No description available.

In this thesis we propose a feasible bibliometric assessment framework of research output quality derived from the definition of research proposed by Higher Education Funding Council for England (HEFCE). Based on this basic framework, we show that research output can be assessed from two elements: significance of new insights and effectiveness of sharing based on the new insights. We investigate this issue from two levels: research publication's quality assessment and academic journal's quality assessment. With regard to measurement of research publications, we confirm citation information is accepted as a measure of effectiveness of sharing regardless of various reasons of citation behavior. On the other hand, we observe there are no sufficient studies on bibliometric indices for significance of new insights, based on information other than citations. In this thesis, we theoretically develop some non-citation based bibliometric measurements via utilizing journal characteristics (e.g. journal acceptance rate (JAR) or journal rejection rate (JRR)). Their strength and weakness are shown in our empirical studies. Furthermore, we believe a more complete assessment for research output quality can be achieved by combining information from the two elements. Several combination approaches such as function combination (i.e. production of two indicators) and Data Envelopment Analysis (DEA) approach are proposed and testified on real data sets like the Association of "- Business School (ABS) journal ranking and Research Assessment Exercise (RAE). Secondly, we utilize a part of the HEFCE framework for journal quality assessment from wider perspectives. To this end two ranking approaches are introduced to serve different stakeholders, and Operational Research/Management Science (OR/MS) journals are employed in the empirical studies. Finally, we report a real project of the 3E (i.e. Efficacy, Efficiency, Effectiveness) theory in an international research institute ranking, jointly carried out by the Chinese Academy of Sciences (CAS), China, and the Centre for Evaluation of Research Performance (CERP), University of Kent, UK.

The purpose of the study was to determine the efficacy of touch sensitive computer screens in focusing attention on a specific academic task. Forty nondelayed and forty delayed kindergarteners were compared as to their rates of task completion and performances on traditional computer keyboards versus touch sensitive screens. Two eight cell repeated measures experimental designs were used to compare the selective attention process of the nondelayed and delayed pupils. The two dependent variables manipulated in the study were two types of computer input device and the two developmental levels of the subjects. The dependent variable consisted of the number of previously unlearned French number words mastered through four performance measures involving speed, computer recall, noncomputer recall and noncomputer recognition.FINDINGSAs analyzed by a three factor MANOVA, a significant difference in the rate of task completion was shown in favor of the touch screens for all subjects in touching the sequential letters of the alphabet. Although there appeared to be no significant differences in noncomputer recall and recognition post tests, a four factor MANOVA verified significant differences in the subjects' computer recall post tests.CONCLUSIONSThe data supports the conclusion that the use of the touch sensitive screen facilitates the focus of attention (selective attention) on specific academic tasks and thus increases the rate of learning and degree of integration of new information. The degree of compatibility between the learner and the computer input device is greater with touch screens than with traditional keyboards for both nondelayed and delayed kindergarteners.The speed of completing the sequential touching of the alphabet letters was significantly faster for the touch screen than the traditional keyboard input. For mastery of information learned, the analyzed findings suggest a higher degree of recall for information learned through the touch screen intervention over the same instructional tasks with keyboard input.As the result of this key study, it is suggested future research investigations will expand the use of computers beyond educational drill, repetition, and games. Future investigations into the relationships between cognitive processing and the individualization of CAI could involve various age ranges, exceptionalities, and developmental comparisons. / Department of Special Education

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A networked control system (NCS) is a control system where sensors, actuators, and controllers are interconnected over a communication network. This dissertation presents a framework for modeling, stability analysis, optimal control, and bandwidth allocation of the NCS. A ball magnetic-levitation (maglev) system, four DC motor speed-control systems, and a wireless autonomous robotic wheelchair are employed as test beds to illustrate and verify the theoretical results of this dissertation. This dissertation first proposes an output feedback method to stabilize and control the NCSs. The random time delays in the controller-to-actuator and sensor-to-controller links are modeled with two time-homogeneous Markov chains while the packet losses are treated with Dirac delta functions. An asymptotic mean-square stability criterion is established to compensate for the network-induced random time delays and packet losses in the NCS. Then, an algorithm to implement the asymptotic mean-square stability criterion is presented. Experimental results illustrate effectiveness of the proposed output feedback method compared to conventional controllers. The proposed output feedback controller could reduce the errors of the NCS by 13% and 30–40% for the cases without and with data packet losses, respectively. The optimal bandwidth allocation and scheduling of the NCS with nonlinear-programming techniques is also presented in the dissertation. The bandwidth utilization (BU) of each client is defined in terms of its sampling frequency. Two nonlinear approximations, exponential and quadratic approximations, are formulated to describe the system performance governed by discrete-time integral absolute error (DIAE) versus sampling frequency. The optimal sampling frequencies are obtained by solving the approximations with Karush-Kuhn-Tucker (KKT) conditions. Simulation and experimental results are given to verify the effectiveness of the proposed approximations and the bandwidth allocation and scheduling algorithms. In simulations and experiments, the two approximations could maximize the total BU of the NCS up to about 98% of the total available network bandwidth.

