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Himanshu Sharma

Publications and source records attributed to Himanshu Sharma.

53 records · Page 3Linked to original sources
arXiv2019

Learning a Deep Convolution Network with Turing Test Adversaries for Microscopy Image Super Resolution

Adversarially trained deep neural networks have significantly improved performance of single image super resolution, by hallucinating photorealistic local textures, thereby greatly reducing the perception difference between a real high resolution image and its super resolved (SR) counterpart. However, application to medical imaging requires preservation of diagnostically relevant features while refraining from introducing any diagnostically confusing artifacts. We propose using a deep convolutional super resolution network (SRNet) trained for (i) minimising reconstruction loss between the real and SR images, and (ii) maximally confusing learned relativistic visual Turing test (rVTT) networks to discriminate between (a) pair of real and SR images (T1) and (b) pair of patches in real and SR selected from region of interest (T2). The adversarial loss of T1 and T2 while backpropagated through SRNet helps it learn to reconstruct pathorealism in the regions of interest such as white blood cells (WBC) in peripheral blood smears or epithelial cells in histopathology of cancerous biopsy tissues, which are experimentally demonstrated here. Experiments performed for measuring signal distortion loss using peak signal to noise ratio (pSNR) and structural similarity (SSIM) with variation of SR scale factors, impact of rVTT adversarial losses, and impact on reporting using SR on a commercially available artificial intelligence (AI) digital pathology system substantiate our claims.

cs.CV↗
arXiv2019

Radial Flow and Differential Freeze-out in Proton-Proton Collisions at $\sqrt{s}= 7$ TeV at the LHC

We analyse the transverse momentum ($p_{\rm T}$)-spectra as a function of charged-particle multiplicity at midrapidity ($|y| < 0.5$) for various identified particles such as $π^{\pm}$, $K^{\pm}$, $K_S^0$, $p+\overline{p}$, $ϕ$, $K^{*0} + \overline {K^{*0}}$, and $Λ$ + $\barΛ$ in proton-proton collisions at $\sqrt{s}$ = 7 TeV using Boltzmann-Gibbs Blast Wave (BGBW) model and thermodynamically consistent Tsallis distribution function. We obtain the multiplicity dependent kinetic freeze-out temperature ($T_{\rm kin}$) and radial flow ($β$) of various particles after fitting the $p_{\rm T}$-distribution with BGBW model. Here, $T_{\rm kin}$ exhibits mild dependence on multiplicity class while $β$ shows almost independent behaviour. The information regarding Tsallis temperature and the non-extensivity parameter ($q$) are drawn by fitting the $p_{\rm T}$-spectra with Tsallis distribution function. The extracted parameters of these particles are studied as a function of charged particle multiplicity density ($dN_{ch}/dη$). In addition to this, we also study these parameters as a function of particle mass to observe any possible mass ordering. All the identified hadrons show a mass ordering in temperature, non-extensive parameter and also a strong dependence on multiplicity classes, except the lighter particles. It is observed that as the particle multiplicity increases, the $q$-parameter approaches to Boltzmann-Gibbs value, hence a conclusion can be drawn that system tends to thermal equilibrium. The observations are consistent with a differential freeze-out scenario of the produced particles.

hep-ph↗
arXiv2018

A Transfer Operator Methodology for Optimal Sensor Placement Accounting for Uncertainty

Sensors in buildings are used for a wide variety of applications such as monitoring air quality, contaminants, indoor temperature, and relative humidity. These are used for accessing and ensuring indoor air quality, and also for ensuring safety in the event of chemical and biological attacks. It follows that optimal placement of sensors become important to accurately monitor contaminant levels in the indoor environment. However, contaminant transport inside the indoor environment is governed by the indoor flow conditions which are affected by various uncertainties associated with the building systems including occupancy and boundary fluxes. Therefore, it is important to account for all associated uncertainties while designing the sensor layout. The transfer operator based framework provides an effective way to identify optimal placement of sensors. Previous work has been limited to sensor placements under deterministic scenarios. In this work we extend the transfer operator based approach for optimal sensor placement while accounting for building systems uncertainties. The methodology provides a probabilistic metric to gauge coverage under uncertain conditions. We illustrate the capabilities of the framework with examples exhibiting boundary flux uncertainty.

