Abstract: The literature has focused on transient stability, concentrating on its assessment and control under operational situations and limited contingencies. This often leads to transient stability issues not addressed in studies, making the system vulnerable to imminent collapses. In this context, this work proposes a methodology for identifying critical generators under a broad range of operational scenarios and contingencies, serving as a foundation for the development of an adaptable disconnection scheme that responds to the system's real-time dynamics. The methodology relies on the generation of a database encompassing a wide spectrum of operational scenarios and N-1 contingencies, as well as the systematic disconnection of generators to identify those deemed critical for mitigating transient instability. In a controlled simulation environment (IEEE New England 39-bus system in DigSILENT Power Factory software), the methodology effectively identified critical generators in 99.6% of the simulated cases deemed unstable due to transient stability issues, thereby establishing a solid foundation for training a learning model that operates in real time according to the system's dynamics, which translates into an adaptable generation disconnection scheme.

Resumen: La literatura ha prestado atención a la estabilidad transitoria, centrándose en su evaluación y control en situaciones operativas y contingencias limitadas. Esto con frecuencia conduce a problemas de estabilidad transitoria no contemplados en los estudios que hacen que el sistema sea susceptible a colapsos inminentes. En este sentido, este trabajo propone una metodología para identificar los generadores críticos bajo un amplio universo de escenarios de operación y contingencias, que sirve como base para el desarrollo de un esquema de desconexión adaptable que responda a la dinámica en tiempo real del sistema. La metodología se basa en la generación de una base de datos con un amplio espectro de escenarios operativos y contingencias N-1, así como la desconexión sistemática de generadores que permita identificar aquellos denominados como críticos para la mitigación de inestabilidad transitoria. En un entorno de simulación controlado (sistema New England IEEE de 39 barras en el software DigSILENT Power Factory), la metodología encontró con efectividad los generadores críticos en un 99.6 % de los casos simulados que fueron identificados como inestables por estabilidad transitoria, determinando así una base sólida para el entrenamiento de un modelo de aprendizaje que actúe en tiempo real según la dinámica del sistema, lo que se traduce en un esquema de desconexión de generación adaptable.

Abstract:This study aims to develop a final design for the Northwest Slope of the Cuajone Mine (Peru) by calculating the factor of safety (FS) using finite element methods, proposing that this method enables a more accurate assessment of slope stability. The methodology included geological and geotechnical characterization of the slope through field mapping, sample analysis, and laboratory testing. A three-dimensional model was created using Phase2 software to simulate the interaction between slope geometry and operational conditions, conducting a stability analysis under different loads and disturbances. The results indicate that the finite element method detailedly evaluated the safety factor and the inter-ramp angle (IRA). In the southern zone (section A-A'), it was determined that an IRA of 43° generates an FS of 1.1. In the northern zone (section B-B'), an IRA of 38° is recommended to achieve an FS of 1.57. These findings are essential for ensuring operational safety and efficiency at the mine, as an inadequate slope design could compromise infrastructure integrity and worker safety. Advanced methods, such as finite element analysis and considering factors like IRA and disturbance factors, allow for a precise slope stability assessment and effective stabilization measures to manage risks and develop specific reinforcement solutions according to the slope's geotechnical configuration.

Resumen: El objetivo de este estudio es desarrollar un diseño final para el Talud Noroeste de la Mina Cuajone (Perú) utilizando el cálculo del factor de seguridad (FS) mediante métodos de elementos finitos, planteando que este método permite una evaluación más precisa de la estabilidad del talud. La metodología incluyo la caracterización geológica y geotécnica del talud mediante mapeo de campo, análisis de muestras y pruebas de laboratorio. Se creo un modelo tridimensional usando el software Phase2 para simular la interacción entre la geometría del talud y las condiciones operativas, realizando un análisis de estabilidad bajo diferentes cargas y perturbaciones. Los resultados indican que el método de elementos finitos proporciono una evaluación detallada del factor de seguridad y del ángulo interrampa (IRA). En la zona sur (sección A-A'), se determina que un IRA de 43° genera un FS de 1.1. En la zona norte (sección B-B'), se recomienda un IRA de 38° para lograr un FS de 1.57. Los hallazgos son fundamentales para garantizar la seguridad y eficiencia operativa en la mina, ya que un diseño de talud inadecuado podría comprometer la integridad de la infraestructura y la seguridad de los trabajadores. La aplicación de métodos avanzados como el análisis de elementos finitos y la consideración de factores como el IRA y el factor de perturbación permite una evaluación precisa de la estabilidad del talud y la implementación de medidas de estabilización efectivas para gestionar los riesgos y desarrollar soluciones de refuerzo específicas según la configuración geotécnica del talud.

