• Journal of Korean Society of Forest Science
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• v.88 no.3
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• pp.285-291
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• 1999

Loblolly(Pinus taeda L.) and slash(Pinus elliottii Engelm.) pines are the most important timber producing species in the Southern United States. Site index equations to estimate site index curves(base age 25 years) for loblolly pine and slash pine plantations have been developed based on long-term repeated measurement data sets. To check magnitude of errors in estimating site index, each cumulative measurement cycle data sets and all combined data sets were used to recalculate site index values. The Chapman-Richards' growth function was selected for stand height prediction. Anamorphic base age invariant site index curves were presented based on this height prediction equation. Statistics used in the evaluation were mean of the differences and mean of the absolute differences. For plantation ages less than 5 years, site index values showed very sensitive fur both species based on the evaluation test.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.56-67
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• 2015

In this study, a source locating technique applicable to transversely isotropic media was developed. Wave velocity anisotropy was considered based on the partition approximation method, which simply enabled AE source locating. Sets of P wave arrival time were decided by the two-step AIC algorithm and they were later used to locate the AE sources when having the least error compared with the partitioned elements. In order to validate the technique, pencil lead break test on artificial transversely isotropic mortar specimen was carried out. Defining the absolute error as the distance between the pencil lead break point and the located point, 1.60 mm ~ 14.46 mm of range and 8.57 mm of average were estimated therefore it was regarded as thought to be 'acceptable' considering the size of the specimen and the AE sensors. Comparing each absolute error under different threshold levels, results showed small discrepancies therefore this technique was hardly affected by background noise. Absolute error could be decomposed into each coordinate axis error and through it, effect of AE sensor position could be understood so if optimum sensor position was able to be decided, one could get more precise outcome.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.4
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• pp.319-326
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• 2006

To get the highly-accurate and precise position of a GPS receiver, they should consider the state-of-the-art GPS force and measurement models. Especially, the phase center variations (PCV) of a GPS antenna can cause several centimeters of positioning errors in the vertical direction. In this study, we implemented four different models of PCV and evaluated their impact on the computed coordinates. The test data were taken from the 14 National Geography Information Institute permanent GPS stations and 30 Minisry of Government Administration and Home Affairs sites. For different combinations of calibration methods, an average of 1.3-2.6cm of height difference was observed. Also, we found a maximum error of ${\sim}4mm$ in the estimates of the precipitable water vapors.

• The Journal of Korean Society for Radiation Therapy
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• v.18 no.1
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• pp.1-5
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• 2006

Purpose: IMRT quality assurance(Q.A) is consist of the absolute dosimetry using ionization chamber and relative dosimetry using the film. We have in general used 0.015 cc ionization chamber, because small size and measure the point dose. But this ionization chamber is too small to give an accurate measurement value. In this study, we have examined the degree of calculated to measured dose difference in intensity modulated radiotherapy(IMRT) based on the observed/expected ratio using various kinds of ion chambers, which were used for absolute dosimetry. Materials and Methods: we peformed the 6 cases of IMRT sliding-window method for head and neck cases. Radiation was delivered by using a Clinac 21EX unit(Varian, USA) generating a 6 MV x-ray beam, which is equipped with an integrated multileaf collimator. The dose rate for IMRT treatment is set to 300 MU/min. The ion chamber was located 5cm below the surface of phantom giving 100cm as a source-axis distance(SAD). The various types of ion chambers were used including 0.015cc(pin point type 31014, PTW. Germany), 0.125 cc(micro type 31002, PTW, Germany) and 0.6 cc(famer type 30002, PTW, Germany). The measurement point was carefully chosen to be located at low-gradient area. Results: The experimental results show that the average differences between plan value and measured value are ${\pm}0.91%$ for 0.015 cc pin point chamber, ${\pm}0.52%$ for 0.125 cc micro type chamber and ${\pm}0.76%$ for farmer type 0.6cc chamber. The 0.125 cc micro type chamber is appropriate size for dose measure in IMRT. Conclusion: IMRT Q.A is the important procedure. Based on the various types of ion chamber measurements, we have demonstrated that the dose discrepancy between calculated dose distribution and measured dose distribution for IMRT plans is dependent on the size of ion chambers. The reason is small size ionization chamber have the high signal-to-noise ratio and big size ionization chamber is not located accurate measurement point. Therefore our results suggest the 0.125 cc farmer type chamber is appropriate size for dose measure in IMRT.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.149-149
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• 2016

