• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.11-12
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• 2002

Accidental overexposures by radiotherapy have gathered attention recently in Japan. The widely publicized accidents have occurred at the government official benefit society hospital and at the hospital affiliated to a medical school. The accident at the government official benefit society hospital occurred when one of two existing accelerators was renewed. A radiotherapy planning system was also introduced at that time. Then treatment planning for the old and the new linear accelerator was performed using the system. There were variations in wedge factors for the 30 degrees wedge filter between the old and the new linear accelerator. That is, the difference in the structure of the wedge filter (30 degrees) resulted in variations of the wedge factors between both accelerators. In order to keep strength, a lead board was backed to the lead wedge filter for the new linear accelerator, whereas the wedge filter for the old one was made of the iron. The X-ray attenuation of the iron wedge filter is smaller than that of the lead wedge filter. The basic beam data of the old linear accelerator, however, wasn't delivered properly between the user and the maker. Then, the accident took place because the same wedge factor was used for the old and the new linear accelerator. On the other hand, the accident which occurred at the university hospital was brought about by the input mistake in initialization of the computer system when a linear accelerator was introduced. The input mistake was found when the software of the system was updated. If the dose had been measured and confirmed adequately, the accidents could have been prevented in both cases.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.73-80
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• 2000

The distance correction term -logA0 of the local magnitude scale was estimated for earthquakes in southern Korea using linear least-squares inversion and interpolation scheme. Total 1054 short-period velocity seismograms from 107 local events recorded at hypocentral distances ranging from 10 to 480 km were used in this study. Simulated Wood-Anderson amplitudes were obtained from velocity seismograms with use of revised Wood-Anderson instrument response with static magnification 2080, damping factor 0.7, and natural period 0.8 sec. The estimated distance correction term for southern Korea is found to be -logA0=1.137 log(r/17) + 0.001159(r-17) + 20, where r is hypocentral distance in kilometers. The attenuation rate of this distance correction term falls between those of southern California and eastern North America.

• International Journal of Computer Science & Network Security
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• v.23 no.6
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• pp.27-34
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• 2023

This paper proposed an Inter-Carrier-Interference (ICI) Canceling Orthogonal Frequency Division Multiplexing (OFDM) receiver for 5G mobile system to support 500 km/h linear motor high speed terrestrial transportation service. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceler is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number 𝒏 to receiver sub-carrier number 𝒍 is generated. In case of 𝒏≠𝒍, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 2 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, for modulation schemes below 16QAM, we confirmed that the difference between BER in a 2 path reverse Doppler shift environment and stationary environment at a moving speed of 500 km/h was very small when the number of taps in the multi-tap equalizer was set to 31 taps or more. We also confirmed that the BER performance in high-speed mobile communications for multi-level modulation schemes above 64QAM is dramatically improved by the use of a multi-tap equalizer.

• Nuclear Engineering and Technology
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• v.53 no.6
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• pp.2000-2010
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• 2021

Mechanical moduli, such as Young's modulus (E), Bulks modulus (B), Shear modulus (S), longitudinal modulus (L), Poisson's ratio (σ) and micro Hardness (H) were theoretically calculated for (100-x)TeO₂+x MgO glasses, where x = 10, 20, 30, 40 and 45 mol%, based on the Makishima-Mackenzie model. The estimated results showed that the mechanical moduli and the microhardness of the glasses were improved with the increase of the MgO contents in the TM glasses, while Poisson's ratio decreased with the increase in MgO content. Moreover, the radiation shielding capacity was evaluated for the studied TM glasses. Thus, the linear attenuation coefficient (LAC), mass attenuation coefficient (MAC), transmission factor (TF) and half-value thickness (𝚫_0.5) were simulated for gamma photon energies between 0.344 and 1.406 MeV. The simulated results showed that glass TM10 with 10 mol % MgO possess the highest LAC and varied in the range between 0.259 and 0.711 cm^-1, while TM45 glass with 45 mol % MgO possess the lowest LAC and vary in the range between 0.223 and 0.587 cm^-1 at gamma photon energies between 0.344 and 1.406 MeV. Furthermore, the BXCOM program was applied to calculate the effective atomic number (Z_eff), equivalent atomic number (Z_eq) and buildup factors (EBF and EABF) of the glasses. The effective removal cross-section for the fast neutrons (ERCSFN, ∑_R) was also calculated theoretically. The received data depicts that the lowest ∑_R was achieved for TM10 glasses, where ∑_R = 0.0193 cm² g^-1, while TM45 possesses the highest ERCSFN where ∑_R = 0.0215 cm² g^-1.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1218-1224
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• 2023

