• Composites Research
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• v.32 no.6
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• pp.395-402
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• 2019

The RFI process is an OoA process that fiber mats and resin films are laminated and cured in a vacuum bag. In case that resin film is insufficient to fill empty space in fibers, it makes void defect in composites and this void decrease mechanical properties of the composites. For this reason, non-destructive testing is usually used to evaluate void of manufactured composites. So, in this study, a manufacturing method of standard void specimens, which are able to be used as references in non-destructive testing, was proposed by controlling resin film thickness in the RFI process. Also, a fiber compaction test was proposed as a method to set the resin film thicknesses depending on target voids of manufacturing panels. The target void panels of 0%, 2%, and 4% were made by the proposed methods, and signal attenuation depending on void was measured by non-destructive testing and image analysis. In addition, voids of specimens for tensile, in-plane, short beam and compressive tests were estimated by signal attenuation, and mechanical properties were evaluated depending on the voids.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.2
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• pp.87-96
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• 2017

In this study, 4 gases containing typical chlorinated volatile organic compounds (VOCs) were treated by ultraviolet (UV) irradiation. The typical chlorinated VOCs are dichloromethane (DCM), trichloromethane (TCM), carbon tetrachloride (CTC) and trichloroethylene (TCE). The removal efficiency (RE) and the products of chlorinated VOCs by UV irradiation are investigated. At this time, 2 types of background gas (air and nitrogen) were used to figure out the RE by photooxidation and photolysis. The specification of UV-lamp used in this study was low-pressure mercury lamp emitting wavelength of 185~254 nm. The experimental conditions were set as initial VOC concentration of $180{\pm}10ppm$, empty bed retention time (EBRT) of 53 s, temperature of $23{\pm}2^{\circ}C$ and relative humidity of $65{\pm}5%$. In the photolysis condition with nitrogen ($N_2$) as background gas, the averaged RE of the 4 types of chlorinated VOCs was about 24% higher than that with photooxidation; and the REs of VOCs except CTC were confirmed as >99%. The composition of off-gases after UV photooxidation in air was investigated and several intermediates from DCM, TCM and TCE were detected by GC/MS. Among them, phosgene which is a toxics was detected as an intermediate of TCM. In addition, the concentration of carbon dioxide ($CO_2$) in the off-gases was measured to calculate the mineralization rate (MR). With the photooxidation, TCE showed the highest RE (>99%) while MR was the lowest (17%); and the MR of DCM was the highest (86%). In addition, particulate matters (PM) in the off-gases was also detected and high concentrated $PM_{10}$ ($21,580{\mu}g{\cdot}m^{-3}$) and $PM_{2.5}$ ($6,346{\mu}g{\cdot}m^{-3}$) were detected in TCE off-gas. More than 99% of the chlorinated VOCs could be removed using UV254-185 nm lamp, while it is necessary to conduct further studies on the production and treatment of secondary pollutants.

• Journal of Biosystems Engineering
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• v.6 no.1
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• pp.60-72
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• 1981

This study was carried out to find out the effects of the sheaf size of paddy harvested by the binders on the threshing performance, load characteristics and power requirement of an auto-feed thresher. The results of the study are summarized as follows: 1. The seperating performance of the thresher appeared to be satisfactory for all the sheaf sizes although the amount of rubbishes and empty grains slightly increased with the sheaf size of paddy. 2. There was no significant difference in grain output quality of the thresher among the three sheaf sizes. However, the amount of grains left unthreshed increased with the sheaf size. In the case of the largest sheaf size with the feed rate of 780kg/h, it exceeded the limit set by the national inspection regulations. 3. The position of the feed-chain rail gave a significant effect on the power requirement of the thresher. At the feed rate of 780kg/h, the net power required to convey sheafs through the feed chain was in the range of 0.37 to 0.50 PS for the middle and lowest position of feed-chain rail, and there was no significant difference among the sheaf sizes. At the highest position, however, it appeared that the smallest sheaf required more power than the others. The net power requirements at this position were 1.03, 0.59. 0.65 PS for the smallest, medium and largest sheafs respectively. 4. The torques of both the thresher and the engine shaft increased with the feed rate and were not affected by the sheaf size for the lower two feed rates of 520 and 780kg/h. At the highest feed rate of 1,040 kg/h, however, they were affected by the sheaf size. In this case, the medium sheaf size gave lower values than the others. 5. The variations in the thresher and the engine torque increased with the feed rate and were not affected by the sheaf size for the feed rate of 520kg/h. At the feed rate of 780kg/h, however, they increased with sheaf size. And at the feed rate of 1,040 kg/h, the torque variations increased greatly for all the sheaf sizes due to an over-load operating condition. 6. It appeared that the average and maximum power requirements of the thresher increased with the feed rate. But, there was no significant difference in power requirement among the sheaf sizes for the lower two feed rates. 7. The threshing efficiency of the thresher was in the range of 214-249 kg/ps.h with the feed rates of 520 and 780 kg/h, and it was not affected by both the sheaf size and the feed rate. At the feed rate of 1,040 kg/h, however, it decreased to as low as 171-174 kg/ps.h because of a sudden increase in power requirement. 8. The average power requirements of the engine were slightly higher than those of the thresher due to the slippage of flat belt between the thresher and engine. It appeared that power transmission from the engine to the thresher was maintained properly since slippages were moderately low with the range of 2.78 to 6.51% throughout the tests. 9. The specific fuel consumption of the engine (diesel 8PS) decreased as the feed rate increased. However, there was no significant reduction in specific fuel consumption as the feed rate increased above 780 kg/h.

