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Total pressure

About: Total pressure is a research topic. Over the lifetime, 5199 publications have been published within this topic receiving 66658 citations.


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Journal ArticleDOI
TL;DR: The local pressure contribution for mesh-based Ewald methods is computed, retaining the typical N log N scaling as a function of the lattice nodes N, a considerable improvement on existing methods.
Abstract: The importance of calculating pressure profiles across liquid interfaces is increasingly gaining recognition, and efficient methods for the calculation of long-range contributions are fundamental in addressing systems with a large number of charges. Here, we show how to compute the local pressure contribution for mesh-based Ewald methods, retaining the typical N log N scaling as a function of the lattice nodes N. This is a considerable improvement on existing methods, which include approximating the electrostatic contribution using a large cutoff and the, much slower, Ewald calculation. As an application, we calculate the contribution to the pressure profile across the water/vapor interface, coming from different molecular layers, both including and removing the effect of thermal capillary waves. We compare the total pressure profile with the one obtained using the cutoff approximation for the calculation of the stresses, showing that the stress distributions obtained using the Harasima and Irving–Kirkwoo...

25 citations

Journal ArticleDOI
TL;DR: In this article, a twin-screw extruder-fed slit die viscometer (SDV) and a piston capillary rheometer have been used to measure the end pressure losses of a low density polyethylene, maize grits and potato powder.
Abstract: A twin-screw extruder-fed slit die viscometer (SDV) and a piston capillary rheometer have been used to measure the end pressure losses of a low density polyethylene, maize grits and potato powder. The entrance and exit pressure losses have been measured as a function of extrusion conditions. The entrance pressure losses were found to be less than 10% of the total pressure drop in the SDV for LDPE and maize grits. For the potato material, this loss was found to be as large as 58%. The exit pressures for the potato were between 10–20% of the total pressure drop compared to negligible values for the maize and LDPE. Various approaches due to Bagley, Han and Cogswell were used to investigate the elastic properties of these materials.

24 citations

Journal ArticleDOI
TL;DR: In this article, a drift chamber mass spectrometer was used to study ion-molecule reactions in argon-hydrogen mixtures, and the rate coefficient of the title reaction was found to depend on pressure, decreasing as the total pressure is increased.
Abstract: Ion–molecule reactions in argon– hydrogen mixtures were studied as a function of total and partial pressures, using a drift chamber mass spectrometer. The rate coefficient of the title reaction was found to depend on pressure, decreasing as the total pressure is increased from a value of 3.5×10−10 at low pressure to 3.5×10−11 cm3 molecule −1 s−1 at pressures greater than 0.8 Torr. This behavior is explained by the presence of vibrationally excited ArH+ ions formed in the reaction Ar+ + H2, and their deactivation by collisions with argon atoms. The thermalized ArH+ ions react with hydrogen more slowly than the excited ArH+ ions first formed. Rate coefficients for these processes and for several other ion reactions occurring in argon–hydrogen mixtures are given.

24 citations

Patent
13 Apr 1970
TL;DR: In this paper, an air monitoring system is provided for direct measurement of the volume of air flow, and its velocity and pressure in one or a composite of several air ducts.
Abstract: An air monitoring system is provided for direct measurement of the volume of air flow, and its velocity and pressure in one or a composite of several air ducts. The system includes flow measuring stations which are installed in each duct as a permanent part thereof. Air moving in the duct first passes through a flow straightening section in each station which comprises a honeycomb of short, axially extending passages. Movement of the air through the straightening section eliminates turbulence in the entering air and produces substantially laminar air flow. A plurality of total pressure sensors are positioned in one or more traverses across, immediately adjacent to, and downstream of the straightening section to sense the total pressure of the flowing air. The total pressure values sensed by the several sensors are averaged by a manifold which connects with each of them. The individual total pressure sensors are so distributed as to be at the center of cross-sectional segments of the duct having equal areas. Static pressure at each station is also sensed by static pressure sensing tips, averaged and used with the total pressure to determine air flow. A tube leading directly from a remotely located manometer is connected to the manifold of the total pressure sensors at a point symmetrically arranged with respect to the total pressure sensors.

24 citations

Journal ArticleDOI
TL;DR: In this article, the second-order rate constants of Germylene, GeH2, generated by laser flash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene, have been carried out to obtain rate constants for its bimolecular reaction with C2D4.
Abstract: Time-resolved studies of germylene, GeH2, generated by laser flash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene, have been carried out to obtain rate constants for its bimolecular reaction with C2D4. The reaction was studied in the gas phase, mainly at a total pressure of 10 Torr (in SF6 bath gas) at five temperatures in the range 295–554 K. The second-order rate constants gave the Arrhenius equation: log(k∞/cm3 molecule−1 s−1) = (−10.76 ± 0.06) + (5.79 ± 0.46 kJ mol−1)/RT ln10Pressure variation measurements over the range 1–100 Torr (SF6) at 295, 406 and 554 K showed the rate constants to be pressure independent within experimental error. Comparison with the reaction of GeH2 + C2H4 studied earlier, which was pressure dependent, gave large inverse isotope effects which increased with increasing temperature and decreasing pressure. The data supports a mechanism, involving the reversible isomerisation of initially formed germirane-d4 to ethylgermylene-d4 and is consistent with previously carried out thermochemical and ab initio calculations of the energy surface.

24 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202316
202225
2021127
2020147
2019153
2018128