Search Results (22)

Vapor injection (VPI) can significantly enhance the heating performance of electric vehicle (EV) heat pump systems under low ambient temperatures, making the integrated design and control of the VPI loop essential. This study uses R290 as the working fluid and investigates the gas–liquid flow characteristics of the vapor-injection electronic expansion valve (VPI-EXV) in the VPI loop. The evaporation coefficient in the Lee model is calibrated using four typical operating conditions, keeping the relative errors of both total mass flow rate and injection ratio predictions within 10%. Results show that valve opening is the dominant factor: as the opening increases from 10% to 100%, the injection ratio rises from 0.24 to 0.83, while increasing outlet pressure from 0.58 MPa to 0.78 MPa and inlet subcooling from 0 °C to 10 °C reduces it by about 18% and 9%, respectively. The 90° turning structure inside the VPI-EXV induces recirculation and high turbulent kinetic energy downstream of the throttling region, modifying the outlet gas-liquid distribution, based on which an injection ratio control strategy with valve opening as the primary variable is proposed. Full article

Background and Objectives: Tendon healing is a multifactorial process influenced by inflammation and oxidative stress. Avocado–soybean unsaponifiables (ASU), recognized for their anti-inflammatory and antioxidant properties in osteoarthritis, have not yet been evaluated in tendon repair. This study aimed to investigate the effects of systemic ASU administration on histological, biomechanical, and biochemical parameters of tendon healing in a rat Achilles tendon injury model. Materials and Methods: Twenty male Wistar rats underwent bilateral Achilles tendon transection and repair. The ASU group received intraperitoneal ASU (300 mg/kg/day) for four weeks; controls received saline. Right tendons were analyzed histologically using a semiquantitative scoring system adapted from Curtis–DeLee, Bonar, and Modified Soslowsky criteria. Left tendons were tested biomechanically for maximum force, displacement, stress, stiffness, and energy parameters. Serum interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), total antioxidant status (TAS), total oxidant status (TOS), and oxidative stress index (OSI) were measured by ELISA. Results: ASU markedly improved histological healing with better collagen alignment, reduced inflammation, and normalized tenocyte morphology (p < 0.001). Biomechanical strength increased, with higher maximum force (p = 0.002), displacement (p = 0.004), stress (p = 0.001), and total energy to failure (p = 0.001). Serum IL-1β, IL-6, and TNF-α levels were lower (p < 0.001), while TAS increased and TOS/OSI decreased (p < 0.001). Conclusions: Systemic ASU administration enhances tendon healing by improving tissue organization, increasing mechanical strength, and modulating systemic inflammation and oxidative stress. These findings suggest that ASU may serve as a safe, clinically relevant adjunct therapy to promote tendon regeneration. Full article

This article presents the results of a study on the possibility of using a single-speed multiphase model with free surface allowance for simulating boiling and condensation processes. The simulation is based on the VOF method, which allows the position of the interphase boundary to be tracked. To increase the stability of the iterative procedure for numerically solving volume fraction transfer equations using a finite volume discretization method on arbitrary unstructured grids, the basic VOF method is been modified by writing these equations in a semi-divergent form. The models of Tanasawa, Lee, and Rohsenow are considered models of interphase mass transfer, in which the evaporated or condensed mass linearly depends on the difference between the local temperature and the saturation temperature with accuracy in empirical parameters. This paper calibrates these empirical parameters for each mass transfer model. The results of our study of the influence of the values of the empirical parameters of models on the intensity of boiling and evaporation, as well as on the dynamics of the interphase boundary, are presented. This research is based on Stefan’s problem of the movement of the interphase boundary due to the evaporation of a liquid and the problem of condensation of vapor bubbles water columns. As a result of a series of numerical experiments, it is shown that the average error in the position of the interfacial boundary for the Tanasawa and Lee models does not exceed 3–6%. For the Rohsenow model, the result is somewhat worse, since the interfacial boundary moves faster than it should move according to calculations based on analytical formulas. To investigate the possibility of condensation modeling, the results of a numerical solution of the problem of an emerging condensing vapor bubble are considered. A numerical assessment of its position in space and the shape and dynamics of changes in its diameter over time is carried out using the VOF method, taking into account the free surface. It is shown herein that the Tanasawa model has the highest accuracy for modeling the condensation process using a VOF method taking into account the free surface, while the Rohsenow model is most unstable and prone to deformation of the bubble shape. At the same time, the dynamics of bubble ascent are modeled by all three models. The results obtained confirm the fundamental possibility of using a VOF method to simulate the processes of boiling and condensation and taking into account the dynamics of the free surface. At the same time, the problem of the studied models of phase transitions is revealed, which consists of the need for individual selection of optimal values of empirical parameters for each specific task. Full article

