Pitting corrosion on 316L pipes in terephthalic acid (TA) dryer

Grade 316L is a type of austenitic stainless steel with ultra‐low carbon content and it exhibits superior corrosion resistance. However, pitting is always observed in 316L steel when it is exposed to media containing halide ions. In the present study, we found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer. In order to identify the causes of the failure, metallographic structures and chemical compositions of the matrix material were inspected by an optical microscope (OM) and a photoelectric direct reading spectrometer. Beside these, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as ion chromatography (IC) were used to analyze the micromorphologies of the corrosion pits and the chemical compositions of the corrosion deposits within them. Analysis of the results revealed the sources of halide ions and the factors accelerating the corrosion rate. Beside these, detailed mechanisms of pitting were discussed and six out of all the seven theoretical morphologies of pitting features were obtained in practice.     

Preparation and Fluorescence Properties of Polymethyl Methacrylate Resin Incorporated with Sodium Tris （Pyridine Dicarboxylato）Europate

Based on the strong fluorescence and the highly thermal stability of sodium tris (pyridine dicarboxylato)eruopate(Na3Eu(DPA)3),polymethyl methacrylate(PMMA)composite material incorporated with the complex,PMMA:Na3Eu(DPA)3,was prepared at 250℃，The fluorescence behavior of PMMA:Na3Eu(DPA)3material was examined,The results show that the composite material keeps the luminescent characteristics of the Eu^3 chelate after PMMA is incorporated with Na3Eu(PDA)3,and strong orange-red emission of the composite wsa observed.The fluorescence intensity of the composite material increases with the increase of the weight ratio of Na3Eu(PDA)3to PMMA,but the relationship is not linear.     

浅议技师学院教师培养的途径

文章从利用外部资金技术、搞好教师培训、引进校外人才、以制度保证进修培养的效果四个方面,对培养技师学院教师的途径和方法进行了探讨。     

Comparison of Aqueous Ozone and Chlorine as Sanitizers in the Food Processing Industry: Impact on Fresh Agricultural Produce Quality

The effects of ozone treatment on fresh strawberry and shredded lettuce food quality were tested by varying applied ozone concentration, contact time, pH and temperature to assess ozone a potential food sanitizer. The produce quality was assessed by comparing the changes in texture firmness, browning and decolorization, oxygen consumption and carbon dioxide respiration after the post-treatment storage from 0 to 21 days. The effectiveness of ozonation on natural microfloras including mesophiles, psychotrophes, yeasts and molds, was also evaluated for the improvement in produce shelf-life. As compared to chlorine treatments, ozone treatments slightly increased the lettuce browning but substantially retarded its respiration rates and firmness deterioration even after 21 days of storage. For strawberry, no significant difference in food quality was observed between ozone and chlorine treatments. Finally, ozone treatments at the doses below 10 mg/L were found not effective in killing natural microfloras grown on the produce surfaces.     

Eckert填料层压降通用关联图的关联与应用

对Eckert的通用关联图进行了回归 ,得到了分段的关联式 ,计算的最大误差为 18.5 % ,平均误差为 4.96 % ,可以满足工程设计计算的要求。该关联式用于真空精馏塔的计算 ,得到了满意的结果。同时还对三条泛点线进行了关联。     

Ex situ TEM observation of localized attack on AA 6061

Ex situ transmission electron microscopy (TEM) was used in conjunction with energy dispersed spectrometry (EDS) to monitor evolution near the pre‐selected inclusions during initial stages of localized dissolution on the aluminum alloy (AA) 6061 immersed in 0.1 M NaCl solution. On the alloy TEM foil, Mg₂Si phase particles were observed to preferentially dissolve after 3 min immersion. Nevertheless, different dissolution behaviors were observed to form in the vicinities of the different structure Fe‐rich precipitates; the trenches were observed near the anorthic phase particle, but no obvious priority dissolution was detected in the vicinity of hexagonal phase particles. The preferential sites of alloy dissolution were found to depend on both the component and the structure of the intermetallics. The shift of electrochemical potential was found to relate the dissolution of the heterogeneous phases.     

选尺法求解哥古猜想解答(续)

哥德巴赫猜想与古叶猜想合成哥古猜想( Goldbach -Guye's Conjecture):任何一个非零偶数(z),都可表达为两个素数(y及x)之‘和’或‘差’;即有z+=y+x,或有z=y-x.当知z+或z-时,如何求解y及x配偶成副呢?文章介绍了求解哥古猜想解答的一种选尺法(利用‘y尺’与‘x尺’间的相对位移)...     

FE-model for Titanium alloy (Ti-6Al-4V) cutting based on the identification of limiting shear stress at tool-chip interface

Modeling of metal cutting has proved to be particularly complex, especially for tool-chip interface. The present work is mainly aimed to investigate the limiting shear stress at this interface in the case of Titanium alloy (Ti-6Al-4V) dry cutting based on a FE-model. It is first shown that the surface limiting shear stress was linked to the contact pressure and the coefficient of friction (CoF). A relationship between CoF and the limiting shear stress was given, and the effect of the temperature on the limiting shear stress was also considered. After that, an orthogonal cutting model was developed with an improved friction model through the user subroutine VFRIC in Abaqus/Explicit software. The numerical results obtained were compared with experimental data gathered from literature and a good overall agreement was found. Finally, the effects of cutting speed, CoF and tool-rake angle on chip morphologies were analyzed.