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Electronic Structure of Helium Atom in a Quantum Dot

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Communications in Theoretical Physics 2016年第3期65卷 347-353页

作者： Jayanta K.Saha S.Bhattacharyya T.K.Mukherjee indian Association for the Cultivation of Science Jadavpur Kolkata 700032 India Aliah University IIA/27 New Town Kolkata 700156 India Acharyya Prafulla Chandra College New Barrackpore Kolkata 700131 India Narula Institute of Technology Agarpara Kolkata 700109 India

Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization *** be specific,precise energy eigenvalues of bound 1sns(~1S^e)(n=1-6)states and the resonance parameters *** and widths of^lS^e states due to 2sns(n=2-5)and 2pnp(n=2-5)configurations of confined helium below N=2 ionization threshold of He^+have been *** two-parameter(Depth and Width)finite oscillator potential is used to represent the confining potential due to the quantum *** has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot *** is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters.A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here.

关键词： helium atom variational method quantum dot correlation

Static spherically symmetric wormholes in f(Q,T)gravity

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Chinese Physics C 2022年第11期46卷 275-290页

作者： Moreshwar Tayde Zinnat Hassan P.K.Sahoo Sashideep Gutti Department of Mathematics Birla Institute of Technology and Science-PilaniHyderabad CampusHyderabad-500078India Department of Physics Birla Institute of Technology and Science-PilaniHyderabad CampusHyderabad-500078India

In this study,we obtain wormhole solutions in the recently proposed extension of symmetric teleparallel gravity,known as f(Q,T)***,the gravitational Lagrangian L is defined by an arbitrary function f of Q and T,where Q is a non-metricity scalar,and T is the trace of the energy-momentum *** this study,we obtain field equations for a static spherically symmetric wormhole metric in the context of general f(Q,T)*** study the wormhole solutions using(ⅰ)a linear equation of state and(ⅱ)an anisotropy *** adopt two different forms of f(Q,T),(a)linear f(Q,T)=αQ+βT and(b)non-linear f(Q,T)=Q+λQ^(2)+ηT,to investigate these *** investigate various energy conditions to search for preservation and violation among the obtained solutions and find that the null energy condition is violated in both cases of our assumed forms of f(Q,T).Finally,we perform a stability analysis using the Tolman-Oppenheimer-Volkov equation.

关键词： wormhole EoS energy conditions stability analysis f(Q,T)gravity

Evaluation of flocculation characteristics of kaolinite dispersion system using guar gum:A green flocculant

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International Journal of Mining Science and Technology 2019年第5期29卷 745-755页

作者： R.K.Dwari B.K.Mishra Mineral Processing Department CSIR-Institute of Minerals and Materials TechnologyBhubaneswar 751013India indian Institute of Technology Goa 403401India

This paper reports the systematic investigation on the flocculation,sedimentation and consolidation characteristics of kaolinite using guar gum as a green ***-situ flocculation behavior of kaolinite at various pH,guar gum dosages,and ionic strength were studied using a light scattering *** effect of these parameters on the settling rate,solid consolidation,and supernatant liquid clarity was *** morphology of kaolinite and flocculated kaolinite aggregates were analyzed using *** morphology studies suggest that it is poorly crystalline with multiple steps on edge,broken edge;laminar with high aspect ratio and have rough basal *** complex irregularity on the basal surface and the presence of multiple steps in the edges,broken edges(hydroxyl groups)have facilitated the guar gum *** isoelectric point of kaolinite is pH *** pH,ionic strength and flocculant dosage have a significant effect on the kaolinite settling *** guar gum has exhibited excellent turbidity removal efficiency at pH *** turbidity removal is inefficient at pH ***,guar gum has shown high turbidity removal with 80%transmission at pH 10 in the presence of a KNO3 electrolyte.

关键词： Guar gum Dewatering Kaolinite Light scattering Morphology Flocculation

Dielectric Relaxation and Conductivity of Ba(Mg_(1/3)Ta_(2/3))O_3 and Ba(Zn_(1/3)Ta_(2/3))O_3

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Journal of Materials Science & Technology 2014年第4期30卷 311-320页

作者： Md.Monwar Hoque Alo Dutta Sanjay Kumar Tripurari Prasad Sinha Department of Physics Jadavpur University Department of Physics Bose Institute

