不同燃烧状态下农作物秸秆PM2.5排放因子及主要成分分析

运用自主设计的生物质燃烧系统,对水稻、小麦、大豆、玉米、花生和油菜6种农作物秸秆采用不同燃烧状态(阴燃和明燃)进行实验室模拟燃烧,分析PM_(2.5)的排放因子及其碳质组分和水溶性离子之间的差异.研究结果表明,不同燃烧状态对秸秆PM_(2.5)的排放因子、碳质组分和水溶性离子的排放均具有显著影响.不同农作物秸秆PM_(2.5)排放因子范围在阴燃和明燃时分别是11.45~23.84 g·kg~(-1)和4.51~12.15 g·kg~(-1).有机碳(OC)、元素碳(EC)的排放因子范围阴燃时分别是5.03~11.04 g·kg~(-1)和0.94~2.70 g·kg~(-1),明燃时分别是1.55~6.02 g·kg~(-1)·kg~(-1)和1.04~2.11 g·kg~(-1),阴明燃具有显著差异且阴燃高于明燃.此外,OC/EC、OC/PM_(2.5)和EC/PM_(2.5)在不同燃烧状态均具有显著差别,可作为区分阴明燃的指标.PM_(2.5)中水溶性离子的主要组分阴燃时为K+(1.011 g·kg~(-1))、Cl~-(0.712 g·kg~(-1))、F~-(0.182 g·kg~(-1)g)和SO_4~(2-)(0.166 g·kg~(-1)),明燃时为K+(0.457 g·kg~(-1))、Cl~-(0.271 g·kg~(-1))、SO_4~(2-)(0.086 g·kg~(-1))和F~-(0.048 g·kg~(-1)),且阴燃条件更有利于离子的排放.此外,水溶性离子的相关性也因燃烧状态的不同而有较大的差异.     

郴州市大气PM2.5碳组分污染特征及其来源分析

为研究郴州市PM_2.5中碳组分的污染特征及来源,于2016年7月-2017年4月分4个季度典型时段采集郴州市环境大气中的PM_2.5,测定了样品中OC（有机碳）和EC（元素碳）的质量浓度,对碳气溶胶污染水平、时空分布、SOC（二次有机碳）以及OC和EC相关性等特征进行了分析,并分析了碳组分的来源.结果表明:郴州市ρ（PM_2.5）年均值为（40.2±19.0）μg/m3,ρ（OC）、ρ（EC）占比分别为15.7%和7.2%;ρ（OC）与ρ（EC）相关性分析显示二者来源较为一致,但春季、夏季差异相对较大;ρ（SOC）全年估算值为1.84 μg/m3,占ρ（OC）的29.11%,夏季较高的温度和较低的相对湿度导致夏季ρ（SOC）的估算偏低.结合碳组分丰度分析、PCA（主成分分析）和PMF（正矩阵因子分解分析）结果发现,燃煤/道路尘、机动车排放和生物质燃烧对PM_2.5中TC（总碳）的影响最为明显,贡献率分别为49.25%~56.71%、19.79%~25.36%和9.35%~13.69%.反向轨迹聚类结果显示,广东珠三角区域的汽油车排放、道路尘和生物质燃烧对郴州市PM_2.5中碳组分有较大的影响,而燃煤和柴油车的贡献主要来源于本地.研究显示,郴州市PM_2.5中碳组分污染较为严重,应重点加强本地燃煤和柴油车的控制.      

富集因子法中参比元素的选取方法——以元江底泥中重金属污染评价为例

富集因子法中参比元素的选择对目标元素富集程度评价及源解析结果有至关重要的影响,盲目选用可能会导致偏颇或错误的结论,但目前鲜有针对参比元素的选择所进行的探讨.本文以元江沉积物中重金属元素污染水平评价及来源解析为例,详细介绍了运用顺序提取法、相关分析法、聚类分析法等化学分析和数理统计相结合并联系研究区域地球化学背景、产业分布及元素特性确定参比元素的方法.并采用所选出的参比元素进行富集因子法分析,将所得重金属污染等级评价结果及重金属来源的推论与地积累指数法对重金属污染等级评价的结果和以因子分析法对重金属溯源的推论相比较.结果表明,利用相关分析和顺序提取等方法选择参比元素是可靠可行的.     

