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Bhatt B.,Mmm University Of Technology | Chandra H.,Mmm University Of Technology
Astrophysics and Space Science | Year: 2017

In the present study, we have selected 35 halo Coronal Mass Ejections (CMEs) associated with solar flares, Geomagnetic Storms (GSs) and Forbush decrease (Fd) chosen from 1st January 2000 to 31st December 2007 (i.e., the descending phase of solar cycle 23) observed by the Large Angle Spectrometric Coronagraph (LASCO) on board the SOHO spacecraft. Statistical analyses are performed to look at the distribution of solar flares associated with halo CMEs causing GSs and Fd and investigated the relationship between solar flare and halo CME parameters with GSs and Fd. Forbush decrease is the phenomenon of rapid decrease in cosmic ray intensity following the CME. Our analysis indicates that during 2000 to 2007 the northern region produced 44 % of solar flares associated with halo CMEs, GSs, and Fd, whereas 56 % solar flares associated with halo CMEs, GSs, and Fd were produced in the southern region. The northern and the southern hemispheres between 10° to 20° latitudinal belts are found to be more effective in producing events leading to Fd. From our selected events, we found that about 60 % of super-intense storms (Dst≤−200nT) caused by halo CMEs are associated with X-class flares. Fast halo CMEs associated with X-class flares originating from 0° to 25° latitudes are better potential candidates in producing super-intense GSs than the slow halo CMEs associated with other classes of flares. © 2017, Springer Science+Business Media Dordrecht.


Kumar V.,Krishna Institute of Engineering and Technology | Agarwal S.,Krishna Institute of Engineering and Technology | Dwivedi D.K.,Mmm University Of Technology
Journal of Materials Science: Materials in Electronics | Year: 2016

The use of thin films of polycrystalline chalcogenide semiconductors has attracted much interest in an extensive variety of applications in various electronic, optoelectronic and photovoltaic devices due to their favorable electrical and optical properties. In this paper II–VI compound (cadmium and zinc chalcogenide) binary and ternary semiconductor thick films were deposited on ultraclean glass substrates by screen-printing method followed by sintering process. The polycrystalline nature of these films was confirmed by X-ray diffraction studies. The stoichiometry of the films was confirmed using energy dispersive X-ray analysis. The optical band gap and absorption coefficient of the films were determined by reflectance measurement in wave-length range 350–900 nm using UV/Vis spectrophotometer. The conduction mechanism in these films were studied by measuring the dark DC electrical conductivity in 300–400 K temperature range by using standard two probe method in vacuum. It was observed that conductivity of these films increases with increase in temperature. The linear nature of plot ln σDC against 1000/T for these films indicates that conductivity of films is in close agreement with the Arrhenius relation and conduction in these films is through thermally activated process. © 2016 Springer Science+Business Media New York


Dwivedi D.K.,Mmm University Of Technology | Shukla N.,Mmm University Of Technology | Pathak H.P.,Mmm University Of Technology
Materials Today: Proceedings | Year: 2015

Chalcogenide glassy alloys of Se90Cd10-x Inx (x=2,4,6,8) are synthesized by melt quench technique. The FTIR transmission spectroscopy studies has been carried out in the range 400-4000 cm-1. In the transmittance curve various absorption bands are seen. Dielectric properties of Se90Cd10-x Inx (x=2,4,6,8) chalcogenide glassy system have been studied using impedance spectroscopic technique in the frequency range 42Hz-5MHz at room temperature. It is found that the dielectric constants ε'and dielectric loss factor ε"both depends on frequency. Both ε'and ε"are found to be decreasing with the In content in Se90Cd10-x Inx (x=2,4,6,8) glassy alloys. © 2015 Elsevier Ltd.


Dwivedi D.K.,Mmm University Of Technology | Pathak H.P.,Mmm University Of Technology | Shukla R.K.,H.B.T.I. | Kumar A.,H.B.T.I.
Optik | Year: 2015

Se75-xTe25Sbx (x = 0, 3, 6, and 9) bulk glasses were obtained using conventional melt quenching technique. Thin films of these glasses were prepared by vacuum evaporation technique at a base pressure of 10-6 Torr on to well cleaned glass substrates. a-Se75-xTe25Sbx thin films were annealed at different temperatures below their crystallization temperatures for 2 h. The structure of as prepared and annealed films has been studied by X-ray diffraction. The X-ray pattern indicates that the as-prepared films are amorphous in nature but it shows some polycrystalline structure in amorphous phase after annealing. The optical band gap of as prepared and annealed films as a function of photon energy in the wavelength range 400-1100 nm has been studied. It is found that the optical band gap decreases with increasing annealing temperatures in the present glassy system. © 2015 Elsevier GmbH. All rights reserved.


Shukla N.,Mmm University Of Technology | Mehta N.,B.H.U. | Dwivedi D.K.,Mmm University Of Technology
Electronics Letters | Year: 2016

In the present Letter frequency (5 × 102 Hz-1 × 105 Hz) and temperature (308-333 K) dependence of dielectric parameter of Se90Cd6In4 glassy alloy has been examined. Conventional melt quench technique has been applied to prepare Se90Cd6In4 glassy alloy. It is observed that dielectric constant (ϵ') and dielectric loss factor (ϵ") change with frequency and temperature. The dielectric loss data has been utilised to determine the barrier height Wm, which is in accordance with the Elliott's theory of hoping of charge carriers over potential barrier between charge defect states in case of chalcogenide glasses. © The Institution of Engineering and Technology 2016.


