• Archives of Pharmacal Research
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• v.20 no.6
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• pp.637-642
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• 1997

Degradation of a compound with a hydroxyl group during the course of its diffusion across the skin was investigated. Based on the experimental findings of ashortened retention time of a degradant peak from post-diffusion samples and from the ability to evaporate radioactivity from such samples, it seems that during diffusion the parent compound degrades into a more hydrophilic product which is then oxidized. A tritium label at the carbon with a hydroxyl group was released as a tritiated water. When the post-diffusion samples were left open to the air allowing evaporation of water, there was a corresponding decrease in radioactivity of such samples. There was a linear relationship between the time left open and the fraction of radioactivity lost. When such samples were fractionated by HPLC, and then had their radioactivities measured by scintillation counting, two peaks wre identified. The first peak, which may be attributable to tritiated water, was eluted at the same retention time as the solvent front. The second peak eluted at the retention time of the parent compound. When the evaporation/loss of radioactivity experiment was repeated using a $^{14}C$-labeled compound there was no significant loss of radioactivity, indicating that the earlier loss with $^{3}H$-labeled compound was related to the formation and loas sof tritiated water.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.557-564
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• 1998

A low loss x-cut $LiNbO_3$optical waveguide was fabricated by Yi in-diffusion, and the properties of guided-mode and the total insertion loss of the pigtailed waveguide with polarization maintaining fiber(PMF) were measured at optical wavelength 1550nm. for forming the waveguides, the parameters of diffusion, Ti thickness, waveguide line-width, length, diffusion temperature, time and atmosphere were set $1400{\AA}$, $8{\mu}m$, 3.3cm, $1050^{\circ}C$, 8 hours and wet bubbled oxygen, respectively. And then after the polishing and piatailing, it showed that the total insertion loss was -4.1dB for TM mode, -5.5dB for TE mode, and mode size, that is, the horizontal/ vertical size were $13.8{\mu}m/18{\mu}m$ for TM mode, $9.6{\mu}m/6.5{\mu}m$ for TE mode.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.2
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• pp.219-233
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• 2010

Understanding the Nano size particles is of great interest due to their chemical and physical behaviors such as compositions, size distributions, and number concentrations. Therefore, accurate measurements of size distributions and number concentrations in ultrafine particles are getting required because expected losses such as diffusion for the instrument system from ambient inlet to detector are a significant challenge. In this study, the data using the computed settling losses, impaction losses, diffusion losses for the sampling lines (explored different sampling line diameters, horizontal length, number of bending, line angles, flow rates with and without a bypass), and diffusion losses for the Scanning Mobility Particle Sizers are examined. As expected, the settling losses and impaction losses are very minor under 100 nm, however, diffusion loss corrections for the sampling lines and the size instrument make a large difference for any measurement conditions with high numbers of particles smaller mobility size. Both with and without the loss corrections, which can affect to size distributions and number concentrations are described. First, 80% or more of the smallest particles (less than 10 nm) can be lost in the condition of a flow rate of 0.3 liter per minute and the length of sampling line of 1.0 m, second, total number concentrations of measurements are quite significantly affected, and the mode structure of the size distribution changes dramatically after the loss corrections applied. With compared to the different measurements, statistically diffusion loss corrections yield a required process of the ambient particle concentrations. Based on the current study, as an implication, a possibility of establishing direct revelation mechanisms is suggested.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.73-76
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• 1997

A low loss x-cut LiNbO$_3$ optical waveguide was fabricated by Ti in-diffusion and the guided-mode properties and total insertion loss of pigtailing with polarization maintaining fiber(PMF) were investigated and measured at optical wavelength 15507. For formaing the waveguide, the parameters of diffusion Ti thickness, waveguide line-width, length, diffusion temperature, time and atmosphere were set 1400$\AA$, 8${\mu}{\textrm}{m}$, 3.3cm, 105$0^{\circ}C$, 8 hours and wet bubbled oxygen, respectively. and then After the polishing and pigtailing, it showed that total insertion loss was -4.1dB for TM mode, -5.5dB for TE mode, and mode size, that is, horizontal/vertical sizes were 13.87/18${\mu}{\textrm}{m}$ for TM mode, 9.61${\mu}{\textrm}{m}$/6.5${\mu}{\textrm}{m}$ for TE mode.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.29-35
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• 2001