The frequency dependent dielectric properties of barium magnesium tantalate （BMT）, Ba（Mgl/3Ta2/3）03 and barium zinc tantalate （BZT）, Ba（Znl/3Ta2/3）03 synthesized by solid state reaction technique have been investigated at various temperatures by impedance spectroscopy. BMT and BZT possess cubic structure with lattice parameter a = 0.708 and 0.451 nm, respectively. The resonance peaks due to dielectric relaxation processes are observed in the loss tangent of these oxides. The relaxation in the samples is polydispersive in nature. The temperature dependence of dc conductivity, the most probable relaxation frequency （corn） obtained from tanδ vs logo） plots and ωm obtained from imaginary parts of the complex electrical modulus vs Iogω plots follow the Arrhenius behavior. According to these Arrhenius plots the activation energies of BMT and BZT are about 0.54 and 0.40 eV, respectively. Thus the results indicate that samples are semiconducting in nature. The frequency-dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show qualitative similarities in relaxation time. Our study points that for complex perovskite oxides with general formula A（B＇B＇）03, the dielectric properties significantly depend on the atomic radii of both A and B type cations. BMT and BZT exhibit enhancement in dielectric property compared to their niobate counterparts. They may find several technological applications such as in capacitors, resonators and filters owing to their high dielectric constant and low loss tangent.

关键词： Perovskite oxides Impedance spectroscopy Dielectric properties Electrical conductivity

Field-dependent spin waves in high-aspect-ratio singlecrystal ferromagnetic nanowires

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Nano Research 2016年第5期9卷 1426-1433页

作者： Semanti Pal Susmita Saha M. Venkata Kamalakar Anjan Barman Department of Condensed Matter Physics and Material Sciences S. N. Bose National Centre for Basic Sciences Block JD Sector Ⅲ Salt Lake Kolkata 700 098 India Department of Physics and Astronomy Uppsala University Box 516 75120 Uppsala Sweden

We investigate the spin wave （SW） modes in high-aspect-ratio single-crystal ferromagnetic nanowires （FMNWs） using an all-optical time-resolved magnetooptical Kerr effect （TR-MOKE） microscope. The precessional magnetization dynamics in such FMNWs unveil the presence of uniform and quantized SW modes that can be tuned by varying the bias magnetic field （H）. The frequencies of the modes are observed to decrease systematically with a decreasing magnetic field, and the number of modes in the spectrum is reduced from four to three for H 〈 0.7 kOe. To understand these results, we perform micromagnetic simulations that reveal the presence of edge, standing wave, and uniform SW modes in the nanowires （NWs）. Our simulations clearly show how the standing wave and uniform SW modes coalesce to form a single mode with uniform precession over the entire NW for H 〈 0.7 kOe, reproducing the experimentally observed reduction in modes. Our study elucidates the possibility of manipulating the SW modes in magnetic nanostructures, which is useful for applications in magnonic and spintronic devices.

关键词： Field-dependent high-aspect-ratio nanowires

Characterization of Mullite-Zirconia Composite Processed by Non-Transferred and Transferred Arc Plasma

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Plasma Science and Technology 2009年第2期11卷 200-205页

作者： S.YUGESWARAN V.SELVARAJAN L.LUSVARGHI A.I.Y.TOK D.SIVA RAMA KRISHNA Plasma Physics Laboratory Department of PhysicsBharathiar University Department of Materials and Environmental Engineering University of Modena e Reggio Emilia School of Materials Science & Engineering Nanyang Technological University

The arc plasma melting technique is a simple method to synthesize high temperature reaction composites. In this study, mullite-zirconia composite was synthesized by transferred and non-transferred arc plasma melting, and the results were compared. A mixture of alumina and zircon powders with a mole ratio of 3 ： 2 were ball milled for four hours and melted for two minutes in the transferred and non-transferred mode of plasma arcs. Argon and air were used as plasma forming gases. The phase and microstruetural formation of melted samples were investigated by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The microstructure of the composites was found to be affected by the mode of melting. In transferred arc melting, zirconia flowers with uniform lines along with mullite whiskers were obtained. In the ease of non-transferred are plasma melting, mullite whiskers along with star shape zirconia were formed. Differential thermal analysis （DTA） of the synthesized mullite-zirconia composites provided a deeper understanding of the mechanisms of mullite formation during the two different processes.