Dwivedi D.K.,Mmm University Of Technology | Pathak H.P.,Mmm University Of Technology | Shukla N.,Mmm University Of Technology | Kumar A.,H.B.T.I.
Journal of Ovonic Research | Year: 2014

Thin films of a-Se75-xTe25Sbx were prepared by vacuum evaporation technique in a base pressure of 10-6 Torr on to well cleaned glass substrate. a-Se75-xTe25Sbx thin films were annealed at different temperatures below their crystallization temperatures for 2h. The structural analysis of the films has been investigated using X-ray diffraction technique. The x-ray pattern indicates that the as- prepared films are amorphous in nature but it shows some polycrystalline structure in amorphous phases after annealing. The optical band gap of as prepared and annealed films as a function of photon energy in the wavelength range 400-1100 nm has been studied. It has been found that the optical band gap decreases with increasing annealing temperatures in the present system.


Kumar V.,Krishna Institute of Engineering and Technology | Sharma D.K.,Krishna Institute of Engineering and Technology | Sharma K.,Krishna Institute of Engineering and Technology | Dwivedi D.K.,Mmm University Of Technology
Applied Physics A: Materials Science and Processing | Year: 2016

II–VI nanocrystalline semiconductors offer a wide range of applications in electronics, optoelectronics and photonics. Thin films of CdSe were deposited onto ultra-clean glass substrates by vacuum evaporation method. The as-deposited films were annealed in vacuum at 350 K. The structural, elemental, morphological, optical and electrical investigations of annealed films were carried out. The X-ray diffraction pattern of the films shows that films were polycrystalline in nature having hexagonal structure with preferential orientation of grains along (002) plane. SEM image indicates that the films were uniform and well covered to the glass substrate. EDAX analysis confirms the stoichiometric composition of the film. Raman spectra were used to observe the characteristic vibrational modes of CdSe. The energy band gap of these films was obtained by absorption spectra. The films were found to have a direct type of transition of band gap occurring at 1.75 eV. The dark electrical conductivity and photoconductivity reveals that the films were semiconducting in nature indicating the suitability of these films for photosensor applications. The Hall effect measurement reveals that the films have n-type electrical conductivity. © 2016, Springer-Verlag Berlin Heidelberg.


Kumar P.,ABES Engineering College | Chauhan R.K.,Mmm University Of Technology | Gupta M.,Krishna Institute of Engineering and Technology
International Conference on Advanced Computing and Communication Technologies, ACCT | Year: 2014

In this paper high frequency small-signal model is presented for optimization of device parameters of SiGe HBT with 0.1μm base-width which is based on the technique of direct parameter extraction. For this purpose, we use process simulator ATHENA and device simulator ATLAS from SILAVCO International. Further, a model is proposed to portray the noise in SiGe HBT with uniform Ge concentration in base. The results of the SiGe HBTs are advanced to those of III-V semiconductor devices. © 2014 IEEE.


Pathak H.P.,Mmm University Of Technology | Shukla N.,Mmm University Of Technology | Kumar V.,Krishna Institute of Engineering and Technology | Dwivedi D.K.,Mmm University Of Technology
Optical Materials | Year: 2016

Se75-xTe25Inx (x = 0, 3, 6, & 9) bulk glasses were obtained by melt quench technique. Thin films of thickness 400 nm were prepared by thermal evaporation technique at a base pressure of 10-6 Torr onto well cleaned glass substrate. a-Se75-xTe25Inx thin films were annealed at different temperatures for 2 h. As prepared and annealed films were characterized by X-ray diffraction and UV-Vis spectroscopy. The X-ray diffraction results show that the as-prepared films are of amorphous nature while it shows some poly-crystalline structure in amorphous phases after annealing. The optical absorption spectra of these films were measured in the wavelength range 400-1100 nm in order to derive the extinction and absorption coefficient of these films. It was found that the mechanism of optical absorption follows the rule of allowed non-direct transition. The optical band gap of as prepared and annealed films as a function of photon energy has been studied. The optical band gap is found to decrease with increase in annealing temperature in the present glassy system. It happens due to crystallization of amorphous films. The decrease in optical band gap due to annealing is an interesting behavior for a material to be used in optical storage. The optical band gap has been observed to decrease with the increase of In content in Se-Te glassy system. © 2015 Elsevier B.V.


Singh A.N.,Mmm University Of Technology | Prakash S.,Mmm University Of Technology
2015 International Conference on Computing for Sustainable Global Development, INDIACom 2015 | Year: 2015

In cloud computing model, where resources such as computing power, storage, network and software are abstracted and provided as services on the internet in a remotely accessible fashion. Resource allocation is most emerging research area in cloud environment. Various companies rent the resources from cloud provider for storage and other computational purpose in this way their infrastructure setup cost is reduced. There is big challenge to allocated resources in efficient manner to meet cloud consumer demands and requirements. This paper mainly addresses challenges, opportunities, techniques and key performance issues for resource allocation in cloud computing. And also discuss various existing resource allocation technique and summarize them on the basis of technique used as well as their pros and cons. © 2015 IEEE.

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