This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads to great interest in studying discrete surfaces. With the rich smooth surface theory in hand, one would hope that this elegant theory can still be applied to the discrete counter part. Such a generalization, however, is not always successful. While discrete surfaces have the advantage of being finite dimensional, thus easier to treat, their geometric properties such as curvatures are not well defined in the classical sense. Furthermore, the powerful calculus tool can hardly be applied. The methods in this thesis, including angular defect formula, cotangent formula, parallel meshes, relative geometry etc. are approaches based on offset meshes or generalized offset meshes. As an important application, we discuss discrete minimal surfaces and discrete Koenigs meshes.

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Objective: To evaluate the association between the use of a 3D virtual App and academic performance among Peruvian medical students. In addition, factors associated with academic performance were also assessed. Methods: We conducted an analytical cross-sectional study in students enrolled in the Musculoskeletal System course during the first semester of 2019. Students filled out a data collection form and the "Self-directed learning readiness scale" (SDLRS) questionnaire adapted by Fisher, King, and Tangle. Linear regression models were carried out to assess the association between the appropriate use of the application and academic performance. Additionally, the factors associated with academic performance were evaluated using nested models, and beta coefficients were calculated by manual forward selection. Results: A total of 187 medical students were included. The 61% were female and the median age was 21 [20-22] years. The average grade was 13.5 +/- 2 and 21% reported an adequate use of a 3D App. No association was found between the use of the 3D App and academic performance in the adjusted model (a beta = 0.17; 95% CI: -0.45 to 0.80). We found that age (a beta = -0.22; 95% CI: -0.39 to -0.06), performing extracurricular activities (a beta = 0.75, 95% CI: 0.25 to 1.24) and having failed an anatomy/physiology course before (a beta = -2.11 to 95% CI: -2.9 to -1.8) were factors associated with academic performance. Conclusion: The adequate use of a 3D application to study the anatomy of the musculoskeletal system was not significantly associated with better academic performance. / Revisión por pares

Plasma-assisted processing and deposition of materials is an important component of modern industrial applications, with plasma reactors sharing 30% to 40% of manufacturing steps in microelectronics production [1]. Development of new flexible electronics increases demands for efficient high-throughput deposition methods and roll-to-roll processing of materials. The current work represents an attempt of practical design and numerical modeling of a plasma enhanced chemical vapor deposition system. The system utilizes plasma at standard pressure and temperature to activate a chemical precursor for protective coatings. A specially designed linear plasma head, that consists of two parallel plates with electrodes placed in the parallel arrangement, is used to resolve clogging issues of currently available commercial plasma heads, as well as to increase the flow-rate of the processed chemicals and to enhance the uniformity of the deposition. A test system is build and discussed in this work. In order to improve operating conditions of the setup and quality of the deposited material, we perform numerical modeling of the plasma system. The theoretical and numerical models presented in this work comprehensively describe plasma generation, recombination, and advection in a channel of arbitrary geometry. Number density of plasma species, their energy content, electric field, and rate parameters are accurately calculated and analyzed in this work. Some interesting engineering outcomes are discussed with a connection to the proposed setup. The numerical model is implemented with the help of high-performance parallel technique and evaluated at a cluster for parallel calculations. A typical performance increase, calculation speed-up, parallel fraction of the code and overall efficiency of the parallel implementation are discussed in details.

The CFD simulation of cooling piston compressor Stream, manufactured by Emerson company, is the topic of this diploma thesis. Analysis of moving parts (piston, valves) and refrigerant or physical settings for simulation were based on experimental data provided by Emerson. The goal of the thesis is to test opportunities of Star-CCM+ in simulating the flow inside the compressor. In the end there will be a comparison of experimental data and results from the simulation. The thesis also contains a theoretical background of piston compressors and phenomenon following the operating compressor.

We introduce an adaptive pacing scheme to overcome the drawbacks of TCP in wireless mesh networks with Internet connectivity. The pacing scheme is implemented at the wireless TCP sender as well as at the mesh gateway, and reacts according to the direction of TCP flows running across the wireless network and the Internet. TCP packets are transmitted rate-based within the TCP congestion window according to the current out-of-interference delay and the coefficient of variation of recently measured round-trip times. Opposed to the majority of previous work which builds on simulations, we implement a Linux prototype of our approach and evaluate its feasibility in a real 20-node mesh testbed. In an experimental performance study, we compare the goodput and fairness of our approach against the widely deployed TCP NewReno. Experiments show that our approach, which we denote as Mesh Adaptive Pacing (MAP), can achieve up to 150% more goodput than TCP NewReno and significantly improves fairness between competing flows. MAP is incrementally deployable since it is TCP-compatible, does not require cross-layer information from intermediate nodes along the path, and requires no modifications in the wired domain.

