853 resultados para Exploration-exploitation
Resumo:
Formulating consistent marketing strategies is a difficult task, but successfully implementing them is even more challenging. This is even more pertinent as marketing strategies quite often incorporate inherent conflicts between major breakthroughs and consolidation. Consequently, marketers need to balance exploratory and exploitative strategies. However, the literature lacks concrete insights for marketing managers as to how exploratory and exploitative strategies can be best combined. This paper addresses this issue by introducing a framework of multiple types of ambidexterity. Based on qualitative research, tools and procedures are identified to overcome marketing dilemmas and support strategy implementation by drawing on ambidextrous designs.
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A new approach to optimisation is introduced based on a precise probabilistic statement of what is ideally required of an optimisation method. It is convenient to express the formalism in terms of the control of a stationary environment. This leads to an objective function for the controller which unifies the objectives of exploration and exploitation, thereby providing a quantitative principle for managing this trade-off. This is demonstrated using a variant of the multi-armed bandit problem. This approach opens new possibilities for optimisation algorithms, particularly by using neural network or other adaptive methods for the adaptive controller. It also opens possibilities for deepening understanding of existing methods. The realisation of these possibilities requires research into practical approximations of the exact formalism.
Resumo:
Neuroimaging studies analyzing neurophysiological signals are typically based on comparing averages of peri-stimulus epochs across experimental conditions. This approach can however be problematic in the case of high-level cognitive tasks, where response variability across trials is expected to be high and in cases where subjects cannot be considered part of a group. The main goal of this thesis has been to address this issue by developing a novel approach for analyzing electroencephalography (EEG) responses at the single-trial level. This approach takes advantage of the spatial distribution of the electric field on the scalp (topography) and exploits repetitions across trials for quantifying the degree of discrimination between experimental conditions through a classification scheme. In the first part of this thesis, I developed and validated this new method (Tzovara et al., 2012a,b). Its general applicability was demonstrated with three separate datasets, two in the visual modality and one in the auditory. This development allowed then to target two new lines of research, one in basic and one in clinical neuroscience, which represent the second and third part of this thesis respectively. For the second part of this thesis (Tzovara et al., 2012c), I employed the developed method for assessing the timing of exploratory decision-making. Using single-trial topographic EEG activity during presentation of a choice's payoff, I could predict the subjects' subsequent decisions. This prediction was due to a topographic difference which appeared on average at ~516ms after the presentation of payoff and was subject-specific. These results exploit for the first time the temporal correlates of individual subjects' decisions and additionally show that the underlying neural generators start differentiating their responses already ~880ms before the button press. Finally, in the third part of this project, I focused on a clinical study with the goal of assessing the degree of intact neural functions in comatose patients. Auditory EEG responses were assessed through a classical mismatch negativity paradigm, during the very early phase of coma, which is currently under-investigated. By taking advantage of the decoding method developed in the first part of the thesis, I could quantify the degree of auditory discrimination at the single patient level (Tzovara et al., in press). Our results showed for the first time that even patients who do not survive the coma can discriminate sounds at the neural level, during the first hours after coma onset. Importantly, an improvement in auditory discrimination during the first 48hours of coma was predictive of awakening and survival, with 100% positive predictive value. - L'analyse des signaux électrophysiologiques en neuroimagerie se base typiquement sur la comparaison des réponses neurophysiologiques à différentes conditions expérimentales qui sont moyennées après plusieurs répétitions d'une tâche. Pourtant, cette approche peut être problématique dans le cas des fonctions cognitives de haut niveau, où la variabilité des réponses entre les essais peut être très élevéeou dans le cas où des sujets individuels ne peuvent pas être considérés comme partie d'un groupe. Le but principal de cette thèse est d'investiguer cette problématique en développant une nouvelle approche pour l'analyse des réponses d'électroencephalographie (EEG) au niveau de chaque essai. Cette approche se base sur la modélisation de la distribution du champ électrique sur le crâne (topographie) et profite des répétitions parmi les essais afin de quantifier, à l'aide d'un schéma de classification, le degré de discrimination entre des conditions expérimentales. Dans la première partie de cette thèse, j'ai développé et validé cette nouvelle méthode (Tzovara et al., 2012a,b). Son applicabilité générale a été démontrée avec trois ensembles de données, deux dans le domaine visuel et un dans l'auditif. Ce développement a permis de cibler deux nouvelles lignes de recherche, la première dans le domaine des neurosciences cognitives et l'autre dans le domaine des neurosciences cliniques, représentant respectivement la deuxième et troisième partie de ce projet. En particulier, pour la partie cognitive, j'ai appliqué cette méthode pour évaluer l'information temporelle de la prise des décisions (Tzovara et al., 2012c). En se basant sur l'activité topographique