Compressive and flexural strength are the crucial properties of a material. The strength of recycled aggregate concrete (RAC) is comparatively lower than that of natural aggregate concrete. Several factors, including the recycled aggregate replacement ratio, parent concrete strength, water–cement ratio, water absorption, density of the recycled aggregate, etc., affect the RAC’s strength. Several studies have been performed to study the impact of these factors individually. However, it is challenging to examine their combined impact on the strength of RAC through experimental investigations. Experimental studies involve casting, curing, and testing samples, for which substantial effort, price, and time are needed. For rapid and cost-effective research, it is critical to apply new methods to the stated purpose. In this research, the compressive and flexural strengths of RAC were predicted using ensemble machine learning methods, including gradient boosting and random forest. Twelve input factors were used in the dataset, and their influence on the strength of RAC was analyzed. The models were validated and compared using correlation coefficients (R2), variance between predicted and experimental results, statistical tests, and k-fold analysis. The random forest approach outperformed gradient boosting in anticipating the strength of RAC, with an R2 of 0.91 and 0.86 for compressive and flexural strength, respectively. The models’ decreased error values, such as mean absolute error (MAE) and root-mean-square error (RMSE), confirmed the higher precision of the random forest models. The MAE values for the random forest models were 4.19 MPa and 0.56 MPa, whereas the MAE values for the gradient boosting models were 4.78 MPa and 0.64 MPa, for compressive and flexural strengths, respectively. Machine learning technologies will benefit the construction sector by facilitating the evaluation of material properties in a quick and cost-effective manner.

Pure mode I and mode II fracture toughness of asphalt mixture was investigated both experimentally and theoretically using vertical edge crack semicircular bend (SCB) specimen with symmetric and asymmetric bottom loading spans. The thickness of SCB specimen was considered in the range from 30 to 70 mm, and the fracture toughness tests were performed at three subzero temperatures (−5 C, −15 C and −25 C). The results showed that K Ic and K IIc are increased by reducing the test temperature. The thickness had no sound effect on the fracture toughness, but the thickness of 50 mm was more suitable for fracture study on this material. The fracture load of mode II specimen was significantly greater than the mode I fracture load at the same testing condition. The fracture toughness ratio (K IIc /K Ic) that varies in the range between 1 and 1.4 was predicted theoretically using three well-known stress/strainbased fracture criteria. K E Y W O R D S asphalt mixture, fracture toughness ratio prediction, K Ic and K IIc value, low temperature, symmetric and asymmetric SCB specimens, thickness effect

In this Letter, a polarimetric analyzer is designed for a mid-wave infrared camera. This kind of infrared camera transforms into the mid-wave infrared polarization imaging system to measure the infrared polarization characteristics of the object in the moving scene. The polarimetric analyzer is designed by using the ultra-high-speed and high-position method to drive the polarizer to rotate uniformly at the speed of 900 rpm. The polarization state of the object scene is changed, and the mid-wave infrared camera synchronously acquires the infrared intensity image in different polarized directions, those of 0°, 120°, and 240°. Then, a Stokes vector model is established with the basic rotation angles, and a sort-iteration method is proposed to process the original infrared intensity image. Three continuously neighboring infrared intensity images are used to calculate the degree of linear polarization (DoLP) and the angle of polarization (AoP), which make the infrared polarization image the same imaging frame as the infrared intensity image. Test results show that the mid-wave infrared polarization imaging system can complete the acquisition of the DoLP and the AoP images well with the frame frequency of 45 fps, which is suitable for the infrared polarization detection of the moving scenes. The study has great potential for polarization remote sensing and marine object detection.

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Through the foam concrete block cement type, water reducer type, content and tailings using water reducing powder content of the different experimental groups, analyzed the relationship between raw material composition and amount due to compressive strength of foam concrete and different effects of moisture content and compressive strength, and thus presumably the ideal mix. It can be used for future theoretical study reference.

Extreme impedance mismatch causes sound insulation at water–air interfaces, limiting numerous cross‐media applications such as ocean‐air wireless acoustic communication. Although quarter‐wave impedance transformers can improve transmission, they are not readily available for acoustics and are restricted by the fixed phase shift at full transmission. Here, this limitation is broken through impedance‐matched hybrid metasurfaces assisted by topology optimization. Sound transmission enhancement and phase modulation across the water–air interface are achieved independently. Compared to the bare water–air interface, it is experimentally observed that the average transmitted amplitude through an impedance‐matched metasurface at the peak frequency is enhanced by ≈25.9 dB, close to the limit of the perfect transmission 30 dB. And nearly 42 dB amplitude enhancement is measured by the hybrid metasurfaces with axial focusing function. Various customized vortex beams are experimentally realized to promote applications in ocean‐air communication. The physical mechanisms of sound transmission enhancement for broadband and wide‐angle incidences are revealed. The proposed concept has potential applications in efficient transmission and free communication across dissimilar media.

Acoustic Metasurfaces By utilizing hybrid impedance‐matched metasurfaces floating on the water‐air interface, sound waves under the water can be perfectly transmitted to the air with arbitrary desired wavefronts, such as acoustic vortex, thereby greatly improving ocean‐air communication efficiency. More details can be found in article number 2207181 by Yan‐Feng Wang, Yue‐Sheng Wang, and co‐workers.

The research of light thermal insulation composite wall has great significance to the study of alleviating the energy shortage situation and promoting the sustainable development of China. In this paper, the gray correlation analysis was carried out to determine the indicators that influence the bending resistance, including the thickness of the light steel keel, the thickness of the fiber cement plate and the foaming ratio of the concrete. The results of the gray correlation analysis are consistent with the test results of the wall, which indicates that the method of grey correlation analysis can be used to analyze the bending resistance of thermal insulation composite wall, which has a strong practicality.