AR assistance for efficient dynamic target search

Computational Visual Media - When searching for a dynamic target in an unknown real world scene, search efficiency is greatly reduced if users lack information about the spatial structure of the...     

The smallest target size for a comfortable pointing in freehand space: human pointing precision of freehand interaction

Universal Access in the Information Society - Designing interfaces that suit human pointing precision in freehand space can improve the smoothness and naturalness of gestural interaction. However,...     

Examining the costs of multiple trajectory pointing techniques

Pointing techniques that offer users multiple trajectories to a target have the potential to reduce pointing time by allowing a shorter than normal movement distance. However, such techniques potentially introduce additional elements into the pointing task involving identification of the alternative trajectories, assessment of their relative performance, and selection of the one to use. These additional tasks may reduce or negate the benefits of offering shorter paths. To better understand these issues, we developed a methodology for controlling the relative benefits of alternative target trajectories, and used it to evaluate three interfaces—a ‘pointer wrapping’ technique that allows the cursor to traverse from one screen edge to the opposing edge, and a system allowing users to choose between multiple cursors in two configurations (‘Ninja cursors’). We found that performance with these techniques was significantly worse than that predicted by Fitts' law for a single cursor, suggesting that the additional elements in their use are significant. Detailed analysis of behaviour during acquisitions showed that much of this cost is accrued in the mental preparation that precedes motor action, and in additional volatility in the pointing movements. We discuss how the method and findings may assist those developing enhanced pointing techniques.     

空间光通信精跟瞄处理技术研究

首先介绍了精跟瞄探测器的原理与组成,然后重点介绍了精跟瞄探测器的处理算法。最后对精跟瞄处理算法进行了验证,证明采用这种算法处理跟瞄精度能够达到空间光通信的要求。     

Extended Fitts' law for 3D pointing tasks using 3D target arrangements

This study explored an extended 3D Fitts' model, which was more appropriate than the original Fitts' model for pointing tasks in 3D environment. The inclination angle and azimuth angle for spherical coordinate system were added to Fitts' original model formulation. Experiments were conducted by manipulating the distance to the target, the size of target, and the 3D target arrangement, which were described using the two angles of inclination (θ1) and azimuth (θ2). Given the starting point as the center of the coordinates, θ1 was the angle between the positive y-axis and the target location, while θ2 was the angle between the positive x-axis and the projected target location on the x–z plane. All four variables were found to be significant for the movement time (MT) (p < 0.0001). After incorporating the two variables, θ1 and θ2, into the original Fitts' model, the extended Fitts' model with 3D target arrangements for spherical coordinate system showed better agreement with the empirical data than previous models in terms of the correlation coefficient and the standard error of the residuals for the measured and predicted MTs.Relevance to industryThis study presents an extended Fitts' model with a higher degree of predictability than previous studies for pointing task in three-dimensional space. In many situations, people implement pointing tasks in a three-dimensional environment, so it is important for designers to predict human performance accurately. Instead of using Euclidean coordinate system, spherical coordinate system can be also used for 3D pointing tasks. The extended model with spherical coordinate system can be used during the design and evaluation stage of the development process to help designers and developers.     

A comparison of simulation techniques and algebraic techniques for verifying concurrent systems

Simulation-based assertional techniques and process algebraic techniques are two of the major methods that have been proposed for the verification of concurrent and distributed systems. It is shown how each of these techniques can be applied to the task of verifying systems described as input/output automata; both safety and liveness properties are considered. A small but typical circuit is verified in both of these ways, first using forward simulations, an execution correspondence lemma, and a simple fairness argument, and second using deductions within the process algebra DIOA for I/O automata. An extended evaluation and comparison of the two methods is given.Supported by NSF grant CCR-89-15206, by DARPA contracts N00014-89-J-1988 and N00014-92J-4033, and by ONR contract N00014-91-J-1046.     

Air pointing: Design and evaluation of spatial target acquisition with and without visual feedback

Sensing technologies such as inertia tracking and computer vision enable spatial interactions where users make selections by ‘air pointing’: moving a limb, finger, or device to a specific spatial region. In addition of expanding the vocabulary of possible interactions available, air pointing brings the potential benefit of enabling ‘eyes-free’ interactions, where users rely on proprioception and kinaesthesia rather than vision. This paper explores the design space for air pointing interactions, and presents tangible results in the form of a framework that helps designers understand input dimensions and resulting interaction qualities. The framework provides a set of fundamental concepts that aid in thinking about the air pointing domain, in characterizing and comparing existing solutions, and in evaluating novel techniques. We carry out an initial investigation to demonstrate the concepts of the framework by designing and comparing three air pointing techniques: one based on small angular ‘raycasting’ movements, one on large movements across a 2D plane, and one on movements in a 3D volume. Results show that large movements on the 2D plane are both rapid (selection times under 1 s) and accurate, even without visual feedback. Raycasting is rapid but inaccurate, and the 3D volume is expressive but slow, inaccurate, and effortful. Many other findings emerge, such as selection point ‘drift’ in the absence of feedback. These results and the organising framework provide a foundation for innovation and understanding of air pointing interaction.     

