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Barros, David Alexandre Lampreia. "Analise e caracterização do ruído ambiente urbano. Cidade de Lisboa - Bairro habitacional." Master's thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/4030.
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Mestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaThe work of this dissertation focuses essentially on matters related to the areas of environmental acoustics – noise and discomfort to the urban population. Noise is a source of noise pollution, which is a combination of various sound sources, from commercial activities and services, religious spaces, construction, vehicle traffic, human activities, etc. This raises the level of urban noise and contributes to the emergence of unpleasant sound environments increasingly. With the evolution of society, noise is considered one of the most common environmental problems, degrading the quality of life and the environment. The legislation and international regulations have allowed the quantification by means of noise maps and acoustical prediction, where the legal authorities can view and plan interventional measures for a proper planning of the urban places. This case study describes the noise in the urban environment in the city of Lisbon, more specifically, a typical residential area of the city – Benfica – Igreja de Benfica – Rua dos Arneiros. An environmental noise analysis, through the acquisition levels of sound pressure and frequency spectra in bands 1 / 3 octave, continuously under a period of 7 (seven) days during the month of May 2011. The results showed the characteristic noise of a residential zone of the city of Lisbon, as well as identified what are their main sources. The information drawn from this study may serve as a basis for development and planning of cities in relation to acoustic comfort.
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Martin, Peter. "Uncertainty due to speckle noise in laser vibrometry." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7139.
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This thesis presents fundamental research in the field of laser vibrometry for the application to vibration measurements. A key concern for laser vibrometry is the effect of laser speckle which appears when a coherent laser beam scatters from an optically rough surface. The laser vibrometer is sensitive to changes in laser speckle which result from surface motions not in the direction of the incident beam. This adds speckle noise to the vibrometer output which can be indistinguishable from the genuine surface vibrations. This has been termed ‘pseudo-vibration' and requires careful data interpretation by the vibration engineer. This research has discovered that measurements from smooth surfaces, even when no identifiable speckle pattern is generated, can produce noise and therefore reference to speckle noise, in such circumstances, is inappropriate. This thesis has, therefore, adopted the more general term of pseudo-vibration to include noise generated from any surface roughness or treatment, i.e. including but not limited to speckle noise. This thesis develops and implements novel experimental methods to quantify pseudovibration sensitivities (transverse, tilt and rotation sensitivity) with attention focussed on commercially available laser vibrometers and consideration is given to a range of surface roughnesses and treatments. It investigates, experimentally, the fundamental behaviour of speckles and attempts to formulate, for the first time, a relationship between changes in intensity to pseudo-vibration sensitivity levels. The thesis also develops and implements models for computational simulation of pseudo-vibrations using the fundamental behaviour of speckles. The combination of experimentation and simulation improves current understanding of the pseudo-vibration mechanisms and provides the vibration engineer with a valuable resource to improve data interpretation. Two experimental methods of quantifying pseudo-vibration sensitivity are developed and successfully applied in the evaluation of transverse, tilt and rotation sensitivity for two models of commercial laser vibrometer. These evaluations cover both single beam (translational vibration measurement) and parallel beam (for angular vibration measurement) modes. The first method presented requires correction of the vibrometer measurement with an independent measurement of genuine velocity to produce an iii apparent velocity dominated by the required noise components. The second method requires a differential measurement using two vibrometers to cancel common components such as genuine velocity, leaving only uncorrelated noise from each measurement in the resulting apparent velocity. In each case, a third measurement is required of the surface motion component causing pseudo-vibration and this is used to normalise the apparent velocity. Pseudo-vibration sensitivity is then presented as a map showing the spectral shape of the noise, as a mean and standard deviation of harmonic peaks in the map and as a total rms level across a defined bandwidth. The simulations employ a novel and effective approach to modelling speckle evolution. Transverse and tilt sensitivity are predicted for the first time and are verified by the experimental study. They provide the vibration engineer with the potential to estimate pseudo-vibrations using a simple piece of software. The laser beam spot diameter has a large influence on the pseudo-vibration sensitivity. Transverse sensitivity has been quantified as around 0.03% and 0.01% (per order) of the transverse velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Larger beam spots have been shown to significantly reduce transverse sensitivity and measurements from smoother surfaces have also shown a reduced level of transverse sensitivity. Tilt sensitivity has been quantified at about 0.1 μms-1/degs-1 and 0.3 μms-1/degs-1 (per order) of angular velocity of the surface for beam spot diameters of 100 μm and 600 μm respectively. Smaller beam spot diameters significantly reduce tilt sensitivity. The surface roughness or treatment has been shown to have little effect on the level of tilt sensitivity. Rotation sensitivity has been quantified at approximately 0.6 μms- 1/rads-1 and 1.9μms-1/rads-1 (per order) of rotation velocity of the rotor for 90 μm and 520 μm. Smaller beam spot diameters have shown a significant reduction in rotation sensitivity and measurements on smoother surfaces have shown a reduced rotation sensitivity. Focussing the laser beam approximately on the rotation axis has also shown a significant reduction in rotation sensitivity. Parallel beam rotation sensitivity has been quantified at 0.016 degs-1/rads-1 and it is demonstrated that this can adequately be estimated using the single beam rotation sensitivity.
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Johansson, Marcus. "An indicative case-control study of noise perception due to environmental noise sources." Thesis, KTH, Marcus Wallenberg Laboratoriet MWL, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280546.
