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Search Results: 1 - 10 of 51 matches for " stabilisation "
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Constrained Feedback Stabilization for Bilinear Parabolic Systems  [PDF]
Azzeddine Tsouli, Ali Boutoulout, Abdessamad El Alami
Intelligent Control and Automation (ICA) , 2015, DOI: 10.4236/ica.2015.62011
Abstract: In this paper, we shall study the stabilization and the robustness of a constrained feedback control for bilinear parabolic systems defined on a Hilbert state space. Then, we shall show that stabilizing such a system reduces stabilization only in its projection on a suitable subspace. For this purpose, a new constrained stabilizing feedback control that allows a polynomial decay estimate of the stabilized state is given. Also, the robustness of the considered control is discussed. An illustrating example and simulations are presented.
Stabilisation of Pb in Pb Smelting Slag-Contaminated Soil by Compost-Modified Biochars and Their Effects on Maize Plant Growth  [PDF]
Mary B. Ogundiran, Olamide O. Lawal, Sifau A. Adejumo
Journal of Environmental Protection (JEP) , 2015, DOI: 10.4236/jep.2015.68070
Abstract: Compost has been used to stabilise lead (Pb) in soil. However, compost contains a high level of dissolved organic matter (DOM) which may make Pb bioavailable in plant and thereby limiting its effectiveness and application. Addition of biochar to compost can reduce this effect. Rice husk (RH) and Cashew nut shell (CNS) biochars and compost-modified biochars were used in comparison to compost for stabilizing Pb in lead smelting slag (LSS)-contaminated soil (Pb = 18,300 mg/kg) in Nigeria. Efficiency of Pb stabilisation in control and amended soils was assessed using CaCl2 batch leaching experiment and plant performance. In pot experiments, maize plant was grown on the contaminated soil and on soil treated with minimum and optimum doses of the amendments singly and in combination for 6 weeks. Agronomical and chemical parameters of the plants were measured. CaCl2-extractable Pb in the untreated soil was reduced from 60 mg/kg to 0.55 mg/kg in RHB amended soils and non-detectable in other amended soils. RH-biochar/compost increased plant height, number of leaf and leaf area more than the others. Similarly, at minimum rate, it reduced root and shoot Pb by 91% and 86.0% respectively. Compost-modified rice husk biocharstabilised Pb in lead smelting slag contaminated soil reduced Pb plant uptake and improved plant growth. Lead stabilisation through the use of rice husk biochar with compost may be a green method for remediation of lead smelting slag-contaminated soil.
SPH Particle Collisions for the Reduction of Particle Clustering, Interface Stabilisation and Wall Modelling  [PDF]
Arno Kruisbrink, Stan Korzilius, Frazer Pearce, Hervé Morvan
Journal of Applied Mathematics and Physics (JAMP) , 2018, DOI: 10.4236/jamp.2018.69158
Abstract: The pair-wise forces in the SPH momentum equation guarantee the conservation of momentum, but they cannot prevent particle clustering and wall penetration. Particle clustering may occur for several reasons. A fundamental issue is the tensile instability, which is caused by negative numerical pressures. Clustering may also occur due to certain properties of the kernel gradient. Discontinuities in the pressure and its gradient, due to surface tension and gravity, may cause particle instabilities near the interface between two fluids. Wall penetration is also a form of particle clustering. In this paper the particle collision concept is introduced to suppress particle clustering. Here, the use of kinematic conditions (motion) rather than dynamic conditions (forces) is explored. These kinematic conditions are obtained from kinetic collision theory. Conservation of momentum is maintained, and under elastic conditions conservation of energy as well. The particle collision model only becomes active when needed. It may be seen as a particle shifting method, in the sense that the velocities are changed, and as a consequence of that the particle positions change. It is demonstrated in several case studies that the particle collision model allows for realistic (low) viscosities. It was also found to stabilise the interface between two fluids up to high, realistic density ratios (1000:1) in typical liquid-gas applications. As such it can be used as a multi-fluid model. The concept allows for real wave speed ratios (and far beyond), which, as well as real viscosities, are essential in the modelling of heat transfer applications. The collisions with walls allow for no-slip conditions at real viscosities while wall penetration is suppressed. In summary, the particle collision model makes SPH more robust for engineering.
