• Journal of Radiation Protection and Research
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• 제42권3호
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• pp.154-157
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• 2017

Background: Shielding properties of compound or mixture is presented in terms of mass attenuation coefficients using Monte Carlo simulation. Mass attenuation coefficients of cement, gypsum and the mixture of gypsum and $PbCO_3$ has been investigated using monte carlo MCNPX. Materials and Methods: The mass attenuation coefficients of cement, gypsum and the mixture of gypsum and $PbCO_3$ were calculated for photon energies 365.5, 661.6, 1,173.2, and 1,332.5 keV energies. Results and Discussion: The simulated values of mass attenuation coefficients were compared avaialable experimental results, theoretical values by XCOM and found good comparability of the results. Conclusion: Standard simulation geometry used in the present investigation would be very useful for various types of sample for shielding and dosimetry applications.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.241-246
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• 2024

The study was carried out by numerical integration based on the diffraction properties and elemental composition. The elemental compositions of breast tissues in the literature were tested. The photon attenuation coefficients calculated using the recent elemental composition were found within 0.2-16% for adipose tissue and within 0.04-17% for glandular tissue with the experimental reference data. The attenuation coefficients of cancerous breast tissue calculated according to the elemental content previously measured in breast cancer patients were found within 0-17% with experimental data in the literature. The attenuation coefficients are of great interest to medical research. To calculate realistic attenuation coefficients, the characteristic coherent scatter, which is most intense at small angles, must be considered. For this reason, experimentally measured form factor data were reviewed, and the most compatible one with the theoretical form factor data produced in this study was used at low momentum transfer x (0 < x ≤ 8 nm^-1). The differential linear coherent scattering distributions were calculated for an energy value of 17.44 keV and compared with their experimental counterparts.

• 대한의용생체공학회:의공학회지
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• 제11권1호
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• pp.121-130
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• 1990

In this study, the coefficients of ultrasound attenuation for human liver were determined in 6 normal humans and in 38 patients with diffuse liver disease. The coefficients with linear frequency dependency as well as nonlinear frequency dependency were evaluated. Gaussian pulse propagating in a lossy medium suffers downshifting of a center frequency and decreasing in the bandwidth. Such changes in frequency domain spectrum were quantified in terms of changes in the attenuation coefficients with nonlinear dependency, which in turn improve clinical Implications of the coefficients. Statistical analysis shows that the attenuation coefficients evaluated with nonlinear dependency reflect an improved accuracy for the diffuse liver disease than those with linear dependency. The discriminant analysis also indicate the improved classification with nonlinear dependency(75%) than with linear dependency(61%).

• 대한의용생체공학회:의공학회지
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• 제8권1호
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• pp.41-48
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• 1987

In estimating the freguency-dependent attenuation coefficient, we analyzed the range-dependent ultrasonic beam and proposed the method of calculating the experimental equation of beam pattern in order to reduce the error on the influence of beam pattern. These experimental equations are divided into the spectral centroid and the spec ural standard deviation slope according to axial propagation length. These are repnesented by the first-order equation in the near field of the beam and the second- order eqLlatlon In the far field. In order to prove the validity of this method, the attenuation coefficients of the non-corrected ease and the corrected case are compared. Using the reflected signal from acryle plate, the attenuation coefficients were estimated by the spectral shift method ann the spectral difference method. The result shows attenuation coeffi talents after correction are better than attenuation coefficients before correction. And this method can be applied In vivo measurement.

• 대한전자공학회논문지
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• 제25권1호
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• pp.49-55
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• 1988

To provide a quantitative parameter of evaluating diagnosis of the liver diseases accurately, the ultrasonic attenuation coefficient was estimated from liver phantoms, 15 normal human livers and 30 liver disease patients. Two kind of phantoms(No.1: 1552m/s, No.2: 1562m/s) which have velocity (1560m/s) similar to that in human liver were constructed and their ultrasonic attenuation coefficients were determined. In this paper the spectral-shift approach and spectral-difference approach were used for estimating ultrasonic attenuation coefficient, \ulcornerdB/Cm.MHz). These two approaches were utilized to esitmate for 15 normal humans without any liver disease and 30 liver disease patients. The results indicate that the two types of phantoms produce the value of near the suggested value of 0.5 and the attenuation coefficients of hepatoma, normal liver, corrhosis, fatty liver and hepatitis show decreasing value in order named, suggesting that the present study can be of clinical value incorrelating the estimated attenuation coefficidents with the liver diseases.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1792-1797
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• 2020

The shielding characteristics of two concrete blocks, widely used in the building industry in Mexico have been determined. These characteristics include the mass interaction coefficients, the linear attenuation coefficients and the half-value layers. The energy-dispersed X-ray fluorescence shows that the percentage mass content of each atom in the sample, and the atomic volume of the constituent elements of a material, plays an important role in its shielding capabilities. The total linear attenuation coefficients and the half-value layers were analyzed for a set of photon energies related to X-rays for diagnosis and cancer treatment with linear accelerators. Our results show that the concrete blocks have similar photon attenuation coefficients than the Portland concrete and better features than gypsum.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.130-137
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• 2004

The ultrasonic attenuation coefficients were measured by interfacial crack length in the adhesive components of double-cantilever beam(DCB). The energy release rate, G, was obtained by the experimental measurement of compliance. The numerical analysis by the boundary element method(BEM) and Ripling's equation was investigated. The experimental results represent that the relation between interfacial crack length for the ultrasonic attenuation coefficient and energy release rate is increased proportionally. A measurement method of the interfacial crack length by the ultrasonic attenuation coefficient was proposed and discussed.

