A Universal Calibration Curve for the TSI Aerodynamic Particle Sizer

Interest in mordenite as an inhalation hazard arose when it was discovered that the mineral exists in the subsurface of Yucca Mountain, NV, the site of a federally proposed nuclear waste repository. During preliminary geologic investigations at Yucca Mountain, workers performing air coring (dry-drilling) operations were potentially exposed to aerosols of mordenite. Mordenite is also increasingly used in industrial applications, such as cation exchange, molecular absorbency, and reversible dehydration. Concern that the fibrous nature of mordenite may present an inhalation hazard is supported by the ''Stanton Hypothesis," which states that the carcinogenicity of any fiber type depends upon dimension and durability rather than physicochemical properties. To date, little scientific literature is available on the inhalation health hazards of mordenite. This study initiates research in this area. Mordenite specimens collected from different geologic localities were analyzed macroscopically and microscopically. Mineral verification was performed using energy dispersive x-ray and x-ray diffraction analysis. Fibrous aerosols were generated to simulate aerosols created during air coring operations. Anderson cascade impactors were used to obtain aerosol mass median aerodynamic diameters. Electron microscopy of nucleopore filters allowed for individual aerosol fibers to be morphologically sized and applied to the Stanton Hypothesis for mesothelioma induction. Physical fiber dimensions were used to calculate aerodynamic diameters and to estimate pulmonary deposition. Results obtained from this study indicate that under similar conditions of aerosolization, using similar mordenite materials, inhalation of mordenite fibers could produce substantial deep-lung deposition.     

Calibration and Use of the Aerodynamic Particle Sizer (APS 3300)

The Aerodynamic Particle Sizer (APS) has been in use at the National Institute for Occupational Safety and Health (NIOSH) for over two years, beginning with a prototype model and more recently with a commercial version (Model 3300). The APS has been tested and used in a variety of laboratory and field situations. It has been a very useful instrument for testing aerodynamic sizing devices and provided a much needed means of rapid aerodynamic sizing of particles. Limits to the accuracy of the APS in determining aerodynamic diameter of particles were investigated.

The calibration of the APS was originally carried out by using monodisperse di-octyl phthalate (DOP) oil aerosol in the 3–15 μm range. Using a laser imaging system, the flattening of droplets into oblate spheroids was observed for larger particles (20–100 μm). The APS was recalibrated with solid latex particles and the DOP particles were measured to determine the effect of the droplet flattening. A 15 μm droplet is measured as being 20% smaller by the APS. A semiempirical equation was developed to fit the droplet deformation data. Particle measurement in the APS takes place largely outside the Stokes regime. Therefore, it has been predicted by Wilson and Liu (1980) that the measured diameters will be dependent on density. Monodisperse particles of density 1.15 and 2.15 were generated. In the range of 8–14 μm there was a difference of up to 8% in the measured size for particles of the same aerodynamic diameter. Particle coincidence can modify the measured size distribution in a different way than for other optical particle counters. The APS has circuitry to reduce the effects of coincidence that can also modify the meausred distribution. Calculations were carried out to simulate the effect of coincidence. Several potential problems and improvements for the APS were found.     

A Study of Density Effect and Droplet Deformation in the TSI Aerodynamic Particle Sizer

Effects of particle density and droplet deformation on the performance of a TSI aerodynamic particle sizer (APS) were studied using polystyrene latex (PSL), dioctyl phthalate (DOP), ammonium fluorescein (AF), fused aluminosilicate (FAP), and fused cerium oxide (FCO) monodisperse aerosols. Results indicated that, because of the sensitivity of the instrument, periodic cleaning of the APS inner nozzle is needed to maintain the consistency of its calibration curve. Density effects were experimentally confirmed with PSL, AF, FAP, and FCO aerosols of particle densities ranging from 1.05 to 4.33 g/cm³. Results, however, showed that this effect can only be experimentally detected for particles of density greater than 2 g/cm³ and aerodynamic diameter greater than 5 (μm. Effects of droplet deformation were studied with DOP.     

A Simple Iteration Procedure to Correct for the Density Effect in the Aerodynamic Particle Sizer

A simple iteration procedure is developed to correct for the density effect in the Aerodynamic Particle Sizer. The correction is appreciable for large particles due to ultra-Stokesian drag. For submicron particles, the correction is less than 4% and is caused by the change of the slip correction factor across the accelerating nozzle. Both corrections were included in the procedure to calculate a new calibration curve at a desired particle density from a standard calibration curve. The iterations converge very fast; a microcomputer program has been developed which can calculate a 20-point calibration curve in less than 5 seconds. The results of the present procedure are in excellent agreement with the supercomputer calculations of Ananth and Wilson (1987).     

