The effects of tax incentives for small firms on employment levels

This paper will examine the effects of tax incentives for small businesseson employment level evaluating a program with this purpose implemented in Brazil in the 1990s. We first develop a theoretical framework which guides both the de nition of the parameters of interest and their identi cation. Selection problems both into the treatment group and into the data sampleare tackled by combining fi xed effects methods and regression discontinuity design on alternative sub-samples of a longitudinal database of manufacturing fi rms. The results show that on the one hand the size composition of thetreated fi rms may be changed due to the survival of some smaller fi rms that would have exited had it not been eligible to the program. On the other hand, the treated fi rms who do not depend on the program to survive do employ more workers.

Electronic states and transport properties in the Kronig-Penney model with correlated compositional and structural disorder

We study the structure of the electronic states and the transport properties of a Kronig-Penney model with weak compositional and structural disorder. Using a perturbative approach we obtain an analytical expression for the localisation length which is valid for disorder with arbitrary correlations. We show how to generate disorder with self- and cross-correlations and we analyse both the known delocalisation effects of the long-range self-correlations and new effects produced by cross-correlations. We finally discuss how both kinds of correlations alter the transport properties in Kronig-Penney models of finite size.Comment: 23 pages, 5 figure

A new data reduction scheme to obtain the mode II fracture properties of Pinus Pinaster wood

In this work a numerical study of the End Notched Flexure (ENF) specimen was performed in order to obtain the mode II critical strain energy released rate (GIIc) of a Pinus pinaster wood in the RL crack propagation system. The analysis included interface finite elements and a progressive damage model based on indirect use of Fracture Mechanics. The difficulties in monitoring the crack length during an experimental ENF test and the inconvenience of performing separate tests in order to obtain the elastic properties are well known. To avoid these problems, a new data reduction scheme based on the equivalent crack concept was proposed and validated. This new data reduction scheme, the Compliance-Based Beam Method (CBBM), does not require crack measurements during ENF tests and additional tests to obtain elastic properties.FCT - POCTI/EME/45573/200

Finite element analysis of the ECT test on mode III interlaminar fracture of carbon-epoxy composite laminates

In this work a parametric study of the Edge Crack Torsion (ECT) specimen was performed in order to maximize the mode III component (GIII) of the strain energy release rate for carbon-epoxy laminates. A three-dimensional finite element analysis of the ECT test was conducted considering a [90/0/(+45/-45)2/(-45/+45)2/0/90]S lay-up. The main objective was to define an adequate geometry to obtain an almost pure mode III at crack front. The geometrical parameters studied were specimen dimensions, distance between pins and size of the initial crack. The numerical results demonstrated that the ratio between the specimen length and the initial crack length had a significant effect on the strain energy release rate distributions. In almost all of the tested configurations, a mode II component occurred near the edges but it did not interfere significantly with the dominant mode III state.FCT - POCTI/EME/45573/200

Homotopy Type Theory in Lean

We discuss the homotopy type theory library in the Lean proof assistant. The library is especially geared toward synthetic homotopy theory. Of particular interest is the use of just a few primitive notions of higher inductive types, namely quotients and truncations, and the use of cubical methods.Comment: 17 pages, accepted for ITP 201