ELPI Response and Data Reduction I: Response Functions

Response functions of the ELPI impactor with normal and porous substrates are presented together with fit functions to describe particle collection. In addition to primary collection efficiency, fits for the secondary collection mechanisms, diffusion, image charge force, and space charge field are presented. Charging efficiency for different configurations is also presented. Presented response functions can be used in data reduction and inversion of ELPI data.     

On the Importance of Density in ELPI Data Post-Treatment

This study compared number and mass concentrations obtained using two reference devices, a scanning mobility particle sizer (SMPS) and a tapered element oscillating microbalance (TEOM), with those calculated from raw electrical low-pressure impactor (ELPI) data. ELPI data post-treatment was performed assuming a mobility-dependent effective density and three constant densities: an average effective density, the raw material density, and the standard density (i.e., 1 g/cm³). For the mass concentration, whatever the density considered, the ELPI-determined value was close to the reference. For the number concentration, results indicate good agreement between SMPS and ELPI number concentrations when considering effective density and, to a lesser extent, average effective density. In contrast, with the raw material density or standard density, large uncertainties in number concentration measurements were produced. A good estimation of number concentration was obtained based on ELPI data when assuming a standard density only when there was fortuitous agreement between the number tested aerosol size distribution and its mobility-dependent effective density. Thus, contrary to what some authors recommend, a standard density cannot be universally used.

Copyright © 2015 American Association for Aerosol Research     

Electrical Properties and Defect Structure of Zirconia: II, Tetragonal Phase and Inversion

The defect structure of tetragonal zirconia was investigated by measuring the temperature and oxygen partial pressure dependence of the electrical conductivity and the electronic transference number. Tetragonal zirconia was a mixed electronic and ionic conductor under all conditions studied. The n -type electronic conductivity observed at high temperatures and low oxygen partial pressures was interpreted on the basis of a defect model involving fully ionized oxygen vacancies. The conductivity change associated with the monoclinic ⇒ tetragonal phase transformation was isothermal, but the rate of change was a function of the thermal history and the method of preparation of the sample.     

Electronic Structure and Catalytic Properties of Transition Metal Nanoparticles: The Effect of Size Reduction

Size reduction of metal particles results in the formation of nanoparticles having short-range order and metastable state. Modeling of the nanoparticles can be obtained by various approaches. The major arrangement is the use of a model support on which metal nanoparticles can be created in a controlled way. Another approach is the use of amorphous alloy as precursor in which the ensemble of active sites (normally small metal nuclei embedded into amorphous matrix) is created. The modeling will be illustrated through the paper using SiO₂/Si(100) on which several transition metals will be deposited by pulsed laser deposition. Ultraviolet photoelectron spectroscopic technique as well as transmission electron microscopic technique will be utilized in characterization of the samples. CO chemisorption and CO oxidation as test reaction will be applied to show the connection between catalytic behavior and electronic properties or morphology of nanoparticles.     

Size Distributions of Motor Vehicle Exhaust PM: A Comparison Between ELPI and SMPS Measurements

Particle size measurements using the electrical low pressure impactor (ELPI) and scanning mobility particle sizer (SMPS) are compared from the perspective of characterizing the particulate matter in motor vehicle exhaust. Both steady state vehicle operation and transient drive cycles are considered, and both gasoline and diesel fueled vehicle emissions are compared. Although the ELPI and SMPS measure different physical properties, respectively, the aerodynamic diameter and mobility diameter, the steady state particle size distributions are in close agreement, except for the 37 nm impactor stage of the ELPI which may overestimate particle number by up to a factor of two relative to the SMPS. This has little effect on the volume, or mass, weighted distribution. These, too, are generally in good agreement, though discrepancies appear at large particle size due to multiple charging effects in the SMPS and to electrometer offsets and the small particle loss correction in the ELPI. Selecting particles based on their electrical mobility with the SMPS, and then measuring their aerodynamic diameter with the ELPI, reveals that diesel particulate matter with well-specified mobility diameter exhibits a wide range in aerodynamic diameter and, therefore, also in effective density. Over transient drive cycles, the ELPI provides second by second particle distributions, whereas the SMPS must be run in a fixed particle size mode and size distributions constructed from repeated tests. The ELPI registers higher instantaneous PM emission rates during transients than the SMPS due to the faster time responses of the ELPI. The time integrated ELPI and SMPS size distributions, however, remain in good agreement. The relative merits of the two instruments for steady state and transient tests are discussed.     

