Advanced Materials Research Vol. 413

Abstract: On the base of discussion and analysis of Bailey method for Aggregate Grading Design, the paper expounds particularly how to design Aggregate gradation of continuous dense gradation asphalt mixture by a accurate computational procedure, with the example of AC-20(asphalt cement 20 version) continuous dense gradation asphalt mixture design. It will benefit for designer to design graduation well. This also suggests using three ratios, [CA] Ratio, [FAc] Ratio and [FAf] Ratio, to analyze composite gradation. Thus the designed mixture has good rutting resistance and endurance. The key technologies about this design method were studied. In the context of the same asphalt binder and aggregate, two kinds of AC-20 aggregate gradations have been designed by using Bailey method and the routine method. With these two methods, several kinds of specimens for pavements performance tests has been made at separate optimum asphalt contents. These experiments have shown that the asphalt mixture designed by Bailey method has a better rutting resistance at high temperature, crack resistance at low temperature and durability than the one designed by the routine method. In these experiments, the dynamic stability is enhanced by one time to 6749 times/mm in rutting Test; the Tensile Strength Ratio (TSR) is improved greatly in Water Susceptibility Tensile Strength Ratio Test, which is much larger than the required value in the specification; the maximum bending and tension strain is also enhanced. As a result, Bailey method can be widely used in aggregate grading design in practical engineering.

Abstract: Rapid deposition of hydroxyapatite on Mg-alloy in concentrated simulated body fluid (5×SBF) and modified simulated body fluid (m-SBF) was investigated. By biomineralization method, hydroxyapatite coating was deposited on Mg-alloy with pre-calcification treatment. Scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction instrument (XRD) were applied to analyze the deposition product of biomineralization and the related mechanism. The results showed that pre-calcification treatment on Mg-alloy can lead to a quite rapid deposition of hydroxyapatite. Ionic concentrations in SBF solutions affected the structure of hydroxyapatite greatly. A homogeneous plate-like apatite coating was induced on Mg alloy sample in m-SBF solution which is promising for the future practice.

Abstract: In order to analyze the stability of the tunnel construction of the fault fracture zone, by adopting the three-dimensional finite element, the paper analyzed the construction process of the Qingshashan Tunnel passing through the F₅ fault fracture zone, and the rules and characteristics of deformation, stress distribution and its rules of changes, and the distribution range of the failure zone of the surrounding rock in the construction process, which would have important significance in guiding tunnel construction. Studies have shown that the three-dimensional finite element has a broad application prospect in tunnel projects.

Abstract: In order to analyze the effects of tunnel excavation on the stability of tunnel slope reinforced with anti sliding pile and establish 3D elastic-plastic finite element model, the paper focused on the analysis of the deformation of the structural system, the characteristics of the deformation and the rules of the plastic zone of the surrounding rock. The results showed that in the construction process, the maximum vault settlement was about 28mm; the plastic zone occurred mainly in the place surrounding the sliding pile and part of the earth surface, the plastic zone around the vault at the entry of the tunnel was large and tended to connect with the earth surface; the soil arching effect ensured the stability of the slope during the tunnel excavation and construction.

Abstract: This article reports on the study to evaluate the hydration process of cement by the addition of citric acid. Through the test of citric acid of cement paste, hydration heat performance, resistivity, chemical shrinkage, and combined with XRD, SEM, DSC-TG discusses the influence of citric acid on cement hydration process. The results thus obtained were compared to the hydration process of cement with the blank sample and vary of dosage of citric acid. The results show that: The early hydration about 1~2 h resistivity increases, dissolve balance stage was extended; The chemical shrinkage increased significantly, and increases with dosage; With the increase in citric acid dosage, AFt diffraction peaks increases, while the CH peak decreases, indicating that the citric acid accelerated the initial hydration of C₃A, while inhibiting C₃S hydration and promoting AFt generation. Key words: citric acid, mechanism ,hydration heat, resistivity

Abstract: The micro-grid technologies become one of key spots in the research on distributed energy systems. In this paper, the components, systemic structure and operation modes of micro-grid are presented. From the viewpoint of technical connotation, the present research situation of key technologies for the micro-grid is reviewed. These technologies include new power electronic converter technologies, fault detection and protection, communication technologies, planning and design of micro-grid, as well as issues related to operation control and energy management such as supervisory and control architecture, control strategies and approaches, ancillary services, operation specification, modeling and simulation research in system level and unit level and micro-grid economic evaluation. The authors also point out that the optimal design of micro-grid topology and optimal configuration of distributed energy units are of significance for the implementation of maximum benefit of the whole micro-grid. Besides, the effective economic evaluation of micro-grid is a topic to be researched in detail.

Abstract: Matrix converter is a kind of power electric converter by AC-AC transformation with its excellent input and output characteristics.After analysis of matrix converter system structure in the paper,a digital signal processor based on DSP and CPLD is designed. The design includes the hardware structure and the program flowsheet.DSP and CPLD is the core of the matrix converter - Asynchronous motor vector control system, including system main circuit, other peripheral hardware circuit, control and protection circuits, software design process and so on. The hardware control strategy and software realization scheme of the system are discussed in detail. The experimental results verify that the control strategy of the system is valid and the design of the software and hardware are reasonable.

Abstract: With the increase of Chinese mining depth, the deformation of deep soft rock is an increasingly serious problem, such as floor heave. The shear experiments of the different types of anchor were carried out. The results show that the anti-shear properties of the seamless anchor are higher than that of the seam anchor. It is significant for the anti-shear properties of anchor filled with different materials, like twisted steel, cement. The shear value of anchor inserted steel is the maximum, grouted one is the next and hollow one is the minimum. After steel installed, the anchor has better shear performance, it not only has greater anti-shear property, but has the secondary supported property because of the double-load peak during shear process. At the same time, the experiments also show that the anchor fixed into the floor in some angle, can effectively control the deformation of the floor heave of deep rock roadway. The studies can offer scientific basis for parameter design optimization of the anchor controlling the deformation of the floor heave.

Abstract: Although gold nitride has been produced by Siller and co-workers by irradiating a gold film with low energy nitrogen ions, the unsuccessful reason for previous attempts to produce gold nitride is not clear yet. In general, nitrogen concentration depth profile probably influences gold nitride formation. But it is difficult to measure nitrogen concentration depth profile in the N-implanted layer at a low implantation energy of 500 eV. Ion concentration depth profiles in amorphous solids can be determined rather accurately in the case of low implantation fluences using TRIM code. The sputtering effect of ion implantation of high fluences on the concentration depth profile of implanted nitrogen ions should be considered. A dynamic computer simulation based on a TRIDYN code has been applied to calculate nitrogen concentration depth profile in a N-implanted gold film using the different parameters of the fluence and energy in the present work. The sputtering effect of a high fluence on the concentration depth profile can be considered in the TRIDYN simulation. The parameters of fluence and energy that enable to get the gold nitride in thin film are analyzed based on the simulation results. It is put forward some possible ways to improve the formation of gold nitride further.

Abstract: Aiming at the engineering status of the shortage of natural sand and the contradictory between workability and strength surplus emerging in the design of low strength high flowing concrete (LHC), this paper has proposed a mix design method of LHC with low cement content prepared by manufactured sand (MS).And then verifies the feasibility of the method through experiments. Tests on slump, compressive strength and chloride ion diffusion coefficient were carried out and the results indicate that LHC with low cement content prepared by MS can be successfully produced using this method. Concrete designed by this method has low cement consumption and has utilized MS to replace NS as well as made full use of the industrial by-products of stone fines and fly ash. As a result, it is economical and ecological.