It is best to point for young children: a comparison of children's pointing and dragging

A mouse is the input device children principally use to control a computer in schools. However, somewhat surprisingly, there has been very little research investigating the appropriate mouse control strategies for children. In this paper we report two studies which compared children's performance with two basic mouse operations; pointing and dragging. In Study 1 we investigated 7-year-old children (n=24) who were inexperienced with a computer mouse and found that they were quicker and more accurate with pointing compared to dragging. In Study 2 we examined the performance of children (n=90) from three different age groups: young (5–6 years), medium (8–9 years), and older (11–12 years). These children were more experienced with using a mouse. We found that older children were quicker and made fewer errors than younger children regardless of the mouse operation. We also found that younger children were slower and made more errors with dragging than with pointing. There were no differences in performance between pointing and dragging for the other two age groups. The implications of these findings for the design of interfaces for children are discussed.     

Effects of physical walking on eyes-engaged target selection with ray-casting pointing in virtual reality

Virtual Reality - Target selection in virtual reality (VR) is usually carried out with the need of visual attention. While target selection in VR has been extensively investigated in non-walking...     

Performance comparison of query-based techniques for anti-pattern detection

ContextProgram queries play an important role in several software evolution tasks like program comprehension, impact analysis, or the automated identification of anti-patterns for complex refactoring operations. A central artifact of these tasks is the reverse engineered program model built up from the source code (usually an Abstract Semantic Graph, ASG), which is traditionally post-processed by dedicated, hand-coded queries.ObjectiveOur paper investigates the costs and benefits of using the popular industrial Eclipse Modeling Framework (EMF) as an underlying representation of program models processed by four different general-purpose model query techniques based on native Java code, OCL evaluation and (incremental) graph pattern matching.MethodWe provide in-depth comparison of these techniques on the source code of 28 Java projects using anti-pattern queries taken from refactoring operations in different usage profiles.ResultsOur results show that general purpose model queries can outperform hand-coded queries by 2–3 orders of magnitude, with the trade-off of an increased in memory consumption and model load time of up to an order of magnitude.ConclusionThe measurement results of usage profiles can be used as guidelines for selecting the appropriate query technologies in concrete scenarios.     

基于瞬态相对模型的轨道机动目标运动参数估计

空问目标可能存在未知的机动,针对该类目标相对导航问题,提出一种基于瞬态相对模型的运动参数估计方法.该方法依据轨道密切性思想,在瞬态意义下建立相对运动模型和机动辨识算法,然后通过密切轨道到参考轨道的量测变换对冻结时间模型进行状态滤波,可为目标机动下的自主导航提供所需的相对状态与目标机动参数估值.误差分析表明,所得估值偏差均有界.仿真验证了该方法在目标存在机动情况下的有效性和一般性.     

A comparison of mortar and Nitsche techniques for linear elasticity

Abstract Domain decomposition techniques provide powerful tools for the numerical approximation of partial differential equations. In this paper, we analyze the Nitsche method for the Lamé operator, establish a priori error estimates and compare this method with the mortar method using dual Lagrange multiplier spaces. Both methods can be applied to non-matching triangulations. We use a multigrid algorithm to solve the algebraic systems. Although we have a mesh dependent bilinear form, optimal -cycle convergence rates can be obtained. Numerical results for the two methods with linear and quadratic finite elements illustrate the performance and flexibility of these nonconforming discretization techniques.     

