Linear Flow Research Articles

SC-Net: Symmetrical conical network for colorectal pathology image segmentation

Background and ObjectiveImage segmentation of histopathology of colorectal cancer is a core task of computer aided medical image diagnosis system. Existing convolutional neural networks generally extract multi-scale information in linear flow structures by inserting multi-branch modules, which is difficult to extract heterogeneous semantic information under multi-level and different receptive field and tough to establish context dependency among different receptive field features. MethodsTo address these issues, we propose a symmetric spiral progressive feature fusion encoder-decoder network called the Symmetric Conical Network (SC-Net). First, we design a Multi-scale Feature Extraction Block (MFEB) matching with the Symmetric Conical Network to obtain multi-branch heterogeneous semantic information under different receptive fields, so as to enrich the diversity of extracted feature information. The encoder is composed of MFEB through spiral and multi-branch arrangement to enhance context dependence between different information flow. Secondly, the information loss of contour, color and others in high-level semantic information through causally stacking MFEB, the Feature Mapping Layer (FML) is designed to map low-level features to high-level semantic features along the down-sampling branch and solve the problem of insufficient global feature extraction in deep levels. ResultsThe SC-Net was evaluated on our self-constructed colorectal cancer dataset, a publicly available breast cancer dataset and a polyp dataset. The results revealed that the mDice of segmentation reached 0.8611, 0.7259 and 0.7144. We compare our model with the state-of-art semantic segmentation UNet++, PSPNet, Attention U-Net, R2U-Net and other advanced segmentation networks. The experimental results demonstrate that we achieve the most advanced performance. ConclusionsThe results indicate that the proposed SC-Net excels in segmenting H&E stained pathology images, effectively preserving morphological features and spatial information even in scenarios with weak texture, poor contrast, and variations in appearance.

Stationary dimpled drops under linear flow

The axially symmetric deformation of a drop in a viscous fluid, under the influence of an externally imposed flow having simultaneous rotating and compressional or extensional components, is addressed. In the previous studies, two families of stationary drop shapes were constructed by simulating the dynamics of drop deformation: stable singly connected shapes with respect to axisymmetric disturbances, and unstable toroidal shapes. These two branches coexist at the same flow conditions, but were not connected. In this study, we obtain a new family of branches of unstable highly deformed stationary drops connecting with the stable flattened shapes and the toroidal ones. We use a method based on classical control theory. The controller is designed for a two-state dynamic model of the system and is employed on a high-order nonlinear dynamic model of the drop deformation. Through this feedback-control-centred approach, an extended collection of unstable stationary solutions is constructed, which spans the range from the loss of stability to the dimpled shapes almost collapsed at the centre. In the latter region, which was never obtained in previous studies, a multiplicity of solutions is identified.

Seepage evolution characteristics and water inrush mechanism in collapse column under mining influence

To obtain the seepage evolution rule and water inrush mechanism of the collapse column, a multi-field coupled mechanical model for water inrush disasters caused by the collapse column is established in this paper, on the basis of the specific engineering conditions of the 1908 working face in the Qianjin coal mine. The mechanical model is composed of internal column elements within the collapse column and surrounding rock masses. The research focuses on the seepage evolution rule in the roof collapse column under different mining conditions and investigates the permeation instability mechanism of collapse column based on the transition of flow state. The research results indicate that the seepage pathway evolves continuously, ultimately forming a channel for water inrush, as the working face advances towards the collapse column. Besides, the water inflow increases rapidly when the working face advances 100 m, then gradually stabilizes, indicating that the seepage channel entry of the collapse column is in a stable stage. Meanwhile, mass loss in the collapse column gradually moves upward. the collapse column remains stable as a whole in the initial stage of water flow, with a small permeability, exhibiting linear flow. As time steps increases, particle loss in collapse column gradually extends to the upper part, forming a stable seepage channel. The flow velocity shows fluctuations with a slow declining trend over time.

Chain Recurrence and Selgrade’s Theorem for Affine Flows

AbstractAffine flows on vector bundles with chain transitive base flow are lifted to linear flows and the decomposition into exponentially separated subbundles provided by Selgrade’s theorem is determined. The results are illustrated by an application to affine control systems with bounded control range.

