In this research, a bidirectional seismic isolation device composed of sloped bearing plates and multiple rollers arranged in both orthogonal-in-plane directions is numerically studied. A previous analytical model of a single direction of roller bearing (RB) system is extended to a two-direction RB system. Several experimental tests in a physical building model with and without an RB system are used to validate the numerical model. The model is used to perform the nonlinear response of a four-story multi-column building when subjected to pairs of scaled near-fault earthquake records. The effect of the inclination angle of bearing plates in the range of 1.0° to 4.0°, the sliding friction force, and supplementary damping mechanisms ranging from 0.0 to 0.5 N/kg (i.e. friction force normalized with the structure mass) are also investigated. The results show that the proposed bidirectional RB system is suitable for reducing the seismic response of stiff and flexible multi-column structures. In particular, the RB system reduces the acceleration responses by 5% to 85% in flexible structures and 86% to 96% in stiff structures. Furthermore, bearing plates with an inclination angle greater than or equal to 3.0° have significant benefits in terms of self-centering capacity.

The thermodynamic optimization of a process focuses on consumption, production, and efficient use of energy. The unsteady-state nature of batch reactor processing requires describing the set of processes’ dynamic behavior for energy optimization. This work aims to apply the formalism of chemical thermodynamics to a multistep chemical system in a batch reactor, aiming for a dynamic description of its evolution to the equilibrium state. As the system of study, we selected a mathematical model called the Oregonator, derived from the mechanism of the oscillating Belousov-Zhabotinsky reaction. In the methodology, we used the reaction quotient to evaluate the Gibbs function, the thermodynamic affinity, and the entropy generation as a function of the reaction extent. The results show that the overall reaction fulfills the thermodynamic fundamentals of chemical equilibrium, despite having a non-stoichiometric coefficient. However, the multistep coupled reaction system does not allow verifying compliance with the thermodynamic foundations of chemical equilibrium. We conclude that it is necessary to improve thermodynamic formalism to describe multistep chemical processes as a function of a global reaction extent variable. In this scenario, the entropy production rate emerges as a promising quantity.

In the modern industry, computer modeling and simulation tools have become fundamental to estimating the behavior of rotodynamic systems. These computational tools allow analyzing possible modifications as well as alternative solutions to changes in design, with the aim of improving performance. Nowadays, rotodynamic systems, present in various industrial applications, require greater efficiency and reliability. Although there are deep learning methodologies for monitoring and diagnosing failures which improve these standards, the main challenge is the lack of databases for learning, a problem that can be addressed through experimental monitoring and computer analysis. This work analyzes the vibrations of two induced-draft fans with excess vibration in a thermoelectric plant in Mexico. A vibration analysis was carried out through the instrumentation and monitoring of accelerometers located at crucial points in the fans. The results of this experimental analysis were validated by computer simulation based on FEM. The results show that the operating speed of the induced-draft fans is very close to their natural frequency, causing considerable stress and potential failures due to excessive vibration. Finally, this work presents a practical solution to modify the natural frequency of induced-draft fans, so that they can function correctly at the required operating speed, thus mitigating excessive vibration issues.

The steady-state analysis of electrical machines requires a detailed characterization of their equivalent electrical circuit, which adequately represents the transformation and interaction between electrical and mechanical energy. This research aims to characterize the equivalent circuit of three-phase induction motors by minimizing the mean square error between the measured and calculated torque variables. These torques are obtained from data provided by the manufacturer, including starting, peak, and full-load torques. A metaheuristic optimization technique is applied to solve the resulting nonlinear programming model based on the interactions between the sine and cosine functions. The numerical results obtained with this algorithm demonstrate its efficiency in terms of response quality, reaching objective function values of less than \(1\times10^{-8}\) with regard to the measured and calculated variables. Simulation results in two test systems allow concluding that the parametric estimation problem in three-phase induction motors is a multimodal optimization problem. This implies a potentially infinite set of solutions that minimize the root mean square error and adequately represent the behavior of the motor's output torque under various probable operating conditions.

It is imperative to consider the environmental impact of energy production and its cost in deciding how to meet future energy needs. In this regard, it is possible to harness the power of the sun by using photovoltaic (PV) cells. However, when the temperature of a PV cell increases, its generation efficiency is negatively affected. The open-circuit voltage of PV modules is the most sensitive parameter to temperature changes. As the temperature rises, this parameter decreases, and the short-circuit current increases. The circuit's resistance also rises as the electrons’ speed is reduced. Temperature also affects the lifespan of PV cells, increasing the rate of thermal decay in their materials. On the other hand, when solar radiation is absorbed at lower temperatures, the system’s efficiency, power capacity, and useful life increase. PV module surface temperatures can be reduced in a variety of ways, e.g., the surface can be cooled using water. This work studied hybrid PV-thermal modules under the climate conditions of the Hatay province (Turkey) in order to assess the effect of water cooling on their generation efficiency. The results allow stating that up to 52.6% more electricity can be generated by cooling the module's surface. Additionally, it was found that, in order for PV modules to perform efficiently in Hatay's climate, they must operate at a maximum surface temperature of 55 °C.

