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Drilling is crucial to many industries, including hydrocarbon extraction, CO2 sequestration, geothermal energy, and others. During penetrating the subsurface rocks, drilling fluid (mud) is used for drilling bit cooling, lubrication, removing rock cuttings, and providing wellbore mechanical stability. Significant mud loss from the wellbore into the surrounding formation causes fluid lost-circulation incidents. This phenomenon leads to cost overrun, environmental pollution, delays project time and causes safety issues. Although lost-circulation exacerbates wellbore conditions, prediction of the characteristics of subsurface formations can be obtained. Generally, four formation types cause lost-circulation: natural fractures, and induced fractures, vugs and caves, and porous/permeable medium. The focus in this work is on naturally fractured formations, which is the most common cause of lost circulation. In this work, a novel prediction tool is developed based on analytical solutions and type-curves (TC). Type-curves are derived from the Cauchy equation of motion and mass conservation for non-Newtonian fluid model, corresponding to Herschel-Bulkley model (HB). Experimental setup from literature mimicking a deformed fracture supports the establishment of the tool. Upscaling the model of a natural fracture at subsurface conditions is implemented into the equations to achieve a group of mud type-curves (MTC) alongside another set of derivative-based mud type-curves (DMTC). The developed approach is verified with numerical simulations. Further, verification is performed with other analytical solutions. This proposed tool serves various functionalities; It predicts the volume loss as a function of time, based on wellbore operating conditions. The time-dependent fluid loss penetration from the wellbore into the surrounding formation can be computed. Additionally, the hydraulic aperture of the fracture in the surrounding formation can be estimated. Due to the non-Newtonian behavior of the drilling mud, the tool can be used to assess the fluid loss stopping time. Validation of the tool is performed by using actual field datasets and published experimental measurements. Machine-Learning is finally investigated as a complementary approach to determine the flow behavior of mud loss and the corresponding fracture properties.

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<p><strong>Background:</strong> A better application of evidence-based available therapies and optimal patient care are suggested to have a positive association with patient outcomes for cardiovascular disease (CVD) patients. Electronic integration of care tested in the Computerization of Medical Practices for the Enhancement of Therapeutic Effectiveness (COMPETE) Π study showed that a shared electronic decision-support system to support the primary care of diabetes improved the process of care and some clinical markers of the quality of diabetes care. On the basis of COMPETE Π trial, COMPETE Ш study showed that older adults at increased risk of cardiovascular events, if connected with their family physicians and other providers via an electronic network sharing an intensive, individualized cardiovascular tracking, advice and support program, enhanced their process of care – using a process composite score to lower their cardiovascular risk more than those in conventional care. However, results of the effect of intervention on composite process and clinical outcomes were not similar – there was no significant effect on clinical outcomes.</p> <p><strong>Objectives:</strong> Our objectives were to investigate the robustness of the results based the commonly used statistical models using COMPETE III dataset and explore the validity of the surrogate process composite score using a correlation analysis between the clinical outcomes and process composite score.</p> <p><strong>Methods:</strong> Generalized estimating equations (GEE) were used as a primary statistical model in this study. Three patient-level statistical methods (simple linear regression, fixed-effects regression, and mixed-effects regression) and two center-level statistical approaches (center-level fixed-effects model and center-level random-effects model) were compared to reference GEE model in terms of the robustness of the results – magnitude, direction and statistical significance of the estimated effects on the change of process composite score / on-target clinical composite score. GEE was also used to investigate thecorrelation between the clinical outcomes and surrogate process composite scores.</p> <p><strong>Results:</strong> All six statistical models used in this study produced robust estimates of intervention effect. No significant association between cardiovascular events and on-target clinical composite score and individual component of on-target clinical composite score were found between the intervention group and control group. However, blood pressure, LDL cholesterol, and psychosocial index are significant predictors of cardiovascular events. Process composite score can both predict the cardiovascular events and clinical improvement, but the results were not statistically significant- possibly due to the small number of events. However, the process composite score was significantly associated with the on-target clinical composite score.</p> <p><strong>Conclusions:</strong> We concluded that all five analytic models yielded similar robust estimation of intervention effect comparing to the reference GEE model. The relatively smaller estimate effects in the center-level fixed-effects model suggest that the within-center variation should be considered in the analysis of multicenter RCTs. Process composite score may serve as a good predictor for CVD outcomes.</p> / Master of Science (MSc)

