I/Q imbalance in two-way AF relaying

We analyze the performance of dual-hop two-way amplify-and-forward relaying in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, two power allocation schemes, namely, fixed power allocation and instantaneous power allocation, are proposed to improve the system reliability and robustness against IQI under a total transmit power constraint. For each proposed scheme, the outage probability is investigated over independent, non-identically distributed Nakagami- m fading channels, and exact closed-form expressions and bounds are derived. Our theoretical analysis indicates that, without IQI compensation, IQI can create fundamental performance limits on two-way relaying. However, these limits can be avoided by performing IQI compensation at source nodes. Compared with the equal power allocation scheme, our numerical results show that the two proposed power allocation schemes can significantly improve the outage performance, thus reducing the IQI effects, particularly when the total power budget is large.

Transmit Antenna Selection in Cognitive MIMO Relaying with Multiple Primary Transceivers

We consider transmit antenna selection (TAS) in cognitive multiple-input multiple-output (MIMO) relay networks, as an interference-aware design for secondary users (SUs) to ensure power and interference constraints of multiple primary users (PUs). In doing so, we derive new exact and asymptotic expressions for the outage probability of TAS with maximal ratio combining (TAS/MRC) and with selection combining (TAS/SC) over Rayleigh fading. The proposed analysis and simulations highlight that TAS/MRC and TAS/SC with decode-and-forward relaying achieve the same diversity order in cognitive MIMO networks, which scales with the minimum number of antennas at the SUs. Furthermore, we accurately characterize the outage gap between TAS/MRC and TAS/SC relaying as a concise ratio of their array gains.

Relay Selection for Security Enhancement in Cognitive Relay Networks

This letter proposes several relay selection policies for secure communication in cognitive decode-and-forward (DF) relay networks, where a pair of cognitive relays are opportunistically selected for security protection against eavesdropping. The first relay transmits the secrecy information to the destination,
and the second relay, as a friendly jammer, transmits the jamming signal to confound the eavesdropper. We present new exact closed-form expressions for the secrecy outage probability. Our analysis and simulation results strongly support our conclusion that the proposed relay selection policies can enhance the performance of secure cognitive radio. We also confirm that the error floor phenomenon is created in the absence of jamming.

Facilities management: Tracing its development trajectory

Purpose – The purpose of this paper is to provide facilities management (FM) practitioners and researchers with a better understanding of the FM industry sector by analyzing the trend of its development.
Design/methodology/approach – Semi-structured interview is adopted in this research as the main methodology. In total, 30 FM professionals in the UK were interviewed to explore the past, present and future of FM. The analysis of interview results helps to identify the key areas in which FM has changed, is changing and will change. It also helps to explain the implications of FM development in each key area.
Findings – FM evolves and matures continuously. It is important for FM organizations and practitioners to recognize the dynamic nature of this industry sector, based on which they can develop appropriate strategies to adapt to changing circumstances. This is probably the only way for them to
keep pace with the times.
Originality/value – Both backward looking and forward looking are crucial to the development of an industry sector. However, existing studies on FM development are conducted through either review or outlook. On the other hand, most of these studies focus on one particular management area or one particular industry sector. Based on 30 expert interviews, this research attempts to bridge the knowledge gap and analyze the trend of FM development in a systematic way. A better understanding of the trend provides a possibility and a guide for FM organizations and practitioners to pursue best practice.

I/Q imbalance in AF dual-hop relaying: Performance analysis in Nakagami-m fading

We analyze the performance of amplify-and-forward dual-hop relaying systems in the presence of in-phase and quadrature-phase imbalance (IQI) at the relay node. In particular, an exact analytical expression for and tight lower bounds on the outage probability are derived over independent, non-identically distributed Nakagami-m fading channels. Moreover, tractable upper and lower bounds on the ergodic capacity are presented at arbitrary signal-to-noise ratios (SNRs). Some special cases of practical interest (e.g., Rayleigh and Nakagami-0.5 fading) are also studied. An asymptotic analysis is performed in the high SNR regime, where we observe that IQI results in a ceiling effect on the signal-to-interference-plus-noise ratio (SINR), which depends only on the level of I/Q impairments, i.e., the joint image rejection ratio. Finally, the optimal I/Q amplitude and phase mismatch parameters are provided for maximizing the SINR ceiling, thus improving the system performance. An interesting observation is that, under a fixed total phase mismatch constraint, it is optimal to have the same level of transmitter (TX) and receiver (RX) phase mismatch at the relay node, while the optimal values for the TX and RX amplitude mismatch should be inversely proportional to each other.

