Numerical Studies of the Generalized \u3cem\u3el\u3c/em\u3e₁ Greedy Algorithm for Sparse Signals

The generalized l1 greedy algorithm was recently introduced and used to reconstruct medical images in computerized tomography in the compressed sensing framework via total variation minimization. Experimental results showed that this algorithm is superior to the reweighted l1-minimization and l1 greedy algorithms in reconstructing these medical images. In this paper the effectiveness of the generalized l1 greedy algorithm in finding random sparse signals from underdetermined linear systems is investigated. A series of numerical experiments demonstrate that the generalized l1 greedy algorithm is superior to the reweighted l1-minimization and l1 greedy algorithms in the successful recovery of randomly generated Gaussian sparse signals from data generated by Gaussian random matrices. In particular, the generalized l1 greedy algorithm performs extraordinarily well in recovering random sparse signals with nonzero small entries. The stability of the generalized l1 greedy algorithm with respect to its parameters and the impact of noise on the recovery of Gaussian sparse signals are also studied

Estudio de gestión de riesgos para la prevención ante inundaciones en el sistema de agua potable del distrito de Trujillo – Trujillo – La Libertad

En la presente investigación se desarrolló debido a la problemática de riesgos originados por fenómenos naturales como inundaciones, tal como ocurrió en el año 2017 en la ciudad de Trujillo. Esta problemática provoco daños a la población, las actividades económicas, problemas ambientales y los problemas del sistema de agua potable, como el desgastes y roturas de las redes primarias y secundarias y la antigüedad de los pozos y reservorios. Por lo cual su objetivo fue determinar la influencia del estudio de gestión de riesgos en la prevención ante inundaciones en el sistema de agua potable del distrito de Trujillo. El diseño de investigación del presente estudio según su naturaleza es aplicada descriptiva, la población es igual a la muestra según su naturaleza, debido a que solo posee una única unidad de análisis, cual es el sistema de agua potable del distrito de Trujillo. La población del distrito de Trujillo está conformada por 341,879 habitantes (Boletín SEDALIB S.A., 2019). Se determinó que el nivel de peligrosidad del sistema de agua potable del distrito de Trujillo ante inundaciones pluviales debido a las lluvias intensas fue de nivel muy alto (0.231 ≤ P ≤ 0.413), el nivel de vulnerabilidad se obtuvo que fue de nivel alto tanto para los pozos como las redes primarias y secundarias (0.268 ≤ V ≤ 0.433) y además el nivel de vulnerabilidad para los reservorios fue de nivel medio (0.091 ≤ V ≤ 0.158). Por tanto, se obtuvo que su nivel de riesgo fue de nivel muy alto (0.268 ≤ R ≤ 0.433), por ello su nivel de aceptabilidad y tolerancia del riesgo es Inaceptable y su nivel de priorización es de II. El estudio de gestión de riesgos permite establecer medidas de prevención y reducción del riesgo ante la ocurrencia del fenómeno natural por inundación pluvial ocasionado por las lluvias intensas que afectan a el sistema de agua potable del distrito de Trujillo. Estas medidas de prevención son estructurales y no estructurales, aquellas dan protección al sistema de agua potable y a la población respectivamente, reduciendo sus efectos, por lo cual se propone ejecutar proyectos.This research was developed due to the problem of risks caused by natural phenomena such as floods, as occurred in 2017 in the city of Trujillo. This problem caused damage to the population, economic activities, environmental problems and problems of the drinking water system, such as the wear and tear of primary and secondary networks and the age of wells and reservoirs. Therefore, its objective was to determine the influence of the risk management study on flood prevention in the drinking water system of the district of Trujillo. The research design of the present study according to its nature is applied descriptively, the population is equal to the sample according to its nature, because it only has a single unit of analysis, which is the drinking water system of the district of Trujillo. The population of the district of Trujillo is made up of 341,879 inhabitants (Boletín SEDALIB S.A., 2019). It was determined that the level of danger of the drinking water system of the district of Trujillo to rain floods due to heavy rains was of very high level (0.231 ≤ P ≤ 0.413), the level of vulnerability was obtained that it was of high level both for the wells and the primary and secondary networks (0.268 ≤ V ≤ 0.433) and also the level of vulnerability for the reservoirs was of medium level (0.091 ≤ V ≤ 0.158). Therefore, it was obtained that its level of risk was of very high level (0.268 ≤ R ≤ 0.433), so its level of acceptability and tolerance of risk is Unacceptable and its level of prioritization is II. The risk management study makes it possible to establish measures to prevent and reduce the risk of the occurrence of the natural phenomenon due to a storm flood caused by the intense rains that affect the drinking water system of the district of Trujillo. These prevention measures are structural and non-structural, those give protection to the drinking water system and the population respectively, reducing their effects, for which it is proposed to implement projects.Tesi

Sphericity measures of sand grains

The sphericity of a grain should measure the similitude of its shape with that of a sphere. Sphericity is a shape descriptor of long-standing interest for sedimentology. Now it has gained also interest to facilitate discrete element modelling of granular materials. True sphericity was initially defined by a surface ratio that requires three-dimensional (3D) grain surface measurement. That kind of measurement has been practically impossible until recently and, as a consequence, a number of alternative 3D measures and 2D proxies were proposed. In this work we present results from a study of grain shape based on x-ray tomography of two different sand specimens, containing more than 110.000 particles altogether. Sphericity measures were systematically obtained for all grains. 2D proxy measures were also obtained in samples of oriented and not-oriented grains. It is shown that the 2D proxy best correlated with true sphericity is perimeter sphericity, whereas the traditional Krumbein-Sloss chart proxy is poorly correlated. 2D measures acquired through minor axis projection are more closely related to 3D measures than those acquired using random projections.Peer ReviewedPostprint (author's final draft

