• 한국해양공학회지
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• 제21권1호
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• pp.31-39
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• 2007

Recently, the nonlinear dynamic responses among waves, submarine pipeline and seabed have become a target of analyses for marine geotechnical and coastal engineers. Specifically, the velocity field around the submarine pipeline and the wave-induced responses of soil, such as stress and strain inside seabed, have been recognized as dominant factors in discussing the stability of submarine pipeline. The aim of this paper is to investigate nonlinear dynamic responses of soil in seabed, around submarine pipeline, under wave loading. In order to examine wave-induced soil responses, first, the calculation is conducted in the whole domain, including wave field and the seabed, using the VOF-FDM method. Then, velocities and pressures, which are obtained on the boundary between the wave field and the seabed, are used as the boundary condition to compute the wave-induced stress and strain inside seabed, using the poro-elastic FEM model, which is based on the approximation of the Biot's equations. Based on the numerical results, the characteristics of wave-induced soil responses around submarine pipeline are investigated, in detail, inrelation to relative separate distance of the submarine pipeline from seabed. Also, the velocity field around the submarine pipeline is discussed.

• Nutrition Research and Practice
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• 제11권4호
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• pp.327-333
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• 2017

BACKGROUND/OBJECTIVES: Complications of diabetes, such as cardiovascular disease, are associated with increased mortality among type 2 diabetes mellitus patients. Homocysteine has been recently identified as a predictor of cardiovascular disease-related complications in diabetes. We investigated whether or not supplementation with folic acid tablets can lower homocysteine levels and improve parameters related with vascular complications. SUBJECTS/METHODS: We conducted a non-randomized 8-week trial involving postmenopausal diabetic women (n = 25) supplemented with $800{\mu}g$ of folic acid ($400{\mu}g$ twice a day) daily. Subjects' serum levels of folate, homocysteine, and vitamin $B_{12}$ were measured, along with vascular function and brachial-ankle pulse wave velocity. RESULTS: Folic acid supplementation significantly increased serum folate levels (P < 0.0001), reduced homocysteine levels (P < 0.0001), and increased vitamin $B_{12}$ levels (P = 0.0063). There were significant decreases in low-density lipoprotein cholesterol levels as well as the ratios of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol and total cholesterol to high-density lipoprotein cholesterol. Brachial-ankle pulse wave velocities were not altered by supplementation. Changes in serum vitamin $B_{12}$ after folic acid supplementation were negatively correlated with changes in brachial-ankle pulse wave velocity. CONCLUSIONS: In this study on postmenopausal Korean women with type 2 diabetes mellitus, folic acid supplementation reduced serum homocysteine levels, increased serum folate and vitamin $B_{12}$ levels, and lowered lipid parameters.

• 한국안전학회지
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• 제32권2호
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• pp.98-104
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• 2017

The ultrasonic pulse velocities of pressure, shear, and Rayleigh waves ( P-, S-, and R- waves) have been used for the condition evaluation of various concrete structures, but the statistical distribution according to the wave type has not been studied clearly in view of data reliability and validity. Therefore, this study analyzed the statistical distribution of P-, S-, R-wave velocities in concrete wide beams of $800{\times}3100mm$ (width ${\times}$ length) with a thickness of 300 mm. In addition, we investigated an experimental consistency by the Kolmogorov-Smirnov goodness-of-fit test. The experimental data showed that the R-, S- and P- wave velocities in order have better statistical stability and reliability for in situ evaluation because R- and S-waves are less sensitive to confinement and boundary conditions. Also, good correlations between wave velocities and strength and modulus of elasticity were found, which indicate them as appropriate techniques for estimating the mechanical properties.

