• Ocean and Polar Research
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• v.31 no.1
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• pp.51-61
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• 2009

In this study we define the two different types of El $Ni{\tilde{n}}o$, i.e., the eastern Pacific El $Ni{\tilde{n}}o$ (i.e., EP-El $Ni{\tilde{n}}o$) versus the central Pacific El $Ni{\tilde{n}}o$ (i.e., CP-El $Ni{\tilde{n}}o$), during the boreal summer (June-July-August, JJA) and winter (December-January-February, DJF) using the two NINO indices in the tropical Pacific. The two different types of El $Ni{\tilde{n}}o$ significantly differ in terms of the location of the maximum anomalous sea surface temperature (SST) in the tropical Pacific. The CP-El $Ni{\tilde{n}}o$ has been observed more frequently during recent decades compared to the EP-El $Ni{\tilde{n}}o$. In addition, our analysis indicates that the statistics of CP-El $Ni{\tilde{n}}o$ during JJA is closely associated with the warming trend in the central equatorial Pacific. We also examine the different responses of the East Asian marginal SST to the two types of El $Ni{\tilde{n}}o$ during JJA and DJF. The CP-El $Ni{\tilde{n}}o$ during both JJA and DJF is concurrent with warm SST anomalies around the Korean Peninsula including the East China Sea, which is in contrast to the EP-El $Ni{\tilde{n}}o$. Such different responses are associated with the difference in tropics/mid-latitude teleconnections via atmosphere between the two types of El $Ni{\tilde{n}}o$. Furthermore, our results indicate that atmospheric diabatic forcing in relation to the precipitation variability is different in the tropical Pacific between the EP-El $Ni{\tilde{n}}o$ and the CP-El $Ni{\tilde{n}}o$.

• Electrical & Electronic Materials
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• v.9 no.9
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• pp.906-910
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• 1996

Ferroxplana N $i_{2}$Y(B $a_{2}$N $i_{2}$F $e_{12}$ $O_{22}$ ) magnetic particles, which is one of the hexagonal ferrite were synthesized by a coprecipitation method. The coprecipitates were prepared by adding aqueous solution of BaC $I_{2}$ - 2 $H_{2}$O, NiC $I_{2}$ - 6 $H_{2}$O and FeC $I_{3}$ - 6 $H_{2}$O(of which the mole ratio is $Ba^{+2}$ : N $i^{+2}$ : F $e^{3+}$= 1 : 1 : 6) to a mixture of NaOH and N $a_{2}$C $O_{3}$. The shape of Ferroxplana N $i_{2}$Y magnetic particles obtained at 1, 100(.deg. C) was hexagonal plate-like, average particle size and aspect ratio were 2(.mu.m) and 7, respectively.y.

• Journal of the Korean earth science society
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• v.24 no.1
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• pp.22-29
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• 2003

Temporal and spatial variability of precipitation (P), evaporation (E), and moisture balance (P-E; precipitation minus evaporation) has been investigated over the tropical ocean during the period from January 1998 to July 2001. Our data were analyzed by the EOF method using the satellite P and E observations made by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and the Special Sensor Microwave/Imager (SSM/I). This analysis has been performed for two three-year periods as follow; The first period which includes the El Ni${\tilde{n}}$o in early 1998 ranges from January 1998 to December 2000, and the second period which includes the La Ni${\tilde{n}}$o events in the early 1999 and 2000 (without El Ni${\tilde{n}}$o) ranges from August 1998 to July 2001. The areas of maxima and high variability in the precipitation and in the P-E were displaced from the tropical western Pacific and the ITCZ during the La Ni${\tilde{n}}$o to the tropical middle Pacific during the El Ni${\tilde{n}}$o, consistent with those in previous P studies. Their variations near the Korean Peninsula seem to exhibit a weakly positive correlation with that in the tropical Pacific during the El Ni${\tilde{n}}$o. The evaporation, out of phase with the precipitation, was reduced in the tropical western Pacific due to humid condition in boreal summer, but intensified in the Kuroshio and Gulf currents due to windy condition in winter. The P-E variability was determined mainly by the precipitation of which the variability was more localized but higher by 2-3 times than that of evaporation. Except for the ITCZ (0-10$^{\circ}$N), evaporation was found to dominate precipitation by ${\sim}$2 mm/day over the tropical Pacific. Annual and seasonal variations of P, E, and P-E were discussed.

• Journal of Navigation and Port Research
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• v.37 no.6
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• pp.611-616
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• 2013

This paper studies relationship between typhoon and El Ni$\tilde{n}$o La Ni$\tilde{n}$a events by using 25 years meteorological data of KMA and JMA. The results are listed below. Annual mean number of typhoon's occurrence in El Ni$\tilde{n}$o event year is 23.9, and that in La Ni$\tilde{n}$a event year is 24.9. The number of typhoon's occurrence decreases in El Ni$\tilde{n}$o event year. Mean central minimum pressure and mean maximum wind speed in El Ni$\tilde{n}$o event year are 959.3hPa and 35.8m/s, and those in La Ni$\tilde{n}$a event year are 965.5hPa and 33.7m/s respectively. Intension of typhoon is stronger in El Ni$\tilde{n}$o event year than La Ni$\tilde{n}$a event year. To be more specific mean central minimum pressure is lower 6.2hPa and mean maximum wind speed is stronger 2.1m/s. This result is closely connected with sea area of typhoon's occurrence. Typhoons in El Ni$\tilde{n}$o event year are more likely to occur in east of 150E and south of 10N, but those in La Ni$\tilde{n}$a event year are more likely to occur in 120-150E and north of 20N. Typhoons which occur in east of 150E and south of 10N can be stronger because the typhoons move in broad sea area of high sea surface temperature in western North Pacific.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.18-24
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• 2004

