Financing of research and development, as an important component of innovation, has attracted a renewed attention in academic financing literature. This paper examines the effect of financing constraints on R&D investments of high-tech Swedish companies over the period of 2010 to 2016. Accordingly, balance sheet data related to 49 companies, which has the smaller amount of employees in comparison with the rest of high-tech publicly listed companies is collected. Moreover, a dynamic model based on previous literature about financing constrained is developed to study the relation of both internal and external resources of financing with R&D investments of the selected companies. The result of this study shows that internal resources of financing such as cash holdings have a positive correlation with R&D investments. The coefficient of this financial variable is large enough to conclude that selected firms are financially constrained. However, based on other factors such as consideration of age and occurrence of global financial recession in the period that this study is accomplished, I concluded that dependence of companies to their internal resources for financing their R&D investments is an outcome of the characteristics of their environment.

Yau Po Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 91-92). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.3 / Chapter 2.1 --- Temporal Theories --- p.3 / Chapter 2.2 --- Related Works --- p.4 / Chapter 2.2.1 --- Consistency and Satisfiability of Timing Specifications --- p.4 / Chapter 2.2.2 --- Symbolic Constraint Satisfaction --- p.5 / Chapter 3 --- Previous Developed Work --- p.7 / Chapter 3.1 --- Previous Problem Domain --- p.7 / Chapter 3.1.1 --- Basics of MC68000 Read Cycle --- p.7 / Chapter 3.2 --- Knowledge-based System Structure --- p.9 / Chapter 3.3 --- Diagnostic Reasoning Mechanisms --- p.10 / Chapter 3.4 --- Time Range Approach --- p.11 / Chapter 3.4.1 --- Time Range Representation --- p.11 / Chapter 3.4.2 --- Constraint Satisfaction of Time Ranges --- p.12 / Chapter 3.4.3 --- Constraint Propagation of Time Ranges --- p.13 / Chapter 3.5 --- Fuzzy Time Point Approach --- p.14 / Chapter 3.5.1 --- Fuzzy Time Point Models --- p.14 / Chapter 3.5.2 --- Definition of Fuzzy Time Points --- p.15 / Chapter 3.5.3 --- Constraint Propagation of Fuzzy Time Points --- p.17 / Chapter 3.5.4 --- Constraint Satisfaction of Fuzzy Time Points --- p.18 / Chapter 4 --- The Proposed Segmented Time Range Approach --- p.20 / Chapter 4.1 --- Introduction --- p.20 / Chapter 4.2 --- The Insufficiency of The Existing Time Range Approach --- p.22 / Chapter 4.3 --- Segmented Time Range Approach --- p.23 / Chapter 4.3.1 --- The Representation --- p.23 / Chapter 4.3.2 --- Constraint Propagation and Satisfaction --- p.25 / Chapter 4.3.3 --- Contributions --- p.25 / Chapter 4.3.4 --- Limitations --- p.29 / Chapter 4.4 --- Conclusion --- p.30 / Chapter 5 --- New Problem Domain and Our New System --- p.31 / Chapter 5.1 --- Introduction --- p.31 / Chapter 5.2 --- Pentium-SRAM Interfacing Problem --- p.31 / Chapter 5.2.1 --- Asynchronous SRAM Solution --- p.32 / Chapter 5.2.2 --- Synchronous SRAM Solution --- p.33 / Chapter 5.3 --- The Knowledge Base --- p.35 / Chapter 5.4 --- Characteristics of Our New System --- p.35 / Chapter 6 --- Burst Read Cycle --- p.37 / Chapter 6.1 --- Introduction --- p.37 / Chapter 6.2 --- Asynchronous SRAM Solution --- p.37 / Chapter 6.2.1 --- Implementation --- p.39 / Chapter 6.2.2 --- Implementation Results --- p.45 / Chapter 6.3 --- Synchronous SRAM Solution --- p.48 / Chapter 6.3.1 --- Implementation --- p.49 / Chapter 6.3.2 --- Implementation Results --- p.56 / Chapter 6.4 --- Conclusion --- p.58 / Chapter 7 --- Burst Write Cycle --- p.60 / Chapter 7.1 --- Introduction --- p.60 / Chapter 7.2 --- Asynchronous SRAM Solution --- p.60 / Chapter 7.2.1 --- Implementation --- p.61 / Chapter 7.2.2 --- Implementation Results --- p.67 / Chapter 7.3 --- Synchronous SRAM Solution --- p.71 / Chapter 7.3.1 --- Implementation --- p.71 / Chapter 7.3.2 --- Implementation Results --- p.79 / Chapter 7.4 --- Conclusion --- p.82 / Chapter 8 --- Conclusion --- p.83 / Chapter 8.1 --- Summary of Achievements --- p.83 / Chapter 8.2 --- Future Development --- p.86 / Appendix Some Characteristics of Our New System --- p.89 / Bibliography --- p.91

