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The article presents the results of numerical and experimental studies of a working nozzle for jet-abrasive machining of material surfaces. Nozzle designs with variable geometry were investigated. The aim of the study was to identify reserves for increasing the efficiency of the nozzle to ensure the energy efficiency of the jet-abrasive installation for sustainable production in the context of Industry 5.0. The implementation of numerical modeling made it possible to carry out a series of calculations for the considered nozzle designs using an air-abrasive mixture with flow visualization. The technological parameters of jet-abrasive machining were analyzed. A series of numerical and experimental studies were conducted using the principles of Industry 4.0. Two software packages were used for numerical studies. The results of the calculations that were obtained coincided quite well. Overall, the obtained results made it possible to adjust the settings of the pneumo-abrasive unit in order to get the proper roughness of the processed surface, opt for proper working nozzle design, and determine proper pressure and air consumption for the highest unit efficiency. In a series of studies, the authors proposed a mathematical model for determining the values of mass flow rates of the working medium in the nozzle. The analytical coefficients of the developed model have been obtained. In addition, an approach to determining the main parameters of abrasive blasting based on experimental data was developed. The results obtained were verified by comparing them with the results of experimental studies. It was found that to increase the efficiency of the Venturi nozzle, the outlet cross-section of the considered nozzles should be reduced, and the mass flow rate of the dispersed phase should not significantly affect the speed of the grains of sand at the nozzle outlet. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Transpiration cooling have gradually become the lead candidate for thermal protection technology of hypersonic vehicle also due to its excellent cooling performance. The porous medium with exceptional properties can further improve thermal protection capability and reliability of transpiration cooling. This paper investigates the preparation and properties of C f /SiC porous ceramic composite with low density and remarkable permeability, and probes the transpiration cooling performances of ceramic composites (mass ratio of silicon carbide particles and short chopped carbon fibers of 1:1) in the various heat flux conditions. The research results show that C f /SiC porous ceramic composites prepared by adding short chopped carbon fibers have uniform pore size distributions (3～20 μm) and low densities (1.074 g/cm3 ～ 1.377 g/cm3), as well as outstanding wettability and permeability (6.07 × 10−8 mm2 ～ 12.22 × 10−8 mm2). Besides, The C f /SiC porous ceramic composites (mass ratio of 1:1) display excellent transpiration cooling performance, meanwhile a new interesting phenomenon that the water pressure difference increases with the rising of heat flow is discovered. Such studies can provide an essential reference for developing porous medium in transpiration cooling technology. [ABSTRACT FROM AUTHOR]

Simple Summary: A suitable environment inside broiler houses is crucial to broiler health, welfare, and productivity. High stocking density can easily lead to uneven temperature conditions, which may cause broilers to experience cold or heat stress. Therefore, the objectives of this article were to assess the temperature uniformity inside a commercial broiler barn and to investigate influencing factors on the temperature difference. In this study, temperature, wind velocity, and differential pressure sensors were installed in a commercial stacked-deck cage broiler house for continuously monitoring the environment. Results indicate that the maximum temperature difference increased from 1.85 °C to 6.43 °C, while the daily fluctuation increased from 2.27 °C to 5.80 °C. The lateral temperature distribution is the main reason for the poor overall temperature uniformity and stability. In the lateral direction, the temperature distribution changes periodically, with the maximum temperature difference varying from 1.98 °C to −2.14 °C (− indicating high-temperature location variation) within one day. This variation was significantly influenced by solar radiation and wind speed, which can lead to poor performance and higher mortality rates in broilers. Therefore, it is crucial to consider the influences of solar radiation and wind on the indoor environment when designing and managing chicken houses. The temperature inside broiler houses is crucial to broiler health, welfare, and productivity. High stocking density in broiler houses can easily lead to nonuniform temperature conditions, which would cause broilers to suffer cold and heat stress. It is essential to assess the temperature distribution inside broiler houses and investigate the factors that affect temperature uniformity. Therefore, in this study, temperature, wind velocity, and differential pressure were monitored in the aisle, at the sidewall inlet, and outside the sidewalls of a commercial stacked-deck cage broiler house in Northeast China aiming to continuously monitor the temperature throughout the entire fattening period. Results show that the maximum temperature difference increased from 1.85 °C to 6.43 °C, while the daily fluctuation increased from 2.27 °C to 5.80 °C. The highest temperature was consistently recorded at the side of the exhaust fans (p < 0.001) in the longitudinal direction. In the lateral direction, the temperature difference varies periodically with solar radiation. The average temperature at the southern location (23.58 ± 1.97 °C), which faces the sun, was higher than that at the northern location (23.35 ± 1.38 °C), which is in the shade, during periods of solar radiation (p < 0.001) at the last testing period. However, without solar radiation, the northern location recorded a warmer temperature (23.19 ± 1.41 °C) compared to the southern location (22.30 ± 1.67 °C) (p < 0.001). The lateral temperature differences are strongly positively correlated with solar radiation and wind speed (p < 0.001). In conclusion, the inside temperature nonuniformity and fluctuation increased as the broiler age increased, which affected the production performance of broilers. Nonuniform solar radiation and wind speed can lead to differences in the inlet temperature and air volume between both sidewalls, thereby affecting the uniformity of the lateral temperature inside the house. [ABSTRACT FROM AUTHOR]

