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We describe the biodiversity, seasonal variation, and the possible edge effect of Coleoptera found in the canopy of the cloud forest in Tlanchinol in the state of Hidalgo. The coleopterans were collected by means of three fogging events during the dry season and another three during the rainy season in three sites of the forest: the edge, an intermediate, and an internal site. In total, 3,487 coleopterans were collected, belonging to 325 morphospecies from 52 families. The family with the largest number of morphospecies and abundance was Staphylinidae, followed by Curculionidae and Chrysomelidae. Species richness and abundance were higher in the dry season than in the rainy season. The biodiversity analyses, however, suggest that the rainy season showed the highest biodiversity levels, mainly because of the pronounced dominance of some species in the dry season. Species composition was different between the dry and rainy seasons. The internal site showed the lowest biodiversity compared with the intermediate and edge sites. The main edge effect detected was that species composition in the edge site differed from the intermediate and internal sites. Species composition did not differ significantly between the two latter sites. These results suggest that the study zone had a considerable level of biodiversity of Coleoptera and that it was very likely in a well-preserved condition, which supports the findings of another study previously performed in the same site using flight intercept traps.

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This paper describes a model of a forced circulation waterwalls steam generator, derived from first principles. The distributed parameter criteria were applied to the heat transfer process and to the steam production inside the waterwalls. The model is capable of representing swell and shrink effects as well as the condensation-vaporization phenomena that take place inside the waterwall tubes, when large drum steam pressure variations are introduced. The swell and shrink effects are responsible for water displacement from the waterwalls to the drum and from the drum to the waterwalls. Open loop simulated test were produced with the steam pressure disturbance. Closed loop tests, including the models of the drum level and the combustion system and their control systems are presented.

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The degradation of toxic compounds in Sequencing Batch Reactors (SBRs) poses inhibition problems. Time Optimal Control (TOC) methods may be used to avoid such inhibition thus exploiting the maximum capabilities of this class of reactors. Biomass and substrate online measurements, however, are usually unavailable for wastewater applications, so TOC must use only related variables as dissolved oxygen and volume. Although the standard mathematical model to describe the reaction phase of SBRs is good enough for explaining its general behavior in uncontrolled batch mode, better details are needed to model its dynamics when the reactor operates near the maximum degradation rate zone, as when TOC is used. In this paper two improvements to the model are suggested: to include the sensor delay effects and to modify the classical Haldane curve in a piecewise manner. These modifications offer a good solution for a reasonable complexification tradeoff. Additionally, a new way to look at the Haldane K-parameters (micro(o),K(I),K(S)) is described, the S-parameters (micro*,S*,S(m)). These parameters do have a clear physical meaning and, unlike the K-parameters, allow for the statistical treatment to find a single model to fit data from multiple experiments.

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Discontinuous bioreactors may be further optimized for processing inhibitory substrates using a convenient fed-batch mode. To do so the filling rate must be controlled in such a way as to push the reaction rate to its maximum value, by increasing the substrate concentration just up to the point where inhibition begins. However, an exact optimal controller requires measuring several variables (e.g., substrate concentrations in the feed and in the tank) and also good model knowledge (e.g., yield and kinetic parameters), requirements rarely satisfied in real applications. An environmentally important case, that exemplifies all these handicaps, is toxicant wastewater treatment. There the lack of online practical pollutant sensors may allow unforeseen high shock loads to be fed to the bioreactor, causing biomass inhibition that slows down the treatment process and, in extreme cases, even renders the biological process useless. In this work an event-driven time-optimal control (ED-TOC) is proposed to circumvent these limitations. We show how to detect a "there is inhibition" event by using some computable function of the available measurements. This event drives the ED-TOC to stop the filling. Later, by detecting the symmetric event, "there is no inhibition," the ED-TOC may restart the filling. A fill-react cycling then maintains the process safely hovering near its maximum reaction rate, allowing a robust and practically time-optimal operation of the bioreactor. An experimental study case of a wastewater treatment process application is presented. There the dissolved oxygen concentration was used to detect the events needed to drive the controller.

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The operation of a sequencing batch reactor (SBR) exposed to high concentration peaks (shock loads) of a toxic compound (4-chlorophenol, 4CP) was evaluated. Two control strategies based on on-line measurements of the dissolved oxygen concentration were tested. The first strategy, called variable timing control (VTC), detects the end of the reaction period to stop it. In the second control strategy, called observer-based time optimal control (OB-TOC), the automated system tries to maintain the critical specific growth rate by controlling the feed rate, i.e. the maximum growth rate when the substrate is toxic. The system operating under the VTC strategy presented a stable and efficient operation when the acclimated microorganisms (to an initial concentration of 350 mg 4CP/L) were exposed to punctual concentration peaks of 700 mg 4CP/L. A 4CP concentration peak higher than or equal to 1050 mg/L disturbed the system (1 month to recover). A 1400 mg/L peak caused strong inhibition that shut down the metabolic activity of the microorganisms, leading to reactor failure. With the OB-TOC strategy, the system was stable and worked efficiently when punctual concentration peaks of 700, 1050 and 1400 mg 4CP/L were fed. The system controlled by the OB-TOC strategy treated 1400 mg 4CP/L in less than 8h without affecting the operation of the reactor. The conclusion is that the OB-TOC strategy is more efficient than the VTC strategy to control a bioreactor when there are variations of concentrations of toxic organic compounds.

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Combined anaerobic-aerobic processes are a viable alternative for the treatment of xenobiotic compounds that are difficult to treat by traditional processes. The variable nature of the sequencing batch reactors, SBR, systems allows manipulation of the selective pressure on the microorganisms. Then, the activity of the community can be dynamically adjusted to meet changing effluents conditions. To improve the response of the SBR to changing influent conditions, several efforts have been made to automate and control the duration of the sequential phases of the SBR. The objective of this work is to present and discuss the feasibility of the use of the oxidation-reduction potential, ORP, as a control variable for the determination of the anaerobic phase length in an anaerobic-aerobic SBR used to degrade p-nitrophenol, PNP. The control of the anaerobic phase of the anaerobic-aerobic reactor was achieved with software developed at the Institute of Engineering-UNAM. During the anaerobic stage, the PNP is reduced to p-aminophenol, PAP. As a consequence of the compound transformation, there is a change in the oxidation-reduction potential of the culture medium. This change was used to indicate the minimal concentration of PNP and, as a consequence, the maximal PAP concentration. The feasibility of the algorithm for using the variations in the ORP to determine on-line the length of the anaerobic stage in an anaerobic-aerobic process was demonstrated in our laboratory.

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