A system with two subsystems working in alternating periods

Ambulatory blood pressure monitoring in physicians working in a hospital: is there an increase in the number of subjects with high workplace blood pressures?

The availability of a repairable system having one operating unit supported by n standby units is analyzed. The units have an exponential failure time distribution and the failed units are repaired, one at a time, with a general repair time distribution. An asymptotic formula of the stationary availability is derived, and is shown to give exact results for exponential repair times. Numerical examples show that the asymptotic formula gives a good approximation even for small n.

A warm standby redundant system with common cause failures

This paper investigates the 1‐minimax and 1‐maximin problems when demand weights are random variables with general continuous probability distributions. Properties of the optimal solutions are presented and solution procedures are developed. We also identify some known probability distributions under which it is easier to search for an optimal solution. © 2007 Wiley Periodicals, Inc. NETWORKS, Vol. 50(2), 127–135 2007

A non-invasive device to continuously determine heat strain in humans

Effect of work on utilization of cereal crop residues by oxen

Purpose. To develop a concept for a model for managing the risk of workplace fatigue, taking into account both the intensity of the negative impact of fatigue factors on the employee in the workplace and the intensity of their recovery from such impact to prevent incidents in organizations and industrial accidents and disasters at high-risk facilities. Method. An analysis of scientific literature — to update the purpose and definition of research tasks; methods of the theory of Markov processes — for a formalized description of the random processes of the development of the state of fatigue in the employee and their recovery from the state of fatigue during the work shift. Results. The proposed conceptual models allow the organization to manage the risk of fatigue by adjusting the duration of work and rest periods, depending on the characteristics of the parameters of the intensity of the negative impact of fatigue factors on the employee and the recovery of their body from such an impact. By changing the characteristics of the specified parameters, it is possible to determine the duration of the work periods that maximize the time an employee can work without entering a state of fatigue and the duration of the rest periods that minimize the time required for full recovery. Originality. A conceptual approach for managing the risk of fatigue is proposed, by establishing dependencies between the duration of work and rest periods and the characteristics of the parameters of the intensity of the negative impact of fatigue factors on the worker and their recovery from such an impact, based on the application of the theory of Markov processes. Practical value. The application of the proposed models allows increasing the level of labor productivity in the organization, by determining such durations of work and rest schedules, which provide the opportunity for employees to perform labor activities during the maximum possible time period of the work shift, without reaching a state of fatigue.

Reliability analysis of a two-unit parallel system with dissimilar units and general distributions

In this paper, we evaluate the performance of cloud centers with high degree of virtualization and Poisson batch task arrivals. To this end, we develop an analytical model and validate it with an independent simulation model. Task service times are modeled with a general probability distribution, but the model also accounts for the deterioration of performance due to the workload at each node. The model allows for calculation of important performance indicators such as mean response time, waiting time in the queue, queue length, blocking probability, probability of immediate service, and probability distribution of the number of tasks in the system. Furthermore, we show that the performance of a cloud center may be improved if incoming requests are partitioned on the basis of the coefficient of variation of service time and batch size.

In a series of papers A. V. Hill and Lupton (1, 2) have recently introduced the term “oxygen debt.” They have shown that human muscle just as frog's muscle is capable of “going into debt” for oxygen, of committing itself to future oxidations required to liquidate lactic acid liberated during activity; that it is possible for a healthy man to perform, for a period, muscular exercise so intense that far more oxygen is required than can be supplied through the circulation during the exercise itself, and thus to establish a heavy “oxygen debt,” which is made good during the period of rest following the exertion. Thus in one case they found an “oxygen debt” of about 13 litres following a short period of violent exercise. That an excess of oxygen was required during rest following exercise has been known for many years. Benedict and Cathcart (3) reviewed the older literature in 1913. We quote some interesting statements from this review. In 1845 Vierordt found that following exercise there was a marked and prolonged effect on the carbon dioxide output. In 1859 Edward Smith, in his discussion of the after-effects of work on respiration, wrote, "It is evident that whilst there is during the whole interval of rest an increase in the respiratory changes over that of rest apart from this exertion, the great excess due to the exertion disappears five minutes after rest.” Speck, in 1892, reported the first accurate measurements of the increased metabolism following muscular work. He always found increased CO2 production and O2 consumption long after the cessation of work, and that this increase in metabolism was accompanied by an increase in pulse rate. Benedict and Cathcart also summarise the results obtained in the former’s laboratories. They give figures showing how the metabolism is raised, during sleep after a period of work, above that during sleep after a period of rest. In these observations the work was prolonged for several hours, and they found the metabolism to be 13 per cent, above the normal, 7 or 8 hours after the muscular work had finished. A. V. Hill and Lupton have used shorter periods of more severe exercise in their experiments on man, and have thrown much light on the processes probably concerned in the “oxygen debt.” They have brought into line the results for the recovery oxidative processes in frog’s muscle and those in human muscle. In previous papers it was found that the pulse rate is much greater when working on a bicycle ergometer for 15 minutes (4), or walking on a moving platform for 60 minutes (5) under low cooling powers, that is, warm conditions, than when under cooler conditions. In the present paper, in addition to studying further the pulse rate, we have tested the “oxygen debt” as an indicator of the effects of different atmospheric conditions on man during running on a moving platform. The theory which led to these observations was as follows: the heart has to send much more blood to the skin under hot conditions in order to cool the body; the “oxygen debt” in the muscles may therefore be increased since more lactic acid may be produced in them, as a consequence of less blood, and therefore less oxygen, circulating through them. Fletcher and Hopkins (6) demonstrated that lactic acid was produced in muscle contraction in the absence of oxygen.

Comparative analysis of availability between three systems with general repair times, reboot delay and switching failures

Cost benefit analysis of availability systems with warm standby units and imperfect coverage

IntroductionSupervised exercise training is among the first-line therapies for patients with peripheral artery disease (PAD). Current recommendations for exercise include guidance focusing on claudication pain, programme and session duration, and...

Nitric oxide enhancement supplement containing beet nitrite and nitrate benefits high intensity cycle interval training

Efficient and accurate estimation of the probability distribution of a data stream is an important problem in many sensor systems. It is especially challenging when the data stream is non-stationary, i.e., its probability distribution changes over time. Statistical models for non-stationary data streams demand agile adaptation for concept drift while tolerating temporal fluctuations. To this end, a statistical model needs to forget old data samples and to detect concept drift swiftly. In this paper, we propose FlexSketch, an online probability density estimation algorithm for data streams. Our algorithm uses an ensemble of histograms, each of which represents a different length of data history. FlexSketch updates each histogram for a new data sample and generates probability distribution by combining the ensemble of histograms while monitoring discrepancy between recent data and existing models periodically. When it detects concept drift, a new histogram is added to the ensemble and the oldest histogram is removed. This allows us to estimate the probability density function with high update speed and high accuracy using only limited memory. Experimental results demonstrate that our algorithm shows improved speed and accuracy compared to existing methods for both stationary and non-stationary data streams.