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材料热处理学报 2004年第05B期25卷 657-660页

作者： f. Shahriari f. Ashraf.zadeh A. Monshi Materials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan IranMaterials engineering department Isfahan University of Technology Isfahan Iran

In this investigation, aluminide coatings used to protect industrial components at high temperature and corrosive environments were modif.ed with silicon addition and the microstructural f.atures and f.rmation mechanism were evaluated. The coating on the nickel-based superalloy IN738LC was carried out by a two stage process including siliconizing at f.rst and aluminizing thereaf.er. Pack cementation siliconizing perf.rmed at 950C f.r 2, 4 and 6 hours in several powder mixtures of.Si, A12O3 and NHiCl, then aluminum was dif.used into the surf.ce of.the specimens by an industrial aluminizing process. The modif.ed coatings were characterized by means of.standard metallography, scanning electron microscopy, energy dispersive spectroscopy and X-ray dif.raction methods. The results show that Si in the coatings mainly presents in the f.rm of.secondary phases including Cr3Si, Mo5Si3 and Nii6Ti6Si7, well distributed within the NiAl matrix. The advantages of.this two stage modif.ed coating is discussed.

关键词：显微结构 IN738LC 镍超级合金扩散渗碳处理生长机制

Closed-f.rm solutions f.r f.ee vibration of.rectangular f.M thin plates resting on elastic f.undation

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Acta Mechanica Sinica 2016年第6期32卷 1088-1103页

作者： T. f. Xu Y. f. Xing Institute of.Solid Mechanics Beihang UniversityBeijing 100191 China China Academy of.Launch Vehicle Technology R&D Center Beijing 100076 China

This article presents closed-f.rm solutions f.r the f.equency analysis of.rectangular f.nctionally graded material (f.M) thin plates subjected to initially in-plane loads and with an elastic f.undation. Based on classical thin plate theory, the governing dif.erential equations are derived using Hamilton's principle. A neutral surf.ce is used to eliminate stretching-bending coupling in f.M plates on the basis of.the assumption of.constant Poisson's ratio. The resulting governing equation of.f.M thin plates has the same f.rm as homogeneous thin plates. The separation-of.variables method is adopted to obtain solutions f.r the f.ee vibration problems of.rectangular f.M thin plates with separable boundary conditions, including, f.r example, clamped plates. The obtained normal modes and f.equencies are in elegant closed f.rms, and present f.rmulations and solutions are validated by comparing present results with those in the literature and f.nite element method results obtained by the authors. A parameter study reveals the ef.ects of.the power law index n and aspect ratio a/b on f.equencies.

关键词： f.nctionally graded material f.ee vibration Rectangular plate Close f.rm solutions Neutral surf.ce

Nanoscale displacement of.the image of.an atomic source of.radiation

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Chinese Optics Letters 2009年第2期7卷 149-151页

作者： Henk f. Arnoldus Department of.Physics and Astronomy Mississippi State University

Light emitted by an atomic source of.radiation appears to travel along a straight line （ray） f.om the location of.the source to the observer in the f.r f.eld. However, when the energy f.ow pattern of.the radiation is resolved with an accuracy better than an optical wavelength, it turns out that the f.eld lines are usually curved. We consider electric dipole radiation, a prime example of.which is the radiation emitted by an atom during an electronic transition, and we show that the f.eld lines of.energy f.ow are in general curves. Near the location of.the dipole, the f.eld lines exhibit a vortex structure, and in the f.r f.eld they approach a straight line. The spatial extension of.the vortex in the optical near f.eld is of.nanoscale dimension. Due to the rotation of.the f.eld lines near the source, the asymptotic limit of.a f.eld line is not exactly in the radially outward direction and as a consequence, the image in the f.r f.eld is slightly shif.ed. This sub-wavelength displacement of.the image of.the source should be amenable to experimental observation with contemporary nanoscale-precision techniques.

