200 resultados para Active and Reactive Power


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Background & Aims: Access to sufficient amounts of safe and culturally-acceptable foods is a fundamental human right. Food security exists when all people, at all times, have physical, social, and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life. Food insecurity therefore occurs when the availability or access to sufficient amounts of nutritionally-adequate, culturally-appropriate and safe foods, or, the ability to acquire such foods in socially-acceptable ways, is limited. Food insecurity may result in significant adverse effects for the individual and these outcomes may vary between adults and children. Among adults, food insecurity may be associated with overweight or obesity, poorer self-rated general health, depression, increased health-care utilisation and dietary intakes less consistent with national recommendations. Among children, food insecurity may result in poorer self or parent-reported general health, behavioural problems, lower levels of academic achievement and poor social outcomes. The majority of research investigating the potential correlates of food insecurity has been undertaken in the United States (US), where regular national screening for food insecurity is undertaken using a comprehensive multi-item measurement. In Australia, screening for food insecurity takes place on a three yearly basis via the use of a crude, single-item included in the National Health Survey (NHS). This measure has been shown to underestimate the prevalence of food insecurity by 5%. From 1995 – 2004, the prevalence of food insecurity among the Australian population remained stable at 5%. Due to the perceived low prevalence of this issue, screening for food insecurity was not undertaken in the most recent NHS. Furthermore, there are few Australian studies investigating the potential determinants of food insecurity and none investigating potential outcomes among adults and children. This study aimed to examine these issues by a) investigating the prevalence of food insecurity among households residing in disadvantaged urban areas and comparing prevalence rates estimated by the more comprehensive 18-item and 6-item United States Department of Agriculture (USDA) Food Security Survey Module (FSSM) to those estimated by the current single-item measure used for surveillance in Australia and b) investigating the potential determinants and outcomes of food insecurity, Methods: A comprehensive literature review was undertaken to investigate the potential determinants and consequences of food insecurity among developed countries. This was followed by a cross-sectional study in which 1000 households from the most disadvantaged 5% of Brisbane areas were sampled and data collected via mail-based survey (final response rate = 53%, n = 505). Data were collected for food security status, sociodemographic characteristics (household income, education, age, gender, employment status, housing tenure and living arrangements), fruit and vegetable intakes, meat and take-away consumption, presence of depressive symptoms, presence of chronic disease and body mass index (BMI) among adults. Among children, data pertaining to BMI, parent-reported general health, days away from school and activities and behavioural problems were collected. Rasch analysis was used to investigate the psychometric properties of the 18-, 10- and 6-item adaptations of the USDA-FSSM, and McNemar's test was used to investigate the difference in the prevalence of food insecurity as measured by these three adaptations compared to the current single-item measure used in Australia. Chi square and logistic regression were used to investigate the differences in dietary and health outcomes among adults and health and behavioural outcomes among children. Results were adjusted for equivalised household income and, where necessary, for indigenous status, education and family type. Results: Overall, 25% of households in these urbanised-disadvantaged areas reported experiencing food insecurity; this increased to 34% when only households with children were analysed. The current reliance on a single-item measure to screen for food insecurity may underestimate the true burden among the Australian population, as this measure was shown to significantly underestimate the prevalence of food insecurity by five percentage points. Internationally, major potential determinants of food insecurity included poverty and indicators of poverty, such as low-income, unemployment and lower levels of education. Ethnicity, age, transportation and cooking and financial skills were also found to be potential determinants of food insecurity. Among Australian adults in disadvantaged urban areas, food insecurity was associated with a three-fold increase in experiencing poorer self-rated general health and a two-to-five-fold increase in the risk of depression. Furthermore, adults from food insecure households were twoto- three times more likely to have seen a general practitioner and/or been admitted to hospital within the previous six months, compared to their food secure counterparts. Weight status and intakes of fruits, vegetables and meat were not associated with food insecurity. Among Australian households with children, those in the lowest tertile were over 16 times more likely to experience food insecurity compared to those in the highest tertile for income. After adjustment for equivalised household income, children from food insecure households were three times more likely to have missed days away from school or other activities. Furthermore, children from food insecure households displayed a two-fold increase in atypical emotions and behavioural difficulties. Conclusions: Food insecurity is an important public health issue and may contribute to the burden on the health care system through its associations with depression and increased health care utilisation among adults and behavioural and emotional problems among children. Current efforts to monitor food insecurity in Australia do not occur frequently and use a tool that may underestimate the prevalence of food insecurity. Efforts should be made to improve the regularity of screening for food insecurity via the use of a more accurate screening measure. Most of the current strategies that aim to alleviate food insecurity do not sufficiently address the issue of insufficient financial resources for acquiring food; a factor which is an important determinant of food insecurity. Programs to address this issue should be developed in collaboration with groups at higher risk of developing food insecurity and should incorporate strategies to address the issue of low income as a barrier to food acquisition.

