Studies of Radiation-Induced Defects in Li2SiO3:Sm Phosphor Material

Singh, N.,Singh, V.,Watanabe, S.,Gundu Rao, T. K.,Chubaci, J. F.,Cano, N. F.,Pathak, M. S.,Singh, P. K.,Dhoble, S. J. Springer Science + Business Media 2017 Journal of electronic materials Vol.46 No.1

<P>Li2SiO3:Sm was synthesized by the solution combustion method. Powder x-ray diffraction technique was used to find the phase formation. Li2SiO3:Sm exhibits thermoluminescence (TL) peaks at approximately 140 degrees C, 155 degrees C, 190 degrees C, 250 degrees C, and 405 degrees C. Three defect centers contribute to the observed electron spin resonance spectrum from the gamma irradiated phosphor. Center I with principal g-values g(parallel to) = 2.0206 and g(perpendicular to) = 2.0028 is identified as an O-2(-) ion while center II, with an isotropic g-factor 2.0039, is assigned to an F+-type center. Center III is assigned to a Ti3+ center. The Ti3+ center is related to the 250 degrees C TL peak while the O-2(-) ion also correlates with the main TL peak at 250 degrees C. An additional defect center is observed during thermal annealing experiments, and the center (assigned to F+ center) seems to originate from an F center. The F center appears to be associated with the high temperature TL peak in a Li2SiO3: Sm phosphor. The luminescence spectrum reveals the dominant emission peaks at 605 ((4)G(5/2) -> H-6(7/2)) nm under the excitation wavelength of 402 nm.</P>

Superior pore network retention of carbon derived from naturally dried ginkgo leaves and its enhanced oxygen reduction performance

Razmjooei, F.,Singh, K.P.,Yu, J.S. Elsevier Science Publishers 2016 CATALYSIS TODAY - Vol.260 No.-

<P>Obtaining a highly porous carbon has always been considered as an essential issue in many electrochemical applications. Ginkgo leaves have not only unique shape and color, but also interesting chemical and medical properties, which have inspired us to investigate them. In present approach, the naturally dried yellow ginkgo leaves, collected in autumn season, are directly used to prepare the porous carbon with simple two-step template-free procedure of pyrolysis at different temperatures followed by acid treatment for removal of inherent mineral salts. Interestingly, it is found that inherent salts present in the resulting carbon backbone can play as porogen to create high amount of pores in the carbon framework when the salts are removed by acid treatment. Effect of alternations in ginkgo leaves structure during the climate change, from spring to autumn, on ORR activity is examined for the first time on the carbons obtained by carbonizing different color, greenish and yellowish, ginkgo leaves at 1000 degrees C. Yellow leaves can maintain their original tissue structure during the gradual drying in cold weather of late fall, which results in formation of more stable structure, leading to development of much more pores and larger surface area in the resulting carbon. The unforeseen results exhibit surprisingly higher ORR activity for carbon catalyst obtained from yellow leaves (LY-1000) compared with one prepared from green leaves collected in summer, (LG-1000). Higher surface area of LY-1000 is found to be the most important key factor for its enhanced ORR activity. Furthermore, electrocatalytic property of the carbon greatly depends on the carbonization temperature, which is a crucial factor to make a balance between electrical conductivity, heteroatom doping and surface area. As the temperature increases, the heteroatom doping decreases, which is not favorable for ORR, but at the same time, the conductivity and surface area increase, which is beneficial for ORR, indicating intriguing trade-off between them as a function of temperature, which needs to be optimized for best ORR performance. Moreover, present work enables a large-scale production of efficient heteroatom-doped porous carbon from ginkgo leaf waste without using any activation and templating agents. (C) 2015 Elsevier B.V. All rights reserved.</P>

A novel pentaplex real time (RT)- PCR high resolution melt curve assay for simultaneous detection of emetic and enterotoxin producing Bacillus cereus in food

Forghani, F.,Singh, P.,Seo, K.H.,Oh, D.H. Butterworths ; Taylor Francis ; Elsevier Science 2016 FOOD CONTROL Vol.60 No.-

