To see the other types of publications on this topic, follow the link: Orthogonal time of flight.
Dissertations / Theses on the topic 'Orthogonal time of flight'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Orthogonal time of flight.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Papanastasiou, Dimitris. "Space velocity correlation in orthogonal time-of-flight mass spectrometry." Thesis, Manchester Metropolitan University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423073.
Full text
2
Selby, David Sean School of Chemical Sciences UNSW. "Matrix assisted laser desorption/ionization orthogonal acceleration time-of-flight mass spectrometry: development and characterization of a new instrument." Awarded by:University of New South Wales. School of Chemical Sciences, 2002. http://handle.unsw.edu.au/1959.4/18784.
Full textAbstract:
The performance of a linear matrix assisted laser desorption/ionization mass spectrometer (MALDI-oa-TOFMS) was improved with more reproducible sample preparation methods, a higher rate digitiser for integrating signals and customisable computer control, data acquisition and analysis in the LabVIEW?programming environment. This resulted in a ~20% improvement in resolution (up to 4,400) and enabled measurement of desorption velocities of 1,000 - 1,800 ms-1 for analytes with m/z 615 ?1,350 Da, with matrix ion velocities being 4,000 ?4,800 ms?. Detector limitations and restrictions on source axis energy (and hence velocity) required for the analysis of ions prevented detection of other species with this instrument. A 20 kV reflecting geometry MALDI-oa-TOFMS was constructed to overcome these limitations and extend the mass range. This mass spectrometer was able to analyse ions desorbed with a wide range of energies (32 ?197 eV). The resolution was found to be 8,000 -10,000. Best mass accuracy was 15-80 ppm (internal standards ). External calibration gave larger mass errors, mostly due to timing jitter, but the mass axis was stable for <2 weeks. Mass accuracy was independent of the analyte and matrix used. Ions with m/z of ~10,000 - 20,000 Da were observable with the use of a pulsed lens in the target region. This lens increased signal approximately 20 times, but degraded resolution. The detection limit of the instrument (sample consumed) was estimated to vary from 10 ?90 fmol, by extrapolation, with more moles required at higher m/z. The microsphere plate (MSP) electron multiplier used in the reflecting instrument was found to have a temporal response of >1 ns FWHM, but with a low secondary electron conversion efficiency, making it unsuitable for high m/z species. Experiments were also performed with a novel rectangular mesh grid, which (in correct orientation) provided similar resolution to conventional square mesh grids, but with significantly improved transmission and hence sensitivity.
3
Williams, C. M. "Development of an orthogonal acceleration time-of-flight mass spectrometer : structural and quantitative applications in mass spectrometry." Thesis, Swansea University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636619.
Full textAbstract:
This thesis describes the development of a prototype orthogonal acceleration time-of-flight mass spectrometer, constructed at Swansea University (2002). This instrument incorporated design features to improve the duty-cycle of the time-of-flight mass spectrometer and was designed to conduct MS and MS/MS. Ion optical interfaces for full-beam transmission and collision-induced dissociation were developed. This work characterises the transport efficiency of the interfaces with a SCIEX electrosprayer. Ion transmission was dependent on the ion optical configuration, lens voltages, orifice sizes and stagnation pressure. Due to time limitations the full instrument was not completed and experimental work finalised on a commercial time-of-flight. A study of the ion structure of C4H4+ was carried out. A new method relying on consecutive reactions for controlling the internal energy of ions was used. Collision induced dissociation spectra of C4H4+ allowed the composition of the ion beam to be monitored and the vinylacetylene and methylenecylcopropene structures dominated. An observation was made for the fragmentation C4H4+ ® C3+., C3H1+, C3H2+ and C3H3+ for C4H4+. formed in the ion source, compared to C4H4+ formed in a field-free region. Their collision-induced dissociation mass-analysed ion kinetic energy (CID-MIKE) spectra were very different, which could not be accounted for in terms of structural and possibly internal energy differences. This is a highly reproducible effect requiring further study. Matrix-assisted laser desorption/ionisation (MALDI) was used on a ‘Voyager-DE STR’ to develop a survey technique analysis of nucleotides. The matrix α-cyano-4-hydroxyxinnamic acid matrix provided good sensitivity (<10pmol). MALDI as a quantitative tool was investigated. There are major challenges to overcome before MALDI can be reliably used for quantitation of nucleotides. An experimental survey of over 900 accurate mass measurements was made on 10 compounds and showed that accurate masses could be reliably obtained for 40% of adenosine monoshosphate samples but for quanosine di- and triphosphates this fell to near zero.
4
Ruotolo, Brandon Thomas. "Development of matrix assisted laser desorption ionization-ion mobility-orthogonal time-of-flight mass spectrometry as a tool for proteomics." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2203.
Full textAbstract:
Separations coupled to mass spectrometry (MS) are widely used for large-scale protein identification in order to reduce the adverse effects of analyte ion suppression, increase the dynamic range, and as a deconvolution technique for complex datasets typical of cellular protein complements. In this work, matrix assisted laser desorption-ionization is coupled with ion mobility (IM) separation for the analysis of biological molecules. The utility of liquid-phase separations coupled to MS lies in the orthogonality of the two separation dimensions for all analytes. The data presented in this work illustrates that IM-MS relies on the correlation between separation dimensions for different classes (either structural or chemical) of analyte ions to obtain a useful separation. For example, for a series of peptide ions of increasing mass-to-charge (m/z) a plot drift time in the IM drift cell vs. m/z increases in a near-linear fashion, but DNA or lipids having similar m/z values will have very different IM drift time-m/z relationships, thus drift time vs. m/z can be used as a qualitative tool for compound class identification. In addition, IM-MS is applied to the analysis of large peptide datasets in order to determine the peak capacity of the method for bottom-up experiments in proteomics, and it is found that IM separation increases the peak capacity of an MS-only experiment by a factor of 5-10. The population density of the appearance area for peptides is further characterized in terms of the gas-phase structural propensities for tryptic peptide ions. It is found that a small percentage (~3%) of peptide sequences form extended (i.e., helical or β-sheet type) structures in the gas-phase, thus influencing the overall appearance area for peptide ions. Furthermore, the ability of IM-MS to screen for the presence of phosphopeptides is characterized, and it is found that post translationally modified peptides populate the bottom one-half to one-third of the total appearance area for peptide ions. In general, the data presented in this work indicates that IM-MS offers dynamic range and deconvolution capabilities comparable to liquid-phase separation techniques coupled to MS on a time scale (ms) that is fully compatible to current MS, including TOF-MS, technology.
5
Paxton, Thanai. "Ultra-high sensitivity unambiguous sequencing on a novel geometry quadrupole orthogonal-acceleration time of flight mass spectrometer, the Q-TOF." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322004.
Full text
6
Westberg, Michael. "Time of Flight Based Teat Detection." Thesis, Linköping University, Department of Electrical Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19292.
Full textAbstract:
Time of flight is an imaging technique with uses depth information to capture 3D information in a scene. Recent developments in the technology have made ToF cameras more widely available and practical to work with. The cameras now enable real time 3D imaging and positioning in a compact unit, making the technology suitable for variety of object recognition tasks
An object recognition system for locating teats is at the center of the DeLaval VMS, which is a fully automated system for milking cows. By implementing ToF technology as part of the visual detection procedure, it would be possible to locate and track all four teat’s positions in real time and potentially provide an improvement compared with the current system.
The developed algorithm for teat detection is able to locate teat shaped objects in scenes and extract information of their position, width and orientation. These parameters are determined with an accuracy of millimeters. The algorithm also shows promising results when tested on real cows. Although detecting many false positives the algorithm was able to correctly detected 171 out of 232 visible teats in a test set of real cow images. This result is a satisfying proof of concept and shows the potential of ToF technology in the field of automated milking.
7
Le, Sellier Francois 1974. "Discrete real-time flight plan optimization." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/50629.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.Includes bibliographical references (leaves 117-118).
