The cellphone turned 40 years old in 2013, and its evolution has been phenomenal in these 40 years. Its name has evolved from "cellphone" to "mobile phone" and "smartphone" to "mobile device."] Its transformation has been multi-dimensional in size, functionality, application, and the like. This transformation has allowed the mobile device to be utilized for casual use, personal use, and enterprise use. Usage is further driven by the availability of an enormous number of useful applications for easy download from application (App) markets. Casual download of a seemingly useful application from an untrusted source can cause immense security risks to personal data and any official data resident in the mobile device. Intruding malicious code can also enter the enterprise networks and create serious security challenges. Thus, a mobile device architecture that supports secure multi-persona operation is strongly needed. The architecture should be able to prevent system intrusions and should be able to perform regular integrity checking and auditing. Since Android has the largest user base among mobile device operating systems (OS), the architecture presented here is implemented for Android. This thesis describes how an architecture named the "Android Hypovisor" has been developed and implemented successfully as part of this project work. The key contributions of the project work are: 1. Enhancement of kernel security 2. Incorporation of an embedded Linux distribution layer that supports Glibc/shared libraries so that open-source tools can be added easily 3. Integration of integrity checking and auditing tools (Intrusion Detection and Prevention System; IDPS) 4. Integration of container infrastructure to support multiple OS instances. 5. Analysis shows that the hypovisor increases memory usages by 40-50 MB. As the proposed OS is stripped down to support the embedded hypovisor, power consumption is only minimally increased. This thesis describes how the implemented architecture secures mobile devices through high-performance, light-weight, subsystem isolation with integrity checking and auditing capabilities. / Master of Science

No / The square array was initially tested in the UK during the 1960s by Anthony Clark. However, since the development of the twin probe system, the square array has been seldom used in the UK, although greater use has been reported elsewhere, especially in France (Panissod et al., 1998). In the last few years, re-investigation of the square array¿s potential in an archaeological context has reignited interest and led to the development of a hand-pulled cart system by Dr. Roger Walker (Geoscan Research). This cart system incorporates earth resistance and gradiometer instruments to allow simultaneous surveys with a lightweight device. The main objective of the project is to test the application of the MSP40 on a variety of sites and to encourage the use of appropriate geophysical survey equipment to minimize the impact and therefore protect even the most vulnerable of archaeological sites.

Laser beam welding has gained a significant interest during the last two decades. The suitability of the process for high volume production has the possibility to give a strong advantage compared to several other welding methods. However, it is important to have the process in full control since various quality issues may otherwise occur. During laser welding of boron steels quality issues such as imperfections, changes in local and global geometry as well as strength reduction can occur. The aspects that need to be considered are strongly depending on alloy content, process parameters etc. These problems that can occur could be fatal for the construction and the lowest level of occurrence is wanted, independent of industry. The focus of this study has been to investigate the properties of laser welded boron steel. The study includes laser welding of boron alloyed steels with strengths of 1500 MPa and a recently introduced 1900 MPa grade. Focus has been to investigate weldability and the occurrence of cracks, porosity and strength reducing microstructure that can occur during laser welding, as well as distortion studies for tolerances in geometry. The results show that both conventional and 1900 MPa boron alloyed steel are suitable for laser welding. Due to the martensitic structure of welds the material tends to behave brittle. Cracking and porosity do not seem to be an issue limiting the use of these steels. For tolerances in geometry for larger structures tests has been done simulating laser welding of A-pillars and B-pillars. Measurements have been done with Vernier caliper as well as a more advanced optical method capturing the movements during the welding sequence. Results from the tests done on Ushaped beams indicates that depending on the geometry of the structure and heat input distortions can be controlled to give distortions from 1 to 8 mm, at a welding length of 700 mm. This means that important geometry points can be distorted several millimeters if the laser welding process not is controlled.

