Search Results (633)

The low specific speed centrifugal pump plays a crucial role in industrial applications, and ensuring its efficient and stable operation is extremely important for the safety of the whole system. The pump must operate with an extremely high head, an extremely low flow rate, and a very fast speed. The internal flow structure is complex and there is a strong interaction between dynamic and static components; consequently, the hydraulic excitation force produced becomes a significant factor that triggers abnormal vibrations in the pump. Therefore, this study focuses on a low specific speed centrifugal pump and uses a single-stage model pump to conduct PIV and pressure pulsation tests. The findings reveal that the PIV tests successfully captured the typical jet-wake structure at the outlet of the impeller, as well as the flow separation structure at the leading edge of the guide vanes and the suction surface. On the left side of the discharge pipe, large-scale flow separation and reverse flow happen as a result of the flow-through effect, producing a strong vortex zone. The flow field on the left side of the pressure chamber is relatively uniform, and the low-speed region on the suction surface of the guide vanes is reduced due to the reverse flow. The results of the pressure pulsation test showed that the energy of pressure pulsation in the flow passage of the guide vane occurs at the f_BPF and its harmonics, and the interaction between the rotor and stator is significant. Under the same operating condition, the RMS value distribution and amplitude at f_BPF of each measurement point are asymmetric in the circumferential direction. The amplitude of f_BPF near the discharge pipe is lower, while the RMS value is higher. A complex flow structure is shown by the larger amplitude and RMS value of the f_BPF on the left side of the pressure chamber. With the flow rate increasing, the energy at f_BPF of each measurement point increases first and then decreases, while the RMS value decreases, indicating a more uniform flow field inside the pump. Full article

Background: The pathogenesis of MASLD (metabolic dysfunction-associated steatotic liver disease) is driven by environmental, genetic, metabolic, immune, and inflammatory factors. IL-17 and TLR4 determine hepatic steatosis, inflammation, and finally fibrosis. Objectives: To explore the associations between the plasma levels of inflammatory markers, TLR4, and the cytokines IL17A/F, as well as their connections with the degree of hepatic steatosis and the risk of hepatic fibrosis (defined by the FIB-4 score) in MASLD patients. Methods: The study cohort included 80 patients diagnosed with MASLD. The IL-17A/F and TLR4 serum concentrations were determined using the ELISA method. Results: We found a significant difference in the CAR levels (C-reactive protein to albumin ratio) when comparing MASLD patients with severe steatosis to those with mild/moderate steatosis (Student’s t test, t (71) = 2.32, p = 0.023). The PIV (pan-immune inflammatory value) was positively correlated with the SII (systemic immune inflammation index), (r = 0.86, p < 0.0001) and the CAR (r = 0.41, p = 0.033) in MASLD patients with severe steatosis. In contrast, increased values of the LMR (lymphocyte to monocyte ratio) were significantly associated, with decreased levels of the SII (ρ = −0.38, p = 0.045). We also found a positive correlation between the CAR and the SII (r = 0.41, p = 0.028). In patients with mild/moderate steatosis, a significant positive correlation was observed between the SII and IL17A (r = 0.36, p = 0.010), the PIV and the CAR (r = 0.29, p = 0.011), the PIV and the SII (r = 0.87, p < 0.0001) and the PIV and IL17A (r = 0.3, p = 0.036). A negative correlation was observed between the LMR and the SII (r = −0.55, p < 0.0001) and the CAR and IL17F (r = −0.37, p = 0.011). Regarding the inflammatory markers, the PIV (336.4 vs. 228.63, p = 0.0107), and the SII (438.47 vs. 585.39, p = 0.0238) had significantly lower levels in patients with an intermediate–high risk of hepatic fibrosis as compared with the patients with a low risk of hepatic fibrosis. The PNI (prognostic nutritional index) (47.16 vs. 42.41, p = 0.0392) had significantly different levels in patients with the likelihood of hepatic fibrosis than those with a low risk of hepatic fibrosis. Conclusions: Regarding the inflammatory markers, the PIV and the SII hold promise as biomarkers for discriminating between MASLD patients with an intermediate–high risk and those with a low risk of hepatic fibrosis. Our findings underscore the role of IL-17A and its potential relationship with inflammatory markers in MASLD pathogenesis and the progression to hepatic fibrosis. Full article