Heat stress has posed a significant threat to the laying hens inside the poultry houses in the Northwest region of China. Significant non-uniformities can be found in the thermal distribution and temperature variations in summer. The ventilation system has been the primary measure to regulate the thermal environment in the poultry houses. Excellent airflow arrangement and ventilation strategies are essential for the ventilation efficiency. Still, the continuous operation of fans can inevitably generate the excessive local cold air, thereby wasting the electrical energy for the high cost of environmental control. Alternatively, intermittent ventilation can serve as an efficient way to improve ventilation effectiveness with energy saving. However, it is notably limited to applying to the summer poultry houses so far. In this study, a novel intermittent ventilation was introduced to alleviate the significant temperature fluctuations and ensure the high stability of the thermal environment in the summer poultry houses. According to the internal air temperature, the fan operations were performed on the conventional tunnel-ventilated poultry houses (control house, CH) and sidewall inlets poultry houses (experimental house, EH). Specifically, the fans were regulated, when the temperature exceeded the upper limit. Once the temperature dropped below the lower limit temperature, the fans were deactivated simultaneously, which was different from the continuous operations of fans throughout the summer. The thermal environment was monitored in the operation periods of intermittent ventilation. The environmental conditions inside the poultry houses were also evaluated. The results revealed that the average internal temperatures of experimental and control poultry houses were 25.3 and 26.5 °C, respectively, under the same external environmental temperatures; While the average relative humidity were 65.8% and 62.7%, respectively. The temperature fluctuations during the EH and CH's intermittent and continuous ventilation were 0.6 and 0.7 °C, 1.2 and 1.0 °C, respectively. The maximal difference of temperature in the horizontal direction of EH and CH were 0.3 and 5.2, 0.8 and 4.7 °C, respectively. Temperature variations were assessed in the four-hour intervals. The EH consistently demonstrated more minor temperature fluctuations than the CH when the fans were operated intermittently. The horizontal temperature difference was less than that in the continuous operation in EH. There was no difference in pressure and air velocity under the intermittent and continuous ventilation in the same number of fans. The pressure difference between the interior and the evaporative cooling pad buffer room increased from 17 to 19 Pa from the fan opposite wall to the fan. Average air velocity at the sidewall inlets and along the aisles in the EH were 3.30 and 0.49 m/s, respectively, which were higher by 1.86 and 0.12 m/s, compared with the CH. Therefore, the intermittent ventilation was suitable for the sidewall inlets, to improve the thermal environment within the poultry house significantly. There was great potential for widespread adoption in the Northwest region of China in the summer. The lifespan of the fan was extended for the maximal economic benefits. The intermittent operation times of fans should be determined according to the local climate, poultry houses’ ventilation requirements and the poultry houses’ size. This finding can provide a foundational reference for designing and adjusting the intermittent ventilation in summer poultry houses in the Northwest region of China. [ABSTRACT FROM AUTHOR]

We evaluate and compare the simulation of the main features (low-level westerlies (LLWs) and the Congo basin (CB) cell) of low-level circulation in Central Equatorial Africa (CEA) with eight climate models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) and the corresponding eight previous models from CMIP5. Results reveal that, although the main characteristics of the two features are reasonably well depicted by the models, they bear some biases. The strength of LLWs is generally overestimated in CMIP5 models. The overestimation is attributed to both divergent and rotational components of the total wind with the rotational component contributing the most in the overestimation. In CMIP6 models, thanks to a better performance in the simulation of both divergent and rotational circulation, LLWs are slightly less strong compared to the CMIP5 models. The improvement in the simulated divergent component is associated with a better representation of the near-surface pressure and/or temperature difference between the Central Africa landmass and the coastal Atlantic Ocean. Regarding the rotational circulation, and especially for HadGEM3-GC31-LL and BCC-CSM2-MR, a simulated higher 850 hPa pressure is associated with less pronounced negative vorticity and a better representation of the rotational circulation. Most CMIP5 models also overestimate the CB cell intensity and width in association with the simulated strength of LLWs. However, in CMIP6 models, the strength of key cell characteristics (intensity and width) are reduced compared to CMIP5 models. This depicts an improvement in the representation of the cell in CMIP6 models and this is associated with the improvement in the simulated LLWs. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the relationship between the morphological structure and hemodynamic properties of the compressed iliac vein and explore the reason for the formation of thrombosis in the compressed iliac vein. Materials and Methods: A total of 11 patients with iliac vein compression syndrome (IVCS) were included in this study, and their iliac veins were reconstructed in 3 dimensions (3D). The morphological structures of the iliac veins (confluence angle, degree of stenosis) were analyzed based on the 3D model. Variations in the hemodynamic properties of the iliac vein were investigated at 4 typical moments in one cardiac cycle, and the relationship between the different morphological configurations and the pressure difference was investigated. Results: In the region of the compressed iliac vein, the blood flow velocity is accelerated and the pressure changes abruptly accompanied by the increase in pressure difference. Higher time averaged wall shear stress (TAWSS) and lower relative residence time (RRT) appeared in stenosis regions of compressed iliac vein, while TAWSS was low and RRT was large near the stenosis position. There was a strong positive correlation between the degree of stenosis and the pressure difference (r=0.894), and a positive correlation between the confluence angle of the iliac vein and the pressure difference (r=0.638). Conclusion: The morphological structure of the compressed iliac vein has an obvious influence on the hemodynamic surroundings; the pressure difference becomes larger when the degree of stenosis and the confluence angle increase. The iliac vein luminal areas with low TAWSS and high RRT near the compressed location can impede blood flow and lead to accumulation of blood components, which may increase the risk of thrombosis formation and should be fully considered in the treatment of IVCS. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum Refinery Engineering is the property of Petroleum Refinery Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For shallow buried mines, the cracks generated due to the mining activities will connect the surface ground and the working face through the gob, which may result in the gas exchange between the surface and underground. In this study, we proposed the gob gas flow model and verified its applicability based on the measured data on site in our previous research and discussed the effect of delay time of pressure variation between working face and surface ground on the airflow direction according to the simulation. The results suggest that the delay time of pressure variation is the main factor affecting the pressure difference between surface and working face and airflow direction. Due to the characteristics of the surface pressure changes, the effect of delay time on airflow in gob is small in a short time, but this effect gradually increases with time. According to the airflow law in a cycle of pressure variation, the airflow direction in the gob is predictable when the delay time reaches a certain value, which can be interpreted clearly on the surface pressure variation diagram. This research may provide references for the measures taken against mine disasters caused by different airflow directions. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study aimed to elucidate the foot kinematics and foot pressure difference characteristics of faster swimmers in undulatory underwater swimming (UUS). In total, eight faster and eight slower swimmers performed UUS in a water flume at a flow velocity set at 80% of the maximal effort swimming velocity. The toe velocity and foot angle of attack were measured using a motion capture system. A total of eight small pressure sensors were attached to the surface of the left foot to calculate the pressure difference between the plantar and dorsal sides of the foot. Differences in the mean values of each variable between the groups were analysed. Compared to the slower swimmers, the faster swimmers exhibited a significantly higher swimming velocity (1.53 ± 0.06 m/s vs. 1.31 ± 0.08 m/s) and a larger mean pressure difference in the phase from the start of the up-kick until the toe moved forward relative to the body (3.88 ± 0.65 kPa vs. 2.66 ± 1.19 kPa). The faster group showed higher toe vertical velocity and toe direction of movement, switching from lateral to medial at the time of generating the larger foot pressure difference in the up-kick, providing insight into the reasons behind the foot kinematics of high UUS performance swimmers. [ABSTRACT FROM AUTHOR]

