The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, s...The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, such as safety and security, logistics, and emergency response. High communication and data storage costs, however, lead to a low position update rate with the AVL products available, causing poor track representation, and making the route determined by the vehicle in urban areas almost illegible. This paper proposes a new approach by using intelligent techniques to choose the best position update moment to improve track representations. The principle underlying these techniques is based on vehicle status analysis （speed, direction and timing）, which tries to determine when a position update is required, in order to better represent the path that a vehicle has traced, thus avoiding excessive communication and data storage. Therefore, the better the correspondence between the traced track and the real track followed by the vehicle, the greater the added value offered by system applications. This enhancement to the representation of the track allows the creation of new applications in the realm of AVL systems, particularly for situations where accuracy plays an important role.展开更多
A fundamental understanding of the electrochemical reaction process and mechanism of electrodes is very crucial for developing high-performance electrode materials.In this study,we report the sodium ion storage behavi...A fundamental understanding of the electrochemical reaction process and mechanism of electrodes is very crucial for developing high-performance electrode materials.In this study,we report the sodium ion storage behavior and mechanism of orthorhombic V_(2)O_(5) single-crystalline nanowires in the voltage window of 1.0–4.0 V(vs.Na/Na+).The single-crystalline nanowires exhibit a large irreversible capacity loss during the first discharge/charge cycle,and then show excellent cycling stability in the following cycles.At a current density of 100 mA g^(−1),the nanowires electrode delivers initial discharge/charge capacity of 217/88 mA h g^(−1),corresponding to a Coulombic efficiency of only 40.5%;after 100 cycles,the electrode remains a reversible discharge capacity of 78 mA h g^(−1) with a fading rate of only 0.09%per cycle compared with the 2nd cycle discharge capacity.The sodium ion storage mechanism was investigated,illustrating that the large irreversible capacity loss in the first cycle can be attributed to the initially formed single-crystalline α′-Nax V_(2)O_(5)(0.02<x<0.88),in which sodium ions cannot be electrochemically extracted and the α′-Na0.88 V_(2)O_(5) can reversibly host and release sodium ions via a single-phase(solid solution)reaction,leading to excellent cycling stability.The Na^(+) diffusion coefficient in α′-Nax V_(2)O_(5) ranges from 10^(−12) to 10^(−11.5) cm^(2) s^(−1) as evaluated by galvanostatic intermittent titration technique(GITT).展开更多
文摘The use of AVL （automatic vehicle locator） systems has increased considerably. By using an AVL system, it is possible to know vehicle positions at the dispatch center, which allows the use of several applications, such as safety and security, logistics, and emergency response. High communication and data storage costs, however, lead to a low position update rate with the AVL products available, causing poor track representation, and making the route determined by the vehicle in urban areas almost illegible. This paper proposes a new approach by using intelligent techniques to choose the best position update moment to improve track representations. The principle underlying these techniques is based on vehicle status analysis （speed, direction and timing）, which tries to determine when a position update is required, in order to better represent the path that a vehicle has traced, thus avoiding excessive communication and data storage. Therefore, the better the correspondence between the traced track and the real track followed by the vehicle, the greater the added value offered by system applications. This enhancement to the representation of the track allows the creation of new applications in the realm of AVL systems, particularly for situations where accuracy plays an important role.
基金financially supported by the National Natural Science Foundation of China (51664012)Guangxi Natural Science Foundation (2017GXNSFAA198117 and2015GXNSFGA139006)the Technology Major Project of Guangxi(AA19046001)
文摘A fundamental understanding of the electrochemical reaction process and mechanism of electrodes is very crucial for developing high-performance electrode materials.In this study,we report the sodium ion storage behavior and mechanism of orthorhombic V_(2)O_(5) single-crystalline nanowires in the voltage window of 1.0–4.0 V(vs.Na/Na+).The single-crystalline nanowires exhibit a large irreversible capacity loss during the first discharge/charge cycle,and then show excellent cycling stability in the following cycles.At a current density of 100 mA g^(−1),the nanowires electrode delivers initial discharge/charge capacity of 217/88 mA h g^(−1),corresponding to a Coulombic efficiency of only 40.5%;after 100 cycles,the electrode remains a reversible discharge capacity of 78 mA h g^(−1) with a fading rate of only 0.09%per cycle compared with the 2nd cycle discharge capacity.The sodium ion storage mechanism was investigated,illustrating that the large irreversible capacity loss in the first cycle can be attributed to the initially formed single-crystalline α′-Nax V_(2)O_(5)(0.02<x<0.88),in which sodium ions cannot be electrochemically extracted and the α′-Na0.88 V_(2)O_(5) can reversibly host and release sodium ions via a single-phase(solid solution)reaction,leading to excellent cycling stability.The Na^(+) diffusion coefficient in α′-Nax V_(2)O_(5) ranges from 10^(−12) to 10^(−11.5) cm^(2) s^(−1) as evaluated by galvanostatic intermittent titration technique(GITT).
