Repair of concrete existing micro-cracks by use of microbially induced carbonate precipitation

Micro-crack is the start of concrete deterioration and failure, though it does not decrease the bearing capacity in the beginning. In order to prolong the service life of existing concrete structures, it is important to repair the existing micro-cracks before they develop into large cracks, which are much more harmful. Bio-genic CaCO3 from microbially induced carbonate precipitation (MICP) process is proved to be a promising crack repair material due to its environmental friendliness and super compatibility with cementitious matrix. In this study, MICP based repair technology was applied to repair micro-cracks. The influence of crack environment and repair technique on the precipitation of bio-CaCO3 was investigated. Results shown that moderate alkali pH had limited effect on the properties of bio-CaCO3. Bacteria could still induce the CaCO3 precipitation in crack if it was saturated with Ca2+ containing deposition medium. Crack of a width 0.5mm can be fully sealed within 3 days by use of a controlled injection technique

Impacts of Partial Substitution of Chemical Fertilizer with Organic Manure on the Kinetic and Thermodynamic Characteristics of Soil <i>β</i>–Glucosidase

To study the characteristics of the β–glucosidase enzymatic reaction in wheat field soil under the condition of reducing the application of chemical fertilizer, five fertilization treatments were established, including no fertilizer (CK), chemical fertilizer (F), organic fertilizer (OF), 25% organic fertilizer plus 75% chemical fertilizer (25% OF), and 50% organic fertilizer plus 50% chemical fertilizer (50% OF). The activity of β–glucosidase and its kinetic and thermodynamic characteristics were analyzed by using microplate p–nitrophenol colorimetry. The results showed that the Vmax values of soil β–glucosidase in the organic substitution of chemical fertilizer treatment were higher than those in the chemical fertilizer and no fertilizer treatments, and the Km values were lower than those in the chemical fertilizer and no fertilizer treatments at the different growth stages. The Vmax value in the 25% OF treatment was the highest at the jointing stage and that of the OF treatment was the highest at the booting stage; the Km value in the 50% OF treatment was the lowest at the different growth stages. Compared with the chemical fertilizer and no fertilizer treatments, the application of organic fertilizer effectively reduced thermodynamic parameters such as Ea, Q10, ∆H, ∆G, and ∆S at the jointing and booting stages of wheat. The thermodynamic parameters in the 25% OF treatment were the lowest at the jointing stage and those in the OF treatment were the lowest at the booting stage. A reasonable amount of organic fertilizer is more beneficial to enzymatic reactions and improves the soil quality and the ability to supply nutrients to wheat cultivation

Short-Term Interval Prediction of Wind Power Based on KELM and a Universal Tabu Search Algorithm

Installed wind power has significantly grown in recent years to synchronize with the ever-increasing demand for environment-friendly and renewable energy. However, wind energy has significant uncertainty or random futures, and will give rise to destructive effects on the safety operations of the power system. In this respect, an accurate and reliable wind power prediction is of great significance for improving the power system stability and optimizing the dispatch plan. Compared with traditionally deterministic point forecast techniques, probabilistic forecasting approaches can provide more stochastic information to quantify the random characteristics of wind power and to estimate its impacts on the power system. Moreover, the interval of the output power is a key stochastic information on wind power. In general, an interval prediction needs to compromise the calibration and the average width of the predicted interval. To find the best combination of these two metrics, a methodology based on a kernel extreme learning machine (KELM) and an improved universal tabu search algorithm is proposed. In the proposed methodology, to eliminate the inherent randomness on the weights between the input and hidden lays in the commonly used extreme learning machine, a radial-basis-function-based kernel extreme learning machine is proposed, and an improved tabu search method is introduced to optically compromise the calibration and the average width of the predicted interval to overcome the deficiency of existing algorithms, such as the insufficient global search ability of a particle swarm optimization. A prototype wind farm is utilized as a case study to verify the efficiency and advantage of the proposed methodology

Short-Term Interval Prediction of Wind Power Based on KELM and a Universal Tabu Search Algorithm

