구조 지수 기반 비구형 입자 체적 분률 변화 예측

이정훈(Jeonghoon Lee) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.10

대기 중 초미세먼지는 대부분 육면체, 사슬 모양 또는 판형의 집합체 형상으로 매우 불규칙한 형태를 지니고 있다. 하지만, 미세먼지 측정기의 대부분은 이러한 불규칙한 형태를 고려하지 않고 단순히 구형 입자로 가정하여 농도를 산출한다. 본 연구에서는 집합체 입자의 체적 분률이나 수농도를 RDG(Rayleigh-Debye-Gans) 광산란 이론을 이용하여 추정할 때에 불확실성을 제공하는 구조 지수(structure factor)에 대하여 고찰하였다. 다양한 구조 지수 중에서 다음의 네 가지 구조 지수, (1) Dobbins-Megaridis 구조 지수, (2) Fisher-Burford 구조 지수, (3) 지수형 구조 지수 및 (4) 가우스 구조 지수에 대하여 상호 비교하였다. 프랙탈 차원이 1.5, 2.4인 경우에 대하여 지수형 구조 지수를 기준으로 Dobbins-Megaridis 구조지수는 가우스 구조 지수와 유사한 거동을 보였으며, Fisher-Burford 구조 지수는 지수형 구조 지수와 유사하였다. Particulate matter (PM) consists of irregularly shaped particles, such as hexagonal, chain-like aggregate and plate. However, most PM sensors assume that the particles are spherical. In this study, we investigated the structure factors that may create uncertainty in the estimation of the volume faction and number concentration of aggregate particles under the assumption of spherical particles by using the Rayleigh-Debye-Gans (RDG) theory. Four different structure factors, (1) Dobbins-Megaridis, (2) Fisher-Burford, (3) exponential and (4) Gaussian, were compared according to the fractal dimension (Df). For Df of 1.5 and 2.4, the Dobbins-Megaridis structure factor exhibited a behavior similar to the Gaussian structure factor, whereas the Fisher-Burford structure factor exhibited a behavior similar to the exponential structure factor.

Resonance Elastic Scattering and Interference Effects Treatments in Subgroup Method

Li, Yunzhao,He, Qingming,Cao, Liangzhi,Wu, Hongchun,Zu, Tiejun Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.2

Based on the resonance integral (RI) tables produced by the NJOY program, the conventional subgroup method usually ignores both the resonance elastic scattering and the resonance interference effects. In this paper, on one hand, to correct the resonance elastic scattering effect, RI tables are regenerated by using the Monte Carlo code, OpenMC, which employs the Doppler broadening rejection correction method for the resonance elastic scattering. On the other hand, a fast resonance interference factor method is proposed to efficiently handle the resonance interference effect. Encouraging conclusions have been indicated by the numerical results. (1) For a hot full power pressurized water reactor fuel pin-cell, an error of about +200 percent mille could be introduced by neglecting the resonance elastic scattering effect. By contrast, the approach employed in this paper can eliminate the error. (2) The fast resonance interference factor method possesses higher precision and higher efficiency than the conventional Bondarenko iteration method. Correspondingly, if the fast resonance interference factor method proposed in this paper is employed, the $k_{inf}$ can be improved by ~100 percent mille with a speedup of about 4.56.

Investigation of the Dependency of the Output Factor on the Field Size in Passive Scattering Proton Therapy at the National Cancer Center in Korea

김찬규,Ahn Sang Hee,Kim Kwang Hyeon,Kim Myeongsoo,Kim Tae Ho,Shin Dongho,Kim Haksoo,Lim Young Kyung,Jeong Jong Hwi,Lee Se Byeong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.5

The dependency of the output factor on the field size in the passive scattering proton therapy at the National Cancer Center (NCC) in Korea was investigated through a comparison of the measured output factors. The output factor of the fields of the representative beam options was measured using a Pinpoint chamber with standard circular blocks of less than 5 cm in diameter. The measured output factors for different field sizes show that the dependency of the output factor on the field size is not negligible even in the field for the 5 cm in diameter for long-range proton beams. In addition, the conflicting dependency in shallow fields indicates that the potential contribution of scattered protons should be considered in predicting and modelling of the output factors in small fields.

