Photoluminescence and cathodoluminescence properties of Sr₂Gd₈Si₆O₂₆:RE³⁺(RE³⁺=Tb³⁺or Sm³⁺) phosphors

Hussain, Sk.K.,Rao, G.M.,Raju, G.S.R.,Krishna Bharat, L.,Subba Rao, P.S.V.,Yu, J.S. Elsevier [etc.] 2016 Journal of luminescence Vol.178 No.-

<P>Trivalent terbium (Tb3+) or samarium (Sm3+) ions individually activated green and orange emitting Sr2Gd8Si6O26 (SGSO) phosphors were synthesized by a citrate sol-gel method. The X-ray diffraction patterns of SGSO:Tb3+ and SGSO:Sm3+ phosphors exhibited the characteristic diffraction peaks of oxyapatite in a hexagonal lattice structure. The photoluminescence (PL) properties at ultraviolet (UV) or near-UV excitation wavelengths were measured for Tb3+ or Sm3+ ions doped SGSO phosphors as a function of its respective concentration. The PL spectra of SGSO:Tb3+ phosphors revealed the characteristic emission peaks of both Gd3+ and Tb3+ ions which are associated with 4f-4f transitions under 274 nm of excitation wavelength. When the concentration of Tb3+ ions increased over 0.05 mol (5 mol%), the emission intensities of D-5(3) transitions decreased due to the well-known cross-relaxation process. However, based on the intensities of D-5(4) transitions, the optimum concentration of Tb3+ ions was found to be 0.05 mol. Under 404 nm of excitation wavelength, the SGSO:Sm3+ phosphors exhibited the characteristic orange emission at 600 nm due to the (4)G(5/2) -> H-6(7/2) electronic transition. The optimum concentration of SGSO:Sm3+ phosphors was found to be 0.02 mol. The decay curves of the optimized SGSO:Tb3+ and SGSO:Sm3+ phosphors were well fitted to single exponential functions and their lifetimes were calculated. Furthermore, the optimized phosphor samples showed good thermal stability. Likewise, cathodoluminescence properties were also studied for the optimized samples as a function of filament current and accelerating voltage. The Commission International de I-Eclairage chromaticity coordinates were calculated for the SGSO:Tb3+ and SGSO:Sm3+ phosphors. (C) 2016 Elsevier B.V. All rights reserved.</P>

Synthesis of Alginate Based Silver Nanocomposite Hydrogels for Biomedical Applications

P. Rama Subba Reddy,하창식,K. Madhusudana Rao,K. S. V. Krishna Rao,Yury Shchipunov 한국고분자학회 2014 Macromolecular Research Vol.22 No.8

Sodium alginate and poly(acrylamide-co-N-vinylcaprolactam-co-acrylamidoglycolic acid) based dualresponsive semi-IPN hydrogels (SA-PAVA) were successfully synthesized by free radical redox polymerization. N,N'-Methylene-bis-acrylamide was used as a crosslinker and 5-fluorouracil, an anti-cancer drug, was loaded ontothese semi-IPN hydrogels via equilibrium swelling method. The hydrogels were also used as templates for the productionof silver nanoparticles by using NaBH4 as reducing agent. In order to understand the polymer-drug interactions,pristine, as well as drug loaded, SA-PAVA hydrogels were characterized by Fourier transform infrared spectroscopyand differential scanning calorimetry. The formation of silver nanoparticles was confirmed by UV-visible spectroscopy,thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy(TEM). The swelling behavior of the hydrogel was investigated in distilled water under various pH and temperatureconditions. In vitro release of 5-fluorouracil from these SA-PAVA hydrogels was carried out in gastro-intestinal fluidsdifferent temperatures. The SA-PAVA hydrogel/silver nanocomposites showed excellent anti-bacterial activitytowards Escherichia coli and Bacilli.

E-Learning Platform Development using A Model Driven Methodology Approach

P. Subba Rao,K.B.S. Sastry,Hye-jin Kim 보안공학연구지원센터 2014 International Journal of Smart Home Vol.8 No.6

These days, new advances and stages are developing and evolving continually, which suggests a high exertion for creating of complex frameworks, for example, E-learning stage. This circumstance produces distinctive issues identified with compactness, reusability, versatility, incorporation and interoperability. The Object Management Group (OMG) proposes the Model Driven Architecture (MDA), which enhances mobility of uses by permitting the same model to be acknowledged on various stages. Such MDA characterizes a structural engineering focused around platform independent models (PIM) and platform specific models (PSM). The part approach means to outline and create frameworks from pre-assembled segments, predesigned and pretested, to be reused in different applications, which would encourage application's support and development, would advance flexibility and configurability with a specific end goal to create new peculiarities. In this work we introduce LMSGENERATOR, a multi-target Learning administration framework generator with a model-driven procedure focused around MDA methodology coupled with part approach. Taking into account generative programming, from client determinations (abstract models) and the fancied advances, programming blocks will be created and amassed to deliver a complete arrangement adjusted to zone and clients' necessities. This paper concentrates on the change guidelines actualized in the LMSGENERATOR centers .Also; it introduces a careful investigation to delineate this proposal.

