Neural network meta‐model of fibrous materials based on discrete‐event simulation. Part 2: neural network meta‐model

Part 2 of the paper presents the neural network as a meta‐model for one‐dimensional fibrous materials which was elaborated on the basis of a discrete‐event simulation model that was presented in Part 1 of the paper. The architecture of the full‐size and part‐size network was developed and tested. The training set for the neural networks was obtained from the simulation model. The results of the sensitivity analysis of the neural networks have showed that the standard deviations of the fiber length and the fineness have no affect on the irregularity of the fibrous material. Testing has shown a high‐level coincidence between the simulation results and the prediction of the neural network meta‐model.     

Discrete‐event simulation model of roll‐drafting process

This paper presents a model of the roll‐drafting process which is based on the concept of discrete‐event simulation (DES). This model is free of limitations and simplifications which are inherent in the known models of the roll‐drafting process and is able to trace each separated fiber within the roll‐drafting zone. Due to this feature DES model enables investigation of a wide range of roll‐drafting cases and representations. The influence of the parameters of the basic roll‐drafting model was studied. Models of the first and the second limit schemes, models with a randomly distributed velocity change point, and a model with a shifting velocity change point were elaborated and studied on the basis of the basic model of the roll‐drafting process. The effect of the feedback depth was simulated and analyzed in the frame of the model with the shifting velocity change point. The elaborated model and the obtained results will be useful for creating a neural network meta‐model of the roll‐drafting process.     

Finite element simulation of three‐dimensional angle‐interlock woven fabric undergoing ballistic impact

This paper presents finite element simulations of three‐dimensional (3D) angle‐interlock woven fabric (3DAWF) undergoing ballistic impact. A micro‐structure model of the 3DAWF was established at the fiber tow level. Incorporated with commercial finite element code, ABAQUS/Explicit, the ballistic impact damage of the 3DAWF was simulated and compared with that in the experiment. Residual velocities of the conically cylindrical steel projectile (Type 56 in Chinese Military Standard) with different strike velocities were calculated and verified with those in the experiment. There are good agreements of the impact damage of the 3DAWF and the residual velocities of the projectile between finite element results and experimental results. The acceleration fluctuation record of the projectile and the stress wave propagation in the 3DAWF obtained from the simulation reveal the impact damage mechanisms of the 3DAWF. The strain rate effect of the fiber tows on the ballistic performance are also discussed. Such a micro‐structure model could be extended to the design of the impact behavior of the 3DAWF composites.     

A non‐linear viscoelastic model for describing the fatigue behaviour of braided artificial ligaments

The objective of this paper is the determination of the dynamic fatigue behaviour of braided ligaments made of polypropylene by using a rheological model and an experimental fatigue tester. A non‐linear viscoelastic model has been proposed to describe the time‐dependent deformation behaviour of braided anterior cruciate ligament prosthesis. The elastic modulus and viscous modulus are calculated for different fatigue tests. The developed fatigue tester allows to combine simultaneous cyclic solicitations of bending and traction. These combined cyclic solicitations generate new mechanical properties of the prosthesis such as increasing of the dissipative factor, the material damping and the residual deformation with the number of fatigue cycles.     

Research progress of the brassiere-chest contact simulation based on the finite element mechanical model北大核心CSCD

文胸-胸部有限元力学模型可用于分析服装与人体间接触力学问题,有必要探索二者作用机制。文章从文胸-胸部有限元力学模型的构建过程出发,对文胸和胸部的几何模型构建、材料属性设置、网格划分及接触关系的研究进展进行了总结,并归纳出目前该类模型在压力分布预测、塑形效果预测和位移分布预测方面的应用。最后指出,胸部模型构成及材料属性设置不够完善、文胸模型类别单一和压力分布的探讨多集中于乳房区域是目前研究中的不足。     

Eco‐friendly plasma treatment of linen‐containing fabrics

In the present work, linen‐containing fabrics were treated with atmospheric pressure plasmas of oxygen, air and nitrogen, and the impact of plasma treatment conditions on the surface chemistry and topography was evaluated. Plasma treatment is accompanied by a remarkable improvement in the hydrophilic properties: creation of new functional groups along with a noticeable increase in the affinity of treated substrates for subsequent H₂O₂‐bleaching. The extent of improvement in wettability as well as subsequent bleachability is governed by both the plasma gas, i.e. oxygen > air > nitrogen > none, and the discharge power, i.e. the higher the power supply, the shorter and greater was the modification extent. Oxygen or air plasma treatment significantly upgrades the hydrophilicity, enhances the subsequent bleachability, saves time, water and energy as well as prevents or decreases pollution at the source, i.e. an eco‐friendly substitute for conventional scouring of linen‐based textiles.     

