12,359 research outputs found
Neural Feedback Scheduling of Real-Time Control Tasks
Many embedded real-time control systems suffer from resource constraints and
dynamic workload variations. Although optimal feedback scheduling schemes are
in principle capable of maximizing the overall control performance of
multitasking control systems, most of them induce excessively large
computational overheads associated with the mathematical optimization routines
involved and hence are not directly applicable to practical systems. To
optimize the overall control performance while minimizing the overhead of
feedback scheduling, this paper proposes an efficient feedback scheduling
scheme based on feedforward neural networks. Using the optimal solutions
obtained offline by mathematical optimization methods, a back-propagation (BP)
neural network is designed to adapt online the sampling periods of concurrent
control tasks with respect to changes in computing resource availability.
Numerical simulation results show that the proposed scheme can reduce the
computational overhead significantly while delivering almost the same overall
control performance as compared to optimal feedback scheduling.Comment: To appear in International Journal of Innovative Computing,
Information and Contro
Fuzzy Feedback Scheduling of Resource-Constrained Embedded Control Systems
The quality of control (QoC) of a resource-constrained embedded control
system may be jeopardized in dynamic environments with variable workload. This
gives rise to the increasing demand of co-design of control and scheduling. To
deal with uncertainties in resource availability, a fuzzy feedback scheduling
(FFS) scheme is proposed in this paper. Within the framework of feedback
scheduling, the sampling periods of control loops are dynamically adjusted
using the fuzzy control technique. The feedback scheduler provides QoC
guarantees in dynamic environments through maintaining the CPU utilization at a
desired level. The framework and design methodology of the proposed FFS scheme
are described in detail. A simplified mobile robot target tracking system is
investigated as a case study to demonstrate the effectiveness of the proposed
FFS scheme. The scheme is independent of task execution times, robust to
measurement noises, and easy to implement, while incurring only a small
overhead.Comment: To appear in International Journal of Innovative Computing,
Information and Contro
Nâ˛-(Propan-2-ylÂidene)nicotinohydrazide
Crystals of the title compound, C9H11N3O, were obtained from a condensation reaction of nicotinohydrazide and acetone. In the molÂecular structure, the pyridine ring is oriented at a dihedral angle of 36.28â
(10)° with respect to the amide plane. In the crystal structure, molÂecules are linked via NâHâŻO hydrogen bonds, forming chains
Diurnal modulation of electron recoils from DM-nucleon scattering through the Migdal effect
Halo dark matter (DM) particles could lose energy due to the scattering off
nuclei within the Earth before reaching the underground detectors of DM direct
detection experiments. This Earth shielding effect can result in diurnal
modulation of the DM-induced recoil event rates observed underground due to the
self-rotation of the Earth. For electron recoil signals from DM-electron
scatterings, the current experimental constraints are very stringent such that
the diurnal modulation cannot be observed for halo DM. We propose a novel type
of diurnal modulation effect: diurnal modulation in electron recoil signals
induced by DM-nucleon scattering via the Migdal effect. We set so far the most
stringent constraints on DM-nucleon scattering cross section via the Migdal
effect for sub-GeV DM using the S2-only data of PandaX-II and PandaX-4T with
improved simulations of the Earth shielding effect. Based on the updated
constraints, we show that the Migdal effect induced diurnal modulation of
electron events can still be significant in the low energy region, and can be
probed by experiments such as PandaX-4T in the near future
Study on the Rheological Properties and Constitutive Model of Shenzhen Mucky Soft Soil
In order to obtain the basic parameters of numerical analysis about the time-space effect of the deformation occurring in Shenzhen deep soft-soil foundation pit, a series of triaxial consolidated-undrained shear rheology tests on the peripheral mucky soft soil of a deep foundation pit support were performed under different confining pressures. The relations between the axial strain of the soil and time, as well as between the pore-water pressure of the soil and time, were achieved, meanwhile on the basis of analyzing the rheological properties of the soil, the relevant rheological models were built. Analysis results were proved that the rheology of Shenzhen mucky soft soil was generally viscous, elastic, and plastic, and had a low yield stress between 90 and 150 kPa. The increase in pore-water pressure made the rheological time effect of the mucky soft soil more remarkable. Thus, the drainage performance in practical engineering should be improved to its maximum possibility extent to decrease the soft-soil rheological deformation. Lastly, a six-component extended Burgers model was employed to fit the test results and the parameters of the model were determined. Findings showed that the extended Burgers model could satisfactorily simulate the various rheological stages of the mucky soft soil. The constitutive model and the determination of its parameters can be served as a foundation for the time-space effect analysis on the deformation of deep soft-soil foundation pits
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