排序方式: 共有120条查询结果,搜索用时 348 毫秒
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Jihoon Shin Andrew Y. Chang Lacie V. Brownell Ira O. Racoma Coreen H. Ozawa Ho‐Yong Chung Shufu Peng Chulsung Bae 《Journal of polymer science. Part A, Polymer chemistry》2008,46(11):3533-3545
Hydroxy‐functionalized isotactic poly(1‐butene) was synthesized using transition metal‐catalyzed regioselective C? H borylation at the side chain of the commercial polyolefin and subsequent oxidation of the boronic ester functionality. Functionalization up to ~ 19 mol % of the termini of the ethyl side chain occurred without significant side reactions that could alter the polymer chain length. Esterification of the hydroxy group in the polymer with 2‐bromoisobutyl bromide generated a side chain‐functionalized polyolefin macroinitiator. Atom transfer radical polymerization of tert‐butyl acrylate from the macroinitiator produced a high molecular‐weight graft copolymer of the polyolefin, isotactic poly(1‐butene)‐graft‐poly(tert‐butyl acrylate) (PB‐g‐PtBA). Finally, the hydrolysis of the tert‐butoxy ester group of PB‐g‐PtBA created an amphiphilic polyolefin, isotactic poly(1‐butene)‐graft‐poly(acrylic acid), which contained a short carboxylic acid‐functionalized polymer block at the side chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3533–3545, 2008 相似文献
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Transmit beamforming and receive combining are simple methods for exploiting spatial diversity in multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. Optimal beamforming requires channel state information in the form of the beamforming vectors for each OFDM subcarrier. This paper proposes a limited feedback architecture that combines beamforming vector quantization and smart vector interpolation. In the proposed system, the receiver sends a fraction of information about the optimal beamforming vectors to the transmitter and the transmitter computes the beamforming vectors for all subcarriers through interpolation. A new spherical interpolator is developed that exploits parameters for phase rotation to satisfy the phase invariance and unit norm properties of the transmitted beamforming vectors. The beamforming vectors and phase parameters are quantized at the receiver and the quantized information is provided to the transmitter. The proposed quantization system provides only a moderate increase in complexity versus over comparable approaches. Numerical simulations show that the proposed scheme performs better than existing diversity techniques with the same feedback data rate. 相似文献
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Adaptive MIMO decision feedback equalization for receivers with time-varying channels 总被引:2,自引:0,他引:2
In an attempt to reduce the computational complexity of vertical Bell Labs layered space time (V-BLAST) processing with time-varying channels, an efficient adaptive receiver is developed based on the generalized decision feedback equalizer (GDFE) architecture. The proposed receiver updates the filter weight vectors and detection order using a recursive least squares (RLS)-based time- and order-update algorithm. The convergence of the algorithm is examined by analysis and simulation, and it is shown that the proposed adaptive technique is considerably simpler to implement than a V-BLAST processor with channel tracking, yet the performances are almost comparable. 相似文献
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Jiang Wu Zhiming M. Wang Shibin Li Jihoon Lee Yuriy I. Mazur Gregory J. Salamo 《固体物理学:研究快报》2012,6(7):309-311
We investigate the formation of GaAs quantum dash pairs with different coverages by droplet epitaxy. The GaAs quantum dash pairs of various sizes are fabricated by high temperature droplet epitaxy. Dual‐sized quantum dash pairs are observed along $[01\bar 1]$ orientation. Depending on the Ga cov‐ erage, the width of the quantum dash pairs can be tuned from ~100 nm to ~300 nm while keeping the height in the range of 4 nm to 10 nm. The coverage dependence of quantum dash pairs is also confirmed with photoluminescence measurement. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Truong TN Nayak M Huynh HH Cook T Mahajan P Tran LT Bharath J Jain S Pham HB Boonyasiriwat C Nguyen N Andersen E Kim Y Choe S Choi J Cheatham TE Facelli JC 《Journal of chemical information and modeling》2006,46(3):971-984
With the expansion of the Internet and World Wide Web (or the Web), research environments have changed dramatically. As a result, the need to be able to efficiently and securely access information and resources from remote computer systems is becoming even more critical. This paper describes the development of an extendable integrated Web-accessible simulation environment for computational science and engineering called Computational Science and Engineering Online (CSE-Online; http://cse-online.net). CSE-Online is based on a unique client-server software architecture that can distribute the workload between the client and server computers in such a way as to minimize the communication between the client and server, thus making the environment less-sensitive to network instability. Furthermore, the new software architecture allows the user to access data and resources on one or more remote servers as well as on the computing grid while having the full capability of the Web-services collaborative environment. It can be accessed anytime and anywhere from a Web browser connected to the network by either a wired or wireless connection. It has different modes of operations to support different working environments and styles. CSE-Online is evolving into middleware that can provide a framework for accessing and managing remote data and resources including the computing grid for any domain, not necessarily just within computational science and engineering. 相似文献
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We consider the quasi-geostrophic equation with the dissipation term, κ (-Δ)α θ, In the case , Constantin-Cordoba-Wu [6] proved the global existence of strong solution in H
1
and H
2
under the assumption of small L
∞
-norm of initial data. In this paper, we prove the global existence in the scale invariant Besov space, B
2−2α
2,1
, for initial data small in the B
2−2α
2,1
norm. We also prove a global stability result in B
1
2,1
.