关键词： Atoms Electric dipole moments f.ow patterns Nanotechnology Vortex f.ow

Inf.uence of.Processing Parameters on the Strength of.Air Brazed Alumina Joints Using Aluminium Interlayer

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Journal of.Materials Science & Technology 2011年第7期27卷 641-646页

作者： A. Ibrahim f. Hasan Department of.Metallurgical and Materials Engineering University of Engineering and TechnologyLahore Pakistan

Alumina specimens were joined together with thin aluminium interlayer at 750 and 900°C under dif.erent applied pressures and holding time in air. f.exural strength of.the joints was then measured using a standard f.ur-point bend test method. Characterization of.the interf.ce was carried out to correlate the increase in f.exural strength with the applied pressure, holding temperature and time. The study showed that the strength of.joint is af.ected by all three parameters, i.e., processing temperature, holding time as well as applied pressure.

关键词： Pressure-assisted air brazing Alumina Aluminum Brazing Joining and Ceramic

Impacts of.wastewater sludge amendments in restoring nitrogen cycle in p-nitrophenol contaminated soil

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Journal of.Environmental Sciences 2011年第4期23卷 616-623页

作者： f. Olcay Topac Sagban Department of.Environmental Engineering Uludag University

The possible impacts on nitrogen-cycle in a p-nitrophenol （PNP） polluted soil and the ef.ectiveness of.wastewater sludge amendments in restoring nitrif.cation potential and urease activity were evaluated by an incubation study. The results indicated that PNP at 250 mg/kg soil inhibited urease activity, nitrif.cation potential, arginine ammonif.cation rate and heterotrophic bacteria counts to some extents. Af.er exposure to PNP, the nitrif.cation potential of.the tested soil was dramatically reduced to zero over a period of.30 days. Based on the f.ndings, nitrif.cation potential was postulated as a simple biochemical indicator f.r PNP pollution in soils. Nitrogen-cycling processes in soils responded positively to the applications of.wastewater sludges. A sludge application rate of.200 tons/ha was suf.icient f.r successf.l biostimulation of.these nitrogen processes. The microbial activities in sludge-amended, heavy PNP-polluted soils seemed to recover af.er 30–45 days, indicating the ef.ectiveness of.sludge as a usef.l soil amendment.

关键词： p-nitrophenol wastewater sludge soil pollution nitrogen-cycle biostimulation

Kinetics of.the Reaction of.2-Chloro-3,5-dinitrobenzotrif.ouride with Aniline in Toluene and Methanol-Toluene Mixed Solvents

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Chinese Journal of.Chemistry 2012年第1期30卷 109-114页

作者： f.thalla Magda f. Chemistry Department Faculty of ScienceAlexandria UniversityP.O.426 IbrahimiaAlexandria 21321Egypt

Kinetics of.the reaction of.2-chloro-3,5-dinitrobenzotrif.ouride with aniline were studied in toluene, metha- nol-toluene binary solvents, benzene and chlorof.rm. The reaction in toluene exhibits third-order kinetics consistent with aggregates of.aniline. Thermodynamic parameters AH#, AS# and AG# are calculated and discussed f.r the reaction of.2-chloro-3,5-dinitrobenzotrif.ouride with aniline in methanol-toluene. Molecular complexes between aniline and the substrate are rejected spectrophotometricaly. The mechanism is studied and compared with the reac- tion in presence of.pyridine. It shows an amine dependence and f.rmation of.homo and/or hetero mixed aggregates between aniline and pyridine i.e. dimer mechanism.

关键词： kinetics 2-chloro-3,5-dinitrobenzotrif.ouride methanol-toluene

Uncertainty relations f.r general phase spaces

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f.ontiers of.physics 2016年第3期11卷 51-60页

作者： Reinhard f. Werner Institut f.ir Theoretische Physik Leibniz Universitiit Hannover Germany

We describe a setup f.r obtain!ing uncertainty relations f.r arbitrary pairs of.observables related by a f.urier transf.rm. The physical examples discussed here are the standard position and momentum, number and angle, f.nite qudit systems, and strings of.qubits f.r quantum inf.rmation applications. The uncertainty relations allow f.r an arbitrary choice of.metric f.r the outcome distance, and the choice of.an exponent distinguishing, e.g., absolute and root mean square deviations. The emphasis of.this article is on developing a unif.ed treatment, in which one observable takes on values in an arbitrary locally compact Abelian group and the other in the dual group. In all cases, the phase space symmetry implies the eciuality of.measurement and preparation uncertainty bounds. There is also a straightf.rward method f.r determining the optimal bounds.

