Search

In this paper, a pulsed high voltage discharge (PHVD) reactor composed of a new type of high-voltage (HV) needle electrode and mesh grounding electrode was utilized to degrade 4-chlorophenol (4-CP). The effect of needle installation position on 4-CP degradation efficiency in solution systems with different conductivities was studied. It is verified that the recessed- and flush-tip structures could effectively overcome the main technical problem of protruded-tip HV electrode, which is that how to maintain stable discharge in the solution with high conductivity. When the conductivity of solution surpassed 116 μS cm−1, the recessed-tip and flush-tip electrodes possessed higher energy efficiency than that of the protruded-tip electrode. Within 40 min, the flush-tip electrode had the highest 4-CP removal rate (86.2%) in pure water, which could further increased to 95.8% via increasing immersion depth of net electrode. Comprehensively considering the experimental results of 4-CP removal rate, discharge characteristic and tail gas emission, it is indicated that the optimal installation positions were 0-F and 5-R. Meanwhile, the increase in immersion depth could reduce the generation of tail gas (e.g. O3 and NOX) obviously. The possible mechanism of 4-CP degradation via PHVD was proposed.

Fatigue can harm people's physiology and psychology, and in serious cases it can even endanger people's lives. To meet the needs of real-time detection of human fatigue status, this paper designs and implements an online fatigue detection system which is capable of interactive fatigue status analysis. Based on AdaBoost framework and cascading technology, a classifier which is capable of identifying faces and eyes in video images at the same time is constructed, and the stable tracking of human eyes is realized by KLT algorithm. After extracting the features from the eye area, the eye opening and closing coefficient, or eye aspect ratio (EAR), is obtained. The k-means method is used to determine the thresh value of the eye opening and closing state to achieve the detection of blink frequency. Combined with nodding frequency and yawn frequency, the state of human fatigue is determined. The experimental results of different subjects in different scenarios show that the detection accuracy of this system can reach up to 95%.

In this paper, highly efficient activated carbon fiber (ACF) anode was prepared for the electro-catalytic oxidation of phenol. The ACF was firstly coated with TiO2 via ship-in-a-bottle synthesis, and then loaded with polyaniline (PANI) layer by an in situ polymerization. The TiO2 coating would improve electro-catalysis activity of ACF anode and the PANI coating would enhance its conductivity, transferring more electrons for electro-catalysis process. The cyclic voltammetry (CV) results of ACF, TiO2/ACF, PANI/ACF and PANI/TiO2/ACF anodes implied that the dual coating could not only inhibit the generation of non-conductive polyphenol film on PANI/ACF anode (anti-passivation), but also obviously increase the phenol degradation efficiency of TiO2/ACF anode. The results of OH output and phenol removal rate showed that the working performance and stability of dual-coated ACF anode could be optimized through altering the modification amount of PANI and TiO2. The new mechanism of synergistic electrocatalysis of PANI/TiO2/ACF for phenol oxidative degradation was reported. The experimental results could offer a novel method to prepare highly efficient porous carbon anodic materials.

In this paper, atmospheric pressure dielectric barrier discharge (DBD) plasma was used to treat four kinds of chemical fiber yarns, namely polyacrylonitrile (PAN), polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), for which the air drag force, moisture regain and yarn diameter were measured. Compared with untreated samples, the air drags of treated PAN, PE, PP and PET yarns increased maximally by 10.7%, 43.0%, 40.0% and 18.9%, respectively, in the present experiments. A two-way analysis of variance and correlation analysis were performed to study the effect of plasma treatment on air drag and other properties of these four chemical fiber yarns. The combination of X-ray photoelectron spectroscopy analysis and the determination of the DBD plasma component can further enhance the understanding of the difference between DBD plasma treatment processes among these four chemical fiber yarns. This study provided the experimental basis to improve the air-jet weaving efficiency of chemical fiber fabrics.

In this paper, long-lived free radicals in atmospheric-pressure DBD plasma were used to treat PET yarn surface. Subsequently, the drag force of treated yarns in air flow at four humidities (40 ± 3, 50 ± 3, 60 ± 3, 70 ± 3%) was measured. The results suggest that with the increase of flow humidity, the air drag force of untreated yarn decreased while that of plasma-treated ones on average increased gradually. The average growth rates of the drag force under each humidity were 5.33, 7.58, 10.08 and 12.28% respectively. Meanwhile, the air drag force of the yarns treated at different specific input energy (SIE) densities and treatment time varied obviously under different flow humidity. The X-ray photoelectron spectroscopy analysis was performed to characterize the yarn surfaces chemically. The topology and roughness of PET yarns were measured by atomic force microscopy. The tensile test was carried out to characterize the mechanical strength. The ozone, nitrate and nitrite radicals and total organic carbon in tail gas of plasma were also analyzed. The maximal atomic concentration of N element on PET surface could reach 8.0%. The obtained results can improve the understanding of the property of long-lived reactive species from DBD plasma source generated at different SIE and the difference in PET surface etching and modification during remote treatment at different SIE. Moreover, the results also provide an experimental guideline for the improvement of weaving efficiency in air-jet weaving.

