• Journal of Radiation Protection and Research
• /
• v.27 no.3
• /
• pp.155-164
• /
• 2002

Methodology to evaluate the effective doses to adults undergoing various diagnostic x-ray examinations were established by Monte Carlo simulation of the x-ray examinations. Anthropomorphic mathematical phantoms, the MIRD5 male phantom and the ORNL female phantom, were used as the target body and x-ray spectra were produced by the x-ray spectrum generation code SPEC78. The computational procedure was validated by comparing the resulting doses to the results of NRPB studies for the same diagnostic procedures. The effective doses as well as the organ doses due to chest, abdomen, head and spine examinations were calculated for x-rays incident from AP, PA, LLAT and RLAT directions. For instance, the effective doses from the most common procedures, chest PA and abdomen AP, were 0.029 mSv and 0.44 mSv, respectively. The fact that the effective dose from PA chest x-ray is far lower than the traditional value of 0.3 mSv(or 30 mrem), which results partly from the advances of technology in diagnostic radiology and partly from the differences in the dose concept employed, emphasizes necessities of intensive assessment of the patient doses in wide ranges of medical exposures. The methodology and tools established in this study can easily be applied to dose assessments for other radiology procedures; dose from CT examinations, dose to the fetus due to examinations of pregnant women, dose from pediatric radiology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.2
• /
• pp.199-207
• /
• 2001

In this paper, the technique of prediction and analysis on the characteristics of propagation in indoor environment is presented. This technique needs no reception sphere commonly used in 3D-ray tracing scheme, and thereby it lends us easy code realization. The validity of developed code is verified by comparing with the values of image methods and measurement. The developed technique applied to the structure of rectangular corridor with the iron door and we calculated the path loss for the variation of the iron door angle. The path loss decreased about 15 dB at the distance of30 m from the iron door and the delay spread increased approximately by four times. Based on the computation, we confirmed that indoor propagation in PCS is heavily affected by the iron door in corridor.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.4 no.2
• /
• pp.417-426
• /
• 2000

In this paper, CE-CPSK(Constant Envelope Continuous Phase Shift Keying) modulated DS/SS(Direct Sequence Spread Spectrum) transceiver with 908 MHz carrier frequency and 1.5 MHz PN clock rate is proposed. To overcome the effect of nun-linear power amplifier, CE-CPSK modulation method which has the constant envelope and continuous phase characteristics is proposed. To analyze the DS/SS receiver performance with respect to code tracking loop, multipath fading channel is characterized as a two-ray Rayleigh fading channel. To compensate the demerit of analog delay locked loop, digital delay locked loop is employed for code tracking loop. Simulation and experimental examination has been carried out in AWGN(Additive White Gaussian Noise) and Rayleigh fading channel environment in order to prove validity of the proposed method.

• Nuclear Engineering and Technology
• /
• v.20 no.1
• /
• pp.65-70
• /
• 1988

A Shielding analysis of the shipping cask designed conceptually, of which shielding material are lead and resin, for containing 4 PWR spent fuel assemblies, has been made with the help of a computer code, ANISN. The shielding materials being used in the cask have been selected and arranged to minimize cask weight while maintaining an overall shielding effectiveness. Radiation source terms have been calculated by means of ORIGIN-2 code under the assumptions of 38,000 MWD/MTU burnup and 3-year cooling time. A calculation of gamma-ray and neutron dose rates on the cask surface and 1m from the surface has been done. It is revealed that the total dose rates under the normal transport and hypothetical accident conditions meet the standards specified.

• Nuclear Engineering and Technology
• /
• v.54 no.7
• /
• pp.2625-2634
• /
• 2022

Discretization errors are extremely challenging conundrums of discrete ordinates calculations for radiation transport problems with void regions. In previous work, we have presented a multi-collision source method (MCS) to overcome discretization errors, but the efficiency needs to be improved. This paper proposes a goal-oriented algorithm for the MCS method to adaptively determine the partitioning of the geometry and dynamically change the angular quadrature in remaining iterations. The importance factor based on the adjoint transport calculation obtains the response function to get a problem-dependent, goal-oriented spatial decomposition. The difference in the scalar fluxes from one high-order quadrature set to a lower one provides the error estimation as a driving force behind the dynamic quadrature. The goal-oriented algorithm allows optimizing by using ray-tracing technology or high-order quadrature sets in the first few iterations and arranging the integration order of the remaining iterations from high to low. The algorithm has been implemented in the 3D transport code ARES and was tested on the Kobayashi benchmarks. The numerical results show a reduction in computation time on these problems for the same desired level of accuracy as compared to the standard ARES code, and it has clear advantages over the traditional MCS method in solving radiation transport problems with reflective boundary conditions.

