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Intensity and composition-dependent sign reversal of non-linearity in TiO_2/CeO_2 nanocomposites

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Chinese Physics B 2014年第3期23卷 298-302页

作者： s.divya V.P.N.Nampoori P.Radhakrishnan A.Mujeeb International school of Photonics Cochin University of Science and Technology

CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via sol-gel method. It was found that the band gap of the nanocomposite is tunable by varying Ce/Ti content. The nonlinear response of the sample was studied by using the nanosecond laser pulses from a Q switched Nd：Yag laser employing the Z-scan method. Open aperture Z-scan experiment revealed that with the increase in the CeO2 amount in the nanocomposite, the non-linearity of the composite increases, and it was assumed that this could be due to the modification of TiO2 dipole symmetry by the addition of CeO2. Closed aperture Z-scan experiment showed that when the CeO2 amount increases, positive nonlinear refraction decreases, and this could be attributed to the increase in the two photon absorption which subsequently suppresses the nonlinear refraction.

关键词： sol-gel method non-linearity Z-scan experiment reversesaturation absorption curve

Tailoring optical properties of TiO_2 in silica glass for limiting applications

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Chinese Physics B 2014年第3期23卷 303-307页

作者： s.divya Indu sebastian V.P.N.Nampoori P.Radhakrishnan A.Mujeeb International school of Photonics Cochin University of Science and Technology

We present the linear and nonlinear optical studies on TiO2-siO2 nanocomposites with varying compositions. Opti- cal band gap of the material is found to vary with the amount of siO2 in the composite. The phenomenon of two-photon absorption （TPA） in TiO2/siO2 nanocomposites has been studied using open aperture Z-scan technique. The nanocom- posites show better nonlinear optical properties than pure TiO2, which can be attributed to the surface states and weak dielectric confinement of TiO2 nanoparticles by siO2 matrix. The nanocomposites are thermally treated and similar studies are performed. The anatase form of TiO2 in the nanocomposites shows superior properties relative to the amorphous and rutile counterpart. The involved mechanism is explained by rendering the dominant role played by the excitons in the TiO2 nanoparticles.

关键词： reverse saturable absorption (RsA) optical limiting excitons

Conformally symmetric wormhole solutions supported by non-commutative geometry in f(Q,T)gravity

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Communications in Theoretical Physics 2024年第2期76卷 111-124页

作者： Chaitra Chooda Chalavadi V Venkatesha N s Kavya s V divya Rashmi Department of P.G.studies and Research in Mathematics Kuvempu UniversityShankaraghattaShivamogga 577451KarnatakaIndia Department of Mathematics Vidyavardhaka College of EngineeringMysuru—570002India

This paper investigates wormhole solutions within the framework of extended symmetric teleparallel gravity,incorporating non-commutative geometry,and conformal *** achieve this,we examine the linear wormhole model with anisotropic fluid under Gaussian and Lorentzian *** primary objective is to derive wormhole solutions while considering the influence of the shape function on model parameters under Gaussian and Lorentzian *** resulting shape function satisfies all the necessary conditions for a traversable ***,we analyze the characteristics of the energy conditions and provide a detailed graphical discussion of the matter contents via energy ***,we explore the effect of anisotropy under Gaussian and Lorentzian ***,we present our conclusions based on the obtained results.

关键词： traversable wormhole f(Q T)gravity energy conditions non-commutative geometry conformal motion

Exploring the Reasons for selfie-Taking and selfie-Posting on social Media with Its Effect on Psychological and social Lives:A study among Indian Youths

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International Journal of Mental Health Promotion 2024年第5期26卷 389-398页

作者： divya P.Vijayan Tokani Ghuhato Eslavath Rajkumar Allen Joshua George Romate John John Abraham Department of Psychology Central University of KarnatakaKalaburagi585367India Department of Liberal Arts Indian Institute of Technology BhilaiChhattisgarh491002India Liberal Arts&sciences Indian Institute of Management RanchiJharkhand834001India Department of Family Medicine/Geriatrics St.John’s National Academy of Health SciencesBangalore560034India

‘selfie’taking was introduced to the common people by smartphones and has become a common practice across the globe in no *** technological advancement and the popularity of smartphones,selfie-taking has grown rapidly within a short *** light of the new trend set by the generation,this study aimed to explore reasons for selfie-taking and selfie-posting on social media and their effects on the social and psychological lives of young adults.A purposive sampling method was adopted to select 20 Indian citizens,between 18 and 24 *** data were collected through semi-structured interviews and analysed using thematic ***-taking and posting on social media give positive feelings,and it acts as a mood modifier dependent mostly on the favourability and feedback about the post which in turn affects emotions and self-satisfaction.

