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The emergence of blockchains as a way to organize and protect user data across the internet has come with some concerns, mainly how to deal with the issue of scalability while still maintaining the security standards as well as the decentralized nature inherent to blockchains. Many different implementations, which will be elicited in this thesis, resort to the concept of sharding, which consists of partitioning a blockchain into smaller clusters which would, with proper load-balancing, drastically improve the performance of the overall chain. We will first explore the existing literature on the subject as well as related algorithms. We will then provide a detailed explanation of the functioning of the existing algorithms, both centralized and decentralized, as well as the one proposed by this thesis. We will then elicit the settings and conditions of the simulation environment, both in terms of data collection and preparation. Finally, we will provide the results obtained as well as a comparative analysis of the tested algorithms and give an overview of possible future endeavors in the advancement of load-balancing algorithms in respect to sharded Blockchains.

Rapid innovations in 3D printing technology have allowed highly complex parts to be manufactured quickly and easily, particularly for prototyping purposes. Fused Deposition Modeling of thermoplastic materials is one of the most commonly used techniques in three-dimensional (3D) printing. The major aim of Fused Deposition Modeling (FDM) is to design and manufacture usable parts for fields such as engineering and medicine. Therefore, it is essential to investigate the mechanical properties of such FDM processed structures. One of the most commonly used materials currently on the market is Polylactic Acid (PLA). The main purpose of this paper is to investigate the effects of aging and heat treatment on the tensile properties of PLA printed test specimens. The tensile properties of parts manufactured by the 3D printer are influenced by various parameters such as extrusion temperature, infill density, building direction, layer height, etc. A total of 96 specimens were built by altering building orientation and layer height to estimate and compare the tensile properties of the printed parts. To investigate the aging effect, 30 of 96 specimens were printed 6 months before the tensile experiment. Half of both aged and new specimens were cured in an oven at 57.5 [˚C] for 3 hours while the other half endured no heat treatment. After the performed measurement, it can be concluded that heat treatment generally improves structural strength of the printed parts, while aging decreases it. However, these effects are highly dependent on the layer thickness and printing quality. The tensile test is conducted according to the ASTM D638 standard. The fractured samples were further characterized using an electron microscope.

Kompozitni materijali predstavljaju napredne materijale visokih mehaničkih i fizičkih karakteristika, pa je njihova primena uglavnom zastupljena u specifičnim oblastima industrije, kao što su vazduhoplovstvo i vetroenergetski sistemi. Lopatice vetroturbina kao najkompleksnije komponente, se uglavnom izradjuju od kompozitnih materijala, pa je i njihovom izučavanju i testiranju potrebno posvetiti posebnu pažnju. U radu je prikazano mehaničko ponašanje kompozitnih ploča izloženih dejstvu na istezanje. Tri kompozitne ploče karbon epoksidnog sastava, istih dimenzija, ali sa različitom orijentacijom slojeva su u skladu sa procedurom propisanom standardom D3039, pripremljene i eksperimentalno testirane. Ponašanje uzoraka je najpre simulirano u odgovarajućem softveru, u cilju provere i verifikacije eksperimentalne postavke, a zatim su vršeni testovi pod dejstvom zateznog opterećenja na kidalici SHIMADZU AGS-X 100 kN. Dobijene vrednosti su grafički ilustrovane na dijagramima napon-deformacija. Prikazani rezultati dobijeni ovom metodom ispitivanja su od značaja u cilju boljeg razumevanja ponašanja kompozitnih struktura pod dejstvom različitih vrsta opterećenja, kako statičkih, tako i dinamičkih, jer poznavanje datih vrednosti daje širok spektar mogućnosti u daljim ispitivanjima i uporednim analizama sa ostalim eksperimentalnim metodama.

The aerodynamic performance of an airfoil provides specific information on wing design of HALE UAV and is considered as eminent for enhancing its flight conditions. In this paper, numerical investigation of a wing is conducted to predict its preliminary aerodynamic quality. A concise comparison of lift and drag curve obtained from numerical analysis conducted in two different programs, will be the scope of this research. Preliminary aerodynamic performance study including 12 different wings were previously performed in Fortran program GLAUERT-trapezoidal wing. From those 12 wings, one wing was selected which has the best aerodynamic performance at an operational altitude of 15000 m. Computational fluid dynamic (CFD) software package, ANSYS Fluent is used for numerical analysis of the selected wing. Two different turbulence models were simulated in this work. Lift and drag coefficients were calculated respectively by varying angle of attacks. Hence, the resulted lift and drag curve generated in GLAUERT were compared with those obtained from ANSYS FLUENT. Additionally, other parameters like flow separation, pressure and velocity contours obtained by different turbulent models were also discussed.

Considering aeronautics requirements, academies and industries are developing matrixes and reinforcements with higher mechanical performance. The same occurs with the process where new studies focus on obtaining composites with suitable matrix/reinforcement interface. The use of epoxy resin and carbon fiber with high mechanical performance does not guarantee a composite with high mechanical properties, considering imperfections and void formation along the laminate in case of inappropriate processing parameters. The aim of this article was to analyze and quantify the mechanical behavior of polymer composite reinforced with continuous fibers using finite element methodology and postprocessing software simulation. In addition, the classical laminate theory and finite elements were used to simulate flexural and tensile tests of composite specimens. Simulation results were compared with experimental test results using a carbon fiber noncrimp fabric quadriaxial/epoxy resin composite processed by resin transfer molding. Although void volume fraction for structural materials presenting results under aeronautics requirements regarding of 2%, imperfections like lack of resin and impregnation discontinuity showed an influence in tensile and flexural experimental results. Experimental mechanical behavior decreased 10% of strength, in comparison with simulation results due to imperfection on impregnation measured by C-Scan map. Improvement in processing procedures could able to provide greater impregnation continuity, reducing defect formation and ensuring better matrix/reinforcement interface. As a final conclusion, the process plays a role as important as the characteristics of reinforcement and matrix and, consequently, the mechanical properties.

Aerosols are small, micrometer-sized particles, whose optical effects coupled with their impact on cloud properties is a source of large uncertainty in climate models. While their radiative forcing impact is largely of a cooling nature, there can be significant variations in the degree of their impact, depending on the size and the nature of the aerosols. The radiative and optical impact of aerosols are, first and foremost, dependent on their concentration or number density (an extensive parameter) and secondly on the size and nature of the aerosols (intensive, per particle, parameters). We employed passive (sunphotmetry) and active (backscatter lidar) measurements to retrieve extensive optical signals (aerosol optical depth or AOD and backscatter coefficient respectively) and semi-intensive optical signals (fine and coarse mode OD and fine and coarse mode backscatter coefficient respectively) and compared the optical coherency of these retrievals over a variety of aerosol and thin cloud events (pollution, dust, volcanic, smoke, thin cloud dominated). The retrievals were performed using an existing spectral deconvolution method applied to the sunphotometry data (SDA) and a new retrieval technique for the lidar based on a colour ratio thresholding technique. The validation of the lidar retrieval was accomplished by comparing the vertical integrations of the fine mode, coarse mode and total backscatter coefficients of the lidar with their sunphotometry analogues where lidar ratios (the intensive parameter required to transform backscatter coefficients into extinction coefficients) were (a) computed independently using the SDA retrievals for fine mode aerosols or prescribed for coarse mode aerosols and clouds or (b) computed by forcing the computed (fine, coarse and total) lidar ODs to be equal to their analog sunphotometry ODs. Comparisons between cases (a) and (b) as well as the semi-qualitative verification of the derived fine and coarse mode vertical profiles with