Worldwide, the continuously growing air traffic induces a need for new ATM concepts to be defined. One possibility is using a more decentralized system predicated mainly around free routings (Free Flight), for a more flexible management of airspace. The present study first highlights the discrepancies and inefficiencies of the current best flightplan optimizing software that use the Cost Index concept before departure. It then investigates techniques to perform enhanced flight-plan optimizations en-route, with algorithms that are less complex than using the Cost Index. The long-haul flight leg that is considered through the simulations is London (UK) - Boston (MA, USA), flown on a constant flight level. This study shows that running another optimization at the Top of Climb point reduces the average delay at destination from 6.9 minutes to 5.0 minutes. Then, the more futuristic method of considering discrete flight-plan optimizations, while en-route using updated weather forecasts, provides results that are more interesting. If the weather forecasts and the optimizations are done simultaneously every 3-hour or 1.5-hour, the average delay respectively becomes 2.6 minutes or 2.0 minutes. The second part of this work investigates ways of performing a Linear Program to fly a route close to a 4D-trajectory. This study provides ways of determining the exact weight values for the different state variables used in the cost function to minimize.
by Francois Le Sellier.
S.M.
8
Pettersson, Lucas. "Localization with Time-of-Flight cameras." Thesis, KTH, Numerisk analys, NA, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-273788.
Full textAbstract:
Time-of-Flight (ToF) cameras are becoming an increasingly common sensor in smartphones. These sensors are able to produce depth measurements in a grid at a relatively high rate. Using these depth measurements, point-clouds representing the captured scene can be produced. Previous research has been conducted in using ToF or LIDAR images to localize the camera. In this paper, we investigate several methods to localize the camera using point-clouds and surface meshes. Small alterations were made to some of the algorithms but the concepts remain the same. The main algorithms consisted of ICP variants as well as a relatively recent method called Corrective Gradient Refinement (CGR). The results obtained from generated data indicate that some of the methods are applicable for real-time applications, and the position estimates are comparable to those found in previous results.Time-of-flight (ToF)-kameror blir en allt vanligare sensor i mobiltelefoner. Dessa sensorer kan producera djupmätningar i ett rutnät med relativt hög frekvens. Med hjälp av dessa djupmätningar kan ett punktmoln som representerar den fångade scenen produceras. Tidigare forskning har gjorts med hjälp av ToF- eller LIDAR-bilder för att lokalisera kameran. Här undersöks flera metoder för att lokalisera kameran med hjälp av ett punktmoln och en triangulering av en modell. Algoritmerna bestod till största delen av ICP-varianter samt en relativt ny metod som heter Corrective Gradient Refinement (CGR). Resultaten som erhållits från genererade data indikerar att vissa av metoderna är lämplig för realtidsapplikationer och felet på positioneringen är jämförbart med dem som hittades i tidigare resultat.
9
Tran, Le Chung. "Complex orthogonal space-time processing in wireless communications." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060726.133841/index.html.
Full text
10
Bouziane, R. "Real-time optical orthogonal frequency division multiplexing transceivers." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1383794/.
Full textAbstract:
Optical orthogonal frequency division multiplexing (O-OFDM) is a potential candidate for 100 Gigabit Ethernet (GbE) and beyond due to its high spectral efficiency and strong resilience towards chromatic and polarization mode dispersion. In this thesis, investigations have been performed into the feasibility of O-OFDM in high speed optical fibre communications. First, an overview of OFDM fundamentals and optical fibre communications is given. Numerical simulations which were performed to characterise and optimise real-time OFDM transceivers are then presented. The effects of a variety of design parameters on the performance of the system are studied. Amongst the key parameters included in the study are the quantisation and clipping noise in data converters, and the quantisation errors in the fast Fourier transform and its inverse (FFT/IFFT). Optimum parameters that give the best trade-off between performance and cost in terms of bit precision are determined. It was found that these parameters depend on the modulation format as well as the size of the FFT used in the system. The thesis then presents the design of a multi-gigabit real-time O-OFDM transmitter based on field programmable gate array (FPGA) implementation. The 21.4 GS/s real-time transmitter was built and used to transmit 8.36 Gb/s directly-detected single sideband QPSK-OFDM signals over 1600 km of uncompensated standard single mode fibre. This was one of the first demonstrations of real-time OFDM transmitters operating at such high line rates. It remains the longest transmission distance achieved with a real-time OFDM transmitter. The next step in confirming the feasibility of O-OFDM involves the design and assessment of application-specific integrated circuit (ASIC) implementations. In the final part of the thesis, digital signal processing (DSP) circuits for 21.8 Gb/s and 43.7 Gb/s QPSK- and 16-QAM-encoded O-OFDM transceivers with 50 data subcarriers were designed at the register-transfer-level, and synthesis and simulations were carried out to assess their performance, power consumption, and chip area. The aim of the study is to determine the suitability of OFDM technology for low-cost optical interconnects. Power calculations based on synthesis for a 65nm standard-cell library show that the DSP components of the transceiver consume 18.2 mW/Gb/s and 12.8 mW/Gb/s in the case of QPSK and 16-QAM respectively. The effects of modulation format and FFT size on the area and power consumption of the transceivers are also quantified. Finally, characterisation results showing the trade-offs between energy consumption and chip footprint are presented and analysed to help designers optimise the transceivers according the requirements and specifications.
11
Mei, Jonathan (Jonathan B. ). "Algorithms for 3D time-of-flight imaging." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85609.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 57-58).
This thesis describes the design and implementation of two novel frameworks and processing schemes for 3D imaging based on time-of- flight (TOF) principles. The first is a low power, low hardware complexity technique based on parametric signal processing for orienting and localizing simple planar scenes. The second is an improved method for simultaneously performing phase unwrapping and denoising for sinusoidal amplitude modulated continuous wave ToF cameras using multiple frequencies. The first application uses several unfocused photodetectors with high time resolution to estimate information about features in the scene. Because the time profiles of the responses for each sensor are parametric in nature, the recovery algorithm uses finite rate of innovation (FRI) methods to estimate signal parameters. The signal parameters are then used to recover the scene features. The second application uses a generalized approximate message passing (GAMP) framework to incorporate both accurate probabilistic modeling for the measurement process and underlying scene depth map sparsity to accurately extend the unambiguous depth range of the camera. This joint processing results in improved performance over separate unwrapping and denoising steps.
by Jonathan Mei.
M. Eng.
12
Petcher, P. A. "Time of flight diffraction and imaging (TOFDI)." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/49478/.
Full textAbstract:
Time of flight diffraction and imaging (TOFDI) is based on time of flight diffraction (TOFD), adding cross-sectional imaging of the sample bulk by exploiting the scattering of ultrasonic waves from bulk defects in metals. Multiple wave modes are emitted by a pulsed laser ultrasound ablative source, and received by a sparse array of receiving electromagnetic acoustic transducers (EMATs), for non-contact (linear) scanning, with mode-conversions whenever waves are scattered. Standard signal processing techniques, such as band-pass filters, reduce noise. A B-scan is formed from multiple data captures (A-scans), with time and scan position axes, and colour representing amplitude or magnitude. B-scans may contain horizontal lines from surface waves propagating directly from emitter to receiver, or via a back-wall, and angled lines after reflection off a surface edge. A Hough transform (HT), modified to deal with the constraints of a B-scan, can remove such lines. A parabola matched filter has been developed that identifies the features in the B-scan caused by scattering from point-like defects, reducing them to peaks and minimising noise. Multiple B-scans are combined to reduce noise further. The B-scan is also processed to form a cross-sectional image, enabling detection and positioning of multiple defects. The standard phase correlation technique applied to camera images, has been used to track the relative position between transducer and sample. Movement has been determined to sub-pixel precision, with a median accuracy of 0.01mm of linear movement (0.06 of a pixel), despite uneven illumination and the use of a basic low resolution camera. The prototype application is testing rough steel products formed by continuous casting, but the techniques created to facilitate operation of TOFDI are applicable elsewhere.
13
Costello, Kevin Francis. "Laser desorption time-of-flight mass spectrometry." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/13475.
