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Synthesis and characterization of CaAl_xO_y:Eu^(2+) phosphors prepared using solution-combustion method

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Journal of Rare Earths 2010年第S1期28卷 272-276页

作者： f.b.Dejene D.b.bem H.C.Swart Department of Physics University of the Free State(Qwaqwa Campus)Private Bag X13Phuthaditjhaba9866South Africa Department of Physics University of the Free StateP.O.Box 339Bloemfontein9300South Africa

Europium-doped calcium aluminate(CaAlxOy:Eu2+) phosphors were obtained at low temperatures(500 oC) by the solution-combustion of corresponding metal nitrate-urea solution *** particle size and morphology and the structural and luminescent properties of the as-synthesized phosphors were examined by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),Auger spectroscopy,transmission electron spectroscopy(TEM) and photoluminescence(PL).It was found that the Ca:Al molar ratios showed greatly influence not only on the particle size and morphology,but also on their PL spectra and *** the Ca:Al molar ratios increasing from 6:100 to 26:100,the structure of as-synthesized phosphor changed from CaAl12O19 to monoclinic CaAl2O4 and the dominant emitting light from red to blue,implying that the oxidation state of doped europium ions changed from trivalent to divalent due to the structure variation of host lattice.A blue phosphor with almost pure phase can be easily prepared by solution combustion method with suitable Ca:Al molar ratio.

关键词： CaAlxOy:Eu2+ solution-combustion molar ratio structure luminescence rare earths

Calculation of the VKI turbine blade with LES and DES

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Journal of Thermal Science 2007年第4期16卷 321-327页

作者： f.Magagnato b.Pritz M.Gabi fSM University of KarlsruheGermany

The prediction of the laminar to turbulent transition is essential in the calculation of turbine blades, compressor blades or airfoils of airplanes since a non negligible part of the flow field is laminar or transitional. In this paper we compare the prediction capability of the Detached Eddy Simulation （DES） with the Large Eddy Simulation （LES） using the high-pass filtered （HPf） Smagorinsky model （Stolz et al.[1]） when applied to the calculation of transitional flows on turbine blades. Detailed measurements from Canepa et al.[2] of the well known VKI-turbine blade served to compare our results with the experiments. The calculations have been made on a fraction of the blade （10%） using non-reflective boundary conditions of freund at the inlet and outlet plane extended to internal flows by Magagnato et al.[3] in combination with the Synthetic Eddy Method （SEM） proposed by Jarrin et al.[4]. The SEM has also been extended by Pritz et al.[5] for compressible flows. It has been repeatedly shown that hybrid approaches can satisfactorily predict flows of engineering relevance. In this work we wanted to investigate if they can also be used successfully in this difficult test case.

关键词： Turbine blade LES DES transition

Synthesis and Characterization of Poly(styrene-co-acrylamide) Polymers Prior to Electrospinning

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Advances in Nanoparticles 2013年第2期2卷 87-93页

作者： adebola A. Oketola Nelson Torto Chemistry Department Rhodes University Grahamstown South Africa Chemistry Department Rhodes University Grahamstown South Africa Department of Chemistry University of Ibadan Ibadan Nigeria

Electrospun nanofibers present a new and rapidly growing research area due to their pronounced micro and nano characteristics associated with high surface area to volume ratio. Poly(styrene-co-acrylamide) and polystyrene polymers were synthesized by boiling temperature soap free emulsion polymerization in aqueous medium with potassium peroxosulphate as the initiator. The resulting polymers were dissolved in dimethylformamide and teterahydrofuran (DMf: THf) (4:1) to form polymer solutions that were electrospun into fiber mats with diameters ranging from 1.84 - 2.53 μm and 5.01 μm, respectively. The fibers were characterized by fourier transform infrared spectroscopy (fTIR) equipped with universal ATR sampling accessory (4000 - 400 cm-1). The morphology and size were examined by a scanning electron miscroscope (SEM) and the thermal properties by thermogravimetric analysis (TGA). The fTIR spectra of the poly(styrene-co-acrylamide) revealed the presence of acrylamide on the polystyrene chain. Thus, surface modification of polystyrene with acrylamide is possible in a single step polymerization reaction prior to electrospinning.

关键词： Nanofibers Emulsion Polymerization Electrospinning Poly(styrene-co-acrylamide)

A Large-Update feasible Interior-Point Algorithm for Convex Quadratic Semi-definite Optimization based on a New Kernel function

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Journal of the Operations Research Society of China 2013年第3期1卷 359-376页

作者： b.Kheirfam f.Hasani Department of Mathematics Azarbaijan Shahid Madani UniversityTabrizIran

In this paper we present a large-update primal-dual interior-point algorithm for convex quadratic semi-definite optimization problems based on a new parametric kernel *** goal of this paper is to investigate such a kernel function and show that the algorithm has the best complexity *** complexity bound is shown to be O(√n log n log n/∈).

关键词： Kernel function Interior-point algorithm Polynomial complexity Large-update methods

Impediments to clinical diagnosis and management of juvenile-onset recurrent respiratory papillomatosis in Ilorin, Nigeria

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Open Journal of Pediatrics 2013年第2期3卷 127-132页

