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Kuldeep Kumar

Publications and source records attributed to Kuldeep Kumar.

At least 19 recordsLinked to original sources
arXiv2023

Laser based optical interferometer manometer design for primary pressure standard in India

The SI unit of pressure, i.e. Pascal is realized with mechanical devices such as ultrasonic interferometer manometers and pressure balances for the pressure range 1 Pa to 100 kPa. Recently, optical interferometer manometers are being used to realize Pascal. Such a realization is mercury-free and environmentally friendly and does not depend on any mechanical motions as in piston gauges and is based on physical constants. It consists of an optical Fabry-Perot cavity as a refractometer and is based on the measurement of the resonant frequency of the cavity using lasers. In this paper, we report the theoretical calculations for such an optical cavity and discuss various parameters for the laser required for developing such a cavity-based refractometer system. We present the mechanical design for the dual cavity and an all-fiber optical set-up to be used for the next generation of primary pressure standards in the barometric region of pressure at CSIR-National physical laboratory, India.

physics.ins-det↗
arXiv2021

Efficient Pairwise Neuroimage Analysis using the Soft Jaccard Index and 3D Keypoint Sets

We propose a novel pairwise distance measure between image keypoint sets, for the purpose of large-scale medical image indexing. Our measure generalizes the Jaccard index to account for soft set equivalence (SSE) between keypoint elements, via an adaptive kernel framework modeling uncertainty in keypoint appearance and geometry. A new kernel is proposed to quantify the variability of keypoint geometry in location and scale. Our distance measure may be estimated between $O(N^2)$ image pairs in $O(N~\log~N)$ operations via keypoint indexing. Experiments report the first results for the task of predicting family relationships from medical images, using 1010 T1-weighted MRI brain volumes of 434 families including monozygotic and dizygotic twins, siblings and half-siblings sharing 100%-25% of their polymorphic genes. Soft set equivalence and the keypoint geometry kernel improve upon standard hard set equivalence (HSE) and appearance kernels alone in predicting family relationships. Monozygotic twin identification is near 100%, and three subjects with uncertain genotyping are automatically paired with their self-reported families, the first reported practical application of image-based family identification. Our distance measure can also be used to predict group categories, sex is predicted with an AUC=0.97. Software is provided for efficient fine-grained curation of large, generic image datasets.

eess.IV↗
arXiv2021

DNA Nucleobase Interaction Driven Electronic and Optical Fingerprints in Gallium Selenide Monolayer for DNA Sequencing Devices

The interaction of DNA nucleobases with monolayer GaSe has been studied with in DFT framework using vdW functional. We found that nucleobases are physisorbed on the GaSe monolayer. The order of binding energy per atom is C > T > G > A. The room temperature recovery time estimated to be maximum of 113.88 micro sec. for T+GaSe indicting reusability of the GaSe based devices. The modulation in the electronic structures of GaSe has been clearly captured within the simulated STM measurements. We also demonstrate quantum capacitance as a key parameter for sensing applications. Furthermore, in optical properties, electron energy loss (EEL) spectra show red shift in photon energy on nucleobase adsorption in UV region. In nutshell, GaSe monolayer exhibit anisotropic optical response in UV-region which can be highly beneficial for developing polarized optical sensors. Our results demonstrate that GaSe monolayer can be utilized to fabricate reusable DNA sequencing devices for biotechnology and medical science.

cond-mat.mes-hall↗
arXiv2018

White matter fiber analysis using kernel dictionary learning and sparsity priors

Diffusion magnetic resonance imaging, a non-invasive tool to infer white matter fiber connections, produces a large number of streamlines containing a wealth of information on structural connectivity. The size of these tractography outputs makes further analyses complex, creating a need for methods to group streamlines into meaningful bundles. In this work, we address this by proposing a set of kernel dictionary learning and sparsity priors based methods. Proposed frameworks include L-0 norm, group sparsity, as well as manifold regularization prior. The proposed methods allow streamlines to be assigned to more than one bundle, making it more robust to overlapping bundles and inter-subject variations. We evaluate the performance of our method on a labeled set and data from Human Connectome Project. Results highlight the ability of our method to group streamlines into plausible bundles and illustrate the impact of sparsity priors on the performance of the proposed methods.

cs.CV↗
arXiv2017

New approach to Hamiltonian formulation of Hall magnetohydrodynamics

We present a new Hamiltonian formulation of barotropic Hall magnetohydrodynamics in two complementary approaches based on Dirac's constraint analysis. In one case the Hamiltonian is canonical involving physical variables only but the brackets are noncanonical, while in the other case the phase space is enlarged to retain the canonical structure of brackets.

