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Low Fractal Dimension Cluster-Dilute soot Aggregates from a Premixed Flame

Physical Review Letters 2009年第23期102卷 235504-235504页

作者： Rajan K. Chakrabarty Hans moosmüller W. Patrick Arnott mark A. Garro Guoxun Tian Jay G. slowik Eben s. Cross Jeong-Ho Han Paul Davidovits Timothy B. Onasch Douglas R. Worsnop Desert Research Institute Nevada System of Higher Education Reno Nevada 89512 USA Chemical Physics Program University of Nevada Reno Nevada 89557 USA Department of Physics University of Nevada Reno Nevada 89557 USA Division of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Chemistry University of Toronto Toronto Ontario M5S 3H6 Canada Department of Chemistry Boston College Chestnut Hill Massachusetts 02467 USA Aerodyne Research Inc. Billerica Massachusetts 01821 USA

Using a novel morphology segregation technique, we observed minority populations (≈3%) of submicron-sized, cluster-dilute fractal-like aggregates, formed in the soot-formation window (fuel-to-air equivalence ratio of 2.0–3.5) of a premixed flame, to have m.s. fractal dimensions between 1.2 and 1.51. Our observations disagree with previous observations of a universal m.s. fractal dimension of ≈1.8 for fractal-like aerosol aggregates formed in the dilute-limit via three-dimensional diffusion-limited cluster aggregation processes. A hypothesis is presented to explain this observation. subject to verification of this hypothesis, it may be possible to control the fractal dimension and associated properties of aggregates in the cluster-dilute limit through application of a static electric field during the aggregation process.

关键词： Aggregates

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Ceramic materials (phosphors) for plasma display panel

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IOP Conference series: materials science and Engineering 2009年第1期2卷

作者： K V R murthy A s sai Pasad m Ramalingeswara Rao B subba Rao N V Poornachandra Rao K somaiah Display Materials Laboratory Applied Physics Department Faculty of Technology and Engineering M.S. University of Baroda Baroda-390 001 India Department of Physics VASAVI College of Engineering Hyderabad-400032 India Department of Physics VSR & NVR College Tenali-522 201 AP India Department of Physics Osmania University Hyderabad – 500 007 India

Phosphors the ceramic materials should able to work in tough environment surrounded and bombarded by high energy Vacuum Ultra Violet (VUV) or electron beam radiations in any discharge tube. The plasma display panel (PDP) is increasingly gaining attention over conventional cathode ray tube (CRT)-based TVs as a medium of large format (60+') television(TV), particularly high definition TVs (HDTVs). Improvements have been made not only in size but also in other areas such as resolution, luminescence efficiency, brightness, contrast ratio, power consumption, and cost reduction. The performance of a PDP depends on a complicated set of factors, for instance, phosphors, gas mixture, dielectric layer, reflective layer, black matrix, electrodes, cell dimension and shape, nature, size and shape of electrodes, address waveforms, and operating voltages. The formation of a phosphor host and doping process by solid solution is critical and is highly dependent on the reaction on the reaction temperature and conditions. since the purity of starting chemicals is very important to the synthesis of phosphors, the starting chemicals are typically 99.9–99.999% in purity. Required amounts of starting ingredients are mixed in the presence of an appropriate flux (if necessary) and fired at high temperatures (900-1500°C) in air or in a controlled atm.s.here (N2, C, CO, or N2 with 2–5% of H2). Zn2-xmnxsiO4 is a classical green emitting phosphor, and it has been used in many applications, such as CFL, CRT, PDP etc. In this paper, Zn2siO4:mn2+ green phosphor was synthesized using the solid-state reaction method. Photoluminescence and crystalline properties were examined as functions of the firing temperatures. Zn2-xmnxsiO4 was ground and fired at 1200 °C for 4 hours in air, but intensity of em.s.ion is weak. Therefore the conditions of firing were changed and Zn2-xmnxsiO4 was grinded and fired at 1000°C for 2 hours in air and again grinded and fired at 1200 °C for 4 hour in air respectively. Wh

