83 resultados para high optical-to-optical conversion efficiency
Resumo:
Energy efficiency as a concept has gained significant attention over the last few decades, as governments and industries around the world have grappled with issues such as rapid population growth and expanding needs for energy, the cost of supplying infrastructure for growing spikes in peak demand, the finite nature of fossil based energy reserves, and managing transition timeframes for expanding renewable energy supplies. Over the last decade in particular, there has been significant growth in understanding the complexity and interconnectedness of these issues, and the centrality of energy efficiency to the engineering profession. Furthermore, there has been a realisation amongst various government departments and education providers that associated knowledge and skill sets to achieve energy efficiency goals are not being sufficiently developed in vocational or higher education. Within this context, this poster discusses the emergence of a national energy efficiency education agenda in Australia, to support embedding such knowledge throughout the engineering curriculum, and throughout career pathways. In particular, the posterprovides insights into the national priorities for capacity building in Australia, and how this is influencing the engineering education community, from undergraduate education through to postgraduate studies and professional development. The poster is intended to assist in raising awareness about the central role of energy efficiency within engineering, significant initiatives by major government, professional, and training organisations, and the increasing availability of high quality energy efficiency engineering education resources. The authors acknowledge the support for and contributions to this poster by the federal Department of Resources, Energy and Tourism, through members of the national Energy Efficiency Advisory Group for engineering education.
Resumo:
This paper presents a visual SLAM method for temporary satellite dropout navigation, here applied on fixed- wing aircraft. It is designed for flight altitudes beyond typical stereo ranges, but within the range of distance measurement sensors. The proposed visual SLAM method consists of a common localization step with monocular camera resectioning, and a mapping step which incorporates radar altimeter data for absolute scale estimation. With that, there will be no scale drift of the map and the estimated flight path. The method does not require simplifications like known landmarks and it is thus suitable for unknown and nearly arbitrary terrain. The method is tested with sensor datasets from a manned Cessna 172 aircraft. With 5% absolute scale error from radar measurements causing approximately 2-6% accumulation error over the flown distance, stable positioning is achieved over several minutes of flight time. The main limitations are flight altitudes above the radar range of 750 m where the monocular method will suffer from scale drift, and, depending on the flight speed, flights below 50 m where image processing gets difficult with a downwards-looking camera due to the high optical flow rates and the low image overlap.
Resumo:
This paper aims to present preliminary findings on measuring the technical efficiencies using Data Envelopment Analysis (DEA) in Malaysian Real Estate Investment Trusts (REITs) to determine the best practice for operations which include the asset allocation and scale size to improve the performance of Malaysian REITs. Variables identified as input and output will be assessed in this cross section analysis using the operational approach and Variable Return to Scale DEA (VRS-DEA) by focusing on Malaysian REITs for the year 2013. Islamic REITs have higher efficiency score as compared to the conventional REITs for both models. Diversified REITs are more efficient as compared to the specialised REIT using both models. For Model 1, the negative inefficient value is identified in the managerial inefficiency as compared to the scale inefficiency. This shows that inputs are not fully minimised to produce more outputs. However, when other expenses are considered as different input variables, the efficiency score becomes higher from 60.3% to 81.2%. In model 2, scale inefficiency produce greater inefficiency as compared to the managerial efficiency. The result suggests that Malaysian REITs have been operating at the wrong scale of operations as majority of the Malaysian REITs are operating at decreasing return to scale.
Resumo:
Amongst alternative energy sources, photovoltaics hold a considerable promise for it is a plentiful, easily accessible and renewable source of power. Yet, the overall cost of generating electricity using the most advanced silicon based solar cells remains high compared to both traditional and other renewable power generation approaches. Organic thin film photovoltaics are an emerging economically competitive photovoltaic technology that combines manufacturing adaptability, low-cost processing and a lightweight, flexible device end-product. At present, however, commercial use of organic photovoltaics is hindered by low conversion efficiency and poor overall stability of the devices. Encapsulation with high barrier performance materials and structures is one of the key ways to address these issues and improve device lifetime. This paper will briefly outline the current understanding of the major degradation mechanisms, their interrelation and the internal and external factors that initiate these processes. Then, the paper will provide an overview of currently available encapsulant materials, their utility in limiting chemical (water vapor and oxygen penetration) and mechanical degradation within individual layers and device as a whole, and potential drawbacks to their application in organic photovoltaic devices.
