Decrease In Flow Rate Research Articles

Experimental study on hydrogen pipeline leakage: Negative pressure wave characteristics and inline detection method

This paper presents an experimental study on a potential safety system for hydrogen fuel cells. It focuses on early leakage detection and localization. This would enable effective system response to avoid the effects of catastrophic loss of containment. Experimental results are presented from a pipeline setup wherein the leak is identified utilizing inline pressure sensors and flowmeters. The investigations involve recorded data at two leak locations at different initial pressures, mass flow rates, and leak diameters. The leak detection technique is based on analysis of the negative pressure wave (NPW) intensity and propagation duration, denoted as peak-to-peak amplitude (Δh) and oscillation period (Δτ). They are extracted from filtered pressure records' first derivative (dp/dt). Δh and Δτ increase as the initial mass flow rate and leak diameter decrease. Therefore, this approach is advantageous for detecting leaks from tiny cross-sections. Δh and Δτ measured at two leak positions at different lengths from the system inlet increase at a higher initial flow rate of 1.0 g/s, but they exhibit opposite behavior at a lower rate (0.42 g/s). Increasing the sampling rate in the dp/dt-time graphs enhances the precision of leak localization. Calculation results show an effective leakage localization with an accuracy of 15 mm (2.5%). The leak flow rate during nitrogen leakage tests is about three times that of hydrogen, and it has higher Δh (about two times at 10 bar).

Exergy analysis of a diesel methanol dual fuel engine with different regulatory strategies for meeting China VI emission regulations

To reveal the mechanism for high brake thermal efficiency (BTE) of diesel methanol dual fuel (DMDF) engine meeting China VI emission regulations without urea, experimental and computational methods were used to study the exergy distribution with different regulatory strategies. As the methanol energy ratio (MER) increased, the incomplete combustion exergy loss increased from 0.3 % to 5.5 %, while the exhaust exergy loss and heat transfer exergy loss decreased slightly. As the HP-EGR increased from 3 % to 23 %, exergy losses of incomplete combustion and exhaust decreased, resulting in a reduction in the engine exergy losses. As the LP-EGR increased from 3 % to 21 %, the exergy losses of heat transfer and incomplete combustion slightly decreased. By advancing the main injection timing, the decrease in exhaust flow rate and temperature led to a decrease in exhaust exergy loss and the combustion efficiency was improved from 95.0 % to 96.5 %. Both of them resulted in the highest exergy efficiency of 35.2 % at 12°CA BTDC. Finally, the exergy distributions of DMDF and diesel modes were compared at high and low loads. The research results can provide theoretical basis and engineering practical value for the development and optimization of DMDF engines from the perspective of exergy.

Unsteady Flow Structure of Rotating Instability in a 1.5-Stage Axial Compressor

Abstract The unsteady flow structure of the rotating instability (RI) in a 1.5-stage axial compressor is investigated through experimental and numerical analyses. In the tested compressor, the total pressure rise of the rotor stagnates at a certain flow coefficient before it increases again toward a lower flowrate in a case involving a wide tip clearance. The RI appears beyond this stagnant point as the compressor is throttled. The RI indicates a gentle hump in the frequency spectra of wall pressure or the flow velocity near the tip in a range of approximately 20–40% of the blade-passing frequency. As the flowrate decreases, the mode order of the RI increases, in contrast to the more commonly reported tendency, while the propagation velocity remains constant. These features are well captured by detached eddy simulation (DES) of the half-annulus model, with which the unsteady flow structure is further investigated. At its onset, RI is formed by the collision of the tip leakage vortex onto the pressure surface of the adjacent blade and subsequent vortex segmentation. This vortex structure spans two blade passages and propagates in the direction opposite to the rotor rotation. As the compressor is throttled, RI becomes more dominated by the circumferential propagation of vortex breakdown of tip leakage vortices, which occur simultaneously among neighboring passages with slight phase differences. The mechanism is discussed in relation to the temporal change in the blade tip loading. The frequency of vortex shedding increases with the reduction in flowrate and thus the increase in the number of RI disturbances.

Research on Safety of Aero-Engine Oil Pipe Under Heating Conditions Based on Fluid-Solid Thermal Coupling.

