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Division of labor among the alpha-6 beta-4 integrin, beta-1 integrins and an E3 laminin receptor to signal morphogenesis and beta-casein expression in mammary epithelial cells (open access)

Division of labor among the alpha-6 beta-4 integrin, beta-1 integrins and an E3 laminin receptor to signal morphogenesis and beta-casein expression in mammary epithelial cells

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Date: June 30, 1999
Creator: Muschler, J.; Lochter, A.; Roskelley, C. D.; Yurchenco, P. & Bissell, M. J.
System: The UNT Digital Library
Approaches to rid cathodic arc plasmas of macro- andnanoparticles: A review (open access)

Approaches to rid cathodic arc plasmas of macro- andnanoparticles: A review

A major obstacle for the broad application of cathodic arc plasma deposition is the presence of micro- and nanoparticles in the plasma, also often referred to as 'macroparticles'. This paper reviews the formation of macroparticles at cathode spots, their interaction with the arc plasma and substrate, and macroparticle separation and removal from the plasma by various filtering methods. Nineteen variants of filters are discussed, including Aksenov's classic 90{sup o}-duct filter, filters of open architecture, and the concept of stroboscopic filtering.
Date: June 1, 1999
Creator: Anders, Andre
System: The UNT Digital Library
Characterizing Indoor Airflow and Pollutant Transport using Simulation Modeling for Prototypical Buildings. I. Office Buildings (open access)

Characterizing Indoor Airflow and Pollutant Transport using Simulation Modeling for Prototypical Buildings. I. Office Buildings

This paper describes the first efforts at developing a set of prototypical buildings defined to capture the key features affecting airflow and pollutant transport in buildings. These buildings will be used to model airflow and pollutant transport for emergency response scenarios when limited site-specific information is available and immediate decisions must be made, and to better understand key features of buildings controlling occupant exposures to indoor pollutant sources. This paper presents an example of this approach for a prototypical intermediate-sized, open style, commercial building. Interzonal transport due to a short-term source release, e.g., accidental chemical spill, in the bottom and the upper floors is predicted and corresponding HVAC system operation effects and potential responses are considered. Three-hour average exposure estimates are used to compare effects of source location and HVAC operation.
Date: June 1, 1999
Creator: Sohn, M. D.; Daisey, J. M. & Feustel, H. E.
System: The UNT Digital Library
Implementing Systems Engineering on a CERCLA Project (open access)

Implementing Systems Engineering on a CERCLA Project

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), enacted in 1980, provides a regulatory and legal mechanism to reduce risks from prior disposal of hazardous and toxic chemicals. Regulations, Standards, and Guidelines have been published to further define the CERCLA Process. The OU 7-10 Staged Interim Action Project at the Idaho National Engineering and Environmental Laboratory (INEEL) is a CERCLA project working to remediate the pre-1970 disposal pit in which transuranic materials have been disposed. This paper analyzes the CERCLA process from a systems engineering perspective and describes how systems engineering is implemented on this project.
Date: June 1, 1999
Creator: Beitel, George Alois
System: The UNT Digital Library
Issue Management Risk Ranking Systems (open access)

Issue Management Risk Ranking Systems

Thousands of safety issues have been collected on-line at the Idaho National Engineering and Environmental Laboratory (INEEL) as part of the Issue Management Plan. However, there has been no established approach to prioritize collected and future issues. The authors developed a methodology, based on hazards assessment, to identify and risk rank over 5000 safety issues collected at INEEL. This approach required that it was easily applied and understandable for site adaptation and commensurate with the Integrated Safety Plan. High-risk issues were investigated and mitigative/preventive measures were suggested and ranked based on a cost-benefit scheme to provide risk-informed safety measures. This methodology was consistent with other integrated safety management goals and tasks providing a site-wide risk informed decision tool to reduce hazardous conditions and focus resources on high-risk safety issues. As part of the issue management plan, this methodology was incorporated at the issue collection level and training was provided to management to better familiarize decision-makers with concepts of safety and risk. This prioritization methodology and issue dissemination procedure will be discussed. Results of issue prioritization and training efforts will be summarized. Difficulties and advantages of the process will be reported. Development and incorporation of this process into INEELs lessons learned …
Date: June 1, 1999
Creator: Novack, Steven David; Marshall, Frances Mc Clellan; Stromberg, Howard Merion & Grant, Gary Michael
System: The UNT Digital Library
Microbial Ecology Assessment of Mixed Copper Oxide/Sulfide Dump Leach Operation (open access)

