Pressure Accumulation Research Articles

Effects of design parameters and tension on behavior of a coil using finite element analysis

During the thin strip coiling process, it is necessary to use a sleeve with a mandrel to prevent excessive deformation of the strip. Stress distribution in the sleeve and in the strip is an important factor that determines the quality of the coil. However, owing to the accumulation of high pressure, it is difficult to determine the stress distribution through experimentation. Thus, stress analysis of the strip coiling process was conducted. Finite element analysis was used to investigate the effects of the weight of the strip and the mandrel on the stress distribution and stress concentration near the starting point of the coil. The radial stress was predicted for a coil with a stacked thickness of 384 mm, which corresponds to a strip length of 1486 m, using the stress analysis model developed in a preceding research. A method was presented to reduce the weight and radial stress of a strip coil. It was found that the deformation of the sleeve can be reduced by decreasing the gap between the mandrel segments. The thickness of the sleeve can be reduced from 120 to 106 mm using the stress analysis results. Furthermore, coiling tension can be reduced by 44% compared to the existing value considering the interlayer slip of the strip coil.

The alerting effect of the wake maintenance zone during 40 hours of sleep deprivation

Under entrained conditions, the accumulation of homeostatic sleep pressure in the evening is opposed by a strong circadian arousal signal prior to the dim light melatonin onset, called the Wake Maintenance Zone (WMZ). This study aimed at investigating the impact of the WMZ on different cognitive performance tests, as well as on subjective and objective sleepiness. Twelve young male participants completed a constant routine protocol with 40 h of extended wakefulness that included two WMZs. Cognitive tests and saliva samples were assessed hourly, while the electroencephalogram (EEG) was recorded continuously. Participants improved in cognitive response inhibition during WMZ1 (13.5 h awake) and sustained attention during WMZ2 (37.5 h awake), but not in higher executive function tests. There were significant EEG power density reductions in the delta/theta frequency range during WMZ1 and in delta/theta, alpha, and sigma/beta ranges during WMZ2, with a greater change in the sigma/beta range during WMZ2 compared to WMZ1. EEG power reductions coincided during WMZ1 with stable subjective sleepiness and sustained attention. During WMZ2, EEG power reductions were more pronounced and coincided with improved sustained attention. Our results suggest the circadian arousal signal in the evening differently modulates cognitive functions and EEG power depending on the duration of prior wakefulness.

OPLAH ablation leads to accumulation of 5-oxoproline, oxidative stress, fibrosis, and elevated fillings pressures: a murine model for heart failure with a preserved ejection fraction.

The prevalence of heart failure with a preserved ejection fraction (HFpEF) is increasing, but therapeutic options are limited. Oxidative stress is suggested to play an important role in the pathophysiology of HFpEF. However, whether oxidative stress is a bystander due to comorbidities or causative in itself remains unknown. Recent results have shown that depletion of 5-oxoprolinase (OPLAH) leads to 5-oxoproline accumulation, which is an important mediator of oxidative stress in the heart. We hypothesize that oxidative stress induced by elevated levels of 5-oxoproline leads to the onset of a murine HFpEF-like phenotype. Oplah full body knock-out (KO) mice had higher 5-oxoproline levels coupled to increased oxidative stress. Compared with wild-type (WT) littermates, KO mice had increased cardiac and renal fibrosis with concurrent elevated left ventricular (LV) filling pressures, impaired LV relaxation, yet a normal LV ejection fraction. Following the induction of cardiac ischaemia/reperfusion (IR) injury, 52.4% of the KO mice died compared with only 15.4% of the WT mice (P < 0.03). Furthermore, KO mice showed a significantly increased atrial, ventricular, kidney, and liver weights compared with WT mice (P < 0.05 for all). Cardiac and renal fibrosis were more pronounced following cardiac IR injury in the KO mice and these mice developed proteinuria post-IR injury. To further address the link between 5-oxoproline and HFpEF, 5-oxoproline was measured in the plasma of HFpEF patients. Compared with healthy controls (3.8 ± 0.6 µM), 5-oxoproline levels were significantly elevated in HFpEF patients (6.8 ± 1.9 µM, P < 0.0001). Furthermore, levels of 5-oxoproline were independently associated with more concentric remodelling on echocardiography. Oxidative stress induced by 5-oxoproline results in a murine phenotype reminiscent of the clinical manifestation of HFpEF without the need for surgical or pharmacological interference. Better understanding of the role of oxidative stress in HFpEF may potentially lead to novel therapeutic options.