• Korean Journal of Food Science and Technology
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• v.27 no.6
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• pp.827-833
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• 1995

Temperature distribution tests for a water cascading horizontal retort utilizing superheated water with overpressure as a heating medium were carried out under three different loading conditions, that is, empty(P-0), half-fully(P-3000) and fully(P-6000) loaded operating conditions. Tank volume and full loading capacity of sterilizer used for this study were about 5,900 liter and 1,140 kg(6000 pouches having 190 g weight each), respectively. Set point condition for sterilization was $122^{\circ}C$, 23 minutes and pressure was maintained in the range of $1.8{\sim}2.0\;kg/cm^2$ during sterilization. For each experiment, time-temperature data and F values were obtained from temperature microprocessor($F_0$ monitor). There were significant variations in the temperature distribution at different positions in the sterilizer. The temperature distribution was also affected by the pouch loading condition significantly. The application of the temperature distribution test to a product (retort pouched curry sauce) was conducted at the fully(P-6000) loading condition. Although heat transfer parameters($f_h\;and\;f_c$), and F values were varied with the position of sterilizer, sensory evaluation showed that the temperature distribution of the sterilizer used in this study didn't affect the quality of retorted curry sauce.

• Journal of the Korean Geographical Society
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• v.48 no.2
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• pp.259-271
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• 2013

This paper addresses the efficient facility placements to adopt a super WiFi network, taking significant considerations as the next generation 'information highway'. Since the super WiFi has a wider geographic coverage by utilizing the white spaces of TV broadcasting which are empty and available frequencies for the wireless communications, it would play an important role in releasing digital divide of the internet access for low populated or mountainous areas. The purpose of this paper is to explore systematic and efficient spatial plans for the super WiFi. For doing this, we applied optimal location covering models to Gurye-gun, Jeonlanamdo. From the application, we presented optimal locations for super WiFi facilities and significant analytical results, such as the tradeoff between the number of facilities and coverage and marginal coverage for establishing super WiFi network. The results of this research would be usefully utilized for decision makers who wish to adopt a super WiFi, to extend wireless networks in a city or build a regional infrastructure of wireless facilities.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.1
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• pp.67-75
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• 2011

This paper presents the systematic optimal design of an overlapped ultrasonic sensor ring for high performance obstacle detection using effective beam overlap. Basically, a set of low directivity ultrasonic sensors of the same type are arranged in a circle at regular intervals with their beams overlapped. First, both real and simplified beam patterns of an ultrasonic sensor and several sensor models for obstacle position estimation within its beam pattern are introduced. Second, the obstacle detection range of an overlapped ultrasonic sensor ring and its simple sensor model for obstacle position estimation are described. Third, for both conic and non-conic shaped beam pattern, the design indices of an overlapped ultrasonic sensor ring for minimal positional uncertainty in obstacle detection are defined. Fourth, the constraints imposed on the structural parameters of an overlapped ultrasonic sensor ring to guarantee non empty beam overlap and to avoid excessive beam overlap are derived. Fifth, the optimal number of ultrasonic sensors for a given radius of an overlapped ultrasonic sensor ring and the optimal radius of an overlapped ultrasonic sensor ring are determined. Throughout this paper, the MA40B8 from Murata Inc. is taken as a representative commercial low directivity ultrasonic sensor.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.39 no.3
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• pp.22-32
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• 2021

The Seonwonjeon(璿源殿) in the Deoksugung Palace was initially the ritual space for the royal family affiliated with the Gyeongungung Palace during the Korean Empire. It is currently, however, empty, as a landscape restoration and maintenance plan is established as a part of the restoration project for the Seonwonjeon area. The following results were obtained through the historical investigation of the original form and examination of similar cases. First, the original topography of the backside grove, which had been in the Seonwonjeon area, is 3.0-5.0m higher than the base of the building, and a terraced flower bed(花階) was installed on the border of the green to set off the difference in a scenic way. Second, the backside grove was composed with fruit trees to bear fruits used in rites and pine trees which symbolize the ritual space. Third, resting places were established at both ends of the site for the convenience of visitors without interrupting the atmosphere of the sacred ground. A trail was also created inside the backside grove along with minimum landscape elements, including functionally required items, such as the signboard, bench, tree guard, ramp, street lights, and landscaping lights. Fourth, the information on original planting in the palace and ritual space was extracted through historical materials, such as literatures, antique paintings, and photographs along with site surveys. Based on the information acquired, a planting plan was established for the courtyard, pedestrian road, resting places, terraced flower bed, pine grove, and fruit tree garden, which constitute the landscaping space of the Seonwonjeon area.