关键词： selfie social media social networking sites obsessive selfie-taking Indian youth

Bearing capacity of foundations on rock slopes intersected by non-persistent discontinuity

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International Journal of Mining science and Technology 2020年第5期30卷 669-674页

作者： divya shaunik Mahendra singh Department of Civil Engineering Indian Institute of Technology RoorkeeRoorkee 247667India

Rocks encountered in foundations of heavy structures are invariably intersected by discontinuities(joints).In the past,several studies have been performed by researchers to incorporate the effect of fully persistent joints in the assessment of the load-carrying capacity of ***,in the field,the joints are non-persistent,and an assumption of full persistency will underestimate the ***,shaunik&singh have studied the influence of non-persistency,number of joint segments and discontinuity orientation on the strength behaviour of rock specimens(shaunik and singh,2019).Bell’s approach can be used to obtain the bearing capacity of shallow foundations placed in jointed *** the present study,results of the experimental work(shaunik and singh,2019)conducted by shaunik&singh have been used to suggest expressions by extending Bell’s approach for computing bearing capacity of the foundation placed near the crown of a rock *** to use design charts are also presented for field ***,a real-life problem from Indian Garhwal Himalayas is considered,and the approach suggested in this study is utilised to obtain the bearing capacity of a bridge foundation as a function of uniaxial compressive strength(UCs)of intact rock,joint friction,spacing and orientation of joint,nonpersistency and number of joint segments.

关键词： Uniaxial compressive strength(UCs) Joint segment Discontinuity Non-persistency Bell’s approach

Electronic and optical properties of TiO_2 and its polymorphs by Z-scan method

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Chinese Physics B 2014年第8期23卷 340-344页

作者： s. divya V P N Nampoori P Radhakrishnan A Mujeeb International school of Photonics Cochin University of Science and Technology

TiO2 is a material which has attracted considerable attention from the scientific community for its innumerable prop- erties. TiO2 is known to exist in nature in three different crystalline structures： rutile, anatase, and brookite. Anatase and rutile TiO2 films have been widely characterized for their potential applications in solar cells, self-cleaning coatings, and photocatalysis. In the present report, the third-order nonlinear susceptibilities of TiO2 and its polymorphs, anatase, and rutile, prepared by the sol-gel technique followed by heat treatment are investigated using the Z-scan technique at a wavelength of 532 nm with a duration of 7 ns. Imaginary and real values of Z（3） for amorphous, anatase, and rutile are also calculated and found to be 5 × 10^-19 m2/V2, 27 × 10^-19 m2/V2, 19 × 10^-19 m2/V2, respectively. It is found that the values of the optical constants of amorphous TiO2 after heat treatment vary considerably. It is assumed that this could be due to the variation in the electronic structure of TiO2 synchronous with the formation of its polymorphs, anatase, and rutile. Amorphous TiO2 is marked by the localization of the tail states near the band gap, whereas its crystalline counterparts are characterized by completely delocalized tail states.

关键词： excitons reverse saturable absorption (RsA) excitonic nonlinearity

Lockdown lifted:measuring spatial resilience from London’s public transport demand recovery

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Geo-spatial Information science 2023年第4期26卷 685-702页

作者： divya sharma Chen Zhong Howard Wong Centre for Advanced spatial Analysis University College LondonLondonUK Transport Consulting ArupLondonUK Public Transport service Planning Transport for LondonLondonUK

The disruptive effects of the COVID-19 pandemic has rapidly shifted how individuals navigate in *** are concerned that travel behavior will shift toward a car-driven and homeworking future,shifting demand away from public transport *** concerns place the recovery of public transport in a possible crisis.A resilience perspective may aid the discussion around recovery-particularly one that deviates from pre-pandemic *** paper presents an empirical study of London’s public transport demand and introduces a perspective of spatial resilience to the existing body of research on post-pandemic public transport *** study defines spatial resilience as the rate of recovery in public transport demand within census boundaries over a period after lockdown restrictions were *** relationship between spatial resilience and urban socioeconomic factors was investigated by a global spatial regression model and a localized perspective through Geographically Weighted Regression(GWR)*** this case study of London,the analysis focuses on the period after the first COVID-19 lockdown restrictions were lifted(June 2020)and before the new restrictions in mid-september *** analysis shows that outer London generally recovered faster than inner *** of income,car ownership and density of public transport infrastructure were found to have the greatest influence on spatial patterns in ***,influential relationships vary locally,inviting future research to examine the drivers of this spatial ***,this research recommends transport policymakers capture the influences of homeworking,ensure funding for a minimum level of service,and advocate for a polycentric recovery post-pandemic.

