Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Electric waves Measurement.
Дисертації з теми "Electric waves Measurement"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Electric waves Measurement".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Matandirotya, Electdom. "Measurement and modelling of geomagnetically induced currents (GIC) in power lines." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2459.
Повний текст джерелаАнотація:
Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.<br>Geomagnetically induced currents (GIC) are currents induced in ground-based conductor
networks in the Earth's surface. The GIC are driven by an electric eld induced by geomagnetic
variations which are a result of time-varying magnetospheric-ionospheric currents during adverse
space weather events. Several studies have shown that there is a likelihood of technological
damage (the power grid) in the mid- and low-latitude regions that could be linked to GIC during
some geomagnetic storms over the past solar cycles. The effects of GIC in the power system can
range from temporary damage (e.g. protective relay tripping) to permanent damage (thermal
transformer damage). Measurements of GIC in most substations are done on the
neutral-to-ground connections of transformers using Hall-effect transducers. However, there is a
need to understand the characteristics of GIC in the power lines connected to these transformers.
Direct measurements of GIC in the power lines are not feasible due to the low frequencies of these
currents which make current measurements using current transformers (CT) impractical. This thesis discusses two techniques that can be employed to enhance understanding GIC
characteristics in mid-latitude regions. The techniques involve the measurement of GIC in a power
line using differential magnetometer measurements and modelling GIC using the finite element
method. Low frequency magnetometers are used to measure magnetic felds in the vicinity of the
power lines and the GIC is inferred using the Biot-Savart law. A finite element model, using
COMSOL-Multiphysics, is used to calculate GIC with the measured magnetic field and a realistic
Earth conductivity profile as inputs. The finite element model is used for the computation of
electric field associated with GIC modelling.
2
Chowdhury, Rehana Momtaz Engineering & Information Technology Australian Defence Force Academy UNSW. "Use of Higher Order Harmonics from a Limiter to Improve the Single-Tone Detection Performance of an Envelope Detector." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/43512.
Повний текст джерелаАнотація:
The limiter is a commonly used device in communication receiving systems to remove the amplitude variations of the received signal, but it is usually observed that limiter degrades the envelope detection performance of a single tone. In this thesis, it is demonstrated that the limiter-generated third harmonic can be used to improve the envelope detection performance of a single tone over that of the linearly processed fundamental. Differences in the probability distributions of the limiter-generated harmonics cause differences in their detection probabilities, which lead to differences in the performance of subsequent envelope detection. Comparison of the envelope detection performance of the limiter-generated third harmonic and the input to the limiter shows a maximum detection probability gain of 1.12 and also error probability gain of 2.4 in linear scale, whereas the fundamental harmonic does not show any practically significant gain. The envelope detection performance of the vector sum of the limiter-generated fundamental and third harmonics is also evaluated. This combination provides better performance than do the individual harmonics, especially for a large clipping parameter of the limiter. The combined harmonics shows a maximum detetction probability gain of 1.15 and error probability gain of 14, over that of the envelope detection performance of a tone without limiter. It is also observed that the envelope detection performance of a tone with limiter-generated higher harmonics shows non-monotonic behaviour as functions of either noise or the limiter-clipping parameter, which is a signature of stochastic resonance. The theoretical results from earlier research on the envelope detection of a single tone embedded in additive white Gaussian noise, both with and without a limiter, are presented and shown to match our simulation results. In previous work when a limiter was used in the envelope detection of a single tone, only the envelope of the fundamental harmonic was considered under very specific conditions. By contrast we also take notice of the limiter-generated higher harmonics and obtain improved envelope detection performance in the detection of a single tone.
3
Huang, Liling. "Electromechanical Wave Propagation in Large Electric Power Systems." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11054.
Повний текст джерелаАнотація:
In a large and dense power network, the transmission lines, the generators and the loads are considered to be continuous functions of space. The continuum technique provides a macro-scale analytical tool to gain an insight into the mechanisms by which the disturbances initiated by faults and other random events propagate in the continuum. This dissertation presents one-dimensional and two-dimensional discrete models to illustrate the propagation of electromechanical waves in a continuum system. The more realistic simulations of the non-uniform distribution of generators and boundary conditions are also studied. Numerical simulations, based on the swing equation, demonstrate electromechanical wave propagation with some interesting properties. The coefficients of reflection, reflection-free termination, and velocity of propagation are investigated from the numerical results. Discussions related to the effects of electromechanical wave propagation on protection systems are given. In addition, the simulation results are compared with field data collected by phasor measurement units, and show that the continuum technique provides a valuable tool in reproducing electromechanical transients on modern power systems. Discussions of new protection and control functions are included. A clear understanding of these and related phenomena will lead to innovative and effective countermeasures against unwanted trips by the protection systems, which can lead to system blackouts.<br>Ph. D.
4
Matos, Carmen. "Robotically Controlled Measurement System for Millimeter-Wave Antennas." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1588180162492972.
Повний текст джерела
5
Friedlander, Jeffrey B. "Wireless Strain Measurement with Surface Acoustic Wave Sensors." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306874020.
Повний текст джерела
6
Hamrita, Takoi K. "On-line digital signal processing methods for the correction of errors in high voltage power waveform measurements." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15921.
Повний текст джерела
7
Boykov, Nikolay D. "Measurements of the electrical properties of coal measure rocks." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4715.
Повний текст джерелаАнотація:
Thesis (M.S.)--West Virginia University, 2006.<br>Title from document title page. Document formatted into pages; contains xi, 89 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 88-89).
8
Nordin, Daniel. "Optical frequency modulated continuous wave (FMCW) range and velocity measurements." Doctoral thesis, Luleå, 2004. http://epubl.luth.se/1402-1544/2004/43.
