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21.
H. Potente M. Bastian K. Bergemann M. Senge G. Scheel Th. Winkelmann 《Polymer Engineering and Science》2001,41(2):222-231
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. 相似文献
22.
On measuring the accuracy of SLAM algorithms 总被引:1,自引:0,他引:1
Rainer Kümmerle Bastian Steder Christian Dornhege Michael Ruhnke Giorgio Grisetti Cyrill Stachniss Alexander Kleiner 《Autonomous Robots》2009,27(4):387-407
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. 相似文献
23.
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. 相似文献
24.
Using a Michelson white-light interferometer, we measure the group-delay dispersion and third-order dispersion coefficients, d2(phi)/d(omega)2 and d3(phi)/d(omega)3, of chromium-doped forsterite (Cr:Mg2SiO4) over wavelengths of 1050-1600 nm for light polarized along both the c and b crystal axes. In this interval, the second-order dispersion for the c axis ranges from 35 fs2/mm to -14 fs2/mm, and the third-order dispersion ranges from 36 fs3/mm to 142 fs3/mm. For the b axis the second-order dispersion ranges from 35 fs2/mm to -15 fs2/mm and the third-order from 73 fs3/mm to 185 fs3/mm. Our data are relevant for the development of optimized dispersion compensation tools for Cr:Mg2SiO4 femtosecond lasers. These measurements help to clarify previously published results and show some significant discrepancies that existed, especially in the third-order dispersion. Our results should furthermore be useful to build up an analytic expression for the index of refraction of chromium forsterite. 相似文献
25.
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. 相似文献
26.
CTOD‐R curves of the metal‐clad interface of API X52 pipes cladded with an Inconel 625 alloy by welding overlay 下载免费PDF全文
A. A. de Araújo F. L. Bastian E. M. Castrodeza 《Fatigue & Fracture of Engineering Materials & Structures》2016,39(12):1477-1487
Crack‐tip opening displacement resistance curves (CTOD‐R) of the substrate/cladding interface of an API 5 L X52 steel pipe internally coated with Inconel 625 applied by TIG (GTAW) welding were experimentally evaluated. A small pipe section with 168 mm of outer diameter and 22.5 mm of thickness was internally coated with a 15 mm thick layer of Inconel 625 corrosion resistant alloy. Tension test specimens were obtained from both substrate and cladding, as well as compact tension test specimens (C(T)) for the evaluation of CTOD‐R curves. The fracture testing specimens were notched at the interface in RL orientation. In addition to fracture and tensile testing, microstructural characterization was conducted at the interface using optical microscopy (OM) and scanning electron microscopy (SEM). Qualitative chemical composition scanning and microhardness determination were also performed. The results indicated high fracture toughness for the substrate/cladding interface and the absence of low toughness regions at the interface of the tested samples. 相似文献
27.
Patrick H. Pun Safa Abdalla Geoffrey A. Block Glenn M. Chertow Ricardo Correa‐Rotter Bastian Dehmel Tilman B. Drüeke Jürgen Floege William G. Goodman Charles A. Herzog Gerard M. London Kenneth W. Mahaffey Sharon M. Moe Patrick S. Parfrey David C. Wheeler John P. Middleton 《Hemodialysis international. International Symposium on Home Hemodialysis》2016,20(3):421-431
28.
George Makrides Bastian Zinsser George E. Georghiou Markus Schubert Jürgen H. Werner 《Solar Energy Materials & Solar Cells》2009,93(6-7):1095-1099
This paper describes field investigations performed and the evaluated temperature behaviour of 13 different types of PV modules, which have been exposed to real conditions both in Stuttgart, Germany and Nicosia, Cyprus. The temperature coefficients have been evaluated in two ways. The first using direct outdoor measurements and the second through the application of data manipulation techniques on the measured meteorological and operational data collected by the installed sensors present at the test sites. The results from the two methods are finally compared and validated demonstrating the reasonable agreement with the manufacturers’ data. 相似文献
29.
Comparing Different Synthesis Procedures for Carbide‐Derived Carbon‐Based Structured Catalyst Supports 下载免费PDF全文
Different approaches were analyzed to combine the tuneable micropore structure of carbide‐derived carbons with a foam‐like secondary porosity. The resulting structured catalyst supports were characterized in detail and applied in the model reaction of ethene hydrogenation. Preparation methods studied were dip‐coating using polytetrafluoroethylene as binder on cellular metal structures, a chemical vapor deposition coating of the metal structures with thin carbide layers and subsequent conversion to carbide‐derived carbon, and the partial or full conversion of carbide foams to carbon/carbide composites. For the binder method, optimal parameters for stable slurry preparation as well as for calcination of the slurry were obtained. It could further be demonstrated that the conversion of carbide foams into carbon/carbide composites leads to an appreciation between decreasing mechanical strength and increasing specific surface area. 相似文献
30.
O. Bastian 《Drying Technology》1997,15(9):2145-2164
This paper presents a synthesis of our scientific activity in the area of heat and moisture transfers in capillary-porous bodies. The materials which have been under investigation are essentially in the field of Civil Engineering but our ways of experimentation may be generalized.
Transfers may be characterized by two independent variables : temperature and water content. We have been concerned by the achievement of measurement technics of these quantities and of perturbation technics of materials at equilibrium.
When comparing a fitting model and the temperature or water content response to such perturbations, it is possible to infer the values of parameters which are significant. Then, the experimental results must be compared with results obtained by other authors or by means of different methods.
In the future, the assumption of an unstrained porous skeleton will not be kept any longer and the coupling of transfers with mechanical phenomena will be considered. 相似文献
Transfers may be characterized by two independent variables : temperature and water content. We have been concerned by the achievement of measurement technics of these quantities and of perturbation technics of materials at equilibrium.
When comparing a fitting model and the temperature or water content response to such perturbations, it is possible to infer the values of parameters which are significant. Then, the experimental results must be compared with results obtained by other authors or by means of different methods.
In the future, the assumption of an unstrained porous skeleton will not be kept any longer and the coupling of transfers with mechanical phenomena will be considered. 相似文献