Approximation techniques for response-time analysis of static-priority tasks

We consider sporadic tasks with static priorities and constrained deadlines to be executed upon a uniprocessor platform. Pseudo-polynomial time algorithms are known for computing worst-case response times for this task model. Some applications require to evaluate efficiently upper bounds of response times. For this purpose, we propose parametric algorithms that allow to make a tradeoff between quality of results and computational effort according to an input accuracy parameter. In this paper, we present a parametric polynomial-time algorithm for computing upper bounds of worst-case response times, that is based on an improved fptas (Fully Polynomial Time Approximation Scheme). Then, we show that our bound does not achieve constant error bound in comparison with the exact worst-case response time. However, using the resource augmentation technique, we obtain a performance guarantee that allows to define a compromise between our response-time bound and processor capacity requirements. The algorithm average behavior is then analyzed through numerical experimentations.     

A review of techniques for measurement of contact angles and their applicability on mineral surfaces

Knowledge of the wetting characteristic of mineral surfaces is paramount in enhancing the efficiency of separation of valuable minerals from gangue using froth flotation. The contact angle value is a useful indicator providing the hydrophobic characteristic of the solid mineral surfaces due to a close relationship between this parameter and the floatability of minerals.In this paper, techniques for contact angle measurements and their applicability on mineral surfaces are reviewed. Two main groups of techniques for contact angle measurements are available; one group is applicable to flat and smooth surfaces while the other one has been especially developed for non-ideal surfaces or particles. Capillary penetration methods have been found to be more applicable than the other methods cited in measuring contact angles on real mineral surfaces. The major challenge with this technique is the modification required to overcome the difficulties in the experimental packing technique needed, and more importantly, to obtain the receding contact angle values. The coupling of accurate contact angle measurements with real (batch) flotation data would seem to be area which has had limited attention.     

Optimizing the mixture of wood biomass for greenhouse heating

This paper presents the development of a linear programming model to determine the optimum fuel mix for greenhouse heating. The model is applied to two cases (a 7.5 hectare (ha) vegetable greenhouse and a 2 ha flower greenhouse) in British Columbia, which use a combination of wood pellets and wood residue to provide heat. The objective of the model is to minimize the annual total cost of combusting wood pellets and wood residue, while the heat demand is satisfied and all resources and emission limitations are not exceeded. The boiler system was enhanced with an electrostatic precipitator to limit the particulate matter emissions to acceptable levels. The results show that the optimal fuel mix for a 2 ha flower greenhouse is 641 tonne (t) of wood pellets and 381 t of wood residues, and it is 10 106 t of wood pellets and 3007 t of wood residues for a 7.5 ha vegetable greenhouse. The minimized annual total cost, including amortized capital cost, is estimated to be C$216 030 y^?1 and C$1 611 866 y^?1 for a 2 ha flower greenhouse and a 7.5 ha vegetable greenhouse, respectively. A sensitivity analysis indicated that these optimal solutions would not change even when the variable costs (material cost and emission fee) of wood pellets decreased by 58% or the variable costs of wood residue increased by 150%. Copyright © 2008 John Wiley & Sons, Ltd.     

An electromechanical swing-phase-controlled prosthetic knee joint for conversion of physiological energy to electrical energy: feasibility study

Microprocessor-controlled prostheses facilitate a more natural and efficient gait for individuals with above-knee amputations by continually adjusting the level of swing-phase damping. One caveat associated with these technologies is that the user must charge the onboard batteries on a daily basis. It is, therefore, the aim of this study to examine the feasibility of using an electromechanical system to provide prosthetic swing-phase damping and, concomitantly, the function of converting physiological energy that is normally dissipated during the swing phase, to electrical energy. Gait data from a single subject and data from a kinematic simulator were used to develop an empirical model. The findings in this study indicate that an electromagnetic system has appropriate characteristics for use in swing-phase control and also has the potential to recover energy under particular conditions.     

Improvement in intestinal function and health by the peel fibre derived from Citrus sinensis L cv Liucheng

The water‐insoluble fibre‐rich fraction (WIFF) was isolated from the peel of Citrus sinensis L cv Liucheng in an economical way. The influences of a WIFF‐containing diet on the intestinal function and health in hamsters were investigated and compared with those of cellulose‐added and fibre‐free diets. Our results showed that the inclusion of WIFF in a fibre‐free diet might result in some significant improvements in serum, intestinal, caecal and faecal parameters, such as elevated serum alkaline phosphatase activity (127%), increased intestinal maltase and sucrase activities (180 and 164% respectively), decreased caecal pH (6.30), reduced caecal and faecal ammonia contents (by 25.4 and 34.1% respectively) and decreased activities of faecal β‐D ‐glucosidase (by 48.1%), β‐D ‐glucuronidase (by 52.9%) and urease (by 81.5%). These results suggested that the incorporation of WIFF in the diet at a level of 50 g kg^?1 might exert a favourable effect on intestinal function and health. Accordingly, WIFF could be exploited as a potential functional ingredient in human diets and also offer industries an opportunity to develop new formulations of fibre‐rich functional foods. Copyright © 2005 Society of Chemical Industry     

Aeration Performance of Rectangular Planform Labyrinth Weirs

Maintenance of a high level of dissolved oxygen is important in natural rivers and in some water treatment processes. This can be enhanced by creating turbulence in the water. One method of producing such turbulence is via the overflow jets downstream of weir structures. The aeration characteristics of straight weirs have been measured and analyzed by a number of investigators. However, labyrinth weirs, which are cranked in planform, have received little attention in this respect. The aeration performance of a weir under a particular set of flow conditions is largely determined by the characteristics of the overall jet. The geometry of labyrinth weirs provides increased sill length and often results in the overfall jets colliding with each other, both of which may lead to increased aeration. A series of laboratory experiments were run on rectangular planform labyrinth weirs. These showed that, although detailed geometry of the weir was not important, the labyrinth weirs aerated significantly better than an equivalent straight weir, particularly at low drop heights.     

Xianfeng? Houfeng? Youfeng?—An analysis of selected contemporary Chinese architects,Yung Ho Chang,Liu Jiakun,and Wang Shu (1990s-2000s)

The three contemporary Chinese architects, namely Yung Ho Chang, Liu Jiakun, and Wang Shu, have often been labeled as the ‘avant-garde’ or xianfengarchitects in China. In response to the xianfeng architect label, Wang claims that he is a houfeng(rear-guard) architect because of his obsession with traditions. This paper aims to discuss the appropriateness of labeling these architects as ‘avant-garde,’ xianfeng, or houfeng. Through the theoretical analysis of western discourse, notable attributes of the western architectural avant-garde are identified, and a tentative framework is developed to test its validity and usefulness in a non-western context. The term youfeng is arguably a better phrase to describe these three Chinese architects considering the heterogeneous trajectory of modernity in China.