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A regional model of vegetation dynamics was revised to include land use as a constraint to vegetation dynamics and primary production processes. The model was applied to a forest transect in eastern China (NSTEC, North-South trans...
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A regional model of vegetation dynamics was revised to include land use as a constraint to vegetation dynamics and primary production processes. The model was applied to a forest transect in eastern China (NSTEC, North-South transect of eastern China) to investigate the responses of the transect to possible future climatic change. The simulation result indicated that land use has profound effects on vegetation transition and primary production. In particular, land use reduced competition among vegetation classes and tended to result in less evergreen broadleaf forests but more shrubs and grasses in the transect area. The simulation runs with land use constraint also gave much more realistic estimation about net primary productivity as well as responses of the productivity to future climatic change along the transect. The simulations for future climate scenarios projected by general circulation models (GCM) with doubled atmospheric CO_2 concentration predicted that deciduous broadleaf forests would increase, but conifer forests, shrubs and grasses would decrease. The overall effects of doubling CO_2 and climatic changes on NSTEC were to produce an increased net primary productivity (NPP) at equilibrium for all seven GCM scenarios. The predicted range of NPP variation in the north is much larger than that in the south.
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Starting from famous Schr¨odinger equation within the framework of semi-classical theory of light-matter interaction, we firstly obtain the analytical non-resonant solutions of the driven bipartite system’s entanglement dynamic...
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Starting from famous Schr¨odinger equation within the framework of semi-classical theory of light-matter interaction, we firstly obtain the analytical non-resonant solutions of the driven bipartite system’s entanglement dynamics in independent and coherent double pathways. Numerical simulations show that under non-resonant condition, entanglement sudden death and revival between these transition patterns behave quite differently, indicating the utmost importance of transition pathways’ interference. Furthermore, the laser pulse’s area and detuning exert significant but quite distinct influences on the entanglement dynamics. Our analyses are helpful in manipulating entanglement in current experimental technology.
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It was found that there lies a linear relationship among the thermodynamic data of complicate inorganic compounds with similar components. A method for estimating the thermodynamic data of complicate compound and a thermodynamic d...
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It was found that there lies a linear relationship among the thermodynamic data of complicate inorganic compounds with similar components. A method for estimating the thermodynamic data of complicate compound and a thermodynamic database involving alumina production were developed. It was found that the alumina digestion rate of activated diasporic bauxite by means of heat field increased much due to the structure aberration, i. e, from perfect structure to unstable corundum. The results from thermodynamic calculation and experiments showed that it was feasible for desilication at atmospheric pressure, and the effects on equilibrium concentration of SiO_2 included temperature, mole ratio of Na_2O/Al_2O_3(α_k), caustic and Na~+ concentration. The technology of desilication of green liquor at atmosphere and separation of alumina and silica in aluminate solution with high concentration were established. The reaction activity of compounds containing silica and the converting law among compounds were studied , and the prototype technology of desilication products by hydrotreatment was also developed.
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Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was developed. The ...
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Based on the population balance equation in a batch crystallizer characteristic of seeded precipitation, a model to calculate the rate of apparent crystal growth of aluminum hydroxide from the size distribution was developed. The simulation results indicate that the rate of apparent crystal growth during seeded precipitation exhibits a manifest dependence on the crystal size. In general, there is an obvious increase in the apparent crystal growth rate with the augment in crystal size. The apparent activation energy increases with the increase of characteristic crystal size, which indicates that the growth of small crystals is controlled by surface chemical reaction; it is gradually controlled by both the surface reaction and diffusion with the augment in crystal size.
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Resorting to Debye-Huckel equation, the conception of the apparent dielectric constant e' of sodium alumina to solution is introduced. By supposing that all the influences are attributed to it, e is successfully related to caustic...
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Resorting to Debye-Huckel equation, the conception of the apparent dielectric constant e' of sodium alumina to solution is introduced. By supposing that all the influences are attributed to it, e is successfully related to caustic ratio ax > concentration binboh, t and temperature T. Then an activity coefficient calculation model for NaAl (OH)_4-NaOH-H_2O system from 25 deg C to 100 deg C is established, which can be used in much wider ok and ranges than those covered by the equilibrium solubility data.
