiffness, and tire contact pressure were investigated. The stresses under the interior loads were calculated using the transformed field domain analysis and stresses under the edge loads were obtained using the finite element method. The critical stresses under the interior and the edge loads were compared with respect to various parameters and the equations to predict the ratio between the stresses under the edge and the interior loads were developed and verified. From this study, it was found that the trends of the changes in the critical concrete stresses under the interior and the edge loads were very similar and the critical stress locations under those loads were identical. The critical stress ratio, which was obtained by dividing the critical stress under the edge loads into that under the interior loads, decreased with increasing the number of axles. That ratio became larger as the concrete elastic modulus increased, the slab thickness increased, the foundation stiffness decreased, and the tire contact pressure increased.

• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.85-99
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• 2015

TDI CCD sensors are being used for most of the electro-optical camera mounted on the low earth orbit satellite to meet high performance requirements such as SNR and MTF. However, the CMOS sensors which have a lot of implementation advantages over the CCD, are being upgraded to have the TDI function. A few methods for improving the issue of motion blur which is apparent in the CMOS sensor than the CCD sensor, are being introduced. Each pixel can be divided into a few sub-pixels to be read more than once as is the same case with three or four phased CCDs. The fill factor can be reduced intentionally or even a kind of mask can also be implemented at the edge of pixels to reduce the blur. The motion blur can also be reduced in the TDI CMOS sensor by reducing the integration time from the full line scan time. Because the integration time can be controlled easily by the versatile control electronics, one of two performance parameters, MTF and SNR, can be concentrated dynamically depending on the aim of target imaging. MATLAB simulation has been performed and the results are presented in this paper. The goal of the simulation is to compare dynamic MTFs affected by the different methods for reducing the motion blur in the TDI CMOS sensor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.9-18
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• 2013

Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.13-25
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• 1998

It is necessary to develop methodologies for the application of artificial neural network into hydrologic rainfall-runoff process, although there is so much applicability by using the functions of associative memory based on recognition for the relationships between causes and effects and the excellent fitting capacity for the nonlinear phenomenon. In this study, some problems are presented in the application procedures of artificial neural networks and the simulation of runoff hydrograph experiences are reviewed with nonlinear functional approximator by artificial neural network for rainfall-runoff relationships in a watershed. which is regarded as hydrdologic black box model. The neural network models are constructed by organizing input and output patterns with the deserved rainfall and runoff data in Pyoungchang river basin under the assumption that the rainfall data is the input pattern and runoff hydrograph is the output patterns. Analyzed with the results. it is possible to simulate the runoff hydrograph with processing element of artificial neural network with any hydrologic concepts and the weight among processing elements are well-adapted as model parameters with the assumed model structure during learning process. Based upon these results. it is expected that neural network theory can be utilized as an efficient approach to simulate runoff hydrograph and identify the relationship between rainfall and runoff as hydrosystems which is necessary to develop and manage water resources.