Capital investment in longevity science—research targeting the biological processes of aging through interventions like cellular reprogramming, AI-driven drug discovery, and biological age monitoring—may create significant divergence between traditional actuarial projections and emerging mortality improvements. This paper examines how accelerating investment in life extension technologies affects mortality improvement trajectories beyond conventional actuarial assumptions, building on the comprehensive investment landscape analysis documented in “Investors in Longevity” supported by venture capital databases, industry reports, and regulatory filings. We introduce an Investment-Adjusted Mortality Model (IAMM) that incorporates capital allocation trends as leading indicators of mortality improvement acceleration. Under high-investment scenarios (annual funding of USD 15+ billion in longevity technologies), current insurance products may significantly underestimate longevity risk, creating potential solvency challenges. Our statistical analysis demonstrates that investment-driven mortality improvements—actual reductions in death rates resulting from new anti-aging interventions—could exceed traditional projections by 18–31% by 2040. We validate our model by backtesting historical data, showing improved predictive performance (35% reduction in MAPE) compared to traditional Lee–Carter approaches during periods of significant medical technology advancement. Based on these findings, we propose modified insurance structures, including dynamic mortality-linked products and biological age underwriting, quantifying their effectiveness in reducing longevity risk exposure by 42–67%. These results suggest the need for actuarial science to incorporate investment dynamics in response to the changing longevity investment environment detailed in “Investors in Longevity”. The framework presented provides both theoretically grounded and empirically tested tools for incorporating investment dynamics into mortality projections and insurance product design, addressing gaps in current risk management approaches for long-term mortality exposure. Full article

Obesity is considered a metabolic disease, in which leptin is used as an indicator of energy in the body. This hormone, in turn, is related to the neuroendocrine regulation of the reproductive axis. However, leptin excess secretion due to obesity can have a negative effect on reproduction. Overweight and obesity were induced through high-calorie diets. Lee and gonadosomatic indices were determined to characterize the model and degree of reproductive development in the testis and epididymis. Sperm quality was analyzed using spermatobioscopy. Morphometry was analyzed through histological analysis. The changes described affect testicular function in hormone and sperm production. Exposure of 3-month-old male rats to diets with different fat contents (10% and 60%) induced both overweight and obesity. The animals showed morphological alterations, both testicular and epididymal, the latter being more sensitive to dietary changes by modifying the epididymal index, morphometric parameters (in both organs), and a decrease in cilia length. These changes induced a reduction in sperm viability, as well as an increase in malformed spermatozoa. In conclusion, both overweight and obesity have effects on male reproduction by modifying the morphology and physiology of reproductive organs. Full article

Based on the goals of “high reliability, high frequency, rapid launch, and low cost” for space launch sites, an integrated dual-sided deflector system for convective cooling and thermal protection is presented. The interaction process between the gas jet and liquid water jet and its effect on the flow field environment are thoroughly studied using numerical calculation methods. Furthermore, considering the phase-change heat transfer issue in a compressible gas–liquid two-phase flow, and the varying distribution of different bubble shapes and sizes at the gas–liquid interface, a modified Lee model is derived. The research results show that compared to the classical Lee model, the modified Lee model can achieve a higher numerical accuracy in predicting the heat and mass transfer processes in gas–liquid two-phase flows. Through comparative analysis with the traditional dual-sided deflector and the conventional cooling system, the integrated dual-sided deflector system exhibits significant performance advantages in gas flow regulation and flow field environment improvement at the near-ground region of the space launch site. It not only achieves effective flow deflection, but also mitigates the degree of erosion caused by the gas jet on the deflector. This conclusion can provide theoretical references for the thermal protection design of commercial launch vehicle systems at space launch sites. Full article

