444 research outputs found
Specification of coordination behaviors in software architecture using the Reo coordination language
One of the key goals of a software architecture is to help application designers analyze a software system at a higher level of abstraction than implementation. Software architects often use architecture description languages (ADLs) and their supporting tools to specify software architectures. Existing ADLs often lack formal foundations for design, analysis and reconfiguration of software architectures. The Reo language has a strong formal basis and promotes loose coupling, distribution, mobility, exogenous coordination, and dynamic reconfigurability. This thesis focus on assessing the Reo coordination language as an ADL by doing the following work: a) specify a distributed meeting scheduling system using the Reo coordination language; b) assess the Reo coordination language as an ADL using an existing metho
Adaptive feedforward control design for gust loads alleviation and LCO suppression
An adaptive feedforward controller is designed for gust loads alleviation and limit cycle oscillations suppression. Two sets of basis functions, based on the finite impulse response and modified finite impulse response approaches, are investigated to design the controller for gust loads alleviation. Limit cycle oscillations suppression is shown by using the modified finite impulse response controller. Worst case gust search is performed by using a nonlinear technique of model reduction to speed up the costs of calculations. Both the “one–minus–cosine” and Von Kármán continuous turbulence gusts of different intensities were generated to examine the performance of controllers. The responses of these two types of gust can be reduced effectively by finite impulse response controller in the whole process, while the modified finite impulse response controller is found to increase the loads during the initial transient response. The above two types of gust induced limit cycle oscillations were used to test the modified finite impulse response controller. Results show that it can suppress limit cycle oscillations to some exten
Adaptive feedforward control design for gust loads alleviation and LCO suppression
An adaptive feedforward controller is designed for gust loads alleviation and limit cycle oscillations suppression. Two sets of basis functions, based on the finite impulse response and modified finite impulse response approaches, are investigated to design the controller for gust loads alleviation. Limit cycle oscillations suppression is shown by using the modified finite impulse response controller. Worst case gust search is performed by using a nonlinear technique of model reduction to speed up the costs of calculations. Both the “one–minus–cosine” and Von Kármán continuous turbulence gusts of different intensities were generated to examine the performance of controllers. The responses of these two types of gust can be reduced effectively by finite impulse response controller in the whole process, while the modified finite impulse response controller is found to increase the loads during the initial transient response. The above two types of gust induced limit cycle oscillations were used to test the modified finite impulse response controller. Results show that it can suppress limit cycle oscillations to some exten
A Vector Matroid-Theoretic Approach in the Study of Structural Controllability Over F(z)
In this paper, the structural controllability of the systems over F(z) is
studied using a new mathematical method-matroids. Firstly, a vector matroid is
defined over F(z). Secondly, the full rank conditions of [sI-A|B] are derived
in terms of the concept related to matroid theory, such as rank, base and
union. Then the sufficient condition for the linear system and composite system
over F(z) to be structurally controllable is obtained. Finally, this paper
gives several examples to demonstrate that the married-theoretic approach is
simpler than other existing approaches
Channel Estimation and Uplink Achievable Rates in One-Bit Massive MIMO Systems
This paper considers channel estimation and achievable rates for the uplink
of a massive multiple-input multiple-output (MIMO) system where the base
station is equipped with one-bit analog-to-digital converters (ADCs). By
rewriting the nonlinear one-bit quantization using a linear expression, we
first derive a simple and insightful expression for the linear minimum
mean-square-error (LMMSE) channel estimator. Then employing this channel
estimator, we derive a closed-form expression for the lower bound of the
achievable rate for the maximum ratio combiner (MRC) receiver. Numerical
results are presented to verify our analysis and show that our proposed LMMSE
channel estimator outperforms the near maximum likelihood (nML) estimator
proposed previously.Comment: 5 pages, 2 figures, the Ninth IEEE Sensor Array and Multichannel
Signal Processing Worksho
Gear pitting level diagnosis using vibration signals with an improved inception structure
Gear pitting fault is common in mechanical devices. At present, most of the gear pitting fault detection methods are based on the manual extraction of the frequency domain features from vibration signals. This paper presents a method for gear pitting fault level diagnosis using vibration signals with an improved inception network. The presented method directly applies to the vibration signals to automatically extract features and diagnose the level of the gear pitting fault using deep learning. The presented method has been validated with vibration data collected for 7 gear pitting conditions from gear pitting fault tests. The validation results have shown that the presented method can effectively classify the levels of the gear pitting faults. In comparison with traditional convolutional neural network, the diagnosis accuracy has been significantly improved with the presented method
Boundary stabilization of quasilinear hyperbolic systems of balance laws: Exponential decay for small source terms
We investigate the long-time behavior of solutions of quasilinear hyperbolic
systems with transparent boundary conditions when small source terms are
incorporated in the system. Even if the finite-time stability of the system is
not preserved, it is shown here that an exponential convergence towards the
steady state still holds with a decay rate which is proportional to the
logarithm of the amplitude of the source term. The result is stated for a
system with dynamical boundary conditions in order to deal with initial data
that are free of any compatibility condition
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