<p>Predmet istraživanja ove doktorske disertacije<br />je bio formiranje i proučavanje osobina i<br />pona&scaron;anja organskih aerosola nastalih<br />atomiziranjem stabilnih emulzija dominantno<br />pod dejstvom centrifugalne sile. Kori&scaron;ćene su<br />vodene emulzije komercijalnih sredstava za<br />hlađenje i podmazivanje (SHP), koja se koriste<br />pri obradi metalnih odlivaka. Cilj istraživanja je<br />bio ispitati i objasniti uticaj koncentracije SHP<br />emulzije, brzine strujanja vazduha, prirode kako<br />ulja, tako i osobina emulzija, kao &scaron;to su gustina,<br />viskoznost, povr&scaron;inski napon, kao i udaljenost<br />od mesta atomiziranja na masenu koncentraciju,<br />broj i veličinu kapi aerosola u kontrolisanim<br />laboratorijskim uslovima.<br />Uslovi eksperimenta isključili su uticaj toplote<br />nastale kao posledica trenja alata i delova koji<br />se obrađuju. Pored toga isključeno je prisustvo<br />čvrstih mikronskih čestica koje potiču od delova<br />koji se obrađuju, kao i prisutvo plivajućeg<br />hidrauličnog ulja i mikroorganizama koji uvek<br />prate realan industrijski fluid.<br />Eksperimentalni program je realizovan na tri<br />komercijalna SHP sredstva različitog porekla.<br />Proučavani su aerosoli formirani atomiziranjem<br />emulzije tri različite koncentracije uljne faze: 1,<br />6 i 10 %. Pri jednakim eksperimentalnim<br />uslovima ispitivan je i aerosol formiran, od<br />vode kori&scaron;ćene za pripremu emulzija. Određene<br />su osobine ulja i emulzija koje su od značaja za<br />atomiziranje tečnosti. Proučavan je i uticaj<br />brzine ventilacionog vazduha na osobine<br />aerosola. Eksperimenti su realizovani pri<br />brzinama vazduha od 1, 3, 6, 8 m/s.<br />Uzorkovanje aerosola je realizovano u komori,<br />na ulazu u ventilacini vod i duž ventilacione<br />cevi dužine 8m na pet mernih tačaka koje se<br />nalaze na 0,5, 1, 2, 4, 6, 8 m u odnosu na<br />komoru.<br />Značajan doprinos ove doktorske disertacije je<br />postavljanje teorije da atomiziranjem emulzije<br />kao heterogene tečnosti, nastaje heterogen<br />aerosol, pri čemu mogu nastati kapi različite<br />prirode, između ostalog i kapi čistog ulja. Na taj<br />način je obja&scaron;njen fenomen da porastom<br />koncentracije emulzije raste veličina kapi<br />nastalog aerosola. Aerosoli nastali od<br />koncentrovanijih emulzija pokazuju uređenije<br />strujanje kroz ventilacionu cev, &scaron;to je od<br />značaja za uspe&scaron;nije projektovanje ventilacionih<br />sistema i filtara za njihovu separaciju u cilju<br />za&scaron;tite zdravlja radnika i za&scaron;tite okoline.</p> / <p> This PhD Thesis presents an experimental<br /> study of organic aerosols formed from stable<br /> water emulsions, predominantly by centrifugal<br /> force under laboratory conditions. Emulsions of<br /> metalworking fluids (MWF) were used in the<br /> experiments. The aim of this investigation was<br /> to explain the influence of MWF emulsion<br /> concentration, oil and emulsion properties<br /> (density, viscosity, and surface tension), air<br /> velocity, as well as distance from atomization<br /> generator on aerosol behavior and properties as<br /> size distribution, mass and number<br /> concentration. The experimental conditions<br /> excluded the influence of the heat arising from<br /> the friction between the tool and the<br /> workpieces. In this way the mechanism of<br /> aerosol formation by the<br /> evaporation/condensation is minimized.<br /> Besides, the presence of solid micrometer sized<br /> particulates originated from the work piece is<br /> excluded, as well as the presence of tramp oil<br /> and microorganisms, always accompanying a<br /> real industrial fluid.<br /> Three different commercial MWFs were<br /> investigated at three different oil-in-water<br /> emulsion concentrations, 1, 6, and 10 %<br /> respectively. Water aerosol was investigated<br /> under same experimental conditions. Properties<br /> of MWF oils and emulsion, which are important<br /> for liquid atomization, were determined.<br /> Influence of ventilation air velocity on aerosol<br /> properties was investigated as well.