Investigation of Hydroabrasion in Slurry Pipeline Elbows and T-junctions

The present study demonstrates the comparison of erosion rate of critical pipeline parts, namely elbow and T-junction which face the maximum erosion in a pipeline and may cause an early damage and failure of the system. CFD （computational fluid dynamics） with an Eulerian-Lagrangian approach coupled with an approved erosion model is applied to visualize the 3-D flow behavior of slurry flow in both parts and to predict the erosion rate and the location of erosion at the internal surfaces. The analysis of slurry erosion is performed in five steps; geometry and grid generation, grid study/refinement, fluid flow solution, solid particles tracking and finally, the erosion calculation. In previous publications in literature considering transportation of gas-solid flows in pipe parts, the application ofT-junctions instead of elbows for specified conditions in order to reduce the erosion is recommended. In this article, it is approved that for liquid-solid flows, the Stokes number is reasonably smaller than the values for gas-solid flows. This causes the solid particles tightly couple to the fluid phase and to travel more closely with the fluid streamlines. The effects of important influencing parameters such as feed flow velocity, solid concentration, particle size and shape are investigated in detail in current work. It was found that for liquid-solid flows, the erosion of T-junction for all of the mentioned influencing parameters, due to its geometrical specifications and Stokes number variation in comparison with gas-solid flows, is reasonably higher than erosion of elbow. Due to these findings, in contrary to the gas-solid mixture flows, application of T-junction instead of elbow for liquid-solid flow transportation is not recommended.     

镍铬铸铁的冲蚀磨损行为

利用MCF-30型冲蚀磨损试验机对镍铬铸铁进行冲蚀磨损试验,采用扫描电镜(SEM)、透射电镜(TEM)、XRD技术对其组织和冲蚀磨损后的形貌进行表征,分析了冲蚀角、冲蚀介质酸碱度对其冲蚀磨损性能的影响,总结了其冲蚀磨损规律。结果表明,镍铬铸铁在960℃风淬+250℃回火处理后,Cr与Fe、C形成(Fe,Cr)3C型合金碳化物,呈断续网状分布,起到了抗磨骨架的作用,Ni固溶于铁素体中强化基体;不同冲蚀角下,其冲蚀磨损曲线呈现"M"形,最大冲蚀率出现在60°冲蚀角;强酸对其冲蚀磨损影响较大,当pH≥3的时候,弱酸对其冲蚀磨损量几乎无影响。对其冲蚀磨损机理进行了分析。     

煤炭开采沉陷区土壤有机碳空间变化

为研究矿区土壤碳动态,以焦作矿区为例,分析了沉陷坡与裂缝区两种破坏地表的土壤有机碳空间变化。结果表明:与未沉陷的矿区土壤相比较,沉陷坡与裂缝区表土(0~10 cm)有机碳含量降低且空间变异性增大,土壤剖面各层次有机碳含量均出现降低,特别是10~30 cm的土壤剖面层有机碳含量降低最明显,降幅为29%~38%;两种破坏地表土壤剖面有机碳库损失高达20.8~47.3 t/hm2。沉陷坡上,表土有机碳含量从上坡到中坡明显的降低,从中坡到坡底逐渐增加;中坡、下坡与坡底有机碳含量沿土壤剖面层次向下表现出一致的线性下降趋势,但上坡在土壤剖面内的波动较大;各坡位土壤剖面有机碳储量均出现损失,尤其是坡底以上的坡位有机碳储量损失最大。矿区土壤有机碳的空间变化与土壤侵蚀、土地利用、裂隙渗漏及低生物量输入有关。     

矿热炉铁(渣)口用无水炮泥的技术探讨

为使矿热炉生产顺行,对出铁(渣)口使用的炮泥材质、配方进行了优化改进,采用了高纯原料通过添加不同的非氧化物和有机结合剂,使炮泥不仅具有良好的烧结性、耐侵蚀性、填充性,而且易打开铁(渣)口,同时新旧炮泥间结合强度高,从而提高了矿热炉炉口的整体稳定性,实现了矿热炉顺行、低耗、安全、延长使用寿命的目的。     

Effect of ion supplementation of a commercial soft drink on tooth enamel erosion

Acidic soft drinks are potentially erosive for dental hard tissues. This in vitro study evaluated the effect of calcium, fluoride, iron and phosphate, supplemented alone or in combination to a commercial citric acid-based carbonated beverage on dental erosion. Ninety enamel samples (4 × 4 × 3 mm) were randomly allocated to nine groups (n = 10): G1–pure beverage (control); G2–with 1 mM Ca; G3–with 0.047 mM F; G4–with 1 mM Fe; G5–with 1 mM P; G6 - with 1 mM Ca and 0.047 mM F; G7–with 1 mM Ca and 1 mM P; G8–with 1 mM Fe and 0.047 mM F; and G9–with 1 mM Ca, 1 mM P, 0.047 mM F and 1.0 mM Fe. The samples were subjected to six pH cycles over a 24-h period. In each cycle, the samples were immersed in pure or modified beverage (1 min) and in artificial saliva (59 min). During the remaining period (18 h), the samples were maintained in artificial saliva. Enamel loss was assessed by profilometry (µm). Data were tested using ANOVA and Tukey's tests (p < 0.05). Highest enamel losses were observed in the control group (G1) and in the groups containing Fe (G4 and G8). The groups containing Ca (G2 and G6) showed significantly less wear compared to control. In conclusion, the modification of an erosive soft drink with low concentrations of Ca with or without F may reduced its erosive potential.     

