1,721,008 research outputs found
Variational Optical Flow Algorithms for Motion Estimation
No full textMotion is an intrinsic character of the world and an inherent part of our visual experience, which gives essential source of information to a wide variety of visual tasks, and directly affects the subsequent image processing and other related applications. Since Horn and Schunck (HS) proposed the optical flow method to estimate motion field in 1981, it becomes one of the best approaches for motion estimation. The research described in this dissertation focuses on improving the accuracy of the optical flow estimation by proposing some novel techniques to handle the unsolved challenges. The main contributions of this work are the following: 1) We modify the balance between the data term and the smoothness term in two aspects: First, proposing a weighted root mean square (WRMS) error measure to automatically select an optimal smoothness parameter λ globally. Which achieves by setting a reference λ0 based on the quality of the frame, and then proposes an efficient brute-force approach to assign a group of λ to reduce the number of candidates. The optimal λ corresponds to the minimal RMS. Second, presenting an effective fusion method to fuse multiple flows of different smoothness parameter λ to compose a single superior flow. 2) We handle large displacements by integrating matching information into the continuous variational flow field according to a novel weighted local intensity fusion (WLIF) method. The variational methods usually combines with a coarse-to-fine strategy. However, the sub-sampling scheme that the coarse-to-fine framework used to reduce the size of the images and the motion within, leads to a loss of motion details that any algorithm can recover. Hence, the variational methods perform poorly on image structures with motions larger than their own size. The matching field supplies correct large displacements, which is helpful to recover the lost motion information (both large and small displacements) of traditional variational methods. 3) We remove outliers in either of the intermediate flow fields or the warped interpolation image by designing new filters. In particular, three filters are designed to achieve this goal. First, we present a novel combined post-filtering (CPF) method, which uses a weighted median filter (WMF), a bilateral filter (BF) and a fast MF to post-smooth the detected edges, occlusions, and flat regions of the intermediate flow fields respectively. Second, we present a PatchWMF method, which denpends on an improved color patch similarity measure (ICPSM), to modify the robustness of the WMF of to noise. Third, we present an adaptive guided image filter (AGIF) to correct these errors in the warped interpolation image. Due to this contribution, the accuracy of the discrete temporal derivative It is modified. 4) We achieve to estimate accurate optical flow in the presence of spatially-varying motion blur and, improve the flow accuracy by computing optical flow and restoring images with preserved edges simultaneously
Modeling and Supporting Web-Navigation
No full textNavigation within a website is an important factor for the success of a website. Faster and easy web-navigation leads to better usability and reduces cognitive load on the user. Several cognitive models exist that simulate the web-navigation process. In this paper we propose a new cognitive model – CoLiDeS++Pic (based on Comprehension-based Linked model of Deliberate Search or CoLiDeS) that incorporates path adequacy and backtracking strategies. This model also takes into consideration the semantics of pictures. Firstly, we present here the results of an experiment in which we test the efficacy of support based on the new model CoLiDeS++Pic and multi-tasking under cognitively demanding situations. The results prove that the model-generated support is effective. Secondly, we also propose that in this way navigation behavior can be better modeled when compared to previous models. We verify this hypothesis by simulating the model on a mock-up website and comparing the results with a previous model CoLiDeS+. Extending our previous work we demonstrate that the performance of the new model CoLiDeS++Pic is improved compared to the preceding model CoLiDeS+. We further discuss the challenges and advantages of automating navigation support using the proposed model
Measuring Effectiveness of Persuasive Games Using an Informative Control Condition
Full text linkResearch about the effectiveness of persuasive games is still emerging. This article presents a literature review of studies that empirically evaluate the effectiveness of persuasive games. The review concluded that limited empirical evidence is currently available to prove their effectiveness in attitude change. It further revealed that almost no study employed an informative control condition, making it difficult to conclude that the game was more effective than a control condition. Next, in a pretest-posttest design an empirical study tested whether change in attitude was different for people playing the persuasive game "EnerCities" compared to a control condition where participants read a document with highly similar information. No significant differences in increase of attitude or knowledge between participants that played the game and participants in the informative control condition were found. Based on the results of the literature review and the empirical study presented, it hence cannot be concluded that playing a game leads to a greater change in attitude or knowledge acquisition than experiencing conventional media would. Future work should employ designs with proper control conditions and focus on which game features lead to significant effects
Adaptive guided image filter for warping in variational optical flow computation
Full text linkThe variational optical flow method is considered to be the standard method to calculate an accurate dense motion field between successive frames. It assumes that the energy function has spatiotemporal continuities and appearance motions are small. However, for real image sequences, the temporal continuity assumption is often violated due to outliers and occlusions, causing inaccurate flow vectors at these regions. After each warping operation, errors are generated at the corresponding regions of the warped interpolation image. This results in an inaccurate discrete approximation of the temporal derivative and thus ends up affecting the accuracy of the estimated flow field. In this paper, we propose an adaptive guided image filter to correct these errors in the warped interpolation image. A guidance image is reconstructed by considering both the feature of the reference image as well as the difference between the warped interpolation image and the reference image, to guide the filtering of the warped interpolation image. To adjust the smoothing degree, the regularization parameter in the guided image filter is adaptively selected based on a confidence measure. Extensive experiments on different datasets and comparison with state-of-the-art variational optical flow algorithms demonstrate the effectiveness of our method
Audiovisual navigation in virtual mazes: The benefits of audiovisual landmarks
