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  • 1
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    An Innovative Design of Decoupled Regenerative Braking System for Electric City Bus Based on Chinese Typical Urban Driving Cycle (2020)
    Hindawi
    Details
    Publication Date: 2020-07-18
    Description: This paper proposes a novel decoupled approach of a regenerative braking system for an electric city bus, aiming at improving the utilization of the kinetic energy for rear axle during a braking process. Three contributions are added to distinguish from the previous research. Firstly, an energy-flow model of the electric bus is established to identify the characteristic parameters which affect the energy-saving efficiency of the vehicle, while the key parameters (e.g., driving cycles and the recovery rate of braking energy) are also analyzed. Secondly, a decoupled braking energy recovery scheme together with the control strategy is developed based on the characteristics of the power assistance for electric city bus which equips an air braking system, as well as the regulatory requirements of ECE R13. At last, the energy consumption of the electric city bus is analyzed by both the simulation and vehicle tests, when the superimposed and the decoupled regenerative braking system are, respectively, employed for the vehicle. The simulation and actual road test results show that compared with the superposition braking system of the basic vehicle, the decoupled braking energy recovery system after the reform can improve the braking energy recovery rate and vehicle energy-saving degree. The decoupled energy recovery system scheme and control strategy proposed in this paper can be adopted by bus factories to reduce the energy consumption of pure-electric buses.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 2
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    A Chattering Free Discrete-Time Global Sliding Mode Controller for Optoelectronic Tracking System (2013)
    Hindawi
    Details
    Publication Date: 2013-11-13
    Description: Aiming at the uncertainties including parameter variations and external disturbances in optoelectronic tracking system, a discrete-time global sliding mode controller (DGSMC) is proposed. By the design of nonlinear switching function, the initial state of control system is set on the switching surface. An adaptive discrete-time reaching law is introduced to suppress the high-frequency chattering at control input, and a linear extrapolation method is employed to estimate the unknown uncertainties and commands. The global reachability for sliding mode and the chattering-free property are proven by means of mathematical derivation. Numerical simulation presents that the proposed DGSMC scheme not only ensures strong robustness against system uncertainties and small tracking error, but also suppresses the high-frequency chattering at control input effectively, compared with the SMC scheme using conventional discrete-time reaching law.
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    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
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  • 3
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    Numerical Simulation of the Direct Radiative Effects of Dust Aerosol on the East Asian Winter Monsoon (2015)
    Hindawi
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    Publication Date: 2015-01-01
    Description: Variations of the East Asian winter monsoon (EAWM) induced by dust aerosol are studied by using a regional climate model (RegCM4/Dust). Dust coupled and uncoupled experiments are carried out for the past decade (2000–2009). The coupled RegCM4 captures three centers of dust mixing ratio (DMR) located in the Taklamakan Desert, western Inner Mongolia, and northern Xinjiang, respectively, with maximum values greater than 500 µg kg−1in winter. The surface total radiation change induced by dust is negative, and its central value of −8 W m−2results in surface temperature cooling by 1.5°C in winter. Dust induced radiation change at the top of the atmosphere (TOA) is also negative in Northern China, except over the Tibetan Plateau (TP), and up to −5 W m−2in Central China. Dust cooling effects increase the sea level pressure (SLP) gradient between land and ocean, the cold surge frequency, and the East Asian jet stream (EAJ) intensity and then enhance the EAWM. The dry and cold wind pervade most areas of East Asia, suppressing large-scale precipitation and eventually leading to a rainfall decrease of about 10–30% in Northern China and the middle Yangtze River Valley.
