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The influence of pressure and environment on urban polyethylene (PE) gas pipeline makes structural deterioration and leaking to the pipeline and pipeline easy. This paper proposes an analysis method for optimizing Variational Mode Decomposition (VMD) algorithm. Firstly, the optimal bandwidth is obtained by using the adaptive weighted frequency band entropy (AFBE), and the optimal quadratic penalty factor is obtained by curve fitting. Then, the AFBE is used as the fitness function, and the optimal decomposition level is obtained by the optimized beetle whisker search algorithm. Experimental results show that the signal-to-noise ratio (SNR) is improved by 12.74% on average. [ABSTRACT FROM AUTHOR]

In order to reduce the power of methane explosion in natural gas pipelines and effectively improve the explosion suppression efficiency of a single explosion suppressant, we carry out the explosion suppression of HFC‐227ea/carbon dioxide mixed gas as well as mixed gas/ultrafine water mist through a self‐built methane explosion suppression experimental platform. Based on the changes in parameters such as explosion overpressure, flame propagation velocity, and flame propagation structure, the coupling mechanism of methane explosion suppression between mixed gases and between mixed gases and ultrafine water mist is revealed, which provides scientific support for promoting the development of methane explosion suppression technology. The experimental results show that when the mixed gas HFC‐227ea/carbon dioxide and ultrafine water mist synergistically suppresses methane explosion, the addition of the mixed gas can effectively improve the suppression effect of ultrafine water mist on methane explosion. [ABSTRACT FROM AUTHOR]

This study investigates the correlation between various micromagnetic signature patterns and the yield and tensile strengths of carbon steel (Cr12MoV steel as per Chinese standards). For this purpose, back-propagation neural network (BP-NN) models are established to quantitatively predict the yield and tensile strengths of carbon steels. The accuracy of prediction models is significantly affected by the presence of redundant micromagnetic signature patterns. By carefully screening the input parameters, it is able to effectively mitigate prediction errors arising from unreasonable model inputs. In the field of micromagnetic nondestructive testing (NDT), prediction models calibrated for a specific instrument or sensor cannot be directly applied to another instrument or sensor. In the study, a joint distribution adaptation transfer learning strategy based on auxiliary data is proposed to enhance the generalization of prediction models for cross-instrument applications. When auxiliary data accounts for 30% of the source domain data, the joint distribution adaptation transfer learning method based on auxiliary data improves the robustness of the model. The accuracy of the yield strength and tensile strength calibration models witnesses remarkable improvements of approximately 91.4% and 93.5%, respectively. [ABSTRACT FROM AUTHOR]

In a semi-closed visualization pipeline, this experiment studied the inhibitory effect of ultra-fine pure water mist, ultra-fine water mist containing inorganic salt and ultra-fine water mist containing bacteria-inorganic salt on 9.8% methane explosion under five different quality of spray volume. Combined with the methane explosion suppression experiment, the ability of methane-oxidizing bacteria to degrade 9.8% of methane was studied in a simulated pipeline. Experiments showed that the addition of inorganic salt and the degradation of methane-oxidizing bacteria could improve the suppression explosion effect of ultra-fine water mist, and the suppression explosion effect was related to the volume of water mist. Under the same ultra-fine water mist condition, with the increase of the volume of water mist, the explosion suppression effect was improved. Compared with pure methane, pure water ultra-fine water mist, and inorganic salt ultra-fine water mist, the maximum explosion overpressure and flame propagation speed under the condition of bacteria-inorganic salt ultra-fine water mist were significantly reduced. Compared with the explosion of pure methane, due to the degradation of methane by methane-oxidizing bacteria, when the degradation time was 10 h, and the volume of ultra-fine water mist containing bacteria-inorganic salt was 12.5 mL, the maximum explosion overpressure dropped significantly from 0.663 to 0.343 MPa, a decrease of 48.27%. The appearance time of the maximum explosion overpressure was delayed from 208.8 to 222.6 ms. The peak flame velocity was 4 m s−1, which was 83.3% lower than that of 9.8% pure methane explosion. This study will contribute to the development of efficient ultrafine water mist synergistic inhibitors for the prevention of methane explosion disasters. [ABSTRACT FROM AUTHOR]