Received: 24 April 2002 / Accepted: 29 July 2002 Published online: 10 December 2002
Communicated by P. Constantin 相似文献
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Prof. Yeonho Kim Dong-Won Jeong Dr. Jaewon Lee Dr. Min Young Song Dr. Sang Moon Lee Prof. Jihoon Choi Prof. Du-Jeon Jang Dr. Hae Jin Kim 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10510-10518
In this work, environmentally friendly photocatalysts with attractive catalytic properties are reported that have been prepared by introducing SnO2 quantum dots (QDs) directly onto ZnSe(N2H4)0.5 substrates to induce advantageous charge separation. The SnO2/ZnSe(N2H4)0.5 nanocomposites could be easily synthesized through a one-pot hydrothermal process. Owing to the absence of capping ligands, the attached SnO2 QDs displayed superior photocatalytic properties, generating many exposed reactive surfaces. Moreover, the addition of a specified amount of SnO2 boosted the visible-light photocatalytic activity; however, the presence of excess SnO2 QDs in the substrate resulted in aggregation and deteriorated the performance. The spectroscopic data revealed that the SnO2 QDs act as a photocatalytic mediator and enhance the charge separation within the type II band alignment system of the SnO2/ZnSe(N2H4)0.5 heterojunction photocatalysts. The separated charges in the heterojunction nanocomposites promote radical generation and react with pollutants, resulting in enhanced photocatalytic performance. 相似文献
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Chung YS Shin N Kang J Jo Y Prabhu VM Satija SK Kline RJ Delongchamp DM Toney MF Loth MA Purushothaman B Anthony JE Yoon do Y 《Journal of the American Chemical Society》2011,133(3):412-415
The blend films of small-molecule semiconductors with insulating polymers exhibit not only excellent solution processability but also superior performance characteristics in organic thin-film transistors (OTFTs) over those of neat small-molecule semiconductors. To understand the underlying mechanism, we studied triethylsilylethynyl anthradithiophene (TESADT) with small amounts of impurity formed by weak UV exposure. OTFTs with neat impure TESADT had drastically reduced field-effect mobility (<10(-5) cm(2)/(V s)), and a disappearance of the high-temperature crystal phase was observed for neat impure TESADT. However, the mobility of the blend films of the UV-exposed TESADT with poly(α-methylstyrene) (PαMS) is recovered to that of a fresh TESADT-PαMS blend (0.040 cm(2)/(V s)), and the phase transition characteristics partly return to those of fresh TESADT films. These results are corroborated by OTFT results on "aged" TIPS-pentacene. These observations, coupled with the results of neutron reflectivity study, indicate that the formation of a vertically phase-separated layer of crystalline small-molecule semiconductors allows the impurity species to remain preferentially in the adjacent polymer-rich layer. Such a "zone-refinement effect" in blend semiconductors effectively removes the impurity species that are detrimental to organic electronic devices from the critical charge-transporting interface region. 相似文献