In the field of Internet of Things middleware, this paper analyses the challenges to build application support platform and reviews the current research work. The paper presents a solution combining hardware and software on the basis of hybrid middleware architecture. The solution is designed to enrich interface types of access gateway, improve the flexibility of middleware architecture, and enhance user programming performance through graphical programming. Finally, the process of developing and deploying applications with application support platform is introduced through test experiments, which shows the practicability of application support platform.
Multifocus light field cameras are increasingly gaining attention in the field of computational imaging and machine vision due to their ability to capture spatial and angular information of light rays. Accurate calibration of the geometric parameters of multifocus light field cameras is the prerequisite for implementing computational imaging techniques, such as digital refocusing, depth reconstruction, and three-dimensional reconstruction. We propose an improved blur circle detection method for the calibration of multifocus light field cameras. The circular Hough transform-based circle detection method is used to obtain the subimage centers accurately in white raw images. On this basis, the subimages in the checkerboard images are classified, and the image corners are detected to determine the clusters of image corners corresponding to checkerboard corners. Then, the centers of plenoptic disc features are used as projection points of checkerboard corners on the light field image to calculate the camera pose. Levenberg–Marquardt method is further used to solve the calibration model. Finally, the calibration experiments of multifocus light field cameras are carried out to evaluate the improved blur circle detection method. Experimental results indicated that the improved blur circle detection method has higher calibration accuracy of multifocus light field camera than the blur circle detection method, while the mean reprojection error of the microlens centers and the image corners are 0.12 and 0.33 pixels, and the mean relative distance error between adjacent checkerboards is 2.53%.
Supervisory Control and Data Acquisition (SCADA) system is the core component of the cryogenic propellant loading process control system, used to collect field data in real time and monitor and control scattered field devices. Aiming at the lacking authentication capabilities and other security measures of SCADA system, we proposed a lightweight security authentication scheme mainly using Cryptography for SCADA system. Based on symmetrical encryption technology and message authentication code (HMAC) technology, the proposed scheme could achieve bidirectional identity authentication and message confidentiality between the control server and the controller which could guarantee the availability, confidentiality, integrity of the transmitted data between different devices. Our scheme could also resist security threats such as replay attacks.
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