看世间万象,显生命魅力

【作文欢乐行】写一写你自己了解到的生命现象,也可以是你自己了解到的或身边发生的热爱生命的故事。【写作斑马线】选择自己感受最深的写下来,要写出自己从中获得的感受和启发。(比如,这种现象或这件事,让你对生命有了怎样的认识和感悟。)

Life prediction for vacuum fluorescent display using maximum likelihood estimation

In order to obtain the life information of the vacuum fluorescent display （VFD） in a short time, a model of constant stress accelerated life tests （CSALT） is established with its filament temperature increased, and four constant stress tests are conducted. The Weibull function is applied to describe the life distribution of the VFD, and the maximum likelihood estimation （MLE） and its iterative flow chart are used to calculate the shape parameters and the scale parameters. Furthermore, the accelerated life equation is determined by the least square method, the Kolmogorov-Smirnov test is performed to verify whether the VFD life meets the Weibull distribution or not, and selfdeveloped software is employed to predict the average life and the reliable life. Statistical data analysis results demonstrate that the test plans are feasible and versatile, that the VFD life follows the Weibull distribution, and that the VFD accelerated model satisfies the linear Arrhenius equation. The proposed method and the estimated life information of the VFD can provide some significant guideline to its manufacturers and customers.

台州市人民政府办公室关于印发《政府工作报告》2010年工作目标任务责任分解的通知

台政办发[2010]4号各县(市、区)人民政府,市政府直属各单位:《政府工作报告》2010年工作目标任务责任分解,已经市政府研究同意,现印发给你们,请认真抓好落实,确保按时完成。

Constant-step stress accelerated life test of VFD under Weibull distribution case

Constant-step stress accelerated life test of Vacuum Fluorescent Display (VFD) was conducted with increased cathode temperature. Statistical analysis was done by applying Weibull distribution for describing the life, and Least Square Method (LSM)for estimating Weibull parameters. Self-designed special software was used to predict the VFD life. Numerical results showed that the average life of VFD is over 30000 h, that the VFD life follows Weibull distribution, and that the life-stress relationship satisfies linear Arrhenius equation completely. Accurate calculation of the key parameter enabled rapid estimation of VFD life.

Preparation of Ti/PTFE-F-PbO2 Electrode with a Long Life from the Sulfamic Acid Bath and Its Application in Organic Degradation

A polytetrafluoroethylene （PTFE）-doped PbO2 electrode on a Ti substrate was prepared by galvanostatic method from the sulfamic acid bath （Ti/PTFE-F-PbO2-I） or nitric acid bath （Ti/PTFE-F-PbO2-II）. Scanning Electron Microscopy revealed that the Ti/PTFE-PbO2-I electrode had a more regular morphology with smaller size crystals than the Ti/PTFE-F-PbO2-II electrode. On the basis of the results of both the accelerated electrolysis test and the empirical formula for estimating the service life of an electrode, the service life of the Ti/PTFE-PbO2-I electrode was predicted to be more than 7 years under conventional electrolysis conditions （0.1 A·cm^-2）. During the treatment of 4-chlorophenol-contaminated water, the Ti/PTFE-PbO2-I anode showed both a good electro-catalytic activity and high electrochemical stability, exhibiting an excellent potential application.

High cyclic fatigue performance of Al-Cu-Mg-Ag alloy under T6 and T840 conditions

High cyclic fatigue(HCF)behavior of an AA2139alloy belonging to Al-Cu-Mg-Ag system in T6and T840conditionswas examined.The T840treatment involving cold rolling with a40%reduction prior to peak ageing provides an increase in tensilestrength compared with the T6condition.However,fatigue lifetime for two material conditions was nearly the same since there isweak effect of thermomechanical processing on micro-mechanisms of crack initiation and growth.

Structural evolution of Pt‐based oxygen reduction reaction electrocatalysts

The commercialization of proton exchange membrane fuel cells(PEMFCs)could provide a cleaner energy society in the near future.However,the sluggish reaction kinetics and harsh conditions of the oxygen reduction reaction affect the durability and cost of PEMFCs.Most previous reports on Pt-based electrocatalyst designs have focused more on improving their activity;however,with the commercialization of PEMFCs,durability has received increasing attention.In-depth insight into the structural evolution of Pt-based electrocatalysts throughout their lifecycle can contribute to further optimization of their activity and durability.The development of in situ electron microscopy and other in situ techniques has promoted the elucidation of the evolution mechanism.This mini review highlights recent advances in the structural evolution of Pt-based electrocatalysts.The mechanisms are adequately discussed,and some methods to inhibit or exploit the structural evolution of the catalysts are also briefly reviewed.

