• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.2
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• pp.30-47
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• 2022

This study analyzed the characteristics of cold air flow according to spatial types in urban areas of Changwon-si, Gyeongsangnam-do. The spatial types were classified by cluster analysis considering the land use map, building information, and topographic characteristics produced on the Changwon biotope map. The amount of cold air and wind speed were derived by KLAM_21 modeling. As a result, spatial types were classified into a total of 14 types considering the density and height of buildings, land use types, and topographic characteristics. Cold air flow was found to generate cold air in the valley of the forest area outside urban area, move through roads and open spaces, and accumulate in the low-lying national industrial complex, and then spread cold air throughout the urban areas. There was a lot of cold air flow in the tall building area, and the cold air accumulation was less in the slope and ridge areas. The results of this study were able to understand the characteristics of cold air flow according to building density, land use type, and topography, which will be usefully used as basic data for urban wind road construction to mitigate climate and improve air quality in urban areas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.323-326
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• 2000

In this study, we used Brewster-Angle Microscope(BAM) to study on the molecular orientation of monolayer on the water surface. The behaviors of molecules on three different subphase have been observed. Reproducible $\pi$-A isotherm have been obtained only on information about phase transition by molecular area. BAM facilitates the observation of morphology by optical anisotropy and thickness in monolayer and multilayers as BAM is shown to be sensitive to anisotropy of film. Every transition was found by BAM technique, either as a dramatic change in degree of contrast or as a sudden alteration of molecular action and $\pi$-A isotherm.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.81-83
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• 2001

This paper introduces the improved analysis method for PMDC (Permanent Magnet DC) motors. The effect of field yoke is considered by equivalent area. Overhang effect, caused by different axial length of magnet and armature, is analyzed by 3D EMCN(Equivalent Magnet Circuit Network) method. Then brush contact resistance and mechanical loss extracted by experimental data are used in characteristic analysis. The validity of the proposed method is verified by the comparison of analysis results and experimental ones.

• Journal of Environmental Science International
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• v.31 no.2
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• pp.149-169
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• 2022

Hwapocheon stream is located in Gimhae-si, Gyeongsangnam-do, and a part was declared a protected wetland area in 2017. In 2020 and 2021, we investigated the community structure of benthic macroinvertebrates of the Hwapocheon stream to provide ecological information for the management of the wetland. As a result, 4 phyla, 6 classes, 20 orders, 51 families, 83 species, and 2,621 individuals of benthic macroinvertebrates were identified. The average indices of diversity, richness, and evenness were the highest in the midstream area, whereas the highest average index of dominance was observed upstream. Seven biological water quality evaluations based on the distribution of benthic macroinvertebrates showed that the Biological Monitoring Working Party was an extremely suitable method for environmental evaluation of the Hwapocheon stream. Regarding functional feeding groups, the number of species of predators and gathering-collectors was the highest, and considering habitual dwelling groups, the number of species of clingers and sprawlers was the highest. The species number of Odonata, Hemiptera, and Coleoptera increased toward the downstream area, whereas the community loss index was the highest upstream. We also investigated relative resistance and resilience based on the distribution of aquatic insects and found that community stability was the highest downstream, whereas the lowest upstream.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.459-462
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• 2004

This study assesses groundwater vulnerability to contaminants in 12 administrative districts of the city of Changwon, using DRASTIC technique. DRASTIC was originally applied to situations in which the contamination sources are at the ground surface, and the contaminants flow into the groundwater with infiltration of rainfall. However, groundwater contamination in urban areas can also be related to excessive pumping resulting in a lowering of the water level. The correlation coefficient between minimum DRASTIC indices and the degree of poor water quality for 10 districts is low as 0.40. The correlation coefficients between minimum DRASTIC indices and the groundwater discharge rate, and between minimum DRASTIC indices and well density per unit area are 0.70 and 0.87, respectively. Thus, to evaluate the potential of groundwater contamination in urban areas, it is necessary to consider other factors such as groundwater withdrawal rate and well density per unit area with ratings and weights as well as the existing six DRASTIC factors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.183-186
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• 2004

