Optimization of shift work: physiological contributions

Abstract

Healthy subjects (n= 62) with different circadian phase positions worked up to six weeks in different shift systems. Rotation speed was experimentally varied. On shift days all subjects worked in the Institute but spent their leisure time as usual.

In order to minimize bias through masking effects, ‘control days’ were interpolated (twice a week) into the shift periods. On these control days subjects remained on bedrest for 24 hours under constant conditions.

Results were as follows:

(i) The earlier the circadian phase position the poorer the adaptation to night-shifts. In particular, morning types were not able to adapt even to permanent night-shifts.

(ii) Evening types were able to adjust their circadian systems to a slowly rotating shift system (rotation speed seven days) and a 25 h-sliding system though they failed to do so with more quickly rotating systems. Whereas indifferent subjects were not able to adjust to even the slowly rotating system.

(iii) When stable phase shifts occurred in response to altered working hours they always amounted to about one hour per day if the working hours were not coherent with the usual environmental zeitgebers.

It is concluded that, on physiological criteria, very slow rotating shift systems or permanent night-shifts seem to be acceptable for evening types, but not for morning types who may require special health care in these conditions.     

Reducing understaffing and shift work with Temporal Profile Optimization (TPO)

The ergonomic quality of shift schedules can be improved by reducing time periods with understaffing (resulting in work-pressure, poor quality, etc.) and evening, night and/or weekend work.Improving the quality of forecasts regarding future workforce requirements as well as the optimization of work processes by moving as much work as possible to more suitable time zones are two approaches to this.We introduce and propose Temporal Profile Optimization (TPO) as a systematic approach to question the demand as well as its translation to workforce planning. Temporal profiles describe the number of employees needed over time (e.g. for different days of the week, times of day, for different calendar days) as well as the shift-times and staffing levels planned to meet this workforce demand.With Temporal Profile Forecasts we introduce a forecasting method that is based on time-stamped historical data and methodologically supplements traditional time series models like SARIMA in many ways. With Temporal Profile Reengineering we use systematic and often participatory methods from business process reengineering to identify moveable work and streamline the load lines by (re-)distributing movable work such that shifts and schedules are improved.The approach is illustrated along two business cases. Using TP-Forecasts for air traffic controllers increased forecasting accuracy whereby a different shift design was possible resulting in 3–4% less shift work. In a warehouse of an Austrian freight carrier a TP-Forecast together with TP-Reengineering helped to rearrange work processes such that the resulting workforce requirements curve had a more even form. This allowed for shorter shifts than before (thereby decreasing overtime).Experiences made so far stress the potential of Temporal Profile Optimization.     

Personality factors related to shift work tolerance in two- and three-shift workers

This study aimed to investigate whether different personality variables were associated with shift work tolerance, and whether these potential associations were moderated by various types of shift work. The sample comprised 1505 nurses who worked either two or three rotating shifts. Personality traits were measured in terms of morningness, flexibility, languidity and hardiness. Morningness reflects the tendency to be alert relatively early in the morning and sleepy relatively early in the evening. Flexibility denotes the ability to both work and sleep at odd times of the day, while languidity concerns the tendency to become tired/sleepy when cutting down on sleep. Hardiness relates to resilience to stressful life events. The dependent variables in this study comprised of measures of insomnia, sleepiness, depression and anxiety. Hierarchical regression analyses, which controlled for demographic variables and work load, revealed that Morningness was significantly and negatively related to insomnia. The Morningness by Shift type interaction was overall significant for depressive symptoms. Morningness was near significantly associated with lower levels of depressive symptoms in three-shift workers, but unrelated to depressive symptoms in two-shift workers. Flexibility was associated with higher levels of depressive symptoms. Flexibility by Shift type interaction was significant for insomnia, indicating that flexibility was negatively associated with insomnia for three-shift workers and unrelated with insomnia for two-shift workers. Languidity was associated with higher levels of sleepiness, depressive and anxiety symptoms. Hardiness was associated with lower levels of all four dependent variables.     

