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Pressure System (pressure + system)

Distribution by Scientific Domains

Earth and Environmental Science	63%
Medical Sciences	18%

Kinds of Pressure System

low pressure system

Selected Abstracts

Characteristics of Abnormal Pressure Systems and Their Responses of Fluid in Huatugou Oil Field, Qaidam Basin

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009
Xiaozhi CHEN
Abstract: Based on the comprehensive study of core samples, well testing data, and reservoir fluid properties, the construction and the distribution of the abnormal pressure systems of the Huatugou oil field in Qaidam Basin are discussed. The correlation between the pressure systems and hydrocarbon accumulation is addressed by analyzing the corresponding fluid characteristics. The results show that the Huatugou oil field as a whole has low formation pressure and low fluid energy; therefore, the hydrocarbons are hard to migrate, which facilitates the forming of primary reservoirs. The study reservoirs, located at the Xiayoushashan Formation (N21) and the Shangganchaigou Formation (N1) are relatively shallow and have medium porosity and low permeability. They are abnormal low-pressure reservoirs with an average formation pressure coefficient of 0.61 and 0.72 respectively. According to the pressure coefficient and geothermal anomaly, the N1 and N21 Formations belong to two independent temperature-pressure systems, and the former has slightly higher energy. The low-pressure compartments consist of a distal bar as the main body, prodelta mud as the top boundary, and shore and shallow lake mud or algal mound as the bottom boundary. They are vertically overlapped and horizontally paralleled. The formation water is abundant in the Cl, ion and can be categorized as CaCl2 type with high salinity, which indicates that the abnormal low-pressure compartments are in good sealing condition and beneficial for oil and gas accumulation and preservation. [source]

Ethnic differences in plantar pressures in diabetic patients with peripheral neuropathy

DIABETIC MEDICINE, Issue 4 2008
M. P. Solano
Abstract Aims To compare plantar foot pressures between Caucasian and Hispanic diabetic patients with peripheral neuropathy (PN) without a history of foot ulceration and between Caucasian and Hispanic non-diabetic individuals. Methods Forty-four Hispanic diabetic patients with PN (HDPN), 35 Caucasian diabetic patients with PN (CDPN), 41 non-diabetic Hispanic subjects and 33 non-diabetic Caucasian subjects participated. Total and regional peak plantar pressures (PPs) and pressure time integrals (PTIs) were assessed using the EMED-SF-4 plantar pressure system. Results Hispanic diabetic patients with PN had significantly lower peak PP than Caucasian diabetic patients with PN in the entire foot (552.4 ± 227.9 vs. 810.1 ± 274.6 kPa; P < 0.001), forefoot (464.1 ± 222.6 vs. 699.6 ± 323.1 kPa; P < 0.001), hindfoot (296.3.4 + 101.8 vs. 398.1 + 178.3 kPa; P < 0.01) and at the fifth metatarsal head (MTH5; 204.3 ± 143.2 vs. 388.2 ± 273.9 kPa; P < 0.001). The PTI in the entire foot, forefoot and MTH5 were also lower in HDPN than in CDPN. The ethnic differences between the diabetic groups with PN for the entire foot, forefoot and MTH5 remained significant after adjusting for the effect of age, gender, weight and duration of diabetes. There were no significant differences in peak PP and PTI among non-diabetic individuals, except for a lower peak PP at the MTH5 in Hispanic compared with Caucasian subjects. Conclusions Despite a well-known higher incidence of foot complications in diabetic Hispanic subjects, dynamic plantar pressures are lower in Hispanic diabetic patients with PN when compared with their Caucasian counterparts, suggesting that differences in other risk factors exist between these two ethnic groups. [source]

Cost-Affordable Technique Involving Equal Channel Angular Pressing for the Manufacturing of Ultrafine Grained Sheets of an Al,Li,Mg,Sc Alloy,

