Surface Characteristic Parameters Research Articles

Climate change and land-use policies exacerbate run-off reduction in a semi-arid inland river basin

Semi-arid regions are characterized by scarce water resources and fragile ecosystems, making them highly sensitive to environmental changes. Assessing the impacts of climate change and human activity on hydrological processes in these areas is crucial for ecological conservation and social development. However, due to data limitations and the complex interactions between climate change and human activities, especially at seasonal scales, accurately quantifying their impacts on hydrological processes poses significant challenges. In the present study, the Budyko framework combined with the elasticity coefficient approach was adopted to assess the contribution of environmental changes to variations in annual and intra-annual runoff in the Xilin River Basin from 1963 to 2020. The results showed that annual runoff exhibited a significant declining trend at a rate of 0.05 mm/a (P < 0.05), with an abrupt change in 2001. The underlying surface characteristic parameters were the most sensitive factors affecting the changes in runoff; however, climate change was identified as the primary cause, accounting for 65.96 % of runoff reduction. Increased temperatures accelerated the melting of ice and snow, such that the highest runoff (36.24 % of the annual total) occurred during April. The impact of human activities on runoff varies across seasons, with the greatest impact observed during the snowmelt season, followed by the irrigation, rainy, and dry seasons, respectively. Based on our findings, we conclude that tailored land-use policies and science-based water management are required to mitigate the impacts of human activities on changes in runoff.

Sensitivity Analysis of the Land Surface Characteristic Parameters in Different Climatic Regions of the Loess Plateau

Land surface parameters are crucial in land surface process model simulations. Considering the complex land surface characteristics of the Loess Plateau, a parametric sensitivity analysis was conducted to determine the key parameters of its Noah Multi-Parameterization (Noah-MP) land surface model. Sensitivity analysis can better elucidate the influence of different parameters on the model simulation results and evaluate the rationality of each model parameter. The extended Fourier amplitude sensitivity test (EFAST) method is a classical global sensitivity analysis method, whose theory is derived from the analysis of variance and Fourier transform. In this study, the EFAST method was used to perform sensitivity analyses on the land surface characteristic parameters in different climatic regions of the Loess Plateau. The results showed that the Noah-MP model can represent the land surface characteristics of the Loess Plateau well. With sensible and latent heat fluxes as criteria, the main sensitivity parameters were the vegetation roughness length (Z0), the soil quartz content (QUARTZ), the maximum volumetric soil moisture (MAXSMC), and the soil parameter “b”. The coupling effect between parameters has a greater impact on the sensitivity analysis. The probability densities of the three most sensitive parameters were evenly distributed in each interval, whereas those of the other parameters were distributed within 0–0.2 of the standardized value. Moreover, almost half of the land surface parameters accounted for 80% of the total sensitivity. Based on the seasonal sensitivity distribution of the land surface parameters, Z0 dominated throughout all four seasons, QUARTZ sensitivity was high in spring, and both MAXSMC and QUARTZ showed high sensitivities in winter.

An independent framework-based evapotranspiration model (IFEM) for dual-source: From field to regional scale

The triangle/trapezoid framework model (TFM) is a widely used approach for mapping regional evapotranspiration (ET) based on thermal infrared remote sensing imagery. However, the homogeneity assumption for meteorological forcing and surface properties involved in TFM contradicts the characteristics of heterogeneous regions, leading to high uncertainty at regional scale, especially under energy-limited or strong advection conditions. Therefore, this study examined the linear relationship between soil moisture availability (ΛSM), evapotranspiration efficiency (ΛET) and radiation surface temperature (Trad), and developed an Independent Framework-based dual-source ET Model (IFEM) for heterogeneous regions. By fixing two key meteorological forcing variables, air temperature (Ta) and vapor pressure deficit (VPD), and three surface characteristic parameters, aerodynamic resistance (ra), albedo (α) and the ratio of soil heat flux to net radiation (Γ), the IFEM constructs a uniform fractional vegetation cover (fc)- Trad space. In this uniform fc-Trad space, isolines of ΛSM and ΛET are aligned with those of Trad, and an independent trapezoid framework is constructed for each pixel of RS images. It avoids the systematic bias caused by the distorted trapezoid space involved in traditional TFMs. The proposed model was applied in a hydrologically semi-enclosed irrigation area, the Hetao Irrigation District, with Landsat and MODIS datasets from 2016 to 2020 to evaluate its performance at the field and region scales. Firstly, the IFEM was capable of retrieving latent heat with a mean absolute error (MAE) of 34.43 W m−2 and a mean absolute percentage error (MAPE) of 8.68%, compared with the measurements from flux towers. Secondly, the IFEM reasonably separated the soil (MAPE = 21.33%) and canopy (MAPE = 14.33%) components from ET, compared with the soil evaporation observed by micro-lysimeters and the plant transpiration calculated by sap velocity upscaling technology. Thirdly, the IFEM showed high accuracy in estimating annual total ET with a percentage error range within ±3.0%, compared against the regional water balance calculations. Overall, the IFEM demonstrated high robustness and accuracy for field-scale and regional-scale applications, validating its potential as a reliable method for mapping regional ET in heterogeneous regions.

