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showing 10 items of 3014 documents
CFD Simulation of Particle Distribution in a Multiple-impeller High-Aspect-Ratio Stirred Vessel
2000
Publisher Summary This chapter describes fully predictive simulations of solid–liquid suspensions in a high-aspect-ratio, multiple-impeller stirred tank. These are performed by using the Inner Outer impeller modeling technique coupled with the Multi Fluid Model (MFM) for the treatment of the dispersed phase. The strongly simplified Settling Velocity Model (SVM) is also tested. The effects of free-stream turbulence on the drag coefficient CD and particle settling velocity are accounted for by means of a recently proposed correlation. Comparison of simulation results with experimental particle concentration profiles shows that the MFM approach leads to fair agreement with experimental data. R…
Second-harmonic generation in surface periodically poled lithium niobate waveguides:On the role of multiphoton absorption
2008
Second harmonic generation is investigated in lithium niobate channels realized by proton exchange and quasi-phase-matched by surface periodic-poling. The reduction in conversion efficiency at high powers is interpreted in terms of multi-photon absorption via two-color terms, yielding an estimate of the dominating three-photon process.
Bridging scales with thermodynamics: from nano to macro
2014
We have recently developed a method to calculate thermodynamic properties of macroscopic systems by extrapolating properties of systems of molecular dimensions. Appropriate scaling laws for small systems were derived using the method for small systems thermodynamics of Hill, considering surface and nook energies in small systems of varying sizes. Given certain conditions, Hill's method provides the same systematic basis for small systems as conventional thermodynamics does for large systems. We show how the method can be used to compute thermodynamic data for the macroscopic limit from knowledge of fluctuations in the small system. The rapid and precise method offers an alternative to curre…
Scanning from heating: 3D shape estimation of transparent objects from local surface heating.
2009
Today, with quality becoming increasingly important, each product requires three-dimensional in-line quality control. On the other hand, the 3D reconstruction of transparent objects is a very difficult problem in computer vision due to transparency and specularity of the surface. This paper proposes a new method, called Scanning From Heating (SFH), to determine the surface shape of transparent objects using laser surface heating and thermal imaging. Furthermore, the application to transparent glass is discussed and results on different surface shapes are presented.
Quantifying the limits of transition state theory in enzymatic catalysis
2017
Significance Transition state theory (TST) is the most popular theory to calculate the rates of enzymatic reactions. However, in some cases TST could fail due to the violation of the nonrecrossing hypothesis at the transition state. In the present work we show that even for one of the most controversial enzymatic reactions—the hydride transfer catalyzed by dihydrofolate reductase—the error associated to TST represents only a minor correction to the reaction rate. Moreover, this error is actually larger for the reaction in solution than in the enzymatic active site. Based on this finding and on previous studies we propose an “enzymatic shielding” hypothesis which encompasses various aspects …
The coupling of the electrostatic potential with the transport and adsorption mechanisms in ion-exchange chromatography systems: Theory and experimen…
2005
The coupling of the constitutive expression for the electrostatic potential as specified through Poisson's equation together with the constitutive equations for the mechanisms of convection, diffusion, electrophoretic migration, and adsorption provides the necessary set of constitutive expressions to be employed in the material balance equations of ion-exchange chromatography systems to construct macroscopic continuum models that could be used to design and simulate the dynamic behavior of systems involving a single charged adsorbate or multiple charged adsorbates. A physically relevant and consistent macroscopic continuum model that can predict, as has been observed experimentally by UV co…
Thermal Flux through a Surface of n-Octane. A Non-equilibrium Molecular Dynamics Study
2004
We show using non-equilibrium molecular dynamics that there is local equilibrium in the surface when a two-phase fluid of n-octane is exposed to a large temperature gradient (10 8 K/m). The surface is defined according to Gibbs, and the transport across the surface is described with non-equilibrium thermodynamics. The structure of the surface in the presence of the gradient is the same as if the interface was in equilibrium, as measured by the variation across the surface of the pressure component that is parallel to the surface. The surface is in local equilibrium by this criterion and because the equation of state for the surface was unaltered by a large heat flux. The surface has a small…
Backcasting for desirable futures in Finnish forest-based firms
2020
Purpose In Finland, new forest-based sector (FBS) businesses are seen as important for the transition to the circular bioeconomy. The purpose of this study is to explore the transition of Finnish FBS companies to new business models. The aim is to understand how FBS companies define their ideal future states and related business models for the year 2030. Design/methodology/approach This study uses thematic interviews with managers from various FBS firms and companies from interfacing sectors. In the interviews, the key idea of backcasting was pursued when respondents discussed the desirable future states of their business. Findings The effort to achieve growth of the business and the appea…
Managing Sustainability with Eco-Business Intelligence Instruments
2014
Abstract In response to increasing concerns of society about environmental degradation and increasing demands for a transition to a more sustainable society, the business companies are increasingly active in aligning their processes and services with a sustainability agenda. Production, distribution and supply of goods and services require material and energy consumption, having an impact on natural resources both quantitatively and qualitatively, generating waste, pollution and disrupting ecosystems. Ecobusiness intelligence is the capacity of people, processes and applications/tools to organize business information, to facilitate consistent access to them and analyse them in order to impr…
Liberalising European electricity markets: opportunities and risks for a sustainable power sector
2003
The process of liberalising European electricity markets, encompassing a wide range of restructuring activities, has mainly been spurred by the attempt to increase the economic efficiency of the whole sector. This process might be used to trigger a development towards a sustainable power sector by increasing the use of renewable energy sources and enhancing energy efficiency on the supply and demand side. However, by taking a closer look at the current trends of the European electricity markets, it becomes obvious that the liberalisation not only implies opportunities but also risks for the creation of a sustainable power sector. Many of these risks are due to market distortions and imperfe…