Mountain lee waves present significant hazards to aviation, often inducing turbulence and aircraft icing. The current study focuses on understanding the potential impact of global climate change on the precursor environments to mountain lee wave cloud episodes over central Iberia. We examine the suitability of several Global Climate Models (GCMs) from CMIP6 in predicting these environments using the ERA5 reanalysis as a benchmark for performance. The dataset is divided into two periods: historical data (2001–2014) and projections for the SSP5–8.5 future climate scenario (2015–2100). The variations and trends in precursor environments between historical data and future climate scenarios are exposed, with a particular focus on the expansion of the Azores High towards the Iberian Peninsula, resulting in increased zonal winds throughout the Iberian Peninsula in the future. However, the increase in zonal wind is insufficient to modify the wind pattern, so future mountain lee wave cloud events will not vary significantly. The relative humidity trends reveal no significant changes. Moreover, the risk of icing precursor environments connected with mountain lee wave clouds is expected to decrease in the future, due to rising temperatures. Our results highlight that the EC-EARTH3 GCM reveals the closest alignment with ERA5 data, and statistically significant differences between the historical and future climate scenario periods are presented, making EC-EARTH3 a robust candidate for conducting future studies on the precursor environments to mountain lee wave cloud events. Full article

Flash evaporation processes are widely adopted in the desalination, food processing, waste heat recovery and other industries for heat extraction or product separation. In this paper, a pressure-driven phase transition model is developed by improving the Lee model and combined with the VOF (Volume of Fluid) method to numerically simulate the flash evaporation process. In this modified Lee phase transition model, the driving force for the rates of the local phase transition is calculated using the local temperature and static pressure magnitude. Numerical simulations are carried out in a water-circulating flash chamber and compared with the experimental results to obtain the values of the time relaxation parameters. And the non-equilibrium fraction of the outlet water can be effectively obtained under different conditions of flow rate, inlet temperature and initial liquid level height. The time relaxation factor takes values from 0.195 to 0.43 (P_out,v = 19.9 kPa) and from 0.31 to 0.92 (P_out,v = 31.2 kPa) with increasing superheat. In addition, the model can effectively represent the evolution of the unstable flow flash evaporation from the initial rapid boiling state to dynamic equilibrium. Full article

Flash evaporation processes are widely used in petroleum, food, chemical, power, and other industries to separate products or extract heat. The liquid is often entrained by non-condensing gas components. This study develops a multiphase, multicomponent, and pressure-driven phase-change-coupled model to numerically study water flash evaporation with non-condensing CO₂. The model includes the mass, momentum, energy, volume of fluid (VOF), species transport, turbulence (RNG k-ε), modified phase-change Lee, and non-condensing CO₂ release governing equations. The steam generation rate and mechanism for pure water and different concentrations of CO₂ are considered. The results show that the numerical model can accurately predict the flash evaporation process and has high accuracy compared with the experimental data. Both the dissolved and entrained CO₂ that are released can severely disturb the flow field, leading to an increase in the steam generation rate. Under a 1–10% volume concentration of dissolved CO₂ and 0.0661–0.1688% mass concentration of entrained CO₂, the maximum increase ratio of steam generation can reach 20%. Full article

