Cascaded DC-DC converter connection of photovoltaic modules

New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single dc-ac inverter connected to a series string of pv panels, or many small dc-ac inverters which connect one or two panels directly to the ac grid. This paper proposes an alternative topology of nonisolated per-panel dc-dc converters connected in series to create a high voltage string connected to a simplified dc-ac inverter. This offers the advantages of a "converter-per-panel" approach without the cost or efficiency penalties of individual dc-ac grid connected inverters. Buck, boost, buck-boost, and Cu´k converters are considered as possible dc-dc converters that can be cascaded. Matlab simulations are used to compare the efficiency of each topology as well as evaluating the benefits of increasing cost and complexity. The buck and then boost converters are shown to be the most efficient topologies for a given cost, with the buck best suited for long strings and the boost for short strings. While flexible in voltage ranges, buck-boost, and Cu´k converters are always at an efficiency or alternatively cost disadvantage.

A class B switch-mode assisted linear amplifier

A switch-mode assisted linear amplifier (SMALA) combining a linear (Class B) and a switch-mode (Class D) amplifier is presented. The usual single hysteretic controlled half-bridge current dumping stage is replaced by two parallel buck converter stages, in a parallel voltage controlled topology. These operate independently: one buck converter sources current to assist the upper Class B output device, and a complementary converter sinks current to assist the lower device. This topology lends itself to a novel control approach of a dead-band at low power levels where neither class D amplifier assists, allowing the class B amplifier to supply the load without interference, ensuring high fidelity. A 20 W implementation demonstrates 85% efficiency, with distortion below 0.08% measured across the full audio bandwidth at 15 W. The class D amplifier begins assisting at 2 W, and below this value, the distortion was below 0.03%. Complete circuitry is given, showing the simplicity of the additional class D amplifier and its corresponding control circuitry.

Digitally-implemented naturally sampled PWM suitable for multilevel converter control

For dynamic closed loop control of a multilevel converter with a low pulse number (ratio of switching frequency to synthesized fundamental), natural sampled pulse-width modulation (PWM) is the best form of modulation. Natural sampling does not introduce distortion or a delayed response to the modulating signal. However previous natural sampled PWM implementations have generally been analog. For a modular multilevel converter, a digital implementation has advantages of accuracy and flexibility. Re-sampled uniform PWM is a novel digital modulation technique which approaches the performance of natural PWM. Both hardware and software implementations for a five level multilevel converter phase are presented, demonstrating the improvement over uniform PWM.

A combined method for mitigating sparsity problem in tag recommendation

Tag recommendation is a specific recommendation task for recommending metadata (tag) for a web resource (item) during user annotation process. In this context, sparsity problem refers to situation where tags need to be produced for items with few annotations or for user who tags few items. Most of the state of the art approaches in tag recommendation are rarely evaluated or perform poorly under this situation. This paper presents a combined method for mitigating sparsity problem in tag recommendation by mainly expanding and ranking candidate tags based on similar items’ tags and existing tag ontology. We evaluated the approach on two public social bookmarking datasets. The experiment results show better accuracy for recommendation in sparsity situation over several state of the art methods.

Histogram of weighted local directions for gait recognition

In this paper, we explore the effectiveness of patch-based gradient feature extraction methods when applied to appearance-based gait recognition. Extending existing popular feature extraction methods such as HOG and LDP, we propose a novel technique which we term the Histogram of Weighted Local Directions (HWLD). These 3 methods are applied to gait recognition using the GEI feature, with classification performed using SRC. Evaluations on the CASIA and OULP datasets show significant improvements using these patch-based methods over existing implementations, with the proposed method achieving the highest recognition rate for the respective datasets. In addition, the HWLD can easily be extended to 3D, which we demonstrate using the GEV feature on the DGD dataset, observing improvements in performance.

