A constitutive model for granular materials considering grain breakage

A particle breakage has a significant impact on the mechanical behavior of granular materials. In this paper, we present an elasto-plastic model with two yield surfaces to which the influence of particle breakage has been introduced. The main feature of this model is to incorporate the change in the critical state line (CSL) consequent to the grain breakage induced by isotropic and deviatoric stresses during loading. For this purpose we propose a breakage function which connects the evolution of the CSL to ...     

Corrosion resistance of low‐nickel duplex stainless steel rebars

The use of stainless steel bars in reinforced concrete structures may be an effective method to prevent corrosion in aggressive environments where high amounts of chlorides may penetrate in the concrete cover. For an estimation of the service life of structures where stainless steel bars are used, the chloride threshold for these rebars should be defined, and the influence of chemical composition and metallurgical factors that may affect the corrosion resistance (strengthening, welding, etc.) should be assessed. To reduce the cost of stainless steel reinforcement, duplex stainless steels with low nickel content have been recently proposed as an alternative to traditional austenitic steels, even though, few results are available regarding their corrosion performance in chloride contaminated concrete. This paper deals with the corrosion resistance of low‐nickel duplex stainless steel rebars (1.4362 and 1.4162) as a function of the chloride content. Comparison is made with traditional austenitic steels. An attempt to define a chloride threshold for the different stainless steels is made by comparing the results of several test procedures both in concrete and in solution.     

Temperature wave‐trains of periodically forced networks of catalytic reactors

Networks of N identical catalytic reactors with periodically switched inlet and outlet sections are studied for first‐order irreversible exothermic reactions. Switching strategies with inlet and outlet sections periodically jumping a fixed number n_s of reactors are considered and the mechanisms governing the formation of traveling temperature wave‐trains are analyzed as n_s and N are varied. To this aim, a geometric approach to the analysis of the network energy balance is developed. Based on this approach, infinite domains of traveling temperature wave‐trains are predicted for any n_s and N. Analytical approximations are derived for the stability limits and the spatiotemporal patterns of these regimes. Stability boundaries predicted analytically include for any solution the largest part of the stability region computed by numerical simulation. Moreover, good agreement is found between the structure of the spatiotemporal patterns computed numerically and that predicted based on the proposed approach. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Numerical and Experimental Study on a New Separation Device for Gas-Solid Two-Phase Flows

A novel separation device is designed to separate solid particles from the high-temperature, high-pressure dusty gas based on oblique shock wave theory. Two-dimensional numerical simulations and a series of experiments of the separation of the supersonic gas-solid two-phase flow are carried out. The aim is to validate the conditions for realizing the gas dedusting and to study the performance of the separation device. It is found that the gas dedusting can be realized only when the physical interface which basically overlaps the geometrical interface are stable and the design flow velocities at the dust-carrying and dust-absorbing nozzles are close to each other. Besides, the experimental results show that 57.83%～67.28% particles with a sauter average diameter of 9.84 µm can be separated by the experimental device. 75.73%～80.15% particles with diameters above 8.31 µm and 96%～100% particles with diameters above 15 µm can also be separated. Larger particles correspond to higher separation efficiency. The same conclusions are also drawn from the numerical simulation results. The study indicates that the present method for the separation of gas-solid two-phase flow is feasible and highly efficient.     

精轧机出口带钢头部浪形分析及应对措施

针对精轧机组出口板坯头部浪形不达标的问题,采用实测轧机弹跳曲线的方法找出了轧机的机械推上系统间隙无法有效消除是产生浪形不达标的主要原因。根据实际情况提出改造方案,结果表明其有效性。     

