• Journal of Biomedical Engineering Research
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• v.8 no.1
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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.

• International Journal of Automotive Technology
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• v.5 no.4
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• pp.303-309
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• 2004

In this paper, an interfacial crack length has been detected by using the ultrasonic attenuation coefficient on the adhesively bonded double-cantilever beam (DCB) joints. The correlations between energy release rates which were investigated by experimental measurement, the boundary element method (BEM) and Ripling's equation are compared with each other. The experimental results show that the interfacial crack length for the ultrasonic attenuation coefficient and energy release rate increases proportionally. From the experimental results, we propose a method to detect the interfacial crack length by using the ultrasonic attenuation coefficient and discuss it.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.340-345
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• 2003

In this paper, the ultrasonic attenuation coefficient was measured by variation of crack length for double-cantilever beam(DCB) specimen. The energy release rate, G, was obtained by the experimental measurement of compliance. The experimental results represents that the relation between crack length for the ultrasonic attenuation coefficient and energy release rate is increased proportionally. From the results of experiments, the measurement method of crack length by the ultrasonic attenuation coefficient was proposed and discussed.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1109-1114
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• 2003

The initial crack often occurs on the bonded interface and it is the general cause of the interface fracture. It is very significant to establish the measurement method of interfacial crack by applying the ultrasonic technology into the interface of bonded dissimilar materials. In this paper, the interfacial crack length was measured by ultrasonic attenuation coefficient in the Al/Epoxy bonded dissimilar materials of double-cantilever beam(DCB). The energy release rate, G, was obtained by the experimental and Ripling's equation measurement of compliance. The experimental results represent that the relation between interfacial crack length for the ultrasonic attenuation coefficient and energy release rate is increased proportionally. From the experimental results, a measurement method of the interfacial crack length by the ultrasonic attenuation coefficient was proposed and discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.386-393
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• 2004

In this paper, the ultrasonic attenuation coefficient was measured by variation of crack length for double-cantilever beam(DCB) specimen. The energy release rate, G, was obtained by the experimental measurement of compliance. The experimental results represents that the crack length for the ultrasonic attenuation coefficient and energy release rate is increases proportionally From the experimental results, we proposed a detecting method of the crack length by the ultrasonic attenuation coefficient and discussed it.

• Journal of the Korean Society of Radiology
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• v.10 no.8
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• pp.591-596
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• 2016

The purpose of this study is to determine the equivalent energy of a 6MV X-ray beam in the experiment. The half-value layer (HVL) of lead for the 6 MV X-ray beam was measured using an ionization chamber. The linear attenuation coefficients were calculated with HVL. And, the mass attenuation coefficient was obtained by dividing the linear attenuation coefficient by the density of lead. The equivalent energy of mass attenuation coefficient was determined using the photon energy versus mass attenuation coefficient data of lead given by National Institute of Standards and Technology (NIST). In conclusion, the equivalent energy of the 6 MV X-ray beam was determined to be 1.61 MeV. This equivalent energy was determined to be about 30% lower than reported by Reft. The reason is presumed to be due to the presence of an air cavity between the lead attenuators.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.41-41
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• 2003

Purpose: Even if the wedge filter is widely used for the radiation therapy to modify the photon beam intensity, the wedged photon beam dose calculation is not so easy. Radiation therapy planning systems (RTPS) have been used the empirical or semi-analytical methods such as attenuation method using wedge filter parameters or wedge filter factor obtained from measurement. However, these methods can cause serious error in penumbra region as well as in edge region. In this study, we propose the dose calculation algorithm for wedged field to minimize the error especially in the outer beam region. Materials and Method: Modified intensity by wedge filter was calculated using tissue-maximum ratio (TMR) and scatter-maximum ratio (SMR) of wedged field. Profiles of wedged and non-wedged direction was also used. The result of new dose calculation was compared with measurement and the result from attenuation method. Results: Proposed algorithm showed the good agreement with measurement in the high dose-gradient region as well as in the inner beam region. The error was decreased comparing to attenuation method. Conclusion: Although necessary beam data for the RTPS commissioning was increased, new algorithm would guarantee the improved dose calculation accuracy for wedged field. In future, this algorithm could be adopted in RTPS.

• Journal of the Korean Society of Radiology
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• v.9 no.6
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• pp.375-379
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• 2015

The purpose of this study is to determine the effective energy of a polyenegetic X-ray beam. The half value layer(HVL) of aluminum for 80 kVp X-ray beam was measured by using optically stimulated luminescent nanoDot dosimeters(OSLnDs). The linear attenuation coefficient(${\mu}$) was calculated using the measured HVL. And the mass attenuation coefficient(${\mu}/{\rho}$) was obtained by dividing the linear attenuation coefficient by the density(${\rho}$) of aluminum. The effective energy($E_{eff}$) of the obtained mass attenuation coefficient was determined using data of the X-ray mass attenuation coefficients for photon energies of aluminum given by National Institute of Standards and Technology(NIST). As a result, the HVL value is 2.262 mmAl. The ${\mu}$ value is $3.06cm^{-1}$. The ${\mu}/{\rho}$ value is $1.114cm^2/g$. And the $E_{eff}$ value was determined at 29.79 keV.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.991-996
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• 2011

This study was carried out vibration attenuation of vibration absorber attached to the cantilever beam structure. Modern tank guns are stabilized to allow fire on the move while traversing uneven terrain. However, as the length of the barrel is extended, to meet required muzzle exit velocities, the terrain induced vibrations lead to increased muzzle pointing errors. Thus, reducing these vibrations should lead to increased accuracy. The vibration absorber includes a compliant energy storage device, such as a spring, and a mass secured to the energy storage device. In this study, it accomplished a research in about gun barrel vibration attenuation using tuned mass damper. The barrel was hung from a bungee cord for free-free condition. It accomplished a vibration experiment for verified attenuation efficiency.