Flow Distance Research Articles

Resilience modeling and improvement of metro systems considering statistical behaviors of passenger mobility

As an indispensable infrastructure in modern society, the metro system is threatened by unexpected events (e.g., natural disasters and terrorist attacks). To improve the safety and reliability of the metro system, we need not only to strengthen the management of accident prevention, but also formulate remarkable emergency repair strategies. Nevertheless, there are few research on resilience modeling and improvement methods considering the statistical behaviors of passenger mobility, such as passenger flow and additional travel distance due to certain disaster. Besides, unreasonable repair work can also lead to waste of the metro system performance for multi-station failure under the effects of some hazards. In this paper, we develop a new performance indicator to model the resilience of the metro system, considering the passenger flow, travel distance and potential transfer solution. An emergency operation strategy is proposed for the operation of the normal section following accidents based on the developed resilience model. The station importance is formulated, and the system performance influencing factors are analyzed. According to the metro system resilience assessment results, we improve the repair sequence. Finally, we demonstrate the proposed method by a real case study. The results show that the proposed optimal strategy can improve system resilience by up to 20%.

Equilibrium Position of a Particle in a Microchannel Flow of Newtonian and Power-Law Fluids with an Obstacle

The equilibrium position yep/H of a particle in a microchannel flow of Newtonian and power-law fluids with an obstacle is numerically studied using the lattice Boltzmann method in the range of the ratio of an obstacle to particle diameter 0.5 ≤ β ≤ 2, fluid power-law index 0.4 ≤ n ≤ 1, Reynolds number 20 ≤ Re ≤ 60, and blockage ratio 0.15 ≤ k ≤ 0.3. Some results are validated by comparing them with the available results. The results showed that, when a particle migrates around an obstacle in the flow behind and near the obstacle, the particle with a different initial, y/H, migrates downstream in a different lateral position, yep/H, and the larger the value of β, the closer the value of yep/H is to the centerline. Therefore, the value of yep/H can be controlled by changing β in the wake zone of the obstacle. However, in the flow far downstream from the obstacle, the particle with a different initial y/H tends to have the same yep/H when n, Re and k are fixed, but the values of yep/H are different for different n, Re and k; i.e., the larger the values of n, Re and k, the closer the value of yep/H is to the centerline. The value of β has no effect on the value of yep/H. In the flow far downstream from the obstacle, the flow distance required for the particle to reach yep/H increases with increasing β and n but decreases with decreasing Re and k.

Height Above Nearest Drainage (HAND) as a Model for Rapid Flood Inundation Mapping Based on Remote Sensing and Geographic Information Systems in the Kapuas Sintang Sub Watershed

This study aims to map the flood inundation and the extent of the inundation in the study area using the HAND model. The data used in this study is DEM. The DEM is used to generate a hydrologic framework, including flow accumulation, drainage network, flow direction, elevation, and flow distance. The method used in this study is the HAND descriptor. The analysis in this study used spatial hydrological analysis and hypsometric analysis using zonal statistical tables in ArcGIS. Based on the results of the analysis of height above the nearest drainage it is known that the Kapuas Sintang sub-watershed has five classes of inundation, namely very high inundation, high inundation, moderate inundation, low inundation, and no inundation. Very high, high, and moderate inundation classes are spread over three sub-districts, namely Sintang, Dedai, and Tempunak sections. Sintang District has the widest distribution, followed by Dedai District and Tempunak District is the narrowest. Prediction of inundation area and flood area with HAND can be used to improve the new mapping model without involving additional data sources. The HAND model is a nice and simple tool that is useful for inundation studies as well as in inundation area prediction.

