Статті в журналах: "Low Pressure Systeams"

1

Mostafa, H., and H. H. Thörmann. "On-farm evaluation of low-pressure drip irrigation system for smallholders." Soil and Water Research 8, No. 2 (May 15, 2013): 87–95. http://dx.doi.org/10.17221/29/2012-swr.

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The aim of this paper was to evaluate the performance of a low-pressure drip system (LPS) for three years of service, to calculate the consumptive working time and costs of maintenance and laterals retrieving before harvesting and to determine benefits and problems with drip irrigation. Drip irrigation provides the opportunity to save water and the potential to increase net income by applying water at the right quantity and at the right time. Small to medium fields would benefit from the LPS irrigation system which has the ability to distribute the amount of water applied. LPS is a well-researched system for drip irrigation, typically that available for furrow irrigated crops. There are significant agronomic advantages of using a low-pressure, low-flow drip system. These advantages translate into measured improved distribution uniformity when compared to flood irrigated crops and energy savings compared to flood and sprinkler irrigated crops. The old (reused) drip line leads to a decrease in distribution uniformity and an increase in costs, when the distribution uniformity decreased by 10.5 and 21.6% for reusing the laterals in the second and third year, respectively. Moreover, the cost of repairing laterals was more than 5 and 6.5 times higher for both the 2<sup>nd</sup> and 3<sup>rd</sup> season. Many disadvantages of drip lines retrieval can be observed, because labour and maintenance are more intensive; there is a risk of mechanical damage to laterals especially if they are reused; increased management skills and experience are needed; and increased retrieval costs arise season after season.

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2

Lappegard, Gaute, and Jack Kohler. "Determination of basal hydraulic systems based on subglacial high-pressure pump experiments." Annals of Glaciology 40 (2005): 37–42. http://dx.doi.org/10.3189/172756405781813681.

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AbstractWe have conducted short-term pump experiments with pump pressures exceeding ice overburden to study the seasonality of the subglacial hydraulic system of Engabreen, Norway. Data were collected from load cells installed flush with the ice–bedrock interface and pressure transducers installed in boreholes leading from bedrock tunnels underneath the glacier to the ice–bedrock interface. The water-pressure recordings, seen in relation with the load-cell record, show the existence of hydraulically connected vs unconnected bed areas. Monitored boreholes have been used to inject water at high pressures. Each experiment led to the growth of a high-pressure water cavity whose spatial extent could be inferred from load-cell and pressure transducer records. Post-pump pressures were low after summer pump tests and close to ice-overburden level after winter pump experiments. We conclude that drainage takes place in a fast-flow, low-pressure, channel-based drainage system during summer, and a low-flow, high-pressure, linked-cavity drainage system during winter.

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3

Marzec, Krzysztof. "Low-Pressure Turbine Cooling Systems." Encyclopedia 1, no. 3 (August 31, 2021): 893–904. http://dx.doi.org/10.3390/encyclopedia1030068.

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Modern low-pressure turbine engines are equipped with casings impingement cooling systems. Those systems (called Active Clearance Control) are composed of an array of air nozzles, which are directed to strike turbine casing to absorb generated heat. As a result, the casing starts to shrink, reducing the radial gap between the sealing and rotating tip of the blade. Cooling air is delivered to the nozzles through distribution channels and collector boxes, which are connected to the main air supply duct. The application of low-pressure turbine cooling systems increases its efficiency and reduces engine fuel consumption.

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4

Lee, Juneseok, Vinod K. Lohani, Andrea M. Dietrich, and G. V. Loganathan. "Hydraulic transients in plumbing systems." Water Supply 12, no. 5 (August 1, 2012): 619–29. http://dx.doi.org/10.2166/ws.2012.036.

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This study addresses the issue of pressure transients triggered within premise plumbing or a municipal water distribution system and their potential impact on drinking water service lines and plumbing systems. An instrumented experimental plumbing system was designed to examine the effects of a range of pressures commonly encountered in household plumbing systems. A transient triggered from within the household plumbing system structurally taxed the experimental service line and vertical plumbing sections but did not result in negative pressures. Taken together, these experimental results and observations of gaseous cavitation phenomenon with a high definition video camera demonstrated that a hydraulic transient triggered from a water main resulted in extremely low pressures events (up to −68.95 kpa) in the service line. This low pressure would be sufficient to allow the possible intrusion of microbial and chemical contaminants into the service lines. Homeowners and water utilities should be made aware of the importance of maintaining the structural integrity of their pipe systems and protecting the hydraulic integrity of water systems.

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5

Baum, Heiko, Stefan Eibl, and Jürgen Merk. "Pressure Oscillation Analysis in Low-pressure Fuel Piping Systems." MTZ worldwide 78, no. 10 (September 15, 2017): 60–65. http://dx.doi.org/10.1007/s38313-017-0096-8.

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6

Horton, Donald, and Michael Pollay. "Fluid flow performance of a new siphon-control device for ventricular shunts." Journal of Neurosurgery 72, no. 6 (June 1990): 926–32. http://dx.doi.org/10.3171/jns.1990.72.6.0926.

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✓ Most available cerebrospinal fluid diversion systems utilize differential-pressure valves that often induce overshunting, resulting in complications due to the siphoning of fluid from the ventricular system when the patient is in the erect position. A new siphon-control device (SCD) was tested alone and in combination with four types of differential-pressure valves with low, medium, and high opening pressures (namely PS Medical, Heyer-Schulte, Cordis-Hakim, and Codman valves). The valve inlet and outlet pressures were measured at several fluid inflow rates between 2.0 and 50.0 ml/hr. Inlet pressure and valve resistance were determined when the outlet pressures of the differential-pressure valve or SCD were varied between 0 and −60 cm H2O. Of the differential-pressures valves tested, none provided protection against siphoning without the distal connection of the SCD. The SCD allowed all differential-pressure valves tested to maintain atmospheric pressure regardless of the outlet pressure. The SCD performs in a manner similar to the older anti-siphon device, but with some improvements in design and construction. The results of this investigation suggest that the increased resistance due to the inline SCD is not functionally significant when added to the conventional valve systems with low opening pressure.

