Study on fire-rescue command system and key technology of ultra high-rise building
Ultra high-rise buildings always regarded as a landmark of a city. But it also brings some fire safety problems due to crowded people, long evacuation distance, fast fire spread, etc. So the fire consequences are very serious, and it is also difficult to search the personnel in the building under emergency, which make the fire-rescue action of the ultra high-rise building very difficult. As a result, a set of effective information collection and analysis method are needed, which includes the collection of trapped personnel location information, fire information, evacuation routine, similar fire case in history and so on. There has not been a mature ultra high-rise building fire rescue system worldwide so far. In the study, we focused on several key technologies related to this problem, including indoor personnel locating, multisensory fire information fusion, fire source identification and so on. Based on the above technologies, the framework and functional design of an ultra high-rise building fire command and rescue system has been developed.
Experimental Studies of Electromagnetic Wave Attenuation by Flame and Smoke in Structure Fire
Attenuation of electromagnetic waves in the fire scene is an important issue when the stability of wireless communication is concerned, especially in fire rescue scenarios of high-rise buildings. Therefore, it is of importance to study the effects of flame and smoke on the attenuation of electromagnetic waves in structure fire. In this article, the influence of flame was studied through using alcohol as fuel. Different types of fuels were used to produce different concentrations of smoke. Different ranges of electromagnetic wave frequency from 350 MHz to 400 MHz were also used to investigate the frequency-dependent properties of the attenuation effect. The results show that flame itself does not have significant effects on the electromagnetic wave attenuation, but smoke plays an important role. Smoke from diesel fuel results in larger signal attenuation than other fuels, with attenuation of 1.16 dB at 300 MHz. The relationship between the concentration of smoke and signal attenuation follows the first-order exponential function. It also indicates that electromagnetic wave attenuation is frequency-dependent. The attenuation is 5.43 dB at 360 MHz when the smoke concentration is 20 dB/m, but only 0.26 dB at 400 MHz. It is suggested that a frequency-dependent assessment should be considered for investigating the reliability of the wireless communication system in structure fire in high-rise buildings.
Drivers of Live Cattle Price in the Livestock Trading System of Central Cameroon
Livestock production and trade are critical for the food security and welfare of rural households in sub-Saharan Africa. In Cameroon, animal trade consists mainly of live cattle commercialized through livestock markets. Identifying the factors contributing to cattle price formation is critical for designing effective policies for sustainable production and for increasing food availability. In this study, we evaluated the influence of a range of individual- and market-level factors on the price of cattle that were sold in all transactions (n = 118,017) recorded over a 12-month period from 31 livestock markets in the main cattle production area of the country. An information-theoretic approach using a generalized additive mixed-effect model was implemented to select the best explanatory model as well as evaluate the robustness of the identified drivers and the predictive ability of the model. The age and gender of the cattle traded were consistently found to be important drivers of the price (p < 0.01). Also, strong, but complex, relationships were found between cattle prices and both local human and bovine population densities. Finally, the model highlighted a positive association between the number of incoming trading connections of a livestock market and the price of the traded live cattle (p < 0.01). Although our analysis did not account for factors informing on specific phenotypic traits nor breed characteristics of cattle traded, nearly 50% of the observed variation in live cattle prices was explained by the final model. Ultimately, our model gives a large scale overview of drivers of cattle price formation in Cameroon and to our knowledge is the first study of this scale in Central Africa. Our findings represent an important milestone in designing efficient and sustainable animal health management programme in Cameroon and ensure livelihood sustainability for rural households.