ABSTRACT
In this paper, we propose a non-line of sight (NLOS) visible light positioning (VLP) system using a binocular camera and a single light emitting diode (LED) for the realization of 3D positioning of an arbitrary posture. The proposed system overcomes the challenges of the shadowing/blocking of the line of sight (LOS) transmission paths between transmitters and receivers (Rxs) and the need for a sufficient number of LEDs that can be captured within the limited field of view of the camera-based Rx. We have developed an experimental testbed to evaluate the performance of the proposed system with results showing that the lowest average error and the root mean square error (RMSE) are 26.10 and 31.02 cm following an error compensation algorithm. In addition, a label-based enhanced VLP scheme is proposed for the first time, which has a great improvement on the system performance with the average error and RMSE values of 7.31 and 7.74 cm and a 90th percentile accuracies of < 11 cm.
ABSTRACT
OBJECTIVE: To compare the prevalence of respiratory and atopic disorders, and to assess the role of atopy in the development of asthma in Chinese school children from Beijing, Guangzhou, and Hong Kong. METHODS: Community-based random samples of school children aged 9 approximately 11 years from three Chinese cities (Beijing, Guangzhou and Hong Kong) were recruited for study using the International Study of Asthma and Allergies in Childhood (ISAAC) Phase II protocol. Subjects were studied by parental questionnaires (n = 10 902), skin-prick tests and skin examination (n = 3 479). RESULTS: The prevalence rates of current wheeze, speech limiting wheeze, rhinoconjunctivitis and flexural dermatitis were significantly higher in Hong Kong than in Beijing and Guangzhou. The atopy rate was also higher in Hong Kong (41.2%) than in Beijing (23.9%) and Guangzhou (30.8%). Atopy was strongly correlated with current wheeze (OR = 7.74; 95% CI = 5.70 approximately 10.51). Subgroup analyses of children from Hong Kong revealed that children born in mainland China who had subsequently migrated to Hong Kong had a significantly lower rate of allergic symptoms and atopy than those born in Hong Kong. CONCLUSION: The prevalence of asthma, allergic diseases and atopy was highest in school children from Hong Kong. Atopic sensitizations is an important factor associated with asthma in Chinese children.
