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141.
Sebastian WöckelAuthor Vitae 《Sensors and actuators. A, Physical》2011,172(1):322-329
This paper discusses a tomographic approach focusing on ultrasonic measurements to monitor liquid multiphase mixtures. Separately a capacitive tomography low-cost setup is regarded. Both sensor arrays aim for the localization of variable phase boundaries and the physical characterisation of spatially distributed phases. Focusing on a real time processing, a reduced number of transducers in combination with a fast linear modelling and direct image reconstruction methods are used. Experimental results of a layered 3-phase-system validate the potential and limits of physical resolution of both approaches. Finally, the prospectively intended data fusion of both approaches is discussed. 相似文献
142.
P. Sebastian T. Quirante V. Ho Kon Tiat Y. Ledoux 《International Journal of Thermal Sciences》2010,49(12):2459-2466
Flash evaporation process is currently developing in the wine industry where it is used for flash-cooling or concentration. The design of flash evaporators is faced with specific constraints and must take into account multiple design objectives. In this paper, the development of a multi-objective optimization method is investigated for the joint optimization of design objectives such as process transportability, environmental efficiency, operative cost or cooling power. The optimization method is based on the aggregation of design objectives through desirability functions and indexes. Desirability functions are suitable for formulating design constraints more precisely than inequality relations and, moreover, the global design model results in an unconstrained optimization problem. However, aggregation methods do make it difficult to compute the global optimum of the design problem. This difficulty has been addressed by developing a distributed genetic algorithm which is not so sensitive to this type of numerical solving difficulty. Another difficulty arises from the weighting method for the aggregation of desirability functions since weight parameters have no physical meaning. This weighting problem is approached through a sensitivity analysis of the weight parameters and by observing their relative influence. 相似文献
143.
Sebastian Mack Andreas WolfAlexandra Walczak Benjamin ThaidigsmannEdgar Allan Wotke Jeffrey J. SpiegelmanRalf Preu Daniel Biro 《Solar Energy Materials & Solar Cells》2011,95(9):2570-2575
Thermal silicon oxides are known to very effectively passivate silicon surfaces. Choosing a water vapor ambient instead of a dry oxygen atmosphere increases the oxidation rate by about one order of magnitude and considerably reduces process time and costs. State of the art pyrox systems produce steam by pyrolysis of hydrogen and oxygen gas. A new approach is the purification of vaporized deionized (DI) water. In this work we present a direct comparison of both steam generation systems, which are connected to the same quartz tube of an industrial high quality tube furnace. The higher steam saturation of the direct steam process enhances the growth rate by about 20% compared to a pyrolytic steam based process. On low-resistivity p-type substrates, excellent surface recombination velocities of around 25 cm/s are found for both systems after a forming gas anneal. Detailed characterization shows similar physical properties of the oxide layers grown by either steam from pyrolysis or purified steam. Moreover, thermal oxide rear surface passivated silicon solar cells show similar high efficiencies exceeding 18.0% irrespective of the applied steam generation technology. 相似文献
144.
145.
Sorption behavior of nonylphenol in terrestrial soils 总被引:1,自引:0,他引:1
Nonylphenol (NP) as an intermediate from anaerobic degradation of widely used nonionic surfactants occurs widespread in the environment. Partition behavior of this toxic and endocrine-disrupting chemical between soil and water was not examined until yet. The objective of this investigation was to quantify sorption and desorption behavior of 4-nonyl[14C]phenol in a set of 51 soils using the batch equilibrium approach. Kinetic studies indicated apparent equilibrium within 20 h. Sorption was influenced by sorbate structure as could be shown with branched 4-nonyl[14C]phenol and the linear 4-n-NP, respectively. Linear 4-n-NP behaves differently from the branched isomers of 4-NP. Sorption of 4-nonyl[14C]phenol tested with five different initial concentrations resulted in linearly fitted isotherms that provided calculation of sorption partition coefficients (KP). Desorption partition coefficients (KP-des) revealed hysteresis independent of soil properties but decreasing with decreasing initial NP concentrations. KP values were correlated with organic carbon content of the soils yielding a log KOC of 3.97. 相似文献
146.
Nanoporous materials 总被引:1,自引:0,他引:1
147.
