复合圆柱形壳在径向冲击荷载和轴压荷载作用下的瞬时动力响应

基于首次逼近理论,利用第一阶剪切变形理论对圆柱形壳的自由和强迫振动进行分析。边界条件（BCs）考虑为悬臂状态。分析复合壳体在横向冲击和轴向压力作用下的动力响应（轴压荷载小于临界屈曲荷载）,同时对复合柱形壳进行了建模分析。利用卷积积分对给定荷载状况下的壳体进行分析。揭示纤维方向、轴向荷载及一些几何参数对壳体时间响应的影响。结果表明：动力响应主要由结构的自振周期所控制。     

Thermodynamic analysis and evolutionary algorithm based on multi-objective optimisation of the Rankine cycle heat engine

This study demonstrates the outcomes of a research implement for the power and efficiency optimisation of a Rankine cycle heat engine employing the non-dominated sorting genetic algorithm (NSGA-II) algorithm. Two objective functions comprising the efficiency and power were included concurrently maximised. To assess this idea, multi-objective optimisation approach founded on NSGA-II method has been utilised in which following variables have been considered as decision variables: (1) the inlet temperatures of a heat source, (2) the inlet temperatures of a heat sink, (3) temperature difference (x), (4) temperature difference (y), (5) heat conductance and (6) heat capacitance. By applying the addressed multi-objective optimisation approach, Pareto optimal frontier was determined and utilising different decision-making techniques that include the LINMAP, TOPSIS and fuzzy Bellman–Zadeh approaches help us to figure out the final optimal solution.     

Gasoline permeation behavior and mechanical properties of polyamide 6/nanoclay,polyamide 6/PE‐g‐maleic anhydride blend,and polyamide 6/PE‐g‐maleic anhydride/clay nanocomposite

In this article, polyamide 6 (PA6)/clay nanocomposites, PA6/polyethylene grafted maleic anhydride (PE‐g‐MA) blends, and PA6/PE‐g‐MA/clay nanocomposites were prepared and their gasoline permeation behavior and some mechanical properties were investigated. In PA6/clay nanocomposites, cloisite 30B was used as nanoparticles, with weight percentages of 1, 3, and 5. The blends of PA6/PE‐g‐MA were prepared with PE‐g‐MA weight percents of 10, 20, and 30. All samples were prepared via melt mixing technique using a twin screw extruder. The results showed that the lowest gasoline permeation occurred when using 3 wt % of nanoclay in PA6/clay nanocomposites, and 10 wt % of PE‐g‐MA in PA6/PE‐g‐MA blends. Therefore, a sample of PA6/PE‐g‐MA/clay nanocomposite containing 3 wt % of nanoclay and 10 wt % of PE‐g‐MA was prepared and its gasoline permeation behavior was investigated. The results showed that the permeation amount of PA6/PE‐g‐MA/nanoclay was 0.41 g m^?2 day^?1, while this value was 0.46 g m^?2 day^?1 for both of PA6/3wt % clay nanocomposite and PA6/10 wt % PE‐g‐MA blend. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40150.     

Development of Regional Rainfall Annual Maxima for Southwestern Iran by L-Moments

L-moment procedures are applied to develop regional rainfall annual maxima (maximum 24-h rainfall occurring annually), considering complex physiographic and hydroclimatological features and weather processes as attributes influencing regional homogeneity. Capability of L-moment procedures in breaking down large areas into coherent and homogeneous sub-regions is investigated. The study area of 238,630 km² is located in southwestern Iran, representing 154 rainfall recording gauges of rather complex orographic features. According to the results and considering the extreme value nature of the analysis, i.e., rainfall annual maxima, it was possible to establish four homogeneous sub-regions, representing areas of 80,490 km², 75,880 km², 31,810 km² and 50,450 km². The L-moment procedures successfully evaluated the homogeneity analyses and assignment of appropriate regional probability distribution functions (PDFs) to individual sub-regions. Flood potential maps and associated rainfall depth-area information were provided for individual sub-regions. The proposed heterogeneity measures by Hosking and Wallis (Water Resour Res 29(2):271–289, 1993), known as H ₁, H ₂ and H ₃ tests were further investigated in this research. The results of this research confirmed findings of Hosking and Wallis (Water Resour Res 29(2):271–289, 1993), i.e., strong capability of H ₁ as a heterogeneity measure, and lack of capability of H ₂ and H ₃ measures for distinguishing between homogenous and heterogeneous regions.     

