Simultaneous Adsorption of Aqueous Pb2+, Cu2+, Zn2+, and Cd2+ Using Surfactant-Modified and Unmodified Activated Carbon in a Fixed Bed Column

The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.

Restoring-force model of modified RAC columns with silica fume and hybrid fiber

In order to establish a restoring-force model for modified concrete columns with recycled aggregates concrete(RAC), cyclic loading tests were carried out on five concretes with RAC columns and ordinary concrete frame columns under the combined influence with different admixtures and admixtures ratios(silica fume and hybrid fiber). The expressions for characteristic nodes of the skeleton curve were given by the analysis and numerical regression of the test results. In addition, the hysteretic rules of the restoring-force model and the expression for unloading stiffness were presented. Finally, we summed up the complete calculation method of the hysteretic restoring force, whose results were in good agreement with experiment. The results demonstrated that the proposed model could simulate and reflect the corresponding hysteretic behaviors, and the calculation method can provide the theoretical basis for the engineering application.

A Modified approach for calculating dynamic shear modulus of stiff specimens by resonant column tests

An error analysis of the dynamic shear modulus of stiff specimens from tests performed by a new resonant column device developed by the Institute of Engineering Mechanics, China was conducted. A modified approach for calculating the dynamic shear modulus of the stiff specimens is presented. The error formula of the tests was deduced and parameters that impact the accuracy of the test were identified. Using six steel specimens with known standard stiffness as a base, a revised dynamic shear modulus calculation for stiff specimens was formulated by comparing three of the models. The maximum error between the test results and the calculated results shown by curves from both the free-vibration and the resonant-vibration tests is less than 6%. The free-vibration and resonant-vibration tests for three types of stiff samples with a known modulus indicate that the maximum deviation between the actual and the tested value using the modified approach were less than 10%. As a result, the modified approach presented here is shown to be reliable and the new device can be used for testing dynamic shear modulus of any stiff materials at low shear strain levels

Buckling Analysis of Tapered Continuous Columns by Using Modified Buckling Mode Shapes

Elastic critical buckling load of a column depends on various parameters,such as boundary conditions,material,and crosssection geometry.The main purpose of this work is to present a new method for investigating the buckling load of tapered columns subjected to axial force.The proposed method is based on modified buckling mode shape of tapered structure and perturbation theory.The mode shape of the damaged structure can be expressed as a linear combination of mode shapes of the intact structure.Variations in length in piecewise form can be positive or negative.The method can be used for single-span and continuous columns.Comparison of results with those of finite element and Timoshenko methods shows the high accuracy and efficiency of the proposed method for detecting buckling load.

配置抗冲切钢筋的RC板柱节点受冲切承载力计算

为计算配有常用抗冲切钢筋(箍筋和栓钉)的钢筋混凝土(RC)板柱节点的受冲切承载力,结合梁斜拉破坏机理和修正压力场理论(MCFT)提出一种配有抗冲切钢筋的RC板柱节点的受冲切承载计算方法.首先根据MCFT推导出配有抗冲切钢筋的RC板柱节点的临界斜裂缝倾角计算式;然后,假定冲切破坏时临界截面周长范围内的抗冲切钢筋达到屈服强度,将临界斜裂缝倾角代入MCFT推导出板柱节点的受冲切承载力计算方法;最后,使用该方法和美国规范(ACI 318-19)方法计算62个配有抗冲切钢筋的RC板柱节点试验的冲切承载力,并分析了混凝土强度、板有效厚度、柱截面边长、抗弯钢筋配筋率及抗冲切钢筋配筋率对节点抗冲切承载力的影响.结果表明:由MCFT推导出的节点受冲切承载力计算值与试验值吻合较好,均值为0.96,变异系数为0.20;节点的冲切承载力与上述影响因素呈非线性正相关.该方法可用于配有抗冲切钢筋的RC板柱节点的受冲切承载力计算.

