• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.732-739
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• 2009

Flow phantom with stenosis was manufactured using an auto-injector to obtain angiostenotic flow information and quality assurance (QA) for ultrasound diagnostic instrumentation. Effectiveness of manufactured flow phantom with stenosis was investigated with power Doppler that was known to have diagnostic efficiency for angiostenosis. The flow phantom with stenosis was manufactured to 70% stenosis with 8 mm and 2.4 mm silicon tube, and silicone tube was covered with gelatin that has acoustic characteristics similar to soft tissue. When the linear transducer was used for measurement, the estimated diameter of normal vessel was measured lower than that of normal value, and the estimated diameter of stenosed vessel was measured higher than that of normal value. The measured parameters were not affected except for the radical conditions such as gain of 60%, PRF of 3000 Hz, use of maximal filter or angle. In addition, when the convex transducer was used for measurement, measurement parameters were affected by gain, PRF, filter, and angle. Therefore it is expected that flow phantom with stenosis manufactured with an auto-injector will be utilized effectively for QA of angiostenotic diagnosis.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.12
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• pp.30-40
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• 1998

We have calculated ultra-low energy silicon-self ion implantations and silicon damages through classical molecular dynamics simulation using empirical potentials. We tested whether the recently developed Environment-Dependent Interatomic Potential(EDIP) was suitable for ultra low energy ion implantation simulation, and found that point defects formation energies were in good agreement with other theoretical calculations, but the calculated vacancy migration energy was overestimated. Most of the damages that are produced by collision cascades are concentrated into amorphous-like pockets. Also, We upgraded MDRANGE code for silicon ion implantation process simulation. We simulated ultra-low energy boron ion implantation, 200eV, 500eV, and 1000eV respectively, and calculated boron profiles with silicon substrate temperature and tilt angle. We investigated that below 1000eV, channeling effect must be considered.

• Journal of IKEEE
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• v.26 no.1
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• pp.43-49
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• 2022

This paper compares the sensorless control performance according to the applied voltage waveform by injecting sinusoidal, triangular, and square waveform in the harmonic injection sensorless control method. By injecting various voltage shape waveform with a frequency of 1kHz, the error amount of the estimated angle for each waveform is compared and analyzed. For the experiment, the HILS(hardware in the loop simulation) system was used. The hardware is the control board, and the inverter and motor models implemented in Simulik are located in the real-time simulator. The control algorithm is implemented by the FPGA control board, which includes a PWM interrupt service routine with a frequency of 10 kHz, harmonic injection and position detection sensorless algorithm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.12
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• pp.3360-3371
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• 1995

Hydrodynamic characteristics of a stratified flow at a Y-junction were examined analytically. Gas is supplied through the main horizontal channel and liquid is introduced into the gas stream from the Y-shaped bottom branch. Analysis was performed with irrational flow and inviscid fluid assumptions. The Stokes' inverse transformation technique was adopted to convert the real x-y plane into the x-.psi. plane. The potential flow equation was solved numerically in the transformed (x-.psi.) plane and the interface profile, pressure distribution and the streamlines were obtained. The effects of the inlet conditions, injection angle and the gravity on the flow characteristics were also examined. To check the validity of the present method, the previous resultant the two-dimensional obtuse wedge flow was compared. The inverse transformation technique turned out to be also very useful to predict the hydrodynamic characteristics of a stratified flow with the pressure variation at a Y-shaped mixing junction.

• Journal of Industrial Technology
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• v.20 no.B
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• pp.55-62
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• 2000

The purpose of this research is to find out how the inlet angle of secondary air affects the formation of recirculation zone inside a small incinerator. A commercial code, PHOENICS, is used to simulate the flow field of an incinerator. The computational grid system is constructed by Multi-Block technique. Numerical experiments are done with the five different angles of secondary air inlet. The formation of recirculation zone is evaluated by checking velocity fields. The computational results show that recirculation zone is clearly formed from 60 degree of inlet angle and the zone of recirculation is widen as angle of recirculation is increased to $75^{\circ}$.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.335-336
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• 2015

