• International Journal of Automotive Technology
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• v.8 no.5
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• pp.593-598
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• 2007

A new continuously variable transmission for bicycles(B-CVT) is developed by using a traction drive mechanism having inner and outer spherical rotors. The B-CVT has high power efficiency, large torque capacity, improved drivability and good packageability. The ratio change mechanism for the B-CVT is very simple, in contrast with other traction drive CVTs. After completing a conceptual design, a performance analysis and a detail design, a prototype of the B-CVT has been manufactured. The prototype has rated power of 100 watts, pedal speed of 6 rad/s and an overall speed ratio of 1.0-4.0. A bench test and an actual bicycle test have been performed to verify the practicability of the B-CVT.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.557-563
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• 2009

This study is on the properties of inorganic porous calcium silicate material made from silica powder through the autoclaving curing, the results of this study should be utilized fundamental data for the development of noise reduction porous solid material using siliceous byproduct generated by various manufacture process. For the manufacture of autoclave curing specimen, various calcareous materials used and siliceous materials used silica powder. In this study, properties in density and compressive strength according to the change of W/B and C/S ratio, microscopy for the shape of pore, SEM and XRD for the examination of hydrate after autoclave curing are carried out respectively. The test results shown that the more slurry density decrease, the more W/B increase at the fresh state, this tendency shown similar to in hardened state. Among the specimens of C/S ratio, the compressive strength of C/S ratio of 0.85 gave the highest the compressive strength. In the results of XRD, tobermorite generated by autoclaving curing was created all of specimens regardless of C/S ratio. To ascertain pore structure, we compared with existing porous calcium silicate product(ALC, organic sound absorbing porous material). The results of microscope observation, pore structure of specimen of this study was similar to that of existing inorganic sound absorbing foam concrete. therefore, we could conformed a possibility of sound absorbing porous solid material on the basis of the results.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.169-173
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• 1999

We have experimentally investigated the eye margin characteristics of intensity modulated 10Gb/s NRZ signals in optically amplified systems depending on optical signal-to-noise ratio and chromatic dispersion. For the practical system application, the minimum optical signal-to-noise ratio was 25 dB. We utilized the negative chirped transmitter and a dispersion compensation fiber to compensate the chromatic dispersion in single mode fiber. We found the optimum eye opening and receiver sensitivity in case of the residual dispersion of 0~+935 ps/nm.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.45-56
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• 2006

Recently, the more potential waste sites are being required as increasing the demand of better human life. But the construction of waste disposals has many restrictions because of lack of good quality clay and high cost of liners. So, in this study, we studied the liner materials to develop more cheaper soil liner that can be satisfied the environmental criterion for the coefficient of permeability and shear strength. A series of compaction test and triaxial (consolidation, permeability, and shear) tests were performed to obtain the optimized weight ratio of Bentonite-Soil mixture (B/S) including the least amount of bentonite. A series of soil tests were performed to acquire the appropriate weathered granite soil-bentonite mixture that is satisfied the environmental criterion of soil liner($k=1{\times}10^{-7}cm/sec$). At first, weathered granite soils were classified with four different particle-size soils, and B/S ratio was increased as 5% step for each particle-size. The test results showed that in case of weathered granite soil passing through No. 100 sieve, B/S=15% satisfied the soil liner criterion. The measured coefficient of permeability and the Chapuis's two equations were also compared. And a predicting equation for the coefficient of permeability was suggested, which is suitable for the mixture soil with the B/S ratio used in this study. The optimal weight ratio for the mixture soils used in this study was 15% in the both cases of permeability and shear strength.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.4
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• pp.354-364
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• 1994

Experiments have carried out to investigate the effects of parameters, such as mass ratio of R141b-to-water, stirrer speed, brine inlet temperature, brine flowrate, and additives, on the performance of the cool storage system using R141b clathrate. The cool storage system in this experiment was composed of storage tank, refrigerator, and heater. The results show that the mass ratio of R141b-to-water, 1 : 3~1 : 3.5 gives the best performance and the stirring speed has optimum point as 600rpm. At this speed impeller Reynolds number is $1.01{\times}10^5$. The lower the inlet brine temperature and the highter the brine flowrate, the better performance. The addition of metal powder turned out to reduce the degree of supercooling. The supercooling reduction was proportional to the amount of the metal power. However when metal powder was added more than 0.1 wt%, there was no additional supercooling reduction. The surfactants shortened the time consumed for cool storage to the half of no surfactant added case.