Full textAbstract:
The techniques of supersonic molecular beam cooling and laser multiphoton ionisation (MPI) spectroscopy have been combined to give a potentially powerful analytical technique. Two methods of sample introduction into the molecular beam have been employed, namely resistive heating and laser desorption. The resistive heating method allowed 2-colour MPI spectra of naphthalene, anthracene and perylene to be recorded in a simple free jet apparatus. A sensitivity for anthracene of 600 ppb is estimated. A time-of-flight (TOF) mass spectrometer has been developed, incorporating both linear and reflecting-geometry (reflectron) flight tubes, to allow laser desorption MPI (LD-MPI) mass spectra to be recorded for a number of involatile and thermally unstable compounds. Mass resolutions of 300 (linear) and 850 (reflectron) have been obtained for aniline. The constraints affecting the mass resolving power of both spectrometer designs are discussed. Finally, the potential of LD-MPI mass spectrometry as a sensitive, selective analytical technique is evaluated. The mass spectra of a number of polynuclear aromatic hydrocarbons, porphyrins and amino acids are presented, along with those of a simple mixture of the three aromatic amino acids tryptophan, tyrosine and phenylalanine. A sub-nanomole detection limit is estimated for tryptophan. Means to improve the sensitivity of the technique are discussed. The wider analytical applications of LD-MPI mass spectometry are considered.
14
Von, Zuben Francis S. G., and Alfred S. Jr David. "TIME SYNCHRONIZATION IN FLIGHT TEST DATA ANALYSIS." International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/608278.
Full textAbstract:
International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, CaliforniaA recurring problem in flight testing navigation systems is the need for an accurate, common time reference for the system under test and for the truth source to which it is compared. Lockheed Martin Aeronautics Company and Computer Sciences Corporation have developed software that utilizes all available timing information to reference the times of validity for each navigation measurement to Coordinated Universal Time. This permits accurate comparison and correlation of data necessary for statistical error analysis of the navigation system.
15
Lekpor, Kossi. "Time-varying filtering of time-of-flight mass spectra for proteomics." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81549.
Full textAbstract:
Proteomics is the post-genomic science that aims to identify and characterize the entire protein complement of a cell or organism. Mass spectrometry followed by database search is the core technology used in high-throughput protein identification. A major challenge in Proteomics is the random and chemical noise that corrupts mass spectra. This noise can alter the measured mass-to-charge ratio (m/z) and bias peak intensities, thus leading to errors in peptide ion peak detection. Thus, noise reduction by filtering is necessary prior to data analysis.As mass spectrometer response varies with m/z, an invariant filter would not be optimal; therefore, a time-varying filter was developed to denoise mass spectra. This involved conversion of spectra from the m/z domain to the time domain equivalent, modeling spectral peak shape and Fourier-transforming the model to determine its frequency content. The process was completed by filter design and implementation.
The application of this filter to experimental spectra resulted in improved signal-to-noise ratio (by factor of 45), enabled detection of low abundance peptide ions, and increased the accuracy of peptide mass assignment.
16
Gilkerson, Paul. "Digital signal processing for time of flight sonar." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343467.
Full text
17
Armitage, Nolan Jennifer Claire. "Time of flight mass spectrometry of pharmaceutical systems." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13701/.
Full textAbstract:
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a widely used surface chemical analysis technique that is traditionally employed to characterise the first few molecular layers of a material interface. The ability of this technique to accurately reflect the surface chemistry of polymers, biomaterials and many other solid materials is well documented. However, the majority of research that utilises this technique is based upon a qualitative rather than quantitative assessment of the material under investigation. The qualitative analysis of a range of traditional tablet and bead formulations containing drug and multiple excipients was performed in order to identify key diagnostic ions for all the different components. The lateral distributions of the ions across the surfaces of these formulations were imaged. Two different methods were then used to perform a qualitative analysis of the surfaces and results from these experiments were compared to the bulk composition. The effect of surface roughness on the ability to produce reproducible quantitative analyses from ToF SIMS ion yield data was investigated. A range of samples with different topographies were studied including polytetrafluoroethylene (PTFE), glass microscope slides, gold coated abrasive papers and gold coated precision measurement samples. The surface roughness was assessed by Atomic Force Microscopy and Laser Profilometry. Samples were analysed in imaging mode and the variance in ionization across the total image was measured for each sample. Evidence is presented that there is a relationship between ion yield and surface roughness, and that the surface roughness of the analysed surfaces will effect on any quantification approach in the processing of ToF-SIMS data. In addition, the presence of any orientation/directionality in surface features also needs to be evaluated when considering use of a quantitative approach. To investigate the effect of chemical environment on the ability to derive quantitative data from ToF SIMS analysis of pharmaceutical materials, drug loaded spun cast polymer films with low surface roughness were studied. ToF SIMS data were obtained for two chemically similar drugs in two different polymer matrices. In the majority of the samples there was no quantitative relationship between drug ion intensity and nominal bulk composition. Due to the large sample set, the multivariate technique, Principal Component Analysis (PCA) was employed to look at variance in secondary ion yields from the different samples. PCA is becoming more prevalent in ToF-SIMS data interrogation as it allows for a mathematically un-biased analysis of sample variables through the identification of the ions that account for the majority of the variance in the sample set. PCA successfully highlighted the impact of the chemical environment, showing secondary ion yields of drugs can be dependent on the surrounding matrix. PCA was also used to look at variance in two of the tablet samples and was successfully able to differentiate between the tablet samples with the lowest and highest concentrations of paracetamol. This thesis has demonstrated that surface topography and surface chemical environment or matrix will have a significant impact on ion yields in the ToF-SIMS experiments. These findings suggest caution in the use of ToF-SIMS for the quantitative analysis of complex chemically heterogeneous and topographically diverse pharmaceutical formulations.
18
Teerikoski, Sakari. "A prototype backscattering neutron time-of-flight spectrometer." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256783.
Full textAbstract:
Measuring neutron energies is an essential task in fusion research. The time-of-flight (TOF) of neutrons moving a known distance can be used to determine these energies. Slower neutrons have longer TOFs for fix flight paths. Neutrons are slowed down when they backscatter. A prototype backscattered neutron TOF spectrometer is constructed so that two detectors D1 and D2 are placed on respective sides of a neutron source. The goal is to measure the TOF of neutrons from the source that reach D1 and backscatter and reach D2. There can, however, be lots of background events that will look like a false backscattering event. Scintillation detectors are used as detectors in the prototype and the neutrons are provided by a californium-252 source. Test results from a first prototype show unsatisfying time-of-flight spectra that are dominated by a large background peak, indicating that further work is required for getting measurement results of time-of-flight of backscattered neutrons. Some aspects of improving the results and the prototype are discussed. Test results from a second prototype do show satisfying spectra, although further work is needed to verify that the difference compared to earlier results is due to backscattered neutrons.Uppmätning av neutroners energier är av vikt inom kärnfusionsforskning. Flygtiden för neutroner som rör sig en känd sträcka kan användas för att bestämma dessa energier. För fixa flygsträckor gäller att långsammare neutroner har längre flygtider. Neutroner saktas ner när de bakåtsprids. En flygtidsspektrometerprototyp för bakåtspridda neutroner konstrueras så att två detektorer D1 och D2 placeras på respektive sidor om en neutronkälla. Målet är att mäta flygtiden för sådana neutroner från källan som når D1, bakåtsprids därifrån och till slut nåt D2. Det finns dock utrymme för många slags bakgrundsfenomen som ser ut som bakåtspridning men inte är det. Scintillatordetektorer används som prototypens detektorer och neutronerna ges av en californium-252 källa. Testresultat visar otillfredsställande flygtidsspektra som domineras av en stor bakgrundstopp. Detta indikerar att vidare arbete krävs för att få uppmätta flygtider för bakåtspridda neutroner. Vissa förslag för förbättring av resultaten och av prototypen diskuteras. Testresultat från en efterföljande prototyp ger tillfredsställande spektra. Dock behövs mera arbete med den nya prototypen för att verifiera att förändringen i resultaten verkligen beror på bakåtspridda neutroner.
19
Heatherington, John. "ToF - the Time-of-Flight device for H1." Thesis, Queen Mary, University of London, 1995. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1502.
