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Comprehensive studies on dielectric properties of p-methoxy benzylidene p-decyl aniline with function of temperature and frequency in planar geometry: A potential nematic liquid crystal for display devices

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Chinese Physics B 2021年第6期30卷 329-333页

作者： pankaj kumar tripathi Kunwar Vikram Mithlesh Tiwari Ajay Shriram Department of Physics Lovely Professional UniversityPhagwara-144411PunjabIndia Department of Allied Science Graphic Era(Deemed to be university)Dehradun-248002 India Department of Physics and Electronics Dr.Ram Manohar Lohia Avadh UniversityAyodhya-224001U.P.India School of Computer Science&Information Technology Jain(Deemed-to-be-University)Bengaluru-560069KarnatakaIndia

The dielectric properties of the nematic mesophase, p-methoxy benzylidene p-decyl aniline(MBDA), measured in planar geometry with a function of frequency and temperature are investigated in detail. The complex dielectric permittivity(ε' and ε'') is also studied at a bias voltage of 10 V for planar aligned sample cell of nematic mesophase. The dielectric permittivity with bias voltage attains a higher(> 2 times) value than that without bias voltage at a temperature of 56℃,which is due to the fact that the linking group of nematic molecules is internally interacted with an applied bias *** is supported by observing an enhanced dielectric permittivity of nematic liquid crystal(LC) in the presence of bias voltage, which can be fully explained as the increasing of the corresponding dipole moment. The dielectric relaxation behaviors of nematic LC are also demonstrated for planar aligned sample cell. The remarkable results are observed that the relaxation frequency shifts into low frequency region with the increase of the bias voltage applied to the planar aligned sample cells. The dielectric relaxation spectra are fitted by Cole–Cole nonlinear curve fitting for nematic mesophase in order to determine the dielectric strength.

关键词： dielectric permittivity dielectric loss relaxation frequency nematic mesogen

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Analysis of silicon-based integrated photovoltaic–electrochemical hydrogen generation system under varying temperature and illumination

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Journal of Energy Chemistry 2017年第1期26卷 72-80页

作者： Vishwa Bhatt Brijesh tripathi pankaj Yadav Manoj kumar Department of Solar Energy School of TechnologyPandit Deendayal Petroleum UniversityGandhinagar 382007India Department of Science School of TechnologyPandit Deendayal Petroleum UniversityGandhinagar 382007India Department of Electrical Engineering Incheon National UniversityIncheon 406772Republic of Korea

Last decade witnessed tremendous research and development in the area of photo-electrolytic hydrogen generation using chemically stable nanostructured photo-cathode/anode materials. Due to intimately coupled charge separation and photo-catalytic processes, it is very difficult to optimize individual components of such system leading to a very low demonstrated solar-to-fuel efficiency (SFE) of less than 1%. Recently there has been growing interest in an integrated photovoltaic–electrochemical (PV–EC) system based on GaAs solar cells with the demonstrated SFE of 24.5% under concentrated illumination condition. But a high cost of GaAs based solar cells and recent price drop of poly-crystalline silicon (pc-Si) solar cells motivated researchers to explore silicon based integrated PV–EC system. In this paper a theoretical framework is introduced to model silicon-based integrated PV–EC device. The theoretical framework is used to analyze the coupling and kinetic losses of a silicon solar cell based integrated PV–EC water splitting system under varying temperature and illumination. The kinetic loss occurs in the range of 19.1%–27.9% and coupling loss takes place in the range of 5.45%–6.74% with respect to varying illumination in the range of 20–100 mW/cm2. Similarly, the effect of varying temperature has severe impact on the performance of the system, wherein the coupling loss occurs in the range of 0.84%–21.51% for the temperature variation from 25 to 50 °C. © 2016 Science Press

关键词： Electrochemical cells Electrochemical impedance spectroscopy Gallium arsenide Hydrogen production Nanostructured materials Polysilicon Semiconducting gallium Silicon Silicon solar cells Solar power generation

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Numerical Algorithm Based on Quintic Nonpolynomial Spline for Solving Third-Order Boundary Value Problems Associated with Draining and Coating Flows

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Chinese Annals of Mathematics,Series B 2012年第6期33卷 831-840页

作者： pankaj kumar SRIVASTAVA Manoj kumar Department of Mathematics Jaypee Institute of Information Technology Department of Mathematics Motilal Nehru National Institute of Technology

A numerical algorithm is developed for the approximation of the solution to certain boundary value problems involving the third-order ordinary differential equation associated with draining and coating flows. The authors show that the approximate so- lutions obtained by the numerical algorithm developed by using uonpolynomial quintic spline functions ave better than those produced by other spline and domain decomposition methods. The algorithm is tested on two problems associated with draining and coating flows to demonstrate the practical usefulness of the approach.

