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Structural and Optical Properties of Graphene Oxide Prepared by Modified Hummers’Method

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Computers, Materials & Continua 2016年第6期52卷 175-185页

作者： N.Selvakumar Uday Pradhan S.B.Krupanidhi Harish C.Barshilia Nanomaterials Research lab Surface Engineering DivisionCSIR-National Aerospace LaboratoriesBangalore-560017India Materials Research Center Indian Institute of ScienceBangalore-560012India

Graphene oxide was synthesized from graphite flakes using modified Hummers’*** interlayer spacings of graphite,graphite oxide and graphene oxide were measured using X-ray diffraction *** C/O atomic ratios of graphite oxide and graphene oxide were calculated from XPS *** transformation of graphite to graphite oxide and finally to graphene oxide was clearly observed from the micro-Raman spectroscopy data and was confirmed from the FESEM ***-VIS-NIR spectrophotometer was used to study the absorbance of graphene oxide and reduced graphene oxide ***,the chemically reduced graphene oxide was heat-treated in air to obtain chemically modified graphene.

关键词： Graphene oxide Graphite,modified Hummers’method thermal annealing optical properties

The reason for the amelioration of N-methyl-N-nitrosourea-induced retinitis pigmentosa in rats by hydrogen-rich saline

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International Journal of Ophthalmology(English edition) 2017年第10期10卷 1495-1503页

作者： Wei-Ming Yan Tao Chen Xiao-Cheng Wang Lin-Song Qi Guan-Hua Zhao Guo-Qing Yang Yi-Fei Ma Ye Tao Lei Zhang Zuo-Ming Zhang Department of Clinical Medicine Faculty of Aerospace MedicineKey Laboratory of Aerospace Medicine of the National Education Ministrythe Fourth Military Medical University Department of Health Service Faculty of Aerospacethe Fourth Military Medical University Department of Aviation Physical Examination and Ophthalmology Air Force General Hospital Department of Ophthalmology General Hospital of Chinese PLAOphthalmology &Visual Science Key Lab of PLA

AIM：To investigate the effects of hydrogen-rich saline（HRS）on microglia activation and Sirtuin type 1（Sirt1）in rats with N-methyl-N-nitrosourea（MNU）-induced retinitis pigmentosa（RP）.METHODS：Rats were divided into norm（N）group,model（M）group and HRS（H）*** in M and H groups were given saline and HRS respectively prior to and after administration of *** one day（d1）and d3 afterwards,electroretinogram and histological examination were performed to confirm the effects of HRS on retinal function and structure of MNU-induced *** staining of anti-ionized calcium-binding adapter molecule 1（Iba1）,a maker of microglia cells,was performed,with quantitative real-time polymerase chain reaction（qRT-PCR）for its m RNA ***,Sirt1 m RNA and protein expression in the retinas were detected by Western blot and ***：HRS preserved the retinal function and mitigated the reduction of photoreceptor degeneration in MNU-treated *** presence of microglia cells was somewhat more obvious in H group than that in M group at *** suppressed the further activation of microglia cells,with the number of microglia cells less than that of M group at *** of qRT-PCR of Iba1 were consistent with those of immunofluorescence staining,with the m RNA expression of Iba1 in H group more intensive than that of M group at d1（P〈0.05）,while less than that of M group at d3（P〈0.05）.Furthermore,the Sirt1 m RNA and protein expression decreased after MNU administration,while HRS mitigated the MNU-induced downregulation of ***：HRS can effectively keep microglia activation induced by MNU to an appropriate extent,while upregulate Sirt1 in MNU-induced RP.

关键词： hydrogen hydrogen-rich saline electroretinogram microglia Sirtl retinitis pigmentosa

Investigation of Induced Unbalance Magnitude on Dynamic Characteristics of High-speed Turbocharger with Floating Ring Bearings

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Chinese Journal of Mechanical Engineering 2018年第5期31卷 99-109页

作者： Guang-Fu Bin Yuan Huang Shuai-Ping Guo Xue-Jun Li Gang Wang Health Maintenance for Mechanical Equipment Key lab of Hunan Province Hunan University of Science and Technology Xiangtan 411201 China Department of Mechanical and aerospace Engineering The University of Alabama in Huntsville AL 35899 USA

