Experimental determination of grain density function of AZ91/SiC composite with different mass fractions of SiC and undercoolings using heterogeneous nucleation model

The grain density,Nv,in the solid state after solidification of AZ91/SiC composite is a function of maximum undercooling,ΔT,of a liquid alloy.This type of function depends on the characteristics of heterogeneous nucleation sites and number of SiC present in the alloy.The aim of this paper was selection of parameters for the model describing the relationship between the grain density of primary phase and undercooling.This model in connection with model of crystallisation,which is based on chemical elements diffusion and grain interface kinetics,can be used to predict casting quality and its microstructure.Nucleation models have parameters,which exact values are usually not known and sometimes even their physical meaning is under discussion.Those parameters can be obtained after mathematical analysis of the experimental data.The composites with 0,1,2,3 and 4wt.% of SiC particles were prepared.The AZ91 alloy was a matrix of the composite reinforcement SiC particles.This composite was cast to prepare four different thickness plates.They were taken from the region near to the thermocouple,to analyze the undercooling for different composites and thickness plates and its influence on the grain size.The microstructure and thermal analysis gave set of values that connect mass fraction of SiC particles,and undercooling with grain size.These values were used to approximate nucleation model adjustment parameters.Obtained model can be very useful in modelling composites microstructure.

Influence of Isothermal Treatment on Superelastic Behavior of Cu-13.8Al-4.0Ni(mass fraction) Single Crystals

The superelastic behaviors of different isothermal treated Cu-13.SAl-4.ONi (mass fraction) single crystals were studied by applying tensile stress along <001> of the d phase. The different isothermal specimens have different superelastic behavior due to the change of the ratio of stress-induced r1 and β1. The superelasticity of r1 phase tends to that of g; phase with cycling. Typical stabilization of stress-induced martensite above Ap results in residual deformation. Due to the reverse transformation of 7I, there is a deviation of pseudo-yield stress from linear relation with temperature at relatively low stress.

Numerical prediction of vortex flow and thermal separation in a subsonic vortex tube

This work was aimed at gaining understanding of the physical behaviours of the flow and temperature separation process in a vortex tube. To investigate the cold mass fraction’s effect on the temperature separation, the numerical calculation was carried out using an algebraic Reynolds stress model (ASM) and the standard k-ε model. The modelling of turbulence of com-pressible, complex flows used in the simulation is discussed. Emphasis is given to the derivation of the ASM for 2D axisymmet-rical flows, particularly to the model constants in the algebraic Reynolds stress equations. The TEFESS code, based on a staggered Finite Volume approach with the standard k-ε model and first-order numerical schemes, was used to carry out all the computations. The predicted results for strongly swirling turbulent compressible flow in a vortex tube suggested that the use of the ASM leads to better agreement between the numerical results and experimental data, while the k-ε model cannot capture the stabilizing effect of the swirl.

Physically based analytical model for plateau in gate C-V characteristics of strained silicon pMOSFET

A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.The extracted parameters from our model were tOX=20 nm,ND=1×1016cm 3,tSSi=13.2 nm,consistent with the experimental values.The results show that the simulation results agree with experimental data well.It is found that the plateau can be strongly affected by doping concentration,strained-Si layer thickness and mass fraction of Ge in the SiGe layer.The model has been implemented in the software for strained silicon MOSFET parameter extraction,and has great value in the design of the strained-Si/SiGe devices.

Application of silver nanoparticles in electrically conductive adhesives with silver micro flakes

This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.

Extended activated sludge model no. 1 (ASM1) for simulating biodegradation process using bacterial technology

Phosphorus is one of the most important nutrients required to support various kinds of biodegradation processes. As this particular nutrient is not included in the activated sludge model no. 1 （ASM1）, this study extended this model in order to determine the fate of phosphorus during the biodegradation processes. When some of the kinetics parameters are modified using observed data from the restoration project of the Xuxi River in Wuxi City, China, from August 25 to 31 in 2009, the extended model shows excellent results. In order to obtain optimum values of coefficients of nitrogen and phosphorus, the mass fraction method was used to ensure that the final results were reasonable and practically relevant. The temporal distribution of the data calculated with the extended ASM1 approximates that of the observed data.

