50175 research outputs found
Sort by
Non-equilibrium microstructure, crystallographic texture and morphological texture synergistically result in unusual mechanical properties of 3D printed 316L stainless steel
No full textMechanisms underlying the evolution of texture and microstructure during selective laser melting (SLM) and their combined effects on the mechanical response of 316L stainless steel are presented. Long columnar grains with a fiber texture < 110 > || build direction (BD) evolved in the SLM printed material. Fiber texture was stronger in the horizontal build compared to the vertical build. Use of bidirectional scanning strategy enforced epitaxial growth of grains across melt pools present within a single printed layer. < 110> || BD texture evolved as a consequence of maintaining the balance between epitaxy and growth of 100] along maximum thermal gradient. High dislocation density and not grain size effect of the ultra-fine cellular structure, imparted high strength to 316L. Lower average Schmid factor and smaller effective grain size in the horizontal build by virtues of crystallographic and morphological textures, respectively, imparted higher yield strength than the vertical build. The horizontal build demonstrated higher strain hardening rate in the early stages of deformation compared to the vertical build due to higher crystallographic texture dependent twinning. However, the higher rate of dislocation annihilation led to a continuous decline in the strain hardening rate of the horizontal build. In contrast, a stable strain hardening rate was maintained in the vertical build, which led to higher ductility than the horizontal build. In summary, the roles of non-equilibrium microstructure and texture (crystallographic and morphological) in regulating mechanical properties elucidated here, can be utilized in designing additively manufactured structural components of 316L stainless steel
Noise robust speech rate estimation using signal-to-noise ratio dependent sub-band selection and peak detection strategy
No full textSpeech (syllable) rate estimation typically involves computing a feature contour based on sub-band energies having strong local maxima/peaks at syllable nuclei, which are detected with the help of voicing decisions (VDs). While such a two-stage scheme works well in clean conditions, the estimated speech rate becomes less accurate in noisy condition particularly due to erroneous VDs and non-informative sub-bands mainly at low signal-to-noise ratios (SNR). This work proposes a technique to use VDs in the peak detection strategy in an SNR dependent manner. It also proposes a data-driven sub-band pruning technique to improve syllabic peaks of the feature contour in the presence of noise. Further, this paper generalizes both the peak detection and the sub-band pruning technique for unknown noise and/or unknown SNR conditions. Experiments are performed in clean and 20, 10, and 0 dB SNR conditions separately using Switchboard, TIMIT, and CTIMIT corpora under five additive noises: white, car, high-frequency-channel, cockpit, and babble. Experiments are also carried out in test conditions at unseen SNRs of -5 and 5 dB with four unseen additive noises: factory, sub-way, street, and exhibition. The proposed method outperforms the best of the existing techniques in clean and noisy conditions for three corpora
Dynamics of droplet impingement on bioinspired surface: insights into spreading, anomalous stickiness and break-up
No full textInspired by the self-cleaning ability of lotus leaves and stickiness (towards water) of rose petals, we investigate the droplet impact dynamics on such bioinspired substrates. Impact studies are carried out with water droplets for a range of impact velocities on glass, PDMS and soft lithographically fabricated replicas of the lotus leaf and rose petals, which exhibit near identical wetting properties as that of the original biological entities. In this work, we investigate the spreading, dewetting and droplet break-up mechanisms subsequent to impact. Surprisingly, the rose petal and lotus leaf replicas manifest similar impact dynamics. The observation is extremely intriguing and counterintuitive, as rose petal and its replicas are sticky in contrast to lotus leaves. However, these observations are based on experiments performed with sessile water droplets. By contrast, in the current study, we find that rose petal replicas exhibit non-sticky behaviour at the short time scale similar to(O(10(-3)))s similar to that exhibited by lotus leaf replicas. Air entrapment in the micrometre features of bioinspired surfaces prevent frictional dissipation of droplet kinetic energy, leading to contact edge recession. We have also unveiled interesting universal physics that govern the spreading, recession of the contact edge and subsequent break-up modes (ligament or bulb-ligament) of the droplet
