ISSN 0253-2778

CN 34-1054/N

2011 Vol. 41, No. 10

Display Method:
Fabrication of an organic-inorganic hybrid composite bismuth film electrode for stripping analysis of trace Cd(Ⅱ) and Pb(Ⅱ)
LING Yu, YIN Lijun, LIU Gang, LI Ping, WU Shouguo
2011, 41(10): 847-854. doi: 10.3969/j.issn.0253-2778.2011.10.001
A novel electrochemical sensor (organic-inorganic hybrid composite bismuth film electrode) was fabricated on a glassy carbon substrate electrode by an electrochemical co-deposition of polyaniline and bismuth followed by plating a thin layer of bismuth on the hybrid film. The hybrid composite bismuth film electrode was applied to detect trace Cd(Ⅱ) and Pb(Ⅱ) in 01 mol/L acetate buffer solution (pH 4.7) by square ware anodic stripping voltammetry. The influencing factors of stripping signals and the operational parameters were investigated in detail. The newly developed electrode revealed highly linear behavior in the examined concentration range from 1 to 90 μg·L-1 for both test metal ions, with the detection limits of 02 μg·L-1 and 05 μg·L-1 for Cd(Ⅱ) and Pb(Ⅱ) respectively, offering good coefficients of variation (CVs) of 43% and 61% for Cd(Ⅱ) and Pb(Ⅱ) (50 μg·L-1, n=50) respectively. After 30 d, the stripping peak currents for 50 μg·L-1 Pb(Ⅱ) and Cd(Ⅱ) on the composite film were detected decreasing 32% and 49%, respectively. The long term stability makes it possible to be applied in on-site monitoring of heavy metals in environmental water.
Synthesis of decoupage-like carbon sheets and their adsorption properties
ZHENG Xiandong, ZHU Yongchun, JU Zhicheng, LI Qianwen, QIAN Yitai
2011, 41(10): 855-861. doi: 10.3969/j.issn.0253-2778.2011.10.002
Decoupage-like carbon sheets (DLCSs) were obtained on a large scale by pyrolysis of tetrachloroethylene and ferrocene in an autoclave at 600 ℃ for 10 h. The scanning electron microscopy (SEM) images show that the thickness and the width of DLCSs are about 20~40 nm, 100~200 nm, respectively. The nitrogen adsorption/desorption isotherm experiments reveal that the Brunauer-Emmett-Teller (BET) specific surface area of the product is 1 209 m2/g and the pore-size distribution is concentrated in the range of 058~12 nm. A series of comparative experimental results demonstrate that the most favorable temperature, amount of ferrocene and reaction time are 600 ℃, 0.093 g and 10 h for synthesis of DLCSs. By adjusting reaction parameters, hollow carbon spheres and carbon sheets can also be selectively prepared using one-pot reactions. A possible formation mechanism for the DLCSs was proposed based on the diffusion-limited aggregation(DLA) model. The adsorption behavior of DLCSs were evaluated by the removal of phenol and Rhodamine B (RB), which can remove about 82% of phenol and 48% of RB without any other additives. A possible reason for this phenomenon was also discussed.
Investigation of a new catalyst for dimerization of hexafluoropropylene
LU Dan, DONG Qibao, WANG Hu, WANG Pucheng, BAI Ruke
2011, 41(10): 862-866. doi: 10.3969/j.issn.0253-2778.2011.10.003
The dimerization of hexafluoropropylene was investigated using the coordination complex (copper(Ⅰ) bromide/2,2′-bipyridyl) as a catalyst and acetonitrile as solvent. The influences of the catalyst concentration, reaction temperature and time were also examined. The experimental results demonstrate that, at room temperature the catalyst can effectively catalyze the dimerization of hexafluoropropylene and one of the dimers ((E)-1,1,1,2,3,4,5,5,5-nonafluoro-4-(trifluoromethyl)pent-2-ene) is selectively produced when the concentration of the catalyst is low. Compared the other conventional catalysts such as alkali metal fluoride and alkali metal cyanide, this catalyst has more advantages, such as high activity, high selectivity and environmental friendliness. Moreover, the reaction can be performed at room temperature, which saves energy and brings down production cost.
