层流中固体颗粒运动方程的初值问题和稳定性分析

层流中固体颗粒运动方程的初值问题解的存在唯一性表明悬浮颗粒在圆管层流人口段剪切区中的运动，由进入该区的颗粒初始状态（初始位置和初始速度）确定，其运动轨迹也由该初始状态唯一确定。层流中固体颗粒运动方程稳定性分析表明达到稳定状态的颗粒必定满足条件：up＝uf（∞，c），up＝0，Re（α／R）2（c／R）＜2．8728．     

Co-SiO2颗粒膜中颗粒相互作用的温度和尺寸依赖关系

我们在真空离子束溅射设备中制备了Co-SiO2颗粒膜，其结构和磁性分别利用透射电子显微术（TEM）和铁磁共振（FMR）来研究。TEM分析表明Co纳米颗粒相互独立地分布在SiO2介质中，且尺寸分布非常窄。室温转角FMR实验显示薄膜具有单轴各向异性，变温FMR实验被用来研究在100－300K温度范围内的颗粒间相互作用强度随温度变化的关系（我们利用一理论模型计算了颗粒集合体中的铁磁部分所占比例和超顺磁部分所占比例）。我们发现颗粒间相互作用强度除了与温度有关之外，还与Co颗粒的尺寸直接相关。     

金属颗粒薄膜巨磁电阻效应的影响因素

研究金属颗粒薄膜的颗粒尺寸、磁性组分等对巨磁电阻效应的影响.在自由电子模型和自旋相关散射理论的基础上，计算了金属颗粒膜体系的电子平均散射势.在计算过程中将自旋相关项与宏观量相联系，得到了巨磁电阻效应与磁性成分比例、颗粒尺寸的关系.磁电阻效应的模拟曲线表明，增加磁性成分比例和减小磁性颗粒尺寸可增强颗粒膜的巨磁电阻效应. 关键词：     

二氧化硅纳米颗粒与碳黑纳米颗粒红外漫反射光谱的测量与分析

用FTIR-FTS3000光谱仪和漫反射附件分别采集了二氧化硅纳米颗粒、炭黑纳米颗粒和二氧化硅纳米颗粒与碳黑纳米颗粒的不同配比的混合样品的红外漫反射光谱。通过对测量结果的分析,发现二氧化硅纳米颗粒的红外漫反射光谱较之体材料有蓝移和宽化现象,此现象可以用纳米粒子的小尺寸效应和量子尺寸效应来进行初步解释。而碳黑纳米颗粒因为其强吸光性的原因,实验中没有得到理想的光谱。混合样品中,碳黑纳米颗粒有一个最大吸收临界浓度,此时二氧化硅纳米颗粒与碳黑纳米颗粒的质量比是100:20。在这个比例以内,碳黑纳米颗粒的特征峰位的F(R)函数与浓度符合朗伯-比尔定律。当碳黑纳米颗粒在体系中的含量超过这个比值,随着碳黑在体系中比例的增加,吸光度将不再增大。     

用MEVVA低能离子注入制备表层SiC/Si异质结构及其室温的光致发光特性

利用金属蒸汽真空弧离子源（MEVVA）进行离子束合成,制备了过剂量C^＋离子注入到单晶硅衬底的样品。然后利用热退火,在表层制备了连续8-SiC层,形成表层SiC／Si的异质结构。利用傅里叶变换红外光谱（FTIR）对其成键特征和微结构进行了分析,通过光电子能谱分析（XPS）和原子力显微镜（AFM）分析了样品的成分分布及其表面形貌。最后对其室温下的光致发光特性随热退火的时间和温度的变化进行了研究。结果表明：光致发光谱（PL）表现出430,560nm两个发光峰,分别对应于纳米碳化硅和块状立方碳化硅发光的特征峰。我们认为小颗粒的晶化碳化硅的尺寸及其相对比例对PL发光峰位和强度有较大的影响,用纳米晶粒量子效应（NSUQC）理论和表面态理论对发光现象及其变化规律进行了初步的解释。     