Predicting the directional spectral emissivity for rough surfaces polished by sandpaper

A new method was proposed to accurately predict the emissivity of rough surface polished by sandpaper. The complex rough surface was numerically reestablished based on the surface characteristic parameters extracted from the statistical data of 3D optical profiler measurement. Directional spectral emissivity of the established surface was simulated by the finite element method in the wavelength range of 2–20 µm and in the emission angle range of 0–80°. The influence of roughness on spectral emissivity was carefully studied. The calculated emissivity was compared to the data measured by a self-made emissivity measurement apparatus. The predicted results are in good agreement with the experimental data, which well proves the reliability of the proposed method.

Influence of top-coat thickness of thermal barrier coating on time–frequency domain and dispersion characteristics of laser-induced surface acoustic wave

Thermal barrier coating is commonly used to insulate the hot end components of aero engine and gas turbine in order to meet extreme high temperature service conditions. The performance of the thermal barrier coating will be significantly impacted by thinning or even spalling during the service process. Given the uniqueness of thermal barrier coating in structure and composition materials, and the fact that laser-induced surface acoustic waves are extremely sensitive to material surface characteristic parameters, laser-induced ultrasonic technology is used to detect the thermal barrier coating in this paper. To characterize the size and defect of thermal barrier coating, the excitation mechanism and propagation law of surface acoustic waves are very crucial. Firstly, the surface acoustic wave propagation law is investigated using spectral analysis and wavelet transform. Then, to study the influence of top-coat thickness on laser-induced surface acoustic wave, the surface acoustic wave velocity dispersion curves of thermal barrier coating with different top-coat thicknesses are extracted using wavelet analysis. The simulative and experimental results indicate that the time–frequency domain and dispersion characteristics of laser-induced surface acoustic wave in multilayered heterostructure are strongly affected by the top-coat thickness. By the establishment of the relationship between phase velocity of laser-induced surface acoustic wave and top-coat thickness, a theoretical basis is provided to characterize the top-coat thickness of multilayered heterostructure.

Attribution analysis of runoff evolution in Kuye River Basin based on the time-varying budyko framework

The underlying surface parameters in the Budyko framework (such as parameter n in the Choudhury–Yang equation) are crucial for studying the relationship between precipitation, evapotranspiration, and runoff. It is important to accurately quantify the influence of climate and human activities on the evolution of underlying surface characteristic parameters. However, due to the spatiotemporal heterogeneity of underlying surface parameters, it is often difficult to accurately quantify these relationships. In this study, taking the Kuye River Basin located in the northern Loess Plateau as the research object, we first used trend analysis and non-linear regression methods to estimate the evolution characteristics of runoff and underlying surface parameter n. We then determined the contribution of runoff changes by using the elasticity coefficient method under the 9-year moving average window. The results showed that: 1) the Kuye River Basin runoff underwent a sudden change in 1997, and the complex human activities are the main reasons for the sharp runoff decrease. 2) In addition to precipitation and potential evapotranspiration, temperature changes will alter the basin’s underlying surface parameters, ultimately changing the runoff. Moreover, climate change first inhibited and then promoted the runoff reduction trend. 3) Human activities, represented by changes in vegetation coverage and coal mining, considerably influenced runoff evolution in Kuye River Basin. More importantly, the change of runoff in the Kuye River Basin caused by coal mining is approximately four times that of the normalized vegetation index. This study can improve the applicability of the Budyko framework in the Loess Plateau sub-basin and provide scientific guidance for water resource management.

