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111.
Taeyeon Kwon Jin Young Koo Hee Cheul Choi 《Angewandte Chemie (International ed. in English)》2020,59(38):16436-16439
Together with high conductivity, high flexibility is an important property required for next generation organic electronic components. Both properties are difficult to achieve together especially when the components are crystalline because of the intrinsic high brittleness of organic molecular crystals. We report an organic radical crystal system that has both high flexibility and high conductivity. The crystal consists of 9,10‐bis(phenylethynyl)anthracene radical cation ( BPEA.+ ) units, and shows flexibility under pressure with high conductivity in ambient condition exhibiting average conductivity of 2.68 S cm?1 when normal linear shape, as well as 2.43 S cm?1 when bent. The structural analysis reveals that both a short π–π distance (3.290 Å) between BPEA.+ units that are aligned along the crystal length direction, and the presence of PF6? counter ions induce flexibility and high electrical conductivity. 相似文献
112.
The effect of a market factor on information flow between stocks using the minimal spanning tree 总被引:1,自引:0,他引:1
We empirically investigated the effects of market factors on the information flow created from N(N−1)/2 linkage relationships among stocks. We also examined the possibility of employing the minimal spanning tree (MST) method, which is capable of reducing the number of links to N−1. We determined that market factors carry important information value regarding information flow among stocks. Moreover, the information flow among stocks showed time-varying properties according to the changes in market status. In particular, we noted that the information flow increased dramatically during periods of market crises. Finally, we confirmed, via the MST method, that the information flow among stocks could be assessed effectively with the reduced linkage relationships among all links among stocks from the perspective of the overall market. 相似文献
113.
Alexander Efremov Youngkeun Kim Hyun-Woo Lee Kwang-Ho Kwon 《Plasma Chemistry and Plasma Processing》2011,31(2):259-271
The effects of HBr/Ar and HBr/Cl2 mixing ratios in the ranges of 0–100% Ar or Cl2 on plasma parameters, densities of active species influencing the dry etch mechanisms were analyzed at fixed total gas flow
rate of 40 sccm, total gas pressure of 6 mTorr, input power of 700 W and bias power of 300 W. The investigation combined plasma
diagnostics by Langmuir probes and the 0-dimensional plasma modeling. It was found that the dilution of HBr by Ar results
in maximum effect on the ion energy flux with expected impact on the etch rate in the ion-flux-limited etch regime, while
the addition of Cl2 influences mainly the relative fluxes of Br and Cl atoms on the etched surface with expected impact on the etch rate in the
reaction-rate-limited etch regime. 相似文献
114.
Min‐kyoung Ham Ji HoYouk Yong‐Ku Kwon Young‐Je Kwark 《Journal of polymer science. Part A, Polymer chemistry》2012,50(12):2389-2397
A photoinitiation process was investigated to develop a rapid and well‐controlled RAFT polymerization method applied to vinyl acetate (VAc) using methyl (ethoxycarbonothioyl)sulfanyl acetate (MESA) and bis(2,4,6‐trimethylbenzoyl)phenylphosphine oxide as the RAFT agent and photoinitiator, respectively. MESA was selected as the photochemically inert RAFT agent to minimize photolysis of the thiocarbonylthio groups during polymerization. Poly(vinyl acetate) with a prespecified well‐controlled molecular weight (MW) and a narrow MW distribution was successfully synthesized. The polymerization reaction proceeded as a living polymerization and was remarkably rapid compared with approaches that use thermally initiated processes with a very short induction period. A detailed kinetic study of the mechanism underlying the polymerization reaction, however, revealed that the chain ends containing xanthate moieties were not perfectly stable upon UV‐irradiation, and they generated radicals via homolytic cleavage. This reaction appeared to proceed by a combination of a degenerative transfer RAFT mechanism and a dissociation‐combination mechanism. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
115.
Sang Sub Kim Sun-Woo Choi Han Gil Na Dong Sub Kwak Yong Jung Kwon Hyoun Woo Kim 《Current Applied Physics》2013,13(3):526-532
ZnO–SnO2 branch–stem nanostructures were realized on a basis of a two-step process. In step 1, SnO2-stem nanowires were synthesized. In step 2, ZnO-branch nanowires were successfully grown on the SnO2-stem nanowires through a simple evaporation technique. We have pre-deposited thin Au layers on the surface of SnO2 nanowire stems and subsequently evaporated Zn powders on the nanowires. The ZnO branches, which sprouted from the SnO2 stems, had diameters in a range of 30–35 nm. As-synthesized branches were of single crystalline hexagonal ZnO structures. Since the branch tips were comprised of Au-containing nanoparticles, the Au-catalyzed vapor–liquid–solid growth mechanism was more likely to control the growth process of the ZnO branches. To test a potential use of ZnO–SnO2 branch–stem nanostructures in chemical gas sensors, their sensing performances with respect to NO2 gas were investigated, showing the promising potential in chemical gas sensors. 相似文献
116.
