Showing papers by "Nanjing University published in 1998"
TL;DR: In this article, a bulk aerodynamic algorithm is developed for all stability conditions for the computation of ocean surface fluxes, providing roughness lengths of wind, humidity, and temperature for a wind speed range from 0 to 18 ms.
Abstract: A bulk aerodynamic algorithm is developed for all stability conditions for the computation of ocean surface fluxes. It provides roughness lengths of wind, humidity, and temperature for a wind speed range from 0 to 18 ms 21: zo 5 0.013 /g 1 0.11n/u * and ln(zo/zot) 5 ln(zo/zoq) 5 2.67 2 2.57 as derived using the Tropical 2 1/4 u Re ** Oceans Global Atmosphere (TOGA) Coupled Ocean‐Atmosphere Response Experiment (COARE) data constrained by other observations under high wind conditions. Using the TOGA COARE ship data and the multiyear hourly TOGA Tropical Atmosphere‐Ocean moored buoy data, intercomparison of six different algorithms, which are widely used in research, operational forecasting, and data reanalysis, shows that algorithms differ significantly in heat and momentum fluxes under both very weak and very strong wind conditions, but agree with each other under moderate wind conditions. Algorithms agree better for wind stress than for heat fluxes. Based on past observations, probable deficiencies in roughness lengths (or neutral exchange coefficients) of some of the algorithms are identified along with possible solutions, and significant issues (particularly the trend of the neutral exchange coefficient for heat with wind speed under strong wind conditions) are raised for future experiments. The vapor pressure reduction of 2% over saline seawater has a significant impact on the computation of surface latent heat flux under strong wind conditions and should be considered in any bulk aerodynamic algorithm.
687 citations
TL;DR: This review summarizes mainly the biological results obtained in the past decade from Artemisia species, which are frequently utilized for the treatment of diseases such as malaria, hepatitis, cancer, inflammation, and infections by fungi, bacteria, and viruses.
Abstract: Artemisia species, widespread in nature, are frequently utilized for the treatment of diseases such as malaria, hepatitis, cancer, inflammation, and infections by fungi, bacteria, and viruses Furthermore, some Artemisia constituents were found to be potential insecticides and allelopathic chemicals This genus is receiving growing attention presumably due to: (i) the diversified biology and chemistry of the constituents, (ii) the frequent application in traditional medical practice, and (iii) the rich source of the plant material This review summarizes mainly the biological results obtained in the past decade The significance and trends in this field are briefly discussed
362 citations
TL;DR: In this paper, a new model of gamma-ray bursts (GRBs) based on differentially rotating strange stars was discussed. And the effect of such pulsars on expansion of the postburst fireballs through magnetic dipole radiation was studied.
Abstract: We here discuss a new model of $\gamma$-ray bursts (GRBs) based on differentially rotating strange stars. Strange stars in this model and differentially rotating neutron stars in the Klu\'zniak-Ruderman model can produce extremely relativistic, variable fireballs required by GRBs and then become millisecond pulsars. The effect of such pulsars on expansion of the postburst fireballs through magnetic dipole radiation is studied. We show that these two models can explain naturally not only various features of GRBs but also light curves of afterglows.
311 citations
TL;DR: In this paper, the authors investigated charge storage characteristics in metal-oxide-semiconductor memory structures based on silicon nanocrystals, where various interface traps and defects were introduced by thermal annealing treatment.
Abstract: Charge storage characteristics have been investigated in metal-oxide-semiconductor memory structures based on silicon nanocrystals, where various interface traps and defects were introduced by thermal annealing treatment. The observations demonstrate that traps have strong influence on the charge storage behavior, in which the traps and defects at the internal/surface of silicon nanocrystals and the interface states at the SiO2/Si substrate play different roles, respectively. It is suggested that the injected charges are mainly stored at the deep traps of nanocrystals instead of the conduction band in long-term retention mode. The long-term charge-loss process is dominantly determined by the direct tunneling of the trapped charges to the interface states in the present experiment. An optimum way to improve the retention time would be to introduce a certain number of deep trapping centers in nanocrystals and to decrease the interface states at SiO2/Si substrate.
