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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Teslova bezlopatková turbina / Tesla Bladeless Turbine

Lokaj, Jakub January 2016 (has links)
The diploma thesis describes design of bladeless machine known as a Tesla turbine. The work is divided into theoretical part, practical part involving the design and experimental measurements of made bladeless turbine and a final assessment of thesis. The theoretical part deals with the basic design features of bladeless machines and their design modifications and flow in the nozzles. Furthermore there is a dedicated part of the dynamics of working fluid in the rotor of bladeless turbine represented by CFD modeling. The practical part includes the design and construction of parts of the turbine on a preliminary calculation using an analytical model of the flow in the turbine. The designed turbine components were checked for operational safety with structural calculations of shaft and disk impeller. The thesis was also performed experimental measuring of parameters of designed bladeless turbine. Measured values were compared with the analytical model which predicted turbine efficiency. In conclusion, besides to assessment, thesis also outlines possible proposals for further improvements of constructed bladeless turbine.
72

GNSS Safety and Handling

Björklund, Axel January 2022 (has links)
Satellite navigation (such as GPS) has become widely successful and is used by billions of users daily. Accuratepositioning and timing has a wide range of applications and is increasingly being integrated in safety criticalsystems such as autonomous operations, traffic management, navigation for airplanes and other vehicles. Thesecurity and vulnerabilities of satellite navigation is however often not considered in the same way as for exampledata security, even though the high efficacy of spoofing with off-the-self software-defined radio (SDR) has beendemonstrated repeatedly. The lack of concern comes partially from the lack of options as satellite navigationauthentication has not previously existed in the civil domain.This work benchmarks the anti-spoofing and signal level measurements of commercial receivers in both simulatedand real-world scenarios and implements additional anti-spoofing measures. The additional anti-spoofingmeasures are implemented using no additional information than what the receiver should already have accessto in any modern commercial vehicle. Upcoming EU regulation 2021/1228 for vehicles used in internationaltransport will also mandate the use of these three anti-spoofing measures by August 2023. Here receiver time isverified by the means of Network Time Protocol (NTP) and real time clock (RTC); receiver motion is verifiedby the means of dead reckoning and inertial measurement unit (IMU); receiver navigation data is verified by themeans of asymmetric cryptography and Galileo Open Service Navigation Message Authentication (OSNMA).The computational overhead is analyzed as well as cost and worldwide Market feasibility. We estimate thateven basic timing devices would only have to perform one NTP request every 17 days and a microcontrollerpowerful enough to do OSNMA costs less than $2. Finally, the benefits of multi-band receivers and futuredevelopments in both the user and space segments are discussed.
73

