Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Mach number. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

Surface Roughness and Its Effects on the Heat Transfer Mechanism in Spray Cooling

Abstract: In the spray cooling of a heated surface, variations in the surface texture influence the flow field, altering the maximum liquid film thickness, the bubble diameter, vapor entrapment, bubble departure characteristics, and the ability to transfer heat. A new method for determining and designating the surface texture is proposed, and the effects of surface roughness on evaporation/nucleation in the spray cooling flow field studied. A one-dimensional Fourier analysis is applied to determine experimentally the surface profile of a surface polished with emery paper covering a spectrum of grit sizes between 0.3 to 22 {mu}m. Heat transfer measurements of liquid flow rates between 1 to 5 l/h and air flow rates between 0.1 to 0.4 l/s are presented. Maximum heat fluxes of 1,200 W/cm{sup 2} for the 0.3 {mu}m surface at very low superheats were obtained.

Infrared and Raman Selection Rules for Lattice Vibrations: The Correlation Method:

Abstract: With the recent growth in interest in the ir and Raman spectra of crystals, it has become very important to know which vibrational modes are optically active Hornig, Winston and Halford, and Bhagavantam and Venkatarayudu pioneered in developing methods for this However, heretofore the determination has been a laborious procedure fraught with difficulty and with many points of indecision Among the latter is the choice of the primitive cell and the correct site symmetry of each atom What is needed is a short, straightforward, foolproof method We propose here an alternate procedure for obtaining the activity of the vibrations from the correlation tables which comes close to meeting these goals The calculation is reduced to but a few minutes' work The method will be explained in detail by use of numerous examples

Molecular dynamics study of the stress–strain behavior of carbon-nanotube reinforced Epon 862 composites

Abstract: Single-walled carbon nanotubes (CNTs) are used to reinforce epoxy Epon 862 matrix. Three periodic systems – a long CNT-reinforced Epon 862 composite, a short CNT-reinforced Epon 862 composite, and the Epon 862 matrix itself – are studied using the molecular dynamics. The stress–strain relations and the elastic Young's moduli along the longitudinal direction (parallel to CNT) are simulated with the results being also compared to those from the rule - of - mixture . Our results show that, with increasing strain in the longitudinal direction, the Young's modulus of CNT increases whilst that of the Epon 862 composite or matrix decreases. Furthermore, a long CNT can greatly improve the Young's modulus of the Epon 862 composite (about 10 times stiffer), which is also consistent with the prediction based on the rule - of - mixture at low strain level. Even a short CNT can also enhance the Young's modulus of the Epon 862 composite, with an increment of 20% being observed as compared to that of the Epon 862 matrix.

Ultrafast holographic nanopatterning of biocatalytically formed silica

Abstract: Diatoms are of interest to the materials research community because of their ability to create highly complex and intricate silica structures under physiological conditions: what these single-cell organisms accomplish so elegantly in nature requires extreme laboratory conditions to duplicate1,2—this is true for even the simplest of structures. Following the identification of polycationic peptides from the diatom Cylindrotheca fusiformis, simple silica nanospheres can now be synthesized in vitro from silanes at nearly neutral pH and at ambient temperatures and pressures3,4. Here we describe a method for creating a hybrid organic/inorganic ordered nanostructure of silica spheres through the incorporation of a polycationic peptide (derived from the C. fusiformis silaffin-1 protein) into a polymer hologram created by two-photon-induced photopolymerization. When these peptide nanopatterned holographic structures are exposed to a silicic acid, an ordered array of silica nanospheres is deposited onto the clear polymer substrate. These structures exhibit a nearly fifty-fold increase in diffraction efficiency over a comparable polymer hologram without silica. This approach, combining the ease of processability of an organic polymer with the improved mechanical and optical properties of an inorganic material, could be of practical use for the fabrication of photonic devices.

Dynamic color in stimuli-responsive cholesteric liquid crystals

Abstract: ROY G. BIV is the acronym used around the English-speaking world to aid children in the memorization of the traditional colors of the rainbow (red, orange, yellow, green, blue, indigo, and violet). Color surrounds us and the ability to change color by external stimuli (heat, force, light exposure, magnetic or electric field) continues to be leveraged for many present day applications. This review focuses on the state of the art in the use of cholesteric liquid crystals (CLCs) as color changing optical materials. After a brief summary of thermal and electrically induced color changes, the bulk of the article describes recent efforts in photoresponsive CLCs, materials in which light is used to control the color output.