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受限空间内水下爆轰燃气射流发展特性

水下无人系统学报 2024年第3期32卷 572-581页

作者：徐祗乾康杨李宁黄孝龙李灿翁春生南京理工大学瞬态物理国家重点实验室江苏南京210094

为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型... 详细信息

为探索脉冲爆轰水冲压发动机水下工作时导水器内燃气射流发展特性,利用可燃气体的爆轰在水下受限空间内产生脉动气泡,对爆轰管在圆筒形受限空间内的水下爆轰燃气射流进行了数值仿真与实验验证。基于雷诺时均基本方程组与k-ε两方程模型耦合流体体积气液界面追踪方法的相输运方程建立受限空间中水下单次燃气射流流场流动模型,使用OpenFOAM中的Compressible Inter Foam求解器对受限空间中脉冲爆轰燃气射流进行数值求解。结果表明:受限空间对水下爆轰的前导激波的影响较小,前导激波幅值与自由空间相比变化不大,由爆轰燃气射流所引起的压力扰动大幅升高且持续时间明显增加,受限空间中各处压力显著高于受限空间之外;受限空间中燃气泡的脉动周期延长至60 ms左右,然而受限空间径向尺寸对燃气泡的脉动周期影响较小。可见,受限空间可提高水下爆轰管出口近场压力并延长燃气射流作用时间,研究结果对脉冲爆轰水冲压发动机推力性能提升方法研究具有重要指导作用。

关键词：脉冲爆轰水冲压发动机水下燃气射流受限空间气泡脉动

Generic user revocation systems for attribute-based encryption in cloud storage

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Frontiers of Information Technology & Electronic Engineering 2018年第11期19卷 1362-1384页

作者： Genlang CHEN zhiqian xu Hai JIANG Kuan-ching LI Institute of Ningbo Technology Zhejiang University Independent Scholar Department of Computer Science Arkansas State University Department of Computer Science and Information Engineering Providence University

Cloud-based storage is a service model for businesses and individual users that involves paid or free storage resources. This service model enables on-demand storage capacity and management to users anywhere via the Internet. Because most cloud storage is provided by third-party service providers, the trust required for the cloud storage providers and the shared multi-tenant environment present special challenges for data protection and access control. Attribute-based encryption(ABE) not only protects data secrecy, but also has ciphertexts or decryption keys associated with fine-grained access policies that are automatically enforced during the decryption process. This enforcement puts data access under control at each data item level. However, ABE schemes have practical limitations on dynamic user revocation. In this paper, we propose two generic user revocation systems for ABE with user privacy protection, user revocation via ciphertext re-encryption(UR-CRE) and user revocation via cloud storage providers(UR-CSP), which work with any type of ABE scheme to dynamically revoke users.

关键词： Attribute-based.encryption Generic user revocation User privacy Cloud storage Access control

Sources appointment and health risks of PM_(2.5)-bound trace elements in a coastal city of southeastern China

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Journal of Environmental Sciences 2024年第4期138卷 561-571页

作者： Ziyi Lin Xiaolong Fan Gaojie Chen Youwei Hong Mengren Li Lingling xu Baoye Hu Chen Yang Yanting Chen zhiqian Shao Jinsheng Chen Center for Excellence in Regional Atmospheric Environment Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Key Lab of Urban Environment and Health Institute of Urban EnvironmentChinese Academy ofSciencesXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China Minnan Normal University Zhangzhou 363000China

To gain a comprehensive understanding of sources and health risks of trace elements in an area of China with high population densities and low PM_(2.5)concentrations,15 trace elements(Al,K,Ca,Ti,V,Cr,Mn,Fe,Ni,Cu,Zn,As,Sn,Ba,Pb)in PM_(2.5)were monitored from December 2020 to November 2021 in a representative city,Xiamen.The concentrations of trace elements in Xiamen displayed an obvious seasonal variation and were dominated by K,Fe,Al,Ca and Zn.Based on Positive Matrix Factorization analysis,source appointment revealed that the major sources of trace elements in Xiamen were traffic,dust,biomass and firework combustion,industrial manufacture and shipping emission.According to health risk assessment combined with the source appointment results,it indicated that the average noncarcinogenic risk was below the threshold and cancer risk of four hazardous metals(Cr,Ni,As,Pb)exceeded the threshold(10^(-6)).Traffic-related source had almost half amount of contribution to the health risk induced by PM_(2.5)-bound trace elements.During the dust transport period or Spring Festival period,the health risks exceeded an acceptable threshold even an order of magnitude higher,suggesting that the serious health risks still existed in low PM_(2.5)environment at certain times.Health risk assessment reminded that the health risk reduction in PM_(2.5)at southeastern China should prioritize traffic-related hazardous trace elements and highlighted the importance of controlling vehicles emissions in the future.

