93 research outputs found
Minimal positive realizations for a class of transfer functions
It is a standard result in linear-system theory that an nth-order rational transfer function of a single-input single-output system always admits a realization of order n. In some applications, however, one is restricted to realizations with nonnegative entries (i.e. a positive system), and it is known that this restriction may force the order N of realizations to be strictly larger than n. In this brief we present a class of transfer functions where positive realizations of order n do exist. With the help of our result we give improvements on some earlier results in positive-system theory
An efficient algorithm for positive realizations
We observe that successive applications of known results from the theory of
positive systems lead to an {\it efficient general algorithm} for positive
realizations of transfer functions. We give two examples to illustrate the
algorithm, one of which complements an earlier result of \cite{large}. Finally,
we improve a lower-bound of \cite{mn2} to indicate that the algorithm is indeed
efficient in general
KözönsĂ©ges differenciĂĄlegyenletek a BME Matematika IntĂ©zetĂ©bĆl = Ordinary differential equations from the Mathematical Institute of the BUTE
A kutatĂĄsi feladat kĂ©t fĆ cĂ©lja az volt, hogy eredmĂ©nyeket Ă©rjĂŒnk el (1) a vĂ©gtelen dimenziĂłs dinamika, valamint a (2) numerika, pontosabban differenciĂĄlegyenletek numerikus analĂzise terĂŒletĂ©n. (1) Az elsĆ cĂ©llal kapcsolatos reprezentatĂv eredmĂ©ny HORVĂTH MIKLĂS ''Inverse spectral problems and closed exponential systems, Annals of Mathematics 162(2005), 885-918'' dolgozata, amely -- csakĂșgy mint a kĂsĂ©rĆ Transactions Ă©s Proceedings of the AMS cikkek -- akkor Ă©s csak akkor feltĂ©teleket ad bizonyos tĂpusĂș Schrödinger operatorok potenciĂĄljĂĄnak unicitĂĄsĂĄra. (2) A mĂĄsodik cĂ©llal kapcsolatos fĆ eredmĂ©ny -- közremƱködĆk BĂNHELYI BALĂZS Ă©s CSENDES TIBOR (Informatika IntĂ©zet, Szeged) -- az az Ă©szrevĂ©tel, hogy az intervallum aritmetikĂĄval tĂĄmogatott globĂĄlis optimalizĂĄciĂłk elmĂ©lete kĂ©nyelmes keretet biztosĂt dinamikai rendszerek kaotikus voltĂĄnak szĂĄmĂtĂłgĂ©p ĂĄltal segĂtett bizonyĂtĂĄsĂĄra. Az elmĂ©leti ĂșjdonsĂĄg az, hogy az algebrai topĂłgia eszköztĂĄra, jelesen a korĂĄbbi megközelĂtĂ©sekre annyira jellemzĆ Conley index Ă©s a tovĂĄbbi indexek, legalĂĄbbis az esetek egy rĂ©szĂ©ben, kivĂĄlthatĂłak a Brouwer-fĂ©le fixponttĂ©tel alkalmazĂĄsĂĄval. | The two main goals of the research project have been (1) results in infinite-dimensional dynamics, and (2) results in numerics--more precisely, in the numerics of differential equations. (1) As for the first goal, the representative publication is ''Inverse spectral problems and closed exponential systems, Annals of Mathematics 162(2005), 885-918'' by MIKLĂS HORVĂTH. Together with the accompanying papers in the Transaction and the Proceedings of the AMS, the ''Inverse spectral problems and closed exponential systems'' establishes if and only if conditions on the uniqueness of the potential of certain Schrödinger operators. (2) As for the second goal, the main result - achieved in cooperation with BALĂZS BĂNHELYI and TIBOR CSENDES, Szeged Institute of Informatics--is that interval arithmetics based global optimization constitutes a comfortable framework for computer-assisted proofs of chaotic behaviour of dynamical systems. The theoretical novelty is that tools from algebraic topology including Conley and other indices in earlier approaches can be, at least in several cases, replaced by applications of the Brouwer fixed point theorem
