António Simões

Magnitude Modulation Applied to LINC Transmitters: Paving the Road for Better Efficiency

The linear amplification with nonlinear components (LINC) amplification concept is very important on the developing of the modern mobile and satellite communications systems due to the use of inexpensive high power amplifiers (HPA). This paper analyses the effectiveness of combining an efficient PAPR reducing technique based on magnitude modulation (MM) when applied to a LINC amplification system. The simulation results show that the inclusion of the MM on the LINC processing chain is very favourable in terms of spectral regrowth introduced by signals clipping distortion. The system is also more robust to gain and phase imbalances between amplifiers with only a marginal bit error rate (BER) loss for an uncoded transmission scenario.

Efficient LINC Amplification for 5G through Ring-Type Magnitude Modulation

The upcoming 5G generation is driven the expected huge growth in user bit rates and overall system throughput. This means a substantial spectral efficiency increase, which must be achieved while maintaining or even improving the power efficiency. To overcome the necessity of using inefficient linear HPA in typical communication systems, this paper addresses the use of the LINC technique for power amplification, since it employs grossly NL HPA that are simpler and much more energy efficient than the linear ones. However, this techniques efficiency is harshly damaged for signals with a large PAPR, as for systems employing high order spectral efficient modulations and/or close to Nyquist bandwidth limiting pulse-shaping, due mainly to the LINC signal separation and power combining procedures. However, given that any M-ary constellation can be split as a sum of several OQPSK signals, a new MM method is proposed for OQPSK signals with bandwidth close to Nyquist, that limit both maximum and minimum envelope excursions of the signal without spreading its spectrum. This method is also shown to improve the transmitters resilience to small gain and phase imbalances between the LINCs amplifiers. The proposed scheme can play a critical role on the upcoming 5G, since arranging several units of the proposed transmitter in an array/parallel configuration has the potential to simultaneously achieve the required high power and spectral efficiency.

The State of the Art of Hidden Markov Models for Predictive Maintenance of Diesel Engines

The maintenance of diesel Engines is usually scheduled according to the maintenance procedures defined by manufacturers. However, the state of the art shows that the condition monitoring maintenance associated with adequate prediction algorithms allows performance improvement both by increasing the intervals between interventions and by helping to maintain reliability levels. There are many types of variables that can be used to measure equipment condition, as is the case of several types of pollutant emissions such as NOx, CO2, HC, PM, and NOISE, among others. This is a typical problem that can be solved through a hidden Markov model, taking into account the specificity of this type of equipment. The paper describes two algorithms that can help to increase the quality of assessment of engine states and the efficiency of maintenance planning. Those are the Viterbi and Baum–Welch algorithms. The importance of how to calculate the performance index of the model by the use of the perplexity algorithm is also emphasized. In this paper, a new paradigm is proposed, designated as ecological predictive maintenance. Copyright

Iterative decoding techniques for ring-type magnitude modulated signals

The expectations for fifth generation (5G) systems involve handling huge throughputs together with power consumption. In order to address this issue, massive multiple-input and multiple-output (MIMO) schemes were developed exploring the fact that any M-ary constellation can be decomposed as several offset quadrature phase shift keying (OQPSK) signals, to be amplified by efficient saturated amplifiers and transmitted separately. Since nonlinear amplifiers should be employed with constant envelope signals to avoid nonlinear distortion, a ring-type magnitude modulation (RMM) technique was proposed for bandlimited OQPSK signals to mitigate its envelope fluctuations while maintaining its spectral characteristics. This technique was shown to improve the power amplification efficiency of linear amplification with nonlinear components (LINC) transmitters, although with some degradation of the of the detection performance. This paper proposes an iterative decoding scheme relying on the accuracy of the first iterations log likelihood ratio (LLR) computation to estimate the RMM coefficients of the received symbols. Several LLR computation methods are compared with the ideal case where the receiver knows each symbols RMM coefficients, and it is shown that a few iterations are enough to obtain a bit error rate (BER) performance close to the best case scenario.

Vivências e percepções do estágio curricular em Educação de Adultos: a perspectiva dos alunos

O presente estudo teve como objectivo investigar as vivencias e percepcoes dos estagiarios de Educacao de Adultos, ao longo de um ano curricular, relativamente aos sentimentos dominantes, as fontes de apoio, as dificuldades/obstaculos enfrentados, bem como aos recursos pessoais e externos por si percebidos. Adicionalmente, pretendeu-se determinar se o ano de estagio contribui para aumentar a capacidade para a autodireccao da aprendizagem. Para o efeito, utilizou-se um plano de investigacao em que se combinaram metodologias qualitativas e quantitativas, recorrendo-se a uma amostra de 19 alunos da Faculdade de Psicologia e de Ciencias da Educacao da Universidade e Coimbra. A nivel dos principais resultados obtidos, identificou-se uma sucessao de tres fases relativamente distintas durante o estagio, as quais se revelaram associadas a sentimentos, dificuldades e recursos especificos. No que respeita a segunda questao em estudo, embora se tenha verificado uma tendencia para o aumento da autodireccao na aprendizagem, os resultados alcancados revelaram-se inconclusivos.

