碳纤维复合材料无人机叶片的仿真与分析

为得到碳纤维在无人机叶片中最优的铺层方式,通过Workbench中的ACP(ANSYS Composite PrepPost)模块,对碳纤维复合材料无人机叶片的铺层进行设计。利用SolidWorks三维建模软件建立无人机叶片的三维模型,并采用HyperMesh对叶片进行几何清理、划分网格等,利用Ansys Workbench Fluent对无人机叶片的不同转速进行流体仿真,提取叶片表面压力载荷,对不同铺层的碳纤维复合材料无人机叶片进行仿真与分析,得到碳纤维复合材料无人机叶片的力学仿真结果,并基于Tsai–Wu失效准则,计算每层铺层的失效系数,进而对比得出最优的碳纤维铺层方式为[0°,90°,90°,90°,0°]。     

ANTIOXIDANT CAPACITY,SCAVENGING RADICAL ACTIVITY AND SELECTED CHEMICAL COMPOSITION OF NATIVE APPLE CULTIVARS FROM CENTRAL EUROPE

ABSTRACT

The main aim of this study was to focus on 10 typical native apple cultivars from Central Europe and to determine the basic characteristics such as dry matter, soluble solid content, titrable acidity, the content of pectins, phenolics, ascorbic acid, antioxidant capacity and the scavenging effect of 10% apple fruit extracts on hydroxyl radical, nitric oxide and superoxide radical in them. In our experiments, it was found out that the highest content of organic acids was shown by the “Jeptiska” cultivar (5.40 g/kg of FM). As far as the content of pectins was concerned, the highest levels were found out in the “Strymka” cultivar (32.60 g/kg FM). In case of total phenolic content, antioxidant capacity, ascorbic acid content and scavenging activity of reactive oxygen species (hydroxyl radical, nitric oxide and superoxide anion), high efficiency was determined in the local cultivars, namely, in “Matcino,”“Panenske ceske” and “Strymka.”

PRACTICAL APPLICATIONS

The results shown have wide use in the alimentary industry and human nutrition as apples belong to the most widespread core fruit. There exist many apple cultivars that have not been described in detail in literature and this study provides an insight into 10 not very common cultivars in the world; and although in Central Europe these cultivars are cultivated successfully, so far they have not been utilized commercially. However, their genetic uniqueness represents an irreplaceable ecological wealth and for that reason these local cultivars could become a new and outstanding source of nutrients and food. Today, they can also be used as a potential material for further breeding and selection.     

Modelling and simulation of heat transfer by convection in aerogel treated nonwovens

Simulation and numerical modeling are becoming increasingly popular due to the ability to seek solutions for a problem without undertaking real-life experiments. For the problems of heat transfer, these techniques to generate relevant data by incorporating different changes to the input parameters. Heat transfer property of textile materials is a major concern since it influences comfort properties of clothing. In this paper, numerical simulation was applied to evaluate the heat flux, temperature distributions, and convective heat transfer coefficients of the fibrous insulating materials treated with aerogel. The computational model simulated the insulation behavior of nonwoven fabrics without and with aerogel. Ansys and Comsol were used to model and simulate heat transfer. The simulation was performed assuming laminar flow and since the Mach number was < 0.3, the compressible flow model with Mach number < 0.3 was used. The results of simulation were correlated to experimental measurements for validation. Furthermore, aerogel-treated fabric samples showed better thermal performance. Using this model, the heat transfer properties of the nonwoven fabrics treated with aerogel can be optimized further.     

Aerogels for thermal insulation in high-performance textiles

For many garment applications where protection is needed against hostile environments, part of the requirement is for insulation to shield the wearer from extremes of temperature. For an insulating garment to be fully effective, it needs to allow the wearer to move freely so that they can carry out their intended activity efficiently. Traditional materials achieve their insulation by trapping air within the structure thereby not only limiting heat loss by convection but also making good use of the low thermal conductivity of air to cocoon the wearer within a comfortable environment. To achieve effective protection with conventional textiles, it is usually necessary to have a thick fibrous layer, or series of layers, to trap a sufficient quantity of air to provide the required level of insulation. Several disadvantages arise as a result. For example, thick layers of insulating textile materials reduce the ability of the wearer to move in a normal manner so that the conduct of detailed manual tasks can become very difficult; the layers lose their insulating capacity when the trapped air is lost as they are compressed; the insulating capacity falls rapidly as moisture collects within the fibrous insulator – it does not have to become sensibly wet for this to happen; just 15% moisture regain can give a dramatic reduction in insulating capacity. Not surprisingly therefore, there has been continued interest in developing insulators that might be able to overcome the disadvantages of conventional textile materials and improve the mobility of the wearer by allowing the use of only a very thin layer of extremely-high insulating performance to provide the required thermal protection. One class of materials from which suitable candidates might be drawn is aerogels; their attractiveness derives from the fact that they show the highest thermal insulation capacity of any materials developed so far. Despite sporadic high levels of interest, commercialisation has been slow. Aerogels have been found to possess their own set of disadvantages such as fragility; rigidity; dust formation during working and cumbersome, expensive, batch-wise manufacturing processes. They may well have been destined to become a product of minor interest, confined to very specialist applications where cost was of little concern. However, methods have been developed to combine aerogels and fibres in composite structures which maintain extremely high insulating capacity whilst demonstrating sufficient flexibility for use in garments. Ways have been found to prevent the formation of powder as aerogel composite fabrics are worked. Most significant though, is the achievement, arising from a project supported by the Korean Government, of a simplified one-step production process developed with the express aim of providing a substantial reduction in the cost of aerogels. Suitably-priced aerogel is now available and this should provide fresh stimulus for research and development teams to engage in new product development work utilising aerogels in textiles and garments for thermal insulation. The mechanisms through which aerogels achieve their outstanding thermal insulating ability is unconventional, at least in terms of materials used in textiles. This issue of Textile Progress therefore includes detail about thermal transport in aerogels before reviewing the various forms in which aerogels can now be made, some of their applications and the research priorities that are now beginning to emerge.     