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The subject of the thesis was proposed by the acoustic consultancy firm Brekke & Strand, which is of relevance for their additional understanding and development of services and contribution to robust solutions. The aim with this thesis is to give indicative results and to dig deeper into the relation between environmental noise and the perception of the same, specially focusing on construction related noise but also permanent noise sources that originates from infrastructure. The area of interest to evaluate the study is a central location in Stockholm, specifically around Slussen.The importance of a study within this field is vital, especially when considering possible negative health effects that can be related to the perceived noise exposure. With that background it is worth to consider the amount of healthy-life-years lost in Europe each year, which is assumed to be one million. The correlation between lost life years and noise is one of many, but it is also proven to be a catalyst when it comes to stress related or cardiovascular diseases. For instance, if one is living closer than 50 meters from a major road the risk can be four times higher to be annoyed, which in extension can be coupled to the diseases mentioned above.The practical implementation of the study is conducted with a survey and field measurements, with a psychoacoustical perspective and within the frames of a case-control study. Partially this includes to inform the participants of the study at different stages regarding construction noise. The provided information, survey and field measurements aims to be a substantial part of the evaluation regarding the perceived noise whether it is due to construction work, infrastructure or other stochastic sources.The result is presented and distinguished based on distance to noise source, differentiated by gender as well as which type of source that tends to be most annoying. The implemented ranking is displayed as the ICBEN score of each category or source which aims to measure the perceived impact. Even though the results are indicative, the conclusion yields an information dependency as well as a noise source dependency. Further on, the result yields an interesting pattern between genders where women tend to be more disturbed by construction- and other-noise, whereas men tend to be more disturbed by rail- and road-noise.Ämnet för uppsatsen föreslogs av akustiskkonsultföretaget Brekke & Strand, vilket är av relevans för deras ytterligare förståelse och utveckling av tjänster och bidrag till robusta lösningar. Syftet är att ge vägledande resultat och gräva djupare i förhållandet mellan samhällsbuller och uppfattningen av detsamma, med särskilt fokus på konstruktionsrelaterat buller men också permanenta bullerkällor som härstammar från infrastruktur. Studien och utvärderingen av den samma har fokuserats till Slussenområdet i centrala Stockholm.Betydelsen av en studie inom detta område är avgörande, särskilt när man överväger eventuella negativa hälsoeffekter som kan relateras till den upplevda bullerexponeringen. Med den bakgrunden är det värt att ta hänsyn till hur många hälsosamma levnadsår som går förlorade i Europa varje år, vilket antas vara en miljon. Korrelationen mellan förlorade levnadsår och buller är en av många, men det har också visat sig vara en katalysator när det gäller stressrelaterade eller hjärt- och kärlsjukdomar. Om man till exempel bor närmare än 50 meter från en huvudväg kan risken vara fyra gånger högre för att bli störd och påverkad av buller, vilket i förlängning kan kopplas till ovan nämnda sjukdomar.Det praktiska genomförandet av studien utförsmed en enkätundersökning, fältmätningar,med ett psyko-akustiskt perspektiv och inom ramen för en fallkontrollstudie. Detta inkluderar delvis att informera deltagarna i studien i olika stadier beträffande konstruktionsrelaterat buller. Den tillhandahållna informationen, undersökningen och fältmätningarna syftar till att vara en väsentlig del av utvärderingen av det upplevda bullret oavsett om det beror på byggnadsarbete, infrastruktur eller andra stokastiska källor.Resultatet presenteras och skiljer sig utifrån avstånd till bullerkälla, uppdelat efter kön samt vilken typ av källa som tenderar att vara mest irriterande. Den implementerade rangordningen visas som ICBEN-skalan för varje kategori eller källa, som syftar till att mäta den upplevda effekten. Även om resultaten är vägledande så visar resultaten ett informationsberoende samt ett bullerkällaberoende. Vidare ger resultatet ett intressant mönster mellan könen, där kvinnor tenderar att bli mer störda av konstruktions- och andra-bullerkällor, medan män tenderar att bli mer störda av järnvägs- och väg-buller.
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Nelson, Cory Lee. "Reducing phase noise degradation due to vibration of crystal oscillators." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476330.
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Singh, Abhishek Narayan. "Modeling of recurrent threshold crossings due to noise with long memory." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4806.
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This thesis addresses the recurrent threshold crossing behavior of long-time
correlated noise. The behavior of long-time correlated noise like f / 1 , 5 . 1 / 1 f , and 2 / 1 f
can be associated with the behavior of many phenomena in nature, so it is of interest to
study the behavior of this noise. Our method of modeling their recurring behavior relies
on setting a particular threshold level for a particular level of noise and observing how
frequently the noise crosses the threshold level. We also add a periodic drive to the noise
which enables it to cross the threshold level easily when it is at peak, and vice versa.
This technique provides a model for the changing seasons that occur during every year.
We also compare the recurrence behavior of threshold crossings from our computer
simulations with theoretical results from the Rice formula. We have related the
recurrence of these threshold crossings with the recurrence of natural disasters.
Therefore we are providing a model to predict the recurrence of a natural disaster once
that disaster has previously occurred. From our results, we conclude that once a natural
disaster has occurred, there is a high probability of its recurrence in a short time, and this
probability gradually decreases with time.
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Jurdic, Vincent. "An investigation into fan broadband noise due to rotor-stator interaction." Thesis, University of Southampton, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536289.
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Griffin, Jason Robert. "The Control of Interior Cabin Noise Due to a Turbulent Boundary Layer Noise Excitation Using Smart Foam Elements." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32804.
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In this work, the potential for a smart foam actuator in controlling interior cabin noise due to a turbulent boundary layer excitation has been experimentally demonstrated. A smart foam actuator is a device comprised of sound absorbing foam with an embedded distributed piezoelectric layer (PVDF) designed to operate over a broad range of frequencies. The acoustic foam acts as a passive absorber and targets the high frequency content, while the PVDF serves as the active component and is used to overcome the limitations of the acoustic foam at low frequencies. The fuselage skin of an aircraft was represented by an experimental test panel in an anechoic box mounted to the side of a wind tunnel. The rig was used to simulate turbulent boundary layer noise transmission into and aircraft cabin. An active noise control (ANC) methodology was employed by covering the test panel with the smart foam actuators and driving them to generate a secondary sound field. This secondary sound field, when superimposed with the panel radiation, resulted in a reduction in overall sound in the anechoic box. An adaptive feedforward filtered-x Least-Mean-Squared (LMS) control algorithm was used to drive the smart foam actuators to reduce the sound pressure levels at an array of microphones. Accelerometers measured the response of the test panel and were used as the reference signal for the feedforward algorithm. A detailed summary of the smart foam actuator control performance is presented for two separate low speed wind tunnel facilities with speeds of Mach 0.1 and Mach 0.2 and a single high speed tunnel facility operating at Mach 0.8 and Mach 2.5.Master of Science
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Branner, James Lester. "Noise due to pressure pulsations in a pressure-balanced sliding vane pump." Thesis, Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/101167.
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An experimental investigation of noise in a pressure-balanced sliding vane pump was conducted. The test pump for this research was used in an automobile's hydraulic power steering system. As currently designed, a small portion of the manufactured pumps generate excessive noise during operation.
An experimental test stand facility was used to represent a power steering system for analysis of the excessive noise problem with the objective of determining ways to reduce the noise. Through signature analysis techniques, the sliding vane pump noise was related to the pump's pressure pulsations. The pulsations consisted of three types of pressure oscillations: the pressure ripple with a fundamental component at the vane passage frequency together with harmonics; the low-frequency pressure oscillation with a fundamental component at the rotational frequency together with harmonics; and the high-frequency pressure oscillation. The fundamental vane passage frequency and its harmonics dominated the noise signal frequency spectrum. The pump's internal leakage, which was a function of three clearances in the pumping chamber, determined the magnitude of the pressure pulsations. If the pumping chamber components had inadequate clearances, the pump produced excessive pressure pulsations for a given discharge pressure and, consequently, excessive fluid-borne noise generation. Thus, this study indicated increasing the pump's clearances would minimize the pump's noise generation.M.S.
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Ainslie, Michael Anthony. "The sound pressure field in the ocean due to bottom interacting paths." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314950.
