Routing hijacks have plagued the Internet for decades. These attacks corrupt the routing table entries that networks use to forward traffic, causing affected network devices to route private and possibly sensitive Internet traffic towards the hijacker. Despite many failed attempts to thwart hijackers, recent Internet-wide routing monitoring infrastructures give us hope that future systems can quickly and ultimately mitigate hijacks. Such monitoring infrastructures consist of multiple globally distributed monitoring entities, called Route Collectors. To enable the whole community to monitor the validity and stability of the exchanged routing information, network volunteers disclose their routes to public route collectors. However, hijackers can also exploit this information to avoid being reported to route collectors. This thesis evaluates the effectiveness of monitoring infrastructures against two kinds of hijack scenarios: (i) an omniscient attacker with complete knowledge of both the Internet topology and the routing preferences of networks, and (ii) a realistic attacker which lacks such knowledge but gathers routing information from what networks themselves disclose to the public route collectors. Prior simulations showed that hijacks that affect more than 2% of the Internet are always visible to the public route collector infrastructure. However, our simulations show that omniscient and realistic hijackers that react to the deployment of public collectors could stealthily hijack up to 11.7× more (i.e., 23.5%) and 8.1× (i.e., 16.2%) more of the Internet (respectively) without being observed by the existing public route collector infrastructure. Having evaluated the effectiveness of the existing public route collector infrastructure with current Internet datasets, we evaluated the effectiveness in realistic future scenarios of (i) more interconnected (flatter) Internet topologies as well as (ii) topologies where more network volunteers disclose their routes to the public collectors. Unfortunately, both types of hijackers are more effective in flatter Internet topologies. Omniscient hijackers could stealthily hijack up to 24.5× (i.e., 49.0%) more of the Internet while realistic hijackers up to 22.7× (i.e., 45.5%) more without being observed by route collectors. In topologies with up to 4× more volunteers disclosing their routes to the public route collectors, hijackers could react to these new monitors by modifying their attacks to stealthily hijack up to 4× (i.e., 8.2%) and 2.9× (i.e., 5.9%) more of the Internet (respectively). Finally, we conclude with an analysis of two suggestions for improving the existing public route collector infrastructure: (i) selecting new network volunteers in more strategic locations and (ii) having volunteers disclose more routes to the route collectors. We hope that our findings in simulations will help towards the design of more reliable public route monitoring infrastructures. / Ruttkapningar har plågat internet i årtionden. Dessa attacker korrumperar poster i routingtabeller som används av nätverket för att vidarebefordra trafik, på ett sådant sätt att påverkade enheter dirigerar privat och tänkbart känslig trafik till kaparen. Trots många misslyckade försök att hindra kapare, ger på senare tid internetbred ruttövervakningsinfrastruktur oss förhoppningen att framtida system snabbt och slutgiltigt kan förhindra kapningar. Sådan övervakningsinfrastruktur består av flera globalt distribuerade övervakningsenheter kallade ruttinsamlare. Nätverksvolontärer uppger sina rutter till sådana publika ruttinsamlare så att hela nätverket kan övervaka validiteten och stabiliteten av den utbytta ruttinformationen. Dessvärre kan kapare utnyttja denna information för att undvika att bli rapporterade till ruttinsamlare. I denna avhandling utvärderar vi effektiviteten av sådan övervakningsinfrastruktur mot två typer av kapnings scenarier: Det första innefattar en allvetande attackerare med fullständig vetskap om både internettopologin och ruttpreferenser i nätverken. Det andra innefattar en realistisk attackerare som saknar sådan kunskap men som samlar upp den ruttinformation som nätverken själva lämnar ut till publika ruttinsamlare. Tidigare simuleringar har visat att kapningar som påverkar mer än 2% av internet alltid är synliga för den publika ruttinsamlarinfrastrukturen. Vår simulering visar däremot att allvetande och realistiska kapare som reagerar på utplaceringen av publika ruttinsamlare i smyg kan kapa upp till 11.7 gånger (d.v.s. 23.5%) respektive 8.1 gånger (d.v.s. 16.2%) mer av internet, utan att upptäckas av den existerande publika ruttinsamlarinfrastrukturen. Efter att ha utvärderat effektiviteten i den existerande publika infrastrukturen med nuvarande internet datamängder, utvärderade vi effektiviteten i realistiska framtida scenarier av för det första fler sammanlänkad (plattare) internet topologier samt för det andra topologier där fler nätverksvolontärer uppger sina rutter till publika ruttinsamlare. Dessvärre är båda typer av kapare mer effektiva i plattare internet topologier. Allvetande kapare kunde i smyg kapa upp till 24.5 gånger (d.v.s. 49.0%) mer av internet, medan realistiska kapare kunde kapa upp till 22.7 gånger (d.v.s. 45.5%) mer av internet, utan att upptäckas av ruttinsamlare. I topologier med upp till 4 gånger fler nätverksvolontärer som uppger sina rutter till publika ruttinsamlare, kunde allvetande och realistiska kapare reagerar på nya övervakare genom att modifiera sina attacker till att i smyg kapa upp till 4 gånger (d.v.s. 8.2%) respektive 2.9 gånger (d.v.s. 5.9%) mer av internet. Slutligen sammanfattar vi med en analys av två förslag till förbättring av den existerande ruttinsamlarinfrastrukturen: I det första väljes nya nätverksvolontärer på mer strategiska platser och i det andra låter vi nätverksvolontärer uppge fler rutter till ruttinsamlare. Vi hoppas att våra simuleringsresultat kan bidra till en design av en mer pålitlig publik rutt övervakningsinfrastruktur. / <p>QC 20220524</p>

