Journal articles: 'Pressure cover'

1

Barbour, S. Lee, and Ernest K. Yanful. "A column study of static nonequilibrium fluid pressures in sand during prolonged drainage." Canadian Geotechnical Journal 31, no. 2 (April 1, 1994): 299–303. http://dx.doi.org/10.1139/t94-034.

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In the design of layered soil systems, such as the design of liners or covers over unsaturated soil, a key design concern is the magnitude of negative fluid pressure that will develop along the base of the liner or cover. In the absence of evaporation or vapour migration, the maximum negative fluid pressures will develop near the cessation of drainage. Previous theoretical analyses and numerical modelling of these systems have indicated that this pressure will be the pressure at which an underlying sand reaches its residual water content. The hydraulic conductivity of the sand at these pressures is so small that "static" nonequilibrium pressures are sustained over long periods of time. In this note, laboratory verification is provided for the magnitude of these pressures based on drainage of a fine and coarse sand column. Key words : covers, liners, air-entry value, residual saturation, layering, drainage.

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2

McClung, D. M. "Comparison of analytical snow pressure models." Canadian Geotechnical Journal 30, no. 6 (December 1, 1993): 947–52. http://dx.doi.org/10.1139/t93-092.

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Two analytical models for snow creep and glide forces on structures in deep snow covers are compared theoretically and checked against field data. The results show that the formulations contained in the 1990 Swiss guidelines for avalanche defence are incompatible with a continuum mechanical model based on linear creep and glide constitutive equations. In addition, the formulations in the 1990 Swiss guidelines neglect the pressure from the component of body force in the slope-normal direction, which is an unnecessary simplification. Key words : snow pressure, quasi-static, creep, glide, deep snow cover, continuum.

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3

Kong, Xiangzhe, Hongyan Yang, Shurong Ding, and Xiaoming Peng. "Effects of Rolling Speed and Reduction on Rolling Simulation Results of Monolithic Fuel Plates." International Journal of Nonlinear Sciences and Numerical Simulation 19, no. 6 (September 25, 2018): 605–19. http://dx.doi.org/10.1515/ijnsns-2017-0155.

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AbstractThe in-pile performances of UMo/Zr monolithic nuclear fuel plates are directly related to their manufacturing quality. The interface bonding strength depends on the contact pressures over the surfaces of the Zircaloy covers, the Zircaloy frame and the UMo coupon during rolling. The contact pressures are affected by the process parameters such as the rolling speed and the reduction per pass. These parameters should be carefully investigated to optimize the fabrication process. In this study, a three-dimensional stress updating algorithm is presented for the strain-rate-dependent mechanical constitutive relation of Zircaloy. Three-dimensional FEM simulation of the rolling process for monolithic nuclear fuel plates is carried out. The influences of the rolling speed and reduction on the geometrical shape and the contact pressure between the Zircaloy cover and the coupon will be discussed according to the computational results. The results indicate that (1) along the plate width direction the maximum contact pressure between the coupon and the Zircaloy cover exists at the center and decreases towards the edge; (2) when the rolling speed or reduction increases, the maximum contact pressure increases as well; and the dog-bone shape of the coupon at the back end is more visible.

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4

Ahn, Chang-Kyun, and Seok-Won Lee. "Ground subsidence due to the backfill pressure in tunnel boring machine." Proceedings of the International Association of Hydrological Sciences 382 (April 22, 2020): 19–24. http://dx.doi.org/10.5194/piahs-382-19-2020.

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Abstract. In shield tunnel boring machine constructions, backfill pressure affects surface settlement and the stability of other underground structures nearby. Therefore, it is essential to pre-calculate backfill pressure in the design stage. This study examines and compares the seven internationally known backfill pressure calculation theories and calculates and analyzes the backfill pressures in six virtual ground conditions. The calculated backfill pressure increased as the ground cover increased, but the increase rate decreased. Also, this study performs a numerical analysis to identify the impact on ground settlement and tunnel crown settlement. In the end, settlement was more impacted by face pressure than backfill pressure in the unsaturated and saturated ground conditions. Also, as the ground cover increased, the impact of backfill pressure decreased, and as the applied face pressure decreased, the impact of backfill pressure increased.

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5

Gatt, Alfred, Andrea Briffa, Nachiappan Chockalingam, and Cynthia Formosa. "The Applicability of Plantar Padding in Reducing Peak Plantar Pressure in the Forefeet of Healthy Adults." Journal of the American Podiatric Medical Association 106, no. 4 (July 1, 2016): 246–51. http://dx.doi.org/10.7547/15-025.

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Background: We investigated the effectiveness and durability of two types of plantar padding, the plantar metatarsal pad and the single wing plantar cover, which are commonly used for reducing forefoot plantar pressures. Methods: Mean peak plantar pressure and impulse at the hallux and at the first, second, third, and fourth metatarsophalangeal joints across both feet were recorded using the two-step method in 18 individuals with normal asymptomatic feet. Plantar paddings were retained for 5 days, and their durability and effectiveness were assessed by repeating the foot plantar measurement at baseline and after 3 and 5 days. Results: The single wing plantar cover devised from 5-mm felt adhesive padding was effective and durable in reducing peak plantar pressure and impulse at the first metatarsophalangeal joint (P = .001 and P = .015, respectively); however, it was not found to be effective in reducing peak plantar pressure and impulse at the hallux (P = .782 and P = .845, respectively). The plantar metatarsal pad was not effective in reducing plantar forefoot pressure and impulse at the second, third, and fourth metatarsophalangeal joints (P = .310 and P = .174, respectively). Conclusions: These results imply limited applicability of the single wing plantar cover and the plantar metatarsal pad in reducing hallux pressure and second through fourth metatarsophalangeal joint pressure, respectively. However, the single wing plantar cover remained durable for the 5 days of the trial and was effective in reducing the peak plantar pressure and impulse underneath the first metatarsophalangeal joint.

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Ng, Charles W. W., R. Chen, J. L. Coo, J. Liu, J. J. Ni, Y. M. Chen, L. t. Zhan, H. W. Guo, and B. W. Lu. "A novel vegetated three-layer landfill cover system using recycled construction wastes without geomembrane." Canadian Geotechnical Journal 56, no. 12 (December 2019): 1863–75. http://dx.doi.org/10.1139/cgj-2017-0728.

