Diameter Ratio Research Articles

Phase diagram for nanodroplet impact on solid spheres: From hydrophilic to superhydrophobic surfaces

The impact of droplets on solid surfaces is a crucial fluid phenomenon in the additive industry, biotechnology, and chemistry, where controlling impact dynamics and duration is essential. While extensive research has focused on flat substrates, our understanding of impact dynamics on curved surfaces remains limited. This study seeks to establish phase diagrams for the process of droplet impact on solid spheres and further quantitatively describe the effect of curvature through theoretical analysis. It aims to determine the critical conditions between different impact outcomes and also establish a scaling relationship for the contact time. Here, the post-impact outcome regimes occurring for a wide range of Weber numbers (We) from 1.2 to 173.8, diameter ratio (λ) of solid spheres to nanodroplets from 0.25 to 2, and surface wettability (θ) from 21° to 160°, through the molecular dynamics simulation method (MD) and theoretical analysis. The MD simulations reveal that the phase diagrams of droplet impacts on hydrophilic, hydrophobic, and superhydrophobic spheres differ, with specific distinctions focusing on rebound and three different forms of dripping. Furthermore, a theoretical model based on the principle of energy conservation during impact on superhydrophobic surfaces has been developed to predict the critical conditions between rebound and dripping states, showing good agreement with simulation results. Additionally, a new scaling relationship of contact time for droplet impact on superhydrophobic spherical surfaces has also been established by extending and modifying the existing models, which also agrees well with the simulated results. These insights provide a foundational understanding for designing surface structures.

Design equations for maximum stress concentration factors for concrete-filled steel tubular K-joints

Stress concentration factors (SCFs) for welded tubular joints can be decreased by filling the chord with concrete leading to a longer fatigue life. However, there are currently no design formula available in guidelines to predict the SCF of concrete-filled circular hollow section (CFCHS) K-joints, thus limiting their applicability in bridge design. To address this gap, finite element models for CFCHS K-joints were developed and compared against test results to ensure their accuracy. Then, a comprehensive parametric study was conducted to establish relationships between maximum SCFs and four variables: brace-to-chord diameter ratio (β), chord diameter-to-thickness ratio (2γ), brace-to-chord thickness ratio (τ), and the angle between braces and chord (θ). A total of 480 FE models were examined under three loading conditions including brace and chord loading: balanced axial force, chord axial force, and chord bending. Design equations to predict the maximum SCF for CFCHS K-joints were established by multiple regression analyses of the numerical results. A comparison of maximum SCFs between circular hollow section (CHS) and CFCHS K-joints was made, and it was concluded that average reductions of 42% and 33% in maximum SCFs in CFCHS K-joints at the locations of the chord and brace were found compared to CHS joints for balanced axial force, respectively. Finally, a case study illustrating how to use the proposed equations for fatigue safety verification was presented.

Risk factors for patients with tracheal stenosis: a systematic review and meta-analysis.

To systematically evaluate potential risk factors for tracheal stenosis and to provide a reference for the prevention and management of patients with this condition. Databases were searched to identify studies of the risk factors for tracheal stenosis, from their inception to October 2023, then a meta-analysis was performed. The study was registered with PROSPERO under the registration number CRD42023428906. Ten studies of a total of 2525 patients were included. The meta-analysis showed that tracheotomy, diabetes, the duration of intubation, the duration of mechanical ventilation, respiratory tract infection, a high incision, and a ratio of intratracheal tube cuff diameter (C)/transverse diameter at the level of the clavicle (T) >150% were risk factors for the development of tracheal stenosis. Measures such as shortening the duration of mechanical ventilation and intubation, reducing and avoiding tracheotomy after prolonged intubation, early tracheotomy in patients with obesity who require prolonged mechanical ventilation, appropriate choices of incision location and catheter, the maintenance of appropriate C/T, the prevention of respiratory infection, and the control of diabetes mellitus should limit the risk of tracheal stenosis.

Typical Morphological Characteristics of the Immunohistochemistrical Subtypes of Pituitary Microadenomas: A dual center study.