<p> Tool life during the precision stamping of stainless steel sheet (AISI 301) has been studied with particular emphasis on reduction in the punch diameter and part hole size due to tool wear. Two analytical models for predicting tool life in terms of number of quality parts that could be stamped between two re-grindings have been proposed using a combination of Archard's wear model and punching force. The proposed tool life models have been verified by experiment trials with a round M2 punch and die. The trials were carried out on a precision progressive die in an industrial environment.</p> <p> The first tool life model calculates the pierced hole diameter variation for a given tool from sheet material properties and gives an estimation of number of parts that could be stamped for a given tolerance on a hole size. The second tool life model calculates number of parts with respect to the allowed burr height. Both of the proposed models are derived using sheet material properties such as sheet thickness, strength coefficient (K), strain hardening index (n) and material elongation (A); process parameters such as die clearance and friction coefficient; punch characteristics such as normalized wear rate, punch diameter and punch edge radius. Finite element analysis was also employed to simulate the hole piercing process to predict burr height. The results from the proposed tool life models, FE modeling and the experiments are in good agreement.</p> / Thesis / Master of Applied Science (MASc)

Computer networks security is a topic which has been extensively researched. This research is fully justified when one notices the dimensions of the problem faced. One can easily identify different kinds of networks, a large quantity of network protocols, and an overwhelming amount of user applications that make extensive use of networks for the purposes those applications were built. This conforms a vast research field, where it is possible for a researcher to set his or her interests over a set of threats, vulnerabilities, or types of attacks, and devise a mechanism to prevent the attack, mitigate its effects or repair the final damages, based upon the specific characteristics of the scenario. Our research group on Computer Networks has been researching on certain kinds of computer networks security risks, specially those affecting wireless networks. In previous doctoral works [13], detection and exclusion methods for dealing with malicious nodes in mobile ad hoc networks (MANETs) had been proposed, from the point of view of every individual network node, using a technique called Intrusion Detection Systems (IDS) based on Watchdog methods. In this scope, we pretend to optimize network throughput removing misbehaved nodes from the network communication processes, a task performed specifically by the Watchdog systems. When isolated security techniques obtain good results on dealing with one type of attacks, a way to improve the whole network performance could be establishing mechanisms for cooperatively sharing information between well-behaved nodes to speed up misbehaved node detection and increase accuracy. Obviously, these mechanisms will have a cost in terms of network transmission overhead and also a small computing time overhead needed to analize the received data and to obtain an opinion about a suspect node. The key issue here it to adequately balance the costs and the benefits related to these cooperation techniques to ensure that the overall network performance is increased if compared with a non-collaborative one. / Serrat Olmos, MD. (2013). Cooperation techniques to improve peer-to-peer wireless networks security [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/32831

Yes / Ice cover formed on an alluvial channel can significantly alter the flow characteristics, such as the vertical distributions of streamwise velocity and shear stress, and hence the water and sediment transport process. The vertical profile of the suspended sediment concentration in the ice-covered alluvial channels with steady uniform flows is investigated in this study. To calculate the suspended sediment concentration, we are based on the Schmidt O’Brien equation and deduce an analytical model that employs an existing eddy viscosity model and a modified formula of the sediment fall velocity considering the common effects of the upper and lower boundaries. The proposed analytical model is then validated by using available experimental data reported in the literature. The predicted accuracy of the proposed model is evaluated through error statistics by comparing to previous modeled results. The relative concentration profiles of the suspended sediment are subsequently simulated by applying the validated analytical model with different characteristic parameters. Results show that the relative concentration decreases with the increase of both the ice cover roughness and the sediment fall velocity. The uniformity of the relative concentration distribution is closely related to the value of the proportionality parameter σ, revealing the physical mechanism that the more prominent the turbulent diffusion effect is, the more uniform the relative concentration profile is. / This work was supported by the National Natural Science Foundation of China (grant 604 numbers 52020105006 and 11872285) and the Open Funding of State Key Laboratory of Water Resources and Hydropower Engineering Science (WRHES), Wuhan University (Project number 2018HLG01).

Knowledge of the end winding inductance of electrical machines is decisive for calculating their operating performance. In this article, two different approaches to analytically calculate the stator end winding inductance of large induction machines are discussed. The first method is based on the exact replication of the 3D conductor geometry using serially connected straight filaments, where the inductances are calculated by solving Neumann’s integral. In the second method, the end winding flux is resolved into components excited by the axial and circumferential end winding magnetomotive force, resulting in a far simpler geometrical model. In both cases, end face effects are taken into account by adopting the method of images. The analytical approaches are compared to the known analytical calculation method proposed by Alger [1]. In addition, the stator end winding inductance is computed by means of 3D finite-element analysis. Using experimental validation, it is shown that both the analytical and numerical results reasonably correlate with removed rotor inductance measurements taken for several induction machines with different rated powers and frame sizes, if the permeability of the laminated core is taken into consideration.