• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.115-120
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• 2012

Different colloidal particles generally co-exist in the water and wastewater. Thus, there needs to identify practical electrokinetic characteristics of the particles, comparing with the case when each colloidal material is independently distributed. In this study, changes of overall zeta potential was examined through mixed dispersions of $TiO_{2}$ and $MnO_{2}$. The mixing ratios were classified into 3-type in order to distinguish the effects of the proportions of each particle from those of total concentration in colloidal suspensions. The types are single colloidal dispersions of $TiO_{2}$ and $MnO_{2}$ (1:0, 0:1), mixed dispersions at different ratios (0.75:0.25, 0.5:0.5, 0.25:0.75), and a mixed dispersion with doubled concentration (1:1), respectively. It showed that the overall variation of zeta potential as a function of pH was intensified in a colloidal dispersion with the ratio of 1:1. It was concerned that the double action of ion would contribute to this result. On the one hand, the zeta potentials of each colloidal dispersion commonly decreased at the state of strong acid and base under the influence of compression of the electric double layer. The changing patterns were also considered through calculating total interaction energy between colloidal particles based on DLVO theory and measuring turbidity of the colloidal dispersions.

• Atmosphere
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• v.26 no.3
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• pp.373-386
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• 2016

The future variability of Wind Energy Density (WED) over the Korean Peninsula under RCP climate change scenario is projected using ensemble analysis. As for the projection of the future WED, changes between the historical period (1981~2005) and the future projection (2021~2050) are examined by analyzing annual and seasonal mean, and Coefficient of Variation (CV) of WED. The annual mean of WED in the future is expected to decrease compared to the past ones in RCP 4.5 and RCP 8.5 respectively. However, the CV is expected to increase in RCP 8.5. WEDs in spring and summer are expected to increase in both scenarios RCP 4.5 and RCP 8.5. In particular, it is predicted that the variation of CV for WED in winter is larger than other seasons. The time series of WED for three major wind farms in Korea exhibit a decrease trend over the future period (2021~2050) in Gochang for autumn, in Daegwanryeong for spring, and in Jeju for autumn. Through analyses of the relationship between changes in wind energy and pressure gradients, the fact that changes in pressure gradients would affect changes in WED is identified. Our results can be used as a background data for devising a plan to develop and operate wind farm over the Korean Peninsula.

• Journal of Soil and Groundwater Environment
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• v.21 no.3
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• pp.64-81
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• 2016

To analyze the influence of various groundwater flow rates (specific discharge) on BHE system with balanced and unbalanced energy loads under assuming same initial temperature (15℃) of ground and groundwater, numerical modeling using FEFLOW was used for this study. When groundwater flow is increased from 1 × 10⁻⁷ to 4 × 10⁻⁷m/s under balanced energy load, the performance of BHE system is improved about 26.7% in summer and 22.7% at winter time in a single BHE case as well as about 12.0~18.6% in summer and 7.6~8.7% in winter time depending on the number of boreholes in the grid, their array type, and bore hole separation in multiple BHE system case. In other words, the performance of BHE system is improved due to lower avT in summer and higher avT in winter time when groundwater flow becomes larger. On the contrary it is decreased owing to higher avT in summer and lower avT in winter time when the numbers of BHEs in an array are increased, Geothermal plume created at down-gradient area by groundwater flow is relatively small in balanced load condition while quite large in unbalanced load condition. Groundwater flow enhances in general the thermal efficiency by transferring heat away from the BHEs. Therefore it is highly required to obtain and to use adequate informations on hydrogeologic characterristics (K, S, hydraulic gradient, seasonal variation of groundwater temperature and water level) along with integrating groundwater flow and also hydrogeothermal properties (thermal conductivity, seasonal variation of ground temperatures etc.) of the relevant area for achieving the optimal design of BHE system.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.40 no.3
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• pp.127-136
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• 2003

In this paper, we propose a robust object tracking algorithm based on model and edge, using deformed template and Level-Set theory. The proposed algorithm can track objects in case of background variation, object flexibility and occlusions. First we design a new potential difference energy function(PDEF) composed of two terms including inter-region distance and edge values. This function is utilized to estimate and refine the object shape. The first step is to approximately estimate the shape and location of template object based on the assumption that the object changes its shape according to the affine transform. The second step is a refinement of the object shape to fit into the real object accurately, by using the potential energy map and the modified Level-Set speed function. The experimental results show that the proposed algorithm can track non-rigid objects under various environments, such as largely flexible objects, objects with large variation in the backgrounds, and occluded objects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.93-93
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• 2003

Photoluminescence(PL) properties of Silicon nanocrystals (nc-Si) as a function of temperature is reported to consider the mechanism of PL. Nc-Si has been made by $Si^+$ ion-implantation into thermal $SiO_2$ and subsequent annealing. And after gold had been diffused at the same samples above, the resultant PL spectra has been compared to the PL spectra from the non-gold doped nc-Si. PL peak energy variation from nc-Si is same with the variation of energy bandgap of bulk silicon as temperature changes from 6 K to room temperature. This result may mean nc-Si is still indirect transition material like bulk silicon. Gold doped nc-Si reveals short peak wavelength of PL spectrum than gold undoped one. PL peak shift through gold doing process shows clearly the PL mechanism is not from defect or interface states. PL intensity increases from 6K to a certain temperature and then decrease to room temperature. This characteristic with temperature shows that phonon have a role for the luminescence as theory explains that electron and hole can be recombined radiatively by phonon's assist in nc-Si, which is almost impossible in bulk silicon. Therefore luminescence is observed in nc-Si constructed less than a few of unit cell and the peak energy of luminescence can be higher than the bulk bandgap energy by the bandgap widening effect occurs in nanostructure.

