Browsing by Author "Li, Yanhua"

Now showing 1 - 3 of 3
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    Advancing Social Equity with Shared Autonomous Vehicles: Literature Review, Practitioner Interviews, and Stated Preference Surveys
    (Center for Transportation Studies, University of Minnesota, 2022-01) Fan, Yingling; Wexler, Noah; Douma, Frank; Ryan, Galen; Hong, Chris; Li, Yanhua; Zhang, Zhi-Li
    This report examines preferences and attitudes regarding the implementation and design of a hypothetical publicly-funded Shared Automated Vehicle (SAV) system in the Twin Cities metro area. We provide a brief literature review before delving into our main findings. First, we discuss a series of interviews in which officials at local planning agencies were asked about their vision for SAV in the Twin Cities. According to these interviews, SAV could be especially useful in solving first-and-last-mile problems and connecting with already existing transit and on-demand transportation infrastructure. We then analyze data sourced from an originally designed digital survey instrument implemented over social media in 2020 and specifically targeted at Twin Cities residents. Data from the survey emphasize that people who currently experience barriers to transportation are more likely to value SAV highly. The data also give insight into design considerations, emphasizing flexibility in payment and booking and the importance of security features. Finally, we examine data from a similar survey administered at the 2021 Minnesota State Fair, which we use to gauge preferences toward SAV among people living in the Twin Cities exurbs and Greater Minnesota.
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    Characterizing diverse link patterns in complex networks: theory and applications
    (2013-08) Li, Yanhua
    Complex networks, including the Internet, wireless and cellular networks, and on-line social networks, are becoming indispensable parts of our daily lives. These networks arising from a wide range of applications can be represented and studied as graphs, and the underlying link patterns play an important role in understanding and solving problems in such applications. For example, due to the unreliable and asymmetric wireless channel, ad hoc wireless networks can be viewed as directed graphs, and the link directions contain crucial information about the possibility and efficiency of routing over such networks. Moreover, many online social networks, such as Twitter and Google+, can be viewed as directed graphs with uni-directional "following" relations among users, and the link directions contain crucial information about how users form social communities. In another application, online social networks such as Slashdot and Epinions represent relationships between users as links with positive or negative weights, which correspond to friend and foe relations. These networks are referred to as signed networks, where those signed links generate new challenges in understanding and studying the underlying network properties. In this dissertation, I present my work on developing theories for studying and characterizing various crucial properties and application challenges in undirected, directed, and signed complex networks. First of all, we develop and extend random walk theory and the intrinsically related spectral graph theory for undirected graphs to directed graphs. Then, we explore application challenges raised by various link patterns. To be precise, we introduce a novel social community detection algorithm for social networks with both uni- and bi-directional links. In undirected communication networks, we establish the routing continuum theory that spans from short path routing to "potential" based all-path routing, based on the connection between routing and network flow optimization problems. Moreover, we investigate the social influence diffusion dynamics and influence maximization in social networks with both friend and foe relations.
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    Design of forwarder list selection scheme in opportunistic routing protocol
    (2008-10-22) Li, Yanhua; Chen, Wei; Zhang, Zhi-Li
    Unlike traditional wireless routing protocols which use a single fixed path, opportunistic routing explicitly takes advantage of the broadcast nature of wireless communications by using a set of forwarders to opportunistically perform packet forwarding. A key issue in the design of opportunistic routing protocols is the forwarder list selection problem. In this paper we establish a general theory for analyzing the forwarder list selection problem, and develop an optimal solution, the minimum transmission selection(MTS) algorithm, which minimizes the expected number of transmissions. Through extensive simulations using the MIT Roofnet dataset, we demonstrate that in more than 90% cases the MTS algorithm outperforms the forwarder selection scheme used in ExOR, the best known opportunistic routing protocol in the literature.