In the study of multi-agent systems (MASs), cooperative control is one of the most fundamental issues. As it covers a broad spectrum of applications in many industrial areas, there is a desire to design cooperative control protocols for different system and network setups. Motivated by this fact, in this thesis we focus on elaborating consensus protocol design, via model predictive control (MPC), under two different scenarios: (1) general constrained linear MASs with bounded additive disturbance; (2) linear MASs with input constraints underlying distributed communication networks. In Chapter 2, a tube-based robust MPC consensus protocol for constrained linear MASs is proposed. For undisturbed linear MASs without constraints, the results on designing a centralized linear consensus protocol are first developed by a suboptimal linear quadratic approach. In order to evaluate the control performance of the suboptimal consensus protocol, we use an infinite horizon linear quadratic objective function to penalize the disagreement among agents and the size of control inputs. Due to the non-convexity of the performance function, an optimal controller gain is difficult or even impossible to find, thus a suboptimal consensus protocol is derived. In the presence of disturbance, the original MASs may not maintain certain properties such as stability and cooperative performance. To this end, a tube-based robust MPC framework is introduced. When disturbance is involved, the original constraints in nominal prediction should be tightened so as to achieve robust constraint satisfaction, as the predicted states and the actual states are not necessarily the same. Moreover, the corresponding robust constraint sets can be determined offline, requiring no extra iterative online computation in implementation. In Chapter 3, a novel distributed MPC-based consensus protocol is proposed for general linear MASs with input constraints. For the linear MAS without constraints, a pre-stabilizing distributed linear consensus protocol is developed by an inverse optimal approach, such that the corresponding closed-loop system is asymptotically stable with respect to a consensus set. Implementing this pre-stabilizing controller in a distributed digital setting is however not possible, as it requires every local decision maker to continuously access the state of their neighbors simultaneously when updating the control input. To relax these requirements, the assumed neighboring state, instead of the actual state of neighbors, is used. In our distributed MPC scheme, each local controller minimizes a group of control variables to generate control input. Moreover, an additional state constraint is proposed to bound deviation between the actual and the assumed state. In this way, consistency is enforced between intended behaviors of an agent and what its neighbors believe it will behave. We later show that the closed-loop system converges to a neighboring set of the consensus set thanks to the bounded state deviation in prediction. In Chapter 4, conclusions are made and some research topics for future exploring are presented. / Graduate / 2021-03-31

abstract: Large organizations have multiple networks that are subject to attacks, which can be detected by continuous monitoring and analyzing the network traffic by Intrusion Detection Systems. Collaborative Intrusion Detection Systems (CIDS) are used for efficient detection of distributed attacks by having a global view of the traffic events in large networks. However, CIDS are vulnerable to internal attacks, and these internal attacks decrease the mutual trust among the nodes in CIDS required for sharing of critical and sensitive alert data in CIDS. Without the data sharing, the nodes of CIDS cannot collaborate efficiently to form a comprehensive view of events in the networks monitored to detect distributed attacks. The compromised nodes will further decrease the accuracy of CIDS by generating false positives and false negatives of the traffic event classifications. In this thesis, an approach based on a trust score system is presented to detect and suspend the compromised nodes in CIDS to improve the trust among the nodes for efficient collaboration. This trust score-based approach is implemented as a consensus model on a private blockchain because private blockchain has the features to address the accountability, integrity and privacy requirements of CIDS. In this approach, the trust scores of malicious nodes are decreased with every reported false negative or false positive of the traffic event classifications. When the trust scores of any node falls below a threshold, the node is identified as compromised and suspended. The approach is evaluated for the accuracy of identifying malicious nodes in CIDS. / Dissertation/Thesis / Masters Thesis Computer Science 2020

En stadig grund att stå på- byggt på inkludering, samsyn och goda relationer för elever med NPF.Förväntat kunskapsbidrag: Fördjupa förståelsen för pedagogernas tillgång till resurser och förutsättningar som de använder sig av för att möta elever med NPF-problematik utefter läroplanens krav. / A solid foundation, based on conclusion, consensus and good relations for students with NPF. To gain a deeper understanding of the teachers resources and conditions that they us to meet students with NPF -based the curriculums requirements.

