The goal of this Masters Thesis research is to evaluate alternative transmission systems from remote wind farms to the main grid using low-frequency AC technology. Low frequency means a frequency lower than nominal frequency (60/50Hz). The low-frequency AC network can be connected to the power grid at major substations via cyclo-converters that provide a low-cost interconnection and synchronization with the main grid. Cyclo-converter technology is utilized to minimize costs which result in systems of 20/16.66 Hz (for 60/50Hz systems respectively). Low frequency transmission has the potential to provide an attractive solution in terms of economics and technical merits.

The rapid progress of complementary-metal-oxide-semiconductor (CMOS) integrated circuit technology became feasible through continuous device scaling. The implementation of high-k/metal gates had a significantcontribution to this progress during the last decade. However, there are still challenges regarding the reliability of these devices. One of the main issues is the escalating 1/fnoise level, which leads to degradation of signal-to-noise ratio (SNR) in electronic circuits. The focus of this thesis is on low-frequency noise characterization and modeling of various novel CMOS devices. The devices include PtSi Schottky-barriers  for source/drain contactsand different high-kgatestacksusingHfO2, LaLuO3 and Tm2O3 with different interlayers. These devices vary in the high-k material, high-k thickness, high-k deposition method and interlayermaterial. Comprehensive electrical characterization and low-frequency noise characterization were performed on various devices at different operating conditions. The noise results were analyzed and models were suggested in order to investigate the origin of 1/f noise in these devices. Moreover, the results were compared to state-of-the-art devices. High constant dielectrics limit the leakage current by offering a higher physical dielectric thickness while keeping the Equivalent Oxide Thickness (EOT) low. Yet, the 1/f noise increases due to higher number of traps in the dielectric and also deterioration of the interface with silicon compared to SiO2. Therefore, in order to improve the interface quality, applying an interfacial layer (IL) between the high-k layer and silicon is inevitable. Very thin, uniform insitu fabricated SiO2 interlayers with HfO2 high-k dielectric have been characterized. The required thickness of SiO2 as IL for further scaling has now reached below 0.5 nm. Thus, one of the main challenges at the current technology node is engineering the interfacial layer in order to achieve both high quality interface and low EOT. High-k ILs are therefore proposed to substitute SiOx dielectrics to fulfill this need. In this work, we have made the first experiments on low-frequency noise studies on TmSiO as a high-k interlayer with Tm2O3 or HfO2 on top as high-k dielectric. The TmSiO/Tm2O3 shows a lower level of noise which is suggested to be related to smoother interface between the TmSiO and Tm2O3. We have achieved excellentnoise performancefor TmSiO/Tm2O3 and TmSiO/HfO2 gate stacks which are comparableto state-of-the-art SiO2/HfO2 gate stacks. / <p>QC 20151130</p>

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The aim of the study: to determine and compare the low frequency fatigue of the legs’ muscles of 12–13 years old boys during the isometric and eccentric-concentric physical exercises. The objectives of the study: 1. To determine the exertion of low frequency fatigue during isometric exercises in boys. 2. To determine the exertion of low frequency fatigue during eccentric-concentric exercises in boys. 3. To compare the exertion of low frequency fatigue among isometric and eccentric-concentric exercises in boys. Subjects. Healthy boys (n = 6) aged 12–13 (12,4 ± 0,6) who do not participate in sports regularly but attend the classes of physical education twice a week. The rest period between the studies was three weeks. The tension was set up at 50 % MVS level. After that the values of the contractions and relaxations of the muscles were registered as follows: 1. The strength of muscle contraction caused by a single electric stimulus (Pt); 2. The strength of muscle contraction (P) caused by the following regiments of electrostimulation: 7 Hz (P7), 10 Hz (P10), 15 Hz (P15), 20 Hz (P20), and 100 Hz (P100) (the duration of the stimulation – 1 s, and the rest intervals between stimulations – 5 s); 3. Maximal voluntary strength (MVS) of muscle contractions (three trials every 3 minutes); 4. The workout (10 minutes of slow pedaling on the ergometer: the heart rate contractions from 110 to 130 times per minute); 5. Isometric workload: 18 times, each lasts 15 s, 40 % MVS contraction... [to full text]

