Multiparticle Schrodinger operators with point interactions in the plane

We study a system of N bosons in the plane interacting with delta function potentials. After a coupling constant renormalization we show that the Hamiltonian defines a self-adjoint operator and obtain a lower bound for the energy. The same results hold if one includes a regular inter-particle potential.Comment: 17 pages, Late

Providing value to a business using a lightweight design system to support knowledge reuse by designers

This paper describes an alternative approach to knowledge based systems in engineering than traditional geometry or explicit knowledge focused systems. Past systems have supported product optimisation rather than creative solutions and provide little benefit to businesses for bespoke and low volume products or products which do not benefit from optimisation. The approach here addresses this by supporting the creativity of designers through codified tacit knowledge and encouraging knowledge reuse for bespoke product development, in particular for small to medium sized enterprises. The implementation and evaluation of the approach is described within a company producing bespoke fixtures and tooling in shorter than average lead times. The active support of knowledge management in the company is intended to add value to the business by further reducing the lead times of the designs and creating a positive impact to business processes. The evaluation demonstrates a viable alternative framework to the traditional management of knowledge in engineering, which could be implemented by other small to medium enterprises

Long-Time Dynamics of Variable Coefficient mKdV Solitary Waves

We study the Korteweg-de Vries-type equation dt u=-dx(dx^2 u+f(u)-B(t,x)u), where B is a small and bounded, slowly varying function and f is a nonlinearity. Many variable coefficient KdV-type equations can be rescaled into this equation. We study the long time behaviour of solutions with initial conditions close to a stable, B=0 solitary wave. We prove that for long time intervals, such solutions have the form of the solitary wave, whose centre and scale evolve according to a certain dynamical law involving the function B(t,x), plus an H^1-small fluctuation.Comment: 19 page

High-resolution 3D weld toe stress analysis and ACPD method for weld toe fatigue crack initiation

Weld toe fatigue crack initiation is highly dependent on the local weld toe stress-concentrating geometry including any inherent flaws. These flaws are responsible for premature fatigue crack initiation (FCI) and must be minimised to maximise the fatigue life of a welded joint. In this work, a data-rich methodology has been developed to capture the true weld toe geometry and resulting local weld toe stress-field and relate this to the FCI life of a steel arc-welded joint. To obtain FCI lives, interrupted fatigue test was performed on the welded joint monitored by a novel multi-probe array of alternating current potential drop (ACPD) probes across the weld toe. This setup enabled the FCI sites to be located and the FCI life to be determined and gave an indication of early fatigue crack propagation rates. To understand fully the local weld toe stress-field, high-resolution (5 mu m) 3D linear-elastic finite element (FE) models were generated from X-ray micro-computed tomography (mu-CT) of each weld toe after fatigue testing. From these models, approximately 202 stress concentration factors (SCFs) were computed for every 1 mm of weld toe. These two novel methodologies successfully link to provide an assessment of the weld quality and this is correlated with the fatigue performance

The effects of space radiation on a chemically modified graphite-epoxy composite material

The effects of the space environment on the engineering properties and chemistry of a chemically modified T300/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F/24 C) and elevated temperature (250 F/121 C) on 4-ply unidirectional laminates. From these tests, inplane engineering and strength properties (E sub 1, E sub 2, Nu sub 12, G sub 12, X sub T, Y sub T) were determined. Cyclic tests were also performed to characterize energy dissipation changes due to irradiation and elevated temperature. Large diameter graphite fibers were tested to determine the effects of radiation on their stiffness and strength. No significant changes were observed. Dynamic-mechanical analysis demonstrated that the glass transition temperature was reduced by 50 F(28 C) after irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated material. The chemical modification of the epoxy did not aid in producing a material which was more radiation resistant than the standard T300/934 graphite-epoxy system. Irradiation was found to cause crosslinking and chain scission in the polymer. The latter produced low molecular weight products which plasticize the material at elevated temperatures and cause apparent material stiffening at low stresses at room temperature

On the existence of impurity bound excitons in one-dimensional systems with zero range interactions

