2,551 research outputs found
ITER Coil power supply
No full textAn overview of the present design of the ITER coil power supply system is presented, along with brief descriptions of the main components including the AC/DC converters, switching networks, and discharge circuit
Tesla coil
No full textIn this work the author designs a Tesla coil with long discharges, intended for educational activities and visual and sound effects. In this work author first presents the physical principles of Tesla coils, analyzes various types of circuits, and the possibilities for their construction. It also includes a brief biography of Nikola Tesla. After the theoretical analysis of the circuits and principles, the power section of the Tesla coil is discussed and designed. This chapter includes a description of the power blocks and the principles of switching and control. Next, the author calculates the voltage and current ratios in the power section of the Tesla coil. Based on the calculated parameters, the required electronic components are proportioned and selected. The work also includes the design of a passive heat sink for the power components. Next author focuses on the analysis and calculation of resonant circuits. Based on the performed calculations, the primary and secondary resonant circuit coils are designed by using the online program Javatc. Based on this theoretical knowledge, all components are built and the PCB are designed. Author explains the analysis of individual blocks of the control circuit. At the end, the functionality of the entire device is verified, and the device is assembled
Unenhanced Time-of-Flight MR Angiography versus Gadolinium-Enhanced Time-of-Flight MR Angiography in the Follow-Up of Coil-Embolized Aneurysms
No full textBackground and Purpose Coil embolization of ruptured and unruptured aneurysms has emerged as a widely accepted alternative to clipping. Unfortunately, coil-embolized aneurysms need a long-term imaging follow-up to confirm the stability of the occlusion status. We investigated whether contrast-enhanced time-of-flight (ToF) magnetic resonance angiography (MRA) (gadolinium [Gdi-ToF) provides any diagnostic benefit over conventional ToF MRA (nonenhanced [NE]-ToF) in this context. Material and Methods From October 2013 to January 2015, all patients who were regularly scheduled for their follow-up after coil embolization were examined with GdToF and NE-ToF angiography. The general visibility of the occlusion result was compared between the two MRAs as well as with the last digital subtraction angiography (DSA) available. Subgroups of interest (follow-up after stent-assisted coil embolization, cases with already known aneurysm remnants) were also analyzed. Results A total of 70 patients (44 female) harboring 74 treated aneurysms were examined. The reproducibility of the DSA result in terms of therapeutic relevance was 100%. In 10 of 74 cases (14%), the aneurysm status was more difficult to judge in the NE-ToF images (p = 0.02), and the visualization of small vessels was significantly better in the Gd-ToF (p = 0.003). NE-ToF did not fail to show any aneurysm remnants but were more difficult to depict in 35% of the cases (p = 0.09). Regarding the aneurysms that were coiled with stent assistance, there was no significant difference in terms of the visualization (p = 0.1). Conclusion Gd-ToF angiography is in general not superior to NE-ToF for the follow-up of coil-embolized aneurysms
A rapidly rotating RF coil for MRI
No full textThis article introduces a new concept for spin excitation and,signal acquisition in magnetic resonance imaging (MRI) using rapid rotation of a single radiofrequency (RF) coil about a sample. A rotating RF coil system was constructed for 2 and 4.7 Tesla imaging. The acquired images of biological specimens were comparable to those of a conventional RF coil system. This approach may obviate the need for multiple channels and intricate RF decoupling of many coils, which impede the progress of multichannel array technology. it is hoped that hardware advantages of coil rotation and the additional parameter of rotational velocity will initiate advances in MRI through the development of new sequences and methods. (C) 2009 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 3513: 59-66, 200
Hemolysis following coil embolization of a patent ductus arteriosus
No full textWe describe the development of hemolysis from moderate residual shunting across a patent ductus arteriosus following coil embolization. The fall in hemoglobin levels from 11.6 to 6.0 gm/dl necessitated a second coil procedure which resulted in complete closure of the residual shunting and resolution of hemolysis. Therefore, appearance of anemia following coil embolization of patent ductus arteriosus should be monitored closely; however, repeat coil embolization with elimination of residual shunt will lead to prompt recovery of normal hemoglobin levels. © 1996 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38225/1/17_ftp.pd
Detection of Metallic Foreign Objects and Electric Vehicles Using Auxiliary Coil Sets for Dynamic Inductive Power Transfer Systems
No full textThis paper proposes a new method of electric vehicles detection (EVD) and foreign objects detection (FOD) for dynamic inductive power transfer (DIPT) systems. The proposed detection method applies both passive coil sets (PCSs) and active coil sets (ACSs) to achieve both EVD and FOD with a high detection sensitivity. The operation mechanisms and design of the detection coil sets topology and resonant circuits are elaborated. Finally, both circuit and magnetic field simulation are carried out. The results verify the feasibility and sensitivity of the proposed detection method.Virtual/online event due to COVID-19 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Ruhmkorff Induction Coil