One-pot oligosaccharide synthesis: latent-active method of glycosylations and radical halogenation activation of allyl glycosides
No full textChemical glycosylations occupy a central importance to synthesize tailor-made oligo- and polysaccharides of functional importance. Generation of the oxocarbenium ion or the glycosyl cation is the method of choice in order to form the glycosidic bond interconnecting a glycosyl moiety with a glycosyl/aglycosyl moiety. A number of elegant methods have been devised that allow the glycosyl cation formation in a fairly stream-lined manner to a large extent. The latent-active method provides a powerful approach in the protecting group controlled glycosylations. In this context, allyl glycosides have been developed to meet the requirement of latent-active reactivities under appropriate glycosylation conditions. Radical halogenation provides a newer route of activation of allyl glycosides to an activated allylic glycoside. Such an allylic halide activation subjects the glycoside reactive under acid catalysis, leading to the conversion to a glycosyl cation and subsequent glycosylation with a number of acceptors. The complete anomeric selectivity favoring the 1,2-trans-anomeric glycosides points to the possibility of a preferred conformation of the glycosyl cation. This article discusses about advancements in the selectivity of glycosylations, followed by delineating the allylic halogenation of allyl glycoside as a glycosylation method and demonstrates synthesis of a repertoire of di- and trisaccharides, including xylosides, with varied protecting groups
Water in Carbon Nanotubes: Pronounced Anisotropy in Dielectric Dispersion and Its Microscopic Origin
No full textWe report a remarkable anisotropy in the dielectric properties of water under cylindrical nanoconfinements in carbon nanotubes (CNTs). We employ linear response theory and use a new relation to define and calculate the two distinct eigenvalues of the dielectric tensor, namely, the axial (epsilon(z)) and perpendicular (epsilon(x/y)) components. We discover that not just the dielectric tensor but dielectric relaxation also exhibits strong anisotropy. The present study reveals that the parallel (epsilon(z)) and the orthogonal (epsilon(x/y)) components approach the bulk value in an opposite manner when the diameter of the CNT is increased. Rather unexpectedly, the polarization fluctuations remain quenched in the perpendicular direction even for the largest systems studied. The microscopic origin of the observed anisotropy is attributed to the propagation of surface effects into the confined liquid
Molecular evolution of single chain fragment variable (scFv) for diagnosis of lymphatic filariasis
No full textEndemic countries with lymphatic filariasis are striving towards the Global Program to Eliminate Lymphatic Filariasis (GPELF) by 2020. Efficient and cost-effective diagnostic tools to assess active filarial infection are critical to eradicate lymphatic filariasis. Detection of circulating filarial antigens in sera is one of the precise methods to identify this infection. Monoclonal antibodies and single chain fragment variable (scFv) against Wuchereria bancrofti antigen SXP1 have been developed for antigen detection. Molecular cloning of scFv for recombinant expression has laid a platform for developing novel genetic constructs with enhanced reactivity. In this study, a simple procedure is developed to create diverse libraries of scFv based on a single DNA framework with all the requisites for an in vitro protein synthesis and ribosomal display. Error Prone-PCR was performed to incorporate random mutations and screened by ribosome display technique to isolate evolved scFv. Evolved scFv with six mutations showed tenfold increase in affinity compared to wild-type scFv for rWbSXP1. In silico studies showed that four mutations introduced unique molecular interactions between the evolved scFv and SXP1. Reactivity with asserted clinical samples of endemic normals (EN), microfilariaemic (MF), chronic pathology (CP) and non-endemic normals (NEN) showed significant augment (59.69%, p < 0.0001) in reactivity to MF samples with evolved scFv in comparison to wild-type scFv. Sensitivity of scFv was increased from 15.62 ng to 195 pg by evolved scFv in serum samples. This evolutionary method coupled with ribosome display has facilitated us to improve the reactivity of the ScFv without diminishing the specificity
