Les flux turbulents à l’interface air-mer représentent le lien entre l’océan et l’atmosphère et jouent donc un rôle majeur dans le système climatique. Dans les modèles de climat, les processus turbulents sont des processus sous-maille, non résolus explicitement, et doivent donc être paramétrés. Ils sont estimés à partir des variables d’états atmosphériques et océaniques au moyen de modèles mathématiques qu’on nomme « paramétrisations bulk ». Ce travail de thèse a pour objectif de caractériser et comprendre les liens entre la représentation des flux turbulents à l’interface air-mer et le fonctionnement d’un modèle de climat à différentes échelles de temps dans les régions tropicales. Pour étudier ces liens, j’ai développé une stratégie de modélisation utilisant un modèle 1D atmosphérique (SCM), un modèle de circulation générale océanique (OGCM) où atmosphérique (AGCM) et un modèle couplé (GCM). L’analyse des simulations SCM permet d’étudier la réponse directe d’un modèle à la modification de la paramétrisation des flux turbulents. On montre que cette dernière régule la quantité d’eau, d’énergie et de quantité de mouvement disponible pour le système et donc son fonctionnement. Elle représente plus de 60% des différences de flux de chaleur latente simulées entre deux modèles de climat dans les périodes convectives. L’impact spatial de la paramétrisation des flux turbulents est étudié au travers des simulations AGCM. Elles mettent en évidence le lien entre la paramétrisation, son effet sur les gradients d’humidité et de température à grande échelle, et donc son influence sur la circulation atmosphérique. L’étude des simulations OGCM souligne quant à elle le rôle principal du vent pour le fonctionnement des océans tropicaux. Si le vent pilote les variations de SST dues à son impact sur la dynamique océanique et principalement sur le sous-courant équatorial, l’humidité, la température et les flux radiatifs n’influencent quant à eux que la surface océanique et sont donc d’une moindre importance. Enfin, l’analyse des simulations GCM met en évidence les rétroactions et l’ajustement engendrés par la modification des flux turbulents. Lors du couplage des deux composantes l’océan agi comme un tampon et absorbe la modification des flux turbulents ce qui entraine une modification de la SST. L’ajustement qui se produit entraine une modification des variables atmosphériques qui amène à un nouvel état d’équilibre du système. La paramétrisation des flux turbulents de surface agit au premier ordre sur l'équilibre énergétique d'un modèle couplé et peut donc amener à des climats simulés différents. Cette étude étant centrée sur les tropiques, une perspective intéressante serait d’étendre l’étude de la représentation des flux turbulents à d’autres échelles spatio-temporelles (i.e. zones extratropicales/fréquence journalière). Cela permettrait de valider le fonctionnement systématique des paramétrisations définies dans cette thèse à l’échelle globale. / The turbulent fluxes at the air-sea interface represent the link between the ocean and the atmosphere and therefore play a major role in the climate system. In climate models, turbulent processes are subgrid scale processes, not explicitly resolved, and must therefore be parameterized. They are estimated from atmospheric and oceanic state variables using mathematical models called “bulk parameterizations”. This thesis aims to characterize and understand the links between the representation of turbulent fluxes at the air-sea interface and the behavior of a climate model at different time scales in tropical regions. To study these links, I developed a modeling strategy using an atmospheric 1D model (SCM), an oceanic (OGCM) or atmospheric (AGCM) general circulation model and a coupled model (GCM). The analysis of SCM simulations allows us to study the direct response of a model to modifications of the turbulent fluxes parameterization. It is shown that it regulates the amount of water, energy and momentum available to the system and therefore its behavior. It can thus represent more than 60% of simulated latent heat flux differences between two climate models in convective periods. The spatial impact of the parameterization of turbulent fluxes is studied through AGCM simulations. They highlight the link between parameterization, its effect on large-scale moisture and temperature gradients, and thus its influence on atmospheric circulation. The study of OGCM simulations underlines the main role of the wind for the behavior of the tropical oceans. If the wind drives changes in SST due to its impact on ocean dynamics and mainly on the equatorial undercurrent, humidity, temperature and radiative flux only influence the ocean surface and are therefore of lesser importance. Finally, the analysis of GCM simulations highlights the feedbacks and the adjustment generated by the modification of turbulent fluxes. When coupling the two components, the ocean acts as a buffer and absorbs the modification of the turbulent fluxes, which leads to a modification of the SST. The adjustment that occurs causes a modification of the atmospheric variables which leads to a new state of equilibrium of the system. The parameterization of surface turbulent fluxes acts at first order on the energy equilibrium of a coupled model and can therefore lead to different simulated climate state. Since this study is focused on the tropics, an interesting perspective would be to extend the study of the turbulent fluxes representation to other spatio-temporal scales (i.e. extra-tropical areas / daily frequency). This would make it possible to validate the systematic behavior of the parameterizations defined in this thesis on a global scale.

