Study on cook-off characteristics and thermal safety venting area of RBOE charge

RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.

Deep-large faults controlling on the distribution of the venting gas hydrate system in the middle of the Qiongdongnan Basin, South China Sea

Many locations with concentrated hydrates at vents have confirmed the presence of abundant thermogenic gas in the middle of the Qiongdongnan Basin(QDNB).However,the impact of deep structures on gasbearing fluids migration and gas hydrates distribution in tectonically inactive regions is still unclear.In this study,the authors apply high-resolution 3D seismic and logging while drilling(LWD)data from the middle of the QDNB to investigate the influence of deep-large faults on gas chimneys and preferred gasescape pipes.The findings reveal the following:(1)Two significant deep-large faults,F1 and F2,developed on the edge of the Songnan Low Uplift,control the dominant migration of thermogenic hydrocarbons and determine the initial locations of gas chimneys.(2)The formation of gas chimneys is likely related to fault activation and reactivation.Gas chimney 1 is primarily arises from convergent fluid migration resulting from the intersection of the two faults,while the gas chimney 2 benefits from a steeper fault plane and shorter migration distance of fault F2.(3)Most gas-escape pipes are situated near the apex of the two faults.Their reactivations facilitate free gas flow into the GHSZ and contribute to the formation of fracture‐filling hydrates.

Effect of safety valve types on the gas venting behavior and thermal runaway hazard severity of large-format prismatic lithium iron phosphate batteries

The safety valve is an important component to ensure the safe operation of lithium-ion batteries(LIBs).However,the effect of safety valve type on the thermal runaway(TR)and gas venting behavior of LIBs,as well as the TR hazard severity of LIBs,are not known.In this paper,the TR and gas venting behavior of three 100 A h lithium iron phosphate(LFP)batteries with different safety valves are investigated under overheating.Compared to previous studies,the main contribution of this work is in studying and evaluating the effect of gas venting behavior and TR hazard severity of LFP batteries with three safety valve types.Two significant results are obtained:(Ⅰ)the safety valve type dominates over gas venting pressure of battery during safety venting,the maximum gas venting pressure of LFP batteries with a round safety valve is 3320 Pa,which is one order of magnitude higher than other batteries with oval or cavity safety valve;(Ⅱ)the LFP battery with oval safety valve has the lowest TR hazard as shown by the TR hazard assessment model based on gray-fuzzy analytic hierarchy process.This study reveals the effect of safety valve type on TR and gas venting,providing a clear direction for the safety valve design.

葡萄牙栖盐田菌LLJ914的全基因组测序和比较基因组分析

栖盐田菌属细菌因具有较强渗透压耐受能力而备受关注。然而,目前对其适应高盐或其他海洋极端环境的机制尚未探明。为揭示分离自冲绳海槽热液区的葡萄牙栖盐田菌(Salinicola lusitanus)LLJ914与其同属菌株之间的遗传特征及代谢潜力的差异,探究其在极端海洋生境下的适应机制。通过全基因组测序获得葡萄牙栖盐田菌LLJ914全基因组序列,选取同属其他菌株的基因组进行比较基因组学分析,探究栖盐田菌属各菌株及不同环境来源的葡萄牙栖盐田菌代谢潜力的差异。菌株LLJ914基因组大小为4781556 bp,GC含量为64.0%,共编码4229个蛋白,69个tRNA,12个rRNA。通过构建系统发育树,并进行平均核苷酸和平均氨基酸一致性分析,发现该菌株与马齿苋(Halimione portulacoides)内共生的葡萄牙栖盐田菌CR50^(T)亲缘关系最近。通过功能基因注释分析,发现葡萄牙栖盐田菌具有抵抗各种重金属的相关基因和利用甲基膦酸产生甲烷的phn基因簇;相比于植物内共生菌CR50^(T),菌株LLJ914基因组中包含更多与氨基酸和碳水化合物的运输代谢、能量生产和转换以及转录相关的功能基因。此外,菌株LLJ914基因组中还包含特有的与重金属抵抗、免疫防御及有氧呼吸相关的基因,这可能与其适应复杂极端的深海热液环境有关。本研究揭示了葡萄牙栖盐田菌LLJ914适应深海热液环境的遗传特征及代谢潜力,为更好地认识热液微生物的生态功能提供了参考。

