In the last few years, increasing concern about the harmful effects of the use of fossil fuels in internal combustion engines has been observed. In addition, the limited availability of crude oil has driven the interest in alternative fuels, especially biofuels. In the context of spark ignition engines, bioalcohols are of great interest owing to their similarities and blend capacities with gasoline. Methanol and ethanol have been widely used, mainly due to their knocking resistance. Another alcohol of great interest is butanol, thanks to its potential of being produced as biofuel and its heat value closer to gasoline. In this study, a comparative study of gasoline–alcohol blend combustion, with up to 20% volume, with neat gasoline has been carried out. A single-cylinder, variable compression ratio, Cooperative Fuel Research-type spark ignition engine has been employed. The comparison is made in terms of fuel conversion efficiency and flame development angle. Relevant information related to the impact in the combustion process of the use of the three main alcohols used in blends with gasoline has been obtained.

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Knock remains one of the main limitations for increasing the efficiency in spark-ignition engines. The use of certain alcohol–gasoline blends is an effective way to either mitigate or eliminate knock, allowing the use of higher compression ratios, therefore increasing the efficiency of spark-ignition engines. Methanol and ethanol are alcohols commonly employed for reducing knock, due to their higher octane number and vaporization heat value. Major attention is being paid recently to butanol and its blends with gasoline since they present similar characteristics to gasoline; however, it was found to be the least knock resistant among the three fuels. In the present work, a comparison between the knock performance of methanol–gasoline, ethanol–gasoline and butanol–gasoline blends is carried out, by volume concentrations up to 20 v/v%. This comparison is made in terms of knock intensity and knock probability. Tests are performed in a single-cylinder, variable-compression ratio, Cooperative Fuel Research engine equipped with port fuel injection system, facilitating the comparison against future results obtained by similar experimental facilities. Results obtained allow to reach meaningful conclusions about the capacity of each blend to mitigate knock.

Particulate matter emission from the combustion of fossil fuels is a major concern due to its harmful effects on human health and impact on engine performance. Measurement of the smoke point of these fuels is a key issue in order to assess the tendency of fuels to generate particulate matter. Although certain commercial devices for measuring the smoke point are available, they are very expensive and their precision can still be improved. This paper proposes a novel low-cost device to achieve precise and repetitive smoke point measurements. It is based in an improved image processing algorithm that reduces the measurement error compared to previously developed methods. The device design allows easy adaptation to the smoke point lamp normalized in the American Society for Testing and Materials (ASTM) D1322, without any modification to the lamp.

This paper presents a new assembling for 2 degrees of freedom (DOF) parallel robots for executing rapid pick-and-place operations with low energy consumption, main objectives of pick-and-place operations. A conventional design of 2-DOF parallel robots is based on five-bar mechanisms. Collisions between links are highly possible, restricting the end-effector workspace and/or increasing the trajectory time to avoid collisions. In this work, an alternative assembling for preventing collision is presented. This novel assembling allows exploring the difference between the four five-bar mechanism congurations for the same position of the end-effector. Some of these congurations yield to lower time and/or lower energy consumption for the same motorization. Firstly, a dynamic model of the robot has been developed using Matlab and Simulink and validated by comparison with the results obtained by ADAMS software. A robust cascade PD regulator for controlling joint coordinates has been tuned providing a high accurate end-effector positioning. Finally, simulation results of 4 congurations are presented for executing controlled manoeuvres. The obtained results demonstrate that the conventional conguration is the worst one in terms of trajectory time or energy consumption and, conversely, the best one corresponds to an uncommonly used conguration. A workspace map where all congurations provide faster manoeuvres has been obtained in terms of Jacobian matrix and mechanism elbows distance. The results presented here allow designing a rapid manipulator for pick-and-place operations.

This paper describes the simulation of movement control of a one-degree-of-freedom articulated robot arm SCARA actuated by a pair of McKibben pneumatic artificial muscles. The pneumatic artificial muscle is the actuator and emulates the behavior of biological muscles; due to its nonlinear behavior, there is also a need to develop control systems for robot arms using this type of actuator. Research begins with the transfer function that represents, in mathematical language, the movement of the robot arm's joints; this allows using a PID controller on the transfer function and generating data to train the Multilayer Perceptron Artificial Neural Network (RNAPM). So far, the PID control system has been able to control the movement of robot arms but, based on experimental tests, the RNAPM has proved to outperform the PID control's response time by up to 2.95 seconds, minimizing the angular error by 1.3° and avoiding the oscillation problem due to its continuous, constant behavior.

RESUMENEste artículo pretende dar a conocer un tipo de estructura doméstica poco habitual en la Oretania septentrional, como son los hornos destinados a la producción de pan. El análisis de su distribución, así como sus dimensiones y características constructivas, revela que se trata de estructuras más complejas, de carácter colectivo o comunal, lo que permite aproximarnos al conocimiento de la articulación interna de los principales oppida oretanos. ABSTRACT

The propulsive forces and instantaneous power that are generated by a swimmer have a great influence on the swimming performance. This works presents a new device, called SwimOne, for measuring propulsive force and estimating the instantaneous power of the swimmer. In addition, the detailed prototype is able to exert a customizable opposition force to the swimmer for training purpose. The conceptual idea is presented by describing the differential equation of the swimmer and the protocol for a factible estimation of the instantaneous power. The variables that are to be measured and estimated are identified and, consequently, the sensor and actuator systems can be selected. The high-level and detailed designs of the prototype are presented together with the protocol that is carried out in order to validate the sensor and actuation systems. The device is able to monitor the variables of interest of the swimmer together with the propulsive force and instant power. Finally, some experiments are carried out providing the results of several participants swimming in crawl, backstroke, butterfly, and breaststroke styles in the presence of different opposition force. The preliminary results show that SwimOne is valid for measuring instantaneous force and power with different loads in swimming.