Due to operational wear and uneven carbon absorption in compressor and turbine wheels, the unbalance(me) vibration is induced and could lead to sub?synchronous vibration accidents for high?speed turbocharger(TC). There are very few research works that focus on the magnitude e ects on such induced unbalance vibration. In this paper, a finite element model(FEM) is developed to characterize a realistic automotive TC rotor with floating ring bearings(FRBs). The nonlinear dynamic responses of the TC rotor system with di erent levels of induced unbalance magni?tude in compressor and turbine wheels are calculated. From the results of waterfall and response spectral intensity plots, the bifurcation and instability phenomena depend on unbalance magnitude during the startup of TC. The sub?synchronous component 0.12× caused rotor unstable is the dominant frequency for small induced unbalance. The nonlinear e ects of induced unbalance in the turbine wheel is obvious stronger than the compressor wheel. As the unbalance magnitude increases from 0.05 gbration 1·mm to 0.2 g·mm, the vibration component changes from mainly 0.12× to synchronous vi×. When unbalance increases continuously, the rotor vibration response amplitude is rapidly growing and the 1× caused by the large unbalance excitation becomes the dominant frequency. A suitable un?balance magnitude of turbine wheel and compressor wheel for the high?speed TC rotor with FRBs is proposed: the value of induced un?balance magnitude should be kept around 0.2 g·mm.

关键词： High?speed TC with FRBs Induced unbalance magnitude Nonlinear dynamic response Sub?synchronous vibration Stability

Enhanced mechanical and thermal properties of two-dimensional SiC and GeC with temperature and size dependence

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Chinese Physics B 2023年第7期32卷 101-107页

作者：黄磊任凯张焕萍覃华松 School of Mechanical and Electronic Engineering Nanjing Forestry UniversityNanjing 210037China laboratory for Multiscale Mechanics and Medical Science SV LABSchool of AerospaceXi’an Jiaotong UniversityXi’an 710049China

Two-dimensional materials with novel mechanical and thermal properties are available for sensors,photodetectors,thermoelectric,crystal diode and flexible *** this investigation,the mechanical and thermal properties of pristine SiC and GeC are explored by molecular dynamics ***,the fracture strength and fracture strain behaviors are addressed in the zigzag and armchair directions at 300 *** excellent toughness of SiC and GeC is demonstrated by the maximal fracture strain of 0.43 and 0.47 in the zigzag direction,*** temperature-tunable tensile strength of SiC and GeC is also ***,using non-equilibrium molecular dynamics(NEMD)calculations,the thermal performances of SiC and GeC are *** particular,the thermal conductivity of SiC and GeC shows a pronounced size dependence and reaches up to 85.67 W·m^(-1)-K^(-1)and 34.37 W·m^(-1)-K^(-1),*** goal of our work is to provide a theoretical framework that can be used in the near *** will enable us to design an efficient thermal management scheme for two-dimensional materials in electronics and optoelectronics.

关键词： two-dimensional molecular dynamics mechanical property heat transport

Dragonfly Inspired Nanocomposite Flapping Wing for Micro Air Vehicles

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Journal of Bionic Engineering 2019年第5期16卷 894-903页

作者： David Kumar Preetamkumar Marutrao Mohite Sudhir Kamle Department of aerospace Engineering Indian Institute of Technology KanpurKanpur 208016India

The current research is aimed towards the development of dragonfly inspired nanocomposite flapping wing for micro air vehicles(MAVs).The wing is designed by taking inspiration from the hind wing of dragonfly(Anax Parthenope Julius).Carbon nanotubes(CNTs)/polypropylene nanocomposite and low-density polyethylene are used as the wing *** nanocomposites are developed with varying CNTs'weight percentage(0%-1%)and characterized for dynamic mechanical properties,which revealed that the 0.1 weight percentage case produces highest storage modulus values throughout the frequency range(1 Hz一90 Hz).It is also observed that the storage modulus values are in the range ofYoung^modulus of veins and membrane of natural insect *** is useful to achieve true *** manufacturing technique such as photolithography is used for wing *** length,weight and average thickness of the fabricated wing are^44 mm,26.22 mg and 187 pm,*** structural dynamic properties of the fa bricated wing are obtained experimentally and computationally using DIC and ANSYS,*** developed dragonfly inspired wing showed a natural frequency of 29.4 Hz with a bending mode shape which is close to the characteristic frequency of its natural counterpart.

