The Interpretation of Verbal Probability Expressions Used in the IAS/IFRS: the auditors Rrgistered with the portuguese securities market commission

One of the main arguments in favour of the adoption and convergence with the international accounting standards published by the IASB (i.e. IAS/IFRS) is that these will allow comparability of financial reporting across countries. However, because these standards use verbal probability expressions (v.g. “probable”) when establishing the recognition and disclosure criteria for accounting elements, they require professional accountants to interpret and classify the probability of an outcome or event taking into account those terms and expressions and to best decide in terms of financial reporting. This paper reports part of a research we carried out on the interpretation of “in context” verbal probability expressions used in the IAS/IFRS by the auditors registered with the Portuguese Securities Market Commission, the Comissão do Mercado de Valores Mobiliários (CMVM). Our results provide support for the hypothesis that culture affects the CMVM registered auditors’ interpretation of verbal probability expressions through its influence on the accounting value (or attitude) of conservatism. Our results also suggest that there are significant differences in their interpretation of the term “probable”, which is consistent with literature in general. Since “probable” is the most frequent verbal probability expression used in the IAS/IFRS, this may have a negative impact on financial statements comparability.

Eastwards / westwards: which direction for gender studies in the 21st century?

Eastwards / Westwards: Which Direction for Gender Studies in the XXIst Century? is a collection of essays which focus on themes and methods that characterize current research into gender in Asian countries in general. In this collection, ideas derived from Gender Studies elsewhere in the world have been subjected to scrutiny for their utility in helping to describe and understand regional phenomena. But the concepts of Local and Global – with their discoursive productions – have not functioned as a binary opposition: localism and globalism are mutually constitutive and researchers have interrogated those spaces of interaction between the ‘self’ and the ‘other’, bearing in mind their own embeddedness in social and cultural structures and their own historical memory. Contributors to this collection provided a critical transnational perspective on some of the complex effects of the dynamics of cultural globalization, by exploring the relation between gender and development, language, historiography, education and culture. We have also given attention to the ideological and rhetorical processes through which gender identity is constructed, by comparing textual grids and patterns of expectation. Likewise, we have discussed the role of ethnography, anthropology, historiography, sociology, fiction, popular culture and colonial and post-colonial sources in (re)inventing old/new male/female identities, their conversion into concepts and circulation through time and space. This multicultural and trans-disciplinary selection of essays is totally written in English, fully edited and revised, therefore, it has a good potential for an immediate international circulation. This project may trace new paths and issues for discussion on what concerns the life, practices and narratives by and about women in Asia, as well as elsewhere in the present day global experience. Academic readership: Researchers, scholars, educators, graduate and post-graduate students, doctoral students and general non-fiction readers, with a special interest in Gender Studies, Asia, Colonial and Post-Colonial Literature, Anthropology, Cultural Studies, History, Historiography, Politics, Race, Feminism, Language, Linguistics, Power, Political and Feminist Agendas, Popular Culture, Education, Women’s Writing, Religion, Multiculturalism, Globalisation, Migration. Chapter summary: 1. “Social Gender Stereotypes and their Implication in Hindi”, Anjali Pande, Jawaharlal Nehru University, New Delhi, India. This essay looks at the subtle ways in which gender identities are constructed and reinforced in India through social norms of language use. Language itself becomes a medium for perpetuating gender stereotypes, forcing its speakers to confirm to socially defined gender roles. Using examples from a classroom discussion about a film, this essay will highlight the underlying rigid male-female stereotypes in Indian society with their more obvious expressions in language. For the urban woman in India globalisation meant increased economic equality and exposure to changed lifestyles. On an individual level it also meant redefining gender relations and changing the hierarchy in man-­woman relationships. With the economic independence there is a heightened sense of liberation in all spheres of social life, a confidence to fuzz the rigid boundaries of gender roles. With the new films and media celebrating this liberated woman, who is ready to assert her sexual needs, who is ready to explode those long held notions of morality, one would expect that the changes are not just superficial. But as it soon became obvious in the course of a classroom discussion about relationships and stereotypes related to age, the surface changes can not become part of the common vocabulary, for the obvious reason that there is still a vast gap between the screen image of this new woman and the ground reality. Social considerations define the limits of this assertiveness of women, whereas men are happy to be liberal within the larger frame of social sanctions. The educated urban woman in India speaks in favour of change and the educated urban male supports her, but one just needs to scratch the surface to see the time tested formulae of gender roles firmly in place. The way the urban woman happily balances this emerging promise of independence with her gendered social identity, makes it necessary to rethink some aspects of looking at gender in a gradually changing, traditional society like India. 2. “The Linguistic Dimension of Gender Equality”, Alissa Tolstokorova, Kiev Centre for Gender Information and Education, Ukraine. The subject-matter of this essay is gender justice in language which, as I argue, may be achieved through the development of a gender-related approach to linguistic human rights. The last decades of the 20th century, globally marked by a “gender shift” in attitudes to language policy, gave impetus to the social movement for promoting linguistic gender equality. It was initiated in Western Europe and nowadays is moving eastwards, as ideas of gender democracy progress into developing countries. But, while in western societies gender discrimination through language, or linguistic sexism, was an issue of concern for over three decades, in developing countries efforts to promote gender justice in language are only in their infancy. My argument is that to promote gender justice in language internationally it is necessary to acknowledge the rights of women and men to equal representation of their gender in language and speech and, therefore, raise a question of linguistic rights of the sexes. My understanding is that the adoption of the Universal Declaration of Linguistic Rights in 1996 provided this opportunity to address the problem of gender justice in language as a human rights issue, specifically as a gender dimension of linguistic human rights. 