• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.4
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• pp.411-420
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• 2016

Efforts have continued in recent years to research and develop new alternative energy sources to replace coal and oil. These days interest is exploding in new pollution-free renewable energy due to the rising prices of finite energy sources. In the field of solar energy, one of new renewable energy that has been actively researched and commercialized, research efforts have been focused on solar light energy, whose efficiency has, however, reached a saturation point already. Thus, this paper proposed a solar tracking-type parabolic heat collection device to utilize solar thermal energy rather than solar light energy. The proposed device was designed in a parabolic form to collect solar heat effectively. The investigator made its prototype by incorporating a five-axis censor-based solar tracking technology in it to sense changes to the location of the sun according to the seasons and periods. In addition, an administrator interface was designed and implemented for the efficient management of heat collection device.

• Journal of Power Electronics
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• v.14 no.2
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• pp.271-281
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• 2014

Fluctuating wind conditions necessitate the use of a variable speed wind turbine (VSWT) with a AC/DC/AC converter scheme in order to harvest the maximum power from the wind and to decouple the synchronous generator voltage and frequency from the grid voltage and frequency. In this paper, a combination of a three phase diode bridge rectifier (DBR) and a modified topology of the diode clamped multilevel inverter (DCMLI) has been considered as an AC/DC/AC converter. A control strategy has been proposed for the DCMLI to achieve the objective of grid interface of a wind power system together with local load compensation. A novel fixed frequency current control method is proposed for the DCMLI based on the level shifted multi carrier PWM for achieving the required control objectives with equal and uniform switching frequency operation for better control and thermal management with the modified DCMLI. The condition of the controller gain is derived to ensure the operation of the DCMLI at the fixed frequency of the carrier. The converter current injected into the distribution grid is controlled in accordance with the wind power availability. In addition, load compensation is performed as an added facility in order to free the source currents being fed from the grid of harmonic distortion, unbalance and a low power factor even though the load may be unbalanced, non-linear and of a poor power factor. The results are validated using PSCAD/EMTDC simulation studies.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.4
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• pp.468-476
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• 2006

Hazardous air pollutants (HAPs) have high toxicity and bioaccurnulation potentials into human body even inbsmall amount (levels of ng/$m^3$). As the levels of HAPs might be controversial, it has been become essential to establish the analysis method for correct results. In this study, various analysis methods of VOCs and Aldehydes were compared in order to select the proper methods in our condition. Sampling and analysis method of VOCs were followed to EPA TO-14a and TO-17. VOCs were collected in absorption tube and separated by thermal desorption unit then analyzed by GC/MSD. Aldehydes were sampled in DNPH-cartridge and extracted into solution then analyzed by HPLC as the same condition of EPA TO-13a. This study also shows the results of QA/QC system of selected methods. Some experiments could be improving the data assurance blank test, calibration check, repetition precision check, the determination of detection limit and reproducibility of the retention time. Precisions of VOCs and aldehydes were ranged in 2$\sim$9% and 1$\sim$4% RSD, respectively. Recovery rate of VOCs showed variable ranges from 60 to 133.5%. MDL of VOCs and aldehydes were 0.044$\sim$0.284 ppb and 0.14$\sim$1.02 ng, respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.360-368
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• 2017

This paper proposes the 80-kW high-efficiency bidirectional hybrid SiC boost/buck converter using droop control for DC nano-grid. The proposed converter consists of four 20-kW modules to achieve fault tolerance, ease of thermal management, and reduced component stress. Each module is constructed as a cascaded structure of the two basic bi-directional converters, namely, interleaved boost and buck converters. A six-pack hybrid SiC intelligent power module (IPM) suitable for the proposed cascaded structure is adopted for high-efficiency and compactness. The proposed converter with hybrid switching method reduces the switching loss by minimizing switching of insulated gate bipolar transistor (IGBT). Each module control achieves smooth transfer from buck to boost operation and vice versa, since current controller switchover is not necessary. Furthermore, the proposed parallel control using DC droop with secondary control, enhances the current sharing accuracy while well regulating the DC bus voltage. A 20-kW prototype of the proposed converter has been developed and verified with experiments and indicates a 99.3% maximum efficiency and 98.8% rated efficiency.

• Journal of Biomedical Engineering Research
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• v.25 no.1
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• pp.5-10
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• 2004

Body movement is one of the important factors in sleep analysis. In this study, a thermopile detector with four channels was implemented as a non-contacting detector of body movement in sleep. Using a thermopile mathematical model and several frames of thermal images, the possibility of detecting body movement was evaluated. Instant body movement signals were evaluated for the upper, lower, and entire body using the Haar wavelet. This decomposition shows the points in time when the upper-body or lower-body movement occurred and the level of body movement. Additionally, partial body movement was decomposed in head-only, whole body, and leg-only movement using the ANFIS algorithm. Finally, three subject's data were evaluated for 60 minutes, and the detection rates of instant and partial body movement, on average, were 96.3％ and 89.2％, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.3
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• pp.193-200
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• 2010