Abstract: This research proposes the tuning of a controller for a D-STATCOM distribution static synchronous compensator in order to improve the steady-state and dynamic state voltage profiles for a distribution network with the presence of distributed generation. In this study, a methodology is developed using the Power Factory-DigSILENT (DSL) simulation software and programming in the Python 3.6 environment, for the study, the IEEE 13-node test network is selected, which is an unbalanced distribution network and for the optimization process required in the methodology, the mean variance mapping heuristic optimization algorithm (MVMO) is used, in the case of the location of the FACT device in the test network, the bus with the highest load concentration is selected, the optimal location of the device according to any criterion is not addressed. This work focuses on the importance of using optimization techniques in the tuning of the parameters contained in a D-STATCOM controller, which allows to efficiently determine operating scenarios with voltage regulation that comply with the operating limits established by national regulations, making appropriate use of reactive power compensation in the operation of an electrical network.

Resumen: La presente investigación propone la sintonización de un controlador para un compensador síncrono estático de distribución D-STATCOM con el fin de mejorar los perfiles de voltaje en estado estacionario y estado dinámico para una red eléctrica de distribución con presencia de generación distribuida. En este estudio se desarrolla una metodología empleando de manera conjunta el software de simulación Power Factory-DigSILENT (DSL) y la programación en el entorno de Python 3.6, para el estudio, se selecciona la red de prueba IEEE de 13 nodos, que es una red de distribución desbalanceada y para el proceso de optimización requerido en la metodología , se utiliza el algoritmo de optimización heurística de mapeo de varianza media (MVMO), en el caso de la ubicación del dispositivo FACT en la red de prueba, se selecciona la barra con mayor concentración de carga, no se aborda la ubicación optima del dispositivo de acuerdo algún criterio especifico. Este trabajo se enfoca en la importancia del uso de técnicas de optimización en la sintonización de los parámetros que contiene el controlador de un D-STATCOM, lo que permite determinar de manera eficiente escenarios de operación con regulación de voltaje que cumplen con los límites operativos establecidos por la normativa nacional, haciendo un uso adecuado de la compensación de potencia reactiva en la operación de una red eléctrica.

Abstract Introduction: In Paraguay, the relationship between drug trafficking and politics dates back to the last stage of the dictatorship (1954-1989), although it began an expansive process in the following years. Objective: Analyze how drug trafficking maintained and expanded its influence in the country thanks to the establishment of increasingly close relations between organized crime and the political class that emerged with democracy. Methodology: The production of information combines qualitative and ethnographic approaches, with observations, interviews and informal conversations with different key actors in different regions of the country over the last five years, in addition to an exhaustive documentary review. Conclusions: The findings suggest that for the Paraguayan context the concept of narco-politics may no longer be sufficient, being more appropriate the use of mafia, since there is an overcoming of the classic complicities of exchange of favors (impunity for financing) between politics and organized crime, installing an organic system of diffuse illegality, including: politicians, criminals, white-collar professionals, businessmen; which guarantees widespread profit and impunity. The level of interpenetration between criminality, society and institutions is reaching such deep levels that the very stability of democracy is being called into question.

Resumen Introducción: en Paraguay, la relación entre política y narcotráfico se remonta a la última etapa de la dictadura (1954-1989), aunque inició un proceso expansivo en los años siguientes. Objetivo: analizar cómo el narcotráfico mantuvo y amplió su incidencia en el país gracias a la instalación de relaciones cada vez más estrechas entre el crimen organizado y la clase política surgida con la democracia. Metodología:la producción de información combina los enfoques cualitativo y etnográfico; se han realizado en los últimos cinco años observaciones, entrevistas y conversaciones informales con diferentes actores claves, en distintas regiones del país, además de una exhaustiva revisión documental. Conclusiones:los hallazgos sugieren que, para el contexto paraguayo, el concepto de narcopolítica puede resultar insuficiente, y ser más adecuado el de mafia, ya que existe una superación de las clásicas complicidades de intercambio de favores (impunidad por financiación) entre política y crimen organizado y en su lugar se ha instalado un sistema orgánico de ilegalidad difusa, que incluye: políticos, criminales, profesionales de cuello blanco, empresarios; lo cual garantiza ganancias e impunidad generalizadas. El nivel de compenetración entre criminalidad, sociedad e instituciones está llegando a niveles tan profundos que ponen en entredicho la misma estabilidad democrática.