Cartesian Genetic Programming in an Open-Ended Evolution Environment

In this paper we describe and analyze the use of the Cartesian Genetic Programming method to evolve Artificial Neural Networks (CGPANN) in an open-ended evolution scenario. The issue of open-ended evolution has for some time been considered one of the open problems in the field of Artificial Life. In this paper we analyze the capabilities of CGPANN to evolve behaviors in a scenario without artificial selection, more specifically, without the use of explicit fitness functions. We use the BitBang framework and one of its example scenarios as a proof of concept. The results obtained in these first experiments show that it is indeed possible to evolve CGPANN brains, in an open-ended environment, without any explicit fitness function. We also present an analysis of different parameter configurations for the CGPANN when used in this type of scenario.

Ring-Type Magnitude Modulation for LINC: A Pragmatic Approach to the Efficiency Challenge

This paper considers the use of the linear amplification with nonlinear components (LINC) technique for the power amplification of spectrally compact offset quadrature phase shift keying (OQPSK) signals allowing the use of highly efficient, low cost, and strongly nonlinear high power amplifiers (HPAs). However, the performance of the LINC signal separation and power combining procedures decreases with the rise of the signal’s peak-to-average power ratio (PAPR). A new ring-type magnitude modulation (RMM) method is proposed for OQPSK signals that limits both its maximum and minimum complex envelope excursions avoiding zero crossings, without spreading the transmitted signal’s spectrum. The performance results show that band-limited OQPSK signals whose envelope has low fluctuations produce LINC components with a narrower spectrum, with a considerable impact on the LINC transmitter regardless of the type of combiner chosen: when using a passive/matched combiner, the transmitter’s power efficiency is significantly increased without spreading the combined signal’s spectrum; for the highly efficient non-linear Chireix combiner, there is a reduction of the amount of spectral leakage produced by nonlinearly combining the LINC signal components. Finally, an iterative decoding scheme is also proposed, which employs estimates of the received symbols’ RMM coefficients to compensate the RMM distortion.

(Legal) maintenance plan for building’s energy performance

Res_eng:The EU Directive 2002/91/CE, regarding building’s energy performance was transposed into national law in 2006, recently updated by Legislative Decree 118/2013 which substantiates: Energy Certification System of Buildings (SCE), Regulation of Energy Performance of Residential Buildings (SHR) and Regulation of Energy Performance of Commerce and Services Buildings (RECS). This points to an evaluation of energy performance of buildings based on the thermal behavior and efficiency of the systems, and in the installation, operation and maintenance of technical systems. The TIM (Installation and Maintenance Technician) must perform several maintenance activities related to buildings and technical systems, including: maintenance management; planning; recording occurrences; details of tasks and operations; and other actions and documentation necessary for that purpose. The RECS establishes rules to be observed in building’s maintenance, to promote energy efficiency and indoor air quality. A maintenance plan must: be initiated at the design stage; be put in practice after the completion of the installation of building systems; and to be accomplished during the building’s lifetime. This paper proposes to present a working methodology, to be undertaken by TIM, leading to compliance with legal requirements for maintenance of Commerce and Services Buildings in assessment of the energy performance.

The contribution of self-criticism and rumination to the negative affect

Falamos em auto-criticismo quando assumimos, face ao proprio sofrimento, uma postura dura, intolerante e de auto-avaliacao negativa. A literatura aponta o autocriticismo como um importante preditor de sofrimento, associado a psicopatologia. Perante situacoes de fracasso, as pessoas podem adoptar o estilo de pensamento ruminativo que, por ser marcadamente repetitivo e negativo, se associa a sintomatologia psicopatologica. Esta investigacao pretende contribuir para o conhecimento da relacao entre o auto-criticismo, ruminacao e a experienciacao de afecto negativo, numa amostra nao clinica de 193 sujeitos. Os resultados deste estudo indicam que os individuos mais auto-criticos e ruminadores experienciam mais afecto negativo. Verificamos igualmente que individuos mais auto-criticos tendem a recorrer mais ao pensamento ruminativo. Inversamente, a auto-tranquilizacao em momentos de fracasso, associa-se positivamente com a vivencia de afecto positivo. Os resultados sugerem a importância de uma intervencao terapeutica focada na reducao da auto-critica e ruminacao, em contexto clinico, promovendo a auto-tranquilizacao especialmente util em doentes auto-criticos e com perturbacoes de humor.

Uma “severa doçura”: Esforço e interesse em educação

According to the opinion presented and discussed in this paper, a severe shortcoming of current education consists of assigning a minor role to effort, both in family education and in school education. In order to show that effort is a not-to-be by-passed factor in education, the point of view of some of the most note-worthy pedagogues is presented and based on it we argue that interest does not replace effort, but rather that it energizes and calls for it.