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Particuology 2016年第1期14卷 96-107页

作者： f. Hedayati G. Domairry Young Researchers and Elite Club Neyshabur Branch Islamic Azad University Neyshabur Iran Mechanical Engineering Department Babol University of Technology Babol lran

This study considers the f.rced convection of.laminar TiO2-water nanof.uid f.ow in a parallel plate microchannel. The small length scale associated with microchannels dictates the use of.slip condition at the f.id-solid interf.ce. The modif.ed Buongiorno model was employed f.r the nanof.uid to f.lly account f.r the ef.ects of.non-unif.rm viscosity and thermal conductivity. The partial dif.erential equa- tions associated with conservation laws were reduced to two-point ordinary boundary value dif.erential equations bef.re being numerically solved. Considering Brownian motion and thermophoresis, the ef.ects of.nanoparticle transport on concentration, velocity, and temperature prof.les were analyzed f.r three dif.erent values of.wall heat f.ux. To assess the ef.iciency of.adding nanoparticles, the ratios of.the pres- sure drop and the heat transf.r coef.icient of.the nanof.uid to that of.the base f.uid were studied in detail. f.om analyzing dif.erent heat f.ux ratios, one-sided heating was f.und to be most ef.icient at enhancing the heat transf.r rate in the microchannel. Additionally, in the presence of.the slip velocity, the increase in the value of.the heat transf.r coef.icient f.r the nanof.uid was smaller than that f.r the base f.uid.

关键词： Nanof.uid Microchannel Nanoparticles migration Slip velocity Brownian motion Thermophoresis

Antibacterial properties of.copper-substituted cobalt f.rrite nanoparticles synthesized by co-precipitation method

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Particuology 2017年第1期15卷 158-163页

作者： Alireza Samavati A. f. Ismail Advanced Membrane Technology Research Centre (AMTEC) Universiti Teknologi Malaysia 81310 Skudai Johor Malaysia

Controlled growth and caref.l characterization of.cobalt f.rrite nanoparticles f.r antibacterial applica- tions are challenging. Copper-substituted cobalt f.rrite nanoparticles （CuxCo1-xf.2O4）, where x = 0.0, 0.3, 0.5, 0.7 and 1.0, were synthesized using an economical and simple co-precipitation technique. The crys- tal structure and antibacterial properties of.the samples as a f.nction of.Cu-substituted content were systematically studied. With increasing Cu concentration, the nanopartide size decreased f.om ~30 to ~20 nm. The f.urier transf.rm inf.a-red spectra exhibit two prominent f.ndamental absorption bands, at ~595 and 419 cm^-1. These bands correspond to intrinsic stretching vibrations of.metals at tetrahedral and octahedral sites, respectively. The Raman scattering results reveal that increasing the Cu content enhances the local disorder at both tetrahedral and octahedral sub lattices. The results indicate that the substitution of.Co with Cu in cobalt f.rrite nanoparticles strongly inf.uences the microstructure, crystal structure, and oarticle diameter, and also improves the antibacterial properties.

关键词： Cobalt f.rrite nanoparticles X-ray dif.raction Raman spectroscopy Antibacterial properties

Seasonal size-segregated PM10 and PAH concentrations in a rural area of.sugarcane agriculture versus a coastal urban area in Southeastern f.orida, USA

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Particuology 2016年第5期14卷 52-59页

作者： Orhan Sevimoglu Wolf.ang f. Rogge Department of.Civil and Environmental Engineering Florida International University 10555 W. Flagier Street Miami FL 33174 USA School of.Engineering and Sierra Nevada Research Institute University of California at Merced 5200 North Lake Road Merced CA 95343 USA

Airborne particulate matter （PM） is of.health and environmental concern not only in highly urbanized areas, but also in rural areas that are used f.r intensive agricultural purposes, In this study, PM size- segregated samples were collected simultaneously f.r 12 months in a small town （Belle Glade, f.orida）, which is the center of.a vast sugarcane growing area and at Delray Beach, a coastal city in Palm Beach County, f.orida. During the winter sampling period, when sugarcane f.liage is burned j.st bef.re harvest- ing to reduce the amount of.plant matter to be handled, PM10 levels were 50% or higher than otherwise measured, indicating that sugarcane harvesting and processing is a maj.r local source f.r PM10. f.r the rest of.the year, PM10 levels at both sites are similar, suggesting that ambient PM levels at both sites are impacted by the maj.r urban centers in Southern f.orida. During late j.ly and early August, the PM10 levels at both sites were substantially elevated and revealed the typical red-brownish color of.Saharan dust. This has been reported to occur f.equently with suitable meteorological conditions over the Atlantic Ocean coupled with a Sahara dust storm event. During the sugarcane harvesting season at Belle Glade, the concentrations of.PAHs associated with PM10 were up to 15 times higher than those measured during the summer growing season, indicating a substantially higher exposure of.the rural population to these of.en mutagenic and carcinogenic compounds.

