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Recently fabricated two-dimensional (2D) black phosphorene (BP) is considered to be a promising optoelectronic sheet, but its applications are hindered by the poor stability in air. Thus, it is des...

The extrinsic and intrinsic curvature of a two-dimensional waveguide influences wave propagation therein. While this can already be apprehended from a geometric point of view in terms of geodesics generalizing straight lines as the shortest distance between any two points, in wave optics interference phenomena strongly govern the field evolution, too. Radii of curvature in the order of the wavelength of light modify the local effective refractive index by altering the mode profile. Macroscopic radii only influence light propagation for non-vanishing intrinsic (or Gaussian) curvature. A positive Gaussian curvature leads to refocusing and thus an imaging behavior, whereas negative Gaussian curvature forces the field profile to diverge exponentially. These effects can be explained by an effective transverse potential acting on the electromagnetic field distribution’s envelope. This can also be extended to nonlinear beam propagation. In this review paper we give a thorough introduction to differential geometry in two-dimensional manifolds and its incorporation with Maxwell’s equations. We report on first fundamental experiments in this newly emerging field, which may lead to applications in integrated optical circuits. The close conceptual analogy to phenomena in four-dimensional spacetime with constant curvature as well as toy-models of the Schwarzschild metric and a wormhole topology are also discussed.

Singularities in five-axis machining are a series of deadly positions, which may cause unstable axis movements and deteriorate the performance of machine tools. This paper presents an optimization strategy to locally deform the tool path so that singularities of five-axis machine tools can be avoided. To achieve this purpose, a new concept of “forbidden circle”, which is the projection of the three dimensional “singular cone” associated with tool orientations in a two dimensional space named P-plane, is established for the first time to transform the complicated three dimensional problem into a two dimensional problem. Based on this idea, the projected points in P-plane are interpolated as B-spline first, and then, the B-spline control points are locally optimized by taking the “forbidden circle” as the geometrical constraint to keep the B-spline from crossing it. Especially, in the optimization procedure, the constraints are linearized with the changes of B-spline control points to change the whole optimization problem as a typical positive definite quadratic programming problem, which can achieve one and only global optimal solution. By doing so, singularity is avoided, and at the same time, the machining errors caused by tool path deformation can be minimized. Simulation and experimental results verify the effectiveness of the singularity avoidance method.

A variable length crane system under the external disturbances and constraints is studied in the two-dimensional space. The dynamical analysis of the cable system considers the variable length, variable tension, variable speed, and the coupled vibrations of the cable in longitudinal-transverse directions. Considering output constraint problems, boundary control algorithms with output signal barriers are designed and acted on the boundary of the cable to reduce the coupled vibrations of the flexible crane cable, and to ensure the stability of the system in theory. Effectiveness and performance of the proposed control schemes are depicted via several simulation examples.

Accuracy has been used traditionally to evaluate the performance of classifiers. However, it is well known that accuracy is not able to capture all the different factors that characterize the performance of a multiclass classifier. In this manuscript, accuracy is studied and analyzed as a weighted average of the classification rate of each class. This perspective allows us to propose the dispersion of the classification rate of each class as its complementary measure. In this sense, a graphical performance metric, which is defined in a two dimensional space composed by accuracy and dispersion, is proposed to evaluate the performance of classifiers. We show that the combined values of accuracy and dispersion must fall within a clearly bounded two dimensional region, different for each problem. The nature of this region depends only on the a priori probability of each class, and not on the classifier used. Thus, the performance of multiclassifiers is represented in a two dimensional space where the models can be compared in a more fair manner, providing greater awareness of the strategies that are more accurate when trying to improve the performance of a classifier. Furthermore we experimentally analyze the behavior of seven different performance metrics based on the computation of the confusion matrix values in several scenarios, identifying clusters and relationships between measures. As shown in the experimentation, the graphical metric proposed is specially suitable in challenging, highly imbalanced and with a high number of classes datasets. The approach proposed is a novel point of view to address the evaluation of multiclassifiers and it is an alternative to other evaluation measures used in machine learning.