3. “The Rebirth of an Old Language: Issues of Gender Equality in Kazakhstan”, Maria Helena Guimarães, Polytechnic Institute of Porto, Portugal. The existing language situation in Kazakhstan, while peaceful, is not without some tension. We propose to analyze here some questions we consider relevant in the frame of cultural globalization and gender equality, such as: free from Russian imperialism, could Kazakhstan become an easy prey of Turkey’s “imperialist dream”? Could these traditionally Muslim people be soon facing the end of religious tolerance and gender equality, becoming this new old language an easy instrument for the infiltration in the country of fundamentalism (it has already crossed the boarders of Uzbekistan), leading to a gradual deterioration of its rich multicultural relations? The present structure of the language is still very fragile: there are three main dialects and many academics defend the re-introduction of the Latin alphabet, thus enlarging the possibility of cultural “contamination” by making the transmission of fundamentalist ideas still easier through neighbour countries like Azerbaijan, Uzbekistan and Turkmenistan (their languages belong to the same sub-group of Common Turkic), where the Latin alphabet is already in use, and where the ground for such ideas shown itself very fruitful. 4. “Construction of Womanhood in the Bengali Language of Bangladesh”, Raasheed Mahmood; University of New South Wales, Sydney. The present essay attempts to explore the role of gender-based language differences and of certain markers that reveal the status accorded to women in Bangladesh. Discrimination against women, in its various forms, is endemic in communities and countries around the world, cutting across class, race, age, and religious and national boundaries. One cannot understand the problems of gender discrimination solely by referring to the relationship of power or authority between men and women. Rather one needs to consider the problem by relating it to the specific social formation in which the image of masculinity and femininity is constructed and reconstructed. Following such line of reasoning this essay will examine the nature of gender bias in the Bengali language of Bangladesh, holding the conviction that as a product of social reality language reflects the socio-cultural behaviour of the community who speaks it. This essay will also attempt to shed some light on the processes through which gender based language differences produce actual consequences for women, who become exposed to low self-esteem, depression and systematic exclusion from public discourse. 5. “Marriage in China as an expression of a changing society”, Elisabetta Rosado David, University of Porto, Portugal, and Università Ca’Foscari, Venezia, Italy. In 29 April 2001, the new Marriage Law was promulgated in China. The first law on marriage was proclaimed in 1950 with the objective of freeing women from the feudal matrimonial system. With the second law, in 1981, values and conditions that had been distorted by the Cultural Revolution were recovered. Twenty years later, a new reform was started, intending to update marriage in the view of the social and cultural changes that occurred with Deng Xiaoping’s “open policy”. But the legal reform is only the starting point for this case-study. The rituals that are followed in the wedding ceremony are often hard to understand and very difficult to standardize, especially because China is a vast country, densely populated and characterized by several ethnic minorities. Two key words emerge from this issue: syncretism and continuity. On this basis, we can understand tradition in a better way, and analyse whether or not marriage, as every social manifestation, has evolved in harmony with Chinese culture. 6. “The Other Woman in the Portuguese Colonial Empire: The Case of Portuguese India”, Maria de Deus Manso, University of Évora, Portugal. This essay researches the social, cultural and symbolic history of local women in the Portuguese Indian colonial enclaves. The normative Portuguese overseas history has not paid any attention to the “indigenous” female populations in colonial Portuguese territories, albeit the large social importance of these social segments largely used in matrimonial and even catholic missionary strategies. The first attempt to open fresh windows in the history of this new field was the publication of Charles Boxer’s referential study about Women in lberian Overseas Expansion, edited in Portugal only after the Revolution of 1975. After this research we can only quote some other fragmentary efforts. In fact, research about the social, cultural, religious, political and symbolic situation of women in the Portuguese colonial territories, from the XVI to the XX century, is still a minor historiographic field. In this essay we discuss this problem and we study colonial representations of women in the Portuguese Indian enclaves, mainly in the territory of Goa, using case studies methodologies. 7. “Heading East this Time: Critical Readings on Gender in Southeast Asia”, Clara Sarmento, Polytechnic Institute of Porto, Portugal. This essay intends to discuss some critical readings of fictional and theoretical texts on gender condition in Southeast Asian countries. Nowadays, many texts about women in Southeast Asia apply concepts of power in unusual areas. Traditional forms of gender hegemony have been replaced by other powerful, if somewhat more covert, forms. We will discuss some universal values concerning conventional female roles as well as the strategies used to recognize women in political fields traditionally characterized by male dominance. Female empowerment will mean different things at different times in history, as a result of culture, local geography and individual circumstances. Empowerment needs to be perceived as an individual attitude, but it also has to be facilitated at the macro­level by society and the State. Gender is very much at the heart of all these dynamics, strongly related to specificities of historical, cultural, ethnic and class situatedness, requiring an interdisciplinary transnational approach.

