High-efficiency Carbonation Modification Methods of Recycled Coarse Aggregates

To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put forward.The carbonation effect of modified recycled coarse aggregate with three different carbonation methods was evaluated,and water absorption,apparent density and crush index of modified recycled coarse aggregate were measured.Combined with XRD,SEM,and MIP microscopic analysis,the high-efficiency carbonation strengthening mechanism of modified recycled coarse aggregate was revealed.The experimental results show that,compared with the non-carbonated recycled coarse aggregate,the physical and microscopic properties of carbonated recycled coarse aggregate are improved.The method of carbonation with nano-SiO_(2) pre-soaking can realize the high-efficiency carbonation of recycled coarse aggregate,for modified recycled coarse aggregate with the method,water absorption is reduced by 23.03%,porosity is reduced by 44.06%,and the average pore diameter is 21.82 nm.The high-efficiency carbonation strengthening mechanism show that the pre-socked nano-SiO_(2) is bound to the hydration product Ca(OH)_(2) of the old mortar with nano-scale C-S-H,which can improve the CO_(2) absorption rate,accelerate the carbonation reaction,generate more stable CaCO_(3) and nano-scale silica gel,and bond to the dense three-dimensional network structure to realize the bidirectional enhancement of nano-materials and pressurized carbonation.It is concluded that the method of carbonation with nano-SiO_(2) pre-soaking is a novel high-efficiency carbonation modification of recycled coarse aggregate.

Research on Heredity of Coarse Ferrite Grains

The changes in austenite grain size of the specimens with coarse ferrite grains under different heat treatment process were investigated.The focus was on studying the effect of annealing on refining coarse ferrite grains,as well as the influence of the ferrite grain size on the main technical indicators of gas carburizing.The results show that coarse ferrite grains may not necessarily cause the coarse austenite grains,but may result in mixed austenite grains.After annealing treatment,the coarse ferrite grains can be significantly refined and homogenized.Moreover,the coarse ferrite grains have no significant effects on hardnessand intergranular oxidationof gas carburizing.

Effect of High Temperature Curing on the Frost Resistance of Recycled Aggregate Concrete and the Physical Properties of Second-Generation Recycled Coarse Aggregate under Freeze-Thaw Cycles

With the emphasis on environmental issues,the recycling of waste concrete,even recycled concrete,has become a hot spot in the field of architecture.But the repeated recycling of waste concrete used in harsh environments is still a complex problem.This paper discusses the durability and recyclability of recycled aggregate concrete(RAC)as a prefabricated material in the harsh environment,the effect of high-temperature curing(60℃,80℃,and 100℃)on the frost resistance of RAC and physical properties of the second generation recycled coarse aggregate(RCA_(2))of RAC after 300 freeze-thaw cycles were studied.The frost resistance of RAC was characterized by compressive strength,relative dynamic elastic modulus,and mass loss.As the physical properties of RCA_(2),the apparent density,water absorption,and crushing value were measured.And the SEM images of RAC after 300 freeze-thaw cycles were shown.The results indicated that the frost resistance of RAC cured at 80℃ for 7 days was comparable to that cured in the standard condition(cured for 28 days at 20℃±2℃ and 95%humidity),and the RAC cured at 100℃ was slightly worse.However,the frost resistance of RAC cured at 60℃ deteriorated seriously.The RAC cured at 80℃ for 7 days is the best.Whether after the freeze-thaw cycle or not,the RCA that curd at 60℃,80℃,and 100℃ for 7 days can also meet the requirements of Grade III RCA and be used as the aggregate of non-bearing part of prefabricated concrete components.RCA_(2) which is cured at 80℃ for 7 days had the best physical properties.

CWDM技术在通信网络中的应用分析

文中首先对CWDM技术进行了介绍,包括CWDM的系统组成和系统原理等,然后以城域网为例分析了CWDM技术在通信网络中的应用,并总结了CWDM技术在通信网络中的优势,最后提出了一些可行的应用维护意见。综上所述,目前CWDM在城域网、接入网、企业网、校园网等领域具有广泛的应用前景。

Changes in soil microbial communities induced by warming and N deposition accelerate the CO 2 emissions of coarse woody debris

