An improved model for predicting effective Young's modulus of the twisted structure under cyclic loading:taking into account the untwisting effect

Twist structures have diverse applications, ranging from dragline, electrical cable, and intelligent structure. Among these applications, tension deformation can＇t be avoided during the fabrication and working processes, which often leads to the twist structure rotation （called untwisting effect） and twist pitch increasing. As a consequence, this untwisting behavior has a large effect on the effective Young＇s modulus. In this paper, we present an improved model based on the classical Costello＇s theory to predict the effective Young＇s modulus of the basic structure, twisted by three same copper strands under cyclic loading. Series of experiments were carried out to verify the present model taking into account the untwisting effect. The experimental results have better agreements with the presented model than the common Costello＇s model.

Quantitatively characterizing sandy soil structure altered by MICP using multi-level thresholding segmentation algorithm

The influences of biological,chemical,and flow processes on soil structure through microbially induced carbonate precipitation(MICP)are not yet fully understood.In this study,we use a multi-level thresholding segmentation algorithm,genetic algorithm(GA)enhanced Kapur entropy(KE)(GAE-KE),to accomplish quantitative characterization of sandy soil structure altered by MICP cementation.A sandy soil sample was treated using MICP method and scanned by the synchrotron radiation(SR)micro-CT with a resolution of 6.5 mm.After validation,tri-level thresholding segmentation using GAE-KE successfully separated the precipitated calcium carbonate crystals from sand particles and pores.The spatial distributions of porosity,pore structure parameters,and flow characteristics were calculated for quantitative characterization.The results offer pore-scale insights into the MICP treatment effect,and the quantitative understanding confirms the feasibility of the GAE-KE multi-level thresholding segmentation algorithm.

Application of biochar-based materials in environmental remediation:from multi-level structures to specific devices

The development of biochar has triggered a hot-spot in various research fields including agriculture,energy,environment,and materials.Biochar-based materials provide a novel approach against environmental challenging issues.Considering the rapid development of biochar materials,this review serves as a valuable platform to summarize the recent progress on the theoretical investigation and engineering applications of biochar materials in environmental remediation.For a better understanding of the structure-application relationships,the structural properties of biochar from macroscopic and microscopic aspects are summarized.The multilevel structures including elements,phases,surface chemistry,and molecular are highlighted to elucidate the multi-functional properties of biochars.Sorption,catalysis,redox reaction,and biological activity of biochar are briefly illustrated,which influence the transport,transformation,and removal of organic and inorganic pollutants in the environments.According to the multi-level structures and structure-application relationships of biochar,specific biochar-based materials and devices have been designed for practical environmental application.The important progress on the functionalization and device of biochar-based materials,including magnetic biochars,2D and 3D biochar-based macrostructures,immobilized microorganism on biochar,and biochar-amended biofilters are highlighted.The environmental friendliness and sustainability of biochar-based materials,considering the whole cycle from synthesis to application,are evaluated.

Progress on band structure engineering of twisted bilayer and two-dimensional moiré heterostructures

Artificially constructed van der Waals heterostructures(vdWHs)provide an ideal platform for realizing emerging quantum phenomena in condensed matter physics.Two methods for building vdWHs have been developed:stacking two-dimensional(2D)materials into a bilayer structure with different lattice constants,or with different orientations.The interlayer coupling stemming from commensurate or incommensurate superlattice pattern plays an important role in vdWHs for modulating the band structures and generating new electronic states.In this article,we review a series of novel quantum states discovered in two model vdWH systems—graphene/hexagonal boron nitride(hBN)hetero-bilayer and twisted bilayer graphene(tBLG),and discuss how the electronic structures are modified by such stacking and twisting.We also provide perspectives for future studies on hetero-bilayer materials,from which an expansion of 2D material phase library is expected.

Wafer-scale 30°twisted bilayer graphene epitaxially grown on Cu_(0.75)Ni_(0.25)(111)

Twisted bilayer graphene(TBG) has been extensively studied because of its novel physical properties and potential application in electronic devices.Here we report the synthesis and characterization of 300 TBG naturally grown on Cu_(0.75)Ni_(0.25)(111) film and investigate the electronic structure by angle-resolved photoemission spectroscopy.Compared with other substrates,our TBG with a wafer scale is acquired with a shorter growth time.The Fermi velocity and energy gap of Dirac cones of TBG are comparable with those of a monolayer on Cu_(0.85)Ni_(0.15)(111).The signature of moré lattices has not been observed in either the low-energy electron diffraction patterns or the Fermi surface map within experimental resolution,possibly due to different Cu and Ni contents in the substrates enhancing the different couplings between the substrate and the first/second layers and hindering the formation of a quasiperiodic structure.