본 논문에서는 스위칭 주파수 신호 주입 센서리스 제어를 위한 정밀한 위치 오차 추정 기법을 제안한다. 제안한 방법에서는 위치 오차를 얻을 때에 작은 각도 근사법(Small-Angle Approximation)을 이용하지 않고 Rotation matrix를 이용하여 근사 없이 실제 위치 오차를 계산하였고, 90도까지 회전자 오차 측정 범위를 확대하였다. 이를 통하여 오차가 크게 발생하는 부하 변동이나 가감속 시에 과도상태특성을 개선할 수 있다. 제안한 방법은 실험을 통하여 그 유효성을 검증하였다.

• Journal of IKEEE
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• v.26 no.1
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• pp.95-103
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• 2022

In this paper, the efficiency of a sensorless method with square-wave injection for a low-cost inverter, so called B4 inverter is presented. This inverter comprises only 4 switches to reduce system cost. It is distinguished from the conventional B6 inverter that has 6 of switching elements. The B4 inverter, injected a 1 kHz of harmonic wave, has been modelled using the functions and library in Matlab/Simulink. This paper described each component of sensorless algorithm. Among them, the Notch Filter is used to extract the harmonic component of the phase current and a second-order low-pass filter was used to reduce the ripple of the estimated speed. It is shown through simulation that the rotor angle of a permanent magnet synchronous motor is detected by multiplying the current waveform extracted using the notch filter by the harmonic voltage. The feasibility of the proposed method is shown through Simulink simulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.847-852
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• 2014

As the scaling trend becomes accelerated in process technology for cost reduction in semiconductor chip manufacturing, the requirement for shrink technology has increased. Hot Carrier Injection (HCI) degradation for I/O transistors is most concerning part when shrink. To solve this, the effective channel length (Leff) was increased using liner oxide before Light Doped Drain (LDD) implants and optimized the tilt angle to increase Leff without E-field degradation in LDD region, satisfying the HCI specification.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.309-316
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• 1999

A numerical study for the turbulent reacting flow in an orimulsion gasifier has been carried out to analyze the characteristics of chemical reaction by orimulsion droplets. In this study, our interest has been focused on the effect of oxidizer to orimulsion ratio, which is one of the key parameters of gasification operation, as well as on the distribution of chemical species. In addition, we have conducted numerical calculations to understand the effect of droplet size, spray angle and injection velocity of fuel so as to acquire the basic information on the operating range of orimulsion gasifier. The result of numerical calculations showed that the gas composition of CO and H$_2$concentrations was the highest when the oxidizer to orimulsion ratio was about 0.88 and the reactivity of orimulsion increased as the droplet size reduced with proper spray angle. Also, we have carried out the analysis on the orimulsion gasification in the 100 ton/day-scale gasifier based upon the prior study in order to obtain the basic data for the proper operating condition using orimulsion feed.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.30.3-30.3
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• 2011

한국천문연구원은 Giant Magellan Telescope Fast Steering Mirror prototype을 개발 중이고, 반사경 제작과 tip-tilt 시스템 제작을 목표로 하고 있다. 반사경은 직경이 1.06m, 두께가 약 140mm, 질량이 약 100kg인 meniscus 타입인 비축 비구면 반사경이다. Tip-tilt 시스템은 바람에 의한 반사경의 진동과 망원경의 tracking jitter를 보정하기 위한 장치로써 tip-tilt 각도가 ${\pm}20"$ 범위 내에서 약 30Hz로 작동하는 시스템이다. 반사경 cell은 반사경 뒷면에 조립되어 반사경 cell 내부에 주입되는 진공과 함께 반사경의 무게를 지지하고, tip-tilt 시스템을 작동시키는 액츄에이터가 장착되는 base structure 역할을 한다. 이 논문에서는 반사경 cell의 초기설계와 반사경 cell에 발생할 수 있는 하중 조건에 따른 응력과 변위, 반사경 cell의 두께에 따른 고유진동수를 해석한 결과들에 대해 논한다.