超临界CO_(2)管道泄放特性及参数敏感性

超临界CO_(2)管道的泄放过程是一种具有焦-汤效应和汽化吸热现象的两相瞬态过程,该过程会导致管内温度急剧下降,对管道安全运行产生影响。基于自行搭建的CO_(2)循环管道实验装置,开展4组不同初始温度、初始压力及泄放孔径的超临界CO_(2)管道泄放实验,通过记录管道不同位置处温度与压力的变化,分析并对比不同初始条件下管内水力、热力参数演化特性。研究发现:超临界CO_(2)管道泄放过程中存在非平衡气液相变现象;泄放过程中的温度与压力受到非平衡相变过程的影响,测试工况(Test1—Test3)管内相变起始压力p_(min)和气液两相阶段持续时间分别为:6.95、7.33、6.85 MPa和33.6、36.3、32.1 s,初始压力的升高与初始温度的降低,均会导致超临界CO_(2)进入气液两相区时的压力更高、气液两相阶段持续时间更长、管道所能达到的最低温度更低,加剧了管道发生裂纹延性扩展与低温脆断的风险。

黑冠山雀Parus rubidiventris的巢址特征与繁殖行为

2007年6月,作者在甘肃尕海—则岔自然保护区发现一个黑冠山雀Parus rubidiventris的洞穴巢址并对繁殖行为作了记录。巢址位于云杉树基下,大小27 cm×11 cm、巢深17 cm。巢材由苔藓、草茎须根、羊毛、云杉叶等组成。黑冠山雀育雏频率1次/1.5 min,食物为膜翅目、鳞翅目昆虫。此外,还发现育雏结束后亲鸟有清除巢内异物行为。

建筑走廊内相邻防烟分区不同排烟方式相互影响研究

同一防火分区内相邻防烟分区采用不同排烟方式可能会对排烟造成不利影响。以某一医院走廊为例,采用FDS软件对同一防火分区采用不同排烟方式时的排烟效率进行分析。结果表明:机械排烟对自然排烟的排烟效果会产生影响;自然排烟会对机械排烟的启动时间有影响;对于本建筑排烟系统,自然排烟窗与机械排烟口正对设置情况下的整体控烟效果更好。相邻防烟分区采用不同排烟方式时,建议采用性能化方式进行优化设计。

Characteristic of Intelligent Air Bag Venting Structure Actuating by Electrostrictive Stack Actuator

In this paper the conception of smart materials and structures is firstly combined with research of air bag,and the main theory of self adapting cushioning of intelligent air bag is expatiated.The intelligent venting structure is the main part affecting the cushioning result.Electrostrictive material was found having big force,high response speed and wide linearity,and it is fit to utilize in intelligent venting structure. The characteristic of the dynamic response and cushioning actuating of an electrostrictive stack actuator is analyzed,and the result of the computer simulation of the fuzzy control to intelligent venting structure is given.It is concluded that intelligent venting structure has good actuating characteristic and can satisfy the need of intelligent air bag.

