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Performance Test of Hypocenter Determination Methods under the Assumption of Inaccurate Velocity Models: A case of surface microseismic monitoring (부정확한 속도 모델을 가정한 진원 결정 방법의 성능평가: 지표면 미소지진 모니터링 사례)

  • Woo, Jeong-Ung;Rhie, Junkee;Kang, Tae-Seob
    • Geophysics and Geophysical Exploration
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    • v.19 no.1
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    • pp.1-10
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    • 2016
  • The hypocenter distribution of microseismic events generated by hydraulic fracturing for shale gas development provides essential information for understanding characteristics of fracture network. In this study, we evaluate how inaccurate velocity models influence the inversion results of two widely used location programs, hypoellipse and hypoDD, which are developed based on an iterative linear inversion. We assume that 98 stations are densely located inside the circle with a radius of 4 km and 5 artificial hypocenter sets (S0 ~ S4) are located from the center of the network to the south with 1 km interval. Each hypocenter set contains 25 events placed on the plane. To quantify accuracies of the inversion results, we defined 6 parameters: difference between average hypocenters of assumed and inverted locations, $d_1$; ratio of assumed and inverted areas estimated by hypocenters, r; difference between dip of the reference plane and the best fitting plane for determined hypocenters, ${\theta}$; difference between strike of the reference plane and the best fitting plane for determined hypocenters, ${\phi}$; root-mean-square distance between hypocenters and the best fitting plane, $d_2$; root-mean-square error in horizontal direction on the best fitting plane, $d_3$. Synthetic travel times are calculated for the reference model having 1D layered structure and the inaccurate velocity model for the inversion is constructed by using normal distribution with standard deviations of 0.1, 0.2, and 0.3 km/s, respectively, with respect to the reference model. The parameters $d_1$, r, ${\theta}$, and $d_2$ show positive correlation with the level of velocity perturbations, but the others are not sensitive to the perturbations except S4, which is located at the outer boundary of the network. In cases of S0, S1, S2, and S3, hypoellipse and hypoDD provide similar results for $d_1$. However, for other parameters, hypoDD shows much better results and errors of locations can be reduced by about several meters regardless of the level of perturbations. In light of the purpose to understand the characteristics of hydraulic fracturing, $1{\sigma}$ error of velocity structure should be under 0.2 km/s in hypoellipse and 0.3 km/s in hypoDD.

The Study of Technical Error Analysis on BMD Using DEXA (이중 에너지 X선 흡수 계측법을 이용한 BMD 검사 시 발생할 수 있는 기술적인 오류 분석)

  • Kang, Yeong-Han;Jo, Gwang-Ho
    • Journal of radiological science and technology
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    • v.29 no.4
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    • pp.229-236
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    • 2006
  • Purpose: This study was conducted to search for the type of technical error in DEXA(dual-energy X-ray absorptiometry) and the effect of error to measurement of BMD. Materials and Methods: The changes of BMD($g/cm^2$, T-score) by patients information(Age, Weight, Height, Manopause age) input error and Confirming ROI error were investigated. Using spine phantom, we canned 10 times by age(5, 10), weight(10, 20 kg), height(5, 10 cm), manopause age(5, 10) increase & decrease respectively. Scanning region(L-spine, femur, Forearm) of 10 patients was calculated by changing ROI respectively. Analysis of difference for mean(precision 1%) were carried out. Results: The error of patient information(Age, Weight, Height, Manopause age) was not changed differently. In confirming ROI, the BMD and T-score of L-spine involving T-12 was decreased to $0.063\;g/cm^2$, 0.3 and involving L-5 increased to $0.077\;g/cm^2$, 0.5. In narrowing 1 cm of vertical line of ROI, the BMD and T-score decreased to $0.006\;g/cm^2$, 0.1 and in 2 cm, $0.021\;g/cm^2$, 0.15, each. In hip ROI, Upper and left shift(0.5 cm) of line was not influenced BMD and T-score. In 0.5 cm lower shift(lesser trochanter below), the BMD and T-score increased $0.031\;g/cm^2$, 0.3 and in 1 cm $0.094\;g/cm^2$, 0.65, each. In forearm ROI, the BMD and T-score decreased $0.042\;g/cm^2$, 0.9 involving 1 cm lower wrist. And expanding 1 cm of vertical line, the BMD and T-score decreased $0.008\;g/cm^2$, 0.1 and in 2 cm, $0.021\;g/cm^2$, 0.3, each. The L-spine, hip, forearm ROI error was changed differently. Conclusion: There are so many kinds of technical error in BMD processing. Errors according to age, weight, height, manopause age did not influent to $BMD(g/cm^2)$ and T-score. There are mean differences BMD and T-score in confirming ROI. For the precision exam, in L-spine processing, L1-4 have to confirmed without shift of ROI vertical line. In hip processing, the ROI have to included greater trochanter, femur head and lesser trochanter. In forearm processing, the ROI have to included wrist, radius and ulnar.

