Dynamics for the diffusive Leslie-Gower model with double free boundaries

In this paper we investigate a free boundary problem for the diffusive Leslie-Gower prey-predator model with double free boundaries in one space dimension. This system models the expanding of an invasive or new predator species in which the free boundaries represent expanding fronts of the predator species. We first prove the existence, uniqueness and regularity of global solution. Then provide a spreading-vanishing dichotomy, namely the predator species either successfully spreads to infinity as $t\to\infty$ at both fronts and survives in the new environment, or it spreads within a bounded area and dies out in the long run. The long time behavior of $(u,v)$ and criteria for spreading and vanishing are also obtained. Because the term $v/u$ (which appears in the second equation) may be unbounded when $u$ nears zero, it will bring some difficulties for our study.Comment: 19 page

A Differential Feedback Scheme Exploiting the Temporal and Spectral Correlation

Channel state information (CSI) provided by limited feedback channel can be utilized to increase the system throughput. However, in multiple input multiple output (MIMO) systems, the signaling overhead realizing this CSI feedback can be quite large, while the capacity of the uplink feedback channel is typically limited. Hence, it is crucial to reduce the amount of feedback bits. Prior work on limited feedback compression commonly adopted the block fading channel model where only temporal or spectral correlation in wireless channel is considered. In this paper, we propose a differential feedback scheme with full use of the temporal and spectral correlations to reduce the feedback load. Then, the minimal differential feedback rate over MIMO doubly selective fading channel is investigated. Finally, the analysis is verified by simulations

The nonlocal dispersal equation with seasonal succession

In this paper, we focus on the nonlocal dispersal monostable equation with seasonal succession, which can be used to describe the dynamics of species in an environment alternating between bad and good seasons. We first prove the existence and uniqueness of global positive solution, and then discuss the long time behaviors of solution. It is shown that its dynamics is completely determined by the sign of the principal eigenvalue, i.e., the time periodic problem has no positive solution and the solution of the initial value problem tends to zero when principal eigenvalue is non-negative, while the time periodic positive solution exists uniquely and is globally asymptotically stable when principal eigenvalue is negative.Comment: 17 page

Social Media, Public Discourse and Civic Engagement in Modern China

Drawing on the theoretical view of cyberspace’s role in engagement in public discourse and civic activities, the current study investigates how social media use is related to public discourse and civic engagement in mainland China. Moreover, we examine how political interest, general trust in people, and life satisfaction modify the interdependence of social media use and public discourse and civic engagement. Data analyses based on a survey of 1, 202 online Chinese show that social media use is significantly related to both public discourse and civic engagement. In addition, political interest has a consistent, strong modification on the role of social media use in public discourse and civic engagement. Both general trust in people and life satisfaction moderate some of the relationships examined but not all of them. Theoretical and empirical implications of the results are discussed

Exploring the effects of traditional media, social media, and foreign media on hierarchical levels of political trust in China

Although there is a consensus that mass media play an important role in the rise and fall of political trust in Western democracies, existing research on media use and political trust in China achieved relatively inconclusive findings. By using two surveys conducted in China in 2013 and 2018, we examine the effects of media use, including traditional media, social media, and foreign media, on Chinese citizens’ trust in their central and local governments. Our research shows that traditional media usage such as watching TV and reading newspapers is positively associated with citizens’ trust in the central government but is not related to their trust in local governments. Social media usage is negatively associated with trust in local governments but not with trust in the central government. Using VPNs to access foreign media is negatively associated with Chinese citizens’ trust in the central government but does not affect their trust in local governments. We explain why different types of media have such contrasting effects on political trust in central versus local Chinese governments and discuss the theoretical and empirical implications of these findings

Co-Evolution of Transportation and Land Use: Modeling HIstorical Dependencies in Land Use and Decision-Making

The interaction between land use and transportation has long been the central issue in urban and regional planning. Models of such interactions provide vital information to support many public policy decisions, such as land supply, infrastructure provision, and growth management. Both the transportation and land use systems exhibit historical dependencies in policy decisions. For instance, the expansion of a roadway today will change travel demand patterns, and make certain other roads more or less likely to be expanded in the future. A specific land supply decision made at one point in time, by changing the relative attractiveness of other areas in the region, can have a profound impact on future land supply decisions. Today’s land use decisions clearly influence future transportation policies and vice versa. This project examines the land use-transportation interaction from an evolutionary perspective — once a certain set of goals are determined and pursued by politicians and planners, their land supply and transportation investment decisions are, to a large extent, driven by their previous decisions and supply-demand dynamics in the urban system. Built upon this recognition of historical dependency and a transportation network growth model previously developed by the P.I., a model of the co-evolution of land use and transportation is proposed in this project. Different from existing integrated land use and transportation models that assume exogenous network investment decisions, the co-evolution model considers both land use growth and transportation network growth as endogenous and market-driven. The central research question is how market and policies translate into transportation facilities and land use developments on the ground. The co-evolution model achieves an Urban Growth Equilibrium, which is a useful concept for planning and policy analysis. An agent-based simulation approach is employed to integrate an existing land use model and the transportation network growth model

A differential Feedback Scheme Exploiting the Temporal and Spectral Correlation

International audienceChannel state information (CSI) provided by limited feedback channel can be utilized to increase the system throughput. However, in multiple input multiple output (MIMO) systems, the signaling overhead realizing this CSI feedback can be quite large, while the capacity of the uplink feedback channel is typically limited. Hence, it is crucial to reduce the amount of feedback bits. Prior work on limited feedback compression commonly adopted the block fading channel model where only temporal or spectral correlation in wireless channel is considered. In this paper, we propose a differential feedback scheme with full use of the temporal and spectral correlations to reduce the feedback load. Then, the minimal differential feedback rate over MIMO time-frequency (or doubly) selective fading channel is investigated. Finally, the analysis is verified by simulation results