Properties of Aluminoborate Glasses of Group II Metal Oxides: II, Electrical Properties

The dc resistivities and dielectric properties at 0.060 to 100 kc and temperatures of 100° to 500° C have been determined for the Group II aluminoborate glasses. These glasses have resistivities as high as 10^11.5 ohm-cm at 450°C and activation energies ranging from 26 to 42 kcal per mole. The covalent character of the Group II-B aluminoborates is demonstrated.     

Physical Properties of Triglycerides II: Dispersion

The liquid state dispersions of a number of triglycerides at 20° C and at 40° C are presented. From these data we have calculated the Lorentz-Lorenz and the Gladstone-Dale molar dispersions. A previously derived general equation is used to compute a quantitative relation between the dispersion of a mixture of triglycerides and its refractive index, density, and iodine value.     

叠前弹性参数反演在塔木察格的应用

地震资料的处理和反演从叠后走向叠前是现行地震勘探的发展趋势。以叠前时间偏移和AVO反演技术相结合的叠前弹性参数反演方法是当今研究的热点,该方法为岩性和隐蔽性油气藏的勘探提供了较为有效的识别方法。依据弹性波传播的基本理论和平界面反射透射的Zoeppritz方程,本文给出了计算弹性参数的三项公式。算法实现是先将叠前时间偏移的CRP道集转化为角度道集,然后用最小平方法进行优化求解,得到弹性参数的各属性剖面,最后对计算结果进行反演和分析以对储层的含油气性进行有效预测。本文给出了理论模拟数据的反演计算,其反演结果的计算误差较小,可见本文给出的弹性参数反演计算的精度是很高的。将文中给出的叠前弹性参数反演方法应用于海拉尔—塔木察格盆地研究区块,与现行商业软件就纵波阻抗反演结果进行对比分析,本文方法的分辨率较高,且由钻井资料证实该方法对储层的预测精度较高。理论和实际地震数据的反演计算表明本文算法具有高分辨率、高精度和实用性强的特点。     

The Effects of Surfactant Additives on Properties and Morphologies of Cellulose Acetate Membranes Prepared by Phase Inversion

Theoretical Foundations of Chemical Engineering - Cellulose acetate is frequently used in reverse osmosis (RO) and ultrafiltration (UF) applications. In the present study, effects of different...     

聚氨酯相转化法成膜的性能及其分形描述

采用液-液相转换法通过不同的非溶剂(水、甲醇、乙醇和异丙醇)制备聚氨酯微孔膜,测定了膜的断面形态、孔隙率、孔径、透气性和力学性能。结果表明:聚氨酯膜较容易在醇类非溶剂中形成均一形貌的多孔结构,4种非溶剂所制备聚氨酯膜的孔径由大到小的顺序依次为水、甲醇、异丙醇和乙醇,透气性从大到小的顺序依次是甲醇、异丙醇、乙醇和水,拉伸强度和断裂伸长率从大到小的顺序依次是乙醇、异丙醇、甲醇和水。用分形数学定量表示微孔结构,发现按分形模型计算出的结果与实验测试结果相符。     

Fatty Acid Composition and Some Physicochemical Properties of Oils from Allanblackia gabonensis and A. stanerana Kernels

