Time Delay Conditions Research Articles

Perception of delayed environmental risks: beyond time discounting

Purpose– The purpose of this research is to explore the effect of time delay on the perception of environmental risks beyond time discounting, and thus provide a reference for effective communication related to environment and environmental risks.Design/methodology/approach– Ten risk scenarios across four time delay conditions were designed. Computer program randomly presented different risk scenarios to student subjects. Risk perception was measured through equivalent certain loss elicited by bi-section method. In all, 50 students from Harbin Institute of Technology Shenzhen Graduate School participated in the experiment.Findings– Time delay makes the subjects optimistic toward environmental risk with the exclusion of time discounting. The more distant in time the occurrence of an environmental risk, the less in intensity subjects will perceive it as a severe threat. Also, there is a noticeable difference in environmental risk perception between males and females.Research limitations/implications– This tentative research focusses on exploring the existence of time delay effect on environmental risk perception. Only student subjects are recruited for this research. Future studies are needed to extend the population to people of different backgrounds in order to generalize the finding.Practical implications– Current ethical appeal of zero social discount rate is unlikely to be effective. Time delay effect in people's environmental risk perception should be acknowledged. Such an acknowledgement is the basis of trust in risk communication. Communication effort needs to address this time delay effect to make people alert to long-term environmental risks, and eventually change their environmental behaviors.Originality/value– The explorative research represents the first attempt to investigate the effect of time delay on environmental risk perception when time discounting is excluded. It suggests a new direction to understand public optimism toward delayed environmental risks, and reluctance to take proactive actions, and thus offers a new insight into related communication efforts.

Exploring Communication in Remote Teams

Teamwork in many operational settings, such as air traffic control or telemedicine, involves members who are at different locations and, as in space exploration missions, may communicate under time-delayed conditions. Collaboration and coordination in distributed teams differ from face-to-face interactions in a number of important respects (Brennan & Lockridge, 2006). Remote communication eliminates visual cues and thus requires more effort to establish common ground. Unlike co-present partners, distributed team members cannot rely on gestures and facial expressions to direct the other’s attention and provide feedback on their understanding. Voice communication between remote partners maintains the meaning nuances of face-to-face interactions that is lacking in text-based conversations. On the other hand, writing enables partners to re-read and thus to remember past communications, and to review and revise their messages prior to sharing them with others. These resources are not available in spoken discourse where participants have to rely on their memory or external aids (e.g., note pads) to keep track of the flow of the conversation and to compose their contributions. Transmission delays between partners’ contributions further complicate grounding (Olson, G., & Olson, J., 2000). The timing of turns is challenging, and individual contributions may be out of sequence, making it difficult for team members to follow the thread of a conversation and thus to develop shared situation models. Moreover, distributed teams frequently consist of individuals with different expertise and different goals, differences that may hamper mutual understanding and collaboration (Bearman, Paletz, Orasanu, & Thomas, 2010). This panel brings together researchers who have examined team communication in a variety of domains: healthcare (Morrow), aviation (Mosier), Navy (Miller), disaster response (Veinott), and space missions (Fischer, Miller). Panelists will be asked to characterize the constraints faced by conversational partners in these domains, to present analytic tools for studying remote communication and to discuss procedural or technological solutions to facilitate collaboration and coordination in distributed teams.

Fuel cell fault forecasting system using grey and extension theories

This study proposes a fault forecasting system for proton exchange membrane fuel cells (PEMFCs), which uses a set of wireless sensors to accomplish fuel cell (FC) condition monitoring. The software interface of the FC fault forecast system uses LabVIEW software. Owing to the time delay condition of FC reactions, this study first forecasts all the operation features of the FC using a Grey prediction model. Then, an extension diagnosis method uses the forecasted values of the features to forecast the future operational conditions. Thus, the complex condition monitoring and fault forecasting problem of the FC can be implemented effectively. To demonstrate the effectiveness of the proposed method, comparative studies using a multilayer neural network and k-means algorithm are conducted on 400 sets of field-test patterns of 200 W PEMFC with rather encouraging results.

A review of modeling errors and control for time-delay systems utilizing the LDI criterion

Nonlinear systems sometimes suffer from modeling errors which could potentially result in instability and reduce the control performance of the actual systems. This paper reviews some previous research studies examining the sources of these errors and how to deal with them. In this work, a fuzzy Lyapunov function is defined through fuzzy blending quadratic Lyapunov functions to avoid conservatism in the stability conditions. Therefore, the neural network (NN) model based approach is provided and the fuzzy systems can be transferred into a linear difference inclusion (LDI) formulation. Time-delay stability conditions of closed-loop controlled systems are then derived based on robustness design to deal with the modeling error problems. Key words: Fuzzy Lyapunov method, LDI, T-S fuzzy systems, artificial intelligence.

