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Dissertations / Theses on the topic 'Aeronautical Engineering'
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1
Ivliev. "SPACE X’S ROCKET CONCEPTS – STEP FORWARD IN AERONAUTICAL ENGINEERING." Thesis, Київ 2018, 2018. http://er.nau.edu.ua/handle/NAU/33718.
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Guiho, Audren. "Design, development and use of a mechanism simulator for aeronautical engineering." Thesis, KTH, Flygdynamik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244830.
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This paper deals with the strategy for developing a very specific mechanism simulator. This mechanism is currently designed by Safran Group. A previous version of the same mechanism does exist but the scale is not on a like-for-like basis. Therefore, physical phenomena involved in this mechanism and their magnitude are not comparable to the previous version of the mechanism and this is why a new simulator has been developed (specified, coded and validated) from scratch. The paper addresses the strategy adopted for modelling a mechanism laying on a wide set of parameters as well as its use.Artikeln handlar om en strategi som mål bestå av att utveckla en särskild simulator mekanism, för närvarande utformad av Safran Group. Det finns en tidigare version av samma mekanismen men systemskalor är inte i en like-for-like grund. Alltså, fysiska fenomenen som innebärs i mekanismen och deras magnitud kan inte jämföras med tidigare versionen av systemet. Det är varför en ny simulator har skrivits i kod. Artikeln analyserar strategin som adopterades för att utforma ett system som lägger på en bred uppsättning parametrar.
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Frogget, Jacob William. "Automatic Modulation Recognition for Aeronautical Telemetry." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3826.
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This these explores automatic modulation recognition as applied to PCM/FM, SOQPSK- TG and ARTM CPM. It found that the likelihood based approach is intractable. The statistical features of the amplitude, phase and frequency are ineffective at distinguishing these modulation types. A method based on the phase changes between symbols is developed and shows that as long as symbol timing is established, this method can effectively distinguish PCM/FM, SOQPSK-TG and ARTM CPM for signal-to-noise ratios above 30 dB. Another method, the Bianchi-Loubaton- Sirven technique, was able to distinguish PCM/FM and SOQPSK-TG but was unable to distinguish ARTM CPM. A happy byproduct of this classification algorithm is a reasonably accurate estimate of the bit rate. Simulation results show that this classifier works essentially error-free for signal- to-noise ratios above 20 dB and for sufficiently high resolution in the search algorithms required by the maximizations.
4
Haque, Jamal. "An OFDM Based Aeronautical Communication System." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3143.
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Wireless connectivity is becoming an integral part of our society. A new paradigm for
aeronautical data services is beginning to take shape. The advances in signal processing,
rapid prototyping, an insatiable consumer demand for Internet services, increase in aircraft
traffic, aircraft safety, etc., are driving the demand for high speed data services. Programs
led by the National Aeronautics and Space Administration (NASA), the Federal Aviation
Administration (FAA), EUROCONTROL and Networking the Sky for Civil Aeronautical
Communications (NEWSKY) are all looking into aeronautical platforms as part of their
Aeronautical Data Network (ADN). The desire is to provide low delay, cost effective and
high speed data connectivity for aeronautical platforms. The platforms can also be used
as a relay for ground and airborne nodes. Such a capability could potentially provide data
connectivity to remote areas. Most of the current high altitude platforms, i.e., aircraft,
provide data connectivity through a satellite. However, satellite resources are limited and
expensive, and they offer limited data throughput as compared to a terrestrial network. A
potential solution is connectivity to ground stations that can provide high speed physical
layers. Since the frequency spectrum is a valuable estate and needs to be used efficiently,
the use of spectrum efficient techniques are evaluated. This dissertation discusses issues
and challenges for developing a high speed ground based physical layer for aircraft and
proposes a novel solution. A detailed analytical analysis is presented to show the issues
related to aeronautical channel and its impacts to aeronautical communication system.
Specifically, the impact of Doppler shifts that limit the use of efficient modulation schemes,
such as Orthogonal Frequency Division Multiplexing (OFDM), is presented. OFDM is
sensitive to Doppler shifts. In addition, Doppler spread and shifts in aeronautical channels
depict different characteristics compared to terrestrial networks, i.e., multiple Doppler shifts
xi
and delays. Parametric techniques are investigated to accurately estimate the Doppler
shifts. The results of parametric methods for estimating the Doppler shifts are presented.
The simulation results of MUltiple Signal Classification (MUSIC), Eigenvector (EV) and
Minimum norm methods are considered for an aeronautical channel and their performances
is presented.
5
Gagakuma, Edem Coffie. "Multipath Channel Considerations in Aeronautical Telemetry." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6529.
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This thesis describes the use of scattering functions to characterize time-varying multipath radio channels. Channel Impulse responses were measured at Edwards Air Force Base (EAFB) and scattering functions generated from the impulse response data. From the scattering functions we compute the corresponding Doppler power spectrum and multipath intensity profile. These functions completely characterize the signal delay and the time varying nature of the channel in question and are used by systems engineers to design reliable communications links. We observe from our results that flight paths with ample reflectors exhibit significant multipath events. We also examine the bit error rate (BER) performance of a reduced-complexity equalizer for a truncated version of the pulse amplitude modulation (PAM) representation of SOQPSK-TG in a multipath channel. Since this reduced-complexity equalizer is based on the maximum likelihood (ML) principle, we expect it to perform optimally than any of the filter-based equalizers used in estimating received SOQPSK-TG symbols. As such we present a comparison between this ML detector and a minimum mean square error (MMSE) equalizer for the same example channel. The example channel used was motivated by the statistical channel characterizations described in thisthesis. Our analysis shows that the ML equalizer outperforms the MMSE equalizer in estimating received SOQPSK-TG symbols.
6
Alroqi, Abdurrhman Atig. "Investigation of the heat and wear of aircraft landing gear tyres." Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/68761/.
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In aircraft, the main landing gear wheels skid on the runway at the moment of touchdown because of high slip. A slipping tyre generates enough heat to melt its rubber. Melted rubber is easily eroded by the friction force between the tyre and runway; and part of eroded rubber stays on the runway, and other is burnt off as smoke. Since the early days of airplane use, a number of ideas have been patented to improve tyre safety and decrease the substantial wear and smoke during every landing by spinning the gear wheels before touchdown. In this thesis, there are three parts of research work. First part is to find the effectiveness of the technique of pre-spinning the wheel to reduce the tyre tread heat and wear, and then choosing the initial wheel rotation speed that prevent the tread rubber from melting temperature. For achieving this, a coupled structural – thermal transient analysis in ANSYS has been used to model a single wheel main landing gear as a mass-spring system. This model has been chosen to analyze the wheel's dynamic behaviour and tyre tread temperature and wear during the short period from static to a matching free-rolling velocity in which the wheel is forced to accelerate by the friction between the tyre and ground. The tyre contact surface temperature and wear have been calculated for both the initially static and pre-spun wheels in order to compare the temperature and wear levels for different initial rotation speeds. In the second part, the required torque to spin the aircraft wheel to the required angular speed at approach speed has been calculated using ANSYS CFX, which is used to determine the wheel aerodynamic forces developed by simulation of fluid flows in a virtual environment. In the last part, several types of wind turbines have been simulated.
7
Alkandri, Ahmad. "Design and performance assessment of correlation filters for the detection of objects in high clutter thermal imagery." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/49954/.