The physicochemical properties and chemical composition of oils extracted from two varieties of mature seeds of Allanblackia gabonensis and A. stanerana were assessed. The physicochemical properties of oils from Allanblackia gabonensis and A. stanerana were respectively 5.35 and 22.023 % for the water content; 68.15 and 69.87 % for the extraction yield on a dry basis; 0.35 and 0.30 mg KOH/g oil for the acid index; 35.57 and 29.75 g of I₂/100 g oil for the iodine index; 1.3740 and 1.4150 for the refractive index. The fatty acid profile of those oils showed respectively four saturated fatty acids 60.61 and 70.94 %, two monounsaturated fatty acids 37.46 and 28.22 %, two polyunsaturated fatty acids 0.82 and 0.81 % for Allanblackia gabonensis and A. stanerana oils respectively. In both cases, fatty acids C18:0 and C18:1 were dominant. Most of the physicochemical properties showed significant variation (P < 0.05) from one oil to other, the difference being insignificant (P > 0.05) between the two chemical compositions. The analysis of these characteristics showed interesting application features for these oils.     

Nanocrystalline Aluminum Nitride: II, Sintering and Properties

Nanocrystalline aluminum nitride powders obtained from gas condensation and in situ nitridation in a forced-flow reactor have been sintered successfully without pressure or additives. The resulting densified pellets showed good thermal conductivity and low oxygen content. A comparison of the improvement in densification with micrometer-size and nanocrystalline yttria additives was undertaken and it was found that the nanocrystalline yttria decreased the sintering temperature significantly. Besides spherical nanoparticles, needle-shaped nanocrystalline aluminum nitride particles that resulted in highly textured compacts when hot pressed could also be produced.     

Comparison of Exhaust Particle Number Measured by EEPS,CPC, and ELPI

An Engine Exhaust Particle Sizer (EEPS) Spectrometer, a Condensation Particle Counter (CPC) and an Electrical Low Pressure Impactor (ELPI) were used to determine the exhaust particle number of a Diesel engine on steady speeds and on the New European Driving Cycle (NEDC), upstream and downstream several Diesel Particulate Filters (DPF). In order to obtain different particle numbers, five DPFs with different porosity were used. The above three instruments give quite similar total particle numbers on steady speeds and on the NEDC for the tests upstream DPF. Downstream DPF, EEPS reaches its limit of measurement; however, the total particle numbers obtained by this instrument are still close to the particle numbers obtained by CPC and ELPI. The particle number versus time of the three instruments are quite close in the case of the NEDC measurements upstream DPF. Downstream DPF, CPC, and ELPI give quite similar signals, but EEPS reached its limits of detection. Upstream DPF, ELPI, and EEPS determine quite similar median diameters in the case of steady speeds, despite their different shape in particle size distribution.     

EPDM／St-AN相反转乳液接枝共聚合及AES的结构与性能

以过氧化二苯甲酰为引发剂,正庚烷为溶剂,用"相反转"乳液共聚合法合成了三元乙丙橡胶和苯乙烯-丙烯腈(St-AN)的接枝共聚物(EPDM-g-SAN),并与苯乙烯-丙烯腈共聚物(SAN)熔融共混(共混物简称 AES)。研究了丙烯腈 AN 在共单体中的含量和 EPDM/St-AN 的质量比对单体转化率、接枝率和接枝效率的影响。冲击实验表明,AN 含量为35%～40%时,接枝率约为35%,所制备的 EPDM-g-SAN 对 SAN 树脂有显著的增韧作用,增韧后所制得的工程塑料 AES 的悬臂梁缺口冲击强度最高可达50.7 kJ/m~2;差示扫描量热分析表明 AES 存在界面相;动态热力学分析表明 EPDM-g-SAN 与 SAN 树脂之间的相界面结合紧密;透射电镜和扫描电镜分析表明,AN 在共单体中的含量为35%时,EPDM-g-SAN 在 SAN 树脂基体中有良好的分散性,相界面模糊,因而两相结合紧密,其增韧机理以空穴化为主兼有剪切屈服。     

