• Journal of IKEEE
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• v.24 no.4
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• pp.950-953
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• 2020

A switching differentiator that can estimate the 1st-order time-derivative of a time-varying signal was proposed, and it is extended later to the higher-order switching differentiator(HOSD) that can observe higher-order time-derivatives of a time-varying signal in previous works. By using HOSD, higher-order time-derivatives can be estimated without peaking or chattering, and it has an asymptotic tracking performance. However, there exist many design constants to be determined in HOSD. In this paper, a method of reducing the number of design constants is proposed to solve the problem. Simulations reveal the effectiveness of the proposed method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.10-20
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• 2002

The present paper investigates methods to control dynamic stall using an optimal approach. An unsteady aerodynamic sensitivity analysis code is developed by a direct differentiation method from a two-dimensional unsteady compressible Navier-Stokes solver including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating for a period of time. Unsteady sensitivity derivatives of the objective function are calculated by the sensitivity code, and optimization is carried out using a linear line search method at every physical time step. Numerous examples of dynamic stall control using control parameters such as nose radius, maximum thickness of airfoil, or suction show satisfactory results.

• Bulletin of the Korean Chemical Society
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• v.29 no.6
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• pp.1125-1130
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• 2008

A series of dihydroxylated chalcone derivatives with diverse substitution patterns on a phenyl ring B and the para-substituents on a phenyl ring A were prepared, and their radical scavenging activities were evaluated by simple DPPH test to determine quantitative structure-activity relationship in these series of compounds. The chalcone compounds with the ortho- (i.e. 2',3'- and 3',4'-) and para- (i.e. 2,5'-) substitution patterns show an excellent antioxidant activities (80-90% of control at the concentration of 50 $\mu$M) which are comparable to those of ascorbic acid and $\alpha$ -tocopherol as positive reference materials. On the contrary, the compounds with meta- (i.e. 2',4'-, 3',5'-) substitution pattern demonstrate very dramatic decrease in activities which are around 25% of the control even at the concentration of 200 $\mu$ M (IC50 > 200 $\mu$ M). These dramatic differences could be interpreted in terms of the ease formation of fairly stable semiquinone radicals from the ortho- and parasubstituted chalcone molecules through facilitating electron delocalization. Our results indicate that the substitution patterns of two hydroxyl groups on ring B are very important structural factors for their radical scavenging activity enhancement. Meanwhile, the substituents at para-position of the phenyl ring A of chalcones have no influence on the activity.

• Journal of Ginseng Research
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• v.8 no.2
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• pp.153-166
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• 1984

The anticancer activities of petroleum ether extract of Panax ginseng root(crude GX) and its partially purified fraction from silicic acid column chromatography (7:3 GX) were studied with Sarcoma 180(S-180) or Walker carcinosarcoma 256 (Walker 256) in vivo and with L1210 leukemic lympocyte in vitro. Potential cytotoxic activities of the crude GX and against L1210 cells were compared with those of 5-Fluorouracil (5-FU) and saponin derivatives (Panax-diol, Panax-triol, Diol saponin, Triol saponin) in vitro. In order to observe the physiological effects of the crude GX and 7:3 GX on the animals with cancer, hemoglobin(Hb), red blood cell(R.B.C) and white blood cell after treatment with each GX in comparison with corresponding control groups, respectively. The anticancer effects of the crude GX and 7:3 GX were estimated by measuring the survival time of S-180 bearing mice after treatment with them. The experimental results obtained are summarized as follows; 1. The one unit of cytotoxic activity against L1210 cells was equivalent to 2.54$\mu\textrm{g}$ and 0.88$\mu\textrm{g}$of the crude GX and 7:3 GX per ml of culture medium, respectively. 2. The cytotoxic activities of Panax-diol, Panax=triol, Diol saponin and triol saponin against L1210 cells were not detected. 3. The anticancer activities of 5-FU against L1210, S-180 and Walker 256 were very effective in vivo and vitro tests. 4. The significantly increased W.B.C values of mice after inoculation with S-180 cells were reduced to normal range by the crude GX treatment. 5. The significantly decreased Hb values of rats after inoculation with Walker 256 were recovered to normal range by oral administration of the crude GX. 6. The survival times of mice inoculated with S-180 cells were extended about 1.5 to 2 times by the 7:3 GX treatment compared with their control group.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.389-394
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• 2017