    Print ISSN: 1687-9309
    Electronic ISSN: 1687-9317
    Topics: Geosciences , Physics
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  • 4
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    On the Robustness of the Weakening Effect of Anthropogenic Aerosols on the East Asian Summer Monsoon with Multimodel Results (2015)
    Hindawi
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    Publication Date: 2015-01-01
    Description: Using outputs from 10 CMIP5 models with fixed sea surface temperature, we investigate the fast response of the East Asian summer monsoon (EASM) and summer precipitation in East China to anthropogenic aerosols. To address this topic, we employ two commonly used EASM indices that can represent zonal and meridional land-sea thermal contrast, respectively. The results reveal that the notion of a weakened EASM in response to increased anthropogenic aerosols is a robust one, as well as decreased precipitation in East China. The ensemble mean of decreased precipitation in the aerosol run was about 6.6% in comparison to the CTL run and could be enlarged to 8.3% by excluding the experiments with the aerosol direct effect only. Convective precipitation was found to be the primary contributor (〉80%) to the reduction of total precipitation. The combination of direct and indirect effects of aerosols can decrease solar radiation reaching the Earth’s surface and eventually modulate large-scale EASM circulation and suppress summer precipitation in East China. The uncertainties and discrepancies among the models highlight the complexity of interaction in aerosol-precipitation processes when investigating present and future changes of the EASM.
    Print ISSN: 1687-9309
    Electronic ISSN: 1687-9317
    Topics: Geosciences , Physics
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  • 5
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    Patterns of Biomass and Carbon Allocation across Chronosequence of Chir Pine (Pinus roxburghii) Forest in Pakistan: Inventory-Based Estimate (2018)
    Hindawi
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    Publication Date: 2018-09-18
    Description: The quantitative relationship between carbon sequestration potential and stand ages of Pine (Pinus roxburghii) forest is not documented in Pakistan. Using field inventory data, this study underlines the patterns of biomass and carbon allocation across a chronosequence of Chir Pine forest. Based on the uniform shelterwood silvicultural management system, the forest was classified into three stand age classes representing the young stand ( 75 years). The results showed an increasing trend in living tree biomass carbon with stand age. However, soil carbon showed gradually decreasing trend from young to overmature stand. Similarly, deadwood, litter, and understory biomass carbon showed an increase pattern of changes. Altogether, the results highlighted that the mean carbon values of all components varied between 90.3 t·C·ha−1 in the young stand and 309.5 t·C·ha−1 in the overmature stand. Furthermore, our results confirm that the current management operations affect the forest floor and soil carbon. Therefore, we suggest that different protection measures should be considered during management operations to enhance soil and forest floor carbon.
    Print ISSN: 1687-9309
    Electronic ISSN: 1687-9317
    Topics: Geosciences , Physics
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  • 6
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    Numerical Modeling of Topography-Modulated Dust Aerosol Distribution and Its Influence on the Onset of East Asian Summer Monsoon (2016)
    Hindawi
    Details
    Publication Date: 2016-01-01
    Description: A regional climate model coupled with a dust module was used to simulate dust aerosol distribution and its effects on the atmospheric heat source over the TP, East Asian summer monsoon onset, and precipitation in East Asia modulated by the uplift of the northern TP. We carried out four experiments, including a modern (i.e., high-mountain) experiment with (HMD) and without (HM) the major deserts in Northwest China and a low-mountain experiment with (LMD) and without (LM) the deserts. The results show that dust greatly increases in the Taklamakan Desert accompanied with the uplift of the northern TP, and the increase exceeds 150 µg kg−1in spring. A strong cyclone in the Tarim Basin produced by the uplifted northern TP enhances dust emissions in the Taklamakan Desert in summer. Meanwhile, the dust loading over the TP also increases induced by the uplift of the northern TP, causing the heat source over the TP decreased. Under the condition of the northern TP uplift to present altitude, dust delays the East Asia summer monsoon onset by two pentads and one pentad, respectively, in the southern and northern monsoon regions and greatly suppresses precipitation in East Asia compared with results in the low terrain experiments.
