A general technique for process modeling

In many modeling situations, the structure of the plant model is not well known. This is especially true in the processing industries where models are often nonlinear. The purpose of this technical note is to present a general method for obtaining the structure of a nonlinear plant.     

A comparison of adaptive control strategies for hot steel strip rolling mills

Many modeling situations occur in which the plant has uncertain dynamics, nonlinearities, time varying characteristics and noise corrupted input and output measurements. These processes generally require a human operator whose function is to provide intelligent modeling and control. This exact situation occurs in the modeling and control of roll force in a hot steel rolling mill. It is the purpose of this paper to investigate and compare various adaptive control strategies for this problem.The first strategy uses a parameter identification technique to track the parameters in the roll force setup model from one steel run to the next. The next algorithm provides feedback control from run to run by an adaptive controller which uses a linear reinforcement learning scheme to adjust its parameters. The third method accounts for the above complexities by approaching the problem from a behavioral and structural point of view. The behavior of the model is assessed through a performance evaluator and the model is modified structurally and parametrically to improve the performance of the system as the process evolves. The derivation is based on correlation techniques and linear reinforcement learning theory, the latter of which provides memory and intelligence to the algorithm to model the decision process of the human operator. The results of this work serve to reinforce the opinion that the nonlinear mathematical structure of the model should be able to change from one steel run to the next in order to compensate for changes in mill characteristics and in the mill environment. Modeling results are presented from actual mill data and comparisons are made with time invariant models. In addition, the algorithms are general enough so that they may be easily applied to other processes that seem to defy traditional modeling techniques. They are not case dependent.     

Ruins revisited: modernist conceptions of heritage

The perception westerners have of ruins underwent drastic transformations in the second half of the twentieth century. The realities of World War Two and the growing number of environmental problems made everyone realise that a ruin can be more than some enchanting reminder of distant cultures. Ruins stopped being objects of desire, precious anachronisms for adventurers to appropriate. This paper surveys emerging sensibilities towards ruins in literature, arts, archaeology and architecture. It presents a new vision, quite opposite to, but as powerful as the Beaux-Arts perspective.     

A real-time computer controller for a Robotic Filament Winding system

This paper presents an integrated real-time control system for a Robotic Filament Winding manufacturing cell. The architecture is based on a multiprocessor system employing four processor boards. The system incorporates a hierarchical control layout with the task specification at the highest level and the robot and winder set point tracking at the lowest. Eventual design goals include a PC front-end unit capable of winding path generation and testing prior to actual part production. Preliminary experimental results on cylindrical, elbow and T-shaped pipe-fittings are included.     

The economics of chipping logging residues at roadside: A study of three systems

Three biomass chipping operations of roadside logging residues were studied in New Brunswick and Maine. Two of the operations used a skidder-loader to form the roadside debris into larger piles closer to the road edge prior to chipping. Average chipping productivity ranged from 8.l oven dry Mg per Productive Machine Hour (OdMg PMH⁻¹) to 28.2 OdMg PMH⁻¹ depending on the site and chipping system used. The average cost of chips on board the chip vans ranged from $15.29 CAN OdMg⁻¹ to $25.86 CAN OdMg⁻¹. The chips were transported to three energy plants in Maine. One-way hauling distances varied from 29 km to 105 km.     

Pumped-storage hydro-turbine bidding strategies in a competitive electricity market

This paper develops optimal pumped-storage unit bidding strategies in a competitive electricity market. Starting from a weekly forecasted market clearing price curve, an algorithm to maximize the profit of a pumped-storage unit considering reserve bids is developed. A comparison between the optimal bidding strategy and a fixed-schedule weekly generating and pumping strategy is provided.     

Net flux of nutrients across the rumen wall of lactating dairy cows as influenced by dietary supplements of folic acid

The objective of the present study was to determine whether a dietary supplementation of folic acid, at levels used in our previous studies, would affect ruminal fermentation and the net flux of nutrients across the rumen wall of lactating dairy cows. Approximately 4 wk after calving, 5 lactating multiparous cows were surgically equipped with a ruminal cannula, an ultrasonic flow probe around the right ruminal artery, and indwelling catheters in the right ruminal vein and the ileocolic artery. Cows were fed a total mixed ration served in 7 equal meals per d (i.e., every 3.4 h). The experimental design was an unbalanced crossover arrangement with 3 periods of 4 wk each. The vitamin supplement, incorporated in equal amounts into each meal, was supplied at 0, 3, or 6 mg of folic acid per kg of BW per d. During the last week of each experimental period, blood samples were taken simultaneously from the 2 catheters every 30 min and rumen fluid was collected every 60 min during 2 consecutive meal intervals. Dietary supplementation with folic acid had no effect on milk production (27.2 ± 1.3 kg/d) or DMI (19.9 ± 0.7 kg/d), but milk concentrations and yields of total solids, fat, and protein increased linearly with increasing doses of folic acid ingested. Concentrations of folates in rumen fluid and arterial plasma, averaged over time, increased linearly with the dose of folic acid ingested but the net flux of folates across the rumen wall was not different from zero. Concentrations of butyrate in ruminal fluid decreased quadratically with the daily supply in folic acid. Dietary supplements of folic acid had no effect on pH and osmolality of ruminal fluid, nor on ruminal concentrations of lactate, ammonia, acetate, or propionate, total VFA, or microbial counts. The uptake of urea-N by the rumen wall tended to increase quadratically with the dose ingested but net fluxes of other nutrients were not affected by treatments. These results suggest that the effects of folic acid supplements on lactational performance cannot be explained by effects on rumen metabolism.     

Surgical management of digit disorders in cattle

Digital diseases in cattle are common. Cattle affected by digital disorders do not always respond to medical therapy and often need surgery. A thorough examination of the digits and radiographic evaluation help the clinician to choose the appropriate treatment and surgical approach. Age, sex, weight, type of production, and environment of the cattle also should be considered in choice of therapy.     

Generation of autocorrelated wind speeds for wind energy conversion system studies

This paper describes a new model and a new generator of hourly wind speeds which were obtained using the Box-Jenkins method. All the steps leading to the determination of an autoregressive model are described. Tests were performed to verify the adequacy of the model and comparisons were made between generated and real series to check whether the wind speed behavior is faithfully reproduced. Good results were obtained. In fact, hourly wind speed data prove sufficient to reproduce the main statistical characteristics of wind speed: monthly mean, standard deviation, high hourly autocorrelation and persistence. This simple model is, therefore, easily adaptable to the study of any wind energy conversion system or to mixed power system planning and reliability studies.