Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Fast diffusion line.
Articles de revues sur le sujet « Fast diffusion line »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Fast diffusion line ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Dietrich, Laurent. « Velocity enhancement of reaction-diffusion fronts by a line of fast diffusion ». Transactions of the American Mathematical Society 369, no 5 (13 septembre 2016) : 3221–52. http://dx.doi.org/10.1090/tran/6776.
Texte intégral
2
Berestycki, Henri, Romain Ducasse et Luca Rossi. « Generalized principal eigenvalues for heterogeneous road–field systems ». Communications in Contemporary Mathematics 22, no 01 (26 mars 2019) : 1950013. http://dx.doi.org/10.1142/s0219199719500135.
Texte intégralRésumé :
This paper develops the notion and properties of the generalized principal eigenvalue for an elliptic system coupling an equation in a plane with one on a line in this plane, together with boundary conditions that express exchanges taking place between the plane and the line. This study is motivated by the reaction–diffusion model introduced by Berestycki, Roquejoffre and Rossi [The influence of a line with fast diffusion on Fisher–KPP propagation, J. Math. Biol. 66(4–5) (2013) 743–766] to describe the effect on biological invasions of networks with fast diffusion imbedded in a field. Here we study the eigenvalue associated with heterogeneous generalizations of this model. In a forthcoming work [Influence of a line with fast diffusion on an ecological niche, preprint (2018)] we show that persistence or extinction of the associated nonlinear evolution equation is fully accounted for by this generalized eigenvalue. A key element in the proofs is a new Harnack inequality that we establish for these systems and which is of independent interest.
3
Dietrich, Laurent, et Jean-Michel Roquejoffre. « Front propagation directed by a line of fast diffusion : large diffusion and large time asymptotics ». Journal de l’École polytechnique — Mathématiques 4 (2017) : 141–76. http://dx.doi.org/10.5802/jep.40.
Texte intégral
4
Dietrich, Laurent. « Existence of Travelling Waves for a Reaction–Diffusion System with a Line of Fast Diffusion ». Applied Mathematics Research eXpress 2015, no 2 (2015) : 204–52. http://dx.doi.org/10.1093/amrx/abv002.
Texte intégral
5
Caffarelli, L., et J. M. Roquejoffre. « The leading edge of a free boundary interacting with a line of fast diffusion ». St. Petersburg Mathematical Journal 32, no 3 (11 mai 2021) : 499–522. http://dx.doi.org/10.1090/spmj/1658.
Texte intégralRésumé :
Our goal in this work is to explain an unexpected feature of the expanding level sets of the solutions of a system where a half-plane in which reaction-diffusion phenomena occur exchanges mass with a line having a large diffusion of its own. The system was proposed by H. Berestycki, L. Rossi, and the second author as a model of enhancement of biological invasions by a line of fast diffusion. It was observed numerically by A.-C. Coulon that the leading edge of the front, rather than being located on the line, was in the lower half-plane. We explain this behavior for a closely related free boundary problem. We construct travelling waves for this problem, and the analysis of their free boundary near the line confirms the predictions of the numerical simulations.
6
Berestycki, Henri, Jean-Michel Roquejoffre et Luca Rossi. « The influence of a line with fast diffusion on Fisher-KPP propagation ». Journal of Mathematical Biology 66, no 4-5 (30 octobre 2012) : 743–66. http://dx.doi.org/10.1007/s00285-012-0604-z.
Texte intégral
7
Berestycki, Henri, Anne-Charline Coulon, Jean-Michel Roquejoffre et Luca Rossi. « The effect of a line with nonlocal diffusion on Fisher-KPP propagation ». Mathematical Models and Methods in Applied Sciences 25, no 13 (17 septembre 2015) : 2519–62. http://dx.doi.org/10.1142/s0218202515400175.
Texte intégralRésumé :
We propose a new model of accelerating fronts, consisting of one equation with nonlocal diffusion on a line, coupled via the boundary condition with a reaction–diffusion equation in the upper half-plane. The underlying biological question is to understand how transportation networks may enhance biological invasions. We show that the line accelerates the propagation in the direction of the line and enhances the overall propagation in the plane and that the propagation is directed by diffusion on the line, where it is exponentially fast in time. We also describe completely the invasion in the upper half-plane. This work is a nonlocal version of the model introduced in Ref. 15, where the line had a strong but local diffusion described by the classical Laplace operator.
8
JACQMIN, DAVID. « Very, very fast wetting ». Journal of Fluid Mechanics 455 (25 mars 2002) : 347–58. http://dx.doi.org/10.1017/s0022112001007492.
Texte intégralRésumé :
Just after formation, optical fibres are wetted stably with acrylate at capillary numbers routinely exceeding 1000. It is hypothesized that this is possible because of dissolution of air into the liquid coating. A lubrication/boundary integral analysis that includes gas diffusion and solubility is developed. It is applied using conservatively estimated solubility and diffusivity coefficients and solutions are found that are consistent with industry practice and with the hypothesis. The results also agree with the claim of Deneka, Kar & Mensah (1988) that the use of high-solubility gases to bathe a wetting line allows significantly greater wetting speeds. The solutions indicate a maximum speed of wetting which increases with gas solubility and with reduction in wetting-channel diameter.
9
A. Caffarelli, Luis, et Jean-Michel Roquejoffre. « The shape of a free boundary driven by a line of fast diffusion ». Mathematics in Engineering 3, no 1 (2021) : 1–25. http://dx.doi.org/10.3934/mine.2021010.
Texte intégral
10
Do, Thanh Nhut, Cheng Zhang, Xuanwei Ong, Jie Lian, Yinthai Chan et Howe-Siang Tan. « Measuring the Ultrafast Spectral Diffusion Dynamics of Colloidal CdSe Nanomaterials ». MRS Advances 4, no 1 (2019) : 1–7. http://dx.doi.org/10.1557/adv.2019.38.
Texte intégralRésumé :
AbstractWe use ultrafast coherent two-dimensional electronic spectroscopy (2DES) to study the ultrafast spectral diffusion dynamics of colloidal CdSe quantum dots (QDs) and CdSe nanoplatelets (NPLs). The Center Line Slope (CLS) and Nodal Line Slope (NLS) techniques were employed to analyse the 2DES spectra. We show that no spectral diffusion dynamics occurs for the CdSe QDs. On the other hand, spectral diffusion was observed in the CdSe 5 mono-layers NPLs heavy-hole transition. The normalized Frequency Fluctuation Correlation Function (FFCF) of the CdSe NPLs heavy-hole transition was measured to have a major fast decay component at 140 fs.
11
Bolle, B., A. Tidu et J. J. Heizmann. « X-ray diffraction study of concentration depth profiles of binary alloy coatings during thermal diffusion : application to brass coating ». Journal of Applied Crystallography 32, no 1 (1 février 1999) : 27–35. http://dx.doi.org/10.1107/s0021889898009765.
Texte intégralRésumé :
Using the Houska method based on X-ray diffraction-line profile analysis, new mathematical treatments are proposed to compute directly the concentration depth profile of thin films obtained by diffusion. As an example, concentration depth profiles of a brass layer have been studied during the thermal diffusion process. This nondestructive method is fast (a few minutes) and allows the sample to be used for complementary analysis if necessary.
12
Berestycki, Henri, Jean-Michel Roquejoffre et Luca Rossi. « The Shape of Expansion Induced by a Line with Fast Diffusion in Fisher-KPP Equations ». Communications in Mathematical Physics 343, no 1 (11 février 2016) : 207–32. http://dx.doi.org/10.1007/s00220-015-2517-3.
Texte intégral
13
Berestycki, Henri, Jean-Michel Roquejoffre et Luca Rossi. « Travelling waves, spreading and extinction for Fisher–KPP propagation driven by a line with fast diffusion ». Nonlinear Analysis 137 (mai 2016) : 171–89. http://dx.doi.org/10.1016/j.na.2016.01.023.
Texte intégral
14
Zhang, Zuo Tai, S. Balaji, Ii Ryoung Sohn, B. E. Ydstie et S. Sridhar. « Influence of Fast Path Diffusion on the Oxidation of Mn Strengthened IF Steels ». Defect and Diffusion Forum 283-286 (mars 2009) : 432–38. http://dx.doi.org/10.4028/www.scientific.net/ddf.283-286.432.