The ever increasing demand for video content directed the focus of researchfrom traditional server-based schemes to peer-to-peer systems for videodelivery. In such systems, video data is delivered to the users by utilizing theresources of the users themselves, leading to a potentially scalable solution.Users connect to each other, forming a p2p overlay network on top of theInternet and exchange the video segments among themselves. The performanceof a p2p system is characterized by its capability to deliver the videocontent to all peers without errors and with the smallest possible delay. Thisconstitutes a challenge since peers dynamically join and leave the overlay andalso contribute different amounts of resources to the system.The contribution of this thesis lies in two areas. The first area is theperformance evaluation of the most prominent p2p streaming architectures.We study the streaming quality in multiple-tree-based systems. We derivemodels to evaluate the stability of a multiple tree overlay in dynamic scenariosand the efficiency of the data distribution over the multiple trees. Then, westudy the data propagation in mesh-based overlays. We develop a generalframework for the evaluation of forwarding algorithms in such overlays anduse this framework to evaluate the performance of four different algorithms.The second area of the thesis is a study of streaming in heterogeneous p2poverlays. The streaming quality depends on the aggregate resources that peerscontribute to the system: low average contribution leads to low streamingquality. Therefore, maintaining high streaming quality requires mechanismsthat either prohibit non-contributing peers or encourage contribution. In thisthesis we investigate both approaches. For the former, we derive a model tocapture the evolution of available capacity in an overlay and propose simpleadmission control mechanisms to avoid capacity drainage. For the latter, inour last work, we propose a novel incentive mechanism that maximizes thestreaming quality in an overlay by encouraging highly contributing peers tooffer more of their resources. / QC 20100506

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This study aims to propose a new alternative to optimize drilling and blasting processes from the mathematical and geological viewpoint using simulation software. The main objective is to design a systematic model of steps that can generate a simulation through JkSimBlast. This simulation must represent the best alternative for the design of drilling mesh and explosive selection to be implemented in the field. To achieve this goal, a seven-step process diagram was proposed, including geology, design aspects (burden and spacing across the areas of influence algorithm), analysis of physical parameters such as detonation rate, drill-mesh design, explosives selection and fragmentation analysis, simulation tests that could represent the field designs, and selection of the most optimal simulation. For the collection of parameters in the field, we have used MicroTrap Software and WipFrag, which have allowed the design of a mesh according to the needs of the rocky massif. The most optimal simulation was implemented at Caravelí Mining Company-Estrella Unit and had a positive impact on the optimization of drilling and blasting, as the costs of these processes were reduced by 14.6%. Specifically, the costs of explosives were reduced by 2.6% and the costs of drilling steels by 10.4%. The performance of the loading machine advance/shot increased by 13.2% and 15.6%, respectively. Copyright 2019.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Introduction: Approximately, one in three Peruvian children aged 6 to 59 months old have anaemia. Maternal depression, which may be disabling and affect the proper care of children, is associated with chronic malnutrition in their offspring. Therefore, the aim of this study is to evaluate if there is an association between depressive symptoms of mothers with the presence of anaemia in their children. Methods: Analytical cross-sectional study of the Peruvian Demographic Health Survey 2015, which is nationally representative. Depressive symptoms were measured with the Patient Health Questionnaire-9 (PHQ-9) using a score of 10 as cut-off. The presence of anaemia was measured using HemoCue® and was considered positive when the haemoglobin was less than 11 g/dl. Results: Crude and adjusted prevalence ratios (PR and aPR) were calculated with 95% confidence interval (CI), using generalized linear models of the Poisson family. We analysed 6683 mother–child binomials. The prevalence of anaemia in the children and depressive symptoms in women were 28.7% (95% CI: 27.3–30.2) and 6.9% (95% CI: 6.1–7.9), respectively. We found no statistically significant association between these variables in the bivariable analysis or in the different multivariable models (aPR: 1.05, 95% CI: 0.85–1.30). The sample did not have moderate or severe malnutrition. Conclusions: There is no statistically significant difference between the prevalence of anaemia in children of mothers with or without depressive symptoms. We recommend continuing research in this field to determine more associate factors to childhood anaemia in order to improve primary prevention interventions. Ideally, conducting longitudinal studies such as prospectives cohorts to determine risk factors should be done. / Revisión por pares

COVID-19 is rarely reported in children and they are mildly affected in most cases. The most common clinical presentation of COVID-19 is cough, fever and sore throat; severe cases show tachypnea. The course of the disease is from one to two weeks. Laboratory findings are nonspecific; lymphopenia, elevation of C-reactive protein and procalcitonin have been described. Early chest X-ray is usually normal, and the most common tomographic findings are consolidations with halo, ground-glass opacities and tiny nodules which mainly affects subpleural areas. Management of the disease is supportive; in severe cases, it should be focused on respiratory support. It is recommended to limit the handling of respiratory secretions and to follow the same preventive measures provided to adults. / Revisión por pares