Social gender stereotypes and their implications in Hindi

This essay looks at the subtle ways in which gender identities are constructed and reinforced in India through social norms of language use. Language itself becomes a medium for perpetuating gender stereotypes, forcing its speakers to confirm to socially defined gender roles. Using examples from a classroom discussion about a film, this essay will highlight the underlying rigid male-female stereotypes in Indian society with their more obvious expressions in language. For the urban woman in India globalisation meant increased economic equality and exposure to changed lifestyles. On an individual level it also meant redefining gender relations and changing the hierarchy in man-woman relationships. With the economic independence there is a heightened sense of liberation in all spheres of social life, a confidence to fuzz the rigid boundaries of gender roles. With the new films and media celebrating this liberated woman, who is ready to assert her sexual needs, who is ready to explode those long held notions of morality, one would expect that the changes are not just superficial. But as it soon became obvious in the course of a classroom discussion about relationships and stereotypes related to age, the surface changes can not become part of the common vocabulary, for the obvious reason that there is still a vast gap between the screen image of this new woman and the ground reality. Social considerations define the limits of this assertiveness of women, whereas men are happy to be liberal within the larger frame of social sanctions. The educated urban woman in India speaks in favour of change and the educated urban male supports her, but one just needs to scratch the surface to see the time tested formulae of gender roles firmly in place. The way the urban woman happily balances this emerging promise of independence with her gendered social identity, makes it necessary to rethink some aspects of looking at gender in a gradually changing, traditional society like India.

