The effects of extended work under sleep deprivation conditions on team-based performance

Teamwork is becoming increasingly common in today's workplaces; however, little research has examined how well teams perform under sleep deprivation conditions. The purpose of the current study was to examine the effect of extended work under sleep deprivation conditions on team performance. A total of 24 participants were sleep deprived for 30 h and completed 16 h of sustained operations during the last portion of the sleep deprivation period. The participants completed the Wombat, a complex task including vigilance and cognitive components, with a partner in four 24-min testing sessions during the sustained operations period. The results indicated that team performance increased during the work period while, within each testing session, team performance on vigilance tasks remained stable and overall performance decreased. The current results suggest that performance on two-person teams results in improved performance but does not fully counteract the decreases in performance within each work period. Performance in two-person teams increased across an extended work shift under sleep deprivation conditions. However, vigilance performance remained stable while overall performance decreased when examining performance in 8-min segments. These results suggest that averaging team-based performance over a longer testing period may mask the negative effects of sleep deprivation.

Statement of Relevance: Performance in two-person teams increased across an extended work shift under sleep deprivation conditions. However, vigilance performance remained stable while overall performance decreased when examining performance in 8-min segments. These results suggest that averaging team-based performance over a longer testing period may mask the negative effects of sleep deprivation.     

The sleep and performance of train drivers during an extended freight-haul operation

The sleep and performance of train drivers was monitored across a 106-h rail operation between the Australian cities of Adelaide and Perth. The drivers worked alternating 8-h shift rotations across the operation and rested in specially equipped, crew-van carriages during non-work periods. The crew-van rest opportunities were associated with shorter bedtime spans, less total sleep time, and poorer sleep efficiency than sleeps initiated at home. The duration of crew-van sleeps was primarily dependent on the time of day at which the rest opportunities occurred. Overall, drivers incurred a significant cumulative sleep loss across the duration of the operation. Despite the deficit, drivers were able to sustain vigilance performance across the operation.     

Mental effects of caffeine in fatigued and non-fatigued female and male subjects

Abstract

In experiment I eight male and eight female subjects were randomly assigned to either a caffeine or a placebo condition. Caffeine (150 mg) was given at midnight and at 4 a.m. Oral temperature, subjective ratings of fatigue and mood, and performance in two cognitive tasks (an auditive attention task and a visual coding task) were assessed. Subjective 'drowsiness’ and 'tiredness’ increased significantly more in subjects given placebo than in subjects given caffeine treatment. The effects of drug treatment in performance and temperature were non-significant. However, the temperature of female subjects increased between midnight and 4 a.m. and the temperature of male subjects decreased during the same period of time. On the other hand, at 5 a.m. female subjects rated themselves as more sleepy, tired and 'disorganized’ than the male subjects. In experiment 2 nine female and nine male subjects were assigned randomly to either placebo or caffeine treatment. Caffeine (200 mg) was given at 5 a.m. Oral temperature, subjective ratings of fatigue and mood, and level of performance in three cognitive tasks (the same as above plus Raven's progressive matrices) were assessed. Moreover, the subjects rated the effort of performing each task. The effects of drug treatment in level of performance were non-significant. However, the subjective effort of performing the auditive attention task increased significantly in subjects given placebo treatment, suggesting a compensatory arousal mechanism (Broadbent 1971). The effect of gender on temperature was non-significant. There was a significant interaction between gender and treatment in respect of subjective effort of performing the matrices task. In men caffeine decreased subjective effort and in women subjective effort was increased by caffeine. Experiment 3 was set up to investigate the hypothesis that negative effects of caffeine in women, observed in experiment 2, were due to over-optimal (‘vigilance-related’) arousal for the visual coding and matrices tasks. Ten female and eight male non-sleep deprived subjects were given 200 mg caffeine or placebos at 3 p.m. and tested at 4 p.m. Experiment 3 was not found to support the over-optimal 'vigilance-related-arousal hypothesis. Effects of caffeine in performance and effort were non-significant in experiment 3. Combining data from experiments 2 and 3 gave a significant three-way interaction between caffeine, time for experiment and rule complexity in the visual coding task. When there was a complex rule, caffeine was found to have a positive effect in experiment 3 and a negative effect in experiment 2.     

如何对校园网络的性能进行监视与维护

本文主要分析如何定期收集各种信息,分析网络中各种资源的使用率,及时发现影响网络性能的"瓶颈",并做出相应的优化或者增加网络设备从而提高网络性能.     