de l'EEG au niveau de chaque essai pendant la présentation de la récompense liée à un choix, on a pu prédire les décisions suivantes des sujets (en termes d'exploration/exploitation). Cette prédiction s'appuie sur une différence topographique qui apparaît en moyenne ~516ms après la présentation de la récompense. Ces résultats exploitent pour la première fois, les corrélés temporels des décisions au niveau de chaque sujet séparément et montrent que les générateurs neuronaux de ces décisions commencent à différentier leurs réponses déjà depuis ~880ms avant que les sujets appuient sur le bouton. Finalement, pour la dernière partie de ce projet, je me suis focalisée sur une étude Clinique afin d'évaluer le degré des fonctions neuronales intactes chez les patients comateux. Des réponses EEG auditives ont été examinées avec un paradigme classique de mismatch negativity, pendant la phase précoce du coma qui est actuellement sous-investiguée. En utilisant la méthode de décodage développée dans la première partie de la thèse, j'ai pu quantifier le degré de discrimination auditive au niveau de chaque patient (Tzovara et al., in press). Nos résultats montrent pour la première fois que même des patients comateux qui ne vont pas survivre peuvent discriminer des sons au niveau neuronal, lors de la phase aigue du coma. De plus, une amélioration dans la discrimination auditive pendant les premières 48heures du coma a été observée seulement chez des patients qui se sont réveillés par la suite (100% de valeur prédictive pour un réveil).
Resumo:
Many species are able to learn to associate behaviours with rewards as this gives fitness advantages in changing environments. Social interactions between population members may, however, require more cognitive abilities than simple trial-and-error learning, in particular the capacity to make accurate hypotheses about the material payoff consequences of alternative action combinations. It is unclear in this context whether natural selection necessarily favours individuals to use information about payoffs associated with nontried actions (hypothetical payoffs), as opposed to simple reinforcement of realized payoff. Here, we develop an evolutionary model in which individuals are genetically determined to use either trial-and-error learning or learning based on hypothetical reinforcements, and ask what is the evolutionarily stable learning rule under pairwise symmetric two-action stochastic repeated games played over the individual's lifetime. We analyse through stochastic approximation theory and simulations the learning dynamics on the behavioural timescale, and derive conditions where trial-and-error learning outcompetes hypothetical reinforcement learning on the evolutionary timescale. This occurs in particular under repeated cooperative interactions with the same partner. By contrast, we find that hypothetical reinforcement learners tend to be favoured under random interactions, but stable polymorphisms can also obtain where trial-and-error learners are maintained at a low frequency. We conclude that specific game structures can select for trial-and-error learning even in the absence of costs of cognition, which illustrates that cost-free increased cognition can be counterselected under social interactions.
Resumo:
This case study examined how productivity and renewal are combined in a production organization operating in process industry through the antecedents of organizational ambidexterity; structure, culture, and management. The empirical material consisted of semi-structured interviews, observations and case organization documents. The findings suggest that the case organization structurally separates exploitation and exploration to separate units. However, it was found that the units focusing on exploration also devote resources to exploitation. External networks, such as customers, suppliers, and other factories seemed to play a role in the exploration activities, as well as in learning activities, which were connected to renewal. Productivity was seen as a natural part of a production organization and pursued at manufacturing units. Process management techniques appeared to be spread across the organization and having positive impact on exploitation and negative impact on exploration. The managerial culture and management’s capability to communicate goals, vision and strategy was found to be unsatisfactory. This thesis contributes to the new research paradigm of organizational ambidexterity by providing unique results on how the antecedents of organizational ambidexterity are accomplished in a production organization. Furthermore, the thesis extends the previous research of organizational renewal capability by connecting it to the ambidexterity theory.
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In the study the recently developed concept of strategic entrepreneurship was addressed with the aim to investigate the underlying factors and components constituting the concept and their influence on firm performance. As the result of analysis of existing literature and empirical studies the model of strategic entrepreneurship for the current study is developed with the emphasis on exploration and exploitation parts of the concept. The research model is tested on the data collected in the project ―Factors of growth and success of entrepreneurial firms in Russia‖ by Center for Entrepreneurship of GSOM in 2007 containing answers of owners and managers of 500 firms operating in St. Petersburg and Moscow. Multiple regression analysis showed that exploration and exploitation presented by entrepreneurial values, investments in internal resources, knowledge management and developmental changes are significant factors constituting strategic entrepreneurship and having positive relation to firm performance. The theoretical contribution of the work is linked to development and testing of the model of strategic entrepreneurship. The results can be implemented in management practices of companies willing to engage in strategic entrepreneurship and increase their firm performance.
