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An Analytical Method for Predicting Direct Tensile Creep Fracture in Brittle Solids Containing Initial Microcracks

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Acta Mechanica Solida Sinica 2022年第1期35卷 152-160页

作者： Xiaozhao Li chengzhi Qi School of Civil and Transportation Engineering Beijing University of Civil Engineering and ArchitectureBeijing 100044China Beijing Advanced Innovation Center for Future Urban Design Beijing 100044China Beijing International Scientific and Technological Cooperation Base of Construction of Urban Traffic Infrastructure Beijing 100044China

The tensile creep fracture behaviors in brittle solids are of great significance for the safety evaluation of brittle solid ***,micromechanics-based tensile creep fracture behavior is rarely *** this study,a micromechanics-based method for predicting direct tensile creep fractures is *** method is established by combining the suggested expression of the mode-I stress intensity factor,the subcritical crack growth law,and the relationship between wing crack length and axial *** suggested mode-I stress intensity factor is formulated by the use of the basic theory of fracture mechanics under different loading *** rationality of the proposed tensile creep fracture model is verified by comparing with the experimental *** correspondences of time-dependent axial strain,strain rate,wing crack length,and crack velocity are plotted under constant stress and stepping stress during tensile creep *** effects of the initial crack size,inclination angle and density on the crack initiation stress,tensile strength,tensile creep fracture time,steady-state strain rate,initial strain,crack coalescence strain,and failure strain are discussed.

关键词： Micromechanics Stress intensity factor Direct tensile creep Subcritical cracking Brittle solids

Design and performance analysis of deterministic learning of sampled-data nonlinear systems

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Science China(Information Sciences) 2014年第3期57卷 204-221页

作者： YUAN chengzhi WANG Cong College of Automation and the Center for Control and Optimization South China University of Technology

In this paper,we extend the deterministic learning theory to sampled-data nonlinear *** on the Euler approximate model,the adaptive neural network identifier with a normalized learning algorithm is *** is proven that by properly setting the sampling period,the overall system can be guaranteed to be stable and partial neural network weights can exponentially converge to their optimal values under the satisfaction of the partial persistent excitation(PE)***,locally accurate learning of the nonlinear dynamics can be achieved,and the knowledge can be represented by using constant-weight neural ***,we present a performance analysis for the learning algorithm by developing explicit bounds on the learning rate and *** factors that influence learning,including the PE level,the learning gain,and the sampling period,are *** studies are included to demonstrate the efectiveness of the approach.

关键词： neural network identification deterministic learning persistent excitation sampled-data systems radial basis function networks(RBFNs)

Arsenic species in electronic cigarettes:Determination and potential health risk

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Journal of Environmental Sciences 2020年第5期32卷 168-176页

作者： Qingqing Liu chengzhi Huang XChris Le Chongqing Key Laboratory of Biomedical Analysis(Southwest University) Chongqing Science&Technology CommissionCollege of Chemistry and Chemical EngineeringSouthwest UniversityChongqing 400715China College of Resources and Environment Southwest UniversityChongqing400715China Key Laboratory of Luminescent and Real-Time Analytical System Chongqing Science and Technology BureauCollege of Pharmaceutical SciencesSouthwest UniversityChongqing 400715China Department of Laboratory Medicine and Pathology Faculty of Medicine and DentistryUniversity of Alberta10102 Clinical Sciences BuildingEdmontonAlberta T6G 2G3Canada

Human exposure to contaminants from electronic cigarettes(e-cigarettes)and the associated health effects are poorly *** has been no report on the speciation of arsenic in e-liquid(solution used for e-cigarettes)and *** report here determination of arsenic species in e-liquids and aerosols generated from vaping the *** e-liquid samples of major brands,purchased from local and online stores in Canada and China,were analyzed for arsenic species using high-performance liquid chromatography and inductively coupled plasma mass *** condensed from vaping the eliquids were also analyzed and compared for arsenic *** arsenic species were detected,including inorganic arsenate(iAsⅤ),arsenite(iAsⅢ),monomethylarsonic acid(MMA),and three new arsenic species not reported *** e-liquids,iAsⅢwas detected in 59%,iAsⅤin 94%,and MMA in 47%of the *** the condensate of aerosols from vaping the e-liquids,iAsⅢwas detected in 100%,iAsv in 88%,and MMA in 13%of the *** arsenic species were predominant in e-liquids and aerosols of *** concentration of iAsⅢin the condensate of aerosols(median 3.27μg/kg)was significantly higher than that in the e-liquid(median 1.08μg/kg)*** concentration of inorganic arsenic in the vaping air was approximately 3.4μg/m3,which approaches to the permissible exposure limit(10μg/m3)set by the United States Occupational Safety and Health Administration(OSHA).According to the Environmental Protection Agency’s unit risk factor(4.3×10-3 perμg/m3)for inhalation exposure to inorganic arsenic in the air,the estimated excess lung cancer risk from lifetime exposure to inorganic arsenic in the ecigarette vaping air(3.4μg/m3),assuming e-cigarette vaping at 1%of the time,is as high as1.5×*** results raise health concerns over the exposure to arsenic from electronic cigarettes.

