Phase Equilibria in the Quaternary System Ti-Al-C-N

The quaternary system Ti-Al-C-N and its binary and ternary boundary systems are investigated using powder methods and XRD analysis. Phase equilibria at 1375°C are presented in an isothermal network for alloys up to 50 at.% Ti. In the vertical section Ti₂AIC_1-x-Ti₂AlN_1-x a complete series of solid solutions exists at 1495°C, but a wide miscibility gap occurs at 1375°C. The vertical section Ti₃AlC_1-x-Ti₃AlN_1-x is more complex because of the occurrence of the quaternary, tetragonally distorted phase Ti₃Al(C,N)_1-x ( a = 0.41135(4) nm, c = 0.41366(5) nm) and the transformation of perovskite-type Ti₃AlN_1-x into filled Re₃B-type Ti₃AlN_1-x below 1200°C.     

Oriented crystallization and mechanical properties of polypropylene nucleated on fibrillated polytetrafluoroethylene scaffolds

It is known that friction deposited polytetrafluoroethylene (PTFE) layers are able to nucleate crystallization of thin films of isotactic polypropylene (iPP). In order to investigate the influence of PTFE on the crystallization behavior and morphology of iPP in bulk, PTFE‐particles of two different sizes in various concentrations were melt‐blended with iPP and subsequently processed by injection molding. For one size of particles, high resolution scanning electron microscopy (HR‐SEM) showed the presence of a PTFE scaffold consisting of highly fibrillated PTFE particles. With X‐ray diffraction (WAXD) pole‐figures, it was evidenced that, after melting and recrystallization of the iPP matrix, a strongly oriented crystallization of iPP on this PTFE scaffold takes place (quiescent crystallization conditions). With WAXD it was also shown that under processing conditions, PTFE acts as a nucleating agent for iPP and that PTFE strongly enhances the formation of processing induced morphologies. Impact and tensile performance of the mixtures were measured. Both the strain energy release rate (G_I) and the E‐modulus were found to increase upon introducing PTFE in iPP. POLYM. ENG. SCI., 45:458–468, 2005. © 2005 Society of Plastics Engineers.     

Continuous Levels‐of‐Detail and Visual Abstraction for Seamless Molecular Visualization

Molecular visualization is often challenged with rendering of large molecular structures in real time. We introduce a novel approach that enables us to show even large protein complexes. Our method is based on the level‐of‐detail concept, where we exploit three different abstractions combined in one visualization. Firstly, molecular surface abstraction exploits three different surfaces, solvent‐excluded surface (SES), Gaussian kernels and van der Waals spheres, combined as one surface by linear interpolation. Secondly, we introduce three shading abstraction levels and a method for creating seamless transitions between these representations. The SES representation with full shading and added contours stands in focus while on the other side a sphere representation of a cluster of atoms with constant shading and without contours provide the context. Thirdly, we propose a hierarchical abstraction based on a set of clusters formed on molecular atoms. All three abstraction models are driven by one importance function classifying the scene into the near‐, mid‐ and far‐field. Moreover, we introduce a methodology to render the entire molecule directly using the A‐buffer technique, which further improves the performance. The rendering performance is evaluated on series of molecules of varying atom counts.     

Experience with model-based performance, reliability, and adaptability assessment of a complex industrial architecture

In this paper, we report on our experience with the application of validated models to assess performance, reliability, and adaptability of a complex mission critical system that is being developed to dynamically monitor and control the position of an oil-drilling platform. We present real-time modeling results that show that all tasks are schedulable. We performed stochastic analysis of the distribution of task execution time as a function of the number of system interfaces. We report on the variability of task execution times for the expected system configurations. In addition, we have executed a system library for an important task inside the performance model simulator. We report on the measured algorithm convergence as a function of the number of vessel thrusters. We have also studied the system architecture adaptability by comparing the documented system architecture and the implemented source code. We report on the adaptability findings and the recommendations we were able to provide to the system’s architect. Finally, we have developed models of hardware and software reliability. We report on hardware and software reliability results based on the evaluation of the system architecture.     

A user-friendly PC-based data acquisition and analysis system for respirometric investigations

We have developed an easy-to-use computer-based system for recording, displaying, storing and analyzing signals generated by Clark-type oxygen electrodes. A user-friendly interface of Windows-based program BioMed significantly increases the productivity of investigations. It allows to process, control, present and archive the experimental data in real time. A 12-bit analog-to-digital-converter, analog and digital filters, a possibility to zoom the obtained respiratory curves and calculation of the respiration rates by a linear regression method increase the resolution of the estimated oxygen consumption rates. The new system enables to register even small changes, such as 3-5 ngatoms O/min, in respiration rates of biological objects -- enzymes, mitochondria and permeabilized muscle fibers. The system has been developed and is regularly used for the respirometric investigations at the Laboratory of Biochemistry, Institute for Biomedical Research, Kaunas University of Medicine.