• Radiation Oncology Journal
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• v.14 no.2
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• pp.149-158
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• 1996

Purpose : To get an accute steepness of dose gradients at outside the target volume in intracranial lesion and a less limitation of beam selection avoiding the high dose at normal brain tissue, this Photon Knife Radiosurgery System was developed in order to provide the three-dimensional dose distribution through the reconstruction of CT scan and the combined stereotactic trans-multiarc beam mode based on linear accelerator photon beam. Materials and methods : This stereotactic radiosurgery, Photon Knife based on linear accelerator photon beam was provided the non-coplanar multiarc and trans-multiarc irradiations. The stereotactic trans-multiarc beam mode can be obtained from the patient position in decubitus. This study has provided the 3-dimensional isodose curve and anatomical structures with the surface rendering technique. The dose distribution from the combined two trans-multiarcs (2M 2TM) was compared to that of four non-coplanar multiarcs (4M) with same collimator size of 25 mm in a diameter and total gantry movements. Results : In this study, it shows that the dose distributions of stereotactic beam mode are significantly depended on the selected couch and gantry angle in same collimator size. Practical dose distribution of combined stereotactic trans-multiarc beam has shown a more small rim thickness than that of the non-coplanar multiarc beam mode in axial, sagittal and coronal plane in our study. 3-Dimensional dose line displayed with surface rendering of irregular target shape is helpful to determine the target dose and to predict the prognosis in follow-up radiosurgery. Conclusions : 3-Dimensional dose line displayed with surface rendering of irregular target shape is essential in stereotactic radiosurgery. This combined stereotactic trans-multiarc beam has shown a less limitation of the selection couch and gantry beam angles for the target surrounding critical organs. It has shown that the dose distribution of combined trans-multiarc beam greatly depended on the couch and gantry angles. In our experiments, the absorbed dose has been decreased to $27%$ / mm in maximum at the interval of $50\%$ to $80\%$ of isodose line.

• Journal of Bio-Environment Control
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• v.29 no.2
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• pp.120-129
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• 2020

In Yesan-gun, Korea's main apple-producing region, the area of apple cultivation and yield are declining. In particular, the worsening quality of fruits due to unusually high temperatures amid recent climate change has also become a major challenge for apple orchards located on flatlands. The objective of this research is to investigate quality changes of apples according to different growing environments, depending on the shade of the sun, by covering the trees with different colors of wind nets. A white and blue wind nets with a hole size of 2 × 2 mm is installed on two experimental trees, 17-year-old 'Fuji' and 'Hongro', which are planted 1.5 m × 3.5 m in the north-south direction. Treatment of wind nets effectively lowered fruit surface temperature regardless of apple variety. When measuring the temperature of the fruit surface at 2 pm, the temperature of the air was 34.8℃, but the 'Fuji' of the untreated blocks was the highest at 40.0℃, while the blue wind net and the white wind net were significantly lower at 34.9℃ and 36.6℃, respectively. In 'Hongro', the results showed that the surface temperature was effectively lowered by recording 38.3℃ for the blue wind net and 38.5℃ for the white wind net treatment when the untreated one was 44.2℃. According to the color difference in 'Fuji', the skin redness (a^⁎) was the lowest with untreated control at 16.5, but the blue and white wind net treatment higher at 18.0 and 19.3, respectively. In 'Hongro', the white wind net treated fruit also showed a much higher skin redness than the untreated control of 28.1, showing much higher a^⁎ of 34.9. Sunburn damage in 'Fuji' apples amounted to 9.4% in untreated control. However, the blue and white wind net treatment revealed to 3.8% and 4.2%, respectively. In 'Hongro', those damage in the fruits treated with blue or white wind net, accounted for only 8.8% and 12.4%, respectively, significantly lower than 28.8% occurrence of untreated one. And, these results were understood to be the result of low UV radiation being blocked by the treatment of wind nets.

• Journal of the Korean Society of Radiology
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• v.8 no.6
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• pp.293-299
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• 2014

Compton suppression device is a device by using the Compton scattering reaction and suppress the Compton continuum portion of the spectrum, so can be made more clear analysis of gamma ray peak in the Compton continuum region. Measurements above background occurs or, radioactivity counts of radioactivity concentration value of $^{40}K$ nuclides $^{137}Cs$ and natural radioactivity artificial radioactivity detected from the surface soil sample, unwanted non-target analysis and interference peak who dotted line you know the calibration of the measurement energy is allowed to apply the (Compton suppression) non-suppressed spectrum inhibition spectrum and (Compton Unsuppression) the background to the measured value of the activity concentration value of the standard-ray source is detected relative to the peak of By measuring according to the different distances cause $^{137}Cs$, and comparative analysis of the Monte Carlo simulation, in order to obtain a detection capability for efficient, looking at the Compton inhibitor, as the CSF value increases with increase in the distance, more It was found that the background due to Compton continuum of the measured spectrum suppression mode Compton unrestrained mode can know that the Compton suppression many were made, using a $^{137}Cs$ is reduced.

