1,349 research outputs found
A linear acoustic model for intake wave dynamics in IC engines
No full textIn this paper, a linear acoustic model is described that has proven useful in obtaining a better understanding of the nature of acoustic wave dynamics in the intake system of an internal combustion (IC) engine. The model described has been developed alongside a set of measurements made on a Ricardo E6 single cylinder research engine.
The simplified linear acoustic model reported here produces a calculation of the pressure time-history in the port of an IC engine that agrees fairly well with measured data obtained on the engine fitted with a simple intake system.
The model has proved useful in identifying the role of pipe resonance in the intake process and has led to the development of a simple hypothesis to explain the structure of the intake pressure time history: the early stages of the intake process are governed by the instantaneous values of the piston velocity and the open area under the valve. Thereafter resonant wave action dominates the process. The depth of the early depression caused by the moving piston governs the intensity of the wave action that follows. A pressure ratio across the valve that is favourable to inflow is maintained and maximised when the open period of the valve is such to allow at least, but no more than, one complete oscillation of the pressure at its resonant frequency to occur whilst the valve is open
Measuring wave dynamics in IC engine intake systems
No full textWave dynamics in the intake system are known to strongly influence the performance of naturally aspirated internal combustion (I.C.) engines. Detailed measurements of the wave dynamics are required to: optimise the performance of an engine, to validate the results of an engine performance simulation or to better understand the physics of the intake system. Five different methods for making such measurements are discussed in this paper. Four are based on different forms of pressure measurement and one uses hot wire anemometry.
The different methods are investigated using results obtained on a single cylinder research engine. The different methods are used to produce measurements of fluctuating pressure and velocity as well as the specific acoustic impedance ratio of the intake pipe. Both time and frequency domain results are considered.
The paper concludes that no single method is perfect or indeed universally applicable to all situations and in a typical investigation of wave action more than one method is likely to be used. The combined use of two methods, wave decomposition and an unusual bi-directional pitot-static tube, seems to offer a robust reliable and useful strategy for measuring wave dynamics in the intake pipe that should prove successful on most IC engines
Open strings on the Neveu-Schwarz 5-brane
No full textWe analyze the propagation of open and unoriented strings on the Neveu-Schwarz 5-brane (N5-brane) along the lines of a similar analysis for the SU(2) WZNW models. We discuss the two classes of open descendants of the diagonal models and a series of Z(2) projected models which exist only for even values of the level k and correspond to branes at D-type orbifold singularities. The resulting configurations of branes and planes are T-dual to those relevant to the study of dualities in super Yang-Mills theories, The association of Chan-Paton factors to D-brane multiplicities is possible in the semi-classical limit k --> infinity, but due to strong curvature effects is unclear for finite k, We show that the introduction of a magnetic field implies a twist of the SU(2) current algebra in the open-string sector leading to space-time supersymmetry breaking. (C) 1998 Elsevier Science B.V
Exchange Relations and Correlation Functions for a Quantum Particle on the Group Manifold
No full textElectromagnetic cascades and cascade nucleosynthesis in the early universe