Lateral control assistance for car drivers: a comparison of motor priming and warning systems

OBJECTIVE: This paper's first objective is to determine whether motor priming assistance (consisting of directional steering wheel vibrations) can be of some benefit compared with more traditional auditory (lateralized sound) or vibratory (symmetric steering wheel oscillation) warning devices. We hypothesize that warning devices favor driving situation diagnosis, whereas motor priming can improve the initiation of action even further. Another objective is to assess the possible benefits of using multimodal information by combining auditory warning with simple steering wheel vibration or motor priming. BACKGROUND: Within the context of active safety devices, the experiment dealt with moderately intrusive driving assistance devices that intervene when a certain level of risk in terms of lane departure is reached. METHOD: An analysis of the steering behavior of 20 participants following episodes of visual occlusion was carried out. Five warning and motor priming devices were compared. RESULTS: All tested devices improved the drivers' steering performance, although their effects were modulated by the drivers' risk assessment. However, performance improvements were found to be greater with a motor priming device. No additional performance enhancement was observed when auditory warning was added to steering wheel vibration or motor priming devices. CONCLUSION: This study confirms the hypothesis that the direct intervention of motor priming at the action level is more effective than a simple warning, which intervenes upstream in situation diagnosis. Multimodal information did not seem to improve driver performance. APPLICATION: This study proposes a new kind of lateral control assistance, which acts at a sensorimotor level, in contrast with traditional warning devices.     

Performance comparison of feature extraction algorithms for target detection and classification

This paper addresses the problem of target detection and classification, where the performance is often limited due to high rates of false alarm and classification error, possibly because of inadequacies in the underlying algorithms of feature extraction from sensory data and subsequent pattern classification. In this paper, a recently reported feature extraction algorithm, symbolic dynamic filtering (SDF), is investigated for target detection and classification by using unmanned ground sensors (UGS). In SDF, sensor time series data are first symbolized to construct probabilistic finite state automata (PFSA) that, in turn, generate low-dimensional feature vectors. In this paper, the performance of SDF is compared with that of two commonly used feature extractors, namely Cepstrum and principal component analysis (PCA), for target detection and classification. Three different pattern classifiers have been employed to compare the performance of the three feature extractors for target detection and human/animal classification by UGS systems based on two sets of field data that consist of passive infrared (PIR) and seismic sensors. The results show consistently superior performance of SDF-based feature extraction over Cepstrum-based and PCA-based feature extraction in terms of successful detection, false alarm, and misclassification rates.     

Analysis and comparison of machine learning classifiers and deep neural networks techniques for recognition of Farsi handwritten digits

The Journal of Supercomputing - Handwriting recognition remains a challenge in the machine vision field, especially in optical character recognition (OCR). The OCR has various applications such as...     

Route-following assistance for travelers with cognitive impairments: A comparison of four prompt modes

Navigational skills, which are fundamental to community travel and hence, personal independence, are often disrupted in people with cognitive impairments. Assistive technology, in the form of navigation devices, are being developed that can support community navigation by delivering directional information. Selecting an effective mode to provide route-prompts is a critical design issue. This study evaluated the differential effects on pedestrian route following using different modes of prompting delivered via an electronic device for travelers with severe cognitive impairments.The research design used was a within subject comparison to evaluate potential differences in route-following performance when travelers received directions using four different prompt modes: (1) aerial map image, (2) point of view map image, (3) audio direction/no image and (4) text-based instructions/no image. Twenty travelers with severe cognitive impairments due to acquired brain injury walked four equivalent routes using four different prompting modes delivered via a wrist-worn navigation device. Navigation scores were computed that captured accuracy and confidence during navigation. Results of the repeated measures analysis of variance suggested that participants performed best when given prompts via speech-based audio directions. The majority of the participants also preferred this prompting mode. Findings are interpreted in the context of cognitive resource allocation theory.     

测量目标相对角速度的陀螺传感器

在介绍了陀螺传感器基本特性的基础上 ,详细论述了利用陀螺传感器测量目标相对角速度的基本原理及其工程实现。在陀螺传感器中 ,采用了与陀螺偏侧角的变化率成比例的电磁阻尼 ,使测速系统的稳定性显著提高     

A comparison of pivot selection techniques for permutation-based indexing

Recently, permutation based indexes have attracted interest in the area of similarity search. The basic idea of permutation based indexes is that data objects are represented as appropriately generated permutations of a set of pivots (or reference objects). Similarity queries are executed by searching for data objects whose permutation representation is similar to that of the query, following the assumption that similar objects are represented by similar permutations of the pivots. In the context of permutation-based indexing, most authors propose to select pivots randomly from the data set, given that traditional pivot selection techniques do not reveal better performance. However, to the best of our knowledge, no rigorous comparison has been performed yet. In this paper we compare five pivot selection techniques on three permutation-based similarity access methods. Among those, we propose a novel technique specifically designed for permutations. Two significant observations emerge from our tests. First, random selection is always outperformed by at least one of the tested techniques. Second, there is no technique that is universally the best for all permutation-based access methods; rather different techniques are optimal for different methods. This indicates that the pivot selection technique should be considered as an integrating and relevant part of any permutation-based access method.