Axial Locations Research Articles

Analysis of group evaporation characteristics of droplet clusters in an evaporating spray

Droplet clustering in sprays refers to the dynamic evolution of highly concentrated regions due to the preferential accumulation of the polydisperse droplets in the turbulent airflow entrained by the spray. In the current study, we aim to experimentally investigate the collective vaporization of the droplets in droplet clusters in an air-assisted acetone spray characterized by the Group number, $G$ . The magnitude of $G$ depends on the cluster length scale and interdroplet spacing, and it indicates the vaporization mode that may vary from the isolated mode ( $G \ll 1$ ) to external group mode ( $G \gg 1$ ). The droplet measurements were obtained under atmospheric conditions at different axial and radial locations within the spray. Application of the Voronoi analysis to particle image velocimetry images of the spray droplets facilitated the identification and characterization of the droplet clusters, which allowed the measurement of $G$ for each cluster. The results highlighted that multiscale clustering of the evaporating droplets leads to multimode group evaporation of the clusters (characterized by a wide range of $G$ : 0.001–10). The trend of interdroplet spacing versus cluster area allowed the classification of the droplet clusters into small-scale clusters (which are of the order of the Kolmogorov length scale) and large-scale clusters (that scale with the large-scale turbulent eddies), that are found to exhibit distinct group evaporation behaviour. A theoretical model is invoked to correlate $G$ with the droplet evaporation rate for individual clusters, and some interesting observations are identified, which are explained in the paper.

Detection of Axial Locations of Control Rods Using Movable In-core Detectors

Background Reactivity control in Pressurized Water Reactors (PWRs) relies on Rod Cluster Control Assemblies (RCCAs), or control rods (CRs), and boric acid diluted in primary circuit water. The control rods’ axial location inside the reactor core is typically provided by means of two redundant systems: the Rod Positioning Indicator (RPI) and the Rod Control System (RCS). Methods The current work focuses on the development of an additional method for the detection of control rod axial location inside the reactor core of a Pressurized Water Reactor (PWR) using the Advanced Flux Mapping System (AFMS) and its Movable In-core Detectors (MIDS). The paper presents the methodology employed and the results of the first validation campaigns. Results Two validation campaigns were carried out, targeting respectively equilibrium and non-equilibrium xenon axial distribution. The routine proved successful in identifying control rods’ axial insertion in different operating conditions including Flux Maps (FMs) acquired at 2%, 50% and 75% power. Conclusions The routine developed at Beznau Nuclear Power Plant will serve as an additional core monitoring tool to be employed in case of suspicious or faulty indication coming from the main control rod location methods. The developed method proved able to locate control rods’ axial insertion with few steps error, equivalent to maximum 1.6% of total fuel height (i.e. 5 cm as maximum error). There is room for potential improvements with regards to the uncertainty model currently implemented.

A Study on the interaction of shock tube-generated blast waves with a circular object at different pressure ratios

The interaction of high peak overpressure blast waves with a circular object placed at two different axial locations from the shock tube exit is studied through numerical simulation using an in-house developed multi-component Navier–Stokes solver. The driver and driven sections of the shock tube were 0.8 m and 6 m, respectively. Helium is used in the driver section, while atmospheric air is used in the driven section and outside the shock tube. The evolution of blast waves inside an open-ended shock tube and its interaction with a rectangular object is reported in Murugan et al.. (2022). Here, the blast wave interacting with a circular object is examined for diaphragm pressure ratios of 13 and 57 by placing the objects at 250 mm and 500 mm from the shock tube exit. The flow field is evaluated through numerical Schlieren, vorticity, density, pressure plots, and the enstrophy plot, which shows the vortical structures that originated in the flow field. The blast load acting on the circular object is calculated for two diaphragm pressure ratios and axial locations. This study helps understand the reflection and diffraction of blast waves and associated flow fields around circular objects used in blast wave attenuation.