Повний текст джерела
9
Danielson, James Robert. "Measurement of Landau damping of electron plasma waves in the linear and trapping regimes /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC IP addresses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3044767.
Повний текст джерела
10
Goldberg, Benjamin M. "Electric Field Measurements in Non-Equilibrium ElectricDischarge Plasmas Using Picosecond Four-Wave Mixing." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449236861.
Повний текст джерела
11
Henderson, Gregory N. "Semiconductor quantum electron wave transport, diffraction, and interference : analysis, devices, and measurement." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15716.
Повний текст джерела
12
Smith, Jared. "Improvement of Continuous Wave Radar Measurements in a Partially Controlled Environment." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1496094047730053.
Повний текст джерела
13
Bernstein, Joseph Barry. "Electrical characterization of polymeric insulation by electrically stimulated acoustic wave measurements." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/54340.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.<br>Includes bibliographical references (leaves 207-211).<br>by Joseph Barry Bernstein.<br>Ph.D.
14
Xu, Minnan 1979. "Local measurement of the pulse wave velocity using Doppler ultrasound." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/16868.
Повний текст джерелаАнотація:
Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2002.<br>Includes bibliographical references (p. 77-79).<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cardiovascular disease is the leading cause of death in many developed countries. Arteries of people suffering from this disease become stiff and blocked by fatty deposits. In recent years, non-invasive imaging techniques have been playing an increasingly important role in detecting the development of cardiovascular disease. Several methods focus on the measurement of pulse wave velocity, the velocity at which the pressure wave propagates, because it is directly related to arterial stiffness. The objective of this project is to investigate the feasibility of measuring local pulse wave velocity from the blood flow waveforms acquired by Doppler ultrasound. The proposed method includes the following steps: first acquire flow waveforms by Doppler ultrasound at two locations within the same artery, next detect the delay or difference in arrival time of the flow wave at the two arterial locations, and then calculate the PWV by dividing the length of the arterial segment being imaged by the calculated time delay. Although at the conclusion of this study reliable pulse wave velocity detection is not achieved, the study sheds light on many important issues surrounding this potential application. The project explores how sources of variations such as radial positioning of the probe and noise level affect the accuracy of the delay estimate.<br>by Minnan Xu.<br>M.Eng.and S.B.
15
Chen, Chi-Chih. "Design and applications of two low frequency guided wave electromagnetic measurement structures." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406708013.
Повний текст джерела
16
Kayra, Seda. "Imaging Solar Cells Using Terahertz Waves." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612920/index.pdf.
Повний текст джерелаАнотація:
In this thesis, Terahertz Time-Domain spectroscopy (THz-TDS) was used in order to measure the electrical properties of silicon solar cells. The advantage of THz-TDS is that it allows us to measure the electrical properties without electrical contacts. In order to perform these measurements, a reflection based system was constructed and the changes in the peak amplitude in the time-domain under a, 450mW 808 nm continuous wave laser source were measured. The solar cell that was used in this thesis was manufactured in Middle East Technical University Microelectromechanical Systems (METU-MEMS) research laboratories located in Ankara, Turkey. The solar cell that we used in the measurements had a thickness of 0.45 mm and was produced on a single silicon crystal in <<br>100><br>direction. It is made up of a p-type base and n-type emitter to create p-n junction. Also, it has a Si4N3 AR coating and Al back contacts on it. To compare the THz measurements to that of electrical measurements, some electrical contact measurements were performed on the solar cell under laser illumination. By using these measurements, the energy conversion efficiency and the quantum efficiency of the solar cell were calculated and measured as 3.44 % and 7%, respectively under the 450mW, 808nm illumination on a specific area of the cell. The results that were obtained form the electrical measurements were compared with the THz results. We found that in order to understand the efficiency of the solar cell using THz-TDRS, a more comprehensive study needs to be done where the changes in the reflection of the THz radiation under different excitation powers and different configurations of the system need to be studied.
17
Wendt, Martin. "Experimental Investigations of Wave Motion and Electric Resistance in Collisionfree Plasmas." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3199.
Повний текст джерела
18
Starks, Michael James 1971. "Measurement of the conjugate propagation of VLF waves by matched filter and application to ionospheric diagnosis." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80126.
Повний текст джерелаАнотація:
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.<br>Includes bibliographical references (p. 173-176).<br>by Michael James Starks.<br>Sc.D.
19
Channamallu, Aditya. "Software Defined Radio Based Modulated Scatterer Antenna Measurement." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4447.
Повний текст джерелаАнотація:
The modulated scattering technique is used in conjunction with a Software Defined Radio (SDR) dongle to obtain a software-based modulated signal output. SDR# is the software package used to get spectrum analysis of the modulated signal. A transmitter yagi antenna sends a 2.304GHz signal on to an antenna connected to a reflector coefficient modulator (700Hz) and the modulated waves are received by another yagi. The receiver yagi antenna is then connected to a frequency converter to convert a 2.304GHz signal to a 144MHz dongle input signal which finally puts the scattered output on computer software with a SDR dongle. The output has a center frequency with modulated spectral lines on either side of the measured frequency. Finally, antenna patterns are measured with different types of antennas by rotating the antennas and observing the baseband modulation sidebands.
20
Boyer, Laura L. "Carrier-phase wrap-up caused by rotating a global positioning system antenna and its effect on measurements." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175890688.
Повний текст джерела
21
Pozderac, Jonathan M. "Refractivity Inversion Utilizing X-Band Array Measurement System." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1498690950705285.
