• The Journal of the Acoustical Society of Korea
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• v.21 no.4
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• pp.394-400
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• 2002

In digital speech communications, the quality of service can be increased by speech coding scheme that is adaptive to the error rate of voice packet transmission. However, current communication protocol in cellular and internet communications does not provide the function that transmits the channel error information. To solute this problem, in this paper, new method for real-time transmission of channel error information is proposed, where channel error information is embedded in voice packet. The proposed method utilizes the pulse positions of codevector in ACELP speech codec, which results in little degradation in speech quality and low false alarm rate. The simulations with various speech data show that the proposed method meets the requirement in speech quality, detection rate, and false alarm rate.

• Bulletin of the Korean Chemical Society
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• v.27 no.11
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• pp.1752-1756
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• 2006

This study explores and interprets in a new way the complex solvent and the temperature dependence of the NMR shifts for the N-$CH_2$ protons in tris(N,N-diethyldithiocarbamato) iron(III) in acetone, benzene, carbon disulfide, chloroform, dimethylformamide and pyridine. The NMR shifts are interpreted in terms of the Fermi contact interaction and the dipolar term from the multipole expansion of the interaction of the electron orbital angular momentum and the electron spin dipolar-nuclear spin angular momentum. This analysis yields a direct measure of the effect of the solvent system on the environment of the transition metal ion. The results are analysed in terms of the crystal field environment of the transition metal ion with contributions from (a) the dithiocarbamate ligand (b) the solvent molecules and (c) the interaction of the effective dipole moment of the polar solvent molecule with the transition metal ion complex.

• Membrane and Water Treatment
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• v.7 no.3
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• pp.193-207
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• 2016

Boron is one of the most problematic inorganic pollutants and is difficult to remove in water. Strict standards have been imposed for boron content in water because of their high toxicity at high concentrations. Technologies using membrane processes such as reverse osmosis (RO) and nanofiltration (NF) have increasingly been employed in many industrial sectors. In this work, removal of boron from model water solutions was investigated using polyamide reverse osmosis and nanofiltration membranes. RO-AG, RO-SG, NF-90 and NF-HL membranes were used to reduce the boron from model water at different operational conditions. To understand the boron separation properties a characterization of the four membranes was performed by determining the pure water permeability, surface charge and molecular weight cut-off. Thereafter, the effect of feed pressure, concentration, ionic strength, nature of ions in solution and pH on the rejection of boron were studied. The rejection of boron can reach up to 90% for the three membranes AG, SG and NF-90 at pH = 11. The Spiegler-Kedem model was applied to experimental results to determine the reflection coefficient of the membrane ${\sigma}$ and the solute permeability $P_s$.

• Membrane Journal
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• v.5 no.2
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• pp.81-88
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• 1995

Separation performance was measured for the disc plate and frame type reverse osmosis module using NaCl and sucrose solutions. An analysis of membrane performance was done following the equations proposed by Kimura-Sourirajan[8]. The membrane permeability was $2.17 \times 10^{-6}$(gmol/$cm^2$-sec-bar) and independent of operating pressure. The effect of concentration polarization for sucrose solution was higher than that of NaCl. Permeation flux for sucrose solution above 40 bar was decreased as operating pressure was increased. Solute rejection for NaCl solution was decreased, but that of sucrose was increased as operating pressure was increased.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.15-18
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• 1999

A simple mathematical model for facilitated mass transport through a fixed site carrier membrane was derived by assuming an instantaneous, microscopic concentration (activity) fluctuation. The current model demonstrates that the facilitation factor depends on the extent of concentration fluctuation, the time scale ratios of diffusion to chemical reaction and the ratio of the carrier concentration to the solute solubility in matrix. The model was examined against the experimental data on oxygen transport in membranes containing metallo-porphyrin carriers, and the agreement was exceptional (within 10% error). The basic concept of this approach was applied to separate olefin from olefin/paraffin mixtures. A proprietaty carrier, developed here, resulted that the selectivity of propylene over propane was more than 120 and the propylene permeance exceed 40 gpu.

