Search Results (15)

Wood drying is the most critical and energy-intensive process in the wood industry. However, the complex pore structure of wood significantly affects its thermal performance. Therefore, it is essential to study the relationship between the pore structure and the thermal properties of wood. In this study, X-ray-computed tomography (XCT) technology, combined with digital image processing (DIP) techniques, was used to visualize and characterize the three-dimensional structure of oak samples. Parameters such as porosity, pore size and distribution, and fractal dimensions were obtained to investigate their relationship with thermal conductivity. Subsequently, the thermal conductivities of the oak samples in the tangential, radial, and axial directions were simulated based on their three-dimensional structure. The simulation results were validated using the transient plane source method (TPS). The results showed that there were significant differences in porosity and pore size between earlywood and latewood, which in turn affect the correlation between fractal dimension and thermal conductivity. The higher the self-similarity of the wood structure is, the stronger the correlation between porosity and fractal dimension will be. Due to the limitations of CT resolution and threshold segmentation methods, there may be some axial deviations in the heat transfer simulation based on XCT. However, overall, this method provides a relatively accurate estimate of the effective thermal conductivity of oak wood. In addition, the pit structure and the research on heat conduction of wood-based multi-scale pore structures are of crucial importance to the study of heat conduction in wood. Full article

Hop (Humulus lupulus L.) is a climbing plant that contains essential components for beer production. Although Brazil is the third-largest beer producer in the world, it still relies on imports to meet demand. Some hop varieties have already adapted to the tropical climate, but nitrogen fertilization is essential for the proper development of plants. Digital image processing (DIP) and modeling technologies are emerging as fast and economical alternatives for monitoring the nutritional status of plants. This study evaluated the impact of image quality and the performance of models in classifying hop plants in terms of nitrogen concentration, using predictors extracted from leaf images. A total of 24 plants subjected to six levels of fertilization, ranging from 0 to 200% of the optimal level, were analyzed. The leaves were classified into two nitrogen concentration groups and the data organized into two sets: one containing only significant variables and another including all the variables in the model. Linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) models were estimated. The QDA models demonstrated great efficacy in classifying plants with a high nitrogen concentration, achieving over 80% accuracy, although performance was lower for plants with a lower nitrogen concentration. Full article

The interfacial bonding capacity between cement emulsified asphalt composite binder (CEACB) and reclaimed asphalt pavement (RAP) plays a critical role in improving the pavement performance of cold recycled asphalt emulsion mixtures (CRAEMs). This study aims to investigate the formation and development of the interfacial bonding capacity between CEACB and RAP. First, the dynamic wettability and the spreading behaviors of CEACB on RAP surfaces were explored according to the surface free energy theory. Second, digital image processing (DIP) technology was employed to recognize interfacial failure patterns. Lastly, the influence of internal and external factors on the interfacial bonding capacity between CEACB and RAP during the curing process was analyzed via grey relational analysis (GRA). The results indicate that a moderate cement content with a mass ratio of asphalt to cement equivalent to 1.0 can significantly enhance the wettability of CEACB on RAP surfaces. By appropriately prolonging the curing time and controlling the curing temperature, it is possible to increase the bonding strength between CEACB and RAP. Additionally, a strong correlation exists between initial wettability and ultimate bonding capacity during the bonding strength curing process. The good wettability that developed in the initial stage of interfacial strength formation relates to the decreased spalling rate of CEACB on the RAP surface. This study is not only devoted to understanding the mechanisms that can enhance CRAEM performance but also provides important guidance for practical engineering applications of cold recycled asphalt pavements. Full article

Digital image-correlation (DIC) algorithms rely heavily on the accuracy of the initial values provided by whole-pixel search algorithms for structural displacement monitoring. When the measured displacement is too large or exceeds the search domain, the calculation time and memory consumption of the DIC algorithm will increase greatly, and even fail to obtain the correct result. The paper introduced two edge-detection algorithms, Canny and Zernike moments in digital image-processing (DIP) technology, to perform geometric fitting and sub-pixel positioning on the specific pattern target pasted on the measurement position, and to obtain the structural displacement according to the change of the target position before and after deformation. This paper compared the difference between edge detection and DIC in accuracy and calculation speed through numerical simulation, laboratory, and field tests. The study demonstrated that the structural displacement test based on edge detection is slightly inferior to the DIC algorithm in terms of accuracy and stability. As the search domain of the DIC algorithm becomes larger, its calculation speed decreases sharply, and is obviously slower than the Canny and Zernike moment algorithms. Full article