117.
Kwon BJ 《The Journal of the Acoustical Society of America》2002,112(2):634-641
Comodulation masking release (CMR) refers to an improvement in the detection threshold of a signal masked by noise with coherent amplitude fluctuation across frequency, as compared to noise without the envelope coherence. The present study tested whether such an advantage for signal detection would facilitate the identification of speech phonemes. Consonant identification of bandpass speech was measured under the following three masker conditions: (1) a single band of noise in the speech band ("on-frequency" masker); (2) two bands of noise, one in the on-frequency band and the other in the "flanking band," with coherence of temporal envelope fluctuation between the two bands (comodulation); and (3) two bands of noise (on-frequency band and flanking band), without the coherence of the envelopes (noncomodulation). A pilot experiment with a small number of consonant tokens was followed by the main experiment with 12 consonants and the following masking conditions: three frequency locations of the flanking band and two masker levels. Results showed that in all conditions, the comodulation condition provided higher identification scores than the noncomodulation condition, and the difference in score was 3.5% on average. No significant difference was observed between the on-frequency only condition and the comodulation condition, i.e., an "unmasking" effect by the addition of a comodulated flaking band was not observed. The positive effect of CMR on consonant recognition found in the present study endorses a "cued-listening" theory, rather than an envelope correlation theory, as a basis of CMR in a suprathreshold task. 相似文献
118.
Choi EY Kim D Hong BK Kwon HM Song YG Byun KH Park HY Whang KC Kim HS 《Experimental & molecular medicine》2002,34(6):391-400
Chlamydia pneumoniae infection implicated as an important etiologic factor of atherosclerosis, especially in coronary artery disease (CAD), was found in vitro to be associated with the induction of matrix metalloproteinases (MMPs). An extracellular matrix metalloproteinase inducer (EMMPRIN)/ membrane-type 1 matrix metalloproteinase (MT1-MMP) system which induces and activates MMPs, is suggested to be functional and were upregulated in the failing myocardium. However, the upstream regulation of MMPs by C. pneumoniae within atheroma itself remains unclear. We evaluated the seroepidemiologic study of C. pneumoniae infection in CAD patients (n= 391) and controls (n=97) and performed histopathological and in vitro analysis in atherosclerotic vascular tissues obtained from patients with seropositive to C. pneumoniae (n=20), by using immunochemistry for C. pneumoniae, EMMPRIN/MT1-MMP, MMP-2, and MMP-9. The seropositive rates of both anti-C. pneumoniae IgG and IgA were 56.7% in CAD group and 43.3% in control group (P=0.033). Seropositive rate was increased in subgroups of CAD patients without conventional coronary risk factors compared to those with conventional risk factors. Immunoreactivities of EMMPRIN, MT1-MMP, MMP-2, and MMP-9 were increased in the atheromatous plaque itself, predominantly in immunoreactive macrophages/mononuclear cells to C. pneumoniae. Furthermore, Western blot analysis showed that EMMPRIN and MMP-2 were detected more prominently in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. Zymographic analysis revealed that activities of MMP-2 and MMP-9 were more increased in atherosclerotic tissues infected with C. pneumoniae compared to control tissues. The present study demonstrated upstream regulation of MMPs can be induced by C. pneumoniae within atheromatous plaque itself. These findings help to understand the potential role of C. pneumoniae in the progression of atherosclerosis. 相似文献
119.
We present a microscopic quantum theoretical analysis of the nanoscale superfluid properties of solvating clusters of para-H2 around the linear OCS molecule. Path-integral calculations with N=17 para-H2 molecules, constituting a full solvation shell, show the appearance of a significant superfluid response to rotation around the molecular axis at T=0.15 K. This low-temperature superfluid response is highly anisotropic and drops sharply as the temperature increases to T approximately 0.3 K. These calculations provide definitive theoretical evidence that an anisotropic superfluid state exists for molecular hydrogen in this microscopic solvation layer. 相似文献
120.
Low tropospheric wind measurement with Mie Doppler Lidar 总被引:3,自引:0,他引:3
A double edge Mie Doppler lidar at 1064 nm was developed in Hefei, China in 2005 for low tropospheric wind measurement. Intercomparison
experiments with a wind profiler and a wiresonde were held. Intercomparisons of concurrent lidar and other instrument observations
show good agreement with expected measurement accuracy. The examples of validated lidar wind profiles obtained during these
experiments as well as an example of continuous wind observations are presented. The instrument has demonstrated the capability
of atmospheric wind field measurement from 0.2 to 5 km altitude, achieving below 2 m/s accuracy with 1 min averaging and 21.2
m vertical resolution. 相似文献