This paper investigates the performances of secure communications over non-small-scale fading channels. Specifically, considering three different cases when the main and eavesdropper channels experience independent lognormal fading, correlated lognormal fading, or independent composite fading, we study the average secrecy capacity and secrecy outage [including the probability of nonzero secrecy capacity (PNSC) and secure outage probability (SOP)] for these channel conditions. The approximated closed-form expressions for the average secrecy capacity, PNSC, and SOP are derived for these three different types of non-small fading channels. The accuracy of our performance analysis is verified by simulation.

In this paper, a single-input multiple-output (SIMO) simultaneous wireless information and power transfer system consisting of one base station, one desired information receiver and N (N > 1) energy-harvesting receivers is considered. Each link in the considered system suffers not only from small-scale fading but also path-loss. In particular, we focus on the physical layer security performance including secrecy outage and secrecy capacity in the presence of eavesdroppers. We derive the closed-form analytical expression for the exact and the asymptotic secrecy outage probability while considering each eavesdropping link experiences independent but not necessarily identical Rayleigh fading. The closed-form analytical expression for the average secrecy capacity has also been derived for the case that all eavesdropping links experience independent and identical Rayleigh fading. Numerical and Monte Carlo simulation results are presented to verify our derived analytical models.

An underlay cognitive radio unit over Nakagami- m fading channel, which consists of a source S, a secondary user (SU), and an eavesdropper who wants to eavesdrop the information between S and SU, is considered. The transmit power of S is simultaneously adjusted according to the channel state information of S-PU link and a given threshold interference power that the primary user can tolerate. Closed-form analytical expressions of secrecy outage probability and the probability of nonzero secrecy capacity have been derived. The validity of our analysis models is verified by simulation results.

Measurement and quantification of defects are the key challenges for eddy current pulsed thermography (ECPT), localization and detection of surface, sub-surface defects and the quantification of the defects under complex geometry in particular. To address this issue, this paper proposed a 3D eddy current pulsed thermography system by integration the ECPT system with an RGB-D (3D point cloud with RGB texture information) camera. The thermal image is mapped to the RGB-D image via matched features from the thermal and visible image. In order to establish reliable key-point matches for multi-spectrum image registration, a new Shape Constrained Scale Invariant Feature Transform (SCSIFT) descriptor is proposed, which adds global shape information to SIFT descriptor. The experimental study has validated that the developed feature matching algorithm for the mapping of thermal image to RGB-D image. The newly developed 3D ECPT system provides quantified data including 3D heat distribution as well as the 3D spatial relationship between defect position, the excitation coil and the whole specimen, which shows its potential of quantitative evaluation of the defect characteristics.

To meet the great needs for MFL (magnetic flux leakage) inspection of drill pipes at wellheads, a lift-off-tolerant MFL testing method is proposed and investigated in this paper. Firstly, a Helmholtz coil magnetization method and the whole MFL testing scheme are proposed. Then, based on the magnetic field focusing effect of ferrite cores, a lift-off-tolerant MFL sensor is developed and tested. It shows high sensitivity at a lift-off distance of 5.0 mm. Further, the follow-up high repeatability MFL probing system is designed and manufactured, which was embedded with the developed sensors. It can track the swing movement of drill pipes and allow the pipe ends to pass smoothly. Finally, the developed system is employed in a drilling field for drill pipe inspection. Test results show that the proposed method can fulfill the requirements for drill pipe inspection at wellheads, which is of great importance in drill pipe safety.

This paper investigates a smart sensing technique for online and automatic evaluation for carbon fiber reinforced polymer (CFRP) structures' integrity. A compressed sensing (CS)-based algorithm framework integrating sampling and defect evaluation together is proposed enabling intelligence of an open-ended waveguide imaging system for the first time. Compared to traditional raster scan designs which require complete sampling, this smart CS technique can generate whole damage pattern while the scanning is conducting, the sensor intelligence is achieved by the proposed algorithm framework rather than seeking a hardware update. The CS enables accumulated downsampling and sparse recovery based on the frequency sparsity of impact damages on CFRP structures. Damage pattern in the reconstructed image can be detected using the proposed histogram threshold edge detection (HTED) algorithm when the image is stabilized enough. Edge-preserving smoothing is used to improve the stability of the reconstructed image. The experimental results illustrate time efficiency of the framework and more accurate damage localization using HTED. The proposed smart CS technique is attractive in quality control of CFRPs production. This technique can also be applied to situations where the sampled data is partly lost. Dispensing with hardware updates incurs minimum disruption and also benefits cost control and improves the productivity.