The effects of oxygen concentration, particle size, and heating rate on the coal combustion characteristics under an O 2 /CO 2 atmosphere were investigated. The results indicated that the oxygen concentration played the most important role. As the oxygen concentration increases, the ignition and burnout temperatures decrease and the comprehensive combustion property index S increases. Moreover, the improvement of the oxygen concentration intensified the effects of the other factors. The ignition mechanism changes from heterohomogeneous type to homogeneous type as the oxygen concentration increases. The ignition and burnout temperatures decrease slightly as the mean particle size decreases, and the index S increases measurably as the mean particle size decreases. The heating rate has different effects on the ignition temperature, burnout temperature, and index S at different oxygen concentrations.

The effects of particle size, stoichiometric ratio (λ), atmosphere, temperature, and recycled NO on the emissions of three fractional nitrogens, [N] N2O, [N] NO , and [N] NO2 , during the combustion of superfine pulverized coal in O 2 /CO 2 atmosphere were investigated in the present study. NO 2 has shown little contribution to NOx compared with N 2 O and NO in all the cases. As the stoichiometric ratio increases, the trend is much similar in CO 2 /O 2 and N 2 /O 2 . However, the conversion ratio from fuel-N to NOx in CO 2 /O 2 atmosphere is less than that in N 2 /O 2 atmosphere especially at λ >1.2.[N] NO makes up the largest portion of [N] NOx at λ>1, and [N] N2O dominates at λ<1 resulting from the presence of hydrocarbons and CO at low stoichiometric ratio. For the three coals, [N] N2O increases as the mean particle size increases while [N] NO shows the opposite trend because the evolution of volatile nitrogen was delayed and the reburninglike scheme happened. There exists a minimum for the conversion ratio from fuel-N to NOx at the particle size range of 15-25 μm under the combined effects of [N] N2O and [N] NO . As temperature goes up, [N] NO and the conversion ratio from fuel-N to NOx increase while the [N] N2O decreases obviously. The conversion ratio from fuel-N to NOx decreases while the reduction rate increases as recycled NO increases. Recycled NO is destroyed in the flame through its reactions with hydrocarbon radicals in the form of CHi, and reduction reactions occur between recycled NOx and fuel-N. The increase in NO concentration accelerates the formation reactions of N 2 O and also promotes the conversion of char-N to N 2 O.

We studied the multi-plateau high-order harmonic generation (HHG) from solids numerically. It is found that the HHG spectrum in the second or higher plateau is redshifted in short laser pulses due to the nonadiabatic effect. The corresponding FWHMs also increase, suggesting the step-by-step excitation process of higher conduction bands in the HHG process. Even order harmonics in the higher plateaus of HHG are present due to the break of symmetry in the k space. It may stimulate related experimental work. High-order harmonic generation (HHG) from gases has been well studied. It has been used to generate attosecond laser pulses [1,2]. It is described by the three-step model [3]. The cutoff energy of HHG is around Ip+3.17Up (Ip is the ionization potential, and Up=A0 2 /4 is the ponderomotive energy). The HHG from bulk crystals has been reported recently [4,5] as the development of long-wavelength lasers. It is quite different from the HHG from gases. The cutoff energy of solid HHG depends on the amplitude of the laser field linearly [4]. It also exhibits multi-plateau structure [6]. However, the mechanisms of HHG from solids are much debated. Inter-and intra-band transitions [4,7,8] are proposed. Three-step model in the coordinate space [9] and vector k space [10] are investigated. Recently, multi-plateau HHG from solids are studied theoretically [7,8,11] and experimentally. Our theoretical model [10] propose that the multi-plateau structure reflects the population of higher conduction bands which are pumped step by step.In the solid systems, even-order harmonics are measured experimentally. They may come from the interference of HHG trajectories in the different valence bands [12]. It may also come from the Berry phase [13]. In this work, we will present a new mechanism for even-order harmonic generation in symmetric periodic potentials.Redshifts of HHG spectra were predicted in the HHG from gases and plasmas [14][15][16][17][18][19][20]. They originate from delayed emission times of HHG from the excited state, resonate state, or dissociation of molecules. It is a nonadiabatic effect. The feature is that most of the HHG signals are generated from the trailing edge of the laser pulse, where dI/dt<0. The driving force from the laser fields is weaker than the previous cycle. The electrons obtain less energy compared to the previous cycle and redshifts of HHG occur. They have been experimentally confirmed [18,[21][22][23]. It was reported that redshift was observed in the optical absorption of crystals in the presence of an intense mid-infrared laser field [24]. In this letter, we find that redshift also exists in emission of HHG from solids. It is universal. The higher conduction bands are excited step by step. As a result, the HHG process in the higher plateau is delayed compared to ultrafast process in the lower conduction bands. As will be shown next, even the system is symmetric in the coordinate space, the electron motion is not symmetric in the k space. Consequently, redshifts of HHG and even-order harmonics ar...

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The rapid and onsite detection of glyphosate herbicides in agricultural products is still a challenge. Herein, a novel colorimetric nanozyme sheet for the rapid detection of glyphosate has been successfully prepared through the physical adsorption of porous Co 3 O 4 nanoplates on a polyester fiber membrane. Glyphosate can specifically inhibit the peroxidase-mimicking catalytic activity of porous Co 3 O 4 nanoplates, thereby the visual detection of glyphosate can be realized by distinguishing the change in the color intensity of the established nanozyme sheet. The prepared nanozyme sheet has good sensitivity and selectivity, with a detection limit of 0.175 mg•kg −1 for glyphosate detection just by the naked eyes. It can effectively detect glyphosate within 10 min, and the color spots can maintain more than 20 min. The nanozyme sheet is not easily affected by the external environment in detection and storage. The merits of the nanozyme sheet facilitate its practical application in the large-scale preliminary screening of glyphosate residues in agricultural products.

We synthesized tetraazamacrocycles 1 and 2 bearing two anthryl groups as sidearms, both of which exhibited high selectivity for the Zn II ion in switching-on-type responses in aqueous solution. For ligand 1, Zn II is coordinated by four nitrogen atoms of the macrocycle and two amino groups on the pendent arms, which results in proximity between the two fluorophores. So, 1-Zn II shows obvious excimer emission in aqueous solution. When PPi or ATP was added (pH 7.4), the

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