Multi-level Flocculation Structures of Fresh Cement Paste by Confocal Laser Scanning Microscope

Under saturation dosage of all kinds of SP, the free water amount was examined by centrifuge. The distribution of solution and flocculation microstructures in fresh cement paste was observed in three- dimensional space by confocal laser scanning microscope（CLSM）. Results indicate that SP can increase the free water amount by destroying the flocculated cement particle structure and different free water amount is released by different kinds of SP. The changes of the size of flocculation structures and the dispersion of solution were obviously detected with confocal laser scanning microscope： the size of flocculation structures was smaller and more dispersed in fresh cement paste with polycarboxylate superplasticizer, but the size of flocculation structures was bigger and cannot be dispersed uniformly in fresh cement paste with others SP. The multi- level flocculation structures theoretical model of fresh cement paste was then set up. The theory indicates that different kinds of SP with different dispersion strength will open the flocculation structures at different levels, which in turn present different water reducing rate.

Influence of tension-twisting deformations and defects on optical and electrical properties of B,N doped carbon nanotube superlattices

As the era of nanoelectronics is dawning,CNT（carbon nanotube）,a one-dimensional nano material with outstanding properties and performances,has aroused wide attention.In order to study its optical and electrical properties,this paper has researched the influence of tension-twisting deformation,defects,and mixed type on the electronic structure and optical properties of the armchair carbon nanotube superlattices doped cyclic alternately with B and N by using the first-principle method.Our findings show that if tension-twisting deformation is conducted,then the geometric structure,bond length,binding energy,band gap and optical properties of B,N doped carbon nanotube superlattices with defects and mixed type will be influenced.As the degree of exerted tension-twisting deformation increases,B,N doped carbon nanotube superlattices become less stable,and B,N doped carbon nanotube superlattices with defects are more stable than that with exerted tension-twisting deformations.Proper tension-twisting deformation can adjust the energy gap of the system;defects can only reduce the energy gap,enhancing the system metallicity;while the mixed type of 5%tension,twisting angle of 15° and atomic defects will significantly increase the energy gap of the system.From the perspective of optical properties,doped carbon nanotubes may transform the system from metallicity into semi-conductivity.

A Multi-level Approach for Complex Fault Isolation Based on Structured Residuals

In industrial processes,there exist faults that have complex effect on process variables.Complex and simple faults are defined according to their effect dimensions.The conventional approaches based on structured residuals cannot isolate complex faults.This paper presents a multi-level strategy for complex fault isolation.An extraction procedure is employed to reduce the complex faults to simple ones and assign them to several levels.On each level,faults are isolated by their different responses in the structured residuals.Each residual is obtained insensitive to one fault but more sensitive to others.The faults on different levels are verified to have different residual responses and will not be confused.An entire incidence matrix containing residual response characteristics of all faults is obtained,based on which faults can be isolated.The proposed method is applied in the Tennessee Eastman process example,and the effectiveness and advantage are demonstrated.

Improved Fibroblast Adhesion and Proliferation by Controlling Multi-level Structure of Polycaprolactone Microfiber

Improving wound healing efficiency is a key issue for high performance dressings.The surface topology of fibers in wound dressings plays an important role in regulating cell behaviors during the regeneration.Herein,a polycaprolactone(PCL)scaffold with a shish-kebab structure was prepared by electrospinning and solution-induced crystallization.L929 cells were used to investigate the behavior of fibroblasts on the multi-level microfiber.The results showed that the shish-kebab fiber-based scaffold enhanced the cell proliferation when compared with the normal fiber and the fiber with a porous structure.Protein absorption,cell adhesive force,and cell modulus also increased by the shish-kebab fiber.The shish-kebab fiber-based scaffold with improved fibroblast-regulation ability can be applied in rapid wound healing.

Structure and Properties of Pure Cotton Low-Twist Single Yarn Based on Addition of Long-Staple Cotton

Pure cotton low-twist single yarn has good softness,bulkiness,and wearing comfort,but its lower strength makes the yarn break easily during the spinning process,which seriously affects the spinning effect and progress.The addition of long-staple cotton helps to increase the average length and uniformity of the raw fiber,thereby improving the breaking load and spinnability of pure cotton low-twist single yarn.In this study,the addition of long-staple cotton,the twist factor,and the twist direction were used as variables to spin 22 kinds of combed 14.6 tex pure cotton low-twist single yarn with spinnability,and the breaking load,the hairiness,and the unevenness of the yarn were tested.The result shows that the spinnability of pure cotton low-twist single yarn is mainly related to the breaking load,and with the increase of the twist factor,the breaking load of low-twist single yarn shows an obvious upward trend.When the proportion of long-staple cotton is 70%,the breaking load of low-twist single yarn is the largest,and the harmful hairiness index and unevenness of the yarn are significantly improved.

