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Lift and moment characteristics at subsonic Mach numbers of four 10-percent-thick airfoil sections of varying trailing-edge thickness

Description: Report presenting the results of a wind-tunnel investigation of the lift and moment characteristics of four 10-percent-thick circular-arc airfoil sections. Increases in the trailing-edge thickness were found to result in increases in maximum lift coefficient and lift-curve slope at all Mach numbers as well as increases in lift-divergence Mach number at all lift coefficients.
Date: December 20, 1950
Creator: Summers, James L. & Page, William A.
Partner: UNT Libraries Government Documents Department

Plating Thickness Tester

Description: An electromagnetic eddy current instrument is described that is capable of measuring copper and nickel plating 1 to 8 mils thick plated on bismuth mandrils of various sizes and shapes.
Date: November 15, 1957
Creator: Fitch, C. E., Jr.
Partner: UNT Libraries Government Documents Department

Flight tests to determine the effect of airfoil section profile and thickness ratio on the zero-lift drag of low-aspect-ratio wings at supersonic speeds

Description: Report discussing flight tests of airplane-like models to determine the effect of airfoil section profile and thickness ratio on the zero-lift drag of low-aspect-ratio wings at supersonic speeds. Five rectangular wings with the same aspect ratio and a variety of airfoil thicknesses were tested to determine the effect of thickness ratio.
Date: February 9, 1948
Creator: Katz, Ellis
Partner: UNT Libraries Government Documents Department

Experimental investigation of turbine stator-blade-outlet boundary-layer characteristics and a comparison with theoretical results

Description: Report presenting an investigation of the boundary-layer characteristics at the mean radius immediately downstream of a typical turbine stator blade over a range of blade-outlet critical-velocity ratio from 0.8 to 1.16. Total boundary-layer momentum thickness for the blade and individual thicknesses obtained for the suction and pressure surfaces are compared with values calculated from the turbulent-boundary-layer theory.
Date: March 16, 1956
Creator: Whitney, Warren J.; Stewart, Warner L. & Miser, James W.
Partner: UNT Libraries Government Documents Department

Simulating Nonuniform Properties in Polymer-Electrolyte FuelCells

Description: In this transaction, results from mathematical, pseudo 2-D simulations are shown for four different thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that the position along the gas channel is more important than the local thickness variations, especially for the membrane.
Date: July 1, 2006
Creator: Weber, A.Z. & Newman, J.
Partner: UNT Libraries Government Documents Department

A Graphical Big Picture for Tank Technologies

Description: A graphical method is presented for comparing different tank technologies and evaluating scalability, over wide ranges of volume and pressure. Mass contours are plotted on log-log graphs of pressure versus volume, using either theory or data points representing hardware. The simple theoretical case for infinitely scaleable tanks made of a single isotropic material has a constant value of PV/m over the entire plot, and results in straight diagonal mass contours. The contours become more complicated as a result of practical considerations. The latter include minimum wall thickness limits and non-pressure structural loads, as well as minimum thicknesses for the liner and composite over-wrap of multi-layered tank walls. Given a requirement for a tank at a particular volume and pressure, a set of plots representing different technologies can be used to estimate tank masses and select one or more technologies that would meet the need.
Date: June 15, 2007
Creator: Whitehead, J C
Partner: UNT Libraries Government Documents Department

A Top to Bottom Lithospheric Study of Africa and Arabia

Description: We study the lithospheric structure of Africa, Arabia and adjacent oceanic regions with fundamental-mode surface waves over a wide period range. Including short period group velocities allows us to examine shallower features than previous studies of the whole continent. In the process, we have developed a crustal thickness map of Africa. Main features include crustal thickness increases under the West African, Congo, and Kalahari cratons. We find crustal thinning under Mesozoic and Cenozoic rifts, including the Benue Trough, Red Sea, and East, Central, and West African rift systems. Crustal shear wave velocities are generally faster in oceanic regions and cratons, and slower in more recent crust and in active and formerly active orogenic regions. Deeper structure, related to the thickness of cratons and modern rifting, is generally consistent with previous work. Under cratons we find thick lithosphere and fast upper mantle velocities, while under rifts we find thinned lithosphere and slower upper mantle velocities. There are no consistent effects in areas classified as hotspots, indicating that there seem to be numerous origins for these features. Finally, it appears that the African Superswell has had a significantly different impact in the north and the south, indicating specifics of the feature (temperature, time of influence, etc.) to be dissimilar between the two regions. Factoring in other information, it is likely that the southern portion has been active in the past, but that shallow activity is currently limited to the northern portion of the superswell.
Date: October 31, 2006
Creator: Pasyanos, M
Partner: UNT Libraries Government Documents Department

