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There is a growing interest in extracting more power per turbine by increasing the rotor size in offshore wind turbines. As a result, the turbine blades will become longer and therefore more flexible and a flexible blade is susceptible to flow-induced instabilities, such as classical flutter. In order to design and build stable large wind turbine blades, the onset of instability should be considered in the design process. To observe flow-induced instabilities in wind turbine blades, a small-scale flexible blade was built based on NREL 5MW reference wind turbine blade. The blade was placed in the test section of a wind tunnel and its tip displacement was measured using a non-contacting displacement measurement device. The blade was non-rotating and was subjected to uniform incoming flow. For a range of blade angles of attack, instability was observed beyond a critical wind speed. The amplitude of oscillations increases for wind speeds higher than the critical speed, and the frequency of oscillations remains constant. Flow visualizations and force measurements are conducted and the influence of various system parameters including the angle of attack and the blade twist was examined.

Lightweight cellular concrete (LCC) is an aerated or foamed concrete where 25-80% of the concrete matrix consists of air voids. The high volume of air voids reduces the strength but significantly decreases the weight of the material, which has made it an attractive alternative to soil for retaining structure backfills. Though the use of LCC has increased, little research has been performed on the large-scale behavior of retaining structures containing LCC as backfill. This research test attempts to fill knowledge gaps found with regard to the use of LCC in a mechanically stabilized earth (MSE) wall with a trapezoidal or sliver fill by examining the nature of LCC strength criteria from large-scale failure, failure mechanisms, and failure criteria. A large-scale test box (10 ft. wide x 12 ft. long x 10 ft. high), surrounded by a steel resisting frame, was constructed and filled with a silty sand backfill soil in a 1:1 stair-stepped slope and an LCC sliver fill. The west-facing wall was a two-paneled MSE wall with 16 ribbed steel strip reinforcements running through the LCC backfill. The LCC was poured over three days in equal height lifts to ensure stability. A total of 64 sample cylinder molds and four split mold shear boxes were filled with LCC during placement to help identify LCC material properties, which included density, unconfined compressive strength (UCS), and shear strength. A surcharge test was performed on the large-scale test box six days after initial placement of the LCC due to the unanticipated high strength gain and density found within the placed LCC. Instrumentation collected data on displacement, shear plane, lateral wall pressure, and reinforcement strain throughout testing. Initially, four hydraulic jacks were used during surcharge testing to induce a uniform surcharge load to fail the sliver-fill MSE wall. The strength limit of the steel resisting frame was reached before failure, at which point the number of hydraulic jacks was switched to three for a more critical loading condition. The test was again terminated before complete failure when the steel resisting frame strength limit was met. Though failure was not completed, the sliver-fill MSE wall failure had initiated before testing was terminated at a surcharge load of 70 psi. Results identify the initiation of shear failure within the LCC at about 65 psi, with maximum lateral and axial displacements of about 0.5 in. and 1.2 in., respectively. The shear failure occurs at about 52% of the average UCS of 123 psi. An arcuate shear plane, contrary to the traditional bilinear MSE wall failure surface with inextensible reinforcements, was identified within the LCC backfill, which initiated from the toe of the MSE wall and ended about 8 ft. back from the top of the MSE wall, using lateral displacements from Sondex tube profilometers in the backfill.

Previous small-scale methods for plasmid DNA (pDNA) purification fail to meet theindustry’s demand for sufficient quantities. Greater volumes of bacterial lysates are a consequence of larger volumetric fermentations and traditional large-scale down-stream purification processes have some disadvantages and limitations. The market is believed to continue to expand, hence the need for efficient, cost-effective, andscalable purification processes becomes apparent. A crucial trade-off exists between pDNA yield and purity, necessitating careful consideration in chromatographic pu-rification steps. Each step enhances purity while likely sacrificing yield. In order to achieve a higher degree of pDNA yield, optimal purification entails a single chro-matographic step, specifically anion-exchange chromatography (AEX) in combina-tion with filtration. Alternatively, a two-step purification approach involving AEX followed by hydrophobic interaction chromatography (HIC) is recommended to elim-inate complementary impurities and achieve a high level of purity. Furthermore, the utilization of monolithic chromatographic supports is suggested to facilitate the sug-gested purification strategies. This is due to monoliths promoting higher binding capacities, ensuring robust and consistent results even at high flow rates.

Envisioning an inner-city student housing project, adding life to an office-dominated area, and offering a publicly accessible roof terrace and open landscape park. We are proposing a student housing complex, composed of two 355-metres-long buildings with two and three floor levels, respectively, lifted up on pilotis, with corridor rooms and student apartments accomodating a total of 336 students and thus creating a bustling hub of human interactivity. For the proposal, we claim a large strip of land in the southern part of the property “Kvarteret Garnisonen 3” in Östermalm, Stockholm; the southern-most 15 % of the 84 000-square-metre property, previously used as a launching space for ceremonial marches, but currently used mostly for parking spaces and dog walking. Designing the large-scale structure to house many students, with each contributing to the added life to the space, and encouraging human interactions architecturally, by retaining the accessibility of the ground level by way of pilotis, as well as making the roof terrace open to the public, and offering several alternative routes between the levels of the buildings.

