Electrochemical Study of the Corrosion Inhibitory Capacity of Calcined Attapulgite in Reinforced Concrete Medium

The durability of reinforced concrete structures is greatly influenced by the corrosion of the reinforcement. In addition to air pollution related to the repair of corroded structures, chloride ions are the main factors of corrosion of reinforced concrete structures. This study aims to valorize a clay inhibitor against reinforcement corrosion in reinforced concrete. This clay (Attapulgite) was incorporated into reinforced concretes at different percentages of substitution of calcined attapulgite (0%, 5% and 10%) to cement in the formulation. The corrosion inhibitory power of attapulgite is evaluated in reinforced concretes subjected to the action of chloride ions at different intervals in the NaCl solution (1 day, 21 days and 45 days) by electrochemical methods (zero current chronopotentiometry, polarization curves and electrochemical impedance spectroscopy). This study showed that in the presence of chloride ions, the composition based on 10% attapulgite has an appreciable inhibitory effect with an average inhibitory efficiency of 82%.

Evaluation of the Inhibitory Gel Aloe vera against Corrosion of Reinforcement Concrete in NaCl Medium

Most reinforced concrete structures in seaside locations suffer from corrosion damage to the reinforcement, limiting their durability and necessitating costly repairs. To improve their performance and durability, we have investigated in this paper Aloe vera extracts as a green corrosion inhibitor for reinforcing steel in NaCl environments. Using electrochemical methods (zero-intensity chronopotentiometry, Tafel lines and electrochemical impedance spectroscopy), this experimental work investigated the effect of these Aloe vera (AV) extracts on corrosion inhibition of concrete reinforcing bar (HA, diameter 12mm) immersed in a 0.5M NaCl solution. The results show that Aloe vera extracts have an average corrosion-inhibiting efficacy of around 86% at an optimum concentration of 20%.

Numerical modeling and parametric sensitivity analysis of heat transfer and two-phase oil and water flow characteristics in horizontal and inclined flowlines using OpenFOAM

Estimating the oil-water temperatures in flowlines is challenging especially in deepwater and ultra-deepwater offshore applications where issues of flow assurance and dramatic heat transfer are likely to occur due to the temperature difference between the fluids and the surroundings. Heat transfer analysis is very important for the prediction and prevention of deposits in oil and water flowlines, which could impede the flow and give rise to huge financial losses. Therefore, a 3D mathematical model of oil-water Newtonian flow under non-isothermal conditions is established to explore the complex mechanisms of the two-phase oil-water transportation and heat transfer in different flowline inclinations. In this work, a non-isothermal two-phase flow model is first modified and then implemented in the InterFoam solver by introducing the energy equation using OpenFOAM® code. The Low Reynolds Number (LRN) k-ε turbulence model is utilized to resolve the turbulence phenomena within the oil and water mixtures. The flow patterns and the local heat transfer coefficients (HTC) for two-phase oil-water flow at different flowlines inclinations (0°, +4°, +7°) are validated by the experimental literature results and the relative errors are also compared. Global sensitivity analysis is then conducted to determine the effect of the different parameters on the performance of the produced two-phase hydrocarbon systems for effective subsea fluid transportation. Thereafter, HTC and flow patterns for oil-water flows at downward inclinations of 4°, and 7° can be predicted by the models. The velocity distribution, pressure gradient, liquid holdup, and temperature variation at the flowline cross-sections are simulated and analyzed in detail. Consequently, the numerical model can be generally applied to compute the global properties of the fluid and other operating parameters that are beneficial in the management of two-phase oil-water transportation.

Effect of an Internal Heat Exchanger on the Performances of a Double Evaporator Ejector Refrigeration Cycle

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.

