ABSTRACT Vegetation indices are a quick and practical alternative for monitoring crops due to the availability of satellite images on various platforms for free, allowing a quick analysis of the vegetative state of the crop and interventions in the field in case of signs of diseases and pests. In this context, this study aimed to evaluate the vegetative state of the coffee crop using vegetation indices (NDVI, SAVI, ARVI, EVI, and VDVI) in an agricultural year. The study was carried out on a commercial farm using satellite images from the Planet platform, during an agricultural coffee growing season (2021/2022). The indices selected for the study were the Normalized Difference Vegetation Index (NDVI), Soil-Adjusted Vegetation Index (SAVI), Atmospherically Resistant Vegetation Index (ARVI), Enhanced Vegetation Index (EVI), and Visible Difference Vegetation Index (VDVI). The index data were analyzed using descriptive statistics, Pearson correlation, classification/interpretation proposal, and the Kappa index. NDVI and SAVI are efficient in monitoring coffee cultivation in an agricultural year, as the Kappa index was higher than 90%. ARVI and EVI had Kappa index values close to 90% and can be used to monitor the crop. VDVI was inefficient, with a low Kappa index value when compared to the others. The proposed classification for vegetation indices based on NDVI classes and values consisted of an important tool for classifying and interpreting the values of these indices, assisting monitoring and management of coffee cultivation.

ABSTRACT Operational speed influences the soil preparation quality, the first established according to the working set performance and its traction capacity. The experiment's objective is to determine the influence of working speed on energy and operational performance of an agricultural tractor with Full-Powershift transmission when performing a harrowing operation. We conducted the experiment using lines, in a randomized block design. It had four operational soil preparation speeds, with seven repetitions, totaling 28 experimental units. We measured the following parameters per worked area: slipping, engine rotation, specific and per hour fuel consumption, strength, power, and yield on the drawbar and operating speed. Additionally, we analyzed soil profilometry parameters concerning the mobilized area and working thickness. We also evaluated the variance of the collected data and, when significant, submitted it to a regression test. The data showed that higher operating speeds result in greater operational performance and reduction of the energy demand of the mechanized set under study. In addition, this increase doesn't have a beneficial effect on grid fluctuation, not affecting the quality of soil preparation.

Resumen Esta investigación se centra en la localización georreferenciada de los recursos distribuidos, concretamente en la inyección de potencia activa a través de la generación distribuida. Se tomó como caso de estudio un alimentador marginal rural-urbano de una empresa distribuidora de Ecuador con información georreferenciada, que cuenta con un enlace primario trifásico a media tensión y varios ramales monofásicos a media tensión de gran longitud, para abastecer a usuarios alejados de la red de la empresa local. En consecuencia, para analizar el comportamiento de la red eléctrica, se utilizó el software Cymdist para realizar simulaciones en estado estacionario con y sin la inserción de generación distribuida. Para la ubicación de la generación distribuida, se empleó el índice de predicción de colapso de voltaje como técnica para cuantificar e identificar problemas en los nodos de la red. Además, a partir de la metodología propuesta, se obtuvo la georreferenciación idónea de los sitios donde es necesario inyectar potencia activa para mejorar losperfiles de tensión y reducir el índice de predicciónde colapso de voltaje.

Abstract This research focuses on the georeferenced location ofdistributed resources, specifically in the injection ofactive power through distributed generation. A ruralurbanmarginal feeder of a distribution company inEcuador with georeferenced information was taken asa case study, which has a medium voltage three-phaseprimary link and several medium voltage one-phasebranches of great length to supply users located farfrom the local company’s network. Consequently, toanalyze the behavior of the electrical network, theCymdist software was used to perform simulationsin steady state without and with the insertion of distributedgeneration. For the location of distributedgeneration, the voltage collapse prediction index wasused as a technique to quantify and identify problemsin the network nodes. Moreover, based on theproposed methodology, it was obtained the suitablegeoreferencing of the sites where it is necessary toinject active power to improve the voltage profilesand reduce the voltage collapse prediction index.

Resumen Introducción: El volumen medio plaquetario (VMP) es un biomarcador utilizado en el abordaje integral de la sepsis. Objetivo: Evaluar la asociación entre VMP con la mortalidad en pacientes con sepsis. Métodos: Se realizó una revisión sistemática de estudios observacionales en cinco bases de datos. Se analizó la mortalidad asociada con la sepsis; las intervenciones consideradas fueron VMP, APACHE y lactato sérico. Resultados: Respecto a la mortalidad asociada a sepsis, se encontró un valor significativo en la VMP a las 72 horas (200 fallecidos versus 654 no fallecidos; MD 0.83 IC95% 0.53-1.13, p=< 0.0001, I2 =72.9%); así como el valor de APACHE II (220 muertos frente a 604 no fallecidos; MD 0.81 IC95% 0.62-1.0, p= 0.0001, I2 =32%). No se encontró significancia estadística para las demás variables clínicas. Conclusiones: El aumento de la VMP se asocia con mayor riesgo de mortalidad en pacientes con sepsis, especialmente después de 72 horas de evolución de las características clínicas.

