2,452 research outputs found
Configuration Management of Distributed Systems over Unreliable and Hostile Networks
Economic incentives of large criminal profits and the threat of legal consequences have pushed criminals to continuously improve their malware, especially command and control channels. This thesis applied concepts from successful malware command and control to explore the survivability and resilience of benign configuration management systems.
This work expands on existing stage models of malware life cycle to contribute a new model for identifying malware concepts applicable to benign configuration management. The Hidden Master architecture is a contribution to master-agent network communication. In the Hidden Master architecture, communication between master and agent is asynchronous and can operate trough intermediate nodes. This protects the master secret key, which gives full control of all computers participating in configuration management. Multiple improvements to idempotent configuration were proposed, including the definition of the minimal base resource dependency model, simplified resource revalidation and the use of imperative general purpose language for defining idempotent configuration.
Following the constructive research approach, the improvements to configuration management were designed into two prototypes. This allowed validation in laboratory testing, in two case studies and in expert interviews. In laboratory testing, the Hidden Master prototype was more resilient than leading configuration management tools in high load and low memory conditions, and against packet loss and corruption. Only the research prototype was adaptable to a network without stable topology due to the asynchronous nature of the Hidden Master architecture.
The main case study used the research prototype in a complex environment to deploy a multi-room, authenticated audiovisual system for a client of an organization deploying the configuration. The case studies indicated that imperative general purpose language can be used for idempotent configuration in real life, for defining new configurations in unexpected situations using the base resources, and abstracting those using standard language features; and that such a system seems easy to learn.
Potential business benefits were identified and evaluated using individual semistructured expert interviews. Respondents agreed that the models and the Hidden Master architecture could reduce costs and risks, improve developer productivity and allow faster time-to-market. Protection of master secret keys and the reduced need for incident response were seen as key drivers for improved security. Low-cost geographic scaling and leveraging file serving capabilities of commodity servers were seen to improve scaling and resiliency. Respondents identified jurisdictional legal limitations to encryption and requirements for cloud operator auditing as factors potentially limiting the full use of some concepts
Climate Change and Critical Agrarian Studies
Climate change is perhaps the greatest threat to humanity today and plays out as a cruel engine of myriad forms of injustice, violence and destruction. The effects of climate change from human-made emissions of greenhouse gases are devastating and accelerating; yet are uncertain and uneven both in terms of geography and socio-economic impacts. Emerging from the dynamics of capitalism since the industrial revolution — as well as industrialisation under state-led socialism — the consequences of climate change are especially profound for the countryside and its inhabitants. The book interrogates the narratives and strategies that frame climate change and examines the institutionalised responses in agrarian settings, highlighting what exclusions and inclusions result. It explores how different people — in relation to class and other co-constituted axes of social difference such as gender, race, ethnicity, age and occupation — are affected by climate change, as well as the climate adaptation and mitigation responses being implemented in rural areas. The book in turn explores how climate change – and the responses to it - affect processes of social differentiation, trajectories of accumulation and in turn agrarian politics. Finally, the book examines what strategies are required to confront climate change, and the underlying political-economic dynamics that cause it, reflecting on what this means for agrarian struggles across the world. The 26 chapters in this volume explore how the relationship between capitalism and climate change plays out in the rural world and, in particular, the way agrarian struggles connect with the huge challenge of climate change. Through a huge variety of case studies alongside more conceptual chapters, the book makes the often-missing connection between climate change and critical agrarian studies. The book argues that making the connection between climate and agrarian justice is crucial
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Presidential Administration: An Intellectual and Legal History, 1888-1938
This dissertation explores the intellectual and legal history of presidential administration — that is, the president’s ability to direct the operations of the administrative state. The dissertation argues that presidential administration was closely connected to changing ideas about how to realize democratic government. It shows how, in the late 19th and early 20th century, the presidency acquired the institutions that lay the foundations for executive control of administration. This was a deliberate reform project, driven by ideas about what would make government responsible.