Texte intégralRésumé :
During the in-line coating process of Mn-strengthened-Interstitial-Free-steels, selective oxidation under low dew-point atmospheres may result in surface oxides that are not wetted by the coating alloy. In the current study, we investigate the formation of external and internal oxides in the metal in order to characterize the influence of fast path diffusion. The short-time oxidation in the metal was carried out in a gold-image furnace and the resulting external and internal oxides were characterized through scanning-electron microscopy. An IF steel sample containing 1.5wt.% Mn was used and the effects of dew point (DP) ranging from –75 to –15oC on oxidation was investigated at 800oC by varying the PH2/PH2O ratio in the oxidizing gas. Simulations were carried out by considering the combined effect of diffusion and mass transfer represented by a system of partial differential equations. The model equations were solved using finite element method in a Multiphysics modeling software COMSOL. The experimental and simulated results were found to be in agreement, and showed that, for DP up to –30oC, gas phase mass transport of oxidant gas controls the oxidation which results in exclusively external oxide nodules distributed uniformly on the surface. At –15oC > DP > –30oC, the oxidation evolves as ridges along grain boundaries and the simulations indicate that this is due to solid state diffusion control and the controlling mechanism is fast path diffusion through the alloy. At this point, internal oxides also start to appear.
15
Lukyanov, Alex V., Vladimir V. Mitkin, Tristan Pryer, Penpark Sirimark et Theo G. Theofanous. « Capillary transport in paper porous materials at low saturation levels : normal, fast or superfast ? » Proceedings of the Royal Society A : Mathematical, Physical and Engineering Sciences 476, no 2244 (décembre 2020) : 20200488. http://dx.doi.org/10.1098/rspa.2020.0488.
Texte intégralRésumé :
The problem of capillary transport in fibrous porous materials at low levels of liquid saturation has been addressed. It has been demonstrated that the process of liquid spreading in this type of porous material at low saturation can be described macroscopically by a similar super-fast, nonlinear diffusion model to that which had been previously identified in experiments and simulations in particulate porous media. The macroscopic diffusion model has been underpinned by simulations using a microscopic network model. The theoretical results have been qualitatively compared with available experimental observations within the witness card technique using persistent liquids. The long-term evolution of the wetting spots was found to be truly universal and fully in line with the mathematical model developed. The result has important repercussions for the witness card technique used in field measurements of the dissemination of various low-volatility agents in imposing severe restrictions on collection and measurement times.
16
Pope, Jacob, et Martin Jackson. « FAST-forge of Diffusion Bonded Dissimilar Titanium Alloys : A Novel Hybrid Processing Approach for Next Generation Near-Net Shape Components ». Metals 9, no 6 (4 juin 2019) : 654. http://dx.doi.org/10.3390/met9060654.
Texte intégralRésumé :
Material reductions, weight savings, design optimisation, and a reduction in the environmental impact can be achieved by improving the performance of near-net shape (NNS) titanium alloy components. The method demonstrated in this paper is to use a solid-state approach, which includes diffusion bonding discrete layers of dissimilar titanium alloy powders (CP-Ti, Ti-6Al-4V and Ti-5Al-5Mo-5V-3Cr) using field-assisted sintering technology (FAST), followed by subsequent forging steps. This article demonstrates the hybrid process route, firstly through small-scale uni-axial compression tests and secondly through closed-die forging of dissimilar titanium alloy FAST preforms into an NNS (near-net shape) component. In order to characterise and simulate the underlying forging behaviour of dissimilar alloy combinations, uni-axial compression tests of FAST cylindrical samples provided flow stress behaviour and the effect of differing alloy volume fractions on the resistance to deformation and hot working behaviour. Despite the mismatch in the magnitude of flow stress between alloys, excellent structural bond integrity is maintained throughout. This is also reflected in the comparatively uncontrolled closed-die forging of the NNS demonstrator components. Microstructural analysis across the dissimilar diffusion bond line was undertaken in the components and finite element modelling software reliably predicts the strain distribution and bond line flow behaviour during the multi-step forging process.
17
Pauthier, Antoine. « Uniform dynamics for Fisher-KPP propagation driven by a line of fast diffusion under a singular limit ». Nonlinearity 28, no 11 (1 octobre 2015) : 3891–920. http://dx.doi.org/10.1088/0951-7715/28/11/3891.
Texte intégral
18
Pauthier, Antoine. « The influence of nonlocal exchange terms on Fisher–KPP propagation driven by a line of fast diffusion ». Communications in Mathematical Sciences 14, no 2 (2016) : 535–70. http://dx.doi.org/10.4310/cms.2016.v14.n2.a10.
Texte intégral
19
Kolacek, K., V. Prukner, J. Schmidt, O. Frolov et J. Straus. « A potential environment for lasing below 15 nm initiated by exploding wire in water ». Laser and Particle Beams 28, no 1 (21 janvier 2010) : 61–67. http://dx.doi.org/10.1017/s0263034609990577.
Texte intégralRésumé :
AbstractProximity wall stabilized, fast (>4 × 1011 A/s), high current (>40 kA) discharges are capable to create long, dense, hot, stable, non-equilibrium plasma column, suitable e.g., for radiation amplification or even for lasing in extreme ultraviolet and soft X-ray region. Exploding wire in water resembles a metal-vapor-filled capillary with liquid, ever fresh wall (without any metallic deposit). Modeling of wire explosion (inclusive melting and boiling phase transitions, thermal diffusion, and variable conductivity) by the originally skinned driving current is described. Modeling results are compared with measurement of the discharge current and with side-on and end-on monitoring of H-alpha line emission. Analysis of H-alpha line profile is used for diagnostic of water-vapor layer around the wire. The differences between model and reality are attributed to the fact that the pressure dependence of material constants was neglected in the first approximation.
20
Monteleone, Marcello, Elisa Esposito, Alessio Fuoco, Marek Lanč, Kryštof Pilnáček, Karel Friess, Caterina Bezzu, Mariolino Carta, Neil McKeown et Johannes Jansen. « A Novel Time Lag Method for the Analysis of Mixed Gas Diffusion in Polymeric Membranes by On-Line Mass Spectrometry : Pressure Dependence of Transport Parameters ». Membranes 8, no 3 (3 septembre 2018) : 73. http://dx.doi.org/10.3390/membranes8030073.
Texte intégralRésumé :
This paper presents a novel method for transient and steady state mixed gas permeation measurements, using a quadrupole residual gas analyser for the on-line determination of the permeate composition. The on-line analysis provides sufficiently quick response times to follow even fast transient phenomena, enabling the unique determination of the diffusion coefficient of the individual gases in a gas mixture. Following earlier work, the method is further optimised for higher gas pressures, using a thin film composite and a thick dense styrene-butadiene-styrene (SBS) block copolymer membrane. Finally, the method is used to calculate the CO2/CH4 mixed gas diffusion coefficients of the spirobisfluorene-based polymer of intrinsic microporosity, PIM-SBF-1. It is shown that the modest pressure dependence of the PIM-SBF-1 permeability can be ascribed to a much stronger pressure dependence of the diffusion coefficient, which partially compensates the decreasing solubility of CO2 with increasing pressure, typical for the strong sorption behaviour in PIMs. The characteristics of the instrument are discussed and suggestions are given for even more versatile measurements under stepwise increasing pressure conditions. This is the first report on mixed gas diffusion coefficients at different pressures in a polymer of intrinsic microporosity.
21
Amdursky, Nadav, Yiyang Lin, Noora Aho et Gerrit Groenhof. « Exploring fast proton transfer events associated with lateral proton diffusion on the surface of membranes ». Proceedings of the National Academy of Sciences 116, no 7 (24 janvier 2019) : 2443–51. http://dx.doi.org/10.1073/pnas.1812351116.
Texte intégralRésumé :
Proton diffusion (PD) across biological membranes is a fundamental process in many biological systems, and much experimental and theoretical effort has been employed for deciphering it. Here, we report on a spectroscopic probe, which can be tightly tethered to the membrane, for following fast (nanosecond) proton transfer events on the surface of membranes. Our probe is composed of a photoacid that serves as our light-induced proton source for the initiation of the PD process. We use our probe to follow PD, and its pH dependence, on the surface of lipid vesicles composed of a zwitterionic headgroup, a negative headgroup, a headgroup that is composed only from the negative phosphate group, or a positive headgroup without the phosphate group. We reveal that the PD kinetic parameters are highly sensitive to the nature of the lipid headgroup, ranging from a fast lateral diffusion at some membranes to the escape of protons from surface to bulk (and vice versa) at others. By referring to existing theoretical models for membrane PD, we found that while some of our results confirm the quasi-equilibrium model, other results are in line with the nonequilibrium model.
