Influence of geometry modifications on the permeability of open-cell foams

A stochastic microstructure model based on a random Laguerre tessellation is used to simulate virtual open cell foam structures. Both circular cylindric and concave triangular strut cross section shapes are considered. Additional geometry modifications are introduced by relaxation of the tessellation cells using the Surface Evolver software and by closing a certain percentage of the foam windows. The effect of these modifications on the foams' permeabilities is investigated. In particular, permeability anisotropies resulting from anisotropic closing of the windows are taken into account. The dimensionless permeability (Darcy number) in the different directions is well explained by regression models using porosity, geometric tortuosity, and constrictivity as explanatory variables.     

Flame retardant investigations on carbon fibre-reinforced polyurethane resin parts for aircraft applications produced by wet compression moulding

Epoxy resins are widely used in composite materials for aircraft applications. However, they are difficult to recycle, thus posing an increasing challenge to the aviation sector. By contrast, polyurethane resins (PUR) can be easily chemically recycled by solvolysis, but structural parts made of carbon fibre-reinforced polyurethanes (CF-PURs) are currently not in use in aircraft applications. This is due to a lack of knowledge about the properties of CF-PURs, especially during exposure to higher temperatures and to fire. To increase the recyclability of aircraft parts, for example interior structures like seats, there is a need for CF-PUR components which are able to fulfil the flame retardant regulations as well as the quality and production cycle time requirements of the aviation industry. It was found that a CF-PUR formulation processed by wet compression moulding containing 9 wt% of a phosphorous polyol is able to fulfil these requirements for aviation interior applications.     

Meta-analysis of net energy return for wind power systems

This analysis reviews and synthesizes the literature on the net energy return for electric power generation by wind turbines. Energy return on investment (EROI) is the ratio of energy delivered to energy costs. We examine 119 wind turbines from 50 different analyses, ranging in publication date from 1977 to 2007. We extend on previous work by including additional and more recent analyses, distinguishing between important assumptions about system boundaries and methodological approaches, and viewing the EROI as function of power rating. Our survey shows an average EROI for all studies (operational and conceptual) of 25.2 (n = 114; std. dev = 22.3). The average EROI for just the operational studies is 19.8 (n = 60; std. dev = 13.7). This places wind in a favorable position relative to fossil fuels, nuclear, and solar power generation technologies in terms of EROI.     

1‐Ethynyl Ethers as Efficient Thermal Crosslinking System for Hole Transport Materials in OLEDs

A new crosslinking concept based on a thermally activated one‐component building block with thermally initiated crosslinkable ynol ether is introduced. For polystyrene matrices with glass transition temperatures below the reaction temperature, full conversion is reached within 30 min at 160 °C without employing any catalysts or co‐reactants. The ynol ethers are chemically inert toward a variety of reaction conditions (e.g., radicals and strong bases) and consequently applicable to a wide range of materials for organic electronics. The crosslinkable solid compounds are bench‐stable over more than a year. The broad applicability is demonstrated with a liquid model compound and a specifically designed crosslinking monomer introduced successfully as building block into polystyrenes with pending hole transporting groups. A detailed study of crosslinking kinetics by infrared measurements as well as an alternative method of crosslinker content determination utilizing differential scanning calorimetry is presented. The crosslinkable polymer and the corresponding noncrosslinkable molecule tris(4‐(3,6‐dibutoxy‐9H‐carbazol‐9‐yl)phenyl)amine (BuO₆TCTA) are synthesized and investigated as hole transport layers (HTLs) in phosphorescent organic light emitting diodes (OLEDs). OLEDs with crosslinked and noncrosslinked HTLs show efficiencies around 80 cd A^?1, indicating negligible influence of the crosslinking process on the device performance while yielding better HTL durability against solvent rinsing.     