This paper examines the safety of aero-engine pipelines under different heating conditions. Based on the fire test standard documents, a model of an aero-engine oil pipe was constructed, and its safety under heating conditions that meet the standard was analyzed using fluid-solid thermal coupling. The pipe material was stainless steel 1Cr18Ni9Ti, and the oil inside the pipeline was China RP-3 kerosene. To simulate the different working conditions or pump failure scenarios, various kerosene inlet flow rates were used for the calculations. The results indicate that the pipe wall exhibits an uneven temperature distribution under standard heating conditions. As the kerosene flow rate decreases, the pipe wall temperature rises, and heat transfer deterioration occurs. The increase in the pipe wall temperature reduces the material's strength, while the uneven temperature distribution generates thermal stress, further increasing the safety risk. When the kerosene flow rate is reduced to a certain level, the equivalent stress in the pipe wall exceeds the material's yield strength, leading to a high risk of rupture.

Experimental analysis of the R290 variable geometry ejector with a spindle

The aim of this work was to experimentally analyze the variable geometry gas ejector with a spindle designed for operation with the natural working fluid propane (R290). The performance of the ejector was evaluated based on the mass entrainment ratio and critical temperature, being the most crucial parameters for optimizing the cooling capacity in ejector refrigeration systems, as well as the ejector efficiency using common literature notation. Additionally, local pressure drop measurements allowed for the determination of pressure profiles inside for different spindle positions used for capacity regulation. The experimentally defined ejector efficiency curves demonstrated the ability to control the ejector capacity by means of the spindle, irrespective of the unfavorable operating conditions. By decreasing the effective throat area using spindle, the ejector mass entertainment ratio increased by 35%. Spindle movement allowed for the decrease of the motive nozzle flow rate by up to 65%, while still maintaining the suction of the secondary flow of the ejector. Moreover, the behavior of a slight increase in suction nozzle flow with a decrease in motive nozzle flow has been observed for the initial movement of the spindle followed by a huge drop for further reduction of the effective throat area, confirming the previous conclusions shown in the literature.

Influence of Si flow rate on the performance of MOCVD-deposited Si-doped Ga2O3 films and the applications in ultraviolet photodetectors

In this work, the Metal-organic Chemical Vapor Deposition (MOCVD) technology was used to successfully grow Si-doped β-Ga2O3 films on C-plane sapphire substrates. The effects of Si flow rate on the surface morphology, crystal composition, electrical and optical properties of the films were characterized and analyzed. The experimental results show that the full width at half maximum (FWHM) and root mean square (RMS) of the films are improved with the decrease of Si flow rate. More importantly, only the sample with the lowest Si flow rate showed conductive ability, and its carrier concentration and mobility were 4.20 cm2/V·s and 3.33 × 1016 cm−3, respectively. In addition, we also made photodetectors corresponding to the thin films. The test results showed that the external quantum efficiency (EQE) and responsiveness (R) of the detectors improved with the decrease of Si flow rate.

Synthesis And Efficiency Evaluation of Chitosan-Alginate Hydrogel Polyelectrolyte Complex Filter for Treatment of Oil Spillage

Crude oil spills pose considerable environmental concerns thereby demanding the development of effective, sustainable, and eco-friendly remediation solutions. In this study, we synthesized and evaluated the efficiency of a biodegradable polymer filter using sodium alginate and chitosan for the treatment of oil spillage. The sodium alginate-chitosan hydrogel polyelectrolyte complex (SACHPC) filter was synthesized via dipping method using a layer-by-layer self-assembly technique integrated with cotton wool as the filter medium. The efficiency of the filter was evaluated based on flow rate of recovered oil and reusability of the filter. Simulated oil spillage of 0.5 M was subjected to filtration using the SACHPC filter. The flow rate was determined based on the time taken for 1 L of oil to pass through the filter. The SACHPC filter exhibited underwater superoleophobic behaviour with exceptional filtration efficiency (> 98.3%) in acidic, neutral and alkaline conditions (pH 3, 7 and 11). The flow rate of the filter was 120 mL/min, while the third-use filter exhibited a decrease flow rate of 50 ml/min. Moreover, the filter achieved an impressive crude oil recovery rate of 85%. X-ray diffraction analysis confirmed crude oil adsorption in the presence of an amorphous phase while scanning electron microscopy analysis revealed the structural morphology of the SACPHC filter. Overall, the SACHPC filter maintained high filtration efficiency thereby offering a sustainable strategy for oily wastewater purification and oil spill clean-up.

