본 연구에서는 용액 공정으로 제작된 단분자 기반의 유기 반도체 전계효과 트랜지스터에 적용된 보호막이 유기 트랜지스터의 전기적 안정성에 미치는 영향에 대해여 살펴보았다. Solvay社에서 제공한 용액 공정형 유기 단분자 반도 체를 채널로 사용하여 제작한 유기 트랜지스터는 약 1 cm2/Vs의 상대적으로 높은 이동도를 보였으며, 대략 2.5 ~ 20 k Ωcm 범위의 낮은 접촉저항을 가진 것으로 측정되었다. 무엇보다 중요한 것은, 제작한 유기 트랜지스터에 불소원자가 함유된 Hyflon AD를 보호막으로 적용하였을 때, 보호막을 적용하기 전에 비해 훨씬 더 향상된 전기적 안정성을 보였 다. 이는 불소원자가 함유된 Hyflon AD 고분자막이 대기 중의 수분을 효과적으로 차단하기 때문으로 추측된다.

The structural phase transformations of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) were studied using high resolution x-ray diffraction (HRXRD) as a function of temperature and electric field. A phase transformational sequence of cubic (C)→tetragonal (T)→rhombohedral (R) phase was observed in zero-field-cooled conditions; and a C→T→monoclinic (Mc)→ monoclinic (MA) phase was observed in the field-cooled conditions. The transformation of T to MA phase was realized through an intermediate Mc phase. The results also represent conclusive and direct evidence of a Mc to MA phase transformation in field-cooled conditions. Beginning from the zero-field-cooled condition, a R→MA→Mc→T phase transformational sequence was found with an increasing electric field at a fixed temperature. Upon removal of the field, the MA phase was stable at room temperature. With increasing the field, the transformation temperature from T to Mc and from Mc to MA phase decreased, and the phase stability ranges of both T and Mc phases increased. Upon removal of the field, the phase transformation from R to MA phase was irreversible, but from MA to Mc was reversible, which means that MA is the dominant phase under the electric field. In the M phase region, the results confirmed that lattice parameters and tilt angles were weakly temperature dependent over the range of investigated temperatures.

This study was performed to investigate the exposure levels of magnetic field (MF) in residences near electrical transformer rooms in apartment buildings in Korea. We determined that the location of transformer rooms in apartment buildings in Korea is not same as in other countries. In particular, in Korea, the transformer on the pole near buildings serves residential buildings of less than 5 floors. In the buildings taller than 5 floors transformers are often placed below the parking lots in the basement. We estimated that there were, however, about 85,000 with transformer room adjacent to an apartment and had identified about 1,600 apartment buildings with transformers that can be included in the TransExpos study. The mean value of measured MFs was 1.17 mG in apartments above transformer room and 0.97 mG in other floors from transformer room. This study was concluded that apartments in building with transformer room can be classified into high-exposure category based on their location in relation to transformer room.

Si Nanowire (NW) field effect transistors (FETs) were fabricated on hard Si and flexible polyimide (PI) substrates, and their electrical characteristics were compared. Si NWs used as channels were synthesized by electroless etching method at low temperature, and these NWs were refined using a centrifugation method to get the NWs to have an optimal diameter and length for FETs. The gate insulator was poly(4-vinylphenol) (PVP), prepared using a spin-coating method on the PI substrate. Gold was used as electrodes whose gap was 8 μm. These gold electrodes were deposited using a thermal evaporator. Current-voltage (I-V) characteristics of the device were measured using a semiconductor analyzer, HP-4145B. The electrical properties of the device were characterized through hole mobility, Ion/Ioff ratio and threshold voltage. The results showed that the electrical properties of the TFTs on PVP were similar to those of TFTs on SiO2. The bending durability of SiNWs TFTs on PI substrate was also studied with increasing bending times. The results showed that the electrical properties were maintained until the sample was folded about 500 times. But, after more than 1000 bending tests, drain current showed a rapid decrease due to the defects caused by the roughness of the surface of the Si NWs and mismatches of the Si NWs with electrodes.

