Modeling Packet Delay in Multiplexed Video Traffic

In this paper a Markov chain based characterization of a single video source is used to model multiplexed video traffic and the resulting packet delay. The multiplexed video stream of statistically identical sources is represented using a reduced order approximation of the superposed Markov generator matrix. It is shown that inadequate spectral content in the single source generator matrix is manifested as an underestimate of the packet delay probabilities for the multiplexed stream. A new method for simplifying the generator matrix for the multiplexed video stream that amply models its spectral content is given. The simulated and calculated results using the aforementioned model are shown be in good agreement.     

Raman,photoluminescence analysis on Cu(InAl)Se2 thin films and the fabrication of Cu(InAl)Se2 based thin film solar cells

Cu(InAl)Se₂ (CIAS) thin films have been prepared by chemical bath deposition technique. Thickness of the prepared films has been measured by gravimetric technique. The structure, composition and optical transition as well as bandgap have been estimated by X-ray diffraction, energy dispersive X-ray analysis and spectrophotometer analysis. Raman analysis has been made on the prepared CIAS thin films to assign the fundamental lattice mode and to confirm the films crystallinity and stoichiometry. PL analysis has been carried out to find the effective mass of holes and electron, dielectric constant, the involved defects and their activation energy. Cu(InAl)Se₂-based solar cells with different types of buffer layers such as CdS, CdS:Cu, CdS:In were fabricated. The current and voltage were measured using an optical power meter and an electrometer and the fabricated solar cells were illuminated using 100 mW/cm² white light under AM1 conditions.     

An $\tilde{O}(m^{2}n)$ Algorithm for Minimum Cycle Basis of Graphs

We consider the problem of computing a minimum cycle basis of an undirected non-negative edge-weighted graph G with m edges and n vertices. In this problem, a {0,1} incidence vector is associated with each cycle and the vector space over generated by these vectors is the cycle space of G. A set of cycles is called a cycle basis of G if it forms a basis for its cycle space. A cycle basis where the sum of the weights of the cycles is minimum is called a minimum cycle basis of G. Minimum cycle basis are useful in a number of contexts, e.g. the analysis of electrical networks and structural engineering. The previous best algorithm for computing a minimum cycle basis has running time O(m ^ω n), where ω is the best exponent of matrix multiplication. It is presently known that ω<2.376. We exhibit an O(m ² n+mn ²log n) algorithm. When the edge weights are integers, we have an O(m ² n) algorithm. For unweighted graphs which are reasonably dense, our algorithm runs in O(m ^ω ) time. For any ε>0, we also design an 1+ε approximation algorithm. The running time of this algorithm is O((m ^ω /ε)log (W/ε)) for reasonably dense graphs, where W is the largest edge weight. A preliminary version of this paper appeared in Kavitha et al. (31st International Colloquium on Automata, Languages and Programming (ICALP), pp. 846–857, 2004). T. Kavitha and K.E. Paluch were in Max-Planck-Institut für Informatik, Saarbrücken, Germany, while this work was done.     

How much does guessing influence recall? Comment on Erdelyi, Finks, and Feigin-Pfau.

M. H. Erdelyi et al (see record 1989-38884-001) present evidence that variations in recall criteria can affect the number of items correctly recalled. In this comment, we (a) describe some procedural differences between their work and the earlier experiments of H. L. Roediger and D. G. Payne (see record 1986-13690-001), (b) note that their large manipulations of recall criteria produced only small effects on the amount recalled, and (c) describe recent research complementing that of Erdelyi et al. We observe that variations in recall criteria have larger effects after a 1-week delay than on an immediate test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular dynamics simulations of α- to β-poly(vinylidene fluoride) phase change by stretching and poling

The mechanism of inducing a phase change from α-poly(vinylidene fluoride) (α-PVDF) to β-PVDF is addressed using molecular dynamics simulations based on a molecular mechanics force field. The effect of applying a strain to the α-PVDF crystal along the axis of the molecules is investigated, as well as poling the crystal before or after stretching. Rather large (at least 10¹⁰ V/m) electric fields that are perpendicular to the axis of the PVDF molecules are required to induce α- to β-PVDF phase change when no strain is applied to the α-PVDF crystal. However, at a strain of 1.0475 (i.e., when the crystal is stretched by 4.75%) α-PVDF changes to a β-PVDF like structure, where the β-PVDF molecules orientate anti-parallel relative to each other. Transformation of the anti-parallel β-PVDF to β-PVDF can be induced by poling (even at the lowest electric field of 10⁵ V/m studied here) or by thermal annealing.     

