• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.231-231
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• 2000

It is proposed that a novel method which can compensate the time delay occurs in overall system, when voltage and current is measured, owing to LPF, hysteresis control inverter and microprocessor program computation time. The Proposed scheme estimates the time delay using the difference between Q-axis stator current command and time delayed Q-axis stator current in synchronous reference frame, and compensates the time delay of voltage and current using angular displacement of DQ transformation. The proposed scheme compensates accurately the time delay occurs in overall system. Therefore performance of vector control system is improved highly and it is verified by simulation and experiment.

• Journal of Magnetics
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• v.6 no.3
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.790-798
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• 1990

Al2O3 film was chemically deposited by pyrolytic decom,positio of the Al-tri-isopropoxide/N2 system at 350$^{\circ}C$, 30 and 1.86torr. FTIR analysis showed a deposited film was a hydrated alumina and transformed to an anhydrous one after heat treatment(1hr, >800$^{\circ}C$ or 4hr, >500$^{\circ}C$) in N2 atmosphere. This transformation influenced on the CV-hysteresis of Si-Al2O3 structure. Also, a pH sensitivity of EIS(Electrolyte-Insulator-Semiconductor)structure using Si-Al2O3/SiO2 film was 50mV/pH in the range of pH 3 to 7.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.953-957
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• 2001

To study various relaxation phenomena of $Pb(Mg_{1/3}Nb_{2/3})O_3$ relaxor ferroelectrics, weak electric-field properties as well as strong electric-field properties were investigated in the frequency range from 1 Hz to 100 kHz. The temperature dependence of the dielectric properties were measured under the low electric-field of 1 V/mm in the phase transition temperature range from $-40^{\circ}C$ to $90^{\circ}C$. The dielectric properties obtained from the slope of the dielectric hysteresis loop and the temperature dependence of the pyroelectric properties were also investigated. When fitting all the experimental data with the Vogel-Fulcher relation, experimental data were agreed with the equation closely. Thus, dielectric relaxations could be modeled by the Vogel-Fulcher relation not only for the low electric-field but also for the high electric-field.

• Journal of the Korean Ceramic Society
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• v.35 no.9
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• pp.945-952
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• 1998

Ferroelectric Sr0.8Bi2.4Ta2O9 stock solutions were prepared by MOD(Metaloganic Decompostion) process. The phase transformation for the layered perovskite of the SBT thin films by changing RTA(Rapid her-mal Annealing) temperatuer from 700$^{\circ}C$to 780$^{\circ}C$ were observed using XRD and SEM. Layered perovskite phase began to appear above 740$^{\circ}C$ and then SBT thin films were annealed at 800$^{\circ}C$ for 1hr for its com-plete crystallization. The specimens showed well shaped hysteresis curves without post annealing that car-ried out after deposition of Pt top electrode. The SBT thin films showed the asymmetric ferroelectric pro-perties. It was confirmed that the properties were caused by interface effect to SBT and electrode by leak-age current density measurement and asymmetric properties reduced by post annealing. At post annealing temperature of 800$^{\circ}C$ remanant polarization values (2Pr) were 6.7 9 ${\mu}$C/cm2 and those of leakage current densities were 3.73${\times}$10-7 1.32${\times}$10-6 A/cm2 at 3, 5V respectively. Also bismuth bonding types of SBT thin film surface were observed by XPS.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.705-710
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• 2001

So for the quartz-glassy crucible wastes which was used for pulling up silicon-single-crystal ingot have simply reused for refractory raw-materials, or exhausted. This study is concerned on the advanced recycling-technology that is obtained by the proper micro-particle preparation process in order to fabricate fine amorphous silica filler for EMC (Epoxy Molding Compound). Therefore, this paper will deal with the physical, chemical and thermal pre-treatment process for efficient impurity removal and with the proper micro-particle process for producing the amorphous silicafiller. In view of the results, if the chemical, physical and thermal pre-treatment process for efficient elimination of impurity was passed, the purity of wasted fused glassy crucible is almost equal to the its of first anhydrous quartz glass. Thus, it was understood that this wasted fused glassy crucible was sufficient value of recycling, though it was damaged. When the ingot was fabricated, Phase transformation of crystallization by heat treatment (heat hysteresis phenomenon) was not changed. So, it was understood that as fused silica in the amorphous state, as It is, recycling possibility was very high

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.18-21
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• 2003

The effect of interface bonding strength on the recovery force of SMA wire reinforced polymer matrix composites was investigated by pullout test. Firstly, the recovery forces and transformation temperatures of various prestrained SMA wires were measured and 5% prestrained SMA wires were prepared for the reinforcements of composites. EPDM incorporated with 20vol% silicon carbide particles(SiCp) of 6, 12, $60{mutextrm{m}}$ size were used as matrix. Pullout test results showed that the interface bonding strength increased when the SiCp size decreased due to the increase of elastic modulus of matrix. Cyclic test of composites was performed through control of DC current at the constant displacement mode. The abrupt decrease of recovery force during cycle test at high current was occurred by thermal degradation of matrix. This was in good agreement with temperature related in the thermal degradation of matrix. The hysteresis of recovery force with respect to the temperature was compared between wire and composite and the hysterisis of composites was smaller than the wire due to less thermal conduction.

