• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.57-59
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• 2002

The dissolution process of NAPLs is significantly important in predicting the transport and/or fate of the contaminants and designing remedial systems. In this research, experimental observations on dissolution of TCE pool under various hydrodynamic conditions are done using an aquifer model. Hydrodynamic parameters such as linear pore velocity and dispersion coefficient are estimated from the results of preliminary tracer tests using bromide as conservative tracer before doing the TCE dissolution experiments. It is found that hydrodynamic parameters are distinctly affected by the clay lens imbeded in the aquifer model. Nonequilibrium and transient dissolution rates are observed from the results of TCE dissolution experiments.

• Korean Journal of Materials Research
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• v.26 no.5
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• pp.235-240
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• 2016

Appropriate thermo-mechanical properties of nickel-based superalloys are achieved by heat treatment, which induces precipitation and solid solution hardening; thus, information on the temperature ranges of precipitation and dissolution of the precipitates is essential for the determination of the heat treatment condition. In this study, thermal analyses of nickel-based superalloys were performed by differential scanning calorimetry method under conditions of various heating rates of 5, 10, 20, or 40K/min in a temperature range of 298~1573K. Precipitation and dissolution temperatures were determined by measuring peak temperatures, constructing trend lines, and extrapolating those lines to the zero heating rate to find the exact temperature under isothermal condition. Determined temperatures for the precipitation reactions were 813, 952, and 1062K. Determined onset, peak, and offset temperatures of the first dissolution reaction were 1302, 1388, and 1406K, respectively, and those values of the second dissolution reaction were 1405, 1414, and 1462K. Determined solvus temperature was 1462K. The study showed that it was possible to use a simple method to obtain accurate phase transition temperatures under isothermal condition.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.6
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• pp.89-97
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• 2015

In this study, dissolution characteristics of 60% LiBr aqueous solution for Miscanthus sinensis holocellulose in accordance with heating time and characteristics of regenerated films were analyzed. Miscanthus sinensis holocellulose was made by peracetic acid method. During the dissolution of 60% LiBr solution for the holocellulose, the dissolution was started from the tip of the cellulose fiber after about 7 minutes, and proceeded as it swollen like a balloon. A lot of Si was identified by analyzing hollocellulose regenerated film through SEM/EDS. Cross section of regenerated film as dissolution time till 40 minutes of dissolution showed multilayered structure and fiber orientation. But after 40 minutes, multilayered structure and fiber orientation was not observed. The crystal structure of the holecellulose was transformed cellulose I into cellulose II. Therefore, dissolution for 20 minutes with 60% LiBr solution in the condition of $190^{\circ}C$ hot plate was shown as an optimum condition to manufacture the holocellulose regenerated film.

• Corrosion Science and Technology
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• v.14 no.6
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• pp.273-279
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• 2015

Effects of passive film quality by chemical passivation and solution flow on the corrosion behavior of 304 stainless steel in HCl solution were investigated using a coloration indicator, and by corrosion weight loss, electrochemical polarization and element dissolution measurements. A high redness degree suggests a low passive-film integrity for 304 stainless steel following air exposure, while the minimum redness degree for the samples after chemical passivation suggests a high passive-film integrity. In the static condition, samples subjected to air exposure exhibited a high corrosion rate and preferential dissolution of Fe. Chemical passivation inhibited the corrosion rate due to the intrinsically high structural integrity of the passive film and high concentrations of Cr-rich oxides and hydroxide. Solution flow accelerated corrosion by promoting both the anodic dissolution reaction and the cathodic reaction. Solution flow also altered the preferential dissolution to fast uniform dissolution of metal elements.