Ultrasonic wave characteristics of a monolayer graphene on silicon substrate

The present work deals with an ultrasonic type of wave propagation characteristics of monolayer graphene on silicon (Si) substrate. An atomistic model of a hybrid lattice involving a hexagonal lattice of graphene and surface atoms of diamond lattice of Si is developed to identify the carbon-silicon bond stiffness. Properties of this hybrid lattice model is then mapped into a nonlocal continuum framework. Equivalent force constant due to Si substrate is obtained by minimizing the total potential energy of the system. For this equilibrium configuration, the nonlocal governing equations are derived to analyze the ultrasonic wave dispersion based on spectral analysis. From the present analysis we show that the silicon substrate affects only the flexural wave mode. The frequency band gap of flexural mode is also significantly affected by this substrate. The results also show that, the silicon substrate adds cushioning effect to the graphene and it makes the graphene more stable. The analysis also show that the frequency bang gap relations of in-plane (longitudinal and lateral) and out-of-plane (flexural) wave modes depends not only on the y-direction wavenumber but also on nonlocal scaling parameter. In the nonlocal analysis, at higher values of the y-directional wavenumber, a decrease in the frequency band gap is observed for all the three fundamental wave modes in the graphene–silicon system. The atoms movement in the graphene due to the wave propagation are also captured for all the tree fundamental wave modes. The results presented in this work are qualitatively different from those obtained based on the local analysis and thus, are important for the development of graphene based nanodevices such as strain sensor, mass and pressure sensors, atomic dust detectors and enhancer of surface image resolution that make use of the ultrasonic wave dispersion properties of graphene.     

高Q腔中激发相干态的制备

提出了一种基于高Q光腔中的原子与一行波光场相互作用来制备光场激发相干态和二阶激发相干态的新方法。与已提出的方法比较，该方法具备一些优点：不应用微扰理论且除了最后测量外仅用一步就可完成制备，但该方法成功几率只有50%。     

转换波地震资料处理方法在苏里格地区的应用

在详细分析了转换波资料特征的基础上,以苏里格气田实际采集的多波资料为对象,开展了极性反转、转换波静校正、叠前噪声压制、共转换点道集的抽取等关键处理方法的研究.提出了PS波构造相似法转换波静校正、分频噪声压制技术及共转换点道集抽取解决方案,实际资料的处理结果表明了该方法的正确性及有效性.     

Design of an airlift loop bioreactor and pilot scales studies with fluidic oscillator induced microbubbles for growth of a microalgae Dunaliella salina

This study was conducted to test the feasibility of growing microalgae on steel plant exhaust gas, generated from the combustion of offgases from steel processing, which has a high CO₂ content. Two field trials of batch algal biomass growth, mediated by microbubble transfer processes in an airlift loop bioreactor showed only steady growth of biomass with 100% survival rate. The gas analysis of CO₂ uptake in the 2200 L bioreactor showed a specific uptake rate of 0.1 g/L/h, an average 14% of the CO₂ available in the exhaust gas with a 23% composition of CO₂. This uptake led to a steady production of chlorophyll and total lipid constituency in the bioreactor, and an accelerating exponential growth rate of biomass, with a top doubling time of 1.8 days. The gas analysis also showed anti-correlation of CO₂ uptake and O₂ production, which along with the apparent stripping of the O₂ to the equilibrium level by the microbubbles, strongly suggests that the bioreactor is not mass transfer limited, nor O₂ inhibited. Removing O₂ inhibition results in high growth rates and high density of biomass.     

Future orientation, impulsivity, and problem behaviors: A longitudinal moderation model.

In the current study, based on a sample of 1,873 adolescents between 11.4 and 20.9 years of age from the first 3 waves of the National Longitudinal Study of Adolescent Health, we investigated the longitudinal effects of future orientation on levels of and developmental changes in problem behaviors, while controlling for the effects by impulsivity; we also tested the moderating effects by future orientation on the impulsivity–problem behaviors link over time. Additionally, we examined future orientation operationalized by items measuring education, marriage, and life domains. Findings based on growth curve analyses provided evidence of longitudinal effects by education and life future orientation on both levels of and developmental changes in problem behaviors; the effect of marriage future orientation was not significant for either test. In addition, only life future orientation moderated the effect by impulsivity on levels of problem behaviors over time. More specifically, impulsivity had a weaker effect on levels of problem behaviors over time for adolescents who reported higher levels of life future orientation. (PsycINFO Database Record (c) 2011 APA, all rights reserved)