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7

GÜRBÜZ, Muhammet Tayyip, and Sercan ACARER. "Değişken Çevrimli Mikro Turbofan Jet Motoru için Bütünleşik Düşük Basınç Kompresor Sisteminin Aerodinamik Analizleri." Deu Muhendislik Fakultesi Fen ve Muhendislik 24, no. 72 (September 19, 2022): 939–51. http://dx.doi.org/10.21205/deufmd.2022247222.

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Unmanned Aerial Vehicles (UAVs) are commonly propeller-driven and low-speed. The concept of cost-efficient, much higher speed and longer range applications of micro jet engines was previously addressed such that an existing basic turbojet engine was converted into a single spool turbofan without using additional components of booster and low pressure turbine. Normally, this situation emerges matching problems since two spools are required to adjust the fan speed independently. A simple solution was to use a Continuously Variable Transmission (CVT) gearbox to adjust optimal speed for the fan. As a result, missing of the positive functionality of the booster would lump into the fan root to form a unified low pressure compression system (unified-LPC). Such a unified-LPC demands unique characteristics of having an extreme twist, very high pressure ratio and mass flux at the root section than at the tip section, despite the exact opposite is being enforced due to the wheel speed rise with radius. In light of these challenges, this work aims to investigate detailed aerodynamics of an existing design previously made and reported by the authors. It is shown that, despite the aerodynamic loading contrast throughout the span, the unified-LPC can still have a wide operating range and acceptable off-design aerodynamics. Complementing the previous design-oriented work, this paper aims to provide guidelines for such unified compression systems.

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8

Tarasenko V.F., Baksht E. Kh., Vinogradov N. P., and Sorokin D.A. "Emission spectra of low-pressure air during a diffuse streamer discharge." Optics and Spectroscopy 130, no. 12 (2022): 1499. http://dx.doi.org/10.21883/eos.2022.12.55234.4014-22.

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Attention to the study of the radiation characteristics of streamer discharges in atmospheric air at pressures of a fraction of a Torr unit is primarily associated with obtaining new data on high-altitude discharges, including red sprites. This paper presents the results of studying the characteristics of the radiation of a streamer discharge in low-pressure air upon initiation of ionization waves (streamers) by a repetitively pulsed barrier discharge. It has been established that at air pressures of Delta p=0.08-3 Torr, the lines of the second positive, first negative, and first positive nitrogen systems have the highest intensities in the wavelength range of Deltaλ=280-900 nm, and their contribution to the spectral radiation energy density depends on the discharge region and pressure. The emission bands of the first positive nitrogen system give the red color of the ionization waves, however, the highest intensities under these conditions are recorded on the lines of the second positive and first negative nitrogen systems. It is shown that when the pressure decreases to 0.04 Torr or less, the spectrum and color of the streamer discharge, while maintaining the amplitude of the voltage pulses, changes significantly. New lines and bands appear in it, including intense lines of atomic hydrogen, which is due to an increase in the reduced electric field strength, respectively, in the electron temperature. This leads to the dissociation of molecular gases that are part of the air, as well as those adsorbed by the chamber walls. Keywords: emission spectra, streamer discharge, air, low pressures.

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9

Kim, Jeonghwan, and Francis A. DiGiano. "Fouling models for low-pressure membrane systems." Separation and Purification Technology 68, no. 3 (August 2009): 293–304. http://dx.doi.org/10.1016/j.seppur.2009.05.018.

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10

Singh, Vikram, Butch Berney, and Anantha Krishnan. "Designing low pressure systems with continuum models." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 14, no. 3 (May 1996): 1252–57. http://dx.doi.org/10.1116/1.579937.

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11

Zhang, Xinjie, and Ayobami Elisha Oseyemi. "Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery." Micromachines 10, no. 12 (November 21, 2019): 798. http://dx.doi.org/10.3390/mi10120798.

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The microvalve for accurate flow control under low fluidic pressure is vital in cost-effective and miniaturized microfluidic devices. This paper proposes a novel microfluidic passive valve comprising of a liquid chamber, an elastic membrane, and an ellipsoidal control chamber, which actualizes a high flow rate control under an ultra-low threshold pressure. A prototype of the microvalve was fabricated by 3D printing and UV laser-cutting technologies and was tested under static and time-dependent pressure conditions. The prototype microvalve showed a nearly constant flow rate of 4.03 mL/min, with a variation of ~4.22% under the inlet liquid pressures varied from 6 kPa to 12 kPa. In addition, the microvalve could stabilize the flow rate of liquid under the time-varying sinusoidal pressures or the square wave pressures. To validate the functionality of the microvalve, the prototype microvalve was applied in a gas-driven flow system which employed an air blower or human mouth blowing as the low-cost gas source. The microvalve was demonstrated to successfully regulate the steady flow delivery in the system under the low driving pressures produced by the above gas sources. We believe that this new microfluidic passive valve will be suitable for controlling fluid flow in portable microfluidic devices or systems of wider applications.

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12

He, Chuanjiu, Fred T. Davies, and Ronald Lacey. "(305) Influence of Hypobaria on Gas Exchange and Growth of Lettuce for Advanced Life Support Systems (ALS)." HortScience 40, no. 4 (July 2005): 1011B—1011. http://dx.doi.org/10.21273/hortsci.40.4.1011b.

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There are advantages in growing plants under hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or space-flight environments. Elevated levels of the plant hormone ethylene occur in enclosed crop production systems and in space-flight environments—leading to adverse plant growth and sterility. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa L. cv. Buttercrunch). Growth was comparable in lettuce grown under low (25 kPa) and ambient (101 kPa) total gas pressures. However, tip burn occurred under ambient, but not low pressure—in part because of adverse ethylene levels. Under ambient pressure, there were higher CO2 assimilation rates and dark respiration rates (higher night consumption of metabolites) compared to low pressure. This could lead to greater growth (biomass production) of low pressure plants during longer crop production cycles.

