Optimal control strategy for low speed and high speed four-wheel-active steering vehicle

In this work, based on the optimal control theory approach, a four-wheel-active steering (4WAS) system is proposed for low speed and high speed applications. A model following the control structure is adopted consisting of a feed-forward and feedback compensation strategy that serves as correction inputs to enhance the vehicle’s dynamic behavior. The velocity dependent feed-forward control inputs are based on the driver’s steering intention while the feedback control inputs are based on the vehicle’s state feedback errors, being the sideslip and yaw rate of the vehicle. Numerical simulations are conducted using the Matlab/Simulink platform to evaluate the control system’s performance. The performance of the 4WAS controller is tested in two designated open loop tests, being the constant steer and the lane change maneuver, to evaluate its effectiveness. A comparison with conventional passive front-wheel-steering (FWS) and conventional four-wheel-steering (4WS) systems shows the preeminent result performance of the proposed control strategy in terms of the response tracking capability and versatility of the controller to adapt to the system’s speed environment. In high speed maneuvers, the improvement in terms of yaw rate tracking error in rms is evaluated and the proposed active steering system considerably beat the other two structures with 0.2% normalized error compared to the desired yaw rate response. Meanwhile, in low speed, turning radius reductions of 25% and 50% with respect to the capability of normal or typical FWS vehicles are successfully achieve

PREPARATION AND CHARACTERIZATION OF LAFEO3 USING DUAL-COMPLEXING AGENTS FOR PHOTODEGRADATION OF HUMIC ACID

Humic Acid (HA) is considered as one of the major components that represents a major fraction of dissolved in natural water. Complex mixture of organic compounds on HA lead to the problematic issue for municipal wastewater treatment plants such as undesirable taste, colour to drinking water and fouling in pipe line. The reaction of HA with chlorine during disinfection processes would produce carcinogenic by-products like trihalomethanes. In this study, for the first time, LaFeO3 photocatalyst was successfully synthesized via gel-combustion method using combined glucose/citric acid as chelating agents and was further calcined at 400°C. The photocatalytic activity of samples was investigated by degradation of Humic Acid (HA) in water under visible light irradiation. Results proved that the photocatalytic degradation of HA is dependent on the catalyst dosage, initial concentration of HA, and oxygen availability in the aeration. The photocatalytic degradation also was enhanced by high surface area of synthesized LaFeO3 obtained by amorphous structure. Overall, the percentage removal of HA by varying the catalyst dosage are in the order of 88%, 90%, 98% and 97% for 0.6 g/L, 0.8 g/L, 1.0 g/L, and 1.2 g/L respectively for an irradiation period of 120 minutes. Next, the removal of HA by manipulating its initial concentration are 98%, 90%, 85% and 86% with respect to 10 g/L, 20 g/L, 30 g/L and 40 g/L taken for 120 minutes. Overall, the optimal operational parameters for the removal of HA of catalyst dosage is 1.0 g/L performing at 98%, for initial concentration of HA which was removed efficiently at 97% is 10 g/L and via aeration in this study was about 93%, after 120 min of irradiation times

The blast resistance of a woven carbon fiber-reinforced epoxy composite

The blast resistance of a carbon fiber-reinforced epoxy (CFRE) resin has been investigated through experiments on a range of panels. The panels were subjected to blast loading by detonating small quantities of plastic explosive at a fixed stand-off distance. A ballistic pendulum was used to provide a measure of the impulse imparted to the specimen. Tests were undertaken at impulses up to those required to completely destroy the laminates. An examination of the damaged panels highlighted a number of different fracture mechanisms including delamination, top surface fiber buckling, fiber fracture, and shear failure along the edges of the plates. The impulses associated with the onset of fiber fracture and complete target failure were found to increase in a linear fashion for the range of panels considered here. The experimental data are compared with previously published results from similar tests on a woven carbon fiber-reinforced poly-ether-imide. Here, it was demonstrated that the CFRE offered a similar blast resistance to that of the thermoplastic-matrix composite

The blast behaviour of fiber reinforced thermoplastic laminates

This article presents the results of a series of blast tests on a carbon fiber-reinforced poly-ether-imide (PEI) and a glass fiber-reinforced PEI composite. Initially, the fracture properties of the two composite systems were characterized through a series of flexural and interlaminar fracture tests. Blast testing was then undertaken on a ballistic pendulum facility, capable of measuring the impulse imparted by the plastic explosive. Delamination, localized fiber buckling, fiber fracture, and shear failure at the boundary of the clamped plates were identified as the primary failure mechanisms in the laminates, with their severity depending on the panel thickness and the applied impulse. Delamination was very localized along the center plane of the laminate, a reflection of the very high interlaminar fracture toughness of these composites. The critical impulse for rear surface fiber fracture has been found to increase rapidly with laminate thickness for the range of panels considered here. The impulses associated with the onset of rear-surface fiber fracture and complete failure of the target were similar, suggesting that rear surface fiber fracture is a pre-cursor to complete failure in these laminates. Limited tests on the glass fiber-reinforced PEI system showed that it offers a superior blast resistance to its carbon fiber counterpart

Dealing with creationist challenges: what European biology teachers might expect in the classroom

Creationists are becoming more active in Europe. We expect that European biology teachers will be more frequently challenged by students who introduce creationist misconceptions of evolutionary theory into the classroom. Moreover, research suggests that not all teachers are equally well prepared to deal with them. To make biology teachers aware of what they might be confronted with, we discuss three kinds of misconceptions that are common in creationist literature: misconstruing scientific methodology, making a straw man out of evolutionary theory, and demanding unreasonable evidence. We offer some suggestions as to how to deal with them, but we also note the importance of embedding this approach in a more comprehensive educational program in which students learn to think critically and in which their moral concerns and worldview are taken into account. In addition, we invite biology teachers to reflect on their own knowledge and, if necessary, to refresh it by consulting accessible yet scientifically informed literature. Although our main concern lies with teachers in Europe, our approach might be valuable to biology teachers worldwide