OLED lifetime issues from a mobile‐phone‐industry point of view

Abstract— Lifetime issues have been a hot topic throughout the history of OLEDs. The rapid development of lifetimes since 2002 has enabled OLED displays to become acceptable for mobile phones. The lifetime requirements of 30,000 hours expressed by the representatives of mobile‐phone‐terminal makers were felt to be unrealistic to be obtained in 2003, since the lifetime of the blue color was below 1000 hours. Today, 5 years later, lifetimes of AMOLED panels are over 50,000 hours. OLED displays are suffering from a burn‐in effect due to limited lifetime. After 2003, it was understood by the panel and terminal makers that instead of lifetime, burn‐in sensitivity became the limiting factor from an AMOLED‐panel usability point of view. The burn‐in effect becomes visible at 2–3% luminance degradation levels between adjacent pixels. To take this effect into account in mobile‐phone applications, the lifetime needs to be increased from 30,000 to 60,000 hours, and suitable algorithms need to be used for the display of the terminal. There is also pressure to double the peak luminance values used in the terminals in order to improve the performance of the screen in outdoor environments. The roles of the material developers, panel makers, and terminal makers are reviewed in this paper from a lifetime perspective.     

Can eyes reveal interest? Implicit queries from gaze patterns

We study a new research problem, where an implicit information retrieval query is inferred from eye movements measured when the user is reading, and used to retrieve new documents. In the training phase, the user’s interest is known, and we learn a mapping from how the user looks at a term to the role of the term in the implicit query. Assuming the mapping is universal, that is, the same for all queries in a given domain, we can use it to construct queries even for new topics for which no learning data is available. We constructed a controlled experimental setting to show that when the system has no prior information as to what the user is searching, the eye movements help significantly in the search. This is the case in a proactive search, for instance, where the system monitors the reading behaviour of the user in a new topic. In contrast, during a search or reading session where the set of inspected documents is biased towards being relevant, a stronger strategy is to search for content-wise similar documents than to use the eye movements.     

Visual measurement and tracking in laser hybrid welding

This paper presents a novel system for the automatic analysis of a hybrid welding process. High-speed imaging and laser illumination are used to measure the regularity of electric arc frequency and flight directions of filler metal droplets. A fuzzy c-means clustering method is used to detect arcs and segment the video sequences. The droplets are localized by combining principal component analysis and a support vector machine classifier. The flight of a droplet is tracked using Kalman filtering. Experiments indicate that the system is able to track the flights of droplets and to determine the regularity of the arc frequency with a high accuracy if the imaging conditions are stable.

What makes segmentation good? A case study in boreal forest habitat mapping

Segmentation goodness evaluation is a set of approaches meant for deciding which segmentation is good. In this study, we tested different supervised segmentation evaluation measures and visual interpretation in the case of boreal forest habitat mapping in Southern Finland. The data used were WorldView-2 satellite imagery, a lidar digital elevation model (DEM), and a canopy height model (CHM) in 2 m resolution. The segmentation methods tested were the fractal net evolution approach (FNEA) and IDRISI watershed segmentation. Overall, 252 different segmentation methods, layers, and parameter combinations were tested. We also used eight different habitat delineations as reference polygons against which 252 different segmentations were tested. The ranking order of segmentations depended on the chosen supervised evaluation measure; hence, no single segmentation could be ranked as the best. In visual interpretation among the several different segmentations that we found rather good, we selected only one as the best. In the literature, it has been noted that better segmentation leads to higher classification accuracy. We tested this argument by classifying 12 of our segmentations with the random forest classifier. It was found out that there is no straightforward answer to the argument, since the definition of good segmentation is inconsistent. The highest classification accuracy (0.72) was obtained with segmentation that was regarded as one of the best in visual interpretation. However, almost similarly high classification accuracies were obtained with other segmentations. We conclude that one has to decide what one wants from segmentation and use segmentation evaluation measures with care.     

Designing for privacy and self-presentation in social awareness

Social awareness applications are based on the idea of a group sharing real-time context information via personal and ubiquitous terminals. Studies of such applications have shown that users are not only concerned with the preservation privacy through non-disclosure. Instead, disclosure is manipulated for the constant presentation of self to the group in everyday social situations. Basing on 3 years of research with the mobile social awareness system ContextContacts, established findings in social psychology and ubiquitous computing, we propose a number of design principles to support users in this management of privacy and presentation. These principles are to apply even if disclosure is automated, and include support for lightweight permissions, assuming reciprocity, appearing differently to different audiences, providing for feedback on presentation and allowing lying. These principles are applied in interaction design and protocol engineering for the next version of a mobile awareness system called ContextContacts.

