• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.2005-2013
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• 1996

Particle paths and flow fields in a prototype differential mobility analyzer (DMA) were numerically analyzed solving Navier-Stokes equation, electric field equation and particle motion considering viscous drag force, Coulomb force and polarization force. Analytically predicted particle diameters for the prototype DMA are in good agreement with the measured particle diameters within $\pm$1%. And the analytically predicted particle diameters are also in good agreement with numerical results for the prototype DMA.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1766-1771
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• 2003

House made differential mobility analyzer(DMA) is calibrated with NIST SRM 1691(300 nm PSL). Then the particle size and uncertainty for differential mobility analyzer(DMA) using the NIST SRM 1963(100 nm PSL). In result, calibration of prototype DMA is measured using 300 nm NIST SRM 1691, then sheath air flow was corrected 126.67 ㎤/s. Corrected sheath air flow is used in uncertainty measurement of prototype DMA. Uncertainty analysis is performed using NIST SRM 1963(100 nm PSL). The experimental result shows that NIST SRM 1963 is measured as 102.17 nm with a type A uncertainty of 0.33 nm.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.104-109
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• 2001

The time to measure the size distribution using Condensation Nuclei Counter(CNC) and Differential Mobility Analyzer(DMA) can be shortened by classifying particles ramping the DMA voltage exponentially and continuously. In measurement, particles sampled at different time are mixed together going through sampling tube and CNC. Because the size distribution is inversed by using detector responses to sampling time intervals in this accelerated method, the mixing effects give inversion errors to the size distribution. The mixing effects can be considered by appling the transfer function with mixing effects to the data inversion. The inversion considering this effects gives birth to the size distribution shifted to the opposite direction of the size scanning.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.2
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• pp.39-44
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• 2004

The present paper gives a review of the recent development of a differential mobility analyzer (DMA) available for both particle size measurements and production of monodisperse particles in the nanometer range. Operating principles of a general DMA are introduced as well as characteristics of highly functional DMAs such as those capable of classifying particles in a measurement range as broad as 1-1000nm at low pressures. Some examples of DMA applications are also described.

• Particle and aerosol research
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• v.10 no.1
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• pp.33-43
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• 2014

A differential mobility analyzer (DMA) has been widely used as a standard tool for classifying nanoparticles with a certain size. More recently, several new types of DMA have been tested in an attempt to produce size-monodisperse nanoparticles. It is a bit surprise to see how simple the working theory of the DMA is. Although the theory was demonstrated quite successful, no one can guarantee whether the theory still works in another geometry of the DMA. In this regard, we first investigated the validity of the theory under various working conditions and then moved to check the validity upon minor change in its design. For the valid test, we compared the results with those obtained from a computational fluid dynamics.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.20-20
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• 2002

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2006.04a
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• pp.55-56
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• 2006

This thesis describes the use of measured aerosol size distributions and size-resolved hygroscopic growth to examine the physical and chemical properties of several particle classes. The primary objective of this work was to investigate the optical and cloud forming properties of a range of ambient aerosol types measured in a number of different locations. The tool used for most of these analyses is a differential mobility analyzer / tandem differential mobility analyzer (DMA / TDMA) system developed in our research group. To collect the data described in two of the chapters of this thesis, an aircraft-based version of the DMA / TDMA was deployed to Japan and California. The data described in two other chapters were conveniently collected during a period when the aerosol of interest came to us. The unique aspect of this analysis is the use of these data to isolate the size distributions of distinct aerosol types in order to quantify their optical and cloud forming properties. I used collected data during the Asian Aerosol Characterization Experiment (ACE-Asia) to examine the composition and homogeneity of a complex aerosol generated in the deserts and urban regions of China and other Asian countries. An aircraft-based tandem differential mobility analyzer was used for the first time during this campaign to examine the size-resolved hygroscopic properties of particles having diameters between 40 and 586 nm. Asian Dust Above Monterey (ADAM-2003) study was designed both to evaluate the degree to which models can predict the long-range transport of Asian dust, and to examine the physical and optical properties of that aged dust upon reaching the California coast. Aerosol size distributions and hygroscopic growth are measured in College Station, TX to investigate the cloud nucleating and optical properties of a biomass burning aerosol generated from fires on the Yucatan Peninsula. Measured aerosol size distributions and size-resolved hygroscopicity and volatility were used to infer critical supersaturation distributions of the distinct particle types that were observed during this period. The predicted CCN concentrations were used in a cloud model to determine the impact of the different aerosol types on the expected cloud droplet concentration. RH-dependent aerosol extinction coefficients are calculated at a wavelength of 550 nm.

• Particle and aerosol research
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• v.5 no.2
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• pp.83-90
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• 2009

This paper describes a condensation-evaporation method (CEM) to produce size-controlled spherical silver nanoparticles by perturbing coagulation and coalescence processes in the gas phase. Polydisperse silver nanoparticles generated by the CEM were first introduced into a differential mobility analyzer (DMA) to select a group of silver nanoparticles with same electrical mobility, which also enables to make a group of nanoparticles with elongated structures and same projected area. These silver nanoparticles selected by the DMA were then in-situ sintered at ${\sim}600^{\circ}C$, and then they were observed to turn into spherical shaped nanoparticles by the rapid coalescence process. With the assistance of modified converging-typed quartz reactor, we can also produce the 10 times higher number concentration of silver nanoparticles compared with a general quartz reactor with uniform diameter. Finally, the spherical silver nanoparticles with 30 nm were electrostatically deposited on the surface of silicon substrate with the coverage rate of ~4%/hr. This useful preparation method of size-controlled monodisperse silver nanoparticles developed in this work can be applied to the various studies for characterizing the physical, chemical, optical, and biological properties of nanoparticles as a function of their size.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.95-95
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• 2008

• Journal of Environmental Science International
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• v.16 no.7
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• pp.793-798
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• 2007

During May of 2003, smoke from fires in the Yucatan Peninsula was transported across the Gulf of Mexico and into Texas where it caused significant enhancement in measured aerosol concentrations and reduced visibility. During this event, the formation and growth of aerosol particles has been observed by a differential mobility analyzer (DMA) / tandem differential mobility analyzer (TDMA) system to characterize the size distribution and size-resolved hygroscopicity of the aerosol. The most number concentration is by the particles smaller than 100 nm, but the integrated number concentrations for over 100 nm increased due to the aerosol growth. Hygroscopic growth factor increase from 1.2 to 1.4 for 25, 50, and 100 nm particles during the nucleating period. This distribution and the aerosol properties derived from the TDMA data were used to calculate the growth rate. Particle growth rates were in the range 1-12 nm/hr.