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Plasmon resonance changes of gold nanoparticle arrays upon modification
Ha, Dong Han,Kim, Sanghun,Yun, Yong Ju,Park, Hyung Ju,Yun, Wan Soo,Song, Jung-Hoon IOP Pub 2009 Nanotechnology Vol.20 No.8
<P>Periodic Au nanoparticle arrays, fabricated using electron beam lithography, have been modified by chemical reaction in solutions having various concentrations of a reducing agent. As the nanoparticles enlarge due to the formation of additional Au nanolumps on the surface, both the position and intensity of plasmon absorbance of Au nanoparticle arrays change in proportion to the concentration of the reducing agent. Moreover, the plasmon absorbance is split into dipole and quadrupole modes as conductive connections form between the particles. Our results demonstrate that the changes in both the position and intensity of plasmon absorbance can be employed together as complementary readout values of nanosensors. </P>
Secret Key Agreement With Large Antenna Arrays Under the Pilot Contamination Attack
Sanghun Im,Hyoungsuk Jeon,Jinho Choi,Jeongseok Ha IEEE 2015 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.14 No.12
<P>We present a secret key agreement (SKA) protocol for a multi-user time-division duplex system where a base-station (BS) with a large antenna array (LAA) shares secret keys with users in the presence of non-colluding eavesdroppers. In the system, when the BS transmits random sequences to legitimate users for sharing common randomness, the eavesdroppers can attempt the pilot contamination attack (PCA) in which each of eavesdroppers transmits its target user's training sequence in hopes of acquiring possible information leak by steering beam towards the eavesdropper. We show that there exists a crucial complementary relation between the received signal strengths at the eavesdropper and its target user. This relation tells us that the eavesdropper inevitably leaves a trace that enables us to devise a way of measuring the amount of information leakage to the eavesdropper even if PCA parameters are unknown. To this end, we derive an estimator for the channel gain from the BS to the eavesdropper and propose a rate-adaptation scheme for adjusting the length of secret key under the PCA. Extensive analysis and evaluations are carried out under various setups, which show that the proposed scheme adequately takes advantage of the LAA to establish the secret keys under the PCA.</P>
Effect of Subsurface Drainage Systems on Soil Salinity at Saemangeum Reclaimed Tidal Land
Sanghun Lee,Hui-Su Bae,Soo-Hwan Lee,Yang-Yeol Oh,Jin-Hee Ryu,Jong-Cheol Ko,Ha-Chul Hong,Yong-Doo Kim,Sun-Lim Kim 한국토양비료학회 2015 한국토양비료학회지 Vol.48 No.6
Soil salinity is the most critical factor for crop production at reclaimed tidal saline soil. Subsurface drainage system is recognized as a powerful tool for the process of desalinization in saline soil. The objective of this study was to investigate the effects of subsurface drainage systems on soil salinity and corn development at Saemangeum reclaimed tidal saline soil. The field experiments were carried out between 2012 and 2014 at Saemangeum reclaimed tidal land, Buan, Korea. Subsurface drainage was installed with four treatments: 1) drain spacing of 5 m, 2) drain spacing 10 m, 3) double layer with drain spacing 5 m and 10 m, and 4) the control without any treatment. The levels of water table showed shorter periods above 60 cm levels with the deeper installation of subsurface drainage system. Water soluble cations were significantly greater than exchangeable forms and soluble Na contents, especially in surface layer, were greatly reduced with the installation of subsurface drainage system. Subsurface drainage system improved biomass yield of corn and withering rate. Thus, the biomass yield of corn was improved and the shoot growth was more affected by salinity than was the root growth. The efficiency of double layer was not significant compared with the drain spacing of 5 m. The economic return to growers at reclaimed tidal saline soil was the greatest by the subsurface drainage system with 5 m drain spacing. Our results demonstrated that the installation of subsurface drainage system with drain space of 5 m spacing would be a best management practice to control soil salinity and corn development at Saemangeum reclaimed tidal saline soil.