Microbial Ecology Assessment of Mixed Copper Oxide/Sulfide Dump Leach Operation

Microbial consortia composed of complex mixtures of autotrophic and heterotrophic bacteria are responsible for the dissolution of metals from sulfide minerals. Thus, an efficient copper bioleaching operation depends on the microbial ecology of the system. A microbial ecology study of a mixed oxide/sulfide copper leaching operation was conducted using an "overlay" plating technique to differentiate and identify various bacterial consortium members of the genera Thiobacillus, “Leptospirillum”, “Ferromicrobium”, and Acidiphilium. Two temperatures (30°C and 45°C) were used to select for mesophilic and moderately thermophilic bacteria. Cell numbers varied from 0-106 cells/g dry ore, depending on the sample location and depth. After acid curing for oxide leaching, no viable bacteria were recovered, although inoculation of cells from raffinate re-established a microbial population after three months. Due to low the pH of the operation, very few non-iron-oxidizing acidophilic heterotrophs were recovered. Moderate thermophiles were isolated from the ore samples. Pregnant liquor solutions (PLS) and raffinate both contained a diversity of bacteria. In addition, an intermittently applied waste stream that contained high levels of arsenic and fluoride was tested for toxicity. Twenty vol% waste stream in PLS killed 100% of the cells in 48 hours, indicating substantial toxicity and/or growth inhibition. The data indicate …
Date: June 1, 1999
Creator: Bruhn, Debby Fox; Thompson, David Neal & Noah, Karl Scott
System: The UNT Digital Library
Performance Characteristics of an Extended Throat Flow Nozzle for the Measurement of High Void Fraction Multi-phase Flows (open access)

Performance Characteristics of an Extended Throat Flow Nozzle for the Measurement of High Void Fraction Multi-phase Flows

An extended throat flow nozzle has been examined as a device for the measurement of very high void fraction (a ³ 0.95) multi-phase flows. Due to its greater density and partial contact with the wall, the equilibrium velocity of the liquid phase appreciably lags that of the lighter gas phase. The two phases are strongly coupled resulting in pressure drops across the contraction and in the extended throat that are significantly different than those experienced in single-phase flow. Information about the mass flow rates of the two phases can be extracted from the measured pressure drops. The performance of an extended throat flow nozzle has been evaluated under multi-phase conditions using natural gas and hydrocarbon liquids at 400 and 500 psi. Two hydrocarbon solvents were used as the test liquids, Isopar MÒ (sp = 0.79) and Aromatic 100â (sp = 0.87). These data are compared to prior air-water data at nominally 15 psi. The high and low pressure data were found to be consistent, confirming that the temperature, pressure, and size scaling of the extended throat venturi are correctly represented. This consistency allows different sized devices to be applied under different fluid conditions (temperature, pressure, gas and liquid phase composition, …
Date: June 1, 1999
Creator: Fincke, James Russell; Jeffery, Charles Lee; Ronnenkamp, C.; Kruse, D.; Krogue, J. & Householder, D.
System: The UNT Digital Library
Application of Systems Engineering to U.S. Department of Energy Privatization Project Selection at the Hanford Nuclear Reservation (open access)

Application of Systems Engineering to U.S. Department of Energy Privatization Project Selection at the Hanford Nuclear Reservation

The privatization efforts at the U.S. Department of Energy's Hanford Nuclear Reservation have been very successful primarily due to a disciplined process for project selection and execution. Early in the development of Privatization at Hanford, the Department of Energy determined that a disciplined alternatives generation and analysis (AGA) process would furnish the candidate projects with the best probability for success. Many factors had to be considered in the selection of projects. Westinghouse Hanford Company was assigned to develop this process and facilitate the selection of the first round of candidate privatization projects. Team members for the AGA process were assembled from all concerned organizations and skill groups. Among the selection criteria were legal, financial and technical considerations which had to be weighed.
Date: June 1, 1999
Creator: Layman, John Scott
System: The UNT Digital Library
Function Analysis and Decomposistion using Function Analysis Systems Technique (open access)

