• Journal of the Korean Magnetic Resonance Society
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• v.13 no.1
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• pp.35-55
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• 2009

The two correlation times previously obtained in our coupled $^{13}C$ relaxation measurement for the methyl group in 2,6-dichlorotoluene may be used as a criterion for evaluating the reorientation dynamics of an internal rotor. We numerically tested an extended diffusion model and the Smoluchowski diffusion equation to see how the rotational inertial effect and jump character contribute to the internal correlation time ratio of the internal rotor. We also analytically solved the general jump model with three different rate constants in a sixfold symmetric potential barrier. By assuming that the internal rotation of the methyl group in 2,6-dichlorotoluene can be described in terms of jumps among sixfold harmonic potential wells, we can conclude that the jump model satisfactorily reproduce the experimental data and the rate for sixfold jump is at least 1.53 times as great as that of a threefold jump.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.3
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• pp.65-77
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• 1995

The kinetics of flocculation of heterodisperse suspension like those in water treatment plants and natural water system are usually described by the Smoluchowski equation, which incorporates collision frequency functions for particle collisions by Brownian motion, fluid shear, and differential sedimentation. These collisionfrequeney functions have been based on a rectilinear view of collisions, i.e., one that ignores short-range forces and changes in fluid motion as particles approach one another. In this research, a curvilinear approach, i.e., one that accounts for hydrodynamic forces and particle interaction in the collision of two different size particles is developed. Collision efficiency factors of each mechanism can be calculated by trajectory analysis (fluid shear and differential sedimentation) or the solution of diffusion equation (Brownian motion). The results are presented as a set of corrections to the rectilinear collision frequency functions for each mechanism.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.597-602
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• 2000

In a MEMS(micro-electro mechanical system), the fluid may slip near the surface of a solid and have a discontinuous temperature profile. A numerical prediction in this slip flow region can provide a reasonable guide for the design and fabrication of micro devices. The compressible Navier-Stokes equation with Maxwell/smoluchowski boundary condition is solved for two simple systems; couette flow and pressure driven flow in a long channel. We found that the couette flow could be regarded as an incompressible system in low speed regions. For the pressure driven flow system, we observed nonlinear distribution of pressure in the long channel and numerical results showed a good agreement with the experimental results.

• Journal of Korean Society for Quality Management
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• v.13 no.1
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• pp.26-30
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• 1985

In the light of the properties of colloids, in the surface of disperse phase and dispersion, there exist specific characters such as adsorption or electric double layer, which seems to play important roles in determining the physiochemical properties in the dyeing system. Nylon, wool and silk, the typical amphoteric fibers were dyed with Acid dye and various combinations were prepared by combining pH, temperature and dye concentration, in order to generate flowing electric potential which were measured by microviolt meter and specific conductivity meter. The results were transformed to Zeta potential by Helmholtz-Smoluchowski formular and to surface electric charge density by Suzawa formular, surface dye amount, and effective surface area of fibers, and these data were statistically analysed by principle component analysis.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.33 no.2
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• pp.105-110
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• 2007

The stability of titanium dioxide dispersion was evaluated by zeta ($\zeta$) potential and we intended to apply it for improvement of dispersion stability. Both theories related to $\zeta$ potential (electric double layer, electrophoresis, isoelectric point and electroosmosis) and a method to measure $\zeta$ potential were explained in this study. The change in $\zeta$ potential of $TiO_2$ dispersion was measured by means of Henry's function of Helmholtz-Smoluchowski's equation (H-S equation). The $\zeta$ potentials of $TiO_2$ dispersion were negative in all measured pH values ($3.0{\sim}9.0$), and absolute values of $\zeta$ potentials of $TiO_2$ increased as pH values increased. $TiO_2$ dispersion was maintained in pH 8.0 and 9.0 respectively. From these results, we suggest that $\zeta$ potentials have an effect on $TiO_2$ dispersion and absolute value of $\zeta$ potentials played an important role in the stability of $TiO_2$ dispersion in aqeous medium.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.941-952
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• 2012

In the present contribution the Encounter Theory (ET) (the prototype of the classical Collision Theory in rarefied gases) concepts for widely occurring diffusion assisted irreversible bulk reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in liquid solutions examined by the authors in the literature are analyzed and compared with each other for these different types of reactions. It is shown that for a particular case of equal initial concentrations $[A]_0=[B]_0$ in the reaction A + B ${\rightarrow}$ C, when the kinetics of both reactions A + A ${\rightarrow}$ C and A + B ${\rightarrow}$ C in the framework of formal chemical kinetics and ET are the same, the accumulation of macroscopic correlations breaking the concepts of independent encounters and leading to the Generalized Encounter Theory (GET) are drastically different. The influence of the force interaction and the decay of nonstable reactants on the time behavior the macroscopic correlations is also briefly discussed.

