• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.115-124
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• 1999

The interaction of weak normal shock wave with turbulent boundary layer in a supersonic nozzle was investigated experimentally by wall static pressure measurements and by schlieren optical observations. The lime-mean flow in the interaction region was classified into four patterns according to the ratio of the pressure $p_k$ at the first kink point in the pressure distribution of the interaction region to the pressure $p_1$ just upstream of the shock. It is shown for any flow pattern that the wall static pressure rise near the shock foot can be described by the "free interaction" which is defined by Chapman et al. The ratio of the triple point height $h_t$ of the bifurcated shock to the undisturbed boundary layer thickness ${\delta}_1$ upstream of the interaction increases with the upstream Mach number $M_1$, and for a fixed $M_1$, the normalized triple point height $h_t/{\delta}_1$ decreases with increasing ${\delta}_1/h$, where h is the duct half-height.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.130-136
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• 2014

This paper reviews the research on silicon based phased array system operating from microwave to millimeter wave frequencies. First, the design of phase shifter using CMOS technology is presented. The passive phase shifter is applied to the transmit/receive module from one to 16 channel in a single chip. The 35 GHz 4-element T/R module consumes less than 200 mW both transmit and receive modes. The architecture can extend to 16-channel operating at 44 GHz, thereby improving transmit power and linearity. The Ku-band 2-antenna 4-element receiver was developed using active phase shifter based on vector sum method. It is important to minimize coupling between beams because the chip contains four independent beams. The method of coupling is presented and verified.

• Journal of Sasang Constitutional Medicine
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• v.19 no.2
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• pp.127-142
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• 2007

1. Objectives We studied the characteristics of pulse wave variables in hypertensive patients and healthy subjects and would develope the program diagnosing Sasang Constitution. 2. Methods Healthy subjects and hypertensive patients were measured with pulse analyzer. In each of healthy and hypertensive group, means of pulse analyzer variables were compared among Constitution. On these bases of these results, decision tree composed of several rules were developed. 3. Results and Conclusions Decision tree with 72.13% accuracy were developed. (1) if h5(Cheok) < 2.325 & Wm/t(Cheok) < 0.238281 then class = Soeumin (2) if h5(Cheok) < 2.325 & Wm/t(Cheok) ${\ge}$ 0.238281 then class = Taeumin (3) if h5(Cheok) ${\ge}$ 2.325 & t1(Chon) ${\ge}$ 0.143 then class = Soyangin (4) if h5(Cheok) ${\ge}$ 2.325 & t1(Chon) < 0.143 & h3/h1(Cheok) ${\ge}$ 0.963601 then class = Soyangin (5) if h5(Cheok) ${\ge}$ 2.325 & t1(Chon) < 0.143 & h3/h1(Cheok) < 0.963601 & sum of pulse pressure(SPP) of Gwan ${\ge}$ 618 then class = Taeumin (6) if h5(Cheok) ${\ge}$ 2.325 & t1(Chon) < 0.143 & h3/h1(Cheok) < 0.963601 & sum of pulse pressure(SPP) of Gwan < 618 & t3(Chon) < 0.209 then class = Soeumin (7) if h5(Cheok) ${\ge}$ 2.325 & t1(Chon) < 0.143 & h3/h1(Cheok) < 0.936601 & sum of pulse pressure(SPP) of Gwan < 618 & t3(Chon) ${\ge}$ then class = Taeumin From above results, we concluded that pulse analyzer is useful instrument to decide Sasang Constitution.

• Journal of Physiology & Pathology in Korean Medicine
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• v.23 no.5
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• pp.1035-1040
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• 2009

In this work, we investigate the effect of blood hematocrit level on the radial pulse wave to study the clinical application of the pulse analyzer. For this purpose, we measured the radial pulse wave at the left Gwan for 15 males with abnormal high hematocrit level and 47 males with normal hematocrit level at the age of thirties and forties. Various variables of the radial pulse wave between two groups were analyzed by Student's T test. We found significant differences in several characteristic variables in the amplitude, time-span and the integrated area of the amplitude and time of the pulse wave. The systolic peak in the amplitude of the radial pulse wave was higher in abnormal high hematocrit group. In contrast, the third peak from the second incisure was higher and longer in normal hematocrit group. Our study suggests that the radial pulse wave can be useful in distinguishing the patient group with high hematocrit level and thus with high blood viscosity. Our finding may motivate research activities towards diverse clinical applications of the pulse wave.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.181-182
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• 1998

In previous study for correlation between P-wave Signal Averaged Electrocardiography (SAECG) and Paroxysmal Atrial Fibrillation (PAF) subjects, we showed that the duration of P-wave in subjects is longer than in controls. In this respect, the P-wave SAECG is a new method proving to be an accurate and independent noninvasive marker for the risk of PAF. To prove this suggestion, accurate detection and alignment of P-wave are indispensible. In previous study, we measured P-wave duration by manual. So it was not accurate and consistent. To measure the P-wave duration accurately and automatically, we have developed an automatic algorithm for P-wave duration measurement. We showed that the duration of P- wave in the subjects is longer than in controls with this algorithm.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.456-465
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• 2001

