内氧化制备A1_2O_3/Cu复合材料载流条件下表面磨损形貌和摩擦学性能研究(英文)

Two Al2O3/Cu composites containing 0.24 wt.% Al2O3 and 0.60 wt.% Al2O3 separately are prepared by internal oxidation. Effects of sliding speed and pressure on the frictional characteristics of the composites and copper against brass are investigated and compared. The changes in morphology of the sliding surface and subsurface are examined with scanning electron microscope （SEM） and energy dispersive X-ray spectrum （EDS）. The results show that the wear resistance of the Al2O3/Cu composites is superior to that of copper under the same conditions, Under a given electrical current, the wear rate of Al2O3/Cu composites decreases as the Al2O3-content increases, However, the wear rates of the Al2O3/Cu composites and copper increase as the sliding speed and pressure increase under dry sliding condition. The main wear mechanisms for Al2O3/Cu composites are of abrasion and adhesion; for copper, it is adhesion, although wear by oxidation and electrical erosion can also be observed as the speed and pressure rise.

Design,synthesis and characterization of novel biodegradable macrodiols based on poly(DL-lactic acid) and poly(p-dioxanone)

Integrating poly（lactic acid） （PLA）, glycolic acid （GA） and ethylene glycol （EG） will hopefully result in a novel copolymer that combines such advantages as fastened and controllable release rate and improved flexibility together with good biocompatibility. In this study, p-dioxanone （PDO） was employed to copolymerize with DL-lactide （LA） via ring-opening melt polymerization using Sn（Oct）2 as an initiator and ethylene glycol as a co-initiator. The obtained degradable macrodiols （HO-P（LA-co-PDO）-OH） were just such a copolymer consisting of PLA, GA and EG. 1HNMR was employed to characterize the copolymers, and the effect of PDO/LA molar ratios in the feedstock on the molecular weights of HO-P（LA-co-PDO）-OH was investigated by means of endhydroxyl analysis, 1H NMR or GPC-MALLs. The results confirmed the successful synthesis of HO-P（LA-co-PDO）-OH and revealed that one end-hydroxyl of the micarodiols was donated by LA or PDO and the other one by the co-initiator EG. In addition, the molecular weights of HO-P（LA-co-PDO）-OH increased with decreasing PDO/LA ratios.

Selective Permeation of CO_2 Through Modified PVSA/PS Composite Membrane

A new fixed carder membrane material VSA-SA for CO2 separation was prepared through the chemical modification of PVSA. The selective permeation of CO2 through VSA-SA/PS composite membrane was performed with CO2/CH4 system. The VSA-SA/PS composite membranes possess better CO2 permselectivity than PVSA/PS composite membrane. Keywords： Fixed carder membrane, CO2 separation, PVSA, VSA-SA.

Low-resistance Ohmic contact on polarization-doped AlGaN/GaN heterojunction

High electronic density is achieved by polarization doping without an impurity dopant in graded AIGaN films. Low specific contact resistance is studied on the polarization-doped A1GaN/GaN heterojunctions by using the transmission line method （TLM）. The sheet density of polarization-doped A1GaN/GaN heterojunction is 6 × 10 14 cm-2 at room temperature. The linearly graded material structure is demonstrated by X-ray diffraction. The cartier concentration and mobility are characterized by a temperature-dependent Hall measurement. Multiple-layer metal （Ti/A1/Ti/Au） is deposited and annealed at 650 ℃ to realize the Ohmic contacts on the graded A1GaN/GaN heterojunctions.

Model of hot-carrier induced degradation in ultra-deep sub-micrometer nMOSFET

The degradation produced by hot carrier （HC） in ultra-deep sub-micron n-channel metal oxide semiconductor field effect transistor （nMOSFET） has been analyzed in this paper. The generation of negatively charged interface states is the predominant mechanism for the ultra-deep sub-micron nMOSFET. According to our lifetime model of p-channel MOFET （pMOFET） that was reported in a previous publication, a lifetime prediction model for nMOSFET is presented and the parameters in the model are extracted. For the first time, the lifetime models of nMOFET and pMOSFET are unified. In addition, the model can precisely predict the lifetime of the ultra-deep sub-micron nMOSFET and pMOSFET.

The preparation of functionalized single walled carbon nanotubes as high efficiency DNA carriers

The positively charged single walled carbon nanotubes （SWNTs^＋） were prepared by conjugating with -CONH-C6H12-NH3^＋. The double strand DNA （dsDNA） chains were loaded onto SWNTs^＋ via the electrostatic interactions. SWNTs^＋ shows improved loading efficiency （353.5 μg/mg） toward dsDNA compared with that of charged free single walled carbon nanotubes （SWNTs） （82.9 μg/mg）.

Degraded Characteristics of Absorption Solution of Lampblack Waste Gas by Biological Contact Oxidation Process

We got the sludge from secondary sedimentation tank of wastewater treatment plant. After cultivation by simulating aerobic biological reactor for 30 days,the biofilm system that could degrade the oleaginous materials of absorption solution spraying lampblack waste gas was successfully obtained. From different influent concentration and temperature experiments,it was shown that the degradation efficiency of the oleaginous materials was the most,when the influent concentration and the temperature of the biological contact oxidation reactor were 300 mg/L and35 ℃,especially the effluent concentration and the degradation efficiency of the oleaginous materials was 51 mg/L and 83%. The modified Michaelis-Menten equation was used to analyze the data,and the kinetics parameters were obtained： K_m=（ 164. 867 ± 0. 001） mg/L; vmax=（ 0. 595 ±0. 001） mg/（ L·min）.

Mature versus emerging technologies for CO2 capture in power plants： Key open issues in post-combustion amine scrubbing and in chemical looping combustion

Carbon capture and storage （CCS） have acquired an increasing importance in the debate on global wanning as a mean to decrease the environmental impact of energy conversion technologies, by capturing the CO2 produced from the use of fossil fuels in electricity generation and industrial processes. In this respect, post-combustion systems have received great attention as a possible near-term CO2 capture technology that can be retrofitted to existing power plants. This capture technology is, however, energy-intensive and results in large equipment sizes because of the large volumes of the flue gas to be treated. To cope with the demerits of other CCS technologies, the chemical looping combustion （CLC） process has been recently considered as a solution for CO2 separation. It is typically referred to as a technology without energy penalty. Indeed, in CLC the fuel and the combustion air are never mixed and the gases from the oxidation of the fuel （i.e., CO2 and H2O） leave the system as a separate stream and can be separated by condensation of H2O without any loss of energy. The key issue for the CLC process is to find a suitable oxygen carrier, which provides the fuel with the activated oxygen needed for combustion. The aim of this work is to explore the feasibility of using perovskites as oxygen carriers in CLC and to consider the possible advantages with respect to the scrubbing process with amines, a mature post-combustion technology for CO2 separation.

Interference-Cancellation-Based Carrier Frequency Offset Estimation for OFDMA Uplink Transmissions

A carrier frequency offset （CFO） estimator was developed based on an interference cancellation scheme for an orthogonal frequency division multiplex access uplink. An initial CFO estimate was first ob- tained based on the received training signals at each user＇s prescribed subcarder positions. Then, the re- ceived training signals were compensated by using the initial CFO estimates in the frequency domain and the multi-user interferences were estimated. Finally, the interference-cancelled training signals were used to reliably estimate each user＇s CFO. The CFO estimator performance was evaluated by the bit error rate per- formances of the CFO compensation-based receivers at the base station. Simulations show that with this optima CFO compensation receiver, the performance gain with the esti- mated CFO values is approximately 3 dB better at the 0.1% bit error rate than the initial CFO estimates.