关键词： Third-order boundary value problem Spline functions Nonpolynomial quartic spline Nonpolynomial quintic spline Draining and coating flows

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Rainforests north of the Tropic of Cancer: Physiognomy, floristics and diversity in ‘lowland rainforests’ of Meghalaya, India

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Plant Diversity 2017年第1期39卷 20-36页

作者： Uma Shankar Amit kumar tripathi Department of Botany North-Eastern Hill University Shillong 793 022 India

The lowland rainforests of Meghalaya, India represent the westernmost limit of the rainforests north of the Tropic of Cancer. These forests, on the Shillong plateau, are akin to Whitmore's ‘tropical lowland evergreen rainforest' formation and exhibit striking similarities and conspicuous differences with the equatorial rainforests in Asia-Pacific as well as tropical seasonal rainforests in southwestern China near the Tropic of Cancer. We found these common attributes of the rainforests in Meghalaya: familial composition with predominance of Euphorbiaceae, Lauraceae, Meliaceae, Moraceae, Myrsiticaceae,Myrtaceae and Rubiaceae; deciduousness in evergreen physiognomy; dominance of mega-and mesophanerophytic life-forms; abundance of species with low frequency of occurrence(rare and aggregated species); low proportional abundance of the abundant species; and truncated lognormal abundance distribution. The levels of stand density and stand basal area were comparable with seasonal rainforests in southwestern China, but were lower than equatorial rainforests. Tropical Asian species predominated flora, commanding 95% of the abundance. The differences include overall low stature(height) of the forest, inconspicuous stratification in canopy, fewer species and individuals of liana, thicker understory,higher proportion of rare species, absence of locally endemic species and relatively greater dominance of Fagaceae and Theaceae. The richness of species per hectare(S) was considerably lower at higher latitudes in Meghalaya than in equatorial rainforests, but was comparable with seasonal rainforests. Shannon's diversity index(H’=4.40 nats for ≥10 cm gbh and 4.25 nats for ≥30 cm gbh) was lower on higher latitudes in Meghalaya in comparison to species-rich equatorial rainforests, but it was the highest among all lowland rainforests near the Tropic of Cancer.

关键词： Lowland rainforest Forest structure Floristics Phytosociology Species richness Life-form spectrum

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A high-capacity viologen-based anolyte for high energy density neutral pH aqueous redox-flow batteries

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Journal of Energy Chemistry 2023年第3期78卷 222-231,I0007页

作者： Anubhav kumar Bijay P.tripathi Department of Materials Science and Engineering Indian Institute of Technology DelhiHauz KhasNew Delhi 110016India

Redox-ﬂow batteries(RFBs)are a promising energy storage technology with remarkable scalability and safety for storing vast amounts of renewable energy and mitigating outputﬂuctuations of renewable power *** demonstrate a neutral pH aqueous RFB using a custom-designed 1’,1’’’,1’’’’’-(benzene-1,3,5-triyltris(methylene))tris(1-(3-(trimethyl ammonio)propyl)-[4’’,4’’’-bipyridine]-1,1’-diium)nonachloride(BTTMPB)as a 3 e-storage *** custom design with the high polarization in charge density has led to the excellent water solubility of 4.0 M in H_(2)O(321.6 A h L^(-1))and 2.4 M in 2.0 M NaCl(192.9 A h L^(-1)).The density functional theory(DFT)calculations and electrochemical experiments have shown 3 e-storage response of BTTMPB with a diffusion coefﬁcient of 3.1×10^(-6)cm^(2) s^(-1)and rate con-stant of 1.6×10^(-2)cm s^(-1) for theﬁrst reduction *** synthesized anolyte was paired with(Ferrocenylmethyl)trimethylammonium chloride(FcNCl)as catholyte enabling a 0.92 V aqueous RFB with 125.9 W h L^(-1)theoretical energy *** aqueous RFB has an excellent cycling performance from 10-30 m A cm^(-2),energy efﬁciency up to 80%,capacity retention of 99.96%per cycle at 20 m A cm^(-2),and a high demonstrated energy density of 29.1 W h L^(-1).

关键词： Energy storage Aqueous redox-ﬂow battery Redox-active organic material Viologen derivative Solvation energy

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Flow past a bluff body subjected to lower subcritical Reynolds number

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Journal of Ocean Engineering and Science 2020年第2期5卷 173-179页

作者： pankaj kumar Santosh kumar Singh Department of Mechanical Engineering SRM Institute of Science and TechnologyKattankulathur 603203India

The paper aimed to study the flow structure at the wake of the bluff body with altered blockage ratio(BR)keeping the fixed aspect ratio(AR).The study was conducted by a finite volume technique using commercial software *** CFD analysis of the bluff body is mainly subjected to the lower subcritical Reynolds number range(5000 to 15,000)along with blockage ratio as an important *** flow parameters such as drag coefficient,pressure,and kinetic energy variations are analyzed here for the Reynolds number(Re)and *** was observed that at fixed Re,t he drag coefficient(C_(D))increases with an increase in the BR while decrease with increasing Re for a fixed value of BR.

