Development of an Emergency Radio Beacon for Small Unmanned Aerial Vehicles

Emergency locator transmitters (ELTs) used to locate manned aircrafts are not well suited to find and recover small crashed unmanned aerial vehicles (UAVs). ELTs utilize an international satellite system for search and rescue (Cospas-Sarsat System), which should leverage its expensive resources to save lives as a priority. Besides, ELTs are too big and heavy to be used within small UAVs. Some of the existing solutions for this problem are based on receivers that detect signal strength, which may be a long and tedious process not suitable for user needs. Others do not have enough range or require radio license and expensive amateur radio receivers. This paper presents an emergency radio beacon specifically designed to locate small UAVs. It is triggered automatically in the event of a crash and allows finding and recovering a crashed UAV in a fast and simple way. It meets not only the required specifications of user-friendliness, size and weight of this kind of application, but also it is a high precision and low cost device. Besides, it has enough range and endurance. The experiments carried out show the operation of the proposed system

Las sociedades de capital riesgo en Andalucía. Una modelización causal

Las Sociedades de Capital Riesgo (SCR) se constituyen en una modalidad de inversión temporal que trata de proveer recursos a pequeñas y medianas empresas no financieras y que no coticen en bolsa. En el siguiente artículo pretendemos realizar una descripción sobre el funcionamiento de las Sociedades de Capital Riesgo en Andalucía, para lo cual, definiremos, en primer lugar, las principales variables que caracterizan el desarrollo y desenvolvimiento de su actividad en la Comunidad Autónoma Andaluza. A continuación, estas variables nos servirán de apoyo para la representación gráfica de la estructura interna del sistema que forman las SCR andaluzas, de manera que consigamos establecer las interrelaciones esenciales que las caracterizan. Así, pues, habremos completado la etapa de conceptualización de la problemática que planteamos mediante Dinámica de Sistemas. PALABRAS CLAVE: Capital Riesgo, Empresas Participadas, Proyectos, Variables, Diagrama Causal. ABSTRACT Venture Capital constitutes an investisement temporary way that treat to contribute financial resources to no financial small business that don´t quote on the Stock Exchange. The present article pretends to describe the Venture Capital behaviour in Andalusia. We define, first of all, the principal variables that characterise the development of this activity in Andalusian Autonomous Region. Then, these variables will be useful for graphic display of system internal structure formed by andalusians venture capital, so we got to set up the essentials interrelations that characterise them. So, we´ll have completed the conceptualisation stage of planed problems by Dynamic Systems.Venture Capital constitutes an investisement temporary way that treat to contribute financial resources to no financial small business that don´t quote on the Stock Exchange. The present article pretends to describe the Venture Capital behaviour in Andalusia. We define, first of all, the principal variables that characterise the development of this activity in Andalusian Autonomous Region. Then, these variables will be useful for graphic display of system internal structure formed by andalusians venture capital, so we got to set up the essentials interrelations that characterise them. So, we´ll have completed the conceptualisation stage of planed problems by Dynamic Systems

Correction of errors and harmonic distortion in pulse-width modulation of digital signals

Article number 153991Pulse-Width (PW) modulation is widely used in those applications where an analog or digital signal has to be encoded in the time domain as a binary stream, such as switched-mode power amplifiers in transmitters of modern telecommunication standards, high-resolution digital signal conversion using single-bit digital-to-analog converters, and many others. Due to the fact that digital signals are sampled in the time domain, the quality of the resulting PW modulated waveforms is worsened by harmonic distortion. Multilevel PW modulation has been proposed to reduce these adverse effects, but the modulated waveform is no longer binary. In this paper, the mechanisms by which harmonic distortion is produced are analyzed. As a result, the distortion terms are mathematically quantified and used to correct the errors. Note that a correction network based on a simple subtraction of the distortion terms from the PW modulated signal would produce a waveform that would no longer be binary. The proposed correction network is implemented in the digital domain and, by means of a sigma-delta modulator, preserves the binary feature of the PW modulated output.Ministerio de Ciencia, Innovación y Universidades (España) RTI201- 099189-B-C2

Uso de internet y práctica lectora en bachilleres

Este trabajo presenta una exploración y descripción del uso de Internet en tareas escolares y cómo esto puede sugerir determinados aspectos de la práctica lectora en estudiantes de preparatorias públicas. Se trata de un estudio perceptual, se recogieron datos de las prácticas comunes de los estudiantes a partir de dos instrumentos: cuestionario y entrevista. Los resultados del primero muestran cómo el uso de Internet orienta la práctica lectora de los estudiantes hacia actividades como la localización de información, con un efecto de diversificación de fuentes a las que acuden para consulta de texto, aunque es posible concluir que realizan acciones que implican otros procesos de lectura como la comparación y contraste de fuentes. Los datos de la entrevista reflejan cómo el uso de Internet en relación con ciertas necesidades escolares de los estudiantes provoca lo que podría denominarse una experiencia de la práctica lectora marcada por el contexto en que se realiza la actividad escola

Normative values for anthropometric, adiposity, and handgrip strength in Costa Rican adults aged 53 to 110 yrs. old.