by Choi Mo Fung Kenneth. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 105-112). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Constraint Satisfaction Problems --- p.2 / Chapter 1.2 --- Constraint Satisfaction Techniques --- p.2 / Chapter 1.3 --- Motivation of the Research --- p.4 / Chapter 1.4 --- Overview of the Thesis --- p.5 / Chapter 2 --- Related Work --- p.7 / Chapter 2.1 --- Min-conflicts Heuristic --- p.7 / Chapter 2.2 --- GSAT --- p.8 / Chapter 2.3 --- Breakout Method --- p.8 / Chapter 2.4 --- GENET --- p.9 / Chapter 2.5 --- E-GENET --- p.9 / Chapter 2.6 --- DLM --- p.10 / Chapter 2.7 --- Simulated Annealing --- p.11 / Chapter 2.8 --- Genetic Algorithms --- p.12 / Chapter 2.9 --- Tabu Search --- p.12 / Chapter 2.10 --- Integer Programming --- p.13 / Chapter 3 --- Background --- p.15 / Chapter 3.1 --- GENET --- p.15 / Chapter 3.1.1 --- Network Architecture --- p.15 / Chapter 3.1.2 --- Convergence Procedure --- p.18 / Chapter 3.2 --- Classical Optimization --- p.22 / Chapter 3.2.1 --- Optimization Problems --- p.22 / Chapter 3.2.2 --- The Lagrange Multiplier Method --- p.23 / Chapter 3.2.3 --- Saddle Point of Lagrangian Function --- p.25 / Chapter 4 --- Binary CSP's as Zero-One Integer Constrained Minimization Prob- lems --- p.27 / Chapter 4.1 --- From CSP to SAT --- p.27 / Chapter 4.2 --- From SAT to Zero-One Integer Constrained Minimization --- p.29 / Chapter 5 --- A Continuous Lagrangian Approach for Solving Binary CSP's --- p.33 / Chapter 5.1 --- From Integer Problems to Real Problems --- p.33 / Chapter 5.2 --- The Lagrange Multiplier Method --- p.36 / Chapter 5.3 --- Experiment --- p.37 / Chapter 6 --- A Discrete Lagrangian Approach for Solving Binary CSP's --- p.39 / Chapter 6.1 --- The Discrete Lagrange Multiplier Method --- p.39 / Chapter 6.2 --- Parameters of CSVC --- p.43 / Chapter 6.2.1 --- Objective Function --- p.43 / Chapter 6.2.2 --- Discrete Gradient Operator --- p.44 / Chapter 6.2.3 --- Integer Variables Initialization --- p.45 / Chapter 6.2.4 --- Lagrange Multipliers Initialization --- p.46 / Chapter 6.2.5 --- Condition for Updating Lagrange Multipliers --- p.46 / Chapter 6.3 --- A Lagrangian Reconstruction of GENET --- p.46 / Chapter 6.4 --- Experiments --- p.52 / Chapter 6.4.1 --- Evaluation of LSDL(genet) --- p.53 / Chapter 6.4.2 --- Evaluation of Various Parameters --- p.55 / Chapter 6.4.3 --- Evaluation of LSDL(max) --- p.63 / Chapter 6.5 --- Extension of LSDL --- p.66 / Chapter 6.5.1 --- Arc Consistency --- p.66 / Chapter 6.5.2 --- Lazy Arc Consistency --- p.67 / Chapter 6.5.3 --- Experiments --- p.70 / Chapter 7 --- Extending LSDL for General CSP's: Initial Results --- p.77 / Chapter 7.1 --- General CSP's as Integer Constrained Minimization Problems --- p.77 / Chapter 7.1.1 --- Formulation --- p.78 / Chapter 7.1.2 --- Incompatibility Functions --- p.79 / Chapter 7.2 --- The Discrete Lagrange Multiplier Method --- p.84 / Chapter 7.3 --- A Comparison between the Binary and the General Formulation --- p.85 / Chapter 7.4 --- Experiments --- p.87 / Chapter 7.4.1 --- The N-queens Problems --- p.89 / Chapter 7.4.2 --- The Graph-coloring Problems --- p.91 / Chapter 7.4.3 --- The Car-Sequencing Problems --- p.92 / Chapter 7.5 --- Inadequacy of the Formulation --- p.94 / Chapter 7.5.1 --- Insufficiency of the Incompatibility Functions --- p.94 / Chapter 7.5.2 --- Dynamic Illegal Constraint --- p.96 / Chapter 7.5.3 --- Experiments --- p.97 / Chapter 8 --- Concluding Remarks --- p.100 / Chapter 8.1 --- Contributions --- p.100 / Chapter 8.2 --- Discussions --- p.102 / Chapter 8.3 --- Future Work --- p.103 / Bibliography --- p.105

"We address the problem of performing complex tasks for a robot operating in changing environments. We propose two approaches to the following problem: 1) define task-specific cost functions for motion planning that represent path quality by learning from an expert's preferences and 2) using constraint-based representation of the task inside learning from demonstration paradigm. In the first approach, we generate a set of paths for a given task using a motion planner and collect data about their features (path length, distance from obstacles, etc.). We provide these paths to an expert as a set of pairwise comparisons. We then form a ranking of the paths from the expert's comparisons. This ranking is used as training data for learning algorithms, which attempt to produce a cost function that maps path