Potential antagonism of some Trichoderma strains isolated from Moroccan soil against three phytopathogenic fungi of great economic importance
Dans cette Ă©tude, 17 souches de Trichoderma on Ă©tĂ© isolĂ©es Ă partir dâĂ©chantillons du sol de diffĂ©rentes origines (champs et forĂȘt dâarganier). Les espĂšces ont Ă©tĂ© identifiĂ©es par la caractĂ©risation molĂ©culaire des cultures monospores des isolats de Trichoderma et leur potentiel dâantagonisme a Ă©tĂ© Ă©valuĂ© contre trois champignons phyto-pathogĂšnes telluriques (Fusarium oxyxporum, verticillium dahlia et rhizoctonia solani). AprĂšs lâextraction de lâADN, le facteur dâĂ©longation et de traduction tef1 a Ă©tĂ© utilisĂ© comme marqueur molĂ©culaire pour amplifier, sĂ©quencer et par la suite caractĂ©riser les 17 souches qui ont Ă©tĂ© comparĂ©es avec leur ex-types dĂ©jĂ rĂ©fĂ©rencĂ©s. Par consĂ©quent, lâidentification molĂ©culaire par tef1 a permis la caractĂ©risation de trois espĂšces de Trichoderma Ă savoir T. afroharzianum, et T. guizhouense appartenant Ă la branche Harzianum, et T. longibrachiatum appartenant Ă la branche Longibrachiatum. Les 17 isolats candidats ont Ă©tĂ© sĂ©lectionnĂ©s par une mĂ©thode de criblage basĂ©e sur la PCR (polymerase chain reaction). LâĂ©valuation du potentiel antagoniste des souches de Trichoderma contre les champignons phytopathogĂšnes telluriques (F. oxysporum, R. solani et V. dahliae) a Ă©tĂ© rĂ©alisĂ©e par la mĂ©thode de confrontation sur boĂźtes de pĂ©trie. LâĂ©tude in vitro de lâactivitĂ© antagoniste par le «Pourcentage of Radial Inhibition Growth» (PRIG %) a permis de suivre lâĂ©volution de la croissance radiale du mycĂ©lium des diffĂ©rents champignons phytopathogĂšnes. Le pourcentage le plus Ă©levĂ© (PRIG% = 98%) a Ă©tĂ© observĂ© pour la confrontation entre lâisolat 8A2.3 et R. solani et le pourcentage le plus faible (PRIG% = 67%) a Ă©tĂ© observĂ© pour la confrontation entre lâisolat T9i10 et F. oxysporum. Dâun autre cotĂ©, T9i12 qui est un isolat de lâespĂšce T. reeseia a engendrĂ© une inhibition Ă©levĂ©e de la croissance radiale du mycĂ©lium des diffĂ©rents pathogĂšnes.
Mots clĂ©s: Trichoderma spp, Fusarium oxysporum, Verticillium dahlia, Rhizoctonia solani, champignons antagonistes.In this study, 17 Trichoderma strains were isolated from different soils (crop fields and Argan forests) in Morocco. Purified monospore cultures were identified using molecular methods and tested for their potential antagonism against three phytopathogenic fungi (Fusarium oxyxporum, verticillium dahlia and rhizoctonia solani). After DNA extraction, translation elongation factor (tef1) was amplified in extracts of 17 strains, sequenced and compared with their ex-types. As a result, three species were identified among the strains, which clustered in two different subclades of Trichoderma: the species T. afroharzianum, and T. guizhouense belong to the Harzianum clade, while T. longibrachiatum belongs to the Longibrachiatum clade. Investigation of potential antagonistic effects of these strains against the soil-borne phytopathogens F. oxysporum, R. solani and V. dahliae was conducted in a dual culture plate assay, using 17 promising Trichoderma strains that have been selected based on a polymerase chain reaction (PCR) screening approach. In vitro, Trichoderma isolates showed effective antagonistic performance by decreasing soil borne pathogens mycelium radial growth. Trichoderma afroharzianum showed the highest Percentage of Radial Inhibition Growth (PRIG %). The highest PRIG% = 98% was for 8A2.3 isolate against R. solani and the lowest PRIG%= 67% for T9i10 against F. oxysporum. On the other hand, T9i12, which is T. reesei species, led to a high radial inhibition of pathogensâ mycelium.