扩散式气固分离器内两相流动数值模拟

采用RNG k-ε模型、随机颗粒轨道模型对扩散式气固分离器内的两相流动情况进行了数值模拟研究,讨论了流速对分离效率的影响,颗粒分级分离效率,颗粒轨迹,以及多个几何结构尺寸对分离效率和阻力系数的作用情况.数值模拟结果表明该类分离器流场总体成双层流动结构,分离器对4 μm以下的小颗粒分离效率较低,流速对分离效率的作用比较明显,各结构尺寸对阻力系数和分离效率的影响比较复杂,结构尺寸的取值有一定比例范围.     

SiO2纳米颗粒对R6G-乙醇溶液荧光光谱影响

在3×10－4M和1×10－4M浓度的R6G-乙醇溶液中分别掺杂了8个不同浓度的SiO2纳米颗粒（107～1012 个/mL）.研究了SiO2纳米颗粒（100 nm）对若丹明6G（R6G）荧光光谱的影响,结果表明:n1～n4(1012～1010个/mL)浓度掺杂的SiO2纳米颗粒在549 nm处的有很好的荧光增强作用,对570 nm处的荧光峰有明显的粹灭作用|n5～n8(109~107个/mL)浓度掺杂的SiO2纳米颗粒在549 nm处没有明显的荧光增强作用,但对570 nm处的荧光峰有增强作用,荧光增强因子可达10%~20%.荧光增强与粹灭的原因在于纳米颗粒对荧光的散射作用和R6G无荧光H-型二聚体或荧光J-型二聚体的形成.     

金光栅/金纳米颗粒SERS基底的设计、制备及其性能

表面等离子激元（SPP）和局域表面等离子共振（LSPR）耦合产生的电场增强显著高于单纯LSPR引起的电场增强。因此一种新型高效的表面增强拉曼散射（SERS）基底是寄希望于在一种复合基底中实现SPP-LSPR耦合获得的。基于SPP-LSPR耦合机理,提出一种针对633 nm激光使用的金光栅/金纳米颗粒SERS基底的设计思路以及光栅和纳米颗粒的具体结构参数。为了验证设计方法的正确性,利用电子束光刻法和化学合成法分别制备了具有相应几何尺寸特征的金光栅和金纳米颗粒,并将它们复合在一起得到了光栅/纳米颗粒SPP-LSPR耦合型复合SERS基底,这个基底相比仅有金纳米颗粒制备的LSPR型SERS基底,在检测R6G溶液时浓度可以降低2个数量级,增强因子是后者的72倍,实验结果和时域有限差分（FDTD）法理论拟合的结果基本一致。     

聚合物共混过程中的小角激光光散射在线分析(英文)

利用激光小角背散射法对不相容聚合物体系聚苯乙烯／顺丁橡胶（ＰＳ／ＰｃＢＲ）共混过程中结构变化进行了在线分析。分散相颗粒尺寸由Ｄｅｂｙｅ散射理论中相关距离（αｃ）及平均直径（Ｄ描述）。由相关距离随组成比变化显示,在ＰＳ／ＰｃＢＲ共混质量比为５０／５０时出现相反转,即当ＰＳ含量小于５０％时ＰＳ为分散相,当ＰＳ含量大于５０％时ＰＳ为连续相,ＰＳ含量为５０％时体系为双连续相。分散相平均直径随共混时间延长而降低,其变化过程满足颗粒粉碎理论：ｄｔ＝－ｂＤ－ｎｄＤ,系数ｎ和ｂ与共混条件、共混材料特征及共混物两相含量等有关。共混物经不同共混时间后试样由扫描电子显微镜分析结果与激光小角背散射分析结果一致。     

一种制备金属硅化物的离子束新技术

一种制备金属硅化物的离子束新技术柳百新，朱德华，卢红波（清华大学材料科学与工程系，北京１０００８４）随着目前超大规模集成电路的迅速发展，要求器件尺寸按比例缩小，线宽也要求相应变窄。而多晶硅的薄层电阻极限为３０－６０／口，因此器件尺寸的进一步减小就被栅...     