Study on Surface Characteristic Parameters and Surface Energy Exchange in Eastern Edge of the Tibetan Plateau

Mount Emei is located on the eastern edge of the Tibetan Plateau, on the transition zone between the main body of the Tibetan Plateau and the Sichuan Basin in China. It is not only the necessary place for the eastward movement of the plateau system but also the place where the southwest vortex begins to develop. Its special geographical location makes it particularly important to understand the turbulence characteristics and surface energy balance of this place. Based on the Atmospheric Boundary Layer (ABL) tower data, radiation observation data and surface flux data of Mount Emei station on the eastern edge of the Tibetan Plateau from December 2019 to February 2022, the components of surface equilibrium are estimated by the eddy correlation method and Thermal Diffusion Equation and Correction (TDEC) method, the characteristics of surface energy exchange in the Mount Emei area are analyzed, and the aerodynamic and thermodynamic parameters are estimated. The results show that the annual average value of zero-plane displacement d is 10.45 m, the annual average values of aerodynamic roughness Z0m and aerothermal roughness Z0h are 1.61 and 1.67 m, respectively, and the annual average values of momentum flux transport coefficient CD and sensible heat flux transport coefficient CH are 1.58×10−2 and 3.79×10−3, respectively. The dimensionless vertical wind fluctuation variance in the Mount Emei area under unstable conditions can better conform to the 1/3rd power law of the Monin–Obukhov similarity theory, while the dimensionless horizontal wind fluctuation variance under unstable lamination and the dimensionless 3D wind fluctuation variance under stable condition does not conform to this law. In the near-neutral case, the dimensionless velocity variance in the vertical direction in this area is 1.314. The daytime dominance of sensible and latent heat fluxes varied seasonally, with latent heat fluxes dominating in summer and sensible heat transport dominating in winter. he surface albedo of Mount Emei in four seasons is between 0.04 and 0.08. The surface albedo in summer and autumn is higher than that in Mount Emei. The influence of the underlying surface on surface reflectance is much greater than other factors, such as altitude, longitude and latitude. The non-closure phenomenon is significant in the Mount Emei area. The energy closure rates before and after considering canopy thermal storage are 46% and 48%, respectively. The possible reason for the energy non-closure in this area is that the influence of horizontal advection and vertical advection on the energy closure is not considered.

Attribution Analysis of Runoff Variation in Kuye River Basin Based on Three Budyko Methods

The Loess Plateau is the main soil erosion area within the Yellow River Basin. Quantifying the contribution rate of climate change and human activities to runoff change can provide support for water resources management in the Yellow River Basin. Kuye River Basin is located in the Loess Plateau. As a first-class tributary of the Yellow River, it was selected as the study area. Runoff from the Kuye River Basin has decreased significantly since the 1990s owing to climate change and anthropogenic coal mining. The main objective of this study was to quantify the contribution and sensitivity of climate change and anthropogenic activities to runoff changes using three popular Budyko and elasticity coefficient methods, as well as to compare the similarities and differences among the three methods. The results show that: (1) Through four mutation point test methods, the change point of runoff in the study period of Kuye River Basin is 1997. (2) The elasticity coefficients calculated by the three Budyko methods showed that during the study period, the runoff was more sensitive to changes in precipitation, followed by the catchment surface characteristic parameters and the potential evapotranspiration. (3) All three Budyko methods can yield reasonable contributions of climate change and human activity to runoff changes. The three methods together indicate that the influence of the catchment surface characteristic parameters is the most important factor for the runoff variation in the Kuye River.

EFFECTS OF INTERFACE FRACTAL PARAMETERS ON NORMAL CONTACT STIFFNESS

In this study, the complex rough surface is simplified as the superposition of a series of trigonometric curves based on the least square method. In order to calculate the interface contact stiffness, the optimal substrate modeling thickness is determined by the elastic-plastic finite element method. The relationship between normal contact pressure and normal contact deformation and normal contact stiffness is quantitatively investigated. The mechanism of fractal dimension and characteristic scale parameters of rough surface on normal contact stiffness is revealed. The results show that there is an optimal thickness of the substrate, which can effectively improve the calculation efficiency of the contact stiffness of the rough surface. The normal contact stiffness increases nonlinearly with the increase of normal contact deformation and normal contact pressure. The surface fractal dimension and characteristic scale parameters have significant effects on the normal contact stiffness, and the normal contact stiffness increases with the increase of the fractal dimension. However, the normal contact stiffness decreases with the increase of characteristic scale parameters.

