• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.129-135
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• 1994

Acyclic polyether dicarboxylic acid have been studied as metal cation carriers in a bulk liquid membrane system. The proton-ionizable ligands feature allows the coupling of a cation transport to reverse proton transport. This feature offers promise for the effective separation and concentration of metal cations with the metal cation transport being driven by a pH gradient. Metal cation transport increased regularly with increasing hydroxide($H^-$) concentration of source phase and with proton($H^+$) concentration of receiving phase. Competitive transport by the acyclic polyether dicarboxylic acids is selective for calcium ion over other alkaline-earth cations.

• Analytical Science and Technology
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• v.30 no.1
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• pp.39-48
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• 2017

Roxithromycin (RXT), which is an antibiotic used to treat respiratory tract and urinary infections, is official in Korean Pharmacopoeia (KP) and is marketed in various dosage forms including tablet, granule, suspension, and tablet for suspension in Korea. This study presents how a universal and reliable method to quantify RXT in bulk drug and formulations was developed. Effects of factors including column type, buffer concentration, type and concentration of organic solvent, buffer pH, and type and concentration of mobile phase additive, were examined, and some categorical or crucial factors including the types of column, organic solvent, mobile phase additive and the buffer pH were optimized by one-factor-at-a-time approach. Subsequently, concentrations of the buffer and additive and column temperature were optimized by response surface methodology using Box-Behnken design aiming to acquire the RXT peak of good shape. The optimized method employed a Phenomenex Gemini $5{\mu}$ C18 110A ($150{\times}4.60mm$, $5{\mu}m$) maintained at $30^{\circ}C$ with the mobile phase consisting of 25 mM phosphate buffer (pH 6.0) with 0.3 % tetrabutylammonium hydroxide and methanol at a ratio of 37:63 (v/v). Method validation results showed that the developed method was linear, precise, and accurate. Compared to the compendial methods in KP 10 that exhibited a significant tailing of the RXT peak despite using unfavorably high buffer concentrations and were not harmonized among bulk drug and formulations, this method could be universally applied to RXT bulk drug and marketed products in various dosage forms and thus was adopted in KP 11.

• Bulletin of the Korean Chemical Society
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• v.34 no.7
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• pp.2171-2175
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• 2013

The electronic structure and elastic properties of the 4d transition metal carbides MC (M = Y, Zr, Nb, Rh) were studied by means of extended H$\ddot{u}$ckel tight-binding band electronic structure calculations. As the valence electron population of M increases, the bulk modulus of the MC compounds in the rocksalt structure does not increase monotonically. The dominant covalent bonding in these compounds is found to be M-C bonding, which mainly arises from the interaction between M 4d and C 2p orbitals. The bonding characteristics between M and C atoms affecting the variation of the bulk modulus can be understood on the basis of their electronic structure. The increasing bulk modulus from YC to NbC is associated with stronger interactions between M 4d and C 2p orbitals and the successive filling of M 4d-C 2p bonding states. The decreased bulk modulus for RhC is related to the partial occupation of Rh-C antibonding states.

• YAKHAK HOEJI
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• v.42 no.3
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• pp.284-289
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• 1998

The effect of reaction condition, solvent addition and thermal treatment on the bulk density, crystallinity and chemical properties of the freeze-dried cefazohn sodium was inves tigated to prepare the cefazolin sodium powder for injection with good flowability. Crystalline cefazolin sodium powder with high untapped-bulk density (about 45%) and low compressibility (about 40%) was obtained by solvent addition to the very highly concentrated cefazohn sodium solution followed by subsequent thermal treatment before freeze-drying. The desirable solvent was low substituted alcohol such as isopropyl alcohol and anhydrous ethanol with the final concentration of about 9%. The pH adjustment and nitrogen gas purging during the reaction did not give significant effect on the chemical properties such as content, color, transmittance and pH of the reconstituted cefazolin sodium aqueous solution.

• Journal of Veterinary Clinics
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• v.33 no.5
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• pp.274-277
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• 2016

To determine the concentrations of commercial milks and the effect of different teat dipping methods on iodine concentrations of bulk tank milk, iodine concentration was analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The 59 bulk tank milk samples were collected. The 8 brands of commercial whole milk and 5 brands of commercial organic milk were purchased. The iodine concentrations of bulk tank milks of 59 dairy farms were in the range from 42.7 to $562.5{\mu}g/L$. The iodine levels of 4 different teat dipping methods with pre-dipping, post-dipping, pre & post-dipping, and non-dipping were $138.9{\pm}41.1$, $200.6{\pm}106.9$, $205.1{\pm}93.2$, and $110.9{\pm}70.4{\mu}g/L$, respectively. No significant difference (P > 0.05) was observed among 4 different teat dipping methods. Iodine concentrations of commercial whole milks were in the range from 149.1 to $210.4(178.8{\pm}22.0){\mu}g/L$, and iodine concentrations of commercial organic milks were in the range from 85.0 to $356.9(214.2{\pm}123.3){\mu}g/L$. Iodine concentrations of commercial milk in Korea are relatively low comparing with those of other countries.

