进气道生产一致性对汽油机性能影响及设计优化

采用AVL TIPPLEMAN气道稳态试验台对某现生产气道喷射汽油机缸盖气道性能进行批量测试,结果显示该发动机缸盖气道生产一致性较差。选择了其中高中低3种滚流水平缸盖进行发动机性能试验。试验发现,生产偏差造成的滚流差异对性能有较大的影响,低滚流气道有利于该发动机外特性提升。为此进行了进气道性能鲁棒性CFD模拟分析,研究了气道偏移对气道性能的影响,并通过优化气道局部结构,显著改善了缸盖气道性能设计鲁棒性,优化后气道滚流对气道偏移的敏感度降低了50%,并进行了气道试验验证和发动机性能试验。     

Indoor inhalation intake fractions of fine particulate matter: review of influencing factors

Exposure to fine particulate matter (PM_2.5) is a major contributor to the global human disease burden. The indoor environment is of particular importance when considering the health effects associated with PM_2.5 exposures because people spend the majority of their time indoors and PM_2.5 exposures per unit mass emitted indoors are two to three orders of magnitude larger than exposures to outdoor emissions. Variability in indoor PM_2.5 intake fraction (iF_in,total), which is defined as the integrated cumulative intake of PM_2.5 per unit of emission, is driven by a combination of building‐specific, human‐specific, and pollutant‐specific factors. Due to a limited availability of data characterizing these factors, however, indoor emissions and intake of PM_2.5 are not commonly considered when evaluating the environmental performance of product life cycles. With the aim of addressing this barrier, a literature review was conducted and data characterizing factors influencing iF_in,total were compiled. In addition to providing data for the calculation of iF_in,total in various indoor environments and for a range of geographic regions, this paper discusses remaining limitations to the incorporation of PM_2.5‐derived health impacts into life cycle assessments and makes recommendations regarding future research.     

十三陵电站引水调压井钢衬安装

十三陵蓄能电站引水调压井采用阻抗式结构，由于地层破碎，安装钢衬提高了结构的安全稳定性。     

Assessment of dietary exposure to ochratoxin A in the UK using a duplicate diet approach and analysis of urine and plasma samples

The approach to assess exposure to ochratoxin A from the diet by the analysis of human plasma and urine samples has been developed. Composite duplicate diet samples from 50 individuals and corresponding plasma and urine samples were obtained over 30 days. Samples were analysed using sensitive methods capable of measuring ochratoxin A at 0.001ng g -1 in food, 0.1ng ml -1 in plasma and 0.01ng ml -1 in urine. Analysis of the foods indicated ochratoxin A levels contributing to an average intake in the range 0.26-3.54ng kg -1 bw day -1 over the 30 days. Ochratoxin A was found in all plasma samples and in 46 urine samples. The correlation between the plasma ochratoxin A levels and ochratoxin A consumption was not significant (95% confidence limit). However, a significant correlation was found between ochratoxin A consumption and the urine ochratoxin A concentration expressed as the total amount excreted. This new work offers the possibility of using ochratoxin A in urine as a simple and reliable biomarker to estimate exposure to this mycotoxin.     

Exposure of cadmium from infant formulas and weaning foods

Cadmium levels were determined in 59 baby food samples, including milk-based, cereal and milk-based and soy-based formulas, recommended from 0 to 18 months of age. Determinations were performed by Zeeman graphite furnace atomic absorption spectrophotometry, after dry ashing, with parallel determinations of certified reference samples. Mean cadmium levels were found to range from 1.10 to 23.5 mu g / kg fresh weight concentrated formulas. L evels were related to the composition of the diets. Formulas based on cow's milk had the lowest concentrations. Soy formulas contained approximately six times more cadmium than cow's milk formulas, and diets with a cereal content had 4-21 times higher mean levels. The mean weekly intakes of dietary cadmium were estimated to vary between 0.10 and 3 : 05 mu g / kg body weight of the child, if the recommended amount of formula were to be consumed at the recommended age, and if the child were of average weight. This estimation however does not include the contribution of cadmium from drinking water. The highest intake on a body weight basis was found in 6-month-old children, consuming the recommended amount of wheat-, oat- and milk-based formulas. This intake is below the provisional tolerable weekly intake (PTW I) of 7 mu g / kg body weight, established by a W HO/FAO expert group. However, the risk assessment is based on renal effects in adults. Furthermore, preparations of a formula by adding water with cadmium concentrations at the W HO guideline level could lead to intakes at the PTW I level. Compared to breast-fed children, the exposure of dietary cadmium from weaning diets can be up to 12 times higher in children fed infant formula.     

