Large Pressure Research Articles

Metabolic effects of atypical antipsychotics: Molecular targets.

Atypical antipsychotics (AAPs) are commonly prescribed drugs in the treatment of schizophrenia, bipolar disorder and other mental diseases with psychotic traits. Although the use of AAPs is associated with beneficial effects in these patients, they are also associated with undesired metabolic side effects, including metabolic syndrome (MetS). MeS is defined by the presence of metabolic abnormalities such as large waist circumference, dyslipidemia, fasting hyperglycemia and elevated blood pressure, which predispose to type 2 diabetes (T2D) and cardiovascular disease. In this review, the molecular and cellular mechanisms involved in these undesired metabolic abnormalities induced by AAPs are described. These mechanisms are complex as AAPs have multiple cellular targets which significantly affect the activities of several hormones and neuromodulators. Additionally, AAPs affect all the relevant metabolic organs, namely the liver, pancreas, adipose tissue, skeletal muscle and intestine, and the central and peripheral nervous system as well. A better understanding of the molecular targets linking AAPs with MetS and of the mechanisms responsible for clinically different side effects of distinct AAPs is needed. This knowledge will help in the development of novel AAPs with less adverse effects as well as of adjuvant therapies to patients receiving AAPs.

Regulation of temperature distribution in fixed bed reactor for CO2 methanation through “CHESS” monolith structure catalyst

CO2 methanation suffers from the problem of temperature runaway phenomenon due to its exothermic nature. To mitigate this issue, optimizing catalyst structure becomes crucial. This work established numerical models to investigate the CO2 methanation reaction and heat/mass transfer process in the reactor with porous pellet and monolithic catalysts. Results show that the reactor with porous pellets has the lowest carbon conversion per unit pressure drop due to its large total pressure drop. In contrast, the reactor with monolith exhibits a much larger carbon conversion per unit pressure drop but a smaller absolute carbon conversion. Based on this, an improved “CHESS” monolith structure was proposed and improved, which not only maintains a high absolute carbon conversion (62.6 %) but also enhances the heat transfer process in CO2 methanation. Moreover, compared with the reactor with porous pellets, the maximum temperature in the improved “CHESS” monolith was decreased by around 11.09 %.

Characteristics and rarity of the strong 1940s westerly wind event over the Amundsen Sea, West Antarctica

Abstract. Glaciers in the Amundsen Sea Embayment of West Antarctica are rapidly retreating and contributing to sea level rise. Ice loss is occurring primarily via exposure to warm ocean water, which varies in response to local wind variability. There is evidence that retreat was initiated in the mid-20th century, but the perturbation that may have triggered retreat remains unknown. A leading hypothesis is that large pressure and wind anomalies in the 1940s drove exceptionally strong oceanic ice-shelf melting. However, the characteristics, drivers, and rarity of the atmospheric event remain poorly constrained. We investigate the 1940s atmospheric event using paleoclimate reconstructions and climate model simulations. The reconstructions show that large westerly wind anomalies occurred from ∼1938–1942, a combined response to the very large El Niño event from 1940–1942 and other variability beginning years earlier. Climate model simulations provide evidence that events of similar magnitude and duration may occur tens to hundreds of times per 10 kyr of internal climate variability (∼0.2 to 2.5 occurrences per century). Our results suggest that the 1940s westerly event is unlikely to have been exceptional enough to be the sole explanation for the initiation of Amundsen Sea glacier retreat. Additional factors are likely needed to explain the onset of retreat in West Antarctica, such as naturally arising variability in ocean conditions prior to the 1940s or anthropogenically driven trends since the 1940s.

LES application to wind pressure prediction for tall building on complex terrain

This study conducted numerical simulations based on the large eddy simulation (LES) model, which employs an unstructured grid system and exhibits high performance in parallel computing, to investigate the effects of a circumferential environment, such as real terrain and surrounding buildings, on the unsteady pressure fields acting on a tall building with a rectangular section. There are three numerical examples using an irregularly shaped high-rise building (aspect ratios: height/length = 7/4 and length/width = 24/11), the same building on a complex terrain, and the same building with surrounding buildings on a complex terrain. To elucidate the statistical pressure characteristics, we focused on the mean, fluctuating, and peak values on the surfaces of the target building. The pressures for the present models were validated through a comparison with experimental data obtained under the same conditions. Subsequently, the velocity and pressure fields directly influenced by the complex local terrain and surrounding buildings were studied. A concave terrain located on the leeward side of the target building could cause a large negative pressure on the side surfaces as a result of access to the deformed separating flow. In addition, the surrounding buildings led to the movement of the stagnation point to a higher location on the windward surface and intensification of the conical vortex attached to the side surface.