Toroidal mean flow and complex temperature distribution in a thermoacoustic core

Increasing the capacity of thermoacoustic machines (engines or refrigerators) requires increasing the diameter of the regenerator, which may result in non-uniform temperature distributions inside the regenerator. In the current study, the temperature is measured at different radial and axial locations inside the regenerator of a thermoacoustic refrigerator with a diameter of 148 mm. The working gas is a mixture of helium and Argon at a static pressure of 40 bar. Non-uniform radial temperature distributions are observed at different axial positions. Also, the predicted axial temperature distributions by a 1-D linear model (DeltaEC) do not agree with the measured temperature distributions. We suspect that the non-uniform radial temperature distribution generates a steady flow through the regenerator which increases the radial temperature non-uniformity and results in non-linear axial temperature distribution. Given the measured temperature distribution, the presence of a toroidal steady flow inside the regenerator is suspected. To confirm this hypothesis, the regenerator is divided into three segments connected in parallel in the DeltaEC model. Mean flows are added in each segment of the regenerator to simulate the presence of toroidal flow in the regenerator. The predicted temperature distributions from this modified DeltaEC model agree with the measured temperature distributions.

Study on the self-vibration characteristics of non-circular arches with cracks based on the transfer matrix method

As the span of reinforced concrete arch bridges continues to increase, so does the difficulty of construction. The structure is at risk of cracking. Most of the bridges under construction are non-circular arches, and there are few studies on such arches. The current study tried to investigate the self-vibration characteristics of non-circular arches with existing cracks. A computational approach proposed in the original non-circular arch is substituted with multiple infinitesimal arch segments having different radii of curvature, enabling the determination of natural frequencies and mode shapes of the non-circular arches with cracks. Furthermore, a finite element model (FEM) of the reinforced concrete structure with existing cracks is developed to assess the effects of various factors, including axial location, crack depth, and positions within the same cross-section. The results demonstrate the feasibility of the computational method using multiple infinitesimal arc segments with varied radii of curvature, yielding a maximum error of only 1.58 %, which satisfies engineering application standards. An increase in crack depth leads to a reduction in the natural frequencies of specific modes of the structure, while the effect on others is insignificant. For cracks situated at the top or bottom plates within the same cross-section, the impact differs based on the local deformation being convex or concave. If the deformation is convex, the top plate cracks exhibit a higher rate of change in natural frequencies compared to the bottom plate cracks; conversely, with concave deformation, the bottom plate cracks have a greater influence than the top plate cracks.

Heat transfer efficiency in gas–solid fluidized beds with flat and corrugated walls

Abstract Gas–solid fluidized bed reactors exhibit improved heat and mass transfer performance as compared to packed beds. Corrugated walls installed in narrow gas–solid bubbling fluidized bed (CWBFB) enclosures have been observed to decrease minimum bubbling velocity, reduce bubble size, improve gas distribution, provide stable operation, and minimize particle carryover or loss. Thorough analyses of the wall-to-bed heat transfer coefficient in flat- (FWBFB) and corrugated- (CWBFB) wall bubbling fluidized beds have been performed for a variety of operating conditions and geometric parameters. Fast-response self-adhesive heat flux probes and thermocouples were used to simultaneously measure the wall-to-bed heat flux, surface and bed temperatures, and were used to determine the heat transfer coefficient (HTC) at various axial and lateral locations. For a given set of parameters, a significant increase in HTC was observed at lower gas flow rates in CWBFB as compared to FWBFB. It was shown that CWBFB inventory required lower U mb (gas flow rate) as compared to FWBFB. Full 3-D transient Euler–Euler CFD simulations using the kinetic theory of granular flow were also performed, which confirmed the experimental results.

Assessing turbulence–flame interaction of thermo-diffusive lean premixed H2/air flames towards distributed burning regime

