7,148 research outputs found

    Preliminary feasibility study of a multi-Phobos encounter experiment during the Viking extended mission

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    The Viking '75 Mission to Mars is reported which permits a truly unique opportunity to explore the natural satellite, Phobos, from distances measured in tens of kilometers. A preliminary feasibility study has been made which shows that a science mission involving a Phobos close encounter is technically feasible and within the capabilities of the current Viking design. For less than 20 m/s, the Viking Orbiter can provide approximately two 40-day periods of close observation of Phobos, with the first encounter period in January and the second in March, 1977. Multi-pass images of the entire satellite from nearly all aspect angles and with resolution on the order of 10 meters are possible. Close encounters will permit mass determinations to an accuracy of tens of percent. These experiments can be performed in series with the nominal mission; thus, providing complementary scientific information without compromising the original mission and science objectives

    Thin shell wormhole due to dyadosphere of a charged black hole

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    To explain Gamma Ray Bursts, Ruffini argued that the event horizon of a charged black hole is surrounded by a special region called, the Dyadosphere where electric field exceeds the critical value for e+e^+ e−e^- pair production. In the present work, we construct a thin shell wormhole by performing a thought surgery between two dadospheres. Several physical properties of this thin shell wormhole have been analyzed.Comment: 10 pages, 2 figures. Accepted in Mod.Phys.Lett.

    Parametric testing of a linearly driven Stirling cryogenic refrigerator

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    The parametric testing of a novel Stirling cycle cryogenic refrigerator which incorporates electromagnetic bearings, clearance seals and electronically controlled linear motion was studied. The last feature, which involves the use of two linear motors, position transducers and a highly accurate electronic feedback network, produces the system capability which forms the basis for the tests. The test results provide designers with an understanding of the basic operation of the Stirling cycle and give potential users some indication of the capabilities of this refrigerator under off design conditions

    Estimation of Tracheid Morphological Characteristics of Green Pinus Taeda L. Radial Strips by Near Infrared Spectroscopy

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    The application of near infrared (NIR) spectroscopy to the green wood of radial samples (simulated increment cores) and the development of calibrations for the prediction of several tracheid morphological characteristics are described. Twenty Pinus taeda L. (loblolly pine) radial samples were characterized in terms of coarseness, perimeter, radial and tangential diameter, specific surface, and wall thickness. NIR spectra were obtained in 10-mm steps from the radial-longitudinal and transverse face of each sample and were used to generate calibrations for each property. NIR spectra were collected from all samples when the wood was green (moisture content ranged from approximately 100 to 154%), and when dried to approximately 7% moisture content. The relationships between measured and NIR-estimates for green wood were strong for coarseness, specific surface, and wall thickness, with coefficients of determination (R2) ranging from 0.89 to 0.73. Differences between calibrations developed using radial-longitudinal and transverse face NIR spectra were generally small. Dry wood calibrations demonstrated strong relationships for all parameters apart from perimeter and radial diameter; R2 ranged from 0.59 to 0.91. Calibrations were tested on an independent set; relationships for coarseness, specific surface, and wall thickness were strong. Good calibrations can be obtained for some tracheid morphological characteristics using NIR spectra collected from the surface of green P. taeda wood

    Study of methane fuel for subsonic transport aircraft

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    The cost and performance were defined for commercial transport using liquid methane including its fuel system and the ground facility complex required for the processing and storage of methane. A cost and performance comparison was made with Jet A and hydrogen powered aircraft of the same payload and range capability. Extensive design work was done on cryogenic fuel tanks, insulation systems as well as the fuel system itself. Three candidate fuel tank locations were evaluated, i.e., fuselage tanks, wing tanks or external pylon tanks

    Localized transverse bursts in inclined layer convection

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    We investigate a novel bursting state in inclined layer thermal convection in which convection rolls exhibit intermittent, localized, transverse bursts. With increasing temperature difference, the bursts increase in duration and number while exhibiting a characteristic wavenumber, magnitude, and size. We propose a mechanism which describes the duration of the observed bursting intervals and compare our results to bursting processes in other systems.Comment: 4 pages, 8 figure

    Verbal Compliments As a Differential Source of Mate Poaching Threat For Men and Women

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    Two studies tested whether people feel threatened by another individual verbally complimenting their romantic partner. Such compliments may indicate that the other person is a potential rival who will try to poach their mate. Across two studies, women were more threatened than men when imagining another person complimenting their partner\u27s physical appearance. There were no sex differences in response to imagining another person complimenting their partner\u27s sense of humor. When another person compliments one\u27s partner\u27s physical appearance, this indicates that they may be sexually attracted to the partner. Mediation analyses revealed that the sex difference occurs because women believe men are more open to casual sex, and therefore more vulnerable to mate poaching when another person expresses sexual interest in them

    Shear stress fluctuations in the granular liquid and solid phases

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    We report on experimentally observed shear stress fluctuations in both granular solid and fluid states, showing that they are non-Gaussian at low shear rates, reflecting the predominance of correlated structures (force chains) in the solidlike phase, which also exhibit finite rigidity to shear. Peaks in the rigidity and the stress distribution's skewness indicate that a change to the force-bearing mechanism occurs at the transition to fluid behaviour, which, it is shown, can be predicted from the behaviour of the stress at lower shear rates. In the fluid state stress is Gaussian distributed, suggesting that the central limit theorem holds. The fibre bundle model with random load sharing effectively reproduces the stress distribution at the yield point and also exhibits the exponential stress distribution anticipated from extant work on stress propagation in granular materials.Comment: 11 pages, 3 figures, latex. Replacement adds journal reference and addresses referee comment

    Proton-3^{3}He elastic scattering at low energies

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    We present new accurate measurements of the differential cross section σ(θ)\sigma(\theta) and the proton analyzing power AyA_{y} for proton-3^{3}He elastic scattering at various energies. A supersonic gas jet target has been employed to obtain these low energy cross section measurements. The σ(θ)\sigma(\theta) distributions have been measured at EpE_{p} = 0.99, 1.59, 2.24, 3.11, and 4.02 MeV. Full angular distributions of AyA_{y} have been measured at EpE_{p} = 1.60, 2.25, 3.13, and 4.05 MeV. This set of high-precision data is compared to four-body variational calculations employing realistic nucleon-nucleon (NN) and three-nucleon (3N) interactions. For the unpolarized cross section the agreement between the theoretical calculation and data is good when a 3N3N potential is used. The comparison between the calculated and measured proton analyzing powers reveals discrepancies of approximately 50% at the maximum of each distribution. This is analogous to the existing ``AyA_{y} Puzzle'' known for the past 20 years in nucleon-deuteron elastic scattering.Comment: 22 pages, 9 figures, to be published in Physical Review C, corrected reference 4
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