• Magazine of the Korean Society of Agricultural Engineers
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• v.15 no.3
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• pp.3089-3095
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• 1973

The power transmission to the traction devices may be very important for the tractor performance and therefore this system has been studied very much in the past. On the other hand, the PTO(Power-take-off) has been considered as an accessary on the tractor with a few work for its power transmission. Because of increased use of PTO operation in various kind of farming operations in recent years, the function of PTO may become such important as the traction facilities. In this study, the power transmission characteristics of PTO drive was analyzed theoretically and some experimental work was done to study on it. The results of the study are as follows: 1) The most stable condition of PTO work was obtained when the intersection angle of the two curves for driving and driven torques was about ${\pi}/2$. 2) To obtain the most stable operation it is better to use both the speed control and the full control together. 3) Six steps differential gear may not be enough to use the PTO power smoothly. It is thought that the three steps differential gear on the shaft of PTO may be necessary additionally for a smooth operation. 4) When the traction facilities and the PTO are used at the same time, the torque of crank shaft becomes Tt + Tp, and the high efficiency and good stability of word will be obtained with the small variation of driving speed. 5) When the tractor was operated with 75% of the rated horse power and 70% of maximum speed, the best thermal efficiency could be obtained. 6) The most dangerous sound for human occured at the rated speed of PTO and tus it may be necessary to control the dangerous noise.

• The KSFM Journal of Fluid Machinery
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• v.3 no.4 s.9
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• pp.38-43
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• 2000

Recently, KARI(Korea Aerospace Research Institute, Korea) and CIAM(Central Institute of Aviation Motors, Russia) have made an effort in developing a centrifugal compressor for a small gas turbine engine as part of a collaboration program. This compressor has been designed as a sub-component for an axial-centrifugal compression system for a small turbo-shaft engine aiming adiabatic efficiency higher than 0.81. The geometrical design requirement imposes restrictions to have high inlet hub-to-tip ratio and inlet swirl flow. In this study, the compressor has been designed using the generalized experimental data established from those compressors having pressure ratio of 3.7 to 5. From this generalized empirical correlation, desirable values of design parameters could be obtained. Subsequently, quasi-3D and 3D viscous flow analyses have been performed to ensure the adopted methodology. It is expected that the centrifugal compressor provides total pressure ratio of 4.89, corrected mass flow-rate of 1.64kg/sec, and adiabatic efficiency of 0.815 with inlet hub-to-tip ratio of 0.641. These relatively high total pressure ratio and inlet hub-to-tip ratio are the main distinctive features in this design. Besides, one of the main features of this centrifugal compressor is the adoption of a double-row bladed diffuser to effectively decelerate the transonic flow leaving the impeller. The compressor has been manufactured and will be tested in the near future.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.129-135
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• 2016

There have been many types of development and commercialization efforts for superconducting power applications with the continuous development of High Temperature Superconducting (HTS) conductors. In particular, HTS power cables are going to be commercialized in real power grids. A cryogenic refrigeration system should be used to keep it below 77 K, and its required cooling capacity continuously increases as the unit length of the HTS power cable increases. Among the many kinds of cryogenic refrigerator, a reverse Brayton refrigerator that uses turbo expanders is a promising refrigerator due to its efficiency and reliability. Among the various components in refrigerators, the cryogenic turbo-expander is the most important part for increasing efficiency and assuring reliability. The design of a 300 W class turbo-expander is described in this paper prior to the development of a 10 kW class turbo expander, which is the required capability for the commercialization of a HTS power cable. The impeller shape and rotation speed are determined based on the cycle analysis. The Eigen frequency and harmonic analysis are conducted with gas bearings at cryogenic temperatures to determine the operational stability.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.449-461
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• 2012

Coal ash generated from thermal power plants is planned to use for mine filling in order to prevent subsidence of the ground. In according, the basic physical properties and flow characteristics were grasped using coal ash from generated Yeongdong thermal power plant, and hydraulic filling experiments were performed a total of eight times by manufacturing the model of 1 inclined shaft in Hanbo coal mine. The specific gravity of coal ash is 2.34, and the result of particle size analysis belongs to silty sand (SM). Coal ash of weight ratio of 60% was used in the filling experiments of the model, since liquefaction have shown in coal ash less than weight ratio of 70% from the result of slump and flow test. The outlet should be located at the bottom of the inclined and vertical shaft, this was favorable way in improving the filling efficiency from the experiment results regardless of groundwater exists.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.3
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• pp.459-464
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• 2012

The point of impact, the shot group, and the flight traces depend on the combination of unique features which decide moving traces of the arrow (paradox of the archer, length of the arrow shaft, weight, angle of the feather, and spline of the arrow shaft). The more dense the impact points in the shot group and the earlier elimination of paradox of the archer, the higher assessment is given for the product. However, there is no way to objectively assess the efficiency and quality of the arrow, and there is no numeric data to be used as the basis for comparison with other products. Although capturing the images of flying arrow using a high-speed motion picture camera is possible, we are limited to observation from specific view angle only. Hence, the criteria for efficiency and quality assessment are mostly based on subjective opinions of experts or hunters, or review on consumers' remarks. In this paper, we propose a hardware composition that are based on three detection frames consisting of line lasers and photo diode arrays without the high-speed motion picture camera. Predicated on measured coordinates data, a nobel method for the archer's paradox measurement, a key parameter that determine the arrow's trajectory, and corresponding numerical analysis model is proposed.