The effect of freeze–thaw (F–T) in the seasonal frozen area would lead to damage to asphalt pavement. After water enters asphalt pavement, the water in voids would expand at a lower temperature, which could change the void content and number, affecting the macro mechanical properties of the asphalt mixture. The rapid development of CT scanning and digital image processing (DIP) provides powerful technical support for the research of asphalt mixture meso volume characteristics. In this paper, the mechanical properties of basalt fiber reinforced asphalt mixture subjected to F–T cycles were tested at different temperatures to clarify the decay law of mechanical properties under F–T cycles. Then, the meso images of the asphalt mixture under various F–T cycles could be obtained by using CT tomography. Based on DIP technology, the meso characteristic parameters of CT images for asphalt mixture were extracted, and the development of asphalt mixture freeze–thaw damage was further analyzed. The test results showed that with the F–T cycle, the macro mechanical properties of the asphalt mixture rapidly declined in the early stage of the F–T cycle and gradually tended to be flat. There would be serious damage inside the asphalt mixture in the late stage of the F–T cycle. The damage to the mechanical properties of the asphalt mixture under the F–T cycle can be attributed to the change in the internal mesostructure of the asphalt mixture. Based on the grey relational analysis theory, the formation of the connected void was the main factor affecting the damage in the early stage of the F–T cycle, while the formation of new voids mainly affected the later development of F-T damage. Full article

In this paper, a novel dual microscopic fatigue-crack and tip-deformation-fields measurement method based on a hybrid image-processing technique is proposed that was used to research the physical short fatigue crack (SFC) closure effect and the evolution law of the tip deformation fields of Quenching–Partitioning (Q&P) steel during the crack-closure process. The measurement problems are solved, such as the small SFC tip region, large deformation gradient, and strong material anisotropy. Microscopic crack and speckle images are acquired simultaneously on both sides of a compact tensile (CT) specimen of Q&P steel by dual microscopic cameras. A digital image processing (DIP) method is used to identify crack-growth morphology and measure crack length in Q&P steel, and the SFC growth rates are analyzed under different stress ratios. Microscopic digital image correlation (Micro-DIC) is used to analyze displacement fields at the crack tip of SFC and, combined with virtual extensometer technology, analyze the evolution law of crack closure and the evolution of crack-growing morphologies during the closure process under different lengths and stress ratios. Accordingly, the evolution of strain fields at the crack tip in one load cycle for different crack lengths and stress ratios during the SFC closure process is analyzed. The results show that the stress ratio affects the crack-closure behavior and crack growth rate of Q&P steel in the physical SFC crack-growing stage. The crack-closure effect has an obvious influence on the evolution process of displacement and strain fields at the crack tip. The evolution of short-fatigue-crack-tip morphology and strain field of Q&P steel conforms to the crack-closure law. The research results provide experimental and theoretical support for the further study of the SFC growth mechanism and fatigue life prediction of Q&P steel. Full article

Coal rocks often contain calcite, which has a significant effect on the mechanical properties of coal and the energy evolution during rupture damage. In this study, the meso-scale of rock is considered, and the spatial distribution of the internal structure of coal is characterized by digital image technology. Uniaxial compression tests were conducted using RFPA on coal rocks containing calcite veins with diverse dip angles. The research results show that the different azimuth angles of the calcite veins change the internal stress distribution of the coal, resulting in higher coal compressive strength at low dip angles (0°, 15° and 30°). Under high dip angles (45°, 60°, 75° and 90°), coal has lower compressive strength. The fracture mode of coal is significantly affected by calcite. At low dip angle, the fracture mode of coal and rock is complex, which are inclined Z-type (0°), V-type (15°) and inverted V-type (30°), respectively. At high dip angle, the fracture mode of coal and rock is single, which is type I failure mode. The destruction process of coal rocks is influenced by calcite veins. Under low dip angle, the internal stress distribution of coal is relatively uniform, the weak cementation between matrix and calcite vein in coal is not easy to be damaged, the stress required for coal failure is large and the input energy, accumulated elastic energy and impact energy index are large. Under high dip angle, the internal stress distribution of coal is uneven, the weak cementitious material between matrix and calcite vein in coal is easy to be damaged and the input energy, accumulated elastic energy and impact energy index are small. Full article