With the increase of Internet of Things (IoT) applications, indoor positioning systems have begun to gain importance. Since there is no widespread technique in this area like Global Positioning System (GPS) at outdoors, a vast variety of techniques and technologies are being used in indoor positioning. Triangulation is one of the most frequently used techniques which can be categorized into two techniques: lateration and angulation. Lateration technique uses distance information in the estimation of location while the angulation technique uses angles besides distances. The lateration technique is called as trilateration when it is applied in two dimensional space. In this paper, trilateration technique is analyzed where one of the reference points resides of an uncertain location. The location of an object is estimated as an area by using two certain reference points. The proposed method determines an added value which represents how much the area is reduced. Experiments are performed to calculate an approximate added value without applying the proposed method because of the costly calculation requirements. The results of the experiments and the obtained added values are also reported as final evaluation of the study.

There are many methods that can be used to compute the geographic similarity between regions represented through areas in a two dimensional space. However, it is the rough set based membership function that allows an estimate of the similarity between a subzone formed by the data. The major objective behind this paper is to measure the similarity of GIS subzones on a discrete dataset. This has a varied number of applications not only in GIS and epidemiology but also in clusters analysis and artificial intelligence.

A new photonic platform allows implementing 2D Quantum Walks in the space of transverse wavevector components of a single light beam. Detection of an anomalous velocity demonstrates that this system simulates a Quantum Hall Insulator.

Geometric phase metasurface (GPM) elements are two dimensional space variant gradient structures, which enable exotic light manipulation. Such structures consist of a dense assembly of resonant optical nanoantennas, the size parameters and orientation of which dictate local light-matter interactions. The GPM elements have been extensively studied, showing that they can control of the phase, amplitude, polarization and orbital angular momentum of light beams [1-4]. The GPM elements have been used as flat optical elements with unique features, as polarization control elements, and as spectro-polarimetric devices.

Address-Event Representation is a flowering technology that can change the visual perception of the computer vision world. This paper proposes a methodology to associate the input data from this kind of sensors. A new descriptor computed using an extended LBP operator seeks to characterize the connectivity of the asynchronous incoming events in a two dimensional space. Those features can be organized on histograms and combined with others descriptors, as histograms of oriented events. They can be the input of traditional classifiers to detect or recognize objects from the scene.

Twenty-eight sex- and age-matched participants, half dextrals and half sinstrals, were instructed to move a pen-sized planometer three inches (7.6 cm) while blindfolded. Under separate trials, movements were made at four angles, towards and away from the body, and at two distances from the body (30 cm, 53 cm). Half were made with the right hand and half with the left hand. Line estimates increased in length across blocks of trials in a linear fashion and progressively overestimated the three-inch imagined criterion. Lines made moving towards the body were longer than those made moving away from the body, implying an egocentric frame of reference in making the estimates. Line estimates made at an oblique angle differed significantly from estimates made at other angles. No influences of sex, handedness, or the hand used in making the estimates were observed. The findings suggest that motoric estimates of line lengths made without visual cues—a unique measure of an implicit cognitive concept—are significantly altered by temporal and spatial factors, but not by sex or hemispheric laterality.

To modify the power factor and balance the three-phase currents simultaneously, this paper proposes the instantaneous compensator to calculate the compensation current. The instantaneous compensator utilizes two-dimensional instantaneous space vector and setting the active power as a constant for each cycle which can improve power quality effectively. Moreover, the instantaneous compensator requires an independent power source, whose capacity can be reduce by using a static var compensator (SVC). An SVC does not interfere with the capability of the instantaneous compensator. Field measurement data were analyzed. Simulation results confirmed the feasibility of correcting the power factor and balancing load currents simultaneously using the proposed method.

This newly developed program gives predictions of a climber's fall in two dimensional space. It numerically calculates all forces acting on the climber, the belayer, the rope and various fix points. Also it shows the movement of both the climber and the belayer, taking air drag, friction, deformation of the climber, real rope and belay device characteristics into account. By using a 3-parameter viscoelastic rope model the different behaviour of the rope for dynamic and static loading is correctly simulated. The rope parameters are calibrated using actual rope values which are commonly available from product data sheets of rope manufacturers. A new concept is introduced to describe the rope forces due to the friction at the 1st protection. The climber is modelled with 2-masses to describe the body deformation. An energy analysis shows in detail the significance of all present mechanisms to absorb the fall energy compared to all others.

