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The variational level set approaches are widely used in image segmentation. To extract the objects from the inhomogeneity image, an improved local and global binary fitting active contours model is presented in this paper. The energy functional has been defined by a local intensity fitting term and a global intensity fitting term. The generalized Gaussian distribution has been used as the kernel function of the local binary fitting information. The experiment results of the homogeneity images, artificial and real inhomogeneous images have shown the advantages of LGBF model in terms of accuracy and robustness.

Energy auto-modulation is an important tool in X-ray imaging, as it can improve the quality and longevity of an x-ray imaging system. Because of the complex nature of imaged objects, X-ray energy auto-modulation may be difficult. If there is a physical model about imaging mechanism, one can forecast the best imaging parameters using a pre-scan that can be fed into this model. This paper offers a physical model, which is called the Voltage-Thickness-Gray (VTG) model. Based on equivalent single-energy, this paper uses the empirical formula of X-ray attenuation and X-ray photon intensity to build this VTG model. Then use linear regression to estimate the model's parameters, by multi-voltage imaging about the steel wedge block. At last, by the experiment of the steel step block, verify this model and forecast the imaging tube voltage. The result shows this model can better reflect X-ray attenuation imaging properties, and can be used to forecast the imaging voltage. Also the forecast precision can achieve 90% or so.

In conventional X-ray imaging, the ray image of a complicated structural component (complex in shape or structure or composed of multiple materials) often appears to be overexposed or underexposed. This appearance is because of the variations in the effective thickness of the component along the orientation of the X-ray penetration exceed the limit of the dynamic range of the X-ray imaging system. Complete structural information cannot be obtained, and this lack will impact the quality of the X-ray image. To solve this problem, the technology of multi-voltage image stack reconstruction has been advanced. In this new method, the tube voltage is adjusted several times to accommodate the full necessary range of effective thickness, and then, the extracted images are fused to reconstruct the full projection information. The new technology can adequately enlarge the hardware potential to completely represent the internal structure information of a complicated structural component.

In the industrial CT detection systems, because of the restrictions of noises such as scattering noise, the traditional methods for CT reconstruction have high noise and low resolution, and cannot detect smaller flaws. So this paper has proposed using the algorithm of characteristic reconstruction to reconstruct the characteristic of object. About this algorithm, relying on the inner structure character of detected object, according to the character of wavelet function before and after RADON transform, the characteristic part of the image is reconstructed by prefiltering the projected data. Then some experiment show that the method can protrude the inner small flaw of detected object with the less sacrifice of the resolution of image background.

For complicated structural components characterized by wide X-ray attenuation ranges, the conventional computed tomography (CT) imaging using a single tube-voltage at each rotation angle cannot obtain all structural information. This limitation results in a shortage of CT information, because the effective thickness of the components along the direction of X-ray penetration exceeds the limitation of the dynamic range of the X-ray imaging system. To address this problem, high-dynamic-range CT (HDR-CT) reconstruction is proposed. For this new method, the tube’s voltage is adjusted several times to match the corresponding effective thickness about the local information from an object. Then, HDR fusion and HDR-CT are applied to obtain the full reconstruction information. An accompanying experiment demonstrates that this new technology can extend the dynamic range of X-ray imaging systems and provide the complete internal structures of complicated structural components.

In the process of X-ray digital imaging detection, previous test usually adopts the projection data of 360° to reconstruct. But in practical test, it's often restricted to the installation of the equipment and the cost, so it cannot meet the condition of reconstruction. This paper studies a method to solve the coordinate of circle center about a particular component by some experience information, which is based on the projection values of three views in order to determine the distribution of holes. Experiment shows that the method not only reduces the collection angles and the cost, which satisfies the problem of detection in practical application, but also guarantees the accuracy of the positional information of the internal holes, which is compared with the 900 views under reconstruction.

Fixed-voltage Digital Radiography(DR) image has over-exposed or under-exposed regions since dynamic range of the imaging device is not enough when testing a composite component with a complicated internal structure. Some structure information of the composite component is lost. This problem can be solved by fusing the multi-voltage DR images. A multi-voltage DR images fusion model is proposed based on the gray consistency of the images. It adaptively determines the weights of all images by solving the model. What's more, this method is without prior knowledge. The experiment shows the new method can reconstruct the whole information of the complicated structural component. Also the new method has higher fusion efficiency because of no prior knowledge.

Computer users’ reactions to the outbreak of Internet worm directly determine the defense capability of the computer and play an important role in the spread of worm. In this paper, in order to characterize the impacts of adaptive user protection behaviors, an improved SIS model is proposed to describe the Internet worm propagation. The results of theoretical analysis indicate that the protective campaigns of users can indeed reduce the worm’s reproduction number to values less than one. But it may not be sufficient to eradicate the worm. In certain condition, a backward bifurcation leading to bistability can occur. These are new findings in the worm propagation model that bring new challenges to control the spread of the worm and further demonstrate the importance of user behaviors in controlling the worm propagation. Corresponding to the analysis results, defense and control strategies are provided.

A method that can fast, real-time get the projection matrix in ART reconstruction is proposed based on helical cone-beam CT trajectory in this paper. For a given ray this method can rapidly acquire the indices and corresponding lengths of the voxels passed through by this ray through sorting the intersections between the ray and mesh planes. Meanwhile we only store the projection matrix elements required for a given ray and release them after using them. By doing so the computation time and the storage space are significantly reduced. The experimental results show that this method can heighten the speed and better suppress noise.