• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.5
• /
• pp.2019-2024
• /
• 2011

The effect of the wear of contact tips on the weld beads made by a Gas Metal Arc Welding(GMAW) process was studied. In order to correlate between the wear of tips and beads, the droplet transfer was investigated by a high speed camera and waveform shapes, and the condition of beads was examined by a low magnification camera as well. It was found that the worn contact tip had caused to shift the contact point between the tip and the welding wire which resulted in nonuniform beads. In addition, the worn contact tip had changed the welding resistance and brought about the arc instability during welding.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.11 no.9
• /
• pp.893-900
• /
• 2016

Output response for prototype system is analyzed according to the pole locations and the damping ratio changes. The system modeling is constructed for RLC-circuit and the output response is analyzed for both a unit-step and a sinusoidal input. The survey is conducted to estimate the understanding ability on the automatic control. A high understanding ability is shown up in analysing the transfer functions of control system. And improvement is manifest in the ability to understand the output response according to the parameter changes. But some difficulty is revealed in acquiring the output responses in time domain.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.2 no.3
• /
• pp.44-50
• /
• 1997

This paper describes an indirect sensing method for the rotor flux position of interior permanent magnet (IPM) brushless DC motors. The phase inductances of an IPM motor vary appreciably according to the rotor position. The waveform characteristics of the terminal voltage of IPM brushless DC motors is analysed and a simple and practical method for indirect sensing of the rotor position is proposed. A compact and economical sensorless drive is implemented and tested using a 87c196mc 16-bit one-chip microprocessor. The experimental results show the validity of the proposed method. The drive is applied to drive a compressor of air-conditioner and works well from 1,200 to 6,600 [rpm].

• Journal of the Korean Magnetics Society
• /
• v.1 no.2
• /
• pp.74-78
• /
• 1991

The method for analyzing the recording and reading process of magnetic recording system by numerical simulation is introduced. which can simulate the effect of elements of the magnetic recording system. During the whole simulation, hysteresis characteristics must be included. Preisach model and finite element method are used to construct the algorithm. From the wave of recording current, recorded pattern of magnetization in recording media is simulated in recording process, and then waveform of reading signal in head coil is obtained in reading process. To show the validity of this method, this is applied to perpendicular magnetic recording system. Waveform of recording signal and reproduced signal is obtained in several density. Pattern of reprocuced voltage magnitude according to increase of recording density shows roll-off curve.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.36S no.2
• /
• pp.108-119
• /
• 1999

In this paper, a three phase PWM AC to DC boost converter that operates with unity power factor and sinusodial input currents si presented. The current control of the converter is based on the space vector PWM strategy with fixed switching frequency and the imput current tracks the reference current within one sampling time interval. Space vector PWM strategy for current control was materialized as a digital control method by using DSP. By using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the dc link.

• Korean Journal of Veterinary Research
• /
• v.16 no.2
• /
• pp.121-129
• /
• 1976

실혈견(失血犬)에 있어서 염산(鹽酸)케타민 전신마취(全身麻醉)가 심전도(心電圖), 뇌파(腦波) 및 혈압(血壓)에 미치는 영향(影響)을 조사(調査)하였던 바 그 성적(成積)은 다음과 같았다. 심전도소견(心電圖所見)에 있어서는 동성빈맥(洞性頻脈)이 지속(持續)되었으나 심장조율(心臟調律)에는 특이(特異)한 변화(變化)가 나타나지 아니 하였다. 그러나 건강견(健康犬)에 있어서 염산(鹽酸)케타민 마취군(麻醉群)과 비교(比較)해서 파형(波形)의 변화(變化)와 S-T분절(分節)의 편위(偏位)가 경미(輕微)하게 있었으며 P-Q와 Q-T 간격(間隔)은 상대적(相對的)으로 다소(多少) 연장(延長) 되었다. 뇌파(腦波)는 건강견(健康犬)에 있어서의 염산(鹽酸)케타민 마취군(麻醉群)과 유사(類似)한 양상(樣相)을 보였으나, 그 진폭(振幅)은 약간 감소(減少)되었다. 혈압(血壓)은 마취후(麻醉後) 약간 하락(下落)되었으나 곧 마취전(麻醉前)으로 회복(恢復)되었으며, 악화(惡化)되지는 아니하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.5
• /
• pp.64-71
• /
• 2006

We developed a fiber-optic temperature sensor system, with 10 fiber Bragg gratings, for abnormal high-temperature monitoring in power systems. We used Gaussian line-fitting algorithm to compensate the spectrum distortion in the wavelength-scanned Farby-Perot filter demodulation scheme. Compared with highest-peak-detection method, the proposed algorithm substantially reduced measurement errors. The overall measurement error was less than 1[%] compared with the reference thermocouple and the linearity error was 0.37[%].

• Journal of the Korean Society for Railway
• /
• v.15 no.2
• /
• pp.116-121
• /
• 2012

DC/DC switching power converters produce DC output voltages from different DC input sources. The converter is used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The DC/DC converter is composed of a PWM-IC (pulse width modulation integrated circuit) controller, a MOSFET (metal-oxide semi-conductor field-effect transistor), an inductor, capacitors, and resistors, etc. PWM is applied to control and regulate the total output voltage. In this paper, radiation shows the main influence on the changes in the electrical characteristics of comparator, operational amplifier, etc. in PWM-IC. In the PWM-IC operation, the missing pulses, the changes in pulse width, and the changes of the output waveform are studied by the simulation program with integrated circuit emphasis (SPICE) and compared with experiments.

• Journal of the Korean Magnetics Society
• /
• v.9 no.1
• /
• pp.64-70
• /
• 1999

The inrush current of transformer can flow when the overvoltage caused by surge or external faults is applied. In this paper, an algorithm for the calculation of this inruch current is proposed. The capacitances of windings are precalculated by using 3 dimensional FEM and are appended to circuit of the transformer. And transient characteristics of the transformer are analyzed by axisymmetric FEM which is coupled magnetic field of transformer and circuit of transformer. When a transformer encounters abnormal voltage, using the proposed method, internal magnetic field of transformer, voltages and currents of windings are calculated.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.2
• /
• pp.44-51
• /
• 2001

This Paper the practical echo signal synthesis model to predict the target strength and signal shape of a submarine for a valuable tool to active sonar engineer. It is based on UTAHID (Underwater TArget by Highlight Distribution) model which is relocated highlight points along to external hull for aspect angle, and synthesized echo signal by modified grouping highlights to internal scatter cloud. Proposed model is analyzed target strength characteristics on various incident pulse length, and synthesis signal signature, target time spreading loss, echo elongation effect and so on. Thus it can be efficiently used in various real systems related to underwater target echo signal synthesis, that is, active sonar, acoustic countermeasure and surveillance system.