22
Marshall, W. F., A. F. Straight, A. Murray, J. C. Fung, J. Marko, D. A. Agard et J. W. Sedat. « Direct measurement of chromatin diffusion and constraint in living cells using a gfp-lac repressor fusion protein ». Proceedings, annual meeting, Electron Microscopy Society of America 54 (11 août 1996) : 740–41. http://dx.doi.org/10.1017/s0424820100166166.
Texte intégralRésumé :
The polymer dynamics of interphase chromatin is at present a poorly understood aspect of nuclear organization, but one with profound consequences on events within the nucleus. The rates of many important processes, such as meiotic homolog pairing, site-specific recombination, and chromatin condensation, all involve the motion of chromatin within the nucleus. How fast can such rearrangements occur? Because interphase chromatin is likely to behave as a tangle of random-walk polymers, there is likely to be a substantial hindrance to diffusion. Therefore, the rate at which a given site on a chromosome can diffuse within the nucleus may limit the rate at which events requiring chromatin motion can occur. Furthermore, the polymer physics of interphase chromatin is an interesting line of theoretical research in its own right, and knowledge of diffusion rates is an important experimental parameter to consider when evaluating physical models. Finally, a fundamental aspect of nuclear architecture is the extent to which chromatin is anchored to a nuclear skeleton. Such matrix attachments would result in constrained diffusion, which can be detected by analysis of chromatin motion.
23
Kolesnichenko, Ya I., V. V. Lutsenko et A. V. Tykhyy. « Stochastic diffusion of energetic ions in Wendelstein-line stellarators : Numerical validation of theory predictions and new findings ». Physics of Plasmas 29, no 10 (octobre 2022) : 102506. http://dx.doi.org/10.1063/5.0120179.
Texte intégralRésumé :
Stochastic motion of 3.5-MeV alpha particles with orbits that vary between locally trapped and locally passing states (transitioning particles) in a Helias reactor is observed numerically for the first time. This validates theory prediction that the collisionless stochastic diffusion of these particles represents a mechanism of considerable delayed loss of fast ions in quasi-isodynamic stellarators [Beidler et al., Phys. Plasmas 8, 2731 (2001)]. The numerical calculation has also demonstrated a possibility to prevent the escape of particles to the wall by making the separatrix between the locally trapped and passing states closed, as was proposed in Tykhyy et al. [Plasma Phys. Control. Fusion 49, 703 (2007)]. It is found that stochastic regions can vary from very narrow to very wide that occupy almost the whole plasma cross section. It is shown that the fraction of alpha particles with closed separatrix in the population of transition alphas can be considerable. Potentially, this fraction can be increased, and the number of transitioning particles can be reduced by a special optimization of the magnetic configuration, which decreases delayed losses of alphas by means of reducing the separatrix maximum radius.
24
Zheng, Chunxiong, Qiang Du, Xiang Ma et Jiwei Zhang. « Stability and Error Analysis for a Second-Order Fast Approximation of the Local and Nonlocal Diffusion Equations on the Real Line ». SIAM Journal on Numerical Analysis 58, no 3 (janvier 2020) : 1893–917. http://dx.doi.org/10.1137/19m1285822.
Texte intégral
25
Cua, Francisco, et Steve Reames. « Big Vendor vs. Little Vendor ». International Journal of Information Technology Project Management 4, no 2 (avril 2013) : 50–74. http://dx.doi.org/10.4018/jitpm.2013040104.
Texte intégralRésumé :
The majority of international organizations, especially technologist “fast or first movers” who invest in a new enterprise resource planning systems (ERP) project are considered Laggards or “late arrivers” by a major software vendor. The majority of the Laggards segment does not purchase ERP software from a vendor without an established track record. Obviously, small or less prestigious vendors have difficulty fulfilling their bottom line without tapping the Laggards market. This paper is a critical and non-empirical review to better understand this complex phenomenon. A case study was conducted within a large public sector university in Australasia during a major ERP-managed project utilizing the Diffusion of Innovations theory integrating it with the concepts of internationalization. The findings confirm that small software vendors have a great challenge to overcome. But the Diffusion of Innovation could be one of many social analysis building blocks for promoting the “Little Vendor” over the “Big Vendor.”
26
Zhang, Hui, Xiaoyun Jiang et Fawang Liu. « Error analysis of nonlinear time fractional mobile/immobile advection-diffusion equation with weakly singular solutions ». Fractional Calculus and Applied Analysis 24, no 1 (29 janvier 2021) : 202–24. http://dx.doi.org/10.1515/fca-2021-0009.
Texte intégralRésumé :
Abstract In this paper, a weighted and shifted Grünwald-Letnikov difference (WSGD) Legendre spectral method is proposed to solve the two-dimensional nonlinear time fractional mobile/immobile advection-dispersion equation. We introduce the correction method to deal with the singularity in time, and the stability and convergence analysis are proven. In the numerical implementation, a fast method is applied based on a globally uniform approximation of the trapezoidal rule for the integral on the real line to decrease the memory requirement and computational cost. The memory requirement and computational cost are O(Q) and O(QK), respectively, where K is the number of the final time step and Q is the number of quadrature points used in the trapezoidal rule. Some numerical experiments are given to confirm our theoretical analysis and the effectiveness of the presented methods.
27
Spellenberg, B., J. Zettner, T. Hierl, M. Haller et T. Lenzi. « Thermal Imaging Analysis of Stimulated Heat Diffusion in Sheet Metal for Non-Destructive Metrology and Testing ». Advanced Materials Research 6-8 (mai 2005) : 681–88. http://dx.doi.org/10.4028/www.scientific.net/amr.6-8.681.
Texte intégralRésumé :
Recent developments in infrared camera technology, testing methods and data processing algorithms have brought significant progress for high resolution spatial and temporal analysis of thermal radiation. Together with industry standard automation technology and specific infrared image data processing it became possible to non destructively inspect laser welded seams and other types of joints using heat flux analysis subsequent to thermal stimulation. High thermal diffusion coefficients of the usually metallic samples under test make the availability of high-speed infrared cameras as a key hardware component indispensable. Since high-speed infrared cameras with frame rates of at least 500 Hz have become available for commercial applications, non-destructive testing systems with a new class of performance were designed, manufactured, and implemented at industrial sites. Heat flux analysis as a new and robust method of non-destructive testing has been implemented for various types of equipment, ranging from off-line tools for laboratory use to automated robot based systems enabling fast and operator-free in-line inspection. Depending on environment, implementation surroundings, and geometry of objects to be inspected, different types of pulsed or continuous operating heat sources (e.g. flash light, laser, … ) are selected. Due to its outstanding industrial relevance non-destructive testing of laser welded seams in automobile manufacturing is shown in detail in this paper.
28
Drabczyk, Kazimierz, Edyta Wróbel, Grazyna Kulesza-Matlak, Wojciech Filipowski, Krzysztof Waczynski et Marek Lipinski. « Comparison of diffused layer prepared using liquid dopant solutions and pastes for solar cell with screen printed electrodes ». Microelectronics International 33, no 3 (1 août 2016) : 167–71. http://dx.doi.org/10.1108/mi-03-2016-0031.
Texte intégralRésumé :
Purpose The purpose of this study is comparison of the diffusion processes performed using the commercial available dopant paste made by Filmtronics and the original prepared liquid dopant solution. To decrease prices of industrially produced silicon-based solar cells, the new low-cost production processes are necessary. The main components of most popular silicon solar cells are with diffused emitter layer, passivation, anti-reflective layers and metal electrodes. This type of cells is prepared usually using phosphorus oxychloride diffusion source and metal pastes for screen printing. The diffusion process in diffusion furnace with quartz tube is slow, complicated and requires expensive equipment. The alternative for this technology is very fast in-line processing using the belt furnaces as an equipment. This approach requires different dopant sources. Design/methodology/approach In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution. The investigation was focused on dopant sources fabrication and diffusion processes. The doping solution was made in two stages. In the first stage, a base solution (without dopants) was made: dropwise deionized (DI) water and ethyl alcohol were added to a solution consisting of tetraethoxysilane (TEOS) and 99.8 per cent ethyl alcohol. Next, to the base solution, orthophosphoric acid dissolved in ethyl alcohol was added. Findings Diffused emitter layers with sheet resistance around 60 Ω/sq were produced on solar grade monocrystalline silicon wafers using two types of dopant sources. Originality/value In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution.
