• Journal of applied mathematics & informatics
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• 제28권5_6호
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• pp.1089-1099
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• 2010

An SIR epidemic model with pulse vaccination and time delay describing infection period is investigated. The global attractiveness of the infection-free periodic solution is discussed, and sufficient condition is obtained for the permanence of the system. Our results indicate that a large vaccination rate or a short period of pulsing leads to the eradication of the disease.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.609-612
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• 2002

A new reset waveform is proposed for reducing the reset period. A square pulse is applied to the address electrode while reset pulse ramps and before a discharge between the sustain electrodes occurs. The square pulse induces a discharge between the address electrode and the X electrode, and the induced wall charge is opposite to the applied ramp pulse. Thus, the next discharge between the sustain electrodes becomes weaker. The weaker discharge lowers background luminance and improves contrast ratio. Thus, the new reset waveform can reduce ramp up time in the ramp reset waveform The experimental results show that the ramp up time can be reduced by about 90% compared with the conventional ramp reset waveform.

• Journal of the Optical Society of Korea
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• 제8권1호
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• pp.29-33
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• 2004

We propose and demonstrate a novel optical pulse multiplier applicable to OTDM (Optical Time Division Multiplexing) systems using cascaded long-period fiber gratings. We have exploited the fact that each mode in a fiber has a different propagation constant to obtain time delays among optical pulses. The proposed scheme could realize high-frequency optical pulse multiplication for optical short pulse trains. We have successfully implemented two, four, and eight times multiplications with the maximum repetition rate of 416.7 ㎓. The obtained pulse delays are well matched with the simulated ones.

• 대한기계학회논문집
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• 제17권11호
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• pp.2684-2693
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• 1993

The free vibration and dynamic response of cross-ply for CFRP and GFRP laminated circular cylindrical shells under dynamic loadings are investigated by using the first-order shear deformation shell theory. The modal analysis technique is used to develop the analytical solutions of simply supported cylindrical shells under dynamic load. The analysis is based on an expansion of the loads, displacements and rotations in a double Fourier series which satisfies the and boundary conditions of simply support. Analytical solution is assumed to be separable into a function of time and a function of position. In this paper, the considered load forces are step pulse, sine pulse, triangular(1, 2, 3) pulse and exponential pulse. The solution for a given loading pulse can be found by involving the convolution integral. The results show that the dynamic response are governed primarily by the natural period of the structure.

• Earthquakes and Structures
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• 제7권1호
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• pp.83-99
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• 2014

This study is devoted to estimate higher-mode effects for multi-story structures with considering soil-structure interaction subjected to decomposed parts of near-fault ground motions. The soil beneath the super-structure is simulated based on the Cone model concept. Two-dimensional structural models of 5, 15, and 25-story shear buildings are idealized by using nonlinear stick models. The ratio of base shears for the soil-MDOF structure system to those obtained from the equivalent soil-SDOF structure system is selected as an estimator to quantify the higher-mode effects. The results demonstrate that the trend of higher-mode effects is regular for pulse component and has a descending variation with respect to the pulse period, whereas an erratic pattern is obtained for high-frequency component. Moreover, the effect of pulse component on higher modes is more significant than high-frequency part for very short-period pulses and as the pulse period increases this phenomenon becomes vice-versa. SSI mechanism increases the higher-mode effects for both pulse and high-frequency components and slenderizing the super-structure amplifies such effects. Furthermore, for low story ductility ranges, increasing nonlinearity level leads to intensify the higher-mode effects; however, for high story ductility, such effects mitigates.

• 대한기계학회논문집B
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• 제21권10호
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• pp.1254-1261
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• 1997

Pulse boiling, the unsteady periodic boiling phenomenon appearing in the evaporator of thermosyphons was investigated by many researchers. In the present study investigations were conducted to examine the evolution of flow patterns at the evaporator, and changes in thermodynamic state that each of liquid pool and vapor experiences through 1 cycle of pulse boiling process. For wall and liquid pool the degree of superheat for the onset of nucleation was examined. It revealed that the degree of superheat increased with the increase of pulse period, reaching to 16.5 deg.C and 23 deg.C for liquid pool and evaporator wall respectively at .tau.=80 sec. The data on flow patterns obtained through series of operation tests were plotted in the coordinates of heat flux and vapor pressure to get a regime map. Further this map could be used to figure out the conditions of pulse boiling for a thermosyphon.

