Modelling tire-moist terrain interaction using advanced computational techniques

This paper focuses on predicting and analyzing the tire-moist terrain interaction. The moist terrain (sand) is modelled using Smoothed-Particle Hydrodynamics (SPH) technique. The SPH basic interpolation technique is described, and the necessary interpolation equations are implemented. The soil is modelled using the hydrodynamic elastic-plastic material, while the water is modelled using Murnaghan equation of state. The numerical interaction between both materials is defined using Darcy’s law. The soil moisturizing technique consists of layering water particles on top of sand particles and pressurizing the water into the sand. The moisturizing technique is examined using the direct shear-strength test, and validated against physical measurement carried out in a laboratory under similar soil conditions and bulk density. Finally, the results and the effect of moisture content on tire-moist terrain interaction are discussed and investigated using a previously modelled and validated off-road truck tire size 315/80R22.5.     

超高速转镜扫描相机扫描速度的校准及应用方法

研制了一套超高速转镜扫描相机扫描速度的校准装置,采用严格控制狭缝宽度和边缘质量的双狭缝、超快响应（0.7 ns）的光电倍增管以及相应措施,改善光电倍增管阴极不同部位灵敏度的一致性,使得校准装置的相对测量扩展不确定度达到了0.1％;给出了扫描速度校准的应用方法,并且分析了气压对相机符合转速的影响.     

New calibrations and time stability of the response of the INTERCAST CR-39

We present new calibrations of different production batches (from 1989 to 1999) of the INTERCAST CR-39, using the BNL-AGS 1 A GeV iron beam. The comparison with previous results, obtained with the 158 A GeV lead beam from the CERN-SPS shows that, while each production batch has a different calibration curve (mainly due to minor differences in the production conditions), the aging effect is negligible. We also tested the dependence of the CR-39 response from the time elapsed between exposure and analysis (fading effect). The fading effect, if present, is less then 10%. It may be compatible with the experimental uncertainties on the bulk etching rate v_B.     

Reduction of interferences in graphite furnace atomic absorption spectrometry by multiple linear regression modelling

The multivariate effects of Na, K, Mg and Ca as nitrates on the electrothermal atomisation of manganese, cadmium and iron were studied by multiple linear regression modelling. Since the models proved to efficiently predict the effects of the considered matrix elements in a wide range of concentrations, they were applied to correct the interferences occurring in the determination of trace elements in seawater after pre-concentration of the analytes. In order to obtain a statistically significant number of samples, a large volume of the certified seawater reference materials CASS-3 and NASS-3 was treated with Chelex-100 resin; then, the chelating resin was separated from the solution, divided into several sub-samples, each of them was eluted with nitric acid and analysed by electrothermal atomic absorption spectrometry (for trace element determinations) and inductively coupled plasma optical emission spectrometry (for matrix element determinations). To minimise any other systematic error besides that due to matrix effects, accuracy of the pre-concentration step and contamination levels of the procedure were checked by inductively coupled plasma mass spectrometric measurements. Analytical results obtained by applying the multiple linear regression models were compared with those obtained with other calibration methods, such as external calibration using acid-based standards, external calibration using matrix-matched standards and the analyte addition technique. Empirical models proved to efficiently reduce interferences occurring in the analysis of real samples, allowing an improvement of accuracy better than for other calibration methods.     

Uncertainties of mercury determinations in biological materials using an atomic absorption spectrometer – AMA 254

 The method is based on catalysed ignition of a sample portion in a flow of oxygen, capture of mercury by an amalgamator and measurement of the mercury vapour's absorbance after thermic release from the amalgamator. Three powdered food samples, a certified reference material (CRM) human hair and a reference material (RM) urine (liquid) were measured in the first range of the instrument (the possible contents determined according to our measurement procedure were 0.0003–0.5 ppm). The calibration function used was a line passing through the origin. The combined standard uncertainties of the mercury determinations were computed from uncertainty components of five quantities: absorbance of the sample, absorbance of the sample blank, slope of the calibration line, correction factor of the abscissa axis, and mass or volume of the sample. The most important uncertainty component is the uncertainty of the sample absorbance measurement which amounts to 52% of the determination uncertainty at the minimum (RM urine) and about 90% at the maximum (in our laboratory homogenized powdered food samples; analysis of variance showed their homogeneity to be insufficient). The results of the CRM and RM analyses do not indicate a significant systematic error for this determination. The relative expanded uncertainty (coefficient was 2) of the determination increases from 9 to 13% for the insufficiently homogenized samples with decreasing mercury content (range of 0.004–0.03 ppm); higher homogeneity of samples results in a decrease of the expanded uncertainty, e.g. 4.6% for the liquid sample (RM urine). Received: 26 April 1999 / Accepted: 30 August 1999     