Keywords: Trichoderma spp, Fusarium oxysporum, Verticillium dahlia, Rhizoctonia solani, antagonistic fungi
Investigating physiological effects due to artificial infections of grapevine with <i>Verticillium nonalfalfae</i>
Ailanthus altissima is among the most invasive woody species worldwide, outcompeting native trees. The fungus Verticillium nonalfalfae (VN) is promising for A. altissima biocontrol, and its effects on the host have been studied via visual assessment in a range of host species. However, little research was performed to address fungal effects on the physiological processes of non-target woody plants. We investigated the occurrence of visual and non-visually recognisable perturbations of VN infection on potted vines to evaluate the potential risks of the biocontrol pathogen on viticulture. Eighteen four-years-old Vitis vinifera (cultivar GrĂŒner Veltliner grafted on Kober 5BB) potted plants were inoculated with VN conidial suspension of the fungus (F), while nine plants were treated with sterile water (C, control). Disease symptoms and physiological parameters were monitored throughout the experiment (seven evaluation dates), while leaf water potential, leaf mass per area (LMA) and biomass were measured at the end of the study when plant tissue was sampled for re-isolation of the fungus. In our trial, inoculations with VN induced characteristic wilting symptoms only in Ailanthus (used as side control of the inoculum), while vines remained asymptomatic, thus indicating a high degree of host specificity of VN. Limited or no impact was detected on the physiology of the non-target V. vinifera. Furthermore, the LMA and biomass measured in the two experimental groups were not different. Although fungal colonisation induced vascular discolouration in both species, the fungus could only be re-isolated from dying Ailanthus but not from vine tissue. Results suggest that V. vinifera cv GrĂŒner Veltliner is resistant to the applied VN isolate. However, the susceptibility and physiology of additional grapevine cultivars, as well as other native woody species to VN, should be studied before promoting large-scale use of the biocontrol agent
Data Descriptor: Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease
CMS was funded by the âNornexâ project jointly by UK BBSRC (BBS/E/J/000CA5323) and DEFRA and a BBSRC Tools and Resources grant (BB/N021452/1) awarded to M.G. and D.J.S
Entwicklung eines robusten Algorithmus zur numerischen Beschreibung von Gaspermeations-Prozessen
Abweichender Titel nach Ăbersetzung der Verfasserin/des VerfassersIm Rahmen des Projektes HylyPureÂź wurde am Institut fĂŒr Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften ein Verfahren entwickelt, um Wasserstoff aus einer Mischung mit Erdgas zurĂŒckzugewinnen und so das Erdgasnetz zum Wasserstoffkotransport zu nutzen. Der HylyPureÂź-Prozess besteht aus Gaspermeations- und Druckwechseladsorptionsschritten. Eine Versuchsanlage fĂŒr beide Teile wurde and der TU Wien entwickelt. Zur weiteren Optimierung des Prozesses wird eine Lösung zur effizienten Simulation groĂer Parameterfelder und komplexer FlieĂschemata erforderlich. Ein Algorithmus zur Simulation von Gaspermeation wurde vor einigen Jahren am Insistut entwickelt und publiziert, welcher jedoch nicht alle derzeitigen Anforderungen erfĂŒllt. Diese Diplomarbeit stellt vecgp vor, einen aktualisierten und verbesserten Algorithmus basierend auf der Finite-Differenzen-Methode. Vecgp ermöglicht nichtnur stabile Berechnungen fĂŒr eine groĂe Anzahl an möglichen Prozesskonfigurationen, sondern ist auch deutlich schneller und kann MultikomponentenfĂ€lle, sowie Membranmodule mit hohen RĂŒckgewinnungsraten effizient simulieren. Die neue objektorientierte und modulare Implementierung in MATLAB stellt sicher, dass der Code einfach erweitert und wiederverwendet werden kann. Neben der Simulation des Stofftransportes in Membranmodulen erlaubt vecgp auch Druckverlust- und Energiebilanzberechnungen und ermöglicht die Verwendung von Realgasdaten basierend auf den genauesten derzeit verfĂŒgbaren Modellen. Die Kernfunktionen sind ausgiebig getestet und gegen den existierenden Algorithmus validiert. AuĂerdem wurde vecgp auch schon erfolgreich zur Simulation von komplexen mehrstufigen Prozessen eingesetzt.Within the project HylyPure, a process for the separation of hydrogen from a mixture with methane has been developed at the Institute of Chemical, Environmental, and Biological Engineering. This enables the usage of the natural gas grid for the transport of hydrogen. The HylyPure process includes gas permeation and pressure swing adsorption steps and a test facility for both steps was developed at TU Wien. For further optimizations of the process, a solution to efficiently simulate large parameters sets and complex flow sheets is required. An algorithm for the simulation of gas permeation was developed and published at the institute some years ago, but does not fulfill all the current needs. This thesis presents VECGP, an updated and enhanced algorithm based on the finite difference method. VECGP not only ensures stable calculations for a wide range of gas permeation cases, but also significantly improves performance and is able to solve multi component systems and cases with high recovery rates efficiently. A new object oriented and modular implementation allows easy expansion and re-usage of code while simultaneously improving user-friendliness. Besides evaluating the mass transfer through membrane modules, VECGP also provides pressure drop and energy balance calculation and allows inclusion of real gas properties based on the best currently available models. The core feature set is validated against the existing algorithm and has successfully been used to simulate complex multi-stage processes.11
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