Repositorio Digital Universidad Simón Bolívar
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Neural networks for tea leaf classification
No full textThe process of classification of the raw material, is one of the most important
procedures in any tea dryer, being responsible for ensuring a good quality of the final product.
Currently, this process in most tea processing companies is usually handled by an expert, who
performs the work manually and at his own discretion, which has a number of associated
drawbacks. In this work, a solution is proposed that includes the planting, design, development
and testing of a prototype that is able to correctly classify photographs corresponding to samples
of raw material arrived at a dryer, using intelligence techniques (IA) type supervised for
Classification by Artificial Neural Networks and not supervised with K-means Grouping for
class preparation. The prototype performed well and is a reliable tool for classifying the raw
material slammed into tea dryers
Voltage collapse point evaluation considering the load dependence in a power system stability problem
No full textVoltage Stability has emerged in recent decades as one of the most common phenomena, occurrence in Electrical Power Systems. Prior researches focused on the development of algorithm indices to solve the stability problem and in the determination of factors with most influence in voltage collapse to solve the stability problem. This paper evaluates the influence that the load dependence has with the voltage on the phenomenon of the voltage stability and especially on the characteristics the collapse point or instability point. Load modeling used is detailed and comparisons of the results obtained are made with those described in the bibliography and those obtained with commercial software. The results of the load margin are also compared when a constant load or a voltage-dependent load is considered as well as the values obtained at the maximum load point and the point of voltage instability
Serum Zinc in school children
No full textIntroducción: La primera infancia es una etapa fundamental en el desarrollo y crecimiento del ser humano, época donde el cerebro se desarrolla a la máxima velocidad. La alimentación, uno de los principales condicionantes del desarrollo y las deficiencias de micronutrientes, entre otros, son responsables de daños funcionales. Objetivo: Determinar la concentración de zinc sérico en escolares y comparar resultados con estudios en la misma población de países latinos. Métodos: Estudio descriptivo prospectivo y comparativo en 116 niños escolares entre 7 a 12 años de edad, de la escuela básica primaria, del Municipio Maracaibo, Estado Zulia, Venezuela. Se realizó evaluación antropométrica, clínica y bioquímica. Resultados: Mayor frecuencia de niñas (52,6 %) edad promedio de 8 años y 9 meses y de 8 años y 5 meses para los niños; peso promedio de 25,21 kg y talla de 124,49 cm para las niñas, y peso promedio 25,07 kg y talla de 125,75 cm para los niños. Se encontró una concentración promedio de zinc en los niños de 0,49 μg/mL, y en las niñas de 0,50 μg/mL. La mayoría de los resultados de cuatro países latinos revelaron que el promedio de zinc sérico estuvo entre 0,32 y 95,2 μg/dL. Conclusión: Los niños mostraron concentraciones de zinc séricos por debajo de los valores promedios establecidos. Es necesario implementar estrategias alimentarias para mejorar el estado nutricional del zinc en las poblaciones pediátricas en países de Latinoamérica.Introduction: Early childhood is a crucial stage in the growth and development of the human being; it is the time where the brain develops at maximum speed. Feeding, one of the main determining factors of development and micronutrient deficiencies, among others, are responsible for functional damage.
Objective: To determine the concentration of serum zinc in school children and to compare results with studies in the same population of different Latin American countries.
Methods: Prospective descriptive and comparative study in 116 school children between 7 to 12 years old of the Basic Primary school in Maracaibo Municipality, Zulia State, Venezuela. Anthropometric clinical and biochemical assessment was performed.
Results: Higher frequency in girls (52.6 %) of average age 8 years and 9 months, and 8 years and 5 months for boys; average weight of 25.21 kg and height of 124.49 cm for girls, and average weight of 25.07 kg and height of 125.75 cm for boys. It was found an average concentration of zinc of 0.49 μg/mL in boys, and of 0.50 μg/mL in girls. Most of the results of four Latin American countries revealed that the average serum zinc was between 0.32 and 95.2 μg/dL.