ANALOGUES OF JACOBI AND WEYL THEOREMS FOR INFINITE-DIMENSIONAL TORI

Generalizations of the Jacobi and Weyl theorems on finitedimensional linear flows to the case of linear flows on infinite-dimensional tori are presented. Conditions for periodicity, non-wandering, ergodicity and transitivity of trajectories of an infinite-dimensional linear flow are obtained. It is shown that for infinite-dimensional linear flows there is a new type of trajectories that is absent in the finite-dimensional case

Effect of slip-induced fluid inertial torque on the angular dynamics of spheroids in a linear shear flow

The angular dynamics of tiny spheroidal particles in shear flows have been widely investigated, but most of the studies mainly focus on the effect of strong shear, while the combined effect of both shear and slip velocity at the center of the particle has been less considered. Actually, the fluid inertial torque induced by the slip velocity between particle and fluid plays a significant role in spheroid angular dynamics. However, it is difficult to investigate these dynamics theoretically until the analytical expression of the fluid inertial torque at a small Reynolds number was derived by Dabade et al. [J. Fluid Mech. 778, 133–188 (2015)]. In this study, the effect of the fluid inertial torque on the particle rotations is considered in a linear shear flow with a small streamwise slip velocity at the center of the particle. We find that as the fluid inertial torque dominates, the prolate spheroids tend to logroll while oblate ones have a tendency to tumble or align to a direction with a relative angle to the streamwise direction. These results are opposite to the earlier results in the absence of the fluid inertial torque. Different ultimate rotation modes of spheroids are dependent on the relative importance between the fluid inertial torque and the particle inertia, as well as the initial orientations. This reflects a non-trivial effect of fluid inertial torque on the angular dynamics of inertial spheroidal particles.

Experimental investigation on dynamic characteristics of single bubble near wall in shear flow

The bubble near the wall of shear flow will be subjected to both wall-induced lift and shear-induced lift. The two-lift interaction will markedly change the dynamic behavior of the bubble. In this experiment, the lateral motion of a single bubble (deq=2.33−3.42 mm, Reb=470−680) rising near the vertical wall in a linear shear flow was studied. The positive-synergy and negative-synergy between the wall- and shear-induced lift effects on bubble dynamics were compared. The experiment was carried out in a vertical water tunnel with a curved screen used to generate a stable linear shear flow. Using the shadow method and two charge-coupled device cameras, the movement parameters of the bubble were captured, including the movement trajectory of the bubble, length–diameter ratio, and instantaneous velocity. The lift coefficient CL and drag coefficient CD were obtained by quasi-steady-state analysis and calculation. By fitting the steady lift coefficient, the relation of CL with dimensionless wall distance S* and the Reynolds number Reb was obtained. The results show that there is a critical value of the initial dimensionless distance S* about [S*] = 1.6. When S* > [S*], the bubble is subjected to both wall-induced lift and shear-induced lift. The lift coefficient CL decreases with the increase in S*. When S* < [S*], the bubble receives additional induced lift from the wall. The CL of the smaller bubble was smaller and increases with the increase in S*, while the deformation of the larger bubble will interact with the wall to produce deformation lift away from the wall, presenting larger CL, and decrease with the increase in S*.

Strong prevalence of light regime-specific QTL in Arabidopsis detected using automated high-throughput phenotyping in fluctuating or constant light.

Plants have evolved and adapted under dynamic environmental conditions, particularly to fluctuating light, but plant research has often focused on constant growth conditions. To quantitatively asses the adaptation to fluctuating light, a panel of 384 natural Arabidopsis thaliana accessions was analyzed in two parallel independent experiments under fluctuating and constant light conditions in an automated high-throughput phenotyping system upgraded with supplemental LEDs. While the integrated daily photosynthetically active radiation was the same under both light regimes, plants in fluctuating light conditions accumulated significantly less biomass and had lower leaf area during their measured vegetative growth than plants in constant light. A total of 282 image-derived architectural and/or color-related traits at six common time points, and 77 photosynthesis-related traits from one common time point were used to assess their associations with genome-wide natural variation for both light regimes. Out of the 3000 significant marker-trait associations (MTAs) detected, only 183 (6.1%) were common for fluctuating and constant light conditions. The prevalence of light regime-specific QTL indicates a complex adaptation. Genes in linkage disequilibrium with fluctuating light-specific MTAs with an adjusted repeatability value >0.5 were filtered for gene ontology terms containing "photo" or "light", yielding 15 selected candidates. The candidate genes are involved in photoprotection, PSII maintenance and repair, maintenance of linear electron flow, photorespiration, phytochrome signaling, and cell wall expansion, providing a promising starting point for further investigations into the response of Arabidopsis thaliana to fluctuating light conditions.

