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Abstract Numerous test results at laboratory scale confirm the utility of Recycled Aggregate (RA) for the development of concrete that demonstrates durability and adequate in-fresh and mechanical behavior. However, feasibility evaluations of the use of RA in real industrial applications are necessary, before any large-scale industrial application of these products can begin. In this research, the feasibility of producing precast-concrete components containing large amounts of coarse RA at a precast-concrete plant is analyzed. Two Self-Compacting Concretes (SCC) were produced incorporating 0% and 100% coarse RA, respectively, at both laboratory scale (0.08 m3) and industrial scale (2 m3). Work took place at the industrial-scale facilities of a precast-concrete company that was collaborating in this study. Flowability and mechanical behavior were maintained as concrete production volumes increased, and concrete strength even increased after adding coarse RA, due to a careful mix design. However, the durability performance worsened by around 20% when produced at industrial scale, being this worsening higher whether coarse RA was used. A Multi-Criteria Decision-Making (MCDM) analysis, in which the criteria of the precast-concrete company defined the relative importance of each concrete property, showed the feasibility of manufacturing precast-SCC components containing coarse RA for interior usage, whose fundamental requirement is adequate mechanical strength. The results of the MCDM analysis also underlined the lower cost of coarse RA, making its use in SCC components cast with large concrete volumes advisable. Overall, the addition of coarse RA in the precast-concrete industry is recommended in the interests of a greener construction sector.
Abstract Carbon nanotube/metal oxide based hybrids are envisioned as high performance electrochemical energy storage electrodes since these systems can provide improved performances utilizing an electric double layer coupled with fast faradaic pseudocapacitive charge storage mechanisms. In this work, we show that high performance supercapacitor electrodes with a specific capacitance of ∼192 F/g along with a maximum energy density of ∼3.8 W h/kg and a power density of ∼28 kW/kg can be achieved by synthesizing zinc oxide nanowires (ZnO NWs) directly on top of aligned multi-walled carbon nanotubes (MWCNTs). In comparison to pristine MWCNTs, these constitute a 12-fold of increase in specific capacitance as well as corresponding power and energy density values. These electrodes also possess high cycling stability and were able to retain ∼99% of their specific capacitance value over 2000 charging discharging cycles. These findings indicate potential use of a MWCNT/ZnO NW hybrid material for future electrochemical energy storage applications.
Cancer is hard to cure and radiation therapy is one of the most popular treatment modalities. Even though the benefits of radiation therapy are undeniable, it still has possible side effects. To avoid severe side effects, with clinical evidence, delivering optimal radiation doses to patients is crucial. Intensity-modulated radiation therapy (IMRT) is an advanced radiation therapy technique and will be discussed in this thesis. One important step when creating an IMRT treatment plan is radiation beam geometry generation, which means choosing the number of radiation beams and their directions. The primary goal of this thesis was to find good gantry angles for IMRT plans by combing computer graphics and machine learning. To aid the plan generation process, a new method called reverse beam was introduced in this work. The new solution consists of two stages: angle discovery and angle selection. In the first stage, an algorithm based on the ray casting technique will be used to find all potential angles of the beams. For the second stage, with a predefined beam number, K-means clustering algorithm will be employed to select the gantry angles based on the clusters. The proposed method was tested against non-small cell lung cancer dataset from The Cancer Imaging Archive. By using IMRT plans with seven equidistant fields with 45-degree collimator rotations generated by the Ethos therapy system from Varian Medical Systems as a baseline for comparison, the plans generated by the reverse beam method illustrated good performance with the capability of avoiding organs while targeting tumors.