Changxu Wu

Queuing Network Modeling of Driver Workload and Performance

Drivers overloaded with information significantly increase the chance of vehicle collisions. Driver workload, which is a multidimensional variable, is measured by both performance-based and subjective measurements and affected by driver age differences. Few existing computational models are able to cover these major properties of driver workload or simulate subjective mental workload and human performance at the same time. We describe a new computational approach in modeling driver performance and workload-a queuing network approach based on the queuing network theory of human performance and neuroscience discoveries. This modeling approach not only successfully models the mental workload measured by the six National Aeronautic and Space Administration Task Load Index workload scales in terms of subnetwork utilization but also simulates the driving performance, reflecting mental workload from both subjective- and performance-based measurements. In addition, it models age differences in workload and performance and allows us to visualize driver mental workload in real time. Further usage and implementation of the model in designing intelligent and adaptive in-vehicle systems are discussed.

Queuing Network Modeling of Transcription Typing

Transcription typing is one of the basic and common activities in human-machine interaction and 34 transcription typing phenomena have been discovered involving many aspects of human performance including interkey time, typing units and spans, typing errors, concurrent task performance, eye movements, and skill effects. Based on the queuing network theory of human performance [Liu 1996; 1997] and current discoveries in cognitive and neural science, this article extends and applies the Queuing Network-Model Human Processor (QN-MHP [Liu et al. 2006]) to model 32 transcription typing phenomena. The queuing network model of transcription typing offers new insights into the mechanisms of cognition and human-computer interaction. Its value in proactive ergonomics design of user interfaces is illustrated and discussed.

Electrophysiological and morphological properties of pyramidal and nonpyramidal neurons in the cat motor cortex in vitro.

Electrophysiological and morphological properties of the neurons in cat motor cortex were investigated using intracellular recording and staining techniques in a brain slice preparation. In response to intracellular injection of depolarizing current pulses, four distinct types of firing patterns were observed among cat neocortical neurons. Regular-spiking neurons were characterized by their repetitive firing from which conspicuous frequency adaptation was observed. Doublet-or-burst firing cells were marked with their tendency to fire 2-5 clustered spikes at the onset of depolarizing pulse. In doublet-or-burst firing neurons, but not in regular-spiking neurons, a low-threshold calcium current was revealed by single-electrode voltage clamp. Both regular-spiking and doublet-or-burst firing neurons had relatively wide action potentials. Fast-spiking neurons could fire extremely narrow action potentials at a very high frequency. Their frequency-to-intensity slope of steady-state firing was significantly higher than that of the other neurons. In contrast, narrow-spiking neurons had the smallest frequency-to-intensity slope for steady-state firing, although their action potentials were as narrow as those of the fast-spiking neurons. Both regular-spiking and doublet-or-burst firing neurons were identified as pyramidal neurons, and were found in all layers below layer I. Their apical dendrites were densely coated with dendritic spines. Narrow-spiking neurons were only recorded in layer V. They were large pyramidal cells with scare spines on their apical dendrites. Fast-spiking neurons were all nonpyramidal interneurons. Seven out of eight labelled fast-spiking cells had beaded dendrites without spines. Their axons had a large number of varicosities, and arborized extensively to form a dense plexus of terminals in the vicinity of their soma. The remaining neuron was found to be a spiny nonpyramidal neuron in layer V. These results demonstrate that, in addition to the three types of firing patterns previously identified in rodent neocortex, a group of neurons in the cat motor cortex express another type of firing behaviour which is characterized by extremely narrow action potential and very small frequency-to-intensity slope. Correlation with the morphological data shows that these neurons are large layer V pyramidal cells rather than nonpyramidal interneurons.

Traffic safety for electric bike riders in China: attitudes, risk perception, and aberrant riding behaviors

The use of electric bikes (e-bikes) in China has grown tremendously in the past decade. Traffic safety for e-bike riders is an issue of growing public concern because the number of fatalities and injuries is increasing. A study was conducted to identify risk factors affecting involvement of e-bike riders in accidents and to establish the relationships between safety attitudes, risk perception, and aberrant riding behaviors. The data used for analysis were obtained from a self-reported questionnaire survey of a sample of 603 e-bike riders in two large cities in China. The results showed that both gender and automobile driving experience were significantly associated with at-fault accident involvement. Males were more likely to have at-fault accidents than were females, and riders with an automobile drivers license were less likely to have accidents than were those without a drivers license. Two types of aberrant riding behaviors, errors and aggressive behaviors, were found to be significant factors for predicting at-fault accident involvement. Analysis with a structural equation model indicated that safety attitudes and risk perception both significantly affected aberrant riding behaviors. E-bike riders with stronger positive attitudes toward safety and more worry and concern about their traffic risk tended to be less likely to have aberrant riding behaviors. Practical implications for improving road safety of e-bike riders are discussed.

