International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / Conventional phased arrays nominally sum the signals received by the elements prior to detection. By multiplying rather than summing signals received from pairs of elements, i.e., interferometer pairs, a set of Spatial Frequencies (SFs) is obtained. Obtaining the SFs requires employment of a multiple local oscillator technique. When summed, these spatial frequencies produce a single lobed (voltage) radiation pattern which, when passed through a biased detector, removes all sidelobes from the response at a small loss of desired signal power.

Thesis (MScIng)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The quadrifilar helix antenna has frequently been employed to provide the wide angle, circularly polarized radiation pattern which is preferable for mobile satellite communications. A detailed study of this antenna and its varieties is presented. When used as an element in wide angle scanning arrays for aeronautical satellite tracking applications, the additional requirement of a low profile with light weight applies. This further complicates the realization of good circular polarization close to the horizon. A top disk is incorporated into various antenna structures in an effort to improve the radiation performance when used within a closely spaced array while reducing the height of the radiating element. The array performance of these elements are investigated which hints at a supported traveling mode aiding the ability to accomplish the wide angle beam steering. Subsequent study of leakywave antennas initiated the study and implementation of leaky-wave structures in phased arrays of quadrifilar helix elements. / AFRIKAANSE OPSOMMING: Die vierledige heliksantenna word dikwels gebruik vir toepassings wat ’n wye, sirkulêr gepolariseerde stralingspatroon benodig. ’n Verskeidenheid van hierdie antennas is noukeurig bestudeer en hul toepaslikheid vir mobiele sattelietkommunikasie ondersoek. Wanneer hierdie antennas in fase gestuurde skikkings gebruik word, word dit ook vereis dat die eenhede liggewig is met ’n lae profiel. Dit bemoeilik die verkryging van goeie sirkulêre polarisasie naby die horison aansienlik. In ’n poging om die wyehoek straling met kort antennas te verbeter, is ’n oorhoofse skyf tot verskillende heliksstrukture toegevoeg. In nou gespasieerde skikkings maak hierdie skywe ’n positiewe bydrae to wyehoekstralingeienskappe. Die invloed van lekmodusse wat binne die struktuur voortplant is ondersoek en gebruik in skikkings waarvan die bundel naby aan die horison gestuur word.

The thesis outlines the use of Orthogonal Arrays for the training of Artificial Neural Networks. Such arrays are popularly used in system optimisation and are known as Taguchi Methods. The chief advantage of the method is that the network can learn quickly. Fast training methods may be used in certain Control Systems and it has been suggested that they could find application in ‘disaster control,’ where a potentially dangerous system (for example, suffering a mechanical failure) needs to be controlled quickly. Previous work on the methods has shown that they suffer problems when used with multi-layer networks. The thesis discusses the reasons for these problems and reports on several successful techniques for overcoming them. These techniques are based on the consideration of the neuron, rather then the individual weight, as a factor to be optimised. The applications of technique and further work are also discussed.

