• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1484-1489
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• 2005

An inhomogeneous and anisotropic rock has different properties at different location. Thus, this refers to any of the properties which we may be measuring. There are two concepts of rock mass, namely, CHILE(Continuous, Homogeneous, Isotropic, Linear Elastic) material and DIANE(Discontinuous, Inhomogeneous, Anisotropic, Non-linear Elastic) rock. The former is essentially the properties of intact rock, the latter is essentially the properties governed by the structure of rock. In geotechnical aspect, the most important parameter is strength of rock or rock mass. In particular, characteristics of strength of rock mass depend upon the orientation of discontinuities And this orientation of discontinuities has different properties at different direction of excavation. Therefore, it needs for characterization of different properties of discontinuity orientation against different direction of excavation.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.69-73
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• 2003

In this paper, a synthesis method for the desired scattering pattern is presented when illuminating by TE-polarized and TM-polarized plane waves to arbitrary dielectric material. It is considered that the one-dimensional dielectric media are inhomogeneously distributed with continuously varying dielectric constants. Accordingly the desired patterns and the corresponding source distributions are inversely transformed by the proposed algorithm which are based on the one-dimensional inverse scattering problem. Some bandstop spatial filter are illustrated for applications.

• 한국정밀공학회지
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• 제20권8호
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• pp.175-184
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• 2003

A method of the shape design sensitivity analysis based on the boundary integral equation formulation is presented for two-dimensional inhomogeneous thermal conducting solids with multiple domains. Shape variation of the external and interface boundary is considered. A sensitivity formula of a general performance functional is derived by taking the material derivative to the boundary integral identity and by introducing an adjoint system. In numerical analysis, state variables of the primal and adjoint systems are solved by the boundary element method using quadratic elements. Two numerical examples of a compound cylinder and a thermal diffuser are taken to show implementation of the shape design sensitivity analysis. Accuracy of the present method is verified by comparing analyzed sensitivities with those by the finite difference. As application to the shape optimization, an optimal shape of the thermal diffuser is found by incorporating the sensitivity analysis algorithm in an optimization program.

• Advances in nano research
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• 제12권6호
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• pp.617-627
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• 2022

In the current study, the nonlinear impact of the Von-Kármán theory on the vibrational response of nonhomogeneous structures of functionally graded (FG) nano-scale tubes is investigated according to the nonlocal theory of strain gradient theory as well as high-order Reddy beam theory. The inhomogeneous distributions of temperature-dependent material consist of ceramic and metal phases in the radial direction of the tube structure, in which the thermal stresses are applied due to the temperature change in the thickness of the pipe structure. The general motion equations are derived based on the Hamilton principle, and eventually, the acquired equations are solved and modeled by the Meshless approach as well as a computer simulation via intelligent mathematical methodology. The attained results are helpful to dissect the stability of the MEMS and NEMS.

• Nuclear Engineering and Technology
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• 제54권9호
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• pp.3390-3397
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• 2022

Among the different techniques available, nuclear methods, including gamma-gamma logging tools, are of special importance. Though the real environment which surrounds the drilled borehole is a complex fractured medium which the fluid can flow through the porosities, simulation studies generally use the traditional model of a homogeneous mixture of formation and the liquid. Considering a previously published study, which shows that modeling of fluid flow in fractured reservoirs and simulating the formation as an inhomogeneous fractured medium leads to different results compared with those of homogeneous mixture, here we study the effect of the presence of drilling fluid (mudcake) on the response of the detectors in both the models. To study this effect, a typical gamma-gamma logging tool was modeled by using the MCNPX Monte Carlo code. The results show that the responses of the detectors in the mixture model in the presence of various thicknesses of mudcake are sensitive to the density of the formation material. However, this effect is not notable in the inhomogeneous fractured medium. These results emphasize the importance of the model employed for simulation of the medium in gamma-gamma well-logging.

• 대한방사선치료학회지
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• 제25권2호
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• pp.137-143
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• 2013