ABSTRACT The rapid conversion of water-soluble carbohydrates in sorghum (Sorghum bicolor (L.) Moench) into lactic acid causes an abrupt decrease in silage pH, promoting alcoholic fermentation and aerobic deterioration. Despite the use of microbial and chemical additives, the results remain inconsistent. Mixing sorghum with cactus pear (Nopalea cochenillifera (L.) Salm-Dyck) can improve the stability and fermentative characteristics of silage. The aim of this study was to determine the ideal level of cactus pear that provides a good microbiological profile, as well as decreases losses during the ensiling process of mixed silages of cactus pear and sorghum. The treatments were composed of levels of cactus pear in the sorghum ensilage (0%, 25%, 50%, 75% and 100% cactus pear on a natural matter basis in the mixture), with four replicates each. It was found a quadratic effect (p < 0.05) on lactic acid bacteria counts, DM recovery and gas losses, with maximum estimated values of lactic acid bacteria and DM recovery in the levels of 51.8% and 33.5% of cactus pear, respectively, and minimum value of gas losses in the level of 37.9% of cactus pear in the silage. An increasing linear effect (p < 0.05) was observed on silage aerobic stability, contents of ether extract and non-fiber carbohydrates. When using cactus pear in the production of mixed silages with sorghum, it is recommended 50% cactus pear in the mixture, as it optimizes DM recovery and aerobic stability of the silages.

ABSTRACT Spermidine (Spd), a naturally occurring molecule in plants, is being investigated for its potential to improve the bean’s tolerance to salinity stress. This study explores how common beans (Phaseolus vulgaris L.) can be helped to thrive in salty environments. This research involved a group receiving regular watering with half strength Hoagland’s solution (HS), and other group watered with a modified form of the same solution containing 75 mM NaCl to stimulate salt stress. Seedlings were treated with foliar applications of Spd (0, 0.5, 1 mM) at five intervals: 15, 20, 25, 30, and 35 d after sowing. Applying Spd significantly reduced damage caused by salt and protected essential pigments for photosynthesis (total chlorophyll by 33% and carotenoids by 57% over than the Spd-untreated plants under saline conditions). Additionally, 1 mM Spd enhanced the antioxidant enzyme activities, i.e., superoxide dismutase, catalase, and ascorbate peroxidase by 15%, 55% and 4.6% and promoted the buildup of beneficial compounds like proline, free amino acids and sugars. Remarkably, exogenous Spd application reduced Na+ accumulation while improving K+ content in common beans under salinity stress. Additionally, it enhanced the cell membrane stability index (CMSI) during stressful situations, the maximum CMSI (94.31%) was recorded with 1 mM Spd under non-stress conditions, whereas the minimum CMSI (72.97%) was registered under salinity without Spd. Under salinity condition, the real-time quantitative PCR (qRT-PCR) results demonstrated a significant increase in the expression of the vacuolar-localized Na+/H+ antiporter protein (NHX1), and the multifunctional osmotic protection protein (Osmotin) in comparison to the control. Furthermore, common bean treated with Spd showed significantly higher expression levels of SOS1, NHX1, and Osmotin, under normal and salinity conditions, with the highest gene expression observed under 1 mM spermidine treatment under saline conditions. Spermidine at 1 mM notably decreased malondialdehyde levels compared to 0.5 mM (10.68 vs. 12.11 nmol g-¹ FW). Overall, the findings propose that Spd may be an effective tool for cultivating common beans in saline areas, potentially paving the way for increased food production in challenging environments.

The empirical pillar strength formulae have been widely, and in most cases successfully, applied to design underground pillars for mines in the Bushveld Igneous Complex (BIC). This paper presents the case for combining the empirical method with numerical modelling when it comes to crush pillar stability analyses. The benefits include an understanding of potential failure mechanisms, which may then be accounted for in the designs. In addition, the impact of weak layers, such as shear zones, the impact of the dip of the orebody, differences in layouts, such as holing widths and the presence of advanced strike gulleys (ASGs) immediately adjacent to the crush pillars, and stress regime (k-ratio) may be studied using numerical modelling, as it is not accounted for in the empirical method.