The article presents the results of numerical and experimental studies of a working nozzle for jet-abrasive machining of material surfaces. Nozzle designs with variable geometry were investigated. The aim of the study was to identify reserves for increasing the efficiency of the nozzle to ensure the energy efficiency of the jet-abrasive installation for sustainable production in the context of Industry 5.0. The implementation of numerical modeling made it possible to carry out a series of calculations for the considered nozzle designs using an air-abrasive mixture with flow visualization. The technological parameters of jet-abrasive machining were analyzed. A series of numerical and experimental studies were conducted using the principles of Industry 4.0. Two software packages were used for numerical studies. The results of the calculations that were obtained coincided quite well. Overall, the obtained results made it possible to adjust the settings of the pneumo-abrasive unit in order to get the proper roughness of the processed surface, opt for proper working nozzle design, and determine proper pressure and air consumption for the highest unit efficiency. In a series of studies, the authors proposed a mathematical model for determining the values of mass flow rates of the working medium in the nozzle. The analytical coefficients of the developed model have been obtained. In addition, an approach to determining the main parameters of abrasive blasting based on experimental data was developed. The results obtained were verified by comparing them with the results of experimental studies. It was found that to increase the efficiency of the Venturi nozzle, the outlet cross-section of the considered nozzles should be reduced, and the mass flow rate of the dispersed phase should not significantly affect the speed of the grains of sand at the nozzle outlet.

To improve the efficiency and extend the lifespan of the proton exchange membrane fuel cells (PEMFC), it is imperative to control PEMFC's supply system effectively. A sliding mode controller (SMC) based on adaptive algebraic observer is designed to control the oxygen excess ratio and the pressure difference between the cathode and anode of PEMFC. First, a 9th order physical model of the PEMFC system is established including air supply system, hydrogen supply system and the stack, which is validated against the experimental data with the maximum output voltage error of 2.91%. Then, a SMC is designed based on the control-oriented PEMFC model. An adaptive algebraic observer for the estimation of the gas partial pressure is designed to be used in the SMC. Finally, simulation is conducted and results show that the performance of the designed SMC is superior than that of the PID controller in terms of the oxygen excess ratio settling time (1s less), the pressure difference settling time (50% less) and overshoot (0.5 kPa less). [ABSTRACT FROM AUTHOR]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper presents the results of studies on local resistance coefficients (ζ). The study used pipe aerators with filling made according to the Polish patent PL235924. The hydraulic investigations were performed in real working conditions of a water treatment plant in a testing rig built in the Scientific and Research Water Station of the Warsaw University of Life Sciences (SGGW). The investigation encompassed two plastic pipe aerators of an internal diameter 101.6 and 147.6 mm with steel Białecki rings of 12 and 25 mm in diameter. Measurements of pressure difference (Δp) in the investigated aerators were performed at volumetric water flows ( Q) selected from the range 2–20 m 3∙h –1 with the interval 2 m 3∙s –1. The values of ζ were determined according to the PN-EN 1267:2012 standard. The investigation showed that the ζ depends both on an internal diameter of the plastic pipe aerator and the diameter of Białecki steel rings. The values of ζ increase with a decrease of the internal diameter of the pipe aerator and a decrease of the ring diameter.

