Fast rates for estimation error and oracle inequalities for model section

We consider complexity penalization methods for model selection. These methods aim to choose a model to optimally trade off estimation and approximation errors by minimizing the sum of an empirical risk term and a complexity penalty. It is well known that if we use a bound on the maximal deviation between empirical and true risks as a complexity penalty, then the risk of our choice is no more than the approximation error plus twice the complexity penalty. There are many cases, however, where complexity penalties like this give loose upper bounds on the estimation error. In particular, if we choose a function from a suitably simple convex function class with a strictly convex loss function, then the estimation error (the difference between the risk of the empirical risk minimizer and the minimal risk in the class) approaches zero at a faster rate than the maximal deviation between empirical and true risks. In this paper, we address the question of whether it is possible to design a complexity penalized model selection method for these situations. We show that, provided the sequence of models is ordered by inclusion, in these cases we can use tight upper bounds on estimation error as a complexity penalty. Surprisingly, this is the case even in situations when the difference between the empirical risk and true risk (and indeed the error of any estimate of the approximation error) decreases much more slowly than the complexity penalty. We give an oracle inequality showing that the resulting model selection method chooses a function with risk no more than the approximation error plus a constant times the complexity penalty.

Simulations of the effect of waveguide cross-section on quantum dot – plasmon coupling

Quantum dot - plasmon waveguide systems are of interest for the active control of plasmon propagation, and consequently, the development of active nanophotonic devices such as nano-sized optical transistors. This paper is concerned with how varying aspect ratio of the waveguide crosssection affects the quantum dot - plasmon coupling. We compare a stripe waveguide with an equivalent nanowire, illustrating that both waveguides have a similar coupling strength to a nearby quantum dot for small waveguide cross-section, thereby indicating that stripe lithographic waveguides have strong potential use in quantum dot –plasmon waveguide systems. We also demonstrate that changing the aspect ratio of both stripe and wire waveguides can increase the spontaneous emission rate of the quantum dot into the plasmon mode, by up to a factor of five. The results of this paper will contribute to the optimisation of quantum dot - plasmon waveguide systems and help pave the way for the development of active nanophotonics devices.

A highway for research in science education that no longer leads to the frontier

A review of "Progressing science education: constructing the scientific research programme into the contingent nature of learning science", by Keith S. Taber, Dordrecht, Springer, 2009.

Managing financial implications for sustainable highway infrastructure delivery

Highway construction works have significant bearings on all aspects of sustainability. As they typically involve huge capital funds, stakeholders tend to place all interests on the financial justifications of the project, especially when embedding sustainability principles and practices may demand significant initial investment. Increasing public awareness and government policies demand that infrastructure projects respond to environmental challenges and people start to realise the negative consequences of not to pursue sustainability. Stakeholders are now keen to identify sustainable alternatives and financial implications of including them on a whole lifecycle basis. Therefore tools that aid the evaluation of investment options, such as provision of environmentally sustainable features in roads and highways, are highly desirable. Life-cycle cost analysis (LCCA) is generally recognised as a valuable approach for investment decision making for construction works. However to date it has limited application because the current LCCA models tend to focus on economic issues alone and are not able to deal with sustainability factors. This paper reports a research on identifying sustainability related factors in highway construction projects, in quantitative and qualitative forms of a multi-criteria analysis. These factors are then incorporated into existing LCCA models to produce a new sustainability based LCCA model with cost elements specific to sustainability measures. This presents highway project stakeholders a practical tool to evaluate investment decisions and reach an optimum balance between financial viability and sustainability deliverables.

Section 64 of the Property Law Act 1974 (Qld) and the reluctant buyer

The decision of the Court of Appeal in Dunworth v Mirvac Qld Pty Ltd [2011] QCA 200 arose from unusual circumstances associated with the flood in Brisbane earlier this year. Maris Dunworth (‘the buyer’) agreed to purchase a ground floor residential apartment located beside the Brisbane River at Tennyson from Mirvac Queensland Pty Ltd (‘Mirvac’). The original date for completion was 12 May 2009. In earlier proceedings, the buyer had alleged that she had been induced to purchase the apartment by false, misleading and deceptive representations. This claim was dismissed and an order for specific performance was made with a new completion date of 8 February 2011...

Developing financial decision support for highway infrastructure sustainability

The development of highway infrastructure typically requires major capital input over a long period. This often causes serious financial constraints for investors. The push for sustainability has added new dimensions to the complexity in the evaluation of highway projects, particularly on the cost front. This makes the determination of long-term viability even more a precarious exercise. Life-cycle costing analysis (LCCA) is generally recognised as a valuable tool for the assessment of financial decisions on construction works. However to date, existing LCCA models are deficient in dealing with sustainability factors, particularly for infrastructure projects due to their inherent focus on the economic issues alone. This research probed into the major challenges of implementing sustainability in highway infrastructure development in terms of financial concerns and obligations. Using results of research through literature review, questionnaire survey of industry stakeholders and semi-structured interview of senior practitioners involved in highway infrastructure development, the research identified the relative importance of cost components relating to sustainability measures and on such basis, developed ways of improving existing LCCA models to incorporate sustainability commitments into long-term financial management. On such a platform, a decision support model incorporated Fuzzy Analytical Hierarchy Process and LCCA for the evaluation of the specific cost components most concerned by infrastructure stakeholders. Two real highway infrastructure projects in Australia were then used for testing, application and validation, before the decision support model was finalised. Improved industry understanding and tools such as the developed model will lead to positive sustainability deliverables while ensuring financial viability over the lifecycle of highway infrastructure projects.

