• Tribology and Lubricants
• /
• v.39 no.6
• /
• pp.228-234
• /
• 2023

In this study, reciprocating wear tests are performed on AISI 52100 bearing steel to investigate its tribological behavior in a hexagonal boron nitride (h-BN) water solution. The h-BN-based aqueous lubricant is prepared using an atoxic procedure called ultrasonic sonication in pure water. Ball-on-flat reciprocating sliding experiments are conducted, where the ball is slewed on a fixed flat at 50-㎛ displacement. The lubricating behavior of h-BN is compared with that of deionized (DI) water. Results show that the friction coefficient is higher in h-BN testing than that in DI tests, but the results are equalized as the friction coefficient reaches a stable level. Scanning electron microscopic images reveal significant material loss in the center and mild abrasion on the edge of the wear scar in h-BN tests. However, these effects are minor in DI water situations. The results of energy-dispersive X-ray spectroscopy show that considerable oxidation occurs in the central zone of the wear scar in h-BN cases with strong adhesion and material removal. These findings reveal the importance of determining ideal circumstances that can tolerate material friction and wear.

• Asian-Australasian Journal of Animal Sciences
• /
• v.20 no.2
• /
• pp.208-213
• /
• 2007

The objective of the experiment was to determine the optimum cultural [moisture levels (55, 60 and 70%), days of fermentation (7, 14 and 21), temperature (25 and $35^{\circ}C$) of incubation)] and nutritional parameters (urea addition (0 and 2%) and variable levels of single super phosphate (0.25 and 0.50% SSP)) for bio-processing of the mustard (Brassica campestris) straw (MS) under solid-state fermentation (SSF) system. The performance of SSF was assessed in terms of favorable changes in cell wall constituents, protein content and in vitro DM digestibility of the MS. Sorghum based inoculum (seed culture) of Ganoderma lucidum to treat the MS was prepared. The 50 g DM of MS taken in autoclavable polypropylene bags was mixed with a pre-calculated amount of water and the particular nutrient in the straw to attained the desired levels of water and nutrient concentration in the substrate. A significant progressive increase in biodegradation of DM (p<0.001), NDF (p<0.01) and ADF (p<0.05) was observed with increasing levels of moisture. Among the cell wall constituents the loss of ADF fraction was greatest compared to that of NDF. The loss of DM increased progressively as the fermentation proceeded and maximum DM losses occurred at 28 days after incubation. The protein content of the treated MS samples increased linearly up to the day $21^{th}$ of the incubation and thereafter declined at day $28^{th}$, whereas the improvement in in vitro DM digestibility were apparent only up to the day $14^{th}$ of the incubation under SSF and there after it declined. The acid detergent lignin (ADL) degradation was slower during the first 7 days of SSF and thereafter increased progressively and maximum ADL losses were observed at the day $28^{th}$ of the SSF. The biodegradation of DM and ADL was not affected by the variation in incubation temperature. Addition of urea was found to have inhibitory effect on fungal growth. The effect of both the levels (0.25 and 0.50) of SSP addition in the substrate, on DM, NDF, ADF, cellulose and ADL biodegradation was similar. Similarly, the protein content and the in vitro DM digestibility remain unaffected affected due to variable levels of the SSP inclusion in the substrate. From the results it may be concluded that the incubation of MS with 60 percent moisture for 21 days at $35^{\circ}C$ with 0.25 percent SSP was most suitable for MS treatment with Ganoderma lucidum. Maximum delignification, enrichment in the protein content and improvement in in vitro DM digestibility were achieved by adopting this protocol of bioprocessing of MS.

• Journal of Pharmaceutical Investigation
• /
• v.32 no.3
• /
• pp.185-190
• /
• 2002

To improve the solubility of poorly water-soluble drug and to develop a sustained release tablets, the need for the technique, the formation of solid dispersion with polymeric materials that can potentially enhance the dissolution rate and extent of drug absorption was considered in this study. The 1:1, 1:4, and 1:5 solid dispersions were prepared by spray drying method using PVP K30, ethanol and methylene chloride. The dissolution test was carried out at in phosphate buffer solution at $37^{\circ}C$ in 100 rpm. Solid dispersed drugs were examined using differential scanning calorimetry and scanning electron microscopy, wherein it was found that felodipine is amorphous in the PVP K30 solid dispersion. Felodifine SR tablets were prepared by direct compressing the powder mixture composed of solid dispersed felodipine, lactose, Eudragit and magnesium stearate using a single punch press. In order to develop a sustained-release preparation containing solid dispersed felodipine, a comparative dissolution study was done using commercially existing product as control. The dissolution rate of intact felodipine, solid dispersed felodipine and its physical mixture, respectively, were compared by the dissolution rates for 30 minutes. The dissolution rates of felodipine for 30 minutes from 1:1, 1:4, 1:5 PVP K30 solid dispersion were 70%, 78% and 90%. However, dissolution rate offelodipine from the physical mixture was 5% of drug for 30 minutes. Our developed product Felodipine SR Tablet showed dissolution of 17%, 50% and 89% for 1, 4, and 7 hours. This designed oral delivery system is easy to manufacture, and drug releases behavior is highly reproducible and offers advantages over the existing commercial product. The dissolution rate of felodipine was significantly enhanced, following the formation of solid dispersion. The solid dispersion technique with water-soluble polymer could be used to develop a solid dispersed felodipine SR tablet.