We investigated the radiation shielding competence for TeO₂-V₂O₅-MoO₃ glasses. The Phy-X software was used to report the radiation shielding parameters for the present glasses. With an increase in TeO₂ and MoO₃ content, the samples' linear attenuation coefficient improves. However, at low energies, this change is more apparent. At low energy, the present samples have an effective atomic number (Z_eff) that is relatively high (in order of 16.17-24.48 at 0.347 MeV). In addition, the findings demonstrated that the density of the samples is a very critical factor in determining the half value layer (HVL). The minimal HVL for each sample can be found at 0.347 MeV and corresponds to 1.776, 1.519, 1.391, 1.210 and 1.167 cm for Te1 to Te5 respectively. However, the highest HVL of these glasses is recorded at 1.33 MeV, which corresponds to 3.773, 3.365, 3.218, 2.925 and 2.908 cm respectively. The tenth value layer results indicate that the thickness of the specimens needs to be increased in order to shield the photons that have a greater energy. Also, the TVL results demonstrated that the sample with the greatest TeO₂ and MoO₃ concentration has a higher capacity to attenuate photons.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2324-2331
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• 2024

The current study investigated Saudi Arabian oil fly ash impacts on Egyptian clay bricks' structural and radiation shielding properties. To produce the required bricks, crushed clay minerals from the Hafafit area were mixed with 0, 10, 20, 30, and 40 % wt.% Saudi Arabian oil fly ash and pressed at a pressure rate of 68.55 MPa. Identification of the minerals in the chosen clay was achieved via X-ray diffraction. Additionally, the material's morphology and chemical composition were determined through scanning electron microscope and energy-dispersive X-ray. The fabricated bricks' density was reduced by 36.3 % through increasing the concentration of fly ash from 0 to 40 wt%. Then, the fly ash addition's influence on the fabricated clay bricks' γ-ray shielding properties was investigated by Monte Carlo simulation, which found a reduction in the fabricated bricks' linear attenuation coefficient (LAC) by 41.2, 36.0, 33.8, and 33.8 % at the 0.059, 0.103, 0.662, and 1.252 MeV γ-ray energies, respectively. The LAC reduction caused an increase in the fabricated bricks' half-value thickness, transmission factor, and the equivalent thickness of the lead. Moreover, the thicker fabricated sample thicknesses were found to have high γ-ray shielding capacity and can thus be used in radiation shielding applications.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.774-783
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• 2004

The S wave velocity and Q$s^{-1}$ structure of the uppermost part of the soil in Nakdong Delta area have been obtained to determine the characteristics of the forementioned soil. The phase and attenuation coefficients of multichannel seismic records were inverted to obtain the S wave velocity and Q$s^{-1}$ structure of the soil. The inversion results have been compared with the borehole measurements of the area. The seismic signal of the nearest geophone from a seismic source was used as the source signal to obtain the attenuation coefficients. Amplitude ratios of the signal at each geophone to the source signal wave plotted as a function of distance for the frequency range between 10 Hz and 45 Hz. The slope of a linear regression line which fits amplitude ratio-distance relationship best for a given frequency was used as the attenuation coefficients for the frequency. The dispersion curve of Rayleigh waves and the attenuation coefficients were inverted to obtain the S-wave velocity and Q$s^{-1}$, respectively, in the uppermost 8 meter of soil layer. The borehole measurements of the area show that are two distinct layers; the upper 4 meter of silty-sand and the lower 4 meter of silty-clay. The inversion results indicate that the shear wave velocity of the upper layer is 80 m/sec and 40m/sec in the lower silty-clay layer. The spacial resolution of the shear wave velocity structure is very good down to a depth of 8 meter. The Q$s^{-1}$ in the upper silty-sand layer is 0.02 and increase to 0.03 in the lower silty-sand layer. The spacial resolution of quality factor is relatively good down to a depth of 5 meter, but very poor below the depth. In this study, the S-wave velocity is higher in the silty-clay and the Q$s^{-1}$ is smaller silty-sand than in the silty-clay. However, much more data should be analyzed and accumulated before making any generalization on the shear wave velocity and Q$s^{-1}$ of the sediments.

