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In a recent publication it has been shown that vortex cooling takes place as rotational work is extracted from pressurized gas (Polihronov and Straatman. Phys. Rev. Lett. 109, 054504 (2012)). We show that such rotating systems can be treated as systems with variable mass and thus introduce a rotational analog of the familiar rectilinear rocket motion. In this manner, such propulsion systems are analogous to radial inflow turbines. PACS Nos.: 47.32.Ef, 47.10.ab, 05.70.-a, 45.40.Gj. Il a ete demontre dans une publication recente qu'un refroidissement par vortex apparait lorsque de l'energie rotationnelle est extraite d'un gaz pressurise (Polihronov et Straatman. Phys. Rev. Lett. 109, 054504 (2012)). Nous demontrons ici qu'un tel systeme en rotation peut etre vu comme une masse variable et, de ce fait, qu'il introduit un analogue rotationnel au mouvement rectiligne familier d'une fusee. Ainsi, ces systemes de propulsion sont analogues a des turbines radiales. [Traduit par le Redaction], 1. Introduction Recently, it was shown that vortex cooling occurs when rotational work is extracted from gas under pressure. To explain the lost energy, it was proposed that angular propulsion [...]

We consider the problem of seeking the source of a scalar signal using an autonomous vehicle modeled as the nonholonomic unicycle. The vehicle does not have the capability of sensing its position or the position of the source but is capable of sensing the scalar signal originating from the source. The signal field is assumed to decay away from the position of the source but the vehicle does not have the knowledge of the functional form of the field. We employ extremum seeking to steer the vehicle to the source. Our control strategy keeps the forward velocity constant and tunes the angular velocity, a setting suitable for most autonomous vehicles, including aerial ones. Because of the constant forward velocity constraint, after it has converged near the source, the vehicle exhibits extremely interesting and complex motions. Using averaging theory, we prove local exponential convergence to an "orbit-like" attractor around the source. We also present a thorough analysis of non-local behaviors and attractors that the vehicle can exhibit near the source. The richness and complexity of behaviors makes only some of them amenable to analysis, whereas others are illustrated through a carefully laid out simulation study. Index Terms--Nonholonomic unicycle.

Operational gravity wave parameterization schemes in GCMs are columnar; that is, they are based on a ray-tracing model for gravity wave propagation that neglects horizontal propagation as well as refraction by horizontally inhomogeneous basic flows. Despite the enormous conceptual and numerical simplifications that these approximations provide, it has never been clearly established whether horizontal propagation and refraction are indeed negligible for atmospheric climate dynamics. In this study, a three-dimensional ray-tracing scheme for internal gravity waves that allows wave refraction and horizontal propagation in spherical geometry is formulated. Various issues to do with three-dimensional wave dynamics and wave-mean interactions are discussed, and then the scheme is applied to offline computations using GCM data and launch spectra provided by an operational columnar gravity wave parameterization scheme for topographic waves. This allows for side-by-side testing and evaluation of momentum fluxes in the new scheme against those of the parameterization scheme. In particular, the wave-induced vertical flux of angular momentum is computed and compared with the predictions of the columnar parameterization scheme. Consistent with a scaling argument, significant changes in the angular momentum flux due to three-dimensional refraction and horizontal propagation are confined to waves near the inertial frequency.

