• 한국해양공학회지
• /
• 제37권2호
• /
• pp.49-57
• /
• 2023

Since Chappelear developed a Fourier approximation method, considerable research efforts have been made. On the other hand, Fourier approximations are unsuitable for deep water waves. The purpose of this study is to provide a Fourier approximation suitable even for deep water waves and a numerical method to determine the Fourier coefficients and the wave properties. In addition, the convergence of the solution was tested in terms of its order. This paper presents a velocity potential satisfying the Laplace equation and the bottom boundary condition (BBC) with a truncated Fourier series. Two wave profiles were derived by applying the potential to the kinematic free surface boundary condition (KFSBC) and the dynamic free surface boundary condition (DFSBC). A set of nonlinear equations was represented to determine the Fourier coefficients, which were derived so that the two profiles are identical at specified phases. The set of equations was solved using Newton's method. This study proved that there is a limit to the series order, i.e., the maximum series order is N=12, and that there is a height limitation of this method which is slightly lower than the Michell theory. The reason why the other Fourier approximations are not suitable for deep water waves is discussed.

• 한국세라믹학회지
• /
• 제31권5호
• /
• pp.520-528
• /
• 1994

An investigation was carried out to understand the effect of the amount of free silicon on the tribological properties of Si-SiC. The specimens of dense Si-SiC composites with various amount of free silicon were fabricated in the temperature of 175$0^{\circ}C$ after molding under various pressure. Wear properties were measured by ball-on-plate wear tester under the constant weight of 4 Kgf at constant sliding speed of 500 mm/sec in water. As the result, the Rockwell hardness and fracture strength of Si-SiC composites remained nearly constant up to 16.62 vol% of free silicon in the Si-SiC microstructure. The Si-SiC composites containing the free silicon of 16.62 vol% was considered to be prominent in the tribological properties, which had the friction coefficient of 0.08 and the specific wear rate of 2.4$\times$10-8$\textrm{mm}^2$Kgf-1. The analysis of the wear surface indicated the complicated processes occuring on the surface such as fine polishing, abrasion, microfracture.

• Korean Chemical Engineering Research
• /
• 제49권6호
• /
• pp.823-828
• /
• 2011

오일-물 혼합물에서 물을 제거하기 위하여 FWKO(Free Water Knock Out) vessel에서의 물 분리특성에 대해 연구하였다. 오일을 모사하기 위해 데칸, 톨루엔, 아스팔트를 사용하였다. 데칸을 이용하여 프로토타입 vessel에서 기초실험을 수행하였으며, 기초실험결과를 토대로 최적 water cut이 0.8인 것을 알게 되었다. 이에 이어 톨루엔을 이용하여 성능평가를 실행한 결과로 최적 체류시간이 1,200 sec인 것을 알 수 있었고 아스팔트를 사용하여 방해판의 개수, 실험온도를 변수로 FWKO vessel에서의 최적의 물 분리조건에 대해 조사하였다. 최적의 분리조건은 방해판 3개, 온도 $45^{\circ}C$였다.

• Bulletin of the Korean Chemical Society
• /
• 제24권6호
• /
• pp.805-808
• /
• 2003

Fundamental ideas of the free energy gradient method are briefly reviewed with three applications: the stable structures of glycine and ammonia-water molecule pair in aqueous solution and the transition state (TS) structure of a Menshutkin reaction $NH_3 + CH_3Cl → CH_3NH_3^+ + Cl^-$ in aqueous solution, which is the first example of full TS optimization of all internal degrees of freedom.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 추계학술대회논문집
• /
• pp.228-230
• /
• 2009

The moment-of-fluid (MOF) method is a new volume-tracking method that accurately treats evolving material interfaces. Based on the moment data (volume and centroid) for each material, the material interfaces are reconstructed with second-order spatial accuracy in a strictly conservative manner. The MOF method is coupled with a stabilized finite element incompressible Navier-Stokes solver for two fluids, namely water and air. The effectiveness of the MOF method is demonstrated with a free-surface dam-break problem.

• 한방안이비인후피부과학회지
• /
• 제12권2호
• /
• pp.53-66
• /
• 1999

This study has been carried out to investigate the effects of Dojuksan on the renal functions and internal secretion system, as water balance, urine volume, urinary excretion of sodium and potassium, free water clearance, urinary excretion of creatinine, plasma levels of artrial natriuretic peptide (ANP), plasma levels of aldosterone and plasma renin activity, comparing experimental group which Dojuksan water extract were administrated with control group. Sprague-Dawley rats, about 200-250 g, were used for this experiment. The results of this study were as follows: 1. Water balance decreased significantly after the administration of Dojuksan water extract. 2. Urine volume increased significantly after the administration of $100{\mu}l$ Dojuksan water extract per 100g rat. 3. Urinary excretion of sodium increased significantly but urinary excretion of potassium did not change after the administration of Dojuksan water extract. 4. Free water clearance decreased significantly after the administration of Dojuksan water extract 5. Urinary excretion of creatinine increased significantly after the administration of Dojuksan water extract 6. Plasma renin activity did not change after the administration of Dojuksan water extract 7. Plasma levels of artrial natriuretic peptide (ANP) did not change after the administration of Dojuksan water extract 8. Plasma levels of aldosterone decreased significantly after the administration of 200 ${\mu}Dojuksan water extract per l00g rat The results suggest that Dojuksan increase the urinary excretion of sodium. and thus reduce the water balance, which resulted from suppression of sodium reabsorption into renal tubule by increasing glomerular filtration rate and decreasing aldosterone.

