• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.2
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• pp.75-83
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• 2013

Objectives: This study was conducted to estimate quartz concentrations in the airborne respirable dust from concrete manufacturing industries and to compare performance of two analytical methods, direct on filter(DOF) and the transfer methods in the Fourier Transform Infrared Spectroscopy(FTIR). Methods: Total 36 area samples were collected from 8 concrete manufacturing industries. Each respirable dust sample was collected by a 25 mm cassette attached to a 10 mm Dorr-Oliver nylon cyclone. The quartz content was estimated using the intensity of the absorption peak of quartz at $799cm^{-1}$ by FTIR. Results: By the comparison of quartz content in respirable dust between the two methods, the results of using DOF method were higher than that of transfer method. And the result of quartz concentrations in respirable dust estimated by DOF method were mostly higher than those by transfer method. Statistically significant difference of quartz concentrations in respirable dust were not found in shakeout, input, loading and transporting processes by two methods. But quartz concentrations in the molding process had the statistically significant difference between DOF and transfer method. Conclusions: The results of the study is suggested that, it be needed to correct the influence of the interferences in order to establish the DOF method when interfering minerals have an effect on quantitative analysis of quartz in respirable dust by the direct on filter method with FTIR.

• Journal of Biosystems Engineering
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• v.43 no.2
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• pp.128-137
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• 2018

Purpose: This study was designed to elucidate the energy-utilization patterns for five methods of robo production. Methods: Robo (fried melon cake) was produced using five different methods, and the energy used for each unit operation was calculated using standard equations. The sensory attributes of the products were determined by panelists. Data were analyzed using descriptive analysis and analysis of variance at p < 0.05. Results: The energy demands for processing 2.84 kg of melon seed into robo (fried melon cake) using processes 1 (traditional method), 2, 3, 4, and 5 (improved methods) were 50,599.5, 21,793.6, 20,379.7, 21,842.9, and 20,429.3 kJ, respectively. These are equivalent to energy intensities of 1,7816.7, 7,673.8, 7,175.9, 7,691.2, and 7,193.4 kJ/kg, respectively. For the traditional process, the frying operation consumed the highest energy (21,412.0 kJ), and the mixing operation consumed the lowest energy (675.0 kJ). For the semi-mechanized processes, the molding operation consumed the highest energy (6,120.0 kJ), and the dry milling consumed the lowest energy (14.4 kJ). Conclusions: The energy-consumption patterns were functions of the type of unit operation, the technology involved in the operations, and the size of the equipment used in the whole processing operation. Robo produced via the milling of dried melon seed before oil expression was rated highest with regard to the aroma and taste quality, as well as the overall acceptability of the sensory evaluation, and required the lowest energy consumption. Full mechanization of the process line has potential for further reduction of the energy demand.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.418-423
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• 2018

Recently, research and development of high-value leisure vessels has been carried out in Korea to revitalize the marine leisure industry and tap into the global maritime leisure market. FRP composite materials, which have excellent physical properties and are available for the manufacture of light hulls, are used widely. One of the most important design technologies is to secure structural safety of leisure vessels made from FRP composite materials. In this study, the structural strength was assessed for the design of an 8-meter high-speed planing leisure boat made from FRP composite materials. The design loads to verify the structural safety were calculated according to the rules for the classification of high speed light craft (KR, 2015), and structural analysis was conducted using a finite element model composed of an isotropic shell element, which has equivalent bending rigidity with the FRP sandwich panel. The analysis results were compared with the results of the strength test for fabricated specimens, and all internal structural components are sufficiently satisfied with the structural strength.

• Journal of Conservation Science
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• v.31 no.4
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• pp.489-497
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• 2015

Iron sickle is tool used in various ways and have various form. It has agricultural feature as well as is used in weapon. Previous studies have been focused on features of farming tools. In this study, metallurgical analysis of iron sickles are introduced because examples of analysis for iron sickles is rare. Two sickles form Yeongi Jangjae-ri are investigated and compared to one sickle of Yeongi Songwon-ri. Three sickles have forging molding process and heat treatment process. No.1 sickle of Jangjae-ri have martensite of quenching. No.2 sickle of Jangjae-ri was undergone high temperature as compared with others. This show manufacturing technology of sickles from Jangjae-ri in over the Songwon-ri's.

• Journal of the Korean Applied Science and Technology
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• v.24 no.3
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• pp.278-286
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• 2007

As a part of enhancing the performance of wood-plastic composites (WPC), polypropylene (PP)/ nanoclay (NC)/ wood flour (WF) nanocomposites were prepared using melt blending and injection molding process to evaluate their thermal stability. Thermogravimetric analysis (TGA) was employed to investigate thermal degradation kinetics of the nanocomposites both dynamic and isothermal conditions. Dynamic scans of the TGA showed an increased thermal stability of the nanocomposites at moderate wood flour concentrations (up to 20 phr, percentage based on hundred percent resin) while it decreased with the addition of 30 phr wood flour. The activation energy $(E_a)$ of thermal degradation of nanocomposites increased when nanoclay was added and the concentration of wood flour increased. Different equations were used to evaluate isothermal degradation kinetics using the rate of thermal degradation of the composites, expressed as weight loss (%) from their isothermal TGA curves. Degradation occurred at faster rate in the initial stages of about 60 min., and then proceeded in a gradual manner. However, nanocomposites with wood flour of 30 phr heated at $300^{\circ}C$ showed a drastic difference in their degradation behavior, and reached almost a complete decomposition after 40 min. of the isothermal heating. The degree of decomposition was greater at higher temperatures, and the residual weight of isothermal degradation of nanocomposites greatly varied from about 10 to 90%, depending on isothermal temperatures. The isothermal degradation of nanocomposites also increased their thermal stability with the addition of 1 phr nanoclay and of wood flour up to 20 phr. But, the degradation of PP100/NC1/MAPP3/WF30 nanocomposites with 30 phr wood flour occurs at a faster rate compared to those of the others, indicating a decrease in their thermal stability.