• Korean Journal of Environment and Ecology
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• v.28 no.3
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• pp.326-330
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• 2014

Flowering characteristics and acorn production of Quercus acuta were studied in a Quercus acuta forest at Wando island, Korea. Three sample trees were cut and measured to investigate flowering characteristics during flowering season. Eight $20m{\times}25m$ quadrats were set up and three $1m{\times}1m$ seed traps were established within each quadrat to investigate acorn production. There were no significant differences in number of female and male inflorescence per bearing shoot among crown positions, but these values decreased from the upper part to the lower part of crown. The number of female flowers was 5,025 flowers/tree, and of the total number, 60.3% was in the upper part, 28.4% was in the middle part and 11.3% was in the lower part of crown. The number of male flowers was 7,063 flowers/tree and increased from the lower part to the upper part of crown. Acorn production of total 24 seed traps was 947 acorns/$24m^2$, and of total acorn production, 11.0% was sound, 61.9% was damaged, 25.1% was decayed and 2.0% was empty. Monthly acorn production was 240 acorns/$24m^2$ in August, 632 acorns/$24m^2$ in September, 56 acorns/$24m^2$ in October, 17 acorns/$24m^2$ in November and 2 acorns/$24m^2$ in December. Acorns fallen in October showed higher mean length, diameter and weight than those of other months.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.445-458
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• 2016

Most of water curtain cultivation (WCC) area in Korea has been inveterately suffering from the gradual draw-down of groundwater level and related shortage of water resources at the late stage of WCC peak time. To solve this problem, artificial recharge techniques has been recently applied to some WCC area. This study introduces infiltration gallery, which is one of the artificial recharge methods, and tentatively examined the effectiveness of three galleries installed at Sangdae-ri WCC area of Cheongju City. Seven galleries are set up at each empty space between eight vinyl houses in this area and its dimension is designed as 50 cm in each width and height and 300 cm in each length. Installation process was including bed excavation, backfill with gravels and silica sands, and completion of gallery by equipment of piezometer and covering with non-woven cloth. For each B, C, D gallery, 3 types of test including preliminary, four step and one long-term injection were performed. The first preliminary test showed the rough relations between injection rates and water level rise as follows; 20 cm and 30 cm level rise for $33.29{\sim}33.84m^3/d$ and $45.60{\sim}46.99m^3/d$ in B gallery; 0 cm, 16 cm and 33 cm level rise for $21.1m^3/d$, $33.98m^3/d$ and $41.69m^3/d$ in C gallery; 29 cm and 42 cm level rise for $48.10m^3/d$ and $52.23m^3/d$ in D gallery. Afterwards, more quantitative results estimating effectiveness of artificial recharge were reasoned out through stepped and long-term injection tests, which is expected to be employed for estimating water quantity re-injected into the aquifer through these galleries by natural injection over the period of WCC peak time.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.2
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• pp.78-88
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• 2015

In the 1920s, the period of cultural governance ruled by Japan, the diverse media were founded and various events were conducted to boost circulation. Under the Japanese colonial period in 1920s, a number of media - newspapers and magazines - were published and often they carried out entertaining events in order to obtain more subscribers. A hobby magazine, Samchunri, for instace, set up a media event to selecting Korea's eight beautiful scenary (Bandopalgyong) for the first edition in 1929. The paper aims to analyse and understand the perception of landscape in 1929 through the media event carried out by Samchunri. In particular, the selection was made by well-known writers within Japanese colonial period 1910 - 1945). The selection process and views from the writers on landscape were analysed; firstly, the selection of Bandopalgyong was carried out by questionnaires to writers in 1929 where Korea is under Japanese colonial rules. The conditions of the selection were unknown; however, the purpose was enlightening the people specially the youngs and introduction of beautiful places in Korea. As a result, views and opinions on Bandopalgyong by the writers were progressed. Secondly, within the Bandopalgyong, the natural landscape areas include Gumgansan(金剛山), Daedonggang(大洞江), Buyeo(扶餘), Gyongju(慶州), Myongsasipri (明沙十里), Haundae(海雲臺), Baekdusan(白頭山), and Choksukru(矗石樓). Those chosen places were not cohesive nor did not have any consistant reasons to be chosen in terms of size and location; however, some writers claimed that there were other places to match the chosen ones and therefore, the selection process was highly dependent on access (i.e. transport). Thirdly, the travelogue on Baekdusan and Nackwhaam(洛花岩) illustrated interesting views on landscape in particular. Baekdusan landscape were described in overlaping with long history and national soul. In the Nackwhaam travelogue, it described 'Buyeo (夫餘) was an ancient capital of Backjae Dynasty and empty place' as well as denying Chosun Dynasty. It was assumed that the two places weren't visited but rewritten with existing literatures. Fourthly, edited by Kim Dong Whan, a travelogue style book, 'Bandosanha' was published in 1941. It did repeat the selection of Bandopalgyong, but this time, it was classified the eight beautiful landscape into two categories; historic/cultural places and natural landscape. This paper was able to analyse and understand the perception of landscape in 1929 through the travelogue of Samchunri. It is an empirical study on the process and perception on Korea landscape under Japanese colonical period by views of the selected writers.