Recuperação de calor dos efluentes da tinturaria

Foram utilizados como elemento principal de estudo, os efluentes líquidos dos processos industriais da ENDUTEX, Tinturaria e Acabamento de Malhas, S. A. localizada no município de Caldas de Vizela, distrito de Braga. O estudo foi realizado na empresa devido ao interesse da mesma em poder reaproveitar o calor libertado nos efluentes para aquecimento de parte da água captada no rio de Vizela. O objectivo do trabalho consiste no dimensionamento de um permutador de calor que permita satisfazer o interesse da empresa, assim como, um estudo económico relativo aos custos envolventes. Com o intuito de concretizar os objectivos propostos foram realizadas visitas semanais à empresa para se proceder ao levantamento de dados e para a realização de amostragens do efluente para posterior caracterização. Depois de efectuado o dimensionamento do permutador de placas para diferentes caudais e temperaturas dos fluidos, frio (água do rio) e quente (efluentes), concluiu-se que as condições mais rentáveis correspondiam a um caudal de fluido frio de 17 m3/h em que a temperatura de entrada e de saída no permutador seria de 14 ºC e 48 ºC, respectivamente. O caudal de fluido quente seria de 20 m3/h, sendo a temperatura de entrada e de saída no permutador de 62 ºC e 33,1 ºC, respectivamente. Como resultado do dimensionamento obteve-se um permutador de placas com 167 placas em que o coeficiente global de transferência de calor (U) é de 726,9 W/m2ºC, a área projectada de 55,7 m2 e a queda de pressão de 0,904 KPa. Foi consultada a empresa ARSOPI-THERMAL para verificação das características dos permutadores existentes no mercado. No entanto, para as mesmas condições foi sugerido um permutador com 31 placas em que o coeficiente global de transferência de calor (U) é de 6267 W/m2ºC, a área projectada de 7,39 m2 e a queda de pressão de 76 KPa. A diferença verificada nos resultados apresentados pode ter origem na utilização de diferentes expressões no cálculo do coeficiente pelicular de transferência de calor (h) e pelo facto da ARSOPI desprezar o factor de sujamento no seu dimensionamento Na análise económica do projecto é de referir que para o arranque do projecto foi feito o levantamento das necessidades de investimento, situando-se este num valor total de 9640€, sendo o investimento financiado apenas por capitais próprios. O prazo de recuperação do investimento (Pay Back Period) é de cerca de 2 meses.

Resposta contextual automática a mensagens electrónicas

A evolução tecnológica, associada às mudanças sociais a que temos assistido, nomeadamente nas últimas décadas, originou mudanças significativas na forma como os utentes interagem com as instituições, passando a privilegiar a utilização de meios electrónicos, tais como as mensagens de correio electrónico, em detrimento de formas mais tradicionais, como a carta e o telefone. Neste contexto, sendo o ISEP uma instituição de ensino superior que alberga milhares de alunos e recebe centenas de novos alunos todos os anos, necessita de ter condições para que possa responder de forma atempada às inúmeras mensagens de correio electrónico que recebe. Esta necessidade fez com que surgisse um projecto, de nome SiRAC, que servisse para auxiliar na resposta a essas mensagens. O SiRAC tem como objectivo responder a mensagens de correio electrónico de forma automática. De salientar que se admite não ser possível responder a todas as mensagens, privilegiando-se aquelas que são recorrentemente colocadas à Divisão Académica. Assim será possível encurtar o tempo de comunicação entre os diversos intervenientes, criando uma relação mais próxima entre o ISEP e o público que o contacta. O SiRAC analisa as mensagens e procura responder de forma automática sempre que o seu conteúdo possa ser classificado como fazendo parte de um conjunto de questões previamente identificadas pelos recursos humanos da Divisão Académica como recorrentes e para as quais já exista uma resposta tipo. As questões constantes da mensagem são identificadas através de palavras e expressões normalmente associadas aos diferentes tipos de questão. O envio da resposta pressupõe a identificação correcta dos tipos associados e de acordo com requisitos mínimos definidos, de forma a evitar enviar uma resposta errada a uma mensagem. A implementação do SiRAC permite a libertação de recursos humanos da Divisão Académica que anteriormente estavam afectas à resposta de mensagens para o desempenho de outras funções.

