Abstract: Utilising the strain based approach with exact representation of rigid body motion, an efficient way of constructing membrane elements will be proposed. The major problem encountered in practice is generally the compatibility between degrees of freedom of various elements [1-3]. A simple and efficient triangular and sector element are developed by the use of the strain based approach. They are based on the assumed independent functions for the various components of strain insofar as it is allowed by the compatibility equations. Theses elements produce results which are acceptable within practical engineering accuracy even when few elements are employed.
Abstract: Helical compression spring plays a vital role in vehicle application as it improves ride index, sustains the vehicle against extreme degrees of vibration and stress induced on the suspension system as a result of uneven road. Depending on the extent of load acting on the suspension system, material selection, design considerations and manufacturing processes, longevity and performance of the spring may be sustained, otherwise the spring may fail prematurely under severe loading condition. In this study, compression spring was designed using high carbon steel, stainless steel and chrome vanadium steel and the designed spring models were simulated for maximum Von-mises stress, maximum resultant displacement and resultant strain. Curb weight of the vehicle was considered in the analysis which involves the weight of the car with all fluids and components but without the driver, passengers, and cargo. At the end of the simulation, the three materials remained within the limit of their elasticity without any significant sign of failure under the applied load of 3888N. However, the difference between Von-mises stress obtained for Chrome vanadium and its yield strength was the highest (653MPa) followed by stainless steel (235MPa) before high carbon steel (109MPa). This implies that at increasing loading conditions, high carbon steel will be the first material to fail during operation, whereas, stainless steel and chrome vanadium may exhibit sustained level of longevity before failure as a result of the high chromium content and other alloying elements that gives them a better quality but at relatively high cost compared to high carbon steel which can satisfactorily undergo its service condition at relatively low cost.
Abstract: Gas-slag-forming systems of flux-cored wires for plasma building-up welding surveyed. Application of substances at overlaying welding boron triphtoride is considered, to provide the improvement of formation of the deposited bead, reduces vaporization. Systems of gas-slag-forming substances which are gating out boron triphtoride are proposed excreting boron triphtoride are investigated at overlaying welding.
Abstract: The current study surveys the results of using deionized water and kerosene as dielectrics in the machining outputs of γ-TiAl intermetallic compound obtained in electric discharge machining. Influences of these different dielectrics properties on machining speed, tool wear, surface cracks and roughness were compared. Scanning electron microscopy micrographs were prepared to investigate influences of dielectrics on the surface characteristics of electrically discharged samples. Results indicate which by kerosene dielectric; the material removal rate (MRR) is further compared to another one. But deionized water as dielectric causes higher tool wear ratio than kerosene dielectric. Electrical discharged samples in deionized water have higher surface roughness, in addition it contains surface cracks, whereas kerosene dielectric results better surface finish in low pulse current. According to XRD spectra electric discharge machining in deionized water and kerosene dielectrics produces Ti3 Al intermetallic compound on the produced surface.
Abstract: The aim of this work was to evaluate the possibility of using agroindustrial residues as carbon sources for the production of omega-3 polyunsaturated fatty acids by a native Thraustochytrid strain, and analyze the microorganism growth for each substrate. In this study a Chilean strain, Thraustochytrium kinney VAL-B1, was grown in three alternative carbon sources: lupine residue, fermented wine and residual glycerol from biodiesel canola oil for biomass and polyunsaturated fatty acids production. The highest biomass production values were obtained at the fifth day of growth, which were 7.22±0.56 g L-1, 2.72±0.25 g L-1 and 6.54±0.71 g L-1 for fermentations of lupine residue, fermented wine and residual glycerol from biodiesel canola oil, respectively, while the polyunsaturated fatty acids profile showed a docosahexanoic acid percentage of 21.19%, 13.42% and 35.06% in the fermentations of the above mentioned residues. The highest omega 3 fatty acids production (docosahexanoic and eicosapentanoic acid, 2.53±0.36 g L-1 and 0.25±0.03 g L-1, respectively) was obtained in the fermentation of residual glycerol from biodiesel canola oil. With these results, it was concluded that Thraustochytrium kinney VAL-B1 produces more omega 3 fatty acids (docosahexanoic and eicosapentanoic acid) when is fermented in a medium using residual glycerol from biodiesel canola oil as an alternative carbon source, reaching a productivity of 0.50 g L-1 d-1 for docosahexanoic acid. On the other hand, the highest biomass production was obtained in fermentations of lupine residue (7.22 g L-1). For these reasons, it is feasible to employ agroindustrial by-products for polyunsaturated fatty acids production.
