Simulation of an enhanced TCAS 2 system in operation

Described is a computer simulation of a Boeing 737 aircraft equipped with an enhanced Traffic and Collision Avoidance System (TCAS II). In particular, an algorithm is developed which permits the computer simulation of the tracking of a target airplane by a Boeing 373 which has a TCAS II array mounted on top of its fuselage. This algorithm has four main components: namely, the target path, the noise source, the alpha-beta filter, and threat detection. The implementation of each of these four components is described. Furthermore, the areas where the present algorithm needs to be improved are also mentioned

A study of a collision avoidance system mounted on a curved ground plane

Research conducted on a traffic advisory and collision avoidance system (TCAS 2) mounted on a curved ground plane is described. It is found that a curved finite ground plane can be used as a good simulation model for the fuselage of an aircraft but may not be good enough to model a whole aircraft due to the shadowing of the vertical stabilizer, wings, etc. The surface curvature of this curved disc significantly affects the monopulse characteristics in the azimuth plane but not as much in the elevation plane. These variations of the monopulse characteristics verify the need of a lookup table for the 64 azimuth beam positions. The best location of a TCAS 2 array on a Boeing 737 is to move it as far from the vertical stabilizer as possible

Simulation of the enhanced traffic alert and collision avoidance system (TCAS 2)

The OSU aircraft code is used to analyze and simulate the TCAS 2 circular array which is mounted on the fuselage of a Boeing 737 aircraft. It is shown that the sum and difference patterns radiated by the circular array are distorted by the various structures of the aircraft, i.e., wings, tail, etc. Furthermore, monopulse curves are calculated and plotted for several beam positions and THETA angles. As expected, the worst cases of distortion occur when the beams are pointed toward the tail of the aircraft

Control of trapped-ion quantum states with optical pulses

We present new results on the quantum control of systems with infinitely large Hilbert spaces. A control-theoretic analysis of the control of trapped ion quantum states via optical pulses is performed. We demonstrate how resonant bichromatic fields can be applied in two contrasting ways -- one that makes the system completely uncontrollable, and the other that makes the system controllable. In some interesting cases, the Hilbert space of the qubit-harmonic oscillator can be made finite, and the Schr\"{o}dinger equation controllable via bichromatic resonant pulses. Extending this analysis to the quantum states of two ions, a new scheme for producing entangled qubits is discovered.Comment: Submitted to Physical Review Letter

Nitrous oxide emissions from the Arabian Sea: A synthesis

We computed high-resolution (1º latitude x 1º longitude) seasonal and annual nitrous oxide (N2O) concentration fields for the Arabian Sea surface layer using a database containing more than 2400 values measured between December 1977 and July 1997. N2O concentrations are highest during the southwest (SW) monsoon along the southern Indian continental shelf. Annual emissions range from 0.33 to 0.70 Tg N2O and are dominated by fluxes from coastal regions during the SW and northeast monsoons. Our revised estimate for the annual N2O flux from the Arabian Sea is much more tightly constrained than the previous consensus derived using averaged in-situ data from a smaller number of studies. However, the tendency to focus on measurements in locally restricted features in combination with insufficient seasonal data coverage leads to considerable uncertainties of the concentration fields and thus in the flux estimates, especially in the coastal zones of the northern and eastern Arabian Sea. The overall mean relative error of the annual N2O emissions from the Arabian Sea was estimated to be at least 65%

Dynamic and Energetic Stabilization of Persistent Currents in Bose-Einstein Condensates

We study conditions under which vortices in a highly oblate harmonically trapped Bose-Einstein condensate (BEC) can be stabilized due to pinning by a blue-detuned Gaussian laser beam, with particular emphasis on the potentially destabilizing effects of laser beam positioning within the BEC. Our approach involves theoretical and numerical exploration of dynamically and energetically stable pinning of vortices with winding number up to $S=6$, in correspondence with experimental observations. Stable pinning is quantified theoretically via Bogoliubov-de Gennes excitation spectrum computations and confirmed via direct numerical simulations for a range of conditions similar to those of experimental observations. The theoretical and numerical results indicate that the pinned winding number, or equivalently the winding number of the superfluid current about the laser beam, decays as a laser beam of fixed intensity moves away from the BEC center. Our theoretical analysis helps explain previous experimental observations, and helps define limits of stable vortex pinning for future experiments involving vortex manipulation by laser beams.Comment: 8 pages 5 figure

Leptogenesis implications in models with Abelian family symmetry and one extra real Higgs singlet

We show that the neutrino models, as suggested by Low, which have an additional Abelian family symmetry and a real Higgs singlet to the default see-saw do not hinder the possibility of successful thermal leptogenesis. For these models (neglecting radiative effects), we have investigated the situation of strong washout in both the one-flavor approximation and when flavor effects are included. The result is that while such models predict that theta_{13}=0 and that one light neutrino to be massless, they do not modify or provide significant constraints on the typical leptogenesis scenario where the final asymmetry is dominated by the decays of the lightest right-handed neutrinos.Comment: 18 pages, RevTeX4, accepted by Phys. Rev. D. v2: minor corrections, note and 1 ref. added, same content as published versio

Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of γ\gamma-ray Emission from 3EG J1746-2851

High resolution VLA observations of the Arches cluster near the Galactic center show evidence of continuum emission at $\lambda$3.6, 6, 20 and 90cm. The continuum emission at $\lambda$90cm is particularly striking because thermal sources generally become optically thick at longer wavelengths and fall off in brightness whereas non-thermal sources increase in brightness. It is argued that the radio emission from this unique source has compact and diffuse components produced by thermal and nonthermal processes, respectively. Compact sources within the cluster arise from stellar winds of mass-losing stars (Lang, Goss & Rodriguez 2001a) whereas diffuse emission is likely to be due to colliding wind shocks of the cluster flow generating relativistic particles due to diffuse shock acceleration. We also discuss the possibility that $\gamma$-ray emission from 3EG J1746--2851, located within 3.3$'$ of the Arches cluster, results from the inverse Compton scattering of the radiation field of the cluster.Comment: 15 pages, four figures, ApJL (in press

Leaky cavities with unwanted noise

A phenomenological approach is developed that allows one to completely describe the effects of unwanted noise, such as the noise associated with absorption and scattering, in high-Q cavities. This noise is modeled by a block of beam splitters and an additional input-output port. The replacement schemes enable us to formulate appropriate quantum Langevin equations and input-output relations. It is demonstrated that unwanted noise renders it possible to combine a cavity input mode and the intracavity mode in a nonmonochromatic output mode. Possible applications to unbalanced and cascaded homodyning of the intracavity mode are discussed and the advantages of the latter method are shown.Comment: 13 pages, 7 figures; published versio