Direct observation of the distribution of impurity in phosphorous/boron co-doped Si nanocrystals

Doping in Si nanocrystals is an interesting topic and directly studying the distribution of dopants in phosphorous/boron co-doping is an important issue facing the scientific community.In this study,atom probe tomography is performed to study the structures and distribution of impurity in phosphorous/boron co-doped Si nanocrystals/SiO_(2) multilayers.Compared with phosphorous singly doped Si nanocrystals,it is interesting to find that the concentration of phosphorous in co-doped samples can be significantly improved.Theoretical simulation suggests that phosphorous-boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy,which also reduces the formation energy of phosphorous in Si nanocrystals.The results indicate that co-doping can promote the entry of phosphorous impurities into the near-surface and inner sites of Si nanocrystals,which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals such as the observed enhancement of conductivity and sub-band light emission.

A Computational Analysis of the Influence of Anastomosis Angle on Stenosis-Prone Locations during Radio-Cephalic Arteriovenous Fistula Maturation

In dialysis treatment, the radio-cephalic arteriovenous fistula (RCAVF) is a commonly used fistula, yet its low maturation rate remains a challenge. To enhance surgical outcomes, the relationship between stenosis-prone locations and RCAVF anastomosis angle is studied during maturation by developing two sets of RCAVF models for early (non-mature) and mature RCAVFs at five anastomosis angles. The impact of hemodynamics and wall shear stress (WSS) is examined to determine optimal anastomotic angles. Results indicate that acute angles produce more physiological WSS distributions and fewer disturbed regions, with early stenosis-prone regions located near the anastomosis that shift to the bending venous segment during remodeling. A pilot study comparing clinical and numerical results is conducted for validation.

Experiment/simulation correlation-based methodology for metallic ballistic protection solutions

A methodology is developed based on the coupling of a finite element code with an optimisation module for the design of land vehicle armouring composed of lightweight aluminium alloy and high strength steel plate.Following an experiment/simulation correlation,a numerical model has been built and calibrated considering monolithic plates and then verified considering a bi-metal protection against tungsten carbide projectile mimicking the core of a 7.62×51 AP8 ammunition.In addition,a method is proposed to obtain the v_(res)-v_(i) curve for the full 7.62×51 AP8 bullet from the v_(res)-v_(i) curve obtained from the core only.

Bending and Free Vibration Analysis of Porous-Functionally-Graded(PFG)Beams Resting on Elastic Foundations

The bending and free vibration of porous functionally graded(PFG)beams resting on elastic foundations are analyzed.The material features of the PFG beam are assumed to vary continuously through the thickness according to the volume fraction of components.The foundation medium is also considered to be linear,homogeneous,and isotropic,and modeled using the Winkler-Pasternak law.The hyperbolic shear deformation theory is applied for the kinematic relations,and the equations of motion are obtained using the Hamilton’s principle.An analytical solution is presented accordingly,assuming that the PFG beam is simply supported.Comparisons with the open literature are implemented to verify the validity of such a formulation.The effects of the elastic foundations,porosity volume percentage and span-to-depth ratio are finally discussed in detail.

Vibration-based bearing fault diagnosis of high-speed trains:A literature review

Due to the advantages of comfort and safety,high-speed trains are gradually becoming the mainstream public transport in China.Since the operating speed and mileage of high-speed trains have achieved rapid growth,it is more and more urgent to ensure their reliability and safety.As an important component in the bogies of highspeed trains,the health state of the bearing directly affects the operational safety of the trains.It is therefore necessary to diagnoze the faults of bearings in the bogies of high-speed trains as early as possible.In this paper,the bearing fault diagnostic methods for high-speed trains have been systematically summarized with their challenges and perspectives.First,it briefly introduces the structure of bearings in the bogies as well as the fault characteristic frequencies.Then,a brief review of the research on vibration-based signal processing methods and machine learning methods has been provided.Finally,the challenges and future developments of vibrationbased bearing fault diagnostic methods for high-speed trains have been analyzed.

