Search

Natural gas pipeline construction is developing rapidly worldwide to meet the needs of international and do-mestic energy transportation. Meanwhile, leakage accidents occur to natural gas pipelines frequently due to mechanical failure, personal operation errors, etc., and induce huge economic property loss, environmental damages, and even casualties. However, few models have been developed to describe the evolution process of natural gas pipeline leakage accidents (NGPLA) and assess their corresponding consequences and influencing factors quantitatively. Therefore, this study aims to propose a comprehensive risk analysis model, named EDIB (ET-DEMATEL-ISM-BN) model, which can be employed to analyze the accident evolution process of NGPLA and conduct probabilistic risk assessments of NGPLA with the consideration of multiple influencing factors. In the proposed integrated model, event tree analysis (ET) is employed to analyze the evolution process of NGPLA before the influencing factors of accident evolution can be identified with the help of accident reports. Then, the combination of DEMATEL (Decision-making Trial and Evaluation Laboratory) and ISM (Interpretative Structural Modeling) is used to determine the relationship among accident evolution events of NGPLA and obtain a hier-archical network, which can be employed to support the construction of a Bayesian network (BN) model. The prior conditional probabilities of the BN model were determined based on the data analysis of 773 accident reports or expert judgment with the help of the Dempster-Shafer evidence theory. Finally, the developed BN model was used to conduct accident evolution scenario analysis and influencing factor sensitivity analysis with respect to secondary accidents (fire, vapor cloud explosion, and asphyxia or poisoning). The results show that ignition is the most critical influencing factor leading to secondary accidents. The occurrence time and occur-rence location of NGPLA mainly affect the efficiency of emergency response and further influence the accident consequence. Meanwhile, the weight ranking of economic loss, environmental influence, and casualties on social influence is determined with respect to NGPLAs.

Many construction accidents occur in China each year, leading to a large number of deaths, injures, and property losses. Due to the outbreak of COVID-19, little attention is paid to construction safety, resulting in severe accidents. To prevent construction accidents and learn to how address safety issues in future pandemics, this study proposed an improved STAMP (Systems Theoretic Accident Modeling and Processes) model to analyze the collapse accident of the Xinjia Express Hotel used for COVID-19 quarantine in China. Through the application of the STAMP approach, the causes of the construction accident and the relationship between various causal factors are analyzed from a systematic perspective. The identified causes are divided into five categories: contractors, management of organizations, technical methods, participants, and interactive feedback. Finally, safety recommendations are drawn from this study to improve construction safety and safety management in pandemics.

To objectively grasp the current situation and development trend of resilient cities or communities (RC) research. The articles in Web of Science (WOS) Core Collection databases from 1995 to 2022 were used as a sample, and bibliometrics was used to statistically analyze the year of publication and number of articles, highly cited documents and keyword hotness in this field. VOSviewer was used to explore the knowledge graph of RC research documents. The results show that: the development process is roughly divided into 3 periods: no attention (1995–2004), starting (2005–2014), and rapid growth (2015–2021). The journal “Sustainability” and “International journal of disaster risk reduction” are the key journals publishing RC research. Serre and Shaw are the most productive authors. The USA is still the leading country in this field of RC. Colorado State Univ, Texas a&m Univ, and Delft Univ Technol are the main research institutions. The keyword analysis indicates the hot topics in different periods. Moreover, several limitations and some recommendations for future research on RC are also given based on this.

The aims of this paper are to reveal the surface failure behavior of 70Mn martensite steel under abrasive impact wear by impart wear tests. The wear tests were performed with the MLD-10 abrasive wear testing machine, using SiO 2 abrasive with three different impact loads for 30000 cycles. Worn surfaces and white-etching layers (WEL) were analyzed by scanning electron microscopy, x-ray diffraction and transmission electron microscopy, and the abrasive impact wear mechanism was analyzed. Strain-hardening effects beneath the contact surfaces were researched by Micro-hardness profiles. Results indicated that the main formation mechanism of white-etching layers (WEL) in test steel were the formation of twin martensite and accumulation of dislocations attributing to plastic deformation during impact wear tests. The thickness and hardness of WEL were both increased with test load, which led to an increased brittleness of WEL. Under the effects of impact load, the micro-cracks initiated at subsurface and extended to surface, eventually led to delamination and fracture. Therefore, the delamination and fracture resulting from plastic deformation fatigue were the primary surface failure mechanism of the steel at abrasive impact wear.

