• Journal of Power Electronics
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• v.12 no.2
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• pp.258-267
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• 2012

An interleaved single-stage AC/DC converter with a boost converter and an asymmetrical half-bridge topology is presented to achieve power factor correction, zero voltage switching (ZVS) and load voltage regulation. Asymmetric pulse-width modulation (PWM) is adopted to achieve ZVS turn-on for all of the switches and to increase circuit efficiency. Two ZVS half-bridge converters with interleaved PWM are connected in parallel to reduce the ripple current at input and output sides, to control the output voltage at a desired value and to achieve load current sharing. A center-tapped rectifier is adopted at the secondary side of the transformers to achieve full-wave rectification. The boost converter is operated in discontinuous conduction mode (DCM) to automatically draw a sinusoidal line current from an AC source with a high power factor and a low current distortion. Finally, a 240W converter with the proposed topology has been implemented to verify the performance and feasibility of the proposed converter.

• Fire Science and Engineering
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• v.30 no.4
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• pp.94-102
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• 2016

When establishing shielding facilities for EMP protection, WBC effect is used to protect fire pipes and honeycomb cells are inserted into the fire pipes to improve the shielding effectiveness. At this point, the smaller unit cell of honeycombs becomes, the more likely it interrupts the flow of water, which ends up clogging the fire pipes with sediment. To prevent this phenomenon, I would suggest a design method due to the pilarization loss of water molecules that contributes to increasing the size of honeycomb cells and remaining thin-walled sufficient for required shielding effectiveness.

• Journal of the Korea Society for Simulation
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• v.9 no.3
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• pp.1-11
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• 2000

This paper proposes the practical echo-signal synthesis models - UTAHID (Underwater TArget by Highlight Distribution) & M-UTAHID(Modified UTAHID) - of underwater target for active sonar engineering At high frequencies all the echo components that are the specular reflected waves and various elastic scattering wave scan be regarded the summation of individual echo from some equivalent scattering centers, so the underwater target is characterized by highlights distributed in spatial target structure. Proposed models are compared with characteristics of random distributed model & equivalent interval highlight model, and analyzed target strength, echo-elongation effect, target time spread loss and so on. Thus these can be efficiently used in various real systems related to underwater target echo-signal synthesis on active sonar and acoustic countermeasure.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.08a
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• pp.289-292
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• 2000

선형 자귀회귀(AR) 모델을 근거로한 HRV 파워 스펙트럼해석은 비침습적으로 자율신경의 반응을 정량화하는데 폭넓게 사용된다. 본 연구는 단구간(2분 미만)의 심전도와 맥파 신호로부터 시계열 HRV의 파워스펙트럼을 추정한다. 시계열은 정상인을 대상으로 검출한 심전도와 맥파신호의 특징점 시간간격(RRI, PPI)으로부터 구하였다. 발생된 시계열은 다항식 보간법에 의해 AR모델에 적합하게 재구성하였으며, AR모델 계수는 Burg법에 의해 계산하였다. AR모델을 적용한 단구간의 심전도와 맥파의 심박변동에 대한 파워스펙트럼밀도는 저주파수(LF)와 고주파수(HF)에서 매끄러운 스펙트럼 파워를 나타내고 있다. 또한 동일한 피험자의 심전도와 맥파의 파워스펙트럼밀도를 비교한 결과 동일한 모양을 나타내었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.644-653
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• 2013

In this paper, a formulation for obliquely incident electromagnetic wave has been presented for an analysis of highpower electromagnetic pulse penetration into multilayered dispersive media. Based on generalized models of measured dielectric constants and propagation channels reflecting the Earth's general features, the propagation phenomenon of the obliquely incident early-time(E1) high altitude electromagnetic pulse(HEMP) is analyzed. In addition, the polarization and critical angle are also considered. It is found that the total reflection occurs at an incident angle of about 38 degrees at the soil-rock interface, and that the parallel-polarized E1 HEMP penetrates better than the perpendicular-polarized one. The peak level of the penetrating electric field is found to be 5.6 kV/m at normal incidence, regardless of the type of polarization, and E1 HEMP is greatly reduced near the critical angle. Moreover, the penetrating E1 HEMP is analyzed as a variation of moisture content and depth of materials, resulting E1 HEMP could be useful in determining the levels of shielding required for buried facilities.

