• Proceedings of the Korean Operations and Management Science Society Conference
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• 1993.04a
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• pp.294-300
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• 1993

어떤 무기체계의 임무신뢰도분석에 베이지안기법을 사용하는데 있어 고장율이 주어졌을 때 고장간 시간이 지수분포를 따른다는 가정하에 이의 Conjugate Prior인 감마분포의 추정문제를 다룬다. 임무별 고장간시간에 대한 예측분포를 유도하였으며, 실제 측정된 기존의 임무별 고장간시간이 이 예측분포를 따른다는 전제하에 비선형 최소자승법을 이용하여 감마분포의 두 파라메터를 추정하는 방안을 제시하였다. 또한 대상 무기체계의 실제 고장자료를 이용하여 추정치를 구하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1211-1215
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• 2006

가뭄에 대한 대책을 수립하기 위해서는 가뭄의 심도 및 지속기간 등 가뭄특성을 산정하여 가뭄을 정량화 하는 것이 필요하다. 본 연구에서는 가뭄을 해석하기 위하여 강수를 이용한 표준강수지수(SPI, Standardized precipitation Index)를 이용하여 가뭄 특성을 산정하였다. 서울지점은 강수의 근대 관측 기간이 약 100년 정도(1907년 ${\sim}$ 2003년) 이기 때문에 측우기 자료를 이용하여 조선 말까지(1770년 ${\sim}$ 1907년) 자료를 확장하여 가뭄지수를 산정하였다. 산정된 SPI로부터 절단 수준법 개념을 이용하여 SPI의 -1이하를 가뭄으로 정의 하고, 연속된 가뭄으로부터 가뭄 심도 및 가뭄 지속기간을 구하였다. 가뭄의 지속기간과 심도를 이변수 감마 분포(Bivariate Gamma Distribution)를 이용하여 가뭄의 재현특성을 분석하였고, 가뭄의 지속기간만을 고려한 재현기간과 본 연구에서 산정된 이변수 가뭄 재현기간을 서로 비교하였다.

• The Journal of Korean Society for Radiation Therapy
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• v.23 no.2
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• pp.97-102
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• 2011

Purpose: IMRT QA using 2Dimensional array detector is carried out with condition for discrete dose distribution clinically. And it can affect uncertainty of evaluation using gamma method. We analyze gamma index variation according to grid size and suggest validate range of grid size for IMRT QA in Hospital. Materials and Methods: We performed QA using OniPro I'mRT system software version 1.7b on 10 patients (head and neck) for IMRT. The reference dose plane (grid size, 0.1 cm; location, [0, 0, 0]) from RTP was compared with the dose plane that has different grid size (0.1 cm, 0.5 cm, 1.0 cm, 2.0 cm, 4.0 cm) and different location (along Y-axis 0 cm, 0.2 cm, 0.5 cm, 1.0 cm). The gamma index variation was evaluated by observing the level of changes in Gamma pass rate, Average signal, Standard deviation for each case. Results: The average signal for each grid size showed difference levels of 0%, -0.19%, -0.04%, -0.46%, -8.32% and the standard deviation for each grid size showed difference levels of 0%, -0.30%, 1.24%, -0.70%, -7.99%. The gamma pass rate for each grid size showed difference levels of 0%, 0.27%, -1.43%, 5.32%, 5.60%. The gamma evaluation results according to distance in grid size range of 0.1 cm to 1.0 cm showed good agreement with reference condition (grid size 0.1 cm) within 1.5% and over 5% in case of the grid size was greater than 2.0 cm. Conclusion: We recognize that the grid size of gamma evaluation can make errors of IMRT QA. So we have to consider uncertainty of gamma evaluation according to the grid size and apply smaller than 2 cm grid size to reduce error and increase accuracy clinically.

• Korean Journal of Food Science and Technology
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• v.49 no.1
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• pp.110-116
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• 2017

${\gamma}-Oryzanol-loaded$ calcium-pectin micro- and nanocapsules were prepared by ionic gelation to improve oxidation stability and the effect of particle size on capsule properties was investigated. The physical properties were influenced by preparation conditions such as concentrations of pectin, $CaCl_2$, ${\gamma}-oryzanol$, and hardening time. Particle sizes of micro- and nanocapsules that showed the maximum encapsulation efficiency and sustained release were $2.27{\pm}0.02mm$ and $347.7{\pm}58.1nm$, respectively. Microcapsules showed higher encapsulation efficiency ($50.73{\pm}1.98%$) than nanocapsules ($17.70{\pm}2.04%$), while nanocapsules showed more sustained release and higher stability than microcapsules. Release of ${\gamma}-oryzanol$ from both microand nanocapsules, which was low in gastric environments and promoted in intestinal environments, showed suitable characteristics for oral administration. Furthermore, antioxidant activity of ${\gamma}-oryzanol$ against autoxidation of linoleic acid was prolonged by both micro- and nanoencapsulation in a ferric thiocyanate test. Therefore, micro- and nanoencapsulation using pectin can be effective for improving biodelivery, stability, and antioxidant activity of ${\gamma}-oryzanol$.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.1
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• pp.77-85
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• 2013