<br /> Experiments were realized under four different<br /> air velocities: 1, 3, 6, and 8 m/s. Samples were<br /> taken at three different points: at the camber, at<br /> the entrance of ventilation pipe, and at five<br /> sampling points along the pipe. Ventilation pipe<br /> was 8 m long, and sampling point were at 0.5, 1,<br /> 2, 4, 6, 8 m from the aerosol camber.<br /> The main contribution of this dissertation is<br /> the new theory that atomization of emulsion as a<br /> heterogeneous fluid leads to the formation of<br /> heterogeneous aerosol, containing droplets of a<br /> different nature, including droplets of pure oil.<br /> This theory explains the phenomenon that the<br /> aerosol droplet sizes increase with the increase<br /> of the emulsion concentration. Obtained results<br /> show that aerosols formed from the emulsions<br /> of higher concentration (6 and 10 %) have less<br /> chaotic flow through the ventilation pipe. This<br /> observation is important for better design of<br /> ventilation systems and filters for mist<br /> separation in order to protect human health and<br /> the environment.&nbsp;</p>

Space-time Adaptive Processing (STAP) is a two-dimensional filtering technique for antenna array with multiple spatial channels. The name "space-time" describes the coupling of these spatial channels with pulse-Doppler waveforms. Applications for STAP includes ground moving target indicator (GMTI) for airborne radar systems. Today, there are strong interests to develop STAP algorithms for operations in “sample starved” environments, where intense environmental interference can reduce STAP capacity to detect and track ground targets. Careful applications of STAP can effectively overcome these conditions by suppressing these interferences and maximize the signal to interference plus noise ratio (SINR). The Multi-stage Wiener filter (MWF) and principal component signal dependent (PC-SD) algorithm are two such methods that can suppress these interference through truncation of the signal subspace. This thesis makes contribution in several ways. First it details the importance of rank compression and sample compression for effective STAP operations in “sample starved” environments. Second, it shows how MWF and PC-SD could operate in this type of environment. Third it details how a “soft stop” technique like diagonal loading (DL) could improve STAP performance in target detection for MWF and PC-SD. Fourth, this thesis contrasts the performance of several existing “hard stop” techniques in rank compression and introduces a new one using a-priori knowledge.

The objective of the dissertation research is to investigate noise reduction methods for binaural hearing aids based on array and statistical signal processing and inspired by a human auditory model. In digital hearing aids, wide dynamic range compression (WDRC) is the most successful technique to deal with monaural hearing losses. This WDRC processing is usually performed after a monaural noise reduction algorithm. When hearing losses are present in both ears, i.e., a binaural hearing loss, independent monaural hearing aids have been shown not to be comfortable for most users, preferring a processing that involves synchronization between both hearing devices. In addition, psycho-acoustical studies have identified that under hostile environments, e.g., babble noise at very low SNR conditions, users prefer to use linear amplification rather than WDRC. In this sense, the noise reduction algorithm becomes an important component of a digital hearing aid to provide improvement in speech intelligibility and user comfort. Including a wireless link between both hearing aids offers new ways to implement more efficient methods to reduce the background noise and coordinate processing for the two ears. This approach, called binaural hearing aid, has been recently introduced in some commercial products but using very simple processing strategies. This research analyzes the existing binaural noise-reduction techniques, proposes novel perceptually-inspired methods based on blind source separation (BSS) and multichannel Wiener filter (MWF), and identifies different strategies for the real-time implementation of these methods. The proposed methods perform efficient spatial filtering, improve SNR and speech intelligibility, minimize block processing artifacts, and can be implemented in low-power architectures.