Simulation of cyclic strength degradation of natural clays via bounding surface model with hybrid flow rule

SummaryStrength loss of natural clays subjected to seismic loading is a critical factor contributing to earthquake‐induced ground failure and associated hazards. This work proposes a bounding surface constitutive law to simulate cyclic strength degradation of natural clays resulting from the loss of structure and attendant accumulation of excess pore pressures. The proposed model employs an enhanced plastic flow rule that can simulate accurately the development of pore pressure and explicitly incorporates soil structure effects. The validation of the model with reference to the experimental evidence available for 3 structured clays shows that with a single set of parameters the proposed model can reasonably represent the mechanical behavior of natural clays under various loading conditions (1D compression, monotonic shearing in compression and extension, cyclic loading, and postcyclic shearing). Particularly, its satisfactory performance in terms of quantification of cyclic strength degradation encourages the use of the model in simulating boundary value problems related to the stability of geotechnical facilities under earthquakes.

Long-term behavior of clay-fouled unbound granular materials subjected to cyclic loadings with different frequencies

Experimental studies were conducted to investigate the engineering geological characteristics of clay-fouled unbound granular materials (UGMs) under different-frequency cyclic loadings. The computed tomography (CT) scan was firstly conducted to examine the inner structure of UGMs with various fines contents; then a series of drained large-scale tri-axial tests were conducted on the clay-fouled UGMs under cyclic loadings with various frequencies (f = 0.2 Hz, 1 Hz and 3 Hz). The combined effects of the fines content and the cyclic loading frequency on the excess pore water pressure, accumulated strain and resilient modulus were analyzed. Test results showed that the dominant effects of fines on the UGMs transited from the lubrication, densification to suffocation as the fines content increased. The lubrication effect led to the increase of the accumulated axial and volumetric strain; the densification effects reduced the accumulated strain; and the suffocation effects resulted in the accumulation of excess pore water pressure and thus rapid deterioration of UGMs. The transition point of these effects were closely related to the loading frequency and loading amplitude. The drainage conditions of clay-fouled UGMs transited from full drainage to partially drainage as the fines content, loading amplitude and frequency increased.

Effects of Soil-Resistance Damping on Wave-Induced Pore Pressure Accumulation around a Composite Breakwater

ABSTRACT Zhang, J.; Tong, L.; Zheng, J.; He, R., and Guo, Y., 2018. Effects of soil resistance damping on wave-induced pore pressure accumulation around a composite breakwater. It is important to consider the potential instability of the seabed from the accumulation of wave-induced pore pressure in the design of a composite breakwater because the pore pressure within the seabed can build up considerably under wave loading, which can eventually lead to a sharp decrease in its effective stress. Because of the importance in practical engineering, many theoretical models have been developed to evaluate the magnitude and distribution of residual pore pressure. However, most of these studies treat the soil skeleton as an invariant medium, which ignores the damping of the soil strength from the reduction in the effective stress. In this study, a two-dimensional poroelastoplastic model, in which the influence of the reduction of effective stress on soil strength was considered, is proposed for investigating the a...

Evolution of formation pressure and accumulation of natural gas in the Upper Palaeozoic, eastern‐central Ordos Basin, Central China

The exploration achievements in the eastern‐central Ordos Basin have attracted tremendous attention in recent years. However, only a few studies were carried out on the relationship between formation pressure and distribution of natural gas in this area. The formation pressure of 293 wells, logging data of 154 wells, and fluid inclusion samples of 53 wells were analysed in this paper, and the results show that the mudstones from Permian Upper Shihezi Formation to Permian Taiyuan Formation are mostly undercompacted. Four gas‐bearing layers with significant differences in pressure profile can be further divided into Permian negative pressure system and Carboniferous normal pressure system. The distribution of current formation pressure is high in the east and north areas but low in the west and south areas. The sedimentary facies and distribution of formation pressure in Permian have a good consistency. The vertical development (zonation) of gas reservoirs is controlled by the undercompacted mudstone layers, and the reservoirs can be found in the “low pressure” areas of negative pressure strata in the Permian and “high pressure” regions of normal pressure strata in the Carboniferous. The pressure evolution and accumulation process can be divided into 3 stages: hydrocarbon‐generation supercharging accumulation during Late Jurassic—end of Early Cretaceous, sandstone resilience discharging accumulation during end of Early Cretaceous—Paleogene, and adjusting accumulation during Paleogene—Quaternary. The discovery of the relationship between formation pressure and gas reservoirs is significant to the future natural gas exploration in this area.