Probing the evolution of antiferromagnetism in multiferroics

Description: This study delineates the evolution of magnetic order in epitaxial films of the room-temperature multiferroic BiFeO3 system. Using angle- and temperature-dependent dichroic measurements and spectromicroscopy, we have observed that the antiferromagnetic order in the model multiferroic BiFeO3 evolves systematically as a function of thickness and strain. Lattice-mismatch-induced strain is found to break the easy-plane magnetic symmetry of the bulk and leads to an easy axis of magnetization which can be controlled through strain. Understanding the evolution of magnetic structure and how to manipulate the magnetism in this model multiferroic has significant implications for utilization of such magnetoelectric materials in future applications.
Date: June 9, 2010
Creator: Holcomb, M.; Martin, L.; Scholl, A.; He, Q.; Yu, P.; Yang, C.-H. et al.
Partner: UNT Libraries Government Documents Department

DYNAMIC DELAMINATION IN THROUGH-THICKNESS REINFORCED DCB SPECIMEN

Description: Bridged crack models using beam theory formulation have proved to be effective in the modeling of quasistatic delamination crack growth in through thickness reinforced structures. In this paper, we model dynamic crack propagation in these structures with the beam theory formulation. Steady state crack propagation characteristics unique to the dynamic case are first identified. Dynamic crack propagation and the energetics of steady state dynamic crack growth for a Double Cantilever beam (DCB) configuration loaded with a flying wedge is examined next. We find that steady state crack growth is attainable for this loading configuration provided certain conditions are satisfied.
Date: February 1, 2001
Creator: SRIDHAR, N. & AL, ET
Partner: UNT Libraries Government Documents Department

Characterization of SEI layers on LiMn2O4 cathodes with in-situ spectroscopic ellipsometry

Description: In situ spectroscopic ellipsometry was employed to study the initial stage of SEI layer formation on thin-film LiMn{sub 2}O{sub 4} electrodes. It was found that the SEI layer formed immediately upon exposure of the electrode to EC/DMC (1:1 by vol) 1.0 M LiPF{sub 6} electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles.
Date: August 30, 2004
Creator: Lei, Jinglei; Li, Lingjie; Kostecki, Robert; Muller, Rolf & McLarnon, Frank
Partner: UNT Libraries Government Documents Department

Analysis of formulas used in coupling impedance coaxial-wire measurements for distributed impedances

Description: In this paper we study the validity of coupling impedance bench measurements for distributed impedances, comparing the commonly used log formula to the result obtained applying a modified version of Bethe's theory of diffraction to a long slot in a coaxial beam pipe. The equations found provide a quantitative expression for the influence of the wire thickness used in the measurement of the real and imaginary part of the longitudinal impedance. The precision achievable in an actual measurement is therefore discussed. The method presented has also been applied in the presence of lumped impedances [1].
Date: May 30, 2002
Creator: De Santis, Stefano
Partner: UNT Libraries Government Documents Department

Wind-tunnel investigation at low speed of a wing swept back 63 degrees and twisted and cambered for uniform load at a lift coefficient of 0.5 and with a thickened tip section

Description: Report discusses the result of tests determining the longitudinal-stability characteristics and spanwise distribution of load of a wing model with the leading edge swept back 63 degrees, a thickened tip section, and a twisted and cambered shape. The wing was tested with a fuselage and various devices for altering stall and spanwise boundary-layer flow. Measurements of force, pressure-distribution, and span load distribution are described.
Date: November 21, 1950
Creator: Weiberg, James A. & Carel, Hubert C.
Partner: UNT Libraries Government Documents Department