Introduction. Modern technologies, as well as various methods and schemes currently used in technology, have made it possible to automatically control the damping properties of shock absorbers, which increases the energy intensity of the entire suspension system. However, in order to use these solutions in practice, it is necessary to develop mathematical models of these damping elements. Such models serve as a theoretical tool for studying the described processes in order to implement the correct control action. As for such units as controlled (adjustable) vane shock absorbers, the studies carried out earlier on them are clearly not enough to ensure their effective operation in various conditions.The object of this study is a controlled vane hydraulic shock absorber.The purpose of this work is to carry out theoretical studies and improve the methodology for calculating controlled (adjustable) bladed hydraulic shock absorbers, in which magnetorheological fluid is used as the working fluid of the shock absorber.Research methods. The design and principle of operation of controlled vane hydraulic shock absorber with magnetorheological (MR) throttles are considered. Method of calculation is proposed and theoretical studies are performed on influence of change of volume flow rate of working medium of shock absorber in MR throttle on forces of resistance to rotation on shaft of shock absorber blade.The results of theoretical research. 1) Results of theoretical studies of change of volume flow rate of working medium of controlled hydraulic blade shock absorber are presented. 2) An adequate mathematical model is obtained that is suitable for calculating the characteristics of controlled (adjustable) hydraulic vane shock absorbers, where magnetorheological fluid is used as the working medium of the shock absorber, as well as for selecting control action in the control system. Conclusion. The results of the study are intended for organizations and enterprises engaged in the development and production of heavy high-speed tracked vehicles.The results of the studies can be used to refine the methodology for estimating the smoothness of the heavy high-speed tracked vehicles.

The temperature inside broiler houses is crucial to broiler health, welfare, and productivity. High stocking density in broiler houses can easily lead to nonuniform temperature conditions, which would cause broilers to suffer cold and heat stress. It is essential to assess the temperature distribution inside broiler houses and investigate the factors that affect temperature uniformity. Therefore, in this study, temperature, wind velocity, and differential pressure were monitored in the aisle, at the sidewall inlet, and outside the sidewalls of a commercial stacked-deck cage broiler house in Northeast China aiming to continuously monitor the temperature throughout the entire fattening period. Results show that the maximum temperature difference increased from 1.85 °C to 6.43 °C, while the daily fluctuation increased from 2.27 °C to 5.80 °C. The highest temperature was consistently recorded at the side of the exhaust fans (p < 0.001) in the longitudinal direction. In the lateral direction, the temperature difference varies periodically with solar radiation. The average temperature at the southern location (23.58 ± 1.97 °C), which faces the sun, was higher than that at the northern location (23.35 ± 1.38 °C), which is in the shade, during periods of solar radiation (p < 0.001) at the last testing period. However, without solar radiation, the northern location recorded a warmer temperature (23.19 ± 1.41 °C) compared to the southern location (22.30 ± 1.67 °C) (p < 0.001). The lateral temperature differences are strongly positively correlated with solar radiation and wind speed (p < 0.001). In conclusion, the inside temperature nonuniformity and fluctuation increased as the broiler age increased, which affected the production performance of broilers. Nonuniform solar radiation and wind speed can lead to differences in the inlet temperature and air volume between both sidewalls, thereby affecting the uniformity of the lateral temperature inside the house.

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In high-rise buildings, the excessive pressure differences cause various problems, and architectural and mechanical measures are always applied. In this study, pressure measurements on a 67-story high-rise building were conducted to evaluate the effect of mechanical pressurization on the pressure distribution. Absolute pressure measurement devices were installed at 28 points on 10 floors, a full-scale pressure profile of the test building was derived, and the pressure distributions on the main floors were reviewed. Four pressurization modes for the test building were considered, and the variation in the pressure distribution for each mode was analyzed. The results showed that mechanical pressurization reduced the pressure difference on the lobby floor by approximately 18%. Although it did not exert an apparent impact on the pressure difference due to the stack effect, pressurizing the entire floor serves as the most effective way of reducing the excessive pressure difference. [ABSTRACT FROM AUTHOR]

Hydroelectric power belongs to renewable energy sources and contributes a considerable percentage of the electrical energy generated in the world. Its advantages include no carbon dioxide emission, excellent maneuverability, and high energy effectiveness. However, disadvantages do also exist caused by the influence of hydropower facilities on the bioenvironment. This paper presents a review of the most characteristic effects of elements of the flow path of hydroturbines during their operation on biofauna (fish and plankton). The most popular design solutions are examined, which are aimed at reducing the risk of negative impact of the elements of the flow path of hydraulic turbines on the bioenvironment. Obviously, the implementation of these solutions will deteriorate the performance of hydraulic turbines. However, we should bear in mind that the main purpose of these solutions is to ensure the biological safety of facilities, while their energy characteristics do not receive proper attention. The paper presents in some detail an option for rendering environmental safety, which is the modernization of the runner hub by eliminating the gaps between the blades and the hub. Numerical simulation has revealed that the application of a runner with the modified hub increases the hydraulic resistance, decreases the flowrate, and, as a result, reduces the generated power. An analysis of the simulation results has suggested that, despite some decrease in the energy characteristics, it seems worthwhile to develop biologically safer flow path design versions. In addition, a conclusion has been made that the flow path can be further modified to compensate for power losses. [ABSTRACT FROM AUTHOR]

