Analysis of temporal and spatial distribution characteristics of ammonium chloride smoke particles in confined spaces

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.

Experimental Study on Hydrogen Leakage and Emission of Fuel Cell Vehicles in Confined Spaces

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.

Evaluating acoustic communication performance of micro autonomous underwater vehicles in confined spaces

Micro-sized autonomous underwater vehicles(μAUVs) are well suited to various applications in confined underwater spaces. Acoustic communication is required for many application scenarios of μAUVs to enable data transmission without surfacing. This paper presents the integration of a compact acoustic communication device with a μAUV prototype. Packet reception rate(PRR) and bit error rate(BER) of the acoustic communication link are evaluated in a confined pool environment through experiments while the μAUV is either stationary or moving.We pinpoint several major factors that impact the communication performance. Experimental results show that the multi-path effect significantly affects the synchronization signals of the communication device. The relative motion between the vehicle and the base station also degrades the communication performance. These results suggest future methods towards improvements.

Liquid–liquid phase transition in confined liquid titanium

We report the layering and liquid–liquid phase transition of liquid titanium confined between two parallel panel walls.Abnormal changes in the volume and the potential energy confirm the existence of the liquid–liquid phase transition of the liquid titanium. The typical feature of the liquid–liquid phase transition is layering, which is induced by the slit size,pressure and temperature. We highlight the fact that the slit size and pressure will determine the number of layers. In addition, with the change in the slit size, the density of the confined liquid expresses a fluctuating law. The phase diagram of the layering transition is drawn to clearly understand the layering. This study provides insights into the liquid–liquid phase transition of liquid metal in a confined space.

Effects of asymmetric coupling and boundary on the dynamic behaviors of a random nearest neighbor coupled system

This study investigates the dynamical behaviors of nearest neighbor asymmetric coupled systems in a confined space.First, the study derivative analytical stability and synchronization conditions for the asymmetrically coupled system in an unconfined space, which are then validated through numerical simulations. Simulation results show that asymmetric coupling has a significant impact on synchronization conditions. Moreover, it is observed that irrespective of whether the system is confined, an increase in coupling asymmetry leads to a hastened synchronization pace. Additionally, the study examines the effects of boundaries on the system's collective behaviors via numerical experiments. The presence of boundaries ensures the system's stability and synchronization, and reducing these boundaries can expedite the synchronization process and amplify its effects. Finally, the study reveals that the system's output amplitude exhibits stochastic resonance as the confined boundary size increases.

Synthesis of Nanosized NaY Zeolite by Confined Space Method

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.

Wireless Sensor Network-based Detection of Poisonous Gases Using Principal Component Analysis

This work utilizes a statistical approach of Principal Component Ana-lysis(PCA)towards the detection of Methane(CH_(4))-Carbon Monoxide(CO)Poi-soning occurring in coal mines,forestfires,drainage systems etc.where the CH_(4) and CO emissions are very high in closed buildings or confined spaces during oxi-dation processes.Both methane and carbon monoxide are highly toxic,colorless and odorless gases.Both of the gases have their own toxic levels to be detected.But during their combined presence,the toxicity of the either one goes unidentified may be due to their low levels which may lead to an explosion.By using PCA,the correlation of CO and CH_(4) data is carried out and by identifying the areas of high correlation(along the principal component axis)the explosion suppression action can be triggered earlier thus avoiding adverse effects of massive explosions.Wire-less Sensor Network is deployed and simulations are carried with heterogeneous sensors(Carbon Monoxide and Methane sensors)in NS-2 Mannasim framework.The rise in the value of CO even when CH_(4) is below the toxic level may become hazardous to the people around.Thus our proposed methodology will detect the combined presence of both the gases(CH_(4) and CO)and provide an early warning in order to avoid any human losses or toxic effects.