feature values to a cost that is consistent with the expert's ranking. We test our method on two simulated car-maintenance tasks with the PR2 robot: removing a tire and extracting an oil filter. We found that learning methods which produce non-linear combinations of the features are better able to capture expert preferences for the tasks than methods which produce linear combinations. This result suggests that the linear combinations used in previous work on this topic may be too simple to capture the preferences of experts for complex tasks. In the second approach, we propose to introduce a constraint-based description of the task that can be used together with the motion planner to produce the trajectories. The description is automatically created from the demonstration by performing segmentation and extracting constraints from the motion. The constraints are represented with the Task Space Regions (TSR) that are extracted from the demonstration and used to produce a desired motion. To account for the parts of the motion where constraints are different a segmentation of the demonstrated motion is performed using TSRs. The proposed approach allows performing tasks on robot from human demonstration in changing environments, where obstacle distribution or poses of the objects could change between demonstration and execution. The experimental evaluation on two example motions was performed to estimate the ability of our approach to produce the desired motion and recover a demonstrated trajectory."

Made available in DSpace on 2015-03-05T18:39:04Z (GMT). No. of bitstreams: 0 Previous issue date: 30 / Nenhuma / A despeito de quaisquer outros objetivos que possam ter as organizações empresariais, a principal meta a ser alcançada é o lucro. Para que o lucro seja al-cançado as empresas lançam mão de estratégias que são traduzidas em passos tá-ticos e que seguem implícita ou explicitamente as orientações de uma teoria. Essa teoria é sempre uma projeção racional da realidade. A efetividade das estratégias adotadas é resultado, em primeiro lugar, da correspondência entre a teoria adotada e a realidade. A teoria adotada deve ser capaz de descrever a realidade, indicar meios de interferir nela e de fazer previsões dos resultados dessa interferência. Em segundo lugar, a efetividade das estratégias depende de uma formulação adequada para as condições particulares do meio onde ela será aplicada. Em terceiro lugar, a efetividade da estratégia depende de ações que transformem a realidade segundo os objetivos que se quer alcançar. O Programa Visão Viável da Teoria das Restri-ções é uma dessas estratégias para alavancar o crescime / In spite of any other tasks that commercial organizations have, the main goal to be reached is profit. In the aim to reach that, companies make use of strategies that are translated in tactical steps which follow implicitly or explicitly the orientation of a the-ory. This theory is always a rational projection of reality. The effectiveness of the adopted strategies results, in first place, from the correspondence between the adopted theory and the reality. The adopted theory must be capable to describe the reality, to indicate ways to intervene with it and to make forecasts of the results of this interference. In second place, the effectiveness of the strategies depends on an ap-propriated formularization adjusted for the particular conditions of the environment where it will be applied. In third place, the effectiveness of the strategy depends on objective actions that transform the reality accordingly to the tasks to be reached. The program Viable Vision of the Theory of Constraints is one of these strategi

Este estudo visa à criação e aplicação de um índice de acessibilidade de aeroportos que considera vários perfis de usuários (passageiro com e sem bagagem, estrangeiro, idoso e gestante, cadeirante e deficiente visual) que possuem diferentes restrições de mobilidade. O método tem início com uma seleção de indicadores que surgiram da identificação de potenciais problemas que os passageiros podem enfrentar ao acessar o aeroporto. Os indicadores são agrupados de acordo com o modo de transporte disponível para acesso ao aeroporto: táxi, carona, automóvel próprio, automóvel de aluguel, ônibus regional e ônibus especial. Em seguida os indicadores são avaliados através de pesquisas e levantamentos de campo e recebem