• Journal of Radiation Protection and Research
• /
• v.27 no.1
• /
• pp.1-10
• /
• 2002

High energy photon beams from medical linear accelerators produce large scattered radiation by various components of the treatment head, collimator and walls or objects in the treatment room including the patient. These scattered radiation do not provide therapeutic dose and are considered a hazard from the radiation safety perspective. Scattered dose of therapeutic high energy radiation beams are contributed significant unwanted dose to the patient. ICRP take the position that a dose of 500mGy may cause abortion at any stage of pregnancy and that radiation detriment to the fetus includes risk of mental retardation with a possible threshold in the dose response relationship around 100 mGy for the gestational period. The ICRP principle of as low as reasonably achievable (ALARA) was recommended for protection of occupation upon the linear no-threshold dose response hypothesis for cancer induction. We suggest this ALARA principle be applied to the fetus and testicle in therapeutic treatment. Radiation dose outside a photon treatment filed is mostly due to scattered photons. This scattered dose is a function of the distance from the beam edge, treatment geometry, primary photon energy, and depth in the patient. The need for effective shielding of the fetus and testicle is reinforced when young patients ate treated with external beam radiation therapy and then shielding designed to reduce the scattered photon dose to normal organs have to considered. Irradiation was performed in phantom using high energy photon beams produced by a Varian 2100C/D medical linear accelerator (Varian Oncology Systems, Palo Alto, CA) located at the Yonsei Cancer Center. The composite phantom used was comprised of a commercially available anthropomorphic Rando phantom (Phantom Laboratory Inc., Salem, YN) and a rectangular solid polystyrene phantom of dimensions $30cm{\times}30cm{\times}20cm$. the anthropomorphic Rando phantom represents an average man made from tissue equivalent materials that is transected into transverse 36 slices of 2.5cm thickness. Photon dose was measured using a Capintec PR-06C ionization chamber with Capintec 192 electrometer (Capintec Inc., Ramsey, NJ), TLD( VICTOREEN 5000. LiF) and film dosimetry V-Omat, Kodak). In case of fetus, the dosimeter was placed at a depth of loom in this phantom at 100cm source to axis distance and located centrally 15cm from the inferior edge of the $30cm{\times}30cm^2$ x-ray beam irradiating the Rando phantom chest wall. A acryl bridge of size $40cm{\times}40cm^2$ and a clear space of about 20 cm was fabricated and placed on top of the rectangular polystyrene phantom representing the abdomen of the patient. The leaf pot for testicle shielding was made as various shape, sizes, thickness and supporting stand. The scattered photon with and without shielding were measured at the representative position of the fetus and testicle. Measurement of radiation scattered dose outside fields and critical organs, like fetus position and testicle region, from chest or pelvic irradiation by large fie]d of high energy radiation beam was performed using an ionization chamber and film dosimetry. The scattered doses outside field were measured 5 - 10% of maximum doses in fields and exponentially decrease from field margins. The scattered photon dose received the fetus and testicle from thorax field irradiation was measured about 1 mGy/Gy of photon treatment dose. Shielding construction to reduce this scattered dose was investigated using lead sheet and blocks. Lead pot shield for testicle reduced the scatter dose under 10 mGy when photon beam of 60 Gy was irradiated in abdomen region. The scattered photon dose is reduced when the lead shield was used while the no significant reduction of scattered photon dose was observed and 2-3 mm lead sheets refuted the skin dose under 80% and almost electron contamination. The results indicate that it was possible to improve shielding to reduce scattered photon for fetus and testicle when a young patients were treated with a high energy photon beam.

• Korean journal of applied entomology
• /
• v.55 no.2
• /
• pp.149-160
• /
• 2016

Temperature-dependent development and fecundity of apterious Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were examined at six constant temperatures (10, 15, 20, 25, 30 and $35{\pm}1.0^{\circ}C$, RH 50-70%, 16L:8D). Development time of nymphs decreased with increasing temperature and ranged from 42.9 days at $10^{\circ}C$ to 4.7 days at $30^{\circ}C$. The nymphs did not develop until adult at $35^{\circ}C$ because the nymphs died during the 2nd instar. The lower threshold temperature and thermal constant of nymph were estimated as $8.3^{\circ}C$ and 101.6 degree days, respectively. The relationships between development rates of nymph and temperatures were well described by the nonlinear model of Lactin 2. The distribution of development times of each stage was successfully fitted to the Weibull function. The longevity of apterious adults decreased with increasing temperature ranging from 24.0 days at $15^{\circ}C$ to 4.3 days at $30^{\circ}C$, with abnormally short longevity of 11.1 days at $10^{\circ}C$. R. padi showed the highest fecundity at $20^{\circ}C$ (38.2) and the lowest fecundity at $10^{\circ}C$ (3.9). In this study, we provided component sub-models for the oviposition model of R. padi: total fecundity, age-specific cumulative oviposition rate, and age-specific survival rate as well as adult aging rate based on the adult physiological age.