Conceptual Design of a Novel Megawatt Molten Salt Reactor Cooled by He-Xe Gas

He-Xe gas-cooled micro-molten salt reactor (HX-micro-MSR) is a novel reactor concept that integrates the technologies of molten salt reactor and closed Brayton cycle (CBC), which has a more compact structure compared with the other types of micro-MSRs. The reactor system probed in this paper has a thermal power of 2.5 MWth and consists of the core, fission gas collecting container, and CBC system. The He-Xe gas flows through the coolant channels in the core to transfer the nuclear heat to the CBC for electricity production. To withstand the large pressure difference between the He-Xe gas coolant (7 MPa) and molten salt (nearly atmospheric pressure), the sizes and wall thickness of coolant channels are analyzed and optimized to be 8 mm and 0.5 mm, respectively. In total, 1050 coolant channels are regularly arranged in the core to effectively remove the nuclear heat. The enrichment of U-235 in the fuel UF4 is determined to be 61% to meet the burnup goal of 5 years. To minimize the neutron leakage, the thickness of reflector is selected to be 23 cm. Six control drums with the diameter in 10.5 cm and neutron absorber layer thickness in 1 cm are symmetrically placed in the reflector to realize reactivity control under both normal and accident conditions. Radiation shield is designed and analyzed by varying the thickness of multiple shielding layers, and it is found that a combination of W layer in 14 cm and Mg(BH4)2 layer in 56 cm can satisfy the criterion of radiation dose (<1 mSv/h). The total weight of HX-micro-MSR is estimated to be 35 tonnes and falls into the acceptable range.

Design and Numerical Simulation Study of a Novel AICD for Water Control and Gas Production in Gas Wells.

The automatic inflow control device (AICD) used for water control and gas recovery in gas wells as the core component of gas well intelligent layered/segmented production and water control technology is very important for the development of advanced well completion (AWC) technology in water-producing gas reservoirs. Therefore, the design of AICD to ensure that the gas flows smoothly inside it and to keep water under control to a greater extent can maximize the performance of the AICD, and the most important thing is to restrict the water in the formation from entering the wellbore. However, currently, there are very few designs and research on the AICD used for water control and gas production in the gas wells, and the performance of this type of tool and the law of gas and water flow inside it are not perfect, so more in-depth research is needed. In this paper, a new type of AICD is designed to realize the function of water control and gas flow smoothly, and the DoE of the new AICD is carried out, determining the factors that will affect the key technical indicators and the factors that may have interactive effects, using the numerical simulation method of computational fluid dynamics to carry out optimal design, conducting fluid physical property sensitivity analysis, and flow rate applicability analysis. The results show that the tool is not sensitive to the viscosity of water and gas in different gas reservoirs but is very sensitive to the density of water and gas. When the gas/water flow rate ratio is less than 4, it can exert its water control effect. In addition, the results of multiple sets of physical experiments are well consistent with the simulation results; the average deviation of single-phase water is 10.91% and the average deviation of single-phase gas is 11.85%. Computational fluid dynamics and physical experiment results show that, under these conditions, the difference in fluid flow characteristics can be fully exploited; the channel is automatically identified to produce a small gas pressure drop and a large water flow pressure drop. The research in this paper belongs to the key technology of the AWC technology of gas wells in the new water control strategy of the current and has a certain reference value to make up for the defects of drainage gas recovery technology in the water management strategy..

