Diffusion Width Research Articles

The international dissemination of China’s English academic journals on Twitter: Structure, theme and impact

Objective/Significance: To measure the international communication capacity of China’s English academic journal papers based on social media platforms. Method/Process: Social network analysis, content analysis and emotion analysis were used to describe the diffusion structure of China’s English academic journal papers on Twitter from the aspects of network structure and identify important node users, explore the identity characteristics and emotion characteristics of users as well as diffusion capability of journals of different disciplines. Conclusion/Discovery: Journal articles in the fields of natural sciences and engineering as well as humanities and social sciences exhibit a strong positive correlation between their diffusion structure and network size. Networks with a mixed diffusion structure typically have larger network sizes. The users occupying key positions in the diffusion network typically have profile information that is academically relevant. The retweets and comments are mainly statements without emotional inclination, and the comments are mainly summary descriptions of the papers. The distribution of diffusion width, diffusion strength and diffusion speed of each discipline is significantly different. There is a significant positive correlation between the diffusion structure of papers and their diffusion capabilities. Innovation/Value: To reveal the diffusion structure and characteristics of China’s English academic journal papers on social media platforms, so as to provide reference for expanding the visibility of China’s English academic journals and improving the international dissemination capacity of China’s English journals.

Effects of endwall clearances of variable diffuser vane on centrifugal compressor performance

To ensure the variable diffuser vane can rotate around a pivot fluently in practical applications, there have to be clearances between vanes and diffuser walls. As the compressor pressure ratio increases, the effects of the vane endwall clearances are enhanced and cannot be ignored. This paper investigates the effects of both-side vane endwall clearances on the centrifugal compressor performance. Results show that the existence of endwall clearances mainly enlarges the flow capacity of the vane diffuser and decreases the compressor efficiency, and these effects are more significant as the vane stagger angle decreases. A one-side endwall clearance of 2.7% of the diffuser width increases the choke mass flow rate by as much as 20% and decreases the compressor peak efficiency by 2.7%. Due to the non-uniform flow along span at the impeller outlet, the shroud-side vane endwall leakage plays a more important role than the hub-side in affecting the compressor performance. In additions, the respective contributions of the vane throat, the hub-side and the shroud-side endwall clearances to the increases of the vane choke mass flow rate are quantitatively studied. The flow physics and loss mechanisms of the endwall leakage are revealed.

Experimental study on flow characteristics of jet ventilation in crossflow in confined mine spaces

The increasing depth of mine excavation presents greater challenges in mine ventilation and in managing cooling energy consumption. Therefore, there is an urgent need for comprehensive research on jet ventilation influenced by low-speed crossflows. This study investigated the impact of flow velocity ratios (R) and jet exit diameters (d) on flow-field distribution and flow characteristics through velocity measurements and smoke flow visualization experiments. The results of the study revealed two distinct types of air lakes formed by jet ventilation in crossflow (JVIC), with one being wall-attached and the other suspended. Notably, a significant secondary flow phenomenon was observed in the near-field near the upper wall. Additionally, the deflection angle (θj) of JVIC decreases as R and d/D increase, leading to the formation and movement of a semi-confined point (SP) and a confined point (CP) in the -x direction. Moreover, the wall confinement effect diminishes the jet’s diffusion and deflection ability in the -z direction, leading to increased penetration in the x direction. Before the formation of the SP, the deflection section of the jet lengthens, followed by a rapid shortening upon its formation. Finally, the study further developed empirical equations for the jet axial trajectory and diffusion width.

