The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process ...The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process greatly influences the evolution of confined blast loading and the subsequent structural response,which is crucial in confined blast scenarios.Given the complex nature of the reaction process,accurate analysis of the afterburning effect remains challenging.Previous studies have either overlooked the mechanisms of detonation product combustion or failed to provide experimental validation.This study introduces a three-dimensional model to effectively characterize the combustion of detonation products.The model integrates chemical reaction source terms into the governing equations to consider the combustion processes.Numerical simulations and experimental tests were conducted to analyze the combustion and energy release from the detonation products of fuel-rich explosives in confined spaces.Approximately 50%of the energy was released during the combustion of detonation products in a confined TNT explosion.Although the combustion of these products was much slower than the detonation process,it aligned with the dynamic response of the structure,which enhanced the explosive yield.Excluding afterburning from the analysis reduced the center-point deformation of the structure by 30%.Following the inclusion of afterburning,the simulated quasistatic pressure increased by approximately 45%.Subsequent comparisons highlighted the merits of the proposed approach over conventional methods.This approach eliminates the reliance on empirical parameters,such as the amount and rate of energy release during afterburning,thereby laying the foundation for understanding load evolution in more complex environments,such as ships,buildings,and underground tunnels.展开更多
The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy...The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.展开更多
Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was d...Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was designed to simulate wound conditions, with gelatin used to simulate wound tissue. The distinction between open and confined spaces was explored, and the effects of temperature, humidity, discharge power and the gap size within the confined space on the plasma characteristics were analyzed. It was found that temperature, humidity and discharge power are important factors that affect the concentration distribution of active components and the mode transition between ozone and nitrogen oxides. Compared to open space, the concentration of ozone in confined space was relatively lower, which facilitated the formation of nitrogen oxides. In open space, the discharge was dominated by ozone initially. As the temperature,humidity and discharge power increased, nitrogen oxides in the gas-phase products were gradually detected. In confined space, nitrogen oxides can be detected at an early stage and at much higher concentrations than ozone concentration. Furthermore, as the gap of the confined space decreased, the concentration of ozone was observed to decrease while that of nitrate increased, and the rate of this concentration change was further accelerated at higher temperature and higher power. It was shown that ozone concentration decreased from 0.11 to 0.03 μmol and the nitrate concentration increased from 20.5 to 24.5 μmol when the spacing in the confined space was reduced from 5 to 1 mm, the temperature of the external discharge was controlled at 40 ℃, and the discharge power was 12 W. In summary, this study reveals the formation and transformation mechanisms of active substances in air surface micro-discharge plasma within confined space, providing foundational data for its medical applications.展开更多
Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si...Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si/Al ratio (Si/Al=4.6-6.1), high surface area (1090 m2/g) and the average diameter of nanosized NaY (75 nm) synthesized is 30 nm, it is smaller than that of without starch additive.展开更多
In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investi...In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investigates an experimental laboratory smoke environment using an ammonium chloride smoke agent.The particle size distribution,composition,and mass flow distribution of the smoke were studied.Based on a discrete phase model and a kεturbulence model,a numerical simulation was developed to model the smoke generation and diffusion processes of the smoke agent in a confined space.The temporal and spatial distribution characteristics of the smoke mass concentration,velocity,and temperature in the space after smoke generation were analyzed,and the motion law governing the smoke diffusion throughout the entire space was summarized.Combined with the experimental verification of the smoke environment laboratory,the results showed that the smoke plume changed from fan-shaped to umbrella-shaped during smoke generation,and then continued to spread around.Meanwhile,the mass concentration of smoke in the space decreased from the middle outward;the changes in temperature and velocity were small and stable.In the diffusion stage(after 900 s),the mass concentration of smoke above 0.8 m was relatively uniform across an area of smoke that was 12 m thick.The concentration decreased over time,following a consistent decreasing trend,and the attenuation was negligible in a very short time.Therefore,this system was suitable for conducting experimental research on laser fuzes in a smoke environment.Owing to the stability of the equipment and facilities,the setup could reproduce the same experimental smoke environment by artificially controlling the smoke emission of the smoke agent.Overall,this work provides a theoretical reference for subsequent research efforts regarding the construction of uniform smoke environments and evaluating laser transmission characteristics in smoky environments.展开更多
A miniature process for separating the oil phase from dilute oil/water emulsion is developed.This process applies a confined space apparatus,which is a thin flow channel made of two parallel plastic plates.The space b...A miniature process for separating the oil phase from dilute oil/water emulsion is developed.This process applies a confined space apparatus,which is a thin flow channel made of two parallel plastic plates.The space between the two plates is rather narrow to improve the collisions between oil droplets and the plate surface.Oil droplets have an affinity for the plate surface and thus are captured,and then coalesce onto the surface.The droplet size distribution of the residual emulsion resulted from the separation process is remarkably changed.The oil layer on the plate weakens the further separation of oil droplets from the emulsion.Three types of plate materials,polypropylene(PP),polytetrafluoroethylene(PTFE) and nylon 66,were used.It is found that PP is the best in terms of the oil separation efficiency and nylon 66 is the poorest.The interaction between droplets in the emulsion and plate surface is indicated by the spreading coefficient of oil droplet on the plate in aqueous environment,and the influences of formed oil layer and plate material on the separation efficiency are discussed.展开更多
One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to hap...One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to happen, that＇s why this paper is focusing on differentiating between the manual ＆ more developed equipments used specially in rescuing the crew in such an adequate time, to save the workers＇ life. The manual way is called ＂MUCKY CRANE＂ which is used for rescue purposes onboard tankers, in any of the confined spaces, should be replaced by excel crane which is air or hydraulic driven machine, to achieve better results. As safety precautions measures taken in such tasks are not enough for the required objective achievement. Such safety procedures have been discussed and critical situations have been pointed out.展开更多
Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2)...Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2) management in life-support systems of confined space.Here,a micro/nano-reconfigurable robot is constructed from the CO_(2) molecular hunters,temperature-sensitive molecular switch,solar photothermal conversion,and magnetically-driven function engines.The molecular hunters within the molecular extension state can capture 6.19 mmol g^(−1) of CO_(2) to form carbamic acid and ammonium bicarbonate.Interestingly,the molecular switch of the robot activates a molecular curling state that facilitates CO_(2) release through nano-reconfiguration,which is mediated by the temperature-sensitive curling of Pluronic F127 molecular chains during the photothermal desorption.Nano-reconfiguration of robot alters the amino microenvironment,including increasing surface electrostatic potential of the amino group and decreasing overall lowest unoccupied molecular orbital energy level.This weakened the nucleophilic attack ability of the amino group toward the adsorption product derivatives,thereby inhibiting the side reactions that generate hard-to-decompose urea structures,achieving the lowest regeneration temperature of 55℃ reported to date.The engine of the robot possesses non-contact magnetically-driven micro-reconfiguration capability to achieve efficient photothermal regeneration while avoiding local overheating.Notably,the robot successfully prolonged the survival time of mice in the sealed container by up to 54.61%,effectively addressing the issue of carbon suffocation in confined spaces.This work significantly enhances life-support systems for deep-space exploration,while stimulating innovations in sustainable carbon management technologies for terrestrial extreme environments.展开更多
Understandingmass transport within confined spaces is a key challenge with broad implications across numerous scientific and engineering disciplines.While studies on channel size effects and channel wall dynamics have...Understandingmass transport within confined spaces is a key challenge with broad implications across numerous scientific and engineering disciplines.While studies on channel size effects and channel wall dynamics have deepened our knowledge of material transport,the combined analysis of both factors remains underexplored.This study reports on a fatty acid,heptanoic acid,that spontaneously intercalates into graphene/SiO_(2)in its gaseous state but is controllably intercalated in its liquid state through laser irradiation.Leveraging the diverse local properties of the system—such as the confined spaces between flexible graphene and atomically rough SiO_(2)—we employed time-course Raman spectroscopy to record and analyze multiple dynamic molecular intercalation processes.Through systematic analysis,we propose a model based on the dynamic changes of three key parameters:graphene doping,strain,and 2D-band intensity(I2D)during the liquid molecular intercalation process,derived from time-course Raman spectroscopy data.This model allows for the assessment of the impact of molecular intercalation in confined spaces and the quantification of intercalation efficiency.Additionally,we explore the mechanisms by which laser irradiation regulates molecular intercalation behavior.This study provides a foundation for understanding and optimizing molecular transport within graphene-based systems featuring confined spaces.展开更多
Understanding the flow mechanisms between hydrocarbons and interfaces in nanopores is critical for fluid supply in tight reservoirs with huge reserves.In this paper,the nanoscale liquid-solid interface interaction pot...Understanding the flow mechanisms between hydrocarbons and interfaces in nanopores is critical for fluid supply in tight reservoirs with huge reserves.In this paper,the nanoscale liquid-solid interface interaction potential is analyzed based on the molecular interface theory,and a new nanoscale fluid viscosity model is constructed through the Eyring model,and the fluid velocity and flow flux models in nanopores are derived based on the liquid-solid interface slip condition.In addition,n-pentane flow characteristics in quartz nanopores were investigated with key parameters including:the Hamaker constant,the decay length,the wetting angle,the boundary slip and the flux coefficient.The proposed model is validated in a comparison of theory,simulation and laboratory results.The study results show:(1)influenced by the liquid-solid interfacial effect,there is a viscosity gap between the fluid in the bulk and at the boundary,resulting in a non-linear variation of the flow velocity.Of the multiple microscopic forces considered by the model,Ligshitz-Van der Waals force has the strongest effect in confined pores below 40 nm,and electrostatic force has the weakest effect.When the pore diameter less than 10 nm,the constrained fluid viscosity was improved above 4 times.(2)based on the microscopic liquid-solid interface slip condition,a constrained space velocity model is derived,which indicates that the flow is directly dependent on the effective shear stresses on the fluid and the strength of the liquid-solid interface effect.Under the low shear stress in a tight reservoir,the slip at the liquid-solid interface has obvious linear characteristics,and the slip velocity depends on the effective shear stress.The liquid-solid interfacial effect parameter is increased from 1 to 30,and the slip velocity is reduced to 3.2Å/ps,which is a 55%reduction.(3)in this paper,the hamaker constant of n-pentane-quartz interface based on the molecular spacing variation and the decay constant for different water types and solute concentrations are obtained,and the effect of the decay length on the flow coefficient of the nano confined flow model is explored for different pore radiuses.The flux coefficient increases with pore radius,and the effect of the decay length is greater for pores<100 nm.展开更多
The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is li...The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is limited by the low contact point between the core and shell.Herein,we propose a general strategy of simultaneous construction of sufficient reserved space and multicontinuous active channels by pyrolysis of two carbon substrates.A double-shell structure consisting of Co_(3)O_(4) anchored to hollow carbon sphere and external self-supporting zeolitic imidazolate framework(ZIF)layer was constructed by spray pyrolysis and additional carbon coating in-situ growth.In the process of high-temperature calcination,the carbon and nitrogen layers between the shells separate,creating additional space,while the Co_(3)O_(4) particles between the shells remain are still in close contact to form continuous and fast electron conduction channels,which can realize better charge transfer.Due to the synergy of these design principles,the material has ultra-high initial discharge capacities of 2,183.1 mAh·g^(−1) at 0.2 A·g^(−1) with capacity of 1,121.36 mAh·g^(−1) after 250 cycles,the long-term capacities retention rate is about 92.4%after 700 cycles at 1 A·g^(−1).This unique channel-type double-shell structure fights a way out to prepare novel electrode materials with high performance.展开更多