Cognition and the temporal arts: Investigating audience response to dance using PDAs that record continuous data during live performance

If artists and art explore organization of the brain [Zeki, S., Lamb, M., 1994. The neurology of kinetic art. Brain 117, 607–636], then investigation of response to artistic performance holds promise as a window to perceptual and cognitive processes. A new instrument for recording real-time audience response – the portable Audience Response Facility (pARF) – is described. Twenty, hand-held, Personal Digital Assistants (PDAs) collect responses on customizable skin interfaces. The pARF server transmits the customizable options, synchronizes devices and collects data for export. We report two studies using the pARF that demonstrate respondent agreement of perceived emotion during particular sections of two dance works. Greater agreement was evident in continuous ratings of arousal than valence; arousal appears to be related to surface features of the dance work. Future applications of the pARF to studies of multi-modal perception and cognition are discussed.     

The influence of a 1 h nap on performance overnight

Abstract

The effect on performance overnight of a 1 h nap taken at 0200 h was studied in six young female subjects. The subjects completed three schedules, including one with a nap and two without a nap, during which either a placebo or 300 mg caffeine was ingested at 2315 h. Performance was measured from 1700 h in the evening until 1030 h the next morning. Caffeine improved performance overnight on almost all tasks compared with placebo. The nap had some limited beneficial effect compared with placebo, but most tasks remained impaired.     

The use of continuous variables for labeling objects

A summary is given of the various pattern recognition situations in which continuous variables may be used for labeling objects. Specific problems may arise during the construction of classification functions, e.g. when discontinuities of the assigned labels have to be avoided. Solutions are discussed and an example is given.     

Sleep in a live-in mining operation: The influence of start times and restricted non-work activities

The amount of sleep obtained between shifts is influenced by numerous factors including the length of work and rest periods, the timing of the rest period relative to the endogenous circadian cycle and personal choices about the use of non-work time. The current study utilised a real-world live-in mining environment to examine the amount of sleep obtained when access to normal domestic, family and social activities was restricted. Participants were 29 mining operators (26 male, average age 37.4 ± 6.8 years) who recorded sleep, work and fatigue information and wore an activity monitor for a cycle of seven day shifts and seven night shifts (both 12 h) followed by either seven or fourteen days off. During the two weeks of work participants lived on-site. Total sleep time was significantly less (p < 0.01) while on-site on both day (6.1 ± 1.0 h) and night shifts (5.7 ± 1.5 h) than days off (7.4 ± 1.4 h). Further, night shift sleep was significantly shorter than day-shift sleep (p < 0.01). Assessment of subjective fatigue ratings showed that the sleep associated with both days off and night shifts had a greater recovery value than sleep associated with day shifts (p < 0.01). While on-site, participants obtained only 6 h of sleep indicating that the absence of competing domestic, family and social activities did not convert to more sleep. Factors including shift start times and circadian influences appear to have been more important.     

Application of a stereovision neural network to continuous speech recognition

The two- or three-layered neural networks (2LNN, 3LNN) which originated from stereovision neural networks are applied to speech recognition. To accommodate sequential data flow, we consider a window through which the new acoustic data enter and from which the final neural activities are output. Inside the window, a recurrent neural network develops neural activity toward a stable point. The process is called winner-take-all (WTA) with cooperation and competition. The resulting neural activities clearly showed recognition of continuous speech of a word. The string of phonemes obtained is compared with reference words by using a dynamic programming method. The resulting recognition rate was 96.7% for 100 words spoken by nine male speakers, compared with 97.9% by a hidden Markov model (HMM) with three states and a single gaussian distribution. These results, which are close to those of HMM, seem important because the architecture of the neural network is very simple, and the number of parameters in the neural net equations is small and fixed. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

The effects of caffeine on marksmanship accuracy and reaction time: a systematic review

Abstract

Military and law enforcement personnel are required to maintain optimal marksman accuracy and reaction time during extended duty hours amidst environmental stressors. Although caffeine is commonly used to mitigate the consequences of fatigue, the effects of caffeine on marksmanship accuracy are inconclusive. The purpose of this review was to determine the effect of caffeine on marksman accuracy and reaction time. A literature search was conducted and 17 articles were selected for review based on relevance and methodological quality. Caffeine consistently improved marksman reaction time but did not improve marksmanship accuracy. However, there is some evidence that caffeine attenuates performance decrements in marksman accuracy caused by stress and fatigue if optimal dosing strategies are employed. Dosing strategies timed according to hours of wakefulness and time before testing could prevent performance deterioration. Doses of 100–200?mg every 2?hours may effectively improve accuracy during extended duty; however, further research is needed.