Moderate Modulation of Cardiac PGC-1α Expression Partially Affects Age-Associated Transcriptional Remodeling of the Heart.

Aging is associated with a decline in cardiac function due to a decreased myocardial reserve. This adverse cardiac remodeling comprises of a variety of changes, including a reduction in mitochondrial function and a decline in the expression of the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a central regulator of mitochondrial biogenesis and metabolic adaptation in the myocardium. To study the etiological involvement of PGC-1α in cardiac aging, we used mouse models mimicking the modest down- and upregulation of this coactivator in the old and the exercised heart, respectively. Young mice with reduced cardiac expression of PGC-1α recapitulated part of the age-related impairment in mitochondrial gene expression, but otherwise did not aggravate the aging process. Inversely however, moderate overexpression of PGC-1α counteracts numerous key age-related remodeling changes, e.g., by improving blood pressure, age-associated apoptosis, and collagen accumulation, as well as in the expression of many, but not all cardiac genes involved in mitochondrial biogenesis, dynamics, metabolism, calcium handling and contractility. Thus, while the reduction of PGC-1α in the heart is insufficient to cause an aging phenotype, moderate overexpression reduces pathological remodeling of older hearts and could thereby contribute to the beneficial effects of exercise on cardiac function in aging.

Impact of inner reservoir faults on migration and storage of injected CO2

CO2 geological storage (CGS) is an effective way to mitigate greenhouse gas emissions, and geological security is one of the most important issues in CGS. The faults distributed in geological formations make multi-layered reservoirs interconnected systems. A three-dimensional (3D) numerical model was established to evaluate the effects of inner reservoir faults on the CO2 migration and storage capacity of an actual CGS demonstration project in the Ordos Basin of China. The results show that the faults in the layered reservoir system could significantly affect the migration of injected CO2. The cross-layer faults at the bottom of the faulted reservoir could act as preferential passages between the upper and lower geological formations, causing the CO2 in the reservoir formation to move upward to adjacent layers rather than to lateral migration. CO2 migration along the inner-layer faults widely occurred at the top of the reservoir formation, decreasing the pressure accumulation and CO2 saturation around the injection well. Based on the simulation, CO2 will have migrated into the Heshanggou Formation after 300 years, and most of the CO2 will be trapped in the bottom sub-layers, with no CO2 intruding into the upper caprock. The spatial and temporal evolution of the injected CO2 was well presented for the faulted reservoir system, suggesting that the faults inside the multi-layered reservoir are beneficial to CGS.

Lower limb blood flow and mean arterial pressure during standing and seated work: Implications for workplace posture recommendations.

Sit-stand workstations are a popular workplace intervention. Organizations often require a medical professional's guidance for implementation. Therefore, it is important to understand potential negative outcomes associated with standing work, such as lower limb discomfort and peripheral vascular issues. The objective of this study was to compare changes in lower limb discomfort, blood pressure and blood flow accumulation during a light-load repetitive upper limb work task accomplished from seated and standing postures. At the Jewish Rehabilitation Hospital (Laval, Quebec, Canada), 16 participants were outfitted with Laser Doppler Flow (LDF) electrodes to measure blood flow in the lower limb, and a sphygmomanometer to measure lower limb mean arterial blood pressure (MAP). Participants completed simulated work over 34 min in standing and seated conditions. Repeated measures ANOVAs (Posture x Time) were used to assess the differences. There were significant effects for both Posture (p = 0.003) and Time (p = 0.007) for LDF-measured of blood flow accumulation in the soleus and the foot, with a mean increase of 77% blood flow over time in the standing posture, when compared to seated work. There was a significant ‘Posture × Time’ (p = 0.0034) interaction effect and a significant Posture (p = 0.0001) effect for MAP, with higher values in the standing posture by a mean of 37.2 mmHg. Posture had a significant effect (p < 0.001) on lower limb discomfort, with standing posture reporting higher levels. These results suggest that recommendations for using static standing work postures should be tempered, and physicians' guidance on workstation changes should consider the impacts on the lower limb.

