arXiv subjects

Gurpreet Kaur

Publications and source records attributed to Gurpreet Kaur.

At least 19 recordsLinked to original sources

arXiv2026

Effect of Vacancies on Hydrogen Mobility and Trapping in Elemental Fe and Cr: A DFT and kMC Study

Hydrogen-vacancy interactions play an important role in governing hydrogen transport and embrittlement in body-centered cubic (BCC) metals. In this study, a multiscale approach combining density functional theory (DFT) and kinetic Monte Carlo (kMC) simulations is employed to investigate hydrogen behavior in BCC Fe and Cr. The DFT-calculated binding energies and Bader charge analysis indicate stronger hydrogen trapping in Cr than in Fe. Migration and detrapping energy barriers are determined using the climbing-image nudged elastic band method, showing that the detrapping energy generally decreases with increasing hydrogen occupancy. However, the sixth hydrogen atom in Fe exhibits a finite barrier, contrary to some previous reports. kMC simulations are then used to evaluate hydrogen diffusion over extended time and length scales. The results demonstrate that vacancy defects significantly reduce hydrogen mobility and increase the effective activation energy, with a more pronounced effect observed in Cr due to stronger trapping. The combined DFT-kMC framework provides detailed insight into the mechanisms of hydrogen trapping, detrapping, and diffusion in BCC metals, offering important implications for understanding hydrogen embrittlement in structural materials.

cond-mat.mtrl-sci↗

arXiv2023

KILDST: Effective Knowledge-Integrated Learning for Dialogue State Tracking using Gazetteer and Speaker Information

Dialogue State Tracking (DST) is core research in dialogue systems and has received much attention. In addition, it is necessary to define a new problem that can deal with dialogue between users as a step toward the conversational AI that extracts and recommends information from the dialogue between users. So, we introduce a new task - DST from dialogue between users about scheduling an event (DST-USERS). The DST-USERS task is much more challenging since it requires the model to understand and track dialogue states in the dialogue between users and to understand who suggested the schedule and who agreed to the proposed schedule. To facilitate DST-USERS research, we develop dialogue datasets between users that plan a schedule. The annotated slot values which need to be extracted in the dialogue are date, time, and location. Previous approaches, such as Machine Reading Comprehension (MRC) and traditional DST techniques, have not achieved good results in our extensive evaluations. By adopting the knowledge-integrated learning method, we achieve exceptional results. The proposed model architecture combines gazetteer features and speaker information efficiently. Our evaluations of the dialogue datasets between users that plan a schedule show that our model outperforms the baseline model.

cs.CL↗

arXiv2022

Image Encryption using fractional integral transforms: Vulnerabilities, threats and future scope

With the enormous usage of digital media in almost every sphere from education to entertainment, the security of sensitive information has been a concern. As images are the most frequently used means to convey information, therefore the issue related to the privacy preservation needs to be addressed in each of the application domains. There are various security methods proposed by researchers from time to time. This paper presents a review of various image encryption schemes based on fractional integral transform. As the fractional integral transforms have evolved through their applications from optical signal processing to digital signal and digital image processing over the decades. In this article, we have adopted an architecture and corresponding domain-based taxonomy to classify various existing schemes in the literature. The schemes are classified according to the implementation platform, that may be an optical setup comprising of the Spatial modulators, lenses and charged coupled devices or it can be a mathematical modelling of such transforms. Various schemes are classified according to the methodology adopted in each of them and a comparative analysis is also presented in tabular form. Based on the observations, the work is converged into a summary of various challenges and some constructive guidelines are provided for consideration in future works. Such a narrative review of encryption algorithm based on various architectural schematics in fractional integral transforms has not been presented before at one place.

cs.CR↗

arXiv2022

Emergence of low temperature glassy dynamics in Ru substituted non magnetic insulator CaHfO3

Non magnetic insulators/semiconductors with induced magnetism introduced via transition metal substitution are one of the promising materials in the field of spintronic, magnetoelectronics and magneto optical devices. In this context, here, we focus on magnetism induced in a non magnetic insulator CaHfO3, by the substitution of 4d element Ru, at Hf site. Structural investigations indicate that substitution of Ru4+ (up to 50%) does not affect the original crystal structure of the parent compound. Magnetic studies divulge a crossover from a diamagnetic to paramagnetic state with 20% Ru substitution. Further replacement of Hf results in a glassy magnetic state in CaHf1-xRuxO3 (0.3 < x < 0.5). The nature of the low temperature glassiness (below 20 K) in these compositions is confirmed through Vogel Fulcher and Power law, along with, magnetic memory effect and relaxation dynamics. The observed glassiness is explained through the phenomenological hierarchical model. Our studies indicate that the presence of competing short range interactions among randomly arranged Ru cations in non magnetic insulator CaHfO3 are responsible for the observed low temperature magnetic state in this series with compositions > 0.25.

