931 resultados para terrain avoidance


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The reinforcer devaluation paradigm has been regarded as a canonical paradigm to detect habit-like behavior in animal and human instrumental learning. Though less studied, avoidance situations set a scenario where habit-like behavior may be of great experimental and clinical interest. On the other hand, proactive intolerance of uncertainty has been shown as a factor facilitating responses in uncertain situations. Thus, avoidance situations in which uncertainty is favoured, may be taken as a relevant paradigm to examine the role of intolerance of uncertainty as a facilitatory factor for habit-like behavior to occur. In our experiment we used a free-operant discriminative avoidance procedure to implement a devaluation paradigm. Participants learned to avoid an aversive noise presented either to the right or to the left ear by pressing two different keys. After a devaluation phase where the volume of one of the noises was reduced, they went through a test phase identical to the avoidance phase except for the fact that the noise was never administered. Sensitivity to reinforcer devaluation was examined by comparing the response rate to the cue associated to the devalued reinforcer with that to the cue associated to the still aversive reinforcer. The results showed that intolerance of uncertainty was positively associated to insensitivity to reinforcer devaluation. Finally, we discuss the theoretical and clinical implications of the habit-like behavior obtained in our avoidance procedure.

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Many mental disorders are characterised by the presence of compulsions and incontrollable habits. Most studies on habit learning, both in animals and in humans, are based on positive reinforcement paradigms. However, the compulsions and habits involved in some mental disorders may be better understood as avoidance behaviours, which involve some peculiarities, such as anxiety states, that have been shown to promote habitual responses. Consequently, we studied habit acquisition by using a free-operant discriminated avoidance procedure. Furthermore, we checked whether intolerance of uncertainty could predispose to avoidance habit acquisition. Participants learned to avoid an aversive noise presented either to the right or to the left ear by pressing two different keys. After a devaluation phase where the volume of the noise presented to one of the ears was reduced, participants went through a test phase identical to the avoidance learning phase except for the fact that the noise was never administered. Habit acquisition was inferred by comparing the rate of responses to the stimulus signalling the devalued reinforcer and to the stimulus signalling the non-devalued reinforcer. The results showed that intolerance of uncertainty was related to the absence of differences between the referred conditions, which entail avoidance habit acquisition.

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The purpose of this thesis is to investigate and understand the effect of a servicescape’s ambient and social conditions on consumers’ service encounter experience and their approach/avoidance behavior in a retail context. In three papers, with a total sample of over 1600 participants (including 550 actual consumers) and seven experiments, the author investigates the effect of music (ambient stimuli), employees’ self-disclosure (verbal social stimuli) and employees’ gazing behavior (nonverbal social stimuli) on consumers’ service encounter experience and approach/avoidance behavior in a retail store. Paper I comprised two experiments, and the aim was to investigate the influence of music on emotions, approach/avoidance behavior. Paper II comprised two experiments, and the aim was to investigate the effect of frontline employees’ personal self-disclosure on consumers’ reciprocal behavior. Paper III comprised three experiments, and the aim was to investigate the influence of employee’s direct eye gaze/ averted eye gaze on consumer emotions, social impression of the frontline employee and encounter satisfaction in different purchase situations. The results in this thesis show that music affects consumers in both positive and negative ways (Paper I). Self-disclosure affects consumers negatively, in such a way that it decreases encounter satisfaction  (Paper II) and, finally, eye gaze affects consumers by regulating both positively – and in some cases also negatively – consumers’ social impression of the frontline employee and their encounter satisfaction (Paper III). The conclusions of this thesis are that both ambient and social stimuli in a servicescape affect consumers’ internal responses, which in turn affect their behavior. Depending on the purchase situation, type of retail, and stimuli, the internal and behavioral responses are different.

