Subroutines for some plasma surface interaction processes: physical sputtering, chemical erosion, radiation enhanced sublimation, backscattering and thermal evaporation

A suite of FORTRAN subroutines/functions to generate data using empirical formulas for physical sputtering of mono-atomic targets for any elemental incident ion (atom), chemical erosion of graphite, Radiation Enhanced Sublimation (RES) of graphite, the number and energy backscattering coefficients for any elemental incident ion (atom) on a compound target and thermal evaporation of graphite is presented. Since chemical erosion, RES and thermal evaporation depend on the surface temperature of graphite, a subroutine implementing the 1-D heat diffusion equation to determine the temperature of any plasma-facing graphite surface is implemented. As an example to illustrate the use of these subroutines/functions, a simple model for the erosion of a plasma-facing surface, consisting of a simple collisionless sheath model, a 1-dimensional steady state heat diffusion model and 0-dimensional steady state particle balance at the target is developed and a sample listing of the program is presented.

Program summary

Title of program: Plasma Surface Interaction Codes (PSIC)Catalog identifier: ADTRProgram summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTRProgram obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandComputers for which the program has been designed for and others on which it has been tested: Program is designed for any computer with a FORTRAN-77 compiler. It has been tested on a Linux PC with g77, Absoft f77, f90, f95, Fujitsu f95, Lahey f95Operating systems under which the program has been tested: Linux, UNIXProgramming language used: FORTRAN-77Memory required to execute with typical data: Negligible (executable is 178 861 bytes; add to it the memory used by the Fortran library linked to)No. of bits in a word: 16No. of processors used: 1Has the code been vectorized or parallelized?: NoNo. of bytes in distributed program, including test data, etc.: 11 619No. of lines in distributed program, including test data, etc.: 1015Distribution format: tar gzip fileNature of physical problems: 0-D plasma surface interaction model used to demonstrate calls to subroutines for physical sputtering yield, chemical erosion yield of graphite, RES of graphite, backscattering coefficients, thermal evaporation of graphite and 1-D heat diffusion in graphite.Method of solution: Semi-empirical formulas are used for the PSIs and analytical formulas are used for thermal evaporation and 1-D heat diffusion in graphite.Restrictions on the complexity of the problem: All the PSIs (except for the backscattering coefficients) are valid only for a monoatomic target. The heat diffusion solution is not valid for non-uniform plasmas and for targets for which the heat diffusion is not isotropic.Typical running time: Example program takes much less than 0.01 secondUniversal features of the program: None     

DDT-related compounds bound to the nonextractable particulate matter in sediments of the Teltow Canal,Germany

Sediment samples of the Teltow Canal (Berlin, Germany) were analyzed with respect to extractable and nonextractable organic compounds. The study focused on the identification and quantitation of bound 2,2-bis(chlorophenyl)-1,1,1-trichlorethane (DDT) residues in order to obtain further information about the fate of DDT-derived compounds within the particulate matter of the aquatic environment. Various chemical degradation techniques and a complementary online pyrolysis-GC/MS method were applied to the pre-extracted sediment residues. Generally, the distribution of the bound DDT-related compounds was found to differ distinctly from the substances distribution within the extractable fraction. The main metabolite of the anaerobic degradation pathway (2,2-bis(chlorophenyl)-1,1-dichlorethane, DDD) is most abundant in the sediment extracts but occurred only in insignificant concentrations in the degradation products of all procedures applied. The most abundant DDT-metabolites released after the degradation procedures were 4,4'-DBP, 4,4'-DDA, and 4,4'-DDM. In addition, 4,4'-DDM was detected at rather high concentrations by pyrolytic analysis. The results imply a weak association to the nonextractable particulate matter based on noncovalent interactions for the observed DDT-related contaminants. The release of these compounds was initiated by the modification and degradation of the organic macromolecular matrix as well as of the inorganic material. Furthermore, numerous methoxychlor-related compounds were detected not only in the extracts but also in parts of the hydrolysis products.     

Synthesis of cubic zirconium and hafnium nitride having Th3P4 structure

High-pressure synthesis is a powerful method for the preparation of novel materials with high elastic moduli and hardness. Additionally, such materials may exhibit interesting thermal, optoelectronic, semiconductuing, magnetic or superconducting properties. Here, we report on the high-pressure synthesis of zirconium and hafnium nitrides with the stoichiometry M3N4, where M = Zr, Hf. Synthesis experiments were performed in a laser-heated diamond anvil cell at pressures up to 18 GPa and temperatures up to 3,000 K. We observed formation of cubic Zr3N4 and Hf3N4 (c-M3N4) with a Th3P4-structure, where M-cations are eightfold coordinated by N anions. The c-M3N4 phases are the first binary nitrides with such a high coordination number. Both compounds exhibit high bulk moduli around 250 GPa, which indicates high hardness. Moreover, the new nitrides, c-Zr3N4 and c-Hf3N4, may be the first members of a larger group of transition metal and/or lanthanide nitrides with interesting ferromagnetic or superconducting behaviour.     

