Smart-antenna techniques for energy-efficient wireless sensor networks used in bridge structural health monitoring

Abstract: It is well known that wireless sensor networks differ from other computing platforms in that 1- they typically require a minimal amount of computing power at the nodes; 2- it is often desirable for sensor nodes to have drastically low power consumption. The main benefit of the this work is a substantial network life before batteries need to be replaced or, alternatively, the capacity to function off of modest environmental energy sources (energy harvesting). In the context of Structural Health Monitoring (SHM), battery replacement is particularly problematic since nodes can be in difficult to access locations. Furthermore, any intervention on a bridge may disrupt normal bridge operation, e.g. traffic may need to be halted. In this regard, switchbeam smart antennas in combination with wireless sensor networks (WSNs) have shown great potential in reducing implementation and maintenance costs of SHM systems. The main goal of implementing switch-beam smart antennas in our application is to reduce power consumption, by focusing the radiated energy only where it is needed. SHM systems capture the dynamic vibration information of a bridge structure in real-time in order to assess the health of the structure and to predict failures. Current SHM systems are based on piezoelectric patch sensors. In addition, the collection of data from the plurality of sensors distributed over the span of the bridge is typically performed through an expensive and bulky set of shielded wires which routes the information to a data sink at one end of the structure. The installation, maintenance and operational costs of such systems are extremely high due to high power consumption and the need for periodic maintenance. Wireless sensor networks represent an attractive alternative, in terms of cost, ease of maintenance, and power consumption. However, network lifetime in terms of node battery life must be very long (ideally 5–10 years) given the cost and hassle of manual intervention. In this context, the focus of this project is to reduce the global power consumption of the SHM system by implementing switched-beam smart antennas jointly with an optimized MAC layer. In the first part of the thesis, a sensor network platform for bridge SHM incorporating switched-beam antennas is modelled and simulated. where the main consideration is the joint optimization of beamforming parameters, MAC layer, and energy consumption. The simulation model, built within the Omnet++ network simulation framework, incorporates the energy consumption profiles of actual selected components (microcontroller, radio interface chip). The energy consumption and packet delivery ratio (PDR) of the network with switched-beam antennas is compared with an equivalent network based on omnidirectional antennas. In the second part of the thesis, this system model is leveraged to examine two distinct but interrelated aspects: Gallium Arsenide (GaAs) based solar energy harvesting and switched-beam antenna strategies. The main consideration here is the joint optimization of solar energy harvesting and switchedbeam directional antennas, where an equivalent network based on omnidirectional antennas acts as a baseline reference for comparison purposes.Il est bien connu que les réseaux de capteurs sans fils diffèrent des autres plateformes informatiques étant donné 1- qu’ils requièrent typiquement une puissance de calcul minimale aux noeuds du réseau ; 2- qu’il est souvent désirable que les noeuds capteurs aient une consommation d’énergie dramatiquement faible. La principale retombée de ce travail réside en la durée de vie allongée du réseau avant que les piles ne doivent être remplacées ou, alternativement, la capacité de fonctionner indéfiniment à partir de modestes sources d’énergie ambiente (glânage d’énergie). Dans le contexte du contrôle de la santé structurale (CSS), le remplacement de piles est particulièrement problématique puisque les noeuds peuvent se trouver en des endroits difficiles d’accès. De plus, toute intervention sur un pont implique une perturbation de l’opération normale de la structure, par exemple un arrêt du traffic. Dans ce contexte, les antennes intelligentes à commutation de faisceau en combinaison avec les réseaux de capteurs sans fils ont démontré un grand potentiel pour réduire les coûts de réalisation et d’entretien de systèmes de CSS. L’objectif principal de l’intégration d’antennes à commutation de faisceau dans notre application réside dans la réduction de la consommation énergétique, réalisée en concentrant l’énergie radiée uniquement là où elle est nécessaire. Les systèmes de CSS capturent l’information dynamique de vibration d’une structure de pont en temps réel de manière à évaluer la santé de la structure et prédire les failles. Les systèmes courants de CSS sont basés sur des senseurs piézoélectriques planaires. De plus, la collecte de données à partir de la pluralité de senseurs distribués sur l’étendue du pont est typiquement effectuée par le biais d’un ensemble coûteux et encombrant de câbles blindés qui véhiculent l’information jusqu’à un point de collecte à une extremité de la structure. L’installation, l’entretien, et les coûts opérationnels de tels systèmes sont extrêmement élevés étant donné la consommation de puissance élevée et le besoin d’entretien régulier. Les réseaux de capteurs sans fils représentent une alternative attrayante, en termes de coût, facilité d’entretien et consommation énergétique. Toutefois, la vie de réseau en termes de la durée de vie des piles doit être très longue (idéalement de 5 à 10 ans) étant donné le coût et les problèmes liés à l’intervention manuelle. Dans ce contexte, ce projet se concentre sur la réduction de la consommation de puissance globale d’un système de CSS en y intégrant des antennes intelligentes à commutation de faisceau conjointement avec une couche d’accès au médium (couche MAC) optimisée. Dans la première partie de la thèse, une plateforme de réseau de capteurs sans fils pour le CSS d’un pont incorporant des antennes à commutation de faisceaux est modélisé et simulé, avec pour considération principale l’optimisation des paramètres de sélection de faisceau, de la couche MAC et de la consommation d’énergie. Le modèle de simulation, construit dans le logiciel de simulation de réseaux Omnet++, incorpore les profils de consommation d’énergie de composants réels sélectionnés (microcontrôleur, puce d’interface radio). La consommation d’énergie et le taux de livraison de paquets du réseau avec antennes à commutation de faisceau est comparé avec un réseau équivalent basé sur des antennes omnidirectionnelles. Dans la deuxième partie de la thèse, le modèle système proposé est mis à contribution pour examiner deux aspects distrincts mais interreliés : le glânage d’énergie à partir de cellules solaire à base d’arséniure de Gallium (GaAs) et les stratégies liées aux antennes à commutation de faisceau. La considération principale ici est l’optimisation conjointe du glânage d’énergie et des antennes à commutation de faisceau, en ayant pour base de comparaison un réseau équivalent à base d’antennes omnidirectionnelles

