The internal and external flow fields during vented explosions of methane were characterized through numerical simulation,and the capability of numerical simulation thereof was validated by previous experimental data ...The internal and external flow fields during vented explosions of methane were characterized through numerical simulation,and the capability of numerical simulation thereof was validated by previous experimental data at three ignition positions.The venting mechanism was revealed by the simulated concentration distribution,temperature profile,and airflow velocity.The results show rear ignition results in the external methane mass distribution taking the form of"mushroom"and columnar flames in the external space,which can be expressed as a third-order polynomial relationship with distance;central ignition forms a relationship of the form y=AxB.Front ignition causes the temperature to show a tendency to repeated oscillations(rising,falling,and rising).Central ignition generates the maximum vented airflow velocity(V_(max)=320 m/s)upon vent opening.The results indicate that it is acceptable to apply numerical simulation of methane explosions in practice.展开更多
To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion chara...To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion characteristics and flame propagation characteristics of methane in pipeline and coal mine tunnel are studied by using an explosion test system,combined with FLACS software,under different vented conditions.The numerical simulation results of methane explosion are basically consistent with the physical experiment results,which indicates that the numerical simulation for methane explosion is reliable to be applied to the practice.The results show that explosion parameters(pressure,temperature and product concentration)of methane at five volume fractions have the same change trend.Nevertheless,the explosion intension of 10.0%methane is the largest and that of 9.5%methane is relatively weak,followed by 11.0%methane,8.0%methane and 7.0%methane respectively.Under different vented conditions,the pressure and temperature of methane explosion are the highest in the pipeline without a vent,followed by the pipeline where ignition or vent position is in each end,and those are the lowest in the pipeline with ignition and vent at the same end.There is no significant effect on final product concentration of methane explosion under three vented conditions.For coal mine tunnel,it is indicated that the maximum explosion pressure at the airproof wall in return airway with the branch roadway at 50 m from goaf is significantly decreased while that in intake airway does not change overwhelmingly.In addition,when the branch roadway is longer or its section is larger,the peak pressure of airproof wall reduces slightly.展开更多
By providing a means of separating the airborne emissions of patients from the air breathed by healthcare workers(HCWs),vented individual patient(VIP)hoods,a form of local exhaust ventilation(LEV),offer a new approach...By providing a means of separating the airborne emissions of patients from the air breathed by healthcare workers(HCWs),vented individual patient(VIP)hoods,a form of local exhaust ventilation(LEV),offer a new approach to reduce hospital-acquired infection(HAI).Results from recent studies have demonstrated that,for typical patient-emitted aerosols,VIP hoods provide protection at least equivalent to that of an N95 mask.Unlike a mask,hood performance can be easily monitored and HCWs can be alerted to failure by alarms.The appropriate use of these relatively simple devices could both reduce the reliance on personal protective equipment(PPE)for infection control and provide a low-cost and energy-efficient form of protection for hospitals and clinics.Although the development and deployment of VIP hoods has been accelerated by the coronavirus disease 2019(COVID-19)pandemic,these devices are currently an immature technology.In this review,we describe the state of the art of VIP hoods and identify aspects in need of further development,both in terms of device design and the protocols associated with their use.The broader concept of individual patient hoods has the potential to be expanded beyond ventilation to the provision of clean conditions for individual patients and personalized control over other environmental factors such as temperature and humidity.展开更多
In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during mo...In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during molding process. The effect of dried pellets, non-dried pellets, using an opened-vented hole, and using a closed-vented hole on the miscibility, morphology, thermal properties and mechanical properties of RPET/PC blends was investigated. The results indicated that no drying decreases dispersion, thermal properties, and mechanical properties of RPET/PC blends due to hydrolysis degradation of recycled-PET during the injection molding process. Using the venting system with non-dried RPET/PC blends partially improves dispersion, thermal properties and molecular weight of RPET/PC blends processed without drying, giving results that are similar to those processed with drying. Regarding the flexural properties, using the venting system without drying prevents the flexural properties from decreasing in RPET/PC blends, if the amount of RPET is less than 75 wt%. When the content of RPET is over 75 wt%, using the venting system does not eliminate the decrease in flexural properties of RPET/PC blends. When the venting system is applied to non-dried RPET, despite hydrolysis degradation of RPET not being completely eliminated, the damaging effects are nonetheless reduced compared with those samples processed without the venting system. As a result, vented barrel injection molding hardly prevents non-dried RPET/PC blends from having reduced flexural properties when the content of RPET is greater than 75 wt%.展开更多