The aim of this master's thesis is to design and implement JavaScript interpreter which is designed for purposes of avoiding obfuscation code of various types of computer viruses. This master's thesis also comprises a detailed view into the inner mechanism of the ECMAScript standard.

A predominant amount of energy needed in the industrial sector is in the form of heat. A significant number of industries in the world still relies on fossil fuels for meeting their heat requirements. A transition to renewable energy for heating needs is at a snail's pace due to fossil fuel lock-in, cost superiority of conventional fuels, and less government support for renewable technology for thermal requirements. The dairy industry is one of the sectors that need heat energy for its production process. This study deals with a techno-economic analysis on the integration of parabolic trough collectors in the dairy industry. The thesis finds the barriers for solar-thermal collectors to evolve in the dairy sector and the viewpoint of the dairy industry towards the acceptance of solar thermal for meeting their thermal needs. From a literature review, it is observed that the need for dairy product will increase in the coming year. To meet the demand, the production process has to be increased. For sustainable production, companies have to rely on environment-friendly energy sources to meet the thermal demand. In the thesis work, it was also found that for several solar fractions, the LevelizedCost of Heat (LCoH) of solar-assisted heating system is less than the LCoH of the fossil-fueled conventional boiler. Therefore, it is economically viable to integrate solar thermal collectors in the dairy industry. The project also compares the LCoHof solar-assisted heating system when solar integration is done at a) feed water heating, b) direct steam generation, and c) process integration. The effect of integration point on the solar fraction, LCoH, and carbon mitigation potential is presented for a real case dairy unit in Dubai. The simulations are performed using a dynamic simulation tool. Results show that minimum LCoH and solar fraction are achieved for process integration. The process integration results in up to 90 % of the solar fraction. Through process integration, the LCoH of the conventional boiler can be reduced by 60%.