Job Satisfaction of Academic Staff: An Empirical Research Study on Selected Private Educational Institute at Dhaka City Corporation

The main aim of this research is to discover the factor that influences job satisfaction and the factors that can help improve it. Especially, demographic and environmental factors are given the most importance. The present research is designed with a clear view to find out the satisfaction level of academic staff of different education institute at Dhaka city corporation area. Therefore, the intent of this research is to examine the factors that influence job satisfaction of employees in educational sector. The research is quantified in its nature with a sample size of 100 employees from different education institute at Dhaka City Corporation area. The respective data are analyzed with descriptive statistics, correlation and multiple regressions. And the respective results are interpreted and the conclusion is drawn on the basis of the data analysis. Keywords: Job satisfaction, Academic staff of Educational Institute, Working Environment, Pay and Promotion, Fairness, Relationship with supervisor.

Mining, Resistance and Livelihood in Rural Bangladesh

In 2006, over fifty thousand people in the Phulbari Sub-District of Bangladesh mobilized against an open-pit coal mining-project that posed serious environmental and social risks. The state authorities negotiated with the protesters intensively over four days to reach an agreement. However, the state failed to fulfill the agreement, and the protest movement continued. The agrarian communities successfully halted the mining project for the last nine years. My research aims to understand how the protesters resisted this project. My objectives have been to explore the practices of a grassroots movement, attendant transformations in the sociopolitical landscape and role of the state in a place of uprising. In addition to the Bangalee villagers, two types of stakeholders have played crucial roles in the movement: the indigenous Santals and the migrants. I have used an ethnographic approach to establish an account of the protests as viewed by rural villagers. My hope is that this research has the potential to illuminate how natural resources are contested sources of livelihood and identity and how the quest for capitalist modernity through revenue-based economic growth may threaten destruction of ecosystems, human rights violations and social injustice

