Generating request streams on Big Data using clustered renewal processes

The performance evaluation of large file systems, such as storage and media streaming, motivates scalable generation of representative traces. We focus on two key characteristics of traces, popularity and temporal locality. The common practice of using a system-wide distribution obscures per-object behavior, which is important for system evaluation. We propose a model based on delayed renewal processes which, by sampling interarrival times for each object, accurately reproduces popularity and temporal locality for the trace. A lightweight version reduces the dimension of the model with statistical clustering. It is workload-agnostic and object type-aware, suitable for testing emerging workloads and ‘what-if’ scenarios. We implemented a synthetic trace generator and validated it using: (1) a Big Data storage (HDFS) workload from Yahoo!, (2) a trace from a feature animation company, and (3) a streaming media workload. Two case studies in caching and replicated distributed storage systems show that our traces produce application-level results similar to the real workload. The trace generator is fast and readily scales to a system of 4.3 million files. It outperforms existing models in terms of accurately reproducing the characteristics of the real trace.     

Reduction of the size of L-fuzzy contexts. A tool for differential diagnoses of diseases

ABSTRACT

Information extraction from an L-fuzzy context becomes a hard problem when we work with a large set of objects and/or attributes. The goal of this paper is to present two different and complementary techniques to reduce the size of the context. First, using overlap indexes, we will establish rankings among the elements of the context that will allow us to determine those that do not provide relevant information and eliminate them. Second, by means of Choquet integrals, we will aggregate some objects or attributes of the context in order to jointly use the provided information. One interesting application of the developed theory consists on helping in the differential diagnoses of diseases that share a large number of symptoms and, therefore, that are difficult of distinguish.     

Probabilistic assessment of user's emotions in educational games

We present a probabilistic model to monitor a user's emotions and engagement during the interaction with educational games. We illustrate how our probabilistic model assesses affect by integrating evidence on both possible causes of the user's emotional arousal (i.e., the state of the interaction) and its effects (i.e., bodily expressions that are known to be influenced by emotional reactions). The probabilistic model relies on a Dynamic Decision Network to leverage any indirect evidence on the user's emotional state, in order to estimate this state and any other related variable in the model. This is crucial in a modeling task in which the available evidence usually varies with the user and with each particular interaction. The probabilistic model we present is to be used by decision theoretic pedagogical agents to generate interventions aimed at achieving the best tradeoff between a user's learning and engagement during the interaction with educational games.     

Rethinking the Concepts of Virtual Water and Water Footprint in Relation to the Production–Consumption Binomial and the Water–Energy Nexus

In the field of Ecological Economics, the need of using physical indicators to analyse economic processes, at the same time they serve as tools in decision making, has been lately highlighted. Virtual Water (VW) and Water Footprint (WF) are two useful indicators in achieving this objective, the first one from the perspective of production, the second one from that of consumption. This difference between them is interesting inasmuch as it allows to identify the subjects who are responsible for water consumption, whether producers or consumers, and proves both indicators’ potential when designing water management policies. In this work, we consider a hypothesis according to which there is a clear difference between the two concepts—Virtual Water and Water Footprint—and this difference, although evident in their respective conceptualizations, is not reflected in their estimations and applications. This is true to the point that the two concepts are often used as synonyms, thus wasting the enormous potential associated to their difference. Starting from this hypothesis, our objective is, first of all, to highlight this evident but ignored difference between VW and WF through a deep and thorough literature review of the conceptual definitions and contributions, the methodologies developed and the applications made regarding the two concepts. Second, we intend to make a conceptual and methodological proposition aimed at underlining the differences already mentioned and to identify responsibilities in water consumption. We do it by broadening the context of analysis and by integrating the production–consumption binomial and water–energy nexus.     

