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EN
Planktonic ciliate composition, abundance and its response to environmental change were investigated during four seasons (winter of 2013, spring, summer and autumn of 2014) in Daya Bay, the South China Sea. A total of 41 species belonging to eight orders were identified, 14 of which were dominant. Planktonic ciliate communities showed a distinct seasonal pattern in ciliate abundance and a clear seasonal shift in the taxonomic composition. The largest number of ciliate species occurred in summer, whereas the highest abundance peaked in spring, mainly due to oligotrichids. In terms of spatial distribution, ciliate species were abundant in the area of artificial reefs, and ciliate abundance was higher in the Dapeng Cove aquaculture area and lower at the Daya Bay Nuclear Power Station. Clustering analysis demonstrated that the seasonal variations of the ciliate community structure were more obvious than spatial variations. Multivariate and univariate analyses illustrated that ciliate abundance was significantly correlated with the water nutrient level and chlorophyll-a concentration, temperature, salinity and dissolved oxygen. Moreover, the dominant abiotic environmental factors affecting the spatial pattern of ciliate communities varied between seasons.
EN
Changes in precipitation patterns and the deposition of atmospheric nitrogen (N) increase the possibility of altering soil carbon (C):N:phosphorus (P) stoichiometry through their effects on soil C and nutrient dynamics, especially in water- and N-limited ecosystems. We conducted separate 2-year watering and N addition experiments, and examined soil C:N:P stoichiometry, relative growth rate, and leaf N resorption traits of Glycyrrhiza uralensis Fisch in a desert steppe of northwestern China. Our objectives were to determine how soil C:N:P stoichiometry responded to climate change, and its indications for plant growth and N resorption. The results showed that additional water increased N loss and thus decreased N availability, resulting in high N resorption from senescing leaves of G. uralensis. N addition increased N availability, consequently reducing plant N dependence on leaf resorption. High relative growth rates occurred with intermediate N:P and C:N ratios, while high N resorption occurred with a low N:P ratio but a high C:N ratio. Our results indicate that soil C:N:P stoichiometry also could be a good indicator of N limitation for desert steppe species. Altered soil C:N:P stoichiometry affects the N strategy of plants, and will be expected to further influence the structure and function of the desert steppe community in the near future.
EN
The thermo-optic coupling process of second harmonic generation was numerically simulated in ZnGeP2 crystals pumped by a pulsed CO2 laser at the wavelength of 9.6 mu m, under the strong and weak cooling conditions. The conversion efficiencies, temperature distributions were calculated during the evolution of the thermo-optic coupling. The results showed that the thermo-optic coupling was weak in the strong cooling condition, which nearly did not disturb the conversion processes and temperature distribution, while in the weak cooling case, the temperature distribution showed a great influence on the conversion efficiency and light intensity. Finally, it was found that compensation of the phase mismatch induced by the thermal effect can well recover the conversion efficiency.
4
Content available remote Flex Fatigue Behavior Of Plastic Optical Fibers With Low Bending Cycles
EN
Flex fatigue behaviour of plastic optical fibres (POFs) with the diameters of 0.2 and 0.3 mm under different pretensions is measured with fatigue life curve by flexometer. The fatigue sensitivity coefficient is calculated by the linear fitting curve of normalised stress versus logarithm of bending cycles. The residual modulus is investigated during the flex fatigue processes. The results exhibit the exponential relationship between applied pretension and numbers of bending cycles at break. It is indicated that the flex fatigue of POFs might be sensitive with high swing angle or swing speed. There is an evident loss of modulus for two POFs with pretensions of 4 and 10% of ultimate tensile strength during 10-times bending cycles. The values of residual modulus of two POFs almost keep constant after 10-times bending cycles.