No full textWe describe a calculation of electromagnetic cascading in radiation and matter in the early Universe initiated by the decay of massive particles or by some other process. We have used a combination of Monte Carlo and numerical techniques which enables us to use exact cross sections, where known, for all the relevant processes. In cascades initiated after the epoch of big bang nucleosynthesis γ rays in the cascades will photodisintegrate ⁴He, producing ³He and deuterium. Using the observed ³He and deuterium abundances we are able to place constraints on the cascade energy deposition as a function of cosmic time. In the case of the decay of massive primordial particles we place limits on the density of massive primordial particles as a function of their mean decay time, and on the expected intensity of decay neutrinos.Protheroe, R.J.; Stanev, T.; Berezinsky, V.S
Update On Atmospheric Neutrinos
No full textWe discuss the impact of recent experimental results on the determination of atmospheric neutrino oscillation parameters. We use all published results on atmospheric neutrinos, including the preliminary large statistics data of Super-Kamiokande. We reanalyze the data in terms of both vμ → vτ and vμ → ve channels using new improved calculations of the atmospheric neutrino flux. We compare the sensitivity attained in atmospheric neutrino experiments with those of accelerator and reactor neutrino oscillation searches, including the recent CHOOZ experiment. We briefly comment on the implications of atmospheric neutrino data in relation to future searches for neutrino oscillations with long baselines, such as the K2K, MINOS, ICARUS, and NOE experiments.5833300413300413Gaisser, T.K., (1997) Proceedings of the 17th International Conference on Neutrino Physics and Astrophysics, p. 211. , Neutrino '96, Helsinki, Finland, edited by K. Enquist, K. Huitu, and J. Maalampi (World Scientific, Singapore)Gaisser, T.K., Halzen, F., Stanev, T., (1995) Phys. Rep., 258, p. 174Stanev, T., Proceedings in TAUP '95, , Toledo, Spain, edited by A. Morales, J. Morales, and J. A. Villar(1996) Nucl. Phys. B (Proc. Suppl.), 48, p. 165Kajita, T., (1994) Physics and Astrophysics of Neutrinos, p. 559. , edited by M. Fukugita and A. Suzuki (Springer-Verlag, Tokyo)Akhmedov, E.Kh., (1994) Proceedings of the International School on Cosmological Dark Matter, p. 131. , Cosmological Dark Matter, Valencia, Spain, edited A. Perez and J. W. F. Valle (World Scientific, Singapore)Stanev [1]Barish, B., (1996) Proceedings of Int. Workshop on Elementary Particle Physics: Present and Future, p. 400. , edited by A. Ferrer and J. W. F. Valle (World Scientific, Singapore)Hirata, H.S., (1988) Phys. Lett. B, 205, p. 416(1992) Phys. Lett. B, 280, p. 146Kaneyuki, K., (1993) Proceedings of the XIII Moriond Workshop, p. 211. , Perspectives in Neutrinos, Atomic Physics and Gravitation, edited by J. Tran Thanh Van et al. Editions Frontieres, Villars sur Ollon, SwitzerlandFukuda, Y., (1994) Phys. Lett. B, 335, p. 237Casper, D., (1991) Phys. Rev. Lett., 66, p. 2561Becker-Szendy, R., (1992) Phys. Rev. D, 46, p. 3720Keilczewska, D., Perspectives in Neutrinos, Atomic Physics and Gravitation (1993) Proceedings of the XIII Moriond Workshop, p. 219. , edited by J. Tran Thanh Van et al. Editions Frontieres, Villars sur Ollon, SwitzerlandBerger, Ch., (1989) Phys. Lett. B, 227, p. 489Aglietta, M., (1989) Europhys. Lett., 8, p. 611Nakamura, K., (1997) XVI International Workshop on Weak Interactions and Neutrinos, , Capri, Italy, edited by G. Fiorilo et al(1998) Nucl. Phys. B (Proc. Suppl.), 66, p. 282Kearns, E., (1997) TAUP97, , Laboratori Nazionali del Gran Sasso, Assergi, Italy, hep-ex/9803007Allison, W.W.M., (1997) Phys. Lett. B, 391, p. 491Gallagher, H., XVI International Workshop on Weak Interactions and Neutrinos, p. 290. , 9Kafka, T., (1997) TAU97, , Laboratori