Filters








234 Hits in 1.5 sec

Restoring Chaos Using Deep Reinforcement Learning [article]

Sumit Vashishtha, Siddhartha Verma
2019 arXiv   pre-print
A catastrophic bifurcation in non-linear dynamical systems, called crisis, often leads to their convergence to an undesirable non-chaotic state after some initial chaotic transients. Preventing such behavior has proved to be quite challenging. We demonstrate that deep Reinforcement Learning (RL) is able to restore chaos in a transiently-chaotic regime of the Lorenz system of equations. Without requiring any a priori knowledge of the underlying dynamics of the governing equations, the RL agent
more » ... scovers an effective perturbation strategy for sustaining the chaotic trajectory. We analyze the agent's autonomous control-decisions, and identify and implement a simple control-law that successfully restores chaos in the Lorenz system. Our results demonstrate the utility of using deep RL for controlling the occurrence of catastrophes and extreme-events in non-linear dynamical systems.
arXiv:1912.00947v1 fatcat:uxuvew6j3bc4bj7urknt4wykka

Quantification Of Antioxidant Polyphenols From Boenninghausenia Albiflora

Shikhar Verma Siddhartha Pragyadeep
2017 Zenodo  
The optical density was recorded and percent of inhibition was calculated according to the formula given below [16] (Verma et al., 2012) . % of inhibition of DPPH activity = (A-B/A) × 100, where, A  ... 
doi:10.5281/zenodo.1007286 fatcat:lzzejump2bbf7de6x36dq6scse

Optimal sensing for fish school identification [article]

Pascal Weber, Georgios Arampatzis, Guido Novati, Siddhartha Verma, Costas Papadimitriou, Petros Koumoutsakos
2019 arXiv   pre-print
Verma, Costas Papadimitriou and Petros Koumoutsakos.  ...  Verma and Costas Papadimitriou; Project administration, Petros Koumoutsakos; Resources, Petros Koumoutsakos; Software, Pascal Weber and Guido Novati; Supervision, Georgios Arampatzis and Petros Koumoutsakos  ... 
arXiv:1910.09937v1 fatcat:u75ghiamuvdqrpsnnlntmfmtwq

Porous cylinder arrays for optimal wake and drag characteristics [article]

Aishwarya Nair, Amirkhosro Kazemi, Oscar Curet, Siddhartha Verma
2022 arXiv   pre-print
The sequential steps used for solving Eq. 2.2 may be found in Verma et al. (2017) .  ...  To solve the Navier-Stokes equations, we use an open-source solver based on the remeshed vortex method (Rossinelli et al. 2015; Verma et al. 2017) .  ... 
arXiv:2202.08307v1 fatcat:uriehkegkncm3j2cqpyakw7afe

Efficient collective swimming by harnessing vortices through deep reinforcement learning [article]

Siddhartha Verma and Guido Novati and Petros Koumoutsakos
2018 arXiv   pre-print
Fish in schooling formations navigate complex flow-fields replete with mechanical energy in the vortex wakes of their companions. Their schooling behaviour has been associated with evolutionary advantages including collective energy savings. How fish harvest energy from their complex fluid environment and the underlying physical mechanisms governing energy-extraction during collective swimming, is still unknown. Here we show that fish can improve their sustained propulsive efficiency by
more » ... following, and judiciously intercepting, vortices in the wake of other swimmers. This swimming strategy leads to collective energy-savings and is revealed through the first ever combination of deep reinforcement learning with high-fidelity flow simulations. We find that a 'smart-swimmer' can adapt its position and body deformation to synchronise with the momentum of the oncoming vortices, improving its average swimming-efficiency at no cost to the leader. The results show that fish may harvest energy deposited in vortices produced by their peers, and support the conjecture that swimming in formation is energetically advantageous. Moreover, this study demonstrates that deep reinforcement learning can produce navigation algorithms for complex flow-fields, with promising implications for energy savings in autonomous robotic swarms.
arXiv:1802.02674v1 fatcat:cybjkzof7jfpva4dklp23ba6gu

Fast Motion of Heaving Airfoils

Siddhartha Verma, Guido Novati, Flavio Noca, Petros Koumoutsakos
2017 Procedia Computer Science  
, albeit ⇤ petros@ethz.ch This space is reserved for the Procedia header, do not use it Fast Motion of Heaving Airfoils 1 Siddhartha Verma 1 , Guido Novati 1 , Flavio Noca 2 , and Petros Koumoutsakos  ...  Fast Motion of Heaving Airfoils Verma, Novati, Noca, and Koumoutsakos The next instance we examine, at t = 2.0, corresponds to zero forward-thrust on the airfoil.  ... 
doi:10.1016/j.procs.2017.05.166 fatcat:mjhyzxw5sze2hfouixhnay5r7e

Visualizing droplet dispersal for face shields and masks with exhalation valves [article]