Multilevel spatial modulation

In this paper, a new Multilevel Spatial Modulation technique is proposed. It combines computationally efficient multilevel oding and spatial modulation based on trellis codes to increase coding gain, diversity gain, and bandwidth efficiency. The trellis complexity of the single-stage system increases exponentially, whereas in the proposed multilevel system the complexity increases linearly. The proposed system is analyzed with optimal Viterbi and suboptimal sequential decoding algorithms. The results show that sequential decoding saves 75% of the computational power with a loss of 2 dB SNR approximately, when compared with optimal Viterbi decoding, over both fast- and slow-fading channel conditions. Since the antenna index is used as a source of information in spatial modulation, the number of antennae required increases with the throughput and packing a large number of antennas make cross-correlation unavoidable. In this paper, a low complexity modified decoding technique is also proposed for the multilevel spatial modulation system, in which the correlated received signals are equally combined and decoded by the multistage decoder using the Viterbi algorithm. This technique exploits the receiver antenna correlation and makes the decoding complexity independent of number of antennas. The simulation results indicate that the proposed low complexity algorithm gives approximately 8–10 dB gain when compared with optimal Viterbi decoder with equivalent computational complexity when the eight highly correlated signals are equally combined. This may be a suitable solution for mobile handsets where size and computational complexity are the major issues.     

Time trends in the association of ESRD incidence with area‐level poverty in the US population

The objective of this study was to examine the temporal trends of the association between area‐level poverty status and end‐stage renal disease (ESRD) incidence. We hypothesized that the association between area‐level poverty status and ESRD incidence has increased significantly over time. Patient data from the United States Renal Data System were linked with data from the 2000 and 2010 US census. Area‐level poverty was defined as living in a zip code‐defined area with ≥20% of households living below the federal poverty line. Negative binomial regression models were created to examine the association between area‐level poverty status and ESRD incidence by time period in the US adult population while simultaneously adjusting for the distribution of age, sex, and race/ethnicity within a zip code. Time was categorized as January 1, 1995 through December 31, 2004 (Period 1) and January 1, 2005 through December 31, 2010 (Period 2). The percentage of adults initiating dialysis with area‐level poverty increased from 27.4% during Period 1 to 34.0% in Period 2. After accounting for the distribution of age, sex, and race/ethnicity within a zip code, area‐level poverty status was associated with a 1.24 (95% confidence interval [CI] 1.22, 1.25)‐fold higher ESRD incidence. However, this association differed by time period with 1.04‐fold (95% CI 1.02, 1.05) higher ESRD incidence associated with poverty status for Period 2 compared with the association between ESRD and poverty status in Period 1. Area‐level poverty and its association with ESRD incidence is not static over time.     

Silicon nanowire arrays for label-free detection of DNA

Arrays of highly ordered n-type silicon nanowires (SiNW) are fabricated using complementary metal-oxide semiconductor (CMOS) compatible technology, and their applications in biosensors are investigated. Peptide nucleic acid (PNA) capture probe-functionalized SiNW arrays show a concentration-dependent resistance change upon hybridization to complementary target DNA that is linear over a large dynamic range with a detection limit of 10 fM. As with other SiNW biosensing devices, the sensing mechanism can be understood in terms of the change in charge density at the SiNW surface after hybridization, the so-called "field effect". The SiNW array biosensor discriminates satisfactorily against mismatched target DNA. It is also able to monitor directly the DNA hybridization event in situ and in real time. The SiNW array biosensor described here is ultrasensitive, non-radioactive, and more importantly, label-free, and is of particular importance to the development of gene expression profiling tools and point-of-care applications.