• Journal of Acupuncture Research
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• v.19 no.3
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• pp.126-137
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• 2002

Objective : There is accumulating data that cardiovascular diseases, including hypertension, cerebro-vascular accident, coronary heart disease, relate to atherosclerotic changes. Increased serum levels of lipids could play a role in these circumstances. the SDPTG(the second derivative of photoplethysmogram waveform) is noninvasive methods for evaluating the pulse wave and is correlated with age and other risk factors for atherosclerosis. Methods : To study the effects of serum lipid levels on the SDPTG in the middle-age adults, data on serum lipid levels and the SDPTG were collected in 80 healthy middle age with varying serum lipid concentrations. Biological vascular age was assessed using the SDPTG. the SDPTG consists of an a, b, c, and d wave in systole and an e wave in diastole; an SDPTG aging index(Al) was calculated as (b-c-d-e)/a. Results : Serum triglyceride, total cholesterol, total lipid, phospholipid, HDL cholesterol levels were respectively and significantly correlated with SDPTG Al. Serum lipid levels and blood pressure are age-dependent and the SDPTG is blood pressure-dependent. Restricting analysis to age and blood pressure yield strong positive correlations between serum triglyceride, total lipid levels and SDPTG Al, but no correlations between serum total cholesterol, phospholipid levels and SDPTG Al. Conclusion : The results of this study suggest that preventive acupuncture programs or herbal medications for reducing serum lipid, especially triglyceride, levels in middle-age should include a evaluation of biological vascular aging with the second derivative of photoplethysmogram waveform.

• Journal of Acupuncture Research
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• v.27 no.2
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• pp.23-30
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• 2010

Objectives : The second derivative of photoplethysmogram waveform(SDPTG) is a simple, convenient and non-invasive technique for pulse wave analysis. This study was designed to investigate the differences in the SDPTG between the affected side and the unaffected side in hemiparetic patients after stroke, and the effects of acupuncture at Palsa(BaXie) in hemiparetic patients after stroke. Methods : To evaluate the differences between the affected side and the unaffected side in hemiparetic patients after stroke, their SDPTG were recorded by using a Cardio Peri SA6000. To evaluate the effects of acupuncture at Palsa(BaXie) in 20 hemiparetic patients after stroke and 20 healthy subjects, their SDPTG were recorded 2 times(pre-acupuncture and post-acupuncture). The SDPTG consists of an a, b, c and d wave in systole and an e wave in diastole. Sano aging index was defined as (b-c-d)/a. Results : 1. The affected side in hemiparetic patients after stroke had higher average b/a ratio(p<0.05)and Sano aging index(p<0.05) than the unaffected side 2. In a comparison of pre-acupuncture and post-acupuncture at the Palsa(BaXie), b/a ratio(p<0.05) and Sano aging index(p<0.05) was decreased significantly in both hemiparetic patients and healthy subjects. Conclusions : These findings suggest that acupuncture at Palsa(BaXie) may be effective method of reverting some of the deleterious effects on vascular function produced by stroke.

• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.521-527
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• 1990

The binding characteristics and analytical applications of anilinium ion complexes with 18-crown-6 were studied by polarography and NMR. First, the electrochemical reduction of the 10 species of mono and dimethylsubstituted anilinium ion complexes with 18-crown-6 as host in methanol are examined. The addition of 18-crown-6 to anilinium guest solution the polarographic waves remain well defined but shifted toward more negative potentials, indicating the complex formation. The values of formation constants, log Κ for 10 species of methylsubstituted anilinium ion complexes with 18-crown-6 varies from 2.7 to 4.8 in methanol at $25^{\circ}C$. The stability order of complexes for 18-crown-6 is anilinilum > 4-methyl > 3,4-dimethyl > 3-methyl > 3,5-dimethyl > 2,4-dimethyl > 2,5-dimethyl > 2,3-dimethyl > 2-methyl > 2,6-dimethylanilinium ion. The steric hindrance shows significant effect. Second, Proton NMR was used to elucidate their interaction characteristics. From the results of so called NMR titration techniques, the behaviors of binding sites on complexation, and the stoichiometry and stability order of complex were obtained. And the later results show the satisfactory agreement with the quantitative values obtained by polarography. Finally, the individual determinations of anilinium ion mixtures were also accomplished by addition of 18-crown-6. In some mixtures of methyl or dimethylanilinium ions the reduction peaks of differential pulse method appeared into one unresolved wave attributed to the small difference of half-wave potential, ${\Delta}E_{1/2}$. In the presence of 18-crown-6, the polarographic waves were resolved into individual maxima because of the shift toward more negative direction by the difference of selectivity of anilinium ions with 18-crown-6. It may be concluded that quantitative analysis of methylanilinium ion mixture make possible because the half-wave potential shift by the selectivity difference due to the steric hindrance between methyl group and 18-crown-6 on complexation.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2011-2018
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• 2024

Since RF breakdown is one of the primary limitations to improving the performances of RF accelerators, extensive efforts have been dedicated to locating the breakdowns. However, most existing methods rely on specialized techniques, resulting in high financial burdens. Although the method based on transient response of transmission line (TL) is suitable for facilities with sporadic recoverable breakdowns, practical operations are susceptible to notable errors. This study revisits the fundamental theories of lossless TL and investigates the wave process to understand the characteristics of the reversed pulse induced by the breakdowns. By utilizing steadystate response of the TL and employing phasor method, we derive analytical formulas to determine the exact location of breakdowns within the faulty cell for constant-gradient TW accelerator. Furthermore, the derived formulas demonstrate their independence from RF phase, thereby distinguishing them from traditional phasebased methods. Additionally, experimental validations are conducted at the HUST injector, and the results confirm the consistency of the analysis. Thus, the proposed method represents a promising improvement over the TL-based approaches and serves as a valuable complement to current techniques. Importantly, this method demonstrates particular advantages for constructed TW accelerators seeking to achieve a balance among high performance, low costs, and compact layouts.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.68-79
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• 2008

Aortic AIx(augmentation index) has been used to measure aortic stiffness quantitatively and even to evaluate ventricular load. However, in order to calculate aortic AIx catheters should be inserted to the subjects' artery, which hampers its clinical usage. To overcome such limitation, aortic AIx has been indirectly calculated by estimating aortic pressure wave from the peripheral arterial pulse by applying transfer functions. In this study, central aortic pressure waves using Millar catheter and radial artery pulse waves using tonometry pressure sensor were measured to establish transfer functions for an estimation of central aortic pressure waves from radial artery pulse waves. Also, an algorithm which detects augmentation point for the calculation of AIx were developed. Developed algorithm for the detection of augmentation point gradually increases the differential order to detect inflection point rather than detects the distinctive point that appears after a specific time. Transfer functions were established using 10th order ARX model and were verified for the stability of the transfer function through residual analysis. Evaluation of an algorithm for the detection of augmentation point were performed by comparing the augmentation points obtained from developed algorithm with the known augmentation points synthesized in various conditions. In addition, developed algorithm for the AIx is proved to provide more accurate results than the ones developed by previous studies. The significance of the study was in two folds. Firstly, the results could provide the basis for the measurement of aortic stiffness using easily-measurable radial artery pulse waves, and secondly, extension of the study may enable the early diagnosis of various vascular diseases.