A Novel Method Based on Oblique Projection Technology for Mixed Sources Estimation

Reducing the computational complexity of the near-field sources and far-field sources localization algorithms has been considered as a serious problem in the field of array signal processing. A novel algorithm caring for mixed sources location estimation based on oblique projection is proposed in this paper. The sources are estimated at two different stages and the sensor noise power is estimated and eliminated from the covariance which improve the accuracy of the estimation of mixed sources. Using the idea of compress, the range information of near-field sources is obtained by searching the partial area instead of the whole Fresnel area which can reduce the processing time. Compared with the traditional algorithms, the proposed algorithm has the lower computation complexity and has the ability to solve the two closed-spaced sources with high resolution and accuracy. The duplication of range estimation is also avoided. Finally, simulation results are provided to demonstrate the performance of the proposed method

Topics on String Phenomenology

These lectures present some topics of string phenomenology and contain two parts. In the first part, I review the possibility of lowering the string scale in the TeV region, that provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the submillimeter region, and transverse to a braneworld where our universe must be confined. I review the main properties of this scenario and its implications for observations at both particle colliders, and in non-accelerator gravity experiments. In the second part, I discuss a simple framework of toroidal string models with magnetized branes, that offers an interesting self-consistent setup for string phenomenology. I will present an algorithm for fixing the geometric parameters of the compactification, build calculable particle physics models such as a supersymmetric SU(5) Grand Unified Theory with three generations of quarks and leptons, and implement low energy supersymmetry breaking with gauge mediation that can be studied directly at the string level.Comment: 42 pages, 15 figures, Lectures given at Les Houches 2007 Summer School, Added reference

Structured Sparsity Models for Multiparty Speech Recovery from Reverberant Recordings

We tackle the multi-party speech recovery problem through modeling the acoustic of the reverberant chambers. Our approach exploits structured sparsity models to perform room modeling and speech recovery. We propose a scheme for characterizing the room acoustic from the unknown competing speech sources relying on localization of the early images of the speakers by sparse approximation of the spatial spectra of the virtual sources in a free-space model. The images are then clustered exploiting the low-rank structure of the spectro-temporal components belonging to each source. This enables us to identify the early support of the room impulse response function and its unique map to the room geometry. To further tackle the ambiguity of the reflection ratios, we propose a novel formulation of the reverberation model and estimate the absorption coefficients through a convex optimization exploiting joint sparsity model formulated upon spatio-spectral sparsity of concurrent speech representation. The acoustic parameters are then incorporated for separating individual speech signals through either structured sparse recovery or inverse filtering the acoustic channels. The experiments conducted on real data recordings demonstrate the effectiveness of the proposed approach for multi-party speech recovery and recognition.Comment: 31 page

Damage Localization of Mechanical Structures by Subspace Identification and Krein Space Based H-infinity Estimation

This dissertation is devoted to the theoretical development and experimental laboratory verification of a new damage localization method: The state projection estimation error (SP2E). This method is based on the subspace identification of mechanical structures, Krein space based H-infinity estimation and oblique projections. To explain method SP2E, several theories are discussed and laboratory experiments have been conducted and analysed. A fundamental approach of structural dynamics is outlined first by explaining mechanical systems based on first principles. Following that, a fundamentally different approach, subspace identification, is comprehensively explained. While both theories, first principle and subspace identification based mechanical systems, may be seen as widespread methods, barely known and new techniques follow up. Therefore, the indefinite quadratic estimation theory is explained. Based on a Popov function approach, this leads to the Krein space based H-infinity theory. Subsequently, a new method for damage identification, namely SP2E, is proposed. Here, the introduction of a difference process, the analysis by its average process power and the application of oblique projections is discussed in depth. Finally, the new method is verified in laboratory experiments. Therefore, the identification of a laboratory structure at Leipzig University of Applied Sciences is elaborated. Then structural alterations are experimentally applied, which were localized by SP2E afterwards. In the end four experimental sensitivity studies are shown and discussed. For each measurement series the structural alteration was increased, which was successfully tracked by SP2E. The experimental results are plausible and in accordance with the developed theories. By repeating these experiments, the applicability of SP2E for damage localization is experimentally proven