Full textAbstract:
Event triggering for the H1 detector on the HERA electron-proton ring is dominated by background associated with the proton beam. A 99% reduction in trigger rate is achieved by time resolution of background from physics using ToF -a scintillator detector positioned in the incoming proton direction. Studies on the efficiency of the veto have been carried out to improve background rejection.
20
Grisham, Joe P. 1950. "Phase enhanced time-of-flight magnetic resonance angiography." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/46454.
Full text
21
Kegel, Thomas, and Bruce Lipe. "THE ADAPS REAL-TIME / POST FLIGHT PROCESSING SYSTEM." International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/607324.
Full textAbstract:
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper describes the Real-Time/Post-Flight Processing System (RT/PFP) developed under the Air Force Flight Test Center (AFFTC) Advanced Data Acquisition and Processing Systems (ADAPS) development program. The RT/PFP is currently being deployed at all Range Division Mission Control Facilities as the principal Range Division telemetry processing system. This paper provides an overview of the RT/PFP system, its current capabilities, and future enhancements being developed. The RT/PFP is currently used to support the F-22 flight test program, and to provide telemetry processing support for the AFFTC Range Safety Office. The RT/PFP is also used in a mobile configuration to support the Advanced Fighter Technology Integration program.
22
PATUREAU, Philippe, and Douglas ULLAH. "REAL TIME PRESENTATION FOR RAFALE IN-FLIGHT TESTS." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612913.
Full textAbstract:
International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaThe current control rooms at Dassault Aviation, Istres were built in 1978 for the flight tests of the MIRAGE 2000 GENERATION. After 13 years of gradual improvements, the time has come to renew our instrumentation. New concepts and future technologies have been taken into consideration and the new equipment that is implemented must allow flight tests to be performed throughout the current decade. These changes have occurred to enable testing of a new breed of combat aircraft, i.e. the RAFALE, for the coming years. However, this improvement is in keeping with what has already been achieved over the last 22 years at DASSAULT AVIATION. A brief background reminder will allow assessment of the company’s real time philosophy. A ground control room provides two types of displays, namely: # a decommutator controlled display for minimum refresh rates. It is concerned with flight monitoring and hence safety. # a second display is connected to the host computer dedicated to data handling during flight time. A more accurate description will show how a locally available item of equipment was customized to match specific requirements and to enhance its basic functionalities so as to make up the display chain needed for flight safety.
23
Davies, Stephen James. "Remote techniques for time-of-flight flaw characterisation." Thesis, University of Warwick, 1991. http://wrap.warwick.ac.uk/108293/.
Full textAbstract:
This thesis describes the investigations conducted into the characterisation of various defects within solids using laser - generation and interferometric detection of ultrasound. Laser - generated ultrasound has advantages over the more commonly used piezoelectric transducers in that it is a reproducible, wide bandwidth, non - contact source which, by using appropriate optics, can be focussed to a point or line source and easily scanned over a surface. Used in association with an interferometric detector enables the possibility of a remote inspection system which would be useful for some applications. The properties of such a system for the characterisation of both bulk and surface - breaking defects are ascertained. Part of the research project has been concerned with determining the properties of the ultrasound produced in various solids by different laser pulse profiles. The results obtained indicate that the risetime of the ultrasonic compression wave decreases with decreasing incident laser pulse risetime. However the mechanical and thermal properties of the irradiated solid also affects the risetime of the ultrasound. Modelling of the laser - solid interaction was undertaken to understand this phenomenon in more detail. The wide bandwidth nature of laser - generated ultrasound was used in the characterisation of bulk defects. This has involved determining, using an FFT algorithm, the phase change which occurs when laser - generated ultrasound is scattered from such defects. The aim of the investigation was to assess whether a particular type of defect has a unique phase change which will enable it to be classified. The experimental results obtained compared favourably with the results from theoretical modelling of ultrasonic scattering by defects. Finally the interaction of laser - generated Rayleigh ( surface ) waves with surface - breaking defects was considered. Various techniques for the characterisation of surface - breaking defects by analysis of data in the time and frequency domain were utilised. One such technique involved measurement of the Reflection and Transmission coefficients of various surface discontinuities. The phase change of the scattered Rayleigh wave was determined and compared to the theoretical data available. Also, a technique was established whereby certain features on the waveforms recorded on transmission of a Rayleigh wave through a surface - breaking defect could be used to determine the depth of the defect.
24
Zou, Xiaoming. "Models to measure mobilities by time-of-flight /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486462702468012.
Full text
25
Kuball, Silke. "Emissionsdichteschätzung bei Time-of-Flight Positronen Emissions-Tomographie." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB9935146.
Full text
26
Baumann, Sandra [Verfasser], and Jürgen [Akademischer Betreuer] Hennig. "Time-of-flight-Magnetresonanzangiographie mit kontinuierlich bewegtem Patiententisch." Freiburg : Universität, 2011. http://d-nb.info/1123458413/34.
Full text
27
Lee, Jason W. L. "Novel developments in time-of-flight particle imaging." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:195be057-7ce0-4a15-b639-b08892fde312.
Full textAbstract:
In the field of physical chemistry, the relatively recently developed technique of velocity-map imaging has allowed chemical dynamics to be explored with a greater depth than could be previously achieved using other methods. Capturing the scattering image associated with the products resulting from fragmentation of a molecule allows the dissociative pathways and energy landscape to be investigated. In the study of particle physics, the neutron has become an irreplaceable spectroscopic tool due to the unique nature of the interaction with certain materials. Neutron spectroscopy is a non-destructive imaging technique that allows a number of properties to be discerned, including chemical identification, strain tensor measurements and the identification of beneath the sample surface using radiography and tomography. In both of these areas, as well as a multitude of other disciplines, a flight tube is used to separate particles, distinguishing them based upon their mass in the former case and their energy in the latter. The experiments can be vastly enhanced by the ability to record both the position and arrival time of the particle of interest. This thesis describes several new developments made in instrumentation for experiments involving time-of-flight particle imaging. The first development described is the construction of a new velocity-map imaging instrument that utilises electron ionisation to perform both steps of molecular fragmentation and ionisation. Data from CO2 is presented as an example of the ability of the instrument, and a preliminary analysis of the images is performed. The second presented project is the design of a time-resolved and position-resolved detector developed for ion imaging experiments. The hardware, software and firmware are described and presented alongside data from a variety of the experiments showcasing the breadth of investigations that are possible using the sensor. Finally, the modifications made to the detector to allow time-resolved neutron imaging are detailed, with an in-depth description of the various proof-of-concept experiments carried out as part of the development process.
28
Deng, Yunfei 1974. "Simplified decoding for a Quasi-Orthogonal space-time code family." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81534.
Full textAbstract:
This thesis considers simplified decoding for a type of full-rate non-orthogonal complex space-time block codes (STBCs) over Rayleigh fading channels. More precisely, we propose a decision feedback symbol-by-symbol decoding algorithm for the Quasi-Orthogonal code family, that comprises the Quasi-Orthogonal code and the Improved Quasi-Orthogonal code, by using the QR decomposition. Compared to optimal joint decoding, this algorithm significantly reduces complexity. For performance evaluations of the simplified decoding algorithm for the Quasi-Orthogonal code family over Rayleigh fading channels, we derive upper and lower bounds for symbol error rate. Furthermore, by using high SNR asymptotics we investigate the diversity orders provided by different decoding algorithms. The analysis shows that because of the relative constellation rotation, the diversity order provided by optimal decoding for the Improved Quasi-Orthogonal code is 4. Also, because of the error propagation in the decision feedback, the diversity order provided by the simplified decoding for the Improved Quasi-Orthogonal code is reduced to 2. All analytical results match well the associated computer simulations. Finally, we compare the performances of the simplified and optimal decoding for the Improved Quasi-Orthogonal code over correlated Rayleigh fading channels by using the "one-ring" channel model. Through computer simulations we show that the relative performance loss between the simplified and optimal decoding decreases as channel correlation increases. Therefore, the simplified decoding algorithm is suitable for highly spatially correlated Rayleigh fading channels.
29
Lin, Rui. "Hybrid ARQ Schemes for Non-orthogonal Space-time Block Codes." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1183.
