• Korean Journal of Crystallography
• /
• v.11 no.3
• /
• pp.151-156
• /
• 2000

Yb/YAG single crystals were grown from the melt composition of Y/sub 1-x/Yb/sub x/)₃Al/sub 5/O/sub 12/ where x equal to 5, 10, 15, 20, 25, 33, 50, 75 and 100 at % by floating zone method. Optimum growth parameters to get high quality single crystals were 3.5 mm/h of growth rate and 20 rpm of rotation rate under the N₂ atmosphere. After the growth, color of crystals was appeared with pale blue due to the lack of oxygen, but it was disappeared after annealing at 1450℃ for 2 hr. Absorption coefficients were linearly increased depending on the concentration of Yb/sup 3+/ ions. Broad emission band was measured in the range of 1020 to 1050 nm with the peak intensity at 1031 nm and 1051 nm because of ²F/sub 5/2/(1)→²F/sub 7/2/(3) and ²F/sub 5/2/(1)→²F/sub 7/2/(4) transition respectively. When Yb/sup 3+/ ions were substituted with high rates, there were tendency to decrease the measured fluorescent lifetime for Yb ions depending on the concentration of Yb/sup 3+/ ions.

• Journal of the Korean Society of Safety
• /
• v.16 no.3
• /
• pp.19-25
• /
• 2001

The friction-welding SM25C is a substitute for the suing steel that is utilized in the machinery, airplane, and automobile, ok. This substitution would provide reduction of material and weight of welding parts. From the result we found that the strength of the friction welded joint was 529-617MPa and the toughness 1.2 times higher than that of the base metal. The optimal condition of friction welding was found as follows : n=2000rpm, $P_1$=68㎫, $P_2$=137MPa, $t_2$=2sec, $t_1$=2-4sec, Considering the strength, the hardness, and the reduction of area in the friction welding, the fiction welding using SUP9A and SM25C was found to cause no problem in on-the-job application.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.20 no.1
• /
• pp.71-77
• /
• 2012

In order to find a feasibility of applying an agricultural biomass to the anaerobic digestion system, the effects of pre-treatment of rice straw was investigated by different sizes,temperatures, ultrasonic frequencies, and with/without NaOH treatment on the change of soluble organic matter, which is generated most dominantly in Korea. It was observed that SCOD(soluble chemical oxygen demand) as the index for the decomposition of rice straw increased with the smaller particle size, higher reaction temperature and alkali treatment. With treatment of 5% NaOH, it was shown that the highest concentrations of SCOD were observed at 9,000 mg $L^{-1}$ and 6,000mg $L^{-1}$ at $35^{\circ}C$ and $55^{\circ}C$, respectively. Agitating with ultrasonic irradiation could be enhanced SCOD of rice straw less than 3 cm with 40 kHz of ultrasound. Optimal RPM in this study was at 150 rpm regardless of reaction temperatures.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.5
• /
• pp.19-25
• /
• 2012

This study describes effects of DME additives on combustion and exhaust emissions characteristics including nano-particle in a single cylinder compression ignition engine. Considered additives include bio-diesel, n-butanol, and MTBE for increasing kinematic viscosity. Among three additives, n-butanol showed the greatest kinematic viscosity. In addition MTBE showed the highest vapor pressure. In the present study mixing ratios of additives were kept constant at 1 and 10% by volume. Experiments were performed at 1200rpm engine speed and nano-particles were measured by SMPS (Scanning mobility particle sizer) devices. Results of combustion characteristics showed that considered additives had little effects on combustion pressure. However, patterns of heat release rate were dependent on properties of additives. Nano-particles of MTBE were the lowest among considered additives.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.7
• /
• pp.2320-2324
• /
• 2012