Multi-objective optimization design of the gas-filled bag cushion landing system is investigated.Firstly,the landing process of airbag is decomposed into a adiabatic compression and a release of landing shock energy,a...Multi-objective optimization design of the gas-filled bag cushion landing system is investigated.Firstly,the landing process of airbag is decomposed into a adiabatic compression and a release of landing shock energy,and the differential equation of cylindrical gas-filled bag is presented from a theoretical perspective based on the ideal gas state equation and dynamic equation.Then,the effects of exhaust areas and blasting pressure on buffer characteristics are studied,taking those parameters as design variable for the multiobjective optimization problem,and the solution can be determined by comparing Pareto set,which is gained by NSGA-Ⅱ.Finally,the feasibility of the design scheme is verified by experimental results of the ground test.展开更多
Due to the influence of many factors,the overpressure-time history load model of vented gas explosions is difficult to describe and is not conducive to further structural design.Based on vented gas explosion test data...Due to the influence of many factors,the overpressure-time history load model of vented gas explosions is difficult to describe and is not conducive to further structural design.Based on vented gas explosion test data,this paper obtains three typical overpressure-time history curves and puts forward a new semi-empirical model-double hump model that considers gas concentration and venting pressure,and gives a formula for peak pressure and overpressure-time history model.The scientificity of the model is then verified by the total impulse in the load.The model is able directly reflect the load characteristics,provide reference for calculating key parameters of a vented gas explosion and provide information on the structural response under the load.The model thereby has the potential to help reduce the impact of gas explosion disasters.展开更多
The impacts of elevation on fires in a ceiling vented compartment were investigated experimentally. The flame behavior of elevated fires was recorded. Various parameters including the fuel mass loss rate, the light ex...The impacts of elevation on fires in a ceiling vented compartment were investigated experimentally. The flame behavior of elevated fires was recorded. Various parameters including the fuel mass loss rate, the light extinction coefficient, the oxygen concentration and the gas temperature were measured. Results indicated that the variations of the flame behavior were consistent with that of the fuel mass loss rate. The fire location significantly impacted the light extinction coefficient, the oxygen concentration and the gas temperature, which all showed distinct stratification phenomena. For a higher elevated f＇we, the average fuel loss rate and the overall light extinction co- efficient were smaller, the oxygen concentration was higher and the gas temperature was lower. In addition, the smoke descending was slower. From the perspective of those parameters the fire was less hazardous if the fire was elevated higher, which was totally different from the elevated fires in closed compartments.展开更多
Correlations of fire-induced temperature have been reviewed and revisited.The impact of XY factors,i.e.,the relative locations of the fire source and vent,on temperature models of ceiling-vented compartments could be ...Correlations of fire-induced temperature have been reviewed and revisited.The impact of XY factors,i.e.,the relative locations of the fire source and vent,on temperature models of ceiling-vented compartments could be reflected by the exponents of the two dimensionless terms which represent the ratio of the total energy to energy released through the ceiling vent,and the ratio of the energy lost through the walls to the energy released through the ceiling vent.For fires not located directly below the ceiling vent,the temperature rise was proportional to two thirds of the power of the heat release rate,while for fires immediately beneath this vent,the temperature rise was proportional to four thirds the power of the heat release rate,and was inversely proportional to one sixth the power of the ceiling vent size.展开更多
RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomp...RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.展开更多