Many disciplines are faced with the problem of handling time-series data. This study introduces an innovative visual representation for time series, namely the continuous triangular model. In the continuous triangular model, all subintervals of a time series can be represented in a two-dimensional continuous field, where every point represents a subinterval of the time series, and the value at the point is derived through a certain function (e.g. average or summation) of the time series within the subinterval. The continuous triangular model thus provides an explicit overview of time series at all different scales. In addition to time series, the continuous triangular model can be applied to a broader sense of linear data, such as traffic along a road. This study shows how the continuous triangular model can facilitate the visual analysis of different types of linear data. We also show how the coordinate interval space in the continuous triangular model can support the analysis of multiple time series through spatial analysis methods, including map algebra and cartographic modelling. Real-world datasets and scenarios are employed to demonstrate the usefulness of this approach.

Time intervals are conventionally represented as linear segments in a one-dimensional space. An alternative representation of time intervals is the triangular model (TM), which represents time intervals as points in a two-dimensional space. In this paper, the use of TM in visualising and analysing time intervals is investigated. Not only does this model offer a compact visualisation of the distribution of intervals, it also supports an innovative temporal query mechanism that relies on geometries in the two-dimensional space. This query mechanism has the potential to simplify queries that are difficult to specify using traditional linear temporal query devices. Moreover, a software prototype that implements TM in a geographical information system (GIS) is introduced. This prototype has been applied in a real scenario to analyse time intervals that were detected by a Bluetooth tracking system. This application shows that TM has the potential to support a traditional GIS to analyse interval-based geographical data.

An approach for analysis of shape of composite dowel shear connector focused on finding a location of the point of maximal principal stress in steel dowel is presented. It is based on analogy between equations of boundary of closed area under plane stress conditions and beam in two dimensional space. Equations are derived from Airy's potential and polar coordinates are used.

Objective: The potential advantage of visual momentum in the form of smooth rotation between two-dimensional (2-D) and three-dimensional (3-D) displays of geographic terrain was examined. Background: The relative effectiveness of 2-D and 3-D displays is task dependent, leading to the need for multiple frames of reference as users switch tasks. The use of smooth rotation to provide visual momentum has received little scrutiny in the task-switching context. A cognitive model of the processes involved in switching viewpoints on a set of spatial elements is proposed. Methods: In three experiments, participants judged the properties of two points placed on terrain depicted as 2-D or 3-D displays. Participants indicated whether Point A was higher than Point B, or whether Point B could be seen from Point A. Participants performed the two tasks in pairs of trials, switching tasks and displays within the pair. In the continuous transition condition the display dynamically rotated in depth from one display format to the other. In the discrete condition there was an instantaneous viewpoint shift that varied across experiments (Experiment 1: immediate; Experiment 2: delay; Experiment 3: preview). Results: Performance after continuous transition was superior to that after discrete transition. Conclusion: The visual momentum provided by smooth rotation helped users switch tasks. Application: The use of dynamic transition is recommended when observers examine multiple views of terrain over time. The model may serve as a useful heuristic for designers. The results are pertinent to command and control, geological engineering, urban planning, and imagery analysis domains.

This paper investigates the characteristics of evanescent waves in the generalized nonstandard finite difference time domain (NS-FDTD) method and derives the dispersion equation and stability condition for two-dimensional space. The validity of the dispersion equation is confirmed by comparison with results of numerical simulations. The NS-FDTD method is applied to the analysis of an optical switching device using a photon tunneling effect. It is shown that the NS-FDTD method has highly accurate characteristics not only for propagating waves, but also for evanescent waves compared with the standard FDTD method., application/pdf

This paper describes an experimental system for evaluating the sitting posture of human. This system will be able to be used to make a custom-made chair. A model for the effective support of the upper part of a human is proposed. The upper part is supported by five blocks of the chair back. Each block moves in two dimensional space of horizontal plane around the back bone of the human and is supported by an imaginary spring and an imaginary damper. This proposed model is realized by the impedance control used in the control of robots. The experimental system is developed and the model is implemented. Two types of experiment are performed and the effectiveness of the developed system is shown.

© 2015 EUCA. This paper looks at the design of a distributed control law to solve the formation shape control problem using bearing-only constraints in two-dimensional space while inter-agent collision between the neighbor agents is avoided. We assume each agent can measure the relative position and is only given the desired bearing (and not the distance) to its neighbors in some local coordinate system attached to the agent. We use a relaxed control law that allows each agent to move on any direction on a half-plane to achieve the desired formation shape, and impose some conditions on the motion of the agents such that no collision occurs between the neighbor agents. Simulation results are given that show the performance of the algorithm.