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13

de Jonge, Niels, Elisabeth A. Ring, Wilbur C. Bigelow, and Gabriel M. Veith. "Low-Cost, Atmospheric-Pressure Scanning Transmission Electron Microscopy." Microscopy Today 19, no. 3 (April 28, 2011): 16–20. http://dx.doi.org/10.1017/s1551929511000228.

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Solid materials in subambient gaseous environments have been imaged using in situ transmission electron microscopy (TEM), for example to study dynamic effects: carbon nanotube growth, nanoparticle changes during redox reactions, and phase transitions in nanoscale systems. In these studies the vacuum level in the specimen region of the electron microscope was increased to pressures of up to 10 mbar using pump-limiting apertures that separated the specimen region from the rest of the high-vacuum electron column, but it has not been possible to achieve the higher pressures that are desirable for catalysis research. TEM imaging at atmospheric pressure and at elevated temperature was achieved with 0.2-nm resolution by enclosing a gaseous environment several micrometers thick between ultra-thin, electron transparent silicon nitride windows. Although Ångström-level resolution in situ TEM has been demonstrated with aberration-corrected systems, the key difficulty with TEM imaging is its dependence on phase contrast, which requires ultra-thin specimens, limiting the choice of experiments.

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14

Nerodenko, D. G., and A. V. Moroz. "USE OF GAS EJECTORS IN THE WELLS HOOKUP AND IN THE PROCESS LINES AT GAS COLLECTING SYSTEMS." Oil and Gas Studies, no. 3 (June 30, 2015): 71–77. http://dx.doi.org/10.31660/0445-0108-2015-3-71-77.

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A solution is provided for enhancing the efficiency of using the developed formations energy within one cluster of wells having different reservoir pressures which implies a calculation and further application of gas ejector. The method offered enables not only to improve the performance of low pressure wells, but also helps to extend the life of wells being out of operating because of low wellhead pressure.

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15

Yamashita, Akira, Hisashi Ohki, Koichiro Nakatani, and Terutoshi Tomoda. "OS2-7 Recirculation control logic for Diesel Low Pressure Loop EGR System(OS2 EGR combustion,Organized Session Papers)." Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines 2012.8 (2012): 110–15. http://dx.doi.org/10.1299/jmsesdm.2012.8.110.

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16

Yuan, Chenggang, Vinrea Lim Mao Lung, Andrew Plummer, and Min Pan. "Theoretical and Experimental Studies of a Digital Flow Booster Operating at High Pressures and Flow Rates." Processes 8, no. 2 (February 10, 2020): 211. http://dx.doi.org/10.3390/pr8020211.

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The switched inertance hydraulic converter (SIHC) is a new technology providing an alternative to conventional proportional or servo-valve-controlled systems in the area of fluid power. SIHCs can adjust or control flow and pressure by means of using digital control signals that do not rely on throttling the flow and dissipation of power, and provide hydraulic systems with high-energy efficiency, flexible control, and insensitivity to contamination. In this article, the analytical models of an SIHC in a three-port flow-booster configuration were used and validated at high operating pressure, with the low- and high-pressure supplies of 30 and 90 bar and a high delivery flow rate of 21 L/min. The system dynamics, flow responses, and power consumption were investigated and theoretically and experimentally validated. Results were compared to previous results achieved using low operating pressures, where low- and high-pressure supplies were 20 and 30 bar, and the delivery flow rate was 7 L/min. We concluded that the analytical models could effectively predict SIHC performance, and higher operating pressures and flow rates could result in system uncertainties that need to be understood well. As high operating pressure or flow rate is a common requirement in hydraulic systems, this constitutes an important contribution to the development of newly switched inertance hydraulic converters and the improvement of fluid-power energy efficiency.

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17

Speer, Milton, Lance Leslie, Joshua Hartigan, and Shev MacNamara. "Changes in Frequency and Location of East Coast Low Pressure Systems Affecting Southeast Australia." Climate 9, no. 3 (March 5, 2021): 44. http://dx.doi.org/10.3390/cli9030044.

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Low pressure systems off the southeast coast of Australia can generate intense rainfall and associated flooding, destructive winds, and coastal erosion, particularly during the cool season (April–September). Impacts depend on coastal proximity, strength and latitude. Therefore, it is important to investigate changes in frequency, duration, location, and intensity of these systems. First, an existing observation-based database of these low pressure systems, for 1970–2006, is extended to 2019, focusing on April–September and using archived Australian Bureau of Meteorology MSLP charts. Second, data consistency between 1970 and 2006 and 2007 and 2019 is confirmed. Third, permutation testing is performed on differences in means and variances between the two 25-year intervals 1970–1994 and 1995–2019. Additionally, trends in positions, durations and central pressures of the systems are investigated. p-values from permutation tests reveal statistically significant increases in mean low pressure system frequencies. Specifically, a greater frequency of both total days and initial development days only, occurred in the latter period. Statistically significant lower variance for both latitude and longitude in systems that developed in both subtropical easterly and mid-latitude westerly wind regimes indicate a shift south and east in the latter period. Furthermore, statistically significant differences in variance of development location of explosive low pressure systems that develop in a low level easterly wind regime indicate a shift further south and east. These changes are consistent with fewer systems projected to impact the east coast. Finally, important changes are suggested in the large scale atmospheric dynamics of the eastern Australian/Tasman Sea region.

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18

Yang, Jian, Mark W. LeChevallier, Peter F. M. Teunis, and Minhua Xu. "Managing risks from virus intrusion into water distribution systems due to pressure transients." Journal of Water and Health 9, no. 2 (April 18, 2011): 291–305. http://dx.doi.org/10.2166/wh.2011.102.