Numerical simulation on energy characteristics of pump-turbine under pump condition

Abstract To investigate the energy characteristics of the pump turbine in pump mode, we selected the pump turbine as the research object and employed the SST k-ω turbulence model to conduct three-dimensional steady numerical simulations of the internal flow field of the pump turbine under several typical flow conditions. Our findings indicate that the unit’s energy loss is primarily concentrated in the runner and guide vane areas. In the small flow condition area, the energy loss of the draft tube basin cannot be ignored, while the energy loss in the stay guide vane and spiral casing areas is relatively small due to their low flow velocity. As the flow rate decreases, the energy loss in the draft tube, runner, and guide vane areas increases continuously. Additionally, complex flows such as vortex flow and backflow appear in the double-row cascade flow channel, which obstructs the flow channel and increases dissipation energy. In typical flow conditions, the energy loss in the draft tube, runner, and guide vane areas is a significant factor contributing to the decrease in head.

Adaptability Analysis of Gathering and Transportation Pipelines in W Shale Gas Field at Different Production Stages

Abstract This article analyzes the adaptability of the gathering and transportation pipelines of M well area from W shale gas field in different production stages. The pipelines are divided into three categories according to the degrees of being influenced by new pipelines. Typical pipeline transportation adaptability is analyzed, and improvement measures are proposed. The results show that the proportion of pipelines whose adaptability levels are above “medium” is 100%, 56%, and 39% in the early, middle, and late stages of production, respectively, which shows a decreasing trend. The adaptability level of the first type of pipeline decreases with the decrease of pipeline flow rate. Building a new pipeline can improve the adaptability level of the second type of pipeline downstream of the pipeline network. Building two or more pipelines can maintain the adaptability level of the third type of pipeline downstream of the pipeline network at “high” or “relatively high”. In response to the reduced adaptability in the middle and late stages, pigging and boosting simulations are conducted. A pigging plan and a rolling “platform boosting in coordination with centralized boosting” plan is developed, resulting in a 92% and 87% increase in transport efficiency in the middle and late stages, respectively. It was also demonstrated that cleaning can be one of the measures to enhance gas production. This article proposes the concept of adaptability analysis for different production stages in shale gas fields for the first time, and proposes reasonable measures to improve the adaptability of shale gas pipeline networks.

Citric acid functionalized chitosan hydrogel beads for enhanced Cr(VI) removal: Experimental assessment and COMSOL modelling of adsorption in a fixed-bed system

Chitosan hydrogel beads (CHB) and cross-linked CHB functionalized with tricarboxylic citric acid (CA-GLA-CHB) were synthesized and used for the removal of Cr(VI) from aqueous solutions in batch and dynamic adsorption systems. Applicability of COMSOL Multiphysics software as a tool for predictive modelling of column dynamics using a minimum set of experimental parameters was tested and compared with experimental results. Batch experiments demonstrated that CA-GLA-CHB showed almost 20% higher adsorption capacity and wider operational pH range compared to non-functionalized CHB. In a dynamic system, CA-GLA-CHB was used as column packing material and the column dynamics was investigated at different conditions. The breakthrough and exhaustion time of the column increased with an increase in bed height and a decrease in feed flow rate and initial Cr(VI) concentration. Computational modeling by COMSOL software with implemented Advection-Dispersion-Reaction (ADR) equation was used to simulate breakthrough curves for the applied dynamic system in order to validate the possibility of its application for process design in the scaled-up fixed-bed column systems for wastewater treatment. The simulated breakthrough curves of Cr(VI) adsorption matched well with the experimental, thus proving that COMSOL Multiphysics software can be used for scaling-up fixed-bed column systems packed with low-cost and effective CA-GLA-CHB bioadsorbent.