Phosphorus as a limiting factor on sustainable greywater irrigation

Water reuse through greywater irrigation has been adopted worldwide and has been proposed as a potential sustainable solution to increased water demands. Despite widespread adoption there is limited domestic knowledge of greywater reuse, there is no pressure to produce lowlevel phosphorus products and current guidelines and legislation, such as those in Australia, may be inadequate due to the lack of long-term data to provide a sound scientific basis. Research has clearly identified phosphorus as a potential environmental risk to waterways from many forms of irrigation. To assess the sustainability of greywater irrigation, this study compared four residential lots that had been irrigated with greywater for four years and adjacent non-irrigated lots that acted as controls. Each lot was monitored for the volume of greywater applied and selected physic-chemical water quality parameters and soil chemistry profiles were analysed. The non-irrigated soil profiles showed low levels of phosphorus and were used as controls. The Mechlich3 Phosphorus ratio (M3PSR) and Phosphate Environmental Risk Index (PERI) were used to determine the environmental risk of phosphorus leaching from the irrigated soils. Soil phosphorus concentrations were compared to theoretical greywater irrigation loadings. The measured phosphorus soil concentrations and the estimated greywater loadings were of similar magnitude. Sustainable greywater reuse is possible; however incorrect use and/or a lack of understanding of how household products affect greywater can result in phosphorus posing a significant risk to the environment.

Load frequency control in a microgrid : challenges and improvements

A microgrid can span over a large area, especially in rural townships. In such cases, the distributed generators (DGs) must be controlled in a decentralized fashion, based on the locally available measurements. The main concerns are control of system voltage magnitude and frequency, which can either lead to system instability or voltage collapse. In this chapter, the operational challenges of load frequency control in a microgrid are discussed and few methods are proposed to meet these challenges. In particular, issues of power sharing, power quality and system stability are addressed, when the system operates under decentralized control. The main focus of this chapter is to provide solutions to improve the system performance in different situations. The scenarios considered are (a) when the system stability margin is low, (b) when the line impedance has a high R to X ratio, (c) when the system contains unbalanced and/or distorted loads. Also a scheme is proposed in which a microgrid can be frequency isolated from a utility grid while being capable of bidirectional power transfer. In all these cases, the use of angle droop in converter interfaced DGs is adopted. It has been shown that this results in a more responsive control action compared to the traditional frequency based droop control.

Copyrights and copyfights : copyright law and the digital economy

This paper will consider questions around the reform of copyright law, and how they are increasingly being framed by the challenges of the digital economy. It discusses the review of copyright and the digital economy being undertaken by the Australian Law Reform Commission, with particular reference to the costs and benefits of copyright law to consumers and creative producers. We argue that there is a pressing need to develop fair copyright rules that encourage investment in the digital economy, allow widespread dissemination of knowledge through society, and support the innovative reuse of copyright works. To better align copyright law with these goals, we recommend that Australia introduce an open ended ‘fair use’ style copyright exception, and encourage the development of a digital copyright exchange of the sort discussed in the UK by the Hargreaves and Hooper Reports.

The ACEN Student Scholarship: a profile of financial hardship and Work Integrated Learning

An increasing emphasis on embedding Work-Integrated Learning (WIL) in the curriculum has impacted on teaching and learning approaches in Australian higher education institutions (Higher Education Base Funding Review: Final Report, 2011). Yet whilst the benefits and costs of these approaches have been identified (Bradley, Noonan, Nugent, & Scales, 2008; Patrick et al., 2009) insufficient attention has been paid to financial costs experienced by students studying subjects with a Work Integrated Learning component. In 2010 the Australian Collaborative Education Network (ACEN) responded to this issue by offering three modest student scholarships based on evidence of hardship. Data collected from over 1000 applicants between 2010 and 2012 indicate travel, accommodation, food, clothing, equipment and loss of income are of major concern especially for students on lengthy placements involving relocation. At the same time the Australian Federal Government’s review of base funding has recommended a detailed assessment of the costs of providing student placements across all disciplines - in particular health and education (DEEWR, 2011, p.94). This paper considers costs from the student perspective and highlights major concerns identified through ACEN scholarship applications over a three year period. The implications for ACEN are described and recommendations documented which outline ACEN’s role in ensuring that these issues are given greater consideration across the sector.

