Use Of Air Gap Research Articles

Optimisation of pelvic imaging radiography protocols in plain radiology: a scoping review

Introduction: The purpose of this work is to explore which studies have been performed in the field of radiation dose reduction in pelvic x-ray imaging and to determine optimization techniques for dose reduction.Materials and methods: A scoping review was performed by using databases Science Direct, PubMed, EBSCO Host and Springer Link. The keywords used were "radiography", "dose reduction", "pelvis" and "pelvic". Exclusion criteria were the keywords "CT" and "MRI".Results: 15 scientific articles that analyse the current dose impacts in selected institutions or regions were reviewed as a starting point to optimise protocols, to establish diagnostic reference levels, or to suggest different measures for dose reduction. Studies suggest the use of digital image receptor, adaptation of exposure parameters; they also point out the use of air gap instead of radiographic grid and investigate the usefulness of the gonad protection. A difference was noticed in developing countries that focus more on the establishment of DRLs and following the guidelines provided by other countries rather than developing new dose optimisation techniques.Conclusion: A pelvic x-ray must be performed with a low radiation dose impact that still doesn't compromise the diagnostic value of the image, which can be achieved by following the ALARA principle and with certain adjustments, suggested by the considered studies, especially with exposure parameters. The establishment of national and local diagnostic reference levels is also required.

Investigation of Transformer-Based Solutions for the Reduction of Inrush and Phase-Hop Currents

A comprehensive literature review shows that transformer-based solutions are superior for the mitigation of inrush currents than external (to the transformer) solutions. The use of air gaps and low-permeability (iron) materials are known techniques for this purpose. This paper investigates the effectiveness of these approaches for reducing inrush and phase-hop currents. Studies are carried out on toroidal transformers, due to their broad application in power electronics devices. Contrary to common belief, this paper demonstrates that air gaps do not reduce the inrush currents when a transformer is fully demagnetized. However, inrush currents can be mitigated by the use of low-permeability iron materials. It is also demonstrated that air-gaps significantly reduce inrush currents when transformers have residual flux, e.g., for phase-hop conditions. Analytical expressions are derived to compute the mitigation factor for a specific gap length. The results and formulae presented in this paper are verified with laboratory experiments, transient simulations with validated circuit models, and 2-D finite element simulations.

Mechanical Reliability Testing of Air-Gap Through-Silicon Vias

The use of air gaps instead of SiO2 as insulators for through-silicon vias (TSVs) has been demonstrated to reduce the thermal stresses and the TSV capacitance of a 3-D integrated system. However, since the Cu plug in air-gap TSVs lacks support and fixation at the sidewalls, the mechanical strength is a serious concern. This paper for the first time reports the mechanical and humidity reliabilities of air-gap TSVs. Reliability tests including free drop test, vibration test, and accelerated moisture test are performed, and the failure mechanisms are analyzed. The residual stresses in silicon substrates are also measured using micro-Raman Spectroscopy. Experimental results show that the premetal dielectric that acts as the only support for Cu plugs is the weak point causing mechanical reliability issues, and oxidation of Cu plugs at high moisture and high temperature is the main reason for humidity reliability problems. Multilayer bonding of TSV chips to constitute a 3-D system remarkably increases the mechanical and humidity reliabilities of air-gap TSVs because of the support and protection provided by the bonding chips.

SU‐E‐T‐777: Use of Tennis Racket and Air Gap Between the Body and Carbon Fiber Couch for Skin Sparing in Radiation Therapy of Prone Breast

Purpose:To reduce the skin dose from the carbon fiber couch scatter in radiation treatment of breast cancer in the prone position. If this issue is not addressed, the prone breast touching the solid carbon fiber couch can absorb significant dose to the skin and cause the skin reaction.Methods:1. Use of “tennis racket” instead of the solid couch. To check this hypothesis, we measured the dose at the depth of 5 mm in solid water phantom placed on the couch, using a Farmer chamber. A plan for a patient with 6MV beams, gantry angles of 113 and 286 degrees Varian scale was used. It was found that treatment with “tennis racket” instead of the solid carbon fiber couch reduces the surface dose by 5–7%, depending on the beam direction. 2. Use of the air gap between the couch and the body was analyzed using radiochromic film on the surface of the solid water phantom 10 cm thick. Initially the phantom was placed on the couch with the film sandwiched in between. Two fields at the angles of 135 and 315 degrees were used. The measurements were repeated for the air gap of 2 and 5 cm and 6 and 15 MV beams.Results:It was found that a 2‐cm gap decreased the surface dose by 3% for a 6 MV beam and by 5.5% for a 15 MV beam. A 5‐cm gap reduced the dose by 9% for 6 MV and 13.5% for 15 MV.Conclusion:Use of both methods (combined if possible) can significantly reduce the surface dose in radiation therapy of the prone breast and possible skin reaction. We plan to explore dependence of the dose reduction upon the angle of incidence.

Evisto®, a way to produce ultra-thin gravity die castings

The massive use of air gaps in tooling, per the Evisto® concept, can confine the heat contributed by the cast alloy in a small volume. The resulting high die wall temperatures are turned to account to cast parts having ultra-thin walls, of the order of one millimetre thick. Effective thermal insulation limits thermal exchanges to slow the cooling of a cast alloy. The property that best characterizes this effectiveness is the reciprocal of thermal conductivity, thermal resistance. Air was chosen as the insulating material because of its many advantages: very favourable thermal conductivity, limited application cost, and zero purchase cost. Evisto® , an innovative tooling design, has been used to produce plates 1 mm thick measuring 130 by 200 mm and automobile seat backs 1.2 mm thick measuring 390 by 576 mm. The mechanical properties of the castings so produced complied with standard EN 1706 of May 2010 for aluminium alloy castings. A patent application was filed for the Evisto® concept in August 2010.

Air-gap formation during IMD deposition to lower interconnect capacitance

The use of air-gaps between interconnect metal lines to reduce interconnect capacitance has been explored. Simulations were performed to determine the reduction in capacitance obtainable using air-gaps. The formation of air-gaps in the isolation oxide between metal lines was simulated using Stanford Profile Emulator for Etching and Deposition in IC Engineering (SPEEDIE). The capacitance of the SPEEDIE profiles was then extracted using Raphael (an electrical analysis simulator from TMA). The feasibility of air-gaps was also demonstrated experimentally. Fabricated air-gap structures exhibited a 40% reduction in capacitance when compared to a HDP-CVD oxide gap-fill process with K=4.1. Additionally, the air-gap structures did not exhibit any appreciable leakage current.

High damping composite joint for mechanical vibration and acoustic energy dissipation

A design for a high damping composite joint which dissipates vibrations through the use of air gaps and viscoelastic material minimizing the transfer of vibrations to the metallic coupling. Viscoelastic material is used with adhesive to provide for increased energy dissipation by the joint. As the load increases on the joint, the load transfers from adhesive to the viscoelastic. The viscoelastic begins to take the load of the joint at the point where the adhesive becomes plastic. Acoustic vibrations are then dissipated in the viscoelastic and are prevented from being transferred to the metallic coupling by air gaps provided in the joint. The amount of viscoelastic and adhesive used depends on the anticipated load. Finite element analysis is used to calculate optimal amounts of viscoelastic and adhesive.

The Control Gap for Lightning Protection

The use of air gaps between various forms of electrodes to discharge high surge voltages and thus protect expensive apparatus from damage is general, but such gaps vary in time delay and polarity characteristics and are difficult to co-ordinate with the insulation to be protected. By controlling the electrostatic field, the gap described in this paper provides a wide range of time and polarity characteristics that enables insulation co-ordination to be more readily effected.