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To promote environmental protection and sustainability, the use of plants and recycled wastes in geotechnical construction such as landfill covers is recommended. A landfill cover field test was conducted at the Shenzhen Xiaping landfill site, located in a humid climatic region of China. The main objective was to validate the field performance of a novel vegetated three-layer landfill cover system using recycled construction waste without the need of geomembrane. Unsieved completely decomposed granite and coarsely crushed concrete was used for the top and intermediate layers while sieved completely decomposed granite was used as the lowest layer. One section was transplanted with Bermuda grass while the other section was left bare. To assess the landfill cover performance, pore-water pressure, volumetric water content, percolation, and atmospheric parameters were measured for a period of 13 months under natural climatic conditions. The cumulative rainfall depth was about 2950 mm over the entire monitoring period. During rainfall, the presence of grass led to lower pore-water pressure (or higher suction) and volumetric water content in the three-layer landfill cover system. At the end of monitoring, the cumulative percolation was about 27 and 20 mm for the bare and grass-covered landfill covers, respectively. It is evident that the vegetated three-layer landfill cover system using recycled concrete without geomembrane can be effective in minimizing percolation in humid climates.

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7

Shimizu, Hiromu, Eizi Akitaya, Mitsuo Oh’Izumi, and Yauso Hirabayashi. "Measurement of Strains and Pressure in a Snow Cover on a Slope." Annals of Glaciology 6 (1985): 303–4. http://dx.doi.org/10.3189/1985aog6-1-303-304.

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Four methods of measuring strain and pressure in a snow cover on a slope are presented. The hole-mark method and short-span deformation gauge are used to measure the internal strains of snow, the long-span deformation gauge to measure the local extension/contraction of a snow cover, and snow pressure gauge to measure the pressure in a snow cover.

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8

Shimizu, Hiromu, Eizi Akitaya, Mitsuo Oh’Izumi, and Yauso Hirabayashi. "Measurement of Strains and Pressure in a Snow Cover on a Slope." Annals of Glaciology 6 (1985): 303–4. http://dx.doi.org/10.1017/s0260305500010715.

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Four methods of measuring strain and pressure in a snow cover on a slope are presented. The hole-mark method and short-span deformation gauge are used to measure the internal strains of snow, the long-span deformation gauge to measure the local extension/contraction of a snow cover, and snow pressure gauge to measure the pressure in a snow cover.

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9

Beardsley, Kyle C. "Pain, pressure and political cover: Explaining mediation incidence." Journal of Peace Research 47, no. 4 (March 19, 2010): 395–406. http://dx.doi.org/10.1177/0022343309356384.

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10

Bertroche, J. Tyler, Patrik Pipkorn, Paul Zolkind, Craig A. Buchman, and Jose P. Zevallos. "Negative-Pressure Aerosol Cover for COVID-19 Tracheostomy." JAMA Otolaryngology–Head & Neck Surgery 146, no. 7 (July 1, 2020): 672. http://dx.doi.org/10.1001/jamaoto.2020.1081.

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11

Khoulowa, Joyce. "Esprit HR mattress cover in pressure ulcer prevention." British Journal of Nursing 10, no. 16 (August 13, 2001): 1073–76. http://dx.doi.org/10.12968/bjon.2001.10.16.9377.

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12

Li, Fang Hui, Ming Gu, Zhen Hua Ni, and Shi Zhao Shen. "Mean Wind Pressure Field on the Typical Large-Span Roof Structures." Applied Mechanics and Materials 166-169 (May 2012): 19–24. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.19.

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The wind tunnel tests of some typical large roofs, including a saddle roof, pitched roof and domes, are carried out with various terrains which cover suburban and urban exposures. The wind pressure data of roofs are obtained by using the synchronous multi-pressure scanning technique. The wind pressure coefficient and local shape factors of the wind load was investigated. The effects of various terrains on wind pressures of roofs are discussed. From the results, we can see mean pressures of these roofs exposed to the mean pressures exposed to the suburban terrain are 2 or 3 times those exposed to the urban terrain. And the terrains are no directly influence to the wind pressure shape factors.

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13

Merchant, Henry C., Ritindra N. Khan, and Robert E. Knowlton. "The effect of macrophytic cover on survival of Palaemonetes pugio and P. vulgaris (grass shrimp) in the presence of predatory Fundulus heteroclitus (killifish)." Contributions to Zoology 70, no. 2 (2001): 61–71. http://dx.doi.org/10.1163/18759866-07002001.

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Effects of three different macrophytic covers and the presence of alternative prey on survival of grass shrimp (Palaemonetes pugio and P. vulgaris) subjected to predation by killifish (Fundulus heteroclitus) were studied in the laboratory. Overall, survival of P. vulgaris was significantly greater (82%) than that of P. pugio (70%). This difference in survival was attributed to the greater tendency of P. pugio to swim outside the covers, making it more vulnerable to predation. Both prey species responded similarly to the different cover conditions. Survival without cover (gravel substrate) was 48%. In cover provided by a plastic plant made to resemble Ambulia, 75% of the starting population survived. In cover furnished by field-collected specimens of the flat chlorophyte, Ulva, survival was 71%, compared to 98% survival in the branched green alga, Codium. Predation pressure on neither species was significantly enhanced or diminished by the presence of a second prey species. For both grass shrimp species, increased survival in Codium in the presence of the predator was attributed to the physically more complex nature of this macrophytic cover.

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14

Mei, Fu Liang, and Gui Ling Li. "Study on Gas Pressure Characteristics in Multi-Layered Landfills of Municipal Solid Waste." Advanced Materials Research 518-523 (May 2012): 3507–11. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.3507.

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In this treatise one-dimensional mathematical model of gas migration in multi-layered landfills of MSW on seepage mechanics of multi-pore media and Darcy’s seepage law. Analysis of gas migration in multi-layered landfills is carried out for three different cases. The gas pressure distribution characteristics in multi-layered landfills of MSW, the effects of final/internal soil cover, the permeability and thickness of the final soil cover, the permeability and gas generation rate of MSW on the gas pressure distributions are investigated. Results show that the bigger is the ratio of gas generation rate to gas permeability of MSW, the bigger is the gas pressure in a uniform MSW landfill. The gas generation rate of MSW mainly controls the size of gas pressure, and the gas permeability of MSW dominates the gas pressure distribution characteristics in a uniform MSW landfill with a final soil cover. The smaller is the gas permeability of the final soil cover or the bigger is the gas generation rate of MSW the bigger is the gas pressure gradient inside the final soil cover

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15

Shakib, Sheikh, and Abu Zakir Morshed. "Modeling of Cover Concrete Cracking Due to Uniform Corrosion of Reinforcement." Journal of Engineering Science 12, no. 1 (April 21, 2021): 43–49. http://dx.doi.org/10.3329/jes.v12i1.53100.

