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Status,structure and environmental variations in semi-arid mangroves of India

Journal of Forestry Research 2020年第1期31卷 163-173页

作者： G.A.Thivakaran seema B.sharma Abhiroop Chowdhury Arumugam Murugan Coastal and Marine Ecology Division Gujarat Institute of Desert EcologyBhujGujaratIndia Department of Earth and Environmental Sciences KSKV Kachchh UniversityMundra RoadBhujGujaratIndia Department of Chemistry Manipal University JaipurDehmi KalanJaipur-Ajmer Express WayJaipurRajasthan 303007India Central Marine Fisheries Research Institute Mandapam Regional CentreMarine Fisheries P.OMandapam CampusRamanathapuramTamil Nadu 623520India

The semi-arid mangroves of the Gulf of Kachchh,the largest ecosystems on the west coast of India,are poorly studied in terms of vegetation structure and environmental parameters in spite of their conservation ***,it is necessary to document the structural features of these mangroves in view of ongoing coastal industrial *** forest structure in 10 locations on the northern and southern coasts of the Gulf of Kachchh were assessed using the line intercept transect *** included density of young and mature age classes,tree heights,diameters at breast height(DBH)and aboveground biomass,along with seven significant environmental *** tree densities ranged from 350 to 1567 ***-1,while average height and girth at breast height ranged from 1.0 to 6.8 m and 3.0 to 137.0 cm,*** majority of trees(55.6%)were in B 1.8 m height class followed by a 1.9 to 2.4 m class(25.1%).DBH was most often in class 2 cm or lower than *** the canopy index classes,more trees were recorded in class ≤2 *** regeneration density was greater than the recruitment *** study indicates that the poor structural attributes of Avicennia marina *** Stapf and Mold dominated mangroves are largely due to aridity induced by scarce and erratic rainfall and high soil and water *** results should be valuable in conserving and sustainably managing these mangroves in the face of developmental activities.

关键词： Mangroves Vegetation structure Abiotic factors Biodiversity Forest management Aboveground biomass Conservation

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Defect induced room-temperature ferromagnetism and enhanced photocatalytic activity in Ni-doped ZnO synthesized by electrodeposition

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Chinese Physics B 2020年第10期29卷 566-572页

作者： Deepika Raju Kumar Ritesh Kumar Kamdeo Prasad Yadav Pratyush Vaibhav seema sharma Rakesh Kumar Singh Santosh Kumar College o f Commerce Arts and SciencePatna.BiharIndia Jaypee University o f Engineering and Technology GunaMadhya PradeshIndia Anugrah Narayan College PatnaBiharIndia Aryabhatta Knowledge University PatnaBiharIndia

Zn0.90Ni0.10O nanoparticles have been synthesized by single-bath two-electrode electrodeposition at constant voltage. X-ray diffraction, UV vis and photoluminescence studies reveal that a single-phase polycrystalline hcp wurtzite crystal structure of ZnO is evolved. The material consists of a large number of defects such as oxygen vacancy (Ov) and zinc interstitial (Zi). The magnetization study reveals that the sample exhibits room-temperature global ferromagnetism and the ferromagnetic ordering seems to be defect induced via bound magnetic polaron mechanism, and double exchange is also expected to have played role. Interesting optoelectronic properties have been found in the synthesized sample and the material seems to be a potential candidate to be used as a UV sensor. Such a transition metal doped ZnO based dilute magnetic semiconducting system exhibiting room-temperature ferromagnetism is likely to be first of its kind in the sense that such materials have not yet been reported to be synthesized by the simple method of electrodeposition to the best of our knowledge on the basis of ample literature review.

关键词： dilute magnetic semiconductors(DMS) bound magnetic polaron photoluminescence ferromagnetism

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Evaluation of structure,dielectric and electrical properties of(Li/Ta/Sb)modified(Na,K)NbO_(3) lead-free ceramics with excess Na concentration

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Journal of Advanced Dielectrics 2017年第6期7卷 12-20页

作者： Md.Kashif Shamim Arpana Singh seema sharma Materials Research Laboratory Department of Physics A.N CollegePatna 800013India

Polycrystalline perovskite structured Li_(0.04)(Na_(0.54+x) K_(0.46))_(0.96)(Nb_(0.81)Ta_(0.15)Sb_(0.04))O_(3) ceramics with x¼0:00,0.005 and 0.01 mole excess Na concentration were prepared by solid state sintering *** present study relates the role of excess Na addition with the stoichiometry,density,structure,dielectric and ferroelectric properties of the samples.X-ray diffraction(XRD)pattern exhibits single phase orthorhombic *** characteristic Raman modes were observed due to translational modes of cations and vibrational modes of NbO_(6) octahedra and no structural phase transition were *** confirms the formation of single phase perovskite structure and is consistent with XRD *** dielectric permittivity increases about two times,while dielectric loss decreases by four times for χ=0.01 *** electrical measurements carried by Complex Impedance spectroscopic analysis suggest negative temperature coefficient of resistance(NTCR)behavior.