Aus der Einleitung: "Faser-Kunststoff-Verbund (FKV)-Werkstoffe finden einen immer breiteren Einsatz in allen Bereichen der Industrie, wie zum Beispiel in der Luft- und Raumfahrt, im Automotive-Bereich, im Maschinenbau und bei Sportgeräten. Dabei entstehen besondere Herausforderungen für Entwickler, da Eigenschaften und Verfahren im Zusammenhang dieser Werkstoffe sich deutlich von denen der herkömmlich verwendeten Metalle oder unverstärkten Kunststoffe unterscheiden. Technische Fasern werden in verschiedenen Verarbeitungsformen und in Kombination mit vielfältigen Matrixsystemen angewendet. Ein Großteil der Fasern wird heutzutage in Form von multiaxialen Geweben oder Gelegen verarbeitet. Bei diesen Halbzeugen sind die Fasern in mehreren Lagen unterschiedlicher Ausrichtung übereinandergelegt. Metalle können damit sehr einfach durch leichtere Faser- Kunststoffverbunde ersetzt werden. Diese Technologien versuchen weitestgehend isotrope Bauteileigenschaften aus den eigentlich anisotropen Materialeigenschaften zu erzielen. Dies reizt jedoch das Potential der Werkstoffe nicht aus."

Omnipresence of heterogeneity is conspicuous in all creations of nature. Heterogeneity manifests itself in many forms at different scales, both in time and space. Engineering domain being an exotic fusion of human creativity and ever-increasing demands exemplifies the ubiquity of heterogeneity. Surprisingly, the plethora of materials we see around seem to stem from myriad combination of few base materials identified as elements in chemistry. Further, a simple rearrangement of atoms in these materials leads to allotropes with startling contrasts in properties. Similarly, micro- and meso-scales in heterogeneous materials also dis-play this phenomenon. Human requirements propelled by necessities and wants have leveraged heterogeneity deliberately or naively. In the context of engineering materials, light weight heterogeneous materials like composites and cellular solids are outstanding inventions from the last century. The present thesis highlights this phenomenon on a meso-scale to explore generalized variants of circular and elliptical honeycomb structures (HCSs) with an emphasis on their effective transverse elastic responses, a crucial pillar of engineering design and analysis. Homogenized or effective properties are an extension of continuum hypothesis, conceived for ease in analyses. E ective properties are employed in multi-scale analyses resulting in less complex models for analysis, for example, for predicting the speed of wave propogation. The thesis extends and generalizes existing close-packed circular and elliptical HCSs to more broader configurations. Simpler periodic arrangement of the unit cells from numerous exotic possibilities directly incorporates Design for Manufacture and Assembly (DFMA) philosophy and o ers a potential scope for analysis by simpler tools resulting in handy expressions which are of great utility for designer engineers. In this regard, analytical expressions for moduli having compact forms in the case of circular HCS are developed by technical theories and rigorous theory of elasticity. Regression analysis expressions for the moduli of elliptical HCS are presented, and the elasticity solutions for the same are highlighted. The thesis consists of seven chapters with Chapter 1 presenting generalized circular and elliptical HCSs as a potential avenue beyond composite materials. Following a survey of pertinent HCS literature of these HCSs, research gaps and scope are delineated. Chapter 2 briefly y summarizes the ideas, concepts and tools including analytical and numerical methods. This chapter sets the ground for the analysis of generalized circular and elliptical HCS in the following four chapters. Following the classification of the circular HCSs, Chapter 3 assesses the complete transverse elastic responses of generalized circular HCS through technical theories which are a first-order approximation. Here, thin ring theory and the more elaborate curved beam theory are employed as models to assess the moduli. Normal moduli - E and - are obtained by employing Castigliano method, while shear moduli (G ) are obtained by solving the differential equations derived in terms of displacements. Compact expressions for moduli presented wherever possible furnish the designer with a range of moduli for different configurations and modular ratios (Ey=Ex). The results show the range of applicability of