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Cracking of cover concrete due to the corrosion of reinforcing steel is one of the main causes of deterioration in Reinforced Concrete (RC) structures. An outbound stress is developed in concrete surrounding the reinforcing steels due to the expansive corrosion products of reinforcement leading to cracking of the concrete cover. In this paper, the cracking pressure was simulated through a finite element modeling. The effect of geometrical and material parameters, i.e. concrete cover thickness, bar diameter, and concrete tensile strength, on the cracking pressure was also investigated. Abaqus 6.14 was used as modeling platform. The cracking pressure was found to dependent on the cover thickness and tensile strength of concrete. A higher pressure was required to initiate crack for a higher cover thicknesses and tensile strength. The cracking pressure was decreased with the increase in bar diameter. Finally the crack initiation and propagation has been simulated successfully for different arrangements of reinforcements. Journal of Engineering Science 12(1), 2021, 43-49

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16

Xiao, Jun Jian. "Stress Analysis and Structure Optimization for the Opening Flat Cover of Pressure Vessels." Advanced Materials Research 538-541 (June 2012): 3253–58. http://dx.doi.org/10.4028/www.scientific.net/amr.538-541.3253.

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According to the results of finite element analysis (FEA), when the diameter of opening of the flat cover is no more than 0.5D (d≤0.5D), there is obvious stress concentration at the edge of opening, but only existed within the region of 2d. Increasing the thickness of flat covers could not relieve the stress concentration at the edge of opening. It is recommended that reinforcing element being installed within the region of 2d should be used. When the diameter of openings is larger than 0.5D (d>0.5D), conical or round angle transitions could be employed at connecting location, with which the edge stress decreased remarkably. However, the primary stress plus the secondary stress would be valued by 3[σ].

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17

Larsen, Jan Otto, Jens Laugesen, and Krister Kristensen. "Snow-Creep Pressure on Masts." Annals of Glaciology 13 (1989): 154–58. http://dx.doi.org/10.1017/s0260305500007801.

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Snow-pressure measurements have been carried out on two masts at the NGI avalanche station in Grasdalen, western Norway. These two tubular masts have diameters of 0.22 and 0.42 m, respectively, and are situated on a 25° slope with a deep snow cover. The most important conclusions are that within a homogeneous snow-pack there is a close correlation between snow-creep pressure and the product of acceleration due to gravity, g, density, ρ, and snow depth, H, that the highest pressures are recorded in late winter when the snow-pack is at the 0°C isothermal, and finally that a weak 0° C isothermal snow layer at ground level appears to increase snow pressure.

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18

Cascini, Leonardo, Giovanni Gullà, and Giuseppe Sorbino. "Groundwater modelling of a weathered gneissic cover." Canadian Geotechnical Journal 43, no. 11 (November 1, 2006): 1153–66. http://dx.doi.org/10.1139/t06-066.

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Knowledge of the groundwater regime, which is generally necessary in studying the stability of slopes, is of fundamental importance in the analysis of landslides involving intensely weathered rocks, as in the case of a landslide in the western Sila Massif (southern Italy) reactivated by heavy and prolonged rainfall. For this landslide, the total absence of displacements during the actual quiescence period and the long return period of the critical rainfall events did not allow measurement of the critical pore pressures capable of reactivating the landslide. To solve such a problem, a saturated–unsaturated flow model was calibrated taking into account in situ pore pressure measurements acquired over a long period of time. The analyses permitted determination of the role played by the hydraulic heterogeneity of the involved soils and the hydraulic boundary conditions for simulation of the response of in situ pore pressures to rainfall. Such conditions were therefore used to predict the critical unknown values attained during landslide reactivations and were indirectly tested using different models.Key words: landslide, weathered rocks, groundwater monitoring, unsaturated–saturated flow model, rainfall, critical pore pressures.

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19

Wu, Lan Ying, Xiao Lian Xiang, and Long You. "Research of Casting Process about Cover and Pump Body of Tonghai Pump and Mechanical Properties Test." Advanced Materials Research 631-632 (January 2013): 676–80. http://dx.doi.org/10.4028/www.scientific.net/amr.631-632.676.

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In order to obtain cover and pump body of tin bronze Tonghai pump that is dense and good pressure resistance,the casting mold of the cover of Tonghai pump is metal mold. The casting method of Tonghai pump is vacuum counter-pressure casting.The method of casting pump body of Tonghai pump is vacuum investment casting. This research is about reasonable casting process parameters of vacuum counter-pressure casting and vacuum investment casting.Finally qualified castings of cover and pump body of Tonghai pump can be obtained.

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20

Bakhtar, F., and K. Zidi. "Nucleation Phenomena in Flowing High-Pressure Steam: Experimental Results." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power Engineering 203, no. 3 (August 1989): 195–200. http://dx.doi.org/10.1243/pime_proc_1989_203_027_02.

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The paper describes the results of an experimental investigation of limiting supersaturation in high-pressure steam. It follows an earlier investigation and to avoid the uncertainties associated with leakage past sliding profiles, the test section has been redesigned and the measurements taken with fixed nozzles. Three convergent-divergent nozzles with nominal rates of expansion of 3000, 5000 and 10000 per second have been used and the inlet stagnation pressures cover the range 25–35 bar. The data consist mainly of axial pressure distributions but some droplet measurements have also been recorded.

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21

Yang, Y. W., W. Z. Fu, M. Z. Li, and J. Yang. "Research on Resistance to External Pressure of Automobile Cover." Journal of Physics: Conference Series 1888, no. 1 (April 1, 2021): 012017. http://dx.doi.org/10.1088/1742-6596/1888/1/012017.

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22

Cai, Deng’an, Guangming Zhou, Yuan Qian, and Vadim V. Silberschmidt. "Failure analysis of a frangible composite cover: A transient-dynamics study." Journal of Composite Materials 51, no. 18 (October 13, 2016): 2607–17. http://dx.doi.org/10.1177/0021998316673223.

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A transient-dynamics model based on the approximate Riemann algorithm is proposed for the failure analysis of a frangible composite canister cover. The frangible cover, manufactured with a traditional manual lay-up method, is designed to conduct a simulated missile launch test using a specially developed test device. Deformation of the cover’s centre is determined using a transient-dynamics finite element model; failure pressure for the frangible cover is obtained based on a failure criterion and compared with simulated experimental results. Weak-zone position of the frangible cover has a significant effect on failure pressure compared to that of deformation of the cover’s centre. With the same structure of the weak-zone, an increase in its height can first raise and then reduce the level of failure pressure of the frangible cover. Close agreements between the experimental and numerical results are observed.

