Shedding Process Research Articles

Susceptibility and risk to inhalation of pathogen-laden aerosol in large public spaces: Evidence from Fangcang Shelter Hospitals under multiple ventilation rates

To enhance the prevention and control of pandemic respiratory infections, we constructed an infection risk prediction model for pathogen inhalation based on the dose-response relationship with reference to the long-distance transmission chain of the SARS-CoV-2 pathogen, applying it to the Fangcang Shelter Hospital (FSH). The model quantitatively describes key processes of pathogens shedding, airborne transmission, suspension, inhalation by susceptible individuals, and lung deposition, thus improving the resolution and accuracy of the results. This study considered four ventilation rates and quantitatively assessed their impact on inhalation infection risk. Results indicate that the infection risk within the multi-patient shelter unit is unevenly distributed, with the maximum probability (3.66 %) being more than 30 times higher than the minimum probability (0.10 %) at a ventilation rate of 8 ACH. Poor ventilation (6 ACH) significantly increases average infection probability, with a rise of 35.96 % compared to the average probability (1.14 %) at 8 ACH. However, excessive ventilation (12 ACH) led to diminishing returns on ventilation performance. Lastly, we also found that poor ventilation was a sufficient and non-essential condition for higher infection probability. Our findings can be extended to similar large-scale scenarios, offering positive support for the sustainable development of society.

The Genome-Wide Identification, Characterization, and Expression Patterns of the Auxin-Responsive PbGH3 Gene Family Reveal Its Crucial Role in Organ Development

The regulation of vital plant activities by hormones is governed by a family of macromolecular peptides referred to as GH3 genes. This work analyzed the expression patterns of GH3 family genes in pear tissues using transcriptome data and bioinformatics analysis. In the Bai Li pear genome, a total of 18 PbGH3 genes were identified. Comparative evolutionary studies have shown a strong association between PbGH3 and AtGH3 class I and class II proteins. The role of PbGH3 genes in growth activities and hormone regulation was revealed using gene ontology (GO) and promoter region analysis. In addition, although certain PbGH3 genes exhibited tissue-specific expression in sepals, the majority had a ubiquitous expression across all tissues. Bioinformatics and expression studies suggest that the GH3 gene family in pears may have a role in controlling the abscission of the fruit’s sepals. This work sheds light on the pear fruit sepal shedding process and may inspire further research.

Pengaruh Pemberian Seduhan Kunyit Asam Terhadap Penurunan Tingkat Dismenorea pada Siswi SMPN 19 Bandar Lampung Provinsi Lampung

Background: Menstruation is the process of shedding of the uterine wall (the inner layer of the endometrium) which is accompanied by bleeding that occurs repeatedly every month, except during pregnancy. Dysmenorrhea consists of primary and secondary dysmenorrhea. This study aims to determine the impact of giving sour turmeric infusion on changes in the level of dysmenorrhoea. Giving tamarind turmeric infusion on changes in desmenorrhea in female students at SMPN 19 Bandar Lampung. Research Objective: To determine the impact of giving sour turmeric infusion on changes in the level of dysmenorrhoea in female students at SMPN 19 Bandar Lampung Research Method: The type of research used is quantitative with a cross sectional approach. Pre-experimental research design with a one group pretest-posttest design without a control group. The sampling technique uses the Accidental Sampling technique. The data analysis technique used is the Wilcoxon test. Research result : Giving tamarind turmeric is a feasible intervention given to reduce dysmenorrhea pain experienced by young women. Suggestion for health workers to provide knowledge about treatment non-pharmacological dysmenorrhoea by administering tamarind turmeric drink. Conclusion : Giving tamarind turmeric is a suitable intervention to reduce dysmenorrhea pain experienced by young women. Suggestions for health workers to provide knowledge about non-pharmacological treatment of dysmenorrhoea by giving tamarind turmeric drinks

Deformation of Sessile Droplets under a Gentle Shear Airflow.

