Effect of obstacles on the detonation diffraction and subsequent re-initiation

The DCRFoam solver (density-based compressible solver) built on the OpenFOAM platform is used to simulate the reflection and diffraction processes that occur when detonation waves collide with various objects. Static stoichiometric hydrogen–oxygen mixtures diluted with 70% Ar are used to form stable detonation waves with large cells, with initial conditions of 6.67 kPa pressure and 298 K temperature. The diameters of the cylindrical obstacle range from 6 mm to 22 mm, with x = 230 mm, x = 244 mm, and x = 257 mm being the chosen position. Cylindrical, square, triangular, and inverted triangular obstacles are used, and the quenched detonation re-initiation processes behind them are investigated. In the detonation diffraction process, four triple points exist at the same time due to the effect of cylindrical obstacles of smaller diameters. The re-initiation distance of the detonation wave increases with the increase of cylindrical obstacle diameter. Both the Mach reflection angle and the decoupled angle decrease as the diameter increases. When the location of the cylindrical obstacles is changed, the detonation wave dashes into the obstacles with its different front structures, it is easier to realize the detonation re-initiation when the weak incident shock at the front of a detonation wave strikes the obstacles, and the re-initiation distance decreases by 17.1% when compared with the longest re-initiation distance. The detonation re-initiation distance is shortest under the action of cylindrical obstacles, however the quenched detonation cannot be re-initiated when the inverted triangle and square obstacles are used. The suppression effects of inverted triangle and square obstacles on detonation waves are more evident.     

Defocusing image to pattern contact holes using attenuated phase shift masks

The patterning of contact holes by selecting out-of-focus image plane (defocus) using attenuated phase shift masks (APSM) has been studied. Defocus is found to enhance the image modulation at low partial coherence for contact holes with negative local average of mask function. Semi-dense holes up to 130 nm in 8% APSM have been printed by 0.5 μm defocus at a partial coherence of 0.31 using KrF scanner with highest numerical aperture of 0.68. However, these holes were closed with in-focus imaging. Defocus is also found to be beneficial for patterning the pitches that have extensive side lobes with in-focus imaging.     

一种双光束自动测试光栅绝对与相对光谱衍射效率的原理性方案

提出了一种快速自动测试光栅光谱衍射效率的新方法。重点推导了测试平面光栅绝对光谱衍射效率与相对光谱衍射效率公式，介绍了双光束高精度自动测试光栅光谱衍射效率曲线的基本原理、方案与方法，并分析了测试精度。研究表明，本方案的测试速度和精度均比一般测试方法提高一倍，并能有效地消除光源波动对测量结果的影响，测量误差小于５×１０－３。     

低空间频率银盐明胶全息图的浮雕特性研究及其应用

通过实验研究表明，对低空间频率的振幅型银盐全息图形表面已形成浮雕，经漂白，浮雕深度成倍加深；浮雕深度随空间频率而变化，并且可用不同曝光量进行调制。选择适当条件，可降低零级光强，提高全息图的一级衍射效率。     

多相物质粉末衍射的物相检索

讨论了多相物质粉末衍射的物相检索问题，介绍了XRDS的物相检索软件。这是一种智能型的物相检索程序，考虑了测试数据的不确定度，以及粉末样品和块状样品衍射图谱各自的特点，不仅注意到实际样品中微量物相存在的可能，也注意到块状样品结构有序性的可能。XRDS能够帮助材料工作者同时检出样品中所含的多种物相及其含量，操作简单、结果可靠。     

Nucleation of isolated PO4 units on CeO2 driven by high temperatures and the effect on its oxygen storage and release properties

The chemical nature of P-containing species of varying concentration present in CeO₂ after impregnation with (NH₄)₂HPO₄ and calcination at 1273 K, and their effects on the oxygen storage and release (OSR) properties of ceria are reported for the first time. The samples were characterized by different techniques and the results were compared with those recently reported on the same samples but calcined at 873 K. When P-containing ceria solids were calcined at 1273 K, CePO₄ (monazite) was the predominant P-containing species on the surface of ceria, confirming previous studies that showed that monazite exists for those samples in which the surface P loading (P atoms per nm⁻²) is larger than 5.5. For lower surface P concentrations, isolated orthophosphate units are present at the surface and within the subsurface region of the solid. Severe sintering of CeO₂ after calcination at 1273 K resulted in P concentrations >5.5 P atoms·nm⁻² in all samples. Isolated PO₄ units that could initially be present in the samples calcined at 873 K nucleated and CePO₄ was formed when samples were calcined at 1273 K. OSR properties of CeO₂ deteriorated progressively when P loading increased due to the presence of larger crystals of the very stable Ce(III) phase of CePO₄ at the surface of the P-containing ceria solids.     

超声衍射时差法探伤和定量技术--焊缝超声检测最新欧洲标准介绍

超声衍射时差(TOFD)法是焊缝超声检测和缺陷定量很有发展前景的新技术。它根据入射纵波在缺陷端部产生的衍射波传播时差进行测深定高,是一种可靠性甚高的方法,有A,D,B三种显示方式,探伤结果记录较直观和客观。根据最新欧洲标准(草案)ENV583 6:2000的有关规定,介绍超声TOFD技术应用要领,企望该技术在国内无损检测(NDT)领域迅速推广应用。     

Control of 0.2CaTiO3-0.8Li0.5Nd0.5TiO3 microwave dielectric ceramics by additions of Bi2Ti2O7

Ceramics of 0.2CaTiO₃-0.8Li_0.5Nd_0.5TiO₃) have been prepared by the mixed oxide route using additions of Bi₂O₃-2TiO₂ (up to 15 wt%). Powders were calcined 1100^∘C; cylindrical specimens were fired at temperatures in the range 1250–1325^∘C. Sintered products were typically 95% dense. The microstructures were dominated by angular grains 1–2 μm in size. With increasing levels of Bi₂O₃-2TiO₂ additions, needle and lath shaped second phases developed. For Bi₂Ti₂O₇ additions up to 5 wt%, the relative permittivity increased from 95 to 131, the product of dielectric Q value and measurement frequency increased from 2150 to 2450 GHz and the temperature coefficient of resonant frequency (τ _f ) increased from −28pp/^∘C to +22pp/^∘C. A product with temperature stable τ _f could be obtained at ∼2 wt% Bi₂Ti₂O₇ additions. For high levels of additives, there is minimal change in relative permittivity, the Qxf values degrade and τ _f becomes increasingly negative.     

KSpaceNavigator as a tool for computer-assisted sample tilting in high-resolution imaging, tomography and defect analysis

This article describes a novel software tool, the KSpaceNavigator, which combines sample stage and crystallographic coordinates in a control sphere. It also provides simulated kinematic diffraction spot patterns, Kikuchi line patterns and a unit cell view in real time, thus allowing intuitive and transparent navigation in reciprocal space. By the overlay of experimental data with the simulations and some interactive alignment algorithms, zone axis orientations of the sample can be accessed quickly and with great ease. The software can be configured to work with any double-tilt or tilt–rotation stage and overcomes nonlinearities in existing goniometers by lookup tables. A subroutine for matching the polyhedral shape of a nanoparticle assists with 3D analysis and modeling. The new possibilities are demonstrated with the case of a faceted BaTiO₃ nanoparticle, which is tilted into three low-index zone axes using the piezo-controlled TEAM stage, and with a multiply twinned tetrahedral Ge precipitate in Al, which is tilted into four equivalent zone axes using a conventional double-tilt stage. Applications to other experimental scenarios are also outlined.