Purpose: The accurate movement of gantry rotation, collimator and correct application of dose rate are very important to approach the successful performance of Volumetric Modulated Arc Therapy (VMAT), because it is tightly interlocked with a complex treatment plan. The interruption and restart of dose delivery, however, are able to occur on treatment by various factors of a treatment machine and treatment plan. If unexpected problems of a treat machine or a patient interrupt the VMAT, the movement of treatment machine for delivering the remaining dose will be restarted at the start point. In this investigation, We would like to know the effect of interruptions and restart regarding dose delivery at VMAT. Materials and Methods: Treatment plans of 10 patients who had been treated at our center were used to measure and compare the dose distribution of each VMAT after converting to a form of digital image and communications in Medicine (DICOM) with treatment planning system (Eclipse V 10.0, Varian, USA). We selected the 6 MV photon energy of Trilogy (Varian, USA) and used OmniPro I'mRT system (V 1.7b, IBA dosimetry, Germany) to analyze the data that were acquired through this measurement with two types of interruptions four times for each case. The door interlock and the beam-off were used to stop and then to restart the dose delivery of VMAT. The gamma index in OmniPro I'mRT system and T-test in Microsoft Excel 2007 were used to evaluate the result of this investigation. Results: The deviations of average gamma index in cases with door interlock, beam-off and without interruption on VMAT are 0.141, 0.128 and 0.1. The standard deviations of acquired gamma values are 0.099, 0.091, 0.071 and The maximum gamma value in each case is 0.413, 0.379, 0.286, respectively. This analysis has a 95-percent confidence level and the P-value of T-test is under 0.05. Gamma pass rate (3%, 3 mm) is acceptable in all of measurements. Conclusion: As a result, We could make sure that the interruption of this investgation are not enough to seriously affect dose delivery of VMAT by analyzing the measured data. But this investigation did not reflect all cases about interruptions and errors regarding the movement of a gantry rotation, collimator and patient So, We should continuously maintain a treatment machine and program to deliver the accurate dose when we perform the VMAT for the many kinds of cancer patients.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.15-24
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• 2011

To clarify the distribution of joints and fracture zones in the Cheongju granitic mass, we analyzed drill-core and geophysical well-logging data obtained at two boreholes located 30 m from each other. Lithological properties were investigated from the drill-core data and the samples were classified based on the rock mass rating (RMR) and on rock quality designation (RQD). Subsurface discontinuities within soft and hard rocks were examined by geophysical well-logging and cross-hole seismic tomography. The velocity structures constructed from seismic tomography are well correlated with the profile of bedrock depth, previously mapped from a seismic refraction survey. Dynamic elastic moduli, obtained from full waveform sonic and ${\gamma}-{\gamma}$ logging, were interrelated with P-wave velocities to investigate the dynamic properties of the rock mass. Compared with the correlation graph between elastic moduli and velocities for hard rock at borehole BH-1, the correlation points for BH-2 data showed a wide scatter. These scattered points reflect the greater abundance of joints and fractures near borehole BH-2. This interpretation is supported by observations by acoustic televiewer (ATV) and optical televiewer (OTV) image loggings.

• Journal of radiological science and technology
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• v.46 no.5
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• pp.417-425
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• 2023

The glomerular filtration rate (GFR) has been the subject of much research as a key indicator for diagnosing, treating, and monitoring kidney function. The gamma camera method (Gates method) is simple and allows simultaneous acquisition of GFR and renal scintigraphy for each kidney, however its accuracy is inferior. This study aimed to investigate changes in GFR depending on how region of interest (ROI) are set up, which is one of many factors influencing accuracy. GFR was calculated by setting the ROI for each phase of the image acquisition time (Gates-1: 0~1 minutes, Gates-2: 1~3 minutes, Gates-3: 3~27 minutes), and statistical significance was verified based on probability value 0.05 through ANOVA analysis. While there was no statistically significant difference among results from Gates-1, 2, 3 (p=0.481>0.05), overall results from the Gates method tended to overestimate compared to those from the multiple blood sampling-dual exponential (MBSDE) method. When comparing averages between phases, results from Gates-2 were most similar to those from the MBSDE method. Moreover, paired t-test p-values between MBSDE method and phases were as follows Gates-1: 0.021 (p<0.05), Gates-2: 0.280 (p>0.05), and Gates-3: 0.164 (p>0.05) indicating that only Gates-1 had statistically significant differences compared with MBSDE method. Thus, setting ROI around 2~3 minutes is calculated can aid in accurately determining GFR when Gates Method.