In this paper, a new algorithm for visualization of high-multidimensional data is described. The algorithm follows several steps. At first, centers representing several categories are selected, and Euclidean distances between these centers are calculated in a high-dimensional space. Then these centers are placed in a 2-dimensional space in such a way that distances in this 2-dimensional space are similar to distances in the high-dimensional space. Next individual patterns are placed one-by-one in the 2-dimensional space trying to keep the similar distances in a high-dimensional and 2-dimensional space. With this algorithm, it was possible to visualize many high-dimensional data sets. The algorithm was successfully verified in several real life problems. It turned out that in some cases, which were until now considered as not linearly separable, became easily separable once patterns were transformed in the 2-dimensional space using the proposed algorithm.

International audience; Using a mouse-driven visual pointer, 10 participants made repeated open-loop egocentric localizations of memorized visual, auditory, and combined visual-auditory targets projected randomly across the two-dimensional frontal field (2D). The results are reported in terms of variable error, constant error and local distortion. The results confirmed that auditory and visual maps of the egocentric space differ in their precision (variable error) and accuracy (constant error), both from one another and as a function of eccentricity and direction within a given modality. These differences were used, in turn, to make predictions about the precision and accuracy within which spatially and temporally congruent bimodal visual-auditory targets are localized. Overall, the improvement in precision for bimodal relative to the best unimodal target revealed the presence of optimal integration well-predicted by the Maximum Likelihood Estimation (MLE) model. Conversely, the hypothesis that accuracy in localizing the bimodal visual-auditory targets would represent a compromise between auditory and visual performance in favor of the most precise modality was rejected. Instead, the bimodal accuracy was found to be equivalent to or to exceed that of the best unimodal condition. Finally, we described how the different types of errors could be used to identify properties of the internal representations and coordinate transformations within the central nervous system (CNS). The results provide some insight into the structure of the underlying sensorimotor processes employed by the brain and confirm the usefulness of capitalizing on naturally occurring differences between vision and audition to better understand their interaction and their contribution to multimodal perception.

Robotic manipulators are the most important components in the present manufacturing industry for handling materials and manipulation. It is important to note that these manipulators are used in the complex planar and spatial work spaces to perform the task. Further, it is also very difficult to manipulate and dynamically control the manipulators when the degrees of freedom (DOF) of the manipulator are increased. In the present manuscript, the dynamic analysis and design of PID controller for two different manipulator configurations, namely planar and spatial manipulators have been attempted. Moreover, both the manipulators considered in this study are provided with 4-DOF and dynamic analysis has been carried out using Lagrange-Euler (L-E) formulation. The main difference between the planar and spatial manipulator is that the former works in the two dimensional space and later works in a three dimensional space. In addition to the dynamic analysis, PID controllers have also been designed for the said configurations to follow a path between the given boundary conditions. Further, the developed controllers are tested in simulations, and found working satisfactorily.

Normal human observers compared either the width, height or area of two simultaneously-presented shapes (the standard and the test), with a cue to indicate which decision had to be made. On ‘area’ trials, test width was a random variable, ensuring that neither shape (aspect ratio), width nor height by themselves was a reliable signal. Weber fractions for width and height of both ellipses and rectangles were in the range 5–10%, but for area they were higher (10–20%) than predicted from the combination of noisy width and height decisions. With ellipses, observers were more likely to overestimate width or height when the other dimension differed from the standard in the same direction (e.g. both greater). We conclude that observers have no access to high-precision codes for 2-D area, and that they base their decisions on a variety of heuristics derived from 1-D codes. A second experiment measured acuity for changes in aspect ratio. For ellipses, accuracy for aspect ratio was higher than predicted by the combination of noisy width and height signals; for rectangles it was worse, suggesting that 2-D curvature is a potent cue to shape.

An avoidance/guidance problem of an aircraft against moving obstacle is considered in two dimensional space. The aircraft is modelled as a point mass flying with constant speed. The lateral acceleration is assumed the control input. Artificial potential functions are applied to the terminal point and moving obstacles in order that repulsive forces and an attractive force are produced by the obstacles and the terminal point respectively. A real time guidance/avoidance law is proposed by using the potential forces and relative velocity. The guidance law for a logarithm potential function results the well-known proportional navigation law. The avoidance control command is inverse proportional to the time-to-go to the obstacle and turns the aircraft toward the negative direction of the line-of-sight change. The performance of the proposed guidance/avoidance law is verified with simulations.

