• 한국재료학회지
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• 제25권3호
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• pp.155-164
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• 2015

Porous metals are called as a new material of 21th century because they show not only extremely low density, but also novel physical, thermal, mechanical, electrical, and acoustic properties. Since the late in the 1990's, considerable progress has been made in the production technologies of many kinds of porous metals such as aluminum, titanium, nickel, copper, stainless steel, etc. The commercial applications of porous metals have been increased in the field of light weight structures, sound absorption, mechanical damping, bio-materials, thermal management for heat exchanger and heat sink. Especially, the porous metals are promising in automotive applications for light-weighting body sheets and various structural components due to the good relation between weight and stiffness. This paper reviews the recent progress of production techniques using molten metal bubbling, metal foaming, gas expansion, hollow sphere structure, unidirectional solidification, etc, which have been commercialized or under developing, and finally introduces several case studies on the potential applications of porous metals in the area of heat sink, automotive pannel, cathod for Ni-MH battery, golf putter and medical implant.

• 수산해양교육연구
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• 제21권1호
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• pp.96-105
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• 2009

Recently, the logistics companies are constructing distribution market for logistics service in hinterland which is convenient for management and activity of logistics. Since the expansion of hinterland has physical constraints and related to the adjacent cities, it is vital to select value added types of logistics in the business. This study determines the priority of logistics business types in the hinterland of Busan's new port using DHP, and also it suggests future types of logistics business by comparing result of study with the enterprises located in the hinterland. As a result, the inter-modal transport business has higher weight than the storage business. The distribution manufacturing business also has relatively high weight. Therefore, the inter-modal business and storage business need to keep a present status in hinterland, and the distribution manufacturing business should consolidate the role.

• 한국통신학회논문지
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• 제22권8호
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• pp.1782-1789
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• 1997

인터넷에서 분산 정보를 검색하는 대부분의 시스템들은 사용자가 요구하는 검색 용어의 의미를 반영하지 못해 관련된 정보를 정확히 찾지 못하고 있다. 본 논문에서는 정보 검색 성능을 향상시키는 방안으로 검색 용어의 의미를 반영할 수 있는 용어 분포에 기반한 자동화된 질의어 확장을 제안한다. 먼저, 사용자가 부여한 질의어와 전체 문서에서 용어의 중요도를 반영한 가중치(weight)를 계산하고, LSI의 SVD기법을 이용해 모든 문서에서 질의어와 유사하게 출현하는 용어의 분포를 측정하여, 이들 수치와 질의어 용어의 유사성을 측정하였다. 또한 자동적으로 추가할 용어를 줄이기 위한 방안을 연구하였으며 본 논문에서 제안한 방법을 사용해 검색 성능을 평가하였다.

• 농업과학연구
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• 제50권4호
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• pp.869-881
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• 2023

A genetic improvement program in Korea was implemented to improve the performance of Hanwoo cattle by generating livestock with genetically desirable economic characteristics. In particular, in response to external changes, such as the expansion of Free Trade Agreement (FTA), the livestock genetic improvement program has increased farm income by improving the productivity and quality of Hanwoo cattle. Using production cost data from Statistics Korea, the total input and output indices of Hanwoo feeding cattle from 2008 - 2021 were estimated and the growth and productivity changes were analyzed. The productivity change measures results were used to estimate the cumulative effects of the Hanwoo genetic improvement program on quality improvement, another purpose of the program, using a finite distributed lag model. The average annual increase in output (market weight) of Hanwoo was 0.9%. However, total input increased by 1.6%, resulting in a 0.6% decline in total factor productivity. In contrast, the Hanwoo genetic improvement program contributed significantly to the production of high quality beef, rather than contributing to improved productivity of the cattle. Hanwoo carcass weight, which is used as a performance indicator for the livestock genetic improvement program, has significantly improved and is projected to increase at a slower rate. The collective findings indicate the need for new performance indicators that can comprehensively indicate the performance of the genetic improvement of Hanwoo.

• 한국추진공학회지
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• 제16권3호
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• pp.97-103
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• 2012

액체 로켓 엔진의 연소기는 높은 온도의 연소가스를 발생시키므로 연소실과 노즐은 열적으로 보호되어야 한다. 상단용 엔진의 노즐확장부는 큰 노즐 팽창비를 갖기 때문에 무게가 발사체 성능에 미치는 영향이 크므로 경량 내열 소재가 개발되어 사용되어 왔다. 가스 냉각 방식은 이전에는 널리 사용되었으나 지금은 잘 사용되지 않으며, 니오븀 합금이나 니켈 기반 초합금, 세라믹 복합재를 사용하는 복사 냉각 방식과 흡열 냉각 방식은 지금까지도 발사체 상단에 많이 사용되고 있다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.505-509
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• 2011

액체 로켓 엔진의 연소기는 높은 온도의 연소가스를 발생시키므로 연소실과 노즐은 열적으로 보호되어야 한다. 상단용 엔진의 노즐확장부는 큰 노즐 팽창비를 갖기 때문에 무게가 발사체 성능에 미치는 영향이 크므로 경량 내열 소재가 개발되어 사용되어 왔다. 가스 냉각 방식과 흡열 냉각 방식은 이전에는 널리 사용되었으나 지금은 잘 사용되지 않았으며, 니오븀 합금이나 니켈 기반 초합금, 세라믹 복합재를 사용하는 복사 냉각 방식은 지금까지도 발사체 상단에 많이 사용되고 있었다.