<P>Bacillus cereus causing emetic and diarrheal type of food poisoning is widely distributed in nature and is therefore considered a major foodborne pathogen. There is a growing demand for fast, accurate, reliable and economic detection of potentially toxigenic B. cereus. To improve differential diagnosis of toxigenic B. cereus, a highly sensitive pentaplex RT- PCR high resolution melt curve assay was developed for simultaneous detection of 4 major enterotoxim genes (cytK, entFM, hblD, nheA) and emetic toxin gene (ces). The average melting temperatures (T-m) of PCR products were 72.2 degrees C (ces), 74.23 degrees C (cytK), 76.55 degrees C (nheA), 78.42 degrees C (entFM) and 81.90 (hblD). The multiplex assay was evaluated using 71 bacterial strains including 17 emetic B. cereus reference strains, 9 enterotoxic B. cereus reference strains, 4 B. cereus group members, 23 wild B. cereus strains, 18 non-target strains, and was further tested on artificially inoculated foods. The detection limit in food samples was approximately 10(3) CFU/g without enrichment and 10(1) CFU/g was observed following 7 h enrichment. The DNA intercalating dye SYTO9 used in this study generated high resolution melt curve peaks for the target strains and genes in which the peaks were sharp and easily distinguishable from each other. Thus, the developed multiplex real-time (RT) PCR approach can be a reliable tool for the identification of emetic and enterotoxic strains of B. cereus present in food and food-related samples. (C) 2015 Elsevier Ltd. All rights reserved.</P>

Neutron-shielding behaviour investigations of some clay-materials

S.F. Olukotun,Kulwinder Singh Mann,S.T. Gbenu,F.I. Ibitoye,O.F. Oladejo,Amit Joshi,H.O. Tekin,M.I. Sayyed,M.K. Fasasi,F.A. Balogun,Turgay Korkut 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5

The fast-neutron shielding behaviour (FNSB) of two clay-materials (Ball clay and Kaolin)of SouthwesternNigeria (7.49 N, 4.55 E) have been investigated using effective removal cross section, SRðcm 1Þ, massremoval cross section, SR=rðcm2g 1Þ and Mean free path, l (cm). These parameters decide neutronshielding behaviour of any material. A computer program - WinNC-Toolkit has been used for computationof these parameters. The toolkit evaluates these parameters by using elemental compositions anddensities of samples. The proficiency of WinNC-Toolkit code was probe by using MCNPX and GEANT4 tomodel fast neutron transmission of the samples under narrow beam geometry, intending to representthe actual experimental setup. Direct calculation of effective removal cross section (cm 1) of the sampleswas also carried out. The results from each of the methods for each types of the studied clay-materials(Ball clay and Kaolin) shows similar trend. The trend might be the fingerprint of water content retainedin each of the samples being baked at different temperature. The compositions of each sample have beenobtained by Particle-Induced X-ray Emission (PIXE) technique (Tandem Pelletron Accelerator: 1.7 MV,Model 5SDH). The FNSB of the selected clay-materials have been compared with standard concrete. Thecognizance of various factors such as availability, thermo-chemical stability and water retaining ability bythe clay-samples can be analyzed for efficacy of the material for their FNSB.

Multiset linear extensions with a heuristic algorithm

F. Balogun,D. Singh,S. Aliyu 원광대학교 기초자연과학연구소 2022 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.24 No.2

The paper presents the study of linear extensions on an ordered multiset structure. Results on linear extensions of a partially ordered set are generalized to multisets. A heuristic algorithm for generating these linear extensions is also presented.

On balance of uncertainty in shadowed sets

M. A. Ibrahim,T. O. William-West,A. F. D. Kana,D. Singh 원광대학교 기초자연과학연구소 2020 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.19 No.3

A shadowed set, $S$, facilitates crisp decision-making with a fuzzy set $F$. It is constructed with the aid of different optimization-based principles. Among these principles, the requirement of uncertainty balance guarantees preservation of the uncertainty of $F$ in $S$. In order to gain further insight on uncertainty balance, some essential mathematical properties which characterize uncertainty-balance-based objective function, $J(\alpha)$, are studied. These properties provide theoretical explanation for interpreting and analyzing $J(\alpha)$ and its ensuing optimum partition threshold $\alpha$. Two senses of uncertainty balance are discussed in this paper. Their combined efficiency in enhancing clustering results is illustrated with the aid of synthetic data set used in shadowed $C$-means clustering. Finally a need for five-region shadowed sets, $S_5$, is pointed out. A closed-form formula for determining its optimum thresholds is proposed and exemplified on typical fuzzy set and synthetic dataset.

