• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.11a
• /
• pp.296-299
• /
• 2002

In this paper, a hexagon-type piezoelectric transformer was investigated to increase the output power. The length of its side was 14mm and 17.5mm, respectively. The piezoelectric ceramics was composed to PZT-PMN-PSN. This composition showed the characteristics which had an about 1500 of the mechanical Q-factor, 0.55 of the electromechanical coupling coefficient, $320{\times}10^{-12}C/N$ of the piezoelectric constant $d_{31}$, 0.3 % of the dissipation factor, etc. The voltage step-up ratio increased with increasing the load resistance, $R_{L}$, so it reached 80 with $R_{L}$ of $1M{\Omega}$ and was proportion to the length of side of the hexagon-type piezoelectric transformer. Also, the output power increased with increasing the size of the hexagon-type piezoelectric transformer.

• Journal of ILASS-Korea
• /
• v.12 no.3
• /
• pp.131-137
• /
• 2007

This is an experimental study on characteristics of engine performance and discharged materials in common-rail type diesel engine. The bio-diesel fuel is mixed with the diesel fuel in common use at the ratio of 20% or 100%. The diesel fuel and blended fuel is irradiated by ultrasonic wave energy. The diese1 fuel, blended fuel, reformed diesel fuel and reformed blended fuel by ultrasonic wave energy are applied to the experimental engine individually. The results are compared with one of the diesel fuel in common use and analyzed.

• Proceedings of the KIEE Conference
• /
• 1997.07a
• /
• pp.94-96
• /
• 1997

A mathematical model (hybrid arc model) for arc behaviour in an $SF_6$ puffer gas-blast circuit-breaker has been developed. It has adopted the advantages of integral method and differential method. The method has been applied to model puffer circuit breaker of Noeske et al and good agreement of critical RRRV(Ratio of Rise of Recovery Voltage) has been obtained. Axial or radial distributions of temperature, electric field and arc radius are also presented and analyzed.

• Journal of Surface Science and Engineering
• /
• v.39 no.5
• /
• pp.199-205
• /
• 2006

Titanium nitride (TiN) coatings were produced on AISI 420 stainless steel by DC magnetron sputtering of a Ti target changing the processing variables, such as the flow rate of $N_2/Ar$, substrate temperature and the existence of Ti interlayer between TiN coatings and substrates. The hardness and residual stress in the films were investigated using nanoindentation and a laser scanning device, respectively. The stoichiometry and surface morphology were investigated using X-Ray Diffraction and SEM. The corrosion property of the films was also studied using a polarization method in NaCl (0.9%) solution. Mechanical properties including hardness and residual stress were related to the ratio of $N_2/Ar$ flow rate. The corrosion resistance also was related to the processing variables.

• Journal of Ocean Engineering and Technology
• /
• v.1 no.2
• /
• pp.28-38
• /
• 1987

Experimental studies are conducted for the wave forces acting on the vertically mounted circular piles in the waves. Two-three-cylinder arrays are equally spaced and the spacings(S/D) as well as the incident angles of various waves are changed to study their separate effects on the wave forces. The numerical results based on the diffraction theory are in good agreement with the experimental results, and the diffraction theory well predicts the trend of the wave forces when the spacings and the incident angles are changed.

• Proceedings of the KIEE Conference
• /
• 1998.07a
• /
• pp.22-24
• /
• 1998

The Synchronous reluctance motor is a sinewave ac motor and it has cylindrical surfaces on both sides of the air gap. The stator is a conventional polyphase ac stator, while the rotor has internal flux barriers shaped to maximize the ratio of d-axis to g-axis reactance. This paper presents the finite element analysis and parameter measurement of the synchronous reluctance motor(SRM). The model motor is a 3-phase SRM with the segmental rotor and its rating is 0.175kw. The torque characteristic is analysed by finite element method and compared with that from measurement.

• 한국전산유체공학회:학술대회논문집
• /
• 2003.08a
• /
• pp.106-113
• /
• 2003

Smart UAV Development Program, one of the 21c Frontier R&D Program sponsored by MOST(Ministry of Science and Technology), was launched in 2002. As an air vehicle for the Smart UAV, CRW(Canard Rotor/Wing) concept was one of the candidates compared in trade-off study. The CRW concept has not only been proven completely but its aerodynamic characteristics not known in detail yet. Two calculation methods were adopted in this study to obtain aerodynamic data for the CRW. First method was the superpose DATCOM method which is capable of three lifting surfaces, and second one is the full Navier-Stokes computation around CRW configuration using overset grid method. Basic aerodynamic characteristics of the CRW configuration was analyzed and the minimum drag level with lift to drag ratio is presented. The peculiar flow characteristics around rotor/wing and hub were also examined and considered in the configuration design.

• ETRI Journal
• /
• v.34 no.3
• /
• pp.319-329
• /
• 2012

Closed-loop transmit diversity is considered an important technique for improving the link budget in the third generation and future wireless communication standards. This paper proposes several transmit diversity algorithms suitable for small wireless terminals and presents performance assessment in terms of average signal-to-noise ratio (SNR) and outage improvement, convergence, and complexity of operations. The algorithms presented herein are verified using data from measured indoor channels with variable antenna spacing and the results explained using measured radiation patterns for a two-element array. It is shown that for a two-element array, the best among the proposed techniques provides SNR improvement of about 3 dB in a tightly spaced array (inter-element spacing of 0.1 wavelength at 2 GHz) typical of small wireless devices. Additionally, these techniques are shown to perform significantly better than a single antenna device in an indoor channel considering realistic values of latency and propagation errors.

• Journal of Plant Biology
• /
• v.19 no.2
• /
• pp.33-36
• /
• 1976

Present work was attempted to investigate the karyotype, the reciprocal translocation of chromosomes and the geographical distribution of three Paeonia species grown wild in Korea with the aim of elucidating the taxonomical affinities of the species. Prior to conducting these works, it was required to clarify the karyotypes of the cultivated varieties of P. albiflora which has been grown since long time ago in this coundtry for medicinal value. Present report is part of the series of karyotype studies now being extensively conducted using varieties (or lines) of P. albiflora collected across the country. Arm ratio, number of trabant, kind of trabant chromosomes and karyotype formula are different among the six cultivated varieties. Excepting one, five varieties used had invariably trabants on D and E chromosomes while no trabant was found in C chromosome.

• Korean Journal of Food Science and Technology
• /
• v.37 no.5
• /
• pp.856-860
• /
• 2005

Electronic-nose system was used to discriminate commercial sesame oils (A-F) extracted from imported seeds. Response (delta $R_{gas}/R_{air}$) of sensors gained from electronic nose was analyzed by principal component analysis (PCA). Flavor pattern of sesame oil A was similar to those of sesame oils B, C, and D. Sesame oils blended with corn oil at the ratio of 95:5, 90:10 and 80:20% (sesame oil/corn oil, w/w) could be discriminated from ouch genuine sesame oil.