Helicopter main-rotor speed effects: A comparison of predicted ranges of detection from the aural detection program ICHIN and the electronic detection program ARCAS

NASA LaRC personnel have conducted a strudy of the predicted acoustic detection ranges associated with reduced helicopter main rotor speeds. This was accomplished by providing identical input information to both the aural detection program ICHIN 6, (I Can Hear It Now, version 6) and the electronic acoustic detection program ARCAS (Assessment of Rotorcraft Detection by Acoustics Sensing). In this study, it was concluded that reducing the main rotor speed of the helicopter by 27 percent reduced both the predicted aural and electronic detection ranges by approximately 50 percent. Additionally, ARCAS was observed to function better with narrowband spectral input than with one-third octave band spectral inputs and the predicted electronic range of acoustic detection is greater than the predicted aural detection range

High momentum lepton pairs from jet-plasma interactions

We discuss the emission of high momentum lepton pairs (p_T>4 GeV) with low invariant masses (M << p_T) in central Au+Au collisions at RHIC (\sqrt{s_{NN}}=200 GeV). The spectra of dileptons produced through interactions of quark and antiquark jets with the quark-gluon plasma (QGP) have been calculated. Annihilation and Compton scattering processes, as well as processes benefitting from collinear enhancement, including Landau-Pomeranchuk-Migdal (LPM) effects, are calculated and convolved with a one dimensional hydrodynamic expansion. The jet-induced contributions are compared to thermal dilepton emission and Drell-Yan processes, and are found to dominate around p_T=4 GeV.Comment: Parallel talk given at QM2006, Shanghai November 2006. 4 pages, 3 figure

Helicopter far-field acoustic levels as a function of reduced main-rotor advancing blade-tip Mach number

During the design of a helicopter, the weight, engine, rotor speed, and rotor geometry are given significant attention when considering the specific operations for which the helicopter will be used. However, the noise radiated from the helicopter and its relationship to the design variables is currently not well modeled with only a limited set of full-scale field test data to study. In general, limited field data have shown that reduced main-rotor advancing blade-tip Mach numbers result in reduced far-field noise levels. The status of a recent helicopter noise research project is reviewed. It is designed to provide flight experimental data which may be used to further understand helicopter main-rotor advancing blade-tip Mach number effects on far-field acoustic levels. Preliminary results are presented relative to tests conducted with a Sikorsky S-76A helicopter operating with both the rotor speed and the flight speed as the control variable. The rotor speed was operated within the range of 107 to 90 percent NR at nominal forward speeds of 35, 100, and 155 knots

Economic and social significance of the travel agency

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The concept of revelation

In choosing an experiential approach to the concept of revelation and, in preferring this to either an informative or an instructional view, I have faced head-on a central concern for Christian theists. This appertains to the epistemological problem raised by the assumption at the heart of belief in revelation, that God can, in some way or another, be known by men. For to say that God has revealed Himself to his human creatures implies some kind of knowledge of God. I have rejected attempts to describe this in terms simply of degrees of commitment, evinced by Christian faith and attitudes, and attempted to show that the concept of revelation, as traditionally understood, requires an apperception of reality which enables the verb to know to be suitably used. My method has been to use Wittgenstein's concepts of a language game and a form of life to demonstrate that it makes sense to say that, in Christ, a knowledge of God is possible. I have argued that certain fundamental propositions, implicit within the Kerygma of the Apostolic community, provide the basis for intelligible talk about man's encounter with his Creator. After analysing different sorts of knowledge claim, I reached the conclusion that knowledge by description best suits the demands of the kerygmatic language game. This coheres with my argument, following Wittgenstein, that it is in the learning of an apposite language game and adhering to the rules prescribed by its autonomous grammar that understanding of Christian propositions can be gained. To elucidate this, I discussed Kant's view concerning the place of reason in reaching a posteriori judgements. I introduced Popper's notion of a 'third world of ideas' to justify the Christian's claim that ideas relative to the kerygma and didache etc have stood the test of time. Such ideas might be accorded a certain objectivity. Is the question of God's existence begged in the language game? To answer this I examined a number of views about the verb 'to exist' and adopted Russell's suggestion that it operates in a second order manner. I explored his thinking about significant inexistent objects. 1 proceeded to relate these problems to Wittgenstein's discussion of sense and reference in respect of what he says of the 'mystical' and about significant yet meaningless propositions. Yet the main thrust of my argument was to seek to explicate the notion of man's response to God (who is thus taken to exist and to be active in communication with man), by pointing again to the fact of the form of life of Christian belief. I concluded that it is here that all that can intelligibly be said of God making Himself known, and being known by believers, must be grounded

A Nineteenth-Century Mackenzie Inuit Site near Inuvik, Northwest Territories

A small collection of artifacts obtained from an aboriginal Mackenzie Inuit grave eroded by the Mackenzie River is described. The site appears to date to within the second half of the 19 century, following European contact but before acculturative processes and population decline, which brought about the extinction of traditional Mackenzie Inuit culture.Key words: Inuit, archaeology, Mackenzie delta, nineteenth century, artifacts, erosionMots cl&eacute;s: Inuit, arch&eacute;ologie, delta du Mackenzie, 19e si&egrave;cle, artefacts, &eacute;rosio