The influence of ions’ substitution on the optical properties of A<Subscript>2</Subscript>MX<Subscript>4</Subscript> crystals

In this article, results based on the research of optical properties of A₂MX₄ type crystals (A—organic cation, M—metal, X—halogen) composed of different chemical elements are presented. These crystals were grown by the evaporation method from water solutions of AX and MX₂ compounds in an appropriate molar ratio. The conducted X-ray investigations show a different crystal structures, ranging from tetragonal to triclinic ones. Also, the structure of the ion complex for Cu²⁺ crystals varied. The investigation showed both CuCl₄²⁻ tetrahedral and CuCl₄ · 2H₂O²⁻ octahedral deformed complexes in investigated crystals. Additionally, the optical spectra of the samples were measured in the range of 250–850 nm. Based on the crystal field theory, it was shown that the shape of absorption spectra and colour of the crystals depend on the distortion of these complexes.     

A New Analyzer Based on Pellistor Sensor with Neural Network Data Postprocessing for Measurement of Hydrocarbons in Lower Explosive Limit Range

We present the results of a first stage of development work on a new type of analyzer for hydrogen and C₁–C₃ hydrocarbons concentration measurements in the lower explosive limit range, based on single pellistor sensor with artificial neural network data postprocessing.     

Synthesis and ultraviolet‐visible spectroscopic and electrochemical analyses of dyes derived from 2‐aminobenzothiazole,and study of their adsorption on titanium dioxide

A series of Schiff bases with hydroxyl anchoring group/s in various positions were synthesised. Their visible light absorption and electrochemical and physicochemical adsorption properties were investigated. Results show that the studied compounds have adequate highest‐occupied‐molecular‐orbital and lowest‐unoccupied‐molecular‐orbital levels that match with the conduction band of titanium dioxide and the redox potential of the electrolyte. Adsorption of azomethine compounds with hydroxyl group/s on titanium dioxide was studied. Experimental data show that the introduction of two β‐hydroxyethyl groups can greatly enhance the adsorption efficiency of the studied Schiff base on titanium dioxide. Sorption kinetics was measured for di‐(β‐hydroxyethyl)aminobenzyliden‐2‐aminobenzothiazol. Results show rapid initial sorption (<30 min), followed by a slower rate of increasing uptake between 0.5 and 6 h. Kinetic data were modelled using pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion kinetics equations. These results indicate that the pseudo‐second‐order equation and intraparticle diffusion model can better describe the adsorption kinetics of di‐(β‐hydroxyethyl)aminobenzyliden‐2‐aminobenzothiazol onto titanium dioxide.     

ENDOW (efficient development of offshore wind farms): modelling wake and boundary layer interactions

While experience gained through the offshore wind energy projects currently operating is valuable, a major uncertainty in estimating power production lies in the prediction of the dynamic links between the atmosphere and wind turbines in offshore regimes. The objective of the ENDOW project was to evaluate, enhance and interface wake and boundary layer models for utilization offshore. The project resulted in a significant advance in the state of the art in both wake and marine boundary layer models, leading to improved prediction of wind speed and turbulence profiles within large offshore wind farms. Use of new databases from existing offshore wind farms and detailed wake profiles collected using sodar provided a unique opportunity to undertake the first comprehensive evaluation of wake models in the offshore environment. The results of wake model performance in different wind speed, stability and roughness conditions relative to observations provided criteria for their improvement. Mesoscale model simulations were used to evaluate the impact of thermal flows, roughness and topography on offshore wind speeds. The model hierarchy developed under ENDOW forms the basis of design tools for use by wind energy developers and turbine manufacturers to optimize power output from offshore wind farms through minimized wake effects and optimal grid connections. The design tools are being built onto existing regional‐scale models and wind farm design software which was developed with EU funding and is in use currently by wind energy developers. Copyright © 2004 John Wiley & Sons, Ltd.     

Integro-differential Chapman-Kolmogorov equation for continuous-jump Markov processes and its use in problems of multi-component renewal impulse process excitations

In the present paper the applications of the integro-differential Chapman-Kolmogorov equation to the problems of pure-jump stochastic processes and continuous-jump response processes are discussed. The pure-jump processes considered herein are the counting Poisson process, a two-state jump process, and a multi-state jump process. The differential equations governing the Markov state probabilities are obtained from the degenerate, pure differential form, of the general, integro-differential Chapman-Kolmogorov equation, with the aid of the jump probability intensity functions. The continuous-jump response process is the response of a dynamic system to a multi-component renewal impulse process excitation. The excitation consists of a number of n statistically independent random trains of impulses, each of which is driven by an Erlang renewal process with parameters ν_j,k_j. Each of the impulse processes is characterized by an auxiliary zero-one jump stochastic process, which consists of k_j negative exponential distributed phases. The Markov states for the whole problem are determined by the coincidences of the phases of the individual jump processes. Thus the response probability distribution may be characterized by a joint probability density-discrete distribution of the state variables of the dynamic system and of the states of the pertinent Markov chain. The explicit integro-differential equations governing the joint probability density-discrete distribution of the response are obtained from the general forward integro-differential Chapman-Kolmogorov equation, after the determination of the jump probability intensity functions for the continuous-jump and pure-jump processes.     

Structure and electrochemical reactivity of new sulphur–silicon podands adsorbed on silver or gold surfaces

By the self-assembly monolayer (SAM) organization, three new podands belonging to silylpropanethiols have been tested as to their ability to form nanolayers protecting the noble metal surface (gold or silver) and to form complexes with monovalent metal cations on the metal surfaces. The stable self-assembled chemisorbed layers, providing protection to metal surface against electrooxidation and capable of blocking propylene carbonate (PC) electroreduction and Li electrodeposition were produced. Reflection-absorption infrared spectroscopy (RAIRS) indicated cleavage of the S–H bond upon adsorption of species 1–3 with the formation of S–Ag bonds on the metal surface. By cyclic voltammetry, it was found that the primary adsorbate formed on a Au electrode at E _ad (between −0.2 and −1.2 V vs. SCE) underwent reductive desorption at E < −1.3 V vs. SCE. The structures of 1–3 and their complexes with Na⁺ cations on the Ag surfaces were calculated and visualized by the AM1d semi-empirical method.