Homogeneous Biosensing Based on Magnetic Particle Labels
Schrittwieser, Stefan
2016-06-06
The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.
Homogeneous Biosensing Based on Magnetic Particle Labels
Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang J.; Lentijo-Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Guenther, Annegret; Tschöpe, Andreas; Schotter, Joerg
2016-01-01
The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation. PMID:27275824
Homogeneous Biosensing Based on Magnetic Particle Labels
Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang; Lentijo Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Guenther, Annegret; Tschö pe, Andreas; Schotter, Joerg
2016-01-01
The growing availability of biomarker panels for molecular diagnostics is leading to an increasing need for fast and sensitive biosensing technologies that are applicable to point-of-care testing. In that regard, homogeneous measurement principles are especially relevant as they usually do not require extensive sample preparation procedures, thus reducing the total analysis time and maximizing ease-of-use. In this review, we focus on homogeneous biosensors for the in vitro detection of biomarkers. Within this broad range of biosensors, we concentrate on methods that apply magnetic particle labels. The advantage of such methods lies in the added possibility to manipulate the particle labels by applied magnetic fields, which can be exploited, for example, to decrease incubation times or to enhance the signal-to-noise-ratio of the measurement signal by applying frequency-selective detection. In our review, we discriminate the corresponding methods based on the nature of the acquired measurement signal, which can either be based on magnetic or optical detection. The underlying measurement principles of the different techniques are discussed, and biosensing examples for all techniques are reported, thereby demonstrating the broad applicability of homogeneous in vitro biosensing based on magnetic particle label actuation.
Peripheral nerve magnetic stimulation: influence of tissue non-homogeneity
Papazov Sava P
2003-12-01
Full Text Available Abstract Background Peripheral nerves are situated in a highly non-homogeneous environment, including muscles, bones, blood vessels, etc. Time-varying magnetic field stimulation of the median and ulnar nerves in the carpal region is studied, with special consideration of the influence of non-homogeneities. Methods A detailed three-dimensional finite element model (FEM of the anatomy of the wrist region was built to assess the induced currents distribution by external magnetic stimulation. The electromagnetic field distribution in the non-homogeneous domain was defined as an internal Dirichlet problem using the finite element method. The boundary conditions were obtained by analysis of the vector potential field excited by external current-driven coils. Results The results include evaluation and graphical representation of the induced current field distribution at various stimulation coil positions. Comparative study for the real non-homogeneous structure with anisotropic conductivities of the tissues and a mock homogeneous media is also presented. The possibility of achieving selective stimulation of either of the two nerves is assessed. Conclusion The model developed could be useful in theoretical prediction of the current distribution in the nerves during diagnostic stimulation and therapeutic procedures involving electromagnetic excitation. The errors in applying homogeneous domain modeling rather than real non-homogeneous biological structures are demonstrated. The practical implications of the applied approach are valid for any arbitrary weakly conductive medium.
TWO FERROMAGNETIC SPHERES IN HOMOGENEOUS MAGNETIC FIELD
Yury A. Krasnitsky
2018-01-01
Full Text Available The problem of two spherical conductors is studied quite in detail with bispherical coordinates usage and has numerous appendices in an electrostatics. The boundary-value problem about two ferromagnetic spheres enclosed on homogeneous and infinite environment in which the lack of spheres exists like homogeneous magnetic field is considered. The solution of Laplace's equation in the bispherical system of coordinates allows us to find the potential and field distribution in all spaces, including area between spheres. The boundary conditions in potential continuity and in ordinary density constituent of spheres surfaces induction flux are used. It is supposed that spheres are identical, and magnetic permeability of their material is expressed in >> 0. The problem about falling of electromagnetic plane wave on the system of two spheres, which possesses electrically small sizes, can be considered as quasistationary. The scalar potentials received as a result of Laplace's equation solution are represented by the series containing Legendre polynomials. The concept of two spheres system effective permeability is introduced. It is equal to the advantage in magnitude of magnetic induction flux vector through a certain system’s section arising due to its magnetic properties. Necessary ratios for the effective permeability referred to the central system’s section are obtained. Particularly, the results can be used during the analysis of ferroxcube core clearance, which influences on the magnetic antenna properties.
Homogeneous protein analysis by magnetic core-shell nanorod probes
Schrittwieser, Stefan
2016-03-29
Studying protein interactions is of vital importance both to fundamental biology research and to medical applications. Here, we report on the experimental proof of a universally applicable label-free homogeneous platform for rapid protein analysis. It is based on optically detecting changes in the rotational dynamics of magnetically agitated core-shell nanorods upon their specific interaction with proteins. By adjusting the excitation frequency, we are able to optimize the measurement signal for each analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins (soluble domain of the human epidermal growth factor receptor 2 - sHER2) specifically binding to antibodies (trastuzumab) immobilized on the surface of our nanoprobes and demonstrate direct deduction of their respective sizes. Additionally, we examine the dependence of our measurement signal on the concentration of the analyte protein, and deduce a minimally detectable sHER2 concentration of 440 pM. For our homogeneous measurement platform, good dispersion stability of the applied nanoprobes under physiological conditions is of vital importance. To that end, we support our measurement data by theoretical modeling of the total particle-particle interaction energies. The successful implementation of our platform offers scope for applications in biomarker-based diagnostics as well as for answering basic biology questions.
Magnetic response to applied electrostatic field in external magnetic field
Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)
2014-04-15
We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)
Transport and spin effects in homogeneous magnetic superlattice
Cardoso, J.L.; Pereyra, P.; Anzaldo-Meneses, A.
2000-09-01
Homogeneous semiconductors under spacially periodic external magnetic fields exhibit spin-band splitting and displacements, more clearly defined than in diluted magnetic semiconductor superlattices. We study the influence of the geometrical parameters and the spin-field interaction on the electronic transport properties. We show that by varying the external magnetic field, one can easily block the transmission of either the spin-up or the spin-down electrons. (author)
Sakellariou, Dimitris; Hugon, Cédric; Guiga, Angelo; Aubert, Guy; Cazaux, Sandrine; Hardy, Philippe
2010-12-01
We introduce a cylindrical permanent magnet design that generates a homogeneous and strong magnetic field having an arbitrary inclination with respect to the axis of the cylinder. The analytical theory of 3 D magnetostatics has been applied to this problem, and a hybrid magnet structure has been designed. This structure contains two magnets producing a longitudinal and transverse component for the magnetic field, whose amplitudes and homogeneities can be fully controlled by design. A simple prototype has been constructed using inexpensive small cube magnets, and its magnetic field has been mapped using Hall and NMR probe sensors. This magnet can, in principle, be used for magic angle field spinning NMR and MRI experiments allowing for metabolic chemical shift profiling in small living animals. Copyright © 2010 John Wiley & Sons, Ltd.
Barjhoux, Yves.
1981-01-01
This invention concerns a high homogeneity, double access magnet without a magnetic circuit. It is specially adapted for nuclear magnetic resonance (N.M.R.) imagery. Another advantage worth stressing resides in the possibilities of NMR in biochemical analysis which will enable, for instance, cancerous tumours to be detected in vivo. In order to increase the NMR signal ratio over background noise, it is necessary to increase the homogeneity of the B 0 orientating magnetic field. This magnetic field must orientate the nuclear magnetic moments of the elementary particles which compose the body being examined and in particular the protons. It must therefore be relatively constant in intensity and direction in the entire domain of the examination [fr
A convenient procedure for magnetic field homogeneity evaluation
Teles, J; Garrido, C E; Tannus, A
2004-01-01
In many areas of research that utilize magnetic fields in their studies, it is important to obtain fields with a spatial distribution as homogeneous as possible. A procedure usually utilized to evaluate and to optimize field homogeneity is the expansion of the measured field in spherical harmonic components. In addition to the methods proposed in the literature, we present a more convenient procedure for evaluation of field homogeneity inside a spherical volume. The procedure uses the orthogonality property of the spherical harmonics to find the field variance. It is shown that the total field variance is equal to the sum of the individual variances of each field component in the spherical harmonic expansion. Besides the advantages of the linear behaviour of the individual variances, there is the fact that the field variance and standard deviation are the best parameters to achieve global homogeneity field information
Hydrogen atoms in the presence of a homogeneous magnetic field
Brandi, H.S.; Koiller, B.
1978-01-01
A variational scheme to obtain the spectrum of the hydrogen atom in the presence of an external homogeneous magnetic field is proposed. Two different sets of basis function to diagonalize the Hamiltonian describing the system are used, namely the eigenfunctions of the free hydrogen atom and of the three-dimensional harmonic oscillator; both having their radial coordinates properly scaled by a variational parammeter. Because of its characteristics, the present approach is suitable to describe the ground state as well as an infinite number of excited states also for a wide range of magnetic field strengths [pt
Pires, L.R.
1987-01-01
A method to improve the homogeneity of the distribution of the magnetic flux density in the gap of a dipole magnet. It is based on correcting the magnetic field by means of a system of coils, which employs etching thin copper foils, similarly as those for electronic circuits, is presented. The advantage of this method lies on its simplicity, its small space use, and its low price. The method was applied to correct the field of a dipole magnet, and it worked properly. (author) [pt
Homogeneous Precipitation Synthesis and Magnetic Properties of Cobalt Ferrite Nanoparticles
Zhigang Liu
2008-01-01
Full Text Available Magnetic nanoparticles (NPs of cobalt ferrite have been synthesized via a homogeneous precipitation route using hexamethylenetetramine (HMT as the precipitant. The particle size, crystal structure, and magnetic properties of the synthesized particles were investigated by X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The NPs are of cubic inverse spinel structure and nearly spherical shape. With the increase of oxidation time from 30 to 180 minutes in the reaction solution at 90∘C, the average particle size increases from ~30 nm to ~45 nm. The as-synthesized NPs ~30 nm in size show higher Ms (61.5 emu/g and moderate Hc (945 Oe and Mr/Ms (0.45 value compared with the materials synthesized by coprecipitation method using NaOH as precipitate at high pH value.
Minkowski spacetime does not apply to a homogeneously accelerating medium
Brian Coleman
Full Text Available Home and comoving inertial frame parameters of an individual point of an idealized medium of launch length L uniformly co-accelerating between identical fixed-thrust rockets, are well known. This is not the case with the varying inter-rocket radar periods and related implications regarding a changing ‘noninertial own-length’ Λ which differs from a front rocket’s retrospective separation L from the simultaneously relatively moving rear rocket. On the other hand, the nonhomogeneous acceleration case involving every comoving frame’s unchanging perception of a contrived ‘rigor mortis’ medium (so-called ‘rigid motion’ traditionally associated with ‘Rindler coordinates’ whereby Λ=L=L, constitutes the sole extended accelerating medium scenario where the entrenched Minkowski metric is actually applicable. Paraphrasing Wolfgang Pauli, not only is Minkowski spacetime not correct [in the general sense], it is not even wrong [in the restricted sense]. Keywords: Homogeneous acceleration, Radar intervals, Minkowski metric, Rigor mortis acceleration, Medium-timed photon crossing rate, Retrospective separation
An analysis of the Rose's shim method for improvement of magnetic field homogeneity
Ban, Etsuo
1981-01-01
Well known Rose's method has been applied to the magnets requiring high homogeneity (e.g. for magnetic resonance). The analysis of the Rose's shim is based on the conformal representation, and it is applicable to the poles of any form obtained by the combination of polygons. It provides rims for the magnetic poles of 90 deg edges. In this paper, the solution is determined by the elliptic function to give the magnetic field at any point in the space, directly integrating by the Schwarz-Christoffel transformation, instead of the approximate numerical integration employed by Rose, and compared with the example having applied it to a cylindrical pole. For the conditions of Rose's optimum correction, the exact solution is given as the case that the parameters of Jacobi's third kind elliptic function are equal to a half of first kind perfect elliptic integral. Since Rose depended on the approximate numerical integration, Rose's diagram showed a little insufficient correction. It was found that the pole shape giving excess correction of 10 -4 or so produced a good result for the cylindrical magnetic pole having the ratio of pole diameter to gap length of 2.5. In order to obtain the correction by which the change in homogeneity is small up to considerably intense field, the pole edges are required to be of curved surfaces. (Wakatsuki, Y.)
Damsgaard, Christian Danvad; Hansen, Mikkel Fougt
2008-01-01
We present a systematic theoretical study of the average in-plane magnetic field on square and rectangular magnetic field sensors from a single magnetic bead and a monolayer of magnetic beads magnetized by an in-plane externally applied homogeneous magnetic field. General theoretical expressions...... are derived such that the sensor response and its dependence on the sensor size, spacer layer thickness, bead diameter, and bead susceptibility can easily be evaluated. The average magnetic field from a single bead close to the sensor shows a strong dependence on the position of the bead and a change of sign...... when the bead passes the edge of the sensor in the direction of the applied field. Analytical approximations are derived for the average field from a homogeneous monolayer of beads for beads much smaller than the sensor dimension and for a bead size chosen to minimize the position sensitivity...
Negative-energy waves in a magnetized, homogeneous plasma
Correa-Restrepo, D.; Pfirsch, D.
1991-09-01
The general expression for the second wave energy of a Vlasov-Maxwell system derived by Morrison and Pfirsch is evaluated here for the case of a magnetized, homogeneous plasma. It is again shown that negative-energy waves (which could become nonlinearly unstable and cause anomalous transport) exist for any deviation from monotonicity and/or any (however small) anisotropy in the equilibrium distribution function of any of the particle species. The partly unexpected and particularly interesting feature of the results is that, contrary to the proof of Morrison and Pfirsch, no restricting condition has to be imposed on the perpendicular wave number k perpendicular to of the perturbation (i.e. large k perpendicular to is not required). Finite-gyroradius effects are therefore not expected to improve the situation. Anisotropy alone would, however, impose a restriction on k z , the parallel wave number, relating it to the gyroradius. As far as distribution functions with v z δf v (0) /δv z > 0 in some region of v-space are concerned, however, this result agrees with a result found by Pfirsch and Morrison within the framework of drift-kinetic theory. (orig.)
Dieckhoff, Jan, E-mail: j.dieckhoff@tu-bs.de [Institut fuer Elektrische Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig, Braunschweig (Germany); Schrittwieser, Stefan; Schotter, Joerg [Molecular Diagnostics, AIT Austrian Institute of Technology, Vienna (Austria); Remmer, Hilke; Schilling, Meinhard; Ludwig, Frank [Institut fuer Elektrische Messtechnik und Grundlagen der Elektrotechnik, TU Braunschweig, Braunschweig (Germany)
2015-04-15
In this work, we report on the effect of the magnetic nanoparticle (MNP) concentration on the quantitative detection of proteins in solution with a rotating magnetic field (RMF) based homogeneous bioassay. Here, the phase lag between 30 nm iron oxide single-core particles and the RMF is analyzed with a fluxgate-based measurement system. As a test analyte anti-human IgG is applied which binds to the protein G functionalized MNP shell and causes a change of the phase lag. The measured phase lag changes for a fixed MNP and a varying analyte concentration are modeled with logistic functions. A change of the MNP concentration results in a nonlinear shift of the logistic function with the analyte concentration. This effect results from the law of mass action. Furthermore, the bioassay results are used to determine the association constant of the binding reaction. - Highlights: • A rotating magnetic field based homogeneous bioassay concept was presented. • Here, single-core iron oxide nanoparticles are applied as markers. • The impact of the particle concentration on the bioassay results is investigated. • The relation between particle concentration and bioassay sensitivity is nonlinear. • This finding can be reasonably explained by the law of mass action.
Itoh, Yoshitaka; Yanagi, Yousuke; Nakamura, Takashi
2017-01-01
A new type of superconducting bulk magnet for compact nuclear magnetic resonance (NMR) devices with high magnetic-field homogeneity has been developed by inserting an HTS film cylinder into a bulk superconductor bore. Annular 60 mmϕ Eu-Ba-Cu-O bulk superconductors with a larger inner diameter (ID) of 36 mm were sandwiched between bulk superconductors with a smaller ID of 28 mm, and the total height of the bulk superconductor set was made to be 120 mm. The inner height of central wide bore space was optimized by magnetic-field simulation so that the influence of the bulk superconductor's paramagnetic moment on applied field homogeneity was minimized during the magnetization process. An HTS film cylinder, in which Gd-Ba-Cu-O tapes were wound helically in three layers around a copper cylinder, was inserted into the bulk bore in order to compensate for the inhomogeneous field trapped by the bulk superconductor. The superconducting bulk magnet composed of the above bulk superconductor set and the film cylinder were cooled by a GM pulse tube refrigerator and magnetized at 4.747 T using the field cooling (FC) method and a conventional superconducting coil magnet adjusted to below 0.5 ppm in magnetic-field homogeneity. The NMR measurement was conducted for an H_2O sample with a diameter of 6.9 mm and a length of 10 mm by setting the sample in the center of the 20 mm ID room-temperature bore of the bulk magnet. The magnetic-field homogeneity derived from the full width at half maximum (FWHM) of the "1H spectrum of H_2O was 0.45 ppm. We confirmed that the HTS film inner cylinder was effective in maintaining the homogeneity of the magnetic field applied in the magnetization process, and as a result, a magnetic field with a homogeneity of less than 1 ppm can be generated in the bore of the bulk magnet without using shim coils. (author)
Chou, Ching-Yu; Ferrage, Fabien; Aubert, Guy; Sakellariou, Dimitris
2015-07-17
Standard Magnetic Resonance magnets produce a single homogeneous field volume, where the analysis is performed. Nonetheless, several modern applications could benefit from the generation of multiple homogeneous field volumes along the axis and inside the bore of the magnet. In this communication, we propose a straightforward method using a combination of ring structures of permanent magnets in order to cancel the gradient of the stray field in a series of distinct volumes. These concepts were demonstrated numerically on an experimentally measured magnetic field profile. We discuss advantages and limitations of our method and present the key steps required for an experimental validation.
Field homogeneity improvement of maglev NdFeB magnetic rails from joints.
Li, Y J; Dai, Q; Deng, C Y; Sun, R X; Zheng, J; Chen, Z; Sun, Y; Wang, H; Yuan, Z D; Fang, C; Deng, Z G
2016-01-01
An ideal magnetic rail should provide a homogeneous magnetic field along the longitudinal direction to guarantee the reliable friction-free operation of high temperature superconducting (HTS) maglev vehicles. But in reality, magnetic field inhomogeneity may occur due to lots of reasons; the joint gap is the most direct one. Joint gaps inevitably exist between adjacent segments and influence the longitudinal magnetic field homogeneity above the rail since any magnetic rails are consisting of many permanent magnet segments. To improve the running performance of maglev systems, two new rail joints are proposed based on the normal rail joint, which are named as mitered rail joint and overlapped rail joint. It is found that the overlapped rail joint has a better effect to provide a competitive homogeneous magnetic field. And the further structure optimization has been done to ensure maglev vehicle operation as stable as possible when passing through those joint gaps. The results show that the overlapped rail joint with optimal parameters can significantly reduce the magnetic field inhomogeneity comparing with the other two rail joints. In addition, an appropriate gap was suggested when balancing the thermal expansion of magnets and homogenous magnetic field, which is considered valuable references for the future design of the magnetic rails.
Magnetic cushioning and pressure applying means
Turner, G.F.A.M.
1981-01-01
This invention relates to a novel cushioning and pressure applying means for compressing sheets of film in an X-ray cassette. The cushioning means is provided by two sheets of rubber or plastics material each of which contains an array of magnets, the sheets being held together so that like magnetic poles are in opposition. (author)
Homogeneous protein analysis by magnetic core-shell nanorod probes
Schrittwieser, Stefan; Pelaz, Beatriz; Parak, Wolfgang J; Lentijo Mozo, Sergio; Soulantica, Katerina; Dieckhoff, Jan; Ludwig, Frank; Altantzis, Thomas; Bals, Sara; Schotter, Joerg
2016-01-01
analyte protein size. In addition, due to the locking of the optical signal to the magnetic excitation frequency, background signals are suppressed, thus allowing exclusive studies of processes at the nanoprobe surface only. We study target proteins
Improvement of the field homogeneity with a permanent magnet assembly for MRI
Sakurai, H.; Aoki, M.; Miyamoto, T.
1990-01-01
In the last few years, MRI (Magnetic Resonance imaging) has become one of the most excellent and important radiological and diagnostic methods. For this application, a strong and uniform magnetic field is required in the area where the patient is examined. This requirement for a high order of homogeneity is increasing with the rapid progress of tomographic technology. On the other hand, the cost reduction for the magnet is also strongly required. As reported in the last paper, we developed and mass-produced a permanent type magnet using high energy Nd-Fe-B material. This paper presents a newly developed 15 plane measuring method instead of a 7 plane method to evaluate the homogeneous field precisely. By using this analytical method and linear programing method, a new-shaped pole piece has been developed. In consequence, homogeneity was improved twice as much and the magnet weight was reduced 10 % as compared with the formerly developed pole piece. (author)
Abe, M.; Murata, Y.; Iinuma, H.; Ogitsu, T.; Saito, N.; Sasaki, K.; Mibe, T.; Nakayama, H.
2018-05-01
A magnetic field design method of magneto-motive force (coil block (CB) and iron yoke) placements for g - 2/EDM measurements has been developed and a candidate placements were designed under superconducting limitations of current density 125 A/mm2 and maximum magnetic field on CBs less than 5.5 T. Placements of CBs and an iron yoke with poles were determined by tuning SVD (singular value decomposition) eigenmode strengths. The SVD was applied on a response matrix from magneto-motive forces to the magnetic fields in the muon storage region and two-dimensional (2D) placements of magneto-motive forces were designed by tuning the magnetic field eigenmode strengths obtained by the magnetic field. The tuning was performed iteratively. Magnetic field ripples in the azimuthal direction were minimized for the design. The candidate magnetic design had five CBs and an iron yoke with center iron poles. The magnet satisfied specifications of homogeneity (0.2 ppm peak-to-peak in 2D placements (the cylindrical coordinate of the radial position R and axial position Z) and less than 1.0 ppm ripples in the ring muon storage volume (0.318 m 0.0 m) for the spiral muon injection from the iron yoke at top.
Recent Advances in the Application of Magnetic Nanoparticles as a Support for Homogeneous Catalysts
Govan, Joseph; Gun’ko, Yurii K.
2014-01-01
Magnetic nanoparticles are a highly valuable substrate for the attachment of homogeneous inorganic and organic containing catalysts. This review deals with the very recent main advances in the development of various nanocatalytic systems by the immobilisation of homogeneous catalysts onto magnetic nanoparticles. We discuss magnetic core shell nanostructures (e.g., silica or polymer coated magnetic nanoparticles) as substrates for catalyst immobilisation. Then we consider magnetic nanoparticles bound to inorganic catalytic mesoporous structures as well as metal organic frameworks. Binding of catalytically active small organic molecules and polymers are also reviewed. After that we briefly deliberate on the binding of enzymes to magnetic nanocomposites and the corresponding enzymatic catalysis. Finally, we draw conclusions and present a future outlook for the further development of new catalytic systems which are immobilised onto magnetic nanoparticles. PMID:28344220
Statistical homogeneity tests applied to large data sets from high energy physics experiments
Trusina, J.; Franc, J.; Kůs, V.
2017-12-01
Homogeneity tests are used in high energy physics for the verification of simulated Monte Carlo samples, it means if they have the same distribution as a measured data from particle detector. Kolmogorov-Smirnov, χ 2, and Anderson-Darling tests are the most used techniques to assess the samples’ homogeneity. Since MC generators produce plenty of entries from different models, each entry has to be re-weighted to obtain the same sample size as the measured data has. One way of the homogeneity testing is through the binning. If we do not want to lose any information, we can apply generalized tests based on weighted empirical distribution functions. In this paper, we propose such generalized weighted homogeneity tests and introduce some of their asymptotic properties. We present the results based on numerical analysis which focuses on estimations of the type-I error and power of the test. Finally, we present application of our homogeneity tests to data from the experiment DØ in Fermilab.
Homogenous BSCCO-2212 Round Wires for Very High Field Magnets
Campbell, Scott; Holesinger, Terry; Huang, Ybing
2012-01-01
The performance demands on modern particle accelerators generate a relentless push towards higher field magnets. In turn, advanced high field magnet development places increased demands on superconducting materials. Nb3Sn conductors have been used to achieve 16 T in a prototype dipole magnet and are thought to have the capability for ∼18 T for accelerator magnets (primarily dipoles but also higher order multipole magnets). However there have been suggestions and proposals for such magnets higher than 20 T. The High Energy Physics Community (HEP) has identified important new physics opportunities that are enabled by extremely high field magnets: 20 to 50 T solenoids for muon cooling in a muon collider (impact: understanding of neutrinos and dark matter); and 20+ T dipoles and quadrupoles for high energy hadron colliders (impact: discovery reach far beyond present). This proposal addresses the latest SBIR solicitation that calls for grant applications that seek to develop new or improved superconducting wire technologies for magnets that operate at a minimum of 12 Tesla (T) field, with increases up to 15 to 20 T sought in the near future (three to five years). The long-term development of accelerator magnets with fields greater than 20 T will require superconducting wires having significantly better high-field properties than those possessed by current Nb 3 Sn or other A15 based wires. Given the existing materials science base for Bi-2212 wire processing, we believe that Bi 2 Sr 2 CaCu 2 O y (Bi-2212) round wires can be produced in km-long piece lengths with properties suitable to meet both the near term and long term needs of the HEP community. The key advance will be the translation of this materials science base into a robust, high-yield wire technology. While the processing and application of A15 materials have advanced to a much higher level than those of the copper oxide-based, high T c (HTS) counterparts, the HTS materials have the very significant advantage
Stability of self-gravitating homogeneous spheroid with azimuthal magnetic field. I
Antonov, V.A.; Zheleznyak, O.A.
1988-01-01
The influence of a frozen magnetic field on the stability of a self-gravitating homogeneous spheroid with respect to a deformation that transforms it into a triaxial ellipsoid is investigated. It is shown that an azimuthal magnetic field is a stabilizing factor, allowing the spheroid to be stable at e > e/sub cr/ = 0.95285
Band gaps in periodically magnetized homogeneous anisotropic media
Merzlikin, A. M.; Levy, M.; Vinogradov, A. P.; Wu, Z.; Jalali, A. A.
2010-11-01
In [A. M. Merzlikin, A. P. Vinogradov, A. V. Dorofeenko, M. Inoue, M. Levy, A. B. Granovsky, Physica B 394 (2007) 277] it is shown that in anisotropic magnetophotonic crystal made of anisotropic dielectric layers and isotropic magneto-optical layers the magnetization leads to formation of additional band gaps (BG) inside the Brillouin zones. Due to the weakness of the magneto-optical effects the width of these BG is much smaller than that of usual BG forming on the boundaries of Brillouin zones. In the present communication we show that though the anisotropy suppresses magneto-optical effects. An anisotropic magnetophotonic crystal made of anisotropic dielectric layers and anisotropic magneto-optical; the width of additional BG may be much greater than the width of the usual Brillouin BG. Anisotropy tends to suppress Brillouin zone boundary band gap formation because the anisotropy suppresses magneto-optical properties, while degenerate band gap formation occurs around points of effective isotropy and is not suppressed.
Square Helmholtz coil with homogeneous field for magnetic measurement of longer HTS tapes
Alamgir, A.K.M. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China)]. E-mail: alam643@hotmail.com; Fang, J. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China); Gu, C. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China); Han, Z. [Applied Superconductivity Research Center, Department of Physics, Building Li Zhai, Room 209, Tsinghua University, Beijing 100084 (China)
2005-08-01
Magnetic ac loss measurement of HTS tapes and films at various magnetic field orientations becomes a crucial issue from the view point of measurement precision. In principle, due to tiny loss component and anisotropic properties, longer HTS sample subjected to very good homogeneous field could facilitate the accuracy of this kind of measurement. We investigated field profile of Helmholtz coils with square winding as a magnetizer for HTS tape and films. It is found that square winding exhibits better field-homogeneity than that of conventional circular winding with the similar coil dimensions for ideal condition. Being apart from ideal condition, we investigated field profile of square Helmholtz coil with various combinations of coil parameters and made a conclusion for the best combination based on the field homogeneity and field intensity. The design also provides noise reduction facilities by allowing compact and identical pick up-compensation coil arrangement. In addition, we optimized the final design of Helmholtz coil to compensate the influence of difficulties in square winding on the field distribution. Finally, as small as 0.5% field variation was estimated for 50 mm long sample to be magnetized under a proper combination of fabrication parameters. Investigation of field homogeneity, noise effect and a practical design of square Helmholtz coil as a pick-up coil based magnetizer will be reported.
Square Helmholtz coil with homogeneous field for magnetic measurement of longer HTS tapes
Alamgir, A.K.M.; Fang, J.; Gu, C.; Han, Z.
2005-01-01
Magnetic ac loss measurement of HTS tapes and films at various magnetic field orientations becomes a crucial issue from the view point of measurement precision. In principle, due to tiny loss component and anisotropic properties, longer HTS sample subjected to very good homogeneous field could facilitate the accuracy of this kind of measurement. We investigated field profile of Helmholtz coils with square winding as a magnetizer for HTS tape and films. It is found that square winding exhibits better field-homogeneity than that of conventional circular winding with the similar coil dimensions for ideal condition. Being apart from ideal condition, we investigated field profile of square Helmholtz coil with various combinations of coil parameters and made a conclusion for the best combination based on the field homogeneity and field intensity. The design also provides noise reduction facilities by allowing compact and identical pick up-compensation coil arrangement. In addition, we optimized the final design of Helmholtz coil to compensate the influence of difficulties in square winding on the field distribution. Finally, as small as 0.5% field variation was estimated for 50 mm long sample to be magnetized under a proper combination of fabrication parameters. Investigation of field homogeneity, noise effect and a practical design of square Helmholtz coil as a pick-up coil based magnetizer will be reported
Effects of a homogeneous magnetic field on erythrocyte sedimentation and aggregation
Iino, Masaaki [Nippon Medical School, Tokyo (Japan). Dept. of Physiology I
1997-05-01
Effects of a homogeneous static magnetic field on erythrocyte sedimentation rate (ESR) have been assessed by using the standard Westergren method. A magnetic field of 6.3 T in the vertical direction only slightly enhanced ESR in saline solution, which was consistent with an effect on cell orientation. On the other hand, the magnetic field greatly enhanced ESR in plasma. It took a long time (about 20 min) for an ESR change to occur in plasma in response to the magnetic field. The effects in plasma were too large to originate only from cell orientation and were clearly distinct from a magnetic field-induced Boycott effect under an inhomogeneous magnetic field. A morphological examination and the nonlinear time course of the sedimentation in plasma indicated that the magnetic field increased cell aggregation and thereby enhanced ESR in plasma.
Optimal design of a 7 T highly homogeneous superconducting magnet for a Penning trap
Wu Wei; He Yuan; Ma Lizhen; Huang Wenxue; Xia Jiawen
2010-01-01
A Penning trap system called Lanzhou Penning Trap (LPT) is now being developed for precise mass measurements at the Institute of Modern Physics(IMP). One of the key components is a 7 T actively shielded superconducting magnet with a clear warm bore of 156 mm. The required field homogeneity is 3 x 10 -7 over two 1 cubic centimeter volumes lying 220 mm apart along the magnet axis. We introduce a two-step method which combines linear programming and a nonlinear optimization algorithm for designing the multi-section superconducting magnet. This method is fast and flexible for handling arbitrary shaped homogeneous volumes and coils. With the help of this method an optimal design for the LPT superconducting magnet has been obtained. (authors)
Homogeneous magnetic relaxation in iron-yttrium garnets in the vicinity of a phase transition
Luzyanin, I.D.; Khavronin, V.P.
1977-01-01
Results are presented of an experimental investigation of the dynamics of homogeneous magnetization during a phase transition of the second kind in iron-yttrium garnet (IYG) single crystals of various shapes. It is shown that homogeneous relaxation significantly depends on both the magnitude of 4πchisub(st) (chisub(st) is static magnetic susceptibility) as well as on the relation between the variable field frequency (at which the investigation is carried out) and the characteristic energies. It is shown that beginning from temperatures such as 4πchisub(st) approximately 1, the characteristic dipole interaction energy becomes frequency dependent; this indicates that in this case Lorentz coupling between the dynamic susceptibility and homogeneous relaxation time is invalid. This is a principle point in investigations of homogeneous relaxation by radio-frequency techniques. The temperature dependence of the homogeneous relaxation time and static susceptibility is determined in the exchange region. It is found that the phase transition in IYG involves anomalous phenomena which manifest in release and absorption of heat by a sample and in the appearance of additional singularities in the temperature dependence of the homogeneous relaxation time
Classical calculation of radiative lifetimes of atomic hydrogen in a homogeneous magnetic field
Horbatsch, M.W.; Hessels, E.A.; Horbatsch, M.
2005-01-01
Radiative lifetimes of hydrogenic atoms in a homogeneous magnetic field of moderate strength are calculated on the basis of classical radiation. The modifications of the Keplerian orbits due to the magnetic field are incorporated by classical perturbation theory. The model is complemented by a classical radiative decay calculation using the radiated Larmor power. A recently derived highly accurate formula for the transition rate of a field-free hydrogenic state is averaged over the angular momentum oscillations caused by the magnetic field. The resulting radiative lifetimes for diamagnetic eigenstates classified by n,m and the diamagnetic energy shift C compare well with quantum results
Contreras-Astorga, A.; Negro, J.; Tristao, S.
2016-01-01
This paper deals with the problem of an electron in a non-homogeneous magnetic field perpendicular to a plane. From the classical point of view this is an integrable, but not superintegrable, solvable system. In the quantum framework of the Dirac equation this integrable system is solvable too; the energy levels and wavefunctions of bound states, for its reduction to the plane, are computed. The effective one-dimensional matrix Hamiltonian is shown to belong to a shape-invariant hierarchy. Through this example we will shed some light on the specific properties of a quantum integrable system with respect to those characteristic of superintegrable systems. - Highlights: • The system: an electron in a non-homogeneous magnetic field. • This is a solvable integrable but not superintegrable system. • Solutions to the discrete Dirac spectrum are found. • The shape-invariance of Dirac matrix Hamiltonians is characterized. • Specific properties of integrable, not superintegrable, systems are analyzed.
Contreras-Astorga, A., E-mail: alonso.contreras.astorga@gmail.com [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, IN 46408 (United States); Departamento de Física, Cinvestav, A.P. 14-740, 07000 México D.F. (Mexico); Negro, J., E-mail: jnegro@fta.uva.es [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain); Tristao, S., E-mail: hetsudoyaguiu@gmail.com [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain)
2016-01-08
This paper deals with the problem of an electron in a non-homogeneous magnetic field perpendicular to a plane. From the classical point of view this is an integrable, but not superintegrable, solvable system. In the quantum framework of the Dirac equation this integrable system is solvable too; the energy levels and wavefunctions of bound states, for its reduction to the plane, are computed. The effective one-dimensional matrix Hamiltonian is shown to belong to a shape-invariant hierarchy. Through this example we will shed some light on the specific properties of a quantum integrable system with respect to those characteristic of superintegrable systems. - Highlights: • The system: an electron in a non-homogeneous magnetic field. • This is a solvable integrable but not superintegrable system. • Solutions to the discrete Dirac spectrum are found. • The shape-invariance of Dirac matrix Hamiltonians is characterized. • Specific properties of integrable, not superintegrable, systems are analyzed.
Energy levels of mesic molecules ddμ and dt μ in a homogeneous magnetic field
Choi Nam Chol.
1990-01-01
The energy levels of mesic molecules ddμ and dtμ in a homogeneous magnetic field 0-10 8 Gs have been calculated. Calculations are carried out in the adiabatic representation of three-body problem. It is shown that in really existing fields ( 5 Gs) the shifts of energy levels produce no considerable effect on the process of resonant production of mesic molecules. 13 refs.; 3 figs.; 2 tabs
Charged particles scattering in the presence of an homogeneous magnetic field
Brandi, J.S.; Koiller, B.; Barros, H.G.P.L. de; Miranda, L.C.M.
1977-01-01
The scattering of charged particles in the presence of an homogeneous magnetic field, is studied. Using the Green's function formalism, an appropriate transition amplitude for the scattering process is defined, and an application is done for the scattering by a Coulomb potential in the high energy approximation. For this case, the transition amplitude is obtained in a closed form; its behavior with the magnetic field intensity and initial translational energy is qualitatively discussed. In the ultra-strong field limit, the total transition probability presents periodic resonances with increasing values of the initial translational energy [pt
Magnetic fields produced by rotating symmetrical bodies with homogeneous surface charge density
Espejel-Morales, R; Murguía-Romero, G; Calles, A; Cabrera-Bravo, E; Morán-López, J L
2016-01-01
We present a numerical calculation for the stationary magnetic field produced by different rotating bodies with homogeneous and constant surface charge density. The calculation is done by superposing the magnetic field produced by a set of loops of current which mimic the magnetic field produced by belts of current defined by slices of fixed width. We consider the cases of a sphere, ellipsoids, open and closed cylinders and a combination of these in a dumbbell -like shell. We also plot their magnetic field lines using a technique that make use of the Runge–Kutta fourth-order method. Up to our knowledge, the case of closed cylinders was not calculated before. In contrast to previous results, we find that the magnetic field inside finite hollow bodies is homogeneous only in the case of a sphere. This is consequence of the fact that, for the sphere, the surface of any slice taken perpendicularly to the rotation axis, depends only on its thickness, like in the case of an infinite cylinder. (paper)
Gravador, E.; Yoshiki, Hajime; Feizeng, H. [Ibaraki Univ., Mito (Japan)
1996-08-01
A superthermal UCN edm measuring machine is currently under construction at KEK. It utilizes a magnetically shielded superconducting solenoid at liquid helium temperature to generate a stable and homogeneous magnetic field at 10 milligauss. The design of the magnetic shield and solenoid and preliminary evaluation of shielding effectiveness is presented. (author)
Topology optimization of the permanent magnet type MRI considering the magnetic field homogeneity
Lee, Junghoon; Yoo, Jeonghoon
2010-01-01
This study is to suggest a concept design of the permanent magnet (PM) type magnetic resonance imaging (MRI) device based on the topology optimization method. The pulse currents in the gradient coils in the MRI device will introduce the effect of eddy currents in ferromagnetic material and it may worsen the quality of imaging. To equalize the magnetic flux in the PM type MRI device for good imaging, the eddy current effect in the ferromagnetic material must be reduced. This study attempts to use the topology optimization scheme for equalizing the magnetic flux in the measuring domain of the PM type MRI device using that the magnetic flux can be calculated directly by a commercial finite element analysis package. The density method is adopted for topology optimization and the sensitivity of the objective function is computed according to the density change of each finite element in the design domain. As a result, optimal shapes of the pole of the PM type MRI device can be obtained. The commercial package, ANSYS, is used for analyzing the magnetic field problem and obtaining the resultant magnetic flux.
Hugon, Cedric; D'Amico, Francesca; Aubert, Guy; Sakellariou, Dimitris
2010-07-01
Starting from general results of magnetostatics, we give fundamental considerations on the design and characterization of permanent magnets for NMR based on harmonic analysis and symmetry. We then propose a simple geometry that takes advantage of some of these considerations and discuss the practical aspects of the assembly of a real magnet based on this geometry, involving the characterization of its elements, the optimization of the layout and the correction of residual inhomogeneities due to material and geometry imperfections. We report with this low-cost, light-weight magnet (100 euros and 1.8 kg including the aluminum frame) a field of 120 mT (5.1 MHz proton) with a 10 ppm natural homogeneity over a sphere of 1.5 mm in diameter. Copyright (c) 2010 Elsevier Inc. All rights reserved.
Dark energy homogeneity in general relativity: Are we applying it correctly?
Duniya, Didam G. A.
2016-04-01
Thus far, there does not appear to be an agreed (or adequate) definition of homogeneous dark energy (DE). This paper seeks to define a valid, adequate homogeneity condition for DE. Firstly, it is shown that as long as w_x ≠ -1, DE must have perturbations. It is then argued, independent of w_x, that a correct definition of homogeneous DE is one whose density perturbation vanishes in comoving gauge: and hence, in the DE rest frame. Using phenomenological DE, the consequence of this approach is then investigated in the observed galaxy power spectrum—with the power spectrum being normalized on small scales, at the present epoch z=0. It is found that for high magnification bias, relativistic corrections in the galaxy power spectrum are able to distinguish the concordance model from both a homogeneous DE and a clustering DE—on super-horizon scales.
Toms, D.J.
1994-01-01
It is shown how the effective action formalism and ζ-function regularization can be used to study Bose-Einstein condensation for a relativistic charged scalar field in a general homogeneous magnetic field in a spacetime of arbitrary dimension. In the special case where the magnetic field has only one component, Bose-Einstein condensation occurs at high temperature only for D≥5 where D is the spatial dimension. When Bose-Einstein condensation does occur the ground-state expectation value of the scalar field is not constant and we determine its value. If the magnetic field has p independent nonzero components we show that the condition for Bose-Einstein condensation is D≥3+2p. In particular, Bose-Einstein condensation can never occur if the magnetic field has all of its independent components nonzero. The problem of Bose-Einstein condensation in a cylindrical box in D spatial dimensions with a uniform magnetic field directed along the axis of the cylinder is also discussed
Dipolar local field in homogeneously magnetized quasi-two-dimensional crystals
Leon, H; Estevez-Rams, E
2009-01-01
A formalism to calculate the dipolar local field in homogeneously magnetized quasi-two-dimensional (Q2D) crystals is comprehensively presented. Two fundamental tests for this formalism are accomplished: the transition from the Q2D quantities to the corresponding 3D ones; and the recovering of the macroscopic quantities of the 3D continuum theory. The additive separation between lattice and shape contributions to the local field allows an unambiguous interpretation of the respective effects. Calculated demagnetization tensors for square and circular lateral geometries of dipole layers show that for a single crystal layer an extremely thin film, but still with a finite thickness, is a better physical representation than a strictly 2D plane. Distinct close-packed structures are simulated and calculations of the local field at the nodes of the stacked 2D lattices allow one to establish the number of significantly coupled dipole layers, depending on the ratio between the interlayer distance and the 2D lattice constant. The conclusions drawn are of interest for the study of the dipolar interaction in magnetic ultrathin films and other nanostructured materials, where magnetic nanoparticles are embedded in non-magnetic matrices.
Magnetic properties and microstructural homogeneity in NdFeAl bulk metallic glasses
Ortega-Zempoalteca, R.; Valenzuela, R.; Betancourt, I.
2011-01-01
Bulk metallic glasses of nominal composition Nd 60 Fe 30 Al 10 were prepared by copper mold casting in the form of rods of 3 mm in diameter and 50 mm in length. Preparation conditions were varied to assess the effects of the injection distance and the injection pressure of the melt. In order to determine their microstructure, disk-shaped samples were obtained from different cut zones along the axis rod. A non-homogeneous phase distribution was observed, which resulted from the heat transfer regime during the cooling of the melt in the copper mold. As expected, the nature, distribution and volumetric fraction of the various phases produced play an important role on the resulting magnetic properties. Among the main observed phases are Fe-rich rod-like crystals, Nd-rich dendritic crystals and a ''like-amorphous'' matrix. The hard magnetic properties of these materials can be associated with this matrix. In these cooling regimes, the coercive field increases as the cooling rate of the amorphous matrix increases. Hysteresis loops showed a high degree of coupling between phases with different magnetic order. Both the coercive field and the magnetization showed a significant variation along the rod axis; a maximum appeared as a function of the axis length. In order to gather more information about the coupling between the observed phases, δM (or Henkel) plots were obtained, showing an exchange character for interactions (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Nanosphere lithography applied to magnetic thin films
Gleason, Russell
Magnetic nanostructures have widespread applications in many areas of physics and engineering, and nanosphere lithography has recently emerged as promising tool for the fabrication of such nanostructures. The goal of this research is to explore the magnetic properties of a thin film of ferromagnetic material deposited onto a hexagonally close-packed monolayer array of polystyrene nanospheres, and how they differ from the magnetic properties of a typical flat thin film. The first portion of this research focuses on determining the optimum conditions for depositing a monolayer of nanospheres onto chemically pretreated silicon substrates (via drop-coating) and the subsequent characterization of the deposited nanosphere layer with scanning electron microscopy. Single layers of permalloy (Ni80Fe20) are then deposited on top of the nanosphere array via DC magnetron sputtering, resulting in a thin film array of magnetic nanocaps. The coercivities of the thin films are measured using a home-built magneto-optical Kerr effect (MOKE) system in longitudinal arrangement. MOKE measurements show that for a single layer of permalloy (Py), the coercivity of a thin film deposited onto an array of nanospheres increases compared to that of a flat thin film. In addition, the coercivity increases as the nanosphere size decreases for the same deposited layer. It is postulated that magnetic exchange decoupling between neighboring nanocaps suppresses the propagation of magnetic domain walls, and this pinning of the domain walls is thought to be the primary source of the increase in coercivity.
Arefyev, I.M.; Demidenko, O.V.; Saikin, M.S.
2017-06-01
A special experimental stand has been developed and made to test magnetic fluid. It represents a single-tooth magnetic fluid sealer. The type of dependence of the pressure differential on magnetic fluid sealer operation time is used as a criterion to determine magnetic fluid stability and magnetic fluid sealer service life under such conditions. The siloxane-based magnetic fluid was used as the test sample. The colloidal stability as well as stability of the synthesized magnetic fluid in magnetic fields in static mode were determined. It has been found that the obtained magnetic fluid is stable in static mode and, consequently, can be used to conduct necessary tests on stand. Short-term and life tests on stand have shown that MF remains stable and efficient for at least 360 days of continuous utilization. - Highlights: • An experimental single-tooth magnetic fluid sealer has been developed and made. • The magnetic fluid based on siloxane liquid was used as the test sample. • Short-term and life tests of the magnetic fluid were conducted. • The magnetic fluid stability was determined by necessary tests on stand.
The classical centre-of-mass separation for two particles in a homogeneous magnetic field
Dickinson, A.S.; Patterson, J.M.
1986-01-01
The authors investigate classically the problem of the centre-of-mass separation for a two-body system with net charge in a homogeneous magnetic field. Particular attention is paid to the case where one particle is much heavier than the other. Alternative momenta involving a suggested near-constant of the motion are investigated for use with a translation-invariant internal potential. These lead to a 'near separation' in terms of two coupled particles characterised by vectors which possess a simple classical interpretation, even in the presence of an interaction potential. However it is found that the coupling is not small and is not reduced when one of the particles is much heavier than the other, although the frequencies of the two motions then differ widely. (author)
Losses Approximation for Soft Magnetic Composites Based on a Homogenized Equivalent Conductivity
X. Ren
2016-09-01
Full Text Available Soft magnetic composites (SMC are a promising alternative to laminated steel in many Electrical Engineering applications. This is largely owing to their low level of eddy current losses. The electromagnetic behavior of SMC in electromagnetic devices cannot be easily predicted using standard numerical techniques such as the finite element method, mostly due to the computational cost required to model the material microstructure. Another difficulty lies in the high property contrast between the matrix and the inclusions. In this paper we propose a homogenization strategy to define the equivalent electromagnetic properties of SMC. For components made of SMC, the equivalent conductivity and permeability can be determined. These equivalent properties can be used to calculate eddy current losses or introduced into structural analysis tools to design electromagnetic devices.
An homogeneization method applied to the seismic analysis of LMFBR cores
Brochard, D.; Hammami, L.
1991-01-01
Important structures like nuclear reactor cores, steam generator bundle, are schematically composed by a great number of beams, immersed in a fluid. The fluid structure interaction is an important phenomenon influencing the dynamical response of bundle. The study of this interaction through classical methods would need a refined modelisation at the scale of the beams and lead to important size of problems. The homogeneization method constitutes an alternative approach if we are mainly interested by the global behaviour of the bundle. Similar approaches have been already used for other types of industrial structures (Sanchez-Palencia 1980, Bergman and al. 1985, Theodory 1984, Benner and al. 1981). This method consists in replacing the physical heterogeneous medium by an homogeneous medium, which characteristics are determined from the resolution of a set problems on the elementary cell. In the first part of this paper the main assumptions of the method will be summarized. Moreover, other important phenomena may contribute to the dynamical behaviour of the industrial above mentioned structures: those are the impacts between the beams. These impacts could be due to supports limiting the displacements of the beams or to differences in the vibratory characteristics of the various beams. The second part of the paper will concern the way of taking into account the impacts in the linear hemogeneous formalism. Finally an application to the seismic analysis of the FBR core mock-up RAPSODIE will be presented
Liu, Yan; Guenneau, Sébastien; Gralak, Boris
2013-01-01
We investigate a high-order homogenization (HOH) algorithm for periodic multi-layered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this HOH uncovers a magnetoelectric coupling effect (odd-order approximation) and artificial magnetism (even-order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a centre-symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission property of a stack with two dielectric layers against that of an effective bianisotropic medium: they are in good agreement throughout the low-frequency (acoustic) band until the first stop band, where the analyticity of the logarithm function of the transfer matrix () breaks down. PMID:24101891
Transpermeance Amplifier Applied to Magnetic Bearings
Jossana Ferreira
2017-02-01
Full Text Available The most conventional approach of controlling magnetic forces in active magnetic bearings (AMBs is through current feedback amplifiers: transconductance. This enables the operation of the AMB to be understood in terms of a relatively simple current-based model as has been widely reported on in the literature. The alternative notion of using transpermeance amplifiers, which approximate the feedback of gap flux rather than current, has been in commercial use in some form for at least thirty years, however is only recently seeing more widespread acceptance as a commercial standard. This study explores how such alternative amplifiers should be modeled and then examines the differences in behavior between AMBs equipped with transconductance and transpermeance amplifiers. The focus of this study is on two aspects. The first is the influence of rotor displacement on AMB force, commonly modeled as a constant negative equivalent mechanical stiffness, and it is shown that either scheme actually leads to a finite bandwidth effect, but that this bandwidth is much lower when transpermeance is employed. The second aspect is the influence of eddy currents. Using a very simple model of eddy currents (a secondary short-circuited coil, it is demonstrated that transpermeance amplifiers can recover significant actuator bandwidth compared with transconductance, but at the cost of needing increased peak current headroom.
Huang, Haihong; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng
2016-01-01
Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H p (y), induced by applied magnetic fields with different intensities measured through the tensile tests. The H p (y), its slope coefficient K S and maximum gradient K max changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H p (y) and its slope coefficient K S increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H p (y) and K S reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H p (y) instead of changing the signal curve′s profile; and the magnitude of H p (y), K S , K max and the change rate of K S increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials. - Highlights: • We investigated how applied magnetic field and tensile stress impact H p (y) signals. • Magnitude of H p (y), K S and K max increase with the increase of applied magnetic field. • Both applied magnetic field and tensile stress impact material magnetic permeability. • Applied magnetic field can help to evaluate the stress distribution of components.
