Gradient Ratio Research Articles

Mechanical performance and flow heat transfer characteristics of topologically optimised Ti-6Al-4 V lattice structures

ABSTRACT Novel lattice structures were designed as unit cells through topological optimisation methods. Then the mechanical properties, heat transfer performance, and fluid flow characteristics of functional Ti-6Al-4 V porous components fabricated by laser powder bed melting (LPBF) were investigated, and the comprehensive performance evaluation model was established. Mechanical performance evaluations demonstrated that TopLC-L16 exhibits superior mechanical properties with a compressive strength of 486.87 MPa, a 70.76% improvement over TopFC-L16, and the fracture mechanism reveals a composite mode of ductile and brittle fracture. The temperature distributions indicate that the TopLC-L component exhibits the most efficient heat transfer performance, particularly the TopLC-L16, with a temperature gradient of 242.5 °C and a temperature gradient ratio of 64.7%. A comprehensive evaluation model shows that TopLC-L16 shows the best comprehensive performance. The study highlights the importance of optimising lattice structure design in enhancing mechanical performance and heat transfer efficiency, providing critical insights for advanced engineering applications.

Predictive Value of NT-proBNP, FGF21, Galectin-3 and Copeptin in Advanced Heart Failure in Patients with Preserved and Mildly Reduced Ejection Fraction and Type 2 Diabetes Mellitus.

Background and Objectives: Heart failure (HF) is one of the most common initial presentations of cardiovascular disease (CVD) in patients with type 2 diabetes mellitus (T2DM). There are different cardiac biomarkers related to the pathophysiological mechanisms of HF in T2DM. The current research aims to identify additional biomarkers that could improve the diagnosis and prognosis of HFpEF, which is currently assessed using NT pro-BNP levels. NT pro-BNP is a valuable tool for diagnosing heart failure but may not always correlate with clinical symptom severity or can present normal levels in certain cases, such as obesity. Biomarkers like FGF-21 and galectin-3 could provide greater insight into heart failure severity, especially in diabetic patients. The main objective of the current study is to assess the performance of NT-proBNP, FGF21, Galectin-3 and Copeptin to discriminate between advanced and mild HF. Materials and Methods: A total of 117 patients were enrolled in this study and divided into two groups: 67 patients in NYHA functional class I-II (mild HF) and 50 patients in NYHA III-IV (advanced HF). NT-pro BNP, FGF21, Galectin 3 and Copeptin serum levels were determined with the ELISA method. Receiver operating characteristic (ROC) analysis and binomial logistic regression analysis were used to measure the ability of the studied biomarkers to distinguish between advanced and mild HF patients. Results: In patients with T2DM with advanced HF, serum FGF21 level was significantly positively correlated with eGFR (ρ = 0.35, p = 0.0125) and triglycerides (ρ = 0.28, p = 0.0465) and significantly negatively correlated with serum levels of HDL cholesterol (ρ = -0.29, p = 0.0386) and with RV-RA gradient (ρ = -0.30, p = 0.0358). In patients with mild HF, serum FGF21 level was significantly negatively correlated with NT-proBNP levels (ρ = -0.37, p = 0.0022), E/e' ratio (ρ = -0.29, p = 0.0182), TR velocity (ρ = -0.24, p = 0.0470) and RV-RA gradient (ρ = -0.24, p = 0.0472). FGF21 (AUC = 0.70, 95% CI: 0.60-0.79) and NT-proBNP (AUC = 0.73, 95% CI: 0.63-0.82) demonstrated significant predictive value to discriminate T2DM patients with advanced HF from those with mild HF. Elevated values for FGF21 (≥377.50 ng/mL) or NTproBNP (≥2379 pg/mL) were significantly associated with increased odds of advanced HF after adjusting for demographic and clinical covariates. Conclusions: NTpro-BNP and FGF21 have a similar ability to discriminate T2DM patients with advanced HF from those with mild HF. Univariable and multivariable logistic models showed that, FGF21 and NTproBNP were independent predictors for advanced HF in patients with preserved and mildly reduced ejection fraction and T2DM.