Quantitative consequence analysis using Sedov-Taylor blast wave model. Part II: Case study in an Algerian gas industry

In the oil and gas industry, it is common to use gas liquefaction that allows storage and transport of large quantities of LNG and LPG. One of the main disadvantages of this storage mode is the BLEVE risk, which remains a major concern for risk decision-makers. In order to prevent the occurrence of this risk and reduce its impact, risk analysts often use quantitative risk analysis (QRA), which is based on the understanding and quantification of the accidental phenomena and their consequences (overpressure, thermal radiation, toxicity dose). QRA is a rigorous and advanced approach that requires reliable data in order to obtain a good estimate and control of risks. The main objective of this paper (Part II) is to integrate the Sedov-Taylor model developed in Part I into the QRA approach in order to evaluate BLEVE blast effect, and illustrate it with a case study on a pressurized LPG accumulator located in the MPP3-plant of SONATRACH company in the Hassi R'Mel gas field (the largest gas field in Algeria). A parametric analysis of the fuel mass, temperature at failure and rupture pressure is carried out to study their influence on the evolution of BLEVE overpressure. In addition, the evaluation of BLEVE thermal effect is performed in order to better realize an exhaustive QRA. Through this application, the results show the great relevance of the Sedov-Taylor model in the consequence analysis and also in the development of process safety recommendations.

Regulation of REM and Non-REM Sleep by Periaqueductal GABAergic Neurons

Mammalian sleep consists of distinct rapid eye movement (REM) and non-REM (NREM) states. The midbrain region ventrolateral periaqueductal gray (vlPAG) is known to be important for gating REM sleep, but the underlying neuronal mechanism is not well understood. Here, we show that activating vlPAG GABAergic neurons in mice suppresses the initiation and maintenance of REM sleep while consolidating NREM sleep, partly through their projection to the dorsolateral pons. Cell-type-specific recording and calcium imaging reveal that most vlPAG GABAergic neurons are strongly suppressed at REM sleep onset and activated at its termination. In addition to the rapid changes at brain state transitions, their activity decreases gradually between REM sleep and is reset by each REM episode in a duration-dependent manner, mirroring the accumulation and dissipation of REM sleep pressure. Thus, vlPAG GABAergic neurons powerfully gate REM sleep, and their firing rate modulation may contribute to the ultradian rhythm of REM/NREM alternation.

Analytical Solution and Application for One-Dimensional Consolidation of Tailings Dam

The pore water pressure of tailings dam has a very great influence on the stability of tailings dam. Based on the assumption of one-dimensional consolidation and small strain, the partial differential equation of pore water pressure is deduced. The obtained differential equation can be simplified based on the parameters which are constants. According to the characteristics of the tailings dam, the pore water pressure of the tailings dam can be divided into the slope dam segment, dry beach segment, and artificial lake segment. The pore water pressure is obtained through solving the partial differential equation by separation variable method. On this basis, the dissipation and accumulation of pore water pressure of the upstream tailings dam are analyzed. The example of typical tailings is introduced to elaborate the applicability of the analytic solution. What is more, the application of pore water pressure in tailings dam is discussed. The research results have important scientific and engineering application value for the stability of tailings dam.