Oil removal using agricultural wastes adsorbents in a fixed bed column as a pretreatment in RO systems

Oil removal from seawater is an essential pre-treatment in Reverse Osmosis desalination plants to mitigate membrane fouling. The present paper investigates the feasibility of oil removal from water using agricultural wastes as low-cost adsorbents. Three wastes, rice husk, sugarcane bagasse, and sawdust were tested using two types of water, oily seawater and oily distilled water. For comparison, activated carbon adsorbent was included in the tests as a reference case. The experiments were conducted in a fixed bed column (10 cm diameter and 55 cm height), at an initial oil concentration of 1000, 3000, and 5000 mg/L, bed height of 10, 15, and 20 cm, and flow rate of 75, 145, and 290 mL/min. The parametric study indicated that the breakthrough time and the percentage of oil removal increased with the decrease in initial oil concentration and flow rate, but the breakthrough time increases with increasing the bed height. The oil removal percentage using rice husk was higher than sawdust and sugar cane bagasse and it was 18.9 % lower than that of activated carbon. Thus, rice husk can be a cheap alternative to activated carbon. The effect of oil type and water type was not significant. Additionally, the 50 % breakthrough time was 1388 min for activated carbon, 912 min for rice husk, 580 min for sawdust and 421 min for sugar cane bagasse. Assessing the dynamics models indicated that the non-linear forms of the Thomas, Bohart-Adams, and Yoon-and-Nelson kinetic models perform better than their linear forms, and the difference in performance among these models was not so big, i.e., any of these models can be used to predict the breakthrough curve.

Effect of Different Sizes and Heights on the Removal Efficiency of Composite Clay Filter for Gold Mine Site Wastewater Remediation

Wastewater from mining-related activities contains toxic elements that require remediation, and most available wastewater filters have inconsistent flow rates and removal efficiency due to their thickness. This study, therefore, examined the effect of height and size on the flow rate and removal efficiency of a clay composite filter for wastewater remediation. The developed clay filter and its composites were characterized using various techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The XRF analysis showed that the clay contained 91.38% major minerals, including iron oxide (Fe2O3), aluminum oxide (Al2O3), and silica (SiO2), which could enhance the filtration process. Additionally, FTIR revealed that both the clay and the filter are rich in functional groups, including kaolinite and illite, which could promote the filtration process. Further analysis showed that the filters had an average adsorption rate of 87.32%, an average flow rate of 0.891 L/hr, and an average removal efficiency of 99.6%. An increase in the height of a small-diameter filter resulted in a 0.21% increase in removal efficiency, while for larger diameters, the removal efficiency decreased by 0.11%. Conversely, increasing the diameter of a short filter increased the efficiency by 0.25%, while for taller filters, the removal efficiency decreased by 0.07%. Therefore, this work demonstrated that both height and diameter have noticeable effects on flow rate: as height increases, flow rate decreases, and as diameter increases, flow rate increases. The filter's efficiency is somewhat affected by both height and diameter, with a small increase in efficiency noted at greater heights and a slight decrease in efficiency noted at larger diameters.

Magnetic field modulation of confined water structure and transport in nanochannel

As a simple model of aquaporins, one-dimensional confined water in nanochannels, especially carbon nanotubes (CNTs), has attracted much attention due to its unique structure and rapid transport. The influence of external fields such as pressure, heat, electric field, and terahertz electromagnetic wave on confined water in CNTs has been widely studied. Magnetic field plays an important role in the regulation of water transport, but its research is limited at present. Therefore, in order to fill this gap, the effects of magnetic field with different strengths and directions on the structure and transport property of confined water in CNT were studied by molecular dynamics simulation. Simulation results showed that the magnetic field increased the number of hydrogen bonds by 1.10 % and accelerated the turnover frequency of the confined water (i.e. flipping interval decreased by 36.84 %), finally leading to a decrease in the water flow rate by 16.83 %. The effect of adjusting the magnetic field strength and direction on the hydrogen bond structure of confined water was more obvious. The results will help to understand the effect of magnetic field on confined water and provide guidance for the design of magnetic field regulation in water transport.

Simulating the impact of tumor mechanical forces on glymphatic networks in the brain parenchyma.