Στην διπλωματική εργασία που ακολουθεί, παρουσιάζεται η προσομοίωση και μελέτη ενός υβριδικού συστήματος διανεμημένης παραγωγής. Το σύστημα που εξετάζεται είναι ένα υβριδικό σύστημα ηλεκτροπαραγωγής που αποτελείται από μία ανεμογεννήτρια, μια φωτοβολταϊκή συστοιχία και μία γεννήτρια diesel. Για τη προσομοίωση του συστήματος χρησιμοποιείται το πρόγραμμα σχεδίασης και προσομοίωσης ηλεκτρικών συστημάτων PSCAD. Η εργασία επικεντρώνεται στη δομή και λειτουργία του συστήματος τόσο στην μόνιμη κατάσταση λειτουργίας όσο και στη συμπεριφορά του συστήματος σε διάφορα μεταβατικά φαινόμενα. Τα μεταβατικά φαινόμενα που εξετάζονται είναι τα εξής: • Μείωση προσπίπτουσας ακτινοβολίας σε φωτοβολταϊκη συστοιχία • Αποσύνδεση Ανεμογεννήτριας από το δίκτυο • Τριφασικό βραχυκύκλωμα ως προς την γή στον ζυγό της γεννήτριας diesel • Απότομη αύξηση του φορτίου Στο 1ο Κεφάλαιο, γίνεται μια αναφορά στα υβριδικά συστήματα παραγωγής ηλεκτρικής ενέργειας, στα συστήματα κατανεμημένης παραγωγής, στις δομές τους και στις ανανεώσιμες πηγές ενέργειας. Επίσης αναφέρονται μερικές εφαρμογές τους. Στο 2ο Κεφάλαιο, περιγράφονται ξεχωριστά τα στοιχεία παραγωγής ηλεκτρικής ενέργειας καθώς και τα υπόλοιπα στοιχεία του υβριδικού συστήματος διανεμημένης παραγωγής που απαρτίζουν την εργασία. Ταυτόχρονα παρουσιάζονται και αναλύονται οι μαθηματικές σχέσεις σύμφωνα με τις οποίες λειτουργεί το σύστημα. Στο 3ο Κεφάλαιο, εισερχόμαστε στο περιβάλλον του προγράμματος μοντελοποίησης PSCAD, παρουσιάζεται και περιγράφεται η δομή και τα στοιχεία που αποτελούν το υβριδικό δίκτυο ηλεκτροπαραγωγής, ενώ γίνεται και αναφορά στις προδιαγραφές που πρέπει να τηρούνται από το σύστημα διανεμημένης παραγωγής. Στο 4ο Κεφάλαιο, παρατηρείται η συμπεριφορά ολόκληρου του συστήματος στην μόνιμη κατάσταση λειτουργίας καθώς και των επιμέρους υποσυστημάτων. Στο 5ο Κεφάλαιο, εξετάζεται η συμπεριφορά ολόκληρου του συστήματος καθώς και των επιμέρους υποσυστημάτων στις διαταραχές που έχουμε περιγράψει παραπάνω. Στο 6ο Κεφάλαιο και τελευταίο, καταλήγουμε σε συμπεράσματα τα οποία προέκυψαν από την μελέτη του υβριδικού συστήματος που παρουσιάστηκε. / The thesis that follows, presents the simulation and design of a hybrid distributed system of electrical power generation. The system presented, consists of a wind turbine, a photovoltaic array and a diesel generator. For the system simulation we use the drawing and simulation of electrical systems program, PSCAD. The project focuses on the structure and operation of the system both at steady -permanent state and in system behavior in various transient situations. The transients considered are the following: • Reduction in incident solar radiation into array • Wind Turbine disconnection from the network • Three-phase short circuit as for ground under the rule of the diesel generator • Sharp load increase In 1st chapter, there is a reference to hybrid power generation systems, distributed generation systems, their structures and the renewable sources of energy. Also some applications are mentioned. In 2nd chapter, there is a description of the elements that produce electrical energy and the other elements of the hybrid system of distributed production of electrical energy which are used in the system. At the same time there are presented and analyzed the mathematical relations under which the system operates. In 3rd chapter, we enter the interface of the PSCAD modeling program, present and describe the structure and components of the hybrid power grid, while we also make a reference to the specifications that have to be met by the system of distributed production. In 4th chapter, is examined the behavior of the whole system as well as of the individual subsystems in steady-permanent state. In 5th chapter, is examined the behavior of the entire system as well as of the individual subsections during the disturbances which we have described above. In 6th chapter and last, we come to conclusions that emerged from the study of the hybrid system presented.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

This thesis focuses on addressing some important aspects of the life cycle of interstellar clouds through observational submillimeter and millimeter-wave studies of star formation and molecular cloud environments and the development of instrumentation to enable these studies.We examine the influence of star formation on parent molecular clouds through a case study of protostellar sources in the Mon OB1 northern cloud complex. An energetics analysis of these star forming regions and associated molecular outflows was carried out, suggesting that the cloud complex maintains its overall integrity, except along outflow axes and that the coupling between outflow kinetic energy and cloud turbulent energy is weak, < ~0.5%. In order to study the larger picture of cloud formation and disruption, this work was expanded to explore the molecular environment at cloud boundaries. To this end, acloud edge survey was undertaken consisting of multi-transition strip scan observations of CO and 13CO toward molecular clouds with a broad range of stellar and star forming characteristics. Our work supports the interpretation that cloud formation is taking place along the southeastern edge of Heiles Cloud 2, and the results will be used as a framework for guiding the analysis of other surveyed cloud edges.Achieving observational capabilities enabling effective studies of life cycles of the ISM is becoming possible through a new generation of heterodyne spectroscopic instruments. Here, we report on characterization measurements of a prototype mixer unit for the 64-pixel SuperCam array, an instrument commissioned to mapover 500 square degrees of the Galactic Plane with very high resolution at 345 GHz. These measurements were crucial to verifying the overall array design and anticipating its performance. Spectroscopic capabilities at THz (< 300 microns) frequencies permits access to a host of diagnostic tools (e.g., high-J CO, CI, NII, & CII) uniquely suited to probe crucial properties of the ISM. The development of heterodynetechnology at these frequencies is largely limited by availability of compact, powerful sources of local oscillator power. We explore the use of waveguide spatial filters in conjunction with Quantum Cascade Lasers, a promising power source at frequenciesabove ~ 2 THz.