We investigated, in two experiments, the discrimination of bilateral symmetry in vision and touch using four sets of unfamiliar displays. They varied in complexity from 3 to 30 turns. Two sets were 2-D flat forms (raised-line shapes and raised surfaces) while the other two were 3-D objects constructed by extending the 2-D shapes in height (short and tall objects). Experiment 1 showed that visual accuracy was excellent but latencies increased for raised-line shapes compared with 3-D objects. Experiment 2 showed that unimanual exploration was more accurate for asymmetric than for symmetric judgments, but only for 2-D shapes and short objects. Bimanual exploration at the body midline facilitated the discrimination of symmetric shapes without changing performance with asymmetric ones. Accuracy for haptically explored symmetric stimuli improved as the stimuli were extended in the third dimension, while no such a trend appeared for asymmetric stimuli. Unlike vision, haptic response latency decreased for 2-D shapes compared with 3-D objects. The present results are relevant to the understanding of symmetry discrimination in vision and touch.

In a recent study, Pelli (1999 Science285 844–846) performed a set of perceptual experiments using portrait paintings by Chuck Close. Close's work is similar to the ‘Lincoln’ portraits of Harmon and Julesz (1973 Science180 1194–1197) in that they are composite images consisting of coarsely sampled, individually painted, mostly homogeneous cells. Pelli showed that perceived shape was dependent on size, refuting findings that perception of this type is scale-invariant. In an attempt to broaden this finding we designed a series of experiments to investigate the interaction of 2-D scale and 3-D structure on our perception of 3-D shape. We present a series of experiments where field of view, 3-D object complexity, 2-D image resolution, viewing orientation, and subject matter of the stimulus are manipulated. On each trial, observers indicated if the depicted objects appeared to be 2-D or 3-D. Results for face stimuli are similar to Pelli's, while more geometrically complex stimuli show a further interaction of the 3-D information with distance and image information. Complex objects need more image information to be seen as 3-D when close; however, as they are moved further away from the observer, there is a bias for seeing them as 3-D objects rather than 2-D images. Finally, image orientation, relative to the observer, shows little effect, suggesting the participation of higher-level processes in the determination of the ‘solidness’ of the depicted object. Thus, we show that the critical image resolution depends systematically on the geometric complexity of the object depicted.

The aim of this study was to compare thoracic spine alignment with two- and three-dimensional calculations of shoulder alignment (defined as a line joining the acromion processes of the right and left scapula) when all measures were projected onto the transverse plane. A six-camera Vicon system was used to reconstruct three markers positioned on the plane of the thorax such that the orthogonal vector to the thoracic spine, projected onto the transverse plane, was used as a virtual shoulder alignment during cricket fast bowling. This same measurement system was used to calculate the three-dimensional line between the acromion processes projected onto the transverse plane. These acromion markers were also used to calculate the two-dimensional transverse plane alignment of the shoulders from images recorded by a video camera positioned above ball release. All cameras operated at 50 Hz. A significant association was recorded between thorax alignment and the three- (0.97) and two-dimensional (0.87) shoulder alignment estimations at back-foot impact. The strength of association remained at front-foot impact, when correlations of 0.89 (three-dimensional) and 0.84 (two-dimensional) were recorded. However, at ball release, non-significant associations of 0.58 (three-dimensional) and 0.41 (two-dimensional), representing shoulder alignment differences of approximately 10 degrees, were recorded. The 95% limits of agreement comparisons for shoulder alignment at back-foot impact, front-foot impact and ball release produced mean random errors for the two comparisons of 9.5 degrees, 11.7 degrees and 22.5 degrees respectively. Three- and two-dimensional transverse plane projections of shoulder alignment are reasonable estimates of thorax alignment at back-foot impact and front-foot impact but not at ball release.

Visualization of multidimensional data helps in understanding complex systems and environments. We present here a red, green, blue (RGB) visualization method that can serve to display environmental properties. The saturation of each color is used to represent the concentration of a given property. The implementation of that figure is illustrated through visualization of three dissolved inorganic nutrient concentrations along a vertical transect of the Mediterranean, as well as through a vertical time series of three phytoplankton group cell numbers. The RGB figures show well known properties of the water column. In addition, they reveal some lesser-known properties, such as regions in shallow water in which the ratio of phosphorus and silica to nitrogen is high, and a deep eukariotic phytoplankton community. Visualization of such data is usually performed with three separate contour or surface plots, and occasionally two properties are presented as an overlay in a single figure. The RGB figure offers a better way to visualize the interactions among the three separate plots than is commonly available.

