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Content accesss denied Cascade estimation design for CSTR models
We propose a methodology for observer synthesis for a class of chemical reactions processes. First we present graphic tools in order to decide of the property of observability of the model of the reaction process and/or the best measures to do and which kind of observer to use (high gain observers in the mono output case and Kalman observers). Next we give an attractivity definition. Thanks to these graphic tools and this attractivity property valid for some part of CSTR's, we obtain in many cases, the estimation of the whole state even if some part of the model is not observable. For this purpose, we use cascades of the previous observers and estimators. Moreover we present the methodology via algorithms and we give a simulation example.
An efficient technique, namely simultaneous perturbation with dynamic tunneling for training single hidden layer feedforward network, is proposed. A sigmoidal hidden neuron is added to the single hidden layer neural network after training. Then the cascaded network is trained again using simultaneous perturbation. The dynamic tunneling technique is employed to detrap the local minima in training. The proposed technique is shown to give better convergence results for the selected problems, namely neuro-controller, encoder, adder, demultiplexer, XOR and L-T character recognition problem.
Thermoacoustic engines are promising in practical applications for the merits of simple configuration, reliable operation and environmentally friendly working gas. An acoustic amplifier can increase the output pressure amplitude of a thermoacoustic engine (TE) and improve the matching between the engine and its load. In order to make full use of an acoustic amplifier, the transmission characteristics are studied based on linear thermoacoustic theory. Computational and experimental results show that the amplifying ability of an acoustic amplifier is mainly determined by its geometry parameters and output resistance impedance. The amplifying ability of an acoustic amplifier with appropriate length and diameter reaches its maximum when the output resistance impedance is infinite. It is also shown that the acoustic amplifier consumes an amount of acoustic power when amplifying pressure amplitude and the acoustic power consumption increases with amplifying ratio. Furthermore, a novel cascade acoustic amplifier is proposed, which has a much stronger amplifying ability with reduced acoustic power consumption. In experiments, a two-stage cascade acoustic amplifier amplifies the pressure ratio from 1.177 to 1.62 and produces a pressure amplitude of 0.547MPa with nitrogen of 2.20MPa as working gas. Good agreements are obtained between the theoretical analysis and experimental results. This research is instructive for comprehensively understanding the mechanism and making full use of the acoustic amplifier.
An expedient synthetic route to the fully substituted pyrrolidine ring system of the plakoridines is described using an approach modeled on a plausible biosynthetic pathway.
In the fine chemical industry, the batch or fed-batch reactor functions as the heart of the transformation process. Due to the complexity of chemical synthesis, the control of these reactors remains a problem of temperature control commonly performed indirectly via the jacket of the reactor. This results in a cascade control scheme based on the control a secondary, more responsive process that influences the main process. This control loop is often referred to as the slave loop of the process. This paper highlights that the slave process of batch process units, i.e. the jacket of the reactor, can have more complex dynamics than the master loop has; and very often this could be the reason for the non-satisfying control performance. Since the slave process is determined by the mechanical construction of the unit, the above mentioned problem can be effectively handled by a model-based controller designed using an appropriate nonlinear tendency model. The presented analysis shows that the complex dynamics of the slave process can be decomposed into static nonlinear and dynamic linear parts. This decomposition is beneficial since it allows the effective incorporation of the resulted tendency model into nonlinear model-based control algorithms. Real-time control results show that the proposed methodology gives superior control performance over the widely applied cascade PID-PID control scheme.
Carbamyl chlorides with a proximate alkyne/alkene undergo regioselective Pd catalysed cyclisation–organostannane capture to afford lactams in good yield whilst aryl iodides with a proximal alkene undergo an analagous process with in situ generated exocyclic-dienylstannanes in good yield.
Cyclopalladated, phosphine free, 8-methyl quinoline based complexes (2a–j) are excellent catalysts for the Heck vinylation of aryl iodides and bromides with turnover numbers of greater than 25 million observed in some cases. The catalysts are air and moisture stable.