pontuações de acordo com o seu desempenho. Por fim, os escores dos indicadores são ponderados e um valor final é calculado para cada aeroporto. Para aplicação e avaliação do índice foram selecionados, em São Paulo, os aeroportos Congonhas, Guarulhos e Viracopos; no Rio de Janeiro, Galeão e Santos Dumont, e em Brasília, o aeroporto Juscelino Kubitschek. Em uma escala que vai de zero a um, os aeroportos estudados apresentaram resultados com uma amplitude de 0,16. O maior valor encontrado foi 0,629 para o aeroporto Santos Dumont e o menor valor foi 0,469 para o aeroporto de Guarulhos. Isto evidencia que há muitos aspectos a serem melhorados no que diz respeito à acessibilidade dos aeroportos no Brasil. / This study aims to create an index of accessibility to airports that takes into account several profiles of users (passengers with and without luggage, foreigners, elderly and pregnant women, wheelchair users and visually impaired users) that have different mobility constraints. The method starts with a selection of indicators that emerged from the identification of potential problems that passengers may have when accessing the airport. The indicators are grouped according to the transportations modes available for access the airport: taxi, ride with a third party, own car, rental car, regional bus and shuttle bus. The indicators are then evaluated through surveys and field observations and scored according to their performances. Finally, the scores of the indicators are weighted and an overall score is calculated for each airport. For implementation and evaluation of the index, six important Brazilian airports were selected. In São Paulo, the airports of Congonhas, Guarulhos and Viracopos; in Rio de Janeiro, Galeão and Santos Dumont; and, in Brasília, the airport Juscelino Kubitschek. In a scale that goes from zero to one, the studied airports showed results with an amplitude of 0.16. The highest value was 0.629 for Santos Dumont airport and the lowest value was 0.469, for Guarulhos airport. The results highlight the fact that many aspects must still be improved regarding accessibility to Brazilian airports.

A escolha do modelo de referência é a principal tarefa a ser executada pelo projetista em um projeto de controle por modelo de referência. Uma má escolha do modelo de referência pode resultar em um desempenho de malha fechada que tem pouca semelhança com o especificado e a malha fechada pode até ser instável. Neste trabalho, esse problema será discutido no controle de plantas multivariáveis. O resultado experimental em uma planta de controle de nível de três tanques mostra uma aparentemente correta, ainda que ingênua, escolha do modelo de referência levando a um desempenho muito pobre em malha fechada. O problema é, então, analisado, expondo a ingenuidade do exemplo. Começa-se por reconhecer as restrições fundamentais impostas pelo sistema e, em seguida, deriva-se diretrizes gerais que respeitam essas restrições, para uma escolha eficaz do modelo de referência em sistemas multivariáveis. Também é proporcionada uma nova formulação para calcular o grau relativo mínimo de cada elemento do modelo de referência sem a necessidade de um modelo completo da planta. A aplicação destas orientações em simulações e na planta de três tanques ilustra sua eficácia. / The choice of the reference model is the main task to be performed by the designer in a model reference control design. A poor choice of the reference model may result in a closed-loop performance that bears no resemblance to the specifications and the closedloop may even be unstable. In this work we discuss this issue in the control of multivariable plants. Experimental results in a three tank level control plant show a seemingly correct, yet naive, choice of reference model leading to very poor closed-loop performance. The problem is then analyzed, exposing the naivete of the design example. We start by recognizing the fundamental constraints imposed by the system and then deriving general guidelines respecting these contraints for the effective choice of the reference model in multivariable systems. We also provide a novel formulation to compute the minimal relative degree of each element of the reference model without needing a complete model of the plant. The application of these guidelines to simulations and the three tank plant illustrates their effectiveness.

