Industrielle aspekte der suspensionspolymerisation

Suspension polymerization is one of the most important processes for the production of high polymers. Great demands are made on the technical applicability of the polymers. In order to meet these requirements the distribution of the particle sizes and the morphology of the particles are of great importance. The size and the structure of the particles depend in a complicated interaction on factors such as the chemical structure of the suspending agent, the concentration of the suspending agent and on the agitation conditions. The interdependence of these factors have been and still are explained differently. Important mechanistic and process engineering aspects of the suspension polymerization are demonstrated by the polymerization of vinylchloride and styrene.     

Ventilation of passenger car cabins: comparison of experimental data and numerical calculations

The complex flow in the interior of a passenger car cabin is measured and calculated in a Reynolds number range of practical importance. It turns out that the mean flow field compares quite well, even in minor details. But, experiments and calculations deviate considerably as far as turbulent quantities are concerned. The situation is analysed by a closer look to the physics of the flow field. From this, conclusions are drawn why the k−ɛ model applied here might be inappropriate for the flow field under consideration.     

Rayleigh Mixture Model-Based Hidden Markov Modeling and Estimation of Noise in Noisy Speech Signals

In this paper, we propose a new statistical model for noise periodogram modeling and estimation. The proposed model is a hidden Markov model (HMM) with a Rayleigh mixture model (RMM) in each state. For this new model, we derive an expectation-maximization (EM) training algorithm and a minimum mean-square error (MMSE) noise periodogram estimator. It is shown that when compared to the Gaussian mixture model (GMM)-based HMM, the RMM-based HMM has less computationally complex EM iterations and gives a better fit of the noise periodograms when the mixture models has a low number of components. Furthermore, we propose a specialization of the proposed model, which is shown to provide better MMSE noise periodogram estimates than any other of the tested HMM initializations for cyclo-stationary noise types     

Screening, Nonadiabaticity, and Quantized Acoustoelectric Current

Quantized single-electron transport driven by surface acousticwaves (SAW) through a pinched-off narrow constriction isstudied theoretically. Long-range Coulomb interaction causesthe tunneling coupling between the two-dimensional electrongas (2DEG) and the moving minimum of the SAW-induced potentialto decay rapidly with time. The energy scale /,associated with the characteristic time of this decay ,controls both the width of the transition regions between theplateaus and the slope of the plateaus. This sets a limit forthe accuracy of the quantization of acoustoelectric current atlow temperature.     

Attributed graph transformation with node type inheritance

The aim of this paper is to integrate typed attributed graph transformation with node type inheritance. Borrowing concepts from object oriented systems, the main idea is to enrich the attributed type graph with an inheritance relation and a set of abstract nodes. In this way, a node type inherits the attributes and edges of all its ancestors. Based on these concepts, it is possible to define abstract productions, containing abstract nodes. These productions are equivalent to a number of concrete productions, resulting from the substitution of the abstract node types by the node types in their inheritance clan. Therefore, productions become more compact and suitable for their use in combination with meta-modelling. The main results of this paper show that attributed graph transformation with node type inheritance is fully compatible with the existing concept of typed attributed graph transformation.     

A taxonomy of interaction models for Internet and ATM quality of service architectures

In communication systems there are two worlds at the moment: Internet and ATM. Both possess Quality of Service (QoS) architectures which shall allow them to integrate services of data and telecommunications formerly performed by separate infrastructures. We believe that none of them will be able to oust the other. That means both will exist for at least the middle-term future. Therefore, an interaction between both appears to be necessary, especially in the field of distributed multimedia applications where both worlds meet first. In order to perform gracefully, distributed multimedia applications require a certain QoS provision, in particular from the communication system. Thus, for such applications the existence of heterogeneous IP/ATM networks makes the interaction between Internet and ATM QoS architectures an important issue. In this article a taxonomy of interaction models for the Internet and ATM QoS architectures is developed. We do not let our view be restricted by existing approaches for the interaction between ATM and Internet. Instead we will derive more unconventional models by regarding the possible communication patterns based on different topological variants for heterogeneous IP/ATM networks. The investigation is driven by applications' communication requirements. This is accomplished by examining possibly interacting applications and their communication patterns. The interaction models are contrasted and compared to each other and their assumptions and implications are shown. The derived taxonomy of models allows us to classify proposed approaches for the interaction of Internet and ATM QoS architectures. Thereby we are able to identify the basic assumptions of these approaches and their corresponding restrictions.     

t-ZrO2 toughened Al2O3 free-standing films and as oxidation mitigating thin films on silicon nitride via colloidal processing of flame made nanopowders (NPs)

Zirconia toughened aluminas (ZTAs) are one of the most important engineering ceramics with high melting points, excellent mechanical strength, and chemical stability, and are commonly used as wear resistant and high-temperature components, as prosthetic implants, and electric circuit substrates. In this work, we explore methods of processing fine-grained, dense, thin, free-standing (ZrO₂)_x(Al₂O₃)_1−x films (x = 0-50 mol%, ~40 μm thick) by sintering flame made nanopowders (NPs) to optimize the t-ZrO₂ content, sinterability, and microstructures under select conditions (1120°C-1500°C/5 h in O₂ or 95%N₂/5%H₂). In all cases, the final sintered products retain t-ZrO₂ with average grain sizes (AGSs) of 0.1-1 μm. ZTA film thicknesses were increased to ~200 μm to assess potential as electronic substrates. Excellent fracture toughness (24 MPa m^1/2) and small AGSs of 0.7 μm were found for ~200 μm thick ZTA films sintered at 1500°C/5 h/N₂/H₂ using a three-step binder burnout process. Furthermore, we show that homogeneous ZTA thin films (<5 μm thick) can be sintered on Si₃N₄ substrates (thickness ≈ 300 μm) to provide physical protection against oxidation under extreme conditions (1500°C/1 h/O₂), offering additional practical utility for high-temperature ceramics and power electronic substrates.     

Temperature dependence of indentation size effect,dislocation pile‐ups,and lattice friction in (001) strontium titanate

Nanoindentations with a Berkovich type indenter were performed on (001) strontium titanate (STO) single crystal at 25°C and 350°C, analyzing the influence of temperature on the indentation size effect (ISE) and dislocation structure around the residual impression. It is found that the STO exhibits an ISE, which is strongly reduced at 350°C compared to 25°C. The dislocation structure around the residual impression has been resolved using an etch‐pit technique. At 25°C, the extension of the dislocation pile‐ups were found to be shorter as compared to 350°C. This also correlates with the smaller size effects at 350°C. Peach‐Koehler forces and the elastic‐plastic indentation stress field were used to model the influence of the lattice frictional stress on the dislocation pile‐ups. Based on an equilibrium position of the outermost dislocations, the average lattice frictional stresses were calculated to be 89 MPa and 46 MPa at 25°C and 350°C, respectively.