A procedure to predict the precise seismic response of arch dams in time domain using boundary element formulation

In this context,a new boundary element algorithm based on the time-convoluted traction kernels is employed to evaluate the spatially varying earthquake ground motions of the Pacoima dam in the USA subjected to SH,SV and P incident waves.An accurate three-dimensional(3D)model of the dam canyon is implemented into the computer code BEMSA to investigate the seismic response of the dam.The analyses are performed in time domain with a linearly elastic constitutive model for the medium.This modeling procedure has been validated by the results reported in the existing literature.According to the results of this study,the response of the dam to earthquake waves is generally influenced by predominant frequency of the incident motion,surface topography,relative distance of observation points,and type of the incident seismic wave.For the cases considered,the incident SV wave has led to the maximum amplification of incident motions,especially at the left side of the dam.The results indicate that the proposed procedure can be employed for accurate prediction of a dam response during an earthquake.     

微细铣削表面形貌形成分析

基于最小切削厚度的概念,提出了微细铣削过程槽底表面几何形貌仿真模型。通过微细铣削表面形貌的仿真和表面粗糙度Ra值的计算以及微细铣削实验,对微细铣削表面粗糙度随着每齿进给量变化的规律进行了分析和描述。     

Effects of machined cavity texture on ejection force in micro injection molding

The friction force developed in the demolding phase of the micro injection molding process is mainly determined by mold surface finish, which affects the tribological phenomena occurring at the polymer–tool interface. In this work, the effects on the ejection force of two cavity surfaces machined with different technologies (viz. micro milling and micro electro discharge machining), but with similar value of Ra, were investigated. The relations between different surface topography parameters and the ejection force were then analyzed, in order to identify the parameters that most appropriately describe the friction at the polymer–tool interface. The experimental results showed the strong interactions between the mold surface texture and the micro injection molding process parameters that promote the replication, such as mold temperature and holding pressure. The different machining technologies generated two mold textures that have a similar value of Ra, but their influence on friction can be properly described only using several other surface topography parameters.     

地形和土壤属性对大豆产量的影响

正确理解作物产量的变异性特征及其影响因素是对农田地块进行科学管理的基础。地块的地形特征是导致作物产量变异形成的主要因素。本文选择代表不同地形特征的洼地农田和岗地农田为研究对象,分析地形对土壤属性和大豆产量的影响以及它们之间的相互关系。研究结果显示,洼地农田与岗地农田的土壤属性和大豆产量均存在显著性差异(P<0.05)。洼地农田的土壤养分含量较高,但土壤结构较差,其平均重量直径(MWD)和几何平均直径(GMD)显著小于岗地农田,质量分形维数(Dm)显著大于岗地农田;在两类农田地块中,大豆产量的差别较大,洼地农田的大豆产量仅为岗地农田的62%。相关性分析表明,大豆产量与土壤结构稳定性和地块高程呈极显著正相关(P<0.01);土壤有机碳和土壤养分对大豆产量没有显著影响。     

Coal characterisation by automated coal petrography

Automated imaging techniques were refined to characterise the rank and maceral composition of coals by a full maceral reflectogram of polished coal grain mounts. Precision was improved by processing individual grains in each image separately and correcting within the software for the topography that occurs between the different macerals and minerals in the grains. Maceral group proportions and vitrinite reflectance information extracted from these reflectograms compared well with manual results for a comprehensive suite of Australian coals varying in rank from a mean vitrinite reflectance of 0.48-2.13%. A parameter that combines rank and type calculated from the reflectograms correlated strongly with chemical properties determined by ultimate and proximate analyses. For a limited number of samples, for which coking tests had been performed, this parameter also correlated with estimated coking performance.     

MODELLING OF DISC DRESSING FORCES

A new mathematical model of the dressing of grinding wheels by diamond disc dresser is developed. It predicts the dressing forces between the diamond grits of a rotating disc dresser and the grits of an alumina grinding wheel. This model is based on the fracture of grits, the fracture of the bond and the contact forces between the dresser and grits. It considers the kinematical influences and in particular speed ratio of the dressing process. Also a Weibull distribution was used to predict the probability of bond fracture. Dressing forces are measured experimentally and are compared with those calculated from the new model. Theoretical results closely match with the experimental findings. The dressing forces generated from this model provide a basis for further prediction of wheel topography and the grinding process.     

旋转检偏器移相的微分干涉显微镜

提出了一种干涉相位差与检偏器方位角成线性关系的新型微分干涉显微镜,利用相移干涉技术,可定量测量样品的表面形貌及粗糙度参数,系统的垂直和横向分辨率分别为1nm和0.5μm。     

In lubro 3D measurement of oil film thickness at the interface between tool and workpiece in sheet drawing using a fluorescence microscope

In order to understand quantitatively the micro-contact and lubricant behavior at the interface between a tool and a workpiece in sheet drawing, a method for mapping the oil film thickness in lubro has been developed. This is based on the use of a fluorescence microscope. It is shown, firstly, that the in situ oil film thickness between the tool and the workpiece can be measured three dimensionally, and, secondly, that the in situ surface topography of the workpiece can be visualized clearly. From the 3D surface topography, the permeation of the trapped lubricant into the real contact area can be observed.     

Accuracy,inter-observer and intra-observer reliability in topography assessment of multifocal contact lens centration

PurposeTo evaluate the accuracy and reliability (inter and intra-observer) of a method to assess multifocal contact lenses (MCLs) centration using a corneal topography unit.MethodDaily-disposable MCLs (Fusion 1 day Presbyo) were fitted on both eyes of the subjects. For each lens fit a slit lamp digital picture and videokeratograph image were taken in a rapid but randomised sequence. Photo-editing software was used to assess the position of the MCL centre with respect to pupil centre as taken from the slit lamp photograph. The position of the MCL centre was automatically detected as the point of maximum curvature from the videokeratography. Three further manual and qualitative procedures to detect MCL centre, comparing a template of CLs optic zones to the videokeratographic image were performed by 4 practitioners using 3 different algorithms to represent the topographic map. Each manual reading was repeated 3 times.ResultsTwenty-two subjects (11 males) aged 22.8 ± 1.9 years (range 20.8–27.0 years) were recruited. The accuracy of the 4 topographic assessments in determining the centre coordinates of the MCL with respect to SL assessment was good: no differences were found in the left eyes and although in the right eyes a more temporal and superior position of MCLs was determined (paired t-test, p < 0.05) the difference was clinically negligible (0.16 ± 0.36 mm horizontally, 0.23 ± 0.48 vertically). Amongst the 4 practitioners one-way Anova for repeated measures showed no differences for any of the 3 manual assessments. Intra-class correlation coefficient was calculated among the 3 readings for each manual procedure and was very good (between 0.75 and 0.98) in 3 practitioners and moderate (between 0.49 and 0.92) in the fourth.ConclusionsThe assessment of MCL centration by performing corneal topography over the MCL is an accurate method. Furthermore, inter and intra-practitioner reliability showed by manual procedures appeared very good.     

北京市不同地貌类型开发建设项目新增水土流失预测方法研究

通过对分别位于北京山区和平原区两种地貌类型的2个开发建设项目新增水土流失预测的研究,提出了原地貌和扰动地表水土流失的预测方法。研究表明,新增水土流失的预测,主要是对原地貌和扰动地表土壤侵蚀模数的确定,确定时主要采用实测数据、类比法、水文资料查阅法以及模数修正法等。