Calibration of the Aerodynamic Particle Sizer 3310 (APS-3310) with Polystyrene Latex Monodisperse Spheres and Oleic Acid Monodisperse Particles

We have calibrated the new, extended-range aerodynamic particle sizer (model APS-3310, TSI, Inc.) with polystyrene latex monodisperse spheres and compared the response to that of oleic acid monodisperse particles from 2.5 to 38.7 μm in diameter. The results compare well with previous findings and cover a larger size range permitted by the new instrument.     

An Evaluation of Mass-Weighted Size Distribution Measurements with the Model 3320 Aerodynamic Particle Sizer

The ability of the Model 3320 aerodynamic particle sizer (APS) to make accurate mass-weighted size distribution measurements was investigated. Significant errors were observed in APS size distribution measurements with measured mass median aerodynamic diameters (MMADs) as much as 17 times higher than from cascade impactor measurements. Analysis of APS correlated time-of-flight and light scattering data indicated that the MMAD distortions were due to a few anomalous large particle measurements (～0.1% of the total measurements) with surprisingly low scattered light. Computational fluid dynamics modeling indicated that these anomalous measurements were due to particles that deviated from the intended aerosol pathway and recirculated through the APS measurement volume at low velocities leading to erroneous large particle measurements. A technique for removing erroneous measurements based on correlated aerodynamic diameter and light scattering values is presented. When this technique was used, APS and cascade impactor size distribution measurements agreed well.     

Behavior of Compact Nonspherical Particles in the TSI Aerodynamic Particle Sizer Model APS33B: Ultra-Stokesian Drag Forces

The aerodynamic behavior of aggregates consisting of uniform polystyrene latex (PSL) spheres and unaggregated cuboidal Natrojarosite particles in a TSI aerodynamic particle sizer (Model APS33B) has been studied. In initial tests, monodisperse PSL micro-spheres ranging from 0.3 to 7 μm in geometric diameter were generated from aqueous suspensions using a Lovelace nebulizer. APS33B responses for these uniform-sized particles showed multiple peaks. The major (primary) peak, which resulted from the smallest particle, corresponded to the unaggregated single spheres (singlets); the second, third, and fourth peaks were identified as doublets, triangular triplets, and tetrahedral quadruplets, respectively. Both doublets and triplets moved with their long axes in perpendicular (maximum drag) orientation to the flow direction in the APS33B. In contrast, the tetrahedral particles were isometric and had the same dynamic shape factor (drag resistance) for all three primary orientations. The particle Reynolds numbers (Re _p) for these particles were calculated and ranged from 0.2 to 30 in the sensing volume of the APS33B detector (i.e., ultra-Stokesian conditions). Ultra-Stokesian drag forces for all three types of aggregates were, therefore, estimated and expressed as a function of an empirical factor (1 + aRe ^b _p) to the Stokesian drag force. The ultra-Stokesian drag of a Natrojarosite particle was measured in the range 20 Re _p < 50 and could be described with a similar expression. This approach facilitates the study of the dynamic behavior of nonspherical particles and yields new information about the characteristics of drag forces in the ultra-Stokesian regime     

Calibration of the TSI 3760 Condensation Nucleus Counter for Nonstandard Operating Conditions

The counting efficiency of the TSI 3760 condensation nucleus counter was tested for operation at (a) reduced flow rates and (b)reduced pressures. Circumstances often dictate that these conditions are encountered in sampling atmospheric aerosols. Results indicate that the counting efficiency of the instrument for particles in the range of 0.02–0.1 μm in diameter is not attenuated in operation at flow rates between 0.2 and 1.4 L/min. Furthermore, there does not appear to be any attenuation in the instrument's counting efficiency when operated at pressures between roughly 250 mb and atmospheric pressure.     

MK-101催化剂作用下操作条件对甲醇合成的影响研究

实验模拟低压甲醇合成工艺流程,在压力4～7MPa,温度210～270℃,空速6000～15000h-1,CO2浓度4.5%～14.3%的实验条件下,选用MK-101催化剂,考察了温度、压力、空速和CO2浓度对甲醇合成反应的CO、CO2的单程转化率和甲醇时空收率的影响。     

A Simple and Efficient Method for the Synthesis of 2-Aminothiazoles Under Mild Conditions

NEt₃ was found to be a simple, mild, and efficient catalyst for the synthesis of 2-aminothiazole derivatives from the reaction of different ketones, thiourea, and iodine in EtOH media under mild conditions for the first time. Present methodology offers several advantages, such as simple procedure, shorter reaction times, and milder conditions, and takes place at reflux temperature, with operational simplicity and with excellent yields.     

