Multiscale Symmetry Detection in Scalar Fields by Clustering Contours

The complexity in visualizing volumetric data often limits the scope of direct exploration of scalar fields. Isocontour extraction is a popular method for exploring scalar fields because of its simplicity in presenting features in the data. In this paper, we present a novel representation of contours with the aim of studying the similarity relationship between the contours. The representation maps contours to points in a high-dimensional transformation-invariant descriptor space. We leverage the power of this representation to design a clustering based algorithm for detecting symmetric regions in a scalar field. Symmetry detection is a challenging problem because it demands both segmentation of the data and identification of transformation invariant segments. While the former task can be addressed using topological analysis of scalar fields, the latter requires geometry based solutions. Our approach combines the two by utilizing the contour tree for segmenting the data and the descriptor space for determining transformation invariance. We discuss two applications, query driven exploration and asymmetry visualization, that demonstrate the effectiveness of the approach.

A phylogeny of the only ground-dwelling radiation of Cyrtodactylus (Squamata, Gekkonidae): diversification of Geckoella across peninsular India and Sri Lanka

The subgenus Geckoella, the only ground-dwelling radiation within Cyrtodactylus, closely overlaps in distribution with brookii group Hemidactylus in peninsular India and Sri Lanka. Both groups have Oligocene origins, the latter with over thrice as many described species. The striking difference in species richness led us to believe that Geckoella diversity is underestimated, and we sampled for Geckoella across peninsular India. A multi-locus phylogeny reveals Geckoella diversity is hugely underestimated, with at least seven undescribed species, doubling previously known richness. Strikingly, the new species correspond to cryptic lineages within described Indian species (complexes); a number of these endemic lineages from the hills of peninsular India outside the Western Ghats, highlighting the undocumented diversity of the Indian dry zone. The Geckoella phylogeny demonstrates deep splits between the Indian species and Sri Lankan G. triedrus, and between Indian dry and wet zone clades, dating back to the late Oligocene. Geckoella and brookii group Hemidactylus show contrasting diversification patterns. Geckoella shows signals of niche conservatism and appears to have retained its ancestral forest habitat. The late Miocene burst in speciation in Geckoella may be linked to the expansion of rain forests during the mid-Miocene climatic optimum and subsequent fragmentation with increasing late Miocene aridification. (C) 2014 Elsevier Inc. All rights reserved.

The Relationship Between Solar Coronal X-Ray Brightness and Active Region Magnetic Fields: A Study Using High-Resolution Hinode Observations

By using high-resolution observations of nearly co-temporal and co-spatial Solar Optical Telescope spectropolarimeter and X-Ray Telescope coronal X-ray data onboard Hinode, we revisit the problematic relationship between global magnetic quantities and coronal X-ray brightness. Co-aligned vector magnetogram and X-ray data were used for this study. The total X-ray brightness over active regions is well correlated with integrated magnetic quantities such as the total unsigned magnetic flux, the total unsigned vertical current, and the area-integrated square of the vertical and horizontal magnetic fields. On accounting for the inter-dependence of the magnetic quantities, we inferred that the total magnetic flux is the primary determinant of the observed integrated X-ray brightness. Our observations indicate that a stronger coronal X-ray flux is not related to a higher non-potentiality of active-region magnetic fields. The data even suggest a slightly negative correlation between X-ray brightness and a proxy of active-region non-potentiality. Although there are small numerical differences in the established correlations, the main conclusions are qualitatively consistent over two different X-ray filters, the Al-poly and Ti-poly filters, which confirms the strength of our conclusions and validate and extend earlier studies that used low-resolution data. We discuss the implications of our results and the constraints they set on theories of solar coronal heating.

Modeling of solar radiation management: a comparison of simulations using reduced solar constant and stratospheric sulphate aerosols

The climatic effects of Solar Radiation Management (SRM) geoengineering have been often modeled by simply reducing the solar constant. This is most likely valid only for space sunshades and not for atmosphere and surface based SRM methods. In this study, a global climate model is used to evaluate the differences in the climate response to SRM by uniform solar constant reduction and stratospheric aerosols. Our analysis shows that when global mean warming from a doubling of CO2 is nearly cancelled by both these methods, they are similar when important surface and tropospheric climate variables are considered. However, a difference of 1 K in the global mean stratospheric (61-9.8 hPa) temperature is simulated between the two SRM methods. Further, while the global mean surface diffuse radiation increases by similar to 23 % and direct radiation decreases by about 9 % in the case of sulphate aerosol SRM method, both direct and diffuse radiation decrease by similar fractional amounts (similar to 1.0 %) when solar constant is reduced. When CO2 fertilization effects from elevated CO2 concentration levels are removed, the contribution from shaded leaves to gross primary productivity (GPP) increases by 1.8 % in aerosol SRM because of increased diffuse light. However, this increase is almost offset by a 15.2 % decline in sunlit contribution due to reduced direct light. Overall both the SRM simulations show similar decrease in GPP (similar to 8 %) and net primary productivity (similar to 3 %). Based on our results we conclude that the climate states produced by a reduction in solar constant and addition of aerosols into the stratosphere can be considered almost similar except for two important aspects: stratospheric temperature change and the consequent implications for the dynamics and the chemistry of the stratosphere and the partitioning of direct versus diffuse radiation reaching the surface. Further, the likely dependence of global hydrological cycle response on aerosol particle size and the latitudinal and height distribution of aerosols is discussed.

