Prediction of the solidification structure of casting and heterogeneous nucleation

The frequency of heterogeneous nucleation during the solidification of Al-Sibinary alloy was estimated by comparing experimentally obtained macrostructures of castings withnumerically simulated ones. A molten alloy was unidirectionally solidified from a water-cooledcopper chill in an adiabatic mold. The location of columnar to equiaxed transition (CET) in thesolidified alloy ingot was measured. A numerical simulation for grain structure formation based onthe Monte Carlo method was carried out, and the frequency of heterogeneous nucleation in the alloywas evaluated by producing similar structure with the experimental one. The frequency ofheterogeneous nucleation was expressed as a probabilistic function with an exponential form ofundercooling that deter-mines the probability of nucleation event in the simulation. The value ofthe exponent is regarded as the nucleation parameter. The nucleation parameter of Al-Si binary alloyvaried with initial Si content.

A STUDY OF CLOUD-SYSTEM MODEL:MACRO AND MICRO STRUCTURE SIMULATION OF CLOUD FIELD

The macro and micro cloud physics structures and their evolution with time are the core of describing cloud fields in essence.They are necessary atmospheric environment not only in aviation and spaceflight activities but also for atmos- pheric radiation transfer and acid rain formation research.Unfortunately it is difficult to obtain an entire environmental cloud field by using observation methods directly.Thus,by use of computation physics method to build a cloud-system model may be an indispensable way for this topic.This paper presented a cloud-system model for this goal,and simu- lated a real case.The results of computation showed that the macro structure of the cloud field was better consistent with real observation,and the micro structure was fairly reasonable.The output of model could provide all the information about the cloud field:(1)size-distribution spectrum of hydrometeor particles (point),(2)vertical profile (line),(3)hori- zontal or vertical section of macro and micro parameters (surface),and (4)cloud cover,pattern of cloud and configura- tion of cloud,etc.(body).

China＇s National Income Distribution in the New Normal：Characteristics,Contradictions and Reforms

This paper discusses the evolution and characteristics of China's national income distribution structure after the dawn of the new century and particularly in China's new normal of social and economic development. This paper casts light on the profound national income distribution and redistribution effects of changing ownership and economic reforms, as well as the microscopic household income distribution effects of changes in macroscopic distribution structure. Based on an analysis of changes in macroscopic distribution pattern, this paper explains the structural contradictions of national income distribution in China and their effects on China's economy, providing a theoretical analysis of income distribution for deepening supply-side structural reform.

Behavior of reinforced concrete structural walls with various opening locations: experiments and macro model

Two experimental tests of three-storied reinforced concrete structural walls having large openings were performed.Based on an original macro model,a multiple modified macro-model was proposed to develop a simple method to design a reinforced concrete structural wall with large openings and various opening locations.The interaction between reinforcement ties and concrete struts formed along the perimeter of openings was neglected in the original model.However,the strut-and-tie node was proposed to take account of such interaction in the proposed model.The predicted behavior of two specimens using such a proposed model was compared with the experimental results.It is shown that the behavior of structural walls with large openings could be modeled well using the proposed model.Moreover,the study indicates that the proposed model is applicable even in cases of multi-story structural walls having large openings and various opening locations.

Fabrication and multiscale characterization of 3D silver containing bioactive glass-ceramic scaffolds

In this work,we fabricated and characterized bioactive 3D glass-ceramic scaffolds with inherent antibacterial properties.The sol-gel(solution-gelation)technique and the sacrificial template method were applied for the fabrication of 3D highly porous scaffolds in the 58.6SiO2-24.9CaO-7.2P2O5-4.2Al2O3–1.5Na2O−1.5K2O–2.1Ag2O system(Ag-BG).This system is known for its advanced bioactive and antibacterial properties.The fabrication of 3D scaffolds has potential applications that impact tissue engineering.The study of the developed scaffolds from macro-characteristics to nano-,revealed a strong correlation between the macroscale properties such as antibacterial action,bioactivity with the microstructural characteristics such as elemental analysis,crystallinity.Elemental homogeneity,morphological,and microstructural characteristics of the scaffolds were studied by scanning electron microscopy associated with energy dispersive spectroscopy(SEM-EDS),transmittance electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),and UV-visible spectroscopy methods.The compressive strength of the 3D scaffolds was measured within the range of values for glass-ceramic scaffolds with similar compositions,porosity,and pore size.The capability of the scaffolds to form an apatite-like phase was tested by immersing the scaffolds in simulated body fluid(SBF)and the antibacterial response against methicillin-resistant Staphylococcus aureus(MRSA)was studied.The formation of an apatite phase was observed after two weeks of immersion in SBF and the anti-MRSA effect occurs after both direct and indirect exposure.