Warming and nitrogen(N)deposition are two important drivers of global climate changes.Coarse woody debris(CWD)contains a large proportion of the carbon(C)in the total global C pool.The composition of soil microbial communities and environmental changes(i.e.,N deposition and warming)are the key drivers of CWD decomposition,but the interactive impact between N deposition and warming on the composition of soil microbial communities and CWD decomposition is still unclear.In a laboratory experiment,we study and simulate respiration during decomposition of the CWD(C 98)of Cryptomeria japonica(CR)and Platycarya strobilacea(PL)in response to warming and N deposition over 98 days.Resuts show that either warming or N addition signifi cantly accelerated the C 98 of the two tree species by altering the soil microbial community(bacterial:fungi and G+:G–).The combined treatment(warming+N)resulted in a decomposition eff ect equal to the sum of the individual eff ects.In addition,the species composition of bacteria and fungi was obviously aff ected by warming.However,N deposition had a remarkable infl uence on G+:G–.Our results indicated that N deposition and warming will observably alter the composition and growth of the microbial community and thus work synergistically to accelerate CWD decomposition in forest ecosystems.We also present evidence that N deposition and warming infl uenced the composition and balance of soil microbial communities and biogeochemical cycling of forest ecosystems.

Effect of variations in the polar and azimuthal angles of coarse particles on the structure of drainage channels in thickened beds

The 3D reconstruction and quantitative characterization of drainage channels and coarse tailings particles in a bed were conducted in this study.The influence of variations in the azimuthal angle(θ)and polar angle(φ)of coarse particles on drainage channel structure was analyzed,and the drainage mechanism of the bed was studied.Results showed that water discharge in the bed reduced the size of pores and throat channels,increasing slurry concentration.The throat channel structure was a key component of the drainage process.Theφandθof particles changed predominantly along the length direction.The changes inφhad a cumulative plugging effect on the drainage channel and increased the difficulty of water discharge.The rake and rod formed a shear ring in the tailings bed with shear,and theθdistribution of particles changed from disorderly to orderly during the rotation process.The drainage channel was squeezed during the shearing process with the change inθ,which broke the channel structure,encouraged water discharge in the bed,and facilitated a further increase in slurry concentration.The findings of this work are expected to offer theoretical guidance for preparing high-concentration underflow in the tailings thickening process.

铝合金塑性成形粗晶现象的研究进展

铝合金经过热塑性变形或者塑性变形+热处理后,可能发生晶粒异常长大而形成粗晶。粗晶会大幅降低构件的力学性能、耐腐蚀性能和抗疲劳性能,因此必须得到有效控制。对铝合金塑性成形粗晶的研究主要集中在2×××、6×××、7×××系热处理可强化型铝合金以及5×××系热处理不可强化型铝合金,研究内容已经覆盖塑性成形工艺、热处理制度、微观组织演变、数值仿真模拟等方面。为了明晰铝合金塑性成形构件粗晶现象的研究现状,为相关研究提供参考,对铝合金塑性成形粗晶现象的研究进展进行了梳理。首先,分析了材料成分、变形温度、变形速度、固溶温度、固溶时间和模具结构对晶粒异常长大的影响;其次,从晶粒取向分布、应变诱导储能和第二相钉扎作用的角度总结了晶粒异常长大的机理;再次,归纳了包括改变坯料初始状态、合理的锻造技术和中间形变热处理等有效抑制粗晶产生的方法;最后对未来的研究方向进行了展望。

微量元素对超大线能量EH36船板热影响区粗晶区组织和性能的影响

通过焊接热模拟研究了在超大线能量下焊接时Al元素、Mg元素和Ti元素含量对EH36高强船板钢热影响区粗晶区组织、性能的影响规律,采用Thermo-Calc热力学计算与SEM,EDS测试相结合的方法揭示了Al元素、Mg元素和Ti元素含量与母材中氧化物类型、尺寸、数量及粗晶区相变的关系.结果表明,Al_(2)O_(3)无法诱导针状铁素体相变,当Al元素质量分数低于0.005%时,钢中可形成Mg元素、Ti元素或其复合氧化物,可促进粗晶区针状铁素体相变.Mg元素和Ti元素联合添加时,当Mg元素质量分数由0.0042%降低为0.0013%,氧化物类型由MgO转变为Mg_(2)TiO_(4),经统计20个视场内的氧化物数量由408个提高到503个,平均直径由1.37μm减小到1.10μm,显著提高了非均匀形核的比表面积,抑制了晶界铁素体的形成,使t8/5=300 s时粗晶区热模拟试样-20℃冲击吸收能量由43 J提升到127 J.

