• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.143-149
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• 1995

A simple kinematically admissible velocity field is proposed to drtermine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. The proposed velocity field is applied to the square-die extrusion of trochoidal gear-shaped bars and rectangular-shaped bars, the profile function of a rectangular being approximated by using a Fourier series. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreements in average extruded length between theory and experiment.

• Transactions of Materials Processing
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• v.4 no.4
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• pp.390-397
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• 1995

A simple kinematically admissible velocity field is proposed to determine the final-stage extrusion load and the average extruded length in the square-die forward extrusion of non-axisymmetric bars from circular billets. The proposed velocity field is applied to the square-die extrusion of trochoidal gear-shaped bars and rectangular-shaped bars. The profile function of a rectangle is approximated by using a Fourier series. Experiments have been carried out with hard solder billets at room temperature. The theoretical predictions of the extrusion load are in good agreements with the experimental results and there is generally reasonable agreements in average extruded length between theory and experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.718-722
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• 2014

A method for estimating the cylindrical shape of a sound radiator is presented. It assumes that sound field can be measured by a linear array. A sound field, due to the radiator vibrating with uniform velocity, can be determined by its shape, size, and orientations. Measured data also can be varying from the array's position. To predict the shape of radiators from these measured data, mathematical relation between geometric parameter and measured information is needed. Assume that a radiator is cylinder, the magnitude and phase of measured pressure is related with the length and diameter of radiator, respectively. In this paper, the method for estimating length and shape of a finite cylinder by using its radiated pressure is proposed and verified through experiment.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.540-542
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• 2000

This paper describes the particle-initiated breakdown characteristics of various spacers, which have a ribbed surface, in the presence of a metallic particle. The particle was attached on the surface of each spacer. The breakdown voltages were measured by changing the length and thickness of the rib. Also the electrical field analyses were performed. As a result, the breakdown voltage of the spacer with two ribs was highest, and it was varied by the length and the thickness of the rib. Especially, in case of the rib with round edge, the breakdown voltage was higher than that with rectangular edge, which complied with the result through the field analysis.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1921-1923
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• 2000

This paper describes the particle-initiated breakdown characteristics of various spacers, which have a ribbed surface, in the presence of a metallic particle. The particles was attached on the surface of each spacer. The breakdown voltages were measured by changing the particle position on the spacer, the length and thickness of the rib. Also the electrical field analyses were performed. As a result, the breakdown voltage of the spacer with two ribs was highest, and it was varied by the length and the thickness of the rib. Especially, in case of the rib with round edge the breakdown voltage was higher than that with rectangular edge, which complied with the result through the field analysis.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.5
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• pp.22-29
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• 2002

This study was conducted to suggest develop revegetation methods and to classification of cutting-rock slopes revegetation type. The data was collected from pre-experienced data, reports and journal. Also research result was reflected from field research for the conditions of construction, vegetation types and field conditions. As the result of analyze, the factors affecting the plant coverage rates of cutting-rock slopes were period of construction, revegetation methods, slope gradient and slope length. Classification of cutting-rock slopes revegetation type was fourth from material of revegetation measures and spray type. It is recommended to adjust the proposed factor as environment, field condition and characteristic related with revegetation measures on slopes for the presentation of revegetation standard.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.57-67
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• 2005

Fast scalar multiplication of points on elliptic curve is important for elliptic curve cryptography applications. In order to vary field sizes depending on security situations, the cryptography coprocessors should support variable length finite field arithmetic units. To determine the effective variable length finite field arithmetic architecture, two well-known curve scalar multiplication algorithms were implemented on FPGA. The affine coordinates algorithm must use a hardware division unit, but the projective coordinates algorithm only uses a fast multiplication unit. The former algorithm needs the division hardware. The latter only requires a multiplication hardware, but it need more space to store intermediate results. To make the division unit versatile, we need to add a feedback signal line at every bit position. We proposed a method to mitigate this problem. For multiplication in projective coordinates implementation, we use a widely used digit serial multiplication hardware, which is simpler to be made versatile. We experimented with our implemented ECC coprocessors using variable length finite field arithmetic unit which has the maximum field size 256. On the clock speed 40 MHz, the scalar multiplication time is 6.0 msec for affine implementation while it is 1.15 msec for projective implementation. As a result of the study, we found that the projective coordinates algorithm which does not use the division hardware was faster than the affine coordinate algorithm. In addition, the memory implementation effectiveness relative to logic implementation will have a large influence on the implementation space requirements of the two algorithms.

• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.210-211
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• 2007

Once high current flows through the vacuum interrupter, eddy current occurs due to the time-varying axial magnetic field caused by the current(AC) and it causes a decrease in axial magnetic field generated by current flowing through coil electrode. but if there are slots on contact electrode it is possible to increase the amplitude of axial magnetic field by reducing the influence of eddy current. there has been many studies about the number of slot of the contact electrode[1][2][3]. In this paper, in addition to these previous results we deal with the influence of the length and width of the slots on axial magnetic field at the mid-gap plane in 4 segment coil type vacuum interrupter by using 3D finite element method software.

• Journal of Korean Society of Transportation
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• v.12 no.4
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• pp.21-33
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• 1994

The grade is a very significant factor in designing the bikeways. It affects the cyclist's maneuverability as well as route selection. The objective of this paper is to provide the vertical length by grade for bikeway. Field experiments were conducted by primary school children and university students to collect and analyze bike's climbing capability by grade. Combined data suggests that the desirable vertical length is 360m for 3% grade, 220m for 4%, 160m for 5%, 120m for 6% and 90m for 7% grade.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1592-1596
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• 2010

According to the increase of the channel length with fixed width/length, characteristic curves of drain current as a function of gate bias voltage of indium gallium zinc oxide (IGZO) thin-film transistors moved to a positive direction of gate voltage, and field-effect mobility decreased. In case of fixed length and width of channel, field-effect mobility was lower and subthreshold slope was larger when drain bias voltage was higher. Due to large work function of IGZO, band bending at the junction region between IGZO channel and source/drain electrodes was expected to be in opposite direction to that between silicon and metal electrodes; this could explain the above results.