模拟微重力对植物幼苗光合特性的影响(英文)

目的研究模拟微重力对植物幼苗光合特性的影响。方法采用 1π回转器模拟微重力并处理植物样品 1 2 0h。结果 1 )株高和叶片数有所增加 ;2 )草莓的叶绿素含量降低 47.5 % ,香石竹叶绿素含量增加4.3% ;3)回转后两种幼苗的叶绿素主要吸收峰位不变 ,而每个峰位吸收强度有所增加 ;4)两种幼苗的叶片快速荧光动力学参数 ,回转后除CA/Fo外 ,Fv/Fo ,Fv/Fm和T1 / 2 均有提高 ;5 )对照和处理的叶绿体的两个光系统间的激发能分配有差异。结论微重力对叶绿体的正常光合功能没有显著影响 ,故植物幼苗在微重力条件下可以正常生长。

Effect of trace rare earth element Er on high pure Al

The influence of trace Er addition on high pure aluminum was studied by mechanical properties measurement,hardness measurement, optical microscope,transmission electron microscope and energy spectrum analysis. The results show that minor Er in the studied alloy exists in the form of Al 3Er,only a few of Er in α Al based solid solution .Primary Al 3Er particles formed during solidification were often found at the center of aluminum grains and acted as heterogeneous nucleus, also increased the rate of nucleation, therefore the grain are remarkably refined. Trace Er addition to high pure aluminum is able to increase the mechanical properties of high pure Al, which is caused by fine grain strengthening, substructure strengthening and precipitation strengthening. The recrystallization temperature of Er doped aluminum increases above 50 ℃, which is caused by the pinning effect of highly dispersed fine Al 3Er precipitates on dislocations and sub grain boundaries.

Mathematical model and magnetic-control mechanism of the stability of rotating spray transfer

To realize stable rotating spray transfer in the region of high constant current is the key of realizing high deposition rate MAG welding process without helium in shielding gas and extending the welding current range of traditional MAG welding process. In this paper, the magnetic control mechanism of the rotating spray transfer is stated and mathematical model is given. Theoretic basis is established, which implements high deposition rate MAG welding process with magnetic control instead of helium in shielding gas.

Chemical States of Lanthanum in Carbonized La_2O_3-Mo Thermionic Cathode Materials

The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.

Modified precise time step integration method of structural dynamic analysis

The precise time step integration method proposed for linear time-invariant homogeneous dynamic systems can provide precise numerical results that approach an exact solution at the integration points. However, difficulty arises when the algorithm is used for non-homogeneous dynamic systems, due to the inverse matrix calculation and the simulation accuracy of the applied loading. By combining the Gaussian quadrature method and state space theory with the calculation technique of matrix exponential function in the precise time step integration method, a new modified precise time step integration method （e.g., an algorithm with an arbitrary order of accuracy） is proposed. In the new method, no inverse matrix calculation or simulation of the applied loading is needed, and the computing efficiency is improved. In particular, the proposed method is independent of the quality of the matrix H. If the matrix H is singular or nearly singular, the advantage of the method is remarkable. The numerical stability of the proposed algorithm is discussed and a numerical example is given to demonstrate the validity and efficiency of the algorithm.

Electrode degradation mechanism during resistance spot welding of zinc coated steel using Cu-TiB_2 electrodes

The TiB2 dispersion-reinforced copper-matrix composite used as electrode material in resistance spot welding of zinc coated steels was studied. The service life of the composite electrode reaches （7700） welds, which is 4 times that of the conventional Cu-Cr-Zr electrode. Little gross deformation is observed on the composite （electrodes） because of the higher thermal strength; therefore, it is believed that wear is the only mechanism for the composite （electrode） deterioration. However, both wear and plastic deformation are responsible for the large increase in the tip diameter of the Cu-Cr-Zr electrodes. Moreover, the large deformation of the Cu-Cr-Zr electrodes may contribute to the increased wear rate of the tips.

