• Journal of Powder Materials
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• v.25 no.6
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• pp.475-481
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• 2018

Selective laser melting (SLM), a type of additive manufacturing (AM) technology, leads a global manufacturing trend by enabling the design of geometrically complex products with topology optimization for optimized performance. Using this method, three-dimensional (3D) computer-aided design (CAD) data components can be built up directly in a layer-by-layer fashion using a high-energy laser beam for the selective melting and rapid solidification of thin layers of metallic powders. Although there are considerable expectations that this novel process will overcome many traditional manufacturing process limits, some issues still exist in applying the SLM process to diverse metallic materials, particularly regarding the formation of porosity. This is a major processing-induced phenomenon, and frequently observed in almost all SLM-processed metallic components. In this study, we investigate the mechanical anisotropy of SLM-produced 316L stainless steel based on microstructural factors and highly-oriented porosity. Tensile tests are performed to investigate the microstructure and porosity effects on mechanical anisotropy in terms of both strength and ductility.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.255-261
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• 2005

Recently, the RF inductive discharge or inductively coupled plasma continues to attract growing attention as an effective plasma source in many industrial applications, the best known of which are plasma processing and lighting technology. To the point of lighting sources, the ring-shaped electrodeless fluorescent lamps utilizing an inductively coupled plasma have been objects of interest and research during the last decades, mainly because of their potential for extremely long life, high lamp efficacies, rapid power switching response. In this paper, maxwell 3D finite element analysis program (Ansoft) was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 250 kHz and some specific conditions. The electromagnetic field in the ferrite core was shown to be high and symmetric. An LS-100 luminance meter and a Darsa-2000 spectrum analyzer were used in the experiment. According to data on the lamp tested using high magnetic field ferrite, the optical and thermal wave fields were shown to be high around the ring-shaped electrodeless fluorescent lamp. The optical or light field was high at the center of the bulb rather than around the ferrite core. The light conditions of the bulb were assumed to be complex, depending on the condition of the filler gas, the volume of the bulb, and the frequency of the inverter. Our results have shown coupling between the gas plasma and the field of the light emitted to be nonlinear.

• Journal of the Economic Geographical Society of Korea
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• v.3 no.2
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• pp.5-22
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• 2000

Manufacturing industry in Chonbuk region has experienced relatively consistent increase during period 1975-1999. The importance of labor-intensive sectors such as textiles and clothing, wood and furniture, and food and drink, which had been traditionally major sectors in this region, has declined over the same period. On the other hand, the shares of more complex sectors like automobile, chemistry, communication equipment, and other machinery have gone up. The structural change of Chonbuk manufacturing industry, with increasing diversity, follows the national trend of industrial development, based on national industrial policies. but the speed and level of the change has been slow and low in terms of the national standard of manufacturing development, especially with the weak development of high technology industry. In Chonbuk, the spatial distribution of manufacturing industry has shown a high degree of concentration. Although spatial concentration is apparent in the central area including the cities of Chonju, Iksan, and Kunsan, new tendency towards industrial decentralization within this area has been found. The tendency means manufacturing development at the fringe of this area. There is another tendency towards industrial dispersion into the cities of Kimje and Jeongup close to this central area. The spatial dispersion of manufacturing industry has been accelerated in the form of increasing external investment. But despite the tendency of the spatial dispersion, the development of manufacturing industry in the rest of the region still remains a marked inferiority.

• Polymer(Korea)
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• v.33 no.6
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• pp.525-529
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• 2009

In order to manufacture 2-layer flexible copper clad laminate (FCCL) s having the excellent performance high adhesion properties between copper foil and polyimide film are required. Silane coupling agents with specific functional groups as an adhesion promoter are generally used to enhance the adhesion. In our study, we synthesized a novel silane coupling agent for increasing the adhesive property between copper layer and polyimide layer. The surface morphology of rolled copper foil, as a function of the concentrations of the coated silane coupling agent, was fully characterized. As fabricated 2-layer FCCL, we observed that adhesive properties were changed by the surface morphology and we confirmed that the novel silane coupling agent affects adhesive properties in FCCL with two types of poly (amic acid)s.

• Journal of Microbiology and Biotechnology
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• v.32 no.6
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• pp.749-760
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• 2022

α-Galactosidase is a debranching enzyme widely used in the food, feed, paper, and pharmaceuticals industries and plays an important role in hemicellulose degradation. Here, T26, an aerobic bacterial strain with thermostable α-galactosidase activity, was isolated from laboratory-preserved lignocellulolytic microbial consortium TMC7, and identified as Parageobacillus thermoglucosidasius. The α-galactosidase, called T26GAL and derived from the T26 culture supernatant, exhibited a maximum enzyme activity of 0.4976 IU/ml when cultured at 60℃ and 180 rpm for 2 days. Bioinformatics analysis revealed that the α-galactosidase T26GAL belongs to the GH36 family. Subsequently, the pET-26 vector was used for the heterologous expression of the T26 α-galactosidase gene in Escherichia coli BL21 (DE3). The optimum pH for α-galactosidase T26GAL was determined to be 8.0, while the optimum temperature was 60℃. In addition, T26GAL demonstrated a remarkable thermostability with more than 93% enzyme activity, even at a high temperature of 90℃. Furthermore, Ca²⁺ and Mg²⁺ promoted the activity of T26GAL while Zn²⁺ and Cu²⁺ inhibited it. The substrate specificity studies revealed that T26GAL efficiently degraded raffinose, stachyose, and guar gum, but not locust bean gum. This study thus facilitated the discovery of an effective heat-resistant α-galactosidase with potent industrial application. Meanwhile, as part of our research on lignocellulose degradation by a microbial consortium, the present work provides an important basis for encouraging further investigation into this enzyme complex.

