Computational investigation of the effects of knee airbag design on the interaction with occupant lower extremity in frontal and oblique impacts

Objective: The lower extremity of the occupant represents the most frequently injured body region in motor vehicle crashes. Knee airbags (KABs) have been implemented as a potential countermeasure to reduce lower extremity injuries. Despite the increasing prevalence of KABs in vehicles, the biomechanical interaction of the human lower extremity with the KAB has not been well characterized. This study uses computational models of the human body and KABs to explore how KAB design may influence the impact response of the occupant's lower extremities.

Methods: The analysis was conducted using a 50th percentile male occupant human body model with deployed KABs in a simplified vehicle interior. The 2 common KAB design types, bottom-deploy KAB (BKAB) and rear-deploy KAB (RKAB), were both included. A state-of-the-art airbag modeling technique, the corpuscular particle method, was adopted to represent the deployment dynamics of the unfolding airbags. Validation of the environment model was performed based on previously reported test results. The kinematic responses of the occupant lower extremities were compared under both KAB designs, 2 seating configurations (in-position and out-of-position), and 3 loading conditions (static, frontal, and oblique impacts). A linear statistical model was used to assess factor significance considering the impact responses of the occupant lower extremities.

Results: The presence of a KAB had a significant influence on the lower extremity kinematics compared to no KAB (P <.05) by providing early restraint and distributing contact force on the legs during airbag deployment. For in-position occupants, the KAB generally tended to decrease tibia loadings. The RKAB led to greater lateral motion of the legs compared to the BKAB, resulting in higher lateral displacement at the knee joint and abduction angle change (51.2 ± 21.7 mm and 15° ± 6.0°) over the dynamic loading conditions. Change in the seating position led to a significant difference in occupant kinematic and kinetic parameters (P <.05). For the out-of-position (forward-seated) occupant, the earlier contact between the lower extremity and the deploying KAB resulted in 28.4° ± 5.8° greater abduction, regardless of crash scenarios. Both KAB types reduced the axial force in the femur relative to no KAB. Overall, the out-of-position occupant sustained a raised axial force and bending moment of the tibia by 0.8 ± 0.2 kN and 21.1 ± 8.7 Nm regardless of restraint use.

Conclusions: The current study provided a preliminary computational examination on KAB designs based on a limited set of configurations in an idealized vehicle interior. Results suggested that the BKAB tended to provide more coverage and less leg abduction compared to the RKAB in oblique impact and/or the selected out-of-position scenario. An out-of-position occupant was associated with larger abduction and lower extremity loads over all occupant configurations. Further investigations are recommended to obtain a full understanding of the KAB performance in a more realistic vehicle environment.     

Pyrolysis behaviors of oil sludge based on TG/FTIR and PY-GC/MS

Pyrolysis is an alternative technology for oil sludge treatment. Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy and Pyrolysis-Gas Chromatography/Mass Spectrometry were employed to investigate the pyrolysis process and products of oil sludge. The pyrolysis process was divided into five stages: drying and gas desorption, oil volatilization, main pyrolysis, semi-coke charring, and mineral decomposition. The main reaction temperatures ranged from 497.6 K to 753.2 K. The products were mainly composed of pairs of alkane and alkene (carbon number ranges from 1 to 27). The mechanisms consisted of random chain scission followed by end chain scission at high temperatures with volatilization occurring during the whole process. This study is useful not only for the proper design of a pyrolysis system, but also for improving the utilization of liquid oil products.     

不同底物氧化亚铁硫杆菌生长特性研究

氧化亚铁硫杆菌是脱硫领域的重要微生物之一。文章研究了氧化亚铁硫杆菌对不同含硫底物的利用情况,并用单质硫对其进行驯化培养,将分别以亚铁和单质硫为底物的氧化亚铁硫杆菌的生长特性进行对比分析。结果表明,氧化亚铁硫杆菌对所选的三种含硫底物的利用难易程度依次为Na2S2O3最易利用,单质S其次,而Na2SO3的利用情况最差;氧化亚铁硫杆菌经单质S驯化后,其氧化单质S的能力显著增强,且细菌细胞的形态、结构等与以Fe2+为能源物质相比发生了变化。     

可生物降解材料聚羟基脂肪酸酯（PHA）的合成与应用概述

聚羟基脂肪酸酯（polyhydroxyalkanoates,PHA）是很多微生物合成的一种细胞内聚酯,是一种天然的高分子生物材料。PHA具有良好的生物相容性能、生物可降解性和塑料的热加工等性能。文章主要综述了PHA的合成途径与有关应用方面的研究。     

佛山水道及其支涌复氧试验研究

对几种曝气方式的溶解氧提升情况、充氧动力效率,及COD、氨氮的去除率进行了简单比较,得出微孔雾化曝气和橡胶坝曝气是适合佛山水道及其支涌河流人工复氧的最佳方法.     