Resumo:
Free charge generation in donor-acceptor (D-A) based organic photovoltaic diodes (OPV) progresses through formation of charge-transfer (CT) and charge-separated (CS) states and excitation decay to the triplet level is considered as a terminal loss. On the other hand a direct excitation decay to the triplet state is beneficial for multiexciton harvesting in singlet fission photovoltaics (SF-PV) and the formation of CT-state is considered as a limiting factor for multiple triplet harvesting. These two extremes when present in a D-A system are expected to provide important insights into the mechanism of free charge generation and spin-character of bimolecular recombination in OPVs. Herein, we present the complete cycle of events linked to spin conversion in the model OPV system of rubrene/C60. By tracking the spectral evolution of photocurrent generation at short-circuit and close to open-circuit conditions we are able to capture spectral changes to photocurrent that reveal the triplet character of CT-state. Furthermore, we unveil an energy up-conversion effect that sets in as a consequence of triplet population build-up where triplet-triplet annihilation (TTA) process effectively regenerates the singlet excitation. This detailed balance is shown to enable a rare event of photon emission just above the open-circuit voltage (VOC) in OPVs.
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There has recently been a rapidly increasing interest in solar powered UAVs. With the emergence of high power density batteries, long range and low-power micro radio devices, airframes, and powerful micro-processors and motors, small/micro UAVs have become applicable in civilian applications such as remote sensing, mapping, traffic monitoring, search and rescue. The Green Falcon UAV is an innovative project from Queensland University of Technology and has been developed and tested during these past years. It comprises a wide range of subsystems to be analyses and studied such as Solar Panel Cells, Gas sensor, Aerodynamics of the wing and others. Previous test however, resulted in damage to the solar cells and some of the subsystems including motor and ESC. This report describes the repair and verification process followed to improve the efficiency of the Green Falcon UAV. The report shows some of the results obtained in previous static and flight tests as well as some of recommendations.
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The p-block semiconductors are regarded as a new family of visible-light photocatalysts because of their dispersive and anisotropic band structures as well as high chemical stability. The bismuth oxide halides belong to this family and have band structures and dispersion relations that can be engineered by modulating the stoichiometry of the halogen elements. Herein, we have developed a new visible-light photocatalyst Bi 24 O 31 Cl 10 by band engineering, which shows high dye-sensitized photocatalytic activity. Density functional theory calculations reveal that the p-block elements determine the nature of the dispersive electronic structures and narrow band gap in Bi 24 O 31 Cl 10. Bi 24 O 31 Cl 10 exhibits excellent visible-light photocatalytic activity towards the degradation of Rhodamine B, which is promoted by dye sensitization due to compatible energy levels and high electronic mobility. In addition, Bi 24 O 31 Cl 10 is also a suitable photoanode material for dye-sensitized solar cells and shows power conversion efficiency of 1.5%.
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Oriented, single-crystalline, one-dimensional (1D) TiO2 nanostructures would be most desirable for providing fascinating properties and features, such as high electron mobility or quantum confinement effects, high specific surface area, and even high mechanical strength, but achieving these structures has been limited by the availability of synthetic techniques. In this study, a concept for precisely controlling the morphology of 1D TiO2 nanostructures by tuning the hydrolysis rate of titanium precursors is proposed. Based on this innovation, oriented 1D rutile TiO2 nanostructure arrays with continually adjustable morphologies, from nanorods (NRODs) to nanoribbons (NRIBs), and then nanowires (NWs), as well as the transient state morphologies, were successfully synthesized. The proposed method is a significant finding in terms of controlling the morphology of the 1D TiO2 nano-architectures, which leads to significant changes in their band structures. It is worth noting that the synthesized rutile NRIBs and NWs have a comparable bandgap and conduction band edge height to those of the anatase phase, which in turn enhances their photochemical activity. In photovoltaic performance tests, the photoanode constructed from the oriented NRIB arrays possesses not only a high surface area for sufficient dye loading and better light scattering in the visible light range than for the other morphologies, but also a wider bandgap and higher conduction band edge, with more than 200% improvement in power conversion efficiency in dye-sensitized solar cells (DSCs) compared with NROD morphology.