Performance Evaluation of Waste Stabilisation Ponds  [PDF]
O. P. Gopolang, M. W. Letshwenyo
Journal of Water Resource and Protection (JWARP) , 2018, DOI: 10.4236/jwarp.2018.1011067
Abstract: Waste stabilisation pond system has been used more especially in developing countries for sewage treatment. The objective of this study was to investigate the hydraulic and performance efficiency of Palapye waste stabilisation ponds. The hydraulic efficiency was evaluated through drogue, pond geometry and sludge accumulation assessment. The performance efficiency was evaluated through periodic sampling and analysis of physiochemical and bacteriological parameters of individual units and of the system as a whole. Except for the maturation ponds, the depth of the anaerobic pond had reduced from 4 m to 0.45 m, for facultative ponds from 2.0 m to a range of 0.52 m - 0.91 m. The design hydraulic retention time of the system had reduced from 20 days to 7.1 days. The concentration of some physiochemical parameters in the effluent was 305 mg·L-1, 277 Nephelometric Turbidity Units (NTU), 204 mg·L-1, 156 mg·L-1, 110 mg·L-1, and 15 mg·L-1 being total suspended solids, turbidity, nitrates, chemical oxygen demand, biochemical oxygen demand and phosphate respectively. These values were more than the standard limits of the country. Effluent total coliforms concentration was 3.6 log units and within the threshold of 4.3 log units, faecal coliforms concentration was 3.5 log units, slightly higher than the threshold of 3 log units. Though Escherichia coli have no limits for discharge into other environments, the concentration in the effluent was reasonable at 2.5 log units and also within irrigation limit of 3 log counts. Palapye wastewater treatment system hydraulic efficiency is lower than the design criterion. The system was overall poor in physiochemical parameters removal but better in bacteriological removal.
Modelling and Optimisation of Stabilisation Ponds System for the Treatment of Swine Wastes: organic Matter Evaluation
Costa, Rejane Helena Ribeiro da;Medri, Waldir;
Brazilian Archives of Biology and Technology , 2002, DOI: 10.1590/S1516-89132002000300017
Abstract: the fast increase of the swine production, specially in the west region of santa catarina, brazil, did not have a parallel program for the valorisation of its dejection, not even processes for the treatment of the organic residues. most of the producers keep their animals confined in small areas, having as a consequence the production of a large volume of wastes in the same place. this waste is diluted in water used to clean the bays, resulting in contamination of the watercourse. thus, it is necessary to develop treatment processes to minimise the environmental problems caused by the swine breeding activities. the stabilisation ponds have been used due to its excellent efficiency in the removal of the organic matters, solids, nutrients and faecal coliforms; besides the low implantation and maintenance costs. this work was assisted in a series of four stabilisation ponds, real scale, treating swine wastes in concórdia/sc at cnpsa. the ponds system was evaluated during a period of 20 months, objecting to get its principal work parameters, as well as information about the capital and operational costs, in order to adjust the equations to model and optimise the systems about the removal of the organic matters.
Abordajes toracolumbares anteriores en lesiones raquimedulares: experiencia en 72 casos
Platas,Marcelo; Lambre,Jorge; Cersósimo,Martín; Ortiz,Silvia;
Revista argentina de neurocirug?-a , 2010,
Abstract: objective to analyse retrospectively our experience in two surgical centers in buenos aires, managing 72 cases of spinal lesions of different ethiologies, using anterior surgical approaches to the thoracolumbar spine. material and method. indications, surgical techniques and results, as well as complications in 72 cases requiring a thorcolumbar anterior approach performed between 1996 and 2009 were analised. surgical route was chosen according to the level and extension of the injuries. those between t4 and t10 were approached using a right thoracotomy: for lesions between t11 and l1, we used a left thoracotomy, with or without diaphragmatic section. for levels l2 l3, a left lumbotomy was performed. in most cases, arthtodesis was followed by segemental stabilisation with different devices. in all cases, we were assisted intra and postoperatively by a surgical team (general surgeons, cardiovascular surgeons and urologic surgeons). results. almost 50% of the cases were located between t10 and l2. 14 cases were exclusively lumbar lesions: in one case, the cardiovascular surgical team was required (sternotomy to expose t2t3). trauma was the most common ethiological agent, followed by tumors: degenerative and infectious causes were uncommon. 21 patients required a combined anterior and posterior approach. morbidity related to surgery was of 14% in our series, superficial infections being the most frequent finding (6 cases). mortality related to surgery reached 1.33% (1 case). conclusions. in our experience (72 cases operated on during the last 13 years), and with an adequate patient selection, the anterior approach resulted safe and effective, with an acceptable morbidity grossly equal to that described in the literature.