Growth and characterization of Gd2O3 thin film on Si
LI Tingting, QI Zeming, CHENG Xuerui, ZHANG Wenhua, ZHANG Guobin, ZHOU Hongjun, PAN Guoqiang
2011, 41(10): 867-871. doi: 10.3969/j.issn.0253-2778.2011.10.004
Gd2O3 thin films were deposited on Si (100) substrates by pulsed laser deposition (PLD). The structure, composition and band offset were investigated by X-ray diffraction (XRD), X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). The results show that, the Gd2O3 thin film is amorphous when growing at 300 ℃ and is crystallized into monoclinic structure at 650 ℃. The formation of Gd-silicate interfacial layer due to interface reaction is confirmed by XRR and XPS. The valence band offset (ΔEV) of (-228±01)eV is obtained by XPS.
The phase transition of deformed mesophase of isotactic polypropylene by in situ synchrotron radiation WAXD studies
ZHAO Baijin, MA Zhe, HONG Zhenfei, LI Liangbin
2011, 41(10): 872-877. doi: 10.3969/j.issn.0253-2778.2011.10.005
The phase transition of quench-induced mesophase and deformed mesophase which was prepared by stretching the quench-induced mesophase during heating and isothermal annealing process was studied by in situ synchrotron radiation WAXD. The results show that though the temperature at which the phase transition of the two mesophase taken place is same, the temperature at which the phase transition has a slope increase is higher with deformed mesophase than quench-induced mesophase, and it indicates that the former one is much more stable. It is found that the regular conformation of 31 helices along stretching direction has a larger long-range order in deformed mesophase. That reason is used to explain why the deformed mesophase has a higher melt point.
Beam current calibration for Coulomb sum rule experiment in JLab Hall-A
YAN Xinhu, YE Yunxiu, LV Haijiang, ZHU Pengjia
2011, 41(10): 878-882. doi: 10.3969/j.issn.0253-2778.2011.10.006
To obtain the cross section of electron scattering on different cryogenic targets (2H, 4He, 2C, 56Fe, 208Pb) for the Coulomb sum rule (CSR) measurement in JLab Hall-A, the beam current monitor (BCM) was calibrated more reliable than before at different current settings (02, 05, 1, 2, 5, 10, 20, 40, 60 μA) to determine the beam charge precisely at different kinematic settings.
A low power digital filter solution based on CIC filter and FIR filter
KONG Yang, WU Jie, SONG Hongzhi, WAN Juan
2011, 41(10): 883-889. doi: 10.3969/j.issn.0253-2778.2011.10.007
A low power digital filter solution was proposed to solve data decimation and signal filtering problem in seismic signal acquisition equipment. The filter system is constructed with four front-end CIC filters, three front-end FIR filters and a back-end FIR filter to meet the requirements of acquisition equipment and geological analysis. The frequency and phase responses of each filter and the whole low power digital filter system are analyzed. The simulation proves that the proposed solution can work well in seismic signal acquisition equipment. The low power digital filter system is also compared to the current on-chip digital filter solution currently in use in the industry in total calculation quantity and front-end calculation quantity. The results show that the proposed solution can radically reduce both total calculation quantity and front-end calculation quantity.
Performance of MSAHP in water heating mode under three different work conditions
JIANG Aiguo, JI Jie, PEI Gang, LIU Keliang, HU Guangliang
2011, 41(10): 890-894. doi: 10.3969/j.issn.0253-2778.2011.10.008
The principle and different operating modes of a multifunctional solar assisted heat pump (MSAHP) were briefly introduced. The tests of the prototype of the MSAHP in water heating mode were conducted under three different work conditions, and the results were discussed. The coefficient of performance (COP) can reach 61, and the COP under the lowest ambient temperature ranges from 18 to 59. The results indicate that the MSAHP can obviously save energy in water heating mode.
Burning behavior of compartment pool fires with different ceiling vents
CHEN Bing, LU Shouxiang, LI Qiang, LI Changhai, YUAN Man
2011, 41(10): 895-901. doi: 10.3969/j.issn.0253-2778.2011.10.009
Heptane pool fires were conducted in a compartment with a ceiling vent, and the effect of the ceiling vent size on fire development was investigated, in which two pool fires of different diameters and six vents of varying sizes were used. The fuel mass loss rate, gas temperature distributions at different locations and the gas concentration at the base of the fire were measured during the experiments. Results show that the oxygen-lack regime and fuel-exhaust regime are defined due to the cause of the flame extinction. In the oxygen-lack regime, the vent size has a small influence on the fuel consumption rate, fuel mass loss rate and gas temperature, while it has an increasing impact on them in the fuel-exhaust regime. Moreover, the oxygen concentration at extinction time increases with the increase in vent size. Smoke descends quickly to the floor and the compartment is filled almost completely with smoke, rendering so the “two-zone” model invalid for the fires in compartment with a ceiling vent.