Both analytical and computational methods for solidification problems are introduced. First, the inward solidification process in a spherical vessel is studied. Expressions of the stress, displacement in the solid phase, and the liquid pressure are deduced based on the solidification interface position. A phase-change expansion orientation factor is introduced to characterize the nonisotropic expansion behavior at the freezing interface. Then, an efficient coupled thermomechanical finite-element method is proposed to evaluate the thermal stress, strain, displacement, and pressure in solidification problems with highly nonlinear constitutive relations. Two particular methods for treating the liquid phase with fixed-grid approaches are introduced. The thermal stress is computed at each integration point by integrating the elastoviscoplastic constitutive equations. Then, the boundary value problem described by the global finite-element equations is solved using the full Newton–Raphson method. This procedure is implemented into the finite-element package abaqus via a FORTRAN subroutine UMAT. Detailed implementation steps and the solution procedures are presented. The numerical model is validated first by the analytical solutions and then by a series of benchmark tests. Finally, an example of solidification in an open reservoir with a free liquid surface is introduced. Potential industrial applications of the numerical model are presented.

In this paper, the nano-titanium dioxide/activated carbon fiber (TiO2/ACF) electrodes are prepared by using ship-in-a-bottle method with Ti(OC4H9)4 as a raw material. The amounts of TiO2 immobilized on the activated carbon fiber are 0.14, 0.28 and 0.42 g/g ACF, respectively. The adsorption behavior and electro-catalytic oxidation of phenol with these three kinds of electrodes are investigated. Experimental results show that the maximum adsorption quantities of the phenol decreased by 12.41%, 17.25% and 32.38% respectively with the increase of TiO2, while the adsorption rates decreased by 56.22%, 71.26% and 88.73%, respectively. However, the removal efficiency of phenol and the production rate of hydroxyl radicals ( OH) increased with the increase of TiO2. Compared with sol–gel method, TiO2/ACF electrode prepared by ship-in-a-bottle method not only exhibit better electro-catalytic activity and stability, but also cheaper. Because the amount of Ti(OC4H9)4 used to prepare TiO2 can be reduced by more than 33%. In addition, the nano-TiO2 particles, smaller and more uniform in size, can be immobilized firmly and prepared easily in this method.

In this paper, non-thermal plasma induced by dielectric barrier discharge (DBD) air discharging was used to treat the moving polyethylene terephthalate (PET) yarn samples and the motionless samples, respectively. The air drag force of the resultant samples was tested, and their surface characteristics were analyzed by X-ray photoelectron spectroscopy (XPS) for chemical composition and by scanning electron microscopy (SEM) for microscopic morphology. The results of the drag force of the samples indicated that, compared with the pristine yarn, the drag force of the samples treated via the two types of plasma treatment clearly varied under different processing conditions. The maximal drag force was 28.26cN for the moving sample treated at 34 V control voltage for 30 s in the discharge zone (zone A) and 27.81cN for the motionless sample treated at 36 V control voltage for 60 s in the long-lived plasma species treating zone (zone B), which increased by 18.9% and 17.0% over that of untreated sample (23.77cN), respectively. The fluctuation of the drag force probably depends on the change of the chemical composition and microstructure of the polyethylene terephthalate yarn surface, which implies that the feasibility of weaving efficiency improvement for an air-jet loom could be realized via controlling and optimizing the dielectric barrier discharge operating conditions.

A novel method to prepare durable biphilic surface on cellulose filter paper by atmospheric air plasma treatment is reported. The as-prepared sample possessed excellent separation performance for surfactant-stabilized water-in-oil emulsions, of which the filtration efficiency reached 99.13% and the oil recovery purity exceeded 99.98 wt%. The hydrophobic surface with microscale hierarchical structure was constructed with long-chain alkyl silane and SiO2 nanoparticles via plasma-induced crosslinking, on which amino-grafted SiO2 nanoparticles was then fixed through plasma-induced chemical bonding. The water-amino attraction and oil-alkyl attraction would synergistically destabilize the emulsion and hence separate the two phases. The plasma-fabricated coating was very durable against ultrasonication in acetone and can be stored for 12 months without aging. The coating also exhibited excellent recyclability (over 20 cycles). The study may offer a facile, environment-friendly method to prepare filtering materials for highly efficient separation of water-in-oil emulsions.