关键词： flapping wings biomimicking nanocomposites MAVs

Exit problem of stochastic SIR model with limited medical resource

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Theoretical & Applied Mechanics Letters 2023年第1期13卷 8-13页

作者： Y.C.Mao X.B.Liu State Key lab of Mechanics and Control for Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

Nonlinearity and randomness are both the essential attributes for the real world,and the case is the same for the models of infectious diseases,for which the deterministic models can not give a complete picture of the ***,although there has been a lot of work on stochastic epidemic models,most of them focus mainly on qualitative properties,which makes us somewhat ignore the original meaning of the parameter *** this paper we extend the classic susceptible-infectious-removed(SIR)epidemic model by adding a white noise excitation and then we utilize the large deviation theory to quantitatively study the long-term coexistence exit problem with ***,in order to extend the meaning of parameters in the corresponding deterministic system,we tentatively introduce two new thresholds which then prove rational.

关键词： Stochastic epidemic model Stochastic dynamical system Large deviation theory Exit problem

The effects of redundant control inputs in optimal control

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Science in China(Series F) 2009年第11期52卷 1973-1981页

作者： DUAN ZhiSheng HUANG Lin YANG Ying State Key lab for Turbulence and Complex Systems and Department of Mechanics and aerospace Engineering College of Engineering Peking University Beijing 100871 China

For a stabilizable system, the extension of the control inputs has no use for stabilizability, but it is important for optimal control. In this paper, a necessary and sufficient condition is presented to strictly decrease the quadratic optimal performance index after control input extensions. A similar result is also provided for H2 optimal control problem. These results show an essential difference between single-input and multi-input control systems. Several examples are taken to illustrate related problems.

关键词： redundant control optimal control Riccati equation Hamilton matrix

A goal-based approach for modeling and simulation of different types of system-of-systems

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Journal of Systems Engineering and Electronics 2023年第3期34卷 627-640页

作者： FENG Yimin ZHOU Chenchu ZOU Qiang LIU Yusheng LYU Jiyuan WU Xinfeng State Key lab of CAD&CG Zhejiang UniversityHangzhou 310027China Xi’an aerospace Propulsion Institute Xi’an 710100China China Astronaut Research and Trainning Center Beijing 100094China

A system of systems(SoS)composes a set of independent constituent systems(CSs),where the degree of authority to control the independence of CSs varies,depending on different SoS *** researchers describe four SoS types with descending levels of central authority:directed,acknowledged,collaborative and *** the definitions have been recognized in SoS engineering,what is challenging is the difficulty of translating these definitions into models and simulation ***,we provide a goal-based method including a mathematical baseline to translate these definitions into more effective agent-based modeling and ***,we construct the theoretical models of CS and *** on the theoretical models,we analyze the degree of authority influenced by SoS ***,we propose a definition of SoS types by quantitatively explaining the degree of ***,we recognize the differences between acknowledged SoS and collaborative SoS using a migrating waterfowl flock by an agentbased model(ABM)*** paper contributes to the SoS body of knowledge by increasing our understanding of the degree of authority in an SoS,so we may identify suitable SoS types to achieve SoS goals by modeling and simulation.

关键词： simulation systems agent-based modeling systemsof-systems(SoS) systems thinking

Fabrication and characterization of squama-shape micro/nano multi-scale silicon material

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Science China(Technological Sciences) 2012年第12期55卷 3395-3400页

作者： ZHANG XiaoSheng ZHU FuYun SUN GuangYi ZHANG HaiXia National Key lab of Nano/Micro Fabrication Technology Peking UniversityBeijing 100871China Mechanical and aerospace Engineering Department University of CaliforniaLos AngelesCalifornia 90095USA

This paper presents the fabrication of squama-shape micro/nano multi-scale structures and the analysis of the interaction among different-scale structures during the fabrication processes. Well-designed microstructures made of inverted pyramids and V-shape grooves are fabricated by KOH wet etching. High-dense high-aspect-ratio (HAR) nanostructures are fabricated atop microstructures by an improved maskless deep reactive ion etching (DRIE) process, with an optimized recipe to form micro/nano dual-scale structures (MNDS). Due to the impact of the profile of microstructures on the shape of nanostructures, dissymmetrical (i.e., squama-shape) nanopillars have been formed on the inclined surfaces of microstructures, while the symmetrical nanopillars are formed on the horizontal surfaces with different formation velocities. Furthermore, the optical properties of MNDS are not sensitive to structural parameters of microstructures, making the sample overcome the lithography limitation of conventional processes for photo-devices. Eventually, three-level structures are fabricated by sputtering a gold thin film on the MNDS, and the profile of MNDS is selective in the deposition of gold particles, which is very useful for practical applications.

关键词： deep reactive ion etching (DRIE) multi-scale structures squama-shape hierarchical structure silicon