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Mechanism analysis of foam penetration in EPB shield tunnelling with a focus on FER and soil particle size

Underground Space 2024年第4期17卷 170-187页

作者： He Huang quan Sun Tao xu Wanhuan Zhou State Key Laboratory of Internet of Things for Smart City and Department of Civil and Environmental Engineering University of MacaoMacao 999078China Department of Civil and Environmental Engineering University of MacaoMacao 999078China School of Transportation Southeast UniversityNanjing 210000China

Parameters of foam penetration in earth pressure balance(EPB)shield tunnelling,such as permeability coefficients and penetration distances,significantly impact tunnel face ***,existing studies have faced inaccuracies in analysing these parameters due to imitations in experimental *** study addresses this issue by employing enhanced methods for a more precise analysis of foam *** involving three distinct sand types(coarse,medium,and fine)and three foam expansion ratios(FER)(10,15,and 20)are conducted using a modified model test *** from a novel computer vision-based method,the model test outcomes unveil two distinct foam penetration paths:liquid migration(L_(w))and bubble migration(L_(f)).Three penetration phases-namely,injection,blockage&drainage,and breakage—are identified based on L_(w)and L_(f)*** initial"injection"phase conforms to Darcy’s law and is amenable to mathematical *** foam with FER of 15 has the maximum viscosity and,hence the L_(f)and permeability in the penetration tests with FER of 15 are the lowest in the same *** bubble size distribution of foam with different FER shows minor ***,the characteristics of foam penetration vary due to the distinct particle size distribution(PSD)of different *** penetration creates low-permeability layers in both medium and fine sands due to the larger bubble size of the foam compared to the estimated pore sizes of medium and fine *** the coarse sand results in a different situation due to its large pore *** distinctive characteristics of foam penetration in different sand strata are notably shaped by FER,PSD,and pore size *** insights shed light on the complex interactions during foam penetration at the tunnel face,contributing valuable knowledge to EPB shield tunnelling practices.

关键词： EPB Soil conditioning Foam penetration Permeability Tunnel face

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Correlation Between Additive Noises Induced First-Order Phase Transition in a Two-Mode Laser

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Chinese Physics Letters 1996年第11期13卷 833-836页

作者： long quan CAO Li WU Da-jin LI Zai-guang National Laboratory of Laser Technology Huazhong University of Science and TechnologyWuhan 430074 CCAST(World Laboratory) P.O.Box 8730Beijing 100080 Department of Physics Huazhong University of Science and TechnologyWuhan 430074

A phenomenological theory about the correlation between additive noises,in a two-mode laser arising from scattering of photons by the medium in the laser cavity is *** is applied to an inhomogeneously broadened two-mode ring *** have obtained an approximate expression for the steady-state intensity distribution,in which a first-order phase transition is found.

关键词： Transition additive inhomogeneous

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Carbon quantum dots: An innovative additive for water lubrication

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Science China(Technological Sciences) 2019年第4期62卷 587-596页

作者： XIAO HuaPing LIU ShuHai xu quan ZHANG Hang College of Mechanical and Transportation Engineering China University of Petroleum-Beijing Institute of New Energy China University of Petroleum-Beijing

Water soluble carbon quantum dots(CQDs) were prepared and used as lubricant additives in deionized(DI) water. The impacts of CQDs on the tribological properties of water were evaluated for both Si_3N_4-on-steel and Si_3N_4-on-Si_3N_4 contacts. Experimental results show that the coefficient of friction(COF) reduced in the two types of tribopairs after the addition of *** reductions in COF were found to be 30% and 14% for the Si_3N_4-steel and Si_3N_4-Si_3N_4 contacts, respectively. In terms of wear behaviors, the CQDs notably improved tribofilm formation on the Si_3N_4 disk surface for the Si_3N_4-Si_3N_4 contacts,confirming that the nanoparticles increase friction while providing better protection from wear. This research will help to expand the application of CQDs as promising additives in water-based lubricants.