The hot deformation and dynamic recrystallization (DRX) behavior of austenite-based Fe–27Mn–11.5Al–0.95C steel with a density of 6.55 g cm−3 were investigated by compressive deformation at the temperature range of 900–1150 °C and strain rate of 0.01–10 s−1. Typical DRX behavior was observed under chosen deformation conditions and yield-point-elongation-like effect caused by DRX of δ-ferrite. The flow stress characteristics were determined by DRX of the δ-ferrite at early stage and the austenite at later stage, respectively. On the basis of hyperbolic sine function and linear fitting, the calculated thermal activation energy for the experimental steel was 294.204 kJ mol−1. The occurrence of DRX for both the austenite and the δ-ferrite was estimated and plotted by related Zener–Hollomon equations. A DRX kinetic model of the steel was established by flow stress and peak strain without considering dynamic recovery and δ-ferrite DRX. The effects of deformation temperature and strain rate on DRX volume fraction were discussed in detail. Increasing deformation temperature or strain rate contributes to DRX of both the austenite and the δ-ferrite, whereas a lower strain rate leads to the austenite grains growth and the δ-ferrite evolution, from banded to island-like structure.

The microstructure evolution and tensile properties of the Fe–10Mn–10Al–0.7C low-density steel annealed at the temperature range from 700 °C to 1200 °C for 1 h were investigated in the present study. The phases in the annealed specimens mainly included ferrite (α), austenite (γ) and κ-carbide (κ). The dissolution temperature for κ-carbide is between 850 °C and 900 °C. At the annealing temperature of 700 °C, all the γ phase transformed to α phase and κ-carbide by eutectoid reaction. As the annealing temperature rose from 700 °C to 900 °C, α phase and κ-carbide fraction decreased and γ phase fraction increased, and ultimate elongation increased, while ultimate strength and yield strength had a decreasing trend. The γ phase fraction in the specimen dominated the ultimate elongation, and the κ-carbide strengthened the specimen and weakened ductility. As the annealing temperature rose from 900 °C to 1200 °C, the phase fraction change was small but the grain size increased greatly. The rapid growth of the grains was the main reason why ultimate tensile strength and ultimate elongation decreased with the increase of annealing temperature over 900 °C. The steel designed here possessed a density of 6.80 g/cm3, which is about 13% lower than pure iron. Keywords: Low-density steel, Annealing, κ-Carbide, Tensile properties

In situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were performed on the duplex Fe–27Mn–11.5Al–0.95C steel at room temperature to examine the tensile deformation behavior. The steel consisting of stable austenite matrix and a small amount of ferrite exhibited excellent combination of high strength and ductility (46.5 GPa%) in solid solution state due to the continuous strain hardening behavior. In situ SEM revealed that slip bands appeared in the austenite grain at the early deformation stage, and different slip systems intersected with higher density as the displacement increased. The deformation strains of austenite were obviously larger than that of ferrite, which resulted into the ferrite crack propagation at the later stage. With the stack fault energy (SFE) of ∼80 mJ/m2, the evolution of dislocation substructure with increasing strain shows typical planar glide characteristics, namely, dislocation pile-ups, Taylor lattice, high density dislocation walls, domain boundary and intersected microbands. Grain subdivision by microband intersection at high strains results in stable work hardening rate and continuous strain hardening behavior.

The dry impact wear behavior of bainite ductile cast iron was evaluated under three different impact loads for 30000 cycles. The strain-hardening effects beneath the contact surfaces were analyzed according to the surfaces’ micro-hardness profiles. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the worn surfaces. The results indicated that the material with the highest hardness was the one continuously cooled at 20°C, which exhibited the lowest wear rate under each set of test conditions. The hardness of the worn surface and the thickness of the hardened layer increased with the increases in impact load and in the number of test cycles. The better wear performance of the sample cooled at 20°C is attributed to its finer microstructure and superior mechanical properties. All the samples underwent the transformation induced plasticity (TRIP) phenomenon after impact wear, as revealed by the fact that small amounts of retained austenite were detected by XRD.

Precipitation hardening stainless steel has the advantages of both austenitic stainless steel and martensitic stainless steel, including good corrosion resistance, excellent processability and high strength. With the evolution of microstructure and properties of semi-austenitic precipitation hardening stainless steel (D631) during drawing process and aging treatment, the working hardening behaviors, law of phase transition, dissolution and precipitation state of alloying element are investigated to gain the toughness mechanism of D631. The results show that the tensile strength increases with the increase of the reduction of area, on the contrary, the plasticity decreases gradually. The tensile strength is 1529 MPa while the reduction of area is 54%. By means of X-ray diffraction (XRD) and metallograpic observation, the content of martensite increases with the increase of deformation, and makes the higher strength and lower plasticity. The alloying element dissolved in the matrix precipitates in fine particles by aging treatment, resulting in a higher strength of 1948MPa.