Early development of Grateloupia turuturu (Halymeniaceae, Rhodophyta)

Grateloupia turuturu is a commercial red alga with potential value in nutraceuticals and pharmaceuticals. To supplement information on its life history and verify whether carpospores can be used for seedling culture, early development of G. turuturu was investigated under culture conditions （27~C, 10-13 ~mol/（mZ.s） in irradiance, photoperiod 10：14 h L：D）. Three physiological stages were recognized by continuous microscopic observation： division stage, discoid crust stage, and juvenile seedling stage. At the beginning of the division stage, the carpospores developed germ tubes into which the carpospore protoplasm was evacuated, and then the carpospore protoplasm in the germ tubes began to divide continuously until discoid crusts formed. Finally, upright thalli appeared on the discoid crusts and developed into juvenile seedlings. It took about 60 days for carpospores to develop into juvenile seedlings. The growth parameters, including germination rate for carpospores and discoid crust diameter, were recorded. These results contribute more information on the life cycle, and at the same time are of great significance in the scaling-up of artificial seedling cultures of G. turuturu.

Micro porosity and its effect on fatigue performance of 7050 aluminum thick plates

Micro porosity in aluminum alloys may contribute to fatigue life degradation, which can largely limit the application of alloys. Therefore, the fatigue life of a commercial 7050-T7451 thick plate and an experimental plate with different porosities was compared in this study. The X-ray computed tomography(XCT) was utilized to characterize the size, number density and spatial distribution of porosity inside various samples, and the fracture surface of fatigued specimens was compared by using scanning electron microscope(SEM). The results showed that the fatigue cracks prefer to initiate from constituent particles in the commercial alloy. Whereas the micro porosity is the predominant site for crack nucleation and subsequent failure in the experimental one. The presence of micro porosity in experimental7050-T7451 thick plate may reduce the fatigue life by an order of magnitude or more compared with the defect-free alloy. The pores close to sample surface are the main fatigue crack initiation site, among which larger and deeper pore leads to a shorter fatigue life. The crack initiation is also affected by the pore geometry and direction. Besides, the overall porosity inside the bulk can affect the crack propagation during fatigue tests.

Analysis of Fatigue Fracture with Scanning Electron Microscopy of Valve Spring Steel

Valve spring steel for engines, belonging to the class of super clean steel, must be supported due to their application, high numbers of cycles in fatigue and cannot suffer any type of failure, which would be catastrophic for the vehicle. From these considerations, it was tested in axial fatigue, a test that can detect possible internal defects in their structure, caused by inclusions, a class of valve spring steel, where it aimed to discover the values of their fatigue life, followed by an analysis ofmicrostructural fracture surface by SEM （scanning electron microscopy）. It was proved, after testing, the specimens tested broke up a number of cycles always compatible with the life work of a valve spring and that fractures always occurred by surface defects in the specimens.

Debt Rating Initiations： Natural Evolution or Opportunistic Behavior？

The authors examine a firm＇s decision to begin issuing debt in public bond markets and find that it is a function of both life cycle influences and opportunistic timing. Defining life cycle factors to encompass both a firm＇s age in years and its underlying characteristics, the authors confirm that bond market participation is generally restricted to large, mature firms. Summary statistics show that finns obtain their initial bond ratings on average 9.5 years after their equity initial public offering （IPO） and 11.8 years after initiating dividend payments. Growth rates, capital expenditures, and cash flow volatility all decline as the firm accesses public debt markets, consistent with entry into the mature phase of its life cycle. With respect to opportunistic timing, it is asked whether entry into public bond markets follows strong performance （or precedes weak performance） at both the firm and market levels. At the firm level, the authors find that the debt IPO occurs following periods of strong operating performance and high excess stock returns. At the market level, entry coincides with favorable interest rates and default spreads. The benefits of careful timing result in firms receiving initial bond ratings that are stronger than what would be predicted; however, there is no evidence of abnormal numbers of downgrades for these firms in subsequent years.

Establishment of wear model and life prediction of drum of hot rolling coiler

For the drum of hot rolling coiler is prone to be easily destroyed, the type of MMU-5G abrasion tester was applied to revealing the friction and wear behavior. The morphology observation by scanning electron microscope (SEM) demonstrates the wear mechanism of the drum, and the test data of the influence coefficient of the normal pressure, relative sliding speed and surface lubrication conditions acted on the linear rate of the wear could be obtained by the regression method. A calculation model, which considers the factors of the structure of the drum, coiling tension and coiling strip specifications, was established by the combination method to predict the wear life of the drum. Then the practical production data was applied into this model and the analysis result was in good accordance with that of actual production.

Effect of Cu on the boron segregation at grain boundaries and vacancy-type defects in ultra-low carbon micro-alloy steels

By thermal neutron irradiation particle tracking autoradiography(PTA)technique,the development of boron segregation at grain boundaries in ultra-low carbon micro-alloy steels was investigated during cooling from 1150°C to 850°C,and the effect of Cu on boron segregation at grain boundaries was discussed.By positron annihilation lifetime(PAL)technique,the changes of vacancy-type defects with temperatures and the effect of Cu on vacancy-type defects in the cooling process were discussed.Results show that,the concentration of boron at grain boundaries increases rapidly at the beginning of the cooling;after that,it begins to decrease;and then,it increases gradually again.The addition of Cu not only increases the concentration of boron at grain boundaries but also speeds up the development process of boron segregation at grain boundaries.During the continuous cooling process,the addition of Cu significantly affects the change of vacancy-type defects with temperatures in ultra-low carbon micro-alloy steels.