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Considering the growing energy needs and concern for environmental degradation, clean and inexhaustible energy sources, e.g solar energy are receiving greater attention for various applications. The use of solar energy systems for low temperature applications reduces the burden on conventional fossil fuels and has little or no harmful effects on the environment. The performance of a solar system depends to a great extent on the collector used for the conversion of solar radiant energy to thermal energy. A solar evaporatorcollector (SEC) is basically an unglazed flat plate collector where refrigerant, like R134a, is used as the working fluid. As the operating temperature of SEC is very low, it collects energy both from solar irradiation and ambient energy leading to a much higher efficiency than the conventional collectors. The capability of SEC to utilize ambient energy also enables the system to operate at night. Therefore it is not appropriate to use for the evaluation of performance of SEC by conventional efficiency equation where ambient energy and condensation is not considered as energy input in addition to irradiation. In the National University of Singapore, several Solar Assisted Heat Pump (SAHP) systems were built for the evaluation of performance under the metrological condition of Singapore for thermal applications of desalination and SEC was the main component to harness renewable energy. In this paper, the design and performance of SEC are explored. Furthermore, an attempt is made to develop an efficiency equation for SEC and maximum efficiency attained 98% under the meteorological condition of Singapore.
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Bid opening in e-auction is efficient when a homomorphic secret sharing function is employed to seal the bids and homomorphic secret reconstruction is employed to open the bids. However, this high efficiency is based on an assumption: the bids are valid (e.g., within a special range). An undetected invalid bid can compromise correctness and fairness of the auction. Unfortunately, validity verification of the bids is ignored in the auction schemes employing homomorphic secret sharing (called homomorphic auction in this paper). In this paper, an attack against the homomorphic auction in the absence of bid validity check is presented and a necessary bid validity check mechanism is proposed. Then a batch cryptographic technique is introduced and applied to improve the efficiency of bid validity check.
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The rising problems associated with construction such as decreasing quality and productivity, labour shortages, occupational safety, and inferior working conditions have opened the possibility of more revolutionary solutions within the industry. One prospective option is in the implementation of innovative technologies such as automation and robotics, which has the potential to improve the industry in terms of productivity, safety and quality. The construction work site could, theoretically, be contained in a safer environment, with more efficient execution of the work, greater consistency of the outcome and higher level of control over the production process. By identifying the barriers to construction automation and robotics implementation in construction, and investigating ways in which to overcome them, contributions could be made in terms of better understanding and facilitating, where relevant, greater use of these technologies in the construction industry so as to promote its efficiency. This research aims to ascertain and explain the barriers to construction automation and robotics implementation by exploring and establishing the relationship between characteristics of the construction industry and attributes of existing construction automation and robotics technologies to level of usage and implementation in three selected countries; Japan, Australia and Malaysia. These three countries were chosen as their construction industry characteristics provide contrast in terms of culture, gross domestic product, technology application, organisational structure and labour policies. This research uses a mixed method approach of gathering data, both quantitative and qualitative, by employing a questionnaire survey and an interview schedule; using a wide range of sample from management through to on-site users, working in a range of small (less than AUD0.2million) to large companies (more than AUD500million), and involved in a broad range of business types and construction sectors. Detailed quantitative (statistical) and qualitative (content) data analysis is performed to provide a set of descriptions, relationships, and differences. The statistical tests selected for use include cross-tabulations, bivariate and multivariate analysis for investigating possible relationships between variables; and Kruskal-Wallis and Mann Whitney U test of independent samples for hypothesis testing and inferring the research sample to the construction industry population. Findings and conclusions arising from the research work which include the ranking schemes produced for four key areas of, the construction attributes on level of usage; barrier variables; differing levels of usage between countries; and future trends, have established a number of potential areas that could impact the level of implementation both globally and for individual countries.
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This exploratory study investigated factors associated with the wish to hasten death among a sample of terminally ill cancer patients. Semi-structured interviews conducted on a total of 72 hospice and home palliative care patients were subjected to qualitative analysis using QSRNUDIST. The main themes to emerge suggested that patients with a high wish to hasten death had greater concerns with physical symptoms and psychologica l suffering, perceived themselves to be more of a burden to others, and experienced higher levels of demoralization, while also reporting less confidence in symptom control, fewer social supports, less satisfaction with life experiences and fewer religious beliefs when compared with patients who had a moderate or no wish to hasten death. The implications of these findings will be discussed.
