Showing papers by "Tongji University published in 2000"
TL;DR: In this paper, the main flow of the Kuroshio Current was inferred to re-enter the Okinawa Trough at ∼7.3 calendar (cal.) kyr BP, leading to abrupt changes in sedimentation rate, remarkably increased abundance of Pulleniatina obliquiloculata, increased sea surface temperature (SST) and depth of thermocline (DOT).
328 citations
222 citations
TL;DR: In this article, the dispersal mechanism and source areas of pollen from hemipelagic sediments recovered from the continental slopes of the South China Sea (SCS) reveal that vegetation existed on the exposed shelves at the Last Glacial Maximum and the latter part of the Marine Isotope Stage 3.
216 citations
TL;DR: The postglacial transgressive sedimentary cycle (PTSC) is composed of marsh-nearshore and barrier-lagoon, shallow marine and nearshore-tidal flat units, with a basement in stiff clay as mentioned in this paper.
204 citations
TL;DR: In this paper, the effects of many parameters, such as sand/MPB ratio, water/ MPB (W/W) ratio, kind of sand, fly ash replacement of MPB, specimen volume, temperature and moisture on mechanical properties, and fluidity of PMB mortar were investigated.
176 citations
TL;DR: In this article, the influence of strain history on rock specimen deformation during multi-level loading and unloading cyclic uniaxial compression creep tests is studied with a creep testing machine.
173 citations
TL;DR: In this article, the authors present some research results on characteristics and durability of magnesium phosphate cement-based material, such as strength, coefficient of thermal expansion, drying shrinkage, corrosion protection, deicer-frost resistance, abrasive resistance and strength loss while soaking in water or 3% NaCl solution.
Abstract: This paper presents some research results on characteristics and durability of magnesium phosphate cement-based material, such as strength, coefficient of thermal expansion, drying shrinkage, corrosion protection, deicer-frost resistance, abrasive resistance and strength loss while soaking in water or 3% NaCl solution. Experimental results indicate that MPB materials posses high deicer-frost resistance, high abrasion resistance and high corrosion protection for reinforcing steel. In addition, the MPB materials have good compatibility and bond with old concrete, and very low drying shrinkage. However, for the MPB materials soaked in water or 3% NaCl solution for a long time, the strengh loss occurs. Laboratory and field studies show that the MPB materials are suitable for rapid repair of concrete structures. especially pavements aiport runways, bridge decks and key municipal roads, etc.
157 citations
TL;DR: In this paper, the effect of ultra-fine admixtures (UA), such as blast furnace slag (BFS), silica fume (SF), fly ash (FA), limestone (LS) and anhydrous gypsum (AG), upon the rheological property of cement paste is researched.
139 citations
TL;DR: In this article, an identification method has been developed to extract all the flutter derivatives defined by R.H. Scanlan, which is then used in the identification of flutter derivative of the Jiangyin suspension bridge over Yangtze River.
122 citations
TL;DR: In this article, a relatively new method to adjust refractive index of nano-porous silica films rapidly and continuously was reported, where thin films were prepared with the base/acid two-step catalytic sol-gel process and the dip-coating method.
Abstract: A relatively new method to adjust refractive index of nano-porous silica films rapidly and continuously is reported. The thin films were prepared with the base/acid two-step catalytic sol-gel process and the dip-coating method. The structure, reflective spectra and refractive index of the films were analyzed with TEM, AFM, SEM, spectrophotometer, and ellipsometery, respectively. The experimental results have shown that the base/acid two-step catalysis can adjust the refractive index of the nano-porous silica films from 1.18 to 1.42 rapidly and continuously. And a broadband antireflective coating made with the method has very low reflectance. The average reflectance of the coated glass in the solar energy spectrum decreases to 1.5% from ∼7% of the glass.
111 citations
TL;DR: In this article, a production process for Zn powder by alkaline treatment of an oxidized Zn ore, smithsonite (ZnCO 3 ), was studied, and it was found that over 85% of both Zn and Pb, and less than 10% of Al can be leached from the ore when the leaching operation is conducted at over 95°C using 5 M NaOH solution as leaching agent.
TL;DR: In this paper, a new method utilizing the idea of force equilibrium is presented for the determination of initial cable forces in a prestressed concrete cable-stayed bridge for a given vertical profile of deck under its dead load.
TL;DR: In this paper, the optical propogation losses of ZnO films deposited on SiO 2 /Si(111) substrates were measured using end-coupling method.
TL;DR: In this article, magnetic iron fibres of diameter down to 2 µm were produced by using the bundle-drawing method, and iron fiber-epoxy resin composites were prepared by mixing epoxy resin with the iron fibers.