Cost-effectiveness of energy efficiency programmes—evaluating the impacts of a regional programme in France

This paper presents the evaluation of a regional energy efficiency programme implemented in two “départements” of France. électricité de France (EDF), a French energy company, provides refurbishment advice and financial incentives to end-users in the residential sector as well as specific training courses and certification to local installation contractors and building firms. Refurbishment measures analysed in this paper are efficient space heating equipment (condensing boilers, heat pumps and wood stoves or boilers), solar water heating systems and the installation of double-glazed windows. A billing analysis based on a survey of programme participants’ energy consumption is used to calculate the energy savings attributed to the programme. In order to receive an economic feedback of this demonstration programme, the evaluation of both saved energy and programme costs is of importance. Detailed knowledge of the programme’s cost-effectiveness is essential for EDF to achieve the saving obligations imposed by the French White Certificate scheme at the lowest cost. Results of this evaluation can support the development and implementation of further energy efficiency programmes with similar characteristics in other regions of France. The cost-effectiveness is determined from the perspective of the programme participant and the society as well as the energy company in charge of the programme. All cost and benefit components are calculated in Euro per kilowatt-hour, which allows a direct comparison of levelized costs of conserved energy with the avoidable costs of the energy supply system.     

Electrochemical synthesis of macroporous aluminium films and their behavior towards lithium deposition/stripping

In the present study macroporous aluminium electrodes were made by template assisted electrodeposition from ionic liquids. Polystyrene (PS) spheres (diameter 600 nm) were applied onto polished copper electrodes by immersion into an alcoholic suspension containing PS spheres. Al was deposited from the chloroaluminate ionic liquid [EMIm]Cl/AlCl₃ (40/60 mol.%) on this substrate. After chemical dissolution of the PS spheres a macroporous aluminium electrode was obtained which served as a host material for Li deposition from ionic liquids. Lithium deposition in this matrix is reversible showing certain activation with an increasing number of cycles. After 10 cycles of Li deposition/dissolution the macroporous structure is still visible.     

A large neighborhood search approach for the paint shop scheduling problem

Journal of Scheduling - Minimizing the setup costs caused by color changes is one of the main concerns for paint shop scheduling in the automotive industry. Yet, finding an optimized color sequence...     

Material modeling for parametric,anisotropic finite strain hyperelasticity based on machine learning with application in optimization of metamaterials

Mechanical metamaterials such as open- and closed-cell lattice structures, foams, composites, and so forth can often be parametrized in terms of their microstructural properties, for example, relative densities, aspect ratios, material, shape, or topological parameters. To model the effective constitutive behavior and facilitate efficient multiscale simulation, design, and optimization of such parametric metamaterials in the finite deformation regime, a machine learning-based constitutive model is presented in this work. The approach is demonstrated in application to elastic beam lattices with cubic anisotropy, which exhibit highly nonlinear effective behaviors due to microstructural instabilities and topology variations. Based on microstructure simulations, the relevant material and topology parameters of selected cubic lattice cells are determined and training data with homogenized stress-deformation responses is generated for varying parameters. Then, a parametric, hyperelastic, anisotropic constitutive model is formulated as an artificial neural network, extending a recent work of the author extending a recent work of the author, Comput Mech., 2021;67(2):653-677. The machine learning model is calibrated with the simulation data of the parametric unit cell. The authors offer public access to the simulation data through the GitHub repository https://github.com/CPShub/sim-data . For the calibration of the model, a dedicated sample weighting strategy is developed to equally consider compliant and stiff cells and deformation scenarios in the objective function. It is demonstrated that this machine learning model is able to represent and predict the effective constitutive behavior of parametric lattices well across several orders of magnitude. Furthermore, the usability of the approach is showcased by two examples for material and topology optimization of the parametric lattice cell.     

Countering Malicious DeepFakes: Survey,Battleground, and Horizon

International Journal of Computer Vision - The creation or manipulation of facial appearance through deep generative approaches, known as DeepFake, have achieved significant progress and promoted a...     

Melvin H. Marx (1919-2005).

Presents an obituary for Melvin Herman Marx. Melvin H. Marx was born on June 8, 1919, in Brooklyn, New York. He died peacefully of congestive heart failure in the presence of all of his immediate family on May 9, 2005, in Ft. Pierce, Florida. Marx's entire life was devoted to psychology as a science. He was deeply committed to the belief that the scientific method was the right one for solving human problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)