Search

This paper studies a novel gas cyclone with a cylindrical filter face installed in the center from the vortex finder to the bottom hopper. The experimental results show that this composite cyclone has a higher collection efficiency and a lower pressure drop than the original cyclone. The mechanisms for the improvement are analyzed by both physical experiments and numerical simulations. By measuring dust samples collected at different places it is revealed that the center filter can prevent fine particles from entering the inner vortex and escaping, which accounts for the increase of the collection efficiency. In addition, the flow field of the composite cyclone is simulated by computational fluid dynamics and compared with that of the original cyclone. The analysis shows that with the filter layer installed, the swirling flow disappears in the vortex finder, which decreases the kinetic energy dissipation and hence lowers the pressure drop.

Additional file 1: Supplemental Table 1. Basic characteristics of the two datasets. Supplemental Table 2. Results of multiple linear regression. Supplemental Table 3. Analysis of variance component and SDR. Supplemental Figure 1. Distribution of the thyroid-related hormones in the Reference data set.

In this study, mesoporous TiO2 with various hydrolysis rates were prepared and combined with H2O2 for the photodegradation of unsymmetrical dimethylhydrazine (UDMH) under VUV irradiation. Results showed that the mesoporous TiO2 synthesized by the hydrolysis in water (MT100) exhibited a good mesoporous structure and the largest specific surface area (178.85 m2 g−1). Consequently, MT100 showed the best degradation efficiency, with the rate constant (k) for VUV/MT100 and VUV/MT100/H2O2 of 0.0185 and 0.2595 min−1, respectively, which was 1.4 and 4.0 times of that of P25. The addition of H2O2 significantly enhanced the degradation efficiency by photoactivation of H2O2 and the synergistic effect. The rate constant and the mineralization rate (after a 3-h treatment) increased by 13 and 3.8 times when 40 mM H2O2 was added into VUV/MT100. The weak alkaline condition (pH = 9) would facilitate the degradation of UDMH. The ⋅OH was the key oxidizing species in VUV/MT100/H2O2. Eight intermediates were detected during the degradation and the possible pathways of UDMH degradation in VUV/MT100/H2O2 process were proposed. VUV/MT100/H2O2 provides an efficient method to degrade UDMH.

In this study, α-, β-, and δ-MnO2 were prepared by a uniform hydrothermal method and then coupled with vacuum ultraviolet (VUV) for the degradation of gaseous unsymmetrical dimethylhydrazine (UDMH). The performance in the removal of UDMH, by-product distribution and mechanism were systematically investigated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, Field Emission Scanning Electron Microscopy (FE-SEM), Raman, thermogravimetry (TG), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) to investigate the factors affecting the catalytic activity. The results showed that O2 and H2O were essential for the removal of UDMH. Photooxidation and ozone catalytic oxidation contribute to the removal and mineralization of UDMH. The integrated process considerably improved the removal and mineralization of UDMH by ozone catalytic oxidation. More reactive oxygen species were generated in the integrated process. The catalytic activity of the prepared catalysts follows the order: δ-MnO2 > α-MnO2 > β-MnO2. δ-MnO2 displayed the highest removal rate of 100% and a CO2 concentration of 42 ppmv. The good performance of δ-MnO2 was mainly attributed to the large number of surface oxygen vacancies.