Ni-Zn ferrite powder was synthesized from metal nitrates, Fe(N $O_3$)$_3$$.$9 $H_2$O, Ni(N $O_3$)$_2$$.$6 $H_2$O, Zn(N $O_3$)$_2$$.$6 $H_2$O by wet direct process to make high permeability material. The composition of the ferrite powder is (N $i_{0.284}$F $e_{0.053}$Z $n_{0.663}$)F $e_2$ $O_4$. Ni-Zn ferrite powder is compounded by precipitating metal nitrates with NaOH in vessel at 90$^{\circ}C$ synthetic temperature for 8 hours. Calcination temperature and sintering temperature were 700$^{\circ}C$ and 1150$^{\circ}C$-1250$^{\circ}C$ respectively for 2 hours. The same compound powder was extracted from metal oxide by wet ballmilling. We compared the properties of powder and the electromagnetic characteristics of the sintered cores obtained from the two different processes. Wet direct process produces smaller particle size with narrower distribution and higher purified ferrite which cores has high permeability and high magnetization.

• Atmosphere
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• v.23 no.1
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• pp.63-71
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• 2013

KMA is operationally monitoring El Ni$\tilde{n}$o and La Ni$\tilde{n}$a events, which have tremendous impacts on global climate. Many scientific studies have used to define onset of El Ni$\tilde{n}$o and La Ni$\tilde{n}$a events based on the moving average and persistency of SST indices, and KMA has adopted such definition. Though the definition has been widely accepted, in the operational aspect there is a critical problem to use moving average and condition for the persistence. Because the future values for the SST indices cannot be used in the operational monitoring, the onset timing in El Ni$\tilde{n}$o and La Ni$\tilde{n}$a can be significantly delayed. We suggest here an appropriate definition of El Ni$\tilde{n}$o and La Ni$\tilde{n}$a events in the operational aspect. Instead of using the moving average and the condition for the persistence, the onset is defined based on NINO3.4 SST during last 3 months. In order to compare the new definition with the current KMA definition, we applied them to recent 60-years SST data. It is clear that the new definition can declare the onset timing of El Ni$\tilde{n}$o and La Ni$\tilde{n}$a several months earlier than that of the KMA definition. It suggest that the new definition is more appropriate to the operational monitoring on El Ni$\tilde{n}$o and La Ni$\tilde{n}$a.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.331-334
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• 2001

In this study, the magnetic properties for Ni-Zn ferrite were investigated as the function of $Co_3$ $O_4$ additive contents which was predicted to improve the resonance frequency. Toroid specimens with the composition of N $i_{0.8-x}$Z $n_{0.2+x}$F $e_2$ $O_4$(x = 0, 0.05, 0.1, 0.15) ferrites were preparation by conventional ceramic processing technique. The maximum resonance frequency of 19.905 MHz and the permeability of 90.88 in 10 MHz were attained to the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$0.3 wt%. Both of the permeability in 10 MHz and the resonance increased to 107.11 and 19.005 MHz respectively for the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$with $Co_3$ $O_4$wt% than the N $i_{0.8}$Z $n_{0.2}$F $e_2$ $O_4$/ with the free $Co_3$ $O_4$composition.composition.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.443-446
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• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• Ocean and Polar Research
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• v.24 no.1
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• pp.19-31
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• 2002

Precipitation variability around King Sejong Station related with E1 $Ni\~{n}o$/Southern Oscillation (ENSO) is evaluated using the gauge-based monthly data of its neighboring stations. Though three Ant-arctic Stations of King Sejong (Korea), Frei (Chile), and Artigas (Uruguay) are all closely located within 10 km, their precipitation data show mostly insignificant positive or rather negative correlations among them in the annual, seasonal and monthly precipitation. This result indicates that there are locally large variations in the distribution of precipitation around King Sejong Station. The monthly data of Frei Station for 31 years (1970-2000) are analyzed for examining the ENSO signal in precipitation because of its longer precipitation record compared to other two stations. From the analysis of seasonal precipitation, it is seen that there is a tendency of less precipitation than the average during E1 $Ni\~{n}o$ events. This dryness is more distinct in fall to spring seasons, in which the precipitation decreases down to about 30% of seasonal mean precipitation. However, the precipitation signal related with La $Ni\~{n}a$ events is not significant. From the analysis of monthly precipitation, it is found that there is a strong negative correlation during 1980s and in the late 1990s, and a weak positive correlation in the early 1990s between normalized monthly precipitation at Frei Station and Sea Surface Temperature (SST) anomalies in the $Ni\~{n}o$ 3.4 region. However, this relation may be not applied over the region around King Sejong Station, but at only one station, Frei.

• Atmosphere
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• v.24 no.1
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• pp.89-99
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• 2014

Recently, several studies pointed out that there are distinct two types of El Ni$\tilde{n}$o events based on the spatial pattern of SST. Since the two types of El Ni$\tilde{n}$o have different impacts on global climate, it is quite important to identify the type to assess and predict the regional climate variability. So far, however, there are still many different definitions to identify the two types of El Ni$\tilde{n}$o from the different studies. In this study, we investigated a sensitivity of the impacts on climate variability over the Korean Peninsula corresponding to the definition of two-types of El Ni$\tilde{n}$o. After checking pre-existing definitions and other possible definition, it is suggested here that two different definitions exhibit relatively strong relationship between El Ni$\tilde{n}$o events and the Korean climate variables when two types of El Ni$\tilde{n}$o are separated. In addition to the Korean climate, the two types of El Ni$\tilde{n}$o show quite distinct global teleconnection patterns when the definitions are used.