• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.21-21
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AlN/Co type ten-layered discontinuous films of nanoscaled [AlN (3 nm)/Co (t nm)]...$\sub$10/ with t$\sub$Co/=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer. Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1,2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AlN matrix, and the films showed the superparamagnetic behavior with a high MR value of Δ$\rho$/$\rho$$\sub$0/=1.8 %. As t$\sub$Co/ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. Tunneling barrier called "decay length for tunneling" for the films having the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$\^$-1/.

• Journal of Magnetics
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• v.8 no.2
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• pp.98-102
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• 2003

Microstructure and magnetic transport phenomina in rf sputtered AIN/CO type ten- layered discontinuous films of nanoscaled [AIN(3 nm)/Co(t nm)]…$_10$ with t$_Co$=1.0∼2.0 nm have been investigated. The microstructure and tunneling magnetic resistance of the samples are strongly dependent on the thickness of Co layer, Negative tunneling magneto-resistance due to the spin-dependent transport has been observed along the current-in-plane configuration in the samples having the Co layers below 1.6 nm thick. When the thickness of Co layer was less than 1.2 nm, randomly oriented granular Co particles were completely isolated and embedded in amorphous AIN matrix, and the films showed the superparamagnetic behavior with a high MR value of ${\Delta}p/p_0$=1.8%. As t$_Co$ increases, a transition from the regime of co-existence of superparamagnetic and ferromagnetic behaviors to ferromagnetic behavior was observed. funneling barrier called “decay length far tunneling” fur the films haying the thickness of Co layer from 1.4 to 1.6 nm was measured to be ranged from 0.004 to 0.021 ${\AA}$$^{-1}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.73-76
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• 1999

We have fabricated and tested a Bi-based high temperature superconducting current lead system. Ag sheathed Bi-2223 mono-filament tapes of $I_c=8.4$ A at 77 K under self-field condition were fabricated using powder-in-tube(P1T) method. Multi-layer current leads can be made by stacking of Ag sheathed Bi-2223 mono-filament wires. The critical current of this 10-layer current lead is about 68 A. The contact resistance across the copper-current lead interface has been studied using current-voltage characteristics. At temperature below critical temperature the resistive contribution of the interface to the total contact resistance dominates. We have measured AC transport losses in a current lead at 77 K, 60 Hz by a transport method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.309-313
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• 2024

The key to determining the lifetime of OLED device is how much brightness can be maintained. It can be said that there are internal and external causes for the degradation of OLED devices. The most important cause of internal degradation is bonding and degradation in the excited state due to the electrochemical instability of organic materials. The structure of OLED modeled in this paper consists of a cathode layer, electron injection layer (EIL), electron transport layer (ETL), light emission layer, hole transport layer (HTL), hole injection layer (HIL), and anode layer on a glass substrate from top to bottom. It was confirmed that the temperature generated in OLED was distributed around the maximum of 343.15 K centered on the emission layer. It can be seen that the heat distribution generated in the presented OLED structure has an asymmetrically high temperature distribution toward the cathode, which is believed to be because the sizes of the cathode and positive electrode are asymmetric. Therefore, when designing OLED, it is believed that designing the structures of the cathode and anode electrodes as symmetrically as possible can ensure uniform heat distribution, maintain uniform luminance of OLED, and extend the lifetime. The thermal distribution of OLED was analyzed using the finite element method according to Comsol 5.2.

• Korean Journal of Materials Research
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• v.20 no.6
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• pp.294-300
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• 2010

In this study, we fabricated a polymer light emitting diode (PLED) and investigated its electrical and optical characteristics in order to examine the effects of the PFO [poly(9,9-dioctylfluorene-2-7-diyl) end capped with N,N-bis(4-methylphenyl)-4-aniline] concentrations in the emission layer (EML). The PFO polymer was dissolved in toluene ranging from 0.2 to 1.2 wt%, and then spin-coated. To verify the influence of the TPBI [2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)]electron transport layer, TPBI small molecules were deposited by thermal evaporation. The current density, luminance, wavelength and current efficiency characteristics of the prepared PLED devices with and without TPBI layer at various PFO concentrations were measured and compared. The luminance and current efficiency of the PLED devices without TPBI layer were increased, from 117 to $553\;cd/m^2$ and from 0.015 to 0.110 cd/A, as the PFO concentration increased from 0.2 to 1.0 wt%. For the PLED devices with TPBI layer, the luminance and current efficiency were $1724\;cd/m^2$ and 0.501 cd/A at 1.0 wt% PFO concentration. The CIE color coordinators of the PLED device with TPBI layer at 1.0 wt% PFO concentration showed a more pure blue color compared with the one without TPBI, and the CIE values varied from (x, y) = (0.21, 0.23) to (x, y) = (0.16, 0.11).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.190-195
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• 2018

