扩散光层析技术及其应用

扩散光层析技术是新近发展的一种生物医学无损成像方法,可用于组织和血氧水平的可视化实时探测,对脑成像和肿瘤监测等具有重要意义。本文介绍该技术在实验方法和仪器等方面的进展,及在临床上获得的应用。     

A prediction of bursting failure in tube hydroforming process based on plastic instability

Based on plastic instability, an analytical prediction of bursting failure on tube hydroforming processes under combined internal pressure and independent axial feeding is carried out. Bursting is an irrecoverable phenomenon due to local instability under excessive tensile stresses. In order to predict the bursting failure, three different classical necking criteria – diffuse necking criteria for a sheet, and a tube, and a local necking criterion for a sheet – are introduced. The incremental theory of plasticity for an anisotropic material is adopted and the hydroforming limit, as well as a diagram of bursting failure with respect to axial feeding and hydraulic pressure are presented. In addition, the influences of material properties such as anisotropy parameter, strain hardening exponent and strength coefficient on plastic instability and bursting pressure are investigated. As a result of the above approach, the hydroforming limit with respect to bursting failure is verified with experimental results.     

Assessment of natural fluorescence as a tracer of diffuse agricultural pollution from slurry spreading on intensely-farmed grasslands

The value of natural fluorescence in tracing diffuse pollution, in liquid phase, following slurry application to land was assessed by field experiment using twelve one hectare lysimeters on a heavy clay soil in Devon, UK, during autumn 2007. A strong linear relationship was found between natural fluorescence intensity and slurry concentration. The ratio of indices of tryptophan-like and fulvic/humic-like fluorescence (TI:FI) varied between 2 and 5 for a range of slurries sampled from Devon farms and allowed slurry to be distinguished from uncontaminated drainage waters (TI:FI < 1). Incidental losses of slurry, indicated by significantly enhanced TI:FI ratios, high TI and high ammonium levels, occurred via the drain flow pathway of the drained lysimeters during the first small event following slurry-spreading. The maximum estimated loss from a single lysimeter was 2-8 kg or 0.004-0.016% of the applied slurry. In the second larger storm event, some five weeks later, significantly enhanced TI:FI ratios in the drain flows were not associated with high TI but with high nitrate levels and, compared to the earlier storm, an increase in the humification index. This implies the loss of slurry decomposition products during this event but further work is needed to validate this. There was no significant enhancement of TI:FI in the surface/throughflow pathways of the drained or undrained lysimeters in either of the events. The observed change over a period of weeks in the strength and nature of the fluorescence signal from spread slurry restricts quantification of slurry losses to those immediately after slurry spreading. Nonetheless, this study demonstrates the utility of fluorescence as an indicator of slurry in drainage waters and the importance of field drains in diffuse agricultural pollution.     

Selective catalytic reduction of NO by alcohols on Co- and Fe-Siβ catalysts

Co–Siβ and Fe–Siβ catalysts prepared by a two-step post-synthesis method were characterised by EPR, diffuse reflectance UV–vis, XRD and N₂-physisorption. Iron and cobalt ions are present as isolated lattice tetrahedral Co^II and Fe^III species for low metal contents (0.7 and 0.9 wt.%, respectively). For higher iron content, FeO_x oligomers appear. Zeolites with isolated Co^II and Fe^III species are active in selective catalytic reduction of NO with ethanol. On FeO_x oligomers the oxidation of NO to NO₂ starts to dominate in the selective catalytic reduction of NO with ethanol at the temperatures higher than 700 K.     

Sediment build-up on roads and footpaths of a residential area

This paper presents results on the characterisation of sediment build-up on roads and footpaths of a residential catchment in Dublin, Ireland. Compared to power and exponential functions, the linear function provided the best fit of the road sediment build-up in terms of total and size-fractionated loads. Significant road sediment build-up rates were recorded for the majority of size fractions on the three street zones sampled, however it was not possible to separate build-up rates between size fractions due to random variation in sediment loads. There was a significant difference in total road sediment build-up between two of the sampling zones, which was likely due to the proximity to a highly trafficked road. Build-up rates on footpaths could not be separated from random variation. Footpath sediment loads were between 6% and 22% of road sediment loads, with texture depth identified as an important difference between these surfaces.     

