Search

International audience

As one of the most economically developed and seismically active regions of China, Fujian faces a threat from severe earthquakes, particularly those that occur in Taiwan. Following the worldwide construction of an earthquake early warning (EEW) system, we developed an EEW system in Fujian in 2009 and began online testing in November 2012. During this testing, our EEW system successfully processed several earthquakes in both the Fujian region and Taiwan. The results showed that, for inland events (Fujian region), the first alarm was generated 6.4±0.97 s after the first station was triggered, with a location error of 4.6±4.0 km and magnitude estimation error of 0.6±0.5. For offshore events (Taiwan), the first alarm was generated 13.7±2.9 s after the first station was triggered, with a location error of 30.6±31.4 km and magnitude estimation error of −0.2±0.4. Online testing allows us to continuously improve and perfect our system. In 2017, our system will officially begin providing EEW information to the public in the Fujian region. In addition to the preceding, the architecture, key algorithms, software design, and online testing results are included in this article to provide readers with a comprehensive understanding of our EEW system.

The biosynthetic pathway of diisonitrile chalkophore SF2768 was identified in Streptomyces thioluteus through heterologous expression recently. Isolation and structure elucidation of the N-substituted formamides that coexisted with the diisonitriles implied that a hydration event was involved. In vitro enzymatic assays of an endogenous isonitrile hydratase suggested a rare sequential-hydration of the diisonitriles. Additionally, the results of Cu-CAS assays indicate that both partial and complete hydration led to the loss of the copper-chelating ability of SF2768.

International audience; Thermally Stimulated Current (TSC) measurement, well known technique for trap level detection, was applied to derive the density of occupied states in organic solar cells. The device structure is Glass/ITO/P3HT:PCBM/Al. Analysis of the TSC spectra allows to determine the Fermi level position from the edge of the nearest band (LUMO or HOMO) (~ 0.42 eV). At that time, TSC peaks cannot be evaluated due to multiple traps that contribute to the current signal. In order to achieve a rough picture of the trap structure, Fractional TSC (FTSC) method was applied. The procedure is based on multiple temperature cycles which evaluate activation energies for different ranges of temperatures. The results reveal several plateaus, pointing out the presence of four trap levels (0.12 eV, 0.16 eV, 0.20 eV and 0.35 eV). Additionally, a curve-fitting procedure is done in order to characterize the trap parameters and achieved with five trap levels (0.059 eV, 0.12 eV, 0.14 eV, 0.20 eV and 0.35 eV) in Gaussian or exponential distribution. Four of them are in complete agreement with measured FTSC ones. Those results are very well correlated with our other characterizations by Admittance Spectroscopy (AS). The results presented here show that, in spite of the chemical differences between inorganic materials and conjugated polymers, FTCS technique can still be applied to determine the density of occupied states in these materials, as long as care is taken. Polymers are low-mobility materials with large concentrations of deep impurities.

The electronic structural, magnetic and optical properties of pure and V-doped ZnO are investigated by first-principles calculations based on the density functional theory. With the introduction of V atoms, the spin-splitting near the Fermi level leads to a net magnetic moment of the system. A significant possibility of room temperature ferromagnetism (RTFM) originated from the Ruderman–Kittel–Kassuya–Yosida (RKKY) exchange is predicted. Oxygen vacancy is positive to enhance the ferromagnetism while zinc vacancy is negative. With respect to the optical properties, the presence of V atoms was found to have an obvious influence on the transmittivity, especially in the low energy region. A slight V-doping can keep a high optical transmission and smoothly modulate the optical bandgap.

