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991.
992.
为研究脱灰对龙口油页岩的影响,采用HCl→HF→HNO3三级酸洗法脱灰,用XRD以及FT-IR法分别分析酸洗前后矿物质和化学结构的变化.结果表明:油页岩含氧官能团主要包含醚氧、羧基、羟基和羰基4类,酸洗制得的有机质纯度较高,酸洗后油页岩灰分的质量分数低于1%.酸洗对油页岩的化学结构产生影响,酸洗过程发生了水解反应,油页岩烷基醚、芳基醚含量减少;酸洗破坏了含氧官能团与无机盐之间的离子交联作用,将有机盐转化为有机酸,羧酸和酚羟基含量显著上升;羟基结构在酸洗前后都以环羟基、OH—O和OH—OH这3种形式为主,酸洗对环羟基、OH—O影响较大,对OH—OH影响很小;脂肪族在酸洗后部分CH伸缩振动和不对称的CH3伸缩振动转变成不对称的CH2伸缩振动,脂肪链长度增加. 相似文献
993.
To investigate the corrosion performance of commercial automotive cold rolling sheets under severe atmospheric environment, electrochemical impedance spectroscopy was used to detect the electrochemical behaviors of three types of cold rolling sheets and a humid- temper test was carried out to explore the corrosion behavior under shipping and storage environments. Meanwhile, the effects of surface status and micro- structure of the sheets on the corrosion behaviors were analyzed based upon the results of profile measurements, contact angle tests and metallographic analysis.The results show that with the same load of anti- rust oil, 590DP steel presents the largest electric resistance of oil film and charge transfer resistance, and the longest incubation period of rust under storage environment. All these good properties could be assigned to the surface profile of the steel. However, the generation rate rust turns to be faster later on, which can be attributed to its dual- phase microstructure. In sum, the surface wetting status of different types of sheets are almost the same, which has no significant effect on the corrosion performance of the steels. Comparatively, surface profile of the steels plays an important role during the initial stage of corrosion, and the difference in microstructure has a more remarkable influence on the development stage of corrosion. 相似文献
994.
Guixue Wang Shuping Ge Yang Shen Honggang Wang Qinglei Dong Qin Zhang Jiacheng Gao Yong Wang 《Materials science & engineering. C, Materials for biological applications》2012,32(8):2190-2198
Magnesium alloys have been widely applied in biomedical devices because of their high strength, toughness, processing performance and the trace release of Mg2 +. In this study, we investigated the biodegradability, cytocompatibility and hemocompatibility of four kinds of WE Mg alloys (where “W” indicates the metallic element Y and “E” represents mixed rare earth [RE] elements; Y: 2.5, 5.0, 6.5, and 7.5 wt.%; Nd: 1.0, 2.5, 2.6, and 4.2 wt.%; Zr: 0.8 wt.%) for their application in intravascular stent fabrication. The content of alloying elements affected not only mechanical properties of materials, but also their biocompatibility. We found that addition of RE elements could reduce the corrosion rates. Human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs) were cultured in different extracts of WE Mg alloys. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was used to examine the cytotoxicity. The nitric oxide (NO) and lactate dehydrogenase (LDH) release were used to evaluate effects of Mg alloys on HUVECs. The addition of Y, Nd and Zr increased the cell viability and improved the hemocompatibility. Different alloy elements affected the morphology of samples, Mg2 + release, and pH values in the medium. The results of mechanical properties, biocompatibility and biodegradability showed that Mg–5.0Y–2.6Nd–0.8Zr might be used as alternative materials of stent. However, it still needs to be further modified for clinical use. These findings suggest that selecting suitable alloying elements is particularly important. 相似文献
995.
996.
将溶胶-凝胶法与水热法相结合制备活性碳纤维(ACF)-Ag-TiO2纳米纤维复合材料,利用扫描电镜、透射电镜、能量色散型X射线光谱仪对ACF-Ag-TiO2纳米纤维复合物的表面形貌及晶型进行表征,并以甲基橙的脱色降解为模式反应,考察样品的光催化性能。结果表明,ACF-Ag-TiO2纳米纤维长度为48μm,直径约为58μm,直径约为550 nm;制备的材料中Ag元素的质量分数为0.5%时,ACF-Ag-TiO2的催化效果最优,光照30 min后对甲基橙的降解率为95%。 相似文献
997.