• Geotechnical Engineering
• /
• v.14 no.3
• /
• pp.25-46
• /
• 1998

This paper shows that there are the results of a series of model tests on the behavior of single pipe pile which is subjected to lateral load in, Nak-dong River sand. The purpose of the present paper is to estimate the effect of Non-homogeneity. constraint condition of pile head, lateral load velocity, relative density, and embedded length of pile on the behavior of single pile. These effects can be quantified only by the results of model tests. Also, these are compared with the results of the numerical methods (p-y method, modified Vlasov method; new ${\gamma}$ parameter, Characteristic Load Method'CLM). In this study, a new ${\gamma}$ parameter equation based on the Vlasov method was developed to calculate the modulus of subgrade reaction (E. : nhz.) proportional to the depth. The p-y method of analysis is characterized by nonlinear behavior. and is an effective method of designing deep foundations subjected to lateral loads. The new method, which is called the characteristic load method (CLM). is simpler than p-y analysis. but its results closely approximates p-y analysis results. The method uses dimensional analysis to characterize the nonlinear behavior of laterally loaded piles with respect to be relationships among dimensionless variables. The modulus of subgrade reaction used in p-y analysis and modified Vlasov method obtained from back analysis using direct shear test (DST) results. The coefficients obtained from DST and the modified ones used for the prediction of lateral behavior of ultimate soil reaction range from 0.014 to 0.05. and from 0.2 to 0.4 respectively. It is shown that the predicted numerical results by the new method (CLM), p-y analysis, and modified Vlasov method (new parameter) agree well with measured results as the relative density increases. Also, the characteristic load method established applicability on the Q-Mnu. relationship below y/D=0.2.

• The Korean Journal of Nuclear Medicine
• /
• v.39 no.4
• /
• pp.257-262
• /
• 2005

Purpose: Gastric emptying scan (GES) is usually acquired up to 2 hours. Our study investigated whether a fraction of meal-retention in the stomach at 120 minutes (FR120) was predicted from the data measured for 90 minutes by using non-linear curve fitting. We aimed at saving the delayed imaging by utilizing mathematical models. Materials and Methods: Ninety-six patients underwent GES immediately after taking a boiled egg with 74 MBq (2 mCi) Tc-99m DTPA. The patients were divided into Group I ($T_{1/2}\;{\leq}90\;min$) and Group II ($90\;min). Group I (n=51) had 21 men and 30 women, and Group II (n=45) 15 men and 30 women. There was no significant difference in age and sex between the two groups. Simple exponential, power exponential, and modified power exponential curves were acquired from the measured fraction of meal-retention at each time (0, 15, 30, 45, 60, 75, and 90 min) by non-linear curve fitting ($MATLAB^{\circledR}$ 5.3) and another simple exponential fitting was performed on the fractions at late times (60, 75, and 90 min). A predicted FR120 was calculated from the acquired functional formulas. A correlation coefficient between the measured FR120 and the predicted FR120 was computed ($MedCalc^{\circledR}$ 6.0). Results: Correlation coefficients(r) between the measured FR120 and the predicted FR120 of each mathematical functions were as follows: simple exponential function (Group I: 0.8558, Group II: 0.5982, p<0.0001), power exponential function (Group I: 0.8755, Group II: 0.6008, p<0.0001), modified power exponential function (Group I: 0.8892, Group II: 0.5882, p<0.0001), and simple exponential function at the late times(Group I: 0.9085, Group II: 0.6832, p<0.0001). In all the fitting models, the predicted FR120 were significantly correlated with the measured FR120 in Group I but not in Group II. There was no statistically significant difference in correlation among the 4 mathematical models. Conclusion: In the cases with $T_{1/2}\;{\leq}90\;min$, the predicted FR120 is significantly correlated with the measured FR120. Therefore, FR120 can be predicted from the data measured for 90 minutes by using non-linear curve fitting, saving the delayed imaging after 90 minutes when $T_{1/2}\;{\leq}90\;min$ is ascertained.

