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Indoor Localization Using Magnetic Fields

Description: Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth’s magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth’s magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth’s field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing hallways with different kinds of pillars, doors and elevators. All in all, this dissertation ...
Date: December 2011
Creator: Pathapati Subbu, Kalyan Sasidhar
Partner: UNT Libraries

Preliminary Report on Magnetogasdynamic Aspects

Description: Report describing studies on magnetogasdynamic aspects, presented in three sections: a summary of relevant magnetofluidmechanic fundamentals; a review of relevant literature on flow modification in magnetofluidmechnics; and the results of analytical investigations on highly restricted magnetofluidmechanic flows.
Date: August 1961
Creator: Chenoweth, D. R.
Partner: UNT Libraries Government Documents Department

Experimental Verification of the Hall Effect during Magnetic Reconnection in a Laboratory Plasma

Description: In this letter we report a clear and unambiguous observation of the out-of-plane quadrupole magnetic field suggested by numerical simulations in the reconnecting current sheet in the Magnetic Reconnection Experiment (MRX). Measurements show that the Hall effect is large in collisionless regime and becomes small as the collisionality increases, indicating that the Hall effect plays an important role in collisionless reconnection.
Date: June 16, 2005
Creator: Ren, Yang; Yamada, Masaaki; Gerhardt, Stefan; Ji, Hantao; Kulsrud, Russell & Kuritsyn, Aleksey
Partner: UNT Libraries Government Documents Department


Description: A relatively simple and inexpensive device is described which can be used to provide a highly homogeneous solenoidal magnetic field when the solenoid windings are inadequate. Design considerations and experimental measurements are presented. A field straightness of approximately 10{sup -4} radians has been achieved.
Date: January 1, 1981
Creator: Feinberg, B.; Brown, I.G.; Halbach, K. & Kunkel, W.B.
Partner: UNT Libraries Government Documents Department


Description: A double-focusing magnetic field for a spectrometer of the flat type which gives radial focusing to roughly the sixth order, and which utilizes azimuthal variation of the field coefficients, has been devised.
Date: April 6, 1966
Creator: Bergkvist, Karl-Erik & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department

Test Results on D-12A-2

Description: The purpose of this report is to describe the recent tests of D-12A-2. The tests of D-12A-2 began on April 30 and ended on May 8. The unusually long test period was a result of an extensive series of magnetic field measurements in which we attempted to determine the shielding affects of a sextupole compensating coil and the decay of the currents induced in this coil. This report is short, but much of the data from the tests are included or summarized. We begin with a description of the coil and conductor, continue with the training history, the results of magnetic measurements, including the use of a sextupole compensating coil and then describe the results of heater induced quenches including estimates of axial and transverse quench propagation velocities.
Date: August 8, 1984
Creator: Hassenzahl, W.
Partner: UNT Libraries Government Documents Department

The Reduction of the Critical Currents in Nb3Sn Cables under Transverse Loads

Description: The degradation of the critical current of impregnated Rutherford type Nb{sub 3}Sn cables is investigated as a function of the applied transverse load and magnetic field. The cable is made of TWCA modified jelly-roll type strand material and has a keystone angle of 1.0 degree. The voltage-current characteristics are determined for the magnetic field ranging from 2 to 11 tesla and transverse pressure up to 250 MPa on the cable surface. It is found that the 48-strand cable, made of strands with 6 elements in the matrix, shows a larger critical current degradation than the 26-strand cable with 36 elements per strand. The global degradation of the 48-strand cable is 63% at 150 MPa, and 40% at 150 MPa for the 26-strand cable. Micro-analysis of the cross-section shows permanent damage to the sharp edge of the cable. The influence of the keystone angle on the critical-current degradation is currently under investigation.
Date: August 1, 1992
Creator: Van Oort, J.M.; Scanlan, R.M.; Weijers, H.W.; Wessel, S. & Ten Kate, H.H.J.
Partner: UNT Libraries Government Documents Department