This study aimed to investigate the relation of magnetic resonance image (MRI) features and immunohistochemistrical subtypes of pituitary microadenomas (PMAs) characterized by location and growth pattern. A double-center, retrospective review of MRI characteristics was conducted in 57 PMA cases recorded from February 2014 to September 2023 and identified on the basis of 2017 WHO classification of pituitary gland tumors. The geometric center of the tumor was defined, and the possibility of PMA vertical or lateral growth pattern was evaluated according to ratio of maximum diameter between the X and Y axes. Among the PMAs, somatotroph adenomas (STAs) significantly frequented the lateral-anteroinferior portion of pituitary gland (P=0.036). Lactotroph adenomas (LTAs) showed significant locational preference for the lateral-posteroinferior portion (P=0.037), and gonadotroph adenomas (GTAs) were predominately located in the central-anteroinferior portion (P=0.022). Furthermore, the PMAs in the suprasellar portion exhibited vertical extension with statistical significance (P=0.0). In our cohort, the micro-STAs were predominately located in the lateral-anteroinferior portion of pituitary gland, the micro-LTAs in the lateral-posteroinferior portion, and the micro-GTAs in the central-anteroinferior portion. The growth pattern of the PMAs was highly correlated with their vertical position instead of their immunohistochemistrical subtypes. Therefore, MRI shows potential in differentiating partial PMA subgroups, especially the cases in silent groups.

Numerical investigation of heat transfer characteristics of hydrogen flow in a randomly packed bed

In this study, two randomly packed beds with small tube-to-particle diameter (D/d) ratios of D/d = 4 (PB-4) and D/d = 5 (PB-5) are constructed using the discrete element method (DEM). The pore-scale heat transfer characteristics of hydrogen flow at low pore Reynolds numbers (Rep < 100) are investigated using a DEM-CFD simulation approach, with the temperature-dependent thermo-properties of hydrogen being considered. Distinct local channeling flow patterns are revealed by detailed analyses of the flow fields in PB-4 and PB-5. The overall friction factors for both beds are found to agree well with empirical correlations. Notably, a faster spatial temperature increase is exhibited by PB-5, with a larger D/d ratio, as evidenced by a shorter axial distance for fully-heated hydrogen flow compared to PB-4. For the pore-scale heat transfer in the packed beds, the radial temperature profiles are compared at various heights of the packed beds depending on the radial porosity oscillation, in which the wall effect should be especially considered in the near-wall region. Furthermore, the axial pore-scale Nusselt number (Nup,axial) exhibits an inverse fluctuation with the axial porosity oscillation. Finally, the global Nusselt numbers (Nu) in the packed beds are analyzed under different operating conditions, which are in good agreement with empirical correlations.

Effect of Tulsi Leaf Powder along with Casing Mixture on the Growth Parameters and Yield of White Button Mushroom [Agaricus bisporus (Lange) Imbach

Agaricus bisporus (Lange) Imbach commonly known as white button mushroom, is the most widely accepted food globally with nutritional and medicinal properties. The present experiment was conducted during the Rabi season 2023 - 2024 at Mushroom crop room, Department of Plant Pathology, SHUATS, Prayagraj, Uttar Pradesh to evaluate the effect of tulsi leaf powder at different concentrations (1 %, 1.5 %, 2 %, 2.5 % and 3 %) incorporated into casing mixture (alone and combination) viz., farm yard manure, farm yard manure + cocopeat + sawdust (1:1:1) with an objective to monitor the growth and yield aspects of white button mushroom. Among all treatments used in the study, the results revealed that minimum average time taken for completion of case run (15.14 days) and pinhead initiation (15.57 days) as well as maximum pileus diameter (4.63 cm), stalk length (3.77 cm), stalk diameter (3.01 cm), maximum yield (557.9 g), biological efficiency(12.97 %) and highest cost benfit ratio (1: 3.18) was recorded in farm yard manure + cocopeat + sawdust (1:1:1) + tulsi leaf powder @ 3%. These results indicated that incorporating tulsi leaf powder @3% in casing mixture improves the growth and yield of A. bisporus.