최근 전 세계적으로 이상기후가 발생하고 있으며, 국내에서도 과거에 경험하지 못했던 자연재해가 빈번하게 발생하고 있는 추세이다. 가뭄은 홍수와 더불어 그 피해가 가장 큰 자연재해 중 하나이며, 장주기적이고 광역적으로 발생함에 따라 구체적인 발생시기, 장소, 원인을 파악하는 것이 어렵다. 그동안 국내에서는 가뭄극복을 위해 다양한 대책을 마련해 왔음에도 불구하고 가뭄피해는 지속적으로 증가하고 있다. 실례로 2014~2015 가뭄으로 소양강 댐은 역대 최저수위를 기록하였으며, 일부 지역에서는 제한급수, 농업용수 부족 피해가 발생한 바 있다. 이처럼 가뭄으로 인한 피해는 기후 변화의 영향으로 더욱 빈번할 것이라는 보고가 있어 가뭄해석을 위한 지속적인 노력이 필요하다. 가뭄해석에는 일반적으로 가뭄의 시작, 끝, 지속기간, 발생간격, 누적심도 등을 사용하며, 이를 가뭄특성인자라고 한다. 따라서 본 연구에서는 인위적인 시설물의 영향을 배제한 자연가뭄지수(Natural Drought Index, NDI)를 이용하여 국내 5개 행정구역의 지역별 가뭄특성을 분석하였다. 자연가뭄지수의 산정을 위해 입력자료는 3개월 누적강수량, 누적유출량, 평균토양수분량을 사용하였으며, 강수량은 국내 ASOS 59개 지점 자료, 유출량 및 토양수분량은 지표수문해석모형의 결과를 이용하였다. 가뭄특성 분석기간은 1977~2012년이며, 가뭄특성인자는 가뭄의 시작, 끝, 지속기간, 발생간격을 활용하였다. 과거 가뭄피해사례와, SPI, SRI, SSI 및 NDI의 가뭄특성인자를 비교하였으며, 정량적 비교를 위해 평균오차, 평균절대오차를 사용하였다. 가뭄특성인자 분석 결과 NDI는 가뭄의 시작과 끝을 가장 정확하게 반영하였다. 가뭄의 지속기간은 NDI, 발생간격은 NDI와 SPI가 정확한 것으로 나타났다. 자연가뭄지수는 단일변량 가뭄지수에 비해 지역적 가뭄특성을 정확하게 재현한다는 점에서 추후 가뭄감시에 유용하게 활용될 것으로 판단된다.

• Radiation Oncology Journal
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• v.23 no.3
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• pp.176-185
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• 2005

Purpose: Film dosimetry as a part of patient specific intensity modulated radiation therapy quality assurance (IMRT QA) was peformed to develop a new optimization method of film isocenter offset and to then suggest new quantitative criteria for film dosimetry. Materials and Methods: Film dosimetry was peformed on 14 IMRT patients with head and neck cancers. An optimization method for obtaining the local minimum was developed to adjust for the error in the film isocenter offset, which is the largest part of the systemic errors. Results: The adjust value of the film isocenter offset under optimization was 1 mm in 12 patients, while only two patients showed 2 mm translation. The means of absolute average dose difference before and after optimization were 2.36 and $1.56\%$, respectively, and the mean ratios over a $5\%$ tolerance were 9.67 and $2.88\%$. After optimization, the differences in the dose decreased dramatically. A low dose range cutoff (L-Cutoff) has been suggested for clinical application. New quantitative criteria of a ratio of over a $5\%$, but less than $10\%$ tolerance, and for an absolute average dose difference less than $3\%$ have been suggested for the verification of film dosimetry. Conclusion: The new optimization method was effective in adjusting for the film dosimetry error, and the newly quantitative criteria suggested in this research are believed to be sufficiently accurate and clinically useful.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.565-577
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• 2016

The objective of this study is to propose a method for computing the Natural Drought Index (NDI) that does not consider man-made drought facilities. Principal Component Analysis (PCA) was used to estimate the NDI. Three monthly moving cumulative runoff, soil moisture and precipitation were selected as input data of the NDI during 1977~2012. Observed precipitation data was collected from KMA ASOS (Korea Meteorological Association Automatic Synoptic Observation System), while model-driven runoff and soil moisture from Variable Infiltration Capacity Model (VIC Model) were used. Time series analysis, drought characteristic analysis and spatial analysis were used to assess the utilization of NDI and compare with existing SPI, SRI and SSI. The NDI precisely reflected onset and termination of past drought events with mean absolute error of 0.85 in time series analysis. It explained well duration and inter-arrival time with 1.3 and 1.0 respectively in drought characteristic analysis. Also, the NDI reflected regional drought condition well in spatial analysis. The accuracy rank of drought onset, termination, duration and inter-arrival time was calculated by using NDI, SPI, SRI and SSI. The result showed that NDI is more precise than the others. The NDI overcomes the limitation of univariate drought indices and can be useful for drought analysis as representative measure of different types of drought such as meteorological, hydrological and agricultural droughts.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.3
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• pp.1-6
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• 2016