Bathymodiolus mussels distribute in both deep-sea cold seep and hydrothermal vent environments,whose endosymbiotic gill tissue is a prominent character for the adaptation of extreme habitats.However,few studies explor...Bathymodiolus mussels distribute in both deep-sea cold seep and hydrothermal vent environments,whose endosymbiotic gill tissue is a prominent character for the adaptation of extreme habitats.However,few studies explored the adaptation mechanisms through comparative transcriptome sequencing and analysis of different tissues between seep mussels and vent mussels.We performed the comparative transcriptome sequencing and analysis for three tissue types(gill,mantle,and adductor muscle)of Bathymodiolus mussels collected from a cold seeping site Station S 11 and the 50-km away hydrothermal field Minami-Ensei Knoll in the Okinawa Trough.Results show that gene expression patterns had distinct tissue specificity.Compared with the non-endosymbiotic tissues(mantle and adductor muscle),the significantly strengthened gene functions in endosymbiotic gill included microbial recognition(fibrinogen C domain-containing protein 1-B-like(fibcd),fibrinogen-related protein 8(frp),peptidoglycan recognition proteins(pgrp),and C-type lectin(clec)),cell apoptosis and immunity(interferon regulatory factor 1/2-like 1(ir f),cathepsin D(ctsd),caspase 2(casp 2)),and antioxidant capacity(copper/zinc superoxide dismutase(czsod),glutathione peroxidase(gpx),selenoprotein(sel)),in both seep and vent individuals.Consistent with metal accumulation,high expression levels of genes related to heavy metal detoxification(cytochrome P 450(cyp),ferritin-like(ftl),metallothionein(mt),glutathione S-transferase(gst))were also observed in gill.Moreover,to adapt to high hydrostatic pressure in the deep sea,the Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways associated with cellular community were significantly enriched in all three tissues,suggesting the regulation of cell structure and cell adhesion at transcriptional level.This study obtained gene expression profiles of deep-sea mussels subsisting at cold seep and hydrothermal vent sites,which could lay foundations for comprehensive investigations of molecular basis in adaptation of deep-sea mussels to the two extreme ecosystems.展开更多
Post-reperfusion syndrome(PRS)in liver transplant recipients remains one of the most dreaded complications in liver transplant surgery.PRS can impact the short-term and long-term patient and graft outcomes.The definit...Post-reperfusion syndrome(PRS)in liver transplant recipients remains one of the most dreaded complications in liver transplant surgery.PRS can impact the short-term and long-term patient and graft outcomes.The definition of PRS has evolved over the years,from changes in arterial blood pressures and heart and/or de-creases in the systemic vascular resistance and cardiac output to including the fibrinolysis and grading the severity of PRS.However,all that did not reflect on the management of PRS or its impact on the outcomes.In recent years,new scientific techniques and new technology have been in the pipeline to better understand,manage and maybe prevent PRS.These new methods and techniques are still in the infancy,and they have to be proven not in prevention and management of PRS but their effects in the patient and graft outcomes.In this article,we will review the long history of PRS,its definition,etiology,mana-gement and most importantly the new advances in science and technology to prevent and properly manage PRS.展开更多
In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting...In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.展开更多
The process of explosion venting to air in a cylindrical vent vessel connected to a duct, filling with a stoichiometric methane-oxygen gas mixture, was simulated numerically by using a colocated grid SIMPLE scheme bas...The process of explosion venting to air in a cylindrical vent vessel connected to a duct, filling with a stoichiometric methane-oxygen gas mixture, was simulated numerically by using a colocated grid SIMPLE scheme based on k-epsilon turbulent model and Eddy-dissipation combustion model. The characteristics of the combustible cloud, flame and pressure distribution in the external flow field during venting were analyzed in terms of the predicted results.The results show that the external explosion is generated due to violent turbulent combustion in the high pressure region within the external combustible cloud ignited by a jet flame. And the turbulence and vortex in the external flow field were also discussed in detail. After the jet flame penetrating into the external combustible cloud, the turbulent intensity is greater in the regions with greater average kinetic energy gradient, rather than in the flame front; and the vortex in the external flow field is generated primarily due to the baroclinic effect, which is greater in the regions where the pressure and density gradients are nearly perpendicular.展开更多
Water Tree is a corrosion phenomenon in cross-link polyethylene (XLPE) insulation. It is commonly found in underground cables. Water tree induced fault is difficult to detect due to its high impedance and difficult to...Water Tree is a corrosion phenomenon in cross-link polyethylene (XLPE) insulation. It is commonly found in underground cables. Water tree induced fault is difficult to detect due to its high impedance and difficult to model due to its random nature. In recent years, underground cables have become more popular in the power industry. They are resistant to environmental damage and has reduced space requirement. They are suitable to areas with high environment hazard or heavily populated areas where space is a constraining factor. As a result, studying and modeling the structure and effect of water tree become increasingly important. Since majority of the fault inducing water trees are vented trees which originated from the surface of the cable insulation, the mathematical model focuses on this particular type of water tree. To reduce the complexity of the model, the shape of the water tree afflicted region of the insulation is assumed to be ellipsoidal and the permittivity of the region is assumed to be linearly changing. Finite element analysis is used to analyze the water tree affected region. The resultant capacitance is calculated and compared with a physical model from Comsol. The result obtained using the proposed mathematical model and the result obtained using physical simulation through Comsol package agrees with each other. Hence, this method can be used to analyze the effect of water tree fault in large power systems.展开更多
Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth o...Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth of about 10-20 m off the eastern tip of the tao emits hy-drothermal fluids and volcanic gases such as H2S. A sulfur chimney or mound, formed by condensation of the sulfur contained in the hydrothermal fluid, can usually be seen around the vents. The tallest chimney reaches 6 m. Vents discharging a yellowish fluid have temperatures between 92 and 116 ℃ and flow rates as high as 158 t/h; vents discharging a whitish fluid have lower temperatures of between 48 and 62 ℃ and lower flow rates of about 7.0 t/h. These world-record, breaking low pH (as low as 1.52) fluids are totally different from those found in the black and white-chimneys of the mid-ocean ridges. Magnesium and SiO2 data indicate that these hydrothermal fluids probably originate from a depth of 915-1 350 m below the surface.While the ratios of major ions relative to the sodium of these hydrothermal fluids are quite similar to open ocean water, the ratios of SO4 and chloride to sodium seem to be higher for some of the vents. It is suggested that the volcanic gases contribute SO4 and chlorine to the fluids, hence increasing their ratios relative to sodium. Some hydrothermal fluids, however, are found to be depleted of the major elements which can have been caused by phase separation. The concentrations of iron and manganese in the fluids are much lower than those found in the mid-ocean ridges, while the aluminium content is higher. Four species of benthos (Xenograpsus testudi-natus, a snail, a sea anemone, and a Sipuncala), 1 species of algae (Corallinaceae), and 1 species of fish (Siganus fusescens) were recorded near the hydrothermal vents. A mitochondria DNA sequence comparison of Xenograpsus testudinatus with 6 other decapod species shows the greatest number of nitrogen base differences in the DNA fragments from 225 to 270. The gene diversity in this DNA region possibly results from the unusual habitat. A sediment core was collected at a pond near the eastern side of the tao. No volcanic ash could be detected in the core sample spanning 3 620 a.展开更多
基金supported by the Young Scientists Fund of National Natural Science Foundation of China(Grant Nos.12202202 and 12202494)the National Key Research and Development Program of China(Grant No.2021YFC3100700)。
文摘The internal and external flow fields during vented explosions of methane were characterized through numerical simulation,and the capability of numerical simulation thereof was validated by previous experimental data at three ignition positions.The venting mechanism was revealed by the simulated concentration distribution,temperature profile,and airflow velocity.The results show rear ignition results in the external methane mass distribution taking the form of"mushroom"and columnar flames in the external space,which can be expressed as a third-order polynomial relationship with distance;central ignition forms a relationship of the form y=AxB.Front ignition causes the temperature to show a tendency to repeated oscillations(rising,falling,and rising).Central ignition generates the maximum vented airflow velocity(V_(max)=320 m/s)upon vent opening.The results indicate that it is acceptable to apply numerical simulation of methane explosions in practice.
基金Project(51674193)supported by the National Natural Science Foundation of ChinaProject(2019-JLM-9)supported by the Natural Science Foundation of Shaanxi Province,ChinaProject(2019-M-663780)supported by the Postdoctoral Science Foundation,China。
文摘To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion characteristics and flame propagation characteristics of methane in pipeline and coal mine tunnel are studied by using an explosion test system,combined with FLACS software,under different vented conditions.The numerical simulation results of methane explosion are basically consistent with the physical experiment results,which indicates that the numerical simulation for methane explosion is reliable to be applied to the practice.The results show that explosion parameters(pressure,temperature and product concentration)of methane at five volume fractions have the same change trend.Nevertheless,the explosion intension of 10.0%methane is the largest and that of 9.5%methane is relatively weak,followed by 11.0%methane,8.0%methane and 7.0%methane respectively.Under different vented conditions,the pressure and temperature of methane explosion are the highest in the pipeline without a vent,followed by the pipeline where ignition or vent position is in each end,and those are the lowest in the pipeline with ignition and vent at the same end.There is no significant effect on final product concentration of methane explosion under three vented conditions.For coal mine tunnel,it is indicated that the maximum explosion pressure at the airproof wall in return airway with the branch roadway at 50 m from goaf is significantly decreased while that in intake airway does not change overwhelmingly.In addition,when the branch roadway is longer or its section is larger,the peak pressure of airproof wall reduces slightly.