Elevational variation in anatomical traits of the first-order roots and their adaptation mechanisms

Root anatomical traits play an important role in understanding the link between root physiological function and ecological process. To determine how plants change root anatomical traits to adapt to distinct environments, we measured four key root anatomical traits---stele diameter (SD), cortex thickness (CT), root diameter (RD), and the stele to root diameter ratio (SDRD)---of first-order roots of 82 species were collected from different vegetation zones along a 2000 m altitudinal gradient on the northern slope of Taibai Mountain. Compared with other altitudes, plants located in temperate birch and fir forests had thinner SD, CT, RD, and SDRD. We found that elevational variation in root anatomical traits could largely be explained by phylogenetic taxonomy (clade). In addition, changes in SD were driven by soil bulk density, whereas variations in CT and RD were influenced by soil available nitrogen. When phylogenetic factors were removed from our analysis, allometric relationships between RD and root anatomical traits (SD and CT) were observed across different altitudes. Our study reveals the influence of phylogeny and environment on the elevational variation in root anatomical traits and further supports the allometric relationship between root anatomical traits (SD and CT) and RD. These findings enhance our understanding of the evolutionary and adaptive mechanisms of root anatomical structures, providing a basis for predicting how root anatomical traits respond to global changes.

Effect of web holes on web crippling capacity of rectangular hollow steel sections under two flange loadings

This paper presents experimental and numerical investigations on web crippling behavior of hot rolled rectangular hollow section (RHS) with web holes. A total of 20 rectangular hollow sections, subjected to interior-two-flange (ITF) and end-two-flange (ETF) loading conditions undergoing web crippling, were experimentally tested. The experimental program was designed to obtain web crippling of specimen having slenderness (h/t) value of 21.32, by varying size and offset distance of web holes under two flange loading conditions. Finite element models of experimentally tested beams were developed, and results of finite element analysis showed good agreement with experimental results. A parametric study was then conducted using finite element analysis on different cross section sizes, to demonstrate the effect of size and position of web holes on web crippling capacity of rectangular hollow sections. It was demonstrated that ratio of diameter of web hole to the depth of flat portion of web (a/h) and ratio of offset distance of web hole to the flat portion of web (x/h) are the primary parameters affecting the web crippling strength. Design recommendations in the form of reduction factors for both loading conditions are proposed, that are conservative to both experimental and finite element results. To assess the reliability level of design recommendations, reliability analyses were undertaken.

Research on jet electrochemical machining with coaxial megasonic assistance

In order to address the problem of poor localization in electrochemical machining (ECM), a coaxial megasonic assisted jet ECM method was proposed. Based on theoretical analysis, experiments were conducted to compare the effects of various electrolyte flow rates, electrolytic voltage and megasonic power levels on pit ECM. The results indicate that, in the range of experimental parameters, the increase of electrolyte flow rate and megasonic power can increase the machining depth, so as to improve the depth-diameter ratio of ECM pits. The use of coaxial megasonic-assisted jet ECM can enhance the depth-diameter ratio of etched pits compared to the without megasonic one. When applying a megasonic power of 22 W, the dimensions of the ECM pit were measured as 0.81 mm in depth and 5.73 mm in diameter, resulting in an depth-diameter ratio of 0.140. Under the same conditions, without megasonic assistance, the pit diameter is reduced to 0.65 mm while the pit depth increases to 6.36 mm, resulting in a depth-diameter ratio of 0.102. Additionally, The results also demonstrate that, the increase of electrolytic voltage makes the depth to diameter ratio of pit further increase on the original basis. With an electrolyte flow rate of 0.9 L/min and a megasonic power of 22 W, the use of electrolysis voltage of 50 V increased the depth-diameter ratio of etched pits to 0.173. Using the above preferred parameters, electrolytic milling of the wide groove is carried out. The depth-diameter ratio of the wide groove is increased from 0.039 to 0.059 by appending coaxial megasonic. This further verified the effectiveness of the coaxial megasonic-assisted jet ECM method.

