Hollow tubes constructed by carbon nanotubes self-assembly for CO_(2) capture

Carbon nanotubes(CNTs)have garnered significant attention in the fields of science,engineering,and medicine due to their numerous advantages.The initial step towards harnessing the potential of CNTs involves their macroscopic assembly.The present study employed a gentle and direct self-assembly technique,wherein controlled growth of CNT sheaths occurred on the metal wire’s surface,followed by etching of the remaining metal to obtain the hollow tubes composed of CNTs.By controlling the growth time and temperature,it is possible to alter the thickness of the CNTs sheath.After immersing in a solution containing 1 g/L of CNTs at 60℃ for 24 h,the resulting CNTs layer achieved a thickness of up to 60μm.These hollow CNTs tubes with varying inner diameters were prepared through surface reinforcement using polymers and sacrificing metal wires,thereby exhibiting exceptional attributes such as robustness,flexibility,air tightness,and high adsorption capacity that effectively capture CO_(2) from the gas mixture.

Transmission of N-Atoms Produced by N₂Flowing Microwave Afterglows through Hollow Tubes

Transmission of N-atoms (T N ) through small diameters tubes (1.5 and 3 mm internal diameter (i.d) and 9, 50 and 80 cm length for silicone tubes, 1.5 mm i.d and 6.5 cm length for stainless steel tubes) has been measured in late N2 and Ar-N2 flowing afterglows of microwave plasmas in continuous and pulsed gas injection at a flow rate of 1 and 3 Standard liter by minute (Slm), a gas pressure from 2 to 4 Torr for N2 and 20 Torr for Ar-1%N2 and a plasma power from 150 to 300 Watt. From the experimental TN values, it is deduced the γ-destruction probability inside the tube walls as being y = (1-1.6)×10-3 for the silicon tubes and y = (1.6-2)×10-2 for the stainless steel tubes.

Synthesis of FeOOH scaly hollow tubes based on Cu_(2)O wire templates toward high-efficiency oxygen evolution reaction

For catalytic materials,the characteristics of one-dimension and hollowness are the promotion factors for their full presentation of catalytic activity,and through a template-as sis ted method,both above superiorities can be fused simultaneously.Here,we proposed a novel strategy inspired by Pearson's principle with Cu_(2)O wires as templates,and prepared FeOOH hollow tubes,which covered by FeOOH scales.When applied as oxygen evolution reaction(OER)catalyst,the FeOOH scaly hollow tubes(FeOOH SHTs)showed outstanding catalytic activity with a low overpotential of 245 mV to drive a current density of10 mA·cm^(-2),excellent kinetics manifesting as a low Tafel slope of 46.9 mV·dec^(-1),and robust stability.This work provides a new synthesis strategy for an ideal OER catalyst,FeOOH,with high inherent activity and enhances the feasibility to broaden the design ideas of transition metalbased catalysts.

Structure and Electrochemical Performance of Hollow Tube Activated Carbon Prepared from Cotton as Electrode Material for Electric Double Layer Capacitor

Hollow tube-like activated carbon（HTAC） was fabricated by a simple and efficient carbonization method with cotton as carbon precursor activated by KOH without any template. The activation time from 0 to 90 min showed no significant effect on the micro-morphology, but greatly influenced the specific surface area and electro- chemical performance. In the end, it was found that the sample activated for 60 min（HTAC-60） has a higher specific surface area of 2600 m2/g, a larger pore volume of 1.52 cm3/g and a greater specific capacitance of 483 F/g at a current density of 0.2 A/g in 1 mol/L H2SO4. Moreover, the sample HTAC-60 shows excellent cycle stability（only 12.2% loss after 5000 cycles） and a high energy density of 67.1 or 37.2 W-h.kg-1 at a power density of 200 or 1000 W/kg, respectively, operated in a voltage range of 0--1.0 V in 1 mol/L H2SO4. The results indicate that cotton can potentially be used as a raw material for producing low cost and high performance activated carbon electrode materials for electric double layer capacitor.