29
Guo, Wenjing, Jiyong Hu et Xiong Yan. « Influence of process parameters on the characteristics of electrohydrodynamic-printed UV-curing conductive lines on the fabric ». Journal of Micromechanics and Microengineering 32, no 3 (4 février 2022) : 035003. http://dx.doi.org/10.1088/1361-6439/ac4825.
Texte intégralRésumé :
Abstract As a similar technology to the near-field static electrospinning, the emerging electrohydrodynamic (EHD) printing technology with digital printing process and compatibility of viscous particle-blended inks is one of the simplest methods of fabricating multifunctional electronic textiles. With increasing demands for textile-based conductive lines with controllable width and excellent electrical performance, it is of great importance to know the influence of key process parameters on the morphology and electrical properties of EHD-printed UV-curing conductive lines on the fabric. This work will systematically explore the effect of the EHD printing process parameters (i.e. applied voltage, direct-writing height, flow rate and moving velocity of the substrate) on the morphology and electrical performance of the EHD-printed textile-based conductive lines, especially focus on the diffusion and penetration of inks on the rough and porous fabric. The UV-curing nano-silver ink with low temperature and fast curing features was selected, and the line width and electrical resistance of printed lines under different process parameters were observed and measured. The results showed that, unlike previous results about EHD printing on smooth and impermeable substrates, the ink diffusion related to fabric textures had a greater effect on the fabric-based conductive line width than the applied voltage and direct-writing height in the case of a stable jet. Meanwhile, the relationship between the line width and the flow rate met the equation of d = 407.28 × Q 1 2 , and the minimum volume on fabric per millimeter was 0.67 μl to form continuous line with low electrical resistance. Additionally, the higher substrate moving velocity resulted in a smaller line width, while it deteriorated the thickness uniformity and electrical property of printed lines. Generally, due to the effect of surface structure of the fabric on the spreading and penetrating behavior of inks, the flow rate and the substrate moving velocity are two significant parameters ensuring the electrical property of printed lines. It is believed that these findings will provide some guides for applying EHD printing technology into flexible electronics on the woven fabric.
30
O’Brien, P. J. « Asymmetric zoning profiles in garnet from HP-HT granulite and implications for volume and grain-boundary diffusion ». Mineralogical Magazine 63, no 2 (avril 1999) : 227–38. http://dx.doi.org/10.1180/002646199548457.
Texte intégralRésumé :
AbstractDetailed electron-microprobe line profiles and small-area compositional maps of zoned garnets in a sample of high-pressure-high-temperature granulite show features inconsistent with commonly applied diffusion models. Larger grains of an early garnet generation have their highest Ca contents in domains away from the rim or inclusions but show a sharp fall in Ca balanced by increased Mg and Fe (and slightly higher XMg) towards inclusions and the rim. In domains with secondary biotite, the sharp decrease in Ca is accompanied by variations in XMg dependent upon proximity to biotite, thus producing one-sided, asymmetric profiles with XMg lower against biotite. As a consequence, rim compositions of the same grain are different on the sides adjacent and away from biotite and there is no relationship between grain size and rim XMg. Such a zoning pattern requires that grain-boundary diffusion is as slow as volume diffusion and implies the absence of a diffusion-enhancing grain-boundary fluid phase during the majority of the rock's high-temperature exhumation history. Diffusion models ignoring this probability could yield either cooling rates that were too fast, or extrapolated ages based on closure temperature models that were too old.A second garnet generation in the same rock, grown in a Ca-rich domain resulting from kyanite breakdown, has irregularly distributed patches, identified by compositional mapping, containing higher Ca than the first-formed garnet but at lower XMg. Use of such garnet compositions for geothermobarometrical determination of the high-pressure granulite stage would clearly lead to erroneous results. The presence of such contrasting garnet compositions in a granulite-facies rock is clearly evidence of disequilibrium, and further supports the proposition that there was a lack of an effective transport medium even at the mm scale.
31
Sgobbi, Francesca. « Web design skills and competencies : an empirical analysis ». Human Systems Management 21, no 2 (4 avril 2002) : 115–28. http://dx.doi.org/10.3233/hsm-2002-21203.
Texte intégralRésumé :
The availability of proper human capital represents a key-factor in order to support the current fast pace of diffusion of Internet-based applications. The careful assessment of the skills and competencies required to manage and develop Internet technologies in different application domains represents a necessary step to solve the emerging skill shortage and skill gap problems. While most existing analyses of skill needs in information and communication technologies deal with broad professional categories, the paper focuses the attention on a specific professional figure, the Web designer. By resorting to an on-line questionnaire administered to a sample of Italian Web designers, the paper shows that jobholders recognise greater usefulness to organisational rather than technical knowledge domains. However, perceived skill gaps are larger in the case of technical skills and competencies. Moreover, specialisation paths are emerging.
32
Zhang, Yu Dong, Claude Esling, Xiang Zhao et Liang Zuo. « Diffusion-Controlled Phase Transformation under High Magnetic Field in Medium and High Carbon Steels ». Materials Science Forum 539-543 (mars 2007) : 4768–73. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4768.
Texte intégralRésumé :
The new phase equilibrium of Fe-C diagram under magnetic field has been theoretically calculated. Results show that the magnetic field mainly shifts the γ⁄α+γ equilibrium line and the eutectoid point to the high carbon and high temperature sides. Based on this result, an experimental setup has been launched to investigate the effect of magnetic field on austenite decomposition in medium carbon and high carbon steels. The thermodynamic and kinetic effects of the high magnetic field on proeutectoid transformation at different cooling rates have been studied. It was found that for medium carbon steels, the magnetic field increases the amount of proeutectoid ferrite and accelerates the diffusional decomposition of austenite at medium and relatively fast cooling rates (10°C/min and 46°C/min). But there is no special grain growth along the field direction. The results led to a proposal of a new rapid annealing under a high magnetic field. However, when cooling is slow (2°C/min), the magnetic field shows a strong tendency to promote the proeutectoid ferrite grains to grow along the field direction through the magnetic dipolar interaction, which leads to the formation of an elongated grain structure. Moreover, the magnetic field also exhibits influence on the austenite decomposition in hypereutectoid steel by changing the amount of secondary cementite and lamellar spacing of pearlite.
33
Brailovsky, I., L. Kagan et G. Sivashinsky. « Combustion waves in hydraulically resisted systems ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 370, no 1960 (13 février 2012) : 625–46. http://dx.doi.org/10.1098/rsta.2011.0341.
Texte intégralRésumé :
The effects of hydraulic resistance on the burning of confined/obstacle-laden gaseous and gas-permeable solid explosives are discussed on the basis of recent research. Hydraulic resistance is found to induce a new powerful mechanism for the reaction spread (diffusion of pressure) allowing for both fast subsonic as well as supersonic propagation. Hydraulic resistance appears to be of relevance also for the multiplicity of detonation regimes as well as for the transitions from slow conductive to fast convective, choked or detonative burning. A quasi-one-dimensional Fanno-type model for premixed gas combustion in an obstructed channel open at the ignition end is discussed. It is shown that, similar to the closed-end case studied earlier, the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration, which leads (after an extended induction period) to a localized autoignition that triggers an abrupt transition from deflagrative to detonative combustion. In line with the experimental observations, the ignition at the open end greatly encumbers the transition (compared with the closed-end case), and the deflagration practically does not accelerate up to the very transition point. Shchelkin's effect, that ignition at a small distance from the closed end of a tube facilitates the transition, is described.
34
Pancino, Elena. « Globular cluster chemistry in fast-rotating dwarf stars belonging to intermediate-age open clusters ». Astronomy & ; Astrophysics 614 (juin 2018) : A80. http://dx.doi.org/10.1051/0004-6361/201732351.