In this paper, the captive model test of a submarine using the RA test was carried out in a square basin. The target model submarine consisted of four types varying according to the position of conning tower and control planes. Hydrodynamic derivatives were acquired by multi-regression analysis. As a result, horizontal dynamic stability indexes of the four types presented positive values and satisfied dynamic stability requirements. In addition, the stability index of type 1 and type 4 - each with the same cruciform configuration of the aft planes - scored within the acceptable range of motion stability.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.1-9
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• 2022

In this study, for development of the MDO (Multi Disciplinary Optimization) framework, the flight dynamic characteristic parameters of the ChangGong-91, a light aircraft, were extracted by an analytical method based on various semi-empirical methods, and the flight test method was compared and evaluated. The semi-empirical analysis methods for comparative subjects were the Perkins method, McCormick method, and Smetana method. The major stability/control derivatives and dynamic factors were calculated, using each method. As the comparison criteria, the flight test derivative estimates and dynamic factors were processed, using the output error method. Additionally, the flight characteristics of the light aircraft were analyzed and evaluated according to the provisions of the Korean Airworthiness Standard (KAS) of the Ministry of Land, Infrastructure and Transport, and MIL-F-8785C for the U.S. military.

• Journal of Yeungnam Medical Science
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• v.39 no.4
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• pp.322-331
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• 2022

Background: The combined use of biomaterials for regeneration may have great biological relevance. This study aimed to compare the regenerative potential of biphasic calcium phosphate (BCP) alone and with growth factor enamel matrix derivatives (EMDs) for the regeneration of intrabony defects at 1 year. Methods: This randomized controlled trial included 40 sites in 29 patients with stage II/III periodontitis and 2/3 wall intrabony defects that were treated with BCP alone (control group) or a combination of BCP and EMD (test group). BCP alloplastic bone grafts provide better bio-absorbability and accelerate bone formation. EMDs are commercially available amelogenins. Mean values and standard deviations were calculated for the following parameters: plaque index (PI), papillary bleeding index (PBI), vertical probing pocket depth (V-PPD), vertical clinical attachment level (V-CAL), and radiographic defect depth (RDD). Student paired and unpaired t-tests were used to compare the data from baseline to 12 months for each group and between the groups, respectively. The results were considered statistically significant at p<0.05. Results: At 12 months, the PI and PBI scores of the control and test groups were not significantly different (p>0.05). The mean V-PPD difference, V-CAL gain, and RDD difference were statistically significant in both groups at 12 months (p<0.001 for all parameters). Intergroup comparisons showed that the mean V-PPD reduction (2.13±1.35 mm), V-CAL gain (2.53±1.2 mm), and RDD fill (1.33±1.0 mm) were statistically significant between the groups at 12 months (p<0.001 for all parameters). Conclusion: BCP and EMDs combination is a promising modality for the regeneration of intrabony defects.

• Applied Biological Chemistry
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• v.46 no.4
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• pp.361-366
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• 2003

Anti-aflatoxigenic studies on synthetic pyridione alkaloids were conducted. Seven derivatives using piperlongumine as a leading compound were prepared from 3,4,5-trimethoxycinnamic acid (TMCA). These derivatives were analyzed for their structural confrmation and purity by HPLC, GC, GC/MS and $1^H-NMR$. 1-piperidin-1-yl-3-(3,4,5-trimethoxyphenyl)propenone (1) reaction with piperidine; 1-morpholin-4-yl-3-(3,4,5-trimethoypenyl)propenone (2) with morpholine; 1-(3,5-dimethylpiperidin-1-yl)-3-(3,4,5-trimethoxyphenyl)propenone (3) with 3,5-dimethylpiperdine; 1-(2-methylpiperidine-1-yl)-3-(3,4,5-trimethoxyphenyl)propenone (4) with 2-methylpiperidine; 1-(3-hydroxypiperidin-1-yl)-3- (3,4,5-trimethoxyphenyl)propenone (5) with 3-hydroxypiperidine hydrochloride; 1-[3- (3,4,5-trimethoxyphenyl)acryloyl]piperidin-2-one (6) with ${\delta}-valerolactam;\; and\;ethyl\;1-[3-(3,4,5-trimethoxyphenyl)acyloyl]piperidine-4-carboxylate$ (7) with ethyl isonipectotate were synthesized respectively. All derivatives showed an inhibitory activity on aflatoxin $B_1$ production. In conclusion, we believe that they might be an agent for the control of mycotoxin in agricultural commodities.