Safe Operating Area of Polarization Super-junction GaN HEMTs and Diodes
No full textThis article reports safe operating area (SOA) assessment in polarization super-junction (PSJ)-based GaN high-electron mobility transistor (HEMT) and Schottky diode. The degradation physics, which limits SOA in these devices under high-voltage and high-current-injection conditions is presented. Trap-induced SOA degradation and the role of PSJ in SOA improvement are unveiled. In PSJ-field-effect transistor (FET), the impact of PSJ length and its position on SOA robustness are studied. The role of self-heating and substrate effect on degradation are discussed. PSJ diodes with different configurations of Schottky contact are investigated. The correlation between PSJ length and failure threshold is discovered, besides power and field dependence of SOA boundary. Compared with their conventional counterparts, unique failure modes are discovered in PSJ-based GaN HEMT and diode
Spectral Stochastic FEM for Uncertainty Quantification Due to Multiple Dielectric Variabilities
No full textThe impact of fabrication uncertainties such as random variations in material properties of the media on the electromagnetic system response is usually ignored due to computational cost. This is evaluated in this study using a spectral representation of these random parameters. The finite-element formulation for electromagnetics with edge elements is extended to include these stochastic variations. The numerical results are found to match the Monte Carlo simulation with a very large number of samples. The system matrix is found to be sparse, and hence, the method discussed is shown to be computationally efficient. Since this approach can handle uncertainty in multiple subregions, such as dielectric inserts in a waveguide, it can be used to analyze the sensitivity of practical electromagnetic systems over a range of frequencies
Harvesting energy via stimuli-free water/moisture dissociation by mesoporous SnO2-based hydroelectric cell and CuO as a pump for atmospheric moisture
No full textWater dissociation, in general, requires external stimuli such as light energy or electricity. Here, we present a stimuli-free water dissociation using mesoporous SnO2-based hydroelectric cell that can directly be exploited to generate electric power for portable applications. The device configuration is almost identical to metal-air batteries but follows altogether a different reaction pathway. The mesoporous SnO2-based hydroelectric cell dissociates water molecule into hydroxyl ions (OH-) and hydronium ion without any stimuli, transports hydronium ions to the opposite end, and simultaneously acts as the separator. The OH- react with Al electrode to release the electrons, whereas hydronium ions get reduced at the Ag electrode to produce a potential difference as high as similar to 1000 +/- 20 mV between the electrodes that is stable over 3500 hours. The device also shows its potential toward electric power generation from atmospheric moisture with the help of CuO layer that acts as moisture pump
Optical sensing of ultra-trace As3+ species using 2-mercaptoethanol capped CdTe Quantum Dots in aqueous medium
No full textThis work describes the optical response of luminescent colloidal CdTe quantum dots (QDs) stabilized with 2-mercaptoethanol (ME) and thioglycolic acid (TGA) synthesized by a one-pot hydrothermal method for sensing As3+ ions in aqueous solution. The sensing behavior of CdTe QDs was determined by examining the fluorescence spectra with the varying molar concentration of As3+ ions in the solution. The fluorescence peaks of TGA-CdTe QDs (?=648 nm) depreciated in the presence of As3+ ions. However, ME-CdTe QDs (?=610 nm) peaks got enhanced in the presence of As3+ ions. The quenching responses of TGA-CdTe fluorescence peak is attributed to a non-radiative relaxation process due to the presence of traps states on the surface. On the other hand, luminescence enhancement of ME-CdTe QDs can be ascribed to the active surface related radiative decay, owing to surface passivation of dangling bonds in QDs or due to the formation of higher bandgap AsTe shell structure formed on the ME-CdTe QDs. The detection limit in this method was found to be 10 nM l(?1). Hence, establishing ME-CdTe as a suitable probe for ultra-trace detection of As3+ ion in aqueous solution