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A Closed-Form Formulation for the build-up Factor and Absorbed Energy for Photons and Electrons in the Compton Energy Range in Cartesian Geometry

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World Journal of Nuclear Science and Technology 2012年第1期2卷 23-28页

作者： Volnei Borges Julio Cesar Fernandes Bardo Ernest Bodmann Marco Túllio Vilhena Bárbara Rodriguez 不详

In this work, we report on a closed-form formulation for the build-up factor and absorbed energy, in one and two di- mensional Cartesian geometry for photons and electrons, in the Compton energy range. For the one-dimensional case we use the LTSN method, assuming the Klein-Nishina scattering kernel for the determination of the angular radiation intensity for photons. We apply the two-dimensional LTSN nodal solution for the averaged angular radiation evaluation for the two-dimensional case, using the Klein-Nishina kernel for photons and the Compton kernel for electrons. From the angular radiation intensity we construct a closed-form solution for the build-up factor and evaluate the absorbed energy. We present numerical simulations and comparisons against results from the literature.

关键词： build-up Factor Compton Energy Cartesian Geometry Fokker-Plank Equation

On the build-up Factor from the Multi-Group Neutron Diffusion Equation with Cylindrical Symmetry

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World Journal of Nuclear Science and Technology 2013年第1期3卷 1-5页

作者： Julio Cesar Lombaldo Fernandes Marco Túllio Vilhena Bardo Ernst Bodmann Volnei Borges DepartmentofAppliedMath Universidade Federal do Rio Grande do Sul Porto Alegre Brazil

We consider the time dependent neutron diffusion equation for one energy group in cylinder coordinates, assuming translational symmetry along the cylinder axis. This problem for a specific energy group is solved analytically applying the Hankel transform in the radial coordinate r. Our special interest rests in the build-up factor for a time dependent linear neutron source aligned with the cylinder axis, which in the limit of zero decay constant reproduces also the static case. The new approach to solve the diffusion equation by integral transform technique is presented and results for several parameter sets and truncation in the solution for the flux and build-up factor are shown and found to be compatible to those of literature [1,2].

关键词： build-up Factor Cylindrical Geometry Hankel Transform

Evaluation for the paleodose in thermoluminescence dating of porcelain

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Science China(Technological Sciences) 2008年第3期51卷 260-267页

作者： WANG WeiDa Research Laboratory for Conservation & Archaeology, Shanghai Museum, Shanghai 200050, China Research Laboratory for Conservation & Archaeology Shanghai Museum Shanghai 200050 China

Sources, components and calibration of paleodose were studied for proper evalua- tion of the paleodose of porcelain in thermoluminescence (TL) dating. In the TL dating of porcelain using the pre-dose technique, the β dose from the internal natural radiation in the body of porcelain is the first, the environmental dose the second, and the α dose negligible. Sample thickness of 0.2―0.5 mm was used in the paleodose calibration. For a porcelain sample of such thickness, the distribu- tion of β dose inside the sample was nonlinear when the sample (aluminium re- places porcelain in this experiment) was irradiated by a laboratory 90Sr-90Y β source. Therefore, the β dose used was only an average value. A distribution curve of β dose and the calculation of average β dose in the sample were obtained, according to the build-up and attenuation effects of β dose in the sample. The results showed that a sample thickness of 200 μm resulted in an average dose increment of about 4% compared to the surface whereas for a sample with a thickness of 400 μm, the average dose reduced by the same percentage, and that for a sample of 300 μm in thickness the average dose is equal to surface dose approximately. The average β dose in samples with various thickness can be obtained by the provided equations.

关键词： thermoluminescence dating porcelain paleodose build-up attenuation average beta dose

RCC与不同FR-4基板积层结构的Tg考察

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印制电路信息 2007年第12期15卷 32-34页

作者：佘乃东刘东亮温东华广东生益科技股份有限公司广东东莞523039

文章采用常规RC(C涂树脂铜箔)与不同型号、不同厚度的FR-4基板一次积层制作了不同组成的积层板结构,并对不同型号、不同厚度的基板及其与RCC积层前后的Tg测试分析,结果表明具有不同Tg水平的基板与该RCC积层之后的总Tg几乎不受RCC的Tg影... 详细信息

文章采用常规RC(C涂树脂铜箔)与不同型号、不同厚度的FR-4基板一次积层制作了不同组成的积层板结构,并对不同型号、不同厚度的基板及其与RCC积层前后的Tg测试分析,结果表明具有不同Tg水平的基板与该RCC积层之后的总Tg几乎不受RCC的Tg影响,仍然为芯板的Tg。