关键词： carbon quantum dot water lubrication lubricant additives ceramic tribopairs

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Interlaced optimal-REQUEST and unscented Kalman filtering for attitude determination

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Chinese Journal of Aeronautics 2013年第2期26卷 449-455页

作者： quan Wei xu Liang Zhang Huijuan Fang Jiancheng Science and Technology on Inertial Laboratory Key Laboratory of Fundamental Science for National Defense-Novel Inertial Instrument & Navigation System Technology Beihang University

Aimed at low accuracy of attitude determination because of using low-cost components which may result in non-linearity in integrated attitude determination systems, a novel attitude determination algorithm using vector observations and gyro measurements is presented. The various features of the unscented Kalman filter （UKF） and optimal-REQUEST （quaternion estimator） algorithms are introduced for attitude determination. An interlaced filtering method is presented for the attitude determination of nano-spacecraft by setting the quaternion as the attitude representation, using the UKF and optimal-REQUEST to estimate the gyro drifts and the quaternion, respectively. The optimal-REQUEST and UKF are not isolated from each other. When the optimal-REQUEST algorithm estimates the attitude quaternion, the gyro drifts are estimated by the UKF algorithm synchronously by using the estimated attitude quaternion. Furthermore, the speed of attitude determination is improved by setting the state dimension to three. Experimental results show that the presented method has higher performance in attitude determination compared to the UKF algorithm and the traditional interlaced filtering method and can estimate the gyro drifts quickly.

关键词： Attitude determination Hybrid simulation Interlaced filtering Optimal-REQUEST Unscented Kalman filter

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Sequential nonlinear tracking filter without requirement of measurement decorrelation

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Journal of Systems Engineering and Electronics 2015年第6期26卷 1135-1141页

作者： Gongjian Zhou Junhao Xie Rongqing xu Taifan quan School of Electronics and Information Engineering Harbin Institute of Technology

Sequential measurement processing is of benefit to both estimation accuracy and computational efficiency. When the noises are correlated across the measurement components, decorrelation based on covariance matrix factorization is required in the previous methods in order to perform sequential updates properly. A new sequential processing method, which carries out the sequential updates directly using the correlated measurement components, is proposed. And a typical sequential processing example is investigated, where the converted position measure- ments are used to estimate target states by standard Kalman filtering equations and the converted Doppler measurements are then incorporated into a minimum mean squared error （MMSE） estimator with the updated cross-covariance involved to account for the correlated errors. Numerical simulations demonstrate the superiority of the proposed new sequential processing in terms of better accuracy and consistency than the conventional sequential filter based on measurement decorrelation.

关键词： sequential filter Doppler measurement measurementdecorrelation minimum mean squared error (MMSE).

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Smog Chamber Study on the Ozone Formation Potential of Acetaldehyde

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Advances in Atmospheric Sciences 2021年第7期38卷 1238-1251页

作者： Hailiang ZHANG Yongfu xu long JIA Min xu State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Department of Atmospheric Chemistry and Environmental Sciences College of Earth and Planetary SciencesUniversity of Chinese Academy of SciencesBeijing 100049China

Acetaldehyde is one of the important VOC species of O_(3)precursors in the atmospheric *** influences of relative humidity(RH)and initial VOC/NOx ratio(R_(CN))on the formation of O_(3)are studied in smog chamber experiments,and the MCM v3.3.1 mechanism of acetaldehyde is modified based on the experimental *** low-RH conditions(RH=11.6%±1.1%),the O_(3)concentration at 6 h increases first and then decreases with the increase of R_(CN),and the R_(CN)at the inflection point of O_(3)concentrations is *** high-RH experiments(RH=78.8%±1.0%),variation of the O_(3)concentration at 6 h with R_(CN)is similar to that in low-RH experiments,but the R_(CN)at the inflection point is *** has no significant effect on the O_(3)concentrations under low R_(CN)(3).Compared with the experimental results,original MCM v3.3.1 greatly underestimates the O_(3)*** of both the photolysis process of peroxyacetyl nitrate and the photolysis process of HNO_(3)on the reactor surface into the original MCM can reduce the difference between the simulated O_(3)concentrations and the experimental results at 6 h from 24%−35%and 17%−49%to 6%−26%and 10%−42%under low-and high-RH conditions,*** maximum incremental reactivity(MIR)of acetaldehyde simulated with the modified MCM is 4.0 ppb ppb−1 without considering the effect of other VOCs.

