Robust fuzzy CPU utilization control for dynamic workloads

In a number of real-time applications such as target tracking, precise workloads are unknown a priori but may dynamically vary, for example, based on the changing number of targets to track. It is important to manage the CPU utilization, via feedback control, to avoid severe overload or underutilization even in the presence of dynamic workloads. However, it is challenge to model a real-time system for feedback control, as computer systems cannot be modeled via physics laws. In this paper, we present a novel closed-loop approach for utilization control based on formal fuzzy logic control theory, which is very effective to support the desired performance in a nonlinear dynamic system without requiring a system model. We mathematically prove the stability of thefuzzy closed-loop system. Further, in a real-time kernel, we implement and evaluate our fuzzy logic utilization controller as well as two existing utilization controllers based on the linear and model predictive control theory for an extensive set of workloads. Our approach supports the specified average utilization set-point, while showing the best transient performance in terms of utilization control among the tested approaches

Digital pulse shape discrimination methods for triple-layer phoswich detectors using wavelets and fuzzy logic

A two-channel data acquisition system for simultaneous detection and discrimination of beta particles and gamma rays has been developed. Each channel measures and analyzes the input pulses resulting from the absorption of radiation in the layers of the detector. The detector is a triple-layer phoswich (phosphor sandwich) scintillation detector followed by a photomultiplier tube (PMT). The PMT amplifies the photons and converts them into an electric signal. The signal is digitized and sent to the host computer for further processing. Two new digital algorithms based on Fuzzy Logic and on the Continuous Wavelet Transform have been developed and are discussed in this thesis. In the first method, a de-noising algorithm based on the Wavelet Transform is implemented to reduce the effect of noise introduced by the analog channel and by the photomultiplier tube. Three new timing features are extracted and given as input to a fuzzy interface system. The main goal of fuzziness in a data set is to reduce the system complexity and to provide a model that allows for approximate results. Compared to the method which was originally implemented for this detector, the fuzzy algorithm shows a better performance in separating beta and gamma spectra, especially at high energies. Also, absorption in multiple layers is detected more efficiently. The second algorithm is based on the Continuous Wavelet Transform. The novelty of this method consists in using scale-domain features. Since the output pulse shape of the photomultiplier tube is a non-stationary signal, conventional Fourier methods are not efficient for analyzing these signals and most of the existing pulse shape discrimination methods use time-domain features. Therefore, a time-frequency space is better suited to analyze these non-stationary signals. This method shows better performance over existing time-domain methods in terms of robustness to noise and reliability. The simultaneous detection of beta particles and gamma rays has several applications (for instance detection of underground nuclear explosions). The methods presented in this thesis could also be used in alpha/beta/neutron/gamma discrimination systems for cancer diagnosis and treatment

Ensuring Service Level Agreements for Composite Services by Means of Request Scheduling

Building distributed systems according to the Service-Oriented Architecture (SOA) allows simplifying the integration process, reducing development costs and increasing scalability, interoperability and openness. SOA endorses the reusability of existing services and aggregating them into new service layers for future recycling. At the same time, the complexity of large service-oriented systems negatively reflects on their behavior in terms of the exhibited Quality of Service. To address this problem this thesis focuses on using request scheduling for meeting Service Level Agreements (SLAs). The special focus is given to composite services specified by means of workflow languages. The proposed solution suggests using two level scheduling: global and local. The global policies assign the response time requirements for component service invocations. The local scheduling policies are responsible for performing request scheduling in order to meet these requirements. The proposed scheduling approach can be deployed without altering the code of the scheduled services, does not require a central point of control and is platform independent. The experiments, conducted using a simulation, were used to study the effectiveness and the feasibility of the proposed scheduling schemes in respect to various deployment requirements. The validity of the simulation was confirmed by comparing its results to the results obtained in experiments with a real-world service. The proposed approach was shown to work well under different traffic conditions and with different types of SLAs

Fuzzy Controllers

Trying to meet the requirements in the field, present book treats different fuzzy control architectures both in terms of the theoretical design and in terms of comparative validation studies in various applications, numerically simulated or experimentally developed. Through the subject matter and through the inter and multidisciplinary content, this book is addressed mainly to the researchers, doctoral students and students interested in developing new applications of intelligent control, but also to the people who want to become familiar with the control concepts based on fuzzy techniques. Bibliographic resources used to perform the work includes books and articles of present interest in the field, published in prestigious journals and publishing houses, and websites dedicated to various applications of fuzzy control. Its structure and the presented studies include the book in the category of those who make a direct connection between theoretical developments and practical applications, thereby constituting a real support for the specialists in artificial intelligence, modelling and control fields