Simultaneous laser-induced fluorescence of OH radicals and particle image velocimetry, and quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering measurements are used to investigate the effects of Karlovitz number (by varying the equivalence ratio) and residence time (by varying the axial measurement location) on the internal flame structures of lean premixed hydrogen/air turbulent jet flames. The turbulent flow fields, instantaneous macroscopic flame structures, and thermochemical states of a set of lean premixed hydrogen/air turbulent flames with varying initial equivalence ratio of 0.3, 0.4, and 0.45 at a constant bulk velocity of 100m/s are discussed. With an increasing equivalence ratio, the Karlovitz number derived from the turbulent flow fields decreases rapidly from 7690 to 260 and 100, determined at a downstream location of x/D=7. At the highest Karlovitz number (i.e., the lowest equivalence ratio), a distributed burning is observed in the jet flame as turbulent transport dominates over molecular mixing, and the effects of differential diffusion and flame curvature are suppressed. With decreasing Karlovitz number, intense burning regions characterized by elevated local equivalence ratio, high water mole fraction, and super-adiabatic flame temperatures are observed in association with positive flame curvature. The same combustion diagnostics are applied to another lean premixed hydrogen/air turbulent flame with an initial equivalence ratio of 0.4 and a bulk velocity of 200m/s at selected downstream locations of x/D=3.5, 7, 10.5, and 14 to assess the effects of developing turbulence and residence time. Corresponding Karlovitz numbers are 680, 730, 775, and 690, as the local turbulent intensity changes along downstream locations. While flame structures reveal characteristics towards distributed burning at lower x/D, a locally intense burning region appears at higher x/D together with positive curvature. This is mainly because the turbulence develops with increasing x/D and the flame surface is more disturbed and curved by turbulent eddies with increasing turbulence length scales. The highly diffusive hydrogen is locally concentrated by positively curved flame surfaces, resulting in fuel-rich burning regions at a higher temperature. This indicates that, as velocity fluctuations increase in axial direction, turbulence can also promote thermo-diffusive instabilities to a certain extent, increasing the mixture inhomogeneity in temperature space by interacting with the differential diffusion effect of hydrogen at atmospheric pressure.Novelty and significanceThe novelty of the current work is the focus on turbulence–chemistry interactions of premixed hydrogen/air jet flames at high turbulence and ultra lean conditions. Comprehensive experimental results including the turbulent flow fields (particle image velocimetry), instantaneous flame structures (laser-induced fluorescence of OH radicals) and internal thermochemical states (quasi-simultaneous 1D Raman/Rayleigh and 2D Rayleigh scattering imaging) of hydrogen/air jet flames are analyzed and discussed. The data sets with well-characterized boundary conditions and high measurement accuracy, are crucial for validation and development of numerical simulation models.

Physico-mechanical Properties and Potential Utilization of Melia azedarach L. Grown in Quezon Province, the Philippines

The possible utilization of Bagalunga (Melia azedarach L.) was determined based on its physical and mechanical properties. Tests were done following the ASTM D143-2019 standard. Tree samples were collected from two municipalities of Quezon province, the Philippines – namely Sariaya and Unisan. The results showed that compared to the trees from Sariaya, the trees collected from Unisan had 13.48 and 14.24% higher green moisture content (MC) and basic relative density (RD), respectively. However, their tangential (TS), radial (RS), longitudinal (LS), and volumetric shrinkage (VS) were 12.21, 4.42, 28.94, and 7.83% lower than those of the former. Furthermore, the RD of M. azedarach was similar to that of Gmelina arborea, and Acacia mangium and higher than that of Falcataria falcata. As for VS, it was comparable and in some cases even higher than those of commercially used timber species with medium to low VS. For the strength properties, in both green and 12% MC conditions, the strength of trees from Unisan was significantly higher than trees from Sariaya. However, both remained within the medium strength classification – similar to Swietenia macrophylla, G. arborea, and A. mangium but higher than Eucalyptus deglupta, Hevea brasiliensis, and F. falcata. The significant effect of axial height was observed in MC, RD, LS, and VS, and minimal variation was found in the mechanical properties. Industrial tree plantation developers may consider using M. azedarach as an alternative species, with careful consideration of the axial height and location, as these factors can influence tree properties.

Impurity transport in PISCES-RF*

Abstract Linear plasma devices (LPD) utilizing a helicon plasma source, a high density light ion source, can generate impurities due to progressive erosion of the radio frequency (RF) transmission window caused by rectified sheath voltage. These source-born impurities can entrain and be transported by the plasma toward a target, affecting plasma-material interaction studies. Earlier work on material testing in Prototype-Materials Plasma Exposure eXperiment at ORNL revealed significant source impurity deposition on downstream targets. However, using a similar RF source, no target impurity deposition is observed in Plasma Interaction Surface Component Experimental Station (PISCES)-RF despite evidence of RF window erosion in the source region, thereby motivating the present work. Experimentally, using various magnetic field configurations upstream of the PISCES-RF plasma source and seeding titanium (Ti) impurities at various axial locations, impurity transport and deposition along the machine axis were investigated. It was found that Ti deposition was localized to the side of the plasma source where the Ti impurity was seeded. In contrast, aluminum (Al) deposition, originating from the sputtering of the helicon window, occurred predominantly upstream of the plasma source, suggesting an asymmetry in the axial transport of eroded RF window material. These observations suggest a stagnation of the parallel plasma flow immediately downstream of the plasma source, with impurity ions remaining unmagnetized near the source upstream. Al deposition in magnetic field-free regions in PISCES-RF indicates that sputtered Al impurities likely remained neutral due to their large ionization mean-free path under PISCES-RF conditions. Plasma modeling and simulation supported this, indicating that Al-neutrals transport toward the helicon source upstream for low electron density cases. It was found that the Larmor radius of the Al ions was greater than the plasma radius towards the source upstream and remained weakly magnetized in PISCES-RF, meaning that plasma source-born impurities are not efficiently entrained in the plasma flow. These findings provide critical insights into impurity transport in helicon plasma-based LPDs.