Texte intégralRésumé :
The peculiar chemistry observed in multiple populations of Galactic globular clusters is not generally found in other systems such as dwarf galaxies and open clusters, and no model can currently fully explain it. Exploring the boundaries of the multiple-population phenomenon and the variation of its extent in the space of cluster mass, age, metallicity, and compactness has proven to be a fruitful line of investigation. In the framework of a larger project to search for multiple populations in open clusters that is based on literature and survey data, I found peculiar chemical abundance patterns in a sample of intermediate-age open clusters with publicly available data. More specifically, fast-rotating dwarf stars (v sin i ≥ 50 km s−1) that belong to four clusters (Pleiades, Ursa Major, Come Berenices, and Hyades) display a bimodality in either [Na/Fe] or [O/Fe], or both, with the low-Na and high-O peak more populated than the high-Na and low-O peak. Additionally, two clusters show a Na–O anti-correlation in the fast-rotating stars, and one cluster shows a large [Mg/Fe] variation in stars with high [Na/Fe], reaching the extreme Mg depletion observed in NGC 2808. Even considering that the sample sizes are small, these patterns call for attention in the light of a possible connection with the multiple population phenomenon of globular clusters. The specific chemistry observed in these fast-rotating dwarf stars is thought to be produced by a complex interplay of different diffusion and mixing mechanisms, such as rotational mixing and mass loss, which in turn are influenced by metallicity, binarity, mass, age, variability, and so on. However, with the sample in hand, it was not possible to identify which stellar parameters cause the observed Na and O bimodality and Na–O anti-correlation. This suggests that other stellar properties might be important in addition to stellar rotation. Stellar binarity might influence the rotational properties and enhance rotational mixing and mass loss of stars in a dense environment like that of clusters (especially globulars). In conclusion, rotation and binarity appear as a promising research avenue for better understanding multiple stellar populations in globular clusters; this is certainly worth exploring further.
35
Kravos, Andraž, et Tomaž Katrašnik. « Closed-Form Formulation of the Thermodynamically Consistent Electrochemical Model Considering Electrochemical Co-Oxidation of CO and H2 for Simulating Solid Oxide Fuel Cells ». Catalysts 12, no 1 (4 janvier 2022) : 56. http://dx.doi.org/10.3390/catal12010056.
Texte intégralRésumé :
Achieving efficient solid oxide fuel cell operation and simultaneous prevention of degradation effects calls for the development of precise on-line monitoring and control tools based on predictive, computationally fast models. The originality of the proposed modelling approach originates from the hypothesis that the innovative derivation procedure enables the development of a thermodynamically consistent multi-species electrochemical model that considers the electrochemical co-oxidation of carbon monoxide and hydrogen in a closed-form. The latter is achieved by coupling the equations for anodic reaction rates with the equation for anodic potential. Furthermore, the newly derived model is capable of accommodating the diffusive transport of gaseous species through the gas diffusion layer, yielding a computationally efficient quasi-one-dimensional model. This resolves a persistent knowledge gap, as the proposed modelling approach enables the modelling of multi-species fuels in a closed form, resulting in very high computational efficiency, and thus enable the model’s real-time capability. Multiple validation steps against polarisation curves with different fuel mixtures confirm the capability of the newly developed model to replicate experimental data. Furthermore, the presented results confirm the capability of the model to accurately simulate outside the calibrated variation space under different operating conditions and reformate mixtures. These functionalities position the proposed model as a beyond state-of-the-art tool for model supported development and control applications.
36
Eriksson, Gunnar, et Urban Grén. « Pulp washing : Influence of temperature on lignin leaching from kraft pulps ». Nordic Pulp & ; Paper Research Journal 12, no 4 (1 décembre 1997) : 244–51. http://dx.doi.org/10.3183/npprj-1997-12-04-p244-251.
Texte intégralRésumé :
Abstract The leaching of lignin from the fibre wall was studied in order to investigate the effects in the clean end of the fibre line. The focus was set on the short time intervals representative for the washing operation in industrial applications. The influence of temperature, pulp type and kappa number was investigated. It could be seen that there are different diffusivities for the soluble lignin in the wall at short and long time of leaching, probably due to the existence of a more open structure in an outer layer of the fibre wall, in which the lignin diffuses more easily and which is also emptied relatively fast, while diffusion of the lignin from the inner layers is significantly slower. There is also a relation between the leaching of sodium ions out of the wall and the short diffusion time of lignin, indicating a possible ion-ion interaction with the lignin in the outer layer of the fibre wall. The diffusivity of lignin increases more rapidly at temperatures above 80-90 "C. This temperature effect was confirmed in the results of wash test equipment experiments, giving noticeable differences above 100 "C. It was found that the experimentally determined lignin diffusivity differs for different kappa number and for type of pulp. The general behaviour of the phenomena, however, is the same.
37
Marsh, Derek. « Spin-label Order Parameter Calibrations for Slow Motion ». Applied Magnetic Resonance 49, no 1 (9 septembre 2017) : 97–106. http://dx.doi.org/10.1007/s00723-017-0940-7.
Texte intégralRésumé :
Abstract Calibrations are given to extract orientation order parameters from pseudo-powder electron paramagnetic resonance line shapes of 14N-nitroxide spin labels undergoing slow rotational diffusion. The nitroxide z-axis is assumed parallel to the long molecular axis. Stochastic-Liouville simulations of slow-motion 9.4-GHz spectra for molecular ordering with a Maier–Saupe orientation potential reveal a linear dependence of the splittings, $$2A_{\hbox{max} }$$ 2 A max and $$2A_{\hbox{min} }$$ 2 A min , of the outer and inner peaks on order parameter $$S_{zz}$$ S z z that depends on the diffusion coefficient $$D_{{{\text{R}} \bot }}$$ D R ⊥ which characterizes fluctuations of the long molecular axis. This results in empirical expressions for order parameter and isotropic hyperfine coupling: $$S_{zz} = s_{1} \times \left( {A_{\hbox{max} } - A_{\hbox{min} } } \right) - s_{o}$$ S z z = s 1 × A max - A min - s o and $$a_{o}^{{}} = \tfrac{1}{3}\left( {f_{\hbox{max} } A_{\hbox{max} } + f_{\hbox{min} } A_{\hbox{min} } } \right) + \delta a_{o}$$ a o = 1 3 f max A max + f min A min + δ a o , respectively. Values of the calibration constants $$s_{1}$$ s 1 , $$s_{\text{o}}$$ s o , $$f_{\hbox{max} }$$ f max , $$f_{\hbox{min} }$$ f min and $$\delta a_{o}$$ δ a o are given for different values of $$D_{{{\text{R}} \bot }}$$ D R ⊥ in fast and slow motional regimes. The calibrations are relatively insensitive to anisotropy of rotational diffusion $$(D_{{{\text{R}}//}} \ge D_{{{\text{R}} \bot }} )$$ ( D R / / ≥ D R ⊥ ) , and corrections are less significant for the isotropic hyperfine coupling than for the order parameter.
38
Tenerani, A., et M. Velli. « Spectral signatures of recursive magnetic field reconnection ». Monthly Notices of the Royal Astronomical Society 491, no 3 (27 novembre 2019) : 4267–76. http://dx.doi.org/10.1093/mnras/stz3310.
Texte intégralRésumé :
ABSTRACT We use 2.5D magnetohydrodynamic simulations to investigate the spectral signatures of the non-linear disruption of a tearing unstable current sheet via the generation of multiple secondary current sheets and magnetic islands. During the non-linear phase of tearing mode evolution, there develops a regime in which the magnetic energy density shows a spectrum with a power law close to B(k)2 ∼ k−0.8. Such an energy spectrum is found in correspondence of the neutral line, within the diffusion region of the primary current sheet, where energy is conveyed towards smaller scales via a ‘recursive’ process of fast tearing-type instabilities. Far from the neutral line, we find that magnetic energy spectra evolve towards slopes compatible with the ‘standard’ Kolmogorov spectrum. Starting from a self-similar description of the non-linear stage at the neutral line, we provide a model that predicts a reconnecting magnetic field energy spectrum scaling as k−4/5, in good agreement with numerical results. An extension of the predicted power law to generic current sheet profiles is also given and possible implications for turbulence phenomenology are discussed. These results provide a step forward to understand the ‘recursive’ generation of magnetic islands (plasmoids), which has been proposed as a possible explanation for the energy release during flares, but which, more in general, can have an impact on the subsequent turbulent evolution of unstable sheets that naturally form in the high Lundquist number and collisionless plasmas found in most of the astrophysical environments.
39
Xu, Jing, Dandan Zhao, Zhengwei Ren, Feiran Fu, Yuxin Sun et Ming Fang. « A Parallax Image Mosaic Method for Low Altitude Aerial Photography with Artifact and Distortion Suppression ». Journal of Imaging 9, no 1 (25 décembre 2022) : 5. http://dx.doi.org/10.3390/jimaging9010005.
