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121.
Koo J Park J Tronin A Zhang R Krishnan V Strzalka J Kuzmenko I Fry HC Therien MJ Blasie JK 《Langmuir : the ACS journal of surfaces and colloids》2012,28(6):3227-3238
We show that simply designed amphiphilic 4-helix bundle peptides can be utilized to vectorially orient a linearly extended donor-bridge-acceptor (D-br-A) electron transfer (ET) chromophore within its core. The bundle's interior is shown to provide a unique solvation environment for the D-br-A assembly not accessible in conventional solvents and thereby control the magnitudes of both light-induced ET and thermal charge recombination rate constants. The amphiphilicity of the bundle's exterior was employed to vectorially orient the peptide-chromophore complex at a liquid-gas interface, and its ends were tailored for subsequent covalent attachment to an inorganic surface, via a "directed assembly" approach. Structural data, combined with evaluation of the excited state dynamics exhibited by these peptide-chromophore complexes, demonstrate that densely packed, acentrically ordered 2-D monolayer ensembles of such complexes at high in-plane chromophore densities approaching 1/200 ?(2) offer unique potential as active layers in binary heterojunction photovoltaic devices. 相似文献
122.
Seulah Lee Ja Hoon Koo Jungmok Seo Sung-Dae Kim Kwang Hyun Lee Seongil Im Young-Woon Kim Taeyoon Lee 《Journal of nanoparticle research》2012,14(5):840
Although the aqueous electroless etching (AEE) method has received significant attention for the fabrication of silicon nanowires
(SiNWs) due to its simplicity and effectiveness, SiNWs grown via the AEE method have a drawback in that their surface roughness
is considerably high. Thus, we fabricated surface-modified p–n
+ junction SiNWs grown by AEE, wherein the surface roughness was reduced by a sequential processes of oxide growth using the
rapid thermal oxidation (RTO) cycling process and oxide removal with a hydrofluoric acid solution. High-resolution transmission
electron microscopy analysis confirmed that the surface roughness of the modified SiNWs was significantly decreased compared
with that of the as-fabricated SiNWs. After RTO treatment, the wettability of the SiNWs had dramatically changed from superhydrophilic
to superhydrophobic, which can be attributed to the formation of siloxane groups on the native oxide/SiNW surfaces and the
effect of the nanoscale structure. Due to the enhancement in surface carrier mobility, the current density of the surface-modified
p–n
+ junction SiNWs was approximately 6.3-fold greater than that of the as-fabricated sample at a forward bias of 4 V. Meanwhile,
the photocurrent density of the surface-modified p–n
+ junction SiNWs was considerably decreased as a result of the decreases in the light absorption area, light absorption volume,
and light scattering. 相似文献
123.
Sang Jin LeeTae Jong Baek Min HanSeok Gyu Choi Dong Sik KoSam Dong Kim Jin Koo Rhee 《Current Applied Physics》2012,12(3):773-777
We present a high isolation W-band MMIC drain type cascode single balanced mixer of high LO-to-RF isolation and wide band with conversion characteristic using the high directivity monolithic tandem couplers and 0.1 μm GaAs-based metamorphic high electron mobility transistors (MHEMTs). The fabricated mixer consists of two cascode MHEMT mixers and two tandem couplers using the air-bridge crossovers. We establish a drain type cascode mixer structure where the LO signal is applied to the drain port in the mixing component of common source MHEMT circuit. The tandem coupler exhibits good couplings (2.92-3.8 dB), low return losses (−32.7 dB), and isolations (15.4-39.2 dB) in a wide bandwidth of 75-110 GHz. The mixer shows a conversion loss of 9.8 dB at 94 GHz, an output P1dB of −14.8 dBm at LO frequency of 94.542 GHz, and LO-to-RF isolations of 29.5-39.5 dB at 94-100 GHz. 相似文献
124.
Hyun-Joo Koo 《Solid State Communications》2012,152(13):1116-1118
The causes for the three-dimensional magnetic ordering and the observed spin orientation of the layered oxides Sr2MnSi2O7 and Ba2MnGe2O7 were investigated by evaluating the spin exchange interactions and the preferred spin orientation on the basis of density functional calculations and by calculating the magnetic dipole–dipole interaction energies. 相似文献
125.
Junwye Lee Jonghyun Koo Si Un Hwang Sunmin Min Sang Jung Ahn Yonghan Roh Sung Ha Park 《Current Applied Physics》2012,12(4):1207-1211
We report the structural and functional stabilities of artificially synthesized DNA ultra-thin films. Fully covered DNA ultra-thin films on a silica substrate were fabricated by the silica-assisted growth method and those samples were then incubated in various chemicals and physical conditions. The DNA ultra-thin films showed high maintainability under those harsh conditions and these results would aid to facilitate the use of artificial DNA ultra-thin films in advanced research areas such as biophotonics and bioelectronics. 相似文献
126.
Hyun Sik Yoon Chung Ho Jeon Jae Hwan Jung Bonguk Koo Changyoung Choi Sung Chul Shin 《国际流体数值方法杂志》2013,73(3):250-265
In the present paper, a direct forcing/fictitious domain (DF/FD)–level set method is proposed to simulate the twophase flow–body interaction. The DF/FD does not sacrifice accuracy and robustness by employing a discrete δ (Dirac delta) function to transfer quantities between the Eulerian nodes and Lagrangian points explicitly as the immersed boundary method. The advantages of this approach are the simple concept, the easy implementation and the utilization of original governing equation without modification. The main idea is to combine DF/FD method with the level set method in the Cartesian coordinates. We present the results of a number of test cases to illustrate the effectiveness of the proposed method for single‐phase flow–body interaction problem and the two‐phase flows with a stationary body. Eventually, the simulations of various water entry problems have been conducted to validate the capability and the accuracy of the present method on solving the twophase flow–body interaction. Consequently, the present results are found to be in good agreement with those of previous studies. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
127.
128.
129.
Yonghoi Koo 《偏微分方程通讯》2013,38(5-6):1035-1053
We demonstrate a general situation in which a hypersurface in Rn propagating by mean curvature, plus a nonzero driving force, develops an interior after finite time in the level set formulation of the problem. 相似文献
130.
We prove that for C1 generic diffeomorphisms, every measure-expansive locally maximal homoclinic class is hyperbolic. 相似文献