Assessing the Impact of Transport Phenomena on Modeling and Optimization of Solid-State Fermentation for the Revalorization of Agro-Industrial Residues in a Wall‐Cooled Packed‐Bed Bioreactor

This work assesses the influence of transport phenomena on the growth of Yarrowia lipolytica 2.2ab (Yl2.2ab) and protease production during Solid-State Fermentation (SSF) in a bench-scale wall-cooled tubular bioreactor packed with substrate-based pellets derived from agro-industrial residues. Our engineering methodology, in a novel manner, includes: (i) developing a new pseudo-heterogeneous model, (ii) identifying and quantifying the impact of all transport phenomena on microbial kinetics, (iii) elucidating how fluid dynamics enhances heat and mass transfer processes, and hence microbial kinetics, and (iv) determining the operational and geometric parameters for optimal bioreactor performance. As main results: (i) all transport phenomena occurring within the bench-scale bioreactor are fundamental for its reliable simulation and will be essential for its scale-up, and (ii) the maximum production of proteases, 420 U kgDS‐1−1, is achieved under the following operational conditions: a tube to particle diameter ratio of 5.6, a bath temperature of 45°C, an inlet airflow rate of 1 L min−1, and inlet fluid temperature of 43 °C. Finally, the pseudo-heterogeneous model is assessed by describing SSF-based observations from the literature, appropriately predicting the performance of Yl2.2ab in a bench-scale bioreactor. These results pave the way for future exploration of Yl2.2ab in SSF within larger-scale packed-bed bioreactors.

The Suppression of Flow-Induced Vibrations for a Single and Two Tandem-Arrangement Cylinders Using Three Splitter Plates

Some very useful methods for suppressing the flow-induced vibration (FIV) of a single cylinder are known to potentially have a limited efficiency for tandem-arrangement cylinders. In this paper, three splitter plates uniformly attached around a cylinder with an angle of 120° are proposed to suppress the FIVs of both a single cylinder and two tandem-arrangement cylinders in a wind tunnel at Re = 4000–45,200. The splitter plates’ length to diameter ratios, L/Ds (where L is the length of the splitter plate and D is the cylinder diameter), are set from 0.1 to 0.8. The results show that the proposed method not only effectively suppresses the vortex-induced vibration (VIV) for a single cylinder, but also successfully mitigates the wake-induced galloping (WIG) for two tandem-arrangement cylinders. The vibrations of the single cylinders are effectively suppressed, consistently achieving suppression efficiencies over 95% for L/Ds = 0.2–0.8, with a notable peak efficiency of 98.4% at L/D = 0.2. For the two tandem-arrangement cylinders at S/D = 4.0 (where S is the center-to-center spacing between the two cylinders), the suppression efficiencies of the upstream cylinder exceed 96% for L/D = 0.2–0.8, with an optimal efficiency of 97.4% at L/D = 0.6. The downstream cylinder exhibits vibration only at L/Ds = 0.1, 0.2, and 0.4, resulting in suppression efficiencies of 80.3%, 67.1%, and 91.0%. The vibrations remain fully suppressed throughout the entire reduced velocity range for L/Ds = 0.6–0.8, reaching an optimal efficiency of 98.7% at L/D = 0.6. Three regimes of fs/fn characteristics can be classified for the single cylinder, and the wake structures show that shear layers develop along the front plate before attaching on the cylinder and are then offset to either side of the cylinder by the two rear splitter plates, contributing to the absence of periodic vortex shedding.

Accurate prenatal diagnosis of coarctation of the aorta by 3-step echocardiographic diagnostic protocol

