Design and Characterization of Fabry–Pérot MEMS-Based Short-Wave Infrared Microspectrometers

Microspectrometers based on the monolithic integration of a microelectromechanical system (MEMS) Fabry–Pérot filter and a Hg _x Cd_1–x Te-based infrared detector are discussed and measured results presented. The microspectrometers are designed to operate in the 1.5 μm to 2.6 μm wavelength range. Design equations are presented which account for the mechanical and optical characteristics of the device. Measurements indicate linewidths as narrow as 55 nm, switching times of 40 μs, and a tuning range of 380 nm, which is limited by snap-down. Optical characterization of the distributed Bragg mirrors and the Fabry–Pérot filter are presented, and these are shown to be in good agreement with simple first-order analytical models. Bowing of the movable Fabry–Pérot mirror due to stress gradients is identified as the dominant source of linewidth broadening.     

Tools for Performance Analysis and Design of Space–Time Block Codes

Space-time block codes (STBCs) have attracted recent interest due to their ability to take advantage of both space and time diversity to reliably transmit data over a wireless fading channel. In many cases, their design is based on asymptotically tight performance criteria, such as the worst-case pairwise error probability (PEP) or the union bound. However, these quantities fail to give an accurate performance picture, especially at low signal-to-noise ratio, because the classical union bound is known to be loose in this case. This paper develops tighter performance criteria for STBCs which yield considerably better bounds. First, the union bound is developed as the average of the exact PEPs. By noting that some of the terms in the bound are redundant, a second bound is obtained by expurgation. Since this still yields a loose bound, a tighter bound, denoted as the progressive union bound (PUB), is obtained. Because the PUB cannot be computed in closed form, in its most general case, and to avoid computing a high-dimensional numerical integration, its saddlepoint approximation is developed. In addition to the significant improvement of the PUB analysis over other bounding methods, it is also shown that codes designed to optimize the PUB can perform better than those obtained by the looser criteria     

An algorithm for optimal assignment of a wavelength in a tree topology and its application in WDM networks

In this paper, we present a polynomial time algorithm that gives an optimal solution to the routing and wavelength assignment (RWA) problem in a tree topology. One of the major design issues in wavelength-division multiplexed networks is the assignment of the limited number of wavelengths among network stations so that greater capacity can be achieved. The problem of RWA is known to be NP-hard problem. Many researchers have tackled the problem of RWA with a number of efficient heuristic algorithms. This paper presents an algorithm that optimally assigns a single wavelength to maximize one-hop traffic in a tree topology. The algorithm uses dynamic programming and is shown to be optimal with a time complexity of O(N/sup 4/). We also propose a heuristic scheme to use our optimal algorithm for wavelength assignment in a general graph. The heuristic works on the tree subgraphs of a given graph and the remaining spare wavelengths can be assigned with an existing RWA policy.     

Dramatic Enhancement of Photoluminescence Quantum Yields for Surface‐Engineered Si Nanocrystals within the Solar Spectrum

Substantial improvements of the absolute photoluminescence quantum yield (QY) for surfactant‐free silicon nanocrystals (Si‐ncs) by atmospheric pressure microplasma 3‐dimensional surface engineering are reported. The effect of surface characteristics on carrier multiplication mechanisms is explored using transient induced absorption and photoluminescence QY. Surface engineering of Si‐ncs is demonstrated to lead to more than 120 times increase in the absolute QY (from 0.1% up to 12%) within an important spectral range of the solar emission (2.3–3 eV). The Si‐ncs QY is shown to be stable when Si‐ncs are stored in ethanol at ambient conditions for three months.     

