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A relativistic model of stellar objects with core-crust-envelope division

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Research in Astronomy and Astrophysics 2021年第7期21卷 71-83页

作者： ravindra k.Bisht Satyanarayana Gedela Neeraj Pant Neeraj Tewari Department of Mathematics National Defence AcademyKhadakwaslaPune-411023India Department of Mathematics SSJ CampusKumaun UniversityAlmora-263601India Department of Physics Lajpat Rai CollegeGhaziabad-201005India

In this work, we present a cogent and physically well-behaved solution for neutron stars envisaged with a core layer having quark matter satisfying the MIT-bag equation of state(Eo S), meso layer with Bose-Einstein condensate(BEC) matter satisfying modified BEC Eo S and an envelope having neutron fluid and Coulomb liquids satisfying quadratic Eo S. All the required physical and geometrical parameters like gravitational potentials, pressures, radial velocity, anisotropy, adiabatic index, mass function, compactification factor, and gravitational and surface redshift functions show a feasible trend and are continuous with smooth variation throughout the interior and across the regions of the ***, causality condition, energy conditions, static stability criterion(using Tolman-OppenheimerVolkoff equation) and Herrera cracking stability criterion are met throughout the star. The approach seems to be resulting in more realistic and accurate modeling of stellar objects, particularly realized by us for X-ray binary stars 4 U 1608–52(M = 1.7 M_⊙, R = 9.5 km) and SAX J1808.4–3658(M = 1.2 M_⊙,R = 7.2 km). Furthermore, we have ascertained that the continuity of the stability factor in all three regions of the stars demand a smaller core. As the core region of the star increases, the stability factor becomes discontinuous at all the interfaces inside the star.

关键词： stars:interiors stars:neutron Galaxy:stellar content

Static fluid spheres admitting karmarkar condition

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Chinese Physics C 2020年第3期44卷 137-147页

作者： ksh.Newton Singh ravindra k.Bisht S.k.Maurya Neeraj Pant Department of Physics National Defence AcademyKhadakwaslaPune-411023India Department of Mathematics Jadavpur UniversityKolkata-700032India Department of Mathematics National Defence AcademyKhadakwaslaPune-411023India Department of Mathematical and Physical Sciences College of Arts and ScienceUniversity of NizwaNizwaSultanate of Oman

We explore a new relativistic anisotropic solution of the Einstein field equations for compact stars based on embedding class one *** this purpose,we use the embedding class one methodology by employing the karmarkar *** this methodology,we obtain a particular differential equation that connects both the gravitational potentials e^λ and e^ν.We solve this particular differential equation choosing a simple form of generalized gravitational potential grr to describe a complete structure of the space-time within the stellar *** determining this space-time geometry for the stellar models,we discuss thermodynamical observables including radial and tangential pressures,matter density,red-shift,velocity of sound,etc.,in the stellar *** also perform a complete graphical analysis,which shows that our models satisfy all the physical and mathematical requirements of ultra-high dense collapsed ***,we discuss the moment of inertia and M-R curve for rotating and non-rotating stars.

关键词： karmarkar's condition exact solutions compact star general relativity

Disaster Risk Reduction Including Climate Change Adaptation Over South Asia: Challenges and Ways Forward

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International Journal of Disaster Risk Science 2019年第1期10卷 14-27页

作者： Rajesh k.Mall ravindra k.Srivastava Tirthankar Banerjee Om Prakash Mishra Diva Bhatt Geetika Sonkar Institute of Environment and Sustainable Development Banaras Hindu University DST-Mahamana Centre of Excellence in Climate Change Research Banaras Hindu University Ministry of Home Affairs Ministry of Earth Sciences

South Asia is vulnerable to a variety of hydrometeorological hazards, which are often crossboundary in nature. Climate change is expected to influence many of these hazards. Thus, climate-related risks over South Asia make disaster risk reduction(DRR) and climate change adaptation(CCA) key policy *** there is an increasing consensus that DRR including CCA should be embedded in development planning. Disaster risk reduction including CCA has progressively gained importance in global governance. Across South Asia, however, such integration is only in a preliminary stage. This review was to assess the existing status and scope of DRR including CCA in development projects across South Asia, so that an effective and achievable deliberation may be made to regional policymakers. A total of 371 projects relevant to CCA and DRR were *** project inventory was diverse in nature with respect to location, scale, sectoral focus, and strategic ***, India, and Bhutan were observed to be proactive in implementing DRR-and CCA-related ***-analysis of the project inventory suggests an urgent need for an individual and collaborative convergence of processes for DRR and CCA through policies,plans, strategies, and programs.

