• Clean Technology
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• v.15 no.3
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• pp.180-185
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• 2009

The ethylene-propylene rubber (EPDM) scrap generated from automobile weatherstrip manufacturing process was used to make a thermoplastic elastomer through blending with polypropylene. The surface activated EPDM powder was obtained by the high temperature and shear pulverizer. The addition of surfactant resulted in more surface activated EPDM powder and the optimum loading amounts of surfactant was 1.5 phr. Maleic anhydride was grafted onto polypropylene by reactive blending to give functionalized polypropylene. The wetting property between EPDM scrap and polypropylene was improved by the addition of poly (ethylene-co-acrylic acid) as a compatibilizing agent. Poly(ethylene-co-acrylic acid) decreased the surface tension of polypropylene and thus would contribute to the wettability with EPDM powder.

• Clean Technology
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• v.15 no.1
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• pp.31-37
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• 2009

This study deals with the production process of activated carbons from the sewage sludge char by chemical activation reaction. KOH and NaOH were used as activating agents, which react well with carbon. From the experiments, it was found that activated carbons made with KOH treatment had better physicochemical properties in terms of iodine number and BET value than those made with NaOH treatment. It was also found that the optimal deposition ratio of an activating agent to the sewage sludge char was 75 wt% of KOH and 50 wt% of NaOH. Activated carbons were washed out by distilled water after neutralization with 5 M hydrochloric acid solution. The activated carbons that were produced from a sewage sludge char at this optimal conditions have BET surface areas of approximately $600m^2/g$.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.95-107
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• 2007

This study describes compressive characteristics of marine clay at southwestern coast in Korea by large block and piston samples. Through the analysis of disturbance effect and various consolidation test, consolidation result shows that volumetric strain from large block samples is lower than piston samples and compression index of large block samples is larger than piston samples value. We suggest new empirical equation of compression index by the effect of compression index following sampling method. If consolidation settlement is presumed using empirical equation of compression index, the resort will be more reasonable in predicting settlement than that obtained by the decision of compressibility characteristics from piston samples.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.83-90
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• 2009

Since traffic is aggregated to a MPP that acts as an Internet gateway, if traffic load is not balanced among the MPPs in a WMN, the overall performance of a WMN becomes poor even though the total traffic load is far below the capacity of the WMN. Therefore, in this paper, we propose a stochastic load balancing scheme where each MP (Mesh Point) probabilistically selects its serving MPP according to the congestion levels of MPPs. Through extensive simulations using ns-2, we have verified that our scheme can stabilize a WMN fast when congestion occurs and reduce packet loss rate by distributing traffic load of a congested MPP to multiple MPPs in the inverse proportional to their congestion levels. Compared to queue-based load balancing scheme, our method can decrease network stabilization time by 34 seconds, and reduce packet loss rate by 7.6%. Since the proposed scheme can reduce network stabilization time by efficiently using network resource, it is expected to contribute to the reliable operation of a WMN.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.431-431
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• 2021

4차 산업혁명의 도래로 사회기반시설물의 계획 및 운영관리에 있어 데이터 분석을 통한 가치추출에 대한 관심은 매우 높은 상황이다. 데이터의 가용성과 접근성, 정부 지원 등을 평가하는 공공데이터 개방지수에서 한국은 1점 만점에 0.93점을 획득하여 경제협력개발기구 회원국 중 1위(2019년 기준)를 할 정도로 매우 높은 수준(평균 0.60점)이다. 그러나 공식적으로 발표 및 배포되는 사회기반시설물 관련 정보와 심도 있는 연구 분석이 필요한 정보는 접근이 여전히 제한적이라 할 수 있다. 특히 대표적인 사회기반시설물인 상수도시스템은 대부분 국가중요시설로 지정되어 있어 다양한 정보를 획득하고 분석하는데 제약이 존재하며, 관련 국가통계인 상수도통계에서는 누수사고 등과 같은 비정상적 상황에 대한 사고지점, 원인 등과 같은 세부정보는 제공하고 있지 않다. 본 연구에서는 웹크롤링 및 빅데이터 분석기술을 활용하여 과거 일정기간 발생한 지자체의 상수도 누수사고 관련 뉴스를 전수조사하고 도출된 사고건수를 국가 공인 정보인 상수도통계자료와 비교·분석하였다. 독립적인 누수사고 기사를 추출하기 위해서 중복기사의 제거, 누수 관련 키워드 정립, 상수도분야 이외의 관련기사 제거 등의 절차가 필요하며, 이와 같은 기법은 R프로그래밍을 통해 구현되었다. 추가적으로 뉴스기사의 자연어 처리기반 정보추출기법을 통해 누수사고 건수 뿐만 아니라 사고발생일, 위치, 원인, 피해정도, 그리고 대상 관로의 크기 등을 획득하여 상수도 통계에서 제시하고 있는 정보보다 많은 가치를 추출하여 연계할 수 있는 방안을 제시하였다. 제시된 방법론을 국내 A광역시에 적용하여 누수사고 건수를 비교한 결과 상수도통계에서 제시하고 있는 누수발생건수와 유사한 규모의 사고건수를 뉴스기사분석을 통해 도출할 수 있었다. 제안된 방법론은 추가적인 정보의 추출이 가능하다는 점에서 향후 활용성이 높을 것으로 기대된다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.23-35
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• 2009

This study was performed to investigate the bending stresses of tunnel shotcrete as a function of the coefficient of lateral earth pressure. To perform this study, a large scale model tunnel with an one-lane horseshoe shaped road tunnel was prepared. The 3 dimensional numerical analyses were carried out to verify the results obtained from the model tests. For the loading system during the tests, 11 cylinder pressure jacks which can be controlled individually were used to simulate various loading conditions. The tests were preformed three times with three different lateral earth pressure coefficients of 0.5, 1.0 and 2.0. The bending stresses of shotcrete measured in tests were compared and analyzed with those calculated from numerical analyses. As a result, it was found that the bending compressive stresses obtained from numerical analyses were similar to those of tunnel model tests and bending tensile stresses were slightly overestimated during numerical analyses.