The diurnal and subdiurnal variations of the mass and wind terms of the axial atmospheric angular momentum (AAM) are explored using a 1-yr integration of the Laboratoire de M6t6orologie Dynamique (LMDz) GCM, twelve 10-day ECMWF forecasts, and some ECMWF analysis products. In these datasets, the wind and mass AAMs present diurnal and semidiurnal oscillations for which tendencies far exceed the total torque. In the LMDz GCM, these diurnal and semidiurnal oscillations are associated with axisymmetric (s = 0) and barotropic circulation modes that resemble the second gravest (n = 2) eigensolution of Laplace's tidal equations. This mode induces a Coriolis conversion from the wind AAM toward the mass AAM that far exceeds the total torque. At the semidiurnal period, this mode dominates the axisymmetric and barotropic circulation. At the diurnal period, this n = 2 mode is also present, but the barotropic circulation also presents a mode resembling the first gravest n = 1 eigensolution of the tidal equations. This last mode does not produce anomalies in the mass and wind AAMs. A shallow-water axisymmetric model driven by zonal mean zonal forces, for which the vertical integral equals the zonal mean zonal stresses issued from the GCM, is then used to interpret these results. This model reproduces well the semidiurnal oscillations in mass and wind AAM, and the semidiurnal mode resembling the n = 2 eigensolution that produces them, when the forcing is distributed barotropically in the vertical direction. This model also reproduces diurnal modes resembling the n = l and n = 2 eigensolutions when the forcings are distributed more baroclinically. Among the dynamical forcings that produce these modes of motion, it is found that the mountain forcing and the divergence of the AAM flux are equally important and are more efficient than the boundary layer friction. In geodesy, the large but opposite signals in the mass and wind AAM due to the n = 2 modes can lead to large errors in the evaluation of the AAM budget. The n = 2 responses in surface pressure can affect the earth ellipcity, and the n = 1 diurnal response can affect the geocenter position. For the surface pressure tide, the results suggest that the dynamical forcings of the zonal-mean zonal flow are a potential cause for its s = 0 component.

The use of the pressure distribution at the transducer surface to evaluate degradation of therapeutic transducers that are not visually apparent is studied. It is found that pressure amplitude and phase distributions at the transducer surface determined using the angular spectrum can be used for assessing the degradation of therapeutic transducers.

The analysis of radar observations of the asteroid 4179 Toutatis by Hudson and Ostro (1995, Science 270, 84-86) yielded a complex spin state. We revisit the visible lightcurve data on Toutatis (Spencer et al. 1995, Icarus 117, 71-89) to explore the feasibility of using a rotational lightcurve to recover the signature of an excited spin state. For this, we apply Fourier transform and CLEAN algorithm (WindowCLEAN). WindowCLEAN yields clear and precise frequency signatures associated with the precession of the long axis about the total angular momentum vector and a combination of this precession and rotation about the long axis. For a long-axis mode state, our periodicities for Toutatis yield a mean long-axis precession period, [P.sub.[phi]], of 7.38 days and a rotation period around the long axis, [P.sub.[psi]], of 5.38 days, which compare well with the respective periods of 7.42 and 5.37 days derived by Ostro et al. (1999, Icarus 137, 122-139) and represent an independent confirmation of these values. We explain why the dramatic change in the Earth-Toutatis-Sun geometry during the time that the lightcurve was obtained has little effect on the final results obtained. Using the Toutatis example as a guide, we discuss the capabilities as well as the limitations on deriving information about complex spin states from asteroidal lightcurves. Key Words: asteroids; rotational dynamics; 4179 Toutatis.

Snow-covered surfaces have a very high surface albedo, thereby allowing little energy to be absorbed by the snowpack. As the snowpack ages and/or begins to melt, the snow albedo decreases and more solar energy is absorbed by the snowpack. Therefore, accurate estimation of snow albedo is essential for monitoring the state of the cryosphere. This paper examines the retrieval of snow albedo using data from the Multi-angle Imaging SpectroRadiometer (MISR) instrument over the Greenland ice sheet. Two different methods are developed and examined to derive the snow albedo: one based on the spectral information from MISR and one utilizing the angular information from the MISR instrument. The latter method is based on a statistical relationship between in situ albedo measurements and the MISR red channel reflectance at all MISR viewing angles and is found to give good agreement with the ground-based measurements. Good agreement is also found using the spectral information, although the method is more sensitive to instrument calibration, snow bidirectional reflectance distribution function (BRDF) models, and narrowband-to-broadband relationships. In general, using either method retrieves snow surface albedo values that are within about 6 % of that measured at the stations in Greenland. Index Terms--Greenland, Multi-angle Imaging SpectroRadiometer (MISR), snow albedo.

Research analyzes the rotational bands of weakly deformed nuclei at high angular momentum. Magnetic rotation data point out to the quantized rotation of the anisotropic current in a near spherical nucleus.

The characterization of the chemical and physical reaction dynamics involved in dissociative states of molecules and ions employing coincidence experimental approach is reviewed. Energy- and angle-resolved measurements of photoelectron and photofragment angular distribution in dissociative photodetachment, photoionization, and three-body dissociation processes are discussed.