eess.SY↗
arXiv2018

Anomaly in anomalous Nernst effect at low temperature for C1b-type NiMnSb half-Heusler alloy thin film

The anomaly in the anomalous Nernst effect (ANE) was observed for a C1b-type NiMnSb half-Heusler alloy thin film deposited on a MgO (001) substrate. The Nernst angle (θANE) showed maximum peak with decreasing temperature and reached 0.15 at 80 K, which is considered to be brought by the cross-over from half-metal to normal ferromagnet in NiMnSb at low temperature. This anomaly was also observed for the transport properties, that is, both the resistivity and the anomalous Hall resistivity in the same temperature range.

cond-mat.mes-hall↗
arXiv2018

Effect of B-site bismuth doping on magnetic and transport properties of La0.5Ca0.5Mn1-xBixO3 thin films

The magnetic properties in manganite have been found to be highly sensitive to the doping and structural manipulations. Here, we report the effect of B-site bismuth doping on the magnetic and transport properties in La0.5Ca0.5Mn1-xBixO3 (LCMBO) thin films (for x = 0, 0.02 and 0.05) for high-efficiency spintronics devices. For thin film of LCMBO (with x = 0.02), a significant increase in the magnetization and ferromagnetic ordering temperature (TC) are observed. Also, about 98% magnetoresistance (MR) and unusually large (~ 42%) anisotropic magnetoresistance (AMR) is observed at 50 K in the same LCMBO (for x = 0.02) thin film. This observed improvement in TC, MR and AMR in LCMBO (with x = 0.02) thin film may be attributed to the modulation of the trapped electrons through JT-distortions due to the replacement of Mn+3 ions by larger Bi+3 ions. With further increase in bismuth doping (for x = 0.05) at the B-site, a significant decrease in magnetization and TC have been observed.

cond-mat.mes-hall↗
arXiv2018

Developing a Portable Natural Language Processing Based Phenotyping System

This paper presents a portable phenotyping system that is capable of integrating both rule-based and statistical machine learning based approaches. Our system utilizes UMLS to extract clinically relevant features from the unstructured text and then facilitates portability across different institutions and data systems by incorporating OHDSI's OMOP Common Data Model (CDM) to standardize necessary data elements. Our system can also store the key components of rule-based systems (e.g., regular expression matches) in the format of OMOP CDM, thus enabling the reuse, adaptation and extension of many existing rule-based clinical NLP systems. We experimented with our system on the corpus from i2b2's Obesity Challenge as a pilot study. Our system facilitates portable phenotyping of obesity and its 15 comorbidities based on the unstructured patient discharge summaries, while achieving a performance that often ranked among the top 10 of the challenge participants. This standardization enables a consistent application of numerous rule-based and machine learning based classification techniques downstream.

cs.CL↗
arXiv2018

Transfer Operator Theoretic Framework for Monitoring Building Indoor Environment in Uncertain Operating Conditions

Dynamical system-based linear transfer Perron- Frobenius (P-F) operator framework is developed to address analysis and design problems in the building system. In particular, the problems of fast contaminant propagation and optimal placement of sensors in uncertain operating conditions of indoor building environment are addressed. The linear nature of transfer P-F operator is exploited to develop a computationally efficient numerical scheme based on the finite dimensional approximation of P-F operator for fast propagation of contaminants. The proposed scheme is an order of magnitude faster than existing methods that rely on simulation of an advection-diffusion partial differential equation for contami- nant transport. Furthermore, the system-theoretic notion of observability gramian is generalized to nonlinear flow fields using the transfer P-F operator. This developed notion of observability gramian for nonlinear flow field combined with the finite dimensional approximation of P-F operator is used to provide a systematic procedure for optimal placement of sensors under uncertain operating conditions. Simulation results are presented to demonstrate the applicability of the developed framework on the IEA-annex 2D benchmark problem.