• Journal of Biosystems Engineering
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• v.43 no.1
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• pp.1-13
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• 2018

Purpose: The development of compact tractors that can be used in dry fields, greenhouses, and orchards for pest control, weeding, transportation, and harvesting is necessary. The development and performance evaluation of power transmission units are very important when it comes to tractor development. This study evaluates the performance of a driving power transmission unit of a 50 kW multi-purpose narrow tractor. Methods: The performance of the transmission and forward-reverse clutch, which are the main components of the driving power transmission unit of multi-purpose narrow tractors, was evaluated herein. The transmission performance was evaluated in terms of power transmission efficiency, noise, and axle load, while the forward-reverse clutch performance was evaluated in terms of durability. The transmission's power transmission efficiency accounts for the measurement of transmission losses, which occur in the transmission's gear, bearing, and oil seal. The motor's power was input in the transmission's input shaft. The rotational speed and torque were measured in the final output shaft. The noise was measured at each speed level after installing a microphone on the left, right, and upper sides. The axle load test was performed through a continuous equilibrium load test, in which a constant load was continuously applied. The forward-reverse clutch performance was calculated using the engine torque to axle torque ratio with the assembled engine and transmission. Results: The loss of power in the transmission efficiency test of the driving power unit was 6.0-9.7 kW based on all gear steps. This loss of horsepower was equal to 11-18% of the input power (52 kW). The transmission efficiency of the driving power unit was 81.5-89.0%. The noise of the driving power unit was 50-57 dB at 800 rpm, 70-77 dB at 1600 rpm, and 76-83 dB at 2400 rpm. The axle load test verified that the input torque and axle revolutions were constant. The results of the forward-reverse clutch performance test revealed that hydraulic pressure and torque changes were stably maintained when moving forward or backward, and its operation met the hydraulic design standards. Conclusions: When comprehensively examined, these research results were similar to the main driving power transmission systems from USA and Japan in terms of performance. Based on these results, tractor prototypes are expected to be created and supplied to farmhouses after going through sufficient in-situ adaptability tests.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.402-407
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• 2002

A commercial CFD code is applied to analyze the 3-D viscous flow field within vertical multi-stage centrifugal pimp including impeller with 6 blades and guide vane with 11 blades and is performed by changing flow rate from 10 to $26\;m^3/h$ at the constant 3500rpm. The purpose of this 3-D numerical simulation is to confirm how much the effect of blade inlet angle of guide vane has an influence on the performance of vertical multi-stage centrifugal pimp. these results performed by $20^{\circ},\;30^{\circ}$ inlet angle of guide vane are compared with grundfos performance data. The vertical multi-stage pump consist of the impeller, guide vane, and cylinder. The characteristics such as total pressure coefficient total heat shaft horse power, power efficiency, discharge coefficient are represented according to flow rate changing.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.376-381
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• 2011

CVT(Continuously Variable Transmission) is one of the most promising candidates for the future automobile transmission because of its continuously variable gear ratio and reduced shift shock. It is also possible to operate the power source at its high efficiency region with CVT. The CVT system consists of thrust plate, driving pulley, belt, driven pulley, and preload spring of output shaft. In this paper, the dynamic modeling of a CVT system is completed to obtain the static performances of CVT system. A simulator is implemented on Matlab(Simulink), which can analyse the static performances of a CVT system. The methods for improving the total efficiency of a motorcycle system are also proposed based on the simulation results. In this study we increase the capacity factor of CVT up to the three times of default specification.

• The KSFM Journal of Fluid Machinery
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• v.8 no.5 s.32
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• pp.13-21
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• 2005

This study aims to analyze operating performance of a micro gas turbine with the aid of detailed measurements of various system parameters. In addition to embedded measurements, parameters such as exhaust temperatures, engine inlet temperatures and fuel flow rates are measured. Variations in measured data and estimated performance parameters are analyzed. Those data are processed to calculate losses along the power transmission line and the net gas turbine performance (power and efficiency based on the gas turbine shaft end) is isolated from the overall system performance. A method to estimate characteristic parameters such as component efficiencies, based on the comparison between measured and predicted performance data, is suggested and exemplified for the full load condition.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.6
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• pp.339-346
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• 2019

Multi-axis servo systems are widely used in various fields such as industiral systems for improving production efficiency, robotics and complex systems where many mechanical devices and sensor systems are connected. Such a servo system requires that the servo control technique to realize the synchronization of the drive shaft in the steady state and transient conditions and to control so as to follow the target track in order to improve product precision and production efficiency. In addition, embedded type hardware is required for smooth control of the entire multi-axis system. Therefore, this paper uses hardware based on FPGA which is widely used in digital signal processing field and various control system because hardware design change is easy and parallel processing is possible. In addition, Labview based servo motor control program was studied that can control the servo motor by ensuring the performance and flexibility of the FPGA and follow the target trajectory according to various speed processing and accurate timing synchronization.