Function Analysis and Decomposistion using Function Analysis Systems Technique

The "Father of Value Analysis", Lawrence D. Miles, was a design engineer for General Electric in Schenectady, New York. Miles developed the concept of function analysis to address difficulties in satisfying the requirements to fill shortages of high demand manufactured parts and electrical components during World War II. His concept of function analysis was further developed in the 1960s by Charles W. Bytheway, a design engineer at Sperry Univac in Salt Lake City, Utah. Charles Bytheway extended Mile's function analysis concepts and introduced the methodology called Function Analysis Systems Technique (FAST) to the Society of American Value Engineers (SAVE) at their International Convention in 1965 (Bytheway 1965). FAST uses intuitive logic to decompose a high level, or objective function into secondary and lower level functions that are displayed in a logic diagram called a FAST model. Other techniques can then be applied to allocate functions to components, individuals, processes, or other entities that accomplish the functions. FAST is best applied in a team setting and proves to be an effective methodology for functional decomposition, allocation, and alternative development.
Date: June 1, 1999
Creator: Wixson, James Robert
System: The UNT Digital Library
Numerical Calculations of Wind Flow in a Full-Scale Wind Test Facility (open access)

Numerical Calculations of Wind Flow in a Full-Scale Wind Test Facility

Numerical studies on wind flow around the Texas Tech University (TTU) Wind Engineering Research Field Laboratory (WERFL) building were conducted. The main focus of this paper is wind loads on the TTU building in the INEEL proposed Windstorm Simulation Center. The results are presented in the form of distributions of static pressure, dynamic pressure, pressure coefficients, and velocity vectors on the surface and the vicinity of the TTU building.
Date: June 1, 1999
Creator: Oh, Chang H & Lacey, Jerry Mark
System: The UNT Digital Library
SERA - An Advanced Treatment Planning System for Neutron Therapy (open access)

SERA - An Advanced Treatment Planning System for Neutron Therapy

The technology for computational dosimetry and treatment planning for Boron Neutron Capture Therapy (BNCT) has advanced significantly over the past few years. Because of the more complex nature of the problem, the computational methods that work well for treatment planning in photon radiotherapy are not applicable to BNCT. The necessary methods have, however, been developed and have been successfully employed both for research applications as well as human trials. Computational geometry for BNCT applications can be constructed directly from tomographic medical imagery and computed radiation dose distributions can be readily displayed in formats that are familiar to the radiotherapy community. The SERA system represents a significant advance in several areas for treatment planning. However further improvements in speed and results presentation are still needed for routine clinical applications, particularly when optimizations of dose pattern is required.
Date: June 1, 1999
Creator: Wemple, C. A.; Albright, C. L.; Nigg, D. W.; Wessol, D. W.; Wheeler, F. J.; Harkin, G. J. et al.
System: The UNT Digital Library
Two recent results on B physics from CDF (open access)

Two recent results on B physics from CDF

Preliminary results from two recent CDF b physics analyses are presented. The first obtains sin(2{beta})=0.79<sup>+0.41</sup><sub>-0.44</sub> from a measurement of the asymmetry in B<sup>0</sup>, {anti B<sup>0</sup>} {yields} J/{psi}K<sup>0</sup><sub>s</sub> decays, providing the best direct indication so far that CP invariance is violated in the b sector. The second obtains new results on the parity even (A<sub>0</sub> and A<sub>{parallel}</sub>) and odd (A<sub>{perpendicular}</sub>) polarization amplitudes from full angular analyses of B<sup>0</sup> {yields} J/{psi}K*<sup>0</sup> and B<sup>0</sup><sub>s</sub> {yields} J/{psi}{phi} decays: B<sup>0</sup>: {A<sub>0</sub> = 0.770 &plusmn; 0.039 &plusmn; 0.012; A<sub>{parallel}</sub> = (0.530 &plusmn; 0.106 &plusmn; 0.034)e<sup>(2.16 &plusmn; 0.46 &plusmn; 0.10)i</sup>; A<sub>{perpendicular}</sub> = (0.355 &plusmn; 0.156 &plusmn; 0.039)e<sup>(-0.56 &plusmn; 0.53 &plusmn; 0.12)i</sup>}, B<sup>0</sup><sub>s</sub>: {A<sub>0</sub> = 0.778 &plusmn; 0.090 &plusmn; 0.012; A<sub>{parallel}</sub> = (0.407 &plusmn; 0.232 &plusmn; 0.034)e<sup>(1.12 &plusmn; 1.29 &plusmn; 0.11)</sup>i; {vert_bar}A<sub>{perpendicular}</sub> = 0.478 &plusmn; 0.202 &plusmn; 0.040.
Date: June 29, 1999
Creator: Schmidt, M. P.
System: The UNT Digital Library
Geometric Correction System Capabilities, Processing, and Application (open access)

