• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.337-339
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• 2008

Abstract: As a shock impinges into a vortex of variable strength, complex shock diffraction can occur. Since a vortex has a fixed rotating direction, the shock wave travelling in one direction creates strong asymmetry in the vortex flow field. The process is that first the shock is divided into two parts by the vortex. One part is moving in the adverse direction opposite to the vortex flow which is captured by the vortex center. The other part is moving in the favorable direction, namely, in the direction same as the vortex flow; it is swung around the vortex, accelerating the vortex flow. In this paper we have investigated numerically using ENO scheme how and why the shock-vortex interaction patterns appear so different for different parametric values. Conclusion is that there are three different types of shock-vortex interaction depending on two related parameters: shock Mach number and vortex Mach number. We present a parameter map by which we can discern what type of interaction pattern appears as a shock impinges into a vortex.

• Korean Journal of Computational Design and Engineering
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• v.4 no.1
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• pp.60-68
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• 1999

In reverse engineering (RE) sustems, the quality of the data aquisition process is crucial to the accuracy of the reverse engineered three dimensional computer-aided design (CAD) model. However, these tasks are predominantly done manually, and little work has been done to improve the efficiency of scanning by determining the minimum number of scans and the optimal scanning directions. In this paper, new scanning and registration methods using tooling balls are developed to assist in determining the optimal parameter for these processes. When the object to scanned has no concavity, attaching path of the object and its bounding rectangle are used for optimal scanning and registration. Then minimum number of tooling balls and their positions are calculated automatically. In the case of concave parts, the scanning plan should include a complete scan of the concave area. With the surface normal vector and the scanning direction, the minimum degree of rotating the part can be calculated. But the maximum rotation should be restricted in order to prevent occlusion of the part. Finally tow sample part ar scanned based on the proposed methods and the results are discussed.

• Journal of Power System Engineering
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• v.12 no.6
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• pp.56-63
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• 2008

Many advanced nations have been developing the next generation logistic systems to effectively deal with gradually increased logistic flows over the world. Particularly, dual mode trailer(DMT) systems are significantly focused as a new alternative transportation which basically provides integrating of the land and railroad services. This paper presents new driving mechanism for DMT systems using the hydraulic pressure cylinder systems. Such is mechanically composed of supporting and rotating parts independently, which are mostly important for whole system performance. We analyze feasible operational problem occurred in driving mechanism from the conventional DMT systems and compare our proposed deign specification with the Modalohr DMT system to demonstrate its reliability and practicability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.274-278
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• 2012

Vertical pumps are structurally weak in terms of vibration because of installed heavy motor on top of the pumps in form of cantilever. So high vibration on top of the pumps can occur with low vibration in the bottom. These vibration problems experienced very frequently. Majority of studies have been related to the unbalance of rotating parts or structural resonance. In this paper, we introduce an unusual case, vibration variation caused by VPF(Vane Passing Frequency) according to water level.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.154-159
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• 2012

Condition monitoring(CM) is a method based on Non-destructive test(NDT). Therefore, recently many kind of NDT were applied for CM. Acoustic emission(AE) is widely used for the early detection of faults in rotating machinery in these days also. Because its sensitivity is higher than normal accelerometers and it can detect low energy vibration signals. A machine tool consist of many parts such as the bearings, gears, process tools, shaft, hydro-system, and so on. Condition of Every part is connected with product quality finally. To increase the quality of products, condition monitoring of the components of machine tool is done completely. Therefore, in this paper, acoustic emission method is used to detect a machine fault seeded in a gearbox. The AE signals is saved, and power spectrums and feature values, peak value, mean value, RMS, skewness, kurtosis and shape factor, were determined through Matlab.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.222-225
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• 2004

Alloy 718 is normally used for the stationary and rotating parts of gas turbines due to its excellent combination of high temperature mechanical properties, formability and weldability. The mechanical properties of the Alloy 718 depend very much on grain size, as well as the strengthening phases, ${\gamma}'\;and\;{\gamma}'$. Direct aging is normally used to enhance tensile strengths at high temperatures. The grain structure of the superalloy components is mainly controlled during thermo-mechanical process by the dynamic, meta-dynamic recrystallization and grain growth. In this study, the influence of grain structure and heat treatment on tensile properties of direct-aged Alloy 718 was evaluated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.304-309
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• 2003

A new modal analysis method for rotor systems with periodically time-varying parameters is proposed. The essence of method is to introduce modulated coordinates to derive the equivalent time-invariant equation. This paper presents a modal analysis method using modulated coordinates fur general rotors, of which rotating and stationary parts both possess asymmetric properties. The equation of motion with time-varying parameters is transformed to an infinite order matrix equation with the time-invariant parameters. A theory of modal analysis for the system is presented with the infinite order equation and a couple of reduced order equations. A numerical example with simple asymmetric rotor is provided to demonstrate the effectiveness of the proposed method

• Tribology and Lubricants
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• v.29 no.3
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• pp.186-191
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• 2013

Hydraulic systems are used to transform mechanical energy into fluid energy and vice versa. They are widely applied in various industries; e.g., they are used in automobiles, public works, rockets, machine tools, heavy construction equipment, and airplanes. Hydraulic pumps are used to transform the energy in these systems. In this study, with the basic operation principles as a starting point, I attempted to clarify how the shape of a slipper affects the lubrication characteristics under practical conditions. A swashplate with a tilt angle of zero and capable of rotating motion was used, along with other devices. A slipper was located at 45 mm eccentricity from the center of the swashplate. The results of this experiment indicated that the shape of the bottom surface of a slipper affects the load capacity, leakage flow, and lubrication characteristics and that the slipper is one of the most important parts for improving the pump efficiency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.190-195
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• 2012

Small-scaled Rotor Test facility(GSRTS, General Small-scaled Rotor Test Facility) in KARI could not use the test because facility aging and parts discontinued. Also in order to perform a joint international research, GSRTS modifications should be needed. So requirements of GSRTS modifications were established and according to the requirements, GSRTS modifications were conducted. Facility operation test, 6-component fixed balance calibration, Small-scaled OLS rotor performance test were performed to verify the results of GSRTS modifications. Reasonable results were obtained in comparison to calculation results. Then GSRTS ready was completed to conduct international collaborative research and wind tunnel test.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.129-133
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• 2008

As a rotating machine element, plastic gears are more and more widely used in such as industrial machine element, since plastic gear is lighter, higher wear-resistance, and higher vibration absorbing ability than metal gears. When operating plastic parts, tooth breakage and fatigue life shortened due to increasing number of applying load and tooth flank temperature rising, such that accuracy of plastic gears is divided from allowable range to cause vibration and noise. On this study, a internal plastic gears are developed which improved the filling balance molding process by a new injection mold structure. The new mold structure called HR3P(hot runner type 3plate mold). As the result from this studies, we obtained a very accurate roundness internal gears by using design of experiment.