• 한국소음진동공학회논문집
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• 제22권8호
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• pp.800-807
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• 2012

In this paper, radiation efficiency of the plate surround by an infinite rigid baffle is studied. The plate is simply supported and one side is in contact with air, while other side with water. The pressure and normal velocity over the plate surface are assumed as modal summations, from which a set of linear equations is obtained for fluid-structure coupled problem. It is shown that neglect of the cross modes results in overestimation of the radiation efficiency specifically for mid-frequency ranges. Based on the fact that the responses are mainly determined from the first few cross modes in addition to the diagonal terms, a new algorithm is proposed, where banded matrix is iteratively solved in computing radiation efficiency. In numerical examples, it is found that radiation efficiency obtained from banded matrix is in excellent agreement with the one from the full matrix, while computing time is significantly reduced. It is also found that as frequency grows larger, radiation efficiency considering only diagonal terms is a good approximation.

• 품질경영학회지
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• 제32권2호
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• pp.77-92
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• 2004

It is difficult but very necessary to measure the productivity of container terminals as logistics service provider. It is meaningful to find the appropriate inputs and outputs of the logistics service delivery systems and to measure the relationship between these inputs and outputs. This study proposes a model of evaluating the efficiency of container terminals. The evaluation consists of three phases. First, DEA(Data Envelopment Analysis) phase, determines the efficiency score and weights of DMUs(Decision Making Unit). This phase performs through four steps : selection of DMU, selection of DEA model, determination of input and output factors, calculation of efficiency score and weights for each DMU. Secondly, CEM (Cross Evaluation Model) phase, is to calculate the cross-efficiency scores of DMUs. This phase performs through three steps: selection of CEM, determination of cross-efficiency score for each DMU and development of cross-efficiency matrix. Finally, average cross-efficiency analysis phase is to compute the average cross-efficiency score. The proposed model discriminates among DMUs and ranks DMUs, whether they are efficient or inefficient.

• 통합자연과학논문집
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• 제5권2호
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• pp.135-138
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• 2012

The reduction of efficiency of missing observations on complete diallel cross designs are examined. we studies robustness of optimal block designs for estimating general combining ability against loss of missing observations in diallel cross. A-efficiencies suggest that these designs are fairly robust. Simple g-inverses may be found for the information matrices of the line effects which allow evaluation of expressions for the variances of the differences between the pairs of line effects with missing observations. we numerically calculate the reduction of efficiency for estimating general combining ability against loss of missing observations in diallel cross.

• Structural Engineering and Mechanics
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• 제11권4호
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• pp.423-442
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• 2001

This paper presents a method of elastic-plastic analysis for planar steel frames that provides the accuracy of distributed plasticity methods with the computational efficiency that is greater than that of distributed plasticity methods but less than that of plastic-hinge based methods. This method accounts for the effect of spread of plasticity accurately without discretization through the cross-section of a beam-column element, which is achieved by the following procedures. First, nonlinear equations describing the relationships between generalized stresses and strains of the cross-section are derived analytically. Next, nonlinear force-deformation relationships for the beam-column element are obtained through lengthwise integration of the generalized strains. Elastic-plastic flexibility coefficients are then calculated by differentiating the above element force-deformation relationships. Finally, an elastic-plastic stiffness matrix is obtained by making use of the flexibility-stiffness transformation. Adding the conventional geometric stiffness matrix to the elastic-plastic stiffness matrix results in the tangent stiffness matrix, which can readily be used to evaluate the load carrying capacity of steel frames following standard nonlinear analysis procedures. The accuracy of the proposed method is verified by several examples that are sensitive to the effect of spread of plasticity.