This study utilized particle image velocimetry (PIV) to analyze the kinematic and hydrodynamic characteristics of juvenile goldfish across three swimming modes: forward swimming, burst and coast, and turning. The results demonstrated that C-shaped turning exhibited the highest speed, enabling rapid and agile maneuvers for predator evasion. Meanwhile, forward swimming was optimal for sustained locomotion, and burst-and-coast swimming was suited for predatory behaviors. A vorticity analysis revealed that vorticity around the tail fin was the primary source of propulsive force, corroborating the correlation between vorticity magnitude and propulsion found in previous research. The findings emphasize the crucial role of the tail fin in swimming efficiency and performance. Future research should integrate ethology, biomechanics, and physiology to deepen the understanding of fish locomotion, potentially informing the design of efficient biomimetic underwater robots and contributing to fish conservation efforts. Full article

The paper deals with the issue of determining the optimal setting of input variables in Ansys CFX for modeling pump flow in turbine operation (PAT). The pump model was created in Autodesk Inventor. The mesh for numerical simulations was created using Ansys Fluent Meshing, considering the mesh quality parameters’ skewness and aspect ratio. The Ansys CFX computational model was experimentally verified on an actual pump by measuring the performance parameters on a test circuit and using the PIV (particle image velocimetry) method. The research indicated that the most suitable setting for the model input variables was the inlet pressure and PAT flow rate combination. Another option was to adjust the pressure at the pump inlet and outlet. However, the calculation time in this case was up to 30% longer. The comparison of the model results with the experiment showed that the deviations in the numerical model performance values did not exceed 10% of the values measured on the test circuit. Only the calculated torque was 1.2 ± 0.13 Nm higher on average than the torque measured on the test circuit. This difference is most likely due to the simplification of the geometry of the computational mesh in order to reduce the computation time. Full article

Background: After the removal of the three-year epidemic control restrictions, Chinese children were confronted with heightened risks of respiratory infections. We aimed to investigate the post-pandemic (2023) epidemiology of respiratory infections among pediatric inpatients in a tertiary hospital in Shanghai, China, and compare it with the pre-pandemic (2019) levels. Methods: A total of 2644 pediatric inpatients were enrolled based on discharge time and divided into group 2019 (n = 1442) and group 2023 (n = 1202). Information on the demographic characteristics, diagnoses, and pathogen test results (Mycoplasma pneumoniae, MP; Chlamydia pneumoniae, CP; Legionella pneumophila, LP; Influenza A, IFA; Influenza B, IFB; Parainfluenza virus, PIV; respiratory syncytial virus, RSV; Coxsackie virus, COX; Adenovirus, ADV; Epstein–Barr virus, EBV) was collected and analyzed. Results: Significant increases were found in the overall test positivity rates (64.6% vs. 46.7%), mixed infection rates (17.4% vs. 9%), and proportion of severe cases (25.5% vs. 3.7%) after the pandemic than those before it. Compared with 2019, the incidences of MP, IFA, LP, RSV, and ADV remarkably increased, while those of IFB and COX decreased, with no obvious differences noted for CP, PIV, and EBV in 2023. A significantly higher MP-positive detection rate was noticed in children aged 1–6 years in 2023 than in 2019. The incidence of RSV infection began to rise in August 2023, earlier than the conventional epidemic season. Conclusions: Compared with the pre-pandemic levels, the overall test positivity rates of atypical pathogens and viruses among pediatric inpatients significantly increased, and alterations in the disease spectrum, epidemic season, and age of prevalence were observed after the COVID-19 pandemic. Full article

