392 research outputs found
A compartmental model of anaerobic digester for improved description of the process performance
Understanding anaerobic digester (AD) performance relates to the complex interplay between hydrodynamics and kinetics. The latter is not straightforward and has been tackled by means of models. However, the computational burden to run such a model in a dynamic way is still too large. Here, a simplified compartmental model (CM) is derived from a CFD model (hydrodynamics). Compatibility of the CM and CFD model was tested by comparing the RTD curve of a virtual pulse tracer test. Subsequently, the CM was integrated with ADM1 in each compartment and the steady state performance was compared with that of a CSTR model with ADM1
Investigation of the ice nucleation properties of dust collected in northwest Greenland
第6回極域科学シンポジウム[OM] 極域気水圏11月16日(月) 統計数理研究所 セミナー室2(D304
Aging of the Zero-Field-Cooled Magnetization in Ising Spin Glasses: Experiment and Numerical Simulation
A new protocol of the zero-field-cooled (ZFC) magnetization process is
studied experimentally on an Ising spin-glass (SG)
FeMnTiO and numerically on the Edwards-Anderson Ising SG
model. Although the time scales differ very much between the experiment and the
simulation, the behavior of the ZFC magnetization observed in the two systems
can be interpreted by means of a common scaling expression based on the droplet
picture. The results strongly suggest that the SG coherence length, or the mean
size of droplet excitations, involved even in the experimental ZFC process, is
about a hundred lattice distances or less.Comment: 4 pages, 5 fugure
Linking CFD and kinetic models in anaerobic digestion using a compartmental model approach
Understanding mixing behavior and its impact on conversion processes is essential for the operational stability and conversion efficiency of anaerobic digestion (AD). Mathematical modelling is a powerful tool to achieve this. Direct linkage of Computational Fluid Dynamics (CFD) and the kinetic model is, however, computationally expensive, given the stiffness of the kinetic model. Therefore, this paper proposes a compartmental model (CM) approach, which is derived from a converged CFD solution to understand the performance of AD under non-ideal mixing conditions and with spatial variation of substrates, biomass, pH, and specific biogas and methane production. To quantify the effect of non-uniformity on the reactor performance, the CM implements the Anaerobic Digestion Model 1 (ADM1) in each compartment. It is demonstrated that the performance and spatial variation of the biochemical process in a CM are significantly different from a continuously stirred tank reactor (CSTR) assumption. Hence, the assumption of complete mixed conditions needs attention concerning the AD performance prediction and biochemical process non-uniformities
Detailed Measurements of Characteristic Profiles of Magnetic Diffuse Scattering in ErBC
Detailed neutron diffraction measurements on a single crystalline
ErBC were performed. We observed magnetic diffuse scattering which
consists of three components just above the transition temperatures, which is
also observed in characteristic antiferroquadrupolar ordering compounds
HoBC and TbBC. The result of this experiments indicates that
the antiferroquadrupolar interaction is not dominantly important as a origin of
the magnetic diffuse scattering.Comment: 5 pages, 5 figures, submitted to J. Phys. Soc. Jp
Partial integration of ADM1 into CFD : understanding the impact of diffusion on anaerobic digestion mixing
Sufficient mixing is crucial for the proper performance of anaerobic digestion (AD), creating a homogeneous distribution of soluble substrates, biomass, pH, and temperature. The opaqueness of the sludge and mode of operation make it challenging to study AD mixing experimentally. Therefore, hydrodynamics modelling employing computational fluid dynamics (CFD) is often used to investigate this mixing. However, CFD models mostly do not include biochemical reactions and, hence, ignore the effect of diffusion-induced transport on AD heterogeneity. The novelty of this work is the partial integration of Anaerobic Digestion Model no. 1 (ADM1) into the CFD model. The aim is to better understand the effect of advection–diffusion transport on the homogenization of soluble substrates and biomass. Furthermore, AD homogeneity analysis in terms of concentration distribution is proposed rather than the traditional velocity distributions. The computed results indicate that including diffusion-induced transport affects the homogeneity of AD
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