Electrochemical and analytical study of corrosion inhibition on carbon steel in HCl medium by 1,12-bis(1,2,4-triazolyl)dodecane

1,12-bis(1,2,4-triazolyl)dodecane (dTC12) is an excellent corrosion inhibitor for carbon steel in deaerated 1 M HCl solution. In this work electrochemical and analytical techniques were used to study the inhibition of corrosion on carbon steel in acidic medium. The carbon steel corrosion inhibition of dTC12 was attributed to the synergistic effect between chloride anion and quaternary ammonium ion. The protective efficiency of the film was higher than 90%, indicating that corrosion of carbon steel in 1 M HCl is reduced by dTC12.The effect of dissolved oxygen on the inhibition efficiency was also investigated. The results show that the inhibition efficiency increases in early stage and decreases for a long immersion time.     

Accuracy analysis of the window overlapping technique for velocity measurements using artificial and real signals

The feasibility of using window overlapping processing technique together with cross-correlation method was investigated for measuring instantaneous particle velocities using a fiber optic system. A pair of artificial signal pulses was generated to yield a known velocity field when they were cross-correlated. A parametric analysis was conducted to determine whether the window overlapping technique enhanced the velocity sampling frequency of the fiber optic probe system.The window overlapping technique was found to be effective in improving the accuracy of the instantaneous velocity calculations for relatively shorter data segments (windows). As the length of the window size increased, the efficiency of the window overlapping method diminished. The window overlapping technique was found to be effective only for window sizes up to four times longer than the minimum window size. The minimum window size contains sufficient number of data points that corresponds to the maximum velocity sampling frequency according to the Nyquist Theory. That is, the window overlapping technique could be beneficial for enhancing the velocity sampling frequency only if the velocity data (or the window size used in the cross-correlation function) were sampled at a frequency of four times lower (or better) than the highest frequency in the flow.Due to the hardware limitations, it is not possible to sample data at frequencies high enough to capture the highest frequency velocity fluctuations in a turbulent flow. Therefore, in this study, it was investigated that the velocity sampling frequency of a fiber optic probe could be enhanced by window overlapping technique using data collected from a highly turbulent particle laden pipe flow. The results indicated that the window overlapping technique slightly improved the accuracy of the instantaneous particle velocity measurements. This is believed to be due to the larger window sizes (or low sampling frequencies) relative to the high frequency velocity fluctuations in the flow. Therefore, the particle velocity fluctuations may not be computed accurately using a fiber optic probe due to the nature of the cross-correlation method which filters the velocity variations during the time period of ΔT. In order to obtain reasonably accurate results for measuring the particle velocity fluctuations in real life applications, the time interval (window size) must be sufficiently small such that it corresponds to the frequencies, at most, four times lower than the highest frequency occurring in the flow.     

Corrosion of carbon steel in sodium methanoate solutions

The behaviour of steel electrodes in sodium methanoate solutions was studied by coupling electrochemical techniques (voltammetry, OCP vs. time) with in situ micro-Raman spectroscopy analyses of the corrosion products. The polarisation curves depended strongly on the methanoate concentration. For the smallest concentration (10⁻³ mol L⁻¹), the current density increased regularly with the applied potential. So the behaviour of the electrode was typical of an active material. In contrast, for the largest concentration (10⁻¹ mol L⁻¹), the curves obtained were typical of a passive material. Methanoate ions favoured growth and stability of a passive oxide film more likely by adsorbing on its surface. The polarisation curve obtained for the intermediate concentration (10⁻² mol L⁻¹) was unusual and testified of an imperfect passivation of the steel surface. Finally, steel electrodes were left at the open circuit potential in the methanoate solutions. In any case, the passivity was rapidly lost and a general corrosion of the surface took place. In situ Raman spectroscopy analyses at the early stage of the corrosion process demonstrated that the first product to form was a green rust, GR(HCOO⁻). It was oxidised later into γ-FeOOH (lepidocrocite) by dissolved O₂. The process is then typical of what is usually observed in neutral or alkaline media, whatever the anions present and responsible of the GR formation. A new and detailed characterisation of GR(HCOO⁻) by X-ray diffraction was performed and a crystal structure is proposed.     

A Potent,Selective CBX2 Chromodomain Ligand and Its Cellular Activity During Prostate Cancer Neuroendocrine Differentiation

Polycomb group (PcG) proteins are epigenetic regulators that facilitate both embryonic development and cancer progression. PcG proteins form Polycomb repressive complexes 1 and 2 (PRC1 and PRC2). PRC2 trimethylates histone H3 lysine 27 (H3K27me3), a histone mark recognized by the N-terminal chromodomain (ChD) of the CBX subunit of canonical PRC1. There are five PcG CBX paralogs in humans. CBX2 in particular is upregulated in a variety of cancers, particularly in advanced prostate cancers. Using CBX2 inhibitors to understand and target CBX2 in prostate cancer is highly desirable; however, high structural similarity among the CBX ChDs has been challenging for developing selective CBX ChD inhibitors. Here, we utilize selections of focused DNA encoded libraries (DELs) for the discovery of a selective CBX2 chromodomain probe, SW2_152F. SW2_152F binds to CBX2 ChD with a K_d of 80 nM and displays 24-1000-fold selectivity for CBX2 ChD over other CBX paralogs in vitro. SW2_152F is cell permeable, selectively inhibits CBX2 chromatin binding in cells, and blocks neuroendocrine differentiation of prostate cancer cell lines in response to androgen deprivation.     