O desempenho é foco de diversos estudos atuais, a comunidade técnica está buscando melhorar os sistemas construtivos. Apesar de ser discutido há décadas, este tema foi recentemente revigorado pela elaboração e publicação da norma de desempenho NBR 15575 (ABNT, 2013a). Este documento apresenta requisitos mínimos a serem atingidos pelas edificações, bem como metodologia para a avaliação destes parâmetros. Dentre os ensaios apresentados, consta em seu anexo E um método para avaliação de vedações verticais frente a choques térmicos. Inúmeras pesquisas adotam os choques térmicos como agente de degradação, contudo não existe um consenso quanto às condições de contorno ou mesmo as dimensões dos corpos de prova. A norma brasileira recomenda que as essas possuam 120 cm de largura e altura equivalente a 1 pé direito, entretanto em determinadas situações tais dimensões inviabilizam o programa experimental, dado a falta de equipamentos deste porte. Assim, encontram-se na literatura técnica pesquisas realizadas sobre protótipos reduzidos de sistemas de vedação. Este trabalho buscou identificar a influência das dimensões e condições de contorno dos corpos de prova nos resultados obtidos em ensaios de choques térmicos Para tal, foram ensaiadas amostras em 3 tamanhos diferentes, as dimensões propostas pela NBR 15575 e duas variações reduzidas. Os corpos de prova reduzidos foram ensaiados livres e com restrições as dilatações. Todas as combinações foram sujeitas a 10 e 30 choques térmicos e as avaliações foram realizadas antes e após os ciclos. As variáveis de resposta adotadas foram a resistência à aderência, fissuração e permeabilidade, também foram mensuradas as variações lineares em momentos pré-determinados. Os choques térmicos não provocaram a perda da aderência, uma vez que as amostras apresentaram aderências estatisticamente iguais antes e após os ciclos, com exceção da amostra grande exposta a 30 choques, que teve sua aderência majorada. Apenas nas amostras grandes ocorreu alteração do índice de fissuras decorrente da exposição aos choques. Majoritariamente, a permeabilidade das amostras não foi alterada com a exposição aos choques, com exceção das amostras reduzidas livres expostas a 30 choques que apresentaram uma redução da absorção, indicando o fechamento dos poros. / Performance is the focus of many current researches, the technical community is searching to improve building systems. Despite being discussed for decades, this subject has recently been reinvigorated by the elaboration and publication of performance standard NBR 15575 (ABNT, 2013a). This document presents minimum requirements to be achieved by the buildings, as well a methodology for the evaluation of these parameters. Among the tests presented, attachment E shows a method for evaluating vertical seals against thermal shocks. Numerous researches adopt thermal shocks as a degradation agent, however, there is no consensus regarding the boundary conditions or even about the dimensions of the specimens. The Brazilian standard recommends that these specimens have at least 120 cm wide and height equivalent to room's height, however in certain situations such dimensions make the experimental program unfeasible, given the lack of equipment of this size. Thus, we find in the technical literature researches on reduced prototypes of walls. This study aimed to identify the influence of the dimensions and boundary conditions of the specimens on the results of thermal shock tests. For this, samples were tested in 3 different sizes, the dimensions proposed by NBR 15575 and two reduced variations The reduced specimens were tested without and with dilation restrictions. All combinations were subjected to 10 and 30 thermal shocks and the evaluations were performed before and after the cycles. The tests adopted to evaluate were resistance to adhesion, cracking and permeability, and linear variations were also measured at predetermined moments. The thermal shocks did not cause the loss of adhesion, since the samples had statistically equal adhesions before and after the cycles, except for the large sample exposed to 30 shocks, which had its adherence increased. Only in large samples occurred change of cracks index from exposure to shocks. The permeability of the samples was not altered with the exposure to shocks, except for the unrestricted reduced samples exposed to 30 shocks that showed a reduction of the absorption, indicating the closure of the pores.

