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21.
Automatic Construction and Verification of Isotopy Invariants 总被引:1,自引:0,他引:1
Volker Sorge Andreas Meier Roy McCasland Simon Colton 《Journal of Automated Reasoning》2008,40(2-3):221-243
We extend our previous study of the automatic construction of isomorphic classification theorems for algebraic domains by
considering the isotopy equivalence relation. Isotopism is an important generalisation of isomorphism, and is studied by mathematicians in domains
such as loop theory. This extension was not straightforward, and we had to solve two major technical problems, namely, generating
and verifying isotopy invariants. Concentrating on the domain of loop theory, we have developed three novel techniques for
generating isotopic invariants, by using the notion of universal identities and by using constructions based on subblocks.
In addition, given the complexity of the theorems that verify that a conjunction of the invariants form an isotopy class,
we have developed ways of simplifying the problem of proving these theorems. Our techniques employ an interplay of computer
algebra, model generation, theorem proving, and satisfiability-solving methods. To demonstrate the power of the approach,
we generate isotopic classification theorems for loops of size 6 and 7, which extend the previously known enumeration results.
This work was previously beyond the capabilities of automated reasoning techniques.
The author’s work was supported by EPSRC MathFIT grant GR/S31099. 相似文献
22.
Andreas Ruh Adam-Mwanga Dieckmann Richard Heldele Volker Piotter Robert Ruprecht Christian Munzinger Jürgen Fleischer Jürgen Haußelt 《Microsystem Technologies》2008,14(12):1805-1811
In the field of micro-technology the production of metallic and ceramic micro-components by powder injection molding (PIM)
has become a more and more established fabrication method. But in order to fulfill the demand for more complex-shaped high-precision
micro-components further development work has to be performed. This is especially true if more efficient production routes
for multi-component-micro-assemblies consisting of different materials or sub-components are envisaged. To meet these challenges,
investigations are performed to realize and to establish two primary shape micro-processes. These are two-component micro-injection
molding (2C-MicroPIM) and sinter-joining. The realization of these technologies will lead to a markedly reduction of the efforts
for handling, adjustment, and assembling of metallic and ceramic micro-assemblies. Furthermore, an increased integration level
and functionality can be yielded. For an effective transfer of scientific results to industrial applications the whole process
chain must be considered, from development and construction of the tooling as well as of the components to the quality assurance
and determination of the properties of the assemblies after sintering. These primary shape processes shall enable the mutual
processing of different materials within the fabrication process, so avoiding separate mounting or assembling steps. Additionally
fixed and loose junctions between at least two components shall be realized. The progress in research and development will
be demonstrated especially by the implementation of shaft-to-collar connections between micro-gearwheels and corresponding
shafts. Regarding two-component micro-injection molding, the tool construction for shaft-to-collar connections will be presented
as well as first experimental results on the properties of selected ceramic powders and feedstocks for the special requirements
of the 2C-MicroPIM process. With the assembly step being performed outside the injection molding tool before sinter-joining
different parts and geometries can be combined quite easily. The presented article gives an overview on the concept and on
preliminary testing results for the fabrication of a shaft-to-collar-connection. Additionally, a solution for an automated
assembly of a shaft and a toothed wheel outside the injection molding tool is presented. 相似文献
23.
Nesterov A König K Felgenhauer T Lindenstruth V Trunk U Fernandez S Hausmann M Bischoff FR Breitling F Stadler V 《The Review of scientific instruments》2008,79(3):035106
We examined the high precision deposition of toner and polymer microparticles with a typical size of approximately 10 microm on electrode arrays with electrodes of 100 microm and below using custom-made microelectronic chips. Selective desorption of redundant particles was employed to obtain a given particle pattern from preadsorbed particle layers. Microparticle desorption was regulated by dielectrophoretic attracting forces generated by individual pixel electrodes, tangential detaching forces of an air flow, and adhesion forces on the microchip surface. A theoretical consideration of the acting forces showed that without pixel voltage, the tangential force applied for particle detachment exceeded the particle adhesion force. When the pixel voltage was switched on, however, the sum of attracting forces was larger than the tangential detaching force, which was crucial for desorption efficiency. In our experiments, appropriately large dielectrophoretic forces were achieved by applying high voltages of up to 100 V on the pixel electrodes. In addition, electrode geometries on the chip's surface as well as particle size influenced the desorption quality. We further demonstrated the compatibility of this procedure to complementary metal oxide semiconductor chip technology, which should allow for an easy technical implementation with respect to high-resolution microparticle deposition. 相似文献
24.