Probing the pore space of geothermal reservoir sandstones by Nuclear Magnetic Resonance

Pulsed-Field-Gradient–Nuclear Magnetic Resonance (PFG–NMR) is an interesting method to determine microscopic but volumetrically averaged properties of pore space. In the present paper a number of sandstone samples, taken from drill cores of geothermal wells in North Germany, have been investigated. The time-dependent self-diffusion of water molecules in their confined geometry is used to probe the pore space. The short-time behaviour of the self-diffusion coefficient (anomalous diffusion) in the porous matrix allows the determination of the surface-to-pore volume ratio S/V_p. At long diffusion times, molecules scout the tortuosity of the interconnected pore space of the sandstones. The NMR results were compared with data from petrographic image analysis (PIA), adsorption experiments and electric conductivity measurements. The PFG–NMR measurements give surface-to-pore volume ratios S/V_p that are comparable to those estimated with the petrographic image analysis. The tortuosities match in most cases data from conductivity measurements, so the PFG–NMR is regarded as an appropriate tool to determine this quantity. The results are not influenced by the adherence of ‘scout-molecules’ to the pore walls. The surface-to-pore volume ratios and tortuosities were used to calculate permeabilities of the systems of interest, which were in good agreement with measured core-plug permeabilities. Results of additional NMR relaxation experiments are used to obtain adsorption isotherms for cations at active surface sites.     

Enabling resilient P2P video streaming: survey and analysis

Peer-to-Peer (P2P) techniques for multimedia streaming have been shown to be a good enhancement to the traditional client/server methods when trying to reduce costs and increase robustness. Due to the fact that P2P systems are highly dynamic, the main challenge that has to be addressed remains supporting the general resilience of the system. Various challenges arise when building a resilient P2P streaming system, such as network failures and system dynamics. In this paper, we first classify the different challenges that face P2P streaming and then present and analyze the possible countermeasures. We classify resilience mechanisms as either core mechanisms, which are part of the system, or as cross-layer mechanisms that use information from different communication layers, which might inflict additional costs. We analyze and present resilience mechanisms from an engineering point of view, such that a system engineer can use our analysis as a guide to build a resilient P2P streaming system with different mechanisms and for various application scenarios.     

Eine Dienstgüte unterstützende Webservice-Architektur für flexible Geschäftsprozesse

Web services as a technology to enable distributed business processes gain in importance. However, the support of Quality of Service (QoS) is crucial in this context. Thus, we present an integrated web service architecture with comprehensive QoS support. The architecture we introduce in this paper supports the assessment of web services to assure that only web services will be used in critical business processes that satisfy the requirements defined by the user. The selection and execution of a certain web service depends on its QoS-properties that must be guaranteed in Service Level Agreements (SLAs). The compliance with SLAs is monitored by the system as well. Furthermore we introduce a prototypical implementation of our web service architecture.     

A Parallelization Approach for Hard Real-Time Systems and Its Application on Two Industrial Programs

Applications in industry often have grown and improved over many years. Since their performance demands increase, they also need to benefit from the availability of multi-core processors. However, a reimplementation from scratch and even a restructuring of these industrial applications is very expensive, often due to high certification efforts. Therefore, a strategy for a systematic parallelization of legacy code is needed. We present a parallelization approach for hard real-time systems, which ensures a high reusage of legacy code and preserves timing analysability. To show its applicability, we apply it on the core algorithm of an avionics application as well as on the control program of a large construction machine. We create models of the legacy programs showing the potential of parallelism, optimize them and change the source codes accordingly. The parallelized applications are placed on a predictable multi-core processor with up to 18 cores. For evaluation, we compare the worst case execution times and their speedups. Furthermore, we analyse limitations coming up at the parallelization process.     

Visual signatures in video visualization

Video visualization is a computation process that extracts meaningful information from original video data sets and conveys the extracted information to users in appropriate visual representations. This paper presents a broad treatment of the subject, following a typical research pipeline involving concept formulation, system development, a path-finding user study, and a field trial with real application data. In particular, we have conducted a fundamental study on the visualization of motion events in videos. We have, for the first time, deployed flow visualization techniques in video visualization. We have compared the effectiveness of different abstract visual representations of videos. We have conducted a user study to examine whether users are able to learn to recognize visual signatures of motions, and to assist in the evaluation of different visualization techniques. We have applied our understanding and the developed techniques to a set of application video clips. Our study has demonstrated that video visualization is both technically feasible and cost-effective. It has provided the first set of evidence confirming that ordinary users can be accustomed to the visual features depicted in video visualizations, and can learn to recognize visual signatures of a variety of motion events.