Resumo:
In a modern dynamic environment organizations are facing new requirements for success and competitive advantage. This also sets new requirements for leaders. The term of ambidexterity is used in relation with organizations that are able to manage short-term efficiency and long-term innovation simultaneously. Ambidextrous leaders have the same capability at an individual level. They are able to balance between efficiency and flexibility. This study examined the confrontation of these two competing concepts in the leadership perspective. The aim of the study was to understand this recently arisen concept and its antecedents and examine what is currently known about ambidextrous leadership. This was a case study with data collected through theme interviews in a result orientated customer centre organization that has a cultural change at hand when it comes to leadership and empowerment. Organization wants to be efficient and flexible at the same time (a.k.a. ambidextrous) and that requires new type of leadership. In this study the aim was to describe the capabilities and criteria for ambidextrous leader and examine the leadership roles related to ambidextrous leadership in different hierarchical levels. The case organization had also created systematic means to support this cultural change and the effects of the process related to leadership were studied. This study showed that the area is yet widely unexplored and contradictory views are presented. This study contributes to the deprivation of study of ambidexterity in leadership and individuals. The study presents a description of ambidextrous leadership and describes the capabilities of ambidextrous leader. Ambidextrous leaders are able to make cognitive decisions between their leadership style according to situation that requires either leadership related to efficiency such as transactional leadership or leadership related to flexibility such as transformational leadership. Their leadership style supports both short-term and long-term goals. This study also shows that the role of top management is vital and operational leaders rely on their example.
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En Colombia las actividades de exploración, explotación, transporte y procesamiento de hidrocarburos que se vienen realizando desde comienzos del siglo XX son responsables de grandes procesos de transformación del territorio y de degradación de los ecosistemas en los que se realizan. Estos procesos han impactado negativamente la seguridad de las comunidades indígenas poniendo en riesgo su cultura y en algunos casos su existencia misma. Aunque históricamente los derechos de estas poblaciones frente a la explotación petrolera, y minera en general, han cambiado y su autonomía e integridad es protegida por la Constitución de 1991, las comunidades siguen teniendo una alta vulnerabilidad frente a la intervención de los ecosistema que habitan.La degradación ambiental producida directamente por las actividades petroleras y por los procesos de colonización que estas impulsan se constituye en una amenaza a la seguridad de las comunidades, cuyos territorios y recursos de subsistencia se ven disminuidos. La colonización y la presión sobre los recursos naturales que esta produce son motivadas principalmente por la pobreza de poblaciones campesinas que buscan nuevas tierras para habitar, a su vez estos dos procesos son causa de degradación ambiental que empobrece a las comunidades étnicas debido a que afecta sus fuentes de sustento, situación que genera inseguridad para los indígenas. Adicionalmente, la degradación ambiental y la disminución de los territorios ponen en riesgo la cultura de estos grupos humanos, pues afecta sus valores, tradiciones, autoridades y, en general, su forma de vida lo que constituye una amenaza a su seguridad.-----In Colombia, the exploration, exploitation, transport, and processing of hydrocarbons since the beginning of the 20th century have caused great territory transformations and ecosystem degradation. These processes have impacted adversely the indigenous communities security, exposing their culture and, in some cases, their existence itself. Even though, facing oil and, in general, mineral exploitation, the rights of this population have changed historically and their autonomy and integrity is protected by the 1991 Constitution, the communities are still highly vulnerable to the intervention on the ecosystem they inhabit.The environmental degradation directly arisen from the oil exploitation activities and the colonization they have driven, has become a threat to the security of the communities whose territories and subsistence resources have been reduced. Colonization and the resulting natural resource pressure are mainly caused by the poverty of the country population that seek new lands to occupy and these two facts cause in turn the environmental degradation that impoverish the ethnic communities by affecting their living sources, thereby causing insecurity to the indigenous population. In addition, environmental degradation and territory reduction risk these human groups’ culture by impacting their values, tradition, authorities and, in general, their way of living, and therefore turn into a threat to their security.
