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This article presents an integrated double-sided inductance and double capacitances (DS-LCC) compensation based dual-frequency compatible wireless power transfer (WPT) system. A cascaded single-phase multi-frequency inverter (CSMI) is constructed to generate the independent dual-frequency power transfer signals. In order to achieve the load-independent constant-current output (CCO) at two frequencies, an integrated DS-LCC compensated topology is reconstructed. By configuring the frequency-selective resonating compensation (FSRC) network in the primary side, the power transfer signals at two frequencies can be superimposed into a single transmitting coil, reducing the cost and volume of the system. Furthermore, to implement zero-voltage switching (ZVS) of the CSMI throughout the entire power range, a general parameter design method of the proposed system is also introduced. A 1.5-kW experimental prototype is built to validate the practicability of the presented dual-frequency compatible WPT System. The system can supply power to different loads at two frequencies simultaneously with CCO and ZVS properties. The peak efficiency reaches 91.75% at a 1.2-kW output power. [ABSTRACT FROM AUTHOR]

The loading-unloading effect induced by repeated mining disturbance is an important inducement to cause the rock mass failure in roadway engineering. However, there is a lack of research on the mechanical response of the widely distributed weakly cemented sandy mudstone in west China under loading and unloading conditions. In order to solve this problem, the sandy mudstone in borehole BK209 of Shendong Buertai Coal Mine of National Energy Group is taken as the research object, and the uniaxial graded loading and unloading test scheme is adopted (I, II and III loading and unloading paths are set, wherein the loading and unloading path I adopts displacement control, and the loading and unloading paths II and III adopt load control). This paper studies the mechanical and acoustic emission (AE) characteristics of sandy mudstone under different loading and unloading paths. The result shows the following four points. ① Under the loading and unloading path I, the stress of the sample drops rapidly after the stress peak, showing the characteristics of brittleness. Under the loading and unloading path II, the stress drop after the peak stress of the sample is limited and the stress has a certain residual strength. Under loading and unloading path III, the stress of the sample falls after the peak stress, showing certain ductility characteristics. ② The shorter the loading and unloading path, the greater the increase of elastic modulus in the unloading section. The main reason is that the detritus is produced by shear slip in the interface of the new fracture during loading process. When the unloading path is shorts, the detritus falling off under tensile stress fully fills the nearby gap. Therefore, the friction capacity between the fracture surfaces becomes stronger. ③ In the first loading stage, the AE ringing count under the path I is in a symmetrical change of first increasing and then decreasing. The AE ringing count under the path II is in a left-biased peak change. And the AE ringing count under the path III is in a fluctuation change of increasing and decreasing, and the fluctuation in the middle is large. In the second loading stage, under the load paths I and III, when the stress increases to near the peak value and reaches the yield limit of sandy mudstone, the AE ringing count increases sharply and Kaiser point appears. During the last loading to the peak value, the AE ringing count under path I first occurs uniformly and continuously, and then increases gradually. The AE ringing counts under paths II and III occur uniformly and continuously, and the stress near the peak increases in a leaping manner. ④ In the first loading stage, the AE ringing count is less because of the low stress, and the AE is in relatively quiet period. In the unloading stage, there is basically no ring count, and the AE is in intermittent period. With the increase of stress and loading and unloading times, the AE ringing count increases relatively. The AE is in a fluctuating period. During the last loading to the peak value, the sandy mudstone is in the destruction stage, and the AE ringing count increases sharply. The AE enters the active period.

Polyethylene glycol (PEG) is widely used as a phase change material (PCM) in thermal energy storage systems due to its high latent heat and chemical stability. However, practical application has been hindered by its low thermal conductivity and leakage issues. Therefore, developing shape-stable high thermal conductivity PCM is of great importance. In this study, new shape-stable composite PCM with high thermal conductivity and leak-prevention capabilities were designed. The porous carbon skeleton of diamond foam (DF) and dual-3D carbon nanotube-diamond foam (CDF) were prepared using the microwave plasma chemical vapor deposition method. The composite materials (DF/PEG and CDF/PEG) were produced by vacuum impregnation with PEG and skeletons. The results showed that CDF/PEG had the highest thermal conductivity, measuring 2.30 W·m−1·K−1, which is 707% higher than that of pure PEG. The employing of 3D networks of CNTs, which can improve the phonon mean free path in DF/PEG (1.79 W·m−1·K−1) while reducing phonon dispersion.The phonon vibration of dual-3D CDF plays an important role in heat transfer. PEG was physically absorbed and well-distributed in CDF, alleviating leakage of liquid PEG. The weight loss of CDF/PEG was only 25% at 70 °C for 120 s. Using CDF is an attractive and efficient strategy to increase the heat transfer of PEG and improve heat storage efficiency, alleviate the problem of poor shape-stability. [ABSTRACT FROM AUTHOR]

Acoustic emission and infrared radiation measurements were carried out on medium sandstone, fine sandstone and siltstone in the coal measures of the Ordos Basin under uniaxial compression, the stress, the acoustic energy and the average infrared radiation temperature (AIRT) versus time evolution of characteristics were analyzed, the acoustic and the thermal effects characteristics of different granular sandstones during the rupture process were studied.The results show that the AIRT in the different areas of the same sandstone has the same trend in the compaction and elasticity phase,but the tendency is different in the plasticity and damage stages.It generally shows a wave downward trend; and the temperature in the middle is higher than that in the upper and lower parts.The temperature changes in different sandstones are related to energy accumulation and dissipation,and the overall trend of AIRT on the sandstone surface shows a wave downward trend, acoustic emission (AE) is not obvious at the beginning ,but it raise rapidly during the later stage of plasticity, there are still a large number of AE events after the peak; the precursor of infrared radiation priority to the acoustic emission warning, the average infrared warning time of middle sandstone is 20.533s, fine sandstone is 6.516s ahead, and siltstone is 6.4s, but the sensitivity of the acoustic emission is higher than that of the infrared radiation.The acoustic and the thermal effects of sandstone is closely related to the particle size,the larger the particles, the more pronounced the acoustic thermal effects.The sensitivity of the acoustic thermal effect is in the order of medium sandstone, fine sandstone and siltstone.