• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.6
• /
• pp.144-152
• /
• 1996

In the sequential MPI system with one injection for each cycle, engine performance is influenced by the mixture conditions. It can be said that engine performance is improved by being better identical mixture formation conditions for all cylinders. As the fuel injection timing to the intake port effects on the mixture formation conditions and the engine performance, injection timing must be better adjusted to engine requirements. Engine behavior was clearly different depending on the injection time during intake storke. Therefore it was studied that injection timing of fuel effects on the engine performance I. e. combustion stability, COV(imep), A/F excursion, CO,HC emission concentration and fuel consumption. It was found that late intake-synchronous injection was deteriorated the combustion characteristics and performance characteristics, while early intake-synchronous infection resulted in favorable engine behavior.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.6
• /
• pp.7-13
• /
• 2003

The purpose of this study is to investigate the effect of the in-cylinder flows and different injection timings on fuel behavior in the cylinder of a GDI engine. Three different flows types induced by using masked port, unmasked port, and port deactivation were tumble, swirl&tumble, and high swirl respectively. LIEF technique was applied to investigate the mixture formation and fuel distribution at ignition time in the transparent engine with optical access through the piston top and upper part of cylinder liner. Injection timings of 180,90, and 60 degrees before TDC were examined. It was found that tumble flow was more effective on the homogeneous mixture formation than other flow and swirl flow transported more fuel vapor to the exhaust side at early injection mode, and swirl and swirl & tumble flow made fuel vapor concentrate around the cylinder center at late injection mode.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.5
• /
• pp.86-96
• /
• 2007

A direct-injection stratified-charge(DISC) engine has been considered as a promising alternative in spite of high unburned hydrocarbon emission levels during light load operation. In this paper investigation is made to characterize formation and combustion processes of stratified mixture charge in a simple constant volume combustion chamber. Both experimental and numerical analyses are performed for fluid and combustion characteristics with 3 different induction types for rich, homogeneous and lean mixture conditions. The commercial code FIRE is applied to the turbulent combustion process in terms of measured and calculated pressure traces and calculated distributions of mean temperature, OH radical and reaction rate. It turns out that the highest combustion rate occurs for the rich state condition at the spark ignition location due to existence of stoichiometric mixture and timing.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.10
• /
• pp.2690-2698
• /
• 1995

Fuel atomization and mixture formation in an gasoline engine has influence on the engine performance and pollutant emission. The throttle valve installed in an intake system plays a greater role in control of mixture quantity in accordance with engine drive condition. In this study, the characteristics of secondary atomization developed at the downstream of the valves were observed using an image processing method. Two major kinds of valves, solid and perforated ones, are chosen in order to compare the valve performance with the experimental parameters of air flow rate, valve opening angle, and valve shapes. For the perforated valve, we can obtain the relatively small sized droplets, and nearly uniformed and dense distributed sprays with low loss coefficient than for the solid valve.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.12
• /
• pp.1355-1359
• /
• 1998

The treatment of 1,1-bis(phenylthio)-2,2,3,3,3-pentafluoropropylbenzene (1) with 2 equiv. of phenyllithium in THF at -78 ℃ resulted in the formation of isomeric mixture (70: 30) of trifluoromethylated 1,2-diphenylvinyl sulfide 2 in 87% yield. The further oxidation of 2 with m-chloroperbenzoic acid in methylene chloride afforded isomeric mixture (70:30) of trifluoromethylated 1,2-diphenylvinyl sulfone 3 in 87% yield. When 3 was reacted with carbon nucleophiles such as methyllithium, n-butyllithium, phenyllithium and lithium octylide, the corresponding addition-elimination adducts 4, 5, 6 and 7 were obtained in moderate to good yields. The reaction of 3 with 4 equiv. of tributyltin hydride in benzene at reflux temperature provided isomeric mixture (90 : 10) of trifluoromethylated 1,2-diphenylvinyl stannane 8 in 41% yield. The reaction of 8 with methyllithium in the presence of trimethylsilyl chloride gave isomeric mixtures (90: 10) of trifluoromethylated 1,2-diphenylvinyl silane 9 in 88% yield. Finally, the treatment of 8 with Br2 and 12 resulted in the formation of isomeric mixtures (90: 10) of trifluoromethylated 1,2-diphenylvinyl bromide 10 and iodide 11 in 72% and 90% yields, respectively.

• Archives of Plastic Surgery
• /
• v.35 no.6
• /
• pp.631-636
• /
• 2008

Purpose: Adipose tissue-derived stem cells(ADSC) has an osteoconductive potential and demineralized bone matrix(DBM) is an osteoinductive material. A combination of DBM and ADSC wound probably create osteoinductive properties. The purpose of this study is to determine the effect of the combination of DBM and ADSC mixture on healing of rat calvarial defect. Methods: Thirty adult male Sprague-Dawley rats were randomized into 3 groups(n=10) as 1) Control, 2) DBM alone, 3) DBM with ADSC mixture. DBM with ADSC mixture group has had a 3-day preculture of ADSC from groin fat pad. An 6 mm critical size circular calvarial defect was made in each rat. Defect was implanted with DBM alone or DBM with ADSC mixture. Control defect was left unfilled. 6 and 12 weeks after the implantation, the rats were sacrificed and the defects were evaluated by histomorphometric and radiographical studies. Results: Histomorphometric analysis revealed that DBM with ADSC mixture group showed significantly higher bone formation than DBM alone group(p<0.05). Although radiographs from DBM alone group and DBM with ADSC group revealed similar diffuse radiopaque spots dispersed throughout the defect. Densitometric analysis of calvarial defect revealed DBM with ADSC mixture group significantly higher bone formation than DBM alone(p<0.05). There was correlation of densitometry with new bone formation(Spearman's correlation of coefficient=0.804, 6 weeks, 0.802, 12 weeks). Conclusion: The DBM with ADSC mixture group showed the best healing response and the osteoinductive properties of DBM were accelerated with ADSC mixture. It will be clinically applicable that DBM and ADSC mixture in plastic and reconstructive surgery, such as alveolar cleft and congenital facial deformities that bone graft should be required.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.22 no.1
• /
• pp.1-14
• /
• 2000