In order to explore the influence of the side duct position and venting position on the premixed combustion and explosion characteristics of methane/air, a premixed combustion and explosion experiment of methane/air and a simulation of an explosion of the same size were carried out in a tube with an internal size of 2000 mm × 110 mm × 110 mm. The results showed that the side duct could change the flame structure and accelerate the flame inside the tube. The maximum increase ratio of the flame propagation speed was 106.1%. The side duct had a certain venting effect on the explosion pressure. For different position cases, when the venting film was placed over the bottom section, the maximum overpressure first decreased and then increased. When the venting film was placed over the middle section and the top section, the maximum overpressure first increased and then decreased, and the change trend of the top section was stronger. Turbulence mostly occurred inside the side duct when the venting film of the side duct ruptured. There is no linear relationship between the maximum flame propagation velocity within the tube and the maximum turbulent kinetic energy inside the side duct. The two had a relationship that could be fitted to the Gauss function; the correlation coefficient R2 was 0.836, and the minimum value was at (4767.72, 17.918), suggesting that the side duct had the best venting effect on the flame inside the duct at this maximum turbulent kinetic energy. The analysis results of the influence of the location of the vent on the maximum flame propagation velocity inside the tube are helpful for optimizing the layout design of the underground space, reducing the combustion efficiency, and ensuring the safety of the process. [ABSTRACT FROM AUTHOR]

With the rapid development of urban and social economies, the safety accidents in the construction process of the new chemical plant have caused huge losses to the city. The purpose of this study is to evaluate the risks in the construction process of chemical projects and propose preventive measures. A novel risk assessment model based on multi-intelligence algorithm optimization projection pursuit was developed to assess the construction safety risk and determine the risk level. In this model, the best-worst method and the entropy weight method were used as subjective and objective evaluation methods, respectively. The theory based on the idea of the distance function was applied to the model to calculate the combined weight value. The results showed that the three evaluation objects with the highest risk value were the air compression station plant, regional control room, and hazardous and solid waste temporary repository. The risk values of these three buildings were 2.2557, 2.2160, and 2.1654, respectively, and the corresponding risk level was high. On-site safety managers should take immediate measures in these high-risk buildings to reduce the possibility of accidents. This study is a new attempt to consider the construction safety risk of the new chemical project. [ABSTRACT FROM AUTHOR]

In recent years, fire accidents have occurred frequently in crowded places. The railway passenger station is one of the typical crowded places. Once fire occurs, the consequences will be unimaginable. Therefore, it is of great practical significance to conduct in-depth research on fire safety of railway passenger stations. In order to evaluate the fire risk of railway passenger stations, a risk assessment model based on DEMATEL-entropy weight method combined with extension cloud theory is proposed. Firstly, three railway passenger stations in city M are selected as fire risk assessment objects. Based on the identification of risk factors and expert consultation, a risk assessment index system is established. Secondly, the combination weighting method is used to calculate the comprehensive weight, and experts are invited to score the risk assessment indicators. Finally, in order to eliminate subjective and objective errors and increase the randomness of assessment, the extension cloud theory is introduced to determine the fire risk value. The expected value and entropy of fuzzy grade feature are obtained by repeated calculation of the evaluation process. The confidence factor is set up and the model of risk value is established. The results show that: the expected value and entropy of fuzzy grade are 1.782 2 and 0.015 9 respectively, and the comprehensive risk level of fire is low. The confidence factor is 0.008 9, located in the confidence interval, and the result is credible. This conclusion provides a new idea and method for fire risk assessment of railway passenger stations. [ABSTRACT FROM AUTHOR]