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Low or negative pressure transients in water distribution systems, caused by unexpected events (e.g. power outages) or routine operation/maintenance activities, are usually brief and thus are rarely monitored or alarmed. Previous studies have shown connections between negative pressure events in water distribution systems and potential public health consequences. Using a quantitative microbial risk assessment (QMRA) model previously developed, various factors driving the risk of viral infection from intrusion were evaluated, including virus concentrations external to the distribution system, maintenance of a disinfectant residual, leak orifice sizes, the duration and the number of nodes drawing negative pressures. The most sensitive factors were the duration and the number of nodes drawing negative pressures, indicating that mitigation practices should be targeted to alleviate the severity of low/negative pressure transients. Maintaining a free chlorine residual of 0.2 mg/L or above is the last defense against the risk of viral infection due to negative pressure transients. Maintaining a chloramine residual did not appear to significantly reduce the risk. The effectiveness of ensuring separation distances from sewer mains to reduce the risk of infection may be system-specific. Leak detection/repair and cross-connection control should be prioritized in areas vulnerable to negative pressure transients.

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19

Kardong, Kenneth V., and Pablo A. Lavin-Murcio. "Venom Delivery of Snakes as High-Pressure and Low-Pressure Systems." Copeia 1993, no. 3 (August 18, 1993): 644. http://dx.doi.org/10.2307/1447225.

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20

Strijdom, Louis, Vanessa Speight, and Heinz Erasmus Jacobs. "An assessment of sub-standard water pressure in South African potable distribution systems." Journal of Water, Sanitation and Hygiene for Development 7, no. 4 (October 3, 2017): 557–67. http://dx.doi.org/10.2166/washdev.2017.227.

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Abstract Sub-standard residual water pressures in urban water distribution systems (WDS) are a prevalent phenomenon in developing countries – South Africa being no exception. The phenomenon of sub-standard pressure is poorly understood, with intermittent supply ultimately resulting when there is no residual pressure left in the system. This research addressed the prevalence and extent of sub-standard pressures by using hydraulic models of potable WDS for 71 South African towns, located in 17 different South African municipalities geographically spread over the country. The hydraulic models included 539,388 modelled nodes, which were analysed to determine the number of nodes with sub-standard pressure heads during peak hour flow conditions. The results show that the residual pressure head was <24 m at 16.5% of the model nodes under peak hour flow conditions, with 6.7% of the nodes having pressure heads <12 m. In contrast, the results also report relatively high pressures in certain parts of the systems, far in excess of the minimum requirement, underlining the need for better pressure management at both high and low ranges. It was also noted that the South African design criterion is relatively stringent compared with some other countries and could potentially be relaxed in future.

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21

Heenan, Megan, Jose D. Rojas, Z. Maria Oden, and Rebecca Richards-Kortum. "In vitro comparison of performance including imposed work of breathing of CPAP systems used in low-resource settings." PLOS ONE 15, no. 12 (December 3, 2020): e0242590. http://dx.doi.org/10.1371/journal.pone.0242590.

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Respiratory distress due to preterm birth is a significant cause of death in low-resource settings. The introduction of continuous positive airway pressure (CPAP) systems to treat respiratory distress significantly reduced mortality in high-resource settings, but CPAP was only recently introduced in low-resource settings due to cost and infrastructure limitations. We evaluated pressure stability and imposed work of breathing (iWOB) of five CPAP systems used in low resource settings: the Fisher and Paykel bubble CPAP, the Diamedica baby CPAP, the Medijet nCPAP generator, and the first (2015) and second (2017) generation commercially available Pumani CPAPs. Pressure changes due to fresh gas flow were evaluated for each system by examining the relationship between flow and pressure at the patient interface for four pressures generated at the bottle (0, 3, 5, and 7 cm H2O); for the Medijet nCPAP generator, no bottle was used. The slope of the resulting relationship was used to calculate system resistance. Poiseuille’s law of resistance was used to investigate significant contributors to resistance. Resistance ranged from 0.05 to 1.40 cmH2OL/min; three CPAP devices had resistances < 0.4 cmH2OL/min: the Fisher and Paykel system, the Diamedica system, and the second generation Pumani bubble CPAP. The other two systems, the Medijet nCPAP generator and the first generation Pumani bCPAP, had resistances >1.0 cmH2OL/min. Imposed WOB was measured using an ASL5000 test lung to simulate the breath cycle for an infant (5.5 kg), a term neonate (4.0 kg), and a preterm neonate (2.5 kg). Imposed WOB ranged from 1.4 to 39.5 mJ/breath across all systems and simulated infant sizes. Changes in pressure generated by fresh gas flow, resistance, and iWOB differ between the five systems evaluated under ideal laboratory conditions. The available literature does not indicate that these differences affect clinical outcomes.

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22

AALTONEN, Jussi, Kari KOSKINEN, Matti VILENIUS, and Pekka KUNTTU. "EXPERIENCES ON THE LOW PRESSURE WATER HYDRAULIC SYSTEMS." Proceedings of the JFPS International Symposium on Fluid Power 1999, no. 4 (1999): 357–63. http://dx.doi.org/10.5739/isfp.1999.357.

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23

Klemm, David L. "Low Pressure Sanitary Sewer Systems – A Case Study." Proceedings of the Water Environment Federation 2010, no. 14 (January 1, 2010): 2889–910. http://dx.doi.org/10.2175/193864710798170874.

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Shkarovskiy, Alexander, and Maciej Kotuła. "ACCIDENT ANALYSIS OF LOW PRESSURE GAS DISTRIBUTION SYSTEMS." Architecture and Engineering 3, no. 4 (December 28, 2018): 42–48. http://dx.doi.org/10.23968/2500-0055-2018-3-4-42-48.

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25

Wilson, Emma L., and Wendy A. Brown. "Low Pressure RAIRS Studies of Model Catalytic Systems." Journal of Physical Chemistry C 114, no. 15 (March 18, 2010): 6879–93. http://dx.doi.org/10.1021/jp912080t.