• Journal of Radiation Protection and Research
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• v.23 no.3
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• pp.123-138
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• 1998

Characteristics of element responses of Panasonic UD802 personnel dosimeters in the X, ${\beta}$, ${\gamma}$, ${\gamma}/X$, ${\gamma}/{\beta}$ and ${\gamma}$/neutron mixed fields were assessed. A dose-response algorithm has been developed to decide the high probability of a radiation type and energy by using the distribution in all six ratios of the multi-element TLD. To calculate the 4-element response factors and ratios between the elements of the Panasonic TLDs in the X, $\beta$, and $\gamma$ radiation fields, Panasonic’s UD802 TLDs were irradiated with KINS’s reference irradiation facility. In the photon radiation field, this study confirms that element-3 (E3) and element-4 (E4) of the Panasonic TLDs show energy dependent both in low- and intermediate-energy range, while element-1 (E1) and element-2 (E2) show little energy dependency in the entire whole range. The algorithm, which was developed in this study, was applied to the Panasonic personnel dosimetry system with UD716AGL reader and UD802 TLDs. Performance tests of the algorithm developed was conducted according to the standards and criteria recommended in the ANSI N13.11. The sum of biases and standard deviations was less than 0.232. The values of biases and standard deviations are distributed within a triangle of a lateral value of 0.3 in the ordinate and abscissa, With the above algorithm, Panasonic TLDs satisfactorily perform optimum dose assessment even under an abnormal response of the TLD elements to the energy imparted. This algorithm can be applied to a more rigorous dose assessment by distinguishing an unexpected dose from the planned dose for the most practical purposes, and is useful in conducting an effective personnel dose control program.

• Journal of Korea Water Resources Association
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• v.40 no.4
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• pp.335-343
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• 2007

Drought characteristics need to be preceded before establishing a drought mitigation plan. In this study, using a Standardized Precipitation Index (SPI), a hydrologic drought was defined as an event during which the SPIs are continuously below a certain truncation level. Then, a methodology of drought frequency analysis was performed to quantitatively characterize droughts considering drought duration and severity simultaneously. The theory of runs was used to model drought recurrence and to determine drought properties like duration and severity. Short historical records usually do not allow reliable bivariate analyses. However, more than hundred years of precipitation data (1770 ${\sim}$ 1907) collected in Chosun Kingdom Age using an old Korean rain gage called Chukwooki can provide valuable information about past events. It is shown that a bivariate gamma distribution well represented the joint probabilistic properties of Korean drought duration and severity. The overall results of this study show that the proposed bivariate drought frequency analysis overcomes the drawbacks of the conventional univariate frequency analysis by providing a consistent representation of the drought recurrent property.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.125-125
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• 2017

최근 들어 내수용 및 수출용 자동차 보증 제도를 살펴보면 부품에 대한 방식 보증기간이 점차 연장되는 추세이며, 이에 따라 자동차사에서 요구하는 방식 및 내식성 평가 기준이 상향되어 가고 있다. 실제로 수출차에 대한 방청 품질 보증기간이 차체 구멍 발청 10년에서 12년으로 연장할 움직임을 보이는 등 점차 방식에 대한 관심이 높아지고 있다. 따라서 내식성 향상에 대한 끊임없는 연구가 지속적으로 이루어지고 있으며, 내식성 향상을 위해 구조/형상 변화, 도장 품질 향상, 최적화 설계 등 다방면에서 노력을 기울이고 있다. 그 중에서도 가장 근본적인 해결책인 소재의 내식성 향상에 대한 관심은 날로 높아지고 있는 실정이다. 특히 일본 등지에서는 GA 도금재의 사용이 증가하고 있으나, 아직은 내식성에 대한 효율적이고 체계적인 관리가 부족한 면이 있다. GA재는 합금화 과정에서 야기되는 Fe% 합금화도, 합금화 상분율(감마, 델타, 제타상), crater 등 복잡한 소재의 특성으로 인해 소재의 내식성 분석에 고려할 사항이 많다. 실제 여러 실험들을 통해서 GA재가 내식성에 영향이 있는 인자들에 대해 많은 연구가 진행되었지만 명확히 정량화되어 있지 않은 관계로 GA재의 내식성 관리 기준에 대해서도 명확하진 않은 상황이다. 본 연구에서는 당사재와 타사재의 고강도 GA재 (>440 MPa) 11종에 대해 crater분율, zeta상, 합금화도, 도금량 등의 다양한 도금 물성들을 조사하였다. 또한 이 시편들을 34일 동안의 복합염수 분무법(CCT)을 통해 얻은 최대 및 평균 블리스터 폭과 소재 표면품질 물성과의 상관관계를 통해서 부식과 연관된 관련인자들을 도출하고 정량적인 관계를 살펴보았다. GA재의 경우 다양한 물성들 중에서 도금 크레이터, 제타상, 합금화도 순으로 내식성에 영향을 주는 것으로 확인이 되었으며 이 세 인자들을 내식성 평가 지수화하여 GA재 생산시 효율적인 관리범위를 지정하는데 이용 가능할 수 있도록 diagram을 도출하였다. 따라서, 본 연구를 통하여 자동차사에서 요구하는 내식성 기준을 만족하기 위한 내식성 상관 인자들의 관리 수준을 정량화함으로써 보다 우수한 소재의 관리를 할 수 있도록 하고자 한다.