• 드라이브 ㆍ 컨트롤
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• 제11권4호
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• pp.46-52
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• 2014

This study suggests a small-sized screw decanter specialized for dredging sites. Generally, conventional screw decanters are composed of a cylinder and a cone. However, the suggested screw decanter simply has a cone based on a cone-type bowl structure. In this research, a commercial analysis tool is used to establish an optimal design for the bowl and the screw conveyor. Moreover, the base frame, where the main bearings that support the spindle of the bowl and the screw conveyor are installed, is optimally designed considering the weight of the rotating body and the deflection caused by the high centrifugal force. Furthermore, the natural frequency range of the spinning body, the bowl and the screw conveyor, is applied to this base frame; it is designed not to correspond to the resonance frequency range and achieves stability as a result. This study suggests an optimal design for the rotating body and the base frame of a screw decanter considering its vibration characteristics. Such a design will prevent overuse of materials and help to reduce the weight and volume-and the price-of a screw decanter.

• 한국정보통신학회논문지
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• 제11권2호
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• pp.430-435
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• 2007

본 논문에서는 센서 네트워크의 원활한 전송을 위해 SOFM을 이용한 센서 네트워크의 지능적인 배치를 제안한다. 제안한 방법은 무선 채널 분석을 통해서 센서 노드 사이의 통신이 가능한 거리를 구하고, 신경회로망의 SOFM(Self-Organizing Feature Map)방식을 이용하여 지능적으로 최적의 센서 노드의 개수와 센서 노드가 배치할 최적 위치를 결정한다. Log-normal path loss 모델을 이용하여 거리에 따른 PRR(Packet Reception Rate)을 구하고, 이것으로부터 센서 노드의 통신 범위를 결정한다. 제안한 방식의 유용성을 확인하기 위하여 센서 노드의 지능적인 위치 탐색과 센서 네트워크의 연결 상태에 대한 시뮬레이션을 수행하였다.

• Current Optics and Photonics
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• 제7권4호
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• pp.398-407
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• 2023

We explored a method to evaluate imaging performance for the optimal assembly of an endoscopic miniature lens and a sensor constituting an imaging module at the distal end of gastrointestinal endoscopy. For the assembly of the imaging module, the image sensor was precisely located at the focal plane when collimated light passed through the endoscopic lens. As another method, the distance between the lens and sensor was adjusted to obtain the highest focus index from images measured the star chart of the International Organization for Standardization (ISO) standard at various positions. We analyzed the slanted-edge modulation transfer function (MTF), corresponding depth of field, and number of line pairs for MTF 50% and 20% at each working distance within the range of 5-100 mm for imaging modules assembled in different ways. Assembly conditions of the imaging module with better MTF performance were defined for each working distance range of 5-30 mm and 30-100 mm, respectively. In addition to the MTF performance, the focus index of each assembled module was also compared. In summary, we examined the performance of imaging modules assembled with different methods within the suggested working distance and tried to establish the optimal assembly protocol.

• Industrial Engineering and Management Systems
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• 제11권2호
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• pp.196-201
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• 2012

This study has developed a packaging criterion to minimize the level of discomfort which drivers using their vehicles for daily life purposes may experience due to ill designed vehicle packaging of mid-size sedan based on users' daily-life scenario. To find out optimal range of packaging dimension criterion, discomfort levels the test participants with different physical conditions suffer while performing various activities were analyzed. One hundred two test participants were carefully selected to represent entire Korean mid-size sedan owner-drivers. They were directed to test drive on the course designed to simulate mid-size sedan daily-usage scenario. At pre-designed locations, each of questions was asked to the test participants to be answered in the form of 10 point discomfort level score. By analyzing the test results, the optimal range for packaging dimensions was defined to be used as a packaging criterion.

• 한국기계가공학회지
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• 제15권3호
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• pp.102-108
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• 2016

A dental ultrasonic surgical instrument, commercially known as a scaler, is a high-value-added advanced technology that is used for tartar removal, implant operations, and gum and jaw bone surgery. In this study, the piezoelectric phenomenon for making linear motion associated with input electrical signals was studied, and the behavior of the ultrasonic vibrator was investigated by using the commercially available finite element program ANSYS(R) for the purpose of designing dental surgery tools. Modal analysis was carried out, and the optimal frequency range was calculated from the analyzed results. The ultrasonic vibrator was then redesigned based on the calculated optimal frequency range. The performance of the system was tested, and consequently, the proposed methodology was proven useful in vibrator design.