290 citations
TL;DR: In this article, the evolution of the anatase phase upon annealing was characterized by frequency downshift, intensity increase, and linewidth sharpening of the lowest frequency Eg mode.
Abstract: ) prepared by a colloidal chemistry method. The evolution of the anatase phase upon annealing was characterized by frequency downshift, intensity increase, and linewidth sharpening of the lowest-frequency Eg mode. The rutile phase was shown to be stabilized at temperatures below 350 °C and was postulated to reside in the surface region of the nanophase. The beginning and ending temperatures for the anatase–rutile transformation in the nanophase were found to be lower than those in single crystals or polycrystalline powders. The microscopic mechanism of the phase transformation was analyzed and the surface effect was suggested. An anomalous phenomenon of amorphization was also detected at the end of the anatase–rutile transformation in the nanophase TiO2.
223 citations
TL;DR: In this article, a review of the chemical preparation of ultrafine amorphous alloy particles (UAAP) consisting of transition metal (M) and metalloid elements (B, P) and their applications in catalysis is presented.
203 citations
TL;DR: In this paper, the effects of radiative correction and the non-uniformity of the medium on a gamma-ray burst afterglow analytically were studied, assuming that the expansion of a relativistically expanding fireball is adiabatic and that the density of a medium is a power-law function of shock radius.
Abstract: The afterglow of a gamma-ray burst (GRB) is commonly thought to be the result of continuous deceleration of a relativistically expanding fireball in the surrounding medium. Assuming that the expansion of the fireball is adiabatic and that the density of the medium is a power-law function of shock radius, i.e. n(ext) proportional to R-k, we study the effects of the first-order radiative correction and the non-uniformity of the medium on a GRB afterglow analytically. We first derive a new relation among the observed time, the shock radius and the Lorentz factor of the fireball: t(+) = R/4(4 - k)gamma(2)c, and also derive a new relation among the comoving time, the shock radius and the Lorentz factor of the fireball: t(co) = 2R/(5 - k)gamma c. We next study the evolution of the fireball by using the analytic solution of Blandford & McKee. The radiation losses may not significantly influence this evolution. We further derive new scaling laws both between the X-ray flux and observed time and between the optical flux and observed time. We use these scaling laws to discuss the afterglows of GRB 970228 and GRB 970616, and find that if the spectral index of the electron distribution is p = 2.5, implied from the spectra of GRBs, the X-ray afterglow of GRB 970616 is well fitted by assuming k = 2.
182 citations
TL;DR: In this paper, the applicability of this procedure, originally developed for Europe, to assign modern surface samples from China to biomes was tested, and the procedure successfully delineated the major vegetation types of China.
Abstract: Biomization provides an objective and robust method of assigning pollen spectra to biomes so that pollen data can be mapped and compared directly with the output of biomgeographic models. We have tested the applicability of this procedure, originally developed for Europe, to assign modern surface samples from China to biomes. The procedure successfully delineated the major vegetation types of China. When the same procedure was applied to fossil pollen samples for 6000 years ago, the reconstructions showed systematic differences from present, consistent with previous interpretations of vegetation changes since the mid-Holocene. In eastern China, the forest zones were systematically shifted northwards, such that cool mixed forests displaced taiga in northeastern China, while broad-leaved evergreen forest extended c. 300 km and temperate deciduous forestc. 500–600 km beyond their present northern limits. In northwestern China, the area of desert and steppe vegetation was reduced compared to present. On the Tibetan Plateau, forest vegetation extended to higher elevations than today and the area of tundra was reduced. These shifts in biome distributions imply significant changes in climate since 6000 years ago that can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Asian monsoon.
172 citations
TL;DR: In this paper, the effects of radiative correction and the nonuniformity of the medium on gamma-ray burst afterglow were analyzed under the assumption that the expansion of a relativistically expanding fireball is adiabatic and the density of a medium is a power-law function of shock radius.
