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71.
72.
Beatriz López-Walle Michaël Gauthier Nicolas Chaillet 《International Journal of Thermal Sciences》2010,49(11):2108-2116
Thermal actuators are extensively used in microelectromechanical systems (MEMS). Heat transfer through and around these microstructures are very complex. Knowing and controlling them in order to improve the performance of the micro-actuator, is currently a great challenge. This paper deals with this topic and proposes a dynamic thermal modelling of thermal micro-actuators. Thermal problems may be modelled using electrical analogy. However, current equivalent electrical models (thermal networks) are generally obtained considering only heat transfers through the thickness of structures having considerable height and length in relation to width (walls). These models cannot be directly applied to micro-actuators. In fact, micro-actuator configurations are based on 3D beam structures, and heat transfers occur through and around length. New dynamic and static thermal networks are then proposed in this paper. The validities of both types of thermal networks have been studied. They are successfully validated by comparison with finite elements simulation and analytical calculations. 相似文献
73.
Glaucia M. F. Aragao Maria G. Corradini Micha Peleg 《Journal of the American Oil Chemists' Society》2008,85(12):1143-1153
During isothermal lipid oxidation at relatively high temperatures, the peroxide concentration frequently peaks while at relatively
low temperatures it only rises slowly. These are two manifestations of a process where formation and degradation happen simultaneously
on different time scales. A phenomenological mathematical model, comprising a decay factor superimposed on an accumulation
term can describe these scenarios. Each has a characteristic time constant shortened by raising the temperature and a rate
constant that increases with it. The model’s mathematical structure and the magnitude of its coefficients depend on the particular
system. However, regardless of the chosen expressions, if the degradation characteristic time falls within or just beyond
the experiment’s duration, a peak peroxide value will be observed whose height and shape will primarily depend on the other
model’s parameters. If this characteristic time is far outside the time of the experiment , no peak will be recorded. The
model need not be unique and no detailed knowledge of the oxidation mechanisms is required for its formulation. Consequently
it can be derived directly from experimental peroxide value versus time relationships, without the need to monitor the intermediate
reactions by specialized instrumental methods such as DSC. Through the formation term adjustment, the model can also account
for the temperature dependent lag in the rise of the peroxide value and/or the appearance of its peak. 相似文献
74.
Osvaldo H Campanella Micha Peleg 《Journal of the science of food and agriculture》2001,81(11):1069-1076
When published isothermal survival data of Clostridium botulinum spores in the range 101–121 °C were plotted in the form of logS(t) vs t relationships, where S(t) is the momentary survival ratio, they were all non‐linear. They had a noticeable upward concavity, in violation of the assumption that sporal inactivation is a process that follows first‐order reaction order kinetics. They could be described by the power law model logS(t) = ? b(T)t n(T), where b(T) and n(T) are temperature‐dependent coefficients of the order of 0.1–6 and about 0.4 respectively. These coefficients were used to construct simulated survival curves under different heating regimes with a recently proposed model. The model is based on the assumption that the local slope of the non‐isothermal survival curve, or the momentary inactivation rate, is determined solely by the momentary temperature and survival ratio, which in turn are functions of the population thermal history. The survival curves calculated with this model differ considerably from those produced by the standard method based on the traditional D and Z values. The shortcomings of the standard model are that these values depend on the number of points taken for the regression, and that its predicted survival ratios depend on the selected reference temperature. The differential equation which is proposed to replace it can be solved numerically using a program such as Mathematica®. Its predictions solely depend on the observed survival patterns under isothermal conditions and not on any preconceived kinetic model. Nevertheless, the method still needs verification with experimental non‐isothermal survival data, as has already been done with Listeria and Salmonella cells. © 2001 Society of Chemical Industry 相似文献
75.
Marcin Wierszycki Krzysztof Szajek Tomasz Łodygowski Michał Nowak 《Computational Mechanics》2014,54(2):287-298
In this paper the numerical implementation of two-scale modelling of bone microstructure is presented. The study is a part of long-term project on bone remodelling which drives bone microstructure change based directly on trabeculae surface energy. The proposed approach is based on a first-order computational homogenization technique. The coincidence of macro- and micro-model kinematics is done with the use of uniform displacement and traction boundary conditions. The computational homogenization procedure is driven by a self-prepared manager which is coded in Python. The computation on real bone structure (a piece of female Wistar rat bone) is performed as well. 相似文献
76.
77.
78.
Micha? Zaborowski Daniel Tomaszewski Piotr Dumania Piotr Grabiec 《Microelectronics Reliability》2011,51(7):1162-1165
Development of Si nanowire-based FETs, suitable for sensor applications is reported. Process sequences for SOI and bulk p-channel FinFETs are described. SEM observations of the fabricated devices (180 nm wide, 87 nm or 175 nm high) are presented and discussed. Electrical characteristics measurements and basic characterisation results obtained for these devices are described. A procedure for serial resistance extraction has been mentioned in more detail, due to its high value inherent in the process used. Several aspects of the device sensitivity to front- and back-gate control have been discussed from the point of view of its application in biochemical detectors. 相似文献
79.
Michał Tadeusiewicz Stanisław Hałgas 《International Journal of Circuit Theory and Applications》2010,38(3):275-290
The paper offers an efficient method for simulation of multiple catastrophic faults in linear AC circuits. The faulty elements are either open circuits or short circuits. The method exploits the well‐known Householder formula in matrix theory to find the node voltages deviations due to the perturbations of some circuit elements. The main achievement of the paper is a systematic method for performing the simulation of all combinations of the multiple catastrophic faults. The method includes two new procedures enabling us to find very efficiently the node impedance matrix of the nominal circuit and inverses of some matrices corresponding to different fault combinations. The procedures are the crucial point of this approach and make it very efficient. Consequently, the amount of the computing power needed to carry out all the simulations is significantly reduced. Numerical examples illustrating the proposed approach are provided. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
80.
VM12-SHC steel is the newest grade of 12% Cr steel developed by the V&M company. At the present moment, there are works being conducted in order to make use of this steel in steam superheaters. It is also planned to implement VM12-SHC steel to the fabrication of water-walls for prototype boilers operated at very high temperature and pressure parameters. In this article, test materials and welding consumbables are characterized and the process of preparation of pipes to be welded is discussed. The results of metallographic examination and mechanical testing of the test joints are presented. 相似文献