If we use computer to simulate simple form of three-dimensional dynamic process that is virtual or very difficult to achieve in reality directly in the two-dimensional space, we will reduce the development difficulty of simulation process. This paper introduces the simulation methods and key technologies by some relevant examples in “Audio and Video Electronic Textbook of Mechanical Drawing.” The examples include the formation process of gyration curved surface, the process of an object being cut by a plane, the decomposition process of a combined object. The Flash animation software is mainly used in the simulation process, and AutoCAD software and Photoshop software are the tools used for preparing materials. The results show that simple form of three-dimensional dynamic process can be simulated very realistically in the two-dimensional space, not using the tools of three-dimensional animation.

Objective: Instead of the linear model (LM), time intervals can be represented by a two-dimensional (2D) model, which is called the triangular model (TM). Although the TM has been introduced for decades and applied in some areas, there still a lack of empirical studies on its usability. To fill this gap, this study aims to evaluate how people perform when using the TM to answer questions on time intervals, in comparison with using the traditional LM. Method: Around 250 novice participants took part in the experiment, which consisted of a video training, a pretest and posttest. The video training introduced the basic knowledge of temporal relations and the two representations. The pretest allowed participants to practice the knowledge they have learned and receive feedbacks of the answers. In the posttest, participants' accuracy and speed when answering the questions were recorded for analysis. The results of using the TM and the LM were compared in pairs. The null hypothesis is that the participants produce equal results with the two models. Result: The results showed that the participants scored better and spent less time when answering questions with the TM, which rejected the null hypothesis. Moreover, the score and speed when they used the TM did decline in the questions containing a larger number of intervals. In contrast, the score and accuracy when they used the LM declined when questions containing a large number of intervals. Conclusion: *The TM is easy to learn. After a 20-min training, novice participants can use it to solve questions and produce satisfactory result. *The TM is easy and efficient for visual queries of time intervals. *The TM is easy to use for handling a large number of intervals. Implication: *The TM can be widely applied in analysing time intervals and linear data. *Tools implementing the TM can be learned and used by novice users.

The application of X-ray mapping in reciprocal space to the measurement of subtle strain modifications in heterostructures is analysed, focussing on strain analysis in non-cubic crystals. Special attention is paid to the enhancement of the precision of the mapping technique in comparison with conventional diffraction profile measurements. The capabilities of the mapping-based strain analysis are illustrated by selected examples of epitaxially grown structures (obeying Vegard's rule), as well as implanted structures with unknown mismatches between the lattice parameters of the damaged layer and of the crystal bulk.

In design, problem analysis is as important as solution synthesis. Strategic knowledge is required not only for constructing a solution but also for framing a problem. While externalized representations play critical roles in design tasks, different types of representations are necessary for different stages of a design task. In early stages of a design task, design support tools need to provide hands-on representations with which a designer can easily perform trial-and-error and examine the whole as well as parts of the whole, allowing the designer to represent any levels of preciseness, as he/she likes. Sketching and drawing with paper and pencil provide an ideal representation for this process. But what about supporting design domains, such as writing or programming, where no sketching exists? In this paper, we argue that two-dimensional positioning of objects in a design support tool serves for the same purpose as sketching does for architectural design. Two-dimensional positioning allows a designer to produce hands-on representations that “talk back” to him/her without forcing the designer to formalize or verbalize what to be externalized. Two systems, ART for writing and RemBoard for component-based programming, illustrate the framework.

