arXiv subjects

Akshay Kumar

Publications and source records attributed to Akshay Kumar.

At least 37 records · Page 2Linked to original sources

arXiv2023

Reflexive extended locally convex spaces

For an extended locally convex space (elcs) $(X,τ)$, the authors in [10] studied the topology $τ_{ucb}$ of uniform convergence on bounded subsets of $(X,τ)$ on the dual $X^*$ of $(X,τ)$. In the present paper, we use the topology $τ_{ucb}$ to explore the reflexive property of extended locally convex spaces. It is shown that an elcs is (semi) reflexive if and only if any of its open subspaces is (semi) reflexive. For an extended normed space, we show that reflexivity is a three-space property.

math.FA↗

arXiv2023

Barreled extended locally convex spaces and Uniform boundedness principle

For an extended locally convex space $(X,τ)$, in [8], the authors studied the finest locally convex topology (flc topology) $τ_F$ on $X$ coarser than $τ$. One can often prove facts about $(X, τ)$ by applying classical locally convex space theory on $(X, τ_F)$. This paper employs the flc topology to analyze barreled extended locally convex spaces and establish the uniform boundedness principle in the extended setting. One of the key results of this paper is the relationship between the barreledness of an extended locally convex space $(X,τ)$ and the barreledness of the associated finest locally convex space $(X, τ_F)$. This is achieved by examining the lower semi-continuous seminorms on these spaces.

math.FA↗

arXiv2023

Predissociation dynamics of negative ion resonances of H$_2$ near 12 eV and 14.5 eV using velocity slice imaging technique

Dissociative electron attachment (DEA) is an important tool for investigating negative ion resonances. We have studied the negative ion resonances of H2 at 10 eV and 14 eV using the improved velocity slice imaging technique. We obtained modulations in the kinetic energy spectrum of H$^-$ ions obtained at 12 eV and 14.5 eV electron energy, consistent with the earlier reported vibrational state contributions from the higher lying bound resonances. We show that structures obtained at 12 eV are due to predissociation of the $C^2Σ_g^+$ resonance consistent with the current understanding. However, based on our angular distribution measurements, we propose that the structures obtained at 14.4 eV are due to predissociation of bound resonance of $^2Σ_g^+$ symmetry as against $δ_g$ that was proposed earlier. We also report that the bound $^2Σ_g^+$ resonance contributes to the observed inversion symmetry breaking near 14 eV.

physics.chem-ph↗

arXiv2023

Dual of an extended locally convex space

This paper aims to study the dual of an extended locally convex space. In particular, we study the weak and weak* topologies as well as the topology of uniform convergence on bounded subsets of an extended locally convex space. As an application to function spaces, we show that the weak topology for the space C(X) of all real-valued continuous functions on a metric space (X,d) endowed with the topology of strong uniform convergence on bornology coincides with its finest locally convex topology if and only if the bornology is of all finite subsets of X.

math.FA↗

arXiv2022

The finest locally convex topology of an extended locally convex space

Salas and Garcia introduced the concept of an extended locally convex space in [D. Salas and S. Tapia-Garcia. Extended seminorms and extended topological vector spaces. Topology and its Applications, 2016] which extends the idea of an extended normed space (introduced by Beer in G. Beer. Norms with infinite values. Journal of Convex Analysis, 2015). This article gives an attractive formulation of the finest locally convex topology of an extended locally convex space and provides a systematic study of the resulting locally convex space. As an application, we characterize the coincidence of the finest locally convex topologies corresponding to the topologies of uniform and strong uniform convergences on a bornology for the function space C(X).

math.FA↗

arXiv2022

Quantum coherence in molecular dynamics induced by inelastic free electron scattering

This paper presents the inversion symmetry breaking observed in ion-pair formation from molecular hydrogen on electron impact. We explain these observations using quantum interference of two dissociation paths coherently accessed by multiple angular momentum transfer channels. The results point to the generic nature of quantum coherence induced into the molecular dynamics by single electron non-resonant scattering ubiquitous in a plasma environment, planetary atmosphere, astrochemistry, etc.