Optical 3-D dynamic measurement system and its application to polymer membrane inflation tests

An optical surface measurement system, which is capable of measuring transient surface shape, has been developed by using a high-speed digital camera. The system is based on the grating projection and Fourier transform technique. A calibration procedure is developed to allow the system to generate Cartesian coordinates directly, which are with respect to a fixed coordinate system in 3-D space. The measurement accuracy (±50 μm) is defined and verified as the maximum error between measured values and the known values of standard objects both flat and curved. The camera and a grating projector are mounted into a portable sensor head to allow in situ measurements. In addition, external force or pressure signals can be correlated with each measurement through a device called the multi-channel data link. The system is capable of digitizing a 3-D curved surface into an array of points with known xyz coordinates at a sampling rate from 30 to 1000 Hz. As an application, the system is used to measure the transient surface shape during a polymer membrane inflation test. The measurement results along with the pressure information provide an approach to determine the material parameters used in different material models.     

低浓度多元糖混合水溶液体系的近红外分析

利用近红外光谱分析了葡萄糖、果糖、单糖和蔗糖的二元以及三元混合溶液。水在近红外区域的吸收十分强烈,近红外光谱分析更多应用于干燥的或者低水分的样品,而不适用于新鲜的果蔬样品。文章试图将近红外用于水溶液体系的分析,在不回避水的强干扰因素的情况下,探讨如何改进分析手段,优化分析结果。实验中样品浓度分布在0.01～0.25 mol·L-1的范围。对于物理化学性质都比较接近的低浓度单糖溶液,通过比较它们在不同组分中的近红外谱图,特别是C—H,O—H等基团的近红外吸收在不同条件下的变化,以及选择不同波数区间或者全谱建立分析模型对于分析结果的影响,优化波数区间的选择,结合化学计量学优化计算,以获得质量较高的校正模型,改善分析结果,克服水的影响。     

基础数据准确性对近红外光谱分析结果的影响

基础数据的准确性是影响近红外光谱分析结果的一个重要因素。文章以人工配制的四组分混合物体系和实际的汽油校正集样本为例,通过人为增加基础数据误差的方法,研究了基础数据的准确性对近红外光谱分析结果的影响。结果表明,基础数据的准确性对近红外分析模型及其预测结果都有一定的影响,基础数据越准确,所建立模型的精度越高,其对未知样本的预测结果也越准确。对于精度相对较差测试方法提供的基础数据,通过大量样本的光谱分析和化学计量学统计处理,近红外方法有可能得到更精确的预测结果。     

玉米杂交种品质性状的近红外光谱分析技术研究

以我国常用玉米自交系、杂交种样品为材料,采用偏最小二乘(PLS)回归法,建立了近红外反射光谱测定玉米完整籽粒的粗蛋白、粗淀粉和油分含量的校正模型。并利用40个玉米杂交后代材料对3个模型的实际预测效果进行了验证,预测值与化学值间的相关系数(r)可达0.98(粗蛋白)、0.93(粗淀粉) 和0.97(油分), 最大相对误差仅为2.46%(粗淀粉)～7%(油分)。文章还从理论上研究了以数量相对较少的亲本自交系为建模样品、建立可适用于分析大量杂交种样品的近红外数学模型的可行性,提出了作物近红外光谱某些特征具有遗传性这一新的观点。     

Simultaneous calibration of TLDs using the ICRU slab and photon beams

Adoption of the ICRU slab enables several dosimeters to be calibrated simultaneously. In order to allow use of identical conversion coefficients, these dosimeters should be exposed to the same irradiation conditions to within a given tolerance, account being taken of both incident and backscattered radiations. In the present study evaluation has been made of the variation in irradiation conditions for simultaneous irradiation of multiple numbers of TLDs, examination also being made of suitable gap sizes between TLDs. For simultaneous irradiation of four TLDs, a 5 cm gap is required to ensure approximate identical irradiation conditions. Approximate identical irradiation conditions have not been found possible when making simultaneous irradation of nine TLDs.