Nine healthy subjects performed 2D pointing movements using a joystick that controlled a screen cursor. Continuous visual feedback was provided until movement completion. Three variables were systematically manipulated: (1) target distance, (2) target size and (3) target direction. A four-way factorial ANOVA was used to analyze the effects of these fixed factors and of the random factor of subject on several movement parameters. Movement time increased with increasing distance and decreasing target size and as predicted from Fitts' law. The target direction did not affect movement time. In contrast the direction, distance and size of the target significantly affected the movement time until the first zero crossing on the speed record reflecting the time to bring the arm into the vicinity of the target. Movements on the lateral axis of the horizontal plane (horizontal movements) resulted in a decrease in initial movement time compared to movements on the anterior axis of the horizontal plane (vertical movements). A significant effect of target distance and direction but not target size was observed for the magnitude of maximum acceleration, maximum speed and maximum deceleration. Horizontal movements had a larger maximum acceleration, speed and deceleration. Furthermore the maximum speed and deceleration occurred earlier in time for these horizontal movements. Finally the number of secondary peaks on the speed record increased with decreasing target size and was not affected by the target distance or target direction. In conclusion our results indicate that different movement parameters are affected by target distance, size and direction. The crucial distinction was between parameters affected by target size and direction. These parameters did not overlap. Target direction affects the first part of movement execution while target size affects the final part of movement execution. Thus a clear segmentation of movement execution in two phases is supported by these results. The implications of these results for theoretical models of speed-accuracy trade-off are discussed.

This paper provides a unified theoretical framework for analytical characterization of grasping and manipulation capability of robotic grippers and hands as well as fixing capability of fixtures and vises. The concept of passive closure and active closure for general constraining mechanisms consisting of fixed and/or articulated constraining limbs is introduced. These concepts are useful for explicitly distinguishing the two kinds of capabilities of the constraining mechanism: Passive closure represents the ability of fixing devices and active closure represents the ability of manipulating devices. Passive closure is further classified into passive form closure and passive force closure. Passive form closure is essentially the same as Reuleaux’s classical form closure and passive force closure is a substantial generalization of classical force closure to the case where articulated constraining limbs exist. Conditions for these closures to hold are studied. After a brief review of conditions for passive form closure, several conditions for passive force closure are given. One outcome is that, under the assumption that the contact points are frictionless and the active contact points are independent, for the existence of passive force closure there must be at least six (three) fixed contact points and one active contact point in the case of three-dimensional (two-dimensional, respectively) space. Finally, a necessary and sufficient condition for active closure is given for the case of frictional point contacts by constraining limbs with enough degrees-of-freedom. This condition consists of a general positioning condition of contact points and the existence condition of nonzero internal force. This condition has a quite natural physical interpretation.

An isoluminant color grating usually appears to move more slowly than a luminance grating that has the same physical speed. Yet a grating defined by both color and luminance is seen as perceptually unified and moving at a single intermediate speed. In experiments measuring perceived speed and direction, it was found that color- and luminance-based motion signals are combined differently in the perception of 1-D motion than they are in the perception of 2-D motion. Adding color to a moving 1-D luminance pattern, a grating, slows its perceived speed. Adding color to a moving 2-D luminance pattern, a plaid made of orthogonal gratings, leaves its perceived speed unchanged. Analogous results occur for the perception of the direction of 2-D motion. The visual system appears to discount color when analyzing the motion of luminance-bearing 2-D patterns. This strategy has adaptive advantages, making the sensing of object motion more veridical without sacrificing the ability to see motion at isoluminance.

This paper deals with the development of 2-D space maps during navigation in unknown environments, by synthesizing the shapes of consecutive free spaces. Each shape extracted from each current-free navigation space is represented by attributed graphs. Thus, the synthesis of the shapes is based on the synthesis of graphs for the generation of new graph forms that represent the new shape traveled by an autonomous robot. Illustrative examples from a space with obstacles are presented.

Recent developments in the field of simple human movement modelling provide new ways in which to view complete models for analysing and understanding complex movements. Based on a kinematic theory and a vectorial delta-lognormal model recently proposed by Plamondon, 1993a , Plamondon, 1995a , Plamondon, 1995b , Plamondon, 1995c , Plamondon, 1998 , a new method for exploring and understanding the inherent mechanisms that govern planar movement generation and predict human behaviour is presented here. This paper describes an approach for analysing simple as well as complex movements such as cursive handwriting. It highlights some difficulties encountered in the analysis of complex movements. Problems such as the development of robust approaches to solve the reverse engineering problem of automatic parameter extraction of a succession of time-overlapped nonlinear functions are discussed. The analysis of natural cursive handwriting shows many interesting properties of the model and proposes new ways to study perturbed movement phenomena.

