Phase Diagram of Interacting Bosons on the Honeycomb Lattice

We study the ground state properties of repulsively interacting bosons on the honeycomb lattice using large-scale quantum Monte Carlo simulations. In the hard-core limit the half-filled system develops long ranged diagonal order for sufficiently strong nearest-neighbor repulsion. This staggered solid melts at a first order quantum phase transition into the superfluid phase, without the presence of any intermediate supersolid phase. Within the superfluid phase, both the superfluid density and the compressibility exhibit local minima near particle- (hole-) density one quarter, while the density and the condensate fraction show inflection points in this region. Relaxing the hard-core constraint, supersolid phases emerge for soft-core bosons. The suppression of the superfluid density is found to persist for sufficiently large, finite on-site repulsion.Comment: 4 pages with 5 figure

Solid-state time-to-pulse-height converter developed

Solid-state circuit produces an output pulse with an amplitude directly proportional to the time interval between two input pulses. It uses selected circuit options to achieve variable mode operation and a tunnel diode controls the charging time of a capacitor in proportion to the time interval being measured

Schema Vacuuming in Temporal Databases

Temporal databases facilitate the support of historical information by providing functions for indicating the intervals during which a tuple was applicable (along one or more temporal dimensions). Because data are never deleted, only superceded, temporal databases are inherently append-only resulting, over time, in a large historical sequence of database states. Data vacuuming in temporal databases allows for this sequence to be shortened by strategically, and irrevocably, deleting obsolete data. Schema versioning allows users to maintain a history of database schemata without compromising the semantics of the data or the ability to view data through historical schemata. While the techniques required for data vacuuming in temporal databases have been relatively well covered, the associated area of vacuuming schemata has received less attention. This paper discusses this issue and proposes a mechanism that fits well with existing methods for data vacuuming and schema versioning

Pre-treatments for removing colour from secondary effluent: Effectiveness and influence on membrane fouling in subsequent

The effects of different pre-treatments for colour removal on membrane fouling in the microfiltration (MF) of a coloured activated sludge (AS) effluent were investigated. It was found that a 80% colour removal target could be achieved by pre-treatment of the raw AS effluent with either ozone (10mgO 3L -1, 10-min contact time), a powdered activated carbon (150mgL -1, 30-min contact time), or a strong base anion exchange resin (10mLL -1, 20-min contact time)

Superfluid Suppression in d-Wave Superconductors due to Disordered Magnetism

The influence of static magnetic correlations on the temperature-dependent superfluid density \rho_s(T) is calculated for d-wave superconductors. In self-consistent calculations, itinerant holes form incommensurate spin density waves (SDW) which coexist with superconductivity. In the clean limit, the density of states is gapped, and \rho_s(T << T_c) is exponentially activated. In inhomogeneously-doped cases, the SDW are disordered and both the density of states and \rho_s(T) obtain forms indistinguishable from those in dirty but pure d-wave superconductors, in accordance with experiments. We conclude that the observed collapse of \rho_s at x\approx 0.35 in underdoped YBCO may plausibly be attributed to the coexistence of SDW and superconductivity.Comment: 6 pages, 5 figures. Expanded discussio

SemGrAM - Integrating semantic graphs into association rule mining

To date, most association rule mining algorithms have assumed that the domains of items are either discrete or, in a limited number of cases, hierarchical, categorical or linear. This constrains the search for interesting rules to those that satisfy the specified quality metrics as independent values or as higher level concepts of those values. However, in many cases the determination of a single hierarchy is not practicable and, for many datasets, an item’s value may be taken from a domain that is more conveniently structured as a graph with weights indicating semantic (or conceptual) distance. Research in the development of algorithms that generate disjunctive association rules has allowed the production of rules such as Radios V TVs -> Cables. In many cases there is little semantic relationship between the disjunctive terms and arguably less readable rules such as Radios V Tuesday -> Cables can result. This paper describes two association rule mining algorithms, SemGrAMG and SemGrAMP, that accommodate conceptual distance information contained in a semantic graph. The SemGrAM algorithms permit the discovery of rules that include an association between sets of cognate groups of item values. The paper discusses the algorithms, the design decisions made during their development and some experimental results.Sydney, NS

Experiences in building a tool for navigating association rule result sets

Practical knowledge discovery is an iterative process. First, the experiences gained from one mining run are used to inform the parameter setting and the dataset and attribute selection for subsequent runs. Second, additional data, either incremental additions to existing datasets or the inclusion of additional attributes means that the mining process is reinvoked, perhaps numerous times. Reducing the number of iterations, improving the accuracy of parameter setting and making the results of the mining run more clearly understandable can thus significantly speed up the discovery process. In this paper we discuss our experiences in this area and present a system that helps the user to navigate through association rule result sets in a way that makes it easier to find useful results from a large result set. We present several techniques that experience has shown us to be useful. The prototype system – IRSetNav – is discussed, which has capabilities in redundant rule reduction, subjective interestingness evaluation, item and itemset pruning, related information searching, text-based itemset and rule visualisation, hierarchy based searching and tracking changes between data sets using a knowledge base. Techniques also discussed in the paper, but not yet accommodated into IRSetNav, include input schema selection, longitudinal ruleset analysis and graphical visualisation techniques.Adelaide, S