Key theoretical and technical issues and countermeasures for effective development of Gulong shale oil, Daqing Oilfield, NE China

Aiming at the four issues of underground storage state,exploitation mechanism,crude oil flow and efficient recovery,the key theoretical and technical issues and countermeasures for effective development of Gulong shale oil are put forward.Through key exploration and research on fluid occurrence,fluid phase change,exploitation mechanism,oil start-up mechanism,flow regime/pattern,exploitation mode and enhanced oil recovery(EOR)of shale reservoirs with different storage spaces,multi-scale occurrence states of shale oil and phase behavior of fluid in nano confined space were provided,the multi-phase,multi-scale flow mode and production mechanism with hydraulic fracture-shale bedding fracture-matrix infiltration as the core was clarified,and a multi-scale flow mathematical model and recoverable reserves evaluation method were preliminarily established.The feasibility of development mode with early energy replenishment and recovery factor of 3o%was discussed.Based on these,the researches of key theories and technologies for effective development of Gulong shale oil are proposed to focus on:(1)in-situ sampling and non-destructive testing of core and fluid;(2)high-temperature,high-pressure,nano-scale laboratory simulation experiment;(3)fusion of multi-scale multi-flow regime numerical simulation technology and large-scale application software;(4)waterless(CO_(2))fracturing technique and the fracturing technique for increasing the vertical fracture height;(5)early energy replenishment to enhance oil recovery;(6)lifecycle technical and economic evaluation.Moreover,a series of exploitation tests should be performed on site as soon as possible to verify the theoretical understanding,optimize the exploitation mode,form supporting technologies,and provide a generalizable development model,thereby supporting and guiding the effective development and production of Gulong shale oil.

Superwettable interface towards biodetection in confined space

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.

Workers’Cerebrocortical Activity in Hot and Humid Condition:An Electroencephalogram Study

Hyperthermal environments can harm workers’health and safety.However,it is difficult to include effective protection into standards because heat-related impacts vary significantly accord-ing to individual workers and multiple factors.Studies suggested obvious relationship between en-vironment condition and bio-electricity signal,including electroencephalogram(EEG)signal.We used a detector with 64 electrodes to perform dedicated EEG measurements of nine individual sub-jects to analyze human cerebral activity under hyperthermal(35℃,80%RH)and standard condi-tions(25℃,30%RH).Amplitude changes of the frequency wavebands were analyzed using statist-ical analysis.Seven participants showed increasing beta activity due to high temperature and high humidity in the primary somatosensory cortex(electrode C3)and the temporopolar region(elec-trode FT 8).The amplitude value of alpha wave is increased from 0.194 to 0.213 while the amp-litude value of beta wave is increased from 0.144 to 0.160.Value is decreased due to hyperthermal environment for most people.The results of this study could be used to inform the development of wearable equipment to monitor the health of on-site workers,which is fundamental to improve worker safety and wellbeing.

Effects of magnetic field on photon-induced quantum transport in a single dot-cavity system

In this study,we show how a static magnetic field can control photon-induced electron transport through a quantum dot system coupled to a photon cavity.The quantum dot system is connected to two electron reservoirs and exposed to an external perpendicular static magnetic field.The propagation of electrons through the system is thus influenced by the static magnetic and the dynamic photon fields.It is observed that the photon cavity forms photon replica states controlling electron transport in the system.If the photon field has more energy than the cyclotron energy,then the photon field is dominant in the electron transport.Consequently,the electron transport is enhanced due to activation of photon replica states.By contrast,the electron transport is suppressed in the system when the photon energy is smaller than the cyclotron energy.

Characteristics of the recirculation zone in a cylindrical confined space and its suppression by an annular orifice plate

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.

Frameworked electrolytes:Ionic transport behavior and high mobility for solid state batteries

All solid-state batteries(ASSBs)are the holy grails of rechargeable batteries,where extensive searches are ongoing in the pursuit of ideal solid-state electrolytes.Nevertheless,there is still a long way off to the satisfactorily high(enough)ionic conductivity,long-term stability and especially being able to form compatible interfaces with the solid electrodes.Herein,we have explored ionic transport behavior and high mobility in the sub-nano pore networks in the framework structures.Macroscopically,the frameworked electrolyte behaves as a solid,and however in the(sub)-nano scales,the very limited number of solvent molecules in confinement makes them completely different from that in liquid electrolyte.Differentiated from a liquid-electrolyte counterpart,the interactions between the mobile ions and surrounding molecules are subject to dramatic changes,leading to a high ionic conductivity at room temperature with a low activation energy.Li+ions in the sub-nano cages of the network structure are highly mobile and diffuse rather independently,where the rate-limiting step of ions crossing cages is driven by the local concentration gradient and the electrostatic interactions between Li^(+)ions.This new class of frameworked electrolytes(FEs)with both high ionic conductivity and desirable interface with solid electrodes are demonstrated to work with Li-ion batteries,where the ASSB with LiFePO_(4)shows a highly stable electrochemical performance of over 450 cycles at 2℃ at room temperature,with an almost negligible capacity fade of 0.03‰ each cycle.In addition,the FE shows outstanding flexibility and anti-flammability,which are among the key requirements of large-scale applications.