We examined the 2D surface formed by 3D eye positions of normal subjects to determine whether the shape and thickness changed in tasks that differed in saccadic directions; random, horizontal, vertical, radial, clockwise and counter-clockwise. Eye positions during the random task did not lie precisely on Listing's plane but on a surface with a small twist. This twist was present before, during, and after saccades. The degree of twist changed with the task; becoming less twisted for horizontal tasks and more twisted in the vertical tasks. The surface thickness changed with the task becoming thicker for multidirectional tasks. This greater thickness may occur because surfaces obtained in multidirectional tasks are the composite of surfaces with slightly different shapes.

The spatial properties of a motion illusion (the Ouchi illusion) that occurs in a stationary pattern were examined by means of a variety of two-dimensional periodic patterns (formed by multiplying pairs of various one-dimensional periodic functions). In two experiments, observers rated the magnitude of the illusion. The results showed that (1) patterns having large energy and steep saddle-shaped contrast gradients tended to generate stronger illusions, (2) the composite pattern made up of the sum of the fundamental and harmonic components exhibited a stronger illusion than either the fundamental or the harmonic pattern, (3) patterns possessing an element orientation and phase shift similar to those of a rectangular checkerboard, and with element sizes of 15–50 min in width and 4–8 min in height yielded a larger illusion, (4) equiluminant colors largely abolished the effect, and (5) blurring the boundary between the test and surround did not reduce the illusion. Interactions between spatially overlapping ON and OFF units was discussed as a possible underlying cause of this phenomenon.

Two-dimensional sum-of-sines waveforms were pursued by the eye with very small phase delays compared with visual feedback delays estimated in the same monkeys. Processing delays in making smooth corrections averaged 90msec after infrequent right-angle perturbations from a circular trajectory. These feedback delays were much larger than component phase delays during pursuit that averaged: 10msec for sinusoids, 3msec for circles, 20msec for sum-of-two-sines trajectories, and 19msec for sum-of-three-sines trajectories. This suggests that predictive control can play a strong role during tracking for a variety of simple and complex target trajectories.

We measured the perceived spatial orientation of the low contrast regions of contrast modulated sine gratings. Subjects make systematic errors which depend upon the carrier spatial frequency and the angle between the carrier grating and the modulation. The results for the spatial orientation task are compared with a motion domain analogue. The difference in the pattern of results for these two tasks suggests there exist separate strategies for encoding orientation in two-dimensional space and space-time.

Time-varying spectral modulation for arbitrary ultrafast signal generation is demonstrated as one of applications of ultrafast time-to-two-dimensional-space-to-time conversion. The continuous sequence of a spectral-decomposed pulse is generated from a seed ultrashort pulse and its spectrum on each timing is independently modulated in the space domain. As a result of preliminary experiments, the ultrashort pulse sequence composed of four pulses of a 1-ps interval with three wavelength channels can be generated after time-varying spectral modulation.

When hoarding food within a circular arena, golden hamsters, Mesocricetus auratus W., return along a direct path from the feeding place at the centre to their nest at the periphery. The homing direction depends on dead reckoning (updated internal signals derived from locomotion) and, if available, on landmarks outside the arena. This study was aimed at defining the conditions under which a landmark panorama predominates over dead reckoning during conflict situations. In agreement with previous results, this was found to be the case only when the panorama contained at least one prominent vertical feature aligned with the apex of a two-dimensional, continuous background pattern. The minimal landscape that controlled homing was a solid cylinder presented in front of the background pattern, or its two-dimensional projection on the pattern itself. Contrary to a previous hypothesis, depth did not appear to be a critical factor in an effective landmark panorama.

In this paper the two-dimensional space-time clutter is simulated for arbitrary postures of aircraft. First the detection area is divided into many scattering cells, and for each scattering cell the return signal is calculated according to the radar equation, then the received signal of radar for sidelooking arrays or forward looking arrays is presented. Finally the simulation experiment is performed and the results shows the effectiveness of our method.

In various data mining applications performing the task of extracting information from large databases is serious problem, which occurs in many fields e.g.: bioinformatics, commercial behaviour of Internet users, social networks analysis, management and investigation of various databases in static or dynamic states. In recent years many techniques discovering hidden structures in the data set like clustering and projection of data from high-dimensional spaces have been developed. In this paper, we propose a model for multiple view unsupervised clustering based on Kohonen self-organizing-map algorithm. The results of simulations in two dimensional space using three views of training sets having different statistical properties have been presented.

A general-purpose package for the solution of problems in two space dimensions, both steady and unsteady, is described. The type of grid used is unstructured triangular. Emphasis is placed on concepts underlying the package, rather than on implementation.