• Economic and Environmental Geology
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• v.51 no.1
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• pp.39-48
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• 2018

We carried out the standoff compensation data from 2007 to 2011 into four different density borehole models to find out the most effectiveness of standoff compensation charts. First, we investigated the irregular collapse characteristics of gamma ray and cut the non-ideal gamma response to improve the effectiveness of the standoff compensation error data. Effectiveness of detector combinations, density of borehole, and spine and ribs techniques from the modified standoff compensation data was analyzed. As the result of comparison, LSD-MSD combination has been suitable for standoff compensation more than LSD-SSD combination and it is possible to do standoff compensation for soil or weathered zone under groundwater level without fatal errors. Even though error scales of density transformed spine and ribs techniques were generally large compared to the conventional standoff compensation, standoff compensation for soil and weathered zone under groundwater level were sufficiently effective.

• The Journal of Engineering Geology
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• v.25 no.4
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• pp.525-532
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• 2015

After comparing the effectiveness of standoff compensation between current techniques using data obtained from a series of borehole model experiments for standoff compensation in 2007, 2008, and 2009, a follow-up study was conducted to find a more effective standoff compensation algorithm, Comparing the results of the application of the conventional spine and ribs technique, and the spine and ribs technique in terms of apparent density shows that the standoff compensation error obtained from the latter method is more than twice that obtained from the former. The larger size of the compensation error from the spine and ribs plot using the radioactive decay equation indicates that there are no benefits in using this equation in standoff compensation. Based on these results, we propose a reverse transform spine and ribs technique by essentially combining the conventional spine and ribs technique and the spine and ribs technique in terms of apparent density.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.217-225
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• 2009

A series of model borehole experiments and analyses for density compensation were performed to achieve the effective density correction of gamma-gamma log obtained from PVC cased boreholes. A follow-up survey was made for clarifying the variation property of detector responses depending on casing types, the presence of borehole fluid, and the degree of separation between probe and borehole wall. A special emphasis was placed on the comparison of gamma responses obtained from above and below ground water tables. Finally, we could quantify the detector responses as a function of separation between the probe and borehole wall, construct standoff compensation charts, and the limitations of the compensation have been discussed for the environments of both above and below ground water tables.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.137-144
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• 2008

The stand-off errors due to the different separations between the sonde and the borehole wall were measured and analyzed in 4 physical borehole models located in Kangwon National University having different densities with cylindrical and half cylindrical PVC and/or acrylic casings. The analysis of the stand-off error data based on the "spine and ribs" technique suggests a well defined rib line for each model irrespectively of the types and thicknesses of the casing, and that the gradients of the ribs are proportional to the densities of the models. By using these characteristics successful density correction could be made for the plastic casings in NX sized boreholes.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.319-319
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• 2021

유량측정은 측정방법에 따라 측정위치가 변동된다. 도섭법은 관측자가 직접 하천을 횡단하며 측정하는 방법이며 수심이 얕은 경우 가능하다. 보트법의 경우 상대적으로 공간적 제약을 덜 받으며 교량법의 경우 이용 가능한 교량이 있어야 한다. 따라서 교량법은 현장여건에 따라 관측소와 멀리 떨어져 있는 경우가 있으며 이 경우 측정된 유량을 이용하여 수위-유량관계곡선식을 개발한다면 그 정확도가 떨어질 수 있다. 미국지질조사국(USGS)에서는 관측소와 측정위치가 멀리 떨어진 경우 측정된 유량을 보정하도록 규정하고 있다. 우리나라의 경우 유량 보정을 실시하지 않는 것으로 파악되었다. 하지만 이는 수위-유량관계곡선식, 특히 외삽부분에서 큰 오류를 유발할 수도 있어 신중할 필요가 있다. 본 연구에서는 수위관측소와 측정위치가 현저하게 먼 경우 유량 보정방법을 살펴보고 실측유량과 보정유량의 차이를 확인하였다. 대상지점인 낙동강 유역의 안동시(운산리) 지점은 홍수측정위치와 수위관측소 위치가 약 1.7km 이격되어 있으며, 2020년 측정성과(부자)를 이용하여 이를 보정하고 그 차이를 확인하였다. 보정결과 실측유량과 보정유량이 최고 5.0%, 평균 3.7% 차이를 보이는 것으로 확인되었다. 안동시(운산리)지점은 2020년 측정 최고수위가 3.35m이며, 이는 평수위에서 약 2.00m 가량 상승한 것으로 최고 홍수위로 보기는 어렵다. 즉 이보다 더 큰 홍수 사상이 발생하여 수위가 더 상승한다면 실측유량과 보정유량의 차이는 더 커질 것으로 예상된다. 또한 수위관측소와 측정위치가 이격된 경우 측정된 성과가 루프(Loop) 형태를 보일 수 있어 보정이 필요한 것으로 판단된다.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.190-198
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• 2012

