Subcentimeter-size particle distribution functions in planetary rings from Voyager radio and photopolarimeter occultation data

Analysis of measurements of the scattered and direct components of Voyager 1 radio occultation signals at 3.5 and 13 cm wavelengths yield estimates of the distribution functions of supracentimeter-size particles and thickness of relatively broad regions in Saturn's rings. If mearurements of signal amplitude at a shorter wavelength are combined with the previously analyzed data, the shape of the distribution functions characterizing the smaller particles can be constrained. If size distributions of arbitrary form were considered, many solutions are found that are consistent with the three available observations of signal amplitude. The best-fit power law was calculated to the three observations at three wavelengths for several of the embedded Saturn ringlets. Mie scattering theory predicts that the measured phase of the radio occultation signal is highly sensitive to particles ranging from 0.1 to 1.0 wavelengths in size, thus additional constraints on the subcentimeter-size distribution functions for both the Saturn and Uranus rings can in principle be derived from radio phase measurements

Radio Occultation Investigation of the Rings of Saturn and Uranus

The proposed work addresses two main objectives: (1) to pursue the development of the random diffraction screen model for analytical/computational characterization of the extinction and near-forward scattering by ring models that include particle crowding, uniform clustering, and clustering along preferred orientations (anisotropy). The characterization is crucial for proper interpretation of past (Voyager) and future (Cassini) ring, occultation observations in terms of physical ring properties, and is needed to address outstanding puzzles in the interpretation of the Voyager radio occultation data sets; (2) to continue the development of spectral analysis techniques to identify and characterize the power scattered by all features of Saturn's rings that can be resolved in the Voyager radio occultation observations, and to use the results to constrain the maximum particle size and its abundance. Characterization of the variability of surface mass density among the main ring, features and within individual features is important for constraining the ring mass and is relevant to investigations of ring dynamics and origin. We completed the developed of the stochastic geometry (random screen) model for the interaction of electromagnetic waves with of planetary ring models; used the model to relate the oblique optical depth and the angular spectrum of the near forward scattered signal to statistical averages of the stochastic geometry of the randomly blocked area. WE developed analytical results based on the assumption of Poisson statistics for particle positions, and investigated the dependence of the oblique optical depth and angular spectrum on the fractional area blocked, vertical ring profile, and incidence angle when the volume fraction is small. Demonstrated agreement with the classical radiative transfer predictions for oblique incidence. Also developed simulation procedures to generate statistical realizations of random screens corresponding to uniformly packed ring models, and used the results to characterize dependence of the extinction and near-forward scattering on ring thickness, packing fraction, and the ring opening angle

A procedure to analyze nonlinear density waves in Saturn's rings using several occultation profiles

Cassini radio science experiments have provided multiple occultation optical depth profiles of Saturn's rings that can be used in combination to analyze density waves. This paper establishes an accurate procedure of inversion of the wave profiles to reconstruct the wave kinematic parameters as a function of semi-major axis, in the nonlinear regime. This procedure is achieved from simulated data in the presence of realistic noise perturbations, to control the reconstruction error. By way of illustration we have applied our procedure to the Mimas 5:3 density wave. We were able to recover precisely the kinematic parameters from the radio experiment occultation data in most of the propagation region; a preliminary analysis of the pressure-corrected dispersion allowed us to determine new but still uncertain values for the opacity ($K\simeq 0.02$ cm$^2$/g) and velocity dispersion of ($c_o\simeq 0.6$ cm/s) in the wave region. Our procedure constitutes the first step in our planned analysis of the density waves of Saturn's rings. It is very accurate and efficient in the far-wave region. However, improvements are required within the first wavelength. The ways in which this method can be used to establish diagnostics of ring physics are outlined.Comment: 50 pages,13 figures, 2 tables. Published in Icarus

Some biological characteristics of the Batrachedra amydraula Meyrick (Lepidoptera: Batrachedridae) on main varieties of dry and semi-dry date palm of Iran

Although Iran is the leading producer of dates in the world, only 10% of its product is exported. One of the factors which limits exportation is postharvest pests. Lesser date moth (Batrachedra amydraula) is one of these postharvest pests. This pest is found in all date palm plantations of Iran. The biology of this pest has not been studied under laboratory conditions on main varieties of stored date in Iran. In this research some biological characteristics including survivorship, developmental time, fecundity, oviposition and postoviposition period, and longevity of adults on date palm varieties Zahedi, Ghasb, Rabbi, Deyri and a semi-artificial diet were studied. All experiments carried out at constant temperature room (30 ± 0.5 °C and 55 ± 5% r.h.). Highest survivorship of egg and combined larval and pupal stages were 86 and 85% respectively on semi-artificial diet. Shortest total development time from egg to adult was 43 days for males and 43 days for females on semi-artificial diet. Longest total development time was 69 days for male and 65 days for female on Ghasb variety. The highest (45 eggs per female) and lowest (25 eggs per female) fecundity occurred on the Deyri variety and semi-artificial diet, respectively. Results of this study would be useful for making pest management decisions in date palm storage.Keywords: Lesser date moth, Batrachedra amydraula, Biology, Date pal

