Search

Commercial complexes integrate various business formats, and a fire outbreak can lead to widespread, continuous, and chain-reaction social disturbances, including severe casualties, economic losses, and social impacts. To deeply explore the characteristics and influencing factors of fire accidents in urban commercial complexes in China, this study first analyzed fire accident cases in commercial complexes that occurred from 2002 to 2022. Using mathematical statistics, the analysis examined the year and month of the accidents, their severity, and their causes to identify key risk factors associated with fire hazards in urban commercial complexes. Subsequently, based on the WSR methodology, an index system for assessing the influencing factors of fire accidents in commercial complexes was constructed, encompassing four aspects: personnel, equipment, environment, and management, including 11 cause indicators and 9 outcome indicators. Then, the Decision Experiment and Evaluation Laboratory Method (DEMATEL) was used to quantitatively analyze the relationships among influencing factors, combined with Interpretative Structural Modeling (ISM) to perform a hierarchical categorization of the factors and identify those critically influencing commercial complex fires. This research indicates that critical influencing factors include inadequate regulations, insufficient fire safety inspections, inadequate safety training, careless use of fire during operations, inadequate government supervision, illegal renovations, unimplemented corporate fire safety responsibilities, and poor routine maintenance and management. These results provide a theoretical reference for effectively preventing and controlling fires in commercial complexes. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an efficient and high-precision process for fabricating large-area microlens arrays using thermal reflow combined with ICP etching. When the temperature rises above the glass transition temperature, the polymer cylinder will reflow into a smooth hemisphere due to the surface tension effect. The dimensional differences generated after reflow can be corrected using etching selectivity in the following ICP etching process, which transfers the microstructure on the photoresist to the substrate. The volume variation before and after reflow, as well as the effect of etching selectivity using process parameters, such as RF power and gas flow, were explored. Due to the surface tension effect and the simultaneous molding of all microlens units, machining a 3.84 × 3.84 mm2 silicon microlens array required only 3 min of reflow and 15 min of ICP etching with an extremely low average surface roughness Sa of 1.2 nm. [ABSTRACT FROM AUTHOR]

The simple solution and aging treatment processes were adopted to rejuvenate the microstructure of creep damaged DZ411 superalloy. The microstructure evolution of superalloy during rejuvenation process was investigated by OM and SEM, and then the mechanical properties were evaluated by tensile and creep rupture tests. The results show that creep damaged superalloy obtained from interrupted test at the end of secondary stage of creep suffers from the spheroidization and rafting of the prime γ′ phase and vanishing of the secondary γ′ phase, but no creep cavities. It is also found that the solution treatment plays a prime role in dissolution of deformed γ′ phase, and then re-precipitation of fine γ′ phase. The proper solution temperature can effectively avoid incipient melting and recrystallization. The two stages of aging are the dominant procedures of optimizing the size, shape and volume ratio of bimodal size γ′ phase. By the appropriate rejuvenation schedule, the bimodal size γ′ particles with coarse secondary γ′ particles and fine tertiary γ′ particles can be obtained. The average diameters of bimodal size γ′ particles are about 0.38 μm and 0.07 μm, and the volume fraction are 47.5% and 6.5% respectively. Rejuvenation heat treatment can successfully recover the room temperature strength close to that of the original alloy. The creep rupture life and elongation of rejuvenated DZ411 superalloy under condition of 980 ℃/220 MPa are 121 h and 13%, these values are slightly lower than that of the original alloy.

In this study, to comprehensively reveal the damage mechanisms of NiTi alloys, molecular dynamics (MD) simulations were applied to examine the void evolution process under uniaxial and triaxial intensive dynamic loading. A single-crystal model was first used in the MD simulations. The calculation results revealed that the single-crystal NiTi model exhibited a similar damage response to brittle fracture. The corresponding damage mechanism was the rapid growth and coalescence of voids inside the material. Meanwhile, the defect influence was also examined for the single-crystal model, and the reduction effect of the ultimate stress value due to the stress concentration was analyzed quantitatively by the MD simulations. In addition, a polycrystalline model of NiTi was used in the MD simulations. Compared with the single-crystal model, the polycrystalline model showed an evident plastic stage under uniaxial loading due to dislocation slip. The MD simulation proved that the dislocations accumulated on the grain boundaries, which led to a stress concentration effect on the grain boundaries and sequentially resulted in void generation. However, the propagation and coalescence of voids were hindered by the grain interactions, which resulted in a ductile damage behavior inside the material. Based on this mechanism, the grain size influence was also studied in the MD simulations. It was discovered that the grain size effect in the damage stage resulted in a damage ductility enhancement with the decrease in the average grain size value. Finally, based on the relationships between the stress-strain curve, void fraction, and damage behavior, novel constitutive and state equations were proposed with damage terms to consider the void evolution process during the damage stage. The prediction results showed good agreement with the MD simulation data. [ABSTRACT FROM AUTHOR]

There were contradictory results about the effect of particle size on coal combustion during thermogravimetric (TG) experiments in previous reported papers. For the ascertainment of the actual role of particle size, three samples of group A coal from Huainan Mining area with a range of 60–100 mesh, 100–200 mesh, and less than 200 mesh, respectively, were prepared. They were characterized by proximate analysis, ultimate analysis, and TG experiments with different heating rates (5, 10, 20, and 40°C/min). The proximate and ultimate analyses indicated that group A coal has a characteristic with ultra-low content of moisture, extremely low content of ash, medium-high content of volatiles, and special low content of total sulfur. TG results showed that the whole combustion process of group A coal can be divided into four typical stages and includes seven characteristic temperatures. Based on TG results, the kinetic parameter of the combustion reaction was analyzed using Coast-Rdefern and Flynn-Wall-Ozawa methods. It showed that the group A coal is belonged to the easy spontaneous combustion coal seam, and the tendency of spontaneous combustion increases with a decrease in particle size in the whole range. [ABSTRACT FROM AUTHOR]