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Studies on the Overflow from Torrential Stream -A Case Study at the Samsung-cheon in Mt. Kwanak- (야계(野溪)의 월류발생(越流發生)에 관(關)한 연구(硏究) -관악산(冠岳山) 삼성천(三聖川)에서의 시험사례(試驗事例)-)

  • Woo, Bo Myeong;Kim, Kyong Ha;Jeong, Do Hyeon
    • Journal of Korean Society of Forest Science
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    • v.77 no.3
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    • pp.269-275
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    • 1988
  • To investigate the cause of overflow in the torrential stream, the estimated peak flow of run-off and the maximum tarring capacity of the stream were measured at the upstream of Samsung-cheon located in Kwanak Aboretum during July, 1987. The results obtained from this study could be summarized as follows : 1. The surveyed catchment area was 477ha, which was 116 of the designed area (410ha) by the plan. 2. The maximum rainfall intensity measured was 99.5mm/hr and was almost same as the designed intensity(100mm/hr). 3. The surveyed run-off coefficient was 0.672 that was about twice as much as designed one(0.35). 4. The surveyed peak flow of run-off was $88.59m^3/sec$, 222% as large the designed one($39.9m^3/sec$). 5. The designed cross-sectional area of the stream was $17.25m^2$, which was 68% of the designed one$25.43m^2$. 6. The surveyed hydraulic mean radius was 0.94m, which was shorter than the designed one(1.28m). 7. The surveyed mean stream-bed gradient(0.998%) was almost the same as the designed one(1.00%). 8 The surveyed maximum velocity of flow passing through the stream was 2.87m/sec, 78.0 of the designed one(3.68m/sec). 9 The surveyed run-off capacity of the stream was $49.51m^3/sec$, 53% of the designed one ($93.5m^3/sec$).

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Deep inspiration breath-hold (DIBH) 적용한 림프절이 포함된 왼편 유방암의 방사선 치료계획에 따른 주변 장기 선량 평가

  • Jeong, Da-Lee;Gang, Hyo-Seok;Choe, Byeong-Jun;Park, Sang-Jun;Lee, Geon-Ho;Lee, Du-Sang;An, Min-U;Jeon, Myeong-Su
    • The Journal of Korean Society for Radiation Therapy
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    • v.29 no.1
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    • pp.27-35
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    • 2017
  • Purpose: On the left side, breast cancer patients have more side effects than those on the right side because of unnecessary doses in normal organs such as heart and lung. DIBH is performed to reduce this. To evaluate the dose of peripheral organs in the left breast cancer including supraclavicular lymph nodes and internal mammary lymph nodes according to the treatment planning method of Conventional Radiation Therapy, Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy. Materials and Methods: We performed CT-simulation using free breathing and deep inspiration breath-hold technique for 8 patients including left supraclavicular lymph nodes and internal mammary lymph nodes. Based on the acquired CT images, the contour of the body is drawn and the convention is performed so that $95%{\leftarrow}PTV$, $Dmax{\leftarrow}110%$. Conventional Radiation Therapy used a one portal technique on the supraclavicular lymph node and used a field in field technique tangential beam on the breast. Intensity Modulated Radiation Therapy was composed of 7 static fields. Volumetric Modulated Arc Therapy was planned using 2 ARC with a turning radius of $290^{\circ}$ to $179^{\circ}$. The peripheral normal organs dose was analyzed by referring to the dose volume of Eclipse. Results: By applying the deep inspiration breath-hold technique, the mean interval between the heart and chest wall increased $1.6{\pm}0.6cm$. The mean dose of lung was $19.2{\pm}1.0Gy$, which was the smallest value in Intensity Modulated Radiation Therapy. The V30 (%) of the heart was $2.0{\pm}1.9$, which was the smallest value in Intensity Modulated Radiation Therapy. In the left anterior descending coronary artery, the dose was $25.4{\pm}5.4Gy$, which was the smallest in Intensity Modulated Radiation Therapy. The maximum dose value of the Right breast was $29.7{\pm}4.3Gy$ at Intensity Modulated Radiation Therapy. Conclusion: When comparing the values of surrounding normal organs, Intensity Modulated Radiation Therapy and Volumetric Modulated Arc Therapy were applicable values for treatment. Among them, Intensity Modulated Radiation Therapy is considered to be a suitable treatment planning method.