• The Journal of Korean Society for Radiation Therapy
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• v.15 no.1
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• pp.67-77
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• 2003

I. Purpose Uniform dose distribution of the whole body is essential factor for the total body irradiation(TBI). In order to achieved this goal, we used to compensation filter to compensate body contour irregularity and thickness differences. But we can not compensate components of body, namely lung or bone. The purpose of this study is evaluation of dose attenuation in bone tissue when TBI using diode detectors and TLD system. II. Materials and Methods The object of this study were 5 patients who undergo TBI at our hospital. Dosimetry system were diode detectors and TLD system. Treatment method was bilateral and delivered 10MV X-ray from linear accelerator. Measurement points were head, neck, pelvis, knees and ankles. TLD used two patients and diode detectors used three patients. III. Results Results are as followed. All measured dose value were normalized skin dose. TLD dosimetry : Measured skin dose of head, neck, pelvis, knees and ankles were $92.78{\pm}3.3,\;104.34{\pm}2.3,\;98.03{\pm}1.4,\;99.9{\pm}2.53,\;98.17{\pm}0.56$ respectably. Measured mid-depth dose of pelvis, knees and ankles were $86{\pm}1.82,\;93.24{\pm}2.53,\;91.50{\pm}2.84$ respectably. There were $6.67\%{\sim}11.65\%$ dose attenuation at mid-depth in pelvis, knees and ankles. Diode detector : Measured skin dose of head, neck, pelvis, knees and ankles were $95.23{\pm}1.18,\;98.33{\pm}0.6,\;93.5{\pm}1.5,\;87.3{\pm}1.5,\;86.90{\pm}1.16$ respectably. There were $4.53\%{\sim}12.6\%$ dose attenuation at mid-depth in pelvis, knees and ankles. IV. Conclusion We concluded that dose measurement with TLD or diode detector was inevitable when TBI treatment. Considered dose attenuation in bone tissue, We must have adequately deduction of compensator thickness that body portion involved bone tissue.

• International Journal of Computer Science & Network Security
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• v.23 no.10
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• pp.1-10
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• 2023

This paper proposes a method to extend Inter-Carrier Interference (ICI) canceling Orthogonal Frequency Division Multiplexing (OFDM) receivers for 5G mobile systems to spatial multiplexing 2×2 MIMO (Multiple Input Multiple Output) systems to support high-speed ground transportation services by linear motor cars traveling at 500 km/h. In Japan, linear-motor high-speed ground transportation service is scheduled to begin in 2027. To expand the coverage area of base stations, 5G mobile systems in high-speed moving trains will have multiple base station antennas transmitting the same downlink (DL) signal, forming an expanded cell size along the train rails. 5G terminals in a fast-moving train can cause the forward and backward antenna signals to be Doppler-shifted in opposite directions, so the receiver in the train may have trouble estimating the exact channel transfer function (CTF) for demodulation. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceller is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number n to receiver sub-carrier number l is generated. In case of n≠l, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 8 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, 2×2MIMO QPSK and 16QAM modulation schemes, BER (Bit Error Rate) improvement was observed when the number of taps in the multi-tap equalizer was set to 31 or more taps, at a moving speed of 500 km/h and in an 8-pass reverse doppler shift environment.

• Nuclear Engineering and Technology
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• v.55 no.1
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• pp.278-284
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• 2023

The synthetic B₂O₃-As₂O₃ glass ceramic are prepared to investigate the physical properties and the radiation shielding capabilities with the variation of concentration of the As₂O₃ with 10, 20, 30, and 40%, respectively. XRD analyses are performed on the fabricated glass-ceramic and depicted the improvement of crystallinity by adding As₂O₃. The radiation shielding properties are studied for the B₂O₃-As₂O₃ glass ceramic. The values of linear attenuation coefficient (LAC) are varied with the variation of incident photon gamma energy (23.1-103 keV). The LAC values enhanced from 12.19 cm^-1-37.75 cm^-1 by raising the As₂O₃ concentration from 10 to 40 mol% at low gamma energy (23.1 keV) for BAs10 and BAs40, respectively. Among the shielding parameters, the half-value layer, transmission factor, and radiation protection efficiency are estimated. Furthermore, the fabricated samples of glass ceramic have low manufacturing costs and good shielding features compared to the previous work. It can be concluded the B₂O₃-As₂O₃ glass ceramic is appropriate to apply in X-ray or low-energy gamma-ray shielding applications.