• 한국방사선학회논문지
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• 제13권5호
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• pp.773-778
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• 2019

X-선을 이용한 영상은 진단에 필수적인 요소지만 영상에서의 noise발생이 불가피하다. 이를 보완하기 위해 환자의 피폭선량은 낮추면서 영상의 질은 높여주는 total variation (TV) 알고리즘이 제시되었다. 본 연구의 목적은 시뮬레이션을 통해 부가 여과판의 두께에 따라 방사선 영상 촬영 시 영상의 화질에 미치는 영향을 확인하고, TV 알고리즘의 유용성을 평가하는 것이다. 부가 여과판의 두께변화에 따른 각 알고리즘 적용 시 Geant4 Application for Tomographic Emission (GATE) 시뮬레이션 영상을 이용하여 Polymethylmethacrylate(PMMA) 팬텀의 실제 크기, 모양과 재질을 동일하게 하고 대조도 대 잡음비 (contrast to noise ratio, CNR)과 변동계수 (coefficient of variation, COV)값을 비교하였으며 그 결과 TV 알고리즘 적용 시 CNR 값이 가장 높고 COV 값이 가장 낮다는 것을 확인할 수 있었다. 또한, 모든 알고리즘에서 0 mmAl을 사용할 경우 가장 우수한 CNR과 COV값을 얻을 수 있었다.

• 제어로봇시스템학회논문지
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• 제9권5호
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• pp.398-406
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• 2003

In modular fixturing systems, a given part or a subassembly is fixed by placing fixture elements such as locators and clamps adequately on a plate with a lattice of holes. It is known that the minimal number of point contacts to restrict translational and rotational motions on a plane is four and the type of three locators and a clamp(3L/1C) is the minimal future. Brost and Goldberg developed the complete algorithm to automatically synthesize 3L/1C types of fixtures which satisfy the condition of form closure. Due to the nature of the fixture, the clearance between the fixture and the part is extremely small. It is hard to load the part repeatedly and accurately for human as well as for robot. However the condition of loadability has not been taken into account in the B&G algorithm. In this paper, a new method to decide a given fixture to be loadable by using configuration space is proposed. A method to plan for a part to be loaded by using compliance safely even in the presence of control and sensing uncertainty is proposed is well.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.701-709
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• 2017

One of the components that used in the satellite thermal control subsystem is the Mechanically Pumped Fluid Loop (MPFL) system; this system mostly used in geosynchronous orbit (GEO) satellites, and can transfer heat from a hot point to a cold point using the fluid which circulated in a closed loop. Heat radiates to the deep space at the cold plate to cool down the fluid temperature. In this research, the radiative heatexchanger (RHX) for a MPFL system is optimized. The genetic algorithm has been used for minimizing the total mass and pressure drop by considering a constant transferred heat rate at the heat exchanger. The optimization has been done in two cases. In case I, two parameters are considered as a goal function, so optimization is performed using NSGA-II method. Results of optimization are shown in the pareto diagram. In case II, the diameter of pipe is considered constant, so the optimized value for distances of the parallel pipes is obtained by using the genetic algorithm, in which the system has the least total mass. Results show that in the RHX, by increasing the pipe diameter, pressure drop decreases and total mass increases. Also by considering a constant value for pipe diameter, an optimum distance between pipes and pipe length are obtained in which the system has a minimum mass.

• Advances in Energy Research
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• 제5권1호
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• pp.31-55
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• 2017

In the present study, PV/T collector was modeled via analysis of governing equations and physics of the problem. Specifications of solar radiation were computed based on geographical characteristics of the location and the corresponding time. Temperature of the collector plate was calculated as a function of time using the energy equations and temperature behavior of the photovoltaic cell was incorporated in the model with the aid of curve fitting. Subsequently, operational range for reaching to maximal efficiency was studied using Genetic Algorithm (GA) technique. Optimization was performed by defining an objective function based on equivalent value of electrical and thermal energies. Optimal values for equipment components were determined. The optimal value of water flow rate was approximately 1 gallon per minute (gpm). The collector angle was around 50 degrees, respectively. By selecting the optimal values of parameters, efficiency of photovoltaic collector was improved about 17% at initial moments of collector operation. Efficiency increase was around 5% at steady condition. It was demonstrated that utilization of photovoltaic collector can improve efficiency of solar energy-based systems.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.49-60
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• 1999

