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  • 0203 mechanical engineering

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  • Authors: 
    Ming Xue; Gao Chao; Feng Liu; Luo Shijun;
    Publisher: American Institute of Aeronautics and Astronautics
  • Open Access English
    Authors: 
    Frédéric Jurie;
    Publisher: HAL CCSD
    Country: France

    International audience; We propose an efficient method for tracking 3D modelled objects in cluttered scenes. Rather than tracking objects in the image, our approach relies on the object recognition aspect of tracking. Candidate matches between image and model features define volumes in the space of transformations. The volumes of the pose space satisfying the maximum number of correspondences are those that best align the model with the image. Object motion defines a trajectory in the pose space. We give some results showing that the presented method allows tracking of objects even when they are totally occluded for a short while, without supposing any motion model and with a low computational cost (below 200 ms per frame on a basic workstation). Furthermore, this algorithm can also be used to initialize the tracking.

  • Closed Access
    Authors: 
    Ayman Younis; Tuyen X. Tran; Dario Pompili;
    Publisher: IEEE

    Task offloading with Mobile-Edge Computing (MEC) is envisioned as a promising technique for prolonging battery lifetime and enhancing the computation capacity of mobile devices. In this paper, we consider a multi-user MEC system with a Base Station (BS) equipped with a computation server assisting mobile users in executing computation-intensive real-time tasks via offloading technique. We formulate the Energy-Latency-aware Task Offloading and Approximate Computing (ETORS) problem, which aims at optimizing the trade-off between energy consumption and application completion time. Due to the centralized and mixed-integer natures of this problem, it is very challenging to derive the optimal solution in practical time. This motivates us to employ the Dual-Decomposition Method (DDM) to decompose the original problem into three subproblems—namely the Task-Offloading Decision (TOD), the CPU Frequency Scaling (CFS), and the Quality of Computation Control (QoCC). Our approach consists of two iterative layers: in the outer layer, we adopt the duality technique to find the optimal value of Lagrangian multiplier associated prime problem; and in the inner layer, we formulate the subproblems that can be solved efficiently using convex optimization techniques. We show that the computation offloading selection depends not only on the computing workload of a task, but also on the maximum completion time of its immediate predecessors and on the clock frequency as well as on the transmission power of the mobile device. Simulation results coupled with real-time experiments on a small-scale MEC testbed show the effectiveness of our proposed resource allocation scheme and its advantages over existing approaches.

  • Open Access
    Publisher: Educational and Instructional Center for Railway Transportation

    The device of flexitanks, as well as technical and technological features of the transportation of goods with their use, are considered. The relevance of the topic is due to the fact that at present almost 80 % of international transit in the world takes place in containers, on the domestic markets of the largest countries of the world, goods flows also go mainly in containers. Flexitanks are studied as innovative tools for organizing the chains of delivery of goods and goods in containers, having all the necessary equipment for transporting various kinds of cargo.Analytical and marketing methods are applied, taking into account the principles of the theory of logistics, logic, as well as shared materials.A comparison of this type of packaging with other transportation means is presented. It was revealed that flexitara is more oriented to non-hazardous liquid cargo in terms of its characteristics. The use of flexitanks allows to reduce transportation costs, reduce labor, time and transportation costs, as well as to carry out multimodal transportation using various modes of transport.It is established that flexitanks can act as a full-fledged and multi-functional alternative to tanks, tank containers and other containers for transporting bulk materials that are non-hazardous cargoes. The use of technology for the transportation of goods in flexitanks will contribute to the further innovative development of multi-modal freight transportation and the growth of containerization of goods exchange in general. 

  • Open Access English
    Authors: 
    Kai Yuan Wang; Kin Ho Lo; Chi Tat Kwok; Man Meng Wong; In Wa Iong; Wenji Ai;
    Publisher: ABM, ABC, ABPol

    This paper looks into the influences of martensitic transformations on the cavitation-erosion (CE) damage initiation mechanism and pitting corrosion resistance of a lean austenitic stainless steel. The e and α' martensites are prime sites of CE damage initiation for this steel, whereas grain boundaries are more favourable damage initiation sites for other similar steels. The profusion of e and α' results in fast surface roughening during the CE process, which may cause a compromise in performance when this steel (or similar steels that have the same CE damage mechanism) is used for such applications as hydro-machinery or piping. e and α' also detrimentally affect the pitting resistance of this steel and so they are expected to affect CE resistance adversely due to the synergism between CE and corrosion.

  • Closed Access
    Authors: 
    Luo Xi; Yingjie Zhang; Lin Zhang;
    Publisher: Emerald

    Purpose The purpose of this paper is to improve the positioning accuracy of 6-Dof serial robot by the way of error compensation and sensitivity analysis. Design/methodology/approach In this paper, the Denavit–Hartenberg matrix is used to construct the kinematics models of the robot; the effects from individual joint and several joints on the end effector are estimated by simulation. Then, an error model based on joint clearance is proposed so that the positioning accuracy at any position of joints can be predicted for compensation. Through the simulation of the curve path, the validity of the error compensation model is verified. Finally, the experimental results show that the error compensation method can improve the positioning accuracy of a two joint exoskeleton robot by nearly 76.46%. Findings Through the analysis of joint error sensitivity, it is found that the first three joints, especially joint 2, contribute a lot to the positioning accuracy of the robot, which provides guidance for the accuracy allocation of the robot. In addition, this paper creatively puts forward the error model based on joint clearance, and the error compensation method which decouples the positioning accuracy into joint errors. Originality/value It provides a new idea for error modeling and error compensation of 6-Dof serial robot. Combining sensitivity analysis results with error compensation can effectively improve the positioning accuracy of the robot, and provide convenience for welding robot and other robots that need high positioning accuracy.

