Highly transparent terbium gallium garnet crystal fabricated by the floating zone method for visible–infrared optical isolators

Highly transparent terbium gallium garnet (Tb₃Ga₅O₁₂; TGG) single crystal having a large Verdet constant based on the visible and near-infrared region (VIS–NIR) Faraday rotator was grown by Floating Zone (FZ) growth machine. We successfully grew TGG single-crystal rods of 8–10 mm in diameter, which was suitable for the use in optical devices. The crystal showed a full-width at half-maximum as little as 18 arcsec by the X-ray rocking curve measurement. The Faraday rotation (B = 0.55T) was investigated at wavelength of 532, 632.8, 1064 nm at room temperature. The lower weak absorption coefficient, higher Verdet constant, thermal conductivity and laser induced damage threshold (LIDT) compared to the commercial TGG gives the great potential of using this new method to meet the increasing demand of VIS–NIR Faraday rotators (FRs).     

Slag eye formation in single and dual bottom purged industrial steelmaking ladles

ABSTRACT

Argon gas is often injected from the bottom of the ladle during steel refining operations. The injected gas interacts with the liquid (metal and slag) bath and enhances the momentum, heat, and mass transfer rate in the melt. However, during these gas–liquid interactions, an opening of the slag layer called slag eye is formed, which exposes the molten metal surface to the atmosphere, which is generally undesirable. In the current work, a transient, three-dimensional mathematical model is used to study the turbulent gas–liquid interactions in single as well as dual bottom blown industrial steelmaking ladles. A Coupled Level Set Volume of Fluid (CLSVOF) model is used for tracking the steel-argon, steel-slag, and argon-slag interfaces, from which the slag-eye area has been predicted. It is found that the inlet gas purging rate, melt height, slag layer thickness, angular and radial positions of the gas inlets affect the slag opening area. Non-dimensional empirical correlations are proposed to predict the slag opening area in both single as well as dual purged ladles, using non-linear regression analysis.     

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。     

A油区清垢剂与缓蚀剂的优选分析

随着油田开发进程的深入,注水驱油早已成为最为常见的开采方式之一。实践表明,不论是从水体的配伍性还是经济性的角度来看,经过多重技术处理的采出污水都是回注水体的最佳选择。但是由于作业废水和废置液包含化学成分较多,常会因其间的相互反应而腐蚀堵塞管线等设备。因此,本文以A油区为例,基于其实际的生产状况,根据采出污水结垢趋势和腐蚀原因,进行清垢剂与缓蚀剂的优选,以期为实际生产提供一点理论参考。     

断口附近组织对GH4080A合金缺口持久性能的影响

本文以630 ℃汽轮机紧固件备选合金GH4080A合金为研究对象,对美国Special Metals和抚顺特钢冶炼的材料经过标准热处理后分别在不同载荷下进行高温缺口持久实验,并结合光学显微镜(OM)和扫描电镜(SEM)及背散射电子衍射(EBSD)分析,研究合金持久寿命的分散性与持久样品断口附近组织的关联性。结果表明：GH4080A抚钢边缘和芯部持久寿命不同的主要原因是两者晶粒大小不同；抚钢边缘与SMC边缘持久寿命不同的主要原因是两者变形机制不同,前者为晶界滑移,后者为晶内变形与晶界变形协调作用。     

Influence of hexagonal to orthorhombic phase transformation on diffusion-controlled dendrite evolution in directionally solidified Sn–Ni peritectic alloy

The hexagonal to orthorhombic (HO) transformation from β-Ni₃Sn₂ (hexagonal) phase to α’-Ni₃Sn₂ (orthorhombic) phase was confirmed in directionally solidified Sn–Ni peritectic alloys. It is shown that the remelting/resolidification process which is caused by both the temperature gradient zone melting (TGZM) and Gibbs?Thomson (G?T) effects can take place on secondary dendrites. Besides, the intersection angle between the primary dendrite stem and secondary branch (θ) is found to increase from π/3 to π/2 as the solidification proceeds. This is the morphological feature of the HO transformation, which can change the diffusion distance of the remelting/ resolidification process. Thus, a diffusion-based analytical model is established to describe this process through the specific surface area (S_V) of dendrites. The theoretical prediction demonstrates that the remelting/resolidification process is restricted when the HO transformation occurs during peritectic solidification. In addition, the slope of the prediction curves is changed, indicating the variation of the local remelting/resolidification rates.     

A general n-fractal aperiodic zone plate

We propose a general n-fractal aperiodic zone plate generating a beam with the first-order foci with more chosen positions. The construction method of the general n-fractal aperiodic zone plate can apply to many aperiodic zone plates, e.g. fractal, Thue-Morse and Fibonacci zone plates, and the general n-fractal aperiodic zone plates can generate more adjustable first-order foci. Parameters of the n-fractal aperiodic zone plate such as the substitution rule and the fractal order are examined and found not to affect the fractal distribution of the first-order foci. The more adjustable first-order foci generated by the general n-fractal aperiodic zone plate have been verified with both simulations and experiments.     

CONTROLS ON FRACTURE FLOW POTENTIAL IN A TIGHT CARBONATE RESERVOIR: SAYINDERE FORMATION (CAMPANIAN), WEST ADIYAMAN BASIN,SE TURKEY

Identifying controls on the permeability of fluid‐conductive fractures is critical in tight reservoirs, but this is challenging in tectonically complex regions such as foothills belts where there may have been multiple stages of deformation and fracturing. Fracture permeability depends on fracture aperture and connectivity, both of which are affected by tectonism and cementation. Among the many factors that control the cementation history, oil charging may play an important role. Important challenges in studies of fractured reservoirs in tectonically complex regions include determining the timing (and intensity) of fracturing events relative to that of the oil charge, verifying the presence of matrix storage, and establishing the fracture cementation history. This paper reports on a comparative fracture study of four small‐scale oilfields in the west Ad?yaman Basin, located within the foothills belt of the Tauride suture zone in SE Turkey. Here the tight reservoir carbonates of the Say?ndere Formation (Campanian) were subjected to repeated phases of structural deformation. Major deformation phases took place in Campanian and Maastrichtian times, before oil charging into the reservoir began in the Eocene; and in the Late Eocene – Oligocene and Late Miocene, after the oil charge. Fractures that were generated before oil emplacement appear to have been cemented or partially cemented by calcite as indicated by cross‐cutting cemented fractures on borehole images. Partially‐cemented fractures in cores are oil‐stained with cement‐lined walls, suggesting cementation began before oil emplacement but was not completed. Image logs and cores also show the presence of clean, open fractures with no cement present on the walls. These open fractures cut across the cemented or partially‐cemented fractures, and are in general related to Late Miocene compressional folding. Open fracture density is correlated to Late Miocene fold curvature and asymmetry in the four oilfields studied. Of these fields, the ?ambayat structure is the tightest and most asymmetric anticline and hence has the maximum open fracture density; this field also has the highest oil potential. Although the available data is not sufficient to evaluate the effects of oil charging on fracture cementation definitively, the observations are consistent with a model that oil charge into the fractured Say?ndere Formation carbonates inhibited or slowed calcite cementation. Hence fracturing of a carbonate reservoir after oil emplacement may significantly enhance the fracture permeability, and may even render a tight reservoir prospective.