The mechanics of buckling fiber in relation to fabric‐evoked prickliness: a theory model of single fiber prickling human skin

The simple Euler model of buckling of a slender rod has been commonly used to explain the mechanics in relation to the buckling of fabric‐evoked prickliness. Unfortunately, few works have paid attention to its applicability into the buckling behavior of fiber prickling human skin to evoke prickliness, though the friction between the fiber end and the skin and the firmness of a fiber end held in fabric (denoted as elastic stiffness) are considered to be among the main factors for fabric‐evoked prickliness. To model the mechanics of buckling of a fiber in relation to fabric‐evoked prickliness, the fiber–skin friction, the elastic stiffness, and the initial inclined angle of the fiber are introduced into the simple Euler model of buckling of a slender rod. Then, a sensitivity analysis is performed on these three factors to observe their role in the buckling behavior of a fiber. The results demonstrate that the fiber–skin friction and the elastic stiffness have a significant effect on the buckling behavior of fiber end prickling skin and the stimulus intensity to skin. Additionally, the fiber with an initial inclined angle can exert compression force on skin above the average force threshold of nociceptors responsible for fabric‐evoked prickliness, and the force size depends on the fiber property and its end‐restraint intensity. Therefore, it is not appropriate for the assumption of a fixed‐hinged boundary of the fiber end prickling human skin. In this sense, a developed fiber–skin coupling model provides a good modeling for the buckling behavior of fiber end pricking human skin.     

Tensile characteristics of Dref‐III friction core‐spun yarns

The tensile characteristics of Dref‐III friction spun yarns with jute as core and cotton as sheath components have been studied. Three yarns with different core–sheath proportions such as 55/45, 65/35 and 75/25 jute/cotton friction spun yarns were produced by using the Dref‐III friction spinning system. The influence of core and sheath components on the tensile properties at three different traverse rates at 150 mm/min, 750 mm/min and 1500 mm/min, respectively, have been reported. The work of rupture and specific work of rupture at break of these yarns were also analysed. From the test results, the maximum work of rupture was found in 55/45 core–sheath (jute/cotton) friction spun yarn when compared to 65/35 and 75/25 core–sheath (jute/cotton) friction spun yarns. It is due to the higher core–sheath interaction factor (CSI_T = 26.14) and better yarn‐packing density because of higher proportion of cotton fibres in the sheath component. The breaking tenacity and contribution factor of core and sheath component (CSI_T) of jute/cotton friction spun yarns were also analysed using multivariable ANOVA analysis.     

Physical and compressional characteristics of a novel 3D fibrous structure – application in comparison between PU foam and 3D fibrous structure

The question of the recycling of the polyurethane (PU) foam, especially in the automotive industry represents one of the main technology thrust and challenge of the car manufacturers and the Original Equipment Manufacturers’ (OEM) since 2000. Indeed, it is nowadays necessary for car industry to promote ecological methods of development in regard to new consumer sensibility. New textile products present the best alternative solutions to answer this issue of replacement of the PU foam. Based on this fact, a new three-dimensional (3D) fibrous structure made of polyester (PET) material has been developed in order to replace PU foam in automotive trim. These new manufactured 3D fibrous structures are laminated with needle-punched and spun-bonded sheets. The sheets are made of 100% PET, in order to obtain a mono component product. Characterization of physical and mechanical properties of these new 3D fibrous structures, testing methods have to be developed. Based on the automotive specifications, a methodology has been set up to test the compression behavior of these new products. In order to answer the issue of replacement, some PU foam products have also been characterized, and comparisons with alternative products have been conducted. The results of this study show interesting properties of the new 3D fibrous structure in terms of compression behavior when compared to the PU foam.     

Optimal geometry design of the melt‐blowing slot die with high stagnation temperature via the orthogonal array method and numerical simulation

In this paper, a method combining the orthogonal array design and the numerical simulation is proposed to optimize the geometry parameters of the melt‐blowing slot die. An index, the stagnation temperature, is used to evaluate the performance of the slot die. The stagnation temperature is obtained by simulating the subsonic compressible air jet from the melt‐blowing slot die, whereas the optimization is accomplished by the orthogonal array method. Three geometry parameters of the slot die: slot width, nose piece width, and slot angle are investigated. The results show that smaller slot angle and larger slot width will result in a higher stagnation temperature, which is beneficial to the air drawing of the polymer melt and thus to reducing fiber diameter, whereas the effect of nose piece width is insignificant. The optimal geometry parameters of the melt‐blowing slot die achieved in this study are: slot width of 1.5 mm, slot angle of 30°, and nose piece width of 2 mm.     