基于coarse-fine思想蛇算法的测量仪器几何参数标定

针对研发的正交轴系三维激光扫描设备进行几何参数标定从而提升精度问题,提出了一种基于coarse-fine思想的蛇优化标定算法,对设备装配几何误差进行测量和矫正,以提高仪器测量精度。首先对数据空间进行粗寻优,之后利用蛇算法进行精确寻优;对设备参数进行迭代优化并确定标定值;最后进行了基于标准棋盘标定板的标定实验。实验结果表明,基于coarse-fine思想的蛇优化标定算法一定程度上避免局部最优解的问题,大幅提高了标定算法的收敛速度以及适应度计算可靠性,在具体对房屋内部的实测实验中表明,于房屋的进深、标宽、净高的测量上,经过算法标定后降低的误差分别为75、23、4 mm,较大提高了设备的测量精度。该标定方法为正交轴系的测量设备的几何参数标定提供了一种新的方法。

复杂应力条件下粗粒料的剪胀性研究进展

粗粒料的剪胀性是其强度和变形研究的重要问题之一,它取决于颗粒排列、粒间压力等细微观作用;在宏观层面,受相对密度与应力状态的影响。围绕复杂应力条件下粗粒料的剪胀问题,从粗粒料力学特性的试验研究、粗粒料的剪胀性强度准则以及临界状态与剪胀性方面,对国内外的研究进展进行了系统论述。在此基础上,提出该领域呈现如下发展态势:①通过大型真三轴试验开展粗粒料剪胀率的试验研究与理论分析,能够促进粗粒料本构理论的发展进步;②结合应力路径试验中的应力变形规律研究,可实现从常规三轴条件下向复杂应力条件下的剪胀方程的进一步发展,从而体现强度与变形问题的统一;③采用状态参量去评价土体的松密状态与剪胀性,能够耦合应力状态与孔隙比,尽量避免“一种材料,多组参数”。研究结果表明状态参量和应力路径相结合的方法,使得粗粒料的力学特性研究更加具有科学性和系统性。

MMA强化再生粗骨料混凝土力学性能试验研究

目的为了提高再生粗骨料混凝土的性能,扩大再生粗骨料混凝土在工程中的使用范围。方法采用聚合物-甲基丙烯酸甲酯(MMA)单体浸渍,然后聚合的方法对再生粗骨料进行了强化研究。对聚合温度、聚合时间、再生粗骨料含水率等因素对MMA强化再生粗骨料效果的影响及强化后的再生粗骨料对再生粗骨料混凝土力学性能的影响进行了分析。结果研究结果表明:MMA强化再生粗骨料时的最佳聚合温度为60℃,最佳聚合时间为24 h,MMA强化可以有效改善再生粗骨料的吸水率和压碎指标等物理性能,对再生粗骨料进行预干燥处理可以使再生粗骨料的吸水率和压碎指标等物理性能得到进一步提升;MMA强化处理后的再生粗骨料混凝土3d、7d、14d和28d立方体抗压强度分别比普通再生粗骨料混凝土提高了26.9%,20.3%,21.4%,23.9%,轴心抗压强度、劈裂抗拉强度、抗折强度和弹性模量等力学性能分别比普通再生粗骨料混凝土提高了20.9%、14.7%、12.2%和8.3%,同时再生粗骨料混凝土的延性也得到了显著改善。结论MMA单体浸渍,然后进行聚合的方法可以有效改善再生粗骨料性能,从而提高再生粗骨料混凝土的力学性能。

再生粗骨料混凝土应力-应变关系

再生粗骨料混凝土应力-应变关系是实现其材料到结构力学分析的桥梁纽带,成为再生粗骨料混凝土结构基础理论的基石。介绍了作者团队多年来在再生粗骨料混凝土应力-应变关系方面取得的研究进展:采用模型化再生粗骨料方法,研究了复杂界面过渡区对再生粗骨料混凝土破坏行为的影响,揭示了再生粗骨料混凝土细观损伤本质与演化机理;从静力作用到动力作用,系统地开展了不同工况下再生粗骨料混凝土应力-应变行为试验研究,探明了载荷条件对再生粗骨料混凝土应力与变形的影响规律并建立了相适应的力学与数学模型;进一步考虑再生粗骨料性能时空变异性,发现了再生粗骨料混凝土力学响应的概率分布特征,提出了再生粗骨料混凝土随机损伤本构关系;基于获得的本构模型,完成了再生粗骨料混凝土构件时变可靠度分析和结构动力非线性分析,为再生粗骨料混凝土在实际工程中的安全应用提供了理论支撑;提炼了相关研究结论并对未来研究工作进行了展望。