花卉废物和牛粪联合堆肥中的氮迁移

以花卉废物和牛粪为原料,进行了温度反馈的通气量控制联合堆肥中的氮迁移中试研究.采用自制的静态好氧床进行一次发酵,过程控制采用温度反馈通气量控制方法,发酵周期20d;采用周期性翻堆进行物料二次腐熟,腐熟周期40d.研究了堆肥过程中总氮、有机氮、无机氮、氨氮、硝氮等氮素形态转化随时间的变化特征及温度反馈的通气量控制对氮迁移的影响.结果表明:堆肥初期的氨化作用和反硝化作用显著,氮素总量损失累计达41.98%,其中主要是有机氮的损失,99.95%的氮损失发生在一次发酵阶段;氮素损失主要是在pH和温度较高条件下的氨气大量挥发造成的.对通风进行有效控制、提高物料C/N及添加酸性物质有望减少N损失.对于C/N较低,硝态氮含量较高的物料堆肥,NH₄⁺-N≤0.04%、NH₄/NO₃≤0.16不能作为腐熟度指标.     

特低渗透油层含油污水处理工艺新技术

针对大庆油田低渗透油层水处理工艺存在的问题,设计了金刚砂过滤工艺。进行过滤效果及现场应用稳定性试验,通过工艺的调整及参数的优化,使其出水指标稳定,确定其最佳滤速、反洗再生、级配等运行工艺参数。并对其技术、经济性评价分析,确定为适合油田的精细过滤技术。     

大气中黑碳的健康效应及机制研究进展

虽然人类社会不断进步发展,但大量工业和自然排放也导致了严重的空气污染。大气颗粒物是大气污染物的主要成分之一,黑碳是其中的重要组成成分,被国际癌症研究机构(IARC)归类为2B类致癌物。黑碳可以吸附其他致癌物质,会对环境和人体健康产生不利影响,因此黑碳暴露对人类的危害得到越来越多的重视。空气中黑碳的水平与心血管、呼吸和神经系统疾病的发生都有关系;黑碳主要通过引起氧化应激和炎症反应,诱发基因突变等一系列损伤。虽然现今对于黑碳健康效应的研究已取得了一些进展,但研究多数处于起步阶段,且仅针对黑碳本身进行单独研究,未来还需要加强开展对黑碳和其他污染物联合毒性效应及机制的研究。本综述主要针对近年来已开展的研究进行了总结归纳。     

低剂量丙烯酰胺多世代持续暴露对秀丽隐杆线虫的损伤作用

论文研究了丙烯酰胺(acrylamide,AA)低剂量多代持续暴露对模式生物秀丽隐杆线虫(Caenorhabditis elegans,C.elegans)的发育、生殖、寿命和捕食行为能力的影响。将线虫暴露于不同剂量水平的AA中,检测对当代线虫的发育周期、后代数量、寿命和捕食行为的影响,结果显示,1.0 mmol·L~(-1)AA水平可诱发当代线虫发育周期延长和后代数量减少(P 0.05),0.05mmol·L~(-1)和0.001 mmol·L~(-1)水平可分别诱发捕食行为能力下降和寿命缩短(P0.05)。进一步选取对当代线虫不产生明显损伤效应的AA剂量,将线虫进行多代持续暴露处理,结果显示,0.01 mmol·L~(-1)AA分别可在第2代g1和第3代g2诱发发育周期延长和后代数量减少(P0.05),0.005 mmol·L~(-1)AA可在第2代g1引起摄食行为能力下降,0.0001 mmol·L~(-1)(约7μg·L~(-1),低于推测人的平均AA暴露水平)的AA在第2代g1即可诱发寿命缩短(P0.05)。以上结果表明AA生物学毒性可以在后代间积累,极低剂量AA多代持续暴露仍可诱发生物学损伤。