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Disertacijoje nagrinėjama triukšmo sklaidos nuo vėjo jėgainių problema. Pagrindiniai tyrimo objektai yra vėjo jėgainių parkų skleidžiamas triukšmas ir aplinkai nekenksmingos, cilindrinę struktūrą turinčios, žemo dažnio triukšmą slopinančios medžiagos. Darbe sprendžiami keli pagrindiniai uždaviniai: nustatomas ir įvertinamas žemo dažnio triukšmo ir infragarso susidarymas ir sklaida pramoninių vėjo jėgainių parkuose ir jų išorėje, taip pat nustatomos efektyvios gyvenviečių apsaugos priemonės nuo vėjo jėgainių keliamo žemo dažnio triukšmo. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, rekomendacijos, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius skirtas literatūros analizei. Jame pateikta vėjo jėgainių ir jų keliamo triukšmo apžvalga. Apžvelgtos vėjo energetikos būklė Lietuvoje, vėjo jėgainių konstrukcijos, vėjo jėgainių triukšmo formavimosi principas, triukšmo matavimo metodikos. Analizuojamos skleidžiamo aerodinaminio triukšmo mažinimo priemonės bei žemo dažnio triukšmo slopinimo būdai ir izoliuojančių medžiagų panaudojimas. Skyriaus... [toliau žr. visą tekstą] / The dissertation examines the issue of noise emission from the wind farms. The objects of investigation are wind farm noise and environmentally friendly low-frequency noise-deadening materials with cylindrical structure. The paper addresses a number of key objectives: to determine and assess low frequency noise and infrasound emission and dispersion both inside and outside the industrial wind farms, as well as to establish effective measures for protection of settlements against low-frequency noise generated by wind turbines. The dissertation consists of an introduction, three chapters, conclusions, recommendations, list of references and the author's publications on the topics. The introductory chapter discusses the research problem, the relevance of the investigation, describes the object of the research, states the aims and objectives, presents the research methodology, scientific novelty, practical significance of the results, and the statements for defending. It also highlights practical significance of the dissertation presents the author's publications and presentations at conferences, and explains the structure of the thesis. The first chapter is devoted to literature review. It provides an overview of general problems related to wind and noise produced by wind turbines, an overview of the outlook on wind energy in Lithuania, and a discussion of wind turbine constructions. The chapter presents the analysis of aerodynamic noise emitted by means of low-frequency noise... [to full text]

The dissertation examines the issue of noise emission from the wind farms. The objects of investigation are wind farm noise and environmentally friendly low-frequency noise-deadening materials with cylindrical structure. The paper addresses a number of key objectives: to determine and assess low frequency noise and infrasound emission and dispersion both inside and outside the industrial wind farms, as well as to establish effective measures for protection of settlements against low-frequency noise generated by wind turbines. The dissertation consists of an introduction, three chapters, conclusions, recommendations, list of references and the author's publications on the topics. The introductory chapter discusses the research problem, the relevance of the investigation, describes the object of the research, states the aims and objectives, presents the research methodology, scientific novelty, practical significance of the results, and the statements for defending. It also highlights practical significance of the dissertation presents the author's publications and presentations at conferences, and explains the structure of the thesis. The first chapter is devoted to literature review. It provides an overview of general problems related to wind and noise produced by wind turbines, an overview of the outlook on wind energy in Lithuania, and a discussion of wind turbine constructions. The chapter presents the analysis of aerodynamic noise emitted by means of low-frequency noise... [to full text] / Disertacijoje nagrinėjama triukšmo sklaidos nuo vėjo jėgainių problema. Pagrindiniai tyrimo objektai yra vėjo jėgainių parkų skleidžiamas triukšmas ir aplinkai nekenksmingos, cilindrinę struktūrą turinčios, žemo dažnio triukšmą slopinančios medžiagos. Darbe sprendžiami keli pagrindiniai uždaviniai: nustatomas ir įvertinamas žemo dažnio triukšmo ir infragarso susidarymas ir sklaida pramoninių vėjo jėgainių parkuose ir jų išorėje, taip pat nustatomos efektyvios gyvenviečių apsaugos priemonės nuo vėjo jėgainių keliamo žemo dažnio triukšmo. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, rekomendacijos, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius skirtas literatūros analizei. Jame pateikta vėjo jėgainių ir jų keliamo triukšmo apžvalga. Apžvelgtos vėjo energetikos būklė Lietuvoje, vėjo jėgainių konstrukcijos, vėjo jėgainių triukšmo formavimosi principas, triukšmo matavimo metodikos. Analizuojamos skleidžiamo aerodinaminio triukšmo mažinimo priemonės bei žemo dažnio triukšmo slopinimo būdai ir izoliuojančių medžiagų panaudojimas. Skyriaus... [toliau žr. visą tekstą]