physics.plasm-ph↗
arXiv2017

White Matter Fiber Segmentation Using Functional Varifolds

The extraction of fibers from dMRI data typically produces a large number of fibers, it is common to group fibers into bundles. To this end, many specialized distance measures, such as MCP, have been used for fiber similarity. However, these distance based approaches require point-wise correspondence and focus only on the geometry of the fibers. Recent publications have highlighted that using microstructure measures along fibers improves tractography analysis. Also, many neurodegenerative diseases impacting white matter require the study of microstructure measures as well as the white matter geometry. Motivated by these, we propose to use a novel computational model for fibers, called functional varifolds, characterized by a metric that considers both the geometry and microstructure measure (e.g. GFA) along the fiber pathway. We use it to cluster fibers with a dictionary learning and sparse coding-based framework, and present a preliminary analysis using HCP data.

cs.CV↗
arXiv2017

Multi-modal analysis of genetically-related subjects using SIFT descriptors in brain MRI

So far, fingerprinting studies have focused on identifying features from single-modality MRI data, which capture individual characteristics in terms of brain structure, function, or white matter microstructure. However, due to the lack of a framework for comparing across multiple modalities, studies based on multi-modal data remain elusive. This paper presents a multi-modal analysis of genetically-related subjects to compare and contrast the information provided by various MRI modalities. The proposed framework represents MRI scans as bags of SIFT features, and uses these features in a nearest-neighbor graph to measure subject similarity. Experiments using the T1/T2-weighted MRI and diffusion MRI data of 861 Human Connectome Project subjects demonstrate strong links between the proposed similarity measure and genetic proximity.

cs.CV↗
arXiv2016

Superunitary operator and BRST transformations for non-Abelian two-form

Using superspace unitary operator formalism, we derive various (anti-)BRST symmetry transformations explicitly for the non-Abelian 2-form gauge theories. We introduce a new Lagrangian with a coupling of matter fields not only with 1-from background field but also with a 2-form field. Moreover, the two gauge fields couple mutually as well. A new covariant derivative involving the 2-form gauge field is introduced. We also put forth a conjecture to generalise this idea to any p-form gauge theory.

hep-th↗
arXiv2016

Ab Initio Calculation of stressed Cesium Iodide lattices and resulting Surface Plasmon Resonance Peak shifts

Alkali halides like Cesium Iodide have received renewed attention as a material with potential application as detector coating due to the appearance of Surface Plasmon Resonance absorption peak in their UV-visible absorption spectrum. The formation of Surface Plasmon Resonance peak has been traced to the formation of Cesium metal clusters due to the aglomeration of color centers embedded in Cesium Iodide background. This paper, based on experimental observation that cubic Cesium Iodide experiences stress due to color centers forming in the neighborhood and take up tetragonal lattice structure, investigates the tetragonal Cesium Iodide's band structure and dielectric constant using ab initio calculations. Both, the band-gap and dielectric constant of Cesium Iodide, show a systematic variation with changing lattice constant. While the band-gap is seen to strongly depend on the lattice parameter `c', the dielectric constant's variation along `a' direction (${\rm 0.2~nm^{-1}}$) was found to be stronger than that along the `c' direction (${\rm -2.5~nm^{-1}}$). The calculated dielectric constants were used as input parameter for Gan model calculations of the extinction coefficient and evaluation of Surface Plasmon Resonance peak position (${\rm \lambda_{max}}$). A red-shift in ${\rm \lambda_{max}}$ was seen with increasing dielectric constant that appears with stress acting on Cesium Iodide's lattice.

cond-mat.mtrl-sci↗
arXiv2016

New approach to nonrelativistic ideal magnetohydrodynamics

We provide a novel action principle for nonrelativistic ideal magnetohydrodynamics in the Eulerian scheme exploiting a Clebsch-type parametrisation. Both Lagrangian and Hamiltonian formulations have been considered. Within the Hamiltonian framework, two complementary approaches have been discussed using Dirac's constraint analysis. In one case the Hamiltonian is canonical involving only physical variables but the brackets have a noncanonical structure, while the other retains the canonical structure of brackets by enlarging the phase space. The special case of incompressible magnetohydrodynamics is also considered where, again, both the approaches are discussed in the Hamiltonian framework. The conservation of the stress tensor reveals interesting aspects of the theory.

physics.flu-dyn↗
arXiv2013

Contribution of Halides in CsX (X=Cl, Br and I) Thin Films on the formation of SPR peaks

