The role of space in urban housing market

This presentation emphasizes the quantitative analysis of space in relation to hedonic housing price models. Three aspects of space will be highlighted: i) spatial heterogeneity (spatial patterns): hedonic housing amenities may be valued differently in different locations which are related to specific housing sub-markets; ii) spatial dependence (spillovers): the degree by which price increases (or decreases) in a given sub-market is influenced by other sub-markets, or by another property within the same sub-market. iii) spatial scale: the study of heterogeneity and spillovers crucially depends on the level of geographical scale at which submarkets are defined. In the literature the difficulty of defining sub-markets and understanding the relationship between them is broadly identified, and appropriate methods for defining housing markets are also presented. However, there is not a consensus on which methodologies should be used. As a contribution to understand spatial structure (heterogeneity and spillovers) in urban spaces some empirical results will be presented. A new methodology to analyse spatial spillovers [rather than an ex ante definition of a spatial weight matrix (W)] will be developed. This procedure based on non-parametric approach will be applied to a rich database. An interesting outcome of this methodology is possibility of finding meaningful values of negative interaction

Spatial Interactions in Hedonic Pricing Models:The Urban Housing Market of Aveiro, Portugal

Spatial heterogeneity, spatial dependence and spatial scale constitute key features of spatial analysis of housing markets. However, the common practice of modelling spatial dependence as being generated by spatial interactions through a known spatial weights matrix is often not satisfactory. While existing estimators of spatial weights matrices are based on repeat sales or panel data, this paper takes this approach to a cross-section setting. Specifically, based on an a priori definition of housing submarkets and the assumption of a multifactor model, we develop maximum likelihood methodology to estimate hedonic models that facilitate understanding of both spatial heterogeneity and spatial interactions. The methodology, based on statistical orthogonal factor analysis, is applied to the urban housing market of Aveiro, Portugal at two different spatial scales

Reversing the depressive dynamics of the Portuguese peripheral areas: DEMOSPIN model

Portugal is divided in two major parts: i) the coastal zone, with a higher demographic density and where the main economic activities are concentrated; ii) the periphery, where a low economic performance and a depressed demographic dynamics coexist. Economy and demography interact, reinforcing each other, and many European peripheral regions are characterised by a negative circle of cumulative causation between the economic and demographic evolution. So, policies to reverse such a dynamics must address simultaneously the demographic and economic dimensions, requiring models able to simulate this interactive process. This is the main objective of DEMOSPIN project which develops a model combining an input-output growth approach with population forecasts where migrations are driven by the positive or negative employment opportunities generated by economic growth. The model has two integrated modules: an economic component and a demographic one. The first component corresponds to regional input-output matrices, one for each NUTS III regions under study; these matrices are estimated for 2007, based on the national input-output matrix and assuming three types of products: i) regionally non-tradable products, ii) regionally tradable products and iii) fully tradable products. The regional 2007 matrices are the basis for projections up to 2030, based on a set of economic scenarios which assume several levels of exogenous demand growth and hypotheses concerning sectoral productivity growth. The use of the input-output matrices allows the estimation of employment growth rates, which in turn will feed the demographic component of the integrated model, in order to estimate net migrations for each region, age-group and sex, linking the economic and the demographic components. The demographic component estimates, in a first step, population growth for each region, age group and sex, assuming zero net migrations: they are based on mortality and fertility projections. Such estimates give us values about the supply of labour force which would be expected if the employment rates were made constant. These rates are calculated from the age groups employment distribution given by census data. The comparison between this (demographic) employment with the figures provided by the economic component is the basis for migration estimates, which are the last element of demographic projections. The net migrations estimations are calculated for each region, age group and sex, using a simultaneous estimation technique. This paper will present a detailed description of the used methodology and of the obtained results concluding with the policy guidelines which such results suggest

Efeitos da adição de níquel em ligas ferro-cromo. Parte I: propriedades mecânicas