As oil spills cause harm to the survival and environment of the ocean, the objective of the present paper is to study the oil migration range using the key indicator kv, which is defined as the ratio of oil spill speed to ocean current speed. The correctness of diffusion models created and estimated for subsea oil spills can be verified by experiments. We also considered the effect of key indicators on the horizontal and vertical dispersion ranges of oil spills. The study's findings show that, under various kv settings, the horizontal and vertical spreading heights of oil spills both increase as kv rises. When kv is equal, the leakage velocity and water flow velocity increase synchronously, and over time, the horizontal distance and vertical diffusion height of the oil spill gradually increase. In the early stages of an oil spill, when kv = 50, 100, or 150, the vertical spreading velocity will rapidly decrease. The vertical spreading speed of spilled oil increases as kv rises when the water flow rate remains constant. The horizontal migration distance grows as kv decreases when the leakage rate is constant. Fitting curves for the vertical rise height and horizontal spreading distance for the same and various kv settings were also obtained in order to anticipate the migration mode of oil spills. This is critical for dealing with environmental damage caused by maritime oil spills, as well as emergency responses. [ABSTRACT FROM AUTHOR]

To solve the difficult problem of low-frequency noise processing in pipeline infrasonic leakage detection signals, a pipeline infrasonic leakage signal denoising method based on improved Prony algorithm and differential energy model was proposed to reduce the low-frequency interference noise in the signal and to improve the signal denoising effect. First, the frequency window of the effective signal is obtained according to the spectrogram of the infrasound signal. Aiming at the problem that the Prony algorithm is affected by noise, a difference energy model is proposed. The difference energy model is used to filter out the part of the frequency domain signal with large energy fluctuation, and a relatively stable preprocessing signal is obtained. In view of the instability of the traditional Prony algorithm, a Hankel matrix is established in the operation process. The stability is improved by extracting the extremum and residue of the signal instead of directly solving the sampling data points, and the extremum and residue of the effective signal are selected by combining the frequency window of the active ingredient. Finally, the effective signal is reconstructed to obtain a relatively stable infrasound leakage noise reduction signal. Experimental results show that the noise reduction technology based on the improved Prony algorithm and differential energy model can effectively reduce the noise of pipeline leakage signals. Compared with the traditional Prony algorithm, the noise reduction effect of the proposed method is up to 38.01% higher. Compared with the empirical mode decomposition method, the noise reduction effect of this method is improved by 9.25% at least, which opens up a new idea for pipeline leakage signal noise reduction. [ABSTRACT FROM AUTHOR]

A method of urban pipeline leakage infrasound signal processing based on spectrum analysis is proposed in order to address the issues of low recognition rate of infrasound signal of urban nonmetallic pipeline leakage and the existence of false signal interference, which results in low accuracy of pipeline leakage location. Firstly, the frequency spectrum of leakage and nonleakage signals is analyzed on the basis of a large number of tests, and the frequency spectrum characteristics and leakage judgment criteria of urban nonmetallic pipeline infrasound leakage signals are summarized. Secondly, the improved complementary ensemble empirical mode decomposition (ICEEMD) method is used to decompose the infrasonic leakage signal into the effective signal component and noise signal component to remove the false signal. Finally, the fine composite multiscale entropy algorithm is used to screen and reconstruct the entropy value of each signal component to extract effective and pure infrasonic leakage signal data. The experimental application demonstrated that the proposed method's signal-to-noise ratio (SNR) increased from 13 to 25 dB and its average root-mean square error (RMSE) decreased from 24.82% to 3.39%. This significantly increases the accuracy of the identification of infrasound signals of urban nonmetallic pipeline leakage and provides a basis for pipeline leakage location. [ABSTRACT FROM AUTHOR]

With the rapid development of high-pressure combustible gas pipelines, it brings convenience and also buries potential safety hazards. This paper presents an in-depth exploration of the thermal radiation hazards of fireball accidents caused by leakage and provides a reference for the prevention and control of this type of accident and on-site rescue. Based on the basic principle of fluid mechanics and the calculation model of the leakage rate, a three-dimensional pipeline model was constructed by FDS software to simulate the fireballs with different positions of low, middle and high. The simulation shows that the ground temperature field of the low and middle fireballs is quite different from that of the high fireball, and the temperature level is: low position > middle position > high position. On this basis, the observation elevation angle is introduced to improve the classical fireball thermal radiation model formula, the model calculation value is compared with the numerical simulation value and the optimal threshold is determined by combining the thermal radiation flux criterion. The results show that the numerical simulation is basically consistent with the calculation results of the improved model. The smaller the observation elevation angle, the closer the target receives the thermal radiation flux to the optimal threshold and the calculated hazard range is more reliable. [ABSTRACT FROM AUTHOR]

