• Solar Energy
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• v.12 no.3
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• pp.70-83
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• 1992

The interaction between the surface radiation and the mixed convection transport from an isolated thermal source, with a uniform surface heat flux input and located in a rectangular enclosure, is stuied numerically. The enclosure simulates a practical system such an air cooled electric device, where an air-stream flows through the openings on the two vertical walls. The heat source represents an electric component located in such an enclosure. The size of this cavity is $0.1[m]{\times}0.1[m]$. The inlet velocity is assumed as 0.07[m/s] and the inlet temperature is maintained as $27^{\circ}C$. The inflow is kept at a fixed position. Laminar, two dimensional flow is assumed, and the problem lies in the mixed convection regime, governed by buoyancy force and surface readiation. The significant variables include the location of the out-flow opening, of the heat source and the wall emissivity. The basic nature of the resulting interaction betwwn the externally induced air stream and the buoyancy-driven flow generated by the source is investigated. As a result, the best location of the heat source to make the active heat transfer is 0.075[m] from the left wall on the floor. The trends observed are also discussed in terms of heat removal from practical systems such as electric circuitry.

• Journal of Radiation Protection and Research
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• v.26 no.4
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• pp.393-398
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• 2001

The non-combustible RI wastes disposed of in hospital every year emit ${\gamma}$-ray or ${\beta}$-ray but their activities are very low to the extent of background. Development of more simple methods is needed because the conventional detection methods are so ineffective and complex. In this study, to solve this problem, detection method using efficiency curve for ${\gamma}$-ray emitting radioactive wastes measurement is proposed and experimental detection efficiency equation is also determined through HPGe's standard specimen measurement. For ${\beta}$-emitting radioisotopes detection, new measurement method using detection efficiency estimated by Monte Carlo simulation and SBD measurements is also proposed. According to the results of this paper, the unknown activity of low-level radioactive wastes without LSC requiring the preparation of standard sample and measurement for standard source detection efficiency could be determined efficiently and simply about ${\pm}17%$ in errors by using the theoretical detection efficiency and the SBD measurement result.

• Nuclear Engineering and Technology
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• v.25 no.1
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• pp.51-62
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• 1993

A computational program ［TDET］ of the particle transport equation is developed on radiation shielding problem in two-dimensional cartesian geometry based on the discrete element method. Not like the ordinary discrete ordinates method, the quadrature set of angles is not fixed but steered by the spatially dependent angular fluxes. The angular dependence of the scattering source term in the particle transport equation is described by series expansion in spherical harmonics, and the energy dependence of the particles is considered as well. Three different benchmark tests are made for verification of TDET : For the ray effect analysis on a square absorber with a flat isotropic source, the results of TDET calculation are quite well conformed to those of MORSE-CG calculation while TDET ameliorates the ray effect more effectively than S$_{N}$ calculation. In the analysis of the streaming leakage through a narrow vacuum duct in a shield, TDET shows conspicuous and remarkable results of streaming leakage through the duct as well as MORSE-CG does, and quite better than S$_{N}$ calculation. In a realistic reactor shielding situation which treats in two cases of the isotropic scattering and of linearly anisotropic scattering with two groups of energy, TDET calculations show local ray effect between neighboring meshes compared with S$_{N}$ calculations in which the ray effect extends broadly over several meshes.eshes.

• Journal of Animal Science and Technology
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• v.49 no.4
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• pp.515-522
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• 2007

To develop the manufacturing method of ice cream with microbiologically safe and proper sensory quality using irradiation for sensitive consumer, 3 different flavors, which were resistant to their flavors against irradiation, were selected and used for ice cream manufacturing to reduce the irradiation-induced off-flavor problem. The general composition was not different among treatments. Total aerobic bacteria were detected as 2.38, 1.23, 1.38, and 1.15 log CFU/g level in ice cream with control(no flavor added), spearmint, mint, and citrus flavor, respectively. No viable cells were observed by irradiation at 1 kGy except for the control. Sensory evaluation indicated that the irradiated ice cream with spearmint flavor at 1 kGy and citrus flavor at 3 kGy had higher overall acceptability. Therefore, a low dose irradiation (less than 3 kGy) with mint or citrus flavors may enhance the safety of ice cream with proper sensory quality for sensitive consumer.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.14-15
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• 2010

Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

• Journal of the Korean Society of Radiology
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• v.14 no.7
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• pp.891-898
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• 2020

