Static electrical contact resistance (ECR) has been well researched. To investigate the dynamic performance of electrical connector under vibration, a test apparatus is built to measure the ECR with high precision. The ECRs are tiny and suffer from noise. Therefore, a wavelet packet transform-based denoising method is proposed. This method can filter noise with frequency components ranging from low to high. The dynamic characteristics of ECR are presented after an analysis of the measured results. Moreover, the connector intermittent fault (IF) performance under vibration is characterized and analyzed. Finally, an ECR model for rough surfaces under vibration is proposed, based on which the discovered laws are theoretically analyzed. The detected dynamic characteristic of ECR and IF can support an online diagnosis of connectors in further research.

The lateral line is a critical mechanosensory organ that enables fish to perceive the surroundings accurately and rapidly. Massive efforts have been made to build an artificial lateral line system rivaling that of fish for underwater vehicles. Dipole source localization has become a standard problem for evaluating the sensing capabilities of the developed systems. In this paper we propose, for the first time, the MUSIC (multiple signal classification) method in order to achieve high-resolution dipole source localization based on spatial spectrum estimation. We also present the MVDR (minimum variance distortionless response) method by making an improvement to the previous Capon's method. Experiments are conducted on a linear prototype of lateral line canal and the localization performance of these two methods are compared. The results show that the MUSIC method provides an overall localization resolution improvement of 10.4% and maintains similar levels of localization accuracy compared with the MVDR method. Further studies show that the MUSIC method has the potential of localizing two closer incoherent dipole sources with a minimum lateral separation of 20 mm, versus 70 mm for the MVDR method, at a dipole-array distance of half the array length. Both localization methods have strong robustness to the vibrational state of the dipole source. Our work provides a promising and robust way to meet the high-resolution and multi-source sensing requirements of underwater vehicles.

Based on the dynamic properties of electrical connector intermittent failure, the model and methods for residual life prediction for electrical connectors are studied in this paper. Firstly, the mechanism of electrical connector intermittent failure is analyzed, and the area enclosed by the contact resistance curve and the fault threshold is defined as the generalized severity of intermittent failure to describe how severe the electrical connector’s intermittent failure is. Then, the Hidden Semi-Markov Model (HSMM) is introduced to build the residual life prediction model of the electrical connector. Further, the evaluation method of using the state and prediction method for residual life are studied. Finally, by carrying out the residual life prediction test, the effectiveness of the residual life prediction method for electrical connectors based on intermittent failure and HSMM is verified.

Suspended graphene can perfectly present the excellent material properties of graphene, which has a good application prospect in graphene sensors. The existing suspended graphene pressure sensor has several problems that need to be solved, one of which is the fabrication of a suspended sample. It is still very difficult to obtain large-size suspended graphene films with a high integrity that are defect-free. Based on the simulation and analysis of the kinetic process of the traditional suspended graphene release process, a novel setup for large-size suspended graphene release was designed based on the inverted floating method (IFM). The success rate of the single-layer suspended graphene with a diameter of 200 μm transferred on a stainless-steel substrate was close to 50%, which is greatly improved compared with the traditional impregnation method. The effects of the defects and burrs around the substrate cavity on the stress concentration of graphene transfer explain why the transfer success rate of large-size suspended graphene is not high. This research lays the foundation for providing large-size suspended graphene films in the area of graphene high-precision sensors.

Testability is a new critical characteristic of equipment, and testability demonstration test plays an important role in assuring the designed testability levels. As a result of the complex structure and higher cost of the current equipment, a reasonable testability demonstration test plan can both guarantee the desired testability level and effectively decrease the test cost. This article considers the testability demonstration test planning with the binomial distribution. The sequential posterior odds test method that combines Bayesian method and sequential probability ratio test method is used to form a sequential decision process by calculating the Bayes factor and making judgment according to the test result sequentially. With a sequential decision criterion, the test result space is divided into three subspaces, based on which a Bayes factor threshold calculation method is presented according to the restriction parameters and prior probability density function of the testability index. Operation characteristic and average sampling number are compared among the classical method, sequential probability ratio test method and the sequential posterior odds test method, which shows that with nearly the same operation characteristic, sequential posterior odds test method has smaller average sampling number than sequential probability ratio test method and classical method. The impact of prior parameters on the sequential posterior odds test method is analyzed, and the results indicate that the sequential posterior odds test method can perform well with a range of prior parameters. Physical testability demonstration tests are carried out to verify the features of sequential posterior odds test and sequential probability ratio test methods. The result indicates that with the same restriction parameters and test condition, the sample size of sequential posterior odds test is smaller than the sample size of sequential probability ratio test as a result of the introduction of prior information.