Blockchain is a decentralized database that is distributed among a computer network. To enable a smooth decision making process without any authority, different blockchain applications use their own consensus algorithms. The problem is that for a new blockchain application, there is limited aid in deciding which algorithm it should implement. Selecting consensus algorithms is crucial because reaching consensus is the fundamental issue of a decentralized system. Different algorithms are designed with their own advantages and limitations, making it complex to navigate one’s way through a list of consensus algorithms. This thesis attempts to contribute to solving this problem by surveying 15 existing cryptocurrencies’ consensus algorithms used in their blockchain application and then producing a decision tree as the aid for algorithm selection. The top 5 algorithms from each category in Proof of Work (PoW), Proof of Stake (PoS), and Hybrid Proof of Work + Proof of Stake (PoW + PoS) are selected. The research method is qualitative. The study shows that different consensus algorithms often share some properties, but they are usually built to solve the issues of another algorithm, which means they also have their own distinctive advantages. Therefore, the decision tree reveals how these algorithms are logically connected and the key properties blockchain consensus algorithms possess. Based on the result of this thesis, further research can be conducted to include more algorithms in order to make the decision tree more comprehensive. Implementations of these algorithms in similar network setup can also be done to experiment with their claimed properties. The decision tree can be sent to industry for further feedback. / Blockchain är en decentraliserad databas som distribueras i ett datornätverk. För att möjliggöra en smidig beslutsprocess utan någon auktoritet använder olika blockkedjeapplikationer sina egna konsensusalgoritmer. Problemet är att för en ny blockchain-applikation finns det begränsad hjälp för att bestämma vilken algoritm den ska implementera. Att välja konsensusalgoritmer är avgörande eftersom att nå konsensus är den grundläggande frågan för ett decentraliserat system. Olika algoritmer är designade med sina egna fördelar och begränsningar, vilket gör det komplicerat att navigera sig igenom en lista med konsensusalgoritmer. Forskningsmetoden är kvalitativ. Det här dokumentet försöker bidra till att lösa detta problem genom att kartlägga 15 befintliga kryptovalutors konsensusalgoritmer som används i deras blockkedjeapplikation och sedan ta fram ett beslutsträd som hjälp för val av algoritmer. De 5 bästa algoritmerna från varje kategori i Proof of Work (PoW), Proof of Stake (PoS) och Hybrid Proof of Work + Proof of Stake (PoW + PoS) väljs. Studien visar att olika konsensusalgoritmer ofta delar vissa egenskaper, men de är vanligtvis byggda för att lösa problem med en annan algoritm, vilket innebär att de också har sina egna distinkta fördelar. Därför avslöjar beslutsträdet hur dessa algoritmer är logiskt kopplade och de nyckelegenskaper som blockchain konsensusalgoritmer besitter. Baserat på resultatet av denna artikel kan ytterligare forskning utföras för att inkludera fler algoritmer för att göra beslutsträdet mer heltäckande. Implementeringar av dessa algoritmer i liknande nätverksuppsättningar kan också göras för att experimentera med deras påstådda egenskaper. Beslutsträdet kan skickas till industrin för vidare feedback.

[pt] A adoção de políticas econômicas neoliberais de matriz americana,conjuntamente, pelos países latino-americanos, a partir da década de 80, passou a ser denominado de Consenso de Washington. A natureza de tamanha unanimidade, presente entre países de realidades econômica, social e política tão diversas foi motivo de questionamento por vários autores, tendo em vista a falta de originalidade do conteúdo dessas políticas econômicas. Defende-se, neste trabalho, a posição de que a grande novidade apresentada por este Consenso foi, justamente, a adoção conjunta de suas medidas e o discurso legitimador e universalizante que as promoveu, elementos atribuídos a uma revolução intelectual. É identificada, assim, a importância do papel das ideias enquanto influenciadoras das políticas governamentais. Papel este, que esta dissertação trata sob o arcabouço teórico de neogramscianos como Robert Cox e Stephen Gill, a partir da concepção desses autores de hegemonia, estabelecida por um país, numa sociedade civil global em formação, através das suas bases materiais e sociais, dentre estas, a ideologia. No caso brasileiro, um elemento especial é apresentado como facilitador da incorporação das diretrizes neoliberais hegemônicas, conformadoras do Consenso de Washington, no país: transnacionalização dos meios dirigentes em macroeconomia. O que esta dissertação objetiva demonstrar é que o trânsito dessa elite de economistas por organismos internacionais, notadamente norte-americanos, tende a aproximá-los de seus posicionamentos, além de conferir-lhes maior notoriedade. Esta notoriedade, por sua vez, aumenta as chances desses profissionais ocuparem cargos no governo. Uma vez ocupando esses cargos, maior a probabilidade de aplicarem as políticas econômicas importadas do país hegemônico, como aquelas reconhecias por caracterizarem o Consenso de Washington. / [en] The adoption of neoliberal economic policies of american patterns by latin-american countries in their entireness since the 80s has been called the Washington Consensus. The nature of such entirety among such different economic, social and political countries has been questioned by many authors as regards the lack of originality in these policies.The adoption of these policies by latin-american countries in their entireness and the universalizing and legitimating discourse that has promoted it, which has derived from an intelectual revolution, stand for the greater novelty of this Consensus.Thus, the ideas, in their influencing feature upon governmental policies, have been identified. This feature is here supported by neogramscians works as in Robert Coxs and Stephen Gills. Their hegemony conception is that one established by a country in a civil global society through its material and social bases, as for ideology.In Brazil, there is a special element which facilitates the incorporation of the neoliberal directions of the Washington Consensus: the transnationalization of the macroeconomy directing sectors. This work aims to demonstrate how this economists elite passage through international organisms, mainly north American, tends to draw them near to their positions as well as confer them greater evidence.This evidence, at its turn, enlarges the chances for these professionals to take offices. Once in office, the more probable it is for them to apply the economic policies, imported from the hegemonic country, as those known as the Washington Consensus ones.