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26

Hurley, John V., and William R. Boos. "A global climatology of monsoon low-pressure systems." Quarterly Journal of the Royal Meteorological Society 141, no. 689 (October 28, 2014): 1049–64. http://dx.doi.org/10.1002/qj.2447.

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27

Lappegard, Gaute, Jack Kohler, Miriam Jackson, and Jon Ove Hagen. "Characteristics of subglacial drainage systems deduced from load-cell measurements." Journal of Glaciology 52, no. 176 (2006): 137–48. http://dx.doi.org/10.3189/172756506781828908.

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AbstractRock tunnels beneath Engabreen, northern Norway, permit access to the ice-bedrock interface beneath a 210 m thick glacier. Eight load cells have been installed in the bedrock of the glacier sole along a 22 m transect. With some interruptions, the load cells have been logged at 15 min intervals since December 1992; here we analyse the records until 2003. Load-cell signals measure stresses acting normal to the bedrock, and usually log the pressure of the thin water film between the basal ice and the bed. Occasionally there are distinct pressure events, characterized by short-lived (hours) local minima, often followed by a maximum before decaying to background load-cell pressure. The amplitudes of these pressure events are of the order of 0.01–1 MPa and depend on the placement of the sensor and the state of the subglacial drainage system. We identify winter and summer pressure regimes. The winter regime is characterized by few pressure events of large pressure amplitude influencing all load cells. A lag of 0–6 days is observed between surface forcing (rain) and pressure events during winter. The summer regime typically has periods of daily pressure events of low amplitude. No delay is seen between surface forcing and pressure events during the summer regime. In summer, the onset of a pressure event is correlated with a local maximum of the derivative of the subglacial discharge record, whereas no such relation is found during the winter regime. The transition from winter to summer (May/June) is easily detectable and is strongly correlated with a rapid increase in subglacial discharge and the transition to a dominating R-channel system. The autumn transition is less clearly defined, but has usually occurred by the beginning of November. Stress bridging, an increase in bed pressure at the edge of low-pressure channels, is recorded during the summer regime. Water pressures at the bed are connected or unconnected to the drainage system. Pressure increases in the connected system, beyond local normal stress values, lead to an uplift of the connected system and a pressure drop in the unconnected system. The occurrence of pressure events is determined by the capacity of the drainage system. Uplift is controlled by local normal stress values and not mean ice-overburden pressure.

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Parkinson, J. S., and R. J. Wynne. "Systems Modelling and Control Applied to a Low-Pressure Gas Distribution Network." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 206, no. 1 (February 1992): 35–44. http://dx.doi.org/10.1243/pime_proc_1992_206_196_02.

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A control system has been designed and implemented to provide more effective energy management of low-pressure gas distribution networks. The key to this is the provision of a control scheme that maintains low pressures across a network. The work was approached from first principles and a modelling technique has been developed which provides reduced order models that adequately describe the characteristics of multi-feed gas networks. The models were then used for the control system design, which in this case also included the selection of the optimal measurement points for most effective control. Following extensive design studies a relatively straightforward control scheme resulted which has been implemented and proved to be effective.

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WANG, Z., Y. GONG, X. H. WU, W. H. ZHANG, and Y. L. LU. "THERMODYNAMIC ANALYSIS AND EXPERIMENTAL RESEARCH OF TRANSCRITICAL CO2 CYCLE WITH INTERNAL HEAT EXCHANGER AND DUAL EXPANSION." International Journal of Air-Conditioning and Refrigeration 21, no. 01 (March 2013): 1350005. http://dx.doi.org/10.1142/s2010132513500053.

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This work presents the experimental evaluation of the energy performance of transcritical CO2 refrigeration and heat pump systems. The optimal gas cooler pressures and the optimal COP have been analyzed from a thermodynamic point of view. The systems used a new dual expansion valve and a balance CO2 liquid receiver adjustment device, which can control high and low side pressure effectively. Moreover, we demonstrate the influence of the internal heat exchanger (IHX) on the systems' performances, on the basis of the analysis of the relative COP index RCOPI, the compressor power index RPCI and other parameters which can confirm the truth of. The experimental evaluation covers five evaporating levels (-10 to 10°C) and in a wide range of gas cooler pressures (75 to 120 bar). It is concluded that with the IHX system, compressor power is relatively low when the high side pressure is over 100 bar, and the evaporation temperature is below 0°C. The COP of the system without the IHX is slightly higher than the system with the IHX; it is increasing about 3% to 5%, when the evaporation temperature is over 5°C. Relative to the single expansion process, the dual expansion cycle can decrease the influence of pressure fluctuations of CO2 supercritical fluid and liquid mixture on the systems.

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30

Feng, Guobao, Yun Li, Xiaojun Li, Heng Zhang, and Lu Liu. "Characteristics of electron evolution during initial low-pressure discharge stage upon microwave circuits." AIP Advances 12, no. 11 (November 1, 2022): 115129. http://dx.doi.org/10.1063/5.0130735.

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High-power microwave-induced low-pressure discharges seriously threaten the reliability of space payload systems. Under extremely low-pressure conditions, the evolution of ionized and secondary electrons at the initial stage of discharge is crucial to figure out the discharge process. Therefore, this paper investigates the development of multiple electrons in the discharge process under a highly low-pressure environment using numerical simulation. A three-dimensional simulation model based on the Monte Carlo algorithm is established by considering various electron-gas collisions and secondary electron emissions from different material surfaces. The evolution characteristics of various electrons' populations, energy, and distribution patterns during the discharge process are analyzed. In addition, the influence of the critical conditions at different air pressures on the electron evolution during the discharge process and the intrinsic causes are also investigated. This study is significant in revealing the transition characteristics between multipactor and low-pressure discharge and exploring their inherent mechanisms.

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31

Li, S., and D. H. Willits. "Comparing low-pressure and high-pressure fogging systems in naturally ventilated greenhouses." Biosystems Engineering 101, no. 1 (September 2008): 69–77. http://dx.doi.org/10.1016/j.biosystemseng.2008.06.004.

