Effect of crystal orientation,structure and dimension on vickers microhardness anisotropy of β-, α-Si3N4, α-SiO2 and α-SiC single crystals

Variation of Vickers microhardness on planes parallel to [VMH(∥C)] and perpendicular to the C-axis [VMH(⊥C)] of hexagonal β-Si₃N₄, α-Si₃N₄, α-SiO₂ (α-quartz) and α-SiC(6H) single crystals has been studied. The $\text{VMH}\text{(∥}\text{C}\text{)}\text{VMH}\text{(⊥}\text{C}\text{)}$ ratios have been correlated with $\text{a}\text{c}$ ratios, a and c being unit cell parameters of the single crystals. VMH(⊥C) was found to be independent of orientation of Vickers indenter on basal plane (0001) of α-SiC, while VMH(∥C) was found to vary with Vickers indenter direction on prismatic plane (10-10) of α-SiC.VMH(∥C) of β-Si₃N₄ single crystals was found to depend on the aspect ratio of β-Si₃N₄, while VMH(⊥C) was found to be independent of the dimension of basal plane. VMH(⊥C) of α-SiC single crystals was also found to be independent of the dimension of basal plane of α-SiC.     

A deteriorating multi-item inventory model with price discount and variable demands via fuzzy logic under resource constraints

An inventory model of deteriorating seasonal products with Maximum Retail Price (MRP) for a wholesaler having showrooms at different places under a single management system is considered under random business periods with fuzzy resource constraints. The wholesaler replenishes the products instantaneously and earns commissions on MRP which vary with the ordered quantities following All Unit Discount (AUD), Incremental Quantity Discount (IQD) or IQD in AUD policy. Demand at showrooms are imprecise and related to selling prices by ‘verbal words’ following fuzzy logic. The wholesaler shares a part of commission with customers. The business periods follows normal distribution and converted to deterministic ones through chance constraint technique. The fuzzy space and budget constraints and fuzzy relations are defuzzified using possibility measures, surprise function and Mumdani fuzzy inference technique. The model is formulated as profit maximization for the wholesaler and solved using a real coded Genetic Algorithm (GA) and illustrated through some numerical examples and some sensitivity analysis. A real-life problem of a developing country is presented, solved using the above mentioned procedures and an appropriate inventory policy is suggested.     

Human action recognition using an ensemble of body‐part detectors

This paper describes an approach to human action recognition based on a probabilistic optimization model of body parts using hidden Markov model (HMM). Our method is able to distinguish between similar actions by only considering the body parts having major contribution to the actions, for example, legs for walking, jogging and running; arms for boxing, waving and clapping. We apply HMMs to model the stochastic movement of the body parts for action recognition. The HMM construction uses an ensemble of body‐part detectors, followed by grouping of part detections, to perform human identification. Three example‐based body‐part detectors are trained to detect three components of the human body: the head, legs and arms. These detectors cope with viewpoint changes and self‐occlusions through the use of ten sub‐classifiers that detect body parts over a specific range of viewpoints. Each sub‐classifier is a support vector machine trained on features selected for the discriminative power for each particular part/viewpoint combination. Grouping of these detections is performed using a simple geometric constraint model that yields a viewpoint‐invariant human detector. We test our approach on three publicly available action datasets: the KTH dataset, Weizmann dataset and HumanEva dataset. Our results illustrate that with a simple and compact representation we can achieve robust recognition of human actions comparable to the most complex, state‐of‐the‐art methods.     

Methodology to classify rice cultural types based on water regimes using multi-temporal RADARSAT-1 data

This study presents a methodology to classify rice cultural types based on water regimes using multi-temporal synthetic aperture radar (SAR) data. The methodology was developed based on the theoretical understanding of radar scattering mechanisms with rice crop canopy, considering crop phenology and variation in water depth in the rice field, emphasizing the sensitivity of SAR to crop geometry and water. The logic used was the characteristic decrease in SAR backscatter that is associated with the puddled or transplanted field due to specular reflection for little exposure of crop, with increase in backscatter as the crop growth progresses due to volume scattering. Besides, the multiple interactions between SAR and vegetation/water also lead to an increase in backscatter as the crop growth progresses. Classification thresholds were established based on the information provided by each pixel in each image, the pixel's typical temporal behaviour due to crop phenology and changing water depth in rice field and their corresponding SAR signature. Based on this logic, the study site (i.e. South 24 Paraganas district, West Bengal) was classified into three major rice cultural types, namely shallow water rice (SWR; 5 cm ≤ water depth ≤ 30 cm), intermediate water rice (IWR; 30 cm ≤ water depth ≤ 50 cm) and deep water rice (DWR; water depth > 50 cm) during the kharif season. These three types represent most of the traditional rice-growing areas of India. The methodology was validated with the field data collected synchronously with the satellite passes. Classification results showed an overall accuracy of 98.5% (95.5% kappa coefficient) compared with a maximum-likelihood classifier (MLC) with an overall accuracy of 95.5% (84.2% of kappa coefficient) with 95% confidence interval. The relationship between field parameters, especially exposed plant height and water depth with SAR backscatter, was explored to design empirical models for each of the three rice classes. Significant relationships were observed in all the rice classes (coefficient of determination, R ², value more than 0.85) even though they had similar growth profiles but varied with water depth. The two main conclusions drawn from this study are (i) the importance of multi-temporal SAR data for the classification of rice culture types based on water regimes and (ii) the advantages and flexibility of the knowledge-based classifier for classification of RADARSAT-1 data. However, being empirical, the approach needs modification according to the current rainfall pattern and rice-growing practice.     

