Visible light positioning (VLP) is a promising technology since it can provide high accuracy indoor localization based on the existing lighting infrastructure. However, existing approaches often require dense LED distributions and persistent line-of-sight (LOS) between transmitter and receiver. What's more, sensors are imperfect, and their measurements are prone to errors. Through multi sensors fusion, we can compensate the deficiencies of stand-alone sensors and provide more reliable pose estimations. In this work, we propose a loosely-coupled multi-sensor fusion method based on VLP and Simultaneous Localization and Mapping (SLAM), using light detection and ranging (LiDAR), odometry, and rolling shutter camera. Our multi-sensor localizer can provide accurate and robust robot localization and navigation in LED shortage/outage situations. The experimental results show that our proposed scheme can provide an average accuracy of 2.5 cm with around 42 ms average positioning latency.
Indoor robotic localization is one of the most active areas in robotics research nowadays. Visible light positioning (VLP) is a promising indoor localization method, as it provides high positioning accuracy and allows for leveraging the existing lighting infrastructure. Apparently, accurate positioning performance is mostly shown by the VLP system with multiple LEDs, while such strict requirement of LED numbers is more likely to lead to VLP system failure in actual environments. In this paper, we propose a single-LED VLP system based on image sensor with the help of angle sensor estimation, which efficiently relaxes the assumption on the minimum number of simultaneously captured LEDs from several to one. Aiming at improving the robustness and accuracy of positioning in the process of continuous change of robot pose, two methods of visual-inertial message synchronization are proposed and used to obtain the well-matched positioning data packets. Various schemes of single-LED VLP system based on different sensor selections and message synchronization methods have been listed and compared in an actual environment. The effectiveness of the proposed single-LED VLP system based on odometer and image sensor as well as the robustness under LED shortage, handover situation and background non-signal light interference, are verified by real-world experiments. The experimental results show that our proposed system can provide an average accuracy of 2.47 cm and the average computational time in low-cost embedded platforms is around 0.184 s.
BACKGROUND Gastric cancer (GC) is one of the most common malignant tumors in the world. Although in recent years tremendous progress has been made in its early detection, the postoperative overall survival (OS) of GC patients remains extremely low. A number of studies have shown that age, to varying degrees, affects the prognosis of patients with GC. Therefore, this study retrospectively analyzed the clinical and pathologic data of patients with GC to explore the differences in the clinical characteristics and prognostic factors in different age groups. AIM To explore the difference in clinicopathological characteristics and prognostic factors in GC patients in different age groups. METHODS In this retrospective study, we analyzed 1037 GC patients admitted to Renji Hospital Affiliated to Shanghai Jiao Tong University School of Medicine from May 2010 to January 2013. The patients were divided into two groups based on age: Younger group (less than 70 years old) and older group (no less than 70 years old). In the younger group, we subdivided the patients in two subgroups by a cut-off value of 45 years. The clinical features and prognostic factors were analyzed in both groups. Subsequently, we retrieved studies that evaluated the predictive role of neutrophil-lymphocyte ratio (NLR) by searching two medical databases, PubMed and EMBASE, to conduct a meta-analysis. Random-effects model was used to pool the data. RESULTS In the retrospective study, the mean OS time of the younger group (64.7 mo) was significantly longer than that of the older group (48.1 mo) ( P < 0.001). Among patients under 70 years of age, hospitalization time, tumor–node–metastasis (TNM) stage, vascular invasion, and preoperative low pre-albumin were independently associated with OS ( P < 0.005). In patients aged 70 years and above, TNM stage, esophageal invasion, histological type, and preoperative NLR were independent factors for OS ( P < 0.05). The OS of these older patients was also significantly shorter ( P < 0.05). In the meta-analysis, 19 retrieved studies included a total of 8312 patients, among whom 3558 had elevated NLR values. The results showed that high NLR value was a risk factor for the prognosis of GC ( P < 0.01). CONCLUSION The OS of elderly patients is significantly worse than that of younger patients. There are significant differences in clinicopathological characteristics and prognostic factors between younger and older patients. NLR is a convenient, inexpensive, and reproducible marker that can be used as an important predictor of the prognosis of GC.
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