关键词： spatial resilience demand recovery public transport COVID-19 pandemic London

Experimental study of the interspecific competition between two sibling marine herbivorous rotifers in relation to food availability and initial population density

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Acta Oceanologica sinica 2012年第4期31卷 113-126页

作者： divya s P Kathiresan K Asha P sekar V Rajasekaran R Centre of Advanced study in Marine Biology Faculty of Marine SciencesAnnamalai University school of Environmental studies Cochin University of Science and Technology

Our laboratory study concerns the competitive interaction between two marine rotifer species Bra- chionus plicatilis and Brachionus rotundiformis at five algal （ Nannochloropsis salina） concentrations （0.4＊106 to 32.4x106 cells/ml） and at four initial inoculation densities （numerically, 100% B. pli- catilis; 75% B. plicatilis and 25% B. rotundiforrnis, 50% each of the two species; 25% B. plicatilis and 75% B. rotundiformis and 100% B. rotundiforrnis. The initial biomass varied as 0.33 and 0.22 #g/ml for B. plicatilis and B. rotundiformis respectively. Experiments were performed at （25±1）C. Population densities were enumerated and the medium was changed daily up to 8 d in the ex- periment. At the lowest food level tested, B. rotundiformis formed superior competitor than B. plicatilis, regardless of starting inoculation density. Generally when the food concentrations in- creased, B. plicatilis showed a greater increase in biomass than B. rotundiforrnis. B. rotundiformis formed the largest in population growth, regardless of increasing food concentrations. When grown alone, B. plicatilis reached peak abundances of （1.311 5±0.028） and （137.5±0.014） μg/ml at low and high food densities respectively. The corresponding values of B. rotundiformis were 0.724 5±0.016 and 18.15±0.021. The adverse effects of B. rotundiforrnis on the peak abundances of B. plicatilis were observed at the lowest food level and higher initial density. The rate of population growth in controls varied from （0.792±0.162） to （1.482±0.132） ttm/d for B. plicatilis and （0.445~0.041） to （0.856±0.012） μm/d for B. rotundiformis, depending on food level. When both species were intro- duced together, low food levels favoured higher abundance of B. rotundiforrnis than B. plicatilis, suggesting that increased population density of the smaller B. rotundiforrnis was more successfull than larger B. plicatilis in brackish waters. Our work reveals that available food （type and quan- tity） along with starting inoculat

关键词： competition food level B. plicatilis B. rotundiformis population density interspecificcompetition

A secure Three-Party Authenticated Key Exchange Protocol for social Networks

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Computers, Materials & Continua 2022年第6期71卷 6293-6305页

作者： Vivek Kumar sinha divya Anand Fahd s.Alharithi Ahmed H.Almulihi Department of Computer science and Engineering Lovely Professional UniversityPhagwaraPunjab144411India Department of Computer science College of Computers and Information TechnologyTaif UniversityTaif21944Saudi Arabia

The 3PAKE(Three-Party Authenticated Key Exchange)protocol is a valuable cryptographic method that offers safe communication and permits two diverse parties to consent to a new safe meeting code using the trusted *** have been explored numerous 3PAKE protocols earlier to create a protected meeting code between users employing the trusted ***,existing modified 3PAKE protocols have numerous drawbacks and are incapable to provide desired secrecy against diverse attacks such as manin-the-middle,brute-force attacks,and many others in social *** this article,the authors proposed an improved as well as safe 3PAKE protocol based on the hash function and the symmetric encryption for the social *** authors utilized a well-acknowledged AVIsPA tool to provide security verification of the proposed 3PAKE technique,and findings show that our proposed protocol is safer in opposition to active as well as passive attacks namely the brute-force,man-in-the-middle,parallel attack,and many ***,compared to other similar schemes,the proposed protocol is built with a reduced computing cost as our proposed protocol consumes less time in execution and offers high secrecy in the social networks with improved *** a result,this verified scheme is more efficient as well as feasible for implementation in the social networks in comparison to previous security *** multifarious authors carried out extensive research on 3PAKE protocols to offer safe communication,still there are vital opportunities to explore and implement novel improved protocols for higher safety in the social networks and mobile commerce environment in the future in opposition to diverse active as well as passive attacks.

关键词： AVIsPA tool 3PAKE protocol hash function symmetric encryption social networks