• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.340-345
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• 2001

In this paper, We have studied on the critical vibration limits of spindle unit for the high speed ball pen tip processing machine. The vibration of bearing can be measured by FFT, and the influence of vibration amplitude due to the Unbalance, bearing deflect, bite and timing belts tension are analyzed. So, the critical vibration limits of spindle is determined by the X, Z directional vibration of spindle Unit.

• Journal of Korean Elementary Science Education
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• v.21 no.2
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• pp.201-212
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• 2002

This paper aims to find out how did elementary students understand scientific units in science textbooks. The subjects were 191 students of the 6th grade from 7 elementary schools in 3 different areas, consisting of 70 from 4 village schools of, 64 from 2 town schools of Gyeongnam province, and 57 from one city school in Ulsan Metro City. A test was developed based on the analysis of scientific units in the science textbooks and teacher's manuals constructed according to the 6th and 7th National Science Curriculum. The understanding of elementary students' on the scientific units(Temperature, Length, Weight, Volume, Speed, Plane Angle) were surveyed. The result are as follows: Regarding the temperature unit, the students generally well understand why to measure and how to read temperature, but had some problem in recording it, in confusion with the plane angle sign. As for the length unit, they obtained high scores in understanding the purpose of measuring length as well as recording and reading it. Which indicates that they are well aware of and use the unit appropriately. With respect to the weight unit, they got high scores in reading and recording weight, which means most students have no problem using the unit. However, it was found that they do not understand why to use the plate balance scale. The volume unit was one in which the students got relatively lower scores. They do not perceive the object of using a scale cylinder and confuse it with a device of length measurement. The unit of speed is the most difficult one for children's of science to understand, presumably, because it is an derived unit from two basic units. It is also assumed that the students got the highest score in the plane angle unit because they studied the unit immediately before the test. From the children's understanding of science units above the teacher's understanding and teaching methods presumed to play a major role for children to understand and use the science units properly.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.476-486
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• 2010

Fishing efficiency of a trawl vessel can be enhanced by increasing the swept area per unit time, which can be attained either by increasing the mouth size of the net, or by increasing the towing speed. To improve fishing and fuel efficiency of trawl vessels targeting fishes of greater mobility, in which the towing speed is more critical in determining fishing efficiency, we conducted a series of model tests to evaluate the performance of the newly-designed nozzle propeller before installing it in a trawl vessel to verify its towing speed and fuel efficiency in the sea. By conducting further model tests in the experimental basin, we redesigned the propeller of stern trawler to improve the resistance and propulsion performance. Through actual fishing operations, we evaluated the improvement in fuel and fishing efficiency by installing the new nozzle propeller. The trawling speed increased by 0.6kts at the same engine power (RPM), while the engine margin increased by more than 20%. The increased towing speed by installing the redesigned propeller is expected to enhance fishing performance through increasing the number of hauling- and casting operations per unit times, while shortening the towing duration. Analysis of the Catch-Per-Unit-Effort (CPUE) data indicated that the mean CPUE of trawl fishery increased from 3.04kg/m in year 2007 to 6.15kg/m in year 2008, confirming enhanced fishing efficiency by adopting the redesigned propeller.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3731-3735
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• 2015

This study reports the relationship between rollingstock weight and acceleration performance for HEMU-430X, the first electric multiple unit developed in Korea. While maintaining the consumed power, the total train weight was deliberately varied by 2%, by adding and removing weights, and the it was shown that the lighter train was found to have higher acceleration performance and hence better suited for maximum speed tests below the speed of 413km/h. According to the power consumption analysis based on the velocity data collected per 0.1 second, the balanced speed, when the traction force and air resistance become equal, was determined to be 419km/h for HEMU-430X, which is in agreement with tested result. It is expected that the analyses in this study will be utilized for the speed tests in the future.