Achieving highly uniform two-dimensional PbI2 flakes for photodetectors via space confined physical vapor deposition

Two-dimensional(2D) PbI_2 flakes have been attracting intensive attention as one potential candidate for the modern optoelectronics. However, suffered from the instability of kinetics-driven growth, the fabricated 2D PbI_2 flakes have a wide dimensional distribution even under the same conditions. Herein, a novel facile space confined physical vapor deposition(PVD) process is provided to synthesize uniform triangle PbI_2 flakes with high quality. The confined space provides a relatively stable growth environment that renders more control on the growth kinetics, leading to highly uniform triangle PbI_2 flakes with the average size of 5 mm and thickness of 17 nm. Moreover, as-fabricated PbI_2-based photodetectors show promising stable and flexible optoelectronic performances to 470 nm light, including high responsivity(0.72 AW^(-1)), large on/off ratio up to 900, fast photoresponse speed(rise time of 13.5 ms and decay time of 20 ms) and high detectivity(1.04×10^(10) Jones). The well-controllable growth of the uniform triangle PbI_2 flakes and the detailed exploration of their optoelectronic properties are particularly valuable for their further practical applications.

Space-confined vapor deposition synthesis of two dimensional materials

Two dimensional （2D） nanomaterials are promising fundamental building blocks for use in the next-generation semiconductor industry due to their unique geometry and excellent （opto）-electronic properties. However, large scale high quality fabrication of 2D nanomaterials remains challenging. Thus, the development of controllable fabrication methods for 2D materials is essential for their future practical application. In this review, we will discuss the importance of the space-confined vapor deposition strategy in the controllable fabrication of 2D materials and summarize recent progress in the utilization of this strategy for the synthesis of novel materials or structures. Using this method, various high quality ultrathin 2D materials, including large-area graphene and boron nitride, ReS2/ReSe2 HfS2, pyramid-structured multilayer MoS2, and the topological insulators BiaSe3 and BiaTe3, have been successfully obtained. Additionally, by utilizing van der Waals epitaxy growth substrates such as mica or other 2D materials, patterned growth of 2D nanomaterials can be easily achieved via a surface-induced growth mechanism. Finally, we provide a short prospect for future development of this strategy.

Space-confined growth of metal halide perovskite crystal films

Metal halide perovskites,as a new generation of optoelectronic materials,have attracted a great deal of interest due to their remarkable intrinsic properties.Due to the excellent optoelectronic properties,the perovskite crystals are widely used in lasers,photodetectors,X-ray detectors and solar cells.Considering the device performance and fabrication requirements,proper thickness of the crystal is required to avoid carrier loss and simultaneously ensure sufficient light absorption,which can realize the full potential of its excellent carrier transport property.Thus,the fabrication of perovskite crystal in a thin film with an adjustable thickness is highly desirable.The space-confined method has been demonstrated to be an effective way of preparing perovskite with controlled thickness.In this method,the thickness of perovskite can be regulated flexibly in a geometric confined space.Moreover,the size,quality and architecture of perovskite crystal films are also major concerns for practical photoelectric devices,which can also be optimized by the space-confined method owing to its good adaptability towards various modified strategies.In a word,the space-confined method is not only a simple and conventional way to adjust the thickness of perovskite crystal films,but also provides a platform to optimize their size,quality and architecture through applying appropriate strategies to the confined space.Herein,we review the space-confined growth of perovskite crystal films.Particularly,various modified strategies based on the space-confined method applied to the optimization of thickness,size,quality and architecture are highlighted.Then the stability investigating and component regulating of perovskite crystal films would be also mentioned.Furthermore,the correlation between the perovskite thickness and the device performance is discussed.Finally,several key challenges and proposed solutions of perovskite thin films based on the space-confined method are discussed.

Synchronous constructing ion channels and confined space of Co_(3)O_(4) anode for high-performance lithium-ion batteries

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.

Confined space synthesis of Ni(OH)_(2)-impregnated three-dimensional ordered mesoporous carbon as a high-performance supercapacitor electrode

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.

Fabrication of bimetallic Cu–Zn adsorbents with high dispersion by using confined space for gas adsorptive separation

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.

Novel synthesis approaches for new structures in confined space inspired by natural structure-forming processes

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.