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32

Jones, Trevor, Virginia Osterman, and Donald Jordan. "Copper Evaporation During Low Pressure Carburization." AM&P Technical Articles 176, no. 2 (February 1, 2018): 63–64. http://dx.doi.org/10.31399/asm.amp.2018-02.p063.

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Abstract Stringent pressure control and gas species type both play an important role in minimizing the evaporation rate of not only copper, but other elements susceptible to evaporation in vacuum systems. The article describes a study investigating the effect of temperature, pressure, and carrier gas species on the amount of copper evaporation that occurs from copper foil test samples in low pressure carburizing.

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Sokol, Julia, Susan Amrose, Vinay Nangia, Samer Talozi, Elizabeth Brownell, Gianni Montanaro, Khaled Abu Naser, et al. "Energy Reduction and Uniformity of Low-Pressure Online Drip Irrigation Emitters in Field Tests." Water 11, no. 6 (June 7, 2019): 1195. http://dx.doi.org/10.3390/w11061195.

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A promising way of addressing the issue of growing water scarcity is through wider use of drip irrigation, which delivers water and fertilizer to crops in a slow, targeted manner, and has been shown to increase yields and water use efficiency. Yet, drip irrigation system adoption is low, primarily due to the high capital cost of the pressurized piping network and the pump, and operating energy cost. Lowering the water pressure needed for drip emitters to deliver water can reduce both capital and operating costs of drip systems. Here we present the results from field trials of new pressure-compensating online drip emitters that operate with a minimum compensating inlet pressure of 15 kPa (0.15 bar), in comparison to typical commercial emitters with minimum pressures of 50–100 kPa (0.5–1.0 bar). The field trials were carried out on nine farms in Morocco and Jordan over the course of one irrigation season with freshwater and treated wastewater. Low-pressure emitters are shown to reduce hydraulic energy per unit volume of water delivered by 43% on average compared to commercial emitters, without significantly sacrificing water emission uniformity (low-pressure emitters show uniformities of 81–91%, compared to 87–96% for commercial emitters). This energy reduction could lead to savings of 22–31% in the capital cost of a pump and emitters and the energy cost for a typical drip irrigation system. Thus, the low-pressure online emitters can be used as substitutes to commercial emitters that require higher water pressures, leading to reduced environmental impact and lower system costs.

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34

Pearson, Robert, Shona Mackenzie, Lyle Burke, and Keith Reimer. "Planning and optimisation of large, complex, low pressure gas and water gathering systems." APPEA Journal 50, no. 2 (2010): 683. http://dx.doi.org/10.1071/aj09047.

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Modelling low pressure gas gathering systems for unconventional gas (UCG) and coal seam gas (CSG) or coal bed methane (CBM) developments is challenged by: the sensitivity of well performance to system back-pressure; statistical uncertainties over well performance and areal variability in pay quality; the rapid build-up of friction with gas velocity; the rate of conversion from planning assumptions to real data on wells and lines; commissioning and initial well test reliability issues; modelling transient well performance using steady state solutions; unpredictable peak rates and rapid initial declines from those peak rates; well interference effects; large development areas with multiple gathering stations; line looping and bi-directional lines required to accommodate compressor outages; and, new gas treatment and transmission facilities being added onto existing system during development drilling operations. Moreover, many of these systems have multiple gas delivery points at different delivery pressures. Similarly, low pressure water gathering, storage, processing and delivery systems involve features that are not common in conventional water injection or salt water disposal networks, such as: large numbers of wells tied-in using lines with very low pressure ratings; water storage ponds or tanks that may involve evaporation losses; gravity feed or back-flow during intermittent pumping; infield modifications to accommodate overload situations that had not gone through a formal design change process; and, intermittent transfer operations to take advantage of reduced power costs during the night, or to avoid peak demand penalties. This paper will look at two case histories from North America that had to address many of these problems. The objective is to capture lessons learned to assist in the challenges that we are currently facing in ramping-up CSG production in eastern Australia.

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35

Wünderlich, Dirk, Rudi Riedl, Markus Fröschle, Ursel Fantz, and Bernd Heinemann. "Operation of Large RF Driven Negative Ion Sources for Fusion at Pressures below 0.3 Pa." Plasma 4, no. 1 (March 9, 2021): 172–82. http://dx.doi.org/10.3390/plasma4010010.

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The large (size: 1 m × 2 m) radio frequency (RF) driven negative ion sources for the neutral beam heating (NBI) systems of the future fusion experiment ITER will be operated at a low filling pressure of 0.3 Pa, in hydrogen or in deuterium. The plasma will be generated by inductively coupling an RF power of up to 800 kW into the source volume. Under consideration for future neutral beam heating systems, like the one for the demonstration reactor DEMO, is an even lower filling pressure of 0.2 Pa. Together with the effect of neutral gas depletion, such low operational pressures can result in a neutral gas density below the limit required for sustaining the plasma. Systematic investigations on the low-pressure operational limit of the half-ITER-size negative ion source of the ELISE (Extraction from a Large Ion Source Experiment) test facility were performed, demonstrating that operation is possible below 0.2 Pa. A strong correlation of the lower pressure limit on the magnetic filter field topology is found. Depending on the field topology, operation close to the low-pressure limit is accompanied by strong plasma oscillations in the kHz range.

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36

Nasibullayev, I. Sh, and E. Sh Nasibullaeva. "The effect of temperature on the fluid flow dynamics in technical systems with jets." Proceedings of the Mavlyutov Institute of Mechanics 11, no. 1 (2016): 1–9. http://dx.doi.org/10.21662/uim2016.1.001.

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In this paper the steady flow of technical fluid induced pressure drop in the channel with a cylindrical jet for the entire working temperature range have been studied. The Navier–Stokes equations are solved numerically in axially symmetric geometry by the finite element method. The temperature dependence of the material parameters of a number of liquids, most commonly used in technical devices have been obtained. A model of a cylindrical jet was built in the form of a computing element of the stand, which takes into account the pressure drop, the radius of passage opening jet and the liquid temperature for the areas with low and high pressure drops. This model allows without significant loss of accuracy replace the complete numerical simulation, requires more computational resources, by simple analytical formulas admitting modeling in computational stand in real time. The model can be used in various technical applications of microelectromechanical systems (at low pressure drops) to the fuel metering elements (at high pressures drops).