Abstract Introduction: Platelet mean volume (MVP) is a biomarker used in the integral approach to sepsis. Objective: To assess the association between MVP and mortality in patients with sepsis. Methods: A systematic review of observational studies in five databases was performed. Mortality associated with sepsis was analysed; interventions considered were MPV, APACHE and serum lactate. Results: Regarding mortality associated with sepsis, a significant value was found in the MVP at 72 hours (200 deceased versus 654 not deceased; MD 0.83 IC95% 0.53-1.13, p=<0.0001, I2 =72.9%); as well as the value of APACHE II (220 dead versus 604 not deceased; MD 0.81 IC95% 0.62-1.0, p= 0.0001, I2 =32%). No statistical significance was found for the other clinical variables. Conclusions: Increased MVP is associated with increased risk of mortality in patients with sepsis, especially after 72 hours of evolution of clinical features.

Abstract Stability analysis in electrical power systems is based on the study, in dynamic state, of the voltage and frequency, because when there is some contingency it fluctuates drastically due to the primary and secondary controls of the voltage and frequency to the power systems that act on the generators. In order to solve the possible stability problems that may arise in power systems, various techniques have been developed that act on the generating machines for their protection, as well as on the loads for the power cut. The present resarch proposes an alternative methodology for load disconnection by low frequency as an option to save the power system from a possible blackout due to instability caused by a fall in the frequency, managing to improve the results affected by other improved techniques, the frequency change range, frequency deviation and the effects of demand disconnection. The proposed methodology was tested in the IEEE 14 bus system.

Resumen El análisis de la estabilidad en los sistemas eléctricos de potencia se fundamenta en el estudio en estado dinámico del voltaje y frecuencia, ya que cuando se presenta alguna contingencia, estos fluctúan drásticamente debido a los controles primarios y secundarios de tensión y frecuencia de los sistemas de potencia que actúan sobre los generadores. Para solventar los posibles problemas de estabilidad que se pueden presentar en los sistemas de potencia, se han desarrollado diversas técnicas que actúan sobre las máquinas generadoras para su protección como sobre las cargas para el corte de energía. La presente investigación plantea una metodología alternativa para la desconexión de carga por baja frecuencia como opción para salvar al sistema de potencia de un posible colapso por inestabilidad por caída de la frecuencia, logrando mejorar los resultados expuestos por otras técnicas, mejorando el rango de cambio de frecuencia, la desviación de frecuencia y los efectos de la desconexión de la demanda. La metodología propuesta se la probó en el sistema de 14 buses del IEEE.

ABSTRACT Machinery traffic intensification has been recurrent in intensive agriculture in annual crops, which may lead to structural soil degradation and, consequently, a reduction of its productive capacity. Therefore, this study aimed to assess the influence of tractor traffic intensification on soil physical attributes and soybean yield components. The study was performed in an Oxisol under no-tillage for 10 years, using a randomized block design with five tractor traffic intensities (0, 2, 4, 6, 8, and 12 passes) and five replications. Density, porosity, macroporosity, microporosity, and penetration resistance were assessed in the soil and stem diameter, number of pods per plant, number of grains per pod, grain weight per plant, thousand-grain weight, and grain yield were assessed in the soybean crop. Tractor traffic intensification changed soil physical attributes, which were not limiting factors to soybean yield under the no-tillage system, providing higher stem diameter, number of pods per plant, grain weight per plant, and grain yield after 12 passes.

ABSTRACT Seed metering system and tractor-seeder forward speed are factors that affect sowing. Therefore, this study aimed to evaluate sowing and agronomic components of corn as a function of seed metering mechanism and tractor-seeder forward speed, in addition to evaluating the yield data obtained from a harvester with a yield monitor. The soil of the area is classified as Distroferric Red Latosol. The experiment was set up in the second crop season of 2018 and treatments consisted of two seed metering mechanisms (M) (pneumatic and mechanical), and tractor-seeder forward speeds (S) (3, 5, 7, and 9 km h−1). The pneumatic system promoted the best longitudinal distribution, with values above 90%, and the increased sowing forward speed reduced normal spacings and increased failure. The interaction M × S indicated that pneumatic seeder promotes the best stand at the highest forward speed, normal spacing, and less failure. The yield data showed less variation with increasing forward speed, and the best result was observed for the mechanical seeder at 5 km h−1 when these data are grouped into yield classes.