cond-mat.str-el↗

arXiv2022

A novel conservative chaos driven dynamic DNA coding for image encryption

In this paper, we propose a novel conservative chaotic standard map-driven dynamic DNA coding (encoding, addition, subtraction and decoding) for the image encryption. The proposed image encryption algorithm is a dynamic DNA coding algorithm i.e., for the encryption of each pixel different rules for encoding, addition/subtraction, decoding etc. are randomly selected based on the pseudorandom sequences generated with the help of the conservative chaotic standard map. We propose a novel way to generate pseudo-random sequences through the conservative chaotic standard map and also test them rigorously through the most stringent test suite of pseudo-randomness, the NIST test suite, before using them in the proposed image encryption algorithm. Our image encryption algorithm incorporates a unique feed-forward and feedback mechanisms to generate and modify the dynamic one-time pixels that are further used for the encryption of each pixel of the plain image, therefore, bringing in the desired sensitivity on plaintext as well as ciphertext. All the controlling pseudorandom sequences used in the algorithm are generated for a different value of the parameter (part of the secret key) with inter-dependency through the iterates of the chaotic map (in the generation process) and therefore possess extreme key sensitivity too. The performance and security analysis has been executed extensively through histogram analysis, correlation analysis, information entropy analysis, DNA sequence-based analysis, perceptual quality analysis, key sensitivity analysis, plaintext sensitivity analysis, etc., The results are promising and prove the robustness of the algorithm against various common cryptanalytic attacks.

cs.CR↗

arXiv2022

Experimental validation of density functional theory calculations on the Zr/Al oxide nanocluster formation in bcc Fe

Ab initio simulations carried out in different atomic cluster configurations in bcc Fe matrix containing Zr and Al suggest energetic favorability of Y-Zr-O phase nucleation, preferably with trigonal Y4Zr3O12 structure. Subsequently, the HRTEM investigation of the as-prepared Fe - 14 Cr-0.3 Y2O3 - 0.6 Zr - 4Al oxide dispersion strengthened (ODS) alloy shows 78% of precipitates with Y4Zr3O12 structure, thereby confirming the predictive power of ab initio simulations on the secondary formation in multi-component alloys.

cond-mat.mtrl-sci↗

arXiv2021

Effect of Zr and Al Addition on Nanocluster Formation in Oxide Dispersion Strenghthened Steel-an ab initio Study

Conventional Oxide dispersion strengthened steels are characterized by thermally stable, high density of Y-Ti-O nanoclusters, which are responsible for their high creep strength. Ti plays a major role in obtaining a high density of ultrafine particles of optimum size range of 2-10 nm. In Al-containing ODS steels developed for corrosion resistance, Y-Al-O clusters formed are of size range 20 -100 nm, and Ti fails in making dispersions finer in the presence of Al. Usage of similar alloying elements like Zr in place of Ti is widely considered. In this study, binding energies of different stages of Y-Zr-O-Vacancy and Y-Al-O-Vacancy complexes in the bcc Iron matrix are studied by first-principle calculations. It is shown that in all the stages of formation, Y-Zr-O-Vacancy clusters have higher binding energy than Y-Al-O-Vacancy clusters and hence in ferritic steel containing both Zr and Al, Y-Zr-O-Vacancy clusters are more stable and more favored to nucleate than Y-Al-O-Vacancy clusters. The bonding nature in each stage is analyzed using charge density difference plots for the plausible reason for higher stability of Y-Zr-O-Vacancy clusters.

cond-mat.mtrl-sci↗

arXiv2021

Ab initio Molecular Dynamics Simulation of Threshold Displacement Energies and Defect Formation Energies in Y4Zr3O12