The brain glymphatic system is currently being explored in the context of many neurological disorders and diseases, including traumatic brain injury, Alzheimer's disease, and ischemic stroke. However, little is known about the impact of brain tumors on glymphatic function. Mechanical forces generated during tumor development and growth may be responsible for compromised glymphatic transport pathways, reducing waste clearance and cerebrospinal fluid (CSF) transport in the brain parenchyma. One such force is solid stress, i.e., growth-induced forces from cell hyperproliferation and excess matrix deposition. Because there are no prior studies assessing the impact of tumor-derived solid stress on glymphatic system structure and performance in the brain parenchyma, this study serves to fill an important gap in the field. We adapted a previously developed Electrical Analog Model using MATLAB Simulink for glymphatic transport coupled with Finite Element Analysis for tumor mechanical stresses and strains in COMSOL. This allowed simulation of the impact of tumor mechanical force generation on fluid transport within brain parenchymal glymphatic units-which include perivascular spaces, astrocytic networks, interstitial spaces, and capillary basement membranes. We conducted a parametric analysis to compare the contributions of tumor size, tumor proximity, and ratio of glymphatic subunits to the stress and strain experienced by the glymphatic unit and corresponding reduction in flow rate of CSF. Mechanical stresses intensify with proximity to the tumor and increasing tumor size, highlighting the vulnerability of nearby glymphatic units to tumor-derived forces. Our stress and strain profiles reveal compressive deformation of these surrounding glymphatics and demonstrate that varying the relative contributions of astrocytes vs. interstitial spaces impact the resulting glymphatic structure significantly under tumor mechanical forces. Increased tumor size and proximity caused increased stress and strain across all glymphatic subunits, as does decreased astrocyte composition. Indeed, our model reveals an inverse correlation between extent of astrocyte contribution to the composition of the glymphatic unit and the resulting mechanical stress. This increased mechanical strain across the glymphatic unit decreases the venous efflux rate of CSF, dependent on the degree of strain and the specific glymphatic subunit of interest. For example, a 20% mechanical strain on capillary basement membranes does not significantly decrease venous efflux (2% decrease in flow rates), while the same magnitude of strain on astrocyte networks and interstitial spaces decreases efflux flow rates by 7% and 22%, respectively. Our simulations reveal that solid stress from growing brain tumors directly reduces glymphatic fluid transport, independently from biochemical effects from cancer cells. Understanding these pathophysiological implications is crucial for developing targeted interventions aimed at restoring effective waste clearance mechanisms in the brain. This study opens potential avenues for future experimental research in brain tumor-related glymphatic dysfunction.

Hydrogen storage and refueling options: A performance evaluation

This study focuses on the comparative modeling and refueling simulations of hydrogen refueling stations for hydrogen-powered vehicles and high-pressure hydrogen storage options in tanks. The study further aims to simulate these under actual conditions in Ontario, Canada for better assessment which can be treated as a case study as well. The specific tests explore the modeling of hydrogen flow between the recharging station to the car's tank, as well as the optimization of transient variations in temperature, pressure and mass flow rate of hydrogen throughout the process of refueling a fuel cell electric vehicle. The H2FILLS program is utilized to assist for the simulation studies. The primary objective is to replicate various practical weather conditions, tank pressures, flow rates, and refueling periods for different categories of high-pressure hydrogen storage tanks and analyze their storage efficiency. The three different commercially available high-pressure type-IV hydrogen storage tanks were considered in the study as tank-I, tank-II and tank-III with working pressures of 500 bar, 700 bar, 700 bar, and hydrogen storage capacity of 9.5 kg, 4.6 kg, and 5 kg, respectively. Seven different ambient temperatures were selected to mimic seasonal effects. When the power output is constant, with temperature increases, flow rate decreases, and therefore time required to refuel also increases. There is a linear relationship between the final mass flow rate and the ambient temperature, where the mass flow rate drops by approximately 1.8 kg/h for every 10 °C rise in temperature. The variation in ultimate mass flow rate between the highest and lowest ambient temperatures is roughly 5.4 kg/h. Based on the refueling time and docking, undocking, downtime it’s been found that approximately five minutes is wasted between each vehicle. This can help reduce average of 230.02 kt, 231.70 kt, and 235.06 kt CO2 emission per year for vehicle-III, vehicle-II, and vehicle-I, respectively. Lastly, yearly CO2 reduction forecast shows that it may reach 0.9 Mt, 1.6 Mt, 2.7Mt, 3.76 Mt, and 4.73 Mt in the year 2030, 2035, 2040, 2045, and 2050, respectively corresponding to the Global Net-Zero scenario.