As the problem of shields made of lead has recently emerged, research on replacement shields is essential, and studies on the manufacture of diagnostic X-ray shields with 3D printers are also being actively conducted. Recently, with the development of metal mixed filaments, it has become possible to manufacture shielding materials easily, but studies on the nozzle size and output setting of 3D printers are insufficient. Therefore, this study aims to compare and analyze the results through a shielding rate experiment using a brass filament and a 3D printer, outputting the shield according to the nozzle size and layer height, and using a diagnostic radiation generator. The nozzle size was changed to 0.4, 0.8 mm, layer height 0.1, 0.2, 0.3, 0.4 mm, and output. The shielding rate test was fixed at 40 mAs, and the shielding rate was analyzed by experimenting with 60, 80, and 100 kVp, respectively. As a result of the analysis, it was analyzed that the printing time could be reduced to 1/10 according to the nozzle size and the layer height, and the shielding rate could be increased by 1% or more.

• Journal of Radiation Protection and Research
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• v.47 no.2
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• pp.99-106
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• 2022

Background: The radionuclide inventory calculation codes such as ORIGEN and FISPACT collapse neutron reaction libraries with energy spectra and generate an effective one-group cross-section. Since the nuclear cross-section data, energy group (g) structure, and other input details used by the two codes are different, there may be differences in each code's activation inventory calculation results. In this study, the calculation results of neutron-induced activation inventory using ORIGEN and FISPACT were compared and analyzed regarding radioactive waste classification and worker exposure during nuclear decommissioning. Materials and Methods: Two neutron spectra were used to obtain the comparison results: Watt fission spectrum and thermalized energy spectrum. The effective one-group cross-sections were generated for each type of energy group structure provided in ORIGEN and FISPACT. Then, the effective one-group cross-sections were analyzed by focusing on ⁵⁹Ni, ⁶³Ni, ⁹⁴Nb, ⁶⁰Co, ¹⁵²Eu, and ¹⁵⁴Eu, which are the main radionuclides of stainless steel, carbon steel, zircalloy, and concrete for decommissioning nuclear power plant (NPP). Results and Discussion: As a result of the analysis, ¹⁵⁴Eu and ⁵⁹Ni may be overestimated or underestimated depending on the code selection by up to 30%, because the cross-section library used for each code is different. When ORIGEN-44g, -49g, and -238g structures are selected, the differences of the calculation results of effective one-group cross-section according to group structure selection were less than 1% for the six nuclides applied in this study, and when FISPACT-69g, -172g, and -315g were applied, the difference was less than 1%, too. Conclusion: ORIGEN and FISPACT codes can be applied to activation calculations with their own built-in energy group structures for decommissioning NPP. Since the differences in calculation results may occur depending on the selection of codes and energy group structures, it is appropriate to properly select the energy group structure according to the accuracy required in the calculation and the characteristics of the problem.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1251-1251
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• 2001

The routine analysis of milk chemical components is of major importance both for the management of animals in dairy farms and for quality control in dairy industries. NIRS technology is an analytical technique which greatly simplifies this routine. One of the most critical aspects in NIRS analysis of milk is sample preparation and analysis modes which should be fast and straightforward. An important difficulty when obtaining NIR spectra of milk is the high water content (80 to 90%) of this product, since water absorbs most of the infrared radiation, and, therefore, limits the accuracy of calibrating for other constituents. To avoid this problem, the DESIR system was set up. Other ways of radiation-sample interaction adapted for liquids or semi-liquids exist, which are practically instantaneous and with limited or null necessity of sample preparation: Transmission and Folded Transmission or Transflectance. The objective of the present work is to compare the precision and accuracy of milk calibration equations in two analysis modes: Reflectance (dry milk) and Folded Transmission (liquid milk). A FOSS-NIR Systems 6500 I spectrophotometer (400-2500 nm) provided with a spinning module was used. Two NIR spectroscopic methods for milk analysis were compared: a) folded transmission: liquid milk samples in a 0.1 pathlength sample cell (ref. IH-0345) and b) reflectance: dried milk samples in glass fibre filters placed in a standard ring cell. A set of 101 milk samples was used to develop the calibration equations, for the two NIR analysis modes, to predict casein, protein, fat and dry matter contents, and 48 milk samples to predict Somatic Cell Count (SCC). The calibrations obtained for protein, fat and dry matter have an excellent quantitative prediction power, since they present $r^2$ values higher than 0.9. The $r^2$ values are slightly lower for casein and SCC (0.88 and 0.89 respectively), but they still are sufficiently high. The accuracy of casein, protein and SCC equations is not affected by the analysis modes, since their ETVC values are very similar in reflectance and folded transmission (0.19% vs 0.21%; 0.16% vs 0.19% and 55.57% vs 53.11% respectively), Lower SECV values were obtained for the prediction of fat and dry matter with the folded transmission equations (0.14% and 0.25% respectively) compared to the results with the reflectance ones (0.43% and 0.34% respectively). In terms of accuracy and speed of analytical response, NIRS analysis of liquid milk is recommended (folded transmission), since the drying procedure takes 24 hours. However, both analysis modes offer satisfactory results.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.115-121
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• 2013

