Thermionic emission-tunnelling theory of charge transport through a schottky contact at low injection

The contribution presents a thermionic emission-tunnelling theory of the charge transport through a Schottky contact, valid for low injection. The approach extends the classical thermionic emission theory by incorporating the mechanism of tunnelling across the Schottky barrier. The novelty of this transport model is in considering the transfer of charge carriers in both directions, which is accomplished by introducing the Richardson constant also for electrons in the metal, and in the use of the Global Transfer Matrix technique to compute the relevant transmission coefficients.     

Harnack inequalities,exponential separation,and perturbations of principal Floquet bundles for linear parabolic equations

We consider the Dirichlet problem for linear nonautonomous second order parabolic equations with bounded measurable coefficients on bounded Lipschitz domains. Using a new Harnack-type inequality for quotients of positive solutions, we show that each positive solution exponentially dominates any solution which changes sign for all times. We then examine continuity and robustness properties of a principal Floquet bundle and the associated exponential separation under perturbations of the coefficients and the spatial domain.     

Experimental and theoretical evidence for U(C6H6) and Th(C6H6) complexes

The vibrational spectra of UBz and ThBz have been measured in solid argon. Complementary quantum chemical calculations have allowed the assignments of the vibrational spectra. According to the calculations, AcBz are stable molecules, as well as other species like BzAcBz and BzAc2Bz. Experimentally, there is no evidence for the sandwich compounds BzAcBz and BzAc2Bz due to the limitations in the reagent concentrations.     

Combination of large volume sample stacking and dynamic pH junction for on-line preconcentration of weak electrolytes by capillary electrophoresis in comparison with isotachophoretic techniques

An on-line preconcentration capillary electrophoresis (CE) technique, which combines a large volume sample stacking with a dynamic pH junction technique, is introduced in this paper. This dynamic pH junction with co-electroosmotic migration is formed between sodium borate pH 9.5 and sodium phosphate pH 2.5 with 150 mM sodium dodecylsulfate (SDS). A full capillary based injection allows determination of weak acidic compounds at ppb concentration levels (achieved LOD for benzoic acid was 11 nmol L(-1)). The proposed preconcentration method was compared with ITP/ITP (LOD 120 nmol L(-1)), ITP/CZE (LOD 740 nmol L(-1)) and a simple CZE method (LOD 23,330 nmol L(-1)). The analytical potential of this method was assessed with juice test samples.     

A Critical Review of Vlasov's General Theory of Stability of In-Plane Bending of Thin-Walled Elastic Beams

In Vlasov's approach to the problem of stability of thin-walled elastic beams of open cross section simultaneously subjected to transverse bending and to centric compression or tension, a certain inconsistency in derivation of differential equations of stability has been noticed. A consistently carried through derivation leads to equations that differ from Vlasov's ones. The comparison of Vlasov's equations with the results achieved by the classics in the field and by the more recent authors reveals good correspondence. The equations obtained by a consistent derivation, instead, turn out to be correspondent with the equations obtained by the classics Timoshenko and Bleich and with Ojalvo's equations of a second-order theory which determines the orientation of normal planes with the line of shear centers and assumes the validity of the Wagner hypothesis. Sommario. Nellapproccio di Vlasov al problema di stabilita delle travi elastiche a parete sottile e sezione trasversale aperta, contemporaneamente soggete a flessione trasversale ed a pressione o trazione centrale, e stata notata una certa incoerenza nell derivazione delle equazioni differenziali di stabilita. Un procedimento coerente ci porta delle equazioni che si differenziano da quelle di Vlasov. It confronto tra le equazioni di Vlasovedi risultati ottenuti da autori classici e da quelli piu a recenti mostra che esiste un buon accordo, mentre e evidente che le equazioni, ottenute con il procediments coerente, collimano con le equazioni ottenute dai classici Timoshenko e Bleich e con le equazioni di Ojalvo della teoria del secondo ordine, che definisce lorientazione dei piani normali con la linea dei centri di taglio e che presuppone la validita della ipotesi di Wagner.     

Monitoring 60Co activity for the characterization of the sorption process of Co2+ ions in municipal activated sludge

In large volumes produced activated sludges from wastewater treatment plants (WWTPs) with low concentrations of heavy metals can be utilized as agricultural fertilizers and soil conditioners. Increased contents of toxic xenobiotics are limiting factors that affect the utilization of these heterogeneous wastes. The main aim of our paper was to show the utilization of dried activated sludge (DAS) from municipal WWTP as potential Co²⁺ ions sorbent i.e. for non-agricultural purposes. The radio indicator method by radionuclide ⁶⁰Co and γ-spectrometry for characterization DAS sorption properties was used. DAS soluble and solid fractions were characterized by biochemical, ETAAS and CEC analysis. The sorption of Co²⁺ ions by DAS was rapid process and equilibrium was reached within 2 h. Sorption capacity of DAS (Q) increased with the initial concentration of CoCl₂ in the range from 100 to 4,000 μmol l^?1, reaching 20 and 160 μmol g^?1. Obtained Q values were depent on pH value from 2.0 to 8.0. The maximum sorption capacity (Q _max) of DAS at pH 6 calculated from mathematical model of Langmuir adsorption isotherm was 175 ± 9 μmol g^?1. FT-IR analyses showed the crucial role of carboxyl functional groups of DAS surfaces on cobalt uptake. For confirmation ion-exchange mechanism in sorption process of Co²⁺ ions by DAS scanning electron microscopy and EDX analysis were used.     

2‐(Acridin‐9‐yl­imino)‐3‐di­methyl­amino‐1,3‐thia­zolidin‐4‐one

In the title compound, C₁₈H₁₆N₄OS, prepared by the reaction of 4‐(acridin‐9‐yl)‐1,1‐di­methyl­thio­semicarbazide with methyl bromo­acetate, the acridine and thia­zolidine ring systems are both non‐planar and, because of steric requirements, almost perpendicular, with a dihedral angle between their planes of 99.69 (6)°. C—H·O and C—H·π(arene) hydrogen bonds stabilize the crystal structure in the solid state.     

HAZOP study of a fixed bed reactor for MTBE synthesis using a dynamic approach

A methodology for hazard investigation based on the integration of a mathematical model approach into hazard and operability analysis is presented. This approach is based on mathematical modelling of a process unit where both steady-state analysis, including analysis of the steady states multiplicity and stability, and dynamic simulation are used. The dynamic simulation serves for the investigation of consequences of failures of the main controlled parameters, i.e. inlet temperature, feed temperature and feed composition. This simulation is also very useful for the determination of the influence of failure duration on the reactor behaviour. On the other hand, the steady state simulation can predict the reactor behaviour in a wide range of failure magnitude and determine the parametric zones, where shifting from one steady state to another one may occur. A fixed bed reactor for methyl tertiary-butyl ether synthesis was chosen to identify potential hazard and operational problems of a real process. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.