Search

The aim of this work is the simulation of volumetric strain of tuberous crop during drying. We propose a poroelastic model for predicting the drying kinetics and volume loss of potato cubes during convective drying. The Biot’s theory of poroelasticity was used, which considers the Lamé parameters, Young’s modulus and Poisson’s ratio. Drying kinetics and volumetric strain were modeled and compared versus experimental data. An X-ray microtomograph coupled with image analysis was used to visualize the shape and size of the samples during drying. Drying experiments were conducted at 50, 60 and 70 °C, 20% RH, with an air velocity of 1 and 2 m/s. The drying process was interrupted several times to perform tomographic acquisitions. We found a period of ideal shrinkage, nevertheless, the volumetric strain reveals a kinetic behavior over time. The model computes the volumetric strain, which describes correctly the experimental data obtained by microtomography.

Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO

Due to the current COVID-19 pandemic, guaranteeing thermal comfort and low CO2 levels in classrooms through efficient ventilation has become vitally important. This study presents three-dimensional simulations based on computational fluid dynamics of airflow inside an air-conditioned classroom located in Veracruz, Mexico. The analysis included various positions of an air extractor, Reynolds numbers up to 3.5 × 104, four different concentrations of pollutant sources, and three different times of the day. The simulations produced velocity, air temperature, and CO2 concentrations fields, and we calculated average air temperatures, average CO2 concentrations, and overall ventilation effectiveness. Our results revealed an optimal extractor position and Reynolds number conducive to thermal comfort and low CO2 levels due to an adequate ventilation configuration. At high pollutant concentrations, it is necessary to reduce the number of students in the classroom to achieve safe CO2 levels.

A reduced set of reaction kinetic mechanism was obtained for the combustion of n-butanol in air, including low temperature ignition phenomena. Fourteen chemical-kinetic reactions are identified, and their associated reaction-rate parameters are given and added to an existing short chemical-kinetic mechanism (the San Diego mechanism); this entails introducing six new additional chemical species. Two important features of the reaction of the hydroxybutyl radical C4H8OH-1 radical with molecular oxygen involve a path competition of low and high temperature reactions, and low total available heat release not promoting NTC behavior. Tests of predictions against measured ignition delay times and laminar burning velocities are reported and compared with recent measurements in jet-stirred reactors. The comparisons support the predictions of the mechanism, which may be useful in combustion computations, especially when larger mechanisms would be too time-consuming to be accommodated.

This article presents a practical implementation of an ECG compression algorithm using a Max-Lloyd quantizer, to optimize the low resources of an ECG acquisition and transmission system (telemetry system) for dolphins and human divers. The algorithm scheme is based on a first-order differential pulse code modulation (DPCM) and uses a Max-Lloyd quantizer to code the difference between the current and predicted samples. The use of the non-uniform quantizer instead of a uniform quantizer improves the percent root mean-square difference (PRD), thereby producing a low distortion in the reconstructed signals. Due to its low computational complexity, the compression process can be accomplished on-line during the ECG acquisition process.

Abdominal pregnancy is uncommon and associated with higher fetal and maternal mortality. It is rare to grow to term and furthermore obtain a newborn in good conditions. A case of abdominal pregnancy at term ( 40,5 weeks) which was successfully treated in the Clinica General del Norte, Barranquilla, Colombia, by the obstetrics and gynecologist department; was an obstetric patient of 33 years old, G2P1 with initial diagnosis of 40,5 weeks of gestation, abruptio placentae and pre-eclampsia; with postoperative diagnosis of abdominal pregnancy at term with a newborn in good conditions. This article is a case report. It has a general interest for two reasons: 1) Its an uncommon event in obstetrics, the abdominal pregnancies with an alive fetus have very now frequency in the world. 2) A brief revision and how to confront this kind of cases is made.

In the present paper, an electronic prototype designed to acquire electrocardiographic signals from marine mammals has been developed. The system consists of a portable device that allows the on-line acquisition of EKG signals through a parallel port interface that is connected to a laptop computer. The EKG waveform, the voltage level, the bandwidth and the most relevant information from this type of signals is stored and analysed under real-time conditions by means of specifically implemented software. The whole system has been successfully tested to obtain the EKG from captive dolphins. The characteristics of the equipment presented here, with its low cost, size and energy requirements accomplish a portable system suitable for the acquisition of this type of signals in conductive media such as the seawater.

A simple and low-cost acquisition device using the computer parallel port has been used to implement a full acquisition system composed of an analogue interface, a 12-bit analogue-to-digital converter, a quad three to one multiplexer and a software package aimed at managing the acquisition process. The features of this system make its implementation a suitable educational resource for undergraduate students from Engineering, Physics and Computer Sciences faculties.