The mechanisms involved in premixed magnesium and hydrogen hybrid and synthetic MgH2 dust cloud explosions were investigated. The results revealed that trace amounts of H2 in Mg explosions can ...markedly increase explosion severity. Furthermore, H2 addition can weaken the influence of oxygen deficiency on Mg explosion. Moreover, the explosion intensity of synthetic MgH2 was far stronger than that of premixed Mg/H2 mixture or Mg alone because the vacancy defects in Mg and H atoms can form after dehydrogenation of MgH2, which caused that Mg and H2 are prone to oxidation and nitrification in air atmosphere at a low temperature, thereby promoting the explosion. This demonstrates that the explosion risk of MgH2 (even other H2 storage materials) is related to its H2 storage capacity and dehydrogenation temperature. Therefore, for H2 storage materials, the better H2 storage performances can exhibit higher explosion risks.
Three types of self‐prepared chemical dust suppressants (CDSs) were investigated for their inhibitory effects on nitrocellulose (NC) cloud dust explosion. The results revealed that NC is extremely ...sensitive to electric sparks and has a high explosion intensity. CaCl2‐CDS effectively increased the particle size to control fly dust substantially inhibiting dust cloud explosions. However, both Na2SO4‐CDS and MgCl2‐CDS exhibited poor abilities and even promoted explosion. Therefore, neither Na2SO4‐CDS nor MgCl2‐CDS is recommended as a CDS for NC. Inappropriately using CDSs may engender severe explosions. Furthermore, a mechanism underlying NC dust cloud combustion and explosion was proposed. NC has three stages of heat release: autoxidation, thermal decomposition, and combustion. Thermal decomposition, combustion, and explosion were triggered depending on the energy provided from autoxidation. CaCl2‐CDS inhibited only combustion. This study reveals the mechanism underlying NC dust cloud explosions and provides useful information for the development of more optimized CDSs.
The primary function of fire detection is to detect fires and raise the alarm early. A detection algorithm is a key element of image fire detection (IFD) technology because it directly determines the ...IFD’s performance. In this study, an IFD algorithm based on the YOLOv3 network was developed to detect smoke and flame simultaneously. Subsequently, six improvements were applied to promote the algorithm’s ability to detect fire early. The results demonstrated that the modified YOLOv3 network achieved an average accuracy of 95%, which is 14.1% higher than that of the same model without modifications. The detection speed reached 22 Frames Per Second (FPS), which satisfies the requirements of real-time detection.
In the production of magnesium hydride, hybrid Mg/H2 mixtures has a risk of explosion; therefore, systematic experiments were conducted to study its explosion characteristics and suppression. ...According to the results, the maximum rate of explosion pressure rise (dP/dt)max of hybrid Mg/H2 mixtures was more the twice than that of pure Mg. Five common explosion suppressants were individually added to hybrid Mg/H2 mixtures to inhibit dust explosion. Na2CO3, CaCO3, and (NH4)2HPO3 exhibited great inhibitory abilities for hybrid Mg/H2 mixtures explosion; however, melamine–cyanurate acid (MCA) and melamine polyphosphate (MPP) could stimulate the explosion. The mechanisms underlying MCA and MPP promotion of the hybrid Mg/H2 mixtures explosion were determined, namely the high concentration of flammable gases, such as ammonia, released after their thermal decomposition. These gases can ignite and intensify the explosion of hybrid Mg/H2 mixtures. This study provides a reference for reducing the risk in the H2 storage system of Mg.
Display omitted
•Hybrid Mg/H2 dust explosion was more violent than pure Mg explosion.•MCA and MPP suppressants can promote the dust explosion of hybrid Mg/H2.•Inhibitory mechanism of hybrid Mg/H2 dust explosion was investigated.
Summary
Five inhibitors—Zn/Mg/Al‐CO3 layered double hydroxides (LDHs), thermosensitive hydrogel (P(NIPA‐co‐SA)), diammonium phosphate ((NH4)2HPO4), sodium phosphate (Na3PO4), and magnesium chloride ...(MgCl2)—commonly used to forestall the spontaneous combustion of anthracite and coke coal were investigated in this study, and the inhibition effects were quantified. According to the results of thermogravimetry, differential scanning calorimetry, Fourier transform infrared spectroscopy, and kinetic analysis, Zn/Mg/Al‐CO3‐LDHs, P(NIPA‐co‐SA), and (NH4)2HPO4 all exert substantial inhibiting effects on anthracite and coke coal. Specifically, P(NIPA‐co‐SA) was altered during the liquid‐to‐gel phase, which isolated the oxygen from the coal surface and produced an endothermic reaction that decreased the environmental temperature; this reaction further inhibited spontaneous combustion. Conversely, MgCl2 promoted a combustion reaction and reduced the apparent activation energy of coal, increasing the risk of spontaneous combustion. This study provides a reference for selecting suitable inhibitors to prevent the spontaneous combustion of coal.
