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排序方式: 共有90条查询结果,搜索用时 15 毫秒
1.
Sirisha Nerella Debendra K. Das Godwin A. Chukwu Abhijit Y. Dandekar Santanu Khataniar Shirish L. Patil 《Petroleum Science and Technology》2003,21(7):1275-1294
Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations. 相似文献
2.
Reconfigurable antenna solution for MIMO-OFDM systems 总被引:2,自引:0,他引:2
A reconfigurable microstrip dipole antenna solution for multiple-input multiple-output (MIMO) communication systems making use of orthogonal frequency division multiplexing (OFDM) is presented. When applied to closely spaced antenna arrays, this method can increase link capacity. The benefits of this novel antenna solution are demonstrated by channel capacity measurements taken in an indoor environment with a 2/spl times/2 MIMO system. 相似文献
3.
Wasps of genus Asobara, a larval parasitoid of Drosophila, have become model organisms for the study of host-parasite interactions. However, little is known about the role of pheromones in locating mates and courtship behavior in this genus. In the present study, we aimed to identify the female courtship pheromone in Asobara tabida. The chemical compositions of solvent extracts from male and female wasps were analyzed by GC/MS. These extracts, fractions thereof, and synthetic pheromone candidates were tested for their activity in behavioral bioassays. The results demonstrate that the courtship pheromone of A. tabida is characterized by a remarkable chemical diversity. A multi-component blend of female-specific compounds including methyl 6-methylsalicylate (M6M), fatty alcohol acetates (FAAs), and cuticular hydrocarbons (CHCs) released male courtship behavior. Using a combinatory approach that included both purified natural products and synthetic analogs, it was shown that none of the three chemical classes alone was sufficient to release a full behavioral response in males. However, a blend of M6M and FAAs or combinations of one or both of these with female-derived CHCs resulted in wing-fanning responses by males comparable to those elicited by the crude extract of females. Thus, components from all three chemical classes contribute to the bioactivity of the pheromone, but none of the elements plays a key role or is irreplaceable. The fact that one of the FAAs, vaccenyl acetate, is also used as a kairomone by Asobara females to locate Drosophila hosts suggests that a pre-existing sensory responsiveness to vaccenyl acetate might have been involved in the evolution of the female sex pheromone in Asobara. 相似文献
4.
A multi-scale finite element model (FEM) is developed to predict the post machined sub-surface damage in a particle reinforced metal matrix composite (MMC) subjected to laser-assisted machining (LAM). The MMC studied is an A359 aluminum matrix composite reinforced with 20% by volume fraction silicon carbide particles. In this model, molecular dynamics (MD) simulations are carried out to parameterize traction–separation laws for the aluminum–silicon carbide interface. The parameterized traction–separation laws are then input into a finite element model, in the form of a cohesive zone model to subsequently simulate the sub-surface damage. In this manner, the multi-scale hierarchical model successfully bridges the atomic, micro and macro scales. Average values of the predicted quantities are compared with experimental results, and the favorable agreement confirms the validity of the multi-scale FEM. 相似文献
5.
By exploiting the rapid increase in available sequence data, the definition of medically relevant protein targets has been improved by a combination of: (i) differential genome analysis (target list): and (ii) analysis of individual proteins (target analysis). Fast sequence comparisons, data mining, and genetic algorithms further promote these procedures. Mycobacterium tuberculosis proteins were chosen as applied examples. 相似文献
6.
