In order to test and quantify the effect of heat of rewetting on the propensities for spontaneous combustion of coals, especially low rank coals, a new experimental procedure and a mathematical model ...were developed based on the standard R70 adiabatic oxidation method. Dry and moist tests were performed on coal samples collected from Powder River Basin and from South America coal fields. Based on the linear and moving average parts of the self-heating curves, self-heating indices in terms of Moist R70 and R100 were proposed. The developed analytical model, calibrated with the experimental data, was used to simulate self-heating of coal with different amount of water condensation (2%, 5%, 10% and 20%) and relative humidity (40%, 60% and 90%). It was shown that an increase of water condensation and relative humidity significantly promotes the self-heating rate of coal. A practical consequence of this finding is the heat of rewetting mechanism should not be neglected in any precautionary or preventive measures to avoid potential spontaneous combustion in PRB and Colombia coal mines.
•Spontaneous combustion behaviors of PRB and Colombia coal samples have been tested with standard R70 self-heating method.•A new experimental procedure, moist R70 test, has been proposed.•Effect of heat of rewetting on spontaneous combustion of PRB and Colombia coal samples have been tested.•Self-heating indices in terms of Moist R70 and R100 have been proposed.•Experiment-based analytical model, capable of quantifying heat of rewetting, has been developed.
Firstly we qualitatively analyze the formation of the dip and peak structures of the kurtosis
κ
σ
2
of net baryon number fluctuation along imagined freeze-out lines and discuss the signature of the ...existence of the QCD critical end point (CEP) in the Nambu–Jona-Lasinio (NJL) model, Polyakov-NJL (PNJL) model as well as
μ
-dependent PNJL(
μ
PNJL) model with different parameter sets, and then we apply a realistic PNJL model with parameters fixed by lattice data at zero chemical potential, and quantitatively investigate its
κ
σ
2
along the real freeze-out line extracted from experiments. The important contribution from gluodynamics to the baryon number fluctuations is discussed. The peak structure of
κ
σ
2
along the freeze-out line is solely determined by the existence of the CEP mountain and can be used as a clean signature for the existence of CEP. The formation of the dip structure is sensitive to the relation between the freeze-out line and the phase boundary, and the freeze-out line starts from the back-ridge of the phase boundary is required. To our surprise, the kurtosis
κ
σ
2
produced from the realistic PNJL model along the experimental freeze-out line agrees with BES-I data well, which indicates that equilibrium result can explain the experimental data. It is worth to point out that the extracted freeze-out temperatures from beam energy scan measurement are indeed higher than the critical temperatures at small chemical potentials, which supports our qualitative analysis.
We derive a general expression for the absorptive part of the one-loop photon polarization tensor in a strongly magnetized quark-gluon plasma at nonzero baryon chemical potential. To demonstrate the ...application of the main result in the context of heavy-ion collisions, we study the effect of a nonzero baryon chemical potential on the photon emission rate. The rate and the ellipticity of photon emission are studied numerically as a function the transverse momentum (energy) for several values of temperature and chemical potential. When the chemical potential is small compared to the temperature, the rates of the quark and antiquark splitting processes (i.e.,
q
→
q
+
γ
and
q
¯
→
q
¯
+
γ
, respectively) are approximately the same. However, the quark splitting gradually becomes the dominant process with increasing the chemical potential. We also find that increasing the chemical potential leads to a growing total photon production rate but has only a small effect on the ellipticity of photon emission. The quark-antiquark annihilation (
q
+
q
¯
→
γ
) also contributes to the photon production, but its contribution remains relatively small for a wide range of temperatures and chemical potentials investigated.
Hydrogen evolution and hydration kinetics of aluminum-particle-water reaction are investigated by a series of isothermal experiments. Morphology development of the Al particle during the hydration ...reaction process is characterized by SEM and XRD. An improved multi-stage analytical model has been developed and validated with the experimental data. The pre-exponential factor and activation energy for the alumina hydrolysis, Al-water reaction, and diffusion in the product layer are estimated based on the proposed model. The effects of growing particle size, formation and breakage of initial porous boehmite (AlOOH) layer, multi-stage reaction kinetics on the overall reaction rate are incorporated in the model. The study results show that the overall reaction rate is jointly controlled by simultaneous action of individual driving force, including mass transfer, chemical reaction and diffusion. The improved model enables the predictions of induction period and the evolution rate of hydrogen as a function of time, temperature and particle size.