Multi-transmitter multi-receiver null coupled systems forinductive detection and characterization of metallic objects

Description: Equivalent dipole polarizabilities are a succinct way tosummarize the inductive response of an isolated conductive body atdistances greater than the scale of the body. Their estimation requiresmeasurement of secondary magnetic fields due to currents induced in thebody by time varying magnetic fields in at least three linearlyindependent (e.g., orthogonal) directions. Secondary fields due to anobject are typically orders of magnitude smaller than the primaryinducing fields near the primary field sources (transmitters). Receivercoils may be oriented orthogonal to primary fields from one or twotransmitters, nulling their response to those fields, but simultaneouslynulling to fields of additional transmitters is problematic. Iftransmitter coils are constructed symmetrically with respect to inversionin a point, their magnetic fields are symmetric with respect to thatpoint. If receiver coils are operated in pairs symmetric with respect toinversion in the same point, then their differenced output is insensitiveto the primary fields of any symmetrically constructed transmitters,allowing nulling to three (or more) transmitters. With a sufficientnumber of receivers pairs, object equivalent dipole polarizabilities canbe estimated in situ from measurements at a single instrument sitting,eliminating effects of inaccurate instrument location on polarizabilityestimates. The method is illustrated with data from a multi-transmittermulti-receiver system with primary field nulling through differencedreceiver pairs, interpreted in terms of principal equivalent dipolepolarizabilities as a function of time.
Date: October 17, 2005
Creator: Smith, J. Torquil; Morrison, H. Frank; Doolittle, Lawrence R. & Tseng, Hung-Wen
Partner: UNT Libraries Government Documents Department

Interium Report on An Exact Analysis of a Limited Plane Plasma in a Magnetic Field

Description: Prior analyses of a plasma in a magnetic field have been limited, as far as the writer is aware, to cases in which the relative change in field over the orbital distance and the relative change in ion concentration are both small, or in which the relations have been viewed in a purely hydrodynamical way. The first approach excludes cases which can be of considerable interest, for it fails for a plasma edge. The second loses all sight of the structure imposed by the orbital motions.
Date: January 1, 1947
Creator: Tonka, Lewi
Partner: UNT Libraries Government Documents Department

Cosmological AMR MHD with Enzo

Description: In this work, we present EnzoMHD, the extension of the cosmological code Enzoto include magnetic fields. We use the hyperbolic solver of Li et al. (2008) for the computation of interface fluxes. We use constrained transport methods of Balsara & Spicer (1999) and Gardiner & Stone (2005) to advance the induction equation, the reconstruction technique of Balsara (2001) to extend the Adaptive Mesh Refinement of Berger & Colella (1989) already used in Enzo, though formulated in a slightly different way for ease of implementation. This combination of methods preserves the divergence of the magnetic field to machine precision. We use operator splitting to include gravity and cosmological expansion. We then present a series of cosmological and non cosmologjcal tests problems to demonstrate the quality of solution resulting from this combination of solvers.
Date: January 1, 2009
Creator: Xu, Hao; Li, Hui & Li, Shengtai
Partner: UNT Libraries Government Documents Department

Design of the National Bureau of Standards Isotropic Magnetic Field Meter (MFM-10) 300 kHz to 100 MHz

Description: From introduction: In this report the following will he discussed: (1) design consideration of the broadband magnetic field sensor, (2) overall design of the magnetic field meter, (3) performance of the meter, (4) calibration and operating procedures, (5) alignment and adjustment procedures, and (6) summary and conclusions.
Date: October 1985
Creator: Cruz, J. E.; Driver, L. D. & Kanda, Motohisa
Partner: UNT Libraries Government Documents Department

Field driven ferromagnetic phase nucleation and propagation from the domain boundaries in antiferromagnetically coupled perpendicular anisotropy films

Description: We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that reveal the underlying energetics driving the overall reversal mechanisms.
Date: December 9, 2008
Creator: Hauet, Thomas; Gunther, Christian M.; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter et al.
Partner: UNT Libraries Government Documents Department

