Roughness Attenuation Research Articles

Refined semi-empirical models for soil moisture retrieval in spaceborne GNSS-Reflectometry: Evaluation across diverse land cover types

The satellite-based Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a promising technique for detecting surface soil moisture (SSM), which plays a pivotal role in various applications. Different approaches have been developed for SSM retrieval, including parametric semi-empirical models and non-parametric machine learning methods. This study, however, specifically focuses on constructing and evaluating semi-empirical fit models. To this end, the study compares the effectiveness of our enhanced pixel-by-pixel model, the land cover-based linear model, and the Reflectivity-Vegetation-Roughness (R-V-R) model across different land surface types, aiming to both evaluate their efficacy and identify potential limitations. In the assessment, various factors were taken into consideration, such as the correction for vegetation and roughness attenuation, fitting functions employed, and the utilization of a lookup table (LUT). The results of the evaluation showed variations in the performance of the retrieval models across different land cover types, highlighting the impact of the choice of fitting functions and attenuation correction strategies on the accuracy of soil moisture retrieval. The pixel-by-pixel model demonstrated the highest prediction accuracy, with an unbiased root mean square difference (ubRMSD) of 0.056 cm3/cm3 and a correlation coefficient of 0.896. By showcasing these outcomes, this research underscores the significance of accounting for surface conditions and integrating relevant data to enhance the accuracy of GNSS-R SSM retrieval, thereby contributing to the advancement of SSM monitoring methodologies.

Variable speed rolling force prediction with theoretical and data-driven models

The variations in thickness at the head and tail significantly impact the product quality in tandem cold rolling. Improving rolling force calculation accuracy under speed-up and speed-down conditions is essential to enhance thickness control. This paper proposes a sequential coupled model combining data-driven and theoretical models to predict rolling force under speed variation conditions. To enhance accuracy and overcome the limitations of traditional velocity field, a linear cross-section dynamic velocity field taking into account the effects of roll gap changes on the deformation zone is established. Moreover, a long short-term memory (LSTM) network is constructed to capture sequential information from production data and compensate for changes in friction state caused by speed variation and roughness attenuation in the theoretical model. 12 coils, totaling 12,000 samples, are selected from the process data acquisition system (PDA) and utilized as the dataset after normalization. Mutual information (MI) theory is employed for feature selection to improve the prediction accuracy and reduce the computing consumption. Learning rate (LR) adjustment is applied to enhance the stability of initial network and the convergence speed. Compared to evaluated models, the proposed model has relative error within ±2.5 %, R2 of it is 0.9935 and the prediction time is only around 2.5 ms. The results suggest that the proposed model demonstrates the most favorable overall performance. Additionally, some key rolling parameters whose physical relationship with rolling force remains uncertain are investigated.

On roughness attenuation in elastohydrodynamic lubricated line and circular contacts

The commonly accepted “roughness attenuation” theory offers a description of the deformation of surface features as they travel through elastohydrodynamic lubricated contacts, based on the Boussinesq half-space approximation. Through a finite element model, incorporating surface features into the contact geometry (which cannot be done with the half-space approach), this work reveals three shortcomings in the theory. First, contact pressures are assumed normal to the substrate rather than the surface features lying on it. Second, it uses reduced solid properties that are invalid in the presence of surface features. Third, it does not account for the deformation of the features themselves. A correction procedure is devised, allowing for the theory to be rectified, without the need to incorporate surface features into the contact geometry, which can be computationally prohibitive.

Anisotropic Superattenuation of Capillary Waves on Driven Glass Interfaces.

Metrological atomic force microscopy measurements are performed on the silica glass interfaces of photonic band-gap fibers and hollow capillaries. The freezing of attenuated out-of-equilibrium capillary waves during the drawing process is shown to result in a reduced surface roughness. The roughness attenuation with respect to the expected thermodynamical limit is determined to vary with the drawing stress following a power law. A striking anisotropic character of the height correlation is observed: glass surfaces thus retain a structural record of the direction of the flow to which the liquid was submitted.

