•Higher temperature or wind speed, or lower humidity affected interlayer properties of concrete negatively.•Mechanism for the effects of environmental condition was discussed.•Relationship between ...damage degree and loss rate of tensile splitting strength was established.
Dam concrete is usually poured layer by layer. Interlayer as a “weak section” or “defect” inside the concrete, may lead to an increase in the risks of seepage and bedding slip of dams. This study investigated effects of environmental condition (i.e. ambient temperature, relative humidity and wind speed) on interlayer properties of dam concrete, in terms of tensile splitting strength, resistance to chloride ion penetration and pore structure. In addition, damage degree of concrete caused by the interlayer was evaluated by means of ultrasonic non-destructive test. The results show that increasing temperature or wind speed on the lower layer surface decreases the interlayer tensile splitting strength and resistance to chloride ion penetration of concrete significantly. Meanwhile, reducing relative humidity has an adverse effect on the interlayer properties of concrete. It is attributed to that higher temperature or wind speed, or lower relative humidity can accelerate water evaporation, reducing surface water content and speeding up hardening process of the lower layer concrete obviously. It causes not only a worse bonding quality but also a pore-structure coarsening effect near the interlayer. Moreover, the reduction of surface water content of the lower layer concrete may decrease final degree of hydration reaction, which should be responsible for the decrease in the interlayer properties as well. Furthermore, there was a linear relationship between the damage degree and loss rate of tensile splitting strength of concrete. Therefore, the damage degree calculated from wave velocity can be adopted to predict the loss rate of tensile splitting strength effectively.
The influence of a combined curing composed of precuring in hot water and heating in dry air on mechanical properties and explosive spalling of ultra-high performance concrete (UHPC) subjected to ...high temperature was investigated in this experiment. Meanwhile, the microstructure of UHPC was determined by means of X-ray diffraction (XRD) with Rietveld method, thermogravimetric analysis (TGA), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). The results indicate that the combined curing improves the mechanical properties of UHPC remarkably. More importantly, it is quite efficient to enhance the resistance of UHPC to explosive spalling under high temperature, which should be a novel approach to prohibit spalling occurrence, different from adding polypropylene fiber. During dry air heating in the combined curing, a high temperature steam environment is established in the dense structure framework of UHPC formed in the preceding hot water curing. Both further hydration of residual cement and pozzolanic reaction of mineral admixtures can be activated during the dry air heating, leading to not only the formation of a large amount of dense hydrates (such as C-S-H gels, katoite, tobermorite and xonotlite, etc.), which accumulate in the aforementioned existing framework, but also the consumption of most of internal free water. Therefore, both mechanical properties of UHPC and its resistance to explosive spalling under high temperature can be enhanced significantly.
•The combined curing can significantly enhance the resistance of UHPC to explosive spalling under high temperature.•The combined curing can improve the mechanical properties of UHPC remarkably.•Both further hydration of residual cement and pozzolanic reaction are activated under a high temperature steam condition.
•Nano-clay particles are new types of nano-materials with high pozzolanic activity.•Appropriate content of nano-clay improves properties of cement-based materials.•Mechanism for the effects of ...environmental condition was summarized.
Nano-clay and calcined nano-clay are new types of nano-materials with high pozzolanic activity. In recent years, numerous studies have been done about the effects of nano-clay and calcined nano-clay. However, a comprehensive review is lacked to better understanding their mechanism. Therefore, properties including workability, mechanical properties, durability, shrinkage, hydration and microstructure of cement-based materials incorporating nano-clay and calcined nano-clay are reviewed in this paper. Based on the results of various literatures, the mechanism of nano-clay and calcined nano-clay are summarized. Furthermore, in view of problems existing in the current studies, some suggestions are put forward for the future research. The results show that appropriate content of nano-clay or calcined nano-clay has beneficial effects on improving the properties of cement-based materials, which is mainly attributed to their filling effect, pozzolanic effect, nucleation effect, bridging effect and barrier effect.
We discuss the effects of many-body coherence on the speed of evolution of ultracold atomic gases and the relation to quantum speed limits. Our approach is focused on two related systems, spinless ...fermions and the bosonic Tonks-Girardeau gas, which possess equivalent density dynamics but very different coherence properties. To illustrate the effect of the coherence on the dynamics, we consider squeezing an anharmonic potential which confines the particles and find that the speed of the evolution exhibits subtle but fundamental differences between the two systems. Furthermore, we explore the difference in the driven dynamics by implementing a shortcut to adiabaticity designed to reduce spurious excitations. We show that collisions between the strongly interacting bosons can lead to changes in the coherence which result in different evolution speeds and therefore different fidelities of the final states.
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•The composite of CoSe and FeCo2O4 shows excellent electrochemical performance.•The unique layered core–shell structure provides a large number of active sites for ionic ...reactions.•Binder-free effectively reduced the resistance of the electrode material.