Microscopic calibration of rolling friction to mimic particle shape effects in DEM

It is widely recognised that particle shape influences the mechanical response of granular materials [1-2]. Rolling resistance elasto-plastic contact models are frequently used to approximate particle shape effects in simulations using the Discrete Element Method (DEM) [3-4]. Such contact models require calibration of several micro-parameters, most importantly a rolling resistance coefficient. In this work, the rolling resistance has been calibrated to reproduce the triaxial tests – in terms of mechanical and kinematic responses – of two different sands: Hostun and Caicos sands. The value of rolling resistance is directly linked to true sphericity, a basic measure of grain shape, as originally proposed in Rorato et al. (2018) [5]. When shape measurements are performed [6], this link enables independent evaluation of the rolling resistance coefficient for each particle. It does also allow the characteristic shape variability of natural soils to be easily taken into account

Low-cost system for the rapid diagnosis of sleep apnea, caused by the covid-19 pandemic

ABSTRACT Sleep Apnea is one of the lesser-known pathologies that many people do not take into consideration when conducting a medical check-up, but it is one of the indicators of levels of fatigue, stress that are shown by lack of sleep, bad sleeping habits or other silent indicators such as problems breathing when sleeping, snoring among others. In these moments of confinement in our homes caused by COVID-19, where most of them cannot work, study or do other activities in person, certain levels of stress begin to emerge in both adults and children, these manifestations are shown in problems at bedtime. In the present work an analysis is carried out on the possible consequences of Sleep Apnea, as well as a methodology based on the use of Weareable Devices is presented, to be able to analyze how our way of sleeping is and thus be attentive to any changes in the demonstrations at bedtime. My methodology presents some previous steps for the configuration of the device, the acquisition of information when we are sleeping and the analysis of the results of the signals captured at the time of sleep, the analysis is very intuitive. In this way we can know if we are changing habits when sleeping

Rapid Determination of the ‘Legal Highs’ 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy

The synthetic cathinones mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) are two designer drugs that represent the rise and fall effect of this drug category within the stimulants market and are still available in several countries around the world. As a result, the qualitative and quantitative determination of ‘legal highs’, and their mixtures, are of great interest. This work explores for the first time the spectroelectrochemical response of these substances by coupling cyclic voltammetry (CV) with Raman spectroscopy in a portable instrument. It was found that the stimulants exhibit a voltammetric response on a gold screen-printed electrode while the surface is simultaneously electro-activated to achieve a periodic surface-enhanced Raman spectroscopy (SERS) substrate with high reproducibility. The proposed method enables a rapid and reliable determination in which both substances can be selectively analyzed through the oxidation waves of the molecules and the characteristic bands of the electrochemical SERS (EC-SERS) spectra. The feasibility and applicability of the method were assessed in simulated seized drug samples and spiked synthetic urine. This time-resolved spectroelectrochemical technique provides a cost-effective and user-friendly tool for onsite screening of synthetic stimulants in matrices with low concentration analytes for forensic applications.Universidad de Costa Rica//UCR/Costa RicaMinisterio de Innovación, Ciencia, Tecnología y Telecomunicaciones//MICITT/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Electroquímica y Energía Química (CELEQ)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Químic

Detecting Argument Selection Defects

Identifier names are often used by developers to convey additional information about the meaning of a program over and above the semantics of the programming language itself. We present an algorithm that uses this information to detect argument selection defects, in which the programmer has chosen the wrong argument to a method call in Java programs. We evaluate our algorithm at Google on 200 million lines of internal code and 10 million lines of predominantly open-source external code and find defects even in large, mature projects such as OpenJDK, ASM, and the MySQL JDBC. The precision and recall of the algorithm vary depending on a sensitivity threshold. Higher thresholds increase precision, giving a true positive rate of 85%, reporting 459 true positives and 78 false positives. Lower thresholds increase recall but lower the true positive rate, reporting 2,060 true positives and 1,207 false positives. We show that this is an order of magnitude improvement on previous approaches. By analyzing the defects found, we are able to quantify best practice advice for API design and show that the probability of an argument selection defect increases markedly when methods have more than five arguments.</jats:p

Fortalecimiento del proceso educativo, a través de la evaluación curricular y fundamentación de un modelo pedagógico institucional

El trabajo de profundización, tiene como objeto fortalecer el proceso educativo a través de la evaluación curricular y la fundamentación de un modelo pedagógico institucional. Este se desarrolló bajo un tipo de investigación evaluativa, con un enfoque cualitativo, respondiendo al método de estudio de caso, con una muestra no probabilística de 46 participantes, que incluyen a estudiantes, docentes, directivos docentes y padres de familia de una institución educativa de Soledad - Atlántico. Este trabajo, se ejecutó en dos fases: la evaluación curricular y el diseño de un plan de mejoramiento. En la primera, se emplearon diferentes técnicas: el análisis documental, entrevista estructurada, grupos focales, la observación no participante. Como resultado de esta fase se evidenció que el horizonte institucional, se encontraba en proceso de reconstrucción. Así mismo, se vislumbró la existencia de un modelo pedagógico Institucional, que carece de fundamentación teórica y metodológica, los planes de áreas hallados están desactualizados y no existe un plan de estudio. En la segunda fase, se priorizaron las oportunidades de mejora y se diseñó un plan de mejoramiento, empleando como técnica el grupo nominal, permitiendo contribuir a la fundamentación de un modelo pedagógico para fortalecer el proceso educativo de la Institución. De esta manera, surge como producto de la investigación un documento directriz del modelo pedagógico Constructivismo Social