Flow behavior of laval nozzle sets in steam turbine governing stage at low loads

To achieve carbon neutrality, thermal power units (TPU) will be deeply involved in peak regulation, which is crucial for the development of renewable energy generation. However, the efficiency of TPU is significantly reduced at low loads. The main reason for this is that the convergent nozzles in conventional TPU are difficult to efficiently expand steam with large pressure differentials (i.e., pressure ratios below a critical value), and thus the unit is designed to operate in sliding-pressure mode, resulting in a low Rankine cycle efficiency. To reveal the mechanism of energy loss in the governing stage under peak shaving conditions, the flowing behavior of governing stage nozzle sets of a 330 MW steam turbine is investigated by CFD simulation in this study. The results indicated that the shock waves generated by the supercritical streamflow and the angle deviation at the exit of nozzle sets are the main factors leading to energy efficiency degradation. Based on this, two supersonic Laval nozzles were designed and analyzed in the 10 %∼40 % load range. Compared with conventional nozzles, the designed supersonic nozzles I and II showed average efficiency improvements of 4.9 % and 5.8 %, respectively, and maximum efficiencies of 6.6 % and 9.5 %, respectively. The research in this paper can provide theoretical support for the design and development of nozzle sets under deep peaking conditions, which can help achieve carbon neutrality.

Experimental analysis of boron dilution transient flow mixing characteristics based on planar laser induced fluorescence measurement

In Reactor Pressure Vessels (RPV), flow mixing between high and low concentration coolants will cause uneven distribution of boric acid. Severe cases will lead to boron dilution transient and re-criticality safe operation accident. Therefore, accurate measurement of coolant flow mixing characteristics and boron concentration distribution in RPV and study of the mechanism affecting the mixing process are of great significance to improve reactor operation safety. Based on the structural characteristics of large advanced pressurized water reactor pressure vessel, a large-scale visual experimental device was built by 1:6 scale modular design. Optical path correction scheme is used to solve the problem of optical path distortion existing in PLIF technology, and improved ratio calibration method is used to reduce the experimental error of concentration field distribution measurement. Flow mixing process and boron concentration field distribution in pressure vessel under single loop conditions were obtained based on plane laser induced fluorescence technique (PLIF). The influence of Reynolds number on boron diffusion behavior was studied. The experimental results show that during single loop operation, the localized eddy current formed in the left area of the lower head will result in a high concentration retention zone and a V-shaped boric acid concentration distribution in the core. With the increase of the ratio of cold tube flow to injection flow, the time when the high concentration coolant reaches the core hardly changes with the boric acid solution flow rate. The mixing diffusion behavior of boron concentration is the best when the ratio of injection to Reynolds number in the cold tube is at a certain value.

Pressure control for pneumatic pressing roller in automated fiber placement

In automated fiber placement (AFP), the contact pressure between the roller and the mold is an important process parameter. Too small or too large contact pressure will result in unacceptable laying defects. This paper focuses on the control method of contact pressure in AFP. Firstly, the dynamic model of the pressing foot mechanism is established, and a mathematical relationship of input air pressure and output force is developed. Then, a self-tuning PI control algorithm is used to implement servo control of the roller output force based on the Slowly Time-Varying Recursive Identification Algorithm. Also, using Abaqus/CAE, the mapping relationship between the contact area and measurements from displacement sensors is established to predict the contact area in real time. Finally, the contact pressure control method is established by combining the servo control method of contact force and the prediction method of contact area. Experimental results show that the constant pressure control method can effectively stabilize the contact pressure, with a pressure fluctuation of less than 4% under the experimental conditions set in this paper.

Numerical study of flow in low-pressure turbines with undulated suction surface

The low-pressure turbine is an important component of the aero engine, and its efficiency greatly influences on the performance of the aero-engine. In order to improve the efficiency of low-pressure turbines, flow control methods can be adopted to overcome the large adverse pressure gradient in the passage of high-load blades, suppress the flow separation at the rear of the suction surface, thereby reducing losses in low-pressure turbines. Based on the understanding of the separated flow mechanism on the suction surface, a new passive control method using undulations on the suction surface to suppress the separated boundary layer is proposed in the current study. It is found that the counter rotating vortices generated by the undulation is attributed to the suppression of the separation bubble, reductions in the loss coefficient and the deviation in the exit flow angle by 15% and 23%, respectively.