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Smith, Elwyn D. J. "Noise limits due to light mixing in optical code-division multiple-access systems." Thesis, University of Canterbury. Electrical and Electronic Engineering, 1998. http://hdl.handle.net/10092/5742.
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This thesis is concerned with the performance limits arising in optical code-division multiple-access (OCDMA) networks due to the mixing of light from the independent sources of each user. The scheme of spectral-amplitude OCDMA is shown here to be significantly limited by the phase-induced intensity noise arising from such mixing, and the corresponding signal-to- noise ratio and network capacity limits are of the same order as those arising in coherence-multiplexing systems, also due to such noise. Mixing can only occur between spatially coherent light, and this typically takes place through the combination of the signals into a single-mode fibre. The use of multimode fibre instead of single-mode can thus significantly reduce the levels and effects of phase-induced intensity noise, and this is experimentally demonstrated.
It is shown that in general, assuming independent sources, there are only four possible ways in which to alleviate or eliminate noise limits of the form found for spectral-amplitude OCDMA. These are to separate the signals from each user in either the temporal, spectral, or spatial domains, or else to coherently despread the received signal. Neither spectral separation nor coherent de spreading are practical for spectral-amplitude OCDMA, but spatial separation via multimode fibre may be applied. The use of pulse-position modulation (PPM) with spectral-amplitude OCDMA is shown to be able to improve the performance beyond the limits found earlier, and this is because of the temporal separation it introduces. However, unlike the direct reduction of source duty cycle, PPM signalling can be applied without increasing, relative to the bit rate, the modulation or detection bandwidths, nor the dispersion sensitivity. Such PPM signalling and the associated decoding can also be applied to other similarly limited systems, including those based upon coherence multiplexing.
If an OCDMA system is incoherent, has independent sources of the same spectrum, and has only a single-mode fibre to and from each user, then it can only avoid the significant noise limits found for spectral-amplitude OCDMA by the temporal separation of the signals from each user. This is the case for incoherent unipolar OCDMA systems, since the sparse codes of these systems rely on such temporal separation. Bipolar codes are not sparse, and in bipolar systems there is ordinarily no significant temporal separation between the signals from each user. Consequently, assuming sole single-mode-fibre paths and independent sources with identical spectra, every incoherent bipolar OCDMA system must encounter performance limits at least as bad as those found for spectral-amplitude OCDMA. These worst-case limits are identified for each of the incoherent bipolar OCDMA proposals to date.
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Hipsey, Stephen J. "Ambient noise due to the shearing of the boundary layer under sea ice." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/22869.
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Lee, Chun-ming Angus, and 李俊明. "Reduction of electromagnetic interference due to electric field coupling on printed circuit board." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B29957709.
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Webster, Lesley Helen. "The sound field due to a moving body in the presence of plane boundaries." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313007.
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Ren, Qunyan. "Remote sensing of sediment characteristics from the noise field due to a moving ship." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/222087.
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Qun-yan Ren received his Diploma in Electronic and Information Engineering, master degree in Underwater Acoustics Engineering both from Harbin Engineering University (HEU) in 2006 and 2009, respectively. Then he became a PhD student at the Environmental Hydroacoustics Laboratory, Ecole polytechnique de Bruxelles, Faculty of Applied Sciences, Universitie libre de Bruxelles (U.L.B.), Belgium, in co-tutelle with the National Key Laboratory of Underwater Acoustic Technology, HEU, China, under the co-supervision of Prof. Jean-Pierre Hermand and Prof. Piao Shengchun from U.L.B. and HEU, respectively. Since 2013, he became a full PhD student at the ULB. In Oct 2011, he obtained a four-year `Aspirantq{} grant from the Belgian National Fund for Scientific Research (F.R.S.-F.N.R.S.).Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Arbinge, Peter. "The effect on noise emission from wind turbines due to ice accretion on rotor blades." Thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118267.
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Swedish EPA (Naturvårdsverket) noise level guide-lines suggest that equivalent A-weighted sound pressure levels (SPL) must not exceed 40 dBA at residents. Thus, in the planning of new wind farms and their location it is crucial to estimate the disturbance it may cause to nearby residents. Wind turbine noise emission levels are guaranteed by the wind turbine manufacturer only under ice-free conditions. Thus, ice accretion on wind turbine may lead to increased wind turbine noise resulting in noise levels at nearby residents to exceed 40 dBA SPL. The purpose of the project is to evaluate the effect on wind turbine noise emission due to ice accretion. This, by trying to quantify the ice accretion on rotor blades and correlate it to any change in noise emission. A literature study shows that the rotor blades are to be considered the primary noise source. Hence, ice accretion on rotor blades are assumed to be the main influence on noise character. A field study is performed in two parts; as a long term measurement based on the method out-lined by IEC 61400-11 and as a short term measurement in strict accordance with IEC 61400-11. These aim to obtain noise emission levels for the case of icing conditions and ice-free conditions (reference conditions) as well as background noise levels. An analysis is performed, which sets out to correlate ice measurements with wind turbine performance and noise emission. Data reduction procedures are performed according to IEC 61400-11.The apparent sound power levels are evaluated. This is performed for the case of icing conditions as well as for the case of ice-free onditions. A statistical evaluation of icing event is carried out. The results show that ice accretion on wind turbine (rotor blades) may lead to drastically higher noise emission levels. The sound power levels show an average increase of 10.6 dB at 8 m/s. However, this can occur at all wind speeds from 6 m/s to 10 m/s. Higher levels of noise, (55 to 65 dBA SPL) may be caused by very small amounts of ice accretion. Occurrences of higher levels of noise, in the range of 50 to 65 dBA SPL, are not common. Noise levels exceeding 50 dBA SPL are to expected 10.3 % of the time during the winter or 3 % of the time during one year. Correlation between measured ice accumulation and noise level is weak apart from large amounts of ice. This due to statistical noise. Taking into account the noise level guide-lines of 40 dBA SPL at residents, as is recommended by Swedish EPA (Naturvårdsverket), the increased levels of windturbine noise under icing conditions may force the power production to a halt.
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Storm, Richard. "HEALTH RISKS DUE TO EXPOSURE OF LOW-FREQUENCY NOISE : HÄLSORISKER VID EXPONERING AV LÅGFREKVENT BULLER." Thesis, Örebro University, School of Science and Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-8295.
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This paper was made with an aim to prepare the risk assessment of operators’ noise exposure in Atlas Copco’s existing machines. This work is divided into three major parts: low-frequency noise, hearing protection and sound propagation in mines. Several studies, regulations and books have been examined in order to collect data of relevance to this work.
The existence of man-made low-frequency noise (20-200 Hz) has been reported in many environments as a critical pollution problem. Symptoms like hearing loss, tinnitus, annoyance, disturbance of rest and sleep, fatigue, lower performance and social orientation, feeling of pressure on the eardrum and head, headache, disorientation, nausea, and balance disturbance, have among other ailments been reported by exposure to low-frequency noise.
