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Physicochemical Properties of Nanocrystallite Copper Ferrite Prepared by a Novel Self Flash Combustion of Acetate Precursors

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Journal of materials Science & Technology 2005年第5期21卷 675-680页

作者： m.H.Khedr A.A.Farghali Chemistry Department Faculty of Science(Beni-Suef Branch)Cairo UniversityBeni-Suef EgyptChemistry DepartmentFaculty of Science(Beni-Suef Branch)Cairo UniversityBeni-Suef Egypt

Copper ferrite, CuFe2O4, one of the important ferrites due to its interesting electrical, magnetic and structural properties, is obtained by a novel self flash combustion of a homogeneous mixture of one mole copper acetate monohydrate, Cu（CH3COO）2·H2O, and two moles of iron （Ⅲ） acetate basic, Fe（CHCOO）2·OH. Nanocrystalite （89 nm） Copper ferrite （less than 100%） is obtained at lower temperatures, whereas 100% copper ferrite is obtained after calcination at 1000℃. Thermal analysis （Tg and DTA）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, photo microscopy, magnetic and porosity obtained after calcinations at 700, 800, 900 and 1000℃ to measurements have been carried out for the specimens characterize the conversion efficiency of the powder precursors to copper ferrite. It was found that increasing temperature leads to great improvement in the magnetic properties. By increasing calcination temperature from 700～1000℃saturation magnetic flux density （Bs） increased from 17.8 to 40.8 emu/g, while remnant magnetic flux density （Br） increased from 10.1 to 17.11 emu/g.

关键词： Copper ferrite Flash combustion Synthesis Characterization magnetic properties microstructure

Terrestrial denitrification:challenges and opportunities

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Ecological Processes 2012年第1期1卷 1-11页

作者： Peter m groffman Cary Institute of Ecosystem Studies 2801 Sharon TurnpikeMillbrookNY 12545USA

Denitrification is a process of great environmental importance but is difficult to study in terrestrial *** for quantifying the process are problematic,variability in activity is high,and temporal and spatial scaling challenges are *** methods are problematic for a variety of reasons;they change substrate concentrations,disturb the physical setting of the process,lack sensitivity or are prohibitively costly in time and *** fundamentally,it is very difficult to quantify the dominant end-product(N_(2))of denitrification given its high background concentration in the *** and temporal variation in denitrification is high due to control of the process by multiple factors(oxygen,nitrate,carbon,pH,salinity,temperature etc.)that each vary in time and space.A particular challenge is that small areas(hotspots)and brief periods(hot moments)frequently account for a high percentage of N gas flux *** phenomena are challenging to account for in measurement,modeling and scaling *** need for scaling is driven by the fact that there is a need for information on this microscale process at the ecosystem,landscape and regional scales where there are concerns about nitrogen effects on soil fertility,water quality and air *** this review,I outline the key challenges involved with denitrification and then describe specific opportunities for making progress on these challenges including advances in measurement methods,new conceptual approaches for addressing hotspot and hot moment dynamics,and new remote sensing and geographic information system–based scaling *** of these opportunities suggests that we are poised to make great improvements in our understanding of terrestrial *** improvements will increase our basic science understanding of a complex biogeochemical process and our ability to manage widespread nitrogen pollution problems.

关键词： scaling process landscape

On controlled propagation of nonautonomous dispersive coupled Whitham-Broer-Kaup equation in shallow water

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Journal of Ocean Engineering and Science 2017年第3期2卷 217-222页

作者： m.Tantawy Department of mathematics Faculty of ScienceCairo UniversityGizaEgypt

In this paper,the dispersive coupled Whitham-Broer-Kaup(DCWBK)equation with time-dependent coefficients describing the propagation of the shallow water waves are *** propagation of solitons and elliptic(or chirped)waves can be manipulated by suitable variations of the dispersion ***,controllable transmission of the surface waves for soliton similariton pairs with the snoidal backgrounds is *** is found that,when the dispersion coefficient is taken as increasing,the velocity is increasing with the dispersion coefficient *** this holds vice versa for the height of propagation wave.