嗜酸铁还原菌JF-5改性镧膨润土吸附砷及其矿物颗粒迁移研究

利用嗜酸铁还原菌(Acidiphilium cryputum JF-5),通过生物还原技术释放膨润土中的Fe^(2+)以强化镧改性,从而得到一种新型生物镧改性膨润土。通过等温吸附实验考察生物镧改性膨润土对As(Ⅴ)的吸附效果,并与国际上商用的锁磷剂(Phoslock)进行对比,通过柱实验探讨生物镧改性膨润土在石英砂柱中的迁移行为。结果表明:(1)JF-5能够强化膨润土还原释放Fe^(2+),从而加强La^(3+)负载,低固液比(1.6 g/L)下制备生物镧改性膨润土具有最高的La^(3+)负载量(370 mg/g)。(2)生物镧改性膨润土对As(Ⅴ)的吸附行为符合Freundlich模型,最大吸附量为7.58 mg/g,与Phoslock的最大吸附量(3.08 mg/g)相比大幅提高;对As(Ⅴ)的吸附动力学过程与Phoslock相似,均能在4 h内快速去除As(Ⅴ)。(3)生物镧改性膨润土在石英砂柱中的迁移行为可以用对流扩散模型描述,在0.38、0.77、1.54 mL/min的流速下,生物镧改性膨润土在石英砂柱中的滞留量分别为3.68、3.77、2.29 mg,可见中等流速条件下溶液在石英柱中能够更充分接触介质从而提高滞留量。

柱上甲基化-碘化钾改性硅胶还原法分离石油样品中芳香类含硫化合物

研究开发了一种通过层析柱上甲基化-碘化钾改性硅胶还原法分离石油芳香类含硫化合物的新方法。通过填充担载了六氟锑酸银的硅藻土制备固相萃取柱,实现含硫化合物的快速甲基化和对甲基锍盐的富集;再通过碘化钾改性硅胶对芳香类甲基锍盐进行快速还原,最终得到高纯度的芳香类含硫化合物。利用模型化合物对该方法进行验证,同时将该方法应用于柴油和原油样品,并结合气相色谱串联硫化学发光检测器和气相色谱串联质谱对分离组分进行分析。模型化合物分析结果表明,该方法对包含屏蔽型结构在内的二苯并噻吩类化合物回收率可达95%以上。石油样品的分析结果表明,该方法可实现对不同类型芳香类含硫化合物的高纯度分离,且操作简单、快捷。

基于改进简化拉-压杆模型的钢纤维混凝土梁柱节点受剪承载力计算方法

在简化拉-压杆模型(Simplified softened strut-and-tie model,SSSTM)基础上,考虑轴压比对混凝土斜压杆倾角的影响,修正斜压杆倾角计算公式,并基于剪滞模型,考虑裂缝面纤维数量及纤维取向特性,建立裂缝面单位面积纤维拉应力计算公式,从而提出适用于钢纤维混凝土梁柱节点受剪承载力计算的改进简化拉-压杆模型(Modified simplified softened strut-and-tie model,MSSSTM).采用MSSSTM模型、SSSTM模型对36个钢纤维混凝土梁柱节点受剪承载力进行计算.结果表明:MSSSTM模型、SSSTM模型的试验值与计算值之比的平均值分别为1.01、1.05,变异系数分别为0.04、0.09;按照MSSSTM模型计算得到的钢纤维混凝土梁柱节点受剪承载力试验值与计算值吻合较好,离散性较小,且该模型亦能较合理地反映轴压比、混凝土强度等对节点受剪承载力的影响.

改良腔内心电图定位技术在乳腺外科颈内静脉输液港中的应用

目的探讨改良腔内心电图定位技术应用于乳腺外科颈内静脉输液港的效果。方法选取2020年4月至2022年4月于菏泽市立医院乳腺中心行乳腺癌术后植入颈内静脉输液港的90例患者作为研究对象,按入院手术时间分为A组、B组与对照组,每组30例。A组采用金属导丝法,B组选取30例行盐水柱法,对照组采用传统体表测量计算植入长度。比较3组导管尖端位置正常、最佳及异位发生率,心脏事件发生率。结果A组和B组尖端位置正常率、最佳率、异位率比较差异无统计学意义;A组和B组尖端位置正常率、最佳率、异位率均高于对照组,差异有统计学意义(P<0.05)。3组心脏事件发生率比较差异无统计学意义。实际操作过程中,正常心电图波形和腔内心电图诱导出现的特异性P波;采用导线线径>2 mm时信号衰减明显,线径<1.5 mm的线材能在普通心电监护仪上诱导成功,其中效果最好的是PICC适用鳄鱼夹线。结论改良腔内心电图定位技术应用于颈内静脉输液港植入,可通过选用适宜的导线和溶液介质,在无需额外专业设备和专业人员的情况下完成术中导管定位,且不增加心脏事件的发生,具有较高安全性,值得临床广泛应用。

Active set truncated-Newton algorithm for simultaneous optimization of distillation column

An active set truncated-Newton algorithm (ASTNA) is proposed to solve the large-scale bound constrained sub-problems. The global convergence of the algorithm is obtained and two groups of numerical experiments are made for the various large-scale problems of varying size. The comparison results between ASTNA and the subspace limited memory quasi-Newton algorithm and between the modified augmented Lagrange multiplier methods combined with ASTNA and the modified barrier function method show the stability and effectiveness of ASTNA for simultaneous optimization of distillation column.