Winner-take-all networks have been proposed to underlie many of the brain's fundamental computational abilities. However, not much is known about how to extend the grouping of potential winners in these networks beyond single neuron or uniformly arranged groups of neurons. We show that competition between arbitrary groups of neurons can be realized by organizing lateral inhibition in linear threshold networks. Given a collection of potentially overlapping groups (with the exception of some degenerate cases), the lateral inhibition results in network dynamics such that any permitted set of neurons that can be coactivated by some input at a stable steady state is contained in one of the groups. The information about the input is preserved in this operation. The activity level of a neuron in a permitted set corresponds to its stimulus strength, amplified by some constant. Sets of neurons that are not part of a group cannot be coactivated by any input at a stable steady state. We analyze the storage capacity of such a network for random groups--the number of random groups the network can store as permitted sets without creating too many spurious ones. In this framework, we calculate the optimal sparsity of the groups (maximizing group entropy). We find that for dense inputs, the optimal sparsity is unphysiologically small. However, when the inputs and the groups are equally sparse, we derive a more plausible optimal sparsity. We believe our results are the first steps toward attractor theories in hybrid analog-digital networks. 相似文献
148.
Simplified protein models are used for investigating general properties of proteins and principles of protein folding. Furthermore,
they are suited for hierarchical approaches to protein structure prediction. A well known protein model is the HP-model of
Lau and Dill [Lau, K. F., & Dill, K. A. (1989)]. A lattice statistical mechanics model of the conformational and sequence
spaces of proteins. Macromolecules, 22, 3986–3997) which models the important aspect of hydrophobicity. One can define the HP-model for various lattices, among
them two-dimensional and three-dimensional ones. Here, we investigate the three-dimensional case. The main motivation for
studying simplified protein models is to be able to predict model structures much more quickly and more accurately than is
possible for real proteins. However, up to now there was a dilemma: the algorithmically tractable, simple protein models can
not model real protein structures with good quality and introduce strong artifacts.
We present a constraint-based method that largely improves this situation. It outperforms all existing approaches for lattice
protein folding in HP-models. This approach is the first one that can be applied to two three-dimensional lattices, namely
the cubic lattice and the face-centered-cubic (FCC) lattice. Moreover, it is the only exact method for the FCC lattice. The ability to use the FCC lattice is a significant
improvement over the cubic lattice. The key to our approach is the ability to compute maximally compact sets of points (used
as hydrophobic cores), which we accomplish for the first time for the FCC lattice. 相似文献
149.
Sebastian Fischer Harald Beyer Ralf Janke Stefan Hartwig Jürgen Wilde 《Microsystem Technologies》2006,12(10-11):1005-1009
Due to the piezoresistive and the piezo-Hall effect in semiconductor materials, Hall sensors show a strong temperature dependency and also a drift when subjected to temperature cycles Manic et al. (2000). Four factors mainly influence the mechanical stress in the sensitive layer. These are the geometry of the device, the differences of the coefficients of thermal expansion of the package materials, the temperature-dependent material properties and the time-dependent, viscous material properties. The objective of this investigation was to determine the mechanical stress in a moulded Hall sensor during the packaging process by finite-element simulation in comparison to experimental methods. It is shown that after each process-step the mechanical stress in the sensitive layer changes over time depending on the absolute value and the rate of the temperature change. Measurements of the inverse bending radius of glued and moulded chips show good agreement to the simulations. 相似文献
150.
Chien‐Hui Wen Sebastian Gauza Shin‐Tson Wu 《Journal of the Society for Information Display》2005,13(9):805-811
Abstract— Photostability of liquid‐crystal (LC) materials and surface alignment layers was evaluated using a UV lamp and a blue laser beam. Both organic polyimide (PI) and inorganic silicon‐dioxide (SiO2) alignment layers were studied under nitrogen environment. Two commercial TFT‐grade LC mixtures (low‐birefringence MLC‐9200‐000 and high‐birefringence TL‐216) were used for comparisons. Results indicate that SiO2 alignment layers are much more robust than PI layers, and low birefringence LCs are more stable than the high‐birefringence ones. At the He‐Cd laser wavelength (λ = 442 nm), both LC mixtures and SiO2 alignment layers are hardly damaged. To lengthen the lifetime of an LCD projector, inorganic SiO2 alignment layers, high‐optical‐density UV filter, long cutoff‐wavelength blue filter, and short‐conjugation (low birefringence) LC materials should be considered. 相似文献