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23

Akindunni, Festus F., R. W. Gillham, and R. V. Nicholson. "Numerical simulations to investigate moisture-retention characteristics in the design of oxygen-limiting covers for reactive mine tailings." Canadian Geotechnical Journal 28, no. 3 (June 1, 1991): 446–51. http://dx.doi.org/10.1139/t91-054.

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Acid generation in reactive mine tailings is an oxidation process that is dependent on availability of molecular oxygen. As a consequence of the diffusion coefficient of oxygen being several orders of magnitude higher in air than in water, influx of atmospheric oxygen into a material at depth can theoretically be minimized by maintaining a protective cover layer at high moisture content. Such oxygen-limiting covers are generally of finer texture than the material being protected. A numerical model was used to investigate the importance of moisture-retention characteristics in the transient drainage of such two-layer systems. The results show that the effectiveness of a material as a moisture-retaining cover is dependent on the magnitude of its air-entry value. The thickness of the cover maintained at full saturation after prolonged drainage also depends on the pressure head at which the underlying material approaches residual saturation. Key words: geologic covers, tailings, numerical simulations, air-entry value, residual saturation, textural layering.

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24

Blach, A. E., V. S. Hoa, C. K. Kwok, and A. K. W. Ahmed. "Rectangular Pressure Vessels of Finite Length." Journal of Pressure Vessel Technology 112, no. 1 (February 1, 1990): 50–56. http://dx.doi.org/10.1115/1.2928587.

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Design Rules in the ASME Code, Section VIII, Division 1, cover the design of unreinforced and reinforced rectangular pressure vessels. These rules are based on “infinitely long” vessels of non-circular cross section and stresses calculated are based on a linearized “small deflection” theory of plate bending. In actual practice, many pressure vessels can be found which are of finite length, often operating successfully under pressures two to three times as high as those permitted under the Code rules cited. This paper investigates the effects of finite length on the design formulae given by the ASME Code, and also a design method based on “large deflection” theory coefficients for short rectangular pressure vessels. Results based on analysis are compared with values obtained from finite element computations, and with experimental data from strain gage measurements on a test pressure vessel.

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25

Oh’Izumi, MLtsuo, and Tosio Huzioka. "Determination of the Principal Stresses of a Snow Cover on a Mountain Slope Using Snow Pressure Gauges." Annals of Glaciology 6 (1985): 215–17. http://dx.doi.org/10.1017/s0260305500010387.

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Principal stresses in a snow cover on a uniform slope were determined by two methods, each using thin pressure gauges to measure snow pressure in the snow. These snow pressures were principal stress σ2on a vertical plane perpendicular to the contour lines and normal compressive stress σθon a plane perpendicular to the vertical plane. In addition, plastic Poisson’s ratio v was estimated in a snow cover on level ground. Estimates of principal strain rates were used to calculate principal stresses and viscosity by two different methods, using estimates of v and the constitutive equations of Yosida (1980) and the derived values of σ2and σθ.For dry and compact snow, σ1and σ3calculated by both methods agreed well with each other, and also with values obtained by the hole-mark method reported by Shimizu and Huzioka (1975).

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26

Moitzi, Gerhard, Elisabeth Sattler, and Helmut Wagentristl. "Effect of Cover Crop, Slurry Application with Different Loads and Tire Inflation Pressures on Tire Track Depth, Soil Penetration Resistance and Maize Yield." Agriculture 11, no. 7 (July 8, 2021): 641. http://dx.doi.org/10.3390/agriculture11070641.

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Agricultural soils can be affected in their ecological functions by in-field traffic of agricultural machinery. A three-factorial research design was carried out in a field experiment to test the effect of slurry tanker filling level (filled, half-filled, empty), tire inflation pressure of the slurry tanker (high: 300 kPa, low: 100 kPa), and ground covering (+cover crop, −cover crop) on tire track and soil penetration resistance (averaged, 0–20 cm, 21–40 cm) after application on the fields in spring. Additionally, the effect on grain yield of the subsequent culture was considered. The total weight of the tractor slurry tanker combination was 16,470 kg (empty), 25,940 kg (half-filled), and 34,620 kg (filled). The low tire inflation pressure of the slurry tanker increased the mean tire–soil contact area by 75% (filled), 38% (half-filled), and 16% (empty tanker). The results obtained show a significant effect of tire inflation pressure and ground covering on the measured parameters. The tire inflation pressure reduction effect on track depth was highest in the filled slurry tanker (−17.8%). With increasing wheel load, the effect of reduced tire inflation pressure on soil penetration resistance (0–20 cm) increased. In the subsoil (21–40 cm), the effect of tire inflation pressure was much lower, indicating that a reduction of tire inflation pressure preserves the upper layers rather than the lower ones. Furthermore, cover crops are linked to a higher degree of soil deformation after traffic with the tractor–slurry combination due to their loosening effect on the topsoil. Tire tracks were 15.0% deeper in the cover crop field than in the field without a cover crop. It is assumed that cover crop mixtures with different types of root mass can influence the mitigation of soil compaction in an ameliorative way.

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Parker, Bethanie A., Rodney P. McAffee, and Arun J. Valsangkar. "Field Performance and Analysis of 3-m-Diameter Induced Trench Culvert under a 19.4-m Soil Cover." Transportation Research Record: Journal of the Transportation Research Board 2045, no. 1 (January 2008): 68–76. http://dx.doi.org/10.3141/2045-08.

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An induced trench installation was instrumented to monitor earth pressures and settlements during construction. Some of the unique features of this case study are as follows: (a) both contact and earth pressure cells were used; (b) part of the culvert is under a new embankment and part was installed in a wide trench within an existing embankment; (c) a large stockpile was temporarily placed over the induced trench; and (d) the compressible material was placed in two stages. The maximum vertical pressure measured in the field at the crown of the culvert was 0.24 times the overburden pressure. The maximum horizontal pressure measured on the side of the culvert at the springline was 0.45 times the overburden pressure. The column of soil directly above the compressible zone settled approximately 40% more than did the adjacent fill. The field results at the crown and springline compared reasonably with those observed with numerical modeling. However, the overall pressure distribution on the pipe was expected to be nonuniform, the average vertical pressure calculated by using numerical analysis on top of the culvert over its full width was 0.61 times the overburden pressure, and the average horizontal pressure calculated on the side of the culvert over its full height was 0.44 times the overburden pressure. When the full pressure distribution on the pipe is considered, the recommended design loads from the Marston–Spangler theory slightly underpredict the maximum loads, and the vertical loads control the design.