Experimental and numerical investigation of the effect of deep-sea mining vehicles on the discharge plumes

During mining activities, deep-sea mining vehicles (DSMVs) are highly susceptible to causing massive disturbance to the seafloor sediment, resulting in the formation of plumes due to underlying turbulence and currents. To gain a better understanding of the dispersion mechanism of sediment plumes, both experimental and numerical methods were employed. The numerical model was primarily used to characterize the solidity and liquidity of the sediment plume through volume of fluid and discrete phase model methods, respectively. The experimental data were validated against the numerical results. The plume distribution was studied in physical experiments for three different DSMV parameters. The study findings indicate that the discharge of the plume in the near field occurs in three stages due to a combination of plume release inertial forces, negative buoyancy in the water column, and wall restoring forces. Additionally, the increase in the travel velocity of the DSMV reduces the propagation of the plume in the direction of discharge and instead increases its lateral spread across the bottom surface. As the size of the DSMV decreases in three dimensions, changes in the vertical vortex structure become dominant in the plume distribution. This leads to a reduction in the length of the plume head and a faster sinking of the plume. When the wake Froude number Frw is between 0.7 and 6.8, representing the wake turbulence effect of DSMV on plume discharge, the diffusion width of the plume on the bottom surface is linearly related to Frw.

Field-induced interfacial instabilities in a two-phase ferrofluid flow

Forming a stable ferrofluid and non-magnetic interface in a microchannel is essential for biomedical applications with two miscible aqueous solutions. Here, we report the interface profile and its instability of aqueous ferrofluid and water co-flow in a microchannel under the influence of a magnetic field. The scaling law related to diffusion width and dimensionless Pe number is introduced by solving the momentum and diffusion equation and combining the experimental results. It is found that the dimensionless number of diffusion width δ/h ∝ X/Peα, when core flow concentration cf, residual magnetic flux density Br, sheath flow and core flow ratio Qw/Qf, and core flow velocity Qf are changed, α is 0.633–1.071, α ∝ Qβ, β = −0.059,0.147, 0.019 and −0.101, respectively. Altering the core flow velocity and magnetic field intensity can quickly impact the interface's stability by improving the transport efficiency by 32.9 % and counteracting the impacts of material diffusion by 51.8 %, respectively. Elevating the proportion of sheath flow to core flow and magnetic field will impede the diffusion of core flow. This will result in a drop of 11.9 % in the magnetic convection effect and a 20.8 % counteraction of material diffusion effects.

Sonic boom propagation in urban canyons using a combined ray tracing/radiosity method.

Sonic boom propagation over land is being studied to ensure a minimal impact on the population in the event that supersonic flight over land becomes permissible. Sonic boom behavior in and around urban areas is particularly important due to the high density of people residing in cities and the increased probability of impacting large numbers of people if urban areas lie in the flight path. This study models sonic booms around urban canyons using a combined ray tracing/radiosity method. The impacts of several parameters, such as diffusion, arrival angle, building heights, and canyon width, on the sound field were explored. The results showed that without diffusion, there was no real trend as the canyon height and width and arrival angles were varied. There were strong shadow zones where no sound was detected as this model does not include diffraction. In other locations, between one and four boom events were received. The resulting perceived level in dB (PLdB) varied from 0 in the shadow zones to 94 dB. Diffuse reflections was the parameter that had the greatest impact on the resulting signatures. Parameters that caused an increased number of reflections showed significant changes in the signature shape and a dramatic reduction in the PLdB.

Numerical Simulation of Crude Oil Leakage from Damaged Submarine-Buried Pipeline

Oil spill accidents in damaged submarine-buried pipelines cause tremendous economic losses and serious environmental pollution. The accurate prediction of oil spills from subsea pipelines is important for emergency response. In this study, the volume-of-fluid model, realizable k–ε turbulence model, and porous-medium model were employed to describe the process of an oil spill from a submarine pipeline to the sea surface. The effects of seawater density, seawater velocity, and pipeline buried depth on the transverse diffusion distance of crude oil and the time at which crude oil reaches the sea surface were obtained through numerical calculations. The calculation results show that, with a decrease in seawater density and an increase in seawater velocity and pipeline depth, the diffusion rate of crude oil decreases significantly, the maximum transverse diffusion distance increases and crude oil takes a long time to reach the sea surface. In particular, compared with a sea density of 1045 kg/m3, the transverse distance of a sea density of 1025 kg/m3 is increased by 0.091 m. When the seawater velocity is greater than 1.5 m/s, the diffusion of crude oil in seawater is significantly affected, the seawater velocity increases to 0.35 m/s, and the transverse diffusion distance of oil to the sea surface increases to 12.693 m. When the buried depth of the pipeline reaches 0.7 and 1.3 m compared to 0.1 m, the diffusion widths of crude oil in sea mud rise by 20% and 32.5%, respectively. The time required for crude oil to reach the sea surface and the transverse diffusion distance of crude oil migrating to the sea surface were analyzed using multiple regression, and the fitting formulas were obtained. The results provide theoretical support for accurately predicting the leakage range of submarine-buried pipelines and provide valuable guidance for submarine-buried pipeline leakage accident treatment schemes.