Detection of Axial Locations of Control Rods Using Movable In-core Detectors

Background Reactivity control in Pressurized Water Reactors (PWRs) relies on Rod Cluster Control Assemblies (RCCAs), or control rods (CRs), and boric acid diluted in primary circuit water. The control rods’ axial location inside the reactor core is typically provided by means of two redundant systems: the Rod Positioning Indicator (RPI) and the Rod Control System (RCS). Methods The current work focuses on the development of an additional method for the detection of control rod axial location inside the reactor core of a Pressurized Water Reactor (PWR) using the Advanced Flux Mapping System (AFMS) and its Movable In-core Detectors (MIDS). The paper presents the methodology employed and the results of the first validation campaigns. Results Two validation campaigns were carried out, targeting respectively equilibrium and non-equilibrium xenon axial distribution. The routine proved successful in identifying control rods’ axial insertion in different operating conditions including Flux Maps (FMs) acquired at 2%, 50% and 75% power. Conclusions The routine developed at Beznau Nuclear Power Plant will serve as an additional core monitoring tool to be employed in case of suspicious or faulty indication coming from the main control rod location methods. The developed method proved able to locate control rods’ axial insertion with few steps error, though there is room for potential improvements with regards to the uncertainty model currently implemented.

Experimental and Numerical Study on the Plasma-Laser-Induced Ignition of Strut Stabilizer at Different Locations

The minimum ignition equivalence ratio of the strut stabilizer is an important parameter in the design of integrated afterburners. The ignition location significantly affects the ignition equivalence ratio and flame propagation, and therefore, it should be deeply studied. The ignition equivalence ratio and flame propagation at different axial ignition locations downstream of the strut stabilizer are studied in this paper. When the ignition distance is approximately the bluff body trailing edge width, a lower ignition equivalence ratio is required for ignition, and the flame propagates faster through the entire combustion chamber. For different ignition locations, the generated flame kernel at different locations all first propagates to the shear layer. Subsequently, the unilateral flame rapidly extends, ultimately igniting the entire combustion chamber. The flame propagation trajectory depends on the ignition location controlled by the non-reacting flow field and the distribution of kerosene concentration. The flame propagation trajectory mainly includes three paths: (1) the flame kernel is directly downstream the shear layer when the ignition location is close to the tail edge of the stabilizer, (2) the flame propagates upstream into the shear layer in a U-shape when the ignition location is far from the stabilizer but still in the recirculation zone, and (3) the flame propagates upstream into the recirculation zone and shear layer in a U-shape when the ignition location is outside the recirculation zone. In addition, the time for flame propagation to the shear layer is directly related to the ignition performance when the ignition location is within the recirculation zone. If the flame reaches the shear layer in a longer time, there will be more energy loss during the flame propagation process, and the ignition performance will deteriorate. The speed of the flame-trailing edge extension is directly related to the ignition fuel-air ratio, and the downstream extension of the flame is mainly affected by the turbulence velocity in the shear layer.