Research on the Mechanism and Control Strategy of Microbubble Cleaning Sludge

Microbubble cleaning technology has the characteristics of environmental protection and low energy consumption and has been initially applied in the field of oil sludge cleaning. For the controllability of microbubbles in the cleaning process, this paper adopted the numerical simulation method to quantitatively study the growth and collapse mechanism of bubbles in the cleaning process, the influence law of flow field, and parameter changes on the dynamic behavior of bubbles from the perspective of micro-dynamics. It was found that the dynamic characteristics of the flow field around the bubble in the free field show a symmetrical distribution, while the motion of the fluid near the wall is blocked by the wall, and the flow field between the bubble and the wall becomes irregular. It was also found that the large amplitude pressure changes in microbubbles produced a “plastic hinge” alternating impact on the wall, the bubble collapse, and wall pulsation pressure change are mainly controlled by the driving pressure. The liquid temperature mainly affects the dynamic characteristics of the bubble by causing a change in the viscosity of the medium. Under the condition of Pd = 0.1 MPa and γ = 1.5, when the liquid viscosity decreases from 0.110 to 0.00314 Pa·s, the maximum pressure affected by the first bubble collapse increases from 200.71 to 317.74 Kpa. Compared with the bubble distribution, the impact of increasing the number of bubbles on the wall is more significant. Under the condition of γ = 1 and Pd = 0.1 MPa, compared with the single bubble, the pulse pressure of nine bubbles’ collapse on the wall increases by 100 KPa. The research results can provide technical support for the development of microbubble cleaning technology.

Ammonia Adsorption Performance of Zeolitic Imidazolate Frameworks for Cooling.

Promoting the cooling performance of adsorption chillers (ACs) greatly relies on the exploration of high-performance adsorbent/refrigerant working pairs. Ammonia is not only an environmentally friendly refrigerant but also favorable for heat and mass transfer in ACs owing to its large vapor pressure and enthalpy of evaporation. Zeolite imidazolate frameworks (ZIFs) with excellent ammonia stability are identified as a class of potential adsorbents for practical ammonia-based ACs. However, high-performing ZIF/ammonia working pairs with excellent AC performance are still to be developed. In this work, the cooling performance including the coefficient of performance for cooling (COPC) and the specific cooling effects (SCEs) of 26 ZIFs with the same composites but different topologies was evaluated by combining molecular simulation and mathematical modeling. Five high-performing ZIFs with COPC > 0.45 and SCE > 250 kJ/kg were identified, among which gis-ZIF with the highest COPC of 0.51 and lta-ZIF with the highest SCE of 354 kJ/kg both are promising to be synthesized and applied further. Besides, the quantitative structure-performance relationship (QSPR) was extracted that can help quickly identify and design high-performing ZIFs according to their ammonia adsorption isotherms and structural characteristics. Moreover, "S"-shaped adsorption isotherms with high saturation adsorption capacity (>0.2 g/g), suitable step position (0.2-0.4), and relatively low Henry's constant (<1 × 10-5 mol/(kg·Pa)) are more favorable for excellent COPC and SCE. From the perspective of structure characteristics, ZIFs possessing low crystal density (<0.9 g/cm3), high accessible surface area (>2000 m2/g), balanced largest cavity diameter (∼15 Å), and accessible pore volume (∼0.65 cm3/g) are beneficial for high-efficient cooling performance.

Hydrogen combustion in two-stage high-pressure gas turbine—thermal and flow simulations for performance comparison with fossil fuels

Hydrogen energy forms an attractive solution for reducing greenhouse gas emissions from gas turbine systems. Although hydrogen combustion has been widely studied for combustors, only a few studies have considered the combustion effect downstream of the combustor. This study conducted an integral simulation of the combustion and flow of a GE-E3 aero-engine under hydrogen fuel and compared its performance with that of representative fossil fuels such as Jet A in an aero-engine and methane in an industrial gas turbine. All simulations were conducted under a constant heat input at the combustor and turbine inlet temperatures. During combustion simulation, the HyChem mechanism was applied to evaluate the composition of the products in an equilibrium model. Specifically, Reynolds-averaged Navier–Stokes steady simulation of a two-stage high-pressure gas turbine was conducted using the calculated boundary condition from the combustion simulation and k − ω shear stress transport γ turbulence model. The results revealed the high velocity of the hydrogen combustion flue gas owing to its low density under a large pressure difference. Overall, the power output, thermal efficiency, and fuel consumption were improved by hydrogen combustion. The thermal and flow results of the simulation can be used to develop hydrogen gas turbines.