Estimations of Land Surface Characteristic Parameters and Turbulent Heat Fluxes over the Tibetan Plateau Based on FY-4A/AGRI Data

Accurate estimates of land surface characteristic parameters and turbulent heat fluxes play an important role in the understanding of land–atmosphere interaction. In this study, Fengyun-4A (FY-4A) Advanced Geostationary Radiation Imager (AGRI) satellite data and the China Land Data Assimilation System (CLDAS) meteorological forcing dataset CLDAS-V2.0 were applied for the retrieval of broadband albedo, land surface temperature (LST), radiation flux components, and turbulent heat fluxes over the Tibetan Plateau (TP). The FY-4A/AGRI and CLDAS-V2.0 data from 12 March 2018 to 30 April 2018 were first used to estimate the hourly turbulent heat fluxes over the TP. The time series data of in-situ measurements from the Tibetan Observation and Research Platform were divided into two halves—one for developing retrieval algorithms for broadband albedo and LST based on FY-4A, and the other for the cross validation. Results show the root-mean-square errors (RMSEs) of the FY-4A retrieved broadband albedo and LST were 0.0309 and 3.85 K, respectively, which verifies the applicability of the retrieval method. The RMSEs of the downwelling/upwelling shortwave radiation flux and downwelling/upwelling longwave radiation flux were 138.87/32.78 W m−2 and 51.55/17.92 W m−2, respectively, and the RMSEs of net radiation flux, sensible heat flux, and latent heat flux were 58.88 W m−2, 82.56 W m−2 and 72.46 W m−2, respectively. The spatial distributions and diurnal variations of LST and turbulent heat fluxes were further analyzed in detail.

Calculation of Stress/Displacement Field of Mechanical Joint Structure Based on Layered Elastic Theory

Various types of machinery are not a continuous whole, but are assembled from various parts according to specific requirements. The surfaces that contact each other between different parts are often called mechanical joints. The stress/displacement field of the mechanical joint structure is the basis for predicting the mechanical properties of the assembly, optimizing the structure and the assembly process, and the existence of the mechanical joint surface destroys the continuity of the whole structure, which challenges the traditional calculation based on elastic mechanics. In view of the discontinuity of mechanical joints and the material difference of the parts matched with each other, this paper based on the layered elastic theory (LET), the discontinuity of the mechanical joint surface and the difference of the materials of the joint parts are analyzed. The mechanical joints are described by layers on the basis of the analysis of the discontinuity of typical mechanical joints. The stress and displacement equations are established by combining the surface characteristic parameters, and the established equations are solved by setting the boundary conditions. The calculation model of the stress/displacement field of the joint surface under the normal load is obtained. Finally, the model is used to calculate the experimental setting joint surface’s pressure distribution. In this paper, pressure distribution tests and finite element simulation are carried out on the joints with the same parameters. The results show that the model can accurately obtain the stress/displacement distribution law of the joints. The model can be directly used to calculate the pressure and displacement of the joint and the internal component. This model provides an effective method to analyze the stress and deformation of discontinuous structures, the distribution of pressure interface and the slip of interface. It can be directly used to calculate the joint position and the internal pressure and displacement of components, and the calculation efficiency is high.

Precise Burden Charging Operation During Iron-Making Process in Blast Furnace

The burden charging operation in blast furnace is one of the most important operations during iron-making process. In this paper, we focus on the study of precise burden charging operation, which involves two aspects: How to obtain and form the optimal burden surface shape. For the first problem, we construct a mapping model between the burden surface characteristic parameters and the comprehensive operational performance indicators of the blast furnace, and transform the search of optimal burden surface shape into the target optimization problem. The second problem refers to establishing a suitable burden charging strategy based on the basic burden surface and the optimal burden surface. In our work, by adaptively adjusting the opening degree of the throttle valve, it is possible to control accurate burden volume during the rotation of the charging chute, which can make sure to spill the appropriate burden volume on the suitable charging units. In the simulation of experiments, we collected the real industrial data during iron-making process and demonstrated the efficiency of the proposed model.