The dissertation tells this story by tracking transformations in democratic thought and law through attention to court cases and scholarship, among other genres, and looks at both published and archival sources. It draws on methods from legal history, intellectual history, and American Political Development, and occasionally makes use of an Atlantic perspective. Besides historians, law professors, and political scientists, it may be of interest to scholars of the presidency, public administration, and analysts of current legal debates about presidential power and administration
Restoring and valuing global kelp forest ecosystems
Kelp forests cover ~30% of the world’s coastline and are the largest biogenic marine habitat on earth. Across their distribution, kelp forests are essential for the healthy functioning of marine ecosystems and consequently underpin many of the benefits coastal societies receive from the ocean. Concurrently, rising sea temperatures, overgrazing by marine herbivores, sedimentation, and water pollution have caused kelp forests populations to decline in most regions across the world. Effectively managing the response to these declines will be pivotal to maintaining healthy marine ecosystems and ensuring the benefits they provide are equitably distributed to coastal societies.
In Chapter 1, I review how the marine management paradigm has shifted from protection to restoration as well as the consequences of this shift. Chapter 2 introduces the field of kelp forest restoration and provides a quantitative and qualitative review of 300 years of kelp forest restoration, exploring the genesis of restoration efforts, the lessons we have learned about restoration, and how we can develop the field for the future. Chapter 3 is a direct answer to the question faced while completing Chapter 2. This chapter details the need for a standardized marine restoration reporting framework, the benefits that it would provide, the challenges presented by creating one, and the solutions to these problems. Similarly, Chapter 4 is a response to the gaps discovered in Chapter 2. Chapter 4 explores how we can use naturally occurring positive species interactions and synergies with human activities to not only increase the benefits from ecosystem restoration but increase the probability that restoration is successful. The decision to restore an ecosystem or not is informed by the values and priorities of the society living in or managing that ecosystem. Chapter 5 quantifies the fisheries production, nutrient cycling, and carbon sequestration potential of five key genera of globally distributed kelp forests.
I conclude the thesis by reviewing the lessons learned and the steps required to advance the field kelp forest restoration and conservation
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Novel Mathematical Framework for Performance Analysis of Energy Harvesting-Based Point-to-Point Communications
This paper presents a novel performance evaluation framework for energy harvesting communications. As the harvested energy may not always be at the required levels in the transmitter’s battery, possible energy outage may hinder the transmission, especially in weak channel conditions. Herein, we analyze the performance of an energy harvesting communication link by allowing a certain level of energy outage to occur. Such operation is challenging, given that the energy coming into the battery from an uncontrollable source, e.g., solar energy, does not relate to the channel conditions and quality-of-service (QoS) requirement, whereas energy going out of the battery is directly dependent on both. Hence, the incoming energy and outgoing energy become independent of each other. Knowing the exact level of energy that is accumulated in the battery is therefore challenging. To deal with these challenges, a probabilistic energy-outage approach and a virtual battery queuing model are proposed and used to develop the target performance evaluation framework while leveraging the large deviation principle theorem. The derived energy-outage probability of the communication system relates the system parameters, namely, QoS component, channel conditions, and harvested energy. Numerical results are presented to confirm the analytical findings and discuss the performance of energy harvesting based communication with tolerable energy-outage as a function of the system parameters
Investigating Middle Stone Age foraging behaviour in the Karoo, South Africa
