Azo disperse dyes for synthetic fibres. 3: 2-Styrylquinazolone derivatives

Fifteen variously substituted derivatives ( IVa–o ) of 2-styrylquinazolone have been prepared for use as dye-stuffs. The effects of the nature and orientation of substituents on the colour and dyeing properties of these dyes on polyester and acrylic fibres were assessed.     

Photovoltages exceeding the band gap observed with WSe2/I− solar cells

Photovoltages ranging between 1.2 and 2.1 V have been observed with single-crystal WSe₂, grown without transport agent, in contact with I^–/I ₃ ^–3 solutions. This effect is found only with surfaces which have not been renewed by peeling. They show negligible dark currents and both cathodic and anodic photocurrents. The abnormally high photovoltage sometimes disappeared without evident reason but it could nevertheless be used to drive a stable solar cell with an efficiency between 1.5 and 5% for a period of five days. Optical and electrochemical studies show that the phenomenon is due to the presence of two different types of material which coexist at the same surface with different band gaps and flat band potentials. One type shows a compensated behaviour, the other n-type behaviour. High photovoltages are obtained when anodic and cathodic photocurrents, generated simultaneously but at different wavelengths, compensate each other, thus shifting the zero-current point towards more negative potential values. Large photovoltages are therefore only possible while photocurrents are circulating through the two interfaces, thus dissipating energy. The observed phenomenon, though at present fragmentarily understood, could be of some value for the development of semiconductor electrodes with high photovoltages for the decomposition of water.     

Sequential approximate optimization using dual subproblems based on incomplete series expansions

In this paper, dual formulations for nonlinear multipoint approximations with diagonal approximate Hessian matrices are proposed; these approximations for example derive from the incomplete series expansion (ISE) proposed previously. A salient feature of the ISE is that it may be used to formulate strictly convex and separable (recast) primal approximate subproblems for use in sequential approximate optimization (SAO). In turn, this allows for the formulation of highly efficient dual formulations, and different combinations of direct, reciprocal, and exponential intervening variables for the objective and the constraint functions may be used. Two frequently encountered problems in structural optimization, namely the weight minimization problem with sizing design variables and the minimum compliance topology optimization problem, are degenerate cases of the formulations we present. Computational experiments confirm the efficiency of our proposed methodology; to this end, comparative results for the method of moving asymptotes (MMA) are presented. Based on the paper entitled “Duality in Convex Nonlinear Multipoint Approximations with Diagonal Approximate Hessian Matrices Deriving from Incomplete Series Expansions,” presented at the 11th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, Portsmouth, VA, USA, September 2006, paper no. AIAA-2006-7090.     

Generation of a function-component-parameter multi-domain matrix from structured textual function specifications

This study introduces a method to build a multi-domain matrix (MDM), visualizing the intended architecture of a system within the component, function, and parameter domains. The MDM is generated from textual function specifications that are subject to a specific grammatical structure and vocabulary based upon the functional basis and interaction basis as presented in the literature. Two types of functions are distinguished: functions specifying what functionality a particular component provides to another component, and functions specifying the internal working (transformation of flow) of a particular component. The fixed grammar for the specification of the two types of functions allows for the automated derivation of dependencies between components, between functions of components, and between system parameters. A case study on a navigation lock demonstrates that the system architecture generated from function specifications matches the architecture of the real lock system fairly well. As such the method can be used in the early design phase to reveal the product architecture that is embodied in the function specifications of system components. The method may also support modeling of high-definition DSMs of existing engineering systems.     

Framework for sequential approximate optimization

An object-oriented framework for sequential approximate optimization (SAO) is proposed. The framework aims to provide an open environment for the specification and implementation of SAO strategies. The framework is based on the Python programming language and contains a toolbox of Python classes, methods, and interfaces to external software. The framework distinguishes modules related to the optimization problem, the SAO sequence, and the numerical routines used in the SAO approach. The problem-related modules specify the optimization problem, including the simulation model for the evaluation of the objective function and constraints. The sequence-related modules specify the sequence of SAO steps. The routine-related modules represent numerical routines used in the SAO steps as black-box functions with predefined input and output, e.g., from external software libraries. The framework enables the user to (re-) specify or extend the SAO dependent modules, which is generally impossible in most available SAO implementations. This is highly advantageous since many SAO approaches are application-domain specific due to the type of approximation functions used. A ten-bar truss design problem with fixed loads as well as uncertain loads is used as an illustration and demonstrates the flexibility of the framework.     

Pyrene-modified quartz crystal microbalance for the detection of polynitroaromatic compounds

The synthesis of a dithiol-functionalized pyrene derivative is reported, together with studies of interactions between this receptor (and other related pyrenes) and nitroaromatic compounds (NACs), in both solution and in the solid state. Spectroscopic analysis in solution and X-ray crystallographic analysis of cocrystals of pyrene and NACs in the solid state indicate that supramolecular interactions lead to the formation of defined π-π stacked complexes. The dithiol-functionalized pyrene derivative can be used to modify the surface of a gold quartz crystal microbalance (QCM) to create a unique π-electron rich surface, which is able to interact with electron poor aromatic compounds. For example, exposure of the modified QCM surface to the nitroaromatic compound 2,4-dinitrotoluene (DNT) in solution results in a reduction in the resonant frequency of the QCM as a result of supramolecular interactions between the electron-rich pyrenyl surface layer and the electron-poor DNT molecules. These results suggest the potential use of such modified QCM surfaces for the detection of explosive NACs.