• Journal of Environmental Health Sciences
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• v.33 no.2 s.95
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• pp.123-131
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• 2007

Many environmental contaminants including several metals, polycyclic aromatic hydrocarbons, and pharmaceuticals, have been identified to be phototoxic in the water environment. Concerns regarding photo-enhancement of toxicity of several environmental contaminants have been increasing because of the increased level of ultraviolet irradiation on the earth surface. However, there exist arguments that there might be certain defense mechanisms taking place in the aquatic ecosystem, which may include behavioral characteristics or genetic acclimation. This study was conducted to understand the potential responses of aquatic receptors to several phototoxic metals in the real environment, where long-term acclimation of such organisms to low dose UV-B may take place. For this purpose, water flea Daphnia magna was acclimated to environmentally relevant dose of UV-B (12 to $18uW/cm^2$) for >11 generations. The differences in developmental and life history characteristics, and toxicity responses were evaluated. Acclimation did not affect the daphnids' growth, longevity, and reproduction characteristics such as time to first brood, and brood size: After 21 d, survival of D. magna was not influenced by UV-B acclimation. When the number of young per female was compared. the daphnids acclimated for 11 generations tend to produce less number of neonates than the un-acclimated individuals but with no statistical significance (p>0.05). Four metals that were reported to be phototoxic elsewhere were employed in this evaluation, that include As, Cd. Cu, and Ni. UV-B level being applied in acclimation did increase the toxicity of Cd and Cu, significantly (p<0.05). However, the toxicities of As and Ni were not affected by irradiation of UV-B. Phototoxic responses were evaluated between the acclimated and the un-acclimated daphnids. For Cu, UV-B acclimation led to reduction of the photo-induced toxicity $(p\approx0.1)$ in daphnids. Non-acclimated Daphnia were affected by 50% at 4.18 ug/l Cu. but UV-B acclimated individuals exhibited $EC_{50}$ of 5.89 ug/l. With Cd, UV-B acclimation appeared to increase phototoxicity (p>0.05). With As and Ni, UV-B acclimation did not influence photo-induced toxicity. This observation may be in part explained by the type of reactive oxygen species that were generated by each metal. Similar to UV-B light, Cu is known to generate superoxide anion by acting as redox cycling toxicant. This is one of the first studies that employed_laboratory based UV-B acclimated test species for photoenhanced toxicity evaluation.

• Korean Journal of Remote Sensing
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• v.28 no.5
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• pp.501-508
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• 2012

Albedo is known as a factor that directly impacts on the surface energy balance one of the elements of earth radiation balance. The change of albedo includes the change of soil moisture, vegetation, solar zenith angle, snow, and so on. In addition, it operates as a crucial path to understanding feedback mechanisms between radiation balance and its influence on climate and vegetation dynamics and therefore, observing the variation of albedo is a one of the essential procedures for anticipating climate change. In this study, we used MODIS 16-Day composited Albedo data from 2001 to 2011 years with the purpose of observing the change of albedo over Northeast Asia. According to the tendency of albedo for 11 years, albedo in the area of an active vegetation has increased in near-infrared (NIR) domain and decreased in visible (VIS) domain. On the basis of local changes in vegetation in 2002, the both area of the Gobi Desert and the Manchuria was enormously changed and chosen the research area and furthermore, the vegetation of both regions had deteriorated due to the change of the minimum value since 2010.

• Journal of the Korean Geographical Society
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• v.30 no.3
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• pp.230-241
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• 1995

The Characteristics of nocturnal temperature fields were analyzed to understand the factors of freezing-and-cold damages on orange orchards in Cheju Island. Temperatures were measured from January 7th through 27, 1995 at 25 sites in an area of 1x1.25$ extrm{km}^2$, Wasan-ri, Chochon-up, Pukcheju-kun located on the northeastern slope of Mt.Hanla. Several other weather elements such as wind and cloud were observed as supplementary data. Surface weather maps were also analyzed to clarify the influence of prevailing pressure patterns on the temperature fields. The vertical temperature profiles were obtained at the height from the ground up to 360 cm in 30 cm intervals at site 3, a frost hollow, and site 10 on the upper slope. The results show that freezing damages occured in the hollows, terrain depressions, rather than at the upper slope due to nocturnal radiation cooling as well as accumulation of cold airflow from Mt.Hanla. Windbreaks of densely planted Japanese ceders with stone-walls also roled as obstacles to the cold airflow in nights with Clear skies and light winds. The maximum intensity of temperature inversion in hollows, quasi-cold air lake, was 3.1$^{\circ}C$. Cold air from Mt.Hanla was trapped in the depressions up to a height of 90cm forming frost pocket. Man-made facilities such as shelterbelt or stone-wall which are built to prevent the penetration of cold north-westeries in winter aggravated the cold damage. The differance of daily minimum temperatures between before and behind shelterbelts was 2.$0^{\circ}C$. The man-made convection by smudgin which raised the temperatures up to 3.8$^{\circ}C$ can reduce the cold damage in the hellows.