S-FHMC710型煤泥重介质旋流器在吕家坨选煤厂的应用

吕家坨矿选煤厂为了解决粗煤泥分选效果差的问题,采用S-FHMC710型超级煤泥重介质旋流器分选粗煤泥,并通过工业性试验对超级煤泥重介质旋流器进行工艺性能进行检测。试验结果表明:大于0.5 mm粒级可能偏差0.050 kg/L,数量效率99.64%;0.50~0.25 mm粒级可能偏差0.060 kg/L,数量效率98.76%;0.25~0.10 mm粒级可能偏差0.087 kg/L,数量效率96.99%,有效分选下限达到0.10 mm。该超级煤泥重介质旋流器应用效果良好,对于提高精煤质量、产率和选煤厂经济效益具有显著的效果。

粗骨料超高性能混凝土应用研究

为满足桥梁工程中桥面板材料轻质高强的市场需求,在活性粉末混凝土中掺入粒径不大于8 mm的粗骨料,制成含粗骨料超高性能混凝土。这种混凝土具有力学性能佳、材料自重轻、早期收缩小和造价较低等特点。首先阐述含粗骨料超高性能混凝土的配制原理及各掺合料对其性能的影响,其次分析其力学性能、疲劳性能和高温性能,最后展示了其在南京江心洲长江大桥的工程应用状态,并提出了其尚待深入研究的问题和发展方向。

固体力学跨尺度计算若干问题研究

本文展示了固体力学领域跨尺度计算的若干问题和研究概况。(1)建立位错动力学与有限元耦合DDD-FEM的计算模型,实现了能够基于纳米尺度离散位错运动机制计算分析连续介质有限变形晶体塑性问题,提出微纳尺度(200 nm~10μm)晶体塑性流动应力解析公式,结合试验数据揭示了在无应变梯度下强度和变形的尺寸效应;(2)建立具有微相分离结构的纳米尺度粗粒化分子动力学模型CG-MD,计算获得聚脲材料在时域和频域下的存储模量和损耗模量,通过动态加载分析的DMA试验和超声波试验的数据验证,解决了连续介质尺度下微相分离高分子共聚物的设计难题;(3)通过数据驱动关联高分辨率的微米尺度CT影像和临床低分辨率的毫米尺度CT影像的特征值,建立了围关节松质骨小梁的等效模量和结构张量,为骨组织增材制造点阵结构设计和实现个性化骨缺损重建奠定了基础。

轻质高强混凝土制备与性能分析

基于轻质高强混凝土竞赛,文中对我国企业和高校制备轻质高强混凝土的能力进行了调研和分析,对46家企业、19家高校制备的轻质高强混凝土配合比、抗压强度、劈裂强度、粗骨料含量进行汇总、测试和分析,探究了原材料品质、配合比参数对混凝土力学性能和结构效率系数(强度容重比)的影响。分析结果表明,基于对轻质高强混凝土微观结构与宏观性能关系的理解,通过原材料选择、配合比设计和粗骨料优化等措施,在容重不大于1500 kg/m^(3)的控制条件下,轻质高强混凝土的抗压强度可达120 MPa,结构效率系数世界领先,达83.2 kPa/(kg·m^(-3))。文中所展示的轻质高强混凝土制备方法和材料性能,对轻质高强混凝土制备和建筑行业发展有促进作用。