Giant actuation in bulk carbon nanotubes under coupled electric and magnetic fields

We report an enhanced actuation in bulk carbon nanotubes (CNTs) under coupled electric and magnetic fields, which is much higher than that evaluated in the presence of individual fields. Coupled electric and magnetic fields induce a directional actuation demonstrating a transformation from polarity independent to dependent actuation behavior of CNTs. Both qualitative and quantitative analyses are performed to understand this transformation in the bulk CNTs. Moreover, actuations along radial and axial directions of CNTs have also demonstrated a similar directional behavior.

Prediction of Land Surface Temperature under Cloudy Conditions using Microwave Remote Sensing and ANN

Land surface temperature (LST) is an important variable in climate, hydrologic, ecological, biophysical and biochemical studies (Mildrexler et al., 2011). The most effective way to obtain LST measurements is through satellites. Presently, LST from moderate resolution imaging spectroradiometer (MODIS) sensor is applied in various fields due to its high spatial and temporal availability over the globe, but quite difficult to provide observations in cloudy conditions. This study evolves of prediction of LST under clear and cloudy conditions using microwave vegetation indices (MVIs), elevation, latitude, longitude and Julian day as inputs employing an artificial neural network (ANN) model. MVIs can be obtained even under cloudy condition, since microwave radiation has an ability to penetrate through clouds. In this study LST and MVIs data of the year 2010 for the Cauvery basin on a daily basis were obtained from MODIS and advanced microwave scanning radiometer (AMSR-E) sensors of aqua satellite respectively. Separate ANN models were trained and tested for the grid cells for which both LST and MVI were available. The performance of the models was evaluated based on standard evaluation measures. The best performing model was used to predict LST where MVIs were available. Results revealed that predictions of LST using ANN are in good agreement with the observed values. The ANN approach presented in this study promises to be useful for predicting LST using satellite observations even in cloudy conditions. (C) 2015 The Authors. Published by Elsevier B.V.

Sources of black carbon aerosols in South Asia and surrounding regions during the Integrated Campaign for Aerosols, Gases and Radiation Budget (ICARB)

This study examines differences in the surface black carbon (BC) aerosol loading between the Bay of Bengal (BoB) and the Arabian Sea (AS) and identifies dominant sources of BC in South Asia and surrounding regions during March-May 2006 (Integrated Campaign for Aerosols, Gases and Radiation Budget, ICARB) period. A total of 13 BC tracers are introduced in the Weather Research and Forecasting Model coupled with Chemistry to address these objectives. The model reproduced the temporal and spatial variability of BC distribution observed over the AS and the BoB during the ICARB ship cruise and captured spatial variability at the inland sites. In general, the model underestimates the observed BC mass concentrations. However, the model-observation discrepancy in this study is smaller compared to previous studies. Model results show that ICARB measurements were fairly well representative of the AS and the BoB during the pre-monsoon season. Elevated BC mass concentrations in the BoB are due to 5 times stronger influence of anthropogenic emissions on the BoB compared to the AS. Biomass burning in Burma also affects the BoB much more strongly than the AS. Results show that anthropogenic and biomass burning emissions, respectively, accounted for 60 and 37% of the average +/- standard deviation (representing spatial and temporal variability) BC mass concentration (1341 +/- 2353 ng m(-3)) in South Asia. BC emissions from residential (61 %) and industrial (23 %) sectors are the major anthropogenic sources, except in the Himalayas where vehicular emissions dominate. We find that regional-scale transport of anthropogenic emissions contributes up to 25% of BC mass concentrations in western and eastern India, suggesting that surface BC mass concentrations cannot be linked directly to the local emissions in different regions of South Asia.

