• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.10-17
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• 2004

The results of the combustion performance tests of gas generator which supplies hot gas into the turbine of turbo-pump for liquid rocket engine and uses LOx and kerosene as propellant are described. The gas generator consists of a injector head with F-O-F impinging injector, a water cooled combustion chamber, a gas torch igniter, a turbulence ring and an instrument ring. The effect of turbulence ring and combustion chamber length on performance of gas generator are investigated. The ignition and combustion at design point are stable and the pressure and gas temperature at gas generator exit meets the target. The turbulence ring installed at middle of chamber effectively mixes hot gas with cold gas and the effect of residence time of hot gas in gas generator on combustion efficiency is small. Test results show that the main parameter controlling the gas temperature at gas generator exit is overall O/F ratio.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2551-2556
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• 2009

The principal operation of a ring laser gyroscope depends on the phase difference for the counter-propagating waves within a closed path. The reflection mirrors mounted on the resonator block form the traveling waves. Thus, the dimension accuracy of resonator block influences the traveling path of beam. In order to maintain the stable optical beam path in the ring resonator, the piezo-driven moveable mirror is adopted for the path length control under the thermal expansion or mechanical strain of resonator block. This paper presents the mathematical description of the elastic behavior of piezo-driven mirror. This description can be applied for the concept design of piezo-driven mirror.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.12A
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• pp.1177-1181
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• 2006

In this paper, we proposed the new wavelength tunable filter for wide tunability of fiber ring laser. The proposed filter consists of the cascaded connection of Fiber Reflection Mach-Zehnder Interferometer and Sagnac filter or of hybrid filter and fiber Reflection Mach-Zehnder Interferometer. The simulation shows that the continuous tunable range of 50nm can be obtained and that more stable single mode operation of ring laser can be expected due to narrow FWHM. of filter spectrum.

• Journal of Chest Surgery
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• v.26 no.3
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• pp.191-195
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• 1993

Among 25 consecutive cases having undergone mitral valve surgery between March 1991 and June 1992 in Gill General Hospital, 11 patients[44%] who had undergone mitral valve reconstruction using prosthetic rings is evaluated and presented. Patients` mean age is 43 + 19 years[range:16-72], and they are consisted with 4 males and 7 females. Mitral valve insufficiency is due to degenerative disease in 6 cases[55%] and rheumatic disease in 5 patients[45%]. Carpentier`s functional classification I is 2 cases, II is 6 cases, and III is 2 cases. Surgical techniques include prosthetic ring annuloplasty[11 patients, 100%], chorda shortening[6, 55%], leaflet mobilization[4,36%], new chorda formation[2, 18%], chorda transposition[1, 9%] commissurotomy[3, 27%], and papillary muscle splitting[3, 27%]. Average number of mitral anatomic lesions per patient are 2.7 and we used average 2.8 procedures upon mitral valve apparatus per patient. There were no surgical mortality and no late valve related admission during the mean follow up period of 17 months. The mean functional class[NYHA] is 2.81 preoperatively and improved to 1.10 postoperatively. Doppler echocardiography showed much improvement from grade II MR [1 case], grade III MR [1 case] and 9 cases of grade IV MR to 6 cases of patients showed no MR, only trace MR in 4 cases, and grade I MR was found only in one patient with NYHA functional class II postoperatively. The postoperative mean mitral valve area is $2.10+0.28cm^2$. We conclude that mitral reconstruction is a predictable and stable operation.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.216-216
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• 2011

We will investigate the bonding configurations of phenylalanine and tyrosine adsorbed on the Ge(100) surface using CLPES and DFT calculations. First, the C 1s, N 1s, and O 1s spectra obtained at 300 K revealed that both the amine and carboxyl groups of phenylalanine and tyrosine concurrently participated in adsorption on the Ge(100) surface without bond breaking using CLPES, depending on the extent of coverage. In the second place, we confirmed that the "O-H dissociated-N dative bonded structure" is the most stable structure implying kinetically favorable structure, and the "O-H dissociation bonded structure" is another stable structure manifesting thermodynamically advantageous structure using DFT calculations. This tendency turns up both phenylalanine and tyrosine, similarly. Furthermore, through the CLPES data and DFT calculation data, we discovered that the "O-H dissociated-N dative bonded structure" and the "O-H dissociation bonded structure" are preferred at 0.30 ML and 0.60 ML, respectively. Moreover, we found that the phenyl ring of phenylalanine is located in axial position to Ge(100) surface, but the phenyl ring of tyrosine is located in parallel to Ge(100) surface using DFT calculations.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1315-1320
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• 2012

