354 research outputs found
Irreversible quantum graphs
Irreversibility is introduced to quantum graphs by coupling the graphs to a
bath of harmonic oscillators. The interaction which is linear in the harmonic
oscillator amplitudes is localized at the vertices. It is shown that for
sufficiently strong coupling, the spectrum of the system admits a new continuum
mode which exists even if the graph is compact, and a {\it single} harmonic
oscillator is coupled to it. This mechanism is shown to imply that the quantum
dynamics is irreversible. Moreover, it demonstrates the surprising result that
irreversibility can be introduced by a "bath" which consists of a {\it single}
harmonic oscillator
A study into customer's perceptions of service delivery and its impact on an outsourced fm service provider
This report discusses the issues of service delivery and the impact on an outsourced FM service provider. It focuses on HBML, one of the UK's leading FM providers and part of the Balfour Beatty Group. The issues facing outsourcing is one of how to ensure the customers are delighted in the service they receive and their perceptions are positive. This can be a difficult prospect when the customer has a higher expectation than the service delivery model requires, or the provider is unable to deliver to this standard. Meeting these expectations is one of the conundrums facing HBML, particularly in London where there has been a haemorrhaging of business in the past 12 months leading to loss of revenue in excess of £7m. To discover how customers perceive the service, a survey based on the five dimensions of the ServQual model was distributed to determine how they measured the delivery by HBML. This was also sent to HBML managers to ascertain what gaps there were in assessment of the service provision. This produced a set of results which indicated the customer's perception of HBML was not positive, with the majority of answers suggesting they had neutral views or were slightly either side of this position. The results from the CSM's were more positive, indicating gaps in both appraisals of the service. This is likely to lead to an imbalance between customer and service provider which could ultimately lead to damaged relationships and loss of business. It is essential that action is taken to prevent this situation escalating and to reverse the effects of current customer perceptions. The introduction of a service delivery system, such as the input-transformation-output model, could lead to an improved service, which could see benefits as described in The Service Profit Chain, Heskett et al. (2000). Based on this study it is recommended this model or similar are implemented or others explored to stem the outward flow of business
Deep retrofit approaches: managing risks to minimise the energy performance gap
Energy use in buildings remains a significant part of overall energy demand. Deep renovation projects, delivered at scale, remain a challenging task to achieve a lower carbon building stock.The complexity of building renovation beyond standards and building specifications is related to inherent characteristics of buildings which require distinct project management techniques. While there are now more projects focusing on achieving operational performance, there is still very little research on the management of the renovation and retrofit process itself.
Recognising that each project working on an existing building is unique in type, timing, energy goals and the roles/characteristics of people involved, the aim of this paper is to add to the current debate of how intervention approaches (one-off or over-time, whole-house, fabric-first room-by-room, measure-by-measure) are promoted by different policies, and with what impact.
The paper discusses the complexity of a deep renovation project in terms of planning and management and the ways current policies can lead to unintended consequences in the short and long term, as well in lock-in effects that contribute to energy performance, and to the gap between designed and actual energy performance.
Using a typology of risks, the issues associated with renovation processes and technologies were explored in a sample of cases studies from deep retrofits across the EU. The evidence from these shows that despite holistic planning for renovation, interventions tend to be carried out in phases. These contrasting time dimensions and the different retrofit approaches are discussed with risk profiles for each retrofit project, suggesting how risks emerge throughout a project. A series of risk mitigation strategies are suggested which, taken in combination to suit a specific project’s risk profile, may serve to reduce and potentially eliminate the building renovation energy performance gap
The dynamics of the 3D radial NLS with the combined terms
In this paper, we show the scattering and blow-up result of the radial
solution with the energy below the threshold for the nonlinear Schr\"{o}dinger
equation (NLS) with the combined terms iu_t + \Delta u = -|u|^4u + |u|^2u
\tag{CNLS} in the energy space . The threshold is given by the
ground state for the energy-critical NLS: . This
problem was proposed by Tao, Visan and Zhang in \cite{TaoVZ:NLS:combined}. The
main difficulty is the lack of the scaling invariance. Illuminated by
\cite{IbrMN:f:NLKG}, we need give the new radial profile decomposition with the
scaling parameter, then apply it into the scattering theory. Our result shows
that the defocusing, -subcritical perturbation does not
affect the determination of the threshold of the scattering solution of (CNLS)
in the energy space.Comment: 46page
Fabric first: is it still the right approach?