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Analytical and Dielectric studies of the Ferroelectric Ba5Ti2O7Cl4

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AIP Conference Proceedings 2008年第1期1004卷 196-201页

作者： N. m. Patil N. V. Pradnyakar s. H. shamkuwar aLecturer & Head Department of Applied Physics Laxminarayan Institute of Technology Rashtrasant Tukadoji Maharaj Nagpur University Nagpur‐440 033 (M.S.) India bResearch Scholar Department of Applied Physics Laxminarayan Institute of Technology Rashtrasant Tukadoji Maharaj Nagpur University Nagpur‐440 033 (M.S.) India

The thermo analytic analyses are necessary for general characterization of the materials, i.e. to know if any important changes are occurring in the material. The important changes are basically of two types: 1) changes occurring as a result of chemical reaction, and 2) hanges occurring as a result of some physical change, e.g. change of crystal structure, change of some atomic groups within the given crystal structure, some physical change involving m.s.ion or absorption of thermal energy, as for example, change of electron structure or electronic interactions. The changes involving chemical reactions usually involve variation in m.s. content of the material system, and these changes are studied by thermo gravimetric analysis (TGA). The changes of the second type are studied by differential thermal analysis (DTA) and/or by differential scanning calorimetry (DsC). The present work reports the studies of DTA and DsC, while TGA studies showed no significant changes.

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Dielectric relaxation mechanism in mixtures of 1-Butanol and fluorobenzene at lower microwave frequencies

Dielectric relaxation mechanism in mixtures of 1-Butanol and...

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International Conference on Recent Advances in microwave Theory and Applications, mICROWAVE

作者： A.N. Prajapati A. D. Vyas V. A. Rana s. P. Bhatnagar Department of Applied Physics Faculty of Technology and Engineering M.S. University of Baroda Vadodara India Department of Physics School of Sciences Gujarat University Ahmedabad India Department of Physics Bhavnagar University Bhavnagar India

Complex permittivity of 1-butanol and its mixtures with fluorobenzene over a range of concentration were obtained in the radio and lower microwave frequency range at constant temperature. Vector network analyzer (VNA) operating in the frequency range 0.03 mHz to 3.0 GHz was used to obtain complex permittivity spectra. Complex permittivity data points at different frequencies were fitted into Debye model to evaluate dielectric relaxation parameters like, a relaxation time (tau), static permittivity (isin 0 ) permittivity at high frequency (isin infin ). Various dielectric parameters like excess inverse relaxation time (1/tau) E , excess permittivity (isin 0 E ) and Kirkwood correlation factor (g) were also evaluated. These parameters were used to interpret the molecular interaction between the molecular species of the liquid mixtures.

关键词： microwave frequencies Dielectric liquids Dielectric measurements Permittivity measurement physics Probes Volume relaxation Chemicals Frequency measurement Dielectric constant

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CONTROL sYsTEm DEsIGN CONsIDERING A TRADEOFF BETWEEN EVALUATED UNCERTAINTY RANGEs AND CONTROL PERFORmANCE

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Asian Journal of Control 2008年第1期1卷

作者： Y. Wakasa Y. Yamamoto Dept. of Applied Analysis and Complex Dynamical Systems Graduate School of Informatics Kyoto University Kyoto Japan. Yuji Wakasa was born in Okayama Japan in 1968. He received the B.S. and M.S. degrees in engineering from Kyoto university Japan in 1992 and 1994 respectively. From 1994 to 1998 he was a Research Associate in the Department of Information Technology Okayama University. Since April 1998 he has been a Research Associate in the Graduate School of Informatics Kyoto University. His current research interests include robust control and control system design via mathematical programming. Yutaka Yamamoto received his B.S. and M.S. degrees in engineering from Kyoto University Kyoto Japan in 1972 and 1974 respectively and the M.S. and Ph.D. degree in mathematics from the University of Florida in 1976 and 1978 respectively. From 1978 to 1987 he was with Department of Applied Mathematics and Physics Kyoto University and from 1987 to 1997 with Department of Applied System Science. Since 1998 he is a professor at the current position. His current research interests include realization and robust control of distributed parameter systems learning control sampled-data systems and digital signal processing. Dr. Yamamoto is a receipient of the Sawaragi memorial paper award (1985) the Outstanding Paper Award of SICE (1987) Best Author Award of SICE (1990) the George Axelby Outstanding Paper Award of IEEE CSS in 1996 Takeda Paper Prize of SICE in 1997. He is a Fellow of IEEE. He was an associate editor of Automatica. He is currently an associate editor of IEEE Transactions on Automatic Control Systems and Control Letters and Mathematics of Control Signals and Systems. He is a member of the IEEE the Society of Instrument and Control Engineers (SICE) and the Institute of Systems Control and Information Engineers.