Investigation on the Electrostatics Saturation of Flow Electrification in the Liquid Hydrogen Transportation

Research on the flow electrification characteristic is of paramount importance for ensuring the electrostatic safety of liquid hydrogen transportation systems. However, the discussion about electrostatic saturation in flow electrification has been lacking. To address this gap, a theoretical model governing the process of flow electrification is constructed which couples the charge conservation equation with the Navier-Stokes equations and applies the Neumann boundary conditions at the solid-liquid interface, and the application of this model is validated by existing experimental data with the simulation parameters of At and n being 9.08 × 1012 and 0.85 for liquid hydrogen. A comparison with benzene reveals that benzene almost reaches the electrostatic saturation state after flowing one meter, whereas the flow of liquid hydrogen remains in the linear growth stage. However, with an increase in pipe length, a gradual saturation trend emerges in the curves of streaming current versus flow distance when the flow distance exceeds 10 m. At the outlet, the corresponding streaming current and charge density are approximately 160 pA and 3 μC/m3, respectively, significantly higher than those observed at one-meter flow distance. Furthermore, the influences of pipe radius and flow velocity on the arrival of electrostatic saturation are analyzed, and the results show that increasing both the pipe radius and flow velocity leads to a delay in the arrival of electrostatic saturation and enhances the saturation value of the streaming current. In conclusion, this study thoroughly discusses the development of flow electrification along with the flow distance and the phenomenon of electrostatic saturation in the long-distance flow of liquid hydrogen, which is crucial for the safe transportation of liquid hydrogen over extended distances.

Research results on underground cotton irrigation through artificial pipes

The article presents the results of laboratory-field tests of a working body that creates an artificial pipe for irrigation of cotton with a row spacing of 60 cm from under the soil. As evaluation criteria, water flow distance and moisture dispersion were taken from inside the formed pipe without spilling onto the field surface. When using this working body, it was found that a pipe with dense walls was formed under the soil with low energy consumption, and water flow was observed for a long distance. Generated to the proximity of the constructed artificial pipes to the cotton roots, the water demand is met quickly and the irrigation time and water consumption are reduced.

Development of the viscosity biosensor for the detection of DNase I based on the flow distance on the paper with DNA mucus

Deoxyribonuclease I (DNase I) is a biomarker which has important applications in various biological processes. Thus, it is highly important to develop a user-friendly method for the detection of DNase I. Here, we present a paper-based distance sensor for the rapid detection of DNase I based on changes in the viscosity of DNA mucus. The viscosity of DNA mucus varies with different concentrations of DNase I, showing different water flow lengths on the pH test papers, this makes the quantification of DNase I possible. This method has a wide linear range (0.01–10 U/mL), excellent sensitivity, remarkable specificity and excellent reproducibility. The detection limit reaches 0.003 U/mL. Additionally, it can be well applied to detection of DNase I inhibitors, assay of DNase I in human serum and quality evaluation of nucleic acid scavengers. In general, this study offers a brief, convenient, label-free, and economical method to construct paper-based distance sensors using DNA mucus, which is very promising in the detection of DNase I in various applications.

Air sparging remediation of VOCs contaminated low-permeability soil based on pressure gradient control

Air sparging (AS) is deemed unacceptable for remediating VOCs contaminated soil with low-permeability. To improve air flow and contaminant removal in sparging process, an original approach, termed as pressure gradient-enhanced air sparging (PGEAS) approach, is proposed by controlling pressure gradient in soil. Then the remediation efficiency, mass transfer characteristics, and remediation mechanism are investigated. Results showed that, the PGEAS approach accelerates gaseous contaminant exhaust, reduces residue contamination in soil, and promotes total contaminant removal, finally results in an improved remediation efficiency compared to the conventional approach. Controlled by sparging pressure and flow distance, the pressure gradient is created in soil, and a critical value needs to be exceeded to enhance the VOCs removal and mass transfer characteristics. The measured results of pore pressure and liquid saturation confirm a notable pressure gradient and drainage behavior in soil, which indicate the massive air subchannel formation during air sparging. At a two-dimensional scale, discrete distributions of contaminant concentrations in exhaust air and soil are presented, the removal extent and area are both enhanced using the PGEAS approach with a pressure gradient higher than the critical value. The reached conclusions are of great importance to contaminant removal in heterogeneous stratigraphy at sites.