文摘By providing a means of separating the airborne emissions of patients from the air breathed by healthcare workers(HCWs),vented individual patient(VIP)hoods,a form of local exhaust ventilation(LEV),offer a new approach to reduce hospital-acquired infection(HAI).Results from recent studies have demonstrated that,for typical patient-emitted aerosols,VIP hoods provide protection at least equivalent to that of an N95 mask.Unlike a mask,hood performance can be easily monitored and HCWs can be alerted to failure by alarms.The appropriate use of these relatively simple devices could both reduce the reliance on personal protective equipment(PPE)for infection control and provide a low-cost and energy-efficient form of protection for hospitals and clinics.Although the development and deployment of VIP hoods has been accelerated by the coronavirus disease 2019(COVID-19)pandemic,these devices are currently an immature technology.In this review,we describe the state of the art of VIP hoods and identify aspects in need of further development,both in terms of device design and the protocols associated with their use.The broader concept of individual patient hoods has the potential to be expanded beyond ventilation to the provision of clean conditions for individual patients and personalized control over other environmental factors such as temperature and humidity.
文摘In this research, recycled-polyethylene terephthalate (PET) and polycarbonate (RPET/PC) blends fabricated by vented barrel injection molding were presented to better understand the effect of devolatilization during molding process. The effect of dried pellets, non-dried pellets, using an opened-vented hole, and using a closed-vented hole on the miscibility, morphology, thermal properties and mechanical properties of RPET/PC blends was investigated. The results indicated that no drying decreases dispersion, thermal properties, and mechanical properties of RPET/PC blends due to hydrolysis degradation of recycled-PET during the injection molding process. Using the venting system with non-dried RPET/PC blends partially improves dispersion, thermal properties and molecular weight of RPET/PC blends processed without drying, giving results that are similar to those processed with drying. Regarding the flexural properties, using the venting system without drying prevents the flexural properties from decreasing in RPET/PC blends, if the amount of RPET is less than 75 wt%. When the content of RPET is over 75 wt%, using the venting system does not eliminate the decrease in flexural properties of RPET/PC blends. When the venting system is applied to non-dried RPET, despite hydrolysis degradation of RPET not being completely eliminated, the damaging effects are nonetheless reduced compared with those samples processed without the venting system. As a result, vented barrel injection molding hardly prevents non-dried RPET/PC blends from having reduced flexural properties when the content of RPET is greater than 75 wt%.
文摘Multi-objective optimization design of the gas-filled bag cushion landing system is investigated.Firstly,the landing process of airbag is decomposed into a adiabatic compression and a release of landing shock energy,and the differential equation of cylindrical gas-filled bag is presented from a theoretical perspective based on the ideal gas state equation and dynamic equation.Then,the effects of exhaust areas and blasting pressure on buffer characteristics are studied,taking those parameters as design variable for the multiobjective optimization problem,and the solution can be determined by comparing Pareto set,which is gained by NSGA-Ⅱ.Finally,the feasibility of the design scheme is verified by experimental results of the ground test.
基金The authors gratefully acknowledge the financial support from Natural Science Foundation of Jiangsu Province of China(Grant No.BK20180081)National Key R&D Program of China(Great No.2020YFB2103300)National Basic Research Program of China(973 Program)(Grant No.2015CB058000).
文摘Due to the influence of many factors,the overpressure-time history load model of vented gas explosions is difficult to describe and is not conducive to further structural design.Based on vented gas explosion test data,this paper obtains three typical overpressure-time history curves and puts forward a new semi-empirical model-double hump model that considers gas concentration and venting pressure,and gives a formula for peak pressure and overpressure-time history model.The scientificity of the model is then verified by the total impulse in the load.The model is able directly reflect the load characteristics,provide reference for calculating key parameters of a vented gas explosion and provide information on the structural response under the load.The model thereby has the potential to help reduce the impact of gas explosion disasters.