• Journal of Radiation Protection and Research
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• v.21 no.2
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• pp.125-129
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• 1996

The energy response of HPGe detector for low energy Photons was determined by using three Monte Carlo codes. MCNP4A. EGS4, and CYLTRAN in ITS3. In this study. bare HPGe detector$(100 mm^2{\times}10mm)$ was used and a pencil beam was incident perpendicularly on the center of the detector surface. The photopeak efficiency, $K_{\alpha}$ and $K_{\beta}$ escape fractions were calculated as a function of incident X-ray energies ranging from 12 to 60 keV in 2-keV increments. Since the Compton. elastic. ana penetration fraction were negligible in this energy range. they were ignored in the calculation. Although MCNP. EGS, and CYLTRAN codes calculated slightly different energy response of HPGe detector for low energy Photons, it appears that the three Monte Carlo codes can Predict the low energy Photon scattering Processes accurately. The MCNP results, which are generally known as to be less accurate at low energy ranges than the EGS and ITS results. are comparable to the results of EGS and ITS and are applicable to the calculation of the low energy response data of a detector.

• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.2
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• pp.95-102
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• 2002

Spatial interpolation has become a common procedure in converting temperature forecasts and observations at irregular points for use in regional scale ecosystem modeling and the model based decision support systems for resource management. Neglection of terrain effects in most spatial interpolations for short term temperatures may cause erroneous results in mountainous regions, where the observation network hardly covers full features of the complicated terrain. A spatial interpolation model for daytime hourly temperature was formulated based on error analysis of unsampled site with respect to the site topography. The model has a solar irradiance correction scheme in addition to the common backbone of the lapse rate - corrected inverse distance weighting. The solar irradiance scheme calculates the direct, diffuse and reflected components of shortwave radiation over any surfaces based on the sun-slope geometry and compares the sum with that over a reference surface. The deviation from the reference radiation is used to calculate the temperature correction term by an empirical conversion formula between the solar energy and the air temperature on any sloped surfaces at an hourly time scale, which can be prepared seasonally for each land cover type. When this model was applied to a 14 km by 22 km mountainous region at a 10 m horizontal resolution, the estimated hourly temperature surfaces showed a better agreement with the observed distribution than those by a conventional method.

• Progress in Medical Physics
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• v.6 no.2
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• pp.51-60
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• 1995

Lithium Fluoride (LiF; TLD-100) crystal chips are normally used as thermolu minescence dosimeters (abbreviated as NC-100) for estimating the absorbed dose to the skin of a patient or in a solid water phantom undergoing radiotherapy with megavoltage photon (6 and 15MV) beams. In general, investigation has revealed a reduction in the sensitivity of NC-100 chips after many runs through heating cycles. A TLD-100 chip laminated with gold plate (140${\mu}{\textrm}{m}$) on the upper surface layer of its face toward the photon beam (abbreviated as GC-100) has properties different from that of a NC-100 chip activated by incident photons and contaminant electrons with various lower energies coming from the gantry head and air. Activation of the valence band electrons of GC-100 chips by incident photons, positrons and electrons-which come from the gold plate by mainly pair production process and partly from Compton scattering-results in more enhanced signal intensity, higher response per monitor unit, as well as a good linearity with monitor units and independence of dose rate. Since the electron beams (6 and 15 MeV) do not have the probability of pair production process with gold plate, there is only a small difference (about a 3.3％ increase for 15 MeV) in the signal gaps in the TL readout for electron beams between GC- and NC-100 chips. The 3.3％ increase is entirely due to the buildup caused by the 140 m gold plate. The sensitivity of GC-100 chips is much more susceptible to high energy photon beams than electron one because of pair production. The interaction of high energy photon with a material of high atomic number, such as the good plate in this case, results in a considerably significant probability of pair production. The gold plate on the NC-100 chips acts as not only an intensifier of their signals but also acts as a filter of contaminant electrons in therapeutic high energy X-ray beams.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.5
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• pp.282-287
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• 2017

The purpose of this study was predicted the effects of mixing and diffusion due to the operation of the apparatus before the development of the mixed diffusion device for the decontamination absorbent to minimize the influence of contaminant inflow due to radiation accident. The tracer used for the flow characteristics was $^{68}Ga$, $^{99m}Tc$, which is a radioactive isotope, and 2 inch NaI radiation detector was used to detect it. The impeller of the decontamination mixed diffusion system applied to this study was made into three types and the mixing diffusion effect was compared. As a result of analyzing the flow characteristics of the radio-isotope with decontamination mixed diffusion device, mixing, diffusion and flow pattern were obtained. The radial mixing type impeller was able to diffuse to the water surface by the upflow flow, and the fin structure was adjusted for finding optimal conditions. The model 3 type consists of a fin guiding part and an auxiliary fin so that the diffusion speed is higher than that of other types of impellers. It also showed a short time to reach complete mixing.