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Zeidan, Mohamad, and Avi Ostfeld. "Hydraulic Ram Pump Integration into Water Distribution Systems for Energy Recovery Application." Water 14, no. 1 (December 22, 2021): 21. http://dx.doi.org/10.3390/w14010021.

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This study presents the potential of integrating Hydrams in modern water distribution systems (WDSs) for managing excess pressure and reducing energy costs. Hydrams, which are also termed Hydraulic ram pumps in the literature, is a cyclic water pump powered by hydropower, generally used to pump drinking and irrigation water in mountainous and rural areas having short of power. The Hydrams is introduced as a sustainable low-cost alternative solution to the more conventional pressure reducing valves (PRVs) approach for managing pressure zones in WDSs. Unlike PRVs, where the pressure is lost and not put into good use, Hydrams mitigate excess pressure at high-pressure zones and direct it to much-needed low-pressure zones. In addition, Hydrams are cheap, simple, environmentally friendly, and require little maintenance. The proposed approach integrates a Hydram in parallel to the original centrifugal pump, where they can be operated interchangeably according to the system’s hydraulic needs. Nevertheless, it is vital to correctly size the Hydram at the feed line and accompany it with a proper storage tank at the low-pressure zone. The storage tank serves as a buffer between the intermittent water supply and consumer demand pattern. Moreover, the tank introduces flexibility into the system that allows more sustainable operating schedules. Two case study applications of increasing complexity are presented to demonstrate the potential of this Hybrid system, later referred to as Hybrid Pumping Unit (HPU). The Hydram and tank sizing is done by a simple heuristic approach, while the operation of the system is dictated by a genetic algorithm. The results demonstrate the potential of integrated Hydrams in reducing excess pressures and energy costs.

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38

Varsegova, Evgenia, Lilia Osipova, and Daniel Bugembe. "A study of flow characteristics in a low-pressure ejector installation." E3S Web of Conferences 274 (2021): 08006. http://dx.doi.org/10.1051/e3sconf/202127408006.

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Production processes sometimes are accompanied by the release of hazardous substances, the composition and volume of which is determined by the production technology. When designing ventilation systems for paint departments, special attention is paid to safety concerns, since all paint coatings are corrosive and flammable substances. Besides, solvent vapors are explosive. For local ventilation of painting chambers, it is rational to use safe exhaust systems with an ejector, which works sturdily, regardless of the release of flammable and explosive impurities. The ejector is simple in design and can operate in a wide range of changes in the parameters of the state of airflow. The model of the ejection unit is synthesized using the universal modeling package ChemCad, which contains a highly developed database of airflow parameters, which allows for solving various applied problems. Numerical modeling was carried out using the software package - FLUENT. In work, a calculation was carried out and a low-pressure ejector was designed for a typical painting booth. The calculation results are presented in the form of graphs and tables of pressures, velocities, flow rates in characteristic sections, pressure losses in the sections of the ejector installation.The ejection coefficient was also calculated.

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39

Abdelghani Djemaa, Abderrezak Merabet, Redha Rebhi, Giulio Lorenzini, Rachid Bessaih, and Younes Menni. "Simulations and Optimizations for a Low-Temperature Hybrid Geothermal-Solar Power Plant." Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 90, no. 2 (January 18, 2022): 109–23. http://dx.doi.org/10.37934/arfmts.90.2.109123.

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The possibility of producing electrical power in Algeria from low geothermal and solar heat resources is addressed using a hybrid power generation hypothetical system based on a combined flash-binary cycle with equal contributions from solar and geothermal energy. To improve their efficiency, energy integration techniques were used to recover waste heat from the steam turbine by preheating the working fluid R134a in the bottoming binary, which represents 30% of the energy acquired from the ORC cycle. The Aspen HYSYS application was used for power cycle simulation and modeling. A contact between the wane pressure and the pressure at the ORC binary cycle turbine's intake must be made to obtain the greatest power out of the hybrid power plant. According to the findings, the perfect flashing pressure of the flash cycle and the optimal intake pressure of the working fluid to the binary cycle's turbine are 450 kPa and 3340 kPa, respectively. The overall power generation and thermal efficiency of the hybrid plant were calculated to be 3823 kW and 16.1 %, respectively, at these pressures, demonstrating a significant thermodynamic advantage over each of the component systems.

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40

Ridout, J., and M. R. Probert. "High-pressure/low-temperature polymorphism in simple aromatic systems." Acta Crystallographica Section A Foundations of Crystallography 68, a1 (August 7, 2012): s71. http://dx.doi.org/10.1107/s0108767312098625.

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41

Smout, Ian K. "Use of low-pressure pipe systems for greater efficiency." Agricultural Water Management 40, no. 1 (March 1999): 107–10. http://dx.doi.org/10.1016/s0378-3774(98)00089-4.

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42

Stratton, P. F., S. Bruce, and V. Cheetham. "Low-pressure carburizing systems: A review of current technology." BHM Berg- und Hüttenmännische Monatshefte 151, no. 11 (November 2006): 451–56. http://dx.doi.org/10.1007/bf03165206.

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43

Hasheminia, Seyed Majid. "Controlling runoff under low pressure center pivot irrigation systems." Irrigation and Drainage Systems 8, no. 1 (1994): 25–34. http://dx.doi.org/10.1007/bf00880796.

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44

Dong, Wenhao, Yi Ming, and V. Ramaswamy. "Projected Changes in South Asian Monsoon Low Pressure Systems." Journal of Climate 33, no. 17 (September 1, 2020): 7275–87. http://dx.doi.org/10.1175/jcli-d-20-0168.1.