CCUS管道阀室放空工艺技术研究

CCUS管输中的流动保障问题对于实现双碳目标至关重要,为研究合理的CCUS管道阀室放空方案,基于模拟软件建立了放空物理模型,分析了不同因素对放空过程的影响,考察了地形起伏对放空过程的动态规律,提出了间歇放空作业方案。结果表明:放空口的温降是由于压力下降引起的焦汤效应造成的,低点处的温降是由于节流效应和相变吸热造成的,且低点处的温降更大,风险性更强;通过降低初始压力、提高初始温度,并设计合适的放空系统,可显著提高沿线温度;间歇放空过程经历了4次开阀和4次关阀,放空时间为1.21 h,放空总量为586 t,该方案可降低管道放空带来的低温风险。研究结果可为同类CCUS管道的投产和运行提供实际参考。

整车降温性能优化试验研究

针对客户认为汽车空调降温性能还有优化的空间,经过分析,增加HVAC总成出风模式功能和仪表板出风口通风面积。按照汽车行业标准QC/T658一2000进行环境仓试验验证,试验结果表明可以达到快速降温目的。

常低压储罐超压与真空工况研究

在常压储罐与低压储罐操作使用过程中,储存介质的进罐与出罐、环境温度升降、大气压变化、发生火灾、设备故障、人员误操作等因素会引起储罐压力过高或储罐内出现负压。SH/T 3007-2014《石油化工储运系统罐区设计规范》与API 2000-2014《Venting Atmospheric and Low-Pressure Storage Tanks》等对储罐发生超压与真空的工况及引起的呼吸量进行了详细论述。文章结合这两个规范,分析了常低压储罐的各种超压与真空工况,并结合某项目中地上保温固定顶储罐,计算多种工况下所需通气量,为选定通气装置提供计算依据和设计指导。

Multi-objective Optimization Design of Vented Cylindrical Airbag Cushioning System for Unmanned Aerial Vehicle

Multi-objective optimization design of the gas-filled bag cushion landing system is investigated.Firstly,the landing process of airbag is decomposed into a adiabatic compression and a release of landing shock energy,and the differential equation of cylindrical gas-filled bag is presented from a theoretical perspective based on the ideal gas state equation and dynamic equation.Then,the effects of exhaust areas and blasting pressure on buffer characteristics are studied,taking those parameters as design variable for the multiobjective optimization problem,and the solution can be determined by comparing Pareto set,which is gained by NSGA-Ⅱ.Finally,the feasibility of the design scheme is verified by experimental results of the ground test.

Microbial community structure and diversity in deep-sea hydrothermal vent sediments along the Eastern Lau Spreading Centre

The aim of this study is to investigate microbial structures and diversities in five active hydrothermal fields＇ sediments along the Eastern Lau Spreading Centre （ELSC） in the Lau Basin （southwest Pacific）. Microbial communities were surveyed by denatured gradient gel electrophoresis （DGGE） and clone library analysis of 16S rRNA genes. The differences in microbial community structures among sediment samples from the five deep-sea hydrothermal sites were revealed by DGGE profiles. Cluster analysis of DGGE profiles sepa- rated the five hydrothermal samples into two groups. Four different 16S rRNA gene clone libraries, repre- senting two selected hydrothermal samples （19-4TVG8 and 19-4TVG11）, were constructed. Twenty-three and 32 phylotypes were identified from 166 and 160 bacterial clones respectively, including Proteobacteria, Bacteroidetes, Firmicutes, Nitrospirae and Planctomycetes. The phylum Proteobacteria is dominant in both bacterial libraries with a predominance of Gamma-Proteobacteria. A total of 31 and 25 phylotypes were obtained from 160 and 130 archaeal clones respectively, including Miscellaneous Crenarchaeotic Group, Marine Group Ⅰ and Ⅲ, Marine Benthic Group E, Terrestrial Hot Spring Crenarchaeota and Deep-sea Hy- drothermal Vent Euryarchaeota. These results show a variety of clones related to those involved in sulfur cycling, suggesting that the cycling and utilization of sulfur compounds may extensively occur in the Lau Basin deep-sea hydrothermal ecosystem.