Robust, fractal theory, and FEM-based temperature field analysis for machine tool spindle

The friction heat of spindle bearing has a significant impact on the precision and dynamic performance of spindle unit, which is the main factor restricting the machining precision and efficiency of the machine tool (MT). In this research, fractal theory, which characterizes rough surface by fractal dimension and surface characteristic parameters, hybrid genetic algorithm is used to study the temperature field of a FANUC machining center spindle. The thermal contact resistance (TCR) of each contact surface is computed according to the geometric characteristics and assembly load characteristics of each contact surface of the spindle. Adopting central composite design experiment and finite element method, an in-deep analysis of the thermal characteristics of machine tool in different thermal boundary conditions was conducted and the influence of thermal contact resistances and instability of thermal boundary conditions on the temperature field analysis of machine tool was discussed. Through the temperature rise experiment on the machine tool, the results of simulation analysis and experiment show that the method introduced in this research to calculate the temperature field of machine tool is effective. The work introduced in this research is helpful for the thermal analysis of spindle in machine tool, which can be seen as a guide on spindle’s design and performance optimization.

Spatial distribution and driving force analysis of urban heat island effect based on raster data: A case study of the Nanjing metropolitan area, China

Human activities do not only change the land use/land cover (LULC), but also release a large amount of anthropogenic heat through intensive activities above ground, which drives the formation of urban heat island (UHI). This study used the Nanjing metropolitan area as the research area and taken 2017 as the observation time and chosen land surface characteristic parameters, point of interest (POI) density and urban functional area data to quantify the driving mechanism of human activities at a grid scale. The results indicated as follows: i) The response relationships between the LST and its driving factors have a clear scale effect at the grid scale. The driving factors had the highest explanatory power at the 300 m grid; ii) LULC had a significant effect on LST, impervious layers and bare soil increased the LST, vegetation and water relieved it; iii) In different urban functional areas, the relationship between LST and POI density was piecewise. In addition to density, the types of human activities also have a significant impact on the UHI, in which industrial heat release has the most significant effect on the local temperature of the city, followed by daily heat production and transportation heat release.

Research on the hot surface ignition of hydrogen-air mixture under different influencing factors

To further reveal the pre-ignition characteristics of hydrogen internal combustion engine, the effect of hot surface characteristic parameters on the ignition characteristics of hydrogen-air mixture was investigated in this research. Based on the prototype of the constant volume combustion bomb with an overhead glow plug, the duration from the heating of the hot surface to the combustion of hydrogen-air mixture, the so-called heating duration, was firstly researched under different fuel-air equivalence ratio, initial temperature, initial pressure, hot surface temperature, and hot surface area, and the influence of each factor on the heating duration was analyzed. The results show that the order of the effect of each factor on the hot surface ignition is as follows: hot surface temperature > initial pressure of hydrogen-air mixture > equivalent ratio > initial temperature of hydrogen-air mixture > hot surface area. The influence of the hot surface characteristic parameters on the heating duration was further analyzed in detail. On this basis, the relationship among the critical ignition temperature, the heating duration and the hot surface area was researched and established. The results show that the heating duration is the only major factor affecting the critical ignition temperature. Finally, the research results were applied to analysis the pre-ignition in hydrogen internal combustion engine.

An active manufacturing method of surface micro structure based on ordered grinding wheel and ultrasonic-assisted grinding

At present, many studies have shown that crosshatch micro structures can effectively improve surface performance. This paper presents a method for manufacturing micro structure based on ultrasonic-assisted grinding (UAG) and ordered grinding wheel. Firstly, the parameters of ordered grinding wheel and the surface characteristic parameters in relation to working performance are proposed. According to the kinematics of grinding, the governing equation between the surface characteristic parameters and the machining parameters is established. Based on the proposed characteristic parameters, the pattern parameters and machining parameters are inversely solved by the governing equation. The crosshatch micro structure manufacturing based on ordered grinding wheel and ultrasonic-assisted grinding is achieved, and because the fabrication technology of the grinding wheel is not mature, its correctness and feasibility are preliminary verified by the numerical simulation method and grinding experiment. The paper method is original for the active manufacturing of the crosshatch micro structure and is of reference value for the micro structure active manufacturing.