Objective To evaluate the safety and immunogenicity of the therapeutic dual-plasmid HBV DNA vaccine mediated by electroporation (EP) in vivo against the hepatitis B virus in healthy adult volunteers. Methods The enrolled 30 healthy volunteers were randomly divided into three dosage groups (10 volunteers in each group), namely: high-dose (4mg), middle-dose (2mg) and low-dose (1mg) groups. Volunteers received four intramuscular injections of HBV DNA vaccine mediated by in vivo EP at the 0, 4th, 12th and 24th week. Each dose group was further divided into 2 sub-groups (5 persons/per group) with different EP frequencies, i.e. 36 and 60 volt. The changes in response was determined by physical diagnosis (ECG, chest X-ray, type-B ultrasound), lab findings (blood and urine routine, blood biochemistry, prothrombin time, thyroid function, tumor biomarkers), immunological variables (IFN-γ, ANA, anti-dsDNA Ab), serological variables pertaining to HBV (HBsAg, HBcAb, HBeAg, HBeAb, HBV DNA) and serum anti-HBs status in volunteers before and after receiving EP mediated HBV DNA vaccination. Results The dual-plasmid HBV DNA vaccination mediated by in vivo EP was well tolerated in all healthy volunteers with a stable life signs. It was found that EP-mediated immunization of the therapeutic DNA vaccine against hepatitis B virus had a specific and obvious anti-HBs humoral immune response in one volunteer (17.22mU/ml). Four repeated intramuscular injections of the vaccine did not show any significant adverse effects in the receptors. Although mild elevation of serum ALT and enlarged spleen were found in one individual, the abnormalities disappeared spontaneously at the end of the trial. Conclusions EP-mediated dual-plasmid HBV DNA vaccine is safe and well tolerated with certain degree of humoral immunogenicity.

Based on the analysis of whole mining process in metal mines, it was pointed out that the investigation of the heavy metal pollution of tailings should be taken as an important project for a metal mine. Combined with the anlysis of the characteristics of tailings, it is found that the transformation of the heavy metal dissolution process, the heavy metal ions migration with groundwater and the heavy metal transport in porous media are three key aspects. Accordingly, the models of heavy metal pollution were established with providing boundary conditions. Depending upon a case of Tonglushan Copper Mine tailings and its relevant area from Google maps’, a three-dimensional grid view of the tailings was set up. By application of Fluent software, the contaminated process of the heavy metal pollutants in the tailings was shown through digital visualization pattern.

The samples were pretreated by controlling PH in the process of Pechini, and after sintering and grind, the nano Eu-doped tungstate with different granularity was obtained in the result. The structure was characterized by XRD, and the diffuse scattering spectra and the crystal microstructure were characterized by HRTEM and spectrometer. It was found from high efficient decomposition of rhodamine that the nano-materials obtained have good catalytic effect of light.

Objective To establish the hepatitis B virus(HBV) transgenic mice with YMDD mutation,and provide an animal model for research of HBV prevention and therapeutic approach.Methods 1.3 copies HBV genome containing YMDD mutation associated with lamivudine resistance was injected into the zygote of FVB/N female mice by microinjection.Integration and passage of exogenous gene in transgenic mice was confirmed by PCR.The expression of HBsAg in liver and kidney tissues in transgenic mice was identified by ELISA and immunohistochemistry.Results A total of 3401 zygotes were injected and 269 F0 pups were born.PCR analysis indicated that 33 out of 269 pups were positive,and the integrating rate of exogenous gene was 12.3% in F0.Fluorescent quantitative PCR showed that HBV DNA was weakly positive in serum samples in 9 transgenic mice,less than 103copies/ml.The expression of HBsAg in transgenic mice was observed in liver and kidney tissues by immunohistochemistry,and it was higher in kidney than in liver.The target gene was detected by PCR in 27.6% of 47 F1 offsprings.The expression of HBsAg could be observed in liver and kidney tissues in F1,which was similar to that in F0.Conclusion 1.3 copies HBV transgenic mice model containing YMDD mutation associated with lamivudine resistance is successfully produced by microinjection,and HBsAg expression can be transmitted through germline cells.