• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.297-306
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• 2014

The paper presents the numerical analysis of wave run-up over rubble-mound breakwaters covered by antifer units using a technique integrating Computer-Aided Design (CAD) and Computational Fluid Dynamics (CFD) software. Direct application of Navier-Stokes equations within armour blocks, is used to provide a more reliable approach to simulate wave run-up over breakwaters. A well-tested Reynolds-averaged Navier-Stokes (RANS) Volume of Fluid (VOF) code (Flow-3D) was adopted for CFD computations. The computed results were compared with experimental data to check the validity of the model. Numerical results showed that the direct three dimensional (3D) simulation method can deliver accurate results for wave run-up over rubble mound breakwaters. The results showed that the placement pattern of antifer units had a great impact on values of wave run-up so that by changing the placement pattern from regular to double pyramid can reduce the wave run-up by approximately 30%. Analysis was done to investigate the influences of surface roughness, energy dissipation in the pores of the armour layer and reduced wave run-up due to inflow into the armour and stone layer.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.5-9
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• 2007

The construction method for Foamed-Concrete has not been important due to following process of construction work. However, according to the code about enhance of energy saving design policy and impact noise, noised isolation has been used in construction site so that the resistance for cracking and capability for insulating of Foamed-Concrete has been required. Therefore, new alternatives are demanded. Optimum mixing design, which can get the improvement of insulation and resistance of crack for Foamed-Concrete adding EVA chip, was derived and also the device, applying to construction site, was invented to equalize quality. This device can measure quantity of all input and placement, and show up the sum of placement and mixing design on a touch screen. This valuable construction method is friendly environment and recycling method because of using EVA chip, by-product of an EVA insole scrap burned or embedded, as a light-weight aggregate.

• Smart Structures and Systems
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• 제16권2호
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• pp.243-262
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• 2015

Optimal sensor placement (OSP) is a critical issue in construction and implementation of a sophisticated structural health monitoring (SHM) system. The uncertainties in the identified structural parameters based on the measured data may dramatically reduce the reliability of the condition evaluation results. In this paper, the information entropy, which provides an uncertainty metric for the identified structural parameters, is adopted as the performance measure for a sensor configuration, and the OSP problem is formulated as the multi-objective optimization problem of extracting the Pareto optimal sensor configurations that simultaneously minimize the appropriately defined information entropy indices. The nondirective movement glowworm swarm optimization (NMGSO) algorithm (based on the basic glowworm swarm optimization (GSO) algorithm) is proposed for identifying the effective Pareto optimal sensor configurations. The one-dimensional binary coding system is introduced to code the glowworms instead of the real vector coding method. The Hamming distance is employed to describe the divergence of different glowworms. The luciferin level of the glowworm is defined as a function of the rank value (RV) and the crowding distance (CD), which are deduced by non-dominated sorting. In addition, nondirective movement is developed to relocate the glowworms. A numerical simulation of a long-span suspension bridge is performed to demonstrate the effectiveness of the NMGSO algorithm. The results indicate that the NMGSO algorithm is capable of capturing the Pareto optimal sensor configurations with high accuracy and efficiency.

• Smart Structures and Systems
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• 제15권5호
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• pp.1373-1392
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• 2015

Placing sensors at appropriate locations is an important task in the design of an efficient structural health monitoring (SHM) system for a large-scale civil structure. In this paper, a hybrid optimization algorithm called virus monkey algorithm (VMA) based on the virus theory of evolution is proposed to seek the optimal placement of sensors. Firstly, the dual-structure coding method is adopted instead of binary coding method to code the solution. Then, the VMA is designed to incorporate two populations, a monkey population and a virus population, enabling the horizontal propagation between the monkey and virus individuals and the vertical inheritance of monkey's position information from the previous to following position. Correspondingly, the monkey population in this paper is divided into the superior and inferior monkey populations, and the virus population is divided into the serious and slight virus populations. The serious virus is used to infect the inferior monkey to make it escape from the local optima, while the slight virus is adopted to infect the superior monkey to let it find a better result in the nearby area. This kind of novel virus infection operator enables the coevolution of monkey and virus populations. Finally, the effectiveness of the proposed VMA is demonstrated by designing the sensor network of the Canton Tower, the tallest TV Tower in China. Results show that innovations in the VMA proposed in this paper can improve the convergence of algorithm compared with the original monkey algorithm (MA).

