1,385 research outputs found
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Scaling and intermittency in ocean turbulence: analysis of coastal water optical properties and sea surface temperature (SST)
No full textWe consider here some scaling and intermittency properties of oceanic turbulence, with a general aim of considering the impact of turbulence on the bio-optical dynamics. For that purpose, we tried two different approaches, using in situ and satellite data. For the in situ study we adopted one dimensional and for the satellite two dimensional approaches. Different techniques such as Fourier power spectrum, Empirical mode of decomposition (EMD), Hilbert spectral analysis (HSA) have been used for analyzing the intermittency characteristics of the in situ data. For analyzing the multi-scale properties of the satellite images, we have considered Structure functions (SF) and Fourier power spectrum (1D and 2D). The general objective is to understand the multi-scale oceanic variability using scaling tools developed in the field of intermittent turbulence studies
The organization of industry in the P.R. China: A new start or resort to old concepts?
No full textThe Chinese have let it be known since the death of Mao Zedong and the purge of the “Gang of Four” that they would in future draw on credits from foreign governments as well as other sources to finance imports of technology. According to western conjectures China’s capital requirements may be between US $ 25 and 50 bn or even a good deal higher. Many observers have taken the view that the Chinese have thereby put all their former development principles behind them. The author of the following article was in the P.R. China about the middle of this year at the invitation of the National Planning Commission. His assessment is that the P.R. China is far from embarking on an entirely new course in its development policy
Constant approximation for virtual backbone construction with guaranteed routing cost in wireless sensor networks
No full textExperimental investigation of the mechanical properties of synthetic magnesium sulfate hydrates: Implications for the strength of hydrated deposits on Mars
No full textWe have carried out uniaxial compression experiments to determine the mechanical properties of three crystalline magnesium sulfate hydrates that may be present in the near-surface environment of Mars. Our synthetic samples of kieserite (MgSO4 center dot H2O), epsomite (MgSO4 center dot 7H(2)O), and meridianiite (MgSO4 center dot 11H(2)O) have mean values of unconfined compressive strength of 6.3 +/- 0.7, 12.9 +/- 1.8, and 30.1 +/- 4.5 MPa, respectively, Young's modulus of 0.8 +/- 0.1, 2.9 +/- 0.4, and 5.9 +/- 0.8 GPa, respectively, and mean porosity values of 47.8% +/- 0.5%, 11.1% +/- 0.6%, and 2.9% +/- 0.2%, respectively. Although our tests cannot quantify a systematic relationship between hydration state and mechanical properties, the different porosities produced by consistent sample preparation methods suggest that the addition of non-cation-coordinated water molecules likely reduces the strength of individual sulfate hydrate phases. However, the bulk mechanical properties of our synthetic specimens are instead controlled predominantly by the sample porosity; generally, the strength increases as the porosity decreases. We expect the mechanical properties of sulfate hydrate deposits on Mars to be governed by the bulk porosity rather than the strength of the pure solid phase. We have performed cyclic stressing tests, replicating possible periodic depositional and erosional periods on Mars resulting from obliquity changes. A gradual compaction and reduction in sample porosity, rather than an increase in crack damage, is observed with each loading cycle, suggesting that the evolution of mechanical properties will depend on local factors such as bulk density, in addition to the overall stress history
Economic potential of the P.R. Spring oil-impregnated deposit, Uinta Basin, Utah
No full textreportThe P.R. Spring oil-impregnated sandstone (tar sand) deposit is located in the southeastern portion of the Uinta Basin, approximately 50 miles northwest of Grand Junction, Colorado. These oil impregnated sandstones are in the Eocene Green River Formation and five zones have been identified. These zones consist of one or more lenticular beds of lacustrine sandstone, separated by intervals of barren lithologies. The degree of impregnation of individual beds within the five zones is controlled by the lateral extent of the bed, its porosity and permeability, and the distance the oil has migrated within the bed. The degree of saturation varies both laterally and vertically. The purpose of this report was to 1) determine the total hydrocarbon content of each zone in blocks of 640 acres or less, and 2) relate this data to current economic and mining feasibility. This study incorporates the results of 38 measured sections and 26 core holes. The oil extracted from the P.R. Spring tar sands is a naturally occurring, brown to black, highly viscous or solid mixture of hydrocarbons. Its composition indicates that the oil was formed in situ or migrated only a short distance. The author has calculated the total barrels of oil in place for the deposit to be approximately 3.3 billion barrels. This is less than other published calculations of 3.7 and 4.0 to 4.5 billion barrels (Byrd, 1967; Ritzma, 1974). Problems associated with the method of economic recovery of the oil remain to be solved. Only the southeastern corner of the field is strip rninable. Other areas will probably have to be exploited by in situ recovery methods and several are being tested. The only known active operation in P.R. Spring is by Bighorn Oil, located in the southeastern part of the deposit. Their operation consists of an open-pit mine and a 200-barrel-per-day extraction plant utilizing a solvent solution process. Surface water availability in the area is limited, but may be sufficient if storage, reuse and ground-water potential are considered. Oil extraction will require a fuel supply, possibly from generated coke and other byproduct fuels generated by the tar refining process or by local natural gas or coal production. Further work is needed in the area, specifically more core holes and associated analyses. Strategic drilling in T. 11 S., R. 22 and 24 E., and T. 12 S., R. 22 E., could be used to verify assumed saturation
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