作者： Stephen Oluwatosin adebola Adekunle David Dunmade Department of Otorhinolaryngology LAUTECH Teaching Hospital Ogbomoso Nigeria Department of Otorhinolaryngology University of Ilorin Teaching Hospital Ilorin Nigeria

background: To report the impediments to the diagnosis and management of children with JuvenileOnset Recurrent Respiratory Papillomatosis as seen in a teaching hospital in West Africa. Methods: Retrospectively analysed study of participants requiring surgical intervention for histologically confirmed juvenile onset recurrent respiratory papillomatosis managed at the Department of Otorhinolaryngology, University of Ilorin Teaching Hospital, Ilorin over a 10-year period (2002-2011) using prospectively collated database. Results: Juvenile-Onset Recurrent Respiratory Papillomatosis constituted 8.8% of 307 laryngeal pathologies seen during the study period. 18 (66.7%) were males and 9 (33.3%) females with a sex ratio (M:f) of 2:1. Age ranged from 1 year 4 months to 12 years with a mean age of 6.1 years (SD = 2.78), with the 6 - 10 age group constituting the largest categories in 51.9% of patients seen. Patients from low socioeconomic class constituted slightly over half of the patients studied (51.9%). 55.5% of the patients presented late (>13 months). All patients presented with hoarseness, stridor and difficulty in breathing. Misdiagnosis made by the referring clinician included Asthma, Laryngo-tracheo-bronchitis, foreign body aspiration and Laryngomalacia. Involvement of the glottis occurred in 70.4% of cases seen, while bilateral involvement was present in 91.3% of cases operated. Recurrence was seen in 63.0% of the patients and the best attendance at follow-up clinic was during the first three months post surgical extirpation. Emergency tracheostomy was done to relieve airway obstruction in 17 (63.0%) patients. Conclusion: Impediments to diagnosis and management of JORRP are multifactorial. Misdiagnosis, late presentation and poor follow-up clinic attendance of patients with JORRP is still a common occurrence among the physicians. Recommendations on how to improve management and outcome of JORRP were made.

关键词： Juvenile-Onset Recurrent Respiratory Papillomatosis Paediatrics Nigeria Management

Predictive fatigue crack growth law of high-strength steels

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Journal of Materials Science & Technology 2022年第5期100卷 46-50页

作者： H.f.Li P.Zhang b.Wang Z.f.Zhang Laboratory of fatigue and fracture for Materials Shi-changxu Innovation Center for Advanced MaterialsChinese Academy of SciencesInstitute of Metal ResearchShenyang 110016China State Key Laboratory of Mechanical behavior and System Safety of Traffic Engineering Structures Shijiazhuang Tiedao UniversityShijiazhuang 050043China

The fatigue resistance of metallic materials is generally attributed to both strength and ***,these properties are mutually exclusive in most *** theories like Paris’law only provide some data correlation schemes rather than a predictive capability,which cannot satisfactorily guide the anti-fatigue *** this study,for the first time,the predictive fatigue crack growth rate law is proposed by considering the effects of both strength and ***,a quantitative criterion is established for judging the fatigue crack resistance of high-strength *** predictive law would provide a unique view to the quantitative anti-fatigue design of metallic materials.

关键词： fatigue crack growth Strength and toughness Paris’law High-strength steels

Modelling and mapping third dimension in a spatial database

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International Journal of Digital Earth 2011年第6期4卷 505-520页

作者： f.Donera C.bıyık Department of Geomatics Engineering Gumushane UniversityGumushaneTurkey Department of Geomatics Engineering Karadeniz Technical UniversityTrabzonTurkey

In this paper,an overview of phases for modelling and mapping third dimension of spatial objects in a database is presented based on a selected spatial database management system(DbMS).These phases include(1)defining a spatial reference system for representing three-dimensional(3D)objects with real-world coordinates,(2)geometric modelling of 3D objects in the database,(3)3D spatial indexing for fast accessing/querying the 3D data,3D spatial queries and representation of 3D ***,a case study is performed to assess needs,possibilities and potential limitations of 3D data modelling in the spatial database.

关键词： spatial database geo-data 3D data modelling GIS digital earth

An improved optimal elemental method for updating finite element models

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Earthquake Engineering and Engineering Vibration 2004年第1期3卷 67-74页

作者：段忠东 Spencer b.f. 闫桂荣欧进萍 School of Civil Engineering Harbin Institute of Technology Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign

The optimal matrix method and optimal elemental method used to update finite element models may not provide accurate *** situation occurs when the test modal model is incomplete,as is often the case in *** improved optimal elemental method is presented that defines a new objective function,and as a byproduct,circumvents the need for mass normalized modal shapes,which are also not readily available in *** solve the group of nonlinear equations created by the improved optimal method,the Lagrange multiplier method and Matlab function fmincon are *** deal with actual complex structures, the float-encoding genetic algorithm(fGA)is introduced to enhance the capability of the improved *** examples,a 7- degree of freedom(DOf)mass-spring system and a 53-DOf planar frame,respectively,are updated using the improved method. The example results demonstrate the advantages of the improved method over existing optimal methods,and show that the genetic algorithm is an effective way to update the models used for actual complex structures.

关键词： model updating optimal elemental method Lagrangc multiplier method genetic algorithm

Cooling Augmentation with Microchanneled Structures

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Journal of Thermal Science 1993年第2期2卷 98-110页

作者： X.f.Peng b.X.Wang ThermalEngineeringDepartment TsinghuaUniversityBeijing100084China ThermalEngineeringDepartment Tsin

Experiments were conducted to investigate the heat transfer characteristics and cooling performance of subcooled liquid, water, flowing through rectangular cross-section microchanneled structures machined on a stainless steel plate. Heat transfer or flow mode transition was observed when the heating rate or wall temperature was increased. This transition was found to be suggestively induced by the variation in liquid thermophysical properties due to the significant rise of liquid temperature in the microstructures. The influence of such parameters as liquid velocity, subcooling, property variation, and microchannel geometric configuration on the heat transfer behavior, cooling performance and the heat transfer and liquid flow mode transition were also investigated. The experiments indicated that both slngle-phase forced convection and flow boiling characteristics were quite different from those in normal-sized tubes and the heat transfer was obviously intensified.

关键词： heat transfer convection flow boiling microchanneled structure cooling