Effect of homogenization time on quench sensitivity of 7085 aluminum alloy

The effect of homogenization time on quench sensitivity of a cast 7085 aluminum alloy was investigated by means of end-quenching test, optical microscope （OM）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that with the increase of homogenization time from 48 h to 384 h, quench sensitivity increased slightly as the largest difference in the hardness was increased from 5.2% to 6.9% in the end-quenched and aged specimens. Prolonging homogenization had little effect on the grain structure, but improved the dissolution of soluble T phase and resulted in larger Al3Zr dispersoids with a low number density. Some small quench-induced η phase particles on Al3Zr dispersoids were observed inside grains during slow quenching, which decreased hardness after subsequent aging. The change in the character of Al3Zr dispersoids exerted slight influence on quench sensitivity.

Grain structure effect on quench sensitivity of Al-Zn-Mg-Cu-Cr alloy

The effect of grain structure on quench sensitivity of an Al-Zn-Mg-Cu-Cr alloy was investigated by hardness testing, optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and scanning transmission electron microscopy. The results show that with the decrease of quenching rate from 960 ℃/s to 2 ℃/s, the hardness after aging is decreased by about 33% for the homogenized and solution heat treated alloy（H-alloy） with large equiaxed grains and about 43% for the extruded and solution heat treated alloy（E-alloy） with elongated grains and subgrains. Cr-containing dispersoids make contribution to about 33% decrement in hardness of the H-alloy due to slow quenching; while in the E-alloy, the amount of（sub） grain boundaries is increased by about one order of magnitude, which leads to a further 10% decrement in hardness due to slow quenching and therefore higher quench sensitivity.

Effect of Surface-Covered Annealing on the Optical Properties of ZnO Films Grown by MOCVD

ZnO films grown by metal organic chemical vapor deposition at atmospheric pressure are annealed at 850℃ ,with the film surfaces exposed to air or covered by a sapphire wafer. The optical properties of the as-grown and the annealed samples are studied by photoluminescence （PL） spectroscopy. It is found that the air-exposure annealing effectively removes the hydrogen impurities from the ZnO films but greatly increases the deep-level emission. In the surface-covered annealed sample, an elimination of the hydrogen impurities is also observed, and the deep-level emission disappears completely. The free exciton emission is significantly enhanced in the ZnO film after surface-covered annealing.

Effects of Interdiffusion on Luminescence of InAs/GaAs Quantum Dots Covered by InGaAs Overgrowth Layer

WT8.BZ]The effects of postgrowth rapid thermal annealing have been studied on the optical properties of 3-nm-height InAs/GaAs quantum dots covered by 3-nm-thick In xGa 1-x As (x=0,0 1 and 0 2) overgrowth layer.At a higher annealing temperature (T≥750℃),the photoluminescence peak of InGaAs layer has been observed at the lower-energy side of InAs quantum-dot peak.In addition,a similar blueshift in photoluminescence (PL) emission energy is observed for all samples when the annealing temperature increases from 650 to 850℃.However,the trend of photoluminescence linewidth towards narrowing is totally different for InAs quantum dots with different In mole fraction in InGaAs overgrowth layer.The results suggest that the intermixing in the lateral direction plays an important role in obtaining a better understanding of the modification of optical properties induced by the rapid thermal annealing.

Supercritical Water as a Reaction Medium for Nitrogen-Containing Heterocycles

Supercritical water has been focused on as an environmentally attractive reaction media, in which organic materials can be decomposed into smaller molecules. The reaction behavior of pyrrole as a simple model compound of nonbasic nitrogen compounds found in petroleum residua was studied in supercritical water with a batch type reactor. The reaction was carried out at temperatures of 698-748 K and at various pressures under an argon atmosphere. The chemical species in the aqueous products were identified by GCMS （gas chromatography mass spectrometry） and quantified using GC-FID （gas chromatography flame ionization detector）. The effect of temperature and reaction time on the conversion process of pyrrole is presented. Under supercritical water conditions, pyrrole underwent successful decomposition in water into its derived compounds. The conversion of pyrrole could approach 81.12 wt% at 723 K and 40 MPa within 240 min of reaction time. The decomposition process was accelerated with the existence of water at the same temperature. Ultimate analysis of solid products was also conducted using a CHN analyzer. The process investigated in this study may form the basis for an efficient method of nitrogen compound decomposition in future.

Immunogenicity and protective efficacy of Vibrio harveyi pcFlaA DNA vaccine in Epinephelus awoara

The FlaA gene from Vibrio harveyi marker, was cloned into the eukaryotic expression with a short nucleotide sequence encoding the Flag vector pcDNA3.1（＋） （designated as pcFlaA）. Ninety grouper （Epinephelus awoara） were separated into three equal size groups. An experimental group was immunized with pcFlaA, Control I group was immunized with the vector pcDNA3.1（＋）, and Control 1I group was immunized with PBS. The expression of pcFlaA mRNA and protein was examined using reverse transcription-polymerase chain reaction （RT-PCR） and immunohistochemistry. We also evaluated the immunogenicity and protective efficacy of pcFlaA against V. harveyi by measuring the lymphocyte proliferation response and serum levels of specific antibody and conducting a bacterial challenge test. We successfully transfected the fish muscle with pcFlaA. The pcFlaA mRNA and protein was expressed in the muscle cells for up to one month following injection. The proliferation response of lymphocytes in fish immunized with pcFlaA was significantly higher than in control group II. Furthermore, the immunized fish generated specific antibody. The vaccination also resulted in significantly higher survival during the bacterial challenge test.

