Systematic Study of High-pT Direct Photon Production with the PHENIX Experiment at RHIC

When studying the initial state and evolution of the matter created in relativistic heavy ion collisions, high-pT direct photons are a powerful probe. They are created in initial hard processes and in parton fragmentation, and possibly in interactions of partons with the hot and dense medium. We present systematic measurements of high-pT direct photon production in \sqrt{s_{NN}} = 200 GeV p+p and Au+Au collisions. The nuclear modification factor of direct photons is shown for 5 < pT < 18 GeV/c, and at very high transverse momenta it seems to be below unity in the most central Au+Au collisions.Comment: 4 pages, 4 figures. Invited parallel talk at The 19th International Conference On Ultra relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai China, Nov. 14-20, 200

Structural analysis of hollow blades: Torsional stress analysis of hollow fan blades for aircraft jet engines

A torsional stress analysis of hollow fans blades by the finite element method is presented. The fans are considered to be double circular arc blades, hollowed 30 percent, and twisted by a component of the centrifugal force by the rated revolution. The effects of blade hollowing on strength and rigidity are discussed. The effects of reinforcing webs, placed in the hollowed section in varying numbers and locations, on torsional rigidity and the convergence of stresses, are reported. A forecast of the 30 percent hollowing against torsional loadings is discussed

Search for resonances decaying into top quark pairs with ATLAS

Some models, including the so-called Randall-Sundrum model, predict the existence of heavy Kaluza-Klein resonances decaying mainly into top quarks. The prospects to discover those resonances at the LHC, using the ATLAS experiment, are discussed. Especial emphasis is given in the techniques used to identify and reconstruct top quarks at high pT

Continuum radiation from active galactic nuclei: A statistical study

The physics of the continuum spectrum of active galactic nuclei (AGNs) was examined using a large data set and rigorous statistical methods. A data base was constructed for 469 objects which include radio selected quasars, optically selected quasars, X-ray selected AGNs, BL Lac objects, and optically unidentified compact radio sources. Each object has measurements of its radio, optical, X-ray core continuum luminosity, though many of them are upper limits. Since many radio sources have extended components, the core component were carefully selected out from the total radio luminosity. With survival analysis statistical methods, which can treat upper limits correctly, these data can yield better statistical results than those previously obtained. A variety of statistical tests are performed, such as the comparison of the luminosity functions in different subsamples, and linear regressions of luminosities in different bands. Interpretation of the results leads to the following tentative conclusions: the main emission mechanism of optically selected quasars and X-ray selected AGNs is thermal, while that of BL Lac objects is synchrotron; radio selected quasars may have two different emission mechanisms in the X-ray band; BL Lac objects appear to be special cases of the radio selected quasars; some compact radio sources show the possibility of synchrotron self-Compton (SSC) in the optical band; and the spectral index between the optical and the X-ray bands depends on the optical luminosity

Effects of Velocity Correlation on Early Stage of Free Cooling Process of Inelastic Hard Sphere System

The free cooling process in the inelastic hard sphere system is studied by analysing the data from large scale molecular dynamics simulations on a three dimensional system. The initial energy decay, the velocity distribution function, and the velocity correlation functions are calculated to be compared with theoretical predictions. The energy decay rate in the homogeneous cooling state is slightly but distinctively smaller than that expected from the independent collision assumption. The form of the one particle velocity distribution is found not to be stationary. These contradict to the predictions of the kinetic theory based on the Enskog-Boltzmann equation and suggest that the velocity correlation is already important in the early stage of homogeneous cooling state. The energy decay rate is analysed in terms of the velocity correlation.Comment: 9 pages (figures included). To be published in J. Phys. Soc. Jpn. Vol. 73 No. 1 (2004) Added two references and removed one. Changed the name of T_{L}. Added unit constants in Sec. 5 and