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Deane, Eugene Pio. "Use of fan rig data for the understanding and prediction of fan broadband noise and noise changes due to a variable area nozzle." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/160877/.
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This thesis presents the results of the research component of this EngD, entitled Use of fan rig data for the understanding and prediction of fan broadband noise and noise changes due to a variable area nozzle As suggested by the title, fan rig noise measurements form an integral part of this thesis. The analysis of a database of rig noise measurements forms the first section of this thesis, in two parts. The first part describes the analysis of a set of fan rig noise measurements, including the variation of fan broadband and tone noise in forward and rearward arcs. The second part examines a large database of fan rig noise measurements, and attempts to derive correlations of fan broadband noise and fan performance parameters. Cluster Analysis, Principle Component Analysis, and Regression Analysis are used to understand and describe the underlying physics of broadband noise generation and the relationships between these predictors. The second section of this thesis uses a cascade broadband noise model to investigate rotorstator broadband noise. Predictions of the broadband noise from this noise model are compared to rig measurements, showing good accuracy. The underlying physics of rotorstator broadband noise generation is investigated by performing two parametric studies using the broadband noise model. The first parametric study investigates the effect on broadband noise of simple flow and geometric parameters, namely number of vanes, vane chord, vane stagger angle, and rotor wake turbulence intensity, turbulent length scale, and flow Mach number onto the cascade. These results are used to derive scaling power laws for the prediction of changes in broadband noise due to changes in these parameters. The second parametric study expands upon this by investigating the effect on broadband noise of the fan design parameters shaft speed, pressure ratio, and efficiency, at approach, cutback and cruise conditions. The variation in broadband noise due to these design parameters is explained by considering the underlying flow and geometric parameters such as number of vanes and Mach number, and the scaling power laws based on these simple parameters are used to predict the change in broadband noise between different performance points. The final section of this thesis investigates the effect of varying exhaust nozzle area on total engine noise. A new method is presented that allows the transfer of changes in fan rig noise to Eugene P. Deane EngD Thesis September 2009 2 engine noise predictions, to estimate the change in fan noise due to the pressure ratio changes brought about by a variable area nozzle. Changes in engine noise are investigated for approach, cutback, and sideline conditions, and the application of the new method assessed. As the research displayed in this thesis is closely linked to industry, the foundation of work presented in several chapters is dependent on data or figures that are commercially sensitive. It has therefore been necessary to create a confidential appendix (Appendix X) to include these commercially sensitive items. These additional results and figures in Appendix X are supplementary in nature, and sufficient results are presented in the public thesis to illustrate the results of the various chapters. Where supplementary information and results are available, this is clearly indicated at the pertinent point in the published thesis, along with the section of Appendix X where the information can be found.
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Algattus, Said S. "Experimental investigation of noise reduction in supersonic jets due to jet rotation and to nozzle geometry changes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0019/NQ43583.pdf.
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Kuan, Gary M. "The effect of interferometric noise due to crosstalk on the bit error rate of an optical network /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2001. http://wwwlib.umi.com/cr/ucsd/fullcit?p3022215.
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Janczak, Teresa Krystyna. "Estimation of Jitter Effects in Oscillators and Frequency Synthesizers Due to Prototypical Perturbation Sources." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1094%5F1%5Fm.pdf&type=application/pdf.
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Gopinath, Kaundinya S. "Reduction of noise due to task correlated motion in event related overt word generation functional magnetic resonance imaging paradigms." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001289.
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Masuda, Michael Curtis Meyer. "Investigation of Degradation Effects Due to Gate Stress in GaN-on-Si High Electron Mobility Transistors Through Analysis of Low Frequency Noise." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1169.
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Gallium Nitride (GaN) high electron mobility transistors (HEMT) have superior performance characteristics compared to Silicon (Si) and Gallium Arsenide (GaAs) based transistors. GaN is a wide bandgap semiconductor which allows it to operate at higher breakdown voltages and power. Unlike traditional semiconductor devices, the GaN HEMT channel region is undoped and relies on the piezoelectric effect created at the GaN and Aluminum Gallium Nitride (AlGaN) heterojunction to create a conduction channel in the form of a quantum well known as the two dimensional electron gas (2DEG). Because the GaN HEMTs are undoped, these devices have higher electron mobility crucial for high frequency operation. However, over time and use these devices degrade in a manner that is not well understood. This research utilizes low frequency noise (LFN) as a method for analyzing changes and degradation mechanisms in GaN-on-Si devices due to gate stress.
LFN is a useful tool for probing different regions of the device that cannot be measured through direct means. LFN generation in GaN HEMTs is based on the carrier fluctuation theory of 1/f noise generation which states fluctuations in the number of charge carriers results in conductance fluctuations that produce a Lorentzian noise spectrum. The summing Lorentzian noise spectra from multiple traps leads to 1/f and random telegraph signal (RTS) noise. The primary cause of carrier fluctuations are electron traps near the 2DEG and in the AlGaN bulk. These traps occur naturally due to dislocations and impurities in the manufacturing process, but new traps can be generated by the inverse-piezoelectric effect during gate stress.
This thesis introduces noise and presents a circuit to bias the devices and measure gate and drain LFN simultaneously. Three measurements are performed before and after gate DC stress at three different temperatures: DC characterization, capacitance-voltage (C-V) measurements, and LFN measurements. The DC characteristics show an increase in gate leakage after stress caused by an increase in traps after degradation consistent with trap assisted tunneling. However, the leakage current on the drain and source side differ before and after stress leading to the conclusion that the source side of the gate is more sensitive to gate stress. Gate leakage current on the drain side is also sensitive to temperature due to thermionic trap assisted tunneling. Hooge parameter calculations agree with previous research. The LFN results show an increase in gate and drain noise power, SIg(f) and SId(f), in accordance with increased gate leakage current under cutoff bias. RTS noise is also observed to increase in frequency with increased temperature. Activation energies for RTS noise are extracted and qualitatively linked to trap depth based on the McWhorter trap model.
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Maigrot, Philéas. "Compréhension des mécanismes perceptifs associés à la gêne due aux bruit et vibrations du trafic ferroviaire en zone urbaine." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI051.