Effect of enzyme and plasma treatments of bark cloth from Ficus natalensis: morphology and thermal behavior

Bark cloth fabric has been in production in Uganda since the thirteenth century. In a move to preserve its cultural heritage, the United Nations Educational, Scientific and Cultural Organization (UNESCO) proclaimed in 2005 that Ugandan bark cloth is a “Masterpiece of the Oral and Intangible Heritage of Humanity.” Plant fibers require surface treatment before aimed at impurity reduction and for enhancement of fiber to matrix adhesion in composites. An exploratory investigation of enzymatic and plasma treatment of bark cloth is reported. The morphology of the fabric was investigated using scanning electron microscope. Thermal behavior of the fabric was studied using thermogravimetric analysis and differential scanning calorimetry. Fourier transform infrared spectroscopy and ultraviolet–visible (UV–vis) spectrophotometer were used to evaluate the surface functional groups. Enzyme-treated fabrics were cleaner and thermally stable compared to plasma and untreated fabrics.     

Effect of TiO2 nanoparticles on basalt/polysiloxane composites: mechanical and thermal characterization

In the present investigation, a novel technique has been developed to fabricate composite materials containing TiO₂ nanoparticles, polysiloxane resin, and basalt fabric. A high-intensity ultrasonic probe was used to obtain a homogenous molecular mixture of TiO₂ nanoparticles and polysiloxane resin, thus the nanoparticles were infused into the resin through sonic cavitation. The loading effect of TiO₂ nanoparticles on the thermal and mechanical properties of basalt fabric reinforced polysiloxane composite materials has been investigated. Composite samples were prepared, each using two layers of basalt fabric with TiO₂ nanoparticles loading from 0.5, 1, 1.5, 2, 2.5, and 3% by weight. Size distribution of nanoparticles was observed by particle size analyzer and the prepared fabric nanocomposites were characterized by scanning electron microscopy, dynamic mechanical analysis (DMA), thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC). Tensile testing was performed as per American standard for testing of materials (ASTM) standards. The dependence of dynamic mechanical parameters E′, E′′, tan (delta), T _g, and heat distortion temperature (HDT) are associated with the filler content and can be controlled by the curing conditions. Tensile results show that 1.5 wt.% loading of TiO₂ nanoparticles in the nanocomposites resulted in highest improvement in tensile modulus compared to the neat system. DMA studies also revealed that 1.5 wt.% doped system exhibits highest storage modulus as compared to the neat and other loading percentages. DSC and TGA studies show that T _g and HDT of the composite increases with the increase in wt.% of nanofillers in the composite. Based on these results, it is clear that miscibility of nanoparticles in the resin is of prime importance with regard to performance.     

Utility of silver‐coated fabrics as electrodes in electrotherapy applications

The present study deals with the deposition of silver particles onto knitted fabrics for possible applications in electrotherapy. The performance of silver‐coated fabrics was evaluated based on number of properties such as electrical conductivity, physiological comfort, antibacterial, and durability. Furthermore, the conductive fabrics were subjected to various repeated extensions and change in electrical resistivity was examined to simulate the performance of electrodes under various movements of human body. With increase in extension till 80%, very small change in volume electrical resistance was observed and after 90% extension, the electrical resistance was found to increase significantly. The volume resistance was found to remain constant for repeated extensions of over 100 cycles and also there was insignificant change in electrical resistivity when constant current was applied over prolonged time. The utility of silver‐coated fabrics can be expected as flexible textile electrodes in transcutaneous electrical nerve stimulation electrotherapy applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46357.     

苏尼特双峰驼鲜驼乳对荷瘤小鼠免疫功能的影向及其抗肿瘤作用

目的:观察苏尼特双峰鸵鲜驼乳的抗肿瘤作用及其对荷瘤小鼠免疫功能的影响.方法:以H22肝癌小鼠为模型,观察苏尼特鲜驼乳的抗肿瘤效果,并对小鼠免疫学指标进行测定.结果:苏尼特双峰驼鲜驼乳对H22肿瘤细胞的生长有一定的抑制作用,并能显著增加荷瘤小鼠的脾指数、胸腺指数,增强巨噬细胞吞噬功能,使小肠Payer's结、小肠黏膜slgA和CD3明显增加.结论:苏尼特双峰驼乳具有抗肿瘤和增强荷瘤小鼠免疫功能的作用.     

Cationization of cellulose fibers for composites

In this work, composites were made by improved bonding of the cationized cellulosic fabric and some anionic matrix like Carboxymethyl Cellulose (CMC). Mercerized cotton fabric was cationized using cationization agent, TEXAMIN ECE with varying percentage from 1 to 10%. Those cationized cotton samples were incorporated in anionic matrices and the resultant composites were tested for mechanical properties on Universal Textile Tensile Testing machine. In the case of CMC as the matrix for the cationized reinforcement, the increasing trend in the tensile strength and elongation at break was observed. Scanning Electron Microscope images showed no extraordinary changes in the physical appearance of the cationized samples. Thermograms derived from Differential Scanning Calorimetry were informative for the evaluation of the thermal behavior of composites.