The Effect of Grid Ratio and Material of Anti-scatter Grid on the Scatter-to-primary Ratio and the Signal-to-noise Ratio Improvement Factor in Container Scanner X-ray Imaging

Lee, Jeonghee,Lim, Chang Hwy,Park, Jong-Won,Kim, Ik-Hyun,Moon, Myung Kook,Lim, Yong-Kon The Korean Association for Radiation Protection 2017 방사선방어학회지 Vol.42 No.4

Background: X-ray imaging detectors for the nondestructive cargo container inspection using MeV-energy X-rays should accurately portray the internal structure of the irradiated container. Internal and external factors can cause noise, affecting image quality, and scattered radiation is the greatest source of noise. To obtain a high-performance transmission image, the influence of scattered radiation must be minimized, and this can be accomplished through several methods. The scatter rejection method using an anti-scatter grid is the preferred method to reduce the impact of scattered radiation. In this paper, we present an evaluation the characteristics of the signal and noise according to physical and material changes in the anti-scatter grid of the imaging detector used in cargo container scanners. Materials and Methods: We evaluated the characteristics of the signal and noise according to changes in the grid ratio and the material of the anti-scatter grid in an X-ray image detector using MCNP6. The grid was composed of iron, lead, or tungsten, and the grid ratio was set to 2.5, 12.5, 25, or 37.5. X-ray spectrum sources for simulation were generated by 6- and 9-MeV electron impacts on the tungsten target using MCNP6. The object in the simulation was designed using metallic material of various thicknesses inside the steel container. Using the results of the computational simulation, we calculated the change in the scatter-to-primary ratio and the signal-to-noise ratio improvement factor according to the grid ratio and the grid material, respectively. Results and Discussion: Changing the grid ratios of the anti-scatter grid and the grid material decreased the scatter linearly, affecting the signal-to-noise ratio. Conclusion: The grid ratio and material of the anti-scatter grid affected the response characteristics of a container scanner using high-energy X-rays, but to a minimal extent; thus, it may not be practically effective to incorporate anti-scatter grids into container scanners.

X선 진단장치의 고압정류방식이 대조도 향상에 미치는 영향

이후민(Hoo-Min Lee),윤준(Joon Yoon),김현주(Hyun-Ju Kim) 대한방사선과학회(구 대한방사선기술학회) 2014 방사선기술과학 Vol.37 No.3