• Journal of Ginseng Research
• /
• v.32 no.4
• /
• pp.390-396
• /
• 2008

For evaluating the quality of ginseng, simple and fast analysis methods are needed to determine the ginsenoside content of the ginseng products. The aim of this study was therefore to optimize conditions for fast analysis of the ginsenosides, the active ingredients in extracts of Korean red ginseng. When tandem HPLC mass spectrometry (HPLC-MS/MS) was used, four forms of ginsenoside, Rb1, Rb2, Rc, and Re, were readily separated in seven minutes using a gradient mobile phase (acetonitrile and water containing acetic acid). This is the shortest separation time reported among the studies of major ginsenoside analysis. When gradient HPLC with UV detection was used, the detection limit was high, but separation of these four ginsenosides required 25 minutes using acetonitrile and water containing formic acid as a mobile phase. HPLC-MS/MS was able to separate ginsenoside Rg1 easily regardless of the mobile phase condition, but the HPLC-UV could not separate Rg1 because acetonitrile concentration in the mobile phase had to be maintained below 20%. Ginsenoside peaks were clearer and had more sensitive detection limits when Korean red ginseng extract was analyzed by the HPLC-MS/MS, but the UV detection was useful for chromatographic fingerprinting of all four major ginsenosides of the extract: Rb1, Rb2, Rc, and Re. Extracts were found to contain 2.17 mg, 1.51 mg, 1.29 mg, and 0.46 mg of ginsenoside Rb1, Rb2, Rc, Re, respectively, per gram weight. The ratios of each ginsenoside in the extracts were 1.0 : 0.7 : 0.6 : 0.2, respectively. Taken together, the results indicate that HPLC-MS/MS spectrometry could be the most useful method for rapid analysis of even small amounts of major ginsenosides, while HPLC with UV detection could also be used for rapid analysis of major ginsenosides and for quality control of ginseng products.

• Journal of Soil and Groundwater Environment
• /
• v.22 no.5
• /
• pp.112-127
• /
• 2017

Groundwater accounts for more than 10% of the total water supply in Korea. However, the contribution of groundwater to public water supply systems has been poorly played role throughout the country except for Jeju Island. Compared with the groundwater uses in foreign countries, the pattern of groundwater use in Korea seems to be very deformed and unreasonable. Currently, the development and use of groundwater in Korea are mostly carried out by the individuals, and public sectors such as central and local governments are not actively involved in such activities. Private groundwater use and management will continue to cause groundwater depletion and pollution problems. It is necessary to actively enhance the role of public authorities in groundwater managements by engaging precise hydrogeological surveys and proper economic evaluation in the development and operation of groundwater sources. Also, in order to solve the problems that public water supply systems overly rely on the surface water sources, it is necessary to take policies that require the water supply companies to secure a variety of water sources.

• Korean Institute of Interior Design Journal
• /
• v.14 no.6 s.53
• /
• pp.193-201
• /
• 2005

In this study we analyzed and interpreted the phenomenologlcal characteristics and meanings of water space in religious architecture through field studies and phenomenologlcal approaches, focusing on the religious architecture Introducing water space in contemporary architecture. The phenomenological experience elements of the research ate light, time, place and context. As the results of this study, first, light as a phenomenological element not only induces a contrast and change between light and the shadow in architectural space and various changes of light in inner space, but also operates as an element which expresses building features outward with time. Second, time as a phenomenological perception experience makes us feel changes of the environment and physical properties and experience space visually and physically. The continuity of time shows the change of a day, night and daytime and seasons. Third, water space makes the sense of place more remarkable, connected closely with surrounding nature In outer space, and creates a new space. Fourth, water space is a contextual element which harmonizes with surrounding environment by connecting surrounding natural environment with architectural space. Fifth, water space in religious architecture is a symbolic and central element, and emphasizes the atmosphere of architectural space. In addition, it makes the people who experience water space perceive the place by triggering sensitive response.