• Smart Structures and Systems
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• v.24 no.1
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• pp.111-125
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• 2019

Metallic shape memory alloys present fascinating physical properties such as their super-elastic behavior in austenite phase, which can be exploited for providing a structure with both a self-centering capability and an increased ductility. More or less accurate numerical models have been introduced to model their behavior along the last 25 years. This is the reason for which the literature is rich of suggestions/proposals on how to implement this material in devices for passive and semi-active control. Nevertheless, the thermo-mechanical coupling characterizing the first-order martensite phase transformation process results in several macroscopic features affecting the alloy performance. In particular, the effects of day-night and winter-summer temperature excursions require special attention. This aspect might imply that the deployment of some devices should be restricted to indoor solutions. A further aspect is the dependence of the behavior from the geometry one adopts. Two fundamental lacks of symmetry should also be carefully considered when implementing a SMA-based application: the behavior in tension is different from that in compression, and the heating is easy and fast whereas the cooling is not. This manuscript focuses on the passive devices recently proposed in the literature for civil engineering applications. Based on the challenges above identified, their actual feasibility is investigated in detail and their long term performance is discussed with reference to their fatigue life. A few available semi-active solutions are also considered.

• Journal of the Korea Fashion and Costume Design Association
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• v.12 no.3
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• pp.93-103
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• 2010

The results of comparison and analysis of dynamical features according to Jacquard structure are as follows. Regarding elongation(E) value in tensile property, the value in the direction of course was found to be larger in all Jacquard structure, except floating Jacquard, than the direction of wale. It could be found that, as to bending strength(B) in Bending Property, the value of bending strength in the direction of course smaller in all the textile(structure) except floating than the direction of wale, so that the ability of curve formation is excellent. And in case of floating Jacquard, it showed the smallest value in the direction of course and wale, so that it was interpreted as Jacquard having a soft feel. Blister Jacquard showed the highest value in both directions of course and wale, so that it was evaluated as Jacquard having the hardest touch. With regard to shearing character(G) and shearing hysteresis(2HG) in Shearing Property, Jacquard indicated the lowest value, so it was evaluated as the textile(structure) having high drape the transformation of whose fabric is easy. In addition, normal Jacquard, transfer Jacquard, blister Jacquard showed a high value, so that it could be known they are Jacquards having stiff touch. The study implies that normal Jacquard, bird's eye Jacquard, etc., which well stretch in the direction of a course like tubular Jacquard course, is better to make the margin a little shorter than the basic margin, and Jacquard that well stretches in the direction of wale like ladder's back Jacquard and floating Jacquard is better to make the margin longer and the length shorter than the basic margin.

• Fashion & Textile Research Journal
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• v.15 no.4
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• pp.620-629
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• 2013

This study examines the rustling sound characteristics of electrospun nanofiber web laminates according to layer structures. This study assesses mechanical properties and frictional sounds (such as SPL); in addition, Zwicker's psychoacoustic parameters (such as Loudness (Z), Sharpness (Z), Roughness (Z), and Fluctuation strength (Z)) were calculated using the Sound Quality Program (ver.3.2, B&K, Denmark). The result determined how to control these characteristics and minimize rustling sounds. A total of 3 specimens' frictional sound (generated at 0.63 m/s) was recorded using a Simulator for Frictional Sound of Fabrics (Korea Patent No. 10-2008-0105524) and SPLs were analyzed with a Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured with a KES-FB system. The SPL value of the sound spectrum showed 6.84~58.47dB at 0~17,500Hz. The SPL value was 61.2dB for the 2-layer PU nanofiber web laminates layered on densely woven PET(C1) and was the highest at 65.1dB for the 3-layer PU nanofiber web laminates (C3). Based on SPSS 18.0, it was shown that there is a correlation between mechanical properties and psychoacoustic characteristics. Tensile properties (LT), weight (T), and bending properties (2HB) showed a high correlation with psychoacoustic characteristics. Tensile linearity (LT) with Loudness (Z) showed a negative correlation coefficient; however, weight (T) with Sharpness (Z) and Roughness (Z), and bending hysteresis (2HB) with Roughness (Z) indicated positive correlation coefficients, respectively.