• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.535-538
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• 2011

The electromodulation methods of photoreflectanceand the related technique of contactless electroreflectance(CER) are valuable tools in the evaluation of important device parameters for structures such as heterojunction bipolar transistors, pseudomorphic high electron mobility transistors, and quantum dots(QDs). CER is a very general principle of experimental physics. Instead of measuring the optical reflectance of the material, the derivative with respect to a modulating electric field is evaluated. This procedure generates sharp, differential-like spectra in the region of interband (intersubband) transitions. We conduct electric-optical studies of both GaAs layers and InAs selfassembled QDs grown by molecular beam epitaxy. Strong GaAsbandgap energy is measured in both structures. In the case of lnAs monolayers in GaAs matrices, the strong GaAsbandgap energy is caused by the lateral quantum confinement.

• The Journal of Information Technology
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• v.9 no.1
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• pp.1-7
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• 2006

In this paper, we describe a study on the relationship between photographic emulsion manufacture and hardening test of films. The hardeners were prepared by condensation of equimolar amounts of trichlorotriazine with benzene- or naphthalene-based amino or oxy acids at 0 to 5$^{\circ}C$ and at pH 7, and used as hardening agents for gelatin. The hardening test of photographic emulsion was studied at pH 5.5. For example I(R=ONa) had strong hardening properties, I substituted with an aminobenzosulfonate moiety (R=$NHC_6H_4-p-SO_3Me$ where Me = K, Na) was a much weaker gelatin hardener, and when substituted with amino- or oxynaphthalene derivative (II, III) did not harden gelatin at all. Compound with 2 dichlorotriazine groups as IV exhibited strong hardening properties. The hardener can be used in photographic emulsion of film and showed very good hardening effect.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.147-147
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• 2016

In general, organic electrochromic (EC) materials have been known to be electrochemically unstable during the ionic exchange process. One effective method to realize stable EC materials is incorporating graphene derivatives in the polymer matrix, by using the strong interaction between graphene derivatives and polymer. However, previous studies are limited graphene derivatives. In this study, we developed a polymer-graphene derivative complex with the chemical assistance of a surfactant (octadecylamine, ODA). Surfactant-assisted graphene oxide (GO-ODA) was introduced as a protective layer on the electrochromic poly (3-hexyl thiophene) (P3HT) films by the Langmuir-Schaefer method. The deposition of GO-ODA protective layer with high coverage was confirmed by atomic force microscopy. The strong interactions between GO-ODA and P3HT were examined with UV-Vis spectrophotometry and X-ray photoelectron spectroscopy. Electrochemical and electrochromic investigations revealed that the GO-ODA layer greatly improved the long-term cyclability of the P3HT film. These findings imply that the GO-ODA complex has a significant role in creating stable EC cycling, due to its strong interaction with the P3HT film.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1515-1515
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• 2001

Retrogradation of starch is one of important quality indexes for food based on starch such as rice. Therefore, in this research, possibility of near infrared spectroscopy to determine the degree of the retrogradation was examined. The degree of the retrogradation was indicated as the degree of geratinization analyzed by BAP(-amylase-pullulanase) method. 20 samples which have a wide range of the degree of the retrogradation were prepared and the NIR spectra of the samples were measured in reflectance mode with the NIR Systems 6500. In the correlation plots calculated from the 2nd derivative values of the MSC treated spectra and the degree of the geratinization, the major negative peaks of 1544 nm and 2258 nm, and the major positive peaks of 1460 nm, 1602 nm, 1766 nm and 2136 nm could be observed, indicating that NIR absorption at the positive peak wavelengths became strong while the absorption at the negative peak wavelengths became weak as the degree of the retrogradation increased. Because there is negative correlation between the degree of the retrogradation and the degree of the geratinization. As a result of MLR using the 2nd derivative values of the MSC treated spectra and the degree of the geratinization, good calibration equation which include 2258 nm as the first wavelength and 1764 nm as the second one could be obtained, indicating that NIR spectroscopy has a possibility to detect the retrogradation of starch. In order to find the assignment of the bands observed in the correlation plots, further study may be needed.

