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From the classical Lü chaotic system a new simple three-dimensional autonomous system is derived, which exhibits a three-scroll chaotic attractor. An approach to control this novel attractor by non-linear feedback functions is proposed. The results obtained reveal that the trajectories of the chaotic attractor can be controlled to reach certain target periodic orbits or points. Finally, some numerical simulations are provided to show the effectiveness and feasibility of the controller design method developed.  相似文献
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A safety shell pattern was defined based on a re-configuration management pattern and inspired by the architectural specifications in Specification PEARL. It is meant to be used for real-time applications to be developed with UML-RT as described. The implementation of the safety shell features as defined in Kornecki and Zalewski (Software Development for Real-Time Safety—Critical Applications. Software Engineering Workshop—Tutorial Notes, 29th Annual IEEE/NASA 03, pp 1–95, 2005), namely, its timing and state guards as well as I/O protection and exception handling mechanisms, is explained. The pattern is parameterised by defining the properties of its components as well as by defining the mapping between software and hardware architectures. Initial and alternative execution scenarios as well as the method for switching between them are defined. The goal pursued with the safety shell is to obtain clearly specified operation scenarios with well-defined transitions between them. To achieve safe and timely operation, the pattern must provide safety shell mechanisms for an application designed, i.e., enable its predictable deterministic and temporally predictable operation now and in the future.  相似文献
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The most accurate analogue-to-digital converter design presently known integrates the input voltage and employs the dual-slope principle for digitisation. However, without additional external components it is only suitable for unipolar operation, and continuous integrations are not possible, because some time is needed for the conversion process after every integration. An extended design, overcoming these two shortcomings, is given in the present paper. Furthermore, its application in multichannel measuring systems is discussed, using star-shaped and bus connections to the controlling unit, with only a single transmission line each.  相似文献
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Owing to the fast growing need for better means of building real-time systems, a number of representative languages used in real-time programming is surveyed. The evaluation focuses on seven languages which possess explicit real-time features. Based on a categorization of the latter, the seven languages are then compared with respect to their real-time capabilities. The strong points and the limitations of Ada and PEARL, the only high-level real-time languages readily applicable in industrial control environments, are covered in more detail. The evaluation reveals that none of the languages actually used in industry is genuinely real-time. Therefore, a number of new features is suggested for incorporation into existing or future languages and their run-time environments. These proposals are meant to advance the inadequate state of affairs, and also to reignite the discussion of this topic in the real-time community.  相似文献
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Wolfgang A. Halang 《Computing》1992,47(3-4):199-213
All intrinsic properties of the earliest deadline taks scheduling discipline are compiled and discussed in order to show that this is the most advantageous scheme at hand, characterised by efficiency and allowing predictable system behaviour. It is then pointed out how the method naturally extends to the scheduling of tasks having non-pre-emptable regions due to resource access constraints. A sufficient condition is derived, which allows, at any arbitrary point in time and under observation of resource constraints, to check the feasible schedulability of the tasks competing for processor allocation. This condition applies to entirely non-pre-emptable tasks as well. Taking the corresponding overhead into consideration, the circumstances are characterised under which the task context-switches imposed by the scheduling algorithm can be avoided. Favourable consequences of deadline scheduling for virtual storage management are mentioned. Finally, application oriented schemes for coping with transient overloads and thus allowing load adaptive dynamic scheduling are introduced. Such overloads can be easily detected at an early stage utilising the here established schedulability criterion.  相似文献
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A computer organisation suitable to improve the performance of embedded systems encountered in hard real-time environments is described, which enhances dependability and efficiency by exploiting possibilities for parallel processing inherent to real-time systems. It is shown that internal data transmissions due to context-switching can be eliminated and that CPUs can be relieved from a considerable amount of routine work by providing a separate module for major functions of real-time operating systems, viz., for interrupt and signal recognition, for time management, and for the administration of task execution plans and states. Considering the layer model of contemporary real-time operating systems, these functions constitute kernel and first layer. The hardware implementation of typical hard real-time support features provides a clear physical separation of the intrinsically independent functions event reaction and (user) task processing. While minimising response times in general, the architecture enables to guarantee predefined, short upper bounds for them. It also incorporates a new approach for and hardware realisation of timers characterised by utmost precision and high handling comfort. Such timers are particularly well-suited to serve in distributed real-time systems, since, by employing the exact UTC received from the satellites of GPS (the global navigation and positioning system), synchronisation is not needed anymore.  相似文献
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