978 resultados para Buck-boost


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The paper investigates the dynamics and volution of issues on the agenda of Baltic environmental non-governmental organisations (NGOs) since the collapse of communism. The past research on Baltic environment activism suggests that these enjoy high visibility because they tapped the core societal views of natural environment as a crucial asset of a nation. As we demonstrate in this paper, the changes in agendas of Baltic environmental non-governmental organisations (ENGOs) make clear that the rhetorical toolbox of ‘national environment’ is often used to mainly achieve greater financial gains for individual members, rather than for society at large. We illustrate how the dearth of economic opportunities for domestic public has impacted perceptions of ‘nature’ advocated by the environmental activists, focussing specifically on national perceptions of ownership and the resulting actions appropriating ‘nature’ as a source for economic development, only tangentially attaining environmental outcomes on the way. The vision that the ‘environment’ is an economic resource allowed ENGO activists to cooperate with the domestic policymaking, while tapping international networks and donors for funding. Throughout the past decades they worked to secure their own and their members' particularistic economic interests and, as we demonstrate, remained disengaged from the political process and failed to develop broader reproach with publics.

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Background: Many school-based interventions are being delivered in the absence of evidence of effectiveness (Snowling & Hulme, 2011, Br. J. Educ. Psychol., 81, 1).Aim: This study sought to address this oversight by evaluating the effectiveness of the commonly used the Lexia Reading Core5 intervention, with 4- to 6-year-old pupils in Northern Ireland.Sample: A total of 126 primary school pupils in year 1 and year 2 were screened on the Phonological Assessment Battery 2nd Edition (PhAB-2). Children were recruited from the equivalent year groups to Reception and Year 1 in England and Wales, and Pre-kindergarten and Kindergarten in North America.
Methods: A total of 98 below-average pupils were randomized (T0) to either an 8-week block (inline image = 647.51 min, SD = 158.21) of daily access to Lexia Reading Core5 (n = 49) or a waiting-list control group (n = 49). Assessment of phonological skills was completed at post-intervention (T1) and at 2-month follow-up (T2) for the intervention group only.
Results: Analysis of covariance which controlled for baseline scores found that the Lexia Reading Core5 intervention group made significantly greater gains in blending, F(1, 95) = 6.50, p = .012, partial η2 = .064 (small effect size) and non-word reading, F(1, 95) = 7.20, p = .009, partial η2 = .070 (small effect size). Analysis of the 2-month follow-up of the intervention group found that all group treatment gains were maintained. However, improvements were not uniform among the intervention group with 35% failing to make progress despite access to support. Post-hoc analysis revealed that higher T0 phonological working memory scores predicted improvements made in phonological skills.
Conclusions: An early-intervention, computer-based literacy program can be effective in boosting the phonological skills of 4- to 6-year-olds, particularly if these literacy difficulties are not linked to phonological working memory deficits.

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In spite of impressive rates of economic growth, the quality of the labor force’s human capital is considered a major challenge for sustaining medium term economic growth in Peru. This note reviews the skills of the Peruvian labor force, and the status of the continuous education and training system. Based on such an assessment and on learnings from international best practices, it proposes a system of continuous education and training that draws from international best practices, but that addresses local capacity and institutional issues.

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This paper presents the development of a boost converter with the possibility of higher gain than the conventional boost converter for applications under similar conditions and increased power. Presents the main concepts involving the boost converter and two variations: the boost converter of three levels and the boost converter interspersed with two converter cells. The breakdown mounting positions, the operating steps, the addressing and the main strengths of each converter in order to check for possible uses in the construction of a prototype joining their main advantages. In the presentation of this converter addresses the operating steps, the equation governing its design, the simulations obtained through software (PSIM), a comparison between the boost converter models studied and the experimental results.

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This paper presents how new paradigms and methodologies for software development are changing rapidly in the last two years. In the current scenario where we live on, occurs a transition that, although slight, reflects the rapid manner in which the software production paradigms are reinvented due to the change of display devices and interaction with the end user. Studies indicate that in 2013 was the turn out of the internet access domain for mobile devices over the traditional desktop device, which is currently at around 60% mobile, against 40% desktop. This field will tend to grow in the coming years and it is expected that the use of internet for a desktop terminal tends to be less each day (comScore). In this context, the software industry has been re-invented and updated with respect to technologies that promote software and mobile applications, building products capable of responding to the user market. The development of software products, such as applications, must be put into production for different user environments, such as Web, iOS and Android in a way to enhance efficiency, optimization and productivity in the software development cycle (Langer, Arthur M.).

