• Journal of the Korean Society for Precision Engineering
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• v.5 no.3
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• pp.43-47
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• 1988

Height micrometer is a kind of end standards. It consists of a stack of gage blocks which is capable of moving up and down by a micrometer head. Height micrometer requires calibration with very high accuracy because its resolution is generally 1 .mu. m and its accuracy is higher than few micro- meters. Conventionally, comparison with gage blocks is used to calibrate height micrometer, but it is less accurate and time consuming method. A height micrometer calibration system using a laser interferometer instead of gage blocks has been developed. The measuring range of the system is 300mm, and the accuracy is better than ${\pm}0.5{\mu}m$ A new method of maintaining the laser-beam alignment is described as well.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.446-450
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• 2002

Pneumatic system has been mainly used as main equipment for actuation and control of compressed air force in manufacturing industry, pneumatic circuit for the most part is used in Meter-Out circuit. Meter-Out circuit method is Flow Control Valve to fit in exhaust part of cylinder port. In the reverse, Meter-In circuit is Flow Control Valve to fit in input part of cylinder port. This study examines the dynamic characteristics comparison of Meter-In and Meter-Out Circuits in the pneumatic circuits. The results of the experimental research are obtained to the followings: i ) System Response is Meter-In Circuit more than Meter-Out one before cushion zone. ii) we conjectured that the collision of piston and head cover is ease to collide Meter-In Circuit more than Meter-Out one at the stroke end part.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.133-139
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• 2009

When two cars impact each other, it is usually known smaller vehicle's passenger likely to be more seriously injured than bigger one's. Generally it is known that SUVs and Light Truck Vehicles (LTVs) are bigger and heavier than passenger vehicles and their drive height such as bumper rail and side member, and front end stiffness are higher than those of passenger vehicles. Because of these characteristics the occupants of passenger vehicle struck by SUVs or LTVs are more likely to experience severe injury or fatal injury. To evaluate SUV and LTV's aggressivity to passenger vehicle, SUV to passenger vehicle and LTV to passenger vehicle head-on crash test have been carried out. And finally the way how to reduce incompatibility between SUV and LTV and passenger vehicles is suggested.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.32-35
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• 2010

This paper presents an efficient monitoring method of a network protocol for a downloadable conditional access system (DCAS) that can securely transmit conditional access software via a bi-directional communication channel. In order to guarantee a secure channel based on mutual authentication between a DCAS head end server and set-top boxes, DCAS messages are encrypted and digitally signed. Owing to applied cryptographic algorithms, it is impossible to get information from messages directly without additional processing. Through categorizing DCAS messages into several groups, the proposed monitoring method can efficiently parse and trace DCAS messages in real-time. In order to verify the stability and effectiveness of the proposed monitoring method, we implement a DCAS monitoring system capable of capturing and parsing all DCAS messages. The experimental results show that the proposed monitoring method is well designed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.33-39
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• 2010

The thickness of original hinge model is changed for structural stability in this study. The front end with the largest deformation of 9.8813 mm or the rear middle part with the largest equivalent stress of 6082.6 MPa is respectively shown at door hinge. The lower part of joint pin head with the largest deformation of 0.17499 mm and the largest equivalent stress of 1540.2 MPa are shown. The advanced model with more thickness and stability is shown to have smaller displacement in half and smaller equivalent stress by 3 times by comparing with the original model.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.206.1-206.1
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• 2011

Recently, various developments in the area of small hydropower have being made and small hydro turbines are suitable for domestic use because it is a clean and renewable energy source. A small hydropower generator produces power by using the different water pressure levels in pipe lines and energy which was initially wasted by use of a reducing valve at the end of the pipeline is instead collected by a tubular-type hydro turbine in the generator. In this study, in order to acquire the performance of tubular-type hydro turbine applied, the output power, head, efficiency characteristics due to the different guide vane and runner vane angle are examined in detail. Moreover, influences of pressure and velocity distributions with the variation of guide vane and runner vane angle on turbine performance are investigated by using a commercial CFD code.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.307-315
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• 1993

A direct draft measurement system was developed based on the swingle tree- the rear component of the single-animal harnessing (or yoking) system . The prototype was made from a tube, on which four strain gages were attached. The pull of the draft animal through the flexible pull chains or ropes causes the beam to bend, The bending strain is sensed by the strain gages and the bridge converts this to a voltage signal. Counterweights keep the tube correctly oriented if the angle of pull changes , while end bearing follow the variations in the angle of pull. Hence, the voltage output is proportional to the draft. the device has highly linear response, acceptable sensitivity negligible error and hysteresis. It is suitable for electronic data acquisition, non-intrusive , easy to attach and detach and is reasonably priced.

• Ocean Systems Engineering
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• v.2 no.1
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• pp.69-81
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• 2012

Presented herein is a study on reducing the hydroelastic response of very large floating structures (VLFS) by altering their plan shapes. Two different categories of VLFS geometries are considered. The first category comprises longish VLFSs with different fore/aft end shapes but keeping their aspect ratios constant. The second category comprises various polygonal VLFS plan shapes that are confined within a square boundary or a circle. For the hydroelastic analysis, the water is modeled as an ideal fluid and its motion is assumed to be irrotational so that a velocity potential exists. The VLFS is modeled as a plate by adopting the Mindlin plate theory. The VLFS is assumed to be placed in a channel or river so that only the head sea condition is considered. The results show that the hydroleastic response of the VLFS could be significantly reduced by altering its plan shape.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.47-56
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• 2013

Rolling speed, roll gap, and cooling pattern in hot strip finishing mill process should be determined before inserting strip into roll. Such parameters are initially calculated by a mathematical set-up model. The technique to find adequate roll speed via a mathematical model has inherently limit because required working conditions are various and rolling process is nonlinear. To improve the accuracy of initial rolling speed for a finishing mill, this paper suggests a correction technology for initial rolling speed. The proposed method was implemented in hot strip mill process. As the results, the magnitude of width error in strip head-end part caused by excessive strip tension was decreased remarkably.

• International Journal of Railway
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• v.5 no.3
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• pp.129-134
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• 2012

Contact fatigue damages on the rail surface, such as head checks and squats are a growing problem. The fatigue cracks forming on the contact surface grow according to load and lubricating conditions and may end up breaking the rail. Rail fracture can be avoided by preventing the cracks from reaching the critical length. Therefore, the crack growth rate needs to be estimated precisely according to the conditions of the track and load to develop a maintenance plan against rail damages. Therefore, it is important to understand the mechanism of cracks initiation and growth on a rail due to repetitive rolling contact. In this study, we have investigated the crack growth behavior on the rail surface by using the twin-disc tests and the finite element analysis.