본 연구는 X선 진단장치의 고압정류방식이 그리드 성능을 측정하는 선택도(selectivity)와 대조도 향상능력 (contrast improvement ability : K factor)에 미치는 영향을 분석하고자 산란선 함유율을 측정하였다. 정류방식이 서로 다른 X선발생장치를 대상으로 각 장치의 관전압과, 관전류량을 측정하여 출력선량의 정확도를 측정 및 교정한 후 각 장치별 노출조건을 동일하게 설정하고 형광량계를 이용하여 아크릴을 투과한 X선의 산 란선 함유율을 측정하였다. Grid 미사용 시 피사체를 투과한 X선의 산란선 함유율 측정 결과는 단상정류방식장치에서 가장 낮은 함유율(34.158%)이 측정되었고, 인버터 정류방식(37.043%)과 삼상24피크 정류방식(37.447%)은 산란선 함유율이 증가하였다. 각 장치들의 산란선 함유율 차이는 최저 0.404%에서 최고 3.289%의 차이를 보였다. 8:1 Gird 사용 시 피사체를 투과한 X선의 산란선 함유율을 측정한 결과는 단상정류방식장치에서 가장 낮은 함유율(18.258%)로 측정되었고, 인버터정류방식(25.502%)과 삼상24피크정류방식에서 산란선 함유율 (24.217%)이 증가하였다. 그리드 선택도에 따라 단상정류방식과 정전압(인버터와 삼상24피크)정류방식에서 산란선함유율의 차이는 최저 1.285%에서 최고 7.244%의 차이를 보였다. 통계분석 결과 단상정류방식 및 정 전압정류방식에서 대조도 향상계수(K factor)에서도 유의한 차이를 보였다. 결론적으로 그리드 선택도와 대조도 향상계수는 정전압정류방식보다는 단상전파방식에서 모두 증가하여 그리드의 사용으로 선택도 향상과 대조도의 개선효과가 증가함을 알 수 있었다. The purpose of this study was to analyze the effect on the selectivity on of high-voltage rectification device that measured the performance of the grid, and the contrast improvement ability (K factor) by measuring the scattered radiation content of the transmitted X-rays. The scattered radiation generated when the X-ray flux comes from the diagnostic X-ray generator that passes through an object. Targeting four dif-ferent rectifications of X-ray generators, the mean value of the tube voltage and the tube current was measured in order to maximize the accuracy of the generating power dose within the same exposure condition. Using fluorescence meter, the content of the scattered rays that are transmitted through the acrylic was measured depending on the grid usage. When grid is not used, the content of the scattered rays was the lowest (34.158%) with the single-phase rectifier, was increased with the inverter rectifier (37.043%) and the three-phase 24-peak rectification method (37.447%). The difference of the scattered radiation content of each device was significant from the lowest 0.404% to the highest 3.289% while using 8:1 grid, the con-tent of the scattered ray was the lowest with the single content of the scattered ray was the lowest with the single-phase rectifier (18.258%), was increased with the rectifier (25.502%) and the 24-peaks rec-tification (24.217%). Furthermore, there was difference up to content 7.244% to the lowest content 1.285% within three-phase 24-peaks rectification, inverter rectifications, and single-phase rectifier depending on the selectivity of the grid. Drawn from the statistical analysis, there was a similar relationship between the contrast improvement factor and the K factor. As a result, the grid selectivity and the contrast were increased within the sin-gle-phase rectifier rather than the constant voltage rectifier.

Polarization Effects in Elastic Electron-Deuteron Scattering and Their Dependence on Modern NN Potentials

Eed M. Darwish,Mohammad Y. Husseiny 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.2

We report on theoretical estimates of the tensor deuteron polarization observables (T20, T21 and T22) and the beam-vector double polarization observables (Te10 and Te11) in elastic electron-deuteron scattering. This is made possible with the advent of recent polarization measurements at the Jefferson Laboratory and the BLAST detector at MIT-Bates with polarized electron beam and polarized deuteron target. The dependence of the results on the deuteron wave functions obtained from different modern high-precision nucleon-nucleon interactions is investigated. We found that the predicted polarization observables agree with one another and with the available experimental data. We report on theoretical estimates of the tensor deuteron polarization observables (T20, T21 and T22) and the beam-vector double polarization observables (Te10 and Te11) in elastic electron-deuteron scattering. This is made possible with the advent of recent polarization measurements at the Jefferson Laboratory and the BLAST detector at MIT-Bates with polarized electron beam and polarized deuteron target. The dependence of the results on the deuteron wave functions obtained from different modern high-precision nucleon-nucleon interactions is investigated. We found that the predicted polarization observables agree with one another and with the available experimental data.

A Novel Isoform of Met Receptor Tyrosine Kinase Blocks Hepatocyte Growth Factor/Met Signaling and Stimulates Skeletal Muscle Cell Differentiation

Park, Minseon,Lee, Bok-Soon,Jeon, Soung-Hoo,Nam, Hyun-Ja,Lee, Gwang,Kim, Chul-Ho,Cho, Hyeseong,Lee, Jae-Ho American Society for Biochemistry and Molecular Bi 2015 The Journal of biological chemistry Vol.290 No.3

