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In certain regions of operating conditions, chemical reactors may exhibit parametric sensitivity; i.e., small changes in one
or more of the reactor input parameters lead to much larger changes in the output variables. Since such behaviour leads to
deleterious performance, it is of practical interest to identify regions of parametric sensitivity in the reactor parameter
space. Until recently, this could be done only to describe thermal runaway, and only for those systems where a temperature
profile could be defined. Both of these limitations can be removed by consideringthe generalized criterion for parametric sensitivity, whereby sensitivity ofany output of the model toany input can be treated. Applications of the generalized criterion are discussed, with specific examples including pseudohomogeneous
and heterogeneous model tubular reactors, a nonisothermal CSTR, and a polymerization reactor.
Dedicated to Dr L K Doraiswamy — Gentleman, Scholar, Friend — on his sixtieth birthday. 相似文献
145.
We developed a photochemical method for the online oxidation of p-hydroxymercurybenzoate (PHMB), an organic mercury species widely used for mercaptan and thiolic compound labeling. The method is based on a fully integrated online UV/microwave (MW) photochemical reactor for the digestion of PHMB, followed by cold vapor generation atomic fluorescence spectrometry (CVG-AFS) detection. The MW/UV process led to the quantitative conversion of PHMB and thiol-PHMB complexes to Hg(II), with a yield between 91% and 98%, without using chemical oxidizing reagents and avoiding the use of toxic carcinogenic compounds. This reaction was followed by the reduction of Hg(II) to Hg(0), performed in a knitted reaction coil with NaBH(4) solution, and AFS detection in an Ar/H(2) miniaturized flame. The low MW power applied (18 W) allowed us to keep constant the temperature of the photochemical reactor (21 ± 1 °C), using a flowing water bath. This avoided peak widening due to diffusion processes generally occurring at high temperatures and in the additional cooling coil. This method has been applied to the determination of thiols in human plasma, blood, and wine. 相似文献
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147.
New Approach to Water Distribution Network Calibration 总被引:1,自引:0,他引:1
A new approach is proposed for calibrating hydraulic network models. This procedure uses a nonlinear optimization algorithm along with a standard, off-the-shelf, network solver. Pipe roughness is adjusted until simulation results agree with the values observed in the field. To achieve realistic calibrated roughness values, the objective is to minimize the sum of the squares of the differences between the calibrated and initial pipe roughness estimates, under a set of constraints determined from a sensitivity matrix. The algorithm is applied to a sample network, and the resulting calibrated network is tested under different loading conditions. 相似文献
148.
Connections for composite concrete slab and LVL flooring systems 总被引:1,自引:1,他引:0
Composite concrete slab and timber flooring systems are commonly used in many parts of the world to exploit the high strength-to-weight
ratio of timber and the good acoustic separation provided by concrete floor slabs. This paper describes the results of an
experimental programme that investigated the suitability of a range of connectors to transfer shear between a concrete slab
and a laminated veneer lumber (LVL) beam. Shear tests on reduced scale specimens were performed with the aim of comparing
the strength, stiffness, and post-peak performance of different connectors such as round and rectangular concrete plugs with
and without screw and steel pipe reinforcement, proprietary (SFS) screws, coach screws with different diameters, sheet brace
anchors, and framing brackets. The rectangular concrete plug reinforced with a coach screw was found to provide the greatest
stiffness and strength, as well as favourable post-peak behaviour. Such a system can be used for cost-effective composite
floor systems due to its efficient cost-to-capacity ratio, which reduces the number of connectors needed along the beam axis
to achieve the composite action. 相似文献
149.
The scope for diffusion of very low-enthalpy geothermal plants in the Piemonte region of Italy, using groundwater heat pumps (GWHP), was analyzed to check environmental sustainability and the benefits in terms of reducing greenhouse gas emissions from fossil fuels. GWHP implementation seemed particularly suitable to the specific characteristics of the Piemonte plain. An important thick and productive shallow aquifer is present across the entire plain beneath the major energy users and is therefore appropriate for geothermal energy development purposes. The building stock could be adapted to heat pumps in different ways, but objective-oriented policies will be required to reach the best results in terms of environmental benefits. 相似文献
150.
Cristiano Nicolella Antonio Bertei Massimo Viviani Antonio Barbucci 《Journal of Applied Electrochemistry》2009,39(4):503-511
This paper presents a mathematical model of mass and charge transport and electrochemical reaction in porous composite cathodes
for application in solid oxide fuel cells. The model describes a porous composite cathode as a continuum, and characterises
charge and mass transfer and electrochemical kinetics using effective parameters (i.e. conductivity, diffusivity, exchange
current) related to morphology and material properties by percolation theory. The model accounts for the distribution of morphological
properties (i.e. porosity, tortuosity, density of contacts among particles) along cathode thickness, as experimentally observed
on scanning electron microscope images of LSM/YSZ cathodes of varying thickness. This feature allows the model to reproduce
the dependence of polarisation resistance on thickness, as determined by impedance spectroscopy on LSM/YSZ cathodes of varying
thickness. Polarisation resistance in these cathodes is almost constant for thin cathodes (up to 10 μm thickness), it sharply
decreases for intermediate thickness, to reach a minimum value for about 50 μm thickness, then it slightly increases in thicker
cathodes. 相似文献