• 한국태양에너지학회:학술대회논문집
• /
• 2008.11a
• /
• pp.214-219
• /
• 2008

This study is describes thermal performance of solar cooling and hot water for demonstration system with ETSC(Evacuated tubular solar collector) installed at Seo-gu culture center of Kwanju. Control condition for solar cooling and hot water system is changed by connection of auxiliary heater. Demonstration system was connected to central air conditioning system. Demonstration system was operated by two types. First type(A) was operated to cooling and hot water supply in that order. Second type(B) was operated to hot water supply and cooling in that order. As a result. it was indicated that the total solar energy consumption of (A) was 799 MJ and the solar energy consumption rate for the cooling and hot water supply was 70% and 30% respectively. Total solar energy consumption of (b) was 898 MJ and the solar energy consumption rate for the cooling and hot water supply was 31% and 69% respectively.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.198-198
• /
• 2017

Climate change causes unpredictable and erratic climatic patterns which affects crop production in agriculture and threatens public health. To cope with the challenges of climate change, sustainable and sound growth environment for crop production should be secured. Recent attention has been given to the development of smart irrigation system using sensors and wireless network as a solution to achieve water conservation as well as improvement in crop yield and quality with less water and labor. This study developed the smart irrigation technique for farmlands by monitoring the soil moisture contents and real-time climate condition for decision-making support. Central to this design is micro-controller which monitors the farm condition and controls the distribution of water on the farm. In addition, a series of laboratory studies were conducted to determine the optimal irrigation pattern, one time versus plug time. This smart technique allows farmers to reduce water use, improve the efficiency of irrigation systems, produce more yields and better quality of crops, reduce fertilizer and pesticide application, improve crop uniformity, and prevent soil erosion which eventually reduce the nonpoint source pollution discharge into aquatic-environment.

• Journal of Ginseng Research
• /
• v.32 no.4
• /
• pp.283-290
• /
• 2008

Hypercholesterolemia is associated with many pathological states such as fat deposit in the tendon and skin, hepatomegaly, pancreatitis and heart attack. The present study was focused on the effect of Korean red ginseng water extract (RGWE) on the recovery of hepatic function that was deteriorated in high-cholesterol diet fed mice. Mice were divided into 6 groups ; normal diet group (AIN-2WK), 4 week-high-cholesterol diet group (CHOL-4WK), 2 week-high-cholesterol + 2 week-normal diet group (CHOL-2WK), 2 week-high-cholesterol + 2 week-normal diet + RGWE treated group (R100, R300, R500). RGWE treated group received normal diet and RGWE at daily doses of 100, 300, 500 mg/kg b.w. for 2 weeks after the 2 weeks feeding of high-cholesterol diet. The results are as follows : 1. The hepatic weight and total hepatic lipid weight were markedly lower in RGWE treated group than those in the CHOL-4WK or CHOL-2WK group, indicating that ginseng inhibited hepatic hypertrophy. 2. Total hepatic cholesterol and HDL-cholesterol in normal diet conversion group (CHOL-2WK) were significantly reduced compared with the high cholesterol group (CHOL-4WK). The lowering effect was significantly reinforced by RGWE administration. 3. Hepatic triglyceride level of CHOL-4WK group was markedly lower than that of the normal group (AIN-2WK). However, the level was significantly increased in CHOL-2WK and RGWE treated group. The result indicated that ginseng administration and diet conversion exert normalizing effects of hepatic function. 4. The lipid peroxide levels in RGWE treated groups were markedly lower than CHOL-2WK group. These results suggest that Korean red ginseng water extract can be useful as a dietary supplement for the treatment of obesity or hypercholesterolemia by improving lipid metabolism and hepatic function.

• Journal of Ginseng Research
• /
• v.31 no.4
• /
• pp.196-202
• /
• 2007

Skin wrinkles are associated with collagen synthesis and matrix metalloproteinase-I (MMP-1) activity. This study was carried out to select optimum ratio of 3 herbs in skin health food for anti-wrinkle. Human dermal fibroblast cell was incubated with experimental samples, which were Korean red ginseng ethanol extracts (ER), Torilis fructus water extracts (WT), Corni fructus water extracts (WC) and their mixtures (WM1, WM3). And then we determined effects on collagen biosynthesis, MMP-1 activity and SOD activity in human dermal fibroblast cell. In control group, collagen biosynthesis was amounted at 474.8 ng/ml and 533.9 ng/ml, 539.3 ng/ml, 514.1 ng/ml in ER, WT and WC respectively. Furthermore, WM3 (KTNG0345) was increased to 561.45 ng/ml. MMP-1 activity of ER, WT, WC, WM1 were determined to 31.9 ng/ml, 32.85 ng/ml, 32.0 ng/ml, 31.3 ng/ml and WM3 (KTNG0345) was decreased to 28.85 ng/ml. In addition, the experimental samples showed a antioxidative activities. From this results, we conclude that Korean red ginseng ethanol extracts, Torilis fructus water extracts, Corni fructus water extracts and their mixtures have a anti-wrinkle effect and WM3 (KTNG0345) may be regarded as an optimum composition for synergic effect producing. The standardized components of KTNG0345, ginsenoside-$Rb_1$, torilin and loganin were identified at 10.85 mg/g, 0.128 mg/g and 3.92 mg/g respectively.