A model of crack based on dislocations in smectic A liquid crystals

A plastic crack model for smectic A liquid crystals under longitudinal shear is suggested. The solution of the screw dislocation in smectic A is the key to the correct result that we obtained by overcoming a longstanding puzzle. We further use the dislocation pile-up principle and the singular integral equation method to construct the solution of the crack in the phase. From the solution, we can determine the size of the plastic zone at the crack tip and the crack tip opening （tearing） displacement, which are the parameters relevant to the local stability/instability of materials. Our results may be useful for developing soft-matter mechanics.     

Friction and Wear Behavior of Polyamide 66/Poly(vinylidene fluoride) Blends

The tribological performance of PA66 and PVDF blends was investigated by a block‐on ring sliding friction and wear tester. The appropriate amount of PVDF can decrease the friction coefficient and improve the wear resistance of PA66. Moreover, the appropriate amount of PA66 can improve the wear resistance of PVDF. SEM analysis shows that PVDF is noncompatible with PA66, and the blend presents a two‐phase structure. A smooth worn surface is a main reason for improving the frictional and wear properties of the PA66/PVDF blend. Besides, slight debris is an important factor in improving the wear resistance of the PA66/PVDF blend. FT‐IR analysis shows that the oxidation and degradation behavior of PVDF is effectively controlled in the PA66/PVDF blends. Therefore, the blend of PA66 and PVDF is a potential polymer material for tribological applications.     

Behavior of structure defects and hydrogen in neutron-irradiated stainless steels studied by positron annihilation method

Measurements of angular distributions of annihilation photons are applied to investigating structural defects and hydrogen behavior in annealed, plastically deformed, and irradiated stainless steels. It is determined that the whole cycle of investigations performed by positron diagnostics helped in tracing the formation and evolution of the defect structure and hydrogen behavior in different kinds of steels being subjected to complex physical–mechanical influences such as plastic deformation, hydrogenation and irradiation by fission neutrons. The high sensitivity of the electron–positron annihilation method allowed understanding even of details of the changes of the crystalline structure of multi-component materials.     

Simulation of particulate-filled composite deformation diagrams on the basis of a constitutive model of large plastic deformation for a polymer matrix

Deformation diagrams of particulate-filled polymers have been calculated on the basis of specific constitutive equations [1] for large plastic deformation of the polymer. Composite structure is represented by the Hashin polydisperse model [2]. Original finite-element (FE) code with triangular elements has been elaborated and used for the numerical solution of boundary value problems. Local achievement of a critical value by the elastic main strain was used as a fracture criterion. Engineering (force-elongation) diagrams were found to exhibit maxima for arbitrary filler fraction if the interfacial bond was perfect and for low loading at zero adhesion. Stress-strain diagrams with a yield maximum and draw minimum provide macroscopic neck-type localization. Further, the loading in the case of facilitated deboading results in the diminution of the difference between maximum and minimum drawing forces and then in the disappearance of the latter, which in turn provides the transition from localized to macrouni-form deformation. Young's modulus and the yield stress increase with filling in the case of absolute adhesion and decrease in the opposite case. Ultimate elongation sharply drops with an increase in filler fraction, and embrittlement occurs at a small fraction of inorganic particles if a perfect interfacial bond is present. Contrary, a decrease in ultimate elongation is much more gradual, and composites conserve ductile properties of the matrix up to a high portion of inclusions. The laws found qualitatively coincide with what is observed for real materials.     

Isothermal Crystallization Kinetics of Highly Filled Wood Plastic Composites: Effect of Wood Particles Content and Compatibilizer

The isothermal crystallization behavior and crystal structure of the polypropylene (PP) component in wood plastic composites (WPC) with respect to wood particle content and maleic anhydride-grafted polypropylene (MAHPP) compatibilizer were studied by means of polarized optical microscopy, scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry. It was found that under the experimental conditions of this research, the speed of crystallization of PP was faster in WPC with MAHPP than in composites without MAHPP. This is ascribed to the difference in undercooling due to the change in the equilibrium melting temperatures (T ⁰ _m ) of the PP component in WPC due to the addition of wood flour and MAHPP compatibilizer. T ⁰ _m decreased with the increase of wood particle content, and it decreased more severely with the addition of wood flour than the addition of compatibilizer. The half-crystallization time was the smallest in PP/wood composites, intermediate in PP/wood/compatibilizer system, and the largest in pure PP under the same undercooling. The fast crystallization in PP/wood composites is ascribed to the heterogeneous nucleation effects of wood particles, which could be hindered by the MAHPP compatibilizers; this was verified by the higher fold surface free energy in WPC with compatibilizer than in WPC without compatibilizer.     