Full textAbstract:
Automatic Repeat-reQuest (ARQ) schemes are extensively used in communication systems and computer networks to achieve reliable transmission. Using space-time codes (STCs) with multiple input multiple output (MIMO) or multiple input single output (MISO) systems is an effective way to combat multipath fading, which is the most severe impairment for wireless communication systems. STCs are designed to use the rich scattering multipath environment provided by using multiple transmit antennas. The work done in this thesis focuses on the use of ARQ schemes with non-orthogonal space-time block codes (NOSTBCs) based on Reed Solomon codes. The truncated-selective ARQ (TS-ARQ) scheme is considered and three novel hybrid ARQ (HARQ) schemes are proposed. Simulation results reveal that, compared to using TS-ARQ with orthogonal space-time block codes (OSTBCs), using NOSTBCs with any of the three proposed HARQ schemes can provide significant gains in terms of dropped packet rate and spectral efficiency at the cost of increased decoding complexity. The performance can be further improved by using the water filling principle to adaptively allocate transmit power among transmit antennas.
30
Hesse, Matthias. "L2-orthogonal space-time code design for continuous phase modulation." Nice, 2010. http://www.theses.fr/2010NICE4008.
Full textAbstract:
Orthogonal Space-Time block codes (STBC) have been a popular way to implement wireless communications systems with full diversity and simple decoupled maximum-likelihood decoding. However, all these codes rely on pointwise orthogonality which leads to a well-known degradation of data rate for more than two antennas. In this thesis, we introduce the concept of L2-orthogonality for non-linear Space-Time codes (STC). Our approach generalizes code design based on pointwise orthogonality. Hence, we are able to derive new codes with the same advantages as pointwise orthogonal STBC, i. E. Low decoding complexity and diversity gain. At the same time, we are no longer limited by the restrictions of pointwise orthogonal codes, namely the reduction in data rate. Actually, we show how to construct full rate codes for any arbitrary number of transmit antennas. More precisely, a family of codes for continuous phase modulation (CPM) is detailed. The L2-orthogonality of these codes is ensured by a bank of phase correction functions which maintains the phase continuity but also introduces frequency offsets. We prove that these codes achieve full diversity and have full rate. Moreover, these codes don't put any restriction on the CPM parametersLes codes spatio-temporels orthogonaux par blocs (OSTBC) sont devenus populaires en ce qu'ils permettent de construire des systèmes de communications sans-fil à diversité maximale et à décodage simplifié par maximum de vraisemblance découplé. Cependant, ces codes reposent en général sur une orthogonalité ponctuelle, ce qui entraîne une dégradation bien connue du débit de transmission pour les systèmes à plus de deux antennes d'émission. Nous introduisons dans cette thèse le concept d'orthogonalité L2 pour les codes spatio-temporel (STC). Cette approche permet de généraliser naturellement la propriété d'orthogonalité ponctuelle pour des systèmes à codages spatio-temporels non-linéaires. Il devient alors possible de construire de nouveaux systèmes multi-antennes (MIMO) à faible complexité de décodage et gain de diversité maximal. De plus, contrairement aux systèmes reposant sur des codes linéaires orthogonaux, ces nouveaux systèmes ne présentent plus de limitation du débit de transmission pour plus de deux antennes. Nous détaillons la construction générale de diverses familles de codes spatio-temporels L2 à débit maximal reposant sur des modulations de phase continue (CPM) et ceci pour n'importe quel nombre d'antennes d'émission. L'orthogonalité L2 des systèmes construits est obtenue par un banc de fonctions de correction de phase qui induit la diversité par décalage en fréquence tout en maintenant la continuité de la phase pour chaque antenne. L'étude de ces codes permet de démontrer que les systèmes MIMO à décodage simplifié ainsi obtenus sont à diversité maximale et débit optimal. Enfin, notons que la construction de ces codes n'introduit aucune contrainte supplémentaire sur les paramètres des modulations de phase continue utilisées
31
Torbet, Tyler S. "Analysis of Synthetic Cannabinoids by Direct Analysis in Real Time Quadrupole Time-of-Flight Mass Spectrometry and Gas Chromatography Quadrupole Time-of-Flight Mass Spectrometry." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2216.
Full textAbstract:
The aim of this study was to investigate the utility of direct analysis in real time quadrupole time-of-flight mass spectrometry and gas chromatography quadrupole time-of-flight mass spectrometry in the analysis of 162 different synthetic cannabinoids. Direct analysis in real time quadrupole time-of-flight mass spectrometry is shown to be a rapid and accurate analytical method for synthetic cannabinoids. Spectra can be generated with less than 1.5 ng of the drug in under a minute and be successfully searched against previously generated ESI-QTOF libraries in most cases (118/130 drugs tested) as well as can also be applied to the identification of synthetic cannabinoids in a mixture. Gas chromatography quadrupole time-of-flight mass spectrometry, while requiring a much longer analysis time, is shown to accurately distinguish all but 19 compounds (140/159). These two instruments have proven to be viable alternatives in synthetic cannabinoid analysis and will greatly benefit forensic laboratories.
32
Almoric, Jean. "Développement d'un nouvel instrument couplant FIB/SEM UHV et OTOF-SIMS à haute résolution spatiale pour la microélectronique et ses applications." Electronic Thesis or Diss., Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0368.
Full textAbstract:
La spectrométrie de masse d’ion secondaire (SIMS) est probablement la technique d'analyse chimique la plus largement utilisée en science des semi-conducteurs et en métallurgie en raison de sa sensibilité ultime à tous les éléments notamment au plus légers. Avec la réduction de la taille des systèmes, l'imagerie chimique 3D haute résolution devient une condition préalable au développement de nouveaux matériaux. Dans cette thèse, nous rapportons le développement et l’optimisation d'un SIMS innovant implémenté dans un microscope électronique à balayage. L'équipement permet d’obtenir une cartographie chimique élémentaire à très haute résolution (~25nm). La capacité de la technique est démontrée avec la caractérisation à l'échelle nanométrique d’une part de superalliages métalliques nécessaire à la fabrication de pièces moteurs pour l’aviation et d’autre part d’alliages chalcogénures utilisés dans les mémoires à changement de phase de dernière génération développées en microélectroniqueSecondary Ion Mass Spectrometry (SIMS) is probably the most widely used chemical analysis technique in semiconductor science and metallurgy because of its ultimate sensitivity to all elements, especially the lighter ones. With systems downsizing, high-resolution 3D chemical imaging is becoming a prerequisite for the development of new materials. In this thesis, we report the development and optimization of an innovative SIMS implemented in a scanning electron microscope. The equipment makes it possible to obtain elementary chemical mapping at very high resolution (~25nm). The capacity of the technique is demonstrated with the characterization at the nanometric scale on the one hand of metallic superalloys necessary for the manufacture of aircraft engine parts and on the other hand of chalcogenide alloys used in the latest generation phase change memories developed in microelectronics
33
Ates, Tugrul Kagan. "Real-time Arbitrary View Rendering From Stereo Video And Time-of-flight Camera." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612801/index.pdf.
Full textAbstract:
Generating in-between images from multiple views of a scene is a crucial task for both computer vision and computer graphics fields. Photorealistic rendering, 3DTV and robot navigation are some of many applications which benefit from arbitrary view synthesis, if it is achieved in real-time. Most modern commodity computer architectures include programmable processing chips, called Graphics Processing Units (GPU), which are specialized in rendering computer generated images. These devices excel in achieving high computation power by processing arrays of data in parallel, which make them ideal for real-time computer vision applications. This thesis focuses on an arbitrary view rendering algorithm by using two high resolution color cameras along with a single low resolution time-of-flight depth camera and matching the programming paradigms of the GPUs to achieve real-time processing rates. Proposed method is divided into two stages. Depth estimation through fusion of stereo vision and time-of-flight measurements forms the data acquisition stage and second stage is intermediate view rendering from 3D representations of scenes. Ideas presented are examined in a common experimental framework and practical results attained are put forward. Based on the experimental results, it could be concluded that it is possible to realize content production and display stages of a free-viewpoint system in real-time by using only low cost commodity computing devices.