Resumo:
Techniques of optimization known as metaheuristics have achieved success in the resolution of many problems classified as NP-Hard. These methods use non deterministic approaches that reach very good solutions which, however, don t guarantee the determination of the global optimum. Beyond the inherent difficulties related to the complexity that characterizes the optimization problems, the metaheuristics still face the dilemma of xploration/exploitation, which consists of choosing between a greedy search and a wider exploration of the solution space. A way to guide such algorithms during the searching of better solutions is supplying them with more knowledge of the problem through the use of a intelligent agent, able to recognize promising regions and also identify when they should diversify the direction of the search. This way, this work proposes the use of Reinforcement Learning technique - Q-learning Algorithm - as exploration/exploitation strategy for the metaheuristics GRASP (Greedy Randomized Adaptive Search Procedure) and Genetic Algorithm. The GRASP metaheuristic uses Q-learning instead of the traditional greedy-random algorithm in the construction phase. This replacement has the purpose of improving the quality of the initial solutions that are used in the local search phase of the GRASP, and also provides for the metaheuristic an adaptive memory mechanism that allows the reuse of good previous decisions and also avoids the repetition of bad decisions. In the Genetic Algorithm, the Q-learning algorithm was used to generate an initial population of high fitness, and after a determined number of generations, where the rate of diversity of the population is less than a certain limit L, it also was applied to supply one of the parents to be used in the genetic crossover operator. Another significant change in the hybrid genetic algorithm is the proposal of a mutually interactive cooperation process between the genetic operators and the Q-learning algorithm. In this interactive/cooperative process, the Q-learning algorithm receives an additional update in the matrix of Q-values based on the current best solution of the Genetic Algorithm. The computational experiments presented in this thesis compares the results obtained with the implementation of traditional versions of GRASP metaheuristic and Genetic Algorithm, with those obtained using the proposed hybrid methods. Both algorithms had been applied successfully to the symmetrical Traveling Salesman Problem, which was modeled as a Markov decision process
Resumo:
We present a novel surrogate model-based global optimization framework allowing a large number of function evaluations. The method, called SpLEGO, is based on a multi-scale expected improvement (EI) framework relying on both sparse and local Gaussian process (GP) models. First, a bi-objective approach relying on a global sparse GP model is used to determine potential next sampling regions. Local GP models are then constructed within each selected region. The method subsequently employs the standard expected improvement criterion to deal with the exploration-exploitation trade-off within selected local models, leading to a decision on where to perform the next function evaluation(s). The potential of our approach is demonstrated using the so-called Sparse Pseudo-input GP as a global model. The algorithm is tested on four benchmark problems, whose number of starting points ranges from 102 to 104. Our results show that SpLEGO is effective and capable of solving problems with large number of starting points, and it even provides significant advantages when compared with state-of-the-art EI algorithms.
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Machine and Statistical Learning techniques are used in almost all online advertisement systems. The problem of discovering which content is more demanded (e.g. receive more clicks) can be modeled as a multi-armed bandit problem. Contextual bandits (i.e., bandits with covariates, side information or associative reinforcement learning) associate, to each specific content, several features that define the “context” in which it appears (e.g. user, web page, time, region). This problem can be studied in the stochastic/statistical setting by means of the conditional probability paradigm using the Bayes’ theorem. However, for very large contextual information and/or real-time constraints, the exact calculation of the Bayes’ rule is computationally infeasible. In this article, we present a method that is able to handle large contextual information for learning in contextual-bandits problems. This method was tested in the Challenge on Yahoo! dataset at ICML2012’s Workshop “new Challenges for Exploration & Exploitation 3”, obtaining the second place. Its basic exploration policy is deterministic in the sense that for the same input data (as a time-series) the same results are obtained. We address the deterministic exploration vs. exploitation issue, explaining the way in which the proposed method deterministically finds an effective dynamic trade-off based solely in the input-data, in contrast to other methods that use a random number generator.
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In this thesis, we explore the relationship between absorptive capacity and alliances, and their influence on firms’ competitive advantage in the US and European biopharmaceutical sectors. The study undertaken in this thesis is based on data from a large-scale international survey of over 2,500 biopharmaceutical firms in the US, the UK, Germany, France and Ireland. The thesis advanced a conceptual framework, which integrated the multi-dimensions of absorptive capacity, exploration-exploitation alliances, and competitive advantage, into a biopharmaceutical firm’s new product development process. The proposed framework is then tested in the empirical analysis, using truncated models to estimate firms’ sales growth, with zero-inflated negative binominal models capturing the number of alliances in which firms engage, and aspects of realised absorptive capacity analysed by ordinal probit models. The empirical results suggest that both skill-based and exploitation-based absorptive capacity play crucial roles in shaping firms’ competitive advantage, while neither exploratory nor exploitation alliances contribute to the improvement in firms’ competitive position. In terms of the interaction between firms’ absorptive capacity and alliance behaviour, the results suggest that engagement with exploratory alliances depends more strongly on firms’ assimilation capability (skills levels and continuity of R&D activities), while participation in exploitation alliances is more conditional on firms’ relevant knowledge monitoring capability. The results highlight the major differences between the determinants of firms’ alliance behaviour, and competitive advantage in the US and Europe – in the US firms’ skill levels prove more significant in determining firms’ engagement with exploratory alliances, whereas in Europe continuity of R&D proves more important. Correspondingly, while US firms’ engagement with exploitation alliances depends on market monitoring capability, that in Europe is more strongly linked to exploitation-based absorptive capacity. In respect of the determinants of firms’ competitive advantage – in Europe, market monitoring capability, engagement with exploitation alliances, and continuous R&D activities, prove more important, while in the US, it is firms’ market characteristics that matter most.
