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Performance deterioration modeling and optimal preventive maintenance strategy under scheduled servicing subject to mission time

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Chinese Journal of Aeronautics 2014年第4期27卷 821-828页

作者： Li dawei Zhang Zhihua Zhong Qianghui Zhai Yali Department of Weapon Engineering Naval University of Engineering Office of Research & Development Naval University of Engineering Department of Equipment Economics & Management Naval University of Engineering College of Science Naval University of Engineering

Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.

关键词： Dependability Imperfect maintenance Preventive maintenance Reliability Scheduled servicing

Rolling Force and Rolling Moment in Spline Cold Rolling Using Slip-line Field Method

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Chinese Journal of Mechanical Engineering 2009年第5期22卷 688-695页

作者： ZHANG dawei LI Yongtang FU Jianhua ZHENG Quangang School of Materials Science and Engineering Taiyuan University of Science and Technology Taiyuan 030024 China School of Materials Science and Engineering Northwestern Polytechnical University Xi ＇an 710072 China Qingdao Cool Rolling Technological Research and Development Center Qingdao 266100 China

Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.

关键词： external spline cold rolling slip-line field method rolling force rolling moment

Mesocrystal Co3O4 nanoplatelets as high capacity anode materials for Li-ion batteries

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Nano Research 2014年第5期7卷 794-803页

作者： dawei Su Shixue Dou Guoxiu Wang Institute for Superconducting & Electronic Materials University of Wollongong Wollongong NSW 2522 Australia Centre for Clean Energy Technology School of Chemistry and Forensic Science University of Technology Sydney Broadway Sydney NSW 2007 Australia

Faceted crystals with exposed highly reactive planes have attracted intensive investigations for applications. Herein, we demonstrate a general synthetic method to prepare mesocrystal Co3O4 with predominantly exposed {111} reactive facets by the in situ thermal decomposition from Co（OH）2 nanoplatelets. The mesocrystal feature was identified by field emission scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N2 isotherm analyses. When applied as anode material in lithium-ion batteries, mesocrystal Co3O4 nanoplatelets delivered a high specific capacity and an outstanding high rate performance. The superior electrochemical performance should be ascribed to the predominantly exposed {111} active facets and highly accessible surfaces. This synthetic strategy could be extended to prepare other mesocrystal functional nanomaterials.

关键词： msoporous material faceted crystal anode materiallithium ion battery

Analysis of diffusion induced elastoplastic bending of bilayer lithium-ion battery electrodes

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Applied Mathematics and Mechanics(English Edition) 2016年第5期37卷 659-670页

作者： dawei LI Zongzan LI Yicheng SONG Junqian ZHANG Shanghai Institute of Applied Mathematics and Mechanics Shanghai UniversityShanghai 200072China Department of Mechanics College of SciencesShanghai UniversityShanghai 200444China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai 200072China

Bilayer electrode, composed of a current collector layer and an active material layer, has great potential in applications of in-situ electrochemical experiments due to the bending upon lithiation. This paper establishes an elastoplastic theory for the lithiation induced deformation of bilayer electrode with consideration of the plastic yield of current collector. It is found that the plastic yield of current collector reduces the restriction of current collector to an active layer, and therefore, enhances in-plane stretching while lowers down the rate of electrode bending. Key parameters that influence the elastoplastic deformation are identified. It is found that the smaller thickness ratio and lower elastic modulus ratio of current collector to an active layer would lead to an earlier plastic yield of the current collector, the larger in-plane strain, and the smaller bending curvature, due to balance between the current collector and the active layer. The smaller yield stress and plastic modulus of current collector have similar impacts on the electrode deformation.

关键词： bilayer electrode lithium-ion battery plastic yield bending stress

Using triple radio-immunotherapy to overcome cancer immunotherapy resistance

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Cancer Biology & Medicine 2023年第11期20卷 788-794页

作者： Zengfu Zhang Xiaodong Zhang dawei Chen Department of Radiation Oncology Shandong University Cancer CenterJinan 250117China Department of Radiation Oncology Shandong Cancer Hospital and InstituteShandong First Medical University and Shandong Academy of Medical SciencesJinan 250117China

Cancer is a widespread public health issue and has become a leading cause of death in most *** recent decades,immunotherapy,particularly the use of immune checkpoint inhibitors(ICIs),has altered the clinical practice ... 详细信息

关键词： immunotherapy clinical cancer

Advancing sustainable agriculture: Enhancing crop nutrition with next-generation nanotech-based fertilizers

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Nano Research 2023年第12期16卷 13205-13225页

作者： Yiwen Liao dawei Xu Yuhong Cao Yong-Guan Zhu State Key Laboratory of Urban and Regional Ecology Research Centre for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China CAS Key Laboratory for Biological Effects of Nanomaterials and Nanosafety National Center for Nanoscience and TechnologyBeijing 100190China

The pressing need to enhance nutrient use efficiency(NUE)in fertilizers has become increasingly urgent in light of food insecurity and climate-related *** offers promising prospects for the development of effective and environmentally friendly alternatives in the field of *** review focuses on the impact of nanotechnology on conventional fertilizers,encompassing inorganic,organic,and microbial *** emphasize the superior attributes of nano-fertilizers compared with their conventional counterparts and explore their potential and versatility in boosting crop productivity,reducing fertilizer expenses,and mitigating detrimental environmental *** conclusion,given the significant challenges posed by food insecurity and climate change,the application of nano-fertilizers demonstrates immense potential for advancing sustainable and intelligent agricultural practices.