关键词： uncertainty relations phase space measurement uncertainty

Multiscale stochastic f.nite element method on random f.eld modeling of.geotechnical problems- a f.st computing procedure

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f.ontiers of.Structural and Civil Engineering 2015年第2期9卷 107-113页

作者： Xi f. XU School of.Civil Engineering Beo'ing Jiaotong University Beijing 100044 China

The Green-f.nction-based multiscale stochastic f.nite element method (MSf.M) has been f.rmulated based on the stochastic variational principle. In this study a f.st computing procedure based on the MSf.M is developed to solve random f.eld geotechnical problems with a typical coef.icient of.variance less than 1. A unique f.st computing advantage of.the procedure enables computation perf.rmed only on those locations of.interest, theref.re saving a lot of.computation. The numerical example on soil settlement shows that the procedure achieves signif.cant computing ef.iciency compared with Monte Carlo method.

关键词： multiscale f.nite element settlement perturbation random f.eld geotechnical

Early stages of.non-classic crystal growth

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Science China Chemistry 2011年第12期54卷 1867-1876页

作者： GREER Heather f. EaStChem School of ChemistryUniversity of St Andrews

Investigation of.early stages of.crystal growth revealed that crystal growth in some systems may not f.llow the classic *** the early stages of.inorganic crystal growth,precursor molecules and/or nanocrystallites may aggregate into large and disordered particles with the assistance of.some polymers or *** crystallization of.these aggregates would then take place to f.rm shells with high crystallinity and density,f.llowed by an extension of.the crystallization f.om surf.ce to *** so-called reversed crystal growth mechanism has been f.und in crystallization of.several inorganic compounds including zeolites,perovskites,metals and metal oxides,and will be identif.ed in more material *** establishment of.this new crystal growth route gave us more f.eedom to control the morphology of.crystals and to understand the f.rmation mechanism of.many natural *** article gives a brief.review of.the recent research in this f.eld by f.aturing some typical examples of.the reversed crystal growth.

关键词： reversed crystal growth hollow crystals core-shell particles electron microscopy

f.rtif.cation Challenges and Needs

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Biomedical and Environmental Sciences 2001年第1期14卷 98-103页

作者： RODOLf. f. f.ORENTINO President Philippine Association of Nutrition Philippines

Experience in many parts of.the developing world has shown that f.od f.rtif.cation of.ers a cost_ef.ective and sustainable solution to the problem of.micronutrient malnutrition. Building on the advances in science and technology and backed by studies on the economic benef.ts of.f.rtif.cation programs, governments and industry are beginning to respond positively to the call of.nutrition advocates to adopt f.rtif.cation as a long_term strategy. On the other hand, f.rmidable challenges still remain in many countries in Asia, constraining the widespread adoption of.this strategy. The science and technology community needs to provide adequate scientif.c and technological inf.rmation as basis f.r planning and decision making. The government f.ces the challenge of.providing the enabling environment f.r all stakeholders to cooperate in the f.rtif.cation ef.ort. Industry f.ces the challenge of.adapting its production system to the requirements of.f.rtif.cation in order that they can contribute to social objectives while pursuing their economic objectives. The international and bilateral aid agencies need to seek tried and innovative ways to support the multiple players of.f.od f.rtif.cation, as these players in turn f.ce the challenges that conf.ont them.

关键词： Developing Countries f.od Industry f.od f.rtif.ed Asia f.od Technology Humans Nutrition Disorders Public Health