Traffic noise has been shown to have negative effects on exposed persons in the communities along highways. Noise from transportation systems is considered a nuisance in the U.S. and the government agencies require a determination of noise impacts for federally funded projects. There are several models available for assessing noise levels impacts. These models vary from simple charts to computer design models. Some computer models, i.e. Standard Method In Noise Analysis (STAMINA), the Traffic Noise Model (TNM) and the UCF Community Noise Model (CNM), have been used to predict geometric spreading, atmospheric absorption, diffraction, and ground impedance. However, they have largely neglected the atmospheric effects on noise propagation in their algorithms. The purpose of this research was to better understand and predict the meteorological effects on traffic noise propagation though measurements and comparison to acoustic theory. It should be noted that this represents an approach to incorporate refraction algorithms affecting outdoor noise propagation that must also work with algorithms for geometric spreading, ground effects, diffraction, and turbulence. The new empirical model for predicting atmospheric refraction shows that wind direction is a significant parameter and should be included in future modeling for atmospheric refraction. To accomplish this, the model includes a "wind shear" and "lapse rate" terms instead of wind speed and temperature as previously needed for input of the most used models. The model is an attempt to explain atmospheric refraction by including the parameters of wind direction, wind shear, and lapse rate that directly affect atmospheric refraction.

One of the negative effects that a laser beam experiences as it propagates through the atmosphere is intensity fluctuations or scintillation. Because scintillation-- as it pertains to laser radar and laser satellite communication systems-- is the main subject of this research, the assumption of an optical element ( such as a Gaussian lens) along the propagation path in front of the detector is valid. The mathematical addition of optical elements to the propagation path is treated using the ABCD ray matrix method. The expression for scintillation is derived, analyzed, and numerically calculated for positions to the left and right of the image plane, which is behind the collecting lens of a receiver system. Simultaneously, the behavior of the scintillation is investigated when the aperture size of the lens is increased. The results are compared to the aperture averaging effect experienced when the beam is in the image plane. This is a per-unit scintillation decrease because the aperture averages it over the surface of the lens.

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No description available.

No description available.

Earths and mini Neptunes likely have a wide range of atmospheric compositions, ranging from low molecular mass atmospheres of H-2 to higher molecular atmospheres of water, CO2, N-2, or other species. Here we systematically investigate the effects of atmospheric bulk compositions on temperature and wind distributions for tidally locked sub-Jupiter-sized planets, using an idealized 3D general circulation model (GCM). The bulk composition effects are characterized in the framework of two independent variables: molecular weight and molar heat capacity. The effect of molecular weight dominates. As the molecular weight increases, the atmosphere tends to have a larger day-night temperature contrast, a smaller eastward phase shift in the thermal phase curve, and a smaller zonal wind speed. The width of the equatorial super-rotating jet also becomes narrower, and the "jet core" region, where the zonal-mean jet speed maximizes, moves to a greater pressure level. The zonal-mean zonal wind is more prone to exhibit a latitudinally alternating pattern in a higher molecular weight atmosphere. We also present analytical theories that quantitatively explain the above trends and shed light on the underlying dynamical mechanisms. Those trends might be used to indirectly determine the atmospheric compositions on tidally locked sub-Jupiter-sized planets. The effects of the molar heat capacity are generally small. But if the vertical temperature profile is close to adiabatic, molar heat capacity will play a significant role in controlling the transition from a divergent flow in the upper atmosphere to a jet-dominated flow in the lower atmosphere.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / Microfiche copy available in Archives and Barker. / Includes bibliographical references. / by Peter David McQuade. / M.S.

This thesis describes a method for using physically based techniques to model an explosion and the resulting side effects. Explosions are some of the most visually exciting phenomena known to humankind and have become nearly ubiquitous in action films. A realistic computer simulation of this powerful event would be cheaper, quicker, and much less complicated than safely creating the real thing. The immense energy released by a detonation creates a discontinuous localized increase in pressure and temperature. Physicists and engineers have shown that the dissipation of this concentration of energy, which creates all the visible effects, adheres closely to the compressible Navier-Stokes equation. This program models the most noticeable of these results. In order to simulate the pressure and temperature changes in the environment, a three dimensional grid is placed throughout the area around the detonation and a discretized version of the Navier-Stokes equation is applied to the resulting voxels. Objects in the scene are represented as rigid bodies that are animated by the forces created by varying pressure on their hulls. Fireballs, perhaps the most awe-inspiring side effects of an explosion, are simulated using massless particles that flow out from the center of the blast and follow the currents created by the dissipating pressure. The results can then be brought into Maya for evaluation and tweaking.