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Institute for Computational Mechanics in Propulsion (ICOMP)

The Institute for Computational Mechanics in Propulsion (ICOMP) is a combined activity of Case Western Reserve University, Ohio Aerospace Institute (OAI) and NASA Lewis. The purpose of ICOMP is to develop techniques to improve problem solving capabilities in all aspects of computational mechanics related to propulsion. The activities at ICOMP during 1991 are described

Signals and Images in Sea Technologies

Life below water is the 14th Sustainable Development Goal (SDG) envisaged by the United Nations and is aimed at conserving and sustainably using the oceans, seas, and marine resources for sustainable development. It is not difficult to argue that signals and image technologies may play an essential role in achieving the foreseen targets linked to SDG 14. Besides increasing the general knowledge of ocean health by means of data analysis, methodologies based on signal and image processing can be helpful in environmental monitoring, in protecting and restoring ecosystems, in finding new sensor technologies for green routing and eco-friendly ships, in providing tools for implementing best practices for sustainable fishing, as well as in defining frameworks and intelligent systems for enforcing sea law and making the sea a safer and more secure place. Imaging is also a key element for the exploration of the underwater world for various scopes, ranging from the predictive maintenance of sub-sea pipelines and other infrastructure projects, to the discovery, documentation, and protection of sunken cultural heritage. The scope of this Special Issue encompasses investigations into techniques and ICT approaches and, in particular, the study and application of signal- and image-based methods and, in turn, exploration of the advantages of their application in the previously mentioned areas

Localization and litigation of radio frequency interference for interferometric arrays

