An Efficient VLSI Architecture for the Computation of 1-D Discrete Wavelet Transform

This paper presents a new architecture for VLSI implementation of the one dimensional Discrete Wavelet Transform (DWT). The architecture uses single filter for generation of both the DWT coefficients and scaling function for orthogonal wavelets as opposed to the conventional two filter approach. For multilevel decomposition, the fold back architecture principle, which interleaves the decimated scaling function back into the filter for subsequent levels, is applied. Limited use of memory in the design enables efficient implementation of the DWT computation in VLSI.     

Enhancing Data Rates of TH-UWB Systems Using M-ary OPPM-BPSM Modulation Scheme: A System Perspective

This paper proposes and studies a combined modulation scheme for time hopping ultra wideband (TH-UWB) radio system based on orthogonal pulse position modulation (OPPM) and biorthogonal pulse shape modulation (BPSM). The proposed scheme offers a high data rate with satisfactory system performance by using high-level multi-dimensional modulation schemes. It allows one to increase the number of orthogonal pulses in each pulse position and, consequently, be able to adopt shorter pulse repetition intervals than those used in conventional M-ary OPPM or M-ary biorthogonal PPM (BPPM) modulation schemes. The performance is analyzed by using characteristic function and Gaussian approximation in additive white Gaussian and multipath scenarios, respectively. The proposed scheme reduces multiple access interference considerably in multi-user environments. Finally, simulation results are provided to validate the theoretical results.     

Performance analysis of RLC/MAC and LLC Layers in a GPRS protocol stack

In this paper, we analyze the performance of various layers of the general packet radio service (GPRS) protocol stack, including radio link control/medium-access control (RLC/MAC) layer and logical link-control (LLC) layer on the uplink. In the GPRS MAC protocol, several time-slotted uplink radio-frequency channels are shared by the mobiles on a request-reservation-based multiple-access scheme. Using the theory of Markov chains, we derive expressions for the average throughput and delay performance of the GPRS MAC protocol. We evaluate the performance of the RLC layer (in acknowledged mode) using block-level retransmission (BLR), as defined in the current GPRS standard, and compare it with that of using slot-level retransmission (SLR). We show that SLR at the RLC layer performs significantly better than the BLR, particularly when the channel-error rates are moderate to high. We further investigate the choice of parameters (e.g., number of retransmission attempts) for the automatic repeat request schemes at the RLC and LLC layers. Our results show that it is more beneficial to do error recovery by allowing more retransmission attempts at the RLC layer than at the LLC layer. We also evaluate the performance of transmission-control protocol with BLR and SLR at the RLC layer.     

Power generation and organics removal from wastewater using activated carbon nanofiber (ACNF) microbial fuel cells (MFCs)

Carbon-based materials are the most commonly used electrode material for anodes in microbial fuel cell (MFC), but are often limited by their surface areas available for biofilm growth and subsequent electron transfer process. This study investigated the use of activated carbon nanofibers (ACNF) as the anode material to enhance bacterial biofilm growth, and improve MFC performance. Qualitative and quantitative biofilm adhesion analysis indicated that ACNF exhibited better performance over the other commonly used carbon anodes (granular activated carbon (GAC), carbon cloth (CC)). Batch-scale MFC tests showed that MFCs with ACNF and GAC as anodes achieved power densities of 3.50 ± 0.46 W/m³ and 3.09 ± 0.33 W/m³ respectively, while MFCs with CC had a lower power density of 1.10 ± 0.21 W/m³ In addition, the MFCs with ACNF achieved higher contaminant removal efficiency (85 ± 4%) than those of GAC (75 ± 5%) and CC (70 ± 2%). This study demonstrated the distinct advantages of ACNF in terms of biofilm growth and electron transport. ACNF has a potential for higher power generation of MFCs to treat wastewaters.     

Electrochemical degradation of pulp and paper industry waste‐water

BACKGROUND: Conventional biological waste‐water treatment techniques are insufficient to degrade large quantities of dissolved lignin discharged by small‐scale paper mills. The current investigation is aimed at comparing the overall performance of basic electrochemical reactor configurations such as batch, batch recirculation, recycle and single pass systems, in removing the organic part of waste‐water from a small‐scale, agro‐based paper industry. The effect of current density, supporting electrolyte concentration, duration of electrolysis, specific electrode surface and fluid flow rate on the removal of pollutants and energy consumption are critically evaluated. The improvement in biodegradability of the effluent during treatment is also noticed. RESULTS: The batch recirculation mode of operation was found to be superior in comparison with a batch system using the same specific electrode surface for both COD removal (73.3 vs. 64%) and capacity utilization (rate constant 1.112 × 10^?3 vs. 1.049 × 10^?3 cm s^?1). The pollutant removal performance of the batch recirculation system improved considerably with increase in the circulation flow rate. At the best operating point in the recycle system, 59% of COD was removed, corresponding to a current efficiency of 68.9% and specific energy consumption of 18.46 kWh kg^?1. The biodegradability index of the waste‐water was improved from 0.18 ± 0.01 to 0.36 ± 0.01. CONCLUSION: A recycle reactor was the best configuration, because of its flexibility of operation. Circulation flow rate and withdrawal flow rate enable the control of transfer coefficients and treatment duration respectively. Electrochemical treatment not only removes the bulk of the organic matter, but also makes the remaining pollutants more easily biodegradable. Copyright © 2009 Society of Chemical Industry     

Fuzzy state estimator for a semibatch copolymerization reactor

This work describes the development of a fuzzy estimator for determining copolymer composition (F₁) in a semibatch solution copolymerization reactor. Membership functions, fuzzy ranges for input (ζ₁ mole fraction of monomer 1 in polymerizing mass) and output (F₁ mole fraction of monomer 1 in copolymer) are defined. A fuzzy rule base is constructed relating input to output, based on the operator's knowledge. A defuzzification method is selected and the non-fuzzy values of F₁ are obtained. The results are compared with the actual values of F₁ which are obtained by rigorously solving the model equations of the system. The fuzzy ranges and limits for input and output are altered separately so as to test the estimator's performance. Thus obtained standard estimator is tested for other operating conditions. The developed estimator performed well also for wider operating conditions.     

Improved memoryless RNS forward converter based on the periodicity of residues

The residue number system (RNS) is suitable for DSP architectures because of its ability to perform fast carry-free arithmetic. However, this advantage is over-shadowed by the complexity involved in the conversion of numbers between binary and RNS representations. Although the reverse conversion (RNS to binary) is more complex, the forward transformation is not simple either. Most forward converters make use of look-up tables (memory). Recently, a memoryless forward converter architecture for arbitrary moduli sets was proposed by Premkumar in 2002. In this paper, we present an extension to that architecture which results in 44% less hardware for parallel conversion and achieves 43% improvement in speed for serial conversions. It makes use of the periodicity properties of residues obtained using modular exponentiation.