Controllability of Multi-Rate Networked Control Systems with Short Time Delay

Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems. Multi-rate networked control systems mean the sampling rates of notes in networked control systems are not the same. The controllability of multi-rate networked control systems are investigated in this paper for the first time. Based on the mathematic model of multi-rate networked control systems with short time delay, some sufficient or necessary conditions for controllability of multi-rate networked control systems are got using stochastic systems approach.

Dynamics of the density dependent predator–prey system with Beddington–DeAngelis functional response

Two models of a density dependent predator–prey system with Beddington–DeAngelis functional response are systematically considered. One includes the time delay in the functional response and the other does not. The explorations involve the permanence, local asymptotic stability and global asymptotic stability of the positive equilibrium for the models by using stability theory of differential equations and Lyapunov functions. For the permanence, the density dependence for predators is shown to give some negative effect for the two models. Further the permanence implies the local asymptotic stability for a positive equilibrium point of the model without delay. Also the global asymptotic stability condition, which can be easily checked for the model is obtained. For the model with time delay, local and global asymptotic stability conditions are obtained.

Formulas of variation for solutions for some classes of functional differential equations and their applications

For non-linear delay and quasi-linear neutral controlled functional differential equations with mixed initial condition and with distributed delay in controls, linear representations of the variation of solutions (formulas of variation) are obtained with respect to perturbations of the initial moment, of the initial vector, of the initial function, and of the control function. “Mixed initial conditions” means that at the initial moment some coordinates of the trajectory do not coincide with the corresponding coordinates of the initial function. On one hand, variation formulas are used in the proof of necessary optimality conditions [R.V. Gamkrelidze, Principles of Optimal Control Theory, Plenum Press, New York, London, 1978; N.M. Ogustoreli, Time-Delay Control Systems, Academic Press, New York, London, 1966; L.W. Neustadt, Optimization: A Theory of Necessary Conditions, Princeton Univ. Press, Princeton, 1976; G.L. Kharatishvili, T.A. Tadumadze, Variation formulas of solutions and optimal control problems for equations with retarded argument, J. Math. Sci. (NY) 104 (1) (2007) 1–175]; on the other hand, they allow one to obtain approximate solutions of perturbed equations in analytic form. Formulas of variation for non-linear delay differential equations without a control function are proved in [G.L. Kharatishvili, T.A. Tadumadze, Variation formulas for solution of a nonlinear differential equation with time delay and mixed initial condition, J. Math. Sci. (NY) 148 (3) (2008) 302–330]. Moreover, in the present paper, for delay and neutral optimal control problems with non-fixed initial moment and with mixed initial condition, the necessary conditions of optimality are obtained. One of them, the essential novelty, is a necessary condition of optimality for the initial moment containing the effect of the mixed initial condition.

Management of acute myocardial infarction in the real world: a summary report from The Ami-Florence Italian Registry

The Florence Acute Myocardial Infarction registry was a population-based, prospective study aimed at identifying the determinants of coronary reperfusion therapy [CRT, by primary coronary intervention (PCI) in more than 95% of cases] utilization and of prognosis in patients with ST-segment elevation myocardial infarction (STEMI). The registry involved one teaching hospital with, and five district hospitals without PCI facilities. Overall, as many as 45.6% of 930 cases of STEMI did not receive any form of CRT. In multivariable analysis, the direct admission to the teaching hospital was the strongest positive predictor, whereas the time delay, older age, and chronic comorbid conditions were negative predictors of CRT utilization. Compared to conservative therapy, CRT was associated with a remarkably reduced 12-month mortality, after adjusting for age, chronic comorbidities and Killip class, which also were significantly associated with long-term prognosis. The higher crude mortality observed in women was accounted for by older age and other age-related factors. The improvement in prognosis with CRT was larger in older patients and/or in those with a greater burden of chronic comorbidity, who less frequently received CRT. These results suggest the need for interdisciplinary reassessing the adherence to therapeutic guidelines and the criteria adopted in the real clinical world to select patients for CRT during STEMI.

Variation formulas for solution of a nonlinear differential equation with time delay and mixed initial condition

In this paper, we prove the variation formulas for solutions of a differential equation with nonconstant time delay and mixed initial condition. “Mixed initial condition” means that at the initial moment, some coordinates of the trajectory do not coincide with the corresponding coordinates of the initial function. This condition unites continuous and noncontinuous initial conditions, for which the variation formulas were probed in [5–7]. On one hand, variation formulas are used in the proof of necessary optimality conditions [1–4, 6, 8, 9]; on the other hand, they allow one to obtain approximate solutions of perturbed equations in analytic form.

