Pure CCl3F (Freon-11) vapor, initially below its room-temperature saturated vapor pressure, was compressed behind weak incident shock waves. The initial pressure was varied from 26 to 747 mm Hg, and the shock speed was varied from 141 to 321 m/s. The equilibrium cluster-size distribution was thus perturbed to varying degrees. Under the present experimental conditions cluster-forming processes en route to homonuclear condensation were set into motion. The exothermic redistribution of cluster sizes at the new temperature and pressure was monitored using the laser-schlieren technique over a time period of 10–300 μs. A characteristic redistribution time scale was measured as a function of temperature and pressure. The measured temperature and pressure dependence of the redistribution times are different than the classical temperature and pressure dependence of lag times in supersaturated vapors. A negative activation energy is observed, indicative of a strong competition between cluster formation, redissociation, and stabilization. A stability analysis of the nonlinear kinetic mechanism leads to a criterion for the onset of oscillations, and provides a basis for extracting elementary rate constants from the observations.
Abstract. Abstract: Compared with expressway, most of the traffic flow in urban road network can be denoted as interrupted traffic flow. Based on the currently employed equipment for traffic flow collection and traffic signal control in urban roads, different types of traffic flow in urban roads is analyzed with the traffic flow arrival/departure model in transportation engineering. Mathematical models complying with traffic flow changes are utilized to match the traffic flow in both entry and exit road blocks, thus enabling the automatic detection of traffic incident. This algorithm serves as a measure for the automatic judgment of urban road congestion and the expansion utility of intelligent transportation facilities in urban areas.
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