• Journal of Environmental Science International
• /
• v.13 no.2
• /
• pp.175-180
• /
• 2004

A prompt gamma-ray neutron activation (PGNA) system was simulated by the Monte Carlo N-Particle transport code (MCNP-4A) to estimate the level at which the scattered photon fluence rate, the absolute efficiency of the HPGe-detector, the volume of the concrete sample and the $^{35}$ /Cl(n, ${\gamma}$) reaction rate in this sample contribute to the count rate in the NaCl concentration measurement. The n- ${\gamma}$ fluence rates at the ST-2 beam tube exit of the HANARO reactor were used as input data, and the GAMMA-X type HPGe detector was modeled to tally 1.1649 MeV ${\gamma}$ -rays emitted from the $^{35}$ Cl(n, ${\gamma}$) reaction in the concrete sample. For three cylindrical concrete samples of 13.8, 46.8 and 157.1 ㎤ volumes, respectively, the relations between the NaCl weight fractions of 0.1, 1, 2 and 5 % in each of the concrete samples and the 1.1 649 MeV pulses created in the HPGe detector model were studied. As a result, it was found that the count rate at the same NaCl concentration nearly depends on the volume of the samples in a simulated condition of the same NaCl concentration samples, and that the linearities of the NaCl concentration calibration curves were reasonable in the narrow range of the NaCl weight fraction.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.1422-1425
• /
• 2003

In the design of optical system, important variables of optical system (including indices, shapes, spaces, stops. etc.) must manipulate in order to balance out offensive aberration. In this paper, it carried out a basic study on the design of micro optical system usable for the acquaintance of visual information in the particular conditions such as capsule type endoscopes. In this study, specification for design of optical system selected voluntarily and the basic design of optical system carried out by using the ray tracing method on the assumption that ideal lenses without aberrations. In the designed optical system, the optimization including aberration correction and the performance evaluation of optical system carried out by using the CODE-V. The final designed optical system consists of seven sheets of lenses. Also the results of performance evaluation. the micro optical system combined with aspherical lenses was confirmed to have improved optical performance as compared with the micro optical system consisted of spherical lenses.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.04a
• /
• pp.934-938
• /
• 2008

To customize individual characteristics of HRTF, a spherical model has been used for structural modeling technique. A pseudo-code of prolate spheroidal HRTF caused by incident acoustic point source is already developed, and it can be used a head shadow filter for structural modeling of HRTF. In this research, to see the necessity and efficiency of spheroidal head modeling, ITD optimization is performed on CIPIC HRTF database. From given cost function, ITD-optimized spheroidal head model, whose ITD information is the most matched version of measured ITD information, is found by varying head parameters subject by subject. By comparing results of ITD-optimized spheroids and ITD-optimized spheres, we concluded that a spherical head model is more efficient way of generating head shadow effect than a spheroidal head model does.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.42.2-42.2
• /
• 2011

Noise generated from wind turbines has been predicted by numerical methods. Sound pressure level(SPL) on the turbines is predicted after aerodynamic analysis is carried out by Wind Turbine Flow, Aeroacoustics and Structure analysis (WINFAS) code. The level of each panel of acoustic sphere is determined by the sum of tonal, turbulence ingestion and airfoil self noise. With the noise source database, the acoustic sphere, SPL on the ground is calculated using the model based on acoustic ray theory. The model has been designed to consider the effects on the condition of terrain and atmosphere. The variations of SPL on the ground occur not only because of the different source level but also because of the nonuniform distributions of the sound speed along the height. Hence, the profile of an effective sound speed which is the sum of the contribution of sound speed to a temperature gradient and a wind speed variation is used by the theory based on atmospheric stability. With the integrated numerical method, the prediction of sound propagation on the wind farm is carried out with the states of the atmospheric stability.

• Nuclear Engineering and Technology
• /
• v.50 no.6
• /
• pp.929-936
• /
• 2018

A basic characterization of uranium samples was performed using gamma- and X-ray spectroscopy. The studied uranium samples were eight types of certified reference materials with $^{235}U$ enrichments in the range of 1-97%, and the measurements were performed over 24 h using a high-resolution and high-purity planar germanium detector. A general peak analysis of the spectrum and the $XK_{\alpha}$ region of the uranium spectra was carried out by using HyperGam and HyperGam-U, respectively. The standard reference sources were used to calibrate the spectroscopy system. To obtain the absolute detection efficiency, an effective solid angle code, EXVol, was run for each sample. Hence, the peak activities and isotopic activities were determined, and then, the total U content and $^{234}U$, $^{235}U$, and $^{238}U$ isotopic contents were determined and compared with those of the certified reference values. A new method to determine the model age based on the ratio of the activities of $^{223}Ra$ and $^{235}U$ in the sample was studied, and the model age was compared with the known true age. In summary, the present study developed a method for basic characterization of uranium samples by nondestructive gamma-ray spectrometry in 24 h and to obtain information on the sample age.