목 적: 불균질부를 포함하고 있는 치료부위의 치료계획 시 불균질 경계면에서의 TPS상 선량분포와 phantom을 이용하여 측정된 실제 선량분포를 비교하여 그 차이를 알아보고자 한다. 대상 및 방법: 4 cm 두께의 solid water phantom 사이에 폐와 유사한 밀도를 가진 8 cm 두께의 cork (density: 0.23 $g/cm^2$)를 위치시켜 phantom을 제작하여 CT 영상을 획득하였으며, 본원에서 사용하고 있는 Pinnacle 치료계획 시스템의 Collapsed-cone(CC) convolution 선량계산 알고리즘을 이용하여 6/15 MV 광자선으로 치료 계획된 선량분포와 실제 phantom에 EBT2 필름을 삽입해 측정한 선량을 비교 평가하였다. 또한 실제 폐암 환자와 유사한 치료계획을 비교하기 위해 Phantom 내부에 치료하고자 하는 종양부위(target volume)로 가정한 파라핀($3{\times}3{\times}3$ cm)을 Location "A" (일반조직과 떨어져있는 가상의 종양: 섬모델)와 Location "B" (일반조직과 붙어있는 가상의 종양: 반도모델)에 삽입하여 CT scan 후 치료계획을 시행하였다. 선량계획과 동일한 조건으로 Phantom을 set-up 후 Phantom의 paraffin target volume 경계면 A (Ant방향), B (Rt방향), C (Post 방향) point에 필름을 삽입하고 방사선을 조사하여 측정된 선량을 TPS선량과 비교평가 하였다. 결 과: 불균질 phantom을 이용한 계획선량과 측정선량과의 차이는 solid water와 cork 경계면을 제외한 부분에서 선량차이가 크지 않았지만 밀도가 급격히 변화하는 첫 번째 구간과 두 번째 구간에서 -5.4%~-12.6%의 선량감소를 보였다. 또한 paraffin target을 삽입한 실험에서는 Location "A"의 경우 실제 측정선량이 A, B, C point에서 각각 -2.5~-4.7%, -2.3~-2.8%, -4.5~-8.8%의 낮은 선량을 나타냈으며, Location "B"의 경우에도 A, B, C point에서 각각 0.08~5.27%, -3.17~-4.74%, -7.86~-11.56%의 선량 차이를 나타내었다. 결 론: 이번 연구의 결과 불균질부 내에서의 치료계획 시스템의 계획된 선량과 실제 측정된 선량에 오차의 가능성이 확인되었다. 급속도로 발전하고 있는 방사선 치료기술과 그만큼 정밀함을 요하는 치료계획 시 이러한 가능성에 대해 인지하고 선량검증에 대한 여러 방법들을 연구하고 개발하는 것이 치료의 발전과 필수적으로 동반되어야 할 것이며 본원에서도 이번 연구를 통해 치료계획 시 발생할 수 있는 변수에 대해서 더 주의 깊게 판단하고 적용할 수 있을 것으로 사료된다.

• 한국산업보건학회지
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• 제15권1호
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• pp.1-7
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• 2005

Although the Fourier Transform Infra-Red spectrophotometric Direct on Filter(FTIR-DOF) method is a useful analytical technique for quantifying quartz content in respirable dust samples, a number of analytical problems must be taken into consideration such as, to name only a few, inhomogeneous deposition of particles, level of environmental humidity, uneven surface of the filter, and interfering minerals in the sample. This study was designed to select the most suitable wavelength and proper filter material for the method, and to investigate effects of humidity and inhomogeneous deposition of particles on the filter. Samples of respirable dust, created in a dust chamber containing standard material of quartz, were collected using a cyclone equipped with a 25mm filter as a collection medium. The results were as follows; 1. Among seven (7) commercially available filters tested for the FTIR-DOF method, the DM 800 filter showed the best analytical performance having the lowest background absorbance bands and no overlapping peaks at 799, 779, and $695cm^{-1}$. 2. The variations of absorbance due to humidity ranged from 1.0% to 3.3% for $799cm^{-1}$, 1.0% to 3.3% for $779cm^{-1}$, and 8.9%~20.9% for $695cm^{-1}$ peaks, respectively. The $699cm^{-1}$ peak was proved to be most vulnerble to environmental humidity for quantitative analysis of quartz. 3. As for effects of inhomogeneous deposition of samples, the highest variation of absorbance of 10.9% ($13.5{\mu}g$) was observed when using the 695cm-1. The variations of absorbance from the other two peaks, 799 and $779cm^{-1}$, ranged from 1.2 to 3.2%, and 1.4 to 4.1%, respectively. Therefore, the $799cm^{-1}$ peak was considered to be most reliable for quantitative analysis of quartz. The results of this study suggest that, for quantitative analysis of quartz in the respirable dust samples, use of the $799cm^{-1}$ peak can minimize the influence of environmental humidity and inhomogeneous deposition of particles on the filter. The FTIR-DOF method, if adopted for routine analysis of quartz in the respirable dust samples, could save sample preparation time and efforts substantially and also could increase analytical throughputs. Since use of the $799cm^{-1}$ peak is prone to be affected by interferences in the sample, further research on minimizing the effects is needed.