We investigated quantitatively the electronic transport properties of a bulk heterojunction polymer/fullerene solar cell, based on structure Glass/ITO/P3HT:PCBM/Al. The current-voltage I-V characteristics in the intermediate positive bias and temperature regime (0.2 V ≤ V ≤ 1.5 V, 180 K ≤ T ≤ 250 K) can be well fitted by a modified Poole-Frenkel PF detrapping model. Combining these results with the high frequency capacitance measurements, we could then derive independently the absorber thickness and its dielectric constant. At low temperature (80 K ≤ T ≤ 170 K), the I-V data can be well accounted for with Space Charge Limited Current (SCLC) regimes. At intermediate positive bias (1 V ≤ V ≤ 2.3 V), the current is dominated by the trapped space charges with an exponential traps distribution, while at high positive bias (2.5 V ≤ V ≤ 4 V), the space charges due to injected free carrier play an important role for the conduction. From the fits to the two different SCLC models, we could then extract the electrically active defects parameters controlling the transport. These parameters were confirmed by space charge capacitance spectroscopy (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Enhanced oil recovery (EOR) by means of polymer flooding is an important technology for the strategic development of offshore oilfields in China. Hydrophobically associating polyacrylamide (HAPAM) has been recently proposed as a new flooding agent. The solubility of HAPAM is low, which is the bottleneck for further improving the oil recovery through polymer flooding in offshore oilfield. Stirred tanks have been used on offshore platforms to enhance HAPAM dissolving. But there is little literature on the study of HAPAM dissolving characteristics in stirred tanks. In this paper, effects of temperature, salinity, stirring speed, impeller type and stirring method on the dissolution of HAPAM are reported. The experimental results manifest that the dissolving rate of HAPAM increases with temperature and stirring speed, but the viscosity of the polymer solution decreases. There is an optimal range of salinity for polymer dissolving. Combining the operation mode of up-pumping with varying stirring speed, hydrofoil impeller can accelerate the dissolution of HAPAM and maintain a high solution viscosity.

The efficiency of thin-film solar cells using a-Si:H is limited by the decrease in a-Si:H layer optical path length and its poor light absorption at red and near-infrared (NIR) wavelengths. Metal nanoparticles (NPs) such as Au have been shown to increase the absorption in the active material and the cell performances, by exhibiting localized surface plasmon (LSP) resonances. Our work’s goals are to understand NP influence in such cells and to perform an optimal structure by increasing the amount of light absorbed within the cell using NPs scattering. Modeling based on Mie theory is first carried out using bulk Palik data for Au spheres with various diameters and refractive medium indexes. Using modeling results, Au layers were deposited on glass and SnO2 substrates either by thermal evaporation in vacuum or sputtering, followed by thermal annealing (200~500 °C) in order to promote the NP growth. SEM pictures show quasi-spherical Au NP shape with an average size around 100 nm depending on the deposited layer and the annealing temperature and time. This diameter range switches extinction of NPs in scattering regime. Annealing temperature strongly affects the NP morphology. Surface coverage decreases and sphericity appears to increase with T. UV-visible spectroscopy displays distinct LSP resonances around 672 nm after annealing with a red shift while T increases. Based on these results, the thin films a-Si:H solar cells with Au NPs are realized and studied. Confirmed with the modeling results and the experimental values, the configuration in NIP junction with the Au NPs in back contact can optimize the photovoltaic properties, by the backscattering of incident light.

The objective of this work is to study the influence of the copper (Cu) content ( y = [Cu]/([In] + [Ga])) on the electronic properties of wide band gap (1.35 eV, x = [Ga]/([In] + [Ga]) ~ 0.55) Cu(In,Ga)Se 2 (CIGSe) thin film solar cells. For this study, solar cells samples with a variation in y from 0.97 to 0.84 have been fabricated. The efficiencies of solar cells have been divided by two for y varying from 0.97 to 0.84. Junction capacitance methods and photoluminescence were used to get information about space charge and defects properties. The increase of the Cu-content y of the absorber, leads to a widening of the space region, due a decrease of the net carriers concentration. The photoluminescence spectra of the solar cells with high absorber Cu-content y , slightly close to stoichiometry 0.95–0.97) have revealed a defect level of about 0.18 eV, which is not present in the solar cells with y less than 0.95. These observations are discussed in terms of a decrease of the defect complex (2V Cu + M Cu with M = In or Ga) stability at higher Ga contents.

The efficiency of thin-film solar cells using a-Si:H is limited by the decrease in a-Si:H layer optical path length and its poor light absorption at red and NIR wavelengths. Metal NP such as Au have been shown to increase the absorption in the active material and then cell performances, by exhibiting localized surface plasmon (LSP) resonances. Our work’s goal is to understand NP influence in such cells, to perform an optimal structure by increasing the amount of light absorbed within the cell using NP scattering and luminescence. Modeling based on Mie theory is first carried out using bulk Palik data for Au spheres with various diameters and refractive medium indexes. Using modeling parameters, Au layers were deposited on glass and SnO2 substrates respectively by thermal evaporation in vacuum and sputtering, followed by thermal annealing (200 ∼ 500°C) in order to promote the NP growth. MEB pictures show quasispherical Au NP shape with a mean size of 150nm. This diameter range switches extinction of NP in scattering regime. Annealing temperature (T) strongly affects the NP morphology. Surface coverage decreases and sphericity appears to increase with T. UV-Visible spectroscopy displays distinct LSP resonances around 600nm after annealing with a red shift while T increases.