Multiuser relaying over mixed RF/FSO links

A multiuser dual-hop relaying system over mixed radio frequency/free-space optical (RF/FSO) links is investigated. Specifically, the system consists of m single-antenna sources, a relay node equipped with n≥ m receive antennas and a single photo-aperture transmitter, and one destination equipped with a single photo-detector. RF links are used for the simultaneous data transmission from multiple sources to the relay. The relay operates under the decode-and-forward protocol and utilizes the popular V-BLAST technique by successively decoding each user's transmitted stream. Two common norm-based orderings are adopted, i.e., the streams are decoded in an ascending or a descending order. After V-BLAST, the relay retransmits the decoded information to the destination via a point-to-point FSO link in m consecutive timeslots. Analytical expressions for the end-to-end outage probability and average symbol error probability of each user are derived, while closed-form asymptotic expressions are also presented. Capitalizing on the derived results, some engineering insights are manifested, such as the coding and diversity gain of each user, the impact of the pointing error displacement on the FSO link and the V-BLAST ordering effectiveness at the relay.

Exploiting Direct Links for Physical Layer Security in Multi-User Multi-Relay Networks

We present two physical layer secure transmission schemes for multi-user multi-relay networks, where the communication from M users to the base station is assisted by direct links and by N decode-and-forward relays. In this network, we consider that a passive eavesdropper exists to overhear the transmitted information, which entails exploiting the advantages of both direct and relay links for physical layer security enhancement. To fulfill this requirement, we investigate two criteria for user and relay selection and examine the achievable secrecy performance. Criterion I performs a joint user and relay selection, while Criterion II performs separate user and relay selections, with a lower implementation complexity. We derive a tight lower bound on the secrecy outage probability for Criterion I and an accurate analytical expression for the secrecy outage probability for Criterion II. We further derive the asymptotic secrecy outage probabilities at high transmit signal-to-noise ratios and high main-to-eavesdropper ratios for both criteria. We demonstrate that the secrecy diversity order is min (MN, M + N) for Criterion I, and N for Criterion II. Finally, we present numerical and simulation results to validate the proposed analysis, and show the occurrence condition of the secrecy outage probability floor

Da Ideia ao Mercado: um caminho desenvolvido por meio de mapas conceituais para difundir a cultura da inovação e induzir sua gestão

This thesis objective is to build a cognitive model focused on the diffusion of innovation management and its culture, where the sharing method will be the concept maps. For that construction, in addition to detailing the method, will be also presented the bases of knowledge that served to construct the model. Those bases were built through literature survey that will be also presented. This sharing proposition, proposes to strictly use concept maps instead of texts and the non-hierarchical knowledge construction. Besides the introduction of these guidelines, a navigation tool modeled based on conceptual mapping where the user choices, or better explaining, the user’s possibility to opt, or not, for a certain way, will be based on their own knowledge basis and forward thinking.

A decision-support system based on particle swarm optimization for multiperiod hedging in electricity markets

This paper proposes a particle swarm optimization (PSO) approach to support electricity producers for multiperiod optimal contract allocation. The producer risk preference is stated by a utility function (U) expressing the tradeoff between the expectation and variance of the return. Variance estimation and expected return are based on a forecasted scenario interval determined by a price range forecasting model developed by the authors. A certain confidence level is associated to each forecasted scenario interval. The proposed model makes use of contracts with physical (spot and forward) and financial (options) settlement. PSO performance was evaluated by comparing it with a genetic algorithm-based approach. This model can be used by producers in deregulated electricity markets but can easily be adapted to load serving entities and retailers. Moreover, it can easily be adapted to the use of other type of contracts.

A long-term risk management tool for electricity markets using swarm intelligence

This paper addresses the optimal involvement in derivatives electricity markets of a power producer to hedge against the pool price volatility. To achieve this aim, a swarm intelligence meta-heuristic optimization technique for long-term risk management tool is proposed. This tool investigates the long-term opportunities for risk hedging available for electric power producers through the use of contracts with physical (spot and forward contracts) and financial (options contracts) settlement. The producer risk preference is formulated as a utility function (U) expressing the trade-off between the expectation and the variance of the return. Variance of return and the expectation are based on a forecasted scenario interval determined by a long-term price range forecasting model. This model also makes use of particle swarm optimization (PSO) to find the best parameters allow to achieve better forecasting results. On the other hand, the price estimation depends on load forecasting. This work also presents a regressive long-term load forecast model that make use of PSO to find the best parameters as well as in price estimation. The PSO technique performance has been evaluated by comparison with a Genetic Algorithm (GA) based approach. A case study is presented and the results are discussed taking into account the real price and load historical data from mainland Spanish electricity market demonstrating the effectiveness of the methodology handling this type of problems. Finally, conclusions are dully drawn.