<P>Hepatocyte growth factor (HGF) and its receptor, Met, regulate skeletal muscle differentiation. In the present study, we identified a novel alternatively spliced isoform of Met lacking exon 13 (designated Δ13Met), which is expressed mainly in human skeletal muscle. Alternative splicing yielded a truncated Met having extracellular domain only, suggesting an inhibitory role. Indeed, Δ13Met expression led to a decrease in HGF-induced tyrosine phosphorylation of Met and ERK phosphorylation, as well as cell proliferation and migration via sequestration of HGF. Interestingly, in human primary myoblasts undergoing differentiation, Δ13Met mRNA and protein levels were rapidly increased, concomitantly with a decrease in wild type Met mRNA and protein. Inhibition of Δ13Met with siRNA led to a decreased differentiation, whereas its overexpression potentiated differentiation of human primary myoblasts. Furthermore, in notexin-induced mouse injury model, exogenous Δ13Met expression enhanced regeneration of skeletal muscle, further confirming a stimulatory role of the isoform in muscle cell differentiation. In summary, we identified a novel alternatively spliced inhibitory isoform of Met that stimulates muscle cell differentiation, which confers a new means to control muscle differentiation and/or regeneration.</P>

TEM 관련 이론해설 (4): 방사선의 종류와 물질에 의한 산란

이확주,Lee, Hwack-Joo 한국현미경학회 2003 Applied microscopy Vol.33 No.4

In this review, the sources and the characteristics of X-rays and electrons and their interactions with matters were described in terms of the atomic scattering factors. The geometrical diffraction conditions were taken into account in terms of Ewald spheres in reciprocal lattice spaces. The effects of the finite size of sources and detectors on diffractions were also considered. 물질의 구조 특성파악에 많이 사용되는 X-선과 전자선에 대한 소스 원을 살펴보고 물질과의 반응을 atomic scattering factor의 항으로 설명하였다. 물질과의 회절을 역 격자 공간에서의 Ewald sphere로 설명하고 유한 크기의 소스 파장과 검출기의 효과도 함께 고려하였다.

캐리어 산란 메커니즘에 따른 열전반도체의 이론 전자수송 특성 변화

김상일,김현식 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.2

The widespread application of thermoelectric devices in cooling and waste heat recovery systems will be achieved when materials achieve high thermoelectric performance. However, improving thermoelectric performance is not straightforward because the Seebeck coefficient and electrical conductivity of the materials have opposite trends with varying carrier concentration. Here, we demonstrate that carrier scattering mechanism engineering can improve the power factor, which is the Seebeck coefficient squared multiplied by electrical conductivity, by significantly improving the electrical conductivity with a decreased Seebeck coefficient. The effect of engineering the carrier scattering mechanism was evaluated by comparing the band parameters (density-of-states effective mass, non-degenerate mobility) of Te-doped and Te, transition metal co-doped n-type Mg2Sb3 fitted via the single parabolic band model under different carrier scattering mechanisms. Previously, it was reported that co-doping transition metal with Te only changed the carrier scattering mechanism from ionized impurity scattering to mixed scattering between ionized impurities and acoustic phonons, compared to Te-doped samples. The approximately three times enhancement in the power factor of Te, transition metal co-doped samples reported in the literature have all been attributed to a change in the scattering mechanism. However, here it is demonstrated that Te, transition metal co-doping also increased the density-of-states effective mass. Here, the impact of the scattering mechanism change on the electric transport properties of n-type Mg2Sb3 without an effective mass increase was studied. Even without the effective mass increase, carrier scattering mechanism engineering improved the power factor, and its effect was maximized by appropriate carrier concentration tuning.

A Novel Approach to the Evaluation of the Interface Roughness Scattering Form Factor in Intersubband Transitions

Nguyen Thanh Tien,Pham Thi Bich Thao,Le Tuan 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.11

We propose a modification of the interface roughness (IFR) scattering form factor in intersubbandtransitions. We properly derived a formula for the form factor for IFR scattering in terms of theintegrals of the envelope wave functions. This new form factor has a more global natural than theold one (proposed by Ando) and may be suitable for a wide range of applications. In this paper,we calculate and compare the absorption linewidths by applying of the old form factor and thenew one. Different from previous calculations, for the same surface profile (, ), the interfaceroughness scattering absorption linewidth calculated with the new form factor is twice as great asthat calculated with the old one. Our numerical calculations may better explain the experimentalresults for the well-width dependence of the intersubband absorption linewidth.