关键词： Size segregated ambient particles PM10 PAHs Biomass burning Rural versus urban Saharan dust

Magnetic resonance studies of.j.ts in a gas-solid f.uidised bed

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Particuology 2012年第2期10卷 161-169页

作者： Meenal Pore Thusara C. Chandrasekera Daniel j. Holland Aining Wang f.i Wang Qussai Marashdeh Michael D. Mantle Andrew j. Sederman Liang-Shih f.n Lynn f. Gladden j.hn S. Dennis Department of.Chemical Engineering and Biotechnology University of Cambridge Pembroke Street Cambridge CB2 3RA United Kingdom The William G. Lowrie Department of.Chemical and Biomolecular Engineering Ohio State University Columbus OH 43210 USA

Magnetic resonance imaging （MRI） has been used to study the behaviour Of.j.ts at the distributor of.a 50 mm diameter f.uidised bed of.0.5 mm diameter poppy seeds. Two perf.rated-plate distributors were examined, containing either 10 or 14 holes, each 1 mm diameter. Ultra-f.st MR imaging was able to show the transient nature of.the upper parts of.the j.ts, where discrete bubbles are f.rmed. Imaging in 3D showed that the central j.ts were the longest f.r f.ow rates below minimum f.uidisation. Above minimum f.uidisation, the outer j.ts, nearest the wall of.the f.uidised bed, arched inward towards the central axis. In this latter case, interpretation of.the time-averaged 3D image required the use of.ultra-f.st MR imaging to identif. the approximate height above the distributor at which discrete bubbles were f.rmed. The apparently continuous void extending along the central axis above this height in the time-averaged 3D image was thus identif.ed, using ultra-f.st MR imaging, as representing the averaged paths of.released bubbles. Time-averaged MR velocity mapping was also used to identif. dead zones of.stationary particles resting on the distributor between the j.ts. The dead zones could be observed when the superf.cial velocity of.the gas approached minimum f.uidisation, but they were smaller than those observed at lower gas superf.cial velocity. Comparable images of.a single j.t through 1.2 mm diameter poppy seeds f.om MRI and electrical capacitance volume tomography （ECVT） are also demonstrated.

关键词： f.uidised bedMRIECVTj.tsDistributor design

The Mathematical f.undations of.Elasticity and Electromagnetism Revisited

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j.urnal of.Modern Physics 2019年第13期10卷 1566-1595页

作者： j.-f. Pommaret CERMICS Ecole des Ponts Paris Tech Paris France

The f.rst purpose of.this striking but dif.icult paper is to revisit the mathematical f.undations of.Elasticity (EL) and Electromagnetism (EM) by comparing the structure of.these two theories and examining with details their known couplings, in particular piezoelectricity and photoelasticity. Despite the strange Helmholtz and Mach-Lippmann analogies existing between them, no classical technique may provide a common setting. However, unexpected arguments discovered independently by the brothers E. and f. Cosserat in 1909 f.r EL and by H. Weyl in 1918 f.r EM are leading to construct a new dif.erential sequence called Spencer sequence in the f.amework of.the f.rmal theory of.Lie pseudo groups and to introduce it f.r the conf.rmal group of.space-time with 15 parameters. Then, all the previous explicit couplings can be deduced abstractly and one must j.st go to a laboratory in order to know about the coupling constants on which they are depending, like in the Hooke or Minkowski constitutive relations existing respectively and separately in EL or EM. We f.nally provide a new combined experimental and theoretical proof.of.the f.ct that any 1-f.rm with value in the second order j.ts (elations) of.the conf.rmal group of.space-time can be uniquely decomposed into the direct sum of.the Ricci tensor and the electromagnetic f.eld. This result questions the mathematical f.undations of.both General Relativity (GR) and Gauge Theory (GT). In particular, the Einstein operator (6 terms) must be thus replaced by the adj.int of.the Ricci operator (4 terms only) in the study of.gravitational waves.

