The aim of this paper was to effectively reduce environmental pollution and further improve the enzymatic hydrolysis rate of corn straw. Thus, a pretreatment method for activating cellulose by using ionic liquid to treat metal ion solution was developed. By investigating the effects of the three factors of substrate mass fraction, reaction temperature, and reaction time, and the interaction between the factors on the pretreatment effect, the response surface design method was used to optimize the conditions of ionic liquid (1-butyl-3-methylimidazolium chloride) treatment of corn straw after activation, and the physicochemical structure and enzymatic hydrolysis efficiency before and after treatment were compared and analyzed. The experimental results showed that the yield of reducing sugar was increased by 157.85% and 150.41%, respectively, compared with the untreated corn straw. The analysis of chemical composition and structure showed that the cellulose content of the material increased significantly by 68.11% and 60.54%, respectively, after ionic liquid treatment. The results of the scanning electron microscope (SEM) observation and X-ray diffraction (XRD) showed that the relative crystallinity of the material decreased after ionic liquid treatment, which was more conducive to the enzymatic hydrolysis of cellulose.

Abstract. Intermittent structures are ubiquitous in the solar wind turbulence, and they can significantly affect the power spectral index (which reflects the cascading process of the turbulence) of magnetic field fluctuations. However, to date, an analytical relationship between the intermittency level and the magnetic spectral index has not been shown. Here, we present the continuous variation in the magnetic spectral index in the inertial range as a function of the intermittency level. Using the measurements from the Wind spacecraft, we find 42 272 intervals with different levels of intermittency and with a duration of 5–6 min from 46 slow-wind streams between 2005 and 2013. Among them, each of the intermittent intervals is composed of one dominant intermittent structure and background turbulent fluctuations. For each interval, a magnetic spectral index αB is determined for the Fourier spectrum of the magnetic field fluctuations in the inertial range between 0.01 and 0.3 Hz. A parameter Imax, which corresponds to the maximum of the trace of the partial variance increments of the intermittent structure, is introduced as an indicator of the intermittency level. Our statistical result shows that, as Imax increases from 0 to 20, the magnetic spectrum becomes gradually steeper and the magnetic spectral index αB decreases from −1.63 to −2.01. Accordingly, for the first time, an empirical relation is established between αB and Imax: αB=0.4exp⁡(-Imax/5)-2.02. The result will help us to uncover more details about the contributions of the intermittent structures to the magnetic power spectra and, furthermore, about the physical nature of the energy cascade taking place in the solar wind. It will also help to improve turbulence theories that contain intermittent structures.

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Abstract. Intermittent structures are ubiquitous in the solar wind turbulence, and they can significantly affect the power spectral index of magnetic field fluctuations which reflects the cascading process of the turbulence. However, the relationship between intermittency magnitude and the spectral index has not been shown yet. Here we present the continuous variation of the magnetic spectral index in the inertial range as a function of the intermittency magnitude. By using the measurements from the WIND spacecraft, we find 42,272 intervals with different levels of intermittency magnitude and with duration of 5–6 minutes from 46 slow-wind streams between 2005 and 2013. Among them, each of the intermittent intervals is composed of one dominant intermittent structure and background turbulent fluctuations. For each interval, a spectral index αB is determined for the Fourier spectrum of magnetic field fluctuations in the inertial range between 0.01 Hz and 0.3 Hz. A parameter Imax, which corresponds to the maximum of the trace of partial variance increments of the intermittent structure, is introduced as an indicator of the intermittency magnitude. Our statistical result shows that as Imax increases from 0 to 20, the magnetic spectrum becomes steeper gradually and the spectral index αB decreases from -1.63 to -2.01. Accordingly, an empirical relation is established between αB and Imax. The result will help us to know more details about the contributions of the intermittent structures on the power spectra, and further about the physical nature of the energy cascade taking place in the solar wind. It will also help to improve the turbulence theories that contains intermittent structures.