Polarized light is a phenomenon familiar to anyone with a pair of polaroid sunglasses. Optical components that change the nature of the polarization from linear to circular are common in any undergraduate laboratory. Probably only physicists know that circularly polarized light carries with it an angular momentum that results from the spin of individual photons. Few physicists realize, how, ever, that a light beam can also carry orbital angular momentum associated not with photon spin but with helical wavefronts. Beams of this type have been studied only over the last decade. In many instances orbital angular momentum behaves in a similar way to spin. But this is not always so: orbital angular momentum has its own distinctive properties and its own distinctive optical components. This article outlines the general behaviour of such beams; how they can be used to rotate microscopic particles; how they interact with nonlinear materials; the role they play in atom-light interactions and how the rotation of such beams results in a measurable frequency shift.

As in quantum mechanics the operators of different Cartesian components of the angular momentum do not commute these observables cannot simultaneously have sharp values. In this paper we present a simple method to calculate the probability distributions for the measurements of angular momentum components other than (mathematical expression not reproducible in ASCII) in eigenstates of (mathematical expression not reproducible in ASCII) with an arbitrary value of (mathematical expression not reproducible in ASCII), where (mathematical expression not reproducible in ASCII) is the eigenvalue of (mathematical expression not reproducible in ASCII). Surprisingly this method is not found in textbooks, where usually the case (mathematical expression not reproducible in ASCII) is presented in discussions of Stern-Gerlach experiments. For larger values of (mathematical expression not reproducible in ASCII), the probability distributions have a comb-like structure. A detailed discussion of the quasiclassical limit (mathematical expression not reproducible in ASCII) is presented for the measurement of (mathematical expression not reproducible in ASCII). It yields rather surprising results.

Entanglement of the properties of two separated particles constitutes a fundamental signature of quantum mechanics and is a key resource for quantum information science. We demonstrate strong Einstein, Podolsky, and Rosen correlations between the angular position and orbital angular momentum of two photons created by the nonlinear optical process of spontaneous parametric down-conversion. The discrete nature of orbital angular momentum and the continuous but periodic nature of angular position give rise to a special sort of entanglement between these two variables. The resulting corretations are found to be an order of magnitude stronger than those allowed by the uncertainty principle for independent (nonentangled) particles. Our results suggest that angular position and orbital angular momentum may find important apptications in quantum information science. 10.1126/science.1190523

Quantum moment equations are used to simulate ultra-small GaAs metal semiconductor field-effect transistors to study the causes of overshoot in such devices. An electric field is observed forming around the gate of the conduction channel with electrons able to maintain low temperatures and faster movement because of the low electric field emanating from the source. Under these conditions, a very high velocity overshoot is produced. Quantum effect values which reveal its abilities to correct variations in density and potential are achieved using quantum corrections.

An apparatus can be constructed to measure angular momentum and demonstrate its conservation to a precise degree. This T-assembly spins, converting a continuous light beam into a series of pulses, which are sent to a computer. The results of the input are graphed and analyzed to determine the conservation of angular momentum between 2 trials with weights on different positions on the T-assembly.

Several modular studies are conducted to explain the energy levels and the vibration-rotation spectroscopy of the various diatomic molecules that are trapped inside the [C.sub.60] complexes. These molecules are shown to form hot bands at higher temperatures because of the appearance of the low-frequency rattling mode.

An experiment to calculate angular velocity and moment of inertia of merry-go-round, using accelerometer, is described.

Compact DiskEs (CD) rotational motion gives a model of rotational kinematics and is useful in explaining calculus. This example can also be used as a problem to be evaluated with spreadsheet with out need of calculus skills.

Local heat transfer coefficient is seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer is larger for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates.

The demonstration of the conservation of the angular momentum is shown using a thin and flexible rod, an ordinary dish, and a cheap fan. In the absence of the external torque, the angular momentum of any rotating body remains constant.

The angular velocity is an absolute or intrinsic property of a rigid body; that is, all points of a rotating rigid body have the same angular velocity. This fact is well known, but its proof is often erroneous. Here we correct two faulty proofs of this result, one in Goldstein's famous textbook and the other published nearly 30 years ago in this journal. [C] 2000 American Association of Physics Teachers.

Black holes can be described by just two fundamental characteristics: mass and spin. Astronomers have been able to measure the objects' mass for decades, by looking for gravitational effects on [...]