Mingchu Li

Bridge Displacement Monitoring Method Based on Laser Projection-Sensing Technology

Bridge displacement is the most basic evaluation index of the health status of a bridge structure. The existing measurement methods for bridge displacement basically fail to realize long-term and real-time dynamic monitoring of bridge structures, because of the low degree of automation and the insufficient precision, causing bottlenecks and restriction. To solve this problem, we proposed a bridge displacement monitoring system based on laser projection-sensing technology. First, the laser spot recognition method was studied. Second, the software for the displacement monitoring system was developed. Finally, a series of experiments using this system were conducted, and the results show that such a system has high measurement accuracy and speed. We aim to develop a low-cost, high-accuracy and long-term monitoring method for bridge displacement based on these preliminary efforts.

Initial Validation of Mobile-Structural Health Monitoring Method Using Smartphones

The structural health monitoring system has made great development nowadays, especially on bridge structures. Meanwhile, most SHM systems reported were designed, integrated, and installed into large-scale infrastructures by professionals and equipped with expensive sensors, data acquisition devices, data transfer systems, and so forth. And it is impossible to install SHM system for every civilian building. For this status, a kind of new idea for structural health monitoring using smartphone is introduced in this paper. A smartphone, with embedded responding SHM software and inner sensors or external sensors, can be used not only as a single wireless sensor node but also as a mini-SHM system. The method is described in detail, and then the swing test, cable force test in laboratory, and cable force test on an actual bridge based on the iPhone were conducted to validate the proposed method. The experimental results show that Mobile-SHM using smartphone is feasible. The realization of Mobile-SHM method using smartphones may be considered as a milestone in making SHM popular in the lives of people.

Attribute-based ring signcryption scheme

In this paper, we present attribute-based ring signcryption scheme, which realizes the concept of ring signcryption in the attribute-based encryption frame firstly. In our system, it allows a user to signcrypt a message by a set of attributes that are chosen without revealing its identity. In additional, we propose the security models and prove the confidentiality and unforgeability of our schemes. We also present the efficiency of our scheme by comparisons. Copyright

A Cyber-Physical System for Girder Hoisting Monitoring Based on Smartphones

Offshore design and construction is much more difficult than land-based design and construction, particularly due to hoisting operations. Real-time monitoring of the orientation and movement of a hoisted structure is thus required for operators’ safety. In recent years, rapid development of the smart-phone commercial market has offered the possibility that everyone can carry a mini personal computer that is integrated with sensors, an operating system and communication system that can act as an effective aid for cyber-physical systems (CPS) research. In this paper, a CPS for hoisting monitoring using smartphones was proposed, including a phone collector, a controller and a server. This system uses smartphones equipped with internal sensors to obtain girder movement information, which will be uploaded to a server, then returned to controller users. An alarming system will be provided on the controller phone once the returned data exceeds a threshold. The proposed monitoring system is used to monitor the movement and orientation of a girder during hoisting on a cross-sea bridge in real time. The results show the convenience and feasibility of the proposed system.

Experimental Research on Quick Structural Health Monitoring Technique for Bridges Using Smartphone

In the recent years, with the development and popularization of smartphone, the utilization of smartphone in the Structural Health Monitoring (SHM) has attracted increasing attention owing to its unique feature. Since bridges are of great importance to society and economy, bridge health monitoring has very practical significance during its service life. Furthermore, rapid damage assessment of bridge after an extreme event such as earthquake is very important in the recovery work. Smartphone-based bridge health monitoring and postevent damage evaluation have advantages over the conventional monitoring techniques, such as low cost, ease of installation, and convenience. Therefore, this study investigates the implementation feasibility of the quick bridge health monitoring technique using smartphone. A novel vision-based cable force measurement method using smartphone camera is proposed, and, then, its feasibility and practicality is initially validated through cable model test. An experiment regarding multiple parameters monitoring of one bridge scale model is carried out. Parameters, such as acceleration, displacement, and angle, are monitored using smartphone. The experiment results show that there is a good agreement between the reference sensor and smartphone measurements in both time and frequency domains.

On the 2-factor index of a graph

The 2-factor index of a graph G, denoted by f(G), is the smallest integer m such that the m-iterated line graph L^m(G) of G contains a 2-factor. In this paper, we provide a formula for f(G), and point out that there is a polynomial time algorithm to determine f(G).

Self-Healing Key-Distribution Scheme with Collusion Attack Resistance Based on One-Way Key Chains and Secret Sharing in Wireless Sensor Networks

In wireless sensor networks, self-healing key-distribution schemes are used to ensure that, even if the message packets that are broadcast in some sessions get lost, the group nodes can still recover the lost session keys simply by using their personal secret keys and broadcast messages that have been received without requesting additional transmissions from the group manager. These schemes reduce network traffic, decrease the group managers workload, and lower the risk of node exposure through traffic analysis. However, most existing schemes have many deficiencies, such as high overhead for storage and communication and collusion attacks. In this paper, we have proposed a modified, self-healing, key-distribution scheme based on one-way key chains and secret sharing. Our scheme has the properties of constant storage, lower communication overhead, long lifespan, forward secrecy, backward secrecy, and resistance to collusion attacks.

Circumferences and minimum degrees in 3-connected claw-free graphs

In this paper, we prove that every 3-connected claw-free graph G on n vertices contains a cycle of length at least min{n,[emailxa0protected]}, thereby generalizing several known results.

Note: Quadrangularly connected claw-free graphs

A graph G is quadrangularly connected if for every pair of edges e1 and e2 in E(G), G has a sequence of l-cycles ([emailxa0protected][emailxa0protected]?4)C1,C2,...,Cr such that e[emailxa0protected]?E(C1) and e[emailxa0protected]?E(Cr) and E(Ci)@?E(Ci+1) @A for i=1,2,...,r-1. In this paper, we show that every quadrangularly connected claw-free graph without vertices of degree 1, which does not contain an induced subgraph H isomorphic to either G1 or G2 such that N1(x,G) of every vertex x of degree 4 in H is disconnected is hamiltonian, which implies a result by Z. [emailxa0protected]?ek [Hamiltonian circuits in N2-locally connected K1,3-free graphs, J. Graph Theory 14 (1990) 321-331] and other known results.

A new architecture of grid security system construction

Due to the complexity of grid computing, many new security problems have appeared in grid, and so the traditional network security practices can not meet the security demand of grid. As a result, the study of security problems in grid is important, complicated and arduous. In this paper, we propose a new approach to construct grid security systems, and analyze both the disadvantages of current existing grid security systems. Our grid security system framework is positioned as an alternative to the security framework of open grid service architecture (OGSA). Based on our analysis, we conclude that a security system in grid should be composed of two parts: security rule definitions and security rule implementation. We also discuss the advantages of our new security system architecture