Self-similar Buildup and Inside-out Growth: Tracing the Evolution of Intermediate-to-high-mass Star-forming Galaxies since z = 2

We aim to discern scenarios of structural evolution of intermediate-to-high-mass star-forming galaxies (SFGs) since cosmic noon by comparing their stellar mass profiles with present-day stellar masses of log(M*,0/M⊙)=10.3−11 . We addressed discrepancies in the size evolution rates of SFGs, which may be caused by variations in sample selection and methods for size measurements. To check these factors, we traced the evolution of individual galaxies by identifying their progenitors using stellar mass growth histories (SMGHs), integrating along the star-forming main sequence and from the IllustrisTNG simulations. Comparison between the structural parameters estimated from the mass- and light-based profiles shows that mass-weighted size evolves at a slower pace compared to light-based ones, highlighting the need to consider the mass-to-light ratio (M/L) gradients. Additionally, we observed mass-dependent growth in stellar mass profiles: massive galaxies ( log(M*,0/M⊙)≳10.8 ) formed central regions at z ≳ 1.5 and grew faster in outer regions, suggesting inside-out growth, while intermediate-mass and less massive SFGs followed a relatively self-similar mass buildup since z ∼ 2. Moreover, slopes of observed size evolution conflict with the predictions of TNG50 for samples selected using the same SMGHs across our redshift range. To explore the origin of this deviation, we examined changes in angular momentum (AM) retention fraction using the half-mass size evolution and employing a simple disk formation model. Assuming similar dark matter halo parameters, our calculations indicate that the AM inferred from observations halved in the past 10 Gyr while it remained relatively constant in TNG50. This higher AM in simulations may be due to the accretion of high-AM gases into disks.

In situ observation and numerical analysis of temperature gradient effects on growth velocity during directional solidification of silicon

AbstractThe < 110 > directional solidification of silicon under varying overall temperature gradients was investigated using an in situ observation system. The growth velocity of an atomically rough interface was found to decrease with increasing temperature gradient. A theoretical model of the thermal field taking undercooling into account was developed to describe this phenomenon and was demonstrated to be valid. The results of this work indicate that the reported linear relationship between growth velocity (V) and undercooling (ΔT), given by V (mm s−1) = 120ΔT (K), is most accurate in the case of a rough interface. In the case that the overall temperature gradient is small, the melting point isotherm moves rapidly such that it becomes more difficult for the interface to keep pace with the isotherm compared with a large temperature gradient. This effect leads to increased undercooling at the interface and consequently a rapid growth velocity. Thermal field calculations confirm that a rapid increase in the ratio of the temperature gradient in the crystal to that in the melt should increase the latent heat release, again providing a more rapid growth velocity.

Effects of aggregates and fibers on the strength and permeability of concrete exposed to low vacuum environment

The performance and regulation of concrete in low vacuum environments are receiving increasing attention. This study investigates the effects of aggregates and fibers on the strength and permeability of concrete in a low vacuum environment, using varying gradients of sand ratios (37.5 %, 40 %, and 42 %) and aggregate-to-binder ratios (3.27, 3.92, and 4.14). Three types of non-metallic fibers are utilized: polyethylene (PE), polyvinyl alcohol (PVA), and glass fibers. Evaluations focus on concrete strength, mass loss, gas permeability, capillary water absorption, and porosity. Results indicate that higher sand and aggregate-to-binder ratios enhance both flexural and compressive strength. Fiber incorporation improves flexural and compressive toughness, with PE fibers showing the most significant toughening effect. The low vacuum environment increases the strength of the concrete but reduces its axial compression toughness ratio and increases brittleness, while fiber incorporation helps improve the compression toughness of the concrete. Higher sand and aggregate-to-binder ratios reduce mass loss and accelerate drying equilibrium, while fibers increase mass loss and prolong drying equilibrium, with PVA fibers causing greater mass loss. The pattern of concrete mass loss can be explained by the tortuosity of the moisture diffusion path. Additionally, low vacuum significantly increases the gas permeability of concrete. Enhancing the sand and aggregate-to-binder ratios reduces permeability both before and after low vacuum treatment. Although fibers increase the gas permeability, they help mitigate this increase under low vacuum condition. Capillary water absorption tests reveal that concrete under low vacuum condition has a significantly higher water absorption rate compared to air-drying condition. Increasing sand and aggregate-to-binder ratios reduces water absorption and capillary water content, whereas fibers have the opposite effect. Porosity tests show that moisture migration in a low vacuum environment is mainly related to permeable porosity, while total porosity is more closely related to compressive strength.