• 자원환경지질
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• 제35권5호
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• pp.445-454
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• 2002

본 연구에서는 지진 데이터를 이용한 지진 토모그래피 방법을 통해 남한 지역의 3차원 P파 속도모델을 구하였다. 구해진 3차원 속도모델은 정확한 진앙의 위치 결정과 한반도의 지하구조 연구에 이용될 수 있다. 3차원 속도모델을 구하기 위한 지진토모그래피 방법에서 보다 나은 역산 결과를 얻기 위해 초기모델로서 동시역산방법을 이용한 최소 1차원모델을 사용하였다. 최소 1차원모델의 속도는 0~l9 km사이는 6.04 km/s, 19~32 km차이는 6.45 km/s, 그리고 32~55 km사이는 7.78 km/s 였다. 최소 1차원모델을 초기값으로 하여 3차원 속도모델을 구해본 결과 1층(0~3 km) 에서는 경상분지, 영남육괴, 옥천습곡대에서 높은 속도값을 보이고, 경기육괴에서는 낮은 속도값을 보인다. 2층(3~19 km)에서 경상분지와 연일분지를 제외한 영남육괴 지역에서 높은 속도값이 분포한 반면, 경기육괴와 옥천습곡대에서 낮은 속도값이 분포한다. 3층(19~32 km)에서는 한반도 남부의 속도값은 높은 반면, 경기육괴 내의 SNU, YIN관측소를 제외한 대부분의 중부지역은 낮은 속도분포를 보인다. 4층(32 km)에서는 최대 속도값이 한반도의 중부와 남서부에, 최소 속도값이 남동부와 해안선에서 나타난다. 각 층의 깊이 분포는 중력자료에 의한 지각구조의 양상과 비교한 결과 서로 일치한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1415-1426
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• 2008

Stone columns, locally called "GCP (granular compaction pile)" can be used to improve strength and resistance against lateral movement of a foundation soil like rigid piles and piers. Also installation of such a discrete column facilitates drainage, and densifies and reinforces the soil in the sense of ground improvement. The integrity of the GCP has been indirectly controlled with the records of each batch including depth and the quantity of stone filled. An integrity testing was attempted using crosshole S-wave logging. The method is conceptionally same as the crosshole sonic logging (CSL) for drilled piers. The only and critical difference is that S-wave should be used in the logging, because P-wave velocity of the stone column is less than that of ground water. The crosshole sonic logger does not have the capability to measure S-wave propagating through the skeleton of crushed stone. An electro-mechanical source, which can generate either P- or SH-waves, and a 1-D geophone were used to measure SH-waves. Two 76mm diameter cased boreholes were installed 1 meter apart across the nominal 700mm diameter stone column. At every 10cm of depth, shear wave was measured across the stone column. One more borehole was also installed 1 meter outward from the one of the above boreholes to measure the shear wave profile of the surrounding soil. The diametric variation of the stone column with respect to depth was evaluated from the shear wave arrival times across the stone column, and shear wave velocities of crushed stone and surrounding soil. The volume calculated with these variational diameters is very close to the actual quantity of the stone filled.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.49-54
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• 2000

Korea Institute of Geology Mining and Materials(KIGAM) has been operating Korean Earthquake Monitoring System(KEMS) to archive the real-time data stream and to determine event parameters (epicenter origin time and magnitude)by the automatic processing and analyst review. To do this KEMS uses the Vindel Hue's velocity model which was derived from Wonju KSRS data. Because KIGAM now receives the real-time data from many stations including Wonju KSRS Cholwon seismo-acoustic array Uljin Wolsung Youngkwang Taejon Seoul Kimcheon Taegu etc. the proper velocity model should be established around the Korean peninsula, In this study P were velocity structures was derived from VELEST program using 69 events among the 835 events determined by KEMS in 1999 which were recorded by at least 5 stations. General trend of velocity structure was similar to Sang Jo Kim's model but velocity value was low in crust and high in upper mantle. Due to the sensitivity of inversion results to the initial input model the artificial short and blast data might be added.

• 한국터널지하공간학회 논문집
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• 제14권4호
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• pp.421-435
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• 2012

연마재 워터젯을 이용하여 다양한 영향변수에 따라 암석시편에 굴착(제거)실험을 수행하였다. 현장암반굴착 가능성을 판단하기 위해 신선한 경암(화강암) 시편을 기준으로 수압, 노출시간, 그리고 이격거리에 따라 굴착성능 및 굴착형상을 분석하였다. 특히 이격거리는 현장에서 요구하는 높은 수준의 조건에서 실험을 실시였다. 추가적으로 암석에 따른 굴착성능을 비교하기 위해, 실제 굴착현장에서 획득한 암석시편을 대상으로 P파 속도를 측정하여 동일한 조건에서 워터젯 실험을 수행하였다. 획득된 실험결과로부터 워터젯 변수가 암반제거에 미치는 영향을 분석하였다.

