Search results for "BED"

Fogging effect correction of Gafchromic HD-V2 film response for its use in high-dose radiotherapy

2020

GAFChromic® HD-V2 film is a reliable dose measurement device, thin, flexible, inexpensive, simple to use and easy to analyze. The response in terms of net absorbance with respect to absorbed dose was found to be linear in a large dose range, which supports the feasibility of using the film dosimeters in many applications, such as radiotherapy. For its use, a "fogging" effect must be take into account since film response changes with time. To determine a calibration curve valid for any time, fogging effect was investigated for more than 400 days. A correction procedure allows the use of HD-V2 film dosimeters in high-dose radiotheraphy, as brachytherapy, and quality assurance (QA) procedures.

Influence of the simultaneous calibration of multiple ring dosimeters on the individual absorbed dose

2021

Abstract Ring dosimeters for personal dosimetry are calibrated in accredited laboratories following ISO 4037-3 guidelines. The simultaneous irradiation of multiple dosimeters would save time, but has to be carefully studied, since the scattering conditions could change and influence the absorbed dose in nearby dosimeters. Monte Carlo simulations using PENELOPE-2014 were performed to explore the need to increase the uncertainty of H p 0 .07 in the simultaneous irradiation of three and five DXT-RAD 707H-2 (Thermo Scientific) ring dosimeters with beam qualities: N-30, N-80 and N-300. Results show that the absorbed dose in each dosimeter is compatible with each of the others and with the refere…

Role of continuous moisture profile monitoring by inline NIR spectroscopy during fluid bed granulation of an Enalapril formulation

2010

Granulation and tableting are closely related process steps in the supply chain of pharmaceutical products. Even today, these steps are still optimized independently by trial and error. On the framework of a process analytical technology approach, these processes were evaluated in an integrated approach. Enalapril maleate is a low-dose drug substance with poor granulating and tableting behavior. In order to verify how granulation influences tableting properties, different granulation experiments were performed.Granulation experiments with fast spraying rate and fast drying as well as fast spraying rate and slow drying, and also combinations of both were run. The obtained granules were then …

Hydrodynamics of a three-phase fixed-bed reactor operating in the pulsing flow regime at an elevated pressure

2002

Abstract Results are presented for a three-phase reactor operating at an elevated pressure in the pulsing flow regime. For the system air–water and pressures of 0.1– 0.9 MPa lines are determined that define the change of the hydrodynamic model from the gas continuous flow regime (GCF) to the pulsing flow regime (PF). Also, parameters are found that characterize the pulsing flow of fluids, namely the velocity of pulses travelling along the bed, the frequency of pulsations and their structure, i.e., the length of the pulses and that of the liquid-rich zone.

Hydrodynamics of a Pressurised Three-phase Fixed-Bed Reactor, Operating in the Pulsing Flow Regime

2001

Response charactterization of ammonium tartrate solid state pellets for ESR dosimetry with radiotherapeutic photon and electron beams.

2001

Solid state pellets (1 mm thick) for electron spin resonance (ESR) dosimetry were made using ammonium tartrate as the radiation-sensitive substance. Their behaviour was experimentally investigated as a function of dose with 60Co gamma rays. The calibration function obtained permits measurements of absorbed dose in the 2-50 Gy range, with a combined uncertainty of +/-4%. The lowest detectable dose was about 0.5 Gy. These properties are comparable with or even better than those of ESR dosimeters made from other materials. The time stability of the ESR signal of ammonium tartrate dosimeters at different storage conditions after irradiation was studied. A rather complex behaviour was observed, …

Modeling of Magnetic-Field-Assisted Fluidization: Model Development and CFD Simulation of Magnetically Stabilized Fluidized Beds

2014

Magnetic-field-assisted fluidization is starting to be considered as a viable alternative to standard fluidized beds for those operations (such as particle separations, filtration, adsorption) in which the solid phase can be made of magnetic particles or, alternatively, the fluidizing agent is a ferro-fluid; thus the fluid bed responds to the action of magnetic fields, and stabilized fluidization regimes can be generated. One of the major difficulties to be tackled is the development of a predictive model capable of estimating the stabilized-to-bubbling transition velocity for a given magnetic field or, on the other hand, the magnetic field intensity required to stabilize the bed to a quies…

Sensitivity Analysis and Effect of Simulation parameters of CPFD Simulation in Fluidized Beds

2018

Fluidized bed technology is broadly applied in industry due to its distinct advantages. CFD simulation of fluidized beds is still challenging compared to single-phase systems and needs extensive validation. Multiphase particle-in-cell is a recently developed lagrangian modeling technique and this work is devoted to analyze the sensitivity of grid size, time step, and model parameters, which are the essences of accurate results. Barracuda VR 17.1.0 commercial CFD package was used in this study. 500µm sand particles and air was used as the bed material and fluidization gas respectively. Five different grids, having 27378, 22176, 16819, 9000 and 6656 computational cells were analysed, where fi…

A grain boundary formulation for crystal plasticity

2016

Abstract A three-dimensional grain-boundary formulation for small strains crystal plasticity is presented for the first time. The method is developed and implemented for both single grains and polycrystalline aggregates and it is based on the use of a suitable set of boundary integral equations for modelling the individual grains, which are represented as anisotropic elasto-plastic domains. In the boundary integral framework, crystal plasticity is modelled resorting to an initial strains approach and specific aspects, related to the integration of strongly singular volume integrals in the anisotropic elasto-plastic grain-boundary equations, are discussed and suitably addressed for the first…

On the Improved Current Pulse method for the thermal diffusive characterization of lithiated ceramic pebble beds

2012

Abstract Packed pebble beds are granular systems composed of small particles generally arranged in irregular lattices and surrounded by a gas filling their interstitial spaces. They show non-linear and coupled thermal and mechanical behaviours, which are under theoretical and experimental investigation to set-up a realistic constitutive model to be adopted for design-oriented purposes. At the Department of Nuclear Engineering (DIN) of the University of Palermo a realistic constitutive model of fusion-relevant pebble beds thermo-mechanical behaviour was developed adopting a “continuous” approach, based on the assumption that a pebble bed could be considered as a continuous, homogeneous and i…