Ageing effect of plasma‐treated wool

Atmospheric pressure plasma treatment of wool fabric, with a relatively short exposure time, effectively removed the covalently bonded lipid layer from the wool surface. The plasma‐treated fabric showed increased wettability and the fibres showed greater roughness. X‐ray photoelectron spectroscopy (XPS) analysis showed a much more hydrophilic surface with significant increases in oxygen and nitrogen concentrations and a decrease in carbon concentration. Adhesion, as measured by scanning probe microscopy (SPM) force volume analysis, also increased, consistent with the more hydrophilic surface leading to a greater meniscus force on the SPM probe. The ageing of fibres from the plasma‐treated fabric was assessed over a period of 28 days. While no physical changes were observed, the chemical nature of the surface changed significantly. XPS showed a decrease in the hydrophilic nature of the surface with time, consistent with the measured decrease in wettability. This change is proposed to be due to the reorientation of proteolipid chains. SPM adhesion studies also showed the surface to be changing with time. After ageing for 28 days, the plasma‐treated surface was relatively stable and still dramatically different from the untreated fibre, suggesting that the oxidation of the surface and modification or removal of the lipid layer were permanent.     

A cross‐cluster and cross‐region analysis of fashion brand extensions

To obtain sustainable growth in revenue and market share, many fashion brands deploy category extensions and line extensions. In this paper, we examine how different fashion brands in Europe, North America, and Asia execute their brand extension strategies over different periods. By classifying different fashion brands into four clusters according to different price points and fashion contents, we conduct a cross‐region and cross‐cluster analysis to examine how different fashion brands execute their brand extension strategies. Our analysis is based on publicly available data associated with 48 fashion brands over a 90‐year period. We discuss our findings along with managerial insights.     

Effect of polymer‐binding on the specificity of lipases

Abstract

The flavour of a food system is strongly related to the production of free fatty acids (FFA). The controlled lipolysis and liberation of desired fatty acids are therefore of special interest in the food industry. Lipases that meet the food safety regulations, often do not necessarily possess the desired specificity. It was observed that the profile of FFA can be altered by a pre‐treatment of the lipase with synthetic, as well as natural, polymers. The profile of fatty acids released during incubation in milk was strongly correlated to the polarity of polymer used. The higher the polarity of the polymer, the more unsaturated fatty acids were liberated. After an incubation of the untreated lipase in milk, the oleic‐ versus stearic acid was found to be 3:1. However, using a lipase modified with a dimethyl polysiloxane (Mc Reynolds constant is 44), the ratio was found to be 1.5:1 and a modification with cyanoallyl polysiloxane (Mc Reynolds constant: 844) increased the ratio to 5:1. When applied for lipolysis in food systems, a modification with pectin A was found to be most effective. In this case no covalent bonds between the polymer and the lipase were formed, and therefore, its safety status does not change.     

Preparation and properties of high-flux and hydrophilic polysulfone superfine fibrous membrane北大核心CSCD

In this paper, the effects of volume percent of glutaraldehyde in chitosan solution on porous structure, hydrophily, mechanical properties and pure water flux of PSF superfine fibrous membrane which was pretreated by oxygen plasma, and then padded with cross-linked chitosan solution. Results show that the pore size decreases obviously, but the hydrophilicity and pure water flux improve significantly after the treatment. The optimum volume percent of glutaraldehyde is 0.40%. In this condition, the treated membrane still has high porous structure, and the average pore diameter is 2. 62 μm. The mechanical properties improve obviously. The membranes also change from hydrophobic property into hydrophilic property. The pure water flux is (1 624. 7±189.5) L/(m2 • h). © 2017 China Silk Association. All rights reserved.     

Effect of heating–cooling cycle on the opto‐structural properties of low‐density polyethylene fibres using two‐beam interference microscopy

A hot stage attached with a two‐beam interference (Pluta) microscope was used to apply a heating–cooling cycle (HCC) on low‐density polyethylene fibres (LDPE). The variation of the refractive indices (n ^∥ and n ^⊥) with the temperature was carried out during the heating and cooling of the LDPE fibres. The activation energy (E _a) and thermooptic coefficient (dn/dT) were calculated for the investigated LDPE fibres. The spectral dispersion curves, percent crystallinity and orientation function were determined for the treated LDPE fibres. It was found that the HCC for LDPE fibre implies: a reversible behaviour of both optical and structural properties against temperature and an improvement in the fibre crystallinity.     

Study of fiber packing density of lyocell ring‐spun yarns

The study of yarn structure and related yarn properties has been the subject of much research. However, the study of the fiber packing density, which has practical significance for a number of yarns and their characteristics, has been limited to circular yarns because of the disordered yarn structure. In this paper, the fiber packing density of lyocell ring‐spun yarns is determined with the image analysis method. This method does not have any limitation with regard to the fiber cross‐sectional shape. The effect of yarn count, twist factor, spindle speed, traveler weight and front roller diameter on the fiber packing density in the yarn cross‐section is analyzed. The results of this paper and the data published in other scientific works are in good agreement.     

