Nonlinear molecular based modeling of the flash point for application in inherently safer design

New chemical process design strategies utilizing computer-aided molecular design (CAMD) can provide significant improvements in process safety by designing chemicals with required target properties and the substitution of safer chemicals. An important aspect of this methodology concerns the prediction of properties given the molecular structure. This study utilizes one such emerging method for prediction of a hazardous property, flash point (FP), which is in the center of attention in safety studies. Using such a reliable data set comprising 1651 organic and inorganic chemicals, from 79 diverse material classes, and robust dynamic binary particle swarm optimization for the feature selection step resulted in the most efficient molecular features of the FP investigations. Apart from the simple yet precise five-parameter multivariate model, the FP nonlinear behavior was thoroughly investigated by a novel hybrid of particle swarm optimization and support vector regression. Besides, 195 missing experimental FPs of the DIPPR data set are predicted via the presented procedure.     

煤尘挥发分及粒径对爆炸火焰长度的影响研究

为研究煤尘挥发分及粒径对爆炸火焰长度的影响及其变化规律,选取挥发分含量不同的四种典型烟煤煤样,分别制备成31.5、44、62.5、81.5、119、>150 μm六种粒径,利用煤尘爆炸性鉴定装置测试其爆炸火焰长度,并对其爆炸火焰长度变化规律进行分析。结果表明:随着挥发分含量的增加,不同粒径级别的煤尘爆炸火焰长度均呈增长趋势;在挥发分含量较低的区间,挥发分含量增加对爆炸火焰长度影响不大;在挥发分含量较高的区间,随着挥发分含量的增加其爆炸火焰长度也急剧增加,并且粒径越小增加的越快。对于同一实验煤样,随着粒径的增大,其爆炸火焰长度逐渐减小,粒径增大到150 μm以上时爆炸火焰几乎消失。爆炸火焰长度随粒径变化的变化率根据实验煤样的不同,呈现出两种变化规律,挥发分含量为18.99%和27.52%煤样的爆炸火焰变化率先增加再减小再增加,挥发分含量为32.20%和39.74%的煤样呈现先增加再减小的趋势,但四组实验煤样的爆炸火焰长度变化率都在44～62.5 μm的粒径变化量时达到最大值。     

基于非线性渗流模型采空区漏风流场数值模拟

针对采空区非线性渗流模型中颗粒平均粒径的取值问题,利用专业的流体力学软件fluent对刘庄矿151305工作面采空区不同颗粒粒径下的漏风流场进行了模拟,以此确定合适的平均粒径,并利用该采空区颗粒平均粒径对工作面供风量及采空区漏风的影响进行了模拟与分析。结果表明,采空区内平均粒径的取值对工作面风量分布影响较大,瓦斯抽采负压也相差一个数量级;通过与实测工作面风量及实际的瓦斯抽采负压作对比,当采空区颗粒平均粒径取0.1 m时,模拟结果与现场实际最为吻合;工作面供风量越大,采空区的漏风量也越大,两者为二次函数关系。该研究方法为工作面采空区漏风流场数值模拟提供了理论指导。     

鹤山大气超级站旱季单颗粒气溶胶化学特征研究

利用单颗粒气溶胶飞行时间质谱等仪器在鹤山大气超级站开展综合观测,结合ART-2a自适应共振神经网络聚类算法,将2013年11月4日~2013年12月30日期间监测到的1637330个细颗粒分成9类: EC-Fresh颗粒、EC-Nitrate/Sulfate颗粒、K-EC颗粒、Ca-EC颗粒、ECOC颗粒、OC-Levoglucosan颗粒、OC-Nitrate/Sulfate颗粒、K-Nitrate/Sulfate颗粒和Metal-rich颗粒.结果表明:该大气超级站所在地区旱季霾日有利于与水溶性二次无机组分混合的EC-Nitrate/Sulfate颗粒、K-Nitrate/Sulfate颗粒的累积;晴朗天更有利于二次有机组分在气溶胶颗粒中生成,雨天受当地排放源的影响显著,含有较高EC-Fresh和K-EC颗粒.相关性的研究发现,EC-Nitrate/Sulfate颗粒与能见度有良好的相关性,它们对霾的形成有至关重要的作用.     

徐州冬季雾-霾天颗粒物粒径及气溶胶光学特性变化特征

为研究徐州冬季雾-霾天气形成过程中颗粒物粒径及气溶胶光学特性的变化特征,分析了2014年12月1日～2015年2月28日徐州大气颗粒物质量浓度（PM₁₀、PM_2.5、PM₁）、数浓度（0～1μm、1～2.5μm、2.5～10μm）和气溶胶光学特性等数据.结果表明：0～1μm粒径范围细颗粒物的大量增多是引发徐州冬季雾-霾天气的主要因素,徐州冬季地面风速小（静风或轻风天气）,较高的大气相对湿度对雾-霾的形成和维持起着重要影响作用.持续时间较长的雾霾天气,因颗粒物吸湿增长和水汽附着,1～10μm粒径范围大气颗粒物在雾霾时段易发生沉降而减少,后随相对湿度降低雾霾转为短时间的霾天气,1～10μm颗粒物数浓度大幅上升.徐州冬季500nm波段AOD_total和AOD_{fine mode}具有相同的变化趋势,雾-霾日AOD_total和AOD_{fine mode}显著高于非霾日.AOD_{fine mode}与AOD_{coarse mode}的比值雾-霾日亦明显高于非霾日,而且在雾-霾日Angstrom波长指数主要集中在1～1.6,表明徐州冬季雾-霾时段大气中细颗粒物为主控粒子.     