基金supported by National Natural Science Foundation of China (Project no. 50976109 and no. 51206157)the Research Fund for the Doctoral Program of Higher Education of China (Grant no. 20123402110048)a Grant from CityU (Project No. 7002577)
文摘The impacts of elevation on fires in a ceiling vented compartment were investigated experimentally. The flame behavior of elevated fires was recorded. Various parameters including the fuel mass loss rate, the light extinction coefficient, the oxygen concentration and the gas temperature were measured. Results indicated that the variations of the flame behavior were consistent with that of the fuel mass loss rate. The fire location significantly impacted the light extinction coefficient, the oxygen concentration and the gas temperature, which all showed distinct stratification phenomena. For a higher elevated f＇we, the average fuel loss rate and the overall light extinction co- efficient were smaller, the oxygen concentration was higher and the gas temperature was lower. In addition, the smoke descending was slower. From the perspective of those parameters the fire was less hazardous if the fire was elevated higher, which was totally different from the elevated fires in closed compartments.
基金supported by the Anhui Provincial Natural Science Foundation(1408085MKL94)
文摘Correlations of fire-induced temperature have been reviewed and revisited.The impact of XY factors,i.e.,the relative locations of the fire source and vent,on temperature models of ceiling-vented compartments could be reflected by the exponents of the two dimensionless terms which represent the ratio of the total energy to energy released through the ceiling vent,and the ratio of the energy lost through the walls to the energy released through the ceiling vent.For fires not located directly below the ceiling vent,the temperature rise was proportional to two thirds of the power of the heat release rate,while for fires immediately beneath this vent,the temperature rise was proportional to four thirds the power of the heat release rate,and was inversely proportional to one sixth the power of the ceiling vent size.
基金National Natural Science Foundation of china(Grant No.12402468)。
文摘RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.
基金Supported by the National Natural Science Foundation of China(Nos.91858208,92358301)the Laoshan Laboratory(No.LSKJ 202203500),the China Postdoctoral Science Foundation of China(No.2019M663209)the Fundamental Research Funds for the Central Universities in China(No.19lGPY100)。
文摘Bathymodiolus mussels distribute in both deep-sea cold seep and hydrothermal vent environments,whose endosymbiotic gill tissue is a prominent character for the adaptation of extreme habitats.However,few studies explored the adaptation mechanisms through comparative transcriptome sequencing and analysis of different tissues between seep mussels and vent mussels.We performed the comparative transcriptome sequencing and analysis for three tissue types(gill,mantle,and adductor muscle)of Bathymodiolus mussels collected from a cold seeping site Station S 11 and the 50-km away hydrothermal field Minami-Ensei Knoll in the Okinawa Trough.Results show that gene expression patterns had distinct tissue specificity.Compared with the non-endosymbiotic tissues(mantle and adductor muscle),the significantly strengthened gene functions in endosymbiotic gill included microbial recognition(fibrinogen C domain-containing protein 1-B-like(fibcd),fibrinogen-related protein 8(frp),peptidoglycan recognition proteins(pgrp),and C-type lectin(clec)),cell apoptosis and immunity(interferon regulatory factor 1/2-like 1(ir f),cathepsin D(ctsd),caspase 2(casp 2)),and antioxidant capacity(copper/zinc superoxide dismutase(czsod),glutathione peroxidase(gpx),selenoprotein(sel)),in both seep and vent individuals.Consistent with metal accumulation,high expression levels of genes related to heavy metal detoxification(cytochrome P 450(cyp),ferritin-like(ftl),metallothionein(mt),glutathione S-transferase(gst))were also observed in gill.Moreover,to adapt to high hydrostatic pressure in the deep sea,the Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways associated with cellular community were significantly enriched in all three tissues,suggesting the regulation of cell structure and cell adhesion at transcriptional level.This study obtained gene expression profiles of deep-sea mussels subsisting at cold seep and hydrothermal vent sites,which could lay foundations for comprehensive investigations of molecular basis in adaptation of deep-sea mussels to the two extreme ecosystems.
文摘Post-reperfusion syndrome(PRS)in liver transplant recipients remains one of the most dreaded complications in liver transplant surgery.PRS can impact the short-term and long-term patient and graft outcomes.The definition of PRS has evolved over the years,from changes in arterial blood pressures and heart and/or de-creases in the systemic vascular resistance and cardiac output to including the fibrinolysis and grading the severity of PRS.However,all that did not reflect on the management of PRS or its impact on the outcomes.In recent years,new scientific techniques and new technology have been in the pipeline to better understand,manage and maybe prevent PRS.These new methods and techniques are still in the infancy,and they have to be proven not in prevention and management of PRS but their effects in the patient and graft outcomes.In this article,we will review the long history of PRS,its definition,etiology,mana-gement and most importantly the new advances in science and technology to prevent and properly manage PRS.