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28

Lu, Ming Xin, Cun Yu Liu, Zhong Li Zhao, Guo Yong Wang, Ming Zhang, Li Jie Huo, and Guang Jun Sun. "The Research on Reasonable Support Capacity of Workface in Coal Seam with Thin Upper Cover." Advanced Materials Research 361-363 (October 2011): 125–29. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.125.

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The showing of ground pressure is severe in workface of coal seam with thin upper cover, due to the thin upper rock seam and the action of upper incompact cover. Generally, the thin cover coal seam with 90m upper cover can be defined as Coal seam with thin cover. The result of simulation experiment for workface with thin cover and 5m mining height shows that under overburden pressure, the step subsidence is obvious, and balanced structure is still formed in surrounding rock, under overburden pressure. But the shape and form of balanced structure are different from the balanced structure formed upper coal seam with normal buried depth. There appears step or dislocation between the upper rock seam in workface and the balanced structure in the mined-out area, and the quantity of dislocation is 2m. But no step subsidence appears in the simulation for the workface with thin cover and 3m mining height. So the mining height is the key for the step subsidence. This paper gives out the movement model of surrounding rock upper the workface in thin cover coal seam and chooses 1 MPa as the support capacity for the first workface of Gaotouyao Colliery based on calculation.

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29

Oh’Izumi, MLtsuo, and Tosio Huzioka. "Determination of the Principal Stresses of a Snow Cover on a Mountain Slope Using Snow Pressure Gauges." Annals of Glaciology 6 (1985): 215–17. http://dx.doi.org/10.3189/1985aog6-1-215-217.

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Principal stresses in a snow cover on a uniform slope were determined by two methods, each using thin pressure gauges to measure snow pressure in the snow. These snow pressures were principal stress σ2 on a vertical plane perpendicular to the contour lines and normal compressive stress σ θ on a plane perpendicular to the vertical plane. In addition, plastic Poisson’s ratio v was estimated in a snow cover on level ground. Estimates of principal strain rates were used to calculate principal stresses and viscosity by two different methods, using estimates of v and the constitutive equations of Yosida (1980) and the derived values of σ2and σθ. For dry and compact snow, σ1 and σ3 calculated by both methods agreed well with each other, and also with values obtained by the hole-mark method reported by Shimizu and Huzioka (1975).

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30

Børve, J., E. Skaar, L. Sekse, M. Meland, and E. Vangdal. "Rain Protective Covering of Sweet Cherry Trees—Effects of Different Covering Methods on Fruit Quality and Microclimate." HortTechnology 13, no. 1 (January 2003): 143–48. http://dx.doi.org/10.21273/horttech.13.1.0143.

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Three different rain protective covering methods for sweet cherry (Prunus avium) trees were tested with uncovered trees as control. The covers were a pitched cover mounted permanently, a similar cover mounted only when raining, and a permanent umbrella type enveloping the top and sides of single trees. Covers were mounted 3 weeks before and throughout the harvest period in two seasons with different weather conditions. All three covering methods increased the amount of marketable fruit from 54% on uncovered to 89% on covered trees in mean of 2 years. Fruit from umbrella covered trees had lower soluble solid content, lower juice color and lower ripeness compared with fruit from all other trees, reflecting the different microclimate in these trees such as frequently higher maximum temperatures and greater vapor pressure. The two pitched covers produced no significant changes in microclimate or internal fruit quality compared with uncovered trees.

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Sun, Guo Gong, Chang Hua Liu, and Qiang Li. "Optimal Design of Runner for Shell of Mobile Telephone Based on Moldflow Software." Applied Mechanics and Materials 741 (March 2015): 191–94. http://dx.doi.org/10.4028/www.scientific.net/amm.741.191.

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The runner balance of upper cover and back cover of mobile telephone was optimized in view of the runner imbalance of different mould multi-cavity in the design of plastic injection mold by means of Moldflow software. The results that the fill time of the back cover of mobile telephone is 0.8858s, that of the upper cover of mobile telephone is 0.8588s, the imbalance rate is 3.1%. The optimized runner size is φ3.739mma and φ1.666mm while the runner size is φ3mm before optimization. The gate location of V/P switch point is 29.85Mpa and is close to the target pressure 30Mpa, the pressure in the distribution is uniform.

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Fuamba, Musandji, Claude Marche, and Tung Quach. "Analyse expérimentale de l'effet d'un couvert de glace sur la propagation de l'onde de rupture de barrage." Canadian Journal of Civil Engineering 27, no. 5 (October 1, 2000): 1082–87. http://dx.doi.org/10.1139/l00-068.

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Lengthy winter conditions such as those known in the province of Quebec require that one takes the presence of an ice cover into account in the determination of instantaneous safety factors for dams established in cascade and under the effect of a break wave. Not only should the ice load on the structure be considered but also the effects of the pressure wave that is propagated under the ice cover. This study shows that the method currently used to determine the stability of structures subject to a break wave is incomplete. The results obtained in laboratory indeed indicate that the presence of the ice cover increases the sur-elevation and sur-pressure values of both components of the break wave. This might perturb the stabilizing force balance of the downstream dam and increases its risk of failure.Key words: dam safety, break wave, ice cover, sur-pressure, dynamic load.[Journal translation]

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Ndubi, Antony Oduya. "Using Land Cover Change to Predict Forest Degradation Pressure Points, Eastern Mau Forest, Kenya." International Letters of Natural Sciences 71 (September 2018): 17–33. http://dx.doi.org/10.18052/www.scipress.com/ilns.71.17.