关键词： Electronic cigarettes E-liquid E-cigarette aerosol Arsenic speciation Inhalation exposure Metals Lung cancer risk

Application of Analytic Redundancy-based Fault Diagnosis of Sensors to Onboard Maintenance System

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Chinese Journal of Aeronautics 2012年第2期25卷 236-242页

作者： CHI chengzhi ZHANG Weiguo LIU Xiaoxiong School of Automation Northwestern Polytechnical UniversityXi'an 710072China

Analytic redundancy-based fault diagnosis technique （ARFDT） is applied to onboard maintenance system （OMS）. The principle of the proposed ARFDT scheme is to design a redundancy configuration using ARFDT to enhance the functions of redundancy management and built in test equipment （BITE） monitor. Redundancy configuration for dual-redundancy and analytic redundancy is proposed, in which, the fault diagnosis includes detection and isolation. In order to keep the balance between rapid diagnosis and binary hypothesis, a filter together with an elapsed time limit is designed for sequential probability ratio test （SPRT） in the process of isolation. Diagnosis results would be submitted to central maintenance computer （CMC） together with BITE information. Moreover, by adopting reconstruction, the designed method not only provides analytic redundancy to help redundancy management, but also compensates the output when both of the sensors of the same type are faulty. Our scheme is applied to an aircraft’s sensors in a simulation experiment, and the results show that the proposed filter SPRT （FSPRT） saves at least 50% of isolation time than Wald SPRT （WSPRT）. Also, effectiveness, practicability and rapidity of the proposed scheme can be successfully achieved in OMS.

关键词： fault detection analytic redundancy sequential probability ratio test (SPRT) onboard maintenance system (OMS) redundancy management sensors

The Cubic Trigonometric Automatic Interpolation Spline

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IEEE/CAA Journal of Automatica Sinica 2018年第6期5卷 1136-1141页

作者： Juncheng Li Laizhong Song chengzhi Liu College of Mathematics and Finance Hunan University of HumanitiesScience and Technology College of Science China Three Gorges University

A class of cubic trigonometric interpolation spline curves with two parameters is presented in this paper. The spline curves can automatically interpolate the given data points and become C^2 interpolation curves without solving equations system even if the interpolation conditions are fixed. Moreover, shape of the interpolation spline curves can be globally adjusted by the two parameters. By selecting proper values of the two parameters,the optimal interpolation spline curves can be obtained.

关键词： Automatic interpolation interpolation spline shape adjustment trigonometric polynomial

The Effect of Variable Blank-Holder Forces on the Formability of Aluminum Alloy Sheets during Sheet Metal Forming

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上海交通大学学报 2004年第z2期38卷 54-60页

作者： Sun chengzhi Chen Guanlong Lin Zhongqin School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China School of Mechanical Engineering Shanghai Jiaotong University Shanghai200030 China

In this paper, the effect of variable Blank-holder forces (VBHF) on the strain path during sheet metal forming has been investigated by numerical simulation and experiments. The formability of select aluminum alloy sheet was evaluated by theory prediction of forming limit curve based on the M-K method. The effect of different VBHF on the formability was presented. In order to verify the predictions of strain path, experiments are being carried out using a recently-built multi-points variable blank-holder forces hydraulic press. The results show that large side BHF with small comer BHF during rectangular box deep drawing can improve the formability of the selected aluminum alloy

关键词： sheet metal forming variable blank-holder force strain path forming limit curve