Enhanced electrocatalytic activity due to additional phosphorous doping in nitrogen and sulfur-doped graphene: A comprehensive study

Razmjooei, F.,Singh, K.P.,Song, M.Y.,Yu, J.S. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.78 No.-

Effect on oxygen reduction reaction (ORR) of ternary-doped reduced graphene oxide (RGO) as an electrocatalyst is evaluated by employing thiourea as a single source of nitrogen (N) and sulfur (S), and triphenylphosphine for phosphorous (P) as precursors for heteroatom doping. The topographical studies show that by doping the RGO, disruption in surface charge and spin asymmetry is introduced into the carbon matrix due to the difference in the bond length and electronegativity between carbon and heteroatoms, which makes carbon lattice ORR active. Ternary (N, S and P)-doped RGO shows excellent ORR activity, which is ~2 times better than that of binary (N and S)-doped RGO, and ~5 times better than that of single (P)-doped RGO. The catalytic activity of the ternary-doped carbon even exceeds the commercial Pt in alkaline medium. Additional P doping causes remarkable synergistic effect on binary N and S-doped RGO by generating active P-N species, improving graphitic order and increasing surface area as well as mesopore volume, which in turn enhances the ORR activity.

Influence of Al content on surface passivation properties of Al rich ZnO films for solar cell application

Khan, F.,Baek, S.H.,Singh, S.N.,Singh, P.K.,Husain, M.,Kim, J.H. Association for Applied Solar Energy ; Elsevier Sc 2014 SOLAR ENERGY -PHOENIX ARIZONA THEN NEW YORK- Vol.110 No.-

A systematic study of hydrogen sintered aluminum rich zinc oxide (AZO) films is made from the view point of their application as surface passivation layer for silicon solar cell. AZO films of various Al and Zn molar concentration ratios (0<R<SUB>Al/Zn</SUB><40%) are made and their electrical and optical properties are studied. The lowest surface recombination velocity (~10cm/s) is realized in the film with R<SUB>Al/Zn</SUB>~30% as inferred from minority carrier lifetime measurements. The passivation effect of AZO layer may be attributed to presence of hydrogen whose concentration is maximum (~3.93x10<SUP>22</SUP>atoms/cm<SUP>3</SUP>) for R<SUB>Al/Zn</SUB>~30%. Effect of surface passivation is manifested in the efficiency of solar cell where an improvement>4% vis-a-vis the control cell (without AZO layer) is seen after AZO layer is applied on the rear surface of the cell.

Maximal and maximum antichains of ordered multisets

F. Balogun,D. Singh,Y. Tella 원광대학교 기초자연과학연구소 2021 ANNALS OF FUZZY MATHEMATICS AND INFORMATICS Vol.21 No.1

This work studies the concept of maximal and maximum antichains on a partially ordered structure for which repetition is significant. By using set-based partitioning, maximal and maximum antichains of the ordered multiset structure are constructed. Analogous result on antichains and examples are also presented in this multiset setting.

A diagnostic for micrometer sensitive positioning of solid targets in intense laser-matter interaction

Singh, P.K.,Kakolee, K.F.,Jeong, T.W.,Ter-Avetisyan, S. North-Holland 2016 Nuclear Instruments & Methods in Physics Research. Vol.829 No.-

A target position monitoring diagnostic, relevant to intense laser-solid interaction, is presented. The alignment system, having a sensitivity of few micrometers, consist of an infinity corrected long working distance objective, a broadband illuminating source and a CCD camera. The imaging system, placed along the axis of incident laser pulse, serves the dual purpose of laser focus diagnosis and precise positioning of the target in three dimension axis. By employing this technique, solid targets with thickness varying from opaque micrometer thick foils to few nanometer thin transparent foils can be aligned precisely. The effectiveness of the entire alignment system is demonstrated in enhanced acceleration of ions in intense laser-matter interaction, with very high reproducibility.