Soot particle size distributions in a well-stirred reactor/plug flow reactor

A well-stirred reactor (WSR) followed by a plug flow reactor (PFR) is being used to study polycyclic aromatic hydrocarbon (PAH) growth and soot inception. Soot size distributions were measured using a dilution probe followed by a nano-differential mobility analyzer (Nano-DMA). A rapid insertion probe was fabricated to thermophoretically collect particles from the reactor for transmission electron microscopy (TEM) imaging. Results are presented on the effect of equivalence ratio on the soot size distributions obtained for fixed dilution ratio, the effect of dilution ratio on the soot size distributions obtained for fixed equivalence ratio, and the effect of temperature on the soot size distributions obtained for fixed equivalence ratio. In addition to particle sizing measurements, gas samples were analyzed by a gas chromatograph to determine the concentration of gaseous species in the PFR thought to be important in soot formation. Our soot size distribution measurements demonstrate that the mixing conditions in the flame zone affect whether or not a nucleation mode was detected in the size distribution.     

预混式双流体静电喷嘴喷雾特性及荷电性能

为实现高湿环境下脱硫塔内复杂烟气的高效除尘,设计了一种预混式双流体静电雾化喷嘴,并对其喷雾特性及荷电性能进行了试验研究。试验测量了喷雾粒径、锥角和荷质比等参数,通过量纲分析,得到了该喷嘴粒径分布与雷诺数Re的数学模型。试验结果表明:喷雾粒径随气液比(GLR)的增加呈指数减小,当气液比小于0.1时,喷雾粒径随气液比增加迅速减小,当气液比大于0.1时,喷雾粒径减小幅度趋于平缓;喷雾粒径随雷诺数的增加呈线性减小。喷雾锥角随着气液比增加呈先增大后减小的趋势,当气液比为0.1时喷雾锥角最大。气液比增加,喷雾荷质比增加,荷电效果逐渐增强。荷电电压的升高使得喷雾的单分散性提高,弥散空间逐渐增加。     

颗粒介质尺度效应的抗剪试验及物理机理分析

针对颗粒介质力学特性的颗粒尺度效应研究,选用土矿物颗粒制备不同颗粒尺度的抗剪试样,进行一系列直剪快剪和三轴抗剪试验,测得了不同颗粒粒径和体分比试样的变形曲线及剪应力强度;基于颗粒间微观作用力与重力比值和胞元体模型,首次从微观和细观角度解释颗粒尺度效应的物理机理.结果表明,随着介质中粗颗粒的比例增加和粒径减小,介质变形特性增强,剪应力强度也随之提高;体分比对变形和强度特性的影响比粒径的影响更加显著.基于介质特性尺度效应物理机理分析,提出衡量介质颗粒聚集和摩擦效应的微重比判别参数以及应变梯度和变形协调微裂纹引起颗粒尺度效应的细观机理解释;文中提出的胞元体模型大大减少了颗粒物质体系的计算自由度,为工业和工程设计的计算建模提供一种可行途径.     

光学头光束孔径匹配

光学头是光盘存储器的核心部件，光学头光束孔径匹配是光学头设计的一个至关重要的问题。必须合理地确定光源的光束口径与光盘物镜孔径比值，才能保证其光能量耦合效率，并获得较小的光斑尺寸和合理的焦深。本文以衍射光学为基础，详尽地分析了光束孔径匹配对光能耦合效率、光斑尺寸、物镜焦深的影响。     

Effects of benzene and naphthalene addition on soot inception in a well-stirred reactor/plug flow reactor

