• Korean Journal of Metals and Materials
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• v.48 no.10
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• pp.893-900
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• 2010

In the present work, the impact loads and their effects on the surface damage under the simultaneous cavitation bubble and solid particle collapses in the sea water have been quantitatively investigated for the austenitic 304 stainless steel by using a vibratory cavitation test device. To do this, angular $SiO_2$ solid particles with an average size of $150{\mu}m$ were dispersed into the test liquid, and the measured impact amplitudes were converted into the impact loads by a steel ball drop test. The maximum impact load was determined to be 28.2 N in the absence of solid particles, but increased to 33.7 N in the presence of solid particles. In addition, the critical impact loads, $L_{crit}$, required to generate pits with sizes greater than $3{\mu}m$ were measured to be 19.6 N and 16.6 N, respectively, for the cavitation bubble collapse and solid particle collapse. As a result of the cavitation erosion test, the incubation time and erosion rate were 1.2 times lower and 1.5 times higher, respectively, by a solid particle collapse compared to those only by the cavitation bubble collapse, indicating a drastic decrease in a resistance to cavitation erosion by the solid particle collapse.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.457-460
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• 2012

Design and fabrication of a sub-scale thrust chamber for verification of 7 tonf-class thrust chamber injectors were described in this paper. The 7 tonf-class thrust chamber consists of mixing head with 90 coaxial swirl injectors and regeneratively combustion chamber cooled by kerosene. The coaxial swirl injectors with different pressure drop and recess number were designed for 7 tonf full-scale thrust chamber. By applying the designed injectors to the sub-scale thrust chamber before applying them to the full-scale thrust chamber, the injector performance and functioning were verified. The sub-scale thrust chamber consists of 19 injectors, has chamber pressure of 70 bar, total propellant mass flow rate of 4.3 kg/s, mixture ratio(O/F) of 2.45.

• Advances in materials Research
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• v.8 no.1
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• pp.37-46
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• 2019

Electrochemical double layer capacitors (EDLCs) which are fabricated using carbon based electrodes have been emerging at an alarming rate to fulfill the energy demand in the present day world. Activated charcoal has been accepted as a very suitable candidate for electrodes but its cost is higher than natural graphite. Present study is about fabrication of EDLCs using composite electrodes with activated charcoal and Sri Lankan natural graphite as well as a gel polymer electrolyte which is identified as a suitable substitute for liquid electrolytes. Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge Discharge test were done to evaluate the performance of the fabricated EDLCs. Amount of activated charcoal and natural graphite plays a noticeable role on the capacity. 50 graphite : 40 AC : 10 PVdF showed the optimum single electrode specific capacity value of 15 F/g. Capacity is determined by the cycling rate as well as the potential window within which cycling is being done. Continuous cycling resulted an average single electrode specific capacity variation of 48 F/g - 16 F/g. Capacity fading was higher at the beginning. Later, it dropped noticeably. Initial discharge capacity drop under Galvanostatic Charge Discharge test was slightly fast but reached near stable upon continuous charge discharge process. It can be concluded that initially some agitation is required to reach the maturity. However, the results can be considered as encouraging to initiate studies on EDLCs using Sri Lankan natural graphite.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.554-565
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• 2021

Air bubble entrainment is a phenomenon that can significantly reduce the efficiency of liquid motion in piping systems. In the present study, the bubble formation mechanism in a globe valve with 90% water fraction flow is explained by visualization study and pressure oscillation analysis. The shadowgraph imaging technique is applied to illustrate the unsteady flow inside the transparent valve. This helps to study the effect of bubbles induced by the globe valve on pressure distribution and valve flow coefficient. International Society of Automation (ISA) recommends locations for measuring pressure drop of the valve to determine its flow coefficient. This paper presents the comparison of the pressures at different locations along with the upstream and the downstream of the valve with the values at recommended positions by the ISA standard. The results show that in partially filled pipe flow, the discrepancies in pressure between different measurement locations in the valve downstream are significant at valve openings less than 30%. The aerated flow induces the oscillation in pressure and flow rate, which leads to the fluctuation in the flow coefficient of the valve. The flow coefficients have a linear relationship with the Reynolds number. For the same increase of Reynolds number, the flow coefficients grow faster with larger valve openings and level off at the opening of 50%.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.35 no.1
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• pp.24-37
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• 2022