technical theories within 5% of FEA. For hexagonal arrays, these results are more refined than those in literature; while the same are new for other configurations. Surprisingly, the more elaborate curved beam theory offers no better results than the thin ring theory. Chapter 4 extends the aforementioned task of assessing the complete trans-verse elastic moduli of generalized circular HCS by employing rigorous theory of elasticity (TOE) which is a second-order approximation. Utilizing Airy stress function in polar coordinates, the boundary value problems resulting from modeling of the circular HCS under different loads are solved analytically in conjunction with FEA employing contact elements. Contact elements circumvent the point loads which give finite values of displacements in technical theories and singular values in TOE. A widely used idea of employing distributed load, statically equivalent to point load, is invoked to empower TOE. The distributed load is assumed a priori and the contact length is obtained from FEA employing con-tact elements. Thus, FEA compliments the present analytical methods. Results demonstrate a very good match between analytical method in conjunction with FEA and numerical results from FEA; the error is within 5% for very thick ring (thickness-radius ratio 0.5). Further, computationally and numerically efficient expressions for displacements give better results with same computational facility. To illustrate the effect of coating on effective moduli, a limited study based on thin ring theory and elasticity theories is undertaken in Chapter 4. The study explores the effects of moduli and thickness ratios of substrate to coating on the effective normal moduli. Employing thin ring theory with only flexure as the bending mode, we get compact expressions giving good match for very thin rings in all confifigurations. The elasticity approach presented for square array demonstrates a very good match with FEA for thick rings. Coatings offer a strategy to increase the effective moduli with same dimensions. Chapter 5 broadens the scope of circular HCS by considering elliptical HCSs. While generalized circular HCS can cater to anisotropic requirement to an extent, larger spectrum is offered by considering elliptical honeycomb structures. In this regard, a generalized version of concentric thin coated elliptical HCS is investigated for transverse moduli. Thin HCSs are explored by technical theories as in circular HCS. However, a lack of exact compact-form expressions necessitates the use of regression analysis. The resulting expressions are presented in terms of ellipticity ratio describing the ovality of the ellipse and geometric parameters. Normal moduli are obtained by Castigliano method implemented in MATHE-MATICA, but shear moduli are obtained from FEA employing beam elements. The need for FEA employing beam elements stems from the subtle fact that Castigliano method implicitly assumes preclusion of rigid body motions, while shear loading for shear moduli evaluation entails rigid body motions. Interestingly, curved beam theory, as in circular HCS, offers no better refinement in assessing the moduli as compared to thin ring theory. The graphs showing the moduli with respect to thickness and modular ratios are presented as design maps to aid the designer. Chapter 6 extends the works of thin concentric coated elliptical to thicker concentric and a novel confocal elliptical HCS, a variant of elliptical HCS. In this regard, thick concentric and confocal elliptical HCS by elasticity approach are attempted for a simple case. Airy stress function in polar coordinates is tried for concentric elliptical HCS. Confocal HCS analysis employs stress function in terms of elliptical coordinate system. After proving the correctness of the stress function for both the cases by comparing the reconstructed boundary conditions with actual boundary conditions, the restrictions in solving the case of rings under load over a small region is highlighted. A parametric study for moduli is under-taken by employing FEA. These are presented as design graphs which compare and contrast the two variants of elliptical HCS on the same graphs. The modular ratio (Ey=Ex) is conspicuously more for confocal elliptical HCS than concentric elliptical HCS. Chapter 7 gives the conclusions in a nutshell, and explores the feasibility of stress evaluation of heterogeneous media on the lines of effective media theory.