Multi-objective Energy Aware Scheduling of Deadline Constrained Workflows in Clouds using Hybrid Approach

Cloud computing is undoubtedly one of the most significant advances in the domain of information technology. It facilitates elastic and on-demand provisioning of high performance computing capabilities employing pay-per-use model that has snowballed its adoption by scientists and engineers over the past few years. They often exploit workflows to represent their massive applications. Workflow scheduling in cloud has been devoted considerable investigation by researchers owing to its NP-complete nature of problem. Most of the previous studies targeted optimization of schedule length and execution cost within given deadlines/budget restrictions, or both. However, enormous energy consumption in the cloud data centers is not only negatively impacting the environment but also resulting in increased operational costs and thus cannot be ignored. Efficient scheduling strategies can significantly lessen the energy usage while complying with the user’s Quality of Service limitations. This research study proposes a Hybrid Approach for Energy aware scheduling of Deadline constrained workflows (HAED) using Intelligent Water Drops algorithm and Genetic Algorithm, which provides non-dominated solutions to the user. In particular, it focuses on multiple objectives i.e. reduction of schedule length, execution cost and energy usage within deadlines specified by the user. Its performance has been assessed on four scientific workflows from diverse domains using hypervolume and set coverage. The results achieved with the simulations demonstrate that the solutions produced by HAED are of better quality in terms of accuracy and diversity than non-dominated sorting genetic algorithm and hybrid particle swarm optimization.

     

Low complexity hybrid layered tabu-likelihood ascent search for large MIMO detection with perfect and estimated channel state information

In this work, we proposed a low-complexity hybrid layered tabu-likelihood ascent search (LTLAS) algorithm for large multiple-input multiple-output (MIMO) system. The conventional layered tabu search (LTS) approach involves many partial reactive tabu searches (RTSs), and each RTS requires an initialization and searching phase. In the proposed algorithm, we restricted the upper limit of the number of RTS operations. Once RTS operations exceed the limit, RTS will be replaced by low-complexity likelihood ascent search (LAS) operations. The block-based detection approach is considered to maintain a higher signal-to-noise ratio (SNR) detection performance. An efficient precomputation technique is derived, which can suppress redundant computations. The simulation results show that the bit error rate (BER) performance of the proposed detection method is close to the conventional LTS method. The complexity analysis shows that the proposed method has significantly lower computational complexity than conventional methods. Also, the proposed method can reduce almost 50% of real operations to achieve a BER of 10⁻³.     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal,India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50,?250 or 500?µg?l^?1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642?µg?kg^?1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000?µg?day^?1 for initial arsenic concentrations in the cooking water of 50, 250 and 500?µg?arsenic?l^?1, respectively, compared with the tolerable daily intake which is 150?µg?day^?1.     

Inactivation of Surface-Borne Microorganisms and Increased Germination of Seed Specimen by Cold Atmospheric Plasma

Sustaining the quality of seeds is a major task in attempting to supply nutrition to the growing world population. In this study, the seeds of Cicer arietinum were exposed to cold atmospheric plasma (CAP). A significant reduction of the natural microbiota attached to the seed surface was observed for increasing CAP treatment times—2 and 5 min were sufficient to achieve a 1 and 2 log reductions, respectively. Furthermore a 1 min CAP treatment showed a strongly improved seed germination (89.2 %), speed of germination (7.1?±?0.1 seeds/day), and increased seed vigor, beside a decrease in the mean germination time (2.7 days) compared with controls. The roughness profile of the seed cotyledon was altered significantly, only in case of longer treatment times from 5 min. These results suggest that CAP technology has the potentiality to reduce health risks associated with contaminated seeds, while improving food quality.     

Anisotropy of X-ray structural parameters of the three phase model in cellulose I

Anisotropy of X-ray structural parameters of the three phase model proposed by Mitra and Mukherjee (ref.2), has been investigated in the case of cellulose fibres of ramie, hemp and jute. The structural parameters have been determined separately from each of the observable equatorial reflections. It has been found that the parameter degree of crystallinity as defined in the model is in fact anisotropic at least in the samples studied. The parameter degree of paracrystallinity introduced by Mitra and Mukherjee was also found to be anisotropic. Several important correlations between the structural parameters have been drawn. It has been observed, in agreement with the recent findings of Hosemann and Balta Calleja (ref.10) that the greater the paracrystalline distortion, the smaller the ‘paracrystallite size’.