Tension compensation technique based on the roughness attenuation of a furnace roller during continuous annealing

ABSTRACTStrip tension fluctuation caused by the attenuation of a furnace roller’s surface roughness leads to strip deviation in continuous annealing. After several field experiments and theoretical studies, this work established a model for the surface roughness attenuation of a furnace roller during continuous annealing. The model is fully integrated with the equipment and process features of a continuous annealing unit. With the stability of strip travelling as the control object and the absence of strip deviation and buckling as constraints, a tension compensation technique of continuous annealing was developed, and a related theory was applied to production and practise. Software was also developed for predicting the roughness attenuation of a furnace roller during continuous annealing and determining tension compensation for a specific process of the unit. Integrated optimisation of tension parameters in all processes of continuous annealing was also achieved.

Modeling Land Surface Roughness Effect on Soil Microwave Emission in Community Surface Emissivity Model

Soil surface roughness is a crucial factor affecting the land surface microwave emissivity. Presented in this paper is a semiempirical model that analytically accounts for both roughness attenuation and cross-polarization-mixing effects in the frequency range of 1–100 GHz. The model is based on the finite linear superposition of hyperbolic tangent (tanh) functions over the normalized surface roughness and radiative parameter space, which proves to be very flexible and efficient in handling the distinct asymptotic features of roughness effects at the low-frequency end and high-frequency end and the nonlinear structure in between. The model performance was analyzed with the ground-based reflectivity measurements collected from different sources. In comparison with the existing semiempirical models in the literature, the new tanh-based roughness model demonstrated higher accuracy and consistent performance in the frequency range of 1.4–100 GHz and $0^\circ\!\sim\! 60^\circ$ incident angles.

Research on Preparation of Ni/SiO2 Optical Attenuation Slice by Magnetron Sputtering

In order to find new methods for preparing and improving the performance of optical attenuation slice. Vacuum magnetron sputtering method was used to prepare Ni/SiO2 composite film optical attenuation slices, with vacuum magnetron sputtering apparatus, at 5,10,15,20,25min sputtering time, 0.2,0.4,0.6,0.8,1.0Pa sputtering pressure and sputtering power 300~1200W. The XRD, SEM, EDS, AFM and 722 spectrophotometer also were used to study the effects of different sputtering time, sputtering pressure and sputtering power on the film structure, surface morphology, composition, three-dimensional structure, surface roughness and light attenuation rate of optical attenuation slice samples. The results indicated that: Ni/SiO2 composite films were formed, instead of simple physical adsorption between Ni film and SiO2 substrates with magnetron sputtering by XRD analysis and calculation, with uniform grain size of 25.96, 32.38, 32.29,26.95, 25.92nm, respectively. The main component element was Ni, but there were few impurities deposited on the substrates. Impurities were reduced gradually with the increase of sputtering time, mainly resulted from two sputtering of Ni atoms by EDS; The film surface was smooth and dense, flatness and organizational structure of Ni film were better, surface roughness was 1.267nm at 25min sputtering time, 0.4Pa pressure and 400W power with SEM and AFM. Light attenuation rate of optical attenuation slices was different in different process parameters, and the maximum reached 0.52, film flatness, impurities and defects were the main reason by the light attenuation performance analysis.

Biodiesel from saturated and monounsaturated fatty acid methyl esters and their influence over noise and air pollution

A combined analysis of exhaust and noise emissions of an three-cylinder direct injection diesel engine running on palm oil methyl esters (PME) and olive pomace oil methyl esters (OPME), both blended with diesel fuel in different proportions, is proposed to evaluate their suitability as partial substitute to fossil fuels. Moreover, engine sound quality (derived from the use of these fuels) based on loudness and roughness metrics has been analyzed. A strong correlation between sound pressure maximum level and loudness was found. Although it was observed that both parameters improved with the use of both set of blends, PME blends depicted the best behavior. In terms of roughness, OPME blends achieved the maximum attenuation. In addition, roughness attenuation was found to be more meaningful than loudness when the blends were used. Considering the exhaust emissions tests, it was observed that the use of both sets of fatty acid methyl ester blends allows a significant reduction of CO emissions. Moreover, lower NO exhaust emissions were produced when PME blends were used instead of OPME blends or diesel fuel. NOx emissions were lower when PME blends were used instead of OPME blends, though diesel fuel depicts the lowest values. In general terms, it may be concluded that saturated fatty acid methyl esters produce biodiesel with a positive influence over air and noise emissions.

