• 소성∙가공
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• 제18권2호
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• pp.150-155
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• 2009

A shaft for laser printers has to be produced with high dimensional accuracy of a few micrometers. Most companies produce the shaft, therefore, by machining. These days, forging process is tried to be employed in manufacturing the shaft for productivity. In this study, the dimensional inaccuracy of straightness is studied and the underfill is not focused because the shaft shape is simple and the load capacity of press is sufficient. The straightness and concentricity of the shaft is important for the operation of a laser printer. Many design parameters such as preform shapes, tooling dimensions, forging load, and billet geometries may affect on the dimensional accuracy. In the forging process of shafts, a billet which is cut from wires is used. The billet, therefore, may be a little bit curved but not always straight. The elastic recovery is considered to cause the dimensional inaccuracy. Therefore, the effect of the forging load on the elastic recovery and straightness is investigated through the finite element analyses using DEFORM-3D and ABAQUS.

• 한국멀티미디어학회논문지
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• 제20권12호
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• pp.1865-1873
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• 2017

The feature-based visual SLAM requires 3D positions for the extracted feature points to perform 3D-2D motion estimation. LiDAR can provide reliable and accurate 3D position information with low computational burden, while stereo camera has the problem of the impossibility of stereo matching in simple texture image region, the inaccuracy in depth value due to error contained in intrinsic and extrinsic camera parameter, and the limited number of depth value restricted by permissible stereo disparity. However, the sparsity of LiDAR data may increase the inaccuracy of motion estimation and can even lead to the result of motion estimation failure. Therefore, in this paper, we propose three interpolation methods which can be applied to interpolate sparse LiDAR data. Simulation results obtained by applying these three methods to a visual odometry algorithm demonstrates that the selective bilinear interpolation shows better performance in the view point of computation speed and accuracy.

• 한국전자파학회논문지
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• 제16권11호
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• pp.1099-1105
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• 2005

TRL 오차 수정 방법은 PCB 위에 제작된 고주파 소자를 측정할 때 많이 사용되는 방법이지만 오차 수정을 위해 제작된 표준 전송선 패턴의 특성 임피던스를 알아야만 보다 정확하게 측정 오차를 수정할 수 있다. 기존의 방법에서는 저항을 종단 처리한 표준 패턴을 추가로 이용하여 전송선의 단위 길이당 커패시턴스를 계산하고 주파수에 대해 fitting하는 방법으로 표준 전송선의 특성 임피던스를 계산하고 있으나 제작상의 부정확성에 의해 추출된 특성 임피던스가 영향을 받고 있음을 확인하였다. 본 논문에서는 측정된 S-parameter를 이용하여 제작상의 부정확성을 줄일 수 있고 기존 방법보다 정확한 특성 임피던스를 추출할 수 있다.

• 한국해양공학회지
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• 제22권6호
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• pp.95-99
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• 2008

The block assembly of ship consists of a certain type of heat processes such as cutting, bending welding residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. The validity of the prediction method must be also clarified through experiments. This paper proposes a simplified analysis method to predict the welding deformation of panel block structure. For this purpose, a simple prediction model for fillet welding deformations has been derived based on numerical and experimental results through the regression analysis. On the basis of these results, the simplified analysis method has been applied to some examples to show its validity.

• 대한조선학회논문집
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• 제40권2호
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• pp.49-56
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• 2003

The welding deformation of a hull structure in the shipbuilding industry is Inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurateprediction method which can explicitly account for the influence of various factors on the welding deformation. The validity of the prediction method must be also clarified through experiments. This paper is aimed at deriving the simple prediction model for fillet welding deformations. For this purpose, the thermal elasto-plastic analysis varying the welding conditions and plate thickness has been performed. On the basis of numerical results, the formulae for angular distortion and transverse shrinkage have been derived through the regression analysis. Experimental work has been also carried out to clarify the validity of numerical results. It has been found that the numerical results show a good agreement with those of experiments

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3163-3169
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• 2009

치열한 항만간의 경쟁에서 우위를 확보하고 항만의 주요고객인 화주와 선사들의 요구사항을 만족시키기 위해서는 물류서비스를 개선해야한다. 하지만 물류서비스 불만의 대부분은 터미널 내부의 문제이기 보다는 화주의 잦은 운송변경 및 선사로부터 제공되는 하역정보나 운송사로부터 반입되는 화물정보의 부정확성에 기인하고 있다. 따라서 본 연구에서는 이러한 문제들을 해결하기 위해 장치장의 업무흐름을 프로세스 중심으로 재설계하고 장치장관리 프로토타입 시스템을 구현하였다. 또한 장치 할당 계획 수립에 선복예약목록 정보가 불충분한 화물정보를 보완하여 장치장 관리에서 협업적 공급망을 구성하는데 이용될 수 있음을 확인 하였다.