Sistema de animação de personagens virtuais para comunicação não verbal

O principal objectivo da animação de personagens virtuais é o de contar uma história através da utilização de personagens virtuais emocionalmente expressivos. Os personagens têm personalidades distintas, e transmitem as suas emoções e processos de pensamento através dos seus comportamentos (comunicação não verbal). As suas acções muitas das vezes constituem a geração de movimentos corporais complexos. Existem diversas questões a considerar quando se anima uma entidade complexa, tais como, a posição das zonas móveis e as suas velocidades. Os personagens virtuais são um exemplo de entidades complexas e estão entre os elementos mais utilizados em animação computacional. O foco desta dissertação consistiu na criação de uma proposta de sistema de animação de personagens virtuais, cujos movimentos e expressões faciais são capazes de transmitir emoções e estados de espírito. Os movimentos primários, ou seja os movimentos que definem o comportamento dos personagens, são provenientes da captura de movimentos humanos (Motion Capture). As animações secundárias, tais como as expressões faciais, são criadas em Autodesk Maya recorrendo à técnica BlendShapes. Os dados obtidos pela captura de movimentos, são organizados numa biblioteca de comportamentos através de um grafo de movimentos, conhecido por Move Tree. Esta estrutura permite o controlo em tempo real dos personagens através da gestão do estado dos personagens. O sistema possibilita também a transição eficaz entre movimentos semelhantes e entre diferentes velocidades de locomoção, minimizando o efeito de arrastamento de pés conhecido como footskate. Torna-se assim possível definir um trajecto que o personagem poderá seguir com movimentos suaves. Estão também disponíveis os resultados obtidos nas sessões de avaliação realizadas, que visaram a determinação da qualidade das transições entre animações. Propõem-se ainda o melhoramento do sistema através da implementação da construção automática do grafo de movimentos.

Desenvolvimento do sistema de controlo de um braço robotizado e respetiva interface com o utilizador

A robótica tem evoluído de forma significativa nos últimos anos e passa a ser indispensável em várias aplicações nas áreas da engenharia, aeronáutica, medicina, entre outras. O estado da arte do presente trabalho está dividido em duas partes, uma que aborda vários aspetos relacionados com a robótica e outra com os aspetos da fundamentação matemática por de trás da robótica, porque para controlar o robô é necessário implementar expressões matemáticas para o poder controlar. Neste trabalho é apresentado um sistema de controlo do braço robótico MENTOR e o desenvolvimento de uma interface para o utilizador. Para o controlo do braço robótico foi necessário calcular a cinemática direta e inversa, para que se possa obter os ângulos das juntas para uma dada posição ou qual é a posição final do braço robótico para um valor das juntas. O sistema é bastante flexível e foi desenvolvido para ser utilizado essencialmente para aprendizagem de robótica, podendo no entanto ser utilizado em outras aplicações.

Desenvolvimento de uma ferramenta para cálculo de estruturas em material compósito

Os desafios à engenharia moderna são cada vez maiores, pretendendo-se quase sempre obter estruturas mais leves, com propriedades mecânicas atrativas e muitas vezes com geometrias complexas. Com tais requisitos, um dos materiais que tem vindo a ter uma crescente aplicação é o material compósito. Contudo, no que toca ao cálculo estrutural destes materiais, tudo se torna mais complexo, já que são materiais que geralmente são formados por empilhamento de várias camadas de material heterogéneo, podendo estas encontrarem-se dispostas segundo diferentes orientações. Assim, a utilização de um software que permita a previsão das propriedades mecânicas de uma estrutura em material compósito através da micromecânica, a aplicação da Teoria Clássica dos Laminados e de um critério de rotura, como por exemplo o de Tsai-Hill, é fundamental para agilizar o processo de estudo da estrutura a fabricar. Para dar uma resposta a tal necessidade foi desenvolvida uma aplicação, em MATLAB® GUI, denominada CAFE – Composite Analysis For Engineers, com ambiente gráfico apelativo, que permite determinar todas as variáveis importantes no estudo de estruturas em material compósito. Esta aplicação visa suportar e agilizar a aprendizagem desta área do conhecimento, permitindo também o acesso ao código de cálculo por parte do utilizador, de modo a conhecerem-se as equações utilizadas e, eventualmente, ser alvo de futuros desenvolvimentos. O programa desenvolvido foi alvo de validação, recorrendo-se para tal, a uma comparação dos resultados obtidos entre o respetivo programa e por um outro programa de grande fiabilidade. Assim sendo, concluiu-se que o software CAFE apresenta resultados válidos, encontrando-se apto a ser utilizado.