Deformation of sessile droplets under shear flow is widespread in both nature and industry. Previous research focuses on the shedding process of sessile droplets under shear airflow, with insufficient attention paid to the droplet deformation before shedding. In this work, experimental studies on the deformation behaviors of sessile droplets under shear airflow are conducted to investigate the effects of airflow velocity and droplet volume on the tangential and normal droplet deformations. Scaling laws of the droplet deformations are established. The results show that the profile of sessile droplets changes under shear airflow with the topmost point exhibiting periodic oscillations in both tangential and normal directions. The oscillation period of the tangential deformation exceeds that of the normal deformation. The average tangential deformation of droplets increases with the increasing airflow velocity and droplet volume. The average normal deformation of droplets increases with the increasing airflow velocity and is influenced by the droplet volume at a higher airflow velocity. The contact angle on the windward side oscillates periodically, and its average value significantly decreases. The contact angle of droplets on the windward side decreases as the airflow velocity and droplet volume increase, while the contact angle on the leeward side remains almost unchanged. The average deformation of droplets in the tangential and normal directions is linearly related to the effective Weber number and the square of the effective Weber number. These findings could be used to predict the deformation of sessile droplets under shear airflows.

Energy concentration pipe based on passive jet control for enhancing flow induced vibration energy harvesting

Passive control is a classic method for enhancing the energy harvesting from flow-induced vibrations. This study introduces the Energy Concentration Pipe (ECP), a hollow pipe featuring a passive windward suction inlet and jet outlets, mounted on a circular cylinder to improve the performance of flow-induced vibration energy harvester. The effects of ECP configurations—single outlet, symmetrical dual outlet, and asymmetrical dual outlet—are investigated both experimentally and numerically. Experimental results demonstrate that the ECP significantly broadens the lock-in region and generates higher output voltage compared to conventional cylinders. Specifically, the lock-in region of the symmetrical dual outlet configuration increases by 108.33%, meanwhile the maximum output voltage improves by 12.69% over the baseline case. Numerical simulations further elucidate the mechanisms of the ECP, identifying the energy concentration phenomenon. An additional portion of incoming airflow, along with its energy, is channeled through the ECP and jetted into the wake vortex behind the cylinder, altering the wake vortex shedding process. The wake structure is characterized by large primary vortex pairs and smaller secondary vortices. The energy concentration also results in larger and stronger wake vortices, enhancing unsteadiness and broadening the lock-in region. Moreover, a transverse oscillation of vortices induces additional excitation on the cylinder due to pressure oscillation, leading to larger vibration amplitude and higher output voltage.

Dynamic response of a transmission conductor following delayed ice shedding by reduced-scale model test

Ice shedding on conductors of transmission lines can induce severe vertical vibrations and abrupt tension changes, potentially causing structural damage and power outages. Prior experiments and numerical simulations assumed that ice sheds instantaneously from transmission lines, neglecting the practical delays in the ice shedding process, which resulted in unrealistic conductor dynamic responses. This study introduces a reduced-scale modeling system designed to simulate delayed ice shedding on conductors. The jump height and dynamic tension of an isolated-span transmission line following delayed ice shedding are analyzed, and various factors such as the two-dimensional delay duration, shedding sequence, and weight of ice accretion are examined through reduced-scale model tests. Based on the experimental data, simplified formulas are proposed to calculate the conductor's jump height and maximum tension after ice shedding by taking the time delay of the shedding process into account.

Effect of tip clearance on non-synchronous propagating flow disturbances of compressor rotors under high aerodynamic loading conditions

The complex tip flow instability and its induced non-synchronous vibration have become significant challenges, especially as aerodynamic loading continues to increase. This study investigates the effects of tip clearance on non-synchronous propagating flow disturbances of compressor rotors under high aerodynamic loading conditions by conducting full-annulus unsteady numerical simulations with three typical tip clearance values for a 1-1/2 stage transonic compressor. The non-synchronous aerodynamic excitation frequency, circumferential mode characteristics, and annular unstable flow structures are analyzed under near stall conditions. The results show that the total pressure ratio and normalized mass flow parameters first increase and then decrease as the tip clearance increases from 0.5%C (where C represents the tip chord length) to 2%C under high aerodynamic loading conditions, instead of constantly decreasing. For the 0.5%C tip clearance case, the traveling large-scale tornado-like separation vortices cause a low non-synchronous aerodynamic excitation frequency and severe pressure fluctuations. The periodic shedding and reattachment processes of the rotor blades separated by 2 – 3 pitches result in 19 dominant mode orders in the circumferential direction. As the tip clearance increases from 1%C to 2%C, the difference of tip flow structures in each blade passage is significantly weakened, and the dominant mode order of the disturbance is equal to the rotor blade-passing number. The pressure fluctuation is mainly caused by cross-channel tip leakage flow, and the aerodynamic excitation frequency exhibits evident broadband hump characteristics, which has been reported as a rotating instability phenomenon.

