Design Strategies and Modelling of Low-Power Sigma-Delta Analog-to-Digital Converters

Oggi, i dispositivi portatili sono diventati la forza trainante del mercato consumer e nuove sfide stanno emergendo per aumentarne le prestazioni, pur mantenendo un ragionevole tempo di vita della batteria. Il dominio digitale è la miglior soluzione per realizzare funzioni di elaborazione del segnale, grazie alla scalabilità della tecnologia CMOS, che spinge verso l'integrazione a livello sub-micrometrico. Infatti, la riduzione della tensione di alimentazione introduce limitazioni severe per raggiungere un range dinamico accettabile nel dominio analogico. Minori costi, minore consumo di potenza, maggiore resa e una maggiore riconfigurabilità sono i principali vantaggi dell'elaborazione dei segnali nel dominio digitale. Da più di un decennio, diverse funzioni puramente analogiche sono state spostate nel dominio digitale. Ciò significa che i convertitori analogico-digitali (ADC) stanno diventando i componenti chiave in molti sistemi elettronici. Essi sono, infatti, il ponte tra il mondo digitale e analogico e, di conseguenza, la loro efficienza e la precisione spesso determinano le prestazioni globali del sistema. I convertitori Sigma-Delta sono il blocco chiave come interfaccia in circuiti a segnale-misto ad elevata risoluzione e basso consumo di potenza. I tools di modellazione e simulazione sono strumenti efficaci ed essenziali nel flusso di progettazione. Sebbene le simulazioni a livello transistor danno risultati più precisi ed accurati, questo metodo è estremamente lungo a causa della natura a sovracampionamento di questo tipo di convertitore. Per questo motivo i modelli comportamentali di alto livello del modulatore sono essenziali per il progettista per realizzare simulazioni veloci che consentono di identificare le specifiche necessarie al convertitore per ottenere le prestazioni richieste. Obiettivo di questa tesi è la modellazione del comportamento del modulatore Sigma-Delta, tenendo conto di diverse non idealità come le dinamiche dell'integratore e il suo rumore termico. Risultati di simulazioni a livello transistor e dati sperimentali dimostrano che il modello proposto è preciso ed accurato rispetto alle simulazioni comportamentali.

Mobile Access to Cultural and Historical Heritage Web Pages

The main focus of attention in this paper is the access to websites of leading regional, national and world museums. Their accessibility from desktop and mobile devices is hereby evaluated. The paper covers a detailed analysis of the mobile operating systems, their market share in Bulgaria and the opportunities they offer to the users. The need for contemporary cultural and historical heritage websites which maintain lighter but fully-functioning mobile versions, facilitating and making their access from portable devices easier, is also well-grounded here.

Context -aware data caching for mobile computing environments

The deployment of wireless communications coupled with the popularity of portable devices has led to significant research in the area of mobile data caching. Prior research has focused on the development of solutions that allow applications to run in wireless environments using proxy based techniques. Most of these approaches are semantic based and do not provide adequate support for representing the context of a user (i.e., the interpreted human intention.). Although the context may be treated implicitly it is still crucial to data management. In order to address this challenge this dissertation focuses on two characteristics: how to predict (i) the future location of the user and (ii) locations of the fetched data where the queried data item has valid answers. Using this approach, more complete information about the dynamics of an application environment is maintained. ^ The contribution of this dissertation is a novel data caching mechanism for pervasive computing environments that can adapt dynamically to a mobile user's context. In this dissertation, we design and develop a conceptual model and context aware protocols for wireless data caching management. Our replacement policy uses the validity of the data fetched from the server and the neighboring locations to decide which of the cache entries is less likely to be needed in the future, and therefore a good candidate for eviction when cache space is needed. The context aware driven prefetching algorithm exploits the query context to effectively guide the prefetching process. The query context is defined using a mobile user's movement pattern and requested information context. Numerical results and simulations show that the proposed prefetching and replacement policies significantly outperform conventional ones. ^ Anticipated applications of these solutions include biomedical engineering, tele-health, medical information systems and business. ^

