• 응용통계연구
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• 제26권6호
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• pp.1053-1061
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• 2013

본 논문은, 장기기억 특성과 이분산성을 고려한 인터넷 트래픽 예측 모형을 제안하고자 한다. 트래픽 과부하를 대비하기 위해서, 트래픽 용량은 트래픽의 예측치와 트래픽의 변동 크기에 따라 트래픽의 최대용량을 설정하여야 한다. 이를 위하여 교내 트래픽 자료 중 교내로 들어오는 트래픽과 교외로 나가는 트래픽에 이분산성과 장기기억 모형의 유용성을 확인하였다. 이에 대하여 AR-GARCH 모형, ARMA-GARCH 모형과 장기기억모형인 Fractional ARIMA와 장기기억과 이분산성을 고려한 Fractional ARMA-GARCH 모형을 적용하여 모형의 예측성능을 비교하였다.

• 한국컴퓨터정보학회논문지
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• 제28권5호
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• pp.155-161
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• 2023

우리나라 수출의 97.5%, 수입의 87.2%가 해상운송으로 이뤄지며 항만이 한국 경제의 중요한 구성요소이다. 이러한 항만의 효율적인 운영을 위해서는 항만 물동량의 단기 예측을 통해 개선시킬 수가 있으며 과학적인 연구방법이 필요하다. 이전 연구는 주로 장기예측을 기반으로 대규모 인프라투자를 위한 연구에 중점을 두었으며 컨테이너 항만물동량에만 집중한 측면이 크다. 본 연구는 국내 대표적인 석유항만인 울산항의 석유 및 가스화물 물동량에 대한 단기 예측을 수행하였으며 딥러닝 모델인 LSTM(Long Short Term Memory) 모델을 사용하여 RMSE기준으로 예측성능을 확인하였다. 본 연구의 결과는 석유 및 가스화물 물동량 수요 예측의 정확도를 높여 항만 운영의 효율성을 개선하는 근거가 될 수 있을 것으로 기대된다. 또한 기존 연구의 한계로 컨테이너 항만 물동량뿐만 아니라 석유 및 가스화물 물동량 예측에도 LSTM의 활용할 수 있다는 가능성을 확인할 수 있으며 향후 추가 연구를 통해 일반화가 가능할 것으로 기대된다.

• Journal of the Optical Society of Korea
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• 제6권4호
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• pp.172-179
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• 2002

Like the conventional digital storage systems, volume holographic memory can be deteriorated by burst errors due to its high-density storage characteristics. These burst errors are used byoptical defects such as scratches, dust particles, etc. and are two-dimensional in a data page. To deal with these errors, we introduce some concepts for describing them and propose efficient two- dimensional interleaving schemes. The schemes are two-dimensional lattices of an error-correction code word and have equilateral triangular and square structures. Using these structures, we can minimize the number of code words that are interleaved and improve the efficiency of the system. For large size burst errors, the efficient interleaving structure is an equilateral triangular lattice. However, for some small size burst errors, it is reduced to a square lattice.

• 열처리공학회지
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• 제17권6호
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• pp.342-345
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• 2004

In this work, a new method of measuring volume fraction of deformation-induced ${\varepsilon}$ martensite is proposed using endothermic heat on reverse transformation. As grain size increases, the amount of ${\varepsilon}$ martensite forming on cooling increases. However, with a decrease in grain size, more ${\varepsilon}$ is induced by deformation, improving shape memory effect.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.72-73
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• 2003

In volume holographic memory (VHM), two-dimensional data array (i.e. data page) is used for the recording and the retrieving process with the aid of spatial light modulator (SLM) and CCD camera. Due to this two-dimensional parallel data processing, burst errors in this system also have two-dimensional characteristics in a data page domain. In this paper, we present a channel model of the burst noise and burst error for the VHM system using disk type recording media. (omitted)

• 전자공학회논문지D
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• 제35D권12호
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• pp.92-98
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• 1998

본 논문에서는 기준빔의 입사각을 AOD(acoustic-optic device)를 사용하여 전자적으로 제어함으로써 정확한 어드레스와 빠른 엑세스 시간(10㎲)을 갖는 각다중화 고밀도 체적 홀로그래픽 메모리 시스템을 구현하였다. 물체빔의 주파수 보상이 불필요한 AOD 각다중화 메모리 시스템을 설계하고, AOD의 편향각을 렌즈조합으로 확장하여 저장용량을 6배 증가시켜 1㎤의 Fe:LiNbO₃ 광굴절 매질에 51개의 이미지를 저장하는 실험을 수행하였다.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.53-62
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• 1998

A simple analytical and finite element(FE) models are used to study the tensile properties of Al matrix composite with continuous TiNi fibers. The effects of residual stresses caused by the shape momory effects have been compared for various mechanical behaviors as a function of fiber volume fraction and degree of pre-strain and fiber configurations. It is found that both the back stress in the Al matrix induced by stiffness of TiNi fibers and the compressive stress in the matrix are caused of the strengthening mechanisms. Both theoretical and analytical results show quite good agreement and are closed to the experimental data except in high volume content.

• 한국생산제조학회지
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• 제8권5호
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• pp.42-46
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• 1999

The strengthening of a metal matrix composite(MMC) by the shape memory effect(SME) of dispersed TiNi particles was theoretically studied. An analytical model was constructed for the prediction of the average residual stress(<$\delta$>m) on the base of the Eshelby's equivalent inclusion method. The analysis was performed on the TiNi particle/Al metal matrix composites with varying volume fractions and prestrains of the particle. The residual stress caused by the shape memory of predeformed fillers has been predicted to contribute significantly to the strengthening of this composite.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.687-691
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• 2001

Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate mechanical properties. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of pre-strain by using experimental and finite element analysis, and both cases showed that the tensile stress at 363K was higher than that of the room temperature. Especially, the tensile stress of this composite increases with increasing the amount of pre-strain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being pre-strained.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1609-1618
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• 1997

Thermo-mechanical behaviors of polymer matrix composite(PMC) with continuous TiNi fiber are studied using theoretical analysis with 1-D analytical model and numerical analysis with 2-D multi-fiber finite element(FE) model. It is found that both compressive stress in matrix and tensile stress in TiNi fiber are the source of strengthening mechanisms and thermo-mechanical coupling. Thermal expansion of continuous TiNi fiber reinforced PMC has been compared with various mechanical behaviors as a function of fiber volume fraction, degree of pre-strain and modulus ratio between TiNi fiber and polymer matrix. Based on the concept of so-called shape memory composite(SMC) with a permanent shape memory effect, the critical modulus ratio is determined to obtain a smart composite with no or minimum thermal deformation. The critical modulus ratio should be a major factor for design and manufacturing of SMC.