eess.SY↗
arXiv2016

A novel ZnO piezoelectric microcantilever energy scavenger: Fabrication and characterization

This novel piezoelectric zinc oxide (ZnO) thin film microcantilever was fabricated by micromachining technique. To release the cantilever, wet anisotropic etching of Silicon (Si) was performed by tetramethyl ammonium hydroxide (TMAH). The transverse piezoelectric coefficient d31 of the ZnO film, obtained from the deflection of the cantilever with influence of applied voltage, was calculated as 3.32 pC/N. The observed dynamic characterization of the novel piezoelectric microcantilever had linear response with the applied driving voltage. The obtained values of Young Modulus and Hardness were 208 +4 GPa and 4.84+ 0.1 GPa respectively. This inexpensive novel method provides additional design flexibility to fabricate vibrational energy harvesters. The easy steps of fabrication and cost effectiveness of this method may be preferred it over DRIE. The voltage induced due to deformation of ZnO cantilever were measured ~230mV. This microcantilever energy scavenger may be used to power the nano devices and sensors for medical and agricultural applications as a replacement of traditional bulky batteries.

cond-mat.mes-hall↗
arXiv2016

Planar Hall and Nernst effect in patterned ultrathin film of La0.7Sr0.3MnO3

We present the observation of a transverse thermopower, or Planar Nernst Effect, in patterned ultrathin film (8 nm) of La0.7Sr0.3MnO3 (LSMO) driven by heat current applied in-plane of the film and Planar Hall Effect (PHE) in the same LSMO ultrathin film with in-plane current of 100 microA is also investigated. Even for temperature difference of 5 K the Planar Nernst Effect in ultrathin film (8 nm) shows a coercivity of 3 Oe same as observed in Planar Hall Effect measurement and confirms the ferromagnetic nature of thin film. The angular dependence of transverse voltages shows four-fold sin{theta} cos{theta} dependence symmetry at 250 K, which is consistent with Planar Hall Effect measurement.

cond-mat.mes-hall↗
arXiv2016

Magnetism in La$_{0.7}$Sr$_{0.3}$Mn$_{1-x}$Co$_x$O$_3$ ($0 \leq x \leq 1$)

We study the structural and magnetic properties of La$_{0.7}$Sr$_{0.3}$Mn$_{1-x}$Co$_x$O$_3$ ($0 \leq x \leq 1$). Rietveld refinement of X-ray Diffraction (XRD) pattern suggests phase purity of the polycrystalline samples with R$\bar{3}$c space group. Interplay of Ferromagnetic (FM) and Antiferromagnetic (AFM) interaction upon Co substitution at Mn site in La$_{0.7}$Sr$_{0.3}$MnO$_3$ is evident from magnetic measurements. There is an optimal cobalt substitution at which the coercive field is maximum.

cond-mat.mtrl-sci↗
arXiv2016

Extreme Sensitivity of Magnetic Properties on the Synthesis Routes in La$_{0.7}$Sr$_{0.3}$MnO$_3$

La$_{0.7}$Sr$_{0.3}$MnO$_3$ polycrystalline samples have been prepared using different synthesis routes. X-ray Diffraction (XRD) confirms that the samples are of single phase with R$\bar{3}$c space group. The surface morphology and particle size has been measured using Field Emission Scanning Electron Microscopy (FESEM). Magnetic measurement shows that the magnetization in the materials are affected by low crystallite size which destroys the spin ordering due to strain at grain boundaries and in turn also lead to reduction in magnetization as well as an enhanced coercivity in the material.

