Development and Properties of Sulfate-resistant and Corrosion-inhibiting Admixtures

Sulfate and chloride-induced corrosion of concrete and steel reinforcement are the most important causes of premature failure of durability of concrete structures. To prevent damage in concrete structures, the application of sulfate-resistant and corrosion-inhibiting admixtures has proven to be an effective method. In this study, a new type of corrosion-inhibiting admixtures including organic and special inorganic components are developed and the properties of mortar mixed with them was investigated. The results show that NC-CZ series of sulfate-resistant and corrosion-inhibiting admixtures have been successfully developed. The mortar with NC-CZ has good resistance to sulfate attack, whose corrosion resistance coefficient of mortar is 1.07, meeting the standard requirement and even larger than that of moderate sulfate-resistant Portland cement. The diffusion coefficient of chloride ion at 28d decreases by 35% around. Meanwhile, the water absorption is obviously decreased. The steel bars in mortar mixed with corrosion-inhibiting admixtures don’t occur rusting. By contrast, the steel bars in mortar without corrosion-inhibiting admixtures occur rusting, whose area rate of corrosion is more than 20%. This study could lead to significant benefits for durability and service life of reinforced concrete structures in China

Study on Performance of Negative Temperature and High Strength Bed Mortar Material for Wind Power Engineering

As the development process of affordable wind power projects accelerates, the height of tower hub shows a trend of development to 150m above. The technology of steel and concrete is widely applied. Bed mortar material, as the bonding material between precast concrete rings, is the key material to ensure the lifting speed of steel and concrete tower for wind power. In this study, the basic formula of negative temperature and high strength bed mortar material was explored, and its working performance and strength development under different curing conditions were further studied. The results show that the developed bed mortar material has excellent thixotropy and it is still operable at 50min. Under the condition of negative temperature curing, the early strength of bed mortar material is high, and the late strength develops well. Curing at ultra-low temperature of -15℃, the strength of -1d is 35.4MPa, and the strength of -7+21d is over 90MPa. In the outdoor natural curing environment of alternating positive and negative temperatures, the strength of 1d reaches 51.1MPa, the strength of 60d is 113.2MPa. The performance of bed mortar material far meets the requirements of the strength grade of 80MPa which is used in winter construction of wind power engineering

A Solving Algorithm for Nonlinear Bilevel Programing Problems Based on Human Evolutionary Model

An algorithm based on the human evolutionary model is proposed for solving nonlinear bilevel programing problems. In view of the hierarchical structure of this problem, the algorithm is designed through feeding back the optimal solution of the lower-level problem to the upper-level. Based on the quality of individuals at each iteration, this proposed algorithm can independently change the population size to achieve the balance between global and local searching ability during the progress of evolution, which can perform an exhaustive search in the whole landscape through creating an individual by using the tabu search method. Finally, we test four typical bilevel programing problems by using the proposed algorithm to verify its feasibility. The experimental results indicate the proposed algorithm can not only solve bilevel programing problems but also get the global optimal solution

Sensor Distribution Design of Travel Time Tomography in Explosion

Optimal sensor distribution in explosion testing is important in saving test costs and improving experiment efficiency. Aiming at travel time tomography in an explosion, an optimizing method in sensor distribution is proposed to improve the inversion stability. The influence factors of inversion stability are analyzed and the evaluating function on optimizing sensor distribution is proposed. This paper presents a sub-region and multi-scale cell partition method, according to the characteristics of a shock wave in an explosion. An adaptive escaping particle swarm optimization algorithm is employed to achieve the optimal sensor distribution. The experimental results demonstrate that optimal sensor distribution has improved both indexes and inversion stability

An Investigation of the Wear on Silicon Surface at High Humidity

Using an atomic force microscope (AFM), the wear of monocrystalline silicon (covered by a native oxide layer) at high humidity was investigated. The experimental results indicated that tribochemistry played an important role in the wear of the silicon at different relative humidity levels (RH = 60%, 90%). Since the tribochemical reactions were facilitated at 60% RH, the wear of silicon was serious and the friction force was around 1.58 μN under the given conditions. However, the tribochemical reactions were restrained when the wear pair was conducted at high humidity. As a result, the wear of silicon was very slight and the friction force decreased to 0.85 μN at 90% RH. The slight wear of silicon at high humidity was characterized by etching tests. It was demonstrated that the silicon sample surface was partly damaged and the native oxide layer on silicon sample surface had not been totally removed during the wear process. These results may help us optimize the tribological design of dynamic microelectromechanical systems working in humid conditions

Method for compensation of transverse dispersion in electro-holography

In the process of optoelectronic reconstruction of color holograms, the reconstructed images of three colors can't be overlap properly because transverse dispersion caused by different wavelengths of three laser beams of R, G, B colors. In this paper, a novel method is proposed to compress or expand the number of discrete pixels of three component color images for eliminating transverse dispersion in the process of computing holograms. Holograms computed by the iterative Fourier transverse algorithm (IFTA) were loaded on reflective liquid crystal spatial light modulator (LC-SLM) for optoelectronic reconstruction. The experimental result shows that the method is effective.Published versio

Nondestructive tribochemistry-assisted nanofabrication on GaAs surface

A tribochemistry-assisted method has been developed for nondestructive surface nanofabrication on GaAs. Without any applied electric field and post etching, hollow nanostructures can be directly fabricated on GaAs surfaces by sliding a SiO(2) microsphere under an ultralow contact pressure in humid air. TEM observation on the cross-section of the fabricated area shows that there is no appreciable plastic deformation under a 4 nm groove, confirming that GaAs can be removed without destruction. Further analysis suggests that the fabrication relies on the tribochemistry with the participation of vapor in humid air. It is proposed that the formation and breakage of GaAs-O-Si bonding bridges are responsible for the removal of GaAs material during the sliding process. As a nondestructive and conductivity-independent method, it will open up new opportunities to fabricate defect-free and well-ordered nucleation positions for quantum dots on GaAs surfaces

Recent intensified erosion and massive sediment deposition in Tibetan Plateau rivers

Abstract Recent climate change has caused an increase in warming-driven erosion and sediment transport processes on the Tibetan Plateau (TP). Yet a lack of measurements hinders our understanding of basin-scale sediment dynamics and associated spatiotemporal changes. Here, using satellite-based estimates of suspended sediment, we reconstruct the quantitative history and patterns of erosion and sediment transport in major headwater basins from 1986 to 2021. Out of 13 warming-affected headwater regions, 63% of the rivers have experienced significant increases in sediment flux. Despite such intensified erosion, we find that 30% of the total suspended sediment flux has been temporarily deposited within rivers. Our findings reveal a pronounced spatiotemporal heterogeneity within and across basins. The recurrent fluctuations in erosion-deposition patterns within river channels not only result in the underestimation of erosion magnitude but also drive continuous transformations in valley morphology, thereby endangering local ecosystems, landscape stability, and infrastructure project safety