ANN techniques in microwave engineering

In the last two decades, artificial neural network (ANN) technology has leaped forward and is now being applied in different areas such as speech recognition, control, telecommunication, remote sensing, pattern recognition, etc. ANN application to the field of microwaves is very recent. This article reviews the development of neural network techniques, introduces some basic concepts involved in it, and gives a comprehensive survey of neural network application to different branches of microwave engineering     

Epileptic EEG detection using neural networks and post-classification

Electroencephalogram (EEG) has established itself as an important means of identifying and analyzing epileptic seizure activity in humans. In most cases, identification of the epileptic EEG signal is done manually by skilled professionals, who are small in number. In this paper, we try to automate the detection process. We use wavelet transform for feature extraction and obtain statistical parameters from the decomposed wavelet coefficients. A feed-forward backpropagating artificial neural network (ANN) is used for the classification. We use genetic algorithm for choosing the training set and also implement a post-classification stage using harmonic weights to increase the accuracy. Average specificity of 99.19%, sensitivity of 91.29% and selectivity of 91.14% are obtained.     

Parallel Mining of Neuronal Spike Streams on Graphics Processing Units

Multi-electrode arrays (MEAs) provide dynamic and spatial perspectives into brain function by capturing the temporal behavior of spikes recorded from cultures and living tissue. Understanding the firing patterns of neurons implicit in these spike trains is crucial to gaining insight into cellular activity. We present a solution involving a massively parallel graphics processing unit (GPU) to mine spike train datasets. We focus on mining frequent episodes of firing patterns that capture coordinated events even in the presence of intervening background events. We present two algorithmic strategies—hybrid mining and two-pass elimination—to map the finite state machine-based counting algorithms onto GPUs. These strategies explore different computation-to-core mapping schemes and illustrate innovative parallel algorithm design patterns for temporal data mining. We also provide a multi-GPU mining framework, which exhibits additional performance enhancement. Together, these contributions move us towards a real-time solution to neuronal data mining.     

Evaluation of the Role of p53 Tumour Suppressor Posttranslational Modifications and TTC5 Cofactor in Lung Cancer

Mutations in the p53 tumor suppressor are found in over 50% of cancers. p53 function is controlled through posttranslational modifications and cofactor interactions. In this study, we investigated the posttranslationally modified p53, including p53 acetylated at lysine 382 (K382), p53 phosphorylated at serine 46 (S46), and the p53 cofactor TTC5/STRAP (Tetratricopeptide repeat domain 5/ Stress-responsive activator of p300-TTC5) proteins in lung cancer. Immunohistochemical (IHC) analysis of lung cancer tissues from 250 patients was carried out and the results were correlated with clinicopathological features. Significant associations between total or modified p53 with a higher grade of the tumour and shorter overall survival (OS) probability were detected, suggesting that mutant and/or modified p53 acts as an oncoprotein in these patients. Acetylated at K382 p53 was predominantly nuclear in some samples and cytoplasmic in others. The localization of the K382 acetylated p53 was significantly associated with the gender and grade of the disease. The TTC5 protein levels were significantly associated with the grade, tumor size, and node involvement in a complex manner. SIRT1 expression was evaluated in 50 lung cancer patients and significant positive correlation was found with p53 S46 intensity, whereas negative TTC5 staining was associated with SIRT1 expression. Furthermore, p53 protein levels showed positive association with poor OS, whereas TTC5 protein levels showed positive association with better OS outcome. Overall, our results indicate that an analysis of p53 modified versions together with TTC5 expression, upon testing on a larger sample size of patients, could serve as useful prognostic factors or drug targets for lung cancer treatment.     

Silicon Carbide Ceramic Particulate Reinforced AA2024 Alloy Composite - Part I: Evaluation of Mechanical and Sliding Tribology Performance

In this research work, a master batch (comprising of AA2024 alloy, Silicon Nitride (Si3N4) and Graphite particulates) was reinforced by Silicon-Carbide (SiC) ceramic particulates (0–6 wt.-%; at steps of 2%; i.e. four composites samples viz. ASC-0; ASC-2; ASC-4; ASC-6) with the aim of enhancing mechanical and sliding tribology performance. The semi-automatic stir-casting fabrication process was followed as per standard industrial practice in-order-to fabricate the sample plates of the said alloy composites as per design. Thereafter, the sample specimens were prepared via wire EDM cutting followed by polishing over emery paper; as per ASTM standard dimensions and various physical (density and void content), mechanical (tensile strength, flexural strength, impact strength, hardness etc.), sliding tribology performance (steady state sliding wear; ASTM G-99; Pin-on-Disc tribo-meter), thermal (thermal conductivity, Thermo-Gravimetric Analysis (TGA)); thermo-mechanical (Dynamic Mechanical Analysis (DMA)), fracture-analysis, X-ray diffraction (XRD) etc. characterisation were performed and discussed. In Part-1: Physical, mechanical and sliding tribology performances were discussed. The Taguchi design of experiment technique was employed for designing of experimental runs having input controlling parameters like sliding velocity (0.654–2.616 m/s), sliding distance (784.8–3139.2 m), normal load (5–50 N), reinforcement content (0–6 wt.-%) and environment temperature (20–50 °C). The worn surface morphology studies were performed to understand prevalent wear mechanism using Field Emission Scanning Electron Microscope (FESEM) along with Energy-dispersive X-ray spectroscopy (EDS) that reveals elemental composition and its dispersion on the surface. In Part-2: evaluation of characterizations like thermal, thermo-mechanical, fracture-analysis, X-ray diffraction (XRD) etc. were discussed in correlation with mechanical and sliding wear performance. In Part-3: the entire performance data are analysed using hybrid AHP-TOPSIS technique (an MCDM technique; computationally simple and easy to understand) in-order-to rank the composites formulations.     

