Thomas Tamo Tatietse

Optimal scheduling of large-scale hydrothermal power systems using the Lagrangian relaxation technique

This paper describes a method for scheduling large-scale hydrothermal power systems based on the Lagrangian relaxation technique. Lagrangian multipliers are introduced to decompose the original problem into small independent subproblems one for each generating unit, which are solved through a three level calculation structure. Using this approach, a large-scale hydrothermal electric power system could be treated as a precise general problem that takes into account the following among other factors: (a) random load demand; (b) non-linear cost function of thermal production; (c) variations of water head in hydroelectric plants; (d) non-linear function of hydroelectric output; (e) a system of cascaded hydroelectric plants including regulation reservoirs with limited spillage capacity. An economic interpretation of the results is given and an illustrative application of the technique is presented.

Aircraft Cruise Nitrogen Oxides (NOx) Emissions Prediction and Environmental Pollution Factor

Nitrogen oxides (NOx) emitted at low altitude increase ozone formation, thus potentially affecting local air quality. On the other hand supersonic aircraft NOx emitted in the lower stratosphere deplete the ozone layer, which represents a serious health concern according to Richard Miake Lyea and Ulrich Schumannb). The necessity to evaluate aircraft NOx production at cruise is urgent, since ICAO standard on NOx limitations has not yet taken into account cruise NOx emissions. The purpose of this work is to solve the problem of aircraft cruise NOx emissions regulation. The evaluation of nitrogen oxides production according to operational time in mode is realized with the ICAO data bank from different types of aircraft engines. Cruise NOx production is compared to LTO NOx production. A predictive correlation linking cruise NOx production to flight distance is developed and evaluated with good accuracy. Although cruise NOx production prediction is very important, alone it may not be enough to settle a limitation regulation on cruise NOx emissions, then the maximum flight range and the maximum take off weight, as those important factors influencing the NOx emissions are taken into account to develop a specific NOx production parameter which can enable the commercial aircraft classification according to their pollution factor, by so doing, ICAO NOx emissions regulation can be completed using the approach we propose to set up a limit value on aircraft cruise NOx emissions.

Fonction utilité dans la prise de décision pour l’entretien des routes en terre: application au Cameroun

L’état d’une route est donné par plusieurs dégradations existantes sur cette dernière. L’on ne saurait analyser isolément chaque dégradation et prendre une décision fiable. Il est question dans cet article de considérer une combinaison de toutes les dégradations les plus récurrentes sur une route en terre à travers une fonction utilité ou encore fonction de décision pour ces dégradations. Chaque dégradation agit en fonction de son importance d’où l’analyse dans ce travail des différents poids à donner à chaque coefficient. Les intrants de cette fonction utilité seront les matrices de dégradation élaborées dans les travaux précédents. Connaissant la valeur de la fonction utilité, le décideur connaît l’action à entreprendre sur un tronçon de route. The deteriorated state of roads is caused by many warring factors. It is not proper to analyse each cause of degradation in isolation. Therefore, this article sets out to study the different combinations of degradations taking into consideration the recurring deterioration of earth roads. With regard to utility function, each degradation reacts according to its importance. It is in this regard that,input of utility function variables are made according to matrices that were developed in previous work. Knowing the value of the utility function, the decision-maker knows what action to take on a stretch of road.

Application au Cameroun

The paper attempts to model the parameters of recurring degradations on dirt roads, then the development of the matrix known as “matrix of decision” in order to facilitate the implementation of a decision-making system for road maintenance. These matrices are used as an input in the function of decision which will be studied thereafter. We suggest a solution based on a general knowledge of these degradations, then a restriction on a finite number of relevant parameters. The approach is based on the method of the OECD of which the interest is the use of simple tools easily available in the Developing Countries. We take into account in this work parameters such as: the distance between the ridges of corrugation, the width of the gullies and the rutting and the area of the potholes, which were neglected by OECD but which are relevant. The results obtained will make it possible to improve OECD method used so far.

Environmental Profile of CBA (Copper-Boron-Azole)-Treated Wooden Utility Poles: A Developing Country Case

Wood poles are popular and are used worldwide in the power supply industries because of their high strength per unit weight, low installation and maintenance costs, and local availability. However, the environmental sustainability which is another required criterion to appreciate the whole quality of wood utility poles has until now not received attention from the developing countries’ research community. To overcome this lack of interest, this study investigates the gate-to-grave life cycle environmental impacts, related to CBAtreated wooden utility poles used for electricity distribution in a developing country for primary environmental characterization of wood pole related operations. The gate-to-grave LCA covered four life stages of wood utility pole: shaping, treatment, in-service, and final disposal. Five impact categories have been assessed based on an extensive primary data search through a detailed life cycle inventory. Cameroon was taken as the case study and life stage operation data were taken from the national utility company while inputs and outputs emissions data were taken from literature. Impact category scores were expressed per functional unit which was taken as one 9 m eucalypt saligna pole processed and used in power distribution line with a lifetime of 30 years. The results showed that the following scores of 65.60 kg CO2-eq for global warming, 0.76 kg SO2-eq for acidification, 0.08 kg C2H4-eq for photochemical ozone formation, 2.00 kg 1,4-DB-eq for ecotoxicity, and 60.67 kg for solid waste have been recorded as environmental profile characterization values of a wood utility pole. Furthermore, activities related to the wood pole treatment have been identified as the most environmentally harmful with regard to global warming, acidification, and photochemical ozone formation, while in-service and final disposal life stages recorded the highest values in ecotoxicity and solid waste respectively. In spite of the fact that this study was based both on Cameroonian experience and on worldwide used primary emission data, it yielded good quality data unique for power pole LCA research in third world.