    Print ISSN: 1687-9309
    Electronic ISSN: 1687-9317
    Topics: Geosciences , Physics
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  • 7
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    High-Order Fuzzy Time Series Model Based on Generalized Fuzzy Logical Relationship (2013)
    Hindawi
    Details
    Publication Date: 2013-01-01
    Description: In view of techniques for constructing high-order fuzzy time series models, there are three methods which are based on advanced algorithms, computational methods, and grouping the fuzzy logical relationships, respectively. The last kind model has been widely applied and researched for the reason that it is easy to be understood by the decision makers. To improve the fuzzy time series forecasting model, this paper presents a novel high-order fuzzy time series models denoted asGTS(M,N)on the basis of generalized fuzzy logical relationships. Firstly, the paper introduces some concepts of the generalized fuzzy logical relationship and an operation for combining the generalized relationships. Then, the proposed model is implemented in forecasting enrollments of the University of Alabama. As an example of in-depth research, the proposed approach is also applied to forecast the close price of Shanghai Stock Exchange Composite Index. Finally, the effects of the number of orders and hierarchies of fuzzy logical relationships on the forecasting results are discussed.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
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  • 8
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    Robust Tracking Control for Switched Fuzzy Systems with Fast Switching Controller (2012)
    Hindawi
    Details
    Publication Date: 2012-01-01
    Description: This paper addresses the problem of designing robust tracking controls for a class of switched fuzzy (SF) systems with time delay. A switched fuzzy system, which differs from existing ones, is firstly employed to describe a nonlinear system. Next, a fast switching controller consisting of a number of simple subcontrollers is proposed. The smooth transition is governed by using the fast switching controller. Tracking hybrid control schemes which are based upon a combination of theH∞tracking theory, fast switching control algorithm, and switching law design are developed such that theH∞model referent tracking performance is guaranteed. Since convex combination techniques are used to derive the delay independent criteria, some subsystems are allowed to be unstable. Finally, various comparisons of the elaborated examples are conducted to demonstrate the effectiveness of the proposed control design approach. All results illustrate good control performances as desired.
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  • 9
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    On the Shoulders of Giants: Incremental Influence Maximization in Evolving Social Networks (2017)
    Hindawi
    Details
    Publication Date: 2017-01-01
    Description: Influence maximization problem aims to identify the most influential individuals so as to help in developing effective viral marketing strategies over social networks. Previous studies mainly focus on designing efficient algorithms or heuristics on a static social network. As a matter of fact, real-world social networks keep evolving over time and a recalculation upon the changed network inevitably leads to a long running time. In this paper, we propose an incremental approach, IncInf, which can efficiently locate the top-K influential individuals in evolving social networks based on previous information instead of calculation from scratch. In particular, IncInf quantitatively analyzes the influence spread changes of nodes by localizing the impact of topology evolution to only local regions, and a pruning strategy is further proposed to narrow the search space into nodes experiencing major increases or with high degrees. To evaluate the efficiency and effectiveness, we carried out extensive experiments on real-world dynamic social networks: Facebook, NetHEPT, and Flickr. Experimental results demonstrate that, compared with the state-of-the-art static algorithm, IncInf achieves remarkable speedup in execution time while maintaining matching performance in terms of influence spread.
    Print ISSN: 1076-2787
    Electronic ISSN: 1099-0526
    Topics: Computer Science , Mathematics
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  • 10
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    A Chattering Free Discrete-Time Global Sliding Mode Controller for Optoelectronic Tracking System (2013)
    Hindawi
    Details
    Publication Date: 2013-01-01
    Description: Aiming at the uncertainties including parameter variations and external disturbances in optoelectronic tracking system, a discrete-time global sliding mode controller (DGSMC) is proposed. By the design of nonlinear switching function, the initial state of control system is set on the switching surface. An adaptive discrete-time reaching law is introduced to suppress the high-frequency chattering at control input, and a linear extrapolation method is employed to estimate the unknown uncertainties and commands. The global reachability for sliding mode and the chattering-free property are proven by means of mathematical derivation. Numerical simulation presents that the proposed DGSMC scheme not only ensures strong robustness against system uncertainties and small tracking error, but also suppresses the high-frequency chattering at control input effectively, compared with the SMC scheme using conventional discrete-time reaching law.
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    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
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