Addressing the impediments copyright imposes on the use of patent specifications and prior art documents to improve patent quality

This article considers from an Australian perspective the impediments that copyright law places in the path of those who seek to use patent specifications and non-patent prior art documents in ways that are necessary to the proper functioning of the patent system. Until recently, copyright law in Australia had limited the uses to which members of the public could put patent specifications in that country. Those impediments have been removed as a result of an important legislative change to the way in which copyright in patent specifications can be enforced. The change gives the public a greater freedom to make use of patent specifications than it enjoyed before, and removes unwarranted restrictions upon the ways in which the public can reuse valuable information. However, what the amendment does not address is the impediments copyright imposes on using non-patent prior art documents in ways that advance the public interest.

A novel representation of bioacoustic events for content-based search in field audio data

Bioacoustic data can provide an important base for environmental monitoring. To explore a large amount of field recordings collected, an automated similarity search algorithm is presented in this paper. A region of an audio defined by frequency and time bounds is provided by a user; the content of the region is used to construct a query. In the retrieving process, our algorithm will automatically scan through recordings to search for similar regions. In detail, we present a feature extraction approach based on the visual content of vocalisations – in this case ridges, and develop a generic regional representation of vocalisations for indexing. Our feature extraction method works best for bird vocalisations showing ridge characteristics. The regional representation method allows the content of an arbitrary region of a continuous recording to be described in a compressed format.

Corporate social responsibility in Japanese firms in transport sector

Corporate Social Responsibility (CSR) reporting has become common practice for large organisations globally, yet there is variance in the CSR related activities claimed in disclosures. CSR researchers argue that cultural and historical backgrounds are the influential drivers of CSR behaviour. However, the links between actual activities claimed in CSR reports and the cultural systems that underpin these reported activities is an under-explored area. This thesis discusses the uniqueness of Japanese socio-cultural aspects. While Japan is well-known for having the most advanced energy efficient technologies in the world, it is also known for being below international standards for gender equality in the workplace. Therefore, this thesis aims to explore and examine organisational behaviours through the lens of relativism in order to understand what organisations are reporting and how and why managers prioritise these activities. This thesis is based on longitudinal qualitative research focusing on the Japanese transport companies that published CSR reports between 2005 and 2009. The findings from manually coded content analysis revealed: (1) that activities related to providing public safety, waste management and the 3Rs (reduce, reuse and recycle), and environmental innovation were the top three most frequently reported CSR activities; and (2) complying with laws, career planning, flexible work practices, and providing public safety were the three categories that showed the most significant increase in reporting frequency from 2005-2009. This thesis extends the previous literature. Takagaki (2010b) identified that the transport industry, particularly the air and water sub-sectors, is the industry where the environmental problems are serious and require urgent attention. Takagaki (2010b) chose to explore the electronics industry as this industry is considered to be middle ground for its level of seriousness and urgency. This research: (1) examines the transport industry; (2) investigates the links between the actual activities reported, and the activities reported to be influential drivers of these activities.

Non-covalent surface modification of boron nitride nanotubes for enhanced catalysis

Boron nitride nanotubes were functionalized by microperoxidase-11 in aqueous media, showing improved catalytic performance due to a strong electron coupling 10 between the active centre of microperoxidase-11 and boron nitride nanotubes. One main application challenge of enzymes as biocatalysts is molecular aggregation in the aqueous solution. This issue is addressed by immobilization of enzymes on solid supports which 15 can enhance enzyme stability and facilitate separation, and recovery for reuse while maintaining catalytic activity and selectivity. The protein-nanoparticle interactions play a key role in bio-nanotechnology and emerge with the development of nanoparticle-protein “corona”. Bio-molecular coronas provide a 20 unique biological identity of nanosized materials.1, 2 As a structural analogue to carbon nanotubes (CNTs), Boron nitride nanotubes have boron and nitrogen atoms distributed equally in hexagonal rings and exhibit excellent mechanical strength, unique physical properties, and chemical stability at high-temperatures. 25 The chemical inertness of BN materials suits to work in hazardous environments, making them an optimal candidate in practical applications in biological and medical field.3, 4

System level tests of transformer differential protection using an IEC 61850 process bus