34
Hayes, Matthew. "Distributed quasi-orthogonal space-time coding in wireless cooperative relay networks." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9923.
Full textAbstract:
Cooperative diversity provides a new paradigm in robust wireless re- lay networks that leverages Space-Time (ST) processing techniques to combat the effects of fading. Distributing the encoding over multiple relays that potentially observe uncorrelated channels to a destination terminal has demonstrated promising results in extending range, data- rates and transmit power utilization. Specifically, Space Time Block Codes (STBCs) based on orthogonal designs have proven extremely popular at exploiting spatial diversity through simple distributed pro- cessing without channel knowledge at the relaying terminals. This thesis aims at extending further the extensive design and analysis in relay networks based on orthogonal designs in the context of Quasi- Orthogonal Space Time Block Codes (QOSTBCs). The characterization of Quasi-Orthogonal MIMO channels for cooper- ative networks is performed under Ergodic and Non-Ergodic channel conditions. Specific to cooperative diversity, the sub-channels are as- sumed to observe different shadowing conditions as opposed to the traditional co-located communication system. Under Ergodic chan- nel assumptions novel closed-form solutions for cooperative channel capacity under the constraint of distributed-QOSTBC processing are presented. This analysis is extended to yield closed-form approx- imate expressions and their utility is verified through simulations. The effective use of partial feedback to orthogonalize the QOSTBC is examined and significant gains under specific channel conditions are demonstrated. Distributed systems cooperating over the network introduce chal- lenges in synchronization. Without extensive network management it is difficult to synchronize all the nodes participating in the relaying between source and destination terminals. Based on QOSTBC tech- niques simple encoding strategies are introduced that provide compa- rable throughput to schemes under synchronous conditions with neg- ligible overhead in processing throughout the protocol. Both mutli- carrier and single-carrier schemes are developed to enable the flexi- bility to limit Peak-to-Average-Power-Ratio (PAPR) and reduce the Radio Frequency (RF) requirements of the relaying terminals. The insights gained in asynchronous design in flat-fading cooperative channels are then extended to broadband networks over frequency- selective channels where the novel application of QOSTBCs are used in distributed-Space-Time-Frequency (STF) coding. Specifically, cod- ing schemes are presented that extract both spatial and mutli-path diversity offered by the cooperative Multiple-Input Multiple-Output (MIMO) channel. To provide maximum flexibility the proposed schemes are adapted to facilitate both Decode-and-Forward (DF) and Amplify- and-Forward (AF) relaying. In-depth Pairwise-Error-Probability (PEP) analysis provides distinct design specifications which tailor the distributed- STF code to maximize the diversity and coding gain offered under the DF and AF protocols. Numerical simulation are used extensively to confirm the validity of the proposed cooperative schemes. The analytical and numerical re- sults demonstrate the effective use of QOSTBC over orthogonal tech- niques in a wide range of channel conditions.
35
Manna, Mustafa A. "Modified quasi-orthogonal space-time block coding in distributed wireless networks." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/16629.
Full textAbstract:
Cooperative networks have developed as a useful technique that can achieve the same advantage as multi-input and multi-output (MIMO) wireless systems such as spatial diversity, whilst resolving the difficulties of co-located multiple antennas at individual nodes and avoiding the effect of path-loss and shadowing. Spatial diversity in cooperative networks is known as cooperative diversity, and can enhance system reliability without sacrificing the scarce bandwidth resource or consuming more transmit power. It enables single-antenna terminals in a wireless relay network to share their antennas to form a virtual antenna array on the basis of their distributed locations. However, there remain technical challenges to maximize the benefit of cooperative communications, e.g. data rate, asynchronous transmission and outage. In this thesis, therefore, firstly, a modified distributed quasi-orthogonal space-time block coding (M-D-QO-STBC) scheme with increased code gain distance (CGD) for one-way and two-way amplify-and-forward wireless relay networks is proposed. This modified code is designed from set partitioning a larger codebook formed from two quasi-orthogonal space time block codes with different signal rotations then the subcodes are combined and pruned to arrive at the modified codebook with the desired rate in order to increase the CGD. Moreover, for higher rate codes the code distance is maximized by using a genetic algorithm to search for the optimum rotation matrix. This scheme has very good performance and significant coding gain over existing codes such as the open-loop and closed-loop QO-STBC schemes. In addition, the topic of outage probability analysis in the context of multi-relay selection from $N$ available relay nodes for one-way amplify-and-forward cooperative relay networks is considered together with the best relay selection, the $N^{th}$ relay selection and best four relay selection in two-way amplify-and-forward cooperative relay networks. The relay selection is performed either on the basis of a max-min strategy or one based on maximizing exact end-to-end signal-to-noise ratio. Furthermore, in this thesis, robust schemes for cooperative relays based on the M-D-QO-STBC scheme for both one-way and two-way asynchronous cooperative relay networks are considered to overcome the issue of a synchronism in wireless cooperative relay networks. In particular, an orthogonal frequency division multiplexing (OFDM) data structure is employed with cyclic prefix (CP) insertion at the source in the one-way cooperative relay network and at the two terminal nodes in the two-way cooperative network to combat the effects of time asynchronism. As such, this technique can effectively cope with the effects of timing errors. Finally, outage probability performance of a proposed amplify-and-forward cooperative cognitive relay network is evaluated and the cognitive relays are assumed to exploit an overlay approach. A closed form expression for the outage probability for multi-relay selection cooperation over Rayleigh frequency flat fading channels is derived for perfect and imperfect spectrum acquisitions. Furthermore, the M-QO-STBC scheme is also proposed for use in wireless cognitive relay networks. MATLAB and Maple software based simulations are employed throughout the thesis to support the analytical results and assess the performance of new algorithms and methods.
36
Steinmetz, Violette. "Prototype of a back scattering time of flight spectrometer." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257296.
Full text
37
Clipston, Nigel L. "Laser desorption/laser ionization Time-of-Flight Mass Spectrometry." Thesis, University of Salford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360476.
Full text
38
Dale, Michael John. "Laser desorption laser photoionisation time-of-flight mass spectrometry." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/13547.
Full textAbstract:
The work described in this thesis is concerned with the development and application of laser desorption laser photoionisation time-of-flight mass spectrometry (L2TOFMS). This technique has been used to enable photoionisation mass spectra of a very wide variety of involatile and thermally labile molecules to be recorded. The instrument used for this work is described along with an overview of the fundamental principles behind this methodology. A number of specific classes of molecules have been studied using the L2TOFMS. These include polyaromatic hydrocarbons, porphyrins, dyestuffs and a variety of analytically important staining agents. The advantages of this approach for analysing complex mixtures, which yield relatively simple mass spectra, have been demonstrated for both environmental systems and commercially important mixtures. It has also been shown that L2TOFMS can be used for the direct interrogation of target systems adsorbed onto organic substrates. L2TOFMS has been used to probe the photophysics of both porphyrin molecules and a series of azo dyes. Ionising wavelength dependent fragmentation was observed for a number of metallotetraphenylprophyrins and metallo- octaethylporphyrins. Using 193 nm laser photoionisation, molecular dissociation, involving loss of the macrocycle side groups, was shown to be similar to that obtained by electron impact ionisation. Whereas, at 266 nm, fragmentation via a neutral intermediate state, resulting in the loss of the metal from the macrocycle, competes with further photon absorption. Characteristic azo-bond photoreductive cleavage has been observed for azo molecules when using 266 nm laser photoionisation. This behaviour is linked to the cis-trans photoiosomerisation of the azo bond.
39
O'Brien, R. Michael. "REAL-TIME TELEMETRY DATA FORMATTING FOR FLIGHT TEST ANALYSIS." International Foundation for Telemetering, 1994. http://hdl.handle.net/10150/608577.