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The research reported in this thesis has examined means of enhancing the performance of the Optimal Trade-off Maximum Average Correlation Height (OT-MACH) filter for target detection in Forward Looking Infra-Red (FLIR) imagery acquired from a helicopter and border security FLIR camera in northern Kuwait. The data acquired with these FLIR sensors allows real-world evaluation of the comparative performance of the various filters that have been developed in the thesis. The results obtained have been quantified using well known performance measures such as Peak to Side-lobe Ratio (PSR) and Total Detection Error (TDE). The initial focus was to study the effect of modifying the OT-MACH parameters on the correlation metrics. A new optimisation technique has been presented, which computes statistically the filter alpha parameter associated with controlling the response of the filter to clutter noise. A further modification of the OT-MACH filter performance using the Difference of Gaussian bandpass filter (named the D-MACH filter) as a pre-processing stage has been described. The D-MACH has been applied to several test images containing single and multiple targets in the scene. Enhanced performance of the modified filter is demonstrated with improved metrics being obtained with less false side peaks in the correlation plane, especially when multiple targets are present in the test images. A further pre-processing technique was investigated using the Rayleigh distribution as a pre-processing filter (named the R-MACH filter). The R-MACH filter has been applied to multiple target types with tests conducted across various image data sets. The filter demonstrated an improvement over the Difference of Gaussian filter in terms of 6 reducing the number of parameters needing to be tuned whilst producing further enhanced correlation plane metrics. Finally, recommendations for future work has been made to improve the use of the OT-MACH filter in target detection and identification. A novel training image representation is proposed for further investigation, which will minimise the computational intensity of using the MACH filter for unconstrained object recognition.
8
Bramer, Elinor C. "Development of a particle in cell code for the simulation of dual stage ion thrusters." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/48913/.
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This thesis focuses on the design, development and testing of a two dimensional particle in cell (PIC) code (PICSIE) written in Matlab. The code is applied to the specific problem of modelling the performance of dual stage ion thrusters. The code simulates one full aperture within dual stage ion thruster systems, focusing on the flow of ions through the aperture. Only the ions have been included in the simulation in order to minimize running time. The results produced by the simulation code are compared with results obtained from the vacuum chamber testing of the DS4G prototype, along with results from other simulation codes and research papers in order to verify the performance of the simulation code. The Dual-Stage 4-Grid (DS4G) and Dual-Stage 3-Grid (DS3G) thrusters are both sim- ulated in order to compare the performance of the two thrusters and assess the benefits and disadvantages of including the fourth grid in a dual stage thruster system. Different grid configurations are simulated in order to find the most efficient configuration of the ion optics and accelerating voltages for each thruster, with the aim being to find the con- figurations that produce the maximum particle momentum, thrust and specific impulse while minimizing the rate of erosion of the ion optics and maximising the efficiency of the thruster. These simulations are applied to the problem of deciding if the advantages provided in using a 4th grid outweigh the disadvantages compared to the 3 grid design. The results show that if erosion due to backstreaming ions is disregarded, including the fourth grid in the thruster design results in no apparent advantages in terms of the perfor- mance parameters studied in this work. The only noticeable difference between the three and four grid cases is a significant increase in the change in ion momentum observed when the fourth grid is not included in the design. The conclusion of the work is that the fourth grid should not be included in the dual stage design unless a very long lifetime is required and it is thought that erosion due to backstreaming will prevent the three grid thruster from fulfilling this criteria. The concept of propagating waves through the plasma within the ion thruster discharge chamber is investigated, with the aim of discovering any benefits and improvements in performance that may arise and forming a conclusion on whether further study on the topic of waves within the discharge chamber may be beneficial. No improvements in per- formance parameters were observed in this work, although further study in the area may show benefits to introducing waves into the plasma.
9
Langari, Mostafa. "Large eddy simulation of separated boundary layer transition under free-stream turbulence." Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/48940/.
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Physics of laminar-to-turbulent transition in a separated-reattached flow subjected to two free-stream turbulence levels have been explored using Large-Eddy Simulation (LES). Separation of the laminar boundary layer occurs at a curvature change over a flat plate with a semi-circular leading edge. A numerical trip has been used to generate the targeted free-stream turbulence levels. A dynamic Sub-grid-scale (SGS) model has been employed and excellent agreement has been achieved between the LES results and the experimental data. Detailed investigation of the LES data has been carried out to explore the primary instability mechanism at low (< 0.2%) and high free-stream turbulence (5.6%). The flow visualisations and spectral analysis of the separated shear layer reveal that the two-dimensional Kelvin-Helmholtz instability mode, well known to occur at low free-stream turbulence levels, is bypassed at a higher level leading to earlier breakdown to turbulence. The whole transition process leading to breakdown to turbulence has been revealed clearly by the flow visualisations and the differences between the low and high free-stream turbulence cases are clearly evident. Coherent structures are also visualised using iso-surfaces of the Q-criterion and for the high free-stream turbulence case the spanwise oriented two-dimensional rolls, which are clearly apparent in the low free-stream turbulence case, are not visible anymore. Detailed quantitative comparisons between the present LES results against experimental data and the previous LES results at low free-stream turbulence using a staggered grid have been done and a good agreement has been obtained, indicating that the current LES using a co-located grid with pressure smoothing can predict transitional flows accurately. Comprehensive spectral analysis of the separated shear layer at two free-stream turbulence levels has been performed. Under very low free-stream turbulence condition, a distinct regular vortex shedding and trace of the low-frequency flapping phenomena were detected. Under the higher free-stream turbulence however, a mild high-frequency activity was observed. No low frequency oscillations could be detected.
10
Shaw, Christopher G. "Modulation and Synchronization for Aeronautical Telemetry." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/3971.
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Aeronautical telemetry systems have historically been implemented with constant envelope modulations like CPM. Shifts in system constraints including reduced available bandwidth and increased throughput demands have caused many in the field to reevaluate traditional methods and design practices. This work examines the costs and benefits of using APSK for aeronautical telemetry instead of CPM. Variable rate turbo codes are used to improve the power efficiency of 16- and 32-APSK. Spectral regrowth in nonlinear power amplifiers when driven by non-constant envelope modulation is also considered. Simulation results show the improved spectral efficiency of this modulation scheme over those currently defined in telemetry standards. Additionally, the impact of transitioning from continuous transmission to burst-mode is considered. Synchronization loops are ineffective in burst-mode communication. Data-aided feed forward algorithms can be used to estimate offsets in carrier phase, frequency, and symbol timing between the transmitter and the receiver. If a data-aided algorithm is used, a portion of the transmitted signal is devoted to a known sequence of pilot symbols. Optimum pilot sequences for the three synchronization parameters are obtained analytically and numerically for different system constraints. The alternating sequence is shown to be optimal given a peak power constraint. Alternatively, synchronization can be accomplished using blind algorithms that do not rely on a priori knowledge of a pilot sequence. If blind algorithms are used, the observation interval can be longer than for data-aided algorithms. There are combinations of pilot sequence length and packet length where data-aided algorithms perform better than blind algorithms and vice versa. The conclusion is that a sequential arrangement of blind algorithms operating over an entire burst performs better than a CRB-achieving data-aided algorithm operating over a short pilot sequence.
11
Tinubi, Oluwasegun Babatunde. "Wireless Sensor Network Approach to Aeronautical Telemetry." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2454.
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Wireless sensor networks have become a rapidly growing research field in recent years. They are envisioned to have a wide range of applications in military, environmental and many other fields. We examine the performance of wireless sensor network applications to aeronautical telemetry. To date, test ranges have relied on a single telemetry ground station for the reception of packets from all air borne transmitters. We researched an alternate means of achieving this same goal with fewer resources. It is a well known fact that communication power and bandwidth are the most expensive commodities in wireless communications. The telemetry world is ever in need of ways and means to reduce power requirements of its networks while maximizing the use of available bandwidth. In our alternate method, packets will be reliably transported to a centrally located monitoring station in a series of hops. We will effectively reduce the power requirements of the network by minimizing the distance coverage of the sensor nodes. We will also explore different network topologies with a view to maximizing the use of available bandwidth. The alternate method will present a less expensive way to implement telemetry networks. Currently, telemetry networks make use of a single, huge and expensive base station receiving packets from all airplanes in test. Affordable sensor nodes placed strategically on the range and configured properly will achieve the same goal in a cost effective, power saving and bandwidth considerate manner.
12
Deric, Sanjin. "Increased Capacity for VDL Mode 2 Aeronautical Data Communication." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1376063529.
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Hogstrom, Christopher James. "A Survey of Sparse Channel Estimation in Aeronautical Telemetry." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6391.