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Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO centre dot SiO_2 centre dot H_2O and 2CaO centre dot SiO_2 centre dot 1.17 H_2O, were hydro-thermally synthesized at 12...
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Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO centre dot SiO_2 centre dot H_2O and 2CaO centre dot SiO_2 centre dot 1.17 H_2O, were hydro-thermally synthesized at 120 deg C. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO centre dot SiO_2 centre dot H_2 O is more stable than 2CaO centre dot SiO_2 centre dot 1.17 H_2O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO centre dot A1_2O_3 centre dot ,xSiO_2 centre dot (6 - 2x) H_2O (hydro-garnet) is formed and some SiO_2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na_2O centre dot Al_2O_3 centre dot 2SiO_2 centre dot nH_2O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.
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An optical PPM-CDMA communication system with an optical hard-limiter in front of the correlator of a receiver is proposed in order to reduce multi-user interference. The performance of the system is evaluated when the effects of ...
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An optical PPM-CDMA communication system with an optical hard-limiter in front of the correlator of a receiver is proposed in order to reduce multi-user interference. The performance of the system is evaluated when the effects of both multi-user interference and photo detector shot noise are considered. An upper bound on the bit error rate is derived. The comparison of the performance of the above receiver with that of the optical PPM-CDMA system without an optical hard-limiter is made. Simulation results show that the performance of the system with an optical hard-limiter is superior to that of the conventional one.
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Aiming at seeded precipitation of aluminate solution with high caustic ratio(alpha_k>2.4), corresponding to the late period of seeded precipitation, the influence of different types of seed on precipitation ratio was explained wit...
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Aiming at seeded precipitation of aluminate solution with high caustic ratio(alpha_k>2.4), corresponding to the late period of seeded precipitation, the influence of different types of seed on precipitation ratio was explained with respect to solution structure in the interface of seed and the evolution of A1(OH)_3 growth units in this layer. The effects of solid content and seed size on agglomeration were determined by calculating the particle number of product. The results imply that the solution structure in the interface of seed imposes a notable significance on the process in the late period of seeded precipitation. Agglomeration still exists in this period. However, the agglomeration bodies break in the case of prolonging precipitation due to the mechanical effect, which results in the increase of particle number.
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Through X-ray diffraction patterns and scanning electronic micrographs, temperature dependence of the crystal structure of roasted diasporic bauxite at different temperatures and the digestibility of roasting production were inves...
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Through X-ray diffraction patterns and scanning electronic micrographs, temperature dependence of the crystal structure of roasted diasporic bauxite at different temperatures and the digestibility of roasting production were investigated systematically. The lattice parameters of unit cell for chemically purified diaspore and unequilibrium alumina-contained oxide obtained from the diaspore roasted at different temperatures were determined. It is found that, with roasting temperature increasing, the roasting production changes front the original dense and perfect diaspore crystal into imperfect corundum with many microcracks and small pores on its surface and then into perfect corundum with low digestibility. The optimum roasting temperature with hest digestibility is approximately 525 deg C when residence time is shout 25 min. It is thought that the change of crystal structure, formation of microcracks and small pores in the temperature field are the main essential reasons for improving digestibility of diasporic bauxite and its roasting production.
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Based on the thermodynamic calculation, the mole ratio of CaO to SiO_2, temperature and A/S of bauxite have a profound influence on the mole ratio of 2CaO · SiO_2 to CaO · SiO_2 in sinter. CaO · SiO_2 and β-2CaO · SiO_2 appea...
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Based on the thermodynamic calculation, the mole ratio of CaO to SiO_2, temperature and A/S of bauxite have a profound influence on the mole ratio of 2CaO · SiO_2 to CaO · SiO_2 in sinter. CaO · SiO_2 and β-2CaO · SiO_2 appear stable in caustic solution but unstable in soda solution, and CaO · SiO_2 is more stable than β-2CaO · SiO_2 under the same leaching condition. Compared with the conventional sinter, the rate of alumina extraction of the new sinter is large and the secondary reaction is restricted in the leaching, which might be mainly due to the more content of CaO · SiO_2 in sinter and better stability of CaO · SiO_2 in leaching.
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