Electromagnetic Acoustic Transducer (EMAT) has become one of the fastest-growing solutions for pipeline weld inspection over the past decade due to its non-contact advantage. One primary problem of EMAT is that it has relatively lower energy transition efficiency compared to widely used piezoelectric transducers, coupled with the effect of lift-off and the non-uniformity issue of welding material, the Signal-to-Noise Ratio (SNR) can be significantly restricted. This brings great difficulty in interpreting the EMAT signal measured from pipeline girth welds. To overcome this challenge, this paper presents a deep learning-based ultrasonic pattern recognition method to identify the pipeline girth weld cracking automatically. The proposed method utilizes a deep Convolution Neural Network (CNN) integrated with a pre-trained Support Vector Machine (SVM) classifier to extract the high-level features from the time-frequency representation of A-scan signals measured by bulk-wave EMAT and classify these signals into defective or non-defective groups. To validate the proposed method, a set of experiments is carried out to classify A-scan signals measured from the girth welds of an ex-service type 813-X70 gas pipeline. A comparative investigation is also undertaken to demonstrate the superiority of the proposed method against the conventional ultrasonic pattern recognition methods for evaluation.

Magnetic flux leakage (MFL) detection methods are widely used to detect pipeline defects. However, it is limited by the detection orientation and magnetization. Besides, bulky excitation systems are incapable of adapting to the complex detection environments. This article proposes a new electromagnetic structured coupling sensing of merging alternating current field measurement and MFL within a multiparameter system for different types of pipeline defects detection. In particular, a novel electromagnetic coupling sensor structure is proposed, which enables simultaneous interaction between the excitation modes of yoke and coil. Magnetic yoke is integrated to magnetizing the axial pipeline to detect the circumferential surface and subsurface defects while the coil excites the circumferential uniform alternating current field and recognizes the axial defect. The novel structured sensing is highly sensitive to the detection of both surface and subsurface defects. Simulation and experiments on defects in several samples have been conducted to validate the reliability and efficiency of the proposed system.

Eddy current testing (ET) and eddy current thermography (ECT) are both important nondestructive testing methods that have been widely used in the field of conductive materials evaluation. Conventional ECT systems have often employed to test static specimens even though they are inefficient when the specimen is large. In addition, the requirement of high-power excitation sources tends to result in bulky detection systems. To mitigate these problems, in this article, a moving detection mode of multiphysics structured ET and ECT is proposed in which a novel L-shape ferrite magnetic yoke circumambulated with array coils is designed. The theoretical derivation model of the proposed method is developed which is shown to improve the detection efficiency without compromising the excitation current by ECT. The specimens can be speedily evaluated by scanning at a speed of 50–250 mm/s while reducing the power of the excitation current due to the supplement of ET. The unique design of the excitation-receiving structure has also enhanced the detectability of omnidirectional cracks. Moreover, it does not block the normal direction visual capture of the specimens. Both numerical simulations and experimental studies on different defects have been carried out and the obtained results have shown the reliability and detection efficiency of the proposed system.

This article is concerned with thermoelastic behavior of an elastic media with temperature-dependent properties. The formulations of anisotropic media with variable material properties are proposed by the Clausius inequality and generalized theory of thermoelasticity with one relaxation time, where the higher-order expansion of the Helmholtz free energy with respect to increment temperature is used to obtain the relations between each parameter and real temperature. The governing equations of isotropic media with temperature-dependent properties are obtained based on these formulations. The problem of a half-space formed of an isotropic media with variable material properties and subjected to a sudden temperature rise in the boundary has been conducted. The propagations of thermoelastic wave and thermal wave, as well as the distributions of displacement, temperature, and stresses in the different cases, including constant properties and variable properties with specific temperature and real temperature, are obtained and plotted to reveal the effect of variable material properties on thermoelastic behavior.

An AT-cut third-overtone 100-MHz quartz crystal resonator was used to achieve a 100-MHz low-phase-noise voltage-controlled crystal oscillator prototype. The unloaded quality factor of the used resonator is about 132 K, and the equivalent dynamic capacitance is about 1.2 fF. For the characteristic of the large equivalent dynamic capacitance of the resonator, the design method and the actual measured data of the low-phase-noise oscillator prototype are given. An explanation of why larger equivalent dynamic capacitance and higher voltage-control sensitivity can lead to bad phase noise in half-bandwidth is given. The STM32F103RCT6 MCU is used to read the real-time data of temperature sensor of the microprocessor temperature-compensated crystal oscillator (MTCXO) and the real-time control voltage loading on the MTCXO. Therefore, the real-time communication between a personal computer and an MTCXO is achieved. The control voltage $V$ achieved in this way has already considered both the effect of the actual working condition of the MTCXO circuit and the effect of the MTCXO internal reference voltage that it is not accurate enough. After temperature compensation, the measured temperature performance of the 100-MHz low-phase-noise MTCXO are better than ±0.45 ppm/-30 ^° C -+50 ^° C, and measured phase noise results are better than -157 dBc/Hz at 1 KHz and -170 dBc/Hz at 10 KHz.