Graduation date: 1982

In the past two decades, wireless communication systems have grown with an unprecedented speed from radio paging and cellular telephony to multimedia platforms offering voice and video streaming . One undesired outcome of this expansion is a heavy utilization of the available frequency spectrum. Particular pressure comes from new multimedia applications, which require larger operational bandwidth for their implementations. Conventional coding, modulation and multiplexing techniques are unable to overcome the problem associated with the limited frequency spectrum, and therefore modern wireless systems are improved through the utilization of the space/angle domain. In order to improve capacity and reliability with the space/angular domain, wireless systems require the use of multiple element antennas (MEA) accompanied by appropriate signal processing algorithms. Typically multiple antennas are used to steer the beams of the line of sight (LOS) signal toward desired users and nulls in the direction of undesired users. However, in the case of indoor environments, the presence of reflections, scattering and refraction caused by the environment, it is better to make use of non-line of sight (NLOS) signal propagation. As these types of MEA antenna systems are a relatively new concept in wireless communications, their potential needs be tested experimentally in real world conditions. To achieve this goal, prototype systems capable to implement various modulation, coding and transmission schemes for MEA are required. This thesis investigates the benefits of MEA systems by building and testing such systems in indoor environments. The project area spans across many disciplines including wireless communications, antennas, embedded systems and RF hardware design, and therefore the thesis begins with essential background information. This concerns some fundamental concepts of a wireless communication channel and its information capacity. These are accompanied by ample considerations of signal propagation and adverse effects of reflection, scattering and diffraction. Also included are the signal modulation and coding. Following this background information, the main topic concerning diversity and multiple-input multiple output system that involves the use of multiple element antennas is introduced. This background material sets the reasons for investigating of two types wireless communication systems that include multiple element antennas: antenna diversity and MIMO. Following the literature review, the thesis reports on investigations that realize the thesis aims. The first part of the undertaken investigations concerns an indoor 2×2 MEA diversity system in which MEAs accompany conventional transceivers. In the experiments, Bluetooth transceivers aimed for a short range operation at 2.45 GHz are used, which are both connected to a 2-element antenna array. The connection is made via a switched beamforming network which involves 4-port hybrid circuits. Two ports of these hybrids are used for connecting antennas, while the one of the remaining two is connected to the Tx or Rx transceiver. By switching between these two input ports of the hybrid, two different radiation patterns can be formed, at both Tx and Rx. One Bluetooth transceiver is stationary while the other is made mobile by employing a purpose built mechanical sub-system covering the precise movement within a circle of 3 m. Both the movement and collection of the data as well as the display of the obtained results are accomplished with the in-house developed software run on a micro-controller and computer. Experimentally, it is shown that the proper Tx and Rx mode for a given position, improves the received signal strength. This leads to improved signal to noise ratio (SNR) and thus the quality of signal transmission. The implementation of this concept only requires a signal quality indicator, and simple feedback between the receiver and the transmitter. In the selected transceivers, "RSSI" was the quality indicator used, and is present in many modern wireless transceivers. Also, any signal quality indicator can be used. Although the experiments were performed with respect to the transmit/receive pattern diversity, they can also be easily extended to other forms of antenna diversity such as polarization or field diversity. The undertaken investigations are original in terms of the full proof of benefits of pattern diversity for indoor wireless systems. The second part of the undertaken investigations focuses on the design, development and testing of a full indoor multiple element antenna system. This demonstrator system includes two main modules: the baseband processor (based on a field programmable gate array) and the RF front end. The FPGA signal processing module is designed around the Altera Stratix II S260 chip, which is commercially available. Suitable hardware design is required to accomplish MIMO signal transmission. The RF front end module performing direct conversion between baseband and 2.45 GHz or 5 GHz radio frequency bands uses the commercially available MAX2829 chip. The interface between FPGA and RF front end is a set of analogue to digital (ADC) and digital to analogue (DAC) converters that operate on signals between the FPGA and the RF transmitter/receiver modules. They are capable of handling 12/14 bit signals at up to 125 MSmp/sec. The data rate chosen in these investigations is 3.125 Mbps. In addition to the MAX2829 IC chip, amplifiers, switches and antennas are included in the RF module. The development of this wireless communication system has been accomplished through a number of design, development and testing stages. Most of the research effort concerned FPGA based signal processing because this part of the system is where the information processing takes place. For the MIMO system, the transmitted signal has to be modulated and coded, with efficient utilization of the multiple element antennas in both these processes. The prerequisite to signal demodulation is signal synchronization. In turn, the decoding requires the knowledge of characteristics of the channels that are formed between transmitting and receiving antennas. For an efficient FPGA hardware design, all the numerical operations must occur in fixed point arithmetic. To accomplish all of these functions, suitable baseband signal processing algorithms were developed as part of the thesis work. First, they were written in MATLAB and then transferred to C++ which is closer to the FPGA implementation. Having confirmed their validity, they were hardware deployed. In the investigated MIMO demonstrator, QPSK modulation and the Alamouti coding scheme were selected for modulating and coding of the transmitted signal. The implementation of the hardware baseband module was validated using a purpose developed channel emulator. This emulator was capable of implementing the channel properties from actual measurements and from theoretical models. The applied theoretical models concern the single and double bounce scattering models, as well as a full EM model and include full EM interactions within array antennas formed by wire dipoles. These models produce random characteristics of the complex channel matrix which describes the channel properties for narrow or wideband case. With this channel emulator, investigations were performed with respect to channel estimation. The training and semi-blind channel estimation methods were tested using the developed emulator. To schedule signal transmission as well as to obtain suitable insight into individual processes, two extra modules were developed as part of the thesis project. These are the scheduler and visualisation modules. The scheduling hardware controls data packets for at the transmitter, and oversees the packets being decoded at the receiver module. For the visualization module, specialized hardware buffers and analysis modules are created for data storage. The signals resulting from the encoding and decoding processes are stored in these buffers, synchronized to each other, which allows for synchronous visualization of the signals. The data from these buffers is streamed to a PC via a 100 Mbit Ethernet connection and a soft-core processor (running uClinux) in the baseband board. Using a web browser on the PC, a graphical interface using scalable vector graphics (SVG) is used for interaction with the embedded web server to display and control what the hardware is sending and receiving. Due to latency, only a quasi-real time display on PC is possible, as 10 ms of time domain data takes 60 ms to display. The FPGA hardware performs real-time continuous data transmission and decoding, and the latency is only in the visualization system. Using the developed baseband system it was shown that the proposed semi-blind channel estimation was advantageous over the classical training approach when the channel properties change during packets transmissions. The developed channel emulator, semi-blind channel estimation algorithm and the visualisation software are the original contributions of this thesis. Having established the proper functioning of the FPGA baseband processor, the remaining investigations concerned the development of the RF transceiver module. This task was accomplished using guidelines offered by the MAX chip manufacturer. The challenge concerned its manufacturing in 4-layer board format. This part of the project required the outsourcing of the PCB manufacturing and component assembly to obtain successful production of the RF front-end board. The RF tests undertaken as part of the project verified the operation of this RF hardware. With the successful development of individual baseband and RF modules, the last part of project concerned the integration of them. Because most of the benefits of the 2×2 MIMO system were demonstrated via the use of a channel emulator, this part of the thesis consisted of the results of a number of experiments. Considerable effort was spent for the full integration of the RF and baseband modules to make them ready for real-time operation. Some of the undertaken tasks were new, as they were not required for experiments using only the baseband system and channel emulator. One of the new challenges concerned proper symbol synchronization. Two novel algorithms were proposed and verified. One of these were based on a simple comparison between "I" and "Q" components of the received signal and the other one involving a correlation of the signal to a known training sequence. The last experiment involved the experimental measurements of signals transmitted over air using the testbed. As the number of interfaces was limited only one transmitting and one receiving antenna was connected to the 2×2 baseband system. However, the Alamouti scheme is able to function when only one of the two antenna is connected, and therefore real-time performance in an indoor environment was successfully tested. The presented designs, algorithms and visualisation form a strong platform for other researchers to continue and expand the work done in this project.