‘Fabric first’ describes an approach to improving the thermal performance of residential buildings by prioritising the improvement of fabric. It has historically been widely advocated. However, the urgency of complete decarbonisation challenges this approach in existing buildings. Heat decarbonisation is necessary to deliver zero-carbon goals. In many cases, no additional fabric improvement is needed to decarbonise heating; a heat pump, or other zero-carbon heat supply, will be enough. Retrofitting fabric first may not be feasible across the whole housing stock on timescales necessary for rapid decarbonisation and could therefore slow housing decarbonisation. However, fabric improvement will continue to have an important role. Energy use in buildings with a ‘heat pump only’ retrofit will be higher than if insulation were also improved. Fabric should continue to be prioritised in new buildings and where low-cost insulation measures are available. Fabric improvement can have other benefits: lower running costs, improved comfort, reduced damp risk, better heat pump performance, reduced overheating risk and lower requirements for electricity capacity increases. The suitability of a heat-pump-only approach to building decarbonisation should therefore be decided building by building. For national building stocks, complete decarbonisation of heating systems is required, but stock average fabric improvement may be 30–50%
The Status of the Scholarship of Teaching and Learning in Dental Education
The purpose of this study was to determine the current status of the Scholarship of Teaching and Learning (SoTL) within academic dentistry. A twenty-two-item survey was distributed to faculty members of American Dental Education Association (ADEA) member schools asking about their awareness of SoTL practices, perceived barriers to SoTL application, and ways to enhance SoTL activity. Four hundred thirty surveys with equal distribution of assistant, associate, and full professors were received (this may be considered a response rate of 5.4 percent out of roughly 8,000 ADEA faculty members). Almost 70 percent of the respondents indicated that they highly valued SoTL; only 2.1 percent indicated they did not. The extent to which the respondents valued SoTL was positively correlated with their perception of SoTL’s value among other faculty members in their program (r(322)=0.374, p\u3c0.001), school (r(299)=0.204, p\u3c0.001), and institution (r(233)=0.296, p\u3c0.002). However, the respondents were generally unsure how SoTL was applied at their institutions. Respondents from private institutions reported making more SoTL presentations at conferences than did those from public institutions (t(303)=-2.761, p=0.006) and stronger promotion of SoTL in their institutional policies (t(330)=-3.004, p=0.003). Barriers to changing the perception and application of SoTL appeared to exist at both organizational and individual levels, and ADEA was perceived to be well positioned to assist with both
Zeta function regularization in Casimir effect calculations and J.S. Dowker's contribution
A summary of relevant contributions, ordered in time, to the subject of
operator zeta functions and their application to physical issues is provided.
The description ends with the seminal contributions of Stephen Hawking and
Stuart Dowker and collaborators, considered by many authors as the actual
starting point of the introduction of zeta function regularization methods in
theoretical physics, in particular, for quantum vacuum fluctuation and Casimir
effect calculations. After recalling a number of the strengths of this powerful
and elegant method, some of its limitations are discussed. Finally, recent
results of the so called operator regularization procedure are presented.Comment: 16 pages, dedicated to J.S. Dowker, version to appear in
International Journal of Modern Physics
On the 2d Zakharov system with L^2 Schr\"odinger data
We prove local in time well-posedness for the Zakharov system in two space
dimensions with large initial data in L^2 x H^{-1/2} x H^{-3/2}. This is the
space of optimal regularity in the sense that the data-to-solution map fails to
be smooth at the origin for any rougher pair of spaces in the L^2-based Sobolev
scale. Moreover, it is a natural space for the Cauchy problem in view of the
subsonic limit equation, namely the focusing cubic nonlinear Schroedinger
equation. The existence time we obtain depends only upon the corresponding
norms of the initial data - a result which is false for the cubic nonlinear
Schroedinger equation in dimension two - and it is optimal because
Glangetas-Merle's solutions blow up at that time.Comment: 30 pages, 2 figures. Minor revision. Title has been change
Nondispersive solutions to the L2-critical half-wave equation
We consider the focusing -critical half-wave equation in one space
dimension where denotes the
first-order fractional derivative. Standard arguments show that there is a
critical threshold such that all solutions with extend globally in time, while solutions with may develop singularities in finite time.
In this paper, we first prove the existence of a family of traveling waves
with subcritical arbitrarily small mass. We then give a second example of
nondispersive dynamics and show the existence of finite-time blowup solutions
with minimal mass . More precisely, we construct a
family of minimal mass blowup solutions that are parametrized by the energy
and the linear momentum . In particular, our main result
(and its proof) can be seen as a model scenario of minimal mass blowup for
-critical nonlinear PDE with nonlocal dispersion.Comment: 51 page
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