Abstract
A large number of compiler optimizations are nowadays available to users. These optimizations interact with each other and with the input code in several and complex ways. The sequence of application of optimization passes can have a significant impact on the performance achieved. The effect of the optimizations is both platform and application dependent. The exhaustive exploration of all viable sequences of compiler optimizations for a given code fragment is not feasible. As this exploration is a complex and time-consuming task, several researchers have focused on Design Space Exploration (DSE) strategies both to select optimization sequences to improve the performance of each function of the application and to reduce the exploration time. In this article, we present a DSE scheme based on a clustering approach for grouping functions with similarities and exploration of a reduced search space resulting from the combination of optimizations previously suggested for the functions in each group. The identification of similarities between functions uses a data mining method that is applied to a symbolic code representation. The data mining process combines three algorithms to generate clusters: the Normalized Compression Distance, the Neighbor Joining, and a new ambiguity-based clustering algorithm. Our experiments for evaluating the effectiveness of the proposed approach address the exploration of optimization sequences in the context of the ReflectC compiler, considering 49 compilation passes while targeting a Xilinx MicroBlaze processor, and aiming at performance improvements for 51 functions and four applications. Experimental results reveal that the use of our clustering-based DSE approach achieves a significant reduction in the total exploration time of the search space (20x over a Genetic Algorithm approach) at the same time that considerable performance speedups (41% over the baseline) were obtained using the optimized codes. Additional experiments were performed considering the LLVM compiler, considering 124 compilation passes, and targeting a LEON3 processor. The results show that our approach achieved geometric mean speedups of 1.49x, 1.32x, and 1.24x for the best 10, 20, and 30 functions, respectively, and a global improvement of 7% over the performance obtained when compiling with -O2.

Abstract
The Physical layer architectures for the next generation of wireless devices will be characterized by a high degree of flexibility for real-time adaptation to communication conditions variability. OFDM-based architectures are strong candidates for the Physical layer implementation in 5G systems and one of the most important baseband processing operations required by this waveform is the Fast Fourier Transform (FFT). This paper proposes a dynamically reconfigurable FFT processor supporting FFT sizes and throughputs required by the most widely used wireless standards. The FFT reconfiguration was achieved by means of FPGA-based Dynamic Partial Reconfiguration (DPR) techniques, which enables run-time FFT size adaptation according to communication requirements and better resource utilization. The impact of DPR in terms of reconfiguration time and power consumption overhead was evaluated. The obtained results encourage the exploitation of DPR techniques to implement reconfigurable hardware infrastructures for OFDM baseband processing engines.

Abstract
This paper presents a new generation of man portable acoustic navigation buoys. The aim of these buoys is to facilitate the deployment of an underwater acoustic positioning system for the operation of Autonomous Underwater Vehicles. Each buoy includes only the vital modules required for the most typical schemes of underwater acoustic navigation, packed in a small but dynamically stable platform for one day long operations in coastal waters. We will present an overview of the systems hardware and electronics, and also the key features of the deployment and operation of the beacons.

Abstract
The energy consumption in the world continues to increase and this fact contributes to rise pollution levels, environmental degradation and global greenhouse emissions. The construction sector is responsible for significant impacts on the environment as it consumes a lot of resources and also produces a lot of waste. One of the main objectives of the green construction is to reduce the environmental impacts by conserving and using resources more efficiently. This type of construction tends to apply natural raw materials. Tabique is a traditional Portuguese building technique applied until 20th century that use earth and wood as construction materials. This old buildings have high durability that requires maintenance and rehabilitation interventions. In this context, the aim of this study is to evaluate the environmental impact of tabique wall. The life cycle analysis is the tool used for the sustainability evaluation and it is carried out according to international standards ISO 14040/44. The adopted functional unit for these materials is the mass of the material required to provide a thermal resistance of 1 m2ºC/W. The calculation of the impacts is done with GaBi software and the CML 2001 impact category is used to define the Global Warming Potential of the study. The results revealed that most significant component of environmental impact of the tabique wall cocerning the category GWP is related with extraction of raw materials process and landfill.

Abstract

Abstract
There is growing recognition that decarbonisation of existing uses of electricity is only 'part of the story' and that closer attention needs to be given to demand for energy in heating or cooling and in transport, and to all the energy vectors and infrastructures that supply the end-use demand. In this respect, concepts such as 'multi-energy systems' (MES) have been put forward and are gaining increasing momentum, with the aim of identifying how multiple energy systems that have been traditionally operated, planned and regulated in independent silos can be integrated to improve their collective technical, economic, and environmental performance. This paper addresses the need for modelling of MES which is capable of assessing interactions between different sectors and the energy vectors they are concerned with, so as to bring out the benefits and potential unforeseen or undesired drawbacks arising from energy systems integration. Drivers for MES modelling and the needs of different users of models are discussed, along with some of the practicalities of such modelling, including the choices to be made in respect of spatial and temporal dimensions, what these models might be used to quantify, and how they may be framed mathematically. Examples of existing MES models and tools and their capabilities, as well as of studies in which such models have been used in the authors' own research, are provided to illustrate the general concepts discussed. Finally, challenges, opportunities and recommendations are summarised for the engagement of modellers in developing a new range of analytical capabilities that are needed to deal with the complexity of MES.