Objective: The purpose of the study was to develop normative data for anthropometric, adiposity and upper body strength in Costa Rican adults 60 to 110 years old. Method: A representative sample of Costa Rican male and female older adults (n= 2 711) were assessed for body weight and height, knee height, waist, hip and arm circumferences, adiposity, and upper-body strength. The 10th, 25th, 50th, 75th, and 90th percentiles were selected as the normative reference points for each 10-year age groups (60-69, 70-79, 80-89, 90-99, and ≥100). Results: Men and women experience age-related increased adiposity and reductions in upper body strength; however, men increased their upper-body strength at older ages. Conclusion: The normative values allow health professionals to monitor anthropometric, adiposity, and upper-body strength in older adults, and to design comprehensive fitness interventions that promote a healthy lifestyle in the populationFlorida Ice and Farm Co./[072406/Z/03/Z]/FIFCO/Costa RicaNational Institute of Aging/[P30AG012839]/NIH/Estados UnidosNational Institute of Aging/[R01AG031716]/NIH/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Centro de Investigación en Ciencias del Movimiento Humano (CIMOHU)UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Educación::Escuela de Educación FísicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Sociales::Centro Centroamericano de Población (CCP)UCR::Vicerrectoría de Docencia::Ciencias Sociales::Facultad de Ciencias Económicas::Escuela de Estadístic

Analysis and simulation of a novel speed estimation method based on oversampling and noise shaping techniques

Angle measurement is widely used in the servo positioning and speed control of electrical drives, where optical encoders are employed as sensors and coupled to microcontrollers with complex peripherals to provide effective position and speed measurement methods. These methods can achieve high precision and fast response, but are not particularly efficient with computer resources and require high computational costs. Therefore, fast timers, encoder signal oversampling, and a complex post-processing algorithm are used together in a recent research work to achieve a high-precision speed estimation method. Our work will prove that encoder outputs share the oversampling and noise shaping properties typical of sigma-delta modulated signals if they are sampled regularly. Based on this, a new simple and accurate speed estimation method is proposed. Here, encoder outputs are synchronously sampled, differenced, and low-pass filtered. As a result, the speed estimation circuit and its interface with the control unit are greatly simplified, while high accuracy can be achieved. A detailed mathematical analysis of the proposed technique is also performed, and the results obtained are validated by means of a simulation environment using Matlab and Simulink

Sample selection via clustering to construct support vector-like classifiers

This paper explores the possibility of constructing RBF classifiers which, somewhat like support vector machines, use a reduced number of samples as centroids, by means of selecting samples in a direct way. Because sample selection is viewed as a hard computational problem, this selection is done after a previous vector quantization: this way obtaining also other similar machines using centroids selected from those that are learned in a supervised manner. Several forms of designing these machines are considered, in particular with respect to sample selection; as well as some different criteria to train them. Simulation results for well-known classification problems show very good performance of the corresponding designs, improving that of support vector machines and reducing substantially their number of units. This shows that our interest in selecting samples (or centroids) in an efficient manner is justified. Many new research avenues appear from these experiments and discussions, as suggested in our conclusions.Publicad

ASIC-based tachometer without mechanical transducer for induction machines

A classical method for angular position and speed estimation in adjustable speed drives uses an incremental shaft encoder and an electronic circuit. This paper presents SLESS, a tachometer without mechanical transducer implemented on an ASIC using sensorless speed estimation technique. The ASIC is intended to serve as part of an integrated solution developed for fuzzy speed regulation and vector control of induction motors

DSP and FPGA based system to control a wind turbine generator implementing a variable speed vectorial control method

The purpose of this paper is to describe a DSP and FPGA control system to implement a variable speed vectorial control. Two semi-systems, both of them consisting on a DSP, a FPGA and A/D, D/A & digital I/O’s are used. Each one will control an inverter: The first inverter implements a variable speed vector control of the induction generator and the second one handle the power injected into the utility grid. Experimental results will be shown to confirm the validity of the proposed controller