Numerical study of gas pocket distribution and pressurization deterioration mechanism in a centrifugal pump

In the event of a loss-of-coolant accident at a nuclear power plant, a large amount of steam enters the main pump, causing the pump's pressurization to deteriorate or even fail. To reveal the deterioration mechanism of the pump performance, the gas-liquid distribution characteristics in the centrifugal pump were studied by using structured grids and the Eulerian-Eulerian model. Based on the dimensional analysis method, a predictive correlation for bubble size was established, which included factors such as inlet gas volume fraction (IGVF), rotational speed, liquid flow rate, and impeller geometric parameters. When the predictive correlation is applied to the numerical simulation, the numerical two-phase pressurization agrees well with that obtained from the experiment. As the IGVF increases, the gas begins to accumulate at the impeller inlet under the effect of the pressure gradient force. Due to the large increase in liquid velocity, the gas begins to accumulate from the middle of the diffuser flow channel. The area occupied by the gas pocket in the impeller loses its pressurization capability. The pressure vortex formed at the inlet of the channel causes the diffuser to lose its pressurization capacity. An increase in rotational speed and a decrease in liquid flow rate can effectively prevent the formation and development of gas pockets in the impeller.

DEVELOPMENT OF AN EXPRESS ASSESSMENT OF THE RESULTS OF GEOLOGICAL AND TECHNICAL MEASURES TAKEN INTO ACCOUNT OF THE GATHERING SYSTEM

This article provides a rationale for the method of «express» assessment of changes in well flow rate when performing geological and technical measures in an oil field. In view of the cluster configuration of wells that is widespread in Western Siberia, the author identifies two groups of well pads, one of which is influencing, the other is reacting. At the influencing well clusters, as a result of the implementation of geological and technical measures to increase extraction from the productive formation, an increase in the produced fluid occurs. This leads to destabilization of the equilibrium in the “reservoir – well – pipeline” system. The consequence of a violation of this balance is an increase in the load on the reservoir fluid pumped in oil and gas gathering pipelines on individual branches of the field collection system. This leads to a redistribution of wellhead pressures at production wells, which, in turn, also leads to a change in bottomhole pressure and a change in well productivity. The author defines well pads where there is no increase in production, but where there is a change in pressure at the wellheads as reactive. With an increase in linear pressure on the pads, the energy balance in the operating production wells at the reacting well pads shifts towards a decrease in flow rate. Conversely, when wellhead pressure decreases, well productivity increases. These parameters will change until the energy balance of pressures in the wells is achieved. In connection with the above, within the framework of this work, an approach is presented for assessing changes in well operating parameters with increasing production in the field. An example of testing the proposed approach on a complex integrated model is given. To test this approach for adequacy, a comparison was made of theoretical calculations of changes in the operation of real wells with calculations performed on a customized complex integrated model of an oil field. It is worth noting that this type of calculation is characterized as approximate. Its use is advisable exclusively at the stage of preparing programs for performing geological and technical measures to determine reservoir zones in which the negative effect of increasing production will be minimal.

There is No Increased Pulmonary Risk Following Total Hip Arthroplasty in Patients Who Have Obstructive Sleep Apnea Without Underlying Lung Disease