• Journal of the Korean Society of Visualization
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• v.8 no.4
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• pp.13-18
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• 2010

This paper presents an experimental study on the performance of a micro-mixer using AC electro-osmotic flow. The microchannel is made of PDMS for the side and top walls and glass patterned with ITO for the bottom wall. We first investigated the effect of the applied potential as well as the frequency on the slip velocity. We have found that the slip velocity is roughly proportional to the applied voltage in line with the Helmholtz-Smoluchowski equation and there is an optimum frequency at which the slip velocity becomes maximized. To find the optimum parameters for mixing device we tested our device for various design parameters. It turned out that the best mixing effect is obtained approximately when the electrode angle is $30^{\circ}$, electrode width $200\;{\mu}m$, and the frequency of power supply 700 Hz.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.141-146
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• 2007

We examine the wall contact of a $3\;{\mu}m$ tethered DNA chain's free end under shear with a focus on developing schemes for double-tethering in the application of making scaffolds for molecular wires. At this scale our results are found to be highly dependent on small length scale rigidity. Chain-end-wall contact frequency, mean fractional extension deficit upon contact, and standard deviation in extension upon contact are examined for scaling with dimensionless flow strength, Wi. Predictions made using a one dimensional approximation to the Smoluchowski equation for a dumbbell and three dimensional dumbbell simulations produce extension deficit, standard deviation, and frequency scaling exponents of -1/3, -1/3, and 2/3, respectively whereas more fine-grained Kratky-Porod (KP) simulations produce scaling exponents of -0.48, -0.42, and 0.76. The contact frequency scaling of 2/3 is derived from the known results regarding cyclic dynamics Analytical scaling predictions are in agreement with those previously proposed for ${\lambda}-DNA$. [Ladoux and Doyle, 2000, Doyle et al., 2000]. Our results suggest that the differences between the dumbbell and the KP model are associated with the addition of chain discretization and the correct bending potential in the latter. These scaling results will aide future exploration in double tethering of DNA to a surface.

• Journal of Sensor Science and Technology
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• v.31 no.3
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• pp.175-179
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• 2022

The physical properties of biomaterials are important for their isolation and separation from body fluids. In particular, the precise evaluation of the multi-physical properties of single biomolecules is essential in that the correlation between physical and biological properties of specific biomolecule. However, the majority of scientific equipment, can only determine specific-physical properties of single nanoparticles, making the evaluation of the multi-physical properties difficult. The improvement of analytical techniques for the evaluation of multi-physical properties is therefore required in various research fields. In this study, we developed a motion-tracking algorithm to evaluate the multi-physical properties of single-nanoparticles by analyzing their behavior. We observed the Brownian motion and electric-field-induced drift of fluorescent nanoparticles injected in a microfluidic chip with two electrodes using confocal microscopy. The proposed algorithm is able to determine the size of the nanoparticles by i) removing the background noise from images, ii) tracking the motion of nanoparticles using the circular-Hough transform, iii) extracting the mean squared displacement (MSD) of the tracked nanoparticles, and iv) applying the MSD to the Stokes-Einstein equation. We compared the evaluated size of the nanoparticles with the size measured by SEM. We also determined the zeta-potential and surface-charge density of the nanoparticles using the extracted electrophoretic velocity and the Helmholtz-Smoluchowski equation. The proposed motion-tracking algorithm could be employed in various fields related to biomaterial analysis, such as exosome analysis.

• Textile Coloration and Finishing
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• v.1 no.1
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• pp.19-25
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• 1989

In past, dye diffusion and dyeing rate in fibers have been emphasized in dyeing phenomena. However, in the light of the properties of colloids in the surface of disperse phase and dispersion, there exist specific characters such as adsorption or electric double layer, which seems to play important roles in determining the physiochemical properties in the dyeing system. Electrostatic bonding, hydrogen bonding and Van der Waals adsorption are common in dyeing as well as covalent bonding. Particularly, electrostatic bonding is premised on the existance of ionic radicals in fibers. The present study was aimed to clarify the electrokinetic phenomena of dyeing through the role of electric double layer by ion in amphoteric fibers with different ionic effects under different pH. Spectrophotometric analysis method was used to compare dyeing condition of surface, which can be detected by electrokinetic phenomena and the inner of fibers after deceleration of dyed fibers. Nylon and wool, the typical amphoteric fibers were dyed with monoazo acid dyes such as C.I. Acid Orange 20, and C.I. Acid Orange 10. Various combinations were prepared by combining pH, temperature and dye concentration, in order to generate streaming electric potential which were measured by microvolt meter and specific conductivity meter. The results were transformed to zeta potential by Helmholtz-Smoluchowski formular and to surface electric charge density by Suzawa formular, surface dye amount, and effective surface area of fibers. The amount of dyes of inner fibers were also measured by the Lambert-Beer’s law. The main results obtained are as follows. 1. By measuring zeta pontential, it was possible to detect the dyeing mechanism, surface charge density, surface dye amount and effective surface area concerning dye adsorption of the amphoteric fibers. 2. Zeta pontential increases in negative at low pH and high dye concentration in the process of dyeing. This implied that there existed ionic bond formation in the dyeing mechanism between acid dyes and amphoteric fibers. 3. Dibasic acid dye had little changing rate in zeta potential due to the difference in solubility of dye and in number of dissociated ions per dye molecule to bond with amino radicals of amphoteric fibers. The dye adsorption of mono basic acid dye was higher than that of dibasic acid dye. 4. The effective surface areas concerning dyeing were $6.3E+05\;cm^2/g$ in nylon, $1.6E+07\;cm^2/g$ in wool fiber being higher order of wool then nylon.