Preparation and properties of novel flame retardant low-density polyethylene composites
NIE Shibin, ZHANG Mingxu, HU Yuan, YUAN Shujie, CAI Feng
2011, 41(10): 902-906. doi: 10.3969/j.issn.0253-2778.2011.10.010
To improve the poor water resistant property of traditional intumescent flame retardant materials, a novel intumescent flame retardant low-density polyethylene (LDPE) composites were prepared based on a novel char forming agent (CFA) and microencapsulated ammonium polyphosphate (MCAPP). The synergistic effect between CFA and MCAPP on the flame retardant property, the thermal stability, and the water resistance property of flame retardant LDPE composites were investigated to ensure the best CFA/MAPP ratio. The results show that when the ratio of CFA/MAPP is 1∶3, the flame retardant LDPE composites show excellent flame retardant properties, thermal stability and water resistant property.
Research of security technology based on virtualization
LAI Yingxu, HU Shaolong, YANG Zhen
2011, 41(10): 907-914. doi: 10.3969/j.issn.0253-2778.2011.10.011
A universal architecture based on Xen was presented, which had traditional security tools transplanted on it and in the meantime guarantees their functions, such as memory and file system scanning, and active defense. Since most components of the security tools are transplanted out of a protected virtual machine, the architecture provides higher security than traditional ones. Whats more, it uses paravirtuliation I/O technology to minimize the cost of the virtual machines. Finally, this architecture allows current security technologies based on virtual machines to be integrated into itself conveniently, with no need for the operation system and application running on it to be modified.
A network self-protection mechanism based on multivariate abnormality analysis
XIE Lixia, DAI Qikui, YANG Hongyu
2011, 41(10): 915-923. doi: 10.3969/j.issn.0253-2778.2011.10.012
A network self-protection mechanism against network attacks was proposed based on the network self-protection theory and multivariate abnormality analysis. According to PDRR theory model, the main function modules of network self-protection system were designed. By applying multivariate abnormality analysis theory, a flow-based multivariate abnormality analysis network attack detection algorithm was proposed. The algorithm uses a metric of abnormal distance to classify network flow into different types and prioritize the routing of different network flow packets, thus reducing the impact of network attacks against the normal traffic flow. Experimental results demonstrate that the proposed mechanism can significantly protect the network against attacks.
Design and analysis of broadcasting multiple quantum digital signature scheme
YANG Yatao, XUE Ting, LI Zichen
2011, 41(10): 924-927. doi: 10.3969/j.issn.0253-2778.2011.10.013
A broadcast multiple quantum digital signature scheme was proposed, which encrypted messages to be signed by conducting CNOT operation, and used unitary transformation to realize information signature and validation. Analysis shows that, the scheme is not affected by the restrictions of the number of signers, capable of verifiability, high safety and simple technical implementation, and is thus a realizable broadcasting multiple quantum digital signature scheme.
Reliable multicast protocol based on reputation mechanism in wireless multi-hop networks
XU Li, JIANG Jiaming
2011, 41(10): 928-934. doi: 10.3969/j.issn.0253-2778.2011.10.014
To improve the reliability of the multicast tree and the efficiency of multicast, a multicast protocol based on reputation mechanism was proposed. The protocol took into account reputation value of the nodes in constructing the multicast tree, thus excluding the selfish nodes from it, making the multicast path comparably reliable. Simulation results show that proposed protocol can significantly improving the efficiency of multicast at a lower cost.
Data storage and recovery algorithm under spatial failures pattern in wireless sensor networks
XU Lu, ZHENG Shuli, FAN Yuqi, HU Donghui
2011, 41(10): 935-940. doi: 10.3969/j.issn.0253-2778.2011.10.015
In accordance with data storage and recovery at a spatial failure pattern, a storage and recovery algorithm based on data replication was proposed. The algorithm assigns a redundant node for every data node, and it can recover data successfully from the redundant node when the data nodes fail and thus minimise the total cost. Compared with the Greedy algorithm, theoretical analysis and simulation results show that this method can not only reduce the total energy cost but also prolong the lifetime of networks for successful recovery.