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Aeronautical telemetry suffers from multipath interference, which can be resolved through the use of equalizers at the receiver. The coefficients of data-aided equalizers are computed from a channel estimate. Most channels seen in aeronautical telemetry are sparse, meaning that most of the coefficients of the channel are zero or nearly zero. The maximum likelihood (ML) estimate does not always produce a sparse channel estimate. This thesis surveys a number of sparse estimation algorithms that produce a sparse channel estimate and compares the post-equalizer bit error rates (BER) using these sparse estimates with the post-equalizer BER using the ML estimate. I show that the generalized Orthogonal Matching Pursuit (GOMP) performs the best followed by the Sparse Estimation based on Validation Re-estimated Least Squares (SPARSEVA-RE) and the Least Absolute Shrinkage and Selection Operator (LASSO).
14
Sultan, Sultan. "Solaris Project : The Design of a Solar Powered UAV." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-13323.
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Project Solaris is a unique student project that is carried out at Mälardalen University, Sweden. The project involves all the phases of the development and construction of a solar-powered UAV (unmanned aerial vehicle), where every subproject involves a specific assignment in the development-process. The primary task of this project is the investigation of the energy balance for the entire aircraft. In other words, calculating the power that is generated through the solar panels, and the required power to fly the aircraft and operate all the electronic systems. The total thrust from the motors is 6,6 oz (1,834 N) which is completely sufficient to fly the aircraft during cruise-flight and take-off flight. And the provided energy from the solar panels (87,8381 Wp) is enough to operate the motors and the necessary system, including the battery-charging. As a result of these factors, the aircraft will theoretically have the ability to fly “constantly” without the need of landing. The presented data shows the capacity of the aircraft and all the essential parameters. The calculations have been based on the solar-powered UAV Zephyr Qinetiq, due to the fact that Zephyr successfully have managed to fly both day and night. However, the design of the Solaris aircraft has been a little different, regarding the battery and motor choice. But it’s also important to understand that the installation of the exact same components is not fully necessary to achieve the same goal, which is a 24h-flight.
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Valenti, Carlo Alberto. "Development of a control system for an aeronautical engine." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The goal of this thesis is to develop a control system for an aeronautical engine. In particular, the engine considered is an automotive one which will be adapted for aeronautical purposes. Therefore, the engine control unit is built in Simulink®, starting from a model in LabVIEW®. The purpose of this unit is to control the engine next cycle parameters and its setpoints. Then, in order to test its effectiveness a simplified engine model is built and the whole system is tested, after a first trial of the control system. The results are presented and discussed.
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Schincariol, Mathieu. "Writing of supply chain activities manuals for a manufacturer of aeronautical parts." Thesis, KTH, Flygdynamik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265596.
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The main purpose of this project, at Safran Electronics & Defense, Mantes-La-Ville, France, was to write the manual of activities of the Supply Chain. This manual gathers all the documents needed to explain the operation of the unit and was created at the request of the quality management. After sorting out all the existing documents, the obsolete ones were deleted, the useful ones set in order and some new documents were written. The result of this work is a document containing a description of the management, organization chart, rituals, indicators, and methods of operating and the procedures of the Supply Chain unit. In the meantime, several side projects about lean management were led during this mission: a 5S methodology applied on the desktop folder of the Supply Chain, the creation of a MOOC about logistics and the reorganization of the reception part.Huvudsyftet med detta projekt, has Safran Electronics & Defense, Mantes-La-Ville, Frankrike, var att skriva en handbok om Supply Chains verksamhet. Denna handbok samlar alla dokument som behövs för att förklara enhetens funktion och skapades på begäran av kvalitetshanteringen. Efter att ha sorterat ut alla befintliga dokument, raderades de föråldrade, de användbara sattes i ordning och några nya dokument skrevs. Resultatet av detta arbete är ett dokument som innehåller en beskrivning av hantering, organisationsschema, ritualer, indikatorer, arbetssätt och förfaranden i Supply Chain-enheten. Under tiden bedrevs flera sidprojekt om Lean management under detta uppdrag: en 5S-metodik som användes på skrivbordsmappen i Supply Chain, skapandet av en MOOC om logistik och omorganisationen av mottagningsdelen.
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Paje, Vladimir Ignacio. "Equalization Techniques For Multipath Mitigation in Aeronautical Telemetry." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd774.pdf.
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Mann, Christopher Mark. "A novel 183GHz subharmonic Schottky diode mixer." Thesis, Queen Mary, University of London, 1992. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1872.
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The technique of microwave . limb sounding -from space represents a very powerful tool for determining the atmospheric processes involved in ozone depletion, the greenhouse effect, acid rain, etc.. Unfortunately, the technology involved in producing millimetric and submillimetric devices is highly complex, and miniature. The power levels and environmental conditions existing aboard spacecraft in present 'use, 5 differ from those required by the low noise heterodyne receivers employed by the Radio Astronomy community. Therefore, great effort has been spent in the design of radiometers with limited power and weight requirements, so that they can withstand the rigours of launch and operation in space. This thesis describes the design and construction of a subharmonically pumped, double diode mixer which is now used in an airborne atmospheric radiometer. The mixer power requirement and rugged nature make it an ideal option for space operation. The assembly of the millimetric circuit required the development, of novel techniques which enabled the incorporation of discrete circuit elements onto a single quartz substrate. This allowed the physical testing of the millimetric circuit independently of the RF block. A detailed investigation into the `whiskering' technique was carried out. It was thus possible to pinpoint errors that had previously occurred in assembly and which had resulted in the failure of a space flight device. With the adoption of quantified procedures, devices constructed using the `whiskering' technique were shown to be considerably more resilient than had previously been thought. The performance of the mixer is comparable with other designs using Schottky diodes at room temperature (-1200K DSB) and the local oscillator power requirement is easily met with a single solid state source. A simple theoretical analysis using the Seigel and Kerr program was undertaken in conjunction with RF measurements performed on a 65X scale model to determine steps required for further improvement.
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Arnott, Alistair Duncan. "The effect of forward sweep on a wing/body junction." Thesis, Queen Mary, University of London, 1996. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1363.
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A study has been carried out of the aerodynamic interference flow arising at the junction of a swept-forward wing, which is cambered, but without taper or twist and a flat plate on which a fully-developed, turbulent boundary layer approaches the junction. Initial CFD predictions of the pressures over the wing were carried out by the author at BAe, Hatfield. Flow visualisation tests and surface pressure measurements over the wind tunnel model were conducted at wing incidences from -3' to +9'. With the wing at 0' incidence, a single-tube yawmeter was used to explore the flow field around the leading-edge of the junction and an X-wire anemometer to examine the mean velocity and turbulence fields in the streamwise corners and at the trailing edge. The Reynolds number of the tests, based on the streamwise chord and free stream velocity of 30 m/s, was 1.03 A06. At low incidence,, a very weak separation occurred in the plate boundary layer, a very short distance upstream of the junction. However the oncoming stream converges into the junction, appearing to confine any vortical motion at the leading edge to within a very thin layer below the closest point of measurement to the plate. Rudimentary vortical flow developed slightly downstream of the leading edge, but dissipated further downstream. Although weak vortices were measured in the trailing-edge, cross-plane, these were attributed to comer separations just upstream. The turbulence activity in the streamwise corners was found to be surprisingly low, especially in the compression side of the junction. Estimates of skin-friction showed that it was lower over the majority of the trailing-edge cross-plane than in the plate boundary layer upstream of the junction. At higher incidence, flow visualisation showed that the junction region had severe stall characteristics, with 3-dimensional recirculation regions forming.
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Poprawa, Stefan. "Statistical approach to payload capability forecasting for large commercial aircraft operating payload range limited routes." Thesis, University of Pretoria, 2019. http://hdl.handle.net/2263/72847.