Abstract: In this paper, magnetic iron fibres of diameter down to 2 µm were produced by using the bundle-drawing method, and iron fibre-epoxy resin composites were prepared by mixing epoxy resin with the iron fibres The electromagnetic parameters of the iron fibre-epoxy resin composites were measured using the transmission/reflection coaxial line method at microwave frequencies The measured results show that the iron fibre-epoxy resin composites exhibit larger values of µ' and µ'' in the frequency range of 2-18 GHz, and the values of both e' and e'' steeply increase with increase in the fibre concentration Based on a theoretical calculation of the reflection coefficient, the microwave absorbing properties of the iron fibre-epoxy resin composites were examined The calculated results indicate that the iron fibre-epoxy resin composites exhibit good absorption performance in the radar band The optimum absorption can be achieved by optimizing the fibre concentration The absorption peak frequency can be manipulated easily by changing the thickness of the material layer The calculated results also indicate that magnetic iron fibres may be useful in producing thin and lightweight radar absorbing materials
TL;DR: In this paper, the porosity of porous polytetrafluoroethylene (PTFE) films was investigated by means of isothermal surface potential measurements in direct comparison to nominally nonporous samples of the same polymer.
Abstract: Porous polytetrafluoroethylene (PTFE) films were positively or negatively corona charged at room or elevated temperatures. Their charge storage behavior was investigated by means of isothermal surface potential measurements in direct comparison to nominally nonporous samples of the same polymer. It was found that porosity may lead to significantly enhanced surface-charge stability for both polarities. Direct piezoelectricity was studied on quadruple, double, and single layer samples by means of quasi-static measurements. For the determination of indirect piezoelectricity, frequency-dependent acoustical-transducer experiments were carried out. Both applications-relevant measurements yielded piezoelectric d/sub 33/ coefficients of up to approximately 600 pC/N or 600 pm/V. These values are more than one order of magnitude higher than in conventional piezoelectric polymers such as polyvinylidenefluoride (PVDF) and almost comparable to the highest known values of inorganic piezoelectrics. Consequently, the novel piezoelectric porous-fluoropolymer spacecharge electrets exhibit an outstanding potential for various device applications that are very briefly discussed.
TL;DR: In this article, a colloid-based highly reflective coatings consisting of alternating layers of quarterwave thick high and low-refractive index components were deposited on glass substrates by a sol-gel spin-coating method.
TL;DR: In this paper, a finite element (FE) model updating procedure applied to complex structures using an eigenvalue sensitivity-based updating approach is presented, where the objective of the model updating is to reduce the difference between the calculated and the measured frequencies.
Abstract: This paper presents a finite element (FE) model updating procedure applied to complex structures using an eigenvalue sensitivity-based updating approach. The objective of the model updating is to reduce the difference between the calculated and the measured frequencies. The method is based on the first-order Taylor-series expansion of the eigenvalues with respect to some structural parameters selected to be adjusted. These parameters are assumed to be bounded by some prescribed regions which are determined according to the degrees of uncertainty that exist in the parameters. The changes of these parameters are found iteratively by solving a constrained optimization problem. The improvement of the current study is in the use of an objective function that is the sum of a weighted frequency error norm and a weighted perturbation norm of the parameters. Two weighting matrices are introduced to provide flexibility for individual tuning of frequency errors and parameters' perturbations. The proposed method is applied to a 1/150 scaled suspension bridge model. Using 11 measured frequencies as reference, the FE model is updated by adjusting ten selected structural parameters. The final updated FE model for the suspension bridge model is able to produce natural frequencies in close agreement with the measured ones. Copyright © 2000 John Wiley & Sons, Ltd.
TL;DR: In this paper, ammonium persulfate was used as an oxidant in boiling glacial acetic acid for o-phenylenediamine and 2-pyrimidylamine polymers.
TL;DR: In this paper, complete convergence for weighted sums of negatively associated (NA) random variables is discussed and the result on i.i.d. case of Li et al. (J. Theoret. Theory Related Fields 97 (1993) 169-178) is extended.
TL;DR: In this article, a strengthening mechanism for sol-gel derived nano-porous silica films was studied and the results showed that the two-step catalysis strengthened the films and the scratch resistance was further improved after treatment in the mixed gas.
Abstract: A strengthening mechanism for sol–gel derived nano-porous silica films was studied. The silica films were prepared with the dip method from two-step catalyzed silica sols and treated in a mixed atmosphere of ammonia and water vapor afterwards. Properties of the films were analyzed by using atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), ellipsometry and an abrasion test, respectively. The experimental results have shown that the two-step catalysis strengthens the films and the scratch resistance of the silica films is further improved after treatment in the mixed gas. The increase in strength is attributed to the cross-linking of silica particles by randomly branched or/and entangled linear chains in the sols, more Si–O–Si bonds formed by the mixed gas treatment and structural changes in the silica films.
