Showing papers by "Florida Atlantic University published in 1993"
TL;DR: Episodes of increased broad-band coherence among local field potentials from sensory, motor and higher-order cortical sites of macaque monkeys performing a visual discrimination task are described.
Abstract: The way in which the brain integrates fragmentary neural events at multiple locations to produce unified perceptual experience and behaviour is called the binding problem. Binding has been proposed to involve correlated activity at different cortical sites during perceptuomotor behaviour, particularly by synchronization of narrow-band oscillations in the gamma-frequency range (30-80 Hz). In the rabbit olfactory system, inhalation induces increased gamma-correlation between sites in olfactory bulb and cortex. In the cat visual system, coherent visual stimuli increase gamma-correlation between sites in both the same and different visual cortical areas. In monkeys, some groups have found that gamma-oscillations transiently synchronize within striate cortex, superior temporal sulcus and somatosensorimotor cortex. Others have reported that visual stimuli produce increased broad-band power, but not gamma-oscillations, in several visual cortical areas. But the absence of narrow-band oscillations in itself does not disprove interregional synchronization, which may be a broad-band phenomenon. We now describe episodes of increased broad-band coherence among local field potentials from sensory, motor and higher-order cortical sites of macaque monkeys performing a visual discrimination task. Widely distributed sites become coherent without involving other intervening sites. Spatially selective multiregional cortical binding, in the form of broad-band synchronization, may thus play a role in primate perceptuomotor behaviour.
533 citations
TL;DR: In this article, a nurse's exposure to acquired immunodeficiency syndrome (AIDS) patients as part of the work role is positively associated with distress as indexed by negative mood at work.
Abstract: In this study, we hypothesized that a nurse's exposure to acquired immunodeficiency syndrome (AIDS) patients as part of the work role is positively associated with distress as indexed by negative mood at work. Given this expected relation, we sought to identify factors that might reduce the negative effects of caring for AIDS patients on nurses. We predicted that both organizational and social support would moderate the relationship between extent of exposure and negative mood, with the relationship being strongest when support is low and weakest when support is high. The results of tests among a sample of 256 nurses supported all the hypotheses. We discuss implications of this study and directions for future research.
231 citations
02 May 1993
TL;DR: The authors present a numerical method for the solution of both inverse and forward kinematic problems of the actual platform model and demonstrate, through simulation, the effect of the above factors on platform accuracy.
Abstract: Manufacturing tolerances, installation errors and link offsets cause deviations with respect to the nominal kinematic parameters of the platform. As a result, if the nominal values of these parameters are used within the platform control software, the resulting pose of the platform will be inaccurate. In order to evaluate the effects of the above factors on the platform accuracy, the inverse and forward kinematic problems of the actual platform model need to be solved. The authors present a numerical method for the solution of both problems and demonstrate, through simulation, the effect of the above factors on platform accuracy. The simulation results provide insight to the expected accuracy and indicate the major factors contributing to inaccuracies. >
222 citations
TL;DR: In this article, it was shown that for a long enough data string with low enough noise, the plateau onset occurs at m = Ceil(D2), where Ceil (D2) is the smallest integer greater than or equal to D2.
194 citations
TL;DR: It is found that normal control subjects and Broca's aphasic patients are sensitive to the thematic properties of verbs, regardless of sentence type, and there is a double-dissociation between the operation of accessing a verb's thematic Properties and theoperation of computing the trace-antecedent relation.
162 citations
TL;DR: An alternative approach, based on artificial neural networks with the back-propagation algorithm, to map two different transformations: EMG-->joint angles; and (2) EMG -->joint moments, suggesting that neural networks can provide a successful platform for both biomechanical modeling and simulation.
154 citations
TL;DR: Disagreements between school-aged children were examined as a function of friendship status, and assertions were used selectively according to friendship and sex: with friends, girls used assertions accompanied by rationales more frequently than boys whereas boys used assertions without rationalesMore frequently than girls.
Abstract: Disagreements between school-aged children were examined as a function of friendship status. 66 same-sex dyads were selected, including equal numbers of “best friends” and nonfriends, who were then observed while playing a board game (a closed-field situation). Conflicts occurred more frequently among friends than among nonfriends and lasted longer. Friends did not talk more during their conflicts than nonfriends, but assertions were used selectively according to friendship and sex: With friends, girls used assertions accompanied by rationales more frequently than boys whereas boys used assertions without rationales more frequently than girls. These sex differences were not evident during conflicts between nonfriends. Results are discussed in relation to the social constraints intrinsic to closed-field competitive conditions as these apply to friendship relations in middle childhood.