• Journal of Pharmaceutical Investigation
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• v.23 no.3
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• pp.155-163
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• 1993

Inclusion complexation of 1,7,21,27-tetraaza[7.1.7.1]paracyclophane (CPM 55) with 2,7-dihydroxynaphthalene (2,7-DHN) or 1,3-dihydroxynaphthalene (1,3-DHN) in pD 1.17 $DCl-D_2O$ solution was investigated by $^1H$ nuclear magnetic resonance spectroscopy (NMR) using 4,4'-dimethylaminodiphenylmethane (ACM 11) as an acyclic analog of CPM 55. In CPM 55-naphthalene derivative complex, alkyl protons located in the cavity of CPM 55 were shown to be subjected to anisotropic shielding and protons of naphthalene moiety shifted remarkably to upfield. However, in ACM 11-naphthalene derivative systems, chemical shifts for protons of both DHN compounds were not significant. The remarkable chemical shift changes suggested that the naphthalene moiety of 2,7-DHN or 1,3-DHN was included in the hydrophobic cavity of CPM 55 in aqueous solution. From the continuous variation plots of induced chemical shifts of 2,7-DHN, it was found that 2,7-DHN was included in the cavity of CPM 55 at 1:1 molar stoichiometry. Both computer simulation of a inclusion complex and strong upfield chemical shift changes of 2,7-DHN protons supported the conformation of pseudoaxial inclusion as the presumed geometry of the host-guest complex.

• Journal of the Korean Applied Science and Technology
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• v.31 no.1
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• pp.50-58
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• 2014

A novel fullerene derivative with photoresponsive azobenzene group was designed and synthesized, and its photoresponsive properties were reported. Starting from 4-nitrophenol, compound 1, which is containing fullerene moiety connected to azobenzene group through covalent linkage was synthesized by 5 steps. All the intermediates and the final compound were characterized by $^1H$, $^{13}C$-NMR, FAB-Mass or elemental analysis. Compound 1 exhibited the expected photoresponsive behavior. Chloroform solution($10^{-5}M$) of it served to maximize the absorption at 351 nm corresponding to the trans-azobenzene chromophore. Irradiation of this solution with 365 nm light resulted in photoisomerization to cis-azobenzene, as evidenced by decrease in the absorbance at 351 nm and an increase in absorbance at 450nm. A photostationary state was reached within about 150 s. Thermal reversion to the original spectrum was observed over the course of about 6 h at room temperature in the dark. However, exposure to bright sun light for about 5 s also effect almost complete reversion to the trans-isomer. This indicates that there is no strong steric influence on the trans-cis reversible isomerization of compound 1.

• Natural Product Sciences
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• v.4 no.3
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• pp.161-169
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• 1998

The analogues of lichen components showing anti-tyrosinase activities were synthesized. 4-Alkylresorcinol derivatives showed both the inhibitory activity and cytotoxicity in B-16 melanoma cells at the doses of 10 mM to 1.2 mM. Resorcinol and 4-methylresorcinol showed the inhibitory effect with a low cytotoxicity at the doses of 2.5 mM and $600\;{\mu}M$ among 4-alkylresorcinols, respectively. Some diphenylmethane derivatives (Type A, B, and C) had strong activities with a low cytotoxicity. While xanthine derivatives had no effect. Glucosides of 4,5-alkylresorcinol and the diphenylmethane derivative (Type B) were prepared to decrease the cytotoxicity. As a result, no effect were observed. Liposome of the diphenylmethane derivative (Type B) was prepared for the same purpose, and the latter showed a remarkable effect at the dose of $15\;{\mu}M$ with a low cytotoxicity.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1283-1283
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• 2001

