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排序方式: 共有2372条查询结果,搜索用时 15 毫秒
201.
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Mariya Aloshyna Begoa Milin Medina Lars Poulsen Juliette Moreau David Beljonne Jrme Cornil Giuseppe Di Silvestro Michele Cerminara Francesco Meinardi Riccardo Tubino Heiner Detert Sigurd Schrader Hans‐Joachim Egelhaaf Chiara Botta Johannes Gierschner 《Advanced functional materials》2008,18(6):915-921
Perhydrotriphenylene‐based channel‐forming inclusion compounds (ICs) and thin films made of polyphenylenevinylene (PPV)‐type oligomers with terminal alkoxy groups are investigated and compared in a combined experimental and theoretical approach. Interchromophore interactions and host‐guest interactions are elucidated by UV/Vis and Raman spectroscopy. The impact of the local environment of the chromophore on the optical and photophysical properties is discussed in light of quantum‐chemical calculations. In stark contrast to thin films where preferential side‐by‐side orientation leads to quenching of photoluminescence (PL) via non‐emissive traps, the ICs are found to be attractive materials for opto‐electronic applications: they offer high chromophore concentrations, but at the same time behave as quasi‐isolated entities of tightly packed, well‐oriented objects with high PL quantum yields and the possibility of color tuning. 相似文献
205.
Ulf Stalmach Heiner Detert Herbert Meier Volker Gebhardt Dietrich Haarer Andreas Bacher Hans-Werner Schmidt 《Optical Materials》1998,9(1-4):77-81
The preparation of LEDs with poly( p-phenylenevinylene) (PPV) as emitting material is well established. However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-1,4-phenylenevinylene)s with up to 11 repeating units. This series covers the spectrum from monomer to polymer. The influence on the EL can be investigated by preparing single layer LEDs using vapor deposition or spincoating of the oligomers in a polystyrene (PS) matrix. The comparison of photoluminescence (PL)- and EL-spectra shows that the photophysical properties of the oligomers are strongly altered by aggregation phenomena. 相似文献
206.
Based on a polynomial-time test for determining whether a finite special string-rewriting systemR ise-confluent, a procedure for completing a finite special systemR on[e]
R is derived. The correctness and completeness of this procedure are proved. In addition, the special case of finite special string-rewriting systems presenting groups is considered. 相似文献
207.
208.
Alexander von Humboldt fellow, on leave from the Department of Engineering Mechanics, Xi'an Jiaotong University, People's Republic of China. 相似文献
209.
Andreas Seifert Axel Berger Wolfgang Friedrich Müller 《Journal of the American Ceramic Society》1992,75(4):873-877
Sintered AIN specimens were deformed by Vickers hardness (HV) indentations. Compared with Al2 O3 the HV hardness values indicate a much higher plasticity of AIN at room temperature, but above 600°C a higher ductility for Al2 O3 . Deformed AIN specimens were examined by transmission electron microscopy. Basal and prismatic glide with the slip systems (0001) 〈1120〉 and {1 1 00}〈11 2 0〉 were frequently observed. This results in four linearly independent slip systems. The critical resolved shear stress for single prismatic slip seems to be even smaller than for basal slip. However, thermally activated dislocation reactions are frozen up to at least 1000°C. Thus, prismatic slip is suppressed as soon as more than one slip direction is activated. 相似文献
210.
Newly developed magnesium alloys for powertrain applications 总被引:1,自引:0,他引:1
E. Aghion B. Bronfín F. Von Buch S. Schumann H. Friedrich 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(11):30-33
Several new magnesium alloys have been developed recently for high-temperature applications to obtain an optimal combination
of die cast-ability, creep resistance, mechanical properties, corrosion performance, and affordability. Unfortunately, it
is difficult to achieve an adequate combination of properties and, in fact, most of the new alloys can only partially meet
the required performance and cost. The ZE41 alloy, which is used for most gravity-casting applications, has moderate strength
and creep resistance combined with good cast-ability. Although this alloy exhibits poor corrosion resistance, it is still
preferred for certain applications.
For more information, contact E. Aghion, Dead Sea Magnesium Ltd., P.O. Box 1195, Beer Sheva 84111, Israel; +972-8-628-2422;
fax +972-8-628-2431; e-mail eli@dsmag.co.il. 相似文献