145 citations
01 Dec 1993
TL;DR: Invisibility, homophobia and heterosexism: Lesbians, gays and the media as discussed by the authors, a review of the state of the art in the field of mass communication.
Abstract: (1993). Invisibility, homophobia and heterosexism: Lesbians, gays and the media. Critical Studies in Mass Communication: Vol. 10, No. 4, pp. 395-422.
143 citations
Journal Article•
TL;DR: In this article, the concept of "unknowing" is defined as a condition of openness, which is the ability to say, "I never thought about it that way," and at once experience the wonderment of coming upon an "unknown."
136 citations
02 May 1993
TL;DR: A procedure is developed for simultaneous calibration of a robot and a monocular camera, which solves for the kinematic parameters of the robot and camera in one stage, thus eliminating error propagation and improving noise sensitivity.
Abstract: A popular configuration widely used in a variety of robotic applications is to mount a camera on the robot manipulator hand. Before performing a measurement task using such a system, both the camera and the robot need to be calibrated. In this paper, a procedure is developed for simultaneous calibration of a robot and a monocular camera. Unlike conventional approaches based on first calibrating the camera and then calibrating the robot, the algorithm solves for the kinematic parameters of the robot and camera in one stage, thus eliminating error propagation and improving noise sensitivity. Only two parameters are added to a robot calibration model to represent camera geometry. With this addition, different levels of calibration can be done under a unified framework. An error model relating-image measurement residuals to kinematic parameter deviations is derived. Simulation and experimental studies have been conducted to assess the effectiveness of the proposed procedure. >
128 citations
TL;DR: The finding that theta was produced at very short latencies at RPO suggests that RPO, the putative brainstem source for the generation of theta, is modulated by a cholinergic input.
Abstract: The effects of brainstem microinjections of carbachol on the hippocampal theta rhythm were examined in urethane anesthetized rats. The two most effective theta-eliciting sites with carbachol were the nucleus pontis oralis (RPO) and the acetylcholine-containing pedunculopontine tegmental nucleus (PPT) of the dorsolateral pontine tegmentum. RPO injections generated theta at mean latencies of 38.5 +/- 70.8 s and for mean durations of 12.9 +/- 5.1 min. Five of seven RPO injections gave rise to theta virtually instantaneously, i.e., before the completion of the injection. PPT injections generated theta at mean latencies of 1.7 +/- 1.1 min and for mean durations of 11.9 +/- 6.0 min. Injections rostral or caudal to RPO in the caudal midbrain reticular formation (RF) or the caudal pontine RF (nucleus pontis caudalis) generated theta at considerably longer latencies (generally greater than 5 min) or were without effect. Medullary RF injections essentially failed to alter the hippocampal EEG. The finding that theta was produced at very short latencies at RPO suggests that RPO, the putative brainstem source for the generation of theta, is modulated by a cholinergic input. The further demonstration that theta was also very effectively elicited with PPT injections suggests this acetylcholine-containing nucleus of the dorsolateral pons may be a primary source of cholinergic input to RPO in the generation of theta. The hippocampal theta rhythm is a major event of REM sleep. The present results are consistent with earlier work showing that each of the other major events of REM sleep, as well as the REM state, are cholinergically activated at the level of the pontine tegmentum.
02 May 1993
TL;DR: An effective algorithm for the identification of the kinematic parameters of a Stewart platform is presented and verified through simulations, which showed that the platform pose error was reduced by at least one order of magnitude.
Abstract: An effective algorithm for the identification of the kinematic parameters of a Stewart platform is presented and verified through simulations The algorithm can be applied to both the reduced and the full models, which differ by the number of parameters to be identified Compensation procedures for models are also presented The algorithm was tested using simulated measurements that included realistic measurement noise, and the results showed that the platform pose error was reduced by at least one order of magnitude The identification algorithm is computationally expensive and has to be performed on a powerful computer for practical implementation >
TL;DR: In this paper, the authors introduce a simple paradigm to explore how complex, biological systems flexibly recruit and annihilate degrees of freedom according to parametric task requirements, and suggest a theoretical model in which the main qualitative changes observed experimentally are a consequence of two consecutive Hopf bifurcations.