Impact of Rough Wall Surface on Electromagnetic Wave Propagation Characteristics in Mine Tunnels

In this paper ,the mine tunnels is regard as wave-guide which contains kinds of un-beneficial medium, we have study the formulas of electromagnetic waves propagation attenuation and roughness attenuation, the relations between propagation attenuation and roughness and frequency were simulated. The results show that the influence of propagation attenuation in lower frequency is more obvious, and roughness attenuation is increased rapidly as roughness of coal mine tunnels increasing. But tilted attenuation is stronger than roughness attenuation as propagation frequency increasing.

Experimental study of real roughness attenuation in rolling/sliding concentrated contacts

A surface roughness attenuation approach based on the Fourier decomposition of surface roughness into harmonic components may allow predictions of the behavior of real rough surfaces within concentrated lubricated contacts. Recent experiments performed under pure rolling conditions have shown an amplitude reduction of different components that agreed well with the data predicted by the theory. This study represents the next step in the experimental verification of the surface roughness attenuation approach under rolling–sliding conditions. Obviously, the behavior of roughness in the rolling–sliding elastohydrodynamic (EHD) contacts is more complex than for pure rolling. It has been theoretically suggested by other researchers that the modification of the original roughness alone cannot explain all of the major effects that significantly affect film thickness, and a model was proposed in which, along with the roughness attenuation, a complementary wave was generated in the inlet region and moved at the entrainment speed. This paper is focused on the possibility of extracting complementary waves from experiments with real rough surfaces conducted under rolling–sliding conditions and of determining whether the amplitudes of the complementary wave can be determined. This represents the first attempt to study both effects of rough surface behavior separately. The complementary wave was extracted from the measured data by subtracting the attenuated original roughness from the measured film thickness. Although the experimental results were quite scattered, a trend similar to that of the theoretical curves was observed. Based on the results, it can be suggested that the significance of the complementary wave is comparable to the attenuation principle.

Study of Parameters and Technics for Chrome-Plating Texturing

The generally textured techniques used in industry can make the roller surface fall off or damage by burning to form aculeate concave. The textured rollers produced by the method mentioned above have some disadvantage performances that include rapid roughness attenuation, limited use time and more concave. These disadvantages are not suitable for the formation of roughness on the cold roller surface. On account of high hardness and excellent wearable capability, the element chrome, which can be deposited on the cold roller surface, can increase the use life of textured cold roller enormously. In this paper, an experiment of DC superimposed pulse was performed to obtain certain roughness chrome textured and hemisphere-shaped chrome coatings. From the results, it was shown that the roughness and hardness of coating obtained by electroplating was 3.79μm at 850mA/cm2 and 1000 Hv respectively.

Experimental study of real roughness attenuation in concentrated contacts

The understanding of the processes involved in the in-contact deformation of surface roughness represents one of key factors in increasing lubrication capabilities of highly loaded machine components. Two main approaches have been developed in an effort to understand the changes of initial surface topography within highly loaded contacts to provide detailed information about lubrication film thickness and pressure distribution in the vicinity of roughness features. The first approach considers the real surface topography while the other uses the simplified topography features. Numerical solutions based on measured topography data can provide the film thickness and pressure distribution around asperities of realistic scale; nevertheless, obtained results are typically limited to the specific topography configuration measured from a very small area of rubbing surface. That is why some researchers have considered harmonic features of various wavelength and amplitudes to explain the behaviour of real roughness. This study is focused on the experimental validation of an approach based on Fourier decomposition of the surface roughness into harmonic components. Two optical measurement techniques—phase shifting interferometry and thin film colorimetric interferometry are combined to provide the undeformed surface topography and film thickness data within the elastohydrodynamic contact formed between a smooth disk and a ball having a real rough surface. The results obtained under pure rolling conditions not only confirmed the general principle that roughness deformation is component dependent and that long wavelengths deform more than short wavelengths, also the observed deformation for different components agreed well with the data predicted by the theory.