Factors affecting task management in aviation

OBJECTIVE: We investigated the influence of ongoing task display "compellingness" on attention allocation patterns and assessed its interaction with interrupting task salience and importance. BACKGROUND: There are some concerns that the compellingness of flight deck tunnel displays renders the task they support more resistant to interruptions, thus preventing the pilot from noticing cues signaling the need to divert attention to other tasks. METHODS: Forty pilots flew three curved approaches in a high-fidelity simulation using a synthetic vision system (SVS) display. In addition to the primary task of flying, during the last approach they were required to select the approach path on the basis of environmental information concerning weather. The display layout supporting the primary flight task (tunnel vs. baseline display), the nature of the cue signaling the need to divert attention to the path selection task (visual vs. auditory-visual cue), and the cost of not performing the secondary task were manipulated to investigate their influence on task prioritization. RESULTS: The modality and priority of the cue affected the frequency of the switch to the secondary task. Furthermore, pilots flying with a tunnel display were more likely to detect the change in the weather and were easily interrupted by the secondary task when priority was high. CONCLUSION: Our results suggest that some of the concerns regarding the negative consequences of the compelling nature of the tunnel display may not be as pronounced as thought. APPLICATIONS: This study highlights the utility of the tunnel display in improving flight safety.     

Assessing Panamanian hospitals' performance with alternative frontier methods

In the last decades, there has been a growing interest in measuring the efficiency of hospitals using different methodological approaches, mainly represented by data envelopment analysis (DEA) and stochastic frontier analysis (SFA). In this study, we estimate efficiency measures of performance for a sample of Panamanian public hospitals over an 11-year period (2005–2015) using both traditional methods (DEA and SFA) and compare them with efficiencies estimated with an alternative approach, the so-called StoNED (stochastic semi-nonparametric envelopment of data), which combines the virtues of those methods in a unified framework. One of the most interesting features of the public health system in Panama is that it is segmented, as hospitals are operating under two parallel management schemes (the Ministry of Health and the Social Security Fund), thus in our empirical analysis we will also focus on exploring the differences between hospitals operating under each regime. Our results show that there are certain divergences in the efficiency scores estimated with different methodologies, but for all of them it is possible to detect that Panamanian hospitals experienced a clear decrease in their efficiency levels throughout the period evaluated, being this much higher in the hospitals belonging to the Social Security Fund.     

Recognizing shopper demographics from behavioral responses in a virtual reality store

Virtual Reality - The use of virtual reality (VR) technology in the context of retail is a significant trend in current consumer research, as it offers market researchers a unique opportunity to...     

Improving learner quality of experience by content adaptation based on network conditions

Apart from user characteristics, properties of the network over which the content is delivered and device on which the content is displayed affect end-user perceived quality. This paper presents a learner quality of experience (QoE) model that apart from the user-related content adaptation, considers delivery performance-based content personalisation in order to improve user experience when interacting with an online learning system.A comparison-based study on the benefit of using the proposed learner QoE model in adaptive and personalized education was conducted involving the original AHA! and QoEAHA – a version of AHA! enhanced with the learner QoE model. Testing results demonstrate significant benefits in terms of learning achievement, learning performance, learner navigation and user QoE in favour of the learner QoE model-enhanced solution.     

Preservation of Interpolation Features by Fibring

Fibring is a metalogical constructor that permits to combinedifferent logics by operating on their deductive systems undercertain natural restrictions, as for example that the two givenlogics are presented by deductive systems of the same type.Under such circumstances, fibring will produce a new deductivesystem by means of the free use of inference rules from bothdeductive systems, provided the rules are schematic, in thesense of using variables that are open for application to formulaswith new linguistic symbols (from the point of view of eachlogic component). Fibring is a generalization of fusion, a lessgeneral but wider developed mechanism which permits resultsof the following kind: if each logic component is decidable(or sound, or complete with respect to a certain semantics)then the resulting logic heirs such a property. The interestfor such preservation results for combining logics is evident,and they have been achieved in the more general setting of fibringin several cases. The Craig interpolation property and the Maeharainterpolation have a special significance when combining logics,being related to certain problems of complexity theory, someproperties of model theory and to the usual (global) metatheoremof deduction. When the peculiarities of the distinction betweenlocal and global deduction interfere, justifying what we callcareful reasoning, the question of preservation of interpolationbecomes more subtle and other forms of interpolation can bedistinguished. These questions are investigated and several(global and local) preservation results for interpolation areobtained for fibring logics that fulfill mild requirements.     

Virtual Loom: a tool for the interactive 3D representation of historical fabrics

Multimedia Tools and Applications - 3D modelling of man-made objects is widely used in the cultural heritage sector, among others. It is relevant for its documentation, dissemination and...