The transonic aerodynamic characteristics of structurally related wings of low aspect ratio having a spanwise variation in thickness ratio-transonic bump technique

Description: Report presenting an investigation of wings of aspect ratios of 4, 3, and 2 with a plan-form taper ratio of 0.5 and a thickness taper ratio of 0.33 to determine their transonic longitudinal characteristics and effects of tapering thickness ratio. Results regarding the combined effects of aspect ratio and thickness ratio and effects of tapered thickness ratio are provided.
Date: April 12, 1954
Creator: Cleary, Joseph W.
Partner: UNT Libraries Government Documents Department

Direct-reading design charts for 24S-T aluminum-alloy flat compression panels having longitudinal straight-web Y-section stiffeners

Description: "Direct-reading design charts are presented for 24S-T aluminum-alloy flat compression panels having longitudinal straight-web Y-section stiffeners. These charts make possible the direct determination of the stress and all the panel proportions required to carry a given intensity of loading with a given skin thickness and effective length of panel" (p. 1).
Date: January 1949
Creator: Dow, Norris F.; Hubka, Ralph E. & Roberts, William M.
Partner: UNT Libraries Government Documents Department

Relation of Journal Bearing Performance to Minimum Oil-Film Thickness

Description: Note presenting the minimum thickness of the oil film as used as a basic variable in performance curves of plain journal bearings under steady load. The load capacity and the predicted film thickness at the hook point of the friction curves are shown to correlate with the peak-to-valley values of surface roughness when misalignment is absent.
Date: April 1958
Creator: Ocvirk, F. W. & DuBois, G. B.
Partner: UNT Libraries Government Documents Department

Effect of Thickness on the Lateral Force and Yawing Moment of a Sideslipping Delta Wing at Supersonic Speeds

Description: Note presenting calculations, based on linearized supersonic flow theory and on the additional assumption that the Mach cones yaw with the wing, to determine the effect of thickness on the lateral force and yawing moment of a sideslipping delta wing at supersonic speeds. Generalized equations are derived for delta wings with rhombic profile and constant thickness ratio.
Date: January 1949
Creator: Margolis, Kenneth
Partner: UNT Libraries Government Documents Department

Glue Film Thickness Measurements by Spectral Reflectance

Description: Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 μm, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.
Date: September 20, 2010
Creator: Marshall, B. R.
Partner: UNT Libraries Government Documents Department

Equivalent-Circuit Model for the TSM Resonator with a Viscoelastic Layer

Description: This paper describes a new equivalent-circuit model for the thickness shear mode resonator with a surface viscoelastic layer operating near film resonance. The electrical impedance of the film is represented by a simple three-element parallel circuit containing a resistor, a capacitor, and an inductor. These elements describe the film's viscous power dissipation, elastic energy storage, and kinetic energy storage, respectively. Resonator response comparisons between this lumped-element model and the general transmission-line model show good agreement over a range of film phase conditions and not just near film resonance.
Date: September 16, 1999
Creator: BANDEY, HELEN L.; CERNOSEK, RICHARD W.; HILLMAN, A.R. & MARTIN, STEPHEN J.
Partner: UNT Libraries Government Documents Department

TOUGH+/GasH20 study of the effects of a heat source buried in theMartian permafrost

Description: We use TOUGH+/GasH2O to study the effects of a heat sourceburied in the Martian permafrost to evaluate the possibility ofestablishing a wet zone of liquid water, in which terrestrialmicroorganisms could survive and multiply. Analysis of the problemindicates that (1) only a limited permafrost volume (not exceeding 0.35 min radius) is affected, (2) a "wet" zone with limited amounts of liquidwater de-velops (not exceeding 8 and 0.7 kg for a 250 W and a 62.5 Wsource, respectively), (3) the wet zone per-sists for a long time,becomes practically stationary after t = 20 sols because of venting intothe Martian atmosphere, and its thickness is limited and decreases slowlyover time, (4) a "dry" zone (where SG>0.9) evolves, continues toexpand (albeit slowly) with time, but its extent remains limited, and (5)the ice front surrounding the wet zone is self-sharpening. For a range ofinitial conditions investigated, evolution of the liquid water massoccurs at approximately the same rate, reaches roughly the same maximum,and occurs at about the same time (10 to 20 sols; 1 sol = 24.39hours).
Date: May 12, 2006
Creator: Moridis, George J. & Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Effects of Membrane- and Catalyst-layer-thickness Nonuniformitiesin Polymer-electrolyte Fuel Cells