Siddhartha Verma, Manhar Dhanak, John Frankenfield
2020 arXiv   pre-print
., protecting others from a potentially infected wearer), and can help curb a) Electronic mail: vermas@fau.edu; http://www.computation.fau.edu; Also at Harbor Branch Oceanographic Institute, Florida Atlantic  ... 
arXiv:2008.00125v1 fatcat:2cqbwln7yvbarm3dl6lgwxab6a

Optimal Flow Sensing for Schooling Swimmers

Pascal Weber, Georgios Arampatzis, Guido Novati, Siddhartha Verma, Costas Papadimitriou, Petros Koumoutsakos
2020 Biomimetics  
Fish schooling implies an awareness of the swimmers for their companions. In flow mediated environments, in addition to visual cues, pressure and shear sensors on the fish body are critical for providing quantitative information that assists the quantification of proximity to other fish. Here we examine the distribution of sensors on the surface of an artificial swimmer so that it can optimally identify a leading group of swimmers. We employ Bayesian experimental design coupled with numerical
more » ... mulations of the two-dimensional Navier Stokes equations for multiple self-propelled swimmers. The follower tracks the school using information from its own surface pressure and shear stress. We demonstrate that the optimal sensor distribution of the follower is qualitatively similar to the distribution of neuromasts on fish. Our results show that it is possible to identify accurately the center of mass and the number of the leading swimmers using surface only information.
doi:10.3390/biomimetics5010010 pmid:32182929 fatcat:fneqmchr6rbstpkmlcuibadzgm

Optimal sensor placement for artificial swimmers [article]

Siddhartha Verma, Costas Papadimitriou, Nora Luethen, Georgios Arampatzis, Petros Koumoutsakos
2019 arXiv   pre-print
Modeling the the burstcoast motion for the swimmers involves multiplying the curvature amplitude A(s) with a smoothly varying piecewise function f (t), as described in Verma et al. (2017) : f (t) =   ... 
arXiv:1906.07585v2 fatcat:t3ebyjlmbzdodhvmxskxc4uacq

Subfilter scalar-flux vector orientation in homogeneous isotropic turbulence

Siddhartha Verma, G. Blanquart
2014 Physical Review E  
The geometric orientation of the subfilter-scale scalar-flux vector is examined in homogeneous isotropic turbulence. Vector orientation is determined using the eigenframe of the resolved strain-rate tensor. The Schmidt number is kept sufficiently large so as to leave the velocity field, and hence the strain-rate tensor, unaltered by filtering in the viscous-convective subrange. Strong preferential alignment is observed for the case of Gaussian and box filters, whereas the sharp-spectral filter
more » ... eads to close to a random orientation. The orientation angle obtained with the Gaussian and box filters is largely independent of the filter width and the Schmidt number. It is shown that the alignment direction observed numerically using these two filters is predicted very well by the tensor-diffusivity model. Moreover, preferred alignment of the scalar gradient vector in the eigenframe is shown to mitigate any probable issues of negative diffusivity in the tensor-diffusivity model. Consequentially, the model might not suffer from solution instability when used for large eddy simulations of scalar transport in homogeneous isotropic turbulence. Further a priori tests indicate poor alignment of the Smagorinsky and stretched vortex model predictions with the exact subfilter flux. Finally, strong filter dependence of subfilter scalar-flux orientation suggests that explicit filtering may be preferable to implicit filtering in large eddy simulations.
doi:10.1103/physreve.89.063015 pmid:25019887 fatcat:skbi4qmgu5gaxci7qxibx7a5ba

Uncovering dynamically critical regions in near-wall turbulence using 3D Convolutional Neural Networks [article]

Eric Jagodinski, Xingquan Zhu, Siddhartha Verma
2020 arXiv   pre-print
Acknowledgements This work was supported by the Department of Ocean and Mechanical Engineering at the Florida Atlantic University, as part of the start-up package of Siddhartha Verma.  ... 
arXiv:2004.06187v1 fatcat:jprmtrdu75bh7cc5jq2ooybtb4

Protein Based Nanostructures for Drug Delivery

Deepali Verma, Neha Gulati, Shreya Kaul, Siddhartha Mukherjee, Upendra Nagaich
2018 Journal of Pharmaceutics  
The key role of protein based nanostructures has recently revolutionized the nanomedicine era. Protein nanoparticles have turned out to be the major grounds for the transformation of different properties of many conventional materials by virtue of their size and greater surface area which instigates them to be more reactive to some other molecules. Protein nanoparticles have better biocompatibilities and biodegradability and also have the possibilities for surface modifications. These
more » ... ures can be synthesized by using protein like albumin, gelatin, whey protein, gliadin, legumin, elastin, zein, soy protein, and milk protein. The techniques for their fabrication include emulsification, desolvation, complex coacervation, and electrospray. The characterization parameters of protein nanoparticles comprise particle size, particle morphology, surface charge, drug loading, determination of drug entrapment, and particle structure and in vitro drug release. A plethora of protein nanoparticles applications via different routes of administration are explored and reported by eminent researchers which are highlighted in the present review along with the patents granted for protein nanoparticles as drug delivery carriers.
doi:10.1155/2018/9285854 pmid:29862118 pmcid:PMC5976961 fatcat:ss5ux6tkand2pfl6dzk7tj7q6m