In this work, micro air vehicles (MAVs) equipped with bio-inspired wings are investigated experimentally in wind tunnel. The starting point is that insects such as dragonflies, butterflies and locusts have wings with rigid tubular elements (corrugation) connected by flexible parts (profiling). So far, it is important to understand the specific aerodynamic effects of corrugation and profiling as applied to conventional wings for the optimization of low-Reynolds-number aerodynamics. The present study, in comparison to previous investigations on the topic, considers whole MAVs rather than isolated wings. A planform with a low aperture-to-chord ratio is employed in order to investigate the interaction between large tip vortices and the flow over the wing surface at large angles of incidence. Comparisons are made by measuring global aerodynamic loads using force balance, specifically drag and lift, and detailed local velocity fields over wing surfaces, by means of particle image velocimetry (PIV). This type of combined global–local investigation allows describing and relating overall MAV performance to detailed high-resolution flow fields. The results indicate that the combination of wing corrugation and profiling gives effective enhancements in performance, around 50%, in comparison to the classical flat-plate configuration. These results are particularly relevant in the framework of low-aspect-ratio MAVs, undergoing beneficial interactions between tip vortices and large-scale separation. Full article

Rotor-type cross-media vehicles always induce considerably complex mixed air–water flows when approaching the water surface, resulting in relative thrust loss and structural damage on rotor. The interactions between a water surface and rotor wake bring potential risks to the cross-media process, which is known as the near-water effect of the rotor. In this paper, experimental investigations are used to explore the fluid dynamics of the near-water effect of the rotor. Qualitative droplet observation was carried out on the 0.25 m and 0.56 m diameter commercial rotor blades and the 0.07 m diameter ducted fan near the water surface first to gain a qualitative understanding of droplet characteristics. The results show that the rotor wake caused water surface deformation, droplet tearing off, splashing, and entrainment into the rotor disk. The depression formed by the rotor downwash flow impacting the water surface is named as three modes: dimpling, splashing, and penetrating, and the correlation between the depression modes and the aerodynamic characteristics of the rotor is primary analyzed. The flow mechanisms of dimpling mode were studied using the particle image velocimetry (PIV) technique. The results showed that the cavity and liquid crown obviously alter the flow direction of water surface jets, but not all rotors near water enter the vortex ring state. Two splashing mechanisms were revealed, including the direct ejection of droplets at the rim of depression and the tearing of liquid crown by the water surface jets. The blade tip vortex in the surface jet is a potential cause of entrainment into the rotor disk and secondary breakup of the droplet. Full article

Objective: There is increasing evidence for the effect of inflammation on the etiology of febrile seizure (FS) patients. We aimed to investigate the role of easily accessible inflammatory markers such as the neutrophil–lymphocyte ratio (NLR), systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), neutrophil–lymphocyte–platelet ratio (NLPR), and pan-immune-inflammation value (PIV) in febrile seizure. Methods: A total of 300 children, including 100 with febrile convulsions (FS), 100 febrile controls (FCs), and 100 healthy controls (HCs), were included in this retrospective study. The FS group was compared with the FC and HC groups in terms of these inflammatory indexes. Results: Between the FS group and the FC group, the neutrophil count was significantly higher in the FS group (p = 0.001) and the lymphocyte count was significantly lower (p < 0.001). The NLR (p < 0.001), SII (p < 0.001), SIRI (p < 0.001), NLPR (p < 0.001), and PIV (p < 0.001) were significantly higher in the FS group than in both the FC and healthy control groups. The optimal cut-off values for predicting FS in febrile conditions were 3.59> for NLR, >870.47 for SII, >1.96 for SIRI, 0.96> for NLPR, and >532.75 for PIV. Conclusions: The inflammatory indices are inexpensive, easily accessible hematological markers that can contribute to the diagnosis of FS. Full article