关键词： Blockage ratio Bluff body Drag coefficient Reynolds number

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Particle Swarm Optimization Based Support Vector Regression for Blind Image Restoration

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Journal of Computer Science & Technology 2012年第5期27卷 989-995页

作者： Ratnakar Dash pankaj kumar Sa Banshidhar Majhi Computer Science and Engineering Department National Institute of Technology RourkelaRourkela 769008India

This paper presents a swarm intelligence based parameter optimization of the support vector machine （SVM） for blind image restoration. In this work, SVM is used to solve a regression problem. Support vector regression （SVR） has been utilized to obtain a true mapping of images from the observed noisy blurred images. The parameters of SVR are optimized through particle swarm optimization （PSO） technique. The restoration error function has been utilized as the fitness function for PSO. The suggested scheme tries to adapt the SVM parameters depending on the type of blur and noise strength and the experimental results validate its effectiveness. The results show that the parameter optimization of the SVR model gives better performance than conventional SVR model as well as other competent schemes for blind image restoration.

关键词： image restoration support vector regression particle swarm optimization

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Analysis of Dielectric and Electro-optic Responses of Nanomaterials Doped Ferroelectric Liquid Crystal Mixture

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Journal of Materials Science & Technology 2011年第12期27卷 1094-1098页

作者： Neeraj pankaj kumar K.K. Raina Material Research Laboratory School of Physics and Materials Science Thapar University Patiala 147004 India Department of BIN Fusion Technology Chonbuk National University Jeonju Jeonbuk 561-756 Korea Department of Applied Science Chitkara University Jansala Rajpura Patiala-140401 Punjab India

Dielectric and rotational viscosity measurements of a multi-component ferroelectric liquid crystal mixture were performed by adding a small concentration （0.01 wt%） of silica and multi walled carbon nanotubes （MWCNTs）. Liquid crystals turn out to be outstanding hosts for nanomaterials. A remarkable increase in the rotational viscosity was noticed in CNT doped system as compared to silica doped same liquid crystal system. Comparison of dielectric studies shows higher value of permittivity and dielectric losses for silica-doped sample than those of CNT doped sample. The results have been interpreted both experimentally and theoretically.

关键词： Ferroelectric liquid crystals Silica nanoparticles Carbon nanotubes Dielectricpermittivity Rotational viscosity

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Texture evaluation in AZ31/AZ31 multilayer and AZ31/AA5068 laminar composite during accumulative roll bonding

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Defence Technology（防务技术） 2020年第3期16卷 514-519页

作者： pankaj kumar Aviral Madhup Prasad RKalvala Satyam Suwas Chemical and Materials Engineering University of NevadaRenoNV89557USA Materials Engineering Indian Institute of ScienceBangalore560012India

This article presents the texture development of magnesium AZ31 alloy in the accumulative roll bonded(ARB) AZ31/AZ31 multilayer and AZ31/AA5086 laminate *** comparative study demonstrates that the texture evolution in AZ31 in a multilayer system is strongly influenced by the interfaces.A typical basal texture of AZ31 has been observed in AZ31/AZ31 multilayer with texture intensity increased with the rolling *** of AZ31/AA5086 interface in the laminate composite leads to a tilted basal texture along the rolling direction(RD) in AZ31 *** texture intensity of composite increased initially with rolling reduction and weakened at the higher rolling *** of texture in AZ31 during the laminate processing at higher strain has been attributed to the development of wavy interfaces in AZ31/AA5086 laminate.

关键词： Accumulative roll bonding Defence application AZ31 alloy Texture Composite Laminates

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Sustainable remediation of failed slope using helical soil nails

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Journal of Mountain Science 2023年第6期20卷 1742-1758页

作者： Saurabh RAWAT Ashok kumar GUPTA pankaj SHARMA Department of Civil Engineering Jaypee University of Information Technology Department of Civil Engineering Chitkara University Institute of Engineering and TechnologyChitkara University

The performance of a helical soil nailed structure is dependent on the installation torque required and the consequent pullout resistance *** present research work aims at proposing theoretical models to estimate the required torque during installation of helical soil ***,theoretical models are also developed to predict the pullout capacity of single and group of the helical nail for uniform and staggered *** proposed model predicts the pure-elastic and elastic-plastic pullout behavior of different helical *** equation for estimating the capacity-totorque Ratio(Kt)has also been developed for different nail shaft *** results from the proposed models are validated with experimental results obtained from model testing of both single and group of helical *** predicted results are also compared for validation with the published *** results for installation torque and pullout load depict that the developed models predict values which are in accordance with the experimental results and are also found in good agreement with the published ***,the proposed models can effectively be used by the filed engineers for estimating the required installation torque and corresponding pullout capacities for single or double plate helical soil nails in cohesionless soil under surcharge pressure range of 0–50k Pa.

关键词： Theoretical torque Pullout force Pure elastic Elastic plastic Capacity to torque ratio

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