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Land cover change in any ecosystem vary in space and time. The study analyzed spatial-temporal land cover change to predict forest degradation pressure points in Eastern Mau Forest Reserve. The study objectives were to determine types and amount of spatial-temporal land cover change; land cover change drivers and; forest resources use sustainability. The study used mixed sample survey design involving purposive sampling of spatial data and cluster sampling of forest resource use data. Primary data included ground control points, field validation data and forest resource use data. Secondary data included Landsat imagery, forest and administration boundaries and settlements data. Analysis was done for 1986-2014 period using Remote Sensing and Geographical Information System. The analysis techniques used included object based image segmentation and classification, accuracy assessment and land cover change detection. Land cover types in Eastern Mau Forest consisted of indigenous forest, shrubland, grassland, plantation forest, cultivated fields, bare ground and built-up area. The analysis results depicted that cultivated fields coverage increased from 1% to 47%. Indigenous and plantation forests decreased from 43% to 36% and 34% to 7% respectively. Grassland and shrubland decreased from 16% to 8% and 6% to 2% respectively. Bare ground and built up area had a change of less than 1% each. Causes of pressure that lead to forest degradation included crop cultivation, settlement construction, livestock grazing, charcoal burning, firewood collection, logging, bee keeping and medicinal herbs extraction. Land cover change was more on the eastern side than on the western side. Indigenous and plantation forests were likely to disappear if cropland and built up area expansions were to remain unchecked. The study recommendations were: resettlement activities be eliminated in the Eastern Mau Forest; excision of forest land for crop cultivation should be discouraged; and scientific research should be carried out on sustainable plantation forest activities.

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van Bergeijk, Vera M., Jord J. Warmink, and Suzanne J. M. H. Hulscher. "Modelling the Wave Overtopping Flow over the Crest and the Landward Slope of Grass-Covered Flood Defences." Journal of Marine Science and Engineering 8, no. 7 (July 2, 2020): 489. http://dx.doi.org/10.3390/jmse8070489.

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The wave overtopping flow can exert high hydraulic loads on the grass cover of dikes leading to failure of the cover layer on the crest and the landward slope. Hydraulic variables such as the near bed velocity, pressure, shear stress and normal stress are important to describe the forces that may lead to cover erosion. This paper presents a numerical model in the open source software OpenFOAM® to simulate the overtopping flow on the grass-covered crest and slope of individual overtopping waves for a range of landward slope angles. The model provides insights on how the hydraulic forces change along the profile and how irregularities in the profile affect these forces. The effect of irregularities in the grass cover on the overtopping flow are captured in the Nikuradse roughness height calibrated in this study. The model was validated with two datasets of overtopping tests on existing grass-covered dikes in the Netherlands. The model results show good agreement with measurements of the flow velocity in the top layer of the wave, as well as the near bed velocity. The model application shows that the pressure, shear stress and normal stress are maximal at the wave front. High pressures occur at geometrical transitions such as the start and end of the dike crest and at the inner toe. The shear stress is maximal on the lower slope, and the normal stress is maximal halfway of the slope, making these locations vulnerable to cover failure due to high loads. The exact location of the maximum forces depends on the overtopping volume. Furthermore, the model shows that the maximum pressure and maximum normal stress are largely affected by the steepness of the landward slope, but the slope steepness only has a small effect on the maximum flow velocity and maximum shear stress compared to the overtopping volume. This new numerical model is a useful tool to determine the hydraulic forces along the profile to find vulnerable points for cover failure and improve the design of grass-covered flood defences.

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Kam, T. Y., J. H. Wu, and W. T. Wang. "External failure pressure of a frangible laminated composite canister cover." Composite Structures 47, no. 1-4 (December 1999): 563–69. http://dx.doi.org/10.1016/s0263-8223(00)00022-2.

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Pei, Hai-lin, Xue-yi Qi, Hui Li, Jian-hui Li, and Ze-yu Pei. "Fault Caused by Water Pressure in the Head-Cover Chamber." Journal of Hydrodynamics 18, no. 3 (June 2006): 280–86. http://dx.doi.org/10.1016/s1001-6058(06)60004-8.

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HASEGAWA, Shu, and Hirokazu TSUJI. "G0310403 Optimization of Threaded Cover Structure of the Pressure Vessel." Proceedings of Mechanical Engineering Congress, Japan 2014 (2014): _G0310403——_G0310403—. http://dx.doi.org/10.1299/jsmemecj.2014._g0310403-.

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Ferguson, Tanner J., Catherine G. Knier, Uttio Roy Chowdhury, Kjerseten J. Monson, Michael Greenwood, Russell J. Swan, Richard Gorham, John P. Berdahl, and Michael P. Fautsch. "Intraocular Pressure Measurement with Pneumatonometry and a Tonometer Tip Cover." Ophthalmology and Therapy 9, no. 1 (February 20, 2020): 127–37. http://dx.doi.org/10.1007/s40123-020-00235-z.

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Zeng, Wei, and Yi Jiang. "Failure Analysis of a Composite Frangible Cover Based on Transient Dynamics." Applied Mechanics and Materials 395-396 (September 2013): 55–59. http://dx.doi.org/10.4028/www.scientific.net/amm.395-396.55.

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The failure analysis of a fly through frangible canister cover is studied based on transient dynamics via the finite element method. The cover, which is fabricated with five plan-liked parts, is cohesively bonded together forming several weak paths. Five test specimens are designed according to the length of bonded fiber cloth. The cover is subjected to an impulsive blast and the failure process is obtained and analyzed. The failure pressure and time are determined at different cloth length. The result shows that the failure pressure and the corresponding time rise as the length of bonding layer increases.

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Van Hoven, Andre, Bianca Hardeman, Jentsje W. Van der Meer, and Gosse Jan Steendam. "SLIDING STABILITY OF LANDWARD SLOPE CLAY COVER LAYERS OF SEA DIKES SUBJECT TO WAVE OVERTOPPING." Coastal Engineering Proceedings 1, no. 32 (February 2, 2011): 5. http://dx.doi.org/10.9753/icce.v32.structures.5.

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Sea dikes with landward slopes covered by grass and clay cover layers, subject to wave overtopping, can become unstable and slide. Sliding stability of the cover layer is caused by a decrease in shear strength due to an increase in pore pressure in and underneath the clay cover layer. This holds for both clay dikes and sand dikes with a clay cover layer. A method is presented to determine the potential pore pressure build up due to a storm event with wave overtopping. The method combines of the shelf knowledge and is supported by laboratory measurements and field measurements during prototype scale wave overtopping tests and sliding test on Dutch sea dikes. The method contains three steps: 1) determine the infiltration time, depending on the storm duration and the sea state; 2) determine the infiltration capacity of the dike slope, either by choosing a safe value or field measurement and 3) determine the potential pore pressure build up, determined by step 1) and 2) and the dike structure and geometry. The potential pore pressure build up can be used in the standard stability analyses tools published in Dutch guidelines on dike design and dike safety assessment.

