2,518 research outputs found

    A 3-player protocol preventing persistence in strategic contention with limited feedback

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    In this paper, we study contention resolution protocols from a game-theoretic perspective. In a recent work, we considered acknowledgment-based protocols, where a user gets feedback from the channel only when she attempts transmission. In this case she will learn whether her transmission was successful or not. One of the main results of ESA2016 was that no acknowledgment-based protocol can be in equilibrium. In fact, it seems that many natural acknowledgment-based protocols fail to prevent users from unilaterally switching to persistent protocols that always transmit with probability 1. It is therefore natural to ask how powerful a protocol must be so that it can beat persistent deviators. In this paper we consider age-based protocols, which can be described by a sequence of probabilities of transmitting in each time step. Those probabilities are given beforehand and do not change based on the transmission history. We present a 3-player age-based protocol that can prevent users from unilaterally deviating to a persistent protocol in order to decrease their expected transmission time. It is worth noting that the answer to this question does not follow from the results and proof ideas of ESA2016. Our protocol is non-trivial, in the sense that, when all players use it, finite expected transmission time is guaranteed. In fact, we show that this protocol is preferable to any deadline protocol in which, after some fixed time, attempt transmission with probability 1 in every subsequent step. An advantage of our protocol is that it is very simple to describe, and users only need a counter to keep track of time. Whether there exist nn-player age-based protocols that do not use counters and can prevent persistence is left as an open problem for future research.Comment: arXiv admin note: substantial text overlap with arXiv:1606.0658

    Strategic Contention Resolution in Multiple Channels

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    We consider the problem of resolving contention in communication networks with selfish users. In a \textit{contention game} each of n≥2n \geq 2 identical players has a single information packet that she wants to transmit using one of k≥1k \geq 1 multiple-access channels. To do that, a player chooses a slotted-time protocol that prescribes the probabilities with which at a given time-step she will attempt transmission at each channel. If more than one players try to transmit over the same channel (collision) then no transmission happens on that channel. Each player tries to minimize her own expected \textit{latency}, i.e. her expected time until successful transmission, by choosing her protocol. The natural problem that arises in such a setting is, given nn and kk, to provide the players with a common, anonymous protocol (if it exists) such that no one would unilaterally deviate from it (equilibrium protocol). All previous theoretical results on strategic contention resolution examine only the case of a single channel and show that the equilibrium protocols depend on the feedback that the communication system gives to the players. Here we present multi-channel equilibrium protocols in two main feedback classes, namely \textit{acknowledgement-based} and \textit{ternary}. In particular, we provide equilibrium characterizations for more than one channels, and give specific anonymous, equilibrium protocols with finite and infinite expected latency. In the equilibrium protocols with infinite expected latency, all players transmit successfully in optimal time, i.e. Θ(n/k)\Theta(n/k), with probability tending to 1 as n/k→∞n/k \to \infty.Comment: The results of this work are included in the 11th International Symposium on Algorithmic Game Theory (SAGT 2018) and the 16th Workshop on Approximation and Online Algorithms (WAOA 2018

    Border blocking effects in collaborative firm innovation: exploring the factors related with scientist' willingness to incorporating external knowledge

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    Border regions are not often associated with innovation and economic prosperity. Nevertheless, the opening up of borders in Europe has presented new opportunities for firms located in these border regions to co-operate and find necessary resources for their innovation process. Despite the reduction of the importance of borders, firms seeking to access those resources need still ‘cross’ the border and address the various effects it brings. This paper therefore asks the question of how the presence of a border affects the processes by which firms attempt to build up productive co-operations for innovation. We stylise inter-firm innovation across borders as building up through four sequential stages cooperation in four stages, and each of these different stages are susceptible to different kinds of border effects. Using a case study of firms co-operating across the Dutch-Flemish border, we empirically explore these border crossing processes in order to shed further light on how border processes play ou

    Can the Liberal Order be Sustained? Nations, Network Effects, and the Erosion of Global Institutions

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    A growing retreat from multilateralism is threatening to upend the institutions that underpin the liberal international order. This article applies network theory to this crisis in global governance, arguing that policymakers can strengthen these institutions by leveraging network effect pressures. Network effects arise when networks of actors—say language speakers or users of a social media platform—interact and the value one user derives from the network increases as other users join the network (e.g., the more people who speak your language, the more useful it is because there are more people with whom you can communicate). Crucially, network effect pressures produce what is called ‘lock-in’—a situation in which actors are unable to exit the network without incurring high costs and as a result become locked into the network. For example, because of their powerful network effect pressures, users of Facebook and the English language cannot easily exit these networks. International organizations such as the UN, the WTO, the IMF, etc., are networks of sovereign states that likewise produce network effect pressures. As such, intensifying their network effect pressure can lock countries more firmly into these institutions. To that end, this article proposes a suite of strategies policymakers may use to manipulate the network effect pressures generated by international organizations to strengthen these institutions and the multilateral treaties that establish them—an approach the article calls treaty hacking. The article offers a toolkit from which policymakers can draw to bolster the liberal order in the face of growing global instability and change

    Eye quietness and quiet eye in expert and novice golf performance: an electrooculographic analysis

