Linear programming is a technique used to determine the best (or optimal) solution to a problem where there are a number of competing and usually interrelated choices. The technique requires that each restriction on the problem being modeled be formulated as a linear equation. The model consists of a set of linear equations with more unknowns than equations and thus there are many possible solutions. In order to determine the best of these solutions, it is necessary to decide which criteria will be used to determine the best. Once the criteria (usually maximum profit or minimum cost) is chosen, an equation is set up giving the amount each variable (or activity) contributes to the criteria. The linear program then determines which solution will maximize or minimize this criteria. The LP described in this write up was written to determine the best process and set of process conditions for converting steam exploded Aspen wood into a variety of chemical feedstocks. The LP is designed to maximize profit based on the sales value of the chemicals produced, the cost of raw materials and the processing costs incurred. The model is restricted by the raw material availability, the utility and chemical requirements of each process step, the capacity of each process step and the market requirements for each chemical produced. This report will give a detailed description of the model structure, will discuss the validity of the data used in the model as well as future requirements, will discuss the running of the model on the computer and will discuss analysis of the LP solution.
Service records of treated fence posts installed at the Petawawa forest experiment station at Chalk River, Ontarion have been compiled periodically since 1937 to evaluate the effectiveness of various wood preservatives. Untreated control posts of non-durable Eastern Canadian species had an average service life of from 3.0 to 8.3 years. A number of simple application processes as well as pressure treatments have proved to be very effective as indicated in the service life data presented. Posts of 20 species treated full length by the creosote thermal process are in remarkably good condition after 43 years. Those treated (to 36 inch height) were generally sound at the groundline but their tops were degraded after 18 to 25 years. Simple processes such as cold soaking, sap displacement and diffusion methods produced a service life of over 20 years with various wood species and preservative combinations. Some series of posts treated with copper chrome arsenate have attained a service life of 20 years with all of the posts remaining in service to 1980.
Stakes of various wood species as well as composite material of different species (plywood) were pressure-treated using a variety of preservatives and chemical loadings. Each stake is buried to half its length at the Petawawa Forest Experiment Station -- near Chalk River, Ontario. The oldest stakes in the plot are treated with copper abietate/pole oil and after 21 years all of the stakes are still performing well. Red pine stakes treated with copper chrome arsenate type B are also performing well after 19 years of service. Performance of the stakes is monitored yearly by examining each stake and assigning a rating according to the severity of decay present. Performances of the treated stakes are compared to untreated controls of the same species installed in the same plot. Preservative effectiveness is expressed as the average number of years in service over the percent stakes remaining in service at the time of examination. One hundred and twenty seven series of stakes are currently under test. Stakes treated with zinc thiocyanate and zinc thiocyanate/latex are performing better than expected to date.
Spruces are generally considered marginal species for use as utility poles because of their low permeability to wood preservatives in pressure treatments, a tendency to develop checks, and low natural decay resistance. In areas such as Eastern Canada, where other more suitable species are in short supply, a detailed study of locally grown spruces is essential to determine their suitability for use as utility poles. This investigation was initiated in 1977 and has been supported in part by the Canadian Government, the Canadian Electrical Association, and Domtar Chemicals Group Inc, co-operatively. Detailed information on the background, scope, materials and procedures are presented in a working plan prepared by J.Krzyzewski and J.K.Shields (Branch Study No. EFP-23-191) in January 1977. The objective of the investigation was to assess the effect of various factors (time of felling and peeling of poles, storage period, moisture content, kerfing and incising), on the treatability of eastern spruce poles with varied preservatives and treatment methods, and on their quality and performance in use. It was expected that the investigation would provide the information necessary for improved utilization of eastern spruces in the production of pressure treated utility poles. The results were to be made available to the utility companies, the wood treating industry, and to the Canadian Standards Association. Since this was a long-term study it was planned to report the results as the investigation progresses, with a comprehensive report to be prepared at the completion of the study.