Inhibition ability of 2 types of self‐prepared and 3 types of commercial inhibitors were determined as a prevention mechanism of coal spontaneous combustion.
Zn/Mg/Al‐CO3‐LDHs and coke coal(NH4)2HPO4 had effective inhibition ability.
STA technique as advanced thermal analysis method identified the inhibition mechanism of coal spontaneous combustion.
The catalytic effects of magnesium-transition metal (Mg–TM) hydrides on O2 and N2 reduction were examined. The results indicated that magnesium hydrides (MHs) combustion process primarily occurred in ...three stages: dehydrogenation, active Mg combustion, and residual Mg combustion. After the dehydrogenation stage, the active Mg particles and released H atoms became more likely to be oxidised and nitrified in MgFeH than in MgH2. Moreover, a large quantity of NH3 was observed after the combustion of MgFeH. Fe has a rich electronic structure and an active surface position, which enables it to activate N2 and thus facilitate the catalytic reduction of N2. Due to the lower temperature and pressure requirements of the initial reaction in the MgFeH combustion or explosion process, compared to those of the Haber-Bosch process, the combustion and explosion of MgFeH can result in the release of significant amounts of NH3. However, the addition of Ni can prevent the activation of O2 and N2, thereby inhibiting their reduction. This means that Ni not only inhibits N2 reduction but also enhances the dehydrogenation capacity of MHs. Therefore, to develop and design hydrogen storage materials for MHs, Ni is a safer and more environmentally friendly catalyst than Fe.
Display omitted
•The explosion of MgFeH can result in a significant release of NH3.•MgFeH possessed a strong catalytic ability in reducing N2.•The presence of Ni can hinder the process of N2 and O2 reduction.•Compared to Fe, Ni is a safer catalytic agent for MHs.
Whether the modified Glasgow prognostic score (mGPS) is useful for patients with head and neck squamous cell carcinoma (HNSCC) remains controversial. An electronic database search on EMBASE, PubMed, ...and the Cochrane Library from inception to 30 June 2022 was performed for study selection and data extraction. The associations between the mGPS and survival outcomes were evaluated using a random‐effects meta‐analysis and expressed as pooled hazard ratios (HRs) and 95% CIs. We included 11 studies involving a total of 2017 patients with HNSCC. A higher mGPS was associated with poorer progression‐free survival (HR = 2.39, 95% CI 1.69–3.38), overall survival (HR = 2.40, 95% CI 1.94–2.98), disease‐specific survival (HR = 2.57, 95% CI 1.71–3.88), and disease‐free survival (HR = 2.67, 95% CI 1.51–4.73, all p ≤ 0.001) in HNSCC. The mGPS can function as a valid prognostic biomarker for patients diagnosed as having HNSCC.
From TG result, BmimBF
4
has the best inhibition ability of spontaneous coal combustion to delay the initial temperature, maximum temperature, and final temperature of mass loss with oxidation ...process on lignite and long flame coal. Cation of ionic liquid (IL) is the critical factor of the oxidation reaction on lignite, and Bmim
+
can destroy the structure of long flame coal. According to FTIR results, ILs can effectively decrease the easily oxidized functional group on lignite, and the removed ability is BmimBF
4
> EmimBF
4
> BmimNO
3
. EmimBF
4
has the best performance of removed ability on long flame coal. ILs as a green inhibitor and new way is applied to prevent fire in coal industries.
A broadband lightweight circularly polarized (CP) stacked patch antenna is proposed for use in the 1.8-2.3 GHz LEO-to-GEO inter-satellite links. It consists of four meshed aluminum disks supported by ...polyamide spacers. No dielectric substrate is used in the design to avoid heat storage in the substrate and reduce antenna weight. Thanks to the meshed structure, the antenna weight is reduced by half and is only 30 g. The broadband CP radiation is achieved via the sequential rotation feeding structure and the stacked patch topology. For verification, a prototype antenna is built and tested. In addition to the agreement between the simulated and measured results, the prototype antenna exhibits an overlapped 10 dB return loss and 3 dB axial ratio bandwidth of 33.81% and in-band realized gain of 8.4-9.3 dBic at broadside, meeting the requirements of the intended inter-satellite link application.
This study investigated the thermal stability characteristics and developed a thermal explosion model for industrial-scale nitrocellulose (NC) using simultaneous thermal analysis, accelerating rate ...calorimeter (ARC) measurements, and kinetics data. The time to maximum rate under adiabatic conditions was approximately 35 min, and the adiabatic temperature rise recorded by the ARC was 70 °C, which indicated that the NC released considerable amounts of heat and gases in an extremely short time. Moreover, an autocatalytic kinetic model of NC decomposition was developed using nonisothermal differential scanning calorimetry data. The simulation results (of the thermal explosion model) were consistent with the experimental results (ARC data). Furthermore, the heat radiation effect of external fire sources on NC explosions was also investigated. This study aids the prevention and control of NC explosions and for the development of fire extinguishing technology.