Litiumin talteenotto luonnon suola-altaista ionisilla nesteillä

Uusiutuvan energian käytön lisääntyminen lisää sähkön varastoinnin tarvetta. Litiumioniakku-jen on todettu olevan oivallisia keinoja varastoida sähköä esimerkiksi sähköautojen energian-lähteeksi. Tästä syystä akkujen kysyntä kasvaa nopeaa tahtia, jolloin nykyiset litiumlähteet ei-vät enää riitä tuottamaan tarpeeksi litiumia kasvavaan tarpeeseen. Tämän vuoksi litiumin tal-teenottoon tulee valjastaa uusia litiumin lähteitä, joiden hyödynnettävyys nykyisellä tekniikalla on pienen litiumkonsentraation ja muiden alkali- ja maa-alkalimetallien läsnäolon takia vaikeaa. Tällä hetkellä litiumia otetaan talteen eniten korkean litiumpitoisuuden luonnon suolajärvistä. Nykyisin käytössä oleva litiumin erotusprosessi on hidas ja sen käyttö pienten litiumkonsent-raatioiden suola-altailla on kannattamatonta. Tehokkaampana talteenottomenetelmänä luonnon suolajärvillä nähdään litiumin selektiivinen uutto ionisilla nesteillä. Menetelmä on todettu toi-mivaksi suolajärvillä, joilla on matala litiumkonsentraatio. Uusien suolajärvien käyttöönotto ei ratkaise kaikkia litiumin talteenottoon liittyviä ongelmia, sillä suolajärvet ovat alttiita ilmastonmuutokselle, eikä niiden litiumvarannot ole ehtymättömät. Merien litiumvarantoja sen sijaan pidetään lähes ehtymättöminä. Litiumin talteenotto meristä on mahdollista ionisia nesteitä ja membraaneja hyödyntävällä elektrodialyysilaitteistolla, jolla litiumia voidaan ottaa talteen myös hyvin pienistä pitoisuuksista. Lisäksi on mahdollista, että litiumin talteenottoon yhdistetään juomaveden valmistus. Tällainen vedenpuhdistusprosessi olisi myös hyvä kestävän kehityksen näkökulmasta.

Trazer a biblioteca no bolso: os serviços para dispositivos móveis nas bibliotecas académicas

Introdução – Os serviços de comunicação móvel para tablets, smartphones, e-book readers desenvolveram-se de forma extremamente rápida nos últimos anos assumindo-se como uma rede de aprendizagem privilegiada para os estudantes. Em 2012, 55% dos estudantes do ensino superior possuíam um smarthphone, 62% dispunham de um ipod e 21% tinham de um tablet. 67% usavam-nos em contexto académico. Objetivo – Apresentar de forma sucinta a resposta das bibliotecas de ensino superior ao crescimento da utilização dos dispositivos móveis e como é que os parceiros das bibliotecas, em especial os editores, estão a potenciar essa utilização. Métodos – A partir de uma seleção e análise de bibliografia sobre a temática realizou-se uma pesquisa na internet, nos sites de bibliotecas de ensino superior e nas páginas dos editores que permitisse aferir evidências. Resultados – Identificaram-se cinco serviços e 23 recursos. Discussão – Um primeiro serviço prende-se com a adaptação dos conteúdos dos websites das bibliotecas de forma a serem lidos por qualquer tipo de dispositivos. Outro serviço identificado foi a disponibilização do catálogo da biblioteca online tornando-o acessível aos dispositivos móveis, permitindo a pesquisa e a localização de informação, a reserva ou a renovação de documentos. Identificou-se o desenvolvimento de algumas coleções especificamente para os dispositivos móveis. Constatou-se a utilização de códigos QR para divulgar normas de funcionamento da biblioteca, recursos, o mapa, o contacto do serviço de referência e para geolocalização. Por fim verificou-se a utilização de SMS para informar os utilizadores sobre reservas, prazos de empréstimo, entre outras informações. O recurso mais comum na maioria dos sites analisados foi a disponibilização de uma versão do website para dispositivos móveis de que são exemplos a Cambridge Journals Online mobile, o EBSCOhost mobile, o SpringerLink, a OVIDToday, o UpToDate, a PubChase e a BrowZine. Com o objetivo de tornar os seus produtos acessíveis on-the go, oferecem inúmeras possibilidades, nomeadamente de pesquisa, de acesso a textos integrais, de elaboração de listas de interesse personalizadas, de leitura offline, entre outras que podemos encontrar na aplicação da EBSCOhost mobile, na JAMA Network, na OVIDToday, no portal de Periódicos CAPES ou na plataforma Ebrary da ProQuest. Em ferramentas como a UpToDate ou os aplicativos da Elsevier e da Micromedex é disponibilizada informação baseada na evidência e recomendações que podem ser aplicadas em consulta. Os gestores de referências bibliográficas como o Mendeley e o Zotero também acompanharam esta tendência e desenvolveram aplicações para dispositivos móveis. Para além disso funcionam de forma integrada com outras aplicações como a Browzine e a Pubchase. Conclusão – O recurso às tecnologias móveis é uma forma das bibliotecas manterem canais de comunicação com os utilizadores, mas embora existam muitas vantagens no uso das tecnologias móveis a implementação destes serviços implica um esforço financeiro e humano que nem todas as bibliotecas serão capazes de cumprir. Encontrar a forma de gerir este processo é o desafio que se impõe no futuro.

