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排序方式: 共有9140条查询结果,搜索用时 640 毫秒
901.
Sub‐Nanometer Level Size Tuning of a Monodisperse Nanoparticle Array Via Block Copolymer Lithography
Dong Ok Shin Duck Hyun Lee Hyoung‐Seok Moon Seong‐Jun Jeong Ju Young Kim Jeong Ho Mun Heesook Cho Soojin Park Sang Ouk Kim 《Advanced functional materials》2011,21(2):250-254
The fabrication and catalytic application of a size‐tunable monodisperse nanoparticle array enabled by block copolymer lithography is demonstrated. Highly uniform vertical cylinder nanodomains are achieved in poly(styrene‐block‐4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer thin‐films by solvent annealing. The prominent diffusion of the anionic metal complexes into the protonated P4VP cylinder nanodomains occurs through specific electrostatic interactions in a weakly acidic aqueous solution. This well‐defined diffusion with nanoscale confinement enables preparation of the laterally ordered monodisperse nanoparticle array with sub‐nanometer level precise size tuning. The controlled growth of monodisperse nanoparticle arrays is proven by their catalytic use for vertical carbon nanotube (CNT) growth via plasma enhanced chemical vapor deposition (PECVD). Since the size of the catalyst particles is the decisive parameter for the diameters and wall‐numbers of CNTs, the highly selective growth of double‐walled or triple‐walled CNTs could be accomplished using monodisperse nanoparticle arrays. 相似文献
902.
Shinuk Cho Junghoon Lee Minghong Tong Jung Hwa Seo Changduk Yang 《Advanced functional materials》2011,21(10):1910-1916
As a characteristic feature of conventional conjugated polymers, it has been generally agreed that conjugated polymers exhibit either high hole transport property (p‐type) or high electron transport property (n‐type). Although ambipolar properties have been demonstrated from specially designed conjugated polymers, only a few examples have exhibited ambipolar transport properties under limited conditions. Furthermore, there is, as yet, no example with ‘equivalent’ hole and electron transport properties. We describe the realization of an equivalent ambipolar organic field‐effect transistor (FET) by using a single‐component visible–near infrared absorbing diketopyrrolopyrrole (DPP)‐benzothiadiazole (BTZ) copolymer, namely poly[3,6‐dithiene‐2‐yl‐2,5‐di(2‐decyltetradecyl)‐pyrrolo[3,4‐c]pyrrole‐1,4‐dione‐5’,5’’‐diyl‐alt‐benzo‐2,1, 3‐thiadiazol‐4,7‐diyl] ( PDTDPP‐alt‐BTZ ). PDTDPP‐alt‐BTZ shows not only ideally balanced charge carrier mobilities for both electrons (?e = 0.09 cm2V?1s?1) and holes (?h = 0.1 cm2V?1s?1) but also its inverter constructed with the combination of two identical ambipolar FETs exhibits a gain of ~35 that is much higher than usually obtained values for unipolar logic. 相似文献
903.
Software based decoding of low-density parity-check (LDPC) codes frequently takes very long time, thus the general purpose
graphics processing units (GPGPUs) that support massively parallel processing can be very useful for speeding up the simulation.
In LDPC decoding, the parity-check matrix H needs to be accessed at every node updating process, and the size of the matrix is often larger than that of GPU on-chip
memory especially when the code length is long or the weight is high. In this work, the parity-check matrix of cyclic or quasi-cyclic
(QC) LDPC codes is greatly compressed by exploiting the periodic property of the matrix. Also, vacant elements are eliminated
from the sparse message arrays to utilize the coalesced access of global memory supported by GPGPUs. Regular projective geometry
(PG) and irregular QC LDPC codes are used for sum-product algorithm based decoding with the GTX-285 NVIDIA graphics processing
unit (GPU), and considerable speed-up results are obtained. 相似文献
904.
Crystalline germanium (Ge) is a prime candidate as a material for high-performance transistors due to its higher electron and hole mobility with respect to those of silicon. In this study, we present a novel method of fabricating epitaxial Ge structures of high crystalline and morphological quality directly onto Si substrates, in which 3D Ge structures are grown by selective epitaxy then annealed in a hydrogen ambient at 850 °C. Under such annealing, the surface of the Ge structures deform by surface diffusion to form smooth, rounded shapes for which the surface energy is at a local minima. The apparent smoothness of the surface, along with the decreased defect density expected to exist in these heteroepitaxial Ge structures, suggest they are adequate for use as transistor channels. 相似文献
905.
Heon-Bok Lee Hyun Jeong Yang Ju Hyung We Kukjoo Kim Kyung Cheol Choi Byung Jin Cho 《Journal of Electronic Materials》2011,40(5):615-619
A new process for fabricating a low-cost thermoelectric module using a screen-printing method has been developed. Thermoelectric
properties of screen-printed ZnSb films were investigated in an effort to develop a thermoelectric module with low cost per
watt. The screen-printed Zn
x
Sb1−x
films showed a low carrier concentration and high Seebeck coefficient when x was in the range of 0.5 to 0.57 and the annealing temperature was kept below 550°C. When the annealing temperature was higher
than 550°C, the carrier concentration of the Zn
x
Sb1−x
films reached that of a metal, leading to a decrease of the Seebeck coefficient. In the present experiment, the optimized
carrier concentration of screen-printed ZnSb was 7 × 1018/cm3. The output voltage and power density of the ZnSb film were 10 mV and 0.17 mW/cm2, respectively, at ΔT = 50 K. A thermoelectric module was produced using the proposed screen-printing approach with ZnSb and CoSb3 as p-type and n-type thermoelectric materials, respectively, and copper as the pad metal. 相似文献
906.
