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To solve the problem of the high cost of transient temperature simulation in the whole construction process of an asphalt-concrete core wall, a novel adaptive degree of freedom condensation algorithm for simulating transient temperature is proposed. This method establishes the judgment criterion of degree of freedom condensation based on the error estimator of mesh and the artificial energy added by degree of freedom condensation. In this method, the transformation matrix between the master and slave degrees of freedom is constructed based on the shape function interpolation relationship between the initial coarse mesh and the multi-level refined mesh. In the transient calculation process, this method can automatically identify the positions where temperature distribution and value are stable and condense the considered slave degrees of freedom to master degrees of freedom through the transformation matrix at any time to reduce the unnecessary degrees of freedom. In this paper, three numerical examples show that the proposed method can effectively reduce the cost of matrix factorization and the solving the equation in the finite element method at the cost of small precision loss in the long-term transient temperature simulation.

An ultrasound (US) navigation system using global and local information is presented for transcatheter aortic stent deployment. The system avoids the use of contrast agents and radiation required in traditional fluoroscopically-guided procedures and helps surgeons precisely visualize the surgical site. To obtain a global 3D (three-dimensional) navigation map, we use magnetic resonance (MR) to provide a 3D context to enhance 2D (two-dimensional) US images through image registration. The US images are further processed to obtain the trajectory of interventional catheter. A high-resolution aortic model is constructed by using trajectory and segmented intravascular ultrasound (IVUS) images. The constructed model reflects morphological characteristics of the aorta to provide local navigation information. Our navigation system was validated using in vitro phantom of heart and aorta. The mean target registration error is 2.70 mm and the average tracking error of the multi-feature particle filter is 0.87 mm. These results confirm that key parts of our navigation system are effective. In the catheter intervention experiment, the vessel reconstruction error of local navigation is reduced by 80% compared to global navigation. Moreover, the targeting error of the navigation combining global and local information is reduced compared to global navigation alone (1.72 mm versus 2.87 mm). Thus, the US navigation system which integrates the large view of global navigation and high accuracy of local navigation can facilitate transcatheter stent deployment.