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Large commercial aircraft by design typically are not capable of transporting maximum fuel capacity and maximum payload simultaneously. Maximum payload range remains less than maximum range. When an aircraft is operated on a route that may exceed its maximum payload range capability, environmental conditions can vary the payload capability by as much as 20%. An airline’s commercial department needs to know of such restrictions well in advance, to restrict booking levels accordingly. Current forecasting approaches use monthly average performance, at, typically, the 85% probability level, to determine such payload capability. Such an approach can be overly restrictive in an industry where yields are marginal, resulting in sellable seats remaining empty. The analysis of operational flight plans for a particular ultra-long routing revealed that trip fuel requirements are near exclusively predictable by the average wind component for a given route, at a correlation of over 98%. For this to hold, the route must be primarily influenced by global weather patterns rather than localised weather phenomena. To improve on the current monthly stepped approach the average wind components were modelled through a sinusoidal function, reflecting the annual repetitiveness of weather patterns. Long term changes in weather patterns were also considered. Monte Carlo simulation principles were then applied to model the variance around the mean predicted by the sinusoidal function. Monte Carlo simulation was also used to model expected payload demand. The resulting forecasting model thus combines supply with demand, allowing the risk of demand exceeding supply to be assessed on a daily basis. Payload restrictions can then be imposed accordingly, to reduce the risk of demand exceeding supply to a required risk level, if required. With payload demand varying from day of week to seasonally, restricting payload only became necessary in rare cases, except for one particular demand peak period where supply was also most restricted by adverse wind conditions. Repeated application of the forecasting model as the day of flight approaches minimises the risk of seats not sold, respectively of passengers denied boarding.Thesis (PhD)--University of Pretoria, 2019.
Mechanical and Aeronautical Engineering
PhD
Unrestricted
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Karasu, Caglar. "Small-size Unmanned Model Helicopter Guidance And Control." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605595/index.pdf.
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The deployment of unmanned aerial vehicles (UAV) in military applications increased the research about them and the importance of them. The unmanned helicopters are the most agile and maneuverable vehicles among the unmanned aerial vehicles (UAV). The ability of hovering and low speed cruise makes them even more attractive. Such abilities supply more areas to deploy the usage of the unmanned helicopters like search &rescue, mapping, surveillance. Autonomy is the key property for these vehicles. In order to provide autonomy to an unmanned vehicle, the guidance and the autopilot units are designed in the first step. Waypoints are used to track the desired trajectories. The line of sight guidance is used to reach an active waypoint. In order to realize the guidance commands controllers are designed by using LQR. In addition, position and heading controllers are designed by root-locus method. The trimming and linearization are implemented in order to extract linear models used for controller design. Keywords: Helicopter, control, guidance
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Bakir, Huseyin Murat. "Mathematical Model Development Of The Anti Torque System Of A Notar Helicopter." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12610141/index.pdf.
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The anti-torque mechanism of a NOTAR helicopter is a complex system including vertical tail and pressurized tail boom which provides air ejection used for both circulation control around the boom and creating directed jet air at the end of the boom. This thesis targets the modeling of this mechanism and integrating it to a helicopter simulation model. Flight tests are performed on the MD 600N helicopter to verify the results. Finally, the simulation is compared with flight test data.
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Gezguc, Cagri. "Compressor Tandem Blade Aerothermodynamic Performance Evaluation Using Cfd." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614707/index.pdf.
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In this study, loss and loading characteristics of compressor tandem blades are evaluated. Whole study was focused on change of the total camber so called turning angle. Effects of camber change were investigated in terms of loss and loading characteristics. Methodology was increasing overall camber first by aligning angular positions of blades and second, if required, using more cambered airfoils.
2-dimensional cascade flow CFD analyses were performed to obtain loss-loading information of different tandem blade combinations. Acquired results were compared with the classical axial compressor blades&rsquoloading and loss characteristics which were obtained from literature. Results showed that most of the time tandem blade configuration performed better than the single blade counterpart in 2-dimensional cascade flow. Lastly, to clarify the benefit of the study and present the gained performance in numbers, only one cascade flow CFD analysis was performed for a classical single compressor blade. Loss and loading results were compared with the tandem blade counterpart where single and tandem configurations both having the same degree of camber. It was clearly seen that tandem blade performed better again.
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Milton, Johan, and Henrik Johansson. "Development of Trent 700 Thrust Reverser Overhaul Package." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-12492.
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This report describes a thesis project in aeronautical engineering carried out during April and May 2011 at ST Aerospace Solutions, Arlanda. The company is one of Europe’s leading aviation component maintenance companies. The task for this thesis project has been to develop a baseline overhaul work package for the thrust reverser system of the Rolls-Royce Trent 700 jet engine. An overhaul work package is a collection of maintenance work sheets (MWS) used by the maintenance organization to confirm that a specific maintenance procedure has been carried out correctly. Documenting the maintenance work performed on a component is required in order to comply with the regulations of the European Aviation Safety Agency (EASA). To be able to solve the task, the authors had to study maintenance manuals, learn the functions of the thrust reverser and get an overview of how the maintenance organization works. Much of the work has been conducted in consultation with the company’s engineering department. The result is an overhaul package consisting of approximately 40 MWS’s. These have been designed to promote traceability of actions and to be easily revisable.Denna rapport är resultatet av ett examensarbete i flygteknik som genomförts under våren 2011. Arbetet utfördes hos ST Aerospace Solutions, ett av Europas ledande företag för komponentunderhåll inom flygindustrin. Uppgiften har varit att utveckla ett översynspaket för reverseringssystemet på Rolls-Royce jetmotor Trent 700. Ett översynspaket består av en uppsättning dokument, så kallade ”maintenance work sheets” (MWS), som används för att säkerställa att underhållsorganisationen har utfört det underhåll som krävs. Detta är ett krav enligt den Europeiska luftfartsmyndigheten EASA:s Part 145. Metodiken har främst bestått i att sätta sig in i relaterad dokumentation och underhållsmanualer, samt att skapa sig en förståelse för hur reverseringssystemet och underhållsorganisationen är uppbyggda. Större delen av arbetet har utförts på plats för att kunna samarbeta och diskutera med företagets ingenjörs- och verkstadsavdelningar. Slutresultatet är ett översynspaket som innehåller ca 40 MWS:er, vilka behandlar hela underhållsprocessen. Paketet har utformats med god spårbarhet och reviderbarhet i åtanke.
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Kusztelan, Alexander. "An experimental and computational study of a twin-entry turbo charger for downsized internal combustion engines." Thesis, Kingston University, 2015. http://eprints.kingston.ac.uk/34544/.
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Trunins, Jevgenijs. "Experimental and mathematical investigation of the chaotic dripping mode." Thesis, Kingston University, 2018. http://eprints.kingston.ac.uk/41115/.
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The dynamics of fluid flow unveils complicated dynamical behaviour. Systems such as a dripping tap are no exception. Flow through a nozzle produces three different modes: periodic dripping, chaotic dripping and jetting streams. This research concentrates on a study of the chaotic behaviour of a dripping tap. This involves both mathematical model studies and experimental studies. In addition, the work involves the development of an experimental facility to allow future study of the system in microgravity conditions. The facility to achieve microgravity conditions is a Drop Tower type, which uses a novel approach to achieve these conditions. The novelty is in the use of linear electromagnetic motors. The facility was built and is in the final stage of the commissioning process, and when it is ready it will allow up to 2.12 s of test time. The mathematical model uses an existing Mass-Spring-Damper model, with Reynolds numbers between 4 to 175, and a step size of 0.4. The results showed multiple bifurcation regions appearing before chaotic regions. Similarly, experimental results showed that some instabilities exist in this region. The model also explained and showed multiple bifurcations and an increase in dripping time due to instabilities, and has identified that those processes are due either to perturbations of the system or due to initial instabilities of the system. These results were confirmed by experiment. To achieve the required experimental goals a test module was developed whose requirements were set to fulfil the microgravity experiment conditions, in case future research is required. The experimental results showed some similarities with the mathematical model. At the same time, there was found to be quite a lot of disagreement. Results identified two different limit cycle attractors in periodic dripping mode: strong single-point attractors and regional attractors. Also, limit cycle attractors and strange attractors in chaotic mode were identified. More importantly, it has been identified that the chaotic region consists of areas where the system is stable (and produces a single region attractor), and others where the system is not (and this produces strange attractors), and there are points where, depending on the disturbances to the system, both types can be observed. The work done has led to several discoveries and achievements. Although the Drop Tower project could not be completed it may nonetheless be considered as a success. The facility has been fully assembled and calibrated to meet the set of design requirements, and to some extent was commissioned allowing future progress to discover modification requirements. The study of the Mass-Spring-Damper model led to the conclusion that the model is oversimplified and in its current state should be used only for descriptive purposes, when illustrating chaotic behaviour. Additionally, it was found that the model predicts bifurcations outside the experimentally determined chaotic region. Nevertheless, the work identified some possible improvements to the model. Experimentally it was found that the region of chaotic behaviour is located around a Reynolds number of 43 in contrast to what was previously reported. The study of the periodic dripping region showed that the system, if disturbed, can develop history dependent phenomena (where the subsequent drop periods follow a well identified sequence). Satellite drops were discovered to exist beyond the previously predicted value of flow rate. It was discovered that the fluid supply system can have a major effect on the drop dynamics (different types of post-detachment developments were found - termed here regular residual mass and wetted mass - along with the discovery of different types of drop detachment (regular mass, mid-size drops and jets) coexisting within the chaotic region. The drop horizontal disturbance study led to the unconfirmed discovery of two modes of vibrations, where the system response follows a standard damped response and an amplitude modulated damped response.
