燃煤黄铁矿迁移转化模拟的研究

基于已有的动力学数据对单颗粒黄铁矿迁移转化进行了全过程模拟,分析讨论了各种因素对黄铁矿氧化过程和S释放率的影响,结果表明:随着颗粒尺寸的减小和炉膛温度的升高,黄铁矿颗粒的分解氧化过程加快,颗粒在炉内停留很短时间内温度即升高到共融点以上,使颗粒呈混熔态,进而导致灰沉积、结渣.颗粒氧化过程中S的释放主要受扩散控制,其释放速率与颗粒粒径成反比,与氧气浓度和炉膛温度成正比.     

燃煤含铁矿物的迁移转化特性研究

采用场发射扫描电镜结合X射线能谱分析仪(FSEM-EDX)系统研究了燃煤电站静电除尘器下各电场飞灰中磁珠的显微结构和化学组成,并利用热力学软件FACT计算预测了煤中含铁矿物的迁移转化过程．结果表明,外在含铁矿物在燃煤过程中易直接氧化形成结晶程度较好的铁氧化物相;内在含铁矿物与其他矿物在高温下熔合形成含Fe、Al、 Si的复杂的玻璃相,煤中含铁矿物的赋存特征、反应温度和气氛是影响含铁矿物迁移转化的主要因素。燃煤过程中Fe2 中间产物的形成以及Fe-O-S共熔体在炉内的长时间停留是结渣形成的重要原因。     

重金属锌在鱼鳃和鱼肉中的积累

用原子吸收分光光度法研究锌在鱼体内积累行为,结果表明,溶解态和颗粒态锌在鱼鳃和鱼肉中的积累,可分别用模拟方程：y=17.657ln（x）-5.791（溶解态锌,鱼鳃）、y=8.2824ln（x）-1.1144（溶解态锌,鱼肉）、y=35.79ln（x）-4.0646（颗粒态锌,鱼鳃）、y=9.0168ln（x）＋3.1344（颗粒态锌,鱼肉）来表示。锌在鱼鳃和鱼肉中的积累明显超过其他金属的积累量。颗粒态鱼鳃积累尤其大于鱼肉,说明鱼在对颗粒态锌积累过程中,部分颗粒态锌是吸附在鱼鳃上的。由于生理功能不同,金鱼对锌需要量比其他金属多。     

铅在铁路岩石边坡创面人工土壤中的迁移特性研究

山区大规模的铁路建设产生了大量的岩石边坡,前期研究表明边坡创面人工土壤受Pb污染,且有中等程度的富集。土壤类型、植被搭配类型是影响Pb迁移特性的重要因素,而目前却未见人工土壤及植被搭配类型对Pb迁移特性影响的相关报道。该研究以铁路岩石边坡创面人工土壤为对象,利用原子吸收分光光度法、红外光谱法分析了人工土壤对Pb的吸附-解吸特性及机制;运用野外人工模拟降雨实验,进一步考察在暴雨径流作用下,Pb在不同植被搭配类型的边坡人工土壤中的迁移过程。结果表明人工土壤对Pb的吸附量随着溶液平衡浓度的增加而急速增加,等温曲线呈“S”型,Freundlich方程能较好地描述人工土壤对Pb的吸附行为,R2为0.91。二次幂函数方程能较好描述NH₄AC对铅的解吸过程,R2为0.96。人工土壤有高岭石红外光谱特征吸收峰,属于高岭石型图谱。高岭石表面-OH、腐殖质表面-OH和-COOH参与吸附作用,置换出H+。人工土壤易将交通运输产生的Pb固定,但又容易再次释放。不同植被搭配类型边坡Pb流失量表现为草本＞草本+灌木＞草本+灌木+乔木。暴雨径流作用下Pb随沉积物相流失是边坡创面人工土壤Pb流失的主体,边坡土壤的侵蚀是导致Pb迁移扩散的主要原因,因此促进边坡植被的恢复,减小边坡人工土壤的侵蚀作用是防止Pb迁移扩散的关键。     

含油纳米制冷剂沸腾中纳米颗粒相间迁移机制

含油纳米制冷剂沸腾中纳米颗粒相间迁移机制,是评估纳米制冷剂沸腾传热效果和制冷系统中纳米颗粒循环能力的基础。本文基于颗粒捕集理论和气浮理论,提出了各因素对纳米颗粒相间迁移的影响机制;即纳米颗粒迁移率随其密度或粒径的减小而增大,制冷剂动力学黏度越小、密度越大,其完全蒸发时纳米颗粒迁移率越大,纳米颗粒迁移率随润滑油浓度的增大而减小,随热流密度的增大而减小,随初始液位高度的增加而增大。同时通过实验验证了理论分析。     