Instability analysis for MHD boundary layer flow of nanofluid over a rotating disk with anisotropic and isotropic roughness

The study focuses on the instability of local linear convective flow in an incompressible boundary layer caused by a rough rotating disk in a steady MHD flow of viscous nanofluid. Miklavčič and Wang's (Miklavčič and Wang, 2004) [9] MW roughness model are utilized in the presence of MHD of Cu-water nanofluid with enforcement of axial flows. This study will investigate the instability characteristics with the MHD boundary layer flow of nanofluid over a rotating disk and incorporate the effects of axial flow with anisotropic and isotropic surface roughness. The resulting ordinary differential equations (ODEs) are obtained by using von Kàrmàn (Kármán, 1921) [3] similarity transformation on partial differential equations (PDEs). Subsequently, numerical solutions are obtained using the shooting method, specifically the Runge-Kutta technique. Steady-flow profiles for MHD and volume fractions of nanoparticles are analyzed by the partial-slip conditions with surface roughness. Convective instability for stationary modes and neutral stability curves are also obtained and investigated by the formulation of linear stability equations with the MHD of nanofluid. Linear convective growth rates are utilized to analyze the stability of magnetic fields and nanoparticles and to confirm the outcomes of this analysis. Stationary disturbances are also considered in the energy analysis. The investigation indicates the correlation between instability modes Type I and Type II, in the presence of MHD, nanoparticles, and the growth rates of the critical Reynolds number. An integral energy equation enhances comprehension of the fundamental physical mechanisms. The factors contributing to convective instability in the system are clarified using this approach.

Droplet Laplace valve‐enabled glaucoma implant for intraocular pressure management

AbstractGlaucoma, the leading cause of irreversible blindness worldwide, is closely linked to aqueous overaccumulation and elevated intraocular pressure (IOP). For refractory glaucoma, aqueous shunts with valves are commonly implanted for effective aqueous drainage control and IOP stabilization. However, existing valved glaucoma implants have the disadvantages of inconsistent valve opening/closing pressures, poor long‐term repeatability due to their reliance on moving parts, and complex architectures and fabrication processes. Here, we propose a novel valving concept, the droplet Laplace valve (DLV), a three‐dimensional printable moving‐parts‐free microvalve with customizable and consistent threshold valving pressures. The DLV uses a flow discretization unit governed by capillarity, comprising a droplet‐forming nozzle, and a separated reservoir to digitize continuous flow into quantifiable droplets. Unlike the classic one‐time‐use Laplace valves, the DLV's unique design allows for its reusability. The opening pressure is adjustable by varying the nozzle size, like the classic Laplace valves (following the Young–Laplace equation), while the closing pressure can be modified by tuning the separation distance and the reservoir size. Various DLVs with customizable opening pressures from 5 to 11 mmHg have been demonstrated, with opening/closing pressure differences suppressed down to <0.5 mmHg (<0.15 mmHg under the best conditions). Thanks to its moving‐parts‐free nature and digitized flow properties, the DLV shows a highly repeatable valving performance (<1.7%, 1000 cycles) and a predictable linear flow rate–pressure correlation (R2 > 0.99). Preliminary ex vivo validation in an enucleated porcine eye confirms the DLV's efficiency in aqueous shunting and prompt IOP stabilization. The DLV technology holds great promise in glaucoma implants for IOP management and various microsystems for flow control.

Modeling of a Jet Pipe Servovalve Considering Nonlinear Flow Forces Acting on the Spool

The design and analysis of jet pipe servovalves are mostly based on linear models. However, there are some nonlinear factors in this kind of electromechanical–hydraulic structure. The article deduces a linear rotation equation for the armature assembly and a linear flow equation for the control cavity. With the consideration of nonlinear hydraulic reaction forces in the second stage, the nonlinear dynamic equation of the main spool in an ideal jet pipe servovalve is derived. Based on the MATLAB (R2016a) software, the nonlinear model of a certain type of jet pipe servovalve is numerically investigated. The equilibrium points of the nonlinear system are calculated, the phase portraits are plotted, and the Hopf bifurcations caused by the flow-pressure coefficient as the control parameter and the period-doubling bifurcations caused by the variation of the input signal are analyzed. The vibration frequency of the time-domain response of the fifth-order system with a cosine signal as input is 242 Hz, which is similar to the experimental value of 233 Hz. The relative error between the two is 3.9%, verifying the validity of the nonlinear system model.