In this paper, an efficient treatment using water falling film discharge combined with silver catalysis to degrade xylene gas with high concentration was reported. It is found that the composite technique not only effectively removed gaseous xylene, but also eliminated the emission of unexpected by-products (e.g. ozone, toxic organic intermediates and NOX). Under the control voltage of 60V and gas-water ratio of 100:1, the reactor could continuously operate for 6 days to degrade xylene with concentration of 2400 mg/m3, of which the removal rate could still meet the requirement of discharge standard. Moreover, the content of undesirable products in circulating water was also kept at a low level. The synergistic effect of plasma oxidation and selective catalytic reduction of NOX with O3 over Ag catalyst played a key role in mineralization of target pollutant. The research could provide a reference for the design of efficient hybrid system with high safety for the degradation of high-concentration hydrophobic volatile organic compounds.

The effect of pulsed high-voltage discharge on mass transfer and reaction processes in a needle-plate reactor was studied. Bubble size distributions and characteristic parameters were determined by photography, implying that inlet air bubbles could be broken into smaller ones effectively by discharge. The mass transfer parameters including specific interfacial area (a), volumetric mass transfer coefficient (kLa), and liquid-side mass transfer coefficient (kL) were obtained by Danckwerts-plot, reflecting the mass transfer processes. In addition, 4-chlorophenol (4-CP) decomposition was determined under the same experimental conditions. The results showed that the conclusions of 4-CP removal were coincided with the statistical results of bubble images, illustrating that higher peak voltage, pulsed frequency and appropriate air flow rate are beneficial to mass transfer and reaction. However, there was a slight difference between 4-CP removal and mass transfer parameters at higher air flow rate. Therefore, it is more reasonable to optimize the operating conditions of a pulsed high-voltage discharge reactor via combining image acquisition and mass transfer parameters with the results of pollutant degradation.

The role of dissolved oxygen (DO) in a visible Fenton-like degradation of atrazine driven by Ta(O)N was examined in detail. First, Ta(O)N samples were prepared by the nitridation of Ta 2 O 5 nanoparticles, which showed strong absorption in the range of 300–600 nm. Second, the degradation of atrazine, the decomposition of H 2 O 2 , and the formation of intermediates in the visible Ta(O)N-Fenton-like system in the presence of DO were compared with those in the absence of DO. In the visible Ta(O)N–Fenton-like system, atrazine degradation was based on the attack of • OH and the atrazine degradation pathways were similar in the presence and absence of DO. Notably, however, the presence of DO suppressed atrazine degradation. An investigation into the effects of DO on the photoreduction of Fe 3+ and the photodecomposition of H 2 O 2 catalyzed by Ta(O)N showed that the presence of DO suppressed the formation of Fe 2+ but did not affect the decomposition of H 2 O 2 . Therefore, the presence of DO slowed the generation of • OH. The role of DO in atrazine degradation by a visible Ta(O)N-Fenton-like system was proposed on the basis of the experimental results.

Phenol degradation was studied in a novel electrochemical system with TiO2/activated carbon fiber as anode and graphite as cathode. The removal of phenol was investigated in terms of various parameters namely: cathode and anode gap, pH, current density, initial phenol concentration and addition of Na2SO4. At the same time, percentages of phenol degradation and COD removal were observed at different electrodes. The results showed that, at the phenol concentration of 100 mg/L, cathode and anode gap of 2 cm, current density of 7.14 mA/cm2, solution pH 6.20 and 0.0750 mol/L Na2SO4, degradation of 83.26% phenol and removal of 47.03% COD after 1 h electrolysis can be achieved with TiO2/ACF–graphite as anode, while 67.72% phenol and 35.78% COD achieved with ACF/graphite as anode. Under the same conditions mentioned above, no phenol can be detected in 105 min at the initial phenol concentration of 10 mg/L with TiO2/ACF–graphite as anode. The electrochemical oxidation reaction of phenol obeyed pseudo-first order kinetic. The mass adsorbed hydroxyl radicals were generated on the TiO2/ACF electrode due to its three-dimensional space, high oxygen evolution potential and the catalysis of TiO2. With the formation of hydroxyl radicals, the phenol was oxidized to produce hydroquinone, pyrocatechol and benzoquinone during electrochemical process. The concentrations of these three aromatic compounds achieve peak values after 3 h, 2 h and 1 h, respectively. Then, they gradually diminished and were degraded to form ring-opened products such as formic and maleic acids, which were oxidized to CO2 and H2O finally.