Recently, Due to the ongoing increase in cyber attacks and the improved awareness of privacy protection, most Internet services encrypt the traffic by using security protocols. Existing security protocols usually have additional layer between transport layer and application layer, and they incur additional costs because of encrypting all the traffic transmitted. This results in unnecessary performance degradation because it also encrypts data that does not require confidentiality. In this paper, we propose TCP OENC(Optional Encryption) which enables users of the application layer to optionally encrypt only confidential data. TCP OENC operates by TCP option to allow the application layer to encrypt the TCP stream transmitted only on demand. And it ensures transparency between the TCP layer and the application layer. To verify this, we verified that TCP OENC optionally encrypts the stream of TCP session on the embedded board. And then analyzed the performance of the encrypted stream by measuring the elapsed time.

• Journal of KIISE:Information Networking
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• v.35 no.5
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• pp.374-383
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• 2008

IEEE 802.11 WLANs support various data rates in order to adapt to wireless channel condition. It is known that when some WLAN stations use a lower data rate than the others, total throughput is considerably degraded. The concept of temporal fairness which provides equal time to all stations has been introduced to alleviate this performance anomaly problem. However, most previous mechanisms assume that stations have infinite backlogs in the MAC layer and do not consider transport layer. In this paper, we first examine and analyze the performance of previous methods considering transport layer protocols. We then propose two new temporal fairness guarantee methods: AP priority and dynamic CWmin adjustment. We carried out extensive performance study via ns-2 computer simulations. The results show that the proposed methods provide temporal fairness and improve the throughput of WLANs in various environments.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.89-92
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• 2017

The performance of three-layered organic light-emitting diodes (OLEDs) was investigated using TPD hole-transport and injection layers, Teflon-AF, and the electron-injection layer of $Li_2CO_3$ and LiF. The OLEDs were manufactured in a structure of TPD/$Alq_3$/LiF, TPD/$Alq_3$/$Li_2CO_3$, and AF/$Alq_3$/LiF using low-molecular organic materials. In three different three-layered OLEDs, it was found that the device with the TPD/$Alq_3$/LiF structure shows higher performance in maximum luminance, and maximum external quantum efficiency compared to those of the device with TPD/$Alq_3$/$Li_2CO_3$ and TPD/$Alq_3$/LiF by 35% and 17%, and 193% and 133%, respectively. It is thought that the combined LiF/Al cathode contributes to a reduced work function and improves an electrical conduction mechanism due to the electron injection rather than the hole transport, which then increases a recombination rate of charge carriers.

• Atmosphere
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• v.14 no.4
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• pp.3-18
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• 2004

Neglecting the vertical transport from the surface, most of the previous studies on the long-range transport of pollutants have only considered the horizontal transport caused by the free atmosphere wind. I used a three dimensional numerical model, MM5 (The fifth generation Penn State Univ./NCAR Mesoscale Model) for the simulation of vertical transport of pollutants and investigated the mechanism of the vertical transport of atmospheric pollutants between planetary boundary layer(PBL) and free atmosphere by fronts. From the three dimensional simulation of MM5, the amount of pollutants transport from PBL to free atmosphere is 48% within 18 hour after the development of front, 55% within 24 hour, and 53% within 30 hour. The ratios of the vertically transported pollutant for different seasons are 62%, 60%, 54%, and 43% for spring, summer, fall, and winter, respectively. The most active areas for the vertical transport are the center of low pressure and the warm sector located east side of cold front, in which the strong upward motion slanted northward occurs. The horizontal advection of pollutants at the upper level is stronger than at the lower level simply because of the stronger wind speed. The simulation results shows the well known plum shape distribution of pollutants. The high concentration area is located in the center and north of the low pressure system, while the second highest concentration area is in the warm sector. It is shown that the most important mechanism for the vertical transport is vertical advection, while the vertical diffusion process plays an important role in the redistribution of pollutants in the PBL.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.10-15
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• 1995

Organic thin film electroluminescent(EL) cells were fabricated. Their output characteristics and luminance versus voltage characteristics were measured with different work function metal electrodes. The EL structure was Indium-Tin-Oxide(ITO)/hole transport layer/emission layer(electron transport layer)/metal electrode. PMMA+TPD(0.5 wt%), MC homopolymer+TPD(0.005 wt%) and (MC/MMA) copolymer+TPD(0.005 wt%) were used as hole transport layer. Ca, Mg, Mg:Ag(10:l) and Al were used as metal electrode. I-V output showed exponential feature, and the threshold voltage of 5 volts and the luminance of over 700 $Cd/m^{2}$ at 10 volts were observed.