TL;DR: In this paper, the problem of parameter uncertainty in random vibrations of structures is addressed as an anti-optimization problem of finding the least favorable values of the mean-square response.
TL;DR: This paper investigated the predictability of rater leniency from scores on an instrument designed to measure rater discomfort with performance appraisal situations The 20-item Performance Appraisal Discomfort Scale (PADS) was administered twice to a sample of 178 undergraduate business students who rated performance of group members on three group projects under conditions designed to emulate features of actual appraisal situations.
Abstract: This study investigated the predictability of rater leniency from scores on an instrument designed to measure rater discomfort with performance appraisal situations The 20-item Performance Appraisal Discomfort Scale (PADS) was administered twice to a sample of 178 undergraduate business students who rated performance of group members on three group projects under conditions designed to emulate features of actual appraisal situations Results supported the notion that rater leniency is stable and predictable from PADS scores Also, principal-component extracted and varimax rotated factors of the PADS were interpreted as corresponding to four distinct situational demands placed on raters in the course of performance appraisal The results of this limited demonstration of the validity of PADS suggest that future application of the PADS or some like instrument may be useful for enhancing the validity of appraisal ratings and feedback utility
TL;DR: In a paradigm for which two distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability are interdependent.
Abstract: In a paradigm for which 2 distinct patterns are perceived for the same stimulus, perceptual hysteresis (persistence of a percept despite parameter change to values favoring the alternative pattern) and temporal stability (persistence despite intrinsic propensities toward spontaneous change) are interdependent. Greater persistence during parameter change reduces temporal stability, slowing the rate of parameter change reduces hysteresis by increasing opportunity for spontaneous change, and increasing temporal stability (by enlarging the stimulus) increases hysteresis. Hysteresis results in the perception of parametrically disfavored patterns; a parameter can influence a percept without specifying it. The visual system thus exhibits time-dependent behavior analogous to dynamical behavior observed in other systems, both physical and biological, for which there is competition among alternative patterns that vary in relative stability.
TL;DR: In this paper, the authors explore the interaction between the strategic posture of small firms and their propensity to form cooperative relationships, and show that small firms are more likely to cooperate with other small firms.
Abstract: This study extends existing work in the area of interorganizational relationships by exploring the interaction between the strategic posture of small firms and their propensity to form cooperative ...
TL;DR: This article examined the effects of a linguistic-specific treatment on acquisition and generalization of wh-interrogative structures in two aphasic subjects presenting with deficit patterns consistent with agrammatism.
Abstract: The present research examines the effects of a linguistic-specific treatment on acquisition and generalization of wh-interrogative structures in two aphasic subjects presenting with deficit patterns consistent with agrammatism. The underlying linguistic representation of sentence structures selected for treatment and generalization was considered based on aspects of Chomsky's (1981) Government Binding (GB) theory, and a linguistic-based, wh-movement treatment strategy was implemented. Using a single-subject multiple-baseline design across behaviours and subjects, the effects of treatment were explored by examining generalization patterns across wh question forms requiring wh-movement (movement of a direct object NP to COMP). Within question form generalization also was evaluated by examining formulation of untrained sentences of varied complexity—with complexity defined in terms of the number of phrasal nodes in the d-structure representation of sentences. Results indicated that for both subjects...
TL;DR: En route to the transition, regardless of direction of forearm rotation, enhancement of phase fluctuations and an increase in perturbation response times were observed in the relative phasing between the joints, support loss of stability as a central, self-organizing process underlying coordinative change.
Abstract: The coordination dynamics (e.g., stability, loss of stability, switching) of multijoint arm movements are studied as a function of forearm rotation. Rhythmical coordination of flexion and extension of the right elbow and wrist was examined under the following conditions: (1) forearm supine (forearm angle 0°), simultaneous coordination of wrist flexion/elbow flexion and wrist extension/elbow extension (termed in-phase); and (2) forearm prone (forearm angle 160°), simultaneous coordination of wrist flexion/elbow extension and wrist extension/elbow flexion (termed anti-phase). Starting in either pattern, subjects rotated the forearm in nine 20° steps, producing 15 cycles of motion per step at a frequency of 1.25 Hz. Spontaneous transitions from pattern 1 to pattern 2 and from pattern 2 to pattern 1 were observed at a critical forearm angle. The critical angle depended on the direction of forearm rotational change, thus revealing the hysteretic nature of the switching process. En route to the transition, regardless of direction of forearm rotation, enhancement of phase fluctuations and an increase in perturbation response times (critical slowing down) were observed in the relative phasing between the joints. Such observations support loss of stability as a central, self-organizing process underlying coordinative change. Neurophysiological mechanisms supporting multijoint coordinative dynamics are discussed.