Geological,physical,and chemical characteristics of seafloor hydrothermal vent fields

Seafloor hydrothermal vent fields(SHVFs) are located in the mid-ocean ridge(MOR),backarc basin(BAB),island arc and hot-spot environments and hosted mainly by ultramafic,mafic,felsic rocks,and sediments.The hydrothermal vent fluids of SHVFs have low oxygen,abnormal pH and temperature,numerous toxic compounds,and inorganic energy sources,such as sulfuric compounds,methane,and hydrogen.The geological,physical,and chemical characteristics of SHVFs provide important clues to understanding the formation and evolution of seafloor hydrothermal systems,leading to the determination of metal sources and the reconstruction of the physicochemical conditions of metallogenesis.Over the past two decades,we studied the geological settings,volcanic rocks,and hydrothermal products of SHVFs and drawn new conclusions in these areas,including:1) the hydrothermal plumes in the Okinawa Trough are affected by the Kuroshio current;2) S and Pb in the hydrothermal sulfides from MOR are mainly derived from their host igneous rocks;3) Re and Os of vent fluids are more likely to be incorporated into Fe-and Fe-Cu sulfide mineral facies,and Os is enriched under low-temperature(<200℃) hydrothermal conditions in global SHVFs;4) compared with low-temperature hydrothermal sulfides,sulfates,and opal minerals,high-temperature hydrothermal sulfides maintain the helium(He) isotopic composition of the primary vent fluid;5) relatively low temperature(<116℃),oxygenated,and acidic environment conditions are favorable for forming a native sulfur chimney,and a "glue pudding" growth model can be used to understand the origin of native sulfur balls in the Kueishantao hydrothermal field;and 6) boron isotope from hydrothermal plumes and fluids can be used to describe their diffusive processes.The monitoring and understanding of the physical structure,chemical composition,geological processes,and diverse organism of subseafloor hydrothermal systems will be a future hot spot and frontier of submarine hydrothermal geology.

Venting Design for Di-tert-butyl Peroxide Runaway Reaction Based on Accelerating Rate Calorimeter Test

In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic conditions the initial exothermic temperature was 102.6 ℃,the maximum self-heating rate was 3.095×107 ℃·min-1,the maximum self-heating temperature was 375.9 ℃,and the pressure produced by unit mass was 4.512 MPa·g-1.Judged by ARC test,the emergency relief system for DTBP was a hybrid system.Based on Design Institute for Emergency Relief System(DIERS) method,the releasing mass flow rate W was determined by Leung methods,and the mass velocity G was calculated by two modified Omega methods.The two relief sizes calculated by monograph Omega method and arithmetic Omega method are close,with only 0.63% relative error.The monograph Omega method is more convenient to apply.

Microbial community structure and nitrogenase gene diversity of sediment from a deep-sea hydrothermal vent field on the Southwest Indian Ridge

A sediment sample was collected from a deep-sea hydrothermal vent field located at a depth of 2 951 m on the Southwest Indian Ridge. Phylogenetic analyses were performed on the prokaryotic community using polymerase chain reaction（PCR） amplification of the 16 S rRNA and nifH genes. Within the Archaea, the dominant clones were from marine benthic group E（MBGE） and marine group I（MGI） belonging to the phyla Euryarchaeota and Thaumarchaeota, respectively. More than half of the bacterial clones belonged to the Proteobacteria, and most fell within the Gammaproteobacteria. No epsilonproteobacterial sequence was observed. Additional phyla were detected including the Actinobacteria, Bacteroidetes, Planctomycetes, Acidobacteria, Nitrospirae, Chloroflexi, Chlorobi, Chlamydiae, Verrucomicrobia, and candidate divisions OD1, OP11, WS3 and TM6, confirming their existence in hydrothermal vent environments. The detection of nifH gene suggests that biological nitrogen fixation may occur in the hydrothermal vent field of the Southwest Indian Ridge. Phylogenetic analysis indicated that only Clusters I and III NifH were present. This is consistent with the phylogenetic analysis of the microbial 16 S rRNA genes, indicating that Bacteria play the main role in nitrogen fixation in this hydrothermal vent environment.