Study on the effect of structural parameters of the convergence flow conditioner on eccentric jet flow rectification

In flow measurement and control industrial application, installing a flow conditioner is an effective way to rectify irregular and unstable flow to stable flow state within a short flow distance. To effectively rectify the eccentric jet flow caused by valve regulation in pipeline, the convergence flow conditioner with convergent orifice angles has been innovatively designed and investigated. However, the effect of structural parameters (such as flow conditioner thickness and flow area) on improving unstable eccentric jet flow rectification was still not elaborated. Thus, the effect of structural parameters of the convergence flow conditioner on rectifying eccentric jet flow was examined in this paper. The structural parameters of the flow conditioner thickness and the flow area were considered under the fixed convergence angle of 12°. The experimental system of monitoring pressures upstream and downstream of the convergence flow conditioner along the pipeline was developed and corresponding numerical simulation was employed. The flow coefficient and resistance coefficient of a convergence flow conditioner under various valve openings were accessed, and monitored pressures along the pipeline were also discussed for numerical simulation verification. The velocity and streamline distributions downstream the convergence flow conditioners were comparatively analyzed. In addition, the axial velocities on various downstream cross-sections were extracted to evaluate the velocity uniformity. A dimensionless parameter of velocity deviation ratio was introduced to quantify the rectification effect of eccentric jet flow evolving in the downstream pipeline. Results showed that the convergence flow conditioner with the thickness of 6 mm and the flow area of 50% owned a better effect on rectifying the valve-induced eccentric jet flow, that is, a shorter flow length was required for changing the valve-induced eccentric unstable flow to uniform stable flow by installing a convergence flow conditioner with above structural parameters.

Modeling of Agricultural Nonpoint-Source Pollution Quantitative Assessment: A Case Study in the Mun River Basin, Thailand

Agricultural nonpoint-source pollution (ANPSP) is a key cause of global environmental problems. However, the estimation of ANPSP, based on agricultural land use type, crop management, and attenuation of pollutants with distance, is lacking. Using the Mun River Basin as an example, this study established quantitative response relationships between subbasin flows and hydrological and water quality parameters. A good matching of the monitored sections and the control area based on flow relationships was achieved. By determining flow paths and flow distances, the overland and in-river transport attenuations of ANPSP were clarified. The overland and in-river transport and attenuation parameters were also quantified. The land use distribution and structure were further refined through crop management, which included crop types and crop rotation (monocropping or double cropping). Based on the above procedures, quantitative relationships among land use pattern, crop management, attenuation of pollutants with distance, and river water quality were established and used to construct six kinds of regression models. Among these models, the best modeling results were obtained when the parameters of water quality, land use structure, crop management, and soil nutrient attenuation were included. The modeling accuracy in the dry season increased from 0.398 to 0.881 when information about attenuation with distance and crop management was included. Similarly, the modeling accuracy in the wet season increased from 0.365 to 0.727. This study’s findings indicate that the constructed water quality model is effective and has significance for the quantitative determination of ANPSP.

Sea-level, climate, and oceanographic controls on recent deepwater hyperpycnites: A case example from the shenhu slope (northern South China Sea)

Hyperpycnites record information on sedimentary processes and climate change and play a significant role in hydrocarbon exploration. However, deep-water hyperpycnites can hardly be differentiated from intrabasinal turbidites since their control factors are not well understood. More detailed studies are needed to improve the knowledge of hyperpycnites. This study aims to identify and characterize hyperpycnites in the Shenhu slope and investigate their evolution in response to sea-level and climate changes using sediment gravity cores, combined with detailed grain size analysis, X-ray fluorescence scanning, X-ray computed tomography scanning, radiocarbon dating, and microscopic observations. Hyperpycnites and internal wave redistributed deposits were identified in core S19 since 42 cal ka BP. Internal wave redistributed deposits served as background deposit and dominated in the middle-late Holocene, while hyperpycnites dominated the Marine Isotope Stage 3 sequence form the early Holocene. The hyperpycnites facies S3 interbedded with S2L occurred during Marine Isotope Stage 3, facies L appeared in Last Glacial Maximum (LGM) strata, while facies S2L dominated the strata after LGM to the early Holocene. The facies distribution suggested that the strength and distribution of hyperpycnal flow were higher in warm and humid stages with low sea-level. Lower flood flows discharge in cold and dry stages limited the generation and extensional distance of hyperpycnal flows, although the sea-level was low in this stage. However, high sea-level combined with longshore and Surface waters in warm and humid stages, prevented the travel of hyperpycnal flows into deep basin. The study of hyperpycnites in the Shenhu slope reveals that the formation of deep-water hyperpycnites is influenced by a combination of factors, including sea-level fluctuations, climate change, and oceanographic processes. The amount of precipitation in the drainage basin determines the intensity and generation of hyperpycnal flows, while sea-level fluctuations affect their travel distance to the deep-water setting. Additionally, oceanographic processes such as longshore current can significantly alter hyperpycnal flows near the river mouth and shelf area, preventing them from reaching the deep basin.