A novel approach for metabolite extraction and fingerprinting was introduced based upon the nano-baskets and emulsion liquid membrane-nuclear magnetic resonance (ELM-NMR) technique. The objective of this method is optimizing the fingerprints, minimizing the metabolic variation from analysis, increasing the likelihood differences, and obtaining the maximum extraction yield. Low molecular weight metabolites in rat serum were recovered by ELMs using 12 nano-baskets of calixarene, as both emulsifier and carrier. The yields of ELMs were optimized by the method of one-at-a-time. According to NMR data, the maximum metabolic variation was achieved using scaffold 4 (4 wt %), n-decane membrane, stirring rate of 300 rpm, treat and phase ratios of 0.3 and 0.8, respectively. The results revealed that some calixarenes tend to extract non-specific macromolecules; and repeatability of fingerprints for 7-mediated ELM was maximum and for 3-mediated ELM was minimum. The yield of extractions was obtained to be higher for n-decane and lower for carbon tetrachloride. Among different membranes, the fingerprints by chlorinated liquid membranes were more repeatable than using toluene or n-decane.

• Journal of Periodontal and Implant Science
• /
• v.53 no.1
• /
• pp.85-95
• /
• 2023

Purpose: In recent years, guided implant surgery has been widely used for the convenience of patients and surgeons. Further streamlining the surgical procedure would make implant surgery more convenient. Low-speed water-free conditions are often used in guided implant surgery. Therefore, in this study, we attempted to confirm once again whether drilling was safe at a low speed without water. The main purpose of this study was to evaluate whether a simplified drilling protocol that omits some intermediate steps in the drilling process was safe from the viewpoint of heat generation. Methods: D1 density artificial bone blocks were drilled under 50 rpm, 10 N·cm water-free conditions, and the surface temperature was measured using a digital infrared camera. First, drilling was performed with the sequential drilling method, which is the most widely used technique. Second, for each drill diameter, the temperature change was measured while performing simplified drilling with omission of the previous 1, 2, or 3 steps. Results: In sequential drilling, the heat generated during drilling at all diameters was less than the critical temperature of osteonecrosis (47℃) except for the ⌀2 drill. Statistical significance was observed in all groups when comparing sequential and simplified drilling in the ⌀3.2, ⌀3.8, and ⌀4.3 drills (P<0.001). However, in the simplified drilling procedures, the temperature was below the osteonecrosis threshold temperature (47℃) except for the ⌀4.3 drill with the omission of the previous 3 steps (⌀3.0, ⌀3.2, and ⌀3.8). Conclusions: In general, drilling under low-speed, water-free conditions has shown stable results in terms of heat generation. Simplified drilling showed statistically significantly greater heat generation than sequential drilling. However, most of the diameters and omitted steps seem to be clinically acceptable, so it will be useful if an appropriate selection is made according to the patient's clinical condition.

• Journal of Environmental Science International
• /
• v.12 no.10
• /
• pp.1079-1084
• /
• 2003

This study was carried out to check changes of components in the slaughter waste by the bacteria isolated from slaughter wastes from Gyungnam Province from May to June 2000, and to find usefu] organism for treatment of the waste. Bacteria used in this study were Aeromonas hydrophila, as the dominant of the waste. Optimum conditions for bacterial culture were obtained as the temperature of 35$^{\circ}C$, pH 6.5, and shaking of 120 rpm in nutrient broth. The mean values of dissolved oxygen was 4.14 mg/1; biochemical oxygen demand, 1731.21 mg/1; ratio of BOD/COD, 0.53-0.64; ratio of T-P/T-N, 1.0-1.41; and viable counts of the waste, 5.47${\times}$10$\^$7/ CFU. Little change in total nitrogen observed by 36 hr of the culture. The largest amount of increasing NH$_4$$\^$+/-N was observed in the sample that 10% of the waste added in nutrient broth with A. hydrophila showing the value of 29.19 mg/l at the beginning to 570.36 mg/1 by 36 hr of culture. However, the highest increasing ratio between initial amount and finals at 36 hr of culture showed as 41.6 times when 3% of the waste added. NO$_3$ -N was decreased showing the value of 71.27 mg/1 to 32.14 mg/1 by 24 hr of culture with the organism when 10% of the waste added in nutrient broth. Total phosphorus was decreased showing the value from 188.74 mg/1 to 101.41 mg/1 after 12 hr of culture with the organism when 5% of the waste added in nutrient broth, while T-P was decreased gradually by 24 hr of culture from 193.8 to 101.4 mg/1 when 10% of the waste added.