Self-growing FeCo2O4@CoSe/NF layered core–shell composite materials on Ni foam (NF) were prepared by hydrothermal method and electrodeposition method. CoSe shell effectively increased the conductivity of FeCo2O4 core, and the synergistic effects of the two contents effectively improved the overall electrochemical performance. At a current density of 1A/g, FeCo2O4@CoSe/NF achieved a specific capacity of 724.2C/g and capacity retention rate of 94.1% after 5000 cycles. The assembled asymmetric capacitor (ASC) also achieved a high energy density of 57.19Wh/kg when the power density is 750 W/kg.
The cylinder linear induction motor (CLIM) is a variation of the rotary induction motor. Its structure is simple, it has a low manufacturing cost, and it can generate linear thrust without the need ...for a conversion mechanism. It is particularly suitable for electromagnetic catapults, magnetic levitation transport, and industrial production fields, due to its strong environmental adaptability. Designing a high-thrust and high-efficiency CLIM is a great challenge due to its inherent drawbacks, such as the low thrust density and power density of induction motors. In this article, two CLIMs with different topologies are proposed to meet the demand for control-rod drives in high-temperature and high-pressure environments. The article elucidates the topologies of the two CLIMs and proposes an analytical computational approach for the CLIM. Modern optimization algorithms were utilized to optimize the design of the structural parameters of both CLIMs. A 3D-FEA simulation was used to compare and analyze the air-gap magnetism and thrust characteristics of two CLIMs. The results indicate that the copper-ring secondary CLIM has a higher thrust density and is more suitable for use in control-rod drive mechanism (CRDM) systems.
Since the first quantum neural network based on quantum computing was proposed by famous scholar Kak, much attention has been taken focus on designing new quantum neural network models. In this ...paper, a novel efficient quantum feed-forward neural network based on quantum computing is established, which adopts genetic algorithm to improve the traditional back propagation algorithm in parameters learning process. We clearly show the mathematical process of the new proposed quantum network model and improved algorithm. The experimental results of MATLAB simulations show that the new network model which makes the best use of fast quantum neural computation does a better job in function approximation and prediction of educational short video’s spreading capacity than traditional back propagation neural network, and the improved algorithm is more efficient than common back propagation algorithm in the proposed quantum network model. Our model can be widely used in weather prediction, handwriting recognition, speech recognition, and other aspects.
Statistical tests for biomarker identification and classification methods for patient grouping are two important topics in adaptive designs of clinical trials related to genomic studies. In this ...article, we evaluate four test methods for biomarker identification in the first stage of an adaptive design: a model-based identification method, the popular two-sided t-test, the nonparametric Wilcoxon Rank-Sum test (two-sided), and the Regularized Generalized Linear Models. For patients grouping in the second stage, we examine classification methods such as Random Forest, Elastic-net Regularized Generalized Linear Models, Support Vector Machine (SVM), Gradient Boosting Machine (GBM), and Extreme Gradient Boosting (XGBoost). Simulation studies are carried out to assess the performance of the different methods. The best identification methods are chosen based on the well-known
score, while the best classification techniques are selected based on the area under a receiver operating characteristic curve (AUC). The chosen methods are then applied to the Adaptive Signature Design (ASD) with a real data set from breast cancer patients for the purpose of evaluating the performance of ASD in different situations.
We present a quantum BP neural network with the universality of single-qubit rotation gate and two-qubit Controlled-NOT gate. Also, we show the process of the BP learning algorithm for the quantum ...model, and propose an improved BP learning algorithm based on quantum genetic algorithm. The type recognition simulation of the Matlab program shows the efficiencies of the quantum neural network and the improved learning algorithm.
The stator coreless axial flux permanent magnet (AFPM) motor with a compact structure, low torque ripple, and high efficiency is particularly suitable as a motor for electric propulsion systems. ...However, it still requires great effort to design an AFPM motor with higher torque density and lower torque ripple. In this paper, a stator coreless multidisc AFPM (SCM-AFPM) motor with a three-rotor and two-stator topology is proposed. To reduce rotor mass and increase torque density, the proposed SCM-AFPM motor adopts the hybrid permanent magnets (PMs) array with Halbach PMs in the two-terminal rotor and the conventional PMs array in the middle rotor. In addition, a multi-objective optimization model combining response surface method (RSM) and genetic algorithm (GA) is proposed and applied to the proposed SCM-AFPM motor. With the help of the three-dimensional finite-element analysis (3-D FEA), it is found that the torque ripple of the optimized SCM-AFPM motor is 4.73%, while it is 6.21% for the initial motor. Its torque ripple is reduced by 23.8%. Therefore, the proposed multi-objective optimization design method can quickly and reliably obtain the optimal design of the SCM-AFPM motor.
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