4,603 research outputs found
Anomalous transport and phonon renormalization in a chain with transverse and longitudinal vibrations
We study thermal transport in a chain of coupled atoms, which can vibrate in
longitudinal as well as transverse directions. The particles interact through
anharmonic potentials upto cubic order. The problem is treated quantum
mechanically. We first calculate the phonon frequencies self-consistently
taking into account the anharmonic interactions. We show that for all the
modes, frequencies must have linear dispersion with wave-vector for small
irrespective of their bare dispersions. We then calculate the phonon
relaxation rates , where is the polarization index of the
mode, in a self-consistent approximation based on second order perturbation
diagrams. We find that the relaxation rate for the longitudinal phonon,
, while that for the transverse phonon
. The consequence of these results on the thermal
conductivity of a chain of particles is that
Analysis of microsprings for calculating the force produced by microactuators
We present models of two types of microsprings namely box-spring and zig-zag spring that can be used to measure the force generated by microactuators. The spring constant for both springs is calculated by FEM using ANSYS software. In these models, the effects of short beams that act as connectors in the spring structures are considered and analyzed by changing their width. Also, from the results, we find that the box spring appears more balanced than the zig-zag spring when the force is applied in the single central direction. A series of SDAs with box spring have been fabricated and forces ofthose SDAs have been calculated
Sum Throughput Maximization in Multi-Tag Backscattering to Multiantenna Reader
Backscatter communication (BSC) is being realized as the core technology for
pervasive sustainable Internet-of-Things applications. However, owing to the
resource-limitations of passive tags, the efficient usage of multiple antennas
at the reader is essential for both downlink excitation and uplink detection.
This work targets at maximizing the achievable sum-backscattered-throughput by
jointly optimizing the transceiver (TRX) design at the reader and
backscattering coefficients (BC) at the tags. Since, this joint problem is
nonconvex, we first present individually-optimal designs for the TRX and BC. We
show that with precoder and {combiner} designs at the reader respectively
targeting downlink energy beamforming and uplink Wiener filtering operations,
the BC optimization at tags can be reduced to a binary power control problem.
Next, the asymptotically-optimal joint-TRX-BC designs are proposed for both low
and high signal-to-noise-ratio regimes. Based on these developments, an
iterative low-complexity algorithm is proposed to yield an efficient
jointly-suboptimal design. Thereafter, we discuss the practical utility of the
proposed designs to other application settings like wireless powered
communication networks and BSC with imperfect channel state information.
Lastly, selected numerical results, validating the analysis and shedding novel
insights, demonstrate that the proposed designs can yield significant
enhancement in the sum-backscattered throughput over existing benchmarks.Comment: 17 pages, 5 figures, accepted for publication in IEEE Transactions on
Communication
Atmospheric Backscatter Model Development for CO Sub 2 Wavelengths
The results of investigations into the problems of modeling atmospheric backscatter from aerosols, in the lowest 20 km of the atmosphere, at CO2 wavelengths are presented, along with a summary of the relevant aerosol characteristics and their variability, and a discussion of the measurement techniques and errors involved. The different methods of calculating the aerosol backscattering function, both from measured aerosol characteristics and from optical measurements made at other wavelengths, are discussed in detail, and limits are placed on the accuracy of these methods. The effects of changing atmospheric humidity and temperature on the backscatter are analyzed and related to the actual atmosphere. Finally, the results of modeling CO2 backscatter in the atmosphere are presented and the variation with height and geographic location discussed, and limits placed on the magnitude of the backscattering function. Conclusions regarding modeling techniques and modeled atmospheric backscatter values are presented in tabular form
Radiative capture of polarized neutrons by polarized protons
A model-independent irreducible tensor approach to p(n,gamma)d is presented
and an explicit form for the spin-structure of the matrix for the reaction is
obtained in terms of the Pauli spin-matrices for the neutron and the proton.
Expressing the multipole amplitudes in terms of the triplet --> triplet and
singlet --> triplet transitions, we point out how the initial singlet and
triplet contributions to the differential cross section can be determined
empirically.Comment: Revised version; typeset using RevTeX4; 6 pages, no figure
Phase ambiguity of the threshold amplitude in pp -> pp\pi^0
Measurements of spin observables in pp -> {\vec p}{\vec p}\pi^0 are suggested
to remove the phase ambiguity of the threshold amplitude. The suggested
measurements complement the IUCF data on {\vec p}{\vec p} -> pp\pi^0 to
completely determine all the twelve partial wave amplitudes, taken into
consideration by Mayer et.al. [15] and Deepak, Haidenbauer and Hanhart [20].Comment: 4 pages, 1 table
Groundwater markets and water use efficiency: The case of Karnataka
This study, based on primary data collected from 120 groundwater users in eastern dry zone of Karnataka compares the water use efficiency among different categories of water users, viz. well owners who do not sell water, well owners who sell water either for agricultural or non-agricultural use and water buyers (both agricultural and nonagricultural). Some of the important findings are- • The cropping pattern varies between categories, with both the sellers and buyers preferring low water intensive mulberry crop, while the self user's category grew more water intensive crops. • Farmers who sold water for non-agricultural purposes earned the highest return (because of higher end-use price) and also made the most efficient use of water. Thus, making a point that end-use pricing is a key in shaping marginal productivity of water. • Compared to the self-users, farmers selling water for either agricultural or non-agricultural purposes realized higher marginal productivity. Thus,groundwater markets acted as an effective tool in enhancing efficient use of a scarce resource.This study explores efficiency and equity in groundwater markets in the hard rock areas of Karnataka. It compares the water use efficiency of farmers using groundwater for irrigating their land and also selling it for agricultural purpose (WSA, n=30), farmers using water for irrigating their land and also selling for non-agriculture purpose (WSNA, n=15), farmers who do not either sell or buy water but use it on their farms (WO, n=30), farmers who are buying groundwater for agriculture purpose (WBA, n=30), and buyers of water for non-agriculture purpose (WBNA, n=15). The Nash equilibrium framework describing the bargaining power of buyers and sellers of groundwater is used. Sidlaghatta taluk in eastern dry agroclimatic zone (EDZ) of Karnataka is chosen because it supports intensive groundwater markets. The objective of the study is to find out water use efficiencies among different groups of water users with the hypothesis that WSNA obtain higher water use efficiency than WSA, WBA, and WO.Groundwater markets, efficiency, equity, Resource /Energy Economics and Policy,
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