Hydrogen safety is one of the most important safety indicators in fuel cell vehicles(FCVs)(unlike in other types of alternative energy vehicles).This indicator in FCVs is directly related to the user’s personal safet...Hydrogen safety is one of the most important safety indicators in fuel cell vehicles(FCVs)(unlike in other types of alternative energy vehicles).This indicator in FCVs is directly related to the user’s personal safety in daily vehicle usage.This paper analyzes the safety standards of FCVs in confined spaces.A sealed test chamber and an appropriate test method are devel-oped to evaluate vehicle safety based on specific test requirements.Two FCVs are subjected to static hydrogen leakage and hydrogen emission testing performed in a confined space.The results reveal that the hydrogen concentration in the vicinity of the vehicles approximates 0.0004%which is much lower than 1%while parked for 8 h during the hydrogen leakage test.In the hydrogen emission test under operating conditions,the concentration of the hydrogen gas emitted from the vehicles exceeds 2300 ppm in the vicinity,which requires careful consideration.Based on experiment and analysis,recommendations for the hydrogen safety standards of FCVs in confined spaces are proposed.展开更多
Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual form...Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual forms of high-crystalline nanosheet-like Ni(OH)_(2) severally distribute within mesopores or over the outer surface of 3DOMC particles depending on the loading amount(3%^(−1)5%)of Ni(OH)_(2).Benefitted from the highly hybrid combination and efficient electrolyte diffusion,the obtained Ni(OH)_(2)/carbon nanocomposites exhibit an excellent electrochemical performance,and the optimal sample of 6%_Ni(OH)_(2)/3DOMC with confined extrasmall Ni(OH)_(2) nanosheets as dominant shows the highest specific capacitance of 552.5F.g^(−1) at 1.0A⋅g^(−1),which is 330%higher than the contrast sample by using actived carbon as the support.Furthermore,the assembled hybrid supercapacitor by using 6%_Ni(OH)_(2)/3DOMC and 3DOMC as positive and negative electrodes displays an energy density of 11.7 Wh.kg^(−1) at 288.1 W.kg^(−1) and a superior charge/discharge stability.It is expected that the flexible component,well-defined structure,and superior electrochemical performance could promote a great application potential of Ni(OH)_(2)/3DOMC nanocomposites as supercapacitor electrodes and in other energy storage devices.展开更多
The detection of biomarkers with both high sensitivity and specificity is crucial for the diagnosis and treatment of related diseases.However,many current detections employ ex-situ detection method and non-confined co...The detection of biomarkers with both high sensitivity and specificity is crucial for the diagnosis and treatment of related diseases.However,many current detections employ ex-situ detection method and non-confined condition,thus have many problems,which may eventually lead to inaccurate detection results.Compared to detection in non-confined space,detection in confined space can better reflect the real in-vivo situation.Therefore,the construction of detection for target molecules in confined space has great significance for both theoretical research and practical application.To realize the detection of target molecules in confined space,the probes should accurately enter the confined space where the target molecules reside and interact with the interface.Thus,how to explore and utilize the properties of the interface(for example,bioinspired superwettability)has always been a hot and difficult topic in this field.Herein,the recent advances and our efforts in recent 10 years on detection of bio-target molecules in confined space with superwettable interface have been introduced from the perspective of the detection methods.The suitable and most widely employed detection methods for target molecules in confined spaces are introduced firstly.Then,recent progresses for related detections based on visual,optical,and electrochemical detection methods are presented successively.Finally,the perspective for detection in confined space is discussed for the future development of biochemical detection.展开更多
The accumulation of pollutants in the recirculation zone can worsen ventilation.It is critical to reduce recirculation zones to improve the ventilation efficiency of buildings.However,the variation rule of the recircu...The accumulation of pollutants in the recirculation zone can worsen ventilation.It is critical to reduce recirculation zones to improve the ventilation efficiency of buildings.However,the variation rule of the recirculation zone in a cylindrical confined space(CCS)is unclear,and there are few solutions to suppress or eliminate the recirculation zone at present.In this paper,an annular deflector orifice plate for suppressing the recirculation zone was developed based on the structural characteristics of the CCS.This device is simple in structure and can be used flexibly.Through experiments and numerical simulations,the variation rule of the recirculation zone length and the influence of structural parameters of the device on the vortex suppression were explored.Firstly,empirical formulas for calculating the length of the recirculation zone in the CCS were obtained.In addition,it was proved that placing the annular orifice plate inside the CCS effectively reduced the recirculation zone and improved the ventilation efficiency.Compared to the system without the annular orifice plate,the dimensionless length of the recirculation zone was decreased by 76.3%,and the time to completely discharge the pollutants from the CCS was decreased by 16.7%.Finally,parameters of the annular orifice plate that form the best vortex suppression effect were proposed:the porosity range was 40%–50%,uniform in shape with equal ring spacing,and placed more than one inlet diameter away from the inlet.The results help guide the ventilation design of CCS.展开更多
The number of active components and their dispersion degree are two key factors affecting the performance of adsorbents.Here,we report a simple but efficient strategy for dispersing active components by using a confin...The number of active components and their dispersion degree are two key factors affecting the performance of adsorbents.Here,we report a simple but efficient strategy for dispersing active components by using a confined space,which is formed by mesoporous silica walls and templates in the as-prepared SBA-15(AS).Such a confined space does not exist in the conventional support,calcined SBA-15,which does not contain a template.The Cu and Zn precursors were introduced to the confined space in the AS and were converted to CuO and ZnO during calcination,during which the template was also removed.The results show that up to 5 mmol·g^(–1) of CuO and ZnO can be well dispersed;however,severe aggregation of both oxides takes place in the sample derived from the calcined SBA-15 with the same loading.Confined space in the AS and the strong interactions caused by the abundant hydroxyl groups are responsible for the dispersion of CuO and ZnO.The bimetallic materials were employed for the adsorptive separation of propene and propane.The samples prepared from the as-prepared SBA-15 showed superior performance to their counterparts from the calcined SBA-15 in terms of both adsorption capacity of propene and selectivity for propene/propane.展开更多