The IEC 61850 family of standards for substation communication systems were released in the early 2000s, and include IEC 61850-8-1 and IEC 61850-9-2 that enable Ethernet to be used for process-level connections between transmission substation switchyards and control rooms. This paper presents an investigation of process bus protection performance, as the in-service behavior of multi-function process buses is largely unknown. An experimental approach was adopted that used a Real Time Digital Simulator and 'live' substation automation devices. The effect of sampling synchronization error and network traffic on transformer differential protection performance was assessed and compared to conventional hard-wired connections. Ethernet was used for all sampled value measurements, circuit breaker tripping, transformer tap-changer position reports and Precision Time Protocol synchronization of sampled value merging unit sampling. Test results showed that the protection relay under investigation operated correctly with process bus network traffic approaching 100% capacity. The protection system was not adversely affected by synchronizing errors significantly larger than the standards permit, suggesting these requirements may be overly conservative. This 'closed loop' approach, using substation automation hardware, validated the operation of protection relays under extreme conditions. Digital connections using a single shared Ethernet network outperformed conventional hard-wired solutions.

A Bayesian network approach to modelling temporal behaviour of Lyngbya majuscula bloom initiation

Lyngbya majuscula is a cyanobacterium (blue-green algae) occurring naturally in tropical and subtropical coastal areas worldwide. Deception Bay, in Northern Moreton Bay, Queensland, has a history of Lyngbya blooms, and forms a case study for this investigation. The South East Queensland (SEQ) Healthy Waterways Partnership, collaboration between government, industry, research and the community, was formed to address issues affecting the health of the river catchments and waterways of South East Queensland. The Partnership coordinated the Lyngbya Research and Management Program (2005-2007) which culminated in a Coastal Algal Blooms (CAB) Action Plan for harmful and nuisance algal blooms, such as Lyngbya majuscula. This first phase of the project was predominantly of a scientific nature and also facilitated the collection of additional data to better understand Lyngbya blooms. The second phase of this project, SEQ Healthy Waterways Strategy 2007-2012, is now underway to implement the CAB Action Plan and as such is more management focussed. As part of the first phase of the project, a Science model for the initiation of a Lyngbya bloom was built using Bayesian Networks (BN). The structure of the Science Bayesian Network was built by the Lyngbya Science Working Group (LSWG) which was drawn from diverse disciplines. The BN was then quantified with annual data and expert knowledge. Scenario testing confirmed the expected temporal nature of bloom initiation and it was recommended that the next version of the BN be extended to take this into account. Elicitation for this BN thus occurred at three levels: design, quantification and verification. The first level involved construction of the conceptual model itself, definition of the nodes within the model and identification of sources of information to quantify the nodes. The second level included elicitation of expert opinion and representation of this information in a form suitable for inclusion in the BN. The third and final level concerned the specification of scenarios used to verify the model. The second phase of the project provides the opportunity to update the network with the newly collected detailed data obtained during the previous phase of the project. Specifically the temporal nature of Lyngbya blooms is of interest. Management efforts need to be directed to the most vulnerable periods to bloom initiation in the Bay. To model the temporal aspects of Lyngbya we are using Object Oriented Bayesian networks (OOBN) to create ‘time slices’ for each of the periods of interest during the summer. OOBNs provide a framework to simplify knowledge representation and facilitate reuse of nodes and network fragments. An OOBN is more hierarchical than a traditional BN with any sub-network able to contain other sub-networks. Connectivity between OOBNs is an important feature and allows information flow between the time slices. This study demonstrates more sophisticated use of expert information within Bayesian networks, which combine expert knowledge with data (categorized using expert-defined thresholds) within an expert-defined model structure. Based on the results from the verification process the experts are able to target areas requiring greater precision and those exhibiting temporal behaviour. The time slices incorporate the data for that time period for each of the temporal nodes (instead of using the annual data from the previous static Science BN) and include lag effects to allow the effect from one time slice to flow to the next time slice. We demonstrate a concurrent steady increase in the probability of initiation of a Lyngbya bloom and conclude that the inclusion of temporal aspects in the BN model is consistent with the perceptions of Lyngbya behaviour held by the stakeholders. This extended model provides a more accurate representation of the increased risk of algal blooms in the summer months and show that the opinions elicited to inform a static BN can be readily extended to a dynamic OOBN, providing more comprehensive information for decision makers.