Outcome of traumatic head injury in unknown patients

Ankit Ahuja, Siddhartha Verma, Aditya Narayan Chaudhary
2018 International Surgery Journal  
Traumatic brain injury is the most common cause of death in trauma victims accounting for about half of deaths at the accident site. Most commonly, traumatic brain injury occurs in the presence of additional injuries to other major organ systems, but it can also occur in isolation. Complications from closed head injuries are the single largest cause of morbidity and mortality in patients who reach the hospital alive. The objective of this study was to determine the outcome of traumatic head
more » ... ry in patients admitted in the Department of Neurosurgery as unknown.Methods: All patients admitted as "unknown" to Neurosurgery department with traumatic head injury were studied retrospectively. Data was collected regarding demography, mode of injury, clinical presentation at the time of admission, management and outcome of these patients.Results: Data pertaining to 107 unknown patients were collected. Most patients were found to be males in 3rd decade of their lives with vehicular accidents as the common mode of injury. Patients presenting with Glasgow coma scale (GCS) score <8 at the time of admission had poor outcome and associated with higher mortality. Intra-cranial hemorrhage were predominantly found on CT scan. Only one-third of the patients were discharged after treatment while half of them suffered untimely death.Conclusions: Outcome of these neglected patients is poorer in comparison to patients who are accompanied by their relatives. Their management from pre-hospital to treatment and discharge from hospital is fraught with challenges. They need special care from trained nursing staff as well as help from social workers for recovery and rehabilitation.
doi:10.18203/2349-2902.isj20180366 fatcat:f3lcms5thre43iyeknma7ppsny

Visualizing the effectiveness of face masks in obstructing respiratory jets

Siddhartha Verma, Manhar Dhanak, John Frankenfield
2020 Physics of Fluids  
The use of face masks in public settings has been widely recommended by public health officials during the current COVID-19 pandemic. The masks help mitigate the risk of cross-infection via respiratory droplets; however, there are no specific guidelines on mask materials and designs that are most effective in minimizing droplet dispersal. While there have been prior studies on the performance of medical-grade masks, there are insufficient data on cloth-based coverings, which are being used by a
more » ... vast majority of the general public. We use qualitative visualizations of emulated coughs and sneezes to examine how material- and design-choices impact the extent to which droplet-laden respiratory jets are blocked. Loosely folded face masks and bandana-style coverings provide minimal stopping-capability for the smallest aerosolized respiratory droplets. Well-fitted homemade masks with multiple layers of quilting fabric, and off-the-shelf cone style masks, proved to be the most effective in reducing droplet dispersal. These masks were able to curtail the speed and range of the respiratory jets significantly, albeit with some leakage through the mask material and from small gaps along the edges. Importantly, uncovered emulated coughs were able to travel notably farther than the currently recommended 6-ft distancing guideline. We outline the procedure for setting up simple visualization experiments using easily available materials, which may help healthcare professionals, medical researchers, and manufacturers in assessing the effectiveness of face masks and other personal protective equipment qualitatively.
doi:10.1063/5.0016018 pmid:32624649 pmcid:PMC7327717 fatcat:33mgzxjakrbfjglayo2kwvlsei

Visualizing droplet dispersal for face shields and masks with exhalation valves

Siddhartha Verma, Manhar Dhanak, John Frankenfield
2020 Physics of Fluids  
Several places across the world are experiencing a steep surge in COVID-19 infections. Face masks have become increasingly accepted as one of the most effective means for combating the spread of the disease when used in combination with social-distancing and frequent hand-washing. However, there is an increasing trend of people substituting regular cloth or surgical masks with clear plastic face shields and with masks equipped with exhalation valves. One of the factors driving this increased
more » ... ption is improved comfort compared to regular masks. However, there is a possibility that widespread public use of these alternatives to regular masks could have an adverse effect on mitigation efforts. To help increase public awareness regarding the effectiveness of these alternative options, we use qualitative visualizations to examine the performance of face shields and exhalation valves in impeding the spread of aerosol-sized droplets. The visualizations indicate that although face shields block the initial forward motion of the jet, the expelled droplets can move around the visor with relative ease and spread out over a large area depending on light ambient disturbances. Visualizations for a mask equipped with an exhalation port indicate that a large number of droplets pass through the exhale valve unfiltered, which significantly reduces its effectiveness as a means of source control. Our observations suggest that to minimize the community spread of COVID-19, it may be preferable to use high quality cloth or surgical masks that are of a plain design, instead of face shields and masks equipped with exhale valves.
doi:10.1063/5.0022968 pmid:32952381 pmcid:PMC7497716 fatcat:n2orf2hsija25mqkjprmx5melq
« Previous Showing results 1 — 15 out of 234 results