• Food Science and Preservation
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• v.30 no.2
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• pp.311-320
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• 2023

Surfactin, one of the most powerful biosurfactants, can be widely applied in agriculture, food, and pharmaceutics. The purpose of the present study was to establish suitable indicators for a rapid detection method that can confirm the surfactin productivity of cheonggukjang. In the present study, changes in the total number of bacteria were quantified according to the fermentation time of chenggukjang. Furthermore, physicochemical factors, such as pH, color value, surface tension, refractive index, absorbance, and protein contents, were assessed in chenggukjang viscous substances, and a correlation analysis between the physicochemical factors and surfactin contents was performed. We found that the protein contents gradually increased up to 48 h (4.21±0.11 mg/mL) without a change in the surface tension. Furthermore, the refractive index, absorbance at 280 nm, and color value were significantly increased as the fermentation time increased; however, there were no statistically significant differences after 36 h of fermentation. Interestingly, this result exhibited a tendency similar to the surfactin content according to fermentation time. These findings suggest that surfactin can be used as a suitable quality indicator and may provide an experimental basis for the fermented food industry.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.6
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• pp.371-379
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• 2015

This study is purposed to seek the characteristics of both asbestos in accordance with acid and heat treatment for chrysotile and amosite used mainly as building materials. Results of acid treatment, the refractive index, the elongation sign, the extinction of acid-treated chrysotile were mostly similar to those of untreated chrysotile regardless of pH, elapsed time. But the characteristics of acid-treated chrysotile were different from those of untreated chrysotile after 8 weeks, at pH 1.2 acidic solution. When chrysotile treated with acid, weight ratio (%) of O and Mg fluctuated greatly in accordance with acid treatment unlike Si. But the change of constituents ratio (%) was small as time passed after acid treatment. The refractive index, the elongation sign and the extinction of acid-treated amosite were mostly similar to those of untreated amosite regardless of pH, elapsed time. When amosite was treated with acid, weight ratio (%) of Fe slightly increased. But in case of O, a contrary tendency was seen. Results of heat treatment, the higher the temperature, the more increased the refractive index of chrysotile. When chrysotile was heated for 10 minutes at $1,100^{\circ}C$, the elongation sign of chrysotile changed from positive(+) to negative(-). The extinction of chrysotile didn't change apparently in accordance with heat treatment. Also weight ratio (%) of O and Mg fluctuated greatly in accordance with heat treatment unlike Si. The higher the temperature, the more increased the refractive index of amosite. The elongation sign and the extinction of amosite didn't change apparently in accordance with heat treatment. Also weight ratio (%) of O and Fe fluctuated greatly in accordance with heat treatment. But weight ratio (%) of Si and Mg of heated amosite were mostly similar to those of untreated amosite regardless of temperature, heating time.

• Ceramist
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• v.10 no.3
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• pp.86-90
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• 2007

Novel photochromic oxide glasses are presented in this section. These glasses are based on phosphate formers containing both tungsten and antimony atoms. Exposure to visible continuous or pulsed laser beam results in an intense photochromic effect witch is shown to occur in the volume of the glass and results in a broad absorption band in the visible and near infrared. This effect was not identified to be related with a structural change and is assumed to be entirely electronic. A change in the absorption coefficient is observed in function of tungsten content, exposure time and increases with beam power. These glasses have been investigated regarding the possibility of holographic data storage using visible lasers sources. Changes in both refractive index and the absorption coefficient were measured using a holographic setup. The modulation of the optical constants is reversible by heat treatment.

• Journal of the Optical Society of Korea
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• v.8 no.4
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• pp.163-167
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• 2004

We propose and demonstrate an external optical modulation method based on TE/TM-mode absorption nulls in a Multiple Quantum Well(MQW) Fabry-Perot laser diode(FP-LD). The center wavelength of the absorption nulls is rapidly shifted to short-wavelength by the small current change(~1mA) in the FP-LD, which can modulate an optical signal with more than 10 dB of extinction ratio(ER). The shift of the center wavelength comes from the refractive index change due to anomalous dispersion and the plasma effect in MQW FP-LD waveguide. Non-inverting and inverting signals are made by TE- and TM-mode absorption nulls at 155.52 Mbps and BERs for the signals are measured.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.192-193
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• 2002

In this paper we investigate the phase modulation efficiency in the electrooptic phase modulator using PPpinNN GaAs/AlGaAs W-type waveguide. The phase change is affected by the refractive index change taking place inside the depletion region. The behavior of the modulator can be understood in terms of two electric field-related and two carrier-related effects linear electrooptic, quadratic electrooptic, plasma, and bandgap shift. As a result, the phase modulation efficiency was measured about 34.6($^{\circ}$/V$.$mm) for the TE polarized light. The quadratic electrooptic coefficient R 5.82${\times}$10$\^$-15/($\textrm{cm}^2$/V$^2$) is Obtained ant the Phase efficiency Caused by the quadratic electrooptic effect is about 10 times larger than that from the conventional linear electrooptic effect.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.423-427
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• 2013