关键词： Elasticity Electromagnetism Mach-Lippman Analogy Helmholtz Analogy Piezoelectricity Photoelasticity Dif.erential Sequences Adj.int Operator Double Duality

Generating Compatibility Conditions and General Relativity

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j.urnal of.Modern Physics 2019年第3期10卷 371-401页

作者： j.-f. Pommaret CERMICS Ecole des Ponts Paris Tech Paris France

The search f.r the generating compatibility conditions (CC) of.a given operator is a very recent problem met in general relativity in order to study the Killing operator f.r various standard usef.l metrics. Accordingly, this paper can be considered as a natural continuation of.a previous paper recently published in j.P under the title Minkowski, Schwarschild and Kerr metrics revisited. In particular, we prove that the intrinsic link existing between the lack of.f.rmal exactness of.an operator sequence on the j.t level, the lack of.f.rmal exactness of.its corresponding symbol sequence and the lack of.f.rmal integrability (f.) of.the initial operator is of.a purely homological nature as it is based on the long exact connecting sequence provided by the so-called snake lemma in homological algebra. It is theref.re quite dif.icult to grasp it in general and even more dif.icult to use it on explicit examples. It does not seem that any one of.the results presented in this paper is known as most of.the other authors who studied the above problem of.computing the total number of.generating CC are conf.sing this number with the degree of.generality introduced by A. Einstein in his 1930 letters to E. Cartan. One of.the motivating examples that we provide is so striking that it is even dif.icult to imagine that such an example could exist. We hope this paper could be used as a source of.testing examples f.r f.ture applications of.computer algebra in general relativity and, more generally, in mathematical physics.

关键词： f.rmal Theory of Systems of Partial Dif.erential Equations Compatibility Conditions Acyclicity f.rmal Integrability Involutivity Dif.erential Sequence j.net Sequence Spencer Sequence General Relativity Killing Systems

Why Gravitational Waves Cannot Exist

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j.urnal of.Modern Physics 2017年第13期8卷 2122-2158页

作者： j.-f. Pommaret CERMICS Ecole des Ponts Paris Tech Paris France

The purpose of.this short but dif.icult paper is to revisit the mathematical f.undations of.both General Relativity (GR) and Gauge Theory (GT) in the light of.a modern approach to nonlinear systems of.ordinary or partial dif.erential equations, using new methods f.om Dif.erential Geometry (D.C. Spencer, 1970), Dif.erential Algebra (j.f. Ritt, 1950 and E. Kolchin, 1973) and Algebraic Analysis (M. Kashiwara, 1970). The main idea is to identif. the dif.erential indeterminates of.Ritt and Kolchin with the j.t coordinates of.Spencer, in order to study Dif.erential Duality by using only linear dif.erential operators with coef.icients in a dif.erential f.eld K. In particular, the linearized second order Einstein operator and the f.rmal adj.int of.the Ricci operator are both parametrizing the 4 f.rst order Cauchy stress equations but cannot themselves be parametrized. In the f.amework of.Homological Algebra, this result is not coherent with the vanishing of.a certain second extension module and leads to question the proper origin and existence of.gravitational waves. As a byproduct, we also prove that gravitation and electromagnetism only depend on the second order j.ts (called elations by E. Cartan in 1922) of.the system of.conf.rmal Killing equations because any 1-f.rm with value in the bundle of.elations can be decomposed uniquely into the direct sum (R, f. where R is a section of.the Ricci bundle of.symmetric covariant 2-tensors and the EM f.eld f.is a section of.the vector bundle of.skew-symmetric 2-tensors. No one of.these purely mathematical results could have been obtained by any classical approach. Up to the knowledge of.the author, it is also the f.rst time that dif.erential algebra in a modern setting is applied to study the specif.c algebraic f.ature of.most equations to be f.und in mathematical physics, particularly in GR.