This study details the construction and performance testing of a mixed mode solar dryer using a combination of direct and indirect solar energy to dry food. One major benefit of this dryer design is its construction. It was simple to construct and was made with low cost materials, to make it feasible for use in developing countries. Previous research has identified several design factors that affect performance and efficiency: product loading density, number of trays, position of the absorber, and chimney type. Performance testing showed that chimney air speeds were not affected greatly by modifying the design aspects of the dryer, with only a small increase occurring when using a box-type chimney. Overall the temperatures were mostly dependent on irradiance, but using a collector-type chimney generally resulted in higher temperatures throughout the dryer. The RH change across the dehydrator was most affected by the number of trays, but the chimney type did have an effect on the RH right at the chimney exit. Efficiency testing showed that product loading density on the trays was tested at 40% and 60% capacity; there was no statistical difference observed for efficiency between the two levels. Our results show that the dryer was more efficient when using the maximum number of trays. The lowest position of the absorber (5 cm from the ground) was found to be most efficient. A box-type chimney was significantly more efficient than the collector-type chimney in this full factorial study.

Fuel cells are promising candidates for converting chemical energy into electrical energy. The Molten Carbonate Fuel Cell (MCFC) is a high temperature fuel cell that produces electrical energy from a variety of fuels containing hydrogen, hydrocarbons and carbon monoxide. Since the waste heat has a high temperature it can also be used leading to a high overall efficiency. Material degradation and the cost of the components are the problems for the commercialisation of MCFC. Although there are companies around the world starting to commercialise MCFC some further cost reduction is needed before MCFC can be fully introduced at the market. In this work, alternative materials for three different components of MCFC have been investigated. The alternative materials should have a lower cost compared to the state-of-the-art materials but also meet the life-time goal of MCFC, which is around 5 years. The nickel dissolution of the cathode is a problem and a cathode with lower solubility is needed. The dissolution of nickel for three alternative cathode materials was investigated, where one of the materials had a lower solubility than the state-of-the-art nickel oxide. This material was also tested in a cell and the electrochemical performance was found to be comparable with nickel oxide and is an interesting candidate. An inexpensive anode current collector material is also desired. For the anode current collector, the contact resistance should be low and it should have good corrosion properties. The two alternative materials tested had low contact resistance, but some chromium enrichment was seen at the grain boundaries. This can lead to a decreased mechanical stability of the material. In the wet-seal area, the stainless steel used as bipolar/separator plate should be coated. An alternative process to coat the stainless steel, that is less expensive, was evaluated. This process can be a suitable process, but today, when the coating process is done manually there seems to be a problem with the adherence. This work has been a part of the IRMATECH project, which was financed by the European Commission, where the partners have been universities, research institutes and companies around Europe. / QC 20101123

The effects of an industrial gas turbine’s Exhaust Collector Box (ECB) geometry on static pressure recovery and total pressure loss were investigated in this study experimentally and computationally. This study aims to further understand how exit boundary conditions affect the performance of a diffuser system as well as the accuracy of industry standard computational models. A design of experiments approach was taken using a Box-Behnken design method for investigating three geometric parameters of the ECB. In this investigation, the exhaust diffuser remained constant through each test, with only the ECB being varied. A system performance analysis was conducted for each geometry using the total pressure loss and static pressure recovery from the diffuser inlet to the ECB exit. Velocity and total pressure profiles obtained with a hotwire anemometer and Kiel probe at the exit of the diffuser and at the exit of the ECB are also presented in this study. A total of 13 different ECB geometries are investigated at a Reynolds number of 60,000. Results obtained from these experimental tests are used to investigate the accuracy of a 3-dimensional RANS with realizable k-ε turbulence model from the commercial software package Star-CCM+. The study confirms the existence of strong counter-rotating helical vortices within the ECB which significantly affect the flow within the diffuser. Evidence of a strong recirculation zone within the ECB was found to force separation within the exhaust diffuser which imposed a circumferentially asymmetric pressure field at the inlet of the diffuser. Increasing the ECB width proved to decrease the magnitude of this effect, increasing the diffuser protrusion reduced this effect to a lesser degree. The combined effect of increasing the ECB Length and Width increased the expansion area ratio, proving to increase the system pressure recovery iv by as much as 19% over the nominal case. Additionally, the realizable k-ε turbulence model was able to accurately rank all 13 cases in order by performance; however the predicted magnitudes of the pressure recovery and total pressure loss were poor for the cases with strong vortices. For the large volume cases with weak vortices, the CFD was able to accurately represent the total pressure loss of the system within 5%.