Evaluating tensile strength of cement paste using multiscale modeling and in-situ splitting tests with micro-CT

This study investigated a strategy to simulate splitting tests to evaluate the tensile strength of cement paste within a multiscale framework, and validated the approach with in-situ micro-CT measurements. Phase-field fracture model was used to simulate the splitting test using virtual microstructures reconstructed from the macroscale micro-CT measurements. Among the modeling parameters, the range of the diffusive crack width, which is an internal parameter for phase-field fracture model, was further investigated. The cracks propagated through the weaker solid phase, and the predicted strengths and standard deviations were comparable to those obtained from the experiments. It was found that the diffusive crack width should be smaller than the characteristic length of the weaker phase to predict the crack pattern accurately. These findings confirm the effectiveness of the proposed multiscale modeling approach in predicting the tensile strength of cement paste.

Effect of atom diffusion on the efficiency of Bragg diffraction in atom interferometers.

The transition efficiency of atomic Bragg diffraction as mirrors and beam splitters in Bragg atom interferometers plays an essential role in impacting the fringe contrast and measurement sensitivity. This can be attributed to the properties of atomic sources, Bragg pulse shapes, the pulse duration, and the relative position deviation of the atoms and Bragg pulses. Here, we investigate the effect of the atomic source's diffusion and velocity width on the efficiency of Bragg diffraction of the moving cold atomic cloud. The transfer efficiency of Bragg mirrors and beam splitters are numerically simulated and experimentally measured, which are well consistent in comparison. We quantify these effects of atomic diffusion and velocity width and precisely compute how Bragg pulses' efficiencies vary as functions of these parameters. Our results and methodology allow us to optimize the Bragg pulses at different atomic sources and will help in the design of large momentum transfer mirrors and beam splitters in atom interferometry experiments.

Recovering critical parameter for nonlinear Allen–Cahn equation by fully discrete continuous data assimilation algorithms *

The purpose of this study is to recover the diffuse interface width parameter for nonlinear Allen–Cahn equation by a continuous data assimilation algorithm proposed recently. We obtain the large-time error between the true solution of the Allen–Cahn equation and the data assimilated solution produced by implicit–explicit one-leg fully discrete finite element methods due to discrepancy between an approximate diffuse interface width and the physical interface width. The strongly A-stability of the one-leg methods plays key roles in proving the exponential decay of initial error. Based on the long-time error estimates, we develop several algorithms to recover both the true solution and the true diffuse interface width using only spatially discrete phase field function measurements. Numerical experiments confirm our theoretical results and verify the effectiveness of the proposed methods.

Prognostic MRI features to predict postresection survivals for very early to intermediate stage hepatocellular carcinoma