No full textIt has been shown that multisensory presentation can improve perception, attention, and object memory compared with unisensory presentation. Consequently, we expect that multisensory presentation of landmarks can improve spatial memory and navigation. In this study we tested the effect of visual, auditory and combined landmark presentations in virtual mazes on spatial memory and spatial navigation. Nineteen participants explored four different virtual mazes consisting of nodes with landmarks and corridors connecting them. Each maze was explored for 90 s. After each exploration, participants performed the following tasks in fixed order: (1) draw a map of the maze, (2) recall adjacent landmarks for three given landmarks, (3) place all landmarks on the map of the maze, and (4) find their way through the maze to locate five given landmarks in fixed order. Our study shows significant effects of multisensory versus unisensory landmarks for the maze drawing task, the adjacency task, and the wayfinding task. Our results suggest that audiovisual landmark presentations improve spatial memory and spatial navigation performance in virtual environments
Robust Point Cloud Segmentation of Rodents using Close Range Depth Cameras in Controlled Environments
No full textRodent behavior analysis is a extremely important task for pre-clinical testing of new drugs and neurodegenerative diseases. Some of the underlying mechanisms regulating natural interactions among multiple animals require long term interaction, which implies the usage of automated, objective and systematic video analysis system. However, current video analysis systems are limited by idiosyncratic features of the 2D video technology, and requiring a great number of parameters. This early stage work focuses on the first step of a depth-based tracking system, offering some methods to robustly perform rodent segmentation in a controlled environment, fully exploiting its geometrical properties, providing a qualitative overview of the results attained so far
Age-related Differences in the Content of Search Queries when Reformulating
No full textThis study investigated the change in the content of the queries when performing reformulations in relation to age and task difficulty. Results showed that both generalization and specialization strategies were applied significantly more often for difficult tasks compared to simple tasks. Young participants were found to use specialization strategy significantly more often than old participants. Generalization strategy was also used significantly more often by young participants, especially for difficult tasks. Young participants were found to reformulate much longer than old participants. The semantic relevance of queries with the target information was found to be significantly higher for difficult tasks compared to simple tasks. It showed a decreasing trend across reformulations for old participants and remained constant for young participants, indicating that as old participants reformulated, they produced queries that were further away from the target information. Implications of these findings for design of information search systems are discussed
Age-related effects of task difficulty on the semantic relevance of query reformulations
Full text linkThis study examined the semantics of query reformulations in relation to age and task difficulty. Task difficulty was manipulated using a metric called task preciseness defined as the semantic similarity of the task description with the content of the target page(s) containing the answer. A behavioral experiment was conducted in which 24 younger adults and 21 older adults solved six low precise and six high precise information search tasks. The behavioral outcomes were found to be in line with preceding work indicating that the metric was successful in differentiating different levels of task difficulty. Analysis of the semantic relevance of queries showed that for low precise tasks, the queries generated by younger adults had significantly higher mean semantic relevance than that of older adults whereas for high precise tasks, it was the other way round. When analyzed across reformulations, it was found that the mean semantic relevance of queries generated by older adults, decreased for both low and high precise tasks. For younger adults, it remained constant for high precise tasks and even increased for low precise tasks. Implications of these findings for the design of information search systems are discussed
(Re-)Examination of Multimodal Augmented Reality
No full textThe majority of augmented reality (AR) research has been concerned with visual perception, however the move towards multimodality is imminent. At the same time, there is no clear vision of what multimodal AR is. The purpose of this position paper is to consider possible ways of examining AR other than using popular notions and definitions, in order to come to an understanding of multimodal AR. Three concepts are introduced. First, the commonly used terms 'real' and 'virtual' are redefined in terms of stimuli rather than objects, and mediated stimuli are introduced as a new category. This addition facilitates the support of, for example, sensory substitution stimuli in AR. Next, the popular definitions of AR are examined, and a new analysis is presented. Specifically, it is theorized that the core of AR is not necessarily the combination of real and virtual, but the combination of a basis and an augmentation. Such an abstraction allows the re-introduction of augmented virtuality and, more generally, mixed reality. Lastly, a classification system for different forms of multimodal mixed reality that applies this basis-augmentation model is presented
Gamification in a Prototype Household Energy Game
No full textResearch where gamification is used to influence household energy consumption is an emerging field. This paper reviews design features of the prototype Powersaver Game. The aim of this game is to influence household energy consumption in the long-term. The evaluation of the design of the prototype, which is presented in this paper, is part of a larger research project that will give insight into what the influence of gamification is on energy consumption in households by means of electricity and gas usage and on attitudes towards sustainable energy use at home. In the first design step, a comparative literature analysis of eight games developed for related research purposes, provided first suggestions for the design of our game. In the next design step potential players have evaluated its match with the real world. Since our aim is an effective transfer between the game world and real world, we introduced gamification elements from the real world, by energy saving activities, in the game. The perceived match between in-game scenes and activities in the real world indicated improvements for a number of scenes. In the second evaluation the respondents suggested that the design of Powersaver Game is satisfactory, with the exception of some artwork. By involving potential players in the evaluation process we extract promising suggestions for design improvements. The outcomes of these evaluation studies contribute to effectively embedding of real world elements in the game and to improving aspects of the prototype in clarity and attractiveness. In the next stage the Powersaver Game is used in a series of experiments. First, the game will be compared with a control (non-game) version. Next, features such as feedback, personal relevance and competition will be examined
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