Texte intégralRésumé :
In this paper, we propose an aerial images stitching method based on an as-projective-as-possible (APAP) algorithm, aiming at the problem artifacts, distortions, or stitching failure due to fewer feature points for multispectral aerial image with certain parallax. Our method incorporates accelerated nonlinear diffusion algorithm (AKAZE) into APAP algorithm. First, we use the fast and stable AKAZE to extract the feature points of aerial images, and then, based on the registration model of the APAP algorithm, we add line protection constraints, global similarity constraints, and local similarity constraints to protect the image structure information, to produce a panorama. Experimental results on several datasets demonstrate that proposed method is effective when dealing with multispectral aerial images. Our method can suppress artifacts, distortions, and reduce incomplete splicing. Compared with state-of-the-art image stitching methods, including APAP and adaptive as-natural-as-possible image stitching (AANAP), and two of the most popular UAV image stitching tools, Pix4D and OpenDroneMap (ODM), our method achieves them both quantitatively and qualitatively.
40
Secondulfo, Laura, Melissa T. Hooijmans, Joep J. Suskens, Valentina Mazzoli, Mario Maas, Johannes L. Tol, Aart J. Nederveen et Gustav J. Strijkers. « A diffusion tensor-based method facilitating volumetric assessment of fiber orientations in skeletal muscle ». PLOS ONE 17, no 1 (27 janvier 2022) : e0261777. http://dx.doi.org/10.1371/journal.pone.0261777.
Texte intégralRésumé :
Background The purpose of this study was to develop a DTI-based method to quantitatively assess fiber angles and changes therein in leg muscles in order to facilitate longitudinal studies on muscle fiber architectural adaptations in healthy subjects. Methods The upper legs of five volunteers were scanned twice on the same day. The right lower legs of five volunteers were scanned twice with the ankle in three positions, i.e. -15° dorsiflexion, 0° neutral position, and 30° plantarflexion. The MRI protocols consisted of a noise scan, a 3-point mDixon scan and a DTI scan. Fiber-angle color maps were generated for four muscles in the upper legs and two muscles in the lower leg. Voxel-wise fiber angles (θ) were calculated from the angle between the principal eigenvector of the diffusion tensor and a reference line defined between the origo and insertion points of each muscle. Bland-Altman analysis, intraclass correlation coefficient (ICC), coefficient of variation (CV%), minimal detectable change (MDC), standard error (SE) and Friedman test were used for assessing the feasibility of this method and in order to have an indication of the repeatability and the sensitivity. Results Bland-Altman analysis showed good repeatability (CV%<10 and 0.7≤ICC≤0.9) with exception of the Tibialis Anterior (TA) muscle in dorsiflexion position(CV%: 12.2) and the Semitendinosus (ST) muscle (left leg) (CV%: 11.4). The best repeatability metrics were found for the SOL muscle in neutral position (CV%: 2.6). Changes in average θ in TA and SOL with ankle positions were observed in accordance with expected agonist and antagonist functions of both muscles. For example, for the anterior left compartment the change in fiber angle Δθ with respect to the neutral position Δθ = -1.6° ± 0.8° and 2.2° ± 2.8° (p = 0.008), for dorsiflexion and plantarflexion, respectively. Conclusion Our method facilitates fast inspection and quantification of muscle fiber angles in the lower and upper leg muscles in rest and detection of changes in lower-leg muscle fiber angles with varying ankle angles.
41
Hirai, Daniel M., Jesse C. Craig, Trenton D. Colburn, Hiroaki Eshima, Yutaka Kano, Timothy I. Musch et David C. Poole. « Skeletal muscle interstitial Po2 kinetics during recovery from contractions ». Journal of Applied Physiology 127, no 4 (1 octobre 2019) : 930–39. http://dx.doi.org/10.1152/japplphysiol.00297.2019.
Texte intégralRésumé :
The oxygen partial pressure in the interstitial space (Po2 is) drives O2 into the myocyte via diffusion, thus supporting oxidative phosphorylation. Although crucial for metabolic recovery and the capacity to perform repetitive tasks, the time course of skeletal muscle Po2 is during recovery from contractions remains unknown. We tested the hypothesis that Po2 is would recover to resting values and display considerable on-off asymmetry (fast on-, slow off-kinetics), reflective of asymmetric capillary hemodynamics. Microvascular Po2 (Po2 mv) was also evaluated to test the hypothesis that a significant transcapillary gradient (ΔPo2 = Po2 mv − Po2 is) would be sustained during recovery. Po2 mv and Po2 is (expressed in mmHg) were determined via phosphorescence quenching in the exposed rat spinotrapezius muscle during and after submaximal twitch contractions ( n = 12). Po2 is rose exponentially ( P < 0.05) from end-contraction (11.1 ± 5.1), such that the end-recovery value (17.9 ± 7.9) was not different from resting Po2 is (18.5 ± 8.1; P > 0.05). Po2 is off-kinetics were slower than on-kinetics (mean response time: 53.1 ± 38.3 versus 18.5 ± 7.3 s; P < 0.05). A significant transcapillary ΔPo2 observed at end-contraction (16.6 ± 7.4) was maintained throughout recovery (end-recovery: 18.8 ± 9.6; P > 0.05). Consistent with our hypotheses, muscle Po2 is recovered to resting values with slower off-kinetics compared with the on-transient in line with the on-off asymmetry for capillary hemodynamics. Maintenance of a substantial transcapillary ΔPo2 during recovery supports that the microvascular-interstitium interface provides considerable resistance to O2 transport. As dictated by Fick’s law (V̇o2 = Do2 × ΔPo2), modulation of O2 flux (V̇o2) during recovery must be achieved via corresponding changes in effective diffusing capacity (Do2; mainly capillary red blood cell hemodynamics and distribution) in the face of unaltered ΔPo2. NEW & NOTEWORTHY Capillary blood-myocyte O2 flux (V̇o2) is determined by effective diffusing capacity (Do2; mainly erythrocyte hemodynamics and distribution) and microvascular-interstitial Po2 gradients (ΔPo2 = Po2 mv − Po2 is). We show that Po2 is demonstrates on-off asymmetry consistent with Po2 mv and erythrocyte kinetics during metabolic transitions. A substantial transcapillary ΔPo2 was preserved during recovery from contractions, indicative of considerable resistance to O2 diffusion at the microvascular-interstitium interface. This reveals that effective Do2 declines in step with V̇o2 during recovery, as per Fick’s law.
42
Biancolillo, Alessandra, Federico Marini, Cyril Ruckebusch et Raffaele Vitale. « Chemometric Strategies for Spectroscopy-Based Food Authentication ». Applied Sciences 10, no 18 (18 septembre 2020) : 6544. http://dx.doi.org/10.3390/app10186544.
Texte intégralRésumé :
In the last decades, spectroscopic techniques have played an increasingly crucial role in analytical chemistry, due to the numerous advantages they offer. Several of these techniques (e.g., Near-InfraRed—NIR—or Fourier Transform InfraRed—FT-IR—spectroscopy) are considered particularly valuable because, by means of suitable equipment, they enable a fast and non-destructive sample characterization. This aspect, together with the possibility of easily developing devices for on- and in-line applications, has recently favored the diffusion of such approaches especially in the context of foodstuff quality control. Nevertheless, the complex nature of the signal yielded by spectroscopy instrumentation (regardless of the spectral range investigated) inevitably calls for the use of multivariate chemometric strategies for its accurate assessment and interpretation. This review aims at providing a comprehensive overview of some of the chemometric tools most commonly exploited for spectroscopy-based foodstuff analysis and authentication. More in detail, three different scenarios will be surveyed here: data exploration, calibration and classification. The main methodologies suited to addressing each one of these different tasks will be outlined and examples illustrating their use will be provided alongside their description.
43
Ma, Te, Gary Schajer, Tetsuya Inagaki, Zarin Pirouz et Satoru Tsuchikawa. « Optical characteristics of Douglas fir at various densities, grain directions and thicknesses investigated by near-infrared spatially resolved spectroscopy (NIR-SRS) ». Holzforschung 72, no 9 (25 septembre 2018) : 789–96. http://dx.doi.org/10.1515/hf-2017-0213.