In this study, piezoelectric AC-DC converter using ring-dot type multilayer piezoelectric transformer with no anisotropic of polarization was developed. Considering the characteristics of piezoelectric transformer which is very narrow operating frequency range, piezoelectric converter was designed with mixed structure of PFM driving method for feedback control of oscillation frequency and PWM driving method for output control. Maximum power and allowed current of the developed piezoelectric converter showing stable driving with minimum heat was 25W and 900mA, respectively. The output voltage of the piezoelectric converter was controlled by the driving oscillation frequency and showed stable and efficient operating characteristics at the maximum power.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.613-620
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• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• Molecules and Cells
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• v.39 no.11
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• pp.814-820
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• 2016

FtsZ, a tubulin homologue, is an essential protein of the Z-ring assembly in bacterial cell division. It consists of two domains, the N-terminal and C-terminal core domains, and has a conserved C-terminal tail region. Lateral interactions between FtsZ protofilaments and several Z-ring associated proteins (Zaps) are necessary for modulating Z-ring formation. ZapD, one of the positive regulators of Z-ring assembly, directly binds to the C-terminal tail of FtsZ and promotes stable Z-ring formation during cytokinesis. To gain structural and functional insights into how ZapD interacts with the C-terminal tail of FtsZ, we solved two crystal structures of ZapD proteins from Salmonella typhimurium (StZapD) and Escherichia coli (EcZapD) at a 2.6 and $3.1{\AA}$ resolution, respectively. Several conserved residues are clustered on the concave sides of the StZapD and EcZapD dimers, the suggested FtsZ binding site. Modeled structures of EcZapD-EcFtsZ and subsequent binding studies using bio-layer interferometry also identified the EcFtsZ binding site on EcZapD. The structural insights and the results of bio-layer interferometry assays suggest that the two FtsZ binding sites of ZapD dimer might be responsible for the binding of ZapD dimer to two protofilaments to hold them together.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.25-31
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• 2016

This paper has analyzed the structure, applicable regulations and the resistance characteristics of insulation ring type of CSST (Corrugated Stainless Steel Tubing for Gas). With the flammability test conducted in accordance with KS C IEC 60811-1-1, the evaluation of insulation resistance, temperature characteristics, and reliability has been conducted. An insulation ring type CSST consists of protective coating, tube, nut, insulation ring, packing, socket, and ball valve. Connecting an insulation ring type CSST to gas tubings for gas appliance is not permitted, moreover, the product shall be installed inside a sleeve pipe in case of buried installation such as the ceiling. Damages on protective coating and tube were detected when fire was applied to the test sample with a portable torch for 60 seconds. The insulation resistance of a normal product was $49.59M{\Omega}$, while that of the product completed the flammability test reduced to $9.21M{\Omega}$. The mean insulation resistance within the confidence Interval of 95% using the mini tap program 17 was $49.59M{\Omega}$ and the mean insulation resistance within the confidence interval reduced to $9.21M{\Omega}$. In the normal distribution analysis of 95% confidence interval, the value-P of the normal product was stable at 0.075 and AD(Anderson-Darling) statistic value was turned out to be 0.063, which is very normal, and the standard deviation was analyzed as 0.2586. The value P of the product completed the flammability test resulted in 0.005, the AD was 1.355 and the standard deviation reduced to 0.07908.

• Journal of IKEEE
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• v.18 no.1
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• pp.19-24
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• 2014

We report stable, wideband, flat-topped, 10 GHz optical frequency comb generation from a semiconductor-based mode-locked ring laser with an intra-cavity high finesse Fabry-Perot etalon. We demonstrate a stable 10 GHz comb with greater than 200 lines within a spectral power variation below 1 dB, which is the largest value obtained from a similar mode-locked laser in our knowledge. Greater than 20 dB of the spectral peak to deep ratio at 0.02 nm resolution, ~92 femtosecond timing jitter over 1 kHz to 1 MHz range, and non-averaged time traces of pulses confirm very stable optical frequency comb lines.