关键词： General Relativity Riemann Tensor Weyl Tensor Ricci Tensor Einstein Equations Elastic Waves Gravitational Waves Lie Groups Lie Pseudogroups Dif.erential Galois Theory Spencer Operator j.net Sequence Spencer Sequence Dif.erential Modules Algebraic Analysis Homological Algebra Extension Modules Split Exact Sequence

Minkowski, Schwarzschild and Kerr Metrics Revisited

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j.urnal of.Modern Physics 2018年第10期9卷 1970-2007页

作者： j.-f. Pommaret CERMICS Ecole des Ponts ParisTech Paris France

In recent papers, a f.w physicists studying Black Hole perturbation theory in General Relativity (GR) have tried to construct the initial part of.a dif.erential sequence based on the Kerr metric, using methods similar to the ones they already used f.r studying the Schwarzschild geometry. Of.course, such a dif.erential sequence is well known f.r the Minkowski metric and successively contains the Killing (order 1), the Riemann (order 2) and the Bianchi (order 1 again) operators in the linearized f.amework, as a particular case of.the Vessiot structure equations. In all these cases, they discovered that the compatibility conditions (CC) f.r the corresponding Killing operator were involving a mixture of.both second order and third order CC and their idea has been to exhibit only a minimal number of.generating ones. Unhappily, these physicists are neither f.miliar with the f.rmal theory of.systems of.partial dif.erential equations and dif.erential modules, nor with the f.rmal theory of.Lie pseudogroups. Hence, even if.they discovered a link between these dif.erential sequences and the number of.parameters of.the Lie group preserving the background metric, they have been unable to provide an intrinsic explanation of.this f.ct, being limited by the technical use of.Weyl spinors, complex Teukolsky scalars or Killing-Yano tensors. The purpose of.this dif.icult computational paper is to provide dif.erential and homological methods in order to revisit and solve these questions, not only in the previous cases but also in the specif.c case of.any Lie group or Lie pseudogroup of.transf.rmations. These new tools, which are now available as computer algebra packages, question the mathematical f.undations of.GR and the origin of.gravitational waves.

关键词： General Relativity Killing Operator Riemann Tensor Weyl Tensor Bianchi Identities Lie Algebroid Dif.erential Sequence Dif.erential Module Homological Algebra Extension Modules

INSTABILITY Of.HAGEN-POISEUILLE f.OW f.R NON-AXISYMMETRIC MODE

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Applied Mathematics and Mechanics(English Edition) 1989年第5期10卷 407-417页

作者：王发民 j. T. Stuart (f. R. S.) Institute of.Mech. Academia Sinica Beijing Imperial College U. K.

An investigation is described f.r instability problem of.f.ow through a pipe of.circular cross section. As a disturbance motion, we consider a general non-axisym-metric mode. An associated amplitude or modulation equation has been derived f.r this disturbance motion. This equation belongs to a dif.usion *** coef.icient of.it can be negative while Reynolds number increases, because of.the complex interaction between molecular dif.usion and convection. The negative dif.usivity, when it occurs, causes a concentration and f.cussing of.energy within decaying slugs, acting as a role of.reversing natural decays.

关键词： INSTABILITY Of.HAGEN-POISEUILLE f.OW f.R NON-AXISYMMETRIC MODE

HIV-Viral Hepatitis C Coinf.ction or Cross-Reaction of.Rapid Diagnostic Orientation Tests? About a Clinical Case Observed in Brazzaville in 2016

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Open j.urnal of.Gastroenterology 2018年第5期8卷 159-166页

作者： f.rmin Bossali G. Ndziessi D. Gassaye C. Ahoui Apendi M. j. f. mimiesse j. C. Moussoki B. I. Atipo-Ibara j. R. Ibara Department of.Gastro-Enterology General Hospital of Loandjili Pointe-Noire Congo f.culty of.Health Sciences Department of Public Health Brazzaville Congo Department of.Gastro-Enterology University Hospital of Brazzaville Brazzaville Congo WHO Library Brazzaville Congo

Coinf.ction with human immunodef.ciency virus (HIV) and viral hepatitis is associated with high morbidity and mortality in the absence of.clinical management, making identif.cation of.these cases crucial. Screening f.r hepatitis viral-HIV coinf.ction bef.re initiation of.treatment f.r viral hepatitis or HIV is recommended. In this context, we report a case of.possible cross-reaction between the serology of.viral hepatitis C and HIV inf.ction by rapid diagnostic orientation tests. Although these rapid tests are the main diagnostic tools in developing countries, their scientif.c validation must be required bef.re they are made available to practitioners. The knowledge and the rigorous application of.diagnostic algorithms of.viral inf.ctions will make it possible to save money and to better organize the prevention and management strategies f.r patients as part of.an integrated Hepatitis/HIV program.

关键词： HIV HVC Rapid Diagnostic Orientation Test-Brazzaville