Development of an Adaptive Workload Management System Using the Queueing Network-Model Human Processor (QN-MHP)

The risk of vehicle collisions significantly increases when drivers are overloaded with information from in-vehicle systems. One of the solutions to this problem is developing adaptive workload management systems (AWMSs) to dynamically control the rate of messages from these in-vehicle systems. However, existing AWMSs do not use a model of the driver cognitive system to estimate workload and only suppress or redirect in-vehicle system messages, without changing their rate based on driver workload. In this paper, we propose a prototype of a new queueing network-model human processor AWMS (QN-MHP AWMS), which includes a queueing network model of driver workload that estimates the driver workload in several driving situations and a message controller that determines the optimal delay times between messages and dynamically controls the rate of messages presented to drivers. Given the task information of a secondary task, the QN-MHP AWMS adapted the rate of messages to the driving conditions (i.e., speeds and curvatures) and driver characteristics (i.e., age). A corresponding experimental study was conducted to validate the potential effectiveness of this system in reducing driver workload and improving driver performance. Further development of the QN-MHP AWMS, including its use in in-vehicle system design and possible implementation in vehicles, is discussed.

Queuing Network Modeling of a Real-Time Psychophysiological Index of Mental Workload—P300 in Event-Related Potential (ERP)

Modeling and predicting of mental workload are among the most important issues in studying human performance in complex systems. Ample research has shown that the amplitude of the P300 component of event-related potential (ERP) is an effective real-time index of mental workload, yet no computational model exists that is able to account for the change of P300 amplitude in dual-task conditions compared with that in single-task situations. We describe the successful extension and application of a new computational modeling approach in modeling P300 and mental workload - a queuing network approach based on the queuing network theory of human performance and neuroscience discoveries. Based on the neurophysiological mechanisms underlying the generation of P300, the current modeling approach accurately accounts for P300 amplitude both in temporal and intensity dimensions. This approach not only has a basis in its biological plausibility but also has the ability to model and predict workload in real time and can be applied to other applied domains. Further model developments in simulating other dimensions of mental workload and its potential applications in adaptive system design are discussed.

Development and evaluation of an ergonomic software package for predicting multiple-task human performance and mental workload in human-machine interface design and evaluation

Predicting human performance and mental workload in multiple task situations at an early stage of system design can save a significant amount of time and cost. However, existing modeling tools either can only predict human performance or require users of tools to learn a new programming language. Queueing Network-Model Human Processor (QN-MHP) is a new cognitive architecture for modeling both human performance and mental workload in multiple tasks. This paper describes the development of a Visual Basic Application in Excel (VBA) software package and an illustrative case study to evaluate its effectiveness. The software package has an easy-to-use user interface for QN-MHP that assists users of the modeling tool to simulate a dual task including definition of the tasks and interfaces by clicking buttons to select options and filling texts in a table, with no need to learn a simulation language. It allows the model user to intuitively observe the information processing state of the model during simulation, and conveniently compare the simulated human performance and mental workload for different designs. The illustrative case study showed that naive users without prior simulation language programming experience can model human performance and mental workload in a complex multitask situation within 3min; and this software package can save 71% of modeling time and reduce 30% of modeling errors. Further developments of the VBA software package of QN-MHP are also discussed on how to make it a comprehensive proactive ergonomic design and analysis tool.

The effects of sunshields on red light running behavior of cyclists and electric bike riders

Bicycles held an important position in transportation of China and other developing countries. As accidents rate involving electronic and regular bicycles is increasing, the severity of the bicycle safety problem should be paid more attention to. The current research explored the effect of sunshields (a kind of affordable traffic facility built on stop line of non-motor vehicle lanes (According to National Standard in China, e-bikes share the non-motor vehicle lane with regular bikes.) which was undertaken to avoid riders suffering from sunlight and high temperature) on diminishing red light running behavior of cyclists and e-bike riders. An observational study of 2477 riders was conducted to record and analyze their crossing behaviors at two sites across the city of Hangzhou, China. Results from logistic regression and analysis of variance indicated a significant effect of sunshield on reducing red light infringement rate both on sunny and cloudy days, while this effect of sunshield was larger on sunny days than on cloudy days based on further analysis. The effect of intersection type in logistic regression showed that riders were 1.376 times more likely to run through a red light upon approaching the intersection without sunshields compared to with sunshields in general. The results of MANCOVA further confirmed that rates of running behaviors against red lights were significantly lower at the intersections with a sunshield than at intersections without sunshields when other factors including traffic flow were statistically controlled. To sum up, it is concluded that sunshields installed at intersections can reduce the likelihood of red light infringement of cyclists and e-bike riders on both sunny and cloudy days. For those areas or countries with a torrid climate, sunshield might be a recommended facility which offers an affordable way to improve the safety of cyclists and e-bike riders at intersections. Limitations of the current sunshield design and current study are also discussed.

