• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.411-412
• /
• 2006

A high nitrogen PM tool steel has shown to have an excellent galling resistance due to the introduction of a high amount of a low friction phase predominantly consisting of VN. Tool making and heat treatment are according to standard procedures. An increase of tool life of more than two times compared to ordinary tool steels is found. Furthermore, the new low friction tool steel shows a potential for sintered parts with higher densities through the applica bility of increased compaction pressure or minimized lubricant amount.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.7
• /
• pp.81-90
• /
• 2014

This paper proposes new arc algorithm to detect series quasi-arc. This algorithm analyzes odd and even harmonics until 9th using discrete fourier transform (DFT) and detect series arc comparing RMS values of load current. Resistors, lights, dimmer and vacuum cleaner which can be distinguished linearity load and quasi arc load are adopted to perform experiments. This algorithm is confirmed to emulate arc detecting with measuring current data.

• Journal of KIISE:Computer Systems and Theory
• /
• v.30 no.7_8
• /
• pp.434-444
• /
• 2003

In this paper, we consider the hamiltonian properties of m$\times$n (m$\geq$2, n$\geq$3) mesh networks with two wraparound edges on the first row and last row, called M$_2$(m, n), in the presence of a faulty node or link. We prove that M$_2$(m, n) with odd n is hamiltonian-connected and 1-fault hamiltonian. In addition, we prove that M$_2$(m, n) with even n is strongly hamiltonian laceable and 1-vertex fault tolerant strongly hamiltonian laceable.

• Journal of Power Electronics
• /
• v.3 no.4
• /
• pp.224-229
• /
• 2003

The rapid expansion of small computers over the last 10-odd years has brought about great changes in the circumstances affecting UPSs. There are strong demands that UPSs become much smaller and lighter, and more economical, which has resulted in the wide application of the circuit topology without transformer. A disadvantage of such UPS topology is that the DC link voltage is very high, which invites decreased reliability and increased cost of battery bank. Some circuit configurations were proposed to eliminate this disadvantage, but they still had problems. In this paper, a novel circuit configuration which eliminates these problems is proposed and evaluated by the experimental results of prototype UPS.

• Proceedings of the KIEE Conference
• /
• 1993.07b
• /
• pp.575-577
• /
• 1993

In this study, the reponse characteristic of the time-changing magnetic field measurement system by using the self-integrated magnetic sensor is investigated. The measurement system has the frequency bandwidth of 40[Hz]-50[kHz]. The time-changing magnetic fields generated by the operations of small-size electric machines are investigated. The magnetic field generated by the starting and/or the operation of electric appliances mainly includes the odd harmonics such as the third, the fifth, the seventh, and so on.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.10C
• /
• pp.930-935
• /
• 2003

In this paper, using bent functions defined [n the finite field we generalized the construction method of the family of p-ary bent sequences with balanced and optimal correlation property introduced by Kumar and Moreno for an odd prime p[3], called a generalized p-ary bent sequence. It turns out that the family of balanced p-ary sequences with optimal correlation property introduced by Moriuchi and Imamura [6] is a special case of the generalized p-ary bent sequences.

• Proceedings of the KIEE Conference
• /
• 1995.07a
• /
• pp.131-133
• /
• 1995

Inductive high-Tc superconducting fault current limiter using YBCO superconducting ring in the secondary part has many advantages in power networks. It is based on the superconducting to normal transition and this paper describes its operational characteristics and experimental results, especially focused on the harmonic component analysis and recovery time. We fabricated and tested it under various conditions for the analysis of transient fault characteristics. And for the analysis of harmonics we used FFT methods. The superconducting ring was quenched in 240Arms and fault current was effectively limited to the lower current level. In addition, it was fast recovered when the fault condition was removed and after fault the system had odd harmonics.

• Kyungpook Mathematical Journal
• /
• v.56 no.1
• /
• pp.137-146
• /
• 2016

In this paper we study the oscillation criteria for the second order nonlinear differential equation with delay and advanced arguments of the form $$([x(t)+a(t)x(t-{\sigma}_1)+b(t)x(t+{\sigma}_2)]^{\alpha})^{{\prime}{\prime}}+q(t)x^{\beta}(t-{\tau}_1)+q(t)x^{\gamma}(t+{\tau}_2)=0,\;t{\geq}t_0$$ where ${\sigma}_1$, ${\sigma}_2$, ${\tau}_1$ and ${\tau}_2$ are nonnegative constants and ${\alpha}$, ${\beta}$ and ${\gamma}$ are the ratios of odd positive integers. Examples are provided to illustrate the main results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.810-816
• /
• 2001

In this paper, we theoretically analyzed the NRRO(the non-repeatable run-out) of a ball bearing with geometric imperfection. The quasi-static and dynamic analysis of a ball bearing was performed to calculate the displacement of shaft center caused by the form errors while the shaft is rotating. From consideration of the generating mechanism of NRRO, it is found that the waviness of one ball generates vibrations with nf$\sub$b/${\pm}$f$\sub$c/(where n is odd) components. Also it is confirmed that the outer race waviness of the order n = jZ${\pm}$1 generates vibration with jZf$\sub$c/ components. The form errors of ball bearing elements were precisely measured and NRRO of a ball bearing was calculated using the measured data. It is concluded that the ball bearings must has large ball number and small ball diameter to obtain low NRRO.

• Communications of the Korean Mathematical Society
• /
• v.25 no.3
• /
• pp.385-389
• /
• 2010

In 1997, Exton, by mainly employing a widely-used process of resolving hypergeometric series into odd and even parts, obtained some new and interesting summation formulas with arguments 1 and -1. We aim at showing how easily many summation formulas can be obtained by simply combining some known summation formulas. Indeed, we present 22 results in the form of two generalized summation formulas for the generalized hypergeometric series $_4F_3$, including two Exton's summation formulas for $_4F_3$ as special cases.