关键词： Climate change Climate change adaptation Disaster risk reduction SAARC South Asia

Microstructure,mechanical response and fractography of AZ91E/Al_(2)O_(3)_(p) nano composite fabricated by semi solid stir casting method

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Journal of Magnesium and Alloys 2017年第1期5卷 48-55页

作者： Sameer kumar D Suman k.N.S Tara Sasanka C ravindra k Palash Poddar Department of Mechanical Engineering R.V.R.&J.C.College of EngineeringGunturIndia Department of Mechanical Engineering Andhra University College of EngineeringVisakhapatnamIndia CSIR-National Metallurgical Laboratory JamshedpurIndia d Department of Mechanical EngineeringNarasaraopeta Engineering CollegeNarasaraopetIndia

The present study confers to the fabrication and its characterization of magnesium alloy(AZ91E)based nano composites with nano Al_(2)O_(3) particulate reinforcements.A novel Semi Solid stir casting technique was adopted for the fabrication of the *** average particle size of 50 nm was used as reinforcement to disperse in *** effects of change in weight fraction of reinforcements on the distribution of particles,particle–matrix interfacial reactions,physical as well as mechanical properties were *** SEM and EDS analysis has shown the uniform distribution of particles in the composite along with the presence of *** mechanical properties of reinforced and unreinforced composite were evaluated and *** of tensile specimens was also discussed.

关键词： Magnesium alloys Nano composites Semi solid stir casting Al_(2)O_(3)particle

Chemometrics:A new scenario in herbal drug standardization

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Journal of Pharmaceutical Analysis 2014年第4期4卷 223-233页

作者： Ankit Bansal Vikas Chhabra ravindra k.Rawal Simant Sharma Indo-Soviet Friendship(ISF) College of Pharmacy MogaPunjab 142001India

Chromatography and spectroscopy techniques are the most commonly used methods in standardization of herbal medicines but the herbal system is not easy to analyze because of their complexity of chemical composition. Many cutting-edge analytical technologies have been introduced to evaluate the quality of medicinal plants and significant amount of measurement data has been produced. Chemometric techniques provide a good opportunity for mining more useful chemical information from the original data. Then, the application of chemometrics in the field of medicinal plants is spontaneous and necessary. Comprehensive methods and hyphenated techniques associated with chemometrics used for extracting useful information and supplying various methods of data processing are now more and more widely used in medicinal plants, among which chemometrics resolution methods and principal component analysis （PCA） are most commonly used techniques. This review focuses on the recent various important analytical techniques, important chemometrics tools and interpretation of results by PCA, and applications of chemometrics in quality evaluation of medicinal plants in the authenticity, efficacy and consistency,

关键词： ChemometricsHELP Herbal drugs PCA OPA

Application of RP-HPLC method in dissolution testing and statistical evaluation by NASSAM for simultaneous estimation of tertiary combined dosages forms

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Journal of Pharmaceutical Analysis 2015年第5期5卷 307-315页

作者： Yogesh Upadhyay Nitin Sharma G.S.Sarma ravindra k.Rawal Department of Pharmaceutical Analysis Indo-Soviet Friendship College of Pharmacy

A dissolution method with robust high performance liquid chromatographic （HPLC） analysis for im- mediate release tablet formulation was developed and validated to meet the requirement as per Inter- national Conference on Harmonization （ICH） and United States Food and Drug Administration （USFDA） guidelines. The method involved the use of Agilent ZORBAX Eclipse XDB C18 column, and temperature was maintained at 30 ℃. After optimization, the mobile phase was selected as phosphate buffer （kH2PO4, 30 mM）： ACN （60：40, v/v） with pH 3.0, and retention time Rt was found as 3.24, 4.16, and 2.55 min for paracetamol （PCM）, chlorpheniramine maleate （CPM） and phenylephrine hydrochloride （PH） respec- tively at 265 nm and at a flow rate of 1 mL/min. The relative standard deviation （%RSD） for 6 replicate measurements was found to be less than 2%. Furthermore net analyte signal standard addition method （NASSAM） with spectrophotometer was performed for standard and liquid oral suspension. On the basis of selectivity, sensitivity and accuracy analysis, it was confirmed that this novel method could be useful for simultaneous estimation of the given drug combinations. Two-way analysis of variance （ANOVA） was applied for evaluating the statistical difference between the assay results obtained via both NASSAM and RP-HPLC methods and ultimately no significant difference was found between both the methods. All the methods and results were acceptable and confirmed that the method was suitable for intended use.