The gas reservoirs in the Northwestern Sichuan Basin have great development potential. However, their production efficiency is seriously reduced by the complex surface multistage throttling process and frequent hydrate plugging caused by the ultra-high-pressure sour gas. Considering the prevention and control of hydrates, properly designing the throttling temperature and pressure to optimize the surface production process is the key to solving this problem. First, this work presents a method for predicting the hydrate formation conditions of ultra-high-pressure sour natural gas based on the vdW-P (van der Waals–Platteeuw) model and the CPA (cubic-plus-association) equation of state (EoS) and considering the association between acid gases (H₂S, CO₂) and H₂O. Secondly, the throttling temperature prediction method was developed by coupling the isenthalpic throttling model and the modified Lee–Kesler EoS mixing rule; the maximum throttling pressure difference calculation method was constructed based on the critical flow principle. Finally, field cases are given to illustrate the distribution process of assigning the maximum throttling pressure differences. The results show that the proposed model can accurately predict the hydrate formation conditions and throttling temperature of ultra-high-pressure sour natural gas, and reveal their changing laws. The surface throttling technology of the ultra-high-pressure sour gas wells Long 004-X1 and Long 016-H1 was optimized from five-stage to three-stage, and the application of the fixed throttle valve in the field is successfully demonstrated. Full article

In this paper we propose a new mathematical model for describing the complex interplay between skin cell populations with fibroblast growth factor and bone morphogenetic protein, occurring within deformable porous media describing feather primordia patterning. Tissue growth, in turn, modifies the transport of morphogens (described by reaction-diffusion equations) through diverse mechanisms such as advection from the solid velocity generated by mechanical stress, and mass supply. By performing an asymptotic linear stability analysis on the coupled poromechanical-chemotaxis system (assuming rheological properties of the skin cell aggregates that reside in the regime of infinitesimal strains and where the porous structure is fully saturated with interstitial fluid and encoding the coupling mechanisms through active stress) we obtain the conditions on the parameters—especially those encoding coupling mechanisms—under which the system will give rise to spatially heterogeneous solutions. We also extend the mechanical model to the case of incompressible poro-hyperelasticity and include the mechanisms of anisotropic solid growth and feedback by means of standard Lee decompositions of the tensor gradient of deformation. Because the model in question involves the coupling of several nonlinear PDEs, we cannot straightforwardly obtain closed-form solutions. We therefore design a suitable numerical method that employs backward Euler time discretisation, linearisation of the semidiscrete problem through Newton–Raphson’s method, a seven-field finite element formulation for the spatial discretisation, and we also advocate the construction and efficient implementation of tailored robust solvers. We present a few illustrative computational examples in 2D and 3D, briefly discussing different spatio-temporal patterns of growth factors as well as the associated solid response scenario depending on the specific poromechanical regime. Our findings confirm the theoretically predicted behaviour of spatio-temporal patterns, and the produced results reveal a qualitative agreement with respect to the expected experimental behaviour. We stress that the present study provides insight on several biomechanical properties of primordia patterning. Full article

Cylindrical ducts with axial mean temperature gradient and mean flows are typical elements in rocket engines, can combustors, and afterburners. Accurate analytical solutions for the acoustic waves of the longitudinal and transverse modes within these ducts can significantly improve the performance of low order acoustic network models for analyses of acoustic behaviours and combustion instabilities in these kinds of ducts. Here, we derive an acoustic wave equation as a function of pressure perturbation based on the linearised Euler equations (LEEs), and the modified WKB approximation method is applied to derive analytical solutions based on very few assumptions. The eigenvalue system is built based on the proposed solutions and applied to predict the resonant frequencies and growth rate for transverse modes. Validations of the proposed solutions are performed by comparing them to the numerical results directly calculated from the LEEs. Good agreements are found between analytical reconstruction and numerical results of three-dimensional transverse modes. The system with both mean temperature profile and mean flow presents a larger absolute value of the growth rate than the condition of either uniform mean temperature or no mean flow. Full article