不同粒度银粉的Ag-TiB2 触头材料电弧侵蚀行为

采用不同粒度的银粉和放电等离子烧结工艺制备了Ag-4% TiB₂（质量分数,下同）触头材料,测量了Ag-4% TiB₂触头材料的致密度、导电率和硬度,并在真空下对Ag-4% TiB₂触头材料进行了电弧侵蚀实验。采用扫描电子显微镜对Ag-4% TiB₂触头材料电弧侵蚀后的表面形貌进行了表征,采用TDS-2014双通道数字存储示波器记录了燃弧波形,并计算了燃弧时间,对电弧侵蚀机理进行了探讨。结果表明,Ag-4% TiB₂触头材料的致密度、导电率和硬度均随着Ag粒度的降低而增加。另外,采用细银粉制备的Ag-4% TiB₂触头材料具有较长的燃弧时间、较大的侵蚀面积和较浅的蚀坑,表明细小的Ag颗粒有助于电弧分散,能够提高材料的耐电弧侵蚀性能。     

倾动炉自动摇炉及氧化掺氮的应用

倾动炉杂铜冶炼300炉左右,针对精炼侧,烧嘴侧炉墙耐火砖侵蚀严重,需要作业人员对其喷补才能保证安全生产,为了减缓此区域耐火砖的侵蚀,倾动炉技术人员开始尝试自动摇炉和氧化掺氮研究及应用。通过自动摇炉和氧化掺氮的研究应用,减缓了酸性氧化渣对精炼侧、烧嘴侧炉墙耐火砖的侵蚀。     

Effect of the surface modification of the synthetic meshes used in the surgical treatment of pelvic organ prolapse on the tissue adhesion and clinical functionality

Stress urinary incontinence and pelvic organ prolapse represent important conditions affecting adult women’s health. Lately, the properties and performance of the polymer materials used in the treatment of pelvic organ prolapse have been improved by modulating from their formula. Materials investigated in our study are polypropylene meshes used by clinicians in surgical treatment of urinary incontinence and utero-vaginal prolapse. In order to make a comparative analysis, we confronted the structure and surface morphology of native synthetic polypropylene meshes with explanted fragments from the same mesh type after clinical use. FTIR investigations revealed little change in structure after implantation, somehow insignificant. Scanning electron microscopy (SEM) demonstrates modification in surface morphology even just by passing through the transobturator passage, whereas after implantation the surface deteriorates. SEM on explanted meshes proves the encapsulation process of the mesh to be more similar to a foreign body reaction rather than to the adhesion and integration of the synthetic mesh into the organism. Histological analysis of the surrounding tissues near explanted mesh was made in some relevant clinical cases, because the tissue response is an important factor in order to evaluate the tissue adhesion at the polypropylene mesh surface. Based on our experiments and clinical experience we’ve designed an adhesion score. It applies to meshes used in pelvic organ prolapse surgery measuring the following important factors: tenacity, extent of adhesion, macroscopic and microscopic aspects and ease of dissection from surrounding tissues.     

玻璃熔窑蓄热室靶墙热修及结构改进

蓄热室靶墙长期受高温烟尘侵蚀、冲刷,倒塌造成格子体顶部盖帽,堵塞格子体,同时火焰直接烧蚀钢碹碴,危及蓄热室上部结构安全。本文介绍了蓄热室靶墙的热修处理方法,探讨了墙体烧损倒塌的原因,并针对性的对蓄热室墙体结构进行了改进。     

PENETRATION ABILITY OF ABRASIVE WATERJETS IN CUTTING OF ALUMINUM-SILICON CARBIDE PARTICULATE METAL MATRIX COMPOSITES

This article presents a set of studies performed on aluminum-silicon carbide particulate metal matrix composites prepared by adding 5, 10, 15 and 20% of SiC in aluminum alloy and processed with abrasive water jets that are formed with garnet and silicon carbide abrasives of 80 mesh size. These studies are essentially meant to assess the penetration ability of abrasive water jets on different compositions of Al-SiC _p MMCs produced by stir casting method. Abrasive waterjet cutting experiments were conducted on trapezoidal shaped specimens of different composites as well on the constituent materials i.e., 100% aluminum alloy and 100% SiC specimens by varying water pressure, jet traverse speed and abrasive mass flow rate, each at three different levels. The percentage contribution of individual and combined effects of process parameters on penetration ability was analyzed by means of analysis of variance. Contribution of waterjet pressure and traverse speed on jet penetration in these meaterials are found to be more than abrasive flow rate. Among the interaction effects, waterjet pressure and jet traverse speed combinations contribute more to jet penetration. The results presented in this study can be used to build statistical models that can predict the depth of penetration of jet in different MMCs. This study also highlights the need to choose suitable abrasive mass flow rates and jet traverse speeds for effective processing of MMCs with abrasive water jets.