A operação e gerência de empreendimentos mineiros são tarefas normalmente difíceis e complexas. Para otimizar toda a operação, os engenheiros precisam lidar com muitos aspectos técnicos e restrições, como a modelagem geológica, estimativa de reservas, determinação da necessidade de blendagem, projeto das cavas ótimas e operacionais, custos operacionais, questões ambientais, entre outros. Nesse sentido, o posicionamento de infraestruturas de superfície é um dos pontos críticos dentro do planejamento de mina. Aproximar as estruturas da cava, com o intuito de reduzir custos operacionais, pode interferir em eventuais expansões da cava em novos e favoráveis cenários. Nesses casos, impactos no valor presente líquido (VPL) do projeto são inevitáveis e precisam ser tratados tecnicamente, avaliando um grande número de cenários alternativos para delinear uma estratégia que incremente a lucratividade do projeto. O objetivo deste estudo é avaliar, por meio de comparações de VPL entre diferentes cenários de múltiplas restrições de superfície, sob incerteza geológica, a possibilidade de mover pilhas de estéril e outras infraestruturas de suas atuais posições e/ou definir prioridades e mensurar o impacto que cada restrição representa na lucratividade do projeto. A metodologia foi aplicada a uma mina de fosfato para ilustrar como determinar a melhor alternativa em uma perspectiva de planejamento de mina de longo prazo. Utilizando o método de cavas híbridas, aplicado ao modelo de teores simulados, foi possível identificar zonas de probabilidade de ocorrência dentro da cava matemática, o que forneceu informações cruciais para auxiliar na tomada de decisão a respeito da necessidade de relocação de estruturas. / The operation and management of mining enterprises are usually difficult and complex tasks. To optimize the entire operation the engineers must deal with several technical aspects and constraints, such as orebody modelling, reserves estimation, determination of blending necessity, optimum and operational pit designs, operational costs, environmental issues, among others. In this sense, locating surface infrastructures is one of the most critical mine planning concerns. Approximating these structures to the pit, in order to reduce the operational costs, might interfere with future pit expansions in new favorable scenarios. In such cases, impacts on project’s net present value (NPV) are inevitable and must be deal technically, evaluating several alternative scenarios to delineate a strategy to maximize profitability. The aim of this study is to evaluate, through NPV comparisons considering different scenarios with multiple constraints, under geological uncertainty, the possibility of moving waste piles and infrastructure buildings from their current position and/or defining priorities to after measuring the impact that each constraint represents on the project´s profitability. The methodology will be applied to a phosphate mine, to determine the best alternative from a long-term mine planning perspective. Using the hybrid pits method, applied to a simulated grades model, allowed the identification os occurrence probability zones within mathematical pit, providing critical data to support decision making regarding infrastructure relocation.

Les effets à court ou moyen terme de certaines expositions professionnelles biomécaniques sur lerisque de lombalgie sont reconnus. Les effets à long terme sont moins connus. Ces expositionscontribuent aux inégalités sociales de lombalgies,mais ceci est peu documenté une fois la carrièreterminée.Dans un contexte de débat sur l’âge de la retraite et la prise en compte de la pénibilité au travail,l'objectif de cette thèse était d'apporter des éléments de connaissances sur les liens entreexposition aux risques professionnels physiques et lombalgies autour de l’âge de la retraite, ainsique sur la présence d'inégalités sociale de lombalgies parmi des actifs vieillissants et des retraitéset la contribution de ces expositions à ces inégalités.Les lombalgies ayant duré plus de 30 jours au cours des 12 mois précédents ont été étudiéesdans la cohorte Gazel et l'Enquête Décennale Santé 2002 (EDS).Des arguments en faveur de la persistance des effets d'expositions physiques professionnelles audelà de la période d'activité ont été trouvés. Les données de l’EDS suggèrent que ces effetss’estomperaient au-delà d’un certain âge.Les expositions professionnelles, en particulier biomécaniques, jouent un rôle majeur dans lesinégalités sociales de lombalgies chez les hommes de la cohorte Gazel, actifs vieillissants etjeunes retraités. Par contre, de telles inégalités ne sont pas observées chez les retraités de 60 à74 ans de l'EDS.Ce travail montre l'importance en matière de lombalgies persistantes/récidivantes d'expositionsprofessionnelles a priori accessibles à une démarche de prévention, et l'intérêt de considérer leparcours professionnel dans les politiques de retraite / Some biomechanical exposures at work are recognized short term risk factors for low back pain(LBP). However, long term effects, are not well known. In addition, occupational exposures seemto contribute to social inequalities in low back pain, but this contribution is less documented forolder subjects.In many developed countries, governments are now reconsidering retirement policies. In thiscontext, the objective of this work was firstly to provide additional knowledge about the linksbetween physical exposure and LBP among aging workers and retirees, and secondly to assesssocial inequalities in LBP in this age group and the contribution of occupational factors to suchinequalities.Two populations were studied : volunteers from the Gazel cohort and participants to a Frenchnational survey on health (EDS 2002). The same definition for LBP could be used in bothpopulations : LBP which lasted more than 30 days in the previous 12 months.LBP was associated with physical occupational exposures among aging workers and youngretirees in both populations. Results were consistent with the hypothesis of a persistence of effectsonce occupational exposure has ceased, except among the oldest retirees in the EDS 2002.Biomechanical exposures played a major role in social inequalities for LBP among aging workersand young retirees in the GAZEL cohort. Such inequalities were not observed among the retireesaged 60 to 74 years (men and women) from the EDS 2002.The results highlight the importance of past occupational exposures at retirement age.