01 Jul 1993
TL;DR: Comparative simulation studies show that the performance of the iterative algorithm is usually better than that of noniterative two-stage algorithms, regardless of whether the orientation part of B/sub i/ is used or not.
Abstract: An iterative algorithm for calibration of a robotic hand-eye relationship is presented. The hand-eye calibration can be performed by solving a system of homogeneous transformation equations of the form A/sub i/X=XB/sub i/, where X is the unknown sensor position relative to the robot wrist, A/sub i/ is the ith robot motion, and B/sub i/ is the ith sensor motion. Unlike existing approaches, the algorithm presented solves the kinematic parameters of X in one stage, thus eliminating error propagation and improving noise sensitivity. Furthermore, with the iterative algorithm, the parameters of X can be computed even when the rotational part of B/sub i/ is unknown. This is important since position is easier to measure than orientation. Comparative simulation studies show that the performance of the iterative algorithm is usually better than that of noniterative two-stage algorithms, regardless of whether the orientation part of B/sub i/ is used or not. This paper also discusses the application of the proposed method to calibration of a tool mounted on a robot manipulator. >
TL;DR: A measurement procedure proposed in this article allows a great simplification of the kinematic identification and keeps the length of the particular leg, whose parameters are to be identified, fixed while the other legs change their lengths during the measurement phase.
Abstract: A Stewart platform is a six degrees of freedom parallel manipulator composed of six variable-length legs connecting a fixed base to a movable plate. Like all parallel manipulators, Stewart platforms offer high force/torque capability and high structural rigidity in exchange for small workspace and reduced dexterity. Because the solution for parallel manipulators' forward kinematics is in general much harder than their inverse kinematics, a typical control strategy for such manipulators is to specify the plate's pose in world coordinates and then solve the individual leg lengths. The accuracy of the robot critically depends on accurate knowledge of the device's kinematic parameters. This article focuses on the accuracy improvement of Stewart platforms by means of calibration.
Calibration of Stewart platforms consists of construction of a kinematic model, measurement of the position and orientation of the platform in a reference coordinate frame, identification of the kinematic parameters, and accuracy compensation. A measurement procedure proposed in this article allows a great simplification of the kinematic identification. The idea is to keep the length of the particular leg, whose parameters are to be identified, fixed while the other legs change their lengths during the measurement phase. By that, redundant parameters can be eliminated systematically in the identification phase. The method also shows the estimation of each leg's parameters separately because the measurement equations are fully decoupled, which results in a drastical reduction of the computational effort in the parameter identification. Simulation results assess the performance of the proposed approach. © 1993 John Wiley & Sons, Inc.
TL;DR: In this paper, the authors examined the hub structures of six major US airlines based on three different measures of the intensity of hubbing at network nodes and discussed the implications of the analysis results for the hub location models.
TL;DR: In this paper, a spectral-domain integral equation formulation is used to analyze the propagation characteristics of open integrated microstrip transmission lines, and the results obtained are compared to the results of other workers, and good agreement is observed.
Abstract: There has been a resurgence of interest in the propagation characteristics of open integrated microstrip transmission lines. This is due in part to the discovery of diverse propagation regimes for higher-order modes on open lines. In contrast to the dominant EH/sub 0/ mode, three distinct propagation regimes exist for higher-order modes on microstrip transmission lines. In this paper, a rigorous spectral-domain integral equation formulation is used to analyze propagation in all three regimes. This formulation provides a clear physical picture of the different propagation regimes based on the mathematical location of poles and branch points in the complex spectral-variable plane. As an illustration, the formulation is applied to the case of an isolated uniform microstrip transmission line. The integral equation is discretized via the method of moments, and entire-domain basis functions incorporating suitable edge behavior are utilized to provide convergence with relatively few terms. The results obtained are compared to the results of other workers, and good agreement is observed. >
TL;DR: Mating behaviour of the Neotropical lekking frog Ololygon rubra included female choice and three male mating strategies that indicated that female preferences evolve because of their direct benefits to female fitness and not to the genetic effects accruing to progeny from mate choice.