This paper presents a design method of control systems such that a designer can flexibly take account of tradeoffs between evaluated uncertainty ranges and the level of control performance. The problem is reduced to a BmI problem and approximately solved by Lm.s. The convergence of the proposed approximation is proved in a modified sense. A numerical example shows the effectiveness of the proposed method in comparison with the standard robust control.

关键词： Control system design LmI BmI tradeoff curves

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New generation of holographic gratings based on polymer-LC composites: POLICRYPs and POLIPHEm

New generation of holographic gratings based on polymer-LC c...

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作者： Abbate, G. Vita, F. marino, A. Tkachenko, V. slussarenko, s. sakhno, O. stumpe, J. INFM-Coherentia Department of Physical Sciences University of Naples Federico II Napoli Italy Institute of Physics Prospect Nauki 46 Kiev Ukraine Fraunhofer Institute for Applied Polymer Research Science Campus Golm Potsdam Germany INFM-Coherentia Department of Physical Sciences University of Naples Federico II via Cinthia M.S. Angelo 80126 Napoli Italy

soft materials exhibit very attractive mechanical, optical, and electro-optical properties and easy processing techniques. Combined with holographic techniques, they can be patterned quite easily creating many unique structures. We present here few examples, of electrically-switchable passive opto-electronic components based on composite materials obtained from initial mixtures of photocurable monomers and liquid crystalline materials. Holographic exposure results in volume gratings consisting in alternate areas of photo-crosslinked polymer and phase separated LCs, respectively. We discuss the main features of this new generation of gratings and show how m.s. of their performances can be enhanced with respect to other kinds of composite gratings, like H-PDLCs.

关键词： Diffraction gratings

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mechanism of enhanced broadening of the ionization level of Li outside transition metal surfaces

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Physical Review B 2006年第11期74卷 115109-115109页

作者： Keith Niedfeldt Peter Nordlander Emily A. Carter Department of Mechanical and Aerospace Engineering and Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544-5263 USA Department of Physics and Astronomy M.S. 61 Rice University P.O. Box 1892 6100 South Main Street Houston Texas 77251-1892 USA

We show that the d-band of a transition metal surface induces intra-atomic hybridization of an atom in its vicinity. It is demonstrated that such hybridization can have a profound influence on the resonance width and hence lifetime of the atomic ionization level. The degree of Li s−p hybridization is found to be directly correlated to the overlap of the d-band density of states with the Li 2s and 2p levels, and is shown to be not due solely to long-range electrostatic image potential effects.

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Compositional changes in the infrared optical properties of Cr doped CdZnTe crystals

Compositional changes in the infrared optical properties of ...

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2005 materials Research society spring meeting

作者： Hömmerich, U. Bluiett, A.G. Nyein, Eiei Trivedi, s.B. shah, R.T. Hampton University Department of Physics Hampton VA 23668 United States Brimrose Corporation of America 19 Loveton Circle Baltimore MD 21152 United States M.S. University of Baroda Applied Physics Department Faculty of Technology and Engineering Vadodara-390 001 India