Numerical Simulation Study on the Influence of Twist Tape Parameters on Hydrate Particle Deposition

Numerical simulation is used to carry out research on the swirl flow transportation of a hydrate in the pipeline under the condition of the whole rotation of the twist tape using DPM (discrete phase modeling) and RNG (renormalization group) k-ε. The influence of different twist tape parameters on the swirl number and concentration distribution of hydrate particles is analyzed. The structure parameters of the twist tape are optimized, based on the swirl efficiency evaluation parameters of a gas-solid two-phase pipeline. Finally, the twist tape is compared with different working conditions: the local rotation of twist tape and an ordinary pipeline. The results show that the areas of a high concentration of particles are near the twist tapes, and the concentration of particles on the leeward side of the twist tapes is higher than that on the windward side. The minimum concentration area at the axial position gradually increases with the increase of the flow distance, and the hydrate particles do not deposit at the bottom of the whole pipe section. The placement angle of the twist tape is greater, and the particle concentration area near the twist tape is also larger. The best placement angle is 25°. Under the condition of constant swirl strength, the range of the high particle concentration area will not increase indefinitely, and it is constant when the height of the twist tape is D/6 and the optimal height is D/6. There should not be too many twist tapes, as this will affect the carrying effect. The optimal number of twist tapes is three. The particle carrying distance of the local swirl flow generation is about double that of the ordinary pipe. The particle carrying distance of the four twist tape pipes is 3.5 times greater than that of the ordinary pipe. The particle carrying distance of the whole swirl flow generation is 6.6 times higher than that of the ordinary pipe. The particle carrying effect is 89% higher than that of the four twist tape pipes. The particle carrying effect is 230% higher than that of the local swirl flow generation. The particle carrying effect is 560% higher than that of the ordinary pipe.

Antagonistic Effects of Assortative Mating on the Evolution of Phenotypic Plasticity along Environmental Gradients.

AbstractPrevious theory has shown that assortative mating for plastic traits can maintain genetic divergence across environmental gradients despite high gene flow. Yet these models did not examine how assortative mating affects the evolution of plasticity. We here describe patterns of genetic variation across elevation for plasticity in a trait under assortative mating, using multiple-year observations of budburst date in a common garden of sessile oaks. Despite high gene flow, we found significant spatial genetic divergence for the intercept, but not for the slope, of reaction norms to temperature. We then used individual-based simulations, where both the slope and the intercept of the reaction norm evolve, to examine how assortative mating affects the evolution of plasticity, varying the intensity and distance of gene flow. Our model predicts the evolution of either suboptimal plasticity (reaction norms with a slope shallower than optimal) or hyperplasticity (slopes steeper than optimal) in the presence of assortative mating when optimal plasticity would evolve under random mating. Furthermore, a cogradient pattern of genetic divergence for the intercept of the reaction norm (where plastic and genetic effects are in the same direction) always evolves in simulations with assortative mating, consistent with our observations in the studied oak populations.

Lateral variations in the signature of earthquake‐generated deposits in Lake Iznik,NWTurkey

AbstractUsing lake‐sediment cores to document past seismicity requires a comprehensive understanding of possible lateral variations in depositional processes. This study aims to reveal the lateral variations in earthquake‐induced event deposits throughout Lake Iznik, a large lake located on the middle strand of the North Anatolian Fault. Based on stratigraphic, sedimentological and geochemical analyses of 14 sediment cores from two subbasins across the lake, five different types of event deposits (T1–T5) were identified and characterised. One event deposit type (T5) is restricted to a delta mouth, characterised by the occurrence of authigenic Fe‐Mn carbonates and interpreted to result from flood events. The four other types of event deposits are characterised by their synchronicity between cores and their age consistency with historical earthquakes and are interpreted to be likely generated by earthquakes. The locally prominent 1065 CE historical earthquake that ruptured the sub‐lacustrine Iznik Fault produced at least three different types of event deposits. One deposit type (T2) is only observed for this very local earthquake, implying that the type of event deposit might also depend on ground‐motion parameters. At the lake scale, the occurrence of various event deposits depends on the flow distance from the source of sediment destabilisations to the coring site.

