A continuous-time solver for quantum impurity models

We present a new continuous time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on a stochastic sampling of a perturbation expansion in the impurity-bath hybridization parameter. Comparisons to quantum Monte Carlo and exact diagonalization calculations confirm the accuracy of the new approach, which allows very efficient simulations even at low temperatures and for strong interactions. As examples of the power of the method we present results for the temperature dependence of the kinetic energy and the free energy, enabling an accurate location of the temperature-driven metal-insulator transition.Comment: Published versio

Exact Ground States of One-Dimensional Quantum Systems: Matrix Product Approach

By using the so-called matrix-product ground state approach, a few one-dimensional quantum systems, including a frustrated spin-1/2 Heisenberg ladder, the ferromagnetic t-J-V model at half-filling, the antiferromagnetic $J_z-V$ at 2/3 filling and the antiferromagnetic $t-J_z-V$ model at half-filling, are solved exactly. The correlation functions in the ground states are calculated respectively. Some relevant results are also discussed.Comment: Revtex, 16 pages, no figure

Clean intermittent self-catheterization as a treatment modality for urinary retention : perceptions of urologists

Purpose: Clean intermittent self-catheterization (CISC) is now considered the gold standard for the management of urinary retention. In the literature, several articles on patients' perspectives on CISC and adherence to this technique have been published. No studies have yet explored the points of view of professional caregivers, such as nurses and doctors. The aim of this study was to explore the opinions of urologists about CISC and to evaluate the need for dedicated nurses specialized in CISC through a self-administered questionnaire. Methods: A questionnaire was developed to explore the opinions of professional caregivers about self-catheterization and to evaluate the need to provide nurses with specialized education in CISC. Questionnaires were sent to 244 urologists through email. We received 101 completed questionnaires. The response rate was 41.4%. Results: Hand function, the presence or absence of tremor, and visual acuity were rated as the most important determinants for proposing CISC to a patient. Twenty-five percent of the urologists reported that financial remuneration would give them a greater incentive to propose CISC. The lack of dedicated nurses was reported by half of the urologists as a factor preventing them from proposing CISC. A meaningful number of urologists thought that patients perceive CISC as invasive and unpleasant. Although most urologists would choose CISC as a treatment option for themselves, almost 1 urologist out of 5 would prefer a permanent catheter. Conclusions: This questionnaire gave valuable insights into urologists' perceptions of CISC, and could serve as the basis for a subsequent broader international study. Further research should also focus on the opinions of nurses and other caregivers involved in incontinence management. Apart from financial remuneration, it is also clear that ensuring sufficient expertise and time for high-quality CISC care is important. This could be a potential role for dedicated nurses

Model for the environmental impact assessment of neighbourhoods

In order to move towards a sustainable built environment, modern cities need to be planned and organized differently, focussing not only on the characteristics of individual buildings but also on the relations between buildings and infrastructure works. Based on an existing Life Cycle Assessment (LCA) method for buildings, this paper proposes a model to assess the environmental impact of building clusters, together with the required road infrastructure. A hierarchic assessment structure, using the principles of the “element method for cost control” and a subdivision in different scale levels, is presented and methodological issues are discussed. To illustrate the methodology, abstract neighbourhood models are compared consisting of different dwelling types and the related amount of road infrastructure. The results revealed substantial environmental impact differences between the analysed alternatives, showing the importance of optimizing the layout and density of neighbourhoods.status: publishe

Optimizing the ensemble for equilibration in broad-histogram Monte Carlo simulations

We present an adaptive algorithm which optimizes the statistical-mechanical ensemble in a generalized broad-histogram Monte Carlo simulation to maximize the system's rate of round trips in total energy. The scaling of the mean round-trip time from the ground state to the maximum entropy state for this local-update method is found to be O([N log N]^2) for both the ferromagnetic and the fully frustrated 2D Ising model with N spins. Our new algorithm thereby substantially outperforms flat-histogram methods such as the Wang-Landau algorithm.Comment: 6 pages, 5 figure

Investigating the Energy Efficiency, Environmental and Daylighting Performance of Coated Glazing

Facades are a crucial interface between exterior and interior conditions and greatly influence the architectural quality of buildings. Glass plays an important role in the building envelope by providing daylight, views and ventilation and hence can contribute significantly to indoor environmental quality and impact occupants’ comfort and well-being. Glass also plays an important role in the energy balance of the envelope and hence in both energy loads and environmental performance of a building. In order to avoid high energy consumption, reduce environmental impact and increase the quality of the space selecting the appropriate size and type of glazing along with the orientation and shading based on the building’s function, the climatic conditions, site and occupants’ needs are a fundamental part of early design stage decisions and are difficult to change later on. The challenge is to improve the building quality by providing a balance between energy efficiency, comfort and saving resources. To reduce energy consumption through glazing taking into account the thermal insulating properties is insufficient, it is also necessary to consider the coatings impact on the physical properties of glass regarding radiation. Coatings are often used to improve the thermal insulation, solar control, acoustic insulation of glazing in order to reduce heat loss, maximize solar gains in winter and minimize it in summer and improve indoor environmental conditions. Multiple configurations of coatings are available on the market to date. The goal of our study is to determine the impact of coated glazing on the energy performance, daylighting and the environmental performance of buildings where occupants spend substantial time inside. This paper incorporates an integrated performance analysis method and presents an energy analysis, daylighting and a life cycle assessment (LCA) study of several coated glazing for patient rooms in Belgium

Wind Tunnel testing of small Vertical-Axis Wind Turbines in Turbulent Flows

Abstract This study presents an innovative wind tunnel approach to evaluate the efficiency of Vertical-Axis Wind Turbines (VAWT) in turbulent flows, to study their integration in urban environments. The first part of the research is devoted to obtaining highly-turbulent wind profiles in the wind tunnel, with the use of different configurations of square grids. A careful study and validation of this technique is done, in order to obtain uniform wind conditions with the adequate values of turbulence intensity and length scales to model the urban flows. The set-up is used to test a H-Darrieus VAWT under values of turbulence over 5%, in comparison with the operation of the turbine under free stream. The preliminary results show that high levels of turbulence do have a significant effect in turbine performance, causing a drop of power for high rotational speeds, increased vibrations in the structure and more difficult control of the rotor. More tests are advised to validate these observations, as well as to expand the study over higher values of turbulence intensity, in order to present a more detailed study with empirical conclusions

Burnout

B como burnout (ou E como esgotamento profissional) Entre os riscos psicossociais associados ao trabalho, o burnout ou esgotamento profissional, identificado inicialmente no domínio dos cuidados médicos/à pessoa, afeta doravante todas as profissões, todos os setores de atividade, todas as organizações ou instituições tanto do sector privado como do setor público. O conceito de burnout apareceu nos anos ‘70 na sequência dos trabalhos de psicanalistas e psicólogos (Freudenberger, 1974 ; Maslach..