Design of nearly perfect reconstructed non-uniform filter bank by constrained equiripple FIR technique

In this paper, an efficient iterative algorithm is proposed for the design of multi-channel nearly perfect reconstructed non-uniform filter bank. The method employs the constrained equiripple FIR technique to design the prototype filter for filter banks with novelty of exploiting a new perfect reconstruction condition of the non-uniform filter banks instead of using complex objective functions. In the proposed algorithm, passband edge frequency (ω_p) is optimized using linear optimization technique such that the filter coefficients values at quadrature frequency are approximately equal to 0.707. Several design examples are included to illustrate the efficacy of this methodology for designing non-uniform filter bank (NUFB). It was found that the proposed methodology performs better as compared to earlier reported results in terms of reconstruction error (RE), number of iteration (NOI) and computation time (CPU time). The proposed algorithm is very simple, linear in nature, and easy to implement.     

Dielectric-Resonant Antenna Studies of Dysprosium Doped Barium Zirconate Ceramic

The structural properties of the Ba_(1?x)Dy_(2x/3)ZrO₃ system were investigated by means of XRD, FT-Raman, and FTIR spectroscopy. XRD analysis exhibited that lattice parameter gradually decreased with increase of Dy content. FT-Raman and FTIR analyses showed that with increase of Dy content more ordered structure was formed in the composition. The surface morphology of sintered pellets was studied by the SEM. The microwave dielectric constant and quality factor were investigated by the method as proposed by Hakki–Coleman. The microwave dielectric constants of sintered pellets were found to be decreased from 38.40 to 21.13, and the value of τ_f changed from 384.71 to 62.71 ppm/°C. The Q × f values changed from 5731 to 5173 in the composition between x = 0.0 and 0.1. The dielectric resonator antenna (DRA) was investigated experimentally and numerically, using a monopole antenna through an infiniteground plane and Ansoft’s high-frequency structure simulator software, respectively. The required resonance frequency and bandwidth of DRA were investigated in the composition between 0 ≤ x ≤ 0.1.     

Distributed self-tuning of sensor networks

This work is motivated by the need for an ad hoc sensor network to autonomously optimise its performance for given task objectives and constraints. Arguing that communication is the main bottleneck for distributed computation in a sensor network we formulate two approaches for optimisation of computing rates. The first is a team problem for maximising the minimum communication throughput of sensors and the second is a game problem in which cost for each sensor is a measure of its communication time with its neighbours. We investigate adaptive algorithms using which sensors can tune to the optimal channel attempt rates in a distributed fashion. For the team problem, the adaptive scheme is a stochastic gradient algorithm derived from the augmented Lagrangian formulation of the optimisation problem. The game formulation not only leads to an explicit characterisation of the Nash equilibrium but also to a simple iterative scheme by which sensors can learn the equilibrium attempt probabilities using only the estimates of transmission and reception times from their local measurements. Our approach is promising and should be seen as a step towards developing optimally self-organising architectures for sensor networks. Aditya Karnik obtained his B.E. from the University of Pune, Pune, India, and M.E. and Ph.D. (2004) in electrical communication engg. from the Indian Institute of Science, Bangalore, India. He is currently a postdoctoral fellow at the University of Waterloo, Waterloo, Canada. He was a recipient of the IBM Research Fellowship. His research interests are in performance evaluation, optimisation and control of communication networks. Anurag Kumar obtained his B.Tech. degree from the Indian Institute of Technology at Kanpur, and the PhD degree from Cornell University, both in Electrical Engineering. He was then with Bell Laboratories, Holmdel, N.J., for over 6 years. Since 1988 he has been with the Indian Institute of Science (IISc), Bangalore, in the Dept. of Electrical Communication Engineering, where he is now a Professor, and is also the Chairman of the department. From 1988 to 2003 he was the Coordinator at IISc of the Education and Research Network Project (ERNET), India’s first wide-area packet switching network. His area of research is communication networking, specifically, modeling, analysis, control and optimisation problems arising in communication networks and distributed systems. Recently his research has focused primarily on wireless networking. He has been elected Fellow of the IEEE, and the Indian National Science Academy (INSA), both from 2006, and has been a Fellow of the Indian National Academy of Engineering (INAE) since 1998. He is an associate editor of IEEE Transactions on Networking, and of IEEE Communications Surveys and Tutorials. He is a coauthor of the advanced text-book “Communication Networking: An Analytical Approach,” by Kumar, Majunath and Kuri, published by Morgan-Kaufman/Elsevier. Vivek Borkar got his B. Tech. (Elec. Engg.) from Indian Institute of Technology, Mumbai, in 1976, M. S. (Systems and Control) from Case Western Reserve Uni. in 1977, and Ph.D. (Elec. Engg. and Computer Sci.) from the Uni. of California, Berkeley, in 1980. He was with TIFR Centre, Bangalore (1982–1989) and Indian Institute of Science (1989–1999) before taking up his present position at the School of Technology and Computer Science, Tata Inst. of Fundamental Research, Mumbai. He is a Fellow of the Indian Academy of Sciences, Indian National Science Academy, Indian National Academy of Engineers and the IEEE. His research interests are stochastic control, stochastic algorithms and applications. He is on the editorial boards of Sadhana, Systems and Control Letters, SIAM J. Control and Optim., and Applicationes Mathematicae. He is the author of ‘Optimal Control of Diffusion Processes’ (Longman, 1989), ‘Topics in Controlled Markov Chains’ (Longman, 1991), ‘Probability Theory: An Advanced Course’ (Springer, 1995).     