某300 MW机组脱硝前紧凑空间粗颗粒飞灰预脱除关键技术研究及应用

燃煤机组由于煤质及燃烧等原因,锅炉尾部烟道烟气中的粗飞灰颗粒易造成烟道及脱硝催化剂不同程度的磨损。以某300 MW等级机组省煤器出口至脱硝入口烟道为研究对象,建立“A型折流富集+V型高效收灰+T型粗灰通道”的“A-V-T”型脱硝前粗颗粒飞灰预脱除结构,布置于省煤器出口的大截面低流速烟道内,通过数值模拟研究了布置粗颗粒飞灰预脱除装置前后不同粒径分布轨迹、脱除效果、阻力等条件的影响规律,并进行了工程应用。模拟结果表明:采用粗颗粒脱除技术后对原系统烟气侧流场状态影响小;随着飞灰粒径的增大,飞灰脱除率越高,其中50、200、500、1000μm粒径的飞灰脱除率分别为12.15%、59.40%、87.01%、93.62%,对粒径200μm及以上的粗颗粒脱除效率为85.15%,整体的收灰率为15.50%,新增阻力78 Pa。对某300 MW机组实施改造后,经试验,脱硝前对粒径200μm及以上粗颗粒灰脱除率为83.96%,整体灰的脱除率为14.91%,净增阻力73Pa,试验结果验证了数值模拟结果的合理性。

烟台港龙口港区27^(#)~29^(#)通用泊位疏浚工程绞吸船施工工艺优化

烟台港龙口港区27^(#)~29^(#)通用泊位疏浚工程土质主要为起球的黏性土,混有少量粗砂,绞吸船在施工时受黏土起球及黏性等影响,容易出现堵管、绞刀糊堵、输送困难等情况,施工作业关键参数波动幅度较大,作业人员操作控制难度高,平均生产效率低。重点围绕绞吸船的挖掘和输送分析,确定关键施工参数,优化施工工艺,指导作业人员施工。优化后的施工工艺使烟台港龙口港区27^(#)~29^(#)通用泊位疏浚工程绞吸船施工产能提高20%以上,节约了施工成本。

氯盐干湿循环对再生混凝土力学性能研究进展

再生混凝土的应用,不仅能够解决废弃混凝土处理问题;又能降低因资源过度开采所引起的生态环境破坏,因而具有广阔的发展前景。相比于普通混凝土,干湿循环作用下再生混凝土的力学性能更为复杂。综述了氯盐干湿循环环境下再生混凝土力学性能研究进展,剖析了再生混凝土在氯盐侵蚀与干湿循环共同作用下抗压强度、劈裂抗拉强度、抗剪强度、动弹性模量、界面过渡区和孔隙结构等力学性能变化规律,分析了干湿循环与再生粗骨料对再生混凝土力学性能影响机理,总结了其力学性能改善措施。分析结果表明:既有研究存在不足,主要体现在试验早期不同研究者的研究结论离散性较大,需要进一步加强微观结构和破坏机理分析,完善理论体系。

细针穿刺、粗针穿刺及两者联合诊断甲状腺结节的前瞻性对比研究

目的:对比研究超声引导下细针穿刺(FNA)、粗针穿刺(CNB)和粗细针穿刺结合(FNA+CNB)对同一甲状腺结节的诊断效能。方法:选取105例甲状腺结节患者(112个结节)作为研究对象,对每个结节同时行超声引导下细针(FNA)和粗针(CNB)穿刺,分别比较FNA、CNB、FNA+CNB对甲状腺结节的诊断效能;根据超声特征(结节最大径、粗大钙化、纵横比、囊实性)进行分组,比较FNA、CNB的诊断准确度。结果:剔除14个穿刺失败结节后,剩余98个结节进入研究,FNA、CNB取材成功率分别为89.4%、97.3%(P<0.05)。FNA、CNB、FNA+CNB诊断甲状腺结节的敏感度分别为93.1%、75.9%、100%,FNA、FNA+CNB优于CNB(P<0.05);特异度分别为60%、90%、57.5%,CNB优于FNA、FNA+CNB(P<0.05);阴性预测值分别为85.7%、72%、100%,FNA+CNB优于CNB(P<0.05)。ROC曲线分析显示,CNB曲线下面积(AUC)大于FNA(0.829 vs.0.766,P<0.05)。亚组分析中,对于直径<0.5 cm的结节,CNB诊断特异度高于FNA(100%vs.50%,P=0.014),FNA诊断敏感度高于CNB(93.3%vs.46.7%,P=0.033)。结节大小和纵横比可能会影响CNB的诊断结果,直径≥0.5 cm敏感度更高,纵横比≤1准确度更高(P<0.05);结节囊实性可能会影响FNA诊断结果,实性结节准确度更高(P<0.05)。结论:CNB对甲状腺结节良恶性的检出具有更高的诊断价值,但直径<0.5cm的结节使用FNA具有更高的敏感度。