Description: In this paper, results from mathematical, pseudo 2-D simulations are shown for four different along-the-channel thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that for the membrane thickness distributions, cell performance is affected a few percent under low relative-humidity conditions and that the position along the gas channel is more important than the local thickness variations. However, for the catalyst-layer thickness distributions, global performance is not impacted, although for saturated conditions there is a large variability in the local temperature and performance depending on the thickness.
Date: September 1, 2006
Creator: Weber, Adam Z. & Newman, John
Partner: UNT Libraries Government Documents Department

Inf-sup estimates for the Stokes problem in a periodic channel

Description: We derive estimates of the Babuska-Brezzi inf-sup constant {beta} for two-dimensional incompressible flow in a periodic channel with one flat boundary and the other given by a periodic, Lipschitz continuous function h. If h is a constant function (so the domain is rectangular), we show that periodicity in one direction but not the other leads to an interesting connection between {beta} and the unitary operator mapping the Fourier sine coefficients of a function to its Fourier cosine coefficients. We exploit this connection to determine the dependence of {beta} on the aspect ratio of the rectangle. We then show how to transfer this result to the case that h is C{sup 1,1} or even C{sup 0,1} by a change of variables. We avoid non-constructive theorems of functional analysis in order to explicitly exhibit the dependence of {beta} on features of the geometry such as the aspect ratio, the maximum slope, and the minimum gap thickness (if h passes near the substrate). We give an example to show that our estimates are optimal in their dependence on the minimum gap thickness in the C{sup 1,1} case, and nearly optimal in the Lipschitz case.
Date: December 10, 2008
Creator: Wilkening, Jon
Partner: UNT Libraries Government Documents Department

DIFFRACTION RADIATION BY A LINE CHARGE MOVING PAST A COMB: A MODEL OF RADIATION LOSSES IN AN ELECTRON RING ACCELERATOR

Description: A calculation is given of the radiated energy loss from a charged rod which moves at constant speed past an infinite set of parallel semi-infinite conducting plates of infinitesimal thickness, with the rod taken parallel to and at a fixed distance from the plate edges. The problem is analyzed using the Wiener-Hopf technique, and the resulting formulas are evaluated analytically in the limits of high rod speed and low rod speed, and compared with numerical evaluation over the full range of speeds.
Date: April 23, 1970
Creator: Hazeltine, R.D.; Rosenbluth, M.N. & Sessler, A.M.
Partner: UNT Libraries Government Documents Department

Micro-optics for imaging.

Description: This project investigates the fundamental imaging capability of an optic with a physical thickness substantially less than 1 mm. The analysis assumes that post-processing can overcome certain restrictions such as detector pixel size and image degradation due to aberrations. A first order optical analysis quickly reveals the limitations of even an ideal thin lens to provide sufficient image resolution and provides the justification for pursuing an annular design. Some straightforward examples clearly show the potential of this approach. The tradeoffs associated with annular designs, specifically field of view limitations and reduced mid-level spatial frequencies, are discussed and their impact on the imaging performance evaluated using several imaging examples. Additionally, issues such as detector acceptance angle and the need to balance aberrations with resolution are included in the analysis. With these restrictions, the final results present an excellent approximation of the expected performance of the lens designs presented.
Date: September 1, 2010
Creator: Boye, Robert R.
Partner: UNT Libraries Government Documents Department

Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

Description: A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.
Date: February 25, 2007
Creator: Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L & Brown, T A
Partner: UNT Libraries Government Documents Department