The generation of nucleic acid aptamers with high affinity typically entails a time-consuming, iterative process of binding, separation, and amplification. It would therefore be beneficial to develop an efficient selection strategy that can generate these high-quality aptamers rapidly, economically, and reproducibly. Toward this goal, we have developed a method that efficiently generates DNA aptamers with slow off-rates. This methodology, called VDC-MSELEX, pairs the volume dilution challenge process with microfluidic separation for magnetic bead-assisted aptamer selection. This method offers improved aptamer selection efficiencies through the application of highly stringent selection conditions: it retrieves a small number (<10(6)) of magnetic beads suspended in a large volume (>50 mL) and concentrates them into a microfluidic chamber (8 μL) with minimal loss for continuous washing. We performed three rounds of the VDC-MSELEX using streptavidin (SA) as the target and obtained new DNA aptamer sequences with low nanomolar affinity that specifically bind to the SA proteins. 相似文献
907.
White-light scanning interferometry (WLSI) is a useful technique to measure surface profile when a test object contains discontinuous structures or microstructures. A black and white CCD camera is usually utilized to capture interferograms, and a series of corresponding algorithms is used to achieve the profile measurement. However, the color information in the interferograms is lost. A novel profile measurement method that uses phase information in different color channels (red-green-blue) of an interferogram obtained using a three-chip color CCD in WLSI is proposed. The phase values are extracted by a windowed Fourier transform algorithm. Simulation and experimental results are presented to demonstrate the validity of the proposed method. 相似文献
908.
Maenghyo Cho Seunghwa Yang Seongmin Chang Suyoung Yu 《International journal for numerical methods in engineering》2011,85(12):1564-1583
A sequential multi‐scale homogenization method combined with molecular dynamics (MD) simulation is developed for the mechanical characterization of nanoparticulate composites. In order to characterize the particle‐size effect of nanocomposites, the effective interface, which has been adopted in continuum micromechanics approaches, is considered as the characteristic phase. Owing to the existence of the interface and the size‐dependent elastic modulus that is observed from MD simulations, an analysis of the mechanical properties of nanocomposites with continuum micromechanics requires careful consideration of the particle‐concentration effect. Therefore, this study focuses on hierarchical information transfer from the molecular model to the continuum model through the homogenization method in lieu of an analytical micromechanics bridging method. Using the present multi‐scale homogenization method, the elastic properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. In addition, the overall elastic modulus of nanocomposites is obtained from the present model and compared with the results of MD simulation, the micromechanics bridging model, and finite‐element analysis (FEA). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
909.
Kyeong-Jae ByeonEun-Ju Hong Hyoungwon ParkJoong-Yeon Cho Seong-Hwan LeeJunggeun Jhin Jong Hyeob BaekHeon Lee 《Thin solid films》2011,519(7):2241-2246
A UV-imprinting process for a full wafer was developed to enhance the light extraction of GaN-based green light-emitting diodes (LEDs). A polyvinyl chloride flexible stamp was used in the imprinting process to compensate for the poor flatness of the LED wafer. Two-dimensional photonic crystal patterns with pitches ranging from 600 to 900 nm were formed on the p-GaN top cladding layer of a 2 inch diameter wafer using nanoimprint and reactive ion etching processes. As a result, the optical output power of the patterned LED device was increased by up to 44% at a driving current of 20 mA by suppressing the total internal reflection and enhancing the irregular scattering of photons at the patterned p-GaN surface. 相似文献
910.
Y.H. KangK. Ahn S.Y. JeongJ.S. Bae J.S. JinH.G. Kim S.W. HongC.R. Cho 《Thin solid films》2011,519(20):7090-7094
Electrospun polyacrylonitrile (PAN) nanofibers were subjected to surface modification by atmospheric pressure (AP) plasma treatment with reactive gases. There was no damage to the surfaces after this plasma treatment, and no significant changes were observed in the morphologies of the nanofibers. The surface energies of O2- and N2-plasma-treated PAN (abbreviated as OPP and NPP, respectively) nanofibers increased by almost 138.7% and 190.6%, respectively, in comparison with that of an untreated nanofiber (256.6 mJ/m2). The binding energies of both OPP and NPP samples increased through the formation of many hydrophilic bonds involving oxygen. The current-voltage (I-V) characteristics of the nanofibers were determined for the different reactive gases, and the plasma-treated nanofibers showed higher protein immobilization compared to the untreated ones. This result indicates that electrospun PAN nanofibers have the potential to be used in protein biosensor systems. 相似文献