Enhancement of water droplet drainage performance in a cathode flow channel with baffles for a polymer electrolyte membrane fuel cell

A reasonable design of flow channel is crucial for water management of a polymer electrolyte membrane fuel cell (PEMFC), and thus the cell performance. This paper develops newly designed baffles on a cathode flow channel to boost the water droplet drainage ability. The water droplet drainage characteristics within the novel flow channel are investigated by using a volume of fluid (VOF) method. The results show that the baffle height and number have a significant impact on the water droplet drainage performance. An appropriately increased baffle height and number leads to a shorter water droplet drainage time with a relatively low pressure drop. The water droplet drainage time for baffle height and number of 0.25 mm and 7 is reduced to 8.5 ms from 22.5 ms compared with that for the conventional channel. However, a too large baffle height and number could yield a very large pressure drop, thereby causing the water droplet detachment from the GDL surface and finally adsorption to the sidewalls. An optimal non-uniform interval layout of baffles along the channel can further shorten the water droplet drainage time by 6.25%. These findings can guide the optimal design of flow channels with baffles for a high-performance fuel cell.

Experimental study on the influence of maintenance track position on vortex-induced vibration performance of a box girder suspension bridge

To study the influence of maintenance track on the vortex-induced vibration (VIV) performance of main girder, the VIV response and time history of surface pressure data of a section model were obtained by wind tunnel vibration and pressure measurements for a large-span steel box girder suspension bridge. The VIV performance of the main girder was tested at ±5° attack angles of various maintenance track positions, including 1, 2.5, and 5 m away from the outer edge of the girder bottom plate. The mean values, root variances and amplitude spectra of vortex-induced force and the correlation and contribution coefficients of local aerodynamic force to overall aerodynamic force were analyzed. The results show that when the maintenance track is 1 m away from the outer edge of the bottom plate, the main girder exhibits the worst VIV performance with a maximum amplitude of 0.457 m, far beyond the allowable value of the specification. The VIV performance of the main girder was greatly improved by moving the maintenance track inward. The pressure analysis indicates that the large pressure fluctuation at the front and rear parts of the upper surface is attributed to the strong VIV of the main girder. In this sense, the improved VIV performance is mainly contributed by the weakening of pressure fluctuation in these two areas and the reduced local aerodynamic force. When the distance between the maintenance track and bottom plate is adjusted to 2.5 m, a 3.5 m wind barrier with a ventilation rate of 30% effectively inhibits the VIV of the box girder. The main reason for the suppression is that the elimination of pressure fluctuation on the upper surface of the girder disturbs the correlation between local aerodynamic force and overall aerodynamic force, consequently diminishing the contribution of local aerodynamic force to the vortex-induced force.

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

CO2 storage: threshold capillary pressure estimate in a remoulded caprock specimen

Synergistic Effects of Resistive Breathing on Endotoxin-Induced Lung Injury in Mice.