Installed wind power has significantly grown in recent years to synchronize with the ever-increasing demand for environment-friendly and renewable energy. However, wind energy has significant uncertainty or random futures, and will give rise to destructive effects on the safety operations of the power system. In this respect, an accurate and reliable wind power prediction is of great significance for improving the power system stability and optimizing the dispatch plan. Compared with traditionally deterministic point forecast techniques, probabilistic forecasting approaches can provide more stochastic information to quantify the random characteristics of wind power and to estimate its impacts on the power system. Moreover, the interval of the output power is a key stochastic information on wind power. In general, an interval prediction needs to compromise the calibration and the average width of the predicted interval. To find the best combination of these two metrics, a methodology based on a kernel extreme learning machine (KELM) and an improved universal tabu search algorithm is proposed. In the proposed methodology, to eliminate the inherent randomness on the weights between the input and hidden lays in the commonly used extreme learning machine, a radial-basis-function-based kernel extreme learning machine is proposed, and an improved tabu search method is introduced to optically compromise the calibration and the average width of the predicted interval to overcome the deficiency of existing algorithms, such as the insufficient global search ability of a particle swarm optimization. A prototype wind farm is utilized as a case study to verify the efficiency and advantage of the proposed methodology

Multi-phase structure and electrical properties of Bi0.5Li0.5ZrO3 doping K0.48Na0.56NbO3 lead-free piezoelectric ceramics

Abstract (1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 (KNN–xBLZ, x = 0–0.06) lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method, and their phase structures and electric properties as well as T C were systematically investigated. The orthorhombic–tetragonal (O–T) two phases were detected in all (1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 ceramics at 0.01 ≤ x ≤ 0.05. Due to the appropriate ratio between O phase and T phase (C O/C T= 45/55), high piezoelectric properties of d 33 = 239 pC/N, k p = 34%, and P r = 25.23 μC/cm2 were obtained at x = 0.04. Moreover, a high T C = 348°C was also achieved in KNN–xBLZ ceramic at x = 0.04. These results indicate that (1–x)K0.48Na0.56NbO3–xBi0.5Li0.5ZrO3 system is a promising candidate for high-temperature piezoelectric devices

Case reports of collision and composite carcinomas of the thyroid: an insight into their origin and clinical significance

Abstract Background Collision and composite carcinomas of the thyroid are extremely rare, and their clinical and biological characteristics are poorly understood. Case presentation The first case was a 41-year-old female patient with a right thyroid nodule. Pathological diagnosis was papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma composite carcinoma. Surgical treatment was right thyroid lobectomy + left partial thyroidectomy + right central neck lymph node dissection. The second case was a 60-year-old female with bilateral thyroid nodules. Total thyroidectomy was performed, and the pathological diagnosis was thyroid collision carcinoma involving follicular thyroid carcinoma on the left side and PTC on the right side. Summary The clinical, histological and gene changes of collision and composite carcinomas of the thyroid are poorly described. With different biological invasion characteristics, the ideal treatment and the prognosis is currently unknown and individualized treatment is necessary. Conclusions It is recommended that in composite carcinoma, each cancer is evaluated and treated according to the most severe tumor. Collision carcinoma should be treated as two separate synchronous primary tumors. For both collision and composite carcinomas of the thyroid, the follow-up after treatment should be extensive

Manipulating the powder size to achieve enhanced strength and ductility in harmonic structured Al alloy

The present work reports a simple one-step powder metallurgy approach for producing bulk fine-grained Al2024 alloy with a unique harmonic structure and superior mechanical properties. The grain size of the bulk specimen could be easily manipulated by changing the initial powder size. Tensile test suggested that the yield strength of the fine-grained specimen with an average grain size of 3.78 µm (powder size ∼20 µm) was about 265 MPa, which was three times higher than that of the conventional coarse-grained counterpart, maintaining a good ductility (total elongation ∼15%). The reasons for the unique microstructure and the enhanced mechanical properties were discussed