Lateral-confined coaxial jet diffusion flame is common in micro thrusters,and the specific impulse is mainly obtained through thermodynamic calculations with an assumption of fuel combustion with an equivalence ratio,...Lateral-confined coaxial jet diffusion flame is common in micro thrusters,and the specific impulse is mainly obtained through thermodynamic calculations with an assumption of fuel combustion with an equivalence ratio,regardless of the stability of the combustion process.However,the flame behavior plays an important impact on the performance of a micro thruster through the varied combustion efficiency.The stability of confined coaxial jet diffusion flames with air coflow was studied by experiments and numerical simulation.Methane,hydrogen,and propane were used as fuels.Flame attachment,liftoff,blowout(extinction limits of lifted flame),and blowoff(extinction limits of attached flame) behaviors with the effect of confinement ratios and fuel properties were focused on.Among the range of the jet flow velocity in this research,the hydrogen flame is always attached to the jet exit,the flame tip goes from closed to open as the jet velocity increases,while the flame transitions from attachment to liftoff in the case of CH_(4) and C_(3)H_(8) .Further,in a narrow confined space,the attached flame for both CH4 and C_(3)H_(8) undergoes liftoff followed by blowout.However,in a space with a high confinement ratio,the CH4 flame transitions directly from attachment to blowoff.The critical modified Craya-Curtet number,which is used to predict the onset of the recirculation,is determined through simulation and experiment,and the number is about 1.77.This work provides valuable data on flame stability inside a confined space and gives insights into the design of a thruster.展开更多
In living organisms,confined space with specific chemical composition and elaborate spatial distribution regulates the formation of natural structures.Learning from the natural structure-forming process,novel synthesi...In living organisms,confined space with specific chemical composition and elaborate spatial distribution regulates the formation of natural structures.Learning from the natural structure-forming process,novel synthesis approaches in deliberated confined systems have been proposed for obtaining designed structures.Artificial confined systems can effectively regulate the synthesis of materials with defined structures according to the geometry of confinements.Collagen fibrils provide biological confinements for the formation of hierarchical structure with periodic arrangement.Genetically engineered living organisms with designed confinements can direct the synthesis of three-dimensional nanostructures.More novel structures will be rationally fabricated in the future with the aid of deeper understanding of biological processes.展开更多
This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are ex...This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are explored using high-speed photography experiments.Subsequently,based on the circle theorem,the liquid velocity field is qualitatively analyzed and compared with the experimental bubble interface motion.Finally,employing the Kelvin impulse theory,an analysis of the variation in Kelvin impulse at various cylinder spacings is conducted,which shows good consistency with the bubble centroid movement.The main conclusions are summarized as follows:(1)High-velocity regions are observed on both sides of the bubble.Low-velocity regions are observed between the bubble and cylinders.As the cylinder spacing and the bubble abscissa increase,the liquid velocity in the high-velocity regions decreases,and the low-velocity regions expands.(2)The characteristics of the bubble cross-sectional roundness,interface displacement,and cross-sectional area are significantly affected by the cylinder spacing and the bubble abscissa.(3)As the bubble abscissa increases,the Kelvin impulse intensity initially rises rapidly and subsequently declines gradually to a fixed value.As the cylinder spacings increases,the Kelvin impulse intensity decreases.展开更多
Hazardous gas intrusion in tightly sealed and geometrically complex confined spaces,such as armored tanks,poses a critical threat to occupant health.The intricate internal structure of these systems may lead to non-in...Hazardous gas intrusion in tightly sealed and geometrically complex confined spaces,such as armored tanks,poses a critical threat to occupant health.The intricate internal structure of these systems may lead to non-intuitive pollutant transport pathways.However,the spatial and temporal evolution of these structures,as well as the intrinsic mechanisms of the purification systems,remain poorly elucidated.In this study,a high-fidelity,transient three-dimensional computational fluid dynamics(CFD)model was developed to simulate the leakage and dispersion of carbon monoxide(CO)and nitrogen dioxide(NO_(2))using the RNG k-εturbulence model.Scenarios with and without an active purification system were systematically investigated under four leakage rate conditions:0.33,0.66,1.32,and 2.64 m·s^(−1).Our results reveal that,flow recirculation driven by the compartment’s geometry leads to the formation of stable,high-concentration“hazard zones”.Following the activation of the purification system,Log 10 CV decreases from 1 to 0.1,demonstrating that the primary value of the purification system lies in homogenizing the internal flow field and minimizing localized hazardous zones.At leakage rates below 1.32 m/s,the purification system ensures pollutant concentrations at all monitoring points are effectively controlled below limitation.When single-pass purification efficiency increases from 25%to 30%,pollutant concentrations at critical monitoring points decrease by approximately 30%.This work provides crucial mechanistic insights and a quantitative basis for the design of advanced ventilation systems in complex confined environments,advocating a design philosophy shift from simple air exchange to strategic flow-field management.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52171318 and 12202329)Joint Foundation of the Ministry of Education(Grant No.8091B022105)。
文摘The detonation of fuel-rich explosives yields combustible products that persistently burn upon mixing with ambient oxygen,releasing additional energy through a phenomenon known as the afterburning effect.This process greatly influences the evolution of confined blast loading and the subsequent structural response,which is crucial in confined blast scenarios.Given the complex nature of the reaction process,accurate analysis of the afterburning effect remains challenging.Previous studies have either overlooked the mechanisms of detonation product combustion or failed to provide experimental validation.This study introduces a three-dimensional model to effectively characterize the combustion of detonation products.The model integrates chemical reaction source terms into the governing equations to consider the combustion processes.Numerical simulations and experimental tests were conducted to analyze the combustion and energy release from the detonation products of fuel-rich explosives in confined spaces.Approximately 50%of the energy was released during the combustion of detonation products in a confined TNT explosion.Although the combustion of these products was much slower than the detonation process,it aligned with the dynamic response of the structure,which enhanced the explosive yield.Excluding afterburning from the analysis reduced the center-point deformation of the structure by 30%.Following the inclusion of afterburning,the simulated quasistatic pressure increased by approximately 45%.Subsequent comparisons highlighted the merits of the proposed approach over conventional methods.This approach eliminates the reliance on empirical parameters,such as the amount and rate of energy release during afterburning,thereby laying the foundation for understanding load evolution in more complex environments,such as ships,buildings,and underground tunnels.