Micropile groups (MPGs) are typical landslide resistant structures. To investigate the effects of these two factors on the micropile–soil interaction mechanism, seven sets of transparent soil model experiments were conducted on miniature cluster piles. The soil was scanned and photographed, and the particle image velocimetry (PIV) technique was used to obtain the deformation characteristics of the pile and soil during lateral loading. The spatial distribution information of the soil behind the pile was obtained by a 3D reconstruction program. The results showed that a sufficient roughness of the pile surface was a necessary condition for the formation of a soil arch. If the surface of the pile was smooth, stable arch foundation formation was difficult. When the roughness of the pile surface increases, the soil arch range behind the pile and the load-sharing ratio of the pile and soil will increase. After the roughness reaches a certain level, the above indicators hardly change. Pile spacing within the range of 5–7 d (pile diameters) was suitable. The support effect was poor when the pile spacing was too large. No stable soil arch can be formed, and the soil slips out from between the piles. Full article

Background/Objective: Atherosclerosis is becoming increasingly common in modern society. Owing to the increasing number of complex angioplasty procedures, there is an increasing need for training in cases where the risk of periprocedural complications is high. Methods: A procedure was developed to obtain three-dimensional (3D) models and printing of blood vessels. The mechanical and optical properties of the printed materials were also examined. Angioplasty and stent implantation were tested, and the phantom was compared with the clinical data of patients who underwent interventional treatment. Both laser techniques and cone-beam computed tomography of the phantoms were used for comparison. Results: The printed material exhibited mechanical parameters similar to those of blood vessel walls. The refractive index of 1.473 ± 0.002 and high transparency allowed for non-invasive laser examination of the interior of the print. The printed models behaved similarly to human arteries in vivo, allowing training in treatment procedures and considering vessel deformation during the procedure. Models with stents can be analyzed using laser and cone-beam computed tomography to compare stents from different manufacturers. Conclusions: The developed methodology allows for simple and time-efficient production of personalized vessel phantoms. Full article

In this study, ultrasonic sensors were used to measure the vertical vortex at flood discharge outlets in real time, and numerical simulations and model experiments were conducted. When a sound signal passes through a vortex, its propagation characteristics will change, which helps to determine the existence of the vortex. Moreover, its characteristic parameters can be obtained through inversion. In this paper, first, the theories of acoustic measurement methods were introduced and their feasibility was verified through a comparison between Particle Image Velocimetry (PIV) measurement and numerical simulation results. Then, the Computational Fluid Dynamics (CFD) method was used to simulate the vertical vortex at the flood discharge outlets of hydraulic structures and the simulation data were restored to the actual size at scale. Finally, acoustic numerical simulations of actual vortex data were conducted, and ultrasonic sensors were used to measure the velocity of a simplified vertical vortex model under laboratory conditions. The research results indicate that the acoustic measurement method proposed in this article is effective in the measurement of the characteristic parameters of vertical vortex with a core radius of 0.03~0.05 m and a maximum tangential velocity of 0.5 m/s, the measurement error of the maximum tangential velocity is within 10%. Full article

Background: This investigation evaluated the predictive and prognostic efficacy of the newly developed global immune-nutrition-inflammation index (GINI) in patients with grade 4 adult-type diffuse gliomas, comparing it with other established indices such as the systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and pan-immune-inflammation value (PIV). Method: A retrospective cohort included 198 patients diagnosed with isocitrate dehydrogenase (IDH)-mutant gr4 (grade 4) astrocytoma and IDH-wt (wilde-type) glioblastoma (GBM) gr4 treated with surgical resection, radiotherapy, and temozolomide. Patients were stratified into two groups based on their GINI values: low GINI (<5815) and high GINI (≥5815). The primary endpoint was overall survival (OS). Results: High GINI was significantly associated with older age, poor performance status, multifocal tumors, and higher SII, SIRI, and PIV values (p < 0.005). The GINI demonstrated strong correlations with SII (r = 0.694), SIRI (r = 0.516), and PIV (r = 0.657) (p < 0.001). Patients with high GINI exhibited poorer OS (5.0 vs. 17.0 months) and PFS (5.0 vs. 13.0 months) in comparison to those with low GINI. Kaplan–Meier survival analysis revealed significantly prolonged OS and PFS among patients with low GINI (p < 0.001). Multivariate analysis identified high GINI as an independent negative risk factor for both PFS and OS. Conclusions: GINI is a robust predictor of clinical outcomes in IDH-mutant gr4 astrocytoma and IDH-wt GBM gr4, highlighting the crucial impact of nutrition and cancer cachexia. It shows superior prognostic value relative to the SII, SIRI, and PIV. Full article