No full textThe Ruhmkorff induction coil consists of two separate coils of wire one inside the other wound around a cylinder with a central core of soft iron rods. When a current is passed through the first primary coil, current is induced in the secondary coil. The first successful apparatus of this type was made by Heinrich Daniel Rhumkorff in 1851. The induction coil was exhibited at the Paris Exhibition of 1855, after which it became very popular for energizing discharge tubes, and was used in the production of X-rays at the end of the century.si-025.jp
Optimizing a RF Coil for Prostate Imaging at 7 Tesla MRI
No full textUltra-high ?eld prostate MR imaging (?7T) becomes increasingly difficult due to insufficient radio frequency ?eld excitation penetration. RF coils used at ultra-high ?elds are adapted from lower ?eld strengths but their performance is suboptimal. These coils are designed as near-?eld antennas; however, better signal penetration can be obtained using far-?eld concept, speci?cally in the case of prostate which is located deep in the body. In this project the optimization of an RF coil for prostate imaging at 7T Magnetic Resonance system is investigated. This RF coil was designed following far-?eld-based concept recently proposed by Raaijmakers et al., who has demonstrated that higher transmit B1+ at depth can be obtained; thus increasing the transmit performance necessary to acquire good images. The RF coil consists of a fractionated dipole antenna mounted on an acrylic substrate, and it is used as part of a surface array. The optimization is evaluated in terms of safety (local SAR), transmit performance (B1+), and coupling measurements. A parameters study was performed to improve the performance of the RF coil. Numerical simulations were used to evaluate new designs obtained from the parameters study. From the simulated results, three designs were constructed for validation purposes. Two different measurements were performed to validate the simulations: B1 measurements in the 7 Tesla MR scanner and coupling measurements with a network analyzer; these measurements were performed on a phantom with tissue electrical properties. Finally, an in vivo measurement using two identical sinusoidal-shaped snake antennas (s20) aligned on the pelvis was performed to image a healthy prostate. Both, simulations and measurements in the snake antennas demonstrated that despite the improvement gained in safety with lower levels of SAR, the radiation ?eld penetration pattern is less homogeneous affecting the imaging process. Therefore, these antennas might show more efficiency imaging regions of interest where safety has to be ensured such as the heart, but for prostate imaging the fractionated dipole is preferable.Biomedical EngineeringBiomedical EngineeringMechanical, Maritime and Materials Engineerin
A moving-coil designed micro-mechanics tester with application on MEMS
No full textA moving-coil designed micro-mechanics tester, named as MicroUTM (universal testing machine), is in-house developed in this paper for micro-mechanics tests. The main component is a moving coil suspended in a uniform magnetic field through a set of springs. When a current passes through the coil, the electromagnetic force is proportional to the magnitude of the current, so the load can easily be measured by the current. The displacement is measured using a capacitive sensor. The load is calibrated using a Sartorius BP211D analytical balance, with a resolution/range of 0.01 mg/80 g or 0.1 mg/210 g. The displacement is calibrated using a HEIDENHAIN CT-6002 length gauge with an accuracy of +/- 0.1 mu m. The calibration results show that the load range is +/- 1 N and the displacement range is +/- 300 mu m. The noise levels of the load and displacement are 50 mu N and 150 nm, respectively. The nonlinearity of the load is only 0.2%. Several in-plane load tests of the MEMS micro-cantilever are performed using this tester. Experimental results, with excellent repeatability, demonstrate the reliability of the load measurement as well as the flexible function of this tester
Helix-coil transitions re-visited
No full textThe thermally-induced helix-coil transition in polyamino acids is a good model for determining the helix-forming propensities of amino acids but not for the two-state folding/unfolding transition in globular proteins. The equilibrium and kinetic treatments of the helix-coil transition are summarized here together with a description of applications to various types of homopolymers and copolymers. Attention is then focused on the helix-coil transition in poly-L-alanine as an example of a non-polar polyamino acid. To render such a non-polar polymer water soluble, it is necessary to introduce polar amino acids such as lysines, but care must be taken as to the location of such polar residues. If they are attached as end groups, as in a triblock copolymer, they do not perturb the helix-forming tendency of the central poly-L-alanine block significantly, but if they are introduced within the sequence of alanine residues, then the hydration properties of the lysines dominate the behavior of the resulting copolymer, thereby leading to erroneous values of the parameters characterizing the helix-forming tendency of the alanines. Neutral but polar residues, such as glutamines, also exhibit hydration-dominating properties but less so than charged lysines. Some details of the calculations for an alanine/glutamine copolymer are presented here. It is concluded that random copolymers based on a neutral water-soluble host provide reliable information about the helix-forming tendencies of amino acid residues that are introduced as guests among such neutral host residues.Fil: Scheraga, Harold A.. Cornell University; Estados UnidosFil: Vila, Jorge Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Ripoll, Daniel R.. Cornell Theory Center; Estados Unido
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