EN
CO2 laser treatment can increase the surface roughness of plastic optical fibres (POFs) with the diameter of 0.5 mm and enhance the input intensity and attenuation coefficient accordingly, which is supposed to weaken the side emission of POFs in long distance above 375 mm. TiO2 particles were applied to improve the increasing optical loss of POFs by laser treatment. POFs were first modified with fine TiO2 particles and then treated by CO2 laser with the pixel time from 30 to 120 ìs. The surface morphology was observed by scanning electron microscopy to investigate the changes of micro-structure before and after laser treatment and the distribution of TiO2 particles. The illumination intensity and attenuation coefficient were calculated and compared in two methods. It is visible that the evaluation by model LLF2 with two parts is more suitable for the fitting of experimental data and shows higher input intensity and lower attenuation than that by standard power function. Both the evaluation methods exhibit that the utilization of TiO2 particles could play an active role in the enhancement of side emission of POFs treated by CO2 laser.
EN
Rare earth Eu3+-doped MgNb2O6 red-emitting phosphor was prepared by solid-state reaction. Structure and photoluminescence properties of the samples were characterized by X-ray diffraction (XRD), scan electron microscopy (SEM) and fluorescence spectrophotometer. Meanwhile, the effect of the co-activator Bi3+ on the PL of the MgNb2O6:Eu3+ phosphor was studied. The results showed that the pure phase of MgNb2O6 could be available after firing at 1200 °C. The Mg1-xNb2O6:Eu3+ x phosphors could be effectively excited by the UV irradiation (273 nm) and emit red light at 615 nm due to the forced electric dipole 5D0 !7 F2 transitions on Eu3+, which indicated that Eu3+ occupied the non-inversion symmetry sites in the MgNb2O6 host lattice. So, the addition of the co-activator Bi3+ not only increased the excitation band of the MgNb2O6:Eu3+ phosphor at about 330 nm, but also strengthened the PL intensity at 615 nm. Therefore, MgNb2O6:Eu3+, Bi3+ might find application to InGaN chip-based white light emitting diodes.
EN
In the present study, floss silk was treated by scouring and finishing, respectively. The micro structure was observed with scanning electron microscopy (SEM), the mechanical property tested by an Instron 5566 tensile tester, and the crystal structure was analysed with Fourier transform attenuated total reflection infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The results show that the properties of floss silk treated with the refining method are better than with the alkali method.
PL
Badania dotyczyły obróbki wykańczalniczej jedwabiu naturalnego. Mikrostruktura jedwabiu była badana za pomocą skaningowej mikroroskopii elektronowej, a właściwości mechaniczne testowane były klasyczną zrywarką firmy Instron, podczas gdy strukturę krystaliczną analizowano za pomocą spektroskopii w podczerwieni (FTIR) oraz rozproszenia promieniowania rentgenowskiego. Wyniki pozwoliły wytypować najlepszą w danych warunkach metodę obróbki.
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Content available remote A Nonnegative Subspace Approach for Packet Loss Concealment
EN
This paper presents a nonnegative subspace approach for packet loss concealment problem. The magnitude spectrogram of speech signal is projected onto nonnegative subspace using nonnegative matrix factorization algorithm. Consequently, packet loss concealment problem is transformed to linear interpolation of the projective coefficients in nonnegative subspace. Simulation examples, objective tests show that packet loss concealment in the nonnegative subspace results in improved perceptual quality of speech compared to popular packet loss concealment algorithms.
PL
Zaprezentowano metodę subprzestrzeni dla rozwiązania problemu straty pakietu. Spektrogram amplitudowy sygnału mowy .jest poddawany projekcji do nieujemnej podprzestrzeni przy wykorzystaniu macierzy faktoryzacji. W rezultacie problem staje się możliwy do liniowej interpolacji. Osiągnięto dostrzegalną poprawę jakości przetwarzania sygnału mowy.
EN
A data field approach coupled with binary time-frequency masking is presented for the speech enhancement problem. In this proposed approach, data field method is employed to model the time and frequency dependencies of speech. This formulation has proved to be very helpful in enhancing speech quality by exploiting the correlation of speech both in time and in frequency. The experimental results demonstrate that the proposed algorithm offers improved signal to noise ratio and less spectral distortion.
PL
Do poprawy jakości dźwięku mowy zastosowano metodę pola danych (Data field) połączoną z binarnym maskowanie czasowoczęstotliwościowym. Pozwoliło to znacząco poprawić jakość dźwięku przez wykorzystanie korelacji czasowej i częstotliwościowej. Uzyskano poprawę stosunku sygnału do szumu i zmniejszenie poziomu zniekształceń.
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