Particle-surface interactions govern a myriad of interface phenomena, that span from technological applications to naturally occurring biological processes. In the present work, particle-collector DLVO interactions are computed with the grid-surface integration (GSI) technique, previously applied to the computation of particle colloidal interactions with anionic surfaces patterned with O(10 nm) cationic patches. The applicability of the GSI technique is extended to account for interactions with collectors covered with topographical and chemical nanoscale heterogeneity. Surface roughness is shown to have a significant role in the decrease of the energy barriers, in accordance with experimental deposition rates that are higher than those predicted by the DLVO theory for smooth surfaces. An energy- and force-averaging technique is presented as a reformulation of the GSI technique, to compute the mean particle interactions with random heterogeneous collectors. A statistical model based on the averaging technique is also developed, to predict the variance of the interactions and the particle adhesion thresholds. An excellent agreement is shown between the models' predictions and results obtained from GSI calculations for large number of random heterogeneous collectors. Brownian motion effects for particle-collector systems governed by nanoscale heterogeneity are analyzed by introducing stochastic Brownian displacements in particle trajectory equations. It is shown that for the systems under consideration and particle sizes usually used in experiments, it is reasonable to neglect the effects of Brownian motion entirely. Computation of appropriately defined P ́eclet numbers that quantify the relative importance of shear, colloidal and Brownian forces validate that conclusion. An algorithm for the discretization of spherical surfaces into small equal-area elements is implemented in conjunction with the GSI technique and mobility matrix calculations of particle velocities, to obtain interactions and dynamic behaviors of patchy particles in the vicinity of uniform flat collectors. The patchy particle and patchy collector systems are compared in detail, through the computation of statistical measures that include adhesion probabilities and maximum residence times per patch. The lessened tendency of the patchy particle to adhere on the uniform collector is attributed to a larger maximum residence time per patch, which precludes interactions with multiple surface nano-features at a given simulated time. Also briefly described are directions for future work, that involve the modeling of two heterogeneous surfaces, and of surfaces covered with many types of heterogeneity, such as patches, pillars and spring-like structures that resemble polymer brushes or cellular receptors.

The increasing energy demand requires a transition from fossil fuels to renewable resources. Lithium-ion batteries (LIBs) offer a promising solution as efficient energy storage devices. However, the aluminum current collector (CC) in LIBs is susceptible to anodic dissolution above 3 V vs. Li+/Li in commercial carbonate liquid electrolytes, compromising the battery performance. In this study, various approaches were explored to mitigate anodic dissolution in LiFSI EC:DEC at high voltages of the aluminum CC in LIBs, employing cyclic voltammetry (CV) and scanning electron microscopy (SEM). It was found that boiling the Al foil in water in an air atmosphere to increase the thickness of the surface Al2O3 layer improved the anodic stability and offered enhanced protection against proton attack (due to the oxidation of the carbonate solvent at high voltage). However, increasing the LiFSI electrolyte concentration to 2 M did not increase the anodic stability due to the absence of a passivating AlF3 layer. Notably, in 4 M LiFSI, impurity-induced high F- concentration facilitated the formation of a passivating AlF3 layer, resulting in improved anodic stability. Moreover, specific volume ratios of LiFSI EC:DEC and 1 M LiPF6 EC:DEC (1:1) (LP40) yielded the F- concentration necessary for forming a passivating AlF3 layer and significantly enhanced the anodic stability. On the other hand, carbon-coating the Al foil did not show significant improvements regarding the anodic stability. It was found that the corrosion was time-dependent at a low scan rate, a drastic anodic dissolution of the aluminum was seen at higher temperatures, and the corrosion also became more pronounced. At room temperature, carbon-coated Al foils exhibited increased stability.

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