• 전기의세계
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• v.29 no.7
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• pp.460-470
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• 1980

The design of a control unit for a playback-type industrial robot is studied. Implemented for the cylindrical-coordinate type industrial robot with 5 degrees of freedom, the control unit constructed for the study consists of (i) z-80 .mu.p-based .mu.-computer control system (ii) Teach-Box for work command, and (iii) various softwares for generating signals for servo driving unit and operating the robot as playback-type. Softwares are developed by using high level Basic Language and low level z-80 Assembly Language for ease of programming and speed of program execution. To show the effectiveness, and example is included.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.6
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• pp.626-631
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• 1997

This paper represents the design of a real-time image preprocessing system. The preprocessing system performs hardware-wise mask operations and thresholding operations at the speed of camera output single rate. The preprocessing system consists of the preprocessing board and the main processing board. The preprocessing board includes preprocessing unit that includes a $5\times5$ mask processor and LUT, and can perform mask and threshold operations in real-time. To achieve high-resolution image input data($20485\timesn$), the preprocessing board has a linescan camera interface. The main processing board includes the image processor unit and main processor unit. The image processor unit is equipped with TI's TMS320C32 DSP and can perform image processing algorithms at high speed. The main processor unit controls the operation of total system. The proposed system is faster than the conventional CPU based system.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.457-462
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• 2009

In a high speed train, aluminium extruded panel is widely used in floor, side wall and roof structures for high bending stiffness and weight reduction. However, with some inevitable reasons, aluminium extruded panel shows inferior sound insulation performance compared with the flat panel having same weight. Especially, occurrence of local resonance modes in the particular frequency band, is one of the main reason in the deterioration of the sound insulation performance. Local resonance modes are generated in the structure which consists of periodic unit structure, such as the aluminium extruded panel. The local resonance frequency is determined by the specification of the unit structure. In this study, we predict the local resonance frequency band on the aluminium extruded panel used for the high speed train, and investigate how the design modification in the unit structure influences the local resonance frequency band and panel bending stiffness. The purpose of the study is to provide the design information for the effective unit structure in order to improve the sound insulation performance of the aluminium extruded panel.

• Tribology and Lubricants
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• v.30 no.3
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• pp.183-188
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• 2014

In this paper, we present our analysis of tribological failure examples for an anti-lock brake system(ABS) in a car. The study range of this paper is to improve the quality of ABS system by analyzing with sensor, computer, actuator and oil lines. In the first example, the brake leak from hydraulic supply line in a caliper on the rear left side of the ABS hydraulic modulator. This produces the sponge phenomenon, where the car does not brake even when the driver operates the brake pedal. The hydraulic unit operating ABS is actuator that play role regulating drive condition according with the oil pressure supplied with wheel of a car. In the second example, the service man does not completely tighten the fixed bolt after repairing the car. This causes the ABS warning lamp to light up as the ABS wheel speed sensor cannot detect whether the ABS has been activated. In the third example, the ABS electronic control unit is separated from the soldered part of the inner circuit board. Consequently, the ABS fails in control because the ABS motor pump receives no-signal for the hydraulic unit. The wheel speed sensor has to large durability because of giving signal of acting condition to computer by detected the acceleration and deceleration of wheel of a car. In the fourth example, the ABS warning lamp lights up of when cracks propagate in the circuit board soldering part. The circuit of this computer is very important part for input and output the operating signal of system. Such failures can aggravate the durability of the ABS. Thus, the ABS needs to be optimized to eliminate malfunction phenomenon.

• Proceedings of the KWS Conference
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• v.43
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• pp.213-215
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• 2004

Water jet propulsion system has high efficiency on middle to high speed, and it provides better safety than conventional screw propeller because it has not projected propeller and rudder. So many leisure boat and high-speed ferries use this propulsion system. We developed water-jet propulsion unit for small planning boat, and launched that in the boat, after that we tested water-jet unit in the lake. As a result, we certify heat dissipation at the bearing housing and reverse duct's shape for neutral position are important at the design, and alignment water-jet unit and keel line are important at the launching, and ship's resistance performance and jet's propulsion performance also are needed to consideration.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.3
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• pp.28-36
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• 2002

The continuously variable transmission (CVT) mechanism considered here is the output coupled type which combines the functions of a 2K-H I type differential gear unit and a V-belt type continuously variable unit (CVU). One shaft of the CVU is connected directly to the output shaft and another shaft of it is linked to the differential gear unit. It is shown that some fundamental relations (speed ratios, power flows and efficiencies) for twelve mechanisms previously described are valid by various experimental studies, six of them produce a power circulation and the others produce a power split. Parametric analysis is carried out in relation to the efficiency, speed ratio and power ratios in order to assist in the design of an optimum configuration. Some useful properties associated with power flow modes also are discussed in the output coupled type continuously variable transmission.