Abstract: The afterglow of a gamma-ray burst (GRB) is commonly thought to be due to continuous deceleration of a relativistically expanding fireball in the surrounding medium. Assuming that the expansion of the fireball is adiabatic and that the density of the medium is a power-law function of shock radius, viz., $n_{ext}\propto R^{-k}$, we analytically study the effects of the first-order radiative correction and the nonuniformity of the medium on a GRB afterglow. We first derive a new relation among the observed time, the shock radius and the fireball's Lorentz factor: $t_\oplus=R/4(4-k)\gamma^2c$, and also derive a new relation among the comoving time, the shock radius and the fireball's Lorentz factor: $t_{co}=2R/(5-k)\gamma c$. We next study the evolution of the fireball by using the analytic solution of Blandford and McKee (1976). The radiation losses may not significantly influence this evolution. We further derive new scaling laws both between the X-ray flux and observed time and between the optical flux and observed time. We use these scaling laws to discuss the afterglows of GRB 970228 and GRB 970616, and find that if the spectral index of the electron distribution is $p=2.5$, implied from the spectra of GRBs, the X-ray afterglow of GRB970616 is well fitted by assuming $k=2$.
169 citations
TL;DR: In this article, the binding energies of Zn 2p and S 2p are the same as those of bulk single-crystal, but the full widths at half maximum of the XPS peaks are larger than those of the bulk singlecrystal.
Abstract: S solution. ZnS nanoparticles were synthesized under ultrasonic radiation. They were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV spectrophotometry, and X-rayphotoelectron spectrometry (XPS). XRD revealed that the ZnS nanoparticles prepared have a zincblende structure. TEM observations showed that the ZnS nanoparticles are in a spherical form with an average diameter of 40 nm. XPS results proved that, for our sample, the binding energies of Zn 2p and S 2p are the same as those of bulk single-crystal, but the full widths at half maximum of the XPS peaks are larger than those of bulk single-crystal.
146 citations
TL;DR: Results indicate that triptolide induces T cell apoptosis through activating caspases, and suggest the growth arrest and apoptotic effect of triptoide may contribute to the immunosuppressive activity of TWHf extract.
TL;DR: The composite tubular membranes were prepared by applying suspensions of zirconia particles to form separation top-layers on two different porous α-alumina supports and heating the coated supports to partly sinter the particles of top-layer as discussed by the authors.
TL;DR: A few inequalities associated with the alternative direction method of multipliers given by Gabay and Mercier are presented, helpful in understanding the algorithm.
TL;DR: In this article, the recent developments in physics and dynamical behavior of strange stars are reviewed and various observational effects in distinguishing strange stars from neutron stars and related interesting astrophysical phenomena are also discussed.
Abstract: Some historical remarks concerning the strange stars are briefly discussed The recent developments in physics and dynamical behavior of strange stars are reviewed Especially, various observational effects in distinguishing strange stars from neutron stars and related interesting astrophysical phenomena are also discussed
TL;DR: Isoalantolactone, a major sesquiterpene lactone of I. racemosa, was found to be active against the human pathogenic fungi, and the taxonomic significance of the characterized constituents is discussed briefly.
TL;DR: In this article, the influence of calcination temperature on bulk and surface properties of MgAlO binary oxide derived from the hydrotalcite precursor was described. But the authors only focused on the surface acid/base properties of the samples.
TL;DR: Using the extended Hubbard model and sum-over-state method, this article calculated the linear polarizability of carbon nanotubes with finite length and showed that the chiral symmetry has a great effect on their optical properties.
Abstract: Using the extended Hubbard model and sum-over-state method, we have calculated the linear polarizability $\ensuremath{\alpha}$ and the third-order nonlinear polarizability $\ensuremath{\gamma}$ for carbon nanotubes with finite lengths. We find that the chiral symmetry of nanotubes with finite length has a great effect on their optical properties. For example, the finite length $(n,m)$ tubes with $n\ensuremath{-}m$ being not a multiple of 3, will have smaller $\ensuremath{\alpha}$ and much smaller $\ensuremath{\gamma}$ values than other finite length tubes.