关键词： RCC FR-4 build-up Tg

Clinical and Dosimetric Implications of Air Gaps between Bolus and Skin Surface during Radiation Therapy

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Journal of Cancer Therapy 2013年第7期4卷 1251-1255页

作者： Yousaf Khan J. Eduardo Villarreal-Barajas Mona Udowicz Richie Sinha Wazir Muhammad Ahmed N. Abbasi Amjad Hussain Department of Radiation Oncology Tom Baker Cancer Centre Calgary Canada Institute of Nuclear Medicine Oncology and Radiotherapy Abbottabad Pakistan Radiation Oncology Department of Oncology Aga Khan University Hospital Karachi Paki- stan

Purpose: The main objective of the study was to evaluate the effect of air gaps of 0 - 5.0 cm between bolus and skin for 1.0 cm Superflab bolus on surface dose (DSurf) and depth of maximum dose (dmax) in solid water and Rando? phantoms. Methods: In this work, the effects of bolus to surface distance on DSurf and variation in dmax were analyzed in a solid water phantom and in an anthropomorphic Rando? phantom for different field sizes, using Gafchromic? EBT films and farmer chamber. Results: For field sizes of 5 × 5 cm2 the DSurf is significantly affected by increasing air gaps greater than 5 mm. For field sizes larger than 10 × 10 cm2, DSurf is nearly the same for air gaps of 0 - 5.0 cm. For small fields and 6 MV photon beam, dmax increases with increasing air gap, while for 10 MV beam and smaller field sizes (i.e. 5 × 5 and 10 × 10 cm2) the dmax first decreases and then increases with the air gaps. For both 3DCRT and IMRT plans on Rando?, DSurf reduction is more prominent with increasing air gaps. Conclusion: For field sizes larger than 10 × 10 cm2 DSurf is largely unaffected by air gaps. However, smaller air gap results in shallower dmax for both 6 MV and 10 MV photon beams at all fields sizes. Special consideration should be taken to reduce air gaps between bolus and skin for field sizes smaller than 10 × 10 cm2 or when surface contour variations are greater or when the bolus covers small area and at the border of the field.

关键词： Bolus Distance Skin Dose IMRT Dose build-up

Comparative Study on the Surface Dose of Some Bolus Materials

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2015年第4期4卷 348-352页

作者： Iosif Malaescu Catalin Nicolae Marin Marius Spunei Department of Physics West University of Timisoara Timisoara Romania High Energy Radiotherapy Center Timisoara Romania

In order to investigate the possibility of using different materials as bolus in radiotherapy, five samples denoted by S2 - S6 were prepared and analyzed by comparison with one available commercial bolus denoted by S1. Sample S1 was a thermoplastic material from Qfix;S2 was a moldable silicon rubber (RTV-530 from Prochima);S3 and S4 were obtained by adding micrometric particles of Al and Cu respectively (at the same mass concentration of 5.5%);S5 was another moldable silicon rubber (GSP400 from Prochima) and S6 was a mixture of GSP400 and micrometric particles of Cu (at the mass concentration of 5.5%). The measurements of normalized transmitted dose as a function of sample thickness were performed for all samples (S1 - S6) at two values of electron beam energy (6 and 9 MeV) produced by a linear accelerator VARIAN 2100SC. The results showed that the maximum of the normalized transmitted dose of manufactured samples (S2 - S6) is registered at smaller sample thicknesses than for the analyzed commercial bolus (sample S1). The smallest sample thickness corresponding to normalized maximum point dose is obtained for sample S2 (RTV-530). Measurements performed for electron beam energy of 6 and 9 MeV have proven the possibility of using the manufactured samples as bolus in radiotherapy.

关键词： Bolus Materials Surface Dose build-up Region Moldable Silicon Rubber Electron Beams

Global Warming Control to Mitigate Climate Change

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Engineering（科研） 2012年第5期4卷 252-255页

作者： Antipas T. S. Massawe University of Dar es Salaam Dar es Salaam Tanzania

Paper describes a proposed development of empirical model of global warming fit on the collective determinants in all countries. Aim is to enable establishment and comparison of the collective effects of global determinants on global warming in the prescription of the regulations most fit for the collective deployment in each of the determinant countries to enable mitigation of the greenhouse gases build-up caused global warming.

关键词： Global Population Growth Greenhouse Gases build-up Global Warming Climate Change Empirical Models