The macroscopic aspects of adding basalt fiber (BF) to concrete has been the subject of studies that document great increases in compression strength. Research into the microscopic aspects of the reinforcement mechanism is still in an exploratory stage, and the quantitative analysis and visual observation of fibers in the concrete matrix are difficult. In this paper, the reinforcement effect of fiber on concrete is studied by means of computed tomography (CT) scanning technology and digital image processing (DIP) technology, combined with the macro-mechanical properties obtained from the unconfined compression strength test, and quantitative analysis from the micro point of view. At the same time, the fiber visualization is realized with the help of Avizo. The results show that with the increase in fiber dosage, the peak stress of concrete first increases and then decreases. When the fiber dosage is 3 kg/m³, the peak stress is 44.4 MPa, which is 41.85% higher than that of ordinary concrete. Additionally, the proportion of macropores is the least, which is the best fiber dosage. It is found that when the fiber dosage is 3 kg/m³, the angular distribution of φ is relatively uniform, and the uniform distribution of fibers forms a dense network structure, which significantly increases the peak stress of concrete. However, when the fiber dosage is too high, it will lead to the accumulation of fibers and produce macropores, and these excess fibers mainly appear in the horizontal direction and do not contribute to the compression strength. Full article

To study the occurrence process, as well as the temporal and spatial evolution laws, of rockburst disasters, the roof deformation of continuous heading roadways during rockburst was studied through a physical similarity simulation test with a high similarity ratio and low strength. The deformation and failure evolution law of the roadway roof in the process of rockburst were analyzed by using detection systems, including a strain acquisition system and a high-power digital micro-imaging system. The results show that the rockburst of the roadway roof can be divided into four stages: equilibrium, debris ejection, stable failure, and complete failure stage. According to the stress state of a I–II composite crack, the theoretical buckling failure strength of the surrounding rock is determined as 1.43 times the tensile strength. The flexural failure strength of a vanadium-bearing shale is 1.29–1.76 times its compressive strength. With continuous advancement in the mining time, the internal expansion energy of the roadway roof-surrounding rock in the equilibrium stage continuously accumulates. The fracture network continuously increases, developing to the stable failure stage, with bending deformation, accompanied by continuous particle ejection until the cumulative stress in the failure stage increases, and the tensile state of the rock surrounding the roof expands radially into deep rock. A microscopic damage study in similar material demonstrated that the deformation of the roadway roof is non-uniform and uncoordinated. In the four stages, the storage deformation of the rock surrounding the roadway roof changes from small accumulation to continuous deformation, to the left (or deep rock). Finally, the roadway roof-surrounding rock becomes completely tensioned. The research results presented in this study provide a reference for the prediction and control of rockburst in practical engineering. Full article

Icing phenomena are one of the hot issues in the aviation field, which has attracted the attention of many manufacturers. The physical process of water film flow determines the position and amount of icing. In this paper, the flow process of water film on a rough surface is studied. An experimental platform was built in a wind tunnel, and the digital image processing (DIP) technology was used to measure the water film flow. The water film flow under different roughness conditions of the plate was obtained in the experiments. The correction model of interfacial shear coefficient is established, and the influence of roughness on water film flow is deduced. The relationship obtained in this paper can provide data support for the study of gas-water coupled flows on rough surfaces. Full article

Bridge displacement measurement is an important area of bridge health monitoring, which can directly reflect whether the deformation of bridge structure exceeds its safety permission. Target tracking technology and Digital Image Correlation (DIC) are two fast-developing and well-known methods for non-contact bridge displacement monitoring in Digital Image Processing (DIP) methods. The former’s cost of erecting detection equipment is too large for bridges with a large span that need to locate more multi-targets because of its tracking only one target on a camera while the latter is not suitable for remote detection because it requires very high detection conditions. After investigating the evolution of bridge displacement monitoring, this paper proposes a bridge displacement monitoring algorithm based on multi-target tracking. The algorithm takes full account of practical application and realizes accuracy, robustness, real-time, low-cost, simplicity, and self-adaptability, which sufficiently adapts the bridge displacement monitoring in theory. Full article

