225,457 research outputs found
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The U.S. Air Force lithograph series., Set 10
No full textPhotograph of four (4) Northrop T-38 Talon jets with mountains in the background
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Air Force Flight Dynamics Laboratory (U.S.) Technical Report 75-128
No full textReport discussing a program of the Air Force Flight Dynamics Laboratory (FXM), Wright-Patterson Air Force Base, to experimentally investigate steady and intermittent blowing jet flaps and constant percent chord span wise upper surface slots on controlling shock induced boundary layer separation and their effect on transonic performance on a conventional wind (Foreword). A wind tunnel test conducted in the NASA Ames 14 foot wind tunnel is described, along with analyses of jet flap data and steady and constant percent chord span wise upper surface slots
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VC-137 Air Force One
No full textPhotograph of the Boeing V-137, which was specially configured and maintained for use by the President of the United States. Now retired, this air craft was used by Presidents John F. Kennedy, Lyndon Baines Johnson, and Richard M. Nixon
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VC-137 Air Force One
No full textPhotograph of the Boeing V-137, which was specially configured and maintained for use by the President of the United States. Now retired, this air craft was used by Presidents John F. Kennedy, Lyndon Baines Johnson, and Richard M. Nixon
Entropic force between biomembranes
No full textUndulation force, an entropic force, stems from thermally excited fluctuations, and plays a key role in the essential interactions between neighboring surfaces of objects. Although the characteristics of the undulation force have been widely studied theoretically and experimentally, the distance dependence of the force, which constitutes its most fundamental characteristic, remains poorly understood. In this paper, first, we obtain a novel expression for the undulation force by employing elasticity and statistical mechanics and prove it to be in good agreement with existing experimental results. Second, we clearly demonstrate that the two representative forms of the undulation force proposed by Helfrich and Freund were respectively the upper and lower bounds of the present expression when the separation between membranes is sufficiently small, which was intrinsically different from the existing results where Helfrich's and Freund's forms of the undulation force were only suitable for the intermediate and small separations. The investigations show that only in a sufficiently small separation does Helfrich's result stand for the undulation force with a large wave number and Freund's result express the force with a small wave number. Finally, a critical acting distance of the undulation force, beyond which the entropic force will rapidly decay approaching zero, is presented
Comparison between the CENAM (Mexico) 150 kN and the INRIM (Italy) 1 MN force standard machines
No full textThe present paper describes the results of the bilateral comparison carried out between the CENAM (Mexico) 150 kN force standard machine and the INRiM (Italy) 1 MN Force standard machine. The two dead weight machines, their main metrological characteristics and the procedures of the comparison are described. Three different load cells (50 kN, 100 kN and 200 kN capacity) were used as transfer standards, and the test was made at 2 different load levels and at 5 angular positions for each load cell. The main results of the comparison with the relevant uncertainties from the measurements carried out at CENAM and at INRiM are presented and a final evaluation of the agreement between the two National force standard machines is given
First in the Nation in Education : Final Report,1984.
No full textThis report is one step in an ongoing process of change and is a plea for commitment for high standards in education in Iowa. Contains the final reports of the six subcommittees as adopted by the Excellence in Education Task Force, and the five recommendations made by the Task Force
Decomposing changes in the aggregate labor force participation rate
No full textThis paper presents a simple methodology for decomposing changes in the aggregate labor force participation rate (LFPR) over time into demographic group changes in labor force participation behavior and in population share. The purpose is to identify the relative importance of behavioral changes and population changes as driving forces behind changes in the aggregate LFPR.Labor supply
Optomechanical damping of a microcantilever force sensor in liquid
No full textA new instrument, constant deflection atomic force microscopy (CD-AFM) constructed to perform force spectroscopy measurements without mechanical instabilities associated with the use of soft AFM cantilevers has been developed, tested and calibrated.
One of the major limitations associated with the use of soft AFM cantilevers in force spectroscopy measurements is cantilever mechanical instabilities. This includes thermodynamic noise and the cantilever non-equilibrium deflection close to the surface. This limitation can obscure ultrahigh force resolution and short range force measurements, and limits the accessible dynamic range. More stable stiff cantilevers have poor force resolution.
The force resolution of the softest standard cantilever limited by thermodynamic noise has been improved from approximately 30 pN to ~2 pN using the CD-AFM system. It was proved that the discontinuity in the force distance curve close to the surface, approximately 7 nm, was prevented using CD-AFM. The cantilever deflection is kept constant even after the cantilever jumps to the surface. Using CD-AFM, inaccessible regions near the surface can be explored and valuable information about very short tip-surface interactions can be studied.
The need to lock cantilever deflection prevents the use of the deflection signal to record tip-surface interactions. Alternatively, the laser signal used to keep the cantilever deflection constant is employed to record the interactions. The curves obtained using CD-AFM were scaled in force using a new method introduced for this purpose. The new calibration method was tested, and validated through electrostatic force measurements, with curves obtained using conventional AFM or CD-AFM showing the same behavior.
Application of CD-AFM to unfold a five concatamer of the protein immunoglobulin 27 showed that CD-AFM has a wider dynamic range than conventional AFM. For example, loading rate in conventional AFM is limited by the cantilever stiffness and the pulling speed. Using CD-AFM the loading rate increases but without degenerating the force resolution. Moreover, protein L shows no refolding event using conventional AFM due to the tension loaded on the refolded protein by cantilever recoil. Using CD-AFM the cantilever recoil was removed and the refolding events become observable
N3722-L.
No full text1. Amphibious Reconnaissance Battalion Report. 2. Headquarteres Commandant Report
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