Influence of core box vents distribution on flow dynamics of core shooting process based on experiment and numerical simulation

Core shooting process plays a decisive role in the quality of sand cores, and core box vents distribution is one of the most important factor determining the effectiveness of core shooting process. In this paper, the influence of core box vents distribution on the flow dynamics of core shooting process was investigated based on in situ experimental observations with transparent core box, high-speed camera and pressure measuring system. Attention was focused on the variation of both the flow behavior of sand and pressure curves due to different vents distribution. Taking both kinetic and frictional stress into account, a kinetic-frictional constitutive model was established to describe the internal momentum transfer in the solid phase. Two-fluid model(TFM) simulation was then performed and good agreement was achieved between the experimental and simulated results on both the flow behavior of sand and the pressure curves. It was found that vents distribution has direct effect on the pressure difference of different locations in the core box, which determines the buoyancy force exerting on the sand particles and significantly influences the filling process of core sand.

Experimental and numerical evaluations on characteristics of vented methane explosion

To research the characteristics of vented explosion of methane-air mixture in the pipeline,coal mine tunnel or other closed space,the experiments and numerical simulations were carried out.In this work,explosion characteristics and flame propagation characteristics of methane in pipeline and coal mine tunnel are studied by using an explosion test system,combined with FLACS software,under different vented conditions.The numerical simulation results of methane explosion are basically consistent with the physical experiment results,which indicates that the numerical simulation for methane explosion is reliable to be applied to the practice.The results show that explosion parameters(pressure,temperature and product concentration)of methane at five volume fractions have the same change trend.Nevertheless,the explosion intension of 10.0%methane is the largest and that of 9.5%methane is relatively weak,followed by 11.0%methane,8.0%methane and 7.0%methane respectively.Under different vented conditions,the pressure and temperature of methane explosion are the highest in the pipeline without a vent,followed by the pipeline where ignition or vent position is in each end,and those are the lowest in the pipeline with ignition and vent at the same end.There is no significant effect on final product concentration of methane explosion under three vented conditions.For coal mine tunnel,it is indicated that the maximum explosion pressure at the airproof wall in return airway with the branch roadway at 50 m from goaf is significantly decreased while that in intake airway does not change overwhelmingly.In addition,when the branch roadway is longer or its section is larger,the peak pressure of airproof wall reduces slightly.

On Optimal Frequencies of Acoustic in-situ Detector for Seafloor Hydrothermal Vents

The approach to determine working frequencies of acoustic in-situ detector for seafloor hydrothermal fluid is presented. Based on the research of deep-sea noise and the sound generated by mid-ocean ridge black smoker hydrothermal vents, and on the hydrothermal-vent animal hearing ranges, coupled with influences of suspended particles of hydrothermal on acoustic attenuation under different frequencies, the optimal frequency range for detection of acoustical signal near black smokers is determined. The optimal frequencies providing the maximum ratio of receiver signal to background noise are obtained. We have developed a laboratory experimental setup for the optimal frequencies selection. In particular, we evaluated time-of-flight performance with respect to the source signal parameters of center frequency and bandwidth. The experimental results confirm the effectiveness of our approach. Current results indicate that individual transducers operated in the range of 18 - 25 kHz are immune to most interfering sounds and suitable for our system.

A CFD study on optimal venting volume and air flow distribution in a special designed hood system for controlling dust flow

A novel hood structure has been designed for the dust control system in the foundry in order to improve the working environment. A composite strategy has been applied for comparative analysis of the optimal venting volume and the airflow distribution between the conventional hood and the novel one in this study. A Computational Fluid Dynamic (CFD) method is used to simulate the airflow fields and dust-polluted air moving paths. The CFD results show that a two-outlet hood, with one outlet located on the left of the hood, is better for improving dust-polluted air than the hood with one outlet only. It can be concluded that the number of the outlets as well as their location on the hood has a significant influence on the air flow pattern in the hood. The optimal venting volume is also a major consideration that is discussed in the study. The venting volume should be designed by considering both the effective level of air flow velocity around the dust source and the energy saving. The optimal airflow distribution may reduce the turbulence in the hood system.