681 research outputs found

    Classroom demonstration of sunspots

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    Physical science workshop course for elementary teachers

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    Science for elementary school grades K-6 varies somewhat in content from one textbook series to another, but it is fairly common that 40-60% of the material covered is directly related to physics. These texts suggest that certain learning activities such as experiments, demonstrations, and observations be carried out by the teacher and the class. Often the apparatus for a learning activity is to be constructed from simple, readily available materials. The typical elementary school teacher has had little experience in performing experiments and is often frustrated in his/her attempts at carrying out the suggested learning activity. To meet this need we have developed a physical science workshop that is made available to teachers who are returning to the university for additional training

    Wave demonstration device

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    Students often have difficulty gaining an understanding of wave motion without effective demonstrations being performed in the lecture. Many excellent approaches utilizing ripple tanks, waves on a spring, chain, rope, etc., are customarily employed. Perhaps the most well-known device for demonstrating many of the effects of wave motion is the shive or bell wave motion machine.1 The purpose of the present note is to describe a simple, inexpensive device which can be easily constructed by a teacher or student and can be used to demonstrate many of the properties of wave motion

    Linear Response Calculations of Spin Fluctuations

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    A variational formulation of the time--dependent linear response based on the Sternheimer method is developed in order to make practical ab initio calculations of dynamical spin susceptibilities of solids. Using gradient density functional and a muffin-tin-orbital representation, the efficiency of the approach is demonstrated by applications to selected magnetic and strongly paramagnetic metals. The results are found to be consistent with experiment and are compared with previous theoretical calculations.Comment: 11 pages, RevTex; 3 Figures, postscript, high-resolution printing (~1200dpi) is desire

    An augmented space recursion study of the electronic structure of rough epitaxial overlayers

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    In this communication we propose the use of the Augmented Space Recursion as an ideal methodology for the study of electronic and magnetic structures of rough surfaces, interfaces and overlayers. The method can take into account roughness, short-ranged clustering effects, surface dilatation and interdiffusion. We illustrate our method by an application of Fe overlayer on Ag (100) surface.Comment: 22 pages, Latex, 6 postscript figure

    X-ray Study of the Crystallization Processes in Amorphous (ZrO. 64Ni0. 36) 1-xAlx Alloys. [Abstract]

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    The short range order in (Zr0.64Ni0.36)1−xAlx metallic glasses for values of x between 0 and 0.25 was investigated using X-ray diffraction. X-ray intensity patterns and the derived structural functions for the as-quenched samples differed only slightly with the change in aluminum concentration, suggesting that the addition of aluminum does not significantly alter the relative coordination of the zirconium and nickel atoms. Only the first two alloys in the series (x = 0, 0.05) exhibited multiple transitions in the DSC thermograms. The intermediate phase for the x = 0.05 alloy has an amorphous or, perhaps, a very fine crystalline structure. The final crystalline phase of the x = 0 sample consisted predominantly of Zr2Ni crystals. The addition of aluminum to the host Zr0.64Ni0.36 alloy suppressed the formation of Zr2Ni crystals during crystallization so that predominantly ZrNi crystals were formed

    A Liquid Model Analogue for Black Hole Thermodynamics

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    We are able to characterize a 2--dimensional classical fluid sharing some of the same thermodynamic state functions as the Schwarzschild black hole. This phenomenological correspondence between black holes and fluids is established by means of the model liquid's pair-correlation function and the two-body atomic interaction potential. These latter two functions are calculated exactly in terms of the black hole internal (quasilocal) energy and the isothermal compressibility. We find the existence of a ``screening" like effect for the components of the liquid.Comment: 20 pages and 6 Encapsulated PostScript figure

    Properties of a random attachment growing network

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    In this study we introduce and analyze the statistical structural properties of a model of growing networks which may be relevant to social networks. At each step a new node is added which selects 'k' possible partners from the existing network and joins them with probability delta by undirected edges. The 'activity' of the node ends here; it will get new partners only if it is selected by a newcomer. The model produces an infinite-order phase transition when a giant component appears at a specific value of delta, which depends on k. The average component size is discontinuous at the transition. In contrast, the network behaves significantly different for k=1. There is no giant component formed for any delta and thus in this sense there is no phase transition. However, the average component size diverges for delta greater or equal than one half.Comment: LaTeX, 19 pages, 6 figures. Discussion section, comments, a new figure and a new reference are added. Equations simplifie

    Nontrivial, Asymptotically Non-free Gauge Theories and Dynamical Unification of Couplings

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    An evidence for nontriviality of asymptotically non-free (ANF) Yang-Mills theories is found on the basis of optimized perturbation theory. It is argued that these theories with matter couplings can be made nontrivial by means of the reduction of couplings, leading to the idea of dynamical unification of couplings (DUC) The second-order reduction of couplings in the ANF SU(3)SU(3)-gauged Higgs-Yukawa theory, which is assumed to be nontrivial here, is carried out to motivate independent investigations on its nontriviality and DUC
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