• Progress in Superconductivity and Cryogenics
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• v.16 no.2
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• pp.24-28
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• 2014

Magnesium diboride superconductor is still of considerable interest because of its appealing characteristics towards application mainly at around 20 K. Unlike Nb-based superconductors, $MgB_2$ can be operated by cryogen-free cooler which provides a cost effective alternative at low field of around 2-5 T. To explore this operating field region considerable efforts are necessary to marginally improve the superconducting properties of $MgB_2$. Under this situation, even the heat treatment environment during the synthesis is considered as an important factor. The addition of $H_2$ gas in small amount with Ar as a mixed gas during annealing has an adverse effect on the superconducting properties of $MgB_2$. It is although interesting to find that the presence of Mg vapor along with hydrogen during heat treatment results in the appreciable improvement in the flux pinning and the overall response of the critical current density for the ex-situ $MgB_2$ samples.

• Journal of Photoscience
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• v.9 no.2
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• pp.439-441
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• 2002

Cyanobacteria are the dominant micro flora in rice-fields, contributing significantly to fertility as a natural biofertilizer. Recent studies show a continuous depletion of the stratospheric ozone layer, and the consequent increase in solar UV-B (280-315 nm) radiation reaching the Earth's surface. UV-B radiation causes reduction in growth, survival, protein content, heterocyst frequency and fixation of carbon and nitrogen in many cyanobacteria. UV -B induced bleaching of pigments, disassembly of phycobilisomal complexes, thymine dimer formation and alterations in membrane permeability have also been encounterd in a number of cyanobacteria. However, certain cyanobacteria produce photoprotective compounds such as water soluble colorless mycosporine-like amino acids (MAAs) and the lipid soluble yellow-brown colored sheath pigment, scytonemin, to counteract the damaging effects of UV-B. Cyanobacteria, such as Anabaena sp., Nostoc commune, Scytonema sp. and Lyngbya sp. were isolated from rice fields and other habitats in India and screened for the presence of photoprotective compounds. A circadian induction of the synthesis of MAAs by UV -B was noted in a number of cyanobacteria. Polychromatic action spectra for the induction of MAAs in Anabaena sp. and Nostoc commune also show the induction to be UV-B dependent peaking at 290 nm. Another photoprotective compound, scytonemin, with an absorption maximum at 386 nm (also absorbs at 300, 278, 252 and 212 nm), was detected in many cyanobacteria. In conclusion, a particular cyanobacterium having photoprotective compounds may be a potent candidate as biofertilizer for crop plants.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.324-330
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• 2013

This paper presented measurement results of scattering characteristics of dielectric barrier discharge (DBD) plasma at atmospheric pressure. In this paper, plasma actuator is fabricated by parallel connecting of basic configuration of DBD plasma actuator, then plasma could be generated by applying 14 kV, 4 kHz of high voltage generator. In order to measure the scattering characteristics of DBD plasma, in this paper, two horn antennas and vector network analyzer are used to compare the S-parameter. Because of the structure of fabricated plasma generator, different result is obtained as antenna polarization changes. When antenna polarization is parallel to electrodes of plasma generator, the scattered field is reduced by 2 dB in maximum. In addition, for parallel polarization case, PEC is set up behind the plasma generator to measure backward scattered field. When the observation angles are $40^{\circ}C$ and $60^{\circ}C$, the amount of reduced scattered field is 2 dB in maximum at 5 GHz.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.128-134
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• 2012

The performance evaluation and fabrication of integrated-optic electric-field sensor utilizing $Ti:LiNbO_3$ asymmetric Mach-Zehnder intensity modulator with a push-pull lumped electrode and a plate-type probe antenna to measure an electric field strength is described. The modulator has a small device size of $46{\times}7{\times}1\;mm$ and operates at a wavelength $1.3{\mu}m$. The devices are simulated based on the BPM software and fabricated utilizing Ti-diffused $LiNbO_3$ channel optical waveguides. The minimum detectable electric field is 1.02 V/m and 6.91 V/m, corresponding to a dynamic range of ~35 dB and ~10 dB at the frequencies of 500 KHz and 5 MHz, respectively.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.124-127
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• 2007

Magnetic tunnel junctions (MTJs), which consisted of amorphous CoFeSiB layers, were investigated. The CoFeSiB layers were used to substitute for the traditionally used CoFe and/or NiFe layers with an emphasis given on understanding the effect of the amorphous free layer on the switching characteristics of the MTJs. CoFeSiB has a lower saturation magnetization ($M_s\;:\;560\;emu/cm^3$) and a higher anisotropy constant ($K_u\;:\;2800\;erg/cm^3$) than CoFe and NiFe, respectively. An exchange coupling energy ($J_{ex}$) of $-0.003\;erg/cm^2$ was observed by inserting a 1.0 nm Ru layer in between CoFeSiB layers. In the Si/$SiO_2$/Ta 45/Ru 9.5/IrMn 10/CoFe 7/$AlO_x$/CoFeSiB 7 or CoFeSiB (t)/Ru 1.0/CoFeSiB (7-t)/Ru 60 (in nm) MTJs structure, it was found that the size dependence of the switching field originated in the lower $J_{ex}$ using the experimental and simulation results. The CoFeSiB synthetic antiferromagnet structures were proved to be beneficial for the switching characteristics such as reducing the coercivity ($H_c$) and increasing the sensitivity in micrometer size, even in submicrometer sized elements.

