Multi-objective optimization scheme for static and dynamic multicast flows

Muchas de las nuevas aplicaciones emergentes de Internet tales como TV sobre Internet, Radio sobre Internet,Video Streamming multi-punto, entre otras, necesitan los siguientes requerimientos de recursos: ancho de banda consumido, retardo extremo-a-extremo, tasa de paquetes perdidos, etc. Por lo anterior, es necesario formular una propuesta que especifique y provea para este tipo de aplicaciones los recursos necesarios para su buen funcionamiento. En esta tesis, proponemos un esquema de ingeniería de tráfico multi-objetivo a través del uso de diferentes árboles de distribución para muchos flujos multicast. En este caso, estamos usando la aproximación de múltiples caminos para cada nodo egreso y de esta forma obtener la aproximación de múltiples árboles y a través de esta forma crear diferentes árboles multicast. Sin embargo, nuestra propuesta resuelve la fracción de la división del tráfico a través de múltiples árboles. La propuesta puede ser aplicada en redes MPLS estableciendo rutas explícitas en eventos multicast. En primera instancia, el objetivo es combinar los siguientes objetivos ponderados dentro de una métrica agregada: máxima utilización de los enlaces, cantidad de saltos, el ancho de banda total consumido y el retardo total extremo-a-extremo. Nosotros hemos formulado esta función multi-objetivo (modelo MHDB-S) y los resultados obtenidos muestran que varios objetivos ponderados son reducidos y la máxima utilización de los enlaces es minimizada. El problema es NP-duro, por lo tanto, un algoritmo es propuesto para optimizar los diferentes objetivos. El comportamiento que obtuvimos usando este algoritmo es similar al que obtuvimos con el modelo. Normalmente, durante la transmisión multicast los nodos egresos pueden salir o entrar del árbol y por esta razón en esta tesis proponemos un esquema de ingeniería de tráfico multi-objetivo usando diferentes árboles para grupos multicast dinámicos. (en el cual los nodos egresos pueden cambiar durante el tiempo de vida de la conexión). Si un árbol multicast es recomputado desde el principio, esto podría consumir un tiempo considerable de CPU y además todas las comuicaciones que están usando el árbol multicast serán temporalmente interrumpida. Para aliviar estos inconvenientes, proponemos un modelo de optimización (modelo dinámico MHDB-D) que utilice los árboles multicast previamente computados (modelo estático MHDB-S) adicionando nuevos nodos egreso. Usando el método de la suma ponderada para resolver el modelo analítico, no necesariamente es correcto, porque es posible tener un espacio de solución no convexo y por esta razón algunas soluciones pueden no ser encontradas. Adicionalmente, otros tipos de objetivos fueron encontrados en diferentes trabajos de investigación. Por las razones mencionadas anteriormente, un nuevo modelo llamado GMM es propuesto y para dar solución a este problema un nuevo algoritmo usando Algoritmos Evolutivos Multi-Objetivos es propuesto. Este algoritmo esta inspirado por el algoritmo Strength Pareto Evolutionary Algorithm (SPEA). Para dar una solución al caso dinámico con este modelo generalizado, nosotros hemos propuesto un nuevo modelo dinámico y una solución computacional usando Breadth First Search (BFS) probabilístico. Finalmente, para evaluar nuestro esquema de optimización propuesto, ejecutamos diferentes pruebas y simulaciones. Las principales contribuciones de esta tesis son la taxonomía, los modelos de optimización multi-objetivo para los casos estático y dinámico en transmisiones multicast (MHDB-S y MHDB-D), los algoritmos para dar solución computacional a los modelos. Finalmente, los modelos generalizados también para los casos estático y dinámico (GMM y GMM Dinámico) y las propuestas computacionales para dar slución usando MOEA y BFS probabilístico.

Trabalho produtivo e acumulação de capital: uma perspectiva sociopolítica

Esta investigação visa analisar a relação entre trabalho produtivo e acumulação de capital desde a época do mercantilismo. Parte da hipótese de que não é a forma material ou imaterial do produto do trabalho que determina se este é ou não produtivo, mas a função que ele desempenha no processo global de acumulação de capital. Concebemos o capital como uma relação de produção em que trabalhadores assalariados produzem uma mais-valia para os proprietários dos meios de produção que não se limitam a consumi-la improdutivamente, mas a reinvesti-la periodicamente no processo produtivo. Pretendemos demonstrar que com o desenvolvimento do capitalismo a esfera do trabalho produtivo se alarga para além do processo de produção material porque a ciência se transforma numa força produtiva e, por conseguinte, num instrumento de valorização do capital. Além do mais, a revolução cibernética converte uma parte crescente do trabalho intelectual em trabalho produtivo. No entanto, como a desigualdade na repartição de rendimentos não parou de aumentar desde os anos oitenta do século passado, estas transformações tecnológicas não contribuíram para a melhoria das condições de existência de todos mas apenas para o incremento do sobretrabalho que sustenta a acumulação de capital.