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    Quiet eye (QE) is the final ocular fixation on the target of an action (e.g., the ball in golf putting). Camerabased eye-tracking studies have consistently found longer QE durations in experts than novices; however, mechanisms underlying QE are not known. To offer a new perspective we examined the feasibility of measuring the QE using electrooculography (EOG) and developed an index to assess ocular activity across time: eye quietness (EQ). Ten expert and ten novice golfers putted 60 balls to a 2.4 m distant hole. Horizontal EOG (2ms resolution) was recorded from two electrodes placed on the outer sides of the eyes. QE duration was measured using a EOG voltage threshold and comprised the sum of the pre-movement and post-movement initiation components. EQ was computed as the standard deviation of the EOG in 0.5 s bins from –4 to +2 s, relative to backswing initiation: lower values indicate less movement of the eyes, hence greater quietness. Finally, we measured club-ball address and swing durations. T-tests showed that total QE did not differ between groups (p = .31); however, experts had marginally shorter pre-movement QE (p = .08) and longer post-movement QE (p < .001) than novices. A group × time ANOVA revealed that experts had less EQ before backswing initiation and greater EQ after backswing initiation (p = .002). QE durations were inversely correlated with EQ from –1.5 to 1 s (rs = –.48 - –.90, ps = .03 - .001). Experts had longer swing durations than novices (p = .01) and, importantly, swing durations correlated positively with post-movement QE (r = .52, p = .02) and negatively with EQ from 0.5 to 1s (r = –.63, p = .003). This study demonstrates the feasibility of measuring ocular activity using EOG and validates EQ as an index of ocular activity. Its findings challenge the dominant perspective on QE and provide new evidence that expert-novice differences in ocular activity may reflect differences in the kinematics of how experts and novices execute skills

    A Phenomenological Study of Graduated Nursing Student Athletes\u27 Experiences Balancing Academics and Athletics

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    The purpose of this transcendental phenomenological study is to describe the lived experiences of eleven graduated nursing student athletes who completed traditional, four-year nursing programs while concurrently finishing four years of athletic eligibility in their respective sport at three private, Christian, Midwest universities and across three different competitive collegiate athletic divisions. The theories guiding this study are Tinto’s Theory of Individual Departure from Institutions of Higher Learning, Astin’s Theory of Student Involvement, and Lazarus and Folkman’s Transactional Model of Stress Response, as they relate to student athletes’ persistence to graduation and to nursing students who reportedly experience higher levels of stress than other college students. Participants were purposefully selected to answer the following: How do graduated nursing student athletes describe their experiences in balancing sports and academics while completing a traditional, four-year nursing program and participating in intercollegiate sports? Data collection was conducted using journaling, semi-structured individual interviews, and focus groups. Confidentiality was maintained by using pseudonyms for all colleges and participants. Data analysis was conducted via pattern, theme, and content analysis. Validity and trustworthiness were established via expert and member reviews, as well as triangulation of participant groups, data sources, audit trails, enumeration tables, and inclusion of participant quotes

    Establishing cyber situational awareness in industrial control systems

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    The cyber threat to industrial control systems is an acknowledged security issue, but a qualified dataset to quantify the risk remains largely unavailable. Senior executives of facilities that operate these systems face competing requirements for investment budgets, but without an understanding of the nature of the threat cyber security may not be a high priority. Operational managers and cyber incident responders at these facilities face a similarly complex situation. They must plan for the defence of critical systems, often unfamiliar to IT security professionals, from potentially capable, adaptable and covert antagonists who will actively attempt to evade detection. The scope of the challenge requires a coherent, enterprise-level awareness of the threat, such that organisations can assess their operational priorities, plan their defensive posture, and rehearse their responses prior to such an attack. This thesis proposes a novel combination of concepts found in risk assessment, intrusion detection, education, exercising, safety and process models, fused with experiential learning through serious games. It progressively builds a common set of shared mental models across an ICS operation to frame the nature of the adversary and establish enterprise situational awareness that permeates through all levels of teams involved in addressing the threat. This is underpinned by a set of coping strategies that identifies probable targets for advanced threat actors, proactively determining antagonistic courses of actions to derive an appropriate response strategy

    ATTRIBUTES, COMPLIANCE AND EFFECTIVENESS OF NESTED REGIMESTHE BIOLOGICAL WEAPONS REGIME COMPLEX

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    Are non-proliferation regimes effective? If so, under which circumstances? Existing theoretical and empirical studies fall short of providing consistent indications of the constraining power of security institutions and non-proliferation regimes on state decisions. On the one hand, proponents of regimes highlight the overall capacity of institutions to contain the number of proliferators. On the other hand, detractors maintain that regimes have little or no effect on state decision to pursue specific weapons. The empirical associations between framework conventions and the non-proliferation of the weapons under provision have proved unsatisfactory and weak. Moving from a broader idea of regimes and a graduated notion of effectiveness, this project develops a theoretical argument about the importance of networks of individual institutions (regime complexes) in regime analysis. I argue that regime-complex level data can enhance our capacity to explain actual regime effectiveness, as well as the link between specific institutional features and non-proliferation outcomes. The project does so, interalia, by introducing a new dataset, which gathers information on several institutions that are part of the biological non-proliferation regime complex. The work then illustrates the use of the new dataset by developing measures of state exposure to the regime-complex in terms of overall embeddedness and compliance
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