• Particle and aerosol research
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• v.18 no.4
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• pp.87-95
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• 2022

Currently, droplet protective screens (DPSs) are used to prevent the spread of respiratory diseases. As virus particles can maintain their infective in indoor environments, recent studies have investigated the risk of airborne transmission. However, the ability of DPSs to block airborne transmission has not been verified yet. In this study, the preventive ability of DPSs against droplet and airborne transmission was evaluated. Moreover, the effectiveness of a Portable air purifier (PAP) was investigated. According to results, in a simulated room where an infectious person spoke, the DPS blocked more than 90% of the micron-sized droplets (with a diameter larger than 1 ㎛) transmitted to the front of the infectious person. However, sub-micron droplets (with a diameter smaller than 1 ㎛) passed through the DPS and spread in a room. However, the PAP reduced the amount of both micron and sub-micron droplets transmitted to the front of the infectious person. When the PAP airflow direction was set from the DPS surface to the free space near the infectious person, improved prevention against droplet and airborne transmission was recorded. However, airborne transmission was accelerated when the PAP airflow direction was set from the free space to the DPS surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.7-7
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• 2009

In this paper, we investigated the dependence of HCI (Hot Carrier Immunity) degradation and device performance on channel orientation in sub-micron PMOSFET. Although device performance ($I_{D.sat}$ vs. $I_{Off}$) was improved as the transistor angle increased HC immunity was degraded. Therefore, consideration of reliability characteristics as well as dc device performance is highly necessary in channel stress engineering of next generation CMOSFETs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.160-160
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• 2003

This paper describes some of the key issues associated with the patterning of metal electrodes of sub-micron (especially at the critical dimension (CD) of 0.15 $\mu\textrm{m}$) dynamic random access memory (DRAM) devices. Due to reactive ion etching (RIE) lag, the Pt etch rate decreased drastically below the CD of 0.20 $\mu\textrm{m}$ and thus the storage node electrode with the CD of 0.15 $\mu\textrm{m}$ could not be fabricated using the Pt electrodes. Accordingly, we have proposed novel techniques to surmount the above difficulties. The Ru electrode for the stack-type structure is introduced and alternative schemes based on the introduction of the concave-type structure using Pt or Ru as an electrode material are outlined.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.679-682
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• 2003

Improvement in MOS fabrication technology have led to high-density high-performance integrated circuits with MOSFET channel lengths in the sub-micron range. For devices of the size, transistor characteristics become highly sensitive to effective channel length. We propose a new approach to extract the effective channel length of MOSFET by Capacitance-Voltage (C-V) method. Gate-to-Source, Drain capacitance ( $C_{gsd}$) are measured and the effective channel length can be extracted. In addition, compared to l/$\beta$ method and Terada method, which has been point out that it fails to extract the accurate effective channel length of the devices, we prove that our approach still works well for the devices with down to sub-micron regime.e.

• Journal of Powder Materials
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• v.8 no.1
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• pp.26-34
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• 2001

In the present study, the effect of Ni content on densification and grain growth in Ni doped W compacts was investigated by using the dilatometric analysis. The Ni-doped W compacts with various amount of Ni activator from 0.02 to 0.4 wt％ were sintered in hydrogen atmosphere up to 140$0^{\circ}C$. As the amount of Ni and heating rates, the Ni-doped W compacts show a greatly different dilatometric behavior during the sintering. The sintered specimen was densified over 98％ of theoretical density by adding only 0.06 wt％ Wi in sub-micron W powder and the appropriate heating rate. It was also observed that the microstructure development strongly depended on the change of the Ni amount. In addition, it was found that the critical content of Ni showing large grain growth in microstructure was below 0.1 wt％.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.79-80
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• 2008

최근 질화물 계 발광다이오드의 광추출효율을 향상시키기 위하여 발광다이오드의 발광면을 texturing하는 연구가 진행되고 있다. 본 연구에서는 직접 패터닝 방식인 나노 임프린팅 공정을 이용하여 blue 발광다이오드의 indium tin oxide (ITO) 투명전극 층에 sub-micron 크기의 hole이 주기적으로 정렬된 구조의 폴리머 패턴을 형성하였으며 임프린팅 공정 후 건식 식각 공정을 통해서 ITO 층을 식각하였다. 그 결과 ITO 투명전극 층에 발광다이오드의 광추출효율을 향상시키기 위한 sub-micron 급의 주기적인 hole 패턴이 형성되었다.

• Proceedings of the Optical Society of Korea Conference
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• 1991.07a
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• pp.109-114
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• 1991

좋은(sub=micron) 분해능을 갖는 Photoresist film의 방법에 의한 Micro-Lithography의 발달은 반도체, Electro-Optic 등의 첨단산업에 큰 기여를 하였다. 본 내용은 이러한 PR을 이용한 Lithography System의 광학적인 원리에 대해 소개하고자 한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05b
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• pp.155-155
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• 1992

• Korean Journal of Materials Research
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• v.12 no.11
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• pp.840-844
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• 2002

A spherical $BaMgAl_{10}$ $O_{17}$ :Eu phosphor has been synthesized by a multi-step precipitation route. In order to successfully synthesize the phosphor with spherical shape, the hydrated-alumina particles should be controlled for spherical shape. In this process, the hydroxypropyl cellulose (HPC) was used as a dispersing reagent. This reagent plays an important role in that the particles were controlled to have the uniform size of sub-micron. The final product prepared by the multi-step precipitation method maintained spherical shape with uniform size of 0.4$\mu\textrm{m}$. It can be seen in X-ray diffraction patterns, formation of the single phase of $BaMgAl_{10}$ $O_{17}$ :Eu phosphor prepared by the multi-step precipitation method at $1350^{\circ}C$. Also, the emission spectra of spherical $BaMgAl_{O}$ $10_{17}$ :Eu phosphor in the present case was compared with those of commercially-available blue phosphor under VUV (Vacuum Ultra Violet) excitation. The luminescence process of the $BaMgAl_{10}$ $O_{17}$ :Eu phosphor is characterized by the $4f^{6}$$5d^1$longrightarrow4f$^{7}$ transition (blue) of the $Eu^{2+}$ ion acting as an activating center and the maximum luminescence intensity was obtained by reduction treatment at 145$0^{\circ}C$.

• Journal of the Korean Electrochemical Society
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• v.14 no.3
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• pp.184-190
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• 2011

$LiMn_2O_4$ with mesoporous hollow sphere shape was synthesized by precipitation method with silica template. The synthesized $LiMn_2O_4$ has nanosized first particle and mesoporous hollow sphere shape. Silica template was removed by chemical etching method using NaOH solution. When the concentration of NaOH solution was increased, first particle size of manganese oxide was decrease and confirmed mesoporous hollow shpere shape. X-ray diffraction(XRD) patterns revealed that the synthesized samples has spinel structure with Fd3m space group. In case the ratio of silica and maganese salt increased, the size of first particles was decreased. The tetragoanal $LiMn_2O_4$ with micron size was synthesized at ratio of silica and manganese salt over 1 : 9. The prepared samples were assembled as cathode materials of Li-ion battery with 2032 type coin cell and their electrochemical properties are examined by charge-discharge and cyclic performance. Electrochemical measurements show that the nano-size particles had lower capacity than micron-size particles. But, cyclic performance of nano-size particles had better than that of micron-size particles.