Technological change and the challenges for regional development: building social capital in less-favoured regions

The relevance of regional policy for less favoured regions (LFRs) reveals itself when policy-makers must reconcile competitiveness with social cohesion through the adaptation of competition or innovation policies. The vast literature in this area generally builds on an overarching concept of ‘social capital’ as the necessary relational infrastructure for collective action diversification and policy integration, in a context much influenced by a dynamic of industrial change and a necessary balance between the creation and diffusion of ‘knowledge’ through learning. This relational infrastructure or ‘social capital’ is centred on people’s willingness to cooperate and ‘envision’ futures as a result of “social organization, such as networks, norms and trust that facilitate action and cooperation for mutual benefit” (Putnam, 1993: 35). Advocates of this interpretation of ‘social capital’ have adopted the ‘new growth’ thinking behind ‘systems of innovation’ and ‘competence building’, arguing that networks have the potential to make both public administration and markets more effective as well as ‘learning’ trajectories more inclusive of the development of society as a whole. This essay aims to better understand the role of ‘social capital’ in the production and reproduction of uneven regional development patterns, and to critically assess the limits of a ‘systems concept’ and an institution-centred approach to comparative studies of regional innovation. These aims are discussed in light of the following two assertions: i) learning behaviour, from an economic point of view, has its determinants, and ii) the positive economic outcomes of ‘social capital’ cannot be taken as a given. It is suggested that an agent-centred approach to comparative research best addresses the ‘learning’ determinants and the consequences of social networks on regional development patterns. A brief discussion of the current debate on innovation surveys has been provided to illustrate this point.

Dynamic capabilities in a sixth generation family firm: entrepreneurship and the Bibby Line

In this paper we draw on the theory of dynamic capabilities to examine development of the only surviving family-owned Liverpool shipping company. The Bibby Line was founded in 1807 to take advantage of the growing sea-trade based in Liverpool. The company remained in shipping until the mid-1960s, when a series of external crises led the owner, Derek Bibby, to begin a process of diversification. In the last 50 years, the Bibby Line has grown into a £1bn business with interests in retail, distribution and financial services as well as a continuing commitment to shipping. Our intention is to demonstrate how multigenerational ownership contributes to the creation of dynamic capabilities in family firms. The distinctive nature of Bibby as a long-standing family business is related to unique assets such as patient capital, flexible governance structures as well as the ability to mobilise social and human capital.

The career competencies of self-initiated and assigned expatriates: assessing the development of career capital over time

Building on a modern careers approach, we assess the effects of working abroad on individuals’ career capital. Given the dearth of longitudinal studies, we return to a sample of economics graduates in Finland eight years later. We measure changes in three dimensions of career capital; ‘knowing how’, ‘knowing whom’, ‘knowing why’ and find that company assigned expatriates learn more than self-initiated expatriates. All three career capital areas benefit from international experience and all are increasingly valued over time. Based on our findings we conclude that a dynamic notion of career capital acquisition and use is needed. Managerial implications include the need for a wider view of talent management for international businesses.

Solving the non-convexity problem in some shopping-time and human-capital models

Several works in the shopping-time and in the human-capital literature, due to the nonconcavity of the underlying Hamiltonian, use Örst-order conditions in dynamic optimization to characterize necessity, but not su¢ ciency, in intertemporal problems. In this work I choose one paper in each one of these two areas and show that optimality can be characterized by means of a simple aplication of Arrowís (1968) su¢ ciency theorem.

Custos de ajustamento e a dinâmica da estrutura de capital em empresas brasileiras