Adaptation of the Twomey Algorithm to the Inversion of Cascade Impactor Data

The Twomey nonlinear iterative algorithm for inverting aerosol size distribution data has been adapted for use with the Berner cascade impactor. Key factors affecting the performance of the algorithm have been identified. A procedure producing accurate inversions without artifacts includes establishing a set of continuous and smooth kernel functions based on measurements of the impactor cutoff characteristics, using modified weighting functions, placing constraints on the first-guess distribution, treating zero values and the ends of the distribution, and setting stopping criteria based on experimental errors. This general approach should be useful in solving inversion problems for other cascade impactors. The routine was extensively tested with numerically created test distributions and a large data base of ambient aerosol samples. An extended version of the program separates the inverted size distribution into a spectrum of lognormal distributions. Lognormal parameters from 44 ambient nitrate size distributions have been compared to the results of the inversion program of Dzubay and Hasan.     

Thrombin-Binding Aptamer with Inversion of Polarity Sites (IPS): Effect on DNAzyme Activity and Anticoagulant Properties

In this work we examined the properties of thrombin-binding aptamer (TBA) modified by the introduction of inversion of polarity sites (IPS) in order to assess the effect of modification on the activation of TBA to serve as DNAzyme with peroxidase-like activity. Two oligonucleotides were designed to possess one (IPS1) or three (IPS2) inversion sites. TBA typically forms antiparallel G-quadruplexes with two G-tetrads, which exhibits very low DNAzyme peroxidise activity. DNAzyme activity is generally attributed to parallel G-quadruplexes. Hence, inversion of polarity was introduced in the TBA molecule to force the change of G-quadruplex topology. All oligonucleotides were characterized using circular dichroism and UV-Vis melting profiles. Next, the activity of the DNAzymes formed by studied oligonucleotides and hemin was investigated. The enhancement of peroxidase activity was observed when inversion of polarity was introduced. DNAzyme based on IPS2 showed the highest peroxidase activity in the presence of K⁺ or NH₄⁺ ions. This proves that inversion of polarity can be used to convert a low-activity DNAzyme into a DNAzyme with high activity. Since TBA is known for its anticoagulant properties, the relevant experiments with IPS1 and IPS2 oligonucleotides were performed. Both IPS1 and IPS2 retain some anticoagulant activity in comparison to TBA in the reaction with fibrinogen. Additionally, the introduction of inversion of polarity makes these oligonucleotides more resistant to nucleases.     

Investigation of SiC-AlN: Part II, Mechanical Properties

SiC/AIN composites with controlled interfacial solid solution were employed in the present work for investigating the effects of interfacial bonding and A1N polytypes on the mechanical properties. Platelike A1N polytypes and interfacial bonding were found to have substantial effects on the flexural strength, hardness, and fracture toughness.     

Hot-Working of Aluminum Oxide: II, Optical Properties

Polycrystalline Al₂O₃ fabricated into plates or shapes by hot-working techniques exhibits high in-line transmittance from 0.4 to 5.5 μm. Examination of the product by an inverse pole figure technique demonstrated a strong {0001} texture normal to the pressing direction for both equiaxed and textured microstructures. The crystallographic texture was attributed to the dominance of basal slip in deformation. A comparison of transmissivity in the 2 principal directions of a forged plate strongly suggested that a reduction of birefringence resulting from the crystallographic texture was partially responsible for the high transmissivity. The absorption coefficient at 4.5 μm was 0.15 mm^-1, ∼ that for sintered Al₂O₃ and 5 times that for sapphire     

Redox Properties of Cobalt Nitrides for NO Dissociation and Reduction

Redox reactions catalyzed by cobalt nitrides should be carried out below the critical temperature at which bulk oxidation of the nitrides occurs. Then, a catalytic redox cycle could be established by introducing a reducing agent into the system below this temperature so that the oxygen could be removed prior to the occurrence of bulk oxidation.