Nazionali del Gran Sasso, Assergi, Italy, hep-ph/9712281Agrawal, V., (1996) Phys. Rev. D, 53, p. 1314Gaisser, T.K., Stanev, T., (1995) Proceedings of the 24th ICRC, 1, p. 694. , edited by B. D. Piazzoli et al., RomeVolkova, L.V., (1980) Sov. J. Nucl. Phys., 31, p. 784Apollonio, M., (1998) Phys. Lett. B, 420, p. 397Barr, G., Gaisser, T.K., Stanev, T., (1989) Phys. Rev. D, 39, p. 3532(1988) Phys. Rev. D, 38, p. 85Lipari, P., Stanev, T., Proceedings of the 24th ICRC, 1. , 11Honda, M., Kajita, T., Kasahara, K., Midorikawa, S., (1995) Phys. Rev. D, 52, p. 4985Honda, M., Kasahara, K., Hidaka, K., Midorikawa, S., (1990) Phys. Lett. B, 248, p. 193Gaisser, T.K., (1996) Phys. Rev. D, 54, p. 5578Bugaev, E.V., Naumov, V.A., (1989) Phys. Lett. B, 232, p. 391Circella, M., (1997) Proceedings of the 25th ICRC, 7, p. 117. , DurbanGaisser, T.K., Stanev, T., (1998) Phys. Rev. D, 57, p. 1977Lipari, P., Lusignoli, M., Sartogo, F., (1995) Phys. Rev. Lett., 74, p. 4384Smith, C.L., (1972) Phys. Rep., Phys. Lett., 3 C, p. 261Fogli, G.L., Nardulli, G., (1979) Nucl. Phys., B160, p. 116Nakahata, M., (1986) J. Phys. Soc. Jpn., 55, p. 3786Fogli, G.L., Lisi, E., Montanino, D., (1994) Phys. Rev. D, 49, p. 3626(1995) Astropart. Phys., 4, p. 177Fogli, G.L., Lisi, E., Montanino, D., Scioscia, G., (1997) Astropart. Phys., 55, p. 4385Kajita, T., (private communication)see also Kajita [1]Inoue, K., private communicationFogli, G.L., Lisi, E., (1995) Phys. Rev. D, 52, p. 2775Mikheyev, S.P., Smirnov, A.Yu., (1985) Yad. Fiz., 42, p. 1441Wolfenstein, L., (1985) Phys. Rev. D, 17, p. 2369Lisi, E., Montanino, D., (1997) Phys. Rev. D, 56, p. 1792Vidyakin, G.S., (1994) JETP Lett., 59, p. 390Achkar, B., (1995) Nucl. Phys., B424, p. 503Dydak, F., (1984) Phys. Lett., 134 B, p. 281Borodvsky, L., (1992) Phys. Rev. Lett., 68, p. 274Ushida, N., (1986) Phys. Rev. Lett., 57, p. 2897CHORUS Collaboration, N. Armenise et al., Report No. CERN-SPSC/90-42 (1990)NOMAD Collaboration, P. Astier et al., Report No. CERN-SPSLC/91-21 (1991)Report No. CERN-SPSLC/91-48 (1991)Report No. SPSLC/P261 Add. 1 (1991)Di Lella, L., (1997) TAUP97, , Laboratori Nazionali del Gran Sasso, Assergi, ItalyYanagisawa, C., (1997) International Workshop on Physics Beyond the Standard Model: From Theory to Experiment, , Valencia, Spain, to appear in the proceedings, edited by I. Antoniadis, L. Ibanez and J. W. F. Valle (World Scientific, Singapore)Ayres, D., http://www.hep.anl.gov/NDK/HyperText/numi.html, NuMI-L-63 MINOS proposalAmbrosio, M., (1995) Nucl. Instrum. Methods Phys. Res. A, 363, p. 604. , http://www.na.infn.it/SubNucl/accel/noe/noe.htmlhttp://www.aquila.infn.it/icarus/Cavanna, F., (1995) A First 600 Ton ICARUS Detector Installed at the Gran Sasso Laboratory, , addendum to Proposal by the ICARUS Collaboration, Report No. LNGS-95/1
Atmospheric Shower Fluctuations And The Constant Intensity Cut Method
No full textWe explore the constant intensity cut method that is widely used for the derivation of the cosmic ray energy spectrum, for comparisons of data obtained at different atmospheric depths, for measuring average shower profiles, and for estimates of the proton-air cross section from extensive air shower data. The constant intensity cut method is based on the selection of air showers by charged particle or muon size and therefore is subject to intrinsic shower fluctuations. We demonstrate that, depending on the selection method, shower fluctuations can strongly influence the characteristics of the selected showers. Furthermore, a mixture of different primaries in the cosmic ray flux complicates the interpretation of measurements based on the method of constant intensity cuts. As an example we consider data published by the Akeno Collaboration. The interpretation of the Akeno measurements suggests that more than 60-70% of cosmic ray primaries in the energy range 10 16 - 10 17 eV are heavy nuclei. Our conclusions