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La co-exposition au bruit et aux vibrations est source de gêne pour les riverains et peut engendrer des troubles de la santé. L’objectif de la thèse est d’apporter des éléments de compréhension au regard des phénomènes perceptifs mis en jeux lors de l’exposition combinée au bruit et aux vibrations ferroviaires. Des expériences sont menées dans ce but, en conditions contrôlées et à l'aide d'enregistrements acoustiques et vibratoires réalisés à proximité d'une voie ferrée, à l'intérieur d'un logement. Une première étude a été réalisée afin de valider un protocole expérimental permettant de recueillir en laboratoire des réponses de gêne. Pour plusieurs combinaisons d'enregistrements de bruit et de vibrations ferroviaires présentés à différents niveaux, la gêne 1) partielle due au bruit, 2) partielle due aux vibrations et 3) totale due à la co-exposition au bruit et aux vibrations étaient recueillies. Les résultats de cette première étude ont été utilisés afin d'adopter un même protocole expérimental tout au long de ces travaux de thèse. Les études traitant de la gêne due aux bruit et vibrations ferroviaires sont majoritairement basées sur des indices ne reflétant que la quantité d’énergie liée à chaque exposition et leurs résultats peuvent être contradictoires. Une seconde étude a été menée en laboratoire dans le but d'évaluer l’influence de l’intensité (sonore, vibratoire) sur la gêne et afin de déterminer l'origine des différences de résultats dans la littérature. Les hypothèses testées étaient que ces différences pourraient être dues aux différentes plages de niveaux sonores et vibratoires étudiées, ou à des différences de contenus fréquentiels au sein des stimuli utilisés dans les différentes expériences. Dans la littérature, un besoin d’autres études en laboratoire est souligné afin de mieux comprendre l’influence des paramètres autres que le niveau global vibratoire (p. ex. contenu spectral, modulation) sur la gêne due aux vibrations ferroviaires. Un travail a été réalisé afin de mieux comprendre le rôle du contenu spectral vibratoire dans la gêne spécifique due aux vibrations, en l'absence de bruit. Une expérience a été conduite en utilisant des stimuli vibratoires artificiels, créés à partir des spectres d'enregistrements de vibrations ferroviaires. L'importance des paramètres autres que les niveaux de bruit et de vibrations globaux sur les variations de la gêne due à la co-exposition aux bruit et vibrations ferroviaires a fait l'objet d'une dernière étude. Les stimuli utilisés étaient obtenus à partir de 19 enregistrements sonores et vibratoires réalisés chez un riverain d'une voie ferrée, en les ramenant à une durée de 10s et en contrôlant les variations de niveau de bruit et de vibrations. Cette étude a montré que l'importance relative des paramètres temporels et fréquentiels de la co-exposition au bruit et aux vibrations était faible au regard de celle des paramètres énergétiquesVibrations due to railway traffic propagate from the tracks to inside neighbour houses. Residents who are exposed to vibrations are also exposed to railway noise. This combined exposure to noise and vibration leads to annoyance, as well as to some health issues. Few studies have been conducted to investigate this combined exposure in terms of annoyance. The goal of the thesis is to improve the knowledge concerning the perceptual phenomena involved when both railway noise and railway vibration occur at the same time. Experiments are carried out in controlled conditions for that purpose, using acoustic and vibratory recordings obtained in the vicinity of a railway track, inside a dwelling. A first study was conducted in order to test the validity of an experimental procedure allowing to collect annoyance responses in laboratory conditions. For several combinations of noise and vibration at different noise and vibration levels, annoyance responses were collected: 1) partial annoyance due to noise, 2) partial annoyance due to vibration and 3) total annoyance due to combined noise and vibration. Results of this first study led to a common procedure used for the rest of the experiments carried out during this thesis work. Studies about annoyance due to combined railway noise and vibration often use indices which only describe an amount of energy for each single exposure. Results can be contradictory. A second study was conducted in the laboratory in order to evaluate the influence of (noise and vibration) intensity on annoyance and to determine the reason of the contradictory results observed in the literature. The initial hypotheses made in the current work were that those could be due to the different ranges of variation of noise and vibratory levels, or to the different spectral contents of the stimuli used in the studies of interest. In the literature, there is a reported need of further investigations about the influence of parameters not related to vibration level (\textit{e.g.} frequency content, modulation) on railway vibration annoyance. During this thesis, work was done in the aim of a better understanding of the role of vibratory spectral content in specific annoyance due to vibration in the absence of noise. An experiment was conducted using artificial vibration stimuli based on the railway vibration recording spectra. The importance of parameters other than overall noise or vibration levels on variations of the annoyance due to combined railway noise and vibration was investigated during a last study. The stimuli were based on 19 noise and vibration recordings obtained inside a dwelling, after having reduced their duration to 10s and with controlled variations of noise and vibration levels. The results showed that the relative importance of temporal and spectral parameters of the combined exposure to noise and vibration was low as compared to that of energetic parameters
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Fischer, Jan Christoph Heinrich [Verfasser], and A. [Akademischer Betreuer] Albers. "Methoden für die Validierung des Fahrzeuginnengeräusches von Elektrofahrzeugen in Bezug auf tonale Geräusche aufgrund torsionaler Anregung durch den Elektromotor = Methods for the Validation of Electric Vehicle Interior Noise with Regard to Tonal Noise due to Torsional Excitation by the Electric Drive / Jan Christoph Heinrich Fischer ; Betreuer: A. Albers." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1153828553/34.
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Fischer, Jan Christoph Heinrich Verfasser], and Albert [Akademischer Betreuer] [Albers. "Methoden für die Validierung des Fahrzeuginnengeräusches von Elektrofahrzeugen in Bezug auf tonale Geräusche aufgrund torsionaler Anregung durch den Elektromotor = Methods for the Validation of Electric Vehicle Interior Noise with Regard to Tonal Noise due to Torsional Excitation by the Electric Drive / Jan Christoph Heinrich Fischer ; Betreuer: A. Albers." Karlsruhe : KIT-Bibliothek, 2018. http://nbn-resolving.de/urn:nbn:de:swb:90-803149.
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Nilsson, Lucas. "Estimation of Ship Properties for Energy Efficient Automation." Thesis, Linköpings universitet, Reglerteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-133557.
