• 약학회지
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• 제51권3호
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• pp.214-218
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• 2007

In the previous reports, we developed the CO5 by introducing genes for the first and second urea cycle enzymes, carbamoyl phosphate synthetase I (CPS I) and ornithine transcarbamoylase (OTC) into the IBE cell lines producing erythropoietin (EPO). The CO5 have been found out to have 15-20% higher cell growth rate and produce 2-times more EPO than the parental cell line, IBE. To investigate the role of CPS I in CO5 cell line for the cell growth and amount of EPO, we knock-downed CPS I gene expression via siRNA treatment. Expression level of EPO in cell lysate of CO5 was 3-5 fold higher than that of IBE. After siRNA treatment, the cell growth of CO5 was decreased 8-21% and the EPO productivity in the cell Iysate was significantly decreased. However, these changes of the cell growth and EPO productivity were not observed in IBE. These results indicate that CPS I gene expression is important for the increased cell growth and EPO productivity of CO5 cell line.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.317-322
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• 2021

Silicon (Si) has been considered as a promising anode material because of its abundant reserves in nature, low lithium ion (Li⁺) intercalation/de-intercalation potential (below 0.5 V vs. Li/Li⁺) and high theoretical capacity of 4200 mA h/g. In this paper, we prepared a silicon-based (Si-based) anode material containing a small amount of silicon carbide by using magnesiothermic coreduction of silica and hexachlorobenzene. Because of good conductivity of silicon carbide, the cycle performance of the silicon-based anode materials containing few silicon carbide is greatly improved compared with pure silicon. The raw materials were formulated according to a silicon-carbon molar ratio of 10:0, 10:1, 10:2 and 10:3, and the obtained products were purified and tested for their electrochemical properties. After 1000 cycles, the specific capacities of the materials with silicon-carbon molar ratios of 10:0, 10:1, 10:2 and 10:3 were still up to 412.3 mA h/g, 970.3 mA h/g, 875.0 mA h/g and 788.6 mA h/g, respectively. Although most of the added carbon reacted with silicon to form silicon carbide, because of the good conductivity of silicon carbide, the cycle performance of silicon-based anode materials was significantly better than that of pure silicon.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.59-61
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• 2001

Electrostatically actuated test devices were designed to evaluate the elastic modulus of single crystalline Si (100) materials for MEMS device. Elastic modolus was calculated from resonant frequency by applying Rayleigh's energy method. Temperature effect on elastic properties was evaluated by detecting the resonant frequency change with increasing temperature to $600^{\circ}C$. The elastic modulus was decreased with heating and then increased with cooling, but specimen with thermal cycle showed a permanent change which is lower than the initial value. This phenomenon was explained by the change of interatomic force and the formation of $SiO_2$ layer on Si. The thickness of oxide layer was estimated by considering the change of mass and stiffness, and the formation of oxide layer was observed by the SEM photograph.

• 대한기계학회논문집A
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• 제20권6호
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• pp.1753-1761
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• 1996

The wear behaviors of ${Si_3}{N_4}$ under the different sliding conditions were investigated. The cylinder-on-disc wear tester was used. Using the servo-metor, the sliding speed did ot alternate due to the frictional forces. Threekinds of loads and speeds were selected to watch the variation of the wear rates and the frictional forces. Also three kinds of sliding condition under a constant speed were used to see the effects of the oxidationand the abrasion. The contact pressure was more effective than the repeated cycle on the wear behavior of ${Si_3}{N_4}$. With the low loads, the effect of the asperity-failure was more dominant than that of oxidation and abrasion. As increasing the load, the effects of oxidation and abrasion were increased, but the asperity-failure effects were decreased. The wear particles destroyed the ozide layers formed on sliding surfaces. The wear rate could be decreased due to delaying the oxidation. The frictional power and the wear weight per time were usefuel to see the transition of wear.