不同工艺条件对卤化银乳剂颗粒粒径分布的影响

实验研究了乳化过程中,各种工艺条件的不同变化对乳剂颗粒粒径分布及性能的影响。通过扫描电镜及粒径分布测试设备的测定,对不同条件乳化后的颗粒分布及大小变化状态进行了观察、测试及数据分析,结果表明,不同工艺条件的变化,对颗粒分布、大小产生了明显的变化,对感光度及性能均产生一定的影响。     

用原子吸收光谱法测定镁的最佳操作条件研究

主要研究了测定波长、工作电流、燃烧器高度、光谱通带、燃气与助燃气流量等操作条件对测定陶瓷中镁含量的影响．确定了最佳的测试条件。     

热催化可燃气体检测仪在不同环境下的性能探究

针对热催化式可燃气体检测仪的工作准确性及可靠性进行了研究,通过相同测试条件下热催化可燃气体检测仪示数和色谱分析可燃气体的浓度对比值,验证热催化式可燃气体检测仪数值的准确性。并且通过改变不同的检测条件,探究热催化式可燃气体检测仪的适用条件。实验结果证明热催化式可燃气体检测仪可以用于定性检测实际过程,并提出其在使用过程中的注意事项。     

A Microscope-Based Particle Counting System for Determining Collected Aerosol Mass During the Calibration of a Cascade Impactor

It is shown that a simple optical particle-counting system can be efficiently and accurately used for determining the mass of collected particles during the calibration of a cascade impactor. For particles larger than 1 mu m in diameter, the limit of detection was enhanced by a factor 5 compared to the traditional spectrophotometer-based method.     

一种计算间歇过滤机最佳操作周期的新方法

通过引入当量非过滤时间的概念,导出了间歇过滤机最佳操作周期的计算公式,可以快速准确地计算间歇过滤机的最佳操作周期和最大生产能力,附有计算举例。     

A Concentration Rebound Method for Measuring Particle Penetration and Deposition in the Indoor Environment

Continuous, size resolved particle measurements were performed in two houses in order to determine size-dependent particle penetration into and deposition in the indoor environment. The experiments consisted of three parts: (1) measurement of the particle loss rate following artificial elevation of indoor particle concentrations, (2) rapid reduction in particle concentration through induced ventilation by pressurization of the houses with HEPA-filtered air, and (3) measurement of the particle concentration rebound after house pressurization stopped. During the particle concentration decay period, when indoor concentrations are very high, losses due to deposition are large compared to gains due to particle infiltration. During the concentration rebound period, the opposite is true. The large variation in indoor concentration allows the effects of penetration and deposition losses to be separated by the transient, two-parameter model we employed to analyze the data. For the two houses studied, we found that as particles increased in diameter from 0.1 to 10 w m, penetration factors ranged from ～1 to 0.3 and deposition loss rates ranged from 0.1 and 5 h m 1 . The decline in penetration factor with increasing particle size was less pronounced in the house with the larger normalized leakage area.     

The Effects of Operating Conditions on the Performance of a Solid Oxide Steam Electrolyser: A Model‐Based Study

To support the development of hydrogen production by high temperature electrolysis using solid oxide electrolysis cells (SOECs), the effects of operating conditions on the performance of the SOECs were investigated using a one‐dimensional model of a cathode‐supported planar SOEC stack. Among all the operating parameters, temperature is the most influential factor on the performance of an SOEC, in terms of both cell voltage and operation mode (i.e. endothermic, thermoneutral and exothermic). Current density is another influential factor, in terms of both cell voltage and operation mode. For the conditions used in this study it is recommended that the SOEC be operated at 1,073 K and with an average current density of 10,000 A m^–2, as this results in the stack operating at almost constant temperature along the cell length. Both the steam molar fraction at the inlet and the steam utilisation factor have little influence on the cell voltage of the SOEC but their influence on the temperature distribution cannot be neglected. Changes in the operating parameters of the SOEC can result in a transition between endothermic and exothermic operation modes, calling for careful temperature control. The introduction of air into the anode stream appears to be a promising approach to ensure small temperature variations along the cell.     

A 3D Smoothed Particle Hydrodynamics Method with Reactive Flow Model for the Simulation of ANFO

ANFO (ammonium nitrate/fuel oil) is a widely used bulk industrial explosive mixture that is considered to be highly “non‐ideal” with long reaction zones, low detonation energies, and large failure diameters. Thus, its detonation poses great challenge for accurate numerical modeling. Herein, we present a numerical model to simulate ANFO based on improved smoothed particle hydrodynamics (SPH) method, which is a mesh‐free Lagrangian method performing well in simulating situations consist of moving interface and large deformation, as happened in high‐velocity impact and explosion. The improved three‐dimensional SPH method incorporated with JWL++ model is used to simulate the detonation of ANFO. Good agreement is observed between simulation and experiment, which indicates that the proposed method performs well in prediction of behavior of ANFO.