关键词： arc plasma melting composites

Studies on induction hardening of powder-metallurgy-processed Fe–Cr/Mo alloys

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International Journal of Minerals,Metallurgy and Materials 2017年第8期24卷 918-925页

作者： Sandeep Chauhan Vikas Verma Ujjwal Prakash P.C.Tewari Dinesh Khanduja Department of Mechanical Engineering National Institute of Technology Department of Metallurgical & Materials Engineering Indian Institute of Technology

Induction hardening of dense Fe–Cr/Mo alloys processed via the powder-metallurgy route was studied. The Fe-3Cr-0.5Mo, Fe-1.5Cr-0.2Mo, and Fe-0.85 Mo pre-alloyed powders were mixed with 0.4wt%, 0.6wt%, and 0.8wt% C and compacted at 500, 600, and 700 MPa, respectively. The compacts were sintered at 1473 K for 1 h and then cooled at 6 K/min. Ferrite with pearlite was mostly observed in the sintered alloys with 0.4wt% C, whereas a carbide network was also present in the alloys with 0.8wt% C. Graphite at prior particle boundaries led to deterioration of the mechanical properties of alloys with 0.8wt% C, whereas no significant induction hardening was achieved in alloys with 0.4wt% C. Among the investigated samples, alloys with 0.6wt% C exhibited the highest strength and ductility and were found to be suitable for induction hardening. The hardening was carried out at a frequency of 2.0 kHz for 2–3 s. A case depth of 2.5 mm was achieved while maintaining the bulk(interior) hardness of approximately HV 230. A martensitic structure was observed on the outer periphery of the samples. The hardness varied from HV 600 to HV 375 from the sample surface to the interior of the case hardened region. The best combination of properties and hardening depth was achieved in case of the Fe-1.5Cr-0.2Mo alloy with 0.6wt% C.

关键词： Fe–Cr/Mo alloys powder metallurgy sintered density tensile strength induction hardening case depth

Development of carbon composite iron ore micropellets by using the microfines of iron ore and carbon-bearing materials in iron making

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International Journal of Minerals,Metallurgy and Materials 2015年第2期22卷 132-140页

作者： Jagannath Pal Satadal Ghorai Avimanyu Das National Metallurgical Laboratory Council of Scientific and Industrial Research

Iron ore microfines and concentrate have very limited uses in sintering processes. They are used in pelletization; however, this process is cost intensive. Furthermore, the microfines of non-coking coal and other carbon-bearing materials, e.g., blast-furnace flue dust （BFD） and coke frees, are not used extensively in the metallurgical industry because of operational difficu]ties and handling problems. In the present work, to utilize these microfines, coal composite iron oxide micropellets （2-6 mm in size） were produced through an innovative technique in which lime and molasses were used as binding materials in the micropellets. The micropellets were subsequently treated with CO2 or the industrial waste gas to induce the chemical bond formation. The results show that, at a very high carbon level of 22wt% （38wt% coal）, the cold crushing strength and abrasion index of the micropellets are 2.5-3 kg/cm2 and 5wt%-9wt%, respectively; these values indicate that the pellets are suitable for cold handling. The developed micropellets have strong potential as a heat source in smelting reduction in iron making and sintering to reduce coke breeze. The micropellets produced with BFD and coke fines （8wt%-12wt%） were used in iron ore sin- tering and were observed to reduce the coke breeze consumption by 3%-4%. The quality of the produced sinter was at par with that of the conventional blast-furnace sinter.

关键词： ironmaking microfines non-coking coal iron ore concentrates micropellets pelletizing, waste utilization

Study of hysteresis behavior in reactive sputtering of cylindrical magnetron plasma

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Chinese Physics B 2015年第12期24卷 392-399页

作者： H.Kakati S.M.Borah Jorhat Institute of Science and Technology Department of Applied Sciences Gauhati University

In order to make sufficient use of reactive cylindrical magnetron plasma for depositing compound thin films, it is necessary to characterize the hysteresis behavior of the discharge. Cylindrical magnetron plasmas with different targets namely titanium and aluminium are studied in an argon/oxygen and an argon/nitrogen gas environment respectively. The aluminium and titanium emission lines are observed at different flows of reactive gases. The emission intensity is found to decrease with the increase of the reactive gas flow rate. The hysteresis behavior of reactive cylindrical magnetron plasma is studied by determining the variation of discharge voltage with increasing and then reducing the flow rate of reactive gas,while keeping the discharge current constant at 100 m A. Distinct hysteresis is found to be formed for the aluminium target and reactive gas oxygen. For aluminium/nitrogen, titanium/oxygen and titanium/nitrogen, there is also an indication of the formation of hysteresis; however, the characteristics of variation from metallic to reactive mode are different in different cases. The hysteresis behaviors are different for aluminium and titanium targets with the oxygen and nitrogen reactive gases, signifying the difference in reactivity between them. The effects of the argon flow rate and magnetic field on the hysteresis are studied and explained.

关键词： cylindrical magnetron sputtering reactive mode hysteresis