Paired electrocatalytic H2O2-persulfate activation for sulfamethoxazole mineralization in a filter-press cell using BDD and air diffusion electrodes

This paper deals with the paired electrocatalytic H2O2-persulfate (H2O2-PS) activation to yield SO4– and OH for the antibiotic sulfamethoxazole (SMX) mineralization. A filter-press cell with a boron-doped diamond (BDD) anode and a gas diffusion cathode (GDE) was used to form the PS (through the anodic oxidation (AO) of sulfate) and H2O2 (via oxygen reduction reaction, ORR). Bulk electrolysis in the flow cell reached accumulation values of 1.48 mM PS and 4.80 mM H2O2 in 100 mM Na2SO4 at pH 3, with current density and mean linear flow velocity of j = 10 mA cm−2, andu = 39.5 cm s−1. On the other hand, the influence of the initial sulfate concentration 50 ≤ CSO42-≤ 500 mM), applied current density (5 ≤ j ≤ 15 mA cm−2), initial PS and SMX concentrations (0 ≤ CPS ≤ 1 mM, 5 ≤ CSMX ≤ 20 mg L–1) was systematically addressed on the H2O2-PS process performance. The best trial achieved the total abatement of 20 mg L–1 of SMX in a 100 mM Na2SO4 + 0.5 mM PS at pH 3, u = 39.5 cm s−1, and j = 10 mA cm−2. Lastly, a degradation pathway of SMX was proposed in which most of the by-products consisted of short-chained carboxylic acids and ammonium. Scavenger tests revealed that the degradation of SMX is provoked by OH (68.3 %), SO4– (3.9 %), and other oxidants (27.8 %).

The Dynamic Assimilation Technique measures photosynthetic CO2 response curves with similar fidelity to steady-state approaches in half the time.

The net CO2 assimilation (A) response to intercellular CO2 concentration (Ci) is a fundamental measurement in photosynthesis and plant physiology research. The conventional A/Ci protocols rely on steady-state measurements and take 15-40 min per measurement, limiting data resolution or biological replication. Additionally, there are several CO2 protocols employed across the literature, without clear consensus as to the optimal protocol or systematic biases in their estimations. We compared the non-steady-state Dynamic Assimilation Technique (DAT) protocol and the three most used CO2 protocols in steady-state measurements, and tested whether different CO2 protocols lead to systematic differences in estimations of the biochemical limitations to photosynthesis. The DAT protocol reduced the measurement time by almost half without compromising estimation accuracy or precision. The monotonic protocol was the fastest steady-state method. Estimations of biochemical limitations to photosynthesis were very consistent across all CO2 protocols, with slight differences in Rubisco carboxylation limitation. The A/Ci curves were not affected by the direction of the change of CO2 concentration but rather the time spent under triose phosphate utilization (TPU)-limited conditions. Our results suggest that the maximum rate of Rubisco carboxylation (Vcmax), linear electron flow for NADPH supply (J), and TPU measured using different protocols within the literature are comparable, or at least not systematically different based on the measurement protocol used.

Electrophoretic maneuvering of nonuniformly charged particles suspended in linear flows: Impact of the medium viscoelasticity

Electrophoretic maneuvering of nonuniformly charged particles suspended in linear flows: Impact of the medium viscoelasticity

Identification of Distribution Network Topology and Line Parameter Based on Smart Meter Measurements

Accurate line parameters are the basis for the optimal control and safety analysis of distribution networks. The lack of real-time monitoring equipment in grids has meant that data-driven identification methods have become the main tool to estimate line parameters. However, frequent network reconfigurations increase the uncertainty of distribution network topologies, creating challenges in the data-driven identification of line parameters. In this paper, a line parameter identification method compatible with an uncertain topology is proposed, which simplifies the model complexity of the joint identification of topology and line parameters by removing the unconnected branches through noise reduction. In order to improve the solving accuracy and efficiency of the identification model, a two-stage identification method is proposed. First, the initial values of the topology and line parameters are quickly obtained using a linear power flow model. Then, the identification results are modified iteratively based on the classical power flow model to achieve a more accurate estimation of the grid topology and line parameters. Finally, a simulation analysis based on IEEE 33- and 118-bus distribution systems demonstrated that the proposed method can effectively realize the estimation of topology and line parameters, and is robust with regard to both measurement errors and grid structures.