This study aims to investigate the wake of two tandem square cylinders based on the Proper Orthogonal Decomposition (POD) analyses of the PIV and hotwire data. The cylinder centre-to-centre spacing ratio L/w examined is from 1.2 to 4.2, covering the four flow regimes, i.e., extended body, reattachment, transition and co-shedding. The Reynolds number examined was 1.3 × 10⁴. A novel Proper Orthogonal Decomposition (POD) technique (hereafter referred to as POD_HW) is developed to analyse data from single point hotwire measurements, offering a new perspective compared to the conventional POD analysis (POD_PIV) based on Particle Image Velocimetry (PIV) data. A key finding is the identification of two distinct states, reattachment and co-shedding, within the transition flow regime at L/w = 2.8, which POD_PIV fails to capture due to the limited duration of the PIV data obtained. This study confirms, for the first time, the existence of these states as proposed by Zhou et al. (2024), highlighting the advantage of using POD_HW for capturing intermittent flow phenomena. Furthermore, the analysis reveals how the predominant coherent structures contribute to the total fluctuating velocity energy in each individual regime. Other aspects of the flow are also discussed, including the Strouhal numbers, the contribution to the total fluctuating energy of the flow from the first four POD modes, and a comparison between different regimes. Full article

The use of a micropile group is an effective method for small and medium-sized slope management. However, there is limited research on the pile–soil interaction mechanism of micropile groups. Based on transparent soil and PIV technology, a test platform for the lateral load testing of slopes was constructed, and eight groups of transparent soil slope model experiments were performed. The changes in soil pressure and pile top displacement at the top of the piles during lateral loading were obtained. We scanned and photographed the slope, and obtained the deformation characteristics of the soil interior based on particle image velocimetry. A three-dimensional reconstruction program was developed to generate the displacement isosurface behind the pile. The impacts of various arrangement patterns and connecting beams on the deformation attributes and pile–soil interaction mechanism were explored, and the pile–soil interaction model of group piles was summarized. The results show that the front piles in a staggered arrangement bore more lateral thrust, and the distribution of soil pressure on each row of piles was more uniform. The connecting beams enhanced the overall stiffness of the pile group, reduced pile displacement, facilitated coordinated deformation of the pile group, and enhanced the anti-sliding effect of the pile–soil composite structure. Full article

Introduction: Several respiratory viruses have been shown to have seasonal patterns. The aim of our study was to evaluate and compare these patterns in immunocompetent and immunosuppressed patients for five different respiratory viruses. Methods: We performed a retrospective analysis of results for 13,591 respiratory tract samples for human metapneumovirus (HMPV), influenza virus, parainfluenza virus (PIV) and respiratory syncytial virus (RSV) in immunocompetent and immunosuppressed patients. A seasonal pattern was aligned to the data of immunocompetent patients through a logistic regression model of positive and negative test results. Results: A narrow seasonal pattern (January to March) was documented for HMPV. Most RSV infections were detected in the winter and early spring months, from December to March, but occasional cases of RSV could be found throughout the year. The peak season for PIV-3 was during the summer months, and that for PIV-4 was mostly in autumn. A narrow seasonal pattern emerged for influenza virus as most infections were detected in the winter, in January and February. The seasonal patterns of HMPV, RSV, PIV, and influenza virus were similar for both immunocompetent and immunocompromised patients. Conclusions: We found no difference in the seasonality of HMPV, RSV, PIV, and influenza virus infections between immunosuppressed and immunocompetent hosts. Full article