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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

Plasma Confinement at Uniform Temperature

Description: Report discussing the properties of a plasma held in a steady state by a magnetic field. Properties such as "electric and magnetic fields, current density, particle density, and macroscopic velocity" are determined analytically by assuming uniform temperature throughout the plasma.
Date: October 24, 1956
Creator: Woods, Cornelius H.
Partner: UNT Libraries Government Documents Department

The bumpy torus

Description: "In this paper the single particle motion in the magnetic field created by a circular array of circular current loops is investigated." (p. 3)
Date: October 1959
Creator: Gibson, Gordon; Jordan, Willard C. & Lauer, Eugene J.
Partner: UNT Libraries Government Documents Department

Occluded-Gas Ion Source

Description: "Characteristics of a pulsed, occluded-gas ion source, operating in a magnetic field, have been investigated. Mass spectra of hydrogen- and deuterium-loaded sources are presented. Constructional details of the source and its operating characteristics are discussed."
Date: June 27, 1956
Creator: Ehlers, Kenneth W.
Partner: UNT Libraries Government Documents Department

Measurement of the Effect of an Axial Magnetic Field on the Reynolds Number of Transition in Mercury Flowing Through a Glass Tube

Description: Note presenting experiments conducted to determine the effect of a strong axial magnetic field on the flow of mercury through a circular channel. The magnetic induction was 15,000 gauss, and the channel was a pyrex tube 17-1/4 inches long and 0.027 inch inside diameter. The results indicated that the stabilizing effect occurred only at Reynolds number above 5,000, so that the region of practical applicability seems to be at fairly high Reynolds numbers and when there are only slight disturbances in the flow.
Date: May 1958
Creator: Bader, Michel & Carlson, William C. A.
Partner: UNT Libraries Government Documents Department

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

Design and fabrication of solenoids for high magnetic fields

Description: From abstract: "This report consists of papers presented of papers presented at a meeting held in late 1954 to review all the work related to coil design and fabrication."
Date: December 1955
Creator: Coensgen, Frederic H.; Turpen, Oliver S.; Branum, David R.; Meuser, Robert B.; Rhein, Reginald W. & Carlson, Norris W.
Partner: UNT Libraries Government Documents Department

On flow of electrically conducting fluids over a flat plate in the presence of a transverse magnetic field

Description: The use of a magnetic field to control the motion of electrically conducting fluids is studied. The incompressible boundary-layer solutions are found for flow over a flat plate when the magnetic field is fixed relative to the plate or to the fluid. The equations are integrated numerically for the effect of the transverse magnetic field on the velocity and temperature profiles, and hence, the skin friction and rate of heat transfer. It is concluded that the skin friction and the heat-transfer rate are reduced when the transverse magnetic field is fixed relative to the plate and increased when fixed relative to the fluid. The total drag is increased in all of the areas.
Date: March 13, 1957
Creator: Rossow, Vernon J.
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