Dynamically managing sensed context data

This thesis reports on an investigation of the feasibility and usefulness of incorporating dynamic management facilities for managing sensed context data in a distributed contextaware mobile application. The investigation focuses on reducing the work required to integrate new sensed context streams in an existing context aware architecture. Current architectures require integration work for new streams and new contexts that are encountered. This means of operation is acceptable for current fixed architectures. However, as systems become more mobile the number of discoverable streams increases. Without the ability to discover and use these new streams the functionality of any given device will be limited to the streams that it knows how to decode. The integration of new streams requires that the sensed context data be understood by the current application. If the new source provides data of a type that an application currently requires then the new source should be connected to the application without any prior knowledge of the new source. If the type is similar and can be converted then this stream too should be appropriated by the application. Such applications are based on portable devices (phones, PDAs) for semi-autonomous services that use data from sensors connected to the devices, plus data exchanged with other such devices and remote servers. Such applications must handle input from a variety of sensors, refining the data locally and managing its communication from the device in volatile and unpredictable network conditions. The choice to focus on locally connected sensory input allows for the introduction of privacy and access controls. This local control can determine how the information is communicated to others. This investigation focuses on the evaluation of three approaches to sensor data management. The first system is characterised by its static management based on the pre-pended metadata. This was the reference system. Developed for a mobile system, the data was processed based on the attached metadata. The code that performed the processing was static. The second system was developed to move away from the static processing and introduce a greater freedom of handling for the data stream, this resulted in a heavy weight approach. The approach focused on pushing the processing of the data into a number of networked nodes rather than the monolithic design of the previous system. By creating a separate communication channel for the metadata it is possible to be more flexible with the amount and type of data transmitted. The final system pulled the benefits of the other systems together. By providing a small management class that would load a separate handler based on the incoming data, Dynamism was maximised whilst maintaining ease of code understanding. The three systems were then compared to highlight their ability to dynamically manage new sensed context. The evaluation took two approaches, the first is a quantitative analysis of the code to understand the complexity of the relative three systems. This was done by evaluating what changes to the system were involved for the new context. The second approach takes a qualitative view of the work required by the software engineer to reconfigure the systems to provide support for a new data stream. The evaluation highlights the various scenarios in which the three systems are most suited. There is always a trade-o↵ in the development of a system. The three approaches highlight this fact. The creation of a statically bound system can be quick to develop but may need to be completely re-written if the requirements move too far. Alternatively a highly dynamic system may be able to cope with new requirements but the developer time to create such a system may be greater than the creation of several simpler systems.