Structural analysis of multi-level detachments and identification of deep-seated anticline

Based on forward modeling of detachment fold, this study presents a method to analyze multi-level detachment structures and identify the authenticity of deep-seated anticlines using time-domain seismic section. The steps include the conversion of the time-migrated seismic image into depth domain image using a constant velocity field, structural interpretation of the depth seismic image, measurement of each structural relief area and each height above reference level, plotting of area-height relationship chart with piecewise fitting etc. The area-depth correlation can help the division of structural sequences, the definition of detachment levels, the calculation of the tectonic shortening, and the identification of deep-seated structure. The segment area-height relationship is a feature of multi-level detachment structures, while little or no linear correlation between area and height is an indicator of non-deformation or pseudo-anticline. Regardless of the uncertainty of area-height relationship, the segment slopes will correspond to the differential shortenings of multi-level detachments, the intersection between adjacent segments will give the height of detachment surface above reference level and then help define the detachment level in original time-domain seismic section. This method can make use of time-domain seismic data to determine the geologic structure of complicated structure areas and assess risks of deep exploration targets. It has achieved good results in southern Junggar and eastern Sichuan areas.

玄武岩复合纱线的制备及强伸性能分析

为探究玄武岩复合纱线的强伸性能,分别制备了芯纱为单股、双股的玄武岩包覆纱,分析了玄武岩单股无捻结构芯纱包覆纱、玄武岩双股加捻结构芯纱、玄武岩双股无捻及加捻结构芯纱包覆纱在不同条件下的强伸性能变化规律。研究表明:以单股玄武岩为芯纱,外包不同种类材料如芳纶、超高分子量聚乙烯、锦纶及其复合纱时,纱线的强伸性能变化规律不同;以双股玄武岩为芯纱,复捻锭速在750 r/min且捻度为50捻/m时,芯纱强伸性能稳定,是合适的加捻参数;玄武岩双股加捻结构芯纱包覆纱强力较高,且随着包覆捻度的增大,其断裂强力变化明显小于双股无捻结构芯纱包覆纱。

大型风力机新型弯扭耦合叶片结构特性分析

为研究新型弯扭耦合叶片结构性能,以NREL 5 MW风力机叶片为原型,应用NX Open Grip参数化语言建立叶片几何模型,并对其进行复合材料铺层设计,通过计算流体力学(Computational Fluid Dynamics,CFD)方法获得叶片气动力,将其映射至叶片有限元模型中,对叶片进行弯扭耦合特性、谐响应与强度分析。结果表明,叶片叶尖位移随腹板偏转角γ增加而增大;对于同一角度,γ>0叶片叶尖位移均小于γ<0叶片;γ为10°与15°叶片弯扭耦合效应最明显;较于传统叶片,弯扭耦合叶片2阶位移响应均有大幅下降;γ为15°叶片降低表面应力,具有良好的减载性能。

短纤维成纱结构演化与创新

为了进一步理解捻合机制与纱线结构的关系,开发出理想结构纱线,综述了不同纺纱技术的纺纱原理、捻合机制、纱线结构、纱线性能,分析了不同纱线结构的优缺点,进一步阐明了捻合机制对纱线结构的影响以及纱线结构与纱线性能之间的关系,总结了理想纱线结构具有的特点,展望了未来纱线结构的发展趋势。捻合机制的差异导致纱线结构不同,纱线结构影响着纱线品质,为了进一步提升纱线品质,应从创新捻合机制的角度出发,以开发出理想结构纱线。

含裂纹缺陷的预扭壳结构非线性振动特性研究

基于扩展等几何方法和一阶壳体剪切变形理论建立了含裂纹缺陷的功能梯度预扭壳结构的非线性振动控制方程。控制方程中考虑了预扭壳结构的预扭角度及几何非线性,应用扩展等几何方法,采用反映位移变化的富集函数来描述裂纹的位置及长度,一方面可以提高计算精度,另一方面可以避免在裂纹处的网格加密,提高计算效率。采用了直接迭代法求解非线性振动控制方程。通过与现有文献结果对比,证明了本文方法的正确性和稳定性。在此基础上,探究裂纹对功能梯度预扭壳结构非线性振动频率的影响,研究了预扭角度、裂纹位置及长度和材料的功能梯度指数等参数对预扭壳非线性振动特性的影响规律。

面料吸湿速干性能的影响因素研究

探讨棉纤维与CoolMax长丝复合纱线的成纱结构、纱线捻度以及织物组织结构对面料吸湿速干性能和透气性的影响。采用正交试验设计制备了8种织物,并对其各因素进行测试和分析。结果表明:不同的成纱结构、纱线捻度及织物组织结构的组合搭配对面料吸湿速干性能和透气性影响显著。面料的吸湿性在成纱结构为包芯纱、较大的纱线捻度以及斜纹组织的条件下最优;面料的速干性在成纱结构为包缠纱、较大的纱线捻度以及平纹组织的条件下最优;面料的透气性在成纱结构为包缠纱、较大的纱线捻度和斜纹组织的条件下最优。认为:在实际开发具有吸湿速干性能的面料时,可从多方面进行统筹分析设计,从而使性能达到最优。

