• The Journal of Korean Institute of Communications and Information Sciences
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• 제21권12호
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• pp.3183-3195
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• 1996

As a method for effective utilization of the limited power and frequency resources in satellite communications, this paper develops software which can assigns the optimal power of input carrier groups inthe multi-level SCPC systems and performs evaluation to a various satellite link environment. Using the developed software, the paper presents performance according to the frequency plan of carrier groups and suggest a frequency play method for performance improvement of satellite link. A various interference and noise caused by satellite link are analyzed for reliable performance evaluation. The performance criteria for evaluation is classified into 2 categories according to the CNR of destination receiver earth station.

• Journal of Korean Tunnelling and Underground Space Association
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• 제9권4호
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• pp.403-413
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• 2007

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators fur the evaluation of rock bolt integrity.

• Journal of the Korean Geotechnical Society
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• 제25권12호
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• pp.5-12
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• 2009

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these structures. The purpose of this study is the evaluation of rock bolt integrity using wavelet transforms of the guided ultrasonic waves by using transmission test in the field. After several rock bolts with various defect ratios are embedded into a large scale concrete block and rock mass, guided waves are generated by a piezo disk element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the time-frequency domain using the wavelet transform based on a Gabor wavelet. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with an increase in the defect ratio. The suitable curing time for the evergy velocity analysis is proposed by the laboratory test, and in-situ tests are performed in two tunnelling sites to verify the applicability of rock bolt integrity tests performed after proposed curing time. This study proves that time-frequency domain analysis is an effective tool for the evaluation of the rock bolt integrity.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제7권3호
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• pp.155-164
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• 1987

A new design method of rubble mound structures that includes the considerations of stability and wave control is proposed. Using the method, design of structures that reduce the wave reflection and run-up and increase the rubble stability is assured under the given wave conditions. The new design formula is developed so that the allowable prcentage of damage and the wave grouping effects on rubble stability are also considered in design. For this a new definition of the mean run-sum is made. Finally, the new method is applied for the design of uniform and composite slope rubble mound structures and the significant advantages are found.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제20권6호
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• pp.583-588
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• 2008

Swell data observed in the East Sea in February, 2008 were analyzed using wavelet method. The wavelet analyzed results show detailed time series variation of wave group, peak frequency and spectrum. The comparison of time averaged wavelet spectrum with fourier spectrum turn out to be very similar in terms of spectrum shape and peak frequency evolution but the peak frequency wave energy and the significant wave height show discrepancies. Wavelet analysis can detect the change of spectrum in time as well as in frequency and very efficient to study transient and irregular phenomena such as freak waves and abnormal swells in the ocean. More analysis with more wave data are needed for future application.

• Journal of Chest Surgery
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• 제31권1호
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• pp.7-12
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• 1998

The study in detection of perioperative myocardial infarction by serial ECGs and the analysis of risk factors involved was carried out from January 1994 to July 1996 on 87 consecutive patients undergoing coronary artery bypass grafting. There were significant differences in the mean CK-MB peaks and frequencies of flipping in LDH1/LDH2 among the 3 groups(group I: new Q-wave, group II: S-T change, group III: no ECG change). The ECG was considered positive for postoperative myocardial infarction if the new Q-waves appeared in the postoperative period or if S-T segment changes persisted for more than 48 hours. The hospital mortality rate was 3.3% and the perioperative infarction rate was 17.2%. The following risk factors of the perioperative MI were found: endarterectomy, decreased ejection fraction($\leq$40%) and prolonged aortic cross clamping time. Left main disease, triple vessel disease, 3 or more graft, unstable angina and hypertension did not correlate with myocardial infarction. This study suggests that serial ECGs could be used as means of detecting the perioperative myocardial infarction after coronary artery bypass grafting.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제24권1호
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• pp.10-15
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• 2012

Wave characteristics in the presence of energy damping are investigated using the linear shallow water equations. To get the phase and energy velocities, geometric optics approach is used and then these values are validated through numerical experiments. Energy damping affects wave height, phase and energy velocities which result in wave transformation. When the complex wavenumber is used by the Eulerian approach, it is found that the phase velocity decreases as the damping increases while the energy velocity increases showing higher values than the phase velocity. When the complex angular frequency is used by the Lagrangian approach, the energy-damping wave group is found to propagate in the energy velocity. The energy velocity is found to affect shoaling and refraction coefficient which is verified through numerical experiments for waves on a plane slope.