Conclusion: Children showed serum zinc concentrations below the mean values set. It is necessary to implement food strategies to improve the nutritional status of zinc in pediatric populations of Latin American countries
Designing walkable streets in congested touristic cities: the case of Cartagena de Indias, Colombia
No full textThis paper presents the case of Cartagena de Indias, a well-known international touristic destination in Colombia, which experiences serious problems of traffic congestion and accessibility to the city center. Promoting pedestrian mobility is one of the public administration’s main goals, by enhancing and re-designing different pedestrian paths. Designing pedestrian zones is a context-specific multifaceted problem that involves multiple stakeholders and multiple criteria. A participatory multicriteria approach based on the Analytic Network Process (ANP) has been used to understand the most important characteristics affecting pedestrian mobility in Cartagena de Indias, thus deriving a useful decision-support tool for planning and designing pedestrian paths. In this respect, in this paper a set of streets in the city center has been evaluated, by combining the results of ANP with spatial data using Geographic Information Systems (GIS), producing thematic maps and an index of pedestrian priority to derive a priority of intervention. Some streets have been redesigned with the aim to increase their walking attractiveness. Results put the basis for discussion with local administration and stakeholders to validate them and propose further applications of the methodology
Improving the processes of production through risk management and statistical tools
No full textLos enfoques de prevención de riesgos en actividades, funciones o procesos se han convertido en
piezas fundamentales a la hora de minimizar la ocurrencia de eventos que son perjudiciales para las
compañías. Cada producto no conforme está estrechamente ligado con eventos no deseados relacionados
con uno o algunos de los factores que intervienen en el proceso. La identificación, análisis, evaluación,
tratamiento, comunicación y monitoreo de estos eventos no deseados garantizarán el incremento de la
calidad en los productos y la productividad en el proceso productivo. En este artículo, proponemos un
diseño metodológico para la prevención de riesgos en procesos productivos. La metodología propone
una forma novedosa de combinar el uso de herramientas estadísticas de calidad y la norma ISO 31000
de gestión de riesgos. La validación fue hecha sobre un proceso de envasado de productos lácteos. Las
conclusiones de esta investigación muestran que el diseño metodológico propuesto es suficientemente
flexible para ser adaptado a cualquier tipo de proceso de fabricación que se desea monitorear y mejorar.Risk prevention approaches on activities, functions or processes are fundamental elements to prevent
events that are harmful to companies. Each non-conforming product is related to undesirable events
associated with the factors intervened in the process. The identification, analysis, evaluation, treatment,
communication and monitoring of these unwanted events will help to increase the quality of the products
and productivity in the production process. In this paper, we proposed a methodological design for
the prevention of risks in production processes. The methodology proposes a novel way of combining
statistical quality tools and the ISO 31000 standard for risk management. The validation was performed
on a process of packaging of dairy products. The conclusions of this research show that the proposed
methodological design is sufficiently flexible to be adapted to any type of manufacturing process that is
desired to be monitored and improved
Predicting short-term electricity demand through artificial neural networks
No full textForecasting the consumption of electric power on a daily basis allows considerable money savings for the supplying companies, by reducing the expenses in generation and operation. Therefore, the cost of forecasting errors can be of such magnitude that many studies have focused on minimizing the forecasting error, which makes this topic as an integral part of planning in many companies of various kinds and sizes, ranging from generation, transmission, and distribution to consumption, by requiring reliable forecasting systems
Implementation of a wireless system architecture of conductivity temperature and pressure sensors for support the identification of the salt wedge and its impact on safety Maritime in estuary of the Magdalena River - A case study
No full textThis article aims to show the components of a wireless sensor system to measure temperature, conductivity and pressure at the mouth of the Magdalena River - Colombia. This analysis was carried out jointly with the General Maritime Directorate of Colombia. The measurements will be carried out underwater, with the buoys currently available in the navigable channel, which will work with solar energy and the data will be sent via Bluetooth, Wifi or Ethernet. With the data received by the sensor network, different analyzes will be carried out through the implementation of different data mining techniques, which will support the decision making of government entities. Through the implementation of this architecture, different behaviors found in the estuary will be identified and there will be real-time information that favors maritime safety in the navigable channel
Big Data and automatic detection of topics: Social network texts
No full textThis paper proposes the analysis of the influence of terms that express feelings in the
automatic detection of topics in social networks. This proposal uses an ontology-based
methodology which incorporates the ability to identify and eliminate those terms that present a
sentimental orientation in social network texts, which can negatively influence the detection of
topics. To this end, two resources were used to analyze feelings in order to detect these terms.
The proposed system was evaluated with real data sets from the Twitter and Facebook social
networks in English and Spanish respectively, demonstrating in both cases the influence of
sentimentally oriented terms in the detection of topics in social network texts
Economic order quantity for perishables with decreasing willingness to purchase during their life cycle
No full textIn an inventory management model for perishables, depletion due to interacting with the demand is of importance, but also, damage to products is a relevant
variable. This article considers that demand and sales phenomena do not always go hand-in-hand. The demand process relates to the willingness to acquire products
in good condition, giving the customer the power to evaluate the quality of the product before an effective purchase takes place. We also considered the cost of
disposing of unsold units, besides the conventional costs for storage and procurement. We then proposed a mathematical model to derive the Economic
Order Quantity (EOQ) under specific conditions, in order to minimize the expected management cost of perishables, assuming constant demand and linearly
decreasing purchase probability during the product life cycle. We proposed several random instances and validate the mathematical model using simulation. We then
found the optimal parameters for the inventory policy using a third-order numerical approximation. Last, we developed a sensitivity analysis over the product life cycle to prove that the proposed model approximates to a traditional EOQ model for perishables when life cycle is sufficiently large
Optimisation algorithms for improvement of a multihead weighing process
No full textMathematical optimisation is widely used to find the optimal value
for an objective function, subject to constraints that try to simulate reality, and
is fundamental to improving industrial processes. In this paper, we compare
different optimisation approaches to solve the packaging problem in multihead
weighing machines. In this problem, each package is made up from the loads in
a subset of the multihead weigher’s hoppers. The total weight of the packed
product must be as close to a specified target weight as possible. We designed
and evaluated a set of algorithms for this problem, considering both
single-objective and bi-objective optimisation criteria. A new criterion for
creating the packages is considered, and a different way of filling of the
hoppers is studied with the aim of reducing process variability. Numerical
experiments considering both a set of real data and the most important process
performance parameters show the usefulness of our study