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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

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

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

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

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

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

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; Turpen, Oliver S., Jr.; Branum, David R.; Meuser, Robert B.; Rhein, Reginald W. & Carlson, Norris W.
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

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

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

Reaction field induced interatomic forces between atoms in the presense of a strong magnetic field

Description: It is shown that the reaction field induced in an atom by a strong magnetic field is of order B{alpha}² in atomic units (for magnetic field strength B and fine structure constant {alpha}). The reaction field causes a dipole-dipole interatomic potential energy to exist between a pair of atoms of order B<sup>3/2</sup>{alpha}<sup>7/2</sup>, such that B must be of order {alpha}<sup>-7/3</sup> for the interatomic energy to be of order one atomic unit. B of this order corresponds to a field strength of 1.66 x 10<sup>12</sup> G, which is within the regime of field strengths considered in recent studies of atoms and molecules in the presence of a strong magnetic field.
Date: March 23, 1999
Creator: Ritchie, A B
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

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

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


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