Comparison of Cardiac Structural Improvement in Patients with Primary Aldosteronism after Surgical Therapy and Drug Therapy: A Meta-Analysis

Background: At present, in clinical practice, patients with primary hyperaldosteronism (PA) are mainly treated by surgery or medical drugs (spironolactone/spironolactone, epridone, etc.). Some studies show that the left ventricular hypertrophy of patients can be significantly improved after treatment. However, at present, the relevant research is very limited, and there is still controversy on the improvement of cardiac structure and function between the two treatment methods. No reliable conclusions have been drawn. Objective: We conducted this meta-analysis to compare the improvement of cardiac structure of patients after surgical treatment and drug treatment, so as to clarify the efficacy of surgical treatment and drug treatment for PA patients. Methods: In order to examine the cardiac color ultrasound data of PA patients receiving surgical treatment and drug therapy (spironolactone, antisterone), randomized or observational studies were searched through Pubmed, Cochrane Library, and Embase. Meta-analysis was then carried out on the comprehensive and individual outcomes. The ROINBS-I scale is utilized to assess the offset risk of study inclusion. Outcomes: A total of nine studies involving 799 patients with PA into meta analysis, according to the results of the surgery in the treatment of patients with PA, left ventricular mass index (LVMI) changes in value (drop range) is significantly higher than drug therapy (Mean difference IV: —2.32, P In 6 studies, after surgical treatment of interventricular septal thickness (IVSD), changes in value (drop range) are also higher than drug therapy (Mean difference IV: —0.35, P In 2 studies, the surgical treatment of plasma aldosterone concentration (PAC) drop degree is superior to drug therapy (Mean difference IV: —12.63, P < 0.05), and blood pressure to improve the degree of surgery and drug treatment has no obvious difference. Conclusions: This meta-analysis result confirmed that after medical and surgical treatment of PA can obviously improve the patient’s blood pressure, and no difference between the two treatments. But for the heart structure improvement, including left ventricular hypertrophy and interventricular septum thickness, surgical treatment effect is significantly better than the medicine treatment, so the adrenalectomy can be used as unilateral PA optimal choice of treatment.

Numerical Simulation and Performance Assessment of a Nanoparticle Enhanced Vapour Compression Refrigeration System

Cooling in industrial production and refrigeration of perishable and non- perishable products is common practice throughout the world. Research studies have been conducted both experimentally and numerically to simulate Vapor Compression Refrigeration System (VCRS) and its performance respectively, however, experimental procedure often seems to be expensive and time-consuming to carry out due to the function of many variables. This study was therefore designed to numerically simulate the performance assessment of a nanoparticle enhanced VCRS. A numerical model of a vapor compression refrigeration system was developed using standard refrigeration equations on each of the major components of the refrigeration system such as compressor, evaporator, condenser and expansion valve. The model was then simulated on a MATLAB platform with a CoolProp installed packages via Python under two different simulation cases. In the first case, the mass fractions were varied for CuO, TiO2 and Al2O3 nanoparticles while their densities remained constant and a reversed condition was investigated for the second case. The results showed that both the refrigerating effect and the Coefficient Of Performance (COP) of the system increase as both the mass fraction and density of all the nanoparticles increases. It also shows that the compressor work decreases as both the mass fraction and density of all the nanoparticles were increased. On comparing the computational and numerical analysis results, the study established no significant difference in terms of COP and the use of nanoparticles were found to have improved the COP of the system.

Effects of Seeding Rate and Light on the Seed Yield and Bioactive Ingredient Contents of Vernonia anthelmintica

[Objectives]This study was conducted to investigate the effects of seeding rate and light on the seed yield and active ingredients of Vernonia anthelmintica.[Methods]With V.anthelmintica L.Willd as the research object,the seed yield was determined by staged harvesting combined with the actual cutting and measuring method;and the caffeoylquinic acids(CQA)were used as the characterization indexes,and high performance liquid chromatography was used to determine the contents of 3,4-CQA,3,5-CQA and 4,5-CQA of V.anthelmintica seeds under different seeding rate+light treatments,so as to compare the changes in seed yield and chemical composition of V.anthelmintica under different seeding rates and light factors.[Results]In Moyu County,Hetian and similar areas,the suitable planting rate of V.anthelmintica was in the range of 13.5-15.0 kg/hm^(2).For different harvesting purposes,the optimal seeding rate and light conditions of V.Anthelmintica were different.[Conclusions]The seeding rate and light conditions can be used to interfere with the seed yield and quality of V.anthelmintica.