文摘In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.
文摘The process of explosion venting to air in a cylindrical vent vessel connected to a duct, filling with a stoichiometric methane-oxygen gas mixture, was simulated numerically by using a colocated grid SIMPLE scheme based on k-epsilon turbulent model and Eddy-dissipation combustion model. The characteristics of the combustible cloud, flame and pressure distribution in the external flow field during venting were analyzed in terms of the predicted results.The results show that the external explosion is generated due to violent turbulent combustion in the high pressure region within the external combustible cloud ignited by a jet flame. And the turbulence and vortex in the external flow field were also discussed in detail. After the jet flame penetrating into the external combustible cloud, the turbulent intensity is greater in the regions with greater average kinetic energy gradient, rather than in the flame front; and the vortex in the external flow field is generated primarily due to the baroclinic effect, which is greater in the regions where the pressure and density gradients are nearly perpendicular.
文摘Water Tree is a corrosion phenomenon in cross-link polyethylene (XLPE) insulation. It is commonly found in underground cables. Water tree induced fault is difficult to detect due to its high impedance and difficult to model due to its random nature. In recent years, underground cables have become more popular in the power industry. They are resistant to environmental damage and has reduced space requirement. They are suitable to areas with high environment hazard or heavily populated areas where space is a constraining factor. As a result, studying and modeling the structure and effect of water tree become increasingly important. Since majority of the fault inducing water trees are vented trees which originated from the surface of the cable insulation, the mathematical model focuses on this particular type of water tree. To reduce the complexity of the model, the shape of the water tree afflicted region of the insulation is assumed to be ellipsoidal and the permittivity of the region is assumed to be linearly changing. Finite element analysis is used to analyze the water tree affected region. The resultant capacitance is calculated and compared with a physical model from Comsol. The result obtained using the proposed mathematical model and the result obtained using physical simulation through Comsol package agrees with each other. Hence, this method can be used to analyze the effect of water tree fault in large power systems.
文摘Kueishan Tao (24°51′N, 121°55′E) is located at a tectonic junction of the fault system extension of Taiwan and the southern rifting end of the Okinawa Trough. A cluster of over 30 vents, at a water depth of about 10-20 m off the eastern tip of the tao emits hy-drothermal fluids and volcanic gases such as H2S. A sulfur chimney or mound, formed by condensation of the sulfur contained in the hydrothermal fluid, can usually be seen around the vents. The tallest chimney reaches 6 m. Vents discharging a yellowish fluid have temperatures between 92 and 116 ℃ and flow rates as high as 158 t/h; vents discharging a whitish fluid have lower temperatures of between 48 and 62 ℃ and lower flow rates of about 7.0 t/h. These world-record, breaking low pH (as low as 1.52) fluids are totally different from those found in the black and white-chimneys of the mid-ocean ridges. Magnesium and SiO2 data indicate that these hydrothermal fluids probably originate from a depth of 915-1 350 m below the surface.While the ratios of major ions relative to the sodium of these hydrothermal fluids are quite similar to open ocean water, the ratios of SO4 and chloride to sodium seem to be higher for some of the vents. It is suggested that the volcanic gases contribute SO4 and chlorine to the fluids, hence increasing their ratios relative to sodium. Some hydrothermal fluids, however, are found to be depleted of the major elements which can have been caused by phase separation. The concentrations of iron and manganese in the fluids are much lower than those found in the mid-ocean ridges, while the aluminium content is higher. Four species of benthos (Xenograpsus testudi-natus, a snail, a sea anemone, and a Sipuncala), 1 species of algae (Corallinaceae), and 1 species of fish (Siganus fusescens) were recorded near the hydrothermal vents. A mitochondria DNA sequence comparison of Xenograpsus testudinatus with 6 other decapod species shows the greatest number of nitrogen base differences in the DNA fragments from 225 to 270. The gene diversity in this DNA region possibly results from the unusual habitat. A sediment core was collected at a pond near the eastern side of the tao. No volcanic ash could be detected in the core sample spanning 3 620 a.
