A topographical method to quantify scleral contact lens decentration

PurposeTo describe a simple method to quantify scleral contact lens decentration using over-topography captured with a Placido ring videokeratoscope, and its repeatability.MethodsScleral lens over-topography (E300 videokeratoscope, Medmont) was measured on 10 healthy participants following 15 min of lens settling (16.5 mm total diameter ICD miniscleral, Capricornia). Horizontal and vertical lens decentration was quantified from the translation of the front optic zone relative to the pupil centre derived from ellipses manually fitted to tangential power over-topography maps using both a standard and normalised dioptric scale. Intrasession (different maps captured within the same measurement session), intraobserver (identical maps analysed by the same observer), and intertechqniue (standard or normalised tangential power scales) repeatability were calculated.ResultsThe mean lens decentration was 0.62 ± 0.18 mm temporally and 0.91 ± 0.33 mm inferiorly. Lens decentration derived from tangential topography maps with a standard power scale were more repeatable (95% limits of agreement for intraobserver repeatability ± 0.07 mm and intrasession repeatability ± 0.15 mm) than measurements derived from normalised maps (95% limits of agreement for intraobserver repeatability ± 0.11 mm and intrasession repeatability ± 0.20 mm).ConclusionsScleral lens decentration can be reliably quantified using tangential power maps with a standard (fixed) scale captured during over-topography without the need for customised instrumentation or image analysis software. This method has a range of potential applications in research and clinical practice.     

Topographic quantification of non-planar localized surfaces

The topography of non-planar localized surfaces can be quantified by roughness indices as well as by height and angular distributions of the surface elements. For the roughness indices general relationships between the profile and spatial quantities including overlapping have been established. Some measurement methods are briefly considered. The profile analysis has proved to be a reliable, easy and fast way to characterize the topography of surfaces.     

宽范围原子力显微镜在超精加工中应用研究

介绍了用于分析起精加工的原子力显微镜。其垂直方向和水平方向的分辨率可达纳米级，测量范围可达140×140μm。采用探头扫描方法和双扫描工作模式，扩大了该测量方法的应用范围。给出了金刚石刀具钝圆半径与精密玻璃光栅和超精密抛光陶瓷的轮廓形貌的测量结果。     

Influences of the valley morphology and rock mass strength on tunnel convergence: With a case study of Khimti 1 headrace tunnel in Nepal

Underground structures are constructed at the bottom of the valley sides for various purposes and for different reasons. Hydropower projects and transport tunnels are some of the examples of such structures. In this paper, literatures on topographical effects on the in situ stresses in valley and fjord sides are reviewed. An attempt is made to correlate stress anisotropy problems with the valley side topography by using Phase² numerical modelling. Based on an underground construction case study, fifteen in situ stress measurements and the Phase² analysis, stress induced problems have been found to be influenced by the valley morphology. This influence can be monitored by the convergence measurement and by the stress measurement. In addition to the overburden height, the total valley height and the slope need to be considered in the assessment of the stress induced problem. The second aspect dealt with is the influence of the rock strength on the tunnel convergence. In the Khimti 1 headrace tunnel and 66 cases from 15 countries, it has been observed that the tunnel convergence is larger in the weaker rocks than in the stronger rocks though they may have similar Q-values. Rock type such as gneiss or phyllite (corresponding to the rock mass strength) is not considered in the Q-system but it has influence on the convergence that takes place in underground works. Thus, it also needs to be considered in the assessment of potential convergence of an underground structure.     

TOOL PATH SELECTION STRATEGIES FOR COMPLEX SCULPTURED SURFACE MACHINING

High performance machining of complex free form surfaces is very critical in many different industries. In this research, an advanced mathematical model of cutting forces that is based on the kinematics and mechanics of the 3D sculptured surface machining is integrated with CAM packages in order to predict the complex tool-workpiece engagements and machining forces for any tool path. Machined 3D free form topographies and distributions of errors between the desired CAD and machined surfaces are also predicted in advance. Now, an evaluation of different tool path strategies for 3D complex sculptured surfaces can be made. Theoretical simulations of forces and surface topographies for different tool paths are presented and compared with experimental measurements.     

大地“渊薮” ——地形要素在乡土建筑中的建构学解读

从“建构”理论中所涉及的“地形” 因素的回溯及纵深辨析开始,围绕森佩尔建 筑四要素中“基台”与其他三要素的关系展开 探讨,通过对中外极具代表性的典型乡土建 筑案例的类型学归纳与理论探析,阐释了在自 然地形、基台塑造以及其影响下的建筑内部 空间这三个递进层级中,地形要素在实践和 精神层面的现象学转移及其在建构视角下的 多重解读可能性,试图建立面向地形的乡土建 构体系研究视角与方法。     

控制四点法“形状参数”实现地景仿真

将满足插值和离散性质的“四点法”运用于地景仿真,调整其“形状参数”可产生所期望的地形形状。为了产生丰富的地貌特征,一方面,用几何纹理生成法;另一方面,在定义场景的ＧＬ光照中,通过更新材料、光源和光照模型属性,真实感显示地表细节。实验表明,该方法能简单、快速模拟一些受环境、树木、土壤、气候等影响的地景,为自然景观仿真提供了一种有效手段。     

Local concentration of middle and heavy rare earth elements in the col on the weathered crust elution-deposited rare earth ores

This present study focused on investigating the content and relative enrichment multiple of rare earth elements(REEs) in different terrain of weathered ore body, and the value of light rare earth elements/middle and heavy rare earth elements(LREEs/HREEs), in order to understand the mobilization and redistribution of HREEs, Furthermore, the abrasion pH was investigated as well, The results show that the average contents of HREEs in the knap, ridge and col are 37.26, 61.71, and 271.3 μg/g, respectively. The value of LREEs/HREEs is decreased from 16.78 to 7.914 between knap and col and the relative enrichment multiple of HREEs is as follows: C_(Col-HREEs) C_(Ridge-HREEs) 0. It is indicated the HREEs is concentrated in the col and the enrichment degree of HREEs is stronger than the ridge and the knap. Rare earth elements fractionation is exhibited in the different terrain of weathered ore body. Based on this study, the finding that HREEs concentrate in the lower terrain of weathered crust elution-deposited rare earth ores, such as in the col, would become a marker or indicator to search for middle and heavy rare earth enriched zone.     

The transition between high and low wear regimes under multidirectional reciprocating sliding

The wear phenomena and wear characteristics of reciprocating sliding wear with superimposed lateral vibrations were investigated using a ball-on-disc tribometer. The tribometer enabled two orthogonal oscillations, whereas one oscillation had a constant amplitude of 1 mm (primary oscillation) and the other one had a variable amplitude from 0 to 20.2 μm (secondary oscillation). Ball and disc were made of AISI 52100 steel. The ball surface was polished and the disc surface was unidirectionally grinded parallel to the direction of primary oscillation. Two regimes with different wear rates were found, being separated by a characteristic transition amplitude of 2.7 ± 0.4 μm in the secondary oscillation. This transition correlated with a change of wear mechanisms from tribochemically to mechanically dominated wear. A wear model based on surface topography and particle motion was developed. The wear model is able to predict the value of the transition amplitude by means of characteristic topographical data and the size of wear particles.