Fuel oil from ABS using a tandem PEG-enhanced denitrogenation-pyrolysis method: Thermal degradation of denitrogenated ABS

Thermal degradation of ABS and denitrogenated ABS samples (DABS), prepared by sequential hydrolysis of ABS using PEG/NaOH, has been investigated under inert gas and at atmospheric pressure in a temperature range between 40 and 700 °C, by means of TGA, TGA-IR, and TGA-MS, to study the link between original structure of DABS and eventual pyrolysis. For DABS, thermal decomposition begins at the side groups of -CONH₂ and/or -COOH, resulting in a lower initial degradation temperature of DABS (around 330 °C) relative to ABS (372.5 °C). Moreover, less HCN and acrylonitrile evolve from the DABS samples, while the evolution of CO₂ starts earlier and becomes more important, in line with the decreased number of -CN groups and the increased number of -COOH functional groups due to hydrolysis. The results from thermo-analytical experiments were confirmed by batch pyrolysis tests: the nitrogen content of oil produced from DABS pyrolysis is much lower, compared with that from ABS, proving that effective denitrogenation of ABS prior to pyrolysis is beneficial to the quality of pyrolysis oil.     

A new element for analyzing large deformation of thin Naghdi shell model. Part II: Plastic

In this paper a new element is developed that is based on Cosserat theory. In the finite element implementation of Cosserat theory shear locking can occur, especially for very thin shells. In the present investigation the director vector is constrained to remain perpendicular to the mid surface during deformation. It will be shown that this constraint yields accurate results in very large deformation of thin shells also the rate of convergency is very good. For plastic formulation, the model introduced by Simo is used and it has been reduced for constrained director vector and the consistent elasto-plastic tangent moduli is extracted for finite element solution. This model includes both kinematic and isotropic hardening. For numerical investigations an isoparametric nine node element is employed then by linearization of the principle of virtual work, material and geometric stiffness matrices are extracted. The validity and the accuracy of the proposed element is illustrated by the numerical examples and the results are compared with those available in the literature.     

Simulation of beam plastic forming with variable bending moments

A versatile generic elastic/plastic moment/curvature equation is used to simulate beam deflections. Solutions are obtained numerically and used to investigate whether forming equations based on the assumption of pure bending can be extended in a rational way to more complicated loadings. It is concluded that the answer is affirmative, with only knowledge of the elastic/plastic behavior associated with pure bending and the elastic behavior associated with the actual loading being needed to make the extension.     

Hoek–Brown criterion applied to circular tunnel using elastoplasticity and in situ axial stress

Based on the nonlinear Hoek–Brown failure criterion, elastoplastic analytical solutions are developed for the elastoplastic stresses, strains and plastic zones around a circular tunnel subjected to different value of the axial in situ stress. Effects of the transverse in situ stress, the axial in situ stress and the strength parameters of rock masses on the elastoplastic stresses, strains and plastic zones in the surrounding rock masses are investigated. It is found from the numerical results that the stresses, strains, and plastic zones in the surrounding rock depend not only on the transverse in situ stress but also on the axial in situ stress as well as the mechanical parameters of rock masses.     

Mechanical properties of lattice grid composites

An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid com- posite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.     

β晶型聚丙烯塑性形变过程中的形态变化

β晶型聚丙烯塑性形变过程中的形态变化沈静姝，任宏燕，况勋（中国科学院化学研究所高分子物理开放实验室，北京，１０００８０）史观一（中国科学院上海有机所，上海，２０００３２）关键词β晶型聚丙烯，塑性形变，形态全同立构聚丙烯的分子链都是３；螺旋链，但其晶体...     

Plastic multipliers as driving variables of numerical simulation in elastoplasticity

Statics of elasto-plastic media is stated in terms of eigenstrains acting upon a background elastic problem with fixed (initial) stiffness. In order to minimize the number of unknowns and to provide computationally cheap algorithms plastic multipliers are used as main driving variables. Fixed-point type iterations are suggested for computing plastic multipliers within the load increment. Numerical experiments results are shown to be in good correlation with other software results. A range of problems is outlined where the usage of the proposed algorithms can be advantageous.     

近红外光谱方法在颌面外科皮瓣移植术后监测中的应用

近红外光谱技术作为一种无创组织氧监测手段,近年来在整形外科手术术后监测方面得到了越来越多的重视。文章利用一套近红外无损组织氧检测系统对6例手术成功病例的移植皮瓣侧和对照侧正常组织内的氧饱和度进行了长时间对比监测,发现两侧的组织氧饱和度之间存在显著性差异。还对一例血管吻合失败的病例下颌部的多个位置进行了检测,发现坏死部位的氧饱和度和正常组织相比处于很低的水平。实验结果表明,近红外光谱检测技术对于皮瓣内的血氧浓度动态变化具有很好的灵敏度,在移植皮瓣的术后监测方面具有良好的应用前景。     

CFD-based predictive control of melt temperature in plastic injection molding

A unique method of coupling computational fluid dynamics (CFD) to model predictive control (MPC) for controlling melt temperature in plastic injection molding is presented. The methodology is based on using CFD to generate, via open-loop testing, a temperature and input dependent system model for multi-variable control of a three-heater barrel on an injection molding machine. Results clearly show the benefit of temperature and input dependent system models for MPC control, and that CFD can be used to dramatically reduce the time associated with open-loop testing through physical experiments.     

固态富马酸单乙酯在变温1H MAS与CRAMPS研究

富马酸单乙酯(FAME)的单脉冲¹H MAS谱由-高分辨成分与-宽线谱成分组成.高分辨成分可由Hahn回波脉冲序列单独获得.文中通过变温¹H MAS与CRAMPS实验对两组分的性质进行了系统的研究.发现当温度趋于样品的熔点时,其¹H CRAMPS谱可观察到化学位移明显区别的两套谱,它们分别对应于¹H MAS谱的高分辨与宽线组分.实验表明:高分辨成分来自FAME样品的-塑性相,而宽线组分来自通常的刚性相.文中所给出的实验事实充分说明¹H MAS与CRAMPS技术是研究有机塑性固体的强有力的工具.