• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.189-196
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• 2018

Propeller performance measurement system for high altitude UAV was designed and applied to the wind tunnel test for 2 propeller models with a diameter around 1 m. Mechanical power of the propeller was directly measured by using the torque sensor installed on the rotating axis. The thrust of whole operation body including the propeller was measured by thrust road cell. The guide rail system was suggested to reduce the weight influence of operation body on the thrust road cell. The influence of each measured variables on the aerodynamic coefficients was studied with the repeatability and uncertainty analysis. This analysis result shows that the accuracies of the road cell and the wind velocity were major factors for the thrust coefficient. Propeller performance with typical RPM was measured with various wind speeds and the test results was summarized by performance coefficients for 5 different RPM.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.127-135
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• 2008

The objective of sewer rehabilitation is to improve its function while eliminating inflow/infiltration (I/I) and insufficient carrying capacity (ICC). Such rehabilitation efforts, however, have not been particularly successful due to a lack of sewer data and unsystematic field practices. The present study aimed to solve these problems by developing a decision making model consisting of two models: the rehabilitation weighting model (RWM) and the rehabilitation priority model (RPM). In RWM, the I/I of each pipe in a drainage district is estimated according to various defects, with each defect given an individual weighting factor using an analytic hierarchy process (AHP). RPM determines the optimal rehabilitation priority (ORP) using a genetic algorithm (GA). The developed models can be used to overcome the problems associated with unsystematic practices and, in practice, as a decision making tool for urban sewer system rehabilitation.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.107-116
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• 2012

In this study, the trucks(2.9-liter) have been developed to use DME as fuel, and performance test of the vehicle's DME engine, power, emissions, fuel economy and vehicle aspects was conducted. For experiments, the fuel system(common-rail injectors and high-pressure pump included) and the engine control logic was developed, and ECU mapping was performed. As a result, the rail pressure from 40MPa to approximately 65% increase compared to the base injector has been confirmed that. Also, the pump discharge flow is 15.5 kg/h when the fuel rail pressure is 400rpm(40MPa), and the pump discharge flow is 92.1 kg/h when the fuel rail pressure is 2,000rpm(40MPa). The maximum value of full-load torque capability is 25.5 kgfm(based on 2,000 rpm), and more than 90% compared to the level of the diesel engine were obtained. The DME vehicle was developed in this study, 120 km/h can drive to the stable, and calculated in accordance with the carbon-balance method of fuel consumptions is 5.7 km/L.

• Journal of Animal Environmental Science
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• v.19 no.1
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• pp.9-18
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• 2013

Currently, there was no producing system of TMR for pig feeding in Korea. In this study, we examined unrolling, cutting, and softening for the round bale silage. We designed and developed the prototype system of round bale silage for pig feeding. Unroll method were lower chain conveying and upper belt conveying which includes an hydraulic vertical fodder knife. Gathering and cutting method were rotating auger and flywheel which have 10 cutters, input roller of 280 rpm, and cutter rotating speed of 1,750 rpm. Softening device was rotating hammer in inclined cylinder adjustable to $25^{\circ}C$ and rotating speed up to 1,300 rpm. The prototype system was integrated working for unrolling, cutting, and softening. We found that when the round bale silage in unrolling apparatus cut length of 20 cm to input cutting apparatus, the cutting performance was well in continuous working up to input rate of 1,000 kg/h, the softening apparatus was working well.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3135-3140
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• 2010

A 5 kWh composite flywheel rotor was designed and manufactured, and its spin test was performed to monitor strain distribution and burst speed. Strain distribution in radial and circumferential directions of the rotor were measured using a wireless telemetry system based on bluetooth technology for real-time strain measurement. The strains was compared with pre-calculated design values to verify the initial rotor design. We noticed the rotor failed at 19,499 rpm in the spin test, 11 % lower than the predicted burst speed of 22,000 rpm. Failure occurred at the hub which connects the shaft and the composite rotor. The performance of the composite rotor was confirmed in a general sense, and the danger of unexpected failure of composite rotor during high-speed spinning was also demonstrated in this paper. Special attention should be paid to not only composite rotor but also hub when designing a flywheel energy storage system. The telemetry system needs to be further developed, especially enduring the high centrifugal forces, and can be used in a real time monitoring system for the flywheel energy storage system.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.203-212
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• 2002

Active magnetic hearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting. This paper describes a design and test of an active magnetic bearing system with 16-pole radial magnets. The spindle is originally designed for a CNC lathe and driven by outer motor with 5.5 kW power and maximum speed 10,000 rpm. Considering static load condition and geometric restrictions, radial magnet is designed 16-pole type for smaller outer diameter of the spindle system. Dynamic system characteristics such as natural frequency, critical speed, stiffness, damping and system stabilities are simulated with a rigid rotor model including direct feedback controller. The designed spindle system is realized with digital PIDD controller to compensate phase lag of PWM amplifier and magnet coils. With levitation and step response experiment the control system characteristics are tested, and the spindle is rotated up to 10,000 rpm stab1y.

