• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.8
• /
• pp.658-663
• /
• 2002

Hall factor of electrons in $\Gamma$-valley is calculated as functions of temperature, impurity concentration, and nonparabolicity of conduction valleys by taking into account the current density obtained from the Boltzmann transport equation. The dependence of the Hall factor on the temperature is clearly shown in the case of the optical phonon scattering and that on the impurity concentration is obvious in the case of the ionized impurity scattering. As the nonparabolicity of the conduction band increases, the Hall factor due to the acoustic or optic phonon scattering increases, whereas that due to the ionized impurity scattering decreases. The change of the Hall factor can be analysed in terms of the dispersion of relaxation time.

• Earthquakes and Structures
• /
• v.17 no.2
• /
• pp.163-173
• /
• 2019

For Special Concentrically Braced Frame (SCBF), it is common that the damage concentrates at a certain story instead of spreading over all stories. Once the damage occurs, the soft-story mechanism is likely to take place and possibly to result in the failure of the whole system with more damage accumulation. In this study, we use a strongback column which is an additional structural component extending along the height of the building, to redistribute the excessive deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three specimens, namely S73, S42 and S0, which represent different combinations of stiffness and strength factors ${\alpha}$ and ${\beta}$ for the strongback columns, were designed based on results of numerical simulations. Specimens S73 and S42 were the specimens with the strongback columns, and S0 is the specimen without the strongback column. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), we can observe 29% and 11% improvement in Specimen S73 and S42, respectively. This improvement increases the nonlinear demand of the third-story braces and reduces that of the first-story braces where the demand used to be excessive, and, therefore, postpones the rupture of the first-story braces and enhances the ductility and energy dissipation capacity of the whole SCBF system.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.12 no.4
• /
• pp.35-44
• /
• 2008

A self-centering energy-dissipative(SCED) bracing system has recently been developed as a new seismic force resistant bracing system. The advantage of the SCED brace system is that, unlike other comparable advanced bracing systems that dissipate energy such as the buckling restrained brace(BRB) system, it has a self-centering capability that reduces or eliminates residual building deformations after major seismic events. In order to investigate the effects of torsion on the SCED brace and BRB systems, nonlinear time history analyses were used to compare the responses of 3D model structures with three different amounts of frame eccentricity. The results of the analysis showed that the interstory drifts of SCED braced frames are more uniform than those of BRB frames, without regard to irregularity. The residual drift and residual rotation responses tended to decrease as irregularity increased. For medium-rise structures, the drift concentration factors(DCFs) for SCED systems were lower than those for BRB frames. This means that SCED-braced frames deform in a more uniform manner with respect to building height. The effect of the torsional irregularity on the magnitude of the DCFs was small.

• Korean Journal of Remote Sensing
• /
• v.23 no.6
• /
• pp.507-520
• /
• 2007

Satellite passive microwave(PM) sensors have been observing polar sea ice concentration(SIC), ice temperature, and snow depth since 1970s. Among them SIC is playing an important role in the various studies as it is considered the first factor for the monitoring of global climate and environment changes. Verification and correction of PM SIC is essential for this purpose. In this study, we calculated SIC from KOMPSAT-1 EOC images obtained from Arctic sea ice edges from July to August 2005 and compared with SSM/I SIC calculated from NASA Team(NT) algorithm. When we have no consideration of sea ice types, EOC and SSM/I NT SIC showed low correlation coefficient of 0.574. This is because there are differences in spatial resolution and observing time between two sensors, and the temporal and spatial variation of sea ice was high in summer Arctic ice edge. For the verification of SSM/I NT SIC according to sea ice types, we divided sea ice into land-fast ice, pack ice, and drift ice from EOC images, and compared them with SSM/I NT SIC corresponding to each ice type. The concentration of land-fast ice between EOC and SSM/I SIC were calculated very similarly to each other with the mean difference of 0.38%. This is because the temporal and spatial variation of land-fast ice is small, and the snow condition on the ice surface is relatively dry. In case of pack ice, there were lots of ice ridge and new ice that are known to be underestimated by NT algorithm. SSM/I NT SIC were lower than EOC SIC by 19.63% in average. In drift ice, SSM/I NT SIC showed 20.17% higher than EOC SIC in average. The sea ice with high concentration could be included inside the wide IFOV of SSM/I because the drift ice was located near the edge of pack ice. It is also suggested that SSM/I NT SIC overestimated the drift ice covered by wet snow.