Chinmaya R. Dandekar Yung C. Shin John Barnes 《International Journal of Machine Tools and Manufacture》2010,50(2):174-182
Titanium alloy (Ti–6Al–4V) is one of the materials extensively used in the aerospace industry due to its excellent properties of high specific strength and corrosion resistance, but it also presents problems wherein it is an extremely difficult material to machine. The cost associated with titanium machining is also high due to lower cutting speeds (<60 m/min) and shorter tool life. Laser-assisted machining (LAM) and consequently hybrid machining is utilized to improve the tool life and the material removal rate. The effectiveness of the two processes is studied by varying the tool material and material removal temperature while measuring the cutting forces, specific cutting energy, surface roughness, microstructure and tool wear. Laser-assisted machining improved the machinability of titanium from low (60 m/min) to medium-high (107 m/min) cutting speeds; while hybrid machining improved the machinability from low to high (150–200 m/min) cutting speeds. The optimum material removal temperature was established as 250 °C. Two to three fold tool life improvement over conventional machining is achieved for hybrid machining up to cutting speeds of 200 m/min with a TiAlN coated carbide cutting tool. Tool wear predictions based on 3-D FEM simulation show good agreement with experimental tool wear measurements. Post-machining microstructure and microhardness profiles showed no change from pre-machining conditions. An economic analysis, based on estimated tooling and labor costs, shows that LAM and the hybrid machining process with a TiAlN coated tool can yield an overall cost savings of ~30% and ~40%, respectively. 相似文献
7.
Niru Kumari Vaibhav Bahadur Marc Hodes Todd Salamon Paul Kolodner Alan Lyons Suresh V Garimella 《International Journal of Heat and Mass Transfer》2010,53(15-16):3346-3356
Enhancement of forced convective heat transport through the use of evaporating mist flow is investigated analytically and by numerical simulation. A two-phase mist, consisting of finely dispersed water droplets in an airstream, is introduced at the inlet of a longitudinally-finned heat sink. The latent heat absorbed by the evaporating droplets significantly reduces the sensible heating of the air inside the heat sink which translates into higher heat-dissipation capacities. The flow and heat transfer characteristics of mist flows are studied through a detailed numerical analysis of the mass, momentum and energy transport equations for the mist droplets and the airstream, which are treated as two separate phases. The coupling between the two phases is modeled through interaction terms in the transport equations. The effects of inlet mist droplet size and concentration on the thermal performance of the heat sink are analyzed parametrically. The results provide insight into the complex transport processes associated with mist flows. The simulations indicate that significantly higher heat transfer coefficients are obtained with mist flows as compared to air flows, highlighting the potential for the use of mist flows for enhanced thermal management applications. 相似文献
8.
K Ushijima H Sassa R Tao H Yamane AM Dandekar TM Gradziel H Hirano 《Canadian Metallurgical Quarterly》1998,260(2-3):261-268
The ability of histamine H3 receptor ligands to interact with 5-HT3 receptors in NG108-15 cells was studied using the whole cell patch clamp recording technique. Imetit, a histamine H3 receptor agonist, generated inward currents and exhibited weak partial agonist activity at the 5-HT3 receptor (EC50 = 11.8 microM). Imetit-induced currents were slow to desensitize and at a high concentration reduced in size. The histamine H3 receptor antagonists iodophenpropit and thioperamide did not generate inward currents but were able to inhibit 5-hydroxytryptamine (5-HT) responses with an IC50 of 1.57+/-0.3 microM and 13.7+/-3.5 microM, respectively. Thioperamide is probably a non-competitive antagonist which may have more than one binding site on the receptor. 相似文献
9.
Computational electromagnetics is used to characterise the effect of realistic propagation on the capacity of multiple-input, multiple-output (MIMO) communication systems. Mutual information results for a MIMO system operating at 1.8 GHz in an urban micro-cellular environment are presented. 相似文献
10.
Abhijit Y. Dandekar 《Petroleum Science and Technology》2004,22(9):1161-1172
The interfacial tension (IFT) of hydrocarbon fluids is commonly predicted by either the parachor method or the scaling law. The methods require equilibrium liquid and vapor phase composition and density. An equation of state would normally be required if experimental values are not available. However, the computation of density for simple hydrocarbons and reservoir fluids, despite the important advances achieved by cubic equations of state, still remains a weak link in these types of calculations. Thus, there exists a need to investigate the qualitative and quantitative effects, of such inaccuracies in the density, on IFT predictions. Moreover, the study presented in this work would be useful in reservoir engineering and enhanced oil recovery calculations. The results presented in this work indicate that the methods are highly sensitive to the inaccuracies in the density of both the liquid and the vapor phases. An error of around 10% in the liquid or the vapor density can result in an error of up to 200% in the estimated IFT. Two binary and one ternary mixture for which measured data on IFT, composition and density is reported in the literature form the basis of this study. 相似文献