Повний текст джерела
22
Kowalski, Elizabeth J. (Elizabeth Joan). "Miter bend loss and higher order mode content measurements in overmoded millimeter-wave transmission lines." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62444.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 119-121).<br>High power applications require an accurate calculation of the losses on overmoded corrugated cylindrical transmission lines. Previous assessments of power loss on these lines have not considered beam polarization or higher order mode effects. This thesis will develop a theory of transmission that includes the effect of linearly polarized higher order modes on power loss in overmoded corrugated transmission line systems. This thesis derives the linearly polarized basis set of modes for corrugated cylindrical waveguides. These modes are used to quantify the loss in overmoded transmission line components, such as a gap in waveguide or a 900 miter bend. The dependence of the loss in the fundamental mode on the phase of higher order modes (HOMs) was investigated. In addition, the propagation of a multi-mode beam after the waveguide was quantified, and it was shown that if two modes with azimuthal (m) indices that differ by one propagate in the waveguide, the resultant centroid and the tilt angle of radiation at the guide end are related through a constant of the motion. These theoretical calculations are useful for high-power applications, such as the electron cyclotron heating in plasma fusion reactors. In addition, this thesis develops a low-power S-Parameter Response (SPR) technique to accurately measure the loss in ultra-low loss overmoded waveguide components. This technique is used to measure the loss of components manufactured to ITER (an experimental fusion reactor) specifications, operated at 170 GHz with a diameter of 63.5 mm and quarter-wavelength corrugations. The loss in a miter bend was found to be 0.022+0.08 dB. This measurement is in good agreement with theory, which predicts 0.027 dB loss per miter bend, and past measurements [18]. The SPR was used to measure the loss in a gap of waveguide and the results were in good agreement with the well-established theoretical loss due to gap, which demonstrates the accuracy of the SPR technique. For both of these measurements, a baseline analysis determined the effects of a small percentage (1-2%) of higher order modes in the system.<br>by Elizabeth J. Kowalski.<br>S.M.
23
Wachsmuth, Matthew George. "Measurement and Characterization of Terahertz Radiation Propagating Through a Parallel Plate Waveguide." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/317.
Повний текст джерелаАнотація:
As the amount of study into the terahertz (THz) region of the electromagnetic spectrum steadily increases, the parallel plate waveguide has emerged as a simple and effective fixture to perform many experiments. The ability to concentrate THz radiation into a small area or volume enables us to analyze smaller samples and perform more repeatable measurements, which is essential for future research. While the fundamental physics of PPW transmission are understood mathematically, the practical knowledge of building such a fixture for the THz domain and taking measurements on it with a real system needs to be built up through experience. In this thesis, multiple PPW configurations are built and tested. These include waveguides of different lengths and opening heights, using lenses and antennas to focus and collect radiation from the input and output, and different amounts of polish on the waveguide surface. A basic resonator structure is also built and measured as a proof of concept for future research. The two most useful propagation modes through the waveguide, the lowest order transverse magnetic (TEM) and transverse electric (TE) modes, were characterized on all of the setups. Additionally, a flexible fixture was designed and measured which will allow future work in the THz field to be much more reliable and repeatable.
24
Calder, Bruce. "Direct current resistance measurement structure for determining line width and metal thickness variations in surface acoustic wave devices." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq36672.pdf.
Повний текст джерела
25
Park, Sang-Hoon Ph D. Massachusetts Institute of Technology. "Verification of d-wave pairing symmetry by microwave intermodulation distortion measurements in yttrium barium copper oxide." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/39732.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.<br>Includes bibliographical references (p. 113-119).<br>We report measurements of the temperature and power dependence of the microwave frequency intermodulation distortion (IMD) in high quality pulsed laser deposition (PLD) Yttrium Barium Copper Oxide (YBCO) on LaAlO3 substrate. A low-temperature (T < 30 K) increase in IMD is the observation of an upturn of the nonlinear coefficient of the quadratic field dependence of the penetration depth. This IMD upturn is limited by the nonlinear Meissner effect that has been predicted for d-wave high-T, superconductors. Various amounts of IMD increase are observed for different films with impurity (Ni, Zn and Ca) doping and other defects. The demonstration of the IMD upturn and the nonlinear Meissner effect were possible because the IMD measurement is an extremely sensitive method to detect the penetration depth change at even less than 0.01 nm. IMDs from various samples tend to merge at a single universal value at 0 K regardless of disorder, defects, and impurities due to the node singularity at 0 K. There is a similar converging trend in IMD towards the transition temperature T, due to the quasiparticle thermal excitation and depletion of superelectrons. It is most likely that IMD has both intrinsic and extrinsic contributions.<br>(cont.) The 1/T2 divergence at low T of the IMD was theoretically predicted and confirmed with high quality PLD YBCO on LaA103 substrate from below 30 K. We found that Ni-doped YBCO gave an IMD increase comparable to high quality PLD YBCO. This finding agrees with the evidence that Ni (magnetic impurity) does not destroy superconductivity and preserves d-wave symmetry as shown in scanning tunneling microscope experiments. The off-the-resonance excitation experiment indicates that the response time scale of nonlinearity in IMD generation is not affected by the magnitude of two-tone separation [delta]f = f2 - fl in YBCO on LaA103 substrate. But, at low temperature ([delta] < 20 K) and low output power at fundamental frequency (Pit < -30 dBm), the response time scale slows down IMD generation as the [delta]f increases in YBCO on MgO substrate.<br>by Sang-Hoon Park.<br>Ph.D.
26
Gunn, D. A. "Electronic instrumentation for the measurement of velocities and attenuations of shear and compressional seismic waves in rocks and soils under in-situ stress conditions." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690902.