一个男人和他的妻子

一个男人和他的妻子［新西兰］弗兰克·萨吉森赵友斌译经济萧条，市面冷清，生活非常艰难。困难时期和繁荣时期有所不同，人们的习惯也变了。在这个期间，你尽可不必去自找麻烦。譬如，穿戴是否整洁得体就不必去计较啦。在街上你不会碰到多少人象你这么讲究。经济萧条曾给...

老父与牌友

老父买了一箱啤酒,中了一个小奖,一高兴,脚脖子扭了,老母讪笑他:“八合升箩七合命。” 老父拄了拐棍,晃晃悠悠朝三角花园走去,那里有他的牌友,远看三五成群在议论什么。 “老徐呢！”他目数着这些常客。 “上路了！” “哪儿去?” “火葬场,今天下午大殓！” 火性子的老徐,牌品差,一发急脸通红,一下子得了脑溢血,牌友们把他送至医院。

Selective and localized laser annealing effect for high- performance flexible multilayer MoS2 thin-film transistors

We report the use of ultra-short, pulsed-laser annealed Ti/Au contacts to enhance the performance of multilayer MoS2 field effect transistors （FETs） on flexible plastic substrates without thermal damage. An analysis of the temperature distribution, based on finite difference methods, enabled understanding of the compatibility of our picosecond laser annealing for flexible poly（ethylene naphthalate） （PEN） substrates with low thermal budget （〈 200 ℃）. The reduced contact resistance after laser annealing provided a significant improvement in transistor performance including higher peak field-effect mobility （from 24.84 to 44.84 cm2-V-l.s-1）, increased output resistance （0.42 MΩ at Vgs- Vth = 20 V, a three-fold increase）, a six-fold increase in the self-gain, and decreased sub- threshold swing. Transmission electron microscopy analysis and current-voltage measurements suggested that the reduced contact resistance resulted from the decrease of Schottky barrier width at the MoS2-metal junction. These results demonstrate that selective contact laser annealing is an attractive technology for fabricating low-resistivity metal-semiconductor junctions, providing important implications for the application of high-performance two-dimensional semicon- ductor FETs in flexible electronics.

Combustion characteristics of nanofluid fuels in a half-opening slot tube

Combustion characteristics of nanofluid fuels containing aluminum nanoparticles were investigated in half-opening slot tubes from the fundamental view. The effects of particle loading rates(0.25% and 2.5% by weight), type of base fuels(ethanol and butanol),and fuel flow rates(0.2, 0.6, and 1 mL/min) were studied in details. The combustion characteristics of the nanofluid fuels and pure based fuels were also examined to provide a comparison. Flame was unstable with reignition, stable state, nearly extinguishment repeatedly at low flow rate. At medium flow rate, flame height was increased and flame tended to be stable. At high flow rate,flame became unstable and was disturbed by the droplet forming and dripping significantly. Al atoms inside the oxide layer should be melted before the particles combustion, while Al oxide layer should be melted before the particles aggregates combustion. The effects of particles on the combustion characteristics, especially on the evaporation rate of base fuel, were discussed. The reasons for various combustion phenomena of nanofluid fuels were given, which can provide the useful guidance for the experimental research and practical applications of nanofluid fuels.

Effect of Swirl Cup's Secondary Swirler on Flow Field and Ignition Performance

In a gas turbine engine combustor, highly swiding combustion is usually adopted to stabilize flame and reduce pollutant emissions. Swirl cup, as an air blast atomizer, is widely used to provide a uniform presentation of fuel droplets to the combustor dome. This paper investigated the effect of secondary swirler on the flow field down- stream of the swirl cup using particle image velocimetry （PIV）. Three swirl cups＇ non-reacting flow field were studied： case A, B and C with secondary swirler vane angle 53°, 60° and 68° respectively. Detailed mean and transient velocities and vorticity in the center plane were obtained. From the PIV results, a sharp contrast flow field was obtained for case A to other two cases due to the lower secondary swirling intensity. The recirculation zone is collapsed in disorder for the case A. Ignition tests of the three cups were completed in a single cup com- bustor. In general, the ignition performance increases with the increasing of the secondary swirling intensity. For case A, the ignition performance is very unstable and has much randomness and there is no clear lean ignition boundary can be generated. This work can further understand the swirl behavior and ignition mechanism.

Effect of annealing treatment on the performance of organic photovoltaic devices using SPFGraphene as electron-accepter material

We have researched the performances of organic photovoltaic devices with the bulk heterojunction （BHJ） structure using the organic solution-processable functionalized graphene （SPFGraphene） material as the electron-accepter material and P3OT as the donor material. The structural configuration of the device is ITO/PEDOT：PSS/P3OT：PCBM-SPFGraphene/LiF/A1. Given the P3OT/PCBM （1：1） mixture with 8wt% of SPFGraphene, the open-circuit voltage （Voc） of the device reaches 0.64 V, a short-circuit current density （J^c） reaches 5.7 mA/cm2, a fill factor （FF） reaches 0.42, and the power conversion efficiency （7？） reaches 1.53% at illumination at 100 mW/cm2 AM1.5. We further studied the reason for the device performances improvement In the P3OT：PCBM-SPFGraphene composite, the SPFGraphene material acts as exciton dissociation sites and provides the transport pathways of the lowest unoccupied molecular orbital （LUMO）-SPFGraphene-A1. Furthermore, adding SPFGraphene to P3OT results in appropriate energetic distance between the highest occupied molecular orbital （HOMO） and LUMO of the donoffacceptor and provides higher exciton dissociation volume mobility of carrier transport. We have researched the effect of annealing treatment for the devices and found that the devices with annealing treatment at 180℃ show better performances compared with devices without annealed treatment. The devices with annealed treatment show the best performance, with an enhancement of the power conversion efficiency from 1.53% to 1.75%.