Classical regression equations of spirometric parameters are not applicable for diagnosing spirometric abnormalities in adipotic adults

The prevalence of overweighing and obese adults (defined as "adipotic" adults),has markedly increased over the world. A remarkable increase in the adipotic population urgently needs developing the regression equations for predicting spirometric parameters (SPs), which are specifically applicable to adipotic adults.Unfortunately, however, the reliable equations suitable for adipotic adults have not been reported to date. Recently, Yamaguchi et al have proposed the quantitative method to estimate the effects of adiposity on deciding the SPs incorporating with age-specific contributions of various explanatory,independent variables such as age (A), standing height (H), body weight (BW),and fat fraction of body mass(F). Extending the method proposed by Yamaguchi et al, we attempted to elaborate the novel regression equations applicable for diagnosing the spirometric abnormality in adipotic adults. For accomplishing this purpose, never-smoking, adipotic adults with body mass index (BMI) over 25 kg/m^2 and no respiratory illness were recruited from the general population in Japan (n = 3696, including men: 1890 and women: 1806). Introducing the four explanatory variables of A, H, BW, and F, gender-specific and age-dependent regression equations that allowed for prescribing the SPs in adipotic adults were constructed. Comparing the results obtained for non-adipotic adults (i.e., those with normal BMI), the negative or positive impact of height on SPs was preserved in adipotic adults, as well. However, the negative impact of age on SPs was blunted in adipotic men and the positive effect of BW on SPs was impeded in adipotic men and women. The fat fraction of body mass-elicited negative impact on SPs vanished in adipotic women. These results indicate that the regression equations of SPs for adipotic adults differ significantly from those for nonadipotic adults, leading to the conclusion that the regression equations for nonadipotic adults should not be used while judging the spirometric abnormalities in adipotic adults.

Mechanical properties of U-0.95 mass fraction of Ti alloy quenching and aging treatment:a first principles study

First principles plane wave pseudopotential method was executed to calculate the mechanical properties with respect to the uranium-0.95 mass fraction of titanium （U-0.95 mass fraction of Ti） alloy for quenching and aging, including the elastic modulus, the value of shear modulus to bulk modulus （G/B） and the ideal tensile strength. The further research has also been done about the crack mechanism through Griffith rupture energy. These results show that the elastic moduli are 195.1 GPa for quenching orthorhombic ~ phase and 201.8 GPa for aging formed Guinier-Preston （G.P） zones, while G/B values are 0.67 and 0.56, respectively. With the phase change of uranium-titanium （U-Ti） alloy via the quenching treatment, the ideal tensile strength is diverse and distinct with dif- ferent crystal orientations of the anisotropic ~ phase. Comparison of quenching and short time aging treatment, both of the strength and toughness trend to improve slightly. Further analysis about electronic density of states （DOS） in the electronic scale indicates that the strength increases continuously while toughness decreases with the aging proceeding. The equilibrium structure appears in overaging process, as a result of decomposition of metastable quenching 7 phase. Thereby the strength and toughness trend to decrease slightly. Finally, the ideal fracture energies of G.P zones and overaging structure are obtained within the framework of Griffith fracture theory, which are 4.67 J/m2 and 3.83 J/m2, respectively. These results theoretically demonstrate strengthening effect of quenching and aging heat treatment on U-Ti alloy.