Повний текст джерела
27
Choo, Hyunwook. "Engineering behavior and characterization of physical-chemical particulate mixtures using geophysical measurement techniques." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52178.
Повний текст джерелаАнотація:
Natural geomaterials exhibit a wide range in size, physical properties, chemical properties, and mechanical behaviors. Soils that are composed of mixtures of particles with different physical and chemical properties pose a challenge to characterization and quantification of the engineering properties. This study examined the behavior of particulate mixtures composed of differently sized silica particles, mixtures composed of aluminosilicate and organic carbon particles, and mixtures composed of particles with approximately three orders of magnitude difference in particle size. This experimental investigation used elastic, electromagnetic, and thermal waves to characterize and to quantify the small to intermediate strain behavior of the mixtures.
The mechanical property of stiffness of mixed materials (e.g. binary mixtures of silica particles and fly ashes with various carbon and biomass contents) was evaluated through the stiffness of active grain contacts, and the stiffness of particles which carry applied load, using the physical concepts of intergranular void ratio and interfine void ratio. Additionally, the change in both contact mode/stiffness and electrical property due to the presence of nano-sized particles (i.e., iron oxides) on the surface of soil grains was evaluated according to applied stress, packing density, iron coating density, and substrate sand particle size. Finally, the biomass fraction and total organic carbon content of mixtures was used to quantify the electrical and thermal conductivities when particulate organic was mixed with aluminosilicate particles.
28
Kamf, Tobias. "Automated Production Technologies and Measurement Systems for Ferrite Magnetized Linear Generators." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-330866.
Повний текст джерелаАнотація:
The interest in breaking the historical dependence on fossil energy and begin moving towards more renewable energy sources is rising worldwide. This is largely due to uncertainties in the future supply of fossil fuels and the rising concerns about humanity’s role in the currently ongoing climate changes. One renewable energy source is ocean waves and Uppsala University has since the early 2000s been performing active research in this area. The Uppsala wave energy concept is centered on developing linear generators coupled to point absorbing buoys, with the generator situated on the seabed and connected to the buoy on the sea surface via a steel wire. The motion of the buoy then transfers energy to the generator, where it is converted into electricity and sent to shore for delivery into the electrical grid. This thesis will mainly focus on the development and evaluation of technologies used to automate the manufacturing of the translator, a central part of the linear generator, using industrial robotics. The translator is a 3 m high and 0.8 m wide three sided structure with an aluminum pipe at its center. The structure consists of alternating layers of steel plates (pole-shoes) and ferrite magnets, with a total of 72 layers per side. To perform experiments on translator assembly and production, a robot cell (centered on an IRB6650S industrial robot) complimented with relevant tools, equipment and security measures, has been designed and constructed. The mounting of the pole-shoes on the central pipe, using the industrial robot, proved to be the most challenging task to solve. However, by implementing a precise work-piece orientation calibration system, combined with selective compliance robot tools, the task could be performed with mounting speeds of up to 50 mm/s. Although progress has been made, much work still remains before fully automated translator assembly is a reality. A secondary topic of this thesis is the development of stand-alone measurement systems to be used in the linear generator, once it has been deployed on the seabed. The main requirements of such a measurement system is robustness, resistance to electrical noise, and power efficiency. If possible the system should also be portable and easy to use. This was solved by developing a custom measurement circuit, based on industry standard 4–20 mA current signals, combined with a portable submersible logging unit. The latest iteration of the system is small enough to be deployed and retrieved by one person, and can collect data for 10 weeks before running out of batteries. Future work in this area should focus on increasing the usability of the system. The third and final topic of this thesis is a short discussion of an engineering approach to kinetic energy storage, in the form of high-speed composite flywheels, and the design of two different prototypes of such flywheels. Both designs gave important insights to the research group, but a few crucial design faults unfortunately made it impossible to evaluate the full potential of the two designs.
29
Engholm, Marcus. "Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves." Doctoral thesis, Uppsala universitet, Signaler och System, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122189.
Повний текст джерелаАнотація:
Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures. The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques. The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.
30
Wang, Qi. "Estimation of Refractivity Conditions in the Marine Atmospheric Boundary Layer from Range and Height Measurement of X-band EM Propagation and Inverse Solutions." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1565885420888906.
Повний текст джерела
31
Du, Xinpeng. "Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643.
Повний текст джерела
32
Wallace, Jon. "Modeling Electromagnetic Wave Propagation in Electrically Large Structures." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/91.
Повний текст джерелаАнотація:
Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of snow, (2) modeling an optical Bragg resonator, and (3) modeling the MIMO wireless channel.
First, complex snow media is analyzed with a hybrid FDTD/radiative transfer model. FDTD is used to compute phase matrices and extinction coefficients required for radiative transfer. Comparison with exact analytical methods proves the validity of the FDTD method for modest domain sizes ([5λ^3]) and number of Monte Carlo realizations (32). The method is used to illustrate a penetrating sphere model, which is not possible with existing analysis techniques. Backscatter from the resulting model is about 3 times higher than that of existing dense-medium theories, underlying the importance of exact characterization of the media.
Second, a hybrid FD/FDTD/S-parameter analysis is developed to model a large (10^4 section) optical Bragg resonator: a simple FD method computes propagation constants and field profiles, FDTD analysis provides reflection and transmission coefficients for the single section, and S-parameter analysis combines the sections to obtain the complete device response. A detailed study on error suggests that the method provides better than 2% accuracy in reflection and transmission response.