Quality prediction and control of tube hollow

The quality prediction of tube hollow model based on the variance staged multiway partial least square (MPLS) method was proposed.The key aspects of staged decomposition of the productive data,calculation of the variance value,modeling,and on-lined prediction in the variance-staged MPLS method were introduced.Based on the model,iterative optimal control method was used for quality control of tube hollow.The experimental results show that the obvious benefits of this method are low maintenance cost,good real time function,high reliability precision,and practical application to on-line prediction and optimization on the quality of tube hollow.

Numerical Analysis of Conjugated Heat and Mass Transfer of Helical Hollow Fiber Membrane Tube Bank for Seawater Distillation

A numerical study on the conjugated heat-mass transfer of helical hollow fiber membrane tube bank(HFMTB)for seawater desalination was carried out.Physical and mathematical models of fluid flow,temperature and humidity distribution were constructed to investigate the influences of flow type,Reynolds number,and temperature on the conjugated heat-mass transfer performance of hollow fibers in the distillation membrane module.The conjugated heat-mass transfer characteristics of HFMTB were discussed by utilizing the friction coefficient,Nusselt number(Nu),and Sherwood number(Sh).Results demonstrate that a distillation efficiency enhancement of 29%compared to the straight HFMTB has been detected for four-helical HFMTB configuration,though the friction coefficient of such a module is about 4 times of their straight counterparts.The values of average Nu and Sh numbers are increasing with tube number,which improves distillation efficiency.The effect of flow type has been studied by employing the upstream and downstream flows to the double-helical HFMTB,demonstrating upstream flow type is more conducive to the heat-mass transfer process.Both the outlet air humidity(ω)and distillation efficiency(η)decrease with the air-side Reynolds number(Rea)and inlet air temperature in the helical HFMTB while increasing with the solution-side Reynolds number(Re_(S))and inlet solution temperature.Overall,the obtained results indicate that helical HFMTB applying upstream flow has great potential to achieve high-performance SGMD for seawater desalination.It is anticipated that the present work can assist in a better understanding of the membrane desalination process in HFMTB and thus provide theoretical suggestions for further optimization and development.

配筋空心圆钢管高强混凝土轴压短柱工作机理分析

目的 提出一种配筋空心圆钢管高强混凝土新型组合柱,分析其在轴向荷载作用下的工作机理,以解决空心钢管混凝土柱空心率较大和延性差等问题。方法 对配筋空心圆钢管高强混凝土短柱进行轴压试验,利用ABAQUS有限元分析软件建立组合柱的有限元模型,以试验结果验证有限元模型的准确性。对组合柱的受力工作机理进行分析,重点研究其在轴向荷载作用下的受力过程、各组分分担内力比例和应力状态。结果 与空心圆钢管高强混凝土柱相比,未配置普通钢筋的试件峰值承载力提升了6.37%、DI提高了6.64%、SI提高了3.59%,配置普通钢筋的试件峰值承载力提升了13.31%、DI提高了8.12%、SI提高了5.68%。整个受力过程中,管柱混凝土和夹层混凝土承载的内力比例分别为36.2%~39.7%和29.0%~30.6%。结论 配置普通钢筋的试件具有更高的承载能力和延性能力;夹层混凝土和管柱混凝土在加载过程中为主要受力组分;钢筋在加载前期基本不承担内力,进入塑性强化阶段才开始发挥作用。

增强型中空纤维膜及MBR数值模拟的研究

中空纤维膜作为膜生物反应器(MBR),由于其高效性及灵活性被广泛应用于污水处理领域。文中介绍了纤维管增强型中空纤维膜,包括针织管增强膜、编织管增强膜及无纺管增强膜,综述了计算流体力学在MBR优化设计及膜污染清洗等方面的研究,并对增强型中空纤维膜及MBR数值模拟的应用前景进行展望。在未来的研究中,将计算流体力学与理论试验相结合可以提升研究效率,更好地解决水处理问题。