Evaluation of distinct input methods of an intelligent wheelchair in simulated and real environments: a performance and usability study

This paper focuses on evaluating the usability of an Intelligent Wheelchair (IW) in both real and simulated environments. The wheelchair is controlled at a high-level by a flexible multimodal interface, using voice commands, facial expressions, head movements and joystick as its main inputs. A Quasi-experimental design was applied including a deterministic sample with a questionnaire that enabled to apply the System Usability Scale. The subjects were divided in two independent samples: 46 individuals performing the experiment with an Intelligent Wheelchair in a simulated environment (28 using different commands in a sequential way and 18 with the liberty to choose the command); 12 individuals performing the experiment with a real IW. The main conclusion achieved by this study is that the usability of the Intelligent Wheelchair in a real environment is higher than in the simulated environment. However there were not statistical evidences to affirm that there are differences between the real and simulated wheelchairs in terms of safety and control. Also, most of users considered the multimodal way of driving the wheelchair very practical and satisfactory. Thus, it may be concluded that the multimodal interfaces enables very easy and safe control of the IW both in simulated and real environments.

Root-locus practical sketching rules for fractional-order system

For integer-order systems, there are well-known practical rules for RL sketching. Nevertheless, these rules cannot be directly applied to fractional-order (FO) systems. Besides, the existing literature on this topic is scarce and exclusively focused on commensurate systems, usually expressed as the ratio of two noninteger polynomials. The practical rules derived for those do not apply to other symbolic expressions, namely, to transfer functions expressed as the ratio of FO zeros and poles. However, this is an important case as it is an extension of the classical integer-order problem usually addressed by control engineers. Extending the RL practical sketching rules to such FO systems will contribute to decrease the lack of intuition about the corresponding system dynamics. This paper generalises several RL practical sketching rules to transfer functions specified as the ratio of FO zeros and poles. The subject is presented in a didactic perspective, being the rules applied to several examples.

Friction losses of Newtonian and non-Newtonian fluids flowing in laminar regime in a helical coil

This study aimed to carry out experimental work to determine, for Newtonian and non-Newtonian fluids, the friction factor (fc) with simultaneous heat transfer, at constant wall temperature as boundary condition, in fully developed laminar flow inside a vertical helical coil. The Newtonian fluids studied were aqueous solutions of glycerol, 25%, 36%, 43%, 59% and 78% (w/w). The non-Newtonian fluids were aqueous solutions of carboxymethylcellulose (CMC), a polymer, with concentrations of 0.2%, 0.3%, 0.4% and 0.6% (w/w) and aqueous solutions of xanthan gum (XG), another polymer, with concentrations of 0.1% and 0.2% (w/w). According to the rheological study done, the polymer solutions had shear-thinning behavior and different values of viscoelasticity. The helical coil used has an internal diameter, curvature ratio, length and pitch, respectively: 0.00483 m, 0.0263, 5.0 m and 11.34 mm. It was concluded that the friction factors, with simultaneous heat transfer, for Newtonian fluids can be calculated using expressions from literature for isothermal flows. The friction factors for CMC and XG solutions are similar to those for Newtonian fluids when the Dean number, based in a generalized Reynolds number, is less than 80. For Dean numbers higher than 80, the friction factors of the CMC solutions are lower those of the XG solutions and of the Newtonian fluids. In this range the friction factors decrease with the increase of the viscometric component of the solution and increase for increasing elastic component. The change of behavior at Dean number 80, for Newtonian and non-Newtonian fluids, is in accordance with the study of Ali [4]. There is a change of behavior at Dean number 80, for Newtonian and non-Newtonian fluids, which is in according to previous studies. The data also showed that the use of the bulk temperature or of the film temperature to calculate the physical properties of the fluid has a residual effect in the friction factor values.