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The idea of spacecraft formations, flying in tight configurations with maximum baselines of a few hundred meters in low-Earth orbits, has generated widespread interest over the last several years. Nevertheless, controlling the movement of spacecraft in formation poses difficulties, such as in-orbit high-computing demand and collision avoidance capabilities, which escalate as the number of units in the formation is increased and complicated nonlinear effects are imposed to the dynamics, together with uncertainty which may arise from the lack of knowledge of system parameters. These requirements have led to the need of reliable linear and nonlinear controllers in terms of relative and absolute dynamics. The objective of this thesis is, therefore, to introduce new control methods to allow spacecraft in formation, with circular/elliptical reference orbits, to efficiently execute safe autonomous manoeuvres. These controllers distinguish from the bulk of literature in that they merge guidance laws never applied before to spacecraft formation flying and collision avoidance capacities into a single control strategy. For this purpose, three control schemes are presented: linear optimal regulation, linear optimal estimation and adaptive nonlinear control. In general terms, the proposed control approaches command the dynamical performance of one or several followers with respect to a leader to asymptotically track a time-varying nominal trajectory (TVNT), while the threat of collision between the followers is reduced by repelling accelerations obtained from the collision avoidance scheme during the periods of closest proximity. Linear optimal regulation is achieved through a Riccati-based tracking controller. Within this control strategy, the controller provides guidance and tracking toward a desired TVNT, optimizing fuel consumption by Riccati procedure using a non-infinite cost function defined in terms of the desired TVNT, while repelling accelerations generated from the CAS will ensure evasive actions between the elements of the formation. The relative dynamics model, suitable for circular and eccentric low-Earth reference orbits, is based on the Tschauner and Hempel equations, and includes a control input and a nonlinear term corresponding to the CAS repelling accelerations. Linear optimal estimation is built on the forward-in-time separation principle. This controller encompasses two stages: regulation and estimation. The first stage requires the design of a full state feedback controller using the state vector reconstructed by means of the estimator. The second stage requires the design of an additional dynamical system, the estimator, to obtain the states which cannot be measured in order to approximately reconstruct the full state vector. Then, the separation principle states that an observer built for a known input can also be used to estimate the state of the system and to generate the control input. This allows the design of the observer and the feedback independently, by exploiting the advantages of linear quadratic regulator theory, in order to estimate the states of a dynamical system with model and sensor uncertainty. The relative dynamics is described with the linear system used in the previous controller, with a control input and nonlinearities entering via the repelling accelerations from the CAS during collision avoidance events. Moreover, sensor uncertainty is added to the control process by considering carrier-phase differential GPS (CDGPS) velocity measurement error. An adaptive control law capable of delivering superior closed-loop performance when compared to the certainty-equivalence (CE) adaptive controllers is finally presented. A novel noncertainty-equivalence controller based on the Immersion and Invariance paradigm for close-manoeuvring spacecraft formation flying in both circular and elliptical low-Earth reference orbits is introduced. The proposed control scheme achieves stabilization by immersing the plant dynamics into a target dynamical system (or manifold) that captures the desired dynamical behaviour. They key feature of this methodology is the addition of a new term to the classical certainty-equivalence control approach that, in conjunction with the parameter update law, is designed to achieve adaptive stabilization. This parameter has the ultimate task of shaping the manifold into which the adaptive system is immersed. The performance of the controller is proven stable via a Lyapunov-based analysis and Barbalat’s lemma. In order to evaluate the design of the controllers, test cases based on the physical and orbital features of the Prototype Research Instruments and Space Mission Technology Advancement (PRISMA) are implemented, extending the number of elements in the formation into scenarios with reconfigurations and on-orbit position switching in elliptical low-Earth reference orbits. An extensive analysis and comparison of the performance of the controllers in terms of total Δv and fuel consumption, with and without the effects of the CAS, is presented. These results show that the three proposed controllers allow the followers to asymptotically track the desired nominal trajectory and, additionally, those simulations including CAS show an effective decrease of collision risk during the performance of the manoeuvre.

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In sexually reproducing organisms, the specific combinations of parental alleles can have important consequences on offspring viability and fitness. Accordingly, genetic relationship between mates can be used as a criterion for mate choice. Here, we used microsatellite genetic markers to estimate the genetic relationship between mating pairs in the wild boar, Sus scrofa. Males, females and foetuses proceeding from Portugal, Spain and Hungary were genotyped using 14 microsatellite markers. The genetic relationship between mates was estimated using different measures of foetus heterozygosity. We found that the observed heterozygosity of foetuses was lower than that expected under random mating. This result occurred mainly when Sd2 (relatedness of parental genomes) was used as the heterozygosity measure. After simulations, we concluded that the observed low heterozygosity was possibly due to outbreeding avoidance. Outbreeding avoidance based on genetically different genomes might play an important role in species evolution and its genetic conservation.