Full textAbstract:
One method to increase efficiency, robustness and accuracy of automatic control, is to introduce mathematical models of the system in question to increase performance. With these models, it is possible to predict the behavior of the system, which enables control according to the predictions. The problem here is that if these models do not describe the dynamics of the system well enough, this method could fail to increase performance. To address this problem, one idea is to estimate the dynamics of the system during operation, using methods for system identification, signal processing and sensor fusion. In this thesis, the possibilities of estimating a ship's dynamics during operation have been investigated. The mathematical model describing the dynamics of the ship is a graybox model, which is based on the physical and mechanical relations. This model's properties are therefore described by physical quantities such as mass and moment of inertia, all of which are unknown. This means that, when estimating the model, these physical properties will be estimated. For a systematic approach, first a simulation environment with a 4-degrees-of-freedom ship model has been developed. This environment has been used for validation of system identification methods. A model of a podded propulsion system has also been derived and validated. The methods for estimating the properties of the ship have been analyzed using the data collected from the simulations. For system identification and estimation of ship properties, the influence of measurement noise and potential of detecting a change in dynamics has been analyzed. This has been done through Monte Carlo simulations of the estimation method with different noise realizations in the simulations, to analyze how the measurement noise affects the variance and bias for the estimates. The results show that variance and bias vary a lot between the parameters and that even a small change in dynamics is visible in some parameter estimates when only ten minutes of data have been used. A method based on cumulative summation (CUSUM) has been proposed and validated to analyze if such a method could yield fast and effective detection of system deviations. The results show that the method is rather effective a with robust detection of changes in the dynamics after about four minutes of data collection. Finally, the methods have been validated on data collected on a real ship to analyze the potential of the methods under actual circumstances. The results show that the particular data is not appropriate for this kind of application along with some additional problems that can yield impaired results.Genom att inkludera matematiska modeller som beskriver ett systems dynamik i styrningsalgoritmer, kan man åstadkomma en automatisk styrning med förbättrad effektivitet, robusthet och noggrannhet. Med dessa modeller går det att förutsäga beteendet hos systemet och därmed öppnas också möjligheten att använda sig av detta i styrningen. Problemet är att om dessa modeller inte beskriver systemets dynamik tillräckligt bra kan prestandan istället sänkas genom dessa metoder. Den här sortens problem kan man lösa genom att aktivt skatta systemets dynamik under körning, med hjälp av metoder för systemidentifiering, signalbehandling och sensorfusion. I denna exjobbsrapport har möjligheterna att skatta ett skepps girdynamik undersökts. Den matematiska modell som beskriver skeppets dynamik är en grålådemodell som baserar sig på fysikaliska och mekaniska samband. Denna modells egenskaper beskrivs därför av fysikaliska storheter så som massa, tröghetsmoment och tyngdpunkt, vilka alla är okända. Detta innebär att vid modellskattning skattas dessa fysikaliska storheter, vilka kan vara av stort intresse. En simuleringsmiljö med en skeppsmodell med fyra frihetsgrader har skapats och använts för att validera metoder för systemidentifiering. En modell av ett roterbart framdrivningssystem har också härletts och inkluderats i simuleringsmodellen. Vid systemidentifiering och skattning av skeppets egenskaper har dels inverkan av mätbrus analyserats samt även möjligheter till att detektera skillnader i dynamik. Detta har gjorts med Monte Carlo-simuleringar av skattningsmetoden med olika brusrealiseringar för att analysera hur mätbrus påverkar variansen och metodfelet hos skattningarna. Resultaten visar att vissa parametrar skattas med större noggrannhet och hos dessa kan därmed en förändring i dynamik identifieras när endast tio minuter av data har använts. En metod baserad på kumulativ summering av residualer har formulerats och validerats, detta för att undersöka om en sådan metod kan ge snabb och effektiv detektion av systemförändringar. Resultat visar på robusthet i att detektera skillnader i dynamik efter ungefär fyra minuter av datainsamling. Slutligen har metoderna validerats på data insamlad på ett riktigt skepp för att undersöka potentialen under verkliga omständigheter. Resultaten visar att just denna data inte är lämplig för denna applikation samt några problem som kan leda till försämrade resultat.
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LaForest, Stephanie. "Flux Noise due to Spins in SQUIDs." Thesis, 2013. http://hdl.handle.net/1828/4810.
Full textAbstract:
Superconducting Quantum Interference Devices (SQUIDs) are currently being used as flux qubits and read-out detectors in a variety of solid-state quantum computer
architectures. The main limitation of SQUID qubits is that they have a coherence time of the order of 10 us, due to the presence of intrinsic flux noise that is not yet fully understood. The origin of flux noise is currently believed to be related to spin impurities
present in the materials and interfaces that form the device. Here we present a novel numerical method that enables calculations of the flux produced by spin impurities even when they are located quite close to the SQUID wire. We show that the SQUID will be particularly sensitive to spins located at its wire edges, generating flux shifts of up to 4 nano flux quanta, much higher than previous calculations based on the software
package FastHenry. This shows that spin impurities in a particular region along the wire's
surface play a much more important role in producing flux noise than other spin impurities located elsewhere in the device.Graduate
0611
0607
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laforest@uvic.ca
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Adluri, Sirisha. "Contributions to substrate noise due to supply coupling and pin parasitics." Thesis, 2003. http://hdl.handle.net/1957/29861.
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Syu, Jia-Hong, and 徐嘉宏. "Prediction of The Dipole Noise Due to The Unconventional Propeller." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/43jbuz.
Full textAbstract:
碩士國立臺灣海洋大學
系統工程暨造船學系
105
The objective of this paper is to develop the procedure in predicting the dipole noise radiated by the unconventional propeller. The unconventional propeller such as Endplate Propeller (ENDP) is the best choice for submarines and warships to restrain any kind of cavitation without efficiency loss. When the propellers of submarines at diving depth, or warships at cruising speeds are operating in non-uniform wake field, cavitation is not allowable. For these cavitation-free propellers the noises generated by dipoles (i.e. unsteady forces) dominate. Besides, the juncture vortex caused by the sails of submarines will make propeller inflow more non-uniform; thus the dipole strength will be enhanced and the radiated noise will be more remarkable consequently. The unsteady forces of a propeller include three components: the axial thrust, the tangential torque force, and the radial force; but the radial force is generally omitted, because it is much smaller than the first two. Traditional propeller theory cannot be applied in solving the unsteady loadings for the ENDP. In this paper computational fluid dynamics (CFD) technology and linear wave theory will be combined to solve the dipole noise radiated from the unconventional propeller. At first the prediction of unsteady loadings are carried out by CFD. The computed loadings are then transformed as equivalent dipole strengths for the numerical scheme of linear wave theory to calculate both near- field and far- field noises. A surface ship will be treated as computing sample here.
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Sali, Wolobah B. "Removing noise due to aircraft motion from gravity gradient data." Thesis, 2009. http://hdl.handle.net/10539/7190.
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The problem of interpolating an, in general, irregularly sampled gravity gradient eld in the
presence of noise is considered. The interpolation problem is ill posed. To restore uniqueness we
require that the interpolant is consistent with Laplace's equation. The interpolant is tested in a
number of numerical experiments and is found to yield results which are far superior to simple
polynomial interpolation.
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Lee, Ching-Tsan, and 李敬贊. "Jitter Analysis Due to Noise in the Phase-Locked Loop Circuits." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/57009169064196771229.
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碩士國立交通大學
電子工程系
88
The Phase-Locked Loop circuit is usually employed as a clock generator in the digital or communication system. Its stability determines the limiting stability of system. In this thesis ,we propose a behavioral noise model for which the transfer function was deduces by mathematics tools (MatLab). Based on this model , the power supply noises injected from each sub-block of the PLL circuit were analyzed to see how they affect the PLL output frequency ( jitter) . A practical PLL circuit was designed by using the TSMC 0.6u CMOS process. For this circuit ,noise of various frequencies were injected to each sub-block of the PLL .The spice simulation results were compared with those derived from the model .It showed that the spice experimental result agree with those derived from the model .This demonstrates that our proposed mathematical model can be used to analyze noise of the PLL circuit, enabling saving of much computation time.