Dovletgeldi Seyitliyev Xixi Qin Manoj K. Jana Svenja M. Janke Xiaowei Zhong Wei You David B. Mitzi Volker Blum Kenan Gundogdu 《Advanced functional materials》2023,33(21):2213021
Electron–phonon interactions play an essential role in charge transport and transfer processes in semiconductors. For most structures, tailoring electron–phonon interactions for specific functionality remains elusive. Here, it is shown that, in hybrid perovskites, coherent phonon modes can be used to manipulate charge transfer. In the 2D double perovskite, (AE2T)2AgBiI8 (AE2T: 5,5“-diylbis(amino-ethyl)-(2,2”-(2)thiophene)), the valence band maximum derived from the [Ag0.5Bi0.5I4]2– framework lies in close proximity to the AE2T-derived HOMO level, thereby forming a type-II heterostructure. During transient absorption spectroscopy, pulsed excitation creates sustained coherent phonon modes, which periodically modulate the associated electronic levels. Thus, the energy offset at the organic–inorganic interface also oscillates periodically, providing a unique opportunity for modulation of interfacial charge transfer. Density-functional theory corroborates the mechanism and identifies specific phonon modes as likely drivers of the coherent charge transfer. These observations are a striking example of how electron–phonon interactions can be used to manipulate fundamentally important charge and energy transfer processes in hybrid perovskites. 相似文献
25.
Early phase distributed system design can be accomplished using solution spaces that provide an interval of permissible values for each functional parameter. The feasibility property guarantees fulfillment of all design requirements for all possible realizations. Flexibility denotes the size measure of the intervals, with higher flexibility benefiting the design process. Two methods are available for solution space identification. The direct method solves a computationally cheap optimization problem. The indirect method employs a sampling approach that requires a relaxation of the feasibility property through re-formulation as a chance constraint. Even for high probabilities of fulfillment, \(P>0.99\), this results in substantial increases in flexibility, which offsets the risk of infeasibility. This work implements the chance constraint formulation into the direct method for linear constraints by showing that its problem statement can be understood as a linear robust optimization problem. Approximations of chance constraints from the literature are transferred into the context of solution spaces. From this, we derive a theoretical value for the safety parameter \(\varOmega\). A further modification is presented for use cases, where some intervals are already predetermined. A problem from vehicle safety is used to compare the modified direct and indirect methods and discuss suitable choices of \(\varOmega\). We find that the modified direct method is able to identify solution spaces with similar flexibility, while maintaining its cost advantage. 相似文献
26.
27.
Kai Schubert Anne Weibert Volker Wulf 《International journal of human-computer studies》2011,69(10):669-678
Located in socially and culturally diverse neighborhoods, we have built a network of intercultural computer clubs, called come_IN. These clubs offer a place to share practices among children and adults of diverse ethnical backgrounds. We show how this initiative ties into the striving for the integration of migrant communities and host society in Germany. In this paper, we analyze how collaborative project work and the use of mobile media and technologies contribute to integration processes in multicultural neighborhoods. Qualitative data gathered from interviews with club participants, participative observation in the computer clubs, as well as the analysis of artifacts created during project work provides the background needed to match local needs and peculiarities with (mobile) technologies. Based on these findings we present two approaches to add to the technological infrastructure: (1) a mesh-network extending the clubs into the neighborhood and (2) a project management tool, which supports projects and stimulates the sharing of ideas among projects. 相似文献
28.
29.
Bettina Biel Author Vitae Volker Gruhn Author Vitae 《Journal of Systems and Software》2010,83(11):2031-2044
Designing easy to use mobile applications is a difficult task. In order to optimize the development of a usable mobile application, it is necessary to consider the mobile usage context for the design and the evaluation of the user-system interaction of a mobile application. In our research we designed a method that aligns the inspection method “Software ArchitecTure analysis of Usability Requirements realizatioN” SATURN and a mobile usability evaluation in the form of a user test. We propose to use mobile context factors and thus requirements as a common basis for both inspection and user test. After conducting both analysis and user test, the results described as usability problems are mapped and discussed. The mobile context factors identified define and describe the usage context of a mobile application. We exemplify and apply our approach in a case study. This allows us to show how our method can be used to identify more usability problems than with each method separately. Additionally, we could confirm the validity and identified the severity of usability problems found by both methods. Our work presents how a combination of both methods allows to address usability issues in a more holistic way. We argue that the increased quantity and quality of results can lead to a reduction of the number of iterations required in early stages of an iterative software development process. 相似文献
30.
Modelling water dynamics with DNDC and DAISY in a soil of the North China Plain: A comparative study
Roland Kröbel Qinping Sun Joachim Ingwersen Xinping Chen Fusuo Zhang Torsten Müller Volker Römheld 《Environmental Modelling & Software》2010,25(4):583-601
The performance of the DNDC and Daisy model to simulate the water dynamics in a floodplain soil of the North China Plain was tested and compared. While the DNDC model uses a simple cascade approach, the Daisy model applies the physically based Richard's equation for simulating water movement in soil. For model testing a three years record of the soil water content from the Dong Bei Wang experimental station near Beijing was used. There, the effect of nitrogen fertilization, irrigation and straw removal on soil water and nitrogen dynamics was investigated in a three factorial field experiment applying a split-split-plot design with 4 replications. The dataset of one treatment was used for model testing and calibration. Two other independent datasets from further treatments were employed for validating the models. For both models, the simulation results were not satisfying using default parameters. After parameter optimisation and the use of site-specific van Genuchten parameters, however, the Daisy model performed well. But, for the DNDC model, parameter optimisation failed to improve the simulation result. Owing to the fact that many biological processes such as plant growth, nitrification or denitrification depend strongly on the soil water content, our findings bring us to the conclusion that the site-specific suitability of the DNDC model for simulating the soil water dynamics should be tested before further simulation of other processes. 相似文献