No description available.

No description available.

Research Doctorate - Doctor of Philosophy (PhD) / This thesis addresses the problem of robustness in model predictive control (MPC) of discrete-time systems. In contrast with most previous work on robust MPC, our main focus is on robustness in the face of both imperfect state information and dynamic model uncertainty. For linear discrete-time systems with model uncertainty described by sum quadratic constraints, we propose output-feedback MPC policies that: (i) treat soft constraints using quadratic penalty functions; (ii) respect hard constraints using 'tighter' constraints; and (iii) achieve robust closed-loop stability and non-zero setpoint tracking. Our two main tools are: (1) a new linear matrix inequality condition which parameterizes a class of quadratic MPC cost functions that all lead to robust closed-loop stability; and (2) a new parameterization of soft constraints which has the advantage of leading to optimization problems of prescribable size. The stability test we use for MPC design builds on well-known results from dissipativity theory which we tailor to the case of constrained discrete-time systems. The proposed robust MPC designs are shown to converge to well-known nominal MPC designs as the model uncertainty (description) goes to zero. Furthermore, the present approach to cost function selection is independently motivated by a novel result linking MPC and minimax optimal control theory. Specifically, we show that the considered class of MPC policies are the closed-loop optimal solutions of a particular class of minimax optimal control problems. In addition, for a class of nonlinear discrete-time systems with constraints and bounded disturbance inputs, we propose state-feedback MPC policies that input-to-state stabilize the system. Our two main tools in this last part of the thesis are: (1) a class of N-step affine state-feedback policies; and (2) a result that establishes equivalence between the latter class and an associated class of N-step affine disturbance-feedback policies. Our equivalence result generalizes a recent result in the literature for linear systems to the case when N is chosen to be less than the nonlinear system's 'input-state linear horizon'.