• 한국정밀공학회지
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• 제8권1호
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• pp.50-62
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• 1991

In this study, the bending and twisting stiffnesses of corrugated plate are analyzed by applying equivalent idea. And the natural frequencies as an application example of the stiffnesses are analyzed by considering corrugated plate as orthotropic plate. The validity of analytic results is examined by comparing with experimental results by fast Fourier transformation analyzer.

• 대한수학회논문집
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• 제15권2호
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• pp.357-370
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• 2000

In [6], Cheng-Ye You gave a condition equivalent to the Nielsen number product formula for fiber maps. And Jerzy Jezierski also gave a similar condition for coincidences of fiber maps. The main purpose of this paper is to find the condition for which holds the product formula for Nielsen root numbers N(f;a) = N(f;a) N(fb;a).

• 한국전산구조공학회논문집
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• 제26권2호
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• pp.165-171
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• 2013

동하중을 고려하는 구조해석은 전산자원과 시간측면에서 상당한 어려움이 따르기 때문에 외력을 이상적인 정하중으로 가정하는 것이 일반적이다. 그러나 정하중 조건으로 해석된 결과는 구조물의 안전설계 측면에서 충분한 신뢰를 주기 어렵다. 최근에는, 동하중의 영향을 받는 구조물의 효과적인 구조해석을 위해 동하중을 등가정하중으로 변환하는 기법이 제안되어 왔다. 이 기법은 최적화를 통해 구속조건을 만족하는 최소의 등가정하중을 구하는데, 구속조건은 임계시간의 변위를 사용하고, 등가정하중 분포 자유도는 경험적으로 선정하여 왔다. 그러나 안전설계 관점에서는 응력 구속조건을 적용하는 것이 타당하며, 경험적 자유도 선정은 몇 개의 자유도에 과도한 하중이 부과되거나 구조물의 거동에 영향력이 없는 자유도들이 선정될 가능성이 있다. 본 연구에서는 등가응력 구속조건을 고려하는 등가정하중 최적화 방법을 제안하고, 축소시스템 개념을 도입한 주자유도, 구속조건 요소 자유도, 외부하중 자유도로 구성되는 등가정하중 분포 자유도의 구성방법을 제안한다. 수치예제에서는 제안된 방법으로 구해진 등가정하중을 사용하여 등가응력을 구하고 동하중 해석 결과와 비교함으로써 제안된 방법을 통한 구조해석 방법이 구조안전성 측면에서 타당함을 보인다.

• Composites Research
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• 제17권5호
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• pp.54-60
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• 2004

복합재의 사전변형률과 형상기억합금의 형상기억효과를 유발하는 형상기억합금의 상변화량과의 관계를 예측하기 위하여 Eshelby의 등가개재물법과 Mori-Tanaka의 평균장이론을 이용한 새로운 3차원 모델을 제안하였다. 복합재 모델은 가공경화 현상을 갖는 알루미늄을 모재로, 단섬유 TiNi 형상기억합금을 강화재로 사용하였다. 모델 해석에 의하면 사전 변형률이 지극히 작은 영역에서는 사전변형률이 모두 강화재의 형상기억 효과를 유발하고, 이 보다 큰 영역에서 사전 변형률은 강화재의 형상기억 효과와 모재의 소성변형에 의한 것으로 나타났다. 이러한 복합재의 강화기구는 모재의 가공경화 현상과 형상기억 효과에 의한 항복응력 증가를 분리하여 제시되어야 한다.

• Structural Engineering and Mechanics
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• 제90권3호
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• pp.313-323
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• 2024

Most of existing buildings in Mexico City are made of reinforced concrete (RC), however, it has been shown that they are very susceptible to narrow-band long duration ground motions. In recent years, the use of dual systems composed by Buckling Restrained Braces (BRB) has increased due to its high energy dissipation capacity under reversible cyclical loads. Therefore, in this work the behavior of RC buildings with BRB is studied in order to know their performance, specifically, the energy distribution through height and response transformation factors between the RC and simplified systems are estimated. For this propose, seven RC buildings with different heights were designed according to the Mexico City Seismic Design Provisions (MCSDP), in addition, equivalent single degree of freedom (SDOF) systems were obtained. Incremental dynamic analyses on the buildings under 30 narrow-band ground motions in order to compute the relationship between normalized hysteretic energy, maximum inter-story drift and roof displacement demands were performed. The results shown that the entire structural frames participate in energy dissipation and their distribution is independent of the global ductility. The results let propose energy distribution equations through height. Finally, response transformation factors between the SDOF and multi degree of freedom (MDOF) systems were developed aimed to propose a new energy-based approach of BRB reinforced concrete buildings.