RELAÇÃO ENTRE O TEOR ABSOLUTO E RELATIVO DE CLOROFILA EM FOLHAS DE VIMEIRO

Os métodos tradicionais para a quantificação de clorofilas implicam na destruição das folhas, além de serem demorados e dispendiosos. Uma alternativa aos métodos destrutivos é o uso de medidores portáteis, dentre eles o SPAD 502, que mede a intensidade da cor verde das folhas, resultando no índice SPAD (Soil Plant Analysis Development). No entanto, o índice SPAD deve ser ajustado para o teor de clorofilas, conforme a espécie de interesse. O objetivo do presente trabalho foi calibrar o índice SPAD para a quantificação de clorofilas em folhas de plantas de vime ( Salix viminalis ). Folhas desta espécie, com tonalidade variando de verde-amarelada (clorótica) a verde-escura, foram avaliadas individualmente com o SPAD-502, seguido de quantificações destrutivas dos teores de clorofilas a, b e totais, expressos em unidade de área e massa fresca foliar. Houve elevado coeficiente de determinação (R²) entre os valores de índice SPAD e os teores de clorofila a, b e totais nas folhas, expressos em μg cm-2 de área foliar (R² de 0,86; 0,88 e 0,93, respectivamente) e entre os valores de índice SPAD e os teores de clorofilas b e totais, expressos em μg g-1 de massa fresca (R² 0,79 e 0,81, respectivamente). Os resultados mostram que existe viabilidade no uso do clorofilômetro SPAD 502, como alternativa aos métodos destrutivos, para a quantificação de clorofilas (em unidade de área; μg cm-2) em folhas de vimeiro.

MICROFLUIDIC ASSAY PERFORMANCE ENHANCEMENT USING POROUS VOLUMETRIC DETECTION ELEMENTS FOR IMPEDEMETRIC AND OPTICAL SENSING

Microfluidic technologies have great potential to help create automated, cost-effective, portable devices for rapid point of care (POC) diagnostics in diverse patient settings. Unfortunately commercialization is currently constrained by the materials, reagents, and instrumentation required and detection element performance. While most microfluidic studies utilize planar detection elements, this dissertation demonstrates the utility of porous volumetric detection elements to improve detection sensitivity and reduce assay times. Impedemetric immunoassays were performed utilizing silver enhanced gold nanoparticle immunoconjugates (AuIgGs) and porous polymer monolith or silica bead bed detection elements within a thermoplastic microchannel. For a direct assay with 10 µm spaced electrodes the detection limit was 0.13 fM AuIgG with a 3 log dynamic range. The same assay was performed with electrode spacing of 15, 40, and 100 µm with no significant difference between configurations. For a sandwich assay the detection limit was10 ng/mL with a 4 log dynamic range. While most impedemetric assays rely on expensive high resolution electrodes to enhance planar senor performance, this study demonstrates the employment of porous volumetric detection elements to achieve similar performance using lower resolution electrodes and shorter incubation times. Optical immunoassays were performed using porous volumetric capture elements perfused with refractive index matching solutions to limit light scattering and enhance signal. First, fluorescence signal enhancement was demonstrated with a porous polymer monolith within a silica capillary. Next, transmission enhancement of a direct assay was demonstrated by infusing aqueous sucrose solutions through silica bead beds with captured silver enhanced AuIgGs yielding a detection limit of 0.1 ng/mL and a 5 log dynamic range. Finally, ex situ functionalized porous silica monolith segments were integrated into thermoplastic channels for a reflectance based sandwich assay yielding a detection limit of 1 ng/mL and a 5 log dynamic range. The simple techniques for optical signal enhancement and ex situ element integration enable development of sensitive, multiplexed microfluidic sensors. Collectively the demonstrated experiments validate the use of porous volumetric detection elements to enhance impedemetric and optical microfluidic assays. The techniques rely on commercial reagents, materials compatible with manufacturing, and measurement instrumentation adaptable to POC diagnostics.

Security considerations for wireless carrier agonistic bio-monitoring systems

Advances in information and communications technology has led to a significant advances in noncontact portable devices capable of monitoring vital signals of patients. These wearable and implantable bio-monitoring systems allow collections of wearable sensors to be constructed as a Body Area Network (BAN) to record biological data for a subject. Such systems can be used to improve the quality of life and treatment outcomes for patients. One of the main uses for a bio-monitoring system is to record biological data values from a subject and provide them to a doctor or other medical professional. However, wearable bio-monitoring systems raise unique security considerations. In this paper, we discuss some of the security considerations that have arisen in our work around communications agnostic bio-monitoring, and how we have addressed these concerns. Furthermore, the issues related to the identifying and trusting sender and receiver entities are discussed.