• The Korean Journal of Pharmacology
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• v.18 no.1
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• pp.65-72
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• 1982

It has been known that retinoids are intrinsically of critical importance for control of premalignant epithelial cell differentiation. In the absence of retinoids, normal cellular differentiation and growth does not occur in epithelia such as those of trachea and bronchi. Furthermore, it was also reported that retinoid deficiency enhanced susceptibility to chemical carcinogenesis in the respiratory system, in the bladder, and in the colon of the experimental animal. In 1974, Bollag examined the effects of synthetic retinoids in prevention of development of cancer and demonstrated synthetic retinoids to have more favorable therapeutic index than retinoic acid for causing regression of skin papilloma in mice. Therefore, it was assumed that this anticarcinogenic effect of vitamin A derivatives could be due to modification of the metabolism of the carcinogenic polycyclic hydrocarbon, which must first be activated to exert their effect. Hill and Shih reported that vitamin A compounds and analogs had inhibitory effect on drug metabolizing enzyme from liver and lung tissue of mouse and hamster. Lucy suggested that the chemoprevention effect of vitamin A derivatives is due to reaction with molecular oxygen, and it is possible that inhibition of hydroxybenzpyrene formation is a result of this property. On the other hand, butylated hydroxytoluene which is a potent antioxidant strongly inhibited the formation of mammary tumor induced by dimethylbenranthracene. Also, it was observed that this antioxidant inhibited cancer induction in rats by N-2-fluo-renylacetamide. The purpose of this experiment was to investigate the effect of vitamin A derivatives such as retinoic acid and retinoid on drug-metabolizing enzyme and to determine whether riboflavin tetrabutylate or vitamin E could prevent of modify any changes induced by vitamin A delivatives in the rats. The results obtained were as followings. 1) Body weight was significantly reduced by retinoic acid, but not by retinoid. 2) Retinoic acid markedly increased liver weight while retincid showed no effect on liver weight. Treatment of riboflavin tetrabutylate did not affect retinoic acid-induced change in both body weight and liver weight. 3) Both retinoic acid and retinoid remarkably decreased the activity of aminopyrine demethylase. Pretreatment of riboflavin tetrabutylate, however, prevented inhibitory effect of retinoic acid on the enzyme activity. 4) No significant effect of vitamin E on aminopyrine demethylase was observed in both groups treated with retinoic acid and retinoid.

• The Korean Journal of Food And Nutrition
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• v.30 no.5
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• pp.973-982
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• 2017

Gastrodia elata Blume often has been used for the treatment of headaches, convulsions, hypertension, and neurodegenerative diseases. The main active constituents are gastrodin, 4-hydroxybenzyl alcohol, vanillyl alcohol, 4-hydroxybenzylaldehyde and parishin A, B, C and E. Because Gastrodia elata has also unacceptable off-odor (swine barnyard-like) for food, there is a need to reduce it as well as allow for greater utilization as a functional food materials. In this study, a major off-odor producing substance of Gastrodia elata was fractionated by steam distillation and silica gel column chromatography. The substance was identified as p-cresol(4-methyl phenol) by GC-MS analysis and comparison of the retention time with that of an authentic compound in GC. The content of p-cresol in fermented Gastrodia elata was decreased. A fermented sample of Latobacillus sakei for 2 days was reduced to 54.7%, when compared with a unfermented sample. The five parishin derivatives in Gastrodia elata were identified by HPLC-MS analyses, and a comparison of HPLC retention times with those of authentic compounds. When compared with parishin derivatives of an unfermented Gastrodia elata, those of Gastrodia elata fermented by L. sakei, increased to 18.3% for 2 days. Increases of about 14.0~38.4% of the total phenolic compounds and 57.4~77.3% total flavonoids were found in fermented extracts, by 3 lactic acid bacteria strains. They were compared with $97.1{\pm}2.9{\mu}g/g$ and $40.9{\pm}2.0{\mu}g/g$ in the unfermented control, respectively. The extracts of Gastrodia elata Blume that were fermented by lactic acid bacteria had higher DPPH free radical scavenging activity and FRAP reducing power than the unfermented control.