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91.
零相关区非周期互补序列集在多载波码分多址通信系统中有着重要应用.已有的四元零相关区非周期互补序列集构造方法都是基于二元或四元零相关区互补序列集,得到的序列集参数受到初始互补序列集参数的限制.该文给出了一种构造法,利用四元正交序列集来构造四元非周期互补序列集.本文方法得到的序列集参数达到理论界限,并且零相关区长度可以灵活设定以满足不同的应用场合.另外给出了两类基于二元正交矩阵的四元正交序列集的构造方法,得到的四元正交序列集可以用于构造四元零相关区非周期互补序列集.二元正交矩阵存在数目很多,因此本文方法可以为多载波码分多址系统提供大量四元非周期互补序列集. 相似文献
92.
作为应用于浮空器领域的雷达结构杆件,长达12 m,直径为30 mm,长径比为400∶1。为达到其高刚性、轻质、快速组装的要求,在研制过程中采用了分段杆套管连接方式;分段杆端头变厚度缠绕加强;多角度缠绕角交叉缠绕;干法缠绕碳纤维预浸丝等工艺手段,研制出大长径比高刚性轻质碳纤维结构杆。 相似文献
93.
研究了一种基于最小描述长度(MDL)原理的快速在线雷达脉冲信号聚类分选算法,该方法利用幅度或相位差异特征,实现对雷达脉冲数据向量的聚类分选处理。设计了基于MDL原理的在线信号分选算法流程,在每接收到一定数量雷达脉冲信号后,执行一次聚类分选处理;对算法流程中的每个处理模块进行了完备的运算量分析,为工程设计提供有效的理论指导;并对比分析了离线和在线算法的性能。仿真结果表明:在线算法的信号分选正确率与离线方法基本一致,具有很强的工程应用前景。 相似文献
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基于大口径闪烁法和差分到达角起伏法开展了间距为3.95 km近水平路径的大气相干长度测量实验。测量结果表明:在同路径的上下行光传播方向上,闪烁法测量相干长度的相关系数为0.94,而到达角起伏法测量相干长度的相关系数为0.79。路径权重的理论分析揭示了闪烁法对路径中部的湍涡敏感,且路径权重函数关于路径中部呈对称分布;到达角起伏法对接收端附近的湍涡敏感,其路径权重函数从发射端到接收端呈单调递增趋势。因此,实际的长距离光传输实验中,在不能确定路径中湍流强度分布的情况下,采用闪烁法测量路径上的湍流效应更适宜。 相似文献
97.
The free radical copolymerization of acrylic acid (M1) with p-chloromethylstyrene (M2) in dioxane and in the presence of α,α′-azobisisobutyronitrile (AIBN) at 65°C is reported. Copolymer compositions of six copolymer samples obtained from feed ratios of M1:M2 = 95.2:4.8 to 21.4:78.6 were determined by 1H-NMR. The reactivity ratios of AA/p-CMS copolymerization system calculated by the F-R method were r 1 = 0.50 ± 0.06 and r 2 = 1.52 ± 0.15, almost the same as r 1 = 0.43 ± 0.21 and r 2 = 1.31 ± 0.14 by the extended K-T method. On the basis of the reactivity ratios of two monomers, the sequence length distribution in the AA/p-CMS copolymers was obtained. For f2 = 4.77%, the monomer unit of p-CMS is individually separated in the chain of AA; for f2 = 35.53%, the alternating tendency prevails and a large number of mono-sequences are formed. The number-average ( n) and weight-average ( w) molecular weights were determined by gel permeation chromatography. The effect on molecular weights of feed composition is also discussed. In the presence of constant initiator concentration, the gradual increase in the ratio of M2:M1 (from14.7:85.3 to 78.6:21.4) was accompanied by a decrease in molecular weights ( n from 11907 to 3961). 相似文献
98.