• Progress in Medical Physics
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• v.22 no.3
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• pp.107-116
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• 2011

Respiratory gated radiation therapy and stereotactic body radiation therapy require identical tumor motions during each treatment with the motion detected in treatment planning CT. Therefore, this study developed a tumor motion monitoring and analysis system during the treatments employing RPM data, gated setup OBI images and a data analysis software. A respiratory training and guiding program which improves the regularity of breathing was used to patients. The breathing signal was obtained by RPM and the recorded data in the 4D console was read after treatment. The setup OBI images obtained gated at 0% and 50% of breathing phases were used to detect the tumor motion range in crenio-caudal direction. By matching the RPM data recorded at the OBI imaging time, a factor which converts the RPM motion to the tumor motion was computed. RPM data was entered to the institute developed data analysis software and the maximum, minimum, average of the breathing motion as well as the standard deviation of motion amplitude and period was computed. The computed result is exported in an excel file. The conversion factor was applied to the analyzed data to estimate the tumor motion. The accuracy of the developed method was tested by using a moving phantom, and the efficacy was evaluated for 10 stereotactic body radiation therapy patients. For the sine wave motion of the phantom with 4 sec of period and 2 cm of peak-to-peak amplitude, the measurement was slightly larger (4.052 sec) and the amplitude was smaller (1.952 cm). For patient treatment, one patient was evaluated not to qualified to SBRT due to the usability of the breathing, and in one patient case, the treatment was changed to respiratory gated treatment due the larger motion range of the tumor than treatment planed motion. The developed method and data analysis program was useful to estimate the tumor motion during treatment.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.95-95
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• 2017

백미의 품질특성 중 탁도는 쌀을 씻는 과정에서 발생하는 쌀뜨물의 탁한 정도이며, 쌀뜨물은 다량의 유기물을 포함하여 하천으로 유입 될 경우 수질오염의 주요 원인이 되고 있다(Cho et al., 2017). 따라서 본 연구에서는 백미 가공공정 중 백미의 품질 및 탁도 특성을 분석하기 위하여 백미 가공 시스템의 1, 2단 주축 회전속도에 따른 적정 가공조건을 구명하고자 하였다. 공시재료는 전북 김제시에서 생산된 2015년산 신동진 백미를 사용하였고, 가공 중 백미의 품질 및 탁도 특성은 1, 2단 주축 회전속도에 따라 800, 900, 1,000 및 1,100 rpm의 네 가지 조건에서 측정하였다. 가공 후 싸라기율은 주축 회전속도 1,000 rpm 조건에서 0.46%로 비교적 낮았으며, 1,100 rpm 조건의 경우 0.61%로 약간 높은 경향을 보였다. 주축 회전속도에 따른 가공 전후 백미의 탁도 감소는 주축 회전속도가 빠를수록 높은 경향을 보였으며, 주축 회전속도 1,100 rpm 조건에서 19.57 ppm 정도 탁도가 감소하는 것으로 나타났다. 주축 회전속도에 따른 백미 가공 중 에너지 소비량은 주축 회전속도가 빠를수록 증가하였으나, 주축 회전속도 800, 900 및 1,000 rpm 조건의 경우 3.41~4.25 kWh로 큰 차이는 보이지 않았다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.393-400
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• 2014

In this study, an automatic transmission was developed for a bicycle. This transmission uses the pedal rpm and riding speed information for efficient riding. This transmission was installed on a bicycle using an internally geared hub. The automatic transmission was developed for a beginner to ride with proper gear changes. Indoor ride tests were performed to assess the performance of this transmission. Here, a 'beginner' is defined as a bicycle rider who can maintain a riding power of ~150W with a maximum heart rate of ~80%. Furthermore, 'ride with proper gear change' means that the rider could ride the bicycle while maintaining an efficient pedal rpm by the automatic transmission. One expert and four beginners participated in the ride test. The expert was chosen for the comparison with the beginners. To minimize environmental disturbances, the ride test was performed indoors. In this test, two types of gear changes manual and automatic were tested on two types of roads a road with a gradual incline of 0-3% and a road that simulates the bicycle road along the Han river in Seoul. The results of the ride tests show that the algorithm applied for the automatic transmission helps beginners to ride the bicycle efficiently.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.1
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• pp.86-94
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• 1984

In order to improve the rotational performances of NC lathe spindle system in high speed range, a new type(Floating-type driven by V-belt)spindle system was optimally designed and experimented. Through the results of the experiments, the rotational performances of the new type spindle system was discussed and compared with the three equivalent conventional lathe spindle systems. The spindle rotational accuracy( radial error motion of spindle axis), the accelation and the temperature rise of the front spindle bearings for the non-cutting operation were considered as the spindle rotational performances. The radial error motion of the spindle axis was measured by applying the modified L.R.L. method. Compared with the equivalent conventional spindle systems, the following results were obtained. (1) The new type spindle system reduces the radial error motion of the spindle axis in high speed range(1800rpm-2000rpm). (2) The new type spindle system reduces the acceleration and the temperature rise of the spindle bearings considerably with increasing the spindle speed. It is also confirmed that, by this new type spindle system, the max. allowable speed can be increased with satisfying the spindle rotational performances.