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排序方式: 共有580条查询结果,搜索用时 15 毫秒
571.
Ki Baek Kim Min Kyu Kim Yun Ha Kim Kwang Sup Song Eun Duck Park 《Research on Chemical Intermediates》2010,36(6-7):603-611
We prepared Pd catalysts supported on various metal oxides, viz. γ-Al2O3, α-Al2O3, SiO2–Al2O3, SiO2, CeO2 and TiO2 by an incipient wetness method and applied them to propane combustion. Several techniques: N2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), CO chemisorption, temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPO) were employed to characterize the catalysts. Pd/SiO2–Al2O3 showed the least catalytic activity at high temperatures among Pd catalysts supported on irreducible metal oxides, viz. SiO2, Al2O3 and SiO2–Al2O3. Pd/γ-Al2O3 was much superior for this reaction to Pd/α-Al2O3. The Pd catalyst supported on reducible metal oxides (CeO2 and TiO2) with a less specific surface area showed the higher catalytic activity compared with that supported on reducible metal oxides with a higher specific surface area, even though the former had a less Pd dispersion than the latter. In the case of Pd/SiO2–Al2O3, the initially reduced Pd catalyst was superior to the fully oxidized one. The oxidation of metallic Pd occurred in the presence of O2 with increasing reaction temperature, which resulted in the change in the catalytic activity. 相似文献
572.
573.
Kim D Jon S Lee HK Baek K Oh NK Zin WC Kim K 《Chemical communications (Cambridge, England)》2005,(44):5509-5511
New wedge-shaped thermotropic liquid crystalline materials containing a guanidinium moiety at the apex organize into various supramolecular structures such as hexagonal columnar, rectangular columnar and Pm3n cubic mesophases depending on anions illustrating guest-directed self-organization in mesophases. 相似文献
574.
Kyung‐Youl Baek Masami Kamigaito Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2002,40(14):2245-2255
Star poly(methyl methacrylate)s (P*) of various arm lengths and core sizes were synthesized in high yields by the polymer linking reaction in Ru(II)‐catalyzed living radical polymerization. The yields of the star polymers were strongly dependent on the reaction conditions and increased under the following conditions: (1) at a higher overall concentration of arm chains ([P*]), (2) with a larger degree of polymerization (DP) of the arm chains (arm length), and (3) with a larger ratio (r) of linking agents to P* (core size). In particular, the yields sharply increased in a short time at a higher temperature, in a polar solution, and at a higher complex concentration after the addition of linking agents. These star polymers were then analyzed by multi‐angle laser light scattering to determine the weight‐average molecular weight (3.8 × 103 to 1.5 × 106), the number of arm chains per molecule (f = 4–63), and the radius of gyration (Rz = 2–22 nm), which also depended on the reaction conditions (e.g., f and Rz increased as [P*], DP, and r increased). Small‐angle X‐ray scattering analyses of the star polymers showed that they consisted of spheres for which the radius of the microgel core was 2.7 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2245–2255, 2002 相似文献
575.
Sung‐June Baek Aaron Park Aiguo Shen Jimming Hu 《Journal of Raman spectroscopy : JRS》2011,42(11):1987-1993
In this paper, we consider a new background elimination method for Raman spectra. As a background is usually slowly varying with respect to wavelength, it could be approximated by a slowly varying curve. However, the usual curve‐fitting method cannot be applied because there is a constraint that the estimated background must be beneath a measured spectrum. To meet the requirement, we adopt a polynomial as an approximating function and show that background estimation could be converted to a linear programming problem which is a special case of constrained optimization. In addition, we present an order selection algorithm for automatic baseline elimination. According to the experimental results, it is shown that the proposed method could be successfully applied to experimental Raman spectra as well as synthetic spectra. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
576.
Young Baek Kim Chung Wook Chung Hyung Woo Kim Young‐Ha Rhee 《Macromolecular rapid communications》2005,26(13):1070-1074
Summary: A bacterial poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] biosynthesized by Pseudomonas sp. HJ‐2 was found to be a shape memory polymer. Permanent shapes were set by annealing at room temperature the samples that had been pre‐treated above 95 °C in specified shapes. The temporary shapes were set by stretching and holding the elongated samples. Thermal shrinkage began at 45 °C and stopped at 75 °C to recover to their permanent shapes. Apparently, the orientation induced the formation of hard segments that were responsible for setting the temporary shapes. The shape memory effect of this polymer was explained based on the DSC and XRD results at different phases.
577.
Akindinov A.N. Alici A. Anselmo F. Antonioli P. Baek Y. Basile M. Romeo G. Cara Cifarelli L. Cindolo F. Cosenza F. Caro A. De Pasquale S. De Bartolomeo A. Di Girard M. Fusco Guida M. Hatzifotiadou D. Kaidalov A.B. Kim D.W. Kim D.H. Kisselev S.M. Laurenti G. Lee K. Lee S.C. Lioublev E. Luvisetto M.L. Margotti A. Martemiyanov A.N. Nania R. Noferini F. Otiougova P. Pierella F. Polozov P.A. Scapparone E. Scioli G. Sellitto S.B. Smirnitski A.V. Tchoumakov M.M. Valenti G. Vicinanza D. Voloshin K.G. Williams M.C.S. Zagreev B.V. Zampolli C. Zichichi A. 《The European Physical Journal C - Particles and Fields》2004,34(1):s325-s331
The European Physical Journal C - The ALICE TOF array will be built using the Multigap Resistive Plate Chamber(MRPC) configured as a double stack. Each stack contains 5 gas gaps with width of... 相似文献
578.
We report a scalable linear optical scheme for generating entangled states of multiple ququarts in which the individual single-ququart state is prepared with the biphoton polarization state of frequency-nondegenerate spontaneous parametric down-conversion. The output state is calculated with the full consideration of the higher order effect (double-pair events) of spontaneous parametric down-conversion. Scalability to multiple-ququart entanglement is demonstrated with examples: linear optical entanglement of three and four individual biphoton ququarts. 相似文献
579.
Jong-Pil Jeon Yu Jin Kim Dr. Se Hun Joo Dr. Hyuk-Jun Noh Prof. Sang Kyu Kwak Prof. Jong-Beom Baek 《Angewandte Chemie (International ed. in English)》2023,62(12):e202217416
Covalent organic frameworks have recently shown high potential for photocatalytic hydrogen production. However, their structure-property-activity relationship has not been sufficiently explored to identify a research direction for structural design. Herein, we report the design and synthesis of four benzotrithiophene (BTT)-based covalent organic frameworks (COFs) with different conjugations of building units, and their photocatalytic activity for hydrogen production. All four BTT-COFs had slipped parallel stacking patterns with high crystallinity and specific surface areas. The change in the degree of conjugation was found to rationally tune the rate of photocatalytic hydrogen evolution. Based on the experimental and calculation results, the tunable photocatalytic performance could be mainly attributed to the electron affinity and charge trapping of the electron accepting units. This study provides important insights for designing covalent organic frameworks for efficient photocatalysts. 相似文献
580.