93,590 research outputs found

    A concept for magazine Bimat processor

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    Concept utilizes existing film magazines to process photographic film as the film is exposed. A standard magazine can be converted to a Bimat processor by adding three stainless steel rollers. All chemicals required for processing and fixing the negative are contained in the Bimat film

    A New Halo Finding Method for N-Body Simulations

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    We have developed a new halo finding method, Physically Self-Bound (PSB) group finding algorithm, which can efficiently identify halos located even at crowded regions. This method combines two physical criteria such as the tidal radius of a halo and the total energy of each particle to find member particles. Two hierarchical meshes are used to increase the speed and the power of halo identification in the parallel computing environments. First, a coarse mesh with cell size equal to the mean particle separation lmeanl_{\rm mean} is used to obtain the density field over the whole simulation box. Mesh cells having density contrast higher than a local cutoff threshold δLOC\delta_{\rm LOC} are extracted and linked together for those adjacent to each other. This produces local-cell groups. Second, a finer mesh is used to obtain density field within each local-cell group and to identify halos. If a density shell contains only one density peak, its particles are assigned to the density peak. But in the case of a density shell surrounding at least two density peaks, we use both the tidal radii of halo candidates enclosed by the shell and the total energy criterion to find physically bound particles with respect to each halo. Similar to DENMAX and HOP, the \hfind method can efficiently identify small halos embedded in a large halo, while the FoF and the SO do not resolve such small halos. We apply our new halo finding method to a 1-Giga particle simulation of the Λ\LambdaCDM model and compare the resulting mass function with those of previous studies. The abundance of physically self-bound halos is larger at the low mass scale and smaller at the high mass scale than proposed by the Jenkins et al. (2001) who used the FoF and SO methods. (abridged)Comment: 10 pages, 8 figs, submitted to Ap

    Computational methods and software systems for dynamics and control of large space structures

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    Two key areas of crucial importance to the computer-based simulation of large space structures are discussed. The first area involves multibody dynamics (MBD) of flexible space structures, with applications directed to deployment, construction, and maneuvering. The second area deals with advanced software systems, with emphasis on parallel processing. The latest research thrust in the second area involves massively parallel computers

    Preliminary assessment of the microwave landing system requirements for STOL operations

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    The results of an investigation made to assess the Microwave Landing System (MLS) Requirements for use by civil STOL aircraft are described. The principal MLS characteristics investigated in the report were signal accuracy and volume of coverage. The study utilized a nonlinear six-degree-of-freedom digital simulation of a De Havilland Buffalo C-8A aircraft. Fully automatic control of timed curve flight down to touchdown was simulated. Selected MLS accuracy and coverage parameters for the azimuth, primary elevation, flare evelation and DME signals were varied. The resulting STOL aircraft system performance in following a representative curved flight path was statistically determined. Coverage requirements for STOL aircraft operating in the terminal area environment were also investigated

    Influences of an impurity on the transport properties of one-dimensional antisymmetric spin filter

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    The influences of an impurity on the spin and the charge transport of one-dimensional antisymmetric spin filter are investigated using bosonization and Keldysh formulation and the results are highlighted against those of spinful Luttinger liquids. Due to the dependence of the electron spin orientation on wave number the spin transport is not affected by the impurity, while the charge transport is essentially identical with that of spinless one-dimensional Luttinger liquid.Comment: 7 pages, 2 figures. To appear in Physical Review

    Horava Gravity and Gravitons at a Conformal Point

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    Recently Horava proposed a renormalizable gravity theory with higher derivatives by abandoning the Lorenz invariance in UV. Here, I study the Horava model at λ=1/3\lambda=1/3, where an anisotropic Weyl symmetry exists in the UV limit, in addition to the foliation-preserving diffeomorphism. By considering linear perturbations around Minkowski vacuum, I show that the scalar graviton mode is completely disappeared and only the usual tensor graviton modes remain in the physical spectrum. The existence of the UV conformal symmetry is unique to the theory with the detailed balance and it is quite probable that λ=1/3\lambda=1/3 be the UV fixed point. This situation is analogous to λ=1\lambda=1, which is Lorentz invariant in the IR limit and is believed to be the IR fixed point.Comment: Added comments and references, Accepted in GER

    Detection of an exoplanet around the evolved K giant HD 66141

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    Aims. We have been carrying out a precise radial velocity (RV) survey for K giants to search for and study the origin of the lowamplitude and long-periodic RV variations. Methods. We present high-resolution RV measurements of the K2 giant HD 66141 from December 2003 to January 2011 using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO). Results. We find that the RV measurements for HD 66141 exhibit a periodic variation of 480.5 +/- 0.5 days with a semi-amplitude of 146.2 +/- 2.7 m/s. The Hipparcos photometry and bisector velocity span (BVS) do not show any obvious correlations with RV variations. We find indeed 706.4 +/- 35.0 day variations in equivalent width (EW) measurements of H_alpha line and 703.0 +/- 39.4 day variations in a space-born measurements 1.25{\mu} flux of HD 66141 measured during COBE/DIRBE experiment. We reveal that a mean value of long-period variations is about 705 +/- 53 days and the origin is a rotation period of the star and variability that is caused by surface inhomogeneities. For the 480 day periods of RV variations an orbital motion is the most likely explanation. Assuming a stellar mass of 1.1 +/- 0.1 M_Sun? for HD 66141, we obtain a minimum mass for the planetary companion of 6.0 +/- 0.3 M_Jup with an orbital semi-major axis of 1.2 +/- 0.1 AU and an eccentricity of 0.07 +/- 0.03.Comment: 7 pages, 10 figures, 3 tables, accepted for publisation in Astronomy & Astrophysic
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