The combination of multifunctional micromagnetic testing and neural network-based prediction models is a promising way of nondestructive and quantitative measurement of steel surface hardness. Current studies mainly focused on improving the prediction accuracy of intelligent models, but the unavoidable and random uncertainties related to instruments were seldom explored. The robustness of the prediction model considering the repeatability of instruments was seldom discussed. In this work, a self-developed multifunctional micromagnetic instrument was employed to perform the repeatability test with Cr12MoV steel. The repeatability of the instrument in measuring multiple magnetic features under both static and dynamic conditions was evaluated. The magnetic features for establishing the prediction model were selected based on the consideration of both the repeatability of the instrument and the ability of magnetic features in surface hardness evaluation. To improve the robustness of the model in surface hardness prediction, a modelling strategy considering the repeatability of the instrument was proposed. Through removing partial magnetic features with higher mean impact values from input nodes, robust evaluation of surface hardness in Cr12MoV steel was realized with the multifunctional micromagnetic instrument. [ABSTRACT FROM AUTHOR]

The correlation between multiple patterns of micromagnetic signatures and the surface hardness of three types of carbon steels (referred as Cr12MoV steel, 45 steel, and martensitic stainless steel of 3Cr13 in Chinese standards) was investigated in this study. Back-propagation neural network (BP-NN) models were established for the quantitative prediction of surface hardness in carbon steels. The quality of the specimens used for calibration (or more precisely the data distribution of the target properties) greatly affected the accuracy of prediction models. The uniformly distributed data were more suitable for establishing high-accuracy BP-NN models. For the data which did not follow a uniform distribution, a two-step modelling strategy of classification and subsequent regression was proposed to improve the accuracy of micromagnetic and quantitative prediction of surface hardness. The proposed two-step modelling strategy integrating the K-nearest neighbor classification (KNN) algorithm with BP-NN modelling method was verified by external validation experiments. [ABSTRACT FROM AUTHOR]

The explosion of combustible gas is an urgent problem to be solved in production safety accidents. In this paper, the experiment of methanotroph degradation of CH4 and the experiment of the water mist containing methanotroph-inorganic salt inhibiting the methane explosion were carried out respectively based on a self-designed and built semi-closed small-scale experimental platform. We studied different volumes of the water mist containing methanotroph-inorganic salt to inhibit 5%, 8%, 9.5%, 12%, 15% methane explosion, and analyzed the relationship between time and relevant experimental parameters such as flame structure, flame average propagation velocity, maximum explosion overpressure, and average pressure rise rate, etc. The result showed that the water mist containing methanotroph-inorganic salt had a quite restrain effect on the methane explosion. At the same time, for first spray, when the degradation time is constant, with the increase of spraying volume, the explosion suppression effect is better. And when the spraying volume remains the same, the longer the degradation time is, the better the explosion suppression effect. As for the secondary spray, when spraying volume remains the same, the explosion suppression effect under the condition of Degradation with spray + explosion suppression with spray is superior to that of direct explosion suppression, whose reason is that the first spray mainly plays the biodegradation role of methanotroph, while the secondary spray mainly plays the physicochemical synergistic explosion inhibition role of the water mist containing methanotroph-inorganic salt. [ABSTRACT FROM AUTHOR]

With the rapid development of urban modernization, traffic congestion, travel delays, and other related inconveniences have become central features in people's daily lives. The development of subway transit systems has alleviated some of these problems. However, numerous underground subway stations lack adequate fire safety protections, and this can cause rescue difficulties in the event of fire. Once the fire occurs, there will be huge property losses and casualties. In addition, this can have a vicious impact on sustainable development. Therefore, in order to make prevention in advance and implement targeted measures, we should quantify the risk and calculate the fire risk value. In this study, through consulting experts and analysis of data obtained from Changzhou Railway Company and the Emergency Management Bureau, the fire risk index system of subway stations was determined. We calculated the index weight by selecting the combination weighting method of game theory to eliminate the limitations and dependence of subjective and objective evaluation methods. The idea of relative closeness degree in TOPSIS method iwas introduced to calculate the risk value of each subway station. Finally, the subway station risk value model was established, and the risk values for each subway station were calculated and sorted. According to expert advice and the literature review, we divided the risk level into five levels, very high; high; moderate; low and very low. The results shown that 2 subway stations on Line 1 have very high fire risk, 2 subway stations on Line 1 have high fire risk, 2 subway stations on Line 1 have moderate fire risk, 8 subway stations on Line 1 have low fire risk, and 13 subway stations on Line 1 have very low fire risk. We hope that through this evaluation model method and the results to bring some references for local rail companies. Meanwhile, this evaluation model method also promotes resilience and sustainability in social development. [ABSTRACT FROM AUTHOR]

