• 국제강구조저널
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• 제18권5호
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• pp.1525-1540
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• 2018

A test rig with multi-functional purposes was specifically designed and manufactured to study the behavior of multi-planar welded tubular joints subjected to multi-planar concurrent axial loading. An experimental investigation was conducted on full-scale welded tubular joints with each consisting of one chord and eight braces under monotonic loading conditions. Two pairs or four representative specimens (two specimens for each joint type) were tested, in which each pair was reinforced with two kinds of different internal stiffeners at the intersections between the chords using welded rectangular hollow steel sections (RHSSs) and the braces using rolled circular hollow steel sections (CHSSs) and welded RHSSs. The effects of different internal stiffeners at the chord-brace intersection on the load capacity of joints under concurrent multi-planar axial compression/tension are discussed. The test results of joint strengths, failure modes, and load-stress curves are presented. Finite element analyses were performed to verify the experimental results. The study results show that the two different joint types with the internal stiffeners at the chord-brace intersection under axial compression/tension significantly increase the corresponding ultimate strength to far exceed the usual design strength. The load carrying capacity of welded tubular joints decreases with a higher degree of the manufacturing imperfection in individual braces at the tubular joints. Furthermore, the interaction effect of the concurrent axial loading applied at the welded tubular joint on member stress is apparent.

• 한국도로학회논문집
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• 제16권2호
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• pp.53-59
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• 2014

PURPOSES : This study estimated an asphalt pavement internal behavior under uphill lanes considering reducing speed of heavy truck on uphill slope. METHODS : Truck performance curve which has been adapted to "Korea Highway Capacity Manual" was analyzed. And asphalt pavement internal behaviors were estimated with Multi-layered elastic analysis using KPRP(Korea Pavement Research Program) dynamic modulus prediction equations. RESULTS : As a result, it is shown that when the standard truck drives 2.0 km at a speed of 80 km/h in 8% climbing slope, it's speed reduced to 25.4 km/h, at same time frequency in asphalt layer decrease to 67.2% and it's dynamic modulus degrades to 30.9%. Based on these results, internal behavior as decreasing vehicle speed on uphill lanes were estimated. CONCLUSIONS : From the results of Multi-layered elastic analysis, internal behavior showed that when the standard truck drives 2.0 km at a speed of 80 km/h in 8% slope on uphill lanes, vertical strain was increased to 44.4% at the bottom of surface course, and lateral tensile strain was increased to 20.5% at the bottom of base course.

• 소성∙가공
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• 제22권1호
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• pp.17-22
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• 2013

Tube hydroforming is a technology that utilizes hydraulic pressure to form a tube into desired shapes inside die cavities. Due to its advantages, such as weight reduction, increased strength, improved quality, and reduced tooling cost, single-layered tube hydroforming is widely used in industry. However in some special applications, it is necessary to produce multi-layered tubular components which have corrosion resistance, thermal resistance, conductivity, and abrasion resistance. In this study, a hollow forming process to fabricate a part from multi-layered tubes for structural purposes is proposed. To accomplish a successful hydroforming process, an analytical model that predicts optimal load path for various parameters such as tube material properties, thickness of tubes, diameter of holes and the number of holes was developed. Tubular hydroforming experiments to fabricate a hollow part were performed and the optimal loading path developed by the analytical model was successfully verified. The results show that the proposed hydroforming process can effectively produce hollow parts with multi-layered tube without defects such as wrinkling or fracture.

• 한국도로학회논문집
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• 제14권5호
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• pp.21-29
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• 2012

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

• Composites Research
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• 제17권3호
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• pp.38-44
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• 2004

레이다나 전자장비에서 복사되어 나오는 전자기파의 차폐는 상업적으로나 군사적으로 매우 중요한 문제이다. 본 연구에서는 다중벽 탄소나노튜브가 모재에 첨가된 섬유강화 복합재의 전자기적 특성을 고찰하기에 앞서, 다중벽 카본나노튜브와 모재로 이루어진 복합재료를 제작하고 그것에 대한 전자기적 특성을 고찰하였다. 복합재료의 제작 방법을 확립하였고, X-band (8.2GHz~12.4GHz)에서 첨가량과 공정변수에 따른 다중벽 탄소나노튜브/에폭시 복합재료의 유전율을 측정하였다. 또한 MWNT의 재응집 현상을 관찰하였고, 이것이 물성에 미치는 영향을 고찰하였다. 복합재료의 유전율은 MWNT의 분산도에 영향을 받았고, MWNT의 첨가량이 증가함에 따라 거의 선형적인 증가를 보였다.