Texte intégralRésumé :
AbstractA near-infrared spatially resolved spectroscopy (NIR-SRS) system, also called the hyperspectral imaging system, was applied in a line scanning model combined with a concentrated halogen light source (Ø 1 mm), and spatially resolved reflectance images of Douglas fir [Pseudotsuga menziesii(Mirb.) Franco] wood were obtained. The samples with various densities, grain directions and thicknesses were observed in the NIR range of 1000–1600 nm. Then, a nonlinear curve-fitting algorithm was applied based on the steady-state diffusion theory model to estimate the absorption coefficient (μa), and reduced scattering coefficients (${\mu '_s}$) both parallel and perpendicular to the grain direction at each measurement position. The absorption scattering coefficients at 1457 nm and two kinds of reduced scattering coefficients at 1002 nm were highly correlated with wood densities measured by an X-ray densitometer. The correlation coefficients were 0.953 and 0.987 for 3 mm and 5 mm samples, respectively, while three optical profiles were combined. It can be concluded that NIR-SRS is a fast and simple method for measuring the optical characteristics of softwood, although it has a non-homogeneous cellular structure. Sub-surface density and grain direction could be predicted with satisfactory accuracy based on a few key wavelengths without relying on multivariate statistical analysis.
44
Lee, V., A. J. Payne et J. M. Gregory. « A two-layer flow model to represent ice-ocean interactions beneath Antarctic ice shelves ». Geoscientific Model Development Discussions 4, no 1 (14 janvier 2011) : 65–136. http://dx.doi.org/10.5194/gmdd-4-65-2011.
Texte intégralRésumé :
Abstract. We develop a two-dimensional two-layer flow model that can calculate melt rates beneath ice shelves from ocean temperature and salinity fields at the shelf front. The cavity motion is split into two layers where the upper plume layer represents buoyant meltwater-rich water rising along the underside of the ice to the shelf front, while the lower layer represents the ambient water connected to the open ocean circulating beneath the plume. Conservation of momentum has been reduced to a frictional geostrophic balance, which when linearized provides algebraic equations for the plume velocity. The turbulent exchange of heat and salt between the two layers is modelled through an entrainment rate which is directed into the faster flowing layer. The numerical model is tested using an idealized geometry based on the dimensions of Pine Island Ice Shelf. We find that the spatial distribution of melt rates is fairly robust. The rates are at least 2.5 times higher than the mean in fast flowing regions corresponding to the steepest section of the underside of the ice shelf close to the grounding line and to the converged geostrophic flow along the rigid lateral boundary. Precise values depend on a combination of entrainment and plume drag coefficients. The flow of the ambient is slow and the spread of ocean scalar properties is dominated by diffusion.
45
KARAPETSAS, GEORGE, RICHARD V. CRASTER et OMAR K. MATAR. « On surfactant-enhanced spreading and superspreading of liquid drops on solid surfaces ». Journal of Fluid Mechanics 670 (25 janvier 2011) : 5–37. http://dx.doi.org/10.1017/s0022112010005495.
Texte intégralRésumé :
The mechanisms driving the surfactant-enhanced spreading of droplets on the surface of solid substrates, and particularly those underlying the superspreading behaviour sometimes observed, are investigated theoretically. Lubrication theory for the droplet motion, together with advection–diffusion equations and chemical kinetic fluxes for the surfactant transport, leads to coupled evolution equations for the drop thickness, interfacial concentrations of surfactant monomers and bulk concentrations of monomers and micellar, or other, aggregates. The surfactant can be adsorbed on the substrate either directly from the bulk monomer concentrations or from the liquid–air interface through the contact line. An important feature of the spreading model developed here is the surfactant behaviour at the contact line; this is modelled using a constitutive relation, which is dependent on the local surfactant concentration. The evolution equations are solved numerically, using the finite-element method, and we present a thorough parametric analysis for cases of both insoluble and soluble surfactants with concentrations that can, in the latter case, exceed the critical micelle, or aggregate, concentration. The results show that basal adsorption of the surfactant plays a crucial role in the spreading process; the continuous removal of the surfactant that lies upon the liquid–air interface, due to the adsorption at the solid surface, is capable of inducing high Marangoni stresses, close to the droplet edge, driving very fast spreading. The droplet radius grows at a rate proportional to ta with a = 1 or even higher, which is close to the reported experimental values for superspreading. The spreading rates follow a non-monotonic variation with the initial surfactant concentration also in accordance with experimental observations. An accompanying feature is the formation of a rim at the leading edge of the droplet. In some cases, the drop spreads to form a ‘pancake’ or creates a ‘secondary’ front separated from the main droplet.
46
Yunik, A. D., et J. A. Solovjov. « Effect of Rapid Thermal Annealing Conditions on the Specific Resistance of the Ohmic Contacts of Ti/Al/Ni/Au Metallization to the GaN/AlGaN Heterostructure ». Doklady BGUIR 20, no 8 (3 janvier 2023) : 14–20. http://dx.doi.org/10.35596/1729-7648-2022-20-8-14-20.
Texte intégralRésumé :
Effect of rapid thermal annealing conditions on the specific resistance of the ohmic contacts of Ti/Al/Ni/Au metallization with layer thicknesses of 20/120/40/40 nm to the GaN/AlGaN heterostructure with a two-dimensional electron gas on a sapphire substrate has been discovered by transmission line measurement. Rapid thermal annealing of the samples was carried out by the contact heating from the sapphire substrate side in a nitrogen atmosphere at the temperature range from 750 to 1000 °C for 30, 60, and 90 s. It has been discovered that the dependence of the specific contact resistance on the temperature contains two temperature optimums, at which the specific contact resistance of the ohmic contact is less than 1 ⋅ 10–4 Ohm⋅ cm2. The appearance of the first temperature optimum is due to the decrease of the distance from the diffusion front of the low-resistance layer of intermetallic compounds formed during the rapid thermal annealing of the Ti/Al/Ni/Au metallization to the region of the two-dimensional electron gas. Outside the first temperature optimum, an increase in the specific contact resistance of up to 9 ⋅ 10–3 Ohm⋅ cm2 is observed, due to the absorption of the AlGaN layer by a low-resistance layer of intermetallic compounds, which leads to the degradation of the two-dimensional electron gas under the contacts and deterioration of its conductive properties. The second temperature optimum is due to the passage of the diffusion front of the two-dimensional electron gas region and the establishment of a side contact between the low-resistance intermetallic layer and the two-dimensional electron gas, which leads to the decrease in the specific contact resistance. With an increase in the fast thermal annealing time from 30 to 90 s the shift of the interval of the first temperature optimum from 800 to 775 °C for the lower boundary and from 825 to 800 °C for the upper boundary, and for the second temperature optimum from 875 to 850 °C for the lower boundary, and from 950 to 875 °C for the upper boundary is observed, which is due to an equivalent increase in the diffusion depth of the Ti/Al/Ni/Au metallization components. The results obtained can be used in the technology for creating GaN-based products with a two-dimensional electron gas.
47
Parra-Coca, Alexander, Antonio Boix-Montañés, Ana C. Calpena et Helena Colom. « Pharmacokinetic Appraisal of Carprofen Delivery from Intra-Articular Nanoparticles : A Population Modeling Approach in Rabbits ». Proceedings 78, no 1 (1 décembre 2020) : 11. http://dx.doi.org/10.3390/iecp2020-08677.
Texte intégralRésumé :
Osteoarthritis is frequently treated in veterinary settings with non-steroidal anti-inflammatory drugs (NSAID) such as carprofen (CP). Its action over the articular cartilage can be enhanced by increasing drug uptake into the cartilage, alongside its site of action, and anticipating its rapid distribution towards the bloodstream. A pharmacokinetic study to evaluate carprofen nanoparticles (NP) after intraarticular administration (IA) in rabbits was performed through a modeling allometric approach. The pharmacokinetic analysis of plasma profiles showed a rapid CP distribution outwards the synovial chamber but mainly remaining in plasma (Vc = 0.14 L/5 Kg), according to its high protein-binding. The absorption data modeling showed the occurrence of two different release–absorption rate processes after nanoparticle administration in the synovial space, i.e., a fast rate process causing a burst effect and involving the 59.5% of the total CP absorbed amount and a slow rate process, involving 40.5%. Interestingly, the CP burst effect inside the joint space enhances its diffusion towards cartilage resulting in CP accumulation in about three times higher concentrations than in plasma. In line with these results, the normalized-by-dose area under the concentration vs. time curve (AUC) values after IA were 80% lower than those observed after the intravenous. Moreover, the slower slope of the concentration–time terminal phase after IA administration vs. intravenous (IV) suggested a flip-flop phenomenon (0.35 h-1 vs. 0.19 h-1). Notably, CP clearances are predictive of the pharmacokinetic (PK) profile of CP in healthy humans (0.14 L/h/5 kg vs. 2.92 L/h/70 kg) although an over-estimation has been detected for cats or dogs (10 times and 4 times, respectively). This fact could probably be attributed to inter-species metabolic differences. In summary, despite the limited number of animals used, this study shows that the rabbit model could be suitable for a predictive evaluation of the release enhancement of CP-NP towards the biophase in arthritic diseases not due to sterical retention of the formulation.