• Journal of Astronomy and Space Sciences
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• v.27 no.3
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• pp.205-212
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• 2010

To better understand the physical processes that maintain the high-latitude lower thermospheric dynamics, we have identified relative contributions of the momentum forcing and the heating to the high-latitude lower thermospheric winds depending on the interplanetary magnetic field (IMF) and altitude. For this study, we performed a term analysis of the potential vorticity equation for the high-latitude neutral wind field in the lower thermosphere during the southern summertime for different IMF conditions, with the aid of the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR-TIEGCM). Difference potential vorticity forcing and heating terms, obtained by subtracting values with zero IMF from those with non-zero IMF, are influenced by the IMF conditions. The difference forcing is more significant for strong IMF $B_y$ condition than for strong IMF $B_z$ condition. For negative or positive $B_y$ conditions, the difference forcings in the polar cap are larger by a factor of about 2 than those in the auroral region. The difference heating is the most significant for negative IMF $B_z$ condition, and the difference heatings in the auroral region are larger by a factor of about 1.5 than those in the polar cap region. The magnitudes of the difference forcing and heating decrease rapidly with descending altitudes. It is confirmed that the contribution of the forcing to the high-latitude lower thermospheric dynamics is stronger than the contribution of the heating to it. Especially, it is obvious that the contribution of the forcing to the dynamics is much larger in the polar cap region than in the auroral region and at higher altitude than at lower altitude. It is evident that when $B_z$ is negative condition the contribution of the forcing is the lowest and the contribution of the heating is the highest among the different IMF conditions.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.3
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• pp.184-189
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• 2008

To assess the relationship between Cd fraction in paddy soils and Cd in polished rice, soils and rice were analyzed at the 3 Cd contaminated paddy fields near closed mines. Major Cd fractions of A field were organically bound (62.6%) and Fe-Mn oxide bound (25.3%) forms. In case of B field, major Cd fractions of B1 field were carbonate bound (46.3%) and Fe-Mn oxide bound (31.6%) form whereas B2 field were residual (54.3%) and carbonate bound (21.8%) form, respectively. It showed a huge difference of Cd fraction each other. 0.1M HCl extractable Cd in soil was positively correlated with Cd in rice. Specially, the ratios of 0.1M HCl extractable Cd against total Cd content in soils were 13.7%, 2.6%, and 0.45% in A, B1, and B2 fields, respectively. These ratio were largely affected with Cd uptake to rice grain. Also, exchangable, Fe-Mn oxide bound, and carbonate bound form, which are partially bioavailable Cd fraction to the plant, were positively correlated with Cd in rice while organically bound and residual form was not correlated. Multiple regression equation was developed with Rice Cd = -0.02861 + 0.07456 FR 1(exchangeable) + 0.00252 FR 2(carbonate bound) + 0.001075 FR 3(Fe Mn oxide bound) - 0.00095 FR 4(organically bound) - 0.00348 FR 5(residual) ($R^2=0.7893^{***}$) considering Cd fraction in soils.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.2
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• pp.109-115
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• 2008

The comparative molecular field analyses(CoMFA) models between the substituents with changing groups($R_1{\sim}R_4$) of $3{\beta}$-hydroxy-12-oleanen-28-oic acid derivatives as substrate molecule and their inhibitory activities($pI_{50}$) against protein tyrosine phosphatase(PTP)-1B were derived and discussed quantitatively. The optimized CoMFA F1 model have best predictability and fitness($r^2_{cv.}=0.654$ and $r^2_{ncv.}=0.995$). The order of contribution ratio (%) with CoMFA fields on the inhibitory activities was a steric field(53.0%), electrostatic field(36.2%) and hydrophobic field(10.8%). From the analytical results of CoMFA contour maps, the inhibitory activities were dependent on the R4 group in substrate molecules. Particularly, the new active compounds(P1 & P2) with the inhibitory activity against melanin synthesis were expected.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.18-24
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• 2010

A Ka-band microstrip array antenna for wide-range detection of moving targets is analyzed through a photonicassisted reactive-near-field characterization technique. The antenna array employs a 3-dB-tapered feed network to suppress the sidelobe level while retaining a wide azimuth beamwidth for a wide detection range. The relative nearelectric field patterns of the array and its 3-dB-tapered feed lines have been measured using an electro-optic fieldmapping technique for minimally invasive millimeter-wave sensing. A number of typical limitations on the technique, involving bandwidth, low signal-modulation depth, and high laser-induced noise in high-frequency applications, have been overcome by suppressing the carrier portion of the optical interrogation beam.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.222-222
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• 1999

From extensive measurements of the resistance and the dynamic resistance as functions of magnetic field and temperature, we find that the transport in the insulating state beyond the superconductor-insulator (S-I) transition is dominated by bosons(Cooper pairs and/or vortices) and cannot be described by the theory of the fermionic insulating phase. The maximum of the magnetoresistance at B = B$_m$ and the following negative slope in R(B) with increasing field can be explained by the crossover from the "Bose-glass" to the "Fermi-glass" phase as suggested by Paalanen, Hebard, and Ruel. The zero bias peak in dv/dl for biases below the characteristic voltage V$_c$ (or current $I_c$), gives a clue for the assumption of the "dirty boson" model which states that the insulating state above the critical magnetic field is the phase where Cooper pairs are localized due to the Coulomb blockade with a nonvanishing order parameter. The shift to a lower value of the critical magnetic field by overlaying thin Au layer, which is known as a strong spin-orbit scatterer, also supports the bosonic nature of the S-I transition.