Diversos estudos de Finanças Corporativas consideram os custos associados aos ajustes da estrutura de capital das empresas irrelevantes tanto na forma quanto em magnitude. Este estudo analisou empiricamente a influência dos custos de ajustamento na dinâmica dos ajustes da estrutura de capital de empresas brasileiras de capital aberto no período de 1999 a 2007. A alavancagem foi abordada sob três diferentes cenários, considerando a presença de custos fixos, custos proporcionais e por uma composição de custos fixos e proporcionais através de simulações utilizando um modelo reduzido da estrutura de capital. Em seguida a análise não paramétrica da amostra revelou que as empresas apresentam um comportamento dinâmico em suas decisões de financiamento para o ajuste da estruturas de capital, mas que não se revelou contínuo. A utilização de um modelo de duration mostrou-se adequado para mensurar o intervalo de tempo entre os ajustes da estrutura de capital das empresas. Os resultados são extremamente relevantes e suportam a teoria de um comportamento de rebalanceamento dinâmico pelas empresas de suas estruturas de capital em torno de um intervalo ótimo. Entretanto os ajustes não ocorrem de forma imediata e a persistência de choques à estrutura de capital deve-se em sua maior parte aos custos associados aos ajustes do que a uma possível indiferença à estrutura de capital. . Este trabalho constitui-se como pioneiro no mercado brasileiro acerca dos custos de ajustamento da estrutura de capital e abre espaço para a discussão do comportamento ótimo em torno da estrutura de capital de empresas nacionais.

Microeconomic instability and children's human capital accumulation: the effects of idiosyncratic shocks to father's income on child labor, school drop-outs and repetition rates in Brazil

This paper evaluates the long-run effects of economic instability. In particular, we study the impact of idiosyncratic shocks to father’s income on children’s human capital accumulation variables such as school drop-outs, repetition rates and domestic and non-domestic labor. Although, the problem of child labor in Brazil has declined greatly during the last decade, the number of children working is still substantial. The low levels of educational attainment in Brazil are also a main cause for concern. The large rotating panel data set used allows for the estimation of the impacts of changes in occupational and income status of fathers on changes in his child’s time allocation circumstances. The empirical analysis is restricted to families with fathers, mothers and at least one child between 10 and 15 years of age in the main Brazilian metropolitan areas during the 1982-1999 period. We perform logistic regressions controlling for child characteristics (gender, age, if he/she is behind in school for age), parents characteristics (grade attainment and income) and time and location variables. The main variables analyzed are dynamic proxies of impulses and responses, namely: shocks to household head’s income and unemployment status, on the one hand and child’s probability of dropping out of school, of repeating a grade and of start working, on the other. The findings suggest that father’s income has a significant positive correlation with child’s dropping out of school and of repeating a grade. The findings do not suggest a significant relationship between a father’s becoming unemployed and a child entering the non-domestic labor market. However, the results demonstrate a significant positive relationship between a father becoming unemployed and a child beginning to work in domestic labor. There was also a positive correlation between father becoming unemployed and a child dropping out and repeating a grade. Both gender and age were highly significant with boys and older children being more likely to work, drop-out and repeat grades.

Governança corporativa e a velocidade de ajuste da estrutura de capital das empresas brasileiras

O presente trabalho tem por objetivo analisar a relação entre governança corporativa e a velocidade de ajuste para a estrutura ótima de capital das empresas listadas na BM&FBovespa entre 1998 e 2009, sob o prisma da teoria do Trade-Off Dinâmico. O nível de governança corporativa foi medido com base nos segmentos de listagem diferenciada da BM&FBovespa, tendo sido utilizadas algumas variáveis de controle para a determinação da alavancagem ótima. Os resultados indicam que empresas com melhor governança têm menor grau de alavancagem e se ajustam mais rapidamente em direção ao ótimo.

Health and development with imperfect capital markets

This paper investigates the interaction between investment in education and in life-expanding investments, in a simple two-period model in which individuaIs are liquidity constrained in the first period. We show that under low leveIs of health and capital, investments in human capital and in health are complement: since the probability of survival is small, there is littIe incentive to invest in human capital; therefore the return on health investment is also low. This reinforcing effect does not hold for higher leveIs of health or capital, and the two investments become substitute. This property has many consequences. First, subsidizing health care may have dramatically different effects on private investment in human capital, depending on the initial leveI of health and capital. Second, the assumption that mortality is endogenous induces an increase in inequality of income: since health investment is a normal good, the return on education is also lower for poor individuaIs. Third,in a non-overlapping generation madel with non-altruistic agents, the hea1th leveI of the population has strong consequences on growth. For a very low leveI of hea1th, mortality is too high for the investment on education to be profitable. For a higher, but still low, levei of hea1th the economy grows on1y if the initial stock of capital is high enough; bad health and low capital create a poverty trapo Fourth, we compare redistributive income policies versus public hea1th measures. Redistributing income reduces both static and dynamic inequality, but slows growth. In contrast, a paternalistic health policy that forces the poor to invest in hea1th reduces dynamic inequality and may foster growth.

Is there a general criterion for dynamic efficiency?

This paper analyses an overlapping generations model with absolute bequest motive. It is shown that the widely accepted criterion to verify dynamic efficiency does not apply to this case. In our model the social planner maximizes welfare by choosing a capital stock larger than the golden role and a real rate of interest smaller than the rate of growth of the economy.