双向移位寄存器在彩灯控制电路中双向递增控制的实现

双向移位寄存器74LS194是一种廉价的数字集成器件。本文介绍了双向移位寄存器的功能,设计并论述了由其控制的同向递增和反向递增两种彩灯控制电路,实现了对彩灯控制电路的双向递增控制,说明利用中规模集成电路可以实现结构简单、稳定可靠、经济适用的的彩灯控制电路。     

The design of shift systems

All shift systems have advantages and drawbacks. There is no single ‘optimum shift system’ which can be used in industry or commerce at all work places. However, there are shift systems which are more favourable, and others which are less favourable, in the context of physiological, psychological, and social recommendations for the design of shift systems. This article discusses the following recommendations:

(1) Nightwork should be reduced as much as possible. If this is not possible, quickly rotating shift systems are preferable to slowly rotating ones. Permanent nightwork does not seem to be advisable for the majority of shiftworkers.

(2) Extended workdays (9-12 h) should only be contemplated, if the nature of work and the workload are suitable; the shift system is designed to minimize the accumulation of fatigue; there are adequate arrangements for cover of absentees; overtime will not be added; toxic exposure is limited; and if it is likely that a complete recovery after work and a high acceptance of the working time arrangement are possible.

(3) An early start for the morning shift should be avoided. In all shiftsystems flexible working time arrangements- are realizable. The highest flexibility is possible in ‘time autonomous groups’.

(4) Quick changeovers (e.g., from night to afternoon shift at the same day or from afternoon to morning shift) must be avoided. The number of consecutive working days should be limited to 5-7 days. Every shift system should include some free weekends with at least two successive full days off.

(5) The forward rotation of shifts (phase delay, clockwise rotation) would seem to be recommendable at least in continuous shift systems.

Besides the design of a shift system, implementation strategy is of particular importance for the acceptance of the shift system.     

AMT汽车模糊三参数换挡规律研究

为了使AMT汽车自动变速器换挡能够反映路况与车况变化,更好地满足汽车换挡平顺性要求,提出了AMT汽车模糊三参数换挡控制。论文首先给出了模糊三参数换挡控制原理,接着设计了模糊三参数换挡控制器,最后给出了长安羚羊AMT轿车模糊三参数换挡仿真,并与模糊两参数换挡进行了比较。结果表明,采用模糊三参数换挡比采用模糊两参数换挡更加符合驾驶员的换挡经验和习惯,比传统计算法求解换挡规律更简便,易于实现,鲁棒性更强。     

Computer-aided design of shift schedules

The complexities encountered in the design of shift schedules for continuous work, especially if such a design is to perform optimally against the criteria of organizational demands and ergonomics protocols simultaneously, inevitably demand computer support. This paper reports on the concept and development of a PC-based computer program for the design of shift schedules for continuous work with regular or irregular work demands. The results demonstrate that the program produces optimal solutions with respect to the criteria selected.     

Optimal shift partitioning of pharmacies

The pharmacy service requires that some pharmacies are always available and shifts have to be organized: a shift corresponds to a subset of pharmacies that must be open 24 hours a day on a particular week. Under the requirement that each pharmacy belongs to exactly one shift and the assumption that users minimize the distance to the closest open pharmacy during each shift, we want to determine a partition of the pharmacies into a given number of shifts, such that the total distance covered by users is minimized. It may be also required that shift cardinalities are balanced. We discuss different versions and the related computational complexity, showing that the problem is NP-hard in general. A set packing formulation is presented and solved by branch-and-price, together with a fast solution technique based on a tabu search. They have been applied to real and random instances showing that (i) the set packing formulation is very tight and often exhibits no integrality gap; (ii) the branch-and-price solves problems of practical relevance to optimality in a reasonable amount of time (order of minutes); (iii) the tabu search finds optimal or near-optimal solutions in order of seconds.     

Internal locus of control and choice in health service shift workers

This study examined the relationship between shift work-specific locus of control (SH-LOC), active choice of work schedule and health outcomes, personal initiatives and coping behaviours in 1611 Danish Health Service shift workers. The 20-item SH-LOC scale was administered as part of a battery of measures. Multivariate analysis of covariance (controlling for age, workplace experience and weekly work hours) tested for differential responses to shift working and coping strategies. Interactive effects of internality and type of work rota were examined. Higher internality was linked to better tolerance to shift work. This did not appear to be a result of greater personal action in higher internals. The importance of control as a potential moderating factor to shift work exposure and the possible use of this measure in the process of shift worker monitoring is highlighted.     