The relationship between electrical properties of superconductor and externally applied magnetic field was studied to develop a magnetic field sensor. The electrical resistance of the superconductor was increased by applying external magnetic field and even after removal of the magnetic field. This behavior was related to the magnetic flux trapped in the superconductor, which penetrated through the material by the external magnetic field. Some portion of the superconductor was changed to a normal state by the trapped magnetic flux. The appearance of the normal state yielded to enhance the electrical resistance.

단백질 분리를 위한 한외여과에서의 전기장의 영향에 대하여 조사하였다. 실험은 균일한 막간압력차(2.5 bar)에서 알부민과 라이소자임 용액을 이용하여 이루어졌으며 분리막으로는 셀룰로즈 재질의 분획분자량(MWCO) 30 kDa 한외여과막을 사용하였다. 실험결과 전기장은 알부민 용액을 여과할 때의 투과유속(permeation flux)을 크게 증가시키는데에 도움이 되었다. 투과유속의 개선 이외에도 전기장은 또 다른 흥미로운 효과를 보였다. 단백질 분자의 하전 부호에 따라 전기장은 단백질의 투과를 촉진시키기도 하고 저하시키기도 하였다. 이러한 전기장의 효과를 이용하여 한외여과에서의 용액 투과유속뿐만 아니라 투과선택도도 개선할 수 있었다.

기존의 솔레노이드 밸브는 전자부품에 기계적 운동요소를 포함하여 비선형성을 내포하고 있으나, MC 성분의 ER유체를 이용하면, 유동체의 통과부분을 전기장 제어를 통하여 솔레노이드 밸브 기능을 대신할 수 있는 메카니즘을 구현할 수 있을 것으로 사료된다. 유기성인 MC성분 ER유체를 유압시스템에 솔레노이드 밸브 역할에 적용하기 위해, 부과하는 직류 전기장의 사이클 수에 따른 기계적특성에 대한 평가는 다음과 같다. MC성분 ER유체의 전단속도비에 대한 전단응력 분포변화는 2.0kV/mm까지 전기장을 인가했을 경우, 횡축의 전단속도가 증가하여도 종축의 전단응력은 거의 변하지 않았다. 60만 사이클을 반복한 후 ITMC25의 전단응력 실험결과, 2.0kV/mm 이상 전기량을 인가하면 2차원적인 곡선의 형태를 형성하지만 표준편차의 평가치가 오차한계 이내이므로 직선으로 판단하여도 무리가 없을 것으로 사료되었다. 구리 전극으로 전기장을 부과한 경우 MC 성분의 ER유체는 0.1~0.3μm까지의 표면거칠기를 나타냈고, 알루미늄 전극을 사용한 경우는 전기장 부과 초기에 0.3μm의 표면거칠기가 0.2μm로 감소하였으나 40만 사이클의 전기장 부과 이후는 약간의 요철변화가 있었다.(이 논문의 결론 부분임)

Solar electrical conductivity has been calculated, making use of Yun and Wyller's formulation. The computed results arc presented in a tabulated form as functions of temperature and pressure for given magnetic field strengths. The results of the calculation show that the magnetic field does not play any important role in characterizing the electrical conductivity of the ionized gas when the gas pressure is relatively high (e.g., P ≥ 10 4 d y n e s / c m 2 ). However, when the gas pressure is low (e.g., P ≤ 10 d y n e s / c m 2 ), the magnetic field becomes very effective even if its field strength is quite small (e.g., B ≤ 0.01 gauss). It is also found that, except for lower temperature region (e.g., T ≤ 10 4 ∘ K ), there is a certain linear relationship in a log- log graph between the pressure and the critical magnetic field strength, which is defined as a field strength capable of reducing the non-magnetic component of the electrical conductivity by 20%.