Energy Efficient Distributed Volterra Modeling Approach with ADMM-Based Sparse Signal Recovery

Wireless Personal Communications - Modeling the behavior of nonlinear systems in a distributed fashion is of paramount in many industrial applications. Distributed means no sensor node in the...     

Error feedback based noise shaping in a double sampled ADC

A first order error feedback based noise shaping ADC, that obviates the need for high-gain and high output-swing op amps and fast-settling, power-hungry, and noisy reference buffers is proposed. Using a single stage op amp with a gain of 70 (i.e. 37 dB) and output swing of ±75 mV, this topology, realized in GPDK 90-nm CMOS technology, achieves an SNDR of 63 dB operating at 1 GHz (effective sample rate of 2 GHz due to double sampling) with an OSR of 32.     

Waste collection vehicle routing problem with time windows

In this paper, we address a real life waste collection vehicle routing problem with time windows (VRPTW) with consideration of multiple disposal trips and drivers’ lunch breaks. Solomon's well-known insertion algorithm is extended for the problem. While minimizing the number of vehicles and total traveling time is the major objective of vehicle routing problems in the literature, here we also consider the route compactness and workload balancing of a solution since they are very important aspects in practical applications. In order to improve the route compactness and workload balancing, a capacitated clustering-based waste collection VRPTW algorithm is developed. The proposed algorithms have been successfully implemented and deployed for the real life waste collection problems at Waste Management, Inc. A set of waste collection VRPTW benchmark problems is also presented in this paper.Waste collection problems are frequently considered as arc routing problems without time windows. However, that point of view can be applied only to residential waste collection problems. In the waste collection industry, there are three major areas: commercial waste collection, residential waste collection and roll-on-roll-off. In this paper, we mainly focus on the commercial waste collection problem. The problem can be characterized as a variant of VRPTW since commercial waste collection stops may have time windows. The major variation from a standard VRPTW is due to disposal operations and driver's lunch break. When a vehicle is full, it needs to go to one of the disposal facilities (landfill or transfer station). Each vehicle can, and typically does, make multiple disposal trips per day. The purpose of this paper is to introduce the waste collection VRPTW, benchmark problem sets, and a solution approach for the problem. The proposed algorithms have been successfully implemented and deployed for the real life waste collection problems of Waste Management, the leading provider of comprehensive waste management services in North America with nearly 26,000 collection and transfer vehicles.     

Synergetic Surface and Chemical Durability Study of the Aesthetically Enhanced Natural Quartz by Heat Treatment

The change in surface behavior of natural quartz stone before and after heat treatment with metal oxides such as: cobalt oxide (Co₃O₄) and copper oxide (Cu₂O) under vacuum and open atmosphere has been investigated. The surface feature, bulk density and hardness value of quartz changed after heat treatment, converting to a high value product. Difference in crystallinity of quartz, pre- and post-heat treatment was obtained through X-ray diffraction (XRD) study. The electron probe microanalysis results clearly explicated the diffusion of metal ion in quartz matrix exposed under vacuum atmosphere but as coating on the surface under open atmosphere. The structural transformation of quartz after heat treatment has been observed from the XRD data and well corroborated with the nanoindentation results. Durability of such quartz to chemical hazardous environment was observed. Thus, this communication demonstrates the change in physical and chemical characteristics of natural quartz stone after heat treatment under different atmosphere.     

Mechanical Properties and Nanocrystallization Behavior of Al-Ni-La Alloys

Rapidly solidified Al₈₉Ni₆La₅ ribbons were obtained by induction melting and ejecting the melt onto a rotating Cu wheel in an Ar atmosphere. The ribbons were investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), transmission electron microscopy (TEM), microindentation, and nanoindentation techniques. The XRD and TEM studies revealed that the ribbon was fully amorphous; however, DSC did not show any glass transition. The alloy undergoes two stages of crystallization. The growth of fcc-Al is responsible for the first stage, and precipitation of Al₃Ni and Al₁₁La₃ is responsible for the second stage of crystallization. Microhardness of ribbons in the as-melt-spun, partially, and fully devitrified conditions was examined and subsequently correlated with evolved microstructure. Significant improvement in hardness was observed, with the progress of primary nanocrystallization, due to the effective barrier to shear band by a hard La-rich shell around the fcc-Al nanocrystals and enrichment of the remaining amorphous matrix by the solute elements. The pile up of materials in the form of semicircular shear bands was observed around all the indentations. During nanoindentation, it was observed that hardness and modulus values were initially increased and then decreased. The reasons for such observation were also discussed.     

Transformation of flexural gravity waves by heterogeneous boundaries

The transformation of flexural gravity waves due to wave scattering by heterogeneous boundaries is investigated under the assumption of the linearized water-wave theory. The heterogeneous boundaries include step-type bottom topography as well as heterogeneity in the material property of a floating ice-sheet. By applying the generalized expansion formulae along with the corresponding orthogonal mode-coupling relations, the boundary-value problem (BVP) is reduced to linear system of algebraic equations. The system of equations is solved numerically to determine the full solution of the problem under consideration. Energy relations are derived and used to check the accuracy of the computational results of the scattering problem. Explicit relations for the shoaling and scattering coefficients due to the change in water depth and heterogeneous ice-sheet are derived. These derivations are based on the law of conservation of energy flux under the assumptions of the linearized shallow-water theory. The change in water depth and the structural characteristics of the medium significantly contribute to the change in the scattering and shoaling coefficients and the deflection of the structure. The present results are likely to play a significant role in the analysis of flexural gravity-wave propagation in problems of variable topography for which a direct computational approach is being utilized.     

Correlation of atomic force–distance microscopy and spectrophotometric techniques in the analysis of optical multilayer spectral aging process

Aging-related multilayer spectral instabilities can pose severe performance limiting constraints to optical multilayer devices. In this study such instabilities of some periodic Gd₂O₃/SiO₂ optical multilayer systems have been explored using scanning probe force–distance microscopy and spectrophotometric techniques. In the present case, a strong correlation between the spectral instabilities and the viscoelastic properties of the associated thin film layers has been distinctly noticed. From the experimental analysis it was quite evident that the spectral instability, which starts during the nucleation and growth stage in thin films, continues to persist at a much longer time scale following aging processes. In this study it is shown that the elastic properties of the constituent thin films, the layer design and the bilayer thickness have established a strong interrelation which ultimately contributes to the multilayer instabilities. These spectral instabilities also have strong interconnections with the morphological and viscoelastic changes in such multilayers. Other multilayer parameters like the total number of layers, the layer structure, the microroughness evolutions, related stiffness factors and the adhesion properties of the periodic layer systems contribute substantially to this instability process.     

Study on the electronic band structure of ZnO–SnO2 heterostructured nanocomposites with mechanistic investigation on the enhanced photoluminescence and photocatalytic properties

Journal of Materials Science: Materials in Electronics - Sol–gel method of synthesizing nanocomposites (NCs) of two metal oxides (ZnO & SnO2) was implemented along with the pristine...