Can new passenger cars reduce pedestrian lower extremity injury? A review of geometrical changes of front-end design before and after regulatory efforts

Objective: Pedestrian lower extremity represents the most frequently injured body region in car-to-pedestrian accidents. The European Directive concerning pedestrian safety was established in 2003 for evaluating pedestrian protection performance of car models. However, design changes have not been quantified since then. The goal of this study was to investigate front-end profiles of representative passenger car models and the potential influence on pedestrian lower extremity injury risk.

Methods: The front-end styling of sedans and sport utility vehicles (SUV) released from 2008 to 2011 was characterized by the geometrical parameters related to pedestrian safety and compared to representative car models before 2003. The influence of geometrical design change on the resultant risk of injury to pedestrian lower extremity—that is, knee ligament rupture and long bone fracture—was estimated by a previously developed assessment tool assuming identical structural stiffness. Based on response surface generated from simulation results of a human body model (HBM), the tool provided kinematic and kinetic responses of pedestrian lower extremity resulted from a given car's front-end design.

Results: Newer passenger cars exhibited a “flatter” front-end design. The median value of the sedan models provided 87.5 mm less bottom depth, and the SUV models exhibited 94.7 mm less bottom depth. In the lateral impact configuration similar to that in the regulatory test methods, these geometrical changes tend to reduce the injury risk of human knee ligament rupture by 36.6 and 39.6% based on computational approximation. The geometrical changes did not significantly influence the long bone fracture risk.

Conclusions: The present study reviewed the geometrical changes in car front-ends along with regulatory concerns regarding pedestrian safety. A preliminary quantitative benefit of the lower extremity injury reduction was estimated based on these geometrical features. Further investigation is recommended on the structural changes and inclusion of more accident scenarios.     

Comparison of multibody and finite element human body models in pedestrian accidents with the focus on head kinematics

Objective: The objective of this study was to compare and evaluate the difference in head kinematics between the TNO and THUMS models in pedestrian accident situations.

Methods: The TNO pedestrian model (version 7.4.2) and the THUMS pedestrian model (version 1.4) were compared in one experiment setup and 14 different accident scenarios where the vehicle velocity, leg posture, pedestrian velocity, and pedestrian's initial orientation were altered. In all simulations, the pedestrian model was impacted by a sedan. The head trajectory, head rotation, and head impact velocity were compared, as was the trend when various different parameters were altered.

Results: The multibody model had a larger head wrap-around distance for all accident scenarios. The maximum differences of the head's center of gravity between the models in the global x-, y-, and z-directions at impact were 13.9, 5.8, and 5.6 cm, respectively. The maximum difference between the models in head rotation around the head's inferior–superior axis at head impact was 36°. The head impact velocity differed up to 2.4 m/s between the models. The 2 models showed similar trends for the head trajectory when the various parameters were altered.

Conclusions: There are differences in kinematics between the THUMS and TNO pedestrian models. However, these model differences are of the same magnitude as those induced by other uncertainties in the accident reconstructions, such as initial leg posture and pedestrian velocity.     

Experimental investigation of ash deposits on convection heating surfaces of a circulating fluidized bed municipal solid waste incinerator

Incineration of municipal solid waste(MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction, as well as a source of renewable energy.During MSW combustion, increased formation of deposits on convection heating exchanger surfaces can pose severe operational problems, such as fouling, slagging and corrosion.These problems can cause lower heat transfer efficiency from the hot flue gas to the working fluid inside the tubes. A study was performed where experiments were carried out to examine the ash deposition characteristics in a full-scale MSW circulating fluidized bed(CFB) incinerator, using a newly designed deposit probe that was fitted with six thermocouples and four removable half rings. The influence of probe exposure time and probe surface temperature(500, 560, and 700℃) on ash deposit formation rate was investigated. The results indicate that the deposition mass and collection efficiency achieve a minimum at the probe surface temperature of 560℃. Ash particles are deposited on both the windward and leeward sides of the probe by impacting and thermophoretic/condensation behavior. The major inorganic elements present in the ash deposits are Ca,Al and Si. Compared to ash deposits formed on the leeward side of the probe,windward-side ash deposits contain relatively higher Ca and S concentrations, but lower levels of Al and Si. Among all cases at different surface temperatures, the differences in elemental composition of the ash deposits from the leeward side are insignificant.However, as the surface temperature increases, the concentrations of Al, Si, K and Na in the windward-side ash deposits increase, but the Ca concentration is reduced. Finally,governing mechanisms are proposed on the basis of the experimental data, such as deposit morphology, elemental composition and thermodynamic calculations.     