• Journal of electromagnetic engineering and science
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• 제11권2호
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• pp.128-132
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• 2011

In interference tolerance based spectrum sharing systems, primary receivers (PRs) are protected by a predefined peak or average interference power constraint. To implement such systems, cognitive radio (CR) transmitters are required to adjust their transmit power so that the interference power received at the PR receivers is kept below the threshold value. Hence, a CR-transmitter requires knowledge of its channel and the primary receiver in order to allocate the transmit power. In practice, it is impossible or very difficult for a CR transmitter to have perfect knowledge of this channel state information (CSI). In this paper, we investigate the impact of imperfect knowledge of this CSI on the performances of both a primary and cognitive radio network. For fixed transmit power, average interference power (AIP) constraint can be maintained through knowledge of the channel distribution information. To maintain the peak interference power (PIP) constraint, on the other hand, the CR-transmitter requires the instantaneous CSI of its channel with the primary receiver. First, we show that, compared to the PIP constraint with perfect CSI, the AIP constraint is advantageous for primary users but not for CR users. Then, we consider a PIP constraint with imperfect CSI at the CR-transmitter. We show that inaccuracy in CSI reduces the interference at the PR-receivers that is caused by the CR-transmitter. Consequently the proposed schemes improve the capacity of the primary links. Contrarily, the capacities of the CR links significantly degrade due to the inaccuracy in CSI.

• Wind and Structures
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• 제7권2호
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• pp.89-106
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• 2004

The response of tall buildings to gust buffeting is usually evaluated assuming that the structural damping is of a viscous nature. In addition, when dampers are incorporated in the design to mitigate the response, their effect is allowed for increasing the building modal damping ratios by a quantity corresponding to the additional energy dissipation arising from the presence of the devices. Even though straightforward, this procedure has some degree of inaccuracy due to the existence of a memory effect, associated with the damping mechanism, which is neglected by a viscous model. In this paper a more realistic viscoelastic model is used to evaluate the response to gust buffeting of tall buildings provided with energy dissipation devices. Both cases of viscous and hysteretic inherent damping are considered, while for the dampers a generic viscoelastic behaviour is assumed. The Laguerre Polynomial Approximation is used to write the equations of motion and find the frequency response functions. The procedure is applied to a 25-story building to quantify the memory effects, and the inaccuracy arising when the latter is neglected.

• 대한조선학회논문집
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• 제41권2호
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• pp.106-113
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• 2004

The block assembly of ship consists of a certain type of heat processes such as cutting, bending, welding, residual stress relaxation and fairing. The residual deformation due to welding is inevitable at each assembly stage. The geometric inaccuracy caused by the welding deformation tends to preclude the introduction of automation and mechanization and needs the additional man-hours for the adjusting work at the following assembly stage. To overcome this problem, a distortion control method should be applied. For this purpose, it is necessary to develop an accurate prediction method which can explicitly account for the influence of various factors on the welding deformation. Systematic and quantitative theoretical works to clarify the effects of various factors on the welding deformation have rarely been found. Therefore, in this paper, the effects of various factors, such as welding process and gravity on the butt welding deformation have been investigated through a number of numerical analyses. In addition, this paper proposes a simplified analysis method to predict the butt welding deformation in actual plate structure. For this purpose, a simple prediction model for butt welding deformations has been derived based on numerical and experimental results through the regression analysis. Based on these results, the simplified analysis method has been applied to some examples to show its validity.

• 수산경영론집
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• 제46권1호
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• pp.145-155
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• 2015

This study aims to look at the change in consumer awareness and behavior after Japan's 2013 nuclear power plant's radioactive water leakage and draw implications about them. Findings show that 81% of respondents decreased their consumption of fishery products after the nuclear incident, and kept on showing avoidance of imported fishery products including those from Japan. Also it showed that consumers more importantly considered safety when buying imported fishery products after the nuclear incident. The most common channel of receiving radioactivity safety information on fishery products were TV and online. However, the main reason for decreasing the consumption of fishery products was founded to be based on the inaccuracy of the information provided. However, many people said that they will increase their consumption of all fishery products if provided with accurate radioactivity information. Therefore, if accurate radioactivity information were to be spread effectively to the public, positive consumption rates of fishery products can be shown in the future. The inaccuracy of radioactivity safety information caused the rapid decrease of fishery products consumption in 2013 to be amplified. Therefore, this study showed the importance of the delivery of rapid, accurate and consistent information to consumers.