As a short-process hydrometallurgical technology, slurry electrolysis (SE) collects the stirring that improves the suspension of ore, the membrane bag that acts as purifying, and the cathodic and anodic plates that promote ion migration in one tank. The stirring helps to maintain the ore suspended. As the SE tank is stirred, the membrane bag will deform and become damaged, severely limiting production efficiency. In this research, the one-way fluid-structure interaction (FSI) was used to examine the impact of the solid–liquid suspension on membrane deformation, which was based on the computational fluid dynamics (CFD) and solid finite element method (FEM). Through the full 3D quantitative analysis, the database of membrane deformation under various conditions was established. The membrane was extruded to the center during the initial stirring conditions, and the greatest deformation measured 891.66 mm. Primarily, membrane deformation was brought on by the pressure differential brought on by liquid velocity, solid concentration distribution, and liquid level. The maximum deformation of the membrane first decreased and then increased with the increased liquid level difference between the cathode and anode. With the upper fixed constraint, the maximum deformation of the membrane appears at y = 1.2 m. The larger the stirring speed is, the smaller the optimal liquid level difference required to minimize the membrane deformation. The stirring speed changes the overall pressure distribution by changing the dynamic pressure in the anode domain. The maximum deformation of the membrane decreases first and then increases with the increase of electrolyte density in the cathode domain. The membrane bag is extruded to the cathode domain when the pressure in the cathode region is insufficient because of the low electrolyte density in the cathode domain. When the cathode pressure increases, the membrane bag bulges to both sides, and the inner bulge is greater than the outer. With an increase in solid volume concentration (SL) in the anode domain, the maximum membrane deformation first reduces and subsequently increases. When SL = 15%, the membrane deformation reaches the minimum value of 226.7 mm. The closer to the bottom of the tank, the greater the influence of solid content on absolute pressure. The maximum membrane deformation is drastically decreased to 0.664 mm when the frame restrictions are considered. It can support the industrial control process via visual analysis.

Purpose: Hemodynamics play a key role in the management of cerebral aneurysm recanalization after coil embolization; however, the most reliable hemodynamic parameter remains unknown. Previous studies have explored the use of both spatiotemporally averaged and maximal definitions for hemodynamic parameters, based on computational fluid dynamics (CFD) analysis, to build predictive models for aneurysmal recanalization. In this study, we aimed to assess the influence of different spatiotemporal characteristics of hemodynamic parameters on predictive performance. Methods: Hemodynamics were simulated using CFD for 66 cerebral aneurysms from 65 patients. We evaluated 14 types of spatiotemporal definitions for two hemodynamic parameters in the pre-coiling model and five in virtual post-coiling model (VM) created by cutting the aneurysm from the pre-coiling model. A total of 91 spatiotemporal hemodynamic features were derived and utilized to develop univariate predictor (UP) and multivariate logistic regression (LR) models. The model's performance was assessed using two metrics: the area under the receiver operating characteristic curve (AUROC) and the area under the precision-recall curve (AUPRC). Results: Different spatiotemporal hemodynamic features exhibited a wide range of AUROC values ranging from 0.224 to 0.747, with 22 feature pairs showing a significant difference in AUROC value (P-value

Copyright of Journal of Henan University of Science & Technology, Natural Science is the property of Editorial Office of Journal of Henan University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study focuses on laboratory testing of carbon-dioxide adsorption. It compares three methods used to determine the capacity of the adsorbents proposed for CO2 capture. The tests have been performed on two samples, namely natural clinoptilolite and a 13X molecular sieve. Two methods were dynamic and one was static. The first dynamic method evaluated the capacity based on the change in CO2 volume fraction before and after a fixed-bed adsorber. For the same purpose, the second dynamic method used a gravimetric procedure. The static method detected a change in pressure during CO2 adsorption. The capacities determined for carbon-dioxide mole fractions of 5, 10, 13 and 20% at temperatures of 30 and 40 °C at atmospheric pressure were compared. The apparatus with a fixed-bed adsorber made it possible to perform tests also for overpressures of 2 and 5 bar and lower temperatures. The capacity obtained on the three apparatuses showed good agreement. The maximum capacity (3.32 mmol g−1) was determined for the 13X sample at 10 °C and a partial CO2 pressure of 120 kPa and, conversely, the lowest (0.12 mmol g−1) for clinoptilolite at 40 °C and a partial CO2 pressure of 5 kPa. There was no significant difference in capacity standard deviations between the apparatus (0.014–0.036 mmol g−1). The fixed-bed apparatus required one to three orders of magnitude more gas for the experiment and was more challenging to operate and evaluate the data. [ABSTRACT FROM AUTHOR]

The paper presents the results of studies on local resistance coefficients (ζ). The study used pipe aerators with filling made according to the Polish patent PL235924. The hydraulic investigations were performed in real working conditions of a water treatment plant in a testing rig built in the Scientific and Research Water Station of the Warsaw University of Life Sciences (SGGW). The investigation encompassed two plastic pipe aerators of an internal diameter 101.6 and 147.6 mm with steel Białecki rings of 12 and 25 mm in diameter. Measurements of pressure difference (Δp) in the investigated aerators were performed at volumetric water flows (Q) selected from the range 2-20 m³·h-1 with the interval 2 m³·s-1. The values of ζ were determined according to the PN-EN 1267:2012 standard. The investigation showed that the ζ depends both on an internal diameter of the plastic pipe aerator and the diameter of Białecki steel rings. The values of ζ increase with a decrease of the internal diameter of the pipe aerator and a decrease of the ring diameter. [ABSTRACT FROM AUTHOR]

Exploiting coalbed methane can optimize the energy mix and improve safety in coal mines. Coalbed methane production commonly requires that the coal’s permeability be enhanced. However, conventional permeability enhancement techniques commonly used at present have their own shortcomings, such as a limited range of permeability enhancement or high fracture initiation pressures Tree-type fracturing is one of the new techniques that are expected to eliminate the above-mentioned shortcomings and allow the efficient exploitation of coalbed methane reserves. The unclear of gas migration mechanism in tree-type fracturing limits the development of this technology. For this paper, a fluid–solid–gas coupling experimental system was assembled to study the changes in gas pressure and gas flow in gas-bearing coal after hydraulic fracturing. In the experiments, tree-type branch boreholes can effectively connect hydraulic fractures and surrounding natural cracks, increasing the scope and rate of gas extraction. The degree of connectivity of fractures (cracks and pores) will affect the gas desorption rate, which makes the gas flow trace “U” shaped lines. Tree-type hydraulic fracturing can increase the coal’s permeability by factors of 3.1 to 3.9, increase the effective drainage rate by factors of 1.23 to 1.41, and increase the proportion of gas drained by 3.7% to 5.5%. These results provide a reliable basis for additional research on tree-type fracturing and can aid in its engineering application.