The aim of this work was to study the influence of Ni additions on the mechanical properties of Fe-Cr alloys. For this purpose, alloys were prepared with an 18%Cr-0.01%C-0.2%Si-0.4%Mn base composition and variable Ni content (0, 10, 20, 40 and 60 weight %). The alloys were characterized by X-Ray diffraction and thermal analyses. Their hardness was determined before and after cold deformation. Tension tests were carried out at room temperature and 350ºC to verify the effect of temperature on the mechanical behavior of the alloys. The mechanical characterization aim was to use these figures to correlate mechanical properties and machinability (results originating from a parallel study).O objetivo desse trabalho é estudar a influência de adições de níquel sobre as propriedades mecânicas de ligas Fe-Cr. Para atender a esse propósito, foram preparadas diversas ligas com a composição básica 18%Cr - 0,01%C - 0,2%Si - 0,4%Mn, variando-se o teor de níquel (0, 10, 20, 40 e 60 % em peso). A caracterização das ligas foi feita por difração de raios X e análise térmica. Foi determinada a dureza das ligas no estado como recebido e após a imposição de deformação a frio. Foram realizados ensaios de tração à temperatura ambiente e a 350ºC, para verificar o efeito da temperatura sobre o comportamento mecânico das mesmas. O objetivo da caracterização mecânica das ligas é o de associar as propriedades mecânicas com as propriedades de usinabilidade, obtidas em estudo que está sendo desenvolvido em paralelo.149154Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Effect of the temperature on the structure and stability of Fe - 18 Cr - (0 to 60) Ni alloys

The material studied consists of a series of alloys with a basic composition (weight %): 18Cr - 0.01 C - 0.2 Si - 0.4 Mn, and levels of nickel varying from zero to 60%. Alloys in the annealed condition and after deformation at room temperature, 350 and 700°C to simulate the high temperatures achieved during machining were observed by optical microscopy. Equilibrium diagrams were generated by computational thermodynamics (Thermocalc) to predict the behavior of these alloys in a wide range of temperatures. The theoretical thermodynamic equilibrium conditions of the system were compared to the observed microstructures, indicating that the CFC phase in alloys with nickel content between 10% and 30% is, in fact, in a metastable condition at room temperature. Martensitic transformation induced by cold work in the alloy with 10% Ni was observed, validating the computer calculations.O material estudado consiste de uma série de ligas com composição base (% em peso) de 18Cr - 0,01C - 0,2Si - 0,4Mn e teores de níquel variando de zero a 60%. Analisou-se a microestrutura por microscopia ótica das ligas no estado recozido e após deformação à temperatura ambiente, 350 e 700ºC, de modo a simular as altas temperaturas alcançadas na usinagem dessas ligas. Foram também gerados diagramas de equilíbrio das ligas por termodinâmica computacional (Thermocalc) para se prever o comportamento dessas ligas em uma larga faixa de temperaturas. As condições teóricas de equilíbrio termodinâmico do sistema foram comparadas às microestruturas observadas, indicando que a fase CFC nas ligas com teor de níquel entre 10% e 30% em peso está, na realidade, em uma condição metaestável à temperatura ambiente. Foi observada transformação martensítica induzida por trabalho a frio na liga com 10%Ni, validando os cálculos computacionais.455

Effect of temperature and nickel content on the mechanical properties and their correlation with the machinability of Fe-18Cr-Ni alloys

Tensile tests were carried out at room temperature in Fe-18% Cr alloys, with nickel content varying between zero and 60%, and the properties obtained were correlated with the results of machinability previously obtained by the group. The alloys were also tested at 350 and 700°C in order to obtain these properties in the range of temperature compatible with the machining process. The ferritic alloy presented lower elongation and UTS (ultimate tensile strength) than austenitic alloys at room temperature and 350°C, which explains why, in the machining process, the ferritic alloy shows much greater tool life if compared to austenitic alloys (100 against 20 to 50 minutes, respectively). In the test at 350°C, the temperature reached during machining, the increase in nickel content increased the UTS of austenitic alloys, hampering the machining, and also elevated the ductility (elongation) that produces a higher volume of material adhered on the tool. This higher adhesion capacity, allied to a higher mechanical strength, explains the increase of tool wear as a function of increasing nickel content in the alloy with a consequent reduction in the life of the tool.Foram realizados ensaios de tração na temperatura ambiente em ligas Fe-18%Cr, com teor de níquel variando entre zero e 60% e correlacionaram-se as propriedades obtidas com os resultados de usinabilidade obtidos anteriormente pelo grupo. As ligas foram ensaiadas, também, a 350 e 700ºC, de modo a determinar suas propriedades, na faixa de temperatura alcançada, no local da usinagem. A liga ferrítica apresentou alongamento e limite de resistência menores que as ligas austeníticas, tanto à temperatura ambiente, como a 350°C, o que explica porque, na usinagem dessas ligas, a vida da ferramenta foi muito maior que nas ligas austeníticas (100 contra 20 a 50 minutos, respectivamente). No ensaio a 350ºC, temperatura atingida pela peça na região de usinagem, o aumento do teor de níquel elevou, tanto o limite de resistência das ligas austeníticas, o que dificulta a usinagem, como, também, elevou a ductilidade (alongamento), facilitando a adesão da liga sobre a ferramenta de corte e exigindo maior esforço na usinagem, com conseqüente redução da vida da ferramenta.18519