Determining eyewitness identification accuracy using event‐related brain potentials (ERPs)

This study investigated the use of event-related brain potentials (ERPs) as a neurophysiological measure of eyewitness identification accuracy during a lineup task (ERP-lineup). Time delay between viewing the crime and completing the ERP-lineup (no-delay, 1-h delay and 1-week delay conditions) and culprit presence or absence were also manipulated. Results demonstrated that a P300 provided a reliable index of recognition of the culprit relative to the other lineup members across all time delay conditions. Although participants' accuracy decreased at the 1-week time delay compared to no delay and the 1-h time delay, the P300 effect remained strong for participants that made correct identifications irrespective of the time delay. In addition, the P300 was attenuated or was not elicited when the culprit was absent from the lineup.

Ground–Space Bilateral Teleoperation of ETS-VII Robot Arm by Direct Bilateral Coupling Under 7-s Time Delay Condition

A bilateral teleoperation experiment with Engineering Test Satellite 7 (ETS-VII) was conducted on November 22, 1999. Round-trip time for communication between the National Space Development Agency of Japan ground station and the ETS-VII was approximately seven seconds. We constructed a bilateral teleoperator that is stable, even under such a long time delay. Several experiments, such as slope-tracing task and peg-in-hole task, were carried out. Task performance was compared between the bilateral mode and the unilateral mode with force telemetry data visually displayed on a screen. All tasks were possible by bilateral control without any visual information. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such a long time delay, and improves the performance of the task.

大きな通信時間遅れの下での直接バイラテラル制御による技術試験衛星ＶＩＩ型搭載ロボットアームの地上遠隔操作実験

大きな通信時間遅れの下での直接バイラテラル制御による技術試験衛星ＶＩＩ型搭載ロボットアームの地上遠隔操作実験

Comparison of the Effects of Spanish and English Constant Time Delay Instruction on Sight Word Reading by Hispanic Learners with Mental Retardation

This study investigated the effectiveness and efficiency of a 4-second time delay instructional package and language of instruction with regard to the percentage correct of English sight words and incidental information by 4 Puerto Rican middle school students with mental retardation. A multiple probe across students with a parallel treatments design that compared Spanish and English constant time delay intervention conditions was employed to teach sight words from local grocery and department stores. Incidental information was provided contingent on correct responding during intervention. Results indicated that both Spanish and English time delay conditions were equally effective and efficient when compared with a no-treatment condition in promoting English sight word reading for 3 of the 4 participants, whereas Spanish time delay was seen to be more effective and efficient than English time delay and no-treatment conditions for the other participant. All 4 participants generalized word reading from the classroom to the natural setting (i.e., stores in the community) and learned most of the incidental information. Implications for practice and directions for future research with respect to language of instruction are discussed.

Human factors in telesurgery: effects of time delay and asynchrony in video and control feedback with local manipulative assistance.

This paper presents the results of experiments examining the performance of a telesurgeon and an assistant local to the patient performing simulated laparoscopic tasks under a variety of time-delay conditions. Of particular interest is a comparison between the surgeon provided with audio/video and force feedbck synchronously with various time delays, and the surgeon performing asynchronously, where video is delayed relative to force feedback. These conditions are relevant since current telecommunication systems have limited bandwidth, and video signals must be compressed for efficient transmission. This produces a time lag between the video camera and the surgeon's monitor, Force feedback and position commands from a surgical teleoperator require much lower bandwidth, and can be transmitted in near-real time. In the first of two series of experiments, two laparoscopic training tasks were performed under different time-delay conditions, with force and video feedback delayed by equal amounts. In the second series, using the same tasks, the force feedback was more immediate, while the video delay lagged by the time required for compression and decompression. In both experiments, there were various role assignments in terms of whether the telesurgeon or the assistant controlled the laparoscope and/or the various surgical tools required. The three most striking results are that (1) nontrivial time delays significantly degraded the performance of the surgical tasks, (2) asynchronous force feedback resulted in significantly faster task-performance than did synchronous performance when the surgeon operated the laparoscopic tools, and (3) there was no difference between synchrony and asynchrony when the remote surgeon operated the laparoscope and gave commands while the local assistant operated the surgical tools.

Adaptive fuzzy proportional integral power control for a cellular CDMA system with time delay

We investigate the use of fuzzy logic control techniques for adaptive power control in a direct-sequence code-division multiple-access (DS/CDMA) cellular system over the mobile fading radio channels with propagation time delay. A fuzzy PI (proportional-plus-integral) control whose input variables are the received power error and error change is introduced to determine each user transmitting power in order to simultaneously equalize all users' signal powers received at the base station and achieve better system stability and control performance. This control strategy can ensure long loop transmission delays without causing the system to become unstable. According to the well-known phase-plane method, the derivation of the fuzzy PI control has been carried out by analyzing the response areas, cross-over, and extreme points of the system step response with apriori knowledge of the dynamics of the CDMA mobile fading channels. For a long time-delay fading process, a methodology is developed to modify the rule base to contain the delay information for reducing the deadtime effects of the process. Moreover, the additional advantages of fuzzy PI control over conventional control theories are: increased robustness in spite of interference and the ability to handle the time-delay process whose parameters are not accurately known. Simulation results show that a good performance can be achieved both in RMS tracking error and traffic capacity by use of fuzzy PI power control, especially in poor interuser interference and long time delay conditions.