关键词： Perovskite dielectric properties negative temperature coefficient of resistance(NTCR) ferroelectric properties leakage current

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Dielectric,electrical conduction and magnetic properties of multiferroic Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)perovskite compound

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Journal of Advanced Dielectrics 2017年第5期7卷 47-56页

作者： Poonam Kumari Radheshyam Rai seema sharma M.A.Valente School of Physics and Materials Science Shoolini University 173212 Solan H.P.India Ferroelectric Research Laboratory Department of Physics A N CollegePatna 800013India Departamento de Fisica I3NUniversidade de Aveiro Campus Universitario de Santiago 3810193 AveiroPortugal Department of Physics ACBSEternal University Baru Sahib 173101H.P.India

This work focuses on the structural,electrical and magnetic properties of Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3)ceramics,fabricated by solid state reaction *** forms of the samples at RT exhibited perovskite phase through the hexagonal structure at room *** studies of the materials with frequency at different temperatures(25-400℃)exhibit two dielectric anomalies,first at 175℃(ferroelectric-ferroelectric transition)and second at around 320℃(ferroelectric-paraelectric transition).The Curie temperature moved towards the low side temperature with the increase in *** less value of activation energy got for these samples could be attributed to the influence of electronic contribution to the conductivity.A significant change in the magnetic studies was observed for Bi_(0.8)Tb_(0.1)Ba_(0.1)Fe_(0.9)Ti_(0.1)O_(3) *** impedance analysis confirms the non-Debye type nature of the ceramic and relaxation frequency moved to a higher *** Nyquist plot and conductivity studies showed the NTCR behavior of *** highest magnetization field was found at temperature-268.15℃.

关键词： Lead-free ceramics X-ray difraction(XRD) phase transitions electrical conduction magnetic properties multiferroics

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Dielectric relaxation and modulus spectroscopy analysis of(Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics

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Journal of Advanced Dielectrics 2017年第3期7卷 37-47页

作者： Md Kashif Shamim seema sharma Sangeeta Sinha Eqra Nasreen Materials Research Laboratory Department of Physics A.N.College Patna 800013India Department of Environmental Science A.N.College Patna 800013India

We have investigated the structure,dielectric and electrical properties of lead-free polycrystalline (Na_(0.47)K_(0.47)Li_(0.06))NbO_(3) ceramics as a function of temperature and frequency in order to understand the intrinsic contribution of grain/bulk and grain boundary effects toward the dielectric response as well as the electrical conduction mechanism in the samples fabricated by microwave sintering method.X-ray diffraction analysis exhibits perovskite structure with orthorhombic symmetry,which is well supported by the Raman spectroscopic analysis.A minor secondary impurity phase of tungsten bronze structure was observed for samples sintered at 1050℃,which gets weaker for samples sintered at 1150℃.Dielectric permittivity was enhanced by 50%,although there was a reduction in the dielectric loss by about 50%at Curie temperature(450℃)for samples sintered at 1150℃.Complex impedance spectroscopic analysis indicated non-Debye-type dielectric relaxation present in the samples,and this phenomenon followed thermally activated process related to hopping *** plot showed the negative temperature coefficient of resistance,characteristic of the samples.

关键词： Lead-free piezo-ceramics dielectric properties AC impedance spectroscopy dielectric relaxation negative temperature coefficient of resistance(NTCR).

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Preparation and Characterization of SnO₂ Nanofibers via Electrospinning

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Advances in Nanoparticles 2016年第1期5卷 53-59页

作者： Rashmi Rani seema sharma Ferroelectric Research Laboratory Department of Physics A. N. College Patna India

Tin oxide (SnO2) nanofibers are successfully prepared by electrospinning homogeneous viscous solutions of tin acetate in polyvinylpyrrolidone (PVP). The electrospinning is carried out by applying a DC voltage to the tip of a syringe and maintaining the tip to collector distance (TCD), i.e. at DC electric field of 1.25 kV•cm–1. The electrospun nanofibers are calcined between 550℃ and 650℃ for 4 h. Both spun and heat treated nanofibers are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra red spectroscopy (FTIR) etc. XRD analysis of calcined nanofibers confirms the formation of pure tin oxide. TEM study showed that fibers have a polycrystalline structure with multiple nano-grains.