Huang, Haihong, E-mail: huanghaihong@hfut.edu.cn; Yang, Cheng; Qian, Zhengchun; Han, Gang; Liu, Zhifeng
2016-10-15
Stress can induce a spontaneous magnetic field in ferromagnetic steel under the excitation of geomagnetic field. In order to investigate the impact of applied magnetic field and tensile stress on variation of the residual magnetic signals on the surface of ferromagnetic materials, static tensile tests of Q235 structural steel were carried out, with the normal component of the residual magnetic signals, H{sub p}(y), induced by applied magnetic fields with different intensities measured through the tensile tests. The H{sub p}(y), its slope coefficient K{sub S} and maximum gradient K{sub max} changing with the applied magnetic field H and tensile stress were observed. Results show that the magnitude of H{sub p}(y) and its slope coefficient K{sub S} increase linearly with the increase of stress in the elastic deformation stage. Under yield stress, H{sub p}(y) and K{sub S} reach its maximum, and then decrease slightly with further increase of stress. Applied magnetic field affects the magnitude of H{sub p}(y) instead of changing the signal curve′s profile; and the magnitude of H{sub p}(y), K{sub S}, K{sub max} and the change rate of K{sub S} increase with the increase of applied magnetic field. The phenomenon is also discussed from the viewpoint of magnetic charge in ferromagnetic materials. - Highlights: • We investigated how applied magnetic field and tensile stress impact H{sub p}(y) signals. • Magnitude of H{sub p}(y), K{sub S} and K{sub max} increase with the increase of applied magnetic field. • Both applied magnetic field and tensile stress impact material magnetic permeability. • Applied magnetic field can help to evaluate the stress distribution of components.
Raya, Alfredo; Reyes, Edward
2010-01-01
We calculate the condensate and the vacuum current density induced by external static magnetic fields in (2+1) dimensions. At the perturbative level, we consider an exponentially decaying magnetic field along one Cartesian coordinate. Nonperturbatively, we obtain the fermion propagator in the presence of a uniform magnetic field by solving the Schwinger-Dyson equation in the rainbow-ladder approximation. In the large flux limit, we observe that both these quantities, either perturbative (inhomogeneous) and nonperturbative (homogeneous), are proportional to the external field, in agreement with early expectations.
Ranga Rao Pulimi, V.; Jeevanandam, P.
2009-01-01
The effect of using different anions (nitrate, chloride, sulfate, and acetate) during the precursor synthesis, by homogeneous precipitation, on the magnetic properties of the final product (nanocrystalline NiO), has been studied. The precursors and the oxide were characterized by various analytical techniques including powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetry (TGA), and magnetic measurements. The synthesized NiO samples possess crystallite size in the range, ∼2-6 nm, depending on the anion of the nickel salt. The nickel oxide nanoparticles exhibit superparamagnetic behavior. Acetate and sulfate anions lead to NiO with higher saturation magnetization (∼1.2-1.8 emu/g), while chloride and nitrate anions lead to NiO nanoparticles with lower saturation magnetization (∼0.1-0.4 emu/g) values. The observed magnetic behavior has been attributed to the size effect.
Ranga Rao Pulimi, V. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India); Jeevanandam, P. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)], E-mail: jeevafcy@iitr.ernet.in
2009-09-15
The effect of using different anions (nitrate, chloride, sulfate, and acetate) during the precursor synthesis, by homogeneous precipitation, on the magnetic properties of the final product (nanocrystalline NiO), has been studied. The precursors and the oxide were characterized by various analytical techniques including powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetry (TGA), and magnetic measurements. The synthesized NiO samples possess crystallite size in the range, {approx}2-6 nm, depending on the anion of the nickel salt. The nickel oxide nanoparticles exhibit superparamagnetic behavior. Acetate and sulfate anions lead to NiO with higher saturation magnetization ({approx}1.2-1.8 emu/g), while chloride and nitrate anions lead to NiO nanoparticles with lower saturation magnetization ({approx}0.1-0.4 emu/g) values. The observed magnetic behavior has been attributed to the size effect.
Buildup of electrons with hot electron beam injection into a homogeneous magnetic field
Bashko, V.A.; Krivoruchko, A.M.; Tarasov, I.K.
1989-01-01
The injection of the monoenergetic beam of electrons into the vacuum drift channel under the conditions when the beam current exceeds a certain threshold value involves a virtual cathode creation. The process of virtual cathode creation leads to an exchange of one-fluid movement of beam particles to three-fluid one corresponding to incident, reflected and passed through anticathode beam particles. For the monoenergetic beam case when the velocity spread Δv dr (v dr is the beam drift velocity), the beam instability was predicted in theory and was observed in experiment. Meanwhile, the injection in the drift space of the 'hot' beam having finite spread in velocities may be accompanied not only by the reflection of particles if their velocity v 1/2 (where φ is the electrostatic potential dip value, e and m are the electron charge and mass, respectively), but also the mutual Coulomb scattering of incident and reflected electrons. The scattering process leads in its turn to appearance of viscosity forces and to trapping of a part of beam electrons into the effective potential well formed by electrostatic potential dip and the viscous force potential. The interaction of travelling and trapped particles may occur even at the stage preceding the virtual electrode formation and it may influence the process of its appearance and also the current flow through the drift space. In this report there are described the experimental results on accumulation of electrons when electron beam propagates in vacuum and has a large spread in particle velocities Δv dr in the homogeneous longitudinal magnetic field when ω pe He where ω pe is the electron Langmuir frequency of beam electrons, ω He is the electron cyclotron frequency. (author) 6 refs., 2 figs
High gradient magnetic separation applied to environmental remediation
Prenger, F.C.; Stewart, W.F.; Hill, D.D.; Avens, L.R.; Worl, L.A.; Schake, A.; de Aguero, K.J.; Padilla, D.D.; Tolt, T.L.
1993-01-01
High Gradient Magnetic Separation (HGMS) is an application of superconducting magnet technology to the separation of magnetic solids from other solids, liquids, or gases. The production of both high magnetic fields (>4 T) and large field gradients using superconducting magnet technology has made it possible to separate a previously unreachable but large family of paramagnetic materials. This is a powerful technique that can be used to separate widely dispersed contaminants from a host material and may be the only technique available for separating material in the colloidal state. Because it is a physical separation process, no additional waste is generated. We are applying this technology to the treatment of radioactive wastes for environmental remediation. We have conducted tests examining slurries containing nonradioactive, magnetic surrogates. Results from these studies were used to verify our analytical model of the separation process. The model describes the rate process for magnetic separation and is based on a force balance on the paramagnetic species. This model was used to support bench scale experiments and prototype separator design
Marjoram, R.J.; Guilluy, C; Burridge, K.
2015-01-01
Cellular tension has implications in normal biology and pathology. Membrane adhesion receptors serve as conduits for mechanotransduction that lead to cellular responses. Ligand-conjugated magnetic beads are a useful tool in the study of how cells sense and respond to tension. Here we detail methods for their use in applying tension to cells and strategies for analyzing the results. We demonstrate the methods by analyzing mechanotransduction through VE-cadherin on endothelial cells using both permanent magnets and magnetic tweezers. PMID:26427549
A pulsed magnetic stress applied to Drosophila melanogaster flies
Delle Side, D; Giuffreda, E; Nassisi, V; Velardi, L; Bozzetti, M P; Friscini, A; Specchia, V
2014-01-01
We report the development of a system to feed pulsed magnetic stress to biological samples. The device is based on a RLC circuit that transforms the energy stored in a high voltage capacitor into a magnetic field inside a coil. The field has been characterized and we found that charging the capacitor with 24 kV results in a peak field of 0.4 T. In order to test its effect, we applied such a stress to the Drosophila melanogaster model and we examined its bio-effects. We analysed, in the germ cells, the effects on the control of specific DNA repetitive sequences that are activated after different environmental stresses. The deregulation of these sequences causes genomic instability and chromosomes breaks leading to sterility. The magnetic field treatment did not produce effects on repetitive sequences in the germ cells of Drosophila. Hence, this field doesn't produce deleterious effects linked to repetitive sequences derepression.
A pulsed magnetic stress applied to Drosophila melanogaster flies
Delle Side, D.; Bozzetti, M. P.; Friscini, A.; Giuffreda, E.; Nassisi, V.; Specchia, V.; Velardi, L.
2014-04-01
We report the development of a system to feed pulsed magnetic stress to biological samples. The device is based on a RLC circuit that transforms the energy stored in a high voltage capacitor into a magnetic field inside a coil. The field has been characterized and we found that charging the capacitor with 24 kV results in a peak field of 0.4 T. In order to test its effect, we applied such a stress to the Drosophila melanogaster model and we examined its bio-effects. We analysed, in the germ cells, the effects on the control of specific DNA repetitive sequences that are activated after different environmental stresses. The deregulation of these sequences causes genomic instability and chromosomes breaks leading to sterility. The magnetic field treatment did not produce effects on repetitive sequences in the germ cells of Drosophila. Hence, this field doesn't produce deleterious effects linked to repetitive sequences derepression.
Magnetic Phase Transitions of CeSb. II: Effects of Applied Magnetic Fields
Meier, G.; Fischer, P.; Hälg, W.
1978-01-01
For pt.I see ibid., vol.11, p.345 (1978). The metamagnetic phase transition and the associated phase diagram of the anomalous antiferromagnet CeSb were determined in a neutron diffraction study of the magnetic ordering of CeSb single crystals in applied magnetic fields parallel to the (001...... magnetic fields. The observed magnetic structures do not correspond to the stable configurations expected from the molecular field theory of the face-centred cubic lattice. The change from a first-order transition at the Neel temperature in zero field to second-order transition at high fields points...
One-loop QCD thermodynamics in a strong homogeneous and static magnetic field
Rath, Shubhalaxmi; Patra, Binoy Krishna
2017-12-01
We have studied how the equation of state of thermal QCD with two light flavors is modified in a strong magnetic field. We calculate the thermodynamic observables of hot QCD matter up to one-loop, where the magnetic field affects mainly the quark contribution and the gluon part is largely unaffected except for the softening of the screening mass. We have first calculated the pressure of a thermal QCD medium in a strong magnetic field, where the pressure at fixed temperature increases with the magnetic field faster than the increase with the temperature at constant magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. Thus although the presence of a strong magnetic field makes the pressure of hot QCD medium larger, the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase space becomes squeezed resulting in the reduction of number of microstates. Moreover the energy density is seen to decrease and the speed of sound of thermal QCD medium increases in the presence of a strong magnetic field. These findings could have phenomenological implications in heavy ion collisions because the expansion dynamics of the medium produced in non-central ultra-relativistic heavy ion collisions is effectively controlled by both the energy density and the speed of sound.
Heavy quark potential in a static and strong homogeneous magnetic field
Hasan, Mujeeb; Chatterjee, Bhaswar; Patra, Binoy Krishna [Indian Institute of Technology Roorkee, Department of Physics, Roorkee (India)
2017-11-15
We have investigated the properties of quarkonia in a thermal QCD medium in the background of strong magnetic field. For that purpose, we employ the Schwinger proper-time quark propagator in the lowest Landau level to calculate the one-loop gluon self-energy, which in the sequel gives the effective gluon propagator. As an artifact of strong magnetic field approximation (eB >> T{sup 2} and eB >> m{sup 2}), the Debye mass for massless flavors is found to depend only on the magnetic field which is the dominant scale in comparison to the scales prevalent in the thermal medium. However, for physical quark masses, it depends on both magnetic field and temperature in a low temperature and high magnetic field but the temperature dependence is very meager and becomes independent of the temperature beyond a certain temperature and magnetic field. With the above mentioned ingredients, the potential between heavy quark (Q) and anti-quark (anti Q) is obtained in a hot QCD medium in the presence of a strong magnetic field by correcting both short- and long-range components of the potential in the real-time formalism. It is found that the long-range part of the quarkonium potential is affected much more by magnetic field as compared to the short-range part. This observation facilitates us to estimate the magnetic field beyond which the potential will be too weak to bind Q anti Q together. For example, the J/ψ is dissociated at eB ∝ 10 m{sub π}{sup 2} and Υ is dissociated at eB ∝ 100 m{sub π}{sup 2} whereas its excited states, ψ{sup '} and Υ{sup '} are dissociated at smaller magnetic field eB = m{sub π}{sup 2}, 13 m{sub π}{sup 2}, respectively. (orig.)
Wavelet Domain Radiofrequency Pulse Design Applied to Magnetic Resonance Imaging.
Andrew M Huettner
Full Text Available A new method for designing radiofrequency (RF pulses with numerical optimization in the wavelet domain is presented. Numerical optimization may yield solutions that might otherwise have not been discovered with analytic techniques alone. Further, processing in the wavelet domain reduces the number of unknowns through compression properties inherent in wavelet transforms, providing a more tractable optimization problem. This algorithm is demonstrated with simultaneous multi-slice (SMS spin echo refocusing pulses because reduced peak RF power is necessary for SMS diffusion imaging with high acceleration factors. An iterative, nonlinear, constrained numerical minimization algorithm was developed to generate an optimized RF pulse waveform. Wavelet domain coefficients were modulated while iteratively running a Bloch equation simulator to generate the intermediate slice profile of the net magnetization. The algorithm minimizes the L2-norm of the slice profile with additional terms to penalize rejection band ripple and maximize the net transverse magnetization across each slice. Simulations and human brain imaging were used to demonstrate a new RF pulse design that yields an optimized slice profile and reduced peak energy deposition when applied to a multiband single-shot echo planar diffusion acquisition. This method may be used to optimize factors such as magnitude and phase spectral profiles and peak RF pulse power for multiband simultaneous multi-slice (SMS acquisitions. Wavelet-based RF pulse optimization provides a useful design method to achieve a pulse waveform with beneficial amplitude reduction while preserving appropriate magnetization response for magnetic resonance imaging.
Toms, D.J.
1995-01-01
We consider the problem of Bose-Einstein condensation for a system of nonrelativistic spin-0 bosons in a space of arbitrary dimension D. A general static homogeneous magnetic field is imposed. The effective action approach and ζ-function regularization are used. If D=2δ or 2δ+1, a constant magnetic field is characterized by δ independent components. If p≤δ of these components are nonzero, the condition for Bose-Einstein condensation to occur is D-2p≥3. This means that if D=2δ, then Bose-Einstein condensation never occurs for p=δ-1 or δ. If D=2δ+1, Bose-Einstein condensation never occurs for p=δ. For D-2p≥3, Bose-Einstein condensation does occur, and we show how it may be interpreted as symmetry breaking to give a ground state which is not constant
Permanent magnets prepared from Sm10.5Fe88.5Zr1.0Ny without homogenization
Gebel, B.; Kubis, M.; Mueller, K.-H.
1997-01-01
In as-cast Sm 2 Fe 17 the high amount of α-Fe caused by a peritectic reaction can be considerably reduced by a small addition of about 1 at% Zr. X-ray diffraction showed that as-cast Sm 10.5 Fe 88.5 Zr 1.0 mainly consists of a phase with the Th 2 Zn 17 -type structure and SmFe 3 . Non-homogenized Sm 10.5 Fe 88.5 Zr 1.0 was milled and (i) annealed in vacuum or (ii) treated with a hydrogenation-disproportionation-desorp tion-recombination (HDDR) process. The annealed and subsequently nitrogenated powder is magnetically anisotropic and has a coercivity μ 0J H C up to 2.0 T and an energy product (BH) max up to 136 kJ/m 3 . HDDR-treated and nitrogenated powder is isotropic and exhibits values of μ 0J H C = 3.1 T and (BH) max 103 kJ/m 3 . Consequently, Sm 10.5 Fe 88.5 Zr 1.0 N y (y ∼ 16) permanent magnets with very good properties can be prepared without the time-consuming homogenization procedure. (orig.)
Magnetic stirring welding method applied to nuclear power plant
Hirano, Kenji; Watando, Masayuki; Morishige, Norio; Enoo, Kazuhide; Yasuda, Yuuji
2002-01-01
In construction of a new nuclear power plant, carbon steel and stainless steel are used as base materials for the bottom linear plate of Reinforced Concrete Containment Vessel (RCCV) to achieve maintenance-free requirement, securing sufficient strength of structure. However, welding such different metals is difficult by ordinary method. To overcome the difficulty, the automated Magnetic Stirring Welding (MSW) method that can demonstrate good welding performance was studied for practical use, and weldability tests showed the good results. Based on the study, a new welding device for the MSW method was developed to apply it weld joints of different materials, and it practically used in part of a nuclear power plant. (author)
Eltabey, M.M. [Basic Engineering Science Department, Faculty of Engineering, Menoufiya University (Egypt); Physics Department, Faculty of Science, Jazan University, Jazan (Saudi Arabia); Massoud, A.M., E-mail: Amassouda1@yahoo.com [Physics Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo (Egypt); Radu, Cosmin [Lake Shore Cryotronics, Inc., Westerville, OH (United States)
2017-01-15
Nanocrystalline particles of compositions (CoZn){sub x}Mn{sub 1−x}Fe{sub 2}O{sub 4} were prepared by the coprecipitation method from stoichiometric aqueous solutions, where x varies from 0 to 0.3 in steps of 0.05. The synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared spectroscopy (FT-IR). A vibrating sample magnetometer (VSM) was used to measure the hysteresis parameters at 300 and 6 K. Zero field cooling (ZFC) and field cooling (FC) curves were obtained at the temperature range 6–400 K and the blocking temperature values were determined. XRD analysis confirmed the formation of the obtained powder in a single cubic spinel phase and it showed also that the lattice parameter is decreasing with the increase of (Co-Zn) content. FT-IR measurements between 160 and 650 cm{sup −1} also confirmed the intrinsic cation vibrations of the spinel structure. The magnetic measurements showed that the saturation magnetization, coercivity and the values of blocking temperatures were increased with the (Co-Zn) content. TEM micrographs declared the improvement of particle size homogeneity with the increase of (Co-Zn) content without remarkable change in the average particle size. The obtained results were discussed in view of A-B sublattices interaction and superparamagnetic phenomenon. - Highlights: • Nanocrystalline particles of compositions (CoZn){sub x}Mn{sub 1-x}Fe{sub 2}O{sub 4} were prepared by the coprecipitation method. • XRD analysis showed that the lattice parameter is decreased with the increase of (Co,Zn) content. • The saturation magnetization is improved with the (Co,Zn) content. • Particle size homogeneity is enhanced with (Co,Zn) content. • The values of blocking temperatures are enhanced with increasing (Co,Zn) content.
Chen, Hua Hsuan
Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) is a safe non-invasive tool to study the physiological mechanisms of the human brain. MRS has the capability to provide the information regarding neurochemicals in brains of patients with neuropsychiatric disorders. Therefore, to produce measurable and interpretable information in MRI and MRS, a quality control (QC) program is required. Magnetic field homogeneity (MFH) is an important factor for QC when the volume sizes and neurochemical levels are quantified. Poor main (B0) MFH leads to artifacts, signal losses and broadened line widths. The American College of Radiology's (ACR) MRI QC manual mandates annual checks of MFH, suggesting tests using spectral line widths (FWHM) and phase-difference (Deltaϕ) maps. A new method, dubbed the bandwidth-difference (DeltaBW) method, is proposed along with a prototype phantom for determining MFH. The DeltaBW method is compared with standard methods and has also been tested in different model MRI systems from various manufacturers. Direct comparisons of the data obtained using the DeltaBW method demonstrated good agreement with data obtained using the linewidth method and the frequency map data provided by one MRI system manufacturer. As a result, the DeltaBW method produces measurements of MFH at various Diameter Sphere Volume (DSV) values that can be obtained from a single set of phantom images. The conclusion of the study is that the accuracy of DeltaBW B0 homogeneity measurements of MFH is comparable to the other methods tested while the ease of measurement in practical clinical setting is considerably improved.
Vagh, Hardik A.; Baghai-Wadji, Alireza
2008-12-01
Current technological challenges in materials science and high-tech device industry require the solution of boundary value problems (BVPs) involving regions of various scales, e.g. multiple thin layers, fibre-reinforced composites, and nano/micro pores. In most cases straightforward application of standard variational techniques to BVPs of practical relevance necessarily leads to unsatisfactorily ill-conditioned analytical and/or numerical results. To remedy the computational challenges associated with sub-sectional heterogeneities various sophisticated homogenization techniques need to be employed. Homogenization refers to the systematic process of smoothing out the sub-structural heterogeneities, leading to the determination of effective constitutive coefficients. Ordinarily, homogenization involves a sophisticated averaging and asymptotic order analysis to obtain solutions. In the majority of the cases only zero-order terms are constructed due to the complexity of the processes involved. In this paper we propose a constructive scheme for obtaining homogenized solutions involving higher order terms, and thus, guaranteeing higher accuracy and greater robustness of the numerical results. We present
Leyva, Ana G.; Vega, Daniel R.; Trimarco, Veronica G.; Marchi, Daniel E.
1999-01-01
The (U,Gd)O 2 sintered pellets are fabricated by different methods. The homogeneity characterisation of Gd content seems to be necessary as a production control to qualify the process and the final product. The micrographic technique is the most common method used to analyse the homogeneity of these samples, this method requires time and expertise to obtain good results. In this paper, we propose an analysis of the X-ray diffraction powder patterns through the Rietveld method, in which the differences between the experimental data and the calculated from a crystalline structure model proposed are evaluated. This result allows to determine the cell parameters, that can be correlated with the Gd concentration, and the existence of other phases with different Gd ratio. (author)
Martínez-Ortiz, P. [Laboratorio de Evaluación No Destructiva Electromagnética (LENDE), ESIME-SEPI, Edif. Z-4, Instituto Politécnico Nacional, Zacatenco, México D.F. (Mexico); Pérez-Benítez, J.A., E-mail: japerezb@ipn.mx [Laboratorio de Evaluación No Destructiva Electromagnética (LENDE), ESIME-SEPI, Edif. Z-4, Instituto Politécnico Nacional, Zacatenco, México D.F. (Mexico); Espina-Hernández, J.H. [Laboratorio de Evaluación No Destructiva Electromagnética (LENDE), ESIME-SEPI, Edif. Z-4, Instituto Politécnico Nacional, Zacatenco, México D.F. (Mexico); Caleyo, F. [Departamento de Ingeniería Metalúrgica, ESIQIE, UPALM Edif. 7, Instituto Politécnico Nacional, Zacatenco, C.P. 07738 México D.F. (Mexico); Mehboob, N.; Grössinger, R. [Institute of Solid State Physics, Vienna University of Technology, Vienna A-1040 (Austria); Hallen, J.M. [Departamento de Ingeniería Metalúrgica, ESIQIE, UPALM Edif. 7, Instituto Politécnico Nacional, Zacatenco, C.P. 07738 México D.F. (Mexico)
2016-03-01
This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements. - Highlights: • Study the angular dependence of MBN with applied field in three pipeline steels. • Reveals the change of this angular dependence with the increase applied field. • Explains this dependence based on the domain wall dynamics theory.
Martínez-Ortiz, P.; Pérez-Benítez, J.A.; Espina-Hernández, J.H.; Caleyo, F.; Mehboob, N.; Grössinger, R.; Hallen, J.M.
2016-01-01
This work studies the influence of the maximum applied magnetic field on the angular dependence of the energy of the Magnetic Barkhausen Noise signal in three different API5L pipeline steels. The results show that the shape of the angular dependence of the Magnetic Barkhausen Noise energy changes with the increase of the amplitude of the applied magnetic field. This phenomenon is a consequence of the presence of unlike magnetization processes at different magnitudes of the applied magnetic field. The outcomes reveal the importance of controlling the value of the maximum applied field as parameter for the improvement of the MBN angular dependence measurements. - Highlights: • Study the angular dependence of MBN with applied field in three pipeline steels. • Reveals the change of this angular dependence with the increase applied field. • Explains this dependence based on the domain wall dynamics theory.
Weigmann, Hans-Jürgen; de Sainte Claire, Maude Suisse; Schanzer, Sabine; Patzelt, Alexa; Meinke, Martina; Antoniou, Christina; Sterry, Wolfram; Lademann, Jürgen
2012-05-01
The efficacy of sunscreens depends decisively on the homogeneity of its distribution on the skin surface, which is sensitively reflected by two spectroscopic data - the factor of inhomogeneity and the sum transmission - measured after tape stripping. The aim of this study was to investigate the influence of a skin pre-treatment with body lotion on the layout of the formulations. Six healthy volunteers were pre-treated using the body lotion, Nivea Body (Beiersdorf AG, Hamburg, Germany). The sunscreen was an oil/water (o/w) emulsion, Roc SPF 8 (RoC SA, Paris, France). The tape stripped tesa films were measured with a modified UV/VIS spectrometer Lambda 5 (PerkinElmer, Frankfurt/Main, Germany), the data of which were used to calculate both measurands. The obtained results made clear that the original spectroscopic data must be corrected taking into account the changed amounts of horny layer particles removed with the individual tape strips after pre-treatment. As a consequence of the correction, the factors of inhomogeneity as well as the sum transmissions confirm a more homogeneous distribution of the applied sunscreen. The findings confirm that the applied method is well suited to obtain information on the distribution of topically applied substances, and furthermore that the influence of the pre-treatment of the skin with the body lotion enhances the homogeneity of distribution and thus the sunscreen efficacy. © 2011 John Wiley & Sons A/S.
Elżbieta Ciejka
2014-10-01
Full Text Available Background: Free radicals are atoms, molecules or their fragments, whose excess leads to the development of oxidative stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, as well as aging of organisms. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic fields are the major exogenous sources of free radicals. The low frequency magnetic field is commonly applied in physiotherapy. The aim of the present study was to evaluate the effect of extremely low frequency magnetic field (ELF-MF on the concentration of sulfhydryl groups (–SH and proteins in liver tissues of experimental animals depending on the time of exposure to the field. Material and Methods: Twenty one Sprague-Dawley male rats, aged 3–4 months were randomly divided into 3 experimental groups (each containing 7 animals: controls (group I, the rats exposed to ELF-MF of 40 Hz, 7 mT (this kind of the ELF-MF is mostly used in magnetotherapy, 30 min/day for 2 weeks (group II and the rats exposed to 40 Hz, 7 mT for 60 min/day for 2 weeks (group III. The concentrations of proteins and sulfhydryl groups in the liver tissues were determined after exposure to magnetic fields. Results: Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks caused a significant increase in the concentration of –SH groups and total protein levels in the liver tissues. Conclusions: The study results suggest that exposure to magnetic fields leads to the development of adaptive mechanisms to maintain the balance in the body oxidation-reduction and in the case of the studied parameters does not depend on the time of exposure. Med Pr 2014;65(5:639–644
3-D metrology applied to superconducting dipole magnets for LHC
Dupont, M.; Missiaen, D.; Peguiron, L.
1999-01-01
The construction of the Large Hadron Collider (LHC) requires the manufacture of 1232 superconducting dipole magnets containing two beam channels in a common mechanical structure. These dipole magnets, which produce the required magnetic field to deflect the particles along a circular trajectory, have to be bent in their horizontal plane in order to ensure the largest mechanical aperture. Very tight tolerances on the geometry of these magnets have to be imposed during their fabrication in order to minimise, during operation, the possible losses of particles, which circulate in rather small channels and to ensure the alignment of the adjacent magnets in the ring tunnel. This necessitates a thorough metrological inspection of the magnet geometry and an accurate positioning of some of its components. This paper presents the measuring system and the developed methodology to realize these operations. The results on the first 15 m long dipole magnet are shown. (author)
Cao, Derang; Zhu, Zengtai; Feng, Hongmei; Pan, Lining; Cheng, Xiaohong; Wang, Zhenkun [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Qingfang, E-mail: liuqf@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)
2016-10-15
FeCo films were prepared by a simple and convenient electrodeposition method. An external magnetic field was applied to the film to induce magnetic anisotropy during deposition. Comparing with the previous work, the angle between the direction of applied magnetic field and film plane is changed from in-plane to out-plane. The influence of the applied magnetic field on magnetic properties was investigated. As a result, it can be found that the in-plane anisotropy is driven by the in-plane component of the magnetic field applied during growth. In addition, the result can also be confirmed by the dynamic magnetic anisotropy of the film obtained by vector network analyzer ferromagnetic resonance technique. - Highlights: • FeCo films were prepared by electrodeposition method. • An external magnetic field was applied to induce anisotropy during deposition. • The direction of applied magnetic field is changed from in-plane to out-plane. • The magnetic properties of films were investigated by vector network analyzer. • The in-plane anisotropy is driven by the in-plane component of the field.
De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W.; Bustamante Dominguez, A.; Aguiar, J. Albino; Majima, Y.
2013-01-01
In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C 8 H 18 S 2 ), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)
De Los Santos Valladares, L.; Reeve, R.M.; Mitrelias, T.; Langford, R.M.; Barnes, C.H.W., E-mail: luis_d_v@hotmail.com [Cavendish Laboratory, Department of Physics, University of Cambridge Materials and Structures Laboratory (United Kingdom); Bustamante Dominguez, A. [Laboratorio de Ceramicos y Nanomateriales, Facultad de Ciencias Fisicas, Universidad Nacional Mayor de San Marcos, Lima (Peru); Aguiar, J. Albino [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Departamento de Fisica; Azuma, Y. [Materials and Structures Laboratory, Tokyo Institute of Technology, Midori-ku, Yokohama (Japan); Majima, Y. [CREST, Japan Science and Technology Agency (JST), Midori-ku, Yokohama (Japan)
2013-08-15
In this work, we report the mechanical reorientation of thiolated ferromagnetic microspheres bridging a pair of gold electrodes under an external magnetic field. When an external magnetic field (7 kG) is applied during the measurement of the current-voltage characteristics of a carboxyl ferromagnetic microsphere (4 μm diameter) attached to two gold electrodes by self-assembled monolayers (SAMs) of octane dithiol (C{sub 8}H{sub 18}S{sub 2}), the current signal is distorted. Rather than due to magnetoresistance, this effect is caused by a mechanical reorientation of the ferromagnetic sphere, which alters the number of SAMs between the sphere and the electrodes and therefore affects conduction. To study the physical reorientation of the ferromagnetic particles, we measure their hysteresis loops while suspended in a liquid solution. (author)
Levitation performance of YBCO bulk in different applied magnetic fields
Liu, W.; Wang, S.Y.; Jing, H.; Zheng, J.; Jiang, M.; Wang, J.S.
2008-01-01
The maglev performance of bulk high-T c superconductor (HTS) is investigated above three different types of permanent magnet guideways (PMGs). The main difference among these PMGs is the method used to concentrate the magnetic flux. The experimental results indicate that the levitation force depends only in part on the peak value of the magnetic field. The variation of the vertical component of the magnetic field (B z ), and the structure of the magnetic field are also responsible for the levitation force. These results imply that the permanent magnet with high coercive force is better at concentrating flux th an iron. The conclusions contribute in a very helpful way to the design and optimization of PMGs for HTS maglev systems
Levitation performance of YBCO bulk in different applied magnetic fields
Liu, W. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China)], E-mail: asclab@asclab.cn; Wang, S.Y.; Jing, H.; Zheng, J.; Jiang, M.; Wang, J.S. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China)
2008-07-01
The maglev performance of bulk high-T{sub c} superconductor (HTS) is investigated above three different types of permanent magnet guideways (PMGs). The main difference among these PMGs is the method used to concentrate the magnetic flux. The experimental results indicate that the levitation force depends only in part on the peak value of the magnetic field. The variation of the vertical component of the magnetic field (B{sub z}), and the structure of the magnetic field are also responsible for the levitation force. These results imply that the permanent magnet with high coercive force is better at concentrating flux th an iron. The conclusions contribute in a very helpful way to the design and optimization of PMGs for HTS maglev systems.
Chun-Hong Liu
Full Text Available AIM: We sought to use a regional homogeneity (ReHo approach as an index in resting-state functional magnetic resonance imaging (fMRI to investigate the features of spontaneous brain activity within the default mode network (DMN in patients suffering from bipolar depression (BD. METHODS: Twenty-six patients with BD and 26 gender-, age-, and education-matched healthy subjects participated in the resting-state fMRI scans. We compared the differences in ReHo between the two groups within the DMN and investigated the relationships between sex, age, years of education, disease duration, the Hamilton Rating Scale for Depression (HAMD total score, and ReHo in regions with significant group differences. RESULTS: Our results revealed that bipolar depressed patients had increased ReHo in the left medial frontal gyrus and left inferior parietal lobe compared to healthy controls. No correlations were found between regional ReHo values and sex, age, and clinical features within the BD group. CONCLUSIONS: Our findings indicate that abnormal brain activity is mainly distributed within prefrontal-limbic circuits, which are believed to be involved in the pathophysiological mechanisms underlying bipolar depression.
Ciejka, Elżbieta; Kowalczyk, Agata; Gorąca, Anna
2014-01-01
Free radicals are atoms, molecules or their fragments, whose excess leads to the development of oxidative stress, the cause of many neoplastic, neurodegenerative and inflammatory diseases, as well as aging of organisms. Industrial pollution, tobacco smoke, ionizing radiation, ultrasound and magnetic fields are the major exogenous sources of free radicals. The low frequency mag- netic field is commonly applied in physiotherapy. The aim of the present study was to evaluate the effect of extremely low frequency magnetic field (1L.F-MF) on the concentration ofsullhydryl groups (-SH) and proteins in liver tissues of experimental animals de- pending on the time of exposure to the field. Twenty one Sprague-D)awley male rats, aged 3-4 months were randomly divided into 3 experimental groups (each containing 7 animals): controls (group I), the rats exposed to IEI.F-MF of 40 Hz, 7 mT (this kind of the ELF-MF is mostly used in magnetotherapy), 30 min/day for 2 weeks (group II) and the rats exposed to 40 Hz, 7 mT for 60 min/day for 2 weeks (group III). The concentrations of proteins and sulfhydryl groups in the liver tissues were determined after exposure to magnetic fields. Exposure to low magnetic field: 40 Hz, 7 mT for 30 min/day and 60 min/day for 2 weeks caused a significant increase in the concentration of-SH groups and total protein levels in the liver tissues. The study results suggest that exposure to magnetic fields leads to the development of adaptive mechanisms to maintain the balance in the body oxidation-reduction and in the case of the studied parameters does not depend on the time of exposure.
Debussche, A.; Dubois, T.; Temam, R.
1993-01-01
Using results of Direct Numerical Simulation (DNS) in the case of two-dimensional homogeneous isotropic flows, the behavior of the small and large scales of Kolmogorov like flows at moderate Reynolds numbers are first analyzed in detail. Several estimates on the time variations of the small eddies and the nonlinear interaction terms were derived; those terms play the role of the Reynolds stress tensor in the case of LES. Since the time step of a numerical scheme is determined as a function of the energy-containing eddies of the flow, the variations of the small scales and of the nonlinear interaction terms over one iteration can become negligible by comparison with the accuracy of the computation. Based on this remark, a multilevel scheme which treats differently the small and the large eddies was proposed. Using mathematical developments, estimates of all the parameters involved in the algorithm, which then becomes a completely self-adaptive procedure were derived. Finally, realistic simulations of (Kolmorov like) flows over several eddy-turnover times were performed. The results are analyzed in detail and a parametric study of the nonlinear Galerkin method is performed.
Deng, Demao; Duan, Gaoxiong; Liao, Hai; Liu, Yanfei; Wang, Geliang; Liu, Huimei; Tang, Lijun; Pang, Yong; Tao, Jien; He, Xin; Yuan, Wenzhao; Liu, Peng
2016-10-01
According to the Traditional Chinese Medicine theory of acupuncture, Baihui (GV20) is applied to treat neurological and psychiatric disorders. However, the relationships between neural responses and GV20 remain unknown. Thus, the main aim of this study was to examine the brain responses induced by electro-acupuncture stimulation (EAS) at GV20. Functional magnetic resonance imaging (fMRI) was performed in 33 healthy subjects. Based on the non-repeated event-related (NRER) paradigm, group differences were examined between GV20 and a sham acupoint using the regional homogeneity (ReHo) method. Compared with the sham acupoint, EAS at GV20 induced increased ReHo in regions including the orbital frontal cortex (OFC), middle cingulate cortex (MCC), precentral cortex, and precuneus (preCUN). Decreased ReHo was found in the anterior cingulate cortex (ACC), supplementary motor area (SMA), thalamus, putamen, and cerebellum. The current findings provide preliminary neuroimaging evidence to indicate that EAS at GV20 could induce a specific pattern of neural responses by analysis of ReHo of brain activity. These findings might improve the understanding of mechanisms of acupuncture stimulation at GV20.
Tang L
2018-04-01
Full Text Available Li-Yuan Tang,1,* Hai-Jun Li,2,* Xin Huang,1 Jing Bao,1 Zubin Sethi,3 Lei Ye,1 Qing Yuan,1 Pei-Wen Zhu,1 Nan Jiang,1 Gui-Ping Gao,1 Yi Shao1 1Department of Ophthalmology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China; 2Department of Radiology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, China; 3The Department of Medicine, University of Miami, Coral Gables, FL, USA *These authors contributed equally to this work Objective: Previous neuroimaging studies have demonstrated that pain-related diseases are associated with brain function and anatomical abnormalities, whereas altered synchronous neural activity in acute eye pain (EP patients has not been investigated. The purpose of this study was to explore whether or not synchronous neural activity changes were measured with the regional homogeneity (ReHo method in acute EP patients.Methods: A total of 20 patients (15 males and 5 females with EP and 20 healthy controls (HCs consisting of 15 and 5 age-, sex-, and education-matched males and females, respectively, underwent resting-state functional magnetic resonance imaging. The ReHo method was applied to assess synchronous neural activity changes.Results: Compared with HCs, acute EP patients had significantly lower ReHo values in the left precentral/postcentral gyrus (Brodmann area [BA]3/4, right precentral/postcentral gyrus (BA3/4, and left middle frontal gyrus (BA6. In contrast, higher ReHo values in acute EP patients were observed in the left superior frontal gyrus (BA11, right inferior parietal lobule (BA39/40, and left precuneus (BA7. However, no relationship was found between the mean ReHo signal values of the different areas and clinical manifestations, which included both the duration and degree of pain in EP patients.Conclusion: Our study highlighted that acute EP patients showed altered synchronous neural activities in many brain regions, including somatosensory regions. These
Gravitomagnetic effects in conductor in applied magnetic field
Ahmedov, B.J.; Karim, M.
1999-11-01
The electromagnetic measurements of general relativistic gravitomagnetic effects which can be performed within a conductor embedded in the space-time of slow rotating gravitational object in the presence of magnetic field are proposed. (author)
Sanchez Lopez, Hector
2001-01-01
This work describes an alternative algorithm of Simulated Annealing applied to the design of the main magnet for a Magnetic Resonance Imaging machine. The algorithm uses a probabilistic radial base neuronal network to classify the possible solutions, before the objective function evaluation. This procedure allows reducing up to 50% the number of iterations required by simulated annealing to achieve the global maximum, when compared with the SA algorithm. The algorithm was applied to design a 0.1050 Tesla four coil resistive magnet, which produces a magnetic field 2.13 times more uniform than the solution given by SA. (author)
Active magnetic bearings: As applied to centrifugal pumps
Nelik, Lev; Cooper, Paul; Jones, Graham; Galecki, Dennis; Pinckney, Frank; Kirk, Gordon
1992-05-01
Application of magnetic bearings to boiler feed pumps presents various attractive features, such as longer bearing life, lower maintenance costs, and improved operability through control of the rotordynamics. Magnetic bearings were fitted to an eight-stage, 600 hp boiler feed pump, which generates 2600 ft of heat at 680 gpm and 3560 rpm. In addition to the varied and severe operating environment in steady state operation of this pump in a power plant, it is also subjected to transient loads during frequent starts and stops. These loads can now be measured by the in-built instrumentation of the magnetic bearings. Following site installation, a follow-up bearing tune-up was performed, and pump transient response testing was conducted. The bearing response was completely satisfactory, ensuring trouble-free pump operation even in the range of reduced load. The experience gained so far through design and testing proves feasibility of magnetic bearings for boiler feed pumps, which sets the stage for application of even higher energy centrifugal pumps equipped with magnetic bearings.
Applying Standard Industrial Components for Active Magnetic Bearings
Bert-Uwe Koehler
2017-02-01
Full Text Available With the increasing number of active magnetic bearing applications, satisfying additional requirements is becoming increasingly more important. As for every technology, moving away from being a niche product and achieving a higher level of maturity, these requirements relate to robustness, reliability, availability, safety, security, traceability, certification, handling, flexibility, reporting, costs, and delivery times. Employing standard industrial components, such as those from flexible modular motion control drive systems, is an approach that allows these requirements to be satisfied while achieving rapid technological innovation. In this article, we discuss technical and non-technical aspects of using standard industrial components in magnetic bearing applications.
Parallel computation of automatic differentiation applied to magnetic field calculations
Hinkins, R.L.; Lawrence Berkeley Lab., CA
1994-09-01
The author presents a parallelization of an accelerator physics application to simulate magnetic field in three dimensions. The problem involves the evaluation of high order derivatives with respect to two variables of a multivariate function. Automatic differentiation software had been used with some success, but the computation time was prohibitive. The implementation runs on several platforms, including a network of workstations using PVM, a MasPar using MPFortran, and a CM-5 using CMFortran. A careful examination of the code led to several optimizations that improved its serial performance by a factor of 8.7. The parallelization produced further improvements, especially on the MasPar with a speedup factor of 620. As a result a problem that took six days on a SPARC 10/41 now runs in minutes on the MasPar, making it feasible for physicists at Lawrence Berkeley Laboratory to simulate larger magnets
Magnetic Amphiphilic Composites Applied for the Treatment of Biodiesel Wastewaters
Bruno R. S. Lemos
2012-05-01
Full Text Available In this work, new magnetic amphiphilic composites were prepared by chemical vapor deposition with ethanol on the surface of hydrophilic natural chrysotile matrix containing Fe catalyst. XRD, Raman, Mössbauer and SEM analyses suggest the formation of a complex nanostructured material composed of hydrophobic carbon nanotubes/nanofibers grown on the hydrophilic surface of the MgSi fiber mineral and the presence of Fe metallic nanoparticles coated by carbon. These nanostructured particles show amphiphilic properties and interact very well with both oil and aqueous phases. When added to emulsions the amphiphilic particles locate on the oil/water interface and, under a magnetic field, the oil droplets collapsed leading to the separation of the aqueous and oil phases. Preliminary work showed excellent results on the use of these particles to break wastewater emulsions in the biodiesel process.
Quantum Monte Carlo Calculations Applied to Magnetic Molecules
Larry Engelhardt
2006-01-01
We have calculated the equilibrium thermodynamic properties of Heisenberg spin systems using a quantum Monte Carlo (QMC) method. We have used some of these systems as models to describe recently synthesized magnetic molecules, and-upon comparing the results of these calculations with experimental data-have obtained accurate estimates for the basic parameters of these models. We have also performed calculations for other systems that are of more general interest, being relevant both for existing experimental data and for future experiments. Utilizing the concept of importance sampling, these calculations can be carried out in an arbitrarily large quantum Hilbert space, while still avoiding any approximations that would introduce systematic errors. The only errors are statistical in nature, and as such, their magnitudes are accurately estimated during the course of a simulation. Frustrated spin systems present a major challenge to the QMC method, nevertheless, in many instances progress can be made. In this chapter, the field of magnetic molecules is introduced, paying particular attention to the characteristics that distinguish magnetic molecules from other systems that are studied in condensed matter physics. We briefly outline the typical path by which we learn about magnetic molecules, which requires a close relationship between experiments and theoretical calculations. The typical experiments are introduced here, while the theoretical methods are discussed in the next chapter. Each of these theoretical methods has a considerable limitation, also described in Chapter 2, which together serve to motivate the present work. As is shown throughout the later chapters, the present QMC method is often able to provide useful information where other methods fail. In Chapter 3, the use of Monte Carlo methods in statistical physics is reviewed, building up the fundamental ideas that are necessary in order to understand the method that has been used in this work. With these
Quantum Monte Carlo Calculations Applied to Magnetic Molecules
Engelhardt, Larry [Iowa State Univ., Ames, IA (United States)
2006-01-01
We have calculated the equilibrium thermodynamic properties of Heisenberg spin systems using a quantum Monte Carlo (QMC) method. We have used some of these systems as models to describe recently synthesized magnetic molecules, and-upon comparing the results of these calculations with experimental data-have obtained accurate estimates for the basic parameters of these models. We have also performed calculations for other systems that are of more general interest, being relevant both for existing experimental data and for future experiments. Utilizing the concept of importance sampling, these calculations can be carried out in an arbitrarily large quantum Hilbert space, while still avoiding any approximations that would introduce systematic errors. The only errors are statistical in nature, and as such, their magnitudes are accurately estimated during the course of a simulation. Frustrated spin systems present a major challenge to the QMC method, nevertheless, in many instances progress can be made. In this chapter, the field of magnetic molecules is introduced, paying particular attention to the characteristics that distinguish magnetic molecules from other systems that are studied in condensed matter physics. We briefly outline the typical path by which we learn about magnetic molecules, which requires a close relationship between experiments and theoretical calculations. The typical experiments are introduced here, while the theoretical methods are discussed in the next chapter. Each of these theoretical methods has a considerable limitation, also described in Chapter 2, which together serve to motivate the present work. As is shown throughout the later chapters, the present QMC method is often able to provide useful information where other methods fail. In Chapter 3, the use of Monte Carlo methods in statistical physics is reviewed, building up the fundamental ideas that are necessary in order to understand the method that has been used in this work. With these
Muniz, R. F., E-mail: robsonfmuniz@yahoo.com.br [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Ligny, D. de [Department of Materials Science, Glass and Ceramics, University of Erlangen Nürnberg, Martensstr. 5, 91058 Erlangen (Germany); Le Floch, S.; Martinet, C.; Guyot, Y. [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Rohling, J. H.; Medina, A. N.; Sandrini, M.; Baesso, M. L. [Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Andrade, L. H. C.; Lima, S. M. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C.P. 351, Dourados, MS (Brazil)
2016-06-28
From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca{sub 3}Mg(SiO{sub 4}){sub 2}] and diopside [CaMgSi{sub 2}O{sub 6}]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f{sup 6}5d{sup 1} → 4f{sup 7} transition of Eu{sup 2+} was studied in both host systems. Additionally, the {sup 5}D{sub 0} → {sup 7}F{sub J} transition of Eu{sup 3+} was used as an environment probe in the pristine glass and the glass-ceramic.
Optimisation of applied field pulses for microwave assisted magnetic recording
Simon John Greaves
2017-05-01
Full Text Available Grains in a recording medium experience field pulses from a write head during recording. In general, a short head field rise time and a square pulse shape have been viewed as optimal. This work investigates the optimum field pulse shape for microwave assisted magnetic recording on single layer and ECC media. A square pulse was found to give the best recording performance on single layer media, but an initially negative field pulse increasing at a constant rate was more suitable for ECC media.
Investigation of the magnetic field of the permanent magnet applied in the DIRAC experiment
Batyuk, P; Yazkov, V
2012-01-01
An analysis of the experimental data obtained during the run of 2011 has revealed the effect of degradation of the permanent magnet used. This effect is investigated, and average magnetic field is estimated for each day of the run.
Nacev, A.; Beni, C.; Bruno, O.; Shapiro, B.
2010-01-01
In magnetic drug delivery, therapeutic magnetizable particles are typically injected into the blood stream and magnets are then used to concentrate them to disease locations. The behavior of such particles in-vivo is complex and is governed by blood convection, diffusion (in blood and in tissue), extravasation, and the applied magnetic fields. Using physical first-principles and a sophisticated vessel-membrane-tissue (VMT) numerical solver, we comprehensively analyze in detail the behavior of magnetic particles in blood vessels and surrounding tissue. For any blood vessel (of any size, depth, and blood velocity) and tissue properties, particle size and applied magnetic fields, we consider a Krogh tissue cylinder geometry and solve for the resulting spatial distribution of particles. We find that there are three prototypical behaviors (blood velocity dominated, magnetic force dominated, and boundary-layer formation) and that the type of behavior observed is uniquely determined by three non-dimensional numbers (the magnetic-Richardson number, mass Péclet number, and Renkin reduced diffusion coefficient). Plots and equations are provided to easily read out which behavior is found under which circumstances (Figures 5, 6, 7, and 8). We compare our results to previously published in-vitro and in-vivo magnetic drug delivery experiments. Not only do we find excellent agreement between our predictions and prior experimental observations, but we are also able to qualitatively and quantitatively explain behavior that was previously not understood. PMID:21278859
Kulkarni, Sandip, E-mail: sandip.d.kulkarni@gmail.com [Fischell Department of Bioengineering, University of Maryland at College Park, MD 20742 (United States); Ramaswamy, Bharath; Horton, Emily; Gangapuram, Sruthi [Fischell Department of Bioengineering, University of Maryland at College Park, MD 20742 (United States); Nacev, Alek [Weinberg Medical Physics, LLC (United States); Depireux, Didier [The Institute for Systems Research, University of Maryland at College Park, MD 20742 (United States); Otomagnetics, LLC (United States); Shimoji, Mika [Fischell Department of Bioengineering, University of Maryland at College Park, MD 20742 (United States); Otomagnetics, LLC (United States); Shapiro, Benjamin [Fischell Department of Bioengineering, University of Maryland at College Park, MD 20742 (United States); The Institute for Systems Research, University of Maryland at College Park, MD 20742 (United States); Otomagnetics, LLC (United States)
2015-11-01
This article presents a method to investigate how magnetic particle characteristics affect their motion inside tissues under the influence of an applied magnetic field. Particles are placed on top of freshly excised tissue samples, a calibrated magnetic field is applied by a magnet underneath each tissue sample, and we image and quantify particle penetration depth by quantitative metrics to assess how particle sizes, their surface coatings, and tissue resistance affect particle motion. Using this method, we tested available fluorescent particles from Chemicell of four sizes (100 nm, 300 nm, 500 nm, and 1 μm diameter) with four different coatings (starch, chitosan, lipid, and PEG/P) and quantified their motion through freshly excised rat liver, kidney, and brain tissues. In broad terms, we found that the applied magnetic field moved chitosan particles most effectively through all three tissue types (as compared to starch, lipid, and PEG/P coated particles). However, the relationship between particle properties and their resulting motion was found to be complex. Hence, it will likely require substantial further study to elucidate the nuances of transport mechanisms and to select and engineer optimal particle properties to enable the most effective transport through various tissue types under applied magnetic fields.
Sehgal, A K; Gupta, S C [Punjabi Univ., Patiala (India). Dept. of Physics
1982-12-14
The complementary variational principles method (CVP) is applied to the thermal conductivities of a plasma in a uniform magnetic field. The results of computations show that the CVP derived results are very useful.
Rijssel, Jos van; Kuipers, Bonny W.M.; Erné, Ben H.