Objectives : The purpose of this literature review is to analyze process of manufacture and formulation and toxicity of Geumgweyoryak(金匱要略)'s external applicants for modern and safe using. Methods : This study used the Geumgweyoryak(金匱要略) reprinted by Zhao Kaimei(趙開美) as basic data for a understanding of the manufacture and formulation and toxicity for external applicants. Among the 25 chapters, the 22 chapters were studied except for the last three chapters, which are known to be written by later writers. Based on the above, Geumgweyoryeok(金匱要略)'s external applicants was analyzed the process of manufacture, formulation and the toxicity. Results : There are 11 types of external applicants of Geumgweyoryak(金匱要略). Washing method(洗法) was used 2 times, Drop method(瀝法) was used 1 time, Smoke method(熏法) was used 2 times, Rubbing method(摩法) was used 1 time, Plaster method(敷法) was used 2 times, Invading method(浸法) was used 1 time, Suppository method (坐法) was used 2 times, Flatiron method(烙法) was used 1 time. According to classified the modern formulation, there are 4 types of powder formulation, 4 types of liquid formulation, 2 types of suppository, and 1 type of Semi-solid formulation. Especially toxic drugs, such as Realgar(雄黃) or Hydrocerussite(鉛粉), should be careful. When Realgar(雄黃) smokes, a toxic substance called AS2O3 can come out. Hydrocerussite(鉛粉) can cause lead poisoning. Lead increases the risk of anemia, dehydration, and lead neuropathy when chronically exposed. Conclusion : We supposed that this study can serve as a basic data to help clinical Korean doctors to use the prescription for external applicants more safely and to easily apply it in the form of external applicants.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.655-668
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• 1994

Conventional deodorization filters using soil and compost reach the capacity limitation of deodorization in short period, because its removal mechanism primarily depends on adsorption. Therefore, in this study the experiment was performed on the removal of ammonia which is a strong inorganic malodor, frequently emitted from night soil treatment plants and sewage treatment plants, by seeding activated sludges on the bio-peat containing higher organic contents, water conservation capacity, permeability and lower pressure drop. As a result, in raw peat filter natural ammonia outlet was observed in consequence of pH increase resulted from ammonia ionizing in liquid phase. Ammonia removal mechanism primarily depended on the adsorption onto the anion colloidal substances in peat. In peat bio-filter, theoretical ammonium salts ratio was higher than that of raw peat, resulted from slight pH increase by microorganism activity, however, the experimetal value of ammonia-nitrogen accumulated in bio-peat was lower than that of raw peat because of nitrification by nitrifying bacteria. In the initial reaction period, adsorption was predominant in the ammonia removal mechanism, but nitrification was conspicuous after the middle period. Mass balance of nitrogen was established using experimental data of input $NH_3$ loading, output $NH_3$ loading, $NH_4{^+}$-N, $NO_x$-N, and Org-N. The critical time of unsteady state, which is the maximum activating point of microorganism in bio-filter, was determined using experimental data, and the ammonia adsorption curve was computed using regression analysis. On the basis of the results obtained by above analysis, the delay days for the saturation of adsoption capacity in peat bio-filter was calculated.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1027-1033
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• 2010

A two-phase (gas-liquid) flow is a common phenomenon in fluidic systems, e.g., fluidic systems in the electro-magnetic or nuclear power generation industry and in the steel industry. The measurement of a two-phase flow is important for guaranteeing the safety of the system and for achieving the desired performance. The measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient, is very important. The time resolution achieved by employing the impedance method that can be used to calculate the void fraction from the impedance of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the void fraction without distortion of flow in real time by placing electrodes on the walls of the tubes. Coney analytically studied a ring-type impedance meter, which can be employed in a circular tube. The aim of this study is to experimentally verify the robustness of a three-ring impedance meter to variations in the electric conductivity of the fluid; this robustness was suggested by Coney but was not experimentally verified.

• Journal of Korean society of Dental Hygiene
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• v.12 no.3
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• pp.513-520
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• 2012