• 한국항해항만학회지
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• 제30권2호
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• pp.167-172
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• 2006

In this paper, the issue of blind detection of Alamouti-type differential space-time (ST) ${\pi}/2$-shifted BPSK modulation in static Rayleigh fading channels is considered. We introduce a novel transformation to the received signal from each receiver antenna such that this binary ST modulation, which has a second-order transmit-diversity, is equivalent to QPSK modulation with second-order receive-diversity. The pre-detection combining of the result of transformation allows us to apply a low complexity detection technique specifically designed for receive-diversity, namely, scalar multiple-symbol differential detection (MSDD). With receiver complexity proportional to the observation window length, our receiver can achieve the performance 1.5dB better than that of conventional differential detection ST and 0.5dB worse than that qf a coherent maximum ratio combining receiver (with differential decoding) approximately.

• 한국의류산업학회지
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• 제23권3호
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• pp.380-389
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• 2021

This study aimed to reveal the perceptions and trends of digital fashion technology through an informational approach. A big data analysis was conducted after collecting the text shown in a web environment from April 2019 to April 2021. Key words were derived through text mining analysis and network analysis, and the structure of perception of digital fashion technology was identified. Using textoms, we collected 8144 texts after data refinement, conducted a frequency of emergence and central component analysis, and visualized the results with word cloud and N-gram. The frequency of appearance also generated matrices with the top 70 words, and a structural equivalent analysis was performed. The results were presented with network visualizations and dendrograms. Fashion, digital, and technology were the most frequently mentioned topics, and the frequencies of platform, digital transformation, and start-ups were also high. Through clustering, four clusters of marketing were formed using fashion, digital technology, startups, and augmented reality/virtual reality technology. Future research on startups and smart factories with technologies based on stable platforms is needed. The results of this study contribute to increasing the fashion industry's knowledge on digital fashion technology and can be used as a foundational study for the development of research on related topics.

• Composites Research
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• 제17권6호
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• pp.8-13
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• 2004

Eshelby의 등가개재물범과 Mori-Tanaka의 평균장 이론을 이용하여 다공성 형상기억합금에 대한 새로운 3차원 응력-변형률 모델을 제안하였다. 12%의 기공도를 갖는 Ni-Ti 형상기억합금에 대한 압축실험으로부터 구한 응력-변형률 선도와 본 연구에서 제안한 모델링에 의한 응력-변형률 관계를 비교한 결과 잘 일치함을 알 수 있었다. 기존의 다른 연구에서는 대부분 상변태 구간이 선형적으로 예측되었지만 본 연구에서는 비선형으로 예측되어 실험결과를 보다 잘 모사할 수 있었다.

• 대한기계학회논문집A
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• 제29권3호
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• pp.369-386
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• 2005

Various aspects of structural optimization techniques under transient loads are extensively reviewed. The main themes of the paper are treatment of time dependent constraints, calculation of design sensitivity, and approximation. Each subject is reviewed with the corresponding papers that have been published since 1970s. The treatment of time dependent constraints in both the direct method and the transformation method is discussed. Two ways of calculating design sensitivity of a structure under transient loads are discussed - direct differentiation method and adjoint variable method. The approximation concept mainly focuses on re- sponse surface method in crashworthiness and local approximation with the intermediate variable Especially, as an approximated optimization technique, Equivalent Static Load method which takes advantage of the well-established static response optimization technique is introduced. And as an application area of dynamic response optimization technique, the structural optimization in flexible multibody dynamic systems is re- viewed in the viewpoint of the above three themes

• 대한기계학회논문집A
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• 제20권12호
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• pp.3767-3781
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• 1996

Generally, dynamic loads are applied to real structures. Since the analysis with the dynamic load is extremely difficult, static loads are utilized by proper conversions of the dynamic loads. The dynamic loads are usually converted ot static loads by safety foactors of experiences. However, it may increase weight and decrease reliability. In this study, a method is proposed for the conversion process. An equivalent static load is calculated ot generate a same maximum displacement. The method is verified through numerical tests on a spring-mass systems of one and multi degrees-of freedom. It has been found that the duration time of the loads and the natural frequencies of the structures are critical in the conversion process. A road arem is a self-propelled howizer is selected for the application of the proposed method. The shape of the road arm is optimized under the converted static loads.