SENSITIVITY ANALYSIS OF TRACK VIBRATIONS DUE TO VERTICAL STIFFNESS VARIATION IN HIGH-SPEED RAILWAYS

High speed trains, when crossing regions with abrupt changes in vertical stiffness of the track and/or subsoil, may generate excessive ground and track vibrations. There is an urgent need for specific analyses of this problem so as to allow reliable esimates of vibration amplitude. Full understanding of these phenomena will lead to new construction solutions and mitigation of undesirable features. In this paper analytical transient solutions of dynamic response of one-dimensional systems with sudden change of foundation stiffness are derived. Results are expressed in terms of vertical displacement. Sensitivity analysis of the response amplitude is also performed. The analytical expressions presented herein, to the authors’ knowledge, have not been published yet. Although related to one-dimensional cases, they can give useful insight into the problem. Nevertheless, in order to obtain realistic response, vehicle- rail interaction cannot be omitted. Results and conclusions are confirmed using general purpose commercial software ANSYS. In conclusion, this work contributes to a better understanding of the additional vibration phenomenon due to vertical stiffness variation, permitting better control of the train velocity and optimization of the track design.

A Exploração Aeroespacial no Âmbito da Segurança e da Defesa. O Caso da China

Dissertação de Mestrado em Ciência Política e Relações Internacionais Área de Especialização: Relações Internacionais

China's space program : a new tool for PRC "soft power" in international relations?

When China launched an anti-satellite (ASAT) weapon in January 2007 to destroy one of its inactive weather satellites, most reactions from academics and U.S. space experts focused on a potential military “space race” between the United States and China. Overlooked, however, is China’s growing role as global competitor on the non-military side of space. China’s space program goes far beyond military counterspace applications and manifests manned space aspirations, including lunar exploration. Its pursuit of both commercial and scientific international space ventures constitutes a small, yet growing, percentage of the global space launch and related satellite service industry. It also highlights China’s willingness to cooperate with nations far away from Asia for political and strategic purposes. These partnerships may constitute a challenge to the United States and enhance China’s “soft power” among key American allies and even in some regions traditionally dominated by U.S. influence (e.g., Latin America and Africa). Thus, an appropriate U.S. response may not lie in a “hard power” counterspace effort but instead in a revival of U.S. space outreach of the past, as well as implementation of more business-friendly export control policies.

Relações Cabo Verde/China. Balanço dos trinta e dois anos de cooperação

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do Grau de Mestre em Ciência Política e Relações Internacionais

Independência e auto-suficiência: a política externa da República Popular da China entre 1957 e 1965

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Ciência Política e Relações Internacionais

A perspectiva portuguesa do fórum para a cooperação económica e comercial entre a China e os países de língua portuguesa

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Ciência Política e Relações Internacionais

Tinta-da-china: os preâmbulos de uma expansão

Relatório de Estágio apresentado para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Edição de Texto

Effects of Spatial Pattern of GreenSpace on Land Surface Temperature: A case study on Oasis City Aksu, northwest China

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.

O Crescimento Económico da China: implicações na região da Ásia-Pacífico

Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Ciência Política e Relações Internacionais

Structural transformation and specialization patterns in the product space: assessing China and India

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Economics from the NOVA – School of Business and Economics

Internationalization process of Água das Pedras to China

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Internationalization process: GuestCentric Systems Embracing People‟s Republic of China

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Population and railways in Portugal, 1801-1930

Portuguese historiography has mostly adopted a pessimistic view regarding the contribution of the railways to the development of country. Yet, railway access helped to increase population concentration and economic development, favoring migration into towns, the growth of pre-existing urban centers, and the emergence of new centers. But railways tended to be more beneficial to regions that were already prosperous and to aggravate the conditions unfavorable to development in areas with greater structural weaknesses.

China Hoje – Necessidades Energéticas e Relações Internacionais. As Relações com os Países de Língua Portuguesa

Tese apresentada para cumprimento dos requisitos necessários à obtenção do grau de Doutor em Relações Internacionais, Especialidade de Estudos Políticos de Área

Drivers of China's foreign direct investment into Africa

We assess the determinants of Chinese direct investment in Africa compared with those of global FDI. We find that economic size and macroeconomic stability are positively correlated with Chinese and global FDI in Africa. Institutional variables, such as accountability and rule of law, are not significant in either case and the same can be said about FDI-aid complementarities. The presence of oil is a determinant of Chinese FDI but not of global FDI into Africa. Conversely, the openness of the economy is a determinant for global FDI but not of Chinese FDI, which appears to favour closed economies possibly due to industrial organizational concerns. While these differences accord with intuition, we find no evidence for the claim that Chinese FDI in Africa is related to non-economic governance in a specific way that differs from global practice. More refined governance indicators should be used to verify whether Chinese and global FDI into Africa remain indistinguishable on this score: we plan to do this in future research.