• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.84-87
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• 1996

This paper presents a energy function to reflect the control effect of speed governor which has a cut-off property which means position and rate limit The proposed energy function satisfies the semi-negativeness of its time derivative and well reflects the parameters of speed governor to the energy function. The transient stability analysis by the direct method for the single machine infinite bus system has been conducted with the use of the proposed energy function, which shows that the results by the direct method well agree with that by the conventional time simulation method. This thesis shows a possibility of more accurate stability analysis by taking into account the cut-off property of speed governor's output.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.498-503
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• 2012

It happens that the fuel is not injected when the driver doesn't push the acceleration pedal of vehicle with engine speed higher than 1,500rpm above the mid range of vehicle speed. This is called "fuel-cut function" and almost every modern vehicle is equipped with this function. This is activated frequently on the downhill area of highway and the quantity of vehicle-exhausted $CO_2$ gas can be zero on this area. With this fuel-cut function on the test highway, $CO_2$ gas from passenger car(2,000cc engine volume) can be reduced up to 4%. The fuel-cut function with CRUISE made in company AVL is simulated to find the most effective driving pattern on the downhill area. By simulating with CRUISE software, it is found that the lower limit of vehicle speed for fuel-cut should be raised to improve the fuel economy on the steeper downhill road. The fuel economy can be most economical when fuel-cut driving and reacceleration are completed on the section of downhill road.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.86-92
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• 2010

The fuel is not injected when the driver doesn't push acceleration pedal of a vehicle with engine speed higher than about 1,500rpm above mid vehicle speed range. This is called "fuel-cut function" and almost every modern vehicle is equipped with this function. This is activated on downhill part of a highway most often. Therefore the vehicle-exhausted $CO_2$ can be zero in this downhill part if the driver could recognize this part of highway. We compared the vehicle-exhausted $CO_2$ emission when using fuel-cut function with the $CO_2$ mass when without using this function in this study. We found that the $CO_2$ emission reduced with fuel-cut function and measured the reduction rate of vehicle-exhausted $CO_2$ mass with this test results. The exhausted $CO_2$ mass of a passenger car(2,000cc engine volume) is reduced by 4% with this function used. This $CO_2$ reduction effect can be achieved if the downhill part of a highway is painted with a specific color. And this road painting can be included in the highway road rehabilitation policy.

• Korean Journal of Computational Design and Engineering
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• v.6 no.3
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• pp.206-214
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• 2001

This paper describes the wire EDM (Electric Discharge Machining) CAM system considering a variable taper wire-cut and an unmanned wire EDM during the night. Wire EDM is applicable to all materials that are fairly good electrical conductors, including metals, alloys and most carbide. Thus it provides a relatively simple method for making holes of any desired cross section in materials that are too hard or brittle to be machined by most other methods. In this paper we classify variable taper wire-cut machining patterns and variable taper wire-cut geometries. Also we determine unmanned wire EDM patterns fur the productivity of wire EDM industry. Developed system consists of two modules: 1) Variable taper wire EDM module guarantees the length ratio machining function, the parametric ratio machining function and the marking function. 2) Unmanned wire EDM module guarantees the automatic wire EDM during the night. The proposed system has been tested in the fields and found to be a useful system.

• The Pure and Applied Mathematics
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• v.26 no.3
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• pp.199-208
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• 2019

A necessary and sufficient condition in terms of lower cut sets is given for the insertion of a Baire-.5 function between two comparable real-valued functions on the topological spaces that whose $F_{\sigma}$-kernel of sets are $F_{\sigma}$-sets.

• The Pure and Applied Mathematics
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• v.26 no.1
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• pp.1-12
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• 2019

Necessary and sufficient conditions in terms of lower cut sets are given for the strong insertion of a Baire-.5 function between two comparable real-valued functions on the topological spaces that $F_{\sigma}-kernel$ of sets are $F_{\sigma}-sets$.

• Communications of the Korean Mathematical Society
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• v.31 no.1
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• pp.27-40
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• 2016

We define the notion of a residuated lattice valued function on a set as Jun and Song have done in BCK-algebras. We also investigate related properties of residuated lattice valued function. We establish the codes generated by residuated lattice valued function and conversely we give residuated lattice valued function and residuated lattice obtained by the giving binary block-code.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.129-136
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• 1992

A precedure for recovering surface displacement from a time series of pressure measured by a pressure gage in a shallow water (that is, FFTM, LCM. IWM) is investigated with respect to a proper cut-off-frequency of a frequency response function for the accurate recovery of wave height and period. The authors examined the applicability of above mentioned three transformation procedures through field observations and laboratory experiments and the following results are obtained. i) The cut-off-frequency of the frequency response function used in FFTM is deeply depend on both the frequency response of the pressure sensor and the water depth at the sensor. In this study, a relatively accurate surface displacement can be recovered when the frequency response function is cut off at the frequency corresponding to kh=3.0 where k is a wave number at the depth of h. The frequency response function in the region higher than the cut-off-frequency is set constant to be the value at the cut-off-frequency. ii) The transformed surface displacements by LCM are affected by the small waves of short periods included in the measured pressure. It is found that pressure variation whose local frequency is higher than kh=1.5 has to be neglected to recover surface displacement sufficiently. iii) In IWM, the linear pressure response function is usually utilized by multiplying a coefficient N which is a function of the frequency (or kh) and takes a value around unity. However, in this study, a constant value of N(=1.0) gives a relatively accurate recovery of surface displacements.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.3
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• pp.58-65
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• 1996

This thesis is concerned with the study on the characteristics of the cutting resistance occurring in finish machining of hardened steels such as carbon tool steel and alloy tool steel by a ceramic tool with nose radius. For the purpose, the shape of cutting cross-section made at nose part of the tool was analyzed geometrically and the wear mechanism on the flank face of the ceramic tool is investigated. In order to investigate the characteristics of cutting resistance two categories of cutting conditions are suggested, along with geometrical analysis. One category includes the conventional cutting parameters such as feed and depth of cut, another containing new cutting parameters of thickness of cut and width of cut etc. Thickness of cut width of cut and area of undeformed chip section formed by the condition of engagement between workpiece and cutting tool are determined as the function of feed, depth of cut and nose radius of cutting too, And an effective approach angle is determined by depth of cut and nose radius.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.447-454
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• 2011

This paper reports a filtered velocity feedback(FVF) controller, which is an alternative to direct velocity feedback(DVFB) controller. The instability problems due to high frequency response under DVFB can be alleviated by the suggested FVF controller. The FVF controller is designed to filter out the unstable high frequency response. The FVF controller and the dynamics of clamped beams under forces and moments are first formulated. The effects of the design parameters(cut-off frequency, gain, and damping ratio) on the stability and the performance are then investigated. The cut-off frequency should be selected not to affect the system stability. The magnitude of the open loop transfer function(OLTF) at the cut-off frequency should be small. As increasing the gain of the FVF controller, the magnitude of the OLTF is increased, so that the closed loop response can be reduced more. The enhancement of the OLTF at the cut-off frequency is reduced but the phase behavior around the cut-off frequency is distorted, as the damping ratio is increased. The control performance is finally estimated for the clamped beam. More than 10 dB reductions in velocity response can be achieved at the modal frequencies from the first to eighth modes.