Geometric Correction System Capabilities, Processing, and Application

The U.S. Department of Energy's Remote Sensing Laboratory developed the geometric correction system (GCS) as a state-of-the-art solution for removing distortions from multispectral line scanner data caused by aircraft motion. The system operates on Daedalus AADS-1268 scanner data acquired from fixed-wing and helicopter platforms. The aircraft attitude, altitude, acceleration, and location are recorded and applied to the data, thereby determining the location of the earth with respect to a given datum and projection. The GCS has yielded a positional accuracy of 0.5 meters when used with a 1-meter digital elevation model. Data at this level of accuracy are invaluable in making precise areal estimates and as input into a geographic information system. The combination of high-spatial resolution and accurate geo-rectification makes the GCS a unique tool in identifying and locating environmental conditions, finding targets of interest, and detecting changes as they occur over time.
Date: June 30, 1999
Creator: Brewster, S. B.
System: The UNT Digital Library
Thermal Fusing Model of Conducting Particle Composites (open access)

Thermal Fusing Model of Conducting Particle Composites

Composites of carbon black particles in polyethylene are known to exhibit an unusually rapid increase in resistivity as the applied field is increased, making this material useful in automatically resettable fuses. In this application the composite is in series with the circuit it is protecting: at low applied voltages this circuit is the load, but at high applied voltages the composite becomes the load, limiting the current to the circuit. We present a simple model of this behavior in terms of a network of nonlinear conductors. Each conductor has a conductance that depends on its instantaneous Joule heating. It is shown that in the fusing regime, where the current through the composite decreases with increasing voltage, an plate-like dissipation instability develops normal to the applied field. Experimental evidence of this phenomena is described.
Date: June 24, 1999
Creator: Martin, James E.
System: The UNT Digital Library
The Sloan Digital Sky Survey data acquisition system, and early results (open access)

The Sloan Digital Sky Survey data acquisition system, and early results

The Sloan Digital Sky Survey will systematically map one- quarter of the sky, producing detailed images in five color bands and determining the positions and absolute bright- nesses of more than 100 million celestial objects. It will also measure the redshifts of a million selected galaxies and of 100,000 quasars, yielding a three-dimensional map of the universe through a volume one hundred times larger than that explored to date. The SDSS collaboration is currently in the process of commissioning the 2.5-meter survey tele- scope. We describe the data acquisition system used to record the survey data. This system consists of twelve sin- gle board computers and their associated interfaces to the camera and spectrograph CCD electronics, to tape drives, and to online video displays, distributed among several VME crates. A central UNIX computer connected to the VME crates via a vertical bus adapter coordinates the sys- tem and provides the interface to telescope operations. We briefly discuss results from the observing runs to date and plans for the archiving and distribution of data.
Date: June 29, 1999
Creator: J. Annis, J. Bakken, D. Holmgren, D. Petravick, R. Rechenmacher
System: The UNT Digital Library
Surface Micromachine Microfluidics: Design, Fabrication, Packaging, and Characterization (open access)

Surface Micromachine Microfluidics: Design, Fabrication, Packaging, and Characterization

The field of microfluidics is undergoing rapid growth in terms of new device and system development. Among the many methods of fabricating microfluidic devices and systems, surface micromachining is relatively underrepresented due to difficulties in the introduction of fluids into the very small channels produced, packaging problems, and difficulties in device and system characterization. The potential advantages of using surface micromachining including compatibility with the existing integrated circuit tool set, integration of electronic sensing and actuation with microfluidics, and fluid volume minimization. In order to explore these potential advantages we have developed first generation surface micromachined microfluidic devices (channels) using an adapted pressure sensor fabrication process to produce silicon nitride channels, and the SUMMiT process to produce polysilicon channels. The channels were characterized by leak testing and flow rate vs. pressure measurements. The fabrication processes used and results of these tests are reported in this paper.
Date: June 30, 1999
Creator: Galambos, Paul; Eaton, William P.; Shul, Randy; Willison, Christi Gober; Sniegowski, Jeffrey J.; Miller, Samuel L. et al.
System: The UNT Digital Library
Non-SUSY exotic particle searches at the Tevatron (open access)