Ab initio molecular dynamics simulations using VASP was employed to calculate threshold displacement energies and defect formation energies of Y4Zr3O12 δ-phase, which is the most commonly found phase in newly developed Zr and Al-containing ODS steels. The Threshold displacement energy (Ed) values are determined to be 28 eV for Zr3a primary knock-on atom along [111] direction, 40 eV for Zr18f atoms along [111] direction and 50 eV for Y recoils along [110] direction. Minimum Ed values for O and O' atoms are 13 eV and 16 eV respectively. The displacement energies of anions are much smaller compared to cations, thus suggesting that anion disorder is more probable than cation disorder. All directions except the direction in which inherent structural vacancies are aligned, cations tend to occupy another cation site. The threshold displacement energies are larger than that of Y2Ti2O7, the conventional precipitates in Ti containing ODS steels. Due to the partial occupancy of Y and Zr in the 18f position, the antisite formation energy is negligibly small, and it may help the structure to withstand more disorder upon irradiation. These results convey that Zr/Al ODS alloys, which have better corrosion resistance properties compared to the conventional Ti-ODS alloys, may also possess superior radiation resistance.

cond-mat.mtrl-sci↗

arXiv2021

Correlation between anion defects and ion beam induced luminescence in Y4Zr3O12

Potential applications of Zr/Al ODS alloys vests on the irradiation stability of the Y4Zr3O12 dispersoids. Fundamental studies to identify the type of defects are important in order to recognize pathways for damage alleviation. In this context, studies relating to identification of point defects and their clusters by in-situ ionoluminescence spectroscopy were taken up. The ionoluminescence spectrum acquired during 100 keV He+ ion irradiation shows two prominent bands, at 330 nm and 415 nm. Using density functional theory calculations with HSE06 hybrid exchange correlation functional, the luminescent bands have been identified to be arising due to native and irradiation induced oxygen vacancy defects in charged and neutral configurations.

cond-mat.mtrl-sci↗

arXiv2020

Ultrafast Insight into High energy (C, D) Excitons in Few Layer WS2

High energy (C, D) excitons possess remarkable influence over the optical properties of layered transition metal dichalcogenides (TMDCs) and comprehensive understanding of these may have revolutionary effect on 2D opto-electronic devices. Herein, we employed transient absorption spectroscopy to monitor the underlying photo-physical processes involved with C, D excitons in few layer WS2. We observed a strong inter-valley coupling across the momentum space. C, D dynamics were significantly slower as compared to canonical A, B excitons, as a consequence of the indirect Lambda-Gamma relaxation in C, D, unlike K-K direct combination in A, B. Optical behaviour of D excitons was found to be more like A, B, contrary to C, which enjoy unique band nesting effects. Also, C excitons do not hold in any specific position of the momentum space, rather depends upon the photon energy. All these excitons immensely influence each other irrespective of the excitation energy.

cond-mat.mtrl-sci↗

arXiv2020

Magnetocaloric effect and spin-phonon correlations in RFe0.5Cr0.5O3 (R = Er and Yb) compounds

We report the results of our investigation of the physical properties of mixed metal oxides RFe0.5Cr0.5O3 (R = Er and Yb). ErFe0.5Cr0.5O3 undergoes an antiferromagnetic ordering around 270 K followed by spin reorientation (SR) transitions around 150 and 8 K respectively. In contrast, in YbFe0.5Cr0.5O3 a single SR transition is noted at 36 K, below the AFM ordering temperature of 280 K. In ErFe0.5Cr0.5O3, a significant value of magnetic entropy change (ΔSM) ~ -12.4 J/kg-K is noted near the 2nd SR transition, however, this value is suppressed in YbFe0.5Cr0.5O3. Temperature dependent dielectric permittivity of ErFe0.5Cr0.5O3 and YbFe0.5Cr0.5O3 at different frequencies, reveal the presence of Debye-like relaxation behaviour in both compounds, which can be due to the effect of charge carrier hopping between localized states of Fe and Cr ions. Temperature dependent Raman scattering studies divulge that spin-phonon coupling plays a crucial role in defining the physical properties of these compounds.

cond-mat.str-el↗

arXiv2018

Nature of glassy magnetic state in magnetocaloric materials Dy5Pd2-xNix (x = 0 and 1) and universal scaling analysis of R5Pd2 (R = Tb, Dy and Er)

We report a systematic investigation of the magnetic and magnetocaloric properties of Dy5Pd2 and Dy5PdNi. Our study on these compounds gave evidence that they exhibit complex magnetic behaviour along with the presence of glass-like magnetic phase. Furthermore, in these compounds both second order and first order phase transitions were present, which were validated through Arrott plots and Landau parameter analysis. AC susceptibility along with time dependent magnetisation study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy5PdNi. These compounds show significant value of isothermal entropy change and relative cooling power and these values increased with Ni substitution. Beside conventional magnetocaloric effect, inverse magnetocaloric effect was noted in these compounds, which might arise due to the presence of complex non-equilibrium magnetic state. Along with these compounds a universal characteristic curve involving two other members of R5Pd2 family i.e. Er5Pd2 and Tb5Pd2 was constructed. The master curve reaffirmed the presence of both second and first order magnetic phase transition in such compounds which were in analogy to our results of Arrott plots and Landau parameter analysis. Additionally, magnetic entropy change followed the power law and the obtained exponent values indicated the presence of mixed magnetic interactions in these compounds.