关键词： DissolutionRP-HPLCNet analyte signal standard addition meth-odTwo-way ANOVA

Effect of Different Plasmonic Nano-Inclusion on Double Negative-Semiconductor Photonic Crystal in Visible Region:Gain Assistance and All-Angle Negative Refraction

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Journal of Electronic Science and Technology of China 2010年第1期8卷 10-15页

作者： Monika Rajput ravindra k.Sinha Delhi Technological University Formally known as Delhi College of Engineering University of Delhi

A gain assisted double negative- Metallo-semiconductor photonic crystal （DN-MSPC） for visible light with effect of different plasmonic （Al, Ag, Au, Cu） nanorod inclusion, is presented. Negative real values of both permeability （μ） and permittivity （ε） with extremely low imaginary values for visible light is obtained by applying Coupled dipole approximation. All-Angle negative refraction is obtained by applying surface plasmon polariton excitation （SPPE） in DN-MSPC operating in a dispersion regime with anti-parallel refracted wave vector and Poynting vector. Index matched to the incident light and compensated losses due the gain assistance leads the light amplification in the designed structure. Furthermore, extremely high left-handed transmission efficiency （〉99%） is also investigated. Demonstration of near and far-field resonance patterns reveal the nano-photonic device applications potential i.e. highly directional optical nanoantenna, filter, etc.

关键词： Nanorods negative index materials,photonic crystal.

Numerical Investigation of Heave and Pitch Motion Effects on Green Water Loading for a Floating Body

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Journal of Marine Science and Application 2019年第4期18卷 457-471页

作者： k.ravindra Babu R.Datta A.Bhattacharyya Department of Ocean Engineering & Naval Architecture IIT-Kharagpur

In this paper,the influence of heave and pitch motions on green water impact on the deck is numerically *** vessel motions are determined using a potential theory based method and provided as input to finite volume based CFD computations of green water phenomenon.A dynamic mesh approach is adopted to determine instantaneous body positioning in the fluid *** validation studies with published experimental results for 2D and 3D fixed vessel cases are initially performed to validate the present numerical approach before studying the moving vessel *** results show that inclusion of heave and pitch motion changes the disturbed wave field near the bow which influences the free surface as well as the impact loading due to green *** effect of wave steepness on green water impact is also investigated and it is seen that the present numerical method is capable of capturing green water *** is observed that the effects of vessel motions on green water load are not negligible and one should consider this effect *** incorporation of vessel motions in the vertical plane affects the green water loading on the deck.

关键词： Greenwaterimpact pressure Relativewaveheight Vertical bowmotion Heaveand pitchmotions Wave steepness Floating body

Optimization of variables and assessment of in-vitro and in-vivo antihyperlipidemic activity of Eudragit RS nanoparticles containing simvastatin

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Particuology 2024年第7期90卷 189-198页

作者： Bina Gidwani Vishal Jain Veenu Joshi ravindra kumar Pandey Shiv Shankar Shukla Amber Vyas Columbia Institute of Pharmacy Raipur(C.G.)India University Institute of Pharmacy Pt Ravishankar Shukla UniversityRaipur(C.G.)India Center for Basic Science and Research Pt Ravishankar Shukla UniversityRaipur(C.G.)India

Simvastatin, a BCS class II drug, is associated with poor aqueous solubility, first-pass metabolism and short half-life. In the present work, nanoparticles were prepared and evaluated. Optimization of formulation and process parameters was done through the use of independent and dependent variables. Preliminary studies were done to determine suitable range of the concentration of Eudragit polymer (10%–30%) and the ratio of drug to polymer (1:1 to 1:5) for the formation of nanoparticles by emulsification and a solvent evaporation technique. Results revealed that the mean size of nanoparticles was affected by stirring speed from 5000 RPM, 8000 RPM, and 12000 RPM. The results of increase in association efficiency and percent yield with increase in amount of drug from 100 mg, 150 mg, and 200 mg in selected range were observed. In-vitro release studies showed that two formulations possess highest initial burst and slow sustained drug release. There was 2.93-fold decrease in total cholesterol and 3.27-fold increases in triglyceride level during in-vivo study.

关键词： Simvastatin Eudragit RS 100 Nanoparticles Hyperlipidemia