The channel structure of a proton-exchange membrane fuel cell (PEMFC) is very important for sustaining high performance with a reliable lifetime. There have been numerous computational studies to investigate the physics of electrochemical reactions with various flow field phenomena. Because straight channels reduce manufacturing costs, a straight channel was selected as the subject of a numerical study to investigate water removal and oxygen starvation in the channel. In this study, the liquid saturation distribution caused by the baffled obstacle geometry of a PEMFC with channels that were straight and parallel was analyzed in a computational study. Because baffled obstacles generate a vortex in the channel, the flow field structure improves the supply of reactants. When the operating pressure is reduced from 3 atm to 1 atm, the baffled obstacle structure interrupts the flow of reactant and product water so that the accumulation of liquid water increases from 0.75 to 0.86 in catalyst layer. As the number of baffled obstacles was increased from 13 to 19, the current density improved from 0.772 to 0.773 A/cm2 in the reference condition. The baffled obstacle geometry also affects the liquid water accumulation flow field. Results show that the design of the baffled obstacles in a channel should consider the number of baffled obstacles along with the baffled obstacle geometry such that water removal is accelerated. [ABSTRACT FROM AUTHOR]

A previously unnoticed anomaly is recently identified in a stopper rod flow control system for the continuous casting of steel by comparing full‐scale water model experiments with plant data. Despite extensive research previously done on the continuous casting fluid flow phenomena, this anomaly and its background physics are not well understood by researchers. Computational fluid dynamics (CFD) modeling of the molten steel flow in the stopper rod system is performed with predictions matching closely with water model data but deviating from plant measurements. It is thus suggested by this comparison that certain aspects of the liquid steel flow and pressure behavior in the stopper rod system cannot be effectively described by traditional modeling techniques due to their embedded limitations. Through water modeling, CFD simulations, plant measurements, and theoretical analysis, the current study for the first time presents a thorough discussion of this observed anomaly, which brings new insights into understanding the complex fluid flow behavior and pressure distributions inside the stopper rod control system during the continuous casting process. [ABSTRACT FROM AUTHOR]

The pulse-decay method is believed to be more suitable than the steady-state method for permeability measurements on tight porous media because it records pressure variations instead of flow rates and does not require the establishment of a steady state. Most of the previous analytical solutions for the pulse-decay process are based on a linearized governing equation, which may be inapplicable to measurements with large differential pressures. In this study, a nonlinear governing equation is derived through mass conservation and Darcy's law. For rigid porous media such as the sedimentary rock samples, by comparing the magnitude of the pressure sensitivity of the physical properties for both the testing gas and the core sample, we found that only the gas compressibility and the apparent permeability have to be regarded as pressure-dependent, while the others can be regarded as constant. The perturbation method and the eigenfunction expansion method are combined to derive the general solution of the nonlinear governing equation. The results show that in the plot of logarithmic differential pressure versus time, a straight line can be obtained at the late-time stage and its slope value can be used to evaluate the apparent permeability. We further estimate the error in permeability evaluation, induced by selecting mean pore pressure as the characteristic pressure. The theoretical analysis has been verified by both numerical simulation and experimental measurements. [ABSTRACT FROM AUTHOR]

Porous materials are widely adopted in the recovery of high temperature waste heat in power plants. The research on the internal flow and heat transfer is of great significance for the improvement of energy utilization, environmental pollution reduction and realization of “carbon peaking and carbon neutrality”. The characteristics of flow and heat transfer of simulated flue gas, water vapor and dust-laden flue gas in porous alumina ceramic materials were studied by means of simulation. The results show that the average fluid velocity increases, while the fluid temperature difference between the inlet and outlet decreases with the enlargement of materials􀆳 porosity. Among these fluids, the velocity of water vapor is the largest which reaches 66. 64 m/ s at the maximum porosity, the temperature drop of flue gas between the inlet and outlet is the most significant which is 85. 6 K when the porosity is 0. 3. The fluid flow rates increase the rising of pressure differences, and the flow rate of the dust-laden flue gas is slightly affected by the increase of fly ash particles which is from 0. 23 m/ s to 0. 93 m/ s. The heat conduction between the fluid and the wall is weakened due to the increase of velocity, and the temperature drop of the fluid is also reduced. The fluid disturbance of dust-laden flue gas is relatively larger, and the flow velocity increases proportionally with porosity and pressure difference. While, the molecular interaction makes the temperature of dustladen flue gas changes significantly besides the presence of fly ash particles. [ABSTRACT FROM AUTHOR]

The stack effect in high-rise buildings, stemming from an inside/outside temperature difference, may produce a significant pressure difference on the elevator doors, potentially causing elevator malfunctions. This effect can also be influenced by wind action and human behaviors, e.g., opening/closing of building entrances. In this study, a wind tunnel test was conducted to determine the real wind pressure distribution on a high-rise building in northern China. A numerical simulation utilizing the Conjunction of Multizone Infiltration Specialists software (COMIS) was carried out to investigate the pressure difference of elevator doors under the effects of thermal buoyancy, wind action, and opening/closing of the first-floor lobby entrance. An alternative solution of a locally strengthened envelope is proposed and validated for the studied building zone. The study reveals that the opening of the first-floor lobby entrance increases the pressure difference regardless of the environmental conditions, and the increase of wind speed tends to increase the pressure difference in winter but decrease it in summer. The proposed countermeasure combination, involving using revolving doors instead of swing doors, increasing additional partitions, and strengthening the local building envelope, was found to be synergistic and effective in reducing the pressure difference inside the building. The research findings offer practical engineering solutions for mitigating elevator door pressure challenges in high-rise buildings.