配筋空心方钢管高强混凝土纯弯构件受力性能有限元分析

目的 研究配筋空心钢管高强混凝土构件的抗弯性能,推动其在建筑结构中的应用。方法 采用有限元分析软件ABAQUS建立配筋空心钢管混凝土构件有限元模型,在验证模型准确的基础上,分析构件的受力全过程及钢材屈服强度、混凝土抗压强度、钢管壁厚、钢筋直径、普通钢筋数量对构件受弯性能的影响。结果 纯弯试件在荷载作用下受力过程可分为3个阶段:弹性阶段、弹塑性阶段和强化阶段;试件破坏形态均为受弯破坏,表现出较好地延性。结论 组合构件在弯矩作用下可以很好地协同工作;钢材屈服强度和钢管壁厚的增加对构件承载力的提高影响最显著,建议配置普通钢筋数量在6~8根为最优。

空心管型泡沫铝吸声性能的数值模拟分析

为了提高多孔泡沫铝材料的吸声性能,将泡沫铝加工成空心管型结构。首先,利用声学阻抗管测试系统获取吸声系数;其次,基于JCA声学模型,采用COMSOL软件对空心管型泡沫铝进行仿真模拟以获取吸声系数,将吸声系数仿真结果与试验结果进行对比,验证仿真模型的可靠性;最后,通过声压云图和能量耗散云图对空心管型泡沫铝内部声场进行分析,并进一步通过数值模拟探究空心管参数对吸声性能的影响规律。研究结果表明:该空心管型结构属于共振式吸声结构;当声波的频率和结构中固有频率相同时,声波激励结构振动的振幅最大,导致大量的声能被消耗,从而起到吸声的作用;对于空心管型泡沫铝结构,可以通过增大空心管的半径、增加空心管的数量来提高吸声系数;在1000~6300 Hz的频率范围内,背后添加空腔的空心管型泡沫铝结构的平均吸声系数相较于背后添加空腔的均质型泡沫铝结构的平均吸声系数提高了26%。

双参数弹性基功能梯度圆柱管自由振动的高阶梁理论解

基于高阶剪切变形梁理论,推导了Winkler-Pasternak弹性基径向功能梯度空心圆柱管自由振动行为的控制方程。该方法无须引入剪切修正系数,自动满足空心圆柱管内外表面剪应力自由边界条件。通过引入辅助函数,将关于挠度和转角的耦合控制方程化为单一高阶微分控制方程。给出了典型边界条件下功能梯度空心圆柱管的频率和振型。将计算结果与已有文献结果对比,验证了所提理论的精度。可以为工程中常见的Winkler-Pasternak弹性基梁结构提供更高精度的一维弹性理论解,研究结果表明,功能梯度材料的梯度参数和弹性地基刚度系数对固有频率值影响显著。与高阶固有频率相比,刚度系数对低阶固有频率的影响更加明显。

基于两相流欧拉方法的中空纤维管血流动力学数值模拟

对人工肝中空纤维管内血液两相流动进行了三维数值模拟,研究了中空纤维管内血流速度分布、红细胞径向体积分数分布、黏度分布以及壁面条件对红细胞体积分数分布的影响.结果表明,红细胞在轴心附近处黏度高,在壁面处黏度低;红细胞流速略大于血浆流速;红细胞沿径向体积分数分布呈双峰状,随各截面与入口距离增加,邻近壁面处的红细胞体积分数逐渐减小,壁面处的红细胞体积分数逐渐增大;不同壁面条件下,壁面处的红细胞体积分数随所受升力减小而增大,远离壁面运动趋势减弱.