Study on thermodynamics and flow characteristics of jet condensate in subcooled flowing liquid

Steam jet condensation in flow water under different conditions was investigated numerically. A cavitation model considering thermodynamic effects was proposed to study the flow and interfacial heat transfer characteristics. The distribution of thermodynamic parameters and the influence of different incident angles on the jet state were studied. The decrease in steam pressure and water subcooling would have a negative impact on the heat transfer coefficient of the interface and the length of plume. Furthermore, with increased water flow, the steam plume was tapered and its length was gradually shortened. Additionally, the turbulent kinetic energy is the maximum at the outlet of the nozzle and decreases with increasing flow distance. The distribution characteristic of the heat transfer coefficient is similar to and turbulence kinetic energy, which increases with the water mass flux, and reaches the maximum at both sides of the axis. Gradually increases in the middle of the axis. Therefore, the improvement of jet condensation should be achieved by adjusting the incidence angle and the water flow velocity.

Visual perception of travel distance for self-motion through crowds.

Humans can use visual motion to estimate the distance they have traveled. In static environments, optic flow generated by self-motion provides a pattern of expanding motion that is used for the estimation of travel distance. When the environment is populated by other people, their biological motion destroys the one-to-on correspondence between optic flow and travel distance. We investigated how observers estimate travel distance in a crowded environment. In three conditions, we simulated self-motion through a crowd of standing, approaching, or leading point-light walkers. For a standing crowd, optic flow is a veridical signal for distance perception. For an approaching crowd, the visual motion is the sum of the self-motion-induced optic flow and the optic flow produced by the approaching walkers. If only optic flow were to be used, travel distance estimates would be too high because of the approaching direction of the crowd toward the observer. If, on the other hand, cues from biological motion could be used to estimate the speed of the crowd, then the excessive optic from the approaching crowd flow might be compensated. In the leading crowd condition, in which walkers of the crowd keep their distance from the observer as they walk along with the observer, no optic flow is produced. In this condition, travel distance estimation would have to rely solely on biological motion information. We found that distance estimation was quite similar across these three conditions. This suggests that biological motion information can be used (a) to compensate for excessive optic flow in the approaching crowd condition and (b) to generate distance information in the leading crowd condition.

Pore Size Tunable Trypsin@ZIF-90 and Hydrogel Integrated Lateral Flow Point-of-Care Platform for ATP Detection

The cost-effective, convenient, visible, and equipment-free determination of biomarkers is always the priority development concern of disease diagnosis. The paper-based signal output strategy permits output visual signals without instruments and is regarded as a promising approach with simple operation and low cost. Herein, by varying the addition amount of trypsin, we pioneered a novel enzyme mineralization strategy to construct trypsin@ZIF-90 with tunable porosity properties and catalytic activity. The successful synthesis of trypsin@ZIF-90, which is tagged with T1, T3,... (Tx, x is the addition amount of trypsin. Unit: mg), demonstrated the feasibility of this strategy. By serving the constructed trypsin@ZIF-90-T1 as the target recognition module, and a new designed hydrogel-integrated pH indicator strip as the signal reporter, a point-of-care test (POCT) platform was developed for convenient and equipment-free measurement of adenosine triphosphate (ATP). The enzymatic activity measurement of trypsin@ZIF-90 and concurrently the quantitative analysis of ATP can be favorably realized by simple counting the flow distance and coverage area of water released during the reaction on a pH indicator strip. As a result, this portable platform can enable rapid detection of ATP in the linear range of 20-1500 μM and possesses favorable sensitivity, selectivity, and applicability. Thus, the constructions of tunable frameworks and paper-based POCT are of outstanding significance in the fields of porous metal-organic framework synthesis, enzyme mineralization, and rapid detection for medical diagnostics and environmental monitoring applications.