Abstract: The nature and factors that influence the insertion of students in research projects, the roles they assume within them and in the scientific production of students at the National University of Chimborazo, Ecuador, are identified. Variables related to student participation and role in the projects, research groups, service groups and scientific production were analyzed. Data analysis went through two phases: the measurement model or confirmatory factor analysis and the structural analysis, favoring the relationship between latent variables. The results were significant (p< 0,05) and indicate that the successful student scientific production was the product of the relationship between the latent variables with their indicators, and the relationship between the latent variables. This allows to conclude that although student scientific production is low, it represents a germ that, when properly oriented, will become a great institutional strength.

Resumen: Se identifica la naturaleza y los factores que influyen en la inserción de los estudiantes en proyectos de investigación, los roles que asumen en el seno de estos y en la producción científica estudiantil en la Universidad Nacional de Chimborazo, Ecuador. Se analizaron variables relativas a la participación y rol estudiantil en los proyectos, grupos de investigación, grupos de vinculación y en la producción científica. El análisis de los datos atravesó dos fases: el modelo de medición o análisis factorial confirmatorio y el análisis estructural, favoreciendo la relación entre las variables latentes. Los resultados fueron significativos (p< 0,05) e indican que la producción científica estudiantil exitosa fue producto de la relación entre las variables latentes con cada uno de sus indicadores y de la relación que hubo entre esas variables latentes. Esto permiten concluir que a pesar de que la producción científica estudiantil es baja, ello representa un germen que debidamente orientado se convertirá en una gran fortaleza institucional.

ABSTRACT The soil management system affects physical attributes, and the forward sowing speed can increase or decrease its results. Thus, this work aimed to evaluate management systems before and after soil mobilisation and forward sowing speed on soil physical attributes. Thus, an experiment was conduct in a completely randomized block design with four replications and six soil management systems: no tillage (NT), medium harrowing (MH), subsoiling operation (S), subsoiling and medium harrowing operations (S+MH), cross-subsoiling and medium harrowing (S+MH), and ploughing and two medium harrowing (P+2MH), and four forward sowing speeds: 3.1, 5.1, 5.8, and 7.9 km h−1, applied in the subplots. Soil management affects soil penetration resistance (PR) values, pointing out the highest PR occurring in no-tillage beyond critical limits. Soil bulk density (sD) is affected by management and forward sowing speeds. The medium harrowing operation has higher sD and the ideal forward sowing speed range to mitigate this effect would be 5.0 to 7.0 km h−1. Moreover, it also presents a higher amount of macropores in the 0.20–0.30 m layer. Management system without soil mobilisation favours an increase in soil microporosity, and the use of subsoiler as tillage equipment should be carried out at slower speeds to favour the increased micropores.

ABSTRACT The way the soil is managed can influence its structuring and, consequently, crop yield. Thus, this study aimed to evaluate the effect caused by the management systems plowing followed by two intermediate harrowing operations, intermediate harrowing, chiseling, chiseling followed by intermediate harrowing, cross chiseling followed by intermediate harrowing, and non-tillage on soil and agronomic attributes of the soybean crop. A randomized block design with four replications was used. The percentage of soil cover, soil resistance to penetration, number of plants per meter, longitudinal distribution of seedlings, and soybean yield were evaluated. The data were submitted to analysis of variance by the Tukey test at 5% probability, and use of geostatistics for soil resistance to penetration. The system without soil tillage provides the best straw preservation but affects the longitudinal distribution of soybean seedlings. The use of intermediate harrowing for managing crop residues or soil tillage leads to the greatest compaction problems. Chiseling is efficient in maintaining compaction values below critical values up to a depth of 0.20 m when working at 0.35 m. Soil yield is not affected by soil management systems when the pluviometric regime is adequate to crop requirements.

ABSTRACT The inadequate agricultural management in the semiarid region of northeastern Brazil, associated with the fragility of most soils, has caused degradation of the quality of this resource. This study aimed to evaluate the quality of Quartzipsamments under different uses through the multivariate analysis of chemical and physical attributes. Five areas were selected: four of them with agricultural use (onion, banana, cassava, and corn) and the other with Caatinga. Soil samples were collected at depths of 0.00–0.10, 0.10–0.20, and 0.20–0.40 m for chemical and physical analyses. The data were submitted to descriptive analysis and then to the multivariate analysis using the principal component analysis (PCA) technique and Ward’s clustering method. PCA and clustering techniques allowed the identification of different production systems in subsurface layers, suggesting the effect of fertility on the differentiation of areas with onion and banana, as well as the clustering of cassava and corn cultivations. Physical attributes and sodium content of the surface layer of the area with onion showed a tendency of compaction and salinization process of this environment. In general, fertility was the main responsible for the improvement of soil quality with agricultural use when compared to the Caatinga.