文摘The concept of TNT(Trinitrotoluene,C_7H_5N_3O_6)equivalence is often invoked to evaluate the performance and predict the explosion parameters of different types of explosives.However,due to its low prediction accuracy and limited application range,the use of TNT equivalence for predicting explosion parameters in a confined space is rare.Compared with explosions in free fields,the process of explosive energy release in a confined space is closely related to various factors such as oxygen balance,combustible components content,and surrounding oxygen content.Studies have shown that in a confined space,negative oxygen balance explosives react with surrounding oxygen during afterburning,resulting in additional energy release and enhanced blast effects.The mechanism of energy release during afterburning is highly complex,making it challenging to determine the TNT equivalence for blast effects in a confined space.Therefore,this remains an active area of research.In this study,internal blast experiments were conducted using TNT and three other explosives under both air and N_2(Nitrogen)conditions to obtain explosion parameters including blast wave overpressure,quasi-static pressure,and temperature.The influences of oxygen balance and external oxygen content on energy release are analyzed.The author proposes principles for determining TNT equivalence for internal explosions while verifying the accuracy of obtained blast parameters through calculations based on TNT equivalence.These findings can serve as references for predicting blast performance.
基金supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province (No. 1003016001)。
文摘Flexible surface micro-discharge plasma is a non-thermal plasma technique used for treating wounds in a painless way, with significant efficacy for chronic or hard-to-heal wounds. In this study, a confined space was designed to simulate wound conditions, with gelatin used to simulate wound tissue. The distinction between open and confined spaces was explored, and the effects of temperature, humidity, discharge power and the gap size within the confined space on the plasma characteristics were analyzed. It was found that temperature, humidity and discharge power are important factors that affect the concentration distribution of active components and the mode transition between ozone and nitrogen oxides. Compared to open space, the concentration of ozone in confined space was relatively lower, which facilitated the formation of nitrogen oxides. In open space, the discharge was dominated by ozone initially. As the temperature,humidity and discharge power increased, nitrogen oxides in the gas-phase products were gradually detected. In confined space, nitrogen oxides can be detected at an early stage and at much higher concentrations than ozone concentration. Furthermore, as the gap of the confined space decreased, the concentration of ozone was observed to decrease while that of nitrate increased, and the rate of this concentration change was further accelerated at higher temperature and higher power. It was shown that ozone concentration decreased from 0.11 to 0.03 μmol and the nitrate concentration increased from 20.5 to 24.5 μmol when the spacing in the confined space was reduced from 5 to 1 mm, the temperature of the external discharge was controlled at 40 ℃, and the discharge power was 12 W. In summary, this study reveals the formation and transformation mechanisms of active substances in air surface micro-discharge plasma within confined space, providing foundational data for its medical applications.
文摘Nanosized NaY crystals have been prepared from metakaolin and sodium silicate by confined space synthesis with starch additive. It is found that the product has a narrow crystal size distribution (50-100 nm), high Si/Al ratio (Si/Al=4.6-6.1), high surface area (1090 m2/g) and the average diameter of nanosized NaY (75 nm) synthesized is 30 nm, it is smaller than that of without starch additive.
基金the Central University Special Funding for Basic Scientific Research(Grant No.30918012201)the Foundation of JWKJW Field(Grant 2020-JCJQ-JJ-392)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0315).
文摘In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investigates an experimental laboratory smoke environment using an ammonium chloride smoke agent.The particle size distribution,composition,and mass flow distribution of the smoke were studied.Based on a discrete phase model and a kεturbulence model,a numerical simulation was developed to model the smoke generation and diffusion processes of the smoke agent in a confined space.The temporal and spatial distribution characteristics of the smoke mass concentration,velocity,and temperature in the space after smoke generation were analyzed,and the motion law governing the smoke diffusion throughout the entire space was summarized.Combined with the experimental verification of the smoke environment laboratory,the results showed that the smoke plume changed from fan-shaped to umbrella-shaped during smoke generation,and then continued to spread around.Meanwhile,the mass concentration of smoke in the space decreased from the middle outward;the changes in temperature and velocity were small and stable.In the diffusion stage(after 900 s),the mass concentration of smoke above 0.8 m was relatively uniform across an area of smoke that was 12 m thick.The concentration decreased over time,following a consistent decreasing trend,and the attenuation was negligible in a very short time.Therefore,this system was suitable for conducting experimental research on laser fuzes in a smoke environment.Owing to the stability of the equipment and facilities,the setup could reproduce the same experimental smoke environment by artificially controlling the smoke emission of the smoke agent.Overall,this work provides a theoretical reference for subsequent research efforts regarding the construction of uniform smoke environments and evaluating laser transmission characteristics in smoky environments.
基金Supported by the Eleventh Five-Year Plan of national support (2007BAI26B03-04)
文摘A miniature process for separating the oil phase from dilute oil/water emulsion is developed.This process applies a confined space apparatus,which is a thin flow channel made of two parallel plastic plates.The space between the two plates is rather narrow to improve the collisions between oil droplets and the plate surface.Oil droplets have an affinity for the plate surface and thus are captured,and then coalesce onto the surface.The droplet size distribution of the residual emulsion resulted from the separation process is remarkably changed.The oil layer on the plate weakens the further separation of oil droplets from the emulsion.Three types of plate materials,polypropylene(PP),polytetrafluoroethylene(PTFE) and nylon 66,were used.It is found that PP is the best in terms of the oil separation efficiency and nylon 66 is the poorest.The interaction between droplets in the emulsion and plate surface is indicated by the spreading coefficient of oil droplet on the plate in aqueous environment,and the influences of formed oil layer and plate material on the separation efficiency are discussed.
文摘One of the major hazards when working onboard Tankers is working in confined spaces, improving the procedures in working in such spaces is obvious, but developing the equipments used in rescue operation is rare to happen, that＇s why this paper is focusing on differentiating between the manual ＆ more developed equipments used specially in rescuing the crew in such an adequate time, to save the workers＇ life. The manual way is called ＂MUCKY CRANE＂ which is used for rescue purposes onboard tankers, in any of the confined spaces, should be replaced by excel crane which is air or hydraulic driven machine, to achieve better results. As safety precautions measures taken in such tasks are not enough for the required objective achievement. Such safety procedures have been discussed and critical situations have been pointed out.
基金supported by the National Natural Science Foundation of China(22168008,22378085)the Guangxi Natural Science Foundation(2024GXNSFDA010053)+1 种基金the Technology Development Project of Guangxi Bossco Environmental Protection Technology Co.,Ltd(202100039)Innovation Project of Guangxi Graduate Education(YCBZ2024065).