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Bunchek, Jess M., John M. Wallace, William S. Curran, David A. Mortensen, Mark J. VanGessel, and Barbara A. Scott. "Alternative performance targets for integrating cover crops as a proactive herbicide-resistance management tool." Weed Science 68, no. 5 (June 16, 2020): 534–44. http://dx.doi.org/10.1017/wsc.2020.49.

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AbstractIntensified cover-cropping practices are increasingly viewed as a herbicide-resistance management tool but clear distinction between reactive and proactive resistance management performance targets is needed. We evaluated two proactive performance targets for integrating cover-cropping tactics, including (1) facilitation of reduced herbicide inputs and (2) reduced herbicide selection pressure. We conducted corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] field experiments in Pennsylvania and Delaware using synthetic weed seedbanks of horseweed [Conyza canadensis (L.) Cronquist] and smooth pigweed (Amaranthus hybridus L.) to assess winter and summer annual population dynamics, respectively. The effect of alternative cover crops was evaluated across a range of herbicide inputs. Cover crop biomass production ranged from 2,000 to 8,500 kg ha−1 in corn and 3,000 to 5,500 kg ha−1 in soybean. Experimental results demonstrated that herbicide-based tactics were the primary drivers of total weed biomass production, with cover-cropping tactics providing an additive weed-suppression benefit. Substitution of cover crops for PRE or POST herbicide programs did not reduce total weed control levels or cash crop yields but did result in lower net returns due to higher input costs. Cover-cropping tactics significantly reduced C. canadensis populations in three of four cover crop treatments and decreased the number of large rosettes (>7.6-cm diameter) at the time of preplant herbicide exposure. Substitution of cover crops for PRE herbicides resulted in increased selection pressure on POST herbicides, but reduced the number of large individuals (>10 cm) at POST applications. Collectively, our findings suggest that cover crops can reduce the intensity of selection pressure on POST herbicides, but the magnitude of the effect varies based on weed life-history traits. Additional work is needed to describe proactive resistance management concepts and performance targets for integrating cover crops so producers can apply these concepts in site-specific, within-field management practices.

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Ng, C. W. W., and K. S. Wong. "Investigation of passive failure and deformation mechanisms due to tunnelling in clay." Canadian Geotechnical Journal 50, no. 4 (April 2013): 359–72. http://dx.doi.org/10.1139/cgj-2012-0098.

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It is essential to prevent failures at a tunnel face during tunnel construction to protect existing structures and underground utilities. Many studies have investigated active failure in clay, but passive failure is often overlooked. The objectives of this study are to investigate passive failure as well as surface heave and excess pore-water pressure induced by tunnel face displacement in a geotechnical centrifuge. Long-term settlement and dissipation of excess pore-water pressure after passive failure are also investigated. For a tunnel located at a cover to diameter ratio of 2.1, soil in front of the tunnel face is displaced mainly forwards and upwards to the ground surface by the advancing tunnel face. The measured passive failure pressure is closely bounded by the best upper and lower bounds and agrees reasonably well with the cavity expansion solution. For a tunnel located at a cover to diameter ratio of 4.2, a localized failure mechanism is observed. There is a large discrepancy between the measured passive failure pressure and the upper bound solution. Both longitudinal and transverse surface heaves for tunnels located at cover to diameter ratios of 2.1 and 4.2 may be described by two-dimensional Gaussian distributions. The spherical cavity expansion solution appears to overestimate excess pore-water pressure upon passive failure for a tunnel located at a cover to diameter ratio of 2.1. An average of 90% degree of consolidation is reached at time factors of 0.9 and 1.5 for tunnels located at cover to diameter ratios of 2.1 and 4.2, respectively.

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Walsh, Brice D., Angus F. MacKenzie, S. Salmins, and Deborah J. Buszard. "Impact of soil management systems on organic dwarf apple orchards and soil aggregate stability, bulk density, temperature and water content." Canadian Journal of Soil Science 76, no. 2 (May 1, 1996): 203–9. http://dx.doi.org/10.4141/cjss96-028.

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With growing pressure to reduce pesticide use, fruit growers require an alternative to herbicidal control of weeds. One option is the use of mulches or permanent vegetative ground covers, which in turn may have advantages in promoting soil physical properties and improving growth. This study examined the short-term effects of ground cover management in two newly established dwarf apple orchards in Quebec. Effects of cultivation, composted manure mulch, straw mulch, grass cover crops, a cover crop mixture of lupin and wild carrot (mixed flora) and geotextile were determined, comparing soil aggregate stability, bulk density, temperature, volumetric water content and tree growth. Straw and geotextile mulches resulted in higher soil water contents and tree growth relative to soil under grass or mixed flora ground cover. Ground cover maintained soil aggregate stability. Soil temperatures were highest under cultivation and geotextile treatments in spring and summer months, and apple yields and growth rates were greater than for ground cover treatments. Straw mulch buffered soil from temperature variation. Little effect of mulch treatments on soil bulk density was observed. Given that soil water content was the primary factor related to optimum orchard production straw and geotextile mulches promoted soil water retention and could be considered superior management options for growers, depending on costs of establishment and maintenance of the mulches. Key words: Mulches, ground cover, bulk density, aggregate stability, soil temperature, volumetric water content

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Chen, Shu Ping, Zheng Rong Zhang, and Jin Hua Yan. "The Patch Test of Numerical Manifold Schemes with Mixed Cover Coupled Velocity and Pressure for Steady N-S Equations." Advanced Materials Research 378-379 (October 2011): 68–71. http://dx.doi.org/10.4028/www.scientific.net/amr.378-379.68.

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In numerical manifold schemes for direct solution of steady Navier-Stokes equations, mixed cover for velocity and pressure was adopted in finite element cover system. The patch test of numerical schemes was investigated, mixed cover manifold element has been proved to meet the stability conditions, and can be applied to directly solve Navier-Stokes equations coupled velocity and pressure. As an application, the numerical manifold schemes were used to simulate the steady flow past a step. Numerical solutions illustrate the stability of numerical manifold schemes, and it indicates that manifold method is an effective numerical method for steady Navier-Stokes equations.

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T. L. Funk, R. Hussey, Y. Zhang, and M. Ellis. "SYNTHETIC COVERS FOR EMISSIONS CONTROL FROM EARTHEN EMBANKED SWINE LAGOONS PART I: POSITIVE PRESSURE LAGOON COVER." Applied Engineering in Agriculture 20, no. 2 (2004): 233–38. http://dx.doi.org/10.13031/2013.15889.

