• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.4
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• pp.208-211
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• 2018

This paper details the design of a 1,200 V class trench gate field stop IGBT (insulated gate bipolar transistor) with a nano gate structure smaller than 1 um. Decreasing the size is important for lowering the cost and increasing the efficiency of power devices because they are high-voltage switching devices, unlike memory devices. Therefore, in this paper, we used a 2-D device and process simulations to maintain a gate width of less than 1 um, and carried out experiments to determine design and process parameters to optimize the core electrical characteristics, such as breakdown voltage and on-state voltage drop. As a result of these experiments, we obtained a wafer resistivity of $45{\Omega}{\cdot}cm$, a drift layer depth of more than 180 um, an N+ buffer resistivity of 0.08, and an N+ buffer thickness of 0.5 um, which are important for maintaining 1,200 V class IGBTs. Specially, it is more important to optimize the resistivity of the wafer than the depth of the drift layer to maintain a high breakdown voltage for these devices.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.3
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• pp.104-117
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• 1998

Rising concern about climate change has evoked interest in the potential for urban vegetation to help reduce the level of atmospheric CO\sub 2\, a major heat-trapping gas. This study quantified the functio of home energy savings and carbon emission reduction by shading, evapotranspiration and windspeed reduction of urban vegetatioin in Chuncheon. Tree and shrub cover averaged approximately 13% in residential land. The effects of shading, evapotranspiration and windspeed reduction annually saved heating energy by 2.2% and cooling energy by 8.8%. The heating and cooling energy savings reduced carbon emissions by 3.0% annually. These avoided emissions equaled the amount of carbon emitted annually from fossil fuel consumption by a population of about 1,230. Carbon emission reduction per residential building was 55kg for detached buildings and 872 kg for multifamily buildings. Urban vegetation annually decreased heating and cooling energy cost by ￦1.1 billions, which were equivalent to annual savings of ￦10,000 savings and carbon emission reduction due to tree plantings in the wrong locations, while windspeed reduction had a great effect. Plantings fo large trees close to the west and east wall of buildings, full tree plantings on the north, and avoidance of shade-tree plantings or selection of solar-friendlytrees on the south were recommended to improve the function of building energy savings and carbon emission reduction by urban vegetation.

• Journal of the Korean Institute of Navigation
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• v.19 no.1
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• pp.33-48
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• 1995

In the process of containerization, the problem of regional maldistribution of container management plan arises seriously due to several factors like a number of unbalances of containers between loading and discharging ports. This study focus on the minimizing cost. This study is composed of two models which in effective management decision making show decision of the number of containers and transfer of empty containers. One is decision of the number of containers which carriers should possess by appropriate forecasting and the other is effective management decision making which includes the transfer of empty containers on calling ports. This study has suggested as follows, First, the Time Series analysis method, especially the "Exponential Smooting with Trend Adjustment" was used to forecast the trade volumes for the designated traffic route. Second, the Time Series analysis method in deciding the optimal number of owned container at the unbalances trade situation between East Bound and West Bound service, most important variables were found such as total traffic volume, the calling interval at a port, the number of days of voyage and the length of stay on shore of container for the optimal number of owned container. Third, effective management decision making model, which makes it possible to analyze the impacts of change in important matters such as lease and positioning policy, and actually influence decision making.on making.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.803-803
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• 2002

Several environmental problems have occurred and extremely affected throughout the East Asia region. Satellite imageries and spatial information have been used in the applications of environmental and natural hazard management for years. Sharing these data and resources in the community is considered as one of the optimal solution. It would consequently bring cost saving to all participated countries and eventually be beneficial to mankind as a whole. Encouraged by these factors, ASEAN＋3 Satellite Image Archive for Environmental Study project was submitted by Thailand in the 3rd Senior Official Meeting between ASEAN, China, Japan and Korea (SEOM＋3 Meeting) and approved by the SEOM＋3. The main objectives of this project are to share satellite images, information related to natural resources and environmental issues, and to provide data information services to all ASEAN＋3 countries. The proposed system is basically embedded by distributed system. The network of data users, data providers, and the center will be established using the Internet. User can access, navigate, display, and even download some archived contents. Its service site can be generally categorized into two parts, which are environmental related data archive and the Integrated satellite image catalogue. The extension of web based GIS is also planned for future development so that GIS users can conduct some preliminary analysis directly on line. This presentation will indicate scope of work, system, working scenario, and work plan of the project.

• Parasites, Hosts and Diseases
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• v.38 no.3
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• pp.119-138
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• 2000

Korean vivax malaria had been prevalent for longtime throughout the country with low endemicity. As a result of the Korean war (1950-1953), malaria became epidemic. In 1959-1969 when the National Malaria Eradication Service (NMES) was implemented, malaria rates declined, with low endemicity in the south-west and south plain areas and high endemic foci in north Kyongsangbuk-do (province) and north and east Kyonggi-do. NMES activities greatly contributed in accelerating the control and later eradication of malaria. The Republic of Korea (South Korea) was designated malaria free in 1979. However, malaria re-emerged in 1993 and an outbreak occurred in north Kyonggi-do and north-west Kangwon-do (in and/or near the Demilitarized Zone, DMZ) , bordering North Korea. It has been postulated that most of the malaria cases resulted from bites of sporozoite-infected females of An. sinensis dispersed from North Korea across the DMZ. Judging from epidemiological and socio-ecological factors, vivax malaria would not be possible to be endemic in South Korea. Historical data show that vivax malaria in Korea is a typical unstable malaria. Epidemics may occur when environmental, socio-economical, and/or political factors change in favor to malaria transmission, and when such factors change to normal conditions malaria rates become low and may disappear. Passive case detection is a most feasible and recommendable control measure against the unstable vivax malaria in Korea in cost-effect point of view.