Abordajes toracolumbares anteriores en lesiones raquimedulares: experiencia en 72 casos
Platas,Marcelo; Lambre,Jorge; Cersósimo,Martín; Ortiz,Silvia;
Revista argentina de neurocirug?-a , 2010,
Abstract: objective to analyse retrospectively our experience in two surgical centers in buenos aires, managing 72 cases of spinal lesions of different ethiologies, using anterior surgical approaches to the thoracolumbar spine. material and method. indications, surgical techniques and results, as well as complications in 72 cases requiring a thoracolumbar anterior approach performed between 1996 and 2009 were analised. surgical route was chosen according to the level and extension of the injuries. those between t4 and t10 were approached using a right thoracotomy: for lesions between t11 and l1, we used a left thoracotomy, with or without diaphragmatic section. for levels l2 l3, a left lumbotomy was performed. in most cases, arthtodesis was followed by segemental stabilisation with different devices. in all cases, we were assisted intra and postoperatively by a surgical team (general surgeons, cardiovascular surgeons and urologic surgeons). results. almost 50% of the cases were located between t10 and l2. 14 cases were exclusively lumbar lesions: in one case, the cardiovascular surgical team was required (sternotomy to expose t2t3). trauma was the most common ethiological agent, followed by tumors: degenerative and infectious causes were uncommon. 21 patients required a combined anterior and posterior approach. morbidity related to surgery was of 14% in our series, superficial infections being the most frequent finding (6 cases). mortality related to surgery reached 1.33% (1 case). conclusions. in our experience (72 cases operated on during the last 13 years), and with an adequate patient selection, the anterior approach resulted safe and effective, with an acceptable morbidity grossly equal to that described in the literature.
The Potential of Lime and Grand Granulated Blast Furnace Slag (GGBFS) Mixture for Stabilisation of Desert Silty Sands
Journal of Civil Engineering Research , 2012, DOI: 10.5923/j.jce.20120206.07
Abstract: This study describes experimental results achieved on the use of Grand Granulated Blast Furnace Slag (GGBFS) and Lime in stabilising desert silty sand for possible use in geotechnical engineering applications, especially for roadways and railways constructions. The GGBFS and lime were added in percentages of 5, 10 and 15% and 1, 3, and 5% respectively, by dry weight of sand. Different laboratory tests such as mechanical aggregation test, hydrometer analysis, liquid-plastic limit, pH value test, compaction, unconfined compressive strength (UCS), California bearing ratio test CBR , were performed on samples to understand the engineering characteristic of soil and influences of mixtures on the silty sand soil. The study results demonstrate significant improvements in unconfined compressive strength and California bearing ratio strength. Moreover the swelling behaviour of mixtures was decreased effectively. Thus mixture of GGBFS and lime can be suggested to improve engineering characteristic of desert silty sands.
PHYSICOCHEMICAL CHARACTERIZATION OF COMPOST OF THE
MAHDI AHMED,AZNI IDRIS,S. R. SYED OMAR
Journal of Engineering Science and Technology , 2007,
Abstract: It is very important that tannery wastes in the form of sludge are managed in an environmentally sound manner. This study focused on the heavy metal characterization and the influence of changing the physico-chemical properties of the medium throughout the composting on the concentrations, bioavailability or chemical forms of Cr, Cu, Zn, Pb and Cd in tannery sludge. The physical and chemical properties of the composted sludge during treatment show the stability and maturity of end product. Total metal content in the final compost were much lower than the limit values of composts to be used as good soil fertilizer. Furthermore, it was observed in using a sequential extraction method in sludge compost at different phases of treatment, that a large proportion of the heavy metals were associated to the residual fraction (70– 80%) and more resistant fractions to extraction X–NaOH, X–EDTA, X–HNO3 (12–29%). Less than 2% of metals bound to bioavailable fractions X–(KNO3 + H2O). Bioavailable fractions of all elements tend to decrease. Mobile fractions of metals are poorly predictable from the total content.
The study of the psychological difficulties of first-year students in the conditions of adaptation to training in a higher educational institution
Ludmila Pyhacheva
Koncept : Scientific and Methodological e-magazine , 2013,
Abstract: The article is devoted to the difficulties of adaptation of the first-year students to study in the University, the integration of recent entrants to the student forms of collective life.
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