This thesis describes a method for using physically based techniques to model an explosion and the resulting side effects. Explosions are some of the most visually exciting phenomena known to humankind and have become nearly ubiquitous in action films. A realistic computer simulation of this powerful event would be cheaper, quicker, and much less complicated than safely creating the real thing. The immense energy released by a detonation creates a discontinuous localized increase in pressure and temperature. Physicists and engineers have shown that the dissipation of this concentration of energy, which creates all the visible effects, adheres closely to the compressible Navier-Stokes equation. This program models the most noticeable of these results. In order to simulate the pressure and temperature changes in the environment, a three dimensional grid is placed throughout the area around the detonation and a discretized version of the Navier-Stokes equation is applied to the resulting voxels. Objects in the scene are represented as rigid bodies that are animated by the forces created by varying pressure on their hulls. Fireballs, perhaps the most awe-inspiring side effects of an explosion, are simulated using massless particles that flow out from the center of the blast and follow the currents created by the dissipating pressure. The results can then be brought into Maya for evaluation and tweaking.

Astronomical images taken by ground-based telescopes are subject to aberrations induced by the Earth's atmosphere. Adaptive optics (AO) provides a real-time solution to compensate for aberrated wavefronts. The University of Canterbury would like to install an AO system on the 1-m McLellan telescope at Mount John University Observatory (MJUO). The research presented in this thesis is the first step towards this goal. To design an effective AO system it is important to understand the characteristics of the optical turbulence present at a site. Scintillation detection and ranging (SCIDAR) is a remote sensing method capable of measuring the refractive index structure constant, Cn2(h), and the wind velocity profile, V(h). The dominant near ground turbulence (NGT) at MJUO required the use of both pupil-plane and generalised SCIDAR. A purpose-built SCIDAR system was designed and constructed at low cost, using primarily off-the-shelf components. UC-SCIDAR saw first light at MJUO in 2003, and has since undergone several revisions. The current version employs two channels for simultaneous pupil-plane and generalised SCIDAR measurements, and is very portable. Through the use of a different mounting plate the system could be easily placed onto any telescope. Cn2(h) profiling utilised standard analysis techniques. V(h) profiling using data from a 1-m telescope is not common, and existing analysis techniques were extended to provide meaningful V(h) profiles, via the use of partial triplet analysis. Cn2(h) profiling between 2005 and 2007 indicate strong NGT and a weak turbulent layer located at 12 - 14 km above sea level, associated with the tropopause region. During calm weather conditions, an additional layer was detected at 6 - 7 km above sea level. V(h) profiles suggest that the tropopause layer velocity is nominally 12 - 30 m/s, and that NGT velocities range from 2 m/s to over 20 m/s, dependent on weather. Little seasonal variation was detected in either Cn2(h) or V(h) profiles. The average coherence length, $r_0$, was found to be 12+-5 cm and 7+-1 cm for pupil-plane and generalised measurements respectively, for a wavelength of 589 nm. The average isoplanatic angle, $\theta_0$, was 1.5+-0.5 arcseconds and 1.1+-0.4 arcseconds for pupil-plane and generalised profiles respectively. No seasonal trends could be established in the measurements for the Greenwood frequency, $f_G$, due to gaps present in the V(h) profiles obtained. A modified Hufnagel-Valley (HV) model was developed to describe the Cn2(h) profiles at MJUO. The estimated $r_0$ from the model is 6 cm for a wavelength of 589 nm, corresponding to an uncompensated angular resolution, $\theta_{res}$, of 2.5 arcseconds. $\theta_0$ is 0.9 arcseconds. A series of V(h) models were developed, based on the Greenwood wind model with an additional Gaussian peak located at low altitudes, to encompass the various V(h) profiles seen at MJUO. Using the modified HV model for Cn2(h) profiles and the suggested model for V(h) profiles in the presence of moderate ground wind speeds, $f_G$ is estimated at 79 Hz. The Tyler frequency, $f_T$, is estimated at 11 Hz. Due to financial considerations, it is suggested that the initial AO design for MJUO focuses on the correction of tip/tilt only, utilising self-guiding, as it is unlikely that any suitable guide stars would be sufficiently close to the science object. The low $f_T$ suggests that an AO system with a bandwidth in the order of 60 Hz would be adequate for tip/tilt correction.