ABSTRACT Soybean has significant economic importance in Brazil despite high production costs, making it necessary to increase the efficiency of mechanized harvest through the reduction of losses. Thus, this study aimed to evaluate the total losses in the mechanized soybean harvest as a function of the combination of header types, operating speeds, and geometry of collection frames. The study was carried out in a commercial farm in a randomized block design arranged in a 2 × 3 × 3 factorial with 10 replications, totaling 180 replications. The data were analyzed by descriptive statistics, analysis of variance, and quality control. The square frame can be used instead of the rectangular frame for the determination of the total losses. The increasing operating speed increased total losses in the auger header. On the other hand, the lowest losses at the highest operating speed were observed in the belt header. The harvester with belt header was more efficient when compared to that with auger header at the highest operating speed.

ABSTRACT Fertilization systems that allow higher sowing speeds have been used in areas of grain production, as well as the use of intercropping to improve soil physical quality and provide better soil cover. This study aimed to evaluate soil attributes and the initial corn development and intercropping (corn + velvet bean, corn + pigeonpea, and corn + bonavist bean) as a function of fertilization systems (pre-sowing and sowing). The experiment was conducted in an Oxisol in a randomized block design in the 2 × 3 factorial scheme, with four replications. The number of days for emergence, plant stand, intercropping dry matter, soil straw cover, soil straw permanence index, penetration resistance, soil moisture, soil density, degree of compaction, and total soil porosity were measured. The percentage of soil straw cover was affected by fertilization system, mainly by pre-sowing fertilization. Soil physical attributes were not affected by fertilization and intercropping systems, except total porosity, in the 0–0.10 m layer, which has a combined effect of factors. The initial corn development was not affected by fertilization and intercropping systems. Velvet bean presented the highest number of days for the emergence and lower dry matter.

ABSTRACT Machine traffic and conventional tillage can cause structural degradation of the soil, affecting the physical attributes and, consequently, the production and longevity of the sugarcane field. The objective of this study was to evaluate the production components of sugarcane cultivars (RB965902, RB985476, RB966928, RB855156, RB975201, RB975242, RB036066 and RB855536) and physical attributes of a Dystroferric Red Latosol (Oxisol) under no-tillage and reduced-tillage systems. The experiment was conducted using a completely randomized experimental design in an 8 × 2 factorial arrangement, with four replicates. The soil attributes evaluated were density, total porosity, macroporosity, microporosity and penetration resistance. The production components evaluated were stalk length and diameter, number of tillers (NT), tons of cane per hectare (TCH), sucrose content (Pol), tons of sucrose per hectare (TPH), soluble solids content (Brix), total recoverable sugars (TRS) and plant fiber. Cultivars RB965902, RB966928, RB855156 and RB985476 have productivity and technological attributes that are superior to the other cultivars, whereas these are lower for RB036066 in both soil tillage systems. Cultivars RB966928, RB855156, RB975242 and RB855536 exhibited higher TCH and TPH in the no-tillage system, and all cultivars displayed equal or higher performances than those observed in the reduced-tillage system. In the no-tillage system, which exhibits lower penetration resistance values between wheel tracks and in the subsurface layer of the planting row (0.20–0.40 m), cultivars RB985476 and RB975242 had a higher NT, and RB855156 had higher stalk lengths and NT.

ABSTRACT The use of alternative fuels in diesel engines has been the subject of research that seeks new fuels to expand the energy matrix. The aim of this study was to evaluate the performance of the stationary engine with the use of mixtures of biodiesel from soybean and castor bean added to diesel (S500) in two proportions (25% and 40%), evaluating the torque, effective power observed and specific consumption. The five biodiesel mixtures of soybean (S) and castor bean (C) analyzed were: S100C0, S75C25, S50C50, S25C75 and S0C100, which were added to the diesel in proportions B25 and B40, totaling ten treatments, plus the control with diesel S500 (B7). The stationary engine was subjected to the rotations of 3000, 2700, 2400, 2100, 1800 and 1500 rpm. The performance of the engine was similar for all biodiesel mixtures of soybean and castor bean, and commercial diesel (B7). The B40 S100C0 and B40 S75C25 provide better performance in terms of effective power observed and torque at 2700 rpm. The highest effective maximum power (3000 rpm) was obtained with the use of B7 diesel. In the lower rotations, it was possible to identify a similar performance result of the biodiesel mixtures with the B7, in addition to providing better torque and consumption performance compared to the commercial diesel.