No abstract

The alkaline hydrolysis of polyester fabric in NaOH solution in the presence of several 1-alkyl-3-methylimidazolium bromine ionic liquids (ILs), CnMImBr (n=8, 12, 14, 16) was examined in comparison to the use of cetyltrimethyl ammonium bromide (CTAB) as an accelerant. The weight loss of polyester fabric was found to be greatly dependent on the concentrations of ILs and the length of alkyl groups in ILs. C14MImBr and C16MImBr exhibited good catalytic actions. The use of C16MImBr as an accelerator could endow polyester fabrics with slightly higher weight loss in comparison with CTAB. In the presence of C16MImBr, the activation energy of polyester hydrolysis reaction was slightly higher than that for the use of C14MImBr as a catalyst. In summary, the CnMImBr with long carbon chain can be employed as the novel accelerator for the weight reduction process of polyester fabrics.

One-pot synthesis of small size cup-like hollow ZSM-5 single crystals and their oxidative desulfurization performance.

Combinatorial testing is an efficient technique that reveals the faults caused by parameters interaction in software systems. It uses covering arrays as test suites to avoid the combinatorial explosion of parameter values. However, the construction of covering arrays with minimum size is still a challenging problem. This is because most of the existing methods to construct covering arrays result in extensive repetition of coverage. To address this challenging problem, some researchers proposed a randomized post-optimization method to reduce the number of rows in a covering array that has been already constructed. It repeatedly adjusts the array without loss of coverage. However, it seems that this method is not efficient as desired. In order to improve its efficiency, we propose a refined algorithm to replace the randomized algorithm adopted in the method. This avoids the local optima problem that arises in randomized algorithm. Experimental results are presented to confirm the benefits of the refined algorithm. In the cases of CA(N ; 6, k, 2) (38 k 50) generated by IPO, this refined algorithm not only reduces more number of rows than the randomized algorithm, but also produces covering arrays that are smaller than previously best known ones. Furthermore, we provide a reasonable estimator to predict the extent to which covering arrays can be improved by this refined algorithm.

Using a pseudo-random sequence to encode the transmitted waveform can significantly improve the working efficiency and depth of detection of electromagnetic exploration. The selection of parameters of pseudo-random sequence plays an important role in correlation identification and noise suppression. A discrete cycle correlation identification method for extracting the earth impulse response is proposed. It can suppress the distortion in the early stage of the excitation field and the glitches of the cross correlation function by traditional method. This effectively improves the accuracy of correlation identification. The influence of the order and the cycles of m-series pseudo-random coding on its autocorrelation properties is studied. The numerical results show that, with the increase of the order of m-sequence, the maximum out-of-phase periodic autocorrelation function decreases rapidly. Therefore, it is very beneficial to achieve synchronization. The limited-cycle m-sequences have good autocorrelation properties. As the period of the m-sequence increases and the width of the symbol decreases, the overall autocorrelation becomes closer to the impact function. The discussion of the influence of symbol width and period of m-sequence on its frequency bandwidth and power spectral density shows that the narrower the symbol width, the wider its occupied band. The longer the period, the smaller the power spectral line spacing. The abilities of m-sequence to suppress DC (Direct-current) interference, Schumann frequency noise, and sine-wave noise are analyzed. Numerical results show that the m-sequence has excellent ability to suppress DC interference and Schumann frequency noise. However, for high-order harmonic noise, the correlation identification error appears severe oscillation in the middle and late stages of the impulse response. It indicates that the ability of m-sequence to suppress high-frequency sinusoidal noise is deteriorated. In practical applications, the parameters of the transmitted waveform should be reasonably selected in combination with factors including transmitter performance, hardware noise, and ambient noise level to achieve the best identification effect.