增强现实中基于位置安全性的LBS位置隐私保护方法

为了解决基于位置的服务(LBS)和增强现实(AR)技术快速发展带来的用户位置隐私泄露的隐患,分析了现有的位置隐私保护方法的优缺点,提出基于位置安全性的位置隐私保护方法。将区域安全度和伪装区域引入该方法中,将提示某区域是否需要保护这一度量标准定义为区域安全度,非安全区域(即需要给予保护的区域)的区域安全度设置为1,安全区域(即不需要保护的区域)设置为0,通过扩大区域安全度和识别等级来计算位置安全度。实验结果表明,该方法与未引入位置安全性的方法相比降低了平均定位误差,提高了平均安全性,从而有效地保护了用户的位置隐私,提高了LBS的服务质量。     

破碎带单孔循环注浆钻进工艺及应用

针对破碎带深孔施工存在的塌孔、卡钻问题,介绍了单孔循环钻进注浆工艺和新型无机注浆材料,并进行了效果考察。单孔循环注浆钻进工艺只采用一个钻孔,通过循环钻进、退钻、注浆工艺,对破碎带分别加固;新型无机双液注浆材料通过改变水灰比,实现浆液流动和凝结时间调整,解决了不同深度破碎带注浆后快速套孔问题。     

浮选机运输区的结构特征的测试研究

浮选机内各动力学分区的流动特征复杂。本文选取单槽容积0.2m3KYF型充气机械搅拌式浮选机为研究对象,采用PIV测试技术开展运输区的结构特征和动力学特征的研究。研究表明运输区在半个槽体的取截面内的轮廓形状整体呈现为左边为直线,右边折弯线,上下近似直线的近梯形结构,具有高度和宽度两个主要结构特征。运输区轮廓边界处的动力学特征存在明显差异。本研究加深了对浮选机运输区特征的理解,有助于通过调控运输区特征方法解决大型机械搅拌式浮选机粗粒矿物回收率低的难题。     

曙光煤矿1226综采工作面瓦斯抽采技术

采用综合应用理论分析、现场实测的方法,对山西汾西集团曙光煤矿1226高瓦斯综采工作面瓦斯来源进行了分析,提出并实施了分区段“风排+煤层钻孔抽放+裂隙带钻孔抽放”的联合瓦斯抽采技术。现场监测结果显示:1226综采工作面上隅角瓦斯浓度控制在0.45%~0.75%,回风流中瓦斯浓度控制在了0.44%~0.75%,瓦斯治理效果明显改善。     

Al2O3 loss prediction model of selective laser melting Al2O3–Al composite

The element/phase loss is undesirable but existing during selective laser melting (SLM) of materials with volatile element/phase, which not only changes the material composition but also affects the molten pool flow. In the previous researches, the effect of remelting on the element/phase loss was neglected during the SLM process, instead, laser energy density was thought to be uppermost. In fact, the SLM process fabricates the parts in a manner of line by line and layer by layer, i.e., additive character, and the remelting in the overlap zone occurs during the SLM process. In this paper, three different Al₂O₃ loss prediction models of SLM Al₂O₃–Al composite by considering the additive character of SLM and the distribution of the Al₂O₃ associated with the different molten pool driving forces were developed. By comparing with the experimental results and predicted results, it is found that the Al₂O₃ is distributed on both sides of the molten pool under the combined action of the Marangoni flow and the evaporation recoil pressure. This kind of Al₂O₃ distribution enhances the effect of the remelting on the Al₂O₃ loss, i.e., the remelting brings a logarithmic increase in the Al₂O₃ loss rate. This determines the final Al₂O₃ loss rate of the SLMed 3D samples. During this study, although the Al₂O₃ loss rate of the single-track is only 33%, the loss rate of SLMed 3D samples increases significantly to 97% when the hatching space of 60 μm and scanning speed of 200 mm/s are utilized, i.e., almost no Al₂O₃ in the 3D sample. Thus, it is more important to reduce the remelting, i.e., overlap rate for reducing the element/phase loss. This study is a benefit for understanding and reducing the element/phase loss in SLM.     

New approaches to determine the interface height of fire smoke based on a three-layer zone model and its verification in large confined space

Large confined space has high incidence of fires, which seriously threatens the safety of people working there. Understanding the distribution of smoke in such large space is critical to fire development prediction and smoke control. Three improved methods for the stratification interface prediction of fire smoke are developed, including of improved intra-variance, integral ratio and N-percentage methods. In these methods, the interface height is determined by the vertical temperature distribution based on a three-layer smoke zone model, which is an improvement of a two-layer zone model. Thereafter, the three improved methods are applied to several typical fire cases simulated CFD to predict the smoke interface, and their applicability and reliability are verified by comparison of the smoke stratification results with the filed simulation results. Results show that the three improved methods can effectively determine the location of the three-layer zone model's interface, and they have the ability to predict smoke interface for fires with different fire source types and ventilation conditions.     

碳化钒析出对X80管线钢焊接热影响区韧性的影响

通过Gleeble-3500热模拟机对钒(V)含量分别为0.06%和0.02%的X80管线钢进行了峰值温度为1350℃和750℃的焊接热模拟试验,利用硬度计和光学显微镜(OM)分别分析了焊接热模拟试样硬度和试样中马氏体-奥氏体岛状组织(M-A)的数量、尺寸和形貌。利用透射电镜(TEM)对母材、粗晶区和部分相变区中粒子析出进行了表征。结果表明,与0.02%含V量X80管线钢相比,0.06%含V量的X80管线钢由于V含量较高,在受到多道次焊接热循环影响时,部分相变区有较大量碳化钒(VC)粒子析出,明显阻碍位错运动,使其强度明显提高的同时脆性增大、塑性变形难以进行,导致其焊接热影响区韧性下降。