2014-01-01
A numerical inversion method known from the analysis of light scattering by colloidal dispersions is now applied to magnetization curves of ferrofluids. The distribution of magnetic particle sizes or dipole moments is determined without assuming that the distribution is unimodal or of a particular shape. The inversion method enforces positive number densities via a non-negative least squares procedure. It is tested successfully on experimental and simulated data for ferrofluid samples with known multimodal size distributions. The created computer program MINORIM is made available on the web. - Highlights: • A method from light scattering is applied to analyze ferrofluid magnetization curves. • A magnetic size distribution is obtained without prior assumption of its shape. • The method is tested successfully on ferrofluids with a known size distribution. • The practical limits of the method are explored with simulated data including noise. • This method is implemented in the program MINORIM, freely available online
Chowdhury, Adity; Basu, Samita
2006-01-01
The interactions between 9,10-anthraquinone (AQ) and different aromatic amines, N,N-dimethylaniline and 4,4'-bis (dimethylamino) diphenylmethane (DMDPM), have been studied using absorption, steady-state fluorescence, and laser flash photolysis techniques in organic homogeneous and heterogeneous micellar media. In polar organic homogeneous medium, electron transfer (ET) occurs from amines to excited AQ. In micellar medium, similar intermolecular ET is observed. However, in latter medium, ET predominates over hydrogen abstraction from micelles by excited AQ itself. The occurrence of ET has been further supported by the application of an external magnetic field during laser flash photolysis experiments, which modulates the yield of radical ion pairs formed through ET. Another novel feature, which has also been discussed here, is the abnormal behavior of DMDPM in micellar medium pertaining to energy transfer
Akhbarizadeh, Amin; Amini, Kamran; Javadpour, Sirus
2012-01-01
Highlights: ► Deep cryogenic increases the carbide percentage and make a more homogenous distribution. ► Deep cryogenic improve the wear resistance and corrosion behavior of 1.2080 tool steel. ► Applying the magnetic field weaker the carbide distribution and decreases the carbides percentage. ► Magnetized samples showed weaker corrosion and wear behavior. -- Abstract: This work concerns with the effect of applying an external magnetic field on the corrosion behavior, wear resistance and microstructure of 1.2080 (D2) tool steel during the deep cryogenic heat treatment. These analyses were performed via scanning electron microscope (SEM), optical microscope (OM), transmission electron microscope (TEM) and X-ay diffraction (XRD) to study the microstructure, a pin-on-disk wear testing machine to study the wear behavior, and linear sweep voltammetry to study the corrosion behavior of the samples. It was shown that the deep cryogenic heat treatment eliminates retained austenite and makes a more uniform carbide distribution with higher percentage. It was also observed that the deep cryogenic heat treatment improves the wear behavior and corrosion resistance of 1.2080 tool steel. In comparison between the magnetized and non-magnetized samples, the carbide percentage decreases and the carbide distribution weakened in the magnetized samples; subsequently, the wear behavior and corrosion resistance attenuated compared in the magnetized samples.
Magnetic measurements of suspended functionalised ferromagnetic beads under DC applied fields
De Los Santos V, Luis; Llandro, Justin; Lee, Dongwook; Mitrelias, Thanos; Palfreyman, Justin J.; Hayward, Thomas J.; Cooper, Jos; Bland, J.A.C.; Barnes, Crispin H.W.; Arroyo C, Juan L.; Lees, Martin
2009-01-01
In this work, a simple technique to obtain the hysteresis loops of magnetic beads (Spherotech Inc.) in liquid suspension is presented. The magnetic measurements were taken in a DC Magnetic Property Measurement System (MPMS-SQUID sensor). Samples were based on ferromagnetic beads (surface-functionalized NH 2 , mean diameter 4.32 μm) prepared in three conditions: dry, suspended in sucrose solution and in suspension after functionalization with fluorophore. Special small containers (1.3 cm long) made of non magnetic plastic were designed to hold the beads in liquid. The results indicate that the bead's remnant magnetization is half of the value at maximum applied field in all cases. However, due to the additional degrees of rotational freedom, beads suspended in a liquid do not present coercivity. The use of ferromagnetic beads and magnetic elements of different architectures for applications in bioassays is also discussed.
Permanent magnets prepared from Sm{sub 10.5}Fe{sub 88.5}Zr{sub 1.0}N{sub y} without homogenization
Gebel, B.; Kubis, M.; Mueller, K.-H. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe
1997-10-01
In as-cast Sm{sub 2}Fe{sub 17} the high amount of {alpha}-Fe caused by a peritectic reaction can be considerably reduced by a small addition of about 1 at% Zr. X-ray diffraction showed that as-cast Sm{sub 10.5}Fe{sub 88.5}Zr{sub 1.0} mainly consists of a phase with the Th{sub 2}Zn{sub 17}-type structure and SmFe{sub 3}. Non-homogenized Sm{sub 10.5}Fe{sub 88.5}Zr{sub 1.0} was milled and (i) annealed in vacuum or (ii) treated with a hydrogenation-disproportionation-desorp tion-recombination (HDDR) process. The annealed and subsequently nitrogenated powder is magnetically anisotropic and has a coercivity {mu}{sub 0J}H{sub C} up to 2.0 T and an energy product (BH){sub max} up to 136 kJ/m{sup 3}. HDDR-treated and nitrogenated powder is isotropic and exhibits values of {mu}{sub 0J}H{sub C} = 3.1 T and (BH){sub max} 103 kJ/m{sup 3}. Consequently, Sm{sub 10.5}Fe{sub 88.5}Zr{sub 1.0}N{sub y} (y {approx} 16) permanent magnets with very good properties can be prepared without the time-consuming homogenization procedure. (orig.). 11 refs.
Sanchez, R.; Ragusa, J.; Santandrea, S.
2004-01-01
The problem of the determination of a homogeneous reflector that preserves a set of prescribed albedo is considered. Duality is used for a direct estimation of the derivatives needed in the iterative calculation of the optimal homogeneous cross sections. The calculation is based on the preservation of collapsed multigroup albedo obtained from detailed reference calculations and depends on the low-order operator used for core calculations. In this work we analyze diffusion and transport as low-order operators and argue that the P 0 transfers are the best choice for the unknown cross sections to be adjusted. Numerical results illustrate the new approach for SP N core calculations. (Author)
Bayones, F. S.; Abd-Alla, A. M.
2018-06-01
The prime objective of the present paper is to analyze the effect of magnetic field and rotation on the free vibrations of an elastic hollow sphere. The one-dimensional equation of motion is solved in terms of radial displacement. The frequency equation is obtained when the boundaries are free and fixed boundary conditions. The determination is concerned with the eigenvalues of the natural frequency of the free vibrations in the case of harmonic vibrations. The natural frequencies and the mode shapes are calculated numericall and the effects of rotation and magnetic field are discussed. It was shown that the dispersion curves of waves were significantly influenced by the magnetic field and rotation of the elastic sphere.
Effect of an applied pressure gradient on a magnetically collimated arc
Neidigh, R V [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Weaver, C H [University of Tennessee (United States)
1958-07-01
This report describes experimental observations made in connection with a magnetically collimated arc having an applied pressure gradient along its length and presents possible explanations of the phenomena observed. It is believed to be pertinent to thermonuclear research because it involves the transport of plasma across a magnetic field and the acceleration of ions without use of solid electrodes and furnishes evidence concerning the behavior inside magnetically collimated arc discharges as the pressure is decreased. The observations are repeatable to an unusual degree and are believed to be sufficiently interesting to be reported at this time, even though a thorough understanding of the entire mechanism involved has not been reached.
Evidence for a devil's staircase in holmium produced by an applied magnetic field
Cowley, R.A.; Jehan, D.A.; McMorrow, D.F.; McIntyre, G.J.
1991-01-01
The magnetic structure of holmium has been studied using neutron diffraction when a magnetic field is applied along the c axis. The field has the effect of suppressing the onset of the commensurate cone phase found at low temperatures in zero field, and instead produces a series of spin-slip structures. In contrast to the zero-field diffraction experiments, where a continuous variation of the magnetic wave vector q was observed, we find that below ∼15 K the wave vector q is always commensurate and forms a devil's staircase with increasing field
Souza, P E N de; Oliveira, L M de; Ortiz, W A; Camargo, P C de; Oliveira, A J A de
2005-01-01
In this work we present magnetic susceptibility results for Cr-x at.% Nb alloys (x = 0.2, 0.6, 0.7, 1.4, and 2.0), showing that a local short-range order spin-density wave (L-SDW) appears at a characteristic temperature (T loc ) above the Neel temperature. The evidence for L-SDW is based on a Curie-Weiss-like behaviour, which is suppressed when large magnetic fields are applied or for alloys with Nb concentration above x = 2.0 at.%
Sanchez, R.; Ragusa, J.; Santandrea, S. [Commissariat a l' Energie Atomique, Direction de l' Energie Nucleaire, Service d' Etudes de Reacteurs et de Modelisation Avancee, CEA de Saclay, DM2S/SERMA 91 191 Gif-sur-Yvette cedex (France)]. e-mail: richard.sanchez@cea.fr
2004-07-01
The problem of the determination of a homogeneous reflector that preserves a set of prescribed albedo is considered. Duality is used for a direct estimation of the derivatives needed in the iterative calculation of the optimal homogeneous cross sections. The calculation is based on the preservation of collapsed multigroup albedo obtained from detailed reference calculations and depends on the low-order operator used for core calculations. In this work we analyze diffusion and transport as low-order operators and argue that the P{sub 0} transfers are the best choice for the unknown cross sections to be adjusted. Numerical results illustrate the new approach for SP{sub N} core calculations. (Author)
FDTD-based Transcranial Magnetic Stimulation model applied to specific neurodegenerative disorders.
Fanjul-Vélez, Félix; Salas-García, Irene; Ortega-Quijano, Noé; Arce-Diego, José Luis
2015-01-01
Non-invasive treatment of neurodegenerative diseases is particularly challenging in Western countries, where the population age is increasing. In this work, magnetic propagation in human head is modelled by Finite-Difference Time-Domain (FDTD) method, taking into account specific characteristics of Transcranial Magnetic Stimulation (TMS) in neurodegenerative diseases. It uses a realistic high-resolution three-dimensional human head mesh. The numerical method is applied to the analysis of magnetic radiation distribution in the brain using two realistic magnetic source models: a circular coil and a figure-8 coil commonly employed in TMS. The complete model was applied to the study of magnetic stimulation in Alzheimer and Parkinson Diseases (AD, PD). The results show the electrical field distribution when magnetic stimulation is supplied to those brain areas of specific interest for each particular disease. Thereby the current approach entails a high potential for the establishment of the current underdeveloped TMS dosimetry in its emerging application to AD and PD. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.
Auluck, S.K.H.
1982-01-01
A method of treating problems involving strongly nonadiabatic particle orbits in a magnetic field is described for the case when the system is long-lived on the collisional time scale. A canonical distribution P=Z -1 exp-β(H+Ωpsub(theta)) results from maximization of entropy subject to conservation of the Hamiltonian H and canonical angular momentum psub(theta) for an azimuthally symmetric system. By taking the MIGMA problem as an example, the method of determining the constants β,Ω,Z from the average energy, average angular momentum and the total number of particles is illustrated. Associated physical effects are discussed. (author)
Applied Study on Magnetic Nanometer Beads in Preparation of Genechip Samples
陈慧; 高华方; 谢欣; 马雪梅; 杨渝珍
2004-01-01
Summary: A protocol for enrichment and adsorption of karyocyte from whole blood by using magnetic nanometer beads as solid-phase absorbents was presented. The PCR amplification could be accomplished by using the nanobeads with karyocyte as template directly and the PCR products were applied on an oligonucleotide array to do gene typing. The HLA-A PCR amplification system and a small HLA-A oligonucleotide microarray were applied as the platform and an experiment protocol of separating karyocyte from whole blood using the magnetic nanometer beads (Fe2O3) were set up.The experimental conditions were also discussed. It showed that pH level of PBS eluent, Taq enzyme quantity and fragment length of products could influent the amplification results, and the magnetic nano-beads could succeed in sample preparation in microarray to provide a promising way in automatic detection and lab-on-a-chip.
Modeling the current distribution in HTS tapes with transport current and applied magnetic field
Yazawa, T.; Yazawa, Takashi; Rabbers, J.J.; Chevtchenko, O.A.; ten Haken, Bernard; ten Kate, Herman H.J.; Maeda, Hideaki
1999-01-01
A numerical model is developed for the current distribution in a high temperature superconducting (HTS) tape, (Bi,Pb)2Sr2 Ca2Cu3Ox-Ag, subjected to a combination of a transport current and an applied magnetic field. This analysis is based on a two-dimensional formulation of Maxwell's equations in
Serena Fiocchi
2015-04-01
Full Text Available During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.
Kobayashi, Junichi
1979-01-01
The study on the transient flow characteristics in MHD ducts under orthogonal magnetic field is divided into handling two problems: the problem of changing pressure gradient in a uniform orthogonal magnetic field and the problem in which the orthogonal magnetic field itself changes with time. The former has been investigated by many persons, but the latter has not been investigated so often as the former because of its difficulty of handling. In addition, if it is intended to grasp properly the transient flow characteristics in actual MHD ducts, it will be also important that the effects of the electric conductivity of side walls and aspect ratio are clarified. In other words, this paper deals with the problem in which a uniform orthogonal magnetic field is suddenly applied in such manner as Heaviside's step function to or removed from the conductive fluids flowing in sufficiently long rectangular MHD ducts. First, the MHD fundamental equations are described, then they are normalized to give boundary conditions and initial conditions. Next, the transient flow and the derived magnetic field characteristics are numerically analyzed by the difference calculus, and thus the effects of conductor, insulated wall, aspect ratio, Hartmann number, magnetic Prandtl number and others on the above characteristics are clarified. (Wakatsuki, Y.)
Applying torque to the Escherichia coli flagellar motor using magnetic tweezers
van Oene, Maarten M.; Dickinson, Laura E.; Cross, Bronwen; Pedaci, Francesco; Lipfert, Jan; Dekker, Nynke H.
2017-01-01
The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in principle allow the application and active control of a calibrated load torque, to study single flagellar motors in Escherichia coli. We manipulate the external load on the motor by adjusting the magnetic field experienced by a magnetic bead linked to the motor, and we probe the motor’s response. A simple model describes the average motor speed over the entire range of applied fields. We extract the motor torque at stall and find it to be similar to the motor torque at drag-limited speed. In addition, use of the magnetic tweezers allows us to force motor rotation in both forward and backward directions. We monitor the motor’s performance before and after periods of forced rotation and observe no destructive effects on the motor. Our experiments show how magnetic tweezers can provide active and fast control of the external load while also exposing remaining challenges in calibration. Through their non-invasive character and straightforward parallelization, magnetic tweezers provide an attractive platform to study nanoscale rotary motors at the single-motor level. PMID:28266562
Maenchen, J.E.
1983-01-01
The coupling of energy from a high power pulsed accelerator through a long triplate magnetically insulated transmission line (MITL) in vacuum to an annular applied magnetic field insulated extraction ion diode is examined. The narrow power transport window and the wave front erosion of the MITL set stringent impedance history conditions on the diode load. A new ion diode design developed to satisfy these criteria with marginal electron insulation is presented. The LION accelerator is used to provide a positive polarity 1.5 MV, 350 kA, 40 ns FWHM pulse with a 30 kA/ns current rate from a triplate MITL source. A transition converts the triplate into a cylindrical cross section which flares into the ion diode load. Extensive current and voltage measurements performed along this structure and on the extracted ion beam provide conclusive evidence that the self insulation condition of the MITL is maintained in the transition by current loss alone. The ion diode utilizes a radial magnetic field between a grounded cathode annular emission tip and a disk anode. A 50 cm 2 dielectric/metal anode area serves as the ion plasma source subject to direct electron bombardment from the opposing cathode tip under marginal magnetic insulation conditions. The ions extracted cross the radial magnetic field and exit the diode volume as an annular cross section beam of peak current about 100 kA. The diode current gradually converts from the initial electron flow to nearly 100% ion current after 30 ns, coupling 60% of the diode energy into ions
Valence and Magnetic Transitions in YbMn2Ge2-Applied Pressure
Hofmann, M.; Link, P.; Campbell, S.J.; Goncharenko, I.
2005-01-01
Full text: Rare-earth intermetallic compounds containing ytterbium exhibit a wide range of interesting and unusual physical and magnetic properties. This occurs mainly as a result of their mixed valence states (II/III) or changes from one valence state to the other. We have recently determined the magnetic structures of tetragonal YbMn 2 Ge 2 (I4/mmm) by powder neutron diffraction experiments and demonstrated that YbMn 2 Ge 2 has a planar antiferromagnetic structure below T N1 ∼ 510 K with a canted antiferromagnetic structure below T N2 ∼ 185 K. As applied pressure favours changes in the valence character of intermediate valence systems and correspondingly influences the magnetic behaviour, we have investigated the effects of applied pressure on YbMn 2 Ge 2 . Analyses of our in situ neutron diffraction experiments (T=1.5-300 K; p=0-2.7 GPa), reveal a distinct change in magnetic structure and a sharp drop in the a-lattice parameter above ∼ 1.4 GPa with the changes associated with a valence transition. A full account of these effects will be discussed in relation to our current photoelectron spectroscopy measurements of YbMn 2 Ge 2 . (authors)
Partial phase transition and quantum effects in helimagnetic films under an applied magnetic field
El Hog, Sahbi, E-mail: sahbi.el-hog@u-cergy.fr; Diep, H.T., E-mail: diep@u-cergy.fr
2017-05-01
We study the phase transition in a helimagnetic film with Heisenberg spins under an applied magnetic field in the c direction perpendicular to the film. The helical structure is due to the antiferromagnetic interaction between next-nearest neighbors in the c direction. Helimagnetic films in zero field are known to have a strong modification of the in-plane helical angle near the film surfaces. We show that spins react to a moderate applied magnetic field by creating a particular spin configuration along the c axis. With increasing temperature (T), using Monte Carlo simulations we show that the system undergoes a phase transition triggered by the destruction of the ordering of a number of layers. This partial phase transition is shown to be intimately related to the ground-state spin structure. We show why some layers undergo a phase transition while others do not. The Green's function method for non collinear magnets is also carried out to investigate effects of quantum fluctuations. Non-uniform zero-point spin contractions and a crossover of layer magnetizations at low T are shown and discussed. - Highlights: • Monte Carlo simulations were carried out to study a helimagnetic film in a field. • Partial phase transition is found in some layers of the film. • Mechanism leading to the partial disordering is analyzed using the ground state symmetry. • Quantum fluctuations at surface are calculated using the Green's function.
Dynamic regimes in YBCO in applied magnetic field probed by swept frequency microwave measurements
Sarti, S; Silva, E; Giura, M; Fastampa, R; Boffa, M; Cucolo, A M
2004-01-01
We report measurements of the microwave resistivity in YBa 2 Cu 3 O 7-δ (YBCO), in the presence of an applied magnetic field. Measurements are performed as a function of frequency, over a continuum spectrum between 6 and 20 GHz, by means of a Corbino disc geometry. These data allow for a direct identification of different dynamical regimes in the dissipation of YBCO in the presence of an applied magnetic field. While at high temperatures a frequency independent resistivity is observed, at lower temperatures we find a marked frequency dependence. The line in the (H,T) plane at which this change in the dynamical regime is observed is clearly identified and discussed in terms of vortex motion and fluctuational resistivity
Magnetism of soils applied for estimation of erosion at an agricultural land
Kapicka, Ales; Dlouha, Sarka; Grison, Hana; Jaksik, Ondrej; Kodesova, Radka; Petrovsky, Eduard
2013-04-01
A detailed field study on small test site of agricultural land situated in loess region in Southern Moravia (Czech Republic), followed by laboratory analyses, has been carried out in order to test the applicability of magnetic methods in soil erosion estimation. The approach is based on the well-established differentiation in magnetic signature of topsoil from subsoil horizons as a result of "in situ" formation of strongly magnetic iron oxides e.g. (Maher 1986). Introducing a simple tillage homogenization model for predicting magnetic signal after uniform mixing of soil material as a result of tillage and subsequent erosion, Royall (2001) showed that magnetic susceptibility and its frequency dependence can be used to estimate soil loss. Haplic Chernozem is an original dominant soil unit in the wider area, nowadays progressively transformed into different soil units along with intensive soil erosion. The site was characterized by a flat upper part while the middle part, formed by a substantive side valley, is steeper (up to 15°). The side valley represented a major line of concentrated runoff emptying into a colluvial fan (Zadorova et al., 2011; Jaksik et al., 2011). Field measurements of magnetic susceptibility were carried out on regular grid, resulting in 101 data points. Bulk soil material for laboratory investigation was gathered from all grid points. Mass specific magnetic susceptibility χ and its frequency dependence kFD was used to estimate the significance of SP ferrimagnetic particles of pedogenic origin. Thermomagnetic analyses, hysteresis measurement and SEM were used in order to determine dominant ferrimagnetic carriers in top-soil and sub-soil layers. Strong correlation was found between the volume magnetic susceptibility (field measurement) and mass specific magnetic susceptibility measured in the laboratory (R2 = 0.80). At the same time, no correlations were found between the values of kFD and mass specific susceptibility. Values of organic carbon
Longitudinal wave function control in single quantum dots with an applied magnetic field
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-01
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots. PMID:25624018
Longitudinal wave function control in single quantum dots with an applied magnetic field.
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, Jin-An; Gu, Lin; Williams, David A; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
2015-01-27
Controlling single-particle wave functions in single semiconductor quantum dots is in demand to implement solid-state quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the base-apex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electron-hole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electron-hole interaction in single quantum dots.
Nuclear magnetic resonance applied to the study of polymeric nano composites
Tavares, Maria Ines Bruno
2011-01-01
Polymers and nanoparticles based nano composites were prepared by intercalation by solution. The obtained nano composites were characterized mainly by the nuclear magnetic spectroscopy (NMR), applying the analysis of carbon-13 (polymeric matrix), silicon-29 (nanoparticle), and by determination of spin-lattice relaxation of the hydrogen nucleus (T 1 H) (polymeric matrix). The NMR have presented a promising technique in the characterization of the nano charge dispersion in the studied polymeric matrixes.
Electro-magnetostatic homogenization of bianisotropic metamaterials
Fietz, Chris
2012-01-01
We apply the method of asymptotic homogenization to metamaterials with microscopically bianisotropic inclusions to calculate a full set of constitutive parameters in the long wavelength limit. Two different implementations of electromagnetic asymptotic homogenization are presented. We test the homogenization procedure on two different metamaterial examples. Finally, the analytical solution for long wavelength homogenization of a one dimensional metamaterial with microscopically bi-isotropic i...
Perkins, L. John; Logan, B. Grant; Ho, Darwin; Zimmerman, George; Rhodes, Mark; Blackfield, Donald; Hawkins, Steven
2017-10-01
Imposed magnetic fields of tens of Tesla that increase to greater than 10 kT (100 MGauss) under capsule compression may relax conditions for ignition and propagating burn in indirect-drive ICF targets. This may allow attainment of ignition, or at least significant fusion energy yields, in presently-performing ICF targets on the National Ignition Facility that today are sub-marginal for thermonuclear burn through adverse hydrodynamic conditions at stagnation. Results of detailed 2D radiation-hydrodynamic-burn simulations applied to NIF capsule implosions with low-mode shape perturbations and residual kinetic energy loss indicate that such compressed fields may increase the probability for ignition through range reduction of fusion alpha particles, suppression of electron heat conduction and stabilization of higher-mode RT instabilities. Optimum initial applied fields are around 50 T. Off-line testing has been performed of a hohlraum coil and pulsed power supply that could be integrated on NIF; axial fields of 58T were obtained. Given the full plasma structure at capsule stagnation may be governed by 3-D resistive MHD, the formation of closed magnetic field lines might further augment ignition prospects. Experiments are now required to assess the potential of applied magnetic fields to NIF ICF ignition and burn. Work performed under auspices of U.S. DOE by LLNL under Contract DE-AC52-07NA27344.
Ding, Song [College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing, Jiangsu 211816 (China); School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Tian, GuiYun, E-mail: tian280@hotmail.com [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); School of Electrical and Electronic Engineering, Merz Court, University of Newcastle upon Tyne, Newcastle NE1 7RU (United Kingdom); Dobmann, Gerd; Wang, Ping [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China)
2017-01-01
Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness. - Highlights: • The skewness of magnetic Barkhausen noise profile is proposed as a new feature for applied stress determination. • The skewness is sensitive to applied stress and independent to excitation frequency. • Domain wall energy and pinning distance influence the relaxation time of domain wall, which leads to a non-linear behavior of skewness under compressive stress.
Toft, Katrine Nørgaard
The field-induced magnetic structures of ErNi2B2C and TmNi2B2C in are especially interesting because the field suppresses the superconducting order parameter and therefore the magnetic properties can be studied while varying the strength ofsuperconductivity. ErNi2B2C: For magnetic fields along all.......483,0,0). The appearance of the QN phase wasinitially believed to be caused by the suppression of superconductivity. This suppression should make it favorable to create a magnetic order with a Q-vector determined by the maximum in the magnetic susceptibility at the Fermi surface nesting vector QN.The phase diagram...... three symmetry directions, the observed magnetic structures have a period corresponding to the Fermi surface nesting structure. The phase diagrams present all the observed magnetic structures.Two results remain unresolved: 1. When applying the magnetic field along [010], the minority domain (QNB = (0,Q...
Simulation study of magnetically insulated power coupling to the applied-B ion diode
Rosenthal, S.E.
1992-01-01
Power coupling to the applied-B ion diode from magnetically insulated transmission lines is simply described in terms of the voltage-current characteristics of both the diode and the transmission line. The accelerator load line intersects the composite characteristic at the operating voltage and current. Using 2-D PIC simulation, the authors have investigated how modification of either the ion diode or the magnetically insulated transmission line characteristic influences power coupling. Plasma prefill can modify the ion diode characteristic; a partially opened POS in the transmission line upstream of the ion diode is a possible cause of modification of the magnetically insulated transmission line characteristic. It can be useful to consider these two aspects of power coupling separately, but they are actually not independent. A good parameter to characterize the situation is the flow impedance, given by V/(I a 2 I c 2 ) 1/2 . V is the line voltage; I a and I c are the conduction currents flowing through the anode and cathode, respectively. The flow impedance covers a range from one half the vacuum impedance, for saturated magnetically insulated flow, to just below the vacuum impedance, for highly unsaturated flow. As the term ''flow impedance'' implies, low flow impedance coincides with greater electron flow while high flow impedance coincides with less electron flow. The flow impedance is sensitive to both the transmission line and the diode impedance. They show how the two are related, using the flow impedance as a parameter
Experiment and modeling of an atmospheric pressure arc in an applied oscillating magnetic field
Karasik, Max; Roquemore, A. L.; Zweben, S. J.
2000-01-01
A set of experiments are carried out to measure and understand the response of a free-burning atmospheric pressure carbon arc to applied transverse dc and ac magnetic fields. The arc is found to deflect parabolically for the dc field and assumes a growing sinusoidal structure for the ac field. A simple analytic two-parameter fluid model of the arc dynamics is derived, in which the arc response is governed by the arc jet originating at the cathode, with the applied JxB force balanced by inertia. Time variation of the applied field allows evaluation of the parameters individually. A fit of the model to the experimental data gives a value for the average jet speed an order of magnitude below Maecker's estimate of the maximum jet speed [H. Maecker, Z. Phys. 141, 198 (1955)]. An example industrial application of the model is considered. (c) 2000 American Institute of Physics
Cizek, J.; Vrscay, E.R.
1977-01-01
A perturbation procedure based on the use of the SO(4,2) dynamical group, which includes as its most important feature the nonunitary tilting transformation, is applied to the hydrogen atom system in a strong magnetic field and the terms ΔΣ/sub n/ were calculated to 40th order. The difficulty in using this approach is that the series has zero radius of convergence. Nevertheless, the Pade approximant technique may be used for the summation of the series. Surprising accuracy is found for the Pade estimate of the ionization energy. 5 references
Edge-Localized mode control and transport generated by externally applied magnetic perturbations
Joseph, I.
2012-01-01
This article reviews the subject of edge localized mode (ELM) control using externally applied magnetic perturbations and proposes theoretical mechanisms that may be responsible for the induced transport changes. The first question that must be addressed is: what is the structure of magnetic field within the plasma? Although initial hypotheses focused on the possibility of the creation of a region of stochastic field lines at the tokamak edge, drift magnetohydrodynamics theory predicts that magnetic reconnection is strongly suppressed over the region of the pedestal with steep gradients and fast perpendicular rotation. Reconnection can only occur near the location where the perpendicular electron velocity vanishes, and hence the electron impedance nearly vanishes, or near the foot of the pedestal, where the plasma is sufficiently cold and resistive. The next question that must be addressed is: which processes are responsible for the observed transport changes, nonlinearity, turbulence, or stochasticity? Over the pedestal region where ions and electrons rotate in opposite directions relative to the perturbation, the quasilinear Lorentz force decelerates the electron fluid and accelerates the ion fluid. The quasilinear magnetic flutter flux is proportional to the force and produces an outward convective transport that can be significant. Over the pedestal region where the E x B flow and the electrons rotate in opposite directions relative to the perturbation, magnetic islands with a width on the order of the ion gyroradius can directly radiate drift waves. In addition, the combination of quasilinear electron transport and ion viscous transport can lead to a large net particle flux. Since there are many transport mechanisms that may be active simultaneously, it is important to determine which physical mechanisms are responsible for ELM control and to predict the scaling to future devices (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Garcia-Munoz, M; Rodriguez-Ramos, M; Äkäslompolo, S; De Marne, P; Dunne, M G; Dux, R; Fietz, S; Fuchs, C; Geiger, B; Herrmann, A; Hoelzl, M; Kurzan, B; McDermott, R M; Strumberger, E; Evans, T E; Ferraro, N M; Pace, D C; Lazanyi, N; Nocente, M; Shinohara, K
2013-01-01
Phase-space time-resolved measurements of fast-ion losses induced by edge localized modes (ELMs) and ELM mitigation coils have been obtained in the ASDEX Upgrade tokamak by means of multiple fast-ion loss detectors (FILDs). Filament-like bursts of fast-ion losses are measured during ELMs by several FILDs at different toroidal and poloidal positions. Externally applied magnetic perturbations (MPs) have little effect on plasma profiles, including fast-ions, in high collisionality plasmas with mitigated ELMs. A strong impact on plasma density, rotation and fast-ions is observed, however, in low density/collisionality and q 95 plasmas with externally applied MPs. During the mitigation/suppression of type-I ELMs by externally applied MPs, the large fast-ion bursts observed during ELMs are replaced by a steady loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the neutral beam injection (NBI) prompt loss signal without MPs. Multiple FILD measurements at different positions, indicate that the fast-ion losses due to static 3D fields are localized on certain parts of the first wall rather than being toroidally/poloidally homogeneously distributed. Measured fast-ion losses show a broad energy and pitch-angle range and are typically on banana orbits that explore the entire pedestal/scrape-off-layer (SOL). Infra-red measurements are used to estimate the heat load associated with the MP-induced fast-ion losses. The heat load on the FILD detector head and surrounding wall can be up to six times higher with MPs than without 3D fields. When 3D fields are applied and density pump-out is observed, an enhancement of the fast-ion content in the plasma is typically measured by fast-ion D-alpha (FIDA) spectroscopy. The lower density during the MP phase also leads to a deeper beam deposition with an inward radial displacement of ≈2 cm in the maximum of the beam emission. Orbit simulations are used to test different models for 3D
Laser generated hot electron transport in an externally applied magnetic field
Burnett, N.H.; Enright, G.D.
1986-01-01
The authors have investigated the effect of an externally applied DC magnetic field on the generation and transport of hot electrons in CO/sub 2/ laser irradiation of cylindrical targets. The targets used in these studies were 6.3 mm diameter metal rods through which a pulsed current was driven from an external capacitor. Magnetic fields up to 150 kgauss were produced at the target surface. The CO/sub 2/ laser was focused with an f/5 lens resulting in a laser intensity of ≅3 x 10/sup 14/ W/cm/sup 2/ in a 100 μm diameter focal spot. The effect of the external magnetic field on the generation and inward transport of superhot (≥ 100 keV) electrons was studied. Principal diagnostics included a six channel hard x-ray spectrometer, a high energy x-ray pinhole camera, a LiF Laue x-ray spectrograph and a Ross-filtered (W-Ta) pair of x-ray detectors. The latter two diagnostics were designed to detect Au Kα /sub emission at 68.2 keV
Kotani, Yui; Kansha, Yasuki; Ishizuka, Masanori; Tsutsumi, Atsushi
2014-01-01
An experimental investigation into an active magnetic regenerative (AMR) heat circulator based on self-heat recuperation technology, was conducted to evaluate its energy saving potential in heat circulation. In an AMR heat circulator, magnetocaloric effect is applied to recuperate the heat exergy of the process fluid. The recuperated heat can be reused to heat the feed process fluid and realize self-heat recuperation. In this paper, AMR heat circulator has newly been constructed to determine the amount of heat circulated when applied to self-heat recuperation and the energy consumption of the heat circulator. Gadolinium and water was used as the magnetocaloric working material and the process fluid, respectively. The heat circulated amount was determined by measuring the temperature of the process fluid and gadolinium. The net work input for heat circulation was obtained from the magnetizing and demagnetizing forces and the distance travelled by the magnetocaloric bed. The results were compared with the minimum work input needed for heat circulation derived from exergy loss during heat exchange. It was seen that the experimentally obtained value was close to the minimum work input needed for heat circulation. - Highlights: • AMR heat circulator has newly been constructed for experimental evaluation. • Heat circulation in the vicinity of Curie temperature was observed. • Energy consumption of an AMR heat circulator has been measured. • Energy saving for processes near Curie temperature of working material was seen
Janssen, J.L.G.; Paulides, J.J.H.; Lomonova, E.
2010-01-01
This paper presents novel analytical expressions which describe the 3D magnetic field of arbitrarily magnetized triangular-shaped charged surfaces. These versatile expressions are suitable to model triangularshaped permanent magnets and can be expanded to any polyhedral shape. Many applications are
Janssen, J.L.G.; Paulides, J.J.H.; Lomonova, E.
2009-01-01
This paper presents novel analytical expressions which describe the 3D magnetic field of arbitrarily magnetized triangular-shaped charged surfaces. These versatile expressions are suitable to model triangularshaped permanent magnets and can be expanded to any polyhedral shape. Many applications are
BOLSHAKOV V. I.
2017-03-01
Full Text Available Summary. Based on the current understanding of the piles work in clayey soils; that is forming during driving process a compacted core (compacted platform in the pile tip plane and transferring the load from the pile (from the piling foundation not through the pile tip but through the pressed core (compacted platform, the stress in the soil mass by the load applied inside the elastic half-space is determined with the change in the calculated scheme of load transferring to the “homogeneous” soil mass.
Kim, Jong Oh; Kim, Jong Hui; Cho, Wan Sik; Hong, Sung Min; Park, Yun Won
2001-03-01
Magnetic properties of the carbon steel tube which is used as the pipe laying of cooling water in nuclear power plant were measured to research the impediment of thickness diminution of carbon steel tube. Magnetic field distribution of carbon steel tube in the applied magnetic field was simulated by computer program. On the basis of the simulation results, Alnico 5DG and Alnico 5 were selected as the permanent magnets applicable to the carbon steel tube. Sm2Co17 magnet was used to compare the performance of permanent magnets. The experimental apparatus similar to the draining environment of cooling water in nuclear power plant was also manufactured in order to research the impediment of thickness diminution of carbon steel carbon tube
Flow of liquid metals with a transversely applied magnetic field, (8)
Arai, Shigeki; Tomita, Yukio; Sudou, Kouzou
1977-01-01
As one of the researches of liquid metal flow in transversely applied magnetic field concerning the flow in MHD pipes, the influences of the electrical property of channel side walls, aspect ratio, Reynolds number and Hartmann number on laminar and transition flows investigated experimentally are reported in this paper. Mercury flowed in the rectangular ducts, one of which was made with four insulated walls, and another with insulated top and bottom walls and two conductive side walls, with the aspect ratio varying from 8 to 1/8, in the region of relatively low Hartmann number and Reynolds number. The facility, procedure and results of the experiment are explained, and many experimental curves showing the relations among pipe friction coefficient, Hartmann number, Reynolds number, aspect ratio and the property of walls are given. The experimental results show that the Hartmann effect and the aspect ratio effect are evident as the magnetic field is intensified, but the influence by the electric property of walls is little, and three shapes of the curves representing the relation of friction coefficient and Reynolds number are confirmed by this experiment. (auth.)
Vortex configuration in the presence of local magnetic field and locally applied stress
Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena
2017-01-01
Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.
Vortex configuration in the presence of local magnetic field and locally applied stress
Wissberg, Shai; Kremen, Anna; Shperber, Yishai; Kalisky, Beena, E-mail: beena@biu.ac.il
2017-02-15
Highlights: • We discuss different ways to determine vortex configuration using a scanning SQUID. • We determined the vortex configuration by approaching the sample during cooling. • We observed an accumulation of vortices when contact was made with the sample. • We show how we can manipulate local vortex configuration using contact. - Abstract: Vortex configuration is determined by the repulsive interaction, which becomes dominant with increasing vortex density, by the pinning potential, and by other considerations such as the local magnetic fields, currents flowing in the sample, or as we showed recently, by local stress applied on the sample. In this work we describe different ways to control vortex configuration using scanning SQUID microscopy.
Strelniker, Yakov M.; Bergman, David J.; Fleger, Yafit; Rosenbluh, Michael; Voznesenskaya, Anna O.; Vinogradov, Alexey P.; Lagarkov, Andrey N.
2010-01-01
The light transmission through metallic films with different types of nano-structures was studied both theoretically and experimentally. It is shown that the positions of the surface plasmon resonances depend on nano-structural details. Those can be changed from sample to sample or in given sample by applying an external dc electric or magnetic field. The dependence of transmission spectrum on the shape of holes (inclusions) and external fields can be used for manipulation of the light transmission, as well as the polarization of the transmitted light and other optical properties, by external field. Two complementary situations are considered: a metal film with dielectric holes and a dielectric film with metallic islands. A new analytical asymptotic approach for calculation of the optical properties of such plasmonic systems is developed.
Cabral, Leonardo Ribeiro Eulalio; Aguiar, Jose Albino Oliveira de
2002-01-01
Full text: The study of the electromagnetic response of high-T c superconductors is essential for future technological applications. Such materials are hard type II superconductors, where the mixed state (a state characterized by quantized normal flux tubes - also called vortices - immersed in a superconductor phase) occupies most of the phase diagram. Therefore, the electromagnetic properties are dictated by the vortex dynamics in these materials. One has also to consider the presence of structural defects and thermal effects, which turn the vortex dynamics very complex. These difficulties may be overcome throughout a macroscopic description, also known as continuum approximation, of the electromagnetic fields in superconductors, obtained from critical state models and constitutive relations E = E(j) and H = H(B) (where E is the electric field generated by moving vortices, j the current density, B the induction - related to the local density of vortices - and H the reversible magnetic field that is in equilibrium with B). In superconductors with negligible demagnetization factors, such as long cylinders and bars with applied magnetic fields and/or currents along their longer dimensions, the Meissner state and the flux penetration is quite well understood. However, the actual specimen shape plays an important role on the electromagnetic behavior of superconductors. Numerical methods are often employed, since such cases are hard to treat analytically. In this work we studied the electromagnetic response of superconductors with various shapes. The Meissner state is obtained for thin curved strips and long cylinders with arbitrary cross-section, in perpendicular field and with applied currents. The flux penetration is numerically calculated for thin curved strips for the Bean (j c =const.) and the Kim (j c (B) = j c0 /(1 + βB)) models. (author)
Henriksen, Anders Dahl; Wang, Shan Xiang; Hansen, Mikkel Fougt
2015-01-01
Magnetoresistive sensors are widely used for biosensing by detecting the signal from magnetic labels bound to a functionalized area that usually covers the entire sensor structure. Magnetic labels magnetized by a homogeneous applied magnetic field weaken and strengthen the applied field when...
Daboo, C.; Bland, J. A. C.; Hicken, R. J.; Ives, A. J. R.; Baird, M. J.; Walker, M. J.
1993-05-01
We report the magnetization reversal and magnetic anisotropy behavior of ultrathin Co/Cu(111)/Co (dCu=20 and 27 Å) trilayer structures prepared by MBE on a 500-Å Ge/GaAs(110) epilayer. We describe an arrangement in which the magnetization components parallel and perpendicular to the applied field are both determined from longitudinal MOKE measurements. For the samples examined, coherent rotation of the magnetization vector is observed when the magnetic field is applied along the hard in-plane anisotropy axis, with the magnitude of the magnetization vector constant and close to its bulk value. Results of micromagnetic calculations closely reproduce the observed parallel and perpendicular magnetization loops, and yield strong uniaxial magnetic anisotropies in both layers while the interlayer coupling appears to be absent or negligible in comparison with the anisotropy strengths. An absence of antiferromagnetic (AF) coupling has been observed previously [W. F. Egelhoff, Jr. and M. T. Kief, Phys. Rev. B 45, 7795 (1992)] in contrast to recent results, indicating that AF coupling [M. T. Johnson et al., Phys. Rev. Lett. 69, 969 (1992)] and GMR [D. Grieg et al., J. Magn. Magn. Mater. 110, L239 (1992)] can occur in Co/Cu(111)/Co structures grown by MBE, but these properties are sensitively dependent on growth conditions. The absence of coupling in our samples is attributed to the presence of a significant interface roughness induced by the Ge epilayer. The uniaxial anisotropies are assumed to arise from strain or defects induced in the film.
Coaxial twin-shaft magnetic fluid seals applied in vacuum wafer-handling robot
Cong, Ming; Wen, Haiying; Du, Yu; Dai, Penglei
2012-07-01
Compared with traditional mechanical seals, magnetic fluid seals have unique characters of high airtightness, minimal friction torque requirements, pollution-free and long life-span, widely used in vacuum robots. With the rapid development of Integrate Circuit (IC), there is a stringent requirement for sealing wafer-handling robots when working in a vacuum environment. The parameters of magnetic fluid seals structure is very important in the vacuum robot design. This paper gives a magnetic fluid seal device for the robot. Firstly, the seal differential pressure formulas of magnetic fluid seal are deduced according to the theory of ferrohydrodynamics, which indicate that the magnetic field gradient in the sealing gap determines the seal capacity of magnetic fluid seal. Secondly, the magnetic analysis model of twin-shaft magnetic fluid seals structure is established. By analyzing the magnetic field distribution of dual magnetic fluid seal, the optimal value ranges of important parameters, including parameters of the permanent magnetic ring, the magnetic pole tooth, the outer shaft, the outer shaft sleeve and the axial relative position of two permanent magnetic rings, which affect the seal differential pressure, are obtained. A wafer-handling robot equipped with coaxial twin-shaft magnetic fluid rotary seals and bellows seal is devised and an optimized twin-shaft magnetic fluid seals experimental platform is built. Test result shows that when the speed of the two rotational shafts ranges from 0-500 r/min, the maximum burst pressure is about 0.24 MPa. Magnetic fluid rotary seals can provide satisfactory performance in the application of wafer-handling robot. The proposed coaxial twin-shaft magnetic fluid rotary seal provides the instruction to design high-speed vacuum robot.
Utari; Kusumandari; Purnama, B.; Mudasir; Abraha, K.
2016-01-01
We report here on the experimental results of the effect of external magnetic field on the current flow in plane surface of Fe(III)-porphyrin thin layer. The deposition of the Fe(III)- porphyrin thin layer was done by spin coating method. The I-V characteristics of film were measured by means of two point probes. The sample of layer number N = 4 was used to evaluate the magnetic effect on the electrical currents. The ohmic characteristics of the I-V film measurement were obtained. The current decreases when magnetic field is applied to the system and saturated current is obtained at a given magnetic field. Here, the decrease in the current can be attributed to the recombination of carrier charge under the magnetic field. In addition, the magnitude of the saturated current is found to increase with the increase in the voltage used. (paper)
Singh, Akhilesh K.; Barik, Puspendu; Ullrich, Bruno
2014-01-01
We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots
Matsuda, K; Kohara, T; Amitsuka, H; Kuwahara, K; Matsumoto, T
2003-01-01
We have investigated the low-temperature phase appearing below T sub o = 17.5 K in URu sub 2 Si sub 2 by means of sup 2 sup 9 Si nuclear magnetic resonance (NMR) in a pressure range from 0 to 17.5 kbar across the pressure-induced phase transition at P sub c = 15 kbar. At pressures below P sub c , we have observed the sup 2 sup 9 Si NMR lines arising from antiferromagnetic (AF) and paramagnetic (PM) regions in the sample, giving evidence for a phase-separated AF ordering below T sub o. The AF region increases in volume fraction with increasing pressure up to P sub c. In the PM region, the temperature-dependence of the nuclear spin-lattice relaxation rate at Si sites shows a rapid decrease below T sub o , strongly suggesting the occurrence of a phase transition driven by a hidden order parameter. As applied pressure exceeds P sub c , the AF ordering appears uniformly at T sub o throughout the sample. In the pressure range from 0 to 17.5 kbar, the magnitude of the internal field at Si sites in the AF region rema...
Hristov Jordan Y.
2006-01-01
Full Text Available The concept of a variable friction factor of fluid-driven de form able powder beds undergoing fluidization is discussed. The special problem discussed addresses the friction factor and bed permeability relationships of Geldart’s A powders and magnetically stabilized beds in axial fields. Governing equations and scaling relation ships are developed through three approaches (1 Minimization of the pressure drop with respect to the fluid velocity employing the Darcy-Forchheimer equation together with the Richardson-Zaki scaling law, (2 Minimization of the pres sure drop across an equivalent-channel replacing the actual packed beds by a straight pipe with bed-equivalent obstacle of a simple geometry, and (3 Entropy minimization method applied in cases of the Darcy-Forchheimer equation and the equivalent-channel model. Bed-to-surface heat transfer coefficients are commented in the context of the porosity/length scale relationships developed. Both the pressure drop curves developments and phase diagram de signs are illustrated by applications of the intersection of asymptotes technique to beds exhibiting certain degree of cohesion.
Comparison of magnetic nondestructive methods applied for inspection of steel degradation
Takahashi, S.; Kobayashi, S.; Tomáš, Ivan; Dupre, L.; Vértesy, G.
2017-01-01
Roč. 91, Jun (2017), s. 54-60 ISSN 0963-8695 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:68378271 Keywords : magnetic hysteresis * magnetic NDT * steel degradation Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.726, year: 2016
Applied CATIA Secondary Development to Parametric Design of Active Magnetic Bearing
Zhang Li
2016-01-01
Full Text Available Based on the properties of active magnetic bearing, the electromagnetic parameters and structure parameters are analyzed, parametric design method is introduced to study the structure of active magnetic bearing. Through a program personalization process that is in accordance with active magnetic bearing is established. Personalization process aims to build the parametric model of active magnetic bearings and component library by use of CATIA secondary development. Component library is to build assembly model for a multiple degree of freedom magnetic bearing system. Parametric design is a method that provides the direction for its structural design.
Bicheng, LI; Zhonghe, JIANG; Jian, LV; Xiang, LI; Bo, RAO; Yonghua, DING
2018-05-01
Nonlinear magnetohydrodynamic (MHD) simulations of an equilibrium on the J-TEXT tokamak with applied resonant magnetic perturbations (RMPs) are performed with NIMROD (non-ideal MHD with rotation, open discussion). Numerical simulation of plasma response to RMPs has been developed to investigate magnetic topology, plasma density and rotation profile. The results indicate that the pure applied RMPs can stimulate 2/1 mode as well as 3/1 mode by the toroidal mode coupling, and finally change density profile by particle transport. At the same time, plasma rotation plays an important role during the entire evolution process.
Synthesis of Fe3O4 particle-chain microwires in applied magnetic field
Li Fashen; Wang Ying; Wang Tao
2007-01-01
Fe 3 O 4 particle-chain microwires are firstly synthesized under magnetic field by a simple coprecipitation method. The increase of magnetic field caused the lengthening of the wires, and doubled densities of starting solution lead to a halved diameter. It was supposed that the magnetic field gradient and the particular growing process of particles are the main factors of the formation of these microwires. Magnetic hysteresis curves of Fe 3 O 4 microwires were also measured. - Graphical abstract: Fe 3 O 4 particle-chain microwires are firstly synthesized under magnetic field by a simple coprecipitation method. It was supposed that the magnetic field gradient and the particular growing process of particles are the main factors of the formation of these microwires. Magnetic hysteresis curves of Fe 3 O 4 microwires were also measured
Applying the Weighted Horizontal Magnetic Gradient Method to a Simulated Flaring Active Region
Korsós, M. B.; Chatterjee, P.; Erdélyi, R.
2018-04-01
Here, we test the weighted horizontal magnetic gradient (WG M ) as a flare precursor, introduced by Korsós et al., by applying it to a magnetohydrodynamic (MHD) simulation of solar-like flares. The preflare evolution of the WG M and the behavior of the distance parameter between the area-weighted barycenters of opposite-polarity sunspots at various heights is investigated in the simulated δ-type sunspot. Four flares emanated from this sunspot. We found the optimum heights above the photosphere where the flare precursors of the WG M method are identifiable prior to each flare. These optimum heights agree reasonably well with the heights of the occurrence of flares identified from the analysis of their thermal and ohmic heating signatures in the simulation. We also estimated the expected time of the flare onsets from the duration of the approaching–receding motion of the barycenters of opposite polarities before each single flare. The estimated onset time and the actual time of occurrence of each flare are in good agreement at the corresponding optimum heights. This numerical experiment further supports the use of flare precursors based on the WG M method.
Li, Jipeng; Li, Haitao; Zheng, Jun; Zheng, Botian; Huang, Huan; Deng, Zigang
2017-06-01
The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are compared and agreed well with each other. This study combines the experimental and theoretical analyses and provides a deep understanding of the physical phenomenon of the nonlinear vibration and is meaningful for the vibration control of the relevant applications.
Gedik, Engin; Recebli, Ziyaddin; Kurt, Hueseyin; Kecebas, Ali
2012-01-01
The unsteady viscous incompressible and electrically conducting of two-phase fluid flow in circular pipes with external magnetic and electrical field is considered in this present study. Effects of both uniform transverse external magnetic and electrical fields applied perpendicular to the fluid and each other on the two-phase (solid/liquid) unsteady flow is investigated numerically. While iron powders are being used as the first phase of two-phase fluid, pure water was used as the second phase. The system of the derived governing equations, which are based on the Navier-Stokes equations including Maxwell equations, are solved numerically by using Pdex4 function on the Matlab for both phases. The originality of this study is that, in addition to magnetic field, the effect of electrical field on two-phase unsteady fluids is being examined. The magnetic field which is applied on flow decreases the velocity of both phases, whereas the electrical field applied along with magnetic field acted to increase and decrease the velocity values depending on the direction of electrical field. Electrical field alone did not display any impact on two-phase flow. On the other hand, analytical and numerical results are compared and favorable agreements have been obtained. (authors)
Evolution of the magnetic structure of TbRu{sub 2}Al{sub 10} in applied field
White, R., E-mail: Reyner.White@student.adfa.edu.au [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600 (Australia); Hutchison, W.D. [School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600 (Australia); Mizushima, T. [Graduate School of Science and Engineering, University of Toyama, Toyama, 930-8555 (Japan); Studer, A.J. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW, 2232 (Australia)
2016-09-15
TbRu{sub 2}Al{sub 10} is found to undergo two magnetic phase transitions as a function of temperature and three as a function of applied field at low temperature. The Tb{sup 3+} magnetic moments order antiferromagnetically along the c-axis at 15.0(3) K, with an incommensurate sinusoidally modulated structure with a propagation vector of k = (0, 0.759(1), 0). At 6.5(3) K the structure switches to square wave order. Analysis of single crystal TbRu{sub 2}Al{sub 10} has revealed that this square wave structure is altered to a ‘pulse wave’ on application of a 1.30 T magnetic field along the c-axis, with two in fifty of the magnetic moments across the structure changing direction to be aligned parallel with the direction of the field. At 1.85 T a further three moments flip, leading to a duty cycle of 60% and resulting in a total change of one in ten moments from the starting square wave structure. - Highlights: • The magnetic and physical properties of the intermetallic TbRu{sub 2}Al{sub 10} were examined. • TbRu{sub 2}Al{sub 10} was found to order antiferromagnetically at 15.0(3) K. • Neutron powder diffraction revealed sinusoidal magnetic ordering below 15 K. • Single crystal neutron diffraction revealed square wave magnetic order at 2 K. • An applied magnetic field along the c-axis forces the moments into pulse wave order.