TCT-725 Relationship Between Diffuse or Focal CAD Patterns and the Seattle Angina Questionnaire (SAQ) at 2-Year Follow-Up: Using Angio-Based Quantitative Flow Ratio and Pullback Pressure Gradient in Patients With Chronic Coronary Syndrome Successfully Treated With Percutaneous Coronary Intervention

TCT-725 Relationship Between Diffuse or Focal CAD Patterns and the Seattle Angina Questionnaire (SAQ) at 2-Year Follow-Up: Using Angio-Based Quantitative Flow Ratio and Pullback Pressure Gradient in Patients With Chronic Coronary Syndrome Successfully Treated With Percutaneous Coronary Intervention

Filtration compatibility of clay-nonwoven geotextiles under normal stress

Nonwoven geotextiles are commonly utilized as filter materials in drainage and filtration engineering. This study focuses on the clogging phenomenon of the nonwoven geotextile filter wrapping the blind drain in the active anti-floating technology of underground structures. In this paper, the filtration compatibility of clay-nonwoven geotextiles was evaluated using a newly developed gradient ratio test device that can apply normal stress. Two fabrication technics and four specifications of nonwoven geotextiles were used to filter clay, and the geotextiles’ clogging degree was assessed after the test. The influences of normal stresses, hydraulic gradients, and fabrication technics on nonwoven geotextile filtration performance were discussed based on results from a series of gradient ratio tests. Relevant assessment parameters (clogging coefficient, soil retention, and equivalent porosity) were also presented to quantify the clogging degree of nonwoven geotextiles after the test. Furthermore, the clogging process of nonwoven geotextiles filtering clay was initially explored, and the filtration effect of the needle-punched and heat-bonded nonwoven geotextiles was evaluated. The results showed that normal stress had a significant effect on nonwoven geotextile filtration, with needle-punched nonwoven geotextiles having better soil filtration and water permeability. Discussions on nonwoven geotextile applications in specific environments or conditions are also presented.

The novel Vogel's approximation method integrated with a random forest algorithm in the vibration analysis of a two-directional functionally graded taper porous beam: Assessment

A functionally graded material is a class of composite materials characterized by gradual variations in composition and microstructure, which further induces the respective changes in the material properties. This study focuses on evaluating the vibration behavior of two directional functionally graded taper porous beams (FGTPB). This approach adopts a rectangular cross-section in order to deal with the challenges related to fluctuating material characteristics and geometric tapering in both thickness and width dimensions. The research employs a novel approach that merges Vogel's approximation technique with the Random Forest algorithm, an approach that has not been used in analyzing structural vibrations, establish boundary conditions and solve equations of motion. Comparative results of the suggested beam theory with the existing literature on FGTPB materials such as alumina and SUS304 at various taper, porosity, gradient and width ratios verified it. The material gradation and porosity developed a uniform pattern in the first three modes of fundamental frequencies. Higher gradient indices increased the rigidity and natural frequencies of the beams whereas the porosity index decreased the rigidity, resulting in lower natural frequencies. By combining Vogel's approximation method with machine learning techniques, the study improved vibration behavior analysis in FGTPB. The disciplines of materials and structural engineering are significantly impacted by this.

Heat-Induced Liquid Hovering in Liquid-Gas Coexistence under Gravity.

We study a liquid-gas coexistence system in a container under gravity with heat flow in the direction opposite to gravity. By molecular dynamics simulation, we find that the liquid buoys up and continues to float steadily. The height at which the liquid floats is determined by a dimensionless parameter related to the ratio of the temperature gradient to gravity. We confirm that supercooled gas remains stable above the liquid. We provide a phenomenological argument for explaining the phenomenon from a simple thermodynamic assumption.