No description available.

International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / This paper describes the development of a Reed-Solomon (RS) Encoder-Decoder which implements the RS segment of the telemetry channel coding scheme recommended by the Consultative Committee on Space Data Systems (CCSDS)[1]. The Euclidean algorithm has been chosen for the decoder implementation, the hardware realization taking a systolic array approach. The fully pipelined decoder runs on a single clock and the operating speed is limited only by the Galois Field (GF) multiplier's delay. The circuit has been synthesised from VHDL descriptions and the hardware is being realised using programmable logic chips. This circuit was simulated for functional operation and found to perform correction of error patterns exactly as predicted by theory.

To accommodate future power demands, wave energy converters will be deployed in arrays, but largely unanswered questions of the annual energy production and environmental impact of such installations present regulatory dilemmas. In recent years, Sandia National Laboratories (SNL) has developed a modified version of the Simulating Waves Nearshore (SWAN) wave model to simulate WEC energy extraction in a propagating wave field. This thesis presents a novel WEC meta-model that calculates the power intercepted by a WEC from the incident wave field. Two representations were developed with which a user could model a WEC’s impact on the incident waves in a spectral wave model. These alterations are based on power a WEC captures from the sea and power dissipated by hydrodynamic losses calculated in an external six degree of freedom (DOF) time domain WEC simulation. The two WEC meta-models were compared in terms of significant wave height reduction in the WEC’s lee and annual power production. The first WEC representation removes a constant percentage of power from each frequency bin while the second representation employs frequency dependent energy extraction. The representations were then applied in modelling a 54 MW WEC array off of Amphitrite Bank on the West Coast of Vancouver Island. Over the course of a year, the power captured by a farm when represented with a constant percentage extraction is reduced by 2.9% while a frequency dependent percentage extraction reduced the farm’s total captured power by 2.3% when compared to the reference case. Similarly small changes were observed in significant wave height reductions. The significant wave height in the lee of a farm was reduced by less than 2% for both representations at the shoreline, approximately six kilometres behind the farm. / Graduate / 0775, 0547, 0548 / eluczko91@gmail.com

Data mining plays an important role in a variety of fields including bioinformatics, multimedia, business intelligence, marketing, and medical diagnosis. Analysis of today’s huge and complex data involves several data mining algorithms including clustering and classification. The computational complexity of machine learning and data mining algorithms, that are frequently used in today’s applications such as embedded systems, makes the design of efficient hardware architectures for these algorithms a challenging issue for the development of such systems. The aim of this work is to optimize the performance of hardware acceleration for data mining applications in terms of speed and area. Most of the previous accelerator architectures proposed in the literature have been obtained using ad hoc techniques that do not allow for design space exploration, some did not consider the size (number of samples) and dimensionality (number of features in each sample) of the datasets. To obtain practical architectures that are amenable for hardware implementation, size and dimensionality of input datasets are taken into consideration in this work. For one-dimensional data, algorithm-level optimizations are investigated to design a fast and area-efficient hardware accelerator for clustering one-dimensional datasets using the well-known K-Means clustering algorithm. Experimental results show that the optimizations adopted in the proposed architecture result in faster convergence of the algorithm using less hardware resources while maintaining the quality of clustering results. The computation of similarity distance matrices is one of the computational kernels that are generally required by several machine learning and data mining algorithms to measure the degree of similarity between data samples. For these algorithms, distance calculation is considered a computationally intensive task that accounts for a significant portion of the processing time. A systematic methodology is presented to explore the design space of 2-D and 1-D processor array architectures for similarity distance computation involved in processing datasets of different sizes and dimensions. Six 2-D and six 1-D processor array architectures are developed systematically using linear scheduling and projection operations. The obtained architectures are classified based on the size and dimensionality of input datasets, analyzed in terms of speed and area, and compared with previous architectures in the literature. Motivated by the necessity to accommodate large-scale and high-dimensional data, nonlinear scheduling and projection operations are finally introduced to design a scalable processor array architecture for the computation of similarity distance matrices. Implementation results of the proposed architecture show improved compromise between area and speed. Moreover, it scales better for large and high-dimensional datasets since the architecture is fully parameterized and only has to deal with one data dimension in each time step. / Graduate / 2019-12-31