TLC及HPLC测定红曲产品中的桔霉素

阐述了定性及定量测定红曲产品中桔霉素含量的几种方法 .采用板层析 (TLC) ,在点样量为 1mL、点样长度 5cm条件下通过目视法 ,标准桔霉素溶液的最低检测质量浓度可达 0 .2mg/L ,板层析可作为定性检验红曲产品中桔霉素的简便方法 .根据红曲样品预处理方法及HPLC检测器的不同 ,确定了两套准确可靠的定量检测方法 .高效液相色谱结合荧光检测的最低检测限为 0 .60ng .HPLC上样液最低可检测的质量浓度为 0 .1mg/L .在 0 .1～ 1 0mg/L的质量浓度范围内 ,标准桔霉素溶液的质量浓度与峰面积的线性关系良好 ,达到R2 =0 .998.

多重散射对含有气体和颗粒的燃烧介质中辐射传热的影响(英文)

该文采用蒙特卡洛方法研究包括吸收性气体和具有一定浓度颗粒的燃烧环境中的辐射传热。在蒙特卡洛程序被验证之后,研究了多重散射对辐射传热的影响。定义了一个临界颗粒体积份额 fv ,作为区分单次散射区和多重散射区的 c分界。当颗粒云的体积份额位于单次散射区和多重散射区时,其辐射通量的变化表现出不同的行为。在单次散射区,平板的辐射通量随着离子浓度增加而剧烈增长,辐射行为受到颗粒单次散射的影响。在多重散射区,离子浓度的增加不会引起辐射通量的增长,辐射通量趋近于一个固定值,辐射行为受到气体吸收和多重散射的双重影响。

建筑热桥动态附加能耗减秩模型

热桥附加热损失在现代建筑总能耗中占有重要比例。介绍了模型减秩的方法 ,建立了适合于程序植入的热桥附加热损失模型 ,并对减秩模型和完全模型的计算结果进行了比较 。

混合培养微生物利用甘油补料发酵生产乙醇研究

采用浸麻芽孢杆菌和红曲菌9906利用甘油混合发酵生产乙醇.结果表明,分批发酵中高浓度的甘油对乙醇发酵有着较强的抑制作用,分批发酵最佳甘油浓度为0.217molL-1.在分批发酵的基础上补料发酵,考察了不同甘油浓度的补料液和不同补料时间对乙醇发酵的影响.最终确定乙醇补料发酵较优的工艺条件为:反应器1L,装液量700mL红曲发酵液,甘油初始浓度为0.217molL-1,以补料方式每隔60h分5次补加0.217molL-1甘油浓度的红曲发酵液,每次补加100mL,发酵培养360h.当乙醇最高浓度达0.221molL-1,乙醇总产率0.628mmolh-1,乙醇/甘油转化率达87%(molmol-1).与分批发酵相比,补料发酵很大程度解除了高浓度甘油的抑制作用,有效地利用了甘油,提高了乙醇的产量,且乙醇产率较为稳定.

微穿孔板结构在管道声源特性测量中的应用分析

将微穿孔板吸声结构应用到外加旁支管路的管道卢源特性测量方法中,分析和仿真了单层及双层微穿孔板及其后腔结构采用不同参数(板厚、微孔直径、穿孔率、后腔深度等)时改变管道负载声阻抗的作用和影响。研究结果表明:改变板厚、微孔直径、穿孔率、管道横截面积比等参数,可以有效地改变负载声阻;改变后腔深度及微穿孔板与主体管道之间距离,可以有效地改变负载声抗;结合使用单层和双层微穿孔板结构,可以有效实现声抗在宽频带上的变化。通过有流和无流情况下的实验,验证了该方法的正确性和微穿孔板吸声结构在测量中的有效表现。给出了该测量方法实际应用中设计和应用微穿孔板吸卢结构的意见。

非相似余度作动系统设计及工作模式分析

非相似余度配置方式可省去中央液压源并有效克服共性故障,成为多电飞机的发展趋势.利用机械特性匹配的方法对变转速电动静液作动器和直驱式机电作动器组成的非相似余度系统进行总体设计.考虑舵面空气负载和连接刚度建立总体数学模型,对3种典型工作模式进行理论分析和仿真对比,再现带载情况下这3种工作模式的切换瞬态.同时提出电机电流内环零值控制的无载工作模式,控制器结构简单并且切换可靠迅速.分析结果对非相似作动系统的设计、工作模式和故障切换方法提供了理论依据.