Spectral-domain OCT characteristics of intraretinal hyper-reflective foci associated with age-related macular degeneration and diabetic retinopathy

ObjectiveThe purpose of this study was to quantitatively analyze and compare OCT characteristics of intraretinal hyper-reflective foci (IHRF) in eyes with diabetic retinopathy (DR) versus age-related macular degeneration (AMD). Designa retrospective observational study. Participants54 treatment-naïve eyes (27 DR and 27 AMD). MethodsThe IHRF lesions in OCT B-scan were semi-automatically segmented. Mean reflectivity (MR), maximum diameter, circularity index (Cir), area, and the angle between the greatest linear dimension (GLD) and the horizontal were computed for each IHRF lesion. The presence and absence of a posterior shadow and the axial location were assessed. The MR was normalized using the vitreous and nerve fiber layer reflectance as dark and bright reference standards, respectively. ResultsA total of 1149 IHRF (1051 in DR and 98 in the AMD group) were identified, with a mean of 39 ± 36 lesions in DR eyes compared to only 4 ± 4 in AMD eyes (p < 0.001). The mean area of individual IHRF lesions was greater in DR eyes (1305 ± 1647 μm² vs 1031 ± 750 μm²; p = 0.016), but IHRF in AMD eyes had higher reflectivity (1.17 ± 0.14 vs 1.03 ± 0.17; p < 0.001). The angle of the GLD relative to the horizontal was greater in AMD eyes, indicating that IHRF in AMD eyes were more horizontally oriented. In AMD eyes, 88.8% of IHRF were located beneath the inner border of the outer nuclear layer (ONL), while in DR eyes, 56.9% were located there (p < 0.001). ConclusionsIHRF lesions in eyes with DR and AMD demonstrate significant differences, with IHRF in DR eyes tending to be larger and less hyper-reflective compared to AMD eyes.

Impact of septal deviation and turbinate hypertrophy on nasal airway obstruction: insights from imaging and the NOSE scale: a retrospective study

BackgroundThe aim of this study was to evaluate the effects of nasal septum deviation and inferior turbinate hypertrophy on nasal obstruction by utilizing the Nose Obstruction Symptom Evaluation (NOSE) values and paranasal sinus computed tomography (PSCT) findings for correct preoperative evaluation.MethodsNinety-six patients (57 males and 39 females) aged between 18 and 54 years (mean age, 30.3 ± 9.7 years) participated in this study. Among them, 56 patients underwent septoplasty combined with inferior turbinate outfracture, while 40 patients underwent septoplasty alone. Preoperative nasal examinations were performed on all patients. The direction, location, nasal septum deviation classification, and inferior turbinate hypertrophy size classification were carefully evaluated and compared with the NOSE survey results. PSCT of 56 patients were evaluated and classified by calculating the coronal location of septum deviation, the axial location of septum deviation, the coronal angle of septum deviation, and the axial angle of septum deviation.ResultsA positive correlation was found between the coronal location of the septal deviation and the preoperative NOSE 2, and the NOSE total, and the difference of postoperative and preoperative NOSE (p = 0.032, p = 0.007, p = 0.021, respectively). There was a statistically significant relationship between the coronal location of the septal deviation classification and the NOSE preoperative total values (p = 0.26). A negative statistically significant correlation was found between inferior turbinate hypertrophy and preoperative NOSE 5 values (p = 0.029).ConclusionWe conclude that the combination of PSCT and the NOSE scale is helpful in determining the severity of nasal obstruction prior to surgery. Specifically, we found that nasal septum deviations located in the anterior and coronal planes have a greater impact on nasal obstruction compared to deviations in the axial plane. Inferior turbinate fracture does not provide more benefit than septoplasty alone in treating patients’ nasal obstruction. These findings emphasize the importance of a comprehensive approach in addressing nasal obstruction for optimal patient outcomes.

Experimental study on the influence of radial internal clearances of the rolling bearings on dynamics of a flexible rotor system

To investigate the impact of radial internal clearance of rolling bearings on the dynamic response of a flexible rotor system in a turbo-shaft engine, a dynamic similarity model of the power turbine rotor was established. Experimental research was then conducted. Four rolling bearings supporting the rotor were examined, with dynamic response tests carried out under varying radial internal clearances. The influence of the radial internal clearance on the dynamic characteristics of the rotor system was studied using the controlled variable method. The amplitude, orbit, and asynchronous vibration were analyzed through time-domain signal comparison, waterfall diagrams, and spectral analysis. The experimental results demonstrate that: (1) Adjusting the radial internal clearance of the bearings can significantly reduce the dynamic response of the flexible rotor system, with a maximum observed displacement response reduction of 88%. (2) The efficiency of vibration reduction is closely related to the axial location of the bearing. (3) Optimal radial internal clearance is not necessarily achieved at the maximum or minimum values. (4) The "locked-up" frequency phenomenon, which increases the resonance opportunities of the rotor system, can be mitigated by adjusting the radial internal clearance of different bearings. This research is of great significance and engineering value for understanding, diagnosing, and preventing excessive vibration in flexible rotor systems.