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Levermore, Thomas. "Innovative powertrain control systems for a premium vehicle." Thesis, Kingston University, 2017. http://eprints.kingston.ac.uk/40642/.
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In order to meet increasingly strict regulations on vehicle emissions, manufacturers are seeking ways to produce vehicles that emit less pollution and consume less fuel. Eco-driving is the optimisation of velocity and gear selection in existing vehicles to reduce fuel consumption and such reductions can be made at relatively low development costs compared to powertrain modification. However, the driving experience of a premium vehicle could be compromised if the vehicle behaviour differs from that which is expected by the driver and the acceptance of such fuel saving measures may be diminished. Therefore, in order to maintain the driving experience the contribution of this work is the development and implementation of an optimal control algorithm based on Dynamic Programming which optimises, in real time, the vehicle velocity and gear selection based on a vehicle and upcoming road model while consideration is given to objective measures of driveability. The algorithm is deployed on a Raspberry Pi miniature computer with connection to the vehicle data network. Fuel savings and time savings are identified with the optimisation algorithm both with and without violating constraints on driveability, first in simulation and finally in a real-time, in-vehicle eco-driving feedback system. Primarily the application of this system is in internal combustion engine passenger vehicles in both urban and extra-urban road situations, however the approach is deliberately flexible to allow development for other powertrain configurations.
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Bostanci, Sevket Can. "Low carbon sustainable concrete design and construction." Thesis, Kingston University, 2015. http://eprints.kingston.ac.uk/34545/.
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Chiel, Benjamin S. "Autonomous parafoil guidance in high winds." Thesis, Boston University, 2013. https://hdl.handle.net/2144/21117.
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Thesis (M.Sc.Eng.)Guided airdrop systems lacking propulsion may be adversely affected by high winds. Strong winds encountered during Draper Laboratory flight testing prevented lightweight parafoil systems from landing accurately. This thesis introduces and compares multiple guidance strategies designed to address high wind scenarios in cases of differing wind knowledge fidelity. The algorithms presented significantly improve performance in high tailwind and shifting wind scenarios without compromising miss accuracy in standard wind conditions. This adds additional capability to parafoil guidance by substantially increasing the conditions under which accurate landings are possible.
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Marangoz, Alp. "Evaluation Of A New Turbulence Model For Boundary Layer Flows With Pressure Gradient." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606496/index.pdf.
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In this thesis, a new turbulence model developed previously for channel and flat plate flows is evaluated for flat plate flows with pressure gradient. For this purpose a flow solver, which uses boundary layer equations as the governing equations and Von Karman momentum integral equation for the calculation of skin friction, is developed.
It is shown that the error of the new turbulence model, in predicting the velocity profile, is less than 5 % for the flat plate flows without pressure gradient and less than 10 % for the flat plate flows with favorable pressure gradient. It is also shown that results with an error in the order of 20 % can be achieved for the flat plate flows with adverse pressure gradient.
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Ercin, Gulsum Hilal. "Flight Simulation And Control Of A Helicopter." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12610194/index.pdf.
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In this thesis the development of a nonlinear simulation model of a utility helicopter and the design of its automatic flight control system is addressed. In the first part of this thesis, the nonlinear dynamic model for a full size helicopter is developed using the MATLAB/SIMULINK environment. The main rotor (composed of inflow and flapping dynamics parts), tail rotor, fuselage, vertical stabilizer, horizontal stabilizer of the helicopter are modeled
in order to obtain the total forces and moments needed for the flight simulation of the helicopter. Total forces and moments are used in 6 degrees of freedom equations of motion model and helicopter states are calculated for the specified flight conditions such as hover and forward flight. Trim and linearization programs are developed. The linearized models of hover and forward flight conditions are used for the automatic flight control system design. Automatic flight control system model consists of necessary systems in order to ease the pilot control of the helicopter. A classical inner stability loop and outer flight directory mode approach is taken to design the automatic flight control system. For the inner stability loop both classical rate feedback and truncated system state feedback control approaches are used. The outer loop modes implemented are heading hold, attitude hold (pitch, roll), altitude acquire and hold mode for hover condition and heading hold, attitude hold (pitch, roll), altitude acquire and hold mode and airspeed hold for forward flight condition. Finally, the success of the controllers are demonstrated through nonlinear simulations for different flight directory modes in hover and forward flight conditions.
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Prach, Anna. "Robust Controller Design For A Fixed Wing Uav." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610878/index.pdf.
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This study describes the design and implementation of the pitch and roll autopilots for a fixed wing unmanned vehicle. A Tactical Unmanned Aerial Vehicle (TUAV), which is designed at the Middle East Technical University (METU), is used as a
platform. This work combines development of the classical and robust controllers, which are used for the pitch and roll autopilots. One of the important steps in the thesis is development of the non-linear dynamic model of the UAV, which is developed in MATLAB/Simulink environment. Two different strategies of the controller design imply development of the PID and controllers. Simulation results illustrate the performances of the designed controllers. Simulation is
performed for the nominal model of the UAV and for the model that includes uncertainties and sensor noises.
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Yemenici, Oznur. "Investigation Of Rotor Wake Interactions In Helicopters Using 3d Unsteady Free Vortex Wake Methodology." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611374/index.pdf.
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This thesis focuses on developing and examining the capabilities of a new in-house
aerodynamic analysis tool, AeroSIM+, and investigating rotor-rotor aerodynamic
interactions for two helicopters, one behind the other in forward flight. AeroSIM+ is a 3-D
unsteady vortex panel method potential flow solver based on a free vortex wake
methodology. Validation of the results with the experimental data is performed using the
Caradonna-Tung hovering rotor test case. AeroSIM+ code is improved for forward flight
conditions so that, the blades are allowed to move according to the rotor dynamics. In the
simulations, blade airload prediction is seen to be sensitive to changes in vortex core size.
Blade Vortex Interaction (BVI) locations differ depending on the relative position of the rear
rotor with respect to the front rotor as well as on the forward flight speed. It was observed
that the performance characteristics of the rear rotor alter depending on the relative positions
of the rotors within the asymmetric wake flow field. The results of this thesis study such as
the computed forces and moments on each rotor and the frequency characteristics of these
loads can be also used in helicopter dynamics simulators.
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Elfarra, Monier A. K. "Horizontal Axis Wind Turbine Rotor Blade: Winglet And Twist Aerodynamic Design And Optimization Using Cfd." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612987/index.pdf.
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The main purpose of this study is to aerodynamically design and optimize winglet, twist angle distribution and pitch angle for a wind turbine blade using CFD to produce more power. The RANS solver of Numeca Fine/Turbo was validated by two test cases, the NREL II and NREL VI blades. The results have shown a
considerable agreement with measurements for both cases. Two different preconditioners have been implemented for the low Mach number flow. The results have shown the superiority of Merkle preconditioner over Hakimi one and Merkle
was selected for further simulations. In addition to that, different turbulence models have been compared and the Launder &ndashSharma has shown the best agreement with measurements. Launder &ndash
Sharma was chosen for further simulations and for the design process. Before starting the design and optimization, different winglet configurations were studied. The winglets pointing towards the suction side of the blade have yielded higher power output. Genetic algorithm and artificial neural network were implemented in the design and optimization process. The optimized winglet has shown an increase in power of about 9.5 % where the optimized twist has yielded to an increase of 4%. Then the stall regulated blade has been converted into pitch regulated blade to yield more power output. The final design was produced by a combination of the optimized winglet, optimized twist andbest pitch angle for every wind speed. The final design has shown an increase in power output of about 38%.