• 대한전자공학회논문지SD
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• 제43권9호
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• pp.31-37
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• 2006

Low Density Parity Check (LDPC) code는 최근 그 우수한 성능으로 인하여 4세대 무선 이동 통신용 채널 코딩으로 주목받고 있다. 또한 유럽 디지털 위성 방송 규격인 DVB-S2는 LDPC 코드를 채널 코딩방식으로 채택하였다. 본 논문에서는 인코더와 디코더 양쪽 모두 효율적으로 하드웨어 구현이 가능한 hybrid H-matrix 구조를 이용한 DVB-S2 LDPC 복호기 구조를 제안한다. Hybrid H-matrix는 semi-random 방식과 partly parallel 방식을 결합하여 부호기와 복호기를 동시에 효율적으로 구현할 수 있다. 제안된 복호기 구조에서는 다양한 코드율에 사용되는 Variable Node processor Unit (VNU)을 재사용하기 위한 새로운 VNU와 최적화된 블록 메모리 배치 방법을 이용하였다. 제안된 구조를 이용하여 코드율 1/2의 DVB-S2 LDPC 복호기를 설계하였고 그 결과를 기존의 복호기와 비교하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.27-33
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• 1999

This paper describes a new algorithm for irregular shapes allocation (known as nesting) and cutting path optimization, both implemented in PC-based software with graphic user interface (GUI). Main characteristic of the nesting W is that it deals with only vertices of Placed Pieces to reduce calculation time and for effective allocation. And the other characteristic of the nesting program is that every parts are grouped with respect to their areas and placed along the column of placement region. The cutting paths can be determined by an optimization method called simulated annealing. It was shown that the developed code is superior to other previous nesting H in elapsed time and waste ratio.

• Smart Structures and Systems
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• 제17권5호
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• pp.725-742
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• 2016

This paper is focused on stiffness ratio effect and a new method to specify the best pattern of piezoelectric patches placement around a hole in a plate under tension to reduce the stress concentration factor. To investigate the stiffness ratio effect, some different values greater and less than unity are considered. Then a python code is developed by using particle swarm optimization algorithm to specify the best locations of piezoelectric actuators around the hole for each stiffness ratio. The results show that, there is a line called "reference line" for each plate with a hole under tension, which can guide the location of actuator patches in plate to have the maximum stress concentration reduction. The reference line also specifies that actuators should be located horizontally or vertically. This reference line is located at an angle of about 65 degrees from the stress line in plate. Finally two experimental tests for two different locations of the patches with various voltages are carried out for validation of the results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1715-1719
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• 2004

An in-house supersonic ejector was designed to ensure low pressure and high speed scavenging of resonating cavity of chemical lasers. For given primary flow condition, 100g/s secondary mass flow rate was observed at the design pressure. Performance validation of a supersonic ejector system along with an investigation of effects of supersonic diffuser was conducted. Placement of diffuser at the secondary inlet further reduced diffuser upstream pressure to 1/4-1/5 relieving the local to the primary supply unit. In order to increase the secondary flow, we put two ejectors capable of removing 50g/s each of secondary flows together to deal with higher mass flow. Test of the parallel unit demonstrated the secondary flow rate was proportional to the numbers of individual units that were brought together. Additionally, flow calculations with a commercial code were carried out in every case of experiment and compared with results.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 한국컴퓨터종합학술대회 논문집 Vol.32 No.1 (A)
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• pp.784-786
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• 2005

SPM (Scratch-Pad Memory)을 위한 코드 배치 기법과 demand paging기법을 Post pass optimizer를 사용하여 구현한다. 코드 배치 문제는 ILP (Integer Linear Programming) 문제로 변환하여 해결한다. 최적 화기는 ILP 해답의 질을 높이기 위해 응용 프로그램의 프로파일 정보를 사용하고, 코드로부터 natural loop을 추출한다. 또한 SPM을 사용하여 demand paging을 할수 있도록 추가 코드를 삽입한다. 이 기법을 사용해 6개의 내장형 응용 프로그램을 실험하였고, 프로그램 크기의 $20\%$에 해당하는 SPM에 대해 전력 소모는 $75.9\%$로 감소하였고 성능은 $54.5\%$ 증가하였다.