Control on Flow Separation over a Cylinder by a Ferrofluid Film Adsorbed by a Magnet

Flow separation can lead to increased resistance and vibration generation, which is a difficult problem that cannot be ignored in engineering. In this paper, we propose a method of controlling flow separation by adsorbing ferrofluid onto the surface of a magnetized cylinder, taking the common flow around a cylinder as an example. Parametric effects of the ferrofluid film, including its viscosity and thickness, on the flow behavior were investigated in terms of the vortex shedding process, velocity distribution, dominant frequency, pressure distribution, and the flow motion inside the ferrofluid film. The results indicate that the ferrofluid film can suppress the generation of flow separation and achieve effective control, which is mainly caused by wall slip and the internal movement of the ferrofluid film. Furthermore, the flow separation control effect of ferrofluid thin films with different parameters varies, with low-viscosity ferrofluid exhibiting a superior control effect.

Accuracy assessment of Beddoes-Leishman and IAG dynamic stall models for wind turbine applications

The study presents a systematic comparison between two of the most-credited dynamic stall models for wind turbine applications: the original Beddoes-Leishman (BL) model and the newly-developed IAG. The scope of such comparison, supported by experimental data, is to shed new light on the actual suitability of current dynamic stall models for their integration into modern wind turbine simulation codes, and on the best practices to calibrate them. Two different strategies are followed for the calibration of the BL model: 1) standard one, compliant with common practices found in the literature; 2) a physics-oriented one, focusing on the constants defining the dynamic stall onset as well as on the parameters governing the duration of the vortex shedding process. The IAG model, initially developed based on the first-order BL formulation and recently improved by reducing the number of constants and removing compressibility effects, is applied instead in its standard form only. The two models are compared across a range of oscillation mean angles, amplitudes, and reduced frequencies. Results demonstrate that the original BL model, although with a challenging calibration process, when properly tuned, can provide a very good description of aerodynamic unsteady loads. While showing consistent results, the IAG formulation appears to be more robust, as it employs fewer constants and extracts most of the needed information directly from the input polar data. The comparison between the calibrated BL and IAG models highlights critical modelling aspects, the computation of drag and determination of the stall onset above all, offering valuable insights for the future development of dynamic stall formulations.

Semaphorin 7A promotes endothelial permeability and inflammation via plexin C1 and integrin β1 in Kawasaki disease

BackgroundKawasaki disease (KD) is a pediatric systemic vasculitis characterized by endothelial cell dysfunction. Semaphorin 7A (Sema7A) has been reported to regulate endothelial phenotypes associated with cardiovascular diseases, while its role in KD remains unknown. This study aims to investigate the effect of Sema7A on endothelial permeability and inflammatory response in KD conditions.MethodsBlood samples were collected from 68 KD patients and 25 healthy children (HC). The levels of Sema7A and A Disintegrin and Metalloprotease 17 (ADAM17) in serum were measured by enzyme-linked immunosorbent assay (ELISA), and Sema7A expression in blood cells was analyzed by flow cytometry. Ex vivo monocytes were used for Sema7A shedding assays. In vitro human coronary artery endothelial cells (HCAECs) were cultured in KD sera and stimulated with Sema7A, and TNF-α, IL-1β, IL-6, and IL-18 of HCAECs were measured by ELISA and qRT-PCR. HCAECs monolayer permeability was measured by FITC-dextran.ResultsThe serum level of Sema7A was significantly higher in KD patients than in HC and correlated with disease severity. Monocytes were identified as one of the source of elevated serum Sema7A, which implicates a process of ADAM17-dependent shedding. Sera from KD patients induced upregulation of plexin C1 and integrin β1 in HCAECs compared to sera from HC. Sema7A mediated the proinflammatory cytokine production of HCAECs in an integrin β1-dependent manner, while both plexin C1 and integrin β1 contributed to Sema7A-induced HCAEC hyperpermeability.ConclusionsSema7A is involved in the progression of KD vasculitis by promoting endothelial permeability and inflammation through a plexin C1 and integrin β1-dependent pathway. Sema7A may serve as a potential biomarker and therapeutic target in the prognosis and treatment of KD.