ADVANCED ENGINEERING MATERIALS, Issue 8 2010
Rustam Kaibyshev
A two-step process consisting of modified equal channel angular pressing (ECAP) and subsequent isothermal rolling (IR) was developed to produce thin sheets of aluminum alloys with ultra-fine grained (UFG) structure. Significant increase in the efficiency of ECAP was attained by using flat billets and a back pressure system. The incorporation of final IR into technologic route provides a reduced strain which is necessary to impose for the fabrication of thin sheets with UFG structure. In addition, it allows producing relatively "long billets." In order to demonstrate the feasibility of this technique an Al,5.1Mg,2.1Li,0.17Sc,0.08Zr (wt %) alloy was subjected to ECAP at 325,°C to a total strain of ,8 using processing route CX. The operation time of this processing did not exceed 15,min. Subsequent IR at the same temperature with a total reduction of 88% was applied to produce thin sheets with a 1.8,mm thickness and an average size of recrystallized grains of ,1.6,µm. These sheets exhibit extraordinary high superplastic ductilities. In addition, this material demonstrated almost isotropic mechanical behavior at room temperature. The maximum elongation-to-failure of ,2700% was attained at a temperature of 450,°C and an initial strain rate of 1.4,×,10,2 s,1. Thus it was demonstrated that the two-step processing consisting of ECAP with a back pressure followed by IR was a simple technique providing potential capability for the fabrication of superplastic sheets from an Al,Mg,Li,Sc alloy on a commercial scale. [source]

Toward large scale F.E. computation of hot forging process using iterative solvers, parallel computation and multigrid algorithms

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5-6 2001
K. Mocellin
Abstract The industrial simulation code Forge3® is devoted to three-dimensional metal forming applications. This finite element software is based on an implicit approach. It is able to carry out the large deformations of viscoplastic incompressible materials with unilateral contact conditions. The finite element discretization is based on a stable mixed velocity,pressure formulation and tetrahedral unstructured meshes. Central to the Newton iterations dealing with the non-linearities, a preconditioned conjugate residual method (PCR) is used. The parallel version of the code uses an SPMD programming model and several results on complex applications have been published. In order to reduce the CPU time computation, a new solver has been developed which is based on multigrid theory. A detailed presentation of the different elements of the method is given: the geometrical approach based on embedded meshes, the direct resolution of the velocity,pressure system, the use of PCR method as an original smoother and for solving the coarse problem, the full multigrid method and the required preconditioning by an incomplete Cholesky factorization for problems with complex contact conditions. By considering different forging cases, the theoretical properties of the multigrid method are numerically verified, optimizations of the solver are presented and finally, the results obtained on several industrial problems are given, showing the efficiency of the new solver that provides speed-up larger than 5. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Delivery characteristics of a combined nitric oxide nasal continuous positive airway pressure system

PEDIATRIC ANESTHESIA, Issue 6 2002
DEAA, R. Lindwall MD
Summary Background: Nitric oxide (NO), when inhaled, has a synergistic effect with airway recruitment strategies such as positive endexpiratory pressure (PEEP) or continuous positive airway pressure (CPAP) in improving oxygenation in lung injury. Methods: We modified a commercially available nasal CPAP (nCPAP) system to enable the concomitant delivery of inhaled NO (iNO) and nCPAP to neonates and term babies. Oxygen, NO and nitrogen dioxide (NO2) concentrations were measured, comparing the effects of using 50 or 1000 parts per million (p.p.m.) NO stock gas cylinders. Results: Stable and accurate delivery of iNO was found for both stock gas concentrations. Using a 50 p.p.m. NO stock gas resulted in limited NO2 formation, with a maximum inspired NO2 concentration of , 0.3 p.p.m. (dose range up to 37 p.p.m. iNO), which was interpreted as the result of progressive dilution with nitrogen. In contrast, using a 1000 p.p.m. NO stock gas cylinder, inspired NO2 levels increased nonlinearly as expected with an increasing inspired concentration of NO. Conclusions: Inhaled NO can be safely and reliably delivered by the system we describe. The NO2 levels generated by the system are low, at least up to a dose of 37 p.p.m. NO, regardless of a stock gas concentration of 50 or 1000 p.p.m. NO. Using a 50 p.p.m. NO stock gas concentration, up to 80% oxygen can be given at 10 p.p.m. iNO. [source]

An easterly tip jet off Cape Farewell, Greenland.

