A note on the time travel approach for handling time windows in vehicle routing problems

In this paper, we identify two cases in which the proposition for calculating time window penalties presented in Nagata, Y., Bräysy, O. and Dullaert, W. A penalty-based edge assembly memetic algorithm for the vehicle routing problem with time windows, Computers & Operations Research 2010;37(4): 724–37 yields incorrect results. We derive the corrected proposition and use numerical studies to show that a significant proportion of the evaluations performed by a Tabu Search for VRPTW falls under the two incorrect cases. Moreover, we demonstrate that the incorrect time window handling has a significant negative impact on the solution quality of the Tabu Search.     

Thermal and Electrical Conductivity of Amorphous and Graphitized Carbide‐Derived Carbon Monoliths

The influence of graphitization and composition of carbide‐derived carbon (CDC) monoliths on the electrical and thermal conductivity was investigated. Carbon monoliths with varying porosities were synthesized employing biomorphous macroporous TiC and SiC as precursors. Graphitization was carried out in situ during high‐temperature chlorination with and without addition of nickel, iron, and cobalt chloride to the carbide. The graphitized monoliths showed improved properties. The results demonstrate that despite graphitic carbon also glass‐like carbon, stemming from the carbide synthesis, increases the thermal and electrical conductivity significantly.     

Relevance of the acid–base approach in prediction of adhesion properties in two‐component injection moulding

We demonstrate the use of innovative wetting method in prediction of the adhesion properties of biobased polymers for two‐component injection moulding, taking into account the acid–base surface properties of joined materials. The measurements were carried out in accordance with modified Berger method by calculation of the difference in shortened acidity parameter ΔD_short between hard and soft component. Correlation factors up to 0.99 were observed between ΔD_short and peel force. In comparison to results obtained by conventional wetting methods, high potential for the selection of components with high interface adhesion and for prediction of the functionality by the acid–base approach was demonstrated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43048.     

Properties and weldability of plasticized polylactic acid films

The objectives of the presented work were to investigate films based on polylactic acid (PLA) and polyethylene glycol (PEG) in order to improve ductility and weldability of PLA films. The effect of plasticizer amount on the thermal, rheological, and mechanical properties of PLA plasticized films was investigated. The PEG content does affect the glass transition and the cold crystallization temperature of PLA in blends, while the melting temperature was not affected by the addition of PEG. The complex viscosity of the neat PLA granules and of plasticized films showed strong temperature and angular velocity dependence. The Young's modulus and tensile strength of plasticized films were improved with increasing plasticizer concentration, while the elongation at break stays rather constant. Plasticized PLA films were furthermore heat welded. These investigations showed that plasticized PLA films can be welded by heat welding. The obtained weld strength is strongly depending on the PEG amount as well as on selected welding parameters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40394.     

Morphology of polymer blends in the melting section of co‐rotating twin screw extruders

The properties of polymer blends are largely determined by the morphological structure of the polymer combinations that are involved. In terms of extruder design, this means it is necessary to have models available for estimating the development of the morphology over the length of the screws. Since significant morphological changes are observed in the melting section, in particular, is it necessary to analyze not only the plasticizing process for binary material combinations but also the initial formation and further development of the morphology in this section of the extruder. In the framework of this study, experimental investigations were conducted into polypropylene/polyamide 6 (PP/PA6) blends with small components (by weight) of the disperse PA phase. Apart from varying the process conditions of screw speed and throughput, the viscosity ratio was also varied through the use of two different PP grades. The degree of melting and the development of the morphology over the length of the screws were determined for the individual tests. The study of blend morphology in the melting section reveals key findings that must be taken into account for modeling the initial formation and further development of the morphology. It is very clear that, on the second component, which melts at higher temperatures, a kind of melt film removal occurs at the surface of the granules as they melt. The drops of second component in the melting section, which are directly adjacent to components that have not yet fully melted in some cases, have already assumed dimensions (in the μm range) similar to those that are seen at the end of the extrusion process. This means that, in the melting section of the twin‐screw extruder, no volumes become detached from or are worn off the already‐molten granule surfaces. An evaluation of scanning electron micrographs also shows that, in the melting section of co‐rotating twin‐screw extruders, virtually all the degradation mechanisms that can essentially be distinguished, such as quasi‐steady drop breakup, folding, end pinching and decomposition through capillary instabilities, take place in parallel.     

On measuring the accuracy of SLAM algorithms

In this paper, we address the problem of creating an objective benchmark for evaluating SLAM approaches. We propose a framework for analyzing the results of a SLAM approach based on a metric for measuring the error of the corrected trajectory. This metric uses only relative relations between poses and does not rely on a global reference frame. This overcomes serious shortcomings of approaches using a global reference frame to compute the error. Our method furthermore allows us to compare SLAM approaches that use different estimation techniques or different sensor modalities since all computations are made based on the corrected trajectory of the robot. We provide sets of relative relations needed to compute our metric for an extensive set of datasets frequently used in the robotics community. The relations have been obtained by manually matching laser-range observations to avoid the errors caused by matching algorithms. Our benchmark framework allows the user to easily analyze and objectively compare different SLAM approaches.     

Isolation of a novel mycobacterium from an adolescent with cervical lymphadenitis

A slow-growing mycobacterium was isolated from a cervical lymph node of an adolescent male. This isolate produced small, smooth, scotochromogenic colonies after 6 weeks of incubation at 25 degrees C and 30 degrees C (but not at 37 degrees C or 43 degrees C). The results of 16S-rRNA gene sequencing and high-performance liquid chromatography suggest that this isolate belongs to a hitherto unrecognised pathogenic species.     

Material forces for inelastic models at large strains: application to fracture mechanics

Elastomeric materials show a wide range of different elastic and inelastic properties. Additionally, this class of materials is subjected to large deformations. Considering all these effects, fracture mechanical investigations are very challenging tasks and cannot be performed with standard approaches. Effects of inhomogeneities and discontinuities such as cracks can be investigated with the so-called material force approach in an efficient and elegant way. For comprehensive investigations of inelastic materials, the complete balance of the material motion problem has to be formulated. In this case, the material volume forces depend on the internal history variables which are required for the inelastic constitutive model. This paper derives a general formulation for rate-dependent and rate-independent inelastic materials based on a multiplicative split of the deformation gradient to cover viscoelastic and elastoplastic materials at finite deformations.