Non-SUSY exotic particle searches at the Tevatron

Between 1992 and 1995, the CDF and D0 collaborations collected data from p{anti p} collisions at {radical}s = 1.8 TeV. Recently, several analyses of this data have been performed in search of evidence for various non-Supersymmetric exotic particles. As no evidence for the existence of these particles is observed, confidence level limits are established for exotic particle predictions from various theoretical models. Analyses presented here include searches for Standard Model Higgs, technicolor particles, topcolor-assissted technicolor bosons, and flavor-universal colorons.
Date: June 29, 1999
Creator: Cassada, J.
System: The UNT Digital Library
The Diffusion of Simple Penetrants in Tangent Site Polymer Melts (open access)

The Diffusion of Simple Penetrants in Tangent Site Polymer Melts

The diffusive behavior of penetrants in simple polymer melts was investigated by molecular dynamics simulation. For the case where the polymer melt consisted of pearl-necklace chains, the diffusive behavior of the loose pearl penetrants was seen to be qualitatively different than would be expected in realistic models of polymer melts. In particular, there was little or no ''non-Fickiano'' region; the variation of the diffusion coefficient with the penetrant diameter was what one would expect for diffusion through small molecular liquids; and, finally, the long time tail of the velocity auto correlation displayed a ''-3/2'' power law form, also as in the small molecular liquid case. When the chains' backbone motion was further constrained by the introduction of a bond angle potential, the qualitative nature of the penetrant diffusion became more ''polymer-like''. A non-Fickian region developed; the diffusion coefficient varied more rapidly with penetrant diameter; and the velocity autocorrelation function developed a ''-5/2'' power law tail as would be expected for the diffusion of particles with a wide distribution of trapping times.
Date: June 30, 1999
Creator: Rottach, Dana R.; Tillman, Patrick A.; McCoy, John D.; Plimpton, Steven J. & Curro, John G.
System: The UNT Digital Library
Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Radar Imagery (open access)

Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Radar Imagery

Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Original formulation of spatially variant anodization for complex synthetic aperture radar (SAR) imagery oversampled at twice the Nyquist rate (2.OX). Here we report a spatially interpolating, noninteger-oversampled SVA sidelobe. The pixel's apparent IPR location is assessed by comparing its value to the sum of its value plus weighted comparable for exact interpolation. However, exact interpolation implies an ideal sine interpolator3 and large components may not be necessary. Note that P is the summation of IPR diagonal values. The value of a sine IPR on the diagonals is a sine-squared; values much less than cardinal direction (m, n) values. This implies that cardinal direction interpolation requires higher precision than diagonal interpolation. Consequently, we employed a smaller set. The spatially interpolated SVA used an 8-point/4-point sine interpolator described above. Table 1 shows the Table 1 results show a two-times speed-up using the 1.3x oversampled and spatially interpolated SVA over the Figure 1d. Detected results of 1.3x oversampled sine interpolated spatially variant
Date: June 29, 1999
Creator: Eichel, Paul H.; Jakowatz, Charles V., Jr. & Yocky, David A.
System: The UNT Digital Library
FANTM: The First Article NIF Test Module for the Laser Power Conditioning System (open access)

FANTM: The First Article NIF Test Module for the Laser Power Conditioning System

Designing and developing the 1.7 to 2. 1-MJ Power Conditioning System (PCS) that powers the flashlamps for the National Ignition Facility (NIF), currently being constructed at Lawrence Livermore National Labs (LLNL), is one of several responsibilities assumed by Sandia National Labs (SNL) in support of the NIF Project. The test facility that has evolved over the last three years to satisfy the project requirements is called FANTM. It was built at SNL and has operated for about 17,000 shots to demonstrate component performance expectations over the lifetime of NIF. A few modules similar to the one shown in Fig. 1 will be used initially in the amplifier test phase of the project. The final till NIF system will require 192 of them (48 in each of four capacitor bays). This paper briefly summarizes the final design of the FANTM facility and compares its performance with the predictions of circuit simulations for both normal operation and fault-mode response. Applying both the measured and modeled power pulse waveforms as input to a physics-based, semi-empirical amplifier gain code indicates that the 20-capacitor PCS can satisfy the NIF requirement for an average gain coefficient of 5.00 %/cm and can exceed 5.20%/cm with 24 capacitors.
Date: June 24, 1999
Creator: Hammon, Jud; Harjes, Henry C.; Moore, William B.S.; Smith, David L. & Wilson, J. Michael
System: The UNT Digital Library
The Development of a Ceramic Mold for Hot-Forging of Micro-Magnets (open access)

