7,744 research outputs found
Relationship between the column density distribution and evolutionary class of molecular clouds as viewed by ATLASGAL
We present the first study of the relationship between the column density
distribution of molecular clouds within nearby Galactic spiral arms and their
evolutionary status as measured from their stellar content. We analyze a sample
of 195 molecular clouds located at distances below 5.5 kpc, identified from the
ATLASGAL 870 micron data. We define three evolutionary classes within this
sample: starless clumps, star-forming clouds with associated young stellar
objects, and clouds associated with HII regions. We find that the N(H2)
probability density functions (N-PDFs) of these three classes of objects are
clearly different: the N-PDFs of starless clumps are narrowest and close to
log-normal in shape, while star-forming clouds and HII regions exhibit a
power-law shape over a wide range of column densities and log-normal-like
components only at low column densities. We use the N-PDFs to estimate the
evolutionary time-scales of the three classes of objects based on a simple
analytic model from literature. Finally, we show that the integral of the
N-PDFs, the dense gas mass fraction, depends on the total mass of the regions
as measured by ATLASGAL: more massive clouds contain greater relative amounts
of dense gas across all evolutionary classes.Comment: Accepted for publication in A&A (25th June 15) 23 pages, 12 figures.
Additional appendix figures will appear in the journal version of this pape
Strategies for building pathology reports in an urban rehabilitation process: Project of the Old City Centre of Coimbra
The increasing interest on architectural heritage associated to the recognised building value, at economic, social and cultural levels have stimulated, in the recent decades, the urban rehabilitation and renovation o several cities in Europe.
Despite the strategy or method adopted in a city renovation process, its efficiency depends mainly on: type of buildings (structural systems, construction techniques and materials); intervention level (singular buildings, groups of buildings, urban zones, etc.); and, project objective (risk assessment, decision making to support future rehabilitation projects, definition of council maintenance policies, etc.).
In what concerns large renovation programs of old city centres, choosing the most adequate approach for inspection, appraisal and diagnosis is a complex task that can determine the success or failure of the project purpose.
This paper describes the preparation phase of the inspection of 700 buildings located in the old city centre of Coimbra (Portugal), where a global renovation process is planned for the forthcoming years.
In the scope of the renovation and rehabilitation process, the city council contract a complete identification and inspection survey of the buildings, directed on three different domains: (a) architectural typologies, (b) constructive and pathological condition of buildings, and (c) socio-demographic characterisation, of this part of the city. It will be present the check-lists developed and some of the obtained results on point (b), related to roofing systems, and exterior façades.
This diagnosis procedure shows that the inspection results quality is quite dependent on the items surveyed for each construction element (roof, façade, internal members, installation efficiency), as well as on the possibility of their correlation for a single building. The adopted method has been applied on 70% of the buildings inspected within the project perimeter.
Further treatment of the inspection and appraisal data will allow the developing pathology reports and list repair actions, and estimating rehabilitation costs. It will also help to produce defect level diagrams and seismic building risk maps, but, most important, to improve and guide a renewal strategy and intervention methodology for old buildings
"Tying the Manager's Hands": How Firms can make Credible Commitments that make Opportunistic Managerial Intervention Less Likely
We discuss and empirically examine a firm-level equivalent of the ancient problem of "tying the King s hands", namely how to maximize managerial intervention for "good cause", while avoiding intervention for "bad cause". Managers may opportunistically intervene when such intervention produces private benefits. Overall firm performance is harmed as a result, because opportunistic managerial intervention harms employee motivation. The central point of the paper is that various mechanisms and factors, such as managers staking their personal reputation, employees controlling important assets, strong trade unions, corporate culture, etc. may function as constraints on managerial proclivities to opportunistically intervene. Thus, firms can make credible commitments that check managerial proclivities to opportunistically intervene. We derive 5 hypotheses from these ideas, and test them, using path-analysis, on a rich dataset, based on 329 firms in the Spanish food and electric/electronic industries.managerial opportunism; credible commitments; organizational design; transaction cost eco
Seismic vulnerability assessment of the old city centre of Seixal, Portugal
The seismic vulnerability assessment of old traditional masonry building stocks, in a seismic risk mitigation perspective, is truly essential not only for buildings with recognized historical and patrimonial value, but also, in relation to regular buildings. In this sense, this paper approaches the issue of the seismic vulnerability assessment of masonry buildings through the application of a simplified methodology to building stock of the old city centre of Seixal, Portugal. This methodology is based on a vulnerability index, suitable in the evaluation of damage and in the creation of large scale loss scenarios (economical and human). Over 500 buildings were evaluated in accordance with the referred methodology and the results obtained were then integrated into a Geographical Information System tool. The integration of this kind of vulnerability and loss results into a GIS tool allows that city councils or regional authorities make their decisions based on a global view of the site under analysis, which led to more accurate and faster decisions either in terms of risk mitigation strategies or rehabilitation plans. This tool can also assumes great importance in the construction of safety and rescue plans
Vulnerability assessment of urban building stock: a hierarchic approach
In the last decades the evaluation of the seismic risk are of rising concern, considered essential in the activity and
definition of strategy planning and urban management. The evaluation of the seismic vulnerability of the existent building stock
in the perspective of the seismic risk mitigation should not be placed only in relation to the isolated buildings of relevant
historical and cultural importance, but also, in relation to the agglomerate of buildings in urban centres. The chronological
construction process frequently results in characteristic heterogeneity of masonry and wall connection quality. In addition,
buildings do not constitute independent units given that they share the mid-walls with adjacent buildings and the façade walls are
aligned. This way, as post-seismic observations proved, buildings do not have an independent structural behaviour, but they
interact amongst themselves, mainly for horizontal actions and so the structural performance should be studied at the level of the
aggregate and not only for each isolated building. In most cases, for masonry structures there is no need for sophisticated
dynamic analyses for seismic resistance verification or vulnerability assessment. This is even more relevant when an assessment
at the level of a city centre is pursued. In this work, the results of evaluation of the vulnerability will be presented in accordance
to three proposed methodologies based on a vulnerability index that consequently allows the evaluation of damage and creation
of loss scenarios (economical and human) not only at the level of the building and its façade walls but also at the level of the
aggregates. It will be discussed and evaluated the application of the referred methodologies and its integration in an SIG
platform
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