• Journal of Power System Engineering
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• v.15 no.1
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• pp.39-44
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• 2011

This study was to investigate the effects of stress ratio and anisotropy on Fatigue Crack Propagation(FCP) behavior of rolled magnesium alloy AZ31B. The experimental materials were a Mg-Al-Zn magnesium alloy. The FCP test was conducted on compact tension specimen by a servo-hydraulic fatigue testing machine in air at room temperature. Compact tension specimens were prepared from the extruded parallel and vertical rolling direction. The test condition was frequency of 10Hz and sinusoidal load stress ratios are 0.1 and 0.7. The FCP rates was automatically measured by a compliance method. In the case of the FCP of AZ31B, the FCP of both direction of LT and TL by anisotropy of specimens are almost same value. In lower stress ratio, the FCP of the LT, TL specimens are increased in lower ${\Delta}K$ region but higher ${\Delta}K$ regions are almost same value. Finally, the result of observed the surface crack, it expressed the quasi-cleavage fracture in lower ${\Delta}K$ region and straight mark on the aspect of the facet in high ${\Delta}K$ region.

• The Korean Journal of Food And Nutrition
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• v.7 no.2
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• pp.95-99
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• 1994

In order to investigate the fatty acid composition of Korean pumpkins, this study was designed. Three samples of Korean pumpkins, A(yellowish ripe), B(unripe, 30 days old) and C(unripe, 20 days old) were used for fatty acid analysis by gas chromatography. The results were as follows : Pumkin C, B and A showed 10, 12 and 15 kinds of fatty acids, respectively. In case of palmitic acid(C16:0), pumpkin C, B and A showed 22.5%, 22.9% and 26.6%, respectively. In case of u linolenic acid(C18:3), pumpkin C, B and A showed 22.6%, 23.6% and 44.8%, respectively. In case of palmitoleic acid(Cl6:1), pumpkin C. B and A showed 12.4%, 10.1% and 0.5%, respectively. In case of oleic acid(C18:1), pumpkin C. B and A showed 9.2%, 7.7% and 2.8%, respectively, In case of stearic acid(C18:0), pumpkin C, B and A showed B.S%, 3.7% and 3.5%, respectively. The ratio of P/S was 1.4, 1.6 and 1.9 for sample C, B and A, respectively. The ratio of w-3/w-6 was 1.1, 0.9 and 2.6 for sample C, B and A, respectively. Through this study, the ripe pumpkin(sample A) was thought to be good enough in nutritional aspects of fatty acids, particularly a-linoleic acid, Cl8 : 3(u-3) series.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1091-1099
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• 2015

UFMC(Universal-Filtered Multi-carrier) and FBMC(Filter Bank Multi-carrier) system are receiving attention as candidate waveforms for 5G mobile communication system. But, these systems have high PAPR(Peak to Average Power Ratio) problem because these systems use a number of subcarrier. In this paper, we propose DFT(Discrete Fourier Transform) spreading based DFT-s(spreading)-UFMC system and DFT-s-FBMC system in order to overcome the PAPR drawback. In order to evaluate PAPR performance of the proposed systems, we design and simulate OFDM(Orthogonal Frequency Division Multiplexing), UFMC, FBMC, DFT-s-OFDM, DFT-s-UFMC, DFT-s-FBMC system. As simulation results, each PAPR performance of DFT-s-OFDM system, DFT-s-UFMC system, and DFT-s-FBMC system rise by 2.7 dB, 2.8 dB, and 1.1 dB respectively by DFT spreading technique.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.10
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• pp.524-530
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• 2000

This paper presents a transformer protective relaying algorithm using the ratio of induced voltages. The proposed algorithm calculates primary and secondary voltage from currents and voltages of primary and secondary windings. The ratio of primary and secondary induced voltages is equal to the turn ratio in case of the steady state and magnetic inrush. On the other hand, the ratio is different form the turn ratio in case of internal winding faults. The algorithm does not require B-H curve and can reduce the relay's operating time.

• Reproductive and Developmental Biology
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• v.28 no.4
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• pp.227-233
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• 2004

This study was conducted to investigate the effect of various addition and exclusion time of glucose (Control: no addition, A: 24～72 h, B: 24～48 h, C: 48～72 h, D: 0～72 h, E: 0～48 h, F: 0～24 h and 48～72 h, G: 0～24 h) on embryonic developmental capacity of 2-cell embryos in mice. Developed blastocysts were assessed for mean cell number by differential staining. The zona-intact blastocyst (ZiB) rates were higher (p<0.05) in group B than control. However, the zona-escape blastocyst (ZeB) rates were not significantly different in all groups. At 72 h, total blastocyst (ZiB + ZeB) formation rates were not significantly different in all groups. The mean cell number was not significantly different among all groups. The inner cell mass (ICM) cell number was higher (p<0.05) in group F than control, group A, B and G. The trophectoderm (TE) cell number was higher (p<0.05) in control than group A and D. The %ICM was higher (p<0.05) in group C, D and F than control. The ICM : TE ratio was not significantly different in all groups. Between control and glucose group, no significant difference was observed in the total blastocysts (ZiB + ZeB) formation rates. Also, no significant difference was observed in the mean cell number, ICM cell number and ICM : TE ratio. However the TE cell number was higher (p<0.05) in control than glucose group and %ICM was higher (p<0.05) in glucose group than control. In conclusion, glucose added in culture medium was not inhibitory on blastocyst formation but glucose added for 48 ～72 h in culture medium increases %ICM of blastocysts in mice.