Kinetic simulation of uranium migration in granite fissure media of beishan, gansu, China: A case study based on the Laplace transform and inverse transform methods

Deep geological disposal is currently considered the most practical and feasible method for disposing high-level radioactive wastes (HLWs). One of its key scientific issues is the migration of nuclides in fissure media. However, studies on the migration of nuclides like U-238 are relatively limited. In this study, the granite rock masses in Beishan, Gansu were selected to construct a physical and mathematical model of U-238 migration using the Laplace transform and inverse transform methods. Based on the numerical methods, the kinetic migration of nuclide U-238 in the fissure media of granite was simulated, and the effects of parameters such as fissure width, hydraulic gradient, diffusible area ratio and rock porosity on the migration of U-238 were investigated. The following insights were obtained: (1) After 100,000 years, U-238 has a very limited diffusion depth in the matrix domain, with a diffusion range of only a few tens of millimeters, whereas it migrates relatively quickly in the fissure domain, with a maximum migration distance of about 1500 m. (2) Under the same migration time and distance, the relative concentration of nuclide U-238 in the fissure domain increases with larger gap width, hydraulic gradient, and diffusible area ratio, but decreases with higher rock porosity. (3) In the same time range, the rock masses with larger gap widths, hydraulic gradients, and diffusible area ratios have larger migration ranges, while those with higher porosities have smaller migration ranges. (4) While selecting a site for diposal of HLWs, it is recommended to choose rock masses in the granite area of Beishan with no fissures or few fissures; additionally, areas with smaller fissure widths, hydraulic gradients, and diffusible area ratios but higher rock porosity should be prioritized. This study can provide important theoretical support for understanding nuclide migration in the future geological disposal of HLWs.

Mechanical properties of a novel negative Poisson's ratio gradient structure

A novel cellular structure is proposed based on bionic structure with negative Poisson's ratio characteristic, and the cell is periodically expanded in the in-plane direction to create a new honeycomb structure. The influence of gradient changes of the structural parameters on the load-bearing capacity and damping characteristics of the structure is investigated through a combination method of finite element numerical simulations and experiments. The results indicate that the concentric gradient arrangement of cell wall thickness and angle parameters, and the symmetrical gradient arrangement of cell height, wall thickness and angle parameters have the most significant influence on the static bearing capacity of the structure. In contrast, the gradient arrangement under the corner circle diameter has minimal effect on the static bearing capacity of the structure. Under the same conditions, the peak values of the transmissibility of C2 (large angle at constraint end and loading end, and smaller angle in the middle) and C3 structures (angle gradually increases from the loading end to the constraint end) are significantly reduced between the frequency 2 Hz and 1024 Hz. The peak values of the transmissibility of the structures C2 and C3 are respectively decreased by 20% and 25% compared to that of the non-gradient structure. This shows that the vibration damping effect of these two structures is better. The structure with the gradient change and the structure without the gradient change of the new honeycomb structure can both achieve certain vibration reduction and isolation from the middle to high frequency range.

Utilizing spontaneous plants for sustainable development in residential green spaces: Insights from environmental drivers and niche analysis in Fuzhou City, China

This study, aimed at exploring low-maintenance, high-diversity, and sustainable greening strategies for residential areas, conducted a comprehensive survey and analysis of spontaneous plants in residential green spaces in Fuzhou City, documenting 361 species. Employing methods such as variance partitioning, Canonical Correspondence Analysis (CCA), and ecological niche analysis, we investigated the environmental factors influencing the distribution and composition of these plants, as well as their interrelationships. The study found that the composition of spontaneous plants in residential green spaces differs from other urban environments, with a high proportion of alien species (43.77%) due to influences such as resident activities, including a large number of ornamental and edible plants. Maintenance level, urbanization gradient, and green space ratio are common factors affecting the composition and distribution of spontaneous plants in urban environments, while unique residential socio-economic factors like building age, housing prices, and population density significantly affect the spontaneous plants in residential green spaces. The overall dominant plant community shows a significant positive association, indicating a relatively stable stage of succession. Although competition among most species is not significant and interspecific connectivity is weak, the presence of seven dominant invasive species intensifies competition. Based on these findings, the study proposes several specific sustainable management measures: adopting the concept of New Naturalistic Ecological Planting Design, selecting native spontaneous plants with strong adaptability, and constructing plant communities that are ecologically stable and have ornamental value by mimicking natural ecosystems. Additionally, specific methods for managing specific invasive species in residential green spaces using competitive replacement control methods are proposed. These measures aim to promote the health and sustainable development of urban residential green spaces.