Modelling cortical laminae with 7T magnetic resonance imaging

Wähnert, Miriam 12 May 2014 (has links)
To fully understand how the brain works, it is necessary to relate the brain’s function to its anatomy. Cortical anatomy is subject-specific. It is character- ized by the thickness and number of intracortical layers, which differ from one cortical area to the next. Each cortical area fulfills a certain function. With magnetic res- onance imaging (MRI) it is possible to study structure and function in-vivo within the same subject. The resolution of ultra-high field MRI at 7T allows to resolve intracortical anatomy. This opens the possibility to relate cortical function of a sub- ject to its corresponding individual structural area, which is one of the main goals of neuroimaging. To parcellate the cortex based on its intracortical structure in-vivo, firstly, im- ages have to be quantitative and homogeneous so that they can be processed fully- automatically. Moreover, the resolution has to be high enough to resolve intracortical layers. Therefore, the in-vivo MR images acquired for this work are quantitative T1 maps at 0.5 mm isotropic resolution. Secondly, computational tools are needed to analyze the cortex observer-independ- ently. The most recent tools designed for this task are presented in this thesis. They comprise the segmentation of the cortex, and the construction of a novel equi-volume coordinate system of cortical depth. The equi-volume model is not restricted to in- vivo data, but is used on ultra-high resolution post-mortem data from MRI as well. It could also be used on 3D volumes reconstructed from 2D histological stains. An equi-volume coordinate system yields firstly intracortical surfaces that follow anatomical layers all along the cortex, even within areas that are severely folded where previous models fail. MR intensities can be mapped onto these equi-volume surfaces to identify the location and size of some structural areas. Surfaces com- puted with previous coordinate systems are shown to cross into different anatomical layers, and therefore also show artefactual patterns. Secondly, with the coordinate system one can compute cortical traverses perpendicularly to the intracortical sur- faces. Sampling intensities along equi-volume traverses results in cortical profiles that reflect an anatomical layer pattern, which is specific to every structural area. It is shown that profiles constructed with previous coordinate systems of cortical depth disguise the anatomical layer pattern or even show a wrong pattern. In contrast to equi-volume profiles these profiles from previous models are not suited to analyze the cortex observer-independently, and hence can not be used for automatic delineations of cortical areas. Equi-volume profiles from four different structural areas are presented. These pro- files show area-specific shapes that are to a certain degree preserved across subjects. Finally, the profiles are used to classify primary areas observer-independently.:1 Introduction p. 1 2 Theoretical Background p. 5 2.1 Neuroanatomy of the human cerebral cortex . . . .p. 5 2.1.1 Macroscopical structure . . . . . . . . . . . .p. 5 2.1.2 Neurons: cell bodies and fibers . . . . . . . .p. 5 2.1.3 Cortical layers in cyto- and myeloarchitecture . . .p. 7 2.1.4 Microscopical structure: cortical areas and maps . .p. 11 2.2 Nuclear Magnetic Resonance . . . . . . . . . . . . . .p. 13 2.2.1 Proton spins in a static magnetic field B0 . . . . .p. 13 2.2.2 Excitation with B1 . . . . . . . . . . . . . . . . .p. 15 2.2.3 Relaxation times T1, T2 and T∗ 2 . . . . . . . . . .p. 16 2.2.4 The Bloch equations . . . . . . . . . . . . . . . . p. 17 2.3 Magnetic Resonance Imaging . . . . . . . . . . . . . .p. 20 2.3.1 Encoding of spatial location and k-space . . . . . .p. 20 2.3.2 Sequences and contrasts . . . . . . . . . . . . . . p. 22 2.3.3 Ultra-high resolution MRI . . . . . . . . . . . . . p. 24 2.3.4 Intracortical MRI: different contrasts and their sources p. 25 3 Image analysis with computed cortical laminae p. 29 3.1 Segmentation challenges of ultra-high resolution images p. 30 3.2 Reconstruction of cortical surfaces with the level set method p. 31 3.3 Myeloarchitectonic patterns on inflated hemispheres . . . . p. 33 3.4 Profiles revealing myeloarchitectonic laminar patterns . . .p. 36 3.5 Standard computational cortical layering models . . . . . . p. 38 3.6 Curvature bias of computed laminae and profiles . . . . . . p. 39 4 Materials and methods p. 41 4.1 Histology . . . . . p. 41 4.2 MR scanning . . . . p. 44 4.2.1 Ultra-high resolution post-mortem data p. 44 4.2.2 The MP2RAGE sequence . . . . . . . . p. 45 4.2.3 High-resolution in-vivo T1 maps . . . .p. 46 4.2.4 High-resolution in-vivo T∗ 2-weighted images p. 47 4.3 Image preprocessing and experiments . . . . . .p. 48 4.3.1 Fully-automatic tissue segmentation . . . . p. 48 4.3.2 Curvature Estimation . . . . . . . . . . . . p. 49 4.3.3 Preprocessing of post-mortem data . . . . . .p. 50 4.3.4 Experiments with occipital pole post-mortem data .p. 51 4.3.5 Preprocessing of in-vivo data . . . . . . . . . . p. 52 4.3.6 Evaluation experiments on in-vivo data . . . . . .p. 56 4.3.7 Application experiments on in-vivo data . . . . . p. 56 4.3.8 Software . . . . . . . . . . . . . . . . . . . . .p. 58 5 Computational cortical layering models p. 59 5.1 Implementation of standard models . .p. 60 5.1.1 The Laplace model . . . . . . . . .p. 60 5.1.2 The level set method . . . . . . . p. 61 5.1.3 The equidistant model . . . . . . .p. 62 5.2 The novel anatomically motivated equi-volume model p. 63 5.2.1 Bok’s equi-volume principle . . . . . .p. 63 5.2.2 Computational equi-volume layering . . p. 66 6 Validation of the novel equi-volume model p. 73 6.1 The equi-volume model versus previous models on post-mortem samples p. 73 6.1.1 Comparing computed surfaces and anatomical layers . . . . . . . . p. 73 6.1.2 Cortical profiles reflecting an anatomical layer . . . . . . . . .p. 79 6.2 The equi-volume model versus previous models on in-vivo data . . . .p. 82 6.2.1 Comparing computed surfaces and anatomical layers . . . . . . . . p. 82 6.2.2 Cortical profiles reflecting an anatomical layer . . . . . . . . .p. 85 6.3 Dependence of computed surfaces on cortical curvature . . . . .p. 87 6.3.1 Within a structural area . . . . . . . . . . . . . . . . . . p. 87 6.3.2 Artifactual patterns on inflated surfaces . . . . . . . . . .p. 87 7 Applying the equi-volume model: Analyzing cortical architecture in-vivo in different structural areas p. 91 7.1 Impact of resolution on cortical profiles . . . . . . . . . . . . . p. 91 7.2 Intersubject variability of cortical profiles . . . . . . . . . . . p. 94 7.3 Myeloarchitectonic patterns on inflated hemispheres . . . . . . .p. 95 7.3.1 Comparison of patterns with inflated labels . . . . . . . . . .p. 97 7.3.2 Patterns at different cortical depths . . . . . . . . . . . . .p. 97 7.4 Fully-automatic primary-area classification using cortical profiles p. 99 8 Discussion p. 105 8.1 The novel equi-volume model . . . . . . . . . . . . . . . . . . . . .p. 105 8.2 Analyzing cortical myeloarchitecture in-vivo with T1 maps . . . . . .p. 109 9 Conclusion and outlook p. 113 Bibliography p. 117 List of Figures p. 127
74