Dimensioning and worst-case analysis of cluster-tree sensor networks

Modeling the fundamental performance limits of Wireless Sensor Networks (WSNs) is of paramount importance to understand their behavior under the worst-case conditions and to make the appropriate design choices. This is particular relevant for time-sensitive WSN applications, where the timing behavior of the network protocols (message transmission must respect deadlines) impacts on the correct operation of these applications. In that direction this paper contributes with a methodology based on Network Calculus, which enables quick and efficient worst-case dimensioning of static or even dynamically changing cluster-tree WSNs where the data sink can either be static or mobile. We propose closed-form recurrent expressions for computing the worst-case end-to-end delays, buffering and bandwidth requirements across any source-destination path in a cluster-tree WSN. We show how to apply our methodology to the case of IEEE 802.15.4/ZigBee cluster-tree WSNs. Finally, we demonstrate the validity and analyze the accuracy of our methodology through a comprehensive experimental study using commercially available technology, namely TelosB motes running TinyOS.

Real-time communications over cluster-tree sensor networks with mobile sink behaviour

Modelling the fundamental performance limits of wireless sensor networks (WSNs) is of paramount importance to understand the behaviour of WSN under worst case conditions and to make the appropriate design choices. In that direction, this paper contributes with a methodology for modelling cluster tree WSNs with a mobile sink. We propose closed form recurrent expressions for computing the worst case end to end delays, buffering and bandwidth requirements across any source-destination path in the cluster tree assuming error free channel. We show how to apply our theoretical results to the specific case of IEEE 802.15.4/ZigBee WSNs. Finally, we demonstrate the validity and analyze the accuracy of our methodology through a comprehensive experimental study, therefore validating the theoretical results through experimentation.

Modeling and worst-case dimensioning of cluster-tree wireless sensor networks

Time-sensitive Wireless Sensor Network (WSN) applications require finite delay bounds in critical situations. This paper provides a methodology for the modeling and the worst-case dimensioning of cluster-tree WSNs. We provide a fine model of the worst-case cluster-tree topology characterized by its depth, the maximum number of child routers and the maximum number of child nodes for each parent router. Using Network Calculus, we derive “plug-and-play” expressions for the endto- end delay bounds, buffering and bandwidth requirements as a function of the WSN cluster-tree characteristics and traffic specifications. The cluster-tree topology has been adopted by many cluster-based solutions for WSNs. We demonstrate how to apply our general results for dimensioning IEEE 802.15.4/Zigbee cluster-tree WSNs. We believe that this paper shows the fundamental performance limits of cluster-tree wireless sensor networks by the provision of a simple and effective methodology for the design of such WSNs.

Direct search optimization application programming interface with remote access

Search Optimization methods are needed to solve optimization problems where the objective function and/or constraints functions might be non differentiable, non convex or might not be possible to determine its analytical expressions either due to its complexity or its cost (monetary, computational, time,...). Many optimization problems in engineering and other fields have these characteristics, because functions values can result from experimental or simulation processes, can be modelled by functions with complex expressions or by noise functions and it is impossible or very difficult to calculate their derivatives. Direct Search Optimization methods only use function values and do not need any derivatives or approximations of them. In this work we present a Java API that including several methods and algorithms, that do not use derivatives, to solve constrained and unconstrained optimization problems. Traditional API access, by installing it on the developer and/or user computer, and remote API access to it, using Web Services, are also presented. Remote access to the API has the advantage of always allow the access to the latest version of the API. For users that simply want to have a tool to solve Nonlinear Optimization Problems and do not want to integrate these methods in applications, also two applications were developed. One is a standalone Java application and the other a Web-based application, both using the developed API.