The purpose of this study was to evaluate the efficacy of adding autogenous bone to the toothash-plaster mixture in the healing process of bone. Full-thickness round osseous defects with the diameter of 20mm were made at the calvarial bone of adult dogs (n=19) bilaterally, which were thought to be critical size defect. The right defects were repaired with the toothash-plaster mixture plus autogenous bone (compressed volume 0.3cc) and the left defects with only toothash-plaster mixture. At 2-, 4-, 8-, 12- and 20- week after implantation, dogs were sacrificed and evaluated the osseous healing of bony defects clinically, radiographically, and microscopically. The results were as follows; 1. At the clinical observation, the wound healed very well without any problem except severe swelling in the early period after operation. Slight depression was recognized at the both sides when the portions of cranial defect were palpated. 2. There were statistically significant differences between toothash-plaster mixture groups and autogenous bone added groups at the same period, and among the groups in the bone density of the digital radiograms (P<0.001). There was a tendency that bone density was increasing with time. 3. In light microscopic examination, new bone formation was more active in the autogenous bone added groups than toothash-plaster mixture groups at the early period after implantation but there is little difference at 20-week after implantation. 4. In fluorescent microscopic examination, the fluorescent band could be observed at the area of active bone formation and the band was more distinct in the autogenous bone added groups then toothash-plaster mixture groups. 5. In transmitted electron microscopic examination, organelles such as rER, Golgi complex and secretory granule and osteoblast were observed. In summary higher volume ratio of autogenous bone is needed to improve the bone healing in that there is little difference between toothash-plaster mixture group and autogenous bone added group at the 20-week after implantation in spite of new bone formation was more active in the autogenous bone added groups than toothash-plaster mixture groups at the early period after operation.

• Korean Journal of Microbiology
• /
• v.23 no.3
• /
• pp.209-214
• /
• 1985

The optimum conditions of protoplasts formation from Pyricularia oryzae were investigated with lytic enzymes and osmotic stabilizers. The mycelia were begun to refease the protoplasts in response to the complex enzyme solution after 30-60 minutes and reached to maximum after 2-3hrs. Among the lytic enzymes tested, the mixture solution containing ${\beta}-Glucuronidase$(0.01 ml/ml), Cellulase ONOZUKA-RS(20mg/ml), Driselase (10mg/ml), and Macerozyme R-10 (10mg/ml) resulted in the highest rate of protoplasts releasing of Pyricularia oryzae. The best stabilizer was 0.6M KCl at pH 7.0. Shen the mycelia were digested with enzyme mixture, the stationary culture was better than shaking culture for higher protoplast formation.

• Journal of Integrative Natural Science
• /
• v.1 no.2
• /
• pp.84-88
• /
• 2008

The formation and thermal properties of the $BaO_2$ and $TiO_2$ mixtures were prepared by mechanical alloying method was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). The rotating speed of 750 rpm shows more effects on the formation of $BaTiO_3$ single phase. The internal strain calculated using Williamson-Hall method was $4.27{\times}10^{-3}$ for the mixture milled for 300 min, the crystallite size was calculated using the Scherrer method decreased with milling time. The $BaTiO_3$ crystal improved crystallinity was formed by thermal annealing at a temperature of $600^{\circ}C$ for 1 h for the mixture milled for 300 min.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.6
• /
• pp.1633-1637
• /
• 2010

The UV-vis absorption spectrum of protoporphyrin IX shows a very sharp and strong absorption maximum peak at 398 nm in acetonitrile-water mixture solution (1:1 v/v). When divalent metal ions such as $Cu^{2+}$, $Zn^{2+}$, and $Ca^{2+}$ ion were added to protoporphyrin IX, metal protoporphyrin IX complexes were thereby produced. Cu-protoporphyrin IX complexes have the largest formation constant ($K_f$) among them. The fluorescence intensity of protoporphyrin IX was diminished by the presence of $Cu^{2+}$, $Zn^{2+}$, $Ca^{2+}$, $Mn^{2+}$, and $Ni^{2+}$ ions as quenchers. However, $Mg^{2+}$, $Mn^{2+}$, and $Ni^{2+}$ ions are hardly combined with protoporphyrin IX. $Mg^{2+}$ ion does not take part in the fluorescence quenching process of protoporphyrin IX in acetonitrile-water mixture solution. According to the Stern-Volmer plots, fluorescence quenching by $Cu^{2+}$, $Zn^{2+}$, and $Ca^{2+}$ ions involves static quenching, which is due to complex formation. On the contrary, dynamic quenching has a large influence on the overall quenching process, when $Mn^{2+}$ and $Ni^{2+}$ ions were added to protoporphyrin IX in acetonitrile-water mixture solution.