Ultrasonic Nonlinearity Evaluation of the Cracked Interface

This paper derives a novel analytical solution for acoustic nonlinearity evaluation of the cracked interface. When microcracks exist at the interface, the tensile and compressive effective moduli of the cracked interface are considered to be different. It is clearly shown that the tension and compression elastic asymmetry can result in acoustic nonlinearity. In addition, numerical simulations using the finite element method are conducted to validate the theoretical solution. It is shown that numerical results agree well with the analytical solution. Finally, two factors affecting acoustic nonlinearity are studied based on the analytical solution. One is the tension and compression elastic asymmetry and another is the frequency of incident wave. Different from acoustic nonlinearity parameter of the general second harmonics, it is found that acoustic nonlinearity parameter is a function of two factors

Experimental Study on the Fine Iron Ore Tailing Containing Gypsum as Backfill Material

The strength of the filling body is largely affected by the properties of the binder, mineral composition, fineness, and slurry concentration of tailing. In this paper, the rheological test was conducted to determine the slurry concentration of iron ore tailing containing gypsum. Then, the samples made from slurry and three binders, Portland cement, filling plant binder, and Huazhong binder, were tested, respectively. The effects of curing time, binder-tailing ratio by mass (b/t), and slurry concentration on compression strength were investigated. The sample made from Huazhong binder and iron ore tailing presented the largest compression strength

New Potential Biomarker for Methasterone Misuse in Human Urine by Liquid Chromatography Quadrupole Time of Flight Mass Spectrometry

In this study, methasterone urinary metabolic profiles were investigated by liquid chromatography quadrupole time of flight mass spectrometry (LC-QTOF-MS) in full scan and targeted MS/MS modes with accurate mass measurement. A healthy male volunteer was asked to take the drug and liquid–liquid extraction was employed to process urine samples. Chromatographic peaks for potential metabolites were hunted out with the theoretical [M − H]− as a target ion in a full scan experiment and actual deprotonated ions were studied in targeted MS/MS experiment. Fifteen metabolites including two new sulfates (S1 and S2), three glucuronide conjugates (G2, G6 and G7), and three free metabolites (M2, M4 and M6) were detected for methasterone. Three metabolites involving G4, G5 and M5 were obtained for the first time in human urine samples. Owing to the absence of helpful fragments to elucidate the steroid ring structure of methasterone phase II metabolites, gas chromatography mass spectrometry (GC-MS) was employed to obtain structural information of the trimethylsilylated phase I metabolite released after enzymatic hydrolysis and the potential structure was inferred using a combined MS method. Metabolite detection times were also analyzed and G2 (18-nor-17β-hydroxymethyl-2α, 17α-dimethyl-androst-13-en-3α-ol-ξ-O-glucuronide) was thought to be new potential biomarker for methasterone misuse which can be detected up to 10 days

Ultrasonic Nonlinearity Evaluation of the Cracked Interface

This paper derives a novel analytical solution for acoustic nonlinearity evaluation of the cracked interface. When microcracks exist at the interface, the tensile and compressive effective moduli of the cracked interface are considered to be different. It is clearly shown that the tension and compression elastic asymmetry can result in acoustic nonlinearity. In addition, numerical simulations using the finite element method are conducted to validate the theoretical solution. It is shown that numerical results agree well with the analytical solution. Finally, two factors affecting acoustic nonlinearity are studied based on the analytical solution. One is the tension and compression elastic asymmetry and another is the frequency of incident wave. Different from acoustic nonlinearity parameter of the general second harmonics, it is found that acoustic nonlinearity parameter is a function of two factors

Experimental and Numerical Investigation of the Micro-Crack Damage in Elastic Solids by Two-Way Collinear Mixing Method

This study experimentally and numerically investigated the nonlinear behavior of the resonant bulk waves generated by the two-way collinear mixing method in 5052 aluminum alloy with micro-crack damage. When the primary longitudinal and transverse waves mixed in the micro-crack damage region, numerical and experimental results both verified the generation of resonant waves if the resonant condition ωL/ωT=2κ/(κ−1) was satisfied. Meanwhile, we found that the acoustic nonlinearity parameter (ANP) increases monotonously with increases in micro-crack density, the size of the micro-crack region, the frequency of resonant waves and friction coefficient of micro-crack surfaces. Furthermore, the micro-crack damage in a specimen generated by low-temperature fatigue experiment was employed. It was found that the micro-crack damage region can be located by scanning the specimen based on the two-way collinear mixing method

Cost dynamics of onshore wind energy in the context of China's carbon neutrality target