• Informatization Policy
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• v.19 no.3
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• pp.19-35
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• 2012

As Internet users increasingly consume news through the Internet, Internet portals face criticism that they are quickening the softening of public news and molding public opinions. Some portals have started to provide newscast services that directly connect the press, not grouping news sources on their own standards. This study aims to clarify how news grouping models and newscast models are different in terms of news softening and agenda setting. Specifically, authors conduct a content analysis on time-specific news content provided by top three portals-Naver, Daum, and Nate. By doing so, this study examines characteristics of news service models of Internet portals and their social and political implications. According to our study, the softening and tabloidization of portal news had not been improved even after adopting the newscast model. Therefore, portal journalism should be reorganized as a way to circulate healthy and qualified news content.

• Journal of Electrochemical Science and Technology
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• v.6 no.4
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• pp.131-138
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• 2015

Electrical discharge machining is an unconventional machining process in which successive sparks applied to machine the electrically conductive materials. Any changes in electrical discharge machining parameters lead to the pieces with distinct surface roughness. The electrical discharge machining process is well applied for high hardness materials or when it is difficult to use traditional techniques to do material removing. Furthermore, this method is widely applied in industries such as aerospace, automobile, molding, and tool making. CK45 is one of the important steels in industrial and electrical discharge machining can be considered as a proper way for its machining because of high hardness of CK45 after thermal operation of the electrical discharge machining process. Optimization of surface roughness as an output parameters as well as electrical discharge machining parameters including current, voltage and frequency for electrical discharge machining of CK45 has been studied using copper tools and kerosene as the dielectric. For such a purpose and to achieve the precise statistical analysis of the experiment results design of experiment was applied while non linear regression method was chosen to assess the response of surface roughness. Then, the results were analyzed by means of ANOVA method and machining parameters with more effects on the desired outputs were determined. Finally, mathematical model obtained for surface roughness.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.175-181
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• 2015

Because internal space of combat vehicle reachs about $80^{\circ}C$ at high temperature period, Proximity Sensor exposed high temperature and humidity, which has function to sense the distance and transfer signal for control unit, have enlarged sensing distance and finally locked on. Malfunction of sensing itself occur frequently, therefore we carried out cause analysis and improvement. We accomplish improvement activity secondly. Through-out many trial and error, we find out that malfunction of sensor occur at high temperature circumstance. To improve, the another Emitter Coil is added to increase voltage difference and improve sensing accuracy about 5~10 times. And we accomplish design improvement to dull temperature and humity change after increasing molding surface to add vibration and shock resistance. We prove that the improved product do not fail after enduring 136hr at $85^{\circ}C$ temperature and 85% relative humidity circumstance chamber.

• Journal of IKEEE
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• v.24 no.3
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• pp.691-698
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• 2020

The installation cost or the magnitude of the fault current varies depending on the grid connection method of the offshore wind farm. Therefore, there is a need for an efficient power grid connection method considering the capacity and location of the complex. In particular, most power cables in offshore wind farms use 3-core considering cost and efficiency. In the event of a failure such as a short circuit, the entire cable must be replaced, which can lead to significant losses in terms of cost, considering repair costs and turbine downtime. Therefore, in this paper, a radial, ring, and molding method is introduced into a 100 MW wind farm to be installed at Jeju offshore, and a three-phase short circuit failure is performed using a PSCAD/EMTDC program to perform computer analysis. I would like to propose a suitable power grid connection method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.1-6
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• 2018

Hydro-forming technology has spread dramatically throughout automotive industry over the last 20 years. This technology has many advantages for automotive applications in terms of better structural integrity of the parts, lower cost from fewer parts, material savings, weight reduction, lower springback, improved strength, durability, and design flexibility. In this study, various simulation technologies were developed to investigate the formability of hydro-forming components. Through this technology, to establish the effective forming process for appropriate components design, the bending process, pre-forming process, die closing process, etc. were considered for good forming. This paper proposes the forming amount, section length (corresponding to the hydro-forming press capacity), and minimum curvature (curvature effect evaluation according to the hydro-forming pressure) among the considerations in the design of the hydro-forming part. In addition, a design method is proposed for hydro-forming molding by carrying out cross section analysis of a real sub-frame part for automobiles. The effects of pre-bending, axial feed, hydraulic pressure, press load, and friction among the hydro-forming process parameters were analyzed. Therefore, whether these processes are necessary factors for hydro-forming were examined.