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Solar photovoltaic technology is one of the renewable technologies, which has a potential to shape a clean, reliable, scalable and affordable electricity system for the future. This article provides a comprehensive review of solar photovoltaic technology in terms of photovoltaic materials efficiency and globally leading countries. Based on past years review and photovoltaic installations in the year 2014, the major five leading countries identified are China, Japan, USA, Germany and UK. These five countries altogether accounted for 80% of photovoltaic installations in 2014. The article also discusses the driving policies, funding and Research and Development activities: to gauge the reasons behind the success of the leading countries. Finally, this article reviews the photovoltaic cost analysis in terms of the photovoltaic module cost, balance of system cost and project cost with the help of listed 98 globally installed projects.
Resumo:
Regulatory Focus Theory predicts that the motivation to self-regulate goal-directed thought and behavior depends on two distinct regulation strategies: a promotion focus based on attaining gains and a prevention focus based on avoiding losses. This study took a social-cognitive approach predicting that regulatory focus has an impact on how family startups (several family related founders) explore “new ideas”, exploit “old certainties” and achieve the balance of both (ambidexterity), compared to lone founder startups (only one founder present). It was proposed that the social context of family ties among founders leads them to a prevention focus concerned with avoiding the loss of the socio-emotional benefits of those ties. In order to avoid such a loss, family founders were expected to increase their risk perceptions and thus, explore less than lone founders, who lack such socio-emotional ties. It was also proposed that two commonly used psychological traits in entrepreneurship research --achievement motivation and internal locus of control, predispose entrepreneurs to a promotion focus. Founders with a promotion focus, in turn, were hypothesized to lead startups to more risk-seeking behaviors and to more explorative orientation. The previous argument was used as a springboard to derive hypotheses about ambidexterity (the ability to exploit and explore simultaneously) and survival hazards. Using Regulatory Focus Theory, exploitative orientation, conceptualized as the motivational strength to continue on previous paths of action, was hypothesized to be not significantly different from that of lone founder startups. Taking previous arguments together, lone founder startups were hypothesized to be more ambidextrous than family startups. Finally, ambidexterity and internal locus of control were hypothesized to reduce survival hazards in family startups. The findings suggested that family startups explore less than lone founder startups even after controlling for group effects. Interesting but contradictory findings revealed that internal locus of control have both a positive direct effect and a positive interaction that increases the explorative and ambidextrous orientation gap of family startups over lone founder startups. As expected, ambidexterity and internal locus of control reduced survival hazards on family startups. Implications for practitioners were derived based on a sample of 470 nascent entrepreneurs.
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El estatuto de contratación administrativa (Ley 80 de 1993 y Ley 1150 de 2007) por regla general regula todos los negocios jurídicos que surgen de la actividad de la Administración Pública, pero teniendo en cuenta las actividades que desarrollan algunas entidades del Estado esta regla tiende a presentar excepciones, como es el caso de aquellas Entidades que tienen por objeto la Exploración y Explotación de los Recursos Naturales renovables y no renovables. El principal actor del régimen excepcional de contratación para la exploración y explotación de hidrocarburos es la Agencia Nacional de Hidrocarburos (ANH), el cual cuenta con dos reglamentos de contratación especial para la asignación de áreas y de contratación misional, en donde por disposición legal debe dar aplicación a los principios de contratación contemplados en el estatuto General de la Contratación pública (Transparencia, economía, responsabilidad y el deber de selección objetiva), este trabajo de investigación procura realizar una mirada analítica a cada procedimiento para determinar con posterioridad el grado de acatamiento de la orden legal establecida en el artículo 76 de la Ley 80 de 1993 así como sus principales falencias