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•Hydroxide products formed from Aluminum powders hydration were characterized.•An improved multi-stage shrinking core model for Al–H2O reaction was proposed.•The kinetic parameters were estimated by a series of isothermal experiments.•Reactivity of the Aluminum powders depends on temperature and particle size.
Pb-contaminated soil poses serious hazards to humans and ecosystems and is in urgent need of remediation. However, the extensive use of traditional curing materials such as ordinary Portland cement ...(OPC) has negatively impacted global ecology and the climate, so there is a need to explore low-carbon and efficient green cementitious materials for the immobilization of Pb-contaminated soils. A red mud/steel slag-based (RM/SS) geopolymer was designed and the potential use of solidifying/stabilizing heavy metal Pb pollution was studied. The Box–Behnken design (BBD) model was used to design the response surface, and the optimal preparation conditions of RM/SS geopolymer (RSGP) were predicted by software of Design-Expert 8.0.6.1. The microstructure and phase composition of RSGP were studied by X-ray diffractometer, Fourier transform infrared spectrometer, scanning electron microscopy and X-ray photoelectron spectroscopy, and the immobilization mechanism of RSGP to Pb was revealed. The results showed that when the liquid–solid ratio is 0.76, the mass fraction of RM is 79.82% and the modulus of alkali activator is 1.21, the maximum unconfined compressive strength (UCS) of the solidified soil sample is 3.42 MPa and the immobilization efficiency of Pb is 71.95%. The main hydration products of RSGP are calcium aluminum silicate hydrate, calcium silicate hydrate and nekoite, which can fill the cracks in the soil, form dense structures and enhance the UCS of the solidified soil. Pb is mainly removed by lattice immobilization, that is, Pb participates in geopolymerization by replacing Na and Ca to form Si-O-Pb or Al-O-Pb. The remaining part of Pb is physically wrapped in geopolymer and forms Pb(OH)2 precipitate in a high-alkali environment.
Hearing impairment is a common disease, affecting about five percent of the population. It puts great pressure on children, their families and society, and has become an significant problem affecting ...daily life. In recent years, great progress has been made in the study of hearing loss in children. This paper describes the ear structure, the causes of hearing impairment, the assessment and diagnosis of hearing impairment and the current applicable treatment methods through literature review. Previous research on hearing loss in children is summarized in this paper and provides some references for the further research.
With a significant number of mechanical products approaching the retirement phase, the batch recycling of discarded mechanical parts necessitates a preliminary assessment of their surface condition. ...However, the presence of surface rust poses a challenge to defect identification. Therefore, this paper proposes a method for detecting heavily rusted surface defects based on an improved YOLOv8n network. In the Backbone, the C2f-DBB module of re-parameterized deep feature extraction was introduced, and the attention module was designed to improve the accuracy of information extraction. In the Neck part, a Bi-Afpn multiscale feature fusion strategy is designed to facilitate information exchange between features at different scales. Finally, Focal-CIoU is employed as the bounding box loss function to enhance the network's localization performance and accuracy for defects. Experimentally, it is proved that the improved network in this paper improves the Recall, Precision, and mAP0.5 by 1.2%, 2.1%, and 1.9%, respectively, on the original basis, which is better than other network models.
Pine wilt disease (PWD) is a global quarantine disease of forests that mainly affects Pinaceae species. The disease spreads rapidly. Once infected, pine trees have an extremely high mortality rate. ...This paper provides a summary of the common techniques used to detect PWD, including morphological-, molecular-, chemical- and physical-based methods. By comprehending the complex relationship among pinewood nematodes, vectors and host pine trees and employing the available approaches for nematode detection, we can improve the implementation of intervention and control measures to effectively reduce the damage caused by PWD. Although conventional techniques allow a reliable diagnosis of the symptomatic phase, the volatile compound detection and remote sensing technology facilitate a rapid diagnosis during asymptomatic stages. Moreover, the remote sensing technology is capable of monitoring PWD over large areas. Therefore, multiple perspective evaluations based on these technologies are crucial for the rapid and effective detection of PWD.
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