The spread f data obtained over Lanzhou (36.1°N,103.9°E),Chongqing (29.5°N,106.4°E) and Haikou (20.0°N,110.3°E) of China during the period from 1978 to 1997 are used to analyze the occurr...
详细信息
The spread f data obtained over Lanzhou (36.1°N,103.9°E),Chongqing (29.5°N,106.4°E) and Haikou (20.0°N,110.3°E) of China during the period from 1978 to 1997 are used to analyze the occurrence *** statistical results show that the post midnight spread f occurrence is maximum during the summer solstice months of the lower solar activity period,while post sunset spread f is dominant in equinoxes of higher solar activity period over Haikou *** Chongqing and Lanzhou stations,spread f mostly occurs at post midnight and relates negatively with solar *** regression method and fourier expansion,the preliminary single-station model of spread f occurrence is established and the accuracy of the model is evaluated.
The increasingly stringent regulations on sulfur content in fuel require refineries to develop new desulfurization processes. Through the alkylation of thiophene and its derivatives with olefins followed by distillati...
详细信息
The increasingly stringent regulations on sulfur content in fuel require refineries to develop new desulfurization processes. Through the alkylation of thiophene and its derivatives with olefins followed by distillation, alkylation desulfurization is an alternative technology in the case of gasoline for its mild operation conditions and low loss of octane number. In this paper, the application of reactive distillation in gasoline alkylation desulfurization is studied, including a conceptual design and a rigorous steady state simulation. The conceptual design considers three aspects: thermodynamic analysis of the reactive system, benefits and constraints of the reactive distillation, and computation of the reactive residue curve maps. Results show that reactive distillation is feasible for gasoline alkylation desulfurization, and it has no constraints but great potential for its capital savings, improved conversion, reduced by-product formation, improved catalyst stability and avoidance of hot spots. The simulation results show that reactive distillation could obtain product gasoline with sulfur content less than 1 ppmw. It is shown that reactive distillation may be considered a viable technological alternative for gasoline alkylation desulfurization.
High intraglomerular pressure is associated with renal hyperf iltration, leading to the initiation and progression of kidney disease in experimental models of diabetes mellitus (DM). In humans, hyperf iltration is obs...
详细信息
High intraglomerular pressure is associated with renal hyperf iltration, leading to the initiation and progression of kidney disease in experimental models of diabetes mellitus (DM). In humans, hyperf iltration is observed in patients with type 1 and type 2 DM, and is also seen in patients with pre-diabetic conditions, such as the metabolic syndrome. from a mechanistic perspective, both vascular and tubular factors likely contribute to the pathogenesis of hyperf iltration. Until now, human studies have primarily focused on the use of medications that inhibit the renin angiotensin system to reduce efferent vasoconstriction and thereby improve hyperfiltration. More recent advances in the development of investigational adenosine antagonists and inhibitors of sodium glucose cotransport may help to elucidate tubular factors that contribute to afferent vasodilatation. In this review, we summarize available data from experimental and human studies of type 1 and type 2 DM and obesity to provide an overview offactors that contribute to the hyperf iltration state. We have focused on the renin angiotensin system, cyclooxygenase-2 system, nitric oxide, protein kinase C and endothelin as vascular determinants of hyperfiltration. We also dis-cuss relevant tubular factors, since experimental models have suggested that inhibition of sodium-glucose cotransport may be renoprotective.
The dynamic behavior for the fabrication of carbon fiber reinforced SiC matrix composites( C f / SiC ) is investigated by the theory and experiment. The governing differential equation of a composite beam is derived v...
详细信息
The dynamic behavior for the fabrication of carbon fiber reinforced SiC matrix composites( C f / SiC ) is investigated by the theory and experiment. The governing differential equation of a composite beam is derived via Hamilton's principle. The C f / SiC composites have been fabricated by a liquid phase sintering process, using the ultra-fine SiC particles and oxide additive materials. The SiC based materials are fabricated by using a commercial SiC powder with an average size of about 0.3µm. An Al 2 O 3 - Y 2 O 3 - SiO 2 powder mixture is used as a sintering additive. The compositional ratio ( Al 2 O 3 / Y 2 O 3 ) and its total amount ( Al 2 O 3 + Y 2 O 3 ) of additive materials are 1.5 and 10 wt%, respectively. Especially, the content of PVB is changed from 0 wt% to 10 wt%. The SiC based materials are sintered at the temperature of 1820°C under 30 MPa for 1 hr. In this study, the effect of content of PVB on the natural frequency and mode shape is obtained. finally, the relationship between natural frequency and mechanical property of C f / SiC composites is discussed.
functional linguistics has become the most influential linguistic theory in the field of translation study since the last de cade of 20th ***,for the complexity of the context,it is uncommon and insufficient to explor...
详细信息
functional linguistics has become the most influential linguistic theory in the field of translation study since the last de cade of 20th ***,for the complexity of the context,it is uncommon and insufficient to explore literary *** ing a general picture of literary text translation from functional perspectives aims to probe into the functional modes of translation.
暂无评论