In-Place Stabilization of Pond Ash Deposits by Hydrated Lime Columns

Abandoned coal ash ponds cover up vast stretches of precious land and cause environmental problems. Application of suitable in situ stabilization methods may bring about improvement in the geotechnical properties of the ash deposit as a whole, converting it to a usable site. In this study, a technique of in-place stabilization by hydrated lime columns was applied to large-scale laboratory models of ash ponds. Samples collected from different radial distances and different depths of the ash deposit were tested to study the improvements in the water content, dry density, particle size distribution, unconfined compressive strength, pH, hydraulic conductivity, and leachate characteristics over a period of one year. The in-place stabilization by lime column technique has been found effective in increasing the unconfined compressive strength and reducing hydraulic conductivity of pond ash deposits in addition to modifying other geotechnical parameters. The method has also proved to be useful in reducing the contamination potential of the ash leachates, thus mitigating the adverse environmental effects of ash deposits.     

Optimal Design of a Stable Trapezoidal Channel Section Using Hybrid Optimization Techniques

A cost effective channel section for a specified flow rate, roughness coefficients, longitudinal slope, and various cost parameters can be determined using an optimization technique. However, the derived optimal channel section may not be feasible for construction because of in situ conditions. The local soil conditions may not support the optimal side slope of the channel and if constructed, the slope may fail. It is therefore necessary to also incorporate the criteria for side slope stability in designing an optimal open channel section. In this paper, a new methodology has been developed to design a stable and optimal channel section using hybrid optimization techniques. A genetic algorithm based optimization model is developed initially to determine the factor of safety of a channel slope for given soil parameters. This optimization model is then externally linked with a separate sequential quadratic programming based optimization model to evaluate the parameters of the stable and optimal channel section. Solution for various example problems incorporating different soil parameters are illustrated to demonstrate the applicability of the developed methodology.     

An Experimental Investigation on the Fabrication and Testing of Mechanical Properties of Aluminum-Silica Gel Metal Matrix Composite

A metal matrix composite (MMC) was fabricated using Al as the base metal which was reinforced by a ceramic material silica gel. This article shows detail fabrication stages in the production of MMC. The properties were considered with regard to the saturation point of the reinforcement of silica gel into the metal matrix of Al-Si alloy which was found out experimentally. Here the improvement of the mechanical properties of Al-silica gel MMC composite were studied with respect to that of pure Al-Si alloy. Different tests were conducted to show the results. Conventional ingot metallurgy with infiltration technique using vortex method had been employed in the fabrication process. The test results show that there are improvements by 17.14%, 13.46%, 11.48%, and 18.18% on compressive strength, impact strength, Brinell hardness value, and Rockwell hardness no respectively of Al-silica gel MMC over the pure Al-Si alloy.     

Investigations on surface composition and microstructure of sintered barium titanate

The paper describes studies on surface atomic composition, microstructure and microarea elemental distribution in sintered undoped as well as donor or acceptor doped polycrystalline barium titanate ceramics. The specimens examined are derived from barium titanate powders synthesized by two different wet chemical procedures namely oxalate precursor route and gel-to-crystallite conversion. The compositional analysis is carried out by backscattering spectrometry (BS) involving 3.05 MeV ¹⁶O(α,α)¹⁶O resonant scattering while investigations on microstructure and microarea elemental distribution are performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The specimens prepared by either method are monophasic; however, their surface atomic composition, microstructural features as well as electrical characteristics are significantly different. The specimens obtained by oxalate precursor route generally have Ti rich surfaces and exhibit coarse to fine grained microstructure depending on the nature and extent of doping. The Mn-doped specimens exhibit appreciable O deficiency. The specimens prepared by gel to crystallite conversion, in contrast, usually have Ba enriched surfaces and exhibit fine-grained microstructure. EDS measurements show the segregation of acceptors such as Mn, Cu and Zn in the grain boundaries of oxalate precursor derived ceramics. Further, the relative atomic ratio of Ti to Ba at the sites of segregations is higher compared to other locations.     

Dielectric studies of tin based chalcogenide glasses

The dc conductivity and dielectric parameters of glassy system of a-Se₇₀Te_30−x Sn _x (x = 0, 2, 4, 6, 8 and 10) glasses have been investigated. Frequency and temperature dependence of dielectric constants (ε′) and dielectric loss (ε′′) are studied in the frequency range 120–100 kHz and temperature range 300–390 K. Dielectric dispersion is observed when Tin (Sn) is incorporated to a-Se–Te system in the entire temperature range. These results explain that the dc conduction loss is dominated in the present system. From dc conductivity studies it is observed that the dc conductivity and activation energy increases with increasing tin concentration in the present system.     