NIR spectroscopy has been used extensively to investigate the structure of water, alcohol and other self-associate molecules because the frequencies of NIR bands due to OH and NH groups strength of hydrogen bonds. We have studied the structure of water -methanol mixtures by use of NIR spectroscopy. Strong features in the 7200-6300 $cm^{-1}$ / region consist of a number of overlapped bands due to the combination of OH antisymmetric and symmetric stretching modes of water and the first overtone of the OH stretching modes of free and hydrogen bonded methanol, while weak fratures in the 6000-5800 cm-1 region are ascribed to the first overtones of $CH_3$ stretching modes of methanol. We will focus the discussion on the $CH_3$ stretching bands. They seem to show a significant shift is not clear from the spectra shown in figure 1(a). Figure 1(b) depicts the second derivative in the 6000-5700 $cm^{-1}$ / region. Now, it is clear from the second derivative that there are two major bands near 5950 and 5900 $cm^{-1}$ / and that they do show a shift be about 30 $cm^{-1}$ / Why do the $CH_3$ bands show the shift with increasing concentration of methanol\ulcorner Probably, the CH, group interacts directly with OH groups of water. The results in figure 1(b) demonstrate the usefulness of the second derivative in resolution enhancement as well as the potential of NIR spectroscopy in the studies of molecular interactions.(Figure omitted).

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.245-252
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• 2003

There have been many kinds of hair styling sprays with various setting effects. Consumers have used strong setting effect hair sprays to get a long lasting hold. In recent years, however, more and more consumers have come to prefer a "soft ＆ natural" touch feeling, keeping the same long lasting hold. Nonetheless, the existing approaches to this feature could not respond to the consumers′ needs, since products lose the hold strength if the soft feeling is pursued, and vice versa. We have researched and developed a new products to attain a compatible feature with both long lasting hold and natural feeling. Then, we have developed a new multifunctional hair styling material "Poly Amino Acid Derivative (PAAD)." We have focused on the PAAD′s feature that highly diffuses onto a hair and makes thin and even layer on a hair, and have made trials and errors to improve holding strength. "P AAD" excellently makes hair memorize its curl shape which is as the same effect as existing ordinary acrylic resin. Further more, it leaves a soft and natural touch feeling on the hair. We have accomplished a new Poly Amino Acid Derivative with ambivalent features, "soft ＆ natural finish" and "long lasting hold ", and now we report about it.

• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.67-81
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• 2006

Using a strain-controlled rheometer, the dynamic viscoelastic properties of aqueous xanthan gum solutions with different concentrations were measured over a wide range of strain amplitudes and then the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a broad range of angular frequencies. In this article, both the strain amplitude and concentration dependencies of dynamic viscoelastic behavior were reported at full length from the experimental data obtained from strain-sweep tests. In addition, the linear viscoelastic behavior was explained in detail and the effects of angular frequency and concentration on this behavior were discussed using the well-known power-law type equations. Finally, a fractional derivative model originally developed by Ma and Barbosa-Canovas (1996) was employed to make a quantitative description of a linear viscoelastic behavior and then the applicability of this model was examined with a brief comment on its limitations. Main findings obtained from this study can be summarized as follows: (1) At strain amplitude range larger than 10%, the storage modulus shows a nonlinear strain-thinning behavior, indicating a decrease in storage modulus as an increase in strain amplitude. (2) At strain amplitude range larger than 80%, the loss modulus exhibits an exceptional nonlinear strain-overshoot behavior, indicating that the loss modulus is first increased up to a certain strain amplitude(${\gamma}_0{\approx}150%$) beyond which followed by a decrease in loss modulus with an increase in strain amplitude. (3) At sufficiently large strain amplitude range (${\gamma}_0>200%$), a viscous behavior becomes superior to an elastic behavior. (4) An ability to flow without fracture at large strain amplitudes is one of the most important differences between typical strong gel systems and concentrated xanthan gum solutions. (5) The linear viscoelastic behavior of concentrated xanthan gum solutions is dominated by an elastic nature rather than a viscous nature and a gel-like structure is present in these systems. (6) As the polymer concentration is increased, xanthan gum solutions become more elastic and can be characterized by a slower relaxation mechanism. (7) Concentrated xanthan gum solutions do not form a chemically cross-linked stable (strong) gel but exhibit a weak gel-like behavior. (8) A fractional derivative model may be an attractive means for predicting a linear viscoelastic behavior of concentrated xanthan gum solutions but classified as a semi-empirical relationship because there exists no real physical meaning for the model parameters.