A sensing element based on a bent and elongated grooved polymer optical fiber.

An experimental and numerical investigation is performed into the power loss induced in grooved polymer optical fibers (POFs) subjected to combined bending and elongation deformations. The power loss is examined as a function of both the groove depth and the bend radius. An elastic-plastic three-dimensional finite element model is constructed to simulate the deformation in the grooved region of the deformed specimens. The results indicate that the power loss increases significantly with an increasing bending displacement or groove depth. Specifically, the power loss increases to as much as 12% given a groove depth of 1.1 mm and a bending displacement of 10 mm. Based on the experimental results, an empirical expression is formulated to relate the power loss with the bending displacement for a given groove depth. It is shown that the difference between the estimated power loss and the actual power loss is less than 2%.

[The relations between dental fluorosis and economic status in Shuicheng, a fluorosis-endemic County in Guizhou province].

OBJECTIVE: To discuss the relations of dental fluorosis and the social economic status in fluorosis-stricken villages where drying the corn by burning coal was prevail. METHODS: A total of 6 fluorosis-endemic villages and one non-endemic village were involved in the study. The general fluorine intake and the concentrations of fluorine in corn, in the pupils' were tested. Dental fluorosis among the pupils was also examen. A individual interview or household questionnaire survey was conducted to probe the economic condition and staple food structure in 600 adults. RESULTS: The fluorosis prevalence was lower in the villages of transportation convenience, higher income, less coal-dried corn intake. There was a declining trend of dental fluorosis in the corresponding age groups (r: 0.912, 0.916; P < 0.05); There was no significant changes in age-specified dental fluorosis in the low income villages. The correlation (r) of corn fluorine concentration and student's age-specified dental fluorosis prevalence and disparity was 0.755 - 0.980 (P < 0.05) and 0.302 - 0.811; The urine fluorine concentrations were 0.811 and 0.915 (P < 0.05). It was assumed that there was a negative correlation between family cash income and the dental fluorosis. CONCLUSIONS: The corn fluorine concentration is closely related to age-specified dental fluorosis. With the economic improvement, taking less coal-burned corn is the one of major factors in reducing the of dental fluorosis in these areas.