Full textAbstract:
International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, CaliforniaWith today's telemetry systems, an hour-long analog test tape can be digitized in one hour or less. However, the digitized data produced by today's telemetry systems is usually not in a format that can be directly analyzed by the test engineer's analysis tools. The digitized data must be formatted before analysis can begin. The data formatting process can take from one to eight hours depending on the amount of data, the power of the system's host computer, and the complexity of the analysis software's data format. If more than one analysis package is used by the test engineer, the data has to be formatted separately for each package. Using today's high-speed RISC processors and large memory technology, a real-time Flexible Data Formatter can be added to the Telemetry Front End to perform this formatting function. The Flexible Data Formatter (FDF) allows the telemetry user to program the front-end hardware to output the telemetry test data in a format compatible with the user's analysis software. The FDF can also output multiple data files, each in a different format for supporting multiple analysis packages. This eliminates the file formatting step, thus reducing the time to process the data from each test by a factor of two to nine.
40
Moro, Mike, and Paul J. Friedman. "An Integrated Real-Time Turbine Engine Flight Test System." International Foundation for Telemetering, 1990. http://hdl.handle.net/10150/613817.
Full textAbstract:
International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, NevadaNew developments and modifications to existing gas turbine engines require qualification through extensive ground testing followed by flight testing. An increasing work load necessitates productivity improvements in the test platform utilization and the telemetry ground station. This paper addresses the application of a compatible family of commercial offthe-shelf telemetry systems for quick-look to ensure data integrity on board the Boeing 720 test platform, and a distributed architecture ground station to serve multiple engineering disciplines through the use of an acquisition subsystem serving data to independent color graphics workstations via an Ethernet local area network.
41
Calvert, N. "Time-of-flight Compton scatter imaging for cargo security." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1503664/.
Full textAbstract:
By measuring the time of flight of scattered x-ray photons, the point of interaction, assuming a single scatter, can be determined, providing a three dimensional image of cargo containers. The present work introduces the technique, and provides experimental and theoretical results to show the feasibility of such a technique. Monte Carlo simulations were performed to investigate the proportion of multiple scatter detected using a proposed experimental setup, and it was found that it accounted for almost 50% of the recorded signal. Monte Carlo simulations of a scintillation detector were provided and used to design the detectors used. Experimental measurements at a picosecond length x-ray source resulted in the reconstruction of scatter position of photons interacting in a 5 cm thick test object to an accuracy of 12 cm full width at half maximum. Preliminary experiments were also performed using a conventional commercially available linear accelerator with a pulse length of 170 ns. Deconvolution techniques were applied to the recorded data to estimate the position of scatter. An analytic single scatter forward model was derived from the radiative transfer equation, discretised and the inverse problem was solved using a number of different methods. The alternating direction method of multipliers was adapted for nonlinear problems and provided image quality that was comparable to the gold standard linear method.
42
Halter, Ronald Vaughn. "A universal time of flight equation for space mechanics." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43406.
Full textAbstract:
A universal time of flight equation for any orbit is developed as a
function of the initial and final radius, the change in true anomaly
and the initial flight path angle. Lambert's theorem, a new corollary
to this theorem, a trigonometric variable substitution and a continuing
fraction expression are used in this development. The resulting
equation is not explicitly dependent upon eccentricity and is
determinate for -2n < (change in true anomaly) < 2n. A method to
make the continuing fraction converge rapidly is evaluated using a top
down algorithm. Finally, the accuracy of the universal time of flight
equation is examined for a representative set of orbits including near
parabolic and near rectilinear orbits.
Master of Science
43
Chen, Haijian. "Automated peak identification for time -of -flight mass spectroscopy." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539623489.
Full textAbstract:
The high throughput capabilities of protein mass fingerprints measurements have made mass spectrometry one of the standard tools for proteomic research, such as biomarker discovery. However, the analysis of large raw data sets produced by the time-of-flight (TOF) spectrometers creates a bottleneck in the discovery process. One specific challenge is the preprocessing and identification of mass peaks corresponding to important biological molecules. The accuracy of mass assignment is another limitation when comparing mass fingerprints with databases.;We have developed an automated peak picking algorithm based on a maximum likelihood approach that effectively and efficiently detects peaks in a time-of-flight secondary ion mass spectrum. This approach produces maximum likelihood estimates of peak positions and amplitudes, and simultaneously develops estimates of the uncertainties in each of these quantities. We demonstrate that a Poisson process is involved for time-of-flight secondary ion mass spectrometry (TOF-SIMS) and the algorithm takes the character of the Poisson noise into account.;Though this peak picking algorithm was initially developed for TOF-SIMS spectra, it can be extended to other types of TOF spectra as soon as the correct noise characteristics are considered. We have developed a peak alignment procedure that aligns peaks in different spectra. This is a crucial step for multivariate analysis. Multivariate analysis is often used to distill useful information from complex spectra.;We have designed a TOF-SIMS experiment that consists of various mixtures of three bio-molecules as a model for more complicated biomarker discovery. The peak picking algorithm is applied to the collected spectra. The algorithm detects peaks in the spectra repeatably and accurately. We also show that there are patterns in the spectra of pure biomolecules samples. Furthermore, we show it is possible to infer the concentration ratios in the mixture samples by checking the strength of the patterns.
44
Chlebek, David. "Simulation of ultrasonic time of flight in bolted joints." Thesis, KTH, Hållfasthetslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298342.
Full textAbstract:
Ultrasonic measurements of the preload in bolted joints is a very accurate method since it does not depend on the friction and other factors which cause difficulties for common methods. The ultrasonic method works by emitting an ultrasonic pulse into the bolt which is reflected at the end and returned to the transducer, the change in the time of flight (TOF) can be related to the elongation of the bolt and therefore the preload. One must account for the acoustoelastic effect which is the change in sound speed due to an initial stress state. The goal of this thesis project was to implement a Murnaghan hyperelastic material model in order to account for the acoustoelastic effect when conducting a numerical simulation using the finite element method (FEM). An experiment was also performed to validate the numerical simulation. The DeltaTOF as a function of a tensile force was obtained for an M8 and M10 test piece from the experiment. The material model was implemented by creating a user subroutine written in Fortran for the explicit solver Radioss. Hypermesh was used to set-up the numerical simulation. The material model has shown an expected behavior with an increased sound speed with compressive stresses and a decreased speed with tensile stresses. The numerical simulation showed a good correspondence to the experimental results.Ultraljudsmätning av klämklraften i skruvförband är en väldigt noggrann metod eftersom att metoden inte påverkas av friktion eller andra faktorer som innebär svårigheter för vanliga metoder. Ultraljudsmetoden fungerar genom att skicka in en ultraljudsvåg i skruven som reflekteras i botten och återvänder tillbaka till sensorn. Skillnaden i tiden för ekot att återvända kan relateras till förlängningen av skruven och därmed klämkraften. Det är viktigt att ta hänsyn till den akustoelastiska effekten, som är fenomenet där ljudhastigheten av en våg i en solid förändras med spänningstillståndet. Målet med det här arbetet är att implementera en hyperelastisk Murnaghan modell som tar hänsyn till den akustoelastiska effekten med FEM simuleringar. Ett experiment har också genomförts för att validera beräkningsmodellen. Tidsfördröjningen som en funktion av förspänningskraften togs fram för ett M8 och M10 provobjekt. Murnaghans hyperelastiska materialmodell implementerades genom att skapa ett användar material skriven i programmeringsspråket Fortran för den explicita lösaren Radioss. Hypermesh användes för att ställa upp FEM simuleringen. Materialmodellen har visat ett väntat beteende med en ökad ljudhastighet med tryckspänningar och minskad ljudhastighet med dragspänningar. Beräkningsmodellen visade en god överenstämmelse med resultatet från experimentet.
45
Berglund, Johan. "Real-Time Visualization of Flight Data for Suborbital Missions." Thesis, KTH, Rymd- och plasmafysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-211469.