We present the preparation and characteristics of liquid-phase sensors based on nano-porous silicon multilayer structures for determination of organic content in gasoline. The principle of the sensor is a determination of the cavity-resonant wavelength shift caused by refractive index change of the nano-porous silicon multilayer cavity due to the interaction with liquids. We use the transfer matrix method (TMM) for the design and prediction of characteristics of microcavity sensors based on nano-porous silicon multilayer structures. The preparation process of the nano-porous silicon microcavity is based on electrochemical etching of single-crystal silicon substrates, which can exactly control the porosity and thickness of the porous silicon layers. The basic characteristics of sensors obtained by experimental measurements of the different liquids with known refractive indices are in good agreement with simulation calculations. The reversibility of liquid-phase sensors is confirmed by fast complete evaporation of organic solvents using a low vacuum pump. The nano-porous silicon microcavity sensors can be used to determine different kinds of organic fuel mixtures such as bio-fuel (E5), A92 added ethanol and methanol of different concentrations up to 15%.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.59-63
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• 2008

Purpose: Ti thin films were deposited on slide glass and CR-39 lenses using small magnetron sputtering apparatus to of Ti thin films. Methods: The thickness of Ti thin films were measured by cross section SEM, the transmittance and reflectance of them were obtained using spectrophotometer, the refractive index and extinction of them were obtained from VASE data. Results: The transmittances of Ti thin films with 60 nm, 120 nm, 140 nm thickness were a little change within the visual region from 400 nm to 750 nm, but were increased a little amount at near 400 nm. The transmittance of 60 nm, 120 nm, 140 nm Ti thickness in d-line was 30%, 25%, 20%, respectively. Also, it was shown that the refractive indices and extinction coefficients of the Ti thin films obtained from VASE were similar to those of Ti thin film offered macleod program. Conclusions: Ti films on CR-39 with these transmittances were available for sunglass lens. It was indicated that the refractive indices and extinction coefficients of the Ti thin films were decreased with the thickness of Ti thin film, for the thickness of Ti thin films was due to very thin.

• Korean Journal of Food Science and Technology
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• v.14 no.3
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• pp.257-264
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• 1982

In the present stud changes of some chemical and physical properties of a soybean oil, aerated at 120 ml/min through a porous gas distributor and oxidized at $45^{\circ}C{\sim}180^{\circ}C$, was investigated. The results of the study were as follows: The peroxide, thiobarbituric acid, and iodine value of the soybean oil which was aerated at 120 ml/min increased rapidly as oxidation temperature exceeded over $80^{\circ}C$. The acid value of the oil increased very rapidly as the oxidation temperature passed over $160^{\circ}C$. The content of the unsaturated fatty acid of the oil decreased considerably as the oxidation temperature exceeded over $80^{\circ}C$, whereas that of the saturated fatty acid did not change appreciably. This related well to the changes of the iodine value of the oil subjected to the same experimental conditions. The viscosity and refractive index of the oil increased rapidly as the oxidation temperature passed over $180^{\circ}C$. The following linear relationship hold for the viscosity and refractive index of the oil in the present study. $$V=Aexp({\frac{E}{RT}})$$ where V=viscosity(poise), A=constant, E=activation energy for viscous flow, R=gas constant, T=oxidation temperature$(^{\circ}K)$. The following relationship also hold for the viscosity and refractive index$({n^{20}}_D)$ of the oil at the present experimental conditions. $${n^{20}}_D=1.4614+7.333{\times}10^{-5}t+2.9612{\times}10^{-3}\;InV$$ where t=temperature$(^{\circ}C)$ at which the viscosity was measured.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.3
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• pp.235-240
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• 2010

Purpose: In this study, we proposed a simple accommodation-dependent crystalline lens with a constant volume and homogeneous refractive index. Methods: We proposed a human crystalline lens with two aspheric surfaces. Two surfaces intersect in two points and straight line between two points was equator(2b). It assumed that the derivative in axial direction was zero at the equator and the radial derivative was zero at the vertex. Proposed human crystalline lens was divided by the equator into the anterior and posterior parts. It was assume that the volume of each part and refractive index of the human crystalline lens were constant during accommodation. Results: For the changes during accommodation, geometrical parameters were determined by different objective distances. Considering the constant volume of each part with the small decrement of the equator, we obtained the paraxial parameters, such as the anterior and posterior vertex radius of curvature and lens thickness. Compared with the experimental data published in the literature, calculated values using simple approximation showed similar change per accommodative stimulus. Conclusions: These results showed that proposed simple approximation using assumption of constant volume and refractive index of the human crystalline lens made it possible to predict changes of geometrical parameters during accommodation.

• Polymer(Korea)
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• v.31 no.4
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• pp.335-342
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• 2007

The goal of this study is to investigate the effect of molecular structure modifications on the kinetics of physical aging of thin films formed from 6FDA-based polyimides with time. The permeability for 6FDA-based polyimide thin films containing carboxyl acid groups commonly decreased 20-50% after the isothermal aging and the selectivity gained anywhere from 10% to 30% while the rate of permeability loss on the change of polymer structure showed different reciprocal relationship between 6FDA-6FpDA based polyimides and 6FDA-DAM based polyimides. The Lorenz-Lorentz equation was used to relate changes in refractive index to densification and volume relaxation with aging time. The permeability as a function of aging time fits the expected form $P=Ae^{(-B/f)}$. The results matched well with the data for different polymer membranes.