文摘Strategically coupling nanoparticle hybrids and internal thermosensitive molecular switches establishes an innovative paradigm for constructing micro/nanoscale-reconfigurable robots,facilitating energyefficient CO_(2) management in life-support systems of confined space.Here,a micro/nano-reconfigurable robot is constructed from the CO_(2) molecular hunters,temperature-sensitive molecular switch,solar photothermal conversion,and magnetically-driven function engines.The molecular hunters within the molecular extension state can capture 6.19 mmol g^(−1) of CO_(2) to form carbamic acid and ammonium bicarbonate.Interestingly,the molecular switch of the robot activates a molecular curling state that facilitates CO_(2) release through nano-reconfiguration,which is mediated by the temperature-sensitive curling of Pluronic F127 molecular chains during the photothermal desorption.Nano-reconfiguration of robot alters the amino microenvironment,including increasing surface electrostatic potential of the amino group and decreasing overall lowest unoccupied molecular orbital energy level.This weakened the nucleophilic attack ability of the amino group toward the adsorption product derivatives,thereby inhibiting the side reactions that generate hard-to-decompose urea structures,achieving the lowest regeneration temperature of 55℃ reported to date.The engine of the robot possesses non-contact magnetically-driven micro-reconfiguration capability to achieve efficient photothermal regeneration while avoiding local overheating.Notably,the robot successfully prolonged the survival time of mice in the sealed container by up to 54.61%,effectively addressing the issue of carbon suffocation in confined spaces.This work significantly enhances life-support systems for deep-space exploration,while stimulating innovations in sustainable carbon management technologies for terrestrial extreme environments.
基金Financial support from the Research Foundation-Flanders(FWO)(G0A3220N)KU Leuven-Internal Funds(grant no.C14/23/090)is acknowledged+1 种基金supported by FWO(grant nos.G0H2122N and GF9118N)and Fund for Scientific Research(F.R.S.-FNRS)under the Excellence of Science(EOS)program(projects 30489208 and 40007495)the China Scholarship Council(grant no.202006150018).
文摘Understandingmass transport within confined spaces is a key challenge with broad implications across numerous scientific and engineering disciplines.While studies on channel size effects and channel wall dynamics have deepened our knowledge of material transport,the combined analysis of both factors remains underexplored.This study reports on a fatty acid,heptanoic acid,that spontaneously intercalates into graphene/SiO_(2)in its gaseous state but is controllably intercalated in its liquid state through laser irradiation.Leveraging the diverse local properties of the system—such as the confined spaces between flexible graphene and atomically rough SiO_(2)—we employed time-course Raman spectroscopy to record and analyze multiple dynamic molecular intercalation processes.Through systematic analysis,we propose a model based on the dynamic changes of three key parameters:graphene doping,strain,and 2D-band intensity(I2D)during the liquid molecular intercalation process,derived from time-course Raman spectroscopy data.This model allows for the assessment of the impact of molecular intercalation in confined spaces and the quantification of intercalation efficiency.Additionally,we explore the mechanisms by which laser irradiation regulates molecular intercalation behavior.This study provides a foundation for understanding and optimizing molecular transport within graphene-based systems featuring confined spaces.
基金supported by the Key Program of the National Natural Science Foundation of China[No.U24B200683]Natural Science Foundation of Sichuan Provincial,China[No.2024NSFSC2012].
文摘Understanding the flow mechanisms between hydrocarbons and interfaces in nanopores is critical for fluid supply in tight reservoirs with huge reserves.In this paper,the nanoscale liquid-solid interface interaction potential is analyzed based on the molecular interface theory,and a new nanoscale fluid viscosity model is constructed through the Eyring model,and the fluid velocity and flow flux models in nanopores are derived based on the liquid-solid interface slip condition.In addition,n-pentane flow characteristics in quartz nanopores were investigated with key parameters including:the Hamaker constant,the decay length,the wetting angle,the boundary slip and the flux coefficient.The proposed model is validated in a comparison of theory,simulation and laboratory results.The study results show:(1)influenced by the liquid-solid interfacial effect,there is a viscosity gap between the fluid in the bulk and at the boundary,resulting in a non-linear variation of the flow velocity.Of the multiple microscopic forces considered by the model,Ligshitz-Van der Waals force has the strongest effect in confined pores below 40 nm,and electrostatic force has the weakest effect.When the pore diameter less than 10 nm,the constrained fluid viscosity was improved above 4 times.(2)based on the microscopic liquid-solid interface slip condition,a constrained space velocity model is derived,which indicates that the flow is directly dependent on the effective shear stresses on the fluid and the strength of the liquid-solid interface effect.Under the low shear stress in a tight reservoir,the slip at the liquid-solid interface has obvious linear characteristics,and the slip velocity depends on the effective shear stress.The liquid-solid interfacial effect parameter is increased from 1 to 30,and the slip velocity is reduced to 3.2Å/ps,which is a 55%reduction.(3)in this paper,the hamaker constant of n-pentane-quartz interface based on the molecular spacing variation and the decay constant for different water types and solute concentrations are obtained,and the effect of the decay length on the flow coefficient of the nano confined flow model is explored for different pore radiuses.The flux coefficient increases with pore radius,and the effect of the decay length is greater for pores<100 nm.
基金supported by the National Natural Science Foundation of China(Nos.21871005 and 22171005)the Program for Innovative Research Team of Anhui Education Committee,the Project for Collaborative Innovation of Anhui Higher Education Institutes(Nos.GXXT-2020-005,GXXT-2021-012,and GXXT-2021-013)+1 种基金the Natural Science Foundation of the Education Department of Anhui Province(No.KJ2020A0075)the Foundation of the Anhui Province Key Laboratory of Clean Energy Materials and Chemistry for Sustainable Conversion of Natural Resources(No.LCECSC-10).