• 한국환경과학회지
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• 제19권5호
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• pp.639-646
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• 2010

Differently from fly ash, the bottom ash produced from incinerated urban solid waste has been treated as an industrial waste matter, and almost reclaimed a tract form the sea. If this waste material is applicable to foam concrete as an fine aggregate, however, it may be worthy of environmental preservation by recycling of waste material as well as reducing self-weight of high-rising structure and long-span bridge. This research has an objective of evaluating the effects of application of bottom ash on the mechanical properties of foam concrete. Thus, the ratio of bottom ash to cement was selected as a variable for experiment and the effect was tested by compression strength, flexural strength, absorption ratio, density, expansion factor. It can be observed from experiments that the application ratios have different effects on the material parameters considered in this experiment, thus major relationship between application ratio and each material parameter were finally introduced. The result of this study can be applied to decide a optimal mix design proportion of foam light-weight concrete while bottom ash is used as an fine aggregate of the concrete.

• 한국해양공학회지
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• 제25권3호
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• pp.40-46
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• 2011

This paper describes the effects of fly ash replacement on the sulfate resistance of antiwashout underwater concrete which was replaced cement by fly ash from 0% to 50%. and the experimental works were performed on sulfate acceleration test of 5%$Na_2SO_4$ solution to find out the variance of length and weight of specimens. The experimental result shows that the length of specimens of antiwashout underwater concrete age at 180day was highly increased compare with normal concrete by acceleration test. but the mixture which was replaced 50% of fly ash shows reduction of the expansion, weight various, compare with normal concrete specimen. accordingly by using fly ash as admixture in antiwashout underwater concrete in sea environment, it will makes more durable for the attacks of sulfate by sea water.

• 한국지역사회생활과학회지
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• 제28권3호
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• pp.365-375
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• 2017

The purpose of this study was to investigate the maximal elongation rate and area expansion ratio of human skin in various postures. Five males and five females (male: $23{\pm}2yr$ in age, $177.9{\pm}4.8cm$ in height, $76.7{\pm}8.8kg$ in body weight, $24.2{\pm}2.5$ in BMI, $16.2{\pm}3.4%$ in body fat; female: $22{\pm}1yr$, $163.2{\pm}3.6cm$, $51.4{\pm}2.7kg$, $19.3{\pm}1.6$, $27.4{\pm}6.7%BF$) participated in this study. Measurements were conducted using a pen and tape on the elbow, knee, wrist, shoulder, and neck. Subjects held postures so that each joint of the body regions was bent at its maximal level. The results were as follows: 1) The maximal elongation rate of skin showed a significant difference among the regions: $16.6{\pm}3.4%$ for the wrist, $22.4{\pm}5.5%$ for the neck (back), $37.6{\pm}11.3%$ for the shoulder, $42.6{\pm}10.0%$ for the knee, and $43.9{\pm}4.0%$ for the elbow (p<0.05). 2) The maximal expansion rate of the body surface area had the greatest values on the elbow ($93.7{\pm}6.4%$) and knee ($74.8{\pm}10.8%$). 3) No significant difference was found between males and females. In summary, maximal values of skin elongation and expansion rates in vivo were greater than in vitro values known from previous reports. These results can be applied to develop electronic fibers or textiles for wearable tight fit work clothing as well as fitness wear.

• 유기물자원화
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• 제28권4호
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• pp.5-13
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• 2020

본 연구는 수분조절제로서 팽화왕겨(compressed expansion rice hull; CERH) 처리에 따른 계분의 발효 특성 및 발효된 가공계분의 시비에 따른 상추와 청경채의 생육에 미치는 영향을 조사하기 위해 수행되었다. 실험에 사용된 처리구는 톱밥 처리구(계분 90%+톱밥10%; SP), 피트모스 처리구(계분 90%+피트모스10%; PP), 팽화왕겨 1 처리구[계분 90%+CERH1 (��1.3 mm) 10%; PCR1] 및 팽화왕겨 2 처리구[계분 90%+CERH2 (��3.0 mm); PCR2]로 설정하였다. 31일간 진행된 계분 발효 과정에서 발효 더미의 온도, 수분 함량, pH 및 총탄소 함량은 수분조절제의 종류에 따른 차이를 나타내지 않았다. 시험 종료 시 PP 처리구와 PCR1 처리구의 질소 함량은 SP 처리구나 PCR2 처리구보다 높았다. 발효 후 건조된 가공계분의 질소, 인산, 칼리 함량은 각각 2.76~3.65%, 1.69~2.05%, 2.53~2.90%로 나타났다. 수분조절제별 가공계분의 작물 재배 시험에서 SP 처리구와 비교할 때, 상추는 PP와 PCR1 처리구에서 10% 이상 건물중이 증가하였으나, 청경채는 PP 처리구에서만 증가되었다. 상기 결과들을 종합할 때, 1.3 mm 크기의 팽화왕겨는 계분 발효 시 수분조절제로서 피트모스나 톱밥을 대신하여 사용할 수 있었다.