Genetic algorithm‐based detection of the layout of color yarns

In this paper a novel method based on a genetic algorithm is proposed to recognize the layout of color yarns of yarn‐dyed fabric from the color pattern. The principle of a genetic algorithm is described first, and then the theories of roulette wheel selection method, crossover operation, and mutation operation are explained with the practical problem. Elitist selection is used to search for the correct result of the layout of color yarns. Some new chromosomes are added to the new generation in the genetic algorithm to avoid the local optimization. The repeat element of the layout of color yarns is then detected with period extraction. The repeat element of color pattern with the layout of color yarns is output together. Experiments on some color patterns recognized from actual yarn‐dyed fabrics, some color patterns simulated manually, and some color patterns including error color information of floats prove that the method proposed in this paper is effective for detecting the layout of color yarns from the color pattern of yarn‐dyed fabric, and it has a fault‐tolerance ability to some degree.     

Formation of discrete molecular size domains of melanoidins depending on the involvement of several α-dicarbonyl compounds: Part 2

The correlation of several α-dicarbonyl compounds with the melanoidin formation and their molecular size distribution was investigated. The results point out that α-dicarbonyl compounds, which were formed during the Maillard reaction, are not only the most important intermediates but also the direct precursors for carbohydrate-based melanoidins. Discrete molecular size domains are detected by size exclusion chromatography (SEC-DAD/RI), which were formed depending on the involvement of several α-dicarbonyls by thermal treatment of sucrose Maillard reaction solutions. By investigating sucrose Maillard reaction solutions spiked with methylglyoxal and 3-deoxyhexosulose carried on with direct melanoidin formation in aqueous solutions with α-dicarbonyls, molecular size domains of melanoidins could be connected for the first time with the reaction of several involved α-dicarbonyl compounds. High molecular size domains formed on the basis of methylglyoxal, whereas 3-deoxyhexosulose and d-glucosone promote lower molecular size domains. Concerning colour measurement methylglyoxal shows the highest browning activity followed by 3-deoxyhexosulose and d-glucosone. The reactivity of α-dicarbonyls and a correlated colour formation increase with rising alkaline pH-value. At a pH 5 the degradation and colour formation of α-dicarbonyl compounds is suppressed. The results provide new knowledge about colour formation in sucrose solutions. First part with the title, “Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions: Part 1” was accepted in EFRT in January 2006. DOI: 10.1007/s00217-006-0277-1.     

Fabrication of poly(vinylidenefluoride‐co‐hexafluoropropylene) nanofiber yarns by conjugate electrospinning

Conventional electrospinning is an efficient method to fabricate polymer nanofibers which are usually collected as non‐woven mats. Recently, in order to fabricate a nanofiber yarn, conjugate electrospinning has been developed using coupled spinnerets applied with two high electrical voltages of opposite polarities In this paper, poly(vinylidenefluoride‐co‐hexafluoropropylene) (PVDF‐HFP) nanofiber yarns are prepared by conjugate electrospinning. The effects of the concentration and delivery rate of polymer solution and the distance between coupled spinnerets on the structure of PVDF‐HFP nanofiber yarns are investigated. The structure of the nanofiber yarns is observed by scanning electron microscopy (SEM). The mechanical properties of the nanofiber yarns are measured by electronic fiber strength tester. The results show that the PVDF‐HFP nanofiber yarn consists of a large number of nanofibers aligned well along the longitudinal axis of the yarn, and the nanofibers have diameters ranging from several hundred nanometers to a few microns. The diameter of nanofibers in yarns increases with the increase in the polymer concentration, which significantly affects the structure of nanofiber yarns. The PVDF‐HFP nanofiber yarn electrospun from the polymer solution with a concentration of 45% has the highest tensile strength of 0.25 cN/dtex and an elongation of 180.13%.     

A new approach to de‐curling force of single jersey weft‐knitted fabric

In this work, the curling behavior of cotton single jersey weft‐knitted fabric was studied using a new non‐destructive test method. Eighteen series of dry‐relaxed weft‐knitted fabric samples were produced with three different yarn twist levels (724.5 tpm, 807 tpm, and 890 tpm), two yarn twist directions (Z and S), and three different loop lengths (2.7 mm, 2.85 mm, and 3.2 mm). Curling behavior was characterized in terms of curling distance (CD), de‐curling force, and de‐curling energy. The results show that weft‐knitted fabric samples with a lower loop length and higher yarn twist level exhibited higher de‐curling force and de‐curling energy. It is indicated that the de‐curling force of weft‐knitted fabric samples produced from the Z‐twist cotton ring‐spun yarn is higher than that of the samples produced from the S‐twist cotton ring‐spun yarn. The regression analysis results also illustrate that de‐curling force and de‐curling energy are non‐linearly correlated with edge CD, and variation trends follow polynomial equations. The result of this research suggests that the curling behavior of weft‐knitted fabric can be predicted in terms of de‐curling properties.