• Membrane and Water Treatment
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• v.9 no.6
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• pp.435-445
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• 2018

In this work, desalination experiments were performed on vacuum membrane distillation (VMD). Process parameters such as feed flow rate, vacuum degree on permeate side, feed bulk temperature and feed salt concentration were optimized using sensitivity analysis and Taguchi method. The optimum values of process parameters were found to be 2 lpm of feed flow rate, $60^{\circ}C$ of feed bulk temperature, 5.5 kPa of permeate-side pressure and 5000 ppm of salt concentration. The permeate flux at these conditions was obtained as $26.6kg/m^2{\cdot}hr$. The rejection of salt in permeate was found to be 99.7%. The percent contribution of various process parameters using ANOVA results indicated that the most important parameter is feed bulk temperature with its contribution of 95%. The ANOVA results indicate that the percent contribution of permeate pressure gets increased to 5.384% in the range of 2 to 7 kPa as compared to 0.045% in the range of 5.5 to 7 kPa.

• Journal of Astronomy and Space Sciences
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• v.15 no.1
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• pp.151-162
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• 1998

Infrared absorption spectra of 9 bulk samples and 3 acid residues of meteorites were obtained in the mid-infrared region ($4000~400cm^{-1}$). From the know composition of meteorites studied, the possible absorption modes were investigated. Most bands of bulk samples occur in the region below $1200cm^{-1}$ and they are due to metallic oxides and silicates. The spectra of each group can be distinguished by its own characteristic bands. Acid residues show very distinct features from their bulk samples, and absorp-tion bands due to organic compounds are not evident in their spectra. Quantiative analyses for two carbonaceous (Allende CV3 and Murchison CM2) and one ordinary (Carraweena L3.9) chondrites were performed for the presence of fullerene ($C_{60}$) in the meteorites. We calculated the concentration of $C_{60}$ in the acid residues by curve-fitting the spectra with Gaussian functions. The upper limit of $C_{60}$ concentration in these meteorites appears to be less than an order of a few hundred ppm.

• Atmosphere
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• v.29 no.2
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• pp.227-239
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• 2019

This paper reviews various bulk-type cloud microphysics parameterizations (BCMPs). BCMP, predicting the moments of size distribution of hydrometeors, parameterizes the grid-resolved cloud and precipitation processes in atmospheric models. The generalized gamma distribution is mainly applied to represent the hydrometeors size distribution in BCMPs. BCMP can be divided in three different methods such as single-moment, double-moment, and triple-moment approaches depending on the number of prognostic variables. Single-moment approach only predicts the hydrometeors mixing ratio. Double-moment approach predicts not only the hydrometeors mixing ratio but also the hydrometeors number concentration. Triple-moment approach predicts the dispersion parameter of hydrometeors size distribution through the prognostic reflectivity, together with the number concentrations and mixing ratios of hydrometeors. Triple-moment approach is the most time expensive method because it has the most number of prognostic variables. However, this approach can allow more flexibility in representing hydrometeors size distribution relative to single-moment and double-moment approaches. At the early stage of the development of BMCPs, warm rain processes were only included. Ice-phase categories such as cloud ice, snow, graupel, and hail were included in BCMPs with prescribed properties for densities and sedimentation velocities of ice-phase hydrometeors since 1980s. Recently, to avoid fixed properties for ice-phase hydrometeors and ad-hoc category conversion, the new approach was proposed in which rimed ice and deposition ice mixing ratios are predicted with total ice number concentration and volume.

• Environmental Engineering Research
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• v.24 no.3
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• pp.376-381
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• 2019

In this study, a poly(vinyl) alcohol/sodium alginate (PVA/SA) mixture was used to fabricate core-shell structured gel beads for autotrophic single-stage nitrogen removal (ASNR) using aerobic and anaerobic ammonia-oxidizing bacteria (AAOB and AnAOB, respectively). For stable ASNR process, the mechanical strength and oxygen penetration depth of the shell layer entrapping the AAOB are critical properties. The shell layer was constructed by an interfacial gelling reaction yielding thickness in the range of 2.01-3.63 mm, and a high PVA concentration of 12.5% resulted in the best mechanical strength of the shell layer. It was found that oxygen penetrated the shell layer at different depths depending on the PVA concentration, oxygen concentration in the bulk phase, and free ammonia concentration. The oxygen penetration depth was around $1,000{\mu}m$ when 8.0 mg/L dissolved oxygen was supplied from the bulk phase. This study reveals that the shell layer effectively protects the AnAOB from oxygen inhibition under the aerobic conditions because of the respiratory activity of the AAOB.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.06a
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• pp.29-33
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• 1998

Transport phenomena paly an inmportant role in bulk crystal growth processes. During crystal growth, the control of the growth front and the dopant concentration is crucial to crystal quality. The growth feasibility in thus determined by the heat transfer controlling the interface convexity and by the mass transfer controlling the constitutional supercooling. Through numerical modeling, a thorough understanding of the growth processes is possible, which in turn is a key to process improvenment. In this paper, we will summarize some work dine in my laboratory, both numerical and experimental, to illustrate the importance of understanding the transport phenomena during crystal growth processes.