No description available.

Advanced High Strength Steel (AHSS) has become a popular steel grade among automakers to produce vehicle bodies. With improvements in strength and elongation, AHSS has evolved to its 2nd generation, including high manganese steel. Even though it has outstanding strength, the 2nd generation of AHSS faces some production problems due to its high alloying elements. With continual improvement, the 3rd generation of AHSS is currently in production. In this generation, the steel types still have a competitive strength and elongation like the 2nd generation of AHSS while having lower alloying element contents and production costs. One of the types of 3rd generation AHSS is medium manganese steel. Research related to the 2nd and 3rd generation of AHSS mainly focuses on their mechanical properties and microstructures. As there is a strong correlation between mechanical properties and inclusion characteristics, further investigation of the evolution of inclusions is still required. In this study, high-temperature experiments were conducted to investigate the effects of metal chemistry on the inclusion evolution in liquid steel. The concentrations of manganese, aluminum, and nitrogen were varied systematically. Two and three-dimensional analysis techniques were applied to study the number, composition, and size distribution of inclusions. Electrolysis extraction was used to identify the oxide, sulfide, and nitride inclusions, whereas an automated SEM with an ASPEX feature was used to detect a larger number of inclusions for better representation of the steel matrix. This work has established inclusion classification rules to distinguish nitride inclusions from oxide inclusions. To the best of the authors’ knowledge, this is the first discussion of this type of inclusion classification in the open literature. Based on the automated SEM (ASPEX Feature) analysis, the type of detected inclusions in medium and high manganese steels were Al2O3(pure), Al2O3-MnS, AlN(pure), AlN-MnS, AlON, AlON-MnS, and MnS inclusions. As the manganese content in the steel increased from 2% to 20%, the total amount of inclusions, especially AlN-contained inclusions, was raised. This phenomenon occurred due to the increase in nitrogen solubility with increased manganese content in the steel. The thermodynamic calculation also predicted that AlN inclusions would form when the steel was cooled or during the solidification. Moreover, AlN and MnS inclusions were observed to co-precipitate together. Similar to manganese, the increase in the aluminum content (Al = 0.5-6%) increased the total amount of inclusions in the steel, and the dominant inclusion type is AlN. AlN and Al2O3 inclusions can be heterogenous nucleation sites for MnS inclusions. Furthermore, Al2O3 inclusions also became heterogeneous nucleation sites for AlN inclusions. The experimental set-up was further modified to investigate the effect of nitrogen on the formation of inclusions in the medium manganese steels. The nitrogen was introduced by purging or injecting N2 gas into the steel system. Similar to the effect of manganese and aluminum, the increase in the nitrogen content also increased the total amount of inclusions. Once the nitrogen content in the steel exceeded the critical limit for the formation of AlN inclusions, AlN inclusions can be stable in the liquid steel. Moreover, regardless of the nitrogen content in the steel, AlN-MnS inclusions were formed in the slow-cooled steels. In terms of morphology, AlN inclusions can be formed of plate-like, needle, angular, agglomerate, or irregular shapes. Furthermore, a brief investigation on the addition of calcium and nitrogen to the medium manganese steels found that calcium led to the formation of other complex inclusions, such as CAx and CAS-Other inclusions. In the medium manganese steel composition in the present study, the number of CAS-Other inclusions was dominated by (Ca,Mn)S-Oxide inclusions after the addition of Ca. However, with time and after introducing N2 gas into the steel, the number of (Ca,Mn)S-Nitride inclusions also increased. The formation of (Ca,Mn)S-Nitride inclusions resulted from the co-precipitation of CaS, MnS, and AlN. The current work provides a better understanding of the formation mechanism of inclusions in medium manganese steels and high manganese steels. It presents complete information on the characteristics of inclusions, such as the number density, type, and morphology of inclusions. This knowledge can help steelmakers improve the steelmaking process to control the formation of inclusions, which can be problematic for the manufacture and performance of medium manganese steels and high manganese steels. / Dissertation / Doctor of Philosophy (PhD)

When evaluating low volume roads (LVRs), structural capacity emphasis is minimal since deterioration typically results from environmental factors. However, in cases where LVR’s experience rapidly increased traffic loading, structural condition becomes important. The research objective was to determine whether the Light Weight Deflectometer (LWD) can be used as a structural evaluation tool for LVRs in the aforementioned conditions. This study explored the capability of LWD equipment in evaluating major factors that influence flexible pavement structural capacity: load induced deterioration, soil moisture, and asphalt temperature. Falling Weight Deflectometer (FWD) and LWD tests were performed to measure pavement structural condition. LWD was shown applicable for LVRs experiencing accelerated traffic. The LWD is portable and efficient for LVRs when high rut depths are permitted. The LWD and FWD produced similar trends. The LWD, based on this thesis, can be recommended for use in lieu of FWD to assess structural condition of LVRs for rapidly increased traffic loading.