Estimation of dietary intake of pesticide residues by the Italian population during 1997

In 1997 the Italian monitoring programme for pesticide residues in food comprised 7951 samples of 152 different foods for which a total of 275 pesticides were analysed. For 90 pesticides, the National Estimated Daily Intakes (NEDIs) were calculated by using the 90th percentile value and the food consumption data for the general Italian population. The calculated NEDIs were found to represent only a small portion of the respective Acceptable Daily Intake (ADI).     

电离辐射的生物效应——ICRP 60号出版物附件B内容简介及讨论

本文简要介绍了国际放射防护委员会(ICRP)1990年建议书(ICRP 60号出版物)附件 B 的主要内容,并对危险系数、组织权重因子及新的放射性核素年摄入量限值等有关问题进行了初步讨论。     

Long-term human exposure to lead from different media and intake pathways

Lead (Pb) is well known as an environmental pollutant: it can accumulate in various media, so actual lead exposure reflects both historical and present contaminations. Two main challenges then emerge: obtaining updated information to gain an overall picture of the sources of exposure, and predicting the resulting internal body exposure levels and effects that occur under long-term exposure conditions. In this paper, a modeling approach is used to meet these challenges with reference to Danish exposure conditions. Levels of lead content in various media have been coupled with data for lead intake and absorption in the human body, for both children and adults. An age-dependent biokinetic model allows then for determination of the blood lead levels resulting from chronic exposure. The study shows that the actual intake of lead is up to 27% of the Provisional Tolerable Daily Intake (PTDI) for children and around 8% for adults. It is confirmed that the critical route of exposure is via ingestion, accounting for 99% of total lead intake, while inhalation contributes only to 1% of total lead intake. The resulting lead levels in the blood after 2 years of exposure to actual contamination conditions have been estimated as up to 2.2 μg/dl in children and almost 1 μg/dl in adults. Impacts from lead can occur even at such levels. The role of historical and present sources to lead in the environment is discussed, and, for specific child and adult exposure scenarios, external-internal concentration relationships for the direct linkage between lead in environmental media and resulting concentrations of lead in blood are then presented.     

发动机关键配气相位角的分析与优化

发动机的四个配气相位角中,排气提前角和进气晚关角最为重要。运用AVL BOOST软件建立了某款汽油发动机的数值仿真模型,根据台架实验数据对模型进行了标定。保持原气门重叠角和升程不变,按每5°CA的间隔分别对排气提前角和进气晚关角进行改变,研究不同排气提前角和进气晚关角对发动机不同转速扭矩和功率的影响规律,确定最佳的排气提前角和进气晚关角。经过优化发动机的最大扭矩提高了5.39N·M,最大功率提高了2.82kW。     

High concentrations of essential and toxic elements in infant formula and infant foods – A matter of concern

This study assessed concentrations in and intake of toxic and essential elements from formulas and foods intended for infants during their first 6 months of life. Concentrations of the essential elements Ca, Fe, Zn, Mn and Mo were significantly higher in most formulas than in breast milk. Daily intake of Mn from formula varies from ten up to several hundred times the intake of the breast fed infant, levels that may be associated with adverse health effects. One portion of infant food provided significantly more Fe, Mn, Mo, As, Cd, Pb and U than one feeding of breast milk, but less Ca, Cu and Se. Rice-based products in particular contained elevated As concentrations. Drinking water used to mix powdered formula may add significantly to the concentrations in the ready-made products. Evaluation of potentially adverse effects of the elevated element concentrations in infant formulas and foods are warranted.