• 한국인터넷방송통신학회논문지
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• 제16권3호
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• pp.109-113
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• 2016

본 논문에서는 LED 조명 모듈의 소비전력 절감, 램프의 수명 및 열효율 과 점등 제어 효율성을 높인 다윗 스타 마방진 이용한 효율적인 LED 제어 알고리즘을 제안하다. 기존의 마방진 알고리즘 이용한 점등 방식은 LED의 점등 시간이 줄어들고 교차 점등되기 때문에 그만큼의 발열이 줄어들어 LED의 효율을 높일 수 있었으나 점등 제어를 하는데 한계를 가지고 있다. 제안하는 알고리즘을 적용할 경우에는 LED 조명 모듈의 소비전력 절감과 수명 및 열효율 높이는 동시에 LED의 점등 제어의 효율성을 높일 수 있다. 본 논문이 제안하는 알고리즘은 LED Matrix에 변형 마방진을 이용하여 12개의 구역으로 나누어 완전대칭 되는 패턴을 일정시간 간격으로 이동, 회전 및 반전 기법을 교차 수행하여 패턴을 점등을 하게 된다. 본 논문이 제안하는 알고리즘을 수행하여 기존의 마방진을 이용한 점등 방식과 비교한 결과, 조명의 광속과 소비전력 그리고 발열량의 효율성은 기존 마방진을 이용한 LED 점등방식과 동일하고 제어의 효율성을 높일 수 있었다.

• 무역학회지
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• 제41권3호
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• pp.27-42
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• 2016

본 논문에서는 아시아 13개 항만의 2009년, 2010년, 2013년의 자료와, 3개의 투입요소(수심, 총면적 크레인 수)와 1개의 산출요소(컨테이너화물 총 처리량)를 이용하여 교차효율성모형과 메타프론티어 분석방법으로 개별효율성과 그룹효율성, 기술 갭을 측정함으로써, 교차효율성모형에 의해서 측정된 클러스터링이 국내항만들의 메타효율성을 증진시켰는지를 실증적으로 검증하였다. 실증분석의 주요한 결과는 다음과 같다. 첫째, 2010년과 2013년의 경우에는 부산, 인천, 광양항만 모두 그룹효율성이 증가하였다. 둘째, 중국의 항만들이 국내 항만들에 비해서 메타효율성과 그룹효율성 측면에서 더 높은 것으로 나타났다. 셋째, 기술갭 측면에서 보았을 때, 광양항의 기술 격차의 왜곡이 부산항이나 인천항에 비해서 작은 것으로 나타났다. 넷째, 광양항은 2009년(닝보, 칭타오, 토쿄, 카오슝항)과 2013년(두바이항)과 클러스터링을 통해서 효율성을 증진시킬 수 있었다. 부산항은 2010년에 2그룹, 2013년에 1그룹항만, 인천항은 2010년과 2013년에 2그룹 항만들과 클러스터링을 통해서 효율성을 증진시킬 수 있었다. 다섯째, 교차효율성 모형과 메타효율성 분석방법을 통해서 부산, 인천, 광양항은 효율성을 증진시킬 수 있다는 것이 실증적으로 검증되었다. 본 논문의 정책적인 함의는 본 연구에서 실증적으로 검증된 아시아 항만들 간의 클러스터링 방법[부산항은 홍콩, 상하이, 싱가포르항, 인천항과 광양항은 칭타오, 나고야, 닝보, 토쿄, 카오슝항과 클러스터링]을 국내항만들이 적극적으로 정책적인 도입을 해야만 한다.

• 상하수도학회지
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• 제22권4호
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• pp.437-444
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• 2008

Many other countries have investigated the new backwash water treatment process to save the existing water resource. There are various methods for reusing backwash water, but the membrane system has received the most interest for its efficiency. The objective of this study was to certify the application of membrane filtration system for the backwash water treatment. The experiment equipment was composed of Lab scale tubular membrane filtration system. Generally, cross-flow operation mode is used in the tubular membrane system but cross-flow operation mode demands high electric cost mainly for the pump energy. So to cut off electric cost, dead-end operation mode was used in this experiment. Filtration and bleed operation cycle was used in this membrane system. Backwash water was concentrated during the filtration process and when backwash water reached our target suspended solid concentration, it was discharged from this system. For efficient operation of filtration and bleed, mathematical matrix was drawn up and with this matrix we could simulate various sets of filtration and bleed time.

