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A transition model for describing wake-induced transition is presented based on the SST turbulence model by Menter and two dynamic equations for intermittency: one for near-wall intermittency and one for free-stream intermittency. In the Navier-Stokes equations, the total intermittency factor, which is the sum of the two, multiplies the turbulent viscosity computed by the turbulence model. The quality of the transition model is illustrated on the T106A test cascade for two Reynolds numbers, using experimental results by Stieger and Hodson for transition mainly due to kinematic wake impact on a separation bubble. The quality of the model is also revealed on the T106D test cascade using experimental results from Hilgenfeld, Stadtmuller and Fottner for wake turbulence induced transition. The test cases differ in pitch to chord ratio, Reynolds number and inlet free-stream turbulence intensity, causing different transition mechanisms. The unsteady results are presented in space-time diagrams of shape factor and wall shear stress on the suction side. The results show the capability of the model to capture the physics of unsteady transition in separated state. Inevitable shortcomings are revealed as well. 相似文献
144.
We propose a technique for the calculation of characteristics of tunable dispersion filters of infrared radiation of the type of small particles-liquid crystal. The relation between the structural parameters of filters and their transmission spectra is investigated. The dependence of the halfwidth of transmission spectral lines on the thickness of the filter, the concentration of particles, and their size and polydispersity is investigated. 相似文献
145.
A method for studying the thermal stability of PVC compounds by using differential thermal analysis (DTA) is presented. At isothermal conditions and in an oxygen-free nitrogen atmosphere, an exothermal maximum is observed at the moment when all stabilizer is consumed. The time until this maximum appears is taken as a measure of stability of the tested sample. Earlier DTA investigations on the thermal stability of PVC were done by Dunn and Ennis. They needed the addition of a destabilizer, such as ferric or zinc oxide to the PVC compound to get an easily determinable exothermal maximum. This means that applications of their method to industrial PVC compounds or end products were impossible, as neither should contain any of these oxides. Probably due to more sensitive equipment it is now possible to obtain an exothermal maximum without any destabilizer. A stabilizer such as tribasic lead sulfate (TBLS), for example, is still needed though. Plasticized or rigid compounds may be investigated. High amounts of some fillers cause the maximum to broaden, and the evaluation becomes more difficult. The method is easy and time saving. The very small amount of sample required (a few milligrams only) makes the sample preparation possible for all kinds of products. 相似文献
146.
Yu Dong Dr. Ayhan Elmali Prof. Jianzhang Zhao Prof. Bernhard Dick Dr. Ahmet Karatay 《Chemphyschem》2020,21(13):1388-1401
Orthogonal phenoxazine-styryl BODIPY compact electron donor/acceptor dyads were prepared as heavy atom-free triplet photosensitizers (PSs) with strong red light absorption (ϵ=1.33×105 M−1 cm−1 at 630 nm), whereas the previously reported triplet photosensitizers based on the spin-orbit charge transfer intersystem crossing (SOCT-ISC) mechanism show absorption in a shorter wavelength range (<500 nm). More importantly, a long-lived triplet state (τT=333 μs) was observed for the new dyads. In comparison, the triplet state lifetime of the same chromophore accessed with the conventional heavy atom effect (HAE) is much shorter (τT=1.8 μs). Long triplet state lifetime is beneficial to enhance electron or energy transfer, the primary photophysical processes in the application of triplet PSs. Our approach is based on SOCT-ISC, without invoking of the HAE, which may shorten the triplet state lifetime. We used bisstyrylBodipy both as the electron acceptor and the visible light-harvesting chromophore, which shows red-light absorption. Femtosecond transient absorption spectra indicated the charge separation (109 ps) and SOCT-ISC (charge recombination, CR; 2.3 ns) for BDP-1 . ISC efficiency of BDP-1 was determined as ΦT=25 % (in toluene). The dyad BDP-3 was used as triplet PS for triplet-triplet annihilation upconversion (upconversion quantum yield ΦUC=1.5 %; anti-Stokes shift is 5900 cm−1). 相似文献
147.
Zusammenfassung Aus kalorimetrischen Messungen bei stufenweiser Deformation von Weichkautschukproben und gleichzeitiger Kenntnis der mechanischen Arbeit pro Stufe folgt, daß die von der kinetisch-statistischen Theorie vorausgesetzte Bedingung, die Innere Energie hänge nicht von der Dehnung ab, eine Idealisierung darstellt, die man im tatsächlichen Verhalten selbst bei von der Theorie als geeignet angesehenen Fällen selten oder vielleicht überhaupt nicht verifiziert findet. 相似文献
148.
G. Spacu und J. Dick 《Fresenius' Journal of Analytical Chemistry》1929,76(7-8):273-277
Ohne Zusammenfassung 相似文献
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