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T. L. Funk, A. Mutlu, Y. Zhang, and M. Ellis. "SYNTHETIC COVERS FOR EMISSIONS CONTROL FROM EARTHEN EMBANKED SWINE LAGOONS PART II: NEGATIVE PRESSURE LAGOON COVER." Applied Engineering in Agriculture 20, no. 2 (2004): 239–42. http://dx.doi.org/10.13031/2013.15890.

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Fonsêca, Nathan C., Giselle L. Moreira, José Nailson B. Santos, Marília Isabelle O. da Silva, Máida Cynthia D. de Lima, Ana Jéssica S. Barbosa, Jéssica Stéfane A. Cunha, Diogo José O. Pimentel, Flávio Cipriano de A. do Carmo, and Felipe S. Amorim. "Spatial-Temporal Dynamics of Vegetation Cover in a Diversity Hotspot for the Conservation of Brazilian Cerrado." Journal of Agricultural Science 11, no. 15 (September 15, 2019): 200. http://dx.doi.org/10.5539/jas.v11n15p200.

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This work investigates the spatial-temporal dynamics of land use and vegetation covers in a conservation area of Cerrado, in the county of Currais, Piauí, in which the economy depends on large agricultural projects. We used maps of a 32-year time series (1985 to 2017) of land use and cover provided by the Brazilian Annual Land Use and Land Cover Mapping Project (MapBiomas). We assessed six classes of land uses and vegetation covers: forest, savanna, grassland, agriculture/pasture, non-vegetated area, and water bodies. There was a fast increase in pressure on natural ecosystems from 1985 and 2017, primarily from 2000. The land use for agriculture and pasture increased from 0.26% (726.93 ha) in 2000 to 16% (50,772.63 ha) in 2017. During this period, the native vegetation decreased 15.90%, with savannas suffering the largest loss in hectares of vegetation (41,663.73 ha), followed by the forests (9,837.35 ha). The grassland cover, non-vegetated area, and water bodies remained unchanged. These results provide essential information for decision making and can be used to guide public policies for the conservation, monitoring, and sustainable management of remnant vegetation areas.

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Skidmore, Amanda, Neil Wilson, Mark Williams, and Ricardo Bessin. "The impact of tillage regime and row cover use on insect pests and yield in organic cucurbit production." Renewable Agriculture and Food Systems 34, no. 04 (October 26, 2017): 338–48. http://dx.doi.org/10.1017/s1742170517000503.

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AbstractControl of cucurbit pests, such as striped cucumber beetle (Acalymma vittatum), spotted cucumber beetle (Diabrotica undecimpunctata howardi) and squash bug (Anasa tristis), in organic systems is difficult due to a lack of effective insecticide options. This has led to the development of many integrated pest management techniques, such as use of row covers, crop rotation and cover crops. This study explored the novel use of strip tillage and row covers to reduce pest pressure in summer squash (Cucurbita pepe) and muskmelon (Cucumis melo) production systems. Results showed that although strip tillage reduced striped cucumber beetle and squash bug numbers, there was a yield reduction in both crops compared with the plasticulture system. Row cover increased marketable yield in both systems, with the highest yield being in the plasticulture system. Unmarketable fruit directly attributed to insect damage was higher in the plasticulture systems, but was not significantly different when compared with the strip tillage system. Although there are many documented positive attributes of strip tillage, results from this study indicate that a combination of plasticulture and row cover may be a superior system for organic cucurbit production.

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Adugna, Alemayehu, Assefa Abegaz, Asmamaw Legass, and Diogenes L. Antille. "RANDOM AND SYSTEMATIC LAND-COVER TRANSITIONS IN NORTH-EASTERN WOLLEGA, ETHIOPIA." BOIS & FORETS DES TROPIQUES 332 (September 18, 2017): 3–15. http://dx.doi.org/10.19182/bft2017.332.a31329.

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Africa has seen significant changes in land cover at different spatial scales. Changes in Land Use and Land Cover (LULC) include deforestation and subse- quent use of the land for arable cropping, conversion to grassland or urbanization. The work reported in this article was conducted to examine land cover transi- tions in north-eastern Wollega (Ethiopia) between 2005 and 2015. The analysis focused on land cover transitions that occurred systematically or randomly, and identified the main drivers for these changes. Landsat data from 2005 and 2015 were examined to better unders- tand the various dimensions of land cover transitions, namely: swaps, losses, gains, persistency and vulnerability. Results showed that shrubland exhibited the largest gain (22%), with a 63% gain- to-loss ratio, a 47% gain-to-persistence ratio and a positive net change-to-persis- tence ratio of 46%. Cropland showed the largest loss (19%) while grassland was the most stable type of land cover des- pite some fluctuation (»10%) observed during the 10-year period. The land cover transition was dominated by systematic processes, with few random processes of change. Systematic land cover transitions such as agricultural abandonment and vegetation re-growth were attributed to regular or common processes of change. This study suggests that the implementa- tion of practices conducive to sustainable intensification of existing agricultural land, supported by policies that promote increased diversification of Ethiopian agriculture, would mitigate pressure on forests by avoiding their future conver- sion to cropland.

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Hashad, Ahmed Salama, Wladimir Sabuga, Sven Ehlers, and Thomas Bock. "Validation of a PTB force-balanced piston gauge primary pressure standard." ACTA IMEKO 10, no. 1 (March 31, 2021): 271. http://dx.doi.org/10.21014/acta_imeko.v10i1.821.

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Experimental methods using different pressure standards were applied to verify theoretical results obtained for the effective area of the piston-cylinder assembly (PCA) and for pressures measured with a force-balanced piston gauge (FPG). The theoretical effective area was based on the PCA’s dimensional properties defined via diameter, straightness and roundness measurements of the piston and cylinder, derived by gas-flow modelling using principles of the rarefied gas dynamics, and presented as two values: one obtained for absolute and the other for gauge pressure operation mode. Both values have a relative standard uncertainty of 5×10<sup>-6</sup>. The experimental methods chosen were designed to cover the entire operating pressure range of the FPG from 3 Pa to 15 kPa. Comparisons of the FPG with three different PTB pressure standards operated in different pressure ranges – a pressure balance, a mercury manometer and a static expansion system – were performed using the cross-float method and by a direct comparison of the generated pressures. For the theoretical and experimental effective area, as well as for pressures generated by the FPG and the reference standards, all the results demonstrated full agreement within the expanded uncertainties of the standards.

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Journal articles on the topic 'Pressure cover'

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