用改进的sol—gel法制备锆钛酸铅薄膜及其物相转化的研究

利用改进的ｓｏｌ－ｇｅｌ法,在Ｐｔ／Ｔｉ／ＳｉＯ２／Ｓｉ衬底上制备了ＰｂＺｒ０．５Ｔｉ０．５Ｏ３（ＰＶＴ５０／５０）薄膜,采用了一种新的方法,从同一前驱体溶液行到了厚度各异的单一退火层,研究了薄膜的结构和性质随单层退火厚度的改变而发生的变化,发现随着单一退火层度的降低,薄膜（１１１）取向的程度增大,同时薄膜的剩余极化和介电常量也逐渐增高,当单一退火层厚度降低到约为４０ｎｍ时,可行到高度（１１１）择     

润滑油对纳米颗粒在纳米制冷剂相变过程中迁移的影响

本文实验研究了润滑油的存在对纳米制冷剂相变过程中纳米颗粒迁移量的影响以及对不同浓度的纳米制冷剂相变过程中纳米颗粒迁移率的影响.结果表明:润滑油存在时,纳米颗粒的迁移量和迁移率都低于相同情况下无油时纳米颗粒的迁移量和迁移率.同时理论分析了纳米颗粒的迁移过程,并建立了能够预测含油纳米制冷剂相变过程中纳米颗粒迁移量的计算模型.模型计算值与实验值吻合良好.     

含油纳米制冷剂沸腾中纳米颗粒相间迁移特性预测模型

为了评估纳米颗粒对沸腾传热的影响效果和采用纳米制冷剂的制冷系统长期运行稳定性,提出了含油纳米制冷剂沸腾中纳米颗粒相间迁移特性预测模型,通过模拟气泡的脱离和上升过程、纳米颗粒的运动、纳米颗粒与气泡的黏附、气液交界面上纳米颗粒的脱离,最终得到纳米颗粒的迁移量.该模型能够反映热流密度和加热容器几何结构等因素对纳米颗粒迁移特性...     

强磁场作用下Cu熔体中富Fe颗粒的迁移与排列

凝固界面前沿颗粒间的相互作用决定了颗粒的运动轨迹、分布和材料的性能,控制熔体中颗粒的迁移可用于材料的净化和提纯.在Cu-30%Fe合金液固两相区施加不同的强磁场条件,富Fe颗粒的分布和排列不尽相同.当无强磁场作用时,富Fe颗粒较均匀地分布在Cu熔体中;随着施加稳恒强磁场磁感应强度的增加,富Fe颗粒向远离重力方向的试样上端迁移,样品底部几乎无富Fe颗粒;而施加向下的梯度磁场作用后,富Fe颗粒沿重力方向向下迁移.结合强磁场作用下颗粒的受力情况,分析了Fe颗粒的迁移行为.不同磁场条件和不同区域的颗粒直径统计分析表明,随磁感应强度增加,Fe颗粒聚合增加,但施加梯度强磁场后颗粒的团聚又逐渐减弱,对此从影响颗粒运动的Stokes和Marangoni凝并速度进行了讨论.从能量最低的角度解释了富Fe相沿平行磁场方向的取向排列.     

Global Migration Can Lead to Stronger Spatial Selection than Local Migration

The outcome of evolutionary processes depends on population structure. It is well known that mobility plays an important role in affecting evolutionary dynamics in group structured populations. But it is largely unknown whether global or local migration leads to stronger spatial selection and would therefore favor to a larger extent the evolution of cooperation. To address this issue, we quantify the impacts of these two migration patterns on the evolutionary competition of two strategies in a finite island model. Global migration means that individuals can migrate from any one island to any other island. Local migration means that individuals can only migrate between islands that are nearest neighbors; we study a simple geometry where islands are arranged on a one-dimensional, regular cycle. We derive general results for weak selection and large population size. Our key parameters are: the number of islands, the migration rate and the mutation rate. Surprisingly, our comparative analysis reveals that global migration can lead to stronger spatial selection than local migration for a wide range of parameter conditions. Our work provides useful insights into understanding how different mobility patterns affect evolutionary processes.     