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Application and Comparative Analysis of River Discharge Estimation Methods Using Surface Velocity (표면유속을 이용한 하천 유량산정방법의 적용 및 비교 분석)

  • Jae Hyun, Song;Seok Geun Park;Chi Young Kim;Hung Soo Kim
    • Journal of Korean Society of Disaster and Security
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    • v.16 no.2
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    • pp.15-32
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    • 2023
  • There are some difficulties such as safety problem and need of manpower in measuring discharge by submerging the instruments because of many floating debris and very fast flow in the river during the flood season. As an alternative, microwave water surface current meters have been increasingly used these days, which are easy to measure the discharge in the field without contacting the water surface directly. But it is also hard to apply the method in the sudden and rapidly changing field conditions. Therefore, the estimation of the discharge using the surface velocity in flood conditions requires a theoretical and economical approach. In this study, the measurements from microwave water surface current meter and rating curve were collected and then analyzed by the discharge estimation method using the surface velocity. Generally, the measured and converted discharge are analyzed to be similar in all methods at a hydraulic radius of 3 m or over or a mean velocity of 2 ㎧ or more. Besides, the study computed the discharge by the index velocity method and the velocity profile method with the maximum surface velocity in the section where the maximum velocity occurs at the high water level range of the rating curve among the target locations. As a result, the mean relative error with the converted discharge was within 10%. That is, in flood season, the discharge estimation method using one maximum surface velocity measurement, index velocity method, and velocity profile method can be applied to develop high-level extrapolation, therefore, it is judged that the reliability for the range of extrapolation estimation could be improved. Therefore, the discharge estimation method using the surface velocity is expected to become a fast and efficient discharge measurement method during the flood season.

Fish Stock Assessment by Hydroacoustic Methods and its Applications - I - Estimation of Fish School Target Strength - (음향에 의한 어족생물의 자원조사 연구 - I - 어군반사강도의 추정 -)