To clarify the non-enzymatic radical-scavenging activity of β-carotene-related compounds and other polyenes, we used differential scanning calorimetry to study the kinetics of radical polymerization of methyl methacrylate (MMA) by 2,2′-azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) in the absence or presence of polyenes under nearly anaerobic conditions at 70°C, and analyzed the results with an SAR approach. The polyenes studied were all-trans retinol, retinol palmitate, calciferol, β-carotene and lycopene. Polyenes produced a small induction period. The stoichiometric factor (n) (i.e. the number of radicals trapped by each inhibitor molecule) of polyenes was close to 0. Tetraterpenes (β-carotene, lycopene) suppressed significantly more of the initial rate of polymerization (R inh) than did diterpenes (retinol, retinol palmitate). The inhibition rate constants (k inh) for the reaction of β-carotene with AIBN-or BPO-derived radicals were determined to be 1.2–1.6?×?105 l?/?mol?s, similar to published values. A linear relationship between k inh and the kinetic chain length (KCL) for polyenes was observed; as k inh increased, KCL decreased. KCL also decreased significantly as the number of conjugated double bonds in the polyenes increased. Polyenes, particularly β-carotene and lycopene, acted as interceptors of growing poly-MMA radicals. 相似文献
99.
Four new star‐shaped π‐conjugated oligomers ( TPA‐CZ3 , TPA‐TPA3 , TPA‐PTZ3 and TPA‐BT3 ) with triphenylamine as a core and different electron‐donating ability groups, carbazole, triphenylamine, phenothiazine and bithiophene, as peripheral units have been designed and synthesized via the Heck reaction. These oligomers show good solubility in common organic solvents. Their photophysical, electrochemical, electronic structure and charge transfer properties between these star‐shaped π‐conjugated oligomers and N,N′‐bis(1‐ethylpropyl)‐3,4:9,10‐perylene bis(tetracarboxyl diimide) (EP‐PDI) have been investigated by UV‐vis absorption spectra, photoluminescence (PL) spectra, cyclic voltammetry (CV) measurement, theoretical calculations and fluorescence quenching. The results show that the absorptions and fluorescences of TPA‐CZ3 , TPA‐TPA3 and TPA‐PTZ3 are red shifted with the electron‐donating ability of the peripheral unit increasing from carbazole to triphenylamine and phenothiazine. In addition, although the bithiophene group has a weaker electron‐donating ability than carbazole, triphenylamine and phenothiazine, the absorption and fluorescence of TPA‐BT3 have a red shift than those of TPA‐CZ3 , TPA‐TPA3 and TPA‐PTZ3 because TPA‐BT3 has a longer conjugation length than TPA‐CZ3 , TPA‐TPA3 and TPA‐PTZ3 . The triphenylamine core and the peripheral units can constitute a large conjugated structure. The fluorescence quenching properties indicate that efficient charge transfer can happen between the star‐shaped oligomers and EP‐PDI. 相似文献
100.
Lorilee S.L. Arakaki Kenneth A. Schenkman Wayne A. Ciesielski Jeremy M. Shaver 《Analytica chimica acta》2013
We have developed a method to make real-time, continuous, noninvasive measurements of muscle oxygenation (Mox) from the surface of the skin. A key development was measurement in both the visible and near infrared (NIR) regions. Measurement of both oxygenated and deoxygenated myoglobin and hemoglobin resulted in a more accurate measurement of Mox than could be achieved with measurement of only the deoxygenated components, as in traditional near-infrared spectroscopy (NIRS). Using the second derivative with respect to wavelength reduced the effects of scattering on the spectra and also made oxygenated and deoxygenated forms more distinguishable from each other. Selecting spectral bands where oxygenated and deoxygenated forms absorb filtered out noise and spectral features unrelated to Mox. NIR and visible bands were scaled relative to each other in order to correct for errors introduced by normalization. Multivariate Curve Resolution (MCR) was used to estimate Mox from spectra within each data set collected from healthy subjects. A Locally Weighted Regression (LWR) model was built from calibration set spectra and associated Mox values from 20 subjects using 2562 spectra. LWR and Partial Least Squares (PLS) allow accurate measurement of Mox despite variations in skin pigment or fat layer thickness in different subjects. The method estimated Mox in five healthy subjects with an RMSE of 5.4%. 相似文献