Switching of a Sixteen Electrode Array for Wireless EIT System Using a RF-Based 8-Bit Digital Data Transmission Technique

Surface electrode switching of 16-electrode wireless EIT is studied using a Radio Frequency (RF) based digital data transmission technique operating with 8 channel encoder/decoder ICs. An electrode switching module is developed the analog multiplexers and switched with 8-bit parallel digital data transferred by transmitter/receiver module developed with radio frequency technology. 8-bit parallel digital data collected from the receiver module are converted to 16-bit digital data by using binary adder circuits and then used for switching the electrodes in opposite current injection protocol. 8-bit parallel digital data are generated using NI USB 6251 DAQ card in LabVIEW software and sent to the transmission module which transmits the digital data bits to the receiver end. Receiver module supplies the parallel digital bits to the binary adder circuits and adder circuit outputs are fed to the multiplexers of the electrode switching module for surface electrode switching. 1 mA, 50 kHz sinusoidal constant current is injected at the phantom boundary using opposite current injection protocol. The boundary potentials developed at the voltage electrodes are measured and studied to assess the wireless data transmission.

Virtually cool ternary content addressable memory

Fast content addressable data access mechanisms have compelling applications in today's systems. Many of these exploit the powerful wildcard matching capabilities provided by ternary content addressable memories. For example, TCAM based implementations of important algorithms in data mining been developed in recent years; these achieve an an order of magnitude speedup over prevalent techniques. However, large hardware TCAMs are still prohibitively expensive in terms of power consumption and cost per bit. This has been a barrier to extending their exploitation beyond niche and special purpose systems. We propose an approach to overcome this barrier by extending the traditional virtual memory hierarchy to scale up the user visible capacity of TCAMs while mitigating the power consumption overhead. By exploiting the notion of content locality (as opposed to spatial locality), we devise a novel combination of software and hardware techniques to provide an abstraction of a large virtual ternary content addressable space. In the long run, such abstractions enable applications to disassociate considerations of spatial locality and contiguity from the way data is referenced. If successful, ideas for making content addressability a first class abstraction in computing systems can open up a radical shift in the way applications are optimized for memory locality, just as storage class memories are soon expected to shift away from the way in which applications are typically optimized for disk access locality.

A nested linear codes approach to distributed function computation over subspaces

In this paper, we consider a distributed function computation setting, where there are m distributed but correlated sources X1,...,Xm and a receiver interested in computing an s-dimensional subspace generated by [X1,...,Xm]Γ for some (m × s) matrix Γ of rank s. We construct a scheme based on nested linear codes and characterize the achievable rates obtained using the scheme. The proposed nested-linear-code approach performs at least as well as the Slepian-Wolf scheme in terms of sum-rate performance for all subspaces and source distributions. In addition, for a large class of distributions and subspaces, the scheme improves upon the Slepian-Wolf approach. The nested-linear-code scheme may be viewed as uniting under a common framework, both the Korner-Marton approach of using a common linear encoder as well as the Slepian-Wolf approach of employing different encoders at each source. Along the way, we prove an interesting and fundamental structural result on the nature of subspaces of an m-dimensional vector space V with respect to a normalized measure of entropy. Here, each element in V corresponds to a distinct linear combination of a set {Xi}im=1 of m random variables whose joint probability distribution function is given.

Analysis of grating inscribed micro-cantilever for high resolution AFM probe

We present a mathematical modelling and analysis of reflection grating etched Si AFM cantilever deflections under different loading conditions. A simple analysis of the effect of grating structures on cantilever deflection is carried out with emphasis on optimizing the beam and gratings such that maximum amount of diffracted light remains within the detector area.

High speed digital holographic interferometry for hypersonic flow visualization

Optical imaging techniques have played a major role in understanding the flow dynamics of varieties of fluid flows, particularly in the study of hypersonic flows. Schlieren and shadowgraph techniques have been the flow diagnostic tools for the investigation of compressible flows since more than a century. However these techniques provide only the qualitative information about the flow field. Other optical techniques such as holographic interferometry and laser induced fluorescence (LIF) have been used extensively for extracting quantitative information about the high speed flows. In this paper we present the application of digital holographic interferometry (DHI) technique integrated with short duration hypersonic shock tunnel facility having 1 ms test time, for quantitative flow visualization. Dynamics of the flow fields in hypersonic/supersonic speeds around different test models is visualized with DHI using a high-speed digital camera (0.2 million fps). These visualization results are compared with schlieren visualization and CFD simulation results. Fringe analysis is carried out to estimate the density of the flow field.