Radiation-induced oscillatory instability in CH$_4$/Air diffusion flames is numerically investigated by adopting detailed chemistry. Counterflow diffusion flame is employed as a model flamelet and optically thin gas-phase radiation is assumed. Attention is focused on the extinction regime induced by radiative heat loss, which occurs at low strain rate. Once a steady flame structure is obtained for a prescribed value of initial strain rate, transient solution of the flame is calculated after a finite amount of strain-rate perturbation is imposed on the steady flame. Depending on the initial strain rate and the amount of perturbed strain rate, transient evolution of the flame exhibits various types of flame-evolution behaviors. Basically, the dynamic behaviors can be classified into two types, namely oscillatory decaying solution and diverging solution leading to extinction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.903-910
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• 1998

Ti:LiNbO$_3$ optical waveguides have been fabricated by Ti-diffusion in wet oxygen atmosphere. The fabrication conditions of furnace temperature, diffusion time and bubbler temperature were 105$0^{\circ}C$, 8 hours and 9$0^{\circ}C$, respectively and Ti thickness was varied from 700$\AA$ to 1500$\AA$. In this paper, the nearfield patterns, mode sizes (hirizontal/vertical) and insertion loss of waveguides were discussed at wavelength 1550 nm ad function of Ti thickness. With the planar waveguide, the effective index change and diffusion depth were calculated at 632.8nm using the prism coupling method. From these results, the best Ti thickness in our conditions seems like to by 1200$\AA$~1300$\AA$.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.43.2-43.2
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• 2009

Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.75-83
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• 1999

The effect of temperature distributions on soot volume fraction in double-concentric diffusion flames have been investigated experimentally. Using fine thermocouple wires and a rapid insertion mechanism, we have measured temperature without the effect of soot particles attached to the thermocouple junction, which can lower the temperature signal about 100 K by increasing the heat loss from the junction by radiation. The temperature at the flame axis is higher in the double-concentric diffusion flames than in normal co-flow diffusion flames because of the inverse diffusion flame. However, it is almost the same as that at the periphery of normal flames, on which the inverse flame does not have an effect. Thus, the lower soot concentration found in the double-concentric diffusion flame can be explained by the effect of nitrogen diffusion from the central air jet.

• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.74-81
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• 2010

In this study, soot formation characteristics on the instability of laminar diffusion flames were investigated experimentally using a concentric co-flow burner. When a small amount of air was supplied through an inner nozzle, a stable propane laminar diffusion flame became unstable and began to oscillate mainly due to the dilution effect. The increase of air flow rate transformed an oscillating non-sooting flame into a stable nonsooting flame. When the air flow rate was continuously increased an inner flame was formed and the flame was changed to an oscillating sooting flame, an oscillating non-sooting flame and finally a stable non-sooting hollow flame. When the air flow rate was decreased, a non-sooting hollow flame was eventually changed back to a stable non-sooting flame. The presence of an inner flame, however, altered the soot formation characteristics of a flame. More soot production was observed with the presence of an inner flame. The increased or decreased soot formation/oxidation rates, the radiation heat loss, and the heating effect of inner flames are most likely to be responsible for the observed instability of laminar diffusion flames.

• 한국전기화학회:학술대회논문집
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• 2001.06a
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• pp.179-184
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• 2001

The diffusion layer within MEA(membrane electrode assembly) has been evaluated important factor for improvement of cell performance in DMFC. The diffusion layer in MEA structure leads to the reduction of catalyst loss in active catalysts layer as well as prevention of water-flooding in cathode. Cell performance is directly affected by interior properties of diffusion layer materials. Acetylene Black and $RuO_2$ with large pore size and low porosity compared to Vulcan XC-72R gave better performance caused by vigorous methanol diffusion and water removal. And $RuO_2$ as diffusion layer materials showed different behavior in anode and cathode compartment, that is, diffusion layers in anode and cathode side make methanol diffusion and water removal facilitate, respectively.