关键词： Dispersive coupled Whitham-Broer-Kaup(DCWBK)equation Unified method(Um) Dispersion coefficient Controlled

Computational Studies of Flow through Cross Flow Fans-Effect of Blade geometry

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Journal of Thermal Science 2005年第3期14卷 220-229页

作者： m . gOVARDHAN D. LAKSHmANA SAmPAT School of mechanical Engineering Universiti Malaysia Sabah Sabah Malaysia ProfessorThermal Turbomachines Laboratory Department of Mechanical Engineering Indian Institute of Technology Madras Chennai India

This present paper describes three dimensional computational analysis of complex internal flow in a cross flow fan. A commercial computational fluid dynamics (CFD) software code CFX was used for the computation. RNg k-ε two equation turbulence model was used to simulate the model with unstructured mesh. Sliding mesh interface was used at the interface between the rotating and stationary domains to capture the unsteady interactions. An accurate assessment of the present investigation is made by comparing various parameters with the available experimental data. Three impeller geometries with different blade angles and radius ratio are used in the present study. maximum energy transfer through the impeller takes place in the region where the flow follows the blade curvature. Radial velocity is not uniform through blade channels. Some blades work in turbine mode at very low flow coefficients. Static pressure is always negative in and around the impeller region.

关键词： cross flow fans computational fluid dynamics quasi steady state multiple frames of reference

Efficient Flexible Boundary Conditions for Long Dislocations

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Communications in Computational Physics 2022年第8期32卷 671-714页

作者： m.Hodapp Skolkovo Institute of Science and Technology(Skoltech) Center for Energy Science and TechnologyMoscowRussia materials Center Leoben Forschung gmbH(mCL) Austria

We present a novel efficient implementation of the flexible boundary condition(FBC)method,initially proposed by Sinclair et al.,for large single-periodic *** is primarily achieved by constructing a hierarchical matrix(H-matrix)representation of the periodic green matrix,reducing the complexity for updating the boundary conditions of the atomistic problem from quadratic to almost linear in the number of pad *** addition,our implementation is supported by various other tools from numerical analysis,such as a residual-based transformation of the boundary conditions to accelerate the *** assess the method for a comprehensive set of examples,relevant for predicting mechanical properties,such as yield strength or ductility,including dislocation bow-out,dislocation-precipitate interaction,and dislocation *** main result of our analysis is that the FBC method is robust,easy-to-use,and up to two orders of magnitude more efficient than the current state-of-the-art method for this class of problems,the periodic array of dislocations(PAD)method,in terms of the required number of per-atom force computations when both methods give similar *** opens new prospects for large-scale atomistic simulations—without having to worry about spurious image effects that plague classical boundary conditions.

关键词： Atomistic/continuum coupling flexible boundary conditions local/global coupling lattice green functions hierarchical matrices dislocations

Paleoproterozoic Underwater Volcanism and microfossil-Like Structures in the metasedimentary Siliceous Rocks,Hogland Island,Russia

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Journal of Earth Science 2018年第6期29卷 1431-1442页

作者： Anatoly m.Belyaev Institute of Earth Sciences St.Petersburg State University

geological surveys showed that rhyolite and basalt strata with pillow structures typical for underwater volcanism form sheets over the Svecofennian basement. Original geochemical and isotope-geochemical data confirmed that the rhyolites were formed contemporaneously with the rapakivi granites of the Wiborg massif（1 640 ma）, and the basalts are similar to gabbro-anorthosites. Abnormally high content of K2O and relatively low content of Na2O in rhyolites and basalts are interpreted as a result of hydrothermal interaction of eruptive magmas with K-enriched hot seawater. The strata of siliceous metasedimentary rocks（microquartzites） within basaltic and rhyolitic lavas were formed in processes of chemogenic sedimentation and subsequent contact metamorphism during underwater volcanism. microquartzites showed carbon vastly depleted of heavy isotope 13С. This is typical for rocks formed with participation of living substance. The Raman spectra of the remaining carbon-containing substance have graphite bands. In the microquartzites among basalts and rhyolites we found a community of structures with external and internal morphology similar to modern or fossilized marine microorganisms： spiral cyanobacterias, amoebas, diatoms, foraminifers, virus capsids, flagellates and multicellular organisms. It is assumed that these silificated and ferruginizated microfossils represent the Paleoproterozoic community of marine microorganisms.