Demux devices based on A-SiC:H

In this paper we present results about the functioning of a multilayered a-SiC:H heterostructure as a device for wavelength-division demultiplexing of optical signals. The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photogenerated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. This photocurrent is used as an input for a demux algorithm based on the voltage controlled sensitivity of the device. The device functioning is explained with results obtained by numerical simulation of the device, which permit an insight to the internal electric configuration of the double heterojunction.These results address the explanation of the device functioning in the frequency domain to a wavelength tunable photocapacitance due to the accumulation of space charge localized at the internal junction. The existence of a direct relation between the experimentally observed capacitive effects of the double diode and the quality of the semiconductor materials used to form the internal junction is highlighted.

Orçamentação e Gestão da Reconstrução de uma Obra: Caso de estudo de um edifício

O presente relatório, desenvolvido no âmbito do estágio curricular realizado na Cociga-Construções Civis de Gaia, SA, tem como objetivo principal caracterizar as diversas etapas que constituem o desenvolvimento de uma obra, que consiste na reconstrução de um edifício. Para tal, procedeu-se à descrição e análise dos respetivos métodos organizacionais, construtivos e orçamentais aplicados na execução da obra para a Caetano Parts. O trabalho teve início com a caracterização da obra em questão e respetivo enquadramento espacial e regional. De seguida, foram descritas as principais etapas do desenvolvimento da obra, como concurso/adjudicação, preparação, contrato, execução e fecho da mesma. Não esquecendo que uma das tarefas mais importantes na fase inicial da obra, após a adjudicação, foi a organização da documentação necessária para que esta pudesse ter início. Na fase referente à execução, foram descritos de forma detalhada e acompanhados, em alguns casos, de registos de imagens, os procedimentos que constituíram as diferentes fases da obra, assim como os métodos construtivos correspondentes. O presente trabalho engloba o registo e a catalogação dos documentos necessários para as diferentes etapas da obra de reconstrução. Durante a realização das diferentes etapas e respetivo registo das mesmas, foi possível concluir que a boa qualidade da prestação de serviços por parte dos trabalhadores da empresa e dos subempreiteiros, possibilitou a concretização de uma obra com altos padrões de qualidade e de acordo com os objetivos do proprietário e da empresa responsável pela execução da mesma. Por último, a realização deste trabalho possibilitou o registo, análise e posterior reflexão sobre os procedimentos legais, logísticos e técnicos a ter em conta aquando da realização de uma obra e que são fatores fundamentais para que se possam manter os padrões de qualidade, rigor e sucesso da mesma.

Au-delà et à côté de la Quality TV : une alternative esthétique brésilienne

Tout en voulant inclure la fiction télévisuelle brésilienne parmi les fictions de qualité, cette recherche analyse l’émergence et l’évolution du concept de qualité dans le panorama télévisuel brésilien. Examinant l’histoire de la télédramaturgie au Brésil, depuis les téléthéâtres jusqu’aux microséries réalisées par Luiz Fernando Carvalho, en particulier la microsérie Capitu (2008), nous suggérons que la production fictionnelle brésilienne a atteint un niveau de qualité sophistiquée et avant-gardiste qui illustre une alternative au style préconisé par la formule des séries télévisées américaines qui se regroupent sous l’étiquette de la Quality TV. De plus, le raffinement de la microsérie contribue à la légitimation de la valeur artistique de la télévision à partir de caractéristiques télévisuelles, contrairement à la production fictionnelle américaine dont l’esthétique plutôt cinématographique finit par discréditer davantage le petit écran. Finalement, nous souhaitons démontrer l’importance des innovations esthétiques que cette microsérie a apportées au sein d’une sphère médiatique qui semble se diriger progressivement et rapidement vers l’uniformisation du langage télévisuel et de son contenu.

An Improved Technique for Evolving Wavelet Coefficients for Fingerprint Image Compression

In this paper, an improved technique for evolving wavelet coefficients refined for compression and reconstruction of fingerprint images is presented. The FBI fingerprint compression standard [1, 2] uses the cdf 9/7 wavelet filter coefficients. Lifting scheme is an efficient way to represent classical wavelets with fewer filter coefficients [3, 4]. Here Genetic algorithm (GA) is used to evolve better lifting filter coefficients for cdf 9/7 wavelet to compress and reconstruct fingerprint images with better quality. Since the lifting filter coefficients are few in numbers compared to the corresponding classical wavelet filter coefficients, they are evolved at a faster rate using GA. A better reconstructed image quality in terms of Peak-Signal-to-Noise-Ratio (PSNR) is achieved with the best lifting filter coefficients evolved for a compression ratio 16:1. These evolved coefficients perform well for other compression ratios also.

Artificial ants for active routing

Ant colonies in nature provide a good model for a distributed, robust and adaptive routing algorithm. This paper proposes the adoption of the same strategy for the routing of packets in an Active Network. Traditional store-and-forward routers are replaced by active intermediate systems, which are able to perform computations on transient packets, in a way that results very helpful for developing and dynamically deploying new protocols. The adoption of the Active Networks paradigm associated with a cooperative learning environment produces a robust, decentralized routing algorithm capable of adapting to network traffic conditions.