Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto, Instituto Superior Técnico. Universidade de Lisboa, Faculdade de Medicina. Universidade do Porto. 2008

Tese de doutoramento. Ciências de Engenharia. Faculdade de Engenharia. Universidade do Porto. 2004

Tese de doutoramento. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 2009

No description available.

Tese de mestrado. Engenharia do Ambiente. Faculdade de Engenharia. Universidade do Porto. 1998

<p>Denial of Service and the Distributed Denial of Service Attacks have recently emerged as one of the most newsworthy, if not the greatest, weaknesses of the Internet. This paper attempt to explain how they work, why they are hard to combat today, and what will need to happen if they are to be brought under control. It is divided into eight sections. The first is an overview of the current situation and also brief explanatory of the rest of the chapters being covered. The second is a detailed description of exactly how this attack works, and why it is hard to cope with today; of necessity it includes a description of how the Internet works today. The third section is totally about the different attacks in recent years and how they affected the people or the bigorganizations. The fourth section describes the short-term prospects, the tools which are used to rectify these attacks. The fifth is problems being faced with an explanatory of the percentage of attack in recent years and comparing the problems. The sixth is what can be done today to help alleviate this problem. The seventh section describes the legal actions and also legal actions that can be followed against the attack by the victim; and the eighth section describes the long-term picture, what will change to bring this class of problem under control, if not eliminate it entirely. And finally there are some appendices: a bibliography, giving references to original research work and announcements; a brief article on securing servers; and acknowledgments for the many people who helped make this paper possible.</p>

Denial of Service and the Distributed Denial of Service Attacks have recently emerged as one of the most newsworthy, if not the greatest, weaknesses of the Internet. This paper attempt to explain how they work, why they are hard to combat today, and what will need to happen if they are to be brought under control. It is divided into eight sections. The first is an overview of the current situation and also brief explanatory of the rest of the chapters being covered. The second is a detailed description of exactly how this attack works, and why it is hard to cope with today; of necessity it includes a description of how the Internet works today. The third section is totally about the different attacks in recent years and how they affected the people or the bigorganizations. The fourth section describes the short-term prospects, the tools which are used to rectify these attacks. The fifth is problems being faced with an explanatory of the percentage of attack in recent years and comparing the problems. The sixth is what can be done today to help alleviate this problem. The seventh section describes the legal actions and also legal actions that can be followed against the attack by the victim; and the eighth section describes the long-term picture, what will change to bring this class of problem under control, if not eliminate it entirely. And finally there are some appendices: a bibliography, giving references to original research work and announcements; a brief article on securing servers; and acknowledgments for the many people who helped make this paper possible.

Bakgrund: Skolios är en ryggradskrökning och det är viktigt att hitta orsaken då behandlingen är beroende av skoliosens utseende. Röntgenundersökningar bör endast användas när behandling av skoliosen övervägs då onödiga stråldoser bör undvikas. Ju mer strålning en patient får på sig desto större risk för cellskada. Röntgensjuksköterskor bör alltid arbeta för att försöka minimera stråldosen vid röntgenundersökningar. Syfte: Syftet med aktuell studie var att jämföra olika skoliosundersökningar på två röntgenavdelningar för att fastställa om någon skillnad i stråldos uppstod mellan dem. Frågeställning: Är det någon stråldosskillnad mellan en konventionell skoliosundersökning och en skoliosundersökning med genomlysningsutrustning? Metod: I ett konventionellt undersökningsrum och i ett genomlysningsrum tillfrågades 30 patienter om längd samt vikt och undersökningens Dos Area Produkt (DAP)-värde dokumenterades. Patienternas DAP-värden jämfördes efter Body Mass Index (BMI). Medelvärdet av den effektiva dosen räknades ut vid båda modaliteterna. Båda undersökningarna utfördes även på ett Aldersonfantom. Undersökningarna utfördes enligt sjukhusens metodböcker. Hela DAP-värdet skrevs ner. Även vid fantomundersökningarna räknades effektiva dosen ut. Resultat: Konventionella undersökningsutrustningen gav mer än fyra gånger så höga stråldoser än genomlysningsutrustningarna. Både vid patient- och fantomundersökningarna visades stråldosskillnad mellan de två modaliteterna och vid patientundersökningen ökade skillnaden med ökat BMI. Effektiva dosen för patientundersökningarna var tre gånger så hög med konventionell undersökningsutrustning. Slutsats: Undersökning med genomlysningsutrustning gav en avsevärt lägre stråldos än konventionell undersökningsutrustning dock går det inte att säga att den är optimal då bildkvaliteten inte undersökts.

The Denial-of-Service (DoS) attacks with the source IP address spoofing techniques has become a major threat to the Internet. An intrusion detection system is often used to detect DoS attacks and to coordinate with the firewall to block them. However, DoS attack packets consume and may exhaust all the resources, causing degrading network performance or, even worse, network breakdown. A proactive approach to DoS attacks is allocating the original attack host(s) issuing the attacks and stopping the malicious traffic, instead of wasting resources on the attack traffic. In this research, an ant-based traceback approach is proposed to identify the DoS attack origin. Instead of creating a new type or function needed by the router or proceeding the high volume, find-grained data, the proposed traceback approach uses flow level information to spot the origin of a DoS attack. Two characteristics of ant algorithm, quick convergence and heuristic, are adopted in the proposed approach on finding the DoS attack path. Quick convergence efficiently finds out the origin of a DoS attack; heuristic gives the solution even though partial flow information is provided by the network. The proposed method is validated and evaluated through the preliminary experiments and simulations generating various network environments by network simulator, NS-2. The simulation results show that the proposed method can successfully and efficiently find the DoS attack path in various simulated network environments, with full and partial flow information provided by the network.

No description available.