ObjectivesContrast-enhanced MRI can provide individualized prognostic information for hepatocellular carcinoma (HCC). We aimed to investigate the value of MRI features to predict early (≤ 2 years)/late (> 2 years) recurrence-free survival (E-RFS and L-RFS, respectively) and overall survival (OS).Materials and methodsConsecutive adult patients at a tertiary academic center who received curative-intent liver resection for very early to intermediate stage HCC and underwent preoperative contrast-enhanced MRI were retrospectively enrolled from March 2011 to April 2021. Three masked radiologists independently assessed 54 MRI features. Uni- and multivariable Cox regression analyses were conducted to investigate the associations of imaging features with E-RFS, L-RFS, and OS.ResultsThis study included 600 patients (median age, 53 years; 526 men). During a median follow-up of 55.3 months, 51% of patients experienced recurrence (early recurrence: 66%; late recurrence: 34%), and 17% died. Tumor size, multiple tumors, rim arterial phase hyperenhancement, iron sparing in solid mass, tumor growth pattern, and gastroesophageal varices were associated with E-RFS and OS (largest p = .02). Nonperipheral washout (p = .006), markedly low apparent diffusion coefficient value (p = .02), intratumoral arteries (p = .01), and width of the main portal vein (p = .03) were associated with E-RFS but not with L-RFS or OS, while the VICT2 trait was specifically associated with OS (p = .02). Multiple tumors (p = .048) and radiologically-evident cirrhosis (p < .001) were the only predictors for L-RFS.ConclusionTwelve visually-assessed MRI features predicted postoperative E-RFS (≤ 2 years), L-RFS (> 2 years), and OS for very early to intermediate-stage HCCs.Clinical relevance statementThe prognostic MRI features may help inform personalized surgical planning, neoadjuvant/adjuvant therapies, and postoperative surveillance, thus may be included in future prognostic models.Key Points• Tumor size, multiple tumors, rim arterial phase hyperenhancement, iron sparing, tumor growth pattern, and gastroesophageal varices predicted both recurrence-free survival within 2 years and overall survival.• Nonperipheral washout, markedly low apparent diffusion coefficient value, intratumoral arteries, and width of the main portal vein specifically predicted recurrence-free survival within 2 years, while the VICT2 trait specifically predicted overall survival.• Multiple tumors and radiologically-evident cirrhosis were the only predictors for recurrence-free survival beyond 2 years.Graphical

Experimental Investigation on Cross-Impingement Characteristics Under Various Biodiesel-Butanol Blended Proportions and Ambient Conditions

Abstract The cross-impingement phenomenon always appears in several diesel engines with two or more injectors. Meanwhile, the application of biofuels has a great potential in realizing clean and efficient combustion. Therefore, the investigation aims to explore the cross-impingement characteristics at small (10%), middle (30%), and large (50%) biodiesel-butanol blended proportions. Experiments are conducted in a constant-volume combustion chamber with twin injectors. Spray images are captured by optical diagnosis techniques. Several macroscopic parameters are obtained, including diffusion length, collision width, and spray area. Results show that the cross-impingement accelerates the droplet interaction, and the spray presents a “fan-shaped” behavior after the collision, which promotes a more uniform mixing between the fuel and ambient gas. As the twin sprays collide at 120 deg, the vapor-phase vertical diffusion rate is close to the vertical component of the single spray, and the horizontal diffusion rate is about 1.2 times the vertical diffusion rate. The cross-impingement is likely to decrease the spray-wall impingement owing to a change in the diffusion direction. At various blended fuels, the biodiesel blended with 30% n-butanol displays the smallest liquid-phase diffusion length, width, and area. The further increase in the n-butanol mixing ratio leads to larger liquid-phase parameters. Contrary to the biodiesel blended with 10% n-butanol, the biodiesel blended with a higher proportion of n-butanol presents faster vapor-phase diffusion, which promotes fuel-gas mixing.

Analysis and Experiments on the Characteristics of Airflow and the Air Cleanliness Protection Region under Fan Filter Units in Cleanrooms

Cleanrooms often utilize large amounts of supply air to achieve a required cleanliness level. To reduce the overall supply air volume, critical processes demanding the highest cleanliness requirements are suggested to be placed directly beneath the air outlet of fan filter units (FFUs). In order to determine an appropriate supply air volume, it is necessary to quantitatively analyze the particulate concentration distribution downstream of FFUs with various characteristics to determine an adequate but not excessive supply air volume. Three FFU sizes and four supply air velocities were used in this experiment, and the resulting airstream velocities, jet diffusion widths, and characteristics of particulate concentration distribution were obtained. Fitting expressions were statistically acquired based on the respective experimental data sets, which can be used to predict the airflow velocity value at any point in an FFU flow region and the width of the air cleanliness protection range.

Influence of Preheating Temperature on the Microstructure and Mechanical Properties of 6061/TA1 Composite Plates Fabricated by AFSD.