Romanovskii, V.R.
2003-01-01
The physical peculiarities of the flux-creep dynamics of low- and high-temperature superconductors placed in external varying magnetic field are studied. The flux-creep problem was studied for the partial penetration state. The proposed analysis was based on the macroscopic description of the flux creep by power and exponential equations of current-voltage characteristics of superconductors. It is shown that during flux creep the screening current penetrates into the superconductor at a finite velocity. Therefore, inside the superconductor a moving boundary of a magnetization region appears like in the critical state model. The time-dependent equations of screening current front have been written. However, unlike the critical state model nontrivial conditions are fulfilled at the moving boundary. They describe the smooth transition of the electromagnetic field induced by external perturbation to the undisturbed ones. A flux-creep distribution of the differential resistivity of the superconductor has been discussed. The performed analysis reveals that it monotonically decreases toward the moving boundary and depends on the magnetic ramp rate. In accordance with these flux-creep conditions the energy dissipation in the superconductors and their magnetic moment depend on the propagation law of the screening current moving boundary. The applicability of the Bean model for describing the flux-creep states is investigated
Restrepo, R.L., E-mail: pfrire@eia.edu.co [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Escuela de Ingeniería de Antioquia-EIA, Envigado (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia); Ungan, F.; Kasapoglu, E. [Department of Physics, Cumhuriyet University, 58140 Sivas (Turkey); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonóma del Estado de Morelos, Ave. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Morales, A.L.; Duque, C.A. [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia-UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2015-01-15
This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties (the linear and third-order nonlinear refractive index and absorption coefficients) in an asymmetric quantum well. The electric field and intense laser field are applied along the growth direction of the asymmetric quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the asymmetric quantum well, the effective mass approximation and the method of envelope wave function are used. The asymmetric quantum well is constructed by using different aluminium concentrations in both right and left barriers. The confinement in the quantum well is changed drastically by either the effect of electric and magnetic fields or by the application of intense laser field. The optical properties are calculated using the compact density matrix approach. The results show that the effect of the intense laser field competes with the effects of the electric and magnetic fields. Consequently, peak position shifts to lower photon energies due to the effect of the intense laser field and it shifts to higher photon energies by the effects of electric and magnetic fields. In general, it is found that the concentration of aluminum, electric and magnetic fields and intense laser field are external agents that modify the optical responses in the asymmetric quantum well.
Huang Yimin; Hassam, A.B.
2003-01-01
The ideal magnetohydrodynamics stability of a Dean flow plasma supported against centrifugal forces by an axial magnetic field is studied. Only axisymmetric perturbations are allowed for simplicity. Two distinct but coupled destabilization mechanisms are present: flow shear (magnetorotational instability) and magnetic buoyancy (Parker instability). It is shown that the flow shear alone is likely insufficient to destabilize the plasma, but the magnetic buoyancy instability could occur. For a high Mach number (M S ), high Alfven Mach number (M A ) system with M S M A > or approx. πR/a (R/a is the aspect ratio), the Parker instability is unstable for long axial wavelength modes. Implications for the centrifugal confinement approach to magnetic fusion are also discussed
Iterative Spherical Downward Continuation Applied to Magnetic and Gravitational Data from Satellite
Sebera, J.; Šprlák, M.; Novák, P.; Bezděk, Aleš; Valko, M.
2014-01-01
Roč. 35, č. 4 (2014), s. 941-958 ISSN 0169-3298 R&D Projects: GA MŠk LH13071 Grant - others:ESA(XE) AO/1-6367/10/NL/AF Institutional support: RVO:67985815 Keywords : downward continuation * Earth's gravitational and magnetic field * poisson integral equation Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 3.447, year: 2014
M. Kiyasatfar
2011-01-01
Full Text Available In the present study, simulation of steady state, incompressible and fully developed laminar flow has been conducted in a magneto hydrodynamic (MHD pump. The governing equations are solved numerically by finite-difference method. The effect of the magnetic flux density and current on the flow and temperature distributions in a MHD pump is investigated. The obtained results showed that controlling the flow and the temperature is possible through the controlling of the applied current and the magnetic flux. Furthermore, the effects of the magnetic flux density and current on entropy generation in MHD pump are considered. Our presented numerical results are in good agreement with the experimental data showed in literature.
B. Curé
2012-01-01
The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...
Evrard, P; Jacquinot, J; Leloup, C; Poffe, J -P; Waelbroeck, F
1966-07-01
Collisions of plasma puffs, whose characteristics (density and velocity) were varied in a broad domain are studied in a homogeneous longitudinal magnetic field. It has been verified that the puffs meet head on. We show that collisions of dense (n{sub i} {>=} 4.10{sup 14} cm{sup -3}) and relatively slow (V{sub 0} {<=} 10{sup 7} cm. s) puffs are 'efficient', i.e. the initial kinetic energies of the puffs are converted into thermal energy of the ions in the resulting plasma. Faster and less dense puffs interact little: incomplete conversion of kinetic into thermal energy. The limit between efficient and inefficient collisions corresponds to that which is expected from the test particle model. The slowing down of our puffs is thus ensured mainly by particle-particle interactions. The use of electric probes and the examination of the evolution of the plasma produced by the collision show that this plasma does not exhibit any rapid radial-motion. In the magnetic bottle of Bille-en-tete A (mirror ratio 4000/2000- G), the collision of two low density puffs leads to the capture of one liter of plasma with a density n{sub i} {approx} 2,10{sup 13} cm{sup -3} and an ionic temperature T{sub i} {approx} 10{sup 6}. The e-folding time of the plasma diamagnetism reaches 50 to 150 {mu}s; no flute instabilities are detected. The T{sub i} evolution was measured by the Doppler broadening of the 4680 angstrom line of the He{sup +} (added to the injected D{sup +} in the proportion of 5 per cent and the relative evolution of n{sub i} by the intensity of the spectral continuum. T{sub i} decreases rapidly, reaches 5.10{sup 5} to 10{sup 5} deg. K respectively 15 and 120 {mu}s after the maximum of the collision diamagnetic signal. n{sub i} increases slowly, 25 per cent during the first 100 {mu}s after the collision. The presence of cold plasma beyond the mirrors of the bottles allows one to justify the energy losses (thermal conductivity) and the apparent stability of the plasma column
Mechanical Homogenization Increases Bacterial Homogeneity in Sputum
Stokell, Joshua R.; Khan, Ammad
2014-01-01
Sputum obtained from patients with cystic fibrosis (CF) is highly viscous and often heterogeneous in bacterial distribution. Adding dithiothreitol (DTT) is the standard method for liquefaction prior to processing sputum for molecular detection assays. To determine if DTT treatment homogenizes the bacterial distribution within sputum, we measured the difference in mean total bacterial abundance and abundance of Burkholderia multivorans between aliquots of DTT-treated sputum samples with and without a mechanical homogenization (MH) step using a high-speed dispersing element. Additionally, we measured the effect of MH on bacterial abundance. We found a significant difference between the mean bacterial abundances in aliquots that were subjected to only DTT treatment and those of the aliquots which included an MH step (all bacteria, P = 0.04; B. multivorans, P = 0.05). There was no significant effect of MH on bacterial abundance in sputum. Although our results are from a single CF patient, they indicate that mechanical homogenization increases the homogeneity of bacteria in sputum. PMID:24759710
Controlling magnetism of MoS2 sheets by embedding transition-metal atoms and applying strain.
Zhou, Yungang; Su, Qiulei; Wang, Zhiguo; Deng, Huiqiu; Zu, Xiaotao
2013-11-14
Prompted by recent experimental achievement of transition metal (TM) atoms substituted in MoS2 nanostructures during growth or saturating existing vacancies (Sun et al., ACS Nano, 2013, 7, 3506; Deepak et al., J. Am. Chem. Soc., 2007, 129, 12549), we explored, via density functional theory, the magnetic properties of a series of 3d TM atoms substituted in a MoS2 sheet, and found that Mn, Fe, Co, Ni, Cu and Zn substitutions can induce magnetism in the MoS2 sheet. The localizing unpaired 3d electrons of TM atoms respond to the introduction of a magnetic moment. Depending on the species of TM atoms, the substituted MoS2 sheet can be a metal, semiconductor or half-metal. Remarkably, the applied elastic strain can be used to control the strength of the spin-splitting of TM-3d orbitals, leading to an effective manipulation of the magnetism of the TM-substituted MoS2 sheet. We found that the magnetic moment of the Mn- and Fe-substituted MoS2 sheets can monotonously increase with the increase of tensile strain, while the magnetic moment of Co-, Ni-, Cu- and Zn-substituted MoS2 sheets initially increases and then decreases with the increase of tensile strain. An instructive mechanism was proposed to qualitatively explain the variation of magnetism with elastic strain. The finding of the magnetoelastic effect here is technologically important for the fabrication of strain-driven spin devices on MoS2 nanostructures, which allows us to go beyond the current scope limited to the spin devices within graphene and BN-based nanostructures.
Preferred Orientation of Rare Earth (RE)-Doped Alumina Crystallites by an Applied Magnetic Field
2016-06-01
within a magnetic field. The micro -texture of the aligned ceramic was analyzed by X-ray diffraction and the Lotgering factor calculated. Gd:Al2O3...was found to have approximately the same response as Yb:Al2O3 despite inducing different magnetic moments. 15. SUBJECT TERMS grain alignment, micro ...cutoff energy of 800 eV was used for the electronic wave function in conjunction with sampling the Brillouin zone with a 2 × 2 × 2 Monkhorst-Pack grid
Quantum Magnetism Applied to the Iron-Pnictides and Rare Earth Pyrochlores
Applegate, Ryan
This dissertation presents computational studies of two families of magnetic materials of significant current interest. The iron pnictides are new high temperature superconductors with interesting parent compound antiferromagnetism. The rare earth pyrochlore material Yb2Ti2O7 is a candidate quantum spin ice. The magnetic and structural phases of individual iron pnictides have both many common features and material specific differences. In an attempt to unify these behaviors as instances of a larger theoretical picture, we use Monte Carlo simulations of a two-dimensional Hamiltonian with coupled Heisenberg-spin and Ising-orbital degrees of freedom. We introduce spin-space and single-ion anisotropies and study the finite temperature transitions in our model. We develop a phase diagram and propose that the interplay of spin and orbital physics in the presence of anisotropy could explain how material details affect the transitions of the pnictide materials. Nuclear magnetic resonance (NMR) can study magnetic materials via the hyperfine interaction and the coupling between the nuclear moment and the field produced by the samples local moment environment. Recent measurements suggest that Zn doped BaFe2As2 may have quantum fluctuations about the striped phase that produce a distribution of fields at As nuclear sites. The non-magnetic ion Zn replaces Fe and can be treated as an impurity which can be studied by a zero-temperature Ising Series expansion method. We propose a Heisenberg-like J1a-J 1b-J2 model which has small ferromagnetic exchanges along the b axis and strong antiferromagnetic exchanges along the a axis. In our impurity model we find that the magnetic moments are everywhere reduced by quantum fluctuations, except on the nearest neighbor site in the AFM direction. We suggest that the presented impurity model may provide an explanation for the experimental measurements. Based on a recently proposed quantum spin ice model, we use numerical linked cluster (NLC
Duque, C.A.; Kasapoglu, E.; Sakiroglu, S.; Sari, H.; Soekmen, I.
2011-01-01
In this work the effects of intense laser on the electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga 1-x Al x As quantum wells are studied under, applied electric and magnetic field. The electric field is applied along the growth direction of the quantum well whereas the magnetic field has been considered to be in-plane. The calculations were performed within the density matrix formalism with the use of the effective mass and parabolic band approximations. The intense laser effects are included through the Floquet method, by modifying the confining potential associated to the heterostructure. Results are presented for the nonlinear optical absorption, the nonlinear optical rectification and the resonant peak of these two optical processes. Several configurations of the dimensions of the quantum well, the applied electric and magnetic fields, and the incident intense laser radiation have been considered. The outcome of the calculation suggests that the nonlinear optical absorption and optical rectification are non-monotonic functions of the dimensions of the heterostructure and of the external perturbations considered in this work.
An experimental comparison of path planning techniques applied to micro-sized magnetic agents
Scheggi, Stefano; Misra, Sarthak; Haliyo, S.; Sill, A.; Regnier, S.; Fatikow, S.
2016-01-01
Micro-sized agents can be used in applications suchas microassembly, micromanipulation, and minimally invasive surgeries. Magnetic agents such as paramagnetic microparticles can be controlled to deliver pharmaceutical agents to difficult-toaccess regions within the human body. In order to
Applied metrology in the production of superconducting model magnets for particle accelerators
Ferradas Troitino, Jose [CERN; Bestmann, Patrick [CERN; Bourcey, Nicolas [CERN; Carlon Zurita, Alejandro [CERN; Cavanna, Eugenio [ASG Supercond., Genova; Ferracin, Paolo [CERN; Ferradas Troitino, Salvador [CERN; Holik, Eddie Frank [Fermilab; Izquierdo Bermudez, Susana [CERN; Lackner, Friedrich [CERN; Löffler, Christian [CERN; Maury, Gregory [CERN; Perez, Juan Carlos [CERN; Savary, Frederic [CERN; Semeraro, Michela [CERN; Vallone, Giorgio [CERN
2017-12-22
The production of superconducting magnets for particle accelerators involves high precision assemblies and tight tolerances, in order to achieve the requirements for their appropriate performance. It is therefore essential to have a strict control and traceability over the geometry of each component of the system, and also to be able to compensate possible inherent deviations coming from the production process.
Ab initio screening methodology applied to the search for new permanent magnetic materials
Drebov, Nedko; Gumbsch, Peter; Elsässer, Christian; Martinez-Limia, Alberto; Kunz, Lothar; Gola, Adrien; Eckl, Thomas; Shigematsu, Takashi
2013-01-01
In this paper a computational high-throughput screening (HTS) approach to the search for alternative permanent magnetic materials is presented. Systems considered for a start are binary intermetallic compounds composed of rare-earth (RE) and transition metal (TM) elements. With the tight-binding-linear muffin-tin-orbital-atomic-sphere-approximation (TB-LMTO-ASA) method of density functional theory (DFT) a variety of RE–TM intermetallic phases is investigated and their magnetic properties are obtained at rather low computational costs. Next, interstitial elements such as boron, carbon and nitrogen in these phases are considered. For promising candidate phases with high and stable spontaneous ferromagnetic polarization, the calculated local magnetic moments and exchange coupling parameters, as obtained from TB-LMTO-ASA calculations, are then used for Monte Carlo simulations to identify candidates with sufficiently high Curie temperatures (T c ). Finally, magnetocrystalline anisotropy constants (K 1 ) of the most promising candidate phases are calculated with accurate, potential-shape-unrestricted DFT calculations using the Vienna ab initio simulation package. The computational HTS procedure is illustrated by results for a selection of hard-magnetic RE–TM phases like RETM 5 , RE 2 TM 17 and RE 2 TM 14 B. (paper)
Energy Moment Method Applied to Nuclear Quadrupole Splitting of Nuclear Magnetic Resonance Lines
Frank, V
1962-01-01
Expressions giving the sum of the energy values, raised to the second and third power, for a nucleus interacting with a static magnetic field and a static electric field gradient are derived. Several applications of this method for obtaining the values of the components of the electric field...
Applying torque to the Escherichia coli flagellar motor using magnetic tweezers
van Oene, M.M.; Dickinson, L.E.; Cross, B.; Pedaci, F.; Lipfert, J.; Dekker, N.H.
2017-01-01
The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in
A novel Planar Magnetic Bearing and Motor Configuration applied in a Positioning Stage
Molenaar, A.
2000-01-01
This thesis presents the design and implementation of a fully contactless high precision magnetically suspended position stage with large planar stroke. This stage is the first which is suitable for practical application in vacuum. The underlying electromechanical working principles, modelling and
Ribeiro, M. Margarida; Farinha, Sara; Costa, Joana; Mauricio, J. Cruz; O' Neill, J. Goyri
2011-01-01
Purpose: The Magnetization Transfer (MT) obtained by applying a pre-saturation pulse is, in Magnetic Resonance Imaging (MRI), a technique that allows for additional enhancement of lesions on conventional T1 images after contrast administration. This study aims to assess the effectiveness of the technique measuring how MT could improve image quality and diagnostic values through the enhancement of lesions. Methods: Thirteen T1-weighted spin-echo (SE) sequences, obtained by the 1.5 T system after contrast media injection, were analyzed with and without MT. The contrast-to-noise ratio (CNR), as well as the signal-to-noise ratio (SNR) variables were compared in all sequences, according to the reference structures: lateral ventricles, white matter, gray matter, caudate nucleus and internal capsule. The MT ratio average was calculated using the ANOVA scale in order to assess the CNR and the magnetization transfer effect (MTE) for the different lesions and for both sequences (with and without MT). For the assessment of the flow artifact, clinical experts applied a Likert scale with 5 points. Results: For CNR values, the differences between conventional and MT-pulsed images were significant (Student t testp 0,05). Conclusion: In identical conditions of acquisition, the MT does not produce significant differences in the enhancement of lesions, however, it allows a greater capacity to detect the multiple sclerosis plaques, comparing structures around basal nucleus versus gray and white matter.
Functionality and homogeneity.
2011-01-01
Functionality and homogeneity are two of the five Sustainable Safety principles. The functionality principle aims for roads to have but one exclusive function and distinguishes between traffic function (flow) and access function (residence). The homogeneity principle aims at differences in mass,
Tang, Yundong [College of Physics and Information Engineering, Fuzhou University, Fuzhou 350116 (China); Flesch, Rodolfo C.C. [Departamento de Automação e Sistemas, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Jin, Tao, E-mail: jintly@fzu.edu.cn [College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350116 (China)
2017-06-15
Highlights: • The effects of blood vessels on temperature field distribution are investigated. • The critical thermal energy of hyperthermia is computed by the Finite Element Analysis. • A treatment method is proposed by using the MNPs with low Curie temperature. • The cooling effects due to the blood flow can be controlled. - Abstract: Magnetic hyperthermia ablates tumor cells by absorbing the thermal energy from magnetic nanoparticles (MNPs) under an external alternating magnetic field. The blood vessels (BVs) within tumor region can generally reduce treatment effectiveness due to the cooling effect of blood flow. This paper aims to investigate the cooling effect of BVs on the temperature field of malignant tumor regions using a complex geometric model and numerical simulation. For deriving the model, the Navier-Stokes equation for blood flow is combined with Pennes bio-heat transfer equation for human tissue. The effects on treatment temperature caused by two different BV distributions inside a mammary tumor are analyzed through numerical simulation under different conditions of flow rate considering a Fe-Cr-Nb-B alloy, which has low Curie temperature ranging from 42 °C to 45 °C. Numerical results show that the multi-vessel system has more obvious cooling effects than the single vessel one on the temperature field distribution for hyperthermia. Besides, simulation results show that the temperature field within tumor area can also be influenced by the velocity and diameter of BVs. To minimize the cooling effect, this article proposes a treatment method based on the increase of the thermal energy provided to MNPs associated with the adoption of low Curie temperature particles recently reported in literature. Results demonstrate that this approach noticeably improves the uniformity of the temperature field, and shortens the treatment time in a Fe-Cr-Nb-B system, thus reducing the side effects to the patient.
Tang, Yundong; Flesch, Rodolfo C. C.; Jin, Tao
2017-06-01
Magnetic hyperthermia ablates tumor cells by absorbing the thermal energy from magnetic nanoparticles (MNPs) under an external alternating magnetic field. The blood vessels (BVs) within tumor region can generally reduce treatment effectiveness due to the cooling effect of blood flow. This paper aims to investigate the cooling effect of BVs on the temperature field of malignant tumor regions using a complex geometric model and numerical simulation. For deriving the model, the Navier-Stokes equation for blood flow is combined with Pennes bio-heat transfer equation for human tissue. The effects on treatment temperature caused by two different BV distributions inside a mammary tumor are analyzed through numerical simulation under different conditions of flow rate considering a Fe-Cr-Nb-B alloy, which has low Curie temperature ranging from 42 °C to 45 °C. Numerical results show that the multi-vessel system has more obvious cooling effects than the single vessel one on the temperature field distribution for hyperthermia. Besides, simulation results show that the temperature field within tumor area can also be influenced by the velocity and diameter of BVs. To minimize the cooling effect, this article proposes a treatment method based on the increase of the thermal energy provided to MNPs associated with the adoption of low Curie temperature particles recently reported in literature. Results demonstrate that this approach noticeably improves the uniformity of the temperature field, and shortens the treatment time in a Fe-Cr-Nb-B system, thus reducing the side effects to the patient.
Heterotic strings on homogeneous spaces
Israel, D.; Kounnas, C.; Orlando, D.; Petropoulos, P.M.
2005-01-01
We construct heterotic string backgrounds corresponding to families of homogeneous spaces as exact conformal field theories. They contain left cosets of compact groups by their maximal tori supported by NS-NS 2-forms and gauge field fluxes. We give the general formalism and modular-invariant partition functions, then we consider some examples such as SU(2)/U(1)∝S 2 (already described in a previous paper) and the SU(3)/U(1) 2 flag space. As an application we construct new supersymmetric string vacua with magnetic fluxes and a linear dilaton. (Abstract Copyright [2005], Wiley Periodicals, Inc.)
Lin Zhikai; Zhao Lancai
1999-08-01
During the past two decades, medical diagnostic imaging technique has achieved dramatic development such as CT, MRI, PET, DSA and so on. The most striking examples of them are the application of X ray computerized tomography (CT) and magnetic resonance imaging in the field of medical diagnosis. It can be predicted that magnetic resonance imaging (MRI) will definitely have more widespread prospects of applications and play more and more important role in clinical diagnosis looking forward to the development of image diagnostic technique for 21 st century. The authors also present the measuring methods for some parameters. The parameters described can be used for reference by clinical diagnosticians, operators on MRI and medical physicists who engages in image quality assurance (QA) and control (QC) in performing MRI acceptance test and routine test
Lagrangian neoclassical transport theory applied to the region near the magnetic axis
Satake, Shinsuke [The Graduate Univ. for Advanced Studies, Dept. of Fusion Science, Toki, Gifu (Japan); Okamoto, Masao; Sugama, Hideo [National Inst. for Fusion Science, Toki, Gifu (Japan)
2002-06-01
Neoclassical transport theory around the magnetic axis of a tokamak is studied, in which relatively wide ''potato'' orbits play an important role in transport. Lagrangian formulation of transport theory, which has been investigated to reflect finiteness of guiding-center orbit widths to transport equations, is developed in order to analyze neoclassical transport near the axis for a low-collisionality plasma. The treatment of self-collision term in Lagrangian formulation is revised to retain momentum conservation property of it. With directly reflecting the orbital properties of all the types of orbits in calculation, the ion thermal conductivity around the axis is found to decrease than from that predicted by conventional neoclassical theory. This result supports recent numerical simulations which show the reduction of thermal conductivity near the magnetic axis. (author)
Lagrangian neoclassical transport theory applied to the region near the magnetic axis
Satake, Shinsuke; Okamoto, Masao; Sugama, Hideo
2002-01-01
Neoclassical transport theory around the magnetic axis of a tokamak is studied, in which relatively wide 'potato' orbits play an important role in transport. Lagrangian formulation of transport theory, which has been investigated to reflect finiteness of guiding-center orbit widths to transport equations, is developed in order to analyze neoclassical transport near the axis for a low-collisionality plasma. The treatment of self-collision term in Lagrangian formulation is revised to retain momentum conservation property of it. By directly reflecting the orbital properties of all the types of orbits in calculation, the ion thermal conductivity around the axis is found to decrease from that predicted by conventional neoclassical theory. This result supports recent numerical simulations which show the reduction of thermal conductivity near the magnetic axis
Magnetic Resonance Techniques Applied to the Diagnosis and Treatment of Parkinson’s Disease
de Celis Alonso, Benito; Hidalgo-Tobón, Silvia S.; Menéndez-González, Manuel; Salas-Pacheco, José; Arias-Carrión, Oscar
2015-01-01
Parkinson’s disease (PD) affects at least 10 million people worldwide. It is a neurodegenerative disease, which is currently diagnosed by neurological examination. No neuroimaging investigation or blood biomarker is available to aid diagnosis and prognosis. Most effort toward diagnosis using magnetic resonance (MR) has been focused on the use of structural/anatomical neuroimaging and diffusion tensor imaging (DTI). However, deep brain stimulation, a current strategy for treating PD, is guided by MR imaging (MRI). For clinical prognosis, diagnosis, and follow-up investigations, blood oxygen level-dependent MRI, DTI, spectroscopy, and transcranial magnetic stimulation have been used. These techniques represent the state of the art in the last 5 years. Here, we focus on MR techniques for the diagnosis and treatment of Parkinson’s disease. PMID:26191037
Lagrangian neoclassical transport theory applied to the region near the magnetic axis
Satake, Shinsuke; Okamoto, Masao; Sugama, Hideo
2002-06-01
Neoclassical transport theory around the magnetic axis of a tokamak is studied, in which relatively wide ''potato'' orbits play an important role in transport. Lagrangian formulation of transport theory, which has been investigated to reflect finiteness of guiding-center orbit widths to transport equations, is developed in order to analyze neoclassical transport near the axis for a low-collisionality plasma. The treatment of self-collision term in Lagrangian formulation is revised to retain momentum conservation property of it. With directly reflecting the orbital properties of all the types of orbits in calculation, the ion thermal conductivity around the axis is found to decrease than from that predicted by conventional neoclassical theory. This result supports recent numerical simulations which show the reduction of thermal conductivity near the magnetic axis. (author)
Homogenization of Mammalian Cells.
de Araújo, Mariana E G; Lamberti, Giorgia; Huber, Lukas A
2015-11-02
Homogenization is the name given to the methodological steps necessary for releasing organelles and other cellular constituents as a free suspension of intact individual components. Most homogenization procedures used for mammalian cells (e.g., cavitation pump and Dounce homogenizer) rely on mechanical force to break the plasma membrane and may be supplemented with osmotic or temperature alterations to facilitate membrane disruption. In this protocol, we describe a syringe-based homogenization method that does not require specialized equipment, is easy to handle, and gives reproducible results. The method may be adapted for cells that require hypotonic shock before homogenization. We routinely use it as part of our workflow to isolate endocytic organelles from mammalian cells. © 2015 Cold Spring Harbor Laboratory Press.
S100 lathe bed pulse generator applied to pulsed nuclear magnetic resonance
Cernicchiaro, G.R.C.; Rudge, M.G.; Albuquerque, M.P.
1989-01-01
The project and construction of four channel pulse generator in the S100 standard plate and its control software for microcomputer are described. The microcomputer has total control on the pulse generator, which has seven programable parameters, defining the position of four pulses and the width for the three first ones. This pulse generator is controlled by a software developed in c language, and is used in pulsed nuclear magnetic resonance experiences. (M.C.K.) [pt
Gomez R, F.; Ondarza R, R.
2004-01-01
An analytic model is presented for the description of the motion of a charged particle in the interaction of an elliptically electromagnetic pulse polarized propagating along a static and homogeneous external magnetic field in a plasma starting from the force equation. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary and modulated width by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radioactive effects. (Author)
Gomez R, F.; Ondarza R, R.
2004-01-01
An analytical model for the description of the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized propagating along of a static and homogeneous external magnetic field in a plasma starting from the force equation is presented. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary amplitude and modulated by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radiative effects. (Author)
Flow of liquid metals in curved channels under a transversely applied magnetic field, (3)
Arai, Shigeki; Tomita, Yukio; Sudou, Kouzou.
1979-01-01
With the development of electromagnetic pumps in nuclear, metallurgical and casting industries, investigations of not only laminar flow but also transient and turbulent flows in magnetohydrodynamic (MHD) channels are the matters of much concern. However, it is no exaggeration to say that there was no investigation of transient and turbulent flows in curved MHD channels. In this report, the influences of Reynolds number, Hartmann number, radius of curvature and aspect ratio on the coefficient of friction in transient and turbulent flow channels are discussed. In transient flow region, the curve representing the product of the coefficient of channel friction in curved channels and Reynolds number has no clear transition point in the flow of comparatively small Hartmann number. However, as the intensity of magnetic field is increased, the curve transfers to the transition due to the effect of suppressing secondary flow, and if the magnetic field is further increased, it was found that it approached the crisis-free type transition. In turbulent flow region, the coefficient of channel friction can be expressed approximately by the empirical equation given first in this report. Also the effect of magnetic field on the turbulent flow in curved channels can be explained by using Hartmann effect, turbulence suppression effect, and the effect of suppressing secondary flow based on Lorentz's force. (Wakatsuki, Y.)
The magnetostriction in a superconductor-magnet system under non-uniform magnetic field
Li, Xueyi; Jiang, Lang; Wu, Hao [Key Laboratory of Mechanics on Disaster and Environment in Western China attached to the Ministry of Education of China, Lanzhou University, Lanzhou, Gansu 730000 (China); Gao, Zhiwen, E-mail: gaozhw@lzu.edu.cn [Department of Mechanics and Engineering Science, College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou, Gansu 730000 (China)
2017-03-15
Highlights: • We studied firstly magnetostriction in HTS under non-uniform magnetic field. • The superconductors may be homogeneous and nonhomogeneous. • The magnetostrictions response of the HTS is sensitive to the critical current density and amplitude of the applied magnetic field. • The magnetostriction of nonhomogeneous HTS is larger than that of homogeneous HTS. - Abstract: This paper describes a numerical model to examine the magnetostriction of bulk high-temperature superconductor (HTS) under non-uniform magnetic field in conjunction with finite element analysis. Through this model, the magnetostriction of homogeneous and nonhomogeneous HTS can be implemented under non-uniform magnetic field. Further, the effects of critical current density, applied field frequency and amplitude are also considered. The computational study can provide a fundamental mechanistic understanding the effects of non-uniform magnetic field on magnetostriction of HTS.
Rhodes, Scott; Perez, Juan; Elborai, Shihab; Lee, Se-Hee; Zahn, Markus
2005-01-01
New flows and instabilities are presented for a ferrofluid drop contained in glass Hele-Shaw cells with simultaneously applied in-plane clockwise rotating and DC axial uniform magnetic fields. When a ferrofluid drop is stressed by a uniform DC axial magnetic field, up to ∼250 G in 0.9-1.4 mm gap Hele-Shaw cells, the drop forms a labyrinth pattern. With subsequent application of an in-plane uniform rotating magnetic field, up to ∼100 G rms at frequency 20-40 Hz, smooth spirals form from viscous shear due to ferrofluid flow. If the rotating magnetic field is applied first, the drop is held together without a labyrinth. Gradual increase of the DC axial magnetic field, to a critical magnetic field value, results in an abrupt phase transformation from a large drop to many small discrete droplets. A preliminary minimum magnetization and surface energy analysis is presented to model the phase transformation
Sancho-Juan, O.; Cantarero, A.; Garro, N.; Cros, A. [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain); Martinez-Criado, G.; Salome, M.; Susini, J. [ESRF, Polygone Scientifique Louis Neel, 6 rue Jules Horowitz, 38000 Grenoble (France); Olguin, D. [Dept. de Fisica, CINVESTAV-IPN, 07300 Mexico D.F. (Mexico); Dhar, S.; Ploog, K. [Paul Drude Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany)
2006-06-15
We have studied by X-ray absorption spectroscopy the local environment of Mn in highly homogeneous Ga{sub 1-x}Mn{sub x}N (0.06
Vácha, M
1997-10-01
While investigating and describing interactions among living organisms and magnetic fields (MFs) it is imperative to lay great emphasis on independent reproducibility of published experimental results. Mutual confrontation of existing theoretical models with reliable data obtained under comparable conditions can aid gradual mapping of this hitherto badly organized and understood discipline of biology. The objective of our experiment, based on analysing extracardiac pulsations of the pupae of Tenebrio molitor under the influence of a MF, was to verify published data on allegedly accelerated development induced by a MF employing a different procedure. The obtained data are in agreement with a hypothesis of increased pupal metabolism during the period of MF activity. Furthermore, some dependence on the age of the pupae cannot be ruled out.
Direct measurements of the magnetic entropy change
Nielsen, Kaspar Kirstein; Neves Bez, Henrique; von Moos, Lars
2015-01-01
An experimental device that can accurately measure the magnetic entropy change, Δs, as a function of temperature, T, and magnetic field, H, is presented. The magnetic field source is in this case a set of counter-rotating concentric Halbach-type magnets, which produce a highly homogeneous applied...... to the ambient are negligible in terms of the calorimetric determination of the magnetic entropy change, while the losses cannot be ignored when correcting for the actual sample temperature. We apply the device to two different types of samples; one is commercial grade Gd, i.e., a pure second-order phase...
The SPH homogeneization method
Kavenoky, Alain
1978-01-01
The homogeneization of a uniform lattice is a rather well understood topic while difficult problems arise if the lattice becomes irregular. The SPH homogeneization method is an attempt to generate homogeneized cross sections for an irregular lattice. Section 1 summarizes the treatment of an isolated cylindrical cell with an entering surface current (in one velocity theory); Section 2 is devoted to the extension of the SPH method to assembly problems. Finally Section 3 presents the generalisation to general multigroup problems. Numerical results are obtained for a PXR rod bundle assembly in Section 4
Homogeneity of Inorganic Glasses
Jensen, Martin; Zhang, L.; Keding, Ralf
2011-01-01
Homogeneity of glasses is a key factor determining their physical and chemical properties and overall quality. However, quantification of the homogeneity of a variety of glasses is still a challenge for glass scientists and technologists. Here, we show a simple approach by which the homogeneity...... of different glass products can be quantified and ranked. This approach is based on determination of both the optical intensity and dimension of the striations in glasses. These two characteristic values areobtained using the image processing method established recently. The logarithmic ratio between...
Complexity Index as Applied to Magnetic Resonance: Study Based on a Scale of Relative Units
Capelastegui, A.; Villanua, J.
2003-01-01
To analyze the merit and repercussions of measuring magnetic resonance (MR) activity in units of radiological activity, and of using complexity index (CI) as an activity indicator. We studied the MR activity of Osatek, Inc. during an 8-year period (1994-2001). We measured this activity both in number of MR procedures performed and in units of radiological activity, such units being based on the scale of relative units published in the Radiological Services Administration Guidelines published by the Spanish Society or Medical Radiology. We calculated the annual complexity index, this being a quotient between the number of MR procedures performed and corresponding value in units of radiological activity. We also analyzed factors that can have an impact on the CI: type of exploration and power of the equipment's magnetic field. The CL stayed practically stable during the first 4 years of the study, while it increased during the second 4 years. There exists a direct relationship between this increase and the percentage of explorations that we term complex (basically, body-and angio-MR). The increasing complexity of MR studies in the last years is evident from a consideration of CI. MR productivity is more realistically expressed in units of radiological activity than in number of procedures performed by any one center. It also allows for making external comparisons. CI is a useful indicator that can be utilized as an administrative tool. (Author) 13 refs
Jing, C.; Konecny, R.; Antipov, S.; Chang, C.; Gold, S. H.; Schoessow, P.; Kanareykin, A.; Gai, W.
2013-01-01
Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures in many accelerator applications
Koch, Stephan
2009-01-01
This thesis is concerned with the numerical simulation of electromagnetic fields in the quasi-static approximation which is applicable in many practical cases. Main emphasis is put on higher-order finite element methods. Quasi-static applications can be found, e.g., in accelerator physics in terms of the design of magnets required for beam guidance, in power engineering as well as in high-voltage engineering. Especially during the first design and optimization phase of respective devices, numerical models offer a cheap alternative to the often costly assembly of prototypes. However, large differences in the magnitude of the material parameters and the geometric dimensions as well as in the time-scales of the electromagnetic phenomena involved lead to an unacceptably long simulation time or to an inadequately large memory requirement. Under certain circumstances, the simulation itself and, in turn, the desired design improvement becomes even impossible. In the context of this thesis, two strategies aiming at the extension of the range of application for numerical simulations based on the finite element method are pursued. The first strategy consists in parallelizing existing methods such that the computation can be distributed over several computers or cores of a processor. As a consequence, it becomes feasible to simulate a larger range of devices featuring more degrees of freedom in the numerical model than before. This is illustrated for the calculation of the electromagnetic fields, in particular of the eddy-current losses, inside a superconducting dipole magnet developed at the GSI Helmholtzzentrum fuer Schwerionenforschung as a part of the FAIR project. As the second strategy to improve the efficiency of numerical simulations, a hybrid discretization scheme exploiting certain geometrical symmetries is established. Using this method, a significant reduction of the numerical effort in terms of required degrees of freedom for a given accuracy is achieved. The
Benchmarking monthly homogenization algorithms
Venema, V. K. C.; Mestre, O.; Aguilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertacnik, G.; Szentimrey, T.; Stepanek, P.; Zahradnicek, P.; Viarre, J.; Müller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratianni, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Prohom Duran, M.; Likso, T.; Esteban, P.; Brandsma, T.
2011-08-01
The COST (European Cooperation in Science and Technology) Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME) has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative). The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random break-type inhomogeneities were added to the simulated datasets modeled as a Poisson process with normally distributed breakpoint sizes. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide) trend was added. Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including (i) the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii) the error in linear trend estimates and (iii) traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve precipitation data
A low noise photoelectric signal acquisition system applying in nuclear magnetic resonance gyroscope
Lu, Qilin; Zhang, Xian; Zhao, Xinghua; Yang, Dan; Zhou, Binquan; Hu, Zhaohui
2017-10-01
The nuclear magnetic resonance gyroscope serves as a new generation of strong support for the development of high-tech weapons, it solves the core problem that limits the development of the long-playing seamless navigation and positioning. In the NMR gyroscope, the output signal with atomic precession frequency is detected by the probe light, the final crucial photoelectric signal of the probe light directly decides the quality of the gyro signal. But the output signal has high sensitivity, resolution and measurement accuracy for the photoelectric detection system. In order to detect the measured signal better, this paper proposed a weak photoelectric signal rapid acquisition system, which has high SNR and the frequency of responded signal is up to 100 KHz to let the weak output signal with high frequency of the NMR gyroscope can be detected better.
Gebhart, T. E.; Martinez-Rodriguez, R. A.; Baylor, L. R.; Rapp, J.; Winfrey, A. L.
2017-08-01
To produce a realistic tokamak-like plasma environment in linear plasma device, a transient source is needed to deliver heat and particle fluxes similar to those seen in an edge localized mode (ELM). ELMs in future large tokamaks will deliver heat fluxes of ˜1 GW/m2 to the divertor plasma facing components at a few Hz. An electrothermal plasma source can deliver heat fluxes of this magnitude. These sources operate in an ablative arc regime which is driven by a DC capacitive discharge. An electrothermal source was configured with two pulse lengths and tested under a solenoidal magnetic field to determine the resulting impact on liner ablation, plasma parameters, and delivered heat flux. The arc travels through and ablates a boron nitride liner and strikes a tungsten plate. The tungsten target plate is analyzed for surface damage using a scanning electron microscope.
Silva, R.J. da; Chavez-Guajardo, A.E.; Medina-llamas, J.C.; Alcaraz-Espinoza, J.J.; Melo, C.P. de [Universidade Federal de Pernambuco (UFPE), PE (Brazil)
2016-07-01
Full text: Plasmid DNA (pDNA), a special kind of nucleic acid usually found in bacteria, is a small molecule physically distinct from chromosomal DNA that can replicate independently. This genetic material has been used in a wide set of biotechnological methodologies, such as genetic engineering, production of recombinant drugs and gene therapy, among others. In all these applications, the extraction and purification of pDNA appears as a crucial step. In this work, we describe the synthesis of a polyaniline and maghemite (PANI/?-Fe2O3) magnetic nanocomposite (MNC) and its use in a new Escherichia coli (E. coli) pDNA extraction and purification protocol. We have used transmission electron microscopy (TEM), UV-Vis spectroscopy, infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS) and magnetic measurements to characterize the MNC, which was synthesized through an emulsion polymerization method. The yield, purity and quality of the pDNA extracted by using our proposed MNC protocol were evaluated through UV-Vis, agarose gel electrophoreses and PCR techniques, respectively. After comparing our results to those obtained by use of a commercial kit (Promega Wizard Plus SV Minipreps), we suggest that the novel protocol here proposed appears as a competitive alternative methodology. Not only the purification step can be completed within only 10 min, but the high adsorption capacity of the MNC results in pDNA yields that are almost twice the best values obtained by using the commercial kit. Hence, this new MNC methodology can be of general interest and find widespread use in different types of biomedical applications. (author)
Sanchez Lopez, Hector [Universidad de Oriente, Santiago de Cuba (Cuba). Centro de Biofisica Medica]. E-mail: hsanchez@cbm.uo.edu.cu
2001-08-01
This work describes an alternative algorithm of Simulated Annealing applied to the design of the main magnet for a Magnetic Resonance Imaging machine. The algorithm uses a probabilistic radial base neuronal network to classify the possible solutions, before the objective function evaluation. This procedure allows reducing up to 50% the number of iterations required by simulated annealing to achieve the global maximum, when compared with the SA algorithm. The algorithm was applied to design a 0.1050 Tesla four coil resistive magnet, which produces a magnetic field 2.13 times more uniform than the solution given by SA. (author)
Zamani, A.; Setareh, F.; Azargoshasb, T.; Niknam, E.
2018-03-01
A wide variety of semiconductor nanostructures have been fabricated and studied experimentally and alongside theoretical investigations show the great role they have in new generation opto-electronic devices. However, mathematical modeling provide important information due to their definitive goal of predicting features and understanding of such structures' behavior under different circumstances. Hence, in the current work, the effects of applied magnetic field, temperature and dimensions of the structure on the electromagnetically induced transparency (EIT) of a GaAs quantum ring are studied while both Rashba and Dresselhaus spin-orbit interactions (SOI) are taken into account. The Schrödinger equation is solved in cylindrical coordinate with axial symmetry and in order to study the EIT, the imaginary (absorption) and real (refractive index) parts of susceptibility as well as the group velocity of the probe light pulse are investigated. The absorption and refractive index plots show that, for a specific frequency of probe field the absorption vanishes and refractive index becomes unity (known as EIT) while around such frequency the group index is positive (sub-luminal probe propagation) and for higher and lower frequencies it alters to negative (super-luminal probe propagation). The numerical results reveal that the EIT frequency, transparency window and sub(super)-luminal frequency intervals shift as we change applied magnetic field, temperature and also the structure dimensions.
Homogenized description and retrieval method of nonlinear metasurfaces
Liu, Xiaojun; Larouche, Stéphane; Smith, David R.
2018-03-01
A patterned, plasmonic metasurface can strongly scatter incident light, functioning as an extremely low-profile lens, filter, reflector or other optical device. When the metasurface is patterned uniformly, its linear optical properties can be expressed using effective surface electric and magnetic polarizabilities obtained through a homogenization procedure. The homogenized description of a nonlinear metasurface, however, presents challenges both because of the inherent anisotropy of the medium as well as the much larger set of potential wave interactions available, making it challenging to assign effective nonlinear parameters to the otherwise inhomogeneous layer of metamaterial elements. Here we show that a homogenization procedure can be developed to describe nonlinear metasurfaces, which derive their nonlinear response from the enhanced local fields arising within the structured plasmonic elements. With the proposed homogenization procedure, we are able to assign effective nonlinear surface polarization densities to a nonlinear metasurface, and link these densities to the effective nonlinear surface susceptibilities and averaged macroscopic pumping fields across the metasurface. These effective nonlinear surface polarization densities are further linked to macroscopic nonlinear fields through the generalized sheet transition conditions (GSTCs). By inverting the GSTCs, the effective nonlinear surface susceptibilities of the metasurfaces can be solved for, leading to a generalized retrieval method for nonlinear metasurfaces. The application of the homogenization procedure and the GSTCs are demonstrated by retrieving the nonlinear susceptibilities of a SiO2 nonlinear slab. As an example, we investigate a nonlinear metasurface which presents nonlinear magnetoelectric coupling in near infrared regime. The method is expected to apply to any patterned metasurface whose thickness is much smaller than the wavelengths of operation, with inclusions of arbitrary geometry
Newhouse, Vernon L
1975-01-01
Applied Superconductivity, Volume II, is part of a two-volume series on applied superconductivity. The first volume dealt with electronic applications and radiation detection, and contains a chapter on liquid helium refrigeration. The present volume discusses magnets, electromechanical applications, accelerators, and microwave and rf devices. The book opens with a chapter on high-field superconducting magnets, covering applications and magnet design. Subsequent chapters discuss superconductive machinery such as superconductive bearings and motors; rf superconducting devices; and future prospec
Homogenization approach in engineering
Babuska, I.
1975-10-01
Homogenization is an approach which studies the macrobehavior of a medium by its microproperties. Problems with a microstructure play an essential role in such fields as mechanics, chemistry, physics, and reactor engineering. Attention is concentrated on a simple specific model problem to illustrate results and problems typical of the homogenization approach. Only the diffusion problem is treated here, but some statements are made about the elasticity of composite materials. The differential equation is solved for linear cases with and without boundaries and for the nonlinear case. 3 figures, 1 table
Design of SC solenoid with high homogeneity
Yang Xiaoliang; Liu Zhong; Luo Min; Luo Guangyao; Kang Qiang; Tan Jie; Wu Wei
2014-01-01
A novel kind of SC (superconducting) solenoid coil is designed to satisfy the homogeneity requirement of the magnetic field. In this paper, we first calculate the current density distribution of the solenoid coil section through the linear programming method. Then a traditional solenoid and a nonrectangular section solenoid are designed to produce a central field up to 7 T with a homogeneity to the greatest extent. After comparison of the two solenoid coils designed in magnet field quality, fabrication cost and other aspects, the new design of the nonrectangular section of a solenoid coil can be realized through improving the techniques of framework fabrication and winding. Finally, the outlook and error analysis of this kind of SC magnet coil are also discussed briefly. (authors)
Maslovsky, D.; Levitt, B.; Mauel, M. E.
2003-01-01
Interchange instabilities excited by energetic electrons trapped by a magnetic dipole nonlinearly saturate and exhibit complex, coherent spectral characteristics and frequency sweeping [H. P. Warren and M. E. Mauel, Phys. Plasmas 2, 4185 (1995)]. When monochromatic radio frequency (rf) fields are applied in the range of 100-1000 MHz, the saturation behavior of the interchange instability changes dramatically. For applied fields of sufficient intensity and pulse-length, coherent interchange fluctuations are suppressed and frequency sweeping is eliminated. When rf fields are switched off, coherent frequency sweeping reappears. Since low frequency interchange instabilities preserve the electron's first and second adiabatic invariants, these observations can be interpreted as resulting from nonlinear resonant wave-particle interactions described within a particle phase-space, (ψ,φ), comprised of the third adiabatic invariant and the azimuthal angle. Self-consistent numerical simulation is used to study (1) the nonlinear development of the instability, (2) the radial mode structure of the interchange instability, and (3) the suppression of frequency sweeping. When the applied rf heating is modeled as an 'rf collisionality', the simulation reproduces frequency sweeping suppression and suggests an explanation for the observations that is consistent with Berk and co-workers [H. L. Berk et al., Phys. Plasmas 6, 3102 (1999)
Azanza, M.J.
1997-01-01
A very high number of data, obtained from molecular and cell biology experimental work, show that living beings are sensitive to either the static magnetic fields (SMF) or the electromagnetic fields in the extremely low frequency (ELF) range (1). Considering the question of the intensity range of the SMF applied for clinical diagnosis, we have made experiments by applying SMF (0,3-0,7 T) directly to neurons. We have shown that there exist a neuron magneto sensitivity explained as a result of the diamagnetism of the phospholipid and protein molecules of the lipid bilayer plasma membrane. This diamagnetism is working together with electric dipolar interactions (a mixed up interaction coined as super diamagnetism) and binded membrane Ca''2+ cooperative coulomb explosion, which in turn operate Ca''2+ -dependent-K''+ membrane channels (2,3). The specific intrinsic metabolic characteristics of the neurons populations explain two types of responses: either a variation in the firing frequency (increases or decreases) or a decrease in the spikes amplitude. This second effect is explained by the inhibition of the Na''+ -K''+-ATP-ase ionic pumps, inactivated by the same superdiamagnetims mechanism. We show in this paper the dependence of the frequency and amplitude changes, of the electrophysiological activity of the neurons, with the intensity of the applied SMF. (Author) 30 refs
Dynamics of homogeneous nucleation
Toxværd, Søren
2015-01-01
The classical nucleation theory for homogeneous nucleation is formulated as a theory for a density fluctuation in a supersaturated gas at a given temperature. But molecular dynamics simulations reveal that it is small cold clusters which initiates the nucleation. The temperature in the nucleating...
Homogeneous bilateral block shifts
Douglas class were classified in [3]; they are unilateral block shifts of arbitrary block size (i.e. dim H(n) can be anything). However, no examples of irreducible homogeneous bilateral block shifts of block size larger than 1 were known until now.
Tignanelli, H. L.; Vazquez, R. A.; Mostaccio, C.; Gordillo, S.; Plastino, A.
1990-11-01
RESUMEN. Presentamos una metodologia de analisis de la homogeneidad a partir de la Teoria de la Informaci6n, aplicable a muestras de datos observacionales. ABSTRACT:Standard concepts that underlie Information Theory are employed in order design a methodology that enables one to analyze the homogeneity of a given data sample. Key : DATA ANALYSIS
Homogeneous Poisson structures
Shafei Deh Abad, A.; Malek, F.
1993-09-01
We provide an algebraic definition for Schouten product and give a decomposition for any homogenenous Poisson structure in any n-dimensional vector space. A large class of n-homogeneous Poisson structures in R k is also characterized. (author). 4 refs
Zhong, Chongquan; Lin, Yaoyao
2017-11-01
In this work, a model reference adaptive control-based estimated algorithm is proposed for online multi-parameter identification of surface-mounted permanent magnet synchronous machines. By taking the dq-axis equations of a practical motor as the reference model and the dq-axis estimation equations as the adjustable model, a standard model-reference-adaptive-system-based estimator was established. Additionally, the Popov hyperstability principle was used in the design of the adaptive law to guarantee accurate convergence. In order to reduce the oscillation of identification result, this work introduces a first-order low-pass digital filter to improve precision regarding the parameter estimation. The proposed scheme was then applied to an SPM synchronous motor control system without any additional circuits and implemented using a DSP TMS320LF2812. For analysis, the experimental results reveal the effectiveness of the proposed method.