TL;DR: In this paper, the authors infer the existence of an older ophiolitic source, termed the Yarlung-Zangbo paleo-ophiolite, that was dismembered and eroded during an earlier subduction stage not taken into account in current models.
TL;DR: Based on the knowledge developed in structural reliability theories, this paper presented a reliability analysis model, which is formulated as a limit state up-crossing problem, and a probability calculation approach to determine the probability of bridge failure due to flutter.
TL;DR: In this article, the existence of little nanosized monoclinic ZrO2 particles in clear stable ethanolic colloidal suspensions was confirmed by transmission electron microscopic observations.
TL;DR: The long-term predictions for leachate concentrations for the Landfill were made using the mathematical simulation formula established in this paper, and the predictions for concentrations of Cl-, turbidity, and pH values in leachates were also given.
Abstract: Parameters such as pH, concentrations of Cl-, turbidity,NH3-N, CODCr and BOD5 (simplified as COD and BODrespectively in the following text) in leachate generated inthe large-scale testing landfill unit and closed landfill unitsat Shanghai Refuse Landfill were monitored from April 1995 toOctober 1998. The mathematical simulation formula between theseparameters and refuse age were established based on the dataobtained from the testing landfill unit and justified by thedata obtained at the closed landfill units from 1989 to 1993.The long-term predictions for the leachate concentrations forthe Landfill were made using the mathematical simulation formulaestablished. It was predicted that the COD and BOD may bereached to the strictest standard for pollution control on municipal solid wastes landfill in China, i.e., COD < 100 mg L-1 and BOD < 30 mg L-1, after 15 yr natural attenuation. The time predicted for NH3-N concentrations to reach the discharging standard, 15 mg L-1, was found to be at least 23–26 yr or even longer. The predictions for concentrations of Cl-, turbidity, and pH values in leachate are also given. The natural attenuation of Cl- is the slowest and might be decreased to 200 mg Cl- L-1, the agricultural irritation standard, after at least 58 yr.
TL;DR: In this article, acoustic emission (AE) signals from mortar, concrete and steel fiber reinforced concrete beams during the entire fracture process were recorded and analyzed, and the relationship between the AE signal section and the failure mechanism of these materials, analyzed on the meso-structure level was determined.
TL;DR: In this article, the recovery of zinc from synthetic zinc ferrites was investigated and it was found that around 75-80% of the zinc in zinc ferrite can be extracted after being fused directly with NaOH pellets and dissolved in an alkaline leaching solution.
TL;DR: Wang et al. as discussed by the authors presented the development and state of the art of rock mechanics and rock engineering in China, looking back at the history of development and main achievements in rock mechanics.
TL;DR: In this paper, the effects of molecular weight on the thermostability and the decomposition kinetic parameters of poly(trimethylene terephthalate) samples under argon, air, and nitrogen were discussed systematically.
TL;DR: In this article, a V-type three-level atom in a photonic crystal is investigated, and the behavior of the populations in the two upper levels: antitrapping, periodic oscillation, and no population inversion.
Abstract: Spontaneous emission from a V-type three-level atom in a photonic crystal is investigated. Quantum interference between the two atomic transitions affects the constructor of dressed states, and leads to an interesting behavior of the populations in the two upper levels: antitrapping, periodic oscillation, and no population inversion. Those properties depend strongly on the relative position of the upper levels from the forbidden gap and the initial state of the atom, and differ from that of a two-level atom in a photonic crystal. The emitted field, which is composed of localized mode(s) and propagating mode(s), is also studied. Quantum interference can enhance or reduce the energy of the localized field.
TL;DR: In this article, spontaneous emission from a two-level atom embedded in a photonic crystal with three-dimensional dispersion relation is investigated, where the dependence of wave vectors on direction is taken into account.
Abstract: We investigate spontaneous emission from a two-level atom embedded in a photonic crystals with three-dimensional dispersion relation, where the dependence of wave vectors on direction is taken into account. Due to the difference of the density of states of electromagnetic modes between a three-dimensional and a one-dimensional photonic crystal (lack of singularity), the dynamics of the population in the excited state and the emitted field are quite different from those of a one-dimensional photonic crystal. There is no quasi-oscillation for the population evolution. The localized field and the propagating field cannot coexist. When the upper level moves from the gap to the band, the emitted field changes from a localized field to a diffusion field and then to a propagating field. The energy of the diffusion and propagating fields propagates out incoherently and coherently, respectively. An analytical expression for the Lamb shift is obtained. The Lamb shift for the current case is smaller than that in an ordinary vacuum or in one-dimensional photonic crystals.