Comparison on Generation Principle of Carbon Monoxide Concentration in Pine Combustion between Plain and Altiplano Regions

Experiments on carbon monoxide generation principle of pine which has been widely used in the historical buildings in Tibet were conducted in a combustion cabin in high-altitude-region Lhasa and low-altitude-region Hefei respectively. Three pine samples with different sizes were adopted. The surface temperature and CO concentration under radiative heat flux of 42 kW/m2 were measured. The effect of oxygen quantity and pressure on carbon monoxide production were analyzed. It was found from the experimental results that carbon monoxide generation had the same trend in both districts; it was first steadily released to a peak value, subsequently descended to a constant value, and then increased to a second value and decayed in the end. Comparing with those in Hefei, the two peak values and the steady value of carbon monoxide concentration in Lhasa were higher, and also, the time to them was much later. The main reason is that the quicker increasing temperature in lower-oxygen condition in Lhasa accelerated the incomplete oxidation of unburned hydrocarbons. Additionally, low mixing rate of volatile component and oxygen under the condition of low oxygen quantity and the ambient pressure was in favor of incomplete combustion of pine and therefore carbon monoxide production

A mathematical model on interaction of smoke layer with sprinkler spray

A mathematical model was developed for predicting the downward descending behavior of the buoyant smoke layer under sprinkler spray. The behavior of the smoke layer was determined by considering the interaction between the drag force of the sprinkler spray and the buoyancy force of the hot smoke layer itself in the spray region. The smoke layer may be pulled down with its thickness increased at the center of the spray region due to the cooling and drag effects of the sprinkler spray, thus to form a downward “smoke logging” plume. In the mathematical model developed in this paper, the critical condition under which the smoke layer lost its stability, as a serious concern, was predicted. Additionally, the length of the downward plume, which was rarely investigated before, was also further calculated. Full-scale experiments were carried out to validate the model. Results showed that the predictions, including the critical condition and the length of the plume, by the mathematical model agreed well with that observed and measured in the experiments. The length of the downward plume was shown to increase with the sprinkler operating pressure by an approximately linear correlation

A mathematical model on drag effect of sprinkler spray to adjacent horizontal smoke venting

A mathematical model has been developed to investigate the effect of sprinkler spray on adjacent horizontal smoke venting and in particular the drag component from water droplets. The pressure difference at a roof vent and the volumetric flow of smoke venting are determined by considering the interaction between the drag force of the sprinkler spray and the buoyancy of the smoke layer in the spray region. Smoke venting may become progressively more inefficient as the sprinkler operating pressure increases due to the cooling and drag effect of the sprinkler spray. Full scale experiments were carried out to validate the model. The results show that the prediction of decrease in volumetric flow with the increase in sprinkler operating pressure determined by the mathematical model agrees well with the measured values. Experimental results with different smoke venting areas show that the area has little influence on smoke flow once the sprinkler pressure causes a loss in smoke flow efficiency since the vents have already begun to lose their function

Propranolol inhibits the proliferation, migration and tube formation of hemangioma cells through HIF-1α dependent mechanisms

The aim of this study was to investigate the mechanism of propranolol on the regression of hemangiomas. Propranolol-treated hemangioma tissues were collected and the expression of hypoxia inducible factor-1α (HIF-1α) was examined. We also established HIF-1α overexpression and knockdown hemangioma cells, and determined the effects of HIF-1α on the hemangioma cells proliferation, apoptosis, migration and tube formation. Significantly increased HIF-1α level was found in the hemangioma tissues compared to that in normal vascular tissues, whereas propranolol treatment decreased the HIF-1α level in hemangioma tissues in a time- and dose-dependent manner. Moreover, propranolol treatment significantly decreased cell proliferation, migration and tube formation as well as promoted cell apoptosis in HIF-1α overexpression and knockdown hemangioma cells. Propranolol suppressed the cells proliferation, migration and tube formation of hemangioma cells through HIF-1α dependent mechanisms. HIF-1α could serve as a novel target in the treatment of hemangiomas