Towards the design of efficient nonbeacon-enabled ZigBee networks

This paper presents experimental results of the communication performance evaluation of a prototype ZigBee-based patient monitoring system commissioned in an in-patient floor of a Portuguese hospital (HPG – Hospital Privado de Guimar~aes). Besides, it revisits relevant problems that affect the performance of nonbeacon-enabled ZigBee networks. Initially, the presence of hidden-nodes and the impact of sensor node mobility are discussed. It was observed, for instance, that the message delivery ratio in a star network consisting of six wireless electrocardiogram sensor devices may decrease from 100% when no hidden-nodes are present to 83.96% when half of the sensor devices are unable to detect the transmissions made by the other half. An additional aspect which affects the communication reliability is a deadlock condition that can occur if routers are unable to process incoming packets during the backoff part of the CSMA-CA mechanism. A simple approach to increase the message delivery ratio in this case is proposed and its effectiveness is verified. The discussion and results presented in this paper aim to contribute to the design of efficient networks,and are valid to other scenarios and environments rather than hospitals.

Fatores determinantes da política de distribuição de dividendos: Evidência empírica para as empresas não financeiras da Euronext Lisbon

Dividends and their distribution decisions, being a component of the compensation of investors are a constant financial worry within companies, thus revealing one of the themes highlighted in the context of the financial literature. Study will address the factors determining the dividend policy practiced by companies listed in the Portuguese stock market. The latter will be 47 non-financial companies listed on the Euronext Lisbon during 2009 until 2011. The two samples that have been investigated include the representative of the majority of non-financial companies listed on Euronext Lisbon and the other financial companies members of the PSI 20. The methodology adopted is one of the ordinary least squares regression and the amount of dividends per share distributed was used in determining the dependent variable. In relation to the independent variables, six explanatory factors were chosen. These include profitability, stability of dividend policy, size, growth, risk and investment opportunities. The conclusion suggests that the most important factors to explain the amount of dividends distributed are profitability and stability of dividend policy. There after, growth and risk factors, as well as factors that explain the amount of dividends distributed are also relevant. The remaining variables obtained were insufficient evidence pointing to a significant effect in explaining the dividend policy of Portuguese companies in the sample. The conclusion also states that differences exist in the importance of the explanatory factors to the amount of dividends distributed between the study samples, given the differentiation of dividend policies, followed by companies from each group analyzed.

Evidência empírica dos factores explicativos dos dividendos distribuídos pelas empresas cotadas na EURONEXT Lisboa

Companies’ decision to pay dividends to its shareholders is a topic that has received increasing attention in business finance. This paper provides an additional contribution to the development of this topic focusing on the analysis of the determinants of dividend policy by issuing companies in the Portuguese capital market. For this purpose, we use a set of financial and economic information specific to each firm to explain its dividend per share. The sample used in the empirical study contains 54 firms and it refers to the 2005-2009 period. Results suggest that net income, dividends per share paid in the previous financial year and return on assets all present a positive and statistically significant effect on dividends per share paid in a given financial year. Moreover, results show that Lintner’s (1956) model appears to be valid in explaining dividend policy by issuing companies in Euronext Lisbon.

Remote Patient Monitoring Based on ZigBee: Lessons from a Real-World Deployment

AIM: This work presents detailed experimental performance results from tests executed in the hospital environment for Health Monitoring for All (HM4All), a remote vital signs monitoring system based on a ZigBee® (ZigBee Alliance, San Ramon, CA) body sensor network (BSN). MATERIALS AND METHODS: Tests involved the use of six electrocardiogram (ECG) sensors operating in two different modes: the ECG mode involved the transmission of ECG waveform data and heart rate (HR) values to the ZigBee coordinator, whereas the HR mode included only the transmission of HR values. In the absence of hidden nodes, a non-beacon-enabled star network composed of sensing devices working on ECG mode kept the delivery ratio (DR) at 100%. RESULTS: When the network topology was changed to a 2-hop tree, the performance degraded slightly, resulting in an average DR of 98.56%. Although these performance outcomes may seem satisfactory, further investigation demonstrated that individual sensing devices went through transitory periods with low DR. Other tests have shown that ZigBee BSNs are highly susceptible to collisions owing to hidden nodes. Nevertheless, these tests have also shown that these networks can achieve high reliability if the amount of traffic is kept low. Contrary to what is typically shown in scientific articles and in manufacturers' documentation, the test outcomes presented in this article include temporal graphs of the DR achieved by each wireless sensor device. CONCLUSIONS: The test procedure and the approach used to represent its outcomes, which allow the identification of undesirable transitory periods of low reliability due to contention between devices, constitute the main contribution of this work.

Papa Bento XVI e Papa Francisco na grande final!

A chamada Lei do Branqueamento de Capitais - Lei 25/2008, de 5/6 e alterações -, considera que estão sujeitas a especiais obrigações os “Notários, conservadores de registos, advogados, solicitadores e outros profissionais independentes, constituídos em sociedade ou em prática individual, que intervenham ou assistam, por conta de um cliente ou noutras circunstâncias, em operações: § vi) De alienação e aquisição de direitos sobre praticantes de actividades desportivas profissionais;”. Estamos a pensar, como é óbvio, nas transferências de jogadores de futebol, nomeadamente na Europa, as quais atingem somas astronómicas e muitas vezes ocultas. São por demais evidentes as notícias da comunicação social que dão conta que, em muitos dos casos, os verdadeiros valores envolvidos não são os declarados. Quer para fugir aos impostos, quer para esconder o pagamento de avultadas comissões extraordinárias; Abstract: The Call of the Money Laundering Law - Law 25/2008, of 5/6 and change - considers that are subject to the special obligations "notaries, registrars, lawyers, solicitors and other independent professionals, made in society or in practice individual, that participating or assisting, on behalf of a client or other circumstances in operations: § vi) sale and acquisition of rights to practitioners of professional sports activities; ". We are thinking, of course, transfers of football players, particularly in Europe, which reach astronomical sums and often hidden. Are all too apparent the news media that realize that in many cases the true values involved are not declared. Want to evade taxes or to hide the payment of large exceptional fees.