Energy dissipation mechanism and ballistic characteristic optimization in foam sandwich panels against spherical projectile impact

This study systematically examines the energy dissipation mechanisms and ballistic characteristics of foam sandwich panels(FSP)under high-velocity impact using the explicit non-linear finite element method.Based on the geometric topology of the FSP system,three FSP configurations with the same areal density are derived,namely multi-layer,gradient core and asymmetric face sheet,and three key structural parameters are identified:core thickness(t_(c)),face sheet thickness(t_(f))and overlap face/core number(n_(o)).The ballistic performance of the FSP system is comprehensively evaluated in terms of the ballistic limit velocity(BLV),deformation modes,energy dissipation mechanism,and specific penetration energy(SPE).The results show that the FSP system exhibits a significant configuration dependence,whose ballistic performance ranking is:asymmetric face sheet>gradient core>multi-layer.The mass distribution of the top and bottom face sheets plays a critical role in the ballistic resistance of the FSP system.Both BLV and SPE increase with tf,while the raising tcor noleads to an increase in BLV but a decrease in SPE.Further,a face-core synchronous enhancement mechanism is discovered by the energy dissipation analysis,based on which the ballistic optimization procedure is also conducted and a design chart is established.This study shed light on the anti-penetration mechanism of the FSP system and might provide a theoretical basis for its engineering application.

Integration of energy recovery network including recycling residual pressure energy with pinch technology

Work exchange is a promising innovative technology in recovering residual pressure energy. However, at the systematic level, the comprehensive utilization of different energy resources in an energy system has become an issue of concern. In this work, a systematic approach is proposed, one that successively integrates heat, work and adjusts operation parameters. A detailed procedure for building a heat-work coupling transfer network is provided. The synthesis mainly consists of constructing a work exchange sub-network with pinch analysis based on positive displacement type work exchangers. Simultaneously, another kind of sub-network based on turbine-type work exchangers is built as a schematic comparison. The influence of applying a positive displacement work exchanger on the system is investigated. Finally, as a case study, a renovation design of a typical rectisol process in the coal-water slurry gasification section of an ammonia plant is presented. The results show that the added work exchanger has little impact on the existing heat exchange sub-network. Moreover,extra pressure energy is recovered by coupling the transfer network. It is concluded that the heat-work systematic design is a promising and powerful method to use energy more efficiently.

Numerical investigation for the suitable choice of bubble diameter correlation for EMMS/bubbling drag model

Mesoscale bubbles exist inherently in bubbling fluidized beds and hence should be considered in the constitutive modeling of the drag force.The energy minimization multiscale bubbling(EMMS/bubbling)drag model takes the effects of mesoscale structures(i.e.,bubbles)into the modeling of drag coefficient and thus improves the coarse-grid simulation of bubbling and turbulent fluidized beds.However,its dependence on the bubble diameter correlation has not been thoroughly investigated.The hydrodynamic disparity between homogeneous and heterogeneous fluidization is accounted for by the heterogeneity index,H_(d),which can be affected by choice of bubble diameter correlation.How this choice of bubble diameter correlation influences the model prediction calls for further fundamental research.This article incorporated seven different bubble diameter correlations into EMMS/bubbling drag model and studied their effects on H_(d).The performance of these correlations has been compared with the correlation used previously by EMMS/bubbling drag model.We found that some of the correlations predicted lower Hd by order of a magnitude than the correlation used by the original EMMS/bubbling drag.Based on such analysis,we proposed a modification in the EMMS drag model for bubbling and turbulent fluidized beds.A computational fluid dynamics(CFD)simulation using two-fluid model with the modified EMMS/bubbling drag model was performed for two bubbling and one turbulent fluidized beds.Voidage distribution,time averaged solid concentration and axial solid concentration profiles were studied and compared with the previous version of the EMMS/bubbling drag model and experimental data.We found that the right choice of bubble diameter correlations can significantly improve the results for CFD simulations.

A brief review of forensically important flesh flies (Diptera: Sarcophagidae)

Forensic entomology could provide valuable data for the minimum postmortem interval (PMImin) estimation and other relevant information,such as causes and circumstances of death.Some representatives of flesh flies are one of the dominant necrophagous insects during early stages of decomposition,demonstrating unique biological characteristics compared with other necrophagous flies.Moreover,they lead to global health concerns as carriers of various pathogenic micro-organisms,and dominantly result in the traumatic myiasis.Thus,sarcophagid flies are considered important in decomposition processes for PMImin estimation.However,the utility of sarcophagid flies has been seriously hampered by limited ecological,biological and taxonomic knowledge of them.The aim of this paper is to provide a brief review on the species,distribution and biological habit of forensically important sarcophagid flies.In addition,the relation between traumatic myiasis and flesh flies,molecular identification methods and developmental pattern of flesh flies are summarized.

Autopsy results from a COVID-19 patient treated in a tropical area,and a review of the epidemiological history

Since the start of the COVID-19 pandemic,there has been an urgent need to produce accurate and sensitive tests.However,there have been instances where a positive nucleic acid test turns negative after treatment,and then positive again.This case report describes such an instance from the tropical region of Hainan,China.The patient was a 61-year-old female who went to Hainan on vacation from Wuhan during the COVID-19 pandemic in 2020.Symptoms appeared 9 d after arriving in Hainan,and it was confirmed that the nucleic acid test was positive after 4 repeats.Her condition declined rapidly,her heart stopped beating,and she was admitted in a coma to the ICU.After treatment,the SARS-CoV-2 virus nucleic acid test of several nasopharyngeal swabs were negative,and tests on whole blood,anal swabs,and urine were also negative.Later,however,nucleic acid tests on a lower respiratory tract sputum swab and lower respiratory tract lavage fluid were positive.An autopsy examination was carried out 12h after her death,and multi-organ secretions were extracted for nucleic acid testing.The SARS-CoV-2 virus nucleic acid was only detected in the swabs from the end of the bronchus,which was confirmed by the visualization of the coronavirus by electron microscopy.Autopsy confirmed that the damage was mainly concentrated in the lungs and immune organs and tissues throughout the body.Epidemiology indicated that none of the people she came into contact with after arriving in Hainan,including close contacts,were infected.This is in sharp contrast to the highly contagious virus in Wuhan in the temperate zone during the same period.This case report indicates:(1)The high temperatures in tropical areas may have an impact on the spread and harm of COVID-19,and(2)The reason why nucleic acid testing for COVID-19 was initially negative and then positive after treatment may be related to the survival of the SARS-CoV-2 virus in deep lung tissues.