Photocatalytic inactivation of E-Coli by ZnO-Ag nanoparticles under solar radiation

Porous and fluffy ZnO photocatalysts were successfully prepared via simple solution based combustion synthesis method. The photocatalytic inactivation of Escherichia coli bacteria was studied separately for both Ag substituted and impregnated ZnO under irradiation of natural solar light. A better understanding of substitution and impregnation of Ag was obtained by Raman spectrum and X-ray photoelectron analysis. The reaction parameters such as catalyst dose, initial bacterial concentration and effect of hydroxyl radicals via H2O2 addition were also studied for ZnO catalyst. Effective inactivation was observed with 0.25 g L-1 catalyst loading having 10(9) CFU mL(-1) bacterial concentration. With an increase in molarity of H2O2, photocatalytic inactivation was enhanced. The effects of different catalysts were studied, and highest bacterial killing was observed by Ag impregnated ZnO with 1 atom% Ag compared to Ag substituted ZnO. This enhanced activity can be attributed to effective charge separation that is supported by photoluminescence studies. The kinetics of reaction in the presence of different scavengers showed that reaction is significantly influenced by the presence of hole and hydroxyl radical scavenger with high efficiency.

Photoresponse of double-stacked graphene to Infrared radiation

We report the photoresponse of stacked graphene layers towards infrared radiation. Graphene is stacked in two configurations, namely, crossed and parallel layers. Raman analysis demonstrated a strong interaction among the stacked graphene layers. Graphene in the crossed configuration exhibited the presence of both negative and positive conductivities; however, other configurations of graphene exhibited positive conductivity only. The presence of negative photoconductivity is proposed to be due to oxygen or oxygen-related functional group absorbents that are trapped in between two monolayers of graphene and act as scattering centers for free carriers. An interesting trend is reported in differential conductivity when stacked layers are compared with multilayers and parallel-stacked graphene layers.

An addition to the endemic Indian radiation of Eutropis: Phylogenetic position of Eutropis dissimilis Hallowell (Squamata: Scincidae)

Skinks of the genus Eutropis represent one of the most widespread and speciose lizard groups in tropical Asia. Numerous recent studies have utilized a variety of genes and methods to reconstruct the phylogeny of these lizards, however these studies have not resolved the placement of one of the widely distributed Eutropis Fitzinger, E. dissimilis. We have sequenced a specimen of E. dissimilis from the type locality and our result suggests that it is part of the Indian radiation of Eutropis and not related to African Trachylepis Fitzinger or Southeast Asian Dasia Gray as previously suggested. Furthermore, we report that the sequence of E. dissimilis used in an earlier study of the once cosmopolitan genus `Mabuya' may have been erroneously identified and appears to be a sequence of E. novemcarinata. We also demonstrate that the evolution of a clear lower eyelid, which was considered a synapomorphy for the sister genus Trachylepis, has arisen multiple times in Eutropis.

Attenuating microwave radiation by absorption through controlled nanoparticle localization in PC/PVDF blends

Nanoscale ordering in a polymer blend structure is indispensable to obtain materials with tailored properties. It was established here that controlling the arrangement of nanoparticles, with different characteristics, in co-continuous PC/PVDF (polycarbonate/poly(vinylidene fluoride)) blends can result in outstanding microwave absorption (ca. 90%). An excellent reflection loss (RL) of ca. -71 dB was obtained for a model blend structure wherein the conducting (multiwall carbon nanotubes, MWNTs) and the magnetic inclusions (Fe3O4) are localized in PVDF and the dielectric inclusion (barium titanate, BT) is in PC. The MWNTs were modified using polyaniline, which facilitates better charge transport in the blends. Furthermore, by introducing surface active groups on BT nanoparticles and changing the macroscopic processing conditions, the localization of BT nanoparticles can be tailored, otherwise BT nanoparticles would localize in the preferred phase (PVDF). In this study, we have shown that by ordered arrangement of nanoparticles, the incoming EM radiation can be attenuated. For instance, when PANI-MWNTs were localized in PVDF, the shielding was mainly through reflection. Now by localizing the conducting inclusion and the magnetic lossy materials in PVDF and the dielectric materials in PC, an outstanding shielding effectiveness of ca. -37 dB was achieved where shielding was mainly through absorption (ca. 90%). Thus, this study clearly demonstrates that lightweight microwave absorbers can be designed using polymer blends as a tool.