Work/rest cycles in railroad operations: effects of shorter than 24-h shift work schedules and on-call schedules on sleep

The current study examined the frequency with which shorter than 24-h work/rest cycles occur in locomotive engineer work schedules, and what effects these work/rest cycles had on sleep quantity and sleep quality. The results indicated that shorter than 24-h work/rest cycles occurred in 33.6% of the work days reported by 198 locomotive engineers. In addition, the shorter than 24-h work/rest cycles occurred more frequently in work schedules that created an on-call work system, such as road pool turn and extra board assignments, than in work schedules that used more predictable or regular work times, such as regular road assignments and yard/local work. As would be expected, when engineers worked shorter than 24-h work/rest cycles, they reported less sleep and poorer sleep than under the longer than 24-h work/rest cycles. Similarly, on-call work assignments resulted in less sleep and poorer sleep than regular work assignments. These results indicate that specific aspects of the work schedules used in railroad operations, particularly on-call operations that result in shorter than 24-h work/rest cycles, can lead to increased sleep-related problems. Although the North American railroad industry is making significant changes in on-call operations to minimize sleep-related problems from on-call schedules, better fatigue-related models validated within the railroad industry are needed.     

Influence of shift work in process industry on workers' occupational health,productivity, and family and social life: An ergonomic approach

Shift work is a major feature of modern work practices. It involves working at times considered unconventional for most workers, such as at night. Although the community often benefits from such work practices, shift work can be hazardous for both the workers and the community. There are increased risks for accidents and errors, increased sleepiness and fatigue due to difficulties sleeping, increased health problems, and disruptions to family and social life. More shift workers complained of sleep disturbance, poor sleep quality, tiredness at awakening, and sleepiness in work than did non‐shift workers. More shift workers also complained of gastrointestinal disturbances than did non‐shift workers. The aim of this article is to provide general information on shift work, work schedules, and the effects of work schedules on sleep, fatigue, performance, the health of the human operator, and productivity. © 2010 Wiley Periodicals, Inc.     

The impact of negative online social network content on expressed sentiment,executive function,and working memory

Given the paucity of research examining emotional states in social networking, the aim of this study was to examine the impact of negatively valanced social media network content on the amount of sentiment that participants included in their free-text responses, as well as on their executive functioning and working memory. Eighty participants aged between 18 and 67 (M = 29.39, SD = 11.21 years) completed baseline mood and cognitive measures (working memory and executive functioning) before exposure to three control posts and one negative emotional post. For each post, participants wrote a free-text response or indicated that they would not respond. Participants then completed the mood and cognitive measures a second time. After exposure to an emotionally negative post, participants' mood was lower and their executive functioning improved (as measured by reaction time and number of incorrectly identified target words). Participants' responses to an emotional post contained higher levels of sentiment compared to their responses to control posts. After controlling for demographic variables, participants' mood and trait empathy predicted the level of sentiment that they included in their responses to the emotional post. Mood, executive function, and trait empathy contributed to individuals’ online social network engagement for emotionally negative posts.     

基于混沌的反馈移位寄存器设计

针对线性反馈移位寄存器产生的序列周期小,不适用于大数据量信息加密的缺点和单纯的混沌序列在有限精度下易出现小周期的问题,将二者结合,提出一种基于混沌的反馈移位寄存器设计方法,并对这一方法下产生的序列进行了大量的数据试验。分析结果证明,该法产生的二值序列密码具有优良的密码学特性,很适合用于数据加密。     

Robust low power DC-type shift register circuit capable of compensating threshold voltage shift of oxide TFTs

This paper proposes an oxide TFT DC-type shift register that consists of eleven TFTs and one bootstrapping capacitor. The proposed circuit connects drain nodes of large size pull-up TFTs of output drivers to positive supply voltage instead of alternating clock signals for low power consumption. In addition, a robust internal inverter capable of maintaining the high voltage level of the output over the large positive threshold voltage shift by bootstrapping is implemented. For a 120 Hz Full-HD display, the SPICE simulation estimates the clock power consumption of the proposed DC-type circuit as 0.56 mW at 32 shift registers and ensures the robust operation over the wide range of threshold voltage shift from −4 V to 10 V.     

