氟化锂团簇基纳米相薄膜的慢正电子研究

用慢正电子束流装置研究了氟化锂团簇沉积在单晶硅衬底上构成的纳米相薄膜,获得了正电子湮没S参数和有效扩散长度L_eff. 讨论了制备条件(如衬底温度、蒸发速率、惰性气体分压等)对薄膜微观结构的影响.     

Electrochemical behaviors of GMP based on solid-phase extractionon at Cu-Mg-Al hydrotalcite-like compound (HTLC) modified glass carbon electrode

Guanosine-5′-monophosphate (GMP) was investigated the electrochemical behaviors based on solid-phase extractionon (SPE) at Cu-Mg-Al hydrotalcite-like compound (HTLC) modified glass carbon electrode. Cu-Mg-Al hydrotalcite-like compound (HTLC) was proved as a new sorbent for SPE of GMP, which showed an irreversible adsorption oxidation process on the HTLC/GCE with the oxidation peak potential located at 1.15 V (vs. SCE) in a pH 5.0 acetate buffer solution. Influencing factors of the electrochemical behavior of GMP on the HLTC/GCE were optimized and kinetic parameters were calculated. Under the optimal conditions, with differential pulse voltammetry (DPV), a linear relationship was obtained between the oxidation peak current and the GMP concentration in the range from 1.0 × 10^− 6 to 8.0 × 10⁻⁴ mol L⁻¹ with the detection limit as 5.0 × 10⁻⁷ mol L⁻¹ (signal-to-noise ratio of 3). The modified electrode surface has very good reproducibility and stability.     

Influences of Pressure and Substrate Temperature on Epitaxial Growth of γ-Mg2SiO4 Thin Films on Si Substrates

An epitsucial γ-Mg2SiO4 thin film can be a good buffer between the Si substrate and some oxide thin films. For high temperature superconducting multilayer structures, hopefully it can be taken as an insulating layer to replace the widely used MgO film. To explore such possibilities, we carry out systematic studies on the influences of pressure and substrate temperature on the epitaxy of γ-Mg2SiO4 thin films grown on Si （100） substrates using rf magnetron sputtering with an Mg target of purity of 99.95 percent. With the substrate temperature kept at 500℃ and the pressure changing from lO Pa to 15 Pa, in the XRD spectra the 7-Mg2SiO4 （400） peak grows drastically while the MgO （200） peak is suppressed. Keeping the pressure at 15Pa and increasing the temperature from 500℃ to 570℃ further can improve the film epitaxy, while working at 780℃ and 11Pa seems to give very good results. X-ray photoelectronic spectroscopy and φ scan are used to characterize the stoichiometry, crystallinity, and in-plane growth of the samples.     

Stress test for a technology credit guarantee fund based on survival analysis

A technology credit guarantee policy has been established to provide financial support to technology-based SMEs with a limited asset base. For an effective technology credit guarantee policy, risk management is essential. In this paper, we investigate a survival model that predicts start-up SMEs’ loan default probability at a given time based on technology attributes along with the economic environment and the firm’s characteristics at the time of the technology credit guarantee fund application. This, in turn, is used for the estimation of the technology fund risk along with a stress test. Our work is expected to contribute to reducing the risks associated with technology financing.     

The influence of PPV chain aggregated structure on optical properties

A comparison has been made on the fluorescence of the poly (p-phenylenevinylene) (PPV) that without filtering the low molecular weight molecules (sample A) with the PPV of the low molecular weight molecules filtered (sample B). Although there is no obvious difference found in the FT-IR and Raman spectra between two samples, in the photoluminescence spectrum of the sample A, the peak at 510 nm is not appeared and the fluorescence intensity for the peak at 550 nm is increased. Under the high pressure condition the fluorescence peak at 520 nm, which corresponds to the peak at 510 nm of the usual PPV, is observed. Applying high pressure to the sample A or by filtering the low molecular weight molecules, the chain aggregated structure is modified, resulting in a change in the PPV chain distortion degree.     

空间光学遥感器主镜加工过程中疲劳寿命研究

针对空间光学遥感器主镜镜面加工过程中,磨盘与主镜间磨削动作往复运行引起的主镜柔性支撑结构疲劳寿命问题,通过建立主镜组件的有限元模型,利用MSC.Fatigue软件按应力-寿命(S-N)法对主镜组件进行了疲劳寿命分析,确定了支撑结构的薄弱部位,并对仿真过程进行了误差分析,讨论了影响仿真结果的各个因素.对比热真空试验和动力学试验前后主镜镜面面型数据,验证了支撑结构加工、设计参量的合理性.通过疲劳寿命仿真分析,可以有效预示光学结构在加工过程中的疲劳情况,为空间光学遥感器结构的设计、加工提供理论依据和参考.     