  • Lee, Dae-Jae;Shin, Hyeong-Il;Shin, Hyong-Ho
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.31 no.2
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    • pp.142-152
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    • 1995
  • The combined bottom trawl and hydroacoustic survey was conducted by using the training ship Oshoro Maru belong to Hokkaido University in November 1989-1992 and the training ship Nagasaki Maru belong to Nagasaki University in April 1994 in the East China Sea, respectively. The aim of the investigations was to collect the target strength data of fish school in relation to the biomass estimation of fish in the survey area. The hydroacoustic survey was performed by using the scientific echo sounder system operating at three frequencies of 25, 50 and 100kHz with a microcomputer-based echo integrator. Fish samples were collected by bottom trawling and during the trawl surveys, the openings of otter board and net mouth were measured. The target strength of fish school was estimated from the relationship between the volume back scattering strength for the depth strata of bottom trawling and the weight per unit volume of trawl catches. A portion of the trawl catches preserved in frozon condition on board, the target strength measurements for the defrosted samples of ten species were conducted in the laboratory tank, and the relationship between target strength and fish weight was examined. In order to investigate the effect of swimbladder on target strength, the volume of the swimbladder of white croaker, Argyrosomus argentatus, sampled by bottom trawling was measured by directly removing the gas in the swimbladder with a syringe on board. The results obtained can be summarized as follows: 1.The relationship between the mean volume back scattering strength (, dB) for the depth strata of trawl hauls and the weight(C, $kg/\textrm{m}^3$) per unit volume of trawl catches were expressed by the following equations : 25kHz : = - 29.8+10Log(C) 50kHz : = - 32.4+10Log(C) 100kHz : = - 31.7+10Log(C) The mean target strength estimates for three frequencies of 25, 50 and 100 kHz derived from these equations were -29.8dB/kg, -32.4dB/kg and -31.7dB/kg, respectively. 2. The relationship between target strength and body weight for the fish samples of ten species collected by trawl surveys were expressed by the following equations : 25kHz : TS = - 34.0+10Log($W^{\frac{2}{3}}$) 100kHz : TS = - 37.8+10Log($W^{\frac{2}{3}}$) The mean target strength estimates for two frequencies of 25 and 100 kHz derived from these equations were -34.0dB/kg, -37.8dB/kg, respectively. 3. The representative target strength values for demersal fish populations of the East China Sea at two frequencies of 25 and 100 kHz were estimated to be -31.4dB/kg, -33.8dB/kg, respectively. 4. The ratio of the equivalent radius of swimbladder to body length of white croaker was 0.089 and the volume of swimbladder was estimated to be approximately 10% of total body volume.

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Prediction of Seasonal Nitrate Concentration in Springs on the Southern Slope of Jeju Island using Multiple Linear Regression of Geographic Spatial Data (지리 공간 자료의 다중회귀분석을 이용한 제주도 남측사면 용천수의 시기별 질산성 질소 농도 예측)

  • Jung, Youn-Young;Koh, Dong-Chan;Kang, Bong-Rae;Ko, Kyung-Suk;Yu, Yong-Jae
    • Economic and Environmental Geology
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    • v.44 no.2
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    • pp.135-152
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    • 2011
  • Nitrate concentrations in springs at the southern slope of Jeju Island were predicted using multiple linear regression (MLR) of spatial variables including hydrogeological parameters and land use characteristics. Springs showed wide range of nitrate concentrations from <0.02 to 86 mg/L with a mean of 20 mg/L. Spatial variables were generated for the circular buffer when the optimal buffer radius was assigned as 400 m. Selected regression models were tested using the p values and Durbin-Watson statistics. Explanatory variables were selected using the adjusted $R^2$, Cp (total squared error) and AIC (Akaike's Information Criterion), and significance. In addition, mutual linear relations between variables were also considered. Small portion of springs, usually <10% of total samples, were identified as outliers indicating limitations of MLR using circular buffers. Adjusted $R^2$ of the proposed models was improved from 0.75 to 0.87 when outliers were eliminated. In particular, the areal proportion of natural area had the greatest influence on the nitrate concentrations in springs. Among anthropogenic land uses, the influence of nitrate contamination is diminishing in the following order of orchard, residential area, and dry farmland. It is apparent quality of springs in the study area is likely to be controlled by land uses instead of hydrogeological parameters. Most of all, it is worth highlighting that the contamination susceptibility of springs is highly sensitive to nearby land uses, in particular, orchard.

Mechanism and Spray Characteristics of a Mini-Sprinkler with Downward Spray for Prevention of Drop Water (하향 분사식 미니스프링클러의 낙수방지 메카니즘과 살수 특성)

  • Kim, Hong-Gyoo;Chung, Sung-Won
    • Journal of Bio-Environment Control
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    • v.16 no.3
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    • pp.210-216
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    • 2007
  • A study was conducted to find mechanism and spray characteristics of a mini-sprinkler with downward spray to develop a new design type to be able to prevent drop water. The experiments were executed in a plastic greenhouse to minimize the effect of the wind. Data was collected at five different operation pressures and at 4 different raiser heights. Spray characteristics of the sprinkler such as effective radius, effective area, mean application depth, absolute maximum application depth, effective maximum application depth and coefficient of variation were determined. In order to analyze the mechanism and packing supporter of sprinkler, the numerical simulation using ABAQUS was performed. The optimum pressure for preventing drop water was determined.

