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41.
Preparation of anchored ceramic coatings on metal substrates: a modified sol-gel technique using colloidal silica sol 总被引:1,自引:0,他引:1
M. F. M. Zwinkels S. G. Järås P. Govind Menon Knut I. Åsen 《Journal of Materials Science》1996,31(23):6345-6349
A single-step dip-coating technique was developed to produce stable films or washcoats of controlled thickness, surface area and pore-size distribution on alumina whisker-covered metal substrates (both flat plates and monoliths). Dip-coating slurries were prepared by dispersing fine porous powder in a colloidal silica sol. The method provided control over coating thickness and coating properties, such as pore-size distribution and surface area. The coating thickness could be varied between approximately 2 and 40 m by selecting slurry composition and withdrawal speed in the dipping procedure. The pore-size distribution and surface area could be varied by changing type and amount of porous filler material in the dipping slurry. Uniform and bimodal pore-size distributions were obtained using silica and ZSM-5 molecular sieves, respectively, yielding coatings with surface areas between 60 and 400 m2g–1. 相似文献
42.
We have implemented a compiler for key parts of Modelica, an object-oriented language supporting equation-based modeling and simulation of complex physical systems. The compiler is extensible, to support experiments with emerging tools for physical models. To achieve extensibility, the implementation is done declaratively in JastAdd, a metacompilation system supporting modern attribute grammar mechanisms such as reference attributes and nonterminal attributes.This paper reports on experiences from this implementation. For name and type analyses, we illustrate how declarative design strategies, originally developed for a Java compiler, could be reused to support Modelica’s advanced features of multiple inheritance and structural subtyping. Furthermore, we present new general design strategies for declarative generation of target ASTs from source ASTs. We illustrate how these strategies are used to resolve a generics-like feature of Modelica called modifications, and to support flattening, a fundamental part of Modelica compilation. To validate that the approach is practical, we have compared the execution speed of our compiler to two existing Modelica compilers. 相似文献
43.
Markus Kaufmann Dan Zenkert Per Wennhage 《Structural and Multidisciplinary Optimization》2010,41(2):325-334
A methodology for a combined cost/weight optimization of aircraft components is proposed. The objective function is formed
by a simplified form of direct operating cost, i.e. by a weighted sum of the manufacturing cost and the component weight.
Hence, the structural engineer can perform the evaluation of a design solution based on economical values rather than pure
cost or weight targets. The parameter that governs the balance between manufacturing cost and weight is called weight penalty
and incorporates the effect of fuel burn, environmental impact or contractual penalties due to overweight. Unlike previous
work, the analytical cost model and structural models are replaced by commercially available software packages that allow
a more realistic model of the manufacturing costs; further, arbitrary constraints for the structural analysis can be implemented.
By means of parametric studies it is shown that the design solution strongly depends on the magnitude of the weight penalty. 相似文献
44.
Per Bjesse 《Formal Methods in System Design》2009,35(1):56-72
In this paper we present a word-level model checking method that attempts to speed up safety property checking of industrial
netlists. Our aim is to construct an algorithm that allows us to check both bounded and unbounded properties using standard
bit-level model checking methods as back-end decision procedures, while incurring minimum runtime penalties for designs that
are unsuited to our analysis. We do this by combining modifications of several previously known techniques into a static abstraction
algorithm which is guaranteed to produce bit-level netlists that are as small or smaller than the original bitblasted designs.
We evaluate our algorithm on several challenging hardware components. 相似文献
45.
Unit verification, including software inspections and unit tests, is usually the first code verification phase in the software development process. However, principles of unit verification are weakly explored, mostly due to the lack of data, since unit verification data are rarely systematically collected and only a few studies have been published with such data from industry. Therefore, we explore the theory of fault distributions, originating in the quantitative analysis by Fenton and Ohlsson, in the weakly explored context of unit verification in large-scale software development. We conduct a quantitative case study on a sequence of four development projects on consecutive releases of the same complex software product line system for telecommunication exchanges. We replicate the operationalization from earlier studies, analyzed hypotheses related to the Pareto principle of fault distribution, persistence of faults, effects of module size, and quality in terms of fault densities, however, now from the perspective of unit verification. The patterns in unit verification results resemble those of later verification phases, e.g., regarding the Pareto principle, and may thus be used for prediction and planning purposes. Using unit verification results as predictors may improve the quality and efficiency of software verification. 相似文献
46.