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The article examines the evidence of endemic financial crime in the global financial crisis (GFC), the legal impunity surrounding these crimes and the popular revolt against these abuses in the financial, political and legal systems. This is set against a consideration of the development since the 1970s of a conservative politics championing de-regulation, unfettered markets, welfare cuts and harsh law and order policies. On the one hand, this led to massively increased inequality and concentrations of wealth and political power in the hands of the super-rich, effectively placing them above the law, as the GFC revealed. On the other, a greatly enlarged, more punitive criminal justice system was directed at poor and minority communities. Explanations in terms of the rise of penal populism are helpful in explaining these developments, but it is argued they adopt a limited and reductionist view of populism, failing to see the prospects for a progressive populist politics to re-direct political attention to issues of inequality and corporate and white collar criminality.

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This paper addresses challenges part of the shift of paradigm taking place in the way we produce, transmit and use power related to what is known as smart grids. The aim of this paper is to explore present initiatives to establish smart grids as a sustainable and reliable power supply system. We argue that smart grids are not isolated to abstract conceptual models alone. We suggest that establishing sustainable and reliable smart grids depend on series of contributions including modeling and simulation projects, technological infrastructure pilots, systemic methods and training, and not least how these and other elements must interact to add reality to the conceptual models. We present and discuss three initiatives that illuminate smart grids from three very different positions. First, the new power grid simulator project in the electrical engineering PhD program at Queensland University of Technology (QUT). Second, the new smart grids infrastructure pilot run by the Norwegian Centers of Expertise Smart Energy Markets (NCE SMART). And third, the new systemic Master program on next generation energy technology at østfold University College (Hiø). These initiatives represent future threads in a mesh embedding smart grids in models, technology, infrastructure, education, skills and people.

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This study explored the creation, dissemination and exchange of electronic word of mouth, in the form of product reviews and ratings of digital technology products. Based on 43 in-depth interviews and 500 responses to an online survey, it reveals a new communication model describing consumers' info-active and info-passive information search styles. The study delivers an in-depth understanding of consumers' attitudes towards current advertising tools and user-generated content, and points to new marketing techniques emerging in the online environment.

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ZnO is a promising photoanode material for dye-sensitized solar cells (DSCs) due to its high bulk electron mobility and because different geometrical structures can easily be tailored. Although various strategies have been taken to improve ZnO-based DSC efficiencies, their performances are still far lower than TiO2 counterparts, mainly because low conductivity Zn2+–dye complexes form on the ZnO surfaces. Here, cone-shaped ZnO nanocrystals with exposed reactive O-terminated {101̅1} facets were synthesized and applied in DSC devices. The devices were compared with DSCs made from more commonly used rod-shaped ZnO nanocrystals where {101̅0} facets are predominantly exposed. When cone-shaped ZnO nanocrystals were used, DSCs sensitized with C218, N719, and D205 dyes universally displayed better power conversion efficiency, with the highest photoconversion efficiency of 4.36% observed with the C218 dye. First-principles calculations indicated that the enhanced DSCs performance with ZnO nanocone photoanodes could be attributed to the strength of binding between the dye molecules and reactive O-terminated {101̅1} ZnO facets and that more effective use of dye molecules occurred due to a significantly less dye aggregation on these ZnO surfaces compared to other ZnO facets.

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An Artificial Neural Network (ANN) is a computational modeling tool which has found extensive acceptance in many disciplines for modeling complex real world problems. An ANN can model problems through learning by example, rather than by fully understanding the detailed characteristics and physics of the system. In the present study, the accuracy and predictive power of an ANN was evaluated in predicting kinetic viscosity of biodiesels over a wide range of temperatures typically encountered in diesel engine operation. In this model, temperature and chemical composition of biodiesel were used as input variables. In order to obtain the necessary data for model development, the chemical composition and temperature dependent fuel properties of ten different types of biodiesels were measured experimentally using laboratory standard testing equipments following internationally recognized testing procedures. The Neural Networks Toolbox of MatLab R2012a software was used to train, validate and simulate the ANN model on a personal computer. The network architecture was optimised following a trial and error method to obtain the best prediction of the kinematic viscosity. The predictive performance of the model was determined by calculating the absolute fraction of variance (R2), root mean squared (RMS) and maximum average error percentage (MAEP) between predicted and experimental results. This study found that ANN is highly accurate in predicting the viscosity of biodiesel and demonstrates the ability of the ANN model to find a meaningful relationship between biodiesel chemical composition and fuel properties at different temperature levels. Therefore the model developed in this study can be a useful tool in accurately predict biodiesel fuel properties instead of undertaking costly and time consuming experimental tests.

