Thermochromic Langmuir-Blodgett films of a novel amphiphilic azo dye with homogeneous chromophore orientation

Langmuir-Blodgett (LB) multilayers have been prepared from a novel amphiphilic azobenzene derivative. These films were transparent and showed homogeneous polarization of visible light over the whole film area. They exhibit reversible thermochromism with a red shift of 60 nm over a temperature range of less than 10°C. This thermochromism can be explained by a “J-like” aggregation of the azo chromophores that is slightly effected by temperature.     

Performance of organic nanoparticle coatings for hydrophobization of hardwood surfaces

The protection of wood surfaces against water is a primary requirement to enhance their life-time and durability. In this article, a hydrophobic surface modification of selected hardwood surfaces (including high-density (HD) and low-density (LD) samples) is presented, by coating them with waterborne imidized nanoparticles under pure conditions or with vegetable oil. The performance of both nanoparticle coatings relative to noncoated and oil-coated samples was evaluated by water contact angles, microscopy, and optical profilometry. The pure nanoparticle coatings often increase the hydrophobicity, but they do not yet form a fully protective layer due to their porous structure after drying. The nanoparticle coatings with vegetable oil form a continuous layer with a maximum contact angle of 118°. The coating formation highly depends on the wood density (and resulting surface porosity), resulting in spreading of the aqueous dispersion on HD wood and penetration on LD wood. A thin continuous nanoparticle coating with incorporated vegetable oil provides highest contact angles, as the roughness of the original wood fibers remains visible in the surface profile.     

Controlled Gold Nanorod Reorientation and Hexagonal Order in Micromolded Gold Nanorod@pNIPAM Microgel Chain Arrays

A one‐step soft lithography based pathway to manufacture aligned gold nanorod@poly‐(N‐isopropylacrylamide) (GNR@pNIPAM) hybrid chains with hexagonal arrangement of the nanorods and with an anisotropic optical response is presented. After demonstration of an efficient synthesis protocol, yielding uniform composite microgels in high concentration, a micromolding procedure using wrinkled polydimethylsiloxane (PDMS) templates to fabricate aligned hybrid chains is introduced. It is found that the self‐assembled GNR@pNIPAM microgels inside the PDMS wrinkle grooves can be transferred onto solid substrates, on which they exhibit a hexagonal order, as confirmed by small‐angle X‐ray scattering. Further, it is shown that the application of minimized PDMS wrinkle dimensions aligns GNRs inside the pNIPAM microgels, and that the optical response of such molded assemblies is anisotropic.     

MESHMdl event spaces — A coordination middleware for self-organizing applications in ad hoc networks

Mobile ad hoc networks (MANETs) are gaining importance as a promising technology for flexible, proximity-based, mobile communication. However, the inherent dynamics of MANETs imposes strong limitations on the design of distributed applications. They need to be able to adapt to changing conditions quickly and organize themselves in terms of component placement and communication habits. In this paper, we present MESHMdl, a middleware that provides a high level of awareness and decoupling for application components to make them more flexible and adaptable. We focus on the Event Space as the central communication medium of MESHMdl. The Event Space offers a simple, unified communication interface for inter-agent communication as well as for communication with the middleware and resource access. Furthermore, it serves as a means for flexibly extending a MESHMdl daemon. We investigate the performance of the Event Space on different mobile devices and show that it is superior to comparable systems.     

A modified elitist genetic algorithm applied to the design optimization of complex steel structures

This paper shows the implementation of an elitist genetic algorithm that, when applied to steel structures, is able to obtain structural elements with minimum weight and satisfy the safety factors or coefficients (ultimate limit states) of the applicable building code. To this end, a modified objective function has been defined that considers the constraints established by these coefficients. In addition, the codification of the design variables has been modified so that all of them have the same probability of initial selection; a selection operator has been implemented to consider the dispersion of the individuals within the population as well as a crossover operator that interchanges the sections assigned to the structural elements without their prior modification. The final result is a robust genetic algorithm that is simple from a mathematical point of view and is able to work with complex structures under different load and constraint conditions.     

Design and other types of fixation

Design educators often comment on the difficulties that result from a premature commitment by students to a solution to a design problem. Similarly practitioners can find it difficult to move away from an idea they have developed or precedents in a field. In the psychology of problem solving this effect is called functional fixedness or fixation. It is not surprising that these effects should occur in design problem solving. However, while these types of issues have been discussed in the context of design, there has been little systematic evidence available about whether or not and under what conditions design fixation does occur. The paper reviews the results of a series of recent experiments which begin to address these issues. The results of the experiments are examined in terms of what insights they provide into the design process, what implications they have for design education and how they relate to the larger and more general area of human problem solving.     

Computer-aided design by optimization in architecture

This paper shows that optimization concepts are particularly useful in design because of their direct assistance in decision making. In this they subsume evaluation or appraisal techniques. One approach based on dynamic programming is presented as being directly applicable in computer-aided architectural design. Multi-attribute objectives in design can be handled using optimization concepts. Finally, multi-objective design, including multi-attribute multi-objective design, can be handled via the use of Pareto optimality approaches. The result of such processes is a solution database which the designer searches. The solution database contains information about the design decisions themselves as well as the performance of each solution in its various objectives. The designer still assumes responsibility for selecting particular solutions since there is no unique solution produced. It is suggested that any problem which can be manipulated quantitatively can be solved using these concepts.