In this work, TiO2/SBA-15 was synthesized via an in situ hydrothermal method and was used for vacuum-ultraviolet (VUV) photocatalytic degradation of unsymmetrical dimethylhydrazine (UDMH) for the first time. Compared with photocatalysis under UV irradiation, VUV photocatalysis exhibited higher photodegradation efficiency due to the synergetic effect of direct photolysis, indirect photooxidation and photocatalytic oxidation. The synthesized TiO2/SBA-15 catalysts exhibited ordered mesoporous structure and anatase phase TiO2. Titanium content, initial pH and substrate concentration impacted degradation efficiency of UDMH in the VUV photocatalysis process. Among the prepared catalysts, TiO2/SBA-15 with the molar ratio of Ti/Si = 1 : 3 (TS-2) showed the best photocatalytic activity under VUV light, with the rate constant of 0.02511 min−1, which is 1.91 times that with VUV/P25. The superior photocatalytic activity of TS-2 is mainly related to the good balance between the specific surface area and TiO2 contents. The photodegradation efficiency decreases with the increase in the initial UDMH concentration and the maximum degradation rate was obtained at pH 9.0. In the VUV/TS-2 process, ˙OH played a more important role in the degradation of UDMH than ˙O2− and the degradation pathways contained bond breaking, amidation, isomerisation and oxidation reactions. The TS-2 also showed good reusability with the rate constant maintained at above 90% after five cycles and exhibited satisfactory degradation efficiency in tap water.

Supplementary Material 1

Membrane fouling, especially inorganic fouling due to salt crystal formation and deposition on the membrane surface, is still a major technical issue in membrane distillation (MD) applications. In this study, microbubble aeration (MBA) was included in a laboratory-scale vacuum membrane distillation (VMD) rig and its effect on a desalination process was examined. Without MBA, serious membrane scaling occurred during desalination of simulated high-salinity sea water (100 g.L−1 salt concentration), which resulted in a dramatic reduction of permeate flux to essentially zero after 120 min. Scanning electron microscopy showed that a layer of large cuboid salt crystals uniformly covered the membrane surface. However, membrane scaling was mitigated with the introduction of MBA, resulting in the improved VMD desalination performance, which was positively correlated with pump pressure in the microbubble (MB) generator. Results showed that the effective processing time of the VMD desalination processing cycle was respectively prolonged to 150, 180, and more than 300 and 360 min (cf. 120 min without MBA) when the pump pressure was respectively at 0.1, 0.2, 0.3 and 0.4 MPa, leading to the increase of cumulative water production. Further studies found that larger numbers of MBs of smaller size were produced at higher pump pressure, which are more beneficial for increasing water vapor production and alleviating salt precipitation. The difference in zeta potential between the MBs in distilled water (about −30 mV) and that in SW100 solution (about -2 mV) demonstrated that MBA not only effectively mitigated the negative effect of concentration polarization by enhancing the surface shear rate at the membrane surface, but also reduced salt precipitation probably due to the MBs attracting counterions to the gas-water interface. Finally, energy consumption analysis of the modified VMD desalination process revealed that MBA, while itself only adding about 3% to the total energy consumption at varied pump pressures, was able to improve the specific energy consumption, especially at higher pump pressures. Together, these results demonstrate that MBA is an effective way of improving the performance of VMD desalination of water.

As a green advanced process for drinking water treatment, the UV/hydrogen peroxide (UV/H2O2) process has been gradually applied in China. To study the effect and mechanism of organic matter removal and the development of microbial communities in the UV/H2O2-biological activated carbon (UV/H2O2-BAC) process, a pilot-scale UV/H2O2-BAC system was built and operated over one year. Low water temperature affects the UV/H2O2 process efficiency, the biofilms in the BAC system were mature and stable after 240 days, and the contribution rate of BAC adsorption to dissolved organic carbon (DOC) removal was approximately 14.2% after one year of operation. The liquid chromatography-organic carbon detection (LC-OCD) analysis shows that UV/H2O2 process can increase the amounts of Low Molecular Weight (LMW) neutrals, and the specific UV absorbance (SUVA254) value is not suitable for predicting Trihalomethanes (THMs) precursor contents in water after UV/H2O2 treatment. High-throughput sequencing results prove that microbial species in the middle section are the most abundant compared to those in the influent and effluent sections, hydrogen peroxide has lower inhibition on the development of microbial community than ozone and the low concentration of hydrogen peroxide (&lt, 0.25 mg/L) promotes the development of the microbial communities, hydrogen peroxide can reduce Proteobacteria abundance by inhibiting the growth of anaerobes. Acidobacteria may have a certain contribution to the degradation of soil organic matter (SOM), and the effluent section of BAC with low DOC concentration cannot form the dominant species of Rhodobacter.