In this study, composite plates of 6061/TA1 were successfully manufactured using additive friction stir deposition (AFSD). The impact of preheating temperatures (room temperature, 100 °C, 200 °C) on the interfacial microstructure and interface mechanical properties at various deposition zones was studied. The results showed that as the preheating temperature increased or when the deposit zone shifted from the boundary to the center, the diffusion width of Al and Ti increased, accompanied by an increase in bonding shear strength. Moreover, in the boundary zone of the sample preheated at room temperature (P-RT), only mechanical bonding was observed, resulting in the lowest bonding shear strength. Conversely, the other samples exhibited a combination of mechanical and metallurgical bonding. Under the preheating temperature of 200 °C, interfacial intermetallic compounds were observed near the center zone, which exhibited the highest bonding shear strength.

Microstructure and Mechanical Properties of Ti/Al-SiC/Ti Clad Plates Prepared via the Powder-in-Tube Method.

SiC particle-reinforced Ti/Al/Ti clad plates were successfully fabricated by the powder-in-tube method. The surface micrography, element diffusion, peeling strength and tensile property of clad plates were studied after annealing and cold rolling. The experimental results show that 6 wt.% is optimal. The presence of SiC particles has been seen to significantly enhance the diffusion of Ti and Al elements. Additionally, it has been observed that the diffusion width of the intermetallic compound (IMC) increases as the size of SiC particles grows. However, it is worth noting that the average of Ti/Al-SiC/Ti clad plates initially increases and subsequently falls. The optimized diffusion thickness of the Ti/Al-SiC/Ti clad plate's IMC layer determined via the powder-in-tube method is approximately 4.5 μm. The 1 μm SiC-reinforced Ti/Al/Ti clad plate can obtain the best mechanical properties after annealing at 500 °C and further hot rolling, and the peeling strength, ultimate tensile strength and elongation are 31.5 N/mm, 305 MPa and 26%, respectively. The efficacy of Ti/Al-SiC/Ti clad plates in delivering exceptional performance is substantiated by the analysis of peeling surfaces, peeling tests and tensile testing, which collectively demonstrate the presence of compact and homogenous intermetallic compounds.

Effect of Diffuser Vane Height and Position on Diffuser Wall Static Pressures in a Centrifugal Compressor

The present paper reports experimental investigations on the effect of diffuser vane height and its position on diffuser wall static pressures of a low speed centrifugal compressor. Apart from the standard types of diffusers, namely, vaneless, vane and low solidity vane diffusers, a partial vane diffuser, whose height is less than the diffuser width is also tested. The vane height of the partial vane diffuser is varied from 0.3, 0.4 and 0.5 times the diffuser width in vane and low solidity vane diffuser configurations. In addition, the effect of vane position is examined by fixing the partial vanes to the hub, shroud or hub and shroud. It is found that there is an optimum height for the diffuser vane height, which is found to be 0.3 times the diffuser width. The effect of position of the partial vanes on the hub or shroud on the diffuser wall static pressures is found to be negligible. However when partial vanes are fixed on the hub and shroud staggered at half spacing, the diffuser performance based on wall static pressures is improved substantially.

Numerical simulation study on spread angle in oblique cut flip bucket

With the advantages of simple structure, good energy dissipation effect and so on, the sky jump energy dissipation is widely used in energy dissipation of water conservancy project. But at present, the prediction about the range of the free nappe is not complete. The studies show that the ejection angle is different at different locations of the outlet section, but the specific distribution of the outlet section velocity is still unclear. The measurement of free nappe range is mostly the direct measurement, how to accurately control is still difficult, and no systematic study has been made. Especially, the studies on the diffusion width of free nappe are few, the understanding of free nappe diffusion is not enough. In this article, the deflection degree of flow velocity at the outlet section in the lateral direction is quantified by the spread angle. Studied the distribution characteristic of spread angle through numerical simulation. The results show that the distribution characteristics and the maximum value of spread angle are affected by the change of flip bucket size and approach flow condition, and presented a set of equations for calculating the maximum angle.