physics.chem-ph↗

arXiv2021

Gyrogroup extensions and semi cross product

The aim of the article is to study the extension theory of gyrogroups under certain conditions. Consequently, we see that there is an equivalence between the category GEXT of group-gyro extensions and the category GFAC of group-gyro factor systems. We also give a notion of semi cross product of a group and a gyrogroup which is a construction method of a larger class of gyrogroups.

math.GR↗

arXiv2021

Gyrogroup through its Grothendieck Group Completion and Right gyrogroup action

In this article, we discuss the Grothendieck group completion (GGC) of a gyrogroup. Consequently, we show that there is a one to one correspondence between actions and representations of a gyrogroup, and actions and representations of its Grothendieck group completion. We also introduce the concept of an action of a right gyrogroup.

math.GR↗

arXiv2021

CLEVR_HYP: A Challenge Dataset and Baselines for Visual Question Answering with Hypothetical Actions over Images

Most existing research on visual question answering (VQA) is limited to information explicitly present in an image or a video. In this paper, we take visual understanding to a higher level where systems are challenged to answer questions that involve mentally simulating the hypothetical consequences of performing specific actions in a given scenario. Towards that end, we formulate a vision-language question answering task based on the CLEVR (Johnson et. al., 2017) dataset. We then modify the best existing VQA methods and propose baseline solvers for this task. Finally, we motivate the development of better vision-language models by providing insights about the capability of diverse architectures to perform joint reasoning over image-text modality. Our dataset setup scripts and codes will be made publicly available at https://github.com/shailaja183/clevr_hyp.

cs.CV↗

arXiv2021

Understanding the Role of Scene Graphs in Visual Question Answering

Visual Question Answering (VQA) is of tremendous interest to the research community with important applications such as aiding visually impaired users and image-based search. In this work, we explore the use of scene graphs for solving the VQA task. We conduct experiments on the GQA dataset which presents a challenging set of questions requiring counting, compositionality and advanced reasoning capability, and provides scene graphs for a large number of images. We adopt image + question architectures for use with scene graphs, evaluate various scene graph generation techniques for unseen images, propose a training curriculum to leverage human-annotated and auto-generated scene graphs, and build late fusion architectures to learn from multiple image representations. We present a multi-faceted study into the use of scene graphs for VQA, making this work the first of its kind.

cs.CV↗

arXiv2020

Low temperature carrier transport mechanism and photoconductivity of WSe2

This work reports the electrical transport and temperature-dependent photoconductivity in tungsten diselenide (WSe2) thin films. The electrical conductivity analysis shows the presence of the three regions with temperature variation. At lower temperatures (<190K), carriers become localized to small regions in the film due to the Mott hopping mechanism. The middle region (190 to 273 K) follows Seto parameters and obtained low barrier height (0.0873 eV) may be responsible for the improved carrier mobility. At higher temperature (>273K) region, thermally activated conduction is dominated with two activation energies of ~138 meV and 98 meV. The peaks obtained in photoluminescent analysis attributes to the presence of mid-bandgap states or defect states which play an important role in the photoconductivity of WSe2. The transient photoconductivity measurements show consistent temperature-dependent behaviour. The effect of light intensity and wavelength variation on the photoconductivity of WSe2 thin films is also discussed. The photocurrent is 1.19*10-5 A at 125 K while at 350 K it was observed to be 3.12*10-4 A. The light-on/off current cycles show that the current can recover to its initial state which points to the stable and outstanding reversible properties of the WSe2 thin film device to be used in photodetector applications.

cond-mat.mtrl-sci↗

arXiv2020

Convexifying Sparse Interpolation with Infinitely Wide Neural Networks: An Atomic Norm Approach