Pretreatment,Anaerobic Codigestion,or Both? Which Is More Suitable for the Enhancement of Methane Production from Agricultural Waste?

Pretreatment and codigestion are proven to be effective strategies for the enhancement of the anaerobic digestion of lignocellulosic residues. The purpose of this study is to evaluate the effects of pretreatment and codigestion on methane production and the hydrolysis rate in the anaerobic digestion of agricultural wastes (AWs). Thermal and different thermochemical pretreatments were applied on AWs. Sewage sludge (SS) was selected as a cosubstrate. Biochemical methane potential tests were performed by mixing SS with raw and pretreated AWs at different mixing ratios. Hydrolysis rates were estimated by the best fit obtained with the first-order kinetic model. As a result of the experimental and kinetic studies, the best strategy was determined to be thermochemical pretreatment with sodium hydroxide (NaOH). This strategy resulted in a maximum enhancement in the anaerobic digestion of AWs, a 56% increase in methane production, an 81.90% increase in the hydrolysis rate and a 79.63% decrease in the technical digestion time compared to raw AWs. On the other hand, anaerobic codigestion (AcoD) with SS was determined to be ineffective when it came to the enhancement of methane production and the hydrolysis rate. The most suitable mixing ratio was determined to be 80:20 (Aws/SS) for the AcoD of the studied AWs with SS in order to obtain the highest possible methane production without any antagonistic effect.     

Catalytic coprocessing of waste plastics and petroleum residue into liquid fuel oils

Waste plastics of different types were catalytically coprocessed with petroleum residue of light Arabian crude oil in the presence of a number of catalysts. The purpose of the study was to explore effects of various conditions such as catalyst type, amount of catalyst, reaction time, pressure and temperature on the product distribution. The waste plastic studied included low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS) and polypropylene (PP). A series of single (waster plastic with catalyst) and binary (waste plastic and residue with catalyst) reactions were carried out in an autoclave reactor under variable reaction conditions. The reaction conditions used were 1, 3 and 5 wt.% catalysts, 30–120 min reaction time, 400–430 °C reaction temperature and 500–1200 psi hydrogen pressure. The product distribution achieved for residue/plastic/catalyst system showed higher yields of liquid fuels as compared to residue/plastic system. Hydrocarbon gases were formed as well along with heavy oils, insoluble gums and coke. At the reaction conditions of 3 wt.% NiMo catalyst, 90 min reaction time, 1200 psi hydrogen gas pressure, 430 °C temperature and residue to plastic feed ratio of 3:2 (wt.) afforded maximum conversion of the plastics into liquid fuel oils.     

混合废塑料与煤共热解液体产物中氯的含量与赋存形态

采用离子色谱等方法测定了不同热解条件下液体产物（包括焦油和水）中氯的质量分数,讨论了影响煤与废塑料共热解过程中,热解温度、恒温时间、升温速率及气体流量等因素对液体产物中氯质量分数的影响。并通过红外光谱、离子色谱等手段分析了液体产物中氯的赋存形态。结果表明,煤热解过程中加入一定量的废塑料,并没有给焦油中带来大量的有机含氯化合物,但增加了焦油的产率,同时降低了水的产率。水中氯主要以无机盐（NH₄Cl）和有机胺类盐酸盐等含氯化合物的形式存在;焦油的红外光谱中没有明显的C-Cl吸收峰,说明焦油中有机氯的含量非常少。     

On the linearization of nonlinear langevin-type stochastic differential equations

We show that a logical extension of the piecewise optimal linearization procedure leads to the Gaussian decoupling scheme, where no iteration is required. The scheme is equivalent to solving a few coupled equations. The method is applied to models which represent (a) a single steady state, (b) passage from an initial unstable state to a final preferred stable state by virtue of a finite displacement from the unstable state, and (c) a bivariate case of passage from an unstable state to a final stable state. The results are shown to be in very good agreement with the Monte Carlo calculations carried out for these cases. The method should be of much value in multidimensional cases.     

光纤CAN网络节点数计算方法

为电动汽车通信网设计了一种中继型节点的光纤CAN(Fibre--CAN)环型总线网络．采用塑料光纤(POF)作为传输介质，用波长为660nm的红光光电收发器件实现光电转换．在对中继型节点的传输延迟进行详细的分析后，结合CAN协议定义的位周期，给出了基于传输延时的网络最大节点数的计算方法．并对该方法进行了实验验证，实验结果与理论计算具有良好的一致性，表明该方法的有效性．