Practitioner Summary: The purpose of this review was to determine the effect of caffeine on marksman accuracy and reaction time. A literature search was conducted and 17 articles were selected for review based on relevance and methodological quality. Caffeine consistently improved marksman reaction time but did not improve marksmanship accuracy.     

Computer use and the gender gap: The issue of access, use, motivation, and performance

Since the beginning of computerization, it has been of interest whether there are differential effects on computer behavior, in particular in terms of computer access, computer use, and motivational variables, such as computer self-efficacy. The current research addresses the questions if the gender-related differences in this respect persist to the present day and if there is also a difference in actual performance characteristics. A sample of 48 university students (23 male) was administered a technology self-efficacy questionnaire, a survey on computer access, recorded a user diary, and turned in a computer task. Results show that the gender gap is closing as far as computer access and self-efficacy are concerned. Also, female and male students report comparable amounts of computer usage for their studies. User behavior appears to be gender-specific as males spend more time at the computer for personal purposes. There is also some evidence that male students outperform female students at a computer task (remastering of Power-Point slides). Conclusions for creating computer-based learning environments are discussed.     

Operational assessment of the 5-h on/10-h off watchstanding schedule on a US Navy ship: sleep patterns,mood and psychomotor vigilance performance of crewmembers in the nuclear reactor department

We assessed sleep patterns, psychomotor vigilance performance, work demands and mood of 77 crewmembers of USS NIMITZ (CVN-68) on the rotating 5-h on/10-h off (5/10) watchstanding schedule. Within the 3-day cycle of the 5/10, sleep occurred at distinctly different times each day. On two of these days, sailors typically received only brief, 4-h sleep episodes followed by periods of sustained wakefulness (approximately 22 and 20 h). Crewmembers received approximately seven hours of sleep daily, but reported excessive fatigue and dissatisfaction with their schedule. Crewmembers’ mood worsened significantly over the course of the underway phase. Psychomotor vigilance performance (reaction times, lapses) was significantly degraded compared to performance when working circadian-aligned schedules. Overall, standing watch on the 5/10 schedule, combined with other work duties, resulted in poor sleep hygiene. Crewmembers on the 5/10 experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep.

Practitioner summary: We assessed crewmembers’ sleep patterns, psychomotor vigilance performance and work demands when working a rotating 5-h on/10-h off (5/10) watchstanding schedule. The 5/10, combined with other work duties, resulted in poor sleep hygiene. Crewmembers experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep.     

Effects of caffeine and menthol on cognition and mood during simulated firefighting in the heat

This study examined the separate effects of caffeine and menthol on cognition and mood during simulated firefighting in the heat. Participants (N = 10) performed three trials in a counterbalanced order, either with 400 mg caffeine, menthol lozenges, or placebo. The simulated firefighting consisted of 2 bouts of 20-min treadmill exercise and one bout of 20-min stepping exercise in the heat with two brief 15-min rest periods between each exercise phase. Exercise induced significant dehydration (>3%) and elevated rectal temperature (>38.9 °C), for all three conditions. Neither caffeine nor menthol reduced perceived exertion compared to placebo (p > 0.05). Mood ratings (i.e., alertness, hedonic tone, tension) significantly deteriorated over time (p < 0.05), but there was no difference among the three conditions. Simple reaction time, short-term memory, and retrieval memory did not alter with treatments or repeated evaluations. Reaction accuracy from a math test remained unchanged throughout the experimental period; reaction time from the math test was significantly faster after exposure to the heat (p < 0.05). It is concluded that, exhaustive exercise in the heat severely impacted mood, but minimally impacted cognition. These treatments failed to show ergogenic benefits in a simulated firefighting paradigm in a hot environment.     

Temporal strategy and performance during a fatiguing short-cycle repetitive task

This study investigated temporal changes in movement strategy and performance during fatiguing short-cycle work. Eighteen participants performed six 7-min work blocks with repetitive reaching movements at 0.5 Hz, each followed by a 5.5-min rest break for a total duration of 1 h. Electromyography (EMG) was collected continuously from the upper trapezius muscle, the temporal movement strategy and timing errors were obtained on a cycle-to-cycle basis, and perceived fatigue was rated before and after each work block. Clear signs of fatigue according to subjective ratings and EMG manifestations developed within each work block, as well as during the entire hour. For most participants, timing errors gradually increased, as did the waiting time at the near target. Changes in temporal movement strategy were negatively correlated with changes in the level and variability of EMG, suggesting that an adaptive temporal strategy offset the development of unstable motor solutions in this fatiguing, short-cycle work. PRACTITIONER SUMMARY: Sustained performance of operators is essential to maintain competitiveness. In this study of repetitive work, participants gradually changed their temporal movement strategy, for possibly alleviating the effects of fatigue. This suggests that in order to effectively counteract fatigue and sustain performance, industrial production should allow extensive spatial and temporal flexibility.     