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Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of the Leptospira genus. Vaccination with bacterins has severe limitations. Here, we evaluated the N-terminal region of the leptospiral immunoglobulin-like B protein (LigBrep) as a vaccine candidate against leptospirosis using immunisation strategies based on DNA primeprotein boost, DNA vaccine, and subunit vaccine. Upon challenge with a virulent strain of Leptospira interrogans , the prime-boost and DNA vaccine approaches induced significant protection in hamsters, as well as a specific IgG antibody response and sterilising immunity. Although vaccination with recombinant fragment of LigBrep also produced a strong antibody response, it was not immunoprotective. These results highlight the potential of LigBrep as a candidate antigen for an effective vaccine against leptospirosis and emphasise the use of the DNA prime-protein boost as an important strategy for vaccine development.

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In modern power electronic systems, DC-DC converter is one of the main controlled power sources for driving DC systems. But the inherent nonlinear and time-varying characteristics often result in some difficulties mostly related to the control issue. This paper presents a robust nonlinear adaptive controller design with a recursive methodology based on the pulse width modulation (PWM) to drive a DC-DC buck converter. The proposed controller is designed based on the dynamical model of the buck converter where all parameters within the model are assumed as unknown. These unknown parameters are estimated through the adaptation laws and the stability of these laws are ensured by formulating suitable control Lyapunov functions (CLFs) at different stages. The proposed control scheme also provides robustness against external disturbances as these disturbances are considered within the model. One of the main features of the proposed scheme is that it overcomes the over-parameterization problems of unknown parameters which usually appear in some conventional adaptive methods. Finally, the effectiveness of the proposed control scheme is verified through the simulation results and compared to that of an existing adaptive backstepping controller. Simulation results clearly indicate the performance improvement in terms of a faster output voltage tracking response.

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Renewable or sustainable energy (SE) sources have attracted the attention of many countries because the power generated is environmentally friendly, and the sources are not subject to the instability of price and availability. This dissertation presents new trends in the DC-AC converters (inverters) used in renewable energy sources, particularly for photovoltaic (PV) energy systems. A review of the existing technologies is performed for both single-phase and three-phase systems, and the pros and cons of the best candidates are investigated. In many modern energy conversion systems, a DC voltage, which is provided from a SE source or energy storage device, must be boosted and converted to an AC voltage with a fixed amplitude and frequency. A novel switching pattern based on the concept of the conventional space-vector pulse-width-modulated (SVPWM) technique is developed for single-stage, boost-inverters using the topology of current source inverters (CSI). The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the DC input voltage. It is demonstrated that the CSI topology in conjunction with the developed switching pattern is capable of providing the required residential AC voltage from a low DC voltage of one PV panel at its rated power for both linear and nonlinear loads. In a micro-grid, the active and reactive power control and consequently voltage regulation is one of the main requirements. Therefore, the capability of the single-stage boost-inverter in controlling the active power and providing the reactive power is investigated. It is demonstrated that the injected active and reactive power can be independently controlled through two modulation indices introduced in the proposed switching algorithm. The system is capable of injecting a desirable level of reactive power, while the maximum power point tracking (MPPT) dictates the desirable active power. The developed switching pattern is experimentally verified through a laboratory scaled three-phase 200W boost-inverter for both grid-connected and stand-alone cases and the results are presented.

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The Melbourne Decision Making Questionnaire (Mann, Burnett, Radford, & Ford, 1997) measures selfreported decision-making coping patterns. The questionnaire was administered to samples of University students in the US (N = 475), Australia (N = 262), New Zealand (N = 260), Japan (N = 359), Hong Kong (N = 281), and Taiwan (N = 414). As predicted, students from the three Western, individualistic cultures (US, Australia, and New Zealand) were more con® dent of their decision-making ability than students from the three East Asian, group-oriented cultures (Japan, Hong Kong, Taiwan). No cross-cultural differences were found in scores on decision vigilance (a careful decision-making style). However, compared with Western students, the Asian students tended to score higher on buck-passing and procrastination (avoidant styles of decision making) as well as hypervigilance (a panicky style of decision making). Japanese students scored lowest on decision self-esteem and highest on procrastination and hypervigilance. It was argued that the con¯ ict model and its attendant coping patterns is relevant for describing and comparing decision making in both Western and Asian cultures.