This paper presents a study of the performance of a gas cyclone with a cylindrical filter face installed in the center from the vortex finder to the bottom hopper. The experimental results show that this composite cyclone can have a higher collection efficiency and a lower pressure drop than those of the gas cyclone. In addition, the outer vortex of the composite cyclone removes coarse particles and the filter can block fine particles outside the inner vortex, which will significantly increase the collection efficiency, especially for fine particles. The flow field of the composite cyclone is simulated by computational fluid dynamics with the Reynolds stress model to model turbulence and the porous media model for the filter. The result shows that the swirling disappears in the vortex finder and the kinetic energy dissipation lowers with the filter installed, which remarkably decreases the pressure drop.

The characterization of indoor (a naturally ventilated office) and outdoor (adjacent courtyard) metals in PM2.5 during a winter period in Xi'an, China were carried out. The results indicated that t...

Generalized minor component analysis (GMCA) is an essential technique in data classification and signal processing. In this paper, we propose an information criterion for GMCA and derive a fast GMCA algorithm for extracting the first generalized minor component (GMC) by using quasi-Newton method to this information criterion. In order to extract multiple GMCs, through the weighed matrix method, this information criterion is extended into a weighted one, which has a unique global maximum attained if and only if its state matrices converge to the GMCs of the matrix pencil composed of the autocorrelation matrices of two stochastic processes. A gradient algorithm is also derived based on this weighted information criterion. Theoretical analysis shows that the gradient algorithm has self-stabilizing property and does not need the normalization operation required in other algorithms. The global convergence analysis of the proposed algorithm is accomplished through the Lyapunov method. Numerical simulations and real application are carried out to further demonstrate the accuracy and speed advantages of the proposed algorithms.

Boron nitride/ethylene alcohol (BN/EG) nanofluids was synthesized by two-step method. The influence of dispersant on stability, thermal conductivity and viscosity was studied. The experimental results reveal that the stability of BN/EG nanofluids deteriorates rapidly with the addition of anionic dispersants and cationic dispersants, which has no practical application value. While, non-ionic dispersant can improve the stability and fluidity obviously and maintain the enhancement of thermal conductivity at the same time.

Ball milling and annealing method is an important method for synthesis of boron nitride nanotube. How to improve their productivity through this method is a problem that people have been studying all the time. In this paper, the influence of milling time on productivity of boron nitride nanotubes synthesized from B2O3 through ball milling and annealing method was investigated. The result indicated that the optimal milling time for synthesis of BN nanotubes with high productivity is 80h. The reason for formation of these high productivity BN nanotubes can be ascribed to the high chemical reactivity and appropriate amount of catalyst in B2O3 powder milled for 80h. The results of this study can provide guidance for the preparation of high yield BN nanotubes.

Generalized eigendecomposition, which extracts the generalized eigenvector from a matrix pencil, is a powerful tool and has been widely used in many fields, such as data classification and blind source separation. First, to extract the minor generalized eigenvector (MGE), we propose a deterministic discrete-time (DDT) system. Unlike some existing systems, the proposed DDT system does not need to normalize the weight vector in each iteration, since the weight vectors in the proposed DDT system are self-stabilizing. Second, we propose an adaptive algorithm corresponding to the proposed DDT system. Moreover, we study the dynamic behavior and convergence properties of the proposed DDT system and prove that the weight vector must converge to the direction of the MGE of a matrix pencil under some mild conditions. Numerical simulations show that the proposed algorithm has a better performance in terms of convergence speed and estimation accuracy than some existing algorithms. Finally, we conduct two experiments on real data sets to demonstrate its practicability.

The dielectric barrier discharge (DBD) and pulse corona discharge(PCD) plasma generator was used to remove NH3, H2S, C7H8 etc. from atmosphere. The principle and characteristic of the two ways was discussed in the article. The test shows the result of PCD is better than that of DBD.