• 한국세라믹학회지
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• 제37권3호
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• pp.263-270
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• 2000

The Pt/copper oxide/n-Si electrodes were fabricated by depositing copper oxide thin film of 500${\AA}$ and very thin Pt layer on the n-type (100) Si substrate. hotoelectrochemical properties and stability profiles of the electrodes were investigated as a function of deposition time of Pt layer. As the deposition time of Pt layer increased up to 10 seconds, the photocurrent and quantum efficiency were increased and then decreased with further depositing time. The better cell stability was observed for the electrode with longer deposition time. The improvements in above photoelectrochemical properties indicate that Pt layer acts as a catalyst layer at electrode/electrolyte interface as well as a protective layer. The decreasing tendency of the photocurrent and efficiency for the electrode with Pt layer deposited above 20 seconds was explained as an increases in probbility of electron-hole pair recombination and also the absorbing photon loss at electrode surface due to the excessive thickness of Pt layer. The results were confirmed by impedance spectroscopy, mutiple cycle voltammograms and microstructural analyses.

• 한국주조공학회지
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• 제14권6호
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• pp.541-547
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• 1994

The effects of weld repair on the durability in Al-10%Si-0.3%Mg castings were evaluated. The strength and fracture toughness in fusion zone were higher than those in the base metal by rapid cooling of fusion zone after welding. There were no significant differences between fatigue properties in castings and weld repaired specimen as the results of low cycle fatigue and rotating bending fatigue test. Therefore it was concluded that weld repairing did not have any significant effect on the mechanical properties of castings.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.179-182
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• 2007

The compressive fatigue tests on the closed cell Al-Si-Ca alloy foams with two different thicknesses were performed using a load ratio of 0.1. The quasi-static and cyclic compressive behaviors were obtained respectively. The fatigue stress-life (S-N) curves were evaluated from the obtained cyclic compressive behaviors. S-N curves were presented for the onset of progressive shortening. It turned out that the fatigue strength showed higher value for the thicker foam and the onset of shortening of thinner foam took place earlier. The crushing was found to initiate in a single band which broadens gradually with additional fatigue cycles. Progressive shortening of the specimen took place due to a combination of low cycle fatigue failure and cyclic ratcheting.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.1001-1003
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• 1998

In this paper, $Ar^+$ ion laser etching process of single/poly crystalline silicon with $CCl_{2}F_{2}$ gas is studied for MEMS applications. To investigate the effects of process parameters, laser power, gas pressure, scanning speed were varied and multiple scanning was carried out to obtain high aspect ratio. In addition, scanning width was varied to observe the trench profile etched in repeating scanning cycle. From the etching of $2.6{\mu}m$ thick polycrystalline Si deposited on insulator, trench with flat bottom and vertical side wall was obtained and it is possible to apply this results for MEMS applications.

• 전기화학회지
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• 제21권1호
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• pp.12-20
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• 2018

To solve low cycle efficiency of the zinc anode in Zn-air batteries by corrosion, this study examined the effects of Al as a cathodic protection additive to Zn. The Al-mixed Zn anodes were produced by mixing Zn and Al powder (1, 2, and 3 wt. %). To compare the effects of the Al additive, Si was selected under the same conditions. The morphology and elemental composition of the additives in the Zn were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and inductively coupled plasma - mass spectrometry. The anti-corrosion effects of the Al and Si-mixed Zn anodes were examined by linear polarization. Cyclic voltammetry and charge-discharge tests were conducted to evaluate the electrochemical performance of the Al and Si-mixed Zn anodes. As a result, the Al-mixed Zn anodes showed highest corrosion resistance and cycling performance. Among these, the 2 wt.% Al-mixed Zn anodes exhibited best electrochemical performance.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.232-242
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• 1996

In this study, the simulation program for the prediction of volumetric efficiency of the internal combustion engine by the resonator has been developed, when the resonator is mounted on the intake system of 4-cycle SI engines for the improvement of volumetric efficiency. The experimental work has also been carried out for the verification of the program, and it is found that the result of calculation by the simulation program fits qualitatively well with that of experiment. To get the optimal mounting position of resonator on the intake system, the influence of the variation of dimensions of resonator such as neck length, volume and neck diameter were examined by the numerical calculation of the program in advance and the results were compared with the experiments. It is found that the position which is departed 150cm from plenum chamber is better than any other positions, and the average amount of the increase of volumetric efficiency is about 2∼3%