In this study, theorem-based, generally applicable stochastic parameterisation schemes are developed and applied to a quasi-geostrophic model of extratropical atmospheric low-frequency variability (LFV). Hasselmann’s method is developed from limiting theorems for slow-fast systems of ordinary differential equations (ODEs) and applied to this high-dimensional model of intermediate complexity comprised of partial differential equations (PDEs) with complicated boundary conditions. Seamless, efficient algorithms for integrating the parameterised models are developed, which require only minimal changes to the full model algorithm. These algorithms may be readily adapted to a range of climate models of greater complexity in parameterising the effects of fast, sub-grid scale processes on the resolved scales. For comparison, the Majda-Timofeyev-Vanden-Eijnden (MTV) parameterisation method is applied to this model. The seamless algorithms are first adapted to probe the multiple regime behaviour that characterises the full model LFV. In contrast to the conclusions of a previous study, it is found that the multiple regime behaviour is not the result of a nonlinear interaction between the leading two planetary-scale modes, but rather is the result of interactions among these two modes and the leading synoptic-scale mode. The low-dimensional Hasselmann stochastic models perform well in simulating the statistics of the planetary-scale modes. In particular, a model with only one resolved (planetary-scale) mode captures the multiple regime behaviour of the full model. Although a fast-evolving synoptic-scale mode is of primary importance to the multiple regime behaviour, deterministic averaged forcing and not multiplicative noise is responsible for the regime behaviour in this model. The MTV models generate non-Gaussian statistics, but generally do not perform as well in capturing the climate statistics.

Nowadays, fulfillment of the tactical operations in secrecy has great importance for especially subsurface and surface warfare platforms as a result of improvements in weapon technologies. Spreading out of the tactical operations to the larger areas has made discrimination of targets unavoidable. Due to enlargement of the weapon ranges and increasing subtle hostile threats as a result of improving technology, &ldquo / visual&rdquo / target detection methods left the stage to the computerized acoustic signature detection and evaluation methods. Despite this, the research projects have not sufficiently addressed in the field of acoustic signature evaluation. This thesis work mainly investigates classification and recognition techniques with TRN / LOFAR signals, which are emitted from surface and subsurface platforms and proposes possible adaptations of existing methods that may give better results if they are used with these signals. Also a detailed comparison has been made about the experimental results with underwater acoustic signals.

As music production moves from the big professional studios into small bedroom studios, Headphones become more commonly used for monitoring. This brings a new set of problems based on the limitations of headphones compared to loudspeakers. This research explores how a bass enhancement algorithm impacts the results when mixing low frequency audio on headphones. This is done through a simple mixing experiment where subjects are tasked with balancing the amplitude of a low frequency element in a song, both with and without a bass enhancement algorithm enhancing the headphone monitoring. It is shown that while subjects do not perceive a difference in difficulty with this task, the results differ as subjects overall mix the bass frequencies lower in amplitude when aided by the bass enhancement algorithm. It is concluded that the bass enhancement algorithm is useful in this manner.