Dynamic Properties of Pretreated Rubberized Concrete under Incremental Loading

Recycling scrap tyres as alternative aggregates of concrete is an innovative option. To clarify the dynamic properties of the pretreated rubberized concrete with some cumulative damage, the natural frequency, flexural dynamic stiffness, and damping ratio of the specimens under incremental stress level were investigated in this paper. The results indicated that the pretreatment of rubber particles improved the strength, ductility, and crack resistance of the rubberized concrete. The reduction of the flexural dynamic stiffness was clarified with the increase of concrete stress level. The addition of the pretreated rubber particles enhanced the concrete energy dissipation capacity during the destruction, and the specimen dissipated more energy with the increase of rubber content before its failure

Calculation and Expression of the Urban Heat Island Indices Based on GeoSOT Grid

The urban heat island (UHI) effect accelerates the accumulation of atmospheric pollutants, which has a strong impact on the climate of cities, circulation of material, and health of citizens. Therefore, it is of great significance to conduct quantitative monitoring and accurate governance of UHI by calculating the index rapidly and expressing spatial distribution accurately. In this paper, we proposed a model that integrates UHI information with the GeoSOT (Geographic Coordinate Subdividing Grid with One-Dimension Integer Coding on 2n Tree) grid and subsequently designed the calculation method of UHI indices and expression method of UHI spatial distribution. The UHI indices were calculated on Dongcheng and Xicheng District, Beijing, in the Summer of 2014 to 2019. Experimental results showed that the proposed method has higher calculation efficiency, and achieved a more detailed description of the spatial distribution of the urban thermal environment compared with the Gaussian surface fitting method. This method can be used for large-scale and high-frequency monitoring the level of UHI and expressing complicated spatial distribution of UHI inside the city, thus supporting accurate governance of UHI

Random vibration response prediction of electronic device based on hierarchicaly model updating and validation

Electronic device is susceptible to failure due to environmental vibration during transportation and use, even causing the entire device to failure. In recent years, the structure of electronic device has been more complex, the application range has become more and more extensive, and requirements for structural performance under vibration environment of electronic device are more strict, especially in the aviation and aerospace field. Therefore, in order to ensure the safe and reliable work of electronic device, and to control vibration level effectively , it is necessary to carry out environmental vibration simulation analysis and response prediction for electronic device.In this paper, a certain type of aviation airborne electronic device is taken as the research object. The finite element method is used to model the electronic device. In order to obtain an accurate finite element model to simulate the vibration of the electronic device, the hierarchicaly model updating and validation is applied to the vibration simulation for the electronic device. Then the substructure FE model (PCB printed circuit board without electronic items) is firstly calibrated by means of the deterministic model updating technique by comparing with the experiment modal analysis. And a Bayesian method of parameter uncertainty quantification was employed to identify the mass and stiffness distribution (PCB with electronic items). Finally, the established validated model is used to predict the random response of the reference points and verified by random vibration test.<br/

Effect of High-Dispersible Graphene on the Strength and Durability of Cement Mortars

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO2-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO2-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO2-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO2-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO2-RGO cement mortars were conducted, and it was found that with the same amount of TiO2-RGO and GO, the TiO2-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO2-RGO prepared by titanium dioxide (TiO2) intercalation can better improve the strength and durability performance of cement mortars compared to GO

Slicing Resource Allocation for eMBB and URLLC in 5G RAN

This paper investigates the network slicing in the virtualized wireless network. We consider a downlink orthogonal frequency division multiple access system in which physical resources of base stations are virtualized and divided into enhanced mobile broadband (eMBB) and ultrareliable low latency communication (URLLC) slices. We take the network slicing technology to solve the problems of network spectral efficiency and URLLC reliability. A mixed-integer programming problem is formulated by maximizing the spectral efficiency of the system in the constraint of users’ requirements for two slices, i.e., the requirement of the eMBB slice and the requirement of the URLLC slice with a high probability for each user. By transforming and relaxing integer variables, the original problem is approximated to a convex optimization problem. Then, we combine the objective function and the constraint conditions through dual variables to form an augmented Lagrangian function, and the optimal solution of this function is the upper bound of the original problem. In addition, we propose a resource allocation algorithm that allocates the network slicing by applying the Powell–Hestenes–Rockafellar method and the branch and bound method, obtaining the optimal solution. The simulation results show that the proposed resource allocation algorithm can significantly improve the spectral efficiency of the system and URLLC reliability, compared with the adaptive particle swarm optimization (APSO), the equal power allocation (EPA), and the equal subcarrier allocation (ESA) algorithm. Furthermore, we analyze the spectral efficiency of the proposed algorithm with the users’ requirements change of two slices and get better spectral efficiency performance

In Situ Growth of ZIF-8 Nanocrystals on the Pore Walls of 3D Ordered Macroporous TiO2 for a One-Pot Cascade Reaction

It is wise to mimic a bioinspired system to design a nanoreactor as a catalyst containing multiple components for a cascade reaction. Here, we report the uniform growth of well-dispersed nano-scale ZIF-8 crystals on the pore walls of 3DOM TiO2 via the TEA-assisted crystallization process. The UV-vis spectra indicate that the ZIF-8 photosensitizer can extend the visible-light absorption of 3DOM TiO2. The obtained nanoreactor can efficiently catalyze the one-pot aromatic alcohol oxidization and Knoevenagel condensation cascade reaction for larger molecules. This work offers an important strategy for preparing semiconductor–MOF multifunctional composites with a spatially separated compartmentation for the cascade reaction