A Robust Planar Marker-Based Visual SLAM.

Many visual SLAM systems are generally solved using natural landmarks or optical flow. However, due to textureless areas, illumination change or motion blur, they often acquire poor camera poses or even fail to track. Additionally, they cannot obtain camera poses with a metric scale in the monocular case. In some cases (such as when calibrating the extrinsic parameters of camera-IMU), we prefer to sacrifice the flexibility of such methods to improve accuracy and robustness by using artificial landmarks. This paper proposes enhancements to the traditional SPM-SLAM, which is a system that aims to build a map of markers and simultaneously localize the camera pose. By placing the markers in the surrounding environment, the system can run stably and obtain accurate camera poses. To improve robustness and accuracy in the case of rotational movements, we improve the initialization, keyframes insertion and relocalization. Additionally, we propose a novel method to estimate marker poses from a set of images to solve the problem of planar-marker pose ambiguity. Compared with the state-of-art, the experiments show that our system achieves better accuracy in most public sequences and is more robust than SPM-SLAM under rotational movements. Finally, the open-source code is publicly available and can be found at GitHub.

Metabolism of barium in the human body after suicidal ingestion: A CARE-compliant case report.

RATIONALE: Thus far, barium poisoning has been seldom reported and the metabolism of barium in human body has not been explored. PATIENT CONCERNS: A 21-year-old young man was taken to the local hospital by "120 emergency medical services" after a suicidal attempt. About 100 mL of barium chloride solution with a concentration of 100 g/L was ingested, while the actual amount of ingested barium chloride solution was unclear because of immediate vomiting after the ingestion. DIAGNOSES: About 2 hours after the suicidal ingestion, the patient was presented with somnolence, the pulse rate was 67 beats per minute, the blood pressure was 158/92 mm Hg, but he exhibited no nausea or vomiting. About 3 hours after the ingestion, the blood concentration of potassium was 1.5 mmol/L. INTERVENTIONS: The patient received gastric lavage by magnesium sulfate solution, intravenous sodium thiosulfate, and potassium supplementation. Other symptomatic treatments were applied simultaneously. To investigate the metabolism of barium in the human body, we measured the concentration of barium in 9 groups of paired serum and urine samples sequentially collected from the patient. OUTCOMES: The patient was rescued successfully. LESSONS: The serum concentration of barium decreased rapidly in the first 24 hours. In this period, prompt and massive potassium supplementation and other symptomatic treatments are effective and recommended.

Research on Design, Calibration and Real-Time Image Expansion Technology of Unmanned System Variable-Scale Panoramic Vision System.

This paper summarized the research status, imaging model, systems calibration, distortion correction, and panoramic expansion of panoramic vision systems, pointed out the existing problems and put forward the prospect of future research. According to the research status of panoramic vision systems, a panoramic vision system with single viewpoint of refraction and reflection is designed. The systems had the characteristics of fast acquisition, low manufacturing cost, fixed single-view imaging, integrated imaging, and automatic switching depth of field. Based on these systems, an improved nonlinear optimization polynomial fitting method is proposed to calibrate the monocular HOVS, and the binocular HOVS is calibrated with the Aruco label. This method not only improves the robustness of the calibration results, but also simplifies the calibration process. Finally, a real-time method of panoramic map of multi-function vehicle based on vcam is proposed.