Surface-to-volume wave conversion in shallow water with a corrugated bottom

Acoustic transmission between points onshore or in very shallow water and points in deep water is strongly influenced by the shear rigidity of marine sediments, which control the parameters and the very existence of seismoacoustic surface waves. Previously, it was found that coupling between acoustic modes and the seismoacoustic surface waves is normally weak, although not negligible in the case of a gently sloping seafloor and soft sediments. In this paper, the previous work is extended by accounting for the small-scale roughness of the seafloor. The significant role of roughness in coupling between volume and surface waves is demonstrated. The combined effect of bottom topography, roughness, and wave attenuation in soft marine sediments on the sound propagation between points in shallow and deep water is discussed.

Roughness effects on the double-layer charge capacitance: the case of Helmholtz layer induced roughness attenuation

For electrical double layers, the presence of a Helmholtz layer could lead to electrode roughness attenuation. The latter is assumed of self-affine type which is characterized by the roughness amplitude w, the correlation length ξ, and the roughness exponent H. For sufficiently rough metal electrode surfaces ( H≪1 and/or ratios w/ ξ⩾0.1) the diffuse/Helmholtz layer interface would not have the same roughness parameters with the metal electrode surface. If the latter is smoothened at lateral length scales smaller than a healing length Λ (≪ ξ), the diffuse charge capacitance decreases and approaches values close to that of the Gouy–Chapman theory for flat electrodes.

Surface roughness attenuation in line and point contacts

Surface roughness effects in line and point elastohydrodynamically lubricated contacts are compared and it is shown that the underlying behaviours in both types of contact are identical. Long wavelength components of roughness are attenuated; short wavelength components pass through the conjunction unaltered. It is also shown that the roughness attenuation, plotted against a non-dimensional wavelength, follows almost identical curves in both cases.

Elliptic Cylinder Modeling of Obstacles for Low Altitude Radar Systems

In this work obstacle models for wave propagation over irregular terrain are investigated. Obstacles can be modeled both as perfectly conducting wedges or ellipses and impedance wedges and ellipses depending on the terrain structure and electrical properties. The irregularities of the terrain can be taken into account by surface roughness attenuation factor. The effects of different obstacle models, topographical and electrical properties of the terrain are calculated using Uniform Geometrical Theory of Diffraction for perfectly conducting and impedance surfaces. Results are compared to each other. It is shown that there is a significant difference between impedance wedge-wedge and impedance ellipse-ellipse models for low target altitudes. To calculate propagation factor precisely ellipse-ellipse model must be used for some types of terrain geometries.

Effect of Interfacial Roughness on Phonon Radiative Heat Conduction

The interface between a solid and a liquid or two dissimilar solids poses a resistance to heat transport by phonons, which are quanta of lattice vibrational energy. The classical theory explains that the resistance R arises due to a mismatch in acoustic impedances of the two media and predicts R to vary with temperature T as R ~ T−3. Experiments with copper and liquid 3He have shown that first, although RT3 is a constant below 0.1 K, its value is much less than that predicted by the classical theory. Second, at higher temperatures the resistance behaves as R ~ T−n where n > 3. This study explains these observations in the temperature range of 0.06 K−1 K and 3He pressure range from zero atmospheres in liquid state to solid state, by including the effects of surface roughness and phonon attenuation in solids by electrons or dislocations. Roughness measurements have shown that solid surfaces have a fractal structure and are characterized by a fractal dimension D lying between 2 and 3 for a surface. Using the fractal characteristics, the thermal boundary resistance is shown to follow the relation RT3 ~ (1 + ηTβ)−1 where β is a function of the dimension D and η is a scaling constant. The predictions are in excellent agreement with the experimental observations, indicating that, in addition to other surface effects, the fractal surface structure could have a strong influence on thermal boundary resistance.