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Pavelec, Sterling Michael. "The development of turbojet aircraft in Germany, Britain, and the United States : a multi-national comparison of aeronautical engineering, 1935-1946 /." The Ohio State University, 2004. http://www.ohiolink.edu/etd/send-pdf.cgi/Pavelec%20Sterling%20Michael.pdf?acc_num=osu1082396007.
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Kahvecioglu, Alper. "A Tool For Designing Robust Autopilots For Ramjet Missiles." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607058/index.pdf.
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The study presented in this thesis comprises the development of the longitudinal autopilot algorithm for a ramjet powered air-to-surface missile. Ramjet Missiles have short time-of-flight, however they suffer from limited angle of attack margins due to poor operational-region characteristics of the ramjet engine. Because of such limitations and presence of uncertainties involved, Robust Control Techniques are used for the controller design. Robust Control Techniques not only provide an easy limitation/uncertainty/performance handling for MIMO systems, but also, robust controllers promise stability and performance even in the presence of uncertainties of a pre-defined class. All the design process is carried out in such a way that at the end of the study a tool has been developed, that can process raw aerodynamic data obtained by Missile DATCOM program, linearize the equations of motion, construct the system structure and design sub-optimal H∞
controllers to meet the requirements provided by the user. An autopilot which is designed by classical control techniques is used for performance and robustness comparison, and a non-linear simulation is used for validation. It is concluded that the code, which is very easy to modify for the specifications of other missile systems, can be used as a reliable tool in the preliminary design phases where there exists uncertainties/limitations and still can provide satisfactory results while making the design process much faster.
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Susuz, Umut. "Aeroelastic Analysis Of An Unmanned Aerial Vehicle." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609225/index.pdf.
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In this thesis aeroelastic analysis of a typical Unmanned Aerial Vehicle (UAV) using MSC®FlightLoads and Dynamics module and MSC®
NASTRAN Aero 1 solver was performed. The analyses were carried out at sea level, 1000m, 2000m and 4000m altitudes for Mach Numbers M=0.2, 0.4 and 0.6 for the full model of the UAV. The flutter characteristics of the UAV for different flight conditions were obtained and presented. The effect of altitude on flutter characteristics has been examined and compared with the theoretical and experimental trends in the literature. Also the divergence characteristics of the full model UAV was obtained. In the study, some verification and test cases are also included. The results of the analyses of an untapered swept-wing and AGARD 445.6 wing models were compared with wind tunnel data and a maximum error of 1.3 % in the flutter speed prediction was obtained. In two different wing models the effect of taper was investigated.
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Yucekayali, Arda. "Development Of A Comprehensive And Modular Modelling, Analysis And Simulation Tool For Helicopters." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613643/index.pdf.
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Helicopter flight dynamic, rotor aerodynamic and dynamic analyses activities
have been a great dispute since the first helicopters, at both design and test stages.
Predicting rotor aerodynamic and dynamic characteristics, helicopter dynamic
behavior and trimmed flight conditions is a huge challenge to engineers as it
involves the tradeoff between accuracy, fidelity, complexity and computational cost.
Flight dynamic activities such aspredicting trim conditions, helicopter dynamic behavior and simulation of a flight condition or maneuver mostly require analysis tools with low computational cost and complexity. However this decreases accuracy and fidelity of the model. On the other hand, analyses at design stages, such as
blade geometric and structural design mostly requires accurate and higher fidelity aerodynamic load predictions over the rotor disk. Contrarily this brings high computational cost and complexity. Therefore separate analysis tools for each objective or one complete tool that can be used for all purposes are essential. Throughout this study a helicopter mathematical including trim model with a selective and modular structure is developed as a generic analysis tool. The selective structure enables the mathematical model to be used in both flight dynamic and comprehensive analysis while the modular structure plays a role as an infrastructure for further developments. The mathematical model developed is validated with flight test data of several helicopters. Besides, commercial helicopter comprehensive analysis tools are used to validate the mathematical model analyses. Results showed good agreement with the compared data.
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Babahaji, Meibodi Amir. "On-site concrete waste minimisation in Iran." Thesis, Kingston University, 2015. http://eprints.kingston.ac.uk/35583/.
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Construction waste minimization and management plays an efficient role in achieving sustainability by providing appropriate consideration to the environment, community, and social conditions by delivering built assets. The construction industry has a significant effect on the environment in terms of resource consumption and waste production. Recent statistics published by the UK Government disclose that the construction and demolition sector generates approximately 32% of the total waste in the UK, which is three times more than the waste generated by all households combined. Concrete has been a leading construction material for more than a century. However, current and on-going studies in the field of construction waste minimization and management mostly focus on general waste management or examine one specific method of waste minimization. While only a limited number of studies have been conducted to examine on-site concrete waste minimization, the literature reveals that research in this context is required. This research aimed to propose an on-site concrete waste minimisation framework (OCWMF) for construction projects, which could potentially be applicable and achievable in Iran. In this pursuit, six objectuves were determined to guide the research, which are: to identify the common methods on OCWM in the UK as a successful pattern in WM; to rank OCWM methods in UK; to rank OCWM methods in Iran; to identify the differences between common methods of OCWM in the UK and Iran and explore the possible causes of these differences; and to investigate the causes of differences in the favoured methods in the UK and the favoured methods in Iran. Finally, the last objective was to propose a framework for Iran. Both quantitative and qualitative strategies as well as a combination of qualitative and quantitative strategies were adopted for this research. Data was collected through face-to-face semi-structured interviews in the UK (N=5), a self-administered postal questionnaire survey in the UK (N=196 distributed, N=73 received), a self-administered postal questionnaire survey in Iran (N=196 distributed, N=110 received), and face-to-face semi-structured interviews in Iran (N=10). Interviewees were project managers, site superintendents, consultants, and engineers selected from the top 100 contractor companies and the top 100 consultant companies in the UK and in Iram. The questionnaire questions were developed on the findings of the literature review and the semi-structured interviews in the UK. Then, to examine the outcomes of interviews in Iran, three case studies in Iran was observed. Finally, emanating from study results, an OCWMF was developed and refined using discussions (N=2), a questionnaire (N=6), and interviews (N=7). Key findings that emerged from the study include: legislation and regulations in the UK are the main drivers for construction waste reduction; governmental initiatives in reducing waste, use of pre-fabricated building components, and education and training are the most recommended OCWM methods in the UK in terms of overall worthiness or spending to create savings or minimize waste; governmental incentives to reduce waste, education and training, and purchase management are the most recommended methods in Iran; the main differences between proposed OCWM methods in Iran and in the UK are in the use of pre-fabricated concrete elements (PCEs) and ready-mix concrete; the cost of using PCEs in the main cause of difference in methods between the countries; and the consultants and contractors involved in the case study were not interested in using PCEs in their projects due to the high costs involved despite the significant reduction in waste when this method is used. In conclusion, the framework proposed various remedies that could potentially be used for improving OCWM in Iran. This study has also made some recommendations for the industry, policy makers, and for further research. The content should be of interest to contractors, clients, and engineers.
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Cellier, Antony Hermann Guy. "Detection and Identification of Instability and Blow-off/Flashback Precursors in Aeronautical Engines using Deep Learning techniques." Thesis, KTH, Kraft- och värmeteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-272079.
