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Amornchai Arpornwichanop Natthapong Shomchoam 《Korean Journal of Chemical Engineering》2007,24(1):11-15
Fed-batch operation of fermentation processes has been receiving a great deal of interest as it offers the possibility to
control a substrate concentration at a desired condition. However, control of a fed-batch fermentation reactor has been known
to be a difficult task due to its highly nonlinear and complicated behavior. This work addresses an optimization-based control
strategy for a fed-batch bioreactor where an ethanol fermentation process is chosen as a case study. The optimal control problem
is formulated to determine the optimal feeding rate policy giving the highest product yield. The resulting optimization problem
is solved by using an efficient sequential approach with a piecewise constant control parameterization. Due to the limitation
of the sequential approach to cope with inequality path constraints, comparative studies of the methods for handling such
constraints are carried out. Furthermore, the impact of time interval and switching time on the solution of the optimal control
is investigated. 相似文献
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Natthapong Pongpichayakul Suwaphid Themsirimongkon Suphitsara Maturost Kanlayawat Wangkawong Li Fang Burapat Inceesungvorn Paralee Waenkaew Surin Saipanya 《International Journal of Hydrogen Energy》2021,46(3):2905-2916
Catalyst composites based on Pt and CeO2 on carbon for methanol oxidation were successively prepared for application in direct-methanol fuel cells (DMFCs). In this work, the catalyst was modified by decoration of CeO2 onto several carbons, including carbon black (CB), carbon nanotubes (CNT), graphene oxide (GO), reduced graphene oxide (rGO) and mixed carbons, followed by the electrochemical deposition of Pt. The dispersal of CeO2 and Pt nanoparticles onto the carbon surfaces was confirmed with a face-centred cubic structure. The use of single and mixed carbons takes admirable advantage of the coexisting CeO2 and Pt nanoparticles, confirming the positive effect of various carbon structures for electrocatalytic enhancement towards methanol oxidation. The CeO2 also improves the ability for CO oxidation, resulting in a reduction of CO poisoning. The outcomes show an enhancement of the activity and stability so that such alternative as-prepared materials can be introduced to improve the anodic oxidation in DMFCs. 相似文献
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Natthapong Pongpichayakul Kanlayawat Wangkawong Paralee Waenkaew Li Fang Burapat Inceesungvorn Jaroon Jakmunee Surin Saipanya 《International Journal of Hydrogen Energy》2021,46(46):23682-23693
Electrocatalytic preparation of Pt-based nanocomposites has been investigated for improvement of direct ethanol fuel cells (DEFCs). In this study, new alternative catalysts of Pt-decorated cerium zirconium oxide-modified multiwalled carbon nanotubes (Pt/CeZrO4/MCNT) were successively prepared to improve the activity of the ethanol oxidation reaction (EOR). The prepared CeZrO4 with a face-centered cubic (fcc) structure compatibly dispersed onto MCNT provides abundant active Pt sites for highly active catalysts. The fcc-structured Pt was also satisfactorily decorated onto CeZrO4/MCNT, resulting in highly active Pt. The Ce4+/Ce3+ redox property can promote oxygen vacancies to improve the electrochemical activity for oxidation of carbonaceous species. An increase in roughness and a stabilized catalyst structure can also be produced by inserting Zr4+ into the ceria metal oxide. The prepared Pt/20%CeZrO4/MCNT catalysts present excellent electrochemical active surface area, mass activity, CO tolerance and high electron kinetic transfer with low resistance and high stability over commercial PtRu/C toward EOR. This promising catalyst material could be introduced to enhance the anodic oxidation reaction in DEFCs. 相似文献
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Natthapong Sueviriyapan Daniel Granados-Fuentes Tatiana Simon Erik D. Herzog Michael A. Henson 《Journal of the Royal Society Interface》2021,18(182)
In the suprachiasmatic nucleus (SCN), γ-aminobutyric acid (GABA) is a primary neurotransmitter. GABA can signal through two types of GABAA receptor subunits, often referred to as synaptic GABAA (gamma subunit) and extra-synaptic GABAA (delta subunit). To test the functional roles of these distinct GABAA in regulating circadian rhythms, we developed a multicellular SCN model where we could separately compare the effects of manipulating GABA neurotransmitter or receptor dynamics. Our model predicted that blocking GABA signalling modestly increased synchrony among circadian cells, consistent with published SCN pharmacology. Conversely, the model predicted that lowering GABAA receptor density reduced firing rate, circadian cell fraction, amplitude and synchrony among individual neurons. When we tested these predictions, we found that the knockdown of delta GABAA reduced the amplitude and synchrony of clock gene expression among cells in SCN explants. The model further predicted that increasing gamma GABAA densities could enhance synchrony, as opposed to increasing delta GABAA densities. Overall, our model reveals how blocking GABAA receptors can modestly increase synchrony, while increasing the relative density of gamma over delta subunits can dramatically increase synchrony. We hypothesize that increased gamma GABAA density in the winter could underlie the tighter phase relationships among SCN cells. 相似文献
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