TL;DR: In this article, the authors used XRD, laser Raman, and UV-visible DR spectroscopies to study tetragonal zirconia-supported MoO 3 and NiO−MoO 3 oxide systems.
TL;DR: In this paper, major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka.
Abstract: Major and trace element analyses of the Luochuan loess-paleosol sequence in China were performed in order to understand the cheniical weathering processes occurring on the I.oess Plateau during the last 600 ka. Results reveal that most elements in the loess remain immobile durlng chemical weathering. The typical stable elements are Al, K, Ti, Rb and REE, while the main mobile elements are Ca, Sr, P, Mg and Na. 120ess and paleosol experience the incipient stage of chemical weathering characterized by acid leaching and carbonate dissolution. Alteration of silicates in the sequence seems to be limited. Features of less chemical weathering of the loess and paleosol could he indicators for the dry-cold clinlate dominated on the Loess Plateau during the Quaternary.
TL;DR: In this paper, the authors investigated the transport of a spatially periodic system driven by additive and multiplicative Gaussian white noises (between which there is a correlation) in the presence of spatial symmetry.
Abstract: The transport of a spatially periodic system driven by additive and multiplicative Gaussian white noises (between which there is a correlation) is investigated in the presence of spatial symmetry. The probability current shows that the correlation between additive and multiplicative noise is an ingredient for the flux of particles. Using the formulas obtained by us we investigate the transport in the superconducting junction and the transport of motor proteins in the case of environmental perturbation. For the motor proteins we find that the multiplicative noise can also induce the flux of the moleculae, even if the correlation between additive and multiplicative noise is zero. The results of superconducting junction and motor proteins provide a theoretical foundation for further study.
TL;DR: In this paper, the authors show that under some circumstances, inverse Compton scattering may play an important role in the emission spectrum, and this may influence the temporal properties of GRB afterglows.
Abstract: The detection of delayed X-ray, optical, and radio emission, the "afterglow" associated with gamma-ray bursts (GRBs), is consistent with fireball models, in which the emission is produced by a relativistic expanding blast wave, driven by an expanding fireball at cosmological distances. The emission mechanisms of GRB afterglows have been discussed by many authors, and synchrotron radiation is believed to be the main mechanism. The observations show that the optical light curves of two observed gamma-ray bursts, GRB 970228 and GRB 970508, can be described by a simple power law, which seems to support the synchrotron radiation explanation. However, here we show that under some circumstances, inverse Compton scattering (ICS) may play an important role in the emission spectrum, and this may influence the temporal properties of GRB afterglows. We expect that the light curves of GRB afterglows may consist of multiple components, depending on the fireball parameters.
TL;DR: In this paper, the influence of milling conditions on magnetic properties of SrFe12O19 compounds have been systematically investigated and it can be found that annealing treatment at low temperature can play similar role in structural transformation as compared with long time milling process.
TL;DR: The polycrystalline perovskitelike manganese oxides La1-xAxMnO\({3 + \delta }\) (A = Na, and K, 0.05 < x ≤ 0.20) have been fabricated by sol-gel technique as discussed by the authors.
Abstract: The polycrystalline perovskitelike manganese oxides La1-xAxMnO\(_{3 + \delta }\) (A = Na, and K, 0.05 < x ≤ 0.20) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation state is practically constant, at 3.32 ± 0.02 for A = Na, and 3.40 ± 0.04 for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (Tc) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie temperature.
TL;DR: In this paper, the effect of pH on the polymerization process of toluidine blue and the electrochemical characteristics of the resulting polymer-modified electrodes were studied in detail, and the experimental results indicated that the polymerisation process was somewhat similar to that of aniline in acidic media.
TL;DR: In this article, the soft $\ensuremath{\gamma}$-ray repeaters (SGRs) are proposed to result from young, magnetized strange stars with superconducting cores.