基于移位变换的句子层自然语言信息隐藏算法

针对现有的句子层自然语言信息隐藏方法存在的问题,提出一种基于句子层移位变换规则的中文自然语言信息隐藏算法．首先利用汉字数学表达式对中文文本信号数字化;然后通过句子的移位变换改变句子词序以嵌入秘密信息．实验结果和分析表明,该算法实现简单、编码容量较大,同时秘密信息隐藏在自然语言文本句子层词序变换中,不改变文本语法、语义和风格,具有较好的隐蔽性．     

Local autocorrelation of similarities with subspaces for shift invariant scene classification

This paper presents a shift invariant scene classification method based on local autocorrelation of similarities with subspaces. Although conventional scene classification methods used bag-of-visual words for scene classification, superior accuracy of kernel principal component analysis (KPCA) of visual words to bag-of-visual words was reported. Here we also use KPCA of visual words to extract rich information for classification. In the original KPCA of visual words, all local parts mapped into subspace were integrated by summation to be robust to the order, the number, and the shift of local parts. This approach discarded the effective properties for scene classification such as the relation with neighboring regions. To use them, we use (normalized) local autocorrelation (LAC) feature of the similarities with subspaces (outputs of KPCA of visual words). The feature has both the relation with neighboring regions and the robustness to shift of objects in scenes. The proposed method is compared with conventional scene classification methods using the same database and protocol, and we demonstrate the effectiveness of the proposed method.     

最佳动力换档规律自学习算法的收敛性分析

针对汽车电控机械自动变速器 (AMT)最佳动力性换档规律的获取方法工作量大且耗资多,所得换档规律对其它车辆适应性差等问题,根据迭代自学习控制理论,提出了一种在线、实时寻求最佳动力性换档规律的自学习算法,并从理论上证明了该算法的收敛性,给出了收敛条件,讨论了自学习算法的快速收敛问题.分析结果表明,此法可以应用于实际AMT系统.     

Perceived self and behavioral traits as antecedents of an online empathic experience and prosocial behavior: Evidence from South Korea

The current study identified and examined perceived self-traits and behavioral traits as antecedents of online empathic experiences and prosocial behavior. Our findings suggest that perceived self-traits (i.e., self-efficacy in online relationship and self-disclosure) are strongly associated with both empathic experiences and prosocial behavior. Findings for the behavioral trait, interaction pattern of an individual, indicate that patterns of an individual's networking produce mixed results in regard to association with prosocial behavior. Bonding networking was found to positively predict prosocial behavior, while bridging networking showed a negative association with the same dependent measure. Identity discrepancy and writing activities were also found to positively affect prosocial behavior. Overall, the finding of this study indicates that perceived self-traits tend to display stronger explanatory power over both empathy and prosocial behavior than do behavioral traits.     

Analysis of information exchange activities to actualize and validate situation awareness during shift changeovers in nuclear power plants

Shift work situations occur in almost all safety‐critical organizations, and the investigations of some catastrophes like Chernobyl, Exxon Valdez, and the Gol/Legacy mid‐air collision indicated that shift work information exchange played an important role during the evolution of the situation before the accidents. Inadequate communications during shift changeovers challenged operators' work in the moments that preceded these accidents, because they got inadequate information about the current situation. Our research focuses on the information exchange activities (verbal, written, and nonverbal) of nuclear power plant control operators during shift changeovers. Our aim is to investigate how verbal exchanges and other representations enable operator crews to share information regarding the events that occurred in the previous shift to achieve adequate situation awareness. Our findings indicated the importance and richness of the information exchange during the shift changeover process to update and validate individual and collective situation awareness, showing that information adequately shared enables the ad hoc configurations of regulation loops and a safer use of simplified strategies that can be understood and be validated by other operators, reducing the occurrence of cognitive overloads and contributing to the construction of a common cognitive ground that enhances system resilience. © 2010 Wiley Periodicals, Inc.