关键词： ozone acetaldehyde photochemical reaction MCM

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Dynamics and adaptive control of a dual-arm space robot with closed-loop constraints and uncertain inertial parameters

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Acta Mechanica Sinica 2014年第1期30卷 112-124页

作者： Ying-Hong Jia quan Hu Shi-Jie xu School of Astronautics Beihang University

A dynamics-based adaptive control approach is proposed for a planar dual-arm space robot in the presence of closed-loop constraints and uncertain inertial parameters of the payload. The controller is capable of controlling the po- sition and attitude of both the satellite base and the payload grasped by the manipulator end effectors. The equations of motion in reduced-order form for the constrained system are derived by incorporating the constraint equations in terms of accelerations into Kane＇s equations of the unconstrained system. Model analysis shows that the resulting equations perfectly meet the requirement of adaptive controller design. Consequently, by using an indirect approach, an adaptive control scheme is proposed to accomplish position/attitude trajectory tracking control with the uncertain parameters be- ing estimated on-line. The actuator redundancy due to the closed-loop constraints is utilized to minimize a weighted norm of the joint torques. Global asymptotic stability is proven by using Lyapunov＇s method, and simulation results are also presented to demonstrate the effectiveness of the proposed approach.

关键词： Space robot Dynamics. Adaptive control Closed-loop constraint Parameter uncertainty - Kane's equation

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Cross-domain data cloud storage auditing scheme based on certificateless cryptography

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The Journal of China Universities of Posts and Telecommunications 2021年第6期28卷 36-47页

作者： xu Yan Li Zheng Ding long xu Rui School of Computer Science and Technology Anhui UniversityHefei 230039China Anhui Engineering Laboratory of IoT Security Technologies Anhui UniversityHefei 230039China School of Computer University of Geosciences(Wuhan)Wuhan 430078China

With the development of Internet of things(IoT), more and more intelligent terminal devices outsource data to cloud servers(CSs). However, the CS is not fully trusted, and the heterogeneity among different domains makes it difficult for third-party auditor(TPA) to conduct an efficient integrity auditing of outsourced data. Therefore, the cross-domain data cloud storage auditing scheme based on certificateless cryptography is proposed, which can effectively avoid the big burden of certificate management or key escrow problems in identity-based cryptography. At the same time, TPA can effectively audit the integrity of outsourced data in different domains. Formal security proof and analysis show that the cloud storage auditing scheme satisfies the security and privacy requirements. Performance analysis demonstrates that the efficiency is acceptable.

关键词： cloud storage auditing certificateless cryptography cross-domain Internet of things(IoT)

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Dynamics of a spacecraft with large flexible appendage constrained by multi-strut passive damper

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Acta Mechanica Sinica 2013年第2期29卷 294-308页

作者： Ying-Hong Jia Shi-Jie xu quan Hu School of Astronautics Beihang University

This paper is concerned with the dynamics of a spacecraft with multi-strut passive damper for large flexible *** damper platform is connected to the spacecraft by a spheric hinge,multiple damping struts and a rigid *** damping struts provide damping forces while the rigid strut produces a motion constraint of the multibody *** exact nonlinear dynamical equations in reducedorder form are firstly derived by using Kane＇s equation in matrix *** on the assumptions of small velocity and small displacement,the nonlinear equations are reduced to a set of linear second-order differential equations in terms of independent generalized displacements with constant stiffness matrix and damping matrix related to the damping strut *** simulation results demonstrate the damping effectiveness of the damper for both the motion of the spacecraft and the vibration of the flexible appendage,and verify the accuracy of the linear equations against the exact nonlinear ones.

关键词： Dynamics·Motion constraints·Multi-strut passive damper·Kane's equation

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Size Effects of the Properties in a Ferroelectric Bilayer Film with Surface Transition Layers

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Chinese Physics Letters 2012年第3期29卷 212-215页

作者： CUI Lian xu quan HAN Zhi-You xu xu Department of Physics Daqing Normal UniversityDaqing 163712

Using the transverse Ising model theory,a ferroelectric bilayer film,considering the surface transition layer within each constituent slab and an interracial coupling between two slabs,is investigated in the framework of the mean-field *** discuss in detail the thickness effects of the spontaneous polarization and dielectric susceptibility ofa ferroelectric bilayer film under two conditions of interracial coupling:ferroelectric and antiferroelectric *** results show some unexpected phenomena for a small thickness of a ferroelectric bilayer film.

关键词： film ferroelectric layer

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