Evaluation of Seasonal Variability of First-Order Ionospheric Delay Correction at L5 and S1 Frequencies Using Dual-Frequency NavIC System

Wireless Personal Communications - For the precise positioning applications it is important to determine and eliminate the positioning error introduced by various sources such as the ionosphere. To...     

DNA binding and unwinding by self-assembled supramolecular hetero-bimetallacycles

Two new tetracationic hetero-bimetallacycles were prepared from a bis-pyridine amide ligand and metal (Pd and Pt) acceptors. We found that both self-assembled hetero-bimetallacycles bind and unwind supercoiled DNA as established by photophysical and gel electrophoresis analyses, respectively.     

Determination of precipitation inhibitory potential of polymers from amorphous solid dispersions

Abstract

Precipitation inhibitory potential of polymers screened from precipitation study may be altered once it is formulated in amorphous solid dispersions (ASDs).

Objective: Present study was embarked with an objective to determine whether the polymers retain the same inhibitory potential after formulating them into ASDs.

Methods: Screening of polymers was based on a new dimensionless parameter ‘Supersaturation Holding Capacity (SHC)’ calculated from the precipitation study. Nifedipine ASDs were formulated using HPMC E3 and HPMC E50 (high SHC values), and HPMC K100M, PVP K25, and HPC M (low to moderate SHC values). Generated ASDs were characterized by DSC, FTIR, and PXRD and evaluated for stability under accelerated conditions (40?C and 75% RH) for 6 months.

Results: Thermal analysis of the ASDs and theoretical prediction of the glass transition temperature (T_g) suggested a linear dependency of T_g on the content of HPMC E3 and HPMC E50. Under accelerated stability conditions, all ASDs of nifedipine with HPMC E3 and HPMC E50 (except ASDs with 70% drug load) were stable, which could be attributed to the molecular level dispersion of the drug in these polymers. SHC parameter calculated from the apparent solubility profile gave following rank order HPMC E50 (3.4)?>?HPMC E3 (3.2)?>?HPMC K100M (1.29)?>?PVP K25 (1.09)?>?HPC M (0.99). SHC calculated from the apparent solubility profile of ASDs demonstrated good agreement between the solution state and solid state screening of the polymers for precipitation inhibition. During dissolution study, nearly four-fold enhancement has been observed with ASDs comprising HPMC E3 and HPMC E50.

Conclusions: The outcome of the study concluded that SHC can be a promising parameter in the screening of polymers for the development of the ASDs.     

Start of structural damage in stucco walls

A wealth of data about the performance of stucco shear walls under cyclic loading has become available since 2001. Stucco and drywall are the only earthquake and wind lateral force‐resisting systems in many existing residential buildings, especially single and multi‐family homes built before 1980. This paper presents the results of an analysis of cyclic tests conducted at the University of California, Irvine, on solid stucco walls to determine the start of structural damage. Copyright © 2010 John Wiley & Sons, Ltd.     

Design of Sheet-Beam Electron Gun with Planar Cathode for Terahertz Devices

The design of a sheet-beam electron gun with planar cathode was made with the help of a three-dimensional electrostatic field solver that was capable of forming a sheet-beam of 19 mA at 12 kV. It uses one-dimensional three-fold beam cross-sectional area compression meets the specific requirement of a beam to be formed of height 30 μm and width 600 μm at the beam–waist position with over 100 A/cm² uniform current density and 0.068 π-mm-mrad emittance, typically, for 0.5 THz devices. A novel beam focusing electrode (BFE) provided with extended-corner rectangular-aperture geometry alleviating the commonly encountered sheet-beam formation problem with a gun that uses a conventional BFE, as well as it reduced beam emittance more than 50%. The practicability of the design was tested by the high-voltage, the thermal and structural analyses. Work has been initiated to test the performance of special high current scandate cathode using anode-aperture mapping.     

A tutorial survey of topics in wireless networking: Part I

In this two part paper, we provide a survey of recent and emerging topics in wireless networking. We view the area of wireless networking as dealing with problems of resource allocation so that the various connections that utilise the network achieve their desired performance objectives. In the first part of the paper, we first survey the area by providing a taxonomy of wireless networks as they have been deployed. Then, we provide a quick tutorial on the main issues in the wireless ‘physical’ layer, which is concerned with transporting bits over the radio frequency spectrum. Then, we proceed to discuss some resource allocation formulations in CDMA(code division multiple access) cellular networks and OFDMA(orthogonal frequency division multiple access) networks. In the second part of the paper, we first analyse random access wireless networks and pay special attention to 802·11 (Wi-Fi) networks.We then survey some topics in ad hoc multihop wireless networks, where we discuss arbitrary networks, as well as some theory of dense random networks. Finally, we provide an overview of the technical issues in the emerging area of wireless sensor networks.