Discrete sequence prediction and its applications

Learning from experience to predict sequences of discrete symbols is a fundamental problem in machine learning with many applications. We apply sequence prediction using a simple and practical sequence-prediction algorithm, called TDAG. The TDAG algorithm is first tested by comparing its performance with some common data compression algorithms. Then it is adapted to the detailed requirements of dynamic program optimization, with excellent results

Analytical learning and term-rewriting systems

Analytical learning is a set of machine learning techniques for revising the representation of a theory based on a small set of examples of that theory. When the representation of the theory is correct and complete but perhaps inefficient, an important objective of such analysis is to improve the computational efficiency of the representation. Several algorithms with this purpose have been suggested, most of which are closely tied to a first order logical language and are variants of goal regression, such as the familiar explanation based generalization (EBG) procedure. But because predicate calculus is a poor representation for some domains, these learning algorithms are extended to apply to other computational models. It is shown that the goal regression technique applies to a large family of programming languages, all based on a kind of term rewriting system. Included in this family are three language families of importance to artificial intelligence: logic programming, such as Prolog; lambda calculus, such as LISP; and combinatorial based languages, such as FP. A new analytical learning algorithm, AL-2, is exhibited that learns from success but is otherwise quite different from EBG. These results suggest that term rewriting systems are a good framework for analytical learning research in general, and that further research should be directed toward developing new techniques

X-ray properties of BzK-selected galaxies in the deepest X-ray fields

We investigate the X-ray properties of BzK-selected galaxies at z $\sim$ 2 using deep X-ray data in the Chandra Deep Field South and North (CDFS and CDFN). Of these we directly detect in X-rays 49 sBzKs in CDFS and 32 sBzKs in CDFN. Stacking the undetected sources also reveals a significant X-ray signal. Investigating the X-ray detection rate and stacked flux versus the IR excess parameter (i.e. SFRtotal/SFRUV,corr), we find no strong evidence for an increased X-ray detection rate, or a harder X-ray spectrum in IR Excess sBzKs. This is particularly the case when one accounts for the strong correlation between the IR excess parameter and the bolometric IR luminosity (LIR), e.g. when controlling for LIR, the IR Non-Excess sBzKs show a detection rate at least as high. While both direct detections and stacking suggest that the AGN fraction in sBzK galaxies is high, there is no clear evidence for widespread Compton thick activity in either the sBzK population generally, or the IR Excess sBzK subsample. The very hard X-ray signal obtained for the latter in earlier work was most likely contaminated by a few hard X-ray sources now directly detected in deeper X-ray data. The X-ray detection fraction of passive BzK galaxies in our sample is if anything higher than that of sBZKs, so there is no evidence for coeval black hole growth and star formation from X-ray analysis of the BzK populations. Because increased AGN activity in the IR excess population is not indicated by our X-ray analysis, it appears that the bulk of the IR Excess sBzK population are luminous star-forming galaxies whose SFRs are either overestimated at 24 microns, underestimated in the UV, or both. This conclusion reinforces recent results from Herschel which show similar effects.Comment: 17 pages, 8 Figures, 7 Table

Let\u27s get moving with the affordable medium-speed alternatives to the old dream of high-speed rail

More than half a century has passed since high-speed rail (HSR) effectively began operating, in Japan in 1964, and it has been mooted for Australia since 1984. I estimate that the cost of all HSR studies by the private and public sectors in Australia exceeds $125 million, in today\u27s dollars. But the federal government is now less interested in high-speed rail (now defined as electric trains operating on steel rails at maximum speeds of above 250km per hour), and instead favours faster rail or medium-speed rail

East coast mainline rail track: options for 2014

The alignment of the track linking Melbourne, Sydney, Brisbane and Cairns is outlined, along with the current North - South interstate rail upgrade, and the former Queensland MainLine Upgrade. Summaries are given of the 2006 - 07 draft AusLink Corridor Strategies for each corridor along with the ongoing upgrading of the Hume, Pacific and Bruce Highways. Comment is made on track straightening and other upgrading options for each corridor. Such upgrades during 2009 - 2014 would lower transport costs and assist rail to reach a target of 50 per cent mode share on the East Coast (as opposed to less than 12 per cent on the North - South corridor and 25 per cent on the Queensland North Coast line). In turn, this would deliver by 2014, estimated savings in diesel use of 185 million litres per annum along with reductions of greenhouse gas emissions (nearly 500,000 tonnes CO2e pa) and external costs ($325m pa)

Transport is letting Australia down in the race to cut emissions

At a time Australia is meant to be reducing its greenhouse emissions, the upward trend in transport sector emissions continues. The latest National Greenhouse Gas Inventory report released last week shows the transport sector emitted 102 million tonnes (Mt) of carbon dioxide equivalent (MtCO₂-e) in the 12 months to September 2019. This was 18.9% of Australia\u27s emissions

Shifting freight to rail could make the Pacific Highway safer

Articulated trucks such as semi-trailers and B-Doubles are involved in about 30% of fatal road accidents on the Pacific Highway. As the number of trucks carrying freight between Sydney and Brisbane increases, we will see more tragic incidents like the fatal crash involving a B-Double on 8 January 2012 near Urunga

Government rail asset sales, and return to the public sector, in New Zealand and Tasmania

The paper outlines the sale, with a track lease, in 1993 of the state owned New Zealand Railways Corporation to a consortium, TranzRail Holdings formed by the United States and New Zealand interests. It also notes increases in productivity and traffic levels to 1999 with subsequent problems leading to the New Zealand Government agreeing in 2003 to repurchase and rehabilitate the track. The paper then outlines transfer of effective ownership of the trains and related services in 2003 to an Australian company, and in 2008 back to the New Zealand Government at appreciable net cost.After a brief outline of railways in Australia, the paper notes how government rail in Tasmania, then owned and operated by the Australian National Railways Commission, was sold in 1997 with a track lease to a company related to TranzRail Holdings. The paper then notes emerging problems after initial success, and how after a change in ownership in 2004, the Tasmanian track lease was taken back by the public sector in 2007, followed by the trains in 2009.Other rail asset sales in Australia are also noted along with the high total costs of road vehicle operations in Australia and New Zealand

Applications of Genetic Methods to NASA Design and Operations Problems

We review four recent NASA-funded applications in which evolutionary/genetic methods are important. In the process we survey: the kinds of problems being solved today with these methods; techniques and tools used; problems encountered; and areas where research is needed. The presentation slides are annotated briefly at the top of each page