• Geomechanics and Engineering
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• v.11 no.6
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• pp.805-820
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• 2016

A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is verified against the Ghosh and Madabhushi high acceleration field test database. The outputs of this work are aimed to improve the current computer-aided seismic foundation design that relies on ground's packing state and consistency. The results confirm that on seismic excitation of shallow foundations, the likelihood of effective stress loss is greater in deeper depths and across free field. For the benchmark problem, adopting a shallow foundation system instead of piled foundation benefitted in a 75% less emission rate, a marked proportion of which is owed to reduced materials and haulage carbon cost.

• East Asian Economic Review
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• v.23 no.1
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• pp.27-53
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• 2019

I employ search-and-matching to a multi-country and multi-sector Ricardian model with input-output linkages, trade in intermediate goods, and sectoral heterogeneity, in order to quantify the welfare effects from tariff changes. The paper shows that labor market frictions can be a source of comparative advantage in the sense that better labor market conditions contribute to lower cost in production. Labor market frictions play a critical role in determining the probability of exporting goods to trading partners, and interact with bilateral trade share, price, expenditures, etc. Unemployment and changes in unemployment rates due to tariff reductions contribute welfare changes across countries, implying that welfare effects based on quantitative trade models with full-employment are likely to be biased. I confirm the biased welfare effects by revisiting Caliendo and Parro (2015), who conduct an analysis of the welfare effects from the NAFTA from 1993 to 2005. I show that the welfare gap between theirs and mine has a positive correlation with changes in observed unemployment rates across countries. With the constructed model, I further conduct counterfactual exercises by asking what would happen if China's tariffs remain unchanged from 2006 to 2015. It turns out that there are mild welfare effects to trading partners in the world trading system.

• Journal of Home Health Care Nursing
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• v.28 no.2
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• pp.111-123
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• 2021

Purpose: This study aimed to present the management strategies necessary to improve the operational efficiency of visiting nurse centers and evaluate their effectiveness. Methods: The subjects of this study were visiting nurse centers registered as long-term care centers. Based on value chain analysis, cost information analysis, and data envelope analysis, the study was carried out according to the Magerison's management consulting procedure, for six months. This procedure comprised eight sub-steps of approach and application. Results: The following management strategies were agreed upon: establishment of a cooperative network with other visiting care centers, creation of high satisfaction of external customers by providing practical training to care workers, and making rehabilitation and exercise services as the core nursing activities to be focused on. Conclusion: The management consulting process and analysis method applied in this study can referred to as a useful methodological framework for revitalizing visiting nursing centers in the future.

• Fisheries and Aquatic Sciences
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• v.24 no.4
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• pp.139-152
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• 2021

The main purpose of this study is to fit catch-per-unit-effort (CPUE) data about Korea chub mackerel (Scomber japonicus) stock with a state-space production (SSP) model, and to provide stock assessment results. We chose a surplus production model for the chub mackerel data, namely annual yield and CPUE. Then we employed a state-space layer for a production model to consider two sources of variability arising from unmodelled factors (process error) and noise in the data (observation error). We implemented the model via script software ADMB-RE because it reduces the computational cost of high-dimensional integration and provides Markov Chain Monte Carlo sampling, which is required for Bayesian approaches. To stabilize the numerical optimization, we considered prior distributions for model parameters. Applying the SSP model to data collected from commercial fisheries from 1999 to 2017, we estimated model parameters and management references, as well as uncertainties for the estimates. We also applied various production models and showed parameter estimates and goodness of fit statistics to compare the model performance. This study presents two significant findings. First, we concluded that the stock has been overexploited in terms of harvest rate from 1999 to 2017. Second, we suggest a SSP model for the smallest goodness of fit statistics among several production models, especially for fitting CPUE data with fluctuations.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.293-305
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• 2023

To ensure the safety of underground infrastructures, ground can sometimes be first treated by cement slurry and then stabilized using artificial ground freezing (AGF) technique before excavation. The hydration heat produced by cement slurry increases the soil temperature before freezing and results in an extension of the active freezing time (AFT), especially when the Metro Jet System (MJS) treatment is adopted due to a high cement-soil ratio. In this paper, by taking advantage of an on-going project, a case study was performed to evaluate the influence of MJS and AGF on the ground temperature variation through on-site measurement and numerical simulation. Both on-site measurement and simulation results reveal that MJS resulted in a significant increase in the soil temperature after treatment. The ground temperature gradually decreases and then stabilized after completion of MJS. The initiation of AGF resulted in a quick decrease in ground temperature. The ground temperature then slowly decreased and stabilized at later freezing. A slight difference in ground temperature exists between the on-site measurements and simulation results due to limitations of numerical simulation. For the AGF system, numerical simulation is still strongly recommended because it is proven to be cost-effective for predicting the ground temperature variation with reasonable accuracy.