In his 1925 paper describing the Taung Child fossil, Dart makes various assertions about the landscape around Taung, inferring past climate dynamics, and the role these factors play in the evolution of our early prehuman relatives. He argues that this region of southern Africa is dry today and has been for much of the Cenozoic. This notion of long-term aridity and stability has dominated perspectives on southern African landscape evolution. Here, we present a review of this field, starting with the foundational studies from the late 1890s, which underpin Dart's hypothesis. We examine the work of 20th-century researchers who developed models of landscape evolution; however, almost all of these models have been qualitative. With technological advancements, new quantitative techniques have emerged to provide evidence of landscape evolution events and to test previous models, and we present a brief overview of these methods. We call for reflection on the framing and languaging of many of these landscape models, specifically the 'African land surface' model. While the evidence of a homogeneous and stable landscape is continually being challenged through scientific advancement, this terminology is rooted in outdated colonial thinking. We also note that the key narratives that have driven research on landscape evolution have been largely shaped by selected prominent Western-based scientists. As we mark the centenary of the Taung discovery, we look toward a new era of landscape evolution research: one characterised by technological advancements and more diverse, local teams that will produce more quantitative, nuanced models for southern Africa and create richer, more dynamic backdrops for our own human evolution. SIGNIFICANCE: We provide a review of over 100 years of models used to characterise landscape evolution in southern Africa. We argue that it is essential to reconsider current models of landscape evolution and assess their relevance in the southern African context. With technological advancements, we must question whether these models remain applicable or require revision. As scientists, we should also re-evaluate the terminology used in scientific dialogue to ensure it accurately reflects evolving perspectives. Finally, while the use of qualitative and quantitative methods have their unique benefits, we consider the application of more quantitative methods of landscape dating to test the existing models and build new, more complex ones.

Abstract Sapote gum (SG) is a new biopolymer with promissory functional properties. This study aimed to determine if SG is a suitable emulsifier for obtaining stable grape seed oil (GSO) emulsions. In the first stage, coarse emulsion concentrations of SG and grapeseed oil - GSO were evaluated, applying the Central Composite Rotational Design (0.59% to 3.41% of SG and 12.93% to 27.07% GSO). For the second stage, using a Centered Face Design - CFD, the resulting emulsion was sonicated at 90, 270, and 450 Watts at 5, 10, and 15 min. Finally, a validation was made. Emulsions were evaluated through microstructure, droplet size, kinetic stability, heat stress, and rheology. Micrographs of the first-stage emulsions showed droplets up to 3.8 μm diameter and a creaming index between 0.00% and 28.39% after 24 h. Optimization indicates that the higher the concentration of gum (3.5%) and GSO (25%), the more kinetically stable emulsions are produced. Ultrasonic emulsions showed no significant difference in droplet size and kinetic stability before 14 days of rest. Ultrasonic validation was made at 450 W for 6 min, resulting in emulsions stable for 20 days and with rheological characteristics interesting for food or cosmetic industries.

Abstract In this study, we investigated the cerebroprotective effects of fenchone (FEN) against brain ischemia through in silico and in vivo approaches, focusing on the inhibition of nitric oxide synthase (NOS) and the modulation of oxidative stress markers. Molecular docking revealed the potential binding affinity of FEN for the NOS active site, with a binding energy of -6.6 kcal/mol. This was validated through molecular dynamics simulations over a 100 ns time frame, demonstrating stability and favorable interaction profiles. Wistar albino rats underwent bilateral common carotid artery occlusion/reperfusion (BCCAO/R) followed by FEN administration at doses of 100 and 200 mg/kg. Our results indicated a significant reduction in cerebral infarction size and improvements in electroencephalography (EEG) signal magnitude with FEN treatment. Additionally, FEN restored the activity of antioxidant enzymes (catalase and superoxide dismutase) and decreased malondialdehyde (MDA) and nitric oxide (NO) levels and infarct size compared to those in untreated ischemic rats. Histological analysis further corroborated the neuroprotective effects of FEN, demonstrating the structural preservation of neurons in the hippocampal CA1 region. Overall, the results suggest that FEN plays a neuroprotective role in brain ischemia, potentially through the inhibition of NOS, reduction of oxidative stress, and modulation of antioxidants, highlighting the potential of FEN as a therapeutic candidate for ischemic stroke management.

Abstract The paper addresses the stability analysis of a circular tunnel face driven by a pressurized shield by means of the limit analysis kinematic approach implemented in the context of the Mohr-Coulomb strength condition. Emphasis is given to the assessment of the effects of seismic loading on the value of face support pressure that is required to prevent failure. The approach relies upon the pseudo-static method to model the destabilizing effects induced by the inertial forces associated with the passage of seismic waves in the ground. Rigorous limit analysis solutions for the limit face supporting pressure are derived from the analytical implementation of 3D and 2D failure mechanisms specifically devised for dealing with such a stability analysis problem. Indeed, original analytical expressions are provided and allow the evaluation of the pressure stabilizing the tunnel face. The accuracy of the approach predictions is assessed by comparison with available experimental and analytical results as well as with 2D finite element solutions. The influence of some relevant problem parameters in the context of tunnel face stability analysis is finally investigated, thus providing some preliminary guidelines for practical use in tunnel engineering.

