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81.
采用基于Roe解法的有限体积法,对Hartmann共振管中的气体流场进行了数值模拟,研究了当喷嘴轴线处存在针型激励器的情况下流场的振动情况,数值计算的结果与理论和相关的实验结果符合得较好.计算结果表明移除或引入激励器,将会使Hartmann共振管的共振模式发生转换.通过对超音速雾化喷嘴流场的数值模拟,研究了其中Hartmann共振腔和二级共振腔共同作用下的振动现象以及各物理参数对振动的影响,并对喷嘴中气流从亚音速向超音速的转变机理进行了研究. 相似文献
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84.
低温胁迫下香蕉叶片Chla荧光动力学参量的变化及其品种差异性 总被引:7,自引:0,他引:7
低温胁迫下,广东2号香蕉品种和巴西香蕉品种Williams的叶绿素(Chla)荧光动力学参量FⅤ/Fm、ΔFⅤ/FT以及williams品种的FIV/FⅤ均呈下降趋势,两个品种的荧光上升半时间T1/2及广东2号的FIV/FⅤ呈上升趋势.其中,Williams的FⅤ/Fm、ΔFⅤ/FT和T1/2的变化幅度小于广东2号,表明低温胁迫通过抑制光合电子传递速度和PSⅡ无活性中心含量的提高使香蕉叶片PSⅡ原初光能转换效率下降,相同低温对广东2号的影响大于对Williams的影响.FⅤ/Fm和ΔFⅤ/FT可以作为评价香蕉幼苗抗冷性的物理指标. 相似文献
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86.
Petisco C García-Criado B Mediavilla S Vázquez de Aldana BR Zabalgogeazcoa I García-Ciudad A 《Analytical and bioanalytical chemistry》2006,386(6):1823-1833
Near-infrared reflectance spectroscopy (NIRS) was used to estimate N, neutral detergent fibre (NDF), acid detergent fibre
(ADF), lignin and cellulose contents in leaves of a heterogeneous group of 17 woody species from the Central Western region
of the Iberian Peninsula. The sample set consisted of 182 samples of leaves of deciduous and evergreen species, showing a
wide range of concentrations determined by reference methods: 6.60–35.2 g kg−1 (N), 15.5–66.0% (NDF), 10.2–57.3% (ADF), 3.45–27.4% (lignin) and 5.79–31.3% (cellulose). Reflectance spectra, obtained for
samples of dried and ground leaves, were recorded as log1/R (R=reflectance) from 1,100 to 2,500 nm. NIRS calibrations were developed using multiple linear (MLR) and partial least-squares
(PLSR) regressions, and tested by external validation. Spectral data were transformed to the first and second derivative (1D,
2D). The PLSR method and derivative transformations provided the best statistics and showed lower standard errors of calibration
(SEC) and higher coefficients of multiple determination (R
2). In the external validation the standard errors of prediction (SEP) were 0.76 g kg−1 (N), 2.11% (NDF), 1.47% (ADF), 0.85% (lignin) and 0.86% (cellulose). The results obtained show that NIRS is very effective
for the estimation of these organic constituents in leaf tissue of woody species. This technique can be used in ecological
or ecophysiological studies as an alternative to the more time-consuming standard methods. 相似文献
87.
Shi X Takamizawa A Nishimura Y Hiraoka K Akashi S 《Journal of mass spectrometry : JMS》2006,41(8):1086-1095
Laser spray, which is a newly developed ionization technique, can characterize the stability of noncovalent complexes in the solution phase. By using this advantage, laser spray has been applied to probe the intrinsic stability of double-stranded DNA (dsDNA) sequences and their binding affinities with various drugs in the solution phase. Systematic experiments were carried out using six 16-mer and three 22-mer dsDNA oligomers, together with the complexes of the 16-mer dsDNA with minor groove binders: berenil, Hoechst 33342, DAPI, and netropsin. Dissociation curves for each dsDNA or each complex were plotted as a function of laser power. The laser power (E50%), where 50% of each dsDNA or each complex was dissociated, was compared with its melting temperature (Tm) determined by UV spectroscopy. Linear correlations between E50% and Tm were obtained not only for the dsDNA oligomers (correlation factor r = 0.9835) but also for the 16-mer dsDNA complexes with minor groove binders (r = 0.9966). In addition, laser spray has successfully clarified the binding affinities of a 16-mer dsDNA with two intercalators: daunomycin and nogalamycin. In the case of the dsDNA-daunomycin complex, by changing the molar ratio of dsDNA : drug from 1 : 1 to 1 : 5, the concentration-dependent stability of the complex was confirmed by laser spray. The present results demonstrate that laser spray mass spectrometry can be a powerful and convenient method to investigate the relative binding affinities of dsDNA-ligand complexes in the solution phase, which could be applied to the early stage of high-throughput screening of drugs targeting for dsDNA. 相似文献
88.
Fluorine (F) incorporated polycrystalline SnO2 films have been deposited onto glass substrates by ultrasonic spray pyrolysis technique. To possess information about the electrical properties of all films, their electrical conductivities were investigated depending on the temperature, and their activation and trap energies were analyzed. The crystalline structure, surface properties and elemental analysis of the SnO2 films were examined to determine the effect of the F element. After all investigations, it was concluded that each fluorine incorporation rate has a different and important effect on the physical properties, and SnO2:F (3 at%) films were found to be the most promising sample for energy conversion devices, especially as conducting electrode in solar cells with its improved structural and electrical properties as compared to others. 相似文献
89.
Stéphane Bessy 《Discrete Applied Mathematics》2010,158(16):1732-1744
A graph G=(V,E) is a 3-leaf power iff there exists a tree T the leaf set of which is V and such that uv∈E iff u and v are at distance at most 3 in T. The 3-leaf power graph edge modification problems, i.e. edition (also known as the closest 3-leaf power), completion and edge-deletion are FPT when parameterized by the size of the edge set modification. However, polynomial kernels were known for none of these three problems. For each of them, we provide kernels with O(k3) vertices that can be computed in linear time. We thereby answer an open problem first mentioned by Dom et al. (2004) [8]. 相似文献
90.
The purpose of this study was to find optimum treatment conditions for selective photothermolysis by evaluating internal–external heat distributions according to different cooling methods. The 1,064-nm Nd:YAG laser was transmitted into a skin-mimicking phantom with different cooling conditions, and its minimum temperatures and sub-zero times were measured. The cooling methods were classified into a total of eight conditions composed of five cryogen spray cooling conditions and three air cooling conditions. Based on the experimental results, condition 2 was selected as the optimum cooling condition for selective photothermolysis obtained from the cryogen spray cooling method. 相似文献