Nguyen, H; Herman, L [Universite de Paris Sorbonne, Lab. de Recherche Physique, 75 - Paris (France); Drawin, H W [Association Euratom-CEA, Centre d' Etudes Nucleaires de Fontenay-aux-Roses, 92 (France)
1966-07-01
The profiles of the hydrogen lines have been calculated taking into account the intermolecular electric field, the electronic collisions, and an external homogeneous magnetic field in which the plasma is imbedded. We considered electron densities N within the range 10{sup 15} {<=} N {<=} 10{sup 18} cm{sup -3} and magnetic field strengths < 1,2 10{sup 5} gauss. These values cover practically most of the experimental conditions in which one is interested in the present state of research. In the present paper we only present the numerical results for the lines Ly-{alpha}, Ly-{beta} and H-{alpha}. For very small magnetic fields our calculated line profiles coincide with the pure Stark profiles recently calculated by GRIEM, KOLB and SHEN (1960). With increasing magnetic fields, important deviations appear. The essential parameters for these deviations are, firstly: the direction of observation with regard to the direction of the magnetic field, and secondly: the ratio between the Zeeman splitting in a magnetic field only and the Stark splitting due to the mean intermolecular electric field. Experimental line profiles have been obtained using a linear discharge tube surrounded by an induction coil, the comparison of tie theoretical profiles with the experimental ones shows a satisfying agreement. The results for the lines originating from higher principal quantum numbers are actually exploited and will be communicated soon. (author) [French] Les profils des raies de l'hydrogene ont ete calcules en tenant compte des collisions electroniques, du champ electrique intermoleculaire et d'un champ magnetique uniforme exterieur. Nous avons considere des concentrations electroniques comprises entre 10{sup 15} cm{sup -3} et 10{sup 18} cm{sup -3} et des champs magnetiques inferieurs ou egaux a 1,2 10{sup 5} gauss. Ces valeurs couvrent pratiquement toutes les conditions experimentales qui ont un interet a l'heure actuelle. Dans le present travail, nous ne donnons que des resultats
Homogenization scheme for acoustic metamaterials
Yang, Min
2014-02-26
We present a homogenization scheme for acoustic metamaterials that is based on reproducing the lowest orders of scattering amplitudes from a finite volume of metamaterials. This approach is noted to differ significantly from that of coherent potential approximation, which is based on adjusting the effective-medium parameters to minimize scatterings in the long-wavelength limit. With the aid of metamaterials’ eigenstates, the effective parameters, such as mass density and elastic modulus can be obtained by matching the surface responses of a metamaterial\\'s structural unit cell with a piece of homogenized material. From the Green\\'s theorem applied to the exterior domain problem, matching the surface responses is noted to be the same as reproducing the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost exactly with numerical simulations and experiments and the scheme\\'s validity is constrained by the number of dominant surface multipoles instead of the usual long-wavelength assumption. In particular, the validity extends to the full band in one dimension and to regimes near the boundaries of the Brillouin zone in two dimensions.
Nuclear resonance apparatus including means for rotating a magnetic field
Sugimoto, H.
1983-01-01
A nuclear magnetic resonance apparatus including magnet apparatus for generating a homogeneous static magnetic field between its magnetic poles, shims of a magnetic substance mounted on the magnetic poles to apply a first gradient magnetic field intensity distribution in a direction orthogonal as to the direction of line of magnetic force of the static magnetic field, gradient magnetic field generating electromagnetic apparatus for generating a second gradient magnetic field having a gradient magnetic field intensity distribution in superimposition with the static magnetic field and for changing the magnetic field gradient of the first gradient magnetic field, an oscillator for generating an oscillating output having a frequency corresponding to the nuclear magnetic resonance condition of an atomic nucleus to be measured, a coil wound around a body to be examined for applying the output of said oscillator as electromagnetic waves upon the body, a receiver for detecting the nuclear magnetic resonance signals received by the coil, a gradient magnetic field controller making a magnetic field line equivalent to the combined gradient magnetic fields and for rotating the line along the section of the body to be examined by controlling said gradient magnetic field generating electromagnetic apparatus and devices for recording the nuclear magnetic resonance signals, for reconstructing the concentration distribution of the specific atomic nuclei in the section of the body, and a display unit for depicting the result of reconstruction
Homogeneous group, research, institution
Francesca Natascia Vasta
2014-09-01
Full Text Available The work outlines the complex connection among empiric research, therapeutic programs and host institution. It is considered the current research state in Italy. Italian research field is analyzed and critic data are outlined: lack of results regarding both the therapeutic processes and the effectiveness of eating disorders group analytic treatment. The work investigates on an eating disorders homogeneous group, led into an eating disorder outpatient service. First we present the methodological steps the research is based on including the strong connection among theory and clinical tools. Secondly clinical tools are described and the results commented. Finally, our results suggest the necessity of validating some more specifical hypothesis: verifying the relationship between clinical improvement (sense of exclusion and painful emotions reduction and specific group therapeutic processes; verifying the relationship between depressive feelings, relapses and transition trough a more differentiated groupal field.Keywords: Homogeneous group; Eating disorders; Institutional field; Therapeutic outcome
Homogeneous turbulence dynamics
Sagaut, Pierre
2018-01-01
This book provides state-of-the-art results and theories in homogeneous turbulence, including anisotropy and compressibility effects with extension to quantum turbulence, magneto-hydodynamic turbulence and turbulence in non-newtonian fluids. Each chapter is devoted to a given type of interaction (strain, rotation, shear, etc.), and presents and compares experimental data, numerical results, analysis of the Reynolds stress budget equations and advanced multipoint spectral theories. The role of both linear and non-linear mechanisms is emphasized. The link between the statistical properties and the dynamics of coherent structures is also addressed. Despite its restriction to homogeneous turbulence, the book is of interest to all people working in turbulence, since the basic physical mechanisms which are present in all turbulent flows are explained. The reader will find a unified presentation of the results and a clear presentation of existing controversies. Special attention is given to bridge the results obta...
Homogen Mur - et udviklingsprojekt
Dahl, Torben; Beim, Anne; Sørensen, Peter
1997-01-01
Mølletorvet i Slagelse er det første byggeri i Danmark, hvor ydervæggen er udført af homogene bærende og isolerende teglblokke. Byggeriet viser en række af de muligheder, der både med hensyn til konstruktioner, energiforhold og arkitektur ligger i anvendelsen af homogent blokmurværk.......Mølletorvet i Slagelse er det første byggeri i Danmark, hvor ydervæggen er udført af homogene bærende og isolerende teglblokke. Byggeriet viser en række af de muligheder, der både med hensyn til konstruktioner, energiforhold og arkitektur ligger i anvendelsen af homogent blokmurværk....
Homogenization of resonant chiral metamaterials
Andryieuski, Andrei; Menzel, C.; Rockstuhl, Carsten
2010-01-01
Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as, e.g., propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size...... an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all....
Z. W., Lin; J. G., Zhu; Y. G., Guo; J. J., Zhong; W. Y., Yu; Centre for Electrical Machines and Power Electronics, Faculty of Engineering, University of Technology; Centre for Electrical Machines and Power Electronics, Faculty of Engineering, University of Technology; Centre for Electrical Machines and Power Electronics, Faculty of Engineering, University of Technology; Centre for Electrical Machines and Power Electronics, Faculty of Engineering, University of Technology; Baosteel Group Shanghai Iron and Steel Research Institute
2007-01-01
Soft magnetic composite (SMC), as one of soft magnetic materials, is being used increasingly in electromagnetic devices due to its magnetic isotropy, high electrical resistivity and easy formation. This paper presents the magnetic field distribution at the compressing surface of SMC by means of magneto-optical imaging technique. It is found that the flux density is non-uniform inside the sample, even within one particle region. Although there are interactions between neighbouring particles, t...
Figueroa-O’Farrill, José; Ungureanu, Mara
2016-01-01
Motivated by the search for new gravity duals to M2 branes with N>4 supersymmetry — equivalently, M-theory backgrounds with Killing superalgebra osp(N|4) for N>4 — we classify (except for a small gap) homogeneous M-theory backgrounds with symmetry Lie algebra so(n)⊕so(3,2) for n=5,6,7. We find that there are no new backgrounds with n=6,7 but we do find a number of new (to us) backgrounds with n=5. All backgrounds are metrically products of the form AdS 4 ×P 7 , with P riemannian and homogeneous under the action of SO(5), or S 4 ×Q 7 with Q lorentzian and homogeneous under the action of SO(3,2). At least one of the new backgrounds is supersymmetric (albeit with only N=2) and we show that it can be constructed from a supersymmetric Freund-Rubin background via a Wick rotation. Two of the new backgrounds have only been approximated numerically.
Figueroa-O’Farrill, José [School of Mathematics and Maxwell Institute for Mathematical Sciences,The University of Edinburgh,James Clerk Maxwell Building, The King’s Buildings, Peter Guthrie Tait Road,Edinburgh EH9 3FD, Scotland (United Kingdom); Ungureanu, Mara [Humboldt-Universität zu Berlin, Institut für Mathematik,Unter den Linden 6, 10099 Berlin (Germany)
2016-01-25
Motivated by the search for new gravity duals to M2 branes with N>4 supersymmetry — equivalently, M-theory backgrounds with Killing superalgebra osp(N|4) for N>4 — we classify (except for a small gap) homogeneous M-theory backgrounds with symmetry Lie algebra so(n)⊕so(3,2) for n=5,6,7. We find that there are no new backgrounds with n=6,7 but we do find a number of new (to us) backgrounds with n=5. All backgrounds are metrically products of the form AdS{sub 4}×P{sup 7}, with P riemannian and homogeneous under the action of SO(5), or S{sup 4}×Q{sup 7} with Q lorentzian and homogeneous under the action of SO(3,2). At least one of the new backgrounds is supersymmetric (albeit with only N=2) and we show that it can be constructed from a supersymmetric Freund-Rubin background via a Wick rotation. Two of the new backgrounds have only been approximated numerically.
Young, I.R.
1984-01-01
A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)
HOMOGENEOUS NUCLEAR POWER REACTOR
King, L.D.P.
1959-09-01
A homogeneous nuclear power reactor utilizing forced circulation of the liquid fuel is described. The reactor does not require fuel handling outside of the reactor vessel during any normal operation including complete shutdown to room temperature, the reactor being selfregulating under extreme operating conditions and controlled by the thermal expansion of the liquid fuel. The liquid fuel utilized is a uranium, phosphoric acid, and water solution which requires no gus exhaust system or independent gas recombining system, thereby eliminating the handling of radioiytic gas.
Deng, Shaoqiang
2012-01-01
"Homogeneous Finsler Spaces" is the first book to emphasize the relationship between Lie groups and Finsler geometry, and the first to show the validity in using Lie theory for the study of Finsler geometry problems. This book contains a series of new results obtained by the author and collaborators during the last decade. The topic of Finsler geometry has developed rapidly in recent years. One of the main reasons for its surge in development is its use in many scientific fields, such as general relativity, mathematical biology, and phycology (study of algae). This monograph introduc
Homogeneity spoil spectroscopy
Hennig, J.; Boesch, C.; Martin, E.; Grutter, R.
1987-01-01
One of the problems of in vivo MR spectroscopy of P-31 is spectra localization. Surface coil spectroscopy, which is the method of choice for clinical applications, suffers from the high-intensity signal from subcutaneous muscle tissue, which masks the spectrum of interest from deeper structures. In order to suppress this signal while maintaining the simplicity of surface coil spectroscopy, the authors introduced a small sheet of ferromagnetically dotted plastic between the surface coil and the body. This sheet destroys locally the field homogeneity and therefore all signal from structures around the coil. The very high reproducibility of the simple experimental procedure allows long-term studies important for monitoring tumor therapy
Toft, K.N
2004-01-01
The field-induced magnetic structures of ErNi{sub 2}B{sub 2}C and TmNi{sub 2}B{sub 2}C in are especially interesting because the field suppresses the superconducting order parameter and therefore the magnetic properties can be studied while varying the strength of superconductivity. ErNi{sub 2}B{sub 2}C: For magnetic fields along all three symmetry directions, the observed magnetic structures have a period corresponding to the Fermi surface nesting structure. The phase diagrams present all the observed magnetic structures. Two results remain unresolved: 1. When applying the magnetic field along [010], the minority domain (Q{sub N}{sup B} = (0,Q,0) with moments perpendicular to the field) shows no signs of hysteresis. I expected it to be a meta-stable state, which would be gradually suppressed by a magnetic field, and when decreasing the field it would not reappear until some small field of approximately 0.1 T. 2. When the field is applied along [110], the magnetic structure rotates a small angle of 0.5 degrees away from the symmetry direction. TmNi{sub 2}B{sub 2}C: A magnetic field applied in the [100] direction suppresses the zero field magnetic structure Q{sub F} = (0.094,0.094,0) (T{sub N} = 1.6 K), in favor of the Fermi surface nesting structure Q{sub N} = (0.483,0,0). The appearance of the Q{sub N} phase was initially believed to be caused by the suppression of superconductivity. This suppression should make it favorable to create a magnetic order with a Q-vector determined by the maximum in the magnetic susceptibility at the Fermi surface nesting vector Q{sub N}. The phase diagram for the magnetic structures is presented, however several properties of the Q{sub N} magnetic structure cannot be explained within any known models. Quadrupolar ordering is suggested as a possible candidate for explaining these features of the Q{sub N} structure. (au)
Amir Nikbakhsh
2017-12-01
Full Text Available One of the most important ways to reduce fossil fuel consumption and consequently reduce greenhouse gases and environmental pollution is the use of renewable energies such as water, sun, wind, etc. One of the most efficient ways to take advantages of the shallow flowing waters such as rivers and fountains in electrical power generation is the use of hydrodynamic screw in the direction of water flow. The design of the generator for this application results in environmental dangers decrease. On the other hand, it provides some part of electrical energy required for human beings. Generators in hydrodynamic renewable energy system ought to have features such as high efficiency, power density and reliability as well as low volume. Among various generators, the permanent magnet synchronous generator (PMSG meets these requirements very well. In this paper, first, analytical calculations and the design process of PMSG were explained. Then, the ant colony optimization (ACO was used for the optimization of design quantities. PMSG design optimization increased in efficiency and decreased in volume. By improving these two parameters in the designed PMSG, it gets very suitable to be used in hydrodynamic renewable energy system. Finally, the results of the optimized design of PMSG were validated through simulation of it in Maxwell software and applying finite element analysis (FEA. Also the final results have been compared to similar experimental researches results.
Performance of a shallow-focus applied-magnetic-field diode for ion-beam-transport experiments
Young, F.C.; Neri, J.M.; Ottinger, P.F. [Naval Research Lab., Washington, DC (United States); Rose, D.V. [JAYCOR, Vienna (Vatican City State, Holy See); Jones, T.G.; Oliver, B.V.
1997-12-31
An applied-magnetic-field ion diode to study the transport of intense ion beams for light-ion inertial confinement fusion is being operated on the Gamble II generator at NRL. A Large-area (145-cm{sup 2}), shallow-focusing diode is used to provide the ion beam required for self-pinched transport (SPT) experiments. Experiments have demonstrated focusing at 70 cm for 1.2-MV, 40-kA protons. Beyond the focus, the beam hollows out consistent with 20--30 mrad microdivergence. The effect of the counter-pulse B-field on altering the ion-beam trajectories and improving the focus has been diagnosed with a multiple-pinhole-camera using radiachromic film. This diagnostic is also used to determine the radial and azimuthal uniformity of ion emission at the anode for different B-field conditions. Increasing the diode voltage to 1.5 MV and optimizing the ion current are planned before initiating SPT experiments. Experiments to measure the spatial beam profile at focus, i.e., the SPT channel entrance, are in progress. Results are presented.
Hansen, Troels Borum Grave; Damsgaard, Christian Danvad; Dalslet, Bjarke Thomas
2010-01-01
We present a theoretical study of the spatially averaged in-plane magnetic field on square and rectangular magnetic field sensors from a single magnetic bead, a monolayer of magnetic beads, and a half-space filled with magnetic beads being magnetized by the magnetic self-field due to the applied...... bias current through the sensor. The analysis of the single bead response shows that beads always contribute positively to the average magnetic field as opposed to the case for an applied homogeneous magnetic field where the sign of the signal depends on the bead position. General expressions...... and analytical approximations are derived for the sensor response to beads as function of the bead distribution, the bias current, the geometry and size of the sensor, and the bead characteristics. Consequences for the sensor design are exemplified and it is described how the contribution from the self...
Sontu, Uday Bhasker; G, Narsinga Rao; Chou, F. C.; M, V. Ramana Reddy
2018-04-01
Spinel ferrites have come a long way in their versatile applications. The ever growing applications of these materials demand detailed study of material properties and environmental considerations in their synthesis. In this article, we report the effect of temperature and applied magnetic field strength on the magnetic behavior of the cobalt nickel ferrite nano powder samples. Basic structural properties of spinel ferrite nano particles, that are synthesized by an environmentally benign method of auto combustion, are characterized through XRD, TEM, RAMAN spectroscopy. Diffuse Reflectance Spectroscopy (DRS) is done to understand the nickel substitution effect on the optical properties of cobalt ferrite nano particles. Thermo magnetic studies using SQUID in the temperature range 5 K to 400 K and room temperature (300 K) VSM studies are performed on these samples. Fields of 0Oe (no applied field: ZF), 1 kOe (for ZFC and FC curves), 5 kOe (0.5 T), 50 kOe (5T) (for M-H loop study) are used to study the magnetic behavior of these nano particles. The XRD,TEM analysis suggest 40 nm crystallites that show changes in the cation distribution and phase changes in the spinel structure with nickel substitution. Raman micrographs support phase purity changes and cation redistributions with nickel substitution. Diffuse reflectance study on powder samples suggests two band gap values for nickel rich compounds. The Magnetic study of these sample nano particles show varied magnetic properties from that of hard magnetic, positive multi axial anisotropy and single-magnetic-domain structures at 5 K temperature to soft magnetic core shell like structures at 300 K temperature. Nickel substitution effect is non monotonous. Blocking temperature of all the samples is found to be higher than the values suggested in the literature.
The homogeneous marginal utility of income assumption
Demuynck, T.
2015-01-01
We develop a test to verify if every agent from a population of heterogeneous consumers has the same marginal utility of income function. This homogeneous marginal utility of income assumption is often (implicitly) used in applied demand studies because it has nice aggregation properties and
Extension theorems for homogenization on lattice structures
Miller, Robert E.
1992-01-01
When applying homogenization techniques to problems involving lattice structures, it is necessary to extend certain functions defined on a perforated domain to a simply connected domain. This paper provides general extension operators which preserve bounds on derivatives of order l. Only the special case of honeycomb structures is considered.
Homogeneous instantons in bigravity
Zhang, Ying-li; Sasaki, Misao; Yeom, Dong-han
2015-01-01
We study homogeneous gravitational instantons, conventionally called the Hawking-Moss (HM) instantons, in bigravity theory. The HM instantons describe the amplitude of quantum tunneling from a false vacuum to the true vacuum. Corrections to General Relativity (GR) are found in a closed form. Using the result, we discuss the following two issues: reduction to the de Rham-Gabadadze-Tolley (dRGT) massive gravity and the possibility of preference for a large e-folding number in the context of the Hartle-Hawking (HH) no-boundary proposal. In particular, concerning the dRGT limit, it is found that the tunneling through the so-called self-accelerating branch is exponentially suppressed relative to the normal branch, and the probability becomes zero in the dRGT limit. As far as HM instantons are concerned, this could imply that the reduction from bigravity to the dRGT massive gravity is ill-defined.
Rovang, D C; Lamppa, D C; Cuneo, M E; Owen, A C; McKenney, J; Johnson, D W; Radovich, S; Kaye, R J; McBride, R D; Alexander, C S; Awe, T J; Slutz, S A; Sefkow, A B; Haill, T A; Jones, P A; Argo, J W; Dalton, D G; Robertson, G K; Waisman, E M; Sinars, D B; Meissner, J; Milhous, M; Nguyen, D N; Mielke, C H
2014-12-01
Sandia has successfully integrated the capability to apply uniform, high magnetic fields (10-30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1-3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2-7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnostic lines of sight to the target. We describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept.
Approach to magnetic neutron capture therapy
Kuznetsov, Anatoly A.; Podoynitsyn, Sergey N.; Filippov, Victor I.; Komissarova, Lubov Kh.; Kuznetsov, Oleg A.
2005-01-01
Purpose: The method of magnetic neutron capture therapy can be described as a combination of two methods: magnetic localization of drugs using magnetically targeted carriers and neutron capture therapy itself. Methods and Materials: In this work, we produced and tested two types of particles for such therapy. Composite ultradispersed ferro-carbon (Fe-C) and iron-boron (Fe-B) particles were formed from vapors of respective materials. Results: Two-component ultradispersed particles, containing Fe and C, were tested as magnetic adsorbent of L-boronophenylalanine and borax and were shown that borax sorption could be effective for creation of high concentration of boron atoms in the area of tumor. Kinetics of boron release into the physiologic solution demonstrate that ultradispersed Fe-B (10%) could be applied for an effective magnetic neutron capture therapy. Conclusion: Both types of the particles have high magnetization and magnetic homogeneity, allow to form stable magnetic suspensions, and have low toxicity
Minimizing magnetic fields for precision experiments
Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S., E-mail: stefan.stuiber@ph.tum.de; Sturm, M.; Taggart Singh, J.; Taubenheim, B. [Physikdepartment, Technische Universität München, D-85748 Garching (Germany); Rohrer, H. K. [Rohrer GmbH, D-80667 München (Germany); Schläpfer, U. [IMEDCO AG, CH-4614 Hägendorf (Switzerland)
2015-06-21
An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.
Minimizing magnetic fields for precision experiments
Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S.; Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.
2015-01-01
An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application
Hao Wang
2016-01-01
Full Text Available Hysteresis characteristics of grain-oriented electrical steel were studied through the hysteresis loop. Existing hysteresis fitting simulation methods were summarized, and new Fe-3% Si grain-oriented electrical steel hysteresis loop model was proposed. Undetermined coefficients of the magnetic field intensity and magnetic flux density were determined by both the fixed angle method and the least squares method, and the hysteresis loop model was validated with high fitting degree by experimental data.
Phungamngoen Chanthima
2016-01-01
Full Text Available Coconut milk is one of the most important protein-rich food sources available today. Separation of an emulsion into an aqueous phase and cream phase is commonly occurred and this leads an unacceptably physical defect of either fresh or processed coconut milk. Since homogenization steps are known to affect the stability of coconut milk. This work was aimed to study the effect of homogenization steps on quality of coconut milk. The samples were subject to high speed homogenization in the range of 5000-15000 rpm under sterilize temperatures at 120-140 °C for 15 min. The result showed that emulsion stability increase with increasing speed of homogenization. The lower fat particles were generated and easy to disperse in continuous phase lead to high stability. On the other hand, the stability of coconut milk decreased, fat globule increased, L value decreased and b value increased when the high sterilization temperature was applied. Homogenization after heating led to higher stability than homogenization before heating due to the reduced particle size of coconut milk after aggregation during sterilization process. The results implied that homogenization after sterilization process might play an important role on the quality of the sterilized coconut milk.
The relationship between continuum homogeneity and statistical homogeneity in cosmology
Stoeger, W.R.; Ellis, G.F.R.; Hellaby, C.
1987-01-01
Although the standard Friedmann-Lemaitre-Robertson-Walker (FLRW) Universe models are based on the concept that the Universe is spatially homogeneous, up to the present time no definition of this concept has been proposed that could in principle be tested by observation. Such a definition is here proposed, based on a simple spatial averaging procedure, which relates observable properties of the Universe to the continuum homogeneity idea that underlies the FLRW models. It turns out that the statistical homogeneity often used to describe the distribution of matter on a large scale does not imply spatial homogeneity according to this definition, and so cannot be simply related to a FLRW Universe model. Values are proposed for the homogeneity parameter and length scale of homogeneity of the Universe. (author)
Reciprocity theory of homogeneous reactions
Agbormbai, Adolf A.
1990-03-01
The reciprocity formalism is applied to the homogeneous gaseous reactions in which the structure of the participating molecules changes upon collision with one another, resulting in a change in the composition of the gas. The approach is applied to various classes of dissociation, recombination, rearrangement, ionizing, and photochemical reactions. It is shown that for the principle of reciprocity to be satisfied it is necessary that all chemical reactions exist in complementary pairs which consist of the forward and backward reactions. The backward reaction may be described by either the reverse or inverse process. The forward and backward processes must satisfy the same reciprocity equation. Because the number of dynamical variables is usually unbalanced on both sides of a chemical equation, it is necessary that this balance be established by including as many of the dynamical variables as needed before the reciprocity equation can be formulated. Statistical transformation models of the reactions are formulated. The models are classified under the titles free exchange, restricted exchange and simplified restricted exchange. The special equations for the forward and backward processes are obtained. The models are consistent with the H theorem and Le Chatelier's principle. The models are also formulated in the context of the direct simulation Monte Carlo method.
by B. Curé
2011-01-01
The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...
Chen, W.-P.; Huang, W.-N.; Chen, P.-S.; Fan, T.-Y.; Chen, M.-P.; Teng, C.-C.
2006-01-01
In this paper, the novel design concept for highly effective magnetic flux coupling (HEMFC) schemes, based on enhancement of path guiding effect for leakage flux transmitting, is proposed for a non-contact power transfer system. Two implementation techniques are presented herein utilizing simple structure opinions of specific slant air gap as well as adding of metal bushing components. Both simulation and experimental results demonstrate that the improvement of magnetic coupling ratio and overall system efficiency are achieved by applying the two HEMFC schemes as the power transmitting devices
Homogenization of resonant chiral metamaterials
Andryieuski, Andrei; Menzel, Christoph; Rockstuhl, Carsten; Malureanu, Radu; Lederer, Falk; Lavrinenko, Andrei
2010-01-01
Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as e.g. propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size a critical density exists above which increasing coupling between neighboring meta-atoms prevails a reasonable homogenization. On the contrary, a dilution in excess will induce features reminiscent to pho...
Bilipschitz embedding of homogeneous fractals
Lü, Fan; Lou, Man-Li; Wen, Zhi-Ying; Xi, Li-Feng
2014-01-01
In this paper, we introduce a class of fractals named homogeneous sets based on some measure versions of homogeneity, uniform perfectness and doubling. This fractal class includes all Ahlfors-David regular sets, but most of them are irregular in the sense that they may have different Hausdorff dimensions and packing dimensions. Using Moran sets as main tool, we study the dimensions, bilipschitz embedding and quasi-Lipschitz equivalence of homogeneous fractals.
Magnetic field driven domain-wall propagation in magnetic nanowires
Wang, X.R.; Yan, P.; Lu, J.; He, C.
2009-01-01
The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.
WHAMP - waves in homogeneous, anisotropic, multicomponent plasmas
Roennmark, K.
1982-06-01
In this report, a computer program which solves the dispersion relation of waves in a magnetized plasma is described. The dielectric tensor is derived using the kinetic theory of homogeneous plasmas with Maxwellian velocity distribution. Up to six different plasma components can be included in this version of the program, and each component is specified by its density, temperature, particle mass, anisotropy and drift velocity along the magnetic field. The program is thus applicable to a very wide class of plasmas, and the method should in general be useful whenever a homogeneous magnetized plasma can be approximated by a linear combination of Maxwellian components. The general theory underlying the program is outlined. It is shown that by introducing a Pade approximant for the plasma dispersion function Z, the infinite sums of modified Bessel functions which appear in the dielectric tensor may be reduced to a summable form. The Pade approximant is derived and the accuracy of the approximation is also discussed. The subroutines making up the program are described. (Author)
Mihalik, M.; Kolomiyets, O.; Griveau, J.C.; Andreev, Alexander V.; Sechovský, V.
2007-01-01
Roč. 76, Suppl. A (2007), s. 54-55 ISSN 0031-9015 R&D Projects: GA ČR GA202/06/0178 Institutional research plan: CEZ:AV0Z10100520 Keywords : uranium intermetallics * single crystals * antiferromagnetism * high pressure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.212, year: 2007
Homogenization of discrete media
Pradel, F.; Sab, K.
1998-01-01
Material such as granular media, beam assembly are easily seen as discrete media. They look like geometrical points linked together thanks to energetic expressions. Our purpose is to extend discrete kinematics to the one of an equivalent continuous material. First we explain how we build the localisation tool for periodic materials according to estimated continuum medium type (classical Cauchy, and Cosserat media). Once the bridge built between discrete and continuum media, we exhibit its application over two bidimensional beam assembly structures : the honey comb and a structural reinforced variation. The new behavior is then applied for the simple plan shear problem in a Cosserat continuum and compared with the real discrete solution. By the mean of this example, we establish the agreement of our new model with real structures. The exposed method has a longer range than mechanics and can be applied to every discrete problems like electromagnetism in which relationship between geometrical points can be summed up by an energetic function. (orig.)
Benoit Curé
2010-01-01
Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...
B. Curé
2012-01-01
Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...
Gregoratto, D.; Drake, J. R.; Yadikin, D.; Liu, Y. Q.; Paccagnella, R.; Brunsell, P. R.; Bolzonella, T.; Marchiori, G.; Cecconello, M.
2005-09-01
Arrays of magnetic coils and sensors in the EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43 1457 (2001)] reversed-field pinch have been used to investigate the plasma response to an applied resonant magnetic perturbation in the range of the resistive-wall modes (RWMs). Measured RWM growth rates agree with predictions of a cylindrical ideal-plasma model. The linear growth of low-n marginally stable RWMs is related to the so-called resonant-field amplification due to a dominant ∣n∣=2 machine error field of about 2 G. The dynamics of the m =1 RWMs interacting with the applied field produced by the coils can be accurately described by a two-pole system. Estimated poles and residues are given with sufficient accuracy by the cylindrical model with a thin continuous wall.
Repisky, Michal; Komorovsky, Stanislav; Malkina, Olga L.; Malkin, Vladimir G.
2009-01-01
The relativistic four-component density functional approach based on the use of restricted magnetically balanced basis (mDKS-RMB), applied recently for calculations of NMR shielding, was extended for calculations of NMR indirect nuclear spin-spin coupling constants. The unperturbed equations are solved with the use of a restricted kinetically balanced basis set for the small component while to solve the second-order coupled perturbed DKS equations a restricted magnetically balanced basis set for the small component was applied. Benchmark relativistic calculations have been carried out for the X-H and H-H spin-spin coupling constants in the XH 4 series (X = C, Si, Ge, Sn and Pb). The method provides an attractive alternative to existing approximate two-component methods with transformed Hamiltonians for relativistic calculations of spin-spin coupling constants of heavy-atom systems. In particular, no picture-change effects arise in our method for property calculations
Model-based magnetization retrieval from holographic phase images
Röder, Falk, E-mail: f.roeder@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Vogel, Karin [Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Wolf, Daniel [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Hellwig, Olav [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); AG Magnetische Funktionsmaterialien, Institut für Physik, Technische Universität Chemnitz, D-09126 Chemnitz (Germany); HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wee, Sung Hun [HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wicht, Sebastian; Rellinghaus, Bernd [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)
2017-05-15
The phase shift of the electron wave is a useful measure for the projected magnetic flux density of magnetic objects at the nanometer scale. More important for materials science, however, is the knowledge about the magnetization in a magnetic nano-structure. As demonstrated here, a dominating presence of stray fields prohibits a direct interpretation of the phase in terms of magnetization modulus and direction. We therefore present a model-based approach for retrieving the magnetization by considering the projected shape of the nano-structure and assuming a homogeneous magnetization therein. We apply this method to FePt nano-islands epitaxially grown on a SrTiO{sub 3} substrate, which indicates an inclination of their magnetization direction relative to the structural easy magnetic [001] axis. By means of this real-world example, we discuss prospects and limits of this approach. - Highlights: • Retrieval of the magnetization from holographic phase images. • Magnetostatic model constructed for a magnetic nano-structure. • Decomposition into homogeneously magnetized components. • Discretization of a each component by elementary cuboids. • Analytic solution for the phase of a magnetized cuboid considered. • Fitting a set of magnetization vectors to experimental phase images.
Restrepo, R. L.; Kasapoglu, E.; Sakiroglu, S.; Ungan, F.; Morales, A. L.; Duque, C. A.
2017-09-01
The effects of electric and magnetic fields on the second and third harmonic generation coefficients in a Morse potential quantum well are theoretically studied. The energy levels and corresponding wave functions are obtained by solving the Schrödinger equation for the electron in the parabolic band scheme and effective mass approximations and the envelope function approach. The results show that both the electric and the magnetic fields have significant influence on the magnitudes and resonant peak energy positions of the second and third harmonic generation responses. In general, the Morse potential profile becomes wider and shallower as γ -parameter increases and so the energies of the bound states will be functions of this parameter. Therefore, we can conclude that the effects of the electric and magnetic fields can be used to tune and control the optical properties of interest in the range of the infrared electromagnetic spectrum.
Moral Beliefs and Cognitive Homogeneity
Nevia Dolcini
2018-04-01
Full Text Available The Emotional Perception Model of moral judgment intends to account for experientialism about morality and moral reasoning. In explaining how moral beliefs are formed and applied in practical reasoning, the model attempts to overcome the mismatch between reason and action/desire: morality isn’t about reason for actions, yet moral beliefs, if caused by desires, may play a motivational role in (moral agency. The account allows for two kinds of moral beliefs: genuine moral beliefs, which enjoy a relation to desire, and motivationally inert moral beliefs acquired in ways other than experience. Such etiology-based dichotomy of concepts, I will argue, leads to the undesirable view of cognition as a non-homogeneous phenomenon. Moreover, the distinction between moral beliefs and moral beliefs would entail a further dichotomy encompassing the domain of moral agency: one and the same action might possibly be either genuine moral, or not moral, if acted by individuals lacking the capacity for moral feelings, such as psychopaths.
Mehdioui, M.; Fahmi, A.; Lassri, H.; Fahoume, M.; Qachaou, A.
2014-01-01
We have studied the elementary magnetic excitations and their dynamics in multilayer Co(t Co)/Pt(t Pt) and Pt(t Pt)/Co(t Co)/Pt(t Pt) under an applied magnetic field. The Heisenberg hamiltonian used takes into account the magneto-crystalline and surface anisotropies, the exchange and dipolar interactions. The calculated excitation spectrum ε N (k) presents a structure with two sub-bands corresponding to the magnons of surface and volume respectively. The existence of a gap of creating these magnons is also highlighted. The lifetimes deduced from these gaps are in good agreement with the results of previous studies. The thermal evolution of the magnetization m z indicates that the system undergoes a dimensional crossover 3D–2D when the temperature increases. The calculated and measured magnetizations are compared and they are in good agreement. The exchange integral and critical temperature values deduced from these adjustments are in very good agreement with the results of previous works. - Highlights: • The magnons of surface and volume exist in Co/Pt and Pt/Co/Pt. • Samples undergo dimensional crossover (3D–2D) when T increases. • A good agreement is obtained between M(T) measured and calculated. • Deduced exchange integrals and critical temperature values are correct. • The magnetism of the sample is reduced by increasing t Pt or capping Co by two Pt layers
Homogeneous versus heterogeneous zeolite nucleation
Dokter, W.H.; Garderen, van H.F.; Beelen, T.P.M.; Santen, van R.A.; Bras, W.
1995-01-01
Aggregates of fractal dimension were found in the intermediate gel phases that organize prior to nucleation and crystallization (shown right) of silicalite from a homogeneous reaction mixture. Small- and wide-angle X-ray scattering studies prove that for zeolites nucleation may be homogeneous or
Homogeneous crystal nucleation in polymers.
Schick, C; Androsch, R; Schmelzer, J W P
2017-11-15
The pathway of crystal nucleation significantly influences the structure and properties of semi-crystalline polymers. Crystal nucleation is normally heterogeneous at low supercooling, and homogeneous at high supercooling, of the polymer melt. Homogeneous nucleation in bulk polymers has been, so far, hardly accessible experimentally, and was even doubted to occur at all. This topical review summarizes experimental findings on homogeneous crystal nucleation in polymers. Recently developed fast scanning calorimetry, with cooling and heating rates up to 10 6 K s -1 , allows for detailed investigations of nucleation near and even below the glass transition temperature, including analysis of nuclei stability. As for other materials, the maximum homogeneous nucleation rate for polymers is located close to the glass transition temperature. In the experiments discussed here, it is shown that polymer nucleation is homogeneous at such temperatures. Homogeneous nucleation in polymers is discussed in the framework of the classical nucleation theory. The majority of our observations are consistent with the theory. The discrepancies may guide further research, particularly experiments to progress theoretical development. Progress in the understanding of homogeneous nucleation is much needed, since most of the modelling approaches dealing with polymer crystallization exclusively consider homogeneous nucleation. This is also the basis for advancing theoretical approaches to the much more complex phenomena governing heterogeneous nucleation.
Homogenization theory in reactor lattices
Benoist, P.
1986-02-01
The purpose of the theory of homogenization of reactor lattices is to determine, by the mean of transport theory, the constants of a homogeneous medium equivalent to a given lattice, which allows to treat the reactor as a whole by diffusion theory. In this note, the problem is presented by laying emphasis on simplicity, as far as possible [fr
Bridging heterogeneous and homogeneous catalysis concepts, strategies, and applications
Li, Can
2014-01-01
This unique handbook fills the gap in the market for an up-to-date work that links both homogeneous catalysis applied to organic reactions and catalytic reactions on surfaces of heterogeneous catalysts.
Homogenization of discrete media
Pradel, F.; Sab, K. [CERAM-ENPC, Marne-la-Vallee (France)
1998-11-01
Material such as granular media, beam assembly are easily seen as discrete media. They look like geometrical points linked together thanks to energetic expressions. Our purpose is to extend discrete kinematics to the one of an equivalent continuous material. First we explain how we build the localisation tool for periodic materials according to estimated continuum medium type (classical Cauchy, and Cosserat media). Once the bridge built between discrete and continuum media, we exhibit its application over two bidimensional beam assembly structures : the honey comb and a structural reinforced variation. The new behavior is then applied for the simple plan shear problem in a Cosserat continuum and compared with the real discrete solution. By the mean of this example, we establish the agreement of our new model with real structures. The exposed method has a longer range than mechanics and can be applied to every discrete problems like electromagnetism in which relationship between geometrical points can be summed up by an energetic function. (orig.) 7 refs.
Jacobson, Jerry; Sherlag, Benjamin
2015-09-01
A new holistic paradigm is proposed for slowing our genomic-based biological clocks (e.g. regulation of telomere length), and decreasing heat energy exigencies for maintenance of physiologic homeostasis. Aging is considered the result of a progressive slow burn in small volumes of tissues with increase in the quantum entropic states; producing desiccation, microscopic scarring, and disruption of cooperative coherent states. Based upon piezoelectricity, i.e. photon-phonon transductions, physiologic PicoTesla range magnetic fields may decrease the production of excessive heat energy through target specific, bio molecular resonant interactions, renormalization of intrinsic electromagnetic tissue profiles, and autonomic modulation. Prospectively, we hypothesize that deleterious effects of physical trauma, immunogenic microbiological agents, stress, and anxiety may be ameliorated. A particle-wave equation is cited to ascertain magnetic field parameters for application to the whole organism thereby achieving desired homeostasis; secondary to restoration of structure and function on quantum levels. We hypothesize that it is at the atomic level that physical events shape the flow of signals and the transmission of energy in bio molecular systems. References are made to experimental data indicating the aspecific efficacy of non-ionizing physiologic magnetic field profiles for treatment of various pathologic states. Copyright © 2015 Elsevier Ltd. All rights reserved.
Chen Qiao, E-mail: cqhy1127@yahoo.com.c [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Liu Jin [Institute of Theoretical Physics, Chinese Academy of Science, Beijing 100190 (China); Wang Zhiyong [School of Optoelectronic Information, Chongqing University of Technology, Chongqing 400054 (China)
2011-01-17
We have investigated the current for the system of vibrating quantum dot irradiated with a rotating magnetic field and an oscillating magnetic field by nonequilibrium Green's function. The rotating magnetic field rotates with the angular frequency {omega}{sub r} around the z-axis with the tilt angle {theta}, and the time-oscillating magnetic field is located in the z-axis with the angular frequency {omega}. Different behaviors have been shown in the presence of electron-phonon interaction (EPI) which plays a significant role in the transport. The current displays asymmetric behavior as the source-drain bias eV=0, novel side peaks or shoulders can be found due to the phonon absorption and emission procedure, and the negative differential resistance becomes stronger as the parameter g increases. Furthermore, the strong EPI also destroys the quasiperiodic oscillations of current in the region {mu}{sub 0}B{sub 1}>2.5{Delta}. The electron transport properties are also significantly influenced by the linewidth function {Gamma}.
B. Curé
2012-01-01
The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...
B. Curé
2013-01-01
The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...
Benoit Curé
2010-01-01
The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...
B. Curé
2011-01-01
The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...
Ribeiro, R.A.P. [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Lazaro, S.R. de, E-mail: srlazaro@upeg.br [Department of Chemistry, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil); Pianaro, S.A. [Department of Materials Engineering, State University of Ponta Grossa, Av. General Carlos Cavalcanti, 4748, 84030-900 Ponta Grossa, PR (Brazil)
2015-10-01
Antiferromagnetic Mn{sub 3}O{sub 4} in spinel structure was investigated employing the Density Functional Theory at different hybrid functionals with default HF exchange percentage. Structural, electronic and magnetic properties were examined. Structural results were in agreement with experimental and Hartree–Fock results showing that the octahedral site was distorted by the Jahn–Teller effect, which changed the electron density distribution. Band-gap results for B3LYP and B3PW hybrid functionals were closer to the experimental when compared to PBE0. Mulliken Population Analysis revealed magnetic moments very close to ideal d{sup 4} and d{sup 5} electron configurations of Mn{sup 3+} and Mn{sup 2+}, respectively. Electron density maps are useful to determine that oxygen atoms mediate the electron transfer between octahedral and tetrahedral clusters. Magnetic properties were investigated from theoretical results for exchange coupling constants. Intratetrahedral and tetra-octahedral interactions were observed to be antiferromagnetic, whereas, octahedral sites presented antiferromagnetic interactions in the same layer and ferromagnetic in adjacent layers. Results showed that only default B3LYP was successful to describe magnetic properties of antiferromagnetic materials in agreement with experimental results. - Highlights: • We study structural, electronic and magnetic properties of antiferromagnetic Mn{sub 3}O{sub 4}. • B3LYP, B3PW and PBE0 hybrid functionals are compared. • B3LYP and B3PW hybrid functionals are better to band-gap calculations. • Only default B3LYP was successful to describe exchange interactions for Mn{sub 3}O{sub 4}.
Some properties of spatially homogeneous spacetimes
Coomer, G.C.
1979-01-01
This paper discusses two features of the universe which are influenced in a fundamental way by the spacetime geometry of the universe. The first is the growth of density fluctuations in the early stages of the evolution of the universe. The second is the propagation of electromagnetic radiation in the universe. A spatially homogeneous universe is assumed in both discussions. The gravitational instability theory of galaxy formation is investigated for a viscous fluid and for a charged, conducting fluid with a magnetic field added as a perturbation. It is found that the growth rate of density perturbations in both cases is lower than in the perfect fluid case. Spatially homogeneous but nonisotropic spacetimes are investigated next. Two perfect fluid solutions of Einstein's field equations are found which have spacelike hypersurfaces with Bianchi type II geometry. An expression for the spectrum of the cosmic microwave background radiation in a spatially homogeneous but nonisotropic universe is found. The expression is then used to determine the angular distribution of the intensity of the radiation in the simpler of the two solutions. When accepted values of the matter density and decoupling temperature are inserted into this solution, values for the age of the universe and the time of decoupling are obtained which agree reasonably well with the values of the standard model of the universe
Homogeneous Spaces and Equivariant Embeddings
Timashev, DA
2011-01-01
Homogeneous spaces of linear algebraic groups lie at the crossroads of algebraic geometry, theory of algebraic groups, classical projective and enumerative geometry, harmonic analysis, and representation theory. By standard reasons of algebraic geometry, in order to solve various problems on a homogeneous space it is natural and helpful to compactify it keeping track of the group action, i.e. to consider equivariant completions or, more generally, open embeddings of a given homogeneous space. Such equivariant embeddings are the subject of this book. We focus on classification of equivariant em
Yayun Dong
2017-05-01
Full Text Available Shifting medium is a kind of metamaterial, which can optically shift a space or an object a certain distance away from its original position. Based on the shifting medium, we propose a concise pair of shifting slabs covering the transmitting or receiving coil in a two-coil wireless power transfer system to decrease the equivalent distance between the coils. The electromagnetic parameters of the shifting slabs are calculated by transformation optics. Numerical simulations validate that the shifting slabs can approximately shift the electromagnetic fields generated by the covered coil; thus, the magnetic coupling and the efficiency of the system are enhanced while remaining the physical transmission distance unchanged. We also verify the advantages of the shifting slabs over the magnetic superlens. Finally, we provide two methods to fabricate shifting slabs based on split-ring resonators.
Dong, Yayun; Yang, Xijun; Jin, Nan; Li, Wenwen; Yao, Chen; Tang, Houjun
2017-05-01
Shifting medium is a kind of metamaterial, which can optically shift a space or an object a certain distance away from its original position. Based on the shifting medium, we propose a concise pair of shifting slabs covering the transmitting or receiving coil in a two-coil wireless power transfer system to decrease the equivalent distance between the coils. The electromagnetic parameters of the shifting slabs are calculated by transformation optics. Numerical simulations validate that the shifting slabs can approximately shift the electromagnetic fields generated by the covered coil; thus, the magnetic coupling and the efficiency of the system are enhanced while remaining the physical transmission distance unchanged. We also verify the advantages of the shifting slabs over the magnetic superlens. Finally, we provide two methods to fabricate shifting slabs based on split-ring resonators.
Arpaia, P.; Coppier, H.; De Paola, D.; di Bernardo, M.; Guarino, A.; Pedemonte, B. Luz; Pezzetti, M.
2017-12-01
Industrial process controllers for cryogenic systems used in test facilities for superconducting magnets are typically PIDs, tuned by operational expertise according to users’ requirements (covering cryogenic transients and associated thermo-mechanical constraints). In this paper, an alternative fully-automatic solution, equally based on PID controllers, is proposed. Following the comparison of the operational expertise and alternative fully-automatic approaches, a new process control configuration, based on an estimated multiple-input/multiple-output (MIMO) model is proposed. The new MIMO model-based approach fulfils the required operational constraints while improving performance compared to existing solutions. The analysis and design work is carried out using both theoretical and numerical tools and is validated on the case study of the High Field Magnet (HFM) cryogenic test bench running at the SM18 test facility located at CERN. The proposed solution have been validated by simulation using the CERN ECOSIMPRO software tools using the cryogenic library (CRYOLIB [1]) developed at CERN.
B. Curé
2011-01-01
The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....
Qualitative analysis of homogeneous universes
Novello, M.; Araujo, R.A.
1980-01-01
The qualitative behaviour of cosmological models is investigated in two cases: Homogeneous and isotropic Universes containing viscous fluids in a stokesian non-linear regime; Rotating expanding universes in a state which matter is off thermal equilibrium. (Author) [pt
A second stage homogenization method
Makai, M.
1981-01-01
A second homogenization is needed before the diffusion calculation of the core of large reactors. Such a second stage homogenization is outlined here. Our starting point is the Floquet theorem for it states that the diffusion equation for a periodic core always has a particular solution of the form esup(j)sup(B)sup(x) u (x). It is pointed out that the perturbation series expansion of function u can be derived by solving eigenvalue problems and the eigenvalues serve to define homogenized cross sections. With the help of these eigenvalues a homogenized diffusion equation can be derived the solution of which is cos Bx, the macroflux. It is shown that the flux can be expressed as a series of buckling. The leading term in this series is the well known Wigner-Seitz formula. Finally three examples are given: periodic absorption, a cell with an absorber pin in the cell centre, and a cell of three regions. (orig.)
Homogenization methods for heterogeneous assemblies
Wagner, M.R.
1980-01-01
The third session of the IAEA Technical Committee Meeting is concerned with the problem of homogenization of heterogeneous assemblies. Six papers will be presented on the theory of homogenization and on practical procedures for deriving homogenized group cross sections and diffusion coefficients. That the problem of finding so-called ''equivalent'' diffusion theory parameters for the use in global reactor calculations is of great practical importance. In spite of this, it is fair to say that the present state of the theory of second homogenization is far from being satisfactory. In fact, there is not even a uniquely accepted approach to the problem of deriving equivalent group diffusion parameters. Common agreement exists only about the fact that the conventional flux-weighting technique provides only a first approximation, which might lead to acceptable results in certain cases, but certainly does not guarantee the basic requirement of conservation of reaction rates
Spinor structures on homogeneous spaces
Lyakhovskii, V.D.; Mudrov, A.I.
1993-01-01
For multidimensional models of the interaction of elementary particles, the problem of constructing and classifying spinor fields on homogeneous spaces is exceptionally important. An algebraic criterion for the existence of spinor structures on homogeneous spaces used in multidimensional models is developed. A method of explicit construction of spinor structures is proposed, and its effectiveness is demonstrated in examples. The results are of particular importance for harmonic decomposition of spinor fields
A personal view on homogenization
Tartar, L.
1987-02-01
The evolution of some ideas is first described. Under the name homogenization are collected all the mathematical results who help understanding the relations between the microstructure of a material and its macroscopic properties. Homogenization results are given through a critically detailed bibliography. The mathematical models given are systems of partial differential equations, supposed to describe some properties at a scale ε and we want to understand what will happen to the solutions if ε tends to 0
Mohamed Bechir Ben Hamida
2015-10-01
Full Text Available The aim of this paper is to evaluate the magnitude of the external magnetic field to be applied to a horizontal mercury discharge lamp such that the Lorentz forces counterbalance buoyancy forces and the hot region of the arc remains centered inside the lamp with the variation of six parameters of the lamp such as the external temperature of the lamp, envelope thickness, convective loss, Interelectrodeslength, pressure and current supply pointing to the influence of the parameters to the compensating magnetic field value. To achieve this objective, a commercial numerical software “Comsol Multiphysics” is used to implement the model that solves the equations of mass, energy and momentum for laminar compressible flow combined with the Laplace equation for the plasma in a three dimensional.
Scheid, Matthias; Adagideli, İnanç; Richter, Klaus; Nitta, Junsaku
2009-01-01
We investigate the transport properties of narrow quantum wires realized in disordered two-dimensional electron gases in the presence of k-linear Rashba and Dresselhaus spin–orbit interaction, and an applied in-plane magnetic field. Building on previous work (Scheid et al 2008 Phys. Rev. Lett. 101 266401), we find that in addition to the conductance, the universal conductance fluctuations also feature anisotropy with respect to the magnetic field direction. This anisotropy can be explained solely from the symmetries exhibited by the Hamiltonian as well as the relative strengths of the Rashba and Dresselhaus spin–orbit interaction and thus can be utilized to detect this ratio from purely electrical measurements
Wu Qingjie; Guo Kangxian; Liu Guanghui; Wu Jinghe
2013-01-01
Polaron effects on the linear and the nonlinear optical absorption coefficients and refractive index changes in cylindrical quantum dots with the radial parabolic potential and the z-direction linear potential with applied magnetic field are theoretically investigated. The optical absorption coefficients and refractive index changes are presented by using the compact-density-matrix approach and iterative method. Numerical calculations are presented for GaAs/AlGaAs. It is found that taking into account the electron-LO-phonon interaction, not only are the linear, the nonlinear and the total optical absorption coefficients and refractive index changes enhanced, but also the total optical absorption coefficients are more sensitive to the incident optical intensity. It is also found that no matter whether the electron-LO-phonon interaction is considered or not, the absorption coefficients and refractive index changes above are strongly dependent on the radial frequency, the magnetic field and the linear potential coefficient.
Testing homogeneity in Weibull-regression models.