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<p dir="ltr">Privacy serves as a crucial safeguard for personal autonomy and information, enabling control over personal data and space, fostering trust and security in society, and standing as a cornerstone of democracy by protecting against unwarranted interference. This work aims to enhance Tor, a volunteer-operated network providing privacy to over two million users, by improving its programmability, security, and user-friendliness to support wider adoption and underscore the importance of privacy in protecting individual rights in the digital age.</p><p dir="ltr">Addressing Tor's limitations in adapting to new services and threats, this thesis introduces programmable middleboxes, enabling users to execute complex functions on Tor routers to enhance anonymity, security, and performance. This architecture, called Bento, is designed to secure middleboxes from harmful functions and vice versa, making Tor more flexible and efficient.</p><p dir="ltr">Many of the attacks on Tor's anonymity occur when an adversary can intercept a user’s traffic; it is thus useful to limit how much of a user's traffic can enter potentially adversarial networks. We tackle the vulnerabilities of onion services to surveillance and censorship by proposing DeTor_OS, a Bento function enabling geographic avoidance for onion services- which is challenging since no one entity knows the full circuit between user and onion service, providing a method to circumvent adversarial regions and enhance user privacy.</p><p dir="ltr">The final part focuses on improving onion services' usability and security. Despite their importance, these services face high latency, Denial of Service (DoS) and deanonymization attacks due to their content. We introduce CenTor, a Content Delivery Network (CDN) for onion services using Bento, offering replication, load balancing, and content proximity benefits. Additionally, we enhance performance with multipath routing strategies through uTor, balancing performance and anonymity. We quantitatively analyze how geographical-awareness for an onion service CDN and its clients could impact a user’s anonymity- performance versus security tradeoff. Further, we evaluate CenTor on the live Tor network as well as large-scale Shadow simulations.</p><p dir="ltr">These contributions, requiring no changes to the Tor protocol, represent significant advancements in Tor's capabilities, performance, and defenses, demonstrating potential for immediate benefits to the Tor community.</p>

Remediation of contaminated groundwater remains a high-priority national goal in the United States. Water is essential to life, and new sources of water are needed for an expanding population. Groundwater remediation remains a significant technical challenge despite decades of research into this field. New approaches are needed to address the most severely-polluted aquifers, and cost-effective solutions are required to meet remediation objectives that protect human health and the environment. Source reduction combined with Monitored Natural Attenuation (MNA) is a remediation strategy whereby the source of contamination is aggressively treated or removed and the residual groundwater plume depletes due to natural processes in the subsurface. The USEPA requires long-term performance monitoring of groundwater at MNA sites over the remediation timeframe, which often takes decades to complete. Presently, computational tools are lacking to adequately integrate source remediation with economic models. Furthermore, no framework has been developed to highlight the tradeoff between the degree of remediation versus the level of benefit within a cost structure. Using the Natural Attenuation Software (NAS) package developed at Virginia Tech, a set of formulae have been developed for calculating the TOR for petroleum-contaminated aquifers (specifically tracking benzene and MTBE) through statistical techniques. With the knowledge of source area residual saturation, groundwater velocity, and contaminant plume source length, the time to remediate a site contaminated with either benzene or MTBE can be determined across a range of regulatory maximum contaminant levels. After developing formulae for TOR, an integrated and interactive decision tool for framing the decision analysis component of the remediation problem was developed. While MNA can be a stand-alone groundwater remediation technology, significant benefits may be realized by layering a more traditional source zone remedial technique with MNA. Excavation and soil vapor extraction when applied to the front end of a remedial action plan can decrease the amount of time to remediation and while generally more expensive than an MNA-only approach, may accrue long-term economic advantages that would otherwise be foregone. The value of these research components can be realized within the engineering and science communities, as well as through government, business and industry, and communities where groundwater contamination and remediation are of issue. Together, these tools constitute the Sâ ªEâ ªEâ ªPâ ªAGE paradigm, founded upon the concept of sound science for an environmental engineering, effectual economics, and public policy agenda. The TOR formulation simplifies the inputs necessary to determine the number of years that an MNA strategy will require before project closure and thus reduces the specialized skills and training required to perform a numerical analysis that for one set of conditions could require many hours of simulation time. The economic decision tool, that utilizes a life cycle model to evaluate a set of feasible alternatives, highlights the tradeoffs between time and economics can be realized over the lifetime of the remedial project. / Ph. D.