Various forms of fraud have substantially impacted our lives and caused considerable losses to some people. To reduce these losses, many researchers have devoted themselves to the study of fraud detection. After the development of fraud detection from expert-driven to data-driven systems, the scalability and accuracy of fraud detection have been improved considerably. However, most existing fraud detection methods focus on the feature extraction and classification of a certain transaction, ignoring the temporal and spatial long-term information from accounts. In this work, we propose to address these limitations by employing a lightweight memory network (LiMNet), which is a deep neural network that captures causal relations between temporal interactions. We evaluate our approach on two data sets, the Ether-Fraud dataset, and the Elliptic dataset. The former is a brand new dataset collected from Etherscan with data mining, and the latter is published by the homonymous company. As a set of raw collected data never used before, the Ether-Fraud dataset had some issues, such as huge variation among values and incomplete information. Therefore we have processed Ether-Fraud with data supplementation and normalization, which has solved these problems. A series of experiments were designed based on our analysis of the model and helped us to find the best hyper-parameter setting. Then, we compared the performance of the model with other baselines, and the results showed that Lightweight Memory Network (LiMNet) outperformed traditional algorithms on the Ether-Fraud dataset but was not good as the graph-based method on the Elliptic dataset. Finally, we summarized the experience of applying the model to fraud detection, the strengths and weaknesses of the model, and future directions for improvement. / Olika former av bedrägerier har haft en betydande inverkan på våra liv och har orsakat stora förluster för vissa människor. För att minska dessa förluster har många forskare ägnat sig åt att studera upptäckt av bedrägerier. Efter utvecklingen av bedrägeriutredningen från expertdrivna till datadrivna system har skalbarheten och noggrannheten förbättrats avsevärt. De flesta av de befintliga metoderna för upptäckt av bedrägerier fokuserar dock på utvinning av funktioner och klassificering av en viss transaktion och ignorerar den temporala och spatiala långsiktiga informationen från konton. I det här arbetet föreslår vi att vi tar itu med dessa begränsningar genom att använda ett lättviktigt minnesnätverk (LiMNet), som är ett djupt neuralt nätverk som fångar kausala relationer mellan temporala interaktioner. Vi utvärderar vårt tillvägagångssätt på två datamängder, datamängden Ether-Fraud och Elliptic-datamängden. Det förstnämnda är ett helt nytt dataset som samlats in från Etherscan med hjälp av datautvinning, och det sistnämnda är publicerat av det homonyma företaget. Eftersom det rörde sig om råa insamlade data som aldrig använts tidigare hade Ether-Fraud-datasetet vissa problem, t.ex. en stor variation mellan värdena och ofullständig information. Därför har vi bearbetat Ether-Fraud med datatillägg och normalisering, vilket har löst dessa problem. En serie experiment utformades utifrån vår analys av modellen och hjälpte oss att hitta den bästa inställningen av hyperparametrar. Sedan jämförde vi modellens prestanda med andra baslinjer, resultaten visade att LiMNet överträffade traditionella algoritmer på datasetet Ether-Fraud men var inte lika bra som den grafbaserade metoden på datasetet Elliptic. Slutligen sammanfattade vi erfarenheterna av att tillämpa modellen på bedrägeridetektion, modellens styrkor och svagheter samt framtida riktningar för förbättringar.

We show full Li/S cells with the use of balanced and high capacity electrodes to address high power electro-mobile applications. The anode is made of an assembly comprising of silicon nanowires as active material densely and conformally grown on a 3D carbon mesh as a light-weight current collector, offering extremely high areal capacity for reversible Li storage of up to 9 mAh/cm(2). The dense growth is guaranteed by a versatile Au precursor developed for homogenous Au layer deposition on 3D substrates. In contrast to metallic Li, the presented system exhibits superior characteristics as an anode in Li/S batteries such as safe operation, long cycle life and easy handling. These anodes are combined with high area density S/C composite cathodes into a Li/S full-cell with an ether- and lithium triflate-based electrolyte for high ionic conductivity. The result is a highly cyclable full-cell with an areal capacity of 2.3 mAh/cm(2), a cyclability surpassing 450 cycles and capacity retention of 80% after 150 cycles (capacity loss <0.4% per cycle). A detailed physical and electrochemical investigation of the SiNW Li/S full-cell including in-operando synchrotron X-ray diffraction measurements reveals that the lower degradation is due to a lower self-reduction of polysulfides after continuous charging/discharging.