Unipoled piezoelectric transformers were designed with different input and output area ratios. The voltage step-up ratio increased proportionally with increasing the input area. The piezoelectric transformers operated in each transformer's resonance vibration mode. In this paper, ANSYS(FEM program) was used for analysing piezoelectric transformers. We compared with analysis and experimental results. The voltage step-up ratio showed maximum value in output area of small size. Output characteristics of piezoelectric transformers with various size were simulated. The result of analysis showed 2~7 times higher voltage step-up ratio than a experiment result.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.813-816
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• 2004

Unipoled piezoelectric transformers were designed with different input and output area ratios. The voltage step-up ratio increased proportionally with increasing the input area. The piezoelectric transformers operated in each transformer's resonance vibration mode. In this paper, ANSYS(FEM program) was used for analysing piezoelectric transformers. We compared with analysis and experimental results. The voltage step-up ratio showed maximum value in output area of small size. Output characteristics of piezoelectric transformers with various size were simulated. The result of analysis showed $2\sim7$ times higher voltage step-up ratio than a experiment result.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.104-112
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• 2018

Considering the shape of a valve plate in design is important for reducing the pulsation phenomenon, which is a negative factor in pump performance. The purpose of this study is to propose an optimized method for a valve-plate V-type notch of a piston pump by modeling and simulation. The method uses $SimulationX^{(R)}$, a commercial hydraulic analysis program, and to provide data for the designing of the notch. The opening areas are determined by performing kinematic analysis of the notch part where the opening area changes rapidly. After applying the result analysis, the main effects on maximum pressure pulsation and maximum backflow according to the notch design factors are analyzed by using the full factorial method of experimental design. The optimized solutions are derived for the notch design variables, based on the analyzed data.

• Korean Journal of Materials Research
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• v.30 no.9
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• pp.447-452
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• 2020

In this work, α-Fe₂O₃ nanocrystals are synthesized by co-precipitation method and used as adsorbent to remove Cr⁶⁺, Cd²⁺, and Pb²⁺ from wastewater at room temperature. The prepared sample is evaluated by XRD, BET surface area, and FESEM for structural and morphological characteristics. XRD patterns confirm the formation of a pure hematite structure of average particle size of ~ 40 nm, which is further supported by the FESEM images of the nanocrystals. The nanocrystals are found to have BET specific surface area of ~ 39.18 m² g^-1. Adsorption experiments are carried out for the different values of pH of the solutions, contact time, and initial concentration of metal ions. High efficiency Cr⁶⁺, Cd²⁺, and Pb²⁺ removal occur at pH 3, 7, and 5.5, respectively. Equilibrium study reveals that the heavy metal ion adsorption of the α-Fe₂O₃ nanocrystals followed Langmuir and Freundlich isotherm models. The Cr⁶⁺, Cd²⁺, and Pb²⁺ adsorption equilibrium data are best fitted to the Langmuir model. The maximum adsorption capacities of α-Fe₂O₃ nanocrystals related to Cr⁶⁺, Cd²⁺, and Pb²⁺ are found to be 15.15, 11.63, and 20 mg g^-1, respectively. These results clearly suggest that the synthesized α-Fe₂O₃ nanocrystals can be considered as potential nano-adsorbents for future environmental and health related applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.84-87
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• 2010

We manufacture an antifuse OTP (One-time programmable) cell for analog trimming which will be used in power management ICs. For the antifuse cell using dual program voltage of VPP (=7V) and VNN (=-5V), the thin gate oxide is broken down by applying a voltage higher than the hard break-down voltage to the terminals of the antifuse. The area of the manufactured antifuse OTP cell using $0.18{\mu}m$ BCD process is $48.01{\mu}m^2$ and is about 44.6 percent of that of an eFuse cell. The post-program resistances of the antifuse are good with the values under several kilo ohms when we measure twenty test patterns.