Bolfarine, Heleno; Valença, Dione M
2005-10-01
In survival studies with families or geographical units it may be of interest testing whether such groups are homogeneous for given explanatory variables. In this paper we consider score type tests for group homogeneity based on a mixing model in which the group effect is modelled as a random variable. As opposed to hazard-based frailty models, this model presents survival times that conditioned on the random effect, has an accelerated failure time representation. The test statistics requires only estimation of the conventional regression model without the random effect and does not require specifying the distribution of the random effect. The tests are derived for a Weibull regression model and in the uncensored situation, a closed form is obtained for the test statistic. A simulation study is used for comparing the power of the tests. The proposed tests are applied to real data sets with censored data.
Shape optimization in biomimetics by homogenization modelling
Hoppe, Ronald H.W.; Petrova, Svetozara I.
2003-08-01
Optimal shape design of microstructured materials has recently attracted a great deal of attention in material science. The shape and the topology of the microstructure have a significant impact on the macroscopic properties. The present work is devoted to the shape optimization of new biomorphic microcellular ceramics produced from natural wood by biotemplating. We are interested in finding the best material-and-shape combination in order to achieve the optimal prespecified performance of the composite material. The computation of the effective material properties is carried out using the homogenization method. Adaptive mesh-refinement technique based on the computation of recovered stresses is applied in the microstructure to find the homogenized elasticity coefficients. Numerical results show the reliability of the implemented a posteriori error estimator. (author)
Hanzlíček, Tomáš; Perná, Ivana; Brus, Jiří
2013-01-01
Roč. 7, č. 2 (2013), s. 153-164 ISSN 1558-3058 R&D Projects: GA AV ČR IAA300460702 Institutional research plan: CEZ:AV0Z30460519; CEZ:AV0Z40500505 Keywords : mortars * magic angle spinning –nuclear magnetic resonance (MAS-NMR) in solid state * alumina-silicates Subject RIV: DM - Solid Waste and Recycling Impact factor: 0.714, year: 2013 http://www.tandfonline.com/doi/abs/10.1080/15583058.2011.624253
José Soeiro
2016-12-01
Full Text Available The study was carried out while developing an Augmented Reality mobile application that represents 3D virtual models of the brain of a patient over the real image of the patient’s head. The main purpose of the application is to guide doctors during a non-invasive medical procedure called Transcranial Magnetic Stimulation that uses electromagnetic stimulation to treat neurological problems. The tracking of these markers have proven to be one of the more challenging components of such an application and we observe that lighting conditions and distance to the markers are two of the main factors that can influence their accurate recognition
Benoit Curé
2010-01-01
The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...
B. Curé
MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...
Benoit Curé.
The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...
B. Curé
2013-01-01
The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...
The colour analysis method applied to homogeneous rocks
Halász Amadé
2015-12-01
Full Text Available Computer-aided colour analysis can facilitate cyclostratigraphic studies. Here we report on a case study involving the development of a digital colour analysis method for examination of the Boda Claystone Formation which is the most suitable in Hungary for the disposal of high-level radioactive waste. Rock type colours are reddish brown or brownish red, or any shade between brown and red. The method presented here could be used to differentiate similar colours and to identify gradual transitions between these; the latter are of great importance in a cyclostratigraphic analysis of the succession. Geophysical well-logging has demonstrated the existence of characteristic cyclic units, as detected by colour and natural gamma. Based on our research, colour, natural gamma and lithology correlate well. For core Ib-4, these features reveal the presence of orderly cycles with thicknesses of roughly 0.64 to 13 metres. Once the core has been scanned, this is a time- and cost-effective method.
Minkowski spacetime does not apply to a homogeneously accelerating medium
Coleman, Brian
Home and comoving inertial frame parameters of an individual point of an idealized medium of launch length L uniformly co-accelerating between identical fixed-thrust rockets, are well known. This is not the case with the varying inter-rocket radar periods and related implications regarding a changing 'noninertial own-length' Λ which differs from a front rocket's retrospective separation L from the simultaneously relatively moving rear rocket. On the other hand, the nonhomogeneous acceleration case involving every comoving frame's unchanging perception of a contrived 'rigor mortis' medium (so-called 'rigid motion' traditionally associated with 'Rindler coordinates') whereby Λ = L = L , constitutes the sole extended accelerating medium scenario where the entrenched Minkowski metric is actually applicable. Paraphrasing Wolfgang Pauli, not only is Minkowski spacetime not correct [in the general sense], it is not even wrong [in the restricted sense].
Consolidation treatments applied to ceramic tiles: are they homogeneous?
Costa, D.; Leal, A.S.; Mimoso, J.M; Pereira, S.M.R.
2017-01-01
The mass consolidation treatment of azulejos is necessary when ceramic biscuits show signs of disaggregation. Such treatment is often used as a complementary conservation technique to the reestablishment of weakened glaze-ceramic bonds. In this research, two commonly used consolidants (ethyl silicate and acrylic resin) were tested on artisanal ceramic tiles via mass consolidation and the resulting impregnation profiles were evaluated. The results indicated that after consolidation, hard zones frequently formed due to localized consolidant concentration after the polymerization and curing processes. These inhomogeneous hard zones subsequently influenced the results obtained through conventional mechanical strength testing (i.e. flexural and compression), creating a false impression of success. This research demonstrated that by using the Drilling Resistance Measuring System, impregnation characteristics such as penetration depth and distribution of consolidant could be observed that otherwise could not be discerned through the more common testing methods. As such, a more extensive evaluation of consolidation effects was achieved. [es
Consolidation treatments applied to ceramic tiles: are they homogeneous?
D. Costa
2017-01-01
Full Text Available The mass consolidation treatment of azulejos is necessary when ceramic biscuits show signs of disaggregation. Such treatment is often used as a complementary conservation technique to the reestablishment of weakened glaze-ceramic bonds. In this research, two commonly used consolidants (ethyl silicate and acrylic resin were tested on artisanal ceramic tiles via mass consolidation and the resulting impregnation profiles were evaluated. The results indicated that after consolidation, hard zones frequently formed due to localized consolidant concentration after the polymerization and curing processes. These inhomogeneous hard zones subsequently influenced the results obtained through conventional mechanical strength testing (i.e. flexural and compression, creating a false impression of success. This research demonstrated that by using the Drilling Resistance Measuring System, impregnation characteristics such as penetration depth and distribution of consolidant could be observed that otherwise could not be discerned through the more common testing methods. As such, a more extensive evaluation of consolidation effects was achieved.
Mohammad Faraji
2016-10-01
Full Text Available Background and Objectives: The addition of plasticizers (mainly phthalates and adipates makes plastic flexible and popular for packaging, storing and preserving food, water, and so on. The most widely used plasticizer in food contact applications is di-ethylhexyl phthalate (DEHP though being suspected to have carcinogenic and estrogenic properties. The aim of this study is application of magnetic solid phase extraction as new absorbent for determination of DEHP in water samples by gas chromatography (GC. Materials and Methods: Important factors in extraction, separation and determination processes were optimized using the one-variable-at-a-time method. For optimization, all tests were performed two times. Figures of merit of the proposed method were evaluated. The amount of DEHP in some water samples was determined using the proposed method. Results: The results showed that the obtained chromatogram of extract was free of significant interference. The preservatives’ recoveries ranged from 91.6% to 102.2%. Limit of detection and limit of quantitation were 0.1 mg kg-1 and 0.3 µg L-1, respectively. Concentration of DEHP in the studied samples was in the range of N.D-2.3 µg L-1. Conclusions: The acceptable performance and reliability of the proposed method were demonstrated. Temperature and time were fount as the most effective parameters in migration of DEHP. Keywords: Di-ethylhexyl phthalate, Magnetic solid phase extraction, Migration, Gas chromatography
New approaches for searching for the Dirac magnetic monopole
Kukhtin, V.V.; Krivokhizhin, V.G.; Stetsenko, S.G.; Cheplakov, A.P.
2012-01-01
Three new approaches, not applied earlier, are proposed to search for the Dirac monopole - an object whose existence was proposed by P.Dirac more than 80 years ago to explain the electrical charge quantization. The first approach assumes that the monopole must be accelerated by a magnetic field, and such acceleration is constant in the magnetic field which is homogeneous and constant. The conclusion about the object movement nature can be drawn by measuring the time marks for equidistant registering planes. The second approach is supposed to reconstruct the movement trajectory in the homogeneous and permanent electrical field, which is the circle or its part for the magnetic monopole. The third approach is based on the constancy of energy losses by Dirac monopole due to medium ionization in the multilayer passive dielectric tracking detectors placed in the homogeneous and permanent electrical field
Verification of homogenization in fast critical assembly analyses
Chiba, Go
2006-01-01
In the present paper, homogenization procedures for fast critical assembly analyses are investigated. Errors caused by homogenizations are evaluated by the exact perturbation theory. In order to obtain reference solutions, three-dimensional plate-wise transport calculations are performed. It is found that the angular neutron flux along plate boundaries has a significant peak in the fission source energy range. To treat this angular dependence accurately, the double-Gaussian Chebyshev angular quadrature set with S 24 is applied. It is shown that the difference between the heterogeneous leakage theory and the homogeneous theory is negligible, and that transport cross sections homogenized with neutron flux significantly underestimate neutron leakage. The error in criticality caused by a homogenization is estimated at about 0.1%Δk/kk' in a small fast critical assembly. In addition, the neutron leakage is overestimated by both leakage theories when sodium plates in fuel lattices are voided. (author)
Cosmic homogeneity: a spectroscopic and model-independent measurement
Gonçalves, R. S.; Carvalho, G. C.; Bengaly, C. A. P., Jr.; Carvalho, J. C.; Bernui, A.; Alcaniz, J. S.; Maartens, R.
2018-03-01
Cosmology relies on the Cosmological Principle, i.e. the hypothesis that the Universe is homogeneous and isotropic on large scales. This implies in particular that the counts of galaxies should approach a homogeneous scaling with volume at sufficiently large scales. Testing homogeneity is crucial to obtain a correct interpretation of the physical assumptions underlying the current cosmic acceleration and structure formation of the Universe. In this letter, we use the Baryon Oscillation Spectroscopic Survey to make the first spectroscopic and model-independent measurements of the angular homogeneity scale θh. Applying four statistical estimators, we show that the angular distribution of galaxies in the range 0.46 < z < 0.62 is consistent with homogeneity at large scales, and that θh varies with redshift, indicating a smoother Universe in the past. These results are in agreement with the foundations of the standard cosmological paradigm.
Agiotis, L.; Theodorakos, I.; Samothrakitis, S.; Papazoglou, S.; Zergioti, I.; Raptis, Y.S.
2016-01-01
Magnetic nanoparticles (MNPs), such as superparamagnetic iron oxide nanoparticles (SPIONS), have attracted major interest, due to their small size and unique magnetic properties, for drug delivery applications. In this context, iron oxide nanoparticles of magnetite (Fe 3 O 4 ) (150 nm magnetic core diameter), were used as drug carriers, aiming to form a magnetically controlled nano-platform. The navigation capabilities of the iron oxide nanoparticles in a microfluidic channel were investigated by simulating the magnetic field and the magnetic force applied on the magnetic nanoparticles inside a microfluidic chip. The simulations have been performed using finite element method (ANSY’S software). The optimum setup which intends to simulate the magnetic navigation of the nanoparticles, by the use of MRI-type fields, in the human circulatory system, consists of two parallel permanent magnets to produce a homogeneous magnetic field, in order to ensure the maximum magnetization of the magnetic nanoparticles, an electromagnet for the induction of the magnetic gradients and the creation of the magnetic force and a microfluidic setup so as to simulate the blood flow inside the human blood vessels. The magnetization of the superparamagnetic nanoparticles and the consequent magnetic torque developed by the two permanent magnets, together with the mutual interactions between the magnetized nanoparticles lead to the creation of rhabdoid aggregates in the direction of the homogeneous field. Additionally, the magnetic gradients introduced by the operation of the electromagnet are capable of directing the aggregates, as a whole, to the desired direction. By removing the magnetic fields, the aggregates are disrupted, due to the super paramagnetic nature of the nanoparticles, avoiding thus the formation of undesired thrombosis. - Highlights: • Homogeneous field yields an aggregation of particles along the lines of the field. • Additional electromagnet field rotates the
Agiotis, L.; Theodorakos, I.; Samothrakitis, S.; Papazoglou, S.; Zergioti, I.; Raptis, Y.S.
2016-03-01
Magnetic nanoparticles (MNPs), such as superparamagnetic iron oxide nanoparticles (SPIONS), have attracted major interest, due to their small size and unique magnetic properties, for drug delivery applications. In this context, iron oxide nanoparticles of magnetite (Fe{sub 3}O{sub 4}) (150 nm magnetic core diameter), were used as drug carriers, aiming to form a magnetically controlled nano-platform. The navigation capabilities of the iron oxide nanoparticles in a microfluidic channel were investigated by simulating the magnetic field and the magnetic force applied on the magnetic nanoparticles inside a microfluidic chip. The simulations have been performed using finite element method (ANSY’S software). The optimum setup which intends to simulate the magnetic navigation of the nanoparticles, by the use of MRI-type fields, in the human circulatory system, consists of two parallel permanent magnets to produce a homogeneous magnetic field, in order to ensure the maximum magnetization of the magnetic nanoparticles, an electromagnet for the induction of the magnetic gradients and the creation of the magnetic force and a microfluidic setup so as to simulate the blood flow inside the human blood vessels. The magnetization of the superparamagnetic nanoparticles and the consequent magnetic torque developed by the two permanent magnets, together with the mutual interactions between the magnetized nanoparticles lead to the creation of rhabdoid aggregates in the direction of the homogeneous field. Additionally, the magnetic gradients introduced by the operation of the electromagnet are capable of directing the aggregates, as a whole, to the desired direction. By removing the magnetic fields, the aggregates are disrupted, due to the super paramagnetic nature of the nanoparticles, avoiding thus the formation of undesired thrombosis. - Highlights: • Homogeneous field yields an aggregation of particles along the lines of the field. • Additional electromagnet field rotates the
Homogenization of neutronic diffusion models
Capdebosq, Y.
1999-09-01
In order to study and simulate nuclear reactor cores, one needs to access the neutron distribution in the core. In practice, the description of this density of neutrons is given by a system of diffusion equations, coupled by non differential exchange terms. The strong heterogeneity of the medium constitutes a major obstacle to the numerical computation of this models at reasonable cost. Homogenization appears as compulsory. Heuristic methods have been developed since the origin by nuclear physicists, under a periodicity assumption on the coefficients. They consist in doing a fine computation one a single periodicity cell, to solve the system on the whole domain with homogeneous coefficients, and to reconstruct the neutron density by multiplying the solutions of the two computations. The objectives of this work are to provide mathematically rigorous basis to this factorization method, to obtain the exact formulas of the homogenized coefficients, and to start on geometries where two periodical medium are placed side by side. The first result of this thesis concerns eigenvalue problem models which are used to characterize the state of criticality of the reactor, under a symmetry assumption on the coefficients. The convergence of the homogenization process is proved, and formulas of the homogenized coefficients are given. We then show that without symmetry assumptions, a drift phenomenon appears. It is characterized by the mean of a real Bloch wave method, which gives the homogenized limit in the general case. These results for the critical problem are then adapted to the evolution model. Finally, the homogenization of the critical problem in the case of two side by side periodic medium is studied on a one dimensional on equation model. (authors)
7 CFR 58.920 - Homogenization.
2010-01-01
... 7 Agriculture 3 2010-01-01 2010-01-01 false Homogenization. 58.920 Section 58.920 Agriculture... Procedures § 58.920 Homogenization. Where applicable concentrated products shall be homogenized for the... homogenization and the pressure at which homogenization is accomplished will be that which accomplishes the most...
Lamppa, Derek C.; Haill, Thomas A.; Alexander, C. Scott; Asay, James Russell
2010-09-01
A new experimental technique to measure material shear strength at high pressures has been developed for use on magneto-hydrodynamic (MHD) drive pulsed power platforms. By applying an external static magnetic field to the sample region, the MHD drive directly induces a shear stress wave in addition to the usual longitudinal stress wave. Strength is probed by passing this shear wave through a sample material where the transmissible shear stress is limited to the sample strength. The magnitude of the transmitted shear wave is measured via a transverse VISAR system from which the sample strength is determined.
Dimbylow, Peter
2006-01-01
This paper describes the development of 2 mm resolution hybrid voxel-mathematical models of the pregnant female. Mathematical models of the developing foetus at 8-, 13-, 26- and 38-weeks of gestation were converted into voxels and combined with the adult female model, NAOMI. This set of models was used to calculate induced current densities and electric fields in the foetus from applied 50 Hz magnetic and electric fields. The influence of foetal tissue conductivities was investigated and implications for electromagnetic field guidelines discussed
Zheng, J.; Liao, X. L.; Jing, H. L.; Deng, Z. G.; Yen, F.; Wang, S. Y.; Wang, J. S.
2013-10-01
Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems.
Benoit Curé
The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...
B. Curé
During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...
Perevertov, O; Schäfer, R
2012-01-01
The influence of an applied compressive stress on the hysteresis curve and domain structure in conventional (1 1 0) [0 0 1] Fe-3%Si steel cut transverse to the rolling direction is studied. Quasistatic hysteresis loops under compressive stress up to 75 MPa were measured. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of stress. It is shown that the bulk hysteresis loop can be described with a good accuracy by the action of an effective field, which is the product of the stress and a function of magnetization. Domain observations have shown that the reasons for the effective field are demagnetizing fields due to the disappearance of supplementary domains along [0 1 0] and [1 0 0] at low fields and different domain systems in different grains at moderate fields. The latter are caused by differences in grain sensitivity to stress depending on the degree of misorientation. A decrease in the effective field above 1 T is connected with a transformation of all grains into the same domain system—the column pattern. (paper)
Palmer, Grant
1991-01-01
A CFD technique is developed to calculate the electromagnetic phenomena simultaneously with the fluid flow in the shock layer over an axisymmetric blunt body in a thermal-equilibrium chemical-nonequilibrium environment. The flowfield is solved using an explicit time-marching, first-order spatially accurate scheme. The electromagnetic phenomena are coupled to the real-gas flow solver through an iterative procedure. The electromagnetic terms introduce a strong stiffness, which was overcome by using significantly smaller time steps for the electromagnetic conservation equation. The technique is applied in calculating the flow over a Mars return aerobrake vehicle entering the Earth's atmosphere. For the case where no external field is applied, the electromagnetic effects have little impact on the flowfield.
Genetic Homogenization of Composite Materials
P. Tobola
2009-04-01
Full Text Available The paper is focused on numerical studies of electromagnetic properties of composite materials used for the construction of small airplanes. Discussions concentrate on the genetic homogenization of composite layers and composite layers with a slot. The homogenization is aimed to reduce CPU-time demands of EMC computational models of electrically large airplanes. First, a methodology of creating a 3-dimensional numerical model of a composite material in CST Microwave Studio is proposed focusing on a sufficient accuracy of the model. Second, a proper implementation of a genetic optimization in Matlab is discussed. Third, an association of the optimization script and a simplified 2-dimensional model of the homogeneous equivalent model in Comsol Multiphysics is proposed considering EMC issues. Results of computations are experimentally verified.
Lusche, Robert; Semenov, Alexey; Huebers, Heinz-Willhelm [DLR, Institut fuer Planetenforschung, Berlin (Germany); Ilin, Konstantin; Siegel, Michael [Karlsruher Institut fuer Technologie (Germany); Korneeva, Yuliya; Trifonov, Andrey; Korneev, Alexander; Goltsman, Gregory [Moscow State Pedagogical University (Russian Federation)
2013-07-01
The interest in single-photon detectors in the near-infrared wavelength regime for applications, e.g. in quantum cryptography has immensely increased in the last years. Superconducting nanowire single-photon detectors (SNSPD) already show quite reasonable detection efficiencies in the NIR which can even be further improved. Novel theoretical approaches including vortex-assisted photon counting state that the detection efficiency in the long wavelength region can be enhanced by the detector geometry and an applied magnetic field. We present spectral measurements in the wavelength range from 350-2500 nm of the detection efficiency of meander-type TaN and NbN SNSPD with varying nanowire line width from 80 to 250 nm. Due to the used experimental setup we can accurately normalize the measured spectra and are able to extract the intrinsic detection efficiency (IDE) of our detectors. The results clearly indicate an improvement of the IDE depending on the wire width according to the theoretic models. Furthermore we experimentally found that the smallest detectable photon-flux can be increased by applying a small magnetic field to the detectors.
Tshipa, M.; Winkoun, D. P.; Nijegorodov, N.; Masale, M.
2018-04-01
Theoretical investigations are carried out of binding energies of a donor charge assumed to be located exactly at the center of symmetry of two concentric cylindrical quantum wires. The intrinsic confinement potential in the region of the inner cylinder is modeled in any one of the three profiles: simple parabolic, shifted parabolic or the polynomial potential. The potential inside the shell is taken to be a potential step or potential barrier of a finite height. Additional confinement of the charge carriers is due to the vector potential of the axial applied magnetic field. It is found that the binding energies attain maxima in their variations with the radius of the inner cylinder irrespective of the particular intrinsic confinement of the inner cylinder. As the radius of the inner cylinder is increased further, the binding energies corresponding to either the parabolic or the polynomial potentials attain minima at some critical core-radius. Finally, as anticipated, the binding energies increase with the increase of the parallel applied magnetic field. This behaviour of the binding energies is irrespective of the particular electric potential of the nanostructure or its specific dimensions.
Zheng, J.; Liao, X.L.; Jing, H.L.; Deng, Z.G.; Yen, F.; Wang, S.Y.; Wang, J.S.
2013-01-01
Highlights: • The single-layer bulk HTSC with AGSBP obtains better levitation performance than that of MGSBP. • The double-layer bulk with AGSBP obtains better levitation performance than that of MGSBP too. • The double-layer bulk finding is contrast to MGSBP if pursuing high trapped field. • The optimization is highlighted by simple and easy operation, thus economical in the practice. -- Abstract: Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems
Kikuchi, Y; Finken, K H; Jakubowski, M; Lehnen, M; Reiser, D; Sewell, G; Wolf, R C
2006-01-01
The error-field penetration process of the dynamic ergodic divertor (DED) on the TEXTOR tokamak has been investigated analytically in terms of a single fluid MHD model with a finite plasma resistivity and viscosity in a cylindrical geometry. The linear model produces a localization of the induced current at the resonance surface and predicts a vortex structure of the velocity field near the resonance layer. Moreover, effects of the Alfven resonance for the error-field penetration are identified by two peaks in the radial profiles of the perturbed toroidal current and the perturbed magnetic flux when the relative rotation velocity between the DED and the rotating tokamak plasma is set to large. Fine structures of the vorticity induced by the DED in the vicinity of the rational surface disappear by introducing a finite plasma perpendicular viscosity. In addition, it is shown that the two peaks of the perturbed toroidal current overlap by an anomalous plasma perpendicular viscosity. Likewise, a bifurcation of the penetration process from the suppressed to the excited state is obtained by a quasi-linear approach taking into account modifications of the radial profiles of the equilibrium current and the plasma rotation due to the DED. A comparison with real experimental results of the DED on the TEXTOR tokamak is shown
Zheng, J., E-mail: jzheng@swjtu.edu.cn; Liao, X.L.; Jing, H.L.; Deng, Z.G.; Yen, F.; Wang, S.Y.; Wang, J.S.
2013-10-15
Highlights: • The single-layer bulk HTSC with AGSBP obtains better levitation performance than that of MGSBP. • The double-layer bulk with AGSBP obtains better levitation performance than that of MGSBP too. • The double-layer bulk finding is contrast to MGSBP if pursuing high trapped field. • The optimization is highlighted by simple and easy operation, thus economical in the practice. -- Abstract: Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems.
Canfield, P.C.; Bud'ko, S.L.; Ni, N.; Kreyssig, A.; Goldman, A.I.; McQueeney, R.J.; Torikachvili, M.S.; Argyriou, D.N.; Luke, G.; Yu, W.
2009-01-01
At ambient pressure CaFe 2 As 2 has been found to undergo a first order phase transition from a high temperature, tetragonal phase to a low-temperature orthorhombic/antiferromagnetic phase upon cooling through T ∼ 170 K. With the application of pressure this phase transition is rapidly suppressed and by ∼0.35 GPa it is replaced by a first order phase transition to a low-temperature collapsed tetragonal, non-magnetic phase. Further application of pressure leads to an increase of the tetragonal to collapsed tetragonal phase transition temperature, with it crossing room temperature by ∼1.7 GPa. Given the exceptionally large and anisotropic change in unit cell dimensions associated with the collapsed tetragonal phase, the state of the pressure medium (liquid or solid) at the transition temperature has profound effects on the low-temperature state of the sample. For He-gas cells the pressure is as close to hydrostatic as possible and the transitions are sharp and the sample appears to be single phase at low temperatures. For liquid media cells at temperatures below media freezing, the CaFe 2 As 2 transforms when it is encased by a frozen media and enters into a low-temperature multi-crystallographic-phase state, leading to what appears to be a strain stabilized superconducting state at low temperatures.
Spontaneous compactification to homogeneous spaces
Mourao, J.M.
1988-01-01
The spontaneous compactification of extra dimensions to compact homogeneous spaces is studied. The methods developed within the framework of coset space dimensional reduction scheme and the most general form of invariant metrics are used to find solutions of spontaneous compactification equations
Estimation of non-linear effective permeability of magnetic materials with fine structure
Waki, H.; Igarashi, H.; Honma, T.
2006-01-01
This paper describes a homogenization method for magnetic materials with fine structure. In this method, the structures of the magnetic materials are assumed to be periodic, and the unit cell is defined. The effective permeability is determined on the basis of magnetic energy balance in the unit cell. This method can be applied not only for linear problems but also for non-linear ones. In this paper, estimation of the effective permeability of non-linear magnetic materials by using the homogenization method is described in detail, and then the validity for the non-liner problems is tested for two-dimensional problems. It is shown that this homogenization method gives accurate non-linear effective permeability
Sensor Systems with Magnetic and Optomagnetic Readout of Rolling Circle Amplification Products
Hansen, Mikkel Fougt; Donolato, Marco; Fock, Jeppe
2016-01-01
We are developing robust biosensors for homogeneous detection of rolling cirle amplification (RCA) products with magnetic and/or optomagnetic readouts based on surface-functionalized magnetic nanoparticles. Binding of RCA amplicons to nanoparticles modifies their ability to rotate in response...... to an applied oscillating magnetic field. As a result, magnetic or optical measurements of these changes in the rotational response of nanoparticles vs. frequency of the magnetic field can be used to quantitate the number of amplicons, and, hence, the concentration of target nucleic acid analytes. After...
Aboud, Essam; El-Masry, Nabil; Qaddah, Atef; Alqahtani, Faisal; Moufti, Mohammed R. H.
2015-06-01
The Rahat volcanic field represents one of the widely distributed Cenozoic volcanic fields across the western regions of the Arabian Peninsula. Its human significance stems from the fact that its northern fringes, where the historical eruption of 1256 A.D. took place, are very close to the holy city of Al-Madinah Al-Monawarah. In the present work, we analyzed aeromagnetic data from the northern part of Rahat volcanic field as well as carried out a ground gravity survey. A joint interpretation and inversion of gravity and magnetic data were used to estimate the thickness of the lava flows, delineate the subsurface structures of the study area, and estimate the depth to basement using various geophysical methods, such as Tilt Derivative, Euler Deconvolution and 2D modeling inversion. Results indicated that the thickness of the lava flows in the study area ranges between 100 m (above Sea Level) at the eastern and western boundaries of Rahat Volcanic field and getting deeper at the middle as 300-500 m. It also showed that, major structural trend is in the NW direction (Red Sea trend) with some minor trends in EW direction.
Benoit Curé
The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...
B. Curé
The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...
Benoit Curé
2013-01-01
Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...
Investigation of methods for hydroclimatic data homogenization
Steirou, E.; Koutsoyiannis, D.
2012-04-01
We investigate the methods used for the adjustment of inhomogeneities of temperature time series covering the last 100 years. Based on a systematic study of scientific literature, we classify and evaluate the observed inhomogeneities in historical and modern time series, as well as their adjustment methods. It turns out that these methods are mainly statistical, not well justified by experiments and are rarely supported by metadata. In many of the cases studied the proposed corrections are not even statistically significant. From the global database GHCN-Monthly Version 2, we examine all stations containing both raw and adjusted data that satisfy certain criteria of continuity and distribution over the globe. In the United States of America, because of the large number of available stations, stations were chosen after a suitable sampling. In total we analyzed 181 stations globally. For these stations we calculated the differences between the adjusted and non-adjusted linear 100-year trends. It was found that in the two thirds of the cases, the homogenization procedure increased the positive or decreased the negative temperature trends. One of the most common homogenization methods, 'SNHT for single shifts', was applied to synthetic time series with selected statistical characteristics, occasionally with offsets. The method was satisfactory when applied to independent data normally distributed, but not in data with long-term persistence. The above results cast some doubts in the use of homogenization procedures and tend to indicate that the global temperature increase during the last century is between 0.4°C and 0.7°C, where these two values are the estimates derived from raw and adjusted data, respectively.
Banerjee, S. K.; Mellema, J. P.
1976-01-01
A new method (Shaw, 1974) for investigating paleointensity (the ancient magnetic field) was applied to three subsamples of a single, 1-m homogeneous clast from a recrystallized boulder of lunar breccia. Several dating methods established 4 billion years as the age of boulder assembly. Results indicate that the strength of the ambient magnetic field at the Taurus-Littrow region of the moon was about 0.4 oersted at 4 billion years ago. Values as high as 1.2 oersted have been reported (Collison et al., 1973). The required fields are approximately 10,000 times greater than present interplanetary or solar flare fields. It is suggested that this large field could have arisen from a pre-main sequence T-Tauri sun.
Sandeep S. Nair; Sudhir Sharma; Yunqiao Pu; Qining Sun; Shaobo Pan; J.Y. Zhu; Yulin Deng; Art J. Ragauskas
2014-01-01
A new method to prepare nanolignin using a simple high shear homogenizer is presented. The kraft lignin particles with a broad distribution ranging from large micron- to nano-sized particles were completely homogenized to nanolignin particles with sizes less than 100 nm after 4 h of mechanical shearing. The 13C nuclear magnetic resonance (NMR)...
Valdé s, Felipe; Andriulli, Francesco P.; Bagci, Hakan; Michielssen, Eric
2013-01-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis
Observational homogeneity of the Universe
Bonnor, W.B.; Ellis, G.F.R.
1986-01-01
A new approach to observational homogeneity is presented. The observation that stars and galaxies in distant regions appear similar to those nearby may be taken to imply that matter has had a similar thermodynamic history in widely separated parts of the Universe (the Postulate of Uniform Thermal Histories, or PUTH). The supposition is now made that similar thermodynamic histories imply similar dynamical histories. Then the distant apparent similarity is evidence for spatial homogeneity of the Universe. General Relativity is used to test this idea, taking a perfect fluid model and implementing PUTH by the condition that the density and entropy per baryon shall be the same function of the proper time along all galaxy world-lines. (author)
Saito, Kimiyo; Fukui, Satoshi; Maezawa, Masaru; Ogawa, Jun; Oka, Tetsuo; Sato, Takao
2013-01-01
Highlights: ► We develop test spinner for non-contact spinning process in photo mask production. ► This test spinner shows improved spinning ability compared with our previous one. ► Large vertical movement of turn table still occurs during acceleration. ► Method to control vertical movement of turn table should be developed in next step. -- Abstract: In semiconductor devices, miniaturization of circuit patterning on wafers is required for higher integrations of circuit elements. Therefore, very high tolerance and quality are also required for patterning of microstructures of photo masks. The deposition of particulate dusts generated from mechanical bearings of the spin processor in the patterns of the photo mask is one of main causes of the deterioration of pattern preciseness. In our R and D, application of magnetic bearing utilizing bulk high temperature superconductors to the spin processors has been proposed. In this study, we develop a test spinner for the non-contact spinning process in the photo mask production system. The rotation test by using this test spinner shows that this test spinner accomplishes the improvement of the spinning ability compared with the test spinner developed in our previous study. This paper describes the rotation test results of the new test spinner applying the magnetic bearing with bulk high temperature superconductors
Gomez R, F. [UAEM, A.P. 2-139, 50000 Toluca, Estado de Mexico (Mexico); Ondarza R, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)
2004-07-01
An analytical model for the description of the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized propagating along of a static and homogeneous external magnetic field in a plasma starting from the force equation is presented. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary amplitude and modulated by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radiative effects. (Author)
Gomez R, F. [UAEM, Facultad de Ciencias, 50000 Toluca, Estado de Mexico (Mexico); Ondarza R, R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)
2004-07-01
An analytic model is presented for the description of the motion of a charged particle in the interaction of an elliptically electromagnetic pulse polarized propagating along a static and homogeneous external magnetic field in a plasma starting from the force equation. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary and modulated width by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radioactive effects. (Author)
Pedrick, A.P.
1976-01-01
An arrangement is described in which a body is accelerated or maintained in motion along a track that passes through a number of annular electromagnet coils, the length of the body being substantially less than the distance between two adjacent coils. A series if electronmagnetically produced force pulses is applied to the body as it passes through successive coils, by the use of an automatic switch operated by the body. Control is provided so that each coil is de-energized at or before maximum magnetic flux linkage is attained between coil and body, the arrangement being such that the body is accelerated into the coil, but leaves it at a much reduced flux linkage. The possible uses of such an arrangement are mentioned: these include the acceleration of bullets, incorporating D and T in pellet form in their concave noses, to obtain a nuclear fusion reaction. (U.K.)
Conclusions about homogeneity and devitrification
Larche, F.
1997-01-01
A lot of experimental data concerning homogeneity and devitrification of R7T7 glass have been published. It appears that: - the crystallization process is very limited, - the interfaces due to bubbles and the container wall favor crystallization locally but the ratio of crystallized volume remains always below a few per cents, and - crystallization has no damaging long-term effects as far as leaching tests can be trusted. (A.C.)
Is charity a homogeneous good?
Backus, Peter
2010-01-01
In this paper I estimate income and price elasticities of donations to six different charitable causes to test the assumption that charity is a homogeneous good. In the US, charitable donations can be deducted from taxable income. This has long been recognized as producing a price, or taxprice, of giving equal to one minus the marginal tax rate faced by the donor. A substantial portion of the economic literature on giving has focused on estimating price and income elasticities of giving as th...
2018-06-01
Welcome to the special issue of Journal of Magnetism and Magnetic Materials on magnetic skyrmions. We are proud to present, with great pleasure, a timely collection of 9 original research articles on the recent hot topic "magnetic skyrmions" which studies the static and dynamic properties of skyrmions and the methods to control them in a variety of ways, including magnetic field, electric current and applied strain.
Hybrid design method for air-core solenoid with axial homogeneity
Huang, Li; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of); Choi, Suk Jin [Institute for Basic Science, Daejeon (Korea, Republic of)
2016-03-15
In this paper, a hybrid method is proposed to design an air-core superconducting solenoid system for 6 T axial uniform magnetic field using Niobium Titanium (NbTi) superconducting wire. In order to minimize the volume of conductor, the hybrid optimization method including a linear programming and a nonlinear programming was adopted. The feasible space of solenoid is divided by several grids and the magnetic field at target point is approximated by the sum of magnetic field generated by an ideal current loop at the center of each grid. Using the linear programming, a global optimal current distribution in the feasible space can be indicated by non-zero current grids. Furthermore the clusters of the non-zero current grids also give the information of probable solenoids in the feasible space, such as the number, the shape, and so on. Applying these probable solenoids as the initial model, the final practical configuration of solenoids with integer layers can be obtained by the nonlinear programming. The design result illustrates the efficiency and the flexibility of the hybrid method. And this method can also be used for the magnet design which is required the high homogeneity within several ppm (parts per million)
Physical applications of homogeneous balls
Scarr, Tzvi
2005-01-01
One of the mathematical challenges of modern physics lies in the development of new tools to efficiently describe different branches of physics within one mathematical framework. This text introduces precisely such a broad mathematical model, one that gives a clear geometric expression of the symmetry of physical laws and is entirely determined by that symmetry. The first three chapters discuss the occurrence of bounded symmetric domains (BSDs) or homogeneous balls and their algebraic structure in physics. The book further provides a discussion of how to obtain a triple algebraic structure ass
Tom, Nathan; Yeung, Ronald W.
2015-01-01
To further maximize power absorption in both regular and irregular ocean wave environments, nonlinear-model-predictive control (NMPC) was applied to a model-scale point absorber developed at the University of California Berkeley, Berkeley, CA, USA. The NMPC strategy requires a power-takeoff (PTO) unit that could be turned on and off, as the generator would be inactive for up to 60% of the wave period. To confirm the effectiveness of this NMPC strategy, an in-house-designed permanent magnet linear generator (PMLG) was chosen as the PTO. The time-varying performance of the PMLG was first characterized by dry-bench tests, using mechanical relays to control the electromagnetic conversion process. The on/off sequencing of the PMLG was tested under regular and irregular wave excitation to validate NMPC simulations using control inputs obtained from running the choice optimizer offline. Experimental results indicate that successful implementation was achieved and absorbed power using NMPC was up to 50% greater than the passive system, which utilized no controller. Previous investigations into MPC applied to wave energy converters have lacked the experimental results to confirm the reported gains in power absorption. However, after considering the PMLG mechanical-to-electrical conversion efficiency, the electrical power output was not consistently maximized. To improve output power, a mathematical relation between the efficiency and damping magnitude of the PMLG was inserted in the system model to maximize the electrical power output through continued use of NMPC which helps separate this work from previous investigators. Of significance, results from latter simulations provided a damping time series that was active over a larger portion of the wave period requiring the actuation of the applied electrical load, rather than on/off control.
Magnon-mediated Dzyaloshinskii-Moriya torque in homogeneous ferromagnets
Manchon, Aurelien
2014-12-01
In thin magnetic layers with structural inversion asymmetry and spin-orbit coupling, the Dzyaloshinskii-Moriya interaction arises at the interface. When a spin-wave current jm flows in a system with a homogeneous magnetization m, this interaction produces an effective fieldlike torque of the form TFLm×(z×jm) as well as a dampinglike torque, TDLm×[(z×jm)×m], the latter only in the presence of spin-wave relaxation (z is normal to the interface). These torques mediated by the magnon flow can reorient the time-averaged magnetization direction and display a number of similarities with the torques arising from the electron flow in a magnetic two-dimensional electron gas with Rashba spin-orbit coupling. This magnon-mediated spin-orbit torque can be efficient in the case of magnons driven by a thermal gradient.
ISOTOPE METHODS IN HOMOGENEOUS CATALYSIS.
BULLOCK,R.M.; BENDER,B.R.
2000-12-01
The use of isotope labels has had a fundamentally important role in the determination of mechanisms of homogeneously catalyzed reactions. Mechanistic data is valuable since it can assist in the design and rational improvement of homogeneous catalysts. There are several ways to use isotopes in mechanistic chemistry. Isotopes can be introduced into controlled experiments and followed where they go or don't go; in this way, Libby, Calvin, Taube and others used isotopes to elucidate mechanistic pathways for very different, yet important chemistries. Another important isotope method is the study of kinetic isotope effects (KIEs) and equilibrium isotope effect (EIEs). Here the mere observation of where a label winds up is no longer enough - what matters is how much slower (or faster) a labeled molecule reacts than the unlabeled material. The most careti studies essentially involve the measurement of isotope fractionation between a reference ground state and the transition state. Thus kinetic isotope effects provide unique data unavailable from other methods, since information about the transition state of a reaction is obtained. Because getting an experimental glimpse of transition states is really tantamount to understanding catalysis, kinetic isotope effects are very powerful.
Thimm, Andreas; Funke, Klaus
2015-02-15
Theta-burst stimulation (TBS) applied via transcranial magnetic stimulation is able to modulate human cortical excitability. Here we investigated in a rat model how two different forms of TBS, intermittent (iTBS) and continuous (cTBS), affect sensory responses in rat barrel cortex. We found that iTBS but less cTBS promoted late (>18 ms) sensory response components while not affecting the earliest response (8-18 ms). The effect increased with each of the five iTBS blocks applied. cTBS somewhat reduced the early response component after the first block but had a similar effect as iTBS after four to five blocks. We conclude that iTBS primarly modulates the activity of (inhibitory) cortical interneurons while cTBS may first reduce general neuronal excitability with a single block but reverse to iTBS-like effects with application of several blocks. Cortical sensory processing varies with cortical state and the balance of inhibition to excitation. Repetitive transcranial magnetic stimulation (rTMS) has been shown to modulate human cortical excitability. In a rat model, we recently showed that intermittent theta-burst stimulation (iTBS) applied to the corpus callosum, to activate primarily supragranular cortical pyramidal cells but fewer subcortical neurons, strongly reduced the cortical expression of parvalbumin (PV), indicating reduced activity of fast-spiking interneurons. Here, we used the well-studied rodent barrel cortex system to test how iTBS and continuous TBS (cTBS) modulate sensory responses evoked by either single or double stimuli applied to the principal (PW) and/or adjacent whisker (AW) in urethane-anaesthetized rats. Compared to sham stimulation, iTBS but not cTBS particularly enhanced late (>18 ms) response components of multi-unit spiking and local field potential responses in layer 4 but not the very early response (iTBS diminished the suppression of the second response evoked by paired PW or AW-PW stimulation at 20 ms intervals. The effects
Non-homogeneous polymer model for wave propagation and its ...
user
density are functions of space i.e. non-homogeneous engineering material. .... The Solution of equation Eq. (9) in the form of Eq. (10) can be obtained by taking a phase ..... Viscoelastic Model Applied to a Particular Case .... p m i exp m α α σ σ σ. = −. +. −. (35). The progressive harmonic wave which starts from the end. 0 x =.
Homogenization of Large-Scale Movement Models in Ecology
Garlick, M.J.; Powell, J.A.; Hooten, M.B.; McFarlane, L.R.
2011-01-01
A difficulty in using diffusion models to predict large scale animal population dispersal is that individuals move differently based on local information (as opposed to gradients) in differing habitat types. This can be accommodated by using ecological diffusion. However, real environments are often spatially complex, limiting application of a direct approach. Homogenization for partial differential equations has long been applied to Fickian diffusion (in which average individual movement is organized along gradients of habitat and population density). We derive a homogenization procedure for ecological diffusion and apply it to a simple model for chronic wasting disease in mule deer. Homogenization allows us to determine the impact of small scale (10-100 m) habitat variability on large scale (10-100 km) movement. The procedure generates asymptotic equations for solutions on the large scale with parameters defined by small-scale variation. The simplicity of this homogenization procedure is striking when compared to the multi-dimensional homogenization procedure for Fickian diffusion,and the method will be equally straightforward for more complex models. ?? 2010 Society for Mathematical Biology.
Perevertov, Oleksiy; Thielsch, J.; Schäfer, R.
2015-01-01
Roč. 385, Jul (2015), 358-367 ISSN 0304-8853 R&D Projects: GA ČR GA13-18993S Institutional support: RVO:68378271 Keywords : magnetic domains * magnetization process * magnetoelasticity * hysteresis loops * tension * Kerr microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.357, year: 2015
Improving homogeneity by dynamic speed limit systems.
Nes, N. van Brandenberg, S. & Twisk, D.A.M.
2010-01-01
Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12
7 CFR 58.636 - Homogenization.
2010-01-01
... 7 Agriculture 3 2010-01-01 2010-01-01 false Homogenization. 58.636 Section 58.636 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.636 Homogenization. Homogenization of the pasteurized mix shall be accomplished to...
The homogeneous geometries of real hyperbolic space
Castrillón López, Marco; Gadea, Pedro Martínez; Swann, Andrew Francis
We describe the holonomy algebras of all canonical connections of homogeneous structures on real hyperbolic spaces in all dimensions. The structural results obtained then lead to a determination of the types, in the sense of Tricerri and Vanhecke, of the corresponding homogeneous tensors. We use...... our analysis to show that the moduli space of homogeneous structures on real hyperbolic space has two connected components....
Orthogonality Measurement for Homogenous Projects-Bases
Ivan, Ion; Sandu, Andrei; Popa, Marius
2009-01-01
The homogenous projects-base concept is defined. Next, the necessary steps to create a homogenous projects-base are presented. A metric system is built, which then will be used for analyzing projects. The indicators which are meaningful for analyzing a homogenous projects-base are selected. The given hypothesis is experimentally verified. The…
Kauts, V.L.; Savochkin, A.M.; Studenikin, A.I.
2006-01-01
Exact solution of Dirac equation for charged particles in homogenous magnetic field for computation of probability in presence of degenerate magnetized Fermi-gas consisting of protons, neutrons, and electrons has been used. Angular distribution of antineutrino momenta is investigated. Values of main parameters of medium is realistic for physics of neutron stars. This investigation may be applied for consideration of cooling of neutron stars [ru
Fluxball magnetic field analysis using a hybrid analytical/FEM/BEM with equivalent currents
Fernandes, João F.P.; Camilo, Fernando M.; Machado, V. Maló
2016-01-01
In this paper, a fluxball electric machine is analyzed concerning the magnetic flux, force and torque. A novel method is proposed based in a special hybrid FEM/BEM (Finite Element Method/Boundary Element Method) with equivalent currents by using an analytical treatment for the source field determination. The method can be applied to evaluate the magnetic field in axisymmetric problems, in the presence of several magnetic materials. Same results obtained by a commercial Finite Element Analysis tool are presented for validation purposes with the proposed method. - Highlights: • The Fluxball machine magnetic field is analyzed by a new FEM/BEM/Analytical method. • The method is adequate for axisymmetric non homogeneous magnetic field problems. • The source magnetic field is evaluated considering a non-magnetic equivalent problem. • Material magnetization vectors are accounted by using equivalent currents. • A strong reduction of the finite element domain is achieved.
Nuclear magnetic resonance scattering
Young, I.R.
1985-01-01
A nuclear magnetic resonance apparatus is described including a magnet system which is capable of providing a steady magnetic field along an axis, and is constructed so as to define a plurality of regions along the axis in each of which the field is substantially homogeneous so that in each region an imaging operation may be separately carried out. Iron shields increase the field homogeneity. In use, each patient lies on a wheeled trolley which is provided with magnetic field gradient coils and an RF coil system, some of the coils being movable to facilitate positioning of the patient, and there are terminals for connection to a common computing and control facility. (author)
The evaporative vector: Homogeneous systems
Klots, C.E.
1987-05-01
Molecular beams of van der Waals molecules are the subject of much current research. Among the methods used to form these beams, three-sputtering, laser ablation, and the sonic nozzle expansion of neat gases - yield what are now recognized to be ''warm clusters.'' They contain enough internal energy to undergo a number of first-order processes, in particular that of evaporation. Because of this evaporation and its attendant cooling, the properties of such clusters are time-dependent. The states of matter which can be arrived at via an evaporative vector on a typical laboratory time-scale are discussed. Topics include the (1) temperatures, (2) metastability, (3) phase transitions, (4) kinetic energies of fragmentation, and (5) the expression of magical properties, all for evaporating homogeneous clusters
Murase, Kenya; Yamazaki, Youichi; Shinohara, Masaaki
2003-01-01
The purpose of this study was to investigate the feasibility of the autoregressive moving average (ARMA) model for quantification of cerebral blood flow (CBF) with dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSC-MRI) in comparison with deconvolution analysis based on singular value decomposition (DA-SVD). Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various CBFs, cerebral blood volumes and signal-to-noise ratios (SNRs) for three different types of residue function (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The ARMA model and DA-SVD were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIFs, and the estimated values were compared with the assumed values. We found that the CBF value estimated by the ARMA model was more sensitive to the SNR and the delay in AIF than that obtained by DA-SVD. Although the ARMA model considerably overestimated CBF at low SNRs, it estimated the CBF more accurately than did DA-SVD at high SNRs for the exponential or triangular residue function. We believe this study will contribute to an understanding of the usefulness and limitations of the ARMA model when applied to quantification of CBF with DSC-MRI. (author)
Jacquet, N; Vanderghem, C; Danthine, S; Blecker, C; Paquot, M
2013-02-01
The aim of this study is to compare the effect of different homogenization treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. Results obtained show that homogenization treatments improve the enzymatic hydrolysis rate of the cellulose fibers by 25 to 100 %, depending of the homogenization treatment applied. Characterization of the samples showed also that homogenization had an impact on some physicochemical properties of the cellulose. For moderate treatment intensities (pressure below 500 b and degree of homogenization below 25), an increase of water retention values (WRV) that correlated to the increase of the hydrolysis rate was highlighted. Result also showed that the overall crystallinity of the cellulose properties appeared not to be impacted by the homogenization treatment. For higher treatment intensities, homogenized cellulose samples developed a stable tridimentional network that contributes to decrease cellulase mobility and slowdown the hydrolysis process.
A homogeneous catalogue of quasar candidates found with slitless spectroscopy
Beauchemin, M.; Borra, E.F.; Edwards, G.
1990-01-01
This paper gives a list of all quasar candidates obtained from an automated computer search performed on 11 grens plates. The description of the main characteristics of the survey is given along with the latest improvements in the selection techniques. Particular attention has been paid to understanding and quantifying selection effects. This allows the construction of homogeneous samples having well-understood characteristics. The noteworthy aspect of our homogenization process is the correction that we apply to our probability classes in order to take into account the signal-to-noise differences; at a given magnitude, among plates of different limiting magnitudes. (author)
Magnetic nanoparticle imaging using multiple electron paramagnetic resonance activation sequences
Coene, A.; Dupré, L.; Crevecoeur, G.
2015-01-01
Magnetic nanoparticles play an important role in several biomedical applications such as hyperthermia, drug targeting, and disease detection. To realize an effective working of these applications, the spatial distribution of the particles needs to be accurately known, in a non-invasive way. Electron Paramagnetic Resonance (EPR) is a promising and sensitive measurement technique for recovering these distributions. In the conventional approach, EPR is applied with a homogeneous magnetic field. In this paper, we employ different heterogeneous magnetic fields that allow to stabilize the solution of the associated inverse problem and to obtain localized spatial information. A comparison is made between the two approaches and our novel adaptation shows an average increase in reconstruction quality by 5% and is 12 times more robust towards noise. Furthermore, our approach allows to speed up the EPR measurements while still obtaining reconstructions with an improved accuracy and noise robustness compared to homogeneous EPR
Toward whole-core neutron transport without spatial homogenization
Lewis, E. E.
2009-01-01
Full text of publication follows: A long-term goal of computational reactor physics is the deterministic analysis of power reactor core neutronics without incurring significant discretization errors in the energy, spatial or angular variables. In principle, given large enough parallel configurations with unlimited CPU time and memory, this goal could be achieved using existing three-dimensional neutron transport codes. In practice, however, solving the Boltzmann equation for neutrons over the six-dimensional phase space is made intractable by the nature of neutron cross-sections and the complexity and size of power reactor cores. Tens of thousands of energy groups would be required for faithful cross section representation. Likewise, the numerous material interfaces present in power reactor lattices require exceedingly fine spatial mesh structures; these ubiquitous interfaces preclude effective implementation of adaptive grid, mesh-less methods and related techniques that have been applied so successfully in other areas of engineering science. These challenges notwithstanding, substantial progress continues in the pursuit for more robust deterministic methods for whole-core neutronics analysis. This paper examines the progress over roughly the last decade, emphasizing the space-angle variables and the quest to eliminate errors attributable to spatial homogenization. As prolog we briefly assess 1990's methods used in light water reactor analysis and review the lessons learned from the C5G7 benchmark exercises which were originated in 1999 to appraise the ability of transport codes to perform core calculations without homogenization. We proceed by examining progress over the last decade much of which falls into three areas. These may be broadly characterized as reduced homogenization, dynamic homogenization and planar-axial synthesis. In the first, homogenization in three-dimensional calculations is reduced from the fuel assembly to the pin-cell level. In the second
Perevertov, Oleksiy; Schäfer, R.