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This paper discusses how intuitive interaction is a possible way to increase the efficiency and effectiveness of interaction with older adults. It provides insights into existing research on intuitive interaction, and the role of prior experience and familiarity in intuition. An experiment is discussed which investigates differences in familiarity between younger and older adults. A comprehensive coding system has been developed to help analyse the data collected. This research is currently in progress.
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A Positive Buck- Boost (PBB) converter is a known DC-DC converter that can operate in step up and step down modes. Unlike Buck, Boost, and Inverting Buck Boost converters, the inductor current of a PBB can be controlled independently of its voltage conversion ratio. In other words, the inductor of PBB can be utilised as an energy storage unit in addition to its main function of energy transfer. In this paper, the capability of PBB to store energy has been utilised to achieve robustness against input voltage fluctuations and output current changes. The control strategy has been developed to keep accuracy, affordability, and simplicity acceptable. To improve the efficiency of the system a Smart Load Controller (SLC) has been suggested. Applying SLC extra current storage occurs when there is sudden loads change otherwise little extra current is stored.
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The investigation into the encapsulation of gold nanoparticles (AuNPs) by poly(methyl methacrylate) (PMMA) was undertaken. This was performed by three polymerisation techniques including: grafting PMMA synthesised by reversible addition-fragmentation chain transfer (RAFT) polymerisation to AuNPs, grafting PMMA synthesised by atom transfer radical polymerisation (ATRP) from the surface of functionalised AuNPs and by encapsulation of AuNPs within PMMA latexes produced through photo-initiated oil-in-water (o/w) miniemulsion polymerisation. The grafting of RAFT PMMA to AuNPs was performed by the addition of the RAFT functionalised PMMA to citrate stabilised AuNPs. This was conducted with a range of PMMA of varying molecular weight distribution (MWD) as either the dithioester or thiol end-group functionalities. The RAFT PMMA polymers were characterised by gel permeation chromatography (GPC), ultraviolet-visible (UV-vis), Fourier transform infrared-attenuated total reflectance (FTIR-ATR), Fourier transform Raman (FT-Raman) and proton nuclear magnetic resonance (1H NMR) spectroscopies. The attachment of PMMA to AuNPs showed a tendency for AuNPs to associate with the PMMA structures formed, though significant aggregation occurred. Interestingly, thiol functionalised end-group PMMA showed very little aggregation of AuNPs. The spherical polymer-AuNP structures did not vary in size with variations in PMMA MWD. The PMMA-AuNP structures were characterised using scanning electron microscopy (SEM), transition electron microscopy (TEM), energy dispersive X-ray analysis (EDAX) and UV-vis spectroscopy. The surface confined ATRP grafting of PMMA from initiator functionalised AuNPs was polymerised in both homogeneous and heterogeneous media. 11,11’- dithiobis[1-(2-bromo-2-methylpropionyloxy)undecane] (DSBr) was used as the surface-confined initiator and was synthesised in a three step procedure from mercaptoundecanol (MUD). All compounds were characterised by 1H NMR, FTIR-ATR and Raman spectroscopies. The grafting in homogeneous media resulted in amorphous PMMA with significant AuNP aggregation. Individually grafted AuNPs were difficult to separate and characterise, though SEM, TEM, EDAX and UV-vis spectroscopy was used. The heterogeneous polymerisation did not produce grafted AuNPs as characterised by SEM and EDAX. The encapsulation of AuNPs within PMMA latexes through the process of photoinitiated miniemulsion polymerisation was successfully achieved. Initially, photoinitiated miniemulsion polymerisation was conducted as a viable low temperature method of miniemulsion initiation. This proved successful producing a stable PMMA with good conversion efficiency and narrow particle size distribution (PSD). This is the first report of such a system. The photo-initiated technique was further optimised and AuNPs were included into the miniemulsion. AuNP encapsulation was very effective, producing reproducible AuNP encapsulated PMMA latexes. Again, this is the first reported case of this. The latexes were characterised by TEM, SEM, GPC, gravimetric analysis and dynamic light scattering (DLS).