不同转角石墨烯/MoS_(2)异质结电子结构与光学性质的第一性原理研究

基于密度泛函理论的第一性原理计算方法,研究了不同扭转角下石墨烯/MoS_(2)异质结构的电子结构和光学特性。结果表明,转角后的石墨烯/MoS_(2)异质结构仍具备作为单层材料时的部分特征。在费米能级附近,石墨烯层保持了其特殊的线性色散能带结构,狄拉克锥上的直接带隙Eg受到层间旋转调制的影响。异质结构中的MoS_(2)层对层厚具有高度的敏感性,随着厚度的增加,其间接带隙持续增大。当转角为10.9°时,Eg的最大值为11.67 meV。差分电荷密度计算结果表明,随着旋转角度的改变,MoS_(2)层中Mo-S间的电子转移引起了Mo-S键长的变化,从而增大了S-S层间距。同时,通过与MoS_(2)结合形成异质结构,石墨烯获得了较高的载流子浓度,异质结界面间旋转使空穴掺杂载流子浓度提高至9.2×10^(12)cm^(-2),比未转角时提高约6倍。异质结构的光学性质计算结果表明:当转角为27.0°时,其吸收边发生红移,并向低能区移动了0.233 eV;当转角为10.9°时,其吸收边发生蓝移,并向高能区移动0.116 eV,同时,在可见光范围内,异质结构损失函数下降了0.007。研究结果可为设计新型具有转角特征石墨烯异质结构的光学纳米器件提供理论参考。

摩擦纺功能纱线的现状和发展趋势

为了更好了解摩擦纺核壳结构功能纱线在功能性纺织品领域的应用前景,综述了摩擦纺的发展历史、摩擦纺纱原理以及摩擦纺核壳结构功能纱线的种类和应用领域。重点讨论了基于摩擦纺纱技术的传感型纱线、防护型纱线和热管理型纱线的优势和面临的挑战,最后展望了摩擦纺功能纱线的发展趋势。认为:摩擦纺纱技术对于功能性纱线的制备具有独特的优势,摩擦纺解决了高功能性原料的难纺性与稳定成纱之间的矛盾,摩擦纺纱线的分层结构为功能性纱线的结构调控提供了基础。针对功能性摩擦纺纱线存在强力差、加捻效率低、纤维间界面力不足等缺陷,未来应加快提升纱线机械性能,提高纱线的加捻效率,促进摩擦纺功能纱线的产业化。

战国秦汉斜向互绞编织物的编织工艺研究

本文以战国秦汉时期的两件斜向互绞编织物为研究对象,通过模拟复原的方法对战国秦汉时期斜向互绞编织物的组织结构与编织工艺进行分析与探究。对比两者在结构、格眼、纹理、组边上的异同,发现通过变化基础结构中经线交织的方向和次数可以形成不同的组织结构和纹理效果。在编织工艺上,两者都使用斜向穿绞编法。其中普通组各编线间的编结变化和排列顺序以2个经线数为循环,编线在各行编结时的状态与编线数的奇偶和第一行编结时各编线的编结状态有关。

基于非对称铺层的复合材料弯扭耦合结构设计与试验验证

复合材料弯扭耦合结构在前掠翼飞机机翼的结构设计中具有重要的应用价值.现有研究主要基于对称铺层复合材料设计弯扭耦合结构,存在设计域窄及耦合效应不足等问题.非对称铺层复合材料有望解决上述问题,但因其易产生固化变形,目前未能在工程实际中得到应用.文章首先引入层合板的几何因子和材料常数,推导了拉剪多耦合效应层合板的湿热稳定解析条件;其次,利用湿热稳定的拉剪多耦合效应层合板构造了变截面弯扭耦合盒型结构模型,并利用遗传算法-序列二次规划(genetic algorithm-sequential quadratic program,GASQP)混合优化算法实现了结构的非对称铺层优化设计,使得结构在不发生固化变形的同时显著提升了耦合效应;然后,对弯扭耦合结构的湿热稳定性和弯扭耦合效应进行了数值仿真验证,并利用Monte Carlo方法进行了耦合效应的鲁棒性分析;最后,设计并完成了弯扭耦合效应的测量试验,验证了理论设计的正确性和可行性.结果表明:当铺层角度满足湿热稳定条件时,非对称弯扭耦合结构不会发生固化变形;非对称铺层设计可以显著提升耦合效应,最大可达90%以上.