• YAKHAK HOEJI
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• v.57 no.3
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• pp.205-212
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• 2013

Dissolution test has been performed to control drug quality and to predict in vivo drug release profile of solid dosage forms, so there's a drift towards setting dissolution test instead of disintegration test. However, some solid dosage forms in Korea Pharmaceutical Codex (KPC) are not established the dissolution test yet, so these monographs are necessary to set the specification of dissolution test. In this study, we developed the specification and test method of dissolution test for itopride hydrochloride tablets and tiropramide hydrochloride tablets which are not established the dissolution test yet. According to the "Manual for Guideline Application for Validation of Analytical Procedures" and "Guidelines on Specification of Dissolution test for Oral dosage form" of Korean Pharmacopoeia (KP), we validated and established each development method. Based on the preliminary dissolution profile, we set the dissolution condition(paddle apparatus, pH 1.2 media, 50 rpm). For this condition, we performed the main dissolution test to determine the specification (45 min, 85%). Finally, we validated each analytical method by specificity, linearity, accuracy and precision. These developed methods will be included the next supplement of KPC and also contributed to the quality control of medicines.

• Journal of Pharmaceutical Investigation
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• v.23 no.2
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• pp.81-87
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• 1993

Five crystalline forms of cimetidine, four anhydrous and a monohydrate, have been prepared, and their thermal behavriours have been studied by differential thermal analysis and thermo-gravimetry. The dissolution rates of the five forms were determined in distilled water at $37^{\circ}C$. The results showed a significant difference in the dissolution rate. Polymorphic transformation occurred spontaneously during storage at room condition and was accelerated by applied energy during formulation process-milling.

• YAKHAK HOEJI
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• v.40 no.5
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• pp.513-521
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• 1996

The polymorphism of piroxicam was studied. Form I, II, III and monohydrate designated as Form IX were prepared by recrystallization from different solvents. Depending on the coo ling rate of the piroxicam melt, Form IV, V, VI, VII and VIII were prepared. The crystal forms were characterized by DTA, TGA and UV spectroscopy. Their dissolution patterns were also investigated. During storage at ambient condition. Form VIII was transformed into Form I and it was accelerated by milling. The other crystal forms were also transformed into Form I by milling. Form I and Form IX were very stable.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.289-293
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• 2000

Three polymorphic modifications and one amorphous form were prepared by recrystallization under various conditions and characterized by DSC and X-ray crystallography. At $37{\pm}0.5^{\circ}C$, the polymorphic modifications showed significant differences in the dissolution rate. The dissolution rate of Mod. 4, amorphous form, was faster than that of other polymorphic modifications. When all modifications were stored at 52% RH, 95% RH, and in silica gel desiccator, amorphous form was transformed at 95% humidity condition.

• Advances in environmental research
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• v.4 no.1
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• pp.17-24
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• 2015

In this study, we numerically investigated the effect of pressure (100-250 bar), temperature (274-288 K), and salinity (3.5% w/w electrolytes) on $CO_2$ hydrate dissolution rates in the ocean. Mass transfer equations and $CO_2$ solubility data were used to estimate the $CO_2$ hydrate dissolution rates. The higher pressure and lower temperature significantly reduced the $CO_2$ hydrate dissolution rates due to the increase of $CO_2$ particle density. In the high salinity condition, the rates of $CO_2$ hydrate dissolution were decreased compared to pure water control. This is due to decrease of $CO_2$ solubility in surrounding water, thus reducing the mass transfer of $CO_2$ from the hydrate particle to $CO_2$ under-saturated water. The results obtained from this study could provide fundamental knowledge to slow down or prevent the $CO_2$ hydrate dissolution for long-term stable $CO_2$ storage in the ocean as a form of $CO_2$ hydrate.

• YAKHAK HOEJI
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• v.57 no.3
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• pp.226-233
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• 2013

Although the dissolution test can serve as an effective tool for quality control and predictor of in vivo performance, there are a number of drugs with no established dissolution specification in Korean Pharmaceutical Codex (KPC). So, with each reference and test drugs, the dissolution test method and an analytical procedure by HPLC were developed and validated to establish dissolution specification for acebrophylline capsules and bromhexine hydrochloride tablets. The dissolution condition was determined based on the "Guidelines on Specifications of Dissolution tests for Oral dosage forms" of Ministry of Food and Drug Safety (MFDS). The analytical method of HPLC was validated in specificity, linearity, precision and accuracy. Final dissolution test was performed with commercially available samples of 3 lots to establish specification. In addition, no difference was observed by the inter-laboratory evaluation. Dissolution specifications and conditions will be used for revising the monograph of acebrophylline capsules and bromhexine hydrochloride tablets in next supplement of KPC.