• 대한방사선기술학회지:방사선기술과학
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• 제25권1호
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• pp.63-71
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• 2002

The aim of this study Is to develop a simple and fast method which computes in-vivo doses from transmission doses measured doting patient treatment using an ionization chamber. Energy fluence and the dose that reach the chamber positioned behind the patient is modified by three factors: patient attenuation, inverse square attenuation. and scattering. We adopted a straightforward empirical approach using a phantom transmission factor (PTF) which accounts for the contribution from all three factors. It was done as follows. First of all, the phantom transmission factor was measured as a simple ratio of the chamber reading measured with and without a homogeneous phantom in the radiation beam according to various field sizes($r_p$), phantom to chamber distance($d_g$) and phantom thickness($T_p$). Secondly, we used the concept of effective field to the cases with inhomogeneous phantom (patients) and irregular fields. The effective field size is calculated by finding the field size that produces the same value of PTF to that for the irregular field and/or inhomogeneous phantom. The hypothesis is that the presence of inhomogeneity and irregular field can be accommodated to a certain extent by altering the field size. Thirdly, the center dose at the prescription depth can be computed using the new TMR($r_{p,eff}$) and Sp($r_{p,eff}$) from the effective field size. After that, when TMR(d, $r_{p,eff}$) and SP($r_{p,eff}$) are acquired. the tumor dose is as follows. $$D_{center}=D_t/PTF(d_g,\;T_p){\times}(\frac{SCD}{SAD})^2{\times}BSF(r_o){\times}S_p(r_{p,eff}){\times}TMR(d,\;r_{p,eff})$$ To make certain the accuracy of this method, we checked the accuracy for the following four cases; in cases of regular or irregular field size, inhomogeneous material included, any errors made and clinical situation. The errors were within 2.3% for regular field size, 3.0% irregular field size, 2.4% when inhomogeneous material was included in the phantom, 3.8% for 6 MV when the error was made purposely, 4.7% for 10 MV and 1.8% for the measurement of a patient in clinic. It is considered that this methode can make the quality control for dose at the time of radiation therapy because it is non-invasive that makes possible to measure the doses whenever a patient is given a therapy as well as eliminates the problem for entrance or exit dose measurement.

• 대한방사선치료학회지
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• 제18권2호
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• pp.75-80
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• 2006

목 적: 방사선치료에 있어 종양조직이나 정상조직의 정확한 선량계산은 치료의 성패를 좌우하는 가장 큰 요인이다. 이로 인해 방사선치료계획은 컴퓨터 단층 영상의 재구성을 통한 불균질 조직에 선흡수계수를 밀도로 변환하여 CT 번호에 의한 선량 보정이 유효하게 이루어지고 있다. 대상 및 방법: 이에 본 연구는 불균질 조직등가 팬톰을 제작하여 현재 사용 중인 방사선 치료 계획시스템을 이용한 CT 번호의 측정과 질량밀도를 계산하여 물을 기준으로 상대값을 구하였다. 또한 실제 방사선 조사 시 측정된 선량(nC)과 CT영상을 이용한 치료계획 시 선량(PDD)을 상대적으로 비교함으로써 실제 CT 번호를 이용한 불균질 조직의 보정에 대한 유용성과 정확성을 평가하고자 한다. 결 과: 측정결과 CT 번호를 이용하여 계산된 조직등가물질의 질량밀도와 실제 질량밀도는 $0.005{\sim}0.069g/cm^3$의 차이를 보였으며, 방사선 치료계획 시 심부선량(PDD)과 방사선 치료 장치로 조사하여 측정된 선량의 상대오차는 $-2.8{\sim}+1.06%$로 3% 이내의 유효범위이내의 결과를 얻었다. 결 론: 본 실험은 CT 영상을 이용한 불균질 조직의 보정에 대한 유용성을 확인할 수 있었고, 방사선 치료 계획 장치의 정도 관리(Quality Assurance; QA)의 기본 틀을 제공할 수 있을 것으로 사료된다.

• Advances in nano research
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• 제7권1호
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• pp.51-61
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• 2019

This paper develops a four-unknown refined plate theory and the Galerkin method to investigate the size-dependent stability behavior of functionally graded material (FGM) under the thermal environment and the FGM having temperature-dependent material properties. In the current study two scale coefficients are considered to examine buckling behavior much accurately. Reuss micromechanical scheme is utilized to estimate the material properties of inhomogeneous nano-size plates. Governing differential equations, classical and non-classical boundary conditions are obtained by utilizing Hamiltonian principles. The results showed the high importance of considering temperature-dependent material properties for buckling analysis. Different influencing parametric on the buckling is studied which may help in design guidelines of such complex structures.