^18F—FDGPET／CT诊断非小细胞肺癌纵隔淋巴结转移的方法和价值

目的本研究通过目测法、测量法以及模式识别方法对非小细胞肺癌（non—small cell lungcancer，NSCLC）患者纵隔淋巴结的PET／CT图像进行诊断分析，并与病理结果比较，探索各种诊断方法的诊断效能，为临床医生提供有关NSCLC区域淋巴结转移的准确信息。方法选择术前行全身PET／CT检查且经手术根治切除的NSCLC患者28例作为研究对象，由3名有经验的医生分别应用目测法及测量法对淋巴结的CT、PET以及PET／CT图像进行分析，并与病理结果进行对比；同时通过对淋巴结的PET和CT图像的提取，应用工程学一种新的模式识别方法进行分类诊断。结果CT、PET、PET／CT测量法对NSCLC淋巴结诊断的灵敏性分别为53．6％、80．4％、82．1％；特异度分别为92．2％、83．3％、90．6％；阳性预测值分别为68．2％、60．0％、73．0％；阴性预测值分别为86．5％、93．2％、94．2％；诊断符合率分别为83．1％、82．6％、88．6％；CT、PET、PET／CT目测法对NSCLC淋巴结诊断的灵敏性分别为53．6％、71．4％、69．6％；特异度分别为85．0％、82．2％、88．9％；阳性预测值分别为52．6％、55．6％、66．7％；阴性预测值分别为85．5％、90．2％、90．4％；诊断符合率分别为77．5％、79．7％、84．3％。模式识别法计算得出PET的灵敏度为88％，特异度为76％；CT的灵敏度为84％，特异度为66％。结论PET／CT测量法以及目测法对NSCLC淋巴结转移的诊断明显优于单独的CT或单独的PET；PET／CT测量法对NSCLC淋巴结转移的诊断明显优于目测法。初步探索了通过构建多分辨率直方图及支持向量机（SVM）分类判别的工程学方法对淋巴结图像进行分析，为今后多学科联合以及探索更准确的无创检查手段奠定了基础。

机器学习算法诊断PET/CT纵膈淋巴结性能评估

评估4种主流典型的机器学习方法(随机森林、支持向量机、AdaBoost、反向传播人工神经网络)对(^(18 )F-FDG)PET/CT影像中非小细胞肺癌纵膈淋巴结良恶性进行诊断分类的性能.先从168例病人的PET/CT影像中分割出1 397个淋巴结,对每个淋巴结提取出13种图像特征(D_(short)、area、volume、HU_(mean)(2Dor 3D)、HU_(contrast)(2Dor3D)、SUV_(mean)(2Dor 3D)、SUV_(max)(2Dor 3D)、SUV_(std)(2Dor 3D));将提取出的13种图像特征进行组合,得到4种组合变量("All features"、"High AUC features"、"Doctors features"、"3Dfeatures");在4种组合变量下,分别从敏感性、特异性以及ROC曲线下的区域面积(AUC_(ROC))3个方面对随机森林、支持向量机、AdaBoost、反向传播人工神经网络定量地进行诊断性能评估.评估结果显示,4种分类器分割结果的敏感性为77%~84%,特异性为81%~84%,AUC_(ROC)为0.86~0.90.在显著性(p<0.001)条件下对比发现,虽然机器学习方法的特异性略低于人类专家,但是敏感性显著优于人类专家.研究结果表明,三维图像特征及PET/CT影像组合特征可以显著提高AUC_(ROC).基于上述研究结果可以得出结论,虽然4种机器学习方法在(^(18)F-FDG)PET/CT影像的非小细胞肺癌纵膈淋巴结的良恶性诊断中展现了不错的敏感性,但它们的特异性有待进一步提高,在未来需要尝试多种分类方法进行联合实验,使用更高级的机器学习方法如深度学习进行进一步的研究.