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Lin, Yung-chi, and 林永基. "Noise and Vibration of Vehicles due to Expansion Joint at Freeway." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/19849937866249576250.
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碩士逢甲大學
土木工程所
94
In the recent years, a majority of the newly-constructed freeways and expressways at home are built to have many elevated sections and most of the viaducts are designed as long-span or continuous ones, which means expansion joints with larger sizes are required. The more quantity and size of the expansion joint increase ,The more damaged situation of the expansion joint frequent ,apparent .The problems, one after another, of the bridge expansion joints on national freeway No. 3 stand the case. when the noise that residents along the line give a full account and protest the car to be produced by the expansion joint constantly is too loud. in addition, When I was patrolling on public affair is it produce uncomfortable through the expansion joint .It is necessary to research the beat and the noise of expansion joint deeply. This research department collects the expansion joint of one section of bridges as the range from the Kuai-Guan to Cao-Tun on the 3rd of national freeway, carry on the present situation investigation and expansion joint impact ,elevation change , noise examine .All the source which are collected is going to analysis. Through probing and analyzing that obtains the conclusions are as follows: 1、 The code and measured value of the noise are compared . The finger expansion joint is superior to the module expansion joint in control of noise. 2、 The relation of Kinds and vibration in expansion joint. The module expansion joint displays obviously finger expansion joint in vibration, the module expansion joint rail is counted the more, have the tendency to the more obvious to vibrate become. 3、 The relation of Kinds and noise in expansion joint. The noise value of the finger expansion joint is low, but the module expansion joint counts and increases the average noise to have the tendency to reduce with the rail number. 4、 The relation of elevation change and vibration in expansion joint. It may be influenced and vibrated greater than elevation change above 1 cm .The left and right lane depth displacement at crossing have phenomenon of shaking , is it feels to be relatively obvious to beat. 5、 The relation of elevation change and mathematics simulation analyses in expansion joint. If module expansion joint is analyzed with pure rigidity module expansion joint better than finger type . In fact, the module expansion joint is constructed quite soft. It supports the system to make the rail have undulating space from head to foot , cause the deformation response bigger than the finger type.
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薛至宸. "Channel Non-uniformity induced Current Fluctuation due to Random Telegraph Noise in sub-100nm MOSFETs." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/96293395140528389177.
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AlGattus, Said S. "Experimental investigation of noise reduction in supersonic jets due to jet rotation and to nozzle geometry changes." Thesis, 1999. http://spectrum.library.concordia.ca/793/1/NQ43583.pdf.
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The present work deals with two different methods used for noise reduction in supersonic jets. The first method employed consisted of a swirl chamber, which produced axisymmetric jets with a tangential velocity component. This component was found to affect the structure of the jet cell and the internal oblique shocks formed inside. In the second method, the nozzle exit plane of the cylindrical chamber was perturbed such that the nozzle's exit lip was not lying in one plane perpendicular to the axis of symmetry of the nozzle. These two methods were investigated experimentally via spark Schlieren photography, static, Pitot and sound pressure measurements. Schlieren photography was employed to visualize the flow and shock structure associated with any of the above changes. Static and pitot pressure measurements were carried out to obtain the velocity distribution whereas sound pressure measurements were used to determine the resulting gain in noise reduction. The introduction of a small flow rotation was found to weaken the internal shock strength and to reduce the cell length and screech noise generated. Increasing the flow rotation beyond a certain limit was found to effect the shock structure without any noticeable noise reduction. Sinusoidal perturbation was found to affect the symmetry and strength of the oblique shocks in the supersonic cells. A considerable noise reduction was also noted with perturbation amplitude equal to 12.5% of the nozzle inside diameter. Larger perturbation did not result in a further noise reduction. In the first and second methods, a maximum noise reduction of 12 dB and 8 dB were measured, respectively.
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Lin, Hung-Liang, and 林宏亮. "Simulation and reduction strategies of the noise in the ambient area due to operations of the Keelung Harbor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64706503004386527532.
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碩士國立臺灣海洋大學
海洋環境資訊學系
98
Harbor operations do make noises. The objectives of this study is to investigate the characteristics of the noise in the Keelung Harbor and how to mitigate its effects on the ambient environment. The study first collected meterological information, harbor traffic volume and noise levels recorded by the five monitoring stations in the harbor. It was found that the there is no clear relationship between the noise level and each of the following parameters: wind speed, wind directions, atmospheric temperature, humidity and traffic volume. This study also uses the SoundPlan numerical model to simulate the noise in the harbor. The model was setup using the geographic information of the harbor area. The measured noise power level for the noise sources in the harbor as input. The results of the simulation are noise level contours in the simulated area, so that one can see that whether the noise level inside the simulated area exceed the regulation value. Further simulations showed that increasing the sound barrier wall to 4m high is not effective for reducing ambient noise levels. This study suggested that the harbor authority should build shore power facility for the berthed ships. This is especially important for the passenger terminal on the east side of the harbor. The reason is that the main noise source at the passenger terminal is the power generator of the cruise ships.
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Liang, Feng-Tsan, and 梁豐贊. "An Experimental Study for Acoustic High Pitched Noise Caused by MLCC on The Motherboard Due to Piezoelectric Effect." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/01028168112651054954.
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碩士國立臺灣大學
電機工程學研究所
98
Multilayer ceramic capacitor (MLCC) is of small size, low price, excellent frequency response and other characteristics, while at the same time it is surface mount components, so that it can be in rapid production and substantially reduce the share of components on the printed circuit board space, which currently widely used for portable products and laptop computers. As the popularity of laptop computers, users have found that the product may produce a tiny high pitched noise. Because it is extremely subtle, and can be heard only very close to the computer. Although the majority of users think that it does not affect its operation, but remains psychologically difficult to tolerate this unexpected high-pitched noise. The source of this noise is the multilayer ceramic capacitors which intensively used in laptop computers. The dielectric material of multilayer ceramic capacitor is mainly barium-titanate (BaTiO3), which has ceramic piezoelectric properties, so the vibration of its structure will occur under the AC electric field. This thesis verified that through experiments reducing ripple noise in the power trace could effectively reduce the high pitched microphonics phenomenon caused by the multilayer ceramic capacitors. The experimentation results show that the ripple noise was reduces by 26.5%, the loudness of high pitched noise was reduced by 19.4%, and the prominence ratios at 4KHz and 8KHz were lower.
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(8802878), Shaoguang Wang. "MODELING AND ANALYSIS OF HIGHWAY EMISSIONS DISPERSION DUE TO NOISE BARRIER SHAPE EFFECTS AND TRAFFIC FLOW UNDER DIFFERENT INFLOW CONDITIONS." Thesis, 2020.