depend only weakly on the hadronic interaction model chosen to perform the simulations, namely SIBYLL and QGSJET. © 2002 The American Physical Society.6612J. Alvarez-Muñiz et al. (in preparation)Hara, T., (1983) Phys. Rev. Lett., 50, p. 2058Baltrusaitis, R.M., (1984) Phys. Rev. Lett., 52, p. 1380Honda, M., (1993) Phys. Rev. Lett., 70, p. 525Aglietta, M., (1997) Proceedings of the 25th International Cosmic Ray Conference, 6, p. 37. , Durban, South Africa, (World Scientific, Singapore, 1997)Aglietta, M., (1999) Proceedings of the 26th Int'l Cosmic Ray Conference, 1, p. 143. , Salt Lake City, (AIP, Melville, NY)Aglietta, M., (1999) Nucl. Phys. B (Proc. Suppl.), 75 A, p. 222Ellsworth, R.W., (1982) Phys. Rev. D, 26, p. 336Bradt, H., (1965) Proceedings of the 9th International Cosmic Ray Conference, 2, p. 715. , London, (The Institute of Physics and the Physical Society, London, 1965)M. Ave, J. Knapp, J. Lloyd-Evans, M. Marchesini, and A.A. Watson, astro-ph/0112253Alvarez-Munĩz, J., Engel, R., Gaisser, T.K., Ortiz, J.A., Stanev, T., (2002) Phys. Rev. D, 66, p. 033011Nagano, M., Watson, A.A., (2000) Rev. Mod. Phys., 72, p. 689Engel, R., Gaisser, T.K., Lipari, P., Stanev, T., (1999) Proceedings of the 26th Int'l Cosmic Ray Conference, 1, p. 415. , Salt Lake City, (AIP, Melville, NY)Engel, R., Gaisser, T.K., Stanev, T., (2001) Proceedings of the 27th International Cosmic Ray Conference, p. 431. , Hamburg, Germany, (Copernicus Gesellschaft, Katlemburg-Lindau, 2001)Kalmykov, N.N., Ostapchenko, S.S., Pavlov, A.I., (1997) Nucl. Phys. B (Proc. Suppl.), 52 B, p. 17Nagano, M., (1984) J. Phys. G, 10, p. 1295Ulrich, H., (2001) Proceedings of the 27th International Cosmic Ray Conference, p. 97. , Hamburg, Germany, (Copernicus Gesellschaft, Katlemburg-Lindau, 2001)Abu-Zayyad, T., (2001) Astropart. Phys., 16, p. 1Swordy, S.P., (2002) Astropart.Phys., 18, p. 129Gaisser, T., (1974) Nature (London), 248, p. 122Nikolaev, N.N., (1993) Phys. Rev. D, 48, pp. R1904Engel, R., Gaisser, T.K., Lipari, P., Stanev, T., (1998) Phys. Rev. D, 58, p. 014019not
A seasonal model of the Mediterranean Sea general circulation
No full textThis paper describes the seasonal characteristics of the Mediterranean Sea general circulation as simulated by a primitive equation general circulation model. The general circulation is composed of subbasin gyres, and cyclonic motion dominates the northern and anticyclonic motion the southern part of the basin. The Atlantic stream is a coherent structure at the surface. At depth it appears as current segments and jets around a vigorous gyre system. The seasonal variability is manifested by a change in amplitude and location of the gyres and by the appearance of seasonally recurrent gyres in different parts of the basin. For the first time a Mersa-Matruh Gyre is successfully simulated due to the introduction of our heat fluxes at the air-sea interface. The seasonal thermocline is formed each summer, and a deep winter mixed layer is produced in the region of Levantine intermediate water formation. -from Author
Propagation of ultrahigh energy protons in the nearby universe
No full textWe present a new calculation of the propagation of protons with energies above 10¹⁹ eV over distances of up to several hundred Mpc. The calculation is based on a Monte Carlo approach using the event generator SOPHIA for the simulation of hadronic nucleon-photon interactions and a realistic integration of the particle trajectories in a random extragalactic magnetic field. Accounting for the proton scattering in the magnetic field affects noticeably the nucleon energy as a function of the distance to their source and allows us to give realistic predictions on arrival energy, time delay, and arrival angle distributions and correlations as well as secondary particle production spectra.Todor Stanev, Ralph Engel, Anita Mücke, Raymond J. Protheroe, Joerg P. Rache
- …
