Yanshan University

About: Yanshan University is a education organization based out in Qinhuangdao, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 19544 authors who have published 16904 publications receiving 184378 citations. The organization is also known as: Yānshān dàxué.

An adaptive point-of-interest recommendation method for location-based social networks based on user activity and spatial features

Abstract: Point-of-interest (POI) recommendations can help users effectively explore new locations according to their preferences, which is an important research aspect for location-based social networks (LBSNs) However, most existing POI recommendation methods lack adaptability when making recommendations for users with different preferences, which causes unsatisfactory recommendation results To this end, in this paper, we propose an adaptive POI recommendation method by combining user activity and spatial features, which can operate adaptively according to user activity First, we extract three-dimensional user activity, time-based POI popularity and distance features using a probabilistic statistical analysis method from historical check-in datasets on LBSNs Second, we devise a user activity clustering algorithm that is based on fuzzy c-means and compute POI popularity by applying smoothing technology to adjacent continuous time slots Finally, we propose an adaptive recommendation scheme, which includes a two-dimensional Gaussian kernel density estimation algorithm and a one-dimensional power-law function algorithm with POI popularity according to user activity Extensive experiments on Foursquare and Gowalla datasets show that the proposed method outperforms the baseline methods in terms of both precision and recall

Reaction Mechanism of the Low-Temperature Water–Gas Shift Reaction on Au/TiO2 Catalysts

Abstract: The redox and associative mechanisms for the low-temperature water–gas shift (WGS) reaction on Au/TiO2 catalysts are thoroughly examined by density functional theory calculations and microkinetic studies For the redox mechanism, we have observed that the presence of a gold cluster and extra oxygen vacancies on a TiO2 surface is vital for the WGS reaction, especially for the process of H2 release For the associative mechanism via intermediate species, it is very hard for COOH to be generated in the WGS reaction HCOO could be generated, while HCOO should only be a product of side reactions because of the difficulty in H2 release The present results indicate that the WGS reaction on Au/TiO2 catalysts can be well explained by the redox mechanism The present understanding of the mechanism should open a new door for catalyst design in WGS reactions

Output Feedback Distributed Containment Control for High-Order Nonlinear Multiagent Systems

Abstract: In this paper, we study the problem of output feedback distributed containment control for a class of high-order nonlinear multiagent systems under a fixed undirected graph and a fixed directed graph, respectively. Only the output signals of the systems can be measured. The novel reduced order dynamic gain observer is constructed to estimate the unmeasured state variables of the system with the less conservative condition on nonlinear terms than traditional Lipschitz one. Via the backstepping method, output feedback distributed nonlinear controllers for the followers are designed. By means of the novel first virtual controllers, we separate the estimated state variables of different agents from each other. Consequently, the designed controllers show independence on the estimated state variables of neighbors except outputs information, and the dynamics of each agent can be greatly different, which make the design method have a wider class of applications. Finally, a numerical simulation is presented to illustrate the effectiveness of the proposed method.

Taming the collapse of optical fields.

Abstract: Field collapse, which occurs in various nonlinear systems, has attracted much attention, owing to its universality, complexity and applicability. A great challenge and expectation is to achieve the controllable and designable collapsing pattern. Here we predict theoretically and demonstrate experimentally the novel collapsing behaviors of the vector optical fields in a self-focusing Kerr medium. Surprisingly, the results reveal that the collapse of the vector optical field is controllable and designable by engineering the distribution of hybrid states of polarization and has the robust feature insensitive to the random noise. Our idea has its significance which it opens a new window for manipulating the optical field and the different kinds of field and then facilitates to push the related researches.