Abstract: Equilibrium adsorption of quaternary component mixture (phenol, butanol, butan-2-ol and 2-methyl butan-2-ol) onto activated carbon derived from oil-palm empty fruit bunch was studied. Henry isotherm 2-parameter model was used as an improvement to Langmuir and Freundlich 2-parameter isotherm model. The 3-parameter isotherm models applied to the quaternary adsorption system included Redlich Peterson, Sips and Toth. Trial and error method of excel solver was used to evaluate the parameters in the models. Data fitness was based on correlation coefficient (R2) and average percentage error (APE). For the two-parametric isotherm models, Langmuir predicted the adsorption equilibrium well with APE and R2 values of 0.20883 and 0.9868; 0.007669509 and 0.9338; and 3.64355718 and 0.9410 for butanol, butan-2-ol and 2-methyl butan-2-ol respectively. The maximum mono-layer capacity (qm) obtained from Langmuir model for butanol, butan-2-ol and 2-methyl butan-2-ol adsorption were 3558.962mg/g, 2.064233mg/g and 22.6423mg/g respectively. Sip and Toth fitted excellently well among the three- parametric isotherm models. The Sip isotherm model gives APE and R2 values of 0.010536 and 0.9346; and 5.14458 and 0.9250 for phenol and 2-methyl butan-2-ol respectively. The Toth isotherm model gives APE and R2 values of 4.83521 and 0.9866; and 0.02595 and 0.9411 for butanol and butan-2-ol respectively. The isotherm models prove applicable for the quaternary adsorption system.
Abstract: Landfills are one of the groundwater pollution sources in Rwanda. Physical and chemical analyses of water samples were carried out to assure the magnitude of Nduba Landfill on ground water quality. Laboratory tests were conducted to get the results which helped us to study the assessment of leachate effect and to propose mitigation measures of Nduba landfill. The results showed that most of water were contaminated, where concentration of most physical and chemical parameters were above acceptable standard levels required by local and international standards for potable. The analytical results of leachates samples (Cu: 38.5 mg/L, Mn: 13.075mg/l, Zn:15mg/l, TP:4525mg/l, pH:8.52µS/cm, COD:7100mg/l, BOD:182.1mg/l, TN:5mg/l and Fe: 43.025 mg/L) showed that heavy metals are leached out from the MSW. The analytical results of groundwater from the wells located in the vicinity of Nduba landfill site (Cu: 2 mg/L, Zn:3.5-5.5mg/l, SO42-: 250-275mg/l, NO3-: 55-67.5mg/l,NH4+:1.5-2.25mg/l, COD: 39-53.4mg/l, Fe: 1.75-4.25 mg/L, Turbidity: 4.03-4.32NTU, pH:5.31-5.73µS/cm, Temperature: 21°C and BOD:20.7-21.6mg/l) compared to the World Health Organization standard (Cu:0.1mg/L,Fe:0.3mg/L,Zn:5mg/l,SO42-:200mg/l,NO3-:50mg/l,NH4+:1.5mg/l,Turbidity:<5.0 NTU and pH:6.5-9.2µS/cm) revealed that groundwater from the wells located in the vicinity of Nduba landfill site requires further physical chemical treatment to ensure their suitability for human consumption as the levels of some water quality parameters exceeded the EPA guidelines for drinking water. Designing a sanitary landfill was recommended to avoid effects of leachate on environment.
Abstract: To interconnect sources of production, it is necessary to watch that the technical parameters as tension, frequency and phase shift of the sources of production are equal. In Benin, it is difficult for the company in charge of the production and of the transport of the electricity to interconnect the production coming from Nigeria and that coming from Ghana because all the parameters are not equal. It is thus necessary to find a way to interconnect the sources of productions to satisfy not only the request in electrical energy but also to insure the continuity of the service and the stability of the electricity network [1,2]. In this work, we studied the dynamic behavior of the Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) system subjected to an important variation of load and commanded by the Sine-triangle Pulse Width Modulation ( SPWM) to improve the quality of the electrical energy. We developed thus first of all the electric model of all the constituents of the system. These models allowed designing easily the control systems of the static converters VSC (the rectifier and the inverter). The simulation of the inverter showed that the rate of distortion of harmonious varied considerably according to the load for important variations of load. The solution brought by this work is the elaboration of a control system to vectorial PWM who improves the rate of distortion of harmonious.
Abstract: The optimal power flow (OPF) problem is a very complicated task in power systems. OPF problem has a set of equality and inequality constraints. This paper looks at a chaotic cuckoo search (CCS) algorithm for solving non-convex OPF problem. The proposed CCS is a bio-inspired optimization calculation that is inspired by the behaviour of cuckoos people in nature. The chaotic guide is a variation of qualities combined with CS. A sinusoidal chaotic is integrated with CS algorithm and tested on standard IEEE 30-bus test system to the point of improving its global speed of convergence and enhancing its performance. The elitism scheme is also serves to save the best cuckoo during amid the procedure when updating the cuckoo. The results show clearly the superiority of CCS in searching for the best function values results when compared with well-known metaheuristic search algorithms.
Abstract: Integrating Distributed Generation (DG) units into distribution systems can have an impact on the voltage profile, power flow, power losses, and voltage stability. In this paper, a new methodology for DG location and sizing are developed to minimize system losses and maximize voltage stability index (VSI). A proper allocation of DG has to be determined using the fuzzy ranking method to verify best compromised solutions and achieve maximum benefits. Synchronous machines are utilized and its power factor is optimally determined via genetic optimization to inject reactive power to decrease system losses and improve voltage profile and VSI. The Augmented Lagrangian Genetic Algorithm with nonlinear mixed-integer variables and Non-dominated Sorting Genetic Algorithm have been implemented to solve both single/multi-objective function optimization problems. For proposed methodology effectiveness verification, it is tested on 33-bus and 69-bus radial distribution systems then compared with previous works.