离子色谱法同时测定大气降水中的5种阴离子

以保留时间定性、峰面积外标法定量,建立了离子色谱同时测定大气降水中F–,Cl–,NO2–,NO3–,SO42–5种阴离子的分析方法。结果表明,5种阴离子标准曲线线性相关系数均大于0.999 8,检出限(3s/k)在0.000 3~0.006 6 mg/L之间。F–,Cl–,NO2–,NO3–,SO42–测定结果的相对标准偏差(n=10)分别为1.70%,2.46%,9.30%,0.73%,0.67%。用该方法对水样进行测定并进行加标回收试验,5种阴离子加标回收率在91.2%~102.7%之间。该方法灵敏度高,简便、快速,能满足大气降水中阴离子分析的要求。     

The Building Block [FeIII(pzphen)(CN)4]– and its Lanthanide Complexes: Synthesis,Crystal Structure,and Magnetic Properties

The cyanide building block [Fe^III(pzphen)(CN)₄]^– and its four lanthanide complexes [{Fe^III(pzphen)(CN)₄}₂Ln^III(H₂O)₅(DMF)₃] · (NO₃) · 2(H₂O) · (CH₃CN) [Ln = Nd ( 1 ), Sm ( 2 ), DMF = dimethyl formamide] and [{Fe^III(pzphen)(CN)₄}₂Ln^III(NO₃)(H₂O)₂(DMF)₂](CH₃CN) [Ln = Gd ( 3 ), Dy ( 4 )] were synthesized and structurally characterized by single‐crystal X‐ray diffraction. Compounds 1 and 2 are ionic salts with two [Fe^III(pzphen)(CN)₄]^– cations and one Ln^III ion, but compounds 3 and 4 are cyano‐bridged Fe^III‐Ln^III heterometallic 3d‐4f complexes exhibiting a trinuclear structure in the same conditions. Magnetic studies show that compound 3 is antiferromagnetic between the central Fe^III and Gd^III atoms. Furthermore, the trinuclear cyano‐bridged Fe^III₂Dy^III compound 4 displays no single‐molecular magnets (SMMs) behavior by the alternating current magnetic susceptibility measurements.     

Methane Decomposition into Carbon Fibers over Coprecipitated Nickel-Based Catalysts

Decomposition of methane in the presence of coprecipitated nickel-based catalysts to produce carbon fibers was investigated. The reaction was studied in the temperature range of 773 K to 1073 K. At 1023 K, the catalytic activities of three catalysts kept high at the initial period and then decreased with the reaction time. The lifetimes of Ni-Cu-Al and Ni-La-Al catalysts are longer than that of Ni-Al catalyst. With three catalysts, the yield of carbon fibers was very low at 773 K. The yield of carbon fibers for Ni-La-Al catalyst was more than those for Ni-Al and Ni-Cu-Al catalysts. For Ni-La-Al catalyst, the elevation of temperature from 873 K up to 1073 K led gradually to an increase in the yield of carbon fibers. XRD studies on the Ni-La-Al catalyst indicate that La2NiO4 was formed. The formation of La2NiO4 is responsible for the increase in the catalytic lifetime and the yield of carbon fibers synthesized on Ni-La-Al at 773 1073 K. Carbon fibers synthesized on Ni-Al catalyst are thin, long carbon nanotubes. There are bamboo-shaped carbon fibers synthesized on Ni-Cu-Al catalyst. Carbon fibers synthesized on Ni-La-Al catalyst have large hollow core, thin wall and good graphitization.     

Synthesis and Antifungal Activity of Novel 1,2,4‐Triazole Derivatives Containing 1,2,3‐Thiadiazole Moiety

Starting from carbonic acid diethyl ester, a series of 1,2,4‐triazole derivatives containing 1,2,3‐thiadiazole were synthesized. Reactions were performed by microwave irradiation or ultrasonic irradiation as well as by conventional heating. The structure of title compounds was characterized by ¹H‐NMR, MS, and elemental analyses. The fungicidal activities of these compounds were tested in vivo. Most of title compounds exhibited good antifungal activity against Pseudoperonospora cubensis. Some of title compounds displayed moderate antifungal activities against Fusarium oxysporum, Pseudoperonospora cubensis, Sphaerotheca fuligenea, Corynespora cassiicola, and Xanthomonas axonopodis.