This paper addresses a welding task sequencing for robot arc welding process planning. Although welding task sequencing is an essential step in the welding process planning, it has not been considered through a systematic approach, but it depends rather on empirical knowledge. Thus, an effective task sequencing for robot arc welding is required. Welding perations can be classified by the number of welding robots. Genetic algorithms are applied to tackle those welding task sequencing problems. A genetic algorithm for traveling salesman problem (TSP) is utilized to determine welding task sequencing for a MultiWeldline-SingleLayer problem. Further, welding task sequencing for multiWeldline-MultiLayer welding is investigated and appropriate genetic algorithms are introduced. A random key genetic algorithm is also proposed to solve multi-robot welding sequencing : MultiWeldline with multi robots. Finally, the genetic algorithm are implemented for the welding task sequencing of three dimensional weld plate assemblies. Robot welding operations conforming to the algorithms are simulated in graphic detail using a robot simulation software IGRIP.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1451-1456
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• 2013

This paper presents the improved zero power levitation control algorithm for a quadruple hybrid EMS (Electromagnetic Suspension) system. Quadruple hybrid EMS system is a united form of four hybrid EMS systems one on each corner coupled with a metal plate. Technical issue in controlling a quadruple hybrid EMS system is the permanent magnet's equilibrium point deviation caused by design tolerance which eventually leads to a limited zero power levitation control that only satisfies the zero power levitation in one or two hybrid EMS system among the four hybrid EMS system. In order to satisfy a complete zero power levitation control of the quadruple hybrid EMS system, the proposed method presented in this paper adds a compensating algorithm which adjusts the gap reference of each individual axe. Later, this paper proves the stability and effectiveness of the proposed control algorithm via experiment and disturbance test.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.131-134
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• 2007

본 논문에서는 알고리즘의 테스트 패턴중 하나인 1D-CZP패턴의 하드웨어 구현을 제안한다. FPGA를 통한 알고리즘 검증 시 센서로부터 받아들이는 정보로만은 알고리즘의 완벽한 장상작동 유무를 판단하기 어렵기 때문에, 내부 패턴 Generator를 사용하여 센서의 정보와 함께 알고리즘의 정상작동 유무를 판단하게 된다. 본 논문은 필터의 주파수 특성 판단에 용이하며, 입력이 랜덤한 특징을 가지는 1D-CZP패턴을 ROM Table형태로 구현하며, 구현 시 사용되는 Modulus연산을 효율적으로 수정함으로, 하드웨어 사이즈가 작아진 1D-CZP패턴을 제안한다.

• 한국컴퓨터정보학회논문지
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• 제10권1호
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• pp.223-229
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• 2005

본 논문에서는 조세단계의 광류검출 알고리즘을 제안하였다. 검출된 광류 값이 2차원 공간상에서의 영상 움직임에 대하여 신뢰성 있는 근사 값을 얻을 수 있다면 이 광류의 값은 3차원에서의 물체의 움직임에 대한 정보를 역산할 수 있을 것이나 일반적으로 이는 매우 어렵다. 본 논문에서 제안한 방범은 Horn의 방법을 이용하여 광류를 일단 검출하고 이 광류 정보와 TPS를 이용하여 초기 영상을 차기 영상이 되도록 워핑한다. 워핑된 영상과 차기 영상과의 자승평균 오차가 일정 수준 이하로 될 때 까지 이 과정을 반복한다. 이 과정은 또한 저급 해상도의 영상에서 고 해상도의 영상으로 반복된다. 본 논문에서 제안한 알고리즘은 일반 동영상에서 실험하였다. 이 알고리즘은 밀한 광류를 얻을 수 있다.

• 대한조선학회논문집
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• 제46권6호
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• pp.675-687
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• 2009

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In this paper, the curved hull plates are classified by four standard shapes and the combination of them, or saddle, convex, flat, cylindrical shape, and the combination of them, that are related to the forming tasks necessary to form the shapes. In preprocessing, the Gaussian curvature and the mean curvature at the mid-point of a mesh of modeling surface by Coon's patch are calculated. Then the nearest neighbor method to classify the input plate type is applied. Tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Advances in aircraft and spacecraft science
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• 제4권2호
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• pp.169-184
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• 2017

The optimum design of structures with frequency constraints is of great importance in the aeronautical industry. In order to avoid severe vibration, it is necessary to shift the fundamental frequency of the structure away from the frequency range of the dynamic loading. This paper develops a novel topology optimisation method for optimising the fundamental frequencies of structures. The finite element dynamic eigenvalue problem is solved to derive the sensitivity function used for the optimisation criteria. An alternative material interpolation scheme is developed and applied to the optimisation problem. A novel level-set criteria and updating routine for the weighting factors is presented to determine the optimal topology. The optimisation algorithm is applied to a simple two-dimensional plane stress plate to verify the method. Optimisation for maximising a chosen frequency and maximising the gap between two frequencies are presented. This has the application of stiffness maximisation and flutter suppression. The results of the optimisation algorithm are compared with the state of the art in frequency topology optimisation. Test cases have shown that the algorithm produces similar topologies to the state of the art, verifying that the novel technique is suitable for frequency optimisation.