Third, a hybrid electromagnetic/SVA model is developed to study the indoor MIMO wireless channel. A MIMO measurement platform is discussed for simultaneous probing of up to 16 transmit and receive antennas, which was required to assess the validity of later modeling. FDTD or MOM antenna analysis coupled with the SVA model gives capacity predictions which match measured data. The model is used to explore the impact of antenna spacing, directivity, and polarization on channel capacity. Closely spaced antennas lead to an approximate halving of receive power. Directivity effectively doubles receive power for aligned transmit and receive. Dual polarization increases system capacity anywhere from 10% to 70%, depending on the spacing of elements and the amount of multipath richness. This analysis of MIMO systems underlines the need for models that describe both multipath richness and average receive power.
33
Karri, Avinash. "Employment of dual frequency excitation method to improve the accuracy of an optical current sensor, by measuring both current and temperature." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9766/.
Повний текст джерелаАнотація:
Optical current sensors (OCSs) are initially developed to measure relatively large current over a wide range of frequency band. They are also used as protective devices in the event a fault occurs due to a short circuit, in the power generation and distribution industries. The basic principal used in OCS is the Faraday effect. When a light guiding faraday medium is placed in a magnetic field which is produced by the current flowing in the conductor around the magnetic core, the plane of polarization of the linearly polarized light is rotated. The angle of rotation is proportional to the magnetic field strength, proportionality constant and the interaction length. The proportionality constant is the Verdet constant V (λ, T), which is dependent on both temperature and wavelength of the light. Opto electrical methods are used to measure the angle of rotation of the polarization plane. By measuring the angle the current flowing in the current carrying conductor can be calculated. But the accuracy of the OCS is lost of the angle of rotation of the polarization plane is dependent on the Verdet constant, apart from the magnetic field strength. As temperature increases the Verdet constant decreases, so the angle of rotation decreases. To compensate the effect of temperature on the OCS, a new method has been proposed. The current and temperature are measured with the help of a duel frequency method. To detect the line current in the conductor or coil, a small signal from the line current is fed to the reference of the lock in. To detect the temperature, the coil is excited with an electrical signal of a frequency different from the line frequency, and a small sample of this frequency signal is applied to the reference of the lock in. The temperature and current readings obtained are look up at the database value to give the actual output. Controlled environment is maintained to record the values in the database that maps the current and temperature magnitude values at the DSP lock in amplifier, to the actual temperature and current. By this method we can achieve better compensation to the temperature changes, with a large dynamic range and better sensitivity and accuracy.
34
Long, Elena A. "Polarized 3He(e,e'n) Asymmetries in Three Orthogonal Measurements." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1350487441.
Повний текст джерела
35
Kim, Myeongsub. "Microscale optical thermometry techniques for measuring liquid phase and wall surface temperatures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/43754.
Повний текст джерелаАнотація:
Thermal management challenges for microelectronics are a major issue for future integrated circuits, thanks to the continued exponential growth in component density described by Moore¡¯s Law. Current projections from the International Technology Roadmap for Semiconductors predict that local heat fluxes will exceed 1 kW/cm2 within a decade. There is thus an urgent need to develop new compact, high heat flux forced-liquid and evaporative cooling technologies.
Thermometry techniques that can measure temperature fields with micron-scale resolution without disturbing the flow of coolant would be valuable in developing and evaluating new thermal management technologies. Specifically, the ability to estimate local convective heat transfer coefficients, which are proportional to the difference between the bulk coolant and wall surface temperatures, would be useful in developing computationally efficient reduced-order models of thermal transport in microscale heat exchangers.
The objective of this doctoral thesis is therefore to develop and evaluate non-intrusive optical thermometry techniques to measure wall surface and bulk liquid temperatures with O(1-10 micronmeter) spatial resolution. Intensity-based fluorescence thermometry (FT), where the temperature distribution of an aqueous fluorescent dye solution is estimated from variations in the fluorescent emission intensity, was used to measure temperatures in steady Poiseuille flow at Reynolds numbers less than 10. The flow was driven through 1 mm square channels heated on one side to create temperature gradients exceeding 8 ¡ÆC/mm along both dimensions of the channel cross-section. In the evanescent-wave fluorescence thermometry (EFT) experiments, a solution of fluorescein was illuminated by evanescent waves to estimate the solution temperature within about 300 nm of the wall. In the dual-tracer FT (DFT) studies, a solution of two fluorophores with opposite temperature sensitivities was volumetrically illuminated over most of the `cross-section of the channel to determine solution temperatures in the bulk flow. The accuracy of both types of FT is determined by comparing the temperature data with numerical predictions obtained with commercial computational fluid dynamics software. The results indicate that EFT can measure wall surface temperatures with an average accuracy of about 0.3 ¡ÆC at a spatial resolution of 10 micronmeter, and that DFT can measure bulk water temperature fields with an average accuracy of about 0.3 ¡ÆC at a spatial resolution of 50 micronmeter in the image plane. The results also suggest that the spatial resolution of the DFT data along the optical axis (i.e., normal to the image plane) is at least an order of magnitude greater than the depth of focus of the imaging system.
36
Tuncay, Orbay. "Wireless Strain Gauge System in a Multipath Environment." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1222089977.
Повний текст джерела
37
Spencer, Quentin H. "Transmission Strategies for Wireless Multi-user, Multiple-Input, Multiple-Output Communication Channels." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd378.pdf.
Повний текст джерела
38
Shabara, Yahia. "Establishing Large-Scale MIMO Communication: Coding for Channel Estimation." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1618578732285999.
Повний текст джерела
39
Thompson, Dane C. "Characterization and Design of Liquid Crystal Polymer (LCP) Based Multilayer RF Components and Packages." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10498.