• 한국의류학회지
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• 제22권3호
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• pp.374-383
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• 1998

Apparel Quality was one of the most important elements to evaluate the reputations of companies and products which affect the consumer's purchasing behavior. From researches on apparel quality, there was no common concept of quality as well as no common dimensions. The purposes of this study were to identify apparel quality concept and to classify the multi-dimensional concept of apparel quality. The research was carried out in theoretical as well as empirical studies. The theoretical study was conducted to find out apparel quality concept and divide apparel quality concept into four dimensions groups. The empirical study followed the theoretical study to confirm the multi-dimensional concept of apparel quality. The empirical study was investigated that the questionnaire was administered to 634 housewives in Seoul, Kwangju, and Busan during the fall of 1996. The data were analysed by LISREL analysis. This study identified that apparel quality was characteristics of consumer's desires for apparel. The results of the theoretical study verified that apparel quality concept was organized into four different dimensions: physical attribute, physical function, instrumental performance, and expressive performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1805-1824
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• 2013

Recently, the use of wireless body area networks (WBAN) has been increasing rapidly in medical healthcare applications. WBANs consist of smart nodes that can be used to sense and transmit vital data such as heart rate, temperature and ECG from a human body to a medical centre. WBANs depend on limited resources such as energy and bandwidth. In order to utilise these resources efficiently, a very well organized medium access control (MAC) protocol must be considered. In this paper, a new, adaptive and energy-efficient MAC protocol, entitled isMAC, is proposed for WBANs. The proposed MAC is based on multi-channel communication and aims to prolong the network lifetime by effectively employing (i) a collision prevention mechanism, (ii) a coordinator node (WCN) selection algorithm and (iii) a transmission power adjustment approach. The isMAC protocol has been developed and modelled, by using OPNET Modeler simulation software. It is based on a networking scenario that requires especially high data rates such as ECG, for performance evaluation purposes. Packet delay, network throughput and energy consumption have been chosen as performance metrics. The comparison between the simulation results of isMAC and classical IEEE 802.15.4 (ZigBee) protocol shows that isMAC significantly outperforms IEEE 802.15.4 in terms of packet delay, throughput and energy consumption.

• 가정과삶의질연구
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• 제26권3호
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• pp.53-64
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• 2008

This study was to investigate the learning motive types and degree of psychological well-being of middle-aged married women attending the Korea National Open University and to examine the difference in their psychological well-being according to the types of learning motives. For these purposes, a survey was conducted to 263 middle-aged married women from 36 to 60 at the Korea National Open University. The findings were as follows: First, learning motive types of middle-aged women could be classified into 3 types; a non-oriented type, an activity and goal-oriented type and a multi-oriented type. A multi-oriented types were the most popular among those. Second, the overall level of self-respect was above the median, but the life satisfaction level was below the median. Third, there was difference in their self-respect level according to the learning motive types. That is, students who had a multi-oriented learning motive were higher self-respect level than those who had an activity and goal-oriented learning motive. Therefore, lifelong education is very significance in these days when average life span is prolonged.

• 한국정보처리학회논문지
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• 제3권6호
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• pp.1493-1505
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• 1996

인터네트의 사용의 급격한 증가와 멀티미디어 정보의 보편화에 따라 이를 이용하 는 다양한 전자우편 프로토콜들이 나타나고 있다. 이러한 전자우편의 상용화와 전자 우편을 통한 개인정보 및 주요정보 보호를 위해서는 암호화 기법을 이용한 보안기능 이 필수적이다. 논 논문은 멀티미디어를 지원하는 인터네트 전자우편(MIME;Multi -Purpose Internet Mail Extension)에 보안 기능을 추가한 MOSS(MIME Object Security Service)의 효과적 처리에 필요한 라이브러리 함수개발에 관하여 기술하였 다. 이를 위하여 MINE구조로 나타나는 암호화와 복호화, 전자결재 및 검증등의 보안 기능 처리를 위한 MOSS의 특성 및 구조에 관하여 기술하고 이를 실질적으로 개발하기 위한 자료구조 및 필요한 함수들을 정의하였으며 개발시 고려하여야 할 사항들에 대 하여 기술하였다.

• 한국의류학회지
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• 제31권7호
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• pp.1030-1041
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• 2007

The purposes of this study were to identify the sub-dimensions of consumers' attitude and types of loyalty behavior toward fashion brands, and to analyze the influence of consumers' brand attitudes on brand loyalty. A survey was conducted with the questionnaire for consumer's buying experience of fashion brand. A total of 350 questionnaires were distributed, and 341 complete responses were analyzed. Exploratory factor analysis, confirmatory factor analysis, path analysis, and multi-group analysis were used for data analysis. The results of this study were as follows. First, the consumers' brand attitude consisted of four sub-dimensions of affective, familiar, value-expressive, and utilitarian attitude. Second, each brand attitude significantly influenced the brand loyalty behavior(single-brand loyalty, multi-brand loyalty, and brand switching). Finally, the causal relationship between brand attitude and brand loyalty differed by consumer's variety seeking tendency.