Study on the Current Status Analysis of Urban Green Spaces in Seoul Focusing on Elementary School Surroundings - Remote Sensing Based Vegetation Classification - (초등학교 주변을 중심으로 본 서울시 도시녹지 현황 분석 및 고찰 - 원격탐사 방법을 이용한 식생분류 -)

  • Kim, Hyun-Ok
    • Journal of the Korean Institute of Landscape Architecture
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    • v.40 no.5
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    • pp.8-18
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    • 2012
  • Urban nature plays an important role not only in the improvement of the physical environment but also from the perspective of psychological and social function. In particular, schoolyards as well as the green spaces near school surroundings function as a primary space for urban children to experience nature in Korea, as they spend most of their time at school. In this study, the status of urban green spaces near school surroundings was examined. For the analysis, 185 elementary schools in Seoul were selected and the green spaces within a radius of 300m(defined as 'school zone' in this study) were analyzed using the Rapid Eye multispectral satellite image data. The mean green space ratio of school zone accounts to about 21% with a high variation from 74% to 0.7% and more than half of the school zone have a green space ratio of less than 20%. Schools with a high green space ratio in their school zone are mostly located near urban forests, so forest areas particularly contribute to increase the green space ratio. Furthermore, forest vegetation shows relatively higher vitality than other green spaces located in urbanized areas. In contrast, schools with a low green space ratio in their school zone are mostly situated in high-density residential areas and the green spaces show relatively low vegetation vitality. Except for the urban forest, the majority of urban green spaces in urbanized areas are landscape green facilities in apartment districts. The other types of urban open spaces such as environmentally shaped schoolyards or street parks account only for a very small proportion of school surroundings. Therefore, it is needed to establish countermeasures in the context of urban planning; e.g. to promote the school forest projects preferentially by selecting schools with a extremely low green space ratio in their school zone, to foster roof greening in near surroundings, and to connect schoolyards organically with nearby apartment landscape green facilities as an easily accessible urban open space.

Injuries and Prevention methods Associated with In-Line Skate (인라인 스케이트시 발생한 손상 밑 예방)

  • Lim Hong Chul;Chun Seung Joo;Rho Young Jin;Hwang Jin Ho;Park Chan Eung;Kim Tae Un
    • Journal of Korean Orthopaedic Sports Medicine
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    • v.2 no.2
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    • pp.163-167
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    • 2003
  • Purpose: The purpose of this study is to describe causes and injury mechanisms during inline skating and to find preventive measures .Materials and Methods: We have carefully selected 57 patients who have been treated in our hospital and nearby hospital. There are 37 males and 20 females, and mean age is 9 years 9 months (range,6-40 years old) . We have meticulously investigated their injured sites, their favorite location for inline skating , their use of protective means while they were on the wheels and their injury mechanisms . Results: Injury consisted of 50 fractures,1 meniscal tear,2 medial collateral ligament rupture and 4 contusion or sprain. Fracture sites varied as follows : 33(66$\%$) cases in distal radius and ulna,5(10$\%$) in elbow. 3(6$\%$) in diaphysis of humerus, etc Location at the time of injury varied as follows : 22 cases(39$\%$) in their apartment complex, 19 cases in (33$\%$) narrow streets, and 16 cases(28$\%$) in parks Only five patients admitted that any means of protection were used.2 cases only had knee pad on , 1 case put on elbow pad in addition, and 2 cases put on wrist guard as well. However none of the patients had helmet on Conclusion: We would strongly like to stress the importance of using sufficient protections and of choosing area where it is safe to ride, in order to reduce the risk of accidents. In addition, continuous and effective prior education from inline skate circles may be in order before riding the inline skate.

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