cond-mat.mtrl-sci↗
arXiv2015

Electric Field Controlled Magnetization and Charge-Ordering in Pr0.6Ca0.4MnO3

In this paper, we present the observation of the electric field control on the charge-ordering and metamagnetic transitions during the magnetization measurements in a single crystal of Pr0.6Ca0.4MnO3 (PCMO). We have demonstrated that the complete melting of charge ordering can be realized in a single crystal of PCMO by applying a voltage as small as 2.5 V, which otherwise needs magnetic fields in excess of 11 T. The maximum change in magnetization with applied voltage occurs across the charge-ordering transition temperature (TCO = 235 K). Even though the electric field does not seem to affect the magnetic ordering, we see a clear evidence at low temperatures for the occurrence of the metamagnetic transitions at higher fields with the application of electric field.

cond-mat.mes-hall↗
arXiv2015

Electric field controlled magnetization and transport properties of La0.7Ca0.3MnO3 ultrathin film

We have investigated the effect of electric field control on the magnetization and the transport properties in La0.7Ca0.3MnO3 (LCMO) ultrathin film (~10 nm) by using it as the semiconductor channel material of a prototypical field effect device and SiO2 as dielectric gate. A large electroresistance (ER) of ~78% at Vg = -8 V is found in LCMO at 200 K. The direct magnetization measurements confirm the formation of a large ferromagnetic phase with the increase in the applied gate voltage at 200 K.

cond-mat.mes-hall↗
arXiv2015

Growth and angular dependent resistivity of Nb2Pd0.73S5.7 superconducting single crystals fiber

We report the growth of Nb2Pd0.73S5.7 superconducting single crystal fibers via slow cooling solid state reaction method. Superconducting transition temperature (Tc ~ 6.5K) is confirmed from magnetization and transport measurements. A comparative study is performed for determination of superconducting anisotropy, Γ, via conventional method (by taking ration of two superconducting parameters) and scaling approach method. Scaling approach, defined within the framework of the Ginzburg-Landau theory is applied to the angular dependent resistivity measurements to estimate the anisotropy. The value of Γ close to Tc from scaling approach is found to be ~ 2.5 that is slight higher compare to conventional approach (~2.2). Further, variation of anisotropy with temperature suggests that it is a type of multi-band superconductor.

cond-mat.supr-con↗
arXiv2015

Investigation of Magnetic Domain Structure in Bi0.7Dy0.3FeO3 thin films integrated with ZnO film

The magnetic domain structure of the multiferroic Bi1-xDyxFeO3 (BDFO) deposited on ZnO at the macroscopic level has been demonstrated in this paper. Magnetic properties are observed by saturated magnetic and ferroelectric hysteresis loops at room temperature. The coupling behaviour and magnetic transition are verified using Multimode Atomic Force Microscope by applying bias between sample and MFM tip. ZnO thin film of 300 nm was deposited by dielectric sputtering using a ZnO target on Si p-type conducting (.0001-0005 Ω cm) substrate. BDFO thin films of 300 nm were deposited on Si/ZnO using PLD (Pulsed laser deposition) technique. It is observed that BDFO thin films integrated with ZnO film shows the coexistence of ferromagnetic and ferroelectric ordering with significant coupling at room temperature. Integration of BDFO films with ZnO piezoelectric thin film shows the potential in MEMS applications as well as in Memory devices and strong history dependent systems.

cond-mat.mes-hall↗
arXiv2014

Sign Reversal of anisotropic magnetoresistance in La0.7Ca0.3MnO3/STO ultrathin films

We present the observation of strain induced sign reversal of anisotropic magnetoresistance (AMR) in LCMO (LCMO) ultrathin films (thickness 4 nm) deposited on STO (001) substrate (STO). We have also observed unusually large AMR in LCMO/STO thin films with thickness of 6 nm below but close to its Curie temperature (TC) which decrease as the film thickness increases. The sign reversal of AMR (with a maximum value of - 6) with magnetic field or temperature for the 4 nm thin film may be attributed to the increase in tensile strain in the plane of the thin film which in turn facilitates the rotation of the magnetization easy axis.

cond-mat.mes-hall↗