Oxygen plasma effects on the electrical conductance of single-walled carbon nanotube bundles
Kim, Sanghun,Kim, Ho-Jong,Lee, Hyeong Rag,Song, Jung-Hoon,Yi, Sam Nyung,Ha, Dong Han Institute of Physics [etc.] 2010 Journal of Physics. D, Applied Physics Vol.43 No.30
<P>We report the electrical properties of single-walled carbon nanotube bundles aligned between two electrodes with a gap of 8 µm by the alternating current dielectrophoresis method. The resistance increased exponentially as the number of structural defects increased from the oxygen plasma treatment. However, no noticeable change was observed in the carrier concentration and tube–tube interaction. The resistance dependence on the plasma treatment time was explained on the basis of the localization of electron states at defect sites. The aspects of the defects were examined by measuring the effects of ammonia adsorption on the conductance of the device.</P>
Effect of Subsurface Drainage Systems on Soil Salinity at Saemangeum Reclaimed Tidal Land
Lee, Sanghun,Bae, Hui-Su,Lee, Soo-Hwan,Oh, Yang-Yeol,Ryu, Jin-Hee,Ko, Jong-Cheol,Hong, Ha-Chul,Kim, Yong-Doo,Kim, Sun-Lim 한국토양비료학회 2015 한국토양비료학회지 Vol.48 No.6
Soil salinity is the most critical factor for crop production at reclaimed tidal saline soil. Subsurface drainage system is recognized as a powerful tool for the process of desalinization in saline soil. The objective of this study was to investigate the effects of subsurface drainage systems on soil salinity and corn development at Saemangeum reclaimed tidal saline soil. The field experiments were carried out between 2012 and 2014 at Saemangeum reclaimed tidal land, Buan, Korea. Subsurface drainage was installed with four treatments: 1) drain spacing of 5 m, 2) drain spacing 10 m, 3) double layer with drain spacing 5 m and 10 m, and 4) the control without any treatment. The levels of water table showed shorter periods above 60 cm levels with the deeper installation of subsurface drainage system. Water soluble cations were significantly greater than exchangeable forms and soluble Na contents, especially in surface layer, were greatly reduced with the installation of subsurface drainage system. Subsurface drainage system improved biomass yield of corn and withering rate. Thus, the biomass yield of corn was improved and the shoot growth was more affected by salinity than was the root growth. The efficiency of double layer was not significant compared with the drain spacing of 5 m. The economic return to growers at reclaimed tidal saline soil was the greatest by the subsurface drainage system with 5 m drain spacing. Our results demonstrated that the installation of subsurface drainage system with drain space of 5 m spacing would be a best management practice to control soil salinity and corn development at Saemangeum reclaimed tidal saline soil.
하현규(Hyungyu Ha),김상헌(Sanghun Kim),전현표(Hyunpyo Jeon) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5
나노물질은 기술의 발전에 따라 시장에서의 점유율이 늘어나고 있으며, 그에 맞춰 물질확인 및 안전성 확보의 요구가 점차 늘어나고 있다. 나노물질은 나노단위의 작은 크기와 넓은 비표면적으로 인해 일반 화학물질에 비하여 반응성이 높을 뿐 아니라 인체와 환경에 노출될 경우 심각한 영향을 미칠 가능성이 크다. 또한, 해당 나노물질의 조성과 구조에 따라 물질의 유해성 및 위해성이 크게 달라질 수 있다. 2019년 개정된 「화학물질 등록 및 평가 등에 관한 법률(이하 화평법)」에 따라 2030년까지 톤 수에 따른 화학물질의 등록을 완료하여야 하며, 이 등록예정 물질에는 나노물질도 포함된다. 나노물질의 등록을 위해서는 화평법에서 제시한 공동등록시스템에 따라 등록을 준비하여야 하며, 공동등록의 과정에서 화학물질의 동질성을 판단하기 위해 물질확인은 필수적인 과정이다. 그러나 물질확인 과정에 대한 인프라의 부족과 시험방법이 명확히 정립되지 않아 SIP(Substance Identification Profile)의 작성이 어려운 상황이다. 이에 본 연구에서는 나노물질의 정확한 물질확인을 위해 국내에 위치한 4곳의 기관에 Ag nanoparticles, TiO2(nano)의 구조 및 순도, 불순물에 대한 분석, 나노물질의 특성인 크기, 형태, 종횡비, 표면전하에 대한 분석을 의뢰하여 라운드 로빈 테스트를 진행함으로써 획일화되고 신뢰성있는 시험방법을 개발하여 화평법하에서의 나노물질 등록 지원 및 물질확인방법을 보완하고자 하였다. 연구 결과 TiO2와 Ag nanoparticles의 화학조성, 순도 및 불순물, 나노물질 특성이 각 기관마다 결과와 전처리 및 시험방법, 시험에 사용된 기기들이 상이하였고, 물질확인을 위한 체계적인 시험이 마련되어 있지 않은 것을 확인하였다. 향후 나노물질을 포함한 단량체, UVCB 물질, 고분자물질의 체계적인 등록 및 관리를 위해서 물질확인을 위한 인프라 구축과 시험방법의 정립이 필요할 것으로 판단된다.
하동한(Dong Han HA),윤용주(Yong Ju Yun),아칠성(Chil Seong Ah),김상훈(Sanghun Kim),윤완수(Wan Soo Yun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
We show that it is possible to fabricate arbitrarily designed freestanding nano-objects; for example, Au nanogears with overall dimension below 500 ㎚, and to manipulate them so precisely as to assemble them by teeth to teeth without damaging them at all. Nanogears are fabricated by selective etching of single-crystalline Au template nanoplates using the Ga? focused ion beam (FIB). Although nanoparticles with diameters of around 20 ㎚ are easily moved by sharp atomic force microscopy (AFM) tips, blunt tips are needed to manipulate the nanogears. The capability of precise AFM manipulation for the various kinds of nano-objects, combined with the fabrication technique of arbitrarily designed freestanding nano-objects will be a useful tool for the development or repair of sophisticated micro/nano-structures.