Graded identities of block-triangular matrices

Let $F$ be an infinite field and $UT(d_1,\dots, d_n)$ be the algebra of upper block-triangular matrices over $F$. In this paper we describe a basis for the $G$-graded polynomial identities of $UT(d_1,\dots, d_n)$, with an elementary grading induced by an $n$-tuple of elements of a group $G$ such that the neutral component corresponds to the diagonal of $UT(d_1,\dots,d_n)$. In particular, we prove that the monomial identities of such algebra follow from the ones of degree up to $2n-1$. Our results generalize for infinite fields of arbitrary characteristic, previous results in the literature which were obtained for fields of characteristic zero and for particular $G$-gradings. In the characteristic zero case we also generalize results for the algebra $UT(d_1,\dots, d_n)\otimes C$ with a tensor product grading, where $C$ is a color commutative algebra generating the variety of all color commutative algebras.Comment: 24 pages and 39 references. We have added section 5 in the text about tensor products by color commutative superalgebra

Rank-1 Tensor Approximation Methods and Application to Deflation

Because of the attractiveness of the canonical polyadic (CP) tensor decomposition in various applications, several algorithms have been designed to compute it, but efficient ones are still lacking. Iterative deflation algorithms based on successive rank-1 approximations can be used to perform this task, since the latter are rather easy to compute. We first present an algebraic rank-1 approximation method that performs better than the standard higher-order singular value decomposition (HOSVD) for three-way tensors. Second, we propose a new iterative rank-1 approximation algorithm that improves any other rank-1 approximation method. Third, we describe a probabilistic framework allowing to study the convergence of deflation CP decomposition (DCPD) algorithms based on successive rank-1 approximations. A set of computer experiments then validates theoretical results and demonstrates the efficiency of DCPD algorithms compared to other ones

Tomographic Image Reconstruction of Fan-Beam Projections with Equidistant Detectors using Partially Connected Neural Networks

We present a neural network approach for tomographic imaging problem using interpolation methods and fan-beam projections. This approach uses a partially connected neural network especially assembled for solving tomographic\ud reconstruction with no need of training. We extended the calculations to perform reconstruction with interpolation and to allow tomography of fan-beam geometry. The main goal is to aggregate speed while maintaining or improving the quality of the tomographic reconstruction process

Relative returns to policy reform - evidence from controlled cross-country regressions

The authors aim at contributing to understand the dispersion of returns from policy reforms using cross-country regressions. The authors compare the"before reform"with"after reform"GDP growth outcome of countries that undertook import-liberalization and fiscal policy reforms. They survey a large sample (about 54) of developing countries over the period 1980-99. The benefits of openness to trade and fiscal prudence have been extensively identified in the growth literature, but the evidence from simple cross-section analysis can sometimes be inconclusive and remains vulnerable to criticism on estimation techniques, such as identification, endogeneity, multi-colinearity, and the quality of the data. The authors use a different analytical framework that establishes additional controls. First, they construct a counterfactual control group. These are countries that-under specific thresholds-did not introduce policy reforms under scrutiny. Second, the authors also try to use the most appropriate variable of policy reform, for example, exogenous changes in import-tariffs instead of the endogenous sum of all trade flows. Third, the authors try to base the before-after reform comparison on the most accurate date for the beginning of a policy reform period (instead of comparing averages over fixed intervals of time). Once these controls are set, they explain the difference between average GDP growth rates during the country-specific post and the pre-reform periods, relative to the average GDP growth of the relevant control group. The explanatory variables in the regressions include the standard growth-regression controls. The results are the following: 1) With a better measurement and timing of the policy reforms, the growth effect (the"returns on reform") is generally smaller than in previous papers. 2) There is evidence of contingent relationships between policy and growth, corresponding to the country's size, its export profile, and its governance. 2) Within the group of policy reformers, some countries have exhibited a relatively weaker growth response. Overall, the findings suggest that more accurate measurement and definition of the timing of reforms does not strengthen the significance of the effects of reforms on GDP growth. In fact, the effects are weaker than indicated in most cross-section studies. This suggests that the policy implications to be derived from these relationships should be treated with even more caution than previously thought.Environmental Economics&Policies,Trade Policy,Public Health Promotion,Economic Theory&Research,Health Monitoring&Evaluation,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Economic Theory&Research,Achieving Shared Growth,Environmental Economics&Policies,Trade and Regional Integration

Biomechanical models of the lower limb and pelvis, for female human gait in regular and overload conditions related to pregnancy.