• Computers and Concrete
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• 제29권 6호
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• pp.375-391
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• 2022

This paper examined the impact of the cross-sectional structure on the structural results under different loading conditions of reinforced concrete (RC) members' management limited in Carbon Fiber Reinforced Polymers (CFRP). The mechanical properties of CFRC was investigated, then, totally 32 samples were examined. Test parameters included the cross-sectional shape as square, rectangular and circular with two various aspect rates and loading statues. The loading involved concentrated loading, eccentric loading with a ratio of 0.46 to 0.6 and pure bending. The results of the test revealed that the CFRP increased ductility and load during concentrated processing. A cross sectional shape from 23 to 44 percent was increased in load capacity and from 250 to 350 percent increase in axial deformation in rectangular and circular sections respectively, affecting greatly the accomplishment of load capacity and ductility of the concentrated members. Two Artificial Intelligence Models as Extreme Learning Machine (ELM) and Particle Swarm Optimization (PSO) were used to estimating the tensile and flexural strength of specimen. On the basis of the performance from RMSE and RSQR, C-Shape CFRC was greater tensile and flexural strength than any other FRP composite design. Because of the mechanical anchorage into the matrix, C-shaped CFRCC was noted to have greater fiber-matrix interfacial adhesive strength. However, with the increase of the aspect ratio and fiber volume fraction, the compressive strength of CFRCC was reduced. This possibly was due to the fact that during the blending of each fiber, the volume of air input was increased. In addition, by adding silica fumed to composites, the tensile and flexural strength of CFRCC is greatly improved.

• Wind and Structures
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• 제9권3호
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• pp.231-243
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• 2006

An improvement to the spectral representation algorithm for the simulation of wind velocity fields on large scale structures is proposed in this paper. The method proposed by Deodatis (1996) serves as the basis of the improved algorithm. Firstly, an interpolation approximation is introduced to simplify the computation of the lower triangular matrix with the Cholesky decomposition of the cross-spectral density (CSD) matrix, since each element of the triangular matrix varies continuously with the wind spectra frequency. Fast Fourier Transform (FFT) technique is used to further enhance the efficiency of computation. Secondly, as an alternative spectral representation, the vectors of the triangular matrix in the Deodatis formula are replaced using an appropriate number of eigenvectors with the spectral decomposition of the CSD matrix. Lastly, a turbulent wind velocity field through a vertical plane on a long-span bridge (span-wise) is simulated to illustrate the proposed schemes. It is noted that the proposed schemes require less computer memory and are more efficiently simulated than that obtained using the existing traditional method. Furthermore, the reliability of the interpolation approximation in the simulation of wind velocity field is confirmed.

• 로봇학회논문지
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• 제4권2호
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• pp.155-162
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• 2009

A main distributing frame(MDF) is an interface unit that is used to connect office equipment cables in a telephone company to subscriber cables. Until now, there is no automated switching system for MDFs in Korea. Manual handling of an MDF has some drawbacks; It is time-consuming, very cumbersome, and expensive. It also makes maintenance hard. An automated main distributing frame system is proposed and commercialized in Japan. In that system, a robot gripper inserts connecting pins into the cross point holes of a matrix board, which reveals several disadvantages in the aspects of space, maintenance, fault tolerance, and economical efficiency. This paper describes a newly developed robotic switch board system for MDFs. In the developed system, switches are placed at the cross point of a matrix board. There is one robot in between two switch units, so one robot deals with two switch units. In the system, positioning the robot, opening and closing switches can be done by using only a pair of motors and a pair of solenoids. The newly developed system is compact in size, reduces cost, and shows high reliability.