Exceptional Quantum Efficiency Powers Biomass Production in Halotolerant Algae Picochlorum sp.

The green algal genus Picochlorum is of biotechnological interest because of its robust response to multiple environmental stresses. We compared the metabolic performance of P. SE3 and P. oklahomense to diverse microbial phototrophs and observed exceptional performance of photosystem II (PSII) in light energy conversion in both Picochlorum species. The quantum yield (QY) for O2 evolution is the highest of any phototroph yet observed, 32% (20%) by P. SE3 (P. okl) when normalized to total PSII subunit PsbA (D1) protein, and 80% (75%) normalized per active PSII, respectively. Three factors contribute: (1) an efficient water oxidizing complex (WOC) with the fewest photochemical misses of any organism; (2) faster reoxidation of reduced (PQH2)B in P. SE3 than in P. okl. (period-2 Fourier amplitude); and (3) rapid reoxidation of the plastoquinol pool by downstream electron carriers (Cyt b6f/PETC) that regenerates PQ faster in P. SE3. This performance gain is achieved without significant residue changes around the QB site and thus points to a pull mechanism involving faster PQH2 reoxidation by Cyt b6f/PETC that offsets charge recombination. This high flux in P. SE3 may be explained by genomically encoded plastoquinol terminal oxidases 1 and 2, whereas P. oklahomense has neither. Our results suggest two distinct types of PSII centers exist, one specializing in linear electron flow and the other in PSII-cyclic electron flow. Several amino acids within D1 differ from those in the low-light-descended D1 sequences conserved in Viridiplantae, and more closely match those in cyanobacterial high-light D1 isoforms, including changes near tyrosine Yz and a water/proton channel near the WOC. These residue changes may contribute to the exceptional performance of Picochlorum at high-light intensities by increasing the water oxidation efficiency and the electron/proton flux through the PSII acceptors (QAQB).

Skin Factor Consideration in Decline Curve Analysis

Summary This paper introduces an approach for the impact of skin factor on the decline curve analysis of hydraulically fractured reservoirs. The objective is to consider this impact in the production forecasting and the ultimate recovery estimation. The approach focuses on reducing the uncertainties that could be raised from this impact on the production history and increasing the accuracy of the predicted flow rates. It proposes an easy and promising tool for the decline curve analysis that could be applied confidently to different oil- and gas-producing wells and different reservoirs. This approach utilizes the rate-normalized flow rate derivative β behavior of the fractured reservoirs. This derivative demonstrates a constant behavior with time for each flow regime when the production history has not undergone the impact of the skin factor. However, the constant behavior no longer exists when this impact has influenced the production history. Instead, a power-law type model governs the relationship between the flow rate derivative and production time. New analytical flow rate decline curve models, exponential-type, are derived from the flow rate derivative power-law type models for the flow regimes. Different models for calculating the skin factor are developed for the three linear flow regimes that could be observed during the transient state flow conditions. The proposed flow rate models are used to simulate the production history and forecast the future performance. Moreover, the hydraulic fracture conductivity can be calculated using these models as well as the flow rate loss caused by skin factor. Several case studies are examined by the proposed approach where the production history is used to characterize the dominant flow regimes. The study has reached several observations and conclusions. The impact of skin factor is seen clearly throughout transient state flow regimes; however, this impact declines sharply before reaching pseudosteady-state flow (boundary-dominated flow regime). The impact of the skin factor alternates the constant behavior of the flow rate derivative with time to a power-law type relationship. A straight line of a slope (0.5) is diagnosed during hydraulic fracture and formation linear flow regime on the log-log plot of the flow rate derivative β and time, while the bilinear flow regime demonstrates a straight line of a slope (0.25). Because of the skin factor, exponential decline curve models replace the power-law type models of the flow rate during the abovementioned flow regimes. These models exhibit an excellent match between the calculated flow rate and the production history. The maximum flow rate loss occurs during very early production time even though the skin factor during this time is less than the intermediate production time. This study presents a novel approach for the decline curve analysis taking into account the impact of skin factor. The novelty is represented by considering the flow regimes in the production forecasting of hydraulically fractured reservoirs. This approach is smoothly applied to predict the future performance with no need to know the wellbore and reservoir parameters. It can be used to predict the declining flow rate for a constant or varied bottomhole flowing pressure.