2014-01-01
Roč. 47, č. 18 (2014), s. 1-10 ISSN 0022-3727 R&D Projects: GA ČR(CZ) GAP107/11/0391 Grant - others:AVČR(CZ) M100100906 Institutional support: RVO:68378271 Keywords : magnetic domains * magnetization process * magnetoelasticity * hysteresis loops * tension * silicon steel * Kerr microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.721, year: 2014
Spatial homogenization method based on the inverse problem
Tóta, Ádám; Makai, Mihály
2015-01-01
Highlights: • We derive a spatial homogenization method in slab and cylindrical geometries. • The fluxes and the currents on the boundary are preserved. • The reaction rates and the integral of the fluxes are preserved. • We present verification computations utilizing two- and four-energy groups. - Abstract: We present a method for deriving homogeneous multi-group cross sections to replace a heterogeneous region’s multi-group cross sections; providing that the fluxes, the currents on the external boundary, the reaction rates and the integral of the fluxes are preserved. We consider one-dimensional geometries: a symmetric slab and a homogeneous cylinder. Assuming that the boundary fluxes are given, two response matrices (RMs) can be defined concerning the current and the flux integral. The first one derives the boundary currents from the boundary fluxes, while the second one derives the flux integrals from the boundary fluxes. Further RMs can be defined that connects reaction rates to the boundary fluxes. Assuming that these matrices are known, we present formulae that reconstruct the multi-group diffusion cross-section matrix, the diffusion coefficients and the reaction cross sections in case of one-dimensional (1D) homogeneous regions. We apply these formulae to 1D heterogeneous regions and thus obtain a homogenization method. This method produces such an equivalent homogeneous material, that the fluxes and the currents on the external boundary, the reaction rates and the integral of the fluxes are preserved for any boundary fluxes. We carry out the exact derivations in 1D slab and cylindrical geometries. Verification computations for the presented homogenization method were performed using two- and four-group material cross sections, both in a slab and in a cylindrical geometry
Abd El-Gawad, Mona A M; Ahmed, Nawal S; El-Abd, M M; Abd El-Rafee, S
2012-04-02
The name pasta filata refers to a unique plasticizing and texturing treatments of the fresh curd in hot water that imparts to the finished cheese its characteristic fibrous structure and melting properties. Mozzarella cheese made from standardized homogenized and non-homogenized buffalo milk with 3 and 1.5%fat. The effect of homogenization on rheological, microstructure and sensory evaluation was carried out. Fresh raw buffalo milk and starter cultures of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus were used. The coagulants were calf rennet powder (HA-LA). Standardized buffalo milk was homogenized at 25 kg/cm2 pressure after heating to 60°C using homogenizer. Milk and cheese were analysed. Microstructure of the cheese samples was investigated either with an application of transmission or scanning electron microscope. Statistical analyses were applied on the obtained data. Soluble nitrogen total volatile free fatty acids, soluble tyrosine and tryptophan increased with using homogenized milk and also, increased with relatively decrease in case of homogenized Mozzarella cheese. Meltability of Mozzarella cheese increased with increasing the fat content and storage period and decrease with homogenization. Mozzarella cheese firmness increased with homogenization and also, increased with progressing of storage period. Flavour score, appearance and total score of Mozzarella cheese increased with homogenization and storage period progress, while body and texture score decreased with homogenization and increased with storage period progress. Microstructure of Mozzarella cheese showed the low fat cheese tends to be harder, more crumbly and less smooth than normal. Curd granule junctions were prominent in non-homogenized milk cheese. Homogenization of milk cheese caused changes in the microstructure of the Mozzarella cheese. Microstructure studies of cheese revealed that cheese made from homogenized milk is smoother and has a finer texture than
Numerical computing of elastic homogenized coefficients for periodic fibrous tissue
Roman S.
2009-06-01
Full Text Available The homogenization theory in linear elasticity is applied to a periodic array of cylindrical inclusions in rectangular pattern extending to infinity in the inclusions axial direction, such that the deformation of tissue along this last direction is negligible. In the plane of deformation, the homogenization scheme is based on the average strain energy whereas in the third direction it is based on the average normal stress along this direction. Namely, these average quantities have to be the same on a Repeating Unit Cell (RUC of heterogeneous and homogenized media when using a special form of boundary conditions forming by a periodic part and an affine part of displacement. It exists an infinity of RUCs generating the considered array. The computing procedure is tested with different choices of RUC to control that the results of the homogenization process are independent of the kind of RUC we employ. Then, the dependence of the homogenized coefficients on the microstructure can be studied. For instance, a special anisotropy and the role of the inclusion volume are investigated. In the second part of this work, mechanical traction tests are simulated. We consider two kinds of loading, applying a density of force or imposing a displacement. We test five samples of periodic array containing one, four, sixteen, sixty-four and one hundred of RUCs. The evolution of mean stresses, strains and energy with the numbers of inclusions is studied. Evolutions depend on the kind of loading, but not their limits, which could be predicted by simulating traction test of the homogenized medium.
Homogeneous modes of cosmological instantons
Gratton, Steven; Turok, Neil
2001-06-15
We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their properties are important in establishing the meaning of the Euclidean path integral. If negative modes are present, the Euclidean path integral is not well defined, but may nevertheless be useful in an approximate description of the decay of an unstable state. When gravitational dynamics is included, counting negative modes requires a careful treatment of the conformal factor problem. We demonstrate that for an appropriate choice of coordinate on phase space, the second order Euclidean action is bounded below for normalized perturbations and has a finite number of negative modes. We prove that there is a negative mode for many gravitational instantons of the Hawking-Moss or Coleman{endash}De Luccia type, and discuss the associated spectral flow. We also investigate Hawking-Turok constrained instantons, which occur in a generic inflationary model. Implementing the regularization and constraint proposed by Kirklin, Turok and Wiseman, we find that those instantons leading to substantial inflation do not possess negative modes. Using an alternate regularization and constraint motivated by reduction from five dimensions, we find a negative mode is present. These investigations shed new light on the suitability of Euclidean quantum gravity as a potential description of our universe.
Homogeneous modes of cosmological instantons
Gratton, Steven; Turok, Neil
2001-01-01
We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their properties are important in establishing the meaning of the Euclidean path integral. If negative modes are present, the Euclidean path integral is not well defined, but may nevertheless be useful in an approximate description of the decay of an unstable state. When gravitational dynamics is included, counting negative modes requires a careful treatment of the conformal factor problem. We demonstrate that for an appropriate choice of coordinate on phase space, the second order Euclidean action is bounded below for normalized perturbations and has a finite number of negative modes. We prove that there is a negative mode for many gravitational instantons of the Hawking-Moss or ColemanendashDe Luccia type, and discuss the associated spectral flow. We also investigate Hawking-Turok constrained instantons, which occur in a generic inflationary model. Implementing the regularization and constraint proposed by Kirklin, Turok and Wiseman, we find that those instantons leading to substantial inflation do not possess negative modes. Using an alternate regularization and constraint motivated by reduction from five dimensions, we find a negative mode is present. These investigations shed new light on the suitability of Euclidean quantum gravity as a potential description of our universe
Sewage sludge disintegration by high-pressure homogenization: a sludge disintegration model.
Zhang, Yuxuan; Zhang, Panyue; Ma, Boqiang; Wu, Hao; Zhang, Sheng; Xu, Xin
2012-01-01
High-pressure homogenization (HPH) technology was applied as a pretreatment to disintegrate sewage sludge. The effects of homogenization pressure, homogenization cycle number, and total solid content on sludge disintegration were investigated. The sludge disintegration degree (DD(COD)), protein concentration, and polysaccharide concentration increased with the increase of homogenization pressure and homogenization cycle number, and decreased with the increase of sludge total solid (TS) content. The maximum DD(COD) of 43.94% was achieved at 80 MPa with four homogenization cycles for a 9.58 g/L TS sludge sample. A HPH sludge disintegration model of DD(COD) = kNaPb was established by multivariable linear regression to quantify the effects of homogenization parameters. The homogenization cycle exponent a and homogenization pressure exponent b were 0.4763 and 0.7324 respectively, showing that the effect of homogenization pressure (P) was more significant than that of homogenization cycle number (N). The value of the rate constant k decreased with the increase of sludge total solid content. The specific energy consumption increased with the increment of sludge disintegration efficiency. Lower specific energy consumption was required for higher total solid content sludge.
Improved Field Homogeneity for Transmission Line MRI Coils Using Series Capacitors
Zhurbenko, Vitaliy; Dong, Yunfeng
2015-01-01
High field magnetic resonance imaging (MRI) systems often use short sections of transmission lines for generating and sensing alternating magnetic fields. Due to distributed nature of transmission lines, the generated field is inhomogeneous. This work investigates the application of series capaci...... capacitors to improve the field homogeneity. The resulting magnetic field distribution is estimated analytically and evaluated numerically. The results are compared to a case of a conventional transmission line coil realization....
Katarzyna Dudzisz
2016-12-01
Full Text Available We demonstrate the use of the anisotropy of magnetic susceptibility (AMS method to determine the orientation of the principal tectonic strain directions developed during the formation of the West Spitsbergen Fold-and-Thrust Belt (WSFTB. The AMS measurements and extensive rock-magnetic studies of the Lower Triassic rocks reported here were focused on the recognition of the magnetic fabric, the identification of ferromagnetic minerals and an estimation of the influence of ferro- and paramagnetic minerals on magnetic susceptibility. At most sites, the paramagnetic minerals controlled the magnetic susceptibility, and at only one site the impact of ferromagnetic minerals was higher. The AMS technique documented the presence of different types of magnetic fabrics within the sampled sites. At two sites, a normal (Kmin perpendicular to the bedding magnetic fabric of sedimentary origin was detected. This was associated with a good clustering of the maximum AMS axes imposed by tectonic strain. The Kmax magnetic lineation directions obtained here parallel the general NNW–SSE trend of the WSFTB fold axial traces and thrust fronts. The two other investigated sites possessed mixed and inverted fabrics, the latter of which appear to reflect the presence of iron-bearing carbonates.
Perevertov, Oleksiy; Schäfer, R.
2012-01-01
Roč. 45, č. 13 (2012), "135001-1"-"135001-11" ISSN 0022-3727 Grant - others:GA AV ČR(CZ) M100100906 Institutional research plan: CEZ:AV0Z10100520 Keywords : hysteresis curve * magnetic domains * compressive stress * goss steel * effective field Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.528, year: 2012
A method to improve the B0 homogeneity of the heart in vivo.
Jaffer, F A; Wen, H; Balaban, R S; Wolff, S D
1996-09-01
A homogeneous static (B0) magnetic field is required for many NMR experiments such as echo planar imaging, localized spectroscopy, and spiral scan imaging. Although semi-automated techniques have been described to improve the B0 field homogeneity, none has been applied to the in vivo heart. The acquisition of cardiac field maps is complicated by motion, blood flow, and chemical shift artifact from epicardial fat. To overcome these problems, an ungated three-dimensional (3D) chemical shift image (CSI) was collected to generate a time and motion-averaged B0 field map. B0 heterogeneity in the heart was minimized by using a previous algorithm that solves for the optimal shim coil currents for an input field map, using up to third-order current-bounded shims (1). The method improved the B0 homogenelty of the heart in all 11 normal volunteers studied. After application of the algorithm to the unshimmed cardiac field maps, the standard deviation of proton frequency decreased by 43%, the magnitude 1H spectral linewidth decreased by 24%, and the peak-peak gradient decreased by 35%. Simulations of the high-order (second- and third-order) shims in B0 field correction of the heart show that high order shims are important, resulting for nearly half of the improvement in homogeneity for several subjects. The T2* of the left ventricular anterior wall before and after field correction was determined at 4.0 Tesis. Finally, results show that cardiac shimming is of benefit in cardiac 31P NMR spectroscopy and cardiac echo planar imaging.
AQUEOUS HOMOGENEOUS REACTORTECHNICAL PANEL REPORT
Diamond, D.J.; Bajorek, S.; Bakel, A.; Flanagan, G.; Mubayi, V.; Skarda, R.; Staudenmeier, J.; Taiwo, T.; Tonoike, K.; Tripp, C.; Wei, T.; Yarsky, P.
2010-12-03
Considerable interest has been expressed for developing a stable U.S. production capacity for medical isotopes and particularly for molybdenum- 99 (99Mo). This is motivated by recent re-ductions in production and supply worldwide. Consistent with U.S. nonproliferation objectives, any new production capability should not use highly enriched uranium fuel or targets. Conse-quently, Aqueous Homogeneous Reactors (AHRs) are under consideration for potential 99Mo production using low-enriched uranium. Although the Nuclear Regulatory Commission (NRC) has guidance to facilitate the licensing process for non-power reactors, that guidance is focused on reactors with fixed, solid fuel and hence, not applicable to an AHR. A panel was convened to study the technical issues associated with normal operation and potential transients and accidents of an AHR that might be designed for isotope production. The panel has produced the requisite AHR licensing guidance for three chapters that exist now for non-power reactor licensing: Reac-tor Description, Reactor Coolant Systems, and Accident Analysis. The guidance is in two parts for each chapter: 1) standard format and content a licensee would use and 2) the standard review plan the NRC staff would use. This guidance takes into account the unique features of an AHR such as the fuel being in solution; the fission product barriers being the vessel and attached systems; the production and release of radiolytic and fission product gases and their impact on operations and their control by a gas management system; and the movement of fuel into and out of the reactor vessel.
Homogeneity and thermodynamic identities in geometrothermodynamics
Quevedo, Hernando [Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares (Mexico); Universita di Roma ' ' La Sapienza' ' , Dipartimento di Fisica, Rome (Italy); ICRANet, Rome (Italy); Quevedo, Maria N. [Universidad Militar Nueva Granada, Departamento de Matematicas, Facultad de Ciencias Basicas, Bogota (Colombia); Sanchez, Alberto [CIIDET, Departamento de Posgrado, Queretaro (Mexico)
2017-03-15
We propose a classification of thermodynamic systems in terms of the homogeneity properties of their fundamental equations. Ordinary systems correspond to homogeneous functions and non-ordinary systems are given by generalized homogeneous functions. This affects the explicit form of the Gibbs-Duhem relation and Euler's identity. We show that these generalized relations can be implemented in the formalism of black hole geometrothermodynamics in order to completely fix the arbitrariness present in Legendre invariant metrics. (orig.)
A literature review on biotic homogenization
Guangmei Wang; Jingcheng Yang; Chuangdao Jiang; Hongtao Zhao; Zhidong Zhang
2009-01-01
Biotic homogenization is the process whereby the genetic, taxonomic and functional similarity of two or more biotas increases over time. As a new research agenda for conservation biogeography, biotic homogenization has become a rapidly emerging topic of interest in ecology and evolution over the past decade. However, research on this topic is rare in China. Herein, we introduce the development of the concept of biotic homogenization, and then discuss methods to quantify its three components (...
On the decay of homogeneous isotropic turbulence
Skrbek, L.; Stalp, Steven R.
2000-08-01
Decaying homogeneous, isotropic turbulence is investigated using a phenomenological model based on the three-dimensional turbulent energy spectra. We generalize the approach first used by Comte-Bellot and Corrsin [J. Fluid Mech. 25, 657 (1966)] and revised by Saffman [J. Fluid Mech. 27, 581 (1967); Phys. Fluids 10, 1349 (1967)]. At small wave numbers we assume the spectral energy is proportional to the wave number to an arbitrary power. The specific case of power 2, which follows from the Saffman invariant, is discussed in detail and is later shown to best describe experimental data. For the spectral energy density in the inertial range we apply both the Kolmogorov -5/3 law, E(k)=Cɛ2/3k-5/3, and the refined Kolmogorov law by taking into account intermittency. We show that intermittency affects the energy decay mainly by shifting the position of the virtual origin rather than altering the power law of the energy decay. Additionally, the spectrum is naturally truncated due to the size of the wind tunnel test section, as eddies larger than the physical size of the system cannot exist. We discuss effects associated with the energy-containing length scale saturating at the size of the test section and predict a change in the power law decay of both energy and vorticity. To incorporate viscous corrections to the model, we truncate the spectrum at an effective Kolmogorov wave number kη=γ(ɛ/v3)1/4, where γ is a dimensionless parameter of order unity. We show that as the turbulence decays, viscous corrections gradually become more important and a simple power law can no longer describe the decay. We discuss the final period of decay within the framework of our model, and show that care must be taken to distinguish between the final period of decay and the change of the character of decay due to the saturation of the energy containing length scale. The model is applied to a number of experiments on decaying turbulence. These include the downstream decay of turbulence in
Hybrid diffusion–transport spatial homogenization method
Kooreman, Gabriel; Rahnema, Farzad
2014-01-01
Highlights: • A new hybrid diffusion–transport homogenization method. • An extension of the consistent spatial homogenization (CSH) transport method. • Auxiliary cross section makes homogenized diffusion consistent with heterogeneous diffusion. • An on-the-fly re-homogenization in transport. • The method is faster than fine-mesh transport by 6–8 times. - Abstract: A new hybrid diffusion–transport homogenization method has been developed by extending the consistent spatial homogenization (CSH) transport method to include diffusion theory. As in the CSH method, an “auxiliary cross section” term is introduced into the source term, making the resulting homogenized diffusion equation consistent with its heterogeneous counterpart. The method then utilizes an on-the-fly re-homogenization in transport theory at the assembly level in order to correct for core environment effects on the homogenized cross sections and the auxiliary cross section. The method has been derived in general geometry and tested in a 1-D boiling water reactor (BWR) core benchmark problem for both controlled and uncontrolled configurations. The method has been shown to converge to the reference solution with less than 1.7% average flux error in less than one third the computational time as the CSH method – 6 to 8 times faster than fine-mesh transport
Homogenization scheme for acoustic metamaterials
Yang, Min; Ma, Guancong; Wu, Ying; Yang, Zhiyu; Sheng, Ping
2014-01-01
the scattering amplitudes. We verify our scheme by applying it to three different examples: a layered lattice, a two-dimensional hexagonal lattice, and a decorated-membrane system. It is shown that the predicted characteristics and wave fields agree almost
Self-consolidating concrete homogeneity
Jarque, J. C.
2007-08-01
Full Text Available Concrete instability may lead to the non-uniform distribution of its properties. The homogeneity of self-consolidating concrete in vertically cast members was therefore explored in this study, analyzing both resistance to segregation and pore structure uniformity. To this end, two series of concretes were prepared, self-consolidating and traditional vibrated materials, with different w/c ratios and types of cement. The results showed that selfconsolidating concretes exhibit high resistance to segregation, albeit slightly lower than found in the traditional mixtures. The pore structure in the former, however, tended to be slightly more uniform, probably as a result of less intense bleeding. Such concretes are also characterized by greater bulk density, lower porosity and smaller mean pore size, which translates into a higher resistance to pressurized water. For pore diameters of over about 0.5 Î¼m, however, the pore size distribution was found to be similar to the distribution in traditional concretes, with similar absorption rates.En este trabajo se estudia la homogeneidad de los hormigones autocompactantes en piezas hormigonadas verticalmente, determinando su resistencia a la segregación y la uniformidad de su estructura porosa, dado que la pérdida de estabilidad de una mezcla puede conducir a una distribución no uniforme de sus propiedades. Para ello se han fabricado dos tipos de hormigones, uno autocompactante y otro tradicional vibrado, con diferentes relaciones a/c y distintos tipos de cemento. Los resultados ponen de manifiesto que los hormigones autocompactantes presentan una buena resistencia a la segregación, aunque algo menor que la registrada en los hormigones tradicionales. A pesar de ello, su estructura porosa tiende a ser ligeramente más uniforme, debido probablemente a un menor sangrado. Asimismo, presentan una mayor densidad aparente, una menor porosidad y un menor tamaño medio de poro, lo que les confiere mejores
Arima, T; Saito, M
2009-01-01
Contrary to a claim by Lovesey and Staub (2009 J. Phys.: Condens. Matter 21 142201), a careful treatment of symmetry shows that the application of a magnetic field along a twofold axis can induce the crystallographic chirality in a tetragonal system with the point group 4-bar2m like CuB 2 O 4 . The chirality is reversed by a 90 deg. rotation of the magnetic field around the c axis. (comment)
Rare earth permanent magnet with easy magnetization
Kim, A.S.; Camp, F.E.
1998-01-01
Rare earth permanent magnets have high energy products and coercivities, and thus the volume miniaturization of magnetic devices has been possible with improved magnetic performance. Although the high energy products of these rare earth permanent magnets provide substantial advantages for magnetic design and application, the strong magnetic force of the magnetized magnets makes assembly difficult. Therefore, a special device is needed to assemble the magnetized magnets. On the other hand, unmagnetized magnets are assembled and then they are magnetized. The assembled magnets are generally more difficult to magnetize than unassembled magnets because a much less effective magnetic field may be applied to them. This is particularly true for the rare earth permanent magnets because they usually need a much higher magnetic field to be fully magnetized than alnico or ferrite magnets. To obtain optimum magnetic properties, the required minimum magnetizing fields for SmCo 5 , Sm 2 TM 17 and Nd 2 Fe 14 B magnets were reported as 25-30 kOe, 45-60 kOe and 25-30 kOe, respectively. If the required magnetizing field for full saturation could be lowered, the effective utilization of magnetic properties would be maximized and the magnetic design option could be expanded with reduced restrictions. To meet this demand, we have sought to lower the field required for full magnetic saturation, and found that an increase in Dy content in R-(Fe,Co,Cu)-B type magnets lowers the field required for full saturation as well as improves the temperature stability. By increasing the H ci with Dy addition from 14 kOe to 24 and 34 kOe, the field required for full magnetic saturation decreases from about 20 to 15 and 10 kOe, respectively. This dual benefit will open up new application areas with more freedom for magnet design options. The mechanism for the lower magnetizing fields will be discussed. (orig.)
Homogenization models for 2-D grid structures
Banks, H. T.; Cioranescu, D.; Rebnord, D. A.
1992-01-01
In the past several years, we have pursued efforts related to the development of accurate models for the dynamics of flexible structures made of composite materials. Rather than viewing periodicity and sparseness as obstacles to be overcome, we exploit them to our advantage. We consider a variational problem on a domain that has large, periodically distributed holes. Using homogenization techniques we show that the solution to this problem is in some topology 'close' to the solution of a similar problem that holds on a much simpler domain. We study the behavior of the solution of the variational problem as the holes increase in number, but decrease in size in such a way that the total amount of material remains constant. The result is an equation that is in general more complex, but with a domain that is simply connected rather than perforated. We study the limit of the solution as the amount of material goes to zero. This second limit will, in most cases, retrieve much of the simplicity that was lost in the first limit without sacrificing the simplicity of the domain. Finally, we show that these results can be applied to the case of a vibrating Love-Kirchhoff plate with Kelvin-Voigt damping. We rely heavily on earlier results of (Du), (CS) for the static, undamped Love-Kirchhoff equation. Our efforts here result in a modification of those results to include both time dependence and Kelvin-Voigt damping.
Numerical computation of homogeneous slope stability.
Xiao, Shuangshuang; Li, Kemin; Ding, Xiaohua; Liu, Tong
2015-01-01
To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS).
Numerical Computation of Homogeneous Slope Stability
Shuangshuang Xiao
2015-01-01
Full Text Available To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM and particle swarm optimization algorithm (PSO to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759 were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS.
Multilevel Monte Carlo Approaches for Numerical Homogenization
Efendiev, Yalchin R.; Kronsbein, Cornelia; Legoll, Fré dé ric
2015-01-01
it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison
Benchmarking homogenization algorithms for monthly data
Venema, V. K. C.; Mestre, O.; Aguilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertacnik, G.; Szentimrey, T.; Stepanek, P.; Zahradnicek, P.; Viarre, J.; Müller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M. J.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratiannil, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Prohom Duran, M.; Likso, T.; Esteban, P.; Brandsma, T.; Willett, K.
2013-09-01
The COST (European Cooperation in Science and Technology) Action ES0601: Advances in homogenization methods of climate series: an integrated approach (HOME) has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies. The algorithms were validated against a realistic benchmark dataset. Participants provided 25 separate homogenized contributions as part of the blind study as well as 22 additional solutions submitted after the details of the imposed inhomogeneities were revealed. These homogenized datasets were assessed by a number of performance metrics including i) the centered root mean square error relative to the true homogeneous values at various averaging scales, ii) the error in linear trend estimates and iii) traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve precipitation data. Moreover, state-of-the-art relative homogenization algorithms developed to work with an inhomogeneous reference are shown to perform best. The study showed that currently automatic algorithms can perform as well as manual ones.
Investigations into homogenization of electromagnetic metamaterials
Clausen, Niels Christian Jerichau
This dissertation encompasses homogenization methods, with a special interest into their applications to metamaterial homogenization. The first method studied is the Floquet-Bloch method, that is based on the assumption of a material being infinite periodic. Its field can then be expanded in term...
Color Segmentation of Homogeneous Areas on Colposcopical Images
Kosteley Yana
2016-01-01
Full Text Available The article provides an analysis of image processing and color segmentation applied to the problem of selection of homogeneous regions in the parameters of the color model. Methods of image processing such as Gaussian filter, median filter, histogram equalization and mathematical morphology are considered. The segmentation algorithm with the parameters of color components is presented, followed by isolation of the resulting connected component of a binary segmentation mask. Analysis of methods performed on images colposcopic research.
Homogeneity of Prototypical Attributes in Soccer Teams
Christian Zepp
2015-09-01
Full Text Available Research indicates that the homogeneous perception of prototypical attributes influences several intragroup processes. The aim of the present study was to describe the homogeneous perception of the prototype and to identify specific prototypical subcategories, which are perceived as homogeneous within sport teams. The sample consists of N = 20 soccer teams with a total of N = 278 athletes (age M = 23.5 years, SD = 5.0 years. The results reveal that subcategories describing the cohesiveness of the team and motivational attributes are mentioned homogeneously within sport teams. In addition, gender, identification, team size, and the championship ranking significantly correlate with the homogeneous perception of prototypical attributes. The results are discussed on the basis of theoretical and practical implications.
Multilevel Monte Carlo Approaches for Numerical Homogenization
Efendiev, Yalchin R.
2015-10-01
In this article, we study the application of multilevel Monte Carlo (MLMC) approaches to numerical random homogenization. Our objective is to compute the expectation of some functionals of the homogenized coefficients, or of the homogenized solutions. This is accomplished within MLMC by considering different sizes of representative volumes (RVEs). Many inexpensive computations with the smallest RVE size are combined with fewer expensive computations performed on larger RVEs. Likewise, when it comes to homogenized solutions, different levels of coarse-grid meshes are used to solve the homogenized equation. We show that, by carefully selecting the number of realizations at each level, we can achieve a speed-up in the computations in comparison to a standard Monte Carlo method. Numerical results are presented for both one-dimensional and two-dimensional test-cases that illustrate the efficiency of the approach.
Bui The Anh
2007-01-01
Full Text Available We extend the classical Perron-Frobenius theorem for positive quasipolynomial matrices associated with homogeneous difference equations. Finally, the result obtained is applied to derive necessary and sufficient conditions for the stability of positive system.
Dipolar vortex structures in magnetized rotating plasma
Liu Jixing
1990-01-01
Dipolar solitary vortices of both electrostatic and electromagnetic character in low-β, in homogeneous rotating plasma confined in a constant external magnetic field were systematically presented. The main stimulus to this investigation is the expectation to apply this coherent structure as a candidate constituent of plasma turbulance to understand the anomalous transport phenomena in confined plasma. The electrostatic vortices have similar structure and properties as the Rossby vortices in rotating fluids, the electromagnetic vortices obtained here have no analogy in hydrodynamics and hence are intrinsic to magnetized plasma. It is valuably remarked that the intrinsic electromagnetic vortices presented here have no discontinuity of perturbed magnetic field δB and parallel current j(parallel) on the border of vortex core. The existence region of the new type of vortex is found much narrower than the Rossby type one. (M.T.)
Low field magnetic resonance imaging
Pines, Alexander; Sakellariou, Dimitrios; Meriles, Carlos A.; Trabesinger, Andreas H.
2010-07-13
A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.
Bender, P., E-mail: nano@p-bender.de; Tschöpe, A., E-mail: antsch@mx.uni-saarland.de; Birringer, R., E-mail: r.birringer@nano.uni-saarland.de
2014-12-15
The local mechanical coupling of ferromagnetic nanorods in hydrogels was characterized by magnetization measurements. Nickel nanorods were synthesized by the AAO-template method and embedded in gelatine hydrogels with mechanically soft or hard matrix properties determined by the gelatine weight fraction. By applying a homogeneous magnetic field during gelation the nanorods were aligned along the field resulting in uniaxially textured ferrogels. The magnetization curves of the soft ferrogel exhibited not only important similarities but also characteristic differences as compared to the hard ferrogel. The hystereses measured in a field parallel to the texture axis were almost identical for both samples indicating effective coupling of the nanorods with the polymer network. By contrast, measurements in a magnetic field perpendicular to the texture axis revealed a much higher initial susceptibility of the soft as compared to the hard ferrogel. This difference was attributed to the additional rotation of the nanorods allowed by the reduced shear modulus in the soft ferrogel matrix. Two methods for data analysis were presented which enabled us to determine the shear modulus of the gelatine matrix which was interpreted as a local rather than macroscopic quantity in consideration of the nanoscale of the probe particles. - Highlights: • Nanorods are embedded as magnetic probes in gelatine gels. • Elastic rotation of the rods can be induced by applying a homogeneous magnetic field. • Rod rotation has significant influence on the magnetization curves. • Two methods are presented to estimate the shear modulus of the matrix from the magnetization curves.
Gomez, A; Del Valle, J; Gonzalez, E M; Vicent, J L; Chiliotte, C E; Carreira, S J; Bekeris, V; Prieto, J L; Schuller, Ivan K
2014-01-01
Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current I c (H), magnetization M(H) and ac-susceptibility χ ac (H) in a broad temperature range. Due to the coherence length divergence at T c , a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to T c , wire network behaviour is only present in a very narrow temperature window close to T c . In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished. (papers)
String pair production in non homogeneous backgrounds
Bolognesi, S. [Department of Physics “E. Fermi” University of Pisa, and INFN - Sezione di Pisa,Largo Pontecorvo, 3, Ed. C, 56127 Pisa (Italy); Rabinovici, E. [Racah Institute of Physics, The Hebrew University of Jerusalem,91904 Jerusalem (Israel); Tallarita, G. [Departamento de Ciencias, Facultad de Artes Liberales,Universidad Adolfo Ibáñez, Santiago 7941169 (Chile)
2016-04-28
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.
String pair production in non homogeneous backgrounds
Bolognesi, S.; Rabinovici, E.; Tallarita, G.
2016-01-01
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for particles. In the first case the string is suspended between two D-branes in flat space-time, in the second case the string lives in AdS and terminates on one D-brane (this realizes the holographic Schwinger effect). In some regions of parameter space the result is well approximated by the known analytical formulas, either the particle pair production in non-homogeneous background or the string pair production in homogeneous background. In other cases we see effects which are intrinsically stringy and related to the non-homogeneity of the background. The pair production is enhanced already for particles in time dependent electric field backgrounds. The string nature enhances this even further. For spacial varying electrical background fields the string pair production is less suppressed than the rate of particle pair production. We discuss in some detail how the critical field is affected by the non-homogeneity, for both time and space dependent electric field backgrouds. We also comment on what could be an interesting new prediction for the small field limit. The third case we consider is pair production in holographic confining backgrounds with homogeneous and non-homogeneous fields.
Kim, Jun Seong; Lee, Woo Seung; Kim, Jin Sub; Song, Seung Hyun; Nam, Seok Ho; Jeon, Hae Ryong; Beak, Geon Woo; Ko, Tae Kuk [Yonsei University, Seoul (Korea, Republic of)
2016-09-15
Recently, production technique and property of the High-Temperature Superconductor (HTS) tape have been improved. Thus, the study on applying an HTS magnet to the high magnetic field application is rapidly increased. A Nuclear Magnetic Resonance (NMR) spectrometer requires high magnitude and homogeneous of central magnetic field. However, the HTS magnet has fabrication errors because shape of HTS is tape and HTS magnet is manufactured by winding HTS tape to the bobbin. The fabrication errors are winding error, bobbin diameter error, spacer thickness error and so on. The winding error occurs when HTS tape is departed from the arranged position on the bobbin. The bobbin diameter and spacer thickness error occur since the diameter of bobbin and spacer are inaccurate. These errors lead magnitude and homogeneity of central magnetic field to be different from its ideal design. The purpose of this paper is to investigate the effect of winding error, bobbin diameter error and spacer thickness error on the central field and field homogeneity of HTS magnet using the virtual NMR signals in MATLAB simulation.
Magnetically controlled multifrequency invisibility cloak with a single shell of ferrite material
Wang, Xiaohua; Liu, Youwen
2015-02-01
A magnetically controlled multifrequency invisibility cloak with a single shell of the isotropic and homogeneous ferrite material has been investigated based on the scattering cancellation method from the Mie scattering theory. The analytical and simulated results have demonstrated that such this shell can drastically reduce the total scattering cross-section of this cloaking system at multiple frequencies. These multiple cloaking frequencies of this shell can be externally controlled since the magnetic permeability of ferrites is well tuned by the applied magnetic field. This may provide a potential way to design a tunable multifrequency invisibility cloak with considerable flexibility.
Benchmarking homogenization algorithms for monthly data
V. K. C. Venema
2012-01-01
Full Text Available The COST (European Cooperation in Science and Technology Action ES0601: advances in homogenization methods of climate series: an integrated approach (HOME has executed a blind intercomparison and validation study for monthly homogenization algorithms. Time series of monthly temperature and precipitation were evaluated because of their importance for climate studies and because they represent two important types of statistics (additive and multiplicative. The algorithms were validated against a realistic benchmark dataset. The benchmark contains real inhomogeneous data as well as simulated data with inserted inhomogeneities. Random independent break-type inhomogeneities with normally distributed breakpoint sizes were added to the simulated datasets. To approximate real world conditions, breaks were introduced that occur simultaneously in multiple station series within a simulated network of station data. The simulated time series also contained outliers, missing data periods and local station trends. Further, a stochastic nonlinear global (network-wide trend was added.
Participants provided 25 separate homogenized contributions as part of the blind study. After the deadline at which details of the imposed inhomogeneities were revealed, 22 additional solutions were submitted. These homogenized datasets were assessed by a number of performance metrics including (i the centered root mean square error relative to the true homogeneous value at various averaging scales, (ii the error in linear trend estimates and (iii traditional contingency skill scores. The metrics were computed both using the individual station series as well as the network average regional series. The performance of the contributions depends significantly on the error metric considered. Contingency scores by themselves are not very informative. Although relative homogenization algorithms typically improve the homogeneity of temperature data, only the best ones improve
Ikeda, Akihiko; Nomura, Toshihiro; Matsuda, Yasuhiro H.; Tani, Shuntaro; Kobayashi, Yohei; Watanabe, Hiroshi; Sato, Keisuke
2018-05-01
High-speed 100 MHz strain monitor using fiber Bragg grating (FBG) and an optical filter has been devised for the magnetostriction measurements under ultrahigh magnetic fields. The longitudinal magnetostriction of LaCoO 3 has been measured at room temperature, 115, 7 and 4.2 K up to the maximum magnetic field of 150 T. The field-induced lattice elongations are observed, which are attributed to the spin-state crossover from the low-spin ground state to excited spin-states.
Nielsen, H; Nielsen, K; Nielsen, Otto V
1982-01-01
and atf = 400Hz,J_{max} = 0.10T. Measurements are carried out on samples in a stress-relieved state and with magnetic anisotropies induced by stress or field annealing. Atf = 50Hz, a minimum m Ptversus σ is observed. The σ-value (sigma_{min}) corresponding to the minimum PTincreases with increasing |Ku......|. Atf = 400Hz, a minimum in PTversus σ is observed in the samples with induced magnetic anisotropy, whereassigma_{min} = 0in the stress-relieved samiales. However, no correlation between andsigma_{min}and Kuis possible from the present data....
Povolotskaya Anna
2018-01-01
Full Text Available The paper reports results of magnetic measurements made on samples of the 12GB pipe steel (strength group X42SS designed for producing pipes to be used in media with high hydrogen sulphide content, both in the initial state and after exposure to hydrogen sulphide, for 96, 192 and 384 hours under uniaxial elastic-plastic tension. At the stage of elastic deformation there is a unique correlation between the coercive force measured on a minor hysteresis loop in weak fields and tensile stress, which enables this parameter to be used for the evaluation of elastic stresses in pipes made of the 12 GB pipe steel under different conditions, including a hydrogen sulphide containing medium. The effect of the value of preliminary plastic strain, viewed as the initial stress-strain state, on the magnetic behaviour of X70 pipe steels under elastic tension and compression is studied. Plastic strain history affects the magnetic behaviour of the material during subsequent elastic deformation since plastic strain induces various residual stresses, and this necessitates taking into account the initial stress-strain state of products when developing magnetic techniques for the determination of their stress-strain parameters during operation.
Investigations on the magnetization behavior of magnetic composite particles
Eichholz, Christian [Process Research and Chemical Engineering, BASF SE, Ludwigshafen (Germany); Knoll, Johannes, E-mail: johannes.knoll@kit.edu [Institute of Mechanical Engineering and Mechanics, Karlsruhe Institute of Technology, Karlsruhe (Germany); Lerche, Dietmar [L.U.M. GmbH, Berlin (Germany); Nirschl, Hermann [Institute of Mechanical Engineering and Mechanics, Karlsruhe Institute of Technology, Karlsruhe (Germany)
2014-11-15
In life sciences the application of surface functionalized magnetic composite particles is establishing in diagnostics and in downstream processing of modern biotechnology. These magnetic composite particles consist of non-magnetic material, e.g. polystyrene, which serves as a matrix for the second magnetic component, usually colloidal magnetite. Because of the multitude of magnetic cores these magnetic beads show a complex magnetization behavior which cannot be described with the available approaches for homogeneous magnetic material. Therefore, in this work a new model for the magnetization behavior of magnetic composite particles is developed. By introducing an effective magnetization and considering an overall demagnetization factor the deviation of the demagnetization of homogeneously magnetized particles is taken into account. Calculated and experimental results show a good agreement which allows for the verification of the adapted model of particle magnetization. Besides, a newly developed magnetic analyzing centrifuge is used for the characterization of magnetic composite particle systems. The experimental results, also used for the model verification, give both, information about the magnetic properties and the interaction behavior of particle systems. By adding further components to the particle solution, such as salts or proteins, industrial relevant systems can be reconstructed. The analyzing tool can be used to adapt industrial processes without time-consuming preliminary tests with large samples in the process equipments. - Highlights: • New model for magnetizability calculation of magnetic composite particles. • New method for particle bulk characterization relating to their magnetizability. • Model verification due to experimental data.
Investigations on the magnetization behavior of magnetic composite particles
Eichholz, Christian; Knoll, Johannes; Lerche, Dietmar; Nirschl, Hermann
2014-01-01
In life sciences the application of surface functionalized magnetic composite particles is establishing in diagnostics and in downstream processing of modern biotechnology. These magnetic composite particles consist of non-magnetic material, e.g. polystyrene, which serves as a matrix for the second magnetic component, usually colloidal magnetite. Because of the multitude of magnetic cores these magnetic beads show a complex magnetization behavior which cannot be described with the available approaches for homogeneous magnetic material. Therefore, in this work a new model for the magnetization behavior of magnetic composite particles is developed. By introducing an effective magnetization and considering an overall demagnetization factor the deviation of the demagnetization of homogeneously magnetized particles is taken into account. Calculated and experimental results show a good agreement which allows for the verification of the adapted model of particle magnetization. Besides, a newly developed magnetic analyzing centrifuge is used for the characterization of magnetic composite particle systems. The experimental results, also used for the model verification, give both, information about the magnetic properties and the interaction behavior of particle systems. By adding further components to the particle solution, such as salts or proteins, industrial relevant systems can be reconstructed. The analyzing tool can be used to adapt industrial processes without time-consuming preliminary tests with large samples in the process equipments. - Highlights: • New model for magnetizability calculation of magnetic composite particles. • New method for particle bulk characterization relating to their magnetizability. • Model verification due to experimental data
Poisson-Jacobi reduction of homogeneous tensors
Grabowski, J; Iglesias, D; Marrero, J C; Padron, E; Urbanski, P
2004-01-01
The notion of homogeneous tensors is discussed. We show that there is a one-to-one correspondence between multivector fields on a manifold M, homogeneous with respect to a vector field Δ on M, and first-order polydifferential operators on a closed submanifold N of codimension 1 such that Δ is transversal to N. This correspondence relates the Schouten-Nijenhuis bracket of multivector fields on M to the Schouten-Jacobi bracket of first-order polydifferential operators on N and generalizes the Poissonization of Jacobi manifolds. Actually, it can be viewed as a super-Poissonization. This procedure of passing from a homogeneous multivector field to a first-order polydifferential operator can also be understood as a sort of reduction; in the standard case-a half of a Poisson reduction. A dual version of the above correspondence yields in particular the correspondence between Δ-homogeneous symplectic structures on M and contact structures on N
Computational Method for Atomistic-Continuum Homogenization
Chung, Peter
2002-01-01
The homogenization method is used as a framework for developing a multiscale system of equations involving atoms at zero temperature at the small scale and continuum mechanics at the very large scale...
Homogenization and Control of Lattice Structures
Blankenship, G. L
1985-01-01
...., trusses may be modeled by beam equations). Using a technique from the mathematics of asymptotic analysis called "homogenization," the author shows how such approximations may be derived in a systematic way that avoids errors made using...
Homogenization of High-Contrast Brinkman Flows
Brown, Donald L.; Efendiev, Yalchin R.; Li, Guanglian; Savatorova, Viktoria
2015-01-01
, Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point
Unified double- and single-sided homogeneous Green's function representations
Wapenaar, Kees; van der Neut, Joost; Slob, Evert
2016-06-01
In wave theory, the homogeneous Green's function consists of the impulse response to a point source, minus its time-reversal. It can be represented by a closed boundary integral. In many practical situations, the closed boundary integral needs to be approximated by an open boundary integral because the medium of interest is often accessible from one side only. The inherent approximations are acceptable as long as the effects of multiple scattering are negligible. However, in case of strongly inhomogeneous media, the effects of multiple scattering can be severe. We derive double- and single-sided homogeneous Green's function representations. The single-sided representation applies to situations where the medium can be accessed from one side only. It correctly handles multiple scattering. It employs a focusing function instead of the backward propagating Green's function in the classical (double-sided) representation. When reflection measurements are available at the accessible boundary of the medium, the focusing function can be retrieved from these measurements. Throughout the paper, we use a unified notation which applies to acoustic, quantum-mechanical, electromagnetic and elastodynamic waves. We foresee many interesting applications of the unified single-sided homogeneous Green's function representation in holographic imaging and inverse scattering, time-reversed wave field propagation and interferometric Green's function retrieval.
Non-equilibrium statistical theory about microscopic fatigue cracks of metal in magnetic field
Zhao-Long, Liu; Hai-Yun, Hu; Tian-You, Fan; Xiu-San, Xing
2010-01-01
This paper develops the non-equilibrium statistical fatigue damage theory to study the statistical behaviour of micro-crack for metals in magnetic field. The one-dimensional homogeneous crack system is chosen for study. To investigate the effect caused by magnetic field on the statistical distribution of micro-crack in the system, the theoretical analysis on microcrack evolution equation, the average length of micro-crack, density distribution function of micro-crack and fatigue fracture probability have been performed. The derived results relate the changes of some quantities, such as average length, density distribution function and fatigue fracture probability, to the applied magnetic field, the magnetic and mechanical properties of metals. It gives a theoretical explanation on the change of fatigue damage due to magnetic fields observed by experiments, and presents an analytic approach on studying the fatigue damage of metal in magnetic field. (cross-disciplinary physics and related areas of science and technology)
M. Babincová
2010-01-01
Full Text Available The magnetic nanoparticles play a crucial role as a drug carriers in the human body. The wedge like magnetic arrays creatinga strongly non-homogeneous magnetic field are considered as a useful way to focus magnetic nanoparticles functionalizedwith various drugs or genes to desired sites. The goal of this study is to develop a numerical model of drug targetingusing subcutaneously implanted magnetic microarrays. The Finite Element Method is applied to solve partial differentialequations describing electromagnetic field (Maxwell equations and motion of these particles in a given magnetic field isobtained solving set of ordinary differential equations expressed by Newton law of motion. The results are encouragingshowing the potential to target drug to the tumour cell locally, without unwanted side effects.
Homogenized thermal conduction model for particulate foods
Chinesta , Francisco; Torres , Rafael; Ramón , Antonio; Rodrigo , Mari Carmen; Rodrigo , Miguel
2002-01-01
International audience; This paper deals with the definition of an equivalent thermal conductivity for particulate foods. An homogenized thermal model is used to asses the effect of particulate spatial distribution and differences in thermal conductivities. We prove that the spatial average of the conductivity can be used in an homogenized heat transfer model if the conductivity differences among the food components are not very large, usually the highest conductivity ratio between the foods ...
Layout optimization using the homogenization method
Suzuki, Katsuyuki; Kikuchi, Noboru
1993-01-01
A generalized layout problem involving sizing, shape, and topology optimization is solved by using the homogenization method for three-dimensional linearly elastic shell structures in order to seek a possibility of establishment of an integrated design system of automotive car bodies, as an extension of the previous work by Bendsoe and Kikuchi. A formulation of a three-dimensional homogenized shell, a solution algorithm, and several examples of computing the optimum layout are presented in this first part of the two articles.
Optimization study on the magnetic field of superconducting Halbach Array magnet
Shen, Boyang; Geng, Jianzhao; Li, Chao; Zhang, Xiuchang; Fu, Lin; Zhang, Heng; Ma, Jun; Coombs, T. A.
2017-07-01
This paper presents the optimization on the strength and homogeneity of magnetic field from superconducting Halbach Array magnet. Conventional Halbach Array uses a special arrangement of permanent magnets which can generate homogeneous magnetic field. Superconducting Halbach Array utilizes High Temperature Superconductor (HTS) to construct an electromagnet to work below its critical temperature, which performs equivalently to the permanent magnet based Halbach Array. The simulations of superconducting Halbach Array were carried out using H-formulation based on B-dependent critical current density and bulk approximation, with the FEM platform COMSOL Multiphysics. The optimization focused on the coils' location, as well as the geometry and numbers of coils on the premise of maintaining the total amount of superconductor. Results show Halbach Array configuration based superconducting magnet is able to generate the magnetic field with intensity over 1 Tesla and improved homogeneity using proper optimization methods. Mathematical relation of these optimization parameters with the intensity and homogeneity of magnetic field was developed.
Diffusion piecewise homogenization via flux discontinuity ratios
Sanchez, Richard; Dante, Giorgio; Zmijarevic, Igor
2013-01-01
We analyze piecewise homogenization with flux-weighted cross sections and preservation of averaged currents at the boundary of the homogenized domain. Introduction of a set of flux discontinuity ratios (FDR) that preserve reference interface currents leads to preservation of averaged region reaction rates and fluxes. We consider the class of numerical discretizations with one degree of freedom per volume and per surface and prove that when the homogenization and computing meshes are equal there is a unique solution for the FDRs which exactly preserve interface currents. For diffusion sub-meshing we introduce a Jacobian-Free Newton-Krylov method and for all cases considered obtain an 'exact' numerical solution (eight digits for the interface currents). The homogenization is completed by extending the familiar full assembly homogenization via flux discontinuity factors to the sides of regions laying on the boundary of the piecewise homogenized domain. Finally, for the familiar nodal discretization we numerically find that the FDRs obtained with no sub-mesh (nearly at no cost) can be effectively used for whole-core diffusion calculations with sub-mesh. This is not the case, however, for cell-centered finite differences. (authors)
Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe
Gooneratne, Chinthaka P.
2013-11-29
Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe. 2013 Gooneratne et al.
Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe
Gooneratne, Chinthaka P.; Kurnicki, Adam; Yamada, Sotoshi; Mukhopadhyay, Subhas C.; Kosel, Jü rgen
2013-01-01
Magnetic fluid hyperthermia (MFH) therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC) magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR) probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe. 2013 Gooneratne et al.
Analysis of the distribution of magnetic fluid inside tumors by a giant magnetoresistance probe.
Chinthaka P Gooneratne
Full Text Available Magnetic fluid hyperthermia (MFH therapy uses the magnetic component of electromagnetic fields in the radiofrequency spectrum to couple energy to magnetic nanoparticles inside tumors. In MFH therapy, magnetic fluid is injected into tumors and an alternating current (AC magnetic flux is applied to heat the magnetic fluid- filled tumor. If the temperature can be maintained at the therapeutic threshold of 42 °C for 30 minutes or more, the tumor cells can be destroyed. Analyzing the distribution of the magnetic fluid injected into tumors prior to the heating step in MFH therapy is an essential criterion for homogenous heating of tumors, since a decision can then be taken on the strength and localization of the applied external AC magnetic flux density needed to destroy the tumor without affecting healthy cells. This paper proposes a methodology for analyzing the distribution of magnetic fluid in a tumor by a specifically designed giant magnetoresistance (GMR probe prior to MFH heat treatment. Experimental results analyzing the distribution of magnetic fluid suggest that different magnetic fluid weight densities could be estimated inside a single tumor by the GMR probe.
GHz nuclear magnetic resonance
Cross, T.A.; Drobny, G.; Trewhella, J.
1994-12-01
For the past dozen years, 500- and 600-MHz spectrometers have become available in many laboratories. The first 600-MHz NMR spectrometer (at Carnegie Mellon University) was commissioned more than 15 years ago and, until 1994, represented the highest field available for high-resolution NMR. This year, we have witnessed unprecedented progress in the development of very high field magnets for NMR spectroscopy, including the delivery of the first commercial 750-MHz NMR spectrometers. In addition, NMR signals have been obtained from 20-Tesla magnets (850 MHz for {sup 1}H`s) at both Los Alamos National Laboratory and Florida State University in the NHMFL (National High Magnetic Field Laboratory). These preliminary experiments have been performed in magnets with 100-ppm homogeneity, but a 20-Tesla magnet developed for the NHMFL will be brought to field this year with a projected homogeneity of 0.1 ppm over a 1-cm-diam spherical volume.
Computer simulations of equilibrium magnetization and microstructure in magnetic fluids
Rosa, A. P.; Abade, G. C.; Cunha, F. R.