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Pour realiser un bon diagnostic des risques de ruissellement et d'erosion sur un versant, il convient d'observer le fonctionnement hydrique du terrain au cours de la saison des pluies on au moins de tester la capacite d'infiltration des sols soumis a diverses utilisations. Dans cette note est decrit un test au cylindre unique, test simple et peu couteux permettant non seulement de classer les horizons d'un sol en fonction de leur capacite d'infiltration, de leur porosite discussion porte sur l'interet et les limites de cette methode. Deux exemples mountret l'interet pratique de ce test de terrain sur des sols ferrallitiques argileux du Bresil et sur un sol ferrugineux tropical sableux du Cameroun.

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This is the first volume to capture the essence of the burgeoning field of cultural studies in a concise and accessible manner. Other books have explored the British and North American traditions, but this is the first guide to the ideas, purposes and controversies that have shaped the subject. The author sheds new light on neglected pioneers and a clear route map through the terrain. He provides lively critical narratives on a dazzling array of key figures including, Arnold, Barrell, Bennett, Carey, Fiske, Foucault, Grossberg, Hall, Hawkes, hooks, Hoggart, Leadbeater, Lissistzky, Malevich, Marx, McLuhan, McRobbie, D Miller, T Miller, Morris, Quiller-Couch, Ross, Shaw, Urry, Williams, Wilson, Wolfe and Woolf. Hartley also examines a host of central themes in the subject including literary and political writing, publishing, civic humanism, political economy and Marxism, sociology, feminism, anthropology and the pedagogy of cultural studies.

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Smart Skies is an international research project exploring the development and demonstration of future aviation technologies which facilitate the more efficient utilisation of airspace for both manned and unmanned aircraft. These technologies include autonomous vision-based collision avoidance systems, autonomous airspace separation management systems and a mobile ground-based radar system to support non-segregated UAS operations within the NAS. This presentation will provide an introduction to the key programs of research, detail results from recent flight trial activities and will outline future directions for the project.

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This document outlines a framework that could be used by government agencies in assessing policy interventions aimed at achieving social outcomes from government construction contracts. The framework represents a rational interpretation of the information gathered during the multi-outcomes construction policies project. The multi-outcomes project focused on the costs and benefits of using public construction contracts to promote the achievement of training and employment and public art objectives. The origin of the policy framework in a cost-benefit appraisal of current policy interventions is evidenced by its emphasis on sensitivity to policy commitment and project circumstances (especially project size and scope).The quantitative and qualitative analysis conducted in the multi-outcomes project highlighted, first, that in the absence of strong industry commitment to policy objectives, policy interventions typically result in high levels of avoidance activity, substantial administrative costs and very few benefits. Thus, for policy action on, for example, training or local employment to be successful compliance issues must be adequately addressed. Currently it appears that pre-qualification schemes (similar to the Priority Access Scheme) and schemes that rely on measuring, for example, the training investments of contractors within particular projects do not achieve high levels of compliance and involve significant administrative costs. Thus, an alternative is suggested in the policy framework developed here: a levy on each public construction project – set as a proportion of the total project costs. Although a full evaluation of this policy alternative was beyond the scope of the multi-outcomes construction policies project, it appears to offer the potential to minimize the transaction costs on contractors whilst enabling the creation of a training agency dedicated to improving the supply of skilled construction labour. A recommendation is thus made that this policy alternative be fully researched and evaluated. As noted above, the outcomes of the multi-outcomes research project also highlighted the need for sensitivity to project circumstances in the development and implementation of polices for public construction projects. Ideally a policy framework would have the flexibility to respond to circumstances where contractors share a commitment to the policy objectives and are able to identify measurable social outcomes from the particular government projects they are involved in. This would involve a project-by-project negotiation of goals and performance measures. It is likely to only be practical for large, longer term projects.