Eavesdropping Attacks on Modern-Day Connected Vehicles and Their Ramifications / Avlyssningsattacker på moderna uppkopplade bilar och deras följder

Bakhshiyeva, Afruz, Berefelt, Gabriel January 2022 (has links)
Vehicles today are becoming increasingly more connected. Most cars are equipped with Bluetooth, Wi-Fi and Wi-Fi hotspot capabilities and the ability to connect to the internet via a cellular modem. This increase in connectivity opens up new attack surfaces for hackers to exploit. This paper aims to study the security of three different cars, a Tesla Model 3 (2020), an MG Marvel R (2021) and a Volvo V90 (2017), in regards to three different eavesdropping attacks. The performed attacks were a port scan of the vehicles, a relay attack of the key fobs and a MITM attack. The study discovered some security risks and discrepancies between the vehicles, especially regarding the open ports and the relay attack. This hopefully promotes further discussion on the importance of cybersecurity in connected vehicles. / Bilar idag har blivit alltmer uppkopplade. Idag har de inte bara bluetooth och Wi-Fi funktionalitet utan vissa bilar har förmågan att kopplas till internet via ett mobilt bredband. Denna trend har visats ge bilar nya attackytor som hackare kan utnyttja. Målet med denna studie är att testa säkerheten hos tre olika bilar, Tesla Model 3 (2020), MG Marvel R (2021) och Volvo V90 (2017) med åtanke på tre olika avlyssningsattacker. De attackerna som studien valde var port-skanning på bilen, relä-attack på bilnycklarna och mannen-i-mitten attack. Studien hittar vissa säkerhetsrisker och skillnader mellan de olika bilarna särskilt vid reläattacken och port-skanningen som förhoppningsvis främjar en fortsatt diskussion om cybersäkerhetens vikt för säkrare uppkopplade bilar.

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