The nearshore dynamics of Matroos Bay : field and theoretical investigations

Bibliography: pages 113-119.Field and theoretical investigations were made of the nearshore circulation of Matroos Bay, a small embayment on the south-western coast of Africa. The field study revealed two dominant circulation types, denoted "anticlockwise" and "clockwise". The anticlockwise circulation type was characterized by longshore currents flowing from the back of the bay to the northern headland where a rip current was located. The clockwise circulation type was characterized by longshore currents flowing from the northern headland to the back of the bay where a rip current was situated. Anticlockwise circulation types were primarily found to occur during periods of low waves, the clockwise circulation during periods of high waves. Winds and coastal currents were found not to have a major influence on the circulation within the bay. The theoretical study was based on a model of longshore currents in a semi-circular bay (O'Rourke and Le Blond, 1972). This study showed that a change of the height of the wave could lead to a change in the direction of flow of the longshore current. In agreement with the field study, a low wave height was found to result in an anticlockwise circulation type, a high wave height resulting in a clockwise circulation type. The change from one circulation type to the other depended on the relative strength of two opposing mechanisms. One mechanism arose from the obliquity of the wave approach to the shore. This mechanism generated longshore currents towards the back of the bay and was dominant during high waves. The other mechanism resulted from the non-uniformity of the wave height around the bay and generated longshore currents flowing from the back of the bay. Coastal currents were measured as part of the field study. A fair correlation was-observed between the direction of the coastal current and that of the wind, particularly if the winds were moderate to strong. Temperature and salinity measurements were also made. These properties showed seasonal variations in accord with the principles of upwelling. Surface water was found to have a salinity similar to that found at a depth of 400 to 600 metres in the South Atlantic Ocean. The water was upwelled from a greater depth during the summer than during the winter. Heating of the water was found to be greater in summer than in winter whilst dilution of the water, due to rainfall, was found to be negligible, even during winter. The interchange of water between the bay and the coastal circulation was found to be dependent on the circulation type

On work in progress optimisation

In this paper, we investigate how to best optimise the level of work in progress (WIP) in a real world factory. Using a simulation model of the factory, we show that an optimum level of WIP can be attained. By systematically varying the maximum allowable level of WIP within different model runs, results show that the throughput reaches a high level very quickly and then tapers off. The production lead times, in contrast, begin at relatively low levels and increase after the optimum WIP level has been reached. <br /

Modeling a just-in-time plant using sequencing algorithms

An Australian automotive component company plans to assemble and deliver seats to customer on just-in-time basis. The company management has decided to model operations of the seat plant to help them make decisions on capital investment and labour requirements. There are four different areas in seat assembly and delivery areas. Each area is modeled independently to optimise its operations. All four areas are then combined into one model called the plant model to model operations of seat plant from assembly to delivery. Discrete event simulation software is used to model the assembly operations of seat plant.<br /

A decision support tool for resource allocation in batch manufacturing

A decision support tool for production planning is discussed in this paper to perform the job of machine grouping and labour allocation within a machining line. The production plans within the industrial partner have been historically inefficient because the relationship between the cycle times, the machine group size, and the operator\u27s utilisation hasn\u27t been properly understood. Starting with a simulation model, a rule-base has been generated to predict the operator\u27s utilisation for a range of production settings. The resource allocation problem is then solved by breaking the problem into a series of smaller sized tasks. The objective is to minimise the number of operators and the difference between the maximum and minimum cycle times of machines within each group. The results from this decision support tool is presented for the particular case study. <br /

The History, Status and Management of Muskoxen on Banks Island

Historical and archaeological records suggest that muskoxen (Ovibos moschatus) were once abundant on Banks Island. They declined around the turn of the 20th century and remained at very low population levels until the 1970s. The causes of the scarcity of muskoxen are unknown, but severe freezing rains and subsequent forage unavailability likely played a role. Aerial surveys documented an increase in the estimated population size from 3800 in 1972 to 34,225 in 1989. The rapid increase in muskox numbers has been a source of concern to the local users, who view the muskoxen as detrimental to the caribou (Rangifer tarandus pearyi), which have declined in number. Since the mid-1980s, productivity of 3-year-old muskox cows and calf survival have decreased and the prevalence of parasites has increased. Our data do not allow us to distinguish between whether those changes are density-dependent population responses or the effects of the severity of winter weather. Current management focuses on monitoring the trend of population size, the condition and reproduction of the muskoxen.Key words: muskoxen, Ovibos moschatus, Banks Island, numbers, harvest, weather, population regulationMots cl&eacute;s: boeuf musqu&eacute;, Ovibos moschatus, &icirc;le de Banks, nombres, r&eacute;colte, temps, contr&ocirc;e de la populatio

Too good to be true: when overwhelming evidence fails to convince

Is it possible for a large sequence of measurements or observations, which support a hypothesis, to counterintuitively decrease our confidence? Can unanimous support be too good to be true? The assumption of independence is often made in good faith, however rarely is consideration given to whether a systemic failure has occurred. Taking this into account can cause certainty in a hypothesis to decrease as the evidence for it becomes apparently stronger. We perform a probabilistic Bayesian analysis of this effect with examples based on (i) archaeological evidence, (ii) weighing of legal evidence, and (iii) cryptographic primality testing. We find that even with surprisingly low systemic failure rates high confidence is very difficult to achieve and in particular we find that certain analyses of cryptographically-important numerical tests are highly optimistic, underestimating their false-negative rate by as much as a factor of $2^{80}$

Inference of resource-based simulation models from process event-log data

This research was focused on inferring resource-based simulation models from data. and has proven it is realistic to do so. The research has discovered a new Process Mining algorithm with superior performance and has developed methods to identify, quantify and discover resource attributes and resource-based decisions from data