单轴拉伸下PVDF/POSS纳米复合材料的损伤模拟

目的研究PVDF及其氟化POSS纳米复合材料在单轴拉伸载荷下的损伤行为。方法首先依据实验结果和细观力学均匀化方法,建立纯PVDF和三种不同POSS含量PVDF/POSS纳米复合材料的颗粒掺杂有限元模型,并通过在实体单元之间嵌入可破坏的内聚力单元来模拟损伤。结果模拟得到的应力-应变关系与实验结果相吻合,证明了模拟结果的可靠性。损伤破坏的初始时间表明在破坏的初期阶段,POSS对于损伤有抑制作用,并且其效果随着POSS含量的增加而增强。损伤速度和最终的损伤面积和则表明质量分数在5%以下的POSS掺杂对于PVDF的损伤有抑制作用,并且随着POSS质量分数的增加其效果不断增强。当质量分数达到8%时,POSS的掺杂反而加速了PVDF的损伤。结论 POSS掺杂影响PVDF的损伤破坏,掺杂量对PVDF损伤破坏有抑制/促进作用,这一结果有助于理解实验所得到的力学参数的变化规律。     

基于边界元方法的缓蚀剂对结构电偶腐蚀缓蚀效果研究

目的研究THFS-10软膜缓蚀剂和THFS-15长效硬膜缓蚀剂在海洋环境下对于海军某型装备结构电偶腐蚀的缓蚀效果。方法采用等效浸泡测量法,得到ZL115-T5铸铝合金、30Cr Mn Si A钢以及C41500海军黄铜在不同条件下的极化曲线和交流阻抗谱。以此为边界条件,基于边界元方法,对涂覆缓蚀剂后结构的电偶腐蚀行为进行仿真,对比分析两种缓蚀剂对该异种金属连接结构电偶腐蚀的缓蚀效果。结果 THFS-15能够显著减轻上述三种不同材料偶合时的电偶腐蚀,THFS-10则在在一定程度上加速了三者之间的电偶腐蚀。结论根据仿真结果,给出了THFS-10和THFS-15两种缓蚀剂的具体使用建议和注意事项。     

电感耦合等离子体质谱法测定大气颗粒物中微量元素及铂族元素

大气颗粒物样品采集量较少,一般只有5~10mg左右,其中铂族元素含量很低并且受到Cu、Ni、Cd、Zr、Hf等元素的严重干扰,直接测定误差很大,必须要进行分离富集。因此,同时测定其中的微量元素及铂族元素非常困难。本文利用HF和HNO3在封闭溶样装置中对大气颗粒物样品进行消解,样品完全消解后,分取约1/4的样品溶液,以Ir作为内标元素等离子体质谱法测定微量元素,然后将剩余样品通过Dowex,50W X8阳离子树脂和P507萃淋树脂混合交换柱,分离基体元素及干扰元素,以Ir为内标等离子体质谱法测定Pt、Pd、Rh三个铂族元素以及Re和Au。实现了一次溶样同时测定大气颗粒物中的微量元素、稀有分散元素及铂族元素。国际标样结果稳定可靠。     

产品设计中的人性化因素

通过对工业产品人性化设计中人的因素的分析和研究,阐明了人性化各因素之间的关系,提出了产品人性化设计的核心是人,只有把人对工业产品的多元需求、特别是人的精神与文化需求提升到一定高度的设计才是好的设计.