Investigation of cold tube structure on flow characteristics and energy separation in vortex tube based on numerical and thermodynamic analyses

A combined approach of computational fluid dynamics modelling, experimental validation and thermodynamic analysis is used to investigate the effect of cold end tube geometry (namely, straight tube, divergent tube, convergent tube, and convergent-divergent tube) on flow characteristics and energy separation, which to improve the energy efficiency and sustainability of the vortex tube in industrial applications. The analyses indicate that the highest axial velocity (212 m/s) and swirl velocity (193 m/s) at different axial locations in the cold tube are demonstrated in the divergent and convergent-divergent structures, respectively. The divergent tube shows better energy separation at lower cold mass fraction, while the convergent-divergent tube is dominant at higher cold mass fraction. The highest coefficient of performance is found at μc = 0.6, with maximum cooling and heating energy transfer efficiencies of 0.112 and 0.103, respectively. By innovatively incorporating the work-heat transfer theory into structural investigation of cold tubes, it is found that tangential viscous shear effect is the dominant factor in energy separation process. It is noteworthy that the highest net energy transfer of 973 W is achieved by convergent-divergent tube at a cold mass fraction of 0.7.

Development of a diamagnetic loop in KAIMIR

We developed a diamagnetic loop for the estimation of plasma stored energy in the KAIST Magnetic Mirror magnetic mirror device [Oh et al., J. Plasma Phys. 90, 975900202 (2024)]. Diamagnetic loops are used to estimate the plasma stored energy from measurements of the diamagnetic flux in plasma with an applied external magnetic field. However, diamagnetic flux measurements are accompanied by the vacuum flux, which generally exceeds the diamagnetic flux by over 10 000 times. Therefore, it is critical to attain a high signal-to-noise ratio with minimized noise in diamagnetic flux measurements. In this study, we employed a novel method to reduce background noise and improve the signal-to-noise ratio. Using two identical loops with opposite polarities, we successfully removed parasitic capacitive noise from the external insulation while amplifying the inductive signal two times. To eliminate the vacuum flux, we utilized two coaxial loops with different radii positioned at the same axial location. Results obtained from six paired loops confirmed the successful removal of the vacuum flux. The plasma stored energy was also found to agree well with Langmuir probe measurements, which verifies the diamagnetic flux measurements using the developed loop.

Plasma pressure profiles in a sheared-flow-stabilized Z-pinch

We report the plasma pressure reached inside the central plasma column of a sheared-flow-stabilized Z-pinch using Thomson scattering measurements. Building on previously reported experimental results and the analysis methods established for the high temperature and moderate density plasmas generated on the FuZE device, we show evidence of a central plasma region with higher electron temperature and density, which is consistent with a pinch behavior. Elevated electron temperatures up to 2.25 ± 0.8 keV and densities up to (4.9±0.2)×1017 cm−3 are observed to temporally coincide with the fusion neutron production from the plasma. Reconstructed plasma pressure profiles highlight the presence of a several millimeter-wide column with elevated pressure whose location varies shot-to-shot. The plasma pressure rises as neutron production from the deuterium plasma increases, reaching a peak value of 2.6 kBar. This peak value is consistent with a radially force-balanced pinch equilibrium model based on the measured ∼320 kA pinch current. Complete datasets were obtained at two axial locations, 10 and 20 cm axial position from the tip of the central electrode, which corroborate the estimated neutron source axial lengths.

Thermally developing streaming potential-mediated pressure-driven flow of Phan–Thien–Tanner fluid in a microchannel