cond-mat.mtrl-sci↗

arXiv2018

Role of hexadecapole deformation of projectile $^{28}$Si in heavy-ion fusion reactions near the Coulomb barrier

The vast knowledge of strong influence of quadrupole deformation $β_2$ of colliding nuclei on heavy-ion subbarrier fusion reactions inspires a desire to quest the sensitivity of fusion dynamics to higher order deformations, such as $β_4$ and $β_6$ deformations. However, such studies have rarely been carried out, especially for deformation of projectile nuclei. In this article, we investigated the role of $β_4$ of the projectile nucleus in fusion of the $^{28}$Si + $^{92}$Zr system. We demonstrated that the fusion barrier distribution is sensitive to the sign and the value of the $β_4$ parameter of the projectile, $^{28}$Si, and confirmed that the $^{28}$Si nucleus has a large positive $β_4$. This study opens an indirect way to estimate deformation parameters of radioactive nuclei using fusion reactions, which is otherwise difficult due to experimental constraints.

nucl-th↗

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

Fission fragment mass distributions in reactions populating 200Pb

The fission fragment mass distributions have been measured in the reactions 16O + 184W and 19F+ 181Ta populating the same compound nucleus 200Pb? at similar excitation energies. It is found that the widths of the mass distribution increases monotonically with excitation energy, indicating the absence of quasi-fission for both reactions. This is contrary to two recent claims of the presence of quasi-fission in the above mentioned reactions.

nucl-ex↗

arXiv2015

Interplay of fission modes in mass distribution of light actinide nuclei 225,227Pa

Fission-fragment mass distributions were measured for 225,227Pa nuclei formed in fusion reactions of 19F + 206, 208Pb around fusion barrier energies. Mass-angle correlations do not indicate any quasi-fission like events in this bombarding energy range. Mass distributions were fitted by Gaussian distribution and mass variance extracted. At below-barrier energies, the mass variance was found to increase with decrease in energy for both nuclei. Results from present work were compared with existing data for induced fission of 224, 226Th and 228U around barrier energies. Enhancement in mass variance of 225, 227Pa nuclei at below-barrier energies shows evidence for presence of asymmetric fission events mixed with symmetric fission events. This is in agreement with the results of mass distributions of nearby nuclei 224, 226Th and 228U where two-mode fission process was observed. Two-mode feature of fission arises due to the shell effects changing the landscape of the potential energy surfaces at low excitation energies. The excitation-energy dependence of the mass variance gives strong evidence for survival of microscopic shell effects in fission of light actinide nuclei 225, 227Pa with initial excitation energy ~30 - 50 MeV.

nucl-ex↗

arXiv2015

Influence of vibrational excitation on surface diffuseness of inter-nuclear potential: study through heavy-ion quasi-elastic scattering at deep subbarrier energies

We discuss the role of channel coupling in the surface properties of an inter-nuclear potential for heavy-ion reactions. To this end, we analyze the experimental quasi-elastic cross sections for the $^{12}$C + $^{105,106}$Pd and $^{13}$C + $^{105,106}$Pd systems using the coupled-channels approach by including the vibrational excitations in the target nuclei. While earlier studies have reported a negligible influence of vibrational excitation on the surface diffuseness parameter for spherical systems, we find a significant effect for the C+Pd systems. Our systematic study also reveals influence of transfer couplings on the surface diffuseness parameter.

nucl-th↗

arXiv2011

A Survey on Cooperative Diversity and Its Applications in Various Wireless Networks

Cooperative diversity is a technique in which various radio terminals relay signals for each other. Cooperative diversity results when cooperative communications is used primarily to leverage the spatial diversity available among distributed radios. In this paper different cooperative diversity schemes and their applications in various wireless networks are discussed. In this paper the impact of cooperative diversity on the energy consumption and lifetime of sensor network and the impact of cooperation in cognitive radio are discussed. Here, user scheduling and radio resource allocation techniques are also discussed which are developed in order to efficiently integrate various cooperative diversity schemes for the emerging IEEE 802.16j based systems.

cs.NI↗