[Objective] The method for quickly and accurately measuring sediment concentrations in water samples in the field based on differential pressure was studied. [Methods] Four soil types (including Lou soil, sandy soil, saline-alkali soil, and paddy soil) were chosen to prepare 11 water samples with different sediment concentrations based on the principle of pressure difference. The pressure difference between a water sample and the atmosphere was determined by using digital differential pressure meter (abbreviated as pressure difference) in order to establish the relationship between sediment concentration and pressure difference. [Results] Sediment concentration and pressure difference were linearly and positively correlated (significant at p=0.01). The method of pressure difference combined with a theoretical formula to determine sediment concentration was feasible for three of the water samples (including the Lou soil water sample, the sandy soil water sample, and the paddy soil water sample), and the absolute value of the maximum relative error was less than 15%. However, the method was not suitable for the sandy soil water sample. The absolute value of the maximum relative error in the determination of sediment concentration for the sandy soil water sample was as high as 39%. Therefore, to reduce the error, a correction equation was established by determining the pressure difference between pure water and water samples with sediment content of 500 kg/m3, and then combined with the measured pressure difference to calculate the sediment concentration. The absolute value of the maximum relative error was found to be less than 8%. [Conclusion] This method can accurately determine the sediment concentrations of water samples. It could provide a new way for conveniently determining sediment concentration in the field for soil and water conservation monitoring.

A standard procedure for measuring airflow velocity has been developed in order to unify and standardize applied measuring instruments and data processing algorithms, as well as to reduce the time required for the development and certification of such standard procedures. The study examines the sources of error in indirect airflow velocity measurements within the range of 3–105 m/s. The following sources of instrumental error in indirect measurement are analyzed: digital and analog pressure sensors, pitot-static tubes, temperature and relative humidity sensors, and atmospheric pressure sensors. The greatest contribution to the instrumental error is shown to be made by the measurement of pressure difference and atmospheric pressure. The procedural error, which depends on the adopted measurement model, is considered. The authors propose a mathematical measurement model including the optimal expressions for determining the density of humid air and corrections for compressibility, which allows the procedural error to be reduced. In addition, requirements are developed for the metrological characteristics of the used measuring instruments, ensuring that the combined error of indirect airflow velocity measurements complies with the permissible limits of Δperm = ±0.2 m/s. The authors give recommendations on the use of measuring instruments and algorithms of measurement result processing, which enable a 39% measurement error reduction and the creation of a standard procedure for measuring airflow velocity. This procedure can be used in the aviation industry when measuring airflow velocity via the pneumometric method. [ABSTRACT FROM AUTHOR]

This study proposes a new method for predicting the airtightness of a building envelope by using pressure differences that naturally occur in high-rise buildings. The background and principle of the proposed method, which uses the relationship between pressure difference and airflow, are described. The proposed method was validated by applying it to a 42-storey residential building. The differential pressure generated in the building under actual climatic conditions was measured twice during the winter season. Based on the measured pressure difference data, the airtightness of the building envelope was predicted, and those predicted values were compared with detailed measurements taken using the blower door test method. The results show that the difference between the predicted and directly measured airtightness of the building envelope for the upper floors (36th and 42nd floors), where the differential pressure was relatively large, did not differ significantly. Where the differential pressure across a building component formed by the indoor/outdoor temperature difference, the building height, and the distance from the neutral plane of the analyzed building was more than 50 Pa, the results predicted using the method proposed in this study were valid. [ABSTRACT FROM AUTHOR]

The results of studies into geometric characteristics for multistage steam jet ejectors are presented. Various manufacturers' approaches during multistage ejector design optimization are analyzed accounting for the pressure increase levels' distribution and the nozzles' critical diameters of the ejector stages. It was found that, for cogeneration and condensing turbines, an approach to the distribution of geometric and technological parameters over the ejector stages can vary. For cogeneration turbines, the diameters of the nozzles' critical sections decrease with an increase of stage number, while they increase for condensing turbines. It is shown that there is a correlation in multistage ejectors between the distribution of steam flow rates between stages and the main geometric parameter of the ejector's first stage. The test results of three- and two-stage ejectors with external coolers designed by the authors are presented. The main three-stage ejector is employed in the scheme of steam-air mixture evacuation from the turbine condenser, and the two-stage ejector with a precooler is designed to evacuate air from the scheme of the turbine heat extraction plant. The ejector of the heat extraction plant is connected to the main condensate line behind the main ejectors. Steam condensate is removed from the ejector to the hot well of the first delivery water heater. Multistage ejectors are equipped with an extended scheme for pressure measuring along the ejector' steam-air mixture path: in the intake chamber, after the diffuser, and in the intermediate cooler. It is shown that an increase in the pressure of the steam-air mixture, which cannot be explained by the obvious diffuser effect, that is, by the pressure increase as flow decelerates, is observed in the ejectors' coolers (between the stage diffuser and the intake chamber of the next stage). When analyzing the operating modes of multistage ejectors, the spesific feature of their self-regulation is revealed with the possibility of decreasing the steam-air mixture compression ratio in one of the stages. [ABSTRACT FROM AUTHOR]