Aiming at the difficulty of leak detection of urban hazardous chemical pipelines, this paper proposes a method for locating pipeline leaks based on the complementary ensemble local mean decomposition (CELMD) and maximum correlation kurtosis deconvolution (MCKD) secondary noise reduction. First, white noise with opposite sign was added to the original leak signal in pairs, and the noisy signal was decomposed to obtain a series of product functions (PF). Second, select the PF component containing the main leakage information according to the correlation coefficient, and perform the initial noise reduction. Then, the maximum correlation kurtosis deconvolution (MCKD) was used to perform secondary noise reduction on the filtered PF component; Finally, the PF component obtained after two screening was reconstructed, and the pipeline leakage location was completed by calculating the delay parameters of AE signal by cross-correlation. The experimental results show that compared with the cross-correlation method and the ELMD method, the method has higher recognition accuracy and positioning accuracy. [ABSTRACT FROM AUTHOR]

A physical model experiment of flume block landslide was used to study the influence of landslide surge impact on underwater pipeline surface under different water depths. The influence of surge impact pressure on pipelines with different water depths and the impact pressure of surge at different angles of underwater pipelines wall were analyzed. And the relationship between the maximum impact pressure of underwater pipelines and the depth of water was obtained. The results indicated that with the decrease of the water depths, the maximum impact pressure at the wall of the underwater pipeline increases approximately linearly, and the slider is easier to form higher first wave height. The maximum impact pressure of the upper surface of the pipeline wall is greater than that of the lower surface of the pipeline wall under the same working conditions. It is also found that the smaller the depth of water, the larger the maximum pressure and average pressure at the measuring point would be and the greater the pressure fluctuation becomes when slider volume and landslide water inlet angle and speed remain the same. [ABSTRACT FROM AUTHOR]

Pipeline leak detection has always been a relatively difficult technical problem; especially in urban pipeline leak detection, there are still many problems to be solved. A multipoint leak detection and location method for urban gas pipelines based on variational mode decomposition and relative entropy was proposed. Firstly, the experiment pipeline system was built, and the original signal was collected by acoustic emission technology; then, a variational model method was used to decompose the signal to obtain multiple intrinsic mode function (IMF) components with different characteristic scales. According to the characteristics of relative entropy, each component was analyzed, the appropriate IMF component was selected, and the selected component was reconstructed to obtain the observation signal. The multipoint leakage location model of the urban gas pipeline was established. The number of source signals was estimated by singular value decomposition, and the leakage signals were separated; finally, the accurate location of leakage point was achieved by cross-correlation positioning. The results showed that the average relative error of the pipeline leak location results is 2.97%, and the leak location accuracy is significantly improved, achieving the purpose of precise location. [ABSTRACT FROM AUTHOR]

Aiming at problems of multipoint leakage source detection and low positioning accuracy in urban gas pipelines, a multipoint leak location method base on improved variational mode decomposition (VMD) was proposed. By improving the VMD decomposition of the original leakage signal, the parameters of the VMD were optimized to reduce the influence of noise and weak correlation signals on the leak location. Then the multi-point leakage location model of pipeline was established, and the sensitive modal component Intrinsic mode function (IMF) with the most leakage information was selected by multiscale entropy. According to the characteristics of the blind source separation method, the relevant time delays of the simultaneous leakage of multiple points on the pipeline and the frequency of the signal are extracted. Finally, The location of the leak source is determined according to the principle of cross-correlation. The experimental results show that compared with the direct cross-correlation method and the VMD-based method, the proposed multipoint leak diagnosis method has less error, the minimum relative error is 1.61%, and the positioning accuracy is higher. [ABSTRACT FROM AUTHOR]