The idea of Ubiquitous Power Internet of Things (UPIoTs) accelerates the development of intelligent monitoring and diagnostic technologies. In this paper, a diagnostic method suitable for power equipment in an interference environment was proposed based on the deep Convolutional Neural Network (CNN): MobileNet-V2 and Digital Image Processing (DIP) methods to conduct fault identification process: including fault type classification and fault localization. A data visualization theory was put forward in this paper, which was applied in frequency response (FR) curves of transformer to obtain dataset. After the image augmentation process, the dataset was input into the deep CNN: MobileNet-V2 for training procedures. Then a spatial-probabilistic mapping relationship was established based on traditional Frequency Response Analysis (FRA) fault diagnostic method. Each image in the dataset was compared with the fingerprint values to get traditional diagnosing results. Next, the anti-interference abilities of the proposed CNN-DIP method were compared with that of the traditional one while the magnitude of the interference gradually increased. Finally, the fault tolerance of the proposed method was verified by further analyzing the deviations between the wrong diagnosing results with the corresponding actual labels. Experimental results showed that the proposed deep visual identification (CNN-DIP) method has a higher diagnosing accuracy, a stronger anti-interference ability and a better fault tolerance. Full article

In order to investigate the fatigue cracking resistance of engineered cementitious composites (ECC) used in in total life pavement, the semi-circular bending (SCB) test and improved three-point bending fatigue test (ITBF) were utilized in this study. The digital image correlation (DIC) method was also utilized to track the surface strain fields of specimens during the SCB test. X-ray computed tomography (CT) and digital image processing (DIP) technologies were applied to measure the internal-crack distribution of the ITBF specimen. The results of the SCB test showed that the fatigue cracking damage process of ECC can be divided into three stages and that the cracking stable propagating stages occupied the main part, which indicates that ECC has excellent ductility and toughness and could work very well with existing cracks. The ITBF results showed that the fatigue cracking resistance of ECC was better than epoxy asphalt concrete (EAC). In addition, the internal-crack distribution along the depth direction of the ITBF specimen could be presented well by the image pixel statistical (IPS) method based on CT scanning of image slices. It could be found that multiple cracks propagate simultaneously in ECC, instead of a single crack, under the OSBD pavement working condition. Full article

Representative volume element (RVE) is an important parameter in numerical tests of mechanical properties of heterogeneous geomaterials. For this study, a digital image processing (DIP) technology was proposed for estimating the RVE of heterogeneous geomaterials. A color image of soil and rock mixture (SRM) with size of 400 × 400 mm² taken from a large landslide was used to illustrate the determination procedure of the SRM. Six sample sizes ranging from 40 × 40 mm² to 240 × 240 mm² were investigated, and twelve random samples were taken from the binarized image for each sample size. A connected-component labeling algorithm was introduced to identify the microstructure. After establishing the numerical finite difference models of the samples, a set of numerical triaxial tests under different confining pressures were carried out. Results show that the size of SRM sample affects the estimation of the mechanical properties, including compressive strength, cohesion, and internal friction angle. The larger the size of the samples, the less variability of the estimated mechanical properties. The coefficient of variation (CV) was applied to measure the variability of mechanical properties, and the RVE of the SRM was determined easily with a predefined acceptance threshold of the CV. The results show that a DIP-based modeling method is an effective method got the RVE determination of heterogeneous geomaterials. Full article

Research on energy accumulation and releasing in the rock plays a key role on revealing its failure mechanism. This paper establishes a microscopic structure model of granite using Otsu digital image processing (DIP) technology and particle flow code software (PFC2D). A series of numerical compression tests under different confining pressures were conducted to investigate the macro and micro characteristics of energy evolution in granite. The results showed that the energy evolution of granite is divided into three stages: stable accumulation, slow dissipation, and rapid release. With increasing confining pressure, the strain energy accumulation ratio decreased exponentially and the peak value of strain energy increased linearly. It was found that the energy accumulation speed in the pre-peak stage increased as a linear function, while the energy release speed in the post-peak stage decreased as an exponential function. In addition, the feldspar is the main microstructure which played a major part in accumulating energy in granite. However, the unit mineral energy of mica particles was bigger than that of feldspar and quartz. When subjected to increasing confining pressure, the feldspar’s total energy growth rate was fastest. Meanwhile, the mica’s unit energy growth rate was fastest. Full article