• Journal of Environmental Science International
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• v.17 no.7
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• pp.743-753
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• 2008

Gwangyang Bay is often severely confronted by photochemical pollutants due to its location and dense emissions. It is located in a basin on the south coast of the Korean peninsula and is crossed by a remarkable cluster of hills and mountains of a small horizontal scale that forms a channel. Clearly, the air flow field has a great influence on the dispersion of air pollutants. The characteristics of the wind flow patterns have an important effect on the dispersion of pollutants emitted. In these situations, the distribution of the ozone concentration is extremely complicated because of the superposition of circulations of the air flow fields, especially in complex coastal region. In this study, we examined the distribution of the high level ozone on Gwangyang Bay particularly during the episode day (for 5 years). Among these days, A high level ozone was induced by the development of a sea/land breeze local circulation system, as well as by an anabatic/catabatic flow from the mountains and valley with weakening of the synoptic wind. High level ozone distribution pattern(6 types) on Gwangyang bay is analyzed and the comparison of each pattern reveals substantial localized differences in intensity and distribution of ozone concentration from the site coherence and UPA analysis of ozone concentration. The observed VOC concentration had much difference in concentrations and daily variations between Jungdong and Samil.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.653-659
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• 2018

High-rise buildings and complex facilities are a representative urban system for the masses, and it requires an increasing role of commodity and safety. Smoke and toxic gasses can cause accidents due to fire in these systems. The purpose of this study is to develop a fiber screen material for emergency evacuation passages that can be avoided quickly and safely in cases of disasters. The fiber screen material is applicable to folding devices for emergency evacuation passages. The material is different from general steel material in that it is lightweight with less burden during storage for a long time in a roll form in a folding device. It also has an excellent secondary function in that it is less affected by radiant heat. Three kinds of fiber screen materials were selected that have good flame retardancy and post-processing characteristics. A performance evaluation was performed by a heat shrinkage test, contact heat test, combustibility test, flame retardancy test, tensile strength test, and tear strength test. As a result, the lightweight fabric shows excellent performance through post-processing, and silicone resin coating can secure safety of the pizza by the fiber screen material performance and radiant heat. The optimum post-treatment conditions were evaluated by performing a burning test after coating two kinds of glass fibers and four types of flame-retardant silicone resins with different weight and thickness.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.1
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• pp.18-27
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• 2020

Objectives: For testing asbestos stabilizer products which are used for the maintenance and management of asbestos-containing materials, durability assessment should accompany the evaluation of basic properties and performance. Therefore, in this study we designed a testing method and constructed a database of durability performance, thereby providing basic data for reliability studies of asbestos stabilizer. Methods: Since the ceiling materials targeted in this study are interior materials, test conditions of 95% relative humidity and 60℃ temperature were designed in consideration of the effect of high relative humidity in summer and seasonal indoor temperatures. Plate-shaped specimens treated with asbestos stabilizers were maintained in a thermo-hygrostat for 5, 10, and 20 days, and then the asbestos scattering prevention rate was measured by air erosion testing. Results: The scattering concentration tended to increase with time under the single humidity condition, and exceeded the indoor air quality standard of 0.01 f/cc, during the 20 days of maintenance. On the other hand, there was little change according to the temperature condition. In the case of a complex condition with temperature and humidity, the results were similar to the humidity test, but the scattering concentration increased more sharply at 20 days. Conclusions: The main deterioration factor that affects the durability of asbestos stabilizer is humidity, and the deterioration is caused by a mechanism in which the stabilizer coated on the surface is re-dissolved by moisture and evaporates or the coating layer is peeled off, which is accelerated by high temperatures.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.199-201
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• 2021

The Internet of Things (IoT) is a technology that can organically connect people and things without time and space constraints by using communication network technology and sensors, and transmit and receive data in real time. The IoT used in all industrial fields has limitations in terms of storage allocation, such as device size, memory capacity, and data transmission performance, so it is important to manage power consumption to effectively utilize the limited battery capacity. In the prior research, there is a problem in that security is deteriorated instead of improving power efficiency by lightening the security algorithm of the encryption module. In this study, we proposes a low-power security architecture that can utilize high-performance security algorithms in the IoT environment. This can provide high security and power efficiency by using relatively complex security modules in low-power environments by executing security modules only when threat detection is required based on inspection results.

• Korean Journal of Ecology and Environment
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• v.53 no.1
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• pp.91-101
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• 2020

Stormwater runoff is known as a major non-point water pollution source that transports heavy metals, which have accumulated in road surface, to stream and coastal area. Dissolved and particulate metals in stormwater runoffs have been investigated to understand the outflow characteristics of heavy metals during rainfall events and to identify their pollution sources. The concentration of dissolved Co and Ni decreased after the outflow with high concentrations at the beginning of the rainfall, and other metals showed different characteristics depending on the rainfall and rate of discharge. Particulate metals showed a similar trend with the temporal variation of suspended solids concentration in stormwater runoffs. The results of geo-accumulation index (I_geo) indicated that the stormwater runoffs from industrial region were very highly polluted with Cu, Zn and Cd. As a result of comparing the metal concentrations of <125 ㎛ for road dust near the study area, Cu, Zn and Cd were originated from inside of metal manufacturing facilities rather than traffic activities at road surface and these metals accumulated on the surface area of facilities were transported to the water environments during stormwater event. The average discharged amounts of heavy metals for one rainfall event were Cr 128 g, Co 12.35 g, Ni 98.5 g, Cu 607.5 g, Zn 8,429.5 g, As 6.95 g, Cd 3.7 g, Pb 251.75 g, indicating that metal runoff loads in the stormwater runoffs are closely related to surrounding industry types.