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A study was conducted to examine the factorial validity of the Flinders Decision Making Questionnaire (Mann, 1982), a 31-item self-report inventory designed to measure tendencies to use three major coping patterns identified in the conflict theory of decision making (Janis and Mann, 1977): vigilance, hypervigilance, and defensive avoidance (procrastination, buck-passing, and rationalization). A sample of 2051 university students, comprising samples from Australia (n=262), New Zealand (n=260), the USA (n=475), Japan (n=359), Hong Kong (n=281) and Taiwan (n=414) was administered the DMQ. Factorial validity of the instrument was tested by confirmatory factor analysis with LISREL. Five different substantive models, representing different structural relationships between the decision-coping patterns had unsatisfactory fit to the data and could not be validated. A shortened instrument, containing 22 items, yielded a revised model comprising four identifiable factors-vigilance, hypervigilance, buck-passing, and procrastination. The revised model had adequate fit with data for each country sample and for the total sample, and was confirmed. It is recommended that the 22-item instrument, named the Melbourne DMQ, replace the Flinders DMQ for measurement of decision-coping patterns.

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Objective: The aim of this paper was to examine self-efficacy and perceived appropriateness among rural general practitioners (GPs) in regards to screening and intervention for physical, lifestyle and mental health issues. ----- Method: Fifty GPs from 25 practices in eight rural Queensland towns completed a written survey designed for the study. ----- Results: General practitioners rated opportunistic screening or assessment for smoking and for detection of relapse of mental disorders as the most appropriate, with even cardiovascular and diabetes risk falling behind these. Self-efficacy was highest for medical disorders for smoking assessment. It was significantly lower for alcohol, mental health issues, and addressing risks of physical disorder in people with mental disorders. ----- Conclusions: High appropriateness ratings suggest that current strategies to boost self-efficacy of GPs in addressing mental health issues are timely.

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In photovoltaic, fuel cells and storage batteries, the low output DC voltage should be boosted. Therefore, a step-up converter is necessary to boost the low DC voltage for the DC link voltage of the inverter. The main contribution of this chapter is to electrical energy conversion in renewable energy systems based on multilevel inverters. Different configuration of renewable energy systems based on power converters will be discussed in detail. Finally, a new single inductor Multi-Output Boost (MOB) converter is proposed, which is compatible with the diode-clamped configuration. Steady state and dynamic analyses have been carried out in order to show the validity of the proposed topology. Then the joint circuit of the proposed DC-DC converter with a three-level diode-clamped converter is presented in order to have a series regulated voltage at the DC link voltage of the diode-clamped inverter. MOB converter can boost the low input DC voltage of the renewable energy sources and at the same time adjust the voltage across each capacitor to the desired voltage levels, thereby solving the main problem associated with capacitor voltage imbalance in this type of multilevel converter.

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This paper presents the analysis of shaft voltage in different configurations of a doubly fed induction generator (DFIG) and an induction generator (IG) with a back-to-back inverter in wind turbine applications. Detailed high frequency model of the proposed systems have been developed based on existing capacitive couplings in IG & DFIG structures and common mode voltage sources. In this research work, several arrangements of DFIG based wind energy conversion systems (WES) are investigated in case of shaft voltage calculation and its mitigation techniques. Placements of an LC line filter in different locations and its effects on shaft voltage elimination are studied via Mathematical analysis and simulations. A pulse width modulation (PWM) technique and a back-to-back inverter with a bidirectional buck converter have been presented to eliminate the shaft voltage in a DFIG wind turbine.

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This paper presents a new DC-DC Multi-Output Boost (MOB) converter which can share its total output between different series of output voltages for low and high power applications. This configuration can be utilised instead of several single output power supplies. This is a compatible topology for a diode-clamed inverter in the grid connection systems, where boosting low rectified output-voltage and series DC link capacitors is required. To verify the proposed topology, steady state and dynamic analysis of a MOB converter are examined. A simple control strategy has been proposed to demonstrate the performance of the proposed topology for a double-output boost converter. The topology and its control strategy can easily be extended to offer multiple outputs. Simulation and experimental results are presented to show the validity of the control strategy for the proposed converter.