• 한국식생활문화학회지
• /
• 제19권5호
• /
• pp.484-490
• /
• 2004

오미자 추출액의 추출 특성과 추출액의 항산화성을 검토하여 오미자의 추출 조건을 결정함으로써 오미자 유효성분의 식품 소재화를 위한 기초자료를 얻고자 하였다. 용매와의 비율을 결정하기 위해 8배, 10배, 12배, 14배의 water를 가하여 추출 수율을 비교한 결과 water와의 비율이 10배일 때 추출 수율이 가장 좋은 것으로 나타났다. 탁도는 Water 추출액에서 가장 높았으며, 추출용매의 ethanol 농도가 증가할수록 낮아졌다. 적정산도는 추출용매의 50% ethanol에서 가장 높았으나, 전체적으로 산도가 매우 낮았다. 유리당 함량은 fructose $1.24{\sim}4.42mg%$, glucose $3.65{\sim}4.71mg%$, sucrose $0.89{\sim}1.69mg%$로 glucose의 함량이 가장 높았으며, 당질의 대부분을 glucose와 fructose인 것으로 나타났다. 총 폴리페놀 함량을 나타낸 것으로 50% ethanol 추출액은 0.98%, 75% ethanol 추출액은 0.89%, water 추출액은 0.58%로 나타나 50% ethanol 추출액에서 가장 높은 함량을 나타내었으며. water에 비해 유기용매 추출시 높은 함량을 보였다. 전자공여능은 water 추출액 60.87%, 50% ethanol 추출액 57.24%, 75% ethanol 추출액 55.61%로 나타나 용매별 전자공여능 효과가 큰 차이는 나타나지 않았으며. water 추출액이 다른 용매에 비해 높은 전자공여 효과를 보여 주었다. SOD 유사환성 측정 결과는 50% ethanol 추출액에서 33.65%로 가장 높은 활성을 나타냈었으며, 50% ethanol 추출액이 다른 두 용매 보다 우수한 것으로 나타나 총 폴리페놀 함량과 전자공여능 측정 결과 와 비슷한 경향을 보여주었다.

• 동의생리병리학회지
• /
• 제16권5호
• /
• pp.911-913
• /
• 2002

Rubi Fructus (fruit of Rubus coreanus Miq.), oriental medicine, has been used for remedy of the liver diseases and for tonic. In order to investigate the oxygen free radical, a harmful factor of aging, in liver of rats fed diets supplemented with the Rubi Fructus water extract(RX), Sprague-Dawley male rats have been fed a diet supplemented with 3% or 5% RX for a month. In rats fed 3% RX supplemented diet, hepatic cytochrome P-450 contents appeared to be increased, and catalase and superoxide dismutase activities were significantly increased compared with the control. There was no difference in glutathione peroxide and glutathione-S-transferase activities between the rats fed RX supplemented diets and the control diet. In conclusion, it is likely that rats fed a diet supplemented with RX may have the oxygen free radicals detoxication potential.

• 상하수도학회지
• /
• 제18권5호
• /
• pp.580-587
• /
• 2004

The objective of this research is to investigate the electrochemical oxidation process for nitrogen removal in wastewater involving chloride ion and nitrogen compounds. The process experiment of electrochemical oxidation was conducted by using the stainless steel tube type reactor and the $Ti/IrO_2$ as anode. Free chlorine production and current efficiency variation for total nitrogen removal was compared depending on whether electrolyte is added, and the nitrogen type distribution under an operating condition. When chloride was added as electrolyte, it was found that production of free chlorine increased and the concentration of the chloride decreased as retention time passed. The concentration of chloride in influent decreased from 1,660 to 1,198 mg/L at the current density of $6.7A/dm^2$, while concentration of free chlorine increased to 132 mg/L. Current efficiency in removal of ammonium nitrogen was increased when chloride was dosed as electrolyte. It was observed that ammonium nitrogen was oxidized to nitrite and nitrate through electrochemical oxidation and that the concentration of total nitrogen in influent was reduced from 22.58 to 4.00 mg/L at the short retention time of 168 seconds through the electrochemical oxidation of nitrogen.

• 한국식품조리과학회지
• /
• 제7권1호
• /
• pp.27-34
• /
• 1991

This study attempted to set up reasonable extraction time of Omija that was put in water for the various components to soak out. Changes of free sugars, organic acids, reducing sugar, total acid and tannin in Omija with various extraction times were investigated (together with the analysis of each components in Omija fruit). 1. High Performance Liquid Chromatography showed fructose, glucose, and sucrose to be the major free sugars of the Omija fruit. Free sugars and reducing sugar value in Omija beverage increased gradually in according with the extraction time, and marked 75.6% per total free sugars and 82.1% per total reducing sugar at 12 hours. 2. Gas Chromatography showed lactic acid, oxalic acid, fumaric acid, levulinic acid, succinic acid, malic acid, citric acid and pyroglutamic acid to be the major organic acids of the Omija fruit. Organic acids and total acids value in Omija beverage increased gradually on proportion to extraction time, and marked 97.0% per total organic acids at 9 hours and 79.0% per total acids at 12 hours. 3. Tannin content in Omija beverage was increased when extraction time was longer but it showed a low percentage as compared with the reducing sugar and total acid. Tannin content marked 48.8% per total tannin at 12 hours. 4. Sensory evaluation revealed that !1 hours of extraction produced the best quality products based in taste, flavor, color and over-all acceptability, considering the data, it seems possible to conclude that the optimum of time for extraction of Omija to water is 9 hours.