Determining the galactic mass distribution using tidal streams from globular clusters

We discuss how to use tidal streams from globular clusters to measure the mass distribution of the Milky Way. Recent proper motion determinations for globular clusters from plate measurements and Hipparcos astrometry provide several good candidates for Galactic mass determinations in the intermediate halo, far above the Galactic disk, including Pal 5, NGC 4147, NGC 5024 (M53) and NGC 5466; the remaining Hipparcos clusters provide candidates for measurements several kpc above and below the disk. These clusters will help determine the profile and shape of the inner halo. To aid this effort, we present two methods of mass determination: one, a generalization of rotation-curve mass measurements, which gives the mass and potential from complete position-velocity observations for stream stars; and another using a simple chi^2 estimator, which can be used when only projected positions and radial velocities are known for stream stars. We illustrate the use of the latter method using simulated tidal streams from Pal 5 and find that fairly accurate mass determinations are possible even for relatively poor data sets. Follow-up observations of clusters with proper motion determinations may reveal tidal streams; obtaining radial velocity measurements would enable accurate measurements of the mass distribution in the inner Galaxy.Comment: 21 pages, 6 figures, published in A

Comparison of Decision Rules for Subsurface Drip Irrigation Practices Using a Nonlinear Mathematical Programming Model

A comparison of decision rules has been made for case studies of corn production using subsurface drip irrigation under three agricultural management practices (no irrigation, uniform irrigation, and variable rate irrigation). The uniform irrigation strategy appeared to perform the best than the other two management practices under different risk scenarios.corn production, mathematical programming, profitability, risk management, subsurface drip irrigation, variable rate irrigation, Farm Management,

Brush Plated Copper Gallium Sulphide Films and their Properties

Copper gallium sulphide films were deposited for the first time by the brush plating technique at different electrolyte temperatures in the range of 30°C - 80°C and at a constant deposition current density of 5.0 mA cm-2. X-ray diffractograms of the films are single phase with chalcopyrite structure. EDAX measurements indicated that the Cu/Ga ratio decreased from 1.29 to 1.00 as the electrolyte temperature increased from 30°C - 80°C. The grain size increased with increase of electrolyte temperature. The grain size increases from 100 nm to 300 nm as the electrolyte temperature increases

Carrier Transport in High Mobility InAs Nanowire Junctionless Transistors

Ability to understand and model the performance limits of nanowire transistors is the key to design of next generation devices. Here, we report studies on high-mobility junction-less gate-all-around nanowire field effect transistor with carrier mobility reaching 2000 cm2/V.s at room temperature. Temperature-dependent transport measurements reveal activated transport at low temperatures due to surface donors, while at room temperature the transport shows a diffusive behavior. From the conductivity data, the extracted value of sound velocity in InAs nanowires is found to be an order less than the bulk. This low sound velocity is attributed to the extended crystal defects that ubiquitously appear in these nanowires. Analyzing the temperature-dependent mobility data, we identify the key scattering mechanisms limiting the carrier transport in these nanowires. Finally, using these scattering models, we perform drift-diffusion based transport simulations of a nanowire field-effect transistor and compare the device performances with experimental measurements. Our device modeling provides insight into performance limits of InAs nanowire transistors and can be used as a predictive methodology for nanowire-based integrated circuits.Comment: 22 pages, 5 Figures, Nano Letter

Does forest type classification reflect spatial dynamics of vegetation? An analysis using GIS techniques

The existing methods of classification of forest vegetation rely more on the structure and composition of tree vegetation with little information derived from other layers. We suggest that any classificatory process of forest vegetation should consider the spatial dynamics of all the three layers namely, tree, shrub and herb. In this paper we have attempted to offer an objective method of classifying the vegetation at all the three layers utilizing GIS and multivariate statistical tools. Unlike the existing techniques, our method views the forest as a continuously changing mosaic of vegetation and not as an assemblage of discrete patches. Our study suggests that understanding the spatial dynamics of vegetation at one layer may not reflect that at others. Further, as an alternate to the existing methods, we also develop a continuum map of biodiversity of the forest that offers. the conservation value of each patch, an element that IS not conveyed in the existing classificatory processes

Development of three dimensional constitutive theories based on lower dimensional experimental data

Most three dimensional constitutive relations that have been developed to describe the behavior of bodies are correlated against one dimensional and two dimensional experiments. What is usually lost sight of is the fact that infinity of such three dimensional models may be able to explain these experiments that are lower dimensional. Recently, the notion of maximization of the rate of entropy production has been used to obtain constitutive relations based on the choice of the stored energy and rate of entropy production, etc. In this paper we show different choices for the manner in which the body stores energy and dissipates energy and satisfies the requirement of maximization of the rate of entropy production that leads to many three dimensional models. All of these models, in one dimension, reduce to the model proposed by Burgers to describe the viscoelastic behavior of bodies.Comment: 23 pages, 6 figure