48
Amart Sulong, Muhummad Pu,. « Comparison on Understanding of Facebook’s Live Streams According to Shariah Principles for Thai, Malaysian and Indonesian Online Entrepreneurs ». Psychology and Education Journal 58, no 1 (29 janvier 2021) : 1501–7. http://dx.doi.org/10.17762/pae.v58i1.936.
Texte intégralRésumé :
The fast growth of digital marketing, social media live stream is one of the provided tools for business competitive such as Facebook, Line, and Instagram. In today’s Islamic business is still very much less presented a clear understanding about Shariah principles. Since adoption trend on Facebook’s live stream has exponentially increased and become the main issue on digital marketing for Muslim communities. This research aims to study and compare a clear understanding of Facebook’s live streaming according to Shariah principal for Thai, Malaysian, and Indonesian. This qualitative research used interview form. We primarily focus on online entrepreneurs based on in-depth interview. Data were collected from 6 key informants from Thailand, Malaysia, and Indonesia. These qualitative data was proposed and analyzed using content analysis. Results indicated that: 1) they are mostly less concern with Shariah principles for online marketing because quickly diffusion on today’s technologies. They are just only to gain high profit of the worldwide market size from national and international targets. 2) the lack of understanding Islamic Shariah as adapted principle, where it is applied to conceptual business model for Facebook’s live stream in practical. As a result, the streamers unaware the relative impact to online consumers. 3) In particular, the streamers have a significant relationship to online consumers. They are mainly tended attracting only towards live stream advertisements. Future study is actively to encourage Islamic organization to build a framework or platform to train a new entrepreneur on digital marketing for Facebook’s live stream. Additionally, it also can provide the reliable information to the best support for their enterprise
49
Solomon, Joseph Gbenga. « Antibiotics Resistance, Sensitivity Pattern and Development of Antibiogram to Support Empirical Prescription in Health Facilities in South Senatorial District of Kwara State, Nigeria ». TEXILA INTERNATIONAL JOURNAL OF PUBLIC HEALTH 9, no 3 (30 septembre 2021) : 35–45. http://dx.doi.org/10.21522/tijph.2013.09.03.art004.
Texte intégralRésumé :
A major concern in public health is Antibiotic resistance among pathogenic microorganisms. There are several organisms developing resistance to commonly used antibiotics in different locations and time. This study assessed patterns of antibiotic resistance in line with the WHO classification of antibiotics. A cross-sectional study was carried out from September 2020 to January 2021 in 4 randomly selected hospitals. Of all 442 patients recruited for this study, twenty-seven percent (122) were randomly selected for Antimicrobial Susceptibility Testing using the modified Kirby-Bauer disk diffusion method, and SPSS version 23 was used for analysis. The most predominant isolate was Staphylococcus aureus. Resistance by Staphylococcus aureus was noted against Amoxicillin, Trimethoprim-Sulfamethoxazole, Amoxicillin clavulanic acid, Gentamicin, and Cefuroxime. Resistance by E. coli against Chloramphenicol 80%, cefuroxime 100%, Trimethoprim-Sulfamethoxazole 83.3%, Resistance by Klebsiella spp; against Ampicillin Second and third-generation cephalosporin and Gentamicin 100%. Resistance by Streptococcus spp; Ampicillin 100% and Ampicillin cloxacillin 100%, cefuroxime 100%, and Ciprofloxacin 100%. Ciprofloxacin and levofloxacin were active against Salmonella species, Pseudomonas species, klebsiella, and Escherichia coli. Azithromycin, imipenem, and meropenem with high susceptibility to local bacterial isolates sample tested. The access group antibiotics showed a low susceptibility rate to local bacteria isolate with increase resistance to the watch group. Antibiogram was developed to guide empirical treatment type that is predominant in the district. Most bacteria isolated from health facilities in Kwara South were resistant to the access group. The resistance to watch a group of WHO antibiotics classification is building very fast. Keywords: Antibiotic Resistance, Empirical Treatment, Susceptible.
50
Mehrer, Helmut. « Diffusion and Ion Conduction in Cation-Conducting Oxide Glasses ». Diffusion Foundations 6 (février 2016) : 59–106. http://dx.doi.org/10.4028/www.scientific.net/df.6.59.
Texte intégralRésumé :
In this Chapter we review knowledge about diffusion and cation conduction in oxide glasses. We first remind the reader in Section 1 of major aspects of the glassy state and recall in Section 2 the more common glass families. The diffusive motion in ion-conducting oxide glasses can be studied by several techniques – measurements of radiotracer diffusion, studies of the ionic conductivity by impedance spectroscopy, viscosity studies and pressure dependent studies of tracer diffusion and ion conduction. These methods are briefly reviewed in Section 3. Radiotracer diffusion is element-specific, whereas ionic conduction is not. A comparison of both types of experiments can throw considerable light on the question which type of ions are carriers of ionic conduction. For ionic conductors Haven ratios can be obtained from the tracer diffusivity and the ionic conductivity for those ions which dominate the conductivity.In the following sections we review the diffusive motion of cations in soda-lime silicate glass and in several alkali-oxide glasses based mainly on results from our laboratory published in detail elsewhere, but we also take into account literature data.Section 4 is devoted to two soda-lime silicate glasses, materials which are commonly used for window glass and glass containers. A comparison between ionic conductivity and tracer diffusion of Na and Ca isotopes, using the Nernst-Einstein relation to deduce charge diffusivities, reveals that sodium ions are the carriers of ionic conduction in soda-lime glasses. A comparison with viscosity data on the basis of the Stokes-Einstein relation shows that the SiO2 network is many orders of magnitude less mobile than the relatively fast diffusing modifier cations Na. The Ca ions are less mobile than the Na ions but nevertheless Ca is considerably more mobile than the network.Section 5 summarizes results of ion conduction and tracer diffusion for single Na and single Rb borate glasses. Tracer diffusion and ionic conduction have been studied in single alkali-borate glasses as functions of temperature and pressure. The smaller ion is the faster diffusing species in its own glass. This is a common feature of all alkali oxide glasses. The Haven ratio of Na in Na borate glass is temperature independent whereas the Haven ratio of Rb diffusion in Rb borate glass decreases with decreasing temperature.Section 6 reviews major facts of alkali-oxide glasses with two different alkali ions. Such glasses reveal the so-called mixed-alkali effect. Its major feature is a deep minimum of the conductivity near some middle composition for the ratio of the two alkali ions. Tracer diffusion shows a crossover of the two tracer diffusivities as functions of the relative alkali content near the conductivity minimum. The values of the tracer diffusivities also reveal in which composition range which ions dominate ionic conduction. Tracer diffusion is faster for those alkali ions which dominate the composition of the mixed glass.Section 7 considers the pressure dependence of tracer diffusion and ionic conduction. Activation volumes of tracer diffusion and of charge diffusion are reviewed. By comparison of tracer and charge diffusion the so-called Haven ratios are obtained as functions of temperature, pressure and composition. The Haven ratio of Rb in Rb borate glass decreases with temperature and pressure whereas that of Na in Na borate glass is almost constant.Section 8 summarizes additional common features of alkali-oxide glasses. Activation enthalpies of charge diffusion decrease with decreasing average ion-ion distance. The Haven ratio is unity for large ion-ion distances and decreases with increasing alkali content and hence with decreasing ion-ion distance.Conclusions about the mechanism of diffusion are discussed in Section 9. The Haven ratio near unity at low alkali concentrations can be attributed to interstitial-like diffusion similar to interstitial diffusion in crystals. At higher alkali contents collective, chain-like motions of several ions prevail and lead to a decrease of the Haven ratio. The tracer diffusivities have a pressure dependence which is stronger than that of ionic conductivity. This entails a pressure-dependent Haven ratio, which can be attributed to an increasing degree of collectivity of the ionic jump process with increasing pressure. Monte Carlo simulations showed that the number of ions which participate in collective jump events increases with increasing ion content – i.e. with decreasing average ion-ion distance. For the highest alkali contents up to four ions can be involved in collective motion. Common aspects of the motion process of ions in glasses and of atoms in glassy metals are pointed out. Diffusion in glassy metals also occurs by collective motion of several atoms.Section 10 summarizes the major features of ionic conduction and tracer diffusion and its temperature and pressure dependence of oxide glasses.