Seismic structural control using semi-active tuned mass dampers

This paper focuses on how to determine the instantaneous damping of the semi-active tuned mass damper (SATMD) with continuously variable damping.An off-and-towards-equilibrium (OTE) algorithm is employed to examine the control performance of the structure/SATMD system by considering the damping as an assumptive control action.The damping modification of the SATMD is carried out according to the proposed OTE algorithm,which is formulated based on analysis of the structural movement under external excitations,and the measured responses of the structure at every time instant. As examples two numerical simulations of a five-storey and a ten-storey shear structures with a SATMD on the roof are conducted.The effectiveness on vibration reduction of MDOF systems subjected to seismic excitations is discussed.Analysis results show that the behavior of the structure with a SATMD is significantly improved and the feasibility of applying the OTE algorithm to the structural control design of SATMD is also verified.

冗余度柔性机器人动态响应主动控制(英文)

This paper presents an analytical investigation into activevibration control of flexible redundant robot manipulators featuringpiezoelectric actuators and strain gage sensors. The state-sp- aceexpression of the discrete time-varying dynamic system is developedfirstly. The LQR optimal control law is presented based upon thediscrete Minimum Principle. Moreover, an approximate method isproposed for estimating the state information of the system. Finally,a planar 3R flexible redundant manipulator is utilized as anillustration example. The simulation results show that the dy- namicperformance of the manipulator has been improved significantly.

New pattern Zn-Al-Mg-RE coating technics for steel structure sustainable design

Based on the advanced integrated technology of materials preparation and formation, a new pattern Zn-Al-Mg-RE anti-corrosion coating for steel structure sustainable design was manufactured by cored wires and high velocity arc spraying (HVAS) technologies. The developments of thermally sprayed coatings for steel structure protection were described. Based on Al, Zn, Zn-Al and Zn-Al-Mg coatings, the anti-corrosion properties of new-pattern Zn-Al-Mg-RE coating were evaluated through electrochemical methods including electrochemical polarization and electrochemical impedance spectroscopy (EIS) coupled with SEM and XRD. The models of Zn-Al-Mg-RE coating undergoing corrosion with the initial pinhole defect and the latter with accelerated products were also discussed. The results show that Zn-Al-Mg-RE coating exhibites excellent corrosion resistance for long-term immersion, which is helpful for the sustainable design of steel structure in aggressive corrosion conditions. And the corrosion products seem to possess certain self-sealing function.

Optimization of structural parameters for spatial flexible redundant manipulators with maximum ratio of load to mass

Optimization of structural parameters aimed at improving the load carrying capacity of spatial flexible redundant manipulators is presented in this paper. In order to increase the ratio of load to mass of robots, the cross-sectional parameters and constructional parameters are optimized respectively. The cross-sectional and configurational parameters are optimized simultaneously. The numerical simulation of a 4R spatial manipulator is performed. The results show that the load capacity of robots has been greatly improved through the optimization strategies proposed in this paper.

基于机敏材料的冗余度柔性机器人复模态主动控制(英文)

An active control methodology is presented for suppressing the vibratoryresponse of flexible redundant manipulators with bonded piezoceramic actuators and strain gagesensors. Firstly, the dynamic equation of the manipulator is decoupled by means of the complex modetheory and the state-space expression of the controlled system is developed. Secondly, a continuouslinear quadratic regulator (LQR) state feedback controller is designed based on the minimumprinciple. Thirdly, a full-order Luenberger state observer featuring an assigned degree of stabilityis determined via the duality between control and estimation. Finally, a numerical simulation iscarried out on a planar 3R flexible redundant manipulator. The simulation results reveal that thedynamic performance of the system is improved rapidly and significantly.

Theoretical and experimental research on a new system of semi-active structural control with variable stiffness and damping

In this paper,a new system of semi active structural control with active variable stiffness and damping (AVSD) is suggested.This new system amplifies the structural displacement to dissipate more energy,and in turn,effectively reduces the structural response in the case of relatively small story drifts,which occur during earthquakes.A predictive instantaneous optimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table tests of a 1/4 scale single story structural model with a full scale control device have been conducted.From the experimental and analytical results,it is shown that when compared to structures without control or with the active variable stiffness control alone, the suggested system exhibits higher efficiency in controlling the structural response,requires less energy input,operates with higher reliability,and can be manufactured at a lower cost and used in a wider range of engineering applications.