This work examines the problem of exact data interpolation via sparse (neuron count), infinitely wide, single hidden layer neural networks with leaky rectified linear unit activations. Using the atomic norm framework of [Chandrasekaran et al., 2012], we derive simple characterizations of the convex hulls of the corresponding atomic sets for this problem under several different constraints on the weights and biases of the network, thus obtaining equivalent convex formulations for these problems. A modest extension of our proposed framework to a binary classification problem is also presented. We explore the efficacy of the resulting formulations experimentally, and compare with networks trained via gradient descent.

cs.LG↗

arXiv2019

Insights of preferred growth, elemental and morphological properties of BN/SnO2 composite for photocatalytic applications towards organic pollutants

Boron nitride (BN) has been explored these days because of its extraordinary optical, chemical and mechanical properties. BN is sensitive to its crystal structure that slight change in lattice parameters enormously change its properties. Present study deals with synthesis, characterization as well as photocatalytic applications of BN-based composite. When boron nitride was mixed with SnO2 having tetragonal crystal structure, dissociation into smaller sheets occurred and the material oriented to (102) plane. SnO2 particles attached both sides of BN sheets provided high surface area which make the material suitable for catalytic process. Presence of large number of active sites leads to the formation of hydroxyl radicals in BN/SnO2 composite which helps during degradation of organic and colourless pollutants i.e. methyl orange dye up-to ~92% under 7 minutes and salicylic acid in 40 minutes to ~82%. Results suggested that BN/SnO2 composite material possesses good capability for use in environmental as well as industrial applications.

cond-mat.mtrl-sci↗

arXiv2017

Specially designed B4C/SnO2 nanocomposite for photocatalysis: traditional ceramic with unique properties

Boron carbide: A traditional ceramic material shows unique properties when explored in nano-range. Specially designed boron based nanocomposite has been synthesized by reflux method. The addition of SnO2 in base matrix increase the defect states in boron carbide and shows unique catalytic properties. The calculated texture coefficient and Nelson Riley factor shows that the synthesized nanocomposite have very high defect states. Also this composite is explored for the first time for catalysis degradation of industrial used dyes. The industrial pollutants such as Novacron red and methylene blue dye degradation analysis reveal that the composite is an efficient catalyst. Degradation study shows that 1 g/L catalyst concentration of B4C/SnO2 degrade Novacron red Huntsman dye upto 97.38% approximately in 20 minutes under sunlight irradiation time. This water insoluble catalyst can be recovered and reused.

physics.app-ph↗

arXiv2016

A Delay-Optimal Packet Scheduler for M2M Uplink

In this paper, we present a delay-optimal packet scheduler for processing the M2M uplink traffic at the M2M application server (AS). Due to the delay-heterogeneity in uplink traffic, we classify it broadly into delay-tolerant and delay-sensitive traffic. We then map the diverse delay requirements of each class to sigmoidal functions of packet delay and formulate a utility-maximization problem that results in a proportionally fair delay-optimal scheduler. We note that solving this optimization problem is equivalent to solving for the optimal fraction of time each class is served with (preemptive) priority such that it maximizes the system utility. Using Monte-Carlo simulations for the queuing process at AS, we verify the correctness of the analytical result for optimal scheduler and show that it outperforms other state-of-the-art packet schedulers such as weighted round robin, max-weight scheduler, fair scheduler and priority scheduling. We also note that at higher traffic arrival rate, the proposed scheduler results in a near-minimal delay variance for the delay-sensitive traffic which is highly desirable. This comes at the expense of somewhat higher delay variance for delay-tolerant traffic which is usually acceptable due to its delay-tolerant nature.