Passage through a TM slab

Description: The purpose of this short note is to derive the simple but remarkable result that the tranverse impulse given to a particle passing through a \slab" of homo- geneous, stationary, transverse magnetic #12;eld depends only on the properties of the slab and the particle's charge, and not at all on its initial state or its mass.
Date: October 1, 1998
Creator: Michelotti, Leo
Partner: UNT Libraries Government Documents Department

RG analysis of magnetic catalysis in dynamical symmetry breaking

Description: We perform the renormalization group analysis on the dynamical symmetry breaking under strong external magnetic field, studied recently by Gusynin, Miransky and Shovkovy. We find that any attractive four-Fermi interaction becomes strong in the low energy, thus leading to dynamical symmetry breaking. When the four-Fermi interaction is absent, the {beta}-function for the electromagnetic coupling vanishes in the leading order in 1/N. By solving the Schwinger-Dyson equation for the fermion propagator, we show that in 1/N expansion, for any electromagnetic coupling, dynamical symmetry breaking occurs due to the presence of Landau energy gap by the external magnetic field. 5 refs.
Date: May 1, 1996
Creator: Hong, Deog Ki & Kim, Youngman
Partner: UNT Libraries Government Documents Department

Magnetosonic Eigenmodes Near the Magnetic Field Well in a Spherical Torus

Description: The structure and spectrum of magnetosonic Alfven eigenmodes in spherical torus in the presence of magnetic field well are studied. Analytical solution for eigenmodes localized in the well is obtained and compared with the numerical one. The possibility of using the eigenmode spectrum measurements for reconstructing the magnetic field well, and, thus, central magnetic safety factor profile is discussed.
Date: July 10, 1998
Creator: Gorelenkova, M. V. & Gorelenkov, N. N.
Partner: UNT Libraries Government Documents Department

Magnetomorphic Oscillations in Zinc

Description: In making this study it is important to search for ways to enhance and, if possible, make detection of MMO signals simpler in order that this technique for obtaining FS measurements may be extended to other materials. This attempt to improve measurement techniques has resulted in a significant discovery: the eddy-current techniques described in detail in a later section which should allow MMO to be observed and sensitively measured in many additional solids. The second major thrust of the study has been to use the newly discovered eddy-current technique in obtaining the first indisputable observation of MMO in zinc.
Date: August 1970
Creator: Waller, William Marvin
Partner: UNT Libraries

Experimental estimate of beam loading and minimum rf voltage for acceleration of high intensity beam in the Fermilab Booster

Description: The difference between the rf voltage seen by the beam and the accelerating voltage required to match the rate of change of the Booster magnetic field is used to estimate the energy loss per beam turn. Because the rf voltage (RFSUM) and the synchronous phase can be experimentally measured, they can be used to calculate the effective accelerating voltage. Also an RFSUM reduction technique has been applied to measure experimentally the RFSUM limit at which the beam loss starts. With information on beam energy loss, the running conditions, especially for the high intensity beam, can be optimized in order to achieve a higher intensity beam from the Fermilab Booster.
Date: April 1, 2004
Creator: Yang, Xi & Norem, Charles M Ankenbrandt and Jim
Partner: UNT Libraries Government Documents Department

Energy loss estimates at several beam intensities in the Fermilab Booster

Description: The difference between the effective rf voltage and the accelerating voltage required to match the rate of change of the Booster magnetic field can be used to estimate the energy loss per beam turn. Although the effective rf voltage (RFSUM) and the synchronous phase can be experimentally measured and used to calculate the accelerating voltage, the calibration of the signals during the fast change of the Booster rf frequency is difficult and appears to introduce some offset to the beam energy loss estimation. An observed linear relationship between energy loss and beam intensity is used to evaluate the offset, which is then applied to the experimental data. This approach, rather than recalibrating the signals, is simple and suitable for minimizing the error in the data.
Date: June 8, 2004
Creator: MacLachlan, Xi Yang and James
Partner: UNT Libraries Government Documents Department