• 한국해양학회지
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• 제25권1호
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• pp.26-35
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• 1990

한반도 주변 4개 해혁(포항, 부산, 여수, 군산)의 해저 표층축적물에서 얻은 음향 자료로부터 음속과 음파감쇠를 구하여 물성과의 상관성을 검토하고, 기체함량을 추정 함으로써 음파의 기계적 원인을 분석하였다. 음속 및 음파감쇠의 범위는 각각 1470∼ 1616 m/sec 및 0.0565∼0.6604 dB/kHz-m로서 퇴적물의 유형에 밀접하게 관련된다. 음 파는 coarse silt에서 최대이며 표층퇴적물내 기체 함량의 추정값은 8 ppm 이하로서 퇴적물의 입자가 작을수록 증가한다. Find sand보다 입자가 큰 퇴적물에서는 마찰손실 이 절대적인 음파감쇠의 요인으로 작용하며, 점성손실은 무시할 수 있을 뿐만 아니라 퇴적물의 물성에 따라 변하지 않는다. Coarse silt에서 음파감쇠가 최대인 것은 마찰 손실 뿐만 아니라 silt 입자 차이에 존재하는 더 작은 입자들 간의 결합력이 동시에 작용하기 때문이며 fine 및 medium silt를 경계로 입자가 작아짐에 따라 입자간 결합 력이 주된 감쇠 요인으로 작용한다.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.944-949
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• 2018

The mass attenuation coefficients (${\mu}/{\rho}$) of food waste samples (pomegranate peel, acorn cap, lemon peel, mandarin peel, pumpkin peel, grape peel, orange peel, pineapple peel, acorn peel and grape stalk) have been measured employing a Si(Li) detector at 13.92, 17.75, 20.78, 26.34 and 59.54 keV. Also, the theoretical values of the mass attenuation coefficients have been evaluated utilizing mixture rule from WinXCOM program. The results showed that the lemon peel has the highest values of ${\mu}/{\rho}$ among the selected samples. From the obtained mass attenuation coefficients, we determined some absorption parameters such as effective atomic number ($Z_{eff}$), electron density ($N_E$) and molar extinction coefficient (${\varepsilon}$). It was found that the $Z_{eff}$ values of all food wastes lie within the range of 4.034-7.595, whereas the $N_E$ of the studied food wastes was found to be in the range of $0.301-1.720{\times}10^{25}$ (electrons/g) for present energy region.

• 대한핵의학회지
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• 제39권3호
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• pp.182-190
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• 2005

목적: CT기반 감쇠보정 영상의 표준섭취계수(Standard Uptake Value:SUV)가 $^{137}Cs$ 기반 감쇠보정 영상의 SUV보다 높다. 이 연구에서는 이러한 오차가 생기는 원인을 밝히고자 감쇠계수가 정확하게 변환되었는지 여부를 관심영역 분석을 통하여 평가하였다. 대상 및 방법: Philips GEMINI PET/CT는 X-ray CT (평균 40 keV) 혹은 $^{137}Cs$ (662 keV) 투과영상을 감쇠보정에 이용하는데 GEMINI PET/CT에서 사용하는 각각 선원의 에너지는 511 keV에서 얻은 감쇠계수와 틀리기 때문에 스캐너 내부에 장착된 감쇠계수 변환 알고리즘을 이용하여 511 keV에 해당하는 감쇠계수 값으로 변환된 감쇠지도를 사용하므로 감쇠계수의 변환이 정확하게 이루어졌는지 평가하는 것이 중요하다. 각각의 실험과정은 다음과 같다. 먼저 시스템 성능평가 팬텀 CT 투과 영상을 사용하여 Hounsfield units (HU)값을 측정하였다. 다음으로 NEMA 타원형 ECT 팬텀의 CT, $^{137}Cs$ 투과영상을 얻어 $^{68}Ge$ 투과선원을 장착한 Siemens ECAT EXACT 47 PET 스캐너에서 얻은 팬텀 투과 영상과 비교하여 감쇠계수가 511 keV에 해당하는 감쇠계수로 잘 변환되었는지 측정하였고 Gammex 467 electron density CT 팬텀의 CT, $^{137}Cs$ 투과영상에서 관심영역 분석을 하여 다양한 전자밀도 값에 대한 감쇠계수 변환의 정확성을 평가하였다. 또, 재구성한 영상에 미치는 영향을 평가하기 위하여 정상 및 병적 조직에서 CT, $^{137}Cs$ 기반 감쇠계수와 표준섭취계수를 비교하였다. 결과: CT에서 측정한 HU는 신뢰할 수 있는 값임을 확인하였으나 전자밀도와 원자번호가 큰 영역에서 CT 기반 감쇠계수에 오차가 있었는데 NEMA 타원형 ECT 팬텀 실험결과에 의하면 뼈 영역에서 오차는 11%이었다. 임상데이터에서도 마찬가지로 CT를 이용하여 얻은 감쇠계수가 $^{137}Cs$을 이용하여 얻은 감쇠계수보다 낮았고 전자밀도와 원자번호가 큰 영역에서 오차가 컸다. 그러나, 표준섭취계수는 $^{137}Cs$를 사용하여 감쇠보정을 한 영상의 값이 CT를 이용하여 감쇠보정을 한 값보다 오히려 낮았고 표준섭취계수의 백분율 차이는 $6.6{\sim}52.7%$이었다. 결론: CT의 HU가 정확함에도 불구하고 뼈 영역에서 CT 투과영상을 기반으로 한 감쇠계수의 변환이 부정확하고 CT 및 $^{137}Cs$ 투과영상을 기반으로 얻은 표준 섭취계수에 차이가 있으므로 이에 관한 추가적인 연구가 필요할 것으로 생각한다.