The mixing of different sized soil particles is known to affect soil properties such as density, porosity, hydraulic conductivity, and soil water retention. To better understand how the mixing controls soil water rete...
详细信息
The mixing of different sized soil particles is known to affect soil properties such as density, porosity, hydraulic conductivity, and soil water retention. To better understand how the mixing controls soil water retention characteristics, a set of laboratory experiments was performed using binary mixtures of coarse and fine particles with seven different mixing fractions. for each mixture, the water retention characteristics, porosity, and saturated hydraulic conductivity were obtained. To enhance the effects of mixing, coarse and fine sands with a relatively large particle size contrast were used. Results showed that at equal to or above the fine fraction of similar to 0.3, the fine particles controlled the behavior. Starting from the fine-only sample, introducing more coarse particles to the fine particles led to rather gradual changes in the water retention characteristics. Wall effects at the coarse-fine particle interfaces were presumed to be responsible for the changes in the water retention curves. The water retention curves for the mixtures with a fine fraction lower than 0.3 were controlled by the coarse particles yielding the displacement pressure similar to that of the coarse sand. furthermore, it was inferred that different mixing fractions led to different spectra of pore sizes, suggesting that a parametric model with sufficient flexibility is needed to describe the water retention characteristics of binary mixtures.
Through analysis on water quality,planktonic organism,fish resources,and fish species diversity in Yantan water area,this paper evaluated current situation of quality offishery ecological environment in Yantan water ...
详细信息
Through analysis on water quality,planktonic organism,fish resources,and fish species diversity in Yantan water area,this paper evaluated current situation of quality offishery ecological environment in Yantan water area. The survey recorded all 52365 fishes and 1410. 2kg catches obtained by fishermen in half a year,and more than 98% catches are small fishes. The Shannon-Weiner diversity index of Yantan water area is 0. 162,Wilhm improvement index is 1. 814,DG- findex is 0. 083,and the index offish species diversity is far lower than other water areas. The average quantity per unit of phytoplankton is 1. 0134 million ind. / L,and the average quantity per unit of organisms is 1. 1151 mg / L. The average quantity per unit of zooplankton is 459. 6 ind. / L,and the average quantity per unit of organisms is 0. 6422 mg / L. Evaluation results indicate that water quality and planktonic organism in Yantan water area are basically normal,but fish resources are increasingly exhausted,fish resource composition is not reasonable,and fish species diversity is extremely low. from the perspective of biomanipulation,it is required to restore fishery ecological environment of reservoir area through restoring normal composition of aquatic organisms.
El libre comercio es una antigua aspiración que, en rigor, nace con la ciencia económica a fines del siglo xviii , pero que solo ha existido, en forma parcial y limitada, en el último tercio del siglo x...
详细信息
El libre comercio es una antigua aspiración que, en rigor, nace con la ciencia económica a fines del siglo xviii , pero que solo ha existido, en forma parcial y limitada, en el último tercio del siglo xix y hasta la I Guerra. El nacimiento del gatt después de la II Guerra como segunda opción ante la fracasada Carta de Comercio y Empleo obedece a la necesidad de las grandes potencias comerciales de la época de liberalizar el comercio. Éste prevé la formación de zonas de libre comercio y de uniones aduaneras como mecanismos alternos al libre comercio de alcance universal; existen más de 400 y México es parte de 11 de ellos con lo que formaliza, no inicia, su apertura económica y de dos agrupaciones multilaterales (Alianza del Pacífico y Acuerdo Transpacífico), lo que debe ser analizado cuidadosamente. Al final se especula en torno a los acuerdos Transpacífico y Trasatlántico y su posible influencia en el funcionamiento de la economía mundial. The free trade is an ancient aspiration, that in essence was born with the economic science in the late eighteenth century, but that has only existed in partial and limited form in the last third of the nineteenth century and until ww1 . The birth of the gatt comes after the failure of the Havana Conference and obeys the need of the world powers in the time of the commerce liberalization. It proposes the creation offree trade zones and customs unions as side mechanisms of global free trade. There are more than 400 free trade agreements and Mexico has signed 11 of them (with which it formalizes, but does not start, its economic opening) and also has taken part in two free trade transnational alliances ( tpp and Pacific Alliance), which must be carefully analyzed. In the end it's thought around the Transpacific and Transatlantic free trade agreements and their possible influence on the global economy.
We develop the parameterized post-Keplerian approach for class of analytic f ( R ) -gravity models. Using the double binary pulsar system PSR J0737-3039 data we obtain restrictions on the parameters of this class off...
详细信息
We develop the parameterized post-Keplerian approach for class of analytic f ( R ) -gravity models. Using the double binary pulsar system PSR J0737-3039 data we obtain restrictions on the parameters of this class off ( R ) -models and show that f ( R ) -gravity is not ruled out by the observations in strong field regime. The additional and more strong corresponding restriction is extracted from solar system data.
Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and Nbf5 in H2-ambient. Acti-vation energy for the depositi...
详细信息
Low resistive TiO2 layer was deposited by low pressure chemical vapor deposition (LPCVD) at pressure around 0.25 Pa using titanium-tetra-iso-propoxide (TTIP) and Nbf5 in H2-ambient. Acti-vation energy for the deposition rate on the temperature was significantly decreased to 120 kJ/mol as compared with 228 kJ/mol for the deposition in H2 without Nbf5. The deposition rate linearly increased with Nbf5 supply rate but gradually decreased with H2 supply rate indicated that f on the deposition surface acts as catalyst for TTIP-dissociation but is non-activated by hydrogen. Resistivity of the layer was decreased by Nbf5 supply depending on the deposition temperature with the activation energy of 319 kJ/mol, whereas the energy was 244 kJ/mol for the layer deposited in H2 without Nbf5. The dependence of resistivity on Nbf5. and H2 supply rates suggested that the doping should be performed by sufficient Nbf5 and H2 supply rate to improve the crystallinity. As a result of the optimization, the resistivity was successfully reduced to 5 × 10-2 Ω·cm. Optical transmission spectra in UV-Vis region indicated that significant absorption observed for the layer deposited in H2 was notably decreased by using Nbf5. The improved optical property was better than that for the layer deposited in O2-ambient.
暂无评论