Puneet Sharma

Bio: Puneet Sharma is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Subshift of finite type & Shift space. The author has an hindex of 8, co-authored 38 publications receiving 206 citations. Previous affiliations of Puneet Sharma include Indian Institute of Technology Delhi.

Evaluation of a Deep Learning-Based Automated CT Coronary Artery Calcium Scoring Algorithm.

Abstract: The measurement of coronary artery calcium scores (CACS) usually requires the manual input of a human operator to identify and mark calcified coronary lesions in each image section ([1–3][1]). Because this approach is labor intensive and time consuming, a more automated work flow is desirable to

Topological dynamics on hyperspaces

Abstract: In this paper we wish to relate the dynamics of the base map to the dynamics of the induced map. In the process, we obtain conditions on the endowed hyperspace topology under which the chaotic behaviour of the map on the base space is inherited by the induced map on the hyperspace. Several of the known results come up as corollaries to our results. We also discuss some metric related dynamical properties on the hyperspace that cannot be deduced for the base dynamics.

Impact of West Asia, Tibetan Plateau and local dust emissions on intra-seasonal oscillations of the South Asian monsoon rainfall

Abstract: In the present study, we examine the responses of South Asian Monsoon (SAM) rainfall at intra-seasonal scale to remote dust emissions from west Asia, Tibetan Plateau and local dust emissions from within south Asia using a state of the art coupled atmosphere-slab ocean model CESM1-SOM. A series of systematically designed idealized simulations are carried out in such a way that dust emissions from the selected source regions are either perpetually suppressed or enhanced from these source regions and the response of the intra-seasonal oscillations (ISOs) of SAM rainfall to such perturbations in dust emissions are investigated. It is noted that the intra-seasonal variability of SAM rainfall is dominated by three different ISOs with periodicities of 10–20 days, 30–60 days and 60–90 days. Modulations in the characteristics of each of these three ISOs are studied for each of the dust perturbation experiments. Statistically robust K–S test and F test performed on the results from various dust perturbation experiments suggest that the perpetual perturbations in dust emissions from remote sources as well as locally from south Asia can significantly modulate the spatial and temporal structure of the ISOs of rainfall across scales during the monsoon season. Substantial changes are also noted in the spatial scales and propagation characteristics of ISOs attributable to the dust emission changes made over local and remote source regions in our idealized simulations. Our results suggest that perturbations in dust emissions over remote locations can substantially modulate the depth and duration of active and break rainfall events in the south Asian monsoon region. Results presented here have implications for better understanding and predicting the SAM rainfall variability at the intra-seasonal scales or at shorter time scales (~ less than a season) under variable dust emissions from remote and local source regions.

A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

Abstract: Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

Anthropogenic aerosols and the weakening of the South Asian summer monsoon

Abstract: Changes in monsoon rainfall are caused by human-produced aerosols slowing the tropical atmospheric circulation. Observations show that South Asia underwent a widespread summertime drying during the second half of the 20th century, but it is unclear whether this trend was due to natural variations or human activities. We used a series of climate model experiments to investigate the South Asian monsoon response to natural and anthropogenic forcings. We find that the observed precipitation decrease can be attributed mainly to human-influenced aerosol emissions. The drying is a robust outcome of a slowdown of the tropical meridional overturning circulation, which compensates for the aerosol-induced energy imbalance between the Northern and Southern Hemispheres. These results provide compelling evidence of the prominent role of aerosols in shaping regional climate change over South Asia.

Short-term modulation of Indian summer monsoon rainfall by West Asian dust

Abstract: The Indian summer monsoon is influenced by numerous factors, including aerosol-induced changes to clouds, surface and atmospheric heating, and atmospheric circulation. An analysis of satellite data and global climate model simulations suggests that dust aerosol levels over the Arabian Sea, West Asia and the Arabian Peninsula are positively correlated with the intensity of the Indian summer monsoon.

An introduction to chaotic dynamical systems (2nd edition), by Robert L. Devaney. Pp 336. £34·95. 1989. ISBN 0-201-13046-7 (Addison-Wesley)

Abstract: Part One: One-Dimensional Dynamics Examples of Dynamical Systems Preliminaries from Calculus Elementary Definitions Hyperbolicity An example: the quadratic family An Example: the Quadratic Family Symbolic Dynamics Topological Conjugacy Chaos Structural Stability Sarlovskiis Theorem The Schwarzian Derivative Bifurcation Theory Another View of Period Three Maps of the Circle Morse-Smale Diffeomorphisms Homoclinic Points and Bifurcations The Period-Doubling Route to Chaos The Kneeding Theory Geneaology of Periodic Units Part Two: Higher Dimensional Dynamics Preliminaries from Linear Algebra and Advanced Calculus The Dynamics of Linear Maps: Two and Three Dimensions The Horseshoe Map Hyperbolic Toral Automorphisms Hyperbolicm Toral Automorphisms Attractors The Stable and Unstable Manifold Theorem Global Results and Hyperbolic Sets The Hopf Bifurcation The Hnon Map Part Three: Complex Analytic Dynamics Preliminaries from Complex Analysis Quadratic Maps Revisited Normal Families and Exceptional Points Periodic Points The Julia Set The Geometry of Julia Sets Neutral Periodic Points The Mandelbrot Set An Example: the Exponential Function

Introduction of chaotic dynamical systems

Abstract: Abstract : The emerging discipline known as \"chaos theory\" is a relatively new field of study with a diverse range of applications (i.e., economics, biology, meteorology, etc.). Despite this, there is not as yet a universally accepted definition for \"chaos\" as it applies to general dynamical systems. Various approaches range from topological methods of a qualitative description; to physical notions of randomness, information, and entropy in ergodic theory; to the development of computational definitions and algorithms designed to obtain quantitative information. This thesis develops some of the current definitions and discusses several quantitative measures of chaos. It is intended to stimulate the interest of undergraduate and graduate students and is accessible to those with a knowledge of advanced calculus and ordinary differential equations. In covering chaos for continuous systems, it serves as a complement to the work done by Philip Beaver, which details chaotic dynamics for discrete systems.