增强燃烧室内空气紊流降低柴油机油耗,噪声及有害排放物的研究

柴油机燃烧室中空气紊流运动对促进燃烧有重要作用。为改善Ｘ４１０５Ｂ柴油机性能，作采用了高紊流的“Ｑｕａｄｒａｍ”型燃烧室。通过合理选择进气涡流强度、供油速率和供油提前角，取得了良好的效果。不仅改善了燃油经济性，减小了烟度，而且降低了其排放物和噪声。     

紊动强度沿垂线分布规律的分析

在现有研究的基础上，运用超声流速仪进行挟沙水流水槽实验，并结合分析激光流速仪、应变式紊动流速仪的观测结果，建立了纵向紊动强度与流速、流速梯度之间的定量关系。利用数值实验方法，分析了水流最大流速、摩阻流速及卡曼常数对紊动强度最大值出现位置的影响。     

Numerical study of stratified oil-water two-phase turbulent flow in a horizontal tube

Stratified oil-water two-phase turbulent flow in a horizontal tube is numerically simulated using a volume of fluid model. A single momentum equation is solved throughout the domain. The RNG k-ε model combined with a near-wall low-Re turbulence model is applied to each phase, and a continuum surface force approximation is adopted for the calculation of surface tension. The simulation is performed in a time-dependent way and the final solution which corresponds to steady-state flow is analyzed. Results of pressure loss, slip ratio, local phase fraction profile and the axial velocity profile are verified by experimental data in literature. Based on the numerical results of extensive calculations, the flow field characteristics are explored and correlations for pressure loss and hold-up are presented.     

Cocurrent turbulent mixed convection heat and mass transfer in falling film of water inside a vertical heated tube

A detailed numerical study has been conducted in order to analyse the combined buoyancy effects of thermal and mass diffusion on the turbulent mixed convection tube flows. Numerical results for air-water system are presented under different conditions. A low Reynolds number k-ε turbulent model is used with combined heat and mass transfer analysis in a vertical heated tube. The local heat fluxes, Nusselt and Sherwood numbers are reported to obtain an understanding of the physical phenomena. Predicted results show that a better heat transfer results for a higher gas flow Reynolds number Re, a higher heat flux q_w or a lower inlet water flow Γ₀. Additionally, the results indicate that the convection of heat by the flowing water film becomes the main mechanism for heat removal from the wall.     

抑制型降滤失剂AMSC的合成与应用

针对水基钻井液长期存在黏土膨胀、钻井液滤失量大等问题,以2-丙烯酰胺-2-甲基丙磺酸、丙烯酰胺、甲基丙烯酰胺氧基氯化铵及丙烯酸钾为原料合成了一种抑制型降滤失剂AMSC,用响应面法优化了反应条件,并对AMSC的黏土膨胀抑制性和降滤失性能进行了评价。结果表明:在原料单体质量比为2:1:7:1、温度为50℃、单体浓度为15%、引发剂浓度为0.5%、反应4 h时,AMSC防膨率达到84.76%。在100℃以内,AMSC的抑制性与市场同类型抑制剂相比效果相当,同时该抑制剂对钻井液和水泥浆有较好的降滤失效果。应用添加AMSC的缓速酸体系在遭受钻井液污染的碳酸盐岩区块进行了洗井作业,储层岩心的渗透率恢复率达到87%,提高了产能。      

小型亚热带半日潮河口中的湍流

在天然河口,污染物的输送是由湍流动量混合驱动的,而弥散的大小却难以被准确地预测。这是由于对河口的湍流结构缺乏基础的认识而造成的。介绍在一个小型的亚热带半日潮河口进行的高频率及连续50 h的湍流实地测量的情况。在研究的浅水(低潮水深小于0．5 m)小型河口中,使用了最适用于这种水体的声学多普勒流速仪进行测量,并进行了完整的后处理工作。河口水流是一个波动的过程,各种宏观流动参数随潮周期和其它大尺度的过程而波动,但是湍流特性是由即时局部流动特性所决定,它们基本不受流动历程的影响,其结构和瞬时变化受多种机理影响。这导致其只与水流剪切力引起的湍流边界层平衡相关。所有湍流特性在潮周期中均有大波动是本次研究数据的一个显著特征,这一特征在此前少有记载,但本次的测量数据与过往数据的一大差别是,数据连续测量的时间长且频率高。这将为波动特性的动量交换系数及积分时间和长尺度提供新的信息,这些湍流特性不应被视为不变的。