The Betz theory expresses that no horizontal axis wind turbine can extract more than 16/27 (59.3%) of the kinetic energy of the wind. The factor 16/27 (0.593) is known as the Betz limit. Horizontal Axis wind turbine designers try to improve the power performance to reach the Betz limit. Modern operational wind turbines achieve at peak 75% to 80% of the Betz limit. In 1919, Albert Betz used an a...

Recent work on optimization problems in random link models has verified several conjectures originating in statistical physics and the replica and cavity methods. In particular the numerical value 2.0415 for the limit length of a traveling salesman tour in a complete graph with uniform [0, 1] edge lengths has been established. In this paper we show that the crucial integral equation obtained wi...

We give a classical confidence belt construction which unifies the treatment of upper confidence limits for null results and two-sided confidence intervals for non-null results. The unified treatment solves a problem (apparently not previously recognized) that the choice of upper limit or two-sided intervals leads to intervals which are not confidence intervals if the choice is based on the dat...

The distribution of the leading digits in data sets will be influenced by the method used to substitute values below the limits of detection (LOD). If values below the LOD are substituted by a single value, for example LOD/√(2) (Hornung and Reed 1990), all these data points will have one single leading digit. Fig. 2 shows the influence of such a substitution if 30% of the values are below the LOD.

A queueing model has J ≥ 2 heterogeneous service stations, each consisting of many independent servers with identical capabilities. Customers of I ≥ 2 classes can be served at these stations at different rates, that depend on both the class and the station. A system administrator dynamically controls scheduling and routing. We study this model in the Central Limit Theorem (or heavy traffic) reg...

Since the anthrax attacks of October 2001 and the SARS outbreaks of recent years, there has been an increasing interest in developing surveillance systems to aid in the early detection of such illness. Systems have been established which do this is by monitoring primary health-care visits, pharmacy sales, absenteeism records, and other non-traditional sources of data. While many resources have ...

Anaerobic digestion of animal manure in biogas digesters has shown promise as a technology in reducing the microbial load to safe and recommended levels. We sought to treat dairy manure obtained from the Fort Hare Dairy Farm by investigating the survival rates of bacterial pathogens, through a total viable plate count method, before, during and after mesophilic anaerobic digestion. Different mi...

The limit cycles of nonlinear systems under the small stochastic disturbances are considered. The random trajectories of forced system leave the deterministic cycle and form some stochastic bundle around it. The probabilistic description of this bundle near cycle based on stochastic sensitivity function (SSF) is suggested. The SSF is a covariance matrix for periodic solution of linear stochasti...