车用变截面空心管材缩-扩成形规律研究

目为确定车用变截面空心管材缩-扩成形工艺影响因素,提高缩-扩成形工艺制备质量,利用Abaqus软件对车用变截面空心管材缩-扩成形过程进行数值模拟,研究不同工艺参数(合模力、润滑方案、成形速率)对成形过程的影响,确定最佳工艺参数。研究结果表明:合模力为20 kN、采用润滑油和润滑脂混合润滑、成形速率为1 mm/s时,变截面空心管材缩-扩成形均匀性较好,无缩口、起皱现象。针对仿真结果进行空心管材变截面缩-扩成形实验,实验结果与仿真结果基本一致,验证了此工艺参数组合的准确性,可为车用变截面空心管材高性能制造提供参考。

声源音色辨识技术在钢管混凝土检测中的应用

在人耳识别的基础上,采集同尺寸,不同工况、类型的钢管混凝土锤击声,模拟人耳识别的原理提取音色特征值,进而准确识别钢管混凝土有无空洞缺陷。通过在钢管混凝土中提前植入空洞,采集信号且引入锤击声导纳,并与密实钢管混凝土的进行对比。结果表明,锤击声导纳中提取的mfcc10max特征值能很好地识别钢管混凝土中的空洞缺陷;当mfcc10max特征值大于-0.4,均值大于-0.23时,即可初步判定锤击位置存在空洞或脱空缺陷;密实钢管混凝土锤击声导纳中mfcc10max特征值小于-0.5,均值为-0.72。最后将此技术和指标应用在塔楼混凝土结构空洞检测中,结果证明该方法适用性较好。利用具体指标和数值对钢管混凝土中空洞识别进行定量化,提高了识别精度,为后续现场钢管混凝土结构中的空洞缺陷识别提供了强有力的基础。

中空夹层钢管混凝土柱外钢管轴压局部失稳的简化计算模型

轴压作用下中空夹层钢管混凝土短柱的外钢管失稳临界应力计算公式还不够完善。分析认为,中空夹层钢管混凝土短柱的外钢管与实心钢管混凝土短柱的外钢管受力情况基本相同。因此,基于张耀春等的理论模型研究了中空夹层钢管混凝土短柱外钢管的局部失稳。构件夹层混凝土与外钢管条形单元相互作用模型取为文克尔弹性地基上的长梁模型,进而可以利用文克尔弹性地基梁理论计算外钢管的弯曲波长λ。根据实际工程中的钢管厚度t与圆柱构件横截面半径r之比远小于1∶t/r?1的情况,和外钢管失稳波长约为弯曲波长λ,简化了张耀春等模型中的理论推导。类比该模型,推导得出中空夹层钢管混凝土短柱外钢管局部失稳临界应力简化计算公式。该简化计算模型中局部失稳波长与其他学者的试验数据对比,平均误差为7.7%,临界应力计算值的相对误差值为2.7%,表明该简化计算公式可行,可以为工程实践提供参考。

中空夹层钢管混凝土构件轴压性能有限元分析

为探明中空夹层钢管混凝土(CFDST)构件轴压性能的影响因素,在已有钢管混凝土柱轴压试验基础上,构建数值分析模型,开展长径比、空心率、内钢管壁厚、夹层混凝土抗压强度等参数对中空夹层钢管混凝土构件轴压性能的影响规律的研究。研究结果表明:研究参数范围内,轴压极限承载力随内钢管壁厚、夹层混凝土强度的增大,空心率、长径比的减小而增大。内钢管壁厚增大1 mm,轴压极限承载力提高2.9%~3.7%,承载力增长系数增大约0.7%;混凝土强度从C40增加到C90,圆截面试件轴压承载力增大了68%;方截面试件轴压承载力增大了53%;空心率每增大0.1,轴压极限承载力降低3.4%~8.7%,承载力增长系数减小约5%;圆截面试件长径比从2.2增大到7.2,承载力下降了3%。方截面试件长径比从2.2增大到5.7,承载力下降10%。长径比对构件的极限承载力影响,明显低于空心率、内钢管壁厚和内填混凝土强度对构件极限承载力的影响程度。随着试件长径比的增加,试件承载力峰值有所下降,但其承载力达到峰值时的位移量不断增大,表明构件延性有所提高。随内填混凝土强度的提高,试件的承载力峰值和达到峰值时的位移都有所提高,说明增大内填混凝土强度在提高钢管混凝土承载力的同时还能改善试件的延性性能。