Low loss waveguide on chalcogenide glass using ultrafast laser at low repetition rate

In this work, we synthesized bulk amorphous GeGaS glass by conventional melt quenching technique. Amorphous nature of the glass is confirmed using X-ray diffraction. We fabricated the channel waveguides on this glass using the ultrafast laser inscription technique. The waveguides are written on this glass 100 mu m below the surface of the glass with a separation of 50 ae m by focusing the laser beam into the material using 0.67 NA lens. The laser parameters are set to 350 fs pulse duration at 100 KHz repetition rate. A range of writing energies with translation speeds 1 mm/s, 2 mm/s, 3 mm/s and 4 mm/s were investigated. After fabrication the waveguides facets were ground and polished to the optical quality to remove any tapering of the waveguide close to the edges. We characterized the loss measurement by butt coupling method and the mode field image of the waveguides has been captured to compare with the mode field image of fibers. Also we compared the asymmetry in the shape of the waveguide and its photo structural change using Raman spectra.

Real time monitoring of petroleum leakage detection using etched fiber Bragg grating

Detection of petroleum leakages in pipelines and storage tanks is a very important as it may lead to significant pollution of the environment, accidental hazards, and also it is a very important fuel resource. Petroleum leakage detection sensor based on fiber optics was fabricated by etching the fiber Bragg grating (FBG) to a region where the total internal reflection is affected. The experiment shows that the reflected Bragg's wavelength and intensity goes to zero when etched FBG is in air and recovers Bragg's wavelength and intensity when it is comes in contact with petroleum or any external fluid. This acts as high sensitive, fast response fluid optical switch in liquid level sensing, petroleum leakage detection etc. In this paper we present our results on using this technique in petroleum leakage detection.

Device Fabrication of insoluble donor-acceptor-donor structured molecule by pulsed laser deposition- A comparative study using different laser source

Many of the conducting polymers though having good material property are not solution processable. Hence an alternate method of fabrication of film by pulsed laser deposition, was explored in this work. PDTCPA, a donor-acceptor-donor type of polymer having absorption from 900 nm to 300 nm was deposited by both UV and IR laser to understand the effect of deposition parameters on the film quality. It was observed that the laser ablation of PDTCPA doesn't alter its chemical structure hence retaining the chemical integrity of the polymer. Microscopic studies of the ablated film shows that the IR laser ablated films were particulate in nature while UV laser ablated films are deposited as smooth continuous layer. The morphology of the film influences its electrical characteristics as current-voltage characteristic of these films shows that films deposited by UV laser are p rectifying while those by IR laser are more of resistor in nature.

Rainbow colouring of split and threshold Graphs

A rainbow colouring of a connected graph is a colouring of the edges of the graph, such that every pair of vertices is connected by at least one path in which no two edges are coloured the same. Such a colouring using minimum possible number of colours is called an optimal rainbow colouring, and the minimum number of colours required is called the rainbow connection number of the graph. A Chordal Graph is a graph in which every cycle of length more than 3 has a chord. A Split Graph is a chordal graph whose vertices can be partitioned into a clique and an independent set. A threshold graph is a split graph in which the neighbourhoods of the independent set vertices form a linear order under set inclusion. In this article, we show the following: 1. The problem of deciding whether a graph can be rainbow coloured using 3 colours remains NP-complete even when restricted to the class of split graphs. However, any split graph can be rainbow coloured in linear time using at most one more colour than the optimum. 2. For every integer k ≥ 3, the problem of deciding whether a graph can be rainbow coloured using k colours remains NP-complete even when restricted to the class of chordal graphs. 3. For every positive integer k, threshold graphs with rainbow connection number k can be characterised based on their degree sequence alone. Further, we can optimally rainbow colour a threshold graph in linear time.

Locating the attacker of wormhole attack by using the honeypot

Mobile Ad hoc Networks (MANETs) having strikingly superior features also come with notable disadvantage and troubles and the most exigent amongst all being security related issues. Such an ringent network dexterously pave approach for the malicious nodes. Hence providing security is a tedious task. For such a dynamic environment, a security system which dynamically observes the attacker's plans and protect the highly sophisticated resources is in high demand. In this paper we present a method of providing security against wormhole attacks to a MANET by learning about the environment dynamically and adapting itself to avoid malicious nodes. We accomplish this with the assistance of Honeypot. Our method predicts the wormhole attack that may take place and protect the resources well-in advance. Also it cleverly deal with the attacker by using previous history and different type of messages to locate the attacker. Several experiments suggest that the system is accurate in handling wormhole attack.