Hazardous and essential trace elements profile in the different soft tissues of Lithophaga lithophaga (Linnaeus, 1758) from Southern Adriatic Sea (Italy)

A characterization study of 7 hazardous (Hg, Pb, Cd, As, Cr, U, and Ni) and 11 essential (Co, Mo, Se, Cu, Zn, V, Ca, Al, Sr, Mn, and Fe) trace elements in date mussels (Lithophaga lithophaga,Linnaeus, 1758) was carried out by inductively coupled plasma mass spectrometer. Date mussels (231 individuals), caught in the Gulf of Manfredonia (Southern Italy), were divided into 4 size-related groups. The different tissues (muscle, stomach, hepatopancreas and rest of soft tissues) were separated and analyzed to study the capability of absorption of this species. No particular differences were reported on the basis of the shell size; the soft tissues play an important role on the accumulation levels of hazardous and essential trace elements. These marine animals may be considered a good bioindicator of marine environmental pollution for their longevity and habitat permanence peculiarities.     

基于模拟退火的随机取向含核椭球颗粒粒径反演

烟颗粒的光散射数值模拟计算多采用单种匀质的球形、椭球或分形模型。实际上,多种情况下的烟颗粒并非仅由单种匀质组成,例如细水雾灭火和湿式洗涤塔除尘过程中生成的烟颗粒即是一种以碳烟颗粒作为凝结核、水为外壳的含核水凝物气溶胶颗粒。针对随机取向条件下,利用离散偶极子近似方法对轴对称的含核椭球颗粒模型进行数值模拟计算,得到光散射Mueller矩阵,并基于Lorenz-Mie散射理论,采用全局搜索能力很强的模拟退火算法,实现了单分散系的含核椭球颗粒的粒径反演。讨论分析了内核半径与外壳有效半径比q及内核折射率n对轴对称的含核椭球颗粒粒径反演的影响。粒径反演结果表明:q对含核椭球颗粒的粒径反演结果及误差影响较大,n在一定程度上影响颗粒的粒径反演。     

Seasonal variations in trace metal levels,speciation and physicochemical determinants of metal availability in dumpsite soils within Akwa Ibom State,Nigeria

Physicochemical properties, total metals and metal species were investigated in surface soil samples from six urban dumpsites within Akwa Ibom State, Nigeria. Results obtained indicated that Pb, Cd and Cr levels were higher in the dry season than in wet season, whereas Ni levels were higher during the wet season. Soil pH, organic matter and cation-exchange capacity (CEC) showed higher values in wet season than in dry season, whereas sand and clay levels were higher in the dry season. Speciation analysis showed the principal fraction of the metals to be Pb (reducible), Cd (acid extractable) and Ni (residual), whereas Cr existed in the residual fraction during the dry season and in the acid-extractable fraction during the wet season. Soil pH was positively correlated at p<0.1 with all metals in both seasons, sand was negatively correlated with the metals in both seasons, and CEC was negatively correlated with all metals in both seasons, except Pb in the wet season. Organic matter showed variable relationships with metals in both seasons. Seasonal variations affected metal availability and physicochemical properties of the soil. Total metal concentrations followed the order Pb>Ni>Cd>Cr, whereas their bioavailability followed the trend Cd>Pb>Cr>Ni.     

上海地区大气中二噁类分布特征的初步研究

为了研究上海地区大气中二噁英（PCDD/Fs）的污染水平、分布特征和相分配规律,分别选取了上海典型的工业区、居民区和郊区的采样点进行了大气样品的采集。通过对3个采样点的研究发现,上海地区的大气中二噁英的平均毒性当量浓度为0.201 pg/m^3,居民区最高,工业区其次,郊区最低。大气中二噁英排放的平均浓度属于典型的城市工业区水平。在常温下,大气中90%二噁英主要分布在颗粒物相中,从单体看,高氯代同系物主要分布在颗粒相中,而低氯代同系物则分布在气相当中。通过二噁英的气相/颗粒相分配系数Kp与蒸气压PL的关系式评价了污染物的气相/颗粒相分配行为。并应用Junge-Pankow模型预测了大气中的气相/颗粒相分配,通过与实测值的比较发现,上海地区大气中二噁英的气相/颗粒相分布十分接近于模型中的城市地区,郊区采样点和模型预测值最为吻合,工业区和居民区大气中的二噁英在颗粒物上的浓度则要高于模型预测值,对造成偏离的原因进行了分析,并对3个采样点周围的污染源进行了初步的探究。     

车用柴油机燃用棕榈生物柴油的颗粒物排放特性研究

在满足国Ⅳ排放法规的车用柴油机上研究了燃用不同掺混体积比例的棕榈油生物柴油的颗粒物排放特性.试验中棕榈油生物柴油的掺混比例分别为0%、10%、20%、50%和100%,采用DMS500型快速颗粒光谱仪测试分析了发动机在外特性和负荷特性时的颗粒物数量浓度、质量浓度及粒径分布.研究结果表明:随生物柴油掺混比例的增加,颗粒物质量浓度降低.燃用生物柴油后颗粒物的数量浓度在大负荷明显降低,中小负荷呈升高趋势.生物柴油的排气颗粒物呈核态和凝聚态的双峰分布特征,核态数量浓度所占比例高于柴油,凝聚态的质量浓度所占比例略低于柴油.生物柴油颗粒物的几何平均直径小于柴油.