• Corrosion Science and Technology
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• v.6 no.5
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• pp.233-238
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• 2007

Due to the occasional occurrence of a localizedcorrosion such as a SCC and pitting in steam generator tubing(Alloy 600), leading to a significant economical loss, an effective repair technology is needed. For a successful electrodeposition inside a tube, many processes should be developed. Among these processes, an anode to be installed inside a tube, a degreasing condition to remove any dirt and grease, an activation condition for a surface oxide elimination, a strike layer forming condition which needs to be adhered tightly between an electroforming layer and a parent tube and a condition for an electroforming layer should be established. Through a combination of these various process condition parameters, the desired material properties can be acquired. Among these process parameters, various material properties including a mechanical property and its variation along with the height of the electrodeposit inside a tube as well as its thermal stability and SCC resistance should be assessed for an application in a plant. This work deals with the material properties of the Ni electrodeposits formed inside a tube by using the anode developed in this study such as the current efficiency, hardness, tensile property, thermal stability and SCC behavior of the electrodeposit in a 40wt% NaOH solution at $315^{\circ}C$. It was found that a variation of the material properties within the entire length of the electrodeposit was quite acceptable and the Ni electrodeposit showed an excellent SCC resistance.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.155-165
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• 2014

This study measured and compared the variation of ventilation rate and fan energy consumption according to various control strategies after installing wireless sensor-based pilot ventilation system in order to verify the applicability of demand-controlled ventilation (DCV) strategy that was efficient ventilation control strategy for underground parking lot. The underground parking lot pilot ventilation system controlled the ventilation rate by directly or indirectly tracking the traffic load in real-time after sensing data, using vehicle detection sensors and carbon monoxide (CO) and carbon dioxide ($CO_2$) sensor. The ventilation system has operated for 9 hours per a day. It responded real-time data every 10 minutes, providing ventilation rate in conformance with the input traffic load or contaminant level at that time. A ventilation rate of pilot ventilation system can be controlled at 8 levels. The reason is that a ventilation unit consists of 8 high-speed nozzle jet fans. This study proposed vehicle detection sensor based demand-controlled ventilation (VDS-DCV) strategy that would accurately trace direct traffic load and CO sensor based demand-controlled ventilation (CO-DCV) strategy that would indirectly estimate traffic load through the concentration of contaminants. In order to apply DCV strategy based on real-time traffic load, the minimum required ventilation rate per a single vehicle was applied. It was derived through the design ventilation rate and total parking capacity in the underground parking lot. This is because current ventilation standard established per unit floor area or unit volume of the space made it difficult to apply DCV strategy according to the real-time variation of traffic load. According to the results in this study, two DCV strategies in the underground parking lot are considered to be a good alternative approach that satisfies both energy saving and healthy indoor environment in comparison with the conventional control strategies.

• Journal of Magnetics
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• v.21 no.2
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• pp.266-272
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• 2016

Transcranial magnetic stimulation devices has been used mainly for diagnostic purposes by measuring the functions of the nervous system rather than for treatment purposes, and has a problem of considerable energy fluctuations per repeated pulse. The majority of strokes are caused by ischemia and result in brain tissue damage, leading to problems of the central nervous system including hemiparesis, dysfunction of language and consciousness, and dysfunction of perception. Control is difficult and the size is large due to the difficulty of digitalizing the energy stored in a capacitor, and there are many heavy devices. In addition, there are many constraints when it is used for a range of purposes such as head and neck diagnosis, treatment and rehabilitation of nerve palsy, muscle strengthening, treatment of urinary incontinence etc. Output stabilization and minimization of the energy variation rate are required as the level of the transcranial magnetic stimulation device is dramatically improved and the demand for therapeutic purposes increases. This study developed a compact, low cost transcranial magnetic stimulation device with minimal energy variation of a high repeated pulse and output stabilization using a real time capacitor charge discharge voltage. Ischemia was induced in male SD rats by closing off the common carotid artery for 5 minutes, after which the blood was re-perfused. In the cerebrum, the number of PARP reactive cells after 24 hours significantly decreased (p < 0.05) in the TMS group compared to the GI group. As a result, TMS showed the greatest effect on necrosis-related PARP immuno-reactive cells 24 hours after ischemia, indicating necrosis inhibition, blocking of neural cell death, and protection of neural cells.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.4
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• pp.54-63
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• 2010

When MBT(Mechanical Biological Treatment) facility is designed, the management system adequate for domestic circumstance in Korea has been insufficient and power plant's load on seasonal variation has not been resolved yet. Thus, this study introduced MBT facility and MSW(Municipal Solid Waste)'s seasonal emission characteristics were investigated in order to establish new MBT management system. and additional thermal buffer-materials's calorific values were also considered to reduce the power plant's load. The results showed that the screening efficiency of MBT facility and the physical characteristics of each waste can be identified, and the calorific value by seasonal variation for MBT facility can be kept constant all the year round by using an additional thermal buffer-materials.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.11
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• pp.13-22
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• 2018

At the time when zero energy building is expected to be generalized, this study examines whether the investment in the passive element or the active element is more effective in terms of energy in the construction process of zero energy building. In other words, the effect of energy demand by passive element and the change of energy generation by active element are examined in terms of the same investment cost. The purpose of this study is to examine the change of energy demand by passive element and the change of energy generation by active element in zero energy building and to make reasonable investment decision by comparing energy with cost aspect. For this purpose, we selected the buildings to be subjected to energy simulation and derive the required energy amount and energy generation amount by using meteorological data of four regions in Korea. The change of energy demand and energy generation according to the change of application condition was derived. In order to compare and analyze the changes in energy demand and generation at the same cost standard through price survey and quotation of window and photovoltaic power generation equipment.