Development for a Pressure Accumulation System Using the Cold Energy Latent in a Cold District

Development for a Pressure Accumulation System Using the Cold Energy Latent in a Cold District

Impact of Measuring Devices and Data Analysis on the Determination of Gas Membrane Properties

The time-lag method, using a gas permeation experiment, is currently the most popular method for determining the membrane properties: diffusivity coefcient and permeability coefcient, and from which the solubility coefcient can be calculated. In this investigation, the impact of systematic, random (noise), resolution and extrapolation errors associated with gas permeation experiments on the determination of the membrane properties using the time-lag method is investigated. A comprehensive error analysis for each type of errors and their combination is presented. Random and resolution errors have a greater impact on the determination of the time lag for low rates of downstream pressure accumulation which can be alleviated by increasing the capacity parameter. Increasing the feed pressure lowers the resolution errors, but has no effect on random errors. Extrapolation errors associated with the time-lag method, which increase with time, can be reduced by increasing the number of evaluation points and the length of the evaluation window. Because of their strong correlation, it is difcult to decouple solubility and diffusivity coefcients accurately without using the time-lag. A judicious balance between data precision, the drop in the driving force and the duration of an experiment must be considered in the design of a constant-volume membrane system and in the selection of experimental operating conditions to minimize the impact of pressure variability. The necessity of a small capacity parameter for the accurate determination of membrane properties needs to be reconsidered in the presence of experimental noise.

A simplified quasi-static analysis of wave-induced residual liquefaction of seabed around an immersed tunnel

Evaluation of wave-induced soil response is particularly important for coastal geotechnical engineers involved in the foundation design for marine structures such as immersed tunnels, breakwaters, platforms etc. In this study, a finite element model for the wave-induced soil response around an immersed tunnel is developed, in which the seabed is treated as a porous medium and characterized by Biot's consolidation equations, while the tunnel is considered as a single-phase medium and behaves under a linear elastic law. A new conceptual pore-pressure buildup model is developed to investigate the wave-induced residual liquefaction around the tunnel due to the accumulation of pore pressures under cyclic shearing. The consolidation analysis of seabed foundation under the gravitational forces including the body forces of the structure is pre-assessed and incorporated. It is demonstrated from numerical results that the development of residual pore pressure is asymmetric in nature around the tunnel, which may result in the uneven liquefaction depth and deformation in the seabed near the bottom of the tunnel, thus compromising the stability of the structure. Parametric studies show that wave-induced residual liquefaction is more likely to occur in the shallow seabed with lower relative density and permeability under the wave loading with higher wave height and longer period.

Ground deformation source model at Kuchinoerabu-jima volcano during 2006\u20132014 as revealed by campaign GPS observation

We analyzed campaign Global Positioning System observation data in Kuchinoerabu-jima during 2006–2014. Most benchmarks located around Shin-dake crater showed crater-centered radial horizontal displacements. Horizontal displacements at western rim of the Shin-dake crater were tended to be larger compared to those at eastern rim. In addition, benchmark KUC14 which locates near the cliff at Furu-dake showed westward horizontal displacement rather than crater-centered radial (southward) one. Meanwhile, small displacements were detected at the benchmarks located at the foot of Kuchinoerabu-jima. We modeled the observed displacements applying a finite element method. We set entire FE domain as 100 × 100 × 50 km3. We set top of the domain as a free surface, and sides and bottom to be fixed boundaries. Topography was introduced in the area within Kuchinoerabu-jima using digital elevation model data provided by Kagoshima prefecture and elevation information from Google earth, and elevation of the outside area was assumed to be sea level. We assumed a stratified structure based on a one-dimensional P-wave velocity structure. We applied a vertical spheroid source model and searched optimal values of horizontal location, depth, equatorial and polar radiuses, and internal pressure change of the source using the forward modeling method. A spherical source with a radius of 50 m was obtained beneath the Shin-dake crater at a depth of 400 m above sea level. The internal pressure increase of 361 MPa yields its volume increase of 31,700 m3. Taking effects of topography and heterogeneity of ground into account allowed reproduction of overall deformation in Kuchinoerabu-jima. The location of deformation source coincides with hypocenters of shallow volcano-tectonic (VT) earthquakes and the aquifer estimated from a two-dimensional resistivity model by audio-frequency magnetotellurics method. The obtained deformation source may be corresponding to the pressurized aquifer, and shallow VT earthquakes and demagnetization may be caused by pressure and strain accumulation in the rocks around the aquifer. Applying the obtained spherical source to the tilt change before August 3, 2014 eruption, we found that 520 m3 of volcanic materials were supplied toward shallower in 1.5 h before the eruption. The depth and volume change of deformation source before May 2015 eruption detected by precise leveling surveys is deeper and two orders of magnitude greater compared to that before August 2014 eruption.