The Development of a Ceramic Mold for Hot-Forging of Micro-Magnets

A new mold material has been developed for use in making rare-earth permanent magnet components with precise dimensions in the 10 to 1000 µm range by hot-forging. These molds are made from molds poly(methyl)methacrylate (PMMA) made by deep x-ray lithography (DXRL). An alumina bonded with colloidal silica has been developed for use in these molds. This material can be heated to 950°C without changing dimensions where it develops the strength needed to withstand the hot-fmging conditions (750°C, 100 MPa). In addition, it disintegrates in HF so that parts can be easily removed after forging.
Date: June 25, 1999
Creator: Christenson, Todd & Garino, Terry
System: The UNT Digital Library
Plutonium-238 Transuranic Waste Decision Analysis (open access)

Plutonium-238 Transuranic Waste Decision Analysis

Five transuranic (TRU) waste sites in the Department of Energy (DOE) complex, collectively, have more than 2,100 cubic meters of Plutonium-238 (Pu-238) TRU waste that exceed the wattage restrictions of the Transuranic Package Transporter-II (TRUPACT-11). The Waste Isolation Pilot Plant (WIPP) is being developed by the DOE as a repository for TRU waste. With the Waste Isolation Pilot Plant (WIPP) opening in 1999, these sites are faced with a need to develop waste management practices that will enable the transportation of Pu-238 TRU waste to WIPP for disposal. This paper describes a decision analysis that provided a logical framework for addressing the Pu-238 TRU waste issue. The insights that can be gained by performing a formalized decision analysis are multifold. First and foremost, the very process. of formulating a decision tree forces the decision maker into structured, logical thinking where alternatives can be evaluated one against the other using a uniform set of criteria. In the process of developing the decision tree for transportation of Pu-238 TRU waste, several alternatives were eliminated and the logical order for decision making was discovered. Moreover, the key areas of uncertainty for proposed alternatives were identified and quantified. The decision analysis showed that the …
Date: June 29, 1999
Creator: Brown, Mike; Lechel, David J. & Leigh, C.D.
System: The UNT Digital Library
Final Results from the High-Current, High-Action Closing Switch Test Program at Sandia National Laboratories (open access)

Final Results from the High-Current, High-Action Closing Switch Test Program at Sandia National Laboratories

We tested a variety of high-current closing switches for lifetime and reliability on a dedicated 2 MJ, 500 kA capacitor bank facility at Sandia National Laboratories. Our interest was a switch capable of one shot every few minutes, switching a critically damped, DC-charged 6.2 mF bank at 24 kV, with a peak current of 500 kA. The desired lifetime is 24 thousand shots. Typical of high-energy systems, particularly multi-module systems, the primary parameters of interest related to the switch are: (1) reliability, meaning absence of both pre-fires and no-fires, (2) total switch lifetime or number of shots between maintenance, and (3) cost. Cost was given lower priority at this evaluation stage because there are great uncertainties in estimating higher-quantity prices of these devices, most of which have been supplied before in only small quantities. The categories of switches tested are vacuum discharge, high-pressure discharge, and solid-state. Each group varies in terms of triggering ease, ease of maintenance, and tolerance to faults such as excess current and current reversal. We tested at least two variations of each technology group. The total number of shots on the switch test facility is about 50 thousand. We will present the results from the switch …
Date: June 23, 1999
Creator: Savage, M. E.
System: The UNT Digital Library
Anisotropic Magnetism in Field-Structured Composites (open access)

Anisotropic Magnetism in Field-Structured Composites

Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.
Date: June 24, 1999
Creator: Anderson, Robert A.; Martin, James E.; Odinek, Judy & Venturini, Eugene
System: The UNT Digital Library