The Middle Stone Age (MSA) in Africa ~500- 50 kyr is recognised as a key time-period associated with important developments in hominin evolution, including the appearance of earliest genetic markers for Homo sapiens. Despite advances, our knowledge of the behaviour of hominins during this period is limited, especially for the early MSA (EMSA) pre-160ka. This study presents new data on animal bones recovered at the Bundu Farm site, in the upper Karoo region of the Northern Cape, South Africa, dated to circa ~300ka and found in association with EMSA type lithic facies, burning and hearth-like features. Previous analysis of the Bundu fauna compared the site to a G/wi hunter-gatherer 'biltong' processing locale, implying primary access to animal carcasses and socially complex hunting behaviour, circa 400-300 ka. An interpretation at odds with other interpretations of the EMSA data that suggest limited hunting and social complexity, and which would therefore have significant implications for MSA archaeology. To test the biltong hypothesis my study presents new data on the fracture characteristics of non-fresh animal bone broken by hammerstone and new environmental data for the site from an analysis of ostrich eggshell isotopes. Experimental and environmental data are used to provide a new interpretation of the Bundu fauna and my conclusion is that the data while not supporting the biltong model, does indicate evidence of delayed communal food consumption, use of fire and the transformation of foodstuffs into meals presaging and echoing social and ecological adaptations seen in the later MSA and LSA. The data also highlights a greater role for carnivores in the accumulation of the faunal assemblage and expedient hominin foraging similar to the preceding ESA and brings attention to the ecological relationships between hominins and carnivores in a Pleistocene Karoo environment that was markedly different from that of today. The study therefore rejects the biltong hypothesis for Bundu Farm as both inconsistent with likely EMSA social structures and ecology and instead proposes the site as evidence for novel behaviour indicative of a transition from ESA to MSA lifeways. The Bundu Farm site reflecting a rare archaeological occurrence where the shift in the behavioural trajectory that led to our species is observed
Ekologické a evoluční procesy určující strukturu sítí rostlin a opylovačů
Abtrakt Rozmnožování většiny druhů rostlin a potrava značné části diverzity živočichů na této planetě přímo závisí na vztazích mezi květy a opylovači. Donedávna se však převážná většina výzkumu opylování zaměřovala pouze na studium opylování konkrétních rostlin a jen málo pozornosti bylo věnováno celým společenstvům rostlin i opylovačů. V posledních desetiletích se však zaměření ekologie opylování posunulo díky zavedení konceptu opylovacích sítí. Tento koncept umožnil zabývat se opylováním v kontextu celého společenstva, poukázal na rozmanitost i komplexitu vztahů mezi rostlinami a jejich opylovači a otevřel řadu nových možností výzkumu těchto vztahů z pohledu jeho významu pro živočichy nebo z pohledu časové a prostorové dynamiky opylovacích interakcí. Přesto však dosud máme jen matné představy o tom, jaké procesy jsou zodpovědné za strukturu a dynamiku těchto sítí. Podoba opylovací sítě je formována jak ekologickými, tak evolučními procesy. Z ekologického pohledu hraje roli například to, jak se druhy v čase a prostoru potkávají nebo jak si jednotlivé taxony opylovačů vybírají mezi rostlinami v závislosti na kontextu prostředí, aktuálních potravních potřebách či nabídce květních zdrojů. Z evolučního pohledu je pak podoba sítě vztahů mezi rostlinami a opylovači určena tím, jak se druhy na sebe vzájemně...Associations between flowers and pollinators are responsible for reproduction of majority of plant species as well as food supply for substantial part of animal diversity on the Earth. Until recently, the studies on plant-pollinator relationship were focused predominantly on pollination of particular plant species, with only little or no accent on community perspective. In recent decades, however, pollination ecology shifted its focus rather to community context by introducing so called pollination networks. This approach allows us to view the ubiquity and complexity of the interactions between plants and their pollinators and it opened up many new opportunities to study the pollination from animal perspective or to access spatio-temporal variability in the interactions. However, we still have only limited insight into the processes driving the structure and dynamics of such networks. The assembly of plants, pollinators and their interactions are driven by various ecological as well as evolutionary processes. From the ecological point of view, species co-occurrence in time and space may affect the interactions, or species flexibility for various community contexts providing different food sources may play role. In the evolutionary perspective, species may have various co-adaptations due to their...Katedra zoologieDepartment of ZoologyPřírodovědecká fakultaFaculty of Scienc
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