• Tuberculosis and Respiratory Diseases
• /
• v.46 no.6
• /
• pp.786-794
• /
• 1999

Back ground : Arm span measurements provide a practical substitute for standing height to predict normal spirometric values in subjects unable to stand or those with a skeletal deformity such as kyphoscoliosis. The relationship between arm span and height has previously been reported as either a fixed ratio unaffected by age or as a regression equation in which the ratio varies as a function of age. The fixed ratio or regression equation is known to be specific for sex and race. Methods : We studied the relationship between standing height, arm span, and age in 381 Korean adult female subjects (ages 20 to 69 yrs) sampled in a general population. Results : The mean ratio for arm span to height is 1.004. Multiple linear analysis found arm span and age to be predictive of standing height (p=0.0001, $r^2$=0.76). We performed the analysis of the difference between the predicted height using either fixed ratio or regression equation and actual height. At the extremes of arm span and age, the ratio method either underestimated(at smaller arm span or younger age) or overestimated(at larger arm span or older age) as compared with actual height (p=0.0001). Conclusion : This results indicate that the estimated height using the fixed ratio method provides a less acceptable method of estimating height for the prediction of lung volumes in the Korean adult women when compared with the regression equations, especially at the extremes of stature or age.

• Korean journal of applied entomology
• /
• v.55 no.4
• /
• pp.445-452
• /
• 2016

Exorista japonica is one of the major natural enemies of noctuid larvae, Mythimna separata and Spodoptera litura. The examined parasitoid was obtained from host species M. separata, collected at Gimje city and identified by DNA sequences (partial cytochrome oxidase I, 16S, 18S, and 28S). For purposed of this study, laboratory reared S. litura served as the host species for the development of the E. japonica. The developmental period of E. japonica immature stages were investigated at seven constant temperatures (16, 19, 22, 25, 28, 31, $34{\pm}1^{\circ}C$, RH 20~30%). Temperature-dependent developmental rates and development completion models were developed. E. japonica was successfully developed from egg to adult in $16{\sim}31^{\circ}C$ temperature regimes. Developmental duration was the shortest at $34^{\circ}C$ (8.3 days) and the longest at $16^{\circ}C$ (23.4 days) from egg to pupa development. Pupal development duration was the shortest at $28^{\circ}C$ (7.3 days). Total immature-stage development duration decreased with increasing temperature, and was the shortest at $31^{\circ}C$ (16.3 days) and the longest at $16^{\circ}C$ (45.4 days). The lower developmental threshold was $7.8^{\circ}C$ and thermal constant required to complete total immature-stage development was 370.4 degree days. Among four non-linear temperature-dependent developmental rate models, Briere 1 model had the highest adjusted R-squared (0.96). The distribution model of development completion for total immature stage development of E. japonica was well described by all model ($r^2_{adj}=0.90$) based on the standardized development duration. These results of study would be necessary not only to develop population dynamics model but also to understand fundamental biology of E. japonica.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.38 no.3
• /
• pp.281-293
• /
• 2020

Recently, large and small fires have been happening more often in Korea. Fire is one of the most frequent disasters along with traffic accidents in korean cities, and this frequency is closely related to the land use and the type of facilities. Therefore, in this study, the significance of fires was analyzed by considering land use, facility types, human and social factors and using 10 years of fire data in Jinju city. Based on this, OLS (Ordinary Least Square) regression analysis, SLM (Spatial Lag Model) and SEM (Spatial Error Model) using space weights, were compared and analyzed considering the location of the fire and each factor, then a statistical model with high suitability was presented. As a result, LISA analysis of spatial distribution patterns of fires in Jinju city was conducted, and it was proved that the frequency of fires was high in the order as follow, central commercial area, industrial area and residential area. Multiple regression analysis was performed by integrating demographic, social, and physical variables. Therefore, the three models were compared and analyzed by applying spatial weighting to the derived factors. As a result of the significance test, the spatial error model was analyzed to be the most significant. The facilities that have the highest correlation with fire occurrence were second type neighborhood facilities, followed by detached house, first type neighborhood facilities, number of households, and sales facilities. The results of this study are expected to be used as significant data to identify factors and manage fire safety in urban areas. Also, through the analysis of the standard deviation ellipsoid, the distribution characteristics of each facility in the residential area, industrial area, and central commercial area among the use areas were analyzed. In, the second type neighborhood facility with the highest fire risk was concentrated in the center. The results of these studies are expected to be used as useful data for identifying factors and managing fire safety in urban areas.