cs.IT↗

arXiv2016

A Delay Optimal MAC and Packet Scheduler for Heterogeneous M2M Uplink

The uplink data arriving at the Machine-to-Machine (M2M) Application Server (AS) via M2M Aggregators (MAs) is fairly heterogeneous along several dimensions such as maximum tolerable packet delay, payload size and arrival rate, thus necessitating the design of Quality-of-Service (QoS) aware packet scheduler. In this paper, we classify the M2M uplink data into multiple QoS classes and use sigmoidal function to map the delay requirements of each class onto utility functions. We propose a proportionally fair delay-optimal multiclass packet scheduler at AS that maximizes a system utility metric. We note that the average class delay under any work-conserving scheduling policy can be realized by appropriately time-sharing between all possible preemptive priority policies. Therefore the optimal scheduler is determined using an iterative process to determine the optimal time-sharing between all priority scheduling policies, such that it results in maximum system utility. The proposed scheduler can be implemented online with reduced complexity due to the iterative optimization process. We then extend this work to determine jointly optimal MA-AS channel allocation and packet scheduling scheme at the MAs and AS. We first formulate a joint optimization problem that is solved centrally at the AS and then propose a low complexity distributed optimization problem solved independently at MAs and AS. We show that the distributed optimization solution converges quickly to the centralized optimization result with minimal information exchange overhead between MAs and AS. Using Monte-Carlo simulations, we verify the optimality of the proposed scheduler and show that it outperforms other state-of-the-art packet schedulers such as weighted round robin, max-weight scheduler etc. Another desirable feature of proposed scheduler is low delay jitter for delay-sensitive traffic.

cs.IT↗

arXiv2016

A Delay Efficient Multiclass Packet Scheduler for Heterogeneous M2M Uplink

The sensory traffic in Machine-to-Machine (M2M) communications has fairly heterogeneous service delay requirements. Therefore, we study the delay-performance of a heterogeneous M2M uplink from the sensors to a M2M application server (AS) via M2M aggregators (MA). We classify the heterogeneous M2M traffic aggregated at AS into multiple Periodic Update (PU) and Event Driven (ED) classes. The PU arrivals are periodic and need to be processed by a prespecified firm service deadline whereas the ED arrivals are random with firm or soft real-time or non real-time service requirements. We use step and sigmoidal functions to represent the service utility for PU and ED packets respectively. We propose a delay efficient multiclass packet scheduling heuristic that aims to maximize a proportionally fair system utility metric. Specifically, the proposed scheduler prioritizes service to ED data while ensuring that the PU packets meet their service deadline. It also minimizes successive PU failures for critical applications by penalizing their occurrences. Furthermore, the failed PU packets are immediately cleared from the system so as to reduce network congestion. Using extensive simulations, we show that the proposed scheduler outperforms popular packet schedulers and the performance gap increases with heterogeneity in latency requirements and with greater penalty for PU failures in critical applications.

cs.NI↗

arXiv2016

An Online Delay Efficient Packet Scheduler for M2M Traffic in Industrial Automation

Some Machine-to-Machine (M2M) communication links particularly those in a industrial automation plant have stringent latency requirements. In this paper, we study the delay-performance for the M2M uplink from the sensors to a Programmable Logic Controller (PLC) in a industrial automation scenario. The uplink traffic can be broadly classified as either Periodic Update (PU) and Event Driven (ED). The PU arrivals from different sensors are periodic, synchronized by the PLC and need to be processed by a prespecified firm latency deadline. On the other hand, the ED arrivals are random, have low-arrival rate, but may need to be processed quickly depending upon the criticality of the application. To accommodate these contrasting Quality-of-Service (QoS) requirements, we model the utility of PU and ED packets using step function and sigmoidal functions of latency respectively. Our goal is to maximize the overall system utility while being proportionally fair to both PU and ED data. To this end, we propose a novel online QoS-aware packet scheduler that gives priority to ED data as long as that results the latency deadline is met for PU data. However as the size of networks increases, we drop the PU packets that fail to meet latency deadline which reduces congestion and improves overall system utility. Using extensive simulations, we compare the performance of our scheme with various scheduling policies such as First-Come-First-Serve (FCFS), Earliest-Due-Date (EDD) and (preemptive) priority. We show that our scheme outperforms the existing schemes for various simulation scenarios.

cs.NI↗