A dielectric barrier discharge system with a discharging zone apart from a degrading zone is developed to remove 4-chlorophenol from water. Oxygen is fed through the discharging zone where it dissociates to form a plasma stream. The plasma stream is introduced into the degrading zone to make 4-chlorophenol degraded effectively. The removal of 4-chlorophenol was influenced by the processing parameters such as gas flow rate, pH and applied voltage. Increasing the peak voltage or gas flow rate among a certain range, the removal efficiency was enhanced. More than 80% of 4-chlorophenol was removed in 6 min at pH 9.00, resulting in a high energy efficiency of 46.34 × 10 −9 mol J −1 (21.46 g/kW h). Discharging in initial 4-chlorophenol solution, the removal percent was about 90% at 30 min with peak voltage of 14.64 kV and oxygen flow rate of 200 L h −1 . The corresponding energy efficiency was 12.35 × 10 −9 mol J −1 (5.72 g/kW h). During the degradation, aromatic products and organic acids were produced. The main aromatic intermediates were different at different pH, suggesting different pathways of the target contaminant. After the benzene ring was opened, organic acid such as formic acid, oxalic acid, d -(+)-malic acid and maleic acid were formed.

Air is often used as bubbling gas with the purpose of improving the liquid discharge performance in some pulsed high-voltage discharge systems. Nitrogen in air could dissociate into active species that might participate in a series of liquid chemical reactions. In the discharge system with 4-chlorophenol as target contaminant, some more toxic intermediates were formed and the energy efficiency was decreased by bubbling air and nitrogen. The G50 (energy cost at 50% conversion) is about 0.91 g (KW h)−1, 0.70 g (KW h)−1 and 0.49 g (KW h)−1 respectively by bubbling oxygen, air and nitrogen. Nitro- compounds such as 4-chloro-2-nitrophenol and 4-nitrocatechol were identified, providing evidence for the formation of nitro group. Chloride ion (Cl−) dropped in the degradation process could be activated and react with non-degradable 4-chlorophenol to form 2,6-dichlorophenol. Phenol was also identified for higher yield of reductive radicals. Comparing 4-chlorophenol degradation by bubbling air or nitrogen with that by oxygen, the degradation rates of original contaminants and intermediate products were lower under same energy input. By discharging for 60 min with applied input energy density of 175 W L−1, almost all of aromatic substances were removed with bubbling oxygen but they still remained at about 8.83% with bubbling air and 12.79% with nitrogen. Furthermore, nitrogen in the bubbling gas was transformed into inorganic nitrogen such as NO2- and NO3- that increased linearly with discharge time and achieved a formation rate twice as the degradation rate of original target contaminant.

2,4-dichorophenol (2,4-DCP) was degraded in a pulsed high voltage discharge system with particular focus on the optimum of processing parameters and identification of the intermediate products. By increasing peak voltage or frequency, the 2,4-dichorophenol degradation could be sped up. The energy input was mounted up from 0.0057 to 0.0397 kWh and 2,4-DCP degradation efficiency was enhanced from 58% to 99% in 42 min by increasing peak voltage from 18 kV to 26 kV. Under the same 2,4-DCP degradation efficiency, less energy input was required for higher pulse frequency with a shorter discharge time. Higher pH value was advantage for 2,4-DCP degradation while salt content was proved to have little effect on 2,4-DCP degradation in the present discharge reactor. From the identifications of main intermediates resulted from 2,4-DCP degradation, it is illustrated that the degradation is induced by OH, which could mainly attack the Ortho-position of the OH group to form 3,5-dichloro-1,2-benzenediol or substitute the Cl group in 2,4-DCP to produce 2-chlorohydroquinone. The 2-chlorohydroquinone could be further reacted with OH to produce 1,2,4-trihydyoxybenzene. Additional, some ring-opened products such as (e,e)-2,4-hexadienal, formic, oxalic, maleic and d-(+)-malic acid were recognized by GC-MS and Ion Chromatograph detection.