Elasticity of substitution between capital and labor: a panel data approach

This paper estimates the elasticity of substitution of an aggregate production function. The estimating equation is derived from the steady state of a neoclassical growth model. The data comes from the PWT in which different countries face different relative prices of the investment good and exhibit different investment-output ratios. Then, using this variation we estimate the elasticity of substitution. The novelty of our approach is that we use dynamic panel data techniques, which allow us to distinguish between the short and the long run elasticity and handle a host of econometric and substantive issues. In particular we accommodate the possibility that different countries have different total factor productivities and other country specific effects and that such effects are correlated with the regressors. We also accommodate the possibility that the regressors are correlated with the error terms and that shocks to regressors are manifested in future periods. Taking all this into account our estimation resuIts suggest that the Iong run eIasticity of substitution is 0.7, which is Iower than the eIasticity that had been used in previous macro-deveIopment exercises. We show that this lower eIasticity reinforces the power of the neoclassical mo deI to expIain income differences across countries as coming from differential distortions.

Toward a venture capital-backed entrepreneurship model in Brazil

It is well documented venture capital‟s positive impact on creation and development of highly successful innovative companies worldwide. Venture capital not only provides funding to startups and SMEs (small and medium enterprises) that usually have financing gap, especially in emerging markets, but also brings a whole package of valuable resources that reduces companies‟ mortality rates. Using quantitative data obtained from an empirical survey as background, this paper discusses the role of venture capital in the success of innovative startups and SMEs, and it examines if, and to what extent, venture capitalists are supporting the entrepreneurial activity in Brazil. I focused on the portfolio companies analyzes and confirmed the hypothesis that the venture capital industry has been supporting entrepreneurship in Brazil. Second, I identified an important evidence of a venture capital‟s positive impact on economic activity, especially the capital market. Third, it became clear that venture capital-back entrepreneurship is highly concentrated in the Southeast region. And fourth, I identified that private equity expansion is also playing a key role on that dynamics. As consequence, I conclude that the venture capital (and private equity) industry has been very important to build an enormously dynamic and strong local entrepreneurial economy. Its committed capital grew 50% per year between 2005 and 2008 to achieve US$27 billion, which invested US$ 11 billion, which employs 1,400 professionals (75% with post-graduate degrees) and maintains 482 portfolio companies, mostly SMEs. In addition, venture capital-backed companies represented one third of the IPOs that occurred in Brazil between 2004 and 2008 (approximately US$15 billion).

Fostering innovation and entrepreneurship in Brazil through private equity and venture capital public policies

It is well documented the positive impact of the Private Equity and Venture Capital (PE/VC) industry on the creation and development of highly successful innovative companies in a few countries, mainly in the United States. PE/VC firms provide not only capital to startups and small and medium enterprises (SMEs) that usually have financing gap, especially in emerging markets, but also strategic resources that enable these enterprises to commercialize innovation. As consequence, government incentive and nurture of local PE/VC industries would be expected in emerging economies due to innovation‟s importance to economic growth. This paper aims to identify if the Brazilian government has supported local PE/VC industry throughout the years in order to foster favorable conditions to creating and developing successful innovative businesses. It also analyzes Brazil‟s main public policies towards PE/VC and if they encompass all the three stages of its cycle – fundraising, investing and exiting. I conducted an empirical research which collected primary data from a sample of 127 PE/VC firms (90% of the population) operating in Brazil as of June, 2008. All firms answered a webbased questionnaire that collected quantitative data regarding their investment vehicles, portfolio companies, investments and exits. I compared the data obtained from the survey with the main local governmental PE/VC support programs. First, I confirmed the hypothesis that the Brazilian government has been using the PE/VC industry as a public policy towards entrepreneurship and innovation. Second, I identified that although PE/VC public policies in Brazil are mostly concentrated in fundraising phase, they have been able to positively impact the whole cycle. Third, it became clear that the Brazilian government became more concerned about Seed and Venture Capital (VC) Early stages due to their importance to the entire PE/VC value chain. As consequence, I conclude that those public policies have been very important to build a dynamic and strong local PE/VC industry, whose committed capital grew 50% per year between 2005 and 2008 to achieve US$27 billion, which invested US$ 11 billion, which employs 1,400 professionals (75% with postgraduate degrees) and maintains 482 portfolio companies, mostly SMEs. In addition, PE/VCbacked companies represented one third of the Initial Public Offerings (IPOs) that occurred in Brazil between 2004 and 2008 (approximately US$15 billion).