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71.
A critical analysis is presented of the use of an overall single rate reaction equation instead of the true rate equation
corresponding to a complex process consisting of two consecutive reactions. In accordance with this approximation, which is
often used in the kinetic analysis of systems in which several reactions take place, the overall process is described by apparent
activation parameters (the apparent activation energy Eap and the apparent pre-exponential factor Aap) and an apparent conversion function.
The theoretical isotherms (α=α(t), where α is the conversion degree and t is time) were simulated for a system in which two
consecutive reactions occur. In this case, the apparent activation parameters depend on (a) the considered range of temperature;
and (b) the temperature for a given conversion degree. It is shown that the apparent activation parameters are correlated
by the compensation effect relationship: ln Aap = α* + β*Eap where α* and β* are the linear regression parameters.
The possibility of using the apparent kinetic parameters to predict the isotherms α=α(t) for temperatures lower than those
for which these parameters were evaluated is discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
72.
Alla Zablotskaya Izolda Segal Mikhail Maiorov Elmars Blums Ilona Domracheva 《Journal of magnetism and magnetic materials》2009,321(10):1428-1432
We present the results of the interaction of iron oxide nanoparticles with some biologically active surfactants, namely, oleic acid and cytotoxic alkanolamine derivatives. Physico-chemical properties, as magnetization, magnetite concentration and particle diameter, of the prepared magnetic samples were studied. The nanoparticle size of 11 nm for toluene magnetic fluid determined by TEM is in good agreement with the data obtained by the method of magnetogranulometry. In vitro cytotoxic effect of water-soluble nanoparticles with different iron oxide:oleic acid molar ratio were revealed against human fibrosarcoma and mouse hepatoma cells. In vivo results using a sarcoma mouse model showed observable antitumor action. 相似文献
73.
We use techniques from homotopy theory, in particular the connection between configuration spaces and iterated loop spaces,
to give geometric explanations of stability results for the cohomology of the varieties of regular semisimple elements in
the simple complex Lie algebras of classical type A, B or C, as well as in the group . We show that the cohomology spaces of stable versions of these varieties have an algebraic stucture, which identifies them
as “free Poisson algebras” with suitable degree shifts. Using this, we are able to give explicit formulae for the corresponding
Poincaré series, which lead to power series identities by comparison with earlier work. The cases of type B and C involve ideas from equivariant homotopy theory. Our results may be interpreted in terms of the actions of a Weyl group on
its coinvariant algebra (i.e. the coordinate ring of the affine space on which it acts, modulo the invariants of positive
degree; this space coincides with the cohomology ring of the flag variety of the associated Lie group) and on the cohomology
of its associated complex discriminant variety.
Received August 31, 1998; in final form August 1, 1999 / Published online October 30, 2000 相似文献
74.
Hydrogen gas is burned in air to raise and maintain the stagnation temperature of a supersonic combustion test facility to
a desired setpoint. In order to reach the desired operating conditions for stagnation temperature, there are three phases
to the hydrogen control; H2 ignition at facility start-up, H2 ramp-up while the facility is ramped-up, and H2 iteration to achieve the desired temperature setpoint. Each phase incorporates a different type of control. Fuzzy logic is
used to design a computer based supervisory controller that recognizes the different phases of operation and chooses the appropriate
control method.
Received: 28 November 1999/Accepted: 2 November 2000 相似文献
75.
76.
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78.
Yehuda Ben-Shimol Boaz Ben-Moshe Yoav Ben-Yehezkel Amit Dvir Michael Segal 《Journal of Heuristics》2007,13(3):243-263
This article addresses a real-life problem - obtaining communication links between multiple base station sites, by positioning
a minimal set of fixed-access relay antenna sites on a given terrain. Reducing the number of relay antenna sites is considered
critical due to substantial installation and maintenance costs. Despite the significant cost saved by eliminating even a single
antenna site, an inefficient manual approach is employed due to the computational complexity of the problem. From the theoretical
point of view we show that this problem is not only NP hard, but also does not have a constant approximation. In this paper
we suggest several alternative automated heuristics, relying on terrain preprocessing to find educated potential points for
positioning relay stations. A large-scale computer-based experiment consisting of approximately 7,000 different scenarios
was conducted. The quality of alternative solutions was compared by isolating and displaying factors that were found to affect
the standard deviation of the solutions supplied by the tested heuristics. The results of the simulation based experiments
show that the saving potential increases when more base stations are needed to be interconnected. The designs of a human expert
were compared to the automatically generated solutions for a small subset of the experiment scenarios. Our studies indicate
that for small networks (e.g., connecting up to ten base stations), the results obtained by human experts are adequate although
they rarely exceed the quality of automated alternatives. However, the process of obtaining these results in comparison to
automated heuristics is longer. In addition, when more base station sites need to be interconnected, the human approach is
easily outperformed by our heuristics, both in terms of better results (fewer antennas) and in significant shorter calculation
times. 相似文献
79.
80.
A simple procedure to obtain the derivative of the temperature integral with respect to the activation energy is presented. 相似文献