Physiological characteristics of grapevine under irrigation and fertilization management1

ABSTRACT The viticulture in the semiarid region of Brazil stands out in the country due to the expansion of its cultivated area and increased production, especially in the sub-mid São Francisco Valley. However, the supplying of water and an efficient replacement of nutrients to the soil are essential for these crops, due to the intrinsic climatic conditions of this region, such as low rainfall and high evapotranspiration. This study aimed at evaluating the physiological characteristics of ‘Itália’ grapevine (Vitis vinifera L.) under irrigation and fertilization management. The experiment was conducted in a randomized block design, with four replications, in a split-plot arrangement, with four irrigation water depths (0.75, 1.00, 1.25 and 1.5 times the crop coefficient) in the plots and four fertilizer rates (100 %, 75 %, 50 % and 25 %, based on the recommended fertilizer rates for this crop) in the subplots, with addition of organic compounds. The leaf water potential, leaf chlorophyll content, relative water content, photosynthesis, stomatal conductance, internal CO2 partial pressure, leaf temperature and biomass accumulation in the berries were evaluated. The highest leaf chlorophyll contents were found in treatments with fertilizer rates of 70-85 %. Stomatal conductance decreased with the increasing irrigation water depths, thus reducing the internal CO2 partial pressure and increasing the leaf temperature and air vapor pressure deficit. The reduction of 25 % in the conventional fertilization and irrigation of 135 % of the recommended coefficient resulted in the highest average weight of berries. The highest yields were obtained with the lowest irrigation water depths and fertilizer rates of 50-65 %.

Earthquake-induced settlement of a clay layer

A model for pore water pressure accumulation and settlement of saturated clay layer induced by uniform and irregular cyclic shear strains was developed by concerning the direction of cyclic shear strain. To apply this model to any kinds of clay, the effects of Atterberg's limits of cohesive clay on the cyclic shear-induced pore water pressure and the settlement were observed by using the strain-controlled cyclic simple shear test apparatus which can control the cyclic shear direction. In conclusion, the effects of Atterberg's limits of clay on the cyclic shear-induced pore water pressure accumulation and settlement were clarified by using the cumulative shear strain. Based on the experimental results, estimation methods for the pore water pressure accumulation and post-cyclic settlement of clay with a wide range of Atterberg's limits were developed. Furthermore, to apply the proposed methods to the earthquake-induced ground motions, a transformation procedure of irregular cyclic shears to the equivalent uniform ones including the effect of cyclic shear direction was developed and the practical applicability was confirmed.

A novel mitigation on deepwater annular pressure buildup: Unidirectional control strategy

When completing deepwater wells, a significant portion of the completion fluid is often trapped in the casing annuli because of widespread use of multi-layer casing technology. When transferred into testing or production, the temperature field in the immediate vicinity of the wellbore is redistributed by any present thermally conductive fluids. Raising trapped completion fluid to a high temperature can trigger high thermal stress, and this stress has been proven to present a grave threat to the safety of deepwater wells. In this paper, a thermal conductivity model of fluid-filled annuli based on a typical well structure used in the South China Sea is established to determine the effect of different production parameters during the well production or testing process on pressure behavior. A numerical simulation of the effects of fluid trapped in the casing annuli on temperature distribution was conducted. Based on this simulation, a novel method for mitigating the pressure of the trapped fluid by a way of a unidirectional control strategy was studied, and a unidirectional pressure control casing nipple tool was developed. Laboratory simulations were then conducted using a prototype tool to determine the technical feasibility of the unidirectional control strategy. The change in trapped fluid pressure with time was obtained for different release pressures and tool valve orifice diameters, showing the effects of different valve orifice diameters and volumetric injection rates on the pressure release performance. Experimental results demonstrate that the pressure envelope decreases quadratically with the increase in the pressure grade, while the valve working duration decreases linearly with the increase in valve orifice diameter. The increase in the volumetric injection rate was found to have little effect on the cumulative volume displacement. The proposed unidirectional pressure control strategy for controlling the accumulation of pressure in the annuli of deepwater wellbore casings can effectively eliminate the fatal dangers presented by thermal stress. It can also reduce the risk of casing deformation due to thermal stress within trapped annuli and reduce occurrences of wellhead sealing damage.