• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.47-53
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• 2010

Ceramics with perovskite-type structure are interesting functional materials for several energy conversion processes due to their flexible structure and a variety of properties. Prominent examples are electrode materials in fuel cells and batteries, thermoelectric converters, piezoelectrics, and photocatalysts. The very attractive physical-chemical properties of perovskite-type phases can be modified in a controlled way by changing the composition and crystallographic structure in tailor-made soft chemistry synthesis processes. Improved thermoelectric materials such as cobaltates with p-type conductivity and n-type manganates are developed by following theoretical predictions and tested to be applied in oxidic thermoelectric converters.

• Journal of Electrochemical Science and Technology
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• v.11 no.4
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• pp.399-405
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• 2020

Hollow copper oxide/multi-walled carbon nanotubes (CuO/MWCNT) composites were fabricated via an optimized infiltration-reduction-oxidation method, which is more facile and easy to control. The crystalline structure and morphology were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The as-prepared CuO/MWCNT composites deliver an initial capacity of 612.3 mAh·g^-1 and with 80% capacity retention (488.2 mAh·g^-1) after 100 cycles at a current rate of 0.2 A·g^-1. The enhanced electrochemical performance is ascribed to the better electrical conductivity of MWCNT, the hollow structure of CuO particles, and the flexible structure of the CuO/MWCNT composites.

• Wind and Structures
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• v.25 no.4
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• pp.361-379
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• 2017

In view of the importance of the wind-structure interaction for tall and slender structures, an aeroelastic model test of the 610m-high TV tower with a complex and unique structural configuration and appearance carried out successfully. The assembled aeroelastic model of the TV tower with complex shape and structure was designed and made to ensure the similarities of the major natural frequencies and the corresponding mode shapes. The simulation of the atmospheric boundary layer with higher turbulent intensity is presented. Since the displacement and acceleration responses at several measurement sections were directly measured in the wind tunnel test, a multi-mode approach was presented to indirectly estimate the displacement and acceleration responses at arbitrary structural floors based on the measured ones. It can be seen that it is remarkable for the displacement and acceleration responses of the TV tower in the two horizontal directions under wind loads and is small for the dynamic response of the torsional displacement and acceleration.

• Ocean Systems Engineering
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• v.7 no.1
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• pp.53-74
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• 2017

Ship shaped FPSO (Floating Production, Storage and Offloading) units are the most commonly used floating production units to extract hydrocarbons from reservoirs under the seabed. These structures are usually much larger than general cargo ships and have their natural frequency outside the wave frequency range. This results in the response to first order wave forces acting on the hull to be negligible. However, second order difference frequency forces start to significantly impact the motions of the structure. When the difference frequency between wave components matches the roll natural frequency, the structure experiences a significant roll motion which is also termed as second order roll. This paper describes the theory and numerical implementation behind the calculation of second order forces and motions of any general floating structure subjected to waves. The numerical implementation is validated in zero speed case against the commercial code OrcaFlex. The paper also describes in detail the popular approximations used to simplify the computation of second order forces and provides a discussion on the limitations of each approximation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.2
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• pp.128-132
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• 1998

2/65/35 PLZT stock solution prepared by Sol-Gel processing was spin-coated on ITO coated glass and annealed by RTA(Rapid Thermal Annealing). The crystal structure of films was reported based on the observation of crystallization process and microstructure of the film fabricated at different fabrication condition. Films were crystallized into rhombohedral structure by annealing at $750^{\circ}C$ for 5 min. As the annealing temperature increased, the size of rosette structure of the films was grown up from $2.4{\mu}m$ to $15{\mu}m$, dielectric constant was increased, coercive field was decreased 33.82 kV/cm, remnant polarization was increased to 39.84 ${\mu}C/cm^2$ and Optical transmittance was decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.256-259
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• 1996

In this paper, We studied polyethylene thin film to evaluate the effects of crystal structure on breakdown properties and the dielectric strength on the condition of impurity free. Bielectric strength of the finn obtained with self healing method that is able to test repeatedly on the same sample is about 3.58 MV/cm at 0.73 $\mu\textrm{m}$. The film shows outstanding crystal domain an\ulcorner crystal structure. The size of spherulites obtained reach 150-200 $\mu\textrm{m}$ in diameter.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.167-172
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• 2016

We used the 4 m Discovery Channel Telescope (DCT) at Lowell observatory in 2014 to observe the Guitar Nebula, an Hα bow-shock nebula around the high-velocity radio pulsar B2224+65. Since the nebula's discovery in 1992, the structure of the bow-shock has undergone significant dynamical changes. We have observed the limb structure, targeting the "body" and "neck" of the guitar. Comparing the DCT observations to 1995 observations with the Palomar 200-inch Hale telescope, we found changes in both spatial structure and surface brightness in the tip, head, and body of the nebula.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.46-50
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• 2002

In other to evaluate the static and dynamic stiffness of machine tool structure, the accuracy and error from experimental methods are studied in this paper. The F.E.M., impulse tests and exciter tests are performed for the general simple structure whose exact solution can be obtained. So that the parameter and dynamic compliance can be got. From the result, the variation of natural frequency can be verified from the static preload. Further more the relationship of identify and difference for compliance and direction is presented in the exciting direction and measurement direction.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.548-556
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• 2003

Switched reluctance motor(SRM) has simple magnetic structure, and needs simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase. In the vibration and acoustic noise characteristics. the considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural frequency of mechanical structure. This radial vibration force is generated by abrupt change of radial magnetic force in the phase commutation region. This paper studied about simple electromagnetic structure of SRM using auxiliary compensating winding for the reduction of noise and vibration. This auxiliary winding is coupled with all phase windings electromagnetically and absorb and transfer magnetic energy variation from phase to other phase. By this interaction of phase windings and compensating winding can reduce abrupt radial force change and vibration and acoustic noise. In this paper the improvement effect is examined by the test of prototype machine.

• Electrical & Electronic Materials
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• v.8 no.2
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• pp.165-170
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• 1995

This paper describes the fabrication and characteristics of a Si Hall sensor fabricated on a SOI (Si-on-insulator) structure. The SOI structure was formed by SDB(Si-wafer direct bonding) technology and the insulator of the SOI structure was used as the dielectrical isolation layer of a Hall sensor. The Hall voltage and sensitivity of the implemented SDB SOI Hall sensors showed good linearity with respect to the applied magnetic flux density and supplied current. The product sensitivity of the SDB SOI Hall sensor was average 600V/A.T and its value has been increased up to 3 times compared to that of bulk Si with buried layer of 10.mu.m. Moreover, this sensor can be used at high-temperature, high-radiation and in corrosive environments.