Selective super-wetting surfaces maintain the contrasting super-wetting properties for the oil and the water, and that have received widespread attention since 2000 due to their high surface energy, particularly in oil-water separation applications. Concerning about these surfaces, superoleophobic/superhydrophilic surfaces are effective due to their oil-repellent characteristics.In this paper, Ultraviolet light polymerization was used to polymerize fluorinated substances (TFOA) and hydrophilic substances (MMA), forming a coating on chemically etched copper foam . The resulting porous copper foam exhibited superhydrophilicity and superoleophobicity, facilitating effective oil-water separation tests. The fluorinated substances imparted oleophobic properties to the surface, while the hydrophilic substances provided hydrophilic characteristics to the copper foam. Wear resistance tests using sandpaper and a Taber abrasion tester confirmed that the copper foam exhibits good mechanical durability. The superoleophobic/superhydrophilic copper foam can offer the solution that can overcome continuous oil/water separation process, and help us develop antifouling fabrics, together with self-cleaning surfaces.
Building health monitoring is an essential issue in maintaining building sustainability. Thermography has been widely employed for monitoring buildings. Thermography records the surface temperatures of a target. Those areas with abnormal surface temperatures with their neighborhoods can be treated as defects. Image segmentation groups those pixels with similar surface temperatures such that the recorded thermography can comprise several segmented regions. Those segmented regions offer an essential clue for defect detection. Recently, a thermal camera has been installed on an unmanned aerial vehicle (UAV) to collect the surface temperatures of a building. Those collected thermal infrared images are analyzed with image segmentation. With the segmented regions, the potential defects can be identified. On the other hand, a thermal camera installed on the ground is used to record a series of thermal infrared images. The series of thermal infrared images were analyzed using robust principal component analysis (RPCA) to project the given data onto a low-dimension and feature space. The first image extracted from the low-dimension space inherits the significant properties of the recorded images such that the extracted image can be segmented to illustrate the defects. Two processed results are compared. UAVs provide an efficient way to monitor the building's health conditions, and periodic ground observations offer a stable way to monitor the building. Both ways provide an efficient and robust method to monitor the health conditions of a building.
Thermal infrared images have been widely employed to detect defections. However, it is challenging to identify the defects from thermal infrared images contaminated by shadows, noise, etc. Those factors do be recorded in the thermal infrared images such that the recorded pixels not only contain the surface temperatures but also have the impacts from the factors. Those factors illustrated in the recorded pixels can be called intensity inhomogeneity. Several researchers have reported that the multiplicative way is feasible to approximate intensity inhomogeneity. A gaussian function is introduced to make sure that the intensity inhomogeneity works on not only a particular pixel but also its neighborhoods contribute. Usually, the fixed window size illustrated in the Gaussian function is used for the whole image for simplification. Intensity inhomogeneity is not spread uniformly over the given image. For those areas with high-intensity inhomogeneity, the Gaussian function with larger window sizes is introduced; otherwise, the Gaussian function with smaller window sizes is supposed to apply to the low-intensity inhomogeneity areas. Adaptive window sizes were proposed such that each pixel will have the Gaussian function with the specified window sizes according to the amount of intensity inhomogeneity. However, the adaptive approach needs a lot of computation, so defect detection will be slowed down. This study proposes the algorithm to modify the algorithm of adaptive window sizes provide an efficient way for defect detection. The proposed approach is based on image entropy; the image entropy will have a bigger value while the intensity inhomogeneity is larger. The image entropy was classified such that limited window sizes were introduced. In doing so, intensity inhomogeneity can be approximated, and the results of image segmentation can identify the defect.
Thermal infrared images have been widely employed to detect defections. However, it is challenging to identify the defects from thermal infrared images covered with shadows and noise. For a series of thermal infrared images, principal component analysis (PCA) is often applied to transform the given series into a lower-dimensional linear subspace. In the lower-dimensional subspace, a low-rank matrix is generated to serve as an optimal estimation from the series of thermal images. However, the information stored in those thermal infrared images will be kept mostly during the transformation. Full recovery of the lost information is not possible. A template containing the major information from the given series can be extracted by employing PCA. Furthermore, PCA has difficulty finding the template should interferences occur while the thermal images are captured. The unnecessary information collected associated with the interferences causes some unfavorable characteristics of the template extracted by PCA. Robust PCA (RPCA) is less susceptible to the abovementioned constraints. In this study, RPCA is employed to extract a template from a series of thermal infrared images. Local binary functions are built to restore the image free of noise by keeping the local boundaries. The defects can be readily identified from the regional boundaries. The proposed approach combining RPCA and local binary functions to analyze the given images in conjunction with level set functions. The processed results demonstrate that the proposed scheme are more effective than PCA in analyzing a series of thermal infrared images containing interferences.