This manuscript describes the evolution of grain structures in Cesium Halide films which results in appearance of Surface Plasmon Resonance (SPR) peaks in UV-visible absorption spectra. Thin films of Cesium Halide grown by thermal evaporation are polycrystalline in nature with large irregular tightly packed grains with sharp grain boundaries. With time these grain boundaries recede to become smaller and spherical in shape in order to minimize the free surface energy of the system. The process is also assisted by the presence of point defects/color centers in Cesium Halide films. These defects which appear due to the absence of massive halide atoms from the lattice results in residual tensile stress within the lattice which results in defect diffusion. The defects migrate outwards towards the grain surface giving rise to Cesium metal clusters. The lattice mismatch appearing between the lattices at the grain boundary and the bulk giving rise to Core-shell structure further contributes to grain division. Along with this volume diffusion, a surface diffusion of Cesium takes place towards sites of faceted grain boundaries resulting in a necking phenomenon, appearing like bridges between the daughter Cesium Halide grains (grains appearing due to division of a single grain). Breaking away of the daughter Cesium Halide grains results in nano-rods that contribute to the SPR peak seen.

cond-mat.mtrl-sci↗
arXiv2012

Identifying Coordination Problems in Software Development: Finding Mismatches between Software and Project Team Structures

Today's dynamic and iterative development environment brings significant challenges for software project management. In distributed project settings, "management by walking around" is no longer an option and project managers may miss out on key project insights. The TESNA (TEchnical Social Network Analysis) method and tool aims to provide project managers both a method and a tool for gaining insights and taking corrective action. TESNA achieves this by analysing a project's evolving social and technical network structures using data from multiple sources, including CVS, email and chat repositories. Using pattern theory, TESNA helps to identify areas where the current state of the project's social and technical networks conflicts with what patterns suggest. We refer to such a conflict as a Socio-Technical Structure Clash (STSC). In this paper we report on our experience of using TESNA to identify STSCs in a corporate environment through the mining of software repositories. We find multiple instances of three STSCs (Conway's Law, Code Ownership and Project Coordination) in many of the on-going development projects, thereby validating the method and tool that we have developed.

cs.SE↗
arXiv2011

Metal Cluster's Effect on the Optical Properties of Cesium Bromide Thin Films

Cesium Bromide films grown of glass substrates by thermal evaporation showed interesting optical properties. The UV-visible absorption spectra showed peaks which showed red shift with time. Structural and morphological studies suggested decrease in grain size with time which was unusual. Theoretical simulation shows the optical behaviour to be due to surface plasmon resonance resulting from Cesium clyindrical rods embedded in the films.

cond-mat.mtrl-sci↗
arXiv2011

Symmetries of Snyder--de Sitter space and relativistic particle dynamics

We study the deformed conformal-Poincare symmetries consistent with the Snyder--de Sitter space. A relativistic particle model invariant under these deformed symmetries is given. This model is used to provide a gauge independent derivation of the Snyder--de Sitter algebra. Our results are valid in the leading order in the parameters appearing in the model.

hep-th↗
arXiv2008

Aspects of noncommutativity in field theory, strings and membranes

We study certain aspects of noncommutativity in field theory, strings and membranes. We analyse the dynamics of an open membrane whose boundary is attached to p-branes. Noncommutative features of the boundary string coordinates are revealed by algebraic consistency arguments. Next, we derive Seiberg-Witten-type maps relating currents and their divergences in nonabelian U(N) noncommutative gauge theory with the corresponding expressions in the ordinary (commutative) description. We then exploit these maps to obtain the O(θ) structure of the commutator anomalies in noncommutative electrodynamics. Finally, we discuss the issue of violation of Lorentz invariance in noncommutative gauge theories by explicitly deriving, following a Noether-like approach, the criteria for preserving Poincare invariance. We also study general (deformed) conformal-Poincare (Galilean) symmetries consistent with relativistic (nonrelativistic) canonical noncommutative spaces.

hep-th↗
arXiv2008

Considerations for Anderson-Bridge Experiment

Various issues concerned with the design and sensitivity of the Anderson bridge are discussed. We analyse the circuit using the tools of Network Analysis to determine the conditions under which the balance may be obtained with greater sensitivity and discuss how to obtain these under practical circumstances in an undergraduate laboratory.

physics.class-ph↗
arXiv2007

Band Gap of CsCl Film's as a Function of Lattice Constant

The manuscript reports experimental estimation of Cesium Chloride film's band gap and compares it with theoretical simulations. The band gap shows a strong dependence on it's lattice constant. Also, it is seen that the point defects present in the films strongly affects it's optical properties.

cond-mat.mtrl-sci↗