BackgroundCoarctation of the aorta (CoA) is the most common undiagnosed congenital heart defect during prenatal screening. High false positive and false negative rates seriously affect prenatal consultation and postnatal management. The objective of the study was to assess the utility of various measurements to predict prenatal CoA and to derive a diagnostic algorithm.MethodsOne hundred and fifty-four fetuses with suspected CoA who presented at Fuwai Hospital between December 2017 and August 2021 were enrolled and divided into confirmed CoA cases (n = 47) and false positive cases (n = 107), according to their postnatal outcomes. The transverse aortic arch, isthmus, and descending aorta were measured in the long-axis view of the aortic arch. The angle between the transverse aortic arch (TAO) and the descending aortic arch (DAO) was defined as the TAO-DAO angle and measured in the long axis or sagittal view. Based on the database in GE Voluson E10 and the formula (Z = \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{\ ext{x}-{\\mu }}{\\alpha }$$\\end{document}), the standard score (Z-score) of the dimensions of the aorta were calculated in relation to the gestational age. The main echocardiographic indices were combined to design a 3-step diagnostic protocol. The TAO-DAO angle was used as the first step in the diagnostic model. The diameter of the transverse arch and the Z-score of the isthmus were the second step. The third-step indices included a Z-score of the transverse arch, diameter of the isthmus, distance from the left subclavian artery (LSA) to left common carotid artery (LCCA), the ratio of isthmus diameter and LSA diameter and ratio of the distances (the distance between the LSA and LCCA to the distance between the right innominate artery and LCCA). The receiver operating characteristic (ROC) curve determined the predictive capability of each diagnostic parameter, and the kappa test determined the diagnostic accuracy of the proposed model.ResultsThe cases with confirmed CoA had thinner transverse arches (1.92 ± 0.32 mm vs. 3.06 ± 0.67 mm, P = 0.0001), lower Z-scores of the isthmus (-8.97 ± 1.45 vs. -5.65 ± 1.60, P = 0.0001), smaller TAO-DAO angles (105.54 ± 11.51° vs. 125.29 ± 8.97°, P = 0.0001) and larger distance between the LSA and LCCA (4.45 ± 1.75 mm vs. 2.74 ± 1.07 mm, P = 0.0001) than the false positive cases. The area under the curve (AUC) was 0.947 (95% CI 0.91–0.98) for the TAO-DAO angle ≤ 115.75°, 0.942 (95% CI 0.91–0.98) for the transverse arch diameter ≤ 2.31 mm, 0.937 (95% CI 0.90–0.98) for the Z-score of the isthmus ≤ -7.5, and 0.975 (95% CI 0.95–1.00) for the 3-step diagnostic protocol with 97.8% sensitivity and 97.2% specificity. The kappa test showed that the model’s diagnostic accuracy was consistent with postnatal outcomes (kappa value 0.936, P = 0.0001).ConclusionsThe 3-step diagnostic protocol included the three most useful measurements and the additional indices with appropriate cut-off values. The algorithm is useful for the detection of aortic coarctation in fetuses with a high degree of accuracy.Trial registrationRetrospectively registered.

Solid pseudopapillary neoplasms of the pancreas (SPNs): diagnostic accuracy of CT and CT imaging features

PurposeTo summarize the abdominal computed tomography (CT) imaging and clinicopathological data of patients with SPNs of the pancreas and analyze the accuracy of preoperative CT diagnosis and features.Materials and methodsBetween June 2006 and June 2023, CT images of 120 histopathologically proven SPNs in the pancreas were retrospectively reviewed. Fifteen features, including age, sex, and CT-determined features, were included in a multiple stepwise regression analysis. The correlations between features and SPNs, including odds ratios (ORs) and 95% confidence intervals (CIs), were evaluated.ResultsAmong the 120 patients, the diagnostic accuracy of CT was 43.3%. The baseline CT results of patients with a correct diagnosis and misdiagnosis revealed significant differences in sex (P = 0.043), age (P = 0.004), boundary (P = 0.037) and encapsulation (P = 0.002) between the two groups. The preoperative imaging diagnostic accuracy was significantly greater in females than in males (47.9% vs. 25.0%, P = 0.043). The immunohistochemical indices did not significantly differ between the two groups. The results of univariate analysis revealed significant differences in sex (P = 0.048), age (P = 0.014), tumor length (P = 0.023), tumor boundaries (P = 0.039) and capsule type (P = 0.003). The results of multivariate analysis revealed that encapsulation was closely related to the diagnostic accuracy of CT (P = 0.04).ConclusionsThe accuracy of CT in the diagnosis of SPNs is low, but a length‒diameter ratio of the tumor approaching 1.0, encapsulation and clear boundaries are important CT-determined features. The capsule is an independent CT predictor in the diagnosis of SPNs.