• Journal of the Korean Society of Food Culture
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• v.24 no.5
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• pp.525-532
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• 2009

School dietitians are divided into two groups according to their status of employment, school nutrition teachers and dietitians, with the latter being irregularly employed by the institution. In this study, the job satisfaction, communication ability, work performance and importance in feeding services and dietetic counseling of both groups were compared. To accomplish this, 100 regularly employed school nutrition teachers (regularly employed) and 101 dietitians (irregularly employed) were surveyed by questionnaire. The results were as follows: (1) The irregularly employed dietitians showed a lower level of job satisfaction than the school nutrition teachers. This was likely because the school nutrition teachers belonged to the strong inner circle of school teachers and cafeteria workers, and had enough time to prepare for class lectures and consultancy. Conversely, the irregularly employed dietitians generally handle extra office work in addition to their primary duties. Despite these differences, both parties agreed that it was necessary to change the work system. Additionally, school dietitians reported that they had little opportunity for further training for career development. (2) Both parties had good communication skills; however, the irregularly employed dietitians had more conflicts with other staff members than the regular employees. (3) Job performance and job importance level was compared among employees involved in school feeding services and nutrition counseling. No significant differences were observed between dietitians and nutrition teachers in either group (p<0.05). However, the school nutrition teachers showed better skills than school dietitian with respect to public relations, running independent counseling offices, and using effective tools and materials. Job performance level was lower when compared to job importance level for all items, which meant the job was not well performed when compared to the work importance awareness.

• Journal of the Korean Society of Food Culture
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• v.24 no.5
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• pp.533-539
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• 2009

Frying is the most popular cooking style used in food service institutions in Korea because fried dishes are well accepted by students. However, trans fat contents reduction have recently been required in many foods for health reasons Therefore, alternatives to frying such as oven baking or roasting are being used in many institutions. Steam convection ovens provide dry heat as well as steam so that they can be used to make a wide variety of Korean dishes. In this study, a menu acceptance test was conducted over 2 weeks. Pork, chicken, fish and potato dishes cooked by conventional cooking methods were served for 4 successive days, after which the same dishes were prepared using the oven. Overall, 322 junior high school students evaluated the traditionally cooked foods, while 316 evaluated the oven cooked foods. Comparison of the foods prepared using both methods only revealed a significant difference in the acceptability of foods on the fish menu (p<0.05). Specifically, the acceptance of fried fish was higher than that of the oven baked fish. Additionally, overall acceptance of the menu by males was higher than the acceptance by girls. Furthermore, students who had the preference for special ingredients showed a higher menu acceptance for the menu cooked with those ingredients. On average, approximately 25% of the meal was not consumed and left as plate waste. The portion of the fried fish not consumed was smaller than that of the oven cooked fish, but the portion not consumed did not vary based on cooking method for any other foods evaluated. Overall, it is expected that the oven cooking method will be a good substitute for frying or other cooking method for traditional Korean dishes.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3B
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• pp.269-279
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• 2009

The design flood estimation in a large river basin has a lot of uncertainties in areal reduction factors, time-spatial rainfall distribution, and parameters of rainfall-runoff model. The use of historical concurrent rainfall events for estimating design flood would reduce the uncertainties. This study presents a procedure for estimating design floods using historical rainfall events and storage function model. The design rainfall and time-spatial distribution were determined through analyzing concurrent rainfall events, and the design floods were estimated using storage function model with a non-linear hydrology response. To evaluate the applicability of the procedure of this study, the estimated floods were compared to results of frequency analysis of flood data. Both floods gave very similar results. It shows the applicability of the procedure presented in this study for estimating design floods in practices.

• Korean Journal of Community Nutrition
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• v.28 no.6
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• pp.449-465
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• 2023

Objectives: This study aimed to analyze menu patterns and food group diversity in daycare centers managed by the Center for Children's Foodservice Management in South Korea. Methods: Data from 18 Center for Children's Foodservice Management centers across various provinces (excluding Jeju Island) were analyzed. We examined 8,796 meals served in February, May, August, and December 2021, focusing on seasonal lunch and snack menus for children aged 3-5. Foods were categorized into 19 groups for lunch and 21 for snacks. The frequency of food groups and dietary patterns were assessed using the Dietary Diversity Score. Analyses were conducted using Excel 2016 and IBM SPSS Statistics version 28. Results: Most lunch menus (89%) included five menu items, with a ratio of grain, meat, and vegetables at 88%. Snack menus typically had one item (57%), with significantly more items in the afternoon compared to the morning (P < 0.001). Regarding snack patterns, 75.2% of morning snacks and 61.1% of afternoon snacks contained only one solid food and drink (P < 0.001). Fruit and milk (22.4%) was the most prevalent pattern in morning snacks, while grain and milk (31%) dominated afternoon snacks (P < 0.001). Only 48% of daycare center menus (all snacks and lunch) included all five food groups (grain, meat, vegetables, fruit, and milk). Notably, only 83% included milk and 57% included fruit. Conclusions: These findings highlight the need to improve food variety and diversity in the Center for Children's Foodservice Management-managed daycare center menus. Developing more detailed guidelines for menu structure and food composition is crucial to ensure children receive balanced and diverse nutrition.