Analysis on Critical Force of Unidirectional CFRP Slender Column

Carbon Fiber Reinforced Polymer(CFRP) has such characteristics as light weight, high strength and corrosion resistance, so it is suitable for corrosive environment and large-span structures. This study investigated the stability of CFRP slender column, whose slenderness is greater than Euler’s critical load. The columns in this study were formed by a two-step process and the fiber direction was along the same direction of column axis. Firstly, we obtained the basic mechanical properties of the material by tensile experiment. Then, we studied the critical force of 10 CFRP columns with different lengths and widths by axial compression test. Finally, by comparing Euler’s formula with the modified Euler formula and combining with existing literature and experimental result of this paper, we proposed a modified Perry formula which could well predict the critical force of unidirectional CFRP extruded column and could be used for CFRP extruded column research and engineering design.

Design of Pilot Plant Packed Column for the Dehydration of Water from Ethanol-Water Mixtures

This use of biomass-based adsorbent has been explored for the column study of the adsorptive dehydration of water in ethanol-water mixtures. The column study was carried out using enzyme modified corn starch and the breakthrough curve parameters were used to design the packed bed column. The effect of flow rate on the breakthrough curves revealed that adsorption efficiency decreased with increased inflow rate. The empty bed contact time (τ) of the pilot plant packed column was 35.35 min while the breakthrough time is 40.78 min. 66.7% was the fraction of capacity left unused for the pilot plant from the design.

延长探区古生界页岩气水平井一次上返高效封隔固井技术

为提高延长探区古生界页岩气易漏水平井固井质量和水泥环层间封隔效果,在详细分析技术难点的基础之上,通过注替工艺、水泥浆体系及封隔能力评价方法创新,形成了系列固井技术,并进行了两口井现场实施。结果表明:1)陆相页岩气水平井最优化注水泥浆柱结构为钻井液/隔离顶替浆/冲洗液/低密度水泥浆/常规密度水泥浆,可提高顶替效率;2)选取国产人造微珠A为减轻材料、微硅为体系的稳定剂,可研制体系配方“油井水泥+77%微珠+35%微硅+4.0%降失水剂+10%早强剂”,最低可配置密度为0.95 g/cm^(3);3)采用尿素改性碳纳米管配置纳米封隔水泥浆,与未改性碳纳米管体系相比,抗压强度、抗拉强度分别提高32.3%和36.4%;4)采用三轴应力加载装置,对改性碳纳米管加量为0.04%的水泥环进行封隔能力测试,在110 MPa套管内压、11次循环加载作用下,水泥环的密封性仍然保持完好。该技术可以提高水平井一次上返固井成功率和水泥环压后完整性,为区域高效开发提供支撑,也为同类井固井提供了借鉴。

铁改性油菜秸秆生物质炭对酸性茶园土壤氮磷淋失及酶活性的影响

生物质炭是一种具有前景的土壤改良剂,目前针对铁改性油菜秸秆生物质炭对茶园土壤养分淋失的研究相对较少。通过向茶园土壤中添加改性、未改性油菜秸秆生物质炭(炭土质量比分别为1%、3%和5%)后开展土柱淋溶及土壤培养实验,研究铁改性或未改性油菜秸秆生物质炭作用于土壤养分淋失及酶活性(蔗糖酶、酸性磷酸酶、脲酶和过氧化氢酶)的变化规律,旨在分析和比较铁改性及未改性生物质炭对茶园土壤微生物活性及养分循环的影响。结果表明,添加生物质炭可增加茶园土壤的保水能力,土壤水分累积淋溶量随生物质炭添加量的增加显著减少,添加5%的改性生物质炭(g3)及未改性生物质炭(w3)分别较未添加生物质炭的土壤(CK)减小7.70%和16.98%。g3处理对土壤硝态氮和磷酸盐的固持作用最为显著,淋失量较CK处理分别减少31.82%和60.56%。生物质炭对茶园土壤酶活性存在一定促进作用,但添加改性或未改性生物炭对土壤酶活性的影响存在明显差异。其中,w3中土壤脲酶、蔗糖酶分别显著高于其他处理14.85%~25.10%和19.00%~48.98%,添加3%未改性生物质炭(w2)后,土壤过氧化氢酶活性高出其他处理2.14~29.33μmol·h^(-1)·g^(-1);g3处理对酸性磷酸酶促进作用最强。总的来说,未改性生物炭在增强茶园土壤持水能力及促进土壤酶活性方面要优于铁改性生物炭,而改性生物质炭对土壤氮磷养分的固持作用更为显著。因此,为改善茶园土壤质量,提高土壤肥力,应适量选取铁改性生物质炭。