Swedish hunters sometimes appeal to an inviolate ‘right to exist’ for wolves, apparently rejecting NIMBY. Nevertheless, the conditions existence hunters impose on wolves in practice fundamentally contradict their use of right to exist language. Hunters appeal to this language hoping to gain uptake in a conservation and management discourse demanding appropriately objective ecological language. However, their contradictory use of ‘right to exist' opens them up to the charge that they are being deceptive–indeed, right to exist is a 'disguised NIMBY!' We address this situation by distinguishing hunters’ criticisms of wolves from the procedures for reaching objective policy decisions.

Indiana University-Purdue University Indianapolis (IUPUI) / This study proposes and evaluates an average consensus scheme for wireless sensor networks. For this purpose, two communication error models, the fading signal error model and approximated fading signal error model, are introduced and incorporated into the proposed decentralized average consensus scheme. Also, a mathematical analysis is introduced to derive the approximated fading signal model from the fading signal model. Finally, differnt simulation scenarios are introduced and their results analyzed to evaluate the performance of the proposed scheme and its effectiveness in meeting the needs of wireless sensor networks.

Today applications are often designed with a modular approach, dividing functionality into micro services rather than relying on a monolithic structure. This requires solutions for decoupled message exchange throughout the distributed system and can be achieved by implementing a message broker. In some cases, it is interesting to make the message broker itself a distributed system, which has been a development path for systems such as RabbitMQ, Apache Kafka, and others. This thesis seeks to understand the alternative approaches to implementing  a distributed solution for the message broker LavinMQ. To find out which algorithm would be the most suitable for this purpose, a comparative analysis of the most common alternatives was performed based on LavinMQ's requirements and a literature review of related comparisons. The results showed that Raft would be the best choice due to its simple but effective nature. To further investigate the consensus approach in LavinMQ, a Raft prototype was developed in the programming language Crystal. The prototype was then evaluated based on correctness and performance in terms of mean replication time and mean election time. The prototype successfully passed the correctness tests, showing that the prototype successfully achieves correctness according to LavinMQ standard. The mean election time results show that the prototype recovers from a leader failure in 216 ms and that the most effective range for the heartbeat timeout is 150 to 300 ms. The replication time test results show that the mean replication time is 84.45 ms and the most efficient interval for message replication is 0.13 ms. The performance results are consistent with the results of related work, however result in overall slower performance and indicate that some additional features and optimizations need to be implemented in order to consider the prototype for practical use.

<p>OBJECTIVES: The primary objective of this systematic review was to illustrate the various definitions authors of methodology articles have offered for intention to treat (ITT) in relation to loss to follow up (LTFU).</p> <p> METHODS: We searched MEDLINE® for publications appearing between 1950 to 2008. Eligible papers devoted at least one paragraph to ITT and two other paragraphs to either ITT or LTFU. Investigators independently extracted relevant information from each eligible article. Discrepancies between data extractors were adjudicated. Data was extracted and variables used during data extraction were analyzed using the Landis and Koch guidelines kappa values.</p> <p> RESULTS: The MEDLINE® search yielded 1007 articles. One-hundred and ten articles underwent full text screening yielding 66 articles. All kappa's were substantial to near perfect agreement (>0.74). Of the 66 articles, five (8%) did not define ITT, 25 (41%) mentioned LTFU but did not discuss its relationship with ITT, 36 (59%) commented on LTFU in the context of ITT. These 36 articles segregated into three distinctive definitions for ITT: "full-follow-up required" (mentioned 58%), "ITT and LTFU are separate issues" (mentioned 17%), and "ITI involves specific strategy for LTFU" (mentioned 78%). Of the 36 articles, 17 (47%) had multiple definitions for ITT. The most frequent strategies mentioned for handling LTFU were last outcome carried forward (50%), sensitivity analysis (50%), and use of available data to impute (46%). Most articles (81%) specifically excluded complete case analysis under ITI.</p> <p> CONCLUSION : The most striking finding of our systematic review is that there is no meaningful consensus on the definition of ITI. This review, considered alongside previous reviews of RCTs, demonstrates that simply stating a study employed ITT is useless at best and misleading and dangerous at worst. It is the recommendation of this thesis that trialists replace the term ITI with a clear statements about analytic strategies applied to participants who were followed and with those not followed.</p> / Thesis / Master of Science (MS)

Consensus strategies are examined as a possible approach to achieving attitude alignment for a large, close-proximity formation of nanosatellites in low earth orbit (LEO). An attitude-only distributed consensus approach is selected for further consideration due to its comparatively low data transmission requirements. The convergence of a connected network of satellites to the attitude agreement subspace under this control law is shown using a Lyapunov stability approach with a set of idealizing assumptions. A moderate-fidelity simulation demonstrates the performance of the control law under realistic conditions that violate those assumptions. Particular emphasis is placed on the conditions that arise from the limitations of the nanosatellite form factor, namely the low accuracy of sensors and the limited computational resources. The sensitivity of the pointing performance to these factors is characterized, and the control approach is shown to be viable for use in future nanosatellite missions.