• 설비공학논문집
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• 제13권11호
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• pp.1059-1064
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• 2001

This study Investigates the effect of the wave form of pulse energization on the collection characteristics of a wide plate spacing electrostatic precipitator. For the semi-pulse energization, the peak current and voltage of the energization increases with increase of the pulse period, and the corona current increases, as pulse ratio decreases. For the micro-pulse energization, the corona current increases with increase of the pulse voltage. The collection efficiency of semi-pulse and micro-pulse energization is larger than that of DC charge.

• 전기학회논문지
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• 제58권6호
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• pp.1194-1199
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• 2009

Heart rate may be a very important parameter in human health. To extract heart rate, the electrocardiogram(ECG) is commonly used. But the ECG acquisition procedure is very complex. On the other hand, the acquisition of pulse wave or photoplethysmogram(PPG) is very easy. However, the peak of PPG is not so sharp as ECG. This study tries to enhance the performance of peak detection in PPG signal. The method uses the average slopes around the main peak. The crossing point of the increasing and the decreasing slopes is selected as the peak point of heart rate period. The proposed method showed smoothed heart rate graph and reduced irregularity in heart rate values.

• 수산해양기술연구
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• 제28권3호
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• pp.252-261
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• 1992

The accuracy of the position fixing with telemetry techniques depends in general on the accuracy of the location of the receiving point(hydrophone). To increase the accuracy of the coordinates of four hydrophones suspended down at both sides of the vessel anchored, each hydrophone motion is compensated using a depth pinger mounted on the seabed of 30m depth. The pinger location is calculated with a hyperbolic method. Using this technique so called hydrophone coordinates calibration, the movement of the Remotely Operated Vehicle(ROV), which has the same type of pinger mentioned above could be tracked down more accurately. Under the maximum variation ranges of a hydrophone of 5.2m in athwartships, 3.2m in alongship, and about 0.2m/s of the moving velocity in both directions, the ROV track with calibration is more close to the reality than that without calibration Tow depth pingers of same frequency can be distinguished by the use of three factors; The pulse period, the phase and the pulse period variation allowed in acquisition of the pinger as far as its pulse period is varied in smooth.

• 생명과학회지
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• 제13권1호
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• pp.42-46
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• 2003

광전용적맥파는 인체의 말초 부위에서 맥파를 검출하는데 널리 이용되고 있으며 심박동수 측정 및 혈액산소포화도 측정에 이용되고 있다. 본 연구는 940 nm의 적외선을 이용한 광전용적맥파를 이용하여 손목에서 요골동맥의 맥파를 기록하였으며 센서의 측정 위치에 따라 맥파의 모양이 다르게 나타나는 것을 관찰하였다. 요골동맥 바로 위의 피부부위에서 기록되는 광전용적파는 손가락 끝에서 기록되는 맥파에 비하여 반전되어있는 특성을 보였다. 반전된 맥파의 발생기전은 센서의 발광부에서 나오는 940 nm의 적외선이 조직에 입사하여 반사되어 나오는 경로의 용적 변화가 심장주기에 따라 일어나지만 손가락 끝부분에 비하여 반대 작용이 있음을 나타낸다. 요골동맥의 바로 위 피하 조직은 심장주기에 따라 동맥의 확장 또는 수축이 발생하면 동맥외벽과 피부 사이 조직에 혈류량의 변화가 일어나며 동맥의 확장 시에는 혈류량이 감소하고 이완시에는 증가되는 특성으로 인하여 반전맥파를 형성하는 것으로 추측된다. 이러한 결과는 요골동맥의 벽에서 적외선 반사가 있음을 시사한다.