Section moment capacity tests of LiteSteel Beams

The LiteSteel Beam (LSB) is a new cold-formed hollow flange channel section developed by OneSteel Australian Tube Mills using their patented dual electric resistance welding and automated continuous roll-forming process. It has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. In addition to this unique geometry, the LSB sections also have unique characteristics relating to their stress-strain curves, residual stresses, initial geometric imperfections and hollow flanges that are not encountered in conventional hot-rolled and cold-formed steel channel sections. An experimental study including 20 section moment capacity tests was therefore conducted to investigate the behaviour and strength of LSB flexural members. The presence of inelastic reserve bending capacity in these beams was investigated in detail although the current design rules generally limit the section moment capacities of cold-formed steel members to their first yield moments. The ultimate moment capacities from the tests were compared with the section moment capacities predicted by the current cold-formed and hot-rolled steel design standards. It was found that compact and non-compact LSB sections have greater moment capacities than their first yield moments. The current cold-formed steel design standards were found to be conservative in predicting the section moment capacities of compact and non-compact LSB sections while the hot-rolled steel design standards were able to better predict them. This paper has shown that suitable modifications are needed to the current design rules to allow the inclusion of available inelastic bending capacities of LSBs in design.

Plastic bending behaviour and section moment capacities of mono-symmetric LiteSteel Beams with web openings

Recently developed cold-formed LiteSteel beam (LSB) sections have found increasing popularity in residential, industrial and commercial buildings due to their light weight and cost-effectiveness. Currently, there is significant interest in the use of LSB sections as flexural members in floor joist systems, although they can be used as flexural and compression members in a range of building systems. The plastic bending behaviour and section moment capacity of LSB sections with web holes can be assumed to differ from those without, but have yet to be investigated. Hence, no appropriate design rules for determining the section moment capacity of LSB sections with web holes are yet available. This paper presents the results of an investigation of the plastic bending behaviour and section moment capacity of LSB sections with circular web holes. LSB sections with varying circular hole diameters and degrees of spacing were considered. The paper also describes the simplified finite element (FE) modelling technique employed in this study, which incorporates all of the significant behavioural effects that influence the plastic bending behaviour and section moment capacity of these sections. The numerical and experimental test results and associated findings are also presented.

Does section 420A impose ‘strict liability’ upon controllers for acts or omissions of agents and experts?

This article addresses in depth the question of whether section 420A of the Corporations Act 2001 (Cth) imposes ‘strict liability’ upon a controller for the failure of an agent or expert to take reasonable care. The weight of existing authority appears to suggest that controllers are liable under s 420A for the carelessness of their agents or expert advisers. However, a closer analysis of the text of the provision and relevant Australian and UK case law demonstrates that this aspect of the statutory construction of s 420A remains very much an open question. This article ultimately contends for a construction of s 420A which requires a controller to adequately supervise and scrutinise, but which does not render a blameless controller strictly liable for all careless acts and omissions of agents and expert advisers.

Analytical model for fault section estimation and state identification of unobserved protective relays in power systems [电力系统故障诊断与不可观测保护状态识别的解析模型]

In recent years, some models have been proposed for the fault section estimation and state identification of unobserved protective relays (FSE-SIUPR) under the condition of incomplete state information of protective relays. In these models, the temporal alarm information from a faulted power system is not well explored although it is very helpful in compensating the incomplete state information of protective relays, quickly achieving definite fault diagnosis results and evaluating the operating status of protective relays and circuit breakers in complicated fault scenarios. In order to solve this problem, an integrated optimization mathematical model for the FSE-SIUPR, which takes full advantage of the temporal characteristics of alarm messages, is developed in the framework of the well-established temporal constraint network. With this model, the fault evolution procedure can be explained and some states of unobserved protective relays identified. The model is then solved by means of the Tabu search (TS) and finally verified by test results of fault scenarios in a practical power system.

Fire performance of LSF walls made of hollow flange section studs

Load bearing Light Gauge Steel Frame (LSF) walls made of cold-formed steel studs and tracks are commonly used in residential and commercial buildings. Fire safety of these walls is essential to minimize the damage caused by fire related accidents. Past investigations on the fire performance of load bearing LSF wall systems have been limited to LSF walls made of conventional lipped channel section studs. Although structurally efficient hollow flange steel sections are available in the building industry, they are not used as LSF wall studs due to the lack of fire performance data for such walls. The hollow flange sections have torsionally rigid hollow flanges that eliminate the occurrence of local and distortional buckling to an extent, thereby increasing their structural efficiency. The weaknesses of hollow flange sections such as lower lateral distortional buckling capacity are also eliminated when they are used as studs of LSF walls as the plasterboard restraints will prevent any lateral movement. Therefore hollow flange sections can be considered as structurally more efficient studs for use in LSF wall systems. This paper reports the full scale fire tests of LSF walls made of hollow flange section studs under standard fire conditions. The frames were made of 1.6 mm thick and 150 mm deep hollow flange section studs with two closed rectangular flanges of 45 mm width x 15 mm depth. Dual plasterboards were attached on both sides of the test wall panels. The load ratio was varied and the failure times, the lateral deflections and the axial displacements of the test walls were obtained. The failure behaviour of LSF walls made of hollow flange section studs was found to be different to that of LSF walls made of conventional lipped channel section studs. The results of these fire tests show that hollow flange section studs have a higher potential in being used in load bearing LSF Walls.