Immobilized cells of Actinoplanes teichomyceticus ATCC 31121 were used to selectively cleave the acyl group of A40926 yielding the deacylated form of the molecule. The feasibility of this particular biotransformation in a series of three perfectly mixed airlift bioreactors with immobilized cells was examined. A continuously operated airlift cascade was designed using a model for a series of reactors with immobilized biocatalyst beads obeying Michaelis–Menten kinetics. In independent experimental runs the cascade bioreactor system was operated continuously for 56 days with an overall conversion of 99%. Model estimates for reactor volumes and relative conversions were found to be in a good agreement with the experimental results.
Content accesss denied Quenching of Pr3+ 1S0 emission by Eu3+ and Yb3+
Energy transfer between Pr3+ and Eu3+ is studied by luminescence spectroscopy and time-resolved measurements. In earlier experiments, Zachau et al. (Proceedings—Electrochemical Society, 97 (29) (Luminescent Materials, pp. 314–324, 1998)) observed no energy transfer from the 1S0 level of Pr3+ to the 5D3 level of Eu3+ for YF3:Pr, Eu, in spite of the favorable spectral overlap for energy transfer. This unexpected result was not explained. To resolve this issue, we first calculate the critical distance for energy transfer using the Förster theory and show that efficient energy transfer between Pr3+ and nearest Eu3+ neighbors is predicted. Nevertheless, luminescence experiments show no Eu3+ emission upon excitation in the 1S0 level of Pr3+ in YF3:Pr, Eu confirming the results in (Proceedings—Electrochemical Society, 97 (29) (Luminescent Materials, pp. 314–324, 1998)). The experiments do show a strong quenching of the 1S0 emission by Eu3+. The quenching is explained by a low-energy metal-to-metal charge transfer state (Pr4+–Eu2+) for Pr–Eu pairs. Additional support for this quenching mechanism is provided by the observation that addition of Yb3+ also quenches the 1S0 emission.
This paper proposes a continuous process for solvent exchange, a key unit operation for organic synthesis in pharmaceutical manufacturing. This process comprises a counter-current membrane cascade using organic solvent nanofiltration (OSN) membranes. The effect of process parameters, such as number of stages and flow rate ratio of replacing solvent to initial solvent, on solvent exchange performance are tested through simulations and experiments. Experimental results show 47.8%, 59.2%, and 75.3% solvent exchange for single-stage, two-stage and three-stage cascades, values which are close to the 50.0%, 66.6%, and 75.0% predicted by simulations. In general, the feasibility of OSN membrane cascades for continuous solvent exchange is demonstrated in this work.
The development of a ring-opening metathesis/ring-closing metathesis/cross-metathesis (ROM–RCM–CM) cascade strategy to the synthesis of a diverse collection of bi- and tricyclic sultams is reported. In this study, functionalized sultam scaffolds derived from intramolecular Diels–Alder (IMDA) reactions undergo metathesis cascades to yield a collection of tricyclic sultams. Additional appendage-based diversity was achieved by utilizing a variety of CM partners.
Sigmund [P. Sigmund, Appl. Phys. Lett. 25 (1974) 169] analytically predicted that the ratio of cascade volume to energy distribution volume should follow a universal curve that is sigmoidal in shape. Subsequent Monte Carlo simulations by Walker and Thompson [R.S. Walker, D.A. Thompson, Radiat. Eff. 37 (1978) 113] showed that although this curve is sigmoidal in shape, the curve is different for different materials with large deviations from Sigmund’s prediction at high M 2 /M 1 . Our analysis of the Walker and Thompson approach has revealed an error in the analytical equations used. A correct analysis of volume ratios using a different set of equations is presented. Analysis of data produced by SRIM [J.F. Ziegler, J.P. Biersack, U. Littmark, in: The Stopping and Range of Ions in solids, Pergamon, New York, 1985] (Monte Carlo) simulations gives results that are in good agreement with Sigmund’s predictions.
Content accesss denied SmI2-mediated dialdehyde cyclization cascades
Dialdehydes undergo sequenced SmI 2 -mediated cyclization cascades generating four contiguous stereocenters with high diastereocontrol.