Abstract: The soft $\ensuremath{\gamma}$-ray repeaters (SGRs) are proposed to result from young, magnetized strange stars with superconducting cores. As such a strange star spins down, the quantized vortex lines move outward and drag the magnetic flux tubes because of the strong coupling between them. Since the terminations of the tubes interact with the stellar crust, the dragged tubes can produce sufficient tension to crack the crust and pull parts of the broken platelet into the quark core. The deconfinement of crustal matter into strange quark matter will release energy. The model burst energy, duration, time interval, spectrum, and the persistent x-ray emission from SGRs are shown to be in agreement with observed results.
TL;DR: In this paper, the authors obtained polypyrrole (PPY) films with a thickness of 3-4 μm by chemical oxidation of pyrrole at the interface of chloroform and water with an oxidant (NH4)2S2O8.
Abstract: Polypyrrole (PPY) films with a thickness of 3–4 μm were obtained by chemical oxidation of pyrrole (PY) at the interface of chloroform and water with an oxidant (NH4)2S2O8. The films were compact and could be removed with a solid plate. The quality and compositions of these films varied with the molar ratios of the monomer and oxidant of the reaction systems. Overoxidation of polypyrrole was observed and confirmed by the characterizations via infrared spectra and elemental analysis of the films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2169–2172, 1998
TL;DR: The dependence of magnetization on the applied magnetic field and temperature was measured carefully near their Curie temperature for polycrystalline perovskite-type manganese oxides La 1− x Na x MnO 3 (0.05 X ≤ 0.20) prepared by sol-gel technique.
TL;DR: In this paper, the influence of preparation conditions such as thermal treatment temperature (T), molar ratio of citric acid to metallic ions (L/M), and pH value of the starting solution on the oxide particle size has been studied.
TL;DR: In this article, an internal consistency analysis is developed to establish realistic logarithmic velocity profiles, in the estimation of boundary layer parameters associated with intertidal flat environments, and the internal consistency is shown to be enhanced if the data are filtered, before a more detailed analysis.
Abstract: Previous investigations have assumed that a significant linear relationship betweenuz-lnZis sufficient to define a logarithmic velocity profile given by the von Karman–Prandtl equation. However, it is demonstrated here that such a criterion alone is insufficient.
An internal consistency analysis is developed to establish realistic logarithmic velocity profiles, in the estimation of boundary layer parameters associated with intertidal flat environments. The analytical procedure includes: (i) onward linear regression, to establish the relationship between apparentu*values and near-bed current speeds,uz(here, the observedu50is used); (ii) an assessment of the constant and correlation coefficient within theu*–uzrelationship; (iii) calculation ofz0andC50values, on the basis of the slope of the regression line; and (iv) undertaking a comparison between the derivedz0andC50and those obtained using the instantaneous velocity profiles. The internal consistency is shown to be enhanced if the data are filtered, before a more detailed analysis.
This approach is applied to the analysis of 192 current velocity (gradient rig) data sets collected from the intertidal flats of the Loughor Estuary and Swansea Bay (South Wales), and The Wash (eastern England). Overall, less than 40% of the data sets are logarithmic in character, with variations between the various stations. Nevertheless, boundary layer parameters were determined for most locations. Non-logarithmic profiles on intertidal flats are considered to be caused by: (i) rotary tidal currents; (ii) wind effects; (iii) wave action and other short-period oscillations; and (iv) topographically-induced secondary flows. Measurement errors can lead also to deviations from an ‘ idealized ’ logarithmic profile.
TL;DR: In this paper, a nonlinear relativistic mean field model was proposed to reproduce the ground state properties of the proton halo in the excited (1/2)-state of the nucleus.
Abstract: The newly discovered proton halo in the first excited ${(1/2)}^{+}$ state of ${}^{17}$F [R. Morlock et al., Phys. Rev. Lett. 79, 3837 (1997)] is investigated in the nonlinear relativistic mean-field model. It is shown that this model, without introducing any specifically adjusted parameters, can reproduce well not only the ground state properties of ${}^{17}$F but also the proton halo in the excited ${(1/2)}^{+}$ state. The possibility of the existence of a proton halo in the neighboring nucleus ${}^{18}$Ne is also discussed.