THE POTENTIAL USE OF TAR SAND BITUMEN AS PAVING ASPHALT

ABSTRACT

In this paper several research reports describing the preparation of potential paving asphalts from tar sand Bitumen are reviewed and the results of the studies compared. The tar sand asphalts described in the studies were prepared from 1) hot water-recovered bitumen from deposits near San Luis Obispo, California (Edna deposits), and deposits near Vernal and Sunny-side, Utah; and 2) bitumen recovered from the Northwest Asphalt Ridge deposits near Vernal, Utah, by both in situ steamflood and in situ combustion recovery processes. Important properties of the tar sand asphalts compare favorably with those of specification petroleum asphalts. Laboratory data suggest that some tar sand asphalts may have superior aging characteristics and produce more water-resistant paving mixtures than typical petroleum asphalts.     

Analysis of experimental data on diffuse solar radiation in Athens,Greece, for building applications

Proper design and performance prediction of solar energy systems requires accurate information on the availability of solar radiation. The diffuse-to-total radiation correlation, originally developed by Liu and Jordan, has been extensively used as the technique and provided excellent results, although it was latitude dependent and not universally applicable. Thus, diffuse fraction correlations of this type have been developed by few other authors and for different location. This paper presents an analysis of hourly diffuse radiation on a horizontal surface. Hourly pyranometer data from Athens, Greece, are used to establish relationships between the diffuse fraction and the clearness index k _T for hourly and daily values. The results of the proposed equations are then compared with earlier equations. For the urban conditions of Athens the developed correlation fit to the empirical data.     

Estimation of horizontal diffuse solar radiation with measured daily data in China

Three most widely used diffuse radiation models are calibrated using the daily data between January 1 1994 and December 31 1998 from 16 stations all over China. The second-degree polynomial relationship between R_D/R_G and n/N (Iqbal model) is suitable for diffuse radiation estimation in China. The averaged correlation coefficient R² is 0.84 and the maximum value is 0.93 at the 16 stations, and the Iqbal model works better in the eastern part of China than in the west. The A.A. El-Sebaii model could not be used to estimate diffused radiation accurately in China, with an averaged R²=0.47. The Liu and Jordan model could also be used for diffuse radiation estimation in China, and the averaged value of R² and parameter X₀ is 0.81 and 0.233, respectively. There is an evident linear relationship among the parameters X₀, a and b of the Liu and Jordan model.     

Evaluation of 12 models to estimate hourly diffuse irradiation on inclined surfaces

This study evaluates the performance of 12 models to estimate hourly diffuse solar irradiation on inclined surfaces from those measured on horizontal surfaces. Total solar irradiation incident on a tilted surface consists of three components including: beam, diffuse and reflected from the ground. On a semi-hourly basis, the beam component can be calculated by the ratio of the incidence angle to the solar zenith angle. The reflected component has a small effect on calculations and may be calculated with an isotropic model. In contrast, models for estimating the diffuse component show major differences, which justify the validation study that this paper discusses. Twelve models were tested against recorded south- and west-facing slope irradiances at Karaj (35°55^′N; 50°56^′E), Iran. The following models were included: Badescu [Ba], Tian et al. [Ti], Perez et al. [P9], Reindl et al. [Re], Koronakis [Kr], Perez et al. [P8], Skartveit and Olseth [SO], Steven and Unsworth [SU], Hay [Ha], Klucher [Kl], Temps and Coulson [TC], and Liu and Jordan [LJ].The relative root mean square error (RMSE), for the south-facing surface ranges from 10.16% to 54.89% for the SO and TC models, respectively. For the west-facing surface, RMSE ranges from 30.71% for the P9 model to 63.53% for the TC model. Statistical indices show that all models produce large errors for the west-facing surface. Statistical indices for the south-facing surface show reasonably good agreement with measured data.     

KDF4滤棒成型机组丝束拼接头检测剔除装置的设计

为解决KDF4滤棒成型机无法自动检测丝束拼接不合格滤棒等问题,采用高灵敏度光电传感技术设计了一种丝束拼接头检测剔除装置。根据开松丝束宽度的变化识别拼接头,并将丝束宽度变化检测转换为漫反射式红外光电传感器开关信号,通过PLC控制器控制剔除阀,对不合格滤棒进行自动剔除。以KDF4滤棒成型机生产的2 750 Pa规格滤棒为对象进行测试,结果表明:丝束拼接头的剔除准确率达到100%,剔除滤棒的吸阻均值2 346 Pa,均低于工艺标准范围(2 750±245)Pa。该技术可为提高滤棒成型设备的自动化水平提供支持。