La_2O_3-Gd_2O_3-Mo secondary emission material

A new kind of materials La 2O 3-Gd 2O 3-Mo has been produced by powder metallurgy method. The composition and microstructure of the material were studied by XRD and SEM. It shows that no chemical reaction takes place among La 2O 3, Gd 2O 3, Mo and the rare earth oxides exist along molybdenum grain boundaries and in the pores. The emission property measurement results of this material show that adding rare earth oxide into molybdenum can improve the secondary emission coefficient of the emitter, and the emission property depends on the activating temperature. After La 2O 3-Gd 2O 3-Mo was activated at 1 360 ℃, the maximum secondary emission coefficient can be high to 2.62, which has exceeded that for practical uses(2.0).

VISCOELASTIC CHARACTERISTICS OF EXPANDED SKIN AFTER GRAFTING

The expanded skin specimens of dogs and their controls atdifferent stages after grafting were studied. The stress-strain,stress-relaxation viscoelastic characteristics and tensile strengthwere measured. The results show that, during the initial stage aftergrafting, the biomechanical properties of expanded speci- mensdeviate from those controls significantly. But the biomechanicalproperties of expanded speci- mens and their controls begin to closegradually in a longer recovering time. And when the recovering timereaches 24 weeks or longer, the experimental specimens exhibit thesame mechanical characteristics as their controls. It is shown thatviscoelasticity of expansive skin varies with time after grafting.

VIDEO CODING SCHEME FOR ATM NETWORKS

A new variable bit rate layered coding scheme based on subband coding is given in this paper. It can make full use of the merits of ATM transmission, as well as compensation for the quality degradation caused by cell loss, which is an inherent problem of ATM networks, and thus a stable, high quality video transmission is achieved. This paper presents the coding scheme, cell construction and simulation results.

Influence of the Plasma State on the Formation of Nano Crystalline SiC Films

The influence of the plasma state on the microstructure transformation from amorphous to nano-(crystalline) state is emphasized during the formation of the silicon carbide (SiC) films deposited by the plasma enhanced chemical vapor technique. The effect of two key parameters, the working pressure and hydrogen concentration in the gas flow, that perform the dependence by modulating the two essential factors of the plasma state-ions energy and gas composition, is in-depth investigated. The experimental results showed that nanocrystalline SiC films fit for field emitters could be achieved under an appropriate ion energy flow density and gas components in the (plasma.)

干摩擦面上接触应力分布的混合分析法((英文))

A hybrid method is established by combining photoelastic experiment and finite element analysis. The method is used to evaluate contact stress distribution on dry friction interfaces, such as the contact interfaces between shrouds of fan blades and turbine blades. The photoelastic stress frozen experiment method is used to decide the displacement boundary conditions of numerical calculation. Higher accuracy and efficiency of solving problems are improved by the method. Technical difficulty and high cost of experiment are also avoided by the method. Good agreement of the stress distribution by using the hybrid method and experiment is obtained. \{

Growth of α-LiIO_(3) Single Crystal Grown in Space

α-LiIO_(3) single crystals were grown by the aqueous solution method in a Chinese scientific return-satellite.The morphology of the crystals grown in space are similar to that of earth-grown crystals.It is found that the growth rates of the positive and negative sides of the space-grown crystals are almost the same.The perfection of both crystals grown in space and on earth was examined.

Fractal Property of the Cytoskeleton in the Living Cells

The fractal property of the cytoskeleton in the living cells is investigated.Based on the experimental data of intracellular particle movement,the self-similarity of the cytoskeleton in the living cells is observed and the fractal dimensions of different parts of the cytoskeleton determined by means of line-segment method vary from 1.35 to 2.The Quasi-Brownian movements of intracellular particles are clearly shown.

A NEW METHOD FOR THE PERIODIC SOLUTION OF STRONGLY NONLINEAR SYSTEMS

A new method for the periodic solution of strongly nonlinear system is given. By using this method, the existance and stability of the periodic solution can be decided, and the approximate expression of the periodic solution can also be found.