Numerical Investigation of the Flow Structure of Cryogenic Hydrogen in Corrugated Metal Flexhoses Due to Fluid Structure Interactions

Abstract In this paper, details of flow field characteristics and pressure drop of cryogenic hydrogen in corrugated metal flexhoses will be numerically evaluated using multiphase flow physics coupled with fluid structure interactions. Multiphase flow regime is often influenced by concentration ratio, shape factor, and orientation of the piping. Corrugated metal flexhoses are commonly used as part of cryogenic commodity transportation for their ability to operate in a large range of temperatures and pressures with a high degree of geometric flexibility. These sharp changes in the geometry of the flexhose convolutions are one of the leading factors of liquid and gas phase entrainment which can significantly reduce the efficiency of piping systems and fuel delivery systems to the engine components. The entrained gas phase hydrogen can eventually propagate in successive convolutes leading into the permanent entrapment of the gas phase hydrogen in the corrugations. The volume fraction up to 5% gas phase with various convolute heights and pitch will be evaluated, with a hose length to diameter ratio (L/D) range between 20 to 60 and a Reynolds number range between 5,000 to 350,000 based on the hose hydraulic diameter. The findings of the study contribute to a better understanding of multiphase flow physics of hydrogen in corrugated metal flexhoses.

3D printing cross‐scale mold for manufacturing micromixers

AbstractNowadays, the methods of manufacturing microfluidic mixers were not flexible enough to customize and manufacture special sizes. Hence, a novel electrohydrodynamic jet printing method was proposed to fabricate cross‐scale mold for manufacturing micromixers in one step. Polyvinylpyrrolidone (PVP)/polycaprolactone (PCL) composite ink was prepared, and various printing parameters were investigated for fabricating varieties of 2D structures and 3D regular molds. A cross‐scale spiral mixer was successfully printed, various diameter ratio of 5.6, aspect ratio of 7.2. The PVP/PCL lines were direct printed, size of 66 nm deep and 743 nm wide. The circles were size of 564 nm deep and 7.02 μm wide. The mixing conditions of micromixers with different width ratios were simulated and analyzed; and the better mixing effect of micromixers with width ratio of 2:1 was proved, improved the mixing efficiency by 15.6% compared with micromixer without cross‐scale channels. The cross‐scale micromixers are promising for skin chip sensor and drug metabolite analysis, and the printing method proposed in this paper has great application potential in micro‐electro‐mechanical systems (MEMS).

Hydrodynamic study of gas–liquid-solid mini-fluidization based on fluorescence PIV

The fluorescence-based tracer particle image velocimetry (fluorescence PIV) was used to obtain the flow regimes transition, bubble size and velocity, liquid and particle flow field characteristics of the 1 ∼ 3 mm GLSMFBs and 93 ∼ 195 μm glass beads. When the bed-to-particle diameter ratio increased, the bubble size and velocity distribution tended to be more concentrated. Bubble rose as straight line and S-shaped spiral trajectory. The divergence and vorticity of the flow field were preliminarily quantified. There showed a close relationship between the macroscopic hydromechanical behaviors such as bubble size and velocity and the mesoscopic behaviors such as the movement and development of vortices. The upward drag force of liquid and bubble on particles mainly affected the particle axial velocity, while the particle radial motion was mainly caused by bubble wake and surface force among particles. The results provide theoretical reference for the design and optimization of GLSMFB reactors.

Association between calcification and risk stratification in gastric gastrointestinal stromal tumors.

Risk assessment of gastric gastrointestinal stromal tumors (GISTs), particularly those with a diameter ≤ 5cm, remains a clinical challenge. Previous research has primarily focused on tumor size, ulceration, necrosis, and enhancement patterns, with less emphasis on the role of tumor calcification, which remains controversial regarding its correlation with malignancy risk. This study aims to explore the characteristics of calcification in gastric GISTs and its correlation with risk stratification as defined by the National Institutes of Health (NIH), to improve preoperative risk assessment for gastric GISTs ≤ 5cm. A retrospective analysis of 385 pathologically confirmed gastric GIST patients, including 178 with small gastric GISTs (< 2cm), was conducted. Tumors were categorized into low-risk (very low / low) and high-risk (intermediate / high) groups based on NIH criteria. Variables such as age, gender, tumor long-axis diameter, calcification rates, calcification size, the number and distribution of calcification, calcification to tumor long-axis diameter ratio were analyzed. Logistic regression was used to identify independent predictors of malignancy for gastric GISTs, with predictive values assessed via receiver operating characteristic (ROC) curves. Significant differences were found between high-risk and low-risk groups in treatment methods, tumor long-axis diameter, the ratio of calcification to tumor long-axis, and calcification distribution (P < 0.05). Calcification rates varied across risk categories, with 23.6% in very low-risk, 31.6% in low-risk, 9.8% in intermediate-risk, and 31.7% in high-risk categories (P < 0.05). In GISTs ≤ 5cm, both tumor long-axis diameter (OR = 3.07, 95% CI: 2.29-4.10) and calcification (OR = 0.36, 95% CI: 0.13-0.97) were independent predictors of malignancy risk (both P < 0.05). ROC curve analysis yielded areas of 0.849 for tumor long-axis diameter, 0.578 for calcification, and 0.862 for their combination. The study indicates lower calcification rates in intermediate-risk gastric GISTs and higher rates in other risk categories. Additionally, tumors of different sizes exhibit two distinct calcification patterns, suggesting possible differing mechanisms of calcification in tumors. Calcification in gastric GISTs ≤ 5cm acts as a protective factor against higher malignancy risk, and when combined with tumor long-axis diameter, significantly enhances predictive accuracy over long-axis diameter alone.