Heat production accounted in 2021 for 50 % of the energy end use globally, where a strongconnection to fossil sources still exists. Large-scale electrical heat pumps can therefore have akey role in the energy system to enable a decreased reliance on fossil fuels and at the same timecontribute to stable system when incorporating more intermittent renewable sources. To operatea heat pump, a working fluid i.e., refrigerant is required. Historically these substances havebeen ozone depleting with a significant global warming potential. Applied regulations andlegislations have therefore limited the substances possible to implement. This study therefore focuses on investigating potential future refrigerants in LSHPs, by studying both current and potential future legislations and regulations but also the potential performanceof the substances. The performance was evaluated for two operational condition cases wherethe first focused on meeting the supply and demand of a third generation district heating systemwith an evaporation temperature of 0 °C. The second case investigated a middle temperature industrial process with an evaporation temperature of 33 °C. For both cases a two-stage compressor heat pump cycle was considered. Substances available in the database REFPROP were considered, where legislations and regulations, classifications, thermodynamic properties, and the performance were investigated. Substances not fulfilling the set criterions were eliminated. Seven substances were then investigated in depth where e.g., the volume flow rate, performance, operational electricity cost and both footprint and cost of the evaporator were considered. All substances were investigated both with and without an internal liquid-suction HEX, to investigate how such component potentially could affect the performance. The result of the study shows that environmental, safety aspects and thermodynamic propertieshave a large impact on possible refrigerants, with a decrease from 160 available substances to20 possible for each case. If an evaporation pressure in the vacuum range or a transcritical cyclewould have been investigated the number of possible refrigerants would increase. Out of the 20possible substances, seven substances namely isobutane, butane, isobutene, butene, propane,perfluoropentane and isopentane were chosen for further investigation. The performance andelectrical operational cost can be concluded to be fairly similar, with an increase when includingan internal liquid-suction HEX. The performance for case 2, is although slightly higher, whereperfluoropentane performs superior. The high GWP value for perfluoropentane however limitsits possibility to be used. Lastly the size and cost of the evaporator was investigated. It couldbe concluded that case 1 required a smaller design than case 2, related to the size of the HTCvalue.

One focus of research in cosmology regards the growth of structure in the universe: how we end up with stars, galaxies, galaxy clusters, and large scale structure in a universe that appears homogeneous and isotropic on large scales. Using cosmological perturbation theory, we investigate the evolution of density and velocity perturbations corresponding to a universe that is slowly contracting (Ijjas and Steinhardt), testing with and comparing different values for the equation-of-state parameter. This allows for the comparison of the growth of large scale structure in scenarios including a matter-dominated expanding universe, a dark energy-dominated expanding universe, and now, an ekpyrotic scalar field-dominated contracting universe. Further, we consider the timescales on which deviations from ΛCDM in favor of the model considered could become relevant.

Botnets are networks formed with a number of machines infected by malware called bots. Detection of these malicious networks is a major concern as they pose a serious threat to network security. Most of the research on botnet detection is based on particular botnet characteristics which fail to detect other types of botnet. There exist several generic botnet detection methods that can detect varieties of botnets. But, these generic detection methods perform very poorly in real-life dataset as the methods are not developed based on a real-life botnet dataset. A crucial reason for those detection methods not being developed based on a real-life dataset is that there is a scarcity of large-scale real-life botnet dataset. Due to security and privacy concerns, organizations do not publish their real-life botnet dataset. Therefore, there is a dire need for a simulation methodology that generates a large-scale botnet dataset similar to the original real-life dataset while preserving the security and privacy of the network. In this dissertation, we develop a generic bot detection methodology that can detect a variety of bots and evaluate the methodology in a real-life, large, highly class-imbalanced dataset. Numerical results show that our methodology can detect bots more accurately than the existing methods. Realizing the need for real-life large-scale botnet dataset, we develop a simulation methodology to simulate a large-scale botnet dataset from a real-life botnet dataset. Our simulation methodology is based on Markov chain and role–mining process that can simulate the degree distributions along with triangles (community structures). To scale-up the original graph to large-scale graph, we also propose a scaling-up algorithm, Enterprise connection algorithm. We evaluate our simulated graph by comparing with the original graph as well as with the graph generated by Preferential attachment algorithm. Comparisons are done in the following three major categories: comparison of botnet subgraphs, comparison of overall graphs and comparison of scaled-up graphs. Result demonstrates that our methodology outperform Preferential attachment algorithm in simulating the triangle distributions and the botnet structure.

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