Creep and shrinkage behavior of fly ash based geopolymer concrete

The manuscript presented herein is based on the investigation of the short and long term properties of fly ash based geopolymer concrete (GPC) and their link to fly ash characteristics. Fly ash (FA) exhibits a significantly different particle morphology, which impacts the mechanical properties of the resulting GPC and typically contains impurities that fluctuate from one FA source to another. A key contribution of this research work is the capturing of the variability posed by the FA stockpile with a wide range of physical, chemical, and crystallographic characteristics as a source material to select the GPC mix design. In the case of prestressed GPC application, there are concerns on prestress loss caused by elastic shortening, shrinkage, and creep. Thus, the values of mechanical strength, ultimate shrinkage strain, and creep coefficient of the GPC have to be estimated reasonably and accurately at the design stage to avoid any loss of structural capacity the premature structural failure. The test study was conducted to evaluate the mechanical strength of fly ash based geopolymer concrete. Fly ash samples from different sources were tested to see the impact of the chemical and physical properties of the FA element on the fresh and hardened properties of the GPC. Samples from 50 different power plants were collected and analyzed to develop the regression equation. The empirical model was developed to predict the flexural strength from the compressive strength, the unit weight from the density of the FA, the elastic modulus from the unit weight, and compressive strength of the GPC and the compressive strength from the chemical and physical properties of the FA. A second set of 10 FA samples was selected randomly to validate the test results. It was observed that the prediction equation is accurate within 5 to 7 percent of the experimental values. The restrained shrinkage and free shrinkage test was conducted to observe the shrinkage of the GPC. Free shrinkage of the GPC plot was compared with the available empirical model for compatibility. In this study, an apparatus was designed to determine the creep of the GPC and an effective creep testing procedure was developed and documented. Experimental results obtained from this study were compared with the available empirical models. The results obtained from this study show that the compressive strength of the GPC can be presented with reasonable accuracy by analyzing the physical and chemical property of the FA. Also, it was found that the mechanical behavior of the GPC can be predicted with the equations given in the American Concrete Institute\u27s Building Code (ACI 318, 2008) with minor modifications. Experimental results obtained from this study were compared with the available empirical models. It has been observed that the free shrinkage strain and creep compliance prediction equations for the GPC are akin to those given in the SAKATA model and GL 2000 model

Interactions between a gall–inducing wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) and its host plant Acacia longifolia (Fabaceae)