• Proceedings of the Membrane Society of Korea Conference
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• 2004.05a
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• pp.19-24
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• 2004

ED method is employed to effectively remove the organic acid salts in actual PDO fermentation broth. The lower electrical potential is selected to avoid the serious membrane fouling so as to ensure a stable and durative desalination process. Under the selected operation conditions, about 90% of organic acids salts are removed from PDO fermentation broth successfully by ED process. To reduce the loss of PDO product due to the diffusion, the operation time should be considered carefully. And based on mass balance equation and irreversible thermodynamics approach, a mathematical model is developed to describe the desalination process of an aqueous solution containing neutral solute by ED method. While the influence of concentration polarization is reflected by decreasing the conductivity of membrane, the model is verified well to describe the ED processes under varied operation conditions. Through the model, ED process of actual PDO fermentation broth is simulated to get a suitable scope of initial concentration in concentrated compartment.

• The Korean Journal of Ecology
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• v.28 no.2
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• pp.105-112
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• 2005

Environmental factors such as light and low $CO_2$ concentrations trigger events which may result in stomatal opening. Stomatal aperature is largely controlled by the solute contents of guard cells, but not exclusively, by through changes in their content of potassium salts, with $K^+$ balanced either by $Cl^-$ or malate, depending on the species and conditions. However, how these signals are sensed and how they are transduced into driving the ion fluxes that control stomatal movements is not still fully understood. The basic role of stomata is regulating transpiration and photosynthesis. Photosynthesis plays a central role in the physiology of plants and an understanding of its response to light is, therefore, critical to any discussion of how plants sense and respond to light. It had been proposed that the evidences pointed three possible mechanisms for the light response. Firstly, there is a direct response of stomata to light. Secondly. there is an indirect response of stomata to light through the effect of $CO_2$. Lastly, there are some evidences for a third effect of light on stomata. However, attempts to investigate how these three possible mechanisms explained in detail in response to light have not been made. Therefore, this study is examined the differences among these three possible mechanisms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.50-53
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• 1992

The GaP crystals are growth by Synthesis Solute Diffusion(SSD) method and its properties are investigated. Etch pits density along vertical direction of ingot is increased from 3.8${\times}$10$^4$cm$\^$-2/ of first freeze to 2.3${\times}$10$\^$5/cm$\^$-2/ of last freeze part. The carrier concentration and mobilities are measured to 197.49$\textrm{cm}^2$/V. sec and 6.75${\times}$10$\^$15/cm$\^$-3/ at room temperature. The temperature dependence of optical energy gap is empilically fitted to E$\_$g/(T)=2.3383-(6.082${\times}$10$\^$-4/T${\times}$/(373.096+T)[eV]. Photo-luminescence spectra measured at low temperature are consist with sharp line-spectra near band-gap energy and radiative recombination between shallow Si-donor to Zn-acceptor and its phonon reprica, and broad emission. The infrared absorption in GaP is cause to phonon coupling modes of TO, LO, LA, TA$_1$, TA$_2$and vibration modes of Ga$_2$O, Si-donor and Zn-acceptor, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.218-221
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• 2000

Currently, Bi-2223 HTS tape is capable of being fabricated in longer than 100m length by industrial processes. But there are some problems in heat treatment of the degree of longer than 100m tape, which is in term of volume occupied with specimen in furnace. The effects of ceramic coating with variable slurry states were studied in Bi-2223 high-temperature superconductor. The HTS tapes coated with oxide were prepared by using dip-coating method on slurry state. Critical current(I$_{c}$) of tapes coated with ceramic materials were equal with 11.5A at 77K after first heat treatment as different slurries. For final heat treatment, Critical current of HTS tapes coated with zirconia oxide mixed in PMMA and PVA organic solute were 20.8A at 77K. The breakdown voltage of HTS tapes coated with zirconia oxide were 3kV in air and 4~7kV in L$N_2$.>.

• Membrane Journal
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• v.7 no.2
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• pp.95-109
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• 1997

The effects of varing axial flow rate and solute concentration on the performance of both module sets made by different methods for active layer formation were compared and determined. All experiments were conducted simultaneously at the same transmembrane pressure and energy consumption per membrane area. In every comparative run between the presence of Dean vortices in a helical module and absence of such vortices in a linear module from the first module set, the solution fluxes and permeabilities were higher, and in some cases substantially higher for the vortex flow. With pure water, the permeabilities of both modules from the second module set were different and the flux in a linear module was 150% higher than in the helical module. This explained both module membranes were totally different.