• Journal of Life Science
• /
• v.19 no.7
• /
• pp.845-851
• /
• 2009

A vector harboring double cassettes; a heterologous gene expression cassette of pHCE-InaN-antigen and a ghost formation cassette of pAPR-cI-E lysis 37 SDM was constructed and introduced to E. coli DH5a. For the production of a bacterial ghost vaccine, bacterial ghosts from E. coli / Streptococcus iniae with four different types of antigens - enolase, GAPDH, sagA and piaA - were produced by the optimization of fermentation parameters such as a glucose concentration of 1 g/l, agitation of 300 rpm and aeration of 1 vvm. Efficiency of ghost bacteria formation was evaluated with cultures of OD$_{600}$=1.0, 2.0 and 3.0. The efficiency of the ghost bacteria formation was 99.54, 99.67, 99.99 and 99.99% with inductions at OD$_{600}$=3.0, 1.0, 2.0 and 1.0 for E. coli/S. iniae antigens enolase, piaA, GAPDH and sagA, respectively. Ghost bacteria as a vaccine was harvested by centrifugation. The antigen protein expressions were analyzed by SDS-PAGE and western blot analysis, and the molecular weights of the enolase, piaA, GAPDH and sagA were 78, 26, 67 and 26 kDa, respectively. The molecular weights of the expressed antigens were consistent with theoretical sizes obtained from the amino acid sequences.

• Journal of Life Science
• /
• v.12 no.3
• /
• pp.242-249
• /
• 2002

The optimal culture conditions in 500$m\ell$ flask suture, 5$\ell$ jar fermenter and 2,000 $\ell$ large stale culture were investigated to maximize the production of antibiotic on Rhizoctonia solani AC4, the causal agent of vegetables damping-off, by the strain Bacillus ehimensis YJ-37. Starch (1.5%) as a carbon source, peptone (0.6%) as a nitrogen source and MgC1$_2$(0.15%) as a metal ion in the medium containing N $a_2$HP $O_4$(0.3%) showed the highest production of the antibiotic(s) in a rotary shake (200 rpm). Optimal initial pH of the culture medium, culture temperature and culture time for the antibiotic(s) production were pH 8.0, 32$^{\circ}C$ and 54hrs, respertively. Under the optimal renditions in flask culture, cell growth and antifungal activity (clear zone size) were 1.42 $\times$ 10$^{8}$ cfu/$m\ell$ (21g-DCW/ $\ell$) and 13.9 mm, respectively. In 5 $\ell$ jar fermenter (medium 3 $\ell$), optimal air flow, agitation speed and culture time for the antibiotic(s) production were 2 vvm, 200 rpm and 48hrs, respectively. Under the optimal conditions in 5 $\ell$ jar fermenter, tell growth and antifungal activity were 2.06 $\times$ 10$^{8}$ cfu/$m\ell$ (30g-DCW/ $\ell$) and 13.4 mm, respectively. Under the culture conditions of air flow (30 vvm) and agitation speed (200 rpm) at 32$^{\circ}C$ for 10 days in 2,000 $\ell$ large scale culture (medium 1,800 $\ell$, pH 8.0), cell growth and antifungal activity were 0.81$\times$10$^{8}$ cfu/$m\ell$ (12g-DCW/ $\ell$) and 8.6 mm, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.1 s.173
• /
• pp.269-274
• /
• 2000

Frictions and electrical contact voltages of the herringbone-grooved hydrodynamic bearing(HHB) were 9, measured to use in a laser scanner motor. This bearing with varying loads, speeds, oil viscosity, and radial clearances successfully operated up to 28,000rpm and 0.5N. Experimental results under various environments confirmed that this bearing had excellent performance with low friction force, and operated without contact between shaft and sleeve.