Occupational risk assessment is the process of estimating the magnitude of risks that cannot be avoided. Then, the corresponding assessment is carried out, using comparative tables with different evaluation methods. Current risk assessment techniques enable the individual assessment of each potential risk, but there is no method to globally assess potential risks in an organization. The motivation of this research was to develop an objective and quantitative risk assessment system through a diffuse probabilistic model integrating stochastic and non-stochastic uncertainty. To this effect, an empirical collective record was used, whose attribute of interest was the occurrence of different accident types over a period of 52 weeks. Here, each of the collectives represented a linguistic input variable. In the probabilistic fuzzification stage, the frequentist probability of the occurrence of accidents was determined. One of our most important contributions to probabilistic fuzzy systems lies in our classification of language labels based on the linguistic projection of frequentist probabilities via a projection membership function determined by experts. The use of the total probability theorem in the implication stage is also proposed. The output of the system determines the type of risk, its evaluation, and the probability of its occurrence, vital factors to be considered in prevention work. The system’s stages are explicitly described and applied to real data corresponding to construction materials distribution company. One of the relevant conclusions of this research is that the integration of stochastic and imprecise uncertainty allows for a more reliable risk assessment system.

The design of high-speed serial links continues to attract the attention of the electronics industry due to the steady development of different telecommunications standards, generating a constantly growing data rate and new modulation schemes. However, conventional certification metrics can lead to sub-optimal transmit (Tx) and receive (Rx) circuit designs. Therefore, the Ethernet standard IEEE 802.3bj introduced a more effective evaluation method called channel operating margin (COM) to explore the design space at an early stage. Although the advantages of COM have been discussed in the literature and only a few works explore its potential as a backplane design tool, there are no reports on the use of COM as a complementary design tool for transceiver circuits. This work studies the use of COM as a complementary tool for transceiver design. COM performance is evaluated for four 100GBASE-KP4 backplanes and different equalization architectures. The impact of the metric and the challenges associated with incorporating new equalization structures into the COM flow are discussed. The results reveal a conventional Tx-Rx architecture that exceeds the COM threshold and an alternative one that improves the opening of the eye diagram but does not exceed the threshold.

Dissolved gas chromatography (DGA) analysis and Megger DC insulation tests are performed to diagnose the condition of a power transformer. In this context, the objective of this study is to assess whether there is a relationship between both types of tests. To this effect, a database with DGA and Megger DC test protocols is analyzed, using the theory of variable correlation as well as current DGA techniques. The results allow stating that there is indeed a relationship between both tests under specific conditions. Therefore, the DC isolation status of a transformer can be estimated via DGA tests.

The network real-time kinematic (NRTK) positioning technique is currently used in numerous applications. The aim of this study was to better understand the process of obtaining accurate positions by statistically evaluating the significance of differences between repeated measurements for a single point at different times of the day (morning, noon, and evening) using the Virtual Reference Station (VRS), Flächen Korrektur Parameter (FKP), and Master Auxiliary Concept (MAC) correction methods. An analysis of variance (ANOVA) was used to this effect. Further analysis was carried out to determine the accuracy and precision of the coordinate differences obtained via a static GNSS (global navigation satellite system) and by averaging the repeated measurements. It was determined that the accuracy and precision of the vertical component of the coordinates were lower than that of the horizontal component. The FKP correction method yielded the best results. It was observed that the accuracy and precision of the measurements taken at noon were the lowest. The ANOVA showed that the differences between repeated measurements were statistically significant and that there were outlier measurements. The results of this study are important for NRTK users to be able to statistically evaluate different measurement configurations and obtain positions with the desired accuracy and precision.

Portland cement is one of the most used construction materials. However, its production represents between 5 and 7% of the total CO2 emissions. On the other hand, during construction and demolition activities, different wastes are produced, including recycled brick powder (RBP), whose potential as a supplementary cementitious material (SCM) has been demonstrated in the literature. This research aims to evaluate RBP as a partial replacement for Portland cement in concrete. 5 to 10% of Portland cement was replaced with RBP in two strength designs (20 and 25 MPa) in order to propose concretes that meet the requirements for use in construction. Tests involving slump, compressive strength, tensile strength by diametrical compression, absorption, density, and void content were performed. The results show that a 5% RBP replacement does not affect workability in concrete mixes, as it maintains their mechanical resistance and slightly improves their physical properties. On the other hand, 10% RBP replacements adversely affect workability and reduce tensile strength. These results are attributed to pozzolanic activity and the physical effect caused by RBP, whose performance may be improved by reducing RBP particles and increasing their specific surface area (SSA). Using RBP as a replacement for Portland cement to produce concrete is a viable alternative with a sustainable approach.