A series of density log data were obtained from the standoff experiments made in the four physical model boreholes of different densities, and the properties of spine and rib curves have been derived by the analysis of the gamma-gamma data. Particularly, the shape of gamma ray propagation path between source and detector, the geometrical property of spine and rib curves, the influence of borehole density and the detector combination on the properties of the curves, and the adequate detector combination for standoff compensation could be discussed. It was also confirmed that spine and rib slopes can be expressed as proportional to source-to-detector distance ratio between far and near detectors. The result of this experiment was also effectively applied for understanding the basic concept of spine and rib slopes.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.73-82
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• 2005

We constructed a series of calibration models in the campus of Kangwon National University. A series of experiment for calibrating sonde response as well as casing effect in field measurement. Here we explained the process of construction of calibrating facility which consists of three model holes of different density and three model holes of different diameter. It was discussed the calibration equations obtained from its sonde response calibration test. A density correction chart for different separation of detector from hole wall was suggested, and verified the possibility of determining true density from measurements in cased hole.

• Journal of the Korean Society of Radiology
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• v.18 no.2
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• pp.153-159
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• 2024

In X-ray projection, Unskilled radiologists become skilled through fail exam. This causes the patient to be exposed to unnecessary radiation. In this study, pre-position unskilled radiologic technologist presented ways to improve clinical proficiency. presented a skull lateral x-ray projection practice method using visual, spatial, and assistive devices. In addition, the accuracy and usefulness of the use of assistive devices were evaluated. When X-ray images were taken based on learning, the rotational spacing, which indicates image distortion, was 7.85 ± 1.45 mm and the tiliting spacing was 4.84 ± 0.5 mm. When practicing using visual aids, the rotational spacing is 4.4 ± 0.76 mm and the inclination spacing is 3.01 ± 0.87 mm. using a spatial compensation device, the rotational spacing is 5.2 ± 0.69 mm and the tiliting spacing is 3.33 ± 0.61 mm. Skull lateral X-ray Image distortion caused by empirical photography practice decreased by 5.4%, but image distortion caused by tilting increased by 1.2%. When practicing using a visual assistive devices, the degree of rotational spacing by 40.1% and the tiliting spacing decreased by 30.7% compared to the empirical x-ray exposure practice. When using spatial assistive devices, the rotation interval was reduced by 41.7% and the tilting interval by 23.7% compared to conventional empirical x-ray exposure practice. Therefore, if an unskilled radiologist practices using visual and spatial aids,the accuracy will be improved in skull lateral x-ray projection.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.429-435
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• 2006

A preliminary study was made for density correction for the effect of separation between sonde and borehole wall due to the existence of casing in a borehole. Firstly, series of gamma-gamma measurements were obtained with 3 different separations in 3 different density models constructed in Kangwon National University. Secondly, density correction charts were made based on the 'spine and ribs' technique in mud cake correction. Using these charts, we could determine effectively the true density from the measurement in the thinly cased borehole.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.57-57
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• 2019

최근 수문기상학 분야에서 레이더 강수량을 활용한 응용연구가 활발하게 진행되고 있다. 하지만 레이더 강수량은 경험적으로 설정된 레이더 반사도-강우강도 관계식을 활용하여 레이더 강수량을 산정하기 때문에 실제지상에 도달하는 강수량과 정량적인 오차가 필연적으로 발생한다. 따라서 고해상도의 레이더 강수량을 활용한 신뢰도 높은 수문해석을 위하여 레이더 강수량의 편의보정이 필수적으로 선행되어야한다. 본 연구에서는 불확실성을 고려한 레이더 강수량 편의보정을 위하여 Bayesian 추론기법과 일반화 선형모형(generalized linear model)을 연계하여 레이더 강수량 편의보정 매개변수를 산정하였다. 일반화 선형모형을 적용한 레이더 강수량 편의보정 결과는 현재 널리 사용되고 있는 평균보정(mean field bias) 기법에 비하여 통계지표가 개선된 레이더 강수량 편의보정 결과를 도출하였다. 추가적으로 지형학적 특성에 따른 레이더 강수량 편의보정 매개변수의 변동성을 분석하여 고도 및 이격거리에 따른 편의보정 매개변수의 지역화 공식을 제시하였다. 본 연구를 통하여 개발된 레이더 강수량 편의보정 매개변수 산정 및 지역화 연구는 레이더 관측전략 수립과정에 유용한 기초자료로 활용될 것으로 판단된다.