关键词： PM_(2.5)-bound trace elements Seasonal variations Source appointment Health risks Traffic-related source

Gas sealing performance test analysis of non-API casing connection with radial cone sealing structure

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Gas sealing performance test analysis of non-API casing conn...

Studies on Rock mechanical characteristics testing and drill Bit's rock-breaking efficiency in deep wells

2012年海峡两岸破坏科学/材料试验学术会议

作者： xu zhiqian YAN Yifei JANG Tingting YAN Xiangzhen College of Mechanical and Electronic Engineering China University of Petroleum College of Pipeline and Civil Engineering China University of Petroleum

The metal-to-metal radial interference fit construction is the main sealing structure of the non-API casing connection.The sealing performance of the non-API casing connection is superior to the API casing because of the special sealing structure.So,the air tightness test has been done in order to find the sealing forming conditions and influencing factors.The main processing parameters of the test specimen are like the 7 inch casing connection.The main structure type is the cone-to-cone interference fit between two contact interfaces.The leakage rate was measured in the test under different contact pressure,different contact surface roughness and different contact width.The test results analysis show that the higher initial contact pressure is a necessary requisite to air seal.The contact interface has occurred plastic deformation when the contact pressure close to 2 times metal yield strength.In this condition,the leakage rate is unchanged with the increasing of gas pressure,the gas sealing performance in a stable state. Comparing the gas sealing performance of the different contact surface form processes(turning, grinding and lapping),we find that different surface roughness has different contact pressure in stable sealing state.The higher surface roughness come into stable sealing state much more quickly and easily comparing to the lower.Under the same contact and gas pressure and the same surface roughness,the leakage rate decrease dramatically with the increasing of the contact width, and the effect on the sealing performance comes very small when the contact width more than 10 mm.

关键词： Sealing Performance Leakage Rate Non-API Casing Connection Air Tightness Test

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Studies on Rock mechanical characteristics testing and drill...

Generic attribute revocation systems for attribute-based encryption in cloud storage

2012年海峡两岸破坏科学/材料试验学术会议

作者： YANG Shangyu YAN Yifei xu zhiqian YANG Xiujuan College of Pipeline and Civil Engineering China University of Petroleum

Taking the rock core sample on-site,using the triaxial stress test device to simulate the testing of rock mechanics parameters in the original formation environment,the mechanics characters can be obtained.Based on the H-J-C rock failure criteria,a 3D non-linear contact dynamic model of dynamic rock breaking is established using finite element method,in which anisotropy,strata dip and friction factor of drilling bit and rock are considered.The relationship between drill pressure,torque,speed and rock-breaking efficiency are also studied.The results indicate that the depth of broken rock depends on the impact and have nothing to do with the rotation;when the WOB did not meet the crushing pressure of the rock volume,the torque changed a little;but when the WOB exceeded the crushing pressure,the torque changed a lot;at the same time,the drill speed mainly had no effect on the drill torque.The drill bit is the main rock-breaking tool which is used in the deep strata of petroleum well drill progress and its rock-breaking efficiency is the important evidence to evaluate the bit’s performance and improve the design quality.In this paper,the geometric nonlinear characteristics of drill bit is considered, the stress and strain of the drill bit are obtained,which provided a new method to better analyze and evaluate the rock-breaking efficiency of bit and enhanced the scientific nature and reliability of the rock design quality.

关键词： Rock Core Test Rock Breaking Mechanism Drilling Parameters Rock-breaking Efficiency

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Frontiers of Information Technology & Electronic Engineering 2019年第6期20卷 773-786页

作者： Genlang CHEN zhiqian xu Jia-jian ZHANG Guo-jun WANG Hai JIANG Miao-qing HUANG Institute of Ningbo Technology Zhejiang University Ningbo 315100 China Ningbo Research Institute Zhejiang University Ningbo 315100 China Independent Scholar School of Computer Science and Technology Guangzhou University Guangzhou 510006 China Department of Computer Science Arkansas State University Jonesboro 72467 USA Department of Computer Science and Computer Engineering University of Arkansas Jonesboro 72467 USA

Attribute-based encryption(ABE) has been a preferred encryption technology to solve the problems of data protection and access control, especially when the cloud storage is provided by third-party service providers.ABE can put data access under control at each data item level. However, ABE schemes have practical limitations on dynamic attribute revocation. We propose a generic attribute revocation system for ABE with user privacy protection. The attribute revocation ABE(AR-ABE) system can work with any type of ABE scheme to dynamically revoke any number of attributes.