经改良三切口入路手术治疗三柱Lisfranc损伤

目的比较经改良三切口入路与经典双切口入路治疗三柱Lisfranc损伤的临床疗效。方法回顾性选取2017年12月至2020年10月收治的61例三柱Lisfranc损伤病例进行研究。其中观察组33例,男性26例,女性7例,年龄(39.2±12.7)岁(18~59岁);对照组28例,男性20例,女性8例,年龄(38.8±13.9)岁(18~60岁)。观察组采用改良三切口入路进行切开复位内固定,对照组采用经典双切口入路行切开复位内固定术。比较两组患者手术时间、术中X线透视次数、术后引流量、术后并发症情况,评价两组患者末次随访Maryland足部评分。结果观察组和对照组手术时间分别为(91.5±10.7)min和(86.9±5.3)min,两组间存在差异(P<0.05);观察组和对照组术中X线透视分别为(5.4±1.9)次和(7.6±3.6)次,两组间有差异(P<0.05);观察组和对照组术后引流量分别为(21.2±24.3)m L和(21.8±1.5)mL,两组间无差异(P>0.05);观察组发生并发症1例,对照组为6例,两组间存在差异(P<0.05)。观察组和对照组随访时间分别为(14.5±1.6)个月和(14.6±1.6)个月,在末次随访时使用Maryland足部功能评分进行评估,观察组和对照组功能总分分别为(90.9±8.3)分和(91.9±6.4)分,两组间无统计学差异(P>0.05);观察组和对照组优良率分别为90.9%和89.3%,两组间无差异(P>0.05)。结论经改良的三切口入路手术治疗三柱Lisfranc损伤术中暴露好,术中X线透视次数少,术后并发症少,患足功能满意,值得进一步推广使用。

有机物改性麦糟动态吸附水中五价砷的试验研究

随着各国工业化进程的不断加快,全球范围内砷污染成为一个突出的环境问题。本文采用有机物改性麦糟动态吸附处理水中五价砷。通过改变进水流速和砷离子初始浓度来评价动态吸附的性能。随着流速和初始浓度的增加,动态吸附柱穿透时间提前。分别采用Thomas、Adams-Bohart和Yoon-Nelson模型来分析动态吸附过程。从结果可以看出,实验数据和理论数据的趋势具有强而显著的相关性。

改性玉米芯吸附柱处理含Cr^(6+)废水的试验研究

以废弃玉米芯为原料,以磷酸为活化剂制备改性玉米芯,对比研究了玉米芯和活化玉米芯吸附柱对含Cr6+废水的处理效果。结果发现,相同试验条件下,活化改性后的玉米芯吸附柱对Cr6+的处理效果明显优于未改性的玉米芯吸附柱。试验考查了吸附柱有效吸附高度、Cr6+含量、进水流速、废水pH对含铬废水处理效果的影响。在pH=1、吸附柱有效吸附高度≥1.5 m、进水体积流量为≤2.5 L/min时,初始质量浓度为100 mg/L的含Cr6+模拟废水,Cr6+去除率均在99%以上。对所研究的某机械加工废水处理时,进水体积流量≤2.5 L/min、有效吸附高度为2 m时,废水COD去除率在75%左右,Cr6+、总Cr、Zn2+的去除率分别在86%、88%、98%以上。

改性活性氧化铝吸附除氟的连续试验研究

针对不同进水水质、运行条件、设备3个方面,对改性活性氧化铝吸附除氟连续试验进行研究。试验结果表明,进水氟质量浓度、进水pH对吸附柱穿透影响显著,进水氟质量浓度从5 mg/L下降到2 mg/L时,穿透体积提高1.9倍;进水pH从7.6降低到6.0时,穿透体积提高2.6倍以上,当进水pH在6.0～6.5时,穿透体积达到最大值1388倍体积。穿透体积随进水速率提高而下降,在空速1.3～2.0h-1时,穿透体积下降较小;当空速大于2.0h-1时,穿透体积随空速增加而快速下降。吸附柱直径及填充高度对穿透体积无影响。

改性沸石对2,4-二氯苯酚的去除作用

采用溴化十六烷基三甲铵(HDTMAB)制备改性沸石,在与天然沸石对比的基础上,研究了改性沸石在动态条件下去除2,4-DCP的效果。并对影响去除率的主要因素,包括沸石粒径、进水浓度,进水流速,沸石用量,进水pH值等进行研究。结果表明,细粒改性沸石在pH2.5左右时处理低浓度2,4-DCP溶液时,能取得较好的去除效果,流速较低时去除率最高可达80%以上。