Find full textAbstract:
A three-dimensional computational fluid dynamics (CFD) model has been developed to simulate the distribution of automobile emissions on and near a highway. A variety of k-ε turbulence models were adopted to simulate the turbulence flow, and a non-reaction species model was coupled to simulate the dispersion of emissions. The models were first validated by comparing velocity profiles and normalized emission concentration with wind tunnel experiments, and good agreement was observed. Next, further simulation and analysis revealed that T-shaped noise barriers could reduce more emissions concentration in downstream areas than rectangular noise barriers; however, the noise barrier shape effects on the dispersion of emissions were also influenced by inflow conditions. Thirdly, the traffic flow conditions on the highway made a difference to the dispersion of emissions. Automobile wakes not only existed behind vehicles but also induced turbulence on adjacent lanes, causing more emissions on the highway. Low traffic speed, such as congestion, would result in more emissions remaining on the highway as well. At last, vehicle body shapes modified the flow patterns by their slant angles and heights. Vehicles with slant angles on both front and rear sides had the least concentration of emissions at the center of the highway.
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Brewer, Micah K. "Environmental Impacts Due to Fixed and Floating Offshore Wind Turbines." 2012. https://scholarworks.umass.edu/theses/894.
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As has been the case for onshore wind systems, the environmental effects of offshore wind farms are expected to play an important part of the development of future large-scale wind energy systems. This paper presents a detailed review of the status of, and recent developments in, research on the environmental impacts of fixed and floating offshore wind turbine systems. The primary information that has been reviewed has come from European sources where there are a significant number of offshore installations, but some work on this subject has been carried out recently in the United States. Information, from an extensive review, is presented on the environmental impacts of fixed and floating offshore wind turbines on benthic organisms, fish, marine mammals, avian species and bats. The environmental impacts of fixed and floating systems are anticipated to vary due to multiple parameters that need to be taken into account when identifying environmental impacts. Additionally, there are variations in the impact throughout the lifecycle of the offshore wind turbines.
The primary focus for this paper is on the environmental impacts through the scope of barrier and habitat impacts in addition to the anticipated avian and bat fatalities. A noise propagation model is used to determine the extent of effects due to the installation of fixed and floating support structures using piling installation methods. Finally, a summary of progress in all the major environmental impact areas is given along with recommendations for future research.
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Alves, Juliana Araújo. "Os impactes da poluição sonora na saúde e na sustentabilidade dos lugares: estudo de caso no município de Guimarães." Doctoral thesis, 2017. http://hdl.handle.net/1822/50849.
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Tese de Doutoramento em Geografia (especialidade em Geografia Humana)A presente investigação tem como principal objetivo a avaliação dos impactes da poluição sonora na saúde da população nas freguesias de Serzedelo (“expostos”) e Abação (São Tomé – “não-expostos”) pertencentes ao município de Guimarães, pressupondo o desenvolvimento de uma metodologia orientada para a avaliação da incomodidade devida ao ruído de baixa frequência. Do ponto de vista metodológico, o estudo encerra duas dimensões de análise apelidadas de dimensão objetiva e de dimensão subjetiva. Para o desenvolvimento da investigação recorreu-se a fontes primárias e a fontes secundárias, a estatística descritiva e analítica e os níveis sonoros foram medidos e gravados com a ajuda de um sonómetro e o som gravado foi reproduzido em cabine audiométrica para determinar o limiar de audição dos voluntários. Na componente empírica foi usada a metodologia de Salford desenvolvida pelo Department of Environment, Food & Rural Affairs, datada de 2011. A partir da análise integradora das duas dimensões em estudo, foram formuladas algumas ilações. A primeira prende-se com o facto de que os níveis sonoros medidos, independentemente do grupo, ultrapassam a curva critério da metodologia de D.E.F.R.A. (2011). Os níveis sonoros registados para Serzedelo (sudoeste do município) foram mais elevados do que para Abação (São Tomé – sudeste do município de Guimarães). Outra constatação é a de que Serzedelo apresenta um maior número de inquiridos com problemas de saúde, nomeadamente, com doenças cardiovasculares, distúrbios do sono e doenças metabólicas. No que diz respeito aos testes audiométricos, foi testado o som real recolhido a 5 metros de distância projetada, medidos na horizontal, entre o recetor e a fonte. Constatou-se que a esta distância o ruído é considerado incomodativo e apresenta níveis de pressão sonora acima dos considerados seguros para a saúde humana. A partir da análise integradora concretizada, ficou evidente que as duas freguesias apresentam níveis sonoros elevados nas faixas de frequência de 40 Hz a 160 Hz e que, este tipo de ruído, é audível. Por fim, espera-se que esta tese possa contribuir para os estudos de avaliação da incomodidade devida ao ruído de baixa frequência e para a formulação de políticas públicas na definição dos limites para instalação dos postes e linhas de alta tensão em áreas residenciais.
This research main objective is the evaluation of the impacts of noise pollution on the health of the population from the villages of Serzedelo ("exposed") and Abação (São Tomé - "non-exposed"), belonging to the municipality of Guimarães, assuming the development of an oriented methodology for the assessment of discomfort due to the low frequency noise. From the methodological point of view, the study concludes two dimensions of analysis called objective dimension and subjective dimension. For the research development were used primary sources and secondary sources, analytical and descriptive statistics, sound levels were measured and recorded with the help of a sound level meter, the recorded sound was reproduced in an audiometric screening box to determine the hearing threshold of volunteers. In the empirical component it was used the Salford methodology, developed by the Department of Environment, Food & Rural Affairs dated 2011. Conclusions were formulated from the integrative analysis of the two dimensions under study. The first one relates to the fact that the sound levels measured, regardless of the group, go beyond the criterion of D.E.F.R.A. (2011) methodology curve. The sound levels recorded for Serzedelo (south-west of Guimarães municipality) were higher than for Abação (São Tomé - southeastern of Guimarães municipality). Another finding is that Serzedelo presents a larger number of respondents with health problems, namely, cardiovascular diseases, sleep disorders and metabolic diseases. With regard to the audiometric assessments, the actual sound used in the tests, was collected 5 projected meters away, measured horizontally, between the receiver and the source. It was found that at this distance the noise is considered annoying and presents sound pressure levels above those considered safe for human health. From the integrative analysis carried out, it became evident that both locations feature high sound levels in the frequency’s from 40 Hz to 160 Hz, and that this type of noise is audible. Finally, it is hoped, this thesis may contribute to the studies of discomfort evaluation due to low frequency noise and formulation of public policies in the definition of boundaries for power line installations in residential areas.
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES, que financiou esta pesquisa atráves do Programa de Doutorado Pleno no Exterior (Processo BEX 1684-13/2)