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 645 2009
I: Aircraft observations
Abstract An easterly tip jet event off Cape Farewell, Greenland, is described and analysed in considerable detail. In Part I of this study (this paper) comprehensive aircraft-based observations are described, while in Part II of this study numerical simulations and a dynamical analysis are presented. The easterly tip jet of 21 February 2007 took place during the Greenland Flow Distortion experiment. It resulted through the interaction of a barotropic synoptic-scale low pressure system in the central North Atlantic and the high topography of southern Greenland. In situ observations reveal a jet core at the coast with peak winds of almost 50 m s,1, about 600,800 m above the sea surface, and of 30 m s,1 at 10 m. The depth of the jet increased with wind speed from ,1500 m to ,2500 m as the peak winds increased from 30 to 50 m s,1. The jet accelerated and curved anticyclonically as it reached Cape Farewell and the end of the barrier. The easterly tip jet was associated with a tongue of cold and dry air along the coast of southeast Greenland, general cloud cover to the east, and cloud streets to the south of Cape Farewell. Precipitation was observed during the low-level components of the flight. The very high wind speeds generated a highly turbulent atmospheric boundary layer and resulted in some of the highest surface wind stresses ever observed over the ocean. Copyright © 2009 Royal Meteorological Society [source]

Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment.

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 641 2009
II: Multilayer cloud
Abstract Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a deep, multilayered, mixed-phase cloud system observed during the Atmospheric Radiation Measurement (ARM) Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-levels. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate liquid water path and strongly underestimate ice water path, although there is a large spread among models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. These results suggest important differences in the ability of models to simulate deeper Arctic mixed-phase clouds versus the shallow, single-layered mixed-phase clouds in Part I. The observed liquid-ice mass ratios were much smaller than in Part I, despite the similarity of cloud temperatures. Thus, models employing microphysics schemes with temperature-based partitioning of cloud liquid and ice masses are not able to produce results consistent with observations for both cases. Models with more sophisticated, two-moment treatment of cloud microphysics produce a somewhat smaller liquid water path closer to observations. Cloud-resolving models tend to produce a larger cloud fraction than single-column models. The liquid water path and cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by long-wave flux. Copyright © 2009 Royal Meteorological Society [source]

Variability in the characteristics of cut-off low pressure systems over subtropical southern Africa

INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2007
A. T. Singleton
Variability in the characteristics of cut-off low pressure systems over subtropical southern Africa is examined for the 1973,2002 period. These characteristics include their seasonality, frequency, duration, location and size. It is found that on average 11 cut-off lows occur over southern Africa south of 20°S per year and are most common in the March-May season. Potential relationships between the number of cut-off lows over southern Africa with the El Niño Southern Oscillation (ENSO), the Pacific South America pattern, the wave number 3 pattern and the semi-annual oscillation (SAO) are discussed. La Niña years appear to be associated with above average annual frequencies of cut-off lows but the reverse is generally not true for El Niño years. There was a shift in the preferred season for cut-off lows from March,May to June,August in the 1980s, which coincided with a weakening of the SAO and a shift in zonal wave number 3. This period also showed a change in the preferred location of these systems from southwestern subtropical southern Africa to the northeast of the region. The results suggest that there may be a relationship between cut-off lows over subtropical southern Africa, the wave number 3 pattern in the Southern Hemisphere and the SAO. Copyright © 2006 Royal Meteorological Society. [source]