Search results for " Shielding."
showing 10 items of 105 documents
Monte Carlo evaluation of kerma in an HDR brachytherapy bunker
2004
In recent years, the use of high dose rate (HDR) after-loader machines has greatly increased due to the shift from traditional Cs-137/Ir-192 low dose rate (LDR) to HDR brachytherapy. The method used to calculate the required concrete and, where appropriate, lead shielding in the door is based on analytical methods provided by documents published by the ICRP, the IAEA and the NCRP. The purpose of this study is to perform a more realistic kerma evaluation at the entrance maze door of an HDR bunker using the Monte Carlo code GEANT4. The Monte Carlo results were validated experimentally. The spectrum at the maze entrance door, obtained with Monte Carlo, has an average energy of about 110 keV, m…
Superconducting Solenoid System with Adjustable Shielding Factor for Precision Measurements of the Properties of the Antiproton
2019
Physical review applied 12(4), 044012 (2019). doi:10.1103/PhysRevApplied.12.044012
Bone mineral density of the proximal femur after hip resurfacing arthroplasty: 1-year follow-up study
2011
Abstract Background Hip resurfacing arthroplasty (HRA) is considered a bone-preserving procedure and may eliminate proximal femoral stress shielding and osteolysis. However, in addition to implant-related stress-shielding factors, various patient-related factors may also have an effect on bone mineral density (BMD) of the proximal femur in patients with HRA. Thus, we studied the effects of stem-neck angle, demographic variables, and physical functioning on the BMD of the proximal femur in a one-year follow-up. Methods Thirty three patients (9 females and 24 males) with a mean (SD) age of 55 (9) years were included in the study. BMD was measured two days and 3, 6, and 12 months postoperative…
Quantification of Bone Density of the Proximal Femur After Hip Resurfacing Arthroplasty—Comparison of Different DXA Acquisition Modes
2010
Total hip arthroplasty (THA) is a traditional operative procedure in the treatment of osteoarthritis. The hip resurfacing arthroplasty (HRA) provides an alternative to the THA for young active patients. HRA is a bone-preserving procedure eliminating the problem of proximal femoral stress shielding and osteolysis associated to THA. Unfortunately, there is no standardized methodology to monitor the quality of bone after HRA. In this study, areal bone mineral density (BMD) in the operated hip (10 regions of interests [ROIs] of 34 volunteered HRA patients) was measured using Lunar Prodigy dual-energy X-ray absorptiometry, and the agreement of a standard (dual femur) and an orthopedic (orthopedi…
Improving the Efficiency of NFC Systems Through Optimizing the Sintered Ferrite Sheet Thickness Selection
2020
The reduction of embedded portable devices involves a magnetic field interference problem when it integrates near field communication (NFC) due to the presence of conductive surfaces, such as ground planes, batteries, or metallic enclosures. Flexible sintered ferrite sheets (FSFS) represent an interesting shielding solution to prevent electromagnetic interferences problems related to NFC, thanks to their ability to control the magnetic flux. The characterization of FSFS effectiveness is analyzed as a function of the sheet thickness in this contribution. This is performed with the aim of determining which is the optimum thickness value to retune an NFC antenna to its original operation frequ…
Mechanical Properties of CNT/Polymer
2018
Abstract The high mechanical properties, the stiffness-to-weight and strength-to-weight make the carbon nanotubes a perfect reinforcing agents in advanced composites. This interesting potential has attracted the attention of both industry and academia that have committed to this research field an impressive amount of work. Several applications of carbon nanotubes enriched polymer composites have already been seen: aerospace structures, sporting goods, automotive components, medical devices, optical barriers, photovoltaic devices, conducting plastics, electromagnetic interference shielding, efficient electrostatic painting of plastics, composite mirrors, plastics with high thermal dissipatio…
Electromagnetic shielding efficiency in Ka-band: carbon foam versus epoxy/carbon nanotube composites
2012
The wide application of microwaves stimulates searching for new materials with high electrical conductivity and electromagnetic (EM) interference shielding effectiveness (SE). We conducted a comparative study of EM SE in K a -band demonstrated by ultra-light micro-structural porous carbon solids (carbon foams) of different bulk densities, 0.042 to 0.150 g/cm 3 , and conventional flexible epoxy resin filled with carbon nanotubes (CNTs) in small concentrations, 1.5 wt.%. Microwave probing of carbon foams showed that the transmission through a 2 mm-thick layer strongly decreases with decreasing the pore size up to the level of 0.6%, due to a rise of reflectance ability. At the same time, 1 mm…
The Magnetic Properties of Electrical Pulses Delivered by Deep-Brain Stimulation Systems
2020
The aim of this article is to analyze the magnetic field properties for both the monopolar and bipolar electrode configurations of deep-brain stimulation electrodes using 3-D magnetic field measurements and to investigate if the magnetic measurements enable a localization of the electrode as a proof of concept. Therefore, a simplified head phantom with an integrated deep-brain stimulation electrode was created to measure the magnetic flux densities in all the three dimensions with a fluxgate magnetometer over a sensor trajectory of measuring points inside the magnetically shielded chamber. The magnitude of the magnetic flux density for monopolar stimulation and bipolar stimulation is in the…
Neutronic and photonic analysis of the single box water-cooled lithium lead blanket for a DEMO reactor
1998
Abstract The water-cooled Pb–17Li demonstration plant (DEMO) breeding blanket line was selected in 1995 as one of the two EU lines to be further developed in the next decade. In this paper the results of a neutronic and photonic analysis of the `single box' concept is presented. A full three-dimensional model, including the whole assembly and many of the DEMO reactor components, has been developed, together with a three-dimensional neutron source. A tritium breeding ratio (TBR) value of 1.16, with no ports and a Li6 enrichment of 90%, has been obtained and a further analysis has been performed to determine Li6 enrichment that would still ensure tritium breeding self-sufficiency. Selected po…
Design approach for high efficiency NFC systems with magnetic shielding materials
2020
The performance of a Near Field Communication (NFC) antenna may be diminished when it is placed close to any conductive surface such as a metallic case or a battery. This degradation is caused due to the stray magnetic field created by the eddy currents induced on the surface, which is opposite to the intended field generated by the NFC antenna. One of the first solutions that come to mind to designers when facing this problem is the use of high permeability magnetic shielding based on sintered ferrite sheets. This is a good approach but something that is not generally taken into account is that these materials introduce an additional inductance to the NFC antenna. If the permeability of th…