Anode off-gas of high temperature fuel cell still contains combustible components such as hydrogen, carbon monoxide and hydrocarbon. In this study, a catalytic combustor has been applied to the high temperature fuel cell so that the combustion of anode-off gas can be boosted up. Since the performance of catalytic combustor directly depends on the combustion catalyst, this study is designed to perform the experimental investigation on the combustion characteristics of the three commercial catalysts with a different composition. Screening tests with three catalysts are preceded before the performance examination since it is necessary to determine the most suitable catalyst for design configuration of the catalytic combustor. The performance analysis shows that methane conversion rate strongly depends on gas hourly space velocity (GHSV) as well as inlet gas temperature. Additionally, the GSHV optimization results show that the optimum GHSV will be in the range between 18,000 $hr^{-1}$ and 36,000 $hr^{-1}$. It is also shown that the minimum inlet temperature of catalytic reaction of methane is from $100^{\circ}C$ to $150^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.1-7
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• 2017

This study numerically evaluates the heat transfer characteristics of a 360-Wh Li-ion battery pack. The analysis was done in ANSYS CFX using different cell arrangements, cell holders, and case materials for a personal mobility device program. A total of four cases of cell arrangements were considered, along with various materials for both the cell holder and the case, such as polypropylene, aluminum, and magnesium alloy. Out of the four cell arrangements, model 2 showed the best heat transfer performance, while aluminum showed the best heat transfer performance for the cell holder and case.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.1
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• pp.173-178
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• 2020

In this study, we analyzed space heating and domestic hot water(DHW) charges from 2017 to 2018 for 151,206 households in 202 apartment complexes built from 1997 to 2016, in order to evaluate the effectiveness of Korea's insulation standards reinforcement. The applied insulation standards were revised three times(in 1987, 2001 and 2010). We used the Anderson-Darling test to review the normality of the space heating and DHW charges. As a result, each p-value was greater than 0.05 and it followed the normal distribution. The annual average space heating charges per unit area of apartments with the 1987 insulation standards were 5,237￦/㎡a in 2017 and 5,328￦/㎡a in 2018. The heating charges with the 2001 standards were 4,827￦/㎡a in 2017 and 4,817￦/㎡a in 2018. Compared to previous standards(1987 standards), heating charges decreased by 7.8% and 9.6%. Also the heating charges with the 2010 standards were 3,683￦/㎡a in 2017 and 3,734￦/㎡a in 2018. Compared to previous standards(2001 standards), heating charges decreased by 24.3% and 21.5%. On the other hand, compared to each previous standards, DHW charges were decreased by 12.2%, 13.6% or increased by 4.6%, 6.9%, which means there's no correlation between insulation standards reinforcement and DHW charges.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.168-175
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• 1997

In greenhouse, data on evapotranspiration or water consumption is important for the rational water management, irrigation planning, thermal environment analysis, and watering automation. But little investigations have been attempted to make clear the characteristics of water consumption in greenhouse. In this paper, evapotransplrations of lettuce and cucumber by cropping systems were investigated. And the correlations among evapotranspiration, pan evaporation, solar radiation, mean air temperature, and minimum relative humidity were analyzed. Experimental cropping systems of lettuce were soil culture and NFT system. Those of cucumber were soil culture, perlite culture, and rockwool culture. Total water consumption of lettuce was 2.62$\ell$/plant in soil culture and 1.71$\ell$/plant in NFT system. That of cucumber was 45.22$\ell$/plant in soil culture, 27.45$\ell$/plant in rockwool culture and 29.06$\ell$/plant in perlite culture. Therefore total water consumption of soil culture showed higher than soilless culture.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.3
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• pp.227-235
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• 2016

This paper emphasized the necessity of the marine spatial planning (MSP) through the analysis of the major developmental projects which could make a contradiction based on the adequacy of the site selection and environmental impacts. The conflicting affairs between space utilization and management plan happen in the following ways: marine renewable energy development, sand mining, reclamation, construction of golf course in coastal area, thermal effluent and waste heat, erosion causing port development. The conflict of stakeholder continues caused by the accumulated environmental impact. For the reasons mentioned above, we found two things. First, it is necessary to comprehend the fact of developmental planning and MSP. Second, it is still unsatisfactory to connect the relevance of laws related to the spatial planning. For the reinforcement of marine environmental policy management, it is necessary to consolidate the property of site selection and assessment of developmental scale. Especially, while the strategic environmental assessment is in progress based on site selection and property of scale, consistent diagnosis is needed in the following concerns: the fact of the marine spatial planning, the relevance between national developmental plan and regional developmental plan, fisheries regulation, marine protected animals. For the environmentally sound and sustainable development (ESSD), MSP should have to be prepared based in a way of top-down including coastal and EEZ plan, relevance of ocean-use zoning and sector planning, 3-D spatial information. And also integrated information system have to be prepared through high-tech marine spatial information. In conclusion, consistent and relevant strategy for MSP should have to include the whole information related to the maritime affairs such as harbor, fishing port, fishing ground, coastal management, marine ecosystem generally.