With the rising use of the Internet by businesses and individuals for their regular activities and transactions, there has been increased attention to user privacy and data security on the web. While the adoption of dark web networks has ensured that users' privacy and anonymity concerns are being addressed, there has also been a consequential increase in illicit activities on the internet. The dark web remains a critical area for law enforcement investigations, providing a platform for criminal activities to thrive unchecked. This study evaluates the digital traces deposited by dark web browsers on the client side of user devices, providing a deep insight into the security features of Tor and I2P and outlining the potential areas where digital artifacts can be retrieved on a Windows 11 computer. By detailing the forensic acquisition process and subsequent artifact analysis, this research aims to enhance the capabilities of digital forensic examiners in tracking and prosecuting cybercriminals, thereby contributing to the broader field of digital forensics and cybersecurity.

<p>Problem – The expansion of global trade and supply chain integration has put great emphasison logistics, particularly in the intermediary sector, freight forwarders. Whilst in developedcountries freight forwarders benefit from competitive markets and trade facilitatingpolicies, this sector in West coast Africa exhibits low logistics performance levels. Inorder to address such issues, one needs to analyse the problem and identify the causes; thisthesis focuses on identifying the bottlenecks in the freight-forwarding sector in west coastAfrica.Purpose – The main purpose of this study is to identify the bottleneck/s within thefreight-forwarding industry in west coast Africa, namely: Angola, Cameroon, DR of Congo,Gabon, and Nigeria.Method – This thesis employs a pre-study and case study method, to ensure sufficient collectionof relevant material, taking into account the lack of research in this subject. We usedthe material obtained from the interviews and the secondary source, to structure our purpose,research questions, and to define the case of our study.Results – The study concludes with a series of interesting findings; First, the activity of aFreight Forwarder depends on a series of factors that do not depend on the Freight Forwarderper se. And second, Freight Forwarders in order to accomplish their tasks, have accessto services that are shared by all providers, and that are beyond their control. To conclude,the study identifies infrastructure as a major bottleneck in the Freight Forwarding sector.</p>

The issue of this thesis concerns a selection of historical debates in which new Swedish drama is under discussion. The studied debates take place in the cultural and political fields and within the fields of theater and literature and deal with a recurring assumption in Swedish theatre history – that new Swedish drama is insufficient. The primary object of this thesis is to find explanations to: why is the Swedish new drama so often described as defective? The following questions, guiding the analysis, are: How are the crises described? What are the stakes? How has the dramatic text been influenced by being judged either as literary product or a product for the stage? How is the playwright’s role described, and perhaps changed, in the crises? The aim of the analysis is to understand how traditions and conventions are shaping the debates and contribute to perpetrate the myth of the malfunctioning Swedish new play. In a historical perspective several attempts have been made to govern new Swedish drama by legislative and political power. New Swedish drama has, for example, been viewed as a possible expression of the nation, as part of shaping the Swedish Welfare state or creating interactive communication with the audience. Despite its many uses, new Swedish drama continues to be describes as flawed. The study starts with King Gustav III:s Swedish theatre where the purpose was to produce Swedish original plays. The study ends with an analysis of a new government grant for new Swedish drama, which was installed in 1999. The chosen debates are analyzed with the help of concepts borrowed from the French sociologist Pierre Bourdieu, looking at each historical situation as a possible moment for the establishment of the field ”new Swedish drama”. The survey ends with eight interviews with playwrights, who are active today. The conditions for the new Swedish drama are the guiding line in this thesis. These conditions are found in the cultural, social and historical contexts that cooperate when a taste or convention is being shaped. They are part of the discourses in the field, where criteria for the new Swedish drama is formulated. In order to understand the significance of, for example, the expression, ”the newly written Swedish drama” research has been pursued in biographical material, historical surveys, and debates in the daily press and in professional journals. Without being a full bourdieuan analysis, the thesis is using concepts from Bourdieu. The work of British feminist theatre historian Tracy C Davis inspires the critical historic perspective.