A new fracture model is developed to predict the ductile fracture of structural steel under multiaxial stress states. First, the Lee–Mear void growth theory is used to establish the quantitative relationship between the stress triaxiality and material’s ductility. A stress triaxiality dependence function, which accounts for the material’s strain hardening, is derived from modifying the dilatation rate of a spherical void in a typical unit cell. Subsequently, the Tresca failure model is used in conjunction with the Swift hardening law to establish a Lode dependence of fracture strain. Then, the theoretical formula of the new fracture model is obtained by combining both stress triaxiality and Lode angle dependence functions. The proposed fracture model has a unique advantage: i.e., this model has only two material parameters. These two parameters can be easily calibrated through a simple standard coupon test, which significantly reduces the difficulty of model calibration work and facilitates its application in practical engineering. In order to verify the new fracture model, the test results of five types of Q460 steel specimens were used to calibrate the model parameters. The prediction accuracy of the new model is then checked by calculating the average error between the test results and the predicted fracture strain envelope. Finally, the new fracture model was applied in the numerical analysis of two types of steel connections. The validation of the proposed fracture model is verified by comparing the load–displacement curve and failure modes of the steel connections obtained from both test and numerical analysis. Full article

The overall characteristics of the solar and atmospheric neutrino oscillations are approximately consistent with a tribimaximal form of the mixing matrix U of the lepton sector. Exact tribimaximal mixing leads to ${\theta }_{13}=0$. However, the results from the Daya Bay and RENO experiments have established, such that in comparison to the other neutrino mixing angles, ${\theta }_{13}$ is small. Moreover, the atmospheric and solar mass splitting differ by two orders of magnitude. These significant differences constitutes the great enthusiasm and main motivation for our research herein reported. Keeping the behavior of U as tribimaximal, we would make a response to the following questions: at some level, whether or not the small parameters such as the solar neutrino mass splitting and $U_{e3}$, which vanish in a new framework, can be interpreted as a modified FL neutrino mass model? Subsequently, a minimal single perturbation leads to nonzero values for both of them? Our minimal perturbation matrix is constructed solely from computing the third mass eigenstate, using the rules of perturbation theory. Let us point out that, unlike other investigations, this matrix is not adopted on an ad hoc basis, but is created following a series of steps that we will describe. Also in compared to the original FL neutrino mass model which generalize it by inserting phase factors, our work is more accurate. Subsequently, we produce the following results that add new contributions to the literature: (a) we obtain a realistic neutrino mixing matrix with $\delta \ne 0$ and ${\theta }_{23}={45}^{\circ }$; (b) the solar mass splitting term is dominated by an imaginary term, which could induce the existence of Majorana neutrinos, along with explaining a large CP violation in nature; (c) the ordering of the neutrino masses is normal; however, at the end of the allowed range, it becomes more degenerate ($97\%$); (d) we also obtain the allowed range of the mass parameters, which not only are in accordance with the experimental data but also allow falsifiable predictions for the masses of the neutrinos and the CP violating phases which none of these results has been achieved in the original FL neutrino mass model. Finally, let us emphasize that the results obtained by our framework here are much more efficient compared to those obtained in previous works in terms of currently available experimental data (namely, the best fit column). Full article

For the work presented herein nickel catalysts supported on γ-alumina extrudates (Ni/Al) with an egg-shell structure were prepared, using a modified Equilibrium Deposition Filtration (EDF) technique. Their performance was compared, for the biogas dry reforming reaction, with corresponding Ni/Al catalysts with a uniform structure, synthesized via the conventional wet impregnation method. The bulk and surface physicochemical characteristics of all final catalysts were determined using ICP-AES, N₂ adsorption-desorption isotherms, XRD, SEM, and TEM. A theoretical model describing the impregnation process for the EDF extrudates, based on the Lee and Aris model, was also developed. It was concluded that following specific impregnation conditions, the egg-shell macro-distributions can be successfully predicted, in agreement with the experimental results. It was shown that the Ni/Al catalysts with an egg-shell structure had a higher H₂ yield in comparison with the ones with a uniform structure. The difference in catalytic performance was attributed to the improved surface and structural properties of the egg-shell catalysts, resulting from the modified EDF technique used for their preparation. Full article