Convergence of a spreading activation neural network with application of simulating aphasic naming errors in Finnish language

Aphasia is a language disorder caused by brain damage. Difficulties in word processing called anomia constitute the most common type of errors in aphasia. Naming errors are characteristic of aphasia and can be used to investigate the disorder. In this context, naming refers to a psycholinguistic test where the subject is asked to utter the names of target objects presented to him or her in the form of simple pictures. In the case of aphasia the subject may name objects presented or concepts incorrectly by word blends (e.g. semantic error to say “right” for “left”) or even forming nonwords (words without sensible meaning). Previously [[Reference to 5], [Reference to 6], [Reference to 8], [Reference to 10] and [Reference to 11]], we have constructed a simulation technique with a spreading activation algorithm to model the mental word processing of an aphasic by employing a succession of four neural networks with semantic, phonological, syllabic and phonemic processing functions, respectively. Treating words and their component parts as textual units, naming errors are generated in the system by spreading activation in the networks. In this paper we study the convergence properties of the algorithms which are used for spreading activation in these networks. Convergence shows which component parts dominate other parts in the networks employed. It can be reasonable also in the psycholinguistic sense, at least concerning the so-called perseveration in which some word or sound is repeated being unable to form a correct word. To enable to predict and control the behaviour of the model the convergence property is useful to understand.     

Finite element analysis of the Girkmann problem using the modern hp-version and the classical h-version

We perform finite element analysis of the so called Girkmann problem in structural mechanics. The problem involves an axially symmetric spherical shell stiffened with a foot ring and is approached (1) by using the axisymmetric formulation of linear elasticity theory and (2) by using a dimensionally reduced shell-ring model. In the first approach the problem is solved with a fully automatic hp-adaptive finite element solver whereas the classical h-version of the finite element method is used in the second approach. We study the convergence behaviour of the different numerical models and show that accurate stress resultants can be obtained with both models by using effective post-processing formulas.     

A review and comparison of strategies for multi-step ahead time series forecasting based on the NN5 forecasting competition

Multi-step ahead forecasting is still an open challenge in time series forecasting. Several approaches that deal with this complex problem have been proposed in the literature but an extensive comparison on a large number of tasks is still missing. This paper aims to fill this gap by reviewing existing strategies for multi-step ahead forecasting and comparing them in theoretical and practical terms. To attain such an objective, we performed a large scale comparison of these different strategies using a large experimental benchmark (namely the 111 series from the NN5 forecasting competition). In addition, we considered the effects of deseasonalization, input variable selection, and forecast combination on these strategies and on multi-step ahead forecasting at large. The following three findings appear to be consistently supported by the experimental results: Multiple-Output strategies are the best performing approaches, deseasonalization leads to uniformly improved forecast accuracy, and input selection is more effective when performed in conjunction with deseasonalization.     

Comparison of load-balancing approaches for multipath connectivity

During past years, the so-called resource pooling principle in data networks has been studied more carefully. For example, the recent work on routing on the Internet over multiple paths and Multipath TCP both seek to make the best possible use of multiple connecting paths between two end points. In deployments where multiple users could share multiple paths, one of the very first questions that comes to mind is, should we schedule packets from the users on a per-flow or per-packet basis? In this paper we study networking scenarios in which several networks are connected to each other via multiple paths. We seek to understand how a multi-homed router should schedule packets and packet flows out towards other networks. Our primary interests are to study path utilization and analyze the bandwidth fairness of various approaches using different traffic loads.     

Thermochromic Furofurans. IV. Approach to the synthesis of bridgehead substituted furo[3,2-b]furans and side products of McMurry reactions

Substituted dihydroxystilbenes 2 are suitable starting materials for the synthesis of photochromic systems derived from 3 / 4 . Attempts to couple the naphthones 8a - 8e by the McMurry reaction with TiCl₃/LiAlH₄ yielded mainly reduction products such as 8f , g or 9 . However, the furofuran 3b was isolated when using the zinc–copper couple for reduction. The helicene 11 was formed as an unexpected by-product in the McMurry reaction of the pivaloylnaphthalene 8d .