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AbstractMonsoon low pressure systems (MLPSs) are among the most important synoptic-scale disturbances of the South Asian summer monsoon. Potential changes in their characteristics in a warmer climate would have broad societal impacts. Yet, the findings from a few existing studies are inconclusive. We use the Geophysical Fluid Dynamics Laboratory (GFDL) coupled climate model CM4.0 to examine the projected changes in the simulated MLPS activity under a future emission scenario. It is shown that CM4.0 can skillfully simulate the number, genesis location, intensity, and lifetime of MLPSs. Global warming gives rise to a significant decrease in MLPS activity. An analysis of several large-scale environmental variables, both dynamic and thermodynamic, suggests that the decrease in MLPS activity can be attributed mainly to a reduction in low-level relative vorticity over the core genesis region. The decreased vorticity is consistent with weaker large-scale ascent, which leads to less vorticity production through the stretching term in the vorticity equation. Assuming a fixed radius of influence, the projected reduction in MLPSs would significantly lower the associated precipitation over north-central India, despite an overall increase in mean precipitation.

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45

Hwang, T. H., and M. K. Moallemi. "Heat transfer of evaporating droplets in low pressure systems." International Communications in Heat and Mass Transfer 15, no. 5 (September 1988): 635–44. http://dx.doi.org/10.1016/0735-1933(88)90054-1.

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46

Mekhtiyev, Ali, Iossif Breido, Rustam Buzyakov, Yelena Neshina, and Aliya Alkina. "Development of low-pressure electric steam heater." Eastern-European Journal of Enterprise Technologies 4, no. 8(112) (August 31, 2021): 34–44. http://dx.doi.org/10.15587/1729-4061.2021.237873.

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The study was devoted to solving the issue of creating new electric heating devices that can be used in autonomous heat supply systems. The issues were resolved by developing an original low-pressure electric steam heater. The study was aimed at improving the efficiency of heat supply systems for buildings and structures. Given the current trends in the global striving for energy conservation, it cannot be fully realized without the introduction of high-tech and low-energy-consuming electrical equipment. As a result of theoretical studies of a heat pipe with an electric heater, a design of an electrovacuum heating element has been developed. The low-pressure electric steam heater can be used in heat supply systems of autonomous users. Thermal energy transfer is currently accompanied by substantial energy losses since the heat carrier has to pass considerable distances. Switching of the facility to the heating plant is impossible in some cases because of technical problems or significant material costs for laying pipelines. As a result of the study, the dependence of heating the heat pipe at various volumes of the heat carrier and mass of the pipe itself was established. When a certain mass is reached, the temperature of the heating surfaces can reach 70 °C which is considered acceptable. The experimental data obtained have made it possible to develop an electric heater of new generation with a fundamentally new design of the heating element. It combines the efficiency of an electric spiral and comfortable warmth from a traditional radiator. This heater is an explosion and fire-safe and can be integrated into the Smart Home system

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47

Douglas, Robert A., W. DH Woodward, and A. R. Woodside. "Road contact stresses and forces under tires with low inflation pressure." Canadian Journal of Civil Engineering 27, no. 6 (December 1, 2000): 1248–58. http://dx.doi.org/10.1139/l00-069.

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Many field trials have been undertaken to demonstrate the benefits of reducing the inflation pressure of the tires of heavily loaded haul vehicles, but few carefully controlled laboratory studies have been performed. An earlier full scale laboratory study indicated that tire inflation pressure had far less effect on subgrade strains for unpaved, single-layer granular road structures than the tire loading itself, so attention was directed to the behaviour of the granular base at the tire tread - road surface interface. In the present paper, the results of full scale tests performed using a laboratory apparatus designed to measure the dynamic vertical, transverse, and longitudinal contact forces under tires with varying loads and inflation pressures are reported. Vertical contact forces were observed to be highly non-uniform, both across and along the contact patch.Key words: central tire inflation systems, CTI, model study, haul trucks, unbound roads, unpaved roads, access roads.

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Shalaby, Ahmed, and Alan Reggin. "Surface rutting of thin pavements and gravel roads under standard and reduced tire inflation pressures." Canadian Journal of Civil Engineering 29, no. 5 (October 1, 2002): 679–91. http://dx.doi.org/10.1139/l02-056.

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In Canada, over 300 heavy vehicles equipped with central tire inflation systems are being used in forestry, mining, and grain hauling. Since 1995, Saskatchewan Highways and Transportation has permitted truck fleets to operate with primary highway axle loads on secondary highways under a partnership program. This paper reports on the comparison of rutting progression on an accelerated field experiment utilizing standard and reduced tire pressures. The experiment was conducted by Saskatchewan Highways and Transportation in the Big Quill Lake area of southern Saskatchewan. The vehicles used in the experiment were nine-axle B trains, eight-axle B trains, and six-axle semi-trailers. The statistical analysis of rutting data presented in the paper shows that reduced tire pressures can effectively extend the pavement service life of gravel and thin membrane surfaced roads. On the thin membrane pavements, there was less rutting on the low-pressure lane until twice as many vehicles had trafficked the road, and rutting was no worse on the low-pressure lane even when 10 times as many vehicles had trafficked the road. On the gravel surface, rut depth was lower on the low-pressure lane until twice as many trucks had trafficked that lane.Key words: rutting, pavement, central tire inflation, tire pressure, low-volume roads, unsurfaced roads.

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Alijani, Afshin, and Alfred Cuschieri. "Abdominal wall lift systems in laparoscopic surgery: Gasless and low-pressure systems." Seminars in Laparoscopic Surgery 8, no. 1 (March 2001): 53–62. http://dx.doi.org/10.1053/slas.2001.23180.

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50

Alijani, A., and A. Cuschieri. "Abdominal Wall Lift Systems in Laparoscopic Surgery: Gasless and Low-pressure Systems." Surgical Innovation 8, no. 1 (March 1, 2001): 53–62. http://dx.doi.org/10.1177/155335060100800106.

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