FRP-混凝土-钢双壁空心柱的抗爆性能分析

纤维增强复合材料(fiber reinforced polymer,FRP)-混凝土-钢双壁空心柱是一种新型混凝土组合柱,由外层FRP管、内层钢管及两管间填充的混凝土组成。针对FRP-混凝土-钢双壁空心柱在近场爆炸荷载下的抗爆性能进行了数值模拟。采用任意拉格朗日欧拉法(arbitrary Lagrangian Eulerian,ALE)进行建模,并基于已有的试验结果验证所建模型的准确性。利用验证后的数值模型,对爆炸冲击波传递过程、混凝土损伤发展、FRP管环向应变、爆炸后剩余力学性能以及参数进行了分析。结果表明,FRP管能有效约束爆炸区域内的夹层混凝土;爆炸后双壁空心柱的轴向承载力明显减小、轴向刚度明显下降;通过增加FRP管、钢管厚度,以及减小空心率能提高双壁空心柱的抗爆性能,其中前两项的影响更为显著。

多频带声学超构材料的透射性能

为了研究多频带声学超构材料的透射性能,采用声学有限元方法(FEM)模拟不同长度的OE-CE(一端封闭一端连通)空心方管结构单元的声透射谱,分析讨论管长对透射谱的影响,设计出一种占空比较小的由不同长度OE-CE空心方管并联组合的多频带声学超构材料板。结果表明:嵌有9个空心方管声学超构材料的声透射曲线出现声透射阻带,随着空心方管的长度增加,透射阻带峰值和负等效质量密度频带向低频方向移动;透射阻带的个数与不同长度的空心方管数目有关,即2种不同长度的空心方管并联组合的声学超构材料板可以实现2个透射阻带,3种不同长度的则可以实现3个透射阻带;宽频带声学超构材料板则需要在较低频率区域增加对应长度的空心方管数目,在较高频率区域减小相邻空心方管的长度梯度。所提出的采用OE-CE结构单元构建的声学超构材料具有结构简单、响应频带低的优点,并在多个响应频带具有优异的声学透射阻带特性。

装配式空心钢管混凝土支撑技术研究及应用

在“双碳”战略背景下提出一种新型装配式空心钢管混凝土支撑。为了研究其受力性能并将其应用于地下车站深基坑工程中,设计并加工2个足尺寸空心钢管混凝土支撑试件,完成轴压加载试验,2个支撑试件最后均发生了混凝土压碎破坏,同时得到试件承载力指标。采用ABAQUS有限元软件建立空心钢管混凝土支撑的数值模型,开展考虑材料非线性和几何非线性的有限元分析,所得数值分析结果与试验结果吻合良好,验证了有限元模型的准确性。试验和有限元结果充分表明所提出的新型装配式空心钢管混凝土支撑满足常规工程设计要求,已成功应用于“汤马区间”2号风井工程,并与现浇钢筋混凝土支撑和装配式钢管支撑进行比较分析,结果表明该新型支撑可以显著降低碳排放量和经济成本。

配筋空心方钢管高强混凝土轴压中长柱有限元分析

目的 研究配筋空心方钢管高强混凝土轴压中长柱受力性能,改善传统空心钢管混凝土的力学性能,并为该类型柱的设计及试验研究提供依据。方法 基于有限元分析软件ABAQUS,对配筋空心方钢管高强混凝土轴压中长柱的力学性能进行有限元分析,在分析受力全过程的基础上,重点分析长细比、钢管宽厚比,混凝土强度、钢管强度、管桩类型、配筋率等参数对轴压力学性能的影响,并基于统一理论提出承载力计算公式。结果 配筋空心方钢管高强混凝土轴压中长柱各组分之间组合作用良好,内置管柱、增大钢管宽厚比、减小长细比及缩小夹层混凝土强度与管柱混凝土强度差距可以改善构件的延性、提升构件组合作用;笔者提出的修正公式计算结果精确且安全。结论 提高配筋空心方钢管高强混凝土的钢管强度、增大宽厚比、减小夹层混凝土与管柱混凝土强度差距可有效改善空心钢管混凝土脆性破坏,充分发挥构件的性能。