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This study explores teenager perceptions towards advertising in the online social networking environment. The future of online social networking sites is dependant upon the continued support of advertisers in this new medium, which is linked to the acceptance of advertising on these sites by their targeted audience. This exploratory study used the qualitative research methods of focus groups and in-depth personal interviews to gain insights from the teenager participants. The literature review in Chapter Two examined the previous research into advertising theories, consumer attitudes and issues such as advertising avoidance, advertising as a service and trust and privacy in the online social networking environment. The teenage consumer was also examined as were the influences of social identity theory. From this literature review eleven propositions were formed which provided a structure to the analysis of the research. Chapter Three outlined the multi-method research approach of using focus groups and in-depth interviews. The key findings were outlined in Chapter Four and Chapter Five provides discussion regarding these findings and the implications for theory and advertising practice. The main findings from this study suggest that teenagers have very high levels of advertising avoidance and are sceptical towards advertising on their online social networking sites. They have an inherent distrust of commercial messages in the online social networking environment; however they are extremely trusting with the information that they disclose online. They believe that if their site is classified as private, then the information disclosed on this site is not accessible to anyone. The study explores the reasons behind these views. This research has resulted in the identification of seven motivations behind online social networking use. A new model of advertising avoidance in the online social networking environment is also presented and discussed. This model makes a contribution towards filling the gap in available research on online social networking sites and advertising perception. The findings of this study have also resulted in the identification of the characteristics of online social networking sites as an advertising medium. The newness of online social networking sites coupled with the enthusiastic adoption of online social networking by the teenage demographic means that this exploratory study will be of interest to both academics and practitioners alike.

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The decision as to which procurement system to adopt is a complex and challenging task for clients of construction projects. Despite a plethora of tools and techniques available for selecting a procurement method, clients are still uncertain about what method to adopt for a given construction project to achieve success. This paper examines ‘how and why’ procurement methods are selected by public sector clients in Queensland (QLD) and Western Australia (WA). Findings from workshops with senior managers in procurement selection revealed that traditional lump sum methods (TLS) are preferred even though alternative forms could be better suited for a given project. Participants of the workshops agreed that alternative procurement forms should be considered for projects but an embedded culture of uncertainty avoidance meant the selection of TLS methods. It was perceived that only a limited number of contractors operating in the marketplace have the resources and experience to deliver projects using the non-traditional methods.

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The automation of various aspects of air traffic management has many wide-reaching benefits including: reducing the workload for Air Traffic Controllers; increasing the flexibility of operations (both civil and military) within the airspace system through facilitating automated dynamic changes to en-route flight plans; ensuring safe aircraft separation for a complex mix of airspace users within a highly complex and dynamic airspace management system architecture. These benefits accumulate to increase the efficiency and flexibility of airspace use(1). Such functions are critical for the anticipated increase in volume of manned and unmanned aircraft traffic. One significant challenge facing the advancement of airspace automation lies in convincing air traffic regulatory authorities that the level of safety achievable through the use of automation concepts is comparable to, or exceeds, the accepted safety performance of the current system.

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This paper explores the likely efficacy of government agencies using their contracting relationships with private firms to affect training outcomes in the construction industry. Specifically, it reports on the results of a study of two training policies of theWestern Australian government. Empirical data is drawn from the government’s Tender Registration System between 1997 and 2006. The main finding of the quantitative analysis is that in the absence of strong industry commitment to policy objectives, the contracting approach is likely to result in high levels of avoidance activity and generate very few benefits. The results of a qualitative investigation also support these findings.

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A study was conducted to examine the factorial validity of the Flinders Decision Making Questionnaire (Mann, 1982), a 31-item self-report inventory designed to measure tendencies to use three major coping patterns identified in the conflict theory of decision making (Janis and Mann, 1977): vigilance, hypervigilance, and defensive avoidance (procrastination, buck-passing, and rationalization). A sample of 2051 university students, comprising samples from Australia (n=262), New Zealand (n=260), the USA (n=475), Japan (n=359), Hong Kong (n=281) and Taiwan (n=414) was administered the DMQ. Factorial validity of the instrument was tested by confirmatory factor analysis with LISREL. Five different substantive models, representing different structural relationships between the decision-coping patterns had unsatisfactory fit to the data and could not be validated. A shortened instrument, containing 22 items, yielded a revised model comprising four identifiable factors-vigilance, hypervigilance, buck-passing, and procrastination. The revised model had adequate fit with data for each country sample and for the total sample, and was confirmed. It is recommended that the 22-item instrument, named the Melbourne DMQ, replace the Flinders DMQ for measurement of decision-coping patterns.