建筑创作中的城市意识

该文首先分析了我国当前城市空间状况,进而以城市的整体视野提出当前建筑创作的宏观方法,最后从城市景观取向、建筑界面消解、城市生活引领三个方面系统地阐述了建筑创作的城市整体意识。     

Experimental study on cool release process of gas-hydrate with additives

Cool release process of phase change material (PCM) includes the dissolution process of the PCM. Experimental research on the cool release process in a new gas-hydrate cool storage system is performed in this paper. In the system, the inner-heat exchange/outer-crystallization technology and the integrated condenser/evaporator structure design were adopted. The influences of different proportions of calcium hypochlorite or benzenesulfonic acid sodium salt on the dissolution process are studied. The results show that the instantaneous dissolution rate is close to twice as the corresponding instantaneous formation rate of gas-hydrate, and the cold energy release rate, i.e. energy release per unit time, is obviously higher than the corresponding cold energy storage rate at different conditions, which is mainly due to the heat transfer temperature difference of the discharging (release) and charging (store) processes. Both the charging and the discharging processes are simultaneously dominated by the heat transfer and the mass transfer processes. However, as to the dissolution (discharging) process of the gas-hydrate by heating, the effect of the heat transfer process is the main influence factor. The temperature difference between the heating medium and the gas-hydrate in the discharging process, which is larger than that between the cooling medium and the gas-hydrate in the charging process, makes a higher cold energy release rate compared with the cold energy storage rate. The results also indicate that the dissolution rate of gas-hydrate is accelerated, and the cold energy release rate of the cool storage system is increased by adding reasonable proportions of the additives.     

常见塑料溶解性能研究及其混合物的选择性分离

以常见塑料为原料,以有机物为溶剂,研究了塑料在有机溶剂中的溶解性能,提出了选择性分离混合塑料的方案。结果表明,实验所选用的塑料在有机溶剂中的溶解性能和溶解条件不同;可利用塑料与有机溶剂的相容性差别分离混合塑料。     

Investigations on air pressure and air losses in compressed air tunneling through saturated clayey soil

Determination of air pressure and assessment of air losses in clayey soil are of great importance to implementation of compressed air tunneling. In the present work, a series of air flow tests were performed to provide a more reasonable method based on flow characteristics of snap-off pressure and the dissolution/diffusion. Results showed that, the nonlinear air flow behavior and gas breakthrough were presented with the increase in air pressure. After that, the excessive pressure decreased continuously to reach an equilibrium termed as the snap-off. For the tested clayey soil, snap-off pressures around 250 kPa could be adopted as the air pressure, which was significantly lower than the gas breakthrough pressures. Diffusion coefficient of 1.5 × 10^-11 m²/s could be determined in the followed dissolution/diffusion stage, which bring 3 orders of decreasing magnitude in air losses compared to the capillary flow occurred after gas breakthrough. As a conclusion, the adoption of snap-off pressure in compressed air tunneling could effectively prevent the continuous air/water flow in clayey soil and create a more human-friendly environment. Additionally, less air losses could be presented compared to that using gas breakthrough pressure, indicating tremendous energy savings in field implementation.     

THE DISSOLUTION OR GROWTH OF A SPHERE

The problem of the dissolution or growth of an isolated, stationary, sphere in a large fluid body is analyzed. The motion of the boundary as well as the resulting motion in the liquid are properly taken into account. The governing equations are solved using a recently developed technique (Subramanian and Weinberg, 1981) which employs an asymptotic expansion in time. Results for the radius of the sphere as a function of time are calculated. The range of utility of the present solution is established by comparison with a numerical solution of the governing equations obtained by the method of finite differences.     

Dissolution kinetics of dehydroxylated nickeliferous goethite from limonitic lateritic nickel ore

The dissolution kinetics in 2 M H₂SO₄ of variously dehydroxylated nickeliferous goethites was investigated for five oxide-type lateritic nickel deposits. Goethite was the main constituent with minor amounts of quartz, talc, kaolinite and Mn oxides. Dissolution of Fe from heated materials followed the Kabai equation. There was a 9–34-fold increase in the Kabai dissolution rate constant (k) for samples heated at 340–400 °C due to both the increased surface area (1.5–2.6 fold) and higher density of structural defects (5–10 fold) in the variously dehydroxylated products. The presence of structural Al and Cr in goethite appears to reduce dissolution rate possibly through the greater M³⁺–OH, O bond strength relative to Fe³⁺, Ni²⁺–OH, O. Nickel showed congruent dissolution with Fe indicating that Ni was uniformly incorporated in the goethite structure. Pre-heating goethite to 600–800 °C for 30 min resulted in incongruent dissolution of Fe and Ni. It is postulated that some Ni is ejected from the neo-formed hematite structure and resides on the crystal surface or in voids. These results may contribute to the development of more efficient procedures for Ni extraction including heap leaching of lateritic nickel ores.     