The combination of continuous network design and route guidance

In this study, a traffic management measure is presented by combining the route guidance of Advanced Traveler Information System (ATIS) and the continuous network design (CNDP) to alleviate increasing traffic congestion. The route guidance recommends the travelers to choose the shortest path based on marginal travel cost and user constraints. The problem is formulated into a bi-level programming problem. The most distinct property of this problem formulation is that the feasible path set of its lower-level problem is determined by the decision variable of upper-level problem, while in conventional transportation network design problems the feasible path set for lower-level traffic assignment problem is fixed to be all the viable paths between each specific origin-destination pair. The simulated annealing algorithm is improved to solve this bi-level problem. A path-based traffic algorithm is developed to calculate the lower-level traffic assignment problem under the route guidance. Compared to the results of conventional CNDP, the measure presented in this study can better improve the transportation network performance.     

The effects of a self-selected nap opportunity on the psychophysiological,performance and subjective measures during a simulated industrial night shift regimen

This study compared the effects of a 1 h self-selected recovery period to those of a standard night shift arrangement (with a total break time of 1-h) over a simulated three-day night shift schedule in a laboratory setting. Results showed that the inclusion of the flexible nap scheme resulted in higher performance output, improvements in physiological strain responses and reduced sleepiness during each night shift and generally over the three-night cycle. Certain variables also revealed the impact of napping compared with the standard rest break condition on the circadian rhythm. The sleep diary records show that the inclusion of the current intervention did not significantly reduce daytime recovery sleep. The results suggest that the potential benefits of flexible napping may outweigh the logistical effort it requires in a workplace environment.

Practitioner summary: Consensus on appropriate napping strategies for shift work remains a challenge. This simulated night shift laboratory study sought to determine the effects of a 1-h self-selected nap opportunity relative to a normal shift set-up. The nap improved performance and decreased sleepiness, without affecting daytime sleep.     

The use of a quadratic performance index to design multivariable control systems

A quadratic performance index is considered as a generalized criterion for designing linear multivariable control systems. A method is developed for expressing the characteristic polynomial of the optimal system as an explicit function of the weighting matrix elements of the performance index. Since these elements are actually the design parameters it then becomes possible to obtain some general properties of the optimal systems as well as to select the weighting matrix elements, such that more conventional criteria on the system transient response are satisfied. The results are applied to the design of two multivariable systems; in one case, the plant is initially unstable and, in the second case, it is desired to have the system response follow that of a linear model.     

The use of psychophysiology to assess driver status

Twenty subjects completed an on-the-road driving experiment, consisting of two different tests conducted on two separate days. A two-part test was administered while subjects were under the influence of alcohol (BAC<=0·05%); a four-part test was administered without alcohol consisting of a 2·5?h driving test under vigilance conditions on a quiet highway. The order of the tests was balanced across subjects. Changes in relevant physiological parameters, such as ECG and EEG, reflected changes in driver status and predicted driving impairment. Impairment of driving performance was measured in a standard driving test (SD lateral position and SD steering wheel movements) and in a recently developed car-following test (reaction to speed changes of a leading car).     

铜材连续挤压生产设备的监测、控制系统研制

铜材连续挤压生产线控制采用计算机监控系统,以工控机作为上位机对PLC及整套生产设备线的状态进行监控,以INTOUCH软件作为用户可以定制功能的软件平台,开发出良好的人机界面、监控画面以及数据存储、等功能。PLC作为下位机通过通信线缆与上位计算机相连,执行上位机指令,通过梯形图编程完成逻辑控制、顺序控制及实时控制等功能。铜材挤压生产设备结合现代电子技术和计算机构成的控制系统,实现模糊控制,全线自动,其性能稳定可靠、操作简单,完全满足生产工艺的要求。     

Examination of community identification and interpersonal trust on continuous use intention: Evidence from experienced online community members

Members’ continued intention to use a community service is rooted in social identity. Past research has examined social identity but ignored the development of interpersonal trust through community identification. Drawing on social identity theory, one can conclude that community identification is the foundation of a member’s continuous use intention through interpersonal trust. Data come from responses to a two-stage survey of experienced members of an online game-based community. The findings support the belief that the identity of the community will strengthen long-term relationships within it. The projection of community identification on continuous use intention is tied to interpersonal trust.