Critical Nodes Identification: A Non-Cooperative Method for Unknown Topology Information in Ad Hoc Networks

The foundation of ad hoc networks lies in the guarantee of continuous connectivity.However,critical nodes,whose failure can easily destroy network connectivity,will influence the ad hoc network connectivity significantly.To protect the network efficiently,critical nodes should be identified accurately and rapidly.Unlike existing critical node identification methods for unknown topology that identify critical nodes according to historical information,this paper develops a critical node identification method to relax the prior topology information condition about critical nodes.Specifically,we first deduce a theorem about the minimum communication range for a node through the number of nodes and deployment ranges,and prove the universality of the theorem in a realistic two-dimensional scenario.After that,we analyze the relationship between communication range and degree value for each node and prove that the greater number of nodes within the communication range of a node,the greater degree value of nodes with high probability.Moreover,we develop a novel strategy to improve the accuracy of critical node identification without topology information.Finally,simulation results indicate the proposed strategy can achieve high accuracy and low redundancy while ensuring low time consumption in the scenarios with unknown topology information in ad hoc networks.

A Cooperative Security Monitoring Mechanism Aided by Optimal Multiple Slave Cluster Heads for UASNs

As each cluster head(CH)sensor node is used to aggregate,fuse,and forward data from different sensor nodes in an underwater acoustic sensor network(UASN),guaranteeing the data security in a CH is very critical.In this paper,a cooperative security monitoring mechanism aided by multiple slave cluster heads(SCHs)is proposed to keep track of the data security of a CH.By designing a low complexity“equilateral triangle algorithm(ETA)”,the optimal SCHs(named as ETA-based multiple SCHs)are selected from the candidate SCHs so as to improve the dispersion and coverage of SCHs and achieve largescale data security monitoring.In addition,by analyzing the entire monitoring process,the close form expression of the probability of the failure attack identification for the SCHs with respect to the probability of attack launched by ordinary nodes is deduced.The simulation results show that the proposed optimal ETA-based multiple SCH cooperation scheme has lower probability of the failure attack identification than that of the existing schemes.In addition,the numerical simulation results are consistent with the theoretical analysis results,thus verifying the effectiveness of the proposed scheme.

Design and performance analysis of wireless sensor network location node system for underground mine

Aiming at the application of a wireless sensor network to locating miners in underground mine,we design a wireless sensor network location node system,considering the communication performance and the intrinsic safety. The location node system consists of a mobile node,several fixed nodes,and a sink node,all of whose circuits were designed based on CC2430. A varistor and a RC circuit were used in the reset circuit of a sensor node to guarantee the intrinsic safety by reducing discharge energy,the theoretical analysis of the discharge energy shows that the reset circuit is an intrinsic safety one. The analysis and simulation about the performance of the location node system are discussed,such as network communication delay and packet loss rate,the results show that the highest network communication delay of the system is about 0.11 seconds,and the highest packet loss rate is about 0.13,which assures the location node system has a high reliability,and can locate miners in the underground mine.

Location of Sentinel Lymph Node in Gastric Cancer:A Modified,Painless And Noninvasive Approach

Objective： The presence of lymph node metastases is an important factor in the prognosis of gastric cancer patient. Therefore, the precise identification of sentinel lymph nodes （SLN） in these patients is critical. In this work, we investigated the feasibility and preciseness by injection of 99mTc-sulfur colloid （SC） 2 hours before operation after general anesthesia, instead of one day before surgery. Methods： Thirty-one patients of gastric cancer diagnosed as T1-T3 were enrolled in this study. During operation, a SLN was defined as those containing 10 times more radioactivity than surrounding tissue with a hand-held gamma probe and removed. All the patients underwent radical gastrectomy with extended lymphadenectomy. All resected nodes were examined postoperatively by routine H＆E stain and those negative SLNs were examined with further cytokeratin immunohistochemistical staining. Results： The incidence of metastasis was significantly higher in SLNs than in non-SLNs （x2=67.48, P〈0.001）. The overall sensitivity, specificity and accuracy of the SLN status in the diagnosis of the lymph node status of the patient were 86.36%, 100% and 96.77%, respectively. The positive predictive value and negative predictive value of SLN biopsy were 100%, and 75.0%, respectively. SLNs were used to diagnose the lymph node status with 100% accuracy in the T1 group. In the T2 and T3 groups, the sensitivity, specificity, and diagnostic accuracy were 92.3%, 100%, and 94.44%, 60.0%, 100%, and 66.66%, respectively. Most of the SLNs were located in the #1, #2, #3, #4, #5, and #6, except in 3 patients （9.68%）.With cytokeratin immunohistochemical staining, lymphatic pathologic staging in 1 patient was upstaged. Conclusion： SLN biopsy with the above approach is a feasible and accurate diagnostic procedure for detecting lymph node metastasis in patients with gastric cancer, which is painless, noninvasive, easily accepted by patients and suitable for extensive clinical applications.

Real-time localization estimator of mobile node in wireless sensor networks based on extended Kalman filter

Localization of the sensor nodes is a key supporting technology in wireless sensor networks （WSNs）. In this paper, a real-time localization estimator of mobile node in WSNs based on extended Kalman filter （KF） is proposed. Mobile node movement model is analyzed and online sequential iterative method is used to compute location result. The detailed steps of mobile sensor node self-localization adopting extended Kalman filter （EKF） is designed. The simulation results show that the accuracy of the localization estimator scheme designed is better than those of maximum likelihood estimation （MLE） and traditional KF algorithm.

Research on reference nodes placement and selection of ubiquitous computing locating service

Obtaining the location of an unknown node accurately is a key problem of a locating service under a ubiquitous computing environment.The paper proposes and proves three theorems of location reference node placement according to the analysis of the location error produced during location using a polygon location method and three important characteristics of chaos dynamics.Based on the three theorems,the location reference node selection(LRNS)algorithm is proposed by improving on the traditional polygon location algorithm.The simulation results indicate that the reference node placement theorems and the LRNS algo-rithm can meet the requirements of a ubiquitous terminal’s real-time location and possess a preferable precision in location.

Analysis of the influence of node location on transducer performance

This paper, taking the distance between the piezoelectric ceramic center and the displacement node location of the transducer as a parameter, investigates the relation of characteristic parameters of transducer, such as force factor, equivalent resistance, potential maximum electroacoustical efficiency, and loading performance, to the displacement node location. Some design considerations about the selection of node location are noted .