Aiming at the problems of early leakage monitoring of urban nonmetallic pipelines and the large positioning error, an inverse transient urban nonmetallic gas pipelines leakage location method based on Markov quantitative judgment was proposed. A Markov flow state transition probability matrix was established based on the flow data under different pressures obtained by experiments to quantitatively determine the pipeline leakage status. On this basis, an inverse transient leakage control equation suitable for urban nonmetallic gas pipeline leakage location was constructed according to the actual. The difference between the pressure and the calculated pressure was sought for the objective function. Finally, the objective function was optimized in conjunction with the sequential quadratic programming (SQP) method to obtain the actual leakage parameters and calculate the size and location of the leakage source. The results show that the inverse transient leakage localization method based on Markov's quantitative judgment can more accurately determine the leakage status of the pipeline and calculate the early leakage parameters and leakage location of the gas pipeline, which improves the positioning accuracy. [ABSTRACT FROM AUTHOR]

In order to improve the efficiency of β-CD, the inclusion complex of β-CD and resorcinol bisdiphenylphosphate (RDP) (β-CD@RDP) was prepared, which β-CD was as the host component and RDP was as the guest. The structure and thermal stability property of β-CD@RDP was also characterized. EP/β-CD@ RDP composites were prepared by adding β-CD@RDP into EP matrix. The results of thermogravimetric test showed that the flame retardant systems could effectively increase the corresponding temperature of EP matrix to reach the maximum thermal decomposition rate, and exhibited good char-forming property. When the amount of β-CD@RDP in EP was 20wt%, the limiting oxygen index (LOI) value of EP was increased to 26.5% from 19.8%, and the vertical burning test (UL-94) reached V-1 level. The cone calorimeter test indicated that 20wt% loading in EP could reduce the peak of heat release rate (PHRR) and the total heat release (THR) of EP by 94.7% and 93.4% respectively, and the peak of smoke production rate (PSPR) and the total smoke production (TSP) was reduced by 16.7% and 22.2%, respectively. Therefore, the addition of β-CD@RDP could reduce the fire risk of EP effectively. [ABSTRACT FROM AUTHOR]

The early multi-point leakage source signals of urban gas pipeline are weak and can be easily affected by environmental noise and signal interference between adjacent sources, which causes large leakage positioning error. In this paper, an integrated signal processing method combining VMD, BSS and Relative entropy for multi-point pipeline leakage signal and source positioning is presented. Firstly, VMD and Relative entropy were employed to obtain effective IMF mode components and their features during the decomposition for pipeline leakage signal. Relative entropy was used to improve signal-to-noise ratio and extract the features of leakage signal. Then, BSS was used to decompose multi-point mixed leakage signals so as to obtain independent signal components. Finally, the time difference and wave velocity were, respectively, obtained by calculating the time domain distribution of the independent signal components and the main modal guided wave, so the precise positioning of the pipeline leakage was realized. The results show that the combined method proposed can not only select and extract leakage signal adaptively but also separate single independent signal from multi-point mixed signal, which helps to locate pipeline multi-point leakage sources more accurately. [ABSTRACT FROM AUTHOR]

Bulk milky white Al2O3- SiO2 aerogels were prepared by sol-gel process after aging and ambient pressure drying with six water aluminum chloride (AlCl3 ⋅ 6H2O) and tetraethoxysilane (TEOS). Aerogels were calcined at different temperatures, and their properties were analyzed by SEM. TEM. XRD, BET. TG and FT-TR. The results show that Al2O3- SiO2aerogels had good thermal stability. Si(X was amorphous m aerogels, and Al2O3 existed in needle-like or long strip boehmite (y-AlOOH). After calcination at 600-1 000 °C, AUO:! transformed into y-AUO:!. When the calcination temperature reached 1 200 X., mullite phase formed by Al2 O3 and SiO2. which inhibited the conversion of y-Al2O3 to α-Al2O3. At room temperature, the specific surface area of aerogel was 692.7 m²/g, the distribution of pores was more homogeneous and porosity was higher. With the increase of calcination temperature, the specific surface area and pore volume gradually decreased, but the pore size increased gradually. When the calcination temperature reached 1 200 °C, the specific surface area of aerogel was still 67.3 m°/g. [ABSTRACT FROM AUTHOR]