Experimental and numerical investigations on non-synchronous vibration and frequency lock-in of transonic compressor rotor blades

Non-synchronous vibration (NSV) problems in axial compressors are challenging and frequently result in high vibration stress or structural failure within the frequency lock-in region. A deeper understanding of the lock-in phenomenon in NSV is necessary to improve blade reliability and safety. In this study, an experiment was conducted on a multistage transonic axial compressor to obtain frequency lock-in characteristics. The enforced motion of the flexible blade simulation method was used to study the frequency lock-in mechanism between blade vibration and tip unstable flow. The results showed that the aerodynamic frequency characteristic changed from a broadband spectrum to a distinct frequency peak as the NSV onset. The nonlinear vibration pattern could maintain the limited cycle oscillation for 26 s. The vibration stress of the frequency locked-in case was approximately 19 times that of the frequency unlocked one. The pressure fluctuations generated by the large-scale radial separation vortex structures were stronger than those of the tip leakage flow, and the third-order harmonic frequency of the circumferential instability flow was close to the first-order bending model natural frequency. The periodic shedding and reattachment process of flow separation provided the initial non-synchronous aerodynamic excitation source. The frequency lock-in phenomenon occurred at a maximum vibration amplitude of 2 % and 3 % tip chord length. The tip unstable flow characteristics were consistent and entirely dominated by blade vibration.

Fluid-solid interaction simulations of an aeroelastic square prism in sinusoidal oscillatory flows

This study numerically investigates the aerodynamic and aeroelastic characteristics of a square prism (aeroelastic model) and wind field around it in sinusoidal oscillatory flows (SOFs). The reliability of the fluid-solid interaction (FSI) simulation is validated by a free vibration test and wind tunnel tests in smooth flow and SOF. The effects of the amplitude and frequency of SOFs are studied at the mean wind speed of vortex-induced resonance. The results show that increasing the amplitude and frequency of SOFs will amplify the root mean square (RMS) along-wind and across-wind base shear forces of the aeroelastic model but decrease the RMS across-wind displacement at the top of the aeroelastic model. The spectral analysis of the base shear forces indicates that the influence of vortex shedding on the across-wind base shear force is reduced by either increasing the amplitude or increasing the frequency of SOFs. The mean and instantaneous wind fields around the aeroelastic model in SOFs and smooth flow are compared, and the wake characteristics of the aeroelastic model in SOFs are analysed by dynamic mode decomposition. It is observed that when the frequency of SOFs is 1.5 times as large as the fundamental natural frequency of the aeroelastic model, the regular vortex shedding process is substantially affected.

Integrated analysis of the transcriptome and metabolome reveals the molecular mechanism regulating cotton boll abscission under low light intensity

BackgroundCotton boll shedding is one of the main factors adversely affecting the cotton yield. During the cotton plant growth period, low light conditions can cause cotton bolls to fall off prematurely. In this study, we clarified the regulatory effects of low light intensity on cotton boll abscission by comprehensively analyzing the transcriptome and metabolome.ResultsWhen the fruiting branch leaves were shaded after pollination, all of the cotton bolls fell off within 5 days. Additionally, H2O2 accumulated during the formation of the abscission zone. Moreover, 10,172 differentially expressed genes (DEGs) and 81 differentially accumulated metabolites (DAMs) were identified. A KEGG pathway enrichment analysis revealed that the identified DEGs and DAMs were associated with plant hormone signal transduction and flavonoid biosynthesis pathways. The results of the transcriptome analysis suggested that the expression of ethylene (ETH) and abscisic acid (ABA) signaling-related genes was induced, which was in contrast to the decrease in the expression of most of the IAA signaling-related genes. A combined transcriptomics and metabolomics analysis revealed that flavonoids may help regulate plant organ abscission. A weighted gene co-expression network analysis detected two gene modules significantly related to abscission. The genes in these modules were mainly related to exosome, flavonoid biosynthesis, ubiquitin-mediated proteolysis, plant hormone signal transduction, photosynthesis, and cytoskeleton proteins. Furthermore, TIP1;1, UGT71C4, KMD3, TRFL6, REV, and FRA1 were identified as the hub genes in these two modules.ConclusionsIn this study, we elucidated the mechanisms underlying cotton boll abscission induced by shading on the basis of comprehensive transcriptomics and metabolomics analyses of the boll abscission process. The study findings have clarified the molecular basis of cotton boll abscission under low light intensity, and suggested that H2O2, phytohormone, and flavonoid have the potential to affect the shedding process of cotton bolls under low light stress.