• 대한임상전기생리학회지
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• 제1권1호
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• pp.1-15
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• 2003

The purpose of this study was to determine the effect of neuromuscular electrical stimulation(NMES) on the alteration of spinal motor neuron excitability. In this article, I would like to experiment on a standard capacity of clinical electrophysiology, a difference in applying methods and a clinical efficiency of NMES by Nerve conduction velocity. We used normal eight subjects without neuromuscular disease and all subjects participated 3 session, which at least 1 week between session. Participants classified according to each group in Antagonist, Agonist, Antagonist-Agonist by the NMES. The test was measured continuously pre test, post-test, post 20 minute test by EMG including H reflex, F wave, motor nerve conduction velocity(MNCV). The following results were obtained; 1. H-reflex latencies and H/M intervals were significantly increased in agonist and antagonist-agonist group(p<.01). 2. H-reflex amplitudes and H/M ratios were significantly decreased in agonist and antagonist-agonist group(p<.01). In agonist group, H-reflex amplitudes and H/M ratios were more significantly decreased than antagonist group. 3. F-wave latencies were significantly increased in agonist and antagonist-agonist group(p<.01). F/M intervals were significantly increased in antagonist-agonist group(p<.01). F wave conduction velocities were significantly increased in agonist and antagonist-agonist group(p<.01) but F/M ratios were not significant. 4. MNCV were significantly decreased in agonist(p<.01). These results lead us to the conclusion that agonist and Antagonist-agonist was significantly decreased excitability of spinal motor neuron. Conversely, Antagonist does not decreased. Therefore, A further direction of this study will be to provide more evidence that NMES have an effect on excitability of spinal motor neurons in UMN syndrome.

• 지구물리
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• 제5권2호
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• pp.87-97
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• 2002

기상청 광대역 관측소에서 2000~2001년 포착된 원거리 지진들의 종파 초동 시간의 상대적 도달 시간차이를 분석하여 관측소 하부 지각구조차이에 의한 평균 도달시간이상을 도출하였다. 각 광대역 지진 관측소에서 측정되어진 종파의 상대적 도달시간차이들은 최대 1.5 초로 측정되었다. 각 관측소들의 평균적인 도달시간이상은 최대 0.6초의 차이를 보이며 향후 지진요소 결정 시 이런 차이를 보정하여 주면보다 정밀한 지진요소를 산출할 수 있을 것이다. 각 관측소의 속도 대비차원에서는 최대-4~4%의 속도 대비를 가질 수 있는 것으로 추정되었다. 전반적으로 서울, 춘천, 강릉, 울진, 그리고 울릉도 광대역 관측소에서는 상대적으로 0.05~0.3초 늦은 평균도달시간 이상을 보이며 속도대비로는 0~4% 늦은 것으로 계산되었다. 한편 서산, 대전, 광주, 대구, 서귀포, 그리고 부산 광대역 관측소에서는 0.05~0.3초 빠른 평균도달시간 이상을 보여주며 속도대비로는 약 0~4% 빠른 것으로 계산된다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.45-49
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• 2003

The velocity structure beneath the CHNB broadband station is determined by receiver function analysis using by from teleseismic P waveforms. The detailed broadband receiver functions are obtained by stacking method for source-equalized vertical, radial and tangential components of teleseismic P waveforms. A time domain inversion uses the stacked radial receiver function to determine vertical P wave velocity structure beneath the station. The crustal velocity structures beneath the stations are estimated using the receiver function inversion method in the case at the crustal model parameterized by many thin, flat-tying, homogeneous layers. The result of crust at model inversion shows the crustal velocity structure beneath the CHNB station varies smoothly with increasing depth, and there are six discontinuity around 2.5km, 6.25km, 12.5km, 22.5km and 27.5km depth, with Moho discontinuity at about 32.5km depth.