关键词： Attribute-based encryption Generic attribute revocation User privacy Cloud storage Access control

Riverine sulfate sources and behaviors in arid environment,Northwest China:Constraints from sulfur and oxygen isotopes

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Journal of Environmental Sciences 2024年第3期137卷 716-731页

作者： Yifu xu Wenjing Liu Bing xu Zhifang xu Key Laboratory of Cenozoic Geology and Environment Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Innovation Academy for Earth Science Chinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China

The fate of riverine sulfate ion (SO_(4)^(2-)) and its environmental effects in arid environment are difficult to evaluate due to its complicated sources and strongly coupled behaviors with water cycle which is significantly modified by humans.To understand the sulfur cycle in aquatic systems in arid environment,the chemical and sulfur and oxygen isotopic compositions (δ^(34)S_(SO4)and δ^(18)O_(SO4)) of major rivers around the Badain Jaran Desert,northwestern China,were investigated.These rivers had averaged SO_(4)^(2-)content at 1336μmol/L,over 10times higher than the global average.The δ^(34)S_(SO4)and δ^(18)O_(SO4)values ranged from-5.3‰to+11.8‰and+1.6‰to+12.8‰,respectively.The end-member analysis and the inverse model showed that riverine sulfate was mainly derived from evaporites dissolution (0-87%),sulfide oxidation (13%-100%) and precipitation (0-33%),indicating heterogeneity in sulfur sources and behaviors along the river drainage with the lithology variations and climate gradients.Multiple isotopic tools combining with hydro-chemistry compositions could be applied to reveal sulfur cycle in arid environment.Based on the calculation,sulfide oxidation plays the primary role in the headwater and upstream in the Qilian-Mountains area,where sulfide is widely exposed.While the proportion of evaporites dissolution contributing to riverine sulfate is much higher in downstream in a drier environment.Besides,less precipitation and higher temperature can lead to more intensive evaporation,affecting the process of sulfide oxidation and enhancing the rates of evaporites dissolution and sulfate precipitation in the basin.

关键词： Sulfur and oxygen isotopes Source apportionment Inverse model Arid environment Inland rivers Northwestern China

Biohythane production from two-stage anaerobic digestion of food waste:A review

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Journal of Environmental Sciences 2024年第5期139卷 334-349页

作者： Xiaona An Ying xu Xiaohu Dai State Key Laboratory of Pollution Control and Resource Reuse School of Environmental Science and EngineeringTongji UniversityShanghai 200092China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China

The biotransformation of food waste(FW)to bioenergy has attracted considerable research attention as a means to address the energy crisis and waste disposal problems.To this end,a promising technique is two-stage anaerobic digestion(TSAD),in which the FW is transformed to biohythane,a gaseous mixture of biomethane and biohydrogen.This review summarises the main characteristics of FW and describes the basic principle of TSAD.Moreover,the factors influencing the TSAD performance are identified,and an overview of the research status;economic aspects;and strategies such as pre-treatment,co-digestion,and regulation of microbial consortia to increase the biohythane yield from TSAD is provided.Additionally,the challenges and future considerations associated with the treatment of FW by TSAD are highlighted.This paper can provide valuable reference for the improvement and widespread implementation of TSAD-based FW treatment.

关键词： Two-stage anaerobic digestion(TSAD) Food waste(FW) Methane production Hydrogen production

Simulation of electromagnetic pulses generated by escaped electrons in a high-power laser chamber

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Plasma Science and Technology 2018年第11期20卷 45-52页

作者：金晗冰孟萃姜云升吴平徐志谦 Department of Engineering Physics Tsinghua University Key Laboratory of Particle &Radiation Imaging Ministry of Education

Intensive electromagnetic pulses （EMPs） can be generated when a high-power laser strikes a target. The transient electromagnetic field can have an intensity of up to several hundred kV m- 1 with a broad frequency of up to several gigahertz, which may affect diagnostics and interfere with, or even damage, electronic equipment. In this paper, the process in which hot electrons produced by the laser-target interaction radiate EMPs is studied and simulated. The physical process is divided into three stages which are： the production of hot electrons; the escape of hot electrons; and the generation of EMPs. Instead of using a general finite difference time domain （FDTD） method to solve the Maxwell equations, a particle-in-cell method together with a time- biased FDTD method is applied in EMP simulation to restrain high-frequency noise. The results show that EMPs are stronger with higher laser intensity and larger target size.

关键词： laser plasma particle-in-cell electromagnetic pulse