文摘The yolk–shell structure has a unique advantage in lithium-ion batteries applications due to its ability to effectively buffer the volume expansion of the lithiation/delithiation process.However,its development is limited by the low contact point between the core and shell.Herein,we propose a general strategy of simultaneous construction of sufficient reserved space and multicontinuous active channels by pyrolysis of two carbon substrates.A double-shell structure consisting of Co_(3)O_(4) anchored to hollow carbon sphere and external self-supporting zeolitic imidazolate framework(ZIF)layer was constructed by spray pyrolysis and additional carbon coating in-situ growth.In the process of high-temperature calcination,the carbon and nitrogen layers between the shells separate,creating additional space,while the Co_(3)O_(4) particles between the shells remain are still in close contact to form continuous and fast electron conduction channels,which can realize better charge transfer.Due to the synergy of these design principles,the material has ultra-high initial discharge capacities of 2,183.1 mAh·g^(−1) at 0.2 A·g^(−1) with capacity of 1,121.36 mAh·g^(−1) after 250 cycles,the long-term capacities retention rate is about 92.4%after 700 cycles at 1 A·g^(−1).This unique channel-type double-shell structure fights a way out to prepare novel electrode materials with high performance.
基金supported by the Young Elite Scientists Sponsorship Program by CAST and China SAE,the National Key Research and Development Program of China(Grant No.2017YFB0103100)Tianjin Municipal Science and Technology Commission Program(Grant No.17ZXFWGX00040).
文摘Hydrogen safety is one of the most important safety indicators in fuel cell vehicles(FCVs)(unlike in other types of alternative energy vehicles).This indicator in FCVs is directly related to the user’s personal safety in daily vehicle usage.This paper analyzes the safety standards of FCVs in confined spaces.A sealed test chamber and an appropriate test method are devel-oped to evaluate vehicle safety based on specific test requirements.Two FCVs are subjected to static hydrogen leakage and hydrogen emission testing performed in a confined space.The results reveal that the hydrogen concentration in the vicinity of the vehicles approximates 0.0004%which is much lower than 1%while parked for 8 h during the hydrogen leakage test.In the hydrogen emission test under operating conditions,the concentration of the hydrogen gas emitted from the vehicles exceeds 2300 ppm in the vicinity,which requires careful consideration.Based on experiment and analysis,recommendations for the hydrogen safety standards of FCVs in confined spaces are proposed.
基金the National Natural Science Foundation of China(Nos.21978238,21878248,and 21978055)Natural Science Foundation of Shaanxi Provincial Department of Education(No.21JY041).
文摘Regulable loading of Ni(OH)_(2) crystals by using three dimensionally ordered mesoporous carbon(3DOMC)as a support is achieved through a confined growth strategy accompanied by steam-assisted crystallization.Dual forms of high-crystalline nanosheet-like Ni(OH)_(2) severally distribute within mesopores or over the outer surface of 3DOMC particles depending on the loading amount(3%^(−1)5%)of Ni(OH)_(2).Benefitted from the highly hybrid combination and efficient electrolyte diffusion,the obtained Ni(OH)_(2)/carbon nanocomposites exhibit an excellent electrochemical performance,and the optimal sample of 6%_Ni(OH)_(2)/3DOMC with confined extrasmall Ni(OH)_(2) nanosheets as dominant shows the highest specific capacitance of 552.5F.g^(−1) at 1.0A⋅g^(−1),which is 330%higher than the contrast sample by using actived carbon as the support.Furthermore,the assembled hybrid supercapacitor by using 6%_Ni(OH)_(2)/3DOMC and 3DOMC as positive and negative electrodes displays an energy density of 11.7 Wh.kg^(−1) at 288.1 W.kg^(−1) and a superior charge/discharge stability.It is expected that the flexible component,well-defined structure,and superior electrochemical performance could promote a great application potential of Ni(OH)_(2)/3DOMC nanocomposites as supercapacitor electrodes and in other energy storage devices.
基金supported by the National Natural Science Foundation of China(No.22204150)GuangDong Basic and Applied Basic Research Foundation(No.2021A1515110036)+1 种基金the National Key R&D Program of China(Nos.2021YFA1200403 and 2018YFE0206900)the Joint NSFC-ISF Research Grant Program(No.22161142020).
文摘The detection of biomarkers with both high sensitivity and specificity is crucial for the diagnosis and treatment of related diseases.However,many current detections employ ex-situ detection method and non-confined condition,thus have many problems,which may eventually lead to inaccurate detection results.Compared to detection in non-confined space,detection in confined space can better reflect the real in-vivo situation.Therefore,the construction of detection for target molecules in confined space has great significance for both theoretical research and practical application.To realize the detection of target molecules in confined space,the probes should accurately enter the confined space where the target molecules reside and interact with the interface.Thus,how to explore and utilize the properties of the interface(for example,bioinspired superwettability)has always been a hot and difficult topic in this field.Herein,the recent advances and our efforts in recent 10 years on detection of bio-target molecules in confined space with superwettable interface have been introduced from the perspective of the detection methods.The suitable and most widely employed detection methods for target molecules in confined spaces are introduced firstly.Then,recent progresses for related detections based on visual,optical,and electrochemical detection methods are presented successively.Finally,the perspective for detection in confined space is discussed for the future development of biochemical detection.
基金financially sponsored by the Collaborative Innovation Foundation of the Shaanxi Provincial Department of Education (No.20JY035).
文摘The accumulation of pollutants in the recirculation zone can worsen ventilation.It is critical to reduce recirculation zones to improve the ventilation efficiency of buildings.However,the variation rule of the recirculation zone in a cylindrical confined space(CCS)is unclear,and there are few solutions to suppress or eliminate the recirculation zone at present.In this paper,an annular deflector orifice plate for suppressing the recirculation zone was developed based on the structural characteristics of the CCS.This device is simple in structure and can be used flexibly.Through experiments and numerical simulations,the variation rule of the recirculation zone length and the influence of structural parameters of the device on the vortex suppression were explored.Firstly,empirical formulas for calculating the length of the recirculation zone in the CCS were obtained.In addition,it was proved that placing the annular orifice plate inside the CCS effectively reduced the recirculation zone and improved the ventilation efficiency.Compared to the system without the annular orifice plate,the dimensionless length of the recirculation zone was decreased by 76.3%,and the time to completely discharge the pollutants from the CCS was decreased by 16.7%.Finally,parameters of the annular orifice plate that form the best vortex suppression effect were proposed:the porosity range was 40%–50%,uniform in shape with equal ring spacing,and placed more than one inlet diameter away from the inlet.The results help guide the ventilation design of CCS.
