STL模型的分层轮廓数据优化算法

在快速成形系统中 ,由于STL模型在切片后的截面轮廓数据含有大量的数据冗余点 ,严重影响了插补加工的精度和效率。为此 ,作者提出了一种数据冗余点的联合剔除算法 ,在保证加工精度的条件下 ,以进一步提高加工效率与质量     

不同原理的SF6混合气体密度监测技术差异分析

SF_6或SF_6/N2混合绝缘气体的密度直接决定着气体的绝缘性能,因此对气体密度的监测尤为重要。SF_6混合绝缘气体被认为是短期内最具发展前景的SF_6替代介质,国家电网公司目前正大力推广GIS母线用SF_6/N_2混合绝缘气体的应用。由于SF_6混合绝缘气体具有新的特性,原有的SF_6气体密度继电器无法反映设备内SF_6混合绝缘气体密度,为此,亟需开发SF_6混合绝缘气体的密度监测装置。文章对比分析了两种不同原理的SF_6/N_2混合绝缘气体密度监测技术,并探讨了具备混合比监测功能的SF_6/N_2混合绝缘气体密度监测技术。     

陶瓷增强相对金属-陶瓷复合涂层的影响

对电弧喷涂几种不同陶瓷增强相的Fe复合涂层的特点和性能进行了研究，在20钢基体上喷涂含陶瓷TiB2／Al2O3，TiB2-Cr3C2，TiB2，Cr3C2及TiB2-Cr3C2-Al2O3的管状喷涂丝材，采用光学显微镜和XRD对涂层的微观特性进行分析，结果表明，涂层中含有TiB2，Al2O3，Cr3C2，Cr3O2等陶瓷相。通过对涂层常规性能测试表明，含TiB2／Al2O3和Cr3C2的涂层孔隙率较低、结合强度高、并具有优良的耐磨性及抗热震性能。     

酸洗对龙口油页岩化学结构的影响分析

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.     

Corrosion behaviors of cold rolling automotive sheets coated with anti- rust oil

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.     

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介绍了一种全新设计的材料扭转试验机,主要采用了液压回转式夹具装夹试样,通过伺服电机—滚珠丝杆—传感器方式对长线材试样施加恒定的拉紧力,以及伺服电机—减速机构驱控夹头双向旋转,可针对Ф7 mm~Ф14 mm、2 000 MPa级长线材试样开展各类扭转以及低成本的慢速拉扭复合疲劳试验。基于对试样扭矩变化的实时跟踪,可实现0.000 5~30 r/min的变速扭转以及在扭矩陡降(即最大扭转塑性)瞬时临界采样,供后续试样内部组织与外表面形貌评价分析。     

Influence of Inactivation Treatment of Ship's Ballast Water on Corrosion Resistance of Ship Steel Plate

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.     

Find truth in the hands of the few: acquiring specific knowledge with crowdsourcing

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.     

多层螺旋CT多平面重建技术在肝癌射频消融术中的应用

【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。

     

Location privacy preservation approach towards to content sharing on mobile online social network

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.