Comparison of liver stiffness, splenic stiffness and novel hepato-splenic stiffness gradient ratio as a non-invasive predictor of varices in patients with compensated advanced chronic liver disease

Comparison of liver stiffness, splenic stiffness and novel hepato-splenic stiffness gradient ratio as a non-invasive predictor of varices in patients with compensated advanced chronic liver disease

Tectonic evolution of Bursa Yenişehir Basin, Turkey from the Neogene to the Quaternary using a morphotectonic approach

In this study, the morphotectonic features of the Yenişehir pull‐apart basin in Bursa in northwestern Turkey were analysed. The faults in the region are the most important structural elements that characterize the morphology of the Yenişehir pull‐apart basin. The aim of this study is to show the deformation effects of these active faults on the geomorphology with some basic morphometric indices. The morphotectonic features were evaluated using the hypsometric curve and hypsometric integral (Hi), drainage basin asymmetry (the asymmetry factor (AF) and the transverse topographic symmetry factor (T)), river length gradient index, mountain front sinuosity, and valley floor ratio. The morphometric indices that play an important role in the analysis of catchment areas are the Hi, AF, and T indices, which indicate tilting and erosion activities. According to the results of the hypsometric curve and hypsometric integral, the Yenişehir Basin is a young basin with a uniform topography as expected in an active pull‐apart basin formed by faulting in the Quaternary. The relative tectonic activity index (Iat) of the study area was calculated using the values of hypsometric integral, transverse topographic symmetry factor, asymmetry factor, mountain front sinuosity, valley floor ratio and stream length gradient index. The Iat values indicate the tectonic activity of the basin from Pliocene to Recent. Three different tectonic classes were identified in the study area. These are class 1 (high relative tectonic activity), class 2 (moderate relative tectonic activity), and class 3 (low relative tectonic activity). The Iat classification data show that the impact of tectonic activity on the geomorphology is lower in the Iat class 3 indices than in the others. The Iat data show high tectonic activity in the region where active faults of the North Anatolian Fault Zone southern branch are located.

Inhibition of interfacial cracks in 304L-Inconel718 bimetal fabricated via laser powder bed fusion

Multi-material additive manufacturing is crucial for intricate component fabrication, yet challenges, such as interfacial cracks and weak bonding, persist. This work investigated the laser powder bed fusion (L-PBF) of bimetallic components (stainless steel 304L-nickel-based alloy Inconel718) crucial in aerospace and nuclear applications. It is found that the interfacial cracks predominantly occur within the compositional transition zone where the proportion of 304 L is between 45 wt% and 75 wt%, characterized by brittle Laves phases along grain boundaries. Experimental and finite element simulations of melt pool reveal that a higher ratio of temperature gradient (G̅) to the grain growth rate (R̅) (G̅/R̅) results in straight grain boundaries with underdeveloped secondary dendrites. This leads to the formation of continuous liquid film and strip-like Laves phase at grain boundaries, causing interfacial cracks during L-PBF. To suppress these cracks, this work proposes manipulating grain boundaries into a tortuous morphology through promoting the growth of secondary dendrites. By controlling the G̅/R̅ ratios below the critical value (<147.9×106 K∙s/m2) and combining with a high cooling rate (G̅×R̅) during L-PBF, a well-developed secondary dendritic structure and grain refinement are achieved, significantly enhancing grain boundary tortuosity and forming discretely distributed Laves phases. As a result, interfacial cracks are completely suppressed, enabling the successful manufacturing of crack-free 304L-Inconel718 bimetallic components. The approach of tailoring the distribution of brittle precipitates through manipulating grain boundary morphology proposed in this work provides a novel and practical pathway for inhibiting cracks in multi-material additive manufacturing.