关键词： Naonofibers TEM Electrospinning PVP

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Study of the structural and electrical behavior of Bi(Mg,Ti)O_(3)modified(Ba,Ca)TiO_(3)ceramics

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Journal of Advanced Dielectrics 2016年第4期6卷 72-80页

作者： Md.Kashif Shamim seema sharma Arpana Singh Radheshyam Rai Rashmi Rani Ferroelectric Research Laboratory Department of Physics A.N.CollegePatna 800013India School of Physics and Materials Science Shoolini University SolanHimachal PradeshIndia

The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various *** the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in search for new lead-free ferroelectric material and improve their *** this purpose,BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional *** this study,we report the structural and electrical properties of lead free piezo-ceramics(1-x)(Ba_(0.8)Ca_(0.2))TiO_(3–x)Bi(Mg_(0.5)Ti_(0.5))O_(3)with x=0.2,0.4,0.5 prepared by solid-state sintering *** perovskite phase with tetragonal structure is obtained for all the compositions,which is reconfirmed by the Raman Spectroscopic *** study confirm the temperature stable behavior of the dielectric permittivity values above 300℃.The dielectric constant value decreases with increase in BMT doping *** Spectroscopic study confirms non-Debye type dielectric relaxation in the *** Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior(NTCR)of the samples.

关键词： Perovskite Raman analysis non-Debye type XRD ferroelectrics.

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Green Synthesis of Silver Nanoparticles Using Extracts of <i>Ananas comosus</i>

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Green and Sustainable Chemistry 2012年第4期2卷 141-147页

作者： Naheed Ahmad seema sharma Department of Botany Patna University Patna India Department of Physics A. N. College Magadh University Patna India

The biosynthesis of nanoparticles has been proposed as a cost effective and environmental friendly alternative to chemical and physical methods. Plant mediated synthesis of nanoparticles is a green chemistry approach that intercom nects nanotechnology and plant biotechnology. In the present study, synthesis of silver nanoparticles (AgNPs) or (Green-Silver) has been demonstrated using extracts of Ananas comosus reducing aqueous silver nitrate. The AgNPs were characterized by Ultraviolet-Visible (UV-vis) Spectrometer, Energy Dispersive X-ray Analysis (EDAX), Selected Area Diffraction Pattern (SAED) and High Resolution Transmission Electron Microscopy (HRTEM). TEM micrographs showed spherical particles with an average size of 12 nm. The XRD pattern showed the characteristic Bragg peaks of (111), (200), (220) and (311) facets of the face center cubic (fcc) silver nanoparticles and confirmed that these nanoparticles are crystalline in nature. The different types of antioxidants presented in the pineapple juice synergistically reduce the Ag metal ions, as each antioxidant is unique in terms of its structure and antioxidant function. The re- action process was simple for formation of silver nanoparticles and AgNPs presented in the aqueous medium were quite stable, even up to 4 months of incubation. This work proved the capability of using biomaterial towards the synthesis of silver nanoparticle, by adopting the principles of green chemistry.

关键词： AgNPs XRD TEM SAED Green-Silver Ananas comosus

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Influence of Sintering Temperature on Densification, Structure and Microstructure of Li and Sb Co-Modified (K,Na)NbO<sub>3</sub>-Based Ceramics

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Materials Sciences and Applications 2011年第10期2卷 1416-1420页

作者： Rashmi Rani seema sharma 不详

Polycrystalline samples of Lead free (K0.5Na0.5)1-x(Li)x(Sb)x(Nb)1-xO3 ceramics with nominal compositions (x = 0.040 to 0.060) have been prepared by high temperature solid state reaction technique. X-ray diffraction (XRD) pattern shows that the crystal structure transforms from orthorhombic to tetragonal as Li and Sb content increases. Normal sintering process yield compounds with density ~98.2% of the theoretical value. Densification of the Li and Sb co-doped KNN ceramics might be explained by the liquid-phase sintering. This may be attributed to the low melting temperature of Li compounds that appears to promote the formation of a liquid phase during sintering.

关键词： KNN Perovskite XRD SEM

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Effect of Foundation and Non-Homogeneity on the Vibrations of Polar Orthotropic Parabolically Tapered Circular Plates

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Applied Mathematics 2015年第9期6卷 1563-1573页

作者： Shivani Srivastava seema sharma Roshan Lal Department of Mechanical Engineering Indian Institute of Technology Madras Chennai India Department of Mathematics Gurukul Kangri University Haridwar India Department of Mathematics Indian Institute of Technology Roorkee Roorkee India

The effect of Pasternak foundation and non-homogenity on the axisymmetric vibrations of polar orthotropic parabolically varying tapered circular plates has been analyzed on the basis of classical plate theory. Ritz method has been used to find the numerical solution of the specified problem. The efficiency of the Ritz method depends on the choice of basis function based upon deflection of polar orthotropic plates. The effects of different plate parameters viz. elastic foundation, non-homogeneity, taper parameter and that of orthotropy on fundamental, second and third mode of vibration have been studied for clamped and simply-supported boundary conditions. Mode shapes for specified plates have been drawn for both the boundary conditions. Convergence and comparison studies have been carried out for specified plates.

关键词： Pasternak Foundation Parabolically Varying Thickness Circular Plate Polar Orthotropy Non-Homogenity

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