An actively constrained two degree-of-freedom manipulator for passive deployment applications

A two degree-of-freedom manipulator using actively constrained revolute joints is presented in this paper. Each revolute joint drive mechanism consists of two motor-driven worms coupled to a single worm wheel. A mathematical model of the manipulator system is used in order to develop a computed-torque control algorithm. Experimental results show that the position of the end-effector can be successfully controlled to track a path generated from a user-input force command signal while cancelling backlash at the gear interface. This system has been designed for the purpose of following a predefined path under the direct physical control of the user. The joint mechanism and control strategy used in this paper allow for backlash to be continuously cancelled. The safety of the user is ensured by enabling joint motions only if a user force is applied, and this force is in a direction that allows the controller to restrict joint motion along a predefined path

Genetic programming for brick's chemical analysis modelling

This study is part of the search for a sediment management methodology and the basic material that is designed for the manufacture of fired brick, in which we tackle the problem of choosing the mud samples from dredging the Algerian dams in particular (Bouhanifia dam western Algeria) and the choice of clay that comes from different deposits. We propose an approach for sampling using a computer optimization model that allows solving and optimizing a characterization to retain the best adapted sample (chemically) using the genetic algorithm.Keywords: Sludge- Dredging- Sample- Chemical Characterization- Brick-Optimization Methods- Genetic Algorithm

Thanatourism, Caminata Nocturna, and the Complex Geopolitics of Mexico’s Parque EcoAlberto

This article provides readers with a critical analysis of Mexico’s Parque EcoAlberto. Utilizing some of the theoretical work of interdisciplinary scholars who are interested in the study of “thanatourism,” the authors illustrate how this park, with its Caminata Nocturna (night hike), is much more than simply a “dark” tourist attraction that deters those who might travel North to the U.S. border. This study shows how the indigenous Hñähñú in Mexico have to confront a host of symbolic and material forces that are sometimes hidden in the patriotic metanarratives that swirl around this park

Electrochemical Performance of Laser Modified Zinc Electrode

In this work CO2 laser has been utilized to produce textured surface in zinc foil to use in electrochemical cells as a cathode, the modified surface was obtained by making two parallel lines in 1mm, using CO2 laser with (?=10600nm) and power of 90 watts and 10mm/s speed. The experimental evidence of the effect of surface texturing on the performance of the electrochemical cell was demonstrated and investigated. The results show considerable increase in cell voltage with the textured cathode comported to the planar one, also the performance of cell with the textured cathode is more stable

Electrochemical Performance of Laser Modified Zinc Electrode

In this work CO2 laser has been utilized to produce textured surface in zinc foil to use in electrochemical cells as a cathode, the modified surface was obtained by making two parallel lines in 1mm, using CO2 laser with (?=10600nm) and power of 90 watts and 10mm/s speed. The experimental evidence of the effect of surface texturing on the performance of the electrochemical cell was demonstrated and investigated. The results show considerable increase in cell voltage with the textured cathode comported to the planar one, also the performance of cell with the textured cathode is more stable

Drilling resistance: A method to investigate bone quality

Purpose: Bone drilling is a major part of orthopaedic surgery performed during the internal fixation of fractured bones. At present, information related to drilling force, drilling torque, rate of drill-bit penetration and drill-bit rotational speed is not available to orthopaedic surgeons, clinicians and researchers as bone drilling is performed manually. Methods: This study demonstrates that bone drilling force data if recorded in-vivo, during the repair of bone fractures, can provide information about the quality of the bone. To understand the variability and anisotropic behaviour of cortical bone tissue, specimens cut from three anatomic positions of pig and bovine were investigated at the same drilling speed and feed rate. Results: The experimental results showed that the drilling force does not only vary from one animal bone to another, but also vary within the same bone due to its changing microstructure. Drilling force does not give a direct indication of bone quality; therefore it has been correlated with screw pull-out force to provide a realistic estimation of the bone quality. A significantly high value of correlation (r2 = 0.93 for pig bones and r2 = 0.88 for bovine bones) between maximum drilling force and normalised screw pull-out strength was found. Conclusions: The results show that drilling data can be used to indicate bone quality during orthopaedic surgery