Doutoramento em Motricidade Humana na especialidade de BiomecânicaA gravidez é uma fase especial da vida , considerando as adaptações morfológicas, fisiológicas, biomecânicas e hormonais vivenciadas pelas mulheres durante cerca de 40 semanas e no período pós-parto, podendo modificar o padrão de marcha e contribuir para uma sobrecarga no sistema músculo-esquelético, causando dor nos membros inferiores, bacia e zona lombar. Os objetivos do presente trabalho foram: 1) analisar a marcha de mulheres grávidas no segundo trimestre; 2) comparar as adaptações biomecânicas da marcha, entre as mulheres grávidas no segundo trimestre, mulheres não grávidas e mulheres com condições de sobrecarga artificiais; 3) analisar modelos biomecânicos com quatro set ups diferentes de análise; e, 4) analisar um modelo de contacto que determina a força vertical de reação do apoio. Os resultados demonstraram que as mulheres grávidas têm uma padrão de marcha similar ao normal. Observou-se que o ganho do peso no tronco aumenta o tempo das fases de apoio e de duplo apoio, quer nas mulheres grávidas quer nas mulheres com carga adicional. A resposta ao momento externo flexor da anca está relacionada com maior atividade dos extensores para suportar a carga anterior do tronco na direção da translação do centro de massa. Nas mulheres grávidas, o modelo universal-revolução-esférica afetou mais as variáveis cinemáticas quando comparado com o modelo de juntas com seis graus de liberdade. O modelo de contacto entre o pé e o solo, sobrestimou as forças verticais de reação. O aumento da massa do pé, devido ao inchaço consequente da gravidez, reduz a rigidez durante a fase de apoio. Os resultados do presente trabalho serão úteis para promover a investigação biomecânica do padrão de marcha durante a gravidez.FCT - Fundação para Ciência e a Tecnologi

Peri-implantite: regeneração óssea guiada vs osso pristino

Objetivo: Comparar os resultados da colocação de implantes recorrendo a técnicas de regeneração óssea guiada, com situações em que não foi feito qualquer tipo de regeneração (osso pristino). Avaliar os resultados clínicos com foco principal na prevalência de peri-implantite e no nível marginal ósseo ao longo do tempo. Métodos: Realizou-se uma pesquisa bibliográfica, com recurso à base de dados PubMed. Esta pesquisa foi sujeita à aplicação de critérios de inclusão e exclusão. Foram apenas incluídos estudos clínicos comparando os resultados de ambas as técnicas, prevalência de peri-implantite e a taxa de perda óssea marginal. Resultados: Foram obtidos e analisados doze estudos, comparando os níveis marginais ósseos em implantes colocados em locais submetidos a regeneração óssea guiada (ROG), com a colocação em osso pristino. Os parâmetros clínicos analisados foram descritos. Conclusões: Poucos são os estudos atualmente disponíveis que comparam a perda óssea marginal em técnicas de regeneração óssea com as situações em que os implantes são colocados em osso pristino.Objectives: Compare the results of the implant placement by using guided bone regeneration techniques (GBR) with cases where any type of bone regeneration was performed, ie, pristine bone. Evaluate clinical results with a main focus on the prevalene of peri-implantitis and marginal bone level over time. Methods: A bibliographic research was performed, by using the PubMed database. This research was subject to the application of inclusion and exclusion criteria. Only clinical studies comparing the results of both techniques, the prevalence of peri-implantitis and the marginal bone loss values were included. Results: Eleven studies have been obtained and analyzed, comparing bone marginal levels in implantes submitted to guided bone regeneration (ROG), with placement in pristine bone. The clinical parameters analyzed were described. Conclusions: Currently, there are few available studies comparing marginal bone loss in bone regeneration techniques with those others in which the implants are placed in pristine bone