Simple Summary: Weaning is a critical stage in a piglet's life, and the transition from milk to solid feed after weaning is a challenge to the digestive and metabolic capacity of piglets, resulting in lower feed intake and growth rate as well as a higher incidence of post-weaning diarrhoea. Thus, many functional additives have been used as alternatives to antibiotics to improve the health and welfare of piglets since the ban on the use of antibiotic growth promoters in livestock. Plant-derived natural polysaccharides have great potential to replace antibiotic additives. In the field of natural substances, polysaccharides from seaweed species such as kelp are some of the bioactive molecules that have been investigated as feed supplements with positive effects on animal health parameters, which are important for animal nutrition. Bioactive compounds are recognized as attractive dietary interventions for pigs to improve their intestinal health and reduce the incidence of intestinal diseases. Laminaria japonica polysaccharides, as one of them, have prebiotic, anti-microbial, antioxidant, anti-inflammatory and immunomodulatory effects. The aim of this study was to test the hypothesis that the addition of appropriate levels of LJP to the diets of weaned piglets would positively modulate their growth performance, faecal digestive enzyme activity, and serum amino acid content. In this study, we observed that Laminaria japonica polysaccharides could improve growth performance and faecal digestive enzyme activities in weaned piglets. The aim of this experiment was to investigate the effect of Laminaria japonica polysaccharide (LJP) supplementation at levels of 100, 200, or 400 mg/kg on the growth performance, faecal digestive enzyme activity, and serum biochemistry and amino acids of weaned piglets. One hundred and twenty weaned piglets (Barkshire × Licha Black, 21 days old, 6.13 ± 0.16 kg) were randomly divided into four groups with five replicates of six piglets in each group based on body weight. Piglets were fed with different levels (0, 100, 200, and 400 mg/kg) of LJP for a 21-day trial. On day 21, faecal and blood samples were collected from one piglet per pen. The results showed that the supplementation of the 200 and 400 mg/kg LJP significantly increased average daily gain (ADG) and average daily feed intake (ADFI) compared to the control group (p = 0.007; p = 0.002), and dietary LJP linearly increased ADG and ADFI (p = 0.002; p < 0.001). In addition, the supplementation of the 200 and 400 mg/kg LJP significantly increased faecal amylase activity (p < 0.001) compared to the control group, and dietary LJP linearly increased faecal amylase and lipase activities (p = 0.001; p = 0.037). Moreover, dietary LJP at 400 mg/kg increased serum histidine content compared to the other groups (p = 0.002), and dietary LJP linearly increased the contents of serum histidine and asparagine in piglets (p < 0.001; p = 0.046). In conclusion, supplementation of 200 and 400 mg/kg LJP could enhance growth performance and faecal digestive enzyme activity and modulate the serum amino acid content of weaned piglets, potentially contributing to the health of weaned piglets. [ABSTRACT FROM AUTHOR]

This work established a two-dimensional mathematical model to evaluate the thermofluidynamic behavior of a newly developed double-layered cylindrical ZrCo-based hydride bed during the hydrogenation reaction process. Numerical simulations by using COMSOL Multiphysics were conducted to solve the governing partial differential equations associated with chemical reaction and thermal transfer. Importantly, the local thermal nonequilibrium theory was applied to analyze the heat transfer between the ZrCo particle and hydrogen. Detailed analysis revealed the effects of operating conditions, material thermophysical properties, and the bed configuration, in addition to the ZrCo hydride particle sizes on hydrogen recovery characteristics. The simulation results indicated that increasing the heat transfer coefficient, reducing the coolant temperature, improving the thermal conductivity of the metal hydride, using the thinner hydride layer, and being equipped with copper fins were more beneficial to accelerate the heat transfer rate and the hydrogen charging rate of the metal hydride bed (MHB). Furthermore, along the radial direction, tremendous temperature gradient and distribution of absorbed hydrogen were found in the hydrogenated zones. The present model can effectively characterize the reaction kinetic mechanisms of ZrCo hydriding process as to further promote the practical application of the proposed MHB designs. [ABSTRACT FROM AUTHOR]

Hydrogen-terminated diamond surfaces, emerging as a promising two-dimensional (2D) electron platform with great thermal and electronic properties, hold great potential for the next-generation high power and high frequency field effect transistor (FET). However, ideal gate dielectrics with high crystallinity and defect-free surfaces are still largely elusive. In this work, using the contamination-free pickup transfer method, hexagonal boron nitride (h-BN) flakes were fabricated on top of the hydrogen-terminated diamond surface to serve as a gate material and the passivation layer. The morphological and optical characterizations revealed the formation of homogeneous and intimate interface between h-BN and diamond. Benefiting from the h-BN gate dielectric layer, the maximum drain current density, subthreshold swing, and on/off ratio of diamond FET are measured to be −210.3 mA mm−1, 161 mV/dec, and 106, respectively. Especially, the transport measurement shows an almost constant Hall mobility of around 260 cm2 V−1 s−1 in the hole density range of 2 − 6 × 1012 cm−2, suggesting the excellent gate controllability of h-BN. Our results indicate that h-BN could form high-quality interface with hydrogen-terminated diamond, paving the way for the development of diamond-based electronic applications. [ABSTRACT FROM AUTHOR]