In this study, we have conducted a semi-analytical investigation into the streaming potential-mediated pressure-driven flow of hydrodynamically fully developed and thermally developing viscoelastic fluid in a parallel plate microchannel. We have utilized a simplified Phan–Thien–Tanner model to describe the rheology of the viscoelastic fluid. Our approach delved into the full Poisson–Boltzmann equation, deriving exact analytical solutions for the electrostatic potential distribution and velocity profile. Furthermore, we concurrently derived semi-analytical solutions for the temperature distribution and Nusselt number, accounting for the effects of heat generation from viscous dissipation and Joule heating in thermally developing flows. We have demonstrated that an increase in the degree of surface charge triggers the streaming potential field, while the volumetric flow rate escalates with the viscoelastic parameter εWik¯2. Moreover, we have observed that the magnitude of the dimensionless temperature decreases with increasing values of the effective Joule heating parameter Speff. Our analysis reveals that the streaming potential effect hampers fluid flow, resulting in an increase in the bulk fluid temperature and consequently reducing the heat transfer rate. We observe that the magnitude of the Nusselt number decreases with increasing Speff. The entropy generation analysis reveals that increasing the Peclet number amplifies flow and temperature gradients, leading to higher fluid irreversibility in microchannels. The Bejan number experiences a significant decrease across the channel, reaching its minimum at a specific axial location before stabilizing further downstream. We find that heat transfer irreversibility predominantly influences system irreversibility, except for the Brinkmann number Br = 0.01, where convective heat transfer dominates at the entrance region, transitioning to friction losses beyond the thermal entry zone.

Dynamic Prediction of Overall Survival for Patients with Osteosarcoma: A Retrospective Analysis of the EURAMOS-1 Clinical Trial Data.

Current prediction models for patients with ostosarcoma are restricted to predictions from a single, static point in time, such as diagnosis or surgery. These approaches discard information which becomes available during follow-up and may have an impact on patient's prognosis. This study aims at developing a dynamic prediction model providing 5-year overall survival (OS) predictions from different time points during follow-up. The developed model considers relevant baseline prognostic factors, accounting for where appropriate time-varying effects and time-varying intermediate events such as local recurrence (LR) and new metastatic disease (NM). A landmarking approach is applied to 1965 patients with high-grade resectable osteosarcoma from the EURAMOS-1 trial (NCT00143030). Results show that LR and NM negatively affected 5-year OS (HRs: 2.634, 95% CI 1.845-3.761; 8.558, 95% CI 7.367-9.942, respectively). Baseline factors with strong prognostic value (HRs > 2) included poor histological response (≥10% viable tumor), axial tumor location, and the presence of lung metastases. The effect of poor versus good histological response changed over time, becoming non-significant from 3.25 years post-surgery onwards. This time-varying effect, as well as the strong impact of disease-related time-varying variables, show the importance of including updated information collected during follow-up in the model to provide more accurate survival predictions.

Combined radiation and convection in developing flow in a parallel plate channel with real gas behavior: Contrast between gas cooling and heating

Laminar thermally developing gas flow in a two-dimensional parallel plate channel with real gas radiation has been investigated numerically. Real gas spectral radiation effects are accounted for by using the Spectral Line Weighted-sum-of-gray-gases model. Gas mixtures of H2O and CO2, either alone in mixture with N2 or as a mixture of H2O and CO2 are considered. The phenomena are investigated for a range of differences between wall and inlet gas temperature, mole fraction of the radiating species, and total pressure. Predictions for the cases of gas heating and gas cooling are contrasted with results presented by the classical no-radiation case, commonly known as the Graetz solution. The impact of gas radiation on the local mean temperature, convective and radiative wall heat fluxes, and the convective, radiative, and total local Nusselt numbers are studied.The predictions reveal that the inclusion of participating gas radiation results in a much more rapid change in temperature of the gas in the channel than for the convection-only case, for both the gas heating and gas cooling cases. Further, unique differences in the heat transfer behavior for gas cooling (wall temperature below the inlet gas temperature) and gas heating (wall temperature above the inlet gas temperature) scenarios are shown. However, significant differences between the cases of heating and cooling exist. In the classical Graetz solution, for constant thermophysical properties and using appropriately nondimensionalized heat transfer parameters (e.g., Nusselt number, inverse Graetz number) the predictions for fluid heating and cooling are identical. However, the results of this study including the influence of gas radiation demonstrate that the heat transfer behavior depends heavily on whether the gas is heated or cooled. An apparent thermally fully developed condition may exist for the case of gas cooling, whereas the variation in local Nusselt number with dimensionless axial location exhibits a local minimum for the case of gas heating. Further, the case of gas heating results in a more rapid streamwise change in mean temperature in the channel than for the cooling case. The thermal physics of the developing flow for combined convective-radiative transfer with real gas effects are explored for a range of wall and gas inlet temperatures, radiating species mole fractions, and total pressures.