Efficiency of HCl- and H2SO4-acidulated rock phosphates for a rice based cropping system

Pot experiments were conducted with an acid laterite soil and a shallow black calcareous soil to study the effect of initial application of North Carolina and Udaipur rock phosphates, acidulated with HCl or H₂SO₄ to the extent of 25, 50, 75 or 100% of the requirement for complete conversion into superphosphate, on the grain yield and P uptake by crops in rice—wheat and wheat—rice cropping sequences. The products obtained on acidulation with HCl or H₂SO₄ at a given degree behaved similarly. Rock phosphates partially acidulated with HCl or H₂SO₄ to 50–75% could be used successfully for growing rice or wheat on both the soil types. In the rice—wheat sequence, the wheat crop following rice gave very low grain yields compared to the wheat crop in the wheat—rice rotation, while in the wheat—rice rotation the rice crop following wheat gave yields comparable to that of rice in the rice—wheat rotation. The reasons for this differential effect have been made plausible. The studies indicate that a 50–75% H₂SO₄ - or HCl-acidulated rock phosphate may be used as a single application to an upland crop in an upland crop—rice rotation especially on acid soils, where the water soluble fractions of the product are used by the wheat crop. During the process of growth of the upland crop under aerobic soil conditions, the citrate soluble and insoluble fractions undergo such transformations that make it possible for the following rice crop to utilize them under waterlogged conditions.     

An optimization algorithm based on the method of feasible directions

The theory and implementation of an optimization algorithm code based on the method of feasible directions are presented. Although the method of feasible directions was developed during the 1960's, the present implementation of the algorithm includes several modifications to improve its robustness. In particular, the search direction is generated by solving a quadratic program which uses an interior method based on a variation of Karmarkar's algorithm. The constraint thickness parameter is dynamically adjusted to yield usable-feasible directions. The theory is discussed with emphasis on the important and often overlooked role played by the various parameters guiding the iterations within the program. Also discussed is a robust approach for handling infeasible starting points. The code was validated by solving a variety of structural optimization test problems that have known solutions (obtained by other optimization codes). A variety of problems from different infeasible starting points has been solved successfully. It is observed that this code is robust and accurate. Further research is required to improve its numerical efficiency while retaining its robustness.     

Clinicopathological profile of subacute hepatic failure

Sigmoid volvulus is an unusual cause of intestinal obstruction in children. We report two cases of sigmoid volvulus as a complication of segmental dilatation of the colon occurring in two girls (5 years old and 9 years old) previously treated for chronic constipation. In both cases the constipation had been recognised since the neonatal period mimicking a Hirschsprung's disease, a diagnosis which has been excluded after rectal biopsy. The delayed diagnosis of segmental dilatation of the sigmoid colon followed the volvulus. Segmental colonic resection resulted in both cases in the cure of the constipation.     

Low pressure OMVPE of ZnSe with hydrogen selenide and dimethylzinc-triethylamine

The growth and nitrogen doping of ZnSe by low pressure organometallic vapor phase epitaxy (OMVPE) have been investigated in a vertical downflow reactor equipped with a laser interferometer for in-situ growth rate measurements, and a microwave plasma cavity for precracking of ammonia for nitrogen doping. Particular emphasis is placed on understanding growth characteristics obtained with H₂Se and the new adduct source dimethylzincrtriethylamine (DMZn:NEt₃), as compared to those obtained with H₂Se and DMZn. At higher temperatures and pressures, growth results obtained with DMZn:NEt₃ are similar to those obtained using DMZn with the morphology exhibiting familiar hillock-shaped features. At lower temperatures (<300°C) and pressures (<30 Torr), growth rates are higher with the adduct source and the surface morphology is improved relative to films synthesized with DMZn. Hall measurements and photo-luminescence spectra of the grown films demonstrate that DMZn and DMZn:NEt₃ produce material with comparable electronic and optical properties. Microwave plasma decomposition of ammonia is investigated as a possible approach to increasing nitrogen incorporation in ZnSe and photoluminescence spectra are compared to those realized with conventional ammonia doping.     

Organic photoconductors: Dark and photoconduction studies in two p-dimethylamino styryl dyes derived from pyridine-2 and pyridine-4

Results of our experiments on the dark and photoconduction studies in two p-dimethylamino styryl dyes derived from pyridine-2 (PDMS-P2) and pyridine-4 (PDMS-P4) in their pure form without any dopant or additive are reported. Measurements on surface-type (raster pattern) cells show that the dark and photocurrents are dependent on the applied potential, temperature, and the photocurrent on the intensity of the incident radiation and the wavelength. Action spectra of the samples could not be recorded as the intensity of the monochromatic radiation from the monochromator reaching the sample was too low to induce any noticeable photocurrent. The compounds show a low dark conductivity. The dark and photocurrents show a perfect ohmic behaviour in the temperature range studied (288–328 K). Since photoconduction could only be observed in a vacuum, this clearly indicates that the compounds are n-type semiconductors. The observed rise and decay kinetics of the photocurrents indicate the presence of traps in the forbidden zone. The dyes show an enhanced photoconduction on illumination with visible radiation only. The marked open circuit voltage and the short-circuit current observed in these compounds indicate a possible application in solar photovoltaics.