Numerical study of heat transfer of gas-atomized Fe-6.5 %Si （mass and solidification behavior fraction） droplets

During spray atomization process, the heat transfer and solidification of droplets play very important roles for the deposition quality. Due to the difficulties of experimental approach, a numerical model is developed, which integrates liquid undercooling, nucleation recalescence and post-re- calescence growth to present the full solidification process of Fe-6.5%Si （mass fraction） droplet. The droplet velocity, temperature, cooling rate as well as solid fraction profiles are simulated for droplets with different sizes to demonstrate the critical role of the size effect during the solidification process of droplets. The relationship between the simulated cooling rate and the experimentally obtained secondary dendrite arm spacing is in excellent agreement with the well-established formula. The pre-constant and exponent values lie in the range of various rapid solidified Fe-based alloys reported, which indicates the validity of the numerical model.

Durability of Concrete Made with Manganese Slag as Supplementary Cementitious Materials

This paper discusses mineral composition and pore microstructure characteristics of water-cooled manganese slag and its effects on durability of concrete. The Mn slag has an alveolate pore structure, and the ground Mn slag is characterized by multiangular shape which consists of a＇-C2S, C3M82, CaO.MnO-2SiOu and C2AS. Experimental results show that the Mn slag has potential hydraulic reactivity. Concrete made with Mn slag as supplementary cementitious materials （SCMs） exhibits very low strength loss and weight loss in the synthetic seawater corrosion and freezing-thawing cycle tests. The research provides useful reference for knowing about Mn slag and for applying Mn slag to improve the durability of concrete.

Resource economics and coordination among above- and below-ground functional traits of three dominant shrubs from the Chilean coastal desert

Aims Plant functional traits determine how plants respond to environmen-tal factors and influence ecosystem processes.Among them,root traits and analyses of relations between above and below-ground traits in natural communities are scarce.Methods we characterized a set of above-and below-ground traits of three dominant shrub species in a semiarid shrub-steppe that had contrasting leaf pheno-logical habits(deciduous,semideciduous and evergreen).We ana-lysed if there was coordination among above-and below-ground resource economics patterns:i.e.patterns of biomass allocation,construction costs and lifespan.Important Findings Above-and below-ground traits and their resource economics relations pointed to species-specific functional strategies to cope with drought and poor soils and to a species ranking of fast to slow whole-plant strategies in terms of resource uptake,biomass con-struction costs and turnover.The deciduous shrub,Proustia cunei-folia,had relatively deep and even distribution of roots,and high proportion of short-lived tissues of low C construction costs:it had high fine to coarse root and high leaf-to-stem biomass ratios,high specific leaf area(SLA),and stems of low wood density.This strat-egy allows Proustia to maximize and coordinate above-and below-ground resources uptake as long as the most limiting factor(water)is available,but at the cost of having relative high plant biomass turnover.The evergreen Porlieria chilensis,instead,displayed a more conservative and slow strategy in terms of resource econom-ics.It had~80%of the roots in the 40 cm topsoil profile,low pro-portion of fine compared with coarse roots and low leaf-to-stem ratios,low SLA and stems of high wood density,i.e.it invested in C costly tissues that,overall,persist longer but probably at the cost of having lower plant resource uptake rates.Traits in the semide-ciduous Adesmia bedwellii were in between these two functional extremes.Our results revealed high functional diversity and above-and below-ground complementarity in resource economics among these three codominant species in the Chilean coastal desert.

South-hemispheric marine aerosol Hg and S isotope compositions reveal different oxidation pathways

Particle-bound mercury(PBM)records the oxidation of elemental mercury,of which the main oxidation pathways(Br∙/Cl∙/OH∙/O3)remain unclear,especially in the Southern Hemisphere.Here,we present latitudinal covariations of Hg and Sisotopic anomalies in cross-hemispheric marine aerosols that evidence an equator-to-poleward transition of Hg oxidants from OH∙/O3 in tropics to Br∙/Cl∙in polar regions highlighting thus the presence of distinct oxidation processes producing PBM.The correlations between Hg,S and O-isotopic compositions measured in PBM,sulfates and nitrates respectively within the aerosols highlight the implication of common oxidants in their formations at different latitudes.Our results open a new window to better quantify the present-day atmospheric Hg,S and N budgets and to evaluate the influences of aerosols on climate and ecosystems once the isotopic fractionations associated with each process have been determined.