Unobtrusive user authentication is more convenient than explicit interaction and can also increase system security because it can be performed frequently, unlike the current “once explicitly and for a long time” practice. Existing unobtrusive biometrics (e.g., face, voice, gait) do not perform sufficiently well for high-security applications, however, while reliable biometric authentication (e.g., fingerprint or iris) requires explicit user interaction. This work presents experiments with a cascaded multimodal biometric system, which first performs unobtrusive user authentication and requires explicit interaction only when the unobtrusive authentication fails. Experimental results obtained for a database of 150 users show that even with a fairly low performance of unobtrusive modalities (Equal Error Rate above 10%), the cascaded system is capable of satisfying a security requirement of a False Acceptance Rate less than 0.1% with an overall False Rejection Rate of less than 0.2%, while authenticating unobtrusively in 65% of cases.
Dialdehydes undergo ‘radical then aldol’ cyclization cascades upon treatment with SmI 2 , generating four contiguous stereocenters with high diastereocontrol. The scope of the process has been explored and the cascade has been extended to also include lactone reduction.
The novel dual cooperative asymmetric aminocatalysis and Lewis acid catalysis has been successfully developed for promoting cascade Michael-cyclization reaction with high enantio-, regio- and chemo-selectivity. The simple and practical process affords a one-pot approach to synthetically useful cyclopentenes.
The agricultural uses of geothermal energy were the centre of attention during the initial stages of geothermal direct applications in Europe, e.g. in Hungary, Macedonia, Bulgaria, Serbia. The focus now seems to be on district heating systems, integrated systems, large balneological/tourist centres, etc. This paper analyses the problems involved in the development of agricultural uses in different regions of Europe and how this sector can be promoted. An analysis of the situation in Europe and in Hungary, Macedonia and Greece, in particular, has revealed different requirements and potentials, different combinations of influencing factors, and the need for different development strategies. It is, however, clear from this analysis that the agricultural uses of geothermal energy are not in collision with modern trends in direct geothermal developments in Europe. On the contrary, they can improve the economic aspects of any district heating or integrated system by offering excellent possibilities for cascade use of the geothermal water and combinations of users with different day/night and seasonal heat requirements.
This study describes the utilization of a novel conjugated copolymer, namely, poly[2,3-bis(thiophen-2-yl)-acrylonitrile-9,9′-dioctyl-fluorene] (FLC8) for organic solar cell application for the first time. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of FLC8 are −5.68 and −3.55eV, respectively, which lie between the corresponding values of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methylester (PCBM). In addition, both electron and hole mobilities of FLC8 are in the range of 10 −4 (cm 2 /Vs), making it an excellent ambipolar polymer. Such unique properties make FLC8 a good candidate to form a ternary cascade bulk-heterojunction organic solar cell when blending with P3HT and PCBM. The power conversion efficiency (PCE) of the ternary cascade solar cell can be increased by up to 30% as compared with the reference cell without FLC8. We suspect that this enhancement of PCE is caused by the additional charge separation offered by the cascade structure and the fast charge transfer due to the ambipolarity of FLC8.
A cascade sequence between cyclic hemiacetals and tryptamines was developed, which provided efficient access to highly substituted diazaindeno[2,1-α]phenanthrenes in moderate to good yields with high diastereoselectivities and good to excellent enantioselectivities. Hemiacetals were prepared by asymmetric organocatalyzed conjugate addition of cyclic 1,3-diketones to α,β-unsaturated aldehydes. Hemiacetals with various R 1 , both aromatic and aliphatic, were examined for the cascade sequence.
An organocatalyzed one-pot Michael addition-Pictet–Spengler sequence of β-ketoamides and α,β-unsaturated aldehydes was developed, which provided access to highly substituted indolo[2,3-α]quinolizidines and benzo[α]quinolizidines in moderate to good yields and good to excellent enantioselectivities. For aromatic α,β-unsaturated aldehydes 1a–j products 10a–r containing a stable enol configuration were obtained.
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