Thesis (PhD)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Radio telescopes have increased exponentially in sensitivity ever since the first single dish radio telescopes were built in the 1930's. This trend continues with the development of next generation telescopes such as the Square Kilometre Array (SKA). Parallel to the development of radio telescopes, has been the rapid expansion of telecommunication technologies. Consequently, radio telescopes are becoming more sensitive in an environment with ever increasing radio frequency interference (RFI). The ideal solution to RFI that is detected by a radio telescope is to locate its source and then have it removed. Removal of the source is usually only possible if it is occurring in a protected band or the radio telescope is in a radio quiet zone. Unfortunately, most of the radio spectrum has been allocated to active communication services and not all radio telescopes are in radio quiet zones. The alternative is to mitigate its effect using methods such as spatial RFI mitigation. The contributions of this PhD dissertation are twofold: firstly, a source localization algorithm that takes into account the constraints and advantages of the arrays used for radio astronomy has been developed; and secondly, existing spatial RFI mitigation techniques have been adapted to take into account the bandwidth of the RFI signals. The computationally efficient localization algorithm that was developed is best suited for interferometric arrays with low array beam sidelobes. Two variants of the algorithm were developed, one that works for sources in the near-field and the other for far-field sources. In the near-field, the computational complexity of the algorithm is linear with search grid size compared to cubic scaling of the state-of-the-art 3-D MUSIC method. The trade-off is that the proposed algorithm requires a once-off a priori calculation and storing of weighting matrices. In an experiment using a station of the Low Frequency Array (LOFAR) a hexacopter was flown around the array, at a mean radial distance of 190 m, broadcasting a signal. The mean error in distance between the estimated position of the hexacopter and the GPS position of the hexacopter was 2 m for a wavelength of 6.7 m. The non-narrowband RFI mitigation method developed consists of a second order filter that is used to mitigate powerful RFI with bandwidth sufficient to cause aberrations that are below the noise, but with power that competes with the astronomical sources. The second order filter consists of a first order subspace subtraction filter combined with a flat frequency response model for the RFI source. Taking into account mutual coupling as well as a calibration step to account for unknown complex gains, the algorithm was found to process approximately 1.6 times more bandwidth than using just a first order subspace subtraction filter.AFRIKAANSE OPSOMMING: Sedert die eerste enkelskottel radioteleskope in die 1930's gebou is, het die sensitiwiteit van radioteleskope eksponensieël toegeneem. Hierdie tendens gaan voort met die ontwikkeling van volgende generasie teleskope, soos byvoorbeeld die Square Kilometer Array (SKA). In parallel met die ontwikkeling van radioteleskope, het telekommunikasietegnologieë ook vinnig uitgebrei. Gevolglik word radioteleskope meer sensitief in 'n omgewing met toenemende radiofrekwensie-inmenging (RFI). Die optimale oplossing vir RFI is om die bron daarvan op te spoor en te verwyder. Verwydering van die bron is gewoonlik net moontlik as dit teenwoording is in 'n beskermde band of as die radio teleskoop in 'n radio-stil gebied is. Ongelukkig is meeste van die radio spectrum toegeken aan kommunikasiedienste en nie alle radio teleskope is in radio-stil gebiede nie. Die alternatief om die effek daarvan te mitigeer deur middel van metodes soos ruimtelike RFI-mitigasie. Die bydraes van hierdie doktorale proefskrif is tweeledig: eerstens, die ontwikkeling van 'n bronlokaliseringsalgoritme wat die beperkings en voordele van die skikkings wat gebruik word vir radio astronomie in ag neem en tweedens, die aanpassing van bestaande ruimtelike RFI mitigeringstegnieke om die bandwydte van die RFI seine in ag te neem. Die berekeningsdoeltreffende lokaliseringsalgoritme wat ontwikkel is, is die beste geskik vir interferometriese skikkings met lae samestelling-bundel sylobbe. Twee weergawes van die algoritme is ontwikkel, die eerste hanteer bronne in die nabyveld en die ander hanteer vêrveld bronne. In die nabyveld is die berekeningskompleksiteit van die algoritme lineêr met soektogroostergrootte in vergelyking met die kubieke skalering van die 3-D MUSIC-metode. Die nadeel is dat die voorgestelde algoritme 'n eenmalige a priori berekening en stoor van gewigsmatrikse vereis. In 'n eksperiment by 'n stasie van die Low Frequency Array (LOFAR), het 'n heksakopter oor die skikking gevlieg met 'n gemiddelde radiale afstand van 190 m en 'n sein uitgesaai. Die gemiddelde fout in die afstand tussen die beraamde posisie van die heksakopter en die GPS-posisie van die heksakopter was 2 m vir 'n golflengte van 6.7 m. Die nie-smalband RFI mitigasie metode wat ontwikkel is, fasiliteer die de-finieering van 'n tweede-orde filter wat gebruik word om kragtige RFI met bandwydte verwante krag onder die geruis, maar met krag wat met die astronomiese bronne kompeteer, te mitigeer. Die tweede order filter bestaan uit 'n eerste orde subruimte verminderingsfilter gekombineer met 'n plat frekwensie responsmodel vir die RFI bron. Met inagneming van wedersydse koppeling asook 'n kalibrasie stap om vir onbekende komplekse antenna aanwinste voorsiening te maak, is gevind dat die algoritme ongeveer 1.6 meer bandwydte kan verwerk as 'n eerste orde subruimte verminderingsfiter

A Pedagogical Review of Electroweak Symmetry Breaking Scenarios

We review different avenues of electroweak symmetry breaking explored over the years. This constitutes a timely exercise as the world's largest and the highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at CERN near Geneva, has started running whose primary mission is to find the Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel the mysteries of electroweak phase transition. In the beginning, we discuss the Standard Model Higgs mechanism. After that we review the Higgs sector of the Minimal Supersymmetric Standard Model. Then we take up three relatively recent ideas: Little Higgs, Gauge-Higgs Unification, and Higgsless scenarios. For the latter three cases, we first present the basic ideas and restrict our illustration to some instructive toy models to provide an intuitive feel of the underlying dynamics, and then discuss, for each of the three cases, how more realistic scenarios are constructed and how to decipher their experimental signatures. Wherever possible, we provide enough pedagogical details, which the beginners might find useful.Comment: 45 pages, Review based on a series of lectures; v2: 63 pages, substantially expanded, references added, to appear in `Reports on Progress in Physics