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Rationale: Anabolic steroids are drugs of abuse. However, the potential for addiction remains unclear. Testosterone induces conditioned place preference in rats and oral self-administration in hamsters. Objectives: To determine if male rats and hamsters consume testosterone by intravenous (IV) or intracerebroventricular (ICV) self- administration. Methods: With each nose-poke in the active hole during daily 4-h tests in an operant condi- tioning chamber, gonad-intact adult rats and hamsters received 50 mg testosterone in an aqueous solution of b-cyclodextrin via jugular cannula. The inactive nose- poke hole served as a control. Additional hamsters received vehicle infusions. Results: Rats (n=7) expressed a significant preference for the active nose-poke hole (10.0€2.8 responses/4 h) over the inactive hole (4.7€1.2 responses/4 h). Similarly, during 16 days of testosterone self-administration IV, hamsters (n=9) averaged 11.7€2.9 responses/4 h and 6.3€1.1 responses/4 h in the active and inactive nose-poke holes, respectively. By contrast, vehicle controls (n=8) failed to develop a preference for the active nose-poke hole (6.5€0.5 and 6.4€0.3 responses/4 h). Hamsters (n=8) also self-administered 1 mg testosterone ICV (active hole:39.8€6.0 nose-pokes/ 4 h; inactive hole: 22.6€7.1 nose-pokes/4 h). When testosterone was replaced with vehicle, nose-poking in the active hole declined from 31.1€7.6 to 11.9€3.2 responses/ 4 h within 6 days. Likewise, reversing active and inactive holes increased nose-poking in the previously inactive hole from 9.1€1.9 to 25.6€5.4 responses/4 h. However, reducing the testosterone dose from 1 mg to 0.2 mg per 1 ml injection did not change nose-poking. Conclu- sions: Compared with other drugs of abuse, testosterone reinforcement is modest. Nonetheless, these data support the hypothesis that testosterone is reinforcing.

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Governments are challenged by the need to ensure that ageing populations stay active and engaged as they age. Therefore, it is critical to investigate the role of mobility in older people's engagement in out-of-home activities, and to identify the experiences they have within their communities. This research investigates the use of transportation by older people and its implications for their out-of-home activities within suburban environments. The qualitative, mixed-method approach employs data collection methods which include a daily travel diary (including a questionnaire), Global Positioning System (GPS) tracking and semi-structured interviews with older people living in suburban environments in Brisbane, Australia. Results show that older people are mobile throughout the city, and their car provides them with that opportunity to access desired destinations. This ability to drive allows older people to live independently and to assist others who do not drive, particularly where transport alternatives are not as accessible. The ability to transport goods and other people is a significant advantage of the private car over other transport options. People with no access to private transportation who live in low-density environments are disadvantaged when it comes to participation within the community. Further research is needed to better understand the relationship between transportation and participation within the community environment, to assist policy makers and city and transportation planners to develop strategies for age-friendly environments within the community.

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Voltage drop at network peak hours is a significant power quality problem in Low Voltage (LV) distribution feeders. Recently, voltage rise due to high penetration of Photovoltaic cells (PVs) has been creating a new power quality problem during noon periods. In this paper, a voltage control strategy is proposed for the household installed PVs to regulate the voltage along the LV feeder. For this purpose, each PV is controlled to exchange reactive power with the grid. A droop control method is utilized to coordinate the reactive power exchange of each PV. The proposed method is a decentralized local voltage support since it is based on only local measurements and does not require any communication with other PVs. The required converter and filter structure and control algorithms are proposed to ensure the dynamic performance of the system. The study focuses on 3-phase PVs. The network is studied at network peak and off-peak periods, separately. The efficacy of the proposed voltage support concept is verified through numerical and dynamic analyses with MATLAB and PSCAD/EMTDC.

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The University of Queensland (UQ) has extensive laboratory facilities associated with each course in the undergraduate electrical engineering program. The laboratories include machines and drives, power systems simulation, power electronics and intelligent equipment diagnostics. A number of postgraduate coursework programs are available at UQ and the courses associated with these programs also use laboratories. The machine laboratory is currently being renovated with i-lab style web based experimental facilities, which could be remotely accessed. Senior level courses use independent projects using laboratory facilities and this is found to be very useful to improve students' learning skill. Laboratory experiments are always an integral part of a course. Most of the experiments are conducted in a group of 2-3 students and thesis projects in BE and major projects in ME are always individual works. Assessment is done in-class for the performance and also for the report and analysis.