Vitiligo, psoralen, and melanogenesis: some observations and understanding

Since the etiology of vitiligo is still unknown, we searched for some abnormal biochemical parameters, if any, in subjects with vitiligo. Higher urinary excretion of indole metabolites in vitiliginous patients have been noted, in association with higher dioxygenase, superoxide dismutase, and tyrosine aminotransferase activity in their serum. Similar results have also been found in an animal model, Bufo melanostictus, during induced tyrosinase inhibition. Treatment with psoralen can reverse the parameters, except tyrosine aminotransferase, to a normal level. Although psoralens are not the magic bullet for the therapy of vitiligo, they are still being used as a chemotherapeutic agent against vitiligo on a major scale to date. Tryptophan was found to participate in the pathway of melanogenesis, as a precursor as well as a positive regulator of tyrosinase. Its behavior in this regard is much more similar to the conventional substrates tyrosine and dopa (dihydroxyphenylalanine). In consideration of combined participation of tyrosine and tryptophan in the synthesis of melanin and its breakdown, the possible influence of different enzymatic reactions, like mono-oxygenase, dioxygenase, and deamination, has been suggested.     

Neutralizing monoclonal antibodies against listeriolysin: mapping of epitopes involved in pore formation

Six different mouse monoclonal antibodies (MAbs) and a specific rabbit polygonal antibody were raised against listeriolysin. Four of the MAbs also recognized seeligeriolysin, and five cross-reacted with ivanolysin. The hemolytic activity could be neutralized by the polygonal antibody as well as by five of the MAbs. None of the neutralizing antibodies interfered with the binding of listeriolysin to the cellular membrane. The epitopes recognized by the MAbs were localized by using overlapping synthetic peptides between positions 59 and 279, a region hitherto not implicated in mediating hemolytic activity.     

Study of Impact of Access Resistance on High-Frequency Performance of AlGaN/GaN HEMTs by Measurements at Low Temperatures

This letter studies the effect of access resistance on the high-frequency performance of AlGaN/GaN high-electron-mobility transistors. To systematically reduce the sheet access resistance, the transistors were measured at different temperatures. The increase of mobility at lower temperatures allowed more than four-fold reduction in the sheet access resistances. Both the current- and power-gain cutoff frequencies are observed to increase at low temperatures. Also, the intrinsic effective velocity has been estimated in these devices, as well as the parasitic delays involved in the final performance. Channel charging delay, which was expected to be most sensitive to parasitics, is observed to decrease at low temperatures. However, the drain delay, intrinsic delay, and effective electron velocity remain unaffected by temperature     

Reliability of linear structures with parameter uncertainty under non-stationary earthquake

The present work aims towards the development of a general framework of time varying unconditional reliability evaluation of linear elastic multi degree of freedom structures with uncertain parameter subjected to the generalized earthquake ground motion, a non-stationary process both in amplitude and frequency content. The formulation is developed in double frequency spectrum to derive the generalized power spectral density function of the structural responses. The time varying reliability is evaluated using conditional crossing rate following the Vanmarcke’s modification. The perturbation based stochastic finite element method is utilized in deriving unconditional reliability. An idealized three dimensional dam structure subjected to El Centro (1940) earthquake is taken up to elucidate the proposed unconditional time varying reliability computation procedure based on the maximum top displacement and base shear criteria. The results are presented to compare the change in reliabilities of the uncertain system with that of deterministic system and associated variance of the reliability due to parameter uncertainty.     

Transport phenomena in conduction mode laser beam welding of Fe–Al dissimilar couple with Ta diffusion barrier

Fusion welding of dissimilar metals always encounters immense difficulties due to the formation of brittle intermetallic phases that make the joint unsuitable for structural applications. Using a barrier layer that wets well with either component but does not undergo melting itself and prevents intermixing and undesirable phase formation could be a possible remedy. In order to explore this hypothesis, we have made an attempt to numerically simulate and experimentally validate the heat and mass transport phenomena in the fusion zone concerning laser assisted welding of Fe–Al dissimilar couples with 0.2 mm Ta foil as the diffusion barrier butted between Fe and Al. The results suggest that the Fe-side undergoes greater degree of melting resulting in an asymmetric thermal and velocity fields. Furthermore, partial melting of Ta seems unavoidable but proves benign as this leads to good bonding between Fe–Ta and Ta–Al while precluding formation of Fe–Al alloy/intermetallic phases.