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In this paper, a study of the nonlinear dynamical behavior of unmanned aerial vehicles (UAV) is presented. Based on a given mathematical model of quad-rotor UAV, all of the possible operational modes with given control input is discussed. Motion control law is also proposed for achieving a given desired operation mode by using back-stepping control approach. Simulation results are obtained to demonstrate the success of the proposed design.
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The roots of community policing can be traced to Wilson and Kelling’s “broken windows” theory. Since then, community policing has been quite popular among politicians, police managers, and citizens. However, community policing leaves some unanswered questions about its impact: Can it be implemented as its plan? Will it be the prevailing paradigm for policing in the future? In fact, some police organizations succeeded and the others failed when they implemented community policing. It depends on whether the police organization is qualified to implement this strategy. This paper tries to explore how to reduce the resistance of implementing community policing. On this paper, the shortcomings of the traditional policing system are introduced first. Second, the obstacles of implementing community policing are addressed. Third, the implementation of community policing to the real world is presented. Last section is the conclusion.
Due to the development of the advanced technologies, in the recent years, electronic devices for the communication and computer engineering have been considered to implement the so-called “X-by-Wire” scheme for steering control and braking control of the vehicles. It is known that the weight reduction of vehicle systems can decrease the power consumption when the traditional mechanical components can be replaced by electronic devices. Thus, X-by-wire system will be a trend in the automotive industry for saving energy. An event trigger design for vehicle control is proposed in this paper for vehicle control by using the protocol of Controller Area Network (CAN). The proposed design covers the development of CAN communication node, which is developed by using microprocessor chip Microchip PIC18F4585 and MCP2551 CAN transceiver. In addition, an interactive GUI-based utility program developer is also built up for user to easily develop the required function call to cope with the design specification. A wireless electric-driven control vehicle is served as a platform to verify the design of drive-by-wire and brake-by-wire operations. Experimental results demonstrate the success of the proposed design.
Porthole die extrusion has a great advantage in the forming of hollow section of aluminum alloy tube. The proposed paper aims atthe development of an extruding seam square tube of AA7075 high strength aluminum alloy by simulation and experiment. There areseveral factors related to extrusion load such as: billet temperature, billet dimensional, flow stress, die cavity and product geometry. The extrusion loads and die stresses for a hot extruding square tube of AA7075 with respect to different product have beeninvestigated. This study used DEFORM 3D software based on finite element analysis to simulate two different types of hollowextruding die configurations in the square tube extrusion process, namely: Type I welding position at the corners of the square tubeand Type II on the side faces. The welding strengths of these two kinds of extruded tube are studied by expanding test and tensiletest. The die life of these two extrusion die components are studied based on the die stress and die wear information. The results ofFE analysis are compared with those experiments.
Test samples of martensite/ferrite duplex stainless steels (M/Fss) were prepared using thermal-mechanical processes and their slurry erosion behaviors were systematically studied. Test results show that hot rolling is an attractive process for improving erosion resistance. This improvement is more evident at higher impinging angles and larger reduction ratios. The thermal-mechanical-treated samples exhibit higher slurry erosion resistance for all impinging angles compared to that obtained by conventional quenching treatment without rolling. The variation tendency of the erosion rate versus the impinging angle for samples rolled with different degrees of reduction is similar in that the erosion rate initially increases and then decreases as the impinging angles increase from 15° to 90°, reaching a maximum at approximately 30°. After impingement erosion, the surface morphologies of the samples exhibit many long furrows and ridges at a low impinging angle of 30°. At a high impinging angle of 90°, the samples exhibit a worn surface with abundant overlapping and irregular concavities. The surface hardness of the samples after impingement erosion increases as the impinging angles and reduction ratios increase due to the enhanced effects of both work hardening and the formation of straininduced martensite.
The bending stress formula that taking into account the transverse deformation is developedfor plane-curved, untwisted isotropic beams subjected to loadings that result in deformations in the planeof curvature. In order to account the transverse Poisson contraction effect, a new constitutive relationstrains and deformed curvatures for a curved plateis derived in a 6 6 matrix form. This constitutive relation will provide the fundamental basis to theanalyses of curved structures composing of isotropic or anisotropic materials. Then, the bending stressformula of a curved isotropic beam can be deduced from this newly developed curved plate theory. Thestress predictions by the present analysis are compared to those by the analysis that neglected the Poisoncontraction effect. The results show that the Poisson effect becomes more significant as the Poisson ratioand the curvature are getting larger.
A duplex structure of δ-ferrite and lath martensite with interlath retained austenite film is developed in this study by modifying the alloy addition. The presence of δ-ferrite can further strengthen the grain refinement of austenite during hot rolling. As a result, the amount of retained austenite is enhanced. Tempered martensite embrittlement occurs due to the decomposition of retained austenite, and grain refinement can in fact ameliorate the tempered martensite embrittlement by delaying the onset of the embrittlement to a higher temperature. The combined effect of uniform and small grains as well as a large amount of retained austenite provides a further increase in the mechanical properties. After identical tempering treatments, all mechanical properties measured in the as-rolled condition were found to be higher than those of direct quenching without rolling. After hot rolling, the increase in the hardness and tensile strength was not accompanied by a drop in the ductility and toughness. A duplex structure of δ-ferrite and lath martensite with interlath retained austenite film is developed in this study by modifying the alloy addition. The presence of δ-ferrite can further strengthen the grain refinement of austenite during hot rolling. As a result, the amount of retained austenite is enhanced. Tempered martensite embrittlement occurs due to the decomposition of retained austenite, and grain refinement can in fact ameliorate the tempered martensite embrittlement by delaying the onset of the embrittlement to a higher temperature. The combined effect of uniform and small grains as well as a large amount of retained austenite provides a further increase in the mechanical properties. After identical tempering treatments, all mechanical properties measured in the as-rolled condition were found to be higher than those of direct quenching without rolling. After hot rolling, the increase in the hardness and tensile strength was not accompanied by a drop in the ductility and toughness.
This paper is devoted to the development of the equations which describe the elastic response of a curved laminate subjected to in-plane loads and bending moments. Similar to the classic 6 × 6 ABD matrix constitutive relation of a flat laminate, a new 6 × 6 matrix constitutive relation between force resultants, moment resultants, mid-plane strains and deformed curvatures for a curved laminate is formulated. This curved lamination theory will provide the fundamental basis for the analyses of curved laminated structures. The stress predictions by the present curved lamination theory are compared to those by the curved laminate analysis that neglected the nonlinear terms in the derivation of the constitutive relation. The results show that the curved laminate analysis that neglected the nonlinear terms cannot reflect the effect of curvature and can no longer predict the stresses accurately as the curvature becomes noticeable. In this paper, a curved lamination theory that retains the nonlinear terms and, therefore, accounts for the effect of the non-flat geometry of the structure will be developed.
Issue of object’s depth estimation from binocular vision technique is studied in this paper. A binocular vision platform is set up to detect and estimate the object’s depth. Mathematical derivation of object’s depth from the two cameras of the proposed platform is re-visited to reveal the linkage between system parameters such as focal length and the estimation error. Both of simulation and experimental results are obtained for parametric analysis of estimation error. A comparison with Kinect is also given to demonstrate the superiority of the proposed design.