Baryon squishing in synthetic dimensions by effective SU(M) gauge fields

The ``synthetic dimension'' proposal A. Celi et al., Phys. Rev. Lett. 112, 043001 (2014)] uses atoms with M internal states (''flavors'') in a one-dimensional (1D) optical lattice, to realize a hopping Hamiltonian equivalent to the Hofstadter model (tight-binding model with a given magnetic flux per plaquette) on an M-sites-wide square lattice strip. We investigate the physics of SU(M) symmetric interactions in the synthetic dimension system. We show that this system is equivalent to particles with SU(M) symmetric interactions] experiencing an SU(M) Zeeman field at each lattice site and a non-Abelian SU(M) gauge potential that affects their hopping. This equivalence brings out the possibility of generating nonlocal interactions between particles at different sites of the optical lattice. In addition, the gauge field induces a flavor-orbital coupling, which mitigates the ``baryon breaking'' effect of the Zeeman field. For M particles, concomitantly, the SU(M) singlet baryon which is site localized in the usual 1D optical lattice, is deformed to a nonlocal object (''squished baryon''). We conclusively demonstrate this effect by analytical arguments and exact (numerical) diagonalization studies. Our study promises a rich many-body phase diagram for this system. It also uncovers the possibility of using the synthetic dimension system to laboratory realize condensed-matter models such as the SU(M) random flux model, inconceivable in conventional experimental systems.

SPEECH ENHANCEMENT USING DISCRIMINATIVE RANDOM FIELDS

Speech enhancement in stationary noise is addressed using the ideal channel selection framework. In order to estimate the binary mask, we propose to classify each time-frequency (T-F) bin of the noisy signal as speech or noise using Discriminative Random Fields (DRF). The DRF function contains two terms - an enhancement function and a smoothing term. On each T-F bin, we propose to use an enhancement function based on likelihood ratio test for speech presence, while Ising model is used as smoothing function for spectro-temporal continuity in the estimated binary mask. The effect of the smoothing function over successive iterations is found to reduce musical noise as opposed to using only enhancement function. The binary mask is inferred from the noisy signal using Iterated Conditional Modes (ICM) algorithm. Sentences from NOIZEUS corpus are evaluated from 0 dB to 15 dB Signal to Noise Ratio (SNR) in 4 kinds of additive noise settings: additive white Gaussian noise, car noise, street noise and pink noise. The reconstructed speech using the proposed technique is evaluated in terms of average segmental SNR, Perceptual Evaluation of Speech Quality (PESQ) and Mean opinion Score (MOS).

AN INVESTIGATION OF CUTTING MECHANISMS AND STRAIN FIELDS DURING ORTHOGONAL CUTTING IN CFRPs

Fiber-reinforced plastics (FRPs) are typically difficult to machine due to their highly heterogeneous and anisotropic nature and the presence of two phases (fiber and matrix) with vastly different strengths and stiffnesses. Typical machining damage mechanisms in FRPs include series of brittle fractures (especially for thermosets) due to shearing and cracking of matrix material, fiber pull-outs, burring, fuzzing, fiber-matrix debonding, etc. With the aim of understanding the influence of the pronounced heterogeneity and anisotropy observed in FRPs, ``Idealized'' Carbon FRP (I-CFRP) plates were prepared using epoxy resin with embedded equispaced tows of carbon fibers. Orthogonal cutting of these I-CFRPs was carried out, and the chip formation characteristics, cutting force signals and strain distributions obtained during machining were analyzed using the Digital Image Correlation (DIC) technique. In addition, the same procedure was repeated on Uni-Directional CFRPs (UD-CFRPs). Chip formation mechanisms in FRPs were found to depend on the depth of cut and fiber orientation with pure epoxy showing a pronounced ``size effect.'' Experimental results indicate that in-situ full field strain measurements from DIC coupled with force measurements using dynamometry provide an adequate measure of anisotropy and heterogeneity during orthogonal cutting.

Sound radiation from a perforated panel set in a baffle with a different perforation ratio

A finite flexible perforated panel set in a differently perforated rigid baffle is considered. The radiation efficiency from such a panel is derived using a 2-D wavenumber domain formulation. This generalization is later used to represent a more practical case of a perforated panel fixed in an unperforated baffle. The perforations are in the form of an array of uniformly distributed circular holes. A complex impedance model for the holes available in the literature is used. An averaged fluid particle velocity is derived using the continuity equation and the surface pressure is derived using an appropriate momentum equation. The discontinuity in the perforate impedance (due to different hole dimensions or perforation ratio) at the panel-baffle interface is carefully taken into account. It is found that there exists a `coupling' of different wavenumbers of the spatially mean fluid particle velocity field. The change in the resonance frequencies and the modeshapes of the panel due to the perforations is taken into account using the Receptance method. Analytical expressions for the radiated power and radiation efficiency are derived in an integral form and numerical results are presented. Several comparisons are made to understand the radiation efficiency curves. Since both the resistive and reactive components of the hole impedance are taken into account, the model is directly applicable to micro-perforated panels also. (C) 2016 Elsevier Ltd. All rights reserved.