Performance of TiN and TiAlN coated micro-grooved tools during machining of Ti-6Al-4V alloy

In the present investigation, turning experiments were performed on Ti-6Al-4V alloy with coated (TiN, TiAlN) and uncoated cutting tool inserts with different textured patterns fabricated on the rake surface. Performance of coated and uncoated textured tools were evaluated using machinability and surface characteristic parameters such as cutting forces, micro hardness, surface roughness, chip formation and tool wear. Based on the machinability evaluation, a comparative study was also made to identity the better performing tool while machining of Ti-6Al-4V alloy. Experimental results revealed that TiAlN coated perpendicular textured cutting inserts exhibit better machinability in all aspects when compared with the other type of inserts.

Experimental study of heat transfer characteristics of high-velocity small slot jet impingement boiling on nanoscale modification surfaces

Jet impingement boiling is one of the most efficient methods to increase the critical heat flux. Through controlling surface chemical properties and topography, plain nickel foil surface, three kinds of plain nickel-based chemical treatment surfaces and four kinds of nickel-based electrochemical treatment surfaces with nanocone array structure were used in the jet impingement boiling experiments to investigate the quantitative effects and the effect mechanism of the surface characteristic parameters, including nanoscale roughness (Ra): solid–liquid contact angle (CA) and effective heat transfer area ratio (r: the ratio of the actual heat transfer area to its projected area) on the heat transfer coefficient (HTC) and the critical heat flux (CHF). It is revealed that: similar to the heat transfer in pool boiling, changing nanoscale Ra has little effect on the heat transfer characteristics; decreasing solid–liquid CA can enhance the HTC while worsen the CHF obviously; increasing r can intensify both the HTC and the CHF. Predictive correlations of the HTC and the CHF of jet impingement boiling which include the effects of surface characteristics are presented. The predictive correlations presented can be widely used in various conditions with different working fluids and heating surfaces.

Study on the degradation of mechanical properties of corroded steel plates based on surface topography

Degradation laws of mechanical properties of corroded steel plates were studied by experimental method and numerical simulation method based on surface topography in this paper. First, Q235 steel plate was subject to accelerated corrosion with artificial salt spray, and the characteristics of the surface of corroded steel plate were measured by three-dimensional morphology observation instrument to obtain the values related to corrosion damage parameters, and the relationship between the surface characteristic parameters and the corrosion rate was established. Then the stress-strain curves and mechanical properties of the corroded steel plates were obtained by monotonic tensile test. Finally, the mechanical properties of steel plates with real corroded surfaces were studied by numerical simulation method with reverse engineering software Geomagic Studio and finite element software ANSYS, and the stress concentration phenomenon caused by corrosion pit was discussed. The results showed that: (a) the corrosion rate is within 15%, the stress-strain curves have obvious yield plateaus; (b) and with the increase of corrosion rate, yield plateaus, yield strength, ultimate strength, and fracture strength of corroded steel plates does not decrease much, but ductility significantly decreases; (c) when the corrosion rate is over 15%, all the mechanical property index significantly decreases; (d) the constitutive model was established, and the law of the variations of the parameters of the model was summarized; (e) the numerical simulation method is feasible compared with the experimental results.

Experimental study on the saturated pool boiling heat transfer on nano-scale modification surface

Plain nickel foil surface, three kinds of plain nickel-based chemical treatment surfaces and four kinds of nickel-based electrochemical treatment surfaces with nano-cone array structure were used in the pool boiling experiment. The quantitative effects and the effect mechanism of the surface characteristic parameters, including nano-scale roughness (Ra), solid–liquid contact angle (CA) and effective heat transfer area ratio (r: the ratio of the actual heat transfer area and its projected area) on the heat transfer coefficient (HTC) on the modification plain surfaces and nano-cone array surfaces were studied and summarized. By improving the previous proposed the HTC prediction correlation for the common plain surfaces (without considering the effect of r), a new uniform correlation is proposed and it can well predict the HTC of the heated surface with simple convex structure (with considering the effect of r). In addition, the bubble dynamic characteristics including the bubble departure diameter, the bubble departure frequency, the active bubble nucleation site density and the combined bubble were investigated by visualization research. These results proposed some mechanism support for the new predicting correlation.