植入碳纤维蜂窝夹芯结构的光纤光栅热载荷响应光谱研究

针对航天领域复合材料结构在空间服役环境的热响应监测需求,研究了一种热载荷作用下基于光纤Bragg光栅(FBG)反射光谱特征分析的碳纤维蜂窝夹芯结构监测方法。将光纤Bragg光栅传感器分别植入碳纤维蜂窝夹芯结构的不同铺层,通过监测不同热载荷下各铺层位置的光纤光栅反射光谱,得到碳纤维蜂窝夹芯结构相关铺层位置热应变特征。研究表明,碳纤维蜂窝夹芯结构不同材料铺层的热应变特征存在一定差异。植入外蒙皮表面与玻璃布之间的光纤光栅反射光谱随着温度升高,中心波长向长波方向漂移,且波形未出现明显改变。埋植于外蒙皮第二、三层碳纤维织物预浸料之间的光栅反射光谱随着温度降低逐渐出现旁瓣、多峰等啁啾效应,其主峰与右侧次峰中心波长均向短波方向逐渐漂移,主峰峰值幅度变化较小,温度灵敏度约为5.56×10^(-3) dBm·℃^(-1),而右侧次峰幅度显著增大,温度灵敏度约为40.32×10^(-3)dBm·℃^(-1);埋植于内蒙皮和蜂窝芯子之间的光栅反射光谱随着温度降低,其半波峰带宽逐渐增大,变化率约为3.19pm·℃^(-1),且出现显著多峰趋势,这是由于层间热应力分布不均匀所形成。在-70^+60℃温度范围,各植入层热应变均随温度升高而增大,且变化趋势相接近,而在+60^+120℃温度范围内,各植入层热应变变化趋势呈现显著差异。这些特性能够为后继空间环境复合材料航天器结构状态在轨监测提供有益帮助。

光纤光栅传感器与机械结构预处理胶接方法

结构应力应变高精度测量对于实现直升机动静态强度监测与评估具有至关重要的意义。由于光纤光栅传感器具有柔韧性好、芯径细、抗电磁干扰能力强以及便于实现分布式监测等显著优点,使得其在航空航天器结构强度监测领域受到广泛重视。为提升直升机应变监测精度与灵敏度,本文研究了光纤光栅传感器应变感知原理和精度影响因素,构建了基于光纤光栅传感器的板结构应变监测系统。在此基础上,提出剥离光栅栅区涂覆层、施加预应力及其双层胶接等预处理集成方法,实现对板结构光纤光栅传感器应变测量精度的有效提升。

316L奥氏体不锈钢焊接热影响区性能

为了研究 31 6L焊接热影响区性能 ,采用特定的热、应力、应变模拟控制曲线 ,对其在 2 0℃、60 0℃、1 0 0 0℃及 1 1 0 0℃几种温度下进行热模拟拉伸试验 ,获得了此种材料在多种应变速率下的应力 -应变曲线 .结果表明 ,在一定的应变速率下 ,31 6L的弹性模量 E及屈服极限 σ0 .2 都随温度升高明显降低 ;在室温及高温下 ,31 6L存在着 σ0 .2 随应变速率提高而提高的应变率效应 ,且应变率敏感性随温度升高而增加 .同时 ,还观察到 31 6L在高温 (1 0 0 0℃和 1 1 0 0℃ )塑性状态下由粘塑性引起的应力松弛现象及室温下的加工硬化现象 .