Recently, a variety of positioning and tracking methods have been proposed for capsule robots moving in the gastrointestinal (GI) tract to provide real-time unobstructed spatial pose results. However, the current absolute position-based result cannot match the GI structure due to its unstructured environment. To overcome this disadvantage and provide a proper position description method to match the GI tract, we here present a relative position estimation method for tracking the capsule robot, which uses the moving distance of the robot along the GI tract to indicate the position result. The procedure of the proposed method is as follows: firstly, the absolute position results of the capsule robot are obtained with the magnetic tracking method; then, the moving status of the robot along the GI tract is determined according to the moving direction; and finally, the movement trajectory of the capsule robot is fitted with the Bézier curve, where the moving distance can then be evaluated using the integral method. Compared to state-of-the-art capsule tracking methods, the proposed method can directly help to guide medical instruments by providing physicians the insertion distance in patients’ bodies, which cannot be done based on absolute position results. Moreover, as relative distance information was used, no reference tracking objects needed to be mounted onto the human body. The experimental results prove that the proposed method achieves a good distance estimation of the capsule robot moving in the simulation platform.

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Some fixed tubesheet heat exchangers suffer amount of system startup and shutdown causing large thermal stress for tubesheets. It will make an impact on the fatigue damage of the equipment. Transient thermal and stress analysis were carried out in many papers, but the geometry models were simplified, the non-expanded part of the tube and tubesheet were not modeled in detail at the end of tube. In fact, there is a tiny gap enclosed by tube, tubesheet and weld. So in this paper, a simplified model and an accurate model are established, the transient thermal and stress analysis were performed in ANSYS Workbench. The difference between two models was compared and the influence of temperature change rate on thermal stress was discussed.

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