Prediction Based Cost Estimation Model Using Clusters

Subba Rao Peram,Dr. K. Venkata Rao,Dr. P. Suresh Varma 보안공학연구지원센터 2015 International Journal of Software Engineering and Vol.9 No.7

On some parameters Software cost estimation based on development and effort on the project. Every line of code and every method are important to estimate the cost of project. To develop the software project using well defined scientific principles, methods, statements and functions, though there are many costs estimation models are available to estimate the cost of project, but still there is lack of efficient system to predict the cost estimation based on size of project, functionality of project, methods of project. In the existing system cost estimation is done on the basis of lines of code, resource management, in time process. Because of various reasons in the existing system we have identified the drawbacks. In this paper, cost prediction model is defined based on clusters, the number of clusters will form the centroids. Each centroid has a specific number of clusters. Each cluster will be called as rule. In this paper, results will show the prediction of cost estimation is defined.

Tunable emissions <i>via</i> the white region from Sr₂Gd₈(SiO₄)₆O₂:RE³⁺ (RE³⁺: Dy³⁺, Tm³⁺, Eu³⁺) phosphors

Rao, Gattupalli Manikya,Seeta Rama Raju, G.,Hussain, Sk. Khaja,Pavitra, E.,Rao, P. S. V. Subba,Yu, Jae Su The Royal Society of Chemistry 2016 NEW JOURNAL OF CHEMISTRY Vol.40 No.7

<P>Single, double and triple trivalent rare-earth (RE3+ = Dy3+, Tm3+, Tm3+/Dy3+ and Tm3+/Dy3+/Eu3+) ions activated Sr2Gd8(SiO4)(6)O-2 (SGSO) phosphors were synthesized by a sol-gel process. X-ray diffraction profiles confirmed their oxyapatite structure after annealing at 1450 degrees C for 12 h. Morphological studies were performed by taking scanning and transmission electron microscopy images, which displayed rod-like shapes. SGSO phosphors exhibited good photoluminescence (PL) properties in the respective regions when doped with Dy3+ and Tm3+ ions. Dy3+ co-activated SGSO: Tm3+ phosphors revealed tunable emissions from cool white light to warm white light towards the yellow region based on the co-activator concentration. However, Eu3+ ions co-doped SGSO: Tm3+/Dy3+ phosphors tuned the emissions towards the red region. The energy transfers from Tm3+ to Dy3+ ions and Tm3+/Dy3+ to Eu3+ ions were established based on the energy level diagram. The cathodoluminescence properties of these phosphors showed excellent emission behavior when the single, double or triple trivalent RE ions were doped into the SGSO host lattice. Unlike the case of the PL, the energy transfer process was observed to take place. The calculated Commission Internationale de l'Eclairage chromaticity coordinates of Tm3+ and Dy3+ individual ion doped SGSO phosphors confirmed the blue and white emissions, while the co-doped samples exhibited tunable emissions.</P>

Enhanced Ferromagnetic Order in Mn Doped BiFeO₃—Ni_0.5Zn_0.5Fe₂O₄ Multiferroic Composites

Dhanalakshmi, B.,Rao, P. S. V. Subba,Rao, B. Parvatheeswara,Kim, CheolGi American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10

<P>Multiferroic composites of 0.5 BiFeO3-0.5Ni(0.5)Zn(0.5)Fe(2)O(4) and 0.5Bi(0.95)Mn(0.05)FeO(3)-0.5 Ni0.5Zn0.5Fe2O4 were prepared by combining sol-gel autocombustion and solid state methods. X-ray diffraction analysis of the composites reveals that the samples are formed as di-phase compounds while retaining the spinel phase for the Ni-Zn ferrite and perovskite phase for the Bi-ferrite. Fourier transform infrared spectroscopy measurements on the composites confirm their structures with the presence of Fe-O and Bi-O bonds. Dielectric measurements on the composites were used to discuss about the possible polarization/conduction mechanisms, phase transitions and magnetoelectric coupling. Room temperature ferroelectric and magnetic hysteresis loop studies on the samples ensure that the Mn doped composite exhibits enhanced remnant polarization as well as saturation magnetization compared to the undoped composite. Moreover, the Mn doping has further translated the composite into magnetically softened with coercivity almost close to zero. The obtained improvements in the dielectric and multiferroic properties of the composites are attributed to the corresponding structural modifications brought about by the Mn doping.</P>

Structural and Magnetic Characterizations of Ni—Zn—Co Ferrite Nanoparticles Synthesized by Sol—Gel Autocombustion Method

Ramesh, S.,Dhanalakshmi, B.,Sekhar, B. Chandra,Rao, P. S. V. Subba,Rao, B. Parvatheeswara,Kim, CheolGi American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10