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The evolution of injection processes toward more fuel efficient and less polluting combustion systems tend to make them more prone to critical events such as Thermo-Acoustic Instabilities, Blow-Off and Flash-Back. Moreover, the addition of Di-Hydrogen as a secondary or as the main fuel is in discussion by aeronautical engines manufacturers. It drastically modifies the stability of the system and thus raise several interrogations concerning the multiplicity of its use. Being able to predict critical phenomena becomes a necessity in order to efficiently operate a system without having to pre-test every configuration and without sacrificing the safety of the user. Based on Deep Learning techniques and more specifically Speech Recognition, the following study presents the steps to develop a tool able to successfully detect and translate precursors of instability of an aeronautical grade swirled injector confined in a tubular combustion chamber. The promising results obtained lead to proposals for future transpositions to real-size systems.Utvecklingen av injektionsprocesser mot mer bränsleeffektiva och mindre förorenande förbränningssystem, tenderar att göra dem mer benägna att utsättas för kritiska händelser som Thermo-Acoustic Instabilities, Blow-Off och Flash-Back. Dessutom diskuterar flygmotorkonstruktörer möjligheten att använda Dihydrogen som sekundärt eller som huvudbränsle. Det modifierar drastiskt systemets stabilitet och det väcker frågan hur man kan använda det effektivt. Att kunna förutsäga kritiska fenomen blir en nödvändighet för att använda ett system utan att behöva att på förhand testa varje konfiguration och utan att reducera användarens säkerhet. Baserat på Deep-Learning-tekniker och Speech-Recognition-tekniker, presenterar följande studie stegen för att utveckla ett verktyg som kan upptäcka och översätta föregångare till instabilitet hos en swirled flygmotorerinsprutningspump som är innesluten i en förbränningskammare. De lovande resultaten leder till idéer om hur man kan anpassa det här verktyg till ett system i verklig storlek.
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Adnan, Adnan. "Development of outsourcing decision models for small and medium sized manufacturing companies." Thesis, Kingston University, 2011. http://eprints.kingston.ac.uk/20336/.
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Global markets are continuously developing and becoming extremely competitive. The manufacturing organisations are improving their capabilities and responsiveness to satisfy their customer demands. Due to this dynamic change, most of the developed countries, particularly the United Kingdom, Europe and the United States have witnessed a sharp increase in outsourcing. A literature search revealed weakness in outsourcing, due to the lack of suitable decision models and frameworks. However, limited research has been carried out in the area of outsourcing of manufacturing in small and medium sized companies. The main aims of this research are formulating appropriate decision models for small and medium sized companies; in particular, those that have been outsourcing, or planning to outsource, their manufacturing activities. The outsourcer's criteria for outsourcee selection for small and medium sized manufacturing companies are chosen after analysing the data obtained through the literature survey, questionnaire survey and personal interviews. Next, a model is formulated for numerical evaluation of outsourcer's criteria for outsourcee selection. Then, a second model for outsourcee (supplier) selection is formulated. The model comprises analytical hierarchy process, cluster analysis and criteria scoring of outsourcee. In the selection process of the most appropriate outsourcee, three elements has to be considered; the previously defined i) vector of important criteria resulted from the information analysis of literature survey, questionnaire and interviews, ii) the specific criteria ranking scoring identified by a particular outsourcer company and iii) the fulfilment of both general criteria (business / market) and specific criteria (outsourcer company) by the potential outsourcees. The outsourcee that achieves the highest total score based on the priority weights of each criterionand sub-criterion in the model may be considered the most suitable. The numerical results of the second model are compared against the empirical outcome of a test case is satisfactory. The developed method is consistent, faster and objective. A further model for drawing up and implementing a manufacturing level agreement was formulated, based on the information collected through the literature survey, questionnaire survey and interviews. The above models were presented to the managers of the companies and are found to be useful according to the feedback provided by them. They will be using the models in stages, subject to the resource availability.
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Shakouri, Payman. "Designing of the adaptive cruise control system-switching controller." Thesis, Kingston University, 2012. http://eprints.kingston.ac.uk/22970/.
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Over the recent years, a considerable growth in the number of vehicles on the roads has been observed. This increases importance of vehicle safety and of minimization of fuel consumption, subsequently prompting manufacturers of cars to equip their products, with more advanced features such as Adaptive Cruise Control (ACC) and Collision Avoidance and Collision Warning System (CWS). In this thesis we concentrate on new methods for ACC. This work will include: Design of the simulation models suitable for this application, Investigation and design of suitable hybrid control algorithm by using classical and advanced control algorithm's consisting of the gain scheduling PI and Linear Quadratic (LQ) controllers, Design of the Nonlinear Model Predictive Control (NMPC) and the nonlinear Balance-Based Adaptive Control (B-BAC), Real-time implementation and tests of the algorithms by using NI Lab View Starter Kit Robot from National Instruments, Implementation and tests of the models and the controllers in MA TLAB/Simulink(R). The applications of the different control methods in the ACC are tested and compared against different traffic scenarios considering both velocity tracking (CC) and distance tracking (ACC) modes. Judging about the performance of ACC by utilizing the two advanced control methods; B-BAC and NMPC includes trade-offs between tracking-distance and velocity and the vehicle acceleration. However, both the B-BAC and the NMPC has demonstrated significantly smoother responses in controlling the throttle and the brake compared to PI control and linear MPC which in tum could improve the vehicle acceleration and fuel efficiency. The methods in order of producing better performance in terms of the values of control errors and their influences on fuel saving; NMPC, B-BAC, linear MPC and PI control. Improvement of fuel efficiency is investigated in this thesis through two approaches; first, by calculating the optimal control actions corresponding to the throttle and the brake signals through utilising the advanced control methods, second, by reducing the engine speed to idle speed during coast phase of the vehicle which causes the engine friction to be reduced. The engine speed can be reduced through transition between locked and unlocked states of the torque convertor. Possibility of achieving fuel efficiency through coasting in the vehicle has been investigated in the simulation and it has been demonstrated that longer coasting duration could be achieved i.e. more distance can be covered, and the fuel efficiency could be improved.
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Cazan, Adrian Mirel. "Reduction of whirl instability in externally pressurised gas journal bearings." Thesis, Kingston University, 2002. http://eprints.kingston.ac.uk/20696/.
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One major limitation in the use of externally pressurized air bearings (EPB) is their susceptibility to vibrations problems. The most destructive vibration that develops in a gas bearing is self-excited whirl, which commences when the damping force in the bearing becomes zero. The main aim of this research was to undertake a theoretical investigation of cylindrical whirl in a balanced vertical axis EPB, and ways of delaying its onset. In order to do this, it was necessary firstly to find the bearing static stiffness and damping coefficients by means of a compressible flow analysis of the gas. To do this, by employing Mathematica, a novel approach used the 'shooting method' in order to solve the governing differential equation (which included functions of a complex variable). The results obtained compared very favourably with previous theoretical published work that had employed finite difference methods. Having found the bearing coefficients, it was possible to solve the bearing dynamic differential equations and thus create stability maps. This procedure was carried out on various bearing arrangements aimed at raising the stability threshold. These included: A series arrangement involving a non-rotating externally pressurized sleeve round the rotor as well as a series arrangement in parallel with the main bearing. The series-parallel configuration resulted in a bearing with a threshold speed and stiffness between the extremes of a simple EPS and a series EPB, all three designs being of the same length. An optimum adjustment of the series-parallel geometry, created threshold speeds three to four times that of a simple version. This in itself was an excellent achievement. Finally, a further increase in threshold frequency, up to seven times that of an equivalent simple EPB, was attained by an additional novel design round the sleeve of a passive eddy current magnetic damper.
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Mason, Julian. "Guided-wave optical and hybrid sensor systems." Thesis, Kingston University, 1995. http://eprints.kingston.ac.uk/20587/.
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This thesis is concerned with the development of new fibre optic based sensors for liquid level and temperature measurement. For the measurement of fluid level an intrinsic sensor has been developed whereby the fibre itself forms the sensing medium. This fibre is made from a plastic, doped with a dye that fluoresces when illuminated by ultra-violet light. The sensing fibre is continuously illuminated but the fluid around it absorbs the light and hence the fluid level controls the intensity of light generated within the fluorescing fibre. The measurement of temperature forms the bulk of this thesis with liquid crystals being used as the transducing medium. Many different schemes have been investigated and characterised using their thermochromic, light scattering, and electro-optic properties. The latter necessitated the production of miniature photovoltaic devices which, apart from being a novel way of generating quasi-regulated electrical power, provide an alternative approach to energising many other types of hybrid sensor systems that at present are forced to use more complex techniques. Finally a simple theory has been developed to describe the behaviour of the liquid crystal based systems. The theory has been solved numerically and is in good agreement with the experimental results.