Resistive breathing (RB) is characterized by forceful contractions of the inspiratory muscles, mainly the diaphragm, resulting in large negative intrathoracic pressure and mechanical stress imposed on the lung. We have shown that RB induces lung injury in healthy animals. Whether RB exerts additional injurious effects when added to pulmonary or extrapulmonary lung injury is unknown. Our aim was to study the synergistic effect of RB on lipopolysaccharide (LPS)-induced lung injury. C57BL/6 mice inhaled an LPS aerosol (10mg/3mL) or received an intraperitoneal injection of LPS (10 mg/kg). Mice were then anaesthetized, the trachea was surgically exposed, and a nylon band of a specified length was sutured around the trachea, to provoke a reduction of the surface area at 50%. RB through tracheal banding was applied for 24 hours. Respiratory system mechanics were measured, BAL was performed, and lung sections were evaluated for histological features of lung injury. LPS inhalation increased BAL cellularity, mainly neutrophils (p < 0.001 to ctr), total protein and IL-6 in BAL (p < 0.001 and p < 0.001, respectively) and increased the lung injury score (p = 0.001). Lung mechanics were not altered. Adding RB to inhaled LPS further increased BAL cellularity (p < 0.001 to LPS inh.), total protein (p = 0.016), lung injury score (p = 0.001) and increased TNFa levels in BAL (p = 0.011). Intraperitoneal LPS increased BAL cellularity, mainly macrophages (p < 0.001 to ctr.), total protein levels (p = 0.017), decreased static compliance (p = 0.004) and increased lung injury score (p < 0.001). Adding RB further increased histological features of lung injury (p = 0.022 to LPS ip). Resistive breathing exerts synergistic injurious effects when combined with inhalational LPS-induced lung injury, while the additive effect on extrapulmonary lung injury is less prominent.

Single focused-beam acoustical tweezers: Trapping cells in 3-D

Single focused beams have shown great potential in acoustofluidics and medical ultrasound because of their large pressure gradient and acoustic-thermal effect, such as acoustical tweezers and high-intensity focused ultrasound (HIFU) technique. However, the three-dimensional trapping of typical cells is still challenging since cells in water have a positive acoustic contrast factor and will be repulsive from the focus [Gong and Baudoin, Phys. Rev. Applied 18, 044033 (2022)]. In this work, to reverse this positive acoustic contrast factor into negative, we propose to use a cell-friendly medium (made of iodixanol with water) [Augustsson et al., Nat. Commun. 7, 11556 (2016)]. This enables a single focused beam to selectively trap and control cells in 3-D, and more importantly, keeps the manipulated cells with good viability. This work will extend the applications of acoustical tweezers, which may be beneficial to single cell analysis, cellular phenotyping, precise assembly of different cells in tissue engineering, and controlled drug delivery.

Function Optimization of Self-shutoff Protection System for -Valve Chambers of Long-distance Natural Gas Pipelines

The rate of pressure drop set value of shut-off valve in gas pipeline is uncertain to a certain extent, and the function of self-shutoff protection may disable under some leakage conditions. A gas pipeline leakage model is established using simulation software, to simulate the leakage, flow rate reduction, and crossover, and obtain the pressure changes in upstream and downstream shut-off valve chambers under different working conditions[1]-[3]. The rate of pressure drop is calculated by using the rate of pressure drop algorithm adopted by Line Guard 2300 system. Simulation results indicate that the gas transmission volume has little influence on the rate of pressure drop, and the leakage diameter has great influence on the rate of pressure drop, showing a positive correlation. When the pipeline runs in parallel, it is necessary to avoid opening the crossover valve under large pressure difference. Finally, the recommended rate of pressure drop threshold at the trunk line shut-off valve chamber is given, and the leakage condition of 1/2 diameter at 32km upstream can be detected under this recommended value.The simulation software is first applied in multinational pipelines, which can effectively protect pipeline defect points. Reduced methane cold venting, greatly improving the contribution to achieving emission reduction goals.

Large Eddy Simulation and Dynamic Mode Decomposition of Supersonic Combustion Instability in a Strut-Based Scramjet Combustor

Supersonic combustion instability studies are crucial for the future maturation of scramjet engines. In the present paper, the supersonic combustion instability in a strut-based scramjet combustor is investigated through large eddy simulation and dynamic mode decomposition. The results show significant pressure oscillation in the strut-based scramjet combustor when the air parameters at the combustor inlet and the fuel parameters at the injector outlet are under certain conditions, and these pressure oscillation situations correspond to supersonic combustion instability. The oscillations have multiple dominant frequencies, including relatively low frequency of 2984 Hz, high frequency of 62,180 Hz, and very high frequency of 110,562 Hz. Large pressure oscillations in the strut-based scramjet combustor are closely related to wake instability, shear layer instability, shear layer and wave interactions, and combustion. Reducing the air total temperature at the combustor inlet can attenuate the pressure oscillations, and reducing the fuel flow rate at the injector outlet can also attenuate the pressure oscillations.