• Journal of the Society of Naval Architects of Korea
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• 제29권3호
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• pp.131-139
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• 1992

By introducing a body potential, the high-oder spectal method of Dommermuth and Yue(1987) is extended to treat the nonlinear interactions between the free surface and the submerged cylinder. A 2-dimensional numerical wave tank is developed based on this numerical scheme, and applied to the wave resistance problem and the wave maker problem. In the simulations, it is shown that the transient waves due to the impulsive start of the body motion make a practical obstacle to the acquisition of useful data from the numerical experiments. Gradual starting procedures are devised, and successful result of the quasi-steady state or the uniform regular wave group was obtained. Within the author's present knowledge, the present numerical scheme is one of the most efficient numerical schemes which can treat the nonlinear interactions between the free surface and the body motion in time-domain.

• Journal of the Earthquake Engineering Society of Korea
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• 제12권5호
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• pp.39-45
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• 2008

The source parameters of 85 events ($1.6\;{\leq}\;M_L\;{\leq}\;4.9$) that occurred in and around the Korean Peninsula during 2006 and 2007 were analyzed by an iterative spectral fitting procedure. The data set consists of 487 S-wave trains on three-component seismograms recorded at broadband seismograph stations in the southern part of the Korean Peninsula. Moment magnitudes for each event were determined using spectral analyses of the seismograms, and the results were compared with the variation in corner frequencies with hypocentral distance. Corner frequencies have a tendency to decrease with increases in hypocentral distance, and the decrease is smaller the larger the moment magnitude. We define the measured corner frequency on a displacement spectrum as the apparent corner frequency. Although it was reported that the distance dependency of the corner frequency was found in some regions, such as the eastern Canadian Shield and the Baltic Shield, the origin of the phenomenon is not certain yet.

• Journal of Korean Medical classics
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• 제20권1호
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• pp.75-84
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• 2007

본논문천명(本論文闡明) "류경(類經)" 위안등창익의학사상적천원(爲安藤昌益醫學思想的泉源), 종안등창익학습(從安藤昌益學習) "류경(類經)" 적계단래비판(的階段來批判) "류경(類經)", 집중적연구관찰극복계단적전화과정(集中的硏究觀察克服階段的轉化過程). 안등창익(1703-1762)재일본강호시대시개즉독창우진보적사상가야시중의사(安藤昌益(1703-1762)在日本江戶時代是個卽獨創又進步的思想家也是中醫師). 타통과(他通過)'자연진영도(自然眞營道)'등굉대적저술(等宏大的著述), 부근논술료사회철학급자연철학(不僅論述了社會哲學及自然哲學), 이차재일본의학사상난이발현적독특적의학사상급여체계화(而且在日本醫學史上難以發現的獨特的醫學思想給與體系化). 타이유교비판위기초(他以儒敎批判爲基礎), 비판중국의학대유유의적경향(批判中國醫學帶有有醫的傾向), 여후세파(與後世派), 고방파적맥락야부동(古方派的脈絡也不同), 독자제정일본의학(獨自制訂日本醫學). 타대어중국적음양오행설이진퇴론화사행팔기적호성론래대항(他對於中國的陰陽五行設以進退論和四行八氣的互性論來對抗), 대어'내경'적국가유추(analogy)내장관이유기생체적내장관래대치(對於‘內經’的國家類推(analogy)內臟觀以有機生體的內臟觀來對峙). 병차비판숙명론적운기론이제창대소우주론적생태학(ecology)적의학. 이차간래(以此看來), 안등창익적의학사상시이비판'내경'위개단(安藤昌益的醫學思想是以批判‘內經’爲開端). 아문가이통과안등창익적운기론적비판래명백(我們可以通過安藤昌益的運氣論的批判來明白), 타대'내경'적이해시의거장개빈적 "류경"(포괄'도익'화'부익')(他對'內經'的理解是依據張介賓的"類經"(包括'圖翼' 和 '附翼')). 안등창익일방면계승장개빈적운기론영일방면야지유비판적태도. 타주장십기래대체십간(他主張十氣來代替十干), 인위군화여상화시파군신적상하관계정당화(認爲君火與相火是把君臣的上下關係正堂化), 인이반대저양적사고방식(因而反對這樣的思考方式). 병차안등창익부정기성적음운학, 제창자연적운도(提唱自然的韻道), 아문가이확인대어타적사상장개빈적 "류경" 시위중요적기초(我們可以確認對於他的思想張介賓的 "類經" 是爲重要的基礎).