Degradation of 4-chlorophenol by pulsed high voltage discharge is an intricate process involving a series of complex chemical reactions. Hydroxylation of 4-chlorophenol to form hydroquinone, 4-chlororesorcinol and 4-chlorocatechol is the first step, though a very small amount of direct cleavage products of the C1–C2 or C5–C6 bond are observed. The yield of 4-chlorocatechol is about twice as much as that of hydroquinone. Less 4-chloresorcinol is produced. The free chloride ions dropped from the 4-chlorophenol degradation can obtain reactivity again from the discharge, and react with undegraded 4-chlorophenol to form 2,4-dichlorophenol. Some ring-opened products have also been identified and their possible reaction routes are proposed. Several compounds are verified by use of authentic samples. The more stable ring-opened products are low molecular weight (LMW) acids such as formic, acetic, oxalic, malonate, maleic and malic acid. By discharging 4-chlorophenol aqueous solution for 36 min, the amount of carbons obtained from organic acids is more than 50% while that of carbons from aromatic products less than 20% in the carbons of degraded 4-chlorophenol, which is about 94% of initial carbons. After 60 min of discharge, all the 4-chlorophenol and its aromatic intermediates have been removed completely and the organic carbons are mainly presented as organic acid such as acetic and oxalate acid. At the end of the 120 min discharge, the amount of the remaining organic carbons is not more than 14% of the initial carbons.

In this paper, a simple method to prepare PANI-coated conductive PET yarn is reported, which involves pre-applying aniline and HCl vapors on PET surface and subsequent dielectric-barrier discharge (DBD) plasma treatment of the coated yarn under atmospheric pressure. The volume resistivity of the optimal sample was about 1.8 × 10⁵ times lower than that of the control. Moreover, with the increase of coating amount of PANI, the air drag of PET yarns improved gradually. The surface chemistry of the treated yarn was analyzed by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), while the morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). This study offers a new method to prepare conductive fabric via air-jet loom and is expected to increase the weaving efficiency of air-jet loom.

A novel method for preparing durable superamphiphobic fabrics is reported, which involves preapplying a solution consisting of perfluoroalkyl acrylate, epoxide-containing silane, and silica nanoparticles onto fabric and subsequent argon-plasma treatment. The coated fabrics show superphobic to both water and oil fluids (surface tension >21.5 mN m-1 ). The coating is durable to withstand repeated laundries and multicycles of abrasion without apparently altering the superamphiphobicity. The coating is also very stable in boiling water, strong acid, and base, but has little effect on the fabric handle and air permeability. The argon-plasma-enhanced coating may offer a facile way to prepare durable superamphiphobic fabrics.

A novel method to prepare durable superhydrophobic fabrics through pre-applying an alkyl silane (alkyl chain longer than C15) onto fabric substrate and by subsequent vacuum plasma treatment in argon is reported. The treated fabrics show a contact angle of 154.2° with low contact angle hysteresis (sliding angle 4.5°). The coatings are durable and can withstand 150 cycles of standard laundries. The argon plasma treatment is found to significantly enhance SiOSi bonding among the silane molecules, leading to a highly crosslinked silica network. The silane coating also shows high optical transparency. Apart from fabrics, other substrates such as filter paper, plastic film, glass slide, silicon wafer, and metal are treated in a similar way, and all the treated surface show durable hydrophobicity, though the contact angle is lower than that of the coated fabrics. Post-crosslinking of silane through argon plasma treatment may offer a facile but environment-friendly way to prepare durable superhydrophobic fabrics.

Resected specimens of benign and malignant gastric ulcers from 3441 cases were studied and compared clinically and pathologically. Among them, 421 cases of malignant ulcer were found. The malignant ulcers differed notably from the ulcerated gastric carcinoma and showed many similarities to the benign chronic gastric ulcer (CGU). The most distinct feature of malignant ulcer was lack of cancerous infiltration and muscular residue in the scar tissue of ulcer base. The existence of this type of ulcer clinically and pathomophologically supports the viewpoint that CGU can undergo malignant change. The rate of malignant change of CGU in this study was 3. 48%.

In this study, chloridized mesoporous activated carbons (ClMAC) were prepared from used tyres. Their pore structure, surface chemistry and adsorptive capacities of toluene were investigated with nitrogen gas adsorption, Fourier transform infrared spectroscopy (FT-IR) and bench adsorptive experiments. A series of activated carbons were produced by pyrolysis, activation and chlorination under different temperatures. The activated carbons derived from scrap tyres had highly mesoporous volumes and surface areas, for example, the ClMAC prepared under 300 °C was 0.81 cm3 g—1, and 1078.2 m2 g —1, respectively. (Commercial activated carbon—F-400 was 0.16 cm3 g—1, and 1021.1 m 2 g—1). The adsorptive capacities of toluene in the activated carbon-derived waste tyres were compared with the F-400 and the experimental results showed chlorinated activated carbons had exceptional characteristics for toluene adsorption in an aqueous solution; especially, the ClMAC produced in 300 °C had a 471.8 mg g—1 maximum capacity; however, F-400 had a 255.4 mg g— 1 minimum capacity. In short, by using chloridized mesoporous activated carbons the authors significantly improved the toluene removal capacity in aqueous solution.