Spatial and Temporal Characteristics of an Excimer Laser-Induced Lead Plasma Emission

A laser-induced plasma was generated from a lead target using an ArF excimer laser (λ = 193 nm) and characterized by time-resolved and time-integrated spatially resolved spectrometry. The ambient atmosphere (gas composition and pressure) influenced the emission intensity for both atomic and ionic lines. The emission of laser-induced lead plasma varied with time as well as the location in the plasma. Lead ion emission decayed more rapidly than lead atomic line emission. High excitation temperatures and nonlinear optical phenomena were observed in the laser-induced lead plasma. Gas breakdown and the subsequent shielding effect of the incident laser beam in different ambient gas compositions and pressures were discussed to explain the different efficiency of metal ion for matioa in the plasma. The experimental results show that spatial discrimination of the laser-induced plasma emission is desirable for direct spectrochemical analysis.     

Extreme Electromechanical Characteristics and Microstructural Features of Ferro-Piezoceramics Based on Lead Titanate

Microstructural features and electrophysical parameters of a number of solid solutions based on PbTiO₃ are investigated. Solid solutions (Pb_{1–3/2x + z/2}Nd _x )(Ti_1–y–zMn _y Inz)O₃ and Pb_1–xCa _x Ti_1–y(W_1/2Co_1/2) _y O₃ with extreme values of the mechanical Q-factor and electromechanical anisotropy are chosen as the objects of investigation. The ferro-piezoceramic samples are obtained through conventional sintering and hot pressing. X-ray structural and microstructural studies are performed, and the complex elastic, dielectric, and piezoelectric parameters of experimental samples are measured. The frequency dependences of complex parameters of the experimental samples have been studied at frequencies of up to 40 MHz. It is established that the extreme values of the mechanical Q-factor and piezoelectric anisotropy of the investigated PbTiO₃-based solid solutions are due to microstructural features associated with the technological regimes of ferropiezoceramic fabrication.     

含铅金矿和铅精粉中金的测定

采用在样品中加入一定量的硝酸、过滤除去铅对金的干扰,王水溶矿,原子吸收光谱仪测定,可以满足客户对铅精粉中金含量测定的要求。     

国内化妆品中铅的检测方法

对化妆品中微量元素铅的含量的检测方法进行综合评述。     

基于Tessier-AAS法的华中大农区污染红土Pb赋存形态非生物转化机制研究

土壤重金属污染已成为人类面临的共同挑战,典型的重金属污染场地包括金属矿山、公路沿线、工业集中区、农业耕地等。对于事关农业安全生产的大农区,土壤超量重金属往往导致农产品品质下降甚至使用价值丧失,由此造成的经济损失不可估量。实际上,农作物体内累积重金属量与土壤“活性”重金属关系更加密切,这部分重金属主要以可交换态存在,在一定条件下能够与碳酸盐结合态、Fe-Mn氧化态、有机结合态和残渣态相互转换。因此,明确土壤条件对重金属有效性的作用规律,有望从源头上降低重金属对农作物的污染风险。基于前期研究成果,以华中大农区酸性网纹红土为检测对象,采用Tessier连续提取-原子吸收光谱法(AAS)揭示不同条件对红土Pb形态转化的非生物调控机制。结果表明：红土样品Pb总量为32.56 mg·kg-1,低于《土壤环境质量标准》一级标准推荐值,但比全国土壤Pb平均含量要高。不同形态Pb含量分布为残渣态>Fe-Mn氧化态>有机结合态>碳酸盐结合态>可交换态,其中残渣态Pb占Pb总量的54.55%。红土pH值通过改变无机胶体和有机质表面电荷量来控制Pb的结合行为和可交换态含量;不同含水率导致红土氧化还原电位差异,进而影响Pb的形态转化行为。此外,秸秆加入量和老化时间也能改变Pb的形态分布,但残渣态Pb含量始终最高。红土Pb的Muller指数I_geo为0.302 5,表明土样采集区人为污染值得注意。Tessier连续提取-AAS法能有效表征红土Pb赋存形态的非生物转化机制。     

Migration and agglomeration of heliumatoms in copper

The magration and agglomeration of Helium atoms in He irradiated Cu was studied between 10 K and 900 K by perturbed γγ angular correlation (PAC) measurements using the radioactive probe atom¹¹¹In. Trapping of interstitial and substitutional He atoms is observed already after irradiation at 10 K. Substitutional He (He-yacancy pair) is bound in the nearest neighbourhood to the¹¹¹In probe atom and seems to be stable up to 725 K (E _He1V1 ^b ≥2.1 eV). The onset of vacancy assisted He agglomeration in Cu is observed at 250 K.     

荧光光度法测定蔬果类罐头食品中的微量铅

以3mol/L HCl为介质,利用荧光光度计检测PbCl2-4的荧光强度,建立了测定蔬果类罐头食品中微量铅的新方法,该方法的检出限为8.8μg/mL,回收率为;97.0%.