• Journal of the Mineralogical Society of Korea
• /
• v.22 no.4
• /
• pp.313-324
• /
• 2009

We explore the effect of particle shape and size on 3-dimensional (3D) network and pore structure of porous earth materials composed of glass beads and silica gel using NMR micro-imaging in order to gain better insights into relationship between structure and the corresponding hydrologic and seismological properties. The 3D micro-imaging data for the model porous networks show that the specific surface area, porosity, and permeability range from 2.5 to $9.6\;mm^2/mm^3$, from 0.21 to 0.38, and from 11.6 to 892.3 D (Darcy), respectively, which are typical values for unconsolidated sands. The relationships among specific surface area, porosity, and permeability of the porous media are relatively well explained with the Kozeny equation. Cube counting fractal dimension analysis shows that fractal dimension increases from ~2.5－2.6 to 3.0 with increasing specific surface area from 2.5 to $9.6\;mm^2/mm^3$, with the data also suggesting the effect of porosity. Specific surface area, porosity, permeability, and cube counting fractal dimension for the natural mongolian sandstone are $0.33\;mm^2/mm^3$, 0.017, 30.9 mD, and 1.59, respectively. The current results highlight that NMR micro-imaging, together with detailed statistical analyses can be useful to characterize 3D pore structures of various porous earth materials and be potentially effective in accounting for transport properties and seismic wave velocity and attenuation of diverse porous media in earth crust and interiors.

• Radiation Oncology Journal
• /
• v.16 no.4
• /
• pp.517-529
• /
• 1998

Purpose : Although many studies have investigated the dosimetric aspects of stereotactic radiosurgery in terms of target volume, the absorbed doses at extracranial sites: especially the lens or thyroid - which are sensitive to radiation for deterministic or stochastic effect -have infrequently been reported. The aim of this study is to evaluate what effects the parameters of radiosurgery have on the absorbed doses of the lens and thyroid in patients treated by stereotactic radiosurgery, using a systematic plan in a humanoid phantom. Materials and Methods : Six isocenters were selected and radiosurgery was planned using the stereotactic radiosurgery system which the Department of Therapeutic Radiology at Seoul National University College of Medicine developed. The experimental radiosurgery plan consisted of 6 arc planes per one isocenter, 100 degrees for each arc range and an accessory collimator diameter size of 2 cm. After 250 cGy of irradiation from each arc, the doses absorbed at the lens and thyroid were measured by thermoluminescence dosimetry. Results : The lens dose was 0.23$\pm$0.08$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the lens and was 0.76$\pm$0.12$\%$ of the maximum dose for each isocenter when the exit beam passed through the lens. The thyroid dose was 0.18$\pm$0.05$\%$ of the maximum dose for each isocenter when the exit beam did not pass through the thyroid and was 0.41$\pm$0.04$\%$ of the maximum dose for each isocenter when the exit beam Passed through the thyroid. The passing of the exit beam is the most significant factor of organ dose and the absorbed dose by an arc crossing organ decides 80$\%$ of the total dose. The absorbed doses of the lens and thyroid were larger as the isocenter sites and arc planes were closer to each organ. There were no differences in the doses at the surface and 5 mm depth from the surface in the eyelid and thyroid areas. Conclusion : As the isocenter and arc plane were placed closer to the lens and thyroid, the doses increased. Whether the exit beams passed through the lens or thyroid greatly influenced the lens and thyroid dose. The surface dose of the lens and thyroid consistently represent the tissue dose. Even when the exit beam passes through the lens and thyroid, the doses are less than 1$\%$ of the maximum dose and therefore, are too low to evoke late complications, but nevertheless, we should try to minimize the thyroid dose in children, whenever possible.

• Economic and Environmental Geology
• /
• v.55 no.5
• /
• pp.551-561
• /
• 2022

Geophysical exploration methods are very useful for generating high-resolution images of underground structures, and such methods can be applied to investigation of buried cultural properties and for determining their exact locations. In this study, image feature extraction and image segmentation methods were applied to automatically distinguish the structures of buried relics from the high-resolution ground-penetrating radar (GPR) images obtained at the center of Silla Kingdom, Gyeongju, South Korea. The major purpose for image feature extraction analyses is identifying the circular features from building remains and the linear features from ancient roads and fences. Feature extraction is implemented by applying the Canny edge detection and Hough transform algorithms. We applied the Hough transforms to the edge image resulted from the Canny algorithm in order to determine the locations the target features. However, the Hough transform requires different parameter settings for each survey sector. As for image segmentation, we applied the connected element labeling algorithm and object-based image analysis using Orfeo Toolbox (OTB) in QGIS. The connected components labeled image shows the signals associated with the target buried relics are effectively connected and labeled. However, we often find multiple labels are assigned to a single structure on the given GPR data. Object-based image analysis was conducted by using a Large-Scale Mean-Shift (LSMS) image segmentation. In this analysis, a vector layer containing pixel values for each segmented polygon was estimated first and then used to build a train-validation dataset by assigning the polygons to one class associated with the buried relics and another class for the background field. With the Random Forest Classifier, we find that the polygons on the LSMS image segmentation layer can be successfully classified into the polygons of the buried relics and those of the background. Thus, we propose that these automatic classification methods applied to the GPR images of buried cultural heritage in this study can be useful to obtain consistent analyses results for planning excavation processes.