• 한국기계가공학회지
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• 제15권3호
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• pp.109-114
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• 2016

This study presents the optimal hardness range for a coated layer of a workpiece when the diamond tool cuts the corner-cube pattern on the coated plates using an ultra-precision diamond-turning machine. Two kinds of coated plates, which have the hardness range of 211~328 Vickers hardness, are used on the first experiments. The form accuracy for the corner-cube pattern could be achieved through the following experiments using the accumulated thin copper plates in second experiments, having optimal 265~275 Vickers hardness based on the basic first experiments without tool wear. When the number of machining adjustments was increased to seven times, having machining depth was reduced successively in second experiment, a fine surface could be achieved without tool wear.

• 전기학회논문지
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• 제59권6호
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• pp.1064-1069
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• 2010

Active clamp forward converter provides zero voltage switching, low voltage stress and wide input voltage range. The design technique leads to getting a higher efficiency under high switching frequency and optimal operating range. It is designed for notebook computer adapter with free input voltage and 19.5V/120W output ratings. The efficiency is measured to more than 90%. One of the most important circuit parts is the filter inductor besides the transformer in active clamp forward converter. In this paper, the process of inductor design is listed optimally.

• 대한전자공학회논문지
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• 제25권1호
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• pp.42-48
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• 1988

MM(multimode) PWM(pulse width modulation) Suitable for high performance and harmonic effects minimization of VSI (voltabge source invertetr)-IM (induction motor)drive system is proposed. The approximated optimal, suboptimal and optimal PWM are implemented in the low frequency range, while square wave operation is realized in the hibh frequency range. The pulse width Modulator is capable of generating control signals to a transistorized inverter operating at about 1KHz. All functions except digital comparison have been implemented in softyware making the scheme economical, flexible and reliable. Pulse width modulator is built and tested experimentally. In order to confirm the effectiveness and the reliability of the theoretical proposition, this scheme is applied to 1Hp, Three phase IM. As results, it is concluded that the scheme of MM PWM is superior to other conventional switching scheme through the discussions or analysis carried out on the items such as line-to-line voltage, current and spectrum of current harmonic components observed at the output terminal of inverter, noise level of motor.

• Journal of Advanced Marine Engineering and Technology
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• 제30권2호
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• pp.296-303
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• 2006

Recently, micro hydropower attracts attention because of its clean. renewable and abundant energy resources to develop. However, suitable turbine type is not normalized yet in the range of micro hydropower and it is necessary to study for the effective turbine type. Moreover, relatively high manufacturing cost by the complex structure of the turbine is the highest barrier for developing the micro hydropower turbine. Therefore a cross-flow turbine is proposed for micro-hydropower in this study because of its simple structure and high possibility of applying to low head. The purpose of this study Is to further optimize the turbine structure and improve the performance. A guide vane is removed and the runner chamber is made compact using a new air supply method. The results show that the efficiency of the turbine is improved in a wide operating range and the size of the turbine is remarkably reduced.

• ETRI Journal
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• 제41권6호
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• pp.782-796
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• 2019

This paper presents a hierarchical framework for managing the sampling distribution of a particle filter (PF) that estimates the global positions of mobile robots in a large-scale area. The key concept is to gradually improve the accuracy of the global localization by fusing sensor information with different characteristics. The sensor observations are the received signal strength indications (RSSIs) of Wi-Fi devices as network facilities and the range of a laser scanner. First, the RSSI data used for determining certain global areas within which the robot is located are represented as RSSI bins. In addition, the results of the RSSI bins contain the uncertainty of localization, which is utilized for calculating the optimal sampling size of the PF to cover the regions of the RSSI bins. The range data are then used to estimate the precise position of the robot in the regions of the RSSI bins using the core process of the PF. The experimental results demonstrate superior performance compared with other approaches in terms of the success rate of the global localization and the amount of computation for managing the optimal sampling size.