2017-09-01
In this work, Monte Carlo and Brownian Dynamics simulations are developed to compute the equilibrium magnetization of a magnetic fluid under action of a homogeneous applied magnetic field. The particles are free of inertia and modeled as hard spheres with the same diameters. Two different periodic boundary conditions are implemented: the minimum image method and Ewald summation technique by replicating a finite number of particles throughout the suspension volume. A comparison of the equilibrium magnetization resulting from the minimum image approach and Ewald sums is performed by using Monte Carlo simulations. The Monte Carlo simulations with minimum image and lattice sums are used to investigate suspension microstructure by computing the important radial pair-distribution function go(r), which measures the probability density of finding a second particle at a distance r from a reference particle. This function provides relevant information on structure formation and its anisotropy through the suspension. The numerical results of go(r) are compared with theoretical predictions based on quite a different approach in the absence of the field and dipole-dipole interactions. A very good quantitative agreement is found for a particle volume fraction of 0.15, providing a validation of the present simulations. In general, the investigated suspensions are dominated by structures like dimmer and trimmer chains with trimmers having probability to form an order of magnitude lower than dimmers. Using Monte Carlo with lattice sums, the density distribution function g2(r) is also examined. Whenever this function is different from zero, it indicates structure-anisotropy in the suspension. The dependence of the equilibrium magnetization on the applied field, the magnetic particle volume fraction, and the magnitude of the dipole-dipole magnetic interactions for both boundary conditions are explored in this work. Results show that at dilute regimes and with moderate dipole
Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis
Falivene, Laura; Kozlov, Sergey M.; Cavallo, Luigi
2018-01-01
Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.
Using homogenization, sonication and thermo-sonication to inactivate fungi
Bevilacqua, Antonio; Sinigaglia, Milena; Corbo, Maria Rosaria
2016-01-01
Ultrasound (US), Thermo-sonication (TS) and High Pressure Homogenization (HPH) were studied as tools to inactivate the spores of Penicillium spp. and Mucor spp. inoculated in distilled water. For US, the power ranged from 40% to 100%, pulse from 2 to 10 s, and duration of the treatment from 2 to 10 min. TS was performed combining US (40–80% of power, for 8 min and pulse of 2 s) with a thermal treatment (50, 55 and 60°C at 4, 8 and 12 min). Homogenization was done at 30–150 MPa for 1, 2 and 3 times. Power was the most important factors to determine the antifungal effect of US and TS towards the conidia of Penicillium spp.; on the other hand, in US treatments Mucor spp. was also affected by pulse and time. HPH exerted a significant antifungal effect only if the highest pressures were applied for 2–3 times. PMID:27375964
Electrical model of dielectric barrier discharge homogenous and filamentary modes
López-Fernandez, J. A.; Peña-Eguiluz, R.; López-Callejas, R.; Mercado-Cabrera, A.; Valencia-Alvarado, R.; Muñoz-Castro, A.; Rodríguez-Méndez, B. G.
2017-01-01
This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results.
Computer modeling of homogenization of boric acid in IRIS pressurizer
Rives Sanz, Ronny; Montesinos Otero, Maria Elena; Gonzalez Mantecon, Javier
2015-01-01
Integral layout of nuclear reactor IRIS makes possible the elimination of the spray system; which is usually used to mitigate in-surge transient and help to boron homogenization. The study of transients with deficiencies in the boron homogenization in this technology is very important, because they can cause disturbances in the reactor power and insert a strong reactivity in the core. The aim of the present research is to model the IRIS pressurizer using the CFX code searching for designs alternatives that guaranteed its intrinsic security, focused on the phenomena before mentioned. A symmetric tri dimensional model equivalent to 1/8 of the total geometry was adopted to reduce mesh size and minimize processing time. The relationships are programmed and incorporated into the code. This paper discusses the model developed and the behavior of the system for representative transients sequences. The results of the analyzed IRIS transients could be applied to the design of the pressurizer internal structures and components. (Author)
Constructing Bridges between Computational Tools in Heterogeneous and Homogeneous Catalysis
Falivene, Laura
2018-05-08
Better catalysts are needed to address numerous challenges faced by humanity. In this perspective, we review concepts and tools in theoretical and computational chemistry that can help to accelerate the rational design of homogeneous and heterogeneous catalysts. In particular, we focus on the following three topics: 1) identification of key intermediates and transition states in a reaction using the energetic span model, 2) disentanglement of factors influencing the relative stability of the key species using energy decomposition analysis and the activation strain model, and 3) discovery of new catalysts using volcano relationships. To facilitate wider use of these techniques across different areas, we illustrate their potentials and pitfalls when applied to the study of homogeneous and heterogeneous catalysts.
Electrical model of dielectric barrier discharge homogenous and filamentary modes
López-Fernandez, J A; Peña-Eguiluz, R; López-Callejas, R; Mercado-Cabrera, A; Valencia-Alvarado, R; Muñoz-Castro, A; Rodríguez-Méndez, B G
2017-01-01
This work proposes an electrical model that combines homogeneous and filamentary modes of an atmospheric pressure dielectric barrier discharge cell. A voltage controlled electric current source has been utilized to implement the power law equation that represents the homogeneous discharge mode, which starts when the gas breakdown voltage is reached. The filamentary mode implies the emergence of electric current conducting channels (microdischarges), to add this phenomenon an RC circuit commutated by an ideal switch has been proposed. The switch activation occurs at a higher voltage level than the gas breakdown voltage because it is necessary to impose a huge electric field that contributes to the appearance of streamers. The model allows the estimation of several electric parameters inside the reactor that cannot be measured. Also, it is possible to appreciate the modes of the DBD depending on the applied voltage magnitude. Finally, it has been recognized a good agreement between simulation outcomes and experimental results. (paper)
AC magnetic transport on heterogeneous ferromagnetic wires and tubes
Sinnecker, J.P.; Pirota, K.R.; Knobel, M.; Kraus, L.
2002-01-01
The AC current density radial distribution is calculated on heterogeneous composite materials with cylindrical geometry. The composites have an inner core and thin outer shell that can be either from the same material (homogenous material like simple wires) or from different materials with different physical properties. The case in which a non-magnetic inner core is surrounded by a magnetic layer, like electrodeposited wires, is mainly studied. The effect of frequency and applied magnetic field is simulated. The current density distribution as a function of frequency and applied field, as well as the total current over the inner core and outer shells are calculated. The results agree substantially well with the experimentally observed data for simple electrodeposited wires
Maria Imtiaz
Full Text Available This paper looks at the flow of Jeffrey fluid due to a curved stretching sheet. Effect of homogeneous-heterogeneous reactions is considered. An electrically conducting fluid in the presence of applied magnetic field is considered. Convective boundary conditions model the heat transfer analysis. Transformation method reduces the governing nonlinear partial differential equations into the ordinary differential equations. Convergence of the obtained series solutions is explicitly discussed. Characteristics of sundry parameters on the velocity, temperature and concentration profiles are analyzed by plotting graphs. Computations for pressure, skin friction coefficient and surface heat transfer rate are presented and examined. It is noted that fluid velocity and temperature through curvature parameter are enhanced. Increasing values of Biot number correspond to the enhancement in temperature and Nusselt number.
Magnetic particle mixing with magnetic micro-convection for microfluidics
Kitenbergs , Guntars; Erglis , Kaspars; Perzynski , Régine; Cēbers , Andrejs
2015-01-01
International audience; In this paper we discuss the magnetic micro-convection phenomenon as a tool for mixing enhancement in microfluidics systems in cases when one of the mis-cible fluids is a magnetic particle colloid. A system of a water-based magnetic fluid and water is investigated experimentally under homogeneous magnetic field in a Hele-Shaw cell. Subsequent image analysis both qualitatively and quan-titatively reveals the high enhancement of mixing efficiency provided by this method....
Angerer, Andreas; Astner, Thomas; Wirtitsch, Daniel; Majer, Johannes; Sumiya, Hitoshi; Onoda, Shinobu; Isoya, Junichi; Putz, Stefan
2016-01-01
We design and implement 3D-lumped element microwave cavities that spatially focus magnetic fields to a small mode volume. They allow coherent and uniform coupling to electron spins hosted by nitrogen vacancy centers in diamond. We achieve large homogeneous single spin coupling rates, with an enhancement of more than one order of magnitude compared to standard 3D cavities with a fundamental resonance at 3 GHz. Finite element simulations confirm that the magnetic field distribution is homogeneous throughout the entire sample volume, with a root mean square deviation of 1.54%. With a sample containing 10"1"7 nitrogen vacancy electron spins, we achieve a collective coupling strength of Ω = 12 MHz, a cooperativity factor C = 27, and clearly enter the strong coupling regime. This allows to interface a macroscopic spin ensemble with microwave circuits, and the homogeneous Rabi frequency paves the way to manipulate the full ensemble population in a coherent way.
Maci, S.; Neto, A.
2004-01-01
This second part of a two-paper sequence deals with the uniform asymptotic description of the Green's function of an infinite slot printed between two different homogeneous dielectric media. Starting from the magnetic current derived in Part I, the dyadic green's function is first formulated in
Moutsopoulos, George
2013-01-01
We solve the equations of topologically massive gravity (TMG) with a potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre–Petrov types and discuss the warped de Sitter spacetime. (paper)
Moutsopoulos, George
2013-06-01
We solve the equations of topologically massive gravity (TMG) with a potentially non-vanishing cosmological constant for homogeneous metrics without isotropy. We only reproduce known solutions. We also discuss their homogeneous deformations, possibly with isotropy. We show that de Sitter space and hyperbolic space cannot be infinitesimally homogeneously deformed in TMG. We clarify some of their Segre-Petrov types and discuss the warped de Sitter spacetime.
The Application of Homogenate and Filtrate from Baltic Seaweeds in Seedling Growth Tests
Izabela Michalak
2017-02-01
Full Text Available Algal filtrate and homogenate, obtained from Baltic seaweeds, were applied in seedling growth tests. Radish seeds were used in order to assess algal products phytotoxicity and their biostimulant effect on growth and nutrient uptake. Algal filtrate, at concentrations ranging from 5.0% to 100% was used for seed soaking and as a liquid biostimulant (soil and foliar application. Algal homogenate was developed for seed coating. Algal filtrate and homogenate were also enriched with Zn(II ions in order to examine the influence on metal ion complexation. The optimal doses of algal filtrate and homogenate, as well as soaking time were established. Multi-elemental analyses of the raw biomass, filtrate, homogenate, and radish were also performed using ICP-OES (Inductively Coupled Plasma—Optical Emission Spectrometry. The best results in terms of seedlings’ length and weight were obtained using clear filtrate at a concentration of 50% applied to the soil and for homogenate applied at a dose of 50 mg/g of seeds. Clear filtrate at a concentration of 50% used for seed soaking for one hour showed the best results. The applied algal products increased the content of elements in seedlings. Among the tested products, a concentration of 50% algal filtrate is recommended for future pot and field experiments.
Designing a magnet for magnetic refrigeration
Bjoerk, R
2010-03-15
a high performance cylindrical magnet for use in a new magnetic refrigeration device being built at Risoe DTU. This magnet design must have alternating regions of high and low magnetic field. As a basis for the magnet design the concentric Halbach cylinder design is chosen. This design is then optimized by employing several developed optimization schemes that lower the flux density in a specific region and lower the amount of magnet material used in a given magnet assembly. These schemes are applied to a numerical model of the magnet design. Afterwards the magnet design is dimensioned and segmented to allow construction. This design has been constructed and the flux density measured. Finally, the magnetic forces internally in the magnet design and on the magnetocaloric material inside the magnet assembly have been analyzed. (Author)
Guo, Zhanying; Zhao, Gang; Chen, X.-Grant
2016-01-01
The effects of two homogenization treatments applied to the direct chill (DC) cast billet on the recrystallization behavior in 7150 aluminum alloy during post-rolling annealing have been investigated using the electron backscatter diffraction (EBSD) technique. Following hot and cold rolling to the sheet, measured orientation maps, the recrystallization fraction and grain size, the misorientation angle and the subgrain size were used to characterize the recovery and recrystallization processes at different annealing temperatures. The results were compared between the conventional one-step homogenization and the new two-step homogenization, with the first step being pretreated at 250 °C. Al_3Zr dispersoids with higher densities and smaller sizes were obtained after the two-step homogenization, which strongly retarded subgrain/grain boundary mobility and inhibited recrystallization. Compared with the conventional one-step homogenized samples, a significantly lower recrystallized fraction and a smaller recrystallized grain size were obtained under all annealing conditions after cold rolling in the two-step homogenized samples. - Highlights: • Effects of two homogenization treatments on recrystallization in 7150 Al sheets • Quantitative study on the recrystallization evolution during post-rolling annealing • Al_3Zr dispersoids with higher densities and smaller sizes after two-step treatment • Higher recrystallization resistance of 7150 sheets with two-step homogenization
Durand, L.
1995-01-01
We have shown that il was possible to disperse in a very homogeneous way, into the 123 matrix, 211 particles regular in size around 1μm, by directional solidification of a mixture of 123 plus 211 sol-gel powders. The addition of 0.5 wt% of Pt lo this precursor mixture has permitted us to refine further the size of the 211 particles. Moreover, we have established that the finer the 123 powder and the faster the heating rate, the smaller the 211 particles. From another hand, we have found that the size and the microstructure of the solidified single domain was dependant upon numerous parameters. In particular, we have noted that if the cold pressed green body was not sintered before being melted, grains of solid CuO appeared into the liquid which next hardly recombined with it, giving rise to a comb like solidification front, witness of a local un-stability. Moreover, in these particular conditions, the 123 formed was found to be understoichiometric in Cu and the single domains severely limited in extension. Finally, we have observed that the application of a 4 T magnetic field during the solidification of a bar the longest axis of which was horizontal tended to align the c axis of the 123 grains parallel to the field. Incidentally, we have discovered that in the same conditions, the 211 particles trapped into the 123 matrix were also preferentially oriented. (author)
Rapid biotic homogenization of marine fish assemblages
Magurran, Anne E.; Dornelas, Maria; Moyes, Faye; Gotelli, Nicholas J.; McGill, Brian
2015-01-01
The role human activities play in reshaping biodiversity is increasingly apparent in terrestrial ecosystems. However, the responses of entire marine assemblages are not well-understood, in part, because few monitoring programs incorporate both spatial and temporal replication. Here, we analyse an exceptionally comprehensive 29-year time series of North Atlantic groundfish assemblages monitored over 5° latitude to the west of Scotland. These fish assemblages show no systematic change in species richness through time, but steady change in species composition, leading to an increase in spatial homogenization: the species identity of colder northern localities increasingly resembles that of warmer southern localities. This biotic homogenization mirrors the spatial pattern of unevenly rising ocean temperatures over the same time period suggesting that climate change is primarily responsible for the spatial homogenization we observe. In this and other ecosystems, apparent constancy in species richness may mask major changes in species composition driven by anthropogenic change. PMID:26400102
Two-Dimensional Homogeneous Fermi Gases
Hueck, Klaus; Luick, Niclas; Sobirey, Lennart; Siegl, Jonas; Lompe, Thomas; Moritz, Henning
2018-02-01
We report on the experimental realization of homogeneous two-dimensional (2D) Fermi gases trapped in a box potential. In contrast to harmonically trapped gases, these homogeneous 2D systems are ideally suited to probe local as well as nonlocal properties of strongly interacting many-body systems. As a first benchmark experiment, we use a local probe to measure the density of a noninteracting 2D Fermi gas as a function of the chemical potential and find excellent agreement with the corresponding equation of state. We then perform matter wave focusing to extract the momentum distribution of the system and directly observe Pauli blocking in a near unity occupation of momentum states. Finally, we measure the momentum distribution of an interacting homogeneous 2D gas in the crossover between attractively interacting fermions and bosonic dimers.
Bormann, Lorraine; Abrahamson, Kathleen
2014-04-01
Nurse managers leadership behaviors influence the job satisfaction of staff nurses. Transformational leadership is 1 of the 5 components associated with the Magnet Recognition Program®. The aim of this study was to examine the relationship between staff nurse perception of nurse manager leadership behavior and staff nurse job satisfaction in a hospital on the Magnet® journey and the influence of nurse manager leadership style on staff nurse job satisfaction. A descriptive, correlational design using a self-report survey with convenience sampling was used for this quantitative research study. Staff nurses completed the Multifactor Leadership Questionnaire 5X Short Form, the Abridged Job Descriptive Index survey, and a demographic questionnaire. Pearson correlations and regression analyses were completed to explore the relationship and influence of nurse manager leadership style on staff nurse job satisfaction. Transformational and transactional leadership styles of nurse managers were positively related to staff nurse overall job satisfaction and satisfaction with opportunity for promotion. Passive-avoidant leadership style of nurse managers was negatively related to staff nurse satisfaction with work, promotion, supervision, and coworker. Satisfaction with nurse manager leadership was a positive influence on overall nurse job satisfaction when separately controlling for the influence of each leadership style. Transformational and transactional leadership styles should be taught and encouraged among nurse managers to positively influence the job satisfaction of staff nurses.
Magnetic field line Hamiltonian
Boozer, A.H.
1985-02-01
The basic properties of the Hamiltonian representation of magnetic fields in canonical form are reviewed. The theory of canonical magnetic perturbation theory is then developed and applied to the time evolution of a magnetic field embedded in a toroidal plasma. Finally, the extension of the energy principle to tearing modes, utilizing the magnetic field line Hamiltonian, is outlined
Araújo Manuel
2016-01-01
Full Text Available Multi-material domains are often found in industrial applications. Modelling them can be computationally very expensive due to meshing requirements. The finite element properties comprising different materials are hardly accurate. In this work, a new homogenization method that simplifies the computation of the homogenized Young modulus, Poisson ratio and thermal expansion coefficient is proposed, and applied to composite-like material on a printed circuit board. The results show a good properties correspondence between the homogenized domain and the real geometry simulation.
Takeda, T.; Uto, N.
1988-01-01
Several methods to determine cell-averaged group cross sections and anisotropic diffusion coefficients which consider the interaction effect between core fuel cells and control rods or control rod followers have been compared to discuss the physical meaning included in cell homogenization. As the cell homogenization methods considered are the commonly used flux-weighting method, the reaction rate preservation method and the reactivity preservation method. These homogenization methods have been applied to control rod worth calculations in 1-D slab cores to investigate their applicability. (author). 6 refs, 2 figs, 9 tabs
Internal homogenization: effective permittivity of a coated sphere.
Chettiar, Uday K; Engheta, Nader
2012-10-08
The concept of internal homogenization is introduced as a complementary approach to the conventional homogenization schemes, which could be termed as external homogenization. The theory for the internal homogenization of the permittivity of subwavelength coated spheres is presented. The effective permittivity derived from the internal homogenization of coreshells is discussed for plasmonic and dielectric constituent materials. The effective model provided by the homogenization is a useful design tool in constructing coated particles with desired resonant properties.
Statistical methods for assessment of blend homogeneity
Madsen, Camilla
2002-01-01
In this thesis the use of various statistical methods to address some of the problems related to assessment of the homogeneity of powder blends in tablet production is discussed. It is not straight forward to assess the homogeneity of a powder blend. The reason is partly that in bulk materials......, it is shown how to set up parametric acceptance criteria for the batch that gives a high confidence that future samples with a probability larger than a specified value will pass the USP threeclass criteria. Properties and robustness of proposed changes to the USP test for content uniformity are investigated...
Homogenization of High-Contrast Brinkman Flows
Brown, Donald L.
2015-04-16
Modeling porous flow in complex media is a challenging problem. Not only is the problem inherently multiscale but, due to high contrast in permeability values, flow velocities may differ greatly throughout the medium. To avoid complicated interface conditions, the Brinkman model is often used for such flows [O. Iliev, R. Lazarov, and J. Willems, Multiscale Model. Simul., 9 (2011), pp. 1350--1372]. Instead of permeability variations and contrast being contained in the geometric media structure, this information is contained in a highly varying and high-contrast coefficient. In this work, we present two main contributions. First, we develop a novel homogenization procedure for the high-contrast Brinkman equations by constructing correctors and carefully estimating the residuals. Understanding the relationship between scales and contrast values is critical to obtaining useful estimates. Therefore, standard convergence-based homogenization techniques [G. A. Chechkin, A. L. Piatniski, and A. S. Shamev, Homogenization: Methods and Applications, Transl. Math. Monogr. 234, American Mathematical Society, Providence, RI, 2007, G. Allaire, SIAM J. Math. Anal., 23 (1992), pp. 1482--1518], although a powerful tool, are not applicable here. Our second point is that the Brinkman equations, in certain scaling regimes, are invariant under homogenization. Unlike in the case of Stokes-to-Darcy homogenization [D. Brown, P. Popov, and Y. Efendiev, GEM Int. J. Geomath., 2 (2011), pp. 281--305, E. Marusic-Paloka and A. Mikelic, Boll. Un. Mat. Ital. A (7), 10 (1996), pp. 661--671], the results presented here under certain velocity regimes yield a Brinkman-to-Brinkman upscaling that allows using a single software platform to compute on both microscales and macroscales. In this paper, we discuss the homogenized Brinkman equations. We derive auxiliary cell problems to build correctors and calculate effective coefficients for certain velocity regimes. Due to the boundary effects, we construct
Flows and chemical reactions in homogeneous mixtures
Prud'homme, Roger
2013-01-01
Flows with chemical reactions can occur in various fields such as combustion, process engineering, aeronautics, the atmospheric environment and aquatics. The examples of application chosen in this book mainly concern homogeneous reactive mixtures that can occur in propellers within the fields of process engineering and combustion: - propagation of sound and monodimensional flows in nozzles, which may include disequilibria of the internal modes of the energy of molecules; - ideal chemical reactors, stabilization of their steady operation points in the homogeneous case of a perfect mixture and c
Parametric decay instabilities in an infinite, homogeneous, weakly anisotropic plasma
Grandal, B.
1976-01-01
The parametric decay of a transverse electromagnetic (em) wave with a frequency close to, but larger than, the electron plasma frequency is investigated for an infinite, homogeneous, weakly magnetoactive plasma. A two-component fluid description is employed, and the damping of the linear plasma waves is introduced phenomenologically to include both Landau and collisional damping. The transverse em wave will decay into a longitudinal electron plasma wave and an em ion-acoustic wave. Only the latter wave is assumed to be affected by the weak, constant magnetic field. The threshold expression for growth of electron plasma waves is equal to that of the isotropic plasma when the em ion-acoustic wave's direction of propagation lies inside a wide double cone, whose axis is along the constant magnetic field. When the em ion-acoustic wave propagates outside this double cone, an additional factor, which depends directly upon the magnetic field, appears in the threshold expression. This factor can, under certain conditions, reduce the threshold for growth of electron plasma waves below that of the isotropic plasma
Plane wave interaction with a homogeneous warm plasma sphere
Ruppin, R.
1975-01-01
A Mie type theory for the scattering and absorption properties of a homogeneous warm plasma sphere is developed. The theory is applied to the calculation of the extinction cross section of plasma spheres, and the effects of Landau damping and collisional damping on the spectra are discussed. The dependence of the main resonance and of the Tonks-Dattner resonances on the physical parameters characterizing the sphere and its surroundings is investigated. The spectrum is shown to be insenitive to the boundary conditions which specify the behaviour of the electrons at the surface of the sphere (author)
Preliminary development of thermal nuclear cell homogenization code
Su'ud, Z.; Shafii, M. A.; Yudha, S. P.; Waris, A.; Rijal, K.
2012-01-01
Nuclear fuel cell homogenization for thermal reactors usually include three main parts, i.e., fast energy resonance part which usually adopt narrow resonance approximation to treat the resonance, low (intermediate) energy region in which the resonance can not be treated accurately using NR approximation and therefore we should use intermediate resonance treatment, and thermal energy region (very low) in which the effect of thermal must be treated properly. In n this study the application of the intermediate resonance approximation treatment for low energy nuclear resonance is discussed. The method is iterative based. As a sample the method is applied in U-235 low lying resonance and the result is presented and discussed.
Ab initio molecular dynamics in a finite homogeneous electric field.
Umari, P; Pasquarello, Alfredo
2002-10-07
We treat homogeneous electric fields within density functional calculations with periodic boundary conditions. A nonlocal energy functional depending on the applied field is used within an ab initio molecular dynamics scheme. The reliability of the method is demonstrated in the case of bulk MgO for the Born effective charges, and the high- and low-frequency dielectric constants. We evaluate the static dielectric constant by performing a damped molecular dynamics in an electric field and avoiding the calculation of the dynamical matrix. Application of this method to vitreous silica shows good agreement with experiment and illustrates its potential for systems of large size.
Quantum revivals in the motion of electron in magnetic field
Filipowicz, P.; Mostowski, J.
1981-01-01
We show that the motion of a relativistic electron in constant homogeneous magnetic field exhibits quasiperiodic behaviour (quantum revivals) and discuss the possibility of their observation. (author)
van der Burg, Eeke; de Leeuw, Jan; Verdegaal, Renée
1988-01-01
Homogeneity analysis, or multiple correspondence analysis, is usually applied tok separate variables. In this paper we apply it to sets of variables by using sums within sets. The resulting technique is called OVERALS. It uses the notion of optimal scaling, with transformations that can be multiple
Homogenization versus homogenization-free method to measure muscle glycogen fractions.
Mojibi, N; Rasouli, M
2016-12-01
The glycogen is extracted from animal tissues with or without homogenization using cold perchloric acid. Three methods were compared for determination of glycogen in rat muscle at different physiological states. Two groups of five rats were kept at rest or 45 minutes muscular activity. The glycogen fractions were extracted and measured by using three methods. The data of homogenization method shows that total glycogen decreased following 45 min physical activity and the change occurred entirely in acid soluble glycogen (ASG), while AIG did not change significantly. Similar results were obtained by using "total-glycogen-fractionation methods". The findings of "homogenization-free method" indicate that the acid insoluble fraction (AIG) was the main portion of muscle glycogen and the majority of changes occurred in AIG fraction. The results of "homogenization method" are identical with "total glycogen fractionation", but differ with "homogenization-free" protocol. The ASG fraction is the major portion of muscle glycogen and is more metabolically active form.
The design of coils for the production of high homogeneous fields
Desportes, H.
1964-01-01
The discovery of type II superconductors has considerably increased the possibilities of air-core coils, in particular with regard to the production of high homogeneous fields. The design of such magnets,calls for elaborate calculations which, in practise, can only be carried out on computers. The present report describes a complete set of programs for the calculation, in the case of cylindrical systems, of the magnetic field components at any point, the lines of flux, the forces, the self and mutual inductances, as well as the design of compensated coils for the production of high homogeneous fields. These programs have been employed for the calculation of two magnets which are described in detail. (author) [fr
Remmer, Hilke; Dieckhoff, Jan; Schilling, Meinhard; Ludwig, Frank
2015-01-01
We investigated the binding of biotinylated proteins to various streptavidin functionalized magnetic nanoparticles with different dynamic magnetic measurement techniques to examine their potential for homogeneous bioassays. As particle systems, single-core nanoparticles with a nominal core diameter of 30 nm as well as multi-core nanoparticles with hydrodynamic sizes varying between nominally 60 nm and 100 nm were chosen. As experimental techniques, fluxgate magnetorelaxometry (MRX), complex ac susceptibility (ACS) and measurements of the phase lag between rotating field and sample magnetization are applied. MRX measurements are only suited for the detection of small analytes if the multivalency of functionalized nanoparticles and analytes causes cross-linking, thus forming larger aggregates. ACS measurements showed for all nanoparticle systems a shift of the imaginary part's maximum towards small frequencies. In rotating field measurements only the single-core nanoparticle systems with dominating Brownian mechanism exhibit an increase of the phase lag upon binding in the investigated frequency range. The coexistence of Brownian and Néel relaxation processes can cause a more complex phase lag change behavior, as demonstrated for multi-core nanoparticle systems. - Highlights: • Cealization of homogeneous magnetic bioassays using different magnetic techniques. • Comparison of single- and multi-core nanoparticle systems. • ac Susceptibility favorable for detection of small analytes. • Magnetorelaxometry favorable for detection of large analytes or cross-linking assays
Magnetic shielding of an inhomogeneous magnetic field source by a bulk superconducting tube
Hogan, K; Fagnard, J-F; Wéra, L; Vanderheyden, B; Vanderbemden, P
2015-01-01
Bulk type-II irreversible superconductors can act as excellent passive magnetic shields, with a strong attenuation of low frequency magnetic fields. Up to now, the performances of superconducting magnetic shields have mainly been studied in a homogenous magnetic field, considering only immunity problems, i.e. when the field is applied outside the tube and the inner field should ideally be zero. In this paper, we aim to investigate experimentally and numerically the magnetic response of a high-T c bulk superconducting hollow cylinder at 77 K in an emission problem, i.e. when subjected to the non-uniform magnetic field generated by a source coil placed inside the tube. A bespoke 3D mapping system coupled with a three-axis Hall probe is used to measure the magnetic flux density distribution outside the superconducting magnetic shield. A finite element model is developed to understand how the magnetic field penetrates into the superconductor and how the induced superconducting shielding currents flow inside the shield in the case where the emitting coil is placed coaxially inside the tube. The finite element modelling is found to be in excellent agreement with the experimental data. Results show that a concentration of the magnetic flux lines occurs between the emitting coil and the superconducting screen. This effect is observed both with the modelling and the experiment. In the case of a long tube, we show that the main features of the field penetration in the superconducting walls can be reproduced with a simple analytical 1D model. This model is used to estimate the maximum flux density of the emitting coil that can be shielded by the superconductor. (paper)
Synthesis of silica nanosphere from homogeneous and ...
WINTEC
avoid it, reaction in heterogeneous system using CTABr was carried out. Nanosized silica sphere with ... Homogeneous system contains a mixture of ethanol, water, aqueous ammonia and ... heated to 823 K (rate, 1 K/min) in air and kept at this.
Gravitational Metric Tensor Exterior to Rotating Homogeneous ...
The covariant and contravariant metric tensors exterior to a homogeneous spherical body rotating uniformly about a common φ axis with constant angular velocity ω is constructed. The constructed metric tensors in this gravitational field have seven non-zero distinct components.The Lagrangian for this gravitational field is ...
Homogeneous nucleation of water in synthetic air
Fransen, M.A.L.J.; Sachteleben, E.; Hruby, J.; Smeulders, D.M.J.; DeMott, P.J.; O'Dowd, C.D.
2013-01-01
Homogeneous nucleation rates for water vapor in synthetic air are measured by means of a Pulse-Expansion Wave Tube (PEWT). A comparison of the experimental nucleation rates with the Classical Nucleation Theory (CNT) shows that a more elaborated model is necessary to describe supercooled water
Homogeneity in Social Groups of Iraqis
Gresham, J.; Saleh, F.; Majid, S.
With appreciation to the Royal Institute for Inter-Faith Studies for initiating the Second World Congress for Middle Eastern Studies, this paper summarizes findings on homogeneity in community-level social groups derived from inter-ethnic research conducted during 2005 among Iraqi Arabs and Kurds
Abelian gauge theories on homogeneous spaces
Vassilevich, D.V.
1992-07-01
An algebraic technique of separation of gauge modes in Abelian gauge theories on homogeneous spaces is proposed. An effective potential for the Maxwell-Chern-Simons theory on S 3 is calculated. A generalization of the Chern-Simons action is suggested and analysed with the example of SU(3)/U(1) x U(1). (author). 11 refs
Benchmarking homogenization algorithms for monthly data
Venema, V. K. C.; Mestre, O.; Aquilar, E.; Auer, I.; Guijarro, J. A.; Domonkos, P.; Vertačník, G.; Szentimrey, T.; Štěpánek, Petr; Zahradníček, Pavel; Viarre, J.; Mueller-Westermeier, G.; Lakatos, M.; Williams, C. N.; Menne, M. J.; Lindau, R.; Rasol, D.; Rustemeier, E.; Kolokythas, K.; Marinova, T.; Andresen, L.; Acquaotta, F.; Fratianni, S.; Cheval, S.; Klancar, M.; Brunetti, M.; Gruber, C.; Duran, M. P.; Likso, T.; Esteban, P.; Brandsma, T.
2012-01-01
Roč. 8, č. 1 (2012), s. 89-115 ISSN 1814-9324 Institutional support: RVO:67179843 Keywords : climate data * instrumental time-series * greater alpine region * homogeneity test * variability * inhomogeneities Subject RIV: EH - Ecology, Behaviour Impact factor: 3.556, year: 2012
Homogeneous scintillating LKr/Xe calorimeters
Chen, M.; Mullins, M.; Pelly, D.; Shotkin, S.; Sumorok, K.; Akyuz, D.; Chen, E.; Gaudreau, M.P.J.; Bolozdynya, A.; Tchernyshev, V.; Goritchev, P.; Khovansky, V.; Koutchenkov, A.; Kovalenko, A.; Lebedenko, V.; Vinogradov, V.; Gusev, L.; Sheinkman, V.; Krasnokutsky, R.N.; Shuvalov, R.S.; Fedyakin, N.N.; Sushkov, V.; Akopyan, M.; Doke, T.; Kikuchi, J.; Hitachi, A.; Kashiwagi, T.; Masuda, K.; Shibamura, E.; Ishida, N.; Sugimoto, S.
1993-01-01
Recent R and D work on full length scintillating homogeneous liquid xenon/krypton (LXe/Kr) cells has established the essential properties for precision EM calorimeters: In-situ calibration using α's, radiation hardness as well as the uniformity required for δE/E≅0.5% for e/γ's above 50 GeV. (orig.)
Traffic planning for non-homogeneous traffic
Western trafﬁc planning methodologies mostly address the concerns of homogeneous trafﬁc and therefore often prove inadequate in solving problems involving ... Transportation Research and Injury Prevention Programme, Indian Institute of Technology, Hauz Khas, New Delhi 110 016; Civil and Architectural Engineering ...
A generalized model for homogenized reflectors
Pogosbekyan, Leonid; Kim, Yeong Il; Kim, Young Jin; Joo, Hyung Kook
1996-01-01
A new concept of equivalent homogenization is proposed. The concept employs new set of homogenized parameters: homogenized cross sections (XS) and interface matrix (IM), which relates partial currents at the cell interfaces. The idea of interface matrix generalizes the idea of discontinuity factors (DFs), proposed and developed by K. Koebke and K. Smith. The method of K. Smith can be simulated within framework of new method, while the new method approximates hetero-geneous cell better in case of the steep flux gradients at the cell interfaces. The attractive shapes of new concept are:improved accuracy, simplicity of incorporation in the existing codes, equal numerical expenses in comparison to the K. Smith's approach. The new concept is useful for: (a) explicit reflector/baffle simulation; (b)control blades simulation; (c) mixed UO 2 /MOX core simulation. The offered model has been incorporated in the finite difference code and in the nodal code PANBOX. The numerical results show good accuracy of core calculations and insensitivity of homogenized parameters with respect to in-core conditions
Inverse acoustic problem of N homogeneous scatterers
Berntsen, Svend
2002-01-01
The three-dimensional inverse acoustic medium problem of N homogeneous objects with known geometry and location is considered. It is proven that one scattering experiment is sufficient for the unique determination of the complex wavenumbers of the objects. The mapping from the scattered fields...
Mach's principle in spatially homogeneous spacetimes
Tipler, F.J.
1978-01-01
On the basis of Mach's Principle it is concluded that the only singularity-free solution to the empty space Einstein equations is flat space. It is shown that the only singularity-free solution to the empty space Einstein equations which is spatially homogeneous and globally hyperbolic is in fact suitably identified Minkowski space. (Auth.)
Water Filtration through Homogeneous Granulated Charge
A. M. Krautsou
2005-01-01
Full Text Available General relationship for calculation of water filtration through homogeneous granulated charge has been obtained. The obtained relationship has been compared with experimental data. Discrepancies between calculated and experimental values do not exceed 6 % throughout the entire investigated range.
Karabulut, I.; Mora-Ramos, M.E.; Duque, C.A.
2011-01-01
The intersubband electron-related nonlinear optical absorption and nonlinear optical rectification in GaAs-Ga 1-x Al x As asymmetric double quantum wells are studied, under the influence of combined or independent applied electric and magnetic fields as well as hydrostatic pressure. The outcome of the density matrix formalism and the effective mass, and parabolic-band approximations have been considered as main theoretical tools for the description. It is obtained that under particular geometrical conditions, with or without electric and/or magnetic field strength, the optical rectification is null and, simultaneously, in such circumstances the optical absorption has a relative maximum. It is also detected that the influence of the hydrostatic pressure leads to increasing or decreasing behaviors of the nonlinear optical absorption in dependence of the particular regime of pressure values considered, with significant distinction of the cases of opposite electric field orientations. - Highlights: → Maxima of the NOA correspond to zero in the NOR. → Electric fields can couple the double quantum wells. → Hydrostatic pressure can couple the double quantum wells. → NOA can increase/decrease with hydrostatic pressure. → Overlap between wave functions depends on the magnetic field.
Dao Thi Thuy Nguyet
2016-06-01
Full Text Available Dy and Ho iron garnets in form of nanoparticles were synthesized by citrate sol-gel method. Phase formation, lattice constant and average crystallite sizes of the samples were determined via XRD measurements. Morphology and particle size distribution were studied by TEM and chemical composition was checked by EDX. Magnetic measurements in temperature range 5–600 K and in the maximum applied field of 50 kOe were carried out by using SQUID and VSM. Their magnetic parameters, including Curie temperature, magnetization compensation temperature, spontaneous magnetization, high-field susceptibility, magnetic coercivity were discussed in the framework of three interacting magnetic sublattices, magnetocrystalline anisotropy, core-shell model and compared to those of the bulk materials. Based on these analyses further evaluation on the crystallinity and homogeneity of the samples has been made.
An optimized magnet for magnetic refrigeration
Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders
2010-01-01
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction...... of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close...... to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration....
An optimized magnet for magnetic refrigeration
Bjork, R.; Bahl, C.R.H.; Smith, A.; Christensen, D.V.; Pryds, N.
2010-01-01
A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration.
A new concept of equivalent homogenization method
Kim, Young Jin; Pogoskekyan, Leonid; Kim, Young Il; Ju, Hyung Kook; Chang, Moon Hee [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)
1996-07-01
A new concept of equivalent homogenization is proposed. The concept employs new set of homogenized parameters: homogenized cross sections (XS) and interface matrix (IM), which relates partial currents at the cell interfaces. The idea of interface matrix generalizes the idea of discontinuity factors (DFs), proposed and developed by K. Koebke and K. Smith. The offered concept covers both those of K. Koebke and K. Smith; both of them can be simulated within framework of new concept. Also, the offered concept covers Siemens KWU approach for baffle/reflector simulation, where the equivalent homogenized reflector XS are derived from the conservation of response matrix at the interface in 1D simi-infinite slab geometry. The IM and XS of new concept satisfy the same assumption about response matrix conservation in 1D semi-infinite slab geometry. It is expected that the new concept provides more accurate approximation of heterogeneous cell, especially in case of the steep flux gradients at the cell interfaces. The attractive shapes of new concept are: improved accuracy, simplicity of incorporation in the existing codes, equal numerical expenses in comparison to the K. Smith`s approach. The new concept is useful for: (a) explicit reflector/baffle simulation; (b) control blades simulation; (c) mixed UO{sub 2}/MOX core simulation. The offered model has been incorporated in the finite difference code and in the nodal code PANDOX. The numerical results show good accuracy of core calculations and insensitivity of homogenized parameters with respect to in-core conditions. 9 figs., 7 refs. (Author).
Desportes, H [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1964-07-01
The discovery of type II superconductors has considerably increased the possibilities of air-core coils, in particular with regard to the production of high homogeneous fields. The design of such magnets,calls for elaborate calculations which, in practise, can only be carried out on computers. The present report describes a complete set of programs for the calculation, in the case of cylindrical systems, of the magnetic field components at any point, the lines of flux, the forces, the self and mutual inductances, as well as the design of compensated coils for the production of high homogeneous fields. These programs have been employed for the calculation of two magnets which are described in detail. (author) [French] L'interet des bobines sans fer s'est considerablement accru depuis l'apparition recente des supraconducteurs de la deuxieme espece, en particulier pour la realisation d'aimants a champ tres homogene. Le calcul de tels bobinages fait appel a des methodes complexes dont l'execution pratique necessite l'emploi de machines a calculer. Le present rapport decrit un ensemble de programmes permettant de calculer, dans le cas de systemes de revolution de structure quelconque, le champ dans tout l'espace, les lignes de force du champ, les efforts electromagnetiques, les selfs et mutuelles, et de determiner des enroulements de compensation destines a uniformiser le champ. Ces programmes ont servi au calcul de deux aimants particuliers dont les caracteristiques detaillees sont fournies a titre d'application. (auteur)
Anon.
1980-01-01
The Physics Division research program that is dedicated primarily to applied research goals involves the interaction of energetic particles with solids. This applied research is carried out in conjunction with the basic research studies from which it evolved
Mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films
Fu, Yu, E-mail: yu.fu@uni-due.de, E-mail: cangcangzhulin@gmail.com; Meckenstock, R.; Farle, M. [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Barsukov, I., E-mail: ibarsuko@uci.edu [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Physics and Astronomy, University of California, Irvine, California 92697 (United States); Lindner, J. [Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universität Duisburg-Essen, 47057 Duisburg (Germany); Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf e.V., Bautzner Landstr. 400, 01328 Dresden (Germany); Raanaei, H. [Department of Physics, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Hjörvarsson, B. [Department of Physics and Astronomy, Uppsala University, Box 516 SE-75120 Uppsala (Sweden)
2014-02-17
The mechanism of tailored magnetic anisotropy in amorphous Co{sub 68}Fe{sub 24}Zr{sub 8} thin films was investigated by ferromagnetic resonance (FMR) on samples deposited without an applied magnetic field, with an out-of-plane field and an in-plane field. Analysis of FMR spectra profiles, high frequency susceptibility calculations, and statistical simulations using a distribution of local uniaxial magnetic anisotropy reveal the presence of atomic configurations with local uniaxial anisotropy, of which the direction can be tailored while the magnitude remains at an intrinsically constant value of 3.0(2) kJ/m{sup 3}. The in-plane growth field remarkably sharpens the anisotropy distribution and increases the sample homogeneity. The results benefit designing multilayer spintronic devices based on highly homogeneous amorphous layers with tailored magnetic anisotropy.
Valdés, Felipe
2013-03-01
Single-source time-domain electric-and magnetic-field integral equations for analyzing scattering from homogeneous penetrable objects are presented. Their temporal discretization is effected by using shifted piecewise polynomial temporal basis functions and a collocation testing procedure, thus allowing for a marching-on-in-time (MOT) solution scheme. Unlike dual-source formulations, single-source equations involve space-time domain operator products, for which spatial discretization techniques developed for standalone operators do not apply. Here, the spatial discretization of the single-source time-domain integral equations is achieved by using the high-order divergence-conforming basis functions developed by Graglia alongside the high-order divergence-and quasi curl-conforming (DQCC) basis functions of Valdés The combination of these two sets allows for a well-conditioned mapping from div-to curl-conforming function spaces that fully respects the space-mapping properties of the space-time operators involved. Numerical results corroborate the fact that the proposed procedure guarantees accuracy and stability of the MOT scheme. © 2012 IEEE.
Magnetic shielding for MRI superconducting magnets
Ishiyama, A.; Hirooka, H.
1991-01-01
This paper describes an optimal design of a highly homogeneous superconducting coil system with magnetic shielding for Magnetic Resonance Imaging (MRI). The presented optimal design method; which is originally proposed in our earlier papers, is a combination of the hybrid finite element and boundary element method for analysis of an axially symmetric nonlinear open boundary magnetic field problem, and the mathematical programming method for solving the corresponding optimization problem. In this paper, the multi-objective goal programming method and the nonlinear least squares method have been adopted. The optimal design results of 1.5- and 4.7-Tesla-magnet systems with different types of magnetic shielding for whole-body imaging are compared and the advantages of a combination of active and yoke shields are shown
Yuan, Muzhaozi; Wang, Ya; Qin, Yi-Xian
2018-04-05
Neuroregeneration imposes a significant challenge in neuroscience for treating neurodegenerative diseases. The objective of this study is to evaluate the hypothesis that the nerve growth factor (NGF) functionalized superparamagnetic iron oxide (SPIO)-gold (Au) nanomedicine can stimulate the neuron growth and differentiation under external magnetic fields (MFs), and dynamic MFs outperform their static counterparts. The SPIO-Au core-shell nanoparticles (NPs) (Diameter: 20.8 nm) possessed advantages such as uniform quasi-spherical shapes, narrow size distribution, excellent stabilities, and low toxicity (viability >96% for 5 days). NGF functionalization has enhanced the cellular uptake. The promotion of neuronal growth and orientation using NGF functionalized SPIO-Au NPs, driven by both the static and dynamic MFs, were revealed experimentally on PC-12 cells and theoretically on a cytoskeletal force model. More importantly, dynamic MFs via rotation performed better than the static ones, i.e., the cellular differentiation ratio increased 58%; the neurite length elongation increased 63%. Copyright © 2018 Elsevier Inc. All rights reserved.
Dimbylow, Peter
2011-07-21
This paper sets out to explore the effects of voxel resolution, from 2 mm down to 0.1 mm for Cartesian co-ordinates and the differences between Cartesian and spherical polar co-ordinates for a standardized test-bed model of the eye. This model was taken from the work of Yoriyaz et al (2005 Radiat. Prot. Dosim. 115 316-9) who have developed a detailed geometric description of the eye including choroid, retina, sclera, lens, cornea, anterior chamber, vitreous humour and optic nerve for ophthalmic brachytherapy. The spherical co-ordinate model has radial and angular steplengths of 0.1 mm and 0.25°, respectively. The current density averaged over 1 cm(2) and the 99th percentile value of the induced electric field have been calculated in the retina and central nervous system for uniform magnetic fields. The Cartesian co-ordinate calculations proceed in a sequence of grids at 2, 1, 0.5, 0.2 and 0.1 mm resolution with the potentials from the previous calculation at a coarser grid providing the boundary conditions on the finer grid. The 0.2 mm grid provides the boundary conditions for the spherical polar calculations. Comparisons are made with the International Commission on Non-Ionizing Radiation Protection reference levels.
Dimbylow, Peter
2011-01-01
This paper sets out to explore the effects of voxel resolution, from 2 mm down to 0.1 mm for Cartesian co-ordinates and the differences between Cartesian and spherical polar co-ordinates for a standardized test-bed model of the eye. This model was taken from the work of Yoriyaz et al (2005 Radiat. Prot. Dosim. 115 316-9) who have developed a detailed geometric description of the eye including choroid, retina, sclera, lens, cornea, anterior chamber, vitreous humour and optic nerve for ophthalmic brachytherapy. The spherical co-ordinate model has radial and angular steplengths of 0.1 mm and 0.25 0 , respectively. The current density averaged over 1 cm 2 and the 99th percentile value of the induced electric field have been calculated in the retina and central nervous system for uniform magnetic fields. The Cartesian co-ordinate calculations proceed in a sequence of grids at 2, 1, 0.5, 0.2 and 0.1 mm resolution with the potentials from the previous calculation at a coarser grid providing the boundary conditions on the finer grid. The 0.2 mm grid provides the boundary conditions for the spherical polar calculations. Comparisons are made with the International Commission on Non-Ionizing Radiation Protection reference levels.
Rössler, Erik; Mattea, Carlos; Stapf, Siegfried
2015-02-01
Low field Nuclear Magnetic Resonance increases the contrast of the longitudinal relaxation rate in many biological tissues; one prominent example is hyaline articular cartilage. In order to take advantage of this increased contrast and to profile the depth-dependent variations, high resolution parameter measurements are carried out which can be of critical importance in an early diagnosis of cartilage diseases such as osteoarthritis. However, the maximum achievable spatial resolution of parameter profiles is limited by factors such as sensor geometry, sample curvature, and diffusion limitation. In this work, we report on high-resolution single-sided NMR scanner measurements with a commercial device, and quantify these limitations. The highest achievable spatial resolution on the used profiler, and the lateral dimension of the sensitive volume were determined. Since articular cartilage samples are usually bent, we also focus on averaging effects inside the horizontally aligned sensitive volume and their impact on the relaxation profiles. Taking these critical parameters into consideration, depth-dependent relaxation time profiles with the maximum achievable vertical resolution of 20 μm are discussed, and are correlated with diffusion coefficient profiles in hyaline articular cartilage in order to reconstruct T2 maps from the diffusion-weighted CPMG decays of apparent relaxation rates.
Koch, Stephan
2009-03-30
This thesis is concerned with the numerical simulation of electromagnetic fields in the quasi-static approximation which is applicable in many practical cases. Main emphasis is put on higher-order finite element methods. Quasi-static applications can be found, e.g., in accelerator physics in terms of the design of magnets required for beam guidance, in power engineering as well as in high-voltage engineering. Especially during the first design and optimization phase of respective devices, numerical models offer a cheap alternative to the often costly assembly of prototypes. However, large differences in the magnitude of the material parameters and the geometric dimensions as well as in the time-scales of the electromagnetic phenomena involved lead to an unacceptably long simulation time or to an inadequately large memory requirement. Under certain circumstances, the simulation itself and, in turn, the desired design improvement becomes even impossible. In the context of this thesis, two strategies aiming at the extension of the range of application for numerical simulations based on the finite element method are pursued. The first strategy consists in parallelizing existing methods such that the computation can be distributed over several computers or cores of a processor. As a consequence, it becomes feasible to simulate a larger range of devices featuring more degrees of freedom in the numerical model than before. This is illustrated for the calculation of the electromagnetic fields, in particular of the eddy-current losses, inside a superconducting dipole magnet developed at the GSI Helmholtzzentrum fuer Schwerionenforschung as a part of the FAIR project. As the second strategy to improve the efficiency of numerical simulations, a hybrid discretization scheme exploiting certain geometrical symmetries is established. Using this method, a significant reduction of the numerical effort in terms of required degrees of freedom for a given accuracy is achieved. The
Homogenization Issues in the Combustion of Heterogeneous Solid Propellants
Chen, M.; Buckmaster, J.; Jackson, T. L.; Massa, L.
2002-01-01
We examine random packs of discs or spheres, models for ammonium-perchlorate-in-binder propellants, and discuss their average properties. An analytical strategy is described for calculating the mean or effective heat conduction coefficient in terms of the heat conduction coefficients of the individual components, and the results are verified by comparison with those of direct numerical simulations (dns) for both 2-D (disc) and 3-D (sphere) packs across which a temperature difference is applied. Similarly, when the surface regression speed of each component is related to the surface temperature via a simple Arrhenius law, an analytical strategy is developed for calculating an effective Arrhenius law for the combination, and these results are verified using dns in which a uniform heat flux is applied to the pack surface, causing it to regress. These results are needed for homogenization strategies necessary for fully integrated 2-D or 3-D simulations of heterogeneous propellant combustion.
Sewage sludge disintegration by combined treatment of alkaline+high pressure homogenization.
Zhang, Yuxuan; Zhang, Panyue; Zhang, Guangming; Ma, Weifang; Wu, Hao; Ma, Boqiang
2012-11-01
Alkaline pretreatment combined with high pressure homogenization (HPH) was applied to promote sewage sludge disintegration. For sewage sludge with a total solid content of 1.82%, sludge disintegration degree (DD(COD)) with combined treatment was higher than the sum of DD(COD) with single alkaline and single HPH treatment. NaOH dosage ⩽0.04mol/L, homogenization pressure ⩽60MPa and a single homogenization cycle were the suitable conditions for combined sludge treatment. The combined sludge treatment showed a maximum DD(COD) of 59.26%. By regression analysis, the combined sludge disintegration model was established as 11-DD(COD)=0.713C(0.334)P(0.234)N(0.119), showing that the effect of operating parameters on sludge disintegration followed the order: NaOH dosage>homogenization pressure>number of homogenization cycle. The energy efficiency with combined sludge treatment significantly increased compared with that with single HPH treatment, and the high energy efficiency was achieved at low homogenization pressure with a single homogenization cycle. Copyright © 2012 Elsevier Ltd. All rights reserved.