• 항공우주정책ㆍ법학회지
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• 제27권2호
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• pp.211-241
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• 2012

유럽연합(European Union: EU)이 2012년 6월 유엔의 우주의평화적이용위원회(COPUOS) 제 55차 회기에서 공식 제기한 우주활동의 국제 행동규범안(Draft International Code of Conduct for Outer Space Activities)은 그간 우주에서의 국가 활동 규범에 대한 미비한 요소들을 제시한 내용으로서 국제사회의 관심을 끌기에 충분한 내용이다. 현재 우주에서의 미비한 질서는 군비경쟁 금지, 우주쓰레기 경감 등을 통한 우주의 안전과 안보를 위한 지침, 그리고 우주활동의 정보를 참여 국가 간 교환하는 것이라고 할 수 있는 바, EU의 상기 제안은 여사한 문제들에 대한 행동 강령을 정한 것으로서 주목되는 내용이다. 2008년 말부터 시작된 EU의 제안 활동은 그간 일부 우주활동 국가들, 특히 미국과의 비공식 접촉을 통하여 접촉대상국들의 의견도 반영한 가운데 2013년 채택을 목표로 하는 자발적 이행 규범으로서 강제력을 가지고 있지는 않지만 미국은 우주에서의 군축 관련 규범 제정의 필요성에 탄력을 제공하는 계기가 될 가능성에 우려하는 가운데 현재는 방관하고 있는 입장으로 보인다. 이러한 미국의 입장은 우주에서 전략적 우위를 점하고 있다는 자국의 이익이 군축에 관한 규범의 제정으로 손상될 수 있다는 판단을 근거로 하고 있다. 이에 따라 미국은 유엔 총회에서 우주에서의 군비경쟁 방지(PAROS)에 관한 결의에 반대하고 군축회의(Conference on Disarmament: CD)에서 오랫동안 논의되어 왔던 우주에서의 군축을 촉구하는 논의의 장을 마련하는 것에 반대하여 왔다. 중국과 러시아는 2008년 우주에서의 군축에 관한 PPWT (Treaty on Prevention of the Placement of Weapons in Outer Space and of the Threat or Use of Force against Outer Space Objects)채택을 제안하였는 바, EU의 제안은 자신들이 제안한 PPWT의 추력을 저상시키는 내용이 되기 때문에 불편한 심정으로서 역시 소극적인 입장이다. 한편, 미국이 상기 입장의 연장선 상에서 PPWT에 반대 입장을 취하는 것은 이해하기 어렵지 않다. EU의 행동규범안은 주요 우주대국의 군사전략적 측면에서의 이해관계 때문에 그 장래가 명확치 않으나 우주쓰레기의 경감을 위하여 노력하고 우주활동의 정보를 상호교환하면서 우주에서의 안전과 안보를 보장을 통하여 가능한 우주의 평화적 이용과 탐사라는 기본 명제를 극대화 시키는 효과를 가져오는 것으로서 매우 바람직한 조치로 간주된다. 단, 동 규범안은 참여 국가들간의 협조와 연락업무를 수행하기 위하여 상설기구를 설치하도록 되어있지만 이는 기존 조직인 유엔외기권사무소(UN Office for Outer Space Affairs)가 담당하도록 할 경우 효율과 경제를 도모할 수 있을 것이다. 동 규범안에 대한 추후 구체 협상 시 여사한 내용도 논의될 것으로 보지만 EU의 우주활동의 안전과 안보에 관한 조치는 환경문제에서와 같이 국제사회를 이끌어가는 또 하나의 의미있는 기여로 평가받아야 한다.