NiFe2O4 nanoparticles loaded on graphene layers (NiFe2O4@GR) were prepared by the hydrothermal method, and they first combined with intumescent flame retardant (IFR) consisting of polyphosphate (APP) and pentaerythritol (PER) was used to prepare poly(lactic acid) (PLA) composites. Effect of NiFe2O4@GR and IFR on thermal stability and flame retardancy of PLA was investigated. Limit oxygen index (LOI) value of all the PLA composites increased, and the results of UL‐94 tests passed V0 ratings. With the presence of NiFe2O4@GR in intumescent flame‐retarded PLA composites, the initial degradation temperature had a big increase and char residue increased apparently. The ratio of graphite crystalline carbon was increased. The denser and more intumescent char layer was formed. In addition, NiFe2O4@GR had the reinforcing effect for PLA. Therefore, NiFe2O4@GR and IFR had a good synergistic effect in improving thermal stability and flame retardancy of PLA. POLYM. COMPOS., 40:652–656, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In order to study the oxidation capacity of methanotrophs, methanotrophs bacteria solution was used to adsorb and oxidise methane under certain conditions. The experimental results showed that the reduction of CH4 is related to the adsorption and oxidation of methanotrophs bacteria in the coal sample. The formation of CO2 is the result of oxidation metabolism of methanotrophs bacteria. When the methane pressure was 6 MPa and the amount of methanotrophs bacteria solution 14.5%, the reduction of methane in the mixed gas could reach 124.6%. It indicated that neither in aerobic condition nor in anaerobic condition, methanotrophs bacteria solution could oxidise methane. The adsorption and oxidation effect would increase with the amount of methanotrophs bacteria and pressure. The existence of oxygen could promote the adsorption and utilisation of methane. [ABSTRACT FROM AUTHOR]

The mechanism of methane generation and oxidation process was investigated by using the fluorescence in situ hybridisation technique. The amounts of methanogens and methanotrophs were analysed in the soil in a plant-soil ecological system. The result showed that methane generation and oxidation were closely related to the distribution of methanogens and methanotrophs. The methanotrophs were mainly concentrated in the plant rhizosphere, and the amount of methanogens were higher than that of methanotrophs in the soil. Temperature fluctuation and oxidation-reduction potential (ORP) greatly affected the methane generation and oxidation process in the plant-soil ecological system. The methane emissions demonstrated the methane generation and oxidation process directly. The annual average amount of methane emissions was 26.3 mg/(m2h). The methane emissions peak occurred in the summer and was up to 194.2 mg/m2 h). [ABSTRACT FROM AUTHOR]

The MSWI fly ash which contains a large number of heavy metal substances is a subsidiary product of waste incineration power generation technology. If the MSWI fly ash is disposed improperly, heavy metal pollutants will pose a great threat to environmental safety and human health. Based on the technology of electrokinetic remediation, the feasibility of removing heavy metal pollutants from the MSWI fly ash using a modified electrokinetic remediation device - cylinder device was evaluated in this study. Differing from the traditional cuboid device with the volume ratio of the cathode chamber to the anode chamber being 1:1, the volume ratio of the cathode chamber to the anode chamber of the cylinder device was 16:1. Changes in parameters, such as pH values and conductivity in the cathode and the anode chambers as well as current and voltage in the sample area were analysed under the voltage gradient of 2 V/cm. After the experiment, the average removal efficiencies for Zn, Pb, Cd and Cu in the sample area were 53.2%, 31.4%, 42.3% and 30.7%, respectively. It indicates that the cylinder device is effective in removing heavy metals from the MSWI fly ash. Adopting the cylinder device for the experimental study on the electrokinetic remediation technology could provide a better way of thinking for the future engineering practices and applications. [ABSTRACT FROM AUTHOR]