When a fire occurs onboard a ship, ventilation ducts may become hidden pathways for smoke to spread, and this issue has long attracted attention in the industry. In this paper, an experimental and numerical investigation on the smoke movement and indoor temperature characteristics were carried out. The results show that under the effect of thermal buoyancy, ducts with the openings located on the ceiling can easily become pathways for smoke to spread across the cabins. Compared with the scenario where the ducts are removed, the smoke jets from the ducts make the smoke movement in the adjacent cabin more complicated, and the maximum temperature in the cabin is also significantly increased. Moreover, it is found that the mass flow rate (MFR) of the gas in the duct is mainly determined by the pressure difference Δp between the two ends of the duct, and the MFR increases linearly with the increase of A flow (2Δp)1/2, but its maximum value is limited by the cross-sectional area of the duct. The research results will help to better understand the cross-compartment smoke spread under the effect of ventilation ducts and serve as a reference for the quantitative evaluation of the smoke flow in ducts. [ABSTRACT FROM AUTHOR]

Aiming at the problem of controlling the operating velocity of a large-diameter heavy-duty pipeline inspection gauge (PIG), this paper designs the bypass structure to study the velocity change and flow field state when the Ø1219 mm PIG is operating in pipeline with different bypass rates. Fluent is applied to numerical simulation of the fluid-structure interaction flow field based on the dynamic mesh method. The results show that: the bypass rate of 2%–3% can satisfy the velocity of PIG in 3–5 m/s reasonable interval. The larger the bypass rate is, the larger the turbulence intensity is, and the gradual increase of the pressure difference suffered by the PIG. The operating velocity of the PIG can be regulated more accurately by corresponding to the bypass rate and the pressure difference front and rear. Comparing the experimental and simulation results, the error rate of the velocity decrease with bypass rate of 1%–3% is 12.8 %. • Study of fluid-structure coupling simulation based on the dynamic mesh approach. • Pressure, velocity, turbulence intensity analysis of PIG with 1%–3% bypass rate. • Velocity can be regulated by bypass rate corresponding to pressure difference. • In this paper, scaling experiments are performed and compared with simulation. [ABSTRACT FROM AUTHOR]

• Droplet length is found to be the primary factor influencing the splitting pattern. • The presence of tunnels leads to an exponential decrease in the splitting ratio with droplet length. • Capillary number has a negligible impact on the splitting ratio for large-size droplets. In this paper, the phase-field multiphase lattice Boltzmann method is employed to simulate droplet breakup in a T-junction under different outlet pressures. Three behaviors of droplet breakup: non-breakup (flow pattern I), breakup with tunnels (flow pattern II), and breakup with permanent obstruction (flow pattern Ⅲ) are identified. The evolution of morphological characteristics of droplet breakup is quantitatively characterized, based on which the asymmetric splitting mechanisms and the influencing factors are clarified. Additionally, the factors influencing the droplet splitting volume ratio (V II / V I) are elucidated. The results indicate that there is a non-linear relationship between the V II / V I and the flow rate ratio. Moreover, the curve depicting the final V II / V I versus the initial droplet length exhibits a V-shape and has a minimum value. A conclusion is drawn that the Capillary number mainly influences flow pattern II, with the final V II / V I decreasing as the Capillary number increases. Additionally, for flow pattern III, the final V II / V I increases linearly with rising droplet size at low viscosity ratios, whereas it decreases linearly at high viscosity ratios. The growing outlet pressure difference enlarges the flow difference between the two branches, leading to an increase in the final V II / V I. [Display omitted] [ABSTRACT FROM AUTHOR]

In high-rise buildings, the excessive pressure differences cause various problems, and architectural and mechanical measures are always applied. In this study, pressure measurements on a 67-story high-rise building were conducted to evaluate the effect of mechanical pressurization on the pressure distribution. Absolute pressure measurement devices were installed at 28 points on 10 floors, a full-scale pressure profile of the test building was derived, and the pressure distributions on the main floors were reviewed. Four pressurization modes for the test building were considered, and the variation in the pressure distribution for each mode was analyzed. The results showed that mechanical pressurization reduced the pressure difference on the lobby floor by approximately 18%. Although it did not exert an apparent impact on the pressure difference due to the stack effect, pressurizing the entire floor serves as the most effective way of reducing the excessive pressure difference.

U-shaped structures are very common in the facade of buildings, which have a significant impact on fire spread. In this paper, the effect of the geometrical factor (α), the cross-sectional area (A), the height (H) on the upward fire spread in u-shaped structures are analyzed based on the fire spread rate (Vf) and the pressure difference between the top and the bottom (ΔP) through full-scale experiments and simulations. A dimensionless structure parameter α H / A is put forward to analyze the coupling effect of the structure size. It is found that Vf increases in the form of logarithmic function as α increases. ΔPmax increases in the form of exponential function as α increases; both Vf and ΔPmax decrease in the form of exponential function as A increases; Vf is positively correlated with H linearly. ΔPmax increases in the form of quadratic function as H increases; both Vf and ΔPmax increase in the form of Slogistic function as α H / A increases. When α H / A ≤ 17.2 or α H / A ≥ 38.8, α H / A has little effect on ΔPmax. The Vf in the non-overhead structure is very close to that in the overhead structure. This study can provide a theoretical guide for the fire protection design of u-shaped structures covered with insulation materials in practical engineering. [ABSTRACT FROM AUTHOR]