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In this chapter, we discuss four related areas of cryptology, namely, authentication, hashing, message authentication codes (MACs), and digital signatures. These topics represent active and growing research topics in cryptology. Space limitations allow us to concentrate only on the essential aspects of each topic. The bibliography is intended to supplement our survey. We have selected those items which providean overview of the current state of knowledge in the above areas. Authentication deals with the problem of providing assurance to a receiver that a communicated message originates from a particular transmitter, and that the received message has the same content as the transmitted message. A typical authentication scenario occurs in computer networks, where the identity of two communicating entities is established by means of authentication. Hashing is concerned with the problem of providing a relatively short digest–fingerprint of a much longer message or electronic document. A hashing function must satisfy (at least) the critical requirement that the fingerprints of two distinct messages are distinct. Hashing functions have numerous applications in cryptology. They are often used as primitives to construct other cryptographic functions. MACs are symmetric key primitives that provide message integrity against active spoofing by appending a cryptographic checksum to a message that is verifiable only by the intended recipient of the message. Message authentication is one of the most important ways of ensuring the integrity of information that is transferred by electronic means. Digital signatures provide electronic equivalents of handwritten signatures. They preserve the essential features of handwritten signatures and can be used to sign electronic documents. Digital signatures can potentially be used in legal contexts.

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Background Physical activity (PA) patterns are likely to change in young adulthood in line with changes in lifestyle that occur in the transition from adolescence to adulthood. The aim of this study was to ascertain whether key life events experienced by young women in their early twenties are associated with increasing levels of inactivity. Methods This was a 4-year follow-up of 7281 participants (aged 18 to 23 years at baseline) in the Australian Longitudinal Study of Women’s Health, with self-reported measures of PA, life events, body mass index (BMI), and sociodemographic variables. Results The cross-sectional data indicated no change in PA between baseline (57% “active”) and follow-up (56% “active”). However, for almost 40% of the sample, PA category changed between baseline and follow-up, with approximately 20% of the women changing from being “active” to “inactive,” and another 20% changing from being “inactive” to “active.” After adjustment for age, other sociodemographic variables, BMI, and PA at baseline, women who reported getting married, having a first or subsequent child, or beginning paid work were more likely to be inactive at follow-up than those who did not report these events. Conclusions The results suggest that life events such as getting married, having children, and starting work are associated with decreased levels of PA in young adult women. Strategies are needed to promote maintenance of activity at the time when most women experience these key life-stage transitions.

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OBJECTIVES This study examined the associations between physical activity and other health behaviors in a representative sample of US adolescents. METHODS In the 1990 Youth Risk Behavior Survey, 11631 high school students provided information on physical activity; diet; substance use; and other negative health behaviors. Logistic regression analyses examined associations between physical activity and other health behaviors in a subset of 2652 high-active and 1641 low-active students. RESULTS Low activity was associated with cigarette smoking, marijuana use, lower fruit and vegetable consumption, greater television watching, failure to wear a seat belt, and low perception of academic performance. For consumption of fruit, television watching, and alcohol consumption, significant interactions were found with race/ethnicity or sex, suggesting that sociocultural factors may affect the relationships between physical activity and some health behaviors. CONCLUSIONS Low physical activity was associated with several other negative health behaviors in teenagers. Future studies should examine whether interventions for increasing physical activity in youth can be effective in reducing negative health behaviors.

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In this paper, a wind energy conversion system interfaced to the grid using a dual inverter is proposed. One of the two inverters in the dual inverter is connected to the rectified output of the wind generator while the other is directly connected to a battery energy storage system (BESS). This approach eliminates the need for an additional dc-dc converter and thus reduces power losses, cost, and complexity. The main issue with this scheme is uncorrelated dynamic changes in dc-link voltages that results in unevenly distributed space vectors. A detailed analysis on the effects of these variations is presented in this paper. Furthermore, a modified modulation technique is proposed to produce undistorted currents even in the presence of unevenly distributed and dynamically changing space vectors. An analysis on the battery charging/discharging process and maximum power point tracking of the wind turbine generator is also presented. Simulation and experimental results are presented to verify the efficacy of the proposed modulation technique and battery charging/discharging process.

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Modulation and control of a cascade multilevel static synchronous compensator (STATCOM) configuration to improve the quality of voltage generated by wind power systems are presented. The proposed STATCOM configuration needs only four dc-link capacitors and 24 switches to synthesise nine-level operation. In addition to that, switching losses are further reduced by splitting the voltage source inverter of the STATCOM into two units called the `bulk inverter` and the `conditioning inverter`. The high-power bulk inverter is operated at low frequency whereas the low-power conditioning inverter is operated at high frequency to suppress harmonics produced by the bulk inverter. Fluctuations at the point of common coupling voltage, caused by sudden wind changes, are suppressed by controlling reactive power of the STATCOM. Simulation and experimental results are presented to verify the efficacy of the proposed modulation and control techniques used in the STATCOM.