We are currently investigating the infrared (IR) optical properties of Cr doped ternary cadmium chalcogenides for potential applications in solid-state lasers and passive optical Q-switches. In this paper, we present compositional changes in the IR optical properties of Cr doped Cd1-xZn xTe single crystals with x=0.05, 0.1, and 0.2. Undoped CdZnTe crystals were grown by vertical Bridgman technique. Cr doping of CdZnTe was achieved through either in-situ doping or through a thermal diffusion process. For comparison, Cr: CdTe and Cr: ZnTe crystals were also prepared. The optical properties of Cr2+ ions were strongly dependent on the host composition and spectral blue shifts were observed with increasing Zn content in Cr: CdZnTe. The IR absorption peak of Cr2+ ions shifted from ∼ 1910 nm for Cr: CdTe to ∼ 1815 nm for Cr: Cd0.8Zn 0.2 Less pronounced blue shifts were observed for the IR em.s.ion from Cr: CdZnTe crystals. The spectral shifts can be explained by the decrease in bond-length when going from CdTe to CdZnTe leading to an increased crystal-field effect experienced by Cr2+ ions. A slight broadening of the absorption and em.s.ion was also observed in ternary Cr: CdZnTe compounds compared to Cr: CdTe, which suggests that Cr2+ ions were incorporated in multiple lattice sites in CdZnTe. moreover, the Cr2+ em.s.ion dynamics revealed a slightly non-exponential decay behavior for Cr: CdZnTe crystals, whereas the decay time of Cr: CdTe was single-exponential. © 2005 materials Research society.

关键词： Crystalline materials

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REP concept feasibility study

REP concept feasibility study

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International Astronautical Federation - 55th International Astronautical Congress 2004

作者： Edwards, Daryl A. Ensworth, Clinton B. F. Goodnight, Thom.s.W. sheehe, Charles J. Wiersma, stephen C. Adamsen II, Paul B. Frank, Larry NASA John H. Glenn Research Center M.S. 86-12 21000 Brookpark Rd. Cleveland OH 44135 United States NASA John H. Glenn Research Center United States Johns Hopkins University Applied Physics Laboratory United States

Radioisotope Electric Propulsion (REP) may have the potential to provide certain advantages, over conventional chemical propulsion, for outer planetary exploration involving small bodies and long term investigations for medium class m.s.ions requiring power comparable to past outer planetary exploration m.s.ions. This paper describes a study that investigates the concept's feasibility by performing a preliminary conceptual design of an REP-based spacecraft for a design reference m.s.ion. The m.s.ion utilizes a spacecraft with a radioisotope power supply less than one kilowatt while operating for a minimum of 10-years. A key element of the REP spacecraft is to ensure sustained science return by orbiting or flying in formation with selected targets. Utilizing current and impending technological advances, this study finds that at a conceptual design level a small body REP orbiter/explorer appears to be feasible for the design reference m.s.ion selected for this study.

关键词： Nuclear propulsion

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studies of phase-transformation behaviour in Ag-Co system.s.bjected to high-energy milling

Studies of phase-transformation behaviour in Ag-Co system Su...

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Proceedings of the 9th International symposium on metastable mechanically Alloyed and Nanocrystalline materials (IsmANAm-2002)

作者： Joshi, P.B. menghani, J.V. marathe, G.R. Lad, Kirit N. Pratap, A. Dept. of Metallurgical Engineering Fac. of Technology and Engineering M.S. University of Baroda Baroda 390001 India Department of Applied Physics Fac. of Technology and Engineering M.S. University of Baroda Baroda 390001 India

The system Ag-Co has stimulated great interest over the years, being a prominent granular magnetic system exhibiting giant magnetoresistance (GmR). silver and cobalt form a binary system wherein the constituent atoms are imm.s.ible even in liquid state and the system is characterized by a positive heat of mixing. The phase transformation behaviour of Ag80Co 20 powders was studied by high-energy milling of elemental silver and cobalt powder particles in a vibratory attrition mill. The milling was carried out for 8, 16, 32, 48 and 64 h with a ball to charge ratio of 2:1. The powder samples drawn at definite time interval during the course of milling were subjected to X-ray diffraction (XRD), scanning electron microscopy (sEm) and differential scanning calorimetry (DsC). An attempt has been made to examine the possibility of amorphization in this system.

关键词： Nanostructured materials

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