Emotional experience with portable interactive devices

This paper reports on a six month longitudinal study exploring people’s personal and social emotional experience with Portable Interactive Devices (PIDs). The study is concerned with the experience design approach and based on the theoretical framework of Activity Theory. The focus is on emotional experiences and how artefacts mediate and potentially enhance this experience. The outcomes of the study identified interesting aspects of PID interaction. Findings revealed people interact with PIDs emotionally both at a personal and a social level, supporting previous studies. Further, the social level impacts significantly on the emotional experience attained. If negative social experiences exceeded negative personal experiences the emotional experience was constant over six months. If negative personal experiences surpassed negative social experiences the emotional experience was varied over six months. The findings are discussed in regards to their significance to the field of design, their implication for future PID design and future research directions.

Emotional experience with portable health devices

This paper reports on a six month longitudinal study exploring people’s personal and social emotional experience with health related portable interactive devices (PIDs). The focus is on emotions and how health PIDs mediate this experience in everyday contexts. The study reported here is an extension of a previous experiment conducted by the authors exploring media related PIDs [1]. The findings identified interesting aspects of health device interaction. Findings revealed people interact with health PIDs emotionally both at a personal and a social level. However, in contrast to media PIDs, participants reported significantly less social experiences than personal experiences. Nevertheless, the social level plays an important role such that negative social experiences had a significant influence on the perceived emotional experience over the course of six months. When no negative social experiences were reported the emotional experience over the course of six months became neutral. The findings are discussed in regards to their significance to the field of design, their implication for future health PID design and future research directions.

Categorising emotional experiences with portable interactive devices

This paper reports on a six month longitudinal study exploring people’s emotional experience with two categories of portable interactive devices (PIDs); media and health related PIDs. The focus is on emotions and how PIDs mediate these experiences in everyday contexts. Previous findings presented by the authors (Gomez 2009, 2010) revealed that people’s emotional experiences with PIDs over time are influenced by whether interactions were at a personal or social level. This paper presents four categories of activities identified and their relationship to emotional experiences with PIDs that have been developed through further analysis of the data. It concludes with a discussion of the findings and their implications to the field of Design on the design of future PIDs.

A framework to better understand emotional experiences with portable interactive devices : preliminary trial

Two longitudinal experiments were conducted exploring emotional experiences with PIDs over six months including media and medial Portable Interactive Devices (PIDs). Results identifying the impact of negative social and personal interactions on the overall emotional experience as well as different task categories (Features, Functional, Mediation and Auxiliary) and their corresponding emotional responses have previously been reported [2,3,4,5]. This paper builds on these findings and presents the Designing for Evolving Emotional Experience (DE3) framework promoting positive (and deals with negative) emotional experiences with PIDs including a set of principles to better understand emotional experiences. To validate the DE3 framework a preliminary trial was conducted with five practicing industrial designers. The trial required them to consider initial design concepts using the DE3 framework followed by a questionnaire asking about their use of the framework for concept development. The trial aimed to analyse the effectiveness, efficiency and usefulness of the framework in assisting in the development of initial concepts for PIDs taking into account emotional experiences. Common themes regarding the framework are outlined including the ease of use, the effectiveness in focusing on the personal and social contexts and positive ratings regarding its use. Overall the feedback from the preliminary trial was encouraging with responses suggesting that the framework was accessible, rated highly and most importantly permitted designers to consider emotional experiences during concept development. The paper concludes with a discussion regarding the future development of the DE3 framework and the potential implications to design theory and the design discipline.

Beyond Wearables : Experiences and Trends in Design of Portable Medical Devices

The use of Portable Medical Devices (PMDs) has become increasingly widespread over the last few years. A combination of factors; including advances in technology, the pressure to reduce public health costs and the desire to make health solutions accessible to a wider patient base are contributing to the growth in the PMD market. Design has a clear role to play in the current and future context of the PMD landscape. In this paper, we identify emerging trends in the design of PMDs; including changes in the form, purpose and mode of use, and explore how these trends are likely to fundamentally impact the nature of healthcare and the patient experience from an experience design perspective. We conclude by identifying a research opportunity for design within the healthcare and PMD context.