TL;DR: This study explores patients' and nurses' experiences of the art of nursing using a phenomenological-hermeneutic approach to enquiry that allows for exploration of the empirical experience.
Abstract: Historical and contemporary conceptualizations of nursing have not addressed the art of nursing from an experiential research approach This study explores patients’ and nurses’ experiences of the art of nursing using a phenomenological- hermeneutic approach to enquiry that allows for exploration of the empirical experience Explicating a paradigm of the art of nursing, five distinct metathemes express nursing as art and describe the complex artistic processes that are lived through the nurse and patient
TL;DR: Adolescents increasingly resolve disputes in a pragmatic, discriminating fashion, negotiating to avoid harming fragile relationships while pressing demands in some instances and submitting in others.
Abstract: Conflict is a ubiquitous feature in the lives of adolescents. In the course of a given day, a typical high school student participates in an average of seven disagreements with various individuals (Laursen, 1989). Indeed, children and adolescents spend more time each day engaged in conflict than in cooperation (Barker and Wright, 1955). Since conflict is an inevitable part of interactions, constructive management is a requisite skill for social competence. Children of all ages recognize that conflict can disrupt a relationship, but the awareness that successful conflict management involves a resolution satisfactory to both parties does not develop until adolescence (Selman, 1980). Although this awareness is often interpreted as evidence of a more complex understanding of interpersonal relationships, there has been little discussion of the implications that different conflict resolution strategies hold for adolescent relationships. Interpersonal conflict is a microcosm-a brief, insightful event that reflects larger patterns of socialinte~ction wi~hin arelationship (Collins and Laursen, 1992). Cognitive advances provide adolescents with a growing appreciation of the dangers that conflict poses to relationships (Hartup, 1992). Therefore, adolescents increasingly resolve disputes in a pragmatic, discriminating fashion, negotiating to avoid harming fragile relationships while pressing demands (when possible) in some instances and submitting (when necessary) in others.
TL;DR: In this article, a simple kinematic analysis of a primary articulator (the lower lip-jaw complex) can reveal universal and language-specific aspects of temporal organization and prosody.
TL;DR: This paper extends the OGY stabilization method to control Hamiltonian chaos by incorporating the notion of stable and unstable directions at each periodic point and presents an algorithm to calculate the stable and stable directions.
Abstract: The method for stabilizing an unstable periodic orbit in chaotic dynamical systems originally formulated by Ott, Grebogi, and Yorke (OGY) is not directly applicable to chaotic Hamiltonian systems. The reason is that an unstable periodic orbit in such systems often exhibits complex-conjugate eigenvalues at one or more of its orbit points. In this paper we extend the OGY stabilization method to control Hamiltonian chaos by incorporating the notion of stable and unstable directions at each periodic point. We also present an algorithm to calculate the stable and unstable directions. Other issues specific to the control of Hamiltonian chaos are also discussed.
TL;DR: In this paper, a modification to the complete and parametrically continuous (CPC) model is presented, which brings the model closer to the Denavit-Hartenberg (DH) model.
Abstract: Selection of a proper robot kinematic model is a critical step in error-model-based robot calibration. The Denavit-Hartenberg (DH) model exhibits singularities in calibration of robots having consecutive parallel joint axes. The complete and parametrically continuous (CPC) modeling technique is one of the more versatile alternative modeling conventions designated to fit the needs of manipulator calibration. No modeling convention is, however, perfect. One “user-unfriendly” aspect of the CPC model is a condition handling technique needed, when constructing the error model, to avoid model singularities due to the adoption of the direction vectors of the joint axes as link parameters. This paper presents a modification to the CPC model which brings the model closer to the DH model. Rather than using the direction vectors of joint axes, the modified CPC (MCPC) model employs angular parameters to acommodate the required rotations for each link transformation. This modification results in a much simplified error model. The model, like the CPC model, is capable of completely describing the geometry and motion of the manipulator in a reference coordinate frame. Its error model possesses a minimum number of parameters to span the entire geometric error space and it can be made singularity-free by proper selection of the tool axis. This paper presents a calibration study of the PUMA robot using the MCPC model. A moving stereo camera system was employed for end-effector pose measurements. The MCPC error model was then used for kinematic identification. Results on the PUMA arm show that the MCPC performs well for robot calibration. The well-defined structure and user friendliness of the MCPC model may facilitate the implementation of robot calibration techniques on the factory floor.