The Effects of Simulator Time Delays on A Sidestep Landing Maneuver: A Preliminary Investigation

The use of a variety of idealized tracking tasks as a means of studying the effects of simulator time delay has been ongoing for five years at the Armstrong Aerospace Medical Research Laboratory (AAMRL). Results from these studies generated some interest in evaluating more complex tasks. Based on related in-flight research, a sidestep landing task scenario was selected as a means of making the simulator task more realistic and also sensitive to the effects of time delay. In this experiment, twelve subjects were placed in a final-approach landing configuration and later cued to sidestep to an adjacent, parallel runway. Subjects completed 40 trials in each of three time delay conditions (90,200, and 300 ms) in a latin square design. Significant differences were discovered among the delay conditions in the approach and landing performance data.

Time-delay discrimination training: replication with different stimuli and different populations

Two time-delay conditions for teaching complex visual discriminations to normal preschoolers and children with mild and moderate intellectual handicaps were compared. One condition involved spatially separating the distinctive components from the redundant parts of both stimuli (multiple dynamic distinctive-feature prompts). The other condition involved adding a colored field to the correct stimulus (single static nondistinctive-feature prompt). The effect of the latter condition was assessed with unlearned and learned tasks. The study consisted of four experiments. In one experiment, children were also required to use the prompts for self-monitoring responses given before prompting had occured. The results indicated that for all populations and stimuli (a) time delay of multiple dynamic distinctive-feature prompts consistently produced learning, and (b) time delay of the single static nondistinctive-feature prompt almost never produced learning and frequently led to a complete loss of discriminative performance on previously learned tasks. The resistance to disruption was a function of the training history (i.e., with or without time delay) and IQ level. Self-monitoringincreased the efficacy of time delay when multiple dynamic distinctive-feature prompts were used but not when the single static nondistinctive-feature prompt was used.

The Effects of Simulator Delays on the Acquisition of Flight Control Skills: Control of Heading and Altitude

The effects of simulator delays on performance, control behavior, and transfer of training were investigated with a group of subjects who had no experience with flight control tasks. Two types of aircraft were simulated: one with highly responsive dynamics and one with sluggish dynamics. Subjects were assigned to one of four time-delay conditions and to one of the two aircraft types. In the first phase of the experiment, subjects participated in fifty trials (ten trials per day) with a particular time delay (50, 100, 200, or 400 milliseconds). After this “training” phase, all subjects “transferred” to the minimum time-delay condition (50 milliseconds) for another fifty trials. The experimental task required that the subjects maintain constant heading and altitude in the presence of pseudo-random roll-rate and pitch-rate disturbances. There were statistically significant effects of time delay on root-mean-square heading and altitude errors in both the training and transfer phases of the experiment. The effect of delay on transfer of training was greater for the aircraft with sluggish dynamics.

Minimum-Sensitivity Condition of a Time-Delay System with a Given Gain Margin

The relative stability curves, the time-delay sensitivity and loop-gain sensitivity over a wide frequency range have been evaluated for both linear and non-linear time-delay systems designed with a relative stability (6-dB gain margin) and minimum time-delay sensitivity conditions imposed on the system. The resultant system shows an improved performance.

Effects of duration and interaural delays of masking noise on detectability under homophasic and antiphasic signal conditions

Detectability of a 500-Hz tone of either 10 or 100 msec duration in broadband 50-dB spectrum-level noise of identical duration was measured as a function of the interaural delay of the noise. Homophasic or antiphasic signals were presented in a single-interval, forced-choice task employing five randomly presented signal levels. In coherent noise (1) equal energy homophasic signals were equally detectable regardless of noise duration; (2) antiphasic signals were more easily detected than their homophasic counterparts; and (3) antiphasic signals in the 10 msec condition required 6 dB more energy for performance to equal that found in the 100-msec antiphasic condition. Detectability in the 100-msec conditions decreased slowly as a function of time delay and signal conditions provided data which interleaved in a well-known manner [T. L. Langford and L. A. Jeffress, J. Acoust. Soc. Am. 36, 1455–1458 (1964)]. However, the data gathered in the 10-msec conditions revealed severe degradation in the observer's ability to process signals in noises delayed interaurally from 1 to 5 msec.