Problem – The expansion of global trade and supply chain integration has put great emphasison logistics, particularly in the intermediary sector, freight forwarders. Whilst in developedcountries freight forwarders benefit from competitive markets and trade facilitatingpolicies, this sector in West coast Africa exhibits low logistics performance levels. Inorder to address such issues, one needs to analyse the problem and identify the causes; thisthesis focuses on identifying the bottlenecks in the freight-forwarding sector in west coastAfrica.Purpose – The main purpose of this study is to identify the bottleneck/s within thefreight-forwarding industry in west coast Africa, namely: Angola, Cameroon, DR of Congo,Gabon, and Nigeria.Method – This thesis employs a pre-study and case study method, to ensure sufficient collectionof relevant material, taking into account the lack of research in this subject. We usedthe material obtained from the interviews and the secondary source, to structure our purpose,research questions, and to define the case of our study.Results – The study concludes with a series of interesting findings; First, the activity of aFreight Forwarder depends on a series of factors that do not depend on the Freight Forwarderper se. And second, Freight Forwarders in order to accomplish their tasks, have accessto services that are shared by all providers, and that are beyond their control. To conclude,the study identifies infrastructure as a major bottleneck in the Freight Forwarding sector.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-08-22T15:35:41Z No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-09-03T16:33:20Z (GMT) No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) / Made available in DSpace on 2018-09-03T16:33:20Z (GMT). No. of bitstreams: 1 evertonluizmartinsdapaixao.pdf: 15592539 bytes, checksum: 3e2c3d43b62b9fa0edea517213c63a12 (MD5) Previous issue date: 2018-02-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Entender e controlar o movimento de parede de domínio em nanofios é extremamente im-portante para o desenvolvimento de novas tecnologias para a aplicação em dispositivos de ar-mazenamento de dados. É conhecido que defeitos como entalhes ("notches") em nanofios são úteis para fixar paredes de domínio. No entanto, a intensidade de potencial de aprisionamento gerado com esse tipo de defeito é muito forte, e para desprender a parede de domínio é ne-cessário aplicar uma densidade de corrente muito elevada. Entretanto, pode-se criar armadilhas para paredes de domínios variando localmente propriedades magnéticas do nanofio, tais como: tais como constante de troca, magnetização de saturação, constante de anisotropia, parâmetro de amortecimento de Gilbert. Definimos essas regiões como impurezas magnéticas por ter propriedades magnéticas diferentes do nanofio. Neste trabalho, realizamos simulações micro-magnéticas para investigar a dinâmica de uma parede de domínio transversal (PDT) aprisionada em um defeito magnético usando pulsos de corrente elétrica polarizada em spin. Afim de criar armadilhas de aprisionamento para a PDT, consideramos um modelo de impureza magnética variando localmente a constante de troca. Ao ajustar o potencial de interação entre impure-zas magnéticas e uma PDT, verificamos que pulsos de corrente de baixa intensidade e de curta duração são capazes de desprender a PDT. Por fim, demonstramos que é possível controlar a posição de uma PDT aplicando pulsos de corrente sequenciais em uma nanofita contendo uma distribuição linear de impurezas magnéticas igualmente espaçadas. / Understand and control the domain wall movement in nanowires is extremely important for the development of new technologies for an application in data storage devices. It is known that defect as notches in nanowires are useful to pinning domain walls. Nevertheless, the pinning potential intensity generated by this type of defect is strong, and for depinning the domain wall it is necessary to apply a high current density. However, it is possible to create traps for domains walls by locally varying magnetic properties of the nanowire, such as: the exchange constant, saturation magnetization, anisotropy constant, Gilbert damping parameters. We define those regions as magnetic impurities once their magnetic properties differ from the nanowire proper-ties. In this study, we realized micromagnetic simulations in order to investigate the dynamics of a transverse domain wall (TDW) trapped in a magnetic defect using electric current pulses of spin-polarized. In order to create traps to TDW pinning, we have modeled the magnetic impurities by varying the exchange constant locally. When we adjusted the interaction poten-tial between the magnetic impurities and the nanowire we showed that low intensity and short duration current pulses are capable of depinning the TDW. At last, we demonstrated that it is possible to control the TDW position applying sequential current pulses in a nanowire planar containing a linear distribution of magnetic impurities equally distributed.