Base Triggered Enhancement of First Hyperpolarizability of a Keto-Enol Tautomer

This work describes the base triggered enhancement of first hyperpolarizability of a tautomeric organic molecule, namely, benzoylacetanilide (BA). We have used the hyper-Rayleigh scattering technique to measure the first hyperpolarizability (beta) of BA which exists in the pure keto form in water and as a keto-enol tautomer in ethanol. Its anion exists in equilibrium with the keto and enol forms at pH 11 in aqueous solution. The beta value of the anion form is 709 X 10(-30) esu, whereas that of the enol is 232 x 10(-3) esu and of the keto is 88 X 10(-30) esu. There is an enhancement of beta by similar to 8 times for the anion and similar to 3 times for the enol compared to the keto form. All these are achieved by altering the equilibrium between the three forms of BA by simple means. MP2 calculations reproduce the experimental trend, but the computed beta values are much lower than the measured values. DFT calculations with the standard B3LYP functional could not predict the right order in the beta values. The difference between experimental and calculated values is, perhaps, due to the fact that electron correlation effects are important in computing optical nonlinearities of large organic molecules and MP2 and B3LYP calculations done here for different forms of BA could not account for such effects adequately.

Atom Lithography

We review the two kinds of forces that near-resonant light exerts on atoms the spontaneous force that is used for laser cooling, and the stimulated force that is used for coherent manipulation of atoms. We will discuss an experiment where laser cooling is used to collimate an atomic beam of sodium atoms, and the stimulated force within one period of a one-dimensional standing wave is used as a lens to focus the atoms to a narrow line about 20 nm wide. This kind of atom lithography is an example of the general field of atom optics in which light is used to manipulate atoms.

ANRC Hybrid Test Bed Implementation and an End-to-End Performance Characterization of Dynamic Spectrum Access

An abundance of spectrum access and sensing algorithms are available in the dynamic spectrum access (DSA) and cognitive radio (CR) literature. Often, however, the functionality and performance of such algorithms are validated against theoretical calculations using only simulations. Both the theoretical calculations and simulations come with their attendant sets of assumptions. For instance, designers of dynamic spectrum access algorithms often take spectrum sensing and rendezvous mechanisms between transmitter-receiver pairs for granted. Test bed designers, on the other hand, either customize so much of their design that it becomes difficult to replicate using commercial off the shelf (COTS) components or restrict themselves to simulation, emulation /hardware-in-Ioop (HIL), or pure hardware but not all three. Implementation studies on test beds sophisticated enough to combine the three aforementioned aspects, but at the same time can also be put together using COTS hardware and software packages are rare. In this paper we describe i) the implementation of a hybrid test bed using a previously proposed hardware agnostic system architecture ii) the implementation of DSA on this test bed, and iii) the realistic hardware and software-constrained performance of DSA. Snapshot energy detector (ED) and Cumulative Summation (CUSUM), a sequential change detection algorithm, are available for spectrum sensing and a two-way handshake mechanism in a dedicated control channel facilitates transmitter-receiver rendezvous.

Study of Wrist Pulse Signals Using a Bi-Modal Gaussian Model

Wrist pulse signals contain important information about the health of a person and hence diagnosis based on pulse signals has assumed great importance. In this paper we demonstrate the efficacy of a two term Gaussian model to extract information from pulse signals. Results have been obtained by conducting experiments on several subjects to record wrist pulse signals for the cases of before exercise and after exercise. Parameters have been extracted from the recorded signals using the model and a paired t-test is performed, which shows that the parameters are significantly different between the two groups. Further, a recursive cluster elimination based support vector machine is used to perform classification between the groups. An average classification accuracy of 99.46% is obtained, along with top classifiers. It is thus shown that the parameters of the Gaussian model show changes across groups and hence the model is effective in distinguishing the changes taking place due to the two different recording conditions. The study has potential applications in healthcare.

Least squares QR-based decomposition provides an efficient way of computing optimal regularization parameter in photoacoustic tomography

A computationally efficient approach that computes the optimal regularization parameter for the Tikhonov-minimization scheme is developed for photoacoustic imaging. This approach is based on the least squares-QR decomposition which is a well-known dimensionality reduction technique for a large system of equations. It is shown that the proposed framework is effective in terms of quantitative and qualitative reconstructions of initial pressure distribution enabled via finding an optimal regularization parameter. The computational efficiency and performance of the proposed method are shown using a test case of numerical blood vessel phantom, where the initial pressure is exactly known for quantitative comparison. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)