Zi-xi WANG Jing-hui ZHAO Xiao-hong JIA Jian-guo FANG Bo ZHANG Guo-qing DING 《钢铁研究学报(英文版)》2013,20(11):85-89
The effect of seawater after ultraviolet inactivation on corrosion of a shipbuilding steel plate was investigated by means of natural corrosion potential experiments and immersion corrosion test. The effects of natural seawater and treated seawater after ultraviolet inactivation on corrosion of the selected steel plate samples were compared with each other. The results showed that there was no obvious change in the chemical composition of treated seawater compared with natural seawater. The corrosion potential slightly increased by 10 mV, whereas the corrosion rate rose significantly by 20%. The experiments verified the naturally formed biofilm in the natural seawater for the inhibition of corrosion on the shipbuilding steel plate. The possible influences of ballast water treatment on biofilm by ultraviolet and electrolysis inactivation under the condition of practical usage were also investigated. And it was found that ballast water treatment methods with no continuous disinfection could protect original tank biofilm structure, reducing the intensity of tank corrosion. 相似文献
998.
Tao HAN Hailong SUN Yangqiu SONG Yili FANG Xudong LIU 《Frontiers of Computer Science》2021,15(4):154315
Crowdsourcing has been a helpful mechanism to leverage human intelligence to acquire useful knowledge.However, when we aggregate the crowd knowledge based on the currently developed voting algorithms, it often results in common knowledge that may not be expected. In this paper, we consider the problem of collecting specific knowledge via crowdsourcing. With the help of using external knowledge base such as WordNet, we incorporate the semantic relations between the alternative answers into a probabilisticmodel to determine which answer is more specific. We formulate the probabilistic model considering both worker’s ability and task’s difficulty from the basic assumption, and solve it by the expectation-maximization (EM) algorithm. To increase algorithm compatibility, we also refine our method into semi-supervised one. Experimental results show that our approach is robust with hyper-parameters and achieves better improvement thanmajority voting and other algorithms when more specific answers are expected, especially for sparse data. 相似文献
999.
【摘要】 目的 探讨多层螺旋CT多平面重建(MPR)技术在射频消融(RFA)治疗晚期肝癌中的应用。方法 114例晚期肝癌患者行RFA治疗,常规轴位扫描引导组(简称非MPR组)83例,MPR组31例。对两组调整进针方向的次数、穿刺角度和深度差、术前术后CT均值差、操作总时间、术后并发症发生率、平均剂量?长度积(DLP)及瘤体毁损率进行统计学分析。结果 穿刺成功时MPR组进针次数较非MPR组少1.42次(P<0.001)。两组穿刺角度和深度误差分别是0.33°和0.23 mm(P>0.05)。术前术后两组CT均值差为0.36 Hu(P>0.05)。MPR组较非MPR组操作时间平均缩短8 min(P=0.001)。MPR组仅5例(16.1%)出现并发症,而非MPR组有33例(39.8%)出现并发症(P<0.05)。RFA治疗成功后MPR组的平均DLP较非MPR组少131.75 mGy?cm(P<0.001)。术后复查1、3个月的三期CT/MRI,两组患者的瘤体毁损情况均无明显统计学意义(P>0.05)。结论 多层螺旋CT MPR技术更清晰显示射频针与病变及其周围解剖结构的位置关系,减少了进针次数,缩短了操作时间,降低了并发症发生率与辐射剂量,提高了手术效率,因此对RFA治疗肝癌具有重要指导价值。
相似文献
相似文献
1000.
A privacy access control model for content sharing was presented to fine-grained control users' location infor-mation associated with sharing content in mobile social network. A k-anonymity privacy algorithm for privacy settings was given to protect against inference attack on a content sharing service provider server. To balance the privacy and quality of service, a location shifting method was presented. Finally experimental results demonstrate the validity and practicality of the proposed approach. 相似文献