Influence of nozzle profile on submerged pipe jet impingement heat transfer

ABSTRACT Current work focuses on enhancing the performance of solar air heater by employing vertical submerged pipe jets featuring different profiles: circular, square, triangular, and rectangular. The study investigates parameters including jet diameter ratio d / D h ranging from 0.044 to 0.11 and the jet spacing ratio ( Sj / D h ) varying from 0.108 at 0.433 while keeping the streamwise ( X / D h ) and spanwise Y / D h pitch ratio fixed at 0.867. The Reynolds number Re ranges from 3,000 to 18,000. Initial results for all the profiles were obtained through CFD simulations, indicating that the circular pipe jet demonstrates superior heat transfer and thermo-hydraulic performance parameter (THPP). The experimental validation of circular profile pipe jet showed a maximum THPP of 2.69 achieved at a d / D h of 0.066 and Sj / D h of 0.217, with a Reynolds number of 15,000.

Effect of precipitation phase on the flow behavior of a nickel-based superalloy during compressive deformation

Nickel-based superalloys have become indispensable in micro-forming processes owing to their outstanding mechanical properties. The size effect significantly impacts the formability of components at the mesoscopic scale, resulting in compression deformation behaviors distinct from those observed at the macroscopic scale. The classical Hall-Petch formula can hardly express this phenomenon precisely. This study conducted compression tests of a nickel-based superalloy at the mesoscopic scale, exploring the role of the feature size (specifically, the ratio of sample diameter to grain size, D/d) and the precipitation phase on the plastic deformation behavior. The results show that increasing feature size of samples as well as particle size and volume fraction of γ′ and γʺ phases enhance the flow stress of the superalloy. When the feature size exceeds 8.6, the flow stress decreases with decreasing feature size. However, when the feature size is below 8.6, the flow stress increases with decreasing feature size. A model is proposed to comprehensively explain the size effect and the precipitation phase on compressive flow stress. The surfaces of samples experience inhomogeneous deformation during compressive deformation. The trend towards inhomogeneous deformation has become more pronounced as feature size decreases. Furthermore, the increase in particle size and volume fracture of γ′ and γʺ phases limits the inhomogeneous deformation of the sample surface.

Failure analysis of a helical compression spring with relatively low spring index

Design of helical springs are well defined and studied thoroughly. Generally, behavior of stiffness is considered to be in linear regime with desired dimensions. However, as the spring index which is defined as ratio of helical diameter to wire diameter gets lower a correction to calculated stress values must be performed. Furthermore, collision between coils, non-homogenous pitch heights between coils, end conditions are other factors leading to increase in stress values as compared to intended design values. An unexpected premature crack formation in a fatigue tested helical compression spring was investigated. First, geometry was measured using CMM and compared with design tolerances. After, metallurgical inspections regarding composition, hardness and microstructure of the material were performed. An analytical and numerical study was conducted in order to evaluate the stress state in the spring. A finite element model was created using ABAQUS and stress increase due to end condition was observed. A premature failure in a helical spring was studied regarding dimensions, material and stress state. The factors leading to nonlinear response of the spring is addressed and compared with experimental tests.