A modified smoothed particle hydrodynamics method considering residual stress for simulating failure and its application in layered rock mass

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Journal of Mountain Science 2024年第6期21卷 2091-2112页

作者： XIA chengzhi SHI Zhenming KOU Huanjia Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai 200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai 200092China

Residual strength is an indispensable factor in evaluating rock fracture,yet the current Smoothed Particle Hydrodynamics(SPH)framework rarely considers its influence when simulating *** improved cracking strategy considering residual stress in the base bond SPH method was proposed to simulate failures in layered rocks and slopes and verified by experimental results and other simulation methods(i.e.,the discrete element method).Modified Mohr–Coulomb failure criterion was applied to distinguish the mixed failure of tensile and *** fracture markψwas introduced to improve the kernel function after tensile damage,and the calculation of residual stress after the damage was derived after shear *** simulations were carried out to evaluate its performance under different stress and scale conditions and to verify its effectiveness in realistically reproducing crack initiation and propagation and coalescence,even fracture and *** results indicate that the improved cracking strategy precisely captures the fracture and failure pattern in layered rocks and rock *** residual stress of brittle tock is correctly captured by the improved SPH *** improved SPH method that considers residual strength shows an approximately 13%improvement in accuracy for the safety factor of anti-dip layered slopes compared to the method that does not consider residual strength,as validated against analytical *** infer that the improved SPH method is effective and shows promise for applications to continuous and discontinuous rock masses.

关键词： Smoothed particle hydrodynamics Cracking strategy Residual stress Layered rock Crack propagation

Optimum conditions for the formation of Al_(13) polymer and active chlorine in electrolysis process with Ti/RuO_2-TiO_2 anodes

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Journal of Environmental Sciences 2012年第2期24卷 297-302页

作者： chengzhi Hu Huijuan Liu Jiuhui Qu State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China.

A polyaluminum containing a high concentration of Al13 polymer and active chlorine（PACC） was successfully synthesized by a new electrochemical reactor using Ti/RuO2-TiO2 *** can potentially be used as a dual-function chemical reagent for water *** obtained results indicated that the formation of Al13 polymer and active chlorine,were the most active components in PACC responsible for coagulation and disinfection *** components were significantly influenced by electrolyte temperature,current density,and stirring *** was observed that high electrolyte temperature favored the formation of *** current density and stirring rate resulted in high current efficiency of chlorine evolution,thus favoring the generation of Al13 and active chlorine in *** the PACC（AlT = 0.5 mol/L,basicity = 2.3） was prepared at the optimum conditions by electrolysis process,the Al13 polymer and active chlorine in product reached above 70% of AlT and 4000 mg/L,*** the pilot scale experiment with raw polyaluminum chloride used as an electrolyte,PACC was successfully prepared and produced a high content of Al13 and active chlorine *** pilot scale experiment demonstrated a potential industrial approach of PACC preparation.

关键词： Al13 polymer coagulation pre-oxidation electrolysis water treatment

Effect of interplanetary magnetic field B_(x)on the polar electrojets as observed by CHAMP and Swarm satellites

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Earth and Planetary Physics 2024年第2期8卷 382-390页

作者： Hui Wang chengzhi Wang YunFang Zhong Department of Space Physics School of Electronic InformationWuhan UniversityWuhan 430072China

Based on 16 years of magnetic field observations from CHAMP and Swarm satellites,this study investigates the influence of the Interplanetary Magnetic Field(IMF)Bx component on the location and peak current density of the polar electrojets(PEJs).We find that the IMF Bx displays obvious local time,seasonal,and hemispherical effects on the PEJs,as follows:(1)Compared to other local times,its influence is weakest at dawn and dusk.(2)In the midnight sectors of both hemispheres,the IMF Bx tends to amplify the westward PEJ when it is0 in the Southern Hemisphere;this effect is relatively stronger in the local winter hemisphere.(3)At noontime,the IMF Bx intensifies the eastward current when it is0,it reduces the westward current;this effect is notably more prominent in the local summer hemisphere.(4)Moreover,the noontime eastward current shifts towards higher latitudes,while the midnight westward current migrates towards lower latitudes when IMF Bx is0 in the Southern Hemisphere.

关键词： polar electrojet interplanetary magnetic field Bx local time asymmetry hemispheric difference