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1 – 7 of 7César Pacheco, Helcio R.B. Orlande, Marcelo Colaco and George S. Dulikravich
The purpose of this paper is to apply the Steady State Kalman Filter for temperature measurements of tissues via magnetic resonance thermometry. Instead of using classical direct…
Abstract
Purpose
The purpose of this paper is to apply the Steady State Kalman Filter for temperature measurements of tissues via magnetic resonance thermometry. Instead of using classical direct inversion, a methodology is proposed that couples the magnetic resonance thermometry with the bioheat transfer problem and the local temperatures can be identified through the solution of a state estimation problem.
Design/methodology/approach
Heat transfer in the tissues is given by Pennes’ bioheat transfer model, while the Proton Resonance Frequency (PRF)-Shift technique is used for the magnetic resonance thermometry. The problem of measuring the transient temperature field of tissues is recast as a state estimation problem and is solved through the Steady-State Kalman filter. Noisy synthetic measurements are used for testing the proposed methodology.
Findings
The proposed approach is more accurate for recovering the local transient temperatures from the noisy PRF-Shift measurements than the direct data inversion. The methodology used here can be applied in real time due to the reduced computational cost. Idealized test cases are examined that include the actual geometry of a forearm.
Research limitations/implications
The solution of the state estimation problem recovers the temperature variations in the region more accurately than the direct inversion. Besides that, the estimation of the temperature field in the region was possible with the solution of the state estimation problem via the Steady-State Kalman filter, but not with the direct inversion.
Practical implications
The recursive equations of the Steady-State Kalman filter can be calculated in computational times smaller than the supposed physical times, thus demonstrating that the present approach can be used for real-time applications, such as in control of the heating source in the hyperthermia treatment of cancer.
Originality/value
The original and novel contributions of the manuscript include: formulation of the PRF-Shift thermometry as a state estimation problem, which results in reduced uncertainties of the temperature variation as compared to the classical direct inversion; estimation of the actual temperature in the region with the solution of the state estimation problem, which is not possible with the direct inversion that is limited to the identification of the temperature variation; solution of the state estimation problem with the Steady-State Kalman filter, which allows for fast computations and real-time calculations.
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Steve B. Diniz and César C. Pacheco
The purpose of this paper is to identify freezing in pitot tubes at real-time, by means of the estimated heat transfer coefficient (HTC) at the tip of the probe. The prompt…
Abstract
Purpose
The purpose of this paper is to identify freezing in pitot tubes at real-time, by means of the estimated heat transfer coefficient (HTC) at the tip of the probe. The prompt identification of such freezing is paramount to activate and control mechanisms for ice removal, which in turn are essential for the safety of the aircraft and its passengers.
Design/methodology/approach
The proposed problem is solved by means of an inverse analysis, performed within the Bayesian approach of inverse problems, with temperature measurements assumed available along the pitot probe over time. A heat conduction model is used for describing the average temperature of the pitot tube, which is then rewritten in the form of a state estimation problem. The model is linear and time invariant, so that the inverse problem can be solved using the steady-state Kalman filter (SSKF), a computationally efficient algorithm.
Findings
The results show that the SSKF is fully capable of recovering the HTC information from the temperature measurements. Any variation of the HTC – either smooth or discontinuous – is promptly detected with high accuracy. Computational effort is significantly lower than the physical time, so that the proposed methodology is fully capable of estimating the HTC at real-time.
Originality/value
The methodology herein solves the proposed problem not only by estimating the HTC accurately but also doing so with a very small computational effort, so that real-time estimation and freezing control become possible. To the best of the authors’ knowledge, no likewise publications have been found so far.
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Markus Kraiger and Bernhard Schnizer
The purpose of this paper is to present new expressions in Cartesian coordinates for the potential and magnetic field of prolate and oblate spheroids with arbitrary direction of…
Abstract
Purpose
The purpose of this paper is to present new expressions in Cartesian coordinates for the potential and magnetic field of prolate and oblate spheroids with arbitrary direction of the symmetry axis in a homogeneous field.
Design/methodology/approach
The potentials found in prolate or oblate spheroidal coordinates are transformed to Cartesian coordinates. These results are represented in such a form that they depend only on expressions, which are invariant under rotations around the symmetry axis. Thus, it is easy to change to arbitrary directions of both the symmetry axis and of that of the primary field. The gradients of the potentials are calculated and transformed exactly to the simplest form possible.
Findings
The paper presents simple expressions for the magnetic perturbations due to homogeneous prolate or oblate spheroids in a homogeneous magnetic field.
Research limitations/implications
Results are exact for single non‐ferromagnetic spheroids in a homogeneous field.
Practical implications
Superposition of these perturbations presupposes small values of the magnetic susceptibilities of both the spheroids and their environment as in biological tissues.
Originality/value
The paper presents novel formulas for fields of homogeneous spheroids in a homogeneous magnetic field which are very useful for modelling biological tissues in studies of magnetic resonance imaging and magnetic resonance spectroscopy.
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Gives a bibliographical review of the finite element methods (FEMs) applied in biomedicine from the theoretical as well as practical points of view. The bibliography at the end…
Abstract
Gives a bibliographical review of the finite element methods (FEMs) applied in biomedicine from the theoretical as well as practical points of view. The bibliography at the end of the paper contains 748 references to papers, conference proceedings and theses/dissertations dealing with the finite element analyses and simulations in biomedicine that were published between 1985 and 1999.
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Considers the role of a range of materials being used in advanced sensor technology, including diamond, fullerenes, silicon carbide, superconductors, rare earths and III‐V…
Abstract
Considers the role of a range of materials being used in advanced sensor technology, including diamond, fullerenes, silicon carbide, superconductors, rare earths and III‐V compounds. Sensors based on these materials are described and their applications discussed.
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Periods spent in various industries are essential in all applied science courses, and enable the student to keep his academic studies, especially experimentation, in perspective…
Abstract
Periods spent in various industries are essential in all applied science courses, and enable the student to keep his academic studies, especially experimentation, in perspective. The type of sandwich course consisting of six‐monthly periods spent alternately in college and industry for three years followed by a final year completely in college provides the wisest combination of industrial training and academic studies. This sandwich course is a headache for administrators but offers the students a very wide range of experience; the scheme also permits two end‐on streams per year to be accommodated by our universities, so enabling existing academic facilities to be used more efficiently, as well as producing an even demand on industrial training facilities (Probert, 1964).
Most countries seek to impose control on the chemical treatment of both human and animal food. Some, such as the U.S.A., attempt it by highly detailed regulations, in terms most…
Abstract
Most countries seek to impose control on the chemical treatment of both human and animal food. Some, such as the U.S.A., attempt it by highly detailed regulations, in terms most orthodox and almost psychically specific, which seem most complicated compared with our own simplified food ordinances; other countries, such as many of the newer states, treading cautiously in their virgin fields of law‐making, pass broad, enabling laws, leaving details to be filled in later. Although the object is the same in all countries, it is nothing short of amazing how the pattern of legislation manages to be so divergent, and applied for reasons that are not always apparent. In published regulations and laws, there would seem to be less intent on making a country's food exports conform to the legislative requirements of importing countries than in prescribing standards for its home products; the end results have produced food law chaos, rarely seen in other branches of law. A notable exception, the only one, to these irregular developments, and with particular reference to food additive control, are the common decrees and directives of the European Economic Community, representing the six Common Market countries. Its Council prescribes quality standards for individual foods, specific purity standards for preservatives and other additives which may be used for human consumption, and although this standardisation is only beginning, it deserves study, especially the manner in which the community regulations are enforced.