  • Open Access
    Authors: 
    Kaveh Sarrafan; Danny Sutanto; Kashem M. Muttaqi; Graham Town;
    Publisher: Institution of Engineering and Technology (IET)

    Range anxiety is an obstacle to the acceptance of electric vehicles (EVs), caused by drivers’ uncertainty regarding their vehicle's state of charge (SoC) and the energy required to reach their destination. Most estimation methods for these variables use simplified models with many assumptions that can result in significant error, particularly if dynamic and environmental conditions are not considered. For example, the combined efficiency of the inverter drive and electric motor varies throughout the route and is not constant as assumed in most range estimation methods. This study proposes an improved method for SoC and range estimation by taking into account location-dependent environmental conditions and time-varying drive system losses. To validate the method, an EV was driven along a selected route and the measured EV battery SoC at the destination was compared with that predicted by the algorithm. The results demonstrated excellent accuracy in the SoC and range estimation, which should help alleviate range anxiety.

  • Open Access
    Authors: 
    Luca Deseri; G. Gentili; John M. Golden;
    Publisher: Technological University Dublin
    Country: Ireland
    Project: EC | HOTBRICKS (609758), NSF | Center for Nonlinear Anal... (0635983)

    Explicit expressions for the minimum free energy of a linear viscoelastic material and Noll’s definition of state are used here to explore spatial energy decay estimates for viscoelastic bodies, in the full dynamical case and in the quasi-static approximation. In the inertial case, Chirita et al. obtained a certain spatial decay inequality for a space–time integral over a portion of the body and over a finite time interval of the total mechanical energy. This involves the work done on histories, which is not a function of state in general. Here it is shown that for free energies which are functions of state and obey a certain reasonable property, the spatial decay of the corresponding space–time integral is stronger than the one involving the work done on the past history. It turns out that the bound obtained is optimal for the minimal free energy. Two cases are discussed for the quasi-static approximation. The first case deals with general states, so that general histories belonging to the equivalence class of any given state can be considered. The continuity of the stress functional with respect to the norm based on the minimal free energy is proved, and the energy measure based on the minimal free energy turns out to obey the decay inequality derived Chirita et al. for the quasi-static case. The second case explores a crucial point for viscoelastic materials, namely that the response is influenced by the rate of application of loads. Quite surprisingly, the analysis of this phenomenon in the context of Saint-Venant principles has never been carried out explicitly before, even in the linear case. This effect is explored by considering states, the related histories of which are sinusoidal. The spatial decay parameter is shown to be frequency-dependent, i.e. it depends on the rate of load application, and it is proved that of those considered, the most conservative estimate of the frequency-dependent decay is associated with the minimal free energy. A comparison is made of the results for sinusoidal histories at low frequencies and general histories.

  • Open Access
    Authors: 
    Yunjie Huang; Yi Zhang;
    Publisher: July Press Pte. Ltd.

    Learning burnout circumstances appear commonly in the process of English learning. The current research investigates the features of learning burnout of English and a non-English major junior student from three dimensions, including exhaustion, cynicism and decreased professional self-efficacy. Results find that, firstly, these two groups of participants hold a similar degree of learning burnout, while non-English major participants show more individual variability of the learning burnout situation. Based on Krashen’s Input hypothesis and Affective Filter hypothesis, there exist differences and similarities of reasons for participants’ learning burnout. The high degree of learning burnout of these two groups is influenced by the choice of expected jobs as well as the sense of inferiority caused because of peer pressure. Furthermore, learning burnout of English major students is more influenced by teachers, having higher expectations for comprehensible and sufficient input. Therefore, teachers should pay attention to students’ learning burnout situation and understand the specific needs and practical condition of junior students.

  • Open Access

    We propose a general framework for the specification of a sparse representation of millimeter wave vehicular propagation channels and apply this to both synthetic data and real-world observations from channel sounding experiments. The proposed framework is based on the c-LASSO (complex Least Absolute Shrinkage and Selection Operator) which minimizes the mean squared error of the sparse representation for a given number of degrees of freedom. By choosing the number of degrees of freedom, we balance the numerical complexity of the representation in the channel emulation against its accuracy in terms of the mean squared error. A key ingredient is the choice of basis of the representation and we discuss two options: the Fourier basis and its projection onto a given subband. The results indicate that the subband-projected Fourier basis is a low-complexity choice with high fidelity for representing clustered channel impulse responses. Finally, a sequential estimator is formulated which enforces a consistent temporal evolution of the geometry of the interacting objects in the propagation environment. We demonstrate the performance of our approach using both synthetic data and measured 60 GHz vehicular channel traces.

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