An Experimental Study of the Feasibility of Identifying the Impact Damages of Reinforced Concrete Piers Using a Modal Frequency Method

In this research study, horizontal impact tests were carried out on five reduced scale pier models using China’s most advanced multifunctional ultrahigh heavy drop hammer impact test system and DHDAS dynamic signal acquisition and analysis system. Due to the fact that the traditional measurement method can only be used for local measurement damage, and the volatility is high, this paper proposes a test method for the modal frequency identification of the overall damage of reinforced concrete pier and applies the ultrasonic damage measurement method to verify the results. The tests analyzed the modal frequencies and ultrasonic velocity identifications for the purpose of evaluating the impact damages of bridge piers, as well as the relationship between them. The results showed that the modal frequencies were consistent with the ultrasonic waves in identifying and evaluating the damages to the piers. Also, the modal frequency damage factors were determined to be functions of the ultrasonic wave velocity damage factors. Therefore, the results of this study confirmed that it was feasible to characterize the impact damages of piers using a modal frequency method

The preparation and properties of photocatalytic composites based on palygorskite/molybdenum disulfide

The pollution problem resulting from advancements in science and technology is increasingly severe, particularly concerning organic pollution. Photocatalytic technology is considered one of the most effective methods for treating organic pollution due to its cost-effectiveness, simplicity of operation, high efficiency, and versatility. In this study, palygorskite was purified and extracted using techniques such as ultrasonication, high-speed stirring, centrifugation, and others. Molybdenum disulfide (MoS2) was synthesized in situ on the palygorskite surface through hydrothermal synthesis, resulting in palygorskite/MoS2 nanocomposites. The structure and apparent morphology of the palygorskite/MoS2 composites were analyzed using characterization methods such as transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and others. MoS2 interacted with the hydroxyl groups on the palygorskite surface through amino groups, leading to the dispersion of MoS2 nanosheets on the palygorskite surface, forming a unique nanoflower structure. To assess the photocatalytic degradation performance of palygorskite/MoS2 composites, Rhodamine B was employed as the target pollutant. Under conditions of a pH of 6, a reaction time of 170 min, and a solution concentration of 1500 mg/l, palygorskite/MoS2 composites achieved a Rhodamine B removal amount of 371.73 mg/g. Notably, these composites facilitated the degradation of Rhodamine B into intermediate chain-broken products. The findings of this study hold significant implications for the advancement of clay mineral-based photocatalytic composites and the effective removal of organic pollutants

One-Step or Two-Step Acid/Alkaline Pretreatments to Improve Enzymatic Hydrolysis and Sugar Recovery from Arundo Donax L.

Energy crops are not easily converted by microorganisms because of their recalcitrance. This necessitates a pretreatment to improve their biodigestibility. The effects of different pretreatments, as well as their combination on the enzymatic digestibility of Arundo donax L. were systematically investigated to evaluate its potential for bioconversion. Dilute alkaline pretreatment (ALP) using 1.2% NaOH at 120 °C for 30 min resulted in the highest reducing sugar yield in the enzymatic hydrolysis process because of its strong delignification and morphological modification, while ferric chloride pretreatment (FP) was effective in removing hemicellulose and recovering soluble sugars in the pretreatment stage. Furthermore, an efficient two-step ferric chloride-alkaline pretreatment (FALP) was successfully developed. In the first FP step, easily degradable cellulosic components, especially hemicellulose, were dissolved and then effectively recovered as soluble sugars. Subsequently, the FP sample was further treated in the second ALP step to remove lignin to enhance the enzymatic hydrolysis of the hardly degradable cellulose. As a result, the integrated two-step process obtained the highest total sugar yield of 420.4 mg/g raw stalk in the whole pretreatment and enzymatic hydrolysis process; hence, the process is a valuable candidate for biofuel production