Abstract The heterogeneity of microelement strength of rock particle materials is one of the main factors that cause the size effect of the rock particle crushing behavior. In this paper, a numerical model of rock particles that considering the characteristic of microscopic heterogeneous bond strength was established by using Weibull distribution theory through discrete element method. Single particle crushing experiments were carried out on five groups of rock particles and numerical particles with different particle sizes (6-21 mm), the crushing strength and failure modes of rock particles and numerical particles with different sizes were obtained. The results shows that the proposed numerical model can effectively reproduce the size effect of rock particle crushing behavior. The particle crushing strength data are satisfied the Weibull statistical model and have obvious size effect. The particle failure modes can be divided into three different failure types: “brittle” failure, “quasi brittle” failure, and “ductile” failure. As the particle size increase, the particle failure mode changes from “ductile” failure to “brittle” failure. Finally, a microscopic damage function model of particle crushing was established based on the numerical simulation results, which explained the microscopic mechanism of the size effect of particle crushing behavior. This study not only helps to improve the stability of engineering materials, but also optimizes engineering design and construction, and promotes related technological innovation.

Nitroaromatic acids, ubiquitous intermediates in nitro compounds, find broad applications in pharmaceuticals and fine chemical industries, yet their safety often receives inadequate attention. This paper investigates the thermal decomposition process of three isomers of nitrobenzoic acid using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), complemented by calculations of the apparent activation energy using typical kinetic methods. The reaction type was verified using a nonlinear fitting method. Thermal safety parameters including the time to maximum rate (TMR), critical temperature of self-acceleration (TCL), and thermal risk index (TRI) were employed to elucidate the thermal hazards. The thermal decomposition mechanism was further explained using density functional theory (DFT) methods, focusing on the Mayer bond order. The findings revealed that the average apparent activation energies for p-nitrobenzoic acid (PNBA), m-nitrobenzoic acid (MNBA), and o-nitrobenzoic acid (ONBA) were 157.00, 203.43, and 131.31 kJ mol-1, respectively. A single n-order reaction characterized the thermal decomposition process. The TMR and TCL parameters indicated a decomposition tendency at high temperatures, with the thermal stability at elevated temperatures following the order: PNBA < ONBA < MNBA. The TRI parameter indicates the danger level of the nitrobenzoic acids. The thermal decomposition mechanism was elucidated using Mayer bond energies, offering valuable insights into storage and transportation, and contributing to developing predictive models for thermal characteristics.

ABSTRACT Melon (Cucumis melo L.) is cultivated worldwide, with prominence in the Northeast region of Brazil, due to its favorable soil and climate conditions. However, over the years, the genotype × environment (GxE) interaction phenomenon has been occurred, which can complicate the selection process depending on its extent (whether it is a simple or complex interaction). In this context, melon breeding programs aim to identify adaptable and stable genotypes, capable of reaching their maximum potential. Therefore, the objectives of this study were to investigate GxE interactions and identify cultivars with greater adaptability and phenotypic stability using various methods for comparison. Thirteen melon hybrids were assessed in four municipalities in the state of Rio Grande do Norte, across two planting dates, totaling eight distinct environments. The experiments were conducted in randomized complete blocks with three replications. The traits evaluated included the number of fruits per plant and total soluble solids. Several adaptability and stability methods were employed and compared including Wricke, Eberhart and Russell, Lin and Binns, Annicchiarico, GGE Biplot, and Resende (harmonic mean of relative performance of genotypic values). Significant GxE interaction for the number of fruits per plant was found to be simple, whereas for soluble solids, it was crossed. The methods of Linn and Binns, Annicchiarico, and Resende showed strong correlations among them and were all correlated with the trait mean. The HA-08 hybrid emerged as the most promising, exhibiting high number of fruits per plant, high soluble solids content, and exceptional adaptability and stability.

In this study, a novel glass-ceramic (GC) obtained from ZnSO4-B2O3-P2O5-Ho2O3 composition, coded as H0.0, H0.5 and H0.8, was synthesized via molten-solidified approach. The effect of varying content of Ho2O3 from 0.5 to 0.8 mol% on thermal and mechanical properties of the prepared GC were experimentally and theoretically scrutinized. The attained results showed that inclusion of Ho2O3 content amplified crystallite size from 42.3 to 50.5 mm. Besides, the values of elastic moduli (Youngs’s, bulk, shear and longitudinal) computed via Makishima-Mackenzie’s (MM) model were slightly augmented. Finally, the decent value of thermal stability (> 150 °C) and high fracture toughness of > 20000 MPa mm1/2 achieved for the newly fabricated GC may be applicable in protective covers of portable electronics.