关键词： nanobiotechnology nano-fertilizers(NFs) nutrient use efficiency(NUE) slow release sustainable agriculture

Enhanced microwave absorption performance of MOF-derived hollow Zn-Co/C anchored on reduced graphene oxide

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Chinese Physics B 2021年第6期30卷 610-616页

作者： Yue Wang dawei He Yongsheng Wang Key Laboratory of Luminescence and Optical Information Ministry of EducationInstitute of Optoelectronic TechnologyBeijing Jiaotong UniversityBeijing 100044China

Composite materials assembled by metal/carbon nanoparticles and 2 D layered flakes can provide abundant interfaces,which are beneficial for high-performance microwave absorbers. Herein, Zn-Co/C/RGO composites, composed of ZnCo metal-organic framework-derived Zn-Co/C nanoparticles and reduced graphene oxide(RGO), were obtained through a facile method. The multilayer structure was due to the introduction of hollow Zn-Co/C nanoparticles in the RGO sheets. ZnCo/C nanoparticles provided abundant polarization and dipole centers on the RGO surface, which enhanced the microwave absorption abilities. Different concentrations of RGO were introduced to optimize impedance matching. The minimum reflection loss(R_(L)) of Zn-Co/C/RGO with a thickness of 1.5 mm reached-32.56 dB with the bandwidth corresponding to R_(L) at-10 dB, which can reach 3.92 GHz, while a minimum R_(L) of-47.15 dB at 11.2 GHz was also obtained at a thickness of 2.0 mm. The electromagnetic data demonstrate that Zn-Co/C/RGO presented excellent absorption performance and has potential for application in the microwave absorption field.

关键词： microwave absorption metal nanoparticles metal-organic framework(MOF) reduced graphene oxide

A novel layout for single event upset mitigation in advanced CMOS SRAM cells

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Science China(Technological Sciences) 2013年第1期56卷 143-147页

作者： QIN JunRui LI dawei CHEN ShuMing School of Computer Science National University of Defense Technology

A novel layout has been proposed to reduce the single event upset(SEU) vulnerability of SRAM *** 3-D technology computer-aided design(TCAD) simulation analyses show that the proposed layout can recover the upset-state much easier than conventional layout for larger space of PMOS *** the angle incidence,the proposed layout is immune from ion hit in two plans,and is more robust against SEU in other two plans than the conventional *** ability of anti-SEU is enhanced by at least 33% while the area cost reduced by 47%.Consequently,the layout strategy proposed can gain both reliability and area cost benefit simultaneously.

关键词： single event upset layout technique SRAM radiation hardening by design

Research of Luminescence Properties on MO-RE2 O3 -B2 O3: Eu, Mn(M=Mg, Ca, Sr; RE=Y, La, Gd)

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Journal of Rare Earths 2004年第z1期22卷 133-136页

作者： Liang Zhongyi He dawei Shi Yanning Ministry of Education Key Lab Lab of Materials for Information Storage and Display Institute of Photoelectron Technology Northern Jiao Tong University Beijing 100044 China

A series of phosphor of MO-RE2 O3-B2 O3: Eu, Mn ( M = Mg, Ca, Sr; RE = Y, La, Gd) were prepared and *** spectra exhibited high absorption in UV region (370 ~ 400 nm).There existed two valence states for europium ions Eu2+ and Eu 3+, the broad emission band peaking at 515 nm correspond to the 5d-4f emission transition of Eu2+ , the sharp emission peaking at 590 and 610 nm correspond to the 5D0→7FJ(J = 1,2,3,4) emission transition of Eu 3 + By the introduction of Mg and Y into MO-RE2O3-B2O3: Eu, blue-green emission was restrained ultimately and red emission peaking at 610 nm was enhanced strongly, intensity and colorimetric purity of red light were both ***, Mg1-xSrxO-Y2O3-B2O3: Eu was also researched, the introduction of Sr into MgO-Y2O3-B2O3:Eu gives rise to a shift to longer wavelengths of the position of the excitation peak, and the emission spectra varies with the increasing of x simultaneously.

关键词： luminescence long wave-UV excitation phosphor rare earths