Objectives : In this study, contact angle and shore D hardness were measured, and a shark fin test was conducted after selecting five addition silicon(Blu-Mousse, BM; EXABITE II, EX; PERFECT, PF; Regisil$^{(R)}$ Rigid, RE; Silagum$^{(R)}$, SI) in order to figure out the properties of elastomeric interocclusal recording materials and reduce errors at interocclusal recording. 8) Methods : A contact angle was measured using a contact angle analyzer. After placing a drop of liquid on the surface of the specimens of interocclusal recording materials, a contact angle was photographed with a CCD camera on the equipment. In terms of a shark fin test, interocclusal recording materials were mixed for the time proposed by the manufacturer and inserted into the split ring of the Shark fin device. Twenty (20) seconds exactly, a metal rod was removed to make the materials slowly absorbed. Once they hardened, fin height was measured with a caliper after separating molds and trimming the specimens. The shore D hardness was measured with a shore D hardness tester(Model HPDSD, Hans Schmidt & Co. Gmbh, Germany) in sixty (60) minutes after fabricating specimens. In each experiment, five specimens, mean and standard deviation were calculated. A one-way ANOVA test was performed at the p>0.05 level of significance. In terms of correlation among the tests, Pearson correlation coefficient was estimated. For multiple comparison, Scheffe's test was carried out. Results : A contact angle was the highest in EX with $99.23^{\circ}$ (p<0.05) while the result of the shark fin test was the longest in RE with 5.45mm. SI was the lowest (0.27mm) with statistical significance. Among the interocclusal recording materials, significant difference was observed in terms of means (p<0.05). The shore D hardness was the highest in SI with 31.0 while RE was significantly low with 16.4 (p<0.05). Among the materials, statistically significant difference was observed in terms of means when compared to the rest materials (RE), BM, RE and SI (PF and EX) and the remaining materials (BM and SI) (p<0.05). In terms of correlations among the tests, a negative correlation occurred between shore D hardness and shark fin test(r=-0.823, p=0.000). Conclusions : According to the study above, it is necessary to understand the properties of interocclusal recording materials and consider contact angle, shark fin test and properties of shore D hardness to select appropriate materials.

• Herbal Formula Science
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• v.24 no.2
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• pp.80-99
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• 2016

Objectives : Instrumental chemical analysis was utilized to investigate the effect of Add-Omit-Saenghyeoryunbu-eum(AO-SHU) on diabetic treatment. One of the most exciting, yet also controversial, arguments is the safety and biological mechanisms of the natural medicine on human body. Therefore, the aim of this study is to provide a better understanding on bioactive chemical components, hazards of heavy metal contamination and biological mechanism of the diabetic medicine composed of 12 different natural herbs. Methods : To study bioactive compound and metallic component in the diabetic medicine in detail, LC-MS/MS (Liquid Chromatography-Mass/Mass), GC (Gas Chromatography) and ICP (Inductively Coupled Plasma) were utilized to characterize the extract of the diabetic medicine and the result was compared with 18 marker substances selected from literature survey. In addition, in vitro assay experiments including GPR 119 activity and human DGAT-1 inhibition, and OGTT (Oral Glucose Tolerance Test) were performed to verify the effectiveness of this medicine on diabetic treatment. Results : Out of 18 marker substances, 9 bioactive compounds were identified from LC-MS/MS analysis which include Citruline, Catalpol, Berberine, Ginsenoside Rb1, Ginsenoside Rg1, Oleanolic acid, β-Sitosterol, Mangiferin, and Schizandrin. ICP study on 245 residual pesticides revealed that 239 species were not detected but 6 species, Dimethomorph, Trifloxystrobin, Pyraclostrobin, Isoprocarb, Carbaryl and Flubendiamide, while the amounts are trace levels, below permitted concentrations. The biological activity was observed in vitro assay and Oral Glucose Tolerance Test(OGTT), which are consistent with a preliminary clinical test result, a drop in blood sugar level after taking this herbal medicine. Conclusions : Instrumental chemical analysis using LC-MS/MS, GC, and ICP was conducted successfully to identify bioactive compounds in AO-SHU for the treatment of diabetes, finding 9 bioactive compounds. Furthermore, in vitro assay experiments and OGTT show that AO-SHU has its biological activities, which imply that it can be a candidate for the future diabetes remedy.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.304-309
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• 2012

Size verification of small and large bubbles in a bubble column was investigated by employing the dynamic gas disengagement (DGD) method and dual electrical resistivity probe (DRP) method, simultancously. The holdups of large and small bubbles in the bubble column in a given operating condition were obtained by means of the DGD method by measuring the pressure drop variation in the column with a variation of time after stopping the gas input into the column. The size and frequency of bubbles were measured by the DRP method in the same operating condition, from which the bubble holdup of each range of size was obtained. The verification of size in determining the large or small bubbles was decided by comparing the holdups of large or small bubbles measured by the DGD method with that measured by the DRP method. Filtered compressed air and tap water were used as a gas and a continuous liquid medium. The diameter and height of the bubble column were 0.102 m and 1.5 m, respectively. The demarcation size between the large and the small bubbles in the bubble column was 4.0~5.0 mm; the demarcation size was about 5.0 mm when the gas velocity was in the relatively low range, but about 4.0 mm when the gas velocity was in the relatively high range, within this experimental conditions.