Engineering Science, School of

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Facile Fabrication of Super-Hydrophobic Nano-Needle Arrays via Breath Figures Method

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2011
Abstract: 

Super-hydrophobic surfaces which have been fabricated by various methods such as photolithography, chemicaltreatment, self-assembly, and imprinting have gained enormous attention in recent years. Especially 2D arrays ofnano-needles have been shown to have super-hydrophobicity due to their sharp surface roughness. These arrayscan be easily generated by removing the top portion of the honeycomb films prepared by the breath figuresmethod. The hydrophilic block of an amphiphilic polymer helps in the fabrication of the nano-needle arraysthrough the production of well-ordered honeycomb films and good adhesion of the film to a substrate.Anisotropic patterns with water wettability difference can be useful for patterning cells and other materials usingtheir selective growth on the hydrophilic part of the pattern. However, there has not been a simple way togenerate patterns with highly different wettability. Mechanical stamping of the nano-needle array with apolyurethane stamp might be the simplest way to fabricate patterns with wettability difference. In this study,super-hydrophobic nano-needle arrays were simply fabricated by removing the top portion of the honeycombfilms. The maximum water contact angle obtained with the nano-needle array was 150°. By controlling the poresize and the density of the honeycomb films, the height, width, and density of nano-needle arrays weredetermined. Anisotropic patterns with different wettability were fabricated by simply pressing the nano-needlearray at ambient temperature with polyurethane stamps which were flexible but tough. Mechanical stamping ofnano-needle arrays with micron patterns produced hierarchical super-hydrophobic structures.

Document type: 
Article

Surface EMG Pattern Recognition for Real-Time Control of a Wrist Exoskeleton

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2010
Abstract: 

Background: Surface electromyography (sEMG) signals have been used in numerousstudies for the classification of hand gestures and movements and successfullyimplemented in the position control of different prosthetic hands for amputees.sEMG could also potentially be used for controlling wearable devices which couldassist persons with reduced muscle mass, such as those suffering from sarcopenia.While using sEMG for position control, estimation of the intended torque of the usercould also provide sufficient information for an effective force control of the handprosthesis or assistive device. This paper presents the use of pattern recognition toestimate the torque applied by a human wrist and its real-time implementation tocontrol a novel two degree of freedom wrist exoskeleton prototype (WEP), whichwas specifically developed for this work.Methods: Both sEMG data from four muscles of the forearm and wrist torque werecollected from eight volunteers by using a custom-made testing rig. The featuresthat were extracted from the sEMG signals included root mean square (rms) EMGamplitude, autoregressive (AR) model coefficients and waveform length. SupportVector Machines (SVM) was employed to extract classes of different force intensityfrom the sEMG signals. After assessing the off-line performance of the usedclassification technique, the WEP was used to validate in real-time the proposedclassification scheme.Results: The data gathered from the volunteers were divided into two sets, one withnineteen classes and the second with thirteen classes. Each set of data was furtherdivided into training and testing data. It was observed that the average testingaccuracy in the case of nineteen classes was about 88% whereas the averageaccuracy in the case of thirteen classes reached about 96%. Classification and controlalgorithm implemented in the WEP was executed in less than 125 ms.Conclusions: The results of this study showed that classification of EMG signals byseparating different levels of torque is possible for wrist motion and the use of onlyfour EMG channels is suitable. The study also showed that SVM classificationtechnique is suitable for real-time classification of sEMG signals and can be effectivelyimplemented for controlling an exoskeleton device for assisting the wrist.

Document type: 
Article

Signal Processing with Teams of Embedded Workhorse Processors

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2006
Abstract: 

Advanced signal processing for voice and data in wired or wireless environments can require massive computational power. Dueto the complexity and continuing evolution of such systems, it is desirable to maintain as much software controllability in the fieldas possible. Time to market can also be improved by reducing the amount of hardware design. This paper describes an architecturebased on clusters of embedded “workhorse” processors which can be dynamically harnessed in real time to support a wide rangeof computational tasks. Low-power processors and memory are important ingredients in such a highly parallel environment.

Document type: 
Article

A New Reduced-Complexity Detection Scheme for Zero-Padded OFDM Transmissions

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2006
Abstract: 

Recently, zero-padding orthogonal frequency division multiplexing (ZP-OFDM) has been proposed as an alternative solution to the traditional cyclic prefix (CP)-OFDM, to ensure symbol recovery regardless of channels nulls. Various ZP-OFDM receivers have been proposed in the literature, trading off performance with complexity. In this paper, we propose a novel low-complexity (LC) receiver for ZP-OFDM transmissions and derive an upper bound on the bit error rate (BER) performance of the LC-ZP-OFDM receiver. We further demonstrate that the LC-ZP-OFDM receiver brings a significant complexity reduction in the receiver design, while outperforming conventional minimum mean-square error (MMSE)-ZP-OFDM, supported by simulation results. A modified (M)-ZP-OFDM receiver, which requires the channel state information (CSI) knowledge at the transmitter side, is presented. We show that the M-ZP-OFDM receiver outperforms the conventional MMSE-ZP-OFDM when either perfect or partial CSI (i.e., limited CSI) is available at the transmitter side.Index Terms-Zero-padding, orthogonal frequency division multiplexing (OFDM), equalization.

Document type: 
Article

An FPGA-Based MIMO and Space-Time Processing Platform

Author: 
Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2006
Abstract: 

Faced with the need to develop a research unit capable of up to twelve 20MHz bandwidth channels of real-time, space-time,and MIMO processing, the authors developed the STAR (space-time array research) platform. Analysis indicated that the possibledegree of processing complexity required in the platform was beyond that available from contemporary digital signal processors,and thus a novel approach was required toward the provision of baseband signal processing. This paper follows the analysis andthe consequential development of a flexible FPGA-based processing system. It describes the STAR platform and its use throughseveral novel implementations performed with it. Various pitfalls associated with the implementation of MIMO algorithms in realtime are highlighted, and finally, the development requirements for this FPGA-based solution are given to aid comparison withtraditional DSP development.

Document type: 
Article

Complexity of Saliency-Cognizant Error Concealment Based on the Itti-Koch-Niebur Saliency Model

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2012-11-16
Abstract: 

In this technical report, we analyze the computational complexity of the saliency-cognizant error concealment method for video streaming proposed in [1]. We derive an approximate number of operations needed to reconstruct a missing block in a video frame as a function of the block size and frame resolution.

Document type: 
Technical Report
File(s): 

Performance Analysis of RIP, EIGRP, and OSPF Using OPNET

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2011-08
Document type: 
Lecture / Talk

Simulation and Performance Evaluation of WiFi and WiMAX Using OPNET

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2011-08
Document type: 
Lecture / Talk

Performance Analysis of Routing Protocols for Wireless Ad-hoc Networks

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2011-08
Document type: 
Lecture / Talk