Daily Outflow Prediction by Multi Layer Perceptron with Logistic Sigmoid and Tangent Sigmoid Activation Functions

This paper discusses the use of artificial neural network (ANN) models for predicting daily flows from Khosrow Shirin watershed located in the northwest part of Fars province in Iran. A Multi-Layer Perceptron (MLP) neural network was developed using five input vectors leading to five ANN models: MLP1, MLP2, MLP3, MLP4, and MLP5. Two activation functions were used and they were logistic sigmoid and tangent sigmoid. The MLP_Levenberg–Marquardt (LM) algorithm was used for the training of ANN models. A 5-year data record, selected randomly, was used for ANN training and testing. The predicted outflow showed that the tangent sigmoid activation function performed better than did the logistic sigmoid activation function. The values of R ² and RMSE for MLP4 with the tangent sigmoid activation function for the validation period were equal to 0.89 and 1.7 m³/s, respectively. Appropriate input vectors for MLPs were determined by correlation analysis. It was found that antecedent precipitation and discharge with 1 day time lag as an input vector best predicted daily flows. Also, comparison of MLPs showed that an increase in input data was not always useful.     

Strengthening of polysulfone membranes using hybrid mixtures of micro- and nano-scale modifiers

Polysulfone (PSf) membranes were modified by either a new organic modifier (sulfonated poly(ether sulfide sulfone), SPESS) or a traditional modifier (rice hulk). These membranes were further reinforced with either multi-walled carbon nanotubes (MWCNTs) or silica nanoparticles. Having a dye rejection of 98.46%, the reinforced membranes increased more than 50% in strength but no change in solution flux was observed. The morphological and roughness studies were conducted using scanning electron microscopy and atomic force microscopy. Moreover, the PSF membranes were also characterized by differential scanning calorimetry. Modifying the membranes with organic modifier or nanofiller increases the glass transition temperature (T _g ). The highest T _g and strength were observed for the PSf-SPESSMWCNT membrane. SPESS decreases surface roughness but MWCNT increases roughness on the nanoscale. All membranes show a bimodal pore size distribution, whereas the PSf-SPESS-MWCNT membrane exhibits a relatively uniform distribution of macroscopic and microscopic pores.

Open image in new window

     

Effect of casein infusion in the rumen,duodenum or both sites on factors affecting forage intake and performance of dairy cows fed red clover-grass silage

Four lactating dairy cows were used in a balanced 4 x 4 Latin square design to examine the effects of casein infusion in the rumen, duodenum, or both on the intake of red clover-grass silage, chewing behavior, diet digestion, microbial protein synthesis, rumen fermentation, digestion, and passage kinetics, milk production, and milk composition. Duodenal infusion increased eating time, silage intake, rumen neutral detergent fiber pool, yields of milk, protein, and lactose, and concentration of milk protein, and tended to decrease that of milk fat. Ruminal infusion tended to decrease eating time, and increased significantly microbial protein synthesis, rumen ammonia-N concentration, molar proportions of isovalerate and valerate, digestion rate of digestible neutral detergent fiber, passage rate of indigestible neutral detergent fiber, and milk urea content, and decreased rumen neutral detergent fiber pool. Silage intake, and yields of milk, protein, and lactose were highest when casein was simultaneously infused in both sites.     

Wound dressing application of castor oil- and CAPA-based polyurethane membranes

Polymer Bulletin - The objective of this study was to investigate and compare the effects of two different types of polyols on properties of synthesized polyurethanes (PUs), to develop biomedical...     

Numerical study of lap joints with composite adhesives and composite adherends subjected to in-plane and transverse loads

In this paper, single lap joints for joining fibre composites were modeled and a three-dimensional finite element method was used to study the joint strength under in-plane tensile and out-of-plane loadings. The behaviour of all the members was assumed to be linear elastic. The adherends were considered to be orthotropic materials while the adhesive could be neat resin or reinforced one. The largest values of shear and peel stresses occurred near the ends of the adhesive region, as expected. The values and the rate of variation in peel stress was more than that of shear stress. By changing the properties and behaviour of adhesive from neat epoxy (isotropic) to fibre composite adhesive (orthotropic) and with various fibre volume fractions of glass fibre, the ultimate bond strength increased as the fibre volume fraction increased, in both tensile and transverse loadings. Also, changing the orientation of fibres in the adhesive region with respect to the global axes influenced the bond strength.     

More comprehensive 3D modeling of clay‐like material drying

Drying process plays an important role in the manufacturing of many products such as ceramic, kitchenware and building materials, some of which have complex three‐dimensional (3D) geometry. To deal with many restrictions found in literatures, a 3D numerical approach was used to describe the drying process of a porous Clay‐like material. The problem investigated involves highly coupled equations considering heat, mass, and mechanical aspects. The model is validated through the comparison of experimental measurements with simulation result. Simulation results show that increasing the initial moisture content and reducing the initial temperature have the same privilege and without significant increase in drying time, it reduces slightly the amount of maximum stress but delays the occurrence time of maximum stress. The nonuniform heat expansion induced stresses are very small in comparison to nonuniform moisture shrinkage induced stresses and can be neglected in drying simulation. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1469–1478, 2018