Cracks do exist in a concrete building, and the reasons for cracks can be attributed to grouting, force actions, and concrete properties. Detecting existing cracks and monitoring their growth conditions is an important issue in structure health monitoring. This study proposed an integrated approach to fuse the thermal infrared images, high-resolution image, and acoustic tracking. Thermal infrared images can be used to record the surface temperatures. Those defect areas usually have their surface temperatures different from their neighborhoods. Those surface temperature differences can be an important clue to identify the defects. From the high-resolution images, cracks do occur at those discontinuities, and those discontinuities can be treated as the boundaries of the segmented regions. In this study, an approach based on considering the distributions of the segmented regions to segment the given high-resolution images to locate the boundaries of the segmented regions. Then, the defect map is generated by overlaying the thermal infrared image on the segmented regions such that the map can reveal the defect locations, and the surface temperatures can be another evidence to show the defects. Acoustic tracking is introduced to verify the results. All the defect information is stored in a 3D model such that a defect model can be established.
Infrared thermography (IRT) is a matured tool, and it can be employed to monitor the health conditions of structures by measuring surface temperature information in real time and in a non-contact way. The surface temperature information provides an important clue to identifying the defects on the building exterior surfaces. According to the surface temperature measurements, for those parts covered by shadows, the surface temperature information is smaller than it is supposed to be. Similarly, glare effects in IRT can be defined as the excessive and uncontrolled brightness illustrated in IRT such that the surface temperature information is larger than it is supposed to be. In general, the shadow and glare effects are often introduced in the thermal images obtained using the passive IRT when the solar energy is the main heat source. The current study proposes an image model in a multiplicative way to evaluate the shadow and glare effects presented in IRT. The experimental results demonstrate that the proposed image model does efficiently remove the shadow or glare effects. A calibrated thermograph can be generated by introducing proper level set functions in the numerical model.
Defects presented on the facades of a building do have profound impacts on extending the life cycle of the building. How to identify the defects is a crucial issue; destructive and non-destructive methods are usually employed to identify the defects presented on a building. Destructive methods always cause the permanent damages for the examined objects; on the other hand, non-destructive testing (NDT) methods have been widely applied to detect those defects presented on exterior layers of a building. However, NDT methods cannot provide efficient and reliable information for identifying the defects because of the huge examination areas. Infrared thermography is often applied to quantitative energy performance measurements for building envelopes. Defects on the exterior layer of buildings may be caused by several factors: ventilation losses, conduction losses, thermal bridging, defective services, moisture condensation, moisture ingress, and structure defects. Analyzing the collected thermal images can be quite difficult when the spatial variations of surface temperature are small. In this paper the authors employ image segmentation to cluster those pixels with similar surface temperatures such that the processed thermal images can be composed of limited groups. The surface temperature distribution in each segmented group is homogenous. In doing so, the regional boundaries of the segmented regions can be identified and extracted. A terrestrial laser scanner (TLS) is widely used to collect the point clouds of a building, and those point clouds are applied to reconstruct the 3D model of the building. A mapping model is constructed such that the segmented thermal images can be projected onto the 2D image of the specified 3D building. In this paper, the administrative building in Chaoyang University campus is used as an example. The experimental results not only provide the defect information but also offer their corresponding spatial locations in the 3D model.
KEYWORDS: 3D modeling, 3D image processing, 3D acquisition, Feature extraction, 3D image reconstruction, Sensors, Wavelets, 3D vision, Visualization, Synthetic aperture radar
Since ISAR (inverse synthetic aperture radar) can convey information which may not be obtainable by other imaging means, research on applying ISAR to battle field awareness has been intensive. One highly desirable application of ISAR imagery is to reconstruct 3D ground truth, which provides depth information to enhance target recognition and tracking. This paper proposes a stereo vision approach to reconstruct 3D ground truth using ISAR imagery. The proposed approach includes three steps: multiscale feature extraction, stereo matching, and surface interpolation. The multiscale feature extraction is accomplished using a wavelet edge detector, which can smooth the signal and reduce noise at different levels. Stereo matching is implemented using an inverse filtering method, which provides the sparse disparity map for 3D depth information using extracted features. The surface interpolation takes the sparse data generated from stereo matching and interpolate to the dense surface data as the final output. Issues regarding where and how the stereo techniques used for ISAR differ from the ones for video images will be addressed. The initial test shows encouraging results. Future research directions and potential commercial applications are also discussed.
Virtual reality is becoming increasingly important as a tool to provide cost-effective alternatives for training and to provide enhanced capabilities for activities, such as mission preview, planning and rehearsal. The ability to generate virtual reality utilizing a photo database or remote sensed satellite imagery is particularly of interest. The key to ensure the success of remote sensing-based virtual reality is a system that is able to quickly reconstruct a 3D scene in object space with a realistic appearance. This paper proposes a system to accomplish this task. Main issues of the system include: (1) image registration, (2) feature correspondence and extrusion, and (3) realistic 3D feature rendering. The image registration is achieved by employing a novel method based on the higher-dimension concept. To obtain a high speed, the feature correspondence is implemented using a mathematically well-defined, edge-based method in a multiresolution scheme. Realistic 3D feature rendering creates a photo realistic scene. To further accelerate the processing speed, the system is to be implemented on a parallel computer nCUBE 2 with a Silicon Graphics workstation as a host machine. An example is presented in this paper to demonstrate the capability of the system.
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