BackgroundObstructive sleep apnea (OSA) is a frequent comorbidity. The current study evaluated whether there is a difference in the perioperative outcome after total hip arthroplasty (THA) in patients who had a low to moderate risk for OSA and high risk for OSA, respectively. MethodsAfter excluding patients who had concomitant lung disease (chronic obstructive pulmonary disease, asthma, or lung fibrosis) and those missing a STOP-Bang Score, 1,141 THA patients who had OSA were included in this retrospective study. Patients at low to moderate risk for OSA (STOP-Bang Score 0 to 4) and patients at high risk for OSA (STOP-Bang Score 5 to 8) were compared, and SpO2 (oxygen saturation) drops < 90% as well as readmission rates were compared between patients who did and did not use continuous positive airway pressure (CPAP). ResultsThere was no difference in the risk of SpO2 drop below 90% (1 versus 0%, P = 0.398) and readmission rate (2 versus 2%, P = 0.662) between patients who had low to moderate OSA risk (327 THA) and high OSA risk (814 THAs). There was no difference in SpO2 (P > 0.999) and a decrease in oxygen flow rate from the postanesthesia care unit to the morning of the first postoperative day. A CPAP device was used by 41% (467 of 1,141) of patients. There were no differences in SpO2 drop < 90% (0 versus 0%, P = 0.731) and readmission rate (2 versus 2%, P = 0.612) between patients who did and did not use a CPAP machine. ConclusionsThe current study showed no difference in perioperative outcomes between OSA patients undergoing THA who had a low STOP-Bang Score and patients who had a high STOP-Bang Score, regardless of the use of a CPAP machine. These data suggest that an elevated Stop-Bang Score does not indicate an increased perioperative risk for OSA patients when deciding on outpatient discharge.

Evolution law of flow characteristics for straight pipeline after leaking

Aiming at the leakage problem of the fluid loop system for the thermal control system of spacecraft caused by the impact of micro-meteoroid and orbital debris, we investigate the dependence of the leak rate, pressure drop and flow characteristics before and after leaking on leak position, inlet pressure, and leaking aperture, calculated in a straight pipeline with single leakage, using stationary and transient three-dimensional computational fluid dynamics simulations with commercial software (FLUENT). The working fluid adopts single-phase water without gravity. It is found that the pressure increases obviously near the leak point, which is caused by the local peak of pressure. As the length between the leak point and the inlet becomes larger, the local peak of pressure and the dimensionless leak rate are smaller. When the inlet pressure increases, the leaked mass flow rate increases; however, the ratio of the leaked flow rate to inlet flow rate decreases. Furthermore, it is observed that the dependence of dimensionless leaking rate on dimensionless leaking aperture has a scaling relation with the scaling exponent approximating to 2, which may be related to the proportion of the vortex formed by the backward flow at the leak hole, the amplitude, and the affected length along the pipe of the local peak of pressure. This study is instructive and meaningful to the leak detection and plugging of fluid loop in space.

Integrated experiments and numerical simulations for chromium (VI) surface complexation in natural unconsolidated sediments

This study focuses on the adsorption and transport of Cr (VI) on natural sediments from Qiqihar, China. Through batch and column experiments, we assessed the adsorption capacities influenced by factors such as contact time, initial concentration, pH, ionic strength, solid-to-solution ratio, coexisting ions in groundwater, sediment characteristics and flow rate. The adsorption kinetics of Cr (VI) follow the pseudo-first-order model well, while the isotherms of all three sediments are accurately represented by the Freundlich model. The adsorption edges reveal a strong pH dependence in Cr (VI) adsorption: the stronger the acidity, the more favorable it is for adsorption. The adsorption capacity decreases with an increasing solid-to-solution ratio, stabilizing at higher ratios. Coexisting ions in groundwater reduce Cr (VI) adsorption in loam under neutral pH. Additionally, Fourier transform infrared spectroscopy (FTIR) results indicate that the hydroxyl group is the primary reactive functional group in all three sediments. X-ray photoelectron spectroscopy (XPS) results further show partial adsorbed Cr (VI) was reduced to Cr (III) by organic matters. However, surface complexation reactions dominate the removal of Cr (VI). On the base above, we introduced a surface complexation model, optimizing equilibrium complexation constants by fitting adsorption edges. Subsequently, reactive transport models incorporating both surface complexation and reduction processes for Cr (VI) were established to simulate column experiments. As the flow rate decreases, the adsorption capacity and the amount of reduction reaction for Cr (VI) increase, while the reduction rate decreases. Specifically, the reduction for Cr (VI) was found to be more significant in loam compared to sand, correlating with the organic matter content. The results emphasize the existence of surface complexation reactions and the role of organic matters in electron transfer. Our study provides significant information for understanding Cr (VI) adsorption and transport behavior in natural aquifer sediments.