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91.
Experimental study on turbulent features in the negative transport region of asymmetric plane channel flow 总被引:1,自引:0,他引:1
Turbulent features of streamwise and vertical components of velocity in the negative transport region of asymmetric plane
channel flow have been studied experimentally in details. Experiments show that turbulent fluctuations in negative transport
region are suppressed, and their probability distributions are far from Gaussian. Besides, the skewness factors attain their
negative maxima at the position of the maximum mean velocity, whereas the flatness factors attain their positive maxima at
the same position.
The project supported by the National Natural Science Foundation of China (19872043) 相似文献
92.
In this paper, an adaptive nonmonotone line search method for unconstrained minimization problems is proposed. At every iteration,
the new algorithm selects only one of the two directions: a Newton-type direction and a negative curvature direction, to perform
the line search. The nonmonotone technique is included in the backtracking line search when the Newton-type direction is the
search direction. Furthermore, if the negative curvature direction is the search direction, we increase the steplength under
certain conditions. The global convergence to a stationary point with second-order optimality conditions is established. Some
numerical results which show the efficiency of the new algorithm are reported.
相似文献
93.
孙宇锋 《数学的实践与认识》2008,38(16)
证明了具有分布时滞的偶阶中立型泛函微分不等式不存在最终正解的新的充分条件,所得结果推广和改进了相关文献中的条件. 相似文献
94.
为充分利用太阳光的短波部分,将AlxGa1-xAs设计为电池的又一个光伏工作层,并引入固定负电荷,建立界面感应势垒,形成MIp -AlGaAs感应结,有效降低界面对光生电子的复合。以制作工艺简单的p -AlGaAs/p-GaAs界面,将感应结与p/n-GaAs部分连接起来,构成新型高效率复合结构MIp -Al0.3Ga0.7As/p-n-n -GaAs太阳电池。其I-V特性理论研究绐果表明,选择合适的负电荷面密度数和Al0.3Ga0.7As层的掺杂浓度,即:建立合适高度的感应势垒,可显著降低界面复合速度近8个数量级。优化设计得到的整个电池的效率为31.5%,较传统的窗口层电池有明显提高。 相似文献
95.
Katsuhisa Mizoguchi Mitsuru Ueda 《Journal of polymer science. Part A, Polymer chemistry》2008,46(15):4949-4958
A negative‐type photosensitive poly(phenylene ether) (PSPPE) based on poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE), a novel crosslinker 4,4′‐methylene‐bis [2,6‐bis(methoxymethyl)phenol] (MBMP) having good compatibility with PPE, and diphenylidonium 9,10‐dimethoxy anthracene‐2‐sulfonate (DIAS) as a photoacid generator (PAG) has been developed. This resist consisting of PPE (73 wt %), MBMP (20 wt %) and DIAS (7 wt %) showed a high sensitivity (D0.5) of 58 mJ/cm2 and a contrast (γ0.5) of 9.5 when it was exposed to i‐line (365 nm wavelength light), postexposure baked at 145 °C for 10 min, and developed with toluene at 25 °C. A fine negative image featuring 6 μm line‐and‐space pattern was obtained on the film exposed to 300 mJ/cm2 of i‐line by a contact‐printed mode. The resulting polymer film cured at 300 °C for 1 h under nitrogen had a low dielectric constant (ε = 2.46) comparable to that of PPE and a higher Tg than that of PPE. In addition, the cured PSPPE film was pretty low water absorption (<0.05%) as same as PPE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4949–4958, 2008 相似文献
96.
Insight into influence of thermodynamic coefficients on transient negative capacitance in Zr-doped HfO2 ferroelectric capacitors 下载免费PDF全文
Yuan-Yuan Zhang 《中国物理 B》2021,30(12):127701-127701
We study the influence of the thermodynamic coefficients on transient negative capacitance for the Zr-doped HfO2 (HZO) ferroelectric capacitors by the theoretical simulation based on the Landau-Khalatnikov (L-K) theory and experimental measurement of electrical properties in the resistor-ferroelectric capacitor (R-FEC) circuit. Our results show that the thermodynamic coefficients α, β and γ also play a key role for the transient NC effect besides the viscosity coefficient and series resistor. Moreover, the smaller coefficients α and β, the more significant the transient NC effect. In addition, we also find that the thermodynamic process of transient NC does not obey the generally accepted viewpoint of Gibbs free energy minimization. 相似文献
97.
98.
Yang Cai Zhenzhen Mo Nalaka S. Rannulu Bing Guan Srinivasan Kannupal Bruce C. Gibb Richard B. Cole 《Journal of mass spectrometry : JMS》2010,45(3):235-240
Electrospray‐generated precursor ions usually follow the ‘even‐electron rule’ and yield ‘closed shell’ fragment ions. We characterize an exception to the ‘even‐electron rule.’ In negative ion electrospray mass spectrometry (ES‐MS), 2‐(ethoxymethoxy)‐3‐hydroxyphenol (2‐hydroxyl protected pyrogallol) easily formed a deprotonated molecular ion (M‐H)? at m/z 183. Upon low‐energy collision induced decomposition (CID), the m/z 183 precursor yielded a radical ion at m/z 124 as the base peak. The radical anion at m/z 124 was still the major fragment at all tested collision energies between 0 and 50 eV (Elab). Supported by computational studies, the appearance of the radical anion at m/z 124 as the major product ion can be attributed to the combination of a low reverse activation barrier and resonance stabilization of the product ions. Furthermore, our data lead to the proposal of a novel alternative radical formation pathway in the protection group removal of pyrogallol. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
99.
100.