Multibody Analysis of Wave Energy Converters and a Floating Platform in the Time Domain

Generally, new and renewable energy systems generate electricity by installing and operating multiple modules simultaneously. In the Republic of Korea, recent studies and developments have focused on asymmetric wave energy converters (hereafter referred to as rotors) suitable for marine environments off the western coast of Jeju. These rotors are arranged on a large floating truss-structure platform and designed to harness electricity from the rotors’ pitch motion. However, when multiple rotors operate on a platform, their behavior diverges from that of a single module due to hydrodynamic interactions between them. Moreover, because the rotors are connected to the floating platform, their motion is influenced by the platform’s dynamics. In this study, a time-domain multibody motion equation was established to analyze changes in the behavioral characteristics of the rotors, both with and without a floating platform. The hydrostatic and hydrodynamic coefficients were derived in the frequency domain using WAMIT, a commercial code based on linear potential flow theory for three-dimensional diffraction/radiation analyses. The motion equation was then applied under regular and irregular wave conditions using OrcaFlex version 11.3, a marine systems design and analysis program. The resulting behaviors were compared to elucidate the influence of the platform and hydrodynamic interactions on the rotors’ performance.

Motion characteristics of squirmers in linear shear flow

In this study, the two-dimensional lattice Boltzmann method was employed to simulate the motions and distributions of a circular squirmer in a linear shear flow. The objective was to systematically investigate the dynamics of microorganisms or engineered squirmers in a flowing environment. We conducted multiple simulations across a range of self-propelled strengths (0.08 ⩽ α ⩽ 0.8) and squirmer type parameters (−5 ⩽ β ⩽ 5). Initially, we analyzed the swimming motions of the neutral squirmer (β = 0) in the shear flow. Our analysis revealed two distinct distributions depending on α, i.e. near the bottom or the top plate, which differs from conventional particle behavior. Moreover, we observed that the separation point of these two distributions occurs at αc = 0.41. The puller and pusher exhibit similarities and differences, with both showing a periodic oscillation pattern. Additionally, both types reach a steady inclined pattern near the plate, with the distinction that the low-pressure region of the puller’s head is captured by the plate, whereas the pusher is captured by the low-pressure region on the side of the body. The limit cycle pattern (LCP) is unique to the pusher because the response of the pressure distribution around the pusher to the flow field is different from that of a puller. The pusher starts from the initial motion and asymptotes to a closed limit cycle under the influence of flow-solid interaction. The frequency St of LCP is inversely proportional to the amplitude h * because the pusher takes longer to complete a larger limit cycle. Finally, an open limit cycle is shown, representing a swimming pattern that crosses the width of the channel.

A transient production prediction method for tight condensate gas wells with multiphase flow

Considering the phase behaviors in condensate gas reservoirs and the oil-gas two-phase linear flow and boundary-dominated flow in the reservoir, a method for predicting the relationship between oil saturation and pressure in the full-path of tight condensate gas well is proposed, and a model for predicting the transient production from tight condensate gas wells with multiphase flow is established. The research indicates that the relationship curve between condensate oil saturation and pressure is crucial for calculating the pseudo-pressure. In the early stage of production or in areas far from the wellbore with high reservoir pressure, the condensate oil saturation can be calculated using early-stage production dynamic data through material balance models. In the late stage of production or in areas close to the wellbore with low reservoir pressure, the condensate oil saturation can be calculated using the data of constant composition expansion test. In the middle stages of production or when reservoir pressure is at an intermediate level, the data obtained from the previous two stages can be interpolated to form a complete full-path relationship curve between oil saturation and pressure. Through simulation and field application, the new method is verified to be reliable and practical. It can be applied for prediction of middle-stage and late-stage production of tight condensate gas wells and assessment of single-well recoverable reserves.