Purpose: Latest linear accelerator and the introduction of new measurement equipment to the agency that the introduction of this equipment in the future, by analyzing the process of confirming the usefulness of the preparation process for applying it in the clinical causes some problems, should be helpful. Materials and Methods: All measurements TrueBEAM STX (Varian, USA) was used, and a file specific to each energy, irradiation conditions, the dose distribution was calculated using a computerized treatment planning equipment (Eclipse ver 10.0.39, Varian, USA). Measuring performance and cause errors in MapCHECK 2 were analyzed and measured against. In order to verify the performance of the MapCHECK 2, 6X, 6X-FFF, 10X, 10X-FFF, 15X field size $10{\times}10$ cm, gantry $0^{\circ}$, $180^{\circ}$ direction was measured by the energy. IGRT couch of the CT values affect the measurements in order to confirm, CT number values : -800 (Carbon) & -950 (COUCH in the air), -100 & 6X-950 in the state for FFF, 15X of the energy field sizes $10{\times}10$, gantry $180^{\circ}$, $135^{\circ}$, $275^{\circ}$ directionwas measured at, MapPHAN allocated to confirm the value of HU were compared, using the treatment planning computer for, Measurement error problem by the sharp edges MapPHAN Learn gantry direction MapPHAN of dependence was measured in three ways. GANTRY $90^{\circ}$, $270^{\circ}$ in the direction of the vertically erected settings 6X-FFF, 15X respectively, and Setting the state established as a horizontal field sizes $10{\times}10$, $90^{\circ}$, $45^{\circ}$, $315^{\circ}$, $270^{\circ}$ of in the direction of the energy-6X-FFF, 15X, respectively, were measured. Without intensity modulated beam of the third open arc were investigated. Results: Of basic performance MapCHECK confirm the attenuation measured by Couch, measured from the measured HU values that are assigned to the MAP-PHAN, check for calculation accuracy for the angled edge of the MapPHAN all come in a range of valid measurement errors do not affect the could see. three ways for the Gantry direction dependence, the first of the meter built into the value of the Gantry $270^{\circ}$ (relative $0^{\circ}$), $90^{\circ}$ (relative $180^{\circ}$), 6X-FFF, 15X from each -1.51, 0.83% and -0.63, -0.22% was not affected by the AP/PA direction represented. Setting the meter horizontally Gantry $90^{\circ}$, $270^{\circ}$ from the couch, Energy 6X-FFF 4.37, 2.84%, 15X, -9.63, -13.32% the difference. By-side direction measurements MapPHAN in value is not within the valid range can not, because that could be confirmed as gamma pass rate 3% of the value is greater than the value shown. You can check the Open Arc 6X-FFF, 15X energy, field size $10{\times}10$ cm $360^{\circ}$ rotation of the dose distribution in the state to look at nearly 90% pass rate to emerge. Conclusion: Based on the above results, the MapPHAN gantry direction dependence by side in the direction of the beam relative dose distribution suitable for measuring the gamma value, but accurate measurement of the absolute dose can not be considered is. this paper, a more accurate treatment plan in order to confirm, Reduce the tolerance for VMAT, such as lateral rotation investigation in order to measure accurate absolute isodose using a combination of IMF (Isocentric Mounting Fixture) MapCHEK 2, will be able to minimize the impact due to the angular dependence.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.121-124
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• 2008

In this paper, we will design a 800MHz broadband antenna after a problem of the narrow bandwidth is improved. This multiple band antenna unifies the CDMA(Code Division Multiple Access), GSM(Global System for Mobile telecommunication) and TRS(Trunked Radio System) band in the UHF bandwidth, and then it is possible at the shore base station or repeater as the commercial use. It used the duplex resonance effect It had the L-shaped feeding structure which adds the V-slot. And it improved profit using stack structure. It was measured that the frequency bandwidth of the designed antenna which is planed $792{\sim}1040MHz$ with 248MHz(33%). And the antenna gain is 9.4dBi, 3dB beam width $60^{\circ}$ in radiation pattern.