As the convergence speed of time domain adaptive algorithm on the LMS(Least Mean Square) becomes slow when eigen value distribution width is spread, So variable step size algorithm is used widely. But it needs a lot of calculation load. In this paper we consider new algorithm, which can reduce calculations and improve convergence speed, uses instantaneous absolute value of average noise signal adapting the exponential function. For the performance of proposed algorithm is tested and simulated to system generator. As the result we show the variable step size adaptive algorithm in proportion to instantaneous absolute value is more stable and efficient than others.

• The Journal of Korean Society for Radiation Therapy
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• v.13 no.1
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• pp.109-112
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• 2001

1. 목적 : head and neck cancer 환자의, C-T 영상을 이용한 방사선치료계획시 치과 보철물에 의해 발생하는 artifact가 선량 계산에 미치는 영향을 분석하고자 한다. 2. 재료 및 방법:두 경부와 유사한 크기의 Polystyrenes Phantom ($20{\times}20{\times}25cm^3$) 을 제작하고, 팬톰내에 금으로 인공보철물을 제작하여 보철물 부착 전.후를 C-T Scan (High Speed Advantage, GE, US) 하였다. artifact에 의한 영향을 쉽게 분석하기위해 팬톰내에 다른 구조물은 만들지 않았으며 두가지 방법으로 얻어진 영상을 이용하여 조사면의 크기와 조사 방향을 변화 시켜 가며 1문 조사(SSD 100 cm)에 의한 치료 계획(3D RTP system, Prowess, US)을 수립하여 기준점(5,10 cm depth)에서의 선량 변화를 비교 분석하였다. 아울러 3회 반복 scan하여 artifact에 발생 유형과 CTNo을 이용한 density을 분석하였다. 3. 결과: C-T Scan으로 얻어진 image 상에 나타난 Artifact는 CT no $-1000{\sim}+2775$(기준 $-1000{\sim}+3700$)까지의 다양한 값을 가지며 보철물을 기준으로 방사형태로 분포하였다. artifact가 선량 계산에 미치는 영향을 분석한 결과 보철물 사용시 5cm깊이의 기준점에서 절대선량은 평균 $+1.5{\pm}2.8\%$, 10 cm 깊이에서는 $+1.8{\pm}3.5\%$의 오차를 보였다. 조사방향에 의한 오차는 artifact에 대해 측면 조사한(gantry $270^{\circ}$)경우에서 높게 관찰되었다. 4. 결론: 두 경부 종양의 방사선 치료시 치과 보철물에 의한 artifact는 흔히 관찰가능하며 본 실험을 통해 다양한 형태와 다양한 density을 가짐을 알수있었다. 영상에 나타난 정도에 비해 선량계산에 미치는 평균 오차는 낮게 평가되었지만 조사 방향과 보철물의 위치에 따라 변동이 크게 나타날 수 있어 치료 계획시 가능한 artifact의 영향을 적게 받는 빔의 선택이 정확한 선량 계산에 도움을 줄 것으로 사료된다.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1235-1240
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• 2019

It is well known that the ground water level changes rapidly before and after the earthquake, and the variation of ground water level prediction is used to predict the earthquake. In this paper, we predict the ground water level in Miryang City using ANFIS algorithm for earthquake prediction. For this purpose, this paper used precipitation and temperature acquired from National Weather Service and data of underground water level from Rural Groundwater Observation Network of Korea Rural Community Corporation which is installed in Miryang city, Gyeongsangnam-do. We measure the prediction accuracy using RMSE and MAPE calculation methods. As a result of the prediction, the periodic pattern was predicted by natural factors, but the change value of ground water level was changed by other variables such as artificial factors that was not detected. To solve this problem, it is necessary to digitize the ground water level by numerically quantifying artificial variables, and to measure the precipitation and pressure according to the exact location of the observation ball measuring the ground water level.