Influence and prediction of oil film migration in submarine pipeline spills under multiple factors

Oil spills endanger the survival of marine species and the maritime environment. As a result, this study constructs a three-dimensional diffusion model of oil spills from pipeline ruptures and analyses the diffusion law of oil films created on the sea surface under various conditions. The model's accuracy was validated using actual oil spill tests, and the oil spill similarity model was further established using similarity theory. The results show that as the leaking aperture grows within 2–3 s, the high concentration centre area of the oil film on the sea surface expands, and the oil film protrudes to the right. From the inside out, the oil film produces a convex elliptical oil film with a high-low concentration form. As the leakage rate rises, a convex, elliptical, large-area oil film of low-high-low concentration forms. During this time frame, the oil leak has not yet developed an oil film at a flow rate of 0.3 m/s. This is due to the fact that horizontal migration speed has a large influence on vertical migration speed, increasing the horizontal migration distance underwater and lengthening the time needed to achieve the development of the sea surface oil film area. With increasing leakage aperture and leak rate, the lateral diffusion length, longitudinal diffusion breadth, and oil spill area of the oil film rise. However, when the velocity of the water flow increases, it decreases. Furthermore, the quadratic fitting curves of the longitudinal expansion length, longitudinal diffusion width, and oil spill area of the oil film were fitted under various influencing factors to predict the diffusion law of the oil film on the sea surface, which is critical for protecting the marine environment.

Effect of shallow doping on performance parameters of single heterojunction solar cell

Abstract Fill factor and conversion efficiency of single heterojunction solar cell is analytically computed based on the shallow doping at GaAs quantum well region. Poisson’s equation is solved with suitable boundary condition applied at hetero-interface for both dark and illuminated conditions, corresponding to which open-circuit voltage and short-circuit current are computed. Realistic dependence of minority carrier distribution on material layers and diffusion widths are taken into account for simulation purpose. Result exhibits that variation of acceptor density leads to better outcome in terms of both efficiency and fill factor, which is also critically depends on length of quantum well region. Doping of AlGaAs barrier layer has negligible influence on fill factor and conversion efficiency. Optimized dimension of quantum well layer width is the critical parameter for design of efficient solar cell, as revealed from the analysis.

Asymmetric transverse momentum broadening in an inhomogeneous medium

Gradient jet tomography in high-energy heavy-ion collisions utilizes the asymmetric transverse momentum broadening of a propagating parton in an inhomogeneous medium. Such broadening is studied within a path-integral description of the evolution of the Wigner distribution for a propagating parton in medium. Going beyond the eikonal approximation of multiple scattering, the evolution operator in the transverse direction can be expressed as the functional integration over all classical trajectories of a massive particle with the light-cone momentum $\ensuremath{\omega}$ as its mass. With a dipole approximation of the Wilson line correlation function, evolution with the light-cone time $t$ is determined by the jet transport coefficient $\stackrel{^}{q}$ that can vary with space and time. In a uniform medium with a constant ${\stackrel{^}{q}}_{0}$, the analytical solution to the Wigner distribution becomes a typical drifted Gaussian in both transverse momentum and coordinate with the diffusion width $\sqrt{{\stackrel{^}{q}}_{0}t}$ and $\sqrt{{\stackrel{^}{q}}_{0}{t}^{3}/3{\ensuremath{\omega}}^{2}}$, respectively. In the case of a simple Gaussian-like transverse inhomogeneity with a spatial width $\ensuremath{\sigma}$ on top of a uniform medium, the final asymmetrical momentum distribution can be calculated semianalytically. The transverse asymmetry defined for jet gradient tomography that characterizes the asymmetrical distribution is found to linearly correlate with the initial transverse position of the propagating parton within the domain of the inhomogeneity. It decreases with the parton energy $\ensuremath{\omega}$, increases with the propagation time initially and saturates when the diffusion distance is much larger than the size of the inhomogeneity or ${t}^{3}\ensuremath{\gg}3{\ensuremath{\omega}}^{2}{\ensuremath{\sigma}}^{2}/{\stackrel{^}{q}}_{0}$. The transverse momentum broadening due to the inhomogeneity also saturates at late times in contrast to the continued increase with time if the drifted diffusion in space is ignored.