关键词： submarine volcanism siliceous rocks silification Paleoproterozoic microfossils carbon isotopes

Finding vibrations of inclined cable structures by approximately solving governing equations for exterior matrix

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Applied mathematics and mechanics(English Edition) 2015年第11期36卷 1383-1402页

作者： W.PAULSEN m.mANNINg Department of mathematics and Statistics Arkansas State University

In this paper, how to compute the eigenfrequencies of the structures composed of a series of inclined cables is shown. The physics of an inclined cable can be complicated, so solving the differential equations even approximately is difficult. However, rather than solving the system of 4 first-order equations governing the dynamics of each cable, the governing equations are instead converted to a set of equations that the exterior matrix satisfies. Therefore, the exterior matrix method （Emm） is used without solving the original governing equations. Even though this produces a system of 6 first-order equations, the simple asymptotic techniques to find the first three terms of the perturbative solution can be used. The solutions can then be assembled to produce a 6 x 6 exterior matrix for a cable section. The matrices for each cable in the structure are multiplied together, along with the exterior matrices for each joint. The roots of the product give us the eigenfrequencies of the system.

关键词： exterior matrix method (Emm) eigenfrequency inclined cable

Effect of Applied Current Density on morphological and Structural Properties of Electrodeposited Fe-Cu Films

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Journal of materials Science & Technology 2012年第11期28卷 1004-1009页

作者： Umut Sarac m.Celalettin Baykul Department of Elementary Education Bart n University Department of Physics Eskisehir Osmangazi University

A detailed study has been carried out to investigate the effect of applied current density on the composition, crystallographic structure, grain size, and surface morphology of Fe-Cu films. X-ray diffraction （XRD） results show that the films consist of a mixture of face-centered cubic （fcc） Cu and body centered cubic （bcc） ^-Fe phases. The average crystalline size of both Fe and Cu particles decreases as the applied current density becomes more negative. Compositional analysis of Fe-Cu films indicates that the Fe content within the films increases with decreasing current density towards more negative values. Scanning electron microscopy （SEm） and atomic force microscopy （AFm） have been used to investigate the surface morphology of Fe-Cu films. It is observed that the surface morphology of the films changes from dendritic structure to a cauliflower structure as the applied current density becomes more negative. The surface roughness and grain size of the Fe-Cu films decrease with decreasing applied current density towards more negative values.

关键词： Electrodeposition Surface morphology Current density grain size Composition

managing stress granule disassembly with ubiquitin and its cousin

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Signal Transduction and Targeted Therapy 2021年第12期6卷 3377-3378页

作者： Stefan müller Institute of Biochemistry II Gustav Embden ZentrumGoethe University FrankfurtFaculty of MedicineFrankfurtGermany

Recently,maxwell et al.1 revealed a critical function of ubiquitylation in stress granule(Sg)disassembly upon recovery from heat *** are continuously exposed to endogenous or environmental *** stress endangers DNA integrity,whereas proteotoxic stress causes an imbalance in protein homeostasis(proteostasis).genotoxic insults activate DNA damage response pathways that halt the cell-cycle progression and initiate DNA *** quality control(PQC)systems in turn safeguard the integrity of the proteome and prepare for the restart of cellular activities upon stress *** genome and proteome integrity pathways are orchestrated by ubiquitin signaling and the ubiquitin-proteasome system(UPS).

关键词： stress aging integrity