Evaluating methods for controlling depth perception in stereoscopic cinematography.

Existing stereoscopic imaging algorithms can create static stereoscopic images with perceived depth control function to ensure a compelling 3D viewing experience without visual discomfort. However, current algorithms do not normally support standard Cinematic Storytelling techniques. These techniques, such as object movement, camera motion, and zooming, can result in dynamic scene depth change within and between a series of frames (shots) in stereoscopic cinematography. In this study, we empirically evaluate the following three types of stereoscopic imaging approaches that aim to address this problem. (1) Real-Eye Configuration: set camera separation equal to the nominal human eye interpupillary distance. The perceived depth on the display is identical to the scene depth without any distortion. (2) Mapping Algorithm: map the scene depth to a predefined range on the display to avoid excessive perceived depth. A new method that dynamically adjusts the depth mapping from scene space to display space is presented in addition to an existing fixed depth mapping method. (3) Depth of Field Simulation: apply Depth of Field (DOF) blur effect to stereoscopic images. Only objects that are inside the DOF are viewed in full sharpness. Objects that are far away from the focus plane are blurred. We performed a human-based trial using the ITU-R BT.500-11 Recommendation to compare the depth quality of stereoscopic video sequences generated by the above-mentioned imaging methods. Our results indicate that viewers' practical 3D viewing volumes are different for individual stereoscopic displays and viewers can cope with much larger perceived depth range in viewing stereoscopic cinematography in comparison to static stereoscopic images. Our new dynamic depth mapping method does have an advantage over the fixed depth mapping method in controlling stereo depth perception. The DOF blur effect does not provide the expected improvement for perceived depth quality control in 3D cinematography. We anticipate the results will be of particular interest to 3D filmmaking and real time computer games

Coannihilation with a chargino and gauge boson pair production at one-loop

We present a complete calculation of the electroweak one-loop corrections to the relic density within the MSSM framework. In the context of the neutralino as dark matter candidate, we review different scenarios of annihilation and coannihilation with a chargino. In particular we investigate predictions for the annihilation into gauge boson pairs for different kinds of neutralino: bino-, wino- and higgsino-like. We present some interesting effects which are not present at tree-level and show up at one-loop. To deal with the large number of diagrams occuring in the calculations, we have developed an automatic tool for the computation at one-loop of any process in the MSSM. We have implemented a complete on-shell gauge invariant renormalization scheme, with the possibility of switching to other schemes. We emphasize the variations due to the choice of the renormalization scheme, in particular the one-loop definition of the parameter tan(beta).Comment: 4 pages, 5 figures, to appear in the proceedings of the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions (SUSY09), Boston, USA, 5-10 June, 200

Energy and momentum relaxation dynamics of hot holes in modulation doped GaInNAs/GaAs quantum wells

We present the studies of energy and momentum relaxation dynamics of nonequilibrium holes in GaxIn1−xNyAs1−y/GaAs quantum well modulation doped with Be. Experimental results show that the real-space transfer (RST) of hot holes occurs via thermionic emission from the high-mobility GaInNAs quantum wells into the low-mobility GaAs barriers at a threshold electric field of F ∼ 6 kV/cm at T = 13 K. At this field the hole drift velocity saturates at vd ∼ 1×107 cm/s. A slight increase in the field above the threshold leads to the impact ionization of acceptors in the barriers by the nonequilibrium holes. We observe and model theoretically a negative differential mobility effect induced by RST that occurs at an electric field of F ∼ 7 kV/cm. The observed current surge at electric fields above 7 kV/cm is attributed to the hole multiplication induced by shallow impurity breakdown in the GaAs barrier and impact ionization in the high-field domain regime associated with the packet of RST of holes in the well

Simulation of Unsteady Aerdynamic Load for Rigid Coaxial Rotor in Forward Flight with Vortex Particle Method

Co-axial rotor systems are frequently used for high-speed helicopters. Nevertheless, issues related to rotor-head drag, aerodynamic performance and vibration should also be considered. Simulating the unsteady aerodynamic loads for a rigid coaxial rotor, including the aerodynamic interactions between rotors and rotor blades, is an essential part of analyzing their vibration characteristics. In this paper, an unsteady aerodynamic analysis based on the vortex-lattice method is presented. In this method, a reversed flow model on the retreating side of the coaxial rotor is proposed based on the unsteady panel method. To account for reversed flow, shedding a vortex from the leading-edge is used rather than from the trailing-edge. Moreover, vortex-blade aerodynamic interactions are modelled. The model considers the unsteady pressure term induced on a blade by tip vortices of other blades, and thus accounts for the aerodynamic interaction between the rotors and its contribution to the unsteady airloads. Coupling the reversed flow model and the vortex-blade aerodynamic interaction model with a viscous vortex particle method is used to simulate the complex wake of the coaxial rotor, closing the loop in modelling aerodynamic interactions of coaxial rotors. Following this, the unsteady aerodynamic loads on the X2 coaxial rotor are simulated in forward flight, and compared with the results of PRASADUM (Parallelized Rotorcraft Analysis for Simulation And Design, developed at the University of Maryland) and CFD/CSD computations with the OVERFLOW and the CREATE-AV Helios tools. The results of the present method agree with the results of the CFD/CSD method, and compare better than the PRASADUM solutions. Furthermore, the influence of the aerodynamic interaction between the coaxial rotors on the unsteady airloads, frequency, wake structure, induced flow and force distributions are analyzed. Additionally, the results are also compared against computation for a single rotor case, simulated at similar conditions as the coaxial rotor. It is shown that the effect of tip vortex interaction plays a significant role in unsteady airloads of coaxial rotors at low-speeds, while the rotor blade passing effect is obvious strengthened at high-speed

Identification and adaptive control of a high-contrast focal plane wavefront correction system

All coronagraphic instruments for exoplanet high-contrast imaging need wavefront correction systems to reject optical aberrations and create sufficiently dark holes. Since the most efficient wavefront correction algorithms (controllers and estimators) are usually model-based, the modeling accuracy of the system influences the ultimate wavefront correction performance. Currently, wavefront correction systems are typically approximated as linear systems using Fourier optics. However, the Fourier optics model is usually biased due to inaccuracies in the layout measurements, the imperfect diagnoses of inherent optical aberrations, and a lack of knowledge of the deformable mirrors (actuator gains and influence functions). Moreover, the telescope optical system varies over time because of instrument instabilities and environmental effects. In this paper, we present an expectation-maximization (E-M) approach for identifying and real-time adapting the linear telescope model from data. By iterating between the E-step (a Kalman filter and a Rauch smoother) and the M-step (analytical or gradient-based optimization), the algorithm is able to recover the system even if the model depends on the electric fields, which are unmeasurable hidden variables. Simulations and experiments in Princeton's High Contrast Imaging Lab demonstrate that this algorithm improves the model accuracy and increases the efficiency and speed of the wavefront correction

Relic density at one-loop with gauge boson pair production

We have computed the full one-loop corrections (electroweak as well as QCD) to processes contributing to the relic density of dark matter in the MSSM where the LSP is the lightest neutralino. We cover scenarios where the most important channels are those with gauge boson pair production. This includes the case of a bino with some wino admixture, a higgsino and a wino. In this paper we specialise to the case of light dark matter much below the TeV scale. The corrections can have a non-negligible impact on the predictions and should be taken into account in view of the present and forthcoming increasing precision on the relic density measurements. Our calculations are made with the help of \SloopS, an automatic tool for the calculation of one-loop processes in the MSSM. The renormalisation scheme dependence of the results as concerns \tgb is studied.Comment: 25 pages, 10 figures, Citations adde