Different mechanisms underlying the repolarization of narrow and wide action potentials in pyramidal cells and interneurons of cat motor cortex

Two different types of action potentials were observed among the pyramidal cells and interneurons in cat motor cortex: the narrow action potentials and the wide action potentials. These two types of action potentials had similar rising phases (528.8 +/- 77.0 vs 553.1 +/- 71.8 mV/ms for the maximal rising rate), but differed in spike duration (0.44 +/- 0.09 vs 1.40 +/- 0.39 ms) and amplitude (57.31 +/- 8.22 vs 72.52 +/- 8.31 mV), implying that the ionic currents contributing to repolarization of these action potentials are different. Here we address this issue by pharmacological manipulation and using voltage-clamp technique in slices of cat motor cortex. Raising extracellular K+ concentration (from 3 mM to 10 mM), applying a low dose of 4-aminopyridine (2-200 microM) or administering a low concentration of tetraethylammonium (0.2-1.0 mM) each not only broadened the narrow action potentials, but also increased their amplitudes. In contrast, high K+ medium or low dose of tetraethylammonium only broadened the wide action potentials, leaving their amplitudes unaffected, and 4-aminopyridine had only a slight broadening effect on the wide spikes. These results implied that K+ currents were involved in the repolarization of both types of action potentials, and that the K+ currents in the narrow action potentials seemed to activate much earlier than those in the wide spikes. This early activated K+ current may counteract the rapid sodium current, yielding the extremely brief duration and small amplitude of the narrow spikes. The sensitivity of the narrow spikes to 4-aminopyridine may not be mainly attributed to blockade of the classical A current (IA), because depolarizing the membrane potential to inactivate IA did not reproduce the effects of 4-aminopyridine. Blockade of Ca2+ influx slowed the last two-thirds repolarization of the wide action potentials. On the contrary, the narrow action potentials were not affected by Ca(2+)-current blockers, but if they were first broadened by 4-aminopyridine or tetraethylammonium, subsequent application of Ca(2+)-free medium caused further broadening, suggesting that the narrow action potentials were too brief to activate the Ca(2+)-activated potassium currents for their repolarization. Therefore, the effects of low concentrations of tetraethylammonium on the narrow spikes appeared to be mainly due to blockade of an outward current that was different from the tetraethylammonium-sensitive Ca(2+)-activated potassium current (IC). In the neurons with the narrow spikes, voltage-clamp experiments revealed two voltage-gated outward currents that were sensitive to tetraethylammonium and 4-aminopyridine, respectively. Both currents were activated rapidly following the onset of depolarizing steps. Interestingly, the tetraethylammonium-sensitive current was a transient outward current that inactivated rapidly (tau < or = 5 ms), while the 4-aminopyridine-sensitive current was relatively persistent during maintained depolarization. The 4-aminopyridine-sensitive current did not show obvious inactivation even at membrane potential of -40 mV, which completely inactivated the transient tetraethylammonium-sensitive, current. The results indicate that different potassium currents are involved in the repolarization of the narrow and wide action potentials in cat motor cortex. A novel tetraethylammonium-sensitive transient outward current and a 4-aminopyridine-sensitive outward current are responsible for the short duration and small amplitude of the narrow action potentials in the interneurons and some of the layer V pyramidal cells. These two currents are voltage-gated and Ca(2+)-independent. For the wide action potentials that characterize most pyramidal neurons, a Ca(2+)-independent tetraethylammonium-sensitive outward current and a Ca(2+)-activated potassium current are the main contributors to their repolarization.

A computational cognition model of perception,memory,and judgment

The mechanism of human cognition and its computability provide an important theoretical foundation to intelligent computation of visual media. This paper focuses on the intelligent processing of massive data of visual media and its corresponding processes of perception, memory, and judgment in cognition. In particular, both the human cognitive mechanism and cognitive computability of visual media are investigated in this paper at the following three levels: neurophysiology, cognitive psychology, and computational modeling. A computational cognition model of Perception, Memory, and Judgment (PMJ model for short) is proposed, which consists of three stages and three pathways by integrating the cognitive mechanism and computability aspects in a unified framework. Finally, this paper illustrates the applications of the proposed PMJ model in five visual media research areas. As demonstrated by these applications, the PMJ model sheds some light on the intelligent processing of visual media, and it would be innovative for researchers to apply human cognitive mechanism to computer science.