A long-standing aim of quantum information research is to understand what gives quantum computers their advantage. This requires separating problems that need genuinely quantum resources from those for which classical resources are enough. Two examples of quantum speed-up are the Deutsch–Jozsa and Simon’s problem, both efficiently solvable on a quantum Turing machine, and both believed to lack efficient classical solutions. Here we present a framework that can simulate both quantum algorithms efficiently, solving the Deutsch–Jozsa problem with probability 1 using only one oracle query, and Simon’s problem using linearly many oracle queries, just as expected of an ideal quantum computer. The presented simulation framework is in turn efficiently simulatable in a classical probabilistic Turing machine. This shows that the Deutsch–Jozsa and Simon’s problem do not require any genuinely quantum resources, and that the quantum algorithms show no speed-up when compared with their corresponding classical simulation. Finally, this gives insight into what properties are needed in the two algorithms and calls for further study of oracle separation between quantum and classical computation. 相似文献
47.
Spacecraft formation reconfiguration with collision avoidance 总被引:1,自引:0,他引:1
In this paper we present a behavioral control solution for reconfiguration of a spacecraft formation using the Null-Space Based (NSB) concept. The solution is task based, and aims to reconfigure and maintain a rigid formation while avoiding collisions between spacecraft. A model of relative translation is derived, together with a passivity-based sliding surface controller which globally stabilizes the equilibrium point of the closed-loop system. The NSB control method is implemented by giving each task different priorities and then calculating desired velocity and a Jacobian matrix for each spacecraft and each task. The velocity vector for each task is then projected into the null-space for higher prioritized tasks to remove conflicting velocity components. Simulation results are presented, showing that each spacecraft moves into the predefined formation without breaking any rules for the higher priority tasks, and all collisions are avoided. 相似文献
48.
Smith BW Andreassen S Shaw GM Jensen PL Rees SE Chase JG 《Computer methods and programs in biomedicine》2007,86(2):153-160
Diagnosing cardiovascular system (CVS) diseases from clinically measured data is difficult, due to the complexity of the hemodynamic and autonomic nervous system (ANS) interactions. Physiological models could describe these interactions to enable simulation of a variety of diseases, and could be combined with parameter estimation algorithms to help clinicians diagnose CVS dysfunctions. This paper presents modifications to an existing CVS model to include a minimal physiological model of ANS activation. A minimal model is used so as to minimise the number of parameters required to specify ANS activation, enabling the effects of each parameter on hemodynamics to be easily understood. The combined CVS and ANS model is verified by simulating a variety of CVS diseases, and comparing simulation results with common physiological understanding of ANS function and the characteristic hemodynamics seen in these diseases. The model of ANS activation is required to simulate hemodynamic effects such as increased cardiac output in septic shock, elevated pulmonary artery pressure in left ventricular infarction, and elevated filling pressures in pericardial tamponade. This is the first known example of a minimal CVS model that includes a generic model of ANS activation and is shown to simulate diseases from throughout the CVS. 相似文献
49.
Björn Regnell Martin Höst Johan Natt och Dag Per Beremark Thomas Hjelm 《Requirements Engineering》2001,6(1):51-62
When developing packaged software, which is sold ‘off-the-shelf’ on a worldwide marketplace, it is essential to collect needs
and opportunities from different market segments and use this information in the prioritisation of requirements for the next
software release. This paper presents an industrial case study where a distributed prioritisation process is proposed, observed
and evaluated. The stakeholders in the requirements prioritisation process include marketing offices distributed around the
world. A major objective of the distributed prioritisation is to gather and highlight the differences and similarities in
the requirement priorities of the different market segments. The evaluation through questionnaires shows that the stakeholders
found the process useful. The paper also presents novel approaches to visualise the priority distribution among stakeholders,
together with measures on disagreement and satisfaction. Product management found the proposed charts valuable as decision
support when selecting requirements for the next release, as they revealed unforeseen differences among stakeholder priorities.
Conclusions on stakeholder tactics are provided and issues of further research are identified, including ways of addressing
identified challenges. 相似文献
50.