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Papadopoulos, Christopher A. "Aileron augmented directional control and braking." Thesis, Kingston University, 2000. http://eprints.kingston.ac.uk/20656/.
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Current landing and braking systems are associated with the approach, flare and rollout. Automatic and independent brake systems prevent skidding but do not restore the aircraft to the original trajectory. None use the normal aerodynamic surfaces to augment braking effectiveness to steer the aircraft during sudden changes in runway surface conditions. Many aircraft accidents occur during landing. The task of bringing the aircraft to a safe taxing speed from touchdown in variable weather conditions is the most difficult manoeuvre that a pilot has to make. There is no opportunity to recover or reattempt the manoeuvre. It is the only phase of the aircraft operation that has not been effectively improved through the use of autopilot control systems. Improving this regime of operation through the use of formally redundant aerodynamic control surfaces is the subject of this thesis. This thesis describes the development and testing of a controller, auto-pilot and ABS combination that uses ailerons to control the normal loading differential between the main gear of a B747-100 for the purpose of increasing the directional control so that is it possible to either minimising the centre line off-set or to maintain heading of a landing aircraft. The aileron based differential nonnal loading controller uses the brake line pressure differential as an input variable to control the ailerons during touchdown. During the II maximum braking case, the brake line pressure is proportional to the difference in runway friction coefficient, normal loading, and brake disk stack friction coefficient. Landing aircraft are extremely non-linear in function. To overcome this, a model and Controller that generates the appropriate non-linear mathematical description of the aircraft during the landing phase and generates an effective controller that effectively generates an increase in normal gear force on touch down of 100% and thereby allowing the aircraft to be controlled in direction during hazardous conditions was developed. The outcome of the work is that the use of a control scheme and unconventional use of ailerons can significantly improve aircraft landing characteristics during adverse landing weather conditions and reduce the number of accidents. Current advances in future aircraft design are tending towards tailless aircraft such as Boeing's Blended Wing Body aircraft and a similar study by Airbus. These aircraft do not have sufficient rudder or engine yaw control at landing speeds. This work provides a method of steering the aircraft from touchdown to taxi speed through normal force and brake augmentation.
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Petkova, Diana. "Behaviour of RC beams strengthened with CFRP laminates at elevated temperatures." Thesis, Kingston University, 2010. http://eprints.kingston.ac.uk/20332/.
Full textAbstract:
Strengthening of existing structures has become an important aspect of civil engineering. Various methods exist and have been developed in the last few decades one of which has become increasingly popular- strengthening using fibre reinforced polymers. Their excellent mechanical properties and resistance to different environmental conditions make them a viable alternative to the traditional materials like concrete and steel. In this study the effect of elevated temperatures on the behaviour of FRP strengthened reinforced concrete beams is investigated. The behaviour of reinforced concrete beams strengthened with FRF laminates has been investigated by different researchers in the last two decades. Ultimate load, failure modes and improved techniques for strengthening have been the main areas of interest. As a result of the extensive research several classifications and design guidelines have been proposed to ensure better performance and prevent premature failures of the systems. One important aspect of the strengthening is the susceptibility of polymers to significant and rapid reduction of their strength when exposed to elevated temperatures and fire. Little research has been done up-todate on the residual properties of FRP strengthened systems after heating and cooling. Three experiments have been conducted for the purpose of this study. The bond strength of CFRP strengthened systems is first investigated for temperature range of 20°C to 300°C. The behaviour of small-scale strengthened beams during the heating process is presented next. The third experiment is then designed to determine the residual flexural capacity of the heated and cooled minibeams. The results are presented and compared indicating residual strength of the systems to 30% compared to their performance at room temperature
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Duran, Olga. "Automated camera/laser-based pipe inspection." Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407464.
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Hadavinia, Homayoun. "Boundary element with blending shape functions for potential problems." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.554983.
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Ghasemnejad, Hessammaddin. "Effects of delamination failure in crashworthiness of laminated composite box structures." Thesis, Kingston University, 2009. http://eprints.kingston.ac.uk/20058/.
Full textAbstract:
The brittle nature of the most of fibre reinforced polymer (FRP) composites causes they show high capability in absorbing the impact energy in vehicular structures. This energy absorption is introduced by various fracture mechanisms. In this regard, the fracture study is one of the most important areas to be considered in investigating the energy absorption capability of composite box structures. Various fracture mechanisms such as fibre breakage and buckling, matrix cracking and crushing, debonding at the fibre-matrix interface and especially plies delamination play important roles in progressive failure mode and energy absorption of composite tubes. Delamination occurs as results of shear and tensile separation between fronds. The main objective of this research is to study the effects of interlaminar fracture toughness on the progressive energy absorption of composite structures under quasi-static loading. In this regard, Mode-I, Mode-II and mixed-Mode I/II interlaminar fracture toughness of various types of FRP composites with various laminate designs are studied experimentally to investigate the relationship between interlaminar crack propagation and the energy absorption capability and crushing modes of composite structural elements. The combination of brittle fracture, lamina bending, local buckling and transverse shearing crushing modes was found from experimental studies. New analytical solutions based on friction, bending and fracture mechanisms were proposed to predict the mean crushing force for each of these failure modes. The crushing process of composite boxes was also simulated by finite element software LS-DYNA and the results were verified with the relevant experimental and analytical results.
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Claus, Malcolm. "Jet interaction effects on a hypersonic interceptor." Thesis, Kingston University, 2001. http://eprints.kingston.ac.uk/20674/.
Full textAbstract:
A series of experiments were undertaken at the Defence Evaluation Research Agency (DERA) Farnborough, within the Aero Physics group into the phenomenon called Jet Interaction (JI). Jet Interaction (JI) is produced by the interaction of a jet with the external flow around a vehicle. This study focused on investigating the effects of a divert thruster employed to provide a vehicle with a rapid divert capability on the external flow-field and on the induced forces and moments exerted on the vehicle by the jet. The research was based on studying the effects on a hypersonic interceptor sometimes referred to as a KKV (Kinetic Kill Vehicle). There are many important parameters in JI. One of these is the jet Amplification Factor (AF). This is caused by the deflection of the free-stream around and over the jet and results in a pressure increase on the vehicle surface which adds to the divert thrust force. The experiments were carried out in the intermittent hypersonic gun tunnel, at a free-steam Mach number of 12.1. This produced a Reynolds number (based on diameter) Red of 300,000 with a one-tenth scale vehicle; these conditions correspond to a full-scale vehicle flying at an altitude of 41 km. To simulate the divertthruster, nitrogen was supplied to the model through a purpose-made force balance. Measured forces ineluded normal, axial and side as well as pitch and yawing moments. The experimental results have been compared with that of a full size vehicle featuring a 2kN divert thruster. The results have then been matched to the effective altitude as a function of the thrust coefficient (Cr). This allows the experimental data to be interpreted for a full-scale vehicle in order to answer design questions important to system engineers. The results from this investigation show that the effectiveness of a divert jet is influenced by the vehicle's altitude, achieving a negligible increase in AF with a Cr > 2.5 at an altitude > 50 km. The seeker will suffer from jet induced problems at low Cr levels for a. = 10°. An increase in Cr causes the separation region in front of the jet to extend to the nose of the tested configuration for M1 = 12.1 while complete separation is achieved at Cr > 1.2. Injection Mach number (MJ) has a small influence on AF. However it does not influence the separation region. Penetration height (h) of the jet is increased for higher Mach number injection. Both AF and the separation region are influenced by nozzle geometry. A series of different nozzle geometries were tested. These had the effect of reducing the measured amplification factor to a maximum of 1, except for the dual circular orifice combination, which doubled the measured AF achieved for a single circular orifice. The influence of nozzle geometry reduced the Cr levels required to produce a negligible increase in AF and the corresponding altitude. The angle of attack (œ) has a strong influence on AF at low Cr levels, however it becomes negligible when complete separation is achieved.