摘要:

AbstractThe Activation of ultrafine particles as the condensation nuclei, or heterogeneous nucleation of ultrafine particles, has been observed in various supersaturated vapors. Monodisperse NaCl, ZnCl2, Ag and silicon oil particles, 5–15 mm in diameter, are used as the condensation nuclei and water, hexanol, dibutyl phthalate (DBP) and di‐2‐ethyl‐hexyl sebacate (DEHS) are used as teh vapors. The supersaturated atmosphere is formed in the mixing type condensation nucleus counter (CNC) where a room temperature aerosol is mixed with warm air saturated by each vapor and the supersaturation ratio is controlled by changing the temperature of the saturated air. The number ratios of activated particles to total particles are observed at various supersaturation ratios. It is found that the activation of particles depends in a complicated manner on the combination of the substances of particles with condensing vapors, that is, activation in some particle‐vapor systems is explained by the Kelvin effect but not

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020121

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020122

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractAn aerosol sampling inlet has been developed to collect representative samples from the flowing gas stream. The inlet is referred to as the “Universal Aerosol Sampling Probe” because it is capable of efficient sampling over a wide range of free stream velocity without the need to change either the probe tip or sampling flow rate. It is a multi‐nozzle device consisting of one or more outer nozzles to extract a sample isokinetically and decelerate it from the relatively high stream velocity to a relatively low velocity. An inner nozzle is then used to extract a representative particle sample for delivery to the impactor or other particle collectors placed downstream. The approach enables a representative particle sample to be extracted at a fixed flow rate, irrespective of the velocity of the gas stream in which the probe is placed. The theoretical considerations leading to the design of such a universal probe are described. It is followed by the description of an experimental evalution of a prototype device. Good agreement was found between the experimental results and the theoretical predi

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020123

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractHigh capacity preseparators are used to reduce bounce and blow‐off of large particles in cascade impactors. In this paper, results are presented of a detailed analysis of the deposition of particles in two slightly different preseparators of the impactor‐type which are used in connection with the Andersen Stack Sampler. The advantage of using any preseparator for aerosols mixed with large particles (x10 μm) is clearly shown.A preseparator which is integrated into the impactor has the advantages of smaller overall size, accessible surfaces and, therefore, easier handling. The results of the study show that the reduction of unwanted particle losses is rather small when compared with a separate presepar

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020124

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractA measurement method that approximates the spatial distribution of inhomogeneously distributed aerosols in a limited measurement plane is described. It is based on the evaluation of a comparably small number of infrared extinction measurements taken from the measurement plane boundary. The measured data are processed by means of computed tomography. The results are displayed on a monitor in a colour‐coded picture of the aerosol‐“density”‐pattern. The basic design and the principal characteristics of the method are mathematically described and verified by simulation tests and practical results which are obtained from an experimental set up using smoldering wood as an aeros

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020125

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractA technique for measuring the fractal structure of the rugged boundaries exhibited by lunar dust and a cosmic dust fineparticle captured at the outer limits of earth's atmosphere are measured using a equipaced polygon construction measurement procedure. The measurement procedure is described and data illustrating the precision and accuracy of the method are presented. The technique can be automated using inexpensive equipment and is suitable for use in teaching laboratories. Comparative data is presented establishing that the equipaced polygon procedure generates data comparable to that generated by the structured walk exploration technique. It is suggested that the fractal structure of extra terrestrial fineparticles may be of interest not only to the cosmologist but to the mining engineer since lunar dust represents fractured material not subjected to attrition polishing. Models used to simulate the generation of soot in combustion processes are discussed and it is demonstrated that diffusion limited aggregation Monte Carlo routines generate an agglomerate that appears to have similar fractal structure to the cosmic dust fineparticle collected by Brownlee. The data presented also indicates that one should use caution when relating the fractal dimension of a projected perimeter profile in two dimensions to the three dimensional structure of a rugged fineparticle.

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020126

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractTo investigate the influence of the stress history on the yield limit a shear tester was developed, in which stresses or strains inx‐ andy‐direction can be applied independently of each other. Since there are no shear stresses on the boundary surfaces of the sample these stresses are principal stresses and the Mohr stress circles are known for each state of stress. First results from shear tests with limestone show a significant influence of the different ways of consolidation on the yield limit, i. e. the flow properties of a bulk solid will depend on the stress history. The flow function, however, which is essential for silo design, proves to be invariable of the stress hist

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020127

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractThe rheological behaviour of a fluidised bed of alumina powder was determined using a specially designed form of rotating viscometer. Several different geometries of the inner and outer cylinder were tested. In the machine the two cylinders can be rotated independently, in either direction, which enables both their relative velocity and absolute velocity to be varied. Thus, the torque on the inner cylinder, strain‐rate and the absolute velocity have been chosen as the consistency variables. Some examples of the derived consistency surface are given. The characteristics of these surfaces could be explained by assuming different states of structure, to which a certain mobility can be ascribed. It is proposed that any state of structure which can exist in the bed is an intermediate of two extremes the first being the immobile state which is elastic and has a yield value and the second being the dynamic state which behaves like a Newtonian flui

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020128

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

摘要:

AbstractA dual gas flow chromatographic method is proposed. In this method, two different gas streams are introduced separately, one as the carrier gas and the other as the gas for creating the adsorption equilibrium. The thermodesorbed absorbate is eluted by a pure carrier gas. The complete curve of adsorption isotherm can be determined easily; therefore, both the specific area and the pore size distribution can be obtained at ordinary pressure. In addition, this method can be easily changed into the continuous flow method given byNelsenandEggertsen[1]. The relationship amongR(rate) ‐V(volume) ‐A(area) ‐ α (ratio) in elution chromatography are investigated, and the volume of desorbed gas can be obtained fromVd=KRAddirectly withK= (αV)/(RA). The standardization for peak area is simplified and more convenient for the treatment by a microcomputer. Some results of specific surface area and pore size distribution by this method, and their comparison with those from other methods are given altogether, and the coincidence

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020129

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19850020130

出版商:WILEY‐VCH Verlag GmbH    

年代:1985

数据来源: WILEY