Differential confocal effective measurement region extraction method based on dual measurement

Abstract Aiming at the problem that the existing differential confocal measurement (DCM) method lacks the ability to decouple the differential signals from over-range the depth data, which in turn leads to measurement errors, this study proposes a differential confocal effective measurement region extraction method based on dual measurement (D-DCM). The first measurement is a double blur depth measurement, which is a coarse measurement, and the initial acquisition of the depth map is realized by applying a known Gaussian kernel blurring to the focal plane image and calculating the edge gradient ratios between the original image and the blurred image. This depth map is used to determine whether the depth of the measured sample in the field of view is within the differential confocal range and to segment it. The second measurement is a DCM, which is a fine measurement. The effective measurement area of the segmented image is second measured with high precision depth measurement. It is shown by single and multiple step heights experiments that the proposed D-DCM method can effectively solve the problem of decoupling the differential signal from the axial depth in differential confocal.

An Adaptive Radar Target Detection Method Based on Alternate Estimation in Power Heterogeneous Clutter

Multichannel radars generally need to utilize a certain amount of training samples to estimate the covariance matrix of clutter for target detection. Due to factors such as severe terrain fluctuations and complex electromagnetic environments, the training samples usually have different statistical characteristics from the data to be detected. One of the most common scenarios is that all data have the same clutter covariance matrix structure, while different data have different power mismatches, called power heterogeneous characteristics. For detection problems in the power heterogeneous clutter environments, we propose detectors based on alternate estimation, using the generalized likelihood ratio test (GLRT) criterion, Rao criterion, Wald criterion, Gradient criterion, and Durbin criterion. Monte Carlo simulation experiments and real data indicate that the detector based on the Rao criterion has the highest probability of detection (PD). Furthermore, when signal mismatch occurs, the detector based on the GLRT criterion has the best selectivity, while the detector based on the Durbin criterion has the most robust detection performance.

Introducing high-density growth twins in aluminum alloys by laser surface remelting via templated nucleation of grains

It is difficult to generate coherent twin boundaries in bulk Al alloys due to their high intrinsic stacking fault energy. Here, we report a strategy to induce high-density growth twins in aluminum alloys through the heterogeneous nucleation of twinned Al grains on twin-structured TiC nucleants and the preferred growth of twinned dendrites by laser surface remelting of bulk metals. The solidification structure at the surface shows a mixture of lamellar twinned dendrites with ultra-fine twin boundary spacing (∼2 μm), isolated twinned dendrites, and regular dendrites. EBSD analysis and finite element method (FEM) simulations have been used to understand the competitive growth between twinned and regular dendrites, and the solidification conditions for the preferred growth of twinned dendrites during laser remelting and subsequent rapid solidification are established. It is shown that the reduction in the ratio of temperature gradient G to solidification rate V promotes the formation of lamellar twinned dendrites. The primary trunk spacing of lamellar twinned dendrites is refined by the high thermal gradient and solidification rate. The present work paves a new way to generate high-density growth twins in additive-manufactured Al alloys.

The synergistic effects of salinity and pressure gradients on sustainable energy conversion in nanofluidics

In recent years, osmotic energy conversion and electrokinetic energy conversion within nanochannels have received widespread attention. In this work, we propose four kinds of energy conversion models in nanochannels, including pressure-driven power generation, salinity-driven power generation, the positive combination of pressure gradient and salinity gradient and the negative combination. The changes in ion transport behavior and energy conversion characteristics are analyzed. The results show that the combination of salinity gradient and pressure gradient is not a simple superposition. Compared to the power of the single drive mode before optimization, the power under positive combination (PC) can reach 1.02 pW, and the power enhancement ratio is as high as 1.6. The negative combination has a certain optimization potential under a large concentration ratio and small pressure gradient condition. The higher the surface charge density, the greater the output power, but the optimization effect worsens. On the contrary, a larger channel length corresponds to a smaller output power, but the optimization effect becomes better. The reasonable choice of surface charge density and channel length needs to be weighed. These studies provide valuable guidance for the design of future nanofluidic energy conversion devices.

Analysis of Driving Characteristics by Gradient and Heavy Vehicle Ratio in Underground Road

Analysis of Driving Characteristics by Gradient and Heavy Vehicle Ratio in Underground Road