Повний текст джерелаАнотація:
This thesis discusses the investigation and utilization of a new promising thin-film material, liquid crystal polymer (LCP), for microwave and millimeter-wave (mm-wave [>30 GHz]) components and packages. The contribution of this research is in the determination of LCP's electrical and mechanical properties as they pertain to use in radio frequency (RF) systems up to mm-wave frequencies, and in evaluating LCP as a low-cost substrate and packaging material alternative to the hermetic materials traditionally desired for microwave circuits at frequencies above a few gigahertz (GHz).
A study of LCP's mm-wave material properties was performed. Resonant circuit structures were designed to find the dielectric constant and loss tangent from 2-110 GHz under both ambient and elevated temperature conditions. Several unique processes were developed for the realization of novel multilayer LCP-based RF circuits. These processes include thermocompression bonding with tight temperature control (within a few degrees Celsius), precise multilayer alignment and patterning, and LCP laser processing with three different types of lasers. A proof-of-concept design that resulted from this research was a dual-frequency dual-polarization antenna array operating at 14 and 35 GHz.
Device characterization such as mechanical flexibility testing of antennas and seal testing of packages were also performed. A low-loss interconnect was developed for laser-machined system-level thin-film LCP packages. These packages were designed for and measured with both RF micro-electromechanical (MEM) switches and monolithic microwave integrated circuits (MMICs). These research findings have shown LCP to
be a material with uniquely attractive properties/capabilities for vertically integrated, compact multilayer LCP circuits and modules.
40
Gardner, Robert Matthew. "A Wide-Area Perspective on Power System Operation and Dynamics." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26779.
Повний текст джерелаАнотація:
Classically, wide-area synchronized power system monitoring has been an expensive task requiring significant investment in utility communications infrastructures for the service of relatively few costly sensors. The purpose of this research is to demonstrate the viability of power system monitoring from very low voltage levels (120 V). Challenging the accepted norms in power system monitoring, the document will present the use of inexpensive GPS time synchronized sensors in mass numbers at the distribution level. In the past, such low level monitoring has been overlooked due to a perceived imbalance between the required investment and the usefulness of the resulting deluge of information. However, distribution level monitoring offers several advantages over bulk transmission system monitoring. First, practically everyone with access to electricity also has a measurement port into the electric power system. Second, internet access and GPS availability have become pedestrian commodities providing a communications and synchronization infrastructure for the transmission of low-voltage measurements. Third, these ubiquitous measurement points exist in an interconnected fashion irrespective of utility boundaries. This work offers insight into which parameters are meaningful to monitor at the distribution level and provides applications that add unprecedented value to the data extracted from this level. System models comprising the entire Eastern Interconnection are exploited in conjunction with a bounty of distribution level measurement data for the development of wide-area disturbance detection, classification, analysis, and location routines.
The main contributions of this work are fivefold: the introduction of a novel power system disturbance detection algorithm; the development of a power system oscillation damping analysis methodology; the development of several parametric and non-parametric power system disturbance location methods, new methods of power system phenomena visualization, and the proposal and mapping of an online power system event reporting scheme.<br>Ph. D.
41
"Harmonic impedance estimation of a power system implementing frequency domain measurement techniques." Thesis, 2012. http://hdl.handle.net/10210/5585.
Повний текст джерелаАнотація:
M.Ing.<br>The increased used of non-linear loads within the power system during recent years have resulted in deviations from the perfect sinusoidal voltage and current waveform. This deviation from the perfect sinusoidal waveform can be expressed according to Fourier analysis by a set of co-sinusoidal waveforms having frequencies, which are a multiple of the fundamental frequency, referred to as harmonics. Non-linear loads are generally characterised by harmonic currents. It is therefore often preferred to express the harmonic emission limits in terms of harmonic currents rather than harmonic voltages. In order to translate the harmonic currents into harmonic voltages the harmonic impedance of the power system must be known. The power system's harmonic impedance can be assessed via computational, simulation and measurement techniques. The study will concentrate on the estimation of the harmonic impedance of a 33kV power system by implementing two online frequency domain measurement techniques. Both techniques are applied at the point of delivery of a dominant nonlinear load during normal and energisation load conditions with its power factor correction capacitor bank in and out off service. The estimated harmonic impedance is then compared with the calculated and simulated harmonic impedance.
42
Nino, Hernandez Edwin Enrique. "Harmonic impedance and harmonic source determination based on field measurements." Master's thesis, 2009. http://hdl.handle.net/10048/848.
Повний текст джерелаАнотація:
Thesis (M.Sc.)--University of Alberta, 2010.<br>Title from PDF file main screen (viewed on Apr. 13, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Electrical & Computer Engineering, University of Alberta. Includes bibliographical references.
43
Mawrey, Robert Stanley. "Predicted and measured arrival rates of meteors over forward-scatter links." Thesis, 1991. http://hdl.handle.net/10413/6909.
Повний текст джерелаАнотація:
Investigations into currently accepted methods of modelling variations in the
arrival rate of meteors over forward-scatter meteor links have revealed some
shortcomings. In these investigations, particular emphasis is placed on the work
of Rudie due to its current acceptance in the literature. The non-uniform radiant
distribution of meteors measured by Davies and modelled by Rudie, is critically
examined and predictions using these models are compared with measured results
taken over two forward-scatter links in the Southern Hemisphere. A new, alternative
method of including the effect of non-uniform radiant distributions on the
predicted arrival rate of meteors is given. The method used by Rudie to model
Davies' measured radiant distribution is shown to be unnecessarily complicated
and a simpler alternative is given. Furthermore, Rudie's distribution is shown not
to be derived from a particular set of Davies' results as implied by Rudie.