We consider a three-body one-dimensional Schr\"odinger operator with zero range potentials, which models a positive impurity with charge $\kappa > 0$ interacting with an exciton. We study the existence of discrete eigenvalues as $\kappa$ is varied. On one hand, we show that for sufficiently small $\kappa$ there exists a unique bound state whose binding energy behaves like $\kappa^4$, and we explicitly compute its leading coefficient. On the other hand, if $\kappa$ is larger than some critical value then the system has no bound states

Volatile metal deposits on lunar soils: Relation to volcanism

Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of pb 204, Zn, Bi and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils and fractions of pb 204, Zn and Tl that are insoluble under mild, hot pH 5HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Only Bi is predominantly indigenous. The implication is also that the soils over their respective times of evolution were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption

Office buildings and the environment : the increasing role of facility managers

The Australian commercial stock emits 12% of all greenhouse gas emissions however the commercial property market has some inherent barriers to sustainability (DSE, 2005). A substantial proportion of the stock is owned by institutional investors who are unconvinced by the need to improve their stock and pass on running costs to tenants (Callender &amp; Key, 1997). The links between the built environment and sustainability issues such as fossil fuel consumption and climate change is clear. In developed countries buildings contribute around half of all carbon dioxide emissions and offer considerable scope for a significant contribution to sustainability through ecologically aware design and increased energy efficiency (BRE, 1996). As capital values are not greatly affected by sustainability, owners react by doing little or nothing and the effect is to limit sustainability-related investment and undermine efforts to deliver sustainability in the sector. Facility managers are in an influential position to help address sustainability issues via an increased awareness of energy efficiency and CO2 emissions.Even though the efficiency of buildings is primarily focused on new stock, with an existing churn replacement rate of approximately 2-3% the existing stock must be improved if urban built environment greenhouse gas emissions are to be reduced &ndash; clearly the management of existing stock must therefore contribute to substantial savings in energy use. Much of the property and surveying research has previously adopted an illustrative case study approach advocating the benefits of ESD and energy efficiency in existing buildings. This research adopts a radically different approach and profiles the entire office stock of a global CBD, namely Melbourne, which is seeking to become a carbon neutral city by 2020 (City of Melbourne, 2003). The research also employs scenario forecasting to model future changes to the stock over a fifteen year period. This paper sets out the rationale for the research and establishes the methodological approach adopted by the research team. The results provides a unique insight into the variations between different building types and grades of office buildings, which in turn will allow facility managers to gain a better understanding of where gains in energy efficiency can be made.<br /

The structural and behaviourial barriers to sustainable real estate development

Sustainable real estate development appears, on literal translation of both terms, to be an oxymoron - however it is a concept that the real estate profession needs to embrace knowledgably. On one hand it can be argued that real estate development is required for continued economic growth and the adoption of sustainability measures is required to mitigate climate change and global warming. Over the last few years there has been growth in the number of sustainability tools available to designers and operators of buildings. For example, in the US the LEED scheme enables designers to assess the environmental impact of their design and to benchmark the sustainability of the design against industry recognised criteria. LEED follows a similar format to the UK&rsquo;s Building Research Establishment Environmental Assessment Method (BREEAM) introduced in 1990 and the Australian &lsquo;GreenStar&rsquo; introduced in 2004. Even though there are an increasing number of sustainability tools available to designers, it still remains that the degree of uptake of the tools has been sporadic. This paper discusses the barriers to sustainable real estate development. Firstly it identifies the barriers to uptake and secondly it establishes the structural barriers in the market which prevent the wider uptake of tools.<br /

First Kepler results on compact pulsators II: KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode

We present the discovery of nonradial pulsations in a hot subdwarf B star based on 30.5 days of nearly continuous time-series photometry using the \emph{Kepler} spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes whose periods range from 130 to 190 seconds. It also shows one periodicity at a period of 3165 seconds. If this periodicity is a high order g-mode, then this star may be the hottest member of the hybrid DW Lyn stars. In addition to the resolved pulsation frequencies, additional periodic variations in the light curve suggest that a significant number of additional pulsation frequencies may be present. The long duration of the run, the extremely high duty cycle, and the well-behaved noise properties allow us to explore the stability of the periodic variations, and to place strong constraints on how many of them are independent stellar oscillation modes. We find that most of the identified periodicities are indeed stable in phase and amplitude, suggesting a rotation period of 2-3 weeks for this star, but further observations are needed to confirm this suspicion.Comment: 10 pages, accepted for publication in MNRA