Performance Evaluation of Trellis Code Modulated oDQPSK Using the KLSE Method

A direct detection optical differential quadrature phase-shift keying (oDQPSK) system with trellis coded modulation (TCM) is proposed and analyzed. From the results obtained for the symbol-error rate, it is observed that the proposed oDQPSK-TCM system can perform about 5 dB better than the uncoded oDQPSK system. Optical signal-to-noise ratio penalty due to first-order polarization-mode dispersion of the proposed oDQPSK-TCM system is evaluated and compared with that of unequalized as well as electrically equalized oDQPSK systems.     

Notice of Violation of IEEE Publication PrinciplesLDPC decoder: A cognitive radio perspective for next generation (XG) communication

With the rapid growth of multimedia communication systems during the last decade, there has been an increasing demand for improved technology for Error Correcting Code (ECO to enable the communication systems to have a reliable transmission over noisy channels. Low Density Parity Check (LDPC) codes are the best known ECC codes that can achieve data rates very close to the Shannon limit. In addition, superior error correction performance and parallelizable decoding algorithms have made LDPC codes a powerful competitor to turbo codes for reliable high speed communication applications. Recently, Cognitive Radio (CR) has been proposed as a promising technology to solve today's spectrum scarcity problem. CR promises to alleviate this spectrum shortage problem by dynamically accessing free spectrum resources. This implies that the radio has to work in multi-band, cope with various wireless channels and support various services such as voice, data and video. The basic requirement for CR is that it has a reconfigurable architecture to support multi-band and frequency adaptive operations. One of the ambitious design goals of future wireless systems, including 4G, IEEE 802.11n/802.16 standards, is to provide reliably very high data rate transmission in hostile environments: for example, around 100 Mb/s peak rate for downlink and around 30 Mb/s sum rate for uplink transmission with a low frame error rate (FER), typically less than 5 times10^-4. To ensure reliable nd error-free communication, there is a demand to consider implementing LDPC decoders in CR and frequency agile environments. In this article we discuss the design of adaptable as well as efficient LDPC decoders with low bit-error rate (BER) in low signal-to-noise ratio (SNR) channels for CR environments.     

Significance of image representation for face verification

In this paper we discuss the significance of representation of images for face verification. We consider three different representations, namely, edge gradient, edge orientation and potential field derived from the edge gradient. These representations are examined in the context of face verification using a specific type of correlation filter, called the minimum average correlation energy (MACE) filter. The different representations are derived using one-dimensional (1-D) processing of image. The 1-D processing provides multiple partial evidences for a given face image, one evidence for each direction of the 1-D processing. Separate MACE filters are used for deriving each partial evidence. We propose a method to combine the partial evidences obtained for each representation using an auto-associative neural network (AANN) model, to arrive at a decision for face verification. Results show that the performance of the system using potential field representation is better than that using the edge gradient representation or the edge orientation representation. Also, the potential field representation derived from the edge gradient is observed to be less sensitive to variation in illumination compared to the gray level representation of images.     

Enhancement of critical current density of YBa2Cu3O7 − δ thin films by self-assembly of Y2O3 nanoparticulates

YBa₂Cu₃O_7 − δ (YBCO) thin films, possessing high critical current density (J_c), have been synthesized by embedding a homogeneous array of Y₂O₃ non-superconducting nanoclusters/nanoparticles using a pulsed laser deposition technique. The size, interparticle spacing, and density of Y₂O₃ nanoparticles in YBCO thin films were tailored by varying the number of laser pulses in order to determine the optimum size for effective immobilization of vortices. Scanning transmission electron microscopy with atomic number contrast and X-ray diffraction techniques were used to determine the size and structure of the nanoparticles. Both techniques indicate that the Y₂O₃ particles are epitaxial with respect to the surrounding YBCO matrix. The information about pinning of vortices by the nanoparticles was obtained by investigating the behavior of critical current density as a function of temperature and applied field, which in turn determines the vortex density in the sample. The superconducting transition temperature (T_c) of YBCO films with the inclusion of nanoparticles was observed to remain almost the same or decrease marginally (1-2 K) with respect to T_c of pure YBCO films deposited under identical conditions. However, J_cs of YBCO films embedded with self-assembled nanoparticles were found to be significantly higher than that of pure YBCO films. The J_c enhancement was up to five times in high magnetic field, which is a key requirement for practical application of high-T_c materials.     

Optical,structural and electrical investigations on PbTe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> alloys

The fabrication of devices with lead salts and their alloys with detecting and lasing capabilities has been an important technological development. The high quality polycrystalline thin films of PbTe_1−x S _x with variable composition (0 ≤ x ≤ 1) have been deposited onto ultra clean glass substrates by vacuum evaporation technique. Optical, structural and electrical properties of PbTe_1−x S _x thin films have been examined. Absorption coefficient and band gap of the films were determined by absorbance measurements in wavelength range 2,500–5,000 nm using FTIR spectrophotometer. Sample nature, crystal structure and lattice parameter of the films were determined from X-ray diffraction patterns. DC conductivity and activation energy of the films were measured in temperature range 300–380 K through I–V measurements.