Distance-based α-amylase biosensor fabricated with amylopectin-coated mesoporous membrane

Paper-based biosensors are widely employed in point-of-care testing (POCT) due to their convenience, portability, low cost, and ease of use. This study reports an integrated distance-based paper biosensor fabricated with a mesoporous membrane coated with stimuli-responsive polymer. The detection of α-amylase (AMY) using amylopectin-coated mesoporous membrane is demonstrated as an example. After introducing the AMY solution, it is observed that the aqueous solution flows along the paper strip due to AMY-catalyzed hydrolysis of amylopectin. The flow distance is proportional to the concentration of AMY with a detection limit as low as 4 mU/mL. In addition, the detection of AMY is demonstrated in human serum. Furthermore, the inhibitory effect of acarbose on AMY is evaluated. This reagent-free and disposable biosensor allows single-step rapid detection of the analyte. This approach is very promising for the development of user-friendly, equipment-free, and cost-effective biosensors with remarkable sensitivity and excellent selectivity for disease diagnosis and hypoglycemic drug screening.

Performance study of self‐excited oscillatory cyclone drainage tool to improve the efficiency of natural gas well drainage and gas recovery

AbstractThe accumulation of fluid in the wellbore of a natural gas well can seriously affect the production of the well and can even lead to the well flooding and stopping production. The conventional cyclone tool has low kinetic energy, serious energy loss and short effective distance of spiral flow in the process of gas well drainage and gas recovery, thus affecting the efficiency of gas well drainage and gas recovery. In response to the above problems, this paper proposes a new cyclonic drainage solution combining self‐excited oscillating pulse jet and cyclonic flow. The liquid‐carrying air flow through the oscillating chamber forms a large vortex ring and the flow pattern squeezes the central air flow inwards, allowing the return vortex at the wall to develop effectively, increasing the return vortex velocity and increasing the velocity at the centre of the squeezed pulsating flow. In this paper, based on theoretical analysis and experimental research, the numerical simulation results are compared with the various drainage performance of conventional cyclone tools. The results show that the pressure drop and critical fluid‐carrying velocity of the cyclone section are significantly reduced, and the average tangential velocity of the cyclone section and the effective action distance of the cyclone tool are significantly increased, indicating that the new cyclone tool can improve the fluid‐carrying capacity of gas wells by changing the flow pattern of the gas–liquid medium without increasing energy consumption.

Statistical Modelling of Process Variables in the Electrospinning Production of PAN-Based Nanofibers

In this study, the effects of the electrospinning operating parameters such as flow rate (1-5 ml/h), voltage (15-30 kV), and distance to the collector (100-200 mm) on the physical properties of PAN-based nanofibers were investigated statistically by applying the central composite design method. The minimum nanofiber diameter was found to be 366.5 nm, under operating conditions of 5 ml/h flow rate, 30 kV, and 100 mm distance to the collector. Experimental conditions of 15 kV, 5 ml/h flow rate, and a 200 mm distance to the collector, a maximum porosity value of 0.446 was obtained. Similarly to the porosity, the water absorption capacity (WAC) value did not show a linear increase, and the maximum absorption capacity was calculated as 5712%, and at that point where the diameter is relatively large and the porosity is low.

Solving the Single-Row Facility Layout Problem by K-Medoids Memetic Permutation Group

The single-row facility layout problem (SRFLP) is concerned with arranging facilities along a straight line so as to minimize the sum of the products of the flow costs and distances among all facility pairs. SRFLP has rich practical applications and is however NP-hard. In this article, we first investigate a dedicated symmetry-breaking approach based on the permutation group theory for reducing the solution space of SRFLP. Relevant symmetry properties are identified through the alternating group of the original solution space or the corresponding coordinate rotation space. Then, a memetic algorithm is proposed to explore promising search regions regarding the reduced solution space. The memetic algorithm employs a problem-specific crossover operator guided by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> -medoids clustering technique to produce meaningful offspring solutions. The algorithm additionally uses a simulated annealing procedure to intensively exploit a given search region and a distance-and-quality-based population management strategy to ensure a reasonable diversity of the population. Experimental results on commonly used benchmark instances and newly introduced large-scale instances with sizes up to 2000 facilities show that the proposed algorithm competes favorably with state-of-the-art SRFLP algorithms. It attains all but one previous best known upper bounds (BKS) and discovers new upper bounds for 33 instances out of the 93 popular benchmark instances.