Other non-uniform distributions of meteors are also investigated. Comparisons
between monthly-averaged daily cycles of measured and predicted arrival rates
of meteors for a midpath and an endpath meteor link are used to reveal the validity
and limitations of the published distributions. A new graphical method is used to
aid in determining the validity and limitations of the non-uniform distributions.
Discrepancies in the published predicted and measured annual variations in the
arrival rate of meteors are investigated. Contrary to recently published information,
predicted annual variations in the arrival rate of meteors for meteor radiants
close to the ecliptic are shown to be comparable to measured results.<br>Thesis (Ph.D.)-University of Natal, Durban, 1991.
44
Lohmeier, Stephen Paul. "Supervised classification of natural targets using millimeter-wave multifrequency polarimetric radar measurements." 1996. https://scholarworks.umass.edu/dissertations/AAI9619410.
Повний текст джерелаАнотація:
This dissertation classifies trees, snow, and clouds using multiparameter millimeter-wave radar data at 35, 95, and 225 GHz. Classification techniques explored include feedforward multilayer perceptron neural networks trained with standard backpropagation, Gaussian and minimum distance statistical classifiers, and rule-based classifiers. Radar data products, serving as features for classification, are defined, radar and in situ data are presented, scattering phenomenology is discussed, and the effect of data biases are analyzed. A neural network was able to discriminate between white pine trees and other broader-leaved trees with an accuracy of 97% using normalized Mueller matrix data at 225 GHz; wet, dry, melting, and freezing snow could be discriminated 89% of the time using 35, 95, and 225 GHz Mueller matrix data; and metamorphic and fresh snow could be differentiated 98% of the time using either the copolarized complex correlation coefficient or normalized radar cross section at three frequencies. A neural network was also able to discriminate ice clouds from water clouds using vertical and horizontal 95 GHz airborne reflectivity measurements with a success rate of 82% and 86% when viewing the clouds from the side and below respectively. Using 33 and 95 GHz data collected from the ground, a neural net was able to discriminate between ice clouds, liquid clouds, mixed phase clouds, rain, and insects 95% of the time using linear depolarization ratio, velocity, and range. As a precursor to this classification, a rule-based classifier was developed to label training pixels, since in situ data was not available for this particular data set. Attenuation biases in reflectivity were also removed with the aid of the rule-based classifier. A neural network using reflectivity in addition to other features was able to classify pixels correctly 96% of the time.
45
Vuthaluru, Rupa. "MF radar observations of D-region electron densities at Adelaide / by Rupa Vuthaluru." 2003. http://hdl.handle.net/2440/22029.
Повний текст джерелаАнотація:
"July, 2003"<br>Includes bibliographical references (leaves 177-183)<br>xxii, 183 leaves : ill. (some col.) ; 30 cm.<br>Title page, contents and abstract only. The complete thesis in print form is available from the University Library.<br>Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Physics and Mathematical Physics, 2004
46
Li, Lihua. "Retrieval of atmospheric attenuation using ground -based and airborne millimeter-wave cloud radar measurements." 2000. https://scholarworks.umass.edu/dissertations/AAI9988816.
Повний текст джерелаАнотація:
Cloud measurements at millimeter-wave frequencies are affected by attenuation due to atmospheric gases, clouds and precipitation. Estimation of the true equivalent radar reflectivity, Ze, is complicated because extinction mechanisms are not well characterized at these short wavelengths. This dissertation discusses cloud radar calibration and intercomparison of airborne and ground-based radar measurements, and describes two attenuation retrieval algorithms. The first one is the dual-radar method, which is based on dual 95 GHz radar measurements of the same cloud and precipitation volumes collected from opposing viewing angles. True radar reflectivity is retrieved by combining upward-looking and downward-looking radar profiles. This method reduces the uncertainty in radar reflectivity and attenuation estimates since it does not require a priori knowledge of the microphysical properties of hydrometeors. The second one is the modified Hitschfeld and Bordan (HB) algorithm, which uses single radar measurements with path integrated attenuation (PIA) as a constraint. Case studies are performed using data collected during the Summer 1998 NASA DC-8 Cloud Radar Experiment. Atmospheric attenuation and true radar reflectivity are retrieved by applying the dual-radar method. The results are then compared with those obtained using the modified HB algorithm. The analysis shows that the dual-radar method directly calculates the atmospheric attenuation and true radar reflectivity without knowledge of the relationship between clouds/precipitation attenuation rate (k) and true radar reflectivity ( Ze). It also provides a PIA reference to refine the HB algorithm. On the other hand, appropriate k - Z e relationships are essential to improve the performance of the modified HB algorithm. Ice cloud attenuation retrieved from the dual-radar method is related to the particle median volume diameter, which is estimated from MHz/95GHz dual wavelength measurements using theoretical models. Analysis of ice cloud measurements indicates that W-band attenuation is mostly caused by the loss due to scattering from large particles. Based on an IWC - Ze relationship, ice water content (IWC) is obtained. The analysis results show that appropriate attenuation correction significantly improves the accuracy of the IWC retrieval.
47
Spann, Michael Dwight. "An adaptive protocol for use over meteor scatter channels." Thesis, 1987. http://hdl.handle.net/10413/6906.
Повний текст джерелаАнотація:
Modem technology has revived interest in the once popular area of meteor
scatter communications. Meteor scatter systems offer reliable
communications in the 500 to 2000 km range all day, every day. Recent
advances in microprocessor technology have made meteor scatter
communications a viable and cost effective method of providing modest data
rate communications. A return to the basic fundamentals has revealed
characteristics of meteor scatter propagation that can be used to optimize the
protocols for a meteor scatter link.