基金We acknowledge the financial support of this work by the National Natural Science Foundation of China(Grant Nos.22125804,22078155,and21878149).
文摘The number of active components and their dispersion degree are two key factors affecting the performance of adsorbents.Here,we report a simple but efficient strategy for dispersing active components by using a confined space,which is formed by mesoporous silica walls and templates in the as-prepared SBA-15(AS).Such a confined space does not exist in the conventional support,calcined SBA-15,which does not contain a template.The Cu and Zn precursors were introduced to the confined space in the AS and were converted to CuO and ZnO during calcination,during which the template was also removed.The results show that up to 5 mmol·g^(–1) of CuO and ZnO can be well dispersed;however,severe aggregation of both oxides takes place in the sample derived from the calcined SBA-15 with the same loading.Confined space in the AS and the strong interactions caused by the abundant hydroxyl groups are responsible for the dispersion of CuO and ZnO.The bimetallic materials were employed for the adsorptive separation of propene and propane.The samples prepared from the as-prepared SBA-15 showed superior performance to their counterparts from the calcined SBA-15 in terms of both adsorption capacity of propene and selectivity for propene/propane.
基金supported by the Space Application System of China Manned Space Program,and the National Key Research and Development Program of China under grant number 2022YFF0504500.
文摘Lateral-confined coaxial jet diffusion flame is common in micro thrusters,and the specific impulse is mainly obtained through thermodynamic calculations with an assumption of fuel combustion with an equivalence ratio,regardless of the stability of the combustion process.However,the flame behavior plays an important impact on the performance of a micro thruster through the varied combustion efficiency.The stability of confined coaxial jet diffusion flames with air coflow was studied by experiments and numerical simulation.Methane,hydrogen,and propane were used as fuels.Flame attachment,liftoff,blowout(extinction limits of lifted flame),and blowoff(extinction limits of attached flame) behaviors with the effect of confinement ratios and fuel properties were focused on.Among the range of the jet flow velocity in this research,the hydrogen flame is always attached to the jet exit,the flame tip goes from closed to open as the jet velocity increases,while the flame transitions from attachment to liftoff in the case of CH_(4) and C_(3)H_(8) .Further,in a narrow confined space,the attached flame for both CH4 and C_(3)H_(8) undergoes liftoff followed by blowout.However,in a space with a high confinement ratio,the CH4 flame transitions directly from attachment to blowoff.The critical modified Craya-Curtet number,which is used to predict the onset of the recirculation,is determined through simulation and experiment,and the number is about 1.77.This work provides valuable data on flame stability inside a confined space and gives insights into the design of a thruster.
基金This work was financially supported by the National Natural Science Foundation of China(51521001)the Ministry of Science and Technology of China(2015DFR50650)the Fundamental Research Funds for the Central University(WUT 2016IB006).
文摘In living organisms,confined space with specific chemical composition and elaborate spatial distribution regulates the formation of natural structures.Learning from the natural structure-forming process,novel synthesis approaches in deliberated confined systems have been proposed for obtaining designed structures.Artificial confined systems can effectively regulate the synthesis of materials with defined structures according to the geometry of confinements.Collagen fibrils provide biological confinements for the formation of hierarchical structure with periodic arrangement.Genetically engineered living organisms with designed confinements can direct the synthesis of three-dimensional nanostructures.More novel structures will be rationally fabricated in the future with the aid of deeper understanding of biological processes.
基金Project supported by the National Natural Science Foundation of China(Grant No.52076215).
文摘This paper investigates the bubble collapse characteristics near dual cylinders within confined spaces.Firstly,the impacts on the bubble morphology,with respect to the bubble positions and the cylinder spacings,are explored using high-speed photography experiments.Subsequently,based on the circle theorem,the liquid velocity field is qualitatively analyzed and compared with the experimental bubble interface motion.Finally,employing the Kelvin impulse theory,an analysis of the variation in Kelvin impulse at various cylinder spacings is conducted,which shows good consistency with the bubble centroid movement.The main conclusions are summarized as follows:(1)High-velocity regions are observed on both sides of the bubble.Low-velocity regions are observed between the bubble and cylinders.As the cylinder spacing and the bubble abscissa increase,the liquid velocity in the high-velocity regions decreases,and the low-velocity regions expands.(2)The characteristics of the bubble cross-sectional roundness,interface displacement,and cross-sectional area are significantly affected by the cylinder spacing and the bubble abscissa.(3)As the bubble abscissa increases,the Kelvin impulse intensity initially rises rapidly and subsequently declines gradually to a fixed value.As the cylinder spacings increases,the Kelvin impulse intensity decreases.
基金supported by the National Key Research and Development Program of China(Grant No.:2022YFE0210200).
文摘Hazardous gas intrusion in tightly sealed and geometrically complex confined spaces,such as armored tanks,poses a critical threat to occupant health.The intricate internal structure of these systems may lead to non-intuitive pollutant transport pathways.However,the spatial and temporal evolution of these structures,as well as the intrinsic mechanisms of the purification systems,remain poorly elucidated.In this study,a high-fidelity,transient three-dimensional computational fluid dynamics(CFD)model was developed to simulate the leakage and dispersion of carbon monoxide(CO)and nitrogen dioxide(NO_(2))using the RNG k-εturbulence model.Scenarios with and without an active purification system were systematically investigated under four leakage rate conditions:0.33,0.66,1.32,and 2.64 m·s^(−1).Our results reveal that,flow recirculation driven by the compartment’s geometry leads to the formation of stable,high-concentration“hazard zones”.Following the activation of the purification system,Log 10 CV decreases from 1 to 0.1,demonstrating that the primary value of the purification system lies in homogenizing the internal flow field and minimizing localized hazardous zones.At leakage rates below 1.32 m/s,the purification system ensures pollutant concentrations at all monitoring points are effectively controlled below limitation.When single-pass purification efficiency increases from 25%to 30%,pollutant concentrations at critical monitoring points decrease by approximately 30%.This work provides crucial mechanistic insights and a quantitative basis for the design of advanced ventilation systems in complex confined environments,advocating a design philosophy shift from simple air exchange to strategic flow-field management.