<P>Cobalt substituted Ni-Zn ferrite nanoparticles with the formula, Ni0.4Zn0.6-xCoxFe2O4, where x varies from 0.00 to 0.25 in steps of 0.05, were prepared by sol-gel autocombustion method and analyzed for their structural and magnetic properties. The synthesized nanoparticles were subjected to X-ray analysis, transmission electron microscopy, Fourier transform infrared spectroscopy, thermal analysis and magnetic measurements. The X-ray patterns confirm cubic spinel structures with the crystallite sizes in the range from 31.72 nm to 36.87 nm. The particle sizes estimated using electron micrographs are in good agreement with the crystallite sizes obtained from the X-ray data. Infrared data confirms the spinel structure by showing Fe-A-O and Fe-B-O stretching vibrations while the thermal data hints at a slight weight gain due to oxidation. The obtained magnetic data suggests a marginal increase in saturation magnetization with the Co substitution at x = 0.10 and 0.25. The results are analyzed in terms of the compositional and structural modifications, and it was found that the variation of magnetic moment was governed by a corresponding change in the oxygen positional parameter in these materials.</P>

Programming Evaluation Process Using Hybrid Cost Estimation Model

Peram Subba Rao,K. Venkata Rao,P. Suresh Varma,Tai-hoon Kim 보안공학연구지원센터 2014 International Journal of Software Engineering and Vol.8 No.10

Dual Responsive Pectin Hydrogels and Their Silver Nanocomposites: Swelling Studies, Controlled Drug Delivery and Antimicrobial Applications

P. Rama Subba Reddy,S. Eswaramma,K. S. V. Krishna Rao,이용일 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Novel dual responsive pectin hydrogels composed from poly(acrylamidoglycolic acid-co-vinylcaprolactam)/ Pectin (PAV-PC) and also PAV-PC hydrogels are used as templates for the production of silver nanoparticles. 5-Fluorouracil is an anticancer drug and has been loaded in situ into PAV-PC hydrogels. Structure and morphology characterization of PAV-PC hydrogels were investigated by fourier transform infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, X-ray diffraction studies, scanning electron microscopy and transmission electron microscopy. The results revealed a molecular level dispersion of the drug in PAV-PC hydrogels. In vitro release of 5-fluorouracil from the PAV-PC hydrogels has been carried out in GIT fluids as well as in various temperatures. 5-Fluorouracil released from PAV-PC hydrogels was 50% at pH 1.2, and 85% at pH 7.4 within 24 h. The release profile was characterized with PAV-PC hydrogels and initial burst effect was significantly reduced in two buffer media (1.2 and 7.4), followed by a continuous and controlled release phase, the drug release mechanism from polymer was due to Fickian diffusion. In situ fabrication of silver nanoparticles inside the hydrogel network via the reduction of sodium borohydrate by PAV-PC chains led to hydrogel nanocomposites. The diameter of the nanocomposites was about 50-100 nm, suitable for uptake within the gastrointestinal tract due to their nanosize range and mucoadhesive properties. These nanocomposite PAV-PC hydrogels showed strong antimicrobial activity towards Bacillus subtilis (G+ve) and Escherichia coli (G-ve).

Dual Responsive Pectin Hydrogels and Their Silver Nanocomposites: Swelling Studies, Controlled Drug Delivery and Antimicrobial Applications

Reddy, P. Rama Subba,Eswaramma, S.,Krishna Rao, K.S.V.,Lee, Yong Ill Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.8

Novel dual responsive pectin hydrogels composed from poly(acrylamidoglycolic acid-co-vinylcaprolactam)/Pectin (PAV-PC) and also PAV-PC hydrogels are used as templates for the production of silver nanoparticles. 5-Fluorouracil is an anticancer drug and has been loaded in situ into PAV-PC hydrogels. Structure and morphology characterization of PAV-PC hydrogels were investigated by fourier transform infrared spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, X-ray diffraction studies, scanning electron microscopy and transmission electron microscopy. The results revealed a molecular level dispersion of the drug in PAV-PC hydrogels. In vitro release of 5-fluorouracil from the PAV-PC hydrogels has been carried out in GIT fluids as well as in various temperatures. 5-Fluorouracil released from PAV-PC hydrogels was 50% at pH 1.2, and 85% at pH 7.4 within 24 h. The release profile was characterized with PAV-PC hydrogels and initial burst effect was significantly reduced in two buffer media (1.2 and 7.4), followed by a continuous and controlled release phase, the drug release mechanism from polymer was due to Fickian diffusion. In situ fabrication of silver nanoparticles inside the hydrogel network via the reduction of sodium borohydrate by PAV-PC chains led to hydrogel nanocomposites. The diameter of the nanocomposites was about 50-100 nm, suitable for uptake within the gastrointestinal tract due to their nanosize range and mucoadhesive properties. These nanocomposite PAV-PC hydrogels showed strong antimicrobial activity towards Bacillus subtilis (G+ve) and Escherichia coli (G-ve).