The duration of an underdense trail is bounded when its initial amplitude is
known. The upper bound of the duration is determined by maximizing the
classical underdense model. The lower bound is determined by considering
the volume of sky utilized. The duration distribution between these bounds
is computed and compared to measured values.
The duration distribution is then used to specify a fixed data rate, frame
adaptive protocol which more efficaciously utilizes underdense trails, in the
half duplex environment, than a non-adaptive protocol. The performance of
these protocols is verified by modeling.<br>Thesis (Ph.D.)-University of Natal, Durban, 1987.
48
Martin, Gregory Theodore. "Wideband propagation measurements for personal communication systems." Thesis, 2000. https://vuir.vu.edu.au/15767/.
Повний текст джерелаАнотація:
The propagation channel is a vital but invisible part of any wireless communications system. As wavelengths get shorter, multipath effects become more pronounced, causing small scale fading in narrowband channels, and inter-symbol
interference in wideband systems because of delay spread in the channel impulse response. Multipath propagation becomes more pronounced as the wavelength decreases, and at the frequencies around 2GHz assigned for 3rd. generation cellular 'phones and personal communication services, multipath is pervasive, and very dependent on the built environment and topography. Multipath makes non-line-ofsight
(NLOS) operation possible, but also introduces a degree of randomness and unpredictability which complicates radio system design. System designers, and researchers pursuing improved methods of communicating information need realistic
channel statistics and models to progress. At the start of this thesis project, no wideband outdoor propagation data had ever been published for the Australian environment The primary objective of the project was to develop and build wideband channel-sounding instrumentation operating
at 1.89GHz, and to investigate propagation conditions in a variety of cities and locations, to allow the comparison of multipath behaviour in the Australian environment with results from overseas countries.
49
Mow-Lowry, Conor Malcolm. "Thermal noise and optical cooling." Phd thesis, 2011. http://hdl.handle.net/1885/150253.
Повний текст джерелаАнотація:
Thermal noise and optical quantum noise place fundamental limits on the displacement sensitivity of interferometric gravitational wave detectors. Projects such as Advanced LIGO employ a wide range of techniques to reduce thermal noise and use very high optical powers to reduce quantum noise. Thermal noise is Brownian motion caused by the thermal energy in each mode of oscillation. It is fundamentally linked with mechanical loss via the fluctuation-dissipation theorem. The thermal energy of, for example, the fundamental resonance of the suspension of a mirror can be concentrated into the resonant peak by using a very high-Q oscillator. This reduces the spectral density of the fluctuations away from resonance. The shape of the thermal noise spectrum depends on the mechanical loss mechanisms, and can have important implications for interferometer design
This thesis presents, to the best of my knowledge, the first off-resonance thermal noise measurement of a high-Q suspension which includes both above-and below-resonance regions. The measurements do not conform to the accepted 'structural' damping model, but rather seem to suit a model with both structural and viscous damping. A number of potentially spurious loss mechanisms were investigated, but none were found to substantially alter the spectral shape of the measured noise. A lower quality factor suspension material was then employed to see if structural damping was dominant, but again a mixed damping model fitted the data better than structural damping. A coating-free mirror was designed and experimentally characterised. Removing the optical coating removes a significant source of mechanical loss from the mirror, potentially improving thermal noise.
The combination of high optical powers and high-Q oscillators can lead to strong opto-mechanical interactions. The light inside an optical resonator can act as a complex spring, modifying both rigidity and damping. For a very low-loss mechanical system, a small amount of optical anti-damping can lead to instability. Conversely, it is possible to optically damp, or 'cool', an oscillator by extracting thermal energy. Results are presented showing optical cooling of the fundamental mode of a mirror suspension down to an effective temperature of 70 mK. This cooling is measured by the direct observation of the thermal noise spectrum. The measured traces are in agreement with a prediction of the thermal noise spectrum based on the input laser power, optical configuration, and feedback control system used. Results from the suspended gravitational wave detector prototype, the Caltech 40m interferometer, show how a strong optical spring creates an opto-mechancial resonance which alters the frequency response of the interferometer.
50
Lüer, Juliana. "Design and Development of a Measurement System to Track the Motion of a Point Absorber." Thesis, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-416222.
Повний текст джерелаАнотація:
Because of climate change renewable energy field is becoming more and more relevant. Renewable energy can be gained from the sun, from wind but also from ocean waves. To support the research and development in this field reliably measured wave data is collected through a measurement system that shows the exact position of a buoy. The project consists of the design, development and implementation of such a measurement system. It is divided into three subtasks: The power supply based on a solar panel and a battery The measurement part including a sensor and its implementation to the circuit The deployment of a module for data transmission and communication between the measurement system and the on-shore computer The power supply is capable to power the system and to maintain the battery voltage. A suggested stronger power supply will be used in a later state of the project to increase the reliability. The results of the charging test are good. The power supply system is connected to the circuit and the battery charges. For the measurement system the altitude and heading reference system (AHRS) “Ellipse2-D” from SBG Systems has been selected and connected to an Arduino Mega 2560. The AHRS provides raw data and values processed by a Kalman filter. Both data sets are picked up by the microcontroller. The raw data is backed up on a secure digital memory card (SD-card). For the evaluation of the sensor unit, static and dynamic tests are applied to the sensor. In the end it can be seen that the measurement series are aligned with each other. The information from the Kalman model of the AHRS is transmitted with the Adeunis ARF868 ultra-long range (ULR) modem. The transmitter is linked to the Arduino Mega 2560 and the sensor data is transmitted to the receiver. The first field test already shows the reliability of the system for a range of about 3 km. The results of the tests are as expected and in the future this system will be implemented on a buoy.