Sallow Wattle (Acacia longifolia subsp. longifolia) is a native Australian shrub which is an invasive weed in some parts of Australia, and internationally. A gall-forming wasp (Trichilogaster acaciaelongifoliae), also native to Australia, causes abnormal growth of tissues (galls) in Sallow Wattle. This wasp is used outside of Australia to control invasive populations of this plant species. However, in Australia, the wasp is not effective in managing the spread of Sallow Wattle. This study investigates various aspects of the relationship between the wasp and its host plant in Australian ecosystems to better understand the physiological and ecological processes involved. The study shows that this wasp is host-specific on Sallow Wattle. The feeding action of the larval wasps increase secondary plant compounds in gall tissue, which may assist the plant to defend itself chemically against other insects and microorganisms. The growth of the galls redirects resources which are otherwise used by the plant for growth and reproduction. A second insect species was found within the galls and was identified as Megastigmus sp. This second species is likely to be a parasitoid, killing the larvae of the gall-former and occupying the gall. The presence of Megastigmus sp. in Australian ecosystems may be a key factor affecting the ability of T. acaciaelongifoliae to control Sallow Wattle in its native range. The structure of galls formed by each type of gall-inducing insects is unique and the process of gall induction also varies across species. The present study has specifically examined the initiation and development of galls formed by T. acaciaelongifoliae on A. l. longifolia. Unlike other hymenopteran groups, which induce galls during oviposition, T. acaciaelongifoliae appears to form galls on A. l. longifolia via the larval feeding process. Three major stages of gall development were identified and described: induction of gall, growth and maturation of gall, and shrinking and desiccation of gall. These findings have significantly extended our current knowledge of gall induction and development by the hymenopteran group of insects. Total antioxidant capacity (TAC), total phenol (TP), and total anthocyanin (TA) were measured in galls formed by T. acaciaelongifoliae at different growth stages of galls and in other plant tissue samples of A. l. longifolia to understand the effect of gall formation on plant phytochemistry. The results indicated differences in the amounts of phytochemicals in tissue samples from galls of different growth stages of galls and between gall tissue samples and other plant samples of A. l. longifolia. The highest amount of total antioxidant capacity, total phenols and total anthocyanin were recorded in samples of early stages galls, whereas the minimum amounts of phytochemicals were in stems of A. l. longifolia. Amounts of antioxidant capacity, phenols and anthocyanin gradually declined as galls developed and larvae became less active in their feeding activity prior to pupation. It is assumed that the active feeding action of the larvae results in increased amounts of these chemicals in the early growth stages of the galls. The effect of galls formed by the wasp, T. acaciaelongifoliae on the growth and reproduction of A. l. longifolia was investigated in the native home range of both species, where the plant is invasive. Differences in the average number of phyllodes per sub-branch were found between galled and ungalled plants. Galls were also shown to affect the growth rate of branches. The number of galls correlated positively with twig mortality; and negatively with the number of seedpods per sub-branch. While galls formed by T. acaciaelongifoliae have impacts on the growth and reproduction of A. l. longifolia plants, the plant continues to invade Australian ecosystems. An experiment was conducted to investigate the host plant preference of T. acaciaelongifoliae. Ten different native host plant species (co-occurring with A. l. longifolia in the study locations) were tested in two set of experiments; a ‘free choice test’ and ‘no choice test’. The results showed that T. acaciaelongifoliae is highly host-specific on A. l. longifolia plants. Thus, it was concluded that the presence of other plant species does not explain the continued invasiveness of A. l. longifolia in Australia. A second insect species was found in the galls developed by T. acaciaelongifoliae on A. l. longifolia. The insect species has been identified as another hymenopteran from the genus Megastigmus. Since no T. acaciaelongifoliae emerged from the galls occupied by Megastigmus sp, it is proposed that Megastigmus sp. may feed upon T. acaciaelongifoliae larvae and kill them inside the galls. This might be a key factor affecting the performance of the wasp, T. acaciaelongifoliae in controlling A. l. longifolia in its native distribution. Parasitism rates of Megastigmus sp. should be investigated in future experiments.Doctor of Philosoph

Perpetrator Workplace Aggression: Development of a Perpetrator Aggression Scale (PAS)

Perpetrator workplace aggression has always been considered as a uni-dimensional construct from the uni-dimensional perspective. The most popular and widely used scale, interpersonal deviance scale (IDS; Bennett & Robinson, 2000), to assess perpetrator workplace aggression has only seven items (i.e., seven content areas), which lacks a high level of content-related and construct-related validity. Recently, researchers have suggested that perpetrator workplace aggression may be a construct with a general factor at the top (Sackett & DeVore, 2001); however, this general factor can be less clear for a more complex model (Marcus et al., 2016). Using three samples (N = 271, 337, & 264), this research found that perpetrator workplace aggression was also a uni-dimensional construct from the multi-dimensional perspective, the general factor was very clear for a complex model, and developed a new scale with a higher level of content-related (i.e., 24 different content areas of perpetrator workplace aggression) and construct-related validity (by developing a large nomological network). In addition to a higher level of content-related and construct-related validity, the new scale showed a higher level of internal consistency and substantive validity. Hence, I recommend that researchers and practitioners use this new scale in future when assessing perpetrator workplace aggression