A well-stirred reactor (WSR) followed by a plug flow reactor (PFR) is being used to study soot inception. Soot size distributions were measured using two different dilution probes followed by a nano-differential mobility analyzer (nano-DMA). One of the dilution probes was developed for the PFR section, while the second probe was specifically developed for use in the WSR section. Results are presented on the effect of residence time on the soot size distributions obtained for fixed dilution ratio and equivalence ratio. In addition, a technique to inject aromatics and PAH species in the transition region between the WSR and PFR was developed. Results are presented on the effect of benzene and naphthalene on the soot size distributions obtained for differing seeding concentrations and residence times. The results demonstrate for the first time the sensitivity of the soot particle size distribution to the seeding of aromatic species in a WSR/PFR.     

Cassegrain激光发射系统的光路设计

为了提高激光探测系统激光的发射功率，在出射激光为基模的高斯光束的光路设计中，根据高斯光束经过光学系统的变换与传输特性，分析了系统采用Cassegrain望远镜时，其遮拦比以及入射光束束腰半径对光功率透过率的影响。通过具体的数值计算得出，随着遮拦比及入射光束束腰半径的增大，系统光功率透过率将减小，给出了望远镜遮拦比与发射孔径处光斑尺寸之间的最佳匹配关系，最后讨论了离焦误差（安装误差）为0.2mm时对出射光斑尺寸的影响。     

Size effect in (Pr,Sr,Ca)MnO3 manganites

It is well known that the radius of A-site ion is an important parameter to determine the magnetoresistance (MR) ratio of (R,A)MnO₃ manganites. However, the size effect of A-ion is inevitably mingled with the valence effect of Mn-ion when an R-ion of 3+ valence is replaced by an A-ion of 2+. In order to unravel the mystery of the unusually large MR in these materials, it is essential to distinguish the contribution of size effect from that of the valence effect. In this paper, size effect on various physical properties of two compound systems, Pr_0.7Sr_0.3−xCa_xMnO₃ and Pr_0.6Sr_0.4−yCa_yMnO₃ are reviewed extensively. Based on the transport data, the electronic state of Pr_0.7-system is quite different from that of Pr_0.6-system. However, the size effects in these two systems are very similar from the viewpoint of changing their magnetic state and MR ratio. Adopting the mechanism of composite polaron to explain our observations, CMR arises from the depression of spin–wave excitation and the size effect activates its influence on MR ratio via the changing of the effective mass of composite polaron.     

Three-dimensional numerical studies on the effect of the particle charge to mass ratio distribution in the electrostatic coating process

Charge to mass ratio is a crucial parameter that governs the behavior of particle trajectories in a charged cloud of particles. The complex nature of the charging process limits our ability to accurately determine the charging level when particles of varying size are present. Using a numerical approach, it is possible, however, to take into account predefined values for this parameter. In this paper, the average charge to mass ratio and the distribution of the charge to mass ratio in the coating of a flat target were systematically varied to demonstrate their effect on the motion of the charged particles. The results show that the transfer efficiency increases as the average charge to mass ratio increases. It was found that the transfer efficiency is a weak function of the average particle size in the range tested and that it increases as the width of the size distribution increases.     

Segment-sphere size ratio influence on the stability of a polymer-colloid mixture

The influence of the sphere to segment size ratio on the effective depletion layer thickness around a sphere and the resulting phase behaviour of a colloid-polymer mixture is considered. An analytical expression for the excluded volume between an ideal freely jointed chain and a sphere [L. Lue, J. Colloid Interface Sci. 202, 558 (1998)] allows the effect of polymer characteristics (chain length, segment/sphere size ratio) on the depletion interaction in polymer-colloid mixtures to be calculated. For both small and intermediate polymer-to-colloid size ratios the respectively gas-solid and gas-liquid coexistence curves shift to larger polymer coil volume fractions as the relative segment size increases. It is further demonstrated that the conditions for optimal (protein) crystallization are affected when the segment to sphere size is altered.