Full textAbstract:
The aim of this thesis was to systematically develop a tool used for the visualizationof real-time ight data during suborbital mission, on behalf of the Swedish SpaceCorporation. By focusing on requirements, restrictions, and trade-os regarding functionality,communications technologies, geospatial visualization platforms, and manyother aspects, an interactive product visualizing the position, attitude, speed, G-loadsand angular rates of the rockets could be developed, ensuring a visualization as close toreal-time as possible. The resulting product was tested during the ight of the MAXUS9 rocket, Europe's largest sounding rocket, and was subsequently rened based on theresults of that ight.Målet med detta examensarbete vara att utveckla ett verktyg för visualisering avflygdata i realtid under suborbitala uppdrag, på uppdrag av Swedish Space Corporation.Genom att fokusera på krav, restriktioner, och avvägningar gällande funktionalitet,kommunikationstekniker, geospatiell utveckling, och många andra aspekter, kunde eninteraktiv produkt som visualiserar raketens position, attityd, hastighet, G-krafter ochvinkelhastigheter utvecklas, som även säkerställer att visualiseringen sker så nära realtidsom möjligt. Den resulterande produkten testades under uppskjutningen av MAXUS 9,vilket är Europas största sondraket, och förfinades sedan baserat på resultaten av denflygningen.
46
Allison, Timothy Charles. "System Identification via the Proper Orthogonal Decomposition." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/29424.
Full textAbstract:
Although the finite element method is often applied to analyze the dynamics of structures, its application to large, complex structures can be time-consuming and errors in the modeling process may negatively affect the accuracy of analyses based on the model. System identification techniques attempt to circumvent these problems by using experimental response data to characterize or identify a system. However, identification of structures that are time-varying or nonlinear is problematic because the available methods generally require prior understanding about the equations of motion for the system. Nonlinear system identification techniques are generally only applicable to nonlinearities where the functional form of the nonlinearity is known and a general nonlinear system identification theory is not available as is the case with linear theory. Linear time-varying identification methods have been proposed for application to nonlinear systems, but methods for general time-varying systems where the form of the time variance is unknown have only been available for single-input single-output models. This dissertation presents several general linear time-varying methods for multiple-input multiple-output systems where the form of the time variance is entirely unknown. The methods use the proper orthogonal decomposition of measured response data combined with linear system theory to construct a model for predicting the response of an arbitrary linear or nonlinear system without any knowledge of the equations of motion. Separate methods are derived for predicting responses to initial displacements, initial velocities, and forcing functions. Some methods require only one data set but only promise accurate solutions for linear, time-invariant systems that are lightly damped and have a mass matrix proportional to the identity matrix. Other methods use multiple data sets and are valid for general time-varying systems. The proposed methods are applied to linear time-invariant, time-varying, and nonlinear systems via numerical examples and experiments and the factors affecting the accuracy of the methods are discussed.Ph. D.
47
Lloyd, Joseph W. Jr. "POST-FLIGHT DATA DISTRIBUTION SYSTEM." International Foundation for Telemetering, 1993. http://hdl.handle.net/10150/608898.
Full textAbstract:
International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, NevadaDesktop Processors (IBM PC, PC-compatible, and Macintosh) have made a major impact on how the Naval Air Warfare Center Aircraft Division (NAWCAD}, Patuxent River engineering community performs their work in aircraft weapons tests. The personal processors are utilized by the flight-test engineers not only for report preparation, but also for post-flight Engineering Unit (EU) data reduction and analysis. Present day requirements direct a need for improved post-flight data handling than those of the past. These requirements are driven by the need to analyze all the vehicle's parameters prior to the succeeding test flight, and to generate test reports in a more cost effective and timely manner. This paper defines the post-flight data distribution system at NAWCAD, Patuxent River, explains how these tasks were handled in the past, and the development of a real-time data storage designed approach for post-flight data handling. This engineering design is then described explaining how it sets the precedence for NAWCAD, Patuxent River's future plans; and how it provides the flight-test engineer with the test vehicle's EU data immediately available post-flight at his desktop processor.
48
Harkins, Ross Douglas. "A multiple wavelength time-of-flight sensor, based on time-correlated single-photon counting." Thesis, Heriot-Watt University, 2005. http://hdl.handle.net/10399/199.
Full text
49
Rama, Ritesh Rao. "Proper orthogonal decomposition with interpolation-based real-time modelling of the heart." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/26859.
Full textAbstract:
Several studies have been carried out recently with the aim of achieving cardiac modelling of the whole heart for a full heartbeat. However, within the context of the Galerkin method, those simulations require high computational demand, ranging from 16 - 200 CPUs, and long calculation time, lasting from 1 h - 50 h. To solve this problem, this research proposes to make use of a Reduced Order Method (ROM) called the Proper Orthogonal Decomposition with Interpolation method (PODI) to achieve real-time modelling with an adequate level of solution accuracy. The idea behind this method is to first construct a database of pre-computed full-scale solutions using the Element-free Galerkin method (EFG) and then project a selected subset of these solutions to a low dimensional space. Using the Moving Least Square method (MLS), an interpolation is carried out for the problem-at-hand, before the resulting coefficients are projected back to the original high dimensional solution space. The aim of this project is to tackle real-time modelling of a patient-specific heart for a full heartbeat in different stages, namely: modelling (i) the diastolic filling with variations of material properties, (ii) the isovolumetric contraction (IVC), ejection and isovolumetric relation (IVR) with arbitrary time evolutions, and (iii) variations in heart anatomy. For the diastolic filling, computations are carried out on a bi-ventricle model (BV) to investigate the performance and accuracy for varying the material parameters. The PODI calculations of the LV are completed within 14 s on a normal desktop machine with a relative L₂-error norm of 6x10⁻³. These calculations are about 2050 times faster than EFG, with each displacement step generated at a calculation frequency of 1074 Hz. An error sensitivity analysis is consequently carried out to find the most sensitive parameter and optimum dataset to be selected for the PODI calculation. In the second phase of the research, a so-called "time standardisation scheme" is adopted to model a full heartbeat cycle. This is due to the simulation of the IVC, ejection, and IVR phases being carried out using a displacement-driven calculation method which does not use uniform simulation steps across datasets. Generated results are accurate, with the PODI calculations being 2200 faster than EFG. The PODI method is, in the third phase of this work, extended to deal with arbitrary heart meshes by developing a method called "Degrees of freedom standardisation" (DOFS). DOFS consists of using a template mesh over which all dataset result fields are projected. Once the result fields are standardised, they are consequently used for the PODI calculation, before the PODI solution is projected back to the mesh of the problem-at-hand. The first template mesh to be considered is a cube mesh. However, it is found to produce results with high errors and non-physical behaviour. The second template mesh used is a heart template. In this case, a preprocessing step is required where a non-rigid transformation based on the coherent point drift method is used to transform all dataset hearts onto the heart template. The heart template approach generated a PODI solution of higher accuracy at a relatively low computational time. Following these encouraging results, a final investigation is carried out where the PODI method is coupled with a computationally expensive gradient-based optimisation method called the Levenberg- Marquardt (PODI-LVM) method. It is then compared against the full-scale simulation one where the EFG is used with the Levenberg-Marquardt method (EFG-LVM). In this case, the PODI-LVM simulations are 1025 times faster than the EFG-LVM, while its error is less than 1%. It is also observed that since the PODI database is built using EFG simulations, the PODI-LVM behaves similarly to the EFG-LVM one.
50
Olcer, Fahri Ersel. "Linear time invariant models for integrated flight and rotor control." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44921.
Full textAbstract:
Formulation of linear time invariant (LTI) models of a nonlinear system about a periodic equilibrium using the harmonic domain representation of LTI model states has been studied in the literature. This thesis presents an alternative method and a computationally efficient scheme for implementation of the developed method for extraction of linear time invariant (LTI) models from a helicopter nonlinear model in forward flight. The fidelity of the extracted LTI models is evaluated using response comparisons between the extracted LTI models and the nonlinear model in both time and frequency domains. Moreover, the fidelity of stability properties is studied through the eigenvalue and eigenvector comparisons between LTI and LTP models by making use of the Floquet Transition Matrix. For time domain evaluations, individual blade control (IBC) and On-Blade Control (OBC) inputs that have been tried in the literature for vibration and noise control studies are used. For frequency domain evaluations, frequency sweep inputs are used to obtain frequency responses of fixed system hub loads to a single blade IBC input. The evaluation results demonstrate the fidelity of the extracted LTI models, and thus, establish the validity of the LTI model extraction process for use in integrated flight and rotor control studies.