Wind energy has become one of the most important measures for China to achieve its carbon neutrality goal. The spatial and temporal evolvement of economic competitiveness for wind energy becomes an important concern in shaping the decarbonization pathway in China. There has been an urgent need in power system planning to model the future dynamics of cost decline and supply potential for wind power in the context of carbon neutrality until 2060. Existing studies often fail to capture the rapid decline in the cost of wind power generation in recent years, and the prediction of wind power cost decline is more conservative than the reality. This study constructs an integrated model to evaluate the cost-competitiveness and grid parity potential of China's onshore wind electricity at fine spatial resolution with updated parameters. Results indicate that the total onshore wind potential amounts to 54.0 PWh. The average levelized cost of wind power is expected to decline from CNY 0.39 kWh−1 in 2020 to CNY 0.30 and CNY 0.21 kWh−1 in 2030 and 2060. 28.3%, 67.6%, and 97.6% of the technical potentials hold power costs lower than coal power in 2020, 2030, and 2060

Experimental and Numerical Study of Nonlinear Lamb Waves of a Low-Frequency <i>S</i>₀ Mode in Plates with Quadratic Nonlinearity

This paper investigates the propagation of low-frequency S0 mode Lamb waves in plates with quadratic nonlinearity through numerical simulations and experimental measurements. Both numerical and experimental results manifest distinct ultrasonic nonlinear behavior which is mainly presented by the second harmonics. Meanwhile, we find that both the acoustic nonlinearity parameter and dispersion distance show the exponential decay trend with the increase of frequency-thickness. Moreover, the results reveal that the frequency is key to affect the acoustic nonlinearity parameter and dispersion distance with the same frequency-thickness. This study theoretically and experimentally reveals that nonlinear Lamb waves of the low-frequency S0 mode are feasible to quantitatively identify material weak nonlinearity in plates

Construction of Identical [2 + 2] Schiff-Base Macrocyclic Ligands by Ln^III and Zn^II Template Ions Including Efficient Yb^III Near-Infrared Sensitizers

Identical 34-membered [2 + 2] pendent-armed Schiff-base macrocyclic ligands (H₄L_a and H₄L_b) can be constructed via the condensation reactions between rigid <i>o</i>-phenylenediamine and extended dialdehydes (H₂hpdd/H₂pdd) in the presence of either Ln^III or Zn^II template with remarkable distinction on the ion radii and charge. X-ray single-crystal diffraction analyses reveal the formation of mononuclear Ln^III complexes (<b>1</b>–<b>4</b> and <b>7</b>) and dinuclear Zn^II complexes (<b>5</b> and <b>6</b>). It is noted that Ln^III macrocyclic complexes have eight-coordinate sandwich-like mononuclear structures fully surrounded by flexible and large-sized macrocyclic ligands. Photophysical studies have demonstrated that both H₄L_a and H₄L_b can serve as effective sensitizers for the Yb^III ion (<b>2</b> and <b>7</b>) exhibiting near-infrared emission at 974 nm with high quantum yields in solution (C₂H₅OH and CH₃OH, ∼1%). Moreover, the quantum yields of two Yb^III complexes <b>2</b> and <b>7</b> could be increased ∼15% in CH₃OH under weak alkaline condition (pH = 8–9), while no significant changes are observed in C₂H₅OH by contrast. We think the unique sandwich-like macrocyclic structures of Yb^III complexes <b>2</b> and <b>7</b> play important roles in simultaneously guaranteeing the effective match of the energy levels of Yb^III centers as well as shielding from the solvent molecules and counterions

Construction of Identical [2 + 2] Schiff-Base Macrocyclic Ligands by Ln^III and Zn^II Template Ions Including Efficient Yb^III Near-Infrared Sensitizers

Identical 34-membered [2 + 2] pendent-armed Schiff-base macrocyclic ligands (H₄L_a and H₄L_b) can be constructed via the condensation reactions between rigid <i>o</i>-phenylenediamine and extended dialdehydes (H₂hpdd/H₂pdd) in the presence of either Ln^III or Zn^II template with remarkable distinction on the ion radii and charge. X-ray single-crystal diffraction analyses reveal the formation of mononuclear Ln^III complexes (<b>1</b>–<b>4</b> and <b>7</b>) and dinuclear Zn^II complexes (<b>5</b> and <b>6</b>). It is noted that Ln^III macrocyclic complexes have eight-coordinate sandwich-like mononuclear structures fully surrounded by flexible and large-sized macrocyclic ligands. Photophysical studies have demonstrated that both H₄L_a and H₄L_b can serve as effective sensitizers for the Yb^III ion (<b>2</b> and <b>7</b>) exhibiting near-infrared emission at 974 nm with high quantum yields in solution (C₂H₅OH and CH₃OH, ∼1%). Moreover, the quantum yields of two Yb^III complexes <b>2</b> and <b>7</b> could be increased ∼15% in CH₃OH under weak alkaline condition (pH = 8–9), while no significant changes are observed in C₂H₅OH by contrast. We think the unique sandwich-like macrocyclic structures of Yb^III complexes <b>2</b> and <b>7</b> play important roles in simultaneously guaranteeing the effective match of the energy levels of Yb^III centers as well as shielding from the solvent molecules and counterions