In this paper, breakdown voltages in $SF_6-N_2$ mixtures were experimentally investigated to understand characteristics of dielectric strength and physical phenomena in nonuniform field disturbed by a needle shape protrusion. The test voltages are the lightning impulse$(\pm1.2/44 \mus)$ and the damped oscillatory impulse$(\pm400 ns / 0.83 MHz)$ voltages which can be occurred by the operation of disconnecting switches in gas-insulated switchgears(GIS). The effects of the polarity and wave shape of the test voltages, and the gas pressure on the V-t characteristics were in detail examined. The V-t characteristic curves were measured in different two ways : (1) one is the method by taking the maximum voltage recorded at or prior to breakdown against the time to breakdown, that is, the Procedures recommended in IEC 60060-1, (2) the other is the method by taking the voltage at the instant of chopping against the time to breakdown. As a result, the V-t characteristics of $SF_6-N_2$ mixtures in nonuniform electric field were significantly affected by the polarity and wave shape of the applied voltages. The positive breakdown voltages resulted in lower breakdown voltages in the time ranges considered, and the V-t curves for the negative oscillatory impulse voltage were extended over the longer time range. For the lightning impulse voltages, the V-t curves obtained by IEC Pub. 60060-1 were nearly same with the V-t curves obtained by the voltage at the instant of chopping against the time to breakdown. It is clear that the actual breakdown voltages were much lower than the maximum voltages appearing at or prior to breakdown because of the displacement current produced as a result of the dV/dt during the oscillatory transient voltage app1ication. The scattering of the negative actual breakdown voltages was much larger than that of the positive.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.1-6
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• 2008

In this paper, millimeter-wave broadband MHEMT (Metamorphic High Electron Mobility Transistor) cascode amplifiers were designed and fabricated. The $0.1{\mu}m$ InGaAs/InAlAs/GaAs MHEMT was fabricated for cascode amplifiers. The DC characteristics of MHEMT are 670 mA/mm of drain current density, 588 mS/mm of maximum transconductance. The current gain cut-off frequency($f_T$) is 139 GHz and the maximum oscillation frequency($f_{max}$) is 266 GHz. To prevent oscillation of the designed cascode amplifiers, a parallel resistor and capacitor were connected to the drain of common gate device. By using the CPW (Coplanar Waveguide) transmission line, the cascode amplifier was designed and matched for the broadband characteristics. The designed amplifier was fabricated by the MHEMT MMIC process that was developed through this research. As the results of measurement, the amplifier was obtained 3 dB bandwidth of 50.37 GHz between 20.76 to 71.13 GHz. Also, this amplifier represents the S21 gain with the average 7.07 dB gain in bandwidth and the maximum gain of 10.3 dB at 30 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.4
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• pp.825-832
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• 2014

Previous works for detecting arrhythmia have mostly used nonlinear method such as artificial neural network, fuzzy theory, support vector machine to increase classification accuracy. Most methods require accurate detection of P-QRS-T point, higher computational cost and larger processing time. Even if some methods have the advantage in low complexity, but they generally suffer form low sensitivity. Also, it is difficult to detect PVC accurately because of the various QRS pattern by person's individual difference. Therefore it is necessary to design an efficient algorithm that classifies PVC based on QRS pattern in realtime and decreases computational cost by extracting minimal feature. In this paper, we propose PVC classification based on QRS pattern using QS interval and R wave amplitude. For this purpose, we detected R wave, RR interval, QRS pattern from noise-free ECG signal through the preprocessing method. Also, we classified PVC in realtime through QS interval and R wave amplitude. The performance of R wave detection, PVC classification is evaluated by using 9 record of MIT-BIH arrhythmia database that included over 30 PVC. The achieved scores indicate the average of 99.02% in R wave detection and the rate of 93.72% in PVC classification.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.6
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• pp.383-390
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• 2021

The experiments in coastal engineering are very complex and a lot of components should be concerned. The experience has an important role in the successful execution. Hydraulic model experiments have been improved with the development of the wave generator and the advanced measuring apparatus. The hydraulic experiments have the advantage, that is, the stability of coastal structures and the hydraulic characteristics could be observed more intuitively rather than the numerical modelings. However, different experimental results can be drawn depending on the model scale, facilities, apparatus, and experimenters. In this study, two-dimensional hydraulic experiments were performed to suggest the guide of the test wave(random wave) generation, which is the most basic and important factor for the model test. The techniques for generating the random waves with frequency energy spectrum and the range for the incident wave height [(H_S)_M/(H_S)_T = 1~1.05] were suggested. The proposed guide for the test wave generation will contribute to enhancing the reliability of the experimental results in coastal engineering.

• 한국전산유체공학회:학술대회논문집
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• 2001.05a
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• pp.116-120
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• 2001

The impactive Pressure wave induced by pyro valve in the pressurization system of KSR-III may result in fatal failure or malfunction of valves, so it is important to know the pressure wave characteristic in the pressurization system. An unsteady flow analysis in the simplified pressurization system was peformed by Finite difference method.