Creep and relaxation of cement paste caused by stress‐induced dissolution of hydrated solid components

The creep and relaxation of cement paste caused by dissolving solid hydration products is evaluated in this work. According to the second law of thermodynamics, dissolution or precipitation of solid constituents may be altered by the change in stress/strain fields inside cement paste via alteration of the stress power or strain energy. Thus, it is hypothesized that stress‐induced dissolution can affect the overall creep/relaxation behavior of cement composites. A novel, fully coupled thermodynamic, mechanical, and microstructural model (TM²) that uses the finite element method was developed to predict the time‐evolving properties of cement paste under prescribed strains and to test the hypothesis. In the model, the strain energy was incorporated to accurately predict the effect of stress and strain fields on cement microstructure change. From the simulation results, depending on the stress/strain levels and the choice of the domain (over which the thermodynamic equilibrium is enforced), stress‐induced dissolution of solid constituents can lead to significant creep/relaxation.     

Dissolution behavior of a novel Al2O3-SiC-SiO2-C composite refractory in blast furnace slag

Al₂O₃-SiC-SiO₂-C composite refractories are interesting potential blast furnace hearth lining materials that feature several advantageous properties. In this study, the corrosion resistance of a novel Al₂O₃-SiC-SiO₂-C composite refractory to blast furnace slag was investigated by adopting a rotating immersion method (25 r/min) at 1450–1550 °C and comparing it against a conventional corundum-based refractory at 1550 °C as a benchmark. The results showed that the apparent activation energy of Al₂O₃-SiC-SiO₂-C composite refractory over the dissolution process in the slag is 150.4 kJ/mol. Dissolution of the Al₂O₃ and 3Al₂O₃·2SiO₂ phases appeared to be the main cause of Al₂O₃-SiC-SiO₂-C composite refractory corrosion. High-melting-point compounds in the slag layer formed a protective layer which mitigated the corrosion. The novel Al₂O₃-SiC-SiO₂-C composite refractory is better suited to blast furnace hearth lining than the conventional corundum-based refractory, because the carbon phase and SiC phase in the material are not readily wetted by the blast furnace slag and therefore are more resistant to slag penetration. Higher melting point phases also may crystallize on the hot face of the hearth lining due to the high thermal conductivity of the Al₂O₃-SiC-SiO₂-C composite refractory, promoting a more stable protective layer.     

Effects of Ozone-Gas Bubble Size and pH on Ozone/UV Treatment

A series of ozone/UV treatment under injection of ozone with different ozone-gas bubble sizes was performed at pH 1.7 and 7.4. The increase in the bubble size and the decrease in pH enhanced the ozone utilization efficiency. The enhancement of ozone utilization efficiency was caused by the shift of the production pathway of hydroxyl radical (OH) from the OH production via O₃ ^– to the UV photolysis of H₂O₂. The lower pH caused this shift through the chemical equilibrium of H₂O₂ and HO₂ ^–, and the large bubbles caused this shift through the augmentation of H₂O₂ transport from the bubble surface to the bulk solution.     

Delayed release matrix pellet preparation containing an alkalizing pore-former agent

The aim of this study was to develop a delayed-release matrix pellet containing atenolol as active pharmaceutical ingredient. The matrix additionally contained trisodium phosphate dodecahydrate as alkalizing pore-former agent to enhance the dissolution of the atenolol at pH 6.8. The delayed release was ensured by coating with a gastro-resistant polymer. For this purpose, an acryl EZE MP aqueous dispersion was used, which is suggested in the literature for pellet coating. Before this functional film coating, a protective polymer layer was developed, to prevent direct contact between the alkalizing layer and the acryl EZE. The results of in vitro dissolution tests demonstrated that the double-coated pellet preparation is a delayed-release solid dosage form.