Mode decomposition and spatial propagation regularity analysis of cavitation variation on a twisted hydrofoil

The cavitation phenomenon can induce non-uniformity in the fluid, impacting fluid dynamic performance. This paper focuses on the cavitation shedding of the Delft Twist 11 hydrofoil. First, the reliability of numerical simulations is verified by computational fluid dynamics results. Utilizing the variational mode decomposition method, the cavitation signals on two cavitation paths are decomposed. Finally, the cavitation pulsation tracking network method is proposed to extensively investigate the spatial propagation patterns of cavitation signals at various sections above the twisted hydrofoil. The results reveal that typical frequencies at different monitoring planes are 30, 58, and 88 Hz. The corresponding amplitude analysis at these frequencies provides insight into the spatial propagation and attenuation process of cavitation vortices shedding. This study offers a novel perspective for a deeper understanding of cavitation mechanisms. Simultaneously, this provides references for enhancing the performance of mechanical engineering systems, reducing energy consumption, and improving structural reliability.

Numerical investigation of partial cavitation in a Venturi tube by Eulerian-Lagrangian multiscale modelling

The cavitating flow in a Venturi tube has a complex flow structure. In this paper, the partial cavitation in an axisymmetric Venturi tube, dominated by bubbly shock, is investigated by utilizing Eulerian-Lagrangian multiscale modelling. The unsteady partial cavitation is simulated by Large Eddy Simulation coupled with the Volume of Fluid and the Discrete Bubble Model. The numerical results show a well agreement with the high-speed photography. Through a comprehensive analysis of the development and transportation of macro cavities and micro bubbles, a detailed explanation of the cavity shedding process triggered by bubbly shock is provided. The results highlight the precise capability of the multi-scale method in elucidating the intricate flow field induced by partial cavitation. The findings may pave the way for the further investigations on the underlying mechanisms of partial cavitation, fostering a deeper understanding of bubbly shock dominated cavitating flow.

Multiscale modelling of hepatitis B virus at cell level of organization.

Multiscale modelling is a promising quantitative approach for studying infectious disease dynamics. This approach garners attention from both individuals who model diseases and those who plan for public health because it has great potential to contribute in expanding the understanding necessary for managing, reducing, and potentially exterminating infectious diseases. In this article, we developed a nested multiscale model of hepatitis B virus (HBV) that integrates the within-cell scale and the between-cell scale at cell level of organization of this disease system. The between-cell scale is linked to the within-cell scale by a once off inflow of initial viral infective inoculum dose from the between-cell scale to the within-cell scale through the process of infection; the within-cell scale is linked to the between-cell scale through the outflow of the virus from the within-cell scale to the between-cell scale through the process of viral shedding or excretion. The resulting multiple scales model is bidirectionally coupled in such a way that the within-cell scale and between-cell scale sub-models mutually affect each other, creating a reciprocal relationship. The computed reproductive number from the multiscale model confirms that the within-host scale and the between-host scale influence each other in a reciprocal manner. Numerical simulations are presented that also confirm the theoretical results and support the initial assumption that the within-cell scale and the between-cell scale influence each other in a reciprocal manner. This multiple scales modeling approach serves as a valuable tool for assessing the impact and success of health strategies aimed at controlling hepatitis B virus disease system.

Application of singular spectrum analysis to nonstationary time series in flow-induced vibrations of a circular cylinder

In numerical simulations of flow-induced vibrations (FIV) of a circular cylinder, abundant time series data are available, including cylinder displacement and acting forces. Singular spectrum analysis (SSA) is employed to deal with nonstationary multi-component time series produced in two FIV cases with proper interpretation in physics. In the first case, the cylinder displacement time series is decomposed into two oscillatory components using SSA. The instantaneous frequencies of these two components are obtained by Hilbert transform (HT) and found to be in agreement with the wavelet transform of the cylinder displacement. In the second case, three oscillatory components are extracted from the cylinder displacement time series by SSA. The dominant component is characterized by steady oscillations at the vortex shedding frequency, which suggests a relatively steady vortex shedding process behind the rear cylinder. In contrast, the second component, which is closely associated with the alternate boundary layer separations from the front cylinder, features in the increasing amplitude with time. This implies that the unsteady flow field in the gap might be attributed to the nonstationary cylinder oscillations. This work demonstrates that SSA, in conjunction with HT, enables a comprehensive time-frequency analysis of nonstationary time series obtained in FIV.

Precise emergency load shedding approach for distributed network considering response time requirements

Emergency load shedding (ELS) is a vital measure for power systems to manage extreme events, ensuring the safety, stability, and economic operation of the grid. The integration of distributed energy resources and controllable devices in modern power systems has bolstered grid flexibility. Consequently, developing precise load shedding strategies to balance economic and security goals has emerged as a prominent subject in power system optimization. However, existing methods exhibit inadequacies, including overlooking practical operability, privacy concerns, and a lack of adaptability to response time requirements. To address these gaps, this paper introduces a precise ELS approach for distributed networks with a focus on response time needs. Contributions encompass designing load shedding processes for various response times, integrating demand response, and partitioning networks for optimized load shedding. Through validation using standard test cases, the proposed approach effectively utilizes response time and demand-side resources for precise ELS control in distribution networks. It accommodates different scenarios, offering a robust solution for rapid and accurate load shedding during emergencies.

Self-excited vortex-acoustic lock-in in a bluff body combustor

We investigate self-excited vortex-acoustic lock-in in a bluff body combustor. The bluff body not only anchors the flame but also sheds vortices. Mutual interaction between vortex shedding and the combustor acoustic field leads to lock-in. A lower-order model for vortex shedding is coupled to the acoustic equations to obtain a set of discrete dynamical maps, which are then solved numerically. Lock-in is identified when a definite phase relationship between vortex shedding and acoustic field remains unaltered with time. The common frequency during (phase) lock-in is either close to the natural acoustic or vortex shedding frequencies, accordingly termed A- or V-lock-in, respectively. Instability and amplitude suppression occur with most parts of the A- and V-lock-in regions, respectively. Furthermore, we relate the lock-in and pre-lock-in regimes observed in our previous experiments (Singh & Mariappan, Combust. Sci. Technol., 2019, pp. 1–29) to A- and V-lock-in phenomena, respectively. Among the two lock-in phenomena, combustion instability is favoured by $1:1$ A-lock-in, whose boundaries in the parameter space can be obtained from a forced response of the vortex shedding process. Finally, we discuss the bifurcations leading to lock-in.

Effect of Stress Ratio, Constraint, and Load History on the Intrinsic and Extrinsic Components of Threshold Stress Intensity

Abstract Threshold intensity range, ΔKth, was experimentally investigated as the sum of two components, both of which are sensitive to applied loading conditions. The intrinsic component, ΔKth,i, is characterized as a sole function of a near-tip stress parameter, σ*, in much the same way as fatigue limit depends on mean stress or stress ratio